UBC Theses and Dissertations

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UBC Theses and Dissertations

A study on the equilibrium grossular + clinochlore = 3 diopside + 2 spinel + 4 H₂O Wang, Xiaomin 1986

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A STUDY ON THE EQUILIBRIUM GROSSULAR + CLINOCHLORE = 3 DIOPSIDE + 2 SPINEL + 4 H 20 by XIAOMIN WANG A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department of G e o l o g i c a l Sciences We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF June, © Xiaomin BRITISH COLUMBIA 1986 Wang, 1986 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e The U n i v e r s i t y of B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s or h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g .or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f G e o l o g i c a l S c i e n c e s The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5 D a t e : J u n e , 1986 ABSTRACT The e q u i l i b r i u m g r o s s u l a r + c l i n o c h l o r e = 3 d i o p s i d e + 2 s p i n e l + 4 H 2 0 was i n v e s t i g a t e d u s i n g c o l d s e a l p r e s s u r e v e s s e l s f r o m 500°C t o 700°C a t 0.5 k i l o b a r t o 4.0 k i l o b a r s . A l l p h a s e s u s e d i n t h e e x p e r i m e n t s were s y n t h e s i z e d from o x i d e s . Good b r a c k e t s w i t h s t a b l e a s s e m b l a g e s d i o p s i d e + s p i n e l or g r o s s u l a r + c l i n o c h l o r e were made a t c o n d i t i o n s f a r f r o m t h e e q u i l i b r i u m . A s s e m b l a g e s d i o p s i d e + c l i n o c h l o r e were f o u n d a t c o n d i t i o n s c l o s e t o t h e e q u i l i b r i u m o v e r t h e e n t i r e p r e s s u r e r a n g e . A n a l y s i s of i n t e r n a l c o n s i s t e n c y by l i n e a r programming i n d i c a t e s t h a t t h e e x p e r i m e n t a l r e s u l t s f r o m t h i s s t u d y a r e f u l l y c o n s i s t e n t w i t h t h e UBCDATABASE and H e l g e s o n ' s d a t a b a s e and t h e e x p e r i m e n t s , w i t h UBCDATABASE may s a f e l y be u s e d as an i n d i c a t i o n o f t h e meta m o r p h i c c o n d i t i o n s of m e t a r o d i n g i t e s . Run p r o d u c t d i o p s i d e , t h e o n l y p o s s i b l e s o l i d s o l u t i o n p hase i n t h i s s t u d y was e x t e n s i v e l y examined. X - r a y r e f i n e m e n t d e m o n s t r a t e s t h a t t h e c e l l p a r a m e t e r s o f t h e d i o p s i d e a r e w e l l w i t h i n t h e r a n g e f o r p u r e d i o p s i d e and Ca-Tschermak p y r o x e n e . S c a n n i n g e l e c t r o n m i c r o s c o p e and e l e c t r o n m i c r o p r o b e a n a l y s e s showed t h a t t h e s e d i o p s i d e s c o n t a i n aluminum i n t e r p r e t e d a s s u b s t i t u t i o n o f b o t h Ca-Tschermak and Mg-Tschermak p y r o x e n e . T h i s i n t e r p r e t a t i o n s a t i s f i e s t h e m a s s - b a l a n c e r e q u i r e m e n t s o f t h e s e a s s e m b l a g e s . T h e o r e t i c a l t h ermodynamic p r e d i c t i o n of t h e e q u i l i b r i u m a l l o w i n g f o r s o l i d s o l u t i o n s i n p y r o x e n e i n d i c a t e s t h a t d i o p s i d e s h o u l d be t h e main component, w h i c h i s c o n s i s t e n t w i t h t h e i i e x p e r i m e n t s i n t h a t t h e e q u i l i b r i u m c u r v e a c c o r d i n g t o t h e e x p e r i m e n t a l b r a c k e t s d i d n o t show m e a s u r a b l e d i s p l a c e m e n t c a u s e d by t h e low d i o p s i d e a c t i v i t y . Thermodynamic c a l c u l a t i o n u s i n g d i o p s i d e a c t i v i t y c a l c u l a t e d f r o m m i c r o p r o b e a n a l y s i s d a t a shows a s i g n i f i c a n t s h i f t i n t h e e q u i l i b r i u m c u r v e . C o m p a r i s o n of e x p e r i m e n t a l r e s u l t s w i t h n a t u r a l m i n e r a l s r e s u l t s i n c o n t r a d i c t i o n . N a t u r a l d i o p s i d e s ( c l i n o p y r o x e n e ) f o u n d i n s i m i l a r a s s e m b l a g e s a t s i m i l a r c o n d i t i o n s c o n t a i n much l e s s aluminum. U n d e t e c t e d m e t a s t a b l e z o n a t i o n o f aluminum o r even a l u m i n u m - r i c h i n c l u s i o n s a r e p r o b a b l y t h e main c a u s e s f o r t h i s . T a b l e o f C o n t e n t s ABSTRACT i i L I S T OF TABLES v i L I S T OF FIGURES v i i ACKNOWLEDGEMENTS i x I . INTRODUCTION 1 I I . EXPERIMENTAL METHOD 4 A. PROCEDURES 4 B. STARTING MATERIALS 7 C. SYNTHESIS 9 1. S p i n e l 9 2. D i o p s i d e 11 3. C l i n o c h l o r e 13 4. G r o s s u l a r 13 D. EXPERIMENTAL RESULTS 19 I I I . CLINOPYROXENE COMPOSITION 30 A. OPTICAL MICROSCOPE 31 B. X-RAY DIFFRACTION (X.R.D.) 31 C. SCANNING ELECTRON MICROSCOPE (S.E.M.) 32 1. Sample p r e p a r a t i o n 33 2. O b s e r v a t i o n 34 D. ELECTRON MICROPROBE 38 1. Sample p r e p a r a t i o n 38 2. A n a l y s i s p r o c e d u r e 38 3. I n t e r p r e t a t i o n o f d a t a 40 E. COMPOSITION OF CLINOPYROXENES FROM RODINGITES ..52 IV. THERMODYNAMIC ANALYSIS 53 A. PRECALCULATION 53 B. EXPERIMENTAL CONSTRAINTS ON THERMODYNAMIC PROPERTIES 55 C. CLINOPYROXENE SOLID SOLUTION 57 D. DIOPSIDE ACTIVITIES AND DISPLACED EQUILIBRIUM ..65 V. CONCLUSION 69 REFERENCES '. 7 2 APPENDIX 1 ..80 APPENDIX 2 84 v LIST OF TABLES Table I. Oxide weight percentage of minerals studied 10 Table I I . D-spacings and refined c e l l parameters for synthetic diopside 12 Table I I I . Comparison of c e l l parameters of synthetic and natural diopsides 16 Table IV. D-spacings and refined c e l l parameters for synthetic clinochlore 17 Table V. Experimental results for the equilibrium Grossular+Clinochlore=3Diopside + 2Spinel+4H 20 21 Table v(continued). Experimental results for the equilibrium Grossular+Clinochlore=3Diopside+2Spinel+4H 20 22 Table V I . D-spacings and refined c e l l paramenters for diopside (clinopyroxene) from run product 33 Table V I I . Standards used for microprobe analyses 40 Table V I I I . Duplicate of the microprobe analyses of standard diopside 41 Table IX. The results of mass balance c a l c u l a t i o n according to the microprobe analyses 50 Table X. Thermodynamic properties for phases considered in t h i s study 56 Table X I . Range of thermodynamic properties that are consistent with experimental results 57 v i L I S T OF FIGURES F i g . 1 C a l i b r a t i o n of r a t i o s o f X.R.D. peak h e i g h t s from s t a r t i n g m a t e r i a l XRR t o XRE 8 F i g . 2 R e p r e s e n t a t i v e x - r a y powder d i f f r a c t i o n p a t t e r n f o r t h e s y n t h e t i c d i o p s i d e 14 F i g . 3 X - r a y powder d i f f r a c t i o n s t a n d a r d p a t t e r n f o r d i o p s i d e 15 F i g . 4 P r e c a l c u l a t e d c u r v e of t h e e q u i l i b r i u m G r o s s u l a r + C l i n o c h l o r e = 3 D i o p s i d e + 2 S p i n e l + 4 H 2 0 and t h e e x p e r i m e n t a l b r a c k e t s 20 F i g . 5 - a I l l u s t r a t i o n of phase r e l a t i o n s i n t h e r e a c t i o n G r o s s u l a r + C l i n o c h l o r e = 3 D i o p s i d e + 2 S p i n e l + 4 H 2 0 a t h i g h t e m p e r a t u r e 24 F i g . 5 - b I l l u s t r a t i o n of phase r e l a t i o n s i n t h e r e a c t i o n G r o s s u l a r + C l i n o c h l o r e = 3 D i o p s i d e + 2 S p i n e l + 4 H 2 0 a t low t e m p e r a t u r e 25 F i g . 6 I l l u s t r a t i o n of t h e s t a r t i n g m a t e r i a l c o m p o s i t i o n s f o r e x p e r i m e n t s XRBulk-1 t o XRBulk-10 26 F i g . 7 The s c a n n i n g e l e c t r o n m i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m o f s y n t h e t i c d i o p s i d e 35 F i g . 8 - The s c a n n i n g e l e c t r o n m i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m of d i o p s i d e from r u n XRE-10 35 F i g . 9 The s c a n n i n g e l e c t r o n m i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m o f d i o p s i d e f r o m r u n XRR-3 36 F i g . 1 0 The s c a n n i n g e l e c t r o n m i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m of d i o p s i d e from r u n XRE-10 36 v i i Fig.11 The scanning e l e c t r o n microscope E.D.S. chemical spectrum of d i o p s i d e from run XRR-4 37 Fig.12 The scanning e l e c t r o n microscope E.D.S. chemical spectrum of d i o p s i d e from run XRE-10 37 Fig.13 The r e l a t i o n between A l 2 0 3 and CaO (mol) i n run product d i o p s i d e from microprobe analyses 42 Fig.14 The r e l a t i o n between A l 2 0 3 and MgO (mol) i n run product d i o p s i d e from microprobe analyses 43 Fig.15 The r e l a t i o n between A l 2 0 3 and (CaO+MgO) (mol) in run product d i o p s i d e from microprobe a n a l y s e s 44 Fig.16 The r e l a t i o n between A l 2 0 3 and S i 0 2 (mol) in run product d i o p s i d e from microprobe a n a l y s e s 45 Fig.17 The r e l a t i o n between CaO and S i 0 2 (mol) i n run product d i o p s i d e from, microprobe analyses 46 Fig.18 The r e l a t i o n between MgO and S i 0 2 (mol) i n run product d i o p s i d e from microprobe analyses 47 Fig.19 The r e l a t i o n between CaO and MgO (mol) i n run product d i o p s i d e from microprobe analyses 48 Fig.20 C a l c u l a t e d P u _-T diagram f o r dehydration H 2U e q u i l i b r i a among phases found i n m e t a r o d i n g i t e s 54 Fig.21 The range of thermodynamic p r o p e r t i e s that are i n t e r n a l l y c o n s i s t e n t 58 Fig.22 Comparison of the e q u i l i b r i u m curves d e r i v e d from UBCDATABASE, Helgeson's database and t h i s study 59 Fig.23 The d i s p l a c e d e q u i l i b r i a with d i f f e r e n t d i o p s i d e a c t i v i t i e s 67 v i i i ACKNOWLEDGEMENTS I e x p r e s s my d e e p e s t g r a t i t u d e t o t h e f o l l o w i n g p e r s o n s w i t h o u t whose c o n t r i b u t i o n t h i s t h e s i s would not be p o s s i b l e . D r . H.J. Greenwood, my s u p e r v i s o r , f o r h i s e n t h u s i a s m , s u g g e s t i o n s , i n v a l u a b l e e f f o r t s and p a t i e n t g u i d a n c e t h r o u g h t h e c o u r s e of t h i s r e s e a r c h ; my c o m m i t t e e members, D r s . T.H. Brown and E.P. Meagher f o r t h e i r h e l p f u l s u g g e s t i o n s , a d v i c e and c a r e f u l r e v i e w s o f t h e e a r l y m a n u s c r i p t of t h i s t h e s i s ; D r . R.G. Berman f o r h i s h e l p and a d v i c e i n thermodynamic a n a l y s i s work; D r s . J.M. R i c e and S.A. Rawson o f U n i v e r s i t y of Oregon f o r t h e i r k i n d n e s s o f s e n d i n g t h e i r u n p u b l i s h e d a n a l y s i s d a t a u s e d ; t h e t e c h n i c a l s t a f f , n o t a b l y Mr. B. C r a n s t o n , Mr. L. Hammerstrom, M r s. S . J . H o r s k y and Mr J.B. K n i g h t f o r t h e i r p a t i e n t l a b o r a t o r y i n s t r u c t i o n s and p r e p a r a t i o n s ; my f e l l o w g r a d u a t e s t u d e n t s , e s p e c i a l l y C. D e C a p i t a n i and Bear M c P h a i l f o r t h e i r c o n s t r u c t i v e s u g g e s t i o n s and h e l p f u l d i s c u s s i o n s . T h i s r e s e a r c h work was p a r t l y s u p p o r t e d t h r o u g h t h e N a t u r a l S c i e n c e and E n g i n e e r i n g R e s e a r c h C o u n c i l o p e r a t i n g g r a n t number A-4222 h e l d by D r . H.J. Greenwood and f e l l o w s h i p awarded by t h e M i n i s t r y o f E d u c a t i o n o f P e o p l e ' s R e p u b l i c o f C h i n a . i x I . INTRODUCTION R o d i n g i t e s a r e m e t a s o m a t i c r o c k s c o n s i s t i n g m a i n l y o f d i o p s i d e , c h l o r i t e and h y d r o g r o s s u l a r w h i c h o c c u r i n m a f i c b o d i e s a d j a c e n t t o and w i t h i n u l t r a m a f i c r o c k s u n d e r g o i n g s e r p e n t i n i z a t i o n . Metamorphism o f r o d i n g i t e s may r e s u l t i n m i n e r a l p a r a g e n e s e s t h a t c a n be u s e d i n c o n j u n c t i o n w i t h d i a g n o s t i c a s s e m b l a g e s i n t h e a d j a c e n t m e t a p e r i d o t i t e t o p l a c e l i m i t s on t e m p e r a t u r e s and p r e s s u r e s o f metamorphism. The t e r m " r o d i n g i t e " was f i r s t i n t r o d u c e d t o d e s c r i b e a l t e r e d g a b b r o s i n t h e Dun M o u n t a i n s e r p e n t i n i t e s of New Z e a l a n d ( B e l l , C l a r k and M a r s h a l l , 1911). S i n c e t h e n , r o d i n g i t e s have been f o u n d and r e p o r t e d i n a l m o s t e v e r y m ajor a l p i n e u l t r a m a f i c complex o v e r t h e w o r l d (Benson, 1913-1918; T u r n e r , 1930; W e l l s , H o t z and C a r t e r , 1949; M i l e s , 1950; C a r t e r and W e l l s , 1953; S u z u k i , 1953; Bloxam, 1954; J a f f e , 1955; B i l g r a m i and Howie, 1960; C h e s t e r m a n , 1960; S c h l o c k e r , 1960; Coleman, 1961-1967; S e k i and K u r i y a g a w a , 1962; M u l l e r , 1963; D a l P i a z , 1967, 1969; V u a g n a t , 1967). The s i g n i f i c a n c e o f r o d i n g i t e s t o m e t a m o r p h i c p e t r o l o g i s t s i s t w o f o l d ( R i c e , 1983). F i r s t o f a l l , t h e f o r m a t i o n o f r o d i n g i t e i s r e l a t e d e x c l u s i v e l y t o l o w - t e m p e r a t u r e s e r p e n t i n i z a t i o n , so t h e p r e s e n c e o f r o d i n g i t e i n some medium- and h i g h - g r a d e u l t r a m a f i c r o c k s i n d i c a t e s t h a t t h e t e r r a n e was f o r m e r l y under a c o n d i t i o n a p p r o p r i a t e f o r s e r p e n t i n i z a t i o n . S e c o n d l y , c h a n g e s i n m i n e r a l a s s e m b l a g e s t h a t t a k e p l a c e i n t h e r o d i n g i t e d u r i n g 1 2 l a t e r p r o g r e s s i v e metamorphism may be u s e d i n c o n j u n c t i o n w i t h t h o s e a f f e c t i n g t h e s u r r o u n d i n g u l t r a m a f i c r o c k s t o d e l i n e a t e i s o g r a d s and p l a c e l i m i t s on i n t e n s i v e v a r i a b l e s s u c h a s t e m p e r a t u r e , p r e s s u r e and f l u i d c o m p o s i t i o n d u r i n g t h e metamorphism. Thermodynamic c a l c u l a t i o n s o f e q u i l i b r i a among m i n e r a l s commonly f o u n d i n m e t a r o d i n g i t e s have been r e p o r t e d by R i c e ( 1 9 8 3 ) . In t h a t p a p e r , t h e s t a b l e M-,_ - y u ,» t o p o l o g i e s CU 2 H j U r e l a t i n g m i n e r a l s were f i r s t e s t a b l i s h e d a c c o r d i n g t o o b s e r v e d n a t u r a l p a r a g e n e s e s . A v a i l a b l e thermodynamic d a t a were t h e n u s e d t o c a l c u l a t e t h e i n f e r r e d m e t a r o d i n g i t e e q u i l i b r i a i n terms o f t e m p e r a t u r e , p r e s s u r e and c o m p o s i t i o n of a C 0 2 - H 2 0 f l u i d p h a s e . The r e s u l t i n g p e t r o g e n e t i c model was i n agreement w i t h o b s e r v e d n a t u r a l a s s e m b l a g e s i n b o t h low- and h i g h - p r e s s u r e t e r r a n e s and i n d i c a t e d t h a t c e r t a i n r o d i n g i t e p a r a g e n e s e s c a n be u s e d t o p l a c e l i m i t s on t e m p e r a t u r e s and p r e s s u r e s of metamorphism. T h i s s t u d y i s t h e f i r s t r e p o r t on e x p e r i m e n t a l work r e l a t e d d i r e c t l y t o m e t a r o d i n g i t e s . P h a s e s c o n s i d e r e d i n t h i s s t u d y a r e g r o s s u l a r , c l i n o c h l o r e , d i o p s i d e , s p i n e l and wa t e r ( H 2 0 ) . The s y s t e m w h i c h d e s c r i b e t h e s e p h a s e s i s C a O - M g O - A l 2 0 3 - S i 0 2 - H 2 0 . One i m p o r t a n t e q u i l i b r i u m : Grossular + Clinochlore = 3 Diopside + 2 Spinel + 4 H 20 was s t u d i e d and e x p e r i m e n t a l r e v e r s a l s were o b t a i n e d . I t was f o u n d t h a t many r u n s under c o n d i t i o n s n e a r t h e e q u i l i b r i u m 3 ended w i t h d i o p s i d e + c l i n o c h l o r e i n s t e a d o f e i t h e r d i o p s i d e + s p i n e l o r g r o s s u l a r + c l i n o c h l o r e . The c a u s e i s a t t r i b u t e d t o s o l i d s o l u t i o n i n d i o p s i d e t o w a r d t h e Ca-Tschermak and Mg-Tschermak components. The d i o p s i d e from e a c h run was examined by o p t i c a l m i c r o s c o p e , x - r a y d i f f r a c t i o n , s c a n n i n g e l e c t r o n m i c r o s c o p e and e l e c t r o n m i c r o p r o b e . The d i o p s i d e s were f o u n d t o be v e r y a l u m i n u m - r i c h , w h i c h i s not common i n t h e d i o p s i d e from r o d i n g i t e a s s e m b l a g e s . Ca-Tschermak and Mg-Tschermak s u b s t i t u t i o n i n d i o p s i d e a r e shown by thermodynamic c a l c u l a t i o n t o d i s p l a c e t h e e q u i l i b r i u m s t u d i e d f r o m t h e e x p e c t e d p o s i t i o n f o r p u r e end-member p h a s e s . I I . EXPERIMENTAL METHOD A. PROCEDURES A l l e x p e r i m e n t s were c a r r i e d o ut u s i n g s t a n d a r d c o l d s e a l p r e s s u r e v e s s e l s o f e i t h e r S t e l l i t e K-25 o r Rene 41 a l l o y s . F u r n a c e s u s e d were p l a c e d e i t h e r h o r i z o n t a l l y ( f o r 0.5 t o 2.0 k i l o b a r r u n s ) o r v e r t i c a l l y ( f o r 4.0 k i l o b a r r u n s ) . The r e s u l t s f r o m b o t h t y p e s of f u r n a c e s were i n good a g r e e m e n t . T e m p e r a t u r e was measured by s h e a t h e d c h r o m e l - a l u m e l t h e r m o c o u p l e s mounted i n an e x t e r n a l w e l l d e s i g n e d t o h o l d t h e t h e r m o c o u p l e t i p c l o s e t o t h e sample. C a l i b r a t i o n s of t h e t h e r m o c o u p l e were made between 400°C and 800°C a t one at m o s p h e r e f o r e a c h f u r n a c e w i t h a s p e c i f i c bomb and t h e r m o c o u p l e . I t was f o u n d t h a t t h e t e m p e r a t u r e g r a d i e n t s were l e s s t h a n ±1°C o v e r t h e two t o t h r e e c e n t i m e t e r l e n g t h o f t h e sample c a p s u l e . D u r i n g r u n s , t e m p e r a t u r e s were c o n t r o l l e d by f u l l y p r o p o r t i o n a l c o n t r o l l e r s w h i c h u s u a l l y c o n t r o l t h e t e m p e r a t u r e o f bomb w i t h v a r i a t i o n s l e s s t h a n ± 1 ° C . T e m p e r a t u r e measurements were made d a i l y u s i n g a t e m p e r a t u r e c o m p e n s a t e d d i g i t a l thermometer w i t h a r e s o l u t i o n of 1°C. As a c h e c k , a p o t e n t i o m e t e r w i t h an e s t i m a t e d r e s o l u t i o n o f 0.1°C was o c c a s s i o n a l l y u s e d t o measure t e m p e r a t u r e p r e c i s e l y . An a u t o m a t i c d a t a r e c o r d i n g s y s t e m u s i n g an IBM-XT computer and DAS A t o D i n t e r f a c e was u s e d t o measure t e m p e r a t u r e a u t o m a t i c a l l y once e v e r y h a l f h o u r f o r t h e d u r a t i o n o f t h e r u n . No s y s t e m a t i c t e m p e r a t u r e 4 5 d i f f e r e n c e was n o t i c e d between measurements t a k e n w i t h d i g i t a l t h e rmometer, L&N p o t e n t i o m e t e r , or c o m p u t e r . T e m p e r a t u r e s g i v e n i n t h e t a b l e o f e x p e r i m e n t a l r e s u l t s a r e th e a v e r a g e s o f t h e d a i l y measurements. The t o t a l c u m u l a t i v e e r r o r s i n c l u d i n g c a l i b r a t i o n and measurement and v a r i a t i o n a r e e s t i m a t e d t o be l e s s t h a n ± 5 ° C . E i t h e r methane ( f o r r u n s a t l e s s t h a n 2.0 k i l o b a r s ) o r d i s t i l l e d w a ter ( f o r r u n s w i t h 4.0 k i l o b a r s ) was u s e d a s p r e s s u r e m e d i a . P r e s s u r e measurements were made d a i l y w i t h e i t h e r an A s h c r o f t M a x i s a f e gauge w i t h a r e s o l u t i o n o f 15 b a r s o r a H e i s e Bourdon t u b e gauge w i t h a r e s o l u t i o n o f 5 b a r s . I f t h e p r e s s u r e d r o p p e d more t h a n 3%, t h e e x p e r i m e n t was r e p e a t e d . The p r e s s u r e s l i s t e d i n t h e e x p e r i m e n t a l r e s u l t t a b l e a r e t h e a v e r a g e s of d a i l y measurements and t h e t o t a l e r r o r s o f p r e s s u r e were e s t i m a t e d t o be l e s s t h a n ±20 b a r s . Most o f r u n s were i n v e s t i g a t e d w i t h two a d j a c e n t c a p s u l e s o f s t a r t i n g m i x t u r e s h a v i n g d i f f e r e n t p r o p o r t i o n s of low- and h i g h - t e m p e r a t u r e a s s e m b l a g e s . The e x c e p t i o n s a r e th e r u n s h a v i n g c o n d i t i o n s q u i t e f a r from e q u i l i b r i u m f o r w h i c h o n l y one c a p s u l e o f s t a r t i n g m a t e r i a l was u s e d . The two commonly u s e d m i x t u r e s were 20wt% l o w - t e m p e r a t u r e a s s e m b l a g e p l u s 80wt% h i g h - t e m p e r a t u r e a s s e m b l a g e , and t h e o t h e r 80wt% l o w - t e m p e r a t u r e a s s e m b l a g e p l u s 20wt% h i g h - t e m p e r a t u r e a s s e m b l a g e . F o r e a c h c a p s u l e , a p p r o x i m a t e l y 20 m i l l i g r a m s o f s t a r t i n g m i x t u r e were s e a l e d w i t h e x c e s s d i s t i l l e d w a t e r (30wt%) and t h e n w e i g h e d . The s e a l was 6 c h e c k e d by p l a c i n g t h e s e a l e d c a p s u l e i n an oven a t t e m p e r a t u r e of 100°C f o r 30 t o 40 m i n u t e s and r e w e i g h i n g . L o s s of w e i g h t i n d i c a t e d f a i l u r e o f t h e s e a l and a new c a p s u l e was p r e p a r e d . The f u r n a c e was p r e h e a t e d t o t h e d e s i r e d t e m p e r a t u r e b e f o r e t h e p r e s s u r e v e s s e l was i n s e r t e d . A f t e r i n s e r t i o n t h e t e m p e r a t u r e was s t a b l i z e d w i t h i n a b o u t 30 t o 60 m i n u t e s . A f t e r t h e r e q u i r e d d u r a t i o n , t h e p r e s s u r e v e s s e l was removed, p l a c e d i n a s t e e l c o o l i n g j a c k e t and q u e n c h e d by b l o w i n g c o m p r e s s e d a i r a r o u n d t h e v e s s e l . U s u a l l y , t h e t e m p e r a t u r e d r o p p e d t o l e s s t h a n 100°C w i t h i n 5 m i n u t e s . A f t e r t h e r e s i d u a l p r e s s u r e was r e l e a s e d , t h e c a p s u l e was removed, w e i g h e d , p u n c t u r e d and r e w e i g h e d t o make s u r e t h e r e was no l o s s of any m a t e r i a l d u r i n g t h e r u n . A f t e r t h e c h a r g e was d r i e d i n t h e oven a t 100°C f o r 30 m i n u t e s , t h e c a p s u l e was opened f o r e x a m i n a t i o n . Run c h a r g e s were examined under t h e o p t i c a l m i c r o s c o p e and w i t h x - r a y d i f f r a c t i o n . Then t h e y were examined under s c a n n i n g e l e c t r o n m i c r o s c o p e and m i c r o p r o b e i f n e c c e s s a r y . B e c a u s e most o f t h e r u n s showed i n c o m p l e t e r e a c t i o n , an x - r a y d i f f r a c t i o n i n t e n s i t y t e c h n i q u e was u s e d t o o b t a i n h e i g h t r a t i o s o f c e r t a i n p e a k s o f d i f f e r e n t p h a s e s t o d e t e r m i n e t h e e x t e n t and d i r e c t i o n o f r e a c t i o n . T h i s was done as f o l l o w s : f o r e a c h of two s t a r t i n g m i x t u r e s , s i x x - r a y d i f f r a c t i o n p a t t e r n s were made u s i n g d i f f e r e n t s l i d e s w i t h d i f f e r e n t amount o f m a t e r i a l s t o o b t a i n t h e a v e r a g e v a l u e s o f t h e peak r a t i o s b a s e d on t h e known c o m p o s i t i o n (80wt% l o w - t e m p e r a t u r e a s s e m b l a g e p l u s 20wt% h i g h - t e m p e r a t u r e a s s e m b l a g e o r 20wt% 7 l o w - t e m p e r a t u r e a s s e m b l a g e p l u s 80wt% h i g h - t e m p e r a t u r e a s s e m b l a g e , F i g 1 ) . The same method was a p p l i e d t o e a c h r u n c h a r g e w i t h i n c o m p l e t e r e a c t i o n t o f i n d t h e peak r a t i o s . The r a t i o s f r o m s t a r t i n g m a t e r i a l and from r u n p r o d u c t were compared t o d e t e r m i n e t h e e x t e n t and d i r e c t i o n o f r e a c t i o n . O n l y t h e r u n s w i t h l a r g e r a t i o c h a n g e s ( g r e a t e r t h a n 30%) were c o n s i d e r e d t o have r e a c t e d . B. STARTING MATERIALS A l l p h a s e s c o n s i d e r e d i n t h i s s t u d y were s y n t h e s i z e d from o x i d e m i x t u r e s . A L i n d b e r g f u r n a c e was u s e d f o r t h e p r e p a r a t i o n o f t h e o x i d e s . P e r i c l a s e (MgO) was p r e p a r e d by b a k i n g MgO ( F i s h e r C e r t i f i e d R e agent Lot#741694) f o r 24 h o u r s a t 800°C and 1 hour a t 1000°C. C r i s t o b a l i t e ( S i 0 2 ) was made from S i 0 2 . n H 2 0 by b a k i n g a t 1300°C f o r 24 h o u r s . F o r b e t t e r c r y s t a l l i z a t i o n t h e S i 0 2 was b a k e d f o r a n o t h e r 24 h o u r s a t 1200°C. 7 - A l 2 0 3 was p r e p a r e d from aluminum c h l o r i d e ( A 1 C 1 3 . 6 H 2 0 ) ( F i s h e r C e r t i f i e d R e a g e n t Lot#429332) by h e a t i n g i t i n a fume hood u s i n g a gas b u r n e r f o r 1 hour u n t i l f r o t h i n g s t o p s . The A l 2 0 3 was t h e n b a k e d a t 650°C f o r 96 h o u r s . Lime (CaO) was made from c a l c i u m c a r b o n a t e ( C a C 0 3 ) by b a k i n g a t 500°C f o r 24 h o u r s , f o l l o w e d by a t 800°C f o r 12 h o u r s . 8 1 C a l i b r a t i o n of r a t i o s o f peak h e i g h t s f r o m s t a r t i n g m a t e r i a l XRR (80wt% g r o s s u l a r + c l i n o c h l o r e , 20wt% d i o p s i d e + s p i n e l ) t o XRE (80wt% d i o p s i d e + s p i n e l , 20wt% g r o s s u l a r + c l i n o c h l o r e ) . V e r t i c a l b a r s show t h e s t a n d a r d d e v i a t i o n o f mean from 6 measured peak r a t i o s . 9 Eac h p r e p a r e d o x i d e was g r o u n d , under a l c o h o l , i n an a g a t e m o r t a r by hand f o r s e v e r a l h o u r s t o make s u r e t h a t t h e g r a i n s i z e was l e s s t h a n 1 m i c r o n . The o x i d e was t h e n d r i e d i n a f u r n a c e and s t o r e d i n d e s s i c a t o r f o r f u r t h e r u s e . C. SYNTHESIS Phase s y n t h e s e s were c o n d u c t e d u s i n g e i t h e r a L i n d b e r g f u r n a c e a t one a t o m s p h e r e o r i n p r e s s u r e v e s s e l s . E a c h o x i d e was c a r e f u l l y w e i g h e d a c c o r d i n g t o t h e d e s i r e d w e i g h t p r o p o r t i o n f o r e a c h m i n e r a l ( s e e T a b l e I ) . To r e d u c e w e i g h i n g e r r o r s , 5 grams o f m i x t u r e f o r e a c h m i n e r a l was m i x ed. The m i x t u r e was g r o u n d by hand u n d e r a l c o h o l f o r a t l e a s t 2 h o u r s . To e n s u r e h o m o g e n e i t y t h e m i x t u r e was p e r i o d i c a l l y d r i e d and c o l l e c t e d i n t o t h e b o t t o m o f t h e m o r t a r . A f t e r d r y i n g i n an oven a t 100°C f o r a b o u t 30 m i n u t e s , t h e o x i d e m i x t u r e s were s t o r e d i n a d e s s i c a t o r . 1. SPINEL S p i n e l was s y n t h e s i z e d by two methods. One a t o m s p h e r e s y n t h e s i s was made i n a p l a t i n u m c a p s u l e and d i r e c t l y p u t i n a L i n d b e r g f u r n a c e . F o r t h i s s y n t h e s i s two c y c l e s of h e a t i n g and g r i n d i n g were u s e d i n o r d e r t o o b t a i n a h i g h p e r c e n t a g e o f y i e l d ( E n g i , 1983). F o r t h e f i r s t c y c l e , t h e m i x t u r e was h e a t e d a t 1000°C f o r 1 hour and t h e n i t was t a k e n o u t from f u r n a c e and g r o u n d f o r 1 hour by hand under a l c o h o l i n an a g a t e m o r t a r . F o r t h e s e c o n d c y c l e t h e m i x t u r e was h e a t e d t o 10 T a b l e I O x i d e w e i g h t p e r c e n t a g e of t h e m i n e r a l i n v o l v e d M i n e r a l F o r m u l a MgO CaO A 1 2 0 3 S i 0 2 G r o s C a a A l z S i a O ! 2 0.00 37.35 22.64 40.02 D i o p CaMgSi 2 0 6 18.61 25.90 0.00 55.49 C l i n M g 5 A l 2 S i 3 0 1 0 ( 0 H ) 8 41 .66 0.00 21 .08 37.26 S p i n M g A l 2 0 „ 28.33 0.00 71 .67 0.00 1200°C f o r 24 h o u r s . The h y d r o t h e r m a l s y n t h e s i s was made u s i n g a g o l d c a p s u l e s e a l e d w i t h a b o u t 150 m i l l i g r a m s of t h e m i x t u r e p l u s a p p r o x i m a t e l y 20-30wt% d i s t i l l e d w a t e r . The s y n t h e s i s c o n d i t i o n s o f 795°C and 1.0 k i l o b a r were m a i n t a i n e d f o r 12 d a y s . D i f f e r e n t c o n d i t i o n s o f s y n t h e s e s were u s e d b e c a u s e o f c o n s i d e r a t i o n s of o r d e r - d i s o r d e r phenomena i n s p i n e l s . I t has been f o u n d t h a t magnesium and aluminum c a t i o n d i s t r i b u t i o n i n t h e t e t r a h e d r a l and o c t a h e d r a l s i t e s o f t h e s p i n e l s t r u c t u r e may be s e n s i t i v e b o t h t o t e m p e r a t u r e o f f o r m a t i o n and t o c o o l i n g r a t e ( B a r t h and P o s n j a k , 1932; O ' N e i l l and N a v r o t s k y , 1 9 8 4 ) T h e r e a r e t e c h n i q u e s u s i n g powder d i f f r a c t i o n a v a i l a b l e t o measure t h e d e g r e e of o r d e r - d i s o r d e r i n s p i n e l ( F u r u h a s h i , e t a l . 1973). T h e s e t e c h n i q u e s measure t h e d i f f e r e n c e between t h e t h e o r e t i c a l and o b s e r v e d i n t e n s i t i e s o f d i f f e r e n t p e a k s . The t h e o r e t i c a l i n t e n s i t i e s a r e c a l c u l a t e d b a s e d on t h e s c a t t e r i n g f a c t o r s of t h e e l e m e n t s i n v o l v e d . B e c a u s e magnesium and aluminum have s i m i l a r s c a t t e r i n g f a c t o r s t h e c a l c u l a t e d i n t e n s i t i e s a r e n o t v e r y s e n s i t i v e t o o r d e r i n g i n t h e s t r u c t u r e ( L i n d s l e y , 1976). T h e r e f o r e t h e s e t e c h n i q u e s a r e n o t s u i t a b l e f o r m e a s u r i n g o r d e r - d i s o r d e r i n t h e Mg-Al 11 s p i n e l o f t h i s s t u d y . But one would e x p e c t s a m p l e s q u e n c h e d from h i g h t e m p e r a t u r e s t o be d i s o r d e r e d r a t h e r t h a n o r d e r e d . B o t h s y n t h e s e s were s u c c e s s f u l and t h e i r p r o d u c t s were examined u n d e r o p t i c a l m i c r o s c o p e , x - r a y d i f f r a c t i o n and s c a n n i n g e l e c t r o n m i c r o s c o p e . I t was f o u n d t h a t s p i n e l s by b o t h methods were i d e n t i c a l w i t h r e s p e c t t o o p t i c s , x - r a y powder d i f f r a c t i o n , and s c a n n i n g e l e c t r o n m i c r o s c o p y . The s y n t h e t i c s p i n e l t y p i c a l l y c r y s t a l l i z e d a s e u h e d r a l c r y s t a l s w i t h (1 1 1) and ( 1 1 0 ) f a c e s ( p l a t e s 1,2). The g r a i n s i z e r a n g e d f r o m 2 m i c r o n s t o more t h a n 10 m i c r o n s . The c r y s t a l s a r e o p t i c a l l y i s o t r o p i c , w i t h no s i g n of i n h o m o g e n e i t y . No o t h e r p h a s e was d e t e c t e d i n e i t h e r o f t h e s y n t h e s i s c h a r g e s . 2. DIOPSIDE D i o p s i d e was s y n t h e s i z e d a t 795°C and 1 k i l o b a r f o r 15 d a y s . A t t e m p t s t o s y n t h e s i z e d i o p s i d e a t one a t m o s p h e r e f a i l e d b e c a u s e of t h e slow c r y s t a l l i z a t i o n r a t e . The s y n t h e s i s p r o d u c t was examined u n d e r t h e o p t i c a l m i c r o s c o p e , x - r a y d i f f r a c t i o n and s c a n n i n g e l e c t r o n m i c r o s c o p e and no i m p u r i t y was f o u n d . The s y n t h e t i c d i o p s i d e was s u b h e d r a l t o e u h e d r a l , w i t h a g r a i n s i z e of 2 x 5 m i c r o n s ( p l a t e 3 ) . C e l l p a r a m e t e r r e f i n e m e n t was c a r r i e d o u t u s i n g f o u r x - r a y d i f f r a c t i o n s c a n s (two w i t h i n c r e a s i n g 20 and two w i t h d e c r e a s i n g 2 0 ) . S i l i c o n m e t a l was u s e d a s an i n t e r n a l s t a n d a r d (a=5.4305 A ) . CuKa r a d i a t i o n and a s c a n n i n g r a t e 1/4 d e g r e e 20 p e r m i n u t e was u s e d . E l e v e n d i f f r a c t i o n l i n e s were s e l e c t e d . The mean o f t h e peak p o s i t i o n s were o b t a i n e d T a b l e II D - s p a c i n g s and r e f i n e d c e l l p a r a m e t e r s f o r s y n t h e t i c d i o p s i d e s , C a M g S i 2 0 6 S y n t h e t i c 1 S y n t h e t i c 2 s t a n d a r d h k 1 d ( c a l c ) d ( o b s ) I (/100) d ( o b s ) d 0 2 1 3.344 3.344 15 3.346 3.350 2 2 0 3.234 3.232 30 3.232 3.230 2 2-1 2.991 2.990 100 2.990 2.991 3 1 0 2.952 2.949 32 2.950 2.952 3 1-1 2.894 2.892 37 2.893 2.893 1 3-1 2.565 2.564 25 2.565 2.566 3 1 1 2.302 2.303 20 2.300 2.304 3 3 0 2. 1 56 2. 156 1 2 2. 155 2. 1 57 3 3-1 2. 1 33 2. 1 34 20 2.131 2. 1 34 4 2-1 2. 1 08 2. 109 1 2 2. 109 0 4 1 2.041 2.040 2.043 1 3-2 1 .968 1 .970 1 0 1 .970 1 5 0 -- 1 .754 1 .755 5 3-1 — 1 .624 1 .625 a( A ) 9.755(4) 9.748 9.761 b(A) 8.928(6) 8.924 8.926 c ( A ) 5.247(7) 5.251 5.258 105°52' 105°47' 105 °47' V ( A 3 ) 439.51(45) 439.5 440.80 1 S y n t h e t i c d i o p s i d e f r o m t h i s s t u d y . 2 S y n t h e t i c d i o p s i d e f r o m N o l a n and E d g a r ( 1 9 6 3 ) . 3 s t a n d a r d d i o p s i d e from M i n e r a l Powder d i f f r a c t i o n F i l e , D a t a Book by JCPDS. and t h e c e l l p a r a m e t e r s were c a l c u l a t e d u s i n g t h e p r o g r a m o f E v a n s , e t a l ( 1 9 6 3 ) . The r e s u l t s a r e shown i n T a b l e I I . A l s o shown i n t h i s t a b l e a r e c e l l r e f i n e m e n t r e s u l t s o f s y n t h e t i c d i o p s i d e f r o m N o l a n and E d g a r (1963) and d i o p s i d e s t a n d a r d from M i n e r a l Powder D i f f r a c t i o n F i l e , D a t a Book by JCPDS, c a r d #11-654 ( 1 9 8 0 ) . T a b l e I I I shows some d i o p s i d e c e l l r e f i n e m e n t p a r a m e t e r s by v a r i o u s a u t h o r s . Our c e l l r e f i n e m e n t d a t a a r e i n v e r y good agreement w i t h o t h e r s . The X.R.D. p a t t e r n o f s y n t h e t i c d i o p s i d e i s c o m p a r a b l e w i t h t h e 1 3 p a t t e r n of JCPDS d i o p s i d e s t a n d a r d ( F i g 2 and F i g 3 ) . 3. CLINOCHLORE C l i n o c h l o r e was s y n t h e s i z e d f r o m t h e o x i d e m i x t u r e p l u s a p p r o x i m a t e l y 30wt% d i s t i l l e d w a t e r a t 680°C and 4.0 k i l o b a r s f o r 21 d a y s . S y n t h e t i c c l i n o c h l o r e was f i n e g r a i n e d and t h e s i z e r a n g e d from 1 m i c r o n t o 4 m i c r o n s . Under o p t i c a l m i c r o s c o p e and s c a n n i n g e l e c t r o n m i c r o s c o p e , w e l l f ormed p l a t y c r y s t a l s were o b s e r v e d ( p l a t e 4 ) . T r a c e s p i n e l was f o u n d w i t h t h e o p t i c a l m i c r o s c o p e u s i n g i n d e x o i l but t h i s i m p u r i t y was n o t d e t e c t e d by x - r a y d i f f r a c t i o n . The amount o f s p i n e l was e s t i m a t e d t o be much l e s s t h a n 1% j u d g i n g f r o m t h e c o m p a r a t i v e c h a r t s f o r v i s u a l e s t i m a t i o n of volume p e r c e n t a g e ( T e r r y and C h i l i n g a r , 1955). The change i n c l i n o c h l o r e c o m p o s i t i o n c a u s e d by t h e e x t r a n e o u s s p i n e l , i s p r o b a b l y n o t s i g n i f i c a n t ( s e e a l s o M c P h a i l , 1985). The r e s u l t s o f c e l l p a r a m e t e r r e f i n e m e n t a r e l i s t e d i n T a b l e IV. A l s o p r o v i d e d a r e c e l l r e f i n e m e n t r e s u l t s o f s y n t h e t i c c l i n o c h l o r e by C h e r n o s k y ( 1 9 7 4 ) . B o t h r e s u l t s a r e i n v e r y good a g r e e m e n t . 4. GROSSULAR G r o s s u l a r was s y n t h e s i z e d under two d i f f e r e n t c o n d i t i o n s : a t 745°C and 1 k i l o b a r f o r 17 d a y s , and a t 680°C a t 4.0 k i l o b a r s f o r 21 d a y s . E x a m i n a t i o n under t h e m i c r o s c o p e showed t h a t b o t h s y n t h e s i s p r o d u c t s had a d d i t i o n a l phase i m p u r i t i e s ( a n i s o t r o p i c c r y s t a l ) e s t i m a t e d (N1CM 20 30 40 50 60 26(CuK„) 70 F i g 2 Representative x-ray powder d i f f r a c t i o n p a t t e r n f o r a s y n t h e t i c d i o p s i d e . F i g 3 X-ray powder d i f f r a c t i o n standard p a t t e r n f o r d i o p s i d e , D i f f r a c t i o n F i l e , Data Book by JCPDS, card # 11-654. data from M i n e r a l Powder T a b l e m C e l l p a r ameters of s y n t h e t i c and n a t u r a l d i o p s i d e s Samples Reference a (A) b (A) c (A) 0 V ( A 3 ) S y n t h e t i c R u t s t e i n , e t a l . ( 1 9 6 9 ) 9. 752(2) 8. 926(2) 5. 246(2) 105°50' 439.68(15) Synt h e t i c P r e s e n t study 9. 754(4) 8. 927(5) 5. 246(7) 105°52' 439.51(45) S y n t h e t i c C l a r k , e t a l . ( 1 9 6 2 ) 9. 745(1) 8. 925( 1 ) 5. 248(1) 105°52' Sy n t h e t i c Sakata,(1957) 9. 743 8. 923 5. 251 105°56' S y n t h e t i c Nolan and Edgar,(1963) 9. 748 8. 924 5. 251 105°47' 439.5 N a t u r a l Viswanathan,(1966) 9. 754(14) 8. 916(8) 5. 24(9) 105°49' N a t u r a l C l a r k et a l . ( 1 9 6 9 ) 9. 746(4) 8. 899(5) 5. 251(6) 105°39' 438.6 Run D i o p T h i s study 9. 725(4) 8. 891(5) 5. 260(5) 105°55' 437. 13(31 ) Syn. CaTs Okamura et a l . ( 1 9 7 4 ) 9. 609 8. 652 5. 274 106°3' 421.35 1 7 T a b l e IV D - s p a c i n g s and r e f i n e d c e l l p arameters f o r s y n t h e t i c c l i n o c h l o r e , M g § A l , S i 3 0 , 0 ( O H ) 8 and c h l o r i t e Mg«.7 5 A l 2 . 5 S i 3 0 1 0 ( O H ) 8 C l i n 1 C l i n 2 c h i 3 h k 1 d ( c a l c ) d ( o b s ) I ( / I 00) d ( o b s ) d ( o b s ) 0 0 1 14.299 — 14.132 0 0 2 7. 149 -- 7. 1 35 0 0 3 4.766 4.771 xx" 4.757 4.752 0 2 0 4.609 — 4.592 1 1 0 4.581 4.587 40 4.588 - 1 1 1 4.505 — 4.493 4.500 0 2 1 4.387 4.373 4.384 1-1 1 — 4.242 0 2 2 3.874 — 3.883 3.862 1 1 2 3.682 — 3.674 0 0 4 3.575 3.577 X X 3.572 3.560 0 0 5 2.860 2.860 60 2.864 2.846 1 1 4 2.682 -- 2.691 2 0-1 2.655 2.653 1 2 2.656 2.653 2 0-2 2.582 2.581 45 2.584 2.579 2 0 1 2.541 2.540 1 00 2.540 2.538 -2 0 3 2.440 2.440 75 2.441 2.437 0 0 6 2.383 2.383 36 2.385 2.380 2 0-4 2.261 2.261 28 2.260 2.258 1 3 4 2.071 2.071 1 1 0 0 7 2.043 2.042 18 2.041 2.034 2 0 4 2.008 2.009 58 2.008 2.004 2 0-6 1 .889 1 .889 20 1 .889 1 .885 2 0 5 1 .830 1 .830 20 1.831 1 .826 0 0 8 1 .787 — 1 .781 2 0-7 1 .724 2 0 6 1 .669 1 .670 1 1 1 .671 2 0-8 1 .573 1 .573 32 1 .573 1 .568 0 6 0 1 .536 1 .536 53 1 .539 1 .532 0 6 2 1 .502 1 .502 1 5 1 .502 1 .501 0 6 3 1 .462 1 .463 18 1 .463 1 1 9 1 .454 — 1 .455 0 010 1 .430 1 .430 1 0 1 .424 3 3 3 1.411 — 1.412 2 0 8 1 .402 1 .402 24 1 .402 1 .397 a( A ) 5.320(1) 5.324(1) 5.317(1) b(A) 9.218(1) 9.224(3) 9.192(2) c ( A ) 14.409(2) 14.420(5) 14.349(2) & 9 7 ° 5 ' ( T ) 9 7 ° 6 ' ( 1 ' ) 97 ° 8 ' ( 1 1 ) V ( A 3 ) 701.26(16) 702.69 695.83 1 S y n t h e t i c c l i n o c h l o r e from t h i s s t u d y . 2 S y n t h e t i c c l i n o c h l o r e from C h e r n o s k y , ( 1 9 7 4 ) . 3 S y n t h e t i c c h l o r i t e f r o m M c P h a i l , ( 1 9 8 5 ) . * Peak i n t e n s i t y more t h a n 100 r e n o r m a l i z e d . 18 t o be l e s s t h a n 5% by volume. T h i s may have been t h e r e s u l t of t o o low a p r e s s u r e u s e d f o r s y n t h e s e s . A t t e m p t s t o i d e n t i f y t h e s e i m p u r i t i e s by x - r a y d i f f r a c t i o n and s c a n n i n g e l e c t r o n m i c r o s c o p e showed i t t o be w o l l a s t o n i t e . The f a t e of t h e r e l e a s e d aluminum i s unknown as no aluminum r i c h i m p u r i t y was f o u n d . Such a s m a l l p r o p o r t i o n of i m p u r i t y s h o u l d n o t have much e f f e c t on t h e c o m p o s i t i o n o f t h e s y n t h e t i c g r o s s u l a r . S y n t h e t i c g r o s s u l a r was s u b h e d r a l t o e u h e d r a l and r a n g e d i n s i z e f r o m 2 m i c r o n s t o 10 m i c r o n s ( p l a t e 5 , 6 ) . Under t h e l i g h t m i c r o s c o p e i t a p p e a r e d i s o t r o p i c and homogeneous. In n a t u r a l r o d i n g i t e s , h y d r o g r o s s u l a r i s t h e most common m i n e r a l p r e s e n t and i s o f t e n t h e most a b u n d a n t m i n e r a l w i t h i n v o l c a n i c r o c k s a l t e r e d t o r o d i n g i t e s (Coleman, 1 9 6 6 ) . H y d r o g r o s s u l a r w i t h f o r m u l a Ca 3A1 2 (SiOj,) (H i | Oi, ) x was f o u n d t o be t h e r e s u l t o f a c o n t i n u o u s s o l i d s o l u t i o n between C a 3 A l 2 S i 3 0 1 2 and C a 3 A 1 2 ( H a O a ) 3 a t low t e m p e r a t u r e ( F l i n t , e t a l . , 1941). S i l i c a - f r e e C a 3 A 1 2 ( H „ 0 4 ) 3 decomposes above a p p r o x i m a t e l y 2 5 0 ° C . Yoder (1950) s t u d i e d t h e s t a b l e f i e l d s f o r g r o s s u l a r and h y d r o g r o s s u l a r and r e p o r t e d t h a t h y d r o g r o s s u l a r i s s t a b l e a t t e m p e r a t u r e s o n l y below a b o u t 600°C. S h o j i (1974) f o u n d t h a t t h e h y d r o g e n c o n t e n t i n t h e g r o s s u l a r - h y d r o g r o s s u l a r s e r i e s d e c r e a s e s w i t h i n c r e a s i n g t e m p e r a t u r e and t h e d - s p a c i n g o f t h e (4 2 0) p l a n e c a n be u s e d t o d e t e r m i n e t h e H 2 0 c o n t e n t i n h y d r o g r o s s u l a r . The d - s p a c i n g v a l u e of t h e (4 2 0) p l a n e v a r i e s f r o m a b o u t 2.650 (A) f o r g r o s s u l a r t o 2.680 (A) f o r 19 h y d r o g r o s s u l a r . C a r e f u l d e t e r m i n a t i o n of the d-spacing of the (4 2 0) plane f o r the g r o s s u l a r s y n t h e s i z e d i n t h i s study shows that the value (2.6498 (A)) i s i n very good agreement with the value r e p o r t e d by S h o j i (1974). I t i s b e l i e v e d t h e r e f o r e that s y n t h e t i c g r o s s u l a r from t h i s study i s on composition and no hy d r o g r o s s u l a r component i s i n v o l v e d . D. EXPERIMENTAL RESULTS Experimental r e v e r s a l s of the e q u i l i b r i u m ; G r o s s u l a r + C l i n o c h l o r e = 3 Diop s i d e + 2 S p i n e l + 4 H 2 0 were made at press u r e s of 0.5, 1.0, 2.0 and 4.0 k i l o b a r s . The experimental c o n d i t i o n s and r e s u l t s are l i s t e d i n Table V and i l l u s t r a t e d i n F i g 4. A few runs at c o n d i t i o n s f a r from e q u i l i b r i u m achieved complete r e a c t i o n (100% g r o s s u l a r + c l i n o c h l o r e or 100% d i o p s i d e + s p i n e l ) . For most of the runs, the peak height r a t i o s from x-ray d i f f r a c t i o n were used to i n d i c a t e the r e a c t i o n d i r e c t i o n and to estimate extent of r e a c t i o n . For high temperature runs, the common assemblages were d i o p s i d e + s p i n e l + minor c l i n o c h l o r e , i . e . g r o s s u l a r seems to disappear e a s i l y . For low temperature runs, g r o s s u l a r + c l i n o c h l o r e + minor d i o p s i d e was the common phase assemblage, i . e . s p i n e l disappeared e a s i l y . When runs were put at c o n d i t i o n s assumed to be c l o s e to the e q u i l i b r i u m , the f i n a l assemblage was c l i n o c h l o r e + d i o p s i d e 20 F i g 4 P r e c a l c u l a t e d curve of the e q u i l i b r i u m g r o s s u l a r + c l i n o c h l o r e = 3 d i o p s i d e + 2 s p i n e l + 4 H 20 by PTSYSTEM using phase p r o p e r t i e s from UBCDATABASE and the experimental brackets of t h i s study. A - - assemblage g r o s s u l a r + c l i n o c h l o r e s t a b l e . O -- assemblage d i o p s i d e + s p i n e l s t a b l e . • — a b n o r m a l assemblage d i o p s i d e + c l i n o c h l o r e . 21 T a b l e V E x p e r i m e n t a l r e s u l t s ; f o r t h e e q u i l i b r i u m G r o s s u l a r + C l i n o c h l o r e = 3 D i o p s i d e + 2 S p i n e l + 4 H 2 0 Run # P ( b a r ) T ( ° C ) D u r a t i o n R e s u l t s XRR-1 2000 678 3 8 4 ( h r s ) 100% D i + Sp XRE-1 2000 525 336 80% Gr + C l i n o XRR-2 2000 627 360 m a i n l y D i + Sp, m i n o r C l i n o XRE-2 2000 566 504 no r e a c t i o n XRR-3 2000 601 552 D i + C l i n o XRE-3 2000 601 552 D i + Sp s t a b l e XRR-4 2000 580 588 m a i n l y D i + C l i n o , m i n o r Gr XRE-4 2000 580 588 D i + Sp s t a b l e XRR-5 2000 561 552 Gr + C l i n o s t a b l e XRE-5 2000 561 552 Gr + C l i n o grow 40% XRR-7 2000 570 576 Gr + C l i n o s t a b l e XRE-7 2000 570 576 m a i n l y D i + C l i n o , m i n o r Gr XRR-6 1 000 560 600 no o b v i o u s r e a c t i o n XRE-6 1000 560 600 Gr + C l i n o grow XRR-9 1000 520 384 80% Gr + C l i n o XRE-9 1000 520 384 60% Gr + C l i n o XRR- 1 0 1000 581 720 D i + Sp grow XRE-10 1000 581 720 D i + C l i n o XRR-8 500 502 840 100% Gr + C l i n o XRE-8 500 502 840 95% Gr + C l i n o , m i n o r D i XRR-11 500 540 672 D i + Sp grow XRE-11 500 540 672 M a i n l y Gr + C l i n o ? ? •? XRR-17 500 560 648 M a i n l y D i + C l i n o XRE-17 500 560 648 M a i n l y D i + Sp XRR-18 4000 600 600 M a i n l y Gr + C l i n o XRE- 1 8 4000 600 600 M a i n l y Gr + C l i n o XRR- 1 9 4000 640 672 M a i n l y D i + C l i n o XRE-19 4000 640 672 M a i n l y D i + C l i n o XR-13* 2000 600 672 M a i n l y D i + C l i n o XR-14* 1000 570 672 M a i n l y D i + C l i n o XR-20 2000 600 552 M a i n l y D i + C l i n o XRBulk-1 1000 590 1 152 M a i n l y D i + C l i n o X RBulk-3 1000 590 1 152 M a i n l y D i + C l i n o * Runs w i t h s t a r t i n g m a t e r i a l o f 50wt% r e a c t a n t and 50wt% p r o d u c t . 22 T a b l e V ( c o n t i n u e d ) E x p e r i m e n t a l r e s u l t s f o r t h e e q u i l i b r i u m G r o s s u l a r + C l i n o c h l o r e = 3 D i o p s i d e + 2 S p i n e l + 4 H 20 Run # P ( b a r ) T ( ° C ) D u r a t i o n R e s u l t s X R B u l k - 5 1 000 590 1 1 52 M a i n l y D i + C l i n o X R B u l k - 7 1 000 590 1 1 52 M a i n l y D i + C l i n o M i n o r XRBulk- 9 1000- 590 1 1 52 M a i n l y D i + C l i n o M i n o r X RBulk- 2 1 000 530 1 1 52 M a i n l y Gr + M i n o r D i C l i n o + XRBulk- 4 1 000 530 1 1 52. M a i n l y D i + C l i n o + D i + (unknown) XRBulk- 6 1 000 530 1 1 52 M a i n l y Gr + M i n o r D i C l i n o + XRBulk- 8 1 000 530 1 1 52 M a i n l y Gr + M i n o r C l i n o D i + XRBulk- 10 1000 530 1 1 52 M a i n l y Gr + M i n o r C l i n o Sp D i + + M i n o r i n s t e a d of c l i n o c h l o r e + g r o s s u l a r or d i o p s i d e + s p i n e l . T h i s was f i r s t f o u n d i n e x p e r i m e n t s a t 2.0 k i l o b a r s and t h e r e p e a t e d e x p e r i m e n t s a t 2.0 k i l o b a r s showed t h e same r e s u l t s . S i m i l a r r e s u l t s were o b t a i n e d from 0.5, 1.0 and 4.0 k i l o b a r r u n s . T h e r e f o r e o n l y wide r e v e r s a l b r a c k e t s were o b t a i n e d f o r e a c h p r e s s u r e c o n d i t i o n . Some s p e c i a l e x p e r i m e n t s were c o n d u c t e d a f t e r t h e a s s e m b l a g e d i o p s i d e + c l i n o c h l o r e was f o u n d . One e x p e r i m e n t a l p r o d u c t (XRR-3) c o n t a i n i n g o n l y d i o p s i d e + c l i n o c h l o r e was u s e d a s new s t a r t i n g m a t e r i a l . I t i s assumed t h a t t h e p h a s e s d i o p s i d e and c l i n o c h l o r e f r o m t h i s r u n a r e t h e s t a b l e p h a s e s a t t h i s t e m p e r a t u r e and p r e s s u r e c o n d i t i o n s . R e l a t i v e p r o p o r t i o n s o f d i o p s i d e and c l i n o c h l o r e were e s t i m a t e d a c c o r d i n g t o peak i n t e n s i t i e s of t h e X.R.D. 23 p a t t e r n . A p p r o p r i a t e amounts o f s p i n e l and g r o s s u l a r were t h e n added t o t h e d i o p s i d e and c l i n o c h l o r e m i x t u r e f o r 1:1 r a t i o of p r o d u c t and r e a c t a n t (50% r e a c t a n t s and 50% p r o d u c t s i n w e i g h t ) o f t h e r e a c t i o n g r o s s u l a r + c l i n o c h l o r e = 3 d i o p s i d e + 2 s p i n e l + 4 H 2 0 . A f t e r g r i n d i n g u nder a l c o h o l f o r 2 h o u r s , t h e sample was l o a d e d under t h e same c o n d i t i o n s a s t h a t of t h e run from w h i c h p r o d u c e d d i o p s i d e + c l i n o c h l o r e . A f t e r 552 h o u r s d u r a t i o n , t h e r u n (XR —20) p r o d u c t s were examined and f o u n d t o be 100% r e a c t e d t o d i o p s i d e + c l i n o c h l o r e ( s e e t a b l e V ) . F o r t h e e x p e r i m e n t a l r u n s , t h e c a l c u l a t e d wt% of e a c h p h a s e was m i x e d i n t o t h e s t a r t i n g m a t e r i a l . I t i s p o s s i b l e t h u s t o o b t a i n s t a r t i n g a s s e m b l a g e s u c h as g r o s s u l a r + c l i n o c h l o r e + m i n o r d i o p s i d e , and d i o p s i d e + s p i n e l + m i n o r c l i n o c h l o r e ( F i g 5a, 5 b ) . Ten s y n t h e s i s r u n s were made t o t e s t t h i s p o s s i b i l i t y . O x i d e s were u s e d as s t a r t i n g m a t e r i a l s f o r t h e s y n t h e t i c r u n s . The c o m p o s i t i o n s of t h e m i x t u r e s were d e s i g n e d t o be o f f t h e b u l k c o m p o s i t i o n o f t h e r e a c t i o n f o r s t o i c h i o m e t r i c p h a s e s . The o r i g i n a l b u l k c o m p o s i t i o n was p r e p a r e d t o b a l a n c e t h e r e a c t i o n between t h e s t o i c h i o m e t r i c p h a s e s . F o u r new m i x e s were p r e p a r e d so as t o g u a r a n t e e t h a t t h e i r c o m p o s i t i o n s would l i e i n t h e f o u r s e c t o r s d e f i n e d by t h e c r o s s i n g s t o i c h i o m e t r i c t i e - l i n e s ( s e e F i g 6 ) . Two r u n c o n d i t i o n s were u s e d f o r t h e s p e c i a l s y n t h e s i s r u n s ( s e e T a b l e V ) . Long d u r a t i o n s o f t h e r u n s were 24 A1,0, Diop (a) F i g 5 I l l u s t r a t i o n s of phase r e l a t i o n s in the r e a c t i o n g r o s s u l a r + c l i n o c h l o r e = 3 d i o p s i d e + 2 s p i n e l + 4 H 20 at ( a ) high temperature and (b) low temperature. D i o p s i d e i s an A l - b e a r i n g s o l i d s o l u t i o n . Dotted l i n e s are the t i e l i n e s f o r the r e a c t i o n without c o n s i d e r i n g s o l i d s o l u t i o n i n d i o p s i d e . The i n t e r s e c t i o n p o i n t of these t i e l i n e s r e p r e s e n t s the r e a c t i o n bulk composition and the s t a r t i n g m a t e r i a l s used f o r the experiments. Point ss in (a) r e p r e s e n t s the mean composition of run d i o p s i d e s from microprobe a n a l y s e s . 25 AljO, CaO Diop (b) 26 Diop F i g e I l l u s t r a t i o n of t h e s t a r t i n g m a t e r i a l c o m p o s i t i o n s f o r e x p e r i m e n t s XRBulk - 1 t o XRBulk - 1 0 . The s o l i d l i n e s w i t h i n t h e t r i a n g l e a r e t h e t i e l i n e f o r t h e s t o i c h i o m e t r i c r e a c t i o n and t h e i r i n t e r s e c t i o n r e p r e s e n t s t h e b u l k c o m p o s i t i o n f o r t h a t r e a c t i o n . The s t a r t i n g m a t e r i a l c o m p o s i t i o n s f o r o t h e r e x p e r i m e n t s a r e shown as XRBulk - 3 t o XRBulk - 1 0 . 27 m a i n t a i n e d t o e n s u r e a c o m p l e t e r e a c t i o n . The r e s u l t s o f t h e s e s y n t h e s i s r u n s show t h a t t h e i r run p r o d u c t s a r e no d i f f e r e n t f r o m t h o s e o f t h e e q u i l i b r i u m r u n s made e a r l i e r . The e x p e r i m e n t s a l l c o n c l u d e d w i t h e i t h e r d i o p s i d e + c l i n o c h l o r e o r t h e low t e m p e r a t u r e a s s e m b l a g e g r o s s u l a r + c l i n o c h l o r e . O n l y one r u n (XRBulk-4) showed t h r e e u n i d e n t i f i e d p e a k s i n t h e X.R.D. p a t t e r n s w h i c h c o u l d be an i n d i c a t i o n of unknown p h a s e s . The above r e s u l t s s u g g e s t t h a t n o n - s t o i c h i o m e t r i c b e h a v i o u r may o c c u r i n one o r more of t h e p h a s e s i n v o l v e d . S p i n e l i s t h e o n l y p h a s e t h a t may not e x h i b i t s o l i d s o l u t i o n i n t h e c h e m i c a l s y s t e m s t u d i e d . G r o s s u l a r ( C a 3 A 1 2 S i 3 0 , 2 ) was t r e a t e d a s a s t o i c h i o m e t r i c p hase a l t h o u g h p y r o p e - g r o s s u l a r c a n be a c o m p l e t e s o l i d s o l u t i o n a t v e r y h i g h t e m p e r a t u r e and h i g h p r e s s u r e . The m i x i n g p r o p e r t i e s of g r o s s u l a r - p y r o p e s o l i d s o l u t i o n have been d i s c u s s e d by v a r i o u s a u t h o r s e .g. C h i n n e r e t a l . ( 1 9 6 0 ) ; Saxena ( 1 9 6 8 ) ; Boyd ( 1 9 7 0 ) ; W i l k e n ( 1 9 7 7 ) ; G a n g u l y and Kennedy ( 1 9 7 4 ) ; Hensen e t a l . ( 1 9 7 5 ) . S y n t h e s i s s t u d i e s o f g a r n e t a l o n g t h i s j o i n were made by Yode r and C h i n n e r ( 1 9 6 0 ) . The s t a b i l i t i e s of g a r n e t w i t h t h i s c o m p o s i t i o n a r e s t r o n g l y d e p e n d e n t on t h e p r e s s u r e o f f o r m a t i o n . A t 29 k i l o b a r s and 1250°C, a c o m p l e t e r a n g e of s o l i d s o l u t i o n c a n be c r y s t a l l i z e d . But a t 10 k i l o b a r w a ter p r e s s u r e and 950°C, o n l y g a r n e t s w i t h i n t h e narrow r a n g e G r , 0 0 - G r 9 „ P y 6 a r e s t a b l e . T h i s s o l i d s o l u t i o n was a l s o s t u d i e d t h e o r e t i c a l l y and e x p e r i m e n t a l l y by G a n g u l y and 28 Kennedy ( 1 9 7 4 ) ; Hensen, Schmid and Wood ( 1 9 7 5 ) . i t was d e m o n s t r a t e d t h a t p y r o p e - g r o s s u l a r s o l i d s o l u t i o n e x h i b i t e d a s i g n i f i c a n t p o s i t i v e d e v i a t i o n from i d e a l i t y . The d e v i a t i o n i n c r e a s e s w i t h d e c r e a s i n g t e m p e r a t u r e . The t e m p e r a t u r e of c r i t i c a l m i x i n g marks t h e t o p of t h e p y r o p e - g r o s s u l a r s o l v u s . The v a l u e s of 694 ± 5 0 ° C ( G a n g u l y and Kennedy, 1974) and 629±90°C (Hensen e t a l , 1975) a r e b o t h h i g h e r t h a n t h e t e m p e r a t u r e u s e d i n t h i s s t u d y . A l s o i t was d e m o n s t r a t e d e a r l i e r t h a t t h e s y n t h e t i c g r o s s u l a r i s i n c o m p o s i t i o n as shown by c h e c k i n g t h e d - s p a c i n g v a l u e o f (4 2 0) p l a n e w i t h X.R.D. T h e r e f o r e i t seems r e a s o n a b l e t o t r e a t g r o s s u l a r a s a s t o i c h i o m e t r i c p h a s e a t t h e t e m p e r a t u r e a n d p r e s s u r e c o n d i t i o n s u s e d f o r t h i s s t u d y . Changes i n c h l o r i t e c o m p o s i t i o n w i t h i n c r e a s i n g p r e s s u r e were r e p o r t e d by F a w c e t t and Yoder ( 1 9 6 6 ) . I t was c o n c l u d e d t h a t t h e c o m p o s i t i o n o f c h l o r i t e c o e x i s t i n g w i t h o t h e r p h a s e s v a r i e s w i t h p r e s s u r e , becoming more a l u m i n o u s a t h i g h e r p r e s s u r e . C a r e f u l s t u d i e s o f t h i s s h i f t i n c h l o r i t e c o m p o s i t i o n were made by M c P h a i l (1985) by m e a s u r i n g (004) and h i g h e r o r d e r b a s a l p e a k s o f c h l o r i t e a g a i n s t f o r s t e r i t e and s p i n e l p e a k s b e f o r e and a f t e r t h e e x p e r i m e n t s . No s h i f t s i n t h e peak p o s i t i o n f o r c h l o r i t e were n o t i c e d . S i m i l a r work was done by C h e r n o s k y (1974) w i t h c l i n o c h l o r e u s i n g t h e same methods i n w h i c h he showed t h a t c l i n o c h l o r e from d i f f e r e n t t e m p e r a t u r e s and p r e s s u r e s showed no n o n - s t o i c h i o m e t r i c phenomena. I n t h i s s t u d y , t h e same a t t e n t i o n was p a i d and no peak s h i f t was d e t e c t e d f o r 29 c l i n o c h l o r e . C l i n o c h l o r e i n t h i s s t u d y t h e r e f o r e was c o n s i d e r e d t o have t h e same c o m p o s i t i o n ( M g 5 A l 2 S i 3 0 , 0 ( O H ) 8 ) t h r o u g h o u t t h e c o u r s e of t h e e x p e r i m e n t s . A v a r i e t y of t e c h n i q u e s were u s e d t o s t u d y t h e v a r i a t i o n i n c o m p o s i t i o n o f d i o p s i d e . I t was f o u n d t h a t t h e d i o p s i d e has a h i g h aluminum c o n t e n t w h i c h may be d e s c r i b e d by s u b s t i t u t i o n of Ca-Tschermak o r / a n d Mg-Tschermak m o l e c u l e . I l l . CLINOPYROXENE COMPOSITION The e x p e r i m e n t a l r e s u l t s o f t h e p r e v i o u s c h a p t e r s u g g e s t t h a t t h e c l i n o p y r o x e n e may n o t be s t o i c h i o m e t r i c end-member d i o p s i d e b e c a u s e many r u n s c o n c l u d e d w i t h ' d i o p s i d e ' + c l i n o c h l o r e i n s t e a d of e i t h e r d i o p s i d e + s p i n e l o r g r o s s u l a r + c l i n o c h l o r e . G r o s s u l a r , s p i n e l , and c l i n o c h l o r e have been c o n c l u d e d t o be s t o i c h i o m e t r i c , l e a v i n g o n l y e r r o r s i n b u l k c o m p o s i t i o n o f t h e r u n o r v a r i a t i o n i n c l i n o p y r o x e n e c o m p o s i t i o n as t h e s o u r c e o f t h e p r o b l e m . Ten t e s t e x p e r i m e n t s (XRBulk-1 t o XRBulk-10 see T a b l e V ) , w i t h d i f f e r e n t b u l k c o m p o s i t i o n s , have e l i m i n a t e d t h e p o s s i b i l i t y of f i r s t of t h e s e p r o b l e m s , l e a d i n g t o t h e c o n c l u s i o n t h a t t h e c l i n o p y r o x e n e c o n t a i n s aluminum. R e s e a r c h on aluminum i n c l i n o p y r o x e n e has been e x t e n s i v e , i n d i c a t i n g m o s t l y t h a t h i g h A l - c o n t e n t i s t h e r e s u l t of h i g h p r e s s u r e , A l - r i c h b u l k c o m p o s i t i o n s , o r b o t h . The s o l i d s o l u t i o n s between C a M g S i 2 0 6 , C a A l 2 S i 0 6 , M g A l 2 S i 0 6 and M g 2 S i 2 0 6 have been s t u d i e d v e r y e x t e n s i v e l y ( C l a r k , e t a l . , 1962; N e u f v i l l e and S c h a i r e r , 1962; K u s h i r o and Y o d e r , 1965; 1966; M a c G r e g o r , 1965; O'Hara e t a l . , 1971; H e r z b e r g , 1972, 1976a, 1976b; Gupta e t a l . , 1973; Yang, 1973; Okamura e t a l . , 1974; P r e s n a l l , 1976; Y o s h i k a w a , 1977; Onuma and K i m u r a , 1978; H o l l a n d , 1979; J e n k i n s and Newton, 1979; A k a s a k a and Onuma, 1980; G a s p a r i k , 1980a, 1980b, 1984). The s y s t e m d i o p s i d e , Ca-Tschermak, Mg-Tschermak and e n s t a t i t e i s c o m p l e x , f o r m i n g b i n a r y and t e r n a r y s o l i d s o l u t i o n s y s t e m s . D i o p s i d e and Ca-Tschermak p y r o x e n e form a c o n t i n u o u s s o l i d 30 31 s o l u t i o n a t h i g h p r e s s u r e and t e m p e r a t u r e ( C l a r k e t a l . , 1962). L i m i t e d s o l i d s o l u t i o n a l s o o c c u r s between d i o p s i d e and Mg-Tschermak p y r o x e n e ( d e N e u f v i l l e and S c h a i r e r , 1962). In t h i s s t u d y , d i o p s i d e s f r o m t h e s t a r t i n g m a t e r i a l s and from e a c h r u n were examined under t h e l i g h t m i c r o s c o p e , x - r a y d i f f r a c t i o n , s c a n n i n g e l e c t r o n m i c r o s c o p e and e l e c t r o n m i c r o p r o b e t o d e t e r m i n e i f t h e y were A l - b e a r i n g . A. OPTICAL MICROSCOPE E a c h e x p e r i m e n t a l p r o d u c t was examined w i t h t h e o p t i c a l m i c r o s c o p e under i m m e r s i o n o i l s . In some c a s e , t h e sample was d i s p e r s e d w i t h an u l t r a s o n i c e q u i p m e n t b e f o r e e x a m i n a t i o n . The c r y s t a l s f r o m b o t h s y n t h e s i s and e q u i l i b r i u m e x p e r i m e n t s were commonly t o o s m a l l t o measure many o p t i c a l p a r a m e t e r s , b e i n g a n i s o t r o p i c , p r i s m a t i c g r a i n s l e s s t h a n 5 m i c r o n s l o n g . A t t e m p t s t o d e t e r m i n e d i o p s i d e c o m p o s i t i o n s f r om r e f r a c t i v e i n d e x f a i l e d b e c a u s e of t h e i n s e n s i t i v i t y o f r e f r a c t i v e i n d e x t o c o m p o s i t i o n . B. X-RAY DIFFRACTION (X.R.D.) E x p e r i m e n t a l p r o d u c t s were examined by powder X - r a y d i f f r a c t i o n u s i n g c o p p e r r a d i a t i o n on a P h i l i p s XRD u n i t . R o u t i n e i d e n t i f i c a t i o n o f m i n e r a l p h a s e s was done w i t h d i f f T a c t o m e t e r s e t t i n g s o f 2 d e g r e e 20 p e r m i n u t e and c h a r t s p e e d o f 2 c e n t i m e t e r s p e r m i n u t e . Samples were p r e p a r e d by d i s p e r s i n g t h e c h a r g e u s i n g e i t h e r u l t r a s o n i c s e p a r a t i o n i n a l c o h o l o r g r i n d i n g under 32 a l c o h o l i n an a g a t e m o t a r . The sample was mounted on a q u a r t z s l i d e , a l l o w e d t o d r y , and X - r a y e d . The s y n t h e t i c s t o i c h i o m e t r i c end-member d i o p s i d e was v e r y w e l l c r y s t a l l i z e d , w i t h peak p o s i t i o n s and i n t e n s i t i e s c o m p a r a b l e w i t h s t a n d a r d d i o p s i d e ( s e e F i g 2 and F i g 3 ) . C e l l p a r a m e t e r r e f i n e m e n t s were made u s i n g e l e v e n peaks i n t h e p r o g r a m of E v a n s , e t a l (1963) ( s e e T a b l e I I ) . E a c h e x p e r i m e n t a l r u n p r o d u c i n g d i o p s i d e was a l s o e x a mined by powder d i f f r a c t i o n . C e l l p a r a m e t e r r e f i n e m e n t s were c a r r i e d o u t t o t r a c e t h e v a r i a t i o n of d i o p s i d e c o m p o s i t i o n . The run p r o d u c t s u s u a l l y c o n t a i n e d f o u r p h a s e s (due t o i n c o m p l e t e r e a c t i o n ) r e s u l t i n g i n many peak o v e r l a p s . C o n s e q u e n t l y o n l y s e v e n p e a k s c o u l d be measured p r e c i s e l y f o r c e l l r e f i n e m e n t . The r e s u l t s of t h i s c e l l p a r a m e t e r r e f i n e m e n t a r e l i s t e d i n T a b l e V I . The r e s u l t s o f c e l l p a r a m e t e r r e f i n e m e n t show t h a t t h e c e l l p a r a m e t e r s of r u n p r o d u c t d i o p s i d e a r e w e l l w i t h i n t h e c e l l p a r a m e t e r range between t h e j o i n d i o p s i d e and Ca-Tschermak p y r o x e n e a s r e p o r t e d by C l a r k ( 1 9 6 2 ) . C. SCANNING ELECTRON MICROSCOPE (S.E.M.) A l l e x a m i n a t i o n s were c a r r i e d out u s i n g a SEMCO N a n o l a b - 7 s c a n n i n g e l e c t r o n m i c r o s c o p e . Samples were mounted on g r a p h i t e s t u b s and c o a t e d w i t h c a r b o n o r g o l d d e p e n d i n g on whether c o m p o s i t i o n o r m o r p h o l o g y was b e i n g s t u d i e d . 33 T a b l e VI D - s p a c i n g s and r e f i n e d c e l l p a r a m e t e r s f o r d i o p s i d e ( c l i n o p y r o x e n e ) from run p r o d u c t Run p r o d u c t S y n t h e t i c d i o p s i d e d i o p s i d e h k 1 d ( c a l c ) d ( o b s ) I ( / 1 0 0 ) d ( o b s ) 0 2 1 3.338 3.340 22 3.344 2 2 0 3.222 3.222 65 3.234 2 2-1 2.985 2.984 1 00 2.991 3 1 0 2.942 2.943 45 2.952 3 1-1 2.889 2.889 52 2.894 1 3-1 2.558 2.558 70 2.565 3 1 1 2.297 2.297 25 2.302 a( A ) 9.725(3) 9.755 b(A) 8.891(5) 8.928 c ( A ) 5.257(5) 5.247 105°58' 105°52' V ( A 3 ) 437.13(30) 439.51 1. SAMPLE PREPARATION G r a p h i t e d i s c s were p o l i s h e d u s i n g p o l i s h i n g p a p e r s and g l a s s and t h e n a t t a c h e d t o t h e m e t a l s t u b w i t h d o u b l e s i d e d t a p e . The e x p e r i m e n t a l p r o d u c t s were put i n t o i n d i v i d u a l g l a s s v i a l s w i t h a l c o h o l and u l t r a s o n i c a l l y d i s p e r s e d . Good d i s p e r s i o n was n e c c e s s a r y f o r c h e m i c a l a n a l y s i s t o a v o i d s i g n a l s f r o m n e i g h b o u r i n g g r a i n s . To a c h i e v e t h i s s e p a r a t i o n , a s m a l l g l a s s m i c r o p i p e t t e was u s e d t o t r a n s f e r t h e s u s p e n s i o n of g r a i n s i n a l c o h o l t o t h e g r a p h i t e s t u b s . The l o a d e d s t u b s were c h e c k e d w i t h t h e b i n o c u l a r m i c r o s c o p e t o e n s u r e t h e c o r r e c t d i s p e r s i o n b e f o r e c o a t i n g . A D e n t o n Vacuum DV-515 c o a t e r was us e d f o r c a r b o n c o a t i n g t o a t h i c k n e s s o f a b o u t 25 nm. C a r b o n c o a t e d s a m p l e s were u s e d f o r q u a l i t a t i v e c h e m i c a l a n a l y s e s and g o l d c o a t e d s a m p l e s were u s e d f o r p h o t o g r a p h y . 34 2. OBSERVATION A SEMCO N a n o l a b - 7 s c a n n i n g e l e c t r o n m i c r o s c o p e w i t h a Kevex E.D.S. a t t a c h m e n t was o p e r a t e d a t 15 KV a c c e l e r a t i n g p o t e n t i a l a t a u s u a l w o r k i n g d i s t a n c e of 15-18 mm. S y n t h e t i c end-member d i o p s i d e was examined f o r m o r p h o l o g y and c h e m i s t r y a s r e f e r e n c e m a t e r i a l f o r t h e e q u i l i b r i u m e x p e r i m e n t a l p r o d u c t s . P h o t o s were t a k e n and q u a l i t a t i v e c h e m i c a l a n a l y s e s were made u s i n g EDS ( F i g 7) S y n t h e t i c d i o p s i d e s a r e e u h e d r a l t o s u b h e d r a l p r i s m a t i c c r y s t a l s . A l t h o u g h t h e EDS c o u l d n o t g i v e q u a n t i t a t i v e a n a l y s i s , t h e f o l l o w i n g f e a t u r e s may be n o t e d . The c h e m i c a l s p e c t r a show t h a t t h e d i o p s i d e i s v e r y u n i f o r m i n c o m p o s i t i o n w i t h a l l g r a i n s h a v i n g v e r y s i m i l a r s p e c t r a . The peak r a t i o s of Mg/Si and C a / S i a r e v e r y s i m i l a r from one g r a i n t o a n o t h e r . D i o p s i d e from e q u i l i b r a t i o n e x p e r i m e n t s was e a s i l y i d e n t i f i e d by c r y s t a l shape, m o r p h o l o g y and c h e m i c a l a n a l y s i s on t h e b a s i s of r e s u l t s on end-member s y n t h e t i c d i o p s i d e . G r a i n s o f d i o p s i d e a t l e a s t 4 m i c r o n s a p a r t f r o m o t h e r g r a i n s o f any phase were c h o s e n f o r c h e m i c a l a n a l y s i s . I t w a s - f o u n d t h a t i f any o t h e r p h a s e l a y w i t h i n 4 m i c r o n s o f t h e d i o p s i d e , i t s c h e m i c a l s p e c t r u m would show t h e e f f e c t s o f t h e n e i g h b o u r . A s s e m b l a g e s commonly f o u n d i n t h e r u n p r o d u c t s were d i o p s i d e + s p i n e l , C l i n o c h l o r e + g r o s s u l a r , d i o p s i d e + s p i n e l + minor c l i n o c h l o r e , c l i n o c h l o r e + g r o s s u l a r + minor d i o p s i d e and d i o p s i d e ( c l i n o p y r o x e n e ) + c l i n o c h l o r e ( p l a t e s 35 S i O.OOKEV 5.12KEV 7 The Scanning E l e c t r o n Microscope E.D.S. chemical spectrum of s y n t h e t i c d i o p s i d e (105 S e c , 8764 I n t . , V e r t i c a l s c a l e ( f u l l ) 1024, 15 KV a c c e l e r a t i n g v o l t a g e ) Si Ca 0.48KEV 5.60KEV 8 The S c a n n i n g E l e c t r o n M i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m of d i o p s i d e from run XRE-10(70 S e c . , 13093 I n t . , V e r t i c a l s c a l e ( f u l l ) 1024, 15 KV a c c e l e r a t i n g v o l t a g e ) 36 Si Mg Ax 0.48KEV Ca Ca 5.60KEV F i g 9 The S c a n n i n g E l e c t r o n M i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m of d i o p s i d e f r o m r u n XRR-3(78 S e c , 10112 I n t . , V e r t i c a l s c a l e ( f u l l ) 1024, 15 KV a c c e l e r a t i n g v o l t a g e ) Si Mg 0.48KEV Ca Ca 5.60KEV F i g 1 0 The S c a n n i n g E l e c t r o n M i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m o f d i o p s i d e from run XRE-10(73 S e c . , 9346 I n t . , V e r t i c a l s c a l e ( f u l l ) 1024, 15 KV a c c e l e r a t i n g v o l t a g e ) 37 Si Ca 0.48KEV 5.60KEV F i g n The S c a n n i n g E l e c t r o n M i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m o f d i o p s i d e f r o m run XRR-4(62 S e c , 13527 I n t . , V e r t i c a l s c a l e ( f u l l ) 1024, 15 KV a c c e l e r a t i n g v o l t a g e ) Si Ca 0.48KEV 5.60KEV F i g 1 2 The S c a n n i n g E l e c t r o n M i c r o s c o p e E.D.S. c h e m i c a l s p e c t r u m o f d i o p s i d e f r o m run XRE-10(80 S e c , 22193 I n t . , V e r t i c a l s c a l e ( f u l l ) 2048, 15 KV a c c e l e r a t i n g v o l t a g e ) 38 7 - 1 2 ) . No d i f f e r e n c e s of m o r p h o l o g y were f o u n d between t h e s e d i o p s i d e c r y s t a l s and t h e s y n t h e t i c end-member d i o p s i d e s . The c h e m i c a l s p e c t r a show c l e a r l y t h a t some d i o p s i d e s c o n t a i n aluminum. A r e p r o d u c i b l e aluminum peak was o b t a i n e d f r o m most o f t h e s e d i o p s i d e s ( F i g 8 t o F i g 12). The q u a l i t a t i v e s c a n n i n g e l e c t r o n m i c r o s c o p e E.D.S. d a t a show t h a t t h e d i o p s i d e s i n e q u i l i b r i u m w i t h c l i n o c h l o r e c o n t a i n aluminum, i n agr e e m e n t w i t h d e d u c t i o n s f r o m chemography. The e l e c t r o n m i c r o p r o b e was u s e d t o o b t a i n more q u a n t i t a t i v e a n a l y s e s o f d i o p s i d e . D. ELECTRON MICROPROBE 1. SAMPLE PREPARATION Samples were p r e p a r e d f o r m i c r o p r o b e a n a l y s i s i n t h e same way as f o r t h e S.E.M. e x a m i n a t i o n , u s i n g g r a p h i t e s t u b s o f 0.25 i n c h d i a m e t e r . U s i n g t h e same t e c h n i q u e as f o r t h e SEM sample p r e p a r a t i o n , t h e c h a r g e was l o a d e d o n t o t h e g r a p h i t e s t u b s and c a r b o n c o a t e d t o a t h i c k n e s s o f 25 nm. 2. ANALYSIS PROCEDURE An A.R.L. SEMQ m i c r o p r o b e was u s e d f o r a l l t h e a n a l y s e s . Specimen c u r r e n t was s e t a t 40 nA on aluminum a t an a c c e l e r a t i n g p o t e n t i a l o f 15 KV w i t h a 300 Mm a p e r t u r e . C o u n t i n g t i m e f o r b o t h b a c k g r o u n d and peak was 10 s e c o n d s . A n a l y s e s u s i n g t h e minimum s i z e beam were u n s a t i s f a c t o r y b e c a u s e o f Na l o s s i n s t a n d a r d i z a t i o n on j a d e i t e and beam 39 i n s t a b i l i t y on t h e s m a l l g r a i n s a v a i l a b l e . A s m a l l r a s t e r a b o u t 2 m i c r o n s was s u c c e s f u l l y u s e d . O x i d e s d e t e r m i n e d i n t h e a n a l y s e s were A l 2 0 3 , S i 0 2 , CaO and MgO. S t a n d a r d i z a t i o n was made on s y n t h e t i c d i o p s i d e of s i m i l a r s i z e and shape t o t h e unknown. S y n t h e t i c end-member j a d e i t e p r o v i d e d by H.J. Greenwood and s y n t h e t i c end-member d i o p s i d e f r o m t h i s s t u d y were u s e d as s t a n d a r d s ( s e e T a b l e V I I ) . B e c a u s e t h e g r a i n s o f s y n t h e t i c s t a n d a r d m i n e r a l s and run p r o d u c t s were a l l v e r y s m a l l ( l e s s t h a n t h e x - r a y e x c i t a t i o n v o l u m e ) , t h e shape and t h e s i z e of t h e g r a i n s s e l e c t e d were v e r y i m p o r t a n t f a c t o r s i n a c h i e v i n g good a n a l y s e s . I t was e a s i l y shown t h a t d i f f e r e n c e s i n s i z e and o r i e n t a t i o n between s t a n d a r d and unknown m i n e r a l s c a n s i g n i f i c a n t l y a f f e c t t h e a n a l y s e s . To r e d u c e t h i s e f f e c t , g r a i n s o f s i m i l a r shape, o r i e n t a t i o n and s i z e were c h o s e n . B o t h s t a n d a r d and unknown m i n e r a l g r a i n s had t o be w e l l s e p a r a t e d from o t h e r g r a i n s . G r e a t c a r e was needed t o a c q u i r e good a n a l y s e s . A s i d e f r o m t h e above p r e c a u t i o n s i t was f o u n d t h a t t h e beam wo u l d s h i f t s l o w l y o f f t h e c e n t e r o f t h e g r a i n a s t h e s p e c t r o m e t e r s moved. T h i s c a u s e d l o s s of c o u n t s and low t o t a l s . Runs w i t h l e s s t h a n 80% o r more t h a n 120% t o t a l w e i g h t p e r c e n t a g e were not u s e d even f o r c a l c u l a t i n g e l e m e n t r a t i o s . To c h e c k t h e r e p e a t a b i l i t y and r e l i a b i l i t y , many a n a l y s e s were made on t h e same g r a i n . No d i f f e r e n c e s were n o t i c e d f r o m d a t a o b t a i n e d on d i f f e r e n t d a y s . T a b l e V I I I shows t h e d u p l i c a t e a n a l y s e s o f s t a n d a r d d i o p s i d e . A p p e n d i x 40 T a b l e V I I S t a n d a r d s u s e d f o r m i c r o p r o b e a n a l y s e s O x i d e s C o m p o s i t i o n S o u r c e s MgO CaMgSi 2 0 6 S y n t h e t i c endmember d i o p s i d e f r o m t h i s s t u d y CaO C a M g S i 2 0 6 S y n t h e t i c endmember d i o p s i d e from t h i s s t u d y S i 0 2 CaMgSi 2 0 6 S y n t h e t i c endmember d i o p s i d e from t h i s s t u d y A 1 2 0 3 N a A l S i 2 0 6 S y n t h e t i c endmember j a d e i t e f r o m H.J. Greenwood 1 shows t h e a n a l y s i s r e s u l t s i n f o r m u l a t o t a l and w e i g h t t o t a l . A n a l y s e s on d i o p s i d e s from d i f f e r e n t r u n p r o d u c t s d i d not show any o b v i o u s l y r e g u l a r v a r i a t i o n of t h e aluminum c o n t e n t . A l 2 0 3 i n c l i n o p y r o x e n e v a r i e s f r o m 0.3 t o 0.7 p e r f o r m u l a u n i t . MgO and CaO a r e b o t h l e s s t h a n 1.0 p e r f o r m u l a u n i t , w h i c h i s t h e v a l u e i n d i o p s i d e . 3. INTERPRETATION OF DATA The p r e s e n c e of aluminum and t h e d e f i c i e n c i e s o f magnesium and c a l c i u m i n c l i n o p y r o x e n e i n d i c a t e t h a t t h e s o l u t i o n c a n be d e s c r i b e d by s u b s t i t u t i o n o f Tschermak " m o l e c u l e s " . I f o n l y Ca-Tschermak s u b s t i t u t e d f o r d i o p s i d e a c c o r d i n g t o t h e A l A l - - M g S i s u b s t i t u t i o n , t h e n c a l c i u m s h o u l d n o t change i n v a l u e and w o u l d r e m a i n a r o u n d 1.0. Magnesium a n d s i l i c o n c o n t e n t s w o u l d d e c r e a s e w h i l e aluminum i n c r e a s e d . The d e f i c i e n c i e s i n b o t h magnesium and c a l c i u m s u g g e s t t h a t S u b s t i t u t i o n s by b o t h Ca-Tschermak and Mg-Tschermak o c c u r e d . 41 T a b l e V I I I D u p l i c a t e o f t h e m i c r o p r o b e a n a l y s e s of s t a n d a r d d i o p s i d e Time MgO A 1 2 0 3 S i 0 2 CaO T o t a l w t % t o t a l G r a i n A #1 #2 G r a i n B #1 #2 #3 .9957 .9933 .0037 .0034 1 .9773 1.9891 1 .0453 1.0231 4.0211 4.0093 97.96 104.36 .9965 1.0514 1.0207 .0057 .0051 .0041 1 .9944 1 .9828 1 .9975 1.0063 .9753 .9782 4.0029 4.0146 4.0005 1 1 2.49 115.36 110.94 In an a t t e m p t t o see more c l e a r l y t h e r e l a t i o n s between e l e m e n t o x i d e s , v a r i o u s p l o t s were made u s i n g d i f f e r e n t o x i d e v a l u e s i n t h e f o r m u l a . F o r example, A l 2 0 3 v e r s u s S i 0 2 , A l 2 0 3 v e r s u s CaO, A 1 2 0 3 v e r s u s MgO and MgO v e r s u s CaO were p l o t t e d ( s e e F i g 13 t o F i g 1 9 ) . The p l o t s show t h a t t h e d a t a p o i n t s a r e r e l a t i v e l y s c a t t e r e d . T h e o r e t i c a l l y i f a run r e a c h e d e q u i l i b r i u m and t h e a n a l y t i c a l e r r o r s c o u l d be e l i m i n a t e d , t h e n a l l t h e p o i n t s s h o u l d p l o t a t one p o i n t . The d i f f e r e n c e s i n c o m p o s i t i o n s e e n i n t h i s s t u d y a r e c e r t a i n l y b e yond a n a l y t i c e r r o r . A l t h o u g h t h e d a t a f o r aluminum and s i l i c o n v a r y f r o m one a n a l y s i s t o a n o t h e r , t h e p l o t o f A l 2 0 3 v e r s u s S i 0 2 ( F i g 16) shows t h a t t h e d a t a c a n be v e r y w e l l f i t t e d i n a l i n e a r e q u a t i o n . L i n e a r r e g r e s s i o n shows t h a t t h e r e l a t i o n between A l 2 0 3 and S i 0 2 c a n be e x p r e s s e d a s S i 0 2 ( f o r m u l a ) = -0.5298 * A l 2 0 3 ( f o r m u l a ) + 1.9914. I f o n l y Tschermak m o l e c u l e s u b s t i t u t i o n s were i n v o l v e d , t h e n t h e o r e t i c a l l y t h e c o n s t a n t s i n t h i s e q u a t i o n s h o u l d be 0.5 and 2.0 r e s p e c t i v e l y . The c l o s e n e s s o f t h e v a l u e s i n d i c a t e s t h a t 42 ++ + + + + + + + + + + + t 0.3 0.5 0 .6 0 .8 C O O —I— 1 .0 F i g i 3 The r e l a t i o n between A1 ?0 3 and CaO (mol) i n run product d i o p s i d e from microprobe analyses 43 cn O ++ + a in c \ j 0 -+ ++ + + + + + + X + + + + —I— 0.4 1 0.8 MGO 0.3 0.5 0.6 ~1 1 .2 F i g 1 4 The r e l a t i o n between A l 2 0 3 and MgO (mol) in run product diopside from microprobe analyses 44 ++ CO < M o " "+ + + ++ + + + ++ + + + 1.5 1.6 C R O M G O F i g 15 The r e l a t i o n between A1 20 3 and (CaO+MgO) (mol) i n run product d i o p s i d e from microprobe a n a l y s e s . 45 o O O I f i I i 1 ' I I i I I 1.0 1.) 1.2 !.3 I . a 1.5 1.6 1.7 1.8 1.9 2.0 SI02 F i g 1 6 The r e l a t i o n between A 1 2 0 3 and S i 0 2 (mol) in run product d i o p s i d e from microprobe analyses. The s t r a i g h t l i n e i s the r e l a t i o n between A 1 2 0 3 and S i 0 2 for Tschermak's s u b s t i t u t i o n . 46 0 ° ° 5°^ - 1 — 1 . ! SI 02 +++ + ^ + + + + + +++ + + + ^ + + + +  + + + + + + i i 1 r ,! „ 5 1-6 1.7 1 . 1 Fig17 The r e l a t i o n between CaO and S i 0 2 (mol) in run product diopside from microprobe analyses 47 + + + + -H- ++ + ++ -H-1 .5 S iC2 F i g 18 The r e l a t i o n between MgO and S i 0 2 (mol) i n run product d i o p s i d e from microprobe analyses 48 + + + + + - 1 1 1 1 — 0 5 0 . 6 0 . 7 0 8 MGO 1 . 3 F i g 19 The r e l a t i o n between CaO and MgO (mol) i n run product d i o p s i d e from microprobe analyses 49 t h i s i s p r o b a b l y t h e c a s e . The q u e s t i o n a r i s e s as t o t h e r e l a t i v e p r o p o r t i o n of Ca-Tschermak and Mg-Tschermak m o l e c u l e s u b s t i t u t i o n . A l l t h e o x i d e s have been p a r t i t i o n e d and b a l a n c e d between t h e s o l u t i o n p h a s e s o f Ca-Tschermak, Mg-Tschermak and d i o p s i d e . The a n a l y t i c a l d a t a show t h a t t h e a v e r a g e c a l c i u m d e f i c i e n c y i s g r e a t e r t h a n t h a t o f magnesium. T h i s c o u l d be c a u s e d by more Mg-Tschermak t h a n Ca-Tschermak m o l e c u l e s s u b s t i t u t i n g f o r d i o p s i d e m o l e c u l e s , b u t t h i s seems u n l i k e l y t o be t h e c a s e . O h a s h i e t a l . (1975) and O h a s h i and F i n g e r (1976) r e p o r t t h a t t h e r e i s a magnesium and c a l c i u m c a t i o n d i s t r i b u t i o n p r o b l e m between M1 s i t e and M2 s i t e i n t h e d i o p s i d e s t r u c t u r e . F o r our a n a l y t i c a l r e s u l t s , i t may be r e a s o n a b l e t o assume t h a t some magnesium s u b s t i t u t e d f o r ++ ++ c a l c i u m i n t h e M2 s i t e , i e . assume Ca + Mg (M2) =1.0. Then h a l f of t h e aluminum c o u l d be t r e a t e d as s u b s t i t u t i n g f o r magnesium i n M1 s i t e w h i l e t h e o t h e r h a l f s u b s t i t u t e d f o r s i l i c o n i n t h e t e t r a h e d r a l s i t e . A c c o r d i n g t o t h i s p a r t i t i o n m o d e l , m a s s - b a l a n c e c a l c u l a t i o n s were made and t h e r e s u l t s a r e l i s t e d i n T a b l e IX. The r e s u l t s a r e c o n s i s t e n t i e . t h e atom t o t a l s i n M1 a r e v e r y c l o s e t o 1.0 f o r m u l a u n i t and t h e atom t o t a l s i n t h e t e t r a h e d r a l s p a c e a r e v e r y c l o s e t o 2.0 f o r m u l a u n i t s . T h i s may be t h e e v i d e n c e f o r h a v i n g a c h i e v e d an a p p r o p r i a t e model f o r t h e s u b s t i t u t i o n . I t h as been r e p o r t e d ( G a s p a r i k e t a l . , 1980a) t h a t a l u m i n o u s p y r o x e n e s a r e v e r y d i f f i c u l t t o e q u i l i b r a t e and 50 Table IX The results of mass balance calculation according to the microprobe analyses Analysis data by microprobe Data distributed among the different sites CaO MgO A1 S0, S i 0 2 M2 M1 T Activity 0.9514 0.9328 0.4783 1.6992 1.0000 , . 1 233 .9383 0.5755 1 .0062 0.8111 0.5818 1.6552 1.0000 1 . 1 082 .9461 0.5368 0.9016 0.9350 0.5240 1.6887 1.0000 1 .0986 .9507 0.5145 1.0104 0.8391 0.4986 1.7013 1.0000 1 .0988 .9506 0.5942 1.0152 0.9009 0.4281 1.7209 1.0000 1 . 1 301 .9349 0.6509 0.9579 0.9174 0.3046 1.8339 1.0000 1 .0276 .9862 0.6956 0.8641 0.9629 0.3823 1.7998 1.0000 1 .0181 .9909 0.5736 1 .0025 0.8503 0.4082 1.7674 1.0000 1 .0569 .9715 0.6501 0.9875 0.8266 0.4969 1.7193 1.0000 1 .0625 .9677 0.5776 0.8345' 0.9338 0.4865 1 .7510 1.0000 1 .0115 .9943 0.4886 0.7601 0.8557 0.7630 1.6199 1.0000 .9973 .0014 0.3075 0.7781 0.8482 0.7521 1 .6227 1.0000 1 .0023 .9987 0.3204 0.7094 0.8512 0.7103 1.6870 1.0000 .9157 .0421 0.2964 0.9796 0.8809 0.4053 1.7658 1.0000 1 .0631 .9684 0.6380 0.9396 0.8872 0.5309 1.6885 1.0000 1 .0922 .9539 0.531 1 0.8555 0.9625 0.3776 1.8078 1.0000 1 .0068 .9966 0.5698 0.8970 0.9697 0.3357 1.8147 1.0000 1 .0345 .9825 0.6296 0.8474 0.9118 0.5394 1.7159 1.0000 1 .0289 .9856 0.4670 0.8962 0.9246 0.3819 1.8032 1.0000 1 .0117 .9941 0.5945 0.8707 0.9787 0-. 3275 1.8297 1.0000 1 .0131 .9935 0.6150 0.8845 0.9605 0.3210 1.8366 1.0000 1 .0055 .9971 0.6286 0.9288 0.9157 0.5816 1.6416 1.0000 1 . 1353 .9324 0.4986 0.8435 0.8705 0.4877 1.7772 1.0000 .9579 .0210 0.4862 0.8929 0.9893 0.5576 1.6452 1.0000 1 .1610 .9240 0.4961 0.9438 0.8375 0.5224 1.7176 1.0000 1 .0425 .9788 0.5329 0.9437 0.8648 0.5097 1.7135 1.0000 1 .0633 .9683 0.5438 0.9960 0.7772 0.5583 1.6946 1.0000 1 .0523 . 9738 0.5394 0.7962 0.8928 0.6965 1.6381 1.0000 1 .0372 .9863 0.3597 0.9145 0.8855 0.5323 1.7008 1.0000 1 .0661 .9669 0.5131 0.9573 0.8259 0.5524 1.6941 1.0000 1 .0594 .9703 0.5232 0.7466 0.9776 0.6280 1.6669 1.0000 1 .0382 .9809 0.3688 0.9093 0.9986 0.2138 1.8856 1.0000 1 .01 48 .9925 0.7286 0.8990 0.9699 0.1947 1.9195 1.0000 0 .9663 2 .0168 0.7323 0.8229 0.9669 0.3507 1.8421 1.0000 0 .9651 2 .0174 0.5614 0.8730 0.9588 0.3196 1.8444 1.0000 0 .9916 2 .0042 0.6202 0.9532 0.9146 ' 0.3578 1.7978 1.0000 1 .0467 1 .9767 0.6537 0.8976 0.9720 0.4223 1.7485 1.0000 1 . 0 8 0 7 1 .9596 0.5750 0.8603 0.9896 0.3614 1.8040 .1 .0000 1 .0306 1 . 9847 0.5862 0.9029 0.9901 • 0.3281 1.8074 1.0000 1 . 0 5 7 0 1 . 971 4 0.641 1 0.9586 0.8840 0.5035 1.7011 1.0000 1 . 0943 1 . 9529 0.5600 0.9074 0.9119 0.3869 1.8002 1.0000 1 .0127 1 .9937 0.5985 0.9696 0.7589 0.5156 1.7490 1.0000 .9863 .0068 0.5440 0.8533 0.9359 0.4857 1.7341 1.0000 1 .0320 1 .9769 0.5020 0.8906 0.9621 0.5251 1.6798 1.0000 1 . 1 1 52 1 .9423 0.5093 0.9500 0.7691 0.4950 1.7692 1.0000 .9666 .01 67 0.5439 0.9603 0.9805 0.2939 1.8091 1.0000 1 .0877 1 .9560 0.7105 0.9743 0.9339 0.3603 1.7757 1.0000 1 .0883 1 .9558 0.6702 0.8812 0.9558 0.4118 1.7726 1.0000 1 .0429 1 .9785 0.5677 0.7504 1.0388 0.4161 1.7933 1.0000 .9973 .001 3 0.4768 0.8990 0.9574 0.3919 1.7783 1.0000 1 .0523 1 .9742 0.5936 0.8650 0.8866 0.4782 1.7656 1.0000 .9907 .0047 0.5090 0.8454 0.9988 0.5963 1 . 6307 1.0000 1 . 1 423 1 .9288 0.4465 0.8045 1.0151 0.5526 1.6757 1.0000 1 .0959 1 .9520 0.4434 1 .0587 0.9070 0.3218 1.7758 1.0000 1 . 1 266 1 .9367 0.7630 0.8900 0.9926 0.2612 1 .8628 1.0000 1 .0132 1 .9934 0.6770 0.9343 0.9891 0.4389 1.7092 1.0000 1 . 1 428 1 .9286 0.5929 0.8287 0.9741 0.4241 1 . 7805 l.0000 1 .0148 1 .9925 0.5234 1.0349 0.9568 0.2868 1 .7891 1.0000 1 .1351 1 .9325 0.7750 51 may form inhomogeneous c r y s t a l s b e c a u s e of t h e slow d i f f u s i o n o f aluminum. I t would not be s u r p r i s i n g a c c o r d i n g t o G a s p a r i k ' s r e s u l t s t o f i n d an a l u m i n u m - f r e e c e n t e r of d i o p s i d e s e e d c r y s t a l s w i t h an a l u m i n u m - r i c h c l i n o p y r o x e n e o v e r g r o w t h . F u j i i (1977) has a l s o e x p e r i m e n t a l l y d e t e r m i n e d t h e c o m p o s i t i o n s o f o r t h o p y r o x e n e and c l i n o p y r o x e n e c o e x i s t i n g w i t h f o r s t e r i t e and s p i n e l a t 16 kbar and 1100 t o 1375°C, u s i n g b o t h g l a s s and c r y s t a l l i n e m i x t u r e o f s y n t h e t i c c l i n o e n s t a t i t e , d i o p s i d e and s p i n e l a s t h e s t a r t i n g m a t e r i a l . Run t i m e r a n g e d f r o m s i x h o u r s a t 1375°C t o f o u r d a y s a t 1100°C. The r u n p r o d u c t s were a n a l y z e d under e l e c t r o n m i c r o p r o b e . I t was f o u n d t h a t i n t h e r u n p r o d u c t s of h o m o g e n i z a t i o n e x p e r i m e n t s , t h e p y r o x e n e g r a i n s were n o t c o m p l e t e l y e q u i l i b r a t e d , as t h e c o m p o s i t i o n of t h e c o r e s of l a r g e g r a i n s were c l o s e t o t h e c o m p o s i t i o n o f t h e s t a r t i n g m a t e r i a l . However, t h e a n a l y s e s o f s m a l l g r a i n s were s i m i l a r t o t h o s e o f t h e r i m s of t h e l a r g e g r a i n s . A l t h o u g h an e x a m i n a t i o n o f s u c h z o n e d g r a i n s was i m p o s s i b l e i n t h i s s t u d y b e c a u s e o f t h e s m a l l g r a i n s i z e , t h i s c o u l d be t h e main r e a s o n f o r t h e v a r i a t i o n of aluminum c o n t e n t . A l t h o u g h t h e a n a l y s i s beam was a l w a y s p u t as n e a r t h e c e n t e r o f t h e g r a i n a s p o s s i b l e , t h e s h i f t i n g beam makes i t p r o b a b l e t h a t d i f f e r e n t z o n e s were a n a l y s e d i n d i f f e r e n t g r a i n s , i n d i f f e r e n t p r o p o r t i o n s . 52 E . COMPOSITION OF CLINOPYROXENES FROM RODINGITES C l i n o p y r o x e n e s from r o d i n g i t e have been a n a l y s e d by many p e t r o l o g i s t s ( B e l l , C l a r k e and M a r s h a l l , 1911; C h a l l i s , 1965; F r o s t , 1975; E v a n s , T r o m m s d o r f f and R i c h t e r , 1979; Rawson, 1984; R i c e , p e r s o n a l c o m m u n i c a t i o n ) . Rawson ( 1 9 8 4 ) , s t u d i n g t h e r o d i n g i t e s from t h e n o r t h - c e n t r a l K l a m a t h M o u n t a i n s , C a l i f o r n i a ( p r e s s u r e c o n d i t i o n 5 t o 7 k b a r s ) , f o u n d t h a t c l i n o p y r o x e n e i n r o d i n g i t e s i s a complex s o l i d s o l u t i o n o f Mg, Mn, Fe and A l i n d i o p s i d e . Ca c o n t e n t s r a n g e f r o m 0.931 t o 0.993 c a t i o n s p e r f o r m u l a u n i t . X f o r Mg p y r o x e n e i s between 0.94 and 0.81. T s c h e r m a k ' s s u b s t i t u t i o n o f aluminum, f e r r i c i r o n and t i t a n i u m a p p e a r s t o i n c r e a s e w i t h m e t a m o r p h i c g r a d e . Aluminum i s t h e o n l y c a t i o n s u b s t i t u t i n g i n t h e t e t r a h e d r a l s i t e i n t h e s e p y r o x e n e s . The m i n e r a l a s s e m b l a g e s and e l e c t r o n m i c r o p r o b e a n a l y s e s of t h e c l i n o p y r o x e n e s f r o m t h e s e a s s e m b l a g e s a r e shown i n A p p e n d i x 2. A l s o p r e s e n t e d a r e t h e c l i n o p y r o x e n e c o m p o s i t i o n s f r o m t h e Paddy-Go-Easy P a s s , W a s h i n g t o n r o d i n g i t e s ( P = 3 k b a r s ? ) by R i c e ( p e r s o n a l c o m m u n i c a t i o n ) . C o m p o s i t i o n s of c l i n o p y r o x e n e from r o d i n g i t e s show t h a t aluminum c o n t e n t s a r e u s u a l l y low, a l t h o u g h some of t h e s a m p l e s c o n t a i n a s h i g h as 11.48 wt% of A l 2 0 3 (0.48 c a t i o n p e r f o r m u l a u n i t ) (528A1-MB). The a v e r a g e v a l u e of A l 2 0 3 i s a b o u t 2 t o 3 wt%. I t seems c l e a r t h a t d i o p s i d e s f r o m n a t u r a l r o d i n g i t e s metamorphosed under c o n d i t i o n s s i m i l a r t o t h o s e i n t h e e x p e r i m e n t s r e p o r t e d h e r e c o n t a i n much l e s s aluminum t h a n t h e e x p e r i m e n t a l l y p r o d u c e d d i o p s i d e s . IV. THERMODYNAMIC ANALYSIS A. PRECALCULATION Thermodynamic c a l c u l a t i o n s o f r e a c t i o n s among p h a s e s f o u n d i n m e t a r o d i n g i t e were made i n d e t a i l by R i c e ( 1 9 8 3 ) . The t hermodynamic p r o p e r t i e s u s e d i n t h a t c a l c u l a t i o n were m a i n l y from H e l g e s o n e t a l . ( l 9 7 8 ) . The c a l c u l a t e d phase r e l a t i o n s a r e shown i n F i g 20. The f o l l o w i n g e x p r e s s i o n was u s e d by R i c e (1983) f o r e q u i l i b r i a i n v o l v i n g C 0 2 and H 20: R T ( * C 0 2 l n f C 0 2 + "H 20 l n H 2 0 ) RT l n K = -AH° - AV (P-1) + T AS° - ; 1e A C P d T r s G r i o r + T e J ije A C p r d l n T where v .„ i s t h e s t o i c h i o m e t r i c c o e f f i c i e n t o f t h e v o l a t i l e gas s p e c i e s i n t h e r e a c t i o n . T 0 i s t h e thermodynamic r e f e r e n c e t e m p e r a t u r e ( 2 9 8 . 1 5 ° K ) , and T £ i s t h e e q u i l i b r i u m t e m p e r a t u r e . A H ° , A S £ , AV g , and ACp r e f e r t o t h e s t a n d a r d r e a c t i o n e n t h a l p y , t h i r d - l a w e n t r o p y , s o l i d - p h a s e volume c h a n g e , and h e a t c a p a c i t y a t t h e r e f e r e n c e t e m p e r a t u r e and 1 bar p r e s s u r e . P r o gram P-T System by P e r k i n s , Brown and Berman (1986) was u s e d f o r t h i s s t u d y t o c a l c u l a t e t h e ph a s e e q u i l i b r i u m . Thermodynamic p r o p e r t i e s ( h e a t c a p a c i t i e s , e n t h a l p i e s , e n t r o p i e s and v o l u m e s ) f o r t h e p h a s e s i n v o l v e d were a d o p t e d 53 200 300 400 500 600 700 800 T (°C) F i g 20 C a l c u l a t e d P H 2 O ~ t d i a g r a m f o r d e h y d r a t i o n e q u i l i b r i a among p h a s e s f o u n d i n m e t a r o d i n g i t e s . Taken from R i c e ( 1 9 8 3 ) . A n = a n o r t h i t e , C t e = c h l o r i t e , D i = d i o p s i d e , G r = g r o s s u l a r , P r = p r e h n i t e , Q t z = q u a r t z , S p = s p i n e l , T r = t r m o l i t e , Z o = z o i s i t e . *» 55 f r o m UBCDATABASE, d e s c r i b e d by Berman, Brown, and Greenwood ( 1 9 8 6 ) . The h e a t c a p a c i t y f u n c t i o n and t h e c o e f f i c i e n t s u s e d i n t h i s s t u d y a r e from Berman and Brown ( 1 9 8 5 ) : Cp = K 0 + K < / T 0 , 5 + K 2 / T 2 + K 3 / T 3 T a b l e X l i s t s a l l t h e thermodynamic p r o p e r t i e s and h e a t c a p a c i t y f u n c t i o n c o e f f i c i e n t s f o r t h e p h a s e s c o n s i d e r e d h e r e . The e q u i l i b r i u m c u r v e s c a l c u l a t e d a s d e s c r i b e d above a r e shown i n F i g 22, where i t w i l l be seen t h a t t h e y a r e c l o s e t o t h e c u r v e s c a l c u l a t e d by R i c e (1983) u s i n g H e l g e s o n and o t h e r s ' (1978) d a t a . B. EXPERIMENTAL CONSTRAINTS ON THERMODYNAMIC PROPERTIES C r i t i c a l l y - l i m i t i n g e x p e r i m e n t a l r e s u l t s were s e l e c t e d f o r t h e c o n s t r a i n t o f s e t s of AS° (298, 1 b a r ) and AH° (298, 1 b a r ) . T h e s e d a t a were a n a l y z e d by l i n e a r programming (Berman, E n g i , Greenwood, and Brown, 1986). F i g 21 shows t h e r a n g e o f thermodynamic p r o p e r t i e s , d e r i v e d f r o m e x p e r i m e n t a l r e s u l t s w i t h o u t any c o n s t r a i n s of thermodynamic p r o p e r t i e s f r o m UBCDATABASE, t h a t a r e i n t e r n a l l y c o n s i s t e n t f o r t h e r e a c t i o n . A l s o shown i n t h i s f i g u r e a r e t h e v a l u e s o f AS° (298, 1 b a r ) and AH° (298, 1 b a r ) c a l c u l a t e d f r o m UBCDATABASE and H e l g e s o n ' s d a t a b a s e . L i n e a r programming s o l u t i o n s t o p r o b l e m s o f t h i s k i n d c a n a l s o r e s u l t f r o m 56 T a b l e X Thermodynamic p r o p e r t i e s f o r p h a s e s c o n s i d e r e d i n t h i s s t u d y ( a l l from UBCDATABASE) Phase C l i n o c h l o r e M g 5 A l 2 S i 3 0 1 0 ( O H ) B AH£ ( J ) S ° ( J / K ) V (cm 3) -8921085 429.77 209.82 K 0 K, K 2 1214.28 -11217.13 0.0 K 3 -1256253184 D i o p s i d e CaMgSi 2 0 6 AH? ( J ) S ° ( J / K ) -3201898 142.50 K 0 K, 305.41 -1604.93 V (cm 3) 66. 18 K 2 K--7165973 921837568 G r o s s u l a r C a 3 A l 3 S i 3 0 , 2 AH? ( J ) S ° ( J / K ) -6632395 255.00 K 0 K, 573.43 -2039.41 V (cm 3) 125.30 K, K--18887168 2319311872 S p i n e l M g A l 2 0 4 AH£ ( J ) S ° ( J / K ) -2302436 83.67 K 0 K, 235.90 -1766.58 V (cm 3) 39.74 K--1710415 40616928 Water H 20 AH? ( J ) S ° ( J / K ) -241816 188.72 V (cm 3) 24450.30 o p t i m i z i n g some o b j e c t i v e f u n c t i o n , w h i c h may be any l i n e a r c o m b i n a t i o n o f t h e thermodynamic p r o p e r t i e s o f t h e p h a s e s . F o r example, one may f i n d t h e maximum o r minimum o f t h e S° and AH£ of any p h a s e , or t h e AS° and AH° of t h e r e a c t i o n . The l i m i t s on AS° and A H ° r f o r t h e r e a c t i o n t h a t a r e c o n s i s t e n t w i t h t h e e x p e r i m e n t s a r e l i s t e d i n T a b l e X I . 57 T a b l e XI Range of thermodynamic p r o p e r t i e s t h a t a r e c o n s i s t e n t w i t h e x p e r i m e n t a l r e s u l t s C l i n o c h l o r e R e a c t i o n maximum S 627.77(J/K) minimum AS minimum S 6 5.42(J/K) maximum AS maximum H - 8 7 5 5 3 7 6 . ( J ) minimum AH minimum H - 9 2 3 3 9 8 3 . ( J ) maximum AH The r e a c t i o n c u r v e s were c a l c u l a t e d and p l o t t e d ( F i g 22) u s i n g t h e s e two s e t s of AS° (298, 1 b a r ) and AH° (298, 1 b a r ) v a l u e s . A l s o shown a r e t h e e q u i l i b r i u m c a l c u l a t e d w i t h c o e f f i c i e n t s from UBCDATABASE and t h e c u r v e c a l c u l a t e d by R i c e (1983) u s i n g t h e H e l g e s o n ' s d a t a b a s e ( 1 9 7 8 ) . F i g 21 and F i g 22 b o t h i n d i c a t e t h a t t h e e x p e r i m e n t a l r e s u l t s from t h i s s t u d y a r e f u l l y c o n s i s t e n t w i t h UBCDATABASE and H e l g e s o n ' s d a t a b a s e . C. CLINOPYROXENE SOLID SOLUTION The p r e v i o u s c a l c u l a t i o n s were made on t h e a s s u m p t i o n t h a t a l l p h a s e s p r e s e n t a r e p u r e endmembers. The p o s s i b l e s o l i d s o l u t i o n s were i g n o r e d . In p r e v i o u s c h a p t e r s , i t was d e m o n s t r a t e d t h a t d i o p s i d e s f r o m some run p r o d u c t s c o n t a i n aluminum and c o u l d be d e s c r i b e d by s u b s t i t u t i o n o f t h e Ca-Tschermak and Mg-Tschermak " m o l e c u l e s " . Wood and H o l l o w a y (1984) have d i s c u s s e d t h e s o l i d s o l u t i o n o f p y r o x e n e s and t h e i r m i x i n g p r o p e r t i e s . In t h e f o u r - c o m p o n e n t s y s t e m C a O - M g O - A l 2 0 3 - S i 0 2 , o r t h o p y r o x e n e 4 66.99(J/K) 1029.34(J/K) 2 0 9 9 4 1 . ( J ) 6 8 8 5 4 8 . ( J ) 58 F i g 21 The r a n g e o f thermodynamic p r o p e r t i e s , d e r i v e d from e x p e r i m e n t a l r e s u l t s w i t h l i n e a r programming, t h a t a r e i n t e r n a l l y c o n s i s t e n t . X — AS£ and AHg v a l u e s c a l c u l a t e d f r o m UBCDATABASE. + — AS£ and AH£ v a l u e s c a l c u l a t e d f r o m H e l g e s o n ' s d a t a b a s e . 59 Temperature (C) F i g 2 2 The upper (curve #1) and lower (curve #2) l i m i t s of e q u i l i b r i u m from c o n s i s t e n t a n a l y s i s of experimental r e s u l t s taken without r e f e r e n c e to other c o n s t r a i n i n g data. The heavy s o l i d curve i s the p r e c a l c u l a t e d e q u i l i b r i u m using UBCDATABASE and the heavy dashed curve i s c a l c u l a t e d from Helgeson's database by Rice (1983). 60 c o m p o s i t i o n s c a n be r e p r e s e n t e d i n t h e t e r n a r y C a M g S i 2 0 6 , M g 2 S i 2 0 6 and M g A l 2 S i 0 6 . C l i n o p y r o x e n e c o m p o s i t i o n s may r e a d i l y be r e p r e s e n t e d by t h e c o m p o s i t i o n s C a M g S i 2 0 6 , M g 2 S i 2 0 6 and C a A l 2 S i 0 6 . H o l l a n d e t a l . ( l 9 7 9 , 1980) have d e r i v e d m i x i n g p r o p e r t i e s o f C a M g S i 2 0 6 - M g 2 S i 2 0 6 c l i n o p y r o x e n e and o r t h o p y r o x e n e s o l i d s o l u t i o n s . T h e s e m i x i n g p r o p e r t i e s a r e c o n s i s t e n t w i t h e x p e r i m e n t a l d e t e r m i n a t i o n s o f t h e t w o - p y r o x e n e m i s c i b i l i t y gap and w i t h e n t h a l p y of s o l u t i o n d a t a . F o r t h e r e a c t i o n : M g 2 S i 2 0 6 ( o r t h o p y r o x e n e ) = M g 2 S i 2 0 6 ( C l i n o p y r o x e n e ) t h e y d e r i v e d s t a n d a r d s t a t e ( p u r e p h a s e a t P and T) t e m p e r a t u r e - i n d e p e n d e n t e n t h a l p y and e n t r o p y c h a n g e s of 1625 C a l and 0.66 C a l / K (6799.00 J o u l e s and 2.76 J/K) r e s p e c t i v e l y . The f r e e e n e r g y o f s o l u t i o n i n t h e b i n a r y s y s t e m , M g 2 S i 2 0 6 - C a M g S i 2 0 6 c a n be r e p r e s e n t e d as G mix = RT (X M g 2 S i 2 0 6 * l n X M g 2 S i 2 0 6 + X CaMgSi 2 0 6 * l n X CaMgSi 2 0 ) + W * X CaMgSi 2 0 6 * X M g 2 S i 2 0 6 6 where t h e f i r s t two t e r m s on t h e r i g h t hand s i d e a r e i d e a l e n t r o p y c o n t r i b u t i o n s and t h e l a s t t e r m i s t h e e x c e s s f r e e e n e r g y due t o Mg-Ca m i x i n g on t h e l a r g e r c a t i o n p o s i t i o n M 2. 61 The i n t e r a c t i o n p a r a m e t e r , W0 , d e f i n e d i n t e r m s of e x c e s s e n t h a l p y WH , e n t r o p y Wg and Wv , i s as f o l l o w s : WQ = WH - T*Wg + P*WV H o l l a n d e t a l . (1979) have a d o p t e d a t e m p e r a t u r e - i n d e p e n d e n t WQ v a l u e of 8126 C a l / M o l (34000 J o u l e s / M o l ) f o r t h e o r t h o p y r o x e n e s o l i d s o l u t i o n a l t h o u g h t h i s v a l u e was p o o r l y c o n s t r a i n e d by t h e d a t a . F o r t h e c l i n o p y r o x e n e b i n a r y , a Wu v a l u e of 5913 C a l / M o l (24739.99 J / M o l ) , Wg o f 0.0 and W y o f 0.025 C a l / M o l (0.10 J / M o l ) were d e r i v e d . M i x i n g p r o p e r t i e s o f t h e C a M g S i 2 0 6 - M g 2 S i 2 0 6 o r t h o p y r o x e n e and c l i n o p y r o x e n e b i n a r i e s and o f t h e M g 2 S i 2 0 6 - M g A l 2 S i 0 6 o r t h o p y r o x e n e j o i n have a l s o been d e r i v e d by c o m b i n i n g m i x i n g p a r a m e t e r s f o r e a c h of t h e i n d i v i d u a l s i t e s ( S axena and Ghose, 1971) w i t h " c r o s s - s i t e " o r r e c i p r o c a l t e r m s as d e s c r i b e d by Wood and N i c h o l l s ( 1 9 7 8 ) . The o r t h o p y r o x e n e and c l i n o p y r o x e n e s o l i d s o l u t i o n may be c o n s i d e r e d a s c o n t a i n i n g t h r e e b i n a r y s o l u t i o n s i t e s , M 1 ( A l - M g ) , M 2(Ca-Mg), and T ( A l - S i ) . The s o l u t i o n o f M g A l 2 S i 0 6 component i n o r t h o p y r o x e n e was t r e a t e d f o l l o w i n g Wood and Banno ( 1 9 7 3 ) . I n t h i s t r e a t m e n t , A l - S i m i x i n g on t e t r a h e d r a l s i t e s does n o t c o n t r i b u t e t o t h e f r e e e n e r g y o f s o l u t i o n i n d e p e n d e n t l y , b e c a u s e o f c o u p l e d s u b s t i t u t i o n s i n M, and M 2. N e g l e c t i n g t e t r a h e d r a l s i t e s f o r b o t h p y r o x e n e s we c a n e x p r e s s e n t r o p y o f m i x i n g a s f o l l o w s : 62 S . = - R ( X „ w l n X _ „ + X u „ l n X „ ) mix CaM 2 CaM 2 MgM 2 MgM 2 - R M X A L M I mx A 1 M i + x M g M i *mx M g M i ) T h i s e x p r e s s i o n assumes random m i x i n g and n e g l e c t s t h e p o s s i b i l i t y of s h o r t r a n g e o r d e r . E x c e s s f r e e e n e r g y c o n t r i b u t i o n s c o n s i s t of terms f o r eac h o f t h e s i t e s d i s c u s s e d above and a r e c i p r o c a l term AGj f o r t h e i n t e r n a l e q u i l i b r i u m : M g A l 2 S i 0 6 + C a M g S i 2 0 6 = C a A l 2 S i 0 6 + M g 2 S i 2 0 6 . T h i s y i e l d s f o r t h e f r e e e n e r g y o f m i x i n g G . = -T*S + X *X *W ° mix D mix CaM 2 MgM 2 Gm2 X , , M *X w *W _ + X „ „ *X X 1 W *AGi° AIM, MgM, Gm, MgM 2 AIM, f o r c l i n o p y r o x e n e and G . = -T*S + X *X *W ° mix D mix CaM 2 MgM 2 Gm2 + X *X w „ *W _ + X _ w *X , 1 % M *AGi° AIM, MgM, Gm, CaM 2 AIM, f o r o r t h o p y r o x e n e . A G i ° r e f e r s t o t h e s t a n d a r d f r e e e n e r g y change o f t h e i n t e r n a l e q u i l i b r i u m . 63 The W ' s f o r M 2 s i t e s a r e s i m p l y t h o s e g i v e n by H o l l a n d e t a l . ( l 9 7 9 , 1980) f o r d i o p s i d e - e n s t a t i t e s o l i d s o l u t i o n s . The e x c e s s f r e e e n e r g y due t o Mg-Al i n t e r a c t i o n s on t h e o r t h o p y r o x e n e M, s i t e must, t o be c o n s i s t e n t w i t h t h e MAS s y s t e m , be s e t t o z e r o . (Wood and H o l l o w a y , 1984). S u b s t a n t i a l p o s i t i v e e x c e s s e n t h a l p i e s o f m i x i n g i n s y n t h e t i c C a M g S i 2 0 6 - C a A l 2 S i 0 6 c l i n o p y r o x e n e s f r o m h e a t of s o l u t i o n measurement were f o u n d by Newton e t a l . ( l 9 7 7 ) . Wood (1979) i n d i c a t e d t h a t t h e e x c e s s e n t h a l p i e s o f s o l u t i o n w o u l d be c o n s i s t e n t w i t h phase e q u i l i b r i u m measurements on p y r o x e n e c o e x i s t i n g w i t h a n o r t h i t e and q u a r t z p r o v i d e d A l and S i were c o m p l e t e l y d i s o r d e r e d . Phase e q u i l i b r i u m d a t a r e p o r t e d by G a s p a r i k and L i n d s l e y (1980b) t e n d t o s u g g e s t , however, t h a t t h e s e p y r o x e n e s e x h i b i t l a r g e n e g a t i v e d e v i a t i o n s f r o m i d e a l i t y w h i c h c a n n o t r e a d i l y be made c o n s i s t e n t w i t h Newton e t a i ' s e n t h a l p y measurement. Wood and H o l l o w a y (1984) have o p t e d t o use t h e s i m p l e model o u t l i n e d above w i t h an e m p i r i c a l Al-Mg i n t e r a c t i o n p a r a m e t e r i n t h e i r p a p e r . R e v e r s a l s o f c l i n o p y r o x e n e c o m p o s i t i o n i n t h e CMAS s y s t e m s u g g e s t e d t h a t a t e m p e r a t u r e - i n d e p e n d e n t Mg-Al i n t e r a c t i o n p a r a m e t e r of 1800 C a l / G r a m atom (7531.20 J o u l e s / G r a m atom) i s an a p p r o p r i a t e f i t p a r a m e t e r . U s i n g t h e M a r g u l e s p a r a m e t e r s from t h e p r e c e d i n g d i s c u s s i o n , thermodynamic c a l c u l a t i o n was made c o n s i d e r i n g s o l i d s o l u t i o n between j o i n s o r t h o p y r o x e n e C a M g S i 2 0 6 and M g 2 S i 2 0 6 , c l i n o p y r o x e n e C a M g S i 2 0 6 , M g 2 S i 2 0 6 and C a A l 2 S i 0 6 . 64 The p r o g r a m THERIAK by C. D e c a p i t a n i ( p e r s o n a l c o m m u n i c a t i o n ) was u s e d f o r t h e c a l c u l a t i o n . T h i s p r o g r a m i s a f r e e e n e r g y m i n i m i z a t i o n a l g o r i t h m t h a t a c c e p t s UBCDATABASE thermodynamic p a r a m e t e r s , i n c l u d i n g M a r g u l e s p a r a m e t e r s f o r s o l i d s o l u t i o n s , and computes t h e p r o p o r t i o n s and c o m p o s i t i o n s of a l l c o e x i s t i n g p h a s e s f o r a g i v e n b u l k c o m p o s i t i o n a t any c h o s e n p r e s s u r e and t e m p e r a t u r e . The r e a c t i o n : G r o s s u l a r + C l i n o c h l o r e = 3 D i o p s i d e + 2 s p i n e l + 4 H 2 0 , was exam i n e d , a l l o w i n g f o r s o l i d s o l u t i o n i n p y r o x e n e as o u t l i n e d a b o v e . T h i s r e s u l t e d i n d e t e r m i n i n g t h e e q u i l i b r i u m t e m p e r a t u r e s t o be 583°C and 558°C a t 2000 b a r s a n d 1000 b a r s r e s p e c t i v e l y . T h e s e t e m p e r a t u r e s a r e a l m o s t i d e n t i c a l t o t h o s e f o u n d from t h e c a l c u l a t i o n w i t h o u t c o n s i d e r i n g s o l i d s o l u t i o n i n p y r o x e n e s . T h i s c a n be e x p l a i n e d by e x a m i n i n g t h e c o m p o s i t i o n of t h e e q u i l i b r i u m p h a s e s . A t t h e low t e m p e r a t u r e s i d e , t h e a s s e m b l a g e g r o s s u l a r + c l i n o c h l o r e i s s t a b l e and no s o l i d s o l u t i o n was a l l o w e d f o r i n t h i s s t u d y . The c o m p o s i t i o n s o b t a i n e d a r e t h e i d e a l f o r m u l a e w i t h C a 3 A l 2 S i 3 0 1 2 f o r g r o s s u l a r and M g 5 A l 2 S i 3 0 , 0 ( O H ) 8 f o r c l i n o c h l o r e . The m i n e r a l a s s e m b l a g e f o r t h e h i g h t e m p e r a t u r e s i d e c o n s i s t s of c l i n o p y r o x e n e and s p i n e l . C o m p o s i t i o n o f c l i n o p y r o x e n e i s t e m p e r a t u r e and p r e s s u r e d e p e n d e n t , but on t h e w h o l e , d i o p s i d e i s t h e main component o f t h e p y r o x e n e , c o m p r i s i n g more t h a n 98mol% o f p y r o x e n e . T h i s i s a l m o s t p u r e 65 d i o p s i d e and i t s a c t i v i t y i n p y r o x e n e i s more t h a n 0.96. The r e m a i n i n g 2mol% a r e components of c l i n o e n s t a t i t e and C a - T s c h e r m a k . The computed e q u i l i b r i u m c o m p o s i t i o n f o r c l i n o p y r o x e n e a l o n g t h e e q u i l i b r i u m c u r v e i s low i n aluminum w i t h a v a l u e of a b o u t 0.3mol%. D. DIOPSIDE A C T I V I T I E S AND DISPLACED EQUILIBRIUM In t h e r e a c t i o n : G r o s s u l a r + C l i n o c h l o r e = 3 D i o p s i d e + 2 S p i n e l + 4 H 2 0 t h e e q u i l i b r i u m w i l l be d i s p l a c e d f r o m t h e p u r e end-member r e a c t i o n i f any phase i s n o t a p u r e end-member. The e x p e r i m e n t a l e v i d e n c e i s t h a t a l l p h a s e s a r e of end-member c o m p o s i t i o n e x c e p t d i o p s i d e w h i c h a p p e a r s t o c o n t a i n aluminum. T h i s s u b s t i t u t i o n o f A l r e d u c e s t h e f r e e e n e r g y o f d i o p s i d e by an amount AMd^ , where A ^ . = R*T * l n a J r p x D l D l C D X i n w h i c h a'Qi 1 S t h e a c t i v i t y o f d i o p s i d e i n c l i n o p y r o x e n e , w h i c h i s e v a l u a t e d below. T h i s r e d u c t i o n i n f r e e e n e r g y o f d i o p s i d e component s t a b i l i z e s t h e h i g h - t e m p e r a t u r e a s s e m b l a g e , d i s p l a c i n g t h e e q u i l i b r i u m c u r v e t o l o w e r t e m p e r a t u r e . The e x p e r i m e n t a l r e s u l t s i n d i c a t e t h a t d i o p s i d e s from t h e r u n p r o d u c t s a r e a l u m i n u m - b e a r i n g . We must t h e r e f o r e 66 c o n s i d e r t h e a c t i v i t y o f d i o p s i d e i n t h e d i o p s i d i c c l i n o p y r o x e n e . Assuming o t h e r p h a s e s i n t h i s r e a c t i o n a r e p u r e and s e t t i n g t h e i r a c t i v i t i e s t o 1.0, we w i l l have AG = L M I A = EM? + R*T E l n a ^ = 3 u°A.+ 2 M° + 4 M£ Z M° d i sp H 2 0 gr - M ?•+ R*T l n a _ 9 p x c l i n D i = 0 U s i n g t h e above e q u a t i o n we c a n c a l c u l a t e t h e p o s i t i o n of t h e e q u i l i b r i u m c u r v e w i t h d i f f e r e n t d i o p s i d e a c t i v i t i e s a s shown i n F i g . 23. The d i s p l a c e m e n t of e q u i l i b r i u m c u r v e s w i t h d i f f e r e n t d i o p s i d e a c t i v i t y v a l u e s i s s i g n i f i c a n t . E q u i l i b r i u m t e m p e r a t u r e d e c r e a s e s as t h e d i o p s i d e a c t i v i t y v a l u e s d e c r e a s e . T h i s l e a d s t o h a v i n g a l a r g e r s t a b l e f i e l d o f t h e h i g h t e m p e r a t u r e a s s e m b l a g e d i o p s i d e + s p i n e l + H 2 0 . The e q u i l i b r i u m c u r v e w i t h d i o p s i d e a c t i v i t y v a l u e o f 0.96 w h i c h i s f r o m th e c a l c u l a t i o n u s i n g p r o g r a m THERIAK i s a l s o p l o t t e d i n F i g 23. D i o p s i d e a c t i v i t y i n c l i n o p y r o x e n e f r o m e x p e r i m e n t s c a n a l s o be c a l c u l a t e d f r o m t h e m i c r o p r o b e a n a l y s e s o f d i o p s i d e . As d i s c u s s e d i n C h a p t e r 3, t h e M, s i t e s i n t h e d i o p s i d e s t r u c t u r e were o c c u p i e d m a i n l y by Mg + 3+ ++ a n d some A l . M 2 s i t e s were o c c u p i e d m a i n l y by Ca and ++ . . . 4+ some Mg . The t e t r a h e d r a l s i t e s were f i l l e d w i t h S i and 67 500 550 600 T e m p e r a t u r e (C) F i g 2 3 The d i s p l a c e d c u r v e s o f e q u i l i b r i u m g r o s s u l a r + c l i n o c h l o r e = 3 d i o p s i d e + 2 s p i n e l + 4 H 2 0 w i t h d i f f e r e n t d i o p s i d e a c t i v i t i e s . D i o p s i d e a c t i v i t i e s i n c r e a s e from 0.1 ( c u r v e #1) t o 1.0 ( c u r v e #10) by 0.1 e a c h . C u r v e #5 (heavy s o l i d l i n e ) c o r r e s p o n d s t o d i o p s i d e a c t i v i t y (0.5) c a l c u l a t e d f r o m m i c r o p r o b e a n a l y s i s d a t a . The heavy d a s h e d l i n e i s t h e e q u i l i b r i u m c u r v e w i t h d i o p s i d e a c t i v i t y 0.96 c a l c u l a t e d w i t h t h e THERIAK program. 68 3 + some A l . We may c a l c u l a t e t h e d i o p s i d e a c t i v i t y u s i n g s i m p l e s i t e model by m u l t i p l y i n g t h e v a l u e s of M g + + i n M, ++ . 4 + s i t e s , t h e Ca i n M 2 s i t e s and t h e s q u a r e o f S i from t h e t e t r a h e d r a l s i t e s . B a s e d on t h i s m o d e l, t h e d i o p s i d e a c t i v i t i e s were c a l c u l a t e d u s i n g t h e a n a l y s i s d a t a o f m i c r o p r o b e ( s e e T a b l e I X ) . B e c a u s e t h e aluminum v a l u e s v a r y r a t h e r w i d e l y , t h e d i o p s i d e a c t i v i t i e s a l s o v a r y . The a v e r a g e v a l u e , however, i s c l o s e t o 0.5. C o m p a r i n g F i g 23 f o r t h e e q u i l i b r i u m c u r v e w i t h 0.5 d i o p s i d e a c t i v i t y , t h e e q u i l i b r i u m t e m p e r a t u r e s a r e 5 41.81°C and 5 2 0 . 9 2 ° C a t 2000 b a r s and 1000 b a r s r e s p e c t i v e l y , c o r r e s p o n d i n g t o a t e m p e r a t u r e d e c r e a s e o f 44°C a t 2000 b a r s and 39°C a t 1000 b a r s , from t h e c u r v e c a l c u l a t e d f r o m p u r e d i o p s i d e . T h e s e c a l c u l a t i o n s f o c u s on an u n s o l v e d p r o b l e m u n c o v e r e d w i t h t h e e x p e r i m e n t s . The e q u i l i b r i u m c u r v e o b s e r v e d e x p e r i m e n t a l l y i s c l o s e t o t h e c a l c u l a t e d c u r v e u s i n g t h e e q u i l i b r i u m c o m p o s i t i o n computed w i t h THERIAK, u s i n g e x i s t i n g d a t a on c l i n o p y r o x e n e s o l i d s o l u t i o n s . T h i s would be c o n s i d e r e d e x c e l l e n t a g r e e ment, e x c e p t f o r t h e e v i d e n c e t h a t t h e e x p e r i m e n t a l c l i n o p y r o x e n e i s a l u m i n o u s t o a d e g r e e t h a t s h o u l d d i s p l a c e t h e e q u i l i b r i u m a b o u t 40°C t o a l o w e r t e m p e r a t u r e . The o b s e r v e d e q u i l i b r i u m c u r v e has n o t , however, been d i s p l a c e d , l e a d i n g t o a c o n c l u s i o n t h a t t h e e x p e r i m e n t a l c l i n o p y r o x e n e s must c o n t a i n u n d e t e c t e d A l - r i c h i n c l u s i o n s o r m e t a s t a b l e A l - r i c h z o n e s . V. CONCLUSION E x p e r i m e n t a l d e t e r m i n a t i o n of t h e e q u i l i b r i u m g r o s s u l a r + c l i n o c h l o r e = 3 d i o p s i d e + 2 s p i n e l + 4 H 20, an i m p o r t a n t r e a c t i o n i n t h e metamorphism of r o d i n g i t e , i n d i c a t e s t h a t t h i s e q u i l i b r i u m d e v i a t e s o n l y s l i g h t l y f r o m what was t h e o r e t i c a l l y p r e d i c t e d from thermodynamic d a t a from UBCDATABASE. E x p e r i m e n t a l r e s u l t s show t h a t t h e low t e m p e r a t u r e a s s e m b l a g e g r o s s u l a r + c l i n o c h l o r e i s s t a b l e below t e m p e r a t u r e 502°C a t 500 b a r s , 520°C a t 1000 b a r s , 561°C a t 2000 b a r s and 600°C a t 4000 b a r s . The h i g h t e m p e r a t u r e a s s e m b l a g e d i o p s i d e + s p i n e l i s s t a b l e a t t e m p e r a t u r e s h i g h e r t h a n 560°C a t 500 b a r s , 581°C a t 1000 b a r s and 627°C a t 2000 b a r s . Between t h e s e b r a c k e t s t h e r e i s a p r e s s u r e - t e m p e r a t u r e r e g i o n i n w h i c h t h e a s s e m b l a g e d i o p s i d e + c l i n o c h l o r e seems a l w a y s t o be f o u n d . A n a l y s i s f o r i n t e r n a l c o n s i s t e n c y by l i n e a r programming i n d i c a t e s t h a t t h e new v a l u e s of e n t r o p y and e n t h a l p y c o n s t r a i n e d by t h e e x p e r i m e n t s a r e f u l l y c o n s i s t e n t w i t h UBCDATABASE and H e l g e s o n ' s d a t a b a s e . Thus t h e e x p e r i m e n t a l r e s u l t s from t h i s s t u d y s u p p o r t t h e UBCDATABASE and t h e e x p e r i m e n t s , w i t h UBCDATABASE may s a f e l y be u s e d as an i n d i c a t i o n o f t h e m e t a m o r p h i c c o n d i t i o n s o f m e t a r o d i n g i t e s . D i o p s i d e f r om t h e e x p e r i m e n t a l a s s e m b l a g e d i o p s i d e + c l i n o c h l o r e was p r o v e n by m i c r o p r o b e a n a l y s e s t o c o n t a i n aluminum and i s i n t e r p r e t e d t o be c o n s i s t e n t w i t h Tschermak s u b s t i t u t i o n . Aluminum c o n t e n t v a r i e s g r e a t l y f r o m one a n a l y s i s t o a n o t h e r . Some d i o p s i d e g r a i n s c o n t a i n a 69 70 s i g n i f i c a n t amount of aluminum. Z o n a t i o n of aluminum i n d i o p s i d e i s p r o b a b l y t h e main c a u s e f o r t h i s a l t h o u g h no z o n a t i o n c o u l d been seen w i t h SEM, m i c r o p r o b e , o r o p t i c a l m i c r o s c o p e . The p r o b a b l e z o n a t i o n o f A l - b e a r i n g d i o p s i d e may i l l u s t r a t e t h e f a c t t h a t p y r o x e n e s w i t h aluminum a r e v e r y d i f f i c u l t t o e q u i l i b r a t e . I t i s e a s y t o o b t a i n imhomogeneous A l - b e a r i n g p y r o x e n e c r y s t a l s b e c a u s e of t h e slow d i f f u s i o n of aluminum i n p y r o x e n e ( F u j i i , 1977; G a s p a r i k , e t a l . , 1980) T h e o r e t i c a l thermodynamic p r e d i c t i o n o f t h e e q u i l i b r i u m a l l o w i n g f o r s o l i d s o l u t i o n i n p y r o x e n e i n d i c a t e s t h a t d i o p s i d e s h o u l d be t h e dominant component, as h i g h as 98mol%. Ca-Tschermak m o l e c u l e a n d c l i n o e n s t a t i t e ( M g 2 S i 2 0 6 ) make up t h e r e m a i n i n g 2mol%. A c t i v i t y of d i o p s i d e i n t h e p y r o x e n e t h u s s h o u l d be v e r y c l o s e t o 1.0, w h i c h i s c o n s i s t e n t w i t h t h e e x p e r i m e n t s i n t h a t t h e e q u i l i b r i u m c u r v e a c c o r d i n g t o t h e e x p e r i m e n t a l b r a c k e t s d i d not show m e a s u r a b l e d i s p l a c e m e n t c a u s e d by t h e low d i o p s i d e a c t i v i t y . The a v e r a g e o f d i o p s i d e a c t i v i t i e s c a l c u l a t e d f r o m m i c r o p r o b e a n a l y s i s d a t a , however, i s as low as 0.5, and t h i s - sho-uld l o w e r t h e e q u i l i b r i u m t e m p e r a t u r e 44°C a t 2000 b a r s and 39°C a t 1000 b a r s r e s p e c t i v e l y f r o m t h e p r e c a l c u l a t e d e q u i l i b r i u m . B e c a u s e t h i s a c t i v i t y i s t h e a v e r a g e v a l u e and some o f d i o p s i d e s seem t o c o n t a i n a h i g h e r amount o f aluminum, I b e l i e v e t h a t t h e r e a r e some u n d e t e c t e d m e t a s t a b l e a l u m i n u m - r i c h z o n e s o r even a l u m i n u m - r i c h i n c l u s i o n s i n t h e d i o p s i d e c r y s t a l s . 71 The e q u i l i b r i u m s t u d i e d p r e s e n t s i t s e l f as b e i n g an i n t e r e s t i n g a r e a f o r f u r t h e r s t u d i e s . In p a r t i c u l a r t h e c o m p o s i t i o n of c l i n o p y r o x e n e from t h i s r e a c t i o n begs f u r t h e r r e s e a r c h t o c l a r i f y t h e n a t u r e of aluminum d i s t r i b u t i o n i n t h i s p y r o x e n e . T h i s i n f o r m a t i o n , t h o u g h i t would not be s i g n i f i c a n t f o r immediate g e o l o g i c a p p l i c a t i o n , may c o n t r i b u t e d i r e c t l y t o a b e t t e r u n d e r s t a n d i n g of c r y s t a l c h e m i s t r y , thermodynamic m o d e l l i n g o f p y r o x e n e , and s t u d y o f t h e e q u i l i b r i u m i t s e l f f o r r e s e a r c h on m e t a r o d i n g i t e s . F u r t h e r s t u d y m ight be made by s y n t h e s i z i n g a s e r i e s o f c l i n o p y r o x e n e s between t h e j o i n D i o p s i d e - Ca-Tschermak p y r o x e n e a s s t a r t i n g m a t e r i a l s t o d e t e r m i n e t h e s t a b l e c o m p o s i t i o n of c l i n o p y r o x e n e c o e x i s t i n g w i t h o t h e r p h a s e s f r o m t h i s e q u i l i b r i u m . I t m i g h t be p o s s i b l e t o t r a c e t h e c o m p o s i t i o n v a r i a t i o n o f t h e c l i n o p y r o x e n e s from r u n s a t d i f f e r e n t c o n d i t i o n s i n t h i s e q u i l i b r i u m . F u t h e r e x p e r i m e n t s s h o u l d use as h i g h a p r e s s u r e and t e m p e r a t u r e as p o s s i b l e t o i n c r e a s e t h e aluminum d i f f u s i o n r a t e i n p y r o x e n e and t h e r e a c t i o n r a t e of e x p e r i m e n t a l r u n s . REFERENCES A k a s a k a , M. and Onuma, K. (1980) The j o i n C a M g S i 2 0 6 - C a F e A l S i 0 6 - C a T i A l 2 0 6 and i t s b e a r i n g on t h e T i - r i c h p y r o x e n e s . C o n t r i b u t i o n s t o M i n e r a l o g y and P e t r o l o g y , 71, 301-312. B a r t h , T.F.W. and P o s n j a k , E . (1932) S p i n e l s t r u c t u r e s w i t h and w i t h o u t v a r i a t e atom e q u i p o i n t s . Z e i t s c h r i f t f u r K r i s t a l l o g r a p h i e , 82, 325-341. 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APPENDIX 1 M i c r o p r o b e a n a l y t i c r e s u l t s of s y n t h e t i c and e q u i l i b r i u m d i o p s i d e SAMPLE STD XRR-3 STD XRR-3 MgO 1 .0038 1.0033 1 .0318 1.0517 0.9799 1.0696 0.9338 0.8557 0.8482 0.8512 0.8809 0.8872 0.9625 0.9697 0.9118 0.9816 0.9804 0.9916 0.9246 0.9787 0.9605 0.9157 0.8705 0.9893 A 1 2 0 3 .0071 .0074 .0132 .0106 .0088 .0196 .4863 .7630 .7521 .7103 .4053 .5309 .3776 .3357 .5394 .01 65 .0063 .0186 .3819 .3275 .321 0 .581 6 .4877 .5576 S i 0 2 2.0017 2.0032 1.9595 1.9755 1.9731 1.9587 1.7510 1.6199 1.6227 1.6870 1.7658 1.6885 1 .8078 1.8147 1.7159 2.0031 1.9969 1.9640 1.8032 1.8297 1.8366 1.6416 1.7772 1.6452 CaO 0.9821 0.9995 1 .0093 0.9858 1.0607 0.9841 0.8345 0.7601 0.7781 0.7094 0.9796 0.9396 0.8555 0.8970 0.8474 0.9814 1.0164 1.0530 0.8962 0.8707 0.8848 0.9288 0.8435 0.8929 T o t a l 3.9947 4.0134 4.0338 4.0213 4.0223 4.0317 4.0058 3.9987 4.0011 3.9579 4.0316 4.0462 4.0034 4.0173 4.0145 3.9886 4.0000 4.0269 4.0059 4.0066 4.0029 4.0677 3.9789 4.0790 w t % T o t a l 91.10 103.30 83.30 93.92 92.95 104.30 84. 1 1 93.07 81 .08 1 04.25 82.65 85.65 88.88 90.52 93.49 90.77 1 1 1 .29 1 02.67 99.84 88.20 82.08 90.57 109.62 91 .63 80 81 M i c r o p r o b e r e s u l t s of s y n t h e t i c and e q u i l i b r i u m d i o p s i d e SAMPLE MgO A1,0- SiO- CaO T o t a l W t % T o t a l STD XRR-3 STD XRR-3 STD XRR-3 STD 0 .9967 .0052 2.0063 0 .9830 3 .9912 98. 27 1 .0488 .0017 1.9688 1 .0111 4 .0304 1 20. 00 0 .9933 .0034 1.9891 1 .0235 4 .0093 1 04. 36 1 .0214 .0061 2.0035 0 .9626 3 .9926 95. 68 0 .9897 .0061 1.9894 1 .0223 4 .0075 118. 48 0 .9676 .0069 1.9792 1 .0623 4 .0173 96. 81 0 .9791 .0043 1.9862 1 .0420 4 .0118 113. 61 0 .9596 .0039 2.0064 1 .021 7 3 .9916 111. 1 1 1 .0096 .0073 1.9709 1 .0376 4 .0254 84. 87 0 .9746 .0049 1.9968 1 .0245 4 .0008 106. 71 0 .7589 .51 56 1.7490 0 .9696 3 .9931 1 03. 21 0 .9359 .4951 1.7341 0 .8533 4 .0184 86. 1 4 0 .9621 .5251 1.6798 0 .8906 4 .0575 82. 26 0 .7691 .4950 1.7692 0 .9500 3 .9833 92. 49 0 .9805 .2939 1.8091 0 .9603 4 .0438 118. 23 1 .0267 .0032 1.9541 1 .0603 4 .0443 83. 03 0 .9992 .0081 1.9933 1 .0021 4 .0027 84. 80 1 .0073 .0081 2.0028 0 .9751 3 .9932 83. 24 1 .001 4 .0040 1.9825 1 .0276 4 .01 55 117. 34 0 .9339 .3603 1.7757 0 .9743 4 .0442 80. 55 0 .9558 .4118 1.7726 0 .8812 4 .0214 94. 42 1 .0388 .4161 1.7933 0 .7504 3 .9986 97. 05 0 .9574 .391 4 1.7783 0 .8990 4 .0260 82. 60 0 .8866 .4782 1.7656 0 .8650 3 .9954 82. 00 0 .9988 .5963 1.6307 0 .8454 4 .071 2 99. 06 1 .0151 .5526 1.6757 0 .8045 4 .0479 89. 57 1 .0278 .0037 1.9822 1 .0023 4 .01 60 90. 55 1 .0182 .0021 1.981 4 1 .01 58 4 .01 75 90. 18 0 .9802 .0047 1.9669 1 .0789 4 .0307 116. 49 1 .0670 .0038 1.9635 1 .0004 4 .0347 81 . 53 0 .9965 .0057 1.9944 1 .0063 4 .0029 112. 49 0 .9926 .261 2 1.8628 0 .8900 4 .0066 106. 50 0 .9891 .4389 1.7092 0 .9343 4 .0715 83. 95 0 .9741 .4241 1.7805 0 .8287 4 .0075 96. 53 0 .9568 .2868 1.7891 1 .0349 4 .0676 115. 88 1 .0844 .0052 1.9325 1 .0427 4 .0648 105. 83 0 .9523 .021 3 2.0470 0 .9218 3 .9424 1 03. 87 1 .0277 .0065 2.0101 0 .9432 3 .9866 84. 93 1 .0610 .0040 1.9906 0 .9518 4 .0074 92. 08 1 .0551 .0039 1.9826 0 .9719 4 .0145 1 02. 84 1 .0188 .0050 1.9943 0 .9849 4 .0031 85. 20 82 M i c r o p r o b e a n a l y t i c r e s u l t s o f s y n t h e t i c and e q u i l i b r i u m d i o p s i d e SAMPLE MgO A 1 2 0 3 S i 0 2 CaO T o t a l W t % T o t a l STD 1.0218 .0055 1 .9798 1 .0103 4.0174 89.98 0.9527 .0073 2.0455 0.9453 3.9508 1 1 1 .38 0.9349 .0262 2.0403 0.9453 3.9466 92.09 XRR-4 0.9328 .4783 1.6992 0.9514 4.0617 103.49 0.8111 .5818 1.6552 1.0062 4.0520 119.92 0.9350 .5240 1.6887 0.9016 4.0493 110.79 STD 0.9986 .0115 1.9455 1.0933 4.0489 85.81 XRR-4 0.8391 .4986 1.7013 1.0104 4.0494 90.38 0.9009 .4281 1.7209 1 .0152 4.0651 84.46 STD 0.9980 .0073 2.0005 0.9901 3.9959 102.30 0.9557 .0199 2.0103 0.9937 3.9796 82.44 1.0234 .0050 1.9757 1.0177 4.0218 89.68 XRE-10 0.9174 .3046 1.8339 0.9579 4.0138 107.41 0.9629 .3823 1.7998 0.8641 4.0091 87.37 0.8503 .4082 1.7674 1.0025 4.0284 1 16.60 0.8266 .4969 1.7193 0.9875 4.0323 106.66 STD 1.0108 .0078 1.9413 1.0950 4.0549 83.22 1.0319 .0064 2.0210 0.9163 3.9756 82.83 0.9381 .0206 2.0095 1.0119 3.9801 96.67 0.9747 .0038 2.0170 0.9856 3.9811 114.87 83 M i c r o p r o b e a n a l y t i c r e s u l t s of s y n t h e t i c and e q u i l i b r i u m d i o p s i d e SAMPLE MgO A 1 2 0 3 S i 0 2 CaO T o t a l W t % T o t a l STD 1.0669 .0060 1.9568 1.0106 4.0403 85.45 0.9644 .0050 1.9786 1.0709 4.0189 102.36 1.0128 .0064 1.9840 1.0095 4.0127 95. 16 0.9998 .0063 1.9935 1 .0037 4.0033 98.98 XRR-4 0.8371 .5224 1.7176 0.9438 4.0213 104.63 0.8648 .5097 1.7135 0.9437 4.0317 101.18 0.7772 .5583 1.6946 0.9960 4.0261 90.89 0.8928 .6965 1.6381 0.7962 4.0186 107.13 0.8855 .5323 1.7008 0.9145 4.0331 95.31 0.8259 .5524 1.6941 0.9573 4.0297 90.91 0.9776 .6280 1.6669 0.7466 4.0191 98. 19 STD 0.9655 .0050 2.0128 1.0013 3.9846 107.01 0.9835 .0064 1.9906 1.0257 4.0062 80.07 XRR-3 0.9986 .21 38 1.8856 0.9093 4.0073 87.91 0.9699 . 1 947 1.9195 0.8990 3.9831 93.41 0.9669 .3507 1.8421 0.8229 3.9826 89.26 0.9588 .31 96 1.8444 0.8730 3.9958 88.55 0.9146 .3578 1.7978 0.9532 4.0234 96.87 0.9720 .4223 1.7485 0.8976 4.0404 96.03 0.9896 .3614 1.8040 0.8603 4.0153 93.84 0.9901 .3281 1.8074 0.9029 4.0285 84. 16 STD 1.0057 .0090 1.9975 0.9858 3.9980 81.71 1.0053 .0121 1.9804 1.0156 4.0134 89.75 0.9926 .01 27 1.9491 1.0902 4.0446 91 .25 XRE-10 0.8840 .5035 1.7011 0.9586 4.0472 86. 12 0.9119 .3869 1.8002 0.9074 4.0064 95.02 0.8609 .4655 1.7687 0.9034 3.9985 91 .34 STD 0.9737 .0062 1.9900 1.0354 4.0410 89.14 1.0052 .0051 2.0105 0.9661 3.9869 84.35 APPENDIX 2 M i n e r a l a s s e m b l a g e s o f r o d i n g i t e s and d i o p s i d e c o m p o s i t i o n s a n a l y z e d by Rawson (1984) * TABLE Assemblages in Rodingites Sample Cc Cte Ml Di Gr Sp Tr Zo Sph Opa Huckleberry Mountain 34 X X X X X 36 A X* A A A NA NA 38 X X X X X X 39 X X X X 43A X* A A A A A 43B A A A A A X 43C A A A X A 46A-EXT A A A A A A 46A-INT X* A A A X* A 46B-1 X X X X X X 46B-2 A X* A A A A 53 X X X X X X 81A X X X X 81B A A A A 355B1 X* A A X* A 355B2 A X* A A A 355D X X X X X 402A1-2 X X X X X 402B A A X* A NA A 402E X X X X X Grider Ridge 514B2-1 X X X 515B2-2 X X X X X X 522A1-1 X X X X X X X 522A1-2 X X X X X X 522A1-3 X X X X X 522A2 X X X X X X 522B1-1 X X X 522B2-2 X X X 522C X X X X X 84 85 TABLE Continued Sample Cc Cte Mi Di Gr Sp Tr Zo Sph Opa Tyler Meadow 513B2-1T X X X X 513B2-1B X X X X 513C X X X 499A A NA A A 499B X X X X Rattlesnake Ridge 500B1-1G X X X X X 500B1-1 X X X X X K-2-B A A A A 500E A X* A A X* 500F A A A A A 500H X X X X X 501C X X X X 502-1-2 X X X 528A1-MB A A A A A A 528A1-MT A X* A A 27-4-E1 A A A A A 27-4-E2 A ? A A A 27-4-C A A A A A RB104C-T A A A A A RB104C-B A A A A A TABLE Continued Sample Cc Cte Ml Dl Gr Sp Tr Zo Sph Opa Scott Bar Mountains 494A1-1G A A A A X* 494A1-1N A A A X* 494A1-2 A A A A 494C A A A A 494D A A A A A 507B1-1 X X X X X 507B1-2 X X X X 507E1-2 X X X X X 508A1-1 X X X X X 508A1-2 X X X X X 508A1-4 X X X X X 508A1-3 X X X X X 510A X X X X 510B1-1 X X X X 513A X X X X 511A-B X X X X 511A-T X X X X Anorthite absent from a l l samples. X * present in assemblage. A • analyzed. NA - present in probe section / not analyzed. $ • present in assemblage / absent from probe section. 8 7 497A-2 497A1 481D 477A-3R n = 2 n = 12 n = 12 n = 4 S i 0 2 50.81(0.56) 51.54(0.60) 54.31(0.37) 51.92(0 .49) T i 0 2 0.05(0.01) 0.08(0.06) 0.04(0.01) 0.04(0 .00) A 1 2 0 3 0.75(0.00) 1 .07(0.42) 0.48(0.04) 0.64(0 .06) MnO 0.23(0.04) 0. 17(0.04) 0. 1 8(0.04) 0.25(0 .12) MgO 7.58(0.20) 10.24(0.40) 15.84(0.57) 7.63(0 .55) CaO 23.64(0.02) 23.71(0.32) 24.99(0.35) 23.13(0 .27) N a 20 0.09(0.00) 0.11(0.08) 0.08(0.04) 0.14(0 .01 ) K 2 0 0.03(0.00) 0.03(0.00) 0.03(0.00) 0.03(0 .00) FeO 16.27(0.34) 12.19(0.68) 3.57(0.85) 15.99(0 .79) F e 2 0 3 0.45(0.24) 0.38(0.43) 0.02(0.06) 0.00(0 .00) T o t a l 99.89(0.00) 99.51(0.00) 99.54(0.00) 99.76(0 .00) C a t i o n s ( S i ) 1 .973(0.007) 1 .969(0.020) 1 .997(0.006) 2 .011(0. 01 1 ) ( T i ) 0 .001(0.000) 0 .002(0.002) 0 .001(0.000) 0 .001(0. 000) ( A l ) 0 .034(0.000) 0 .048(0.019) 0 .021(0.002) 0 .029(0. 003) (Mn) 0 .007(0.001 ) 0 .005(0.001 ) 0 .006(0.001) 0 .008(0. 004) (Mg) 0 .439(0.008) 0 .583(0.020) 0 .868(0.027) 0 .441(0. 031 ) (Ca) 0 .983(0.007) 0 .970(0.009) 0 .984(0.009) 0 .960(0. 013) (Na) 0 .007(0.000) 0 .008(0.006) 0 .006(0.003) 0 .011(0. 001 ) (K) 0 .001(0.000) 0 .001(0.000) 0 .001(0.000) 0 .001(0. 000) <F a) 0 .528(0.007) 0 .390(0.024) 0 .110(0.027) 0 .518(0. 026) (F,) 0 .026(0.014) 0 .022(0.025) 0 .001(0.003) 0 .000(0. 000) Sum 4 .000(0.000) 3 .999(0.000) 3 .995(0.000) 3 .979(0. 000) 477A-3C 481C1-1R 481C1 - 1 C n = 4 n = 5 n = 5 S i 0 2 51 . 14(0.32) 53.94(0.36) 53.56(0.61) T i 0 2 0.04(0.00) 0.04(0.00) 0.04(0.00) A 1 2 0 3 0.52(0.17) 0.47(0.19) 0.52(0.04) MnO 0.36(0.13) 0.08(0.04) 0. 15(0.09) MgO 7.70(0.61) 13.97(0.73) 1 4 . 20(1.51 ) CaO 23.14(0.42) 24.40(0.23) 24.65(0.30) Na 20 0.14(0.03) 0.13(0.06) 0.12(0.06) K 20 0.03(0.00) 0.03(0.00) 0.03(0.00) FeO 16.13(1.44) 6.34 (1.09) 6.14(2.11) F e 2 0 3 0.00(0.00) 0.00(0.00) 0.00(0.00) T o t a l 99.20(0.00) 99.41(0.00) 99.41(0.00) C a t i o n s ( S i ) 1 .999(0.006) 2 .007(0.008) 1 .995(0.002) ( T i ) 0 .001(0.000) 0 .001(0.000) 0 .001(0.000) ( A l ) 0 .024(0.008) 0 .021(0.008) 0 .023(0.002) (Mn) 0 .012(0.004) 0 .003(0.001 ) 0 .005(0.003) (Mg) 0 .448(0.033) 0 .774(0.037) 0 .788(0.076) (Ca) 0 .969(0.014) 0 .973(0.010) 0 .984(0.012) (Na) 0 .011(0.002) 0 .010(0.004) 0 .009(0.005) (K) 0 .001(0.000) 0 .001(0.000) 0 .001 (0.000) ( F a ) 0 .528(0.050) 0 .197(0.035) 0 . 192(0.067) ( F 3 ) 0 .000(0.000) 0 .000(0.000) 0 .000(0.000) Sum 3 .994(0.000) 3 .987(0.000) 3 .997(0.000) 88 494A1-1 494D 494A1-2-R 494A1-2-C n = 13 n = 8 n = 5 n = 5 S i 0 2 52.18(0.53) 50.72(0.79) 50.85(0.32) 51.52(1.03) T i 0 2 0.21(0.04) 0.10(0.03) 0.10(0.04) 0.10(0.03) A 1 2 0 3 2.88(0.54) 5.38(0.74) 3.94(0.58) 3.88(0.63) MnO 0.13(0.03) 0.10(0.02) 0.16(0.02) 0.16(0.02) MgO 15.32(0.35) 14.66(0.28) 13.90(0.44) 14.01(0.45) CaO 24.43(0.36) 25.04(0.28) 24.56(0.20) 24.48(0.27) Na 20 0.03(0.01) 0.04(0.02) 0.03(0.00) 0.03(0.01) K 2 0 0.03(0.00) 0.03(0.00) 0.03(0.00) 0.03(0.00) FeO 3.37(0.62) 2.10(0.80) 4.25(0.75) 4.85(0.56) F e 2 0 3 0.71(0.66) 1.30(1.01) 1.65(0.54) 0.85(0.92) T o t a l 99.28(0.00) 99.47(0.00) 99.48(0.00) 99.91(0.00) C a t i o n s ( S i ) 1 .917(0.022) 1 .849(0.039) 1 .868(0.015) 1 .893(0.041) ( T i ) 0 .006(0.001) 0 .003(0.001 ) 0 .003(0.001) 0 .003(0.001) ( A l ) 0 .125(0.024) 0 .231 (0.031 ) 0 .170(0.025) 0 .168(0.027) (Mn) 0 .004(0.001) 0 .003(0.001 ) 0 .005(0.001) 0 .005(0.001) (Mg) 0 .839(0.017) 0 .797(0.019) 0 .761(0.022) 0 .767(0.025) (Ca) 0 .961(0.012) 0 .978(0.007) 0 .966(0.003) 0 .964(0.009) (Na) 0 .002(0.000) 0 .003(0.001 ) 0 .002(0.000) 0 .002(0.001) (K) 0 .001(0.000) 0 .001(0.000) 0 .001(0.000) 0 .001(0.000) ( F 2 ) 0 .104(0.019) 0 .064(0.025) 0 .131(0.024) 0 .149(0.018) ( F 3 ) 0 .039(0.036) 0 .071(0.055) 0 .091(0.030) 0 .047(0.051) Sum 3 .997(0.000) 3 .999(0.000) 4 .000(0.000) 3 .999(0.000) 46A-EX1C 46A-EX1R 27-4-E1 27-4-E2 n = 5 n = 5 n = 7 n = 4 S i 0 2 53.28(0.63) 53.76(0.91) 51 .69(0.95) 49.50(0.51) T i 0 2 0. 13(0.05) 0. 1 1 (0.04) 0.28(0.12) 0.18(0.02) A l 2 0 3 1.91(0.29) 2.23(1.02) 4.10(1 .22) 5.80(1.42) MnO 0.17(0.01) 0.22(0.07) 0. 16(0.02) 0.20(0.07) MgO 15.63(0.28) 15.79(0.44) 15.15(0.62) 13.43(0.45) CaO 24.15(0.50) 23.29(1.12) 24.70(0.26) 24.41(0.09) Na 20 0.19(0.06) 0.14(0.08) 0.02(0.00) 0.02(0.00) K 20 0.03(0.00) 0.03(0.00) 0.03(0.00) 0.03(0.00) FeO 3.77(1.12) 4.21(1.32) 2.93(0.49) 3.74(0.88) F e 2 0 3 0.89(0.80) 0.56(1.25) 0.83(0.68) 1.53(0.38) T o t a l 100.16(0.00) 100.34(0.00) 99.89(0.00) 99.84(0.00) C a t i o n s ( S i ) 1 .940(0.022) 1 .952(0.046) 1 .884(0.040) 1 .828(0.035) ( T i ) 0 .004(0.001) 0 .003(0.001 ) 0 .008(0.003) 0 .005(0.000) ( A l ) 0 .082(0.013) 0 .095(0.043) 0 .176(0.052) 0 .252(0.059) (Mn) 0 .005(0.000) 0 .007(0.002) 0 .005(0.001 ) 0 .006(0.002) (Mg) 0 .848(0.009) 0 .855(0.018) 0 .824(0.037) 0 .740(0.028) (Ca) 0 .942(0.014) 0 .906(0.047) 0 .965(0.007) 0 .966(0.009) (Na) 0 .014(0.005) 0 .010(0.005) 0 .002(0.000) 0 .002(0.000) ( F 2 ) 0 . 115(0.034) 0 .128(0.041 ) 0 .089(0.015) 0 . 1 15(0.027) ( F 3 ) 0 .048(0.044) 0 .030(0.068) 0 .045(0.037) 0 .085(0.021) Sum 3 .999(0.000) 3 .988(0.000) 3 .999(0.000) 4 .000(0.000) 89 S i 0 2 T i 0 2 A 1 2 0 3 MnO MgO CaO Na 20 K 2 0 FeO F e 2 0 3 T o t a l 43B-R1 n = 5 53.68(0.96) 0.09(0.03) 1.14(0.22) 0.21(0.04) 15.01(0.90) 23.99(0.84) 0.21(0.06) 0.01(0.01 ) 5.14(1.23) 0.81(0.47) 100.28(0.00) 100.76(0.00) 43B-C n = 5 53.70(0.83) 0.12(0.03) 1.60(0.35) 0.20(0.03) 14.81(1 .04) 23.73(0.61 ) " ,06) ,02) ,09) ,59) 0.23(0 0.02(0 5.97(1 0.39(0 46A-I-R n = 4 52.79(0.92) 0.08(0.03) 2.36(1.26) 0.16(0.07) 15.26(1.07) 24.30(1.04) 0. 12(0.07) 0.01(0.02) 4.08(0.99) 0.71(1.24) 99.87(0.00) 46A-I-C n = 5 52. 1 1 (0.74) 0.07(0.04) 2.44(1.31) 0. 15(0.08) 15.96(0.48) 24.61(1.04) 0.11(0.09) 0.02(0.02) 1.68(1.24) 2.13(1.08) 99.27(0.00) C a t i o n s ( S i ) 1 .963(0. 027) 1 . 962(0. ( T i ) 0 .002(0. 001 ) 0. 003(0. ( A l ) 0 .049(0. 009) 0. 069(0. (Mn) 0 .007(0. 001 ) 0. 006(0. (Mg) 0 .818(0. 047) 0. 807(0. (Ca) 0 .940(0. 032) 0. 929(0. (Na) 0 .015(0. 004) 0. 016(0. (K) 0 .000(0. 000) 0. 001(0. ( F 2 ) 0 .157(0. 038) 0. 182(0. (F,) 0 .045(0. 026) 0. 022(0. Sum 3 .996(0. 000) 3. 998(0. 018) 1 . 933(0 .038) 1 .893(0. 054) 001 ) 0. 002(0 .001 ) 0 .002(0. 001 ) 015) 0. 102(0 .055) 0 .104(0. 055) 001 ) 0. 005(0 .002) 0 .005(0. 003) 055) 0. 832(0 .044) 0 .864(0. 030) 026) 0. 953(0 .056) 0 .957(0. 032) 004) 0. 008(0 .005) 0 .008(0. 007) 001 ) 0. 001 (0 .001 ) 0 .001(0. 001 ) 033) 0. 125(0 .031 ) 0 .052(0. 039) 033) 0. 038(0 .067) 0 . 116(0. 057) 000) 4. 000(0 .000) 4 .000(0. 000) 81BC n = 6 n S i 0 2 53.16 ( 1 . 02 ) 53.34(0 T i 0 2 0.08 (0.06) 0 . 1 0 ( 0 A 1 2 0 3 1.23(0.92) 1.03(0 MnO 0 . 19 (0.05) 0.16(0 MgO 15.51(0.57) 15.69(0 CaO 24 . 21 (0.85) 24.13(0 Na 20 0 . 1 4 ( 0 . 1 2 ) 0.13(0 K 2 0 0 . 0 1 ( 0 . 0 2 ) 0 . 0 0 ( 0 FeO 3.96(1.08) 4.09(1 F e 2 0 3 1.09 ( 1 . 01 ) 0.92(0 T o t a l 99.59 ( 0 . 00 ) 99.59(0 81 BR 355B -2R 355B -2-C = 6 n = 7 n = 5 .35) 54 .77(0. 64) 54 .69(0 .55) .06) 0 .04(0. 00) 0 .04(0 .01 ) .71 ) 0 .17(0. 1 1 ) 0 .13(0 .08) .03) 0 .15(0. 04) 0 .17(0 .05) .58) 1 5 .03(0. 96) 1 4 .58(0 .95) .72) 25 .23(0. 16) 25 .14(0 .27) .11) 0 .04(0. 05) 0 .02(0 .00) .01 ) 0 .04(0. 00) 0 .04(0 .00) .17) 5 .12(1. 38) 5 .31(0 .48) .91 ) 0 .85(2. 06) 0 .34(0 .77) .00) 1 0 1 .45(0. 00) 100 .47(0 .00) C a t i o n s ( S i ) 1 .948(0. 044) 1 .956(0. ( T i ) 0 .002(0. 002) 0 .003(0. ( A l ) 0 .053(0. 040) 0 .044(0. (Mn) 0 .006(0. 001 ) 0 .005(0. (Mg) 0 .847(0. 033) 0 .858(0. (Ca) 0 .950(0. 035) 0 .948(0. (Na) 0 .010(0. 008) 0 .009(0. (K) 0 .001(0. 001 ) 0 .000(0. ( F 2 ) 0 .121(0. 033) 0 .126(0. ( F 3 ) 0 .060(0. 055) 0 .050(0. Sum 3 .999(0. 000) 3 .999(0. 024 ) 1 . 984(0. 058) 2 .004(0. 032) 002 ) 0. 001(0. 000) 0 .001(0. 000) 030) 0. 007(0. 005) 0 .006(0. 003) 001 ) 0. 005(0. 001 ) 0 .005(0. 002) 032 ) 0. 811(0. 038) 0 .796(0. 039) 027 ) 0. 979(0. 024) 0 .987(0. 023) 006) 0. 003(0. 004) 0 .001(0. 000) 001 ) 0. 002(0. 000) 0 .002(0. 000) 037) 0. 156(0. 044) 0 .163(0. 017) 049) 0. 044(0. 107) 0 .018(0. 041 ) 000) 3. 992(0. 000) 3 .984(0. 000) 90 355B-1 46B-2 36 43CP0RPH n = 7 n = 5 n = 6 n = 4 S i 0 2 52.62(0.51) 47.69(0.93) 53.13(0.79) 52.34(0.14) T i 0 2 0.07(0.07) 0.67(0.21) 0.1 1 (0.04) 0. 10(0.02) A 1 2 0 3 0.41(0.22) 6.40(1.42) 1 .11(0.33) 1.43(0.09) MnO 0.19(0.03) 0.05(0.01 ) 0.24(0.03) 0.21(0.04) MgO 15.02(0.46) 14. 1 3(0.56) 14.60(0.87) 14.95(0.16) CaO 24.44(0.58) 24.88(0.16) 24.20(0.35) 23.29(0.61) N a 2 0 0.02(0.00) 0.03(0.01 ) 0.16(0.13) 0.23(0.07) K 2 0 0.03(0.00) 0.03(0.00) 0.03(0.00) 0.04(0.01) FeO 4.51(1.20) 0.46(0.60) 5.18(1.00) 4.82(0.45) F e 2 0 3 2.36(1.26) 5. 1 9(0.42) 0.93(1.05) 0.79(0.67) T o t a l 99.66(0.00) 99.50(0.00) 99.69(0.00) 98.19(0.00) C a t i o n s ( S i ) 1 .926(0.033) 1 .707(0.040) 1 .957(0.028) 1 .953(0.018) ( T i ) 0 .002(0.002) 0 .018(0.006) 0 .003(0.001 ) 0 .003(0.000) ( A l ) 0 .018(0.009) 0 .270(0.059) 0 .049(0.015) 0 .063(0.003) (Mn) 0 .006(0.001) 0 .001(0.000) 0 .008(0.001) 0 .007(0.001) (Mg) 0 .819(0.018) 0 .754(0.034) 0 .801(0.031) 0 .831(0.005) (Ca) 0 .958(0.016) 0 .954(0.010) 0 .955(0.023) 0 .931(0.025) (Na) 0 .002(0.000) 0 .002(0.000) 0 .011(0.010) 0 .016(0.005) (K) 0 .001(0.000) 0 .001 (0.000) 0 .001(0.000) 0 .002(0.000) ( F 2 ) 0 .139(0.039) 0 .014(0.018) - 0 . 160(0.031) 0 . 150(0.015) ( F 3 ) 0 .129(0.067) 0 .279(0.022) 0 .051(0.056) 0 .044(0.037) Sum 4 .000(0.000) 4 .000(0.000) 3 .996(0.000) 4 .000(0.000) 402B-1-R 402B-1-C 42A-1PC 4 3A-1PR n = 7 n = 5 n = 4 n = 4 S i 0 2 51.00(1.27) 50.99(2.07) 53.37(0.62) 53.81(0.16) T i 0 2 0.80(0.33) 0.71(0.36) 0.13(0.03) 0.20(0.11) A 1 2 0 3 4.31(1 .06) 3.95(1.54) 1 .80(0.25) 1.87(0.19) MnO 0.27(0.03) 0.26(0.06) 0.20(0.02) 0.33(0.27) MgO 14.73(0.76) 14.61(0.88) 14.34(0.65) 14.03(0.74) CaO 24.01 (0.57) 24.03(0.69) 23.49(0.62) 23.69(1 .23) N a 20 0.02(0.01) 0.03(0.02) 0.26(0.24) 0.18(0.11) K 2 0 0.03(0.00) 0.03(0.00) 0.03(0.00) 0.03(0.00) FeO 3.68(0.85) 3.82(1.24) 5.27(0.69) 5.47(0.47) F e 2 0 3 0.86(0.88) 0.92(1.46) 0.05(0.10) 0.00(0.00) T o t a l 99.71(0.00) 99.35(0.00) 98.94(0.00) 99.60(0.00) C a t i o n s ( S i ) 1 .868(0.048) 1 .876(0.071) 1 .981(0.01 1 ) 1 .986(0.012) ( T i ) 0 .022(0.009) 0 .020(0.010) 0 .004(0.001) 0 .006(0.003) ( A l ) 0 .186(0.046) 0 .171 (0.066) 0 .079(0.012) 0 .081(0.008) (Mn) 0 .008(0.001 ) 0 .008(0.002) 0 .006(0.001 ) 0 .010(0.008) (Mg) 0 .804(0.038) 0 .801(0.046) 0 .793(0.029) 0 .772(0.040) (Ca) 0 .942(0.016) 0 .947(0.034) 0 .934(0.020) 0 .937(0.045) (Na) 0 .002(0.000) 0 .002(0.001) 0 .019(0.017) 0 .013(0.008) (K) 0 .001(0.000) 0 .001(0.000) 0 .001(0.000) 0 .001(0.000) ( F a ) 0 .119(0.027) 0 . 1 1 8 ( 0 . 0 3 9 ) 0 .164(0.022) 0 .169(0.015) (F,) 0 .047(0.048) 0 .051(0.080) 0 .003(0.006) 0 .000(0.000) Sum 3 .995(0.000) 3 .995(0.000) 3 .984(0.000) 3 .975(0.000) o i n o h - o . N i n o o < * o O II ^  • - O l O O N O O O O O in • • c — o o o o o o o o o o in co io ID co * M " - ( O o o c N O O o o o o c o r - * * n o N O ^ i n o o - o m in — CM cn N ( o - - o i n * < » o o i n o o o O ' i ' o r o . - o o o r o o o o o o o o o o o o o o o o o o o o o o o o «* CM i> — o — r^cno o o o c n o r - c n o o m o o o c n o o o c o c n o o o o o — O O O O O O O O O " * o r«-—r»o«*inr--ooroo o II i n o i n o v o n o o o — o UD c o o o o o o o o o o o r--<*r-T*<Nir>coc>'*«#cr> n o i M O o o o i o o i n o -^ O ' - o i O ^ o o ' - o m LO —-CM (Tt C O O L O O C N — i n o o r - o — O C N O O O — o o o o o o o o o o o o o o o o o o o o o o o o o o o ** — in — invovo — OOCNO cooino — r - o o i n o o CTlOOOCTlCTiOOOOO •"-OOOOOOOOO^ I COCNO — C O i n C N O O O O U II r - o m o ' t N o o o ^ o cn c o o o o o o o o o o o ocncT.vor-ininooa\oovo — o — o—cnoor--**oo " - o m o i n o o o --oio LO T - CM CTl **— O O — 00CNOOOO C M O ' S ' O C N O O O O C M O o o o o o o o o o o o o o o o o o o o o o o r ^ - o c N o c M c o o o L n c M o o o o c M o c o c n o o o o o • - O O O O O O O O O ' * I 00 — VO — C - - O C N O O O O U II r ^ o o o o c o c M o o o o o cn c o o o o o o o o o o o — — ^ — LOOCN^rOLDLOCOCNOCTl i o - - * o « n o o o * o c f t O O t f O ^ O O O N O f f l in —CM cn — o r - o o o o - o o o o C N O O O O C N O O O O O O O O O O O O O O O O O O O O O O O O O O O O C N O O O O - C M - c o — **ooo v o o i ^ o o r - o o r ^ o c r i C O O C M O O O C n O O O O C T l — o o o o o o o o o o o «• fO O O (tt O O " O O O " O O •H .H H C CP (0 (0 nil X O W E - ' ^ S a S O Z t r f D u B u E - ' in c o i J - H . H r l C (Jllll fl^ <N O g o—' — — — >— — — —--^co m co m«#cncN<Ncn — o o vo o i I  i n o>#oro — o o o r- o < c o o o o o o o o o o o co CM CTi CTi CO CN CJi O CN 00 •— 00 in cnoo"# — m o o o o CN — «* c o o — o — •sfoo O r- cn «* — — CM cn — r ~ r - - vooocNO — o O 00 o 1 CTlOCOOtnCMOO O 00 o — I  < o o o o o o o o o o o oo c ^  ^  ^-~--~-— CN O L D - r - i n r o « * r o o v o c M in 0O«#<N — — rOOOCnovO r - o c o o r o * * o o — a* - C M cn oo — cnocncn — o o o o o CNO — o — o o o o r o o o o o o o o o o o o o o o o o o o o o o o o — o o ^ r o r o c N — vo CM o vo — ooo — u « o o o o o o i n o ^ o v o c n o o o o o o — o o o o o o o o o OOCNVO — cnoo — o o i n o C O O C O O C N O O O O ^ O o o o o o o o o o o o o o o o o o o o o o o i n c M c n i n r ^ooo- r - o o o — « # o o r f o o m c N O r ^ o o o o r - c n o o o c N O — o o o o o o o o o * * m n H " O O O HJ O O N O O O " O O «4J • H . r l H C D> U 111 N d) IU O in c o -rH ^ -—. —s .—. -—• i J - H - H H C 0>fl) 10-^  " 6 c O C O t H < S S U Z « C u f c 3 92 M i n e r a l a s s e m b l a g e s o f r o d i n g i t e s and d i o p s i d e c o m p o s i t i o n s a n a l y z e d by J a c k ( p e r s o n a l c o m m u n i c a t i o n ) M i n e r a l a s s e m b l a g e s o f r o d i n g i t e s from Paddy-Go-Easy P a s s , W a s h i n g t o n , ( a l l m i n e r a l a s s e m b l a g e s have c a l c i t e , i c l i n t o n i t e , and i w o l l a s t o n i t e . D i * T r Gr ZO PI Ch Sp IR1 .2 P P p p P IR2. 1 P p p IR2.2 P P p IR3.1 p p IR3.1R P P P p p IR15.1 P p p IR15.2 P p p P P IR18.1 P p p P P IR20 P P p P IR25.2 P p IR27.2 P p IR29.3 P P p IR30.1 P P p p IR36 P P p P IR36.2 P p IR36.3 P P P p IR51.2A P P p IR51.2B P P IR51.4B P IR54.4 P IR57.2 P p P P P * D i = d i o p s i d e , T r = t r m o l i t e , G r = g r o s s u l a r , Z o = z o i s i t e , P l = p l a g i o c l a s e , C h = c h l o r i t e , S p = s p i n e l . 93 IRI .2 IR2. 1 IR2.2 IR3.1R n = 2 n = 10 n = 2 n = 5 ,Si0 2 52.89(0.65) 53.59(0.20) 53.75(0.57) 52.36(0.81 ) T i 0 2 0.10(0.07) 0.08(0.02) 0.08(0.01) 0.07(0.07) A 1 2 0 3 2.78(0.70) 1.47(0.22) 0.78(0.18) 0.89(0.31 ) FeO* 3.26(0.1 1 ) 3.83(0.16) 3.09(0.00) 8.80(1.07) CaO 0.13(0.01) 0.19(0.03) 16.55(0.08) 0.32(0.13) MnO 16.70(0.81) 16.66(0.11 ) 24.29(0.33) 11.98(0.29) MgO 24.49(1.43) 23.27(0.40) 0. 18(0.03) 25.06(0.32) Na 20 0.13(0.14) 0.28(0.03) 0.03(0.01) 0.13(0.04) K 20 0.03(0.01) 0.03(0.02) 0.00(0.00) 0.00(0.00) T o t a l 100.50(0.00) 99.38(0.00) 98.75(0.00) 99.61(0.00) C a t i o n s ( S i ) 1 .929(0.007) 1 .980(0.005) 2 .147(0.008) 1 .942(0.024) ( T i ) 0 .003(0.002) 0 .002(0.001) 0 .002(0.000) 0 .002(0.002) (Al) 0 .119(0.029) 0 .064(0.010) 0 .037(0.008) 0 .039(0.014) (Fe) 0 .099(0.003) 0 .118(0.005) 0 .103(0.001) 0 .273(0.034) (Ca) 0 .005(0.001 ) 0 .007(0.001 ) 0 .708(0.009) 0 .013(0.005) (Mn) 0 .516(0.021) 0 .521(0.003) 0 .822(0.017) 0 .377(0.009) (Mg) 1 .332(0.089) 1 .282(0.028) 0 .011(0.002) 1 .386(0.015) (Na) 0 .009(0.010) 0 .020(0.002) 0 .002(0.001) 0 .009(0.003) (K) 0 .001(0.001 ) 0 .002(0.001 ) 0 .000(0.000) 0 .000(0.000) Sum 4 .014(0.000) 3 .996(0.000) 3 .833(0.000) 4 .041(0.000) IR15.1 IR15.2 IR18.1 IR20 n = 5 " n = 9 n = 7 n = 3 S i 0 2 52.56(1.29) 52.52(0.83) 53.07(1 .36) 53.03(1.41) T i 0 2 0. 12(0.05) 0. 18(0.09) 0.03(0.04) 0.35(0.10) A I 2 O 3 2.15(1.03) 2.68(0.78) 1.77(1.21) 3.04(2.39) FeO* 4.73(1.10) 3.46(0.44) 2.94(0.61) 3.48(0.96) CaO 0. 12(0.02) 0.11(0.03) 0.08(0.03) 0.07(0.03) MnO 1 4.87(0.63) 15.59(0.55) 16.32(0.66) 15.67(1.27) MgO 25.27(0.17) 25.25(0.37) 25.57(0.15) 24.94(0.05) Na 20 0.14(0.13) 0.09(0.04) 0.04(0.04) 0.02(0.02) K 20 0.03(0.01) 0.00(0.00) 0.01(0.02) 0.02(0.01) T o t a l 99.99(0.00) 99.87(0.00) 99.83(0.00) 100.60(0.00) Ca t i o n s (S i ) 1 .927(0.032) 1 .922(0.023) 1 .943(0.038) 1 .924(0.064) ( T i ) 0 .003(0.001 ) 0 .005(0.002) 0 .001(0.001) 0 .009(0.003) (Al) 0 .093(0.045) 0 .116(0.034) 0 .076(0.052) 0 .129(0.101) (Fe) 0 .145(0.035) 0 .106(0.014) 0 .090(0.019) 0 .105(0.028) (Ca) 0 .005(0.001 ) 0 .004(0.001 ) 0 .003(0.001 ) 0 .003(0.001) (Mn) 0 .462(0.016) 0 .483(0.017) 0 .506(0.020) 0 .482(0.042) (Mg) 1 .382(0.006) 1 .377(0.017) 1 .396(0.017) 1 .349(0.012) (Na) 0 .010(0.009) 0 .006(0.003) 0 .003(0.003) 0 .001(0.001) (K) 0 .002(0.001 ) 0 .000(0.000) 0 .000(0.001) 0 .001(0.000) Sum 4 .029(0.000) 4 .019(0.000) 4 .019(0.000) 4 .003(0.000) 94 IR25.2 IR27.2 IR29.3 IR30.1 n - 12 n = 9 n = 8 n = 4 S i 0 2 52.79(1.00) 53.38(0.62) 54.39(0.70) 52.67(0.14) T i 0 2 0.23(0.30) 0.14(0.42) 0.04(0.03) 0.12(0.13) A 1 2 0 3 1 .10(1.32) 1.17(0.35) 0.20(0.09) 0.74(0.29) FeO* 8.81(1.13) 6.07(1.66) 5.58(1.64) 10.40(0.56) CaO 0.29(0.08) 0.34(0.05) 0.29(0.03) 0.20(0.05) MnO 12.70(0.62) 14.20(0.87) 14.94(1.01) 12.29(0.49) MgO 24.21(0.51) 24.76(0.38) 24.49(0.46) 24.12(0.27) Na 20 0.08(0.04) 0.10(0.04) 0.04(0.05) 0.12(0.07) K 20 0.01(0.02) 0.03(0.03) 0.00(0.00) 0.00(0.00) T o t a l 100.24(0.00) 100.20(0.00) 99.97(0.00) 100.66(0.00) C a t i o n s ( S i ) 1 .949(0.041) 1 .958(0.017) 1 .997(0.016) 1 .948(0.013) ( T i ) 0 .007(0.008) 0 .004(0.001) 0 .001(0.001) 0 .003(0.004) (Al) 0 .048(0.057) 0 .051(0.015) 0 .009(0.004) 0 .032(0.013) (Fe) 0 .272(0.036) 0 .186(0.052) 0 .172(0.051) 0 .322(0.018) (Ca) 0 .011(0.003) 0 .014(0.002) 0 .011(0.001) 0 .008(0.002) (Mn) 0 .397(0.020) 0 .441(0.026) 0 .465(0.028) 0 .385(0.013) (Mg) 1 .333(0.024) 1 .354(0.016) 1 .341(0.019) 1 .330(0.018) (Na) 0 .006(0.003) 0 .007(0.003) 0 .003(0.004) 0 .009(0.005) (K) 0 .001(0.001) 0 .001(0.001) 0 .000(0.000) 0 .000(0.000) Sum 4 .024(0.000) 4 .017(0.000) 3 .999(0.000) 4 .037(0.000) IR36 IR36.2 IR36.3 IR51.2A n = 10 n = 9 n = 7 n = 6 S i 0 2 54.30(0.64) 53.36(0.25) 53.31(0.17) 54.52(0.40) TiO 2 0.04(0.03) 0.06(0.04) 0.09(0.04) 0.00(0.01) A 1 2 0 3 0.57(0.46) 0.27(0.23) 0.64(0.50) 0.10(0.05) FeO* 8.15(0.80) 7.45(1.34) 7.16(1.00) 4.47(0.20) CaO 0.25(0.06) 0.45(0.10) 0.21(0.02) 0. 18(0.06) MnO 1 3.03(0.61 ) 13.24(0.89) 13.39(0.41) 15.40(0.53) MgO 24.30(0.52) 24.64(0.30) 24.52(0.27) 25.38(0.19) Na 20 0.07(0.04) 0.02(0.01 ) 0.06(0.02) 0.04(0.01) K 20 0.00(0.01 ) 0.00(0.00) 0.00(0.00) 0.01(0.01) T o t a l 100.70(0.00) 99.49(0.00) 99.37(0.00) 100. 10(0.00) C a t i o n s ( S i ) 1 .986(0.012) 1 .977(0.012) 1 .974(0.012) 1 .994(0.007) ( T i ) 0 .001(0.001 ) 0 .002(0.001) 0 .002(0.001) 0 .000(0.000) (Al) 0 .024(0.020) 0 .012(0.010) 0 .028(0.022) 0 .004(0.002) (Fe) 0 .249(0.024) 0 .231(0.041) 0 .222(0.030) 0 .137(0.006) (Ca) 0 .010(0.002) 0 .018(0.004) 0 .008(0.001) 0 .007(0.002) (Mn) 0 .404(0.019) 0 .415(0.027) 0 .420(0.014) 0 .477(0.015) (Mg) 1 .325(0.029) 1 .361(0.017) 1 .354(0.018) 1 .383(0.014) (Na) 0 .005(0.003) 0 .001(0.001) 0 .004(0.001) 0 .003(0.001) (K) 0 .000(0.000) 0 .000(0.000) 0 .000(0.000) 0 .000(0.000) Sum 4 .004(0.000) 4 .016(0.000) 4 .012(0.000) 4 .005(0.000) V c?«!Z3:3:o r'g>'-3(/ioj ow OHQ a o (t H H - p-3 ^ O n f l D B » H H - H T t rt O " O O O O " O O ^—- - ^ »-•• OJ O * 0 » * N O M W 3 CO rf^OO—OOOOO — O O O C O i ^ O t O O O V D l o o o m - — — i » o c n * > O W U ) ( O C D N 1 0 - - J o o o o o o o o o o o o o o o o o o o o O O O U U O O \ H > O U VO r o — O l I D O O I M A ) O v l O O M CnOOOOCOi»>OVOOVO CO O ir> i f •>! N) (A) U) O O O O O — O — — 0 0 3 CJ1 O O O s l - 0 * 0 0 0 « J II • O O * > U I ^ W C D W W - ' ro * » o o — o o o o o — o o o c o t s > o * » o o v o cnoor f^vo — cn — o r o C A — c r i r o C A C A v o c r i — vo o o o o o o o o o o O O O O O O O O O O O O O - W O N - O O o — c o - o c n — co — o** vo ts) -* cn V O O O O J V O O * » O O - -* » o o o o r o i * » c n c o o o O D W C D - W O U C M O - ' H 0 0 0 0 0 0 0 0 0 0 D cn O O O W m O v l W O N II • oro t f^^ joco—'cn — vo •*» O J O O — o o o o o — V O O O r O ^ O — — » O V O C 0 O ( A I U 0 0 O M U - U I vo—vocncncncn-j- ' -> o o o o o o o o o o O O O O O O O O O O O O O t O — O O N O -o — coi» — — vo cn co *» vo ts) — cn v o o o t s ) c n o * » c o o t o r o o c n * » c n — o - " i t » v o cnco*»-ocnr f»cncn-'fs) o o o o o o o o o o 50 II Ul 0 0 0 * > U 0 M U 1 - ' W #» O i S ) * » 0 1 0 1 f 0 0 0 0 0 - * C D - ' « ^-^>w_^w^^>-^>-^^.Orf* COOO — O O O O O — v o o o c o c n o o o o v o U)OOn>OOU3 0 \ O v l - " O O l O - J s l O N U O ) o o o o o o o o o o o o o o o o o o o o O O O C O — O O M O f S ) OOVO — >P> — VOfS) — 00 o ro — cn o o o * » c f t O f s J - * o * » cnoooocn — vo*»- 'cn O O O O O O M O O U I O V O o o o o o o o o o — 3 W vo cn cn o o — i o c o o c o c n o o II -J o o c o * » c n f o — rocnco P l a t e 1 G e n e r a l is a l s o v i e w of s y n t h e t i c s p i n e l . The f i n e powder s p i n e l a c c o r d i n g t o E.D.S. a n a l y s i s . P l a t e 2 E u h e d r a l c r y s t a l s of s y n t h e t i c s p i n e l w i t h s u r f a c e s of (1 1 1) and ( l I 0 ) . P l a t e 3 S u b h e d r a l t o e u h e d r a l c r y s t a l s o f s y n t h e t i c d i ops i d e . S y n t h e t i c c l i n o c h l o r e w i t h s u b h e d r a l c r y s t a l s . P l a t e 5 S y n t h e t i c g r o s s u l a r w i t h e u h e d r a l t o s u b h e d r a l c r y s t a l s and some f i n e s h o r t p r i s m a t i c w o l l a s t o n i t e a s i m p u r i t i e s . P l a t e 6 C l o s e view of s y n t h e t i c g r o s s u l a r c r y s t a l s w i t h some i n c l u s i o n s of o x i d e s ( ? ) . P l a t e 7 Low t e m p e r a t u r e s t a b l e a s s e m b l a g e of c l i n o c h l o r e + g r o s s u l a r . N o t i c e the e u h e d r a l g r o s s u l a r c r y s t a l s w i t h s u r f a c e s of (1 1 1) and (1 1 0 ) . P l a t e 8 G r o s s u l a r c r y s t a l g r o w i n g near s p i n e l c r y s t a l s t h a t were d i s s o l v e d d u r i n g e q u i l i b r i u m r u n . (Gr = g r o s s u l a r , Sp = s p i n e l ) I N P l a t e 9 G r o s s u l a r c r y s t a l and r e s i d u a l s p i n e l c r y s t a l s w i t h many s m a l l h o l e s . ( G r = g r o s s u l a r , Sp= s p i n e l ) P l a t e 10 The a g g r e g a t e of f i n e s p i n e l s f r o m h i g h t e m p e r a t u r e s t a b l e a s s e m b l a g e d i o p s i d e + s p i n e l . P l a t e s of r e s i d u a l c l i n o c h l o r e a r e v i s i b l e . P l a t e 11 The abnormal assemblage of d i o p s i d e + c l i n o c h l o r e from s t a r t i n g m a t e r i a l 80wt% d i o p s i d e • s p i n e l w i t h 20wt% g r o s s u l a r + c l i n o c h l o r e . N o t i c e the e u h e d r a l c r y s t a l s of b o t h m i n e r a l s . P l a t e 12 The abnormal assemblage d i o p s i d e + c l i n o c h l o r e from s t a r t i n g m a t e r i a l 80wt% g r o s s u l a r • c l i n o c h l o r e w i t h 20wt% d i o p s i d e + s p i n e l . N o t i c e t h a t most c r y s t a l s a r e s u b h e d r a l . 

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