10 inosilicates
-
Upload
- -
Category
Engineering
-
view
268 -
download
1
description
Transcript of 10 inosilicates
![Page 1: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/1.jpg)
Inosilicates: single chains- pyroxenes
Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)
Diopside: CaMg [Si2O6]
b
Where are the Si-O-Si-O chains??
![Page 2: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/2.jpg)
Inosilicates: single chains- pyroxenes
Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)
b
![Page 3: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/3.jpg)
Inosilicates: single chains- pyroxenes
Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)
b
![Page 4: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/4.jpg)
Inosilicates: single chains- pyroxenes
Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)
b
![Page 5: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/5.jpg)
Inosilicates: single chains- pyroxenes
Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)
b
![Page 6: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/6.jpg)
Inosilicates: single chains- pyroxenes
Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)
b
![Page 7: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/7.jpg)
Inosilicates: single chains- pyroxenes
Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)
Perspective view
![Page 8: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/8.jpg)
Inosilicates: single chains- pyroxenes
M1 octahedron
![Page 9: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/9.jpg)
Inosilicates: single chains- pyroxenes
M1 octahedron
![Page 10: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/10.jpg)
Inosilicates: single chains- pyroxenes
M1 octahedron
(+) type by convention
(+)
![Page 11: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/11.jpg)
Inosilicates: single chains- pyroxenes
M1 octahedron
This is a (-) type
(-)
![Page 12: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/12.jpg)
Inosilicates: single chains- pyroxenes
T
M1
T
Creates an “I-beam”
like unit in the
structure.
![Page 13: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/13.jpg)
Inosilicates: single chains- pyroxenes
T
M1
T
Creates an “I-beam”
like unit in the
structure
(+)
![Page 14: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/14.jpg)
The pyroxene
structure is then
composed of
alternating I-beams
Clinopyroxenes have
all I-beams oriented
the same: all are (+)
in this orientation
(+)
(+)(+)
(+)(+)
Inosilicates: single chains- pyroxenes
Note that M1 sites are
smaller than M2 sites, since
they are at the apices of the
tetrahedral chains
![Page 15: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/15.jpg)
The pyroxene
structure is then
composed of
alternation I-beams
Clinopyroxenes have
all I-beams oriented
the same: all are (+)
in this orientation
(+)
(+)(+)
Inosilicates: single chains- pyroxenes
(+)(+)
![Page 16: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/16.jpg)
The tetrahedral chain
above the M1s is thus
offset from that below
The M2 slabs have a
similar effect
The result is a
monoclinic unit cell,
hence clinopyroxenes
Inosilicates: single chains- pyroxenes
c
a
(+) M1
(+) M2
(+) M2
![Page 17: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/17.jpg)
Orthopyroxenes have
alternating (+) and (-)
I-beams
the offsets thus
compensate and result
in an orthorhombic
unit cell
This also explains the
double a cell dimension
and why orthopyroxenes
have {210} cleavages
instead of {110) as in
clinopyroxenes (although
both are at 90o)
Inosilicates: single chains- pyroxenes
c
a
(+) M1
(-) M1
(-) M2
(+) M2
![Page 18: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/18.jpg)
Pyroxene Chemistry
The pyroxene quadrilateral and opx-cpx solvusCoexisting opx + cpx in many rocks (pigeonite only in volcanics)
Diopside Hedenbergite
Wollastonite (pyroxenoid)
Enstatite Ferrosilite
orthopyroxenes
clinopyroxenes
pigeonite (Mg,Fe)2Si2O6 Ca(Mg,Fe)Si2O6
pigeonite
orthopyroxenes
Solvus
1200oC
1000oC
800oC
Augite
Miscibility Gap
![Page 19: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/19.jpg)
Pyroxene Chemistry
“Non-quad” pyroxenesJadeite
NaAlSi2O6
Ca(Mg,Fe)Si2O6
Aegirine
NaFe3+Si2O6
Diopside-Hedenbergite
Ca-Tschermack’s
molecule CaAl2SiO6
Omphaciteaegirine-
augite
Augite
Spodumene:
LiAlSi2O6
![Page 20: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/20.jpg)
Pyroxenoids“Ideal” pyroxene chains
with 5.2 A repeat (2
tetrahedra) become
distorted as other cations
occupy VI sites
Wollastonite
(Ca M1)
3-tet repeat
Rhodonite
MnSiO3
5-tet repeat
Pyroxmangite
(Mn, Fe)SiO3
7-tet repeat
Pyroxene
2-tet repeat
7.1 A12.5 A
17.4 A
5.2 A
![Page 21: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/21.jpg)
Inosilicates: double chains- amphiboles
Tremolite (001) view blue = Si purple = M1 rose = M2 gray = M3 (all Mg)
yellow = M4 (Ca)
Tremolite:
Ca2Mg5 [Si8O22] (OH)2
b
![Page 22: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/22.jpg)
Inosilicates: double chains- amphiboles
Hornblende:
K,<1(Ca, Na)2-3 (Mg, Fe,
Al)5 [(Si,Al)8O22] (OH)2
b
Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2
light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na+K)
little turquoise ball = H
![Page 23: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/23.jpg)
Inosilicates: double chains- amphiboles
Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2
light blue = M3 (all Mg, Fe)
Hornblende:
K,<1(Ca, Na)2-3 (Mg, Fe,
Al)5 [(Si,Al)8O22] (OH)2
Same I-beam
architecture, but
the I-beams are
fatter (double
chains)
![Page 24: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/24.jpg)
Inosilicates: double chains- amphiboles
b
(+) (+)
(+)
(+)
(+)
Same I-beam
architecture, but
the I-beams are
fatter (double
chains)
All are (+) on
clinoamphiboles
and alternate in
orthoamphiboles
Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2
light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na,K)
little turquoise ball = H
Hornblende:
K,<1(Ca, Na)2-3 (Mg, Fe,
Al)5 [(Si,Al)8O22] (OH)2
![Page 25: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/25.jpg)
Inosilicates: double chains- amphiboles
Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2
light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na, K)
little turquoise ball = H
Hornblende:
K,<1(Ca, Na)2-3 (Mg, Fe,
Al)5 [(Si,Al)8O22] (OH)2
M1-M3 are small sites
M4 is larger (Ca)
A-site is really big
Variety of sites
great chemical range
![Page 26: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/26.jpg)
Inosilicates: double chains- amphiboles
Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2
light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na)
little turquoise ball = H
Hornblende:
K,<1(Ca, Na)2-3 (Mg, Fe,
Al)5 [(Si,Al)8O22] (OH)2
(OH) is in center of
tetrahedral ring where O
is a part of M1 and M3
octahedra
(OH)
![Page 27: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/27.jpg)
See handout for more information
General formula:
W0-1 X2 Y5 [Z8O22] (OH, F, Cl)2
W = Na K
X = Ca Na Mg Fe2+ (Mn Li)
Y = Mg Fe2+ Mn Al Fe3+ Ti
Z = Si Al
Again, the great variety of sites and sizes a great chemical range,
and hence a broad stability range
The hydrous nature implies an upper temperature stability limit
Amphibole Chemistry
![Page 28: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/28.jpg)
Ca-Mg-Fe Amphibole “quadrilateral” (good analogy with
pyroxenes)
Amphibole Chemistry
Al and Na tend to stabilize the orthorhombic form in low-Ca amphiboles, so
anthophyllite gedrite orthorhombic series extends to Fe-rich gedrite in more Na-
Al-rich compositions
Tremolite
Ca2Mg5Si8O22(OH)2
Ferroactinolite
Ca2Fe5Si8O22(OH)2
Anthophyllite
Mg7Si8O22(OH)2Fe7Si8O22(OH)2
Actinolite
Cummingtonite-grunerite
Orthoamphiboles
Clinoamphiboles
![Page 29: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/29.jpg)
Hornblende has Al in the tetrahedral site
Geologists traditionally use the term “hornblende” as a catch-all term for
practically any dark amphibole. Now the common use of the microprobe
has petrologists casting “hornblende” into end-member compositions
and naming amphiboles after a well-represented end-member.
Sodic amphiboles
Glaucophane: Na2 Mg3 Al2 [Si8O22] (OH)2
Riebeckite: Na2 Fe2+3 Fe3+
2 [Si8O22] (OH)2
Sodic amphiboles are commonly blue, and often called “blue
amphiboles”
Amphibole Chemistry
![Page 30: 10 inosilicates](https://reader033.fdocuments.us/reader033/viewer/2022052910/559ae3741a28ab87798b4606/html5/thumbnails/30.jpg)
Inosilicates
Cleavage angles can be interpreted in terms of weak bonds in M2
sites (around I-beams instead of through them)
Narrow single-chain I-beams 90o cleavages in pyroxenes while wider
double-chain I-beams 60-120o cleavages in amphiboles
pyroxene amphibole
a
b