Branch of Chemistry of Kilauea and Mauna Loa Lava in Space ... · Mauna Loa is approximately equal...

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Chemistry of Kilauea and Mauna Loa Lava in Space and TimeGEOLOGICAL SURVEY PROFESSIONAL PAPER 735

Chemistry of Kilauea and Mauna Loa Lava in

Space and TimeBy THOMAS L. WRIGHT

GEOLOGICAL SURVEY PROFESSIONAL PAPER 735

An account of the chemical composition of lavas

from Kilauea and Mauna Loa volcanoes.

Hawaii, and an interpretation of the processes

of partial melting and subsequent fractional

crystallization that produced the chemical

variability

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971

UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS G. B. MORTON, Secretary

GEOLOGICAL SURVEY

W. A. Radlinski, A cting Director

Library of Congress catalog-card No. 74-178247

For sale by the Superintendent of Documents, U.S. Government Printing OfficeWashington, D.C. 20402 Price 50 cents (paper.cover)

Stock number 2401-1185

CONTENTS

Abstract ________________________________________Introduction _____________________________________Acknowledgments ________________________________Definitions and terminology _______________________

Tholeiite ____________________________________Mineral control lines _________________________Olivine-controlled and differentiated basalt _____

Previous work ___________________________________Methods of study _________________________________

Sampling ____________________________________Chemical analyses ___________________ Computer reduction of chemical data ___________

Observations _____________________________________Kilauea ___ ____________________________

Olivine-controlled lavas ___________________Petrography _________________________Chemistry ___________________________

Differentiated lavas ______________________Mauna Loa __________________________________

Page

11222445556668889

1516

Observations ContinuedOlivine-controlled lavas _________________

Petrography __________ __ Chemistry _______________________

Differentiated lavas ______ _ ___ Chemical variation within Kilauea lava and differ

ence between Kilauea and Mauna Loa lavas____

Discussion _____________________ ___Olivine-controlled chemical variation in Kilauea

and Mauna Loa lavas ____________________Olivine-pyroxene-plagioclase control of Mauna Loa

lava compositions _ . __High-pressure fractionation of Kilauea lava ____

Long-term chemical variation _____________Short-term chemical variation __

Model for melting and fractionation of Kilauea and Mauna Loa magmas ___________ . __

References cited ______-_____

ILLUSTRATIONS

FIGURE 1. Index map showing the five volcanoes that make up the Island of Hawaii ___ _________2-12. MgO Variations diagrams:

2. Mauna Loa and Kilauea lava flows and minerals that control the chemical variation3. Lavas erupted at Kilauea summit ______ _ ____________________________4. Lavas erupted from the Kileauea southwest rift zone _______ - _________5. Lavas erupted from the Kilauea east rift zone _________ ___________6. Kilauea lavas erupted in 18th and 19th centuries ____________ __________7. Lavas from the summit and northwest slope of Mauna Loa _______________

Lavas from Mauna Loa southwest rift zone __________ _ ____________Lavas from Mauna Loa northeast rift zone ___________________________ Lavas from the Ninole Hills ___________________________________________________Differentiated lavas from Kilauea and Mauna Loa ______________________________Kilauea summit lavas 1952-68 _________________________________________________

8.9.

10.11.12.

Page

16161623

23

23

26

27282931

3339

13. Hypothetical model of Kilauea and Mauna Loa outlining regions of melting, fractionation, and storage of magma prior to eruption _____________________________________________________________________

Page

2

10111213192021222432

34

III

IV CONTENTS

TABLES Page

TABLE 1. Historic eruptions of Mauna Loa __-__ 32. Historic eruptions of Kilauea ______ __ 33. Data for equation y = ax + b to define mineral control lines for suites of olivine-controlled lavas from

Kilauea and Mauna Loa __ ____ _ 8 4 6. Chemical analyses of olivine-controlled lavas from Kilauea

4. Summit ___________________ ___ _____ _ 95. Southwest rift zone __________ _ _ - _ _ 146. East rift zone ____________________________________-______ _ - 15

7. Modal data for selected porphyritic lavas from Mauna Loa _ _ 16 8-11. Chemical analyses of olivine-controlled lavas from Mauna Loa

8. Summit ______________________ _______________________-__ _ _ 169. South rift zone ______________________________________________ _________ 17

10. Northeast rift zone ____________________ _____ _ _ _ 1711. Northwest slope ______________________ _____ _ _ _ 18

12. Chemical analyses of lavas from the Ninole Hills, southeast slope of Mauna Loa _ _ 1813. Chemical analyses of differentiated lavas from Mauna Loa _ _ _ 2314. Summary of chemical composition of historic flows from Mauna Loa and of flows of different ages from

Kilauea ____________________________________________________________ 2315. Analyses of minerals used in differentiation calculations _ ___-____ _ __ _ 25

16-18. Results for differentiation calculations for 16. Kilauea and Mauna Loa control lines __ _ _ _ 2617. Olivine-controlled lavas from Mauna Loa _ 2718. Differentiated lavas from Mauna Loa __ 28

19. Calculated mode and pyroxene composition of a "Mauna Loa" mantle _______________________ 2920. Lava compositions used in high-pressure fractionation calculations - 3021. Results of high-pressure fractionation calculations for Kilauea summit lavas _ _ _ _ ___ 3022. Calculated high-pressure solidus assemblages and pyroxene compositions for Kilauea summit lavas _____ 3123. Sample data for the chemical analyses of tables 4-6 and 8-13 ___________________________ 3524. List of references to published chemical analyses of Kilauea (olivine-controlled) and Mauna Loa flows

other than those reported in this paper ____ - - - 38

CHEMISTRY OF KILAUEA AND MAUNA LOA LAVAIN SPACE AND TIME

By THOMAS L. WRIGHT

ABSTRACT

Kilauea and Mauna Loa, Hawaii's two active shield vol canoes, are composed of tholeiitic basalt having MgO con tents ranging from more than 20 percent to less than 4 per cent. Most eruptive vents are located either within the central caldera or on two rift zones extending to the east and southwest from each volcano's summit. Mauna Loa also has a few isolated vents on its northwest slope that are ap parently unrelated to any rift zone. The chemical variability of Mauna Loa and Kilauea lava having more than about 6.8 percent MgO is principally explained by addition or removal of olivine (olivine control), but other minerals are involved to a lesser degree. The chemical variability of these lavas is described and interpreted in this paper. Lavas having less than 6.8 percent MgO are fractionated by separation of pyroxene, plagioclase, and Fe-Ti oxides in addition to oli vine. Fractionated basalt from Kilauea is confined to the rift zones. The rare fractionated lavas from Mauna Loa are also confined to the rift zones and are less fractionated (higher MgO) than those from Kilauea.

The chemistry of nonfractionated lava from single erup tions of Kilauea may be explained by olivine control alone, and this process is consistent with the observation that oli vine is the only true phenocryst in unfractionated Kilauea lavas. The chemistry of nonfractionated lava from single eruptions of Mauna Loa can be explained by a more complex mineral control involving olivine, hypersthene, augite, and plagioclase, all being commonly present as phenocrysts. The addition or removal of these minerals is inferred to take place at pressures not exceeding 2 kilobars in shallow magma reservoirs located beneath the two volcanoes.

The chemistry of Mauna Loa lavas shows no correlation with either the time of eruption or location of the eruptive vents. By contrast the lavas erupted at Kilauea summit may be subdivided into three groups pre-1750, 18th-19th cen tury, and 20th century on the basis of their chemical com position compared at the same MgO content. The younger lavas are richer in lower melting constituents; for example, K2O, PaOs, and TiOa. The average composition of Mauna Loa lavas is similar to what one would obtain by extrapolating the Kilauea chemical variation backwards in time. It is pos sible that the oldest unexposed Kilauea lavas would be simi lar in composition to Mauna Loa lava. The similarity in the ratio of K20:P2Os both within the lavas of each volcano and between the two volcanoes suggests that Kilauea and Mauna Loa originated by partial melting in a mantle of uniform composition and that no processes other than either melting or crystal-liquid fractionation are needed to explain the chemical variations.

The increase in KzO and PzOs in the more recent Kilauea eruptions suggests that the magma which supplies Kilauea eruptions has been fractionating. The time-related chemical variation can be expressed by two mineral assemblages: (1) olivine-orthopyroxene-plagioclase (An eo-es) where the ratio of orthopyroxene to plagioclase equals 2:1 and (2) olivine- aluminous orthopyroxene-aluminous and jadeitic clinopyroxene where the ratio of orthopyroxene to clinopyroxene equals 2:1. Both assemblages indicate relatively high pressure frac tionation. Neither of the calculated mineral assemblages is of basalt at high pressure, and it may be that the magmas entirely consistent with recent studies on the crystallization have undergone more than one stage of fractionation.

A model is proposed for the origin of Kilauea which em bodies the following points:1. Generation by partial melting of picritic magmas (20-25

percent MgO) at depths of greater than 60 kilometers.2. High-pressure fractionation of these magmas during rel

atively slow ascent to a storage region at 20-30 km depth.

3. Minor fractionation during storage followed by rapid as cent into shallow crustal reservoirs at 2-4 km depth.

4. Settling of olivine during storage at 2-4 km and periodic eruption of the upper parts of these reservoirs, or rarely, the entire reservoir including settled olivine.

INTRODUCTION

Kilauea and Mauna Loa are two active shield vol canoes on the island of Hawaii (fig. 1), which rise to heights above sea level of 1,260 and 4,200 meters, respectively. The undersea part of each volcano is probably composed of overlapping pillow lavas separated by a thin layer of hyaloclastic material from a subaerial section composed of countless thin flows of rather uniform tholeiitic basalt (Moore and Fiske, 1969). At least 10,000 years of geologic time are represented by the section visible above sea level (Rubin and Berthold, 1961; see also Doell and Cox, 1965). Each volcano has erupted lava from its summit and two rift zones. Mauna Loa, in addition, has a number of isolated vents on its northwest slope that are apparently unconnected with any rift zone. The Ninole Hills, on the southeast slope of Mauna Loa, are made of faulted and eroded lavas that have been considered by previous workers to be

CHEMISTRY OF KILAUEA AND MAUNA LOA LAVA IN SPACE AND TIME

30 KILOMETERS

FIGURE 1. Index map showing the five volcanoes that make up the Island of Hawaii. Contour interval, 2,000 feet. Stippled area, underlain chiefly by lava flows from Mauna Loa; hatched area, underlain chiefly by lava flows from Kilauea.

part of the oldest series of exposed lavas erupted from Mauna Loa.

The general characteristics of Mauna Loa erup tions are similar to those of Kilauea, judging from published descriptions. The frequency of eruption at each volcano has been similar throughout historic time, and the volume of magma erupted from Mauna Loa is approximately equal to that erupted from Kilauea over the same period.

Stearns and Macdonald (1946, p. 131-136) have summarized the ideas of previous observers on the relative ages of Kilauea and Mauna Loa. Their own conclusions, based on field observations, are that Ki lauea and Mauna Loa are independent volcanoes, that all lavas exposed in section on the Kilauea shield were erupted from Kilauea, and that the Kilauea shield is younger than the bulk of the Mauna Loa shield.

Petrologic study of Kilauea complements recent geophysical and ground deformation studies which have provided information on the structure of Ki lauea Volcano and its mechanism of eruptions. (For

example, see Fiske and Koyanagi, 1968; Fiske and Kinoshita, 1969; Kinoshita and others, 1969.) Pe trologic interpretation is aided by the extensive knowledge of basaltic crystallization gained from study of the recent lava lakes of Kilauea (Richter and Moore, 1966; Peck and others, 1966; Wright and Weiblen, 1968); there is no comparable knowl edge for Mauna Loa.

This paper uses chemical analyses, many of which are previously unpublished, of historic (1750-present; see tables 1 and 2) and prehistoric lavas of both volcanoes to characterize the chemical composition of flows from the summit and rift zones and to develop the following topics:

1. The chemical variation in both time and space of Mauna Loa lava and how it contrasts with the chemical variation in time and space of Ki lauea lava.

2. Possible explanations of the chemical differences between Kilauea lavas of different age.

ACKNOWLEDGMENTS

H. A. Powers first introduced the writer to the problems of Kilauea and Mauna Loa chemistry. His encouragement and critical evaluation of this work at many stages has been of great value. The quanti tative treatment of differentiation depends on the quality of the chemical data. I would like to extend thanks to L. C. Peck and the individual analysts whose work is included in this paper. The assist ance of P. C. Doherty in making computer calcula tions is gratefully acknowledged. The discussion sections of the paper benefited greatly from commu nication with R. L. Tuthill, T. N. Irvine, E. D. Jack son, and H. R. Shaw. However, the conclusions ex pressed are the author's sole responsibility. The paper was reviewed at different stages by R. L. Tuthill, R. S. Fiske, D. A. Swanson, and W. A. Duf- field, whose comments are greatly appreciated.

DEFINITIONS AND TERMINOLOGY

Petrologic terminology related to basaltic rocks often carries multiple meanings, so that the follow ing explanations of terms which recur frequently in this report are made to avoid confusion.

THOLEIITE

The term "tholeiite" as used in this report em braces both the definitions of tholeiite (oversaturated) and olivine tholeiite (undersatur- ated) used by Yoder and Tilley (1962, p. 353-354).

DEFINITIONS AND TERMINOLOGY

TABLE 1. Historic eruptions of Mauna Loa[This table is repeated with little modification from Stearns and Macdonald (1946, table, p. 79). Additional data for the eruptions of 1949 and 1950

are from Finch and Macdonald (1951, 1953)]

Date of commencement

Year

1832 ....1843 -------1849 -- 1851.- -------1852

1855 1859 1865 1868 1872

1873 1873 .1875 1875 1876

1877 1880 1880 1887 1892

1896 1899 1903 1907 1914

1916 1919 1926 1933 1935

1940- . . 1942-. __-__1949 1950

Month and day

June 20__- __ _Jan. 9- _- __May_ - _-_ Aug. 8. Feb. 17.

Aug. 11-. --.-_-Jan. 23-----.--Dec. 30-_ Mar. 27 Aug. 10-.------

Jan. 6-.- _ _-_Apr. 20- . _ _Jan. 10 _ .-_Aug. 11. ._-----Feb. 13 .

Feb. 14.. May 1 . , - _Nov. 1_ Jan. 16 _-_ .Nov. 30

Apr. 21_ .__ July 4 ------Oct. 6__._ __ __Jan. 9 __ Nov. 25

May 19. -------Sept. 29 ... .Apr. 10. -------Dec. 2---------Nov. 21 .

Apr. 7-. ------Apr. 26---_-_-_Jan. 6June 1 _ _

Approx duration in days

Summit

215

1521

1

1120

160

2(?)54730

7Short

106

3

164

601

48

ShortShort

171

1332

146

Flank

(?)90

_(?)20

450300

15_.-

-__

-__---

1

28010

_-_

19

15-__

144214

142

113

22

Southwest rift. _.--_ __Northeast rift. ___ Mokuaweoweo___ --_-___.do - - - Northeast rift . . _ . _ _ _

do Northwest flank __ -Mokuaweoweo. - _Southwest rift ____Mokuaweoweo __ __

. ...do. . ------------ do . _...do ... _._ ----- do -do-

_.__do ... ----- do Northeast rift_- _-__Southwest rift . _ __Mokuaweoweo _ _ _

-__dO ----------Northeast rift _ _ -Mokuaweoweo _ _ _ _ _Southwest rift.Mokuaweoweo- __- - -

Southwest rift . . _ -__ do do Mokuaweoweo -Northeast rift

Mokuaweoweo- _ _ __-Northeast rift _. _ -

Southwest rift

Approx volume

(cumX10-6)

69191

69107

115459

145--

_

--

230230

--

153

77_-

6126811577

122

777759

390

Tables containing

paper

13_ __

10

1011

9___

_ ___-.

88

109

_-_

10

9_-.

99, 13

10

88, 10

89, 13

1 Includes only lava above sea level. Estimates of lava erupted undersea are given by Stearns and Macdonald (1946, footnotes to table, p. 79) and by Finch and Macdonald (1953; 1950 eruption only). v

TABLE 2. Historic eruptions of Kilauea

[For eruptions through 1934, this table is repeated with little modification from Stearns and Macdonald (1946, table p. 111). Data for 1866(?), 1879, and 1889 eruptions are from H. A. Powers (oral commun., 1967; see also Peterson, 1967). Data for eruptions since 1952 are taken from published and unpublished data, Hawaiian Volcano Observatory]

Date of commencement Af

Year

1750(?)- _ -.---.1790(?) -_-_.-..1790------_.._.1823 1832-------....

1840 1866(?)___ 1868 .1868 1877

1877 1879 .1884 1885 1889

Month and day

Nov. (?)_... Feb.-July. __ ___Jan. 14-. _ . __

May 30-. _ ___?Apr. 2... --------Apr. 2(?)_ __

May 21(?)_.._ ..?Jan. 22 _ _ __ _

?

>prox duration in days

Short Short

26 ?

Short Short

1(?)

" ?

i80(7)

?

Approx volume Location of principal vent(s) of lava ]

(cu mX10-6)

East rift. _ do

Southwest rift

East rift. _

T^POTI a t a 1m i

_---do--_----------- do _do

...__ 15

..... 29

12?

..___ 216

?.____ 1

?

?

??

Reference to analyses

Wright and Fiske, 1971, Do.

This paper, table 4. This paper, table 5. This paper, table 4.

Wright and Fiske, 1971, This paper, table 4.

Do. This paper, table 5. This paper, table 4.

Do. Do.

This naner. table 4.

table 6.

table 6.

See, footnotes at end of table.


TABLE 2. Historic eruptions of Kilauea Continued

Date of commencement

Year

1894.. ____.__.1894- -1911-24 .1918- . 1919

1919-20- -.1921 -1922 1923--- ---.1924----.---.

1924--__.--_.1927--.-.---.1929---.-----.1929- -1930----.--.

1931--------.1934.-. ___-._.1952-. -.__--.1954-----.1955--------.

1959------.I960-------.1961------.

1961---- .1962 .

1963 . .1963 - -.1965 _-._-.1965 .1967-__-----_.

1968 -1968 .1969 .1969- --.

Month and day

Mar. 21 -. July 7 ---.

Feb. 23- - -. Feb. 7___ .

._. Dec. 21

._. Mar. 18

.__ May 28__ _.

._- Aug. 25. ___ _-.

. . May 10 ___ ----.

._. July 19 -------

.-_ July 7- -

.__ Feb. 20-____ .

._ _ July 25- __ ________-. Nov. 19 - .

._- Dec. 23-.-- ___ _-.

.._ Sept. 6 .

._- June 27_ ___ .

.._ May 31- - .

.-. Feb. 28--- .

._- Nov. 14-.---------.

.__ Jan. 13- _ --_-_--_.

._- Feb., Mar., July

.- Sept, 22 _

... Dec. 7_-_ _ .

... Aug. 21-

... Oct. 5 .

. _ Mar. 5 _ _ _-

._- Dec. 24...- __ _--.

... Nov. 5- _

. _ Aug. 22_ . ._ _

.._ Oct. 7 _

.-. Feb. 22

._- May 24- -

Approx duration

6 +4(?)

14294

221721

17

1113

24

19

1433

1364

87

3837

1, 22, 7

33

11

101

238

4155

Continuing

Kilauea caldera . _ .-__. do Halemaumau lava lake _Kilauea caldera....do-- -------

Southwest riftKilauea caldera _ _ _ ___ ___East rift- __ _ _ _

doKilauea caldera

Halemaumau- . . _do do--- ----- _dO _ do _- --- --

.do - do _dO ___ _do - East rift _ _ - - .

Kilauea Iki - _ _East rift_ _ _ _ Halemaumau _ _ __

East rift _ _ - _ _ _ .do- -

-.-.do ------------ _dO ----- ___ _dO---_ -------.--do- ---------Halemaumau

East rift------- _ -do -- -- -do _- - do ----

Approx volume

(cumX10-8)

??

126

486.5?i_-_i2136.5

7.57.0

496.5

92

3911913.7

2.5.3

.87.7

17.6.8

8t

.017

172 >180

This paper, table 4.Do.Do.

This paper, table 5.This paper, table 4.

Wright and Fiske, 1971, table

This paper, table 4.


This paper, table 4.Do.

Wright and Fiske, 1971, table

Murata and Richter, 1966a.Do.

6.

5.

Richter, Ault, Eaton, and Moore,1964.

Do.Wright and Fiske, 1971, table

Do.Do.Do.Do.


6

1 Includes only lava above sea level. Estimates of lava that flowed into the ocean are given by Stearns and Macdonald (1946, footnotes to table, p. 111).

2 As of August 1971.

MINERAL CONTROL LINES

A control line is defined by linear variation of the chemical analyses of a suite of rocks plotted on an oxide-oxide plot. If a single-mineral species of lim ited compositional range is controlling the chemical variation, then it is a necessary but not sufficient condition that the control line extrapolate to the composition of that mineral plotted on the same ox ide-oxide diagram. The sufficient condition for sin gle-mineral control is that the control lines on all possible oxide-oxide plots for a given suite of rocks extrapolate to the composition of a single mineral. If the mineral controlling the chemical trends is of variable composition, then the trends will be curved rather than linear. If more than one mineral con trols the chemical variation, unique control lines will be defined only if the weight ratios among the minerals removed or added to produce the chemical variation are identical for all the lavas defining the

control lines. In general, this situation does not exist, so that it is rarely possible to define quantita tively a multimineral control. However, the sense in which deviations occur from lines that define domi- nantly a single-mineral control may indicate which additional mineral species is causing the chemical variation.

OLIVINE-CONTROLLED AND DIFFERENTIATED BASALT

Olivine control is a specific type of mineral con trol (see preceding definition). The best documented example of olivine control on lava compositions was described by Murata and Richter (1966a, b) for the 1959 eruption of Kilauea Iki.

Wright and Fiske (1971) were able to character ize as olivine-controlled lavas all those erupted at the summit of Kilauea and, in general, all Kilauea lavas whose compositions fall within the range of

PREVIOUS WORK

observed summit lava compositions. They found, empirically, that these olivine-controlled lavas all have 6.8 percent or more MgO; associated lavas having less than 6.8 percent MgO invariably plot well off the extensions of olivine control lines ex trapolated to lower MgO contents. These data sug gest that 6.8 percent is the minimum MgO content of a liquid which can crystallize only olivine for this suite of rocks; liquids of less than 6.8 percent MgO must have crystallized silicate phase (s) in addition to olivine, and thus their compositions cannot fall on olivine control lines. 1 For lavas erupted from Mauna Loa, a value of 6.8 percent MgO also sepa rates olivine-controlled rocks from those whose com positions cannot be explained by simple addition or removal of olivine. Thus, in this paper, lavas from both volcanoes having less than 6.8 percent MgO are defined as differentiated.

While olivine-controlled lavas of Kilauea and Mauna Loa all have more than 6.8 percent MgO, Hawaiian tholeiitic basalts having more than 6.8 percent MgO can result from processes other than olivine control. Wright and Fiske (1971), for exam ple, describe hybrid lavas in which MgO is greater than 6.8 percent, but such rocks are quite distinct chemically from olivine-controlled lavas having comparable MgO contents.

PREVIOUS WORK

The lavas of Kilauea and Mauna Loa have been recognized as tholeiitic basalts for decades. Cross (1915) summarized early analyses of Kilauea lavas in a normative classification, but he did not further interpret the data. Washington (1923a, b) reported new analyses and petrographic descriptions of Ki lauea and Mauna Loa lavas, from which he classi fied the lavas into three types which would now be called olivine-poor basalt, olivine basalt, and picrite. He also noted the similarity in compositions of Ki lauea and Mauna Loa lavas compared with those of lavas from other Hawaiian volcanoes. Powers (1935) dealt briefly with the petrographic character of Kilauea and Mauna Loa lavas, but Macdonald (1949a, b) was the first investigator to describe sys tematically the lavas of both volcanoes. Both Pow ers and Macdonald recognized the common presence of olivine as phenocrysts in contrast to the rarity of clinopyroxene phenocrysts. Macdonald pointed out

1 This empirical observation agrees well with the experimental work of Tilley and his co-workers. (See Thompson and Tilley, 1969, for a recent summary.) They show that clinopyroxene appears when the ratio of (FeO + FeaOs) to <MgO + FeO + Fe2O3 ) in the liquid is about 0.625. Kilauea and Mauna lavas in which MgO is 6.8 percent have a ratio of about 0.620.

that hypersthene is common in the lavas of Mauna Loa but nearly lacking in the lavas of Kilauea, and he noted that chemical analyses of rocks from the two volcanoes are very similar, although subtle yet systematic compositional differences might be sub stantiated as new analyses are reported (Macdon ald, 1949a, p. 72).

Powers (1955) made an important contribution to understanding the petrogenesis of lavas from Ki lauea and Mauna Loa when he recognized that (1) the general chemistry of rocks from each volcano could be explained by differences in olivine content, and (2) systematic chemical differences, particu larly in Si02 and CaO, exist between the historic lavas of Kilauea and the historic lavas of Mauna Loa. Powers concluded that chemically distinctive lavas, both historic and prehistoric, formed from separate "batches" of magma.

Tilley and Scoon (1961) presented new analyses of the contemporaneous 1868 eruptions of Kilauea and Mauna Loa which confirmed Powers' observa tion on the lime-silica differences. They also showed that, on a CaO-Si02 diagram, a straight line sepa rates hypersthene-bearing basalts (principally from Mauna Loa) from hypersthene-free basalts (princi pally from Kilauea). Other papers by Tilley (1960a, b; 1961) gave further definition to the hypersthene-bearing basalts and also treated the mechanism of magmatic differentiation at Kilauea.

Aramaki and Moore (1969) supported Powers' (1955) concept of separate batches of magma by proposing that the Kilauea lavas change composi tion with time in a more or less cyclical manner to explain observed changes in the ratio of K:Na with time.

Recently, Jamieson (1970) has discussed low- pressure fractionation of Kilauea and Mauna Loa lavas from a phase-equilibrium standpoint, and Murata (1970) has proposed a partial-melting model for the origin of Kilauea and Mauna Loa magmas.

METHODS OF STUDY SAMPLING

Samples were collected from nearly all historic lava flows from both Kilauea and Mauna Loa for which chemical analyses were not already available. Unaltered glassy pumice or spatter clots from source vents were collected where possible, because (1) they show most accurately the relations be tween preeruptive phenocryst minerals and magma and (2) the Fe203 :FeO ratio of such samples is probably closest to the value which was characteris tic of the magma prior to eruption. Samples also


were collected from many of the freshest and most readily identified prehistoric vents on both Kilauea and Mauna Loa and from the walls of Kilauea caldera, Makaopuhi Crater (Kilauea), and Moku- aweoweo caldera (Mauna Loa).

The localities at which I collected samples are lo cated on topographic maps (U.S. Geol. Survey 7^-min quad, ser.) by latitude and longitude (to the nearest minute) and elevation (table 23). Most localities for historic eruptions are shown on the geologic map of the Island of Hawaii (Stearns and Macdonald, 1946) and are identified by the date of the lava flow. More recent geologic maps which in clude flows sampled in this study are of the Kilauea Crater quadrangle (Peterson, 1967), Kau Desert quadrangle (Walker, 1969), and the Mauna Loa quadrangle (Macdonald, 1971). Unless otherwise noted, the samples were taken from mapped source vents or cones or from roadcuts. Additional infor mation is given for other samples. The localities of samples taken from the walls of pit craters and calderas, or from the active lava lake in Halemau- mau, are self-explanatory. Information on samples not collected by the author is contained in published references which are given in table 23.

In the course of this study, it was found that a few lava flows from Mauna Loa either are not iden tified or are mismapped on the geologic map of Ha waii (Stearns and Macdonald, 1946), the topo graphic sheets, or both. Evidence for these errors was initially obtained from study of high-altitude aerial photographs taken in 1954 and from helicop ter and ground traverses of flows. Additional evi dence was provided from chemical analyses. In all such situations, sufficient information is given in table 23 to enable re-collection at the same locality.

CHEMICAL ANALYSES

Table 23 lists samples of lavas from Kilauea and Mauna Loa which are cited in this paper and for which new analyses are given. Table 24 gives refer ences to published analyses, some of which are in cluded in this paper. All lavas considered in this study were analyzed in the Denver rock analysis laboratory of the U.S. Geological Survey under the direction of L. C. Peck. The estimated precision of the chemical data, precision being expressed as abso lute weight percent oxide, is as follows:

Si0 2 = ±0.04-0.08 A12O 3 = ±0.07-0.09

±0.05 -0.07 MgO = ±0.05CaO = ±0.03 -0.08

1 Total iron is calculated as FeO.

Na2O = ±0.02-0.045 K2O = ±0.015-0.02 TiO2 = ±0.03-0.045 P2O5 = ±0.005-0.01 MnO= 0.005

These precision figures were obtained empirically by comparing many analyses of single eruptions. The precision figures obtained in this way are some what lower than Peck's own estimates (L. C. Peck, 1964, p. 54). The conclusions of this paper rest on the assumption that, if two rocks differ in their chemical composition by more than twice the ana lytical precision in one or more constituents, the chemical difference must be explained by a petrolog- ical process or processes and is not a consequence of errors in the rock analysis.

COMPUTER REDUCTION OF CHEMICAL DATA

Three computer programs have been used in working with the chemical data.1. Chemical data are plotted on magnesia variation

diagrams using a computer-directed plotter. This program is written to plot any number of chemical oxides against a single oxide des ignated as the abscissa. The abscissa and ordi- nate scales are specified for each plot, as are the type and size of symbol for each data point. This program is titled "B844: Chemical Plot" and is available from the Computer Cen ter Division, U.S. Geological Survey, Wash ington, D.C.20242.

2. Differentiation calculations have been made by a computer program based on least squares and linear programing methods described by Wright and Doherty (1970). The operation of this program is similar to a computer pro gram described by Bryan, Finger, and Chayes (1969) and by Chayes (1968). The program is available as "C129: Mineral Distribution" from the Computer Center Division, U.S. Geo logical Survey, Washington, D.C. 20242.

3. Mineral control lines for suites of related analy ses have been computed using a program enti tled "BmDo5R Polynomial Regression," which computes linear regressions of the form y = ax + b. (Dixon, 1968)

OBSERVATIONS

The following sections summarize the petrogra phy and chemistry of lavas from Kilauea and Mauna Loa. The chemical data are plotted on MgO variation diagrams. For convenience in comparing different sets of lavas, average control lines have been computed and are plotted in some diagrams in place of the actual analyses. The data for the equa tion y=ax + b to define these control lines are given in table 3. Figure 2 summarizes the chemical varia bility of Kilauea and Mauna Loa lavas on magnesia

OBSERVATIONS

o0)

CO

O(N pi/5

s a.

O o>

c So -.-^ o;

13 s

S-S

i«i?&3^> *Q

c3 H

« H s

ft oa'A

« 2 3 S §

II

oO)

C3

I-

-I o> To «

-

ft «"'

111i-I e4 g

I 1 ! .&0 *" ^ ^

.a* ^3£ J5 " ^ ^ hw -P a; « «w co'.S | ° « S

tj, w ^ M

^s'slS a a> o

HH *

9n« M*S

§ i «^ ? ^ 3 02

O OO

CNOZ

O o U

E «w s«H O -S

CHEMISTEY OF KILAUEA AND MAUNA LOA LAVA IN SPACE AND TIME

TABLE 3. Data for equation y =ax+b to define mineral control lines for suites of olivine-controlled lavas from Kilauea and Mauna Loa

Lava suite (MgO meanand range,

in parentheses)

KilaueaPHKILCAL: Oli vine-con- 9.29

trolled prehistoric lavas, (6 . 80-17 . 06)Kilauea caldera and Hilinasections. 14 analyses aregiven in table 4.

PHSWPP: Prehistoric 13.76pahoehoe-picrite, south- (6 . 81-21 . 98)west rift zone. 1 1 analysesare given in table 5.

KI LI 840: Olivine-controlled 16.38lavas of the 1840 erup- (14. 18-17.54)tion, east rift zone. 4analyses given by Wrightand Fiske (1971).

KIL1959: 1959 eruption, 12.36 Kilauea Iki Crater. 20 (7 . 23-19 . 55)analyses are from Murataand Richter (1966a,table 1; unpub. data).

Mauna LoaHISTML: All olivine-con- 8.75

trolled lava flows of his- (6 . 85-23 . 64)toric age. 33 analyses aregiven in tables 8-13.

SiO 2

A12O 3"FeO"

CaO

Na2O

K 2O

TiO 2

P2O 5

SiO 2

A12O 3"FeO"

CaO

Na 2O

K 2O

TiO 2

P 2O 5

SiO 2

A12O 3"FeO"

CaO

Na2O

K2O

TiO 2

P2O 5

SiO2

A1 2O 3"FeO"

CaO

Na 2O

K 2O

TiO2

P 2O 6

SiO 2

AhOs"FeO"

CaO

Na 2O

K 2O

TiOt

P2O 5

-0.31687±.02126-.35384±.02785+.08139±.02986- . 26568±.01639-.06463±.00474-.01185±.00287-.05665±.01244-.00502±.00139

-.30625±.00752- . 35024±.00649+.07281±.01239-.27761±.00833-.05402±.00446-.01543±.00204-.06280±.00255-.00583±.00064

-.26643±.03596-.34318±.00654+ .07719±.05572-.31560±.03702-.05091±.00799-.00468±.00546-.05152±.02515-.00152±.00237

-.26637 ±.00469- . 32485±.00825+ .03520±.00297- . 28370±.00975-.05948±.00164-.01458±.00142-.07162±.00282- . 00708±.00034

-.31233±.01025-.33847±.00715+ .02494±.00581-.26347±.00501-.05872±.00314-.00508±.00180-.04405±.00353-.00394±.00099

+53.327

+16.585

+10.260

+13.044

+2.753

+ .497

+2.843

+ .259

+53.227

+ 16.635

+ 10.394

+12.993

+2.718

+ .581

+2.868

+ .270

+52.854

+ 16.359

+9.938

+ 13.800

+2.564

+ .427

+2.851

+ .210

+51.922

+ 15.945

+ 11.046

+ 13.674

+2.705

+ . 658

+3 . 263

+ .324

+54.200

+16.527

+ 10.747

+ 12.400

+2.702

+ .409

+2.380

+ .246

variation diagrams in which mineral compositions are plotted in addition to control lines for different suites of lavas. This figure is meant to aid the reader in following the description and interpreta tion of variations in lava chemistry.

Values of the ratio of K20:P205 have been com puted for all analyses and are entered in the tables of analytical data. This ratio is important in evaluat ing the processes by which the lavas of each volcano have evolved. (See Anderson and Greenland, 1969, for a discussion of P205 as an indicator of fractionation.)

KILAUEA

OLIVINE-CONTROLLED LAVAS

PETROGRAPHY

Chromite-bearing olivine is the only phenocryst mineral in most Kilauea lavas. Commonly the lavas contain more than 15 percent modal olivine and are properly termed picrites or oceanites (Macdonald, 1949a). A few lavas contain more than 30 percent modal olivine. Lavas with low magnesia content may contain scarce phenocrysts of plagioclase and even scarcer phenocrysts of augite in addition to olivine. Hypersthene is not a phenocryst mineral in olivine-controlled lavas, but hypersthene pheno crysts are found in some differentiated lavas (Wright and Fiske, 1971), and hypersthene also oc curs as a late crystallizing mineral in thick lava flows and intrusive bodies (Evans and Moore, 1968; Murata and Richter, 1961).

The three historic flows erupted in 1823, 1868, and 1919-20 from the southwest rift zone are unu sual in having glomeroporphyritic clots of inter- grown olivine, augite, and plagioclase. This texture is particularly well developed in the flows of 1823 and 1868. A similar texture also has been observed in lava from the later part of the 1967-68 eruption in Halemaumau lava lake (Kinoshita and others, 1969). The 1968 samples in which this texture was observed are from slow-moving flows that developed where the lava, which had been stored within the lake, oozed to the surface through cracks in the pre viously solidifed crust. Thus this texture can be at tributed to cooling of the melt at shallow depth (that is, within the lake) prior to eruption to the surface. By analogy, the glomeroporphyritic clots in the 1823, 1868, and 1919-20 lavas may also have been caused by cooling and crystallization while stored within either the rift zone or shallow summit magma reservoir prior to eruption on the rift.

The groundmass of Kilauea flows consists of pigmented glass, augite, pigeonite, plagioclase, magne tite, ilmenite, and apatite. Olivine is often partly re- sorbed in crystallized flows. Olivine and clinopyroxene are zoned from magnesian cores to more iron-rich rims, and plagioclase shows increas ing NaoO: CaO ratios toward the outer parts of the crystals.

OBSERVATIONS

CHEMISTRY

Analyses of lavas from Kilauea are given in ta bles 4 through 6 and are plotted in figures 3 to 6 on

MgO variation diagrams after-normalization to 100 percent dry weight. "FeO" is total-iron expressed as the sum of FeO and 0.9 Fe203 , calculated after nor malization of the analyses. The chemical data are

TABLE 4. Chemical analyses of olwine-controlled lavas from Kilauea summit[Additional sample data are given in table 23]

SiO 2 -- AljOs - ------

FeO-_-.- MgO - .CaO_. ---------Na 2O.- - KtO. ..........H 20+-- H2O-_ TiO2-_ PiOs---------MnO. ---------COj--.. -------CL--. ---------F -__ -_

Subtotal ____LessO---.

Total.- ...

KtO:P2O 5___--

Date _ .-- - .

SiO 2-- - __AUOa. ---------Fe2O3 -- -FeOMgO ------ .CaO.-- -------NajO------. K2O-. -__H 2O+--.- --H2O--.-_ ---_TiO 2_. ---------P2O 6- MnO. ---------CO.--.-.-..---Cl - - -F... -----------

Subtotal ____

Total.... .

K2O:P2O 6 .----

Date-- --- ._

SiO 2.-_ ..--_--.A1203.- -_-_Fe2O 3 FeO--- _. MgO .-_----.CaO- - -Na2O. --------K2O---_.-----.HiO+.. . HzO-. ..--. _TiO* -------P»Os MnO------ C02 -----Cl - F. ----------

Subtotal _ . Less O-- - ..

Total.- _

K2O:P2O 6---

--. 57F-

_ 49.--. 13.

3.9.

..-- 5-._ 10.

2.

... 3.

--. 100.

1.

1790

50.52 13.35 1.66

10.15 8.29

10.04 2.25

.45

.23

.05 2.63

.25 .18 .01 .01 .04

100.11 .02

100.09

1.80

1924

Hitina series

-18 57F-15 57F-17 57F-66 57F-97 53P-12

.63 48. ,76 11. 69 1. 31 10. .80 15 23 8. 74 1. 61 20 08 49 1. 35 19 02

10 100.

74 1.

1832

50.23 13.50 3.08 8.06 8.49

10.89 2.18

.45

.14

.03 2.44

.24 .17 .04 .01 .04

99.99 .02

99.97

1.87

1931-32

,53 49.40 50.59 50.77 50.98 .15 12.46 13.20 13.46 13.75 15 1.51 1.49 2.07 3.38 71 10.25 9.92 9.24 8.04 .17 10.96 8.38 8.14 7.18 94 10.32 10.88 10.76 11.17 76 2.05 2.19 2.23 2.34 ,33 .38 .39 .38 .43 14 .25 .32 .07 .01 03 .01 .04 .01 .05 91 2.21 2.40 2.51 2.52 18 .22 .23 .24 .23 18 .18 .18 .17 .17 01 .02 .02 .02 .00

19 100.22 100.23 100.07 100.25

83 1.73 1.69 1.59 1.87

1866 1868 1877(?) ___________

Caldera Keanakakoi

50.57 50.57 50.70 50.46 14.26 13.88 13.76 13,96 2.18 1.80 5.54 1.84 9.11 9.50 6.21 9.20 6.61 7.37 7.42 7.38

11.19 10.99 10.69 11.29 2.41 2.27 2.28 2.26

.50 .44 .41 .48

.01 .07 .16 .10

.02 .02 .04 .03 2.70 2.46 2.42 2.61

.26 .25 .23 .25 .17 .17 .17 .17 .03 .01 .01 .01 .01 .01 .01 .01 .04 .04 .04 .04

100.07 100.03 100.09 100.09 .02 .02 .02 .02

100.05 100.01 100.07 100.07

1.92 1.76 1.78 1.92

1952 1954

53P-32

50.52 13.82 3.58 7.90 7.13

11.12 2.20

.44 .26 .06

2.65 .23 .17 .01

100.09

1.91

1879

53P-9

50.41 14. 8 1.98 9.31 6.88

11.22 2.32

.52

.07

.05 2.78

.26 .17 .00

100.05

2.00

1959

Prehisitoric

53P-33 53P-35 53P-30

50.73 13.74 1.83 9.45 7.23

11.22 2.20

.46

.14

.02 2.62

.22

.17

.01

100.04

2.09

1884-85

53P-1 i

50.36 14.02 2.82 8.68 7.12

11.10 2.18

.50

.13

.02 2.64

.25 .18 .00 .01 .04

100.05 .02

100.03

2.00

50.94 51.47 14.04 14.53 2.67 1.32 8.20 9.08 7.24 7.12

11.29 11.18 2.23 2.38

.40 .39 .11 ,08 .04 .01

2.46 2.25 .21 .20 .16 .16 .00 .00

99.99 100.17

1.90 1.95

1889 1911

53P-2 . _

49.97 49.67 13.69 13.61 1.38 1.35 9.63 9.76 8.33 8.84

11.23 10.95 2.21 2.22

.48 .48

.06 .02

.03 .03 2.54 2.63

.23 .25 .17 .17 .00 .00 .01 .01 .03 .04

99.99 100.03 .01 .02

99.98 100.01

2.08 1.92

1961

Puna series

HIGS-2 8X002-0

51.52 14.10 1.70 9.28 6.79

10.92 2.34

.42 .08 .03

2.37 .23 .17 .02 .01 .03

100.01 .01

100.00

1.83

1917

50.08 13.73 1.32 9.79 7.89

11.50 2.18

.56

.00

.02 2.60

.26 .17 .01 .00

100.11

2.15

51.04 14.30 1.59 9.41 6.93

10.78 2.40

.46

.23

.04 2.43

.24

.17

.00 .02 .04

100.08 .02

100.06

1.92

1918

50.02 13.87 1.23 9.86 7.77

11.42 2.23

.53

.06

.02 2.63

.26

.17

.02

.01

.04

100.14 .02

100.12

2.04

8X038-0

51.11 14.67 1.40 9.02 7.35

11.29 2.24

.33

.05 .03

2.10 .19 .17 .00 .01 .03

99 99!oi

99.98

1.74

8X067-0

49.07 12.28 1.16 9.74

13.23 9.75 1.89

.30

.08

.04 2.00

.17

.17

.00

.01

.04

99.93 .02

99.91

1.76

1919

Glass

50.02 13.87 1.35 9.76 7.45

11.45 2.33

.53

.08

.02 2.70

.26

.17

.02

.02

.04

100.07 .02

100.05

2.06

Flow

50.20 14.04 1.83 9.50 7.03

11.49 2.25

.57

.01

.02 2.74

.27

.17

.02

-----

100.14

2.11

8X078-0

47.97 10.48 1.67

10.04 17.03 8.30 1.67

.31

.14

.04 1.98

.18

.17

.01

.01

.03

100.03 .01

100.02

1.82

1921

50.04 13.68 2.29 9.05 7.61

11.38 2.24

.57

.00

.02 2.76

.27

.17

.06

--_-.

100.14

2.11

November 1967-July 1968

February July1

49.73 13.66 1.19 9.72 8.24

11.60 2.26

.54

.06

.02 2.68

.25

.17

.01

.02

.04

.100.19 .02

100.17

2.16

1931HM

49.71 13.58 2.48 9.03 7.46

11.58 2.26

.53

.12

.00 2.78

.25

.17

.00

.02

.06

100.03 .03

100.00

2.12

1952HM ____- TLW67-42 S 1

50.01 50.20 50.09 49.91 13.83 13.73 13.79 13.00 1.85 2.65 1.80 2.56 9.59 8.80 9.59 8.86 7.10 7.20 7.31 8.08

11.29 11.56 11.51 11.92 2.25 2.25 2.28 2.13

.53 .57 .53 .55

.09 .00 .08 .09

.12 .00 .02 .02 2.71 2.72 2.68 2.62

.27 .28 .26 .25

.17 .17 .17 .17

.00 .01 .01 .01 ----- .02 .01 .02 ----- .05 .05 .04

----- 100.21 100.18 100.23 ----- .02 .02 .02

99.81 100.19 100.16 100.21

1.96 2.04 2.04 2.20

S-2

50.07 13.70 1.39

10.00 7.23

11.55 2.30

.60

.00

.02 2.75

.28

.17 .00 .02 .04

100.12 .02

100.10

2.14

Average2

47.90 10.96 11.51

15.42 9.33 1.79

.44

2.16 .23 .18

----.

100.00

1.91

50.22 50. 13.64 13. 1.29 1. 9.63 9. 7.74 7.

11.34 11. 2.32 2.

.55

.04

.04 2.76 2

.27 .17 .01 .02 .04

100.08 100 .03

100.05 100.

2.04 2,

... 1967HM

,38 50.24 69 13.56 ,38 1.36 .60 9.95 .52 7.59 .34 11.06 ,33 2.31 54 .54 02 .04 01 .01 .77 2.65 .27 .26 17 .17

.01 .01

.02 .01

.04 .03

.09 99.79

.02 .01

07 99.78

.00 2.08

HM68-2

50.18 13.63 1.66 9.72 7.63

11.02 2.25

.54

.10

.01 2.57

.25 .17 .01 .01 .05

99.80 .02

99.78

2.16

HM68-4

50.48 13.52 1.49 9.95 7.41

11.08 2.31

.52

.04

.02 2.69

.28 .17 .02 .01 .04

100.03 .02

100.01

1.85

HM68-12

50.24 13.70 1.61 9.77 7.58

11.17 2.29

.53

.02

.00 2.62

.25

.17

.01

.01

.04

100.01 .02

99.99

2.12

HM68-15

50.25 13.61 1.49 9.86 7.63

11.14 2.32

.55

.06

.00 2.62

.26

.17

.00

.02

.06

100.03 .03

100.00

2.11

1 Average of three analyses (Richter and others, 1964, table 1). 2 Weighted average of the entire eruption converted to 100 percent dry weight. Data from Murata and Richter (1966a) and Richter and Moore (1966).

10 CHEMISTRY OF KILAUEA AND MAUNA LOA LAVA IN SPACE AND TIME

0.6

K 2 0 0.4

0.2

0.0

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

12.0

Na,0

10.0

CaO

9.0

80

7.0

6.0

5.0

P2 0 5

Ti02

0.2

0.0

3 0

2.8

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1 ?

t 1 ""::^^^* 1 :

^

: xx*1? :- // />^ ~'' ^*^ *

/' ^ X

''*^^ *'. x :--~ i i i i i i i i i i i i i i i i i i i "

12.0

"FeO"

110

100

1 1 1 1 1 1 1 1 1 1 1 1

i i i i i i i i i i i i i i i I 60

15.0

14.0

130

y /

15

MgO

5 25 15

MgO

12.0

AI 2 0 3

c^o

100

9.0

8.0

7.0

53.0

520

510

50.0

SlO,

49.0

48.0

47.0

46,0

FIGURE 3. MgO variation diagrams showing lavas erupted at Kilauea summit. Analyses are given in table 4. Control lines are as shown in figure 2. , prehistoric lavas, Hilina Pali; X, prehistoric lavas, Kilauea caldera; O, 20th century lavas (except 1959), Kilauea caldera. Analyses are plotted after normalization to 100 percent dry weight.

OBSERVATIONS 11

TiO,

04

P2 0 5 0.2

0.0

3.0

2.8

2.6

2.4

22

20

1.8

1.6

1.4

12

0.8

06

K,0 0.4

0.2

0.0

26

24

22

2.0

18

1.6

14

I.2

120

II.0

i i i i i i i i i i i i i i i i i i 1_

12.0

"FeO"

2

Na,0

*/

i i i i i i i i i i i i i i i i L_J L.

10.0

16.0

150

14.0

130

12.0

10.0

9.0

8.0

CaO

9.0

8.0

7.0

6.0

5.0

xP

5* X

V

520

51.0

50.0

SiO,

490

48.0

47.0

46.015

MgO

5 25 15

MgO

FIGURE 4. MgO variation diagrams showing lavas erupted from the Kilauea southwest rift zone. Analyses are given in table 5. Control lines are as shown in figure 2. X, prehistoric regional pahoehoe picrite; , younger prehistoric lavas; O> 1920 lava.


TiO,

Na,0

12.0

"FeO"

I I I I I I I I I I I I I I I I I ]QQ

-I i i i i | i i i i i i i i i I i i 15.0

14.0

11.0

100

CaO

9.0

8.0

7.0

6.0 -

5.0

1 1 1 1

f S

X

13.0

12.0

11.0

i i i i i i i i i

90

80

70

6.0

52.0

490

SiO,

48.0

47.0

460

45015

MgO5 25 15

MgO

FIGURE 5. MgO variation diagrams showing lavas erupted from the Kilauea east rift zone. Analyses are given in table 6. Control lines are as shown in figure 2. Analyses of historic eruptions and young submarine eruptions are given in Wright and Fiske (1971). X, prehistorie-Makaopuhi lava- lake chill zone (Moore and Evans, 1967); , other prehistoric (subaerial) flows.

OBSERVATIONS 13

04

P2 0 5 02

00

30

Ti02

I 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1

"FeO"

no

0.6

K2 0 04

0.2

00

2.6

2.4

2.2

2.0

18

16

14

12

12.0

Na,0

i i i i i i i i i i i i i i i i i i i

150

140

Al,0,

100

90

80

100

CaO 90

80

70

60

50

T i i I I i i i i i i i i i i i i r

4 '

1 1 1 1 1 1 1 1 1 1 1

520

510

500

SiO?

490

480

470

15

MgO5 25 15

MgO

FIGURE 6. MgO variation diagrams showing Kilauea lavas erupted in 18th and 19th centuries. Anal yses are gives in tables 4 and 5 and Wright and Fiske, 1971 (1840 east rift ruption). Control lines are as shown in figure 2. O. Kilauea caldera 1790-1894; , 1868 eruption, southwest rift zone; X, 1823 eruption, southwest rift zone; , 1790 and 1840 eruptions, east rift »zone.


TABLE 5. Chemical analyses of olivine-controlled lavas from Kilauea southwest rift zone[Additional sample data are given in table 23]

Prehistoric

SiOt-- Al*Os--- -

FeO.. .MgO ....... .CaO -Na*O. -- .K*0 .... H*0+ HiO-. ........TiOi .- ..PzOt - .MnO .. ------COi..... .--Cl. ------------F... ...........

Subtotal .... LessO ...----.-

K*O:P2O5

Regional pahoehoe-picrite complex

'LW67-138A TLW67-139 TLW67-140 TLW67-128 TLW67-134 TLW67-136B TLW67-3 KD-3 KD-32 KD-56 KD-57 KD-91

46.60 11.12 2.84 9.27

16.73 8.05 1.74

.40

.55

.03 2.09

.22

.17

.01

.01

.03

99.86 .01

99.85

1.82

49.48 50.05 51.08 51.08 48.60 47.83 51.15 46.57 49.06 47.88 50.21 13.38 12.96 13.76 14.28 11.63 10.39 14.11 8.95 12.14 10.67 13.67 2.41 1.44 1.37 1.51 1.23 1.43 1.91 1.56 1.06 1.09 1.69 9.18 10.00 9.90 9.49 10.14 10.44 8.86 10.38 10.28 10.74 9.95 9.11 9.99 7.38 6.80 14.72 17.43 7.20 21.97 13.30 17.20 7.95

10.01 9.94 10.78 10.91 8.89 8.01 10.88 6.81 9.50 8.13 11.26 2.07 2.16 2.32 2.39 2.03 1.73 2.39 1.59 1.95 1.79 2.36

.40 .40 .40 .47 .34 .32 .54 .28 .36 .33 .45

.65 .12 .12 .18 .19 .11 .15 .16 .12 .16 .04

.08 .04 .05 .03 .02 .03 .05 .03 .01 .00 .00 2.62 2.33 2.41 2.48 1.90 1.73 2.36 1.52 1.98 1.81 2.48

.24 .21 .22 .25 .19 .16 .21 .15 .19 .18 .22

.18 .17 .17 .17 .17 .17 .16 .17 .16 .17 .17

.01 .01 .01 .00 .00 .01 .01 .01 .00 .00 .00

.01 .01 .01 .01 .01 .01 .00 .01 .00 .00 .01

.03 .02 .04 .04 .03 .03 .03 .02 .03 .03 .03

99.86 99.85 100.02 100.09 100.09 99.83 100.00 100.18 100.14 100.18 100.49 .01 .01 .02 .02 .01 .01 .01 .01 ,01 .01 .01

99.85 99.84 100.00 100.07 100 08 99.82 99.99 100.17 100.13 100.17 100.48

1.67 1.90 1.82 1.88 1.79 2.00 2.57 1.87 1.89 1.83 2.05

Prehistoric Continued

Regional pahoehoe-picrite complex Regional Continued pahoehoe(-) Younger flows

SiO*_._ . A1*O»-. ----------

FeO.. ..-. -------MgO ..........CaO - _ Na2O..-. --------K*O.-- - H*0 + ..........HjO-. ....... ...TiO* P*0« . .MnO..... ....CO*... -_ -.Cl - .-F._... ...........

Subtotal ....LessO.--..-- _ .

Total.... ..

KZO:PZOS _. ----..

Date _ ----- .

SiO*. _.-. .AhOa- ...Fe*Os ---------FeO.. ------..MgO ------CaO.- -Na*O.--.--..--K*0. ...H*0+- .-.H*O-. .--..-... .TiO*. - _ P*0._- _._ MnO ---------CO*.......--....Cl... --...-. ....F...-. ...........

Less O --

Total ,--....

K*0:P206 - .......

-. TLW67-129

47.329.691.34

10.6719.687.661.72

.27

.06

.001.70.15.17.00.00.03

100.46.01

100.45

1.80

A AC-1

-. 50.8813.84

.76.. 10.50

7.2411.152.27

.43

.11

.032.42

.24

.18

.01

.01

.03

.- 100.10.01

-. 100.09

1.79

KD-143 KD-144 TLW67-10 KD-164 KD-172 KD-45 KD-161 TLW67-16 CC-SW TLW67-18 TLW67-28 KD-130

47.69 50.76 50.64 49.83 50.96 51.12 50.54 50.30 51.11 51.15 50.52 50.90 10.38 13.81 13.79 12.72 14.04 14.05 14.05 13.51 13.75 13.52 13.41 13.92 1.08 1.33 1.38 1.57 1.46 1.23 1.65 11.06 1.25 2.23 1.15 1.24

10.98 10.08 9.72 9.72 9.61 9.90 9.61 1.46 9.92 9.18 10.22 9.79 17.56 7.64 7.79 11.04 7.70 7.32 7.47 7.28 7.62 7.65 9.10 7.72 8.15 10.75 11.10 10.14 10.92 10.85 10.85 10.75 10.63 10.17 10.23 10.87 1.62 2.27 2.24 1.87 2.26 2.29 2.34 2.36 2.28 2.22 2.24 2.32

.26 .42 .46 .42 .39 .40 .34 .40 .41 .36 .36 .41

.16 .24 .07 .18 .00 .07 .32 .07 .13 .47 .14 .00

.03 .02 .02 .01 .00 .01 .01 .02 .06 .26 .05 .04 1.73 2.40 2.43 2.21 2.30 2.42 2.48 2.36 2.40 2.22 2.22 2.37 .16 .22 .23 .19 .23 .23 .23 .23 .23 .22 .20 .22 .17 .17 .17 .17 .17 .17 .17 .17 .17 .16 .17 .17 .01 .01 .01 .01 .01 .01 .00 .00 .01 .01 .01 .00 .00 .01 .01 .01 .01 .01 .01 .00 .01 .01 .01 .01 .02 .03 .04 .03 .03 .04 .04 .03 .03 .04 .03 .03

100.00 100.16 100.10 100.12 100.09 100.12 100.11 100.00 100.01 99.87 100.06 100.01 .01 .01 .01 .01 .01 .02 .02 .01 .01 .02 .01 .01

99.99 100.15 100.08 100.11 100.08 100.10 100.09 99.99 100.00 99.85 100.05 100.00

1.63 1.91 2.00 2.21 1.70 1.74 1.48 1.74 1.78 1.64 1.80 1.86

1823 1868 1920

1823-SW TLW67-24 1868-SW TLW67-12 1920-231-3 TLW67-1 TLW67-4 TLW67-6 TLW67-9

50.77 50.87 50.63 51.35 50.18 49.85 49.74 50.21 49.82 13.87 13.88 13.61 13.81 14.12 13.48 13.23 13.87 13.32 2.08 1.36 1.56 1.13 1.17 1.22 1.36 1.24 1.39 9.28 9.90 9.27 10.22 9.86 9.97 9.85 9.72 9.86 7.27 7.27 8.61 6.78 7.14 8.49 9.21 7.48 8.88

11.06 10.93 10.86 10.52 11.57 11.24 10.99 11.50 11.04 2.27 2.27 2.20 2.39 2.30 2.24 2.15 2.28 2.14

.46 .43 .45 .50 .53 .47 .49 .51 .49

.13 .19 .10 .10 .07 .03 .02 .03 .09

.03 .03 .02 .00 .02 .00 .01 .01 .01 2.41 2.42 2.39 2.80 2.70 2.59 2.55 2.68 2.55

.24 .22 .27 .24 .26 .23 .23 .25 .24

.18 .17 .17 .17 .17 .17 .17 .17 .17 .01 .01 .01 .01 .01 .03 .00 .01 .01 .01 .01 .01 .01 .01 .01 .00 .01 .01 .04 .04 .03 .04 .04 .04 .04 .04 .04

100.11 100.00 100.19 100.07 100.15 100.06 100.04 100.01 100.06 .02 .02 .01 .02 .02 .02 .02 .02 .02

100.09 99.98 100.18 100.05 100.13 100.04 100.02 99.99 100.04

1.92 1.95 1.67 2.08 2.04 2.04 2.13 2.04 2.04

grouped according to the age of the lava and the lo cation of the vents from which the lava was erupted. Chemical variation within each group of lavas is approximately linear on these plots. The

slopes of the lines are negative with the exception of the FeO-MgO plot. The control lines for different groups of lavas have similar slopes, but many of the lines are displaced relative to one another on one or

OBSERVATIONS 15

TABLE 6. Chemical analyses of olivine-controtted lavas of prehistoric age from Kilauea east rift zone[Additional sample data are given in table 23. Olivine-controlled lavas of historic age were erupted in 1790(-) and in 1840. Analyses of these lavas are given in

Wright and Fiske (1971, table 4)]

Makaopuhi Crater wall

SiO^.. ..................M,03 .. .................Fe_0 3 --_ ----------FeO. __ ___-___--_MgO.. ... _.CaQ- __-__-_-__ _..Na20_-_--__. -.-......K2O__ ___-_____-_.H 20 + ____- ___ .H20-_ ................TiOi . _-- - --.P205 - MnO. ......-......___.C02------------ .......Cl.... ..................F____ ..................

Subtotal- _--. ...Less O_ _______ . ____..

Total.. -__-.___-__ ..

KiO:P_0._. ..._._...._.

.--.------- TLW67-39

.- ---. 50.75

.-___.___ 14.00-_---._ 2.13.-_.___.. 9.49 ___ . 6.85.-_.-____ 10.54-..__.___ 2.47...._-... .51.-.._-___ .14.-__...__ .00.--.-_.._ 2.75._.___.__ .26.--_--.__ .18.----..._ .00.-----._. .01------- .04

100.12.-_..__._ .02

..._...__ 100.10

--_-__-. 1.96

TLW67-40

50.49 13.30 2.55 9.00 8.45

10.54 2.25

.41

.11

.03 2.58

.24

.17

.00

.00

.03

100.13 .01

100.12

1.71

TLW67-130

50.57 14.00 2.31

10.10 6.11

10.31 2.43

.51

.34

.02 2.91

.28

.18

.00

.01

.04

100.12 .02

100.10

1.82

TLW67-131

49.40 12.74 1.50

10.17 10.04 10.23 2.21

.52

.07

.02 2.67

.25

.17

.00

.01

.04

100.04 .02

100.02

2.08

TLW67-132A

50.43 13.44 2.53 9.17 8.09

10.83 2.24

.45

.04

.01 2.53

.23

.17

.01

.00

.03

100.20 .01

100.19

1.96

Makaopuhi lava lake chill zone

MP-57

50.0213.24 3.19 8.55 8.71

10.61 2.13

.41

.15

.08 2.53

.24

.18

.00

.01

.04

100.09 .02

100.07

1.71

more graphs. Three general time-related chemical groupings are apparent, when compositions at any given MgO content are compared: 1911-present, 1750-1894, and prehistoric (older than 1750). On many of the oxide plots, the 20th century and pre historic lavas are distinguished with little or no ov erlapping of data points (figs. 3 and 4). The compo sition of lavas erupted in the late 18th and throughout the 19th century lies generally between these two groups, but many data points fall within the range of prehistoric or 20th century composi tions on one or more of the oxide plots (fig. 6).

There are two exceptions to the general time-re lated variation. Olivine-rich spatter from Puu Kole- kole, a prehistoric cone on the southwest rift zone (TLW 67-138A, table 5, plotted in fig. 4 at MgO equals 16.86), has a chemistry which falls on the 20th century olivine control line on many of the MgO plots. The 1840 eruption on the east rift zone (fig. 6) stands out by having higher Si0 2 and lower FeO than other 19th century lavas and most of the lavas in the prehistoric sections.

Within the three time-groupings, lava chemistry can be compared as a function of vent location. The chemistry of prehistoric lavas erupted at the sum mit and on the southwest rift zone is sufficiently similar (figs. 3 and 4) that an unambiguous correla tion of composition with eruptive vents is not possi ble. Likewise, historic lavas erupted in the same time span at Kilauea summit and from the south west rift zone proper have a similar chemistry

(figs. 3, 4, and 6). The Hilina-Pali-Kilauea caldera prehistoric lavas and the lavas of the 1959 eruption(fig. 3) are close to the extremes of the time-related chemical variation in olivine-controlled Kilauea lavas.

The relations observed for the southwest rift lavas do not hold for the east rift lavas. Some lavas of prehistoric age and all but two of the historic lavas may be chemically distinguished from lavas erupted at the summit and on the southwest rift zone within the same general time span (Aramaki and Moore, 1969; Wright and Fiske, 1971). The chemistry of east rift lavas is controlled by a com plicated differentiation pattern superimposed on the time-related chemical changes. This differentiation pattern is described and interpreted in a separate paper (Wright and Fiske, 1971).

DIFFERENTIATED LAVAS

The composition of typical differentiated lavas from Kilauea is described elsewhere (Wright and Fiske, 1971). Two additional lavas, one of prehisto ric and one of historic age (table 4, analysis 57F-18, and table 5, analysis TLW67-12), fit the definition of differentiated lava for the present study (MgO is less than 6.8 percent). TLW67-12 is an exceptionally glassy sample of the 1868 eruption; its chemical composition is related to that of a more normal porphyritic sample of the same eruption by removal of the observed phenocryst assemblage olivine-augite-plagioclase. 57F-18 has a peculiar


TABLE 7. Modal data for selected porphyritic lavas from Mauna Loa

Phenocrysts:4 Olivine. __ ____ .

Total-..------.

Microphenocrysts :4

Hypersthene.

Total.----.---.

Glass 4 --

Total.-.------.

... TLW67-66'

0.35

1.352.80

4.50

Trace01.00

.90

1.90

.00... 93.60

.__ 93.60

... 100.00

1843

W-A-22 i

0.35

1.553.00

4.90

001.803.90

5.70

.0089.40

89.40

100.00

W-A-23 i

0.200

.401.25

1.85

.6003.703.90

8.20

86.703.25

89.95

inn on

i?TLW67 64 2

0.35.20

00

.55

.05

.40

.450

90

98.15.40

98.55

inn on

$81

W-A-6 2

2.601.00

.45

.30

4.35

.05

.653.905.95

10.55

no85.10

85.10

100.00

1TLW67-58 2

01.951.11.05

4.10

.85

.153.951.40

6.35

77.9511.60

89.55

100.00

887

TLW67-59 3

01.402.45

.55

4.40

.4501.051.30

2.80

84.658.15

92.80

100.00

1907

TLW67-56

0.05.40.70.65

1.80

.10

.106.655.05

11.90

83.402.90

86.30

100.00

I960

TLW67-75 '

0.60.55.30.05

1.50

.55

.051.051.20

2.85

94 101 55

95.65

100.00

Number of points (0.3X0.3mm grid). 2785 2700 2000 2000 3000 2000 2000 2000 3000

1 Chemical analysis given in table 13.2 No chemical analysis available for these particular samples. TLW67-64 is

probably equivalent in composition to sample (1881-10,000 ft) in table 10; TLW67-58 is probably equivalent in composition to TLW67-59.

3 Chemical analysis given in table 9.4 Modal counting was subdivided as follows:

Phenocrysts: Euhedral crystals generally in excess of 1 mm in the longest dimension

chemistry that cannot be ascribed to processes of ei ther fractionation or mixing of magmas as de scribed by Wright and Fiske (1917). Its origin re mains problematical.

MAUNA LOA

OLIVINE-CONTROLLED LAVAS

PETROGRAPHY

Olivine is commonly the dominant phenocryst mineral in lavas from Mauna Loa, and, like Ki- lauea, modal olivine ranges from trace amounts to more than 30 percent. In contrast to Kilauea, phenocrysts of olivine are generally accompanied by phenocrysts of hypersthene, augite, and plagioclase. Such lavas are especially common on the southwest rift zone. Some glassy samples also contain quench (?) crystals of pigeonite distinguished by a low optic angle, extreme undulatory extinction, and aci- cular habit. The rims of pyroxene and plagioclase phenocrysts tend to be strongly zoned toward more iron-rich and more sodic compositions, respectively. Modal data for selected porphyritic flows other than picrites are summarized in table 7.

The groundmass of Mauna Loa flows consists of pigmented glass, augite, pigeonite, plagioclase, mag netite, ilmenite, and apatite. Olivine shows irregu lar, embayed borders against the groundmass. Hy persthene phenocrysts are invariably rimmed by augite (Muir and Long, 1965), even in rapidly

which can be inferred to be present in the magma chamber prior to eruption tothe surface.

Microphenocrysts: Euhedral crystals smaller than 1 mm in largest dimension whichmay have grown during ascent of magma to the surface.

Glass: Transparent, isotropic quenched liquid. Quench: Fine skeletal or fibrous microlites that are presumed to have formed during

cooling after extrusion on the surface.

quenched glassy samples, and hyersthene is not found as a constituent of the groundmass.

CHEMISTRY

Chemical analyses of olivine-controlled Mauna Loa lavas are given in tables 8 through 12 and are plotted in figures 7 through 10 according to age and location on the volcano.

The Mauna Loa analyses define control lines whose slopes are similar to those defined by analy ses of lava suites from Kilauea. MgO also covers ap proximately the same range as Kilauea, from under

TABLE 8. Chemical analyses of olivine-controlled lavas from Mauna Loa summit

[Additional sample data are given in table 23]

Prehistoric,

Sample......-.,-7D-014 7D-026 7D-420 7D-428 TLW67-84 TLW67-70B

SiOj ----------AHOa- --------FeiOj-----.-----FeO ----------MgO-------CaO---------.--NajO ---------KzO. ---------H 20+ ----------H 2O- ----------TiO2----~ -----PiO«.-- -- MnO --------CO». --- .Cl.__- -----F_ . _ -

Subtotal.Less O __ __-.--

49.0510.601.34

10.0016.907.971.70

.29

.14

.021.65

.16

.17

.01

.00

.04

100.04.02

51.7114.104.626.556.70

10.522.22

.43

.44

.072.16

.22

.17

.00

.01

.03

99.95.01

52.0214.292.608.696.13

10.242.33

.52

.33

.042.27

.26

.17

.02.01.05

99.97.02

51.7513.762.348.687.34

10.202.32

.47

.31

.052.10

.27

.17

.00

.01

.04

99.81.02

48.9910.861.759.36

16.228.191.80

.32

.11

.011.75

.17

.17

.01

.01

.02

99.74.01

52.0314.201.609.256.92

10.502.33

.46

.09

.052.12

.25

.17

.01

.01

.03

100.02.01

Total.

K 2O:P2O 5 .

100.02 99.94 99.95 99.79 99.73 100.01

1.81 1.95 2.00 1.74 1.88 1.84

OBSERVATIONS 17

TABLE 8. Chemical analyses of olivine-controlled lavas from Mauna Loa summit Continued

Date........ 1877(?) 1880(?) 1940 1942 1949a 1949b

Sample. ..... TLW67-88 TLW67-89 1940ML TLW67-68 M-56-2 1949ML

SiO. __ ----- 52.09 51.26 52.01 51.87 52.16 52.04 AhOs. __ ..- 14.29 12.76 14.09 14.11 14.13 13.94FejO!...--.. 1.58 1.25 1.46 1.50 1.12 1.58FeO ------ 9.25 10.08 9.77 9.63 9.90 9.69MgO-------- 6.84 10.73 7.04 7.11 7.07 7.14CaO.. ------ 10.61 9.35 10.74 10.51 10.53 10.63Vra _{"\ o ^9 9 flfi 9 9^ 9 9^ 9 97 9 9^

KjO ------ .41 .30 .35 .36 .40 .33H2O+._ ___ .14 .01 .02 .06 .02 .01HiO- ___ .. .03 .03 .00 .01 .00 .02TiO2-_--. 2.01 1.74 2.08 2.03 2.04 2.05P^Os.. ...... .23 .23 .24 .21 .21 .26 MnO-.----- .16 .17 .18 .17 .17 .18COa... ...... .00 .01 .00 .01 .00 .00Cl_-._ -----. .01 .01 .00 .01 ----- .01F__ ________ .03 .02 --.-_ .04 .02 _____

Subtotal. 100.00 100.03 ..... 99.86 100.04 .....Less O. .. . .01 .01 ..... .02 .01 . .

Total.... 99.99 100.02 100.21 99.84 100.03 100.13

KzOtPiOs-.. 1.78 1.30 1.46 1.71 1.91 1.27

TABLE 9. Chemical analyses of olivine-controlled lavas from Mauna Loa south rift zone


Prehistoric

Sub- Kahuku Kau marine

Series Series lavas

Sample. __.__ E2145 E2146 C819 C820 65MAN-1 65KUH-2 13

SiO2 - ----- 51.25 50.87 46.19 48.71 50.26 51.34 48.50AhOs ----- 13.66 13.12 7.94 15.07 12.00 13.13 10.45Fe2Os---- - 2.33 5.93 6.11 4.11 2.30 2.23 1.69FeO _ ------ 8.79 5.53 6.52 8.55 8.82 8.80 9.41MgO.___-.._ 7.89 9.46 24.20 6.04 13.08 9.92 17. 83CaO. ....... 10.22 9.81 5.76 10.19 8.87 9.74 7.72Na2O __ .... 2.37 2.26 1.23 2.43 1.96 1.95 J1.76KzO ....... .44 .30 .28 .36 .34 .37 .32H 2O+ --._ .32 .17 .14 .84 .13 .10 .52H2O-_ ...... .09 .07 .05 .39 .02 .03 .05TiO... ---___ 2.22 2.17 1.24 2.78 1.65 1.82 1.59P2O6-.------ .26 .23 .15 .28 .19 .24 .16MnO____.___ .17 .17 .17 .18 .17 .17 .17CO.-.-..-.-. .05 .01 -.-_- --.-. .01 .02 .02Cl.. ........ ----- ----- ----- .---. .01 .01 i.03F-. -_----.._ ----- -_.-. .01 .02 .02 .06 -----

Subtotal. --_-. .-._. 99.99 99.95 99.83 99.93 100.21LessO-.-. - -_--. -.-. .00 .01 .01 .03 .02

Total-... 100.06 100.10 99.99 99.94 99.82 99.90 100.19

K2O:P2Os--- 1.69 1.30 1.87 1.29 1.79 1.54 2.00

Date ..... _..-_ 1868 1887

Sample---.----.- W-A-6 W-A-7 W-A-8 1868ML H-19 TLW67-59

SiO_. _ -... .... 51.02 51.23 51.51 46.75 50.58 52.07

Fe2O 3.--__------ 1.18 1.27 2.23 2.29 1.65 1.37FeO- --..-.--.-- 9.88 9.76 8.82 9.27 9.35 9.63MgO.---....-.-_ 9.30 8.81 9.23 23.58 11.08 7.47CaO-----..---.. 9.89 10.02 9.86 6.21 9.44 10.20Na2O- -_--.---- 2.19 2.21 2.14 1.32 2.01 2.22K.O .. ...... .40 .41 .31 .26 .38 .33H.O+ ........ .12 .07 .06 .00 .33 .08H 2O- __ ...._-. .01 .06 .03 .02 .13 .03TiO.-.---. ------ 2.01 2.06 1.89 1.34 1.94 1.94P.O 5 ------.----- .22 .23 .18 .14 .21 .19MnO..----.--... .17 .17 .17 .17 .17 .17CO2.__ --._-.--.- .01 .00 .00 .01 .01 .02Cl--.. -----...-. .01 .01 .01 .01 .02 .01F --_-__.- .- ._ .03 .03 .03 .02 .03 .03

Subtotal.-.-- 99.88 99.86 99.98 99.79 99.96 99.79 LessO.------... .01 .01 .01 .01 .01 .01

Total __ .... 99.87 99.85 99.97 99.78 99.95 99.78

KjOiPzOs -. .. 1.82 1.78 1.72 1.80 1.81 1.74

1 Na 2O corrected for NaCl contamination is 1.75 percent; Cl corrected for NaCl

TABLE 9. Chemical analyses of olivine-controlled lavas from Mauna Loa south rift zone Continued

Date _ ----- 1907 1919 1926

Sample ...... TLW67-56 TLW67-77 H-34 H-36 TLW67-76

SiO2.. ...-.-. 51.76 51.69 51.83 51.89 51.51 A12O 3 ----- 14.17 14.16 13.95 13.90 13.95FezOs...---- 1.24 1.65 1.75 3.24 1.71FeO-, ------ 9.77 9.36 9.17 7.88 9.36MgO-. ---.-_ 7.17 7.31 7.05 7.21 7.79CaO-..---.- 10.44 10.44 10.58 10.61 10.36Na2O ----- 2.26 2.25 2.31 2.25 2.21K.O- _ .. .34 .36 .35 .36 .35H2O+ _ .. .09 .12 .14 .06 .18H 2O- ...... .03 .04 .01 .01 .03TiOz.. .-- 2.04 2.03 2.11 2.10 2.04T> f\ QI oi O1 99 9fi

MnO..-.---. .17 .17 .17 .18 .17CO.------.. .03 .00 .00 .01 .01Cl_. .-----.. .01 .01 .02 .01 .01F _ .03 .03 .02 .03 .03

Subtotal. 99.76 99.83 99.67 99.96 99.91 LessO .. .01 .01 .01 .01 .01

Total-.. 99.75 99.82 99.66 99.95 99.90

K.O:P_O5--- 1.62 1.71 1.66 1.64 1.75

Date ..-- .. 1950

Sample ... TLW67-73 TLW67-74 TLW67-75 TLW67-79 53-2378CD

SiO2 __ ... 51.92 51.58 51.34 51.35 51.40AUOs. .... - 14.27 13.84 13.73 13.19 13.27Fe2O 3..- -- 1.38 1.20 1.37 2.41 2.72FeO-.-.---- 9.65 9.85 9.70 8.80 8.66MgO._------ 6.86 8.13 8.70 9.20 9.14CaO.. .--- 10.56 10.18 10.07 9.97 10.04Na 2O.. ...--- 2.29 2.23 2.16 2.15 2.13K 2O . .37 .36 .36 .36 .31H2O+. . - .02 .07 .06 .00 .04 H2O- ... .04 .01 .00 .04 .00TiO2-. ... - 2.10 2.01 1.94 1.93 1.91 P2O5-------- .22 .21 .20 .21 .22MnO-_-_-__- .17 .17 .17 .18 .17CO 2_. ------- .02 .02 .01 .01 .00Cl--.-._---- .00 .01 .01 .01 -----F .03 .03 .03 .03 .... .

Subtotal. 99.90 99.90 99.85 99.84 ....LessO..---- .01 .01 .01 .01 ... ..

Total- 99.89 99.89 99.84 99.83 100.01

K 2O:P 2O 5 - 1.68 1.71 1.80 1.71 1.41

TABLE 10. Chemical analyses of olivine-controlled lavas from Mauna Loa northeast rift zone


Keamoku flow

Sample 476 TLW67-29 TLW67-61 TLW67-63 W-A-20

SiO2 ---------- 50.94 51.92 48.70 50.59 51.34A12 O 3 ---------- 12.97 14.16 10.98 13.22 13.82Fe2O3 -----_-_- - 1.95 3.49 1.67 1.57 2.18FeO. -_- ----- 8.90 7.52 9.52 9.77 8.87

CaO_ ... ----- 9.88 10.50 7.90 9.90 10.26Na 2O --------- 1.99 2.32 1.69 2.12 2.27K 2O ---------- .37 .41 .33 .38 .43H.O+ .-_.---- .12 .15 .15 .08 .23H.O- .04 .01 .06 .00 .05

PzOii. ---------- .21 .24 .19 .21 .23MnO..--------... .17 .17 .16 .17 .17CO2 - - .04 .01 .01 .01 .00Cl --- -- --- .00 .01 .01 .01F -- - - --. -- --._ .03 .03 .03 .03

LessO--------- ---- .01 .01 .01 .01

Total. ------ 100.10 100.00 99.80 99.82 99.89

K2O:P2O5-------_ 1.79 1.71 1.74 1.81 1.87

18 CHEMISTRY OF KILAUEA AND MAU

TABLE 10. Chemical analyses of olivine-controlled lavas from Mauna Loa northeast rift zone Continued

Date.. _ _ .

SiO! -------AhO, ......FejOa..--- FeO-..--__.-_MgO--.--..--CaO-.--.-.--NasO ......K2O--- __ ..-H*0+ -HjO- -----TiOs---------PtO«._ ....MnO... .. _.CO*... . ------Cl-.. ..--F.. ....... ...

Subtotal. . Less O...- ...

Total .....

KtOiPiOs----.

1881 1899 1935 1942

10,000ft

52.18 13.76 3.25 8.03 7.95

10.16 2.06

.34

.05

.08 1.95

.19

.17

.01

.01

.03

100.22 .01

100.21

1.79

2,200 TLW67- ft 65

52.27 52.05 13.68 14.13 2.31 1.20 9.02 9.88 7.40 7.06

10.24 10.57 2.29 2.25

.37 .34

.04 .05

.03 .01 2.07 2.09

.20 .20

.18 .17

.01 .02

.01 .00

.03 .03

100.15 100.05 .01 .01

100.14 100.04

1.85 1.70

W-A-24 TLW67- W-A-21 TLW67- 67 62

52.10 51.93 13.91 14.20 1.21 1.34 9.76 9.74 7.67 7.14

10.21 10.56 2.25 2.31

.34 .36

.11 .09

.03 .00 1.94 2.04

.20 .21

.17 .17

.02 .01

.00 .01

.03 .03

99.95 100.14 .01 .01

99.94 100.13

1.70 1.71

TABLE 11. Chemical am

Sample. -----

SiO__. ______Al_0i_______FeiOi. ______FeO-_--_-__MgO_ -.--CaO. .--__-.Na_0_____-K_0__ H.O-K ~H_0-____-TiO___ _-P,0.___ -MnO _____CO_____- Cl__________F -------

Subtotal

Total. ..

K20:P205 __-

Beach boulder

TLW67-117A

49.35 11.82 1.50 9.54

14.30 8.73

U.89 .34 .25 .04

1.69 .19 .17 .02

i.03 .03

99.89 .02

99.87

1.79

TLW67-78

51.50 13.65 1.64 9.65 8.13

10.36 2.28

.34

.01

.00 1.98

.19

.17

.00

.00

.02

99.92 .01

99.91

1.79

51.85 51.88 14.14 14.08 1.34 1.55 9.77 9.58 7.07 7.20

10.54 10.55 2.29 2.29

.36 .36

.07 .09

.02 .01 2.05 2.06

.21 .21

.17 .17

.01 .01

.01 .01

.03 .03

99.93 100.08 .01 .01

99.92 100.07

1.71 1.71

NA LOA LAVA IN SPACE AND TIME

7 percent to over 20 percent. Data are given in table 3 for equation y = ax + b to define a set of con trol lines portraying the composition of all historic flows from Mauna Loa.

Unlike Kilauea, the Mauna Loa lavas do not form chemically distinct groups that can be related to time or location of eruption. This uniformity is shown in figures 7-9, in which the analyses for each group of lavas are compared to the position of the average control line for all historic flows. In terms of entire chemistry, therefore, Mauna Loa lavas are more uniform than Kilauea lavas. On a smaller scale, however, lavas from a single eruption or groups of closely related eruptions show more variation from average control lines than do lavas from individual Kilauea eruptions.

ilyses of olivine-controlled lavas from Mauna Loa northwest slope[Additional sample data are given in table 23]

Prehistoric 1859

Puu O Uo Kokoolau Puu Koli

TLW67 119 TLW67 121 TLW67 123 TLW67 125 65P 2 DPH-77

51.91 51.51 51.97 50.50 51.60 51.24 14.24 14.38 14.23 14.10 13.98 13.72 2.49 6.90 1.47 2.04 1.58 2.43 8.39 5.04 9.45 9.14 9.41 8.64 6.69 7.10 6.99 7.80 7.58 7.72

10.31 9.29 10.53 10.35 10.46 10.36 2.22 2.21 2.33 2.36 2.33 2 2.45

.46 .43 .41 .43 .42 .43

.37 .40 .05 .39 .05 .14

.03 .05 .03 .21 .05 .11 2.14 2.17 2.08 2.23 2.16 2.16

.25 .28 .23 .23 .24 .25

.16 .18 .17 .16 .17 .17

.04 .01 .01 .02 .00 .04

.00 .01 .01 .01 .01 2 .18

.03 .04 .02 .03 .03 .03

99.73 100.00 99.98 100.00 100.07 100.07 .01 .02 .01 .01 .01 .05

99.72 99.98 99.97 99.99 100.06 100.02

1.84 1.54 1.78 1.87 1.75 1.721 Na2p corrected for NaCl contamination is 1.88 percent; Cl corrected for NaCl

contamination is 0.01 percent.

TABLE 12.

SiOz ------AhOa ___ -.

FeO ___ .--.MgO--------

Na2O -----KzO .----.H*O+_..---_HzO-__---_TiOj.. -..---PjO 6-------MnO-------COs..-.-...Cl---.-----_F. __ _.

Subtotal- Less O__.__

Total ._

KjO:PsOS---

Chemical analyses of lavas of prehistoric age Ninole Hills, southeast slope of Mauna Loa


C817

48.40 14.33 2.42 9.18 9.78

10.17 2.31

.27

.20

.07 2.52

.22

.16

.02

100.05 .01

100.04

1.23

C818

49.47 14.58 3.97 8.10 7.33 9.33 1.70

.21 1.78

.87 2.27

.16

.18

.02

99.97 .01

99.96

1.31

ID-098-2

50.46 13.84 1.47 9.99 7.16

11.07 2.30

.46

.15

.05 2.68

.26

.18

.00

.01

.04

100.12 .02

100.10

1.77

ID-214-2

47.10 10.80 3.04 9.27

17.30 8.05 1.58

.08

.38

.34 1.60

.14

.19

.00

.01

.02

99.90 .01

99.89

.57

ID-240-2

47.26 11.46 2.48 9.52

16.13 8.52 1.62

.06

.43

.42 1.69

.15

.18

.00

.00

.03

99.95 .01

99.94

.40

from the

ID-275-2

49.74 13.42 2.36 9.27 9.92

10.14 1.99

.09

.35

.36 2.04

.17

.18

.00

.00

.03

100.06 .01

100.05

.53

2 NasO corrected for NaCl contamination is 2.33 percent; Cl corrected for NaC contamination is 0.01 percent.

Chemical analyses (table 12) of lavas from the Ninole Hills are plotted in figure 10. The Ninole lavas are within themselves extremely variable and are chemically distinct from, and older than, the lavas mapped elsewhere on Mauna Loa.2 On the av erage the Ninole lavas differ from the younger lavas of Mauna Loa in having lower SiO2, higher A12 O3 , higher "FeO," lower K20, and higher TiO2 . Na 2O, CaO, and P2O 5 are similar. The Ninole lavas may represent remnants of a separate volcano older than Mauna Loa.

2 One lava flow mapped as Kau Basalt, part of the youngest section of basalts recognized by Stearns and Macdonald (1946), has a composition similar to the lava of the Ninole Hills. This analysis is given in table 9 (C820). The analysis normalized to 100 percent dry weight is plotted in figure 8 at 6.12 percent MgO.

OBSERVATIONS 19

100

CaO

60

n.o"FeO"

110

10.0

90

8.0

i i i i i i i i i i i i__l l l I I i 7.0

53.0

10.0

16.0

150

13.0

120

Al,0,

520

500

490 SiO?

480

470

46.0

MgO

15

MgO

FIGURE 7. MgO variation diagrams showing lavas from the summit (Mokuaweoweo caldera) and northwest slope of Mauna Loa. Analyses are given in tables 8 and 11. Control lines are as shown in figure 2. , prehistoric, summit; X, prehistoric, northwest slope; Q, 1877-1949 (summit) and 1859 (northwest slope).


TiO

06

K,0 04

02

00

Na,0

120 I i i

110

100

90

CaO

50 L-L-

12.0

"Fed"

10.0

15.0

14.0

13.0

12.0

AM),

11.0

10.0

9.0

i i i i i i i i i i i i i i I i I I i I 7.0

53.0

52.0

51.0

50.0

SiO?

15

MgO

5 25 15

MgO

49.0

48.0

47.0

46.0

FIGURE 8. MgO variation diagrams showing lavas from the Mauna Loa southwest rift zone. Analyses are given in table 9. Control lines are as shown in figure 2. , prehistoric; O, 1868-1950.

OBSERVATIONS 21

04

P2 0 5 02

00

30

TiO,

\ i i i i i i i i i i i i i i i I i r

K,0 0.4 -

Na,0

9.0

CaO

7.0

60

50

i i i i r

FeCT

15 MgO

100

160

150

140

130

120

FIGURE 9. MgO variation diagrams showing lavas from the Mauna Loa northeast rift zone. Analyses are given in table 10. Control lines are as shown in figure 2. , prehistoric; O> 1852-1942.


P? 0 5 02

00

30

TiO,

90

CaO

50 i i i i i i i i i i i I i i i i i i

25 20 15 10

MgO

11.0

i i i i i i i i i i i i i i i i i i i I 10.0

16.0

12.0

"FeO"

15.0

140

13.0

12.0

110

100

90

520

510

500

SiO,

490

470

i i i i i i i i i i i i i i i i i i i

5 25 20 15 10 5

MgO

FIGURE 10. MgO variation diagrams showing lavas from the Ninole Hills, southeast slope of Mauna Loa. Analyses are given in table 12. Control lines are as shown in figure 2. Note that the Ninole lavas (X) plot distinctly away from the control lines for younger Mauna Loa lavas.

OBSERVATIONS 23

DIFFERENTIATED LAVAS

The compositions of differentiated lavas from Mauna Loa are shown in table 13 and plotted in

and 1950) barely plot off the extension of olivine control lines for the other historic lavas with which they are associated. The submarine sample (9) has a composition more nearly like that of typical Ki-

figure 11. The historic differentiates (1843, 1926, lauea differentiates.

TABLE 13. Chemical analyses of differentiated lavas from Mauna Loa[Additional sample data are given in table 23]

Date... _ .........

SiO 2 ---__------A12O 3 . ----------Fe2O 3 --------FeO._ .__..__.__MgO---. . ----__CaO_ - ._ ..Na2O---...---_-K2O_-------H 20 + __ _ -_-H 2O-__ _..._....TiO 2-_-_-_---P20S.- ------MnO. ...__... __CO 2 . ---._.._...Cl... -----------F-- ----------

Total-- -

K2O:P2O5 - ------

9

52.1213.412.479.455.508.89

'2.97.72.61.08

3.17.42.17.01

'.20.05

100.24.07

100.17

1.71

1926

TLW67-72

52.0414.111.349.856.68

10.352.36

.42

.05

.022.22

.23

.17

.01

.01

.03

99.89.01

99.88

1.83

TLW67-54

52.0314.221.489.766.39

10.262.44

.46

.03

.022.30

.27

.17

.01

.01

.04

99 89.02

99 87

1.70

1950

TLW07-54A

52.0914.191.559.706.38

10.352.50

.47

.04

.002.28

00

.17

.01

.02

.03

100.11.01

100.10

1.42

TLWC7-66

51.9314.251.389.796.66

10.322.38

.47

.0905

2.16.26.17.01.01.04

99 97.02

99 9*1

1.81

1843

W-A-22

51.6514.432.568.536.75

10.432.39

.46

.10

.042.16

.25

.17

.01

.01

.04

100.03.02

100.01

1.84

W-A-23

51.8914.301.649.236.80

10.502.41

.45

.08

.012.16

.25

.17

.01

.01

.03

99.94.01

99.93

1.801 Na2O corrected for NaCl contamination is 2.84 percent; Cl corrected for NaCl contamination is 0.01 percent.

TABLE 14. Summary of chemical composition of historic flows from Mauna Loa and of flows of different ages from Kilauea

[All averages are normalized to 100 percent dry weight after converting all iron to "FeO". Averages are then normalized to 7.0 percent MgO by subtracting chromite-bearing olivine of composition Fai2.s (Mauna Loa) or Fan.s (Kilauea)]

SiO 2 -AUO,--_._"FeO" MgO.--._CaO ___Na2O__ K20 -_.TiO 2 ---_.P20 B .--_-MnO--._.

Mauna Loa

Historic

52.18 14.17 10.94

7.0 10.58 2.29

.37 2.07

.21

.17

Kilauea caldera

Prehistoric

51.23 14.14 10.86

7.0 11.22 2.30

.41 2.44

.22

.17

1832-89

50.77 14.11 11.06

7.0 11.27 2.30

.48 2.61

.25

.17

1911-24

50.33 14.00 11.09

7.0 11.58 2.28

.55 2.72

.27

.17

1959 S-2

50.18 13.79 11.26

7.0 11.63 2.31

.60 2.77

.28

.17

CHEMICAL VARIATION WITHIN KILAUEA LAVAAND DIFFERENCE BETWEEN KILAUEA AND

MAUNA LOA LAVAS

Figure 2 shows that the lavas of Mauna Loa may be distinguished by their chemistry from any of the lavas of Kilauea. Furthermore, the data indicate that the trend in chemical change (relative to con stant MgO or to the position of olivine control lines) between the lavas of Mauna Loa and the pre historic lavas of Kilauea is similar to that which distinguishes Kilauea's prehistoric lavas from its 20th century lavas. In other words, the extrapola

tion of the time-related chemical variation of Ki lauea lavas backwards in time is toward the aver age composition of Mauna Loa lavas, as is illustrated in table 14.

DISCUSSION

The following sections aim to explain the ob served chemical variation of Kilauea and Mauna Loa in terms of specific petrologic processes. A striking feature of the chemistry of both volcanoes is the uniformity of the ratio K20:P205 . Anderson and Greenland (1969) have discussed the behavior of P205 in basaltic melts, and the same principles apply to K20 in Hawaiian tholeittes. Both oxides are strongly partitioned to the melt until late crys tallization of apatite and potassium-rich feldspar. The uniformity of their ratio suggests (1) melting from a mantle of uniform composition with respect to these elements and (2) subsequent crystal-liquid fractionation (or differences in initial degree of melting) as the dominant processes by which magma compositions are determined.

Other processes have been tested and rejected. The process of mixing of magmas, which is impor tant in explaining the composition of Kilauea rift eruptions (Wright and Fiske, 1971), appears to be


35

TiO, 30

25

20

K,0 05

Na 2 0 25

20

110

CaO

90

8

130

120

"FeO"

110

100

150

14.0 AI 203

130

530

520

510 SiO,

50.0

4907 6 5 48 7 6 5 4

MgO MgO

FIGURE 11. MgO variation diagrams showing differentiated lavas from Kilauea ( ) and Mauna Loa ( X ) . Analyses are given in table 13. Control lines are as shown in figure 2 with the addition of control lines for the early part of the Kilauea 1955 eruption (very short dashes between 5 and 6 percent MgO).

DISCUSSION 25

of minor importance in explaining the chemistry of lavas erupted either at Kilauea summit or from Mauna Loa. Diffusion of chemical species (for exam ple, alkalies) and reactions with wallrocks cannot be quantitatively treated, but there is no evidence that such processes are important in explaining the chemical variability.

Quantitative fractionation calculations (Wright and Doherty, 1970) are made on the assumption that crystal-liquid fractionation and (or) partial melting are the important processes that result in chemical variability of the lavas. Mineral composi tions used in the calculations are given in table 15. The nature of the calculated mineral assemblage

TABLE 15. Analyses 0} minerals used in differentiation calculations

Olivine

SiO2 __-.-.A1203"FeO"--..MgO CaO_--.-.Na2O_---.K20..---Ti02--_---P20S__- -MnO.----

Faio

... 40.79

9.69... 49.00

.25

.29

Faso

37.67

26.78 35.05

.25

.29

Augite Conti nued

SiOi..__._Al<0,_____"FeO"--.-MgO ...CaO-. .Na2O_-_--K20-----_Ti02----_-P206 --_ MnO_ ..

STWATAUG

-_ 51.512.30

11.29. 13.53..__ 20.49

17.01.40.03.28

MPLLAUG

51.49 4.20 7.50

16.20 19.00

.30

.01 1.10

.01

.20

Chromite

KICHRO

0.001 65.00

20.90 11.60

.00

.00

.00 2.10

.00

.20

Jadeite

59.40 25.30

15.30

Olivine -fchromite

KAVOL MLAVOL(Fais.s) (Fa«.j)

39.45 1.17

13.23 45.51

.39

.00

.00

.04

.00

.22

Ca-Tschermak's molecule

27.60 46.70

25.70

39.70 .98

12.08 46.60

.39

.00

.00

.03

.00

.22

Ab

68.29 19.65

.08

.00

.08 11.61

.28

.01

.00

.00

Hypersthene Augite

KUMLHYP MP218HYP STWATHYP LHZAUG MP218AUG

54.88 .75

10.69 30.99

2.14 .10 .04 .25 .00 .16

Ans9.7

53.42 29.74

.20

.12 11.87 4.45

.19

.07

.00

.00

53.39.85

16.99 25.58 2.26

.04

.00

.54

.00

.37

Plagioclase

Anes.s

52.03 30.08

.66

.18 13.00 3.64

.35

.07

.00

.00

51 1

2618.

1

Anes.7

51.01 30.99

.49

.13 13.83 3.29

.20

.06

.00

.00

.50

.36

.40

.68

.13

.04

.01

.27

.02

.59

An

44.00 36.28

.08

.00 19.42

.22

.00

.00

.00

.00

53.20 3.00 4.00

16.50 22.50

.50

.00

.20

.00

.10

Ilmenite

MPILM

0.05 .12

48.99 1.73

.08

.00 48.64

.00

.00

.44

52.53 2.93 7.43

16.86 18.95

.22

.00

.87

.00

.22

Magnetite

MPMAG

0.07 1.90

73.50 1.03

.10

.00 23.06

.00

.00

.38

1 Because Cr2Os was not separately determined in the rock analyses, all Cr2Oshas been converted to equivalent AhOs. True percentages are CrzOs, 43.5; AhOs,13.4.Olivine--__--_----.--_-.__Faio------------ -Stoichiometric composition based

on minor element data for Hawaiian olivines (Murata and others, 1965).

Faso------------. Do.Chromite-------__--_-_--_KICHRO__-___-_Average composition of chromite

phenocrysts and inclusions in olivine of the 1959 eruption of Kilauea (B. W. Evans, unpub. data).

Olivine +chromite . . _ . .. _. -KAVOL (Faia.s)_ Average composition of olivine (in cluding 1.8 percent chromite) which controls the composition of the 1959 eruption of Kilauea.

MLAVOL (Faiz.5)-Average composition of olivine (in cluding 1.5 percent chromite) which controls the composition of the historic flows from Mauna Loa (table 16).

Hypersthene._____________KUMLHYP-..---Hypersthene from a prehistoriclava flow, south rift zone of Mauna Loa. Analysis by H. Kuno (1966, table 1, analysis 1).

MP218HYP--_._.Hypersthene from the prehistoriclava lake in Makaopuhi crater,Kilauea (Evans and Moore,1968, table 3, col. 4, p. 96).

STWATHYP.....Hypersthene from the chill zone ofthe Stillwater Complex, Mon tana (E. D. Jackson and R. E. Stevens, unpub. data).

Augite___.._..-....--_.. LHZAUG-. .----.Average (estimated by T. L.Wright) composition of augite from Iherzolite inclusions in Hawaiian basalts. Data of White (1966).

MP218AUG--. ...Augite from the prehistoric lava lake in Makaopuhi crater, Kilauea, coexisting with MP- 218HYP (Evans and Moore, 1968, table 3, col. 2, p. 96).

STWATAUG----.Augite from the chill zone of the Stillwater Complex, Montana (E. D. Jackson and R. E. Stevens, unpub. data).

MPLLAUG__..Augite quenched near the temper ature of first appearance from the 1965 Makaopuhi lava lake, Kilauea (P. W. Weiblen and T. L. Wright, unpub. data).

Jadeite._-__..__________--_--_--______-_-__.Stoichiometric NaAlSi^Oe.Ca-Tschermak's molecule.__-----_____-------Stoichiometric CaAlzSiOe.Plagioclase, from analyses in Deer, Howie, and Zussman (1963):

Ab---.---_------Table 13, p. 110, analysis 8.Ansg 7_.---.--..Table 16, p. 117, analysis 8.Aness_---___-__Table 16, p. 117, analysis 14.Anes 7_..---.--.Table 17, p. 118, analysis 2.An.---.___..._..Table 18, p. 120, analysis 7.

Ilmenite_..-__________-_..MPILM.- .__._..Quenched near the temperature offirst appearance, from the 1965 Makaopuhi lava lake. (See Wright and Weiblen, 1968, analysis is unpublished.)

Magnetite.. __________ _._.MPMAG__----- Do.

that relates two lavas of different composition gives an idea as to the depth at which fractionation took place. If the assemblage consists only of minerals present as phenocrysts in the lavas, then the frac tionation is deduced to be shallow, corresponding to

pressures not exceeding 2kb (kilobars) . 3 If, however, the calculated mineral assemblage does not match the observed phenocryst assemblage, then the

3 This is based on a depth of 24 km (kilometers) to Kilauea's shallow magma reservoir (see Eaton and Murata, 1960, Fiske and Kinoshita, 1969),


chemical differences must be inherited from a deeper fractionation or melting event. For Kilauea lavas, hypersthene is a critical mineral. It is absent as a phenocryst, so that fractionation in which hyper sthene is a necessary phase is considered to have oc curred at pressures greater than 2kb. Since hyper sthene does occur as a phenocryst in Mauna Loa lavas, its presence in fractionation calculations is not necessarily indicative of a high-pressure event. However, hypersthene always occurs with equal or greater amounts of plagioclase and augite phenocrysts, so that a preponderance of hypersthene in a fractionation calculation is again taken as a sugges tion of a higher pressure event. At higher pres sures, melting is taken to be the reverse of fraction ation as far as the calculations are concerned. Space-time relations of the lavas suggest whether a fractionation (cooling) or melting event is more likely.

OLIVINE-CONTROLLED CHEMICAL VARIATION IN KILAUEA AND MAUNA LOA LAVAS

Figure 2 shows control lines for some major suites of Kilauea and Mauna Loa lavas plotted to

gether with minerals that might control the ob served chemical variation both within and between suites of different lavas. The projection of these control lines shows that addition or removal of olivine is the dominant process explaining the lava chemistry, a conclusion reached by Powers (1955) on the basis of many fewer analytical data. One can ask to what extent the control lines deviate from perfect olivine control and attempt to explain these deviations in a quantitative fashion. The most thor oughly described example of olivine control is the 1959 eruption of Kilauea, for which Murata and Richter (1966b, table 1) calculated the composition of olivine that controlled the major compositional variation of the eruption.4

Tilley (1960a) has demonstrated olivine control for the 1921 Kilauea summit lava. Control lines have been calculated for two additional olivine-rich Kilauea eruptions 1840 east rift (Wright and Fiske, 1971, table 4a) and a prehistoric pahoehoe flow unit from the southwest rift (Walker, 1969; this paper, table 5). The results are shown in table 16. The residuals demonstrate nearly perfect olivine control.

TABLE 16. Results of differentiation calculations for Kilauea and Mauna, Loa control lines[Calculations are set up using the calculated composition of the high-MgO (A) and low-MgO (B) ends of the control lines for each lava suite (see table 3) as follows:

A=B+olivine (Faio)+olivine (Faso)+chromite. Total iron is calculated as FeO]

Kilauea

1840 east rift (KIL1840)

SiO 2 __-_______AliO,.. _______"FeO"________MgO_________CaO__________Na20_________K2O. _________TiOj___. ______P_0B _MnO... ______

NOTE. Solution

Olivine

B __ ..

A

.__ 48.1810.34

___ 11.29___ 17.54

8.261.67

.341.97

.18

.17

(weight percent) :

B

49.08 11.49 11.03 14.18 9.32 1.84

.36 2.17

.19

.17

Residuals (A observed

minus A calc)

0.05 .01

-.01 -.02 -.11

.03

.02

.06

.02

.00

KIL1840 .... 10.66

(Fau.i)

.... 89.24

Prehistoric southwest rift (PHSWPP)

A

46.52 8.96

12.01 22.00 6.90 1.54

.25 1.50

.15

.18

B

51.17 14.27 10.91 6.82

11.12 2.38

.49 2.45

.24

.19


minus A calc)

-0.06 -.01

.01

.01

.03

.12 -.04

.01

.01 -.02

PHSWPP 39.01

(Fa 14.3) .54

60.46

Mauna Loa (HISTML)

A

46.98 8.56

11.37 23.70 6.20 1.32

.28 1.33

.16

.19

B

52.21 14.23 10.95 6.89

10.62 2.31

.38 2.08

.23

.19


minus A calc)

-0.02 -.02 -.02 -.02 -.08 -.01

.07

.12

.03 -.01

HISTML 41.81 (Fan s)

.60 57.60

There are no individual eruptions of Mauna Loa that have as great a range of olivine content as those described from Kilauea. The overall chemical variation, however, is clearly dominated by olivine control. The calculation using the average Mauna Loa control lines (table 3) is also shown in table 16.

Olivine control is inferred to be a shallow process on the basis of the positive correlation between MgO content of a lava and its observed percentage of olivine phenocrysts. Presumably, each subcham-

ber of the shallow reservoir complex inferred to underlie both Kilauea and Mauna Loa is stratified with an olivine-rich lower part and an olivine-poor upper part. The MgO content of a lava then de pends on what level or levels of the chamber were tapped.

4 Their calculated olivine has an abnormally high CaO content. T. L. Wright and D. B. Jackson (unpub. data) explain this by making the 1959 eruption a mixture of two magmas (which differ in CaO relative to MgO), each of which shows virtually perfect olivine-controlled chemical variation.

DISCUSSION 27

OLIVINE-PYROXENE-PLAGIOCLASE CONTROL OF MAUNA LOA LAVA COMPOSITIONS

The occurrence of phenocrysts of hypersthene, augite, and plagioclase in Mauna Loa lavas suggests the possibility of a more complex shallow fractiona tion than the olivine control demonstrated for Ki- lauea eruptions. This possibility was studied by se lecting pairs of Mauna Loa lavas that showed large opposed deviations from the set of average control lines computed for all historic lavas (table 3) and by calculating differences in chemical compo sition in terms of the observed phenocryst assem blage. Equations of the following form were solved (Wright and Doherty, 1970):

Lava A=lava B±olivine±hypersthene±augite±plagioclase

where lava A is arbitrarily taken as the lava with the higher content of MgO. The lava pairs include a picrite and a hypersthene-rich lava from each rift zone (southwest rift, 1887 from 1868 picrite parent; northeast rift, 1881 from 1852 picrite parent) and three sets from single rift eruptions (southwest rift, 1868 and 1950; northeast rift, 1899). The com position of olivine (including 1.5 percent chromite) is fixed at Fa12 . 5 from the control lines for all historic Mauna Loa flows (table 16). The composition of plagioclase is fixed at An66, a value within the ob served range of phenocryst composition (A. T. An- derson, unpub. data.)

Separate calculations were made for each pair using the three sets of pyroxenes shown in table 15; that is, KUMLHYP and LHZAUG (most magnesian), MP218HYP and MP218AUG and STWA- THYP and STWATAUG (most iron-rich). The signs and relative magnitude of the residuals do not vary significantly as a function of assumed pyrox ene Mg:Fe ratio. The solutions using pyroxenes of intermediate Mg:Fe ratio are given in table 17.

The results show that minerals in addition to oli vine are necessary to balance the chemical differ ences. The signs of the solution values indicate whether the mineral is relatively enriched (+) or de pleted ( ) in the sample with higher MgO. The low residuals in the calculations indicate that the chemical differences between lavas can be satisfac torily expressed in terms of minerals present as phenocrysts. However, the observed compositions are probably not simply a result of removal or addi tion of the mineral assemblage present in the porphyritic lavas. The total amount of calculated sili cates other than olivine (5-10 percent, table 17) exceeds by a factor of 2 the observed phenocryst

percentages, and augite is a relatively more impor tant component of the observed phenocryst assem blages (table 7) . Residuals for K20, Na20, and Ti02 tend to exceed the expected analytical error of the rock analyses and are not significantly affected by changing the mineral compositions. It is possible that processes other than shallow crystal-liquid fractionation have contributed to the chemical vari ation of these Mauna Loa lavas.

TABLE 17. Results of differentiation calculations for olivine-controlled lavas from Mauna Loa

A (ML1868)

Si0 2 ---_____. 46.75A1 20 S------- 8.40"FeO" _ 11.33MgO------- 23.58CaO 6.21Na20----_-- 1.32KoO . 26TiOi----- - _ 1.34P206 - .14MnO --. _ .17

Note. Solution l (weight percent):

Hypersthene (MP218HYP).-.Augite (MP'>18AUG)_---__-_

B

A

Si0 2 . - 48.70AlsOs - 10.98"FeO"_---_-- 11.02MgO-_----_- 16.80CaO 7.90Na20__---___ 1.69KiO .-_ .33TiOi__----_- 1.61Pj0 6 ----- - .19MnO-- -- -16

Note. Solution 1 (weight percent):

Hypersthene (MP218HYP)...Augite (MP218AUG). -------

g

1887 from

B(ML1887)

52.07 13.97 10.86 7.47

10.26 2.22

.33 1.94

.19

.17

1881 from

B

52.18 13.76 10.95 7.95

10.16 2.06

.34 1.95

.19

.17

1868 picrite

Residuals (A observed minus A calc)

-0.05 -.05 -.06 -.03 -.02

.02

.07

.15

.03 -.02

-----...-.----------. +41.86

+ Q7

-1.62--------------------- 61.07

1852 picrite


0.02 -.05 -.07

.00 0.02

.06

.06

.02

.03 -.01

-----._...----- ---. +2G.07-------------------- -6.71_----..__.------_--- -1.48

--------------------- 84.49

1868W-A-6 from ML1868

A

SiOj 46.75AhOj -- 8.40"FeO"------. 11.33MgO_ _ 23.58CaO .- 6.21Na20 ----- 1.32KiO - .26Ti0 2 -----_- 1.34Pi0 6 -.--- .14MnO- _- .17

Note. Solution 1 (weight percent):

Hypersthene (MP218HYP). -Augite (MP218AUG) -_-_-.

B

51.02 13.44 10.94 9.30 9.89 2.19

.40 2.01

.22

.17


-0.01 -.03 -.05 -.01 -.02

.02

.03

.13

.02 -.02

. - -_--- ----- +37.35--------------------- +2.69--------------------- +1.03------------- ---. +.65--------------------- 58.30

See footnote at end of table.


TABLE 17. Results of differentiation calculations for olivine-controlled lavas from Mauna Loa Continued

_______1950 (TLW67-75) from 1950 (TLW67-79)______

A B Residuals(A observed minus A calc)

SiOj 51.35A1 20 S------- 13.19"FeO"_ 10.97MgO_-- - 9.20CaO ______ 9.97Na20------_- 2.15K2O-------- .36Ti0 2 -------- 1.93P20 5 ._--_--- .21MnO------- .18

Note. Solution ' (weight percent) : Olivine (Faia.s) + chromite-.-.Hypersthene (MP218HYP). ...Augite (MP218AUG )--.------Plagioclase (Anes s) - - - _--- --B... -..-------.. _ .........

51.3413.7310.938.70

10.072.16

.361.94

.20

.17

0.03-.04-.06

.00-.02

.07

.02

.02

.02

.01

+0.11+1.94+1.33-.4997.14

1899 (TLW67-65) from 1899 (W-A-24)

B Residuals (A observed minus A calc)

SiO2~ A1.0, ."FeO"_ _.MgCL------CaO ._-_.Na20-----_-K20-_-----.Ti02 -_-_-_.P205 -_____.MnO-.---..

52.1013.9110.857.6710.212.25.34

1 Q420.17

52.0514.1310.967.0610.572.25.34

2.09.20.17

0.03_ fte.-.06

on-.01

.08ft?.01.02.00

Note. Solution i (weight percent):Olivine (Fai2.s) + chromite.-------------------.--.-...------ -0.52Hypersthene (MP218HYP)...-.--.------- ------ ---.--... +5.83Augite (MP218AUG)..----____-.-_----.--_..._._._....._... +.18Plagioclase (Anes.s).------------------------_------------- +3.66B.......... -_---.-------__----.-----..._ __-_-----___----- 90.88

1 The sign of the solution value is positive (+) if the more magnesian lava com position (A) is enriched in the components of that mineral phase relative to the lava with less MgO (B). Lava A=lava B±oliv ne±hypersthene±augite±plagioclase.

The differentiated lavas of Mauna Loa have been studied by calculations similar to those outlined above. Lava A is taken as a parent with greater than 7 percent MgO; lava B is the differentiate, and ilmenite is added to the list of possible minerals participating in the fractionation process. Table 18 shows the computed amounts of minerals removed from an assumed parent composition to produce the 1843, 1950, and submarine differentiates whose compositions are given in table 13. The two differ entiates of historic age can be produced by removal of about 5-15 percent of silicates other than olivine. The prehistoric sample 9 is more strongly dif ferentiated, and the calculations show that 38 per cent of silicates in addition to olivine are necessary to produce its composition. The silicates in this case are more iron-rich, as would be expected for a great er degree of fractionation. Removal of iron-titanium oxides is not indicated for any of the differentiates, in contrast to most of the Kilauea differentiates (Wright and Fiske, 1971). Presumably the mechan ism for differentiation of these lavas is separation of phenocrysts during flow in conduits, similar to the

TABLE 18. Results of differentiation calculations 1 for differentiated lavas from Mauna Loa

Minerals (percent): 4

Total (except

Residuals:

185218432

25.7(Fa 12)

«+1.86+0.0

+2.0(Anee)

3.8

.03

.08

1950 TLW67-791950 TLW67-54 »

4.9(Fazo)

+4.9«+4.9

+5.1(Ami)

14.9

.01.01

1950 TLW67-799

6.3(Fan) '+8.5

'+12.7+16.6(Anes)

37.8

.06.17

1 Calculations of the form: parent = differentiate + olivine+hypersthene + augite +plagioclase.

2 Average of the three analyses given in table 13.3 A similar solution obtained for the 1926 eruption with TLW67-76 (parent)

and TLW67-72 (differentiate). See tables 9 and 13.4 The minerals that must be removed from the parent composition to yield the

composition of the differentiate. Only silicate minerals are tabulated because in no case were the residuals significantly reduced by inclusion of either ilmenite or titanium-rich magnetite.

5 Olivine composition derived using Faio and Faso.e Hypersthene and augite are MP218HYP and MP218AUG (table 15),

respectively.' Hypersthene and augite are STWATHYP and STWATAUG (table 15),

respectively.8 Plagioclase composition derived using Ab and An (table 15) as input.

differentiation mechanism inferred for some Kilauea rift lavas (Wright and Fiske, 1971).

HIGH-PRESSURE FRACTIONATION OF KILAUEA LAVA

Perhaps the most difficult problem of Kilauea chemistry is to explain the differences in composi tion of lavas erupted at Kilauea summit. Two kinds of chemical variation are recognized: (1) Short- term variation in which each summit eruption has a chemical composition distinct from that of every other summit eruption, and (2) a long-term varia tion defined by the average composition of lavas erupted at different periods in the volcano's history (table 14). The explanation for these chemical vari ations is crucial to an understanding of the history of Kilauea magma from the time of initial melting to its appearance in the reservoir complex 2-4 km beneath Kilauea summit.

The composition of Mauna Loa lavas (which has not apparently changed composition over the same time interval as the changes of Kilauea lava compo sition) is chemically an end member to the Kilauea long-term variation (table 14). This observation suggests that the unexposed (submarine) section of Kilauea lavas might have a composition similar to that of present-day Mauna Loa lava.

The chemical differences among Kilauea summit lavas are not explainable by olivine control. The chemical differences in SiO2 and CaO tend to be op posed, suggesting that orthopyroxene is an impor tant fractionating phase. This in turn indicates a high-pressure origin for the chemical differences, and the calculations below are arranged to show various possibilities for high-pressure fractionation.

DISCUSSION 29

LONG-TERM CHEMICAL VARIATION

The younger lavas of Kilauea are richer in low- melting constituents (K20, P205 , Ti02 ), and this ob servation leads me to favor some kind of postmelt- ing fractionation model to explain the chemical variation.5 The calculations that follow are based on such a fractionation model.

The compositions given in table 14 are obviously too poor in magnesia to represent mantle-generated magmas. Murata and Richter (1966a) have ana lyzed glass from the highest temperature eruptive phase of the 1959 eruption of Kilauea and found it to have 10 percent MgO. The bulk composition of that same eruption is somewhat higher than 15 per cent MgO (table 4), and this is considered by the author to represent a reasonable average composi tion (magma -f contained olivine) of magma supplied to the 2- to 4-km-deep reservoir. Thus the initial Kilauea magmas must have had at least 15 percent MgO.

Another approach to initial magma composition arises from application of the hypothesis of Jackson and Wright (1970) to the effect that dunite is the refractory residue after melting of tholeiite. On this hypothesis the bulk composition of the mantle un derlying Hawaii should lie on control lines connect ing tholeiite and dunite. The composition and a cal culated mode of a "Mauna Loa" mantle with 35 percent MgO is given in table 19. Hornblende is used as the potash-bearing phase although similar relations hold if phlogopite is used instead or in ad dition to hornblende. Cr203 is assumed to be concen trated entirely in spinel, and Ti02 , in rutile. Bulk pyroxene composition is calculated from the follow ing five end members: MgSi03 , FeSiO;<, CaSi0 3 , NaAlSi206 (jadeite), and A1 203 (Tschermak's com ponents). Actual mantle pyroxenes would contain small amounts of Cr2 O 3 and TiO,2 , but these do not significantly affect the calculation of magma compo sitions. Pyroxene compositions are calculated on the basis of tie line orientations similar to those in co existing pyroxenes from Hawaiian xenoliths (Bee- son and Jackson 1970; M. H. Beeson, unpub. data). The minimum MgO content of tholeiite, assuming all phases except oli vine are melted, is 15-20 percent MgO, depending on the composition of olivine used in the calculation. The mantle calculated in table 19 would yield a tholeiite with a minimum MgO of 19 percent. Since olivine must be melted along with other components-, a magma with 25 percent MgO

5 Murata (1970) has argued that the chemical differences between Mauna Loa and Kilauea are explained by different degrees of melting in a mantle differing: with respect to the low-melting constituents. However, Murata did not treat the temporal variation within Kilauea itself.

TABLE 19. Calculated mode and pyroxene composition of a "Mauna Loa" mantle

Si02 _A1 2(V___.--"FeO" .MgO.-- ..CaO -.Na20 -.K20 _.TK)2--- .P 205 . ______ .MnO _.Cr20 3 -_ -

Bulk' mantle

43.03___. 4.34___. 12.67-_-. 35.00

3.06___. .65 _ .10 .60

.06.___ .18

.31

Ortho- pyroxene

52.338.768.78

29.13.82.18

Clino- pyroxene

51.3712.625.00

13.1914.823.00

Hornblende 2

40.6914.0011.2913.0410.353.072.074.46

.11

Mode

Olivine (Fai 6 . 2 )- Cr-spineL ____..Orthopyroxene_ Clinopyroxene-. Amphibole 2 ___. Apatite 3 - ______Rutile 4 -------

60.121.02

17.7215.794.85

.14

.37

Total___._ 100.00

1 Obtained by adding dunite to Mauna Loa (HISTML) composition.2 Kakanui hornblende used for K2O balance.3 Apatite used for P2O5 balance.4 Rutile used for TiC>2 balance in the absence of Ti02 in pyroxene.

is considered reasonable, and this has been used as a parent in the calculations.

There is no evidence that the average MgO (or potential and actual olivine content) of Kilauea magma supplied to the shallow reservoir has changed as a result of any fractionation process; that is, the incidence of picritic eruptions seems quite as high in the present as any estimates that could be made for earlier lava sections. This also implies that fractionation processes begin with quite MgO-rich magmas and occur at pressures suf ficiently high to stabilize other phases with olivine at high liquidus temperatures.

Magma compositions used in the fractionation calculations are shown in table 20. The compositions were constructed from those given in table 14 (PHKILCAL, Kilauea caldera prehistoric; 1959 S-2) and table 4 (1952Hm, 1967-68Hm) by adding olivine (Fa i:j . T ) containing 1 percent included Cr- spinel. The younger magmas contain less Si0 2 and more CaO relative to MgO than the prehistoric par ent, which suggests that orthopyroxene is an impor tant phase in the fractionation. However, A1 203 de creases slightly and Na2 O remains the same in the younger lavas, which suggests that one or more phases rich in A1 20?, and Na20 must also be impor tant. A simple mineralogy that fits the chemical fractionation is olivine-orthopyroxene-plagioclase (Anr)( ,. 6 .-,). This assemblage would be limited by the upper stability limit of plagioclase to 10 kb or less (Green and Ringwood, 1967, Ito and Kennedy,


1968). Sample fractionation calculations are shown in table 21A. Two lines of evidence indicate that the orthopyroxene-plagioclase assemblage would not be stable relative to clinopyroxene in rocks of Kilauea bulk composition. Irvine (1969) has analyzed the contrasting cumulate sequences from different lay ered intrusives. Orthopyroxene-plagioclase cumu lates do exist, as for example in the Stillwater Com plex (Jackson, 1969), but only in rocks with higher A1203 than either Kilauea or Mauna Loa. The projections of Jamieson (1970) and the experimen tal work of Green and Ringwood on compositions similar to but slightly more aluminous than Kilauea indicate that orthopyroxene and clinopyroxene are favored relative to plagioclase at elevated pressures making it highly unlikely that a clinopyroxene-poor fractionation could occur.

If plagioclase is not a possible major phase in the assemblage, then the Na20 and A1203 must be con centrated in ferromagnesian minerals. A1203 can re-

TABLE 20. Lava compositions 1 used in high-pressure fractionation calculations

Si0 2 ----__Al203--_-"FeO"-_.MgO_---_CaO----_-Na2O-_-K2O -__Ti02 _____P205 _____MnO__-_CrsO* _.

PHKILCAL(25 percent

MgO)

.. 46.177.83

... 11.36-. 25.00

6.291.26

.231.35

.12

.18

.22

1952Hm (20 percent

MgO)

46.819.30

11.9320.00

7.711.51

.351.82

.19

.19

.19

1959S-2 (20 percent

MgO)

46.739.17

11.9020.007.861.54

.401.85

.19

.18

.19

1967-68Hm (20 percent

MgO)

47.009.21

11.8820.007.641.56

.371.79

.18

.19

.201 Obtained from data of table 4 and table 14 by adding the appropriate amount of

olivine (Fa 13.7) containing 1 percent included Cr-spinel.

side in Cr203-poor spinel, aluminous pyroxenes, or garnet. Na20 is restricted to a jadeitic clinopyrox ene. Table 21B summarizes calculations using an as semblage olivine - spinel - orthopyroxene - clinopyrox ene. Pyroxene compositions are again calculated from five end members as above. For comparison with the composition of the fractionated pyroxenes the bulk composition of pyroxene in both the parent and the fractionated lava is calculated and shown in table 22. This assemblage, in which pryoxenes are very rich in A1203 and Na20, would be stable at higher pressures, up to about 20 kb in a garnet-free mantle (Ito and Kennedy, 1968, figs. 1 and 2).

As they stand, these calculations are not com pletely consistent because the bulk Na20 and A1203 of the fractionating clinopyroxene exceeds that of the clinopyroxene in PHKILCAL. Presumably with falling temperature the reverse should be true. The A1203 relations might be modified by consideration of Cr203 and Ti02 in pyroxene or by changing the Al:Cr ratio of the spinel, but the Na,20 could only be reversed by making the earlier clinopyroxenes more calcic than the bulk clinopyroxene. The latter would imply both that the CaO in clinopyroxene was de creasing during fractionation and that the ratio or thopyroxene: clinopyroxene was increasing during fractionation, neither of which should occur with falling temperature.

I conclude that there is no single-stage fractiona tion process that will explain the observed chemical variation. There remains the possibility of a multi stage process in which pyroxenes with lower Na20 and A1203 than those shown in table 22 are fraction ated at high pressure and are joined by a small

TABLE 21. Results of high-pressure fractionation calculations for Kilauea summit lavas A. Results with olivine-spinel-orthopyroxene-clinopyroxene-plagiodase

Parent. --._-.----.....-.-.....................

Fractionated phases : Olivine (Fai2 5 ) - - --_----_-_----_-_Cr-spinel--____________ . __________Orthopyroxene (KUMLHYP)-_---__-Clinopyroxene (MP218AUG) ..._.__..Plagioclase. ___________ __ ______

Total. ..___._....._ .___.._..___..

Residuals:1 Si0 2 _ __--_________-_-_____-._______A\20S .... .........................."FeO"__. ...MgO.___ ..______. --___--- ___CaO__._ ___________________________Na20_____________-_______-._______K20_. _____________________________Ti0 2___. ___________________________P205__. ____________________________MnO, _____________________________Cr203--- ---- _-__- _-._

.----.-- PHKILCAL (25 percent MgO)

---_-_._ 19.26________ .39_ _-__ 4.93_-_-__. 1.91_-_._-__ 3.67

(An59 .7)

.___..__ 30.16

_--_-_._ .01_----_._ -.01_-__._. .00----_-._ .01_.__-__. .01________ .04-_-._-__ -.02__ __- .05________ -.01----_-. -.02_----_-. .01

PHKILCAL (25 percent MgO)1959 S-2 (20 percent MgO)

19.29.39

5.751.214.13

(An59 . 7 )

30.77

.02

.01

.01

.01

.01

.01-.05

.04-.01-.01

.01

PHKILCAL (25 percent MgO)1967-68Hm (20 percent MgO)

19.69.35

3.701.893.62

(An S2.i)

29.25

.02

.01

.01

.01

.01

.00-.04

.06

.00-.02

.01Observed minus calculated composition of parent.

DISCUSSION 31

TABLE 21. Results of high-pressure fractionation calculations for Kilauea summit lavas ContinuedB. Results with olivine-spinel-arthopyroxene-dinopyroxene

Fractionated phases : Olivine (Fai 2 . 6 ) __ .

Total.. .._...__..__._......

Residuals:1 SiO 2 __ _.__.._._.___........._A12O3 . ------.._. ------------"FeO" __------ ----.MgO_. .. ---------_-_------.CaO. ------._..- --------..Na2O. ......._...___._.._.._.K2O__---_-----_ -----TiO2- ------ - --P206 _____ -MnO_. ----..---..----- --.Cr2O3 _---_______ _-

. _ .............. PHKILCAL (25 percent MgO)

.- ----- -----_ 1952Hm (20 percent MgO)

---..-_------ 17.26..... ...... .36_._____._._ 5.35------------- 4.30

..__....._. 27.27

------------ .02._..._.__.._.. .01.........__.._. .01------------- .01_....-_...__.. .01._........_._. .01-_-_-____- -.02. . .- .03------------ -.01.............. .00........_..._. .01

PHKILCAL (25 percent MgO)1959 8-2 (20 percent MgO)

16.94.38

7.234.29

28.84

.02

.01

.01

.01

.01

.01-.05

.04-.01

.01

.01

PHKILCAL (25 percent MgO)1967-68Hm (20 percent MgO)

17.36.32

4.634.11

26.42

.02

.01

.01

.01

.01

.01-.04

.04-.01-.01

.01

Calculated composition of pyroxenes

SiO 2 .. ------------------A12O 3 -. ------ ."FeO". _- -_-_-_ ._-MgO.._._. ........ ...._. _.CaO.-- _-_-.Na2O. .-.-.----..---._._-.

Orthopyroxene

..._...__.__.._.... 53.36- _ .___ 7.85.._..._._._...__._. 7.02..__.._-__._....... 30.63--__ ----- .90- __-__---._ .23

Clinopyroxene

52.6911.524.18

13.4514.713.45

Orthopyroxene

52.598.758.14

29.38.87.28

Clinopyroxene

52.0812.014.95

13.0114.633.32

Orthopyroxene

52.739.026.82

30.36.83.23

Clinopyroxene

51.2912.034.24

14.7515.272.42

1 Observed minus calculated composition of parent.

TABLE 22. Calculated high-pressure solidus assemblage and pyroxene compositions for Kilauea summit lavas

PHKILCAL (25 percent MgO)

1952Hm (20 percent MgO)

1959 S-2 (20 percent MgO)

1967-68 (20 percent MgO)

Mode

Olivine (Fau)-.Cr-spinel _.Orthopyroxene Clinopyroxene-Hornblende 1 ...Apatite... __.Rutile 2 ---.--.

26.21 .70

30.19 30.68 11.15

.28

.84

11.65 .60

33.72 35.62 16.96

.44 1.06

11

32 34 19

.73

.59

.16

.77

.39

.44

.98

11.07 .63

34.03 34.99 17.93

.41

.98

Calculated composition of pyroxenes

Orthopyroxene

SiO 2A1 2O3 . __._.._.

MgO --.--.

Na2O._---.

---- 51.--- 8.---- 13.-.__ 25.

,24 .30.94 .50 .87 .15

Clinopyroxene

51.04 11.94 6.96

12.26 14.99 2.84

Orthopyroxene

50.91 7.96

15.86 24.24

.89

.15

Clinopyroxene

50. 11. 7.

11. 15.

2.

73,72 ,98 ,82 .11 .64

Orthopyroxene

51.287.47

15.77 24.48

.83

.19

Clinopyroxene

50.73 11.46 8.07

11.94 15.27 2.53

Orthopyroxene

51,7.

15. 24,

.21

.58

.60

.69

.78

.14

Clinopyroxene

50.96 11.56 7.94

11.75 15.04 2.75

1 A hornblende from Kakanui with 4.5 percent TiOz, 2.1 percent KzO, and 3.1 percent NazO is used for the K2O balance. * Used for TiOz balance in the absence of any TiOs in pyroxene.

amount of plagioclase as the magma moves to lower pressure. This process would require a virtually iso thermal ascent of magma from the uppermost mantle to the 3-km-deep reservoir in order to move from a field in which plagioclase was stable (at say 8 kb) to the conditions at a depth of 3 km where the magmas lie within the field of olivine just above the stability field of Clinopyroxene and plagioclase. (See, for example, Green and Ringwood, 1967, fig. 4, or Ito and Kennedy, 1968, figs. 1 and 2.)

SHORT TERM CHEMICAL VARIATION

In a previous paper (Wright and Fiske, 1971, app. 2), it is shown that lava from each of the re cent (1952 to 1967-68) summit eruptions of Ki lauea is uniform in composition but differs from the others in ways that are explainable only by addition or removal of a complex silicate assemblage, gener ally including hypersthene. The chemical com position of these lavas is shown on an expanded scale in figure 12. The uniformity of each eruption


CaO

3

0.0

30

2.5

2.0

10

05

0.0

3.0

2.5

2.0

12.0

115

11.0

10.5 8.

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I i 1

X0 X^* X A OAA

I 1 I i 1 1 I I 1 1 1 1 1 1 1 I I I i

1 1 1 I 1 1 1 1 1 1 1 1 1 1 I I 1 1 i

* OAA_ \X A A*^ _V A A

O XX

-

I I 1 I I t I 1 1 I 1 1 1 I 1 1 I I I

1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1

°A

1 1 1 1 1 1 | 1 1 1 1 1 1 ! 1 1 1 1 I

I i i i i I i i i i i i i i i i i i i

*x**x A oAA

o1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1o

-

I * Axx xx x

1 1 1 1 1 1 1 1 1 I 1 1 1 f 1 1 1 I 1

1 1 1 1 1 I I 1 I 1 1 1 1 1 I I i I 1

X Q A 0 X* A A

: . * :i i i i 1 1 i i i i i i i i i i 1 1 11 1 i i 1 1 i i i i i i i i i 1 1 1 1

A -A -

X _

- o

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

-

X

. xx A :A

~~ A o ~S-2

i- OS-l

i i i i i r i i i i i i i i i i i i i5 8.0 7.5 7.0 6.5 8.5 8.0 7.5 7.0 6.

11.5

"FeO'

11.0

10.5

14.5

14.0

13.5 AI 20 3

13.0

12.5

51.0

50.5

50.0

49.5

MgO MgO

FIGURE 12. Mg-O variation diagrams showing Kilauea summit lavas 1952-68. A, 1952 Halemaumau; A. 1954 Halemaumau and Kilauea caldera floor; Q, 1959 Kilauea Iki all samples from the eruption correspond to a mixture of S-l, S-2, and olivine (Fai3 .2-ie.8) ; , 1961 Halemaumau; X, 1967-68 Halemaumau. Each erup tion may be distinguished chemically from every other eruption on one or more of the variation diagrams.

MODEL FOR MELTING AND FRACTIONATION OF KILAUEA AND MAUNA LOA MAGMAS 33

and the necessity for accumulation or removal of hypersthene indicate that these chemical variations are produced at pressures in excess of 2 kb prior to storage of magma in the shallow reservoir complex beneath Kilauea summit. I suggest that these batches are a result of high-pressure fractionation processes similar to those described for the long- term variation and that each batch is produced along a different pressure-temperature-time path in the upper mantle; that is, the original melt is con sidered to move upward in the mantle along paths where both the rate of cooling and velocity of as cent (equals rate of change of pressure) are varia ble, and this determines the amount and kind of phases that are fractionated.

MODEL FOR MELTING ANDFRACTIONATION OF KILAUEA AND

MAUNA LOA MAGMAS

A possible cross section through Kilauea and Mauna Loa is shown at true vertical and horizontal scale in figure 13. The zone of original melting is assumed to be at a depth of at least 60 km (below the deepest recorded earthquakes beneath Kilauea) corresponding to pressures in excess of 20 kb. The amount of melting needed to produce an initial picritic tholeiitic magma with 25 percent MgO is con sidered to be about 50 percent (see Jackson and Wright, 1970) in order to restrict the range of depth to which the mantle is melted.

There is strong evidence for the existence of an intermediate reservoir in the uppermost mantle, a staging area from which magma is efficiently sup plied the 3-km-deep, reservoir. The evidence is con tained in the observation that Halemaumau (sum mit) eruptions are accompanied by only a small collapse of the summit (see for example Kinoshita and others, 1969), implying that magma is resup- plied at virtually the same rate as it is erupted (at least 0.3X 106m3/day for the 1967-68 eruption).

Thus geophysical observation and the chemical petrology lead me to suggest the following model shown in figure 13.

Depth Process (es)

?-60 km ____Melting to produce plcritic (20-25 percent MgO) tholeiitic magma.

60-30 km Upward movement accompanied by frac tionation of olivine-spinel and variable amounts of orthopyroxene and clinopyroxene.

Depth Process(es)

30-20 km ____Accumulation of magma in separate stor age reservoirs which periodically feed the shallow reservoir beneath Kilauea summit. Further removal of olivine and pyroxene and possible fractionation of plagioclase.

20-4 km ____Rapid upward transfer of magma during eruption at Kilauea summit and during periods of inflation between eruptions.

4-2 km _____Storage of magma prior to eruption. Some cooling and further fractionation of oli vine only.

A section through Mauna Loa cannot be specified as closely because there are few geophysical data. The chemistry of the eruptions suggests that there has been relatively little high-pressure fractionation of pyroxenes but significant low-pressure movement of olivine, pyroxene, and plagioclase phenocrysts.

The model of figure 13 is very much like that pro posed by O'Hara (1968, p. 95) for derivation of quartz-normative tholeiitic magmas. The model im plies that the unmelted part of the upper mantle as well as the lower crust contains excess olivine pre cipitated from rising picritic magmas. The Kilauea model would imply accumulation of pyroxene as well.

The model proposed here differs in the following respects from that proposed by Murata (1970):1. The chemical differences between Kilauea and

Mauna Loa are explained by fractionation of Kilauea magma, which may have been origi nally close to the composition of Mauna Loa, instead of by differing degrees of partial melt ing or by melting in a mantle of variable com position.

2. Orthopyroxene alone is not found sufficient to explain the differences in chemistry either within Kilauea or between Kilauea and Mauna Loa. (Compare the residuals in the calcula tions of table 21 with those of Murata, 1970, table 2.) It is important to note in this regard that orthopyroxene fractionation alone would yield alkalic basalt whereas Kilauea has re mained tholeiitic.

3. I find, in agreement with Murata, an excess of K20 and TiO, in the 1959 Kilauea eruption as compared with Mauna Loa. This is true re gardless of what kind of fractionation or melting scheme is proposed. However, these differences are much less accentuated if other recent lavas are compared with Mauna Loa (for example, 1967-68) and are virtually non existent if the comparison is made with older lavas of Kilauea.


Q

10

20

30

40

50

60

70

80

90

100

110

MAUNA LOA

VOLCANIC PILE

OCEANIC CRUST

MANTLE

KILAUEA

SHALLOW ' '&$*' RESERVOIR

10 20 KILOMETERS I

:.:'-'-;"-':- INTERMEDIATE STAGING AREA

; '.: REGION OF ; T; COLLECTION' ': OF MAGMA

REGION OF PARTIAL MELTING

10

15

LLJ CC.a.Q<

20

25

FIGURE 13. A hypothetical model of Kilauea and Mauna Loa at true scale outlining regions of melting, fractionation,and storage of magma prior to eruption.

TABL

E 23.

Sam

ple

data

for

the

chem

ical

ana

lyse

s of

tabl

es J

+-6

and

8-13

All

anal

yses

wer

e do

ne i

n th

e U

.S.

Geo

logi

cal

Sur

vey

unde

r th

e di

rect

ion

of L

. C

. P

eck;

ind

ivid

ual

anal

ysts

are

ide

ntif

ied

as f

ollo

ws:

CL

P,

Chr

iste

l P

arke

r; D

FP

, D

orot

hy

Pow

ers;

EE

, E

dy

the

Eng

lem

an;

EL

M,

Ela

ine

Mun

son;

BS

D,

Ell

en D

anie

ls;

GO

R,

Geo

rge

Rid

dle;

JW

G,

June

Gol

dsm

ith;

LD

T,

Loi

s T

rum

bull

; L

MK

, L

ucil

le K

ehl;

LN

T,

Luc

ille

Tar

ran

t; V

CS,

Ver

tie

Sm

ith]

Fie

ldN

o.L

abor

ator

yN

o.R

epor

tN

o.A

naly

stA

geQ

uadr

angl

eL

atL

ong

Ele

vati

on(f

eet)

Geo

logi

c m

ap o

r ot

her

refe

renc

eS

ampl

e ty

peC

olle

ctor

Tab

le 4

, la

vas

from

Kil

auea

sum

mit

57-F

-18.

15

-

17. _

---

--66

-

53

P-1

2-

.

32

.-- __ _

__

35.-

---

__ -

-

30

.--.

.--.

-

HIG

S-2

. ...

--.-

.

8X

00

2-0

...-

----

.

8X

038-0

-........

8X

067-0

- -

__-.

8X07

8-0 _ ......

1790

. __ ---

----

18

32

.. ...

..--. ..

1866

(?) -

-

1868

__ . ---.

1877

Cald

era

--

1877

K

eana

kako

L

1. -

-.--

. --

-_

2--

-.--

__ -

477.-

--.....-

.-.

64P

-126. -

----

--

1931

HM

__

_ .. ..

Kil

19

54

----

___

TL

W6

7-4

2

Feb

. 19

61 ........

July

196

1 _

_

1967

HM

__ ---

---

HM

68-2

__

_ ...

.

4__

- -

-

12 _

. __ .

15... -

----

E-2

144

E-2

143

E-2

147

E-2

148

EO

1 A

Q

C-8

12

C-8

14

C-8

16

C-8

13

D10

1098

D 1

0218

2

D10

2183

D 1

02 1

84D

102

185

D 1

0197

3D

101

756

D10

1758

D10

1422

D 1

0142

0D

1014

21C

on 1

D 1

0004

4

D 1

0004

5D

1017

59

CD

-53-

2284

D 1

0142

4D

100

700

CD

-53-

2283

D 1

0070

1

D 1

0241

0

53-2

377C

DB

-327

D 1

0179

4H

3562

TT

QK

CQ

K

D10

2012

D 1

0240

7

D 1

0239

9

D 1

0240

8

D 1

0240

9

IDC

-368

IDC

-36

8L

DC

-368

IDC

-368

IDC

-237

IDC

-237

TT

~\/

~1

OQ

*7

IDC

-237

IDC

-237

66-D

C-7

68-D

C-3

5

68-D

C-3

56

8-D

C-3

568

-DC

-35

68

-DC

-16

67-D

C-3

167

-DC

-31

66-D

C-4

2

6C-D

C-4

26

6-D

C-4

2T

T»/

~^

OQ

7

63-D

C-2

1

63-D

C-2

1nrj

T-

V/~<

o

1

IDC

-122

66

-DC

-42

65-D

C-1

7

IDC

-122

65-D

C-1

7

69-D

C-3

9

I DC

- 120

IDC

-17

6

67-D

C-4

4D

C-5

62

68-D

C-1

9

69-D

C-3

9

69-D

C-2

9

69-D

C-3

9

69-D

C-3

9

JWG

JWG

JWG

JWG

JWG

DF

P

DF

P

TM

?T>

DF

P

DF

P

GO

R

CL

P

CL

PC

LP

CL

PE

EE

EE

EG

OR

GO

RG

OR

DF

PD

FP

DF

P1.1

1.1

LN

T

GO

RB

SD

LN

T

T M

T

BS

D

GO

R

LM

KL

DT

EL

ME

LM

EL

MG

OR

GO

R

EL

M

GO

R

GO

R

Pre

hist

oric

-dO

------

-_do -

-dO

-dO

-_dO

-

-.d

O-.-

-.-

.

_.d

o

-dO

-dO

_

-d

O

__dO

------

-do-_

_

__dO

-_-_

-__

_-dO

-

1790

1832

1866

(?)

1868

1877

1877

1884

-85

1889

1917

1918

1919

1919

1924

1931

-32

1952

1954

1954

2/24

/61

1967

1968

1968

1968

1968

Kau

Des

ert.

..d

o..

do

---.

do--

--.....

----

do-.

....

-.K

ilau

ea C

rate

r..

...

-do-

___.

____

d

o

-

dO

- -

_ d

o._

-__dO

-_ .._

._.

-

..-d

o-.

-

.

..-d

o..

....

. .d

o. -

do

- .

.---

do..--

..-

.--d

o.........

...-

do--

-.--

-.-

.--do

----

--

_

dO

.d

o

..._

do ......

d

o _

._

..-d

o.. ..

_._

_-

-dO

-

- d

o

-

do-.

._._

... .d

o..

---

----

do

-

do._

.

---do........

- do-_

_

... _do-_

_--

._ -

do.. .

...

-do.. .-.

-._.

. d

o._ .

-

do._

_ _

__ -

do-.

. _

.-

___ _do _.-

...

__-d

o--

___ _

..--

do

.-. -..--

-_-_

do._

_ ......

_-.

19

°18'

.-.

19°1

8'.-

--

19°1

8'-.

.

19°1

8'1 Q

°l R

'

----

19

°24'

_-__

19

°25'

_._

- 19

°25'

-_-_

19

°24'

---_

19

°24'

----

19

°25'

- .

19°2

5'

--._

19

°25'

--_-

19°2

5'

.-.-

19

°25'

155°

19'

155°

18'

155°

18'

155°

18'

155°

18'

155°

17'

155°

16'

155°

16

155°

16'

155°

16'

155°

17'

155°

17'

155°

17'

155°

17'

155°

17'

155°

17'

1,96

51,

100

1,10

01,

100

1,10

0

3,64

03,

680

3,54

0

3,56

03,

470

3,60

0

3,60

0

3,64

0

3,60

0

3,62

0

Wal

ker,

196

9. _

. .. .. .. .. .

----d

O.--.--.. .. -------------

--..

dO

-.

__

__

__

do .do

Pet

erso

n, 1

967..--

-.

. ......

. do

-.-d

o.-

---

.--

----

- .-

----

-

_. ..d

o..

...

.._

_ _

__ ...

..

. ---dO

---------- --------------

_ dO

_

._

-_

_

do

- .

. .

.. ...dO

----- -

. ------

.do - -

-

do

-----.-

-.-

---

....do ...... ..-

--------_-

do... -d

O----------. --------

. .--

do

---_

- --

----

----

----

---

-. .-do ------ ------

..-d

o.-. --------------

.- -

do.-

--- -.-

-- -

----

----

-

do

-.

--..

--

----

9.

Pet

erso

n, 1

967

and

Mac

dona

ld a

ndE

aton

, 19

55,

tabl

e 9.

Jagg

ar

(Vol

cano

Let

ter

388,

Jun

e19

32).

Mac

dona

ld,

1955

, p.

81

____..

Pet

erso

n,

1967

, an

d

Mac

dona

ldan

d E

aton

, 19

57,

tab

le 1

.P

eter

son,

19

67

..

. .

----

-- _

R

icht

er a

nd o

ther

s, 1

964,

tab

le 1

. . .

-

dO

-

-

--

Kin

oshi

ta a

nd o

ther

s, 1

969,

tab

le 2

.

Flo

w,

Hil

ina

Pal

i se

ctio

n. -

._

.... -d

O-.-..-.-....-... .........

Mul

tipl

e di

ke,

Hil

ina

Pal

i se

ctio

n ..

Dik

e, H

ilin

a P

ali

sect

ion.

---

----

----d

o..

....

....

... -------

Nor

thw

est

wal

l K

ilau

ea

cald

era,

flow

50

ft a

bove

flo

or.

Nor

thw

est

wal

l K

ilau

ea

cald

era,

flow

old

er th

an U

wek

ahun

a A

sh.

---d

o--

----

---.

.... ...

....

...

Nor

thw

est

wal

l K

ilau

ea

cald

era,

flow

res

ting

on

Uw

ekah

una

Ash

.W

est

rim

of

Kil

auea

cal

dera

, fl

owfr

om q

uar

ry a

t N

amak

ani

Pai

o.E

ast

rim

of

Kil

auea

cal

dera

, fl

owne

ar L

ua-m

anu.

Dri

ll

core

, fl

ow

from

no

rthw

est

wal

l, K

ilau

ea c

alde

ra.

d

o_ . .

_-_-

do__

____

. ___

____

____

____

__. do _ _

-G

lass

y bo

mb,

Kil

auea

cal

dera

flo

or-

Flo

w,

Byr

on L

edge

----

----

Flo

w,

Kil

auea

cal

dera

flo

or.

.F

low

, w

all

of K

ilau

ea

Iki

Cra

ter

(cov

ered

by

1959

lav

a).

Spa

tter

, w

est

wal

l K

ilau

ea c

alde

ra.

Flow

, K

eana

kako

i C

rate

r fl

oor.

..

Flo

w,

Kil

auea

cal

dera

fl

oor

(cov

er

ed b

y 19

54 l

ava)

.----do.......-

.---.-

...-

.......

Cra

ter.

. do

d

o. ...

...

Cra

ter.

Flo

w,

Kil

auea

cal

dera

flo

or. .

_

-d

o _

.

Gla

ss f

rom

lava

lake

, H

alem

aum

auC

rate

r.F

low

, H

alem

aum

au C

rate

r fl

oo

r..

Flo

w,

Kil

auea

cal

dera

flo

or. .

. .

d

o. - -

. d

o -------

Pum

ice,

H

alem

aum

au

Cra

ter.

Eru

pte

d N

ov.

5, 1

967-

..

Flo

w c

rust

, H

alem

aum

au

Cra

ter.

Eru

pte

d M

ay 2

9, 1

968.

Flo

w

crus

t,

Hal

emau

mau

Cra

ter.

Eru

pte

d i

n ea

rly

July

, 19

68.

Aa

flow

, H

alem

aum

au

Cra

ter.

Eru

pte

d F

ebru

ary

196

8.S

patt

er,

Hal

emau

mau

C

rate

r.E

rup

ted

Jul

y 13

, 19

68.

Geo

rge

Fra

ser.

Do.

Do.

Do.

Do.

H.

A.

Pow

ers.

Do.

Do.

Do.

Do.

Do.

R.

R.

Doe

ll.

Do.

Do.

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ers.

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ght.

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ers.

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ar.

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ght.

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.

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W 02 H 3 02

d CO 01

TABL

E 23.

Sam

ple

data

for

the

chem

ical

ana

lyse

s oj

tab

les

J+-6

and

8-1

3 C

onti

nued

CO

Oi

Fie

ld

No.

Lab

orat

ory

Rep

ort

No,

N

o.A

naly

st

Age

Qua

dran

gle

Lat

L

ong

Ele

vati

on

Geo

logi

c m

ap o

r ot

her

refe

renc

e S

ampl

e ty

pe

(fee

t)C

olle

ctor

Tab

le 5

, la

vas

from

Kil

auea

sou

thw

est

rift

zon

e

TL

W67-1

38A

-..-

1 Q

Q

12

8-

__-

134 _

---

136B

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3 ---

--K

D~

3_. _

____

____

32. .

.. ---

---

56. .

.. ---

---

57.. ...... ..

91

-..-

.--.

..T

LW

67-1

29.-

-..

KD

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, __

____

144.

-

TL

W67-1

0 .

KD

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---

----

172.

45. -

161.

_-.

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_T

LW

67-1

6 _ ---

CC

-SW

____

-

TL

W67-1

8

28

.

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30

- _

_

A-4

51

. __.. _

----

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- .-

_T

LW

67-2

4

1868

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. ,.._--

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LW

67-1

2 1

92

0-2

31

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T

L W

67-1

. _.-

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4 _ _

--._

B

-- _

9

D 1

0200

9 D

1020

10

D 1

0201

1 D

1019

67

D10

1954

D10

1955

D

1017

48

D10

1946

D

101 9

47

D10

1948

D

101

949

D 1

0195

0 D

1019

61

D10

1952

D

1019

53

D10

1742

D

101

958

D 1

0195

9 D

1019

56

D 1

0 19

57

D10

1751

D

1014

28

D10

1752

D

1017

50

D 1

0196

4

1417

5 D

1014

26

D10

1747

D

101

423

D10

1746

D

1014

25

D10

1749

D

1017

43

D10

1744

D

1017

45

68-D

C-1

9 68

-DC

19

68-D

C-1

9 68

-DC

-16

68

-DC

- 16

68-D

C-1

6 67

-DC

-31

68-D

C-1

6 6

8-D

C- 1

6 68

-DC

-16

68-D

C-1

6 68-D

C- 1

6 68

-DC

-16

68-D

C-1

6 68

-DC

-16

67-D

C-3

168

-DC

-16

68-D

C-1

6 68

-DC

-16

68-D

C- 1

667

-DC

-31

66-D

C-4

2 67

-DC

-31

67-D

C-3

1 68-D

C- 1

6

63

DC

6

66

DC

42

67-D

C-3

16

6-D

C-4

2

67-D

C-3

1 66

-DC

-42

67-D

C-3

1 67

-DC

-31

67-D

C-3

167

-DC

-31

GO

R

GO

R

GO

RE

E

EE

EE

E

E

EE

E

E

EE

E

E

EE

E

E

EE

E

E

EE

E

E

EE

E

E

EE

E

E

GO

R

EE

E

E

EE

DF

P

GO

RE

E

GO

R

EE

G

OR

EE

E

E

EE

E

E

Pre

hist

oric

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o_

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do

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o

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o -..

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o _

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o., .. _

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o --.

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o

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o _

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o ...

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_

1823

18

23

1823

18

68

1868

19

20

1920

19

20

1920

19

20

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------

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alle

y _ .

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-------

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o..

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d V

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ey .

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---

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o -

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iika

kani

Poi

nt -

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. .- --

----

do-.

. --

----

--. .-

dO

_

.-_

--.-

Kil

auea

Cra

ter.

W

ood

Val

ley _

_

d

o

doW

ood

Val

ley _ ...

--do ...

-

_

do_

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o..

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O

-----

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d V

all

ey.-

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,.

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.,

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19

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080

155°

17'

3,2

00

15

5°20

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940

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19'

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0 15

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180

155°

23'

1,66

0 15

5°23

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660

155°

19'

2,70

0 15

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' 2,

700

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22'

2,98

0 15

5°18

' 85

0 15

5°20

' 17

0 15

5°22

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800

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21'

2,66

0 15

5°20

' 3,

160

155°

19'

3,14

0 15

5°19

' 3,

600

155°

24'

2,00

0 15

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' 2,

690

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25'

1,66

0

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23'

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arns

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ld,

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ker,

19

69

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erso

n, 1

967 .... ....

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arns

an

d M

acdo

nald

, W

alke

r, 1

969.

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arns

and

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dona

ld,

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alke

r, 1

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arns

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,

19

46

.

1946...

1946

___

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cald

era.

--

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o..... ..---

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o

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o....... -..--

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do--

----

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.

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.do- ---------------

roun

ded

by 1

920

lava

.

kaia

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ls.

do

T.

L.

Wri

ght.

D

o.

Do.

D

o.

Do.

Do.

D

o.

G.

W.

Wal

ker.

D

o.

Do.

D

o.

Do.

T

. L

. W

righ

t.

G.

W.

Wal

ker.

D

o.

T.

L.

Wri

ght.

G

. W

. W

alke

r.

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o.

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T

. L

. W

righ

t.

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D

o.

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G

. W

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alke

r.

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oore

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ne.

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ght.

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. A

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ggar

. T

. L

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right.

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s.

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ght.

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o.

Do.

D

o.

Tab

le 6

, la

vas

from

Kil

auea

eas

t ri

ft z

one

[Ana

lyse

s of

his

tori

c fl

ows,

Kil

auea

eas

t ri

ft z

one,

are

giv

en i

n W

righ

t an

d F

iske

(19

71]

TL

W6

7-3

9

40 13

0.

131

132A

-

MP

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------

D10

1971

D

1019

72

D10

1968

D10

1970

D10

1969

1417

9

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C-1

6 6

8-D

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668-D

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6

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68-D

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6

63-D

C-6

EE

E

E

EE

EE

EE

DF

P

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hist

oric

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-do

---.

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o

_

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. ...

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dO

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__

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akao

puhi

Cra

ter

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o -

.

19°3

1'

19°3

1'15

4°51

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0 15

4°51

' 20

0S

tear

ns a

nd M

acdo

nald

, .. ..d

o--

--.-

--. ......

1946...

flow

.

dike

.

flow

.

lake

, ea

st p

it,

Mak

aopu

hi C

rate

r.

T.

L.

Wri

ght.

D

o.

Do.

Do.

Do.

J. G

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oore

.

Tab

le 8

, la

vas

from

Mau

na L

oa,

Mok

uaw

eow

eo c

alde

ra

7D

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4..

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02

6

42

0.

42

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TL

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70B

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1940

ML

, ...

....

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LW

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6-2

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0199

9

D 1

0200

0 D

102

001

D 1

0200

2 D

102

003

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0 18

30

D10

1997

D

1019

98

53-2

381

CS

D

D10

1832

C

810

53-2

382C

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68-D

C-1

9

68-D

C-1

9 68

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68-D

C-1

9 68

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68-D

C-5

68-D

C-1

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C-5

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C-2

35

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GO

R

GO

R

GO

R

GO

R

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P

GO

R

GO

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T

CL

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T

LD

T

Pre

hist

oric

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o .

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o ..

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1877

18

80

1940

19

42

1949

1949

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do

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do_-_

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do

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o ....

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o.. - --..

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o ..

....

....

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1'__

19

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...

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9'..

. 19

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._

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9'

155°

35'

12,4

00

155°

37'

13,4

00

155°

36'

13,2

00

155°

35'

13,0

50

155°

36'

13,2

00

Ste

arns

an

d M

acdo

nald

,

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do..

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..

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ld a

nd E

aton

, 1!

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ld a

nd

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on,

1

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1946...

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-.

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nort

h w

all

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uaw

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de

ra.

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cald

era

.

Poh

olo,

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th B

ay.

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sam

ples

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m m

ain

spat

ter

cone

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w,

near

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th B

ay _

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ll.

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o.

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righ

t.

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A.

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dona

ld.

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righ

t.

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A.

Mac

dona

W.

Do.

o W H

W

K.

O d £

>

cj f

O O o H

Tab

le 9

lav

as f

ront

Mau

na

Loa

sou

th r

ift

zon

e

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C-5

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C-5

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C-5

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LN

TL

NT

GO

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OR

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DC

LP

CL

PC

LP

GO

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FP

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PC

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TT

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PC

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PC

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CL

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P

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GO

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R

GO

RG

OR

GO

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o.......

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.18

68

1868

1868

1868

1868

1887

1907

1919

1919

1919

1926

1950

1950

1950

1950

1950

Pre

hist

oric

--dO

_

1852

1855

1855

1881

1881

1899

1899

1935

1935

1942

Pre

hist

oric

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o._

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_.

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o.......

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o.......

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o...... _

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5918

59

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do..__-_---__-

Kea

lake

kua .-...

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a -._

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----

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uku

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ch..

...

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do__

._ .........

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.

Puu

Hou

_

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o K

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...

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ka C

one.

. .. ...

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oli

i.._

_

----

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o------ --- -

____do____. -..-.--.

Sul

phur

Con

e.._

.

.A

lika

Con

e.

__

.. -

do -

-

.K

aulu

oa P

oin

t. ...

.

Tab

le 1

0,

Puu

Ula

ula

-...._

. .do _

_- .

Puu

Ula

ula

- - _

_ _

Pii

ho

nu

a..

..

.

Puu

Ula

ula

. . .

_

Kokoola

u.-

----

.__

Puu

Oo.

___

____

____

Puu

Ula

ula

...

.__

..

Tab

le 1

1

Kih

ok>

_._

_-.

_.

..

. H

uala

lai _

_..-.

_..

. P

uuoU

o.-

-__-

...

. _-

_.do

__ _

____

__

Ko

ko

ola

u..

....

. ..

..

Puu

Koli

--_--

-_._

_.

Kok

oola

u- -

_--

_._

.

Kih

olo.

_-_

-_--

......

18°5

8'

. 19

°35'

. 19

°11'

. 19

°07'

. 19

°06'

- 19

°04'

_ 19

°04'

. 18

°58'

- 19

°12'

. 19

°12'

. 19

°16'

. 19

°14'

. 19

°H'

. 19

°16'

. 19

°23'

. 19

°21'

. 19

°18'

. 19

°16'

155°

42'

155°

42'

155°

57'

155°

45'

155°

41'

155°

41'

155°

41'

155°

41'

155°

43'

155°

44'

155°

45'

155°

44'

155°

54'

155°

54'

155°

45'

155°

38'

155°

40'

155°

43'

155°

53'

500

250

1,00

05,

460

3,20

0

3,10

02,

040

2,04

0 06,

000

6,32

07,

800 0 0

7,70

011

,200

9,68

08,

560

1,34

0

Ste

arns

and

Cla

rk ,

1 930

. ___

___.

-_ d

o _

-

_ _

-

Ste

arns

and

Mac

dona

ld,

1946

. ...

--..do..--

----

-._--

----

-..-

....

Moo

re,

1965

. __

____

____

____

_ .

Ste

arns

an

d

Mac

dona

ld,

1946

;so

urce

of

flow

map

ped

tco

low

on t

opog

raph

ic s

heet

.___-do__._

__.-

_-_ _

_____________

- d

o _

--_

_

dO

- -_

-_

-M

oore

and

Aul

t, 1

965 _

.._

......

Ste

arns

and

Mac

dona

ld,

1946-.

-..

-d

o

.do -

-

- _

_ _

Moo

re a

nd A

ult,

1965

. _

____

___

doS

tear

ns a

nd M

acdo

nald

, 19

46. .

...

-_

--d

o..

...... ---.--_

. _

________

. do _

-

--..--..

-do _ _

.

-do -_ _-

Kah

uku

Pal

i, fl

ow. -

__--

-.-_

_____

....

do

... .......-

........--

____

Flo

w (

sam

ple

19) _

.---

_-.

_ _

.F

low

(sa

mpl

e 35).

-.-

__ ..

__

. .

Flo

w,

road

to

Kai

lua _ ..

--

----

-S

patt

er,

cone

so

uthe

ast

of

Puu

Oho

hia.

Sub

mar

ine

basa

lt,

1200

fat

hom

s. _

_S

patt

er,

uppe

rmos

t ve

nt,

Mau

naL

oa,

sout

h ri

ft z

one.

---

----

----

Spa

tter

- .

..___-_

__--

--.

- ..

.F

low

_ -.-

..--

----

-._

____

.

..P

icri

te,

Mam

alah

oa R

oad

----

---

Lit

tora

l co

ne _

- -_

._--

-_--

_._

___

Spa

tter

, up

perm

ost

vent

s _ ._

__

_

. --do.............. ---

-.._

..

Sp

att

er.

....

....

....

_

_ __

___

Gla

ss s

and,

lit

tora

l co

ne.

_ __

____

Flo

w n

ear

litt

ora

l co

ne. .

_--

......

Spa

tter

, lo

wer

ven

ts .-

----

-___.

Spa

tter

, ve

nts

near

Sul

phur

Gon

e. _

Sp

atte

r _ ...........

_ ..

. _

____

do__

____

__. .

....... ........

Flow

, so

uthe

rn b

ranc

h, M

amal

ahoa

Roa

d.F

low

.. ..

...._._

__-_

._--

.._._

___

Geo

rge

Fra

ser.

Do.

L.

F.

Nob

le.

Do.

E.

D.

Jack

son.

Do.

J. G

. M

oore

.

A.

T.

And

erso

n.

Do.

Do.

T.

L.

Wri

ght.

J. G

. M

oore

.T

. L

. W

righ

t.D

o.D

o.J.

G.

Moo

re.

Do.

T.

L.

Wri

ght.

Do.

Do.

Do.

Do.

lava

s fr

ont

Mau

na L

oa n

orth

east

rif

t zo

ne

. 19

°34'

. 19

°33'

_ 19

°42'

. 19

°32'

. 19

°41'

. 19

°31'

. 19

°3G

'

_ 19

°30'

. 19

°41'

. 1°

°33'

155°

22'

155°

25'

] 55°

28'

155°

14'

155°

28'

155°

12'

155°

32'

155°

28'

155°

34'

155°

27'

155°

27'

3 (\f\f\

8,34

010

,000

2,80

010

,000

2,20

011

,700

8,00

0

12,5

20

6,30

09,

200

Mac

dona

ld a

nd E

aton

, 19

55- .

__

doS

tear

ns

and

Mac

dona

ld,

1946

.S

ourc

e no

t m

appe

d on

ei

ther

geol

ogic

m

ap

or

topo

grap

hic

map

. V

ents

ar

e ab

out

1 m

ile

nort

hwes

t of

P

uu

Ula

ula

be

twee

n th

e m

appe

d 18

99

and

1880

-81

flow

s.

-d

o -

- -

_

_ dO

_

-

- _

Ste

arns

and

Mac

dona

ld,

1946

. T

he18

99 s

ourc

e m

appe

d ab

out 4

00 f

tto

o lo

w o

n b

cth

the

top

ogra

phic

and

geo

logi

c m

ap.

Ste

arns

and

Mac

dona

ld,

1946..

-..

Ste

arns

an

d M

acdo

nald

, 19

46.

The

1935

sou

rce

map

ped

as 1

942

onbo

th t

he

topo

grap

hic

and

geo

logi

c m

ap.

Ste

arns

and

Mac

dona

ld,

1946

. ___

_S

tear

ns

and

Mac

dona

ld,

1946

.S

ourc

e ve

nts

exte

nd 1

00 f

t uph

ill

from

bou

ndar

y of

flow

por

tray

edon

top

ogra

phic

map

.

Flo

w n

ear

Ola

a_. _

____

____

____

__

Spa

tter

, so

urce

ven

ts..

._

__

___-

__do

.___

___

____

____

____

____

__

Flo

w,

Sad

dle

Roa

d ..

__-_

. __

___

Flo

w,

two

sam

ples

ou

t of

fi

vech

osen

to

sh

ow

extr

emes

of

com

posi

tion

var

iati

on.

_ d

o___ ._

_

Flo

w,

road

to

Mau

na L

oa O

bser

va

tory

.S

pat

ter

sour

ce v

ent.

-

.-____._

Flo

w,

Sad

dle

Ro

ad. -.

..._

..

.S

patt

er,

sour

ce v

ent.

-

..--

.---

-

H.

A.

Pow

ers.

T.

L.

Wri

ght.

D

o.D

o.

Do.

J. G

. M

oore

.

Do.

T.

L.

Wri

ght.

Do.

Do.

Do.

Do.

, la

vas

fron

t M

auna

Loa

, no

rthw

est

slop

e

19°5

1'

. 19

°39'

. 19

°30'

. 19

°35'

_ 19

°37'

. 19

°38'

. 19

°32'

. 19

°52'

155°

56'

155°

46'

155°

42'

155°

38'

155°

34'

155°

33'

155°

37'

155°

55'

0 5,

160

8,80

08,

430

7,96

07

,26

011

,000 10

Ste

arns

and

Mac

dona

ld,

1946

. ....

_

do__

_ _

__ _

-_.

_

do

. _

____

____

__

-_-_

do

__

_

__

-_

_

-_ dO

_

_

_ _

do----d

o----..-.-.----...........

Bea

ch b

ould

er,

Kih

olo

Bay

. .

. _.

G

lass

y pa

hoeh

oe t

oe n

ear

Ahu

aU

mi

Hei

au.

Spa

tter

, P

uu o

Uo_

.-

---.

_ .....

Spa

tter

, hi

ll

8471

, ad

jace

nt

tolo

wer

185

9 ve

nts.

Spa

tter

, K

okoo

lau

co

ne..

. .

_ ...

Spa

tter

, P

uu K

oli.

...

. .._

_ ...

Pum

ice,

upp

erm

ost

ven

t _

._._

_F

low

_ .

...

.---

----

--.. _

..

T.

L.

Wri

ght.

W

. E

. B

anko

.

T.

L.

Wri

ght.

Do.

Do.

Do.

D.

L.

Pec

k.D

o.

W GQ H U g

>

cj r

o 2 CQ

O O

H

CO

00

TAB

LE 2

3.

Sam

ple

data

for

the

che

mic

al a

naly

ses

of t

able

s 4~

6 an

d 8-1

3 C

onti

nued

Fie

ldN

o.L

abo

rato

ry

No.

Rep

ort

No.

Anal

yst

Age

Quad

rangle

Lat

Lon

g

Tab

le 1

2, l

avas

fro

m t

he

Nin

ole

Hil

ls

ID-0

98

-2 -

214-2

240-2

.---

--

g TL

W6

7-7

2 .

..

54 _

_ -

54A

_

66 _

__

W

A 22- -

23.-

...-

....

C81

7...

C81

8..-

D10

218G

...

D 1

0218

7_

D10

2188

...

D10

2189

_.

D 1

0069

4

...

D10

1843

..

D10

1845

_ D

1022

88D

101

840

-.

D 1

0184

2

I DC

-23

8

IDC

-238

68-D

C-3

5

68-D

C-3

5

68

-DC

-35

68-D

C-3

5

65

-DC

-17

68-D

C-5

G

8-D

C-5

6

9-D

C-1

368-D

C-5

G8

-DC

-5

68-D

C-5

LN

T

LN

T

CL

P

CL

P

CL

P

CL

P

BS

D

CL

P

CL

P

GO

R

CL

P

CL

P

CL

P

Pre

his

tori

c

do-d

O-

--d

o--

. .-

do

.-

Pre

his

tori

c

1926

19

50

1950

18

43

1843

18

43

Tab

le

d

o ..

-

. do ------

Ele

vat

ion

G

eolo

gic

map

or

oth

er r

efer

ence

(fee

t)

, so

uth

east

slo

pe o

f M

auna

Loa

- , -

- _ _

_ S

tear

ns

and

Cla

rk,

1930

__

. -

. .----

_ d

o -

-- ..-

_ -

------- -

dO

-

--------

----d

O-----------. .. ---------

... .do

Sam

ple

type

Flo

w (

sam

ple

25) _

---

----

.

---_

dO

--_

--.------.--.

--.do-----.-- .

-

do- .

Coll

ecto

r

.....

L.

F.

Nob

le.

...-

D

o...

...

R.

R.

Doe

ll.

..-.

- D

o.--

---

Do.

..-.

Do.

13,

dif

fere

nti

ated

lav

as,

Mau

na

Loa

19°2

G'

19°2

G'

19°2

G'

19°3

2'

19°4

2'

19°4

2'

155°

37'

155°

37'

155°

37'

155°

32'

155°

30'

155°

30'

-------

Moo

re,

1965

.

..._

_._

_._

_.-

.

12,8

00

Mac

donal

d,

1971

12,8

00

d

o

12,8

00

do

1 1 ,

400

Ste

arns

and

Mac

do

nal

d,

1946

. T

he

1843

so

urce

ven

ts

are

expo

sed

wit

hin

the

1935

flo

w a

s p

ort

ray

ed

on

the

geol

ogic

m

ap.

Ven

t lo

ca

ted

about

0.85

mil

es N

. 5°

E.

from

ste

amin

g c

one.

6,6

30

do

Subm

arin

e dre

dge

sam

ple,

fa

tho

ms.

. do _ . -

.

.-.d

o-------------..--.

300

J. G

. M

oo

re.

.. .

T.

L.

Wri

ght.

-.-

R

. S.

Fis

ke.

.

Do.

...-

- T

. L

. W

right.

....

.

Do.

.-.-

. D

o.

O-

a » o i i f £j»

£j»

1 1

TAB

LE 2

4.

Lis

t of

rej

eren

ces

to p

ubli

shed

che

mic

al a

naly

ses

of K

ilau

ea

(oliv

ine-

cont

rolle

d) a

nd M

auna

Loa

flo

ws

othe

r th

an t

hose

rep

orte

d in

thi

s pa

per

Ref

eren

ceV

olca

no a

nd

dat

e of

eru

pti

on

An

aly

st

Mac

dona

ld (

1968

, ta

ble

6)_-

____

____

___-

_---

---_

_ K

ilau

ea,

1832

_-__

____

-_-_

__-_

-.-_

__-_

_.__

____

_ Y

. W

atan

abe.

Do_--

----

----

---_

-_-_

----

- -_

__--

--._

__

Mau

na L

oa,

preh

isto

ric,

185

5, 1

880,

189

9, 1

907_

__._

M

. C

hiba

, H

. A

sari

.M

acdo

nald

and

Kat

sura

(19

61,

tabl

e l)

__

_-_

_--

-_-

Kil

auea

, 1959_______--

--_--

--.-

-_-_

__--

_______

T.

Kat

sura

.M

acdo

nald

and

Kat

sura

(19

64,

tabl

e 8

)---

----

----

M

auna

Loa

, 18

43,

1859

, 18

81,

1887

, 19

26,

1935

.___

_ T

. K

atsu

ra,

K.

Ishi

bash

i.M

mr

and

Til

ley

(195

7, t

able

2)_

----

----

----

----

_

Kil

auea

, 19

21,

preh

isto

ric_

____

____

____

____

____

__

J. H

. Sc

oon.

Mui

r an

d T

ille

y (1

963,

tab

le !

)__

__

__

__

__

__

__

__

K

ilau

ea,

1921

, pr

ehis

tori

c; M

auna

Loa

, 1

88

7--

---.

D

o.M

uir

and

Tit

ley

(196

3, t

able

5)_

__

__

__

__

__

__

__

_

Kil

auea

, 18

68;

Mau

na L

oa,

18

68

---_

_-_

-__

-_-_

__

D

o.M

uir

and

Til

ley

(196

3, t

able

6)_

_______________

Mau

na L

oa,

1935

_ __

____

____

____

____

____

____

__

Do.

Mui

r an

d T

ille

y (1

963,

tab

le 8

)___

___

____

____

____

K

ilau

ea,

19

59

-60

----

----

----

----

----

-__

__

___

Do.

Til

ley

(198

0a,

tabl

e 1,

5 a

naly

ses)

.-.-

-.--

----

----

K

ilau

ea,

1921_-_

_____-_

-___--

_-_

_.-

_____

Do.

Til

ley

(196

0b,

tabl

e 1,

2 a

naly

ses)

.__

__

__

_-_

__

K

ilau

ea,

19

59

__

__

-__

__

--_

---_

_-_

_-_

__

.__

_

Do.

Til

ley

(196

1, t

able

l)_

____

____

____

_-__

___.

____

-_

Mau

na L

oa,

1887 _

___._

...._________..._

____

Do.

Til

ley

and

Scoo

n (1

961,

tab

le l

)__-

_-_-

,___

____

___

Kil

auea

, 18

68

(sou

thw

est

rift

zon

e);

Kil

auea

Iki

D

o.C

rate

r, 1

868

(tw

o an

alys

es).

T

ille

y an

d Sc

oon

(196

1, t

able

2)_

____

__.-

__--

____

_ M

auna

Loa

, 18

68 (

two

anal

yses

).__

____

____

____

_ D

o.T

ille

y an

d Sc

oon

(196

1, t

able

3)_

_-_

____--

--____

Mau

na L

oa,

preh

isto

ric

(thr

eefl

ows)

, 18

87,

18

81

__

D

o.

X CQ O M d

1-3

CHEMISTRY OF KILAUEA AND MAUNA LOA LAVA IN SPACE AND TIME 39

REFERENCES CITEDAnderson, A. T., and Greenland, L. P., 1969, Phosphorous

fractionation diagram as a quantitative indicator of crystallization differentiation of basaltic liquids: Geo- chim. et Cosmochim. Acta, v. 33, p. 493-505.

Aramaki, Shigea, and Moore, J. G., 1969, Chemical composi tion of prehistoric lavas at Makaopuhi crater, Kilauea volcano, and periodic change in alkali content of Hawaiian tholeiitic lavas: Tokyo Univ. Earthquake Re search Inst. Bull., v. 47, pt. 2, p. 257-270.

Beeson, M. H., and Jackson, E. D., 1970, Origin of the gar net pyrovenite xenoliths at Salt Lake crater, Oahu: Min- eralog. Soc. America Spec. Paper 3, 95-112.

Bryan, W. B., Finger, L. W., and Chayes, Felix, 1969, Estimating proportions in petrographic mixing equa tions by least squares approximation: Science, v. 163. p. 926-927.

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