Clay Veins and Clay Minerals in the Granitic Rocks in ......Veins of types 1, 2 and 5 belong mainly...

94
Clay Veins and Clay Minerals in Hiroshima and Shimane Prefecture Effect of the hydrothermal a the decomposition of the grani Bv Ryu:土 K工TAGAWA - - - - ー・l-一 - with 8 Tables, 38 Text-figures a 4t- - - - To be published in Journal of S Hiroshima University, Series C (1986)

Transcript of Clay Veins and Clay Minerals in the Granitic Rocks in ......Veins of types 1, 2 and 5 belong mainly...

Clay Veins and Clay Minerals in the Granitic Rocks in

Hiroshima and Shimane Prefecturesl Southwest Japan

Effect of the hydrothermal activities on

the decomposition of the granitic rocks

Bv

Ryu土 K工TAGAWA

- -      -        -   ーl-一                -

with 8 Tables 38 Text-figures and 9 Plates4t-                                           -               -                           -

To be published in Journal of Science of the

Hiroshima University Series C Vol9 No1

(1986)

ABSTRACT This paper deals with the clay minerals found in

the granitic rocks distributed in Hiroshima and Shimane

Prefectures with special reference to the effects of

hydrothさrmal activities on the decolpPOsition process of the

granxtic rocks Many clay veins and hydrothermal clay

deposits are commonly developed in the granitic rocks and

their mode of occurrences were investigated in detail The

preferred orientations of the clay veins and m土crocracks

found in the constituent minerals of granitic rocks were

examined The constituent clay minerals and their

mineralogical characteristics of clay veins clay deposits

and alteration products of plagioclase in granitic rocks

were investigated by means of X-ray diffractont optical

micrOSCOPe electron micrOSCOpe(TEM and SEM) hydrogen

isotope ratio and so on The major results obtained are as

follows

1) The preferred orientations o micrOcracks within

granitic rocks are very similar to those of clay veins which

have been formed under the regional compression stress

field

2) The constituent clay minerals of clay veins clay

deposits and alteration products from plagioclase and their

mineralogical characteristics are almost identical with each

other

3) Mineral sequence found in the vertical direction of a

clay vein and altered granitic rocks resemble to that

observed in some present geothermal areas

_1 _

4) Mineralogical characteristics of the clay minerals

indicate that the clay minerals werb formed by hydrothermal

solution subsequent to the post granitic activity The

temperature of hydrothermal solution ranges about 50 - 300

C and originated from meteoric water  Ome clay minerals

seem o be directly precipitated from the hydrothemal

solution

Based on the results mentioned above it is considered

that granitic rocks distributed in the investigated areas

have been strongly fractured and characterized by

remarkable alteration to clay minerals at hydrothermal

stage before the weathering stage

 2-

CONTENTS

工工ntroduct土on

H Classif土cat土on and distribution of clay veins and

clay deposits

A Classification

B Mode of occurrence

III Fractures developed in granitic rocks

A Clay veins

B Clay deposits

C Microcracks

工Ⅴ Constituent clay minerals

A Clay veins

B Clay deposits

C Clay minerals derived from plagioclase

V Mineralogical characteristics of clay minerals

A Filling temperature of inclusion

B Hydrもgen and Oxygen isotope

C Microtopograph of crystal surface

D Morphology of halloysite

V工 DISCusslOn

A Formation mechanism and ages of fractures

B Formation condition of clay minerals

VII Concluding remarks

References

- 3 -

I INTRODUCTION

Studies of decomposed rocks are important to prevent

the disasters such as the landslide and the avalanche of

earth and rocks Therefore the decomposition of granitic

rocks has been studied in various field such as pedology

geomorphology and civil engineering as well as in the fields

of geological sciences Nevertheless the mechanism or

process of the decomposition of granitic rocks have not been

systematically explained yet

In the inner zone of southwest Japan granitic rocks of

Cretaceous to palae喝enej age are distributed widely and thel

rocks are characterizedl 土n general by common development

of fractures and extensive alteration The decomposition

extends usually to the depth of ten to twenty meters and 土n

some places the depth reaches more than hundred meters

while conducting the mineralogical study on the alteration

mechanism of plagioclase in the granitic rocks the author

has found that clay veins or veinlets are commonly observed

in the rocks (Kitagawa and Kakitani 1977a) These clay

veins seem to have been formed by filling fissures andor

fractures developed in granitic rocks Subsequent studies

on the mode of occurrenceJ detailed constituent clay

minerals and d土stribut土on of these clay minerals have

revealed that clay veins are intimately associated with the

post-magraatic activities ie hydrothermal activities

(Kitagawa and Kakitani 1977b 1978a b c and 1981) Clay

deposits developed 土n the gran土tic rocks have also been

proved to be related to the hydrothermal activities

ー 4 -

(Kitagawa and Kakitani 1979b Ishihara et al 1980 and

Kitagawa et al 1982)

The constituent minerals of the host granitic rocks

areprime more or less altered to clay minerals 工t土s to be

noted ls that some clay m土neralsof the alteration products

are similar to those of the clay veins in the mineralogical

characteristics such as mineral species and their

paragenesis (Kitagawa et al 1984 Kitagawa 1985) These

facts described above suggest that the hydro-thermal

activities may play an important role on the decomposition

In additionprime preferred or土entat土ons of fractures were

recognized at many localities suggesting that the fracture

patterns were formed under the regional stress field

(Kitagawa and Okunoprime 1984)

Based on the mineralogical and geochemical studies of

the clay veinsprime clay deposits and clay minerals altered from

plagioclase and geometrical analysis of the fractures

developed in the granitic rocks of Chugoku district a

systematic explanation for the effect of the hydrothermal

activity on decomposition process of granitic rocks will be

described in the present paper

- 5-

ACKNOWLEDGEMENTS The author wishes to express his

smcerest gratitude to Professor Satoru KARITANI of the

Hiroshima University for his constant and invaluable advices

rendered durnmg the course of the work as well as for his

critical reading of the manuscript He is also indebted to

Professors AkiraHASEJ Akira SOEDA Ikuo HARA and Assistant

Professor of yuji OKIMURA of the same University for their

guidance and critical advices He also gratefully

acknowleチages Assistant professor Setsuo TAKENO of the same

University for his continuing guidance and discussions and

for critical reading of the manuscript Thanks are also du

to Dr M SUZUKI Dr T SHIMAMOTO Dr A WATANABE and Dr

T MIYAMOTO for their helpful advice and encouragement He

also grateful to Mr A MINAMI of the Hiroshima University

for his kind help with the techniques土n the laboratory and

Mr H TAKAHASHI and Mr A MAGAI for preparing thin

sections He isralso due to Mr A Funaki Mr YNISHIDA

MrH KAMEOKA Mr Y HABU MrT OZAWA MrTOKUNO MrN

HIROSAWA MrKNAGAIJ MrT NOBUSHITA MrK ABE MrM

TAKEMOTOJ MrT BABA MrH MITANI MrJ HIGASIO for

capable assistance in the field Special thanks go to

Prof H TAKAHASHI of Hiroshima University who read the

manuscript and gave helpful comments on the final

manuscript He would like to thank to Miss S KODAMA for

her kind assistance durning the preparation of the

manuscript

1 6 -

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

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cup

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sube

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to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

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-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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- 82 -

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Y(1981)Topographic examination and genesis of clay

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- 84 -

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

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- 8 5-

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MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

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MatsumotoK(1965) On some kaolin deposits related to the

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Miura K(1967)On the granitic rocks and their collapse

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

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Sumi K(1966) Hydrothermal rock alteration of the

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Takashima I1972)Hydrothermal rock alteration in

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9-

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Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

ABSTRACT This paper deals with the clay minerals found in

the granitic rocks distributed in Hiroshima and Shimane

Prefectures with special reference to the effects of

hydrothさrmal activities on the decolpPOsition process of the

granxtic rocks Many clay veins and hydrothermal clay

deposits are commonly developed in the granitic rocks and

their mode of occurrences were investigated in detail The

preferred orientations of the clay veins and m土crocracks

found in the constituent minerals of granitic rocks were

examined The constituent clay minerals and their

mineralogical characteristics of clay veins clay deposits

and alteration products of plagioclase in granitic rocks

were investigated by means of X-ray diffractont optical

micrOSCOPe electron micrOSCOpe(TEM and SEM) hydrogen

isotope ratio and so on The major results obtained are as

follows

1) The preferred orientations o micrOcracks within

granitic rocks are very similar to those of clay veins which

have been formed under the regional compression stress

field

2) The constituent clay minerals of clay veins clay

deposits and alteration products from plagioclase and their

mineralogical characteristics are almost identical with each

other

3) Mineral sequence found in the vertical direction of a

clay vein and altered granitic rocks resemble to that

observed in some present geothermal areas

_1 _

4) Mineralogical characteristics of the clay minerals

indicate that the clay minerals werb formed by hydrothermal

solution subsequent to the post granitic activity The

temperature of hydrothermal solution ranges about 50 - 300

C and originated from meteoric water  Ome clay minerals

seem o be directly precipitated from the hydrothemal

solution

Based on the results mentioned above it is considered

that granitic rocks distributed in the investigated areas

have been strongly fractured and characterized by

remarkable alteration to clay minerals at hydrothermal

stage before the weathering stage

 2-

CONTENTS

工工ntroduct土on

H Classif土cat土on and distribution of clay veins and

clay deposits

A Classification

B Mode of occurrence

III Fractures developed in granitic rocks

A Clay veins

B Clay deposits

C Microcracks

工Ⅴ Constituent clay minerals

A Clay veins

B Clay deposits

C Clay minerals derived from plagioclase

V Mineralogical characteristics of clay minerals

A Filling temperature of inclusion

B Hydrもgen and Oxygen isotope

C Microtopograph of crystal surface

D Morphology of halloysite

V工 DISCusslOn

A Formation mechanism and ages of fractures

B Formation condition of clay minerals

VII Concluding remarks

References

- 3 -

I INTRODUCTION

Studies of decomposed rocks are important to prevent

the disasters such as the landslide and the avalanche of

earth and rocks Therefore the decomposition of granitic

rocks has been studied in various field such as pedology

geomorphology and civil engineering as well as in the fields

of geological sciences Nevertheless the mechanism or

process of the decomposition of granitic rocks have not been

systematically explained yet

In the inner zone of southwest Japan granitic rocks of

Cretaceous to palae喝enej age are distributed widely and thel

rocks are characterizedl 土n general by common development

of fractures and extensive alteration The decomposition

extends usually to the depth of ten to twenty meters and 土n

some places the depth reaches more than hundred meters

while conducting the mineralogical study on the alteration

mechanism of plagioclase in the granitic rocks the author

has found that clay veins or veinlets are commonly observed

in the rocks (Kitagawa and Kakitani 1977a) These clay

veins seem to have been formed by filling fissures andor

fractures developed in granitic rocks Subsequent studies

on the mode of occurrenceJ detailed constituent clay

minerals and d土stribut土on of these clay minerals have

revealed that clay veins are intimately associated with the

post-magraatic activities ie hydrothermal activities

(Kitagawa and Kakitani 1977b 1978a b c and 1981) Clay

deposits developed 土n the gran土tic rocks have also been

proved to be related to the hydrothermal activities

ー 4 -

(Kitagawa and Kakitani 1979b Ishihara et al 1980 and

Kitagawa et al 1982)

The constituent minerals of the host granitic rocks

areprime more or less altered to clay minerals 工t土s to be

noted ls that some clay m土neralsof the alteration products

are similar to those of the clay veins in the mineralogical

characteristics such as mineral species and their

paragenesis (Kitagawa et al 1984 Kitagawa 1985) These

facts described above suggest that the hydro-thermal

activities may play an important role on the decomposition

In additionprime preferred or土entat土ons of fractures were

recognized at many localities suggesting that the fracture

patterns were formed under the regional stress field

(Kitagawa and Okunoprime 1984)

Based on the mineralogical and geochemical studies of

the clay veinsprime clay deposits and clay minerals altered from

plagioclase and geometrical analysis of the fractures

developed in the granitic rocks of Chugoku district a

systematic explanation for the effect of the hydrothermal

activity on decomposition process of granitic rocks will be

described in the present paper

- 5-

ACKNOWLEDGEMENTS The author wishes to express his

smcerest gratitude to Professor Satoru KARITANI of the

Hiroshima University for his constant and invaluable advices

rendered durnmg the course of the work as well as for his

critical reading of the manuscript He is also indebted to

Professors AkiraHASEJ Akira SOEDA Ikuo HARA and Assistant

Professor of yuji OKIMURA of the same University for their

guidance and critical advices He also gratefully

acknowleチages Assistant professor Setsuo TAKENO of the same

University for his continuing guidance and discussions and

for critical reading of the manuscript Thanks are also du

to Dr M SUZUKI Dr T SHIMAMOTO Dr A WATANABE and Dr

T MIYAMOTO for their helpful advice and encouragement He

also grateful to Mr A MINAMI of the Hiroshima University

for his kind help with the techniques土n the laboratory and

Mr H TAKAHASHI and Mr A MAGAI for preparing thin

sections He isralso due to Mr A Funaki Mr YNISHIDA

MrH KAMEOKA Mr Y HABU MrT OZAWA MrTOKUNO MrN

HIROSAWA MrKNAGAIJ MrT NOBUSHITA MrK ABE MrM

TAKEMOTOJ MrT BABA MrH MITANI MrJ HIGASIO for

capable assistance in the field Special thanks go to

Prof H TAKAHASHI of Hiroshima University who read the

manuscript and gave helpful comments on the final

manuscript He would like to thank to Miss S KODAMA for

her kind assistance durning the preparation of the

manuscript

1 6 -

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

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td21

E」=班

一ヽ

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- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

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d蝣H

SJ

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rロC

d

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0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

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d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

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14-1 O

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己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

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3

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primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

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来旨+剥牽(19糾う

4) Mineralogical characteristics of the clay minerals

indicate that the clay minerals werb formed by hydrothermal

solution subsequent to the post granitic activity The

temperature of hydrothermal solution ranges about 50 - 300

C and originated from meteoric water  Ome clay minerals

seem o be directly precipitated from the hydrothemal

solution

Based on the results mentioned above it is considered

that granitic rocks distributed in the investigated areas

have been strongly fractured and characterized by

remarkable alteration to clay minerals at hydrothermal

stage before the weathering stage

 2-

CONTENTS

工工ntroduct土on

H Classif土cat土on and distribution of clay veins and

clay deposits

A Classification

B Mode of occurrence

III Fractures developed in granitic rocks

A Clay veins

B Clay deposits

C Microcracks

工Ⅴ Constituent clay minerals

A Clay veins

B Clay deposits

C Clay minerals derived from plagioclase

V Mineralogical characteristics of clay minerals

A Filling temperature of inclusion

B Hydrもgen and Oxygen isotope

C Microtopograph of crystal surface

D Morphology of halloysite

V工 DISCusslOn

A Formation mechanism and ages of fractures

B Formation condition of clay minerals

VII Concluding remarks

References

- 3 -

I INTRODUCTION

Studies of decomposed rocks are important to prevent

the disasters such as the landslide and the avalanche of

earth and rocks Therefore the decomposition of granitic

rocks has been studied in various field such as pedology

geomorphology and civil engineering as well as in the fields

of geological sciences Nevertheless the mechanism or

process of the decomposition of granitic rocks have not been

systematically explained yet

In the inner zone of southwest Japan granitic rocks of

Cretaceous to palae喝enej age are distributed widely and thel

rocks are characterizedl 土n general by common development

of fractures and extensive alteration The decomposition

extends usually to the depth of ten to twenty meters and 土n

some places the depth reaches more than hundred meters

while conducting the mineralogical study on the alteration

mechanism of plagioclase in the granitic rocks the author

has found that clay veins or veinlets are commonly observed

in the rocks (Kitagawa and Kakitani 1977a) These clay

veins seem to have been formed by filling fissures andor

fractures developed in granitic rocks Subsequent studies

on the mode of occurrenceJ detailed constituent clay

minerals and d土stribut土on of these clay minerals have

revealed that clay veins are intimately associated with the

post-magraatic activities ie hydrothermal activities

(Kitagawa and Kakitani 1977b 1978a b c and 1981) Clay

deposits developed 土n the gran土tic rocks have also been

proved to be related to the hydrothermal activities

ー 4 -

(Kitagawa and Kakitani 1979b Ishihara et al 1980 and

Kitagawa et al 1982)

The constituent minerals of the host granitic rocks

areprime more or less altered to clay minerals 工t土s to be

noted ls that some clay m土neralsof the alteration products

are similar to those of the clay veins in the mineralogical

characteristics such as mineral species and their

paragenesis (Kitagawa et al 1984 Kitagawa 1985) These

facts described above suggest that the hydro-thermal

activities may play an important role on the decomposition

In additionprime preferred or土entat土ons of fractures were

recognized at many localities suggesting that the fracture

patterns were formed under the regional stress field

(Kitagawa and Okunoprime 1984)

Based on the mineralogical and geochemical studies of

the clay veinsprime clay deposits and clay minerals altered from

plagioclase and geometrical analysis of the fractures

developed in the granitic rocks of Chugoku district a

systematic explanation for the effect of the hydrothermal

activity on decomposition process of granitic rocks will be

described in the present paper

- 5-

ACKNOWLEDGEMENTS The author wishes to express his

smcerest gratitude to Professor Satoru KARITANI of the

Hiroshima University for his constant and invaluable advices

rendered durnmg the course of the work as well as for his

critical reading of the manuscript He is also indebted to

Professors AkiraHASEJ Akira SOEDA Ikuo HARA and Assistant

Professor of yuji OKIMURA of the same University for their

guidance and critical advices He also gratefully

acknowleチages Assistant professor Setsuo TAKENO of the same

University for his continuing guidance and discussions and

for critical reading of the manuscript Thanks are also du

to Dr M SUZUKI Dr T SHIMAMOTO Dr A WATANABE and Dr

T MIYAMOTO for their helpful advice and encouragement He

also grateful to Mr A MINAMI of the Hiroshima University

for his kind help with the techniques土n the laboratory and

Mr H TAKAHASHI and Mr A MAGAI for preparing thin

sections He isralso due to Mr A Funaki Mr YNISHIDA

MrH KAMEOKA Mr Y HABU MrT OZAWA MrTOKUNO MrN

HIROSAWA MrKNAGAIJ MrT NOBUSHITA MrK ABE MrM

TAKEMOTOJ MrT BABA MrH MITANI MrJ HIGASIO for

capable assistance in the field Special thanks go to

Prof H TAKAHASHI of Hiroshima University who read the

manuscript and gave helpful comments on the final

manuscript He would like to thank to Miss S KODAMA for

her kind assistance durning the preparation of the

manuscript

1 6 -

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

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Bi喜l蝣51

rdl

E3i

l

E

I

I

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l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

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lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

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別 離 萱

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5

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_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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i

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打 S

=o

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巨≒

l弓

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equiv

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くJ

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a3isin I

1-  ン

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毒-gtサ

=

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C

_ 80 -

l=a

こくc

Et

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く1

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Eq

equiv

=蝣

13

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もカ

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a

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0h

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日1lJh

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primeヽ

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fL

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射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

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CONTENTS

工工ntroduct土on

H Classif土cat土on and distribution of clay veins and

clay deposits

A Classification

B Mode of occurrence

III Fractures developed in granitic rocks

A Clay veins

B Clay deposits

C Microcracks

工Ⅴ Constituent clay minerals

A Clay veins

B Clay deposits

C Clay minerals derived from plagioclase

V Mineralogical characteristics of clay minerals

A Filling temperature of inclusion

B Hydrもgen and Oxygen isotope

C Microtopograph of crystal surface

D Morphology of halloysite

V工 DISCusslOn

A Formation mechanism and ages of fractures

B Formation condition of clay minerals

VII Concluding remarks

References

- 3 -

I INTRODUCTION

Studies of decomposed rocks are important to prevent

the disasters such as the landslide and the avalanche of

earth and rocks Therefore the decomposition of granitic

rocks has been studied in various field such as pedology

geomorphology and civil engineering as well as in the fields

of geological sciences Nevertheless the mechanism or

process of the decomposition of granitic rocks have not been

systematically explained yet

In the inner zone of southwest Japan granitic rocks of

Cretaceous to palae喝enej age are distributed widely and thel

rocks are characterizedl 土n general by common development

of fractures and extensive alteration The decomposition

extends usually to the depth of ten to twenty meters and 土n

some places the depth reaches more than hundred meters

while conducting the mineralogical study on the alteration

mechanism of plagioclase in the granitic rocks the author

has found that clay veins or veinlets are commonly observed

in the rocks (Kitagawa and Kakitani 1977a) These clay

veins seem to have been formed by filling fissures andor

fractures developed in granitic rocks Subsequent studies

on the mode of occurrenceJ detailed constituent clay

minerals and d土stribut土on of these clay minerals have

revealed that clay veins are intimately associated with the

post-magraatic activities ie hydrothermal activities

(Kitagawa and Kakitani 1977b 1978a b c and 1981) Clay

deposits developed 土n the gran土tic rocks have also been

proved to be related to the hydrothermal activities

ー 4 -

(Kitagawa and Kakitani 1979b Ishihara et al 1980 and

Kitagawa et al 1982)

The constituent minerals of the host granitic rocks

areprime more or less altered to clay minerals 工t土s to be

noted ls that some clay m土neralsof the alteration products

are similar to those of the clay veins in the mineralogical

characteristics such as mineral species and their

paragenesis (Kitagawa et al 1984 Kitagawa 1985) These

facts described above suggest that the hydro-thermal

activities may play an important role on the decomposition

In additionprime preferred or土entat土ons of fractures were

recognized at many localities suggesting that the fracture

patterns were formed under the regional stress field

(Kitagawa and Okunoprime 1984)

Based on the mineralogical and geochemical studies of

the clay veinsprime clay deposits and clay minerals altered from

plagioclase and geometrical analysis of the fractures

developed in the granitic rocks of Chugoku district a

systematic explanation for the effect of the hydrothermal

activity on decomposition process of granitic rocks will be

described in the present paper

- 5-

ACKNOWLEDGEMENTS The author wishes to express his

smcerest gratitude to Professor Satoru KARITANI of the

Hiroshima University for his constant and invaluable advices

rendered durnmg the course of the work as well as for his

critical reading of the manuscript He is also indebted to

Professors AkiraHASEJ Akira SOEDA Ikuo HARA and Assistant

Professor of yuji OKIMURA of the same University for their

guidance and critical advices He also gratefully

acknowleチages Assistant professor Setsuo TAKENO of the same

University for his continuing guidance and discussions and

for critical reading of the manuscript Thanks are also du

to Dr M SUZUKI Dr T SHIMAMOTO Dr A WATANABE and Dr

T MIYAMOTO for their helpful advice and encouragement He

also grateful to Mr A MINAMI of the Hiroshima University

for his kind help with the techniques土n the laboratory and

Mr H TAKAHASHI and Mr A MAGAI for preparing thin

sections He isralso due to Mr A Funaki Mr YNISHIDA

MrH KAMEOKA Mr Y HABU MrT OZAWA MrTOKUNO MrN

HIROSAWA MrKNAGAIJ MrT NOBUSHITA MrK ABE MrM

TAKEMOTOJ MrT BABA MrH MITANI MrJ HIGASIO for

capable assistance in the field Special thanks go to

Prof H TAKAHASHI of Hiroshima University who read the

manuscript and gave helpful comments on the final

manuscript He would like to thank to Miss S KODAMA for

her kind assistance durning the preparation of the

manuscript

1 6 -

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

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-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Craig H(1961)Isotopic variations in meteoric water

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Hashikawa K (1978a)On an Anlstotropic effect to the Pr

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Hashikawaprime K(1985)Studies on the planar fracturing

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48-58

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Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

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kaolins collected from diverse environments of origin-

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flint-like clays Clay Clays Miner 24 162-264

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- 82 -

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1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

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359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

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Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

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Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

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0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

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Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

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Suzuoki T and Epstein S(1976) Hydrogen isotope

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Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

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Tazaki K(1977) Formation of clay minerals from

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Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

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Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

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Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

16

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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紙十Ltl聖(19fi招

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来旨+剥牽(19糾う

I INTRODUCTION

Studies of decomposed rocks are important to prevent

the disasters such as the landslide and the avalanche of

earth and rocks Therefore the decomposition of granitic

rocks has been studied in various field such as pedology

geomorphology and civil engineering as well as in the fields

of geological sciences Nevertheless the mechanism or

process of the decomposition of granitic rocks have not been

systematically explained yet

In the inner zone of southwest Japan granitic rocks of

Cretaceous to palae喝enej age are distributed widely and thel

rocks are characterizedl 土n general by common development

of fractures and extensive alteration The decomposition

extends usually to the depth of ten to twenty meters and 土n

some places the depth reaches more than hundred meters

while conducting the mineralogical study on the alteration

mechanism of plagioclase in the granitic rocks the author

has found that clay veins or veinlets are commonly observed

in the rocks (Kitagawa and Kakitani 1977a) These clay

veins seem to have been formed by filling fissures andor

fractures developed in granitic rocks Subsequent studies

on the mode of occurrenceJ detailed constituent clay

minerals and d土stribut土on of these clay minerals have

revealed that clay veins are intimately associated with the

post-magraatic activities ie hydrothermal activities

(Kitagawa and Kakitani 1977b 1978a b c and 1981) Clay

deposits developed 土n the gran土tic rocks have also been

proved to be related to the hydrothermal activities

ー 4 -

(Kitagawa and Kakitani 1979b Ishihara et al 1980 and

Kitagawa et al 1982)

The constituent minerals of the host granitic rocks

areprime more or less altered to clay minerals 工t土s to be

noted ls that some clay m土neralsof the alteration products

are similar to those of the clay veins in the mineralogical

characteristics such as mineral species and their

paragenesis (Kitagawa et al 1984 Kitagawa 1985) These

facts described above suggest that the hydro-thermal

activities may play an important role on the decomposition

In additionprime preferred or土entat土ons of fractures were

recognized at many localities suggesting that the fracture

patterns were formed under the regional stress field

(Kitagawa and Okunoprime 1984)

Based on the mineralogical and geochemical studies of

the clay veinsprime clay deposits and clay minerals altered from

plagioclase and geometrical analysis of the fractures

developed in the granitic rocks of Chugoku district a

systematic explanation for the effect of the hydrothermal

activity on decomposition process of granitic rocks will be

described in the present paper

- 5-

ACKNOWLEDGEMENTS The author wishes to express his

smcerest gratitude to Professor Satoru KARITANI of the

Hiroshima University for his constant and invaluable advices

rendered durnmg the course of the work as well as for his

critical reading of the manuscript He is also indebted to

Professors AkiraHASEJ Akira SOEDA Ikuo HARA and Assistant

Professor of yuji OKIMURA of the same University for their

guidance and critical advices He also gratefully

acknowleチages Assistant professor Setsuo TAKENO of the same

University for his continuing guidance and discussions and

for critical reading of the manuscript Thanks are also du

to Dr M SUZUKI Dr T SHIMAMOTO Dr A WATANABE and Dr

T MIYAMOTO for their helpful advice and encouragement He

also grateful to Mr A MINAMI of the Hiroshima University

for his kind help with the techniques土n the laboratory and

Mr H TAKAHASHI and Mr A MAGAI for preparing thin

sections He isralso due to Mr A Funaki Mr YNISHIDA

MrH KAMEOKA Mr Y HABU MrT OZAWA MrTOKUNO MrN

HIROSAWA MrKNAGAIJ MrT NOBUSHITA MrK ABE MrM

TAKEMOTOJ MrT BABA MrH MITANI MrJ HIGASIO for

capable assistance in the field Special thanks go to

Prof H TAKAHASHI of Hiroshima University who read the

manuscript and gave helpful comments on the final

manuscript He would like to thank to Miss S KODAMA for

her kind assistance durning the preparation of the

manuscript

1 6 -

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

(Kitagawa and Kakitani 1979b Ishihara et al 1980 and

Kitagawa et al 1982)

The constituent minerals of the host granitic rocks

areprime more or less altered to clay minerals 工t土s to be

noted ls that some clay m土neralsof the alteration products

are similar to those of the clay veins in the mineralogical

characteristics such as mineral species and their

paragenesis (Kitagawa et al 1984 Kitagawa 1985) These

facts described above suggest that the hydro-thermal

activities may play an important role on the decomposition

In additionprime preferred or土entat土ons of fractures were

recognized at many localities suggesting that the fracture

patterns were formed under the regional stress field

(Kitagawa and Okunoprime 1984)

Based on the mineralogical and geochemical studies of

the clay veinsprime clay deposits and clay minerals altered from

plagioclase and geometrical analysis of the fractures

developed in the granitic rocks of Chugoku district a

systematic explanation for the effect of the hydrothermal

activity on decomposition process of granitic rocks will be

described in the present paper

- 5-

ACKNOWLEDGEMENTS The author wishes to express his

smcerest gratitude to Professor Satoru KARITANI of the

Hiroshima University for his constant and invaluable advices

rendered durnmg the course of the work as well as for his

critical reading of the manuscript He is also indebted to

Professors AkiraHASEJ Akira SOEDA Ikuo HARA and Assistant

Professor of yuji OKIMURA of the same University for their

guidance and critical advices He also gratefully

acknowleチages Assistant professor Setsuo TAKENO of the same

University for his continuing guidance and discussions and

for critical reading of the manuscript Thanks are also du

to Dr M SUZUKI Dr T SHIMAMOTO Dr A WATANABE and Dr

T MIYAMOTO for their helpful advice and encouragement He

also grateful to Mr A MINAMI of the Hiroshima University

for his kind help with the techniques土n the laboratory and

Mr H TAKAHASHI and Mr A MAGAI for preparing thin

sections He isralso due to Mr A Funaki Mr YNISHIDA

MrH KAMEOKA Mr Y HABU MrT OZAWA MrTOKUNO MrN

HIROSAWA MrKNAGAIJ MrT NOBUSHITA MrK ABE MrM

TAKEMOTOJ MrT BABA MrH MITANI MrJ HIGASIO for

capable assistance in the field Special thanks go to

Prof H TAKAHASHI of Hiroshima University who read the

manuscript and gave helpful comments on the final

manuscript He would like to thank to Miss S KODAMA for

her kind assistance durning the preparation of the

manuscript

1 6 -

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

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Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

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rd

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

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1 蝣蝣蝣 -ff= ー=

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isin 空 ∽ i l 喜一 「

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く1

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Eq

equiv

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日1lJh

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

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排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

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ACKNOWLEDGEMENTS The author wishes to express his

smcerest gratitude to Professor Satoru KARITANI of the

Hiroshima University for his constant and invaluable advices

rendered durnmg the course of the work as well as for his

critical reading of the manuscript He is also indebted to

Professors AkiraHASEJ Akira SOEDA Ikuo HARA and Assistant

Professor of yuji OKIMURA of the same University for their

guidance and critical advices He also gratefully

acknowleチages Assistant professor Setsuo TAKENO of the same

University for his continuing guidance and discussions and

for critical reading of the manuscript Thanks are also du

to Dr M SUZUKI Dr T SHIMAMOTO Dr A WATANABE and Dr

T MIYAMOTO for their helpful advice and encouragement He

also grateful to Mr A MINAMI of the Hiroshima University

for his kind help with the techniques土n the laboratory and

Mr H TAKAHASHI and Mr A MAGAI for preparing thin

sections He isralso due to Mr A Funaki Mr YNISHIDA

MrH KAMEOKA Mr Y HABU MrT OZAWA MrTOKUNO MrN

HIROSAWA MrKNAGAIJ MrT NOBUSHITA MrK ABE MrM

TAKEMOTOJ MrT BABA MrH MITANI MrJ HIGASIO for

capable assistance in the field Special thanks go to

Prof H TAKAHASHI of Hiroshima University who read the

manuscript and gave helpful comments on the final

manuscript He would like to thank to Miss S KODAMA for

her kind assistance durning the preparation of the

manuscript

1 6 -

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

II CLASSIFICATION AND DISTRIBUTION OF CLAY VEINS AND CLAY

DEPOSITS

Clay veins are Observed commonly in the granltic rocks

especially in the decomposed parts as mentioned below The

width of veins varies from one millimeter to one meter

In addition to the clay veins which have been formed filling

fractures by clay minerals aggregates of clay minerals ofj

replacement origin which are aligned in certain directions

resulting vein-like appearance will be亀scussed The mode

of occurrences of clay deposits are similar to that of clay

veins andor vein-like replacement products

A CLASSIFICATION

As will be described laterJ the vein-like replacement

products were caused by the hydrothermal act土Ⅴ土ties by which

the clay veins were formed Therefore the vein-like

replacement producヒs will be 土ncluded in the clay yelns in

this paper In the following these clay veins and vein-

like replacement products will be classified土nto five types

based mainly on their mode of occurrence such as the

characters of fractures andor cracks (Fig 1)

Type 1 Clay veins formed along the interstices of both

sides of a dike rock such as granite porphyry quartz

porphyry and porphyrite (Plate 1) The scale of the veins

varies from one centimeter to one meter

Type 2 Clay veins formed by filling nearly vertical

fissures or cracks (Plate 1) This type occurs most

frequently and can be further divided into three types (Types

- 7 -

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Y(1981)Topographic examination and genesis of clay

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

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ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

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Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

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Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

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Suzuoki T and Epstein S(1976) Hydrogen isotope

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Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

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Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

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Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

2-Aprime 2-B and 2-C) on the bas上s of the character of the

fractures Type 2-A is formed along faults and corresponds

to the fault clay or gouge with relatively large width than

those of the other types Both types2-B and 2-C are formed

along sheared andor open fractures

Type 3 Clay veins formed along vertical or horizontal

joints corresponding to the so-called joint-clay (Miura and

Hataprime 1970)

Type 4 Clay veins formed along small fissures of lmm to

lOmm in width Network development of this type is

observed in some places (plate 1)

Type 5 Aggregates of clay minerals of replacement

products alignes certain directions (Plate 1) Veins of

this type are formed along many micro fractures extending in

certain directions

Although the color of these veins varies complicatedlyprimer

all of the veins were roughly divided into two colors such

as green and white  Veins of types 1 2 and 5 belong

mainly to the green type whereas those of types 3 and 4 to

the white type As was reported in the previous paperprime the

color of the veins reflects their constituent clay mineralsJ

ieprime the veins of white type are composed mainly of kaolin

minerals and green type smectite and mica clay minerals

(Kitagawa et al 1977bprime 1978a)

Suitable outcrops for sucht Observation and for

measurement of the orientations (strike and dip) of the veins

can be often found at the construction places of tunnelprime

- 8 -

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Craig H(1961)Isotopic variations in meteoric water

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Hashikawa K (1978a)On an Anlstotropic effect to the Pr

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Hshikawa K(1978b) Weathering structure of the granitic

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Hayashi M(1973)Hydrothermal alteration in the Ohtake

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geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

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S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

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Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

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I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

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Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N(1968) Weathering-zone structure and landslides

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Takashima I1972)Hydrothermal rock alteration in

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

cave of dam-site housing and so on

A continuous development of veins of types12 and 5 can

be pursued more than several kilometers in thとkamo district

between Nishitakaya and Shiraichi as shown in Fig 2

During the construction of a dam detailed observations of

the development of clay veinsl ma-inly those of type 2 could

be performed at Nukui Kake-cho Hiroshima Prefecture (Fig

3) Thes早 veins can be pursued more than two hundred

meters xn the lateral direction and more than hundered

meters 土n the vertical direction  As is seen in Fig 3J

the dlstr五kmtion pattern of the veins of type 2 is aimost

similar to that of type 4 The only difference between the

two types 土s the scale Veins of types 3 and 4 are found

near the ground surface whereas those of typesl 2 and 5

occur not only near the surface but also under the ground of

more than lOOm 土n depth

The degree of the decomposition were roughly measured

by the alteration degree of plagioclase in the granitic

rocks As seen in Figs 4 5 and 6 all types of clay

veins develop considerably at the relatively more

decomposed parts of the respective granitic rocks

B MODE OF OCCURRENCE OF CLAY DEPOSITS

A number of hydrothermal clay deposits are found mainly

in granitic rocks distributed in relatively restricted areas

of Hiroshima and Shimane Prefectures (Fig 7) Considering

the main constituent clay minerals two kinds of ore

deposits are distingishable in these districts one is

- 9 -

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

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EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

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てこ=UI

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∽ 声C

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agt

gt

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rd 0JS 5h

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deg

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- 25 -

q)

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り0蝣H

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a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

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〇 日 TO

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gt T3U rH0) 0)W 4-1

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prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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283

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- 8 6-

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

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7-

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21-44

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

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18

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iiilt日こHLlllgttこrト1-I

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daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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紙十Ltl聖(19fi招

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来旨+剥牽(19糾う

千V 

Clay vein

Type 1

+     十     十

+     十

+     十     十

十     十

Granitic rock

十    十    十

十     +

十    十    十

十     +

Type 2A Type 2B

+ 十 十

+ 十

十 十 十 十 + 千

I

E十 十 + ン 十 +

l十 十 V + 十

Clay veinl

Type 3

Clay vein

Type 4

+    十

十    十    十

十    十

Granitic rock+    十    十

十    +

+

Clay vein

Type 5

Fig -1 Schematic diagrams of clay veins of five types classified

based on the characteristics of fractures

+

Fig 2こDevelopments of clay veins of Typesl24 and 5 in Kamo

d土str土ctprime H土rosh土ma Prefecture

- 10 -

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

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cup

t叫0巳

cent蝣O

sube

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to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

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覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

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deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

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mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

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alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

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7-

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21-44

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- 8 8-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

11 -

Ln

CD co

昌gSgt1d

=】U

LLI

O

VoGQJhh2Uo

O

LH

O

Q)rロ

sum

e

s

QJヰJ

qiH

PJ

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

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0

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0」

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H  

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g コ

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U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

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EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

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- 25 -

q)

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G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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283

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Vo1ll 6-38

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- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 3 Developments of clay veins at Nukui Kake-cho

Hiroshima Prefecture

- 12 -

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

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tH

0

C

0」

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d蝣H

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g コ

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U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

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-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

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蝣P lta

 isinU

G

Ll ∽V

w  サ

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14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

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lgtyenrATVry^i蝣蝣蝣1

- 24 -

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wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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283

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- 8 6-

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Clay minerals and their ormation sequence in

7-

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21-44

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

- 13 -

-

-pUJ蝣ォ

+J

[fl

drロ

rdJJ

OiiOgt

GE

班MU

0h

UrlA_irl

Cn5hCrl

sE

y)Bltgt

gt

gtd iH 0)U L1

3Iw +J0 U

O)C M-f0 VH U

ta uH Ch n3lU E∽ 11H JC

C】 ∽

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

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V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

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4)

sub

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to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

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significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

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Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

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Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

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alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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Miura K(1967)On the granitic rocks and their collapse

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- 8 6-

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Clay minerals and their ormation sequence in

7-

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21-44

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124

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 5 Distribution of clay veins (mica clay mineral

and kaolin mi去eral) in th占K皿Ogi granite mass

in Kanagi district Shimane Prefecture

- 14 -

+

deg

01日

3P

U

VLH

QlhI

Ua

td21

E」=班

一ヽ

_LJU

rlh_UmJ

Tロ

- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

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w

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propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

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蝣P lta

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Ll ∽V

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14-1 O

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U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

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4)

sub

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①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

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prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

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Hashikawa K and Miyahara K(1974)Fracture of the

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47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

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Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

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district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

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Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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403-416

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

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Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

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Tazaki K(1977) Formation of clay minerals from

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Tazaki K(1978) Micromorphology of halloysite produced by

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microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

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Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

+

deg

01日

3P

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td21

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- 15 -

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

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d

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propl

伝Eh

5

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U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

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Ⅵ sum

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0 V

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14-1 O

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当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

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①n cC lttiLd E

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0 ヰJ

ft OltD -H蝣o u

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gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

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hJコm +j=H

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LH

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覗 r-iamp ltu

n3

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h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

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prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Hashikawa K (1978a)On an Anlstotropic effect to the Pr

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48-58

- 81 -

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Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

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- 82 -

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Japan on field trips of the sixth and seventh clay

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found in an exploration Bore-hole(NoSA-I) Satsunan

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Kitagawa R and Kakitani S(1977) Alteration of

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1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

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Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

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359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

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Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

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Sumi K(1966) Hydrothermal rock alteration of the

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Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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Takashima I1972)Hydrothermal rock alteration in

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Tazaki K(1977) Formation of clay minerals from

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Tazaki K(1978) Micromorphology of halloysite produced by

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9-

Chem Vo15prime 65-81

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Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

kaolin mineral and the other is mica clay mineral

(sericite) All of these clay deposits were formed by

hydrothermal conditions (Minato and Takanoprime 1952 Iwaoprime

1953 Matsumotoprime 1965 Minatoprime 1969 Kitagawa and Kakitani

1979b Kitagawa et alprime 1982 Kitagawa and Kameoka in

press)

Sericite deposit

There occur sericite deposits which have been worked by

underground mining in the Mitoya and Mizuho districts

Shimane Prefecture As shown in Fig 8 many small

sericite deposits are concentrated in an _area of the Mitoya

district (about 4 x 8km) These deposits occur as

lenticular mass of several meters in width and less than

lOOm in length and as fissure-filling within the Palaeogene

granitic rocks These deposits are arranged along certain

directions which are similar to those of clay veins (mainly

types2 and 5) developed in the districtprime as are seen in

Fig 8

The deposits in the Mizuho district on the other hand

occur as fissure fillings of nearly perpendicular fissures

of about 1 to 2m width (Fig 9) Theorientationofclay

veins developed土n this district are aimost s土m土Iar to those

of clay deposits

There are two halloys土te deposits which are sharply

bordered from the host rocks working by open pit mining in

the Yokota districtJ Shimane Prefecture (Yanomaki or Komaki

halloysite deposit) The two ore deposits are about 60m x

30m and loom x 40m lenticular formprime respectively Both

- 16 -

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

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0

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0」

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rロC

d

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propl

伝Eh

5

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g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

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d コJJ

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oi in

0 V

ロ- tocu a

TロQl

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14-1 O

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己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

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∽ 声C

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agt

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①n cC lttiLd E

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0 ヰJ

ft OltD -H蝣o u

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-r1 73

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gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

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LH

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覗 r-iamp ltu

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h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

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Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Keller WD(1976a)Scanningノelectron micrOgraphs of

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- 82 -

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Y(1981)Topographic examination and genesis of clay

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format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

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Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

deposits occur as replacement products of fractured felcitic

rocks in granitic rocks The ores consist mainly of

halloysite and kaoUnite associated with sericite and

smectite Many clay veins (Type2) of 1-50mm width are

found within the both ore deposits (plate 2-A) Anumber

of clay veins of types 2 and 5 occur in the surrounding

granitic rocks of the deposits

工n Khodachi distrlctprime Hiroshima PrefectureJ the

Khodach土kaolin deposit with lenticular form occurs in

biotite granite The deposit occurs as replacement

products of thegraniticrod The ore body is about 250m in

length and lOOm in width extending toward northeast The

ore consists mainly of kaolin土te and halloyslte

The mode of occurrence of these clay deposits are

very similar to that of clay veins eg Types 2 and 5

veins The only difference between them is the scale

- 17 -

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

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to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

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Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

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Sumi K(1968) Hydrothermal rock alteration of the

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Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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Suzuoki T and Epstein S(1976) Hydrogen isotope

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Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

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Tazaki K(1977) Formation of clay minerals from

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Tazaki K(1978) Micromorphology of halloysite produced by

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Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

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Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Kohdachi kaolin depKohdachi district

Fig 7 Hydrothermal clay deposits in granitic rocks in

Hiroshima and Shimane prefectures

- 18 -

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

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4)

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to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

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LH

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覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

- 19 -

LH0

V増H

h

-LJの

tH

0

C

0」

+J

d蝣H

SJ

tTlgt

rロC

d

G

0iH

JJ

d

JコH

w

ltn蝣^

K

propl

伝Eh

5

H  

V∽ h

g コ

H -IP

U Ugt 47

叫h qJlta u

fuo

qJrロ CG dIB E

lin eV CQ

Jrロ ヽ0 JJJコ U

lV hh ~O Ⅵ

-HV rUJJH ITJU hH 0

~ JJ

V

Ⅵ sum

V

U h

d コJJ

-U U蝣rH 0)

oi in

0 V

ロ- tocu a

TロQl

V C

蝣P lta

 isinU

G

Ll ∽V

w  サ

~ 

14-1 O

O -H

EE0) JJ

U Ⅵ

己 HltD T3

当BU コO N

0 sum

tHO 

rdQJ hIロ rtjO 5= H

c

伝h

III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

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Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

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rd

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

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lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

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蝣4-t1y

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5

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isin 空 ∽ i l 喜一 「

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i

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打 S

=o

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巨≒

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_ 80 -

l=a

こくc

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く1

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Eq

equiv

=蝣

13

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もカ

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a

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0h

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日1lJh

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III FRACTURES DEVELOPED IN GRANITIC ROCKS

Common developments of the clay veins 土n the gran土t土c

rocks may suggest that these fractures were formed in

relation to the stress fields during the geological age as

well as the cooling process of the granitic rocks In order

to confirm such poss土b土1土tiesl the orientation of the

fractures (strike and dip) found in the granitic rocks and

in and around the clay deposits were examined In

addition to these fractures m土crocracks observed 土n the

constituent minerals of the host granitic rocks under the

microscope will be also examined from the same view points

A CLAY VEINS

Orientat土on of the fractures (Clay veins) show in

general certain preferred dlrections 土f the area 土s limited

Based on the preliminary measurements of the strikes of the

clay veins the whole district of the granitic rocks are

divided into 10 districts and the preferred orientations ofF

the fractures of each district are shown in Fig 10 and the

results are summarized in Table 1 As is shown in the

figure and the table each district is characterized by two

Or three preferred orientations of the fractures

Concerning the significance of these preferred orientations

will be discussed later

B CLAY DEPOSITS

The relation between the distribution pattern of the

clay deposits and preferred direction of the fractures were

examined concerning several districts First clay

- 20 -

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

てこ=UI

【=OJ

∽ 声C

c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

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重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

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aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

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e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

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I I

i i

I I

I

I

I

I

l

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rdl

E3i

l

E

I

I

I

l

1

1

j

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Bg

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mrJn3W

Q)

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E

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己 U)

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gt H

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

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a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

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1 蝣蝣蝣 -ff= ー=

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_ 80 -

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く1

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Eq

equiv

=蝣

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a

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infinrY7

日1lJh

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- 82 -

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- 8 3-

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Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

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1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

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来旨+剥牽(19糾う

Fig 10 Histgram of strike of -clay veins distributed

in Hiroshima and Shimane prefectures

y

Dlstrict Type

Kure-Higashihiroshima

S trikeDip

N0--20-E E-W N40--70-E     70--90

Ohno

Hiroshima

Kamo

Kohdachi

1 5

2

〕 4

NO-30-W N40-70巳

N0--10E N60--80-E

60deg190deg

60--90-

N60deg190w

N50-90E N40-80degW

N50--90

N20--60degE

N40--80degW

70--90-

70deg-90deg

70deg-90deg

70deg-90-

Mxyoshi        2 3 5  N-S N20--30-EJ N50--60-E   70-90

Ml zuho

Kanagi

Yokota

N40--60-W E-W

N40-7DEprime N30-70-W

E-W

60deg-90=

60deg-90-

50deg-90-

2 4prime    N0--20-巳prime N50--80-W       70二90

2 5    N30deg-60degW NO-20E N80--90E 60--90

Hi toya2 5    N10deg-20-EI N50--60      70--90

Table 1 strike and dip of clay veins in the respecti寸ed土str土cts

- 21 -

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

yen蝣蝣蝣蝣--

iIlyen

lgtyenrATVry^i蝣蝣蝣1

- 24 -

【=U

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c

agt

gt

^

O

U

+

l1

0

t

4)

sub

∽ 志gt

gt8

cup

t叫0巳

cent蝣O

sube

a

to

gtヽ

B

U

①n cC lttiLd E

Btn amp4-gt wKUl  ヽ

0 ヰJ

ft OltD -H蝣o u

+JltD M蝣4-gt -H

-r1 73

U)

gti ITO JJgtH Or」 it

rd 0JS 5h

prime GH -H

膏UB XO U出 ヽー Lh

J UM -Hra vE 40 日C aA Hgt ロ1

a)ロ1Jコ C-P -HI rロ己 G

蝣H コO

U) hC hH 3U ∽gt

Ql

hJコm +j=H

U 已n

LH

O ∽G

覗 r-iamp ltu

n3

L4 h ロiMii 凹O H OV O ltD

h tHcd lta ltu-P sコ h∽ U P」

Bihr1

deg

DlKh

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

E コ`04

Q)

G 

EJ O~

rr)

r1

めB

frj

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

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1

3

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primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

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酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

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来旨+剥牽(19糾う

deposits found in the Mitoya district develop along the two

distinct directions ieint N50 - 60 W and N10- - 200E as is

seen in Fig 8 It should be noted in the figure that the

two directions come土de well with the dominant d土rect五〇ns of

the fractures (clay veins) In the Iwaya deposit (Mizuho

district) the two preferred directions are also recognized

ieprime One is NIO- - 70-w and the otheris N50- - 70-E (Fig

9) As is seen in Fig ll the two deposits of the

Yanomaki(Komaki) mine located 土n the Yokota d土str土ct are

extended in the two d土rectionsJ N20-E and N30-W Clay veins

found perpn both ore deposits and the dlstr土ct are developed in

three directions NO0- 20-E N30-- 60-w and N80- - 90-E

Clay veins developed in the district are also aligned on the

three directions (Fig 12) Kaolin deposit in the Khodachi

district is elongated slightly in the direction of N500E

The orientation of the fractures in the ore body is rather

concentrated ln the same d土rect土on Aimost all thef

fractures described above are nearly vertical and the

preferred orlentat土on of the veins ls aimost similar to

those of clay deposits ln the respective direction

C MICROCRACKS

MicrOSCOpic-micrOcracks developed in the constituent

minerals of the host granitic rocks (mainly in quartz) were

measured on the orientated thin sections Of parallel and

perpendicular to the ground surface using an universal stage

attached to the microscope The microscopic-micrOcracks4

are illustrated in Fig 13 and some photographs of the

- 22 -

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

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i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

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Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

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0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

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柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

y

Deposit II

strongly altered rock

Eexist BioIidaggere granitic rock

Fig ll yanomaki (Komaki) halloysite deposits in

Yokota district Shimane prefecture

- 23 -

Vlt]iiiii|iini^IJ(蝣iiiiigt|ini|flVIJ(yeniiiii|miii^BV

|M|1蝣i蝣niiiiwii蝣蝣gt蝣-蝣^^^

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lgtyenrATVry^i蝣蝣蝣1

- 24 -

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- 25 -

q)

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日 dI」

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rロ Eha) ∽

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聾滋票

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rサ

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prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

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1sup

ajnu

- 33 -

tH

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ち B+J

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gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

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i^amp3

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50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

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くqLl

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- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

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Bi喜l蝣51

rdl

E3i

l

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I

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I

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1

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altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

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lti宗 - _ _- J_ f gt

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isin 空 ∽ i l 喜一 「

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く1

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Eq

equiv

=蝣

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日1lJh

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i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

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1sup

ajnu

- 33 -

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L + 空

ち B+J

3-毘己

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胃jtHlJrロ

subコ

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Q)

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rJ

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fa

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QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

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O4

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50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

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LI41a

a

h

こ=LI

O

a

L-

0)

gt

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くqLl

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(u0

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- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

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軽重 S-i蝣-5Vgt V

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 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

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参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

- 25 -

q)

J)

IS

り0蝣H

EQ

蝣H

ロコ

deg

V  ヽ

a ltuO ∽U am rl0 UH 0O -HH D1

日 dI」

ltD ftC

4-gt 

=」

ygt ampa)r8g 

〇 日 TO

rロ Eha) ∽

gt T3U rH0) 0)W 4-1

q IO bi

Bu貞tdhU O Nh JJU LIH rfl

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wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

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SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

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Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

i瑠葦-- --圭云there4

I)

iKB町Ttf一室-lt-

gt-

=ヽl-しprime1r

Eサ5TS3

聾滋票

KtヽprimeJ

rサ

IF

S

prime   ヽ

- I

wgtLt妄了I there4_IvW一宮

i

A Clay veins in Yanomaki

_(Komaki) halloysite

deposperpt (deposit二)

C Vertxcal mcrocracks

in granitic rocks -

B Fracturer- pattern in granitic

rocks in Yokota district

D Lateral microcracks in

granitic rocks

Plate 2 Fractures developed in clay deposit and granitic

rocks

- 26 -

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

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e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

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I I

i i

I I

I

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I

l

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rdl

E3i

l

E

I

I

I

l

1

1

j

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Bg

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mrJn3W

Q)

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E

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己 U)

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Ql V

gt H

4J tfl

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

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a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

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1 蝣蝣蝣 -ff= ー=

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_ 80 -

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く1

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equiv

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日1lJh

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- 81 -

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Keller WD(1976a)Scanningノelectron micrOgraphs of

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- 82 -

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- 8 3-

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Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

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JGeolSociJapan Vol86 167-177

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Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

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KitagawaR Kakitani S and Minato S(1981) The

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Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

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紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

cracks are shown in plates 2-C and D Since the thin

sections were prepa工ed parallel and pe工rpend土cular to the

ground surface the orientation of microcracks could be

measured only in the horizontal and vertical planes It

has been generally accepted that the microcracks developed

on the vertical plane are caused by the unloading (Plate 2-

C) (Okamura 1965 Hashikawa and Miyahara 1974 Hashikawa

1978a b and 1985) The poles of the orientation of the

micrOcracks were measured on both planes and the results

were plotted on the equal-area stereographic nets The

measurement was performed on the samples collected from

three distr土cts 土n`H土roshima Prefecture and results of the

Kyogoyama in the Ohno district are shown in Fig 14 as a

typical example As is seen in the fperpgureprime two

concentrated directions whose dips are nearly vertical are

recognizable ie NOO - N30-w and N40- - 60-E The

results of the othlt=r two districtsJ One is Nakatsuokagawa in

Ohno district and the other is the western part of

H土roshima city two d土st土net dominant directions have been

confirmed N40 - 80-E土n the former and N- Sin thelatter

(Fig 15) As was already stated th白se directions are

almost coincide with those of clay veins developed in the

respective district (see Figs 14 and 15)

- 27 -

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Keller WD(1976a)Scanningノelectron micrOgraphs of

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- 82 -

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Kitagawa R and Kakitani S(1978b)The white clay vein

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Kitagawa R and KakitaniS(1979a) Modes of occurrence

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Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miura K(1966)On the granitic rocks and their collapse

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283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

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Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

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Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawa K and KuniedaK(1970)Geology and mineralogy

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

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Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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Takashima I1972)Hydrothermal rock alteration in

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Tazaki K(1977) Formation of clay minerals from

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Tazaki K(1978) Micromorphology of halloysite produced by

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fxg 14 Stereo diagram showing the

preferred orientation of

micrOcracks 畠nd clay veins in

granitic rocks at Kyogoyama

Ohno dist士ictprime HirOshima

Prefecture

Microcracks S Contour 4-3-2-1 石

N

Contour4-3-2-1 K

Fig 15- stereo diagram showing the

preferred orientation of

microcracks and clay veins in

granitic rocks in Hiroshima

district

- 28 -

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

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=

equiv

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O

くJ

equiv

a3isin I

1-  ン

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毒-gtサ

=

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qJFJTO

C

_ 80 -

l=a

こくc

Et

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く1

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qI+

呈43

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Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

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infinrY7

日1lJh

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Keller WD(1976a)Scanningノelectron micrOgraphs of

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- 8 3-

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Acta Vol36 1377-1393

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primeヽ

cap

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Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

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来旨+剥牽(19糾う

IV CONSTITUENT CLAY MINERAL

The constituent clay minerals of the clay veins the

alteration products of plagioclase in the- host granitic

rocks and the clay deposits will be described in this

chapter  Deta土Ied procedures o the mineral

identif土cations were already described perpn the previous

papers (Kitagawa et al 1978a b c 1979a and 1981)

A CLAY VEINS

The clay veins consist mainly of mica clay

mineral(ser土C土te) smectite interstratified mineral of mica

and smectite (micasmectite)prime kaolin minerals (kaoUnite畠nd

halloysite) associated with small amount of 土nterstrat土fied

mineral of kaolin and smectite (kaolinsmectlte) and

chlorite Quartz is commonly associated with clay minerals

and calcite andor zeo1土te (laumontiteprime Stilbite and

heulandite) are occasionally found in the clay veins Most

T

of the clay veinsノare composed of more than two kinds of

clay minerals and the main mineral assemblages are presented

in Table 2

工t is to be noted that the constituent minerals

commonly change from the lower to the upper parts in the

vertical direction of the veins Typical examples are

shownin Fig 16 In a vein at Kure City the constituent

mineral changes gradually from mica clay mineral to

土nterstrat土fied mineral (micasmect土te) from the lower t

the upper parts of the vein within only 3m 工n a vein at

Kurahashi-cho (middle in Fig 16) interstratified mineral

- 29 -

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Hashikawa K (1978a)On an Anlstotropic effect to the Pr

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Keller WD(1976a)Scanningノelectron micrOgraphs of

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- 82 -

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1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

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Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

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Y(1981)Topographic examination and genesis of clay

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EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

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alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miyahara K(1977)Study on the weathering o granite in

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Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

M a x n c O n s t i tu e n t

c la y m土n e r a l

A S S O C i a t e d c l ay m i n e r a l

q)U

JJ G己Qq) hコ Lロ1コA Uu uh O

K a o l x n m in e r a l

K a o l i n m i n e r a l S m e c t土te

S m e c t i t e

S m e c t土t e K a O lm m i n e r a l

S m e c t i t e M i c a c la y m in er a l

M i c a c l a y m i n e r a l

M x c a c l a y m i n e r al S m e c t i te

QU

P GUhLlJ3ooO

G喜

U

K a o l in m i n e r a l M i c a c l a y m i n e r a l

Sm e c tperpt e M x c a S m e c t i te

Sm e c t土t e M i c a c l a y m i n e r a l K a o l in m i n e r a l

M i c a Sm e c t i t e

池i c a S m e c t i t e M i c a c l ay m i n e r a l

M i ca S m e c t i t e S m e c t i t e

M i ca c l ay m i n e r a l K ao l in m i n e r a l

M i ca c l ay m i n e r a l Sm e c t i t e K a o l i n m i n e ra l

qJU

C C +0 Q喜t=

o ao oC U=sup0

Sm e c t土t e C h lo r i te

M i Cparti c l ay m i n e r a l C h lo r i te

M x c a S m e c t i t e K ao lx n m in e r a l

M x c a S m e c t i t e S m e c ti t e primeK a O l i n m i n e r a l

K a o lx n m i n e r a l S m ec t x t e primeM i c a c l a y m i n e r a l

Table 2 Mineralogical assemblages of clay minerals in

clay veins

1 30 -

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

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equiv=c

=O

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JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

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equiv[plusmn芦Cgt

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e

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l=

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l

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crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

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日1lJh

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- 8 3-

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1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

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ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

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来旨+剥牽(19糾う

(micasmect土te) and smectite from the lower to the upper

parts In Mirasaka-cho smectite interstratified mineral

(kaolinsmectite) and kaolin m土rieral from the lower part to

the upper parts The variation of the main constituent

clay minerals of the veins in the vertical direction has

been fully confirmed at the Nukui dam-site Kake-cho

Yamagata-gun in Hiroshima Prefecture  As is obvious in

Fl 17prime the mam constituent mineral of the each vein

changes from mica clay mineral in the relatively lower

altitude to smectite in- the higher altitude passing through

the interstratified minerals of mica and smect土te in the

middle altitude The constituent clay minerals of the

veins developed in the Kumogi granite mass Kanagi district

Shimane Prefecture vary markedly from mica clay mineral to

kao1土n土とe as is evident in F土g 18prime the former d土str土butes

mainly at the lower level while the latter at the relatively

higher level

The regional variation of the constituent minerals was

examined in the Kure-Higashihiroshima district Mica clay

m土neral 土s observed at the relatively lower level (less than

200m) while kaolin minerals at the higher level in the Kure

district (0-500m in altitude) In the Higashihiroshima

district on the other hand smectite is restricted at the

lower level of less than 300m altitude whereas kaolin

minerals distribute at all the levels

Based on the facts described above it may be concluded

that the main constituent mineral of the ve土ns varies from

- 31 -

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

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gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

mica clay mineral to interstrat土f土ed minerals of mica and

smectite smectite and kaolin minerals from the lower to the

higher altitudes in the range between 400m and 800m (Fig

19) Between the zones of smect土te and kaolin m土neralsprime

interstratified minerals of kaolin and smectite 土s

observable in some places Moreover within several meters

of a vein change of the clay mineral is recognizable As

is shown in Fig 20 the constituent clay mineral of the

veins found in the granitic rocks varies from place to

placeJ ieprime each district has its characteristic

constituent minerals as are summarized in Table 3  This is

mainly because of the difference of the level of the

respective outcrops situated

as seen in Fig 19

B CLAY DEPOSITS

I MITOYA SERICITE DEPOSITS

Concerning the clay minerals of the sericite (mxca clay

mineral) deposits of the district the author has already

reported in detail especially on the ores of the Nabeyama

and Igi deposits (Kitagawa et al 1982) That is the

ores are composed mainly of mica clay mineral(sericite) with

a small amount of kaoUnite smect土teprime chlor土te and

interstratif土ed minerals of mica and smect土te

2 IWAYA SERICITE DEPOSITS

As is seen in Fig 9 Iwaya deposit is in vein-form and

the ores are consist of mostly mica clay mineral with a

small amount of smectite

- 32 -

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

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JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

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alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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Southwest Japan Mining Geol Special issue No8 49-

65

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Clay minerals and their ormation sequence in

7-

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21-44

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

ill

4J

【L

CL

Bgt)BSB」間   L L Ws叫PJn)1

Eq 増ーl     コ

L-

V蝣

1sup

ajnu

- 33 -

tH

O

U7c

L + 空

ち B+J

3-毘己

o 2JULd

胃jtHlJrロ

subコ

cN h

Q)

rロO  gtI-   O

C4

M   gt1dhJ

〉く

D

rJ

D蝣H

fa

U7

gr4

QJgt

gt1fO h ltaO M

disin ∽0 dh hltH -H

耳rロltU TP CO (0 ltDV h4  コーI C +J0 w OU fc a)

Jコ tH∽ d V1-1日 has P a

h一出o)  10

G  isin

H ltU -H

E l」 亡ロ Ⅵ

gti M 0fd h蝣H -P -H

U rロ コ

^fE^^^^^^^^^HO^EsrrnltmroltQO111subltuCltu巴r-i-ごhellipisinUコJ==gt巴-p+Jom-riltuen--電最

JJflローEcod-ltU-H(0MQJコIJisincogt+Jh蝣H(U蝣H01Ch一mgt召equiv

りォ8最昌

-ccgtI)蝣H-H0J3gt_EMU勺CIiH塁OltBM

i^amp3

蝣3Slq

+JH-r-サ(U034

O4

1-

rヾrl

tnlサ

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

Kao K

amp

H

∵alloysite 」

名コ

二qlメ

250 -300

200-250

200gt

w He2^ こ亡yenS

r十+こ丁there4there4Iiり こhellip

Ll J

KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

h

こ=LI

O

a

L-

0)

gt

0_

dagger

くqLl

A)

gtl

AU

(u0

i

BJU

[烏iequiv

BtJl

蝣i

iA)

て〉

ち(q

amp

rQtTq)

Tahr

ゝ己

[

1

1

1

廿

題I I

l I

三言i

I

I

I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

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日1lJh

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- 8 3-

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Kitagawa R and Kakitani S TakenoS and Nishida

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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紙十Ltl聖(19fi招

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来旨+剥牽(19糾う

50              100

i~-n-~yen----yennyenS m ectite

こて占`--vニ叫ここヲ--

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amp

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∵alloysite 」

名コ

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250 -300

200-250

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KaoH m ineral

加 酵iyen-v一=prime蝣IV昌--蝣丁モprime蒙+++++++++++++++++++++++++++++++++++++++++H+++

Fig 18 Vertical variation of constituent clay minerals of clay

veins in the Kumogi granite mass in Kanagi districtShimane Prefecture

District「 Main cOnstituent clay mineral

Altitude (m)

Kure Mica clay mineral Smectite 0 - 500

Higashihiroshiraa KaOlm mineral Smectite 100-500

Ohno Kaolin mineral Smectite 0 - 600

Hiroshima Smectite Mica clay mineralー0 - 400-

Kamo Mica clay mineral Smectite 200-400

KOhdachi KaOlm minera1 15O-3SO

Miyoshi Kaolin mineral Smectite I 200-300

Mizuho Mica clay mineralンSmectite Kaolin mineral 300-550

Kanagi Mica clay mineral Kaolin mineral 150-350

Yokota Smectite Kaolin mineral 400-600

比xtoya Mica clay mineral Smectite 100-300

Table 3 Maxn constituent clay minerals in respective districts

34 -

n一L

ロ蝣

LI41a

a

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Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

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I I

i i

I I

I

I

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l

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rdl

E3i

l

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I

I

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l

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SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

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rd

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

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日1lJh

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I

I

i

- 35 -

I」

rdHUC

3

gtnJH

U

_PGU13JJEPⅥG0u  

C

MH OO

_PC U0 a)蝣H U

-P -HKm面ISU Hd d

gt oE

CTl -i)C h蝣H ltD

gt gt0fl ltUen jS

5U -Hか

d u)H CT3 -H

qJU gtEヰ」 gt1

昌書Q) U

U LH∽ 0

Tl1

日lrJh

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

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Bi喜l蝣51

rdl

E3i

l

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I

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j

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SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

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rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

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lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

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ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

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別 離 萱

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5

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isin 空 ∽ i l 喜一 「

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打 S

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巨≒

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_ 80 -

l=a

こくc

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く1

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Eq

equiv

=蝣

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日1lJh

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primeヽ

cap

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Fi

fL

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there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

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鉱物学雑誌自97只1

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鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

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酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

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ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 20 Distribution of clay寸eins and their main constituent

clay mineral in granitic rocks in I王iroshima and

Shimane Prefectures

- 36 -

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

3 KOHDACHI KAOLIN DEPOSIT

The ore of the Kohdachi kaolin deposit is composed

mainly of kao1土nite and halloysite with a small amount of

mica clay mineral Moreoverl the deposit can be divided

clearly into two zones as to the mineral assemblages one

is kaoUnite zone and the other kaolinite-halloysite zone

(Kitagawa and Kakitani 1979b)

4 YANOMAKI(KOMAKI) HALLOYSITE DEPOSIT

The Yanomaki deposit is composed of two ore bodies with

sharp boundaries to the host granitic rock The clay

minerals of the ore are composed of halloysite kao1土nite

and mica clay mineral associated with a small amount of

smectite Based on the mineral assemblage the ore body

can be divided into three zonesJ 土eint the central

halloysite zone through the halloysite-kaolinite zone and

the marginal zone of kaolinite-mica clay mineral

The constitu芭nt clay minerals of these clay deposits

are summarized in Table 4

C CLAY MINERALS DERIVED FROM PLAGIOCLASE

Among the constituent minerals of the host granitic

rocks plagioclase is easily altered to clay minerals as

well as biotlte 工n generalJ the mineral in question

alters directly to kaolin minerals (kao11n土te and

halloysite) under the weathering conditions (Nagasawa and

Kunieda 1970 Kitagawa and Kakitani 1977a Nagasawaprime 1978

Tsuzuki 1985) However plagioclase in the granitic rocks

- 37 -

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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403-416

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

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- 8 8-

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Takashima I1972)Hydrothermal rock alteration in

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Clay deposit

Mi toy a   工waya Kahdachi

sericite sericite kaolin

depos土七

Halloys土te

Kao1土nite

Smect土te

MicaSmec

Mica clay

Chlor土te

deposit deposit

+

Yanomak土

halloysite

deposit

+++ abundant ++ moderate + minor

Table 4 Constituent clay minerals of clay deposxts in

granitic rocks in Hiroshima and Shimane prefectures

- 38 -

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Y(1981)Topographic examination and genesis of clay

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The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

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MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miura K(1966)On the granitic rocks and their collapse

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Vo1ll 6-38

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- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Ohyagi N(1968) Weathering-zone structure and landslides

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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ShiraizuH(1972)女aolin mineral transformation during

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Tazaki K(1978) Micromorphology of halloysite produced by

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

of the district of the present study is often altered to

mica clay mineralprime smect土te and土nterstratified mineral

together with or without kaolin minerals Several typical

examples w土11 be described below

General tendency of the alteration of plagioclase to

clay minerals in the granitic rocks are shown in Figs 21

22 and 23 As is evident in Fig 21 in the Kumogi granite

mass Kanagi district the northwestern parts whose altitude

is relatively lower (180-250m)int mica clay mineral is

predominant whereas in the central parts relatively higher

parts (250-350m) smectite is predominant In the Yokota

districtprime sh土mane PrefectureJ plagioclase alters to mica

clay mineral smectite and kaolin minerals (Fig 22)

Furthermore as is clear in the figure kaolin minerals are

found mainly at the higher level whereas mica clay mineral

and smectite at the lower level Regional variation of the

alteration of the mineral in Hiroshima and Shimaney

Prefectures is represented in Fig 23

It may be concluded that plagioclase of the host

granitic rocks alterscommonly to mica clay mineral

smectite and kaolin minerals It is to be noted that

mica clay mineral prevails at the geographically lower

parts whereas kaolin minerals at the highe暫parts

- 39 -

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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7`

Y(1981)Topographic examination and genesis of clay

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Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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Kitagawa R and Kameoka H(1986) The mode of occurrence

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miura K(1967)On the granitic rocks and their collapse

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Miura K and Hata A(1970)The collapse related to rock

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Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 21 Clay minerals altered from plagioclase in the

Kumogi granite mass in Kanagi district shimane

Prefecture

- 40 -

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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- 82 -

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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Kitagawa R and Kameoka H(1986) The mode of occurrence

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

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Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 22 Constituent clay minerals found in plagioclase

xn yokota district shimane prefecture

- 41 -

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 23 -Clay mineral found in plagioclase in granitic rocks

distributed in Hiroshima and Shimane prefectures

- 42 -

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

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Miura K(1966)On the granitic rocks and their collapse

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283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

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0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N(1968) Weathering-zone structure and landslides

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

V MINERALOGICAL CHARACTERISTICS OF CLAY MINERALS

Concerning the clay minerals collected from various

occurrences the writer and his co-workers have reported

some mineralogical characteristics such as filling

temperature of flu土d 土nclusion in calcite hydrogen and

isotopic composition microtopographs of clay mineral

crystals morphology of halloys土teJ dehydration temperature

of constituent water and suspention pH (Kitagawa and

KakitaniJ 1977aJ 1978al bJ c 1979 1981 K土tagawa et alint

1981a b 1982 1983 1984) In Table5 the main results

are summarized with the difference of the mode of occurrence

of clay minerals  Since these characterlsties Of the

mineral are related intimately to the formation conditions

of the mineral the results will be described briefly below

A FILLING TEMPERATURE OF INCLUSION

As was described ln the previous chapter mica clayr

mineral in the sericite deposits of the Mitoya district

coexist intimately with calclte (Plate 3)  ortunatelyprime

fluid inclusions are common in the calcite crystals and the

filling temperatures of these inclusions were measured xn

order to estimate the temperature of formation of the ore

depositprime ie m土ca clay mineral itself As is shown 土n

Fig24 the filling temperatures of the Nabeyama and Igi

deposits are in the range between 220 - 270-C (average is

240-C) and 215 - 280-C (average is 241-C) respectively

B HYDROGEN AND OXYGEN ISOTOPE

- 43 -

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

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0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

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Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Clay vein

Co n s ti tuent DTA chemical

clay mineral color Polytype地suprophology size dehydration composition PH

Mica clay green   出   hexagonal 05-

mineral 慧equivn 王a e圭鮮呈d- sympink      鐙lar-

single s muscovite-

double-   phengitic

endothermic composition

peak(500--

750-C

4-9

MicaSmecgr

pae圭慧恕a-Os一霊霊mi霊慧d霊e2p皿

gr een   悪童王arpeak (500- smectite

700degC)

Smectite green

pink0 5- 星畠認圭e_s montmorillonite2ym (500-700 compositiOn

Kaolimte white hexagonal  0 5-  500-550-c

l鐙琶呈Iar- 2um

Halloysitewhitebular-rm緑lt5004-7

Clay deposit

Micaclaygreen池hexagonal05-singlesmuscovite-mineral票hellip喜n主監el酔宴d-10]jm霊霊mi霊ngit

ipsi霊npink鐙酔r一号禁呈500-)

4-9

MicaSmec- green   要地ま1 02孟つ酔ennic藍喜鑑圭孟占esmectite芸芸np粒至O

ar-2誌~曽禦amp

7-C)moc芸霊Ioniten

Kaolmite white   粗野虹2孟 500-550-C     6-7Hallysitewhite蝣tubf畠ar一緑lt5005-6

Alteration Products of plagioclase in qranitic rock

Mica clay green  2M heagonal    由

mineral 響きn 王a eを慧鑑蔓d-霊~white               `一山  700C)

phengitic

6perpc compositxon

MicaSmec green H雛r霊~ 富呂出ermic主蓋憲蔓圭昌畠epeax

Smectite green

pink

Kao linite white

brown

p悪至宝甲霊つ細圭弓昌C慧芸霊Ilonitein

寧草野圭一霊500-550C

Halloysite white

yellow

tubular 0 2-

3ym

ltso0degC

Table 5 Mineralogical characteristics of clay minerals in

granitic rocks

- 44 -

6-7

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Calcxte and quartz associated with mica clay

mineral

CCalcite QQuartzprime MMica clay mineral

Plate 3 Microphotograph of the thin section

(Nabeyama deposit in Mitooya district)

- 45 -

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

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Bi喜l蝣51

rdl

E3i

l

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I

I

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l

1

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j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

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lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

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別 離 萱

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5

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_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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打 S

=o

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巨≒

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=

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くJ

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毒-gtサ

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C

_ 80 -

l=a

こくc

Et

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く1

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Eq

equiv

=蝣

13

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0h

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日1lJh

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昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

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排常牽雑誌(1980)

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18

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iiilt日こHLlllgttこrト1-I

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daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

U

OQPN3

Oh_

  コ

equiv盲細1

- isin

β

- 46 -

lニiコ

iHd雷

-rt (DQ)己P -H

u isin0)

H gtH (C0 rlU U

QJ dJJ U-iH -i-4U 己Hd sumO H

lこココI

a

蝣H -H

むlC H0h a)

欝等呂召tH Id O

rロJ- V蝣H 1 日

ロ rO Oir-t U

tH O) 0)己 E

叫 H ra

o E ElJ

o) gti-CH d ∽コ H一U U  ヽ

d JJU 3 0ltD O -H

g1昌Bltv in

-p a -h

どこ監

exist邑B班ヨS d) wn3 JコJJh _りrl〇1  U)P 百 OU) 0 DI蝣H J-l CD

[ m -o

寸cap

aEfa

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

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qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

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tH0

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UEJJEd

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infinrY7

日1lJh

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- 82 -

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primeヽ

cap

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Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

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i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

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来旨+剥牽(19糾う

The isotopic ratios of hydrogen and oxygen in mineral

reflect the environmental conditions at the formation

(Matsuhisa et al 1980) Therefore 6D and 60 values of

mica clay mineral smectite interstratified mineraland

kaolin minerals collected from clay veins and deposits were

measured As is evident in Table 6 each mineral has its

own characteristic value regardless of their mode of

occurrence The results clearly suggest that all of the

clay minerals are formed under almost the same environmental

conditions

C MICROTOPOGRAPH OF CRYSTAL SURFACE

Growth pattern on crystal surface varies aceording to

the formation conditions Using the decoration technique

of electron microscopy (Kitagawa et al 1983) surface

micrOtOPOgraphs of as-grown surface have been examinedon

the clay minerals collected from clay veins and deposits as-

well as on the alteration products of plagioclase in the

host granitic rocks Among these minerals spiral growth

pattern is observable only on the crystal surfaces of lM and

2M mica clay minerals and kaolinite (plates 4 5 and 6)

On the crystal surfaces of lMd mica clay mineral and

smectite show no special growth pattern (see plate 4)

Morphologies of the growth spirals are roughly

classified into a) polygonal and b) circular or malformed

circular Characteristics of the observed pattern together

with the range of step separations are listed in Table 7

- 47 -

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

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i

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lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

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_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

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Eq

equiv

=蝣

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infinrY7

日1lJh

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- 82 -

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- 8 3-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

The mode of occurrence of clay veins

Clay mineral

Type 1 Type 2  Type 4  Type 5  Deposit

Kaolinite -675 -658

Smect土te -864 】

-881

-891

MicaSmectitel

-773 -762 -751

-740

Mica clay mineral -681 -676

-693

Table 6 oD values () of clay minerals

- 48 -

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

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Hashikawa K and Miyahara K(1974)Fracture of the

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47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

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Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

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Kitagawa R and OkunoT(1983) Formation mechanism of

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Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

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Kitagawa R and Kameoka H(1986) The mode of occurrence

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

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- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

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MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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- 8 6-

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Clay minerals and their ormation sequence in

7-

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

(1M Nabeyama deposit)    growth(lMd Miyoshi Type 2)

Plate 4 Siユrface microtopographs of mica clay minerals

The scale-line represents lyenJm

- 49 -

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Malformed circular spiral

(Mitoya Type 2 vein)

Circular spiral

(工waya deposit)

Plate 5 Surface microtopographs of mica clay minerals

The scale-line represents ll皿

- 50 -

Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

hDagger曇Dagger蝣v一L _PI I

- ^gtzi7 ォk  こ

i -f -Ll I I tt I

-I I I I Ill-

-J一一 e l一           prime

サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

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Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

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rd

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

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1 蝣蝣蝣 -ff= ー=

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isin 空 ∽ i l 喜一 「

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く1

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Eq

equiv

=蝣

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日1lJh

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cap

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Fi

fL

1上

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射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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Polygonal spiral on kaolinite crystal

surface xn Khoachi kaolin deposit

Plate 6 Surface microtopographs of kaolimte

The scale-line represents lpm

- 51 -

ぎ筆V i三と

軽重 S-i蝣-5Vgt V

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サ蝣蝣

-    -

prime eⅠ ォ蝣

Yamp-蝣蝣gt

14 deg

38KBH

一   三i

 こ       i蝣-CrvXdeg primedeg日日

ユニ王yen--三IL討幕達濫

^ヽt ヽ l

貰iVォi

v-T

Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

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i_廟hellipthere4there4-r蝣---i---「くつ一十i

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hDagger曇Dagger蝣v一L _PI I

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Circular spiral on mica clay mineral showing coalescence

of several crystals (Type 2)

Plate 7 Mica clay mineral showing coalescence of crystals

The scale-line represents lym

- 52 -

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

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oo o o o OSo

o o o

0 o   

           

  

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   0     

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q

243

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享 三言_ILJH rl1

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ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

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ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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- 82 -

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1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

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Kitagawa R and KakitaniS(1979a) Modes of occurrence

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Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

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Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

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282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

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Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

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GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

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283

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

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Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

As is shown in the tableprime C土rcular or malformed circular

patterns are found on the clay minerals from the Type 2 vein

whereas polygonal patterns are on those from the Types 1

and 5 vexnsprime kao1土n and seric土te deposits as well as those

of alteration products of plagioclase It is to be noted

that the step separation of the polygonal pattern is two

to ten times wider than that of circular spirals

Moreover paired step or interlacing pattern is commonly

observed on the surface of mica clay mineral especially on

2M polytype (Plates 4 and 5) Appearance of coalescence

pattern 土s characteristic in the circular spirals which is

mainly found in the minerals from fissure-filling vein (Type

2 (Plate 7)

D MORPHOLOGY OF HALLOYSITE

Among kaolin mineralsprime halloyslte is characteristic in

its crystal morphology of tubular form Moreover theT-

formation of the mineral both under the weathering condition

and by the hydrothermal activity have been well established

by many investigators up to the present (eg Parham 1969

Nagasawa and Kunieda 1970 Shimizu 1972 and 1978 Nagasawa

and Miyazaki 1975 Kelユer 1976a b c and 1977 a b

Kitagawa and Ka~kitani 1977a Tazaki 1977 and 1978

Nagasawa 1978) Therefore it is worthwhile to examine

the variation of the tubular form of the mineral between the

two origmsprime ie weathering and hydrothermal For the

purpose of the comparative studies halloysite of reliably

weathering and hydrothermal origins were collected As for

- 53 -

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

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O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

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tH0

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UEJJEd

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infinrY7

日1lJh

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抽汀ーSfI上酎ro油軸aUn軸hf1977う

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放物牽雑誌自977)

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広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

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18

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iiilt日こHLlllgttこrト1-I

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来旨+剥牽(19糾う

specimen(clayvein)Polygonalspecimen(clayvein)PolygonalCircularlg|esifgi9gCoalescencespacingof

Micaclaymineralspiralspiralspitedlayers(A)

Type1

Takaya(Kamodistrict)0200-1000

Type 2

Ktmo91-3 (Kanag dis)

Kumogi - 4

Mitoys-1

か止toya- 2

Mitoya- 3

Mitoya- 4

Mitoya-5

ぬtoya-6

0

0

o

0

O

O

C)

Type 5

Kumogi- 1

Kumogi- 2

Kure

(Kanagi dis)

Daiwa (Karao district)  

Specimen (Clay deposit)

Iwaya sricita dep

Nabeyama (Mitoya) dep

Nabeyama (朗itoya) dep -

Igi (Mitoya) dep

Yanomaki (Komaki) dep

-r-

Specimen (Clay deposit)Kaolinite

KoI嘘achi kaolin dep

O

C)

0

0

C)

100-500

100-500

50-500

100-500

100-500

50-500

50-500

0      100-500

100-5000

loo-500

300-1000

100-500

0

0

o

O

CI 100-500

100-5000

100-5000

100-500

100-1000

100-1000

Table 7 Summary of surface microtopograph of mica clay

mineral and kaoUnite

- 54 -

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

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日1lJh

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参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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15

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iiilt日こHLlllgttこrト1-I

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ironitie両31川ndllu川S

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紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

the weathering origin halloysite from typical weathering

residual deposits such as Hongkong kaolin were used in

addition to the specimens obtained from the plagioclase in

the granitic rocks in sedimentsJ halloysite from khodachl

(Matsumoto 1965 Kitagawa and Kakitani 1979b) Komaki

(Matsumoto 1965 Kitagawa and Kameoka in press) and

Shokozan deposits (Kinozaki 1963 Matsumoto 1968) were

used as the hydrothermal origin

To describe the morphological characteristics the

length and width of halloysite tubes collected from clay

deposits clay veins and altered products from plagioclase

were measured and the results are shown in Fig24 As is

evident in the figure diameters of halloysite tube of the

hydrothermal origin are concentrated in certain area

especially in the range of 005-006 microns whereas those

of weathering origin show none of such concentration Tube

length on the o上her hand indicates no information

concerning their origin To confirm the characteristic

distribution of the values of the tube diameter the

relation between the mean value and the standard deviation

for the diameter of respective specimens are plotted in Fig

26 The results shown in Figs 25 and 26 clearly suggest

that the tube diameters of halloys土te of the hydrothermal

origin are restricted within the dotted line shown in Fig

26

As an appl土catlon of the established criterion

described above the mean values and the standard deviations

- 55 -

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

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申 _o a larr ht

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equivL

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- 56 -

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享 三言_ILJH rl1

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ltarsロ貞HgtiT3」

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degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

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くつ

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- 58 -

TTくつ

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り ltu uid -p a)

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毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

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g電竃巴むh guvJ= Q C) r-tEh H-4 in m

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gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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SheppardSM-F Nielsen RL and Taylor HP(1969)

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- 8 8-

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

0

0 0

 

C

0

0 0    o 00 0   0 0   0  0

0 0

-0    -      0  0  0 I

0 -00 0   0  0        0o

Oo OftoO

oo o o o OSo

o o o

0 o   

           

  

  悔 `

          J

   0     

o          

0

0

q

243

rB43

3=

月    lBB

1-4ロllq

prime4111

amp蝣

`巴=

O 云  O2coト

申 _o a larr ht

ト畠三

a

equivL

ETAlE=

Ol4

ロgtサ

3=

- 56 -

E

El

I

-

0

声1I-

ニー4

lfgt

lsup

l=I

isin

1_

tL)

E-

Elt

LH

O Hd

h E01 -l

一り 4)

昌男ia o-rl UTJ T3

-a      gt

5  -5-lt0 gti C

t    」 00  」 -Hl_   JJ rロJJc一    日1 V d

享 三言_ILJH rl1

「コ    C L13

V CJ

遥 掌雪ぎ∽   JJ 」u i-1

言 j顎4J J

C -H 4JO a lta蝣H gti ltD

蝣U O 5

HJ r-l

H rJ rロ

jj=I

ul

bB

ロ1If

h

hOgt

ltHAE

CrロOolta-hEu還i岩窟

一H402gt当

どT3JrOJt3tncnS革主-

equiv≒T3

1霊

ha)志蝣OIB3C^HEdコrOJ〕GaltaコdrロコJJ苫召wo召

∽hGHV33exist

isin昌巳

ltarsロ貞HgtiT3」

LON

degDHfa

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

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己 U)

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Ql V

gt H

4J tfl

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rd

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JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

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1 蝣蝣蝣 -ff= ー=

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イ 一

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i

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=

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くJ

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C

_ 80 -

l=a

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く1

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Eq

equiv

=蝣

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a

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0h

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infinrY7

日1lJh

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primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

ofthediameterofhalloysitecrystalscollectedfrom

palgioclaseinthehostgraniticrockswereplottedinFig

27AsisclearinFig27halloysitealteredfrom

plagioclaseshownoremarkableconcentrationsuggestingthat

thehalloysiteareformedbothbyweatheringand

hydrothermalactivityFig28showsthesamevaluesof

halloys土tecrystalscollectedonlyfromtheclayveinsof

varioustypesdevelopedinthegraniticrocksAsisclear

inthefigurethevaluesaremarkedlyconcentratedinthe

restrictedareasuggestingthehydrothermaloriginofthe

minerals

Furthermorethedistributionofthetube-widthofthe

halloysitecrystalscanbedividedintothree乍ypes(TypesA

BandC)bymoredetailedobservationasisshowninFig

29ieTypeAwiththesmallestvaluesconcentratedin

therangeoflessthan001micronsTypeBwithrelatively

widerangeofthevaluesandTypeCwithwiderangeofthe

Yvaluesbutcharacterizedbythemaximumfrequencyinthe

rangelessthan001micronsHalloysitecrystalsofType

AareascribedtothehydrothermaloriginTypeBto

weatheringandTypeCtothemixturesofthetwoorigins

Typicaldistributionsofthetubewidthandtransmission

electronmicrOPhotographsofthethreelttypesareshownin

Fig29andinplates8and9respectively

Usingthismethodhalloysitecrystalsobtainedfrom

plagioclaseofthehostgraniticrocksoftheKariagi

district(Kumogigranitemass)andMizuhodistrictswere

examinedTheresultsclearlyindicatedthathalloysite

- 57 -

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

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一qqJ

31

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 prime

   

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lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

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り ltu uid -p a)

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盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

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示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Y(1981)Topographic examination and genesis of clay

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granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

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Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

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Sumi K(1968) Hydrothermal rock alteration of the

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Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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Suzuoki T and Epstein S(1976) Hydrogen isotope

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Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

く13

subsup

ETq

isin

顎_

こprimeコ

巨iョ

くつ

c

qI

JZ

一qqJ

31

` 7~

     

tV

 

  

 prime

   

-

E一tl

13

lつLl13T9-

jajaumip jo 叫EA UE3m

- 58 -

TTくつ

l=l

O4

くつ

さ可

C DIO F1H   -rH

り ltu uid -p a)

H蝣宗蕾む   ォ gti ォ

芯 0 O lt1)

毒 官exist芸~ロ  tf J3 C

盲 航二こ  4J H qO M ロ 巳

q hJM3 邑 純

冨 忘5サー   巴5 嵩

胃 nS隻竃 冒23忘押3

g電竃巴むh guvJ= Q C) r-tEh H-4 in m

sEiF

示IPl

h

c c0

H

P Qi

ia り-H -Hgt Ⅵ

」   ltD gtu   -o o

r-I

HヨC h

臣 1堅=  ∽ コQ    Q

GI 雲B

gt 吋叫~ロ   Q) 0

コ`「コ   r-l S-l

FE 言4)ltd a

莞 喜郎N

ltu u aJC O r-4

E-i o-i o

(ココ

rq

示dh

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

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日1lJh

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- 8 3-

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JGeolSociJapan Vol86 167-177

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 29 Three typical histgram of diameter

of tubular halloysite

- 59 -

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

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cO

11つォtf

X

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=コ

0=

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1

Ilつ

times

~  O

dJ ミ

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O=

也)u

GVh

EEロUU

0

LH

O_

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isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

月 一一

Type A Kumogi gran土te mass

(Kanagi district)

警Type Cprime Kumogi granite mass

(Kanagi district)

Type A Yanomaki (Komaki)

halloysite deposit

Type B Kamo district

こて-gt

-も

箪亡盛諒-  

Type Cprime Kamo district

Plate 8 Morphology of tubular halloysite in granitic rocks t云ken -

under transmission electron mxcroscope (TEM)

The scale-line represents lpm

- 60 -

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

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UEJJEd

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infinrY7

日1lJh

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Craig H(1961)Isotopic variations in meteoric water

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Hashikawa K (1978a)On an Anlstotropic effect to the Pr

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Hashikawaprime K(1985)Studies on the planar fracturing

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Hayashi M(1973)Hydrothermal alteration in the Ohtake

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conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

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district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

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Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

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found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

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0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

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Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

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plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

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microtopography of metamorphic white micas phys

9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Type B Halloysxte found in plagioclase

(Weathering in origin)

plate 9 Morphology and texture of tubular halloysite七aken

under scanning electron micrdscope (SEM)

The scale-line represents 2ym

- 61 -

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

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l=

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crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

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日1lJh

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- 8 3-

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Kitagawa R and Kakitani S TakenoS and Nishida

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KitagawaR Kakitani S and Minato S(1981) The

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

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ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

crystals of Type A which is ascribed to the hydrothermal

origin are found in the remarkably decomposed regions ie(

in the middle and northwestparts of the Kumogi granite mass

(Fig 30) and in the middle part of the Mizuho district

(Fig 31)

- 62 -

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

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JJUdhり覗rerロ

0Jコ3N

Eequiv

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a

54o

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ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

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- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

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Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Fig 30 Distribution of three types of halloysite

in the Kumogi granite mass in Kanagi district

Shxmane Prefecture

- 63 -

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

U】

JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

OiJ

0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

REFERENCES

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emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

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significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

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Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

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mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

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Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

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JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

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283

Miura K(1967)On the granitic rocks and their collapse

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

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0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

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Ohyagi N(1968) Weathering-zone structure and landslides

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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ShiraizuH(1972)女aolin mineral transformation during

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Shimizu H(1978) Micromorphology of halloysite produced

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SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

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Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

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Takashima I1972)Hydrothermal rock alteration in

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9-

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

+

l

d)lw

3

JJ

a)

LH

d)

h

aI

tgt

C

d伝

l」

蝣a

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JJUdhり覗rerロ

0Jコ3N

Eequiv

JJ

a

54o

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0 U蝣H -H

ヰJ ヰJ

3 -HQ GH q

h h蝣P en

班蝣H G

Q -H

rJ

rr7

l

aEltl

- 64 -

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

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1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

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isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

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rtJ

equiv=c

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Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

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- 76 -

吾Ei

ao3Jg

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acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

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l=

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H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

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1 蝣蝣蝣 -ff= ー=

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i

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ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

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5

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isin 空 ∽ i l 喜一 「

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i

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打 S

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infinrY7

日1lJh

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- 8 3-

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Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

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JGeolSociJapan Vol86 167-177

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Kitagawa R and Kakitani S TakenoS and Nishida

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KitagawaR Kakitani S and Minato S(1981) The

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参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

VI D工scuss工ON

The main purpose of this paper is to establish the

sigmficance Of the hydrothermA1 activities on the

decomposition of the granitic rocks In the preceding

chaptersJ 土mportant characteristic features observed in the

decomposed granitic rocks have been described particularly

on the clay veins and- clay deposits developed commonly in

the granitic rocks distributed widely in Hiroshima and

Shlmane Prefectures Based on the results obtainedprime the

complicated mechan土sms of the decompos土とion process of the

granitic rocks will be discussed from the two important view

points fracturing system related to the paleo-stress fields

and clay mineralogy in relation to the formation conditions

A FORMATION MECHANISM AND AGE OF FRACTURES

F土rst of allJ it may reasonably be assumed that the

clay veins developed in the granitic rocks represent the

fractures which have been formed after the solidification

stage subsequent to the raagmatic activity Furthermore a

systematic fracturning pattern within granitic rocks has

been controlied by the stress fields of the respect土ve

district

The fracture patterns of clay veins developed in the

granitic rocks in Hiroshima and Shimane prefectures will be

analysed

As a typical example of the analysis of the stress

fieldprime the Kamo d土strict土s chosen 工n this districtprime clay

veins of Types 1 2 4 and 5 are commonly developed and the

- 65 -

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

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^^Bjta昌

=コ

0=

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1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

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ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

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別 離 萱

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5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

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int-4

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=

equiv

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くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

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qJFJTO

C

_ 80 -

l=a

こくc

Et

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く1

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qI+

呈43

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Eq

equiv

=蝣

13

s

もカ

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a

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増o

0h

UrlJJKCd空ロ「

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infinrY7

日1lJh

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号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

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来旨+剥牽(19糾う

results of the orientation (strike and dip) analyses are

shown inFig 32 as rose diagrams As shown-in the figure

the strikes of the veins of Types 1 and 5 are concentrated

inthedirectionofN60-- 80 W whとreas thoseof Type 2 are

concentrated 土n two d土rectionsJ N40 - 70-w and N60- - 80-E

It is to be noted that the direction of the former

exactly corresponds to the b土sectional direction of the

latter two Moreover the Type 2 veins have characteristic

features of the conjugated fractures and accompanying

slickensides occasionally These facts strongly suggest

that the Type 2 veins are the shear fractures formed under

the regional stress field of the district Consequently

veins of Types 1 and 5 are ascribed to the tention

fractures The greatest principal stress axis inferred

from the analytical data is N80 - 90-w in the Kamo

district In such manner the stress fields of the

respective districts have been analysed (Fig 10) and the

results obtained are schematically summarized in Fig 33

As is clear in the figure at least four greatest principal

stress axes are distinguishable in the district of Hiroshima

and Shimane Prefectures

Clay veins developed in and around the clay deposits

are also ascribed to the shear and tentperpon fracturesprime since

their orientations coincide with those of clay veins in the

respective granitic rocks

Preferred ori占ntations of the microcracks developed in

the constituent minerals of the host granitic rocks have

- 66 -

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

ササ`q

O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

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0hCLI

UEJJEd

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infinrY7

日1lJh

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- 82 -

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Y(1981)Topographic examination and genesis of clay

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65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

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Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

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Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

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Sumi K(1968) Hydrothermal rock alteration of the

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Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

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Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

占守

tD

EiCI

X

5^V^

V  _∽ a m

gt Wト Tl

O==0=

≧胃

cO

11つォtf

X

Lf)呈q〉

^^Bjta昌

=コ

0=

≧尺

1

Ilつ

times

~  O

dJ ミ

のき諒ロh

O=

也)u

GVh

EEロUU

0

LH

O_

a)rO0

isin

q)E_U

GO

rtj也)tn~a

rOVH

LHパ  ーtn ltu∽ h

d コ1-1 -P

U UQ)

∽ LHC Q)h u

ltU ftgt

rd

h 巳a -hr-l JコU (fl

OLH h

O dK

むht rH IJ

h u4-1 -rH∽ h

ヰ」ltw wO

rO

E

邑sectP 出U】

EKSB -H

Edy

r1

deg

Dda

- 67 -

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

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O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

申cl34J明

qJFJTO

C

_ 80 -

l=a

こくc

Et

qJJJ

く1

芸O白

qI+

呈43

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Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

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infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

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LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

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0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

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Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

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Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

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403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

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124

Savin SM and Epstein S(1970)The oxygen and hydrogen

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Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

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Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

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ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

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Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

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Surv Japan 1-42

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Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

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plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

N

Isi

w 咋甲nagi

Shimane Pref

(32-34Magr) f一-----

ノ-l i I--一一gt^l

w^mらira-ら

yenォV50M

yenyengtitoy嵩

Mitoya

-れ -Å

Ⅵ) kota

(46-52 Magr)

^Yanmaki dep

Miyoshi

+

Mizuho f34-40Ma gr)

ヽ-ヽ

Iwa叫Iep-

Kohdachi  MirasakaKohdachidep

(72Magr)

HiroshimaPrefprimeprimeprimeprime

Fig 33 Schematic representation of tectonic stress

trajectories together with the geological ages

- 68 -

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

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- 8 3-

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KitagawaR Kakitani S and Minato S(1981) The

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Clay minerals and their ormation sequence in

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21-44

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

been analysed using the same analytical method For

example tw里整i聖与 preferr甲d directions f the

microcracks were recognized in the Kyogoyama Ohno district

and Hiroshima district (see Figs 14 and 15) The

greatest principal axis derived from the two directions is

approximately NE-SW based on the assumption that the

raicrocracks are the conjugated fractures The direction

thus obtained well coincides with that of clay ve土nsJ

suggesting that the microcracks and the clay veins have been

formed under the same stress field of the district

Concerning the formation ages of thes声 fractures K-Ar

ages of mica clay minerals obtained from clay veins and clay

deposits will be useful The available data from the

previously published literatures are summarized in Fig 33

The data are taken from Ishihara et al (1980) and Kitagawa

and Kakitani (1981) Furthermore the K-Ar ages of the

host granitic rocks are also available That is the Sanyo

gran土tic complex 土n Hlrosh土ma Prefecture are dated at 70-

92 Ma (Kawano and Ueda 1966 Shibata and Ishihara 1974a

and b) and Sanin granitic complexthere4 in Shimane prefecture

at 25-63Ma (Kawano and Ueda -1966 Shibata and Ishihara

1974 Ishihara 1974 and 1978) These data are also

plotted in Fig 34 As is evidentin the figure the ages

of clay minerals and those of granitic rocks are identical

with each other within the analytical error The

concordance in the ages indicates that the clay minerals in

the clay veins and clay deposits have been formed by亡he

post magmatic activities of the host granitic rocks of the

- 69

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

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rtJ

equiv=c

=O

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JFll

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IIIIII

- 76 -

吾Ei

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equiv[plusmn芦Cgt

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l=

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crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

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日1lJh

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- 8 3-

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参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

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iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

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紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

100     80      60      40      20

08 0      0       0 0300  -   0

00  CD CO c C 〇〕 O

0 O 0

x lOSMa

Sanl in granitic catolexs

Sanyo granitic ccnplexs

Sencite de〇〇sit

in Sanin granitic cコmlexes

ぬe乏clay血a in clay vex三唱-Omd in Sanyo grar止gtic Ccrmle^臼

Fig 34 K-Ar ages of mica clay mineral and granitic rocksin Hiroshima and Shimane prefectures

Locality Age of granite Age of mica clay mineral Greatest principalstress axis

Kanagi district  32 - 34 Ma NW- SE

Mizuho district    34 - 40               -       E - W

Mitoya district     51          50 Ma NW - SE

Yokota district   46 - 62         64           NW - SE

Miyoshi district    72                      NE - SW

Kure district                  68           NE - SW

Kamo district    70 - 79        791 86        ESE - WNW

Table 8 Relation between tectonic stress and its ages

- 70 -

respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

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別 離 萱

E W- E

5

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_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

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=

equiv

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くJ

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a3isin I

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=

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C

_ 80 -

l=a

こくc

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く1

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qI+

呈43

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Eq

equiv

=蝣

13

s

もカ

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a

=e

増o

0h

UrlJJKCd空ロ「

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O

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infinrY7

日1lJh

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1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

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respective districts In Table 8 the formation ages of

the granitic rocks and clay minerals together with the

greatest principal axis of the respective ages are present

Thus it is furthermore reasonably concluded that the

greatest principal stress axis has been changed from ESE-WNW

to NE-SW and finally NW-SE during the geological ages from

Cretaceous to palaeogene periods

B FORMATION CONDITION OF CLAY MINERALS

工n this chapterprime the physico-chemical condition of the

formation stage of clay minerals will be discussed based on

the available data such as temperature estimation derived

from isotopic ratios and filling temperatures sequence of

mineral assemblages and microtopographs of crystals

It has been well established that the formation

temperature and the origin of the water are closely related

to the isotope raをios of hydrogen and oxygen of a given

mineral (Scheppard et alprime 1969 OINeal and Taylorprime 1969

savin and Epstein 1970 Lawrence and Taylor 1971 ONeeal

and Kharaka 1976 Suzuoki and Epstein 1976 Lombard and

Sheppardprime 1977)

The isotopic ratios of oxygen and hydrogen of mica clay

minerals in the Kumogi granite mass (Kanagi district) have

been measured to find the precipitation temperature and土と

was estimated at 250-C (Matsuhisa et al 1980) Although

the isotopic ratio obtained by the present author is only

for hydrogen lt5D valuesト676ォー ー773-) for the mica

ー 71 -

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

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別 離 萱

E W- E

5

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_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

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=

equiv

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くJ

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1-  ン

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毒-gtサ

=

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C

_ 80 -

l=a

こくc

Et

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く1

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qI+

呈43

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Eq

equiv

=蝣

13

s

もカ

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a

=e

増o

0h

UrlJJKCd空ロ「

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O

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infinrY7

日1lJh

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primeヽ

cap

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Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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来旨+剥牽(19糾う

clay minerals collected from the clay veins are very

similar to that (-78o) of Matsuhisa et al(1980)(see Fig

35) Furthermore the 6 D values (-675o) of kaoUnite

collected from the clay veins well coincide with those of

the Khodachi kaolin deposit ト658瑚(Table 6) In spite of

the differences in the mode of occurrences 6D values of the

related mineral also coincide with each other suggesting the

same formation COnditionJ土eJ hydrothermal 工f we piot

these values on the fractionation-temperature diagram

proposed by Marumo et al(1980) the formation temperature

of kaolinite is roughly estimated between 70- and 150-C

(F1  36)

The mineral sequence of mica clay mineral -1-

interstratification of mica and smectite smectite

kaolin minerals from the lower to upper levels obseved in

the alteration products in the host granitic rocks as well

as in a vein also give us some important informationr

concerning the formation conditions of clay minerals That

土Sprime almost the same mineral sequences have been established

in various geothermal areas (Sigvaldason 1962 Sumi 1966

1968 Takashima1972 Hayashi 1973 Hayashi and Yamasaki

1975 Kinbara and Ohkubo 1978) Typical examples of the

mineral- sequences found in Satsunan (Kagoshima Pref) and

Ohnuma (工wate Pref) geothermal areas are presented 土n Fig

37  Mineral sequence of mica clay mineral

interstratification smectite kaolinite is

generally recognized in these areas This sequence exactly

co土nc土ded with those obtained 土n the present study

- 12 -

Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

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=

equiv

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O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

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qJFJTO

C

_ 80 -

l=a

こくc

Et

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く1

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qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

_E蝣UJ

a

=e

増o

0h

UrlJJKCd空ロ「

rロQJtn

O

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tH0

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UEJJEd

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infinrY7

日1lJh

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射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

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酢Eh帥閏(197DI

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十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

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Fig35 Apioted of 5d ven1S 60 for water and mica clay

mineral- from clay vein in the Kumogi granite massLf

in Kanagi district shimane prefecture

The caluculated isotopic composition of the

hydrothermal waters equilibrated with mica clay

mineral (laxge solid circles) in veins is shown

by small solid circles with parameter of temper-

ature (after Matsuhperpsa et alprime 1980))

MWL 1 and 2 Standard for the meteoric water

lines by Craig (1う61) and Sakai and Matsubaya (1977)SMOW Standard mean ocean water

- 73 -

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

IIIIII

- 76 -

吾Ei

ao3Jg

iJ」_

ctl

J3

c

acヽ一primeprime

aqIiCc

equiv[plusmn芦Cgt

_c

4-to

q)

FTf

e

Ctl

l=

=ltfl

J

aGfl

雷C4

5I lllllld

玩1~~

l

l

L

l

E

1

描l

^HEl^^^B

I I

i i

I I

I

I

I

I

l

E

)

Bi喜l蝣51

rdl

E3i

l

E

I

I

I

l

1

1

j

altu-1

SV

Bg

r削rOCnj

mrJn3W

Q)

CE

E

GOEJJdhQ)UHn3

己 U)

a) d

Ql V

gt H

4J tfl

Q)

」i

rd

G EO ゝ1蝣H CD

JJ CrO JJ

H 0m ltuCd D1

deg

「ヽ

ro

D1蝣H

a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

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別 離 萱

E W- E

5

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_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

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i

L

打 S

=o

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巨≒

l弓

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IE4J

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=

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くJ

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=

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C

_ 80 -

l=a

こくc

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く1

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呈43

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Eq

equiv

=蝣

13

s

もカ

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a

=e

増o

0h

UrlJJKCd空ロ「

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infinrY7

日1lJh

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fL

1上

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射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

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蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

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iiilt日こHLlllgttこrト1-I

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来旨+剥牽(19糾う

1 2 3 4 5 6 7 8 9 10 ll 12

106T2 ぐK2)

サ Kaolinxte Dickxte(Ohnuma) (Marumo et al 1930)

A Sheppard and Taylor (Cited m Sheppard et al1969)

Preliminary- laboratory calibrations of kaolinite-H-O

B Shappard et aX (1969) Coexisting kaolmxte and waterfrom Fountain Paxnt Pot Yellowstone

C Savin and Epstexn (cited in Sheppard et al 1969

Data on natural kaolimtes from zones of deep weathering

0equivU

q

ヽ~8

5_=

5苧==」

8-

Fig 36 Temperature dependance of fractionation factors

bとtween kaolinite and water (after Marumo et al

1980) and fractionation of kaolinite in clay vein

and clay deposxt

- 74 -

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

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equivヽ_prime  ノ 

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- 76 -

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crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

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日1lJh

REFERENCES

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Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

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- 82 -

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- 8 3-

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Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

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- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

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ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Moreover the range of formation temperature of the

respective minerals can be obtained from Fig 37

Comparat土ve examinations between the two temperatures

lead to the formation temperatures of mica clay mineral 200

- 300 CJ interstratifperped minerals of mica and smectite 1500

- 200 C smectite 100- - 200-C and kaolin mineral 50-- 150

Cprime respect土vely

Microtopographs of clay minerals are also usuful for

confirming the formation environment of the minerals

Since the development of the decoration technique of

electron micrOSCOpy va-ous kinds of microtQPOgrapjis Of

clay minerals have been observed and character土st土c

microtopographs for the different environmental conditions

have been established (Baronnet 1972 Sunagawa and Koshino

1975 Sunagawa et al 1975 Sunagawa 1977 Toraura et al

1979) The important results of these researches are

summarized as follows 1) Spiral growth indicates that the

crystals are formed in either solution or vapor where

unconstrained growth is possible 2) Coalescence of crystals

cab occur predominantly土n violently moving solution than in

static solution 3) Step separation versus step high ratios

of the crystals growth in vapor phase is much larger than

those formed 土n hydrothermal solutions

Common development of circular spirals with relatively

narrower step separation in the clay minerals from Types lJ

2 and 5 clearly土nd土cates that the minerals have been formed

from hydrothermal solutions and not by solid-state

- 75 -

CJ

oainC叫

冨冒

LA

-143

e

equivsrIa

equivヽ_prime  ノ 

fd ミ」4)Fjq  トr

fG L=

Jォ

呈 邑

重さclqIqカ

rtJ

equiv=c

=O

=cヽl

Csupintt

富T-

JFll

tEl[lllIl1111[

_[壷トIgj

JSIu-

盲IITOII

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- 76 -

吾Ei

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equiv[plusmn芦Cgt

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crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

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_ 80 -

l=a

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equiv

=蝣

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infinrY7

日1lJh

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参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

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柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

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equivsrIa

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- 76 -

吾Ei

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H 0m ltuCd D1

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a

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

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蝣 1B tt o_iiJ tea -蝣一十there4perp - s

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Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

=E

lqE_4)

=

equiv

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O

くJ

equiv

a3isin I

1-  ン

呈三-oi

毒-gtサ

=

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qJFJTO

C

_ 80 -

l=a

こくc

Et

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く1

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qI+

呈43

Pi二

Eq

equiv

=蝣

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s

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a

=e

増o

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UrlJJKCd空ロ「

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O

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tH0

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UEJJEd

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infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

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MinatOH(1969)Mica clay mineral The clays o Japan

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JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

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Vo1ll 6-38

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- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

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Nagasawaprime T and Miyazaki S(1975) Mineralogical

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Proc Int Clay Conf 257-265

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Earth Sci Shizuoka Univ Vol3 17-33

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Clay minerals and their ormation sequence in

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21-44

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403-416

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Geo1prime Vo1 69prime 1207-1214

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across the central part of the Hiroshima granite(土n

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ShiraizuH(1972)女aolin mineral transformation during

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Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

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SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

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Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

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Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

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fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

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microtopography of metamorphic white micas phys

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and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

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に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

crystallization in which growth is constrained (Plates 5 6

and 7) Coalescence is often encountered in the clay

minerals from Type 2 and the fact also suggests the growth

from hydrothermal solutions polygonal spirals from Type

57 0n the other handl indicate the format五〇n condition of

hydrothermal metasomatism Thus all of the observed

m土crotopographs are ascribed to the format五〇n condition

related to certain hydrothermal activity

工n spite Of the previous researches on the formation of

clay minerals under the weathering condition(Kashiwagi

1963 Miura 1966 and 1967 Ohyagi 1968 LOhyagi et al

1969 MiyaharA 1977 KhonoJ 1985) present results strongly

indicate the hydrothermal origin of the clay minerals

Only in the case of kaolin mineralsJ especially for

halloysite evidence of weathering origin is recognized

Considering the fact that decomposition of the granltic

rocks can be represented by the amounts of clay mineral`r

format土onprime it may be concluded that the decomposition of the

granxtic rocks of the investigated area is mainly the

results of hydrothermal activities subsequent to the

granitic activity as well as the weathering during the

geological ages

- 77 -

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

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=

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呈三-oi

毒-gtサ

=

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qJFJTO

C

_ 80 -

l=a

こくc

Et

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く1

芸O白

qI+

呈43

Pi二

Eq

equiv

=蝣

13

s

もカ

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a

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増o

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UrlJJKCd空ロ「

rロQJtn

O

冒00班rO

tH0

Ur4dLH

0hCLI

UEJJEd

EQ)qU∽

infinrY7

日1lJh

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

VII CONCLUDING REMARKS

Based on the results obta土ned土n this study the most

possible decomposition process of the gran土tic rocks of the

district will be explained

First nearly vdrtical fractures and microcracks have

been developed within the granitic rocks under the regional

paleo-stress field of the respective districts after the

solidification stage of the granite The clay veins and

clay deposits were formed f土111ng the fractures by clay

minerals from hydrothermal solution of meteoric origin

To be noted is that the constituent minerals of the

host granitic rocks and clay deposits formed by

the metasomatism I were formed by the same

activity in more or less extent The clay mineral species

have been gradually changed according to their geographical

vertical positions That is the mineral sequence of mica

clay mineral interstratified mineral smectite -V

kaolin minerals from the depth to the upper levels was

gradually formed during the geological ages

The horizontal fractures such as lamination and

sheeting joints have developed near the ground surface by

unloading The horizontal microcracks are ascribed to the

same formation mechanism The part where the fractures are

densely developed is generally decomposed remarkably Thi

is because the place is favorable for weathering process in

addition to the hydrothermal activity of relatively earlier

stage

The fracture system location of clay deposits and clay

- 78 -

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

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日1lJh

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found in an exploration Bore-hole(NoSA-I) Satsunan

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plagioclase in granite during weathering JSciHiroshima

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1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

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Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

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cap

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12

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射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

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iiilt日こHLlllgttこrト1-I

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ironitie両31川ndllu川S

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紙十Ltl聖(19fi招

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来旨+剥牽(19糾う

veins are illustrated schematically in Fig 38 together with

the degree of the decomposition

- 79 -

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

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Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Kaolin mineral zone Smectite zone Mica clay mineral zone

Elequiviq=一一〇」_Clgt1

Ll沖拝ニit-it 「 - l 】 L3 1耳雨迂環 I Ir~- 蝣妻 妾 L十 王車ーhellip L蒜-prime蝣iII威 こ -蝣- 蝣lt一一

lt-lf-こ -

Yir競 tTで

蝣 1B tt o_iiJ tea -蝣一十there4perp - s

1 蝣蝣蝣 -ff= ー=

O噂-i

i

EsS s 串等議事買春rarrI I perp-W -S ~ - 蝣蝣蝣蝣 蝣

lti宗 - _ _- J_ f gt

4 1 荊- 3 gt iM S i歩芋 IE ^Aiォ4【=一一t可4」

イ 一

tコ

ILコ+l S5 l凄至 蝣 蝣蝣11PJ IJK rf K I 巨 室 の 1 三 g1「喜 O

蝣4-t1y

ZJk=--eC

別 離 萱

E W- E

5

苧 ~

_ _i g 毒二 重 言二

isin 空 ∽ i l 喜一 「

一 蔓 ~

_e

0

ae芸 S = 芝 トl~

-= 吾く 0 1看 d I白ユ e

i

L

打 S

=o

dォ2I7341XI-0隻

巨≒

l弓

Iも凸equivEtEI-C甘qJ3=FU

IE4J

int-4

ll47

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=

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REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

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5

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7

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there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

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来旨+剥牽(19糾う

REFERENCES

Baronnet A (1980)Polytypism in mi甲 A survey with

emphasis of the crystal growth aspect Current topics in

materials Sci Vol5 E Kaldis ed North-Holland Pub

Craig H(1961)Isotopic variations in meteoric water

Science Vol133 1702-1703

Hashikawa K and Miyahara K(1974)Fracture of the

weathered granitic rocks and its engeneermg

significance(in Japanese) Engeneering Geol Vol 15

47-57

Hashikawa K (1978a)On an Anlstotropic effect to the Pr

wave velocity affected by the sheeting joint i-n

weathered granitic rocks and its analysis(in Japanese)

Engineering Geol Vol19 21-29

Hshikawa K(1978b) Weathering structure of the granitic

rocks in the dessected pediment (土n Japanese)YI

Engeneering Geol Vol12 22-29

Hashikawaprime K(1985)Studies on the planar fracturing

structures developed in the Surficial part of granite

mass Geo1 rep H土roshlma Un土ⅤJ No25 ト37

Hayashi M(1973)Hydrothermal alteration in the Ohtake

geothermal area Kyushu Chinetsu vo110 9-45

Hayashi M and Yamazaki T(1975)Interstratified 一mineral

of mica and montmor土11on土te from the Ohtake

geothermal area in Ohita Prefecture and environmental

conditions of formation ProfToshio Sudo memorial

48-58

- 81 -

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Ishihara S1977) The magnetite-series and illmenite-

series granitic rocks Mining Geol Vol27 293-305

Ishihara Sint Shibata K Kitagawa Rとnd Kakitani

S(1980) K-Ar ages of sericites from the Chugoku

district Japan Bull Geol Surv Japan Vol31 221-

224

Iwao S(1953)Pale green sericite deposits in Iishi

dlstrlctJ Shimane Prefecture with special reference

to the wall rock alteration (in Japanese)prime Ch土cho

geppou Vo14 223-238

Kak土taniprimeS and K土tagawa R 1977)Clay minerals 土n the

veins and veinlets found in the granitic rocks of

Hiroshima Prefecture JMiner Soci Japan  Vol13

spec 187-196

KawanoY and UedaY(1964) K-Ar dating on the igneous rocks

in Japan(I)(in Japanese)prime JJapan Assoc Miner pet

Econ Geol 51 127-148

Y

Keller WD(1976a)Scanningノelectron micrOgraphs of

kaolins collected from diverse envirOlaments Of origin-

I Clay Clays- Miner24 107-113

Keller WD(1976b)Scanning electron micrographs of

kaolins collected from diverse environments of origin-

II Clay Clays miner 24 114-117

Keller WD(1976c)Scanning electron micrOgraphs of

kaolins collected from diverse environments of origin一

工工工J influence of parent materia1 0n flint clays and

flint-like clays Clay Clays Miner 24 162-264

Keller WD(1977a)Scanning electron micrOgraphs of

- 82 -

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

kaolins from diverse environments of genesis-IVJ

Georgia kaolin and kaolinizing source rocks Clay Clays

Miner 25 311-345

Kellerprime WD(1977b) Kaolins colleeted in Austrar土   and

Japan on field trips of the sixth and seventh clay

conferences Clay Clays Miner 25 347-364

KinbaraK and OhkuboT(1978) Hydrothermal altered rocks

found in an exploration Bore-hole(NoSA-I) Satsunan

geothermal area Japan(in Japanese) JJapan Assoc

Miner Pet Econ Geol 76 176- 179

Kitagawa R and Kakitani S(1977) Alteration of

plagioclase in granite during weathering JSciHiroshima

Un土Ⅴ Cprime Vo17prime 183-197

Kitagawa R and Kakitani S(1978a)The pale green clay

vein in the granitic rock at the Ondo-cho district

Hiroshima Prefecture(in Japanese) JClay Sci Japan 18

1-10

Kitagawa R and Kakitani S(1978b)The white clay vein

in the granitic rock at the Hachihonmatsu district

H土roshima Prefecture土n Japanese)primeJClay Soc土 Japan

Vo1工8prime 31-39

Kitagawa R and Kakitani S(1978c)二modege of occurrence

and mineralogy of clay veins in granitic rocks with

special reference to the genesis of clay minerals in

them(in Japanese) JMiner Soc Japan Vo113 357-

359

Kitagawa R and KakitaniS(1979a) Modes of occurrence

- 8 3-

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

and mineralogy of mica clay minerals in the Hiroshima

and San in granitic complexes(inJapanese) J Miner

Soc Japan Vo114prime 3-19

Kitagawa R and Kakitani S(1979b) The mode of

occurrence and mineralogy of Khodachi kaolin deposit

and clay veins found in 土ts host rock(1n Japanese)int

Miner Geol Vol 29 217-226

Kitagawa R and Kakitani S Kuroda Y MatsuoJ S and

Tsuzuki T(1980)Hydrogen isotope ratios of clay

minerals constituting clay veins found in granitic

rocks of H土roshima Prefecture(in Japanese)

JGeolSociJapan Vol86 167-177

Kitagawa R and Kakitani S(1981)K-Ar ages of mica clay

minerals in clay veins found in granitic and rhyolitic

rocks of Hiroshima PrefectureJ Japanl JJapan Assoc

Miner Pet Econ Geol Vo176寸 176- 179

Kitagawa R and Kakitani S TakenoS and Nishida

7`

Y(1981)Topographic examination and genesis of clay

veins found in the Kumogi granite mass in Shimane

Prefecture SouthwestJapan J Japan AssocMinerPet

EconGeo1 Vo176 262-272

KitagawaR Kakitani S and Minato S(1981) The

format土on process of mica clay mineral montmorillonite

mineral and interstratified mineral of mica-swelling

layer in clay veins found in granitic rocks(in Japanese)

JClay Sci Soci Japan 21 141-152

Kitagawa R and Kakitani S(1981)Lath-shaped mica clay

mineral(in Japanese) JMiner Soci Japan 15 Spec

- 84 -

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

107-115

Kitagawa R Kakitani S and Hunaki A(1982)Mica clay

minerals occurring in the sericite deposits at the

Mitoya district Iishi-gun Shimane Prefecture (in

Japanese)prime JClay SociJapan Vo1 22 54-67

Kitagawa R and OkunoT(1983) Formation mechanism of

clay veins found in granitic rock in Higashihiroshima

district H土roshlma Prefecture)土n Japanese)int J Clay

Sc土 JapanprimeVo1 23prime 45-60

Kitagawa R Takeno S and Sunagawa 1(1983) Surface

microtopograpies of sericite crystals formed in

different environmental conditions MinerJ Volll

282-296

Kitagawa RHirosawa HNagaiKand NobushitaT(1984)

The shape and genesis of halloysite formed by

alteration of granitic and rhyolitic rocks(in Japanese)

JClay SociJapa`n  Vo124 20-33

KitagawaR (1985) The formation mechanism of clay veins

found in gran土七五c rocks and the alteration mechanism of

granitic rocks(in Japanese) Professor Hironao Yoshida

Memorialprime 93-117

Kitagawa R and Kameoka H(1986) The mode of occurrence

and mineralogy of Komaki halloysite deposit and

alteration of its surrounding granitic rock(In

Japanese)prime J Clay Soc土Japan Vo126 (in press)

LawrenceJR and TaylorJr(1972) Hydrogen and oxygen

isotope systematics in weathering profiles Geoc Cosm

- 8 5-

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Acta Vol36 1377-1393

MarumoK NagasawaK and KurodaY(1980) Mineralogy and

hydrogen isotope geochemistry of clay minerals in the

Ohnuma geothermal area Northeastern Japan Earth

and Planetary sci Letter 47 255-262

MatsuhisaY ImaokaII and MurakamiN(1980) Hydrothermal

activity indicated by oxygen and paleogene cauldron

Southwest Japan Mining Geol Special issue No8 49-

65

MatsumotoK(1965) On some kaolin deposits related to the

granite in Chugoku district Japan(in Japanese)

GeolRep Hiroshima Un土Vprime No14 385- 395

Matsumoto K(1968)On the geology and pyrophyllite

deposits of the Yano Shokozan mine Hiroshima

PrefectureJ Geo1 Rep Hirosh土ma Univ No工67 1- 33

MinatOH(1969)Mica clay mineral The clays o Japan

Ed1969 international clay conf Japan 96- 102

Miura K(1966)On the granitic rocks and their collapse

at Kamo d土str土ct Shimane prefecturein Japanese)

JJapan Assoc Miner Pet Econ Geo1 Vo156 256-

283

Miura K(1967)On the granitic rocks and their collapse

at Kano dlstrictprime sh土mane Prefecture土n Japanese)prime

JJapan Assoc Miner Pet Econ Geol Vol57 ll-24

Miura K and Hata A(1970)The collapse related to rock

コOints and existoints clay of weathered granitesprime  Econprime

Vo1ll 6-38

Miyahara K(1977)Study on the weathering o granite in

- 8 6-

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

Hiroshima PrefectureJ JapanJ J Sci Hiroshima Univint

C Vol 7 297-299

Nagasawa K and KuniedaK(1970)Geology and mineralogy

of clay depos土ts 土n the Naegi districtprime   G土fu

Prefecture(in Japanese) Mining Geolf 20 361-377

Nagasawaprime T and Miyazaki S(1975) Mineralogical

properと土es of halloysite as related to its genesis

Proc Int Clay Conf 257-265

Nagasawa K(1978) A study on the formation and

transformation of kaolin minerals(in Japanese) Rep

Earth Sci Shizuoka Univ Vol3 17-33

OkamuraY(1965)Strucuture of the granite mass of the

Kurokami island Tokuyama island Tokuyama city

Yamaguchl Prefecture(in Japanese) Geo1 Rep Hiroshlma

Un土Vprime No 14 307-316

0 NeilJR and Taylor HP Jr(1969)The oxygen isotope

and cation exchange chemistry of feldspar  Amer

Miner Vo152 1414-1437

0 Neil R and KaharakaYK(1976) Hydrogen and oxygen

isotope exchange reactions between clay minerals and

waterprime Geochl Cosmochi Actaprime Vo144prime  241-246

Ohyagi N(1968) Weathering-zone structure and landslides

of the area of granitic rocks in Kamo-daito Shimane

Prefecturedn Japanese) Bousa土ken houkokusyoprime  Vo114

Ohyagi N Uchida T and Suzuki H(1969)Clay minerals

of weathering zone in Kamo-Daito granodiorite region

Clay minerals and their ormation sequence in

7-

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

14_

射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

lthere4there4IXこiii5=こミミ_l一二i

主上1ォサーr十ト1L汗-I

gtLprimeI竃巨ltgtJ上一言il1「銅完工1i冒ltlt蝣て蝣gt1Iprimel--r甘『こ~

-駄星野畢漕禽層駄蜘

敗+魁牽(1F摘日

に一糸ra芸だ淫雨m圧ael的離nera弓等inc-yen肌糟頼S極卓融葎pmInは-W亀融

rhvoiticrocksofHir串油軸Tp匝再ur担knan

i_廟hellipthere4there4-r蝣---i---「くつ一十i

肯汀里純Eit一1I17す1サォサ1-日lr二there4芸I-I言了一帯

来た+魁聖(79只誓う

15

16

lワヰ

18

I「-there4there41一IJ1t吋上-~t_メ4J

iiilt日こHLlllgttこrト1-I

トXitthere4ミ事-白三i冒

daggerI蝣こ^fサri声ここIい主蝣-蝣r捕Hl蝣if-蝣判ま

ironitie両31川ndllu川S

Ti-there4ilTlyen-「い

申there4戸車那there4声-)Lつ冒斗蝣蝣ntU(Ill薫をDagger

紙十Ltl聖(19fi招

柁こ岩TTLthere4圭肯J-蝣モ工作酢の)--fさミ工工六二L-一primeMノーprimeーprime一4一AtIAJ~V-

来旨+剥牽(19糾う

weathering(in Japanese) Bousaiken Houkokusyo Vol2

21-44

ParhamW(1969) Halloysite-rich tropical weathering

products of Hondeg KongJ Proc Intern Clay Conf 17

403-416

Sakai H and Matsubaya 0(1977) Stable isotopic studies

of Japanese geothermal systemsJ GeothermlcsJ Vo15prime 97-

124

Savin SM and Epstein S(1970)The oxygen and hydrogen

isotope geochemistry of ocean sediments and shales

Geoch土 Cosmochi ActaJ Vo1347 43-64

Shibata K and Ishihara S(1974a)K-Ar ages of the

ma^or tungsten and molybdenum deposits in Japan Econ

Geo1prime Vo1 69prime 1207-1214

Sh土bata K and工shihara S(1974)K-Ar ages of b土otites

across the central part of the Hiroshima granite(土n

Japanese) J Geol Soci Japan Vol80 431-433y

ShiraizuH(1972)女aolin mineral transformation during

weathering and d土agenesis(in Japanese)prime J Clay sci

Soci Japanprime Vo14 prime 137-142

Shimizu H(1978) Micromorphology of halloysite produced

by weathering of plagioclase in volcanic ash Int Clay

Conf 4工5-422

SheppardSM-F Nielsen RL and Taylor HP(1969)

Oxygen and hydrogen isotope ratios of clays from

porphyry copper depositsJ Econ Geo1 Vo164J 755-777

SigvaldasonGE(1962) Epidote and related minerals in two

deep geothermal drill holes Reykjavik and Hveragerdi

- 8 8-

Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

T(1975)Growth mechanism of some clay mineral

Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

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射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

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there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

T岬(中一there4トこここithere4tデyen--there4there4H蝣1-メ-~

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Iceland US Geol Surv Prof Paper 450-E 77-79

Sumi K(1966) Hydrothermal rock alteration of the

Matsusaka geothermal area =W云te prefecture(in

Japanese) Mining Geol Vol16 261-271

Sumi K(1968) Hydrothermal rock alteration of the

Matsukawa geothermal area Northeast Japan Rep Geol

Surv Japan 1-42

Sunagawa I KoshinO Y Asakura M and Yamamotoprime

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Fortschr Miner Vol52 217-224

Sunagawa I and Koshino Y(1975) Growthspirals on kaolin

group minerals Amer Miner Vol60 407- 412-

sunagawaprime 工(1977)Natural crystallperpZat土onJ J Crystal

growth Vo142 214-223

Suzuoki T and Epstein S(1976) Hydrogen isotope

fract土onat土on between OH-bearing minerals and water

Geochi Cosmochi Acta Vol 40 1229- 1240

Takashima I1972)Hydrothermal rock alteration in

Takenoyu geothermal area Kumamoto Prefecture Japan(in

Japanese) Bull Geol Surv Japanprime  Vo123prime 721-728

Tazaki K(1977) Formation of clay minerals from

plagioclase Miner J Vo113 172-177

Tazaki K(1978) Micromorphology of halloysite produced by

weathering of plagioclas占in volcanic ash Inter Clay

Confprime 415-422

Tomura S Kitamura M and Sunagawa 1(1979) Surface

microtopography of metamorphic white micas phys

9-

Chem Vo15prime 65-81

TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

5

primeヽ

cap

7

Fi

fL

1上

12

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射穣顆そ蝣ionがnia望ioriaSeinr-rcn沌e由ringup完thPri喝

抽汀ーSfI上酎ro油軸aUn軸hf1977う

there4サ--蝣蝣I裳tthere4丁花there4掛手二つ蝣Ill-Ithere4i-1上二i芋

放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

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TsuzukiY(1985) Thermodynamics and kinetics of weathering

and hydrothermal alteration(in Japanese)prime J Geo1_

Soc土 Japan Vo191 699-718

- 90 -

参 考 諭 文

1

3

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cap

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放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

i蝣圭r-f晋-i-tin二十ミ^蝣ML二半章らつ黒量there4昔

患転+魁牽自978う

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鈷+魁牽(1978)

蝣ALthere41呈yen^吊二二二1-つLI粧Iと『了票巧手上弦物

駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

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放物牽雑誌自977)

昔ころ岩由にみられる粘土魂脈の産状と或匡

鉱物学雑誌自97只1

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患転+魁牽自978う

圭工b-V-ニ甘告町^-i主意了11も11二鴇貯

鈷+魁牽(1978)

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駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

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駐輿亨単--L-Iド

号ト圭守i昌7i∵_ミ1蝣mi三三葦上帯樵

酢Eh帥閏(197DI

K一射罷gesofserieはだ行om紬eC短岩油d即せ証七夕j岬anl

十十I中fォ貫く十

広島県下の発こう若中の確肝として遷す還粘土鉱物とその水素同位体比

排常牽雑誌(1980)

長弓手軒滑空題粘+餅軸cofi)二物萱的蛸I新

患訂妙音牽強吉良自白Rn

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