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Metamorphism and deformation on the northeast margin of the Shuswap metamorphic complex, Azure Lake,… Pigage, Lee Case 1979

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METAMORPHISM AND DEFORMATION ON THE NORTHEAST MARGIN OF THE SHUSWAP METAMORPHIC COMPLEX AZURE LAKE, BRITISH COLUMBIA by LEE CASE PIGAGE B . S c , U n i v e r s i t y o f Wyoming, 1970 M . S c , U n i v e r s i t y o f B r i t i s h Columbia, 1973  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  in THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF GEOLOGICAL SCIENCES  We a c c e p t t h i s t h e s i s as c o n f o r m i n g to t h e r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA December, 1978  ©  Lee Case P i g a g e , 1978  In presenting  this thesis in partial  fulfilment o f the requirements for  an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t freely available for reference  and  study.  I further agree that permission for extensive copying of this thesis for scholarly purposes may by his representatives.  be granted by the Head of my  Department or  It is understood that copying or publication  of this thesis for financial gain shall not be allowed without written permission.  Department of  Geological Sciences  The University of B r i t i s h Columbia  2075 Wesbrook Place Vancouver, Canada V6T 1W5  Date  J a n u a r y 15,  1979  my  ii  ABSTRACT  D e t a i l e d s t r u c t u r a l and p e t r o l o g i c mapping n e a r Azure L a k e ,  British  Columbia p r o v i d e s an overview of g e o l o g i c r e l a t i o n s a l o n g the n o r t h e a s t margin o f the Shuswap Metamorphic Complex. Four phases o f d e f o r m a t i o n have been r e c o g n i z e d i n the Shuswap Complex and the a d j a c e n t lower grade metasediments o f the c o v e r sequence. The  f i r s t deformation c o n s i s t s of west-verging i s o c l i n a l f o l d s plunging  n o r t h and n o r t h w e s t .  The second phase r e s u l t e d i n l a r g e u p r i g h t f o l d s  w i t h a s h a l l o w n o r t h w e s t or s o u t h e a s t plunge. phases are o n l y l o c a l l y developed  The t h i r d and  fourth  as f a u l t s , f r a c t u r e s , and b r i t t l e  folds  t r e n d i n g n o r t h and n o r t h e a s t , r e s p e c t i v e l y . M i n e r a l assemblages range from g a r n e t - b i o t i t e through s i l l i m a n i t e zones o f the B a r r o v i a n f a c i e s s e r i e s . i n c r e a s e s toward the southwest.  first  Metamorphic grade  R e g i o n a l metamorphism i s a s s o c i a t e d  w i t h the f i r s t phase o f d e f o r m a t i o n . The Complex i s s e p a r a t e d from the a d j a c e n t c o v e r sequence by a f i r s t phase t e c t o n i c s l i d e .  S t r u c t u r a l and metamorphic d i s c o n t i n u i t i e s  a c r o s s t h i s s l i d e p r o b a b l y r e s u l t e d from r e a c t i v a t i o n o f the s l i d e s u r f a c e d u r i n g the second phase of d e f o r m a t i o n . Microprobe  a n a l y s e s have been combined w i t h l i n e a r r e g r e s s i o n  t e c h n i q u e s to o u t l i n e p r o b a b l e s i l l i m a n i t e - f o r m i n g r e a c t i o n s i n p e l i t e s of  the Complex.  The r e g r e s s i o n s show t h a t r e a c t i o n t e x t u r e s are p a r t l y  p r e s e r v e d because o f the e x h a u s t i o n of r u t i l e as a r e a c t a n t phase. Metamorphic c o n d i t i o n s i n the Complex are e s t i m a t e d from the m u t u a l i n t e r s e c t i o n of e x p e r i m e n t a l l y s t u d i e d mineral e q u i l i b r i a . conditions are:  P=7600 + 400 b a r s , T=705 + 40°C,  A  =0.5  These +  ^  .  iii  Carbonate m i n e r a l assemblages i n i t i a l l y b u f f e r e d f l u i d phase to h i g h X _ CO  v a l u e s near 0.75  d u r i n g metamorphism.  compositions  T h e r e f o r e the  fluid  2  phase was n o t homogeneous i n c o m p o s i t i o n throughout  a l l r o c k types d u r i n g  metamorphism. Whole rock Rb-Sr dates o f 138 + 12 Ma  ( a l l f i v e samples) and  163 + 7 Ma were o b t a i n e d f o r g r a n o d i o r i t e s t o c k s i n the Azure Lake a r e a . Two  b i o t i t e - w h o l e rock + hornblende  dates o f 119 + 11 Ma and 77 + 20 87  indicate isotopic resetting.  I n i t i a l Sr  Ma  86 -Sr  r a t i o s vary  from  0.7061 + 0.0001 to 0.7103 + 0.0002 f o r r o c k and m i n e r a l d a t e s . dated s t o c k s c r o s s - c u t s t r u c t u r a l t r e n d s f o r the f i r s t two  These  deformations  and impose a h o r n f e l s i c c o n t a c t a u r e o l e on r e g i o n a l metamorphic assemblages. T h e r e f o r e r e g i o n a l metamorphism and d e f o r m a t i o n were completed by L a t e J u r a s s i c time.  iv  TABLE OF CONTENTS  GENERAL INTRODUCTION  1  PAPER 1 - Metamorphic and S t r u c t u r a l R e l a t i o n s on the N o r t h e a s t M a r g i n o f t h e Shuswap Metamorphic Complex, A z u r e L a k e , B r i t i s h Columbia  3  Abstract  4  Introduction  6  Geologic S e t t i n g  11  Stratigraphy Kaza Group Isaac Formation Cunningham F o r m a t i o n Yankee B e l l e F o r m a t i o n Intrusions  14 14 16 18 18 18  Deformation/Metamorphism Shuswap D e f o r m a t i o n (P1,P2,P3) Shuswap Metamorphism Shuswap Summary  19 20 33 39  Cover Cover Cover Cover  D e f o r m a t i o n (Fl,F2,F3,F4) Metamorphism Metamorphic C o n d i t i o n s Summary  Cover-Complex  Correlation  40 59 68 71 73  Regional Tectonics  77  C o n c l u s i o n s and Summary  79  Acknowledgments  80  Selected References  81  PAPER 2 - Metamorphic C o n d i t i o n s i n the Shuswap Metamorphic Complex, A z u r e Lake, B r i t i s h Columbia  105  Abstract  106  Introduction  108  Method o f Study  110  P e l i t i c M i n e r a l Assemblages  112  Tests of E q u i l i b r i u m  113  Mineral Textures  124  Metamorphic R e a c t i o n s  131  L i n e a r R e g r e s s i o n ( T a b l e 2-19)  132  V  Interpretation  150  Metamorphic C o n d i t i o n s Kyanite-Sillimanite S t a u r b l i t e - Q u a r t z-Garne t - A l 5 Muscovite-Quartz-Plagioclase-A^SiO^ Plagioclase-Garnet-Quartz-Al^iO^ Summary  152 157 *5 8 160 169 173  C a l c a r e o u s Assemblages C a l c i t e - Q u a r t z - C a l c i c a m p h i b o l e - C a l c i c pyroxene Calcite-Quartz-Muscovite-Plagioclase-K-feldspar Calcite-Zoisite-Plagioclase Summary  174 186 189 191 195  F l u i d Compositions  196  Summary  199  Acknowledgments  202  Selected References  203  Appendix 2-1  212  Si 0  2  Modes 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  Appendix 2-2 Thermodynamic E q u a t i o n s Fe-staurolite-Quartz-Almandine-A^SiO^ M u s c o v i t e A c t i v i t y Model Grossular-Kyanite-Quartz-Anorthite  237 246 248 252  Appendix 2-3  S t a n d a r d s used f o r M i c r o p r o b e A n a l y s e s  256  PAPER 3 - Rb-Sr Dates f o r G r a n o d i o r i t e I n t r u s i o n s on the N o r t h e a s t M a r g i n o f the Shuswap Metamorphic Complex, C a r i b o o Mountains, B r i t i s h Columbia  274  Abstract  275  Introduction  276  Scope o f Study  276  R e s u l t s and I n t e r p r e t a t i o n  279  Conclusions  284  Acknowledgments  285  Selected References  286  Appendix 3-1 A n a l y t i c a l Methods  288 288  Petrographic  Descriptions  288  vi  LIST OF TABLES  T a b l e 1-1  S t r a t i g r a p h y f o r t h e A z u r e Lake and M c B r i d e a r e a s  15  1-2  R e l a t i o n o f m i n e r a l growth to phases o f d e f o r m a t i o n i n the Shuswap Metamorphic Complex, A z u r e L a k e , B r i t i s h Columbia  37  1-3  Metamorphic m i n e r a l assemblages i n the c o v e r sequence, A z u r e L a k e , B r i t i s h Columbia  62  1-4  R e l a t i o n of m i n e r a l growth to phases o f d e f o r m a t i o n i n the c o v e r sequence, Azure L a k e , B r i t i s h Columbia  66  1- 5  C o r r e l a t i o n of d e f o r m a t i o n and metamorphism between t h e Shuswap Complex and t h e c o v e r sequence, A z u r e L a k e , B r i t i s h Columbia  74  Table 2-1  Assemblages and modes f o r p e l i t e m i c r o p r o b e samples  213  2- 2  Assemblages and modes f o r c a r b o n a t e m i c r p o r o b e samples  214  2-3  Garnet a n a l y s e s from p e l i t i c samples  215  2-4  M u s c o v i t e a n a l y s e s from p e l i t i c samples  218  2-5  B i o t i t e a n a l y s e s from p e l i t i c samples  220  2-6  S t a u r o l i t e a n a l y s e s from p e l i t i c samples  222  2-7  P l a g i o c l a s e a n a l y s e s from p e l i t i c samples  223  2-8  K - f e l d s p a r a n a l y s e s from p e l i t i c samples  225  2-9  I l m e n i t e a n a l y s e s from p e l i t i c samples  226  2-10  C a l c i t e a n a l y s e s from c a r b o n a t e samples  228  2-11  P l a g i o c l a s e a n a l y s e s from c a r b o n a t e samples  229  2-12  K - f e l d s p a r a n a l y s e s from c a r b o n a t e samples  230  2-13  M u s c o v i t e and b i o t i t e a n a l y s e s from c a r b o n a t e samples  231  2-14  C a l c i c amphibole a n a l y s e s from c a r b o n a t e samples  232  2-15  C a l c i c pyroxene a n a l y s e s from c a r b o n a t e samples  233  2-16  Z o i s i t e a n a l y s e s from c a r b o n a t e samples  234  vii  Table 2-17  Sphene a n a l y s e s from c a r b o n a t e samples  235  2-18  S c a p o l i t e a n a l y s i s from c a r b o n a t e samples  236  2-19  R e g r e s s i o n e q u a t i o n s f o r p e l i t i c m i n e r a l assemblages, Shuswap Metamorphic Complex, A z u r e L a k e , B r i t i s h Columbia  135  2-20  C a l c u l a t e d a ( H 0 ) r e q u i r e d f o r e q u i l i b r i a (E8,E9) t o pass through the e s t i m a t e d metamorphic c o n d i t i o n s : P_ „ , = 7600 b a r s , T = 705°C Total  168  2-21  Thermodynamic parameters f o r s e l e c t e d m i n e r a l e q u i l i b r i a  243  2-22  Volume and h e a t c a p a c i t y d a t a f o r s e l e c t e d m i n e r a l s  244  2-23  Experimental uncertainties f o r selected experimental reaction studies  254  2-24  Standards used f o r e l e c t r o n m i c r o p r o b e a n a l y s i s  257  2-25  Standards used f o r g a r n e t a n a l y s e s  258  2-26  Standards used f o r m u s c o v i t e and b i o t i t e a n a l y s e s  259  2-27  Standards used f o r s t a u r o l i t e a n a l y s e s  259  2-28  Standards used f o r p l a g i o c l a s e a n a l y s e s  260  2-29  Standards used f o r K - f e l d s p a r a n a l y s e s  260  2-30  Standards used f o r i l m e n i t e a n a l y s e s  261  2-31  Standards used f o r c a l c i t e a n a l y s e s  261  2-32  Standards used f o r c a l c i c amphibole a n a l y s e s  262  2-33  Standards used f o r c a l c i c pyroxene a n a l y s e s  262  2-34  Standards used f o r z o i s i t e a n a l y s e s  263  2-35  Standards used f o r sphene a n a l y s e s  263  2- 36  Standards used f o r s c a p o l i t e a n a l y s e s  263  Rb-Sr d a t a f o r a l l a n a l y z e d samples  280  I n t e r c e p t s and apparent ages f o r whole r o c k and m i n e r a l s e p a r a t e d a t a l i s t e d i n Table 3-1  281  Table 3-1 3- 2  2  viii LIST OF FIGURES  Figure  1-1  Major s t r u c t u r a l elements of the Canadian C o r d i l l e r a  7  1-2  R e g i o n a l geology of the C a r i b o o Mountains, B r i t i s h Columbia  9  1-3  D i s t r i b u t i o n of metamorphic i s o g r a d s i n the C a r i b o o M o u n t a i n s , B r i t i s h Columbia  10  1-4  D i s t r i b u t i o n of the d i f f e r e n t s t r u c t u r a l domains i n the A z u r e Lake a r e a  12  1-5  D i s t r i b u t i o n of metamorphic zones i n the Azure Lake a r e a  13  1-6  I s o c l i n a l P I minor f o l d i n the Shuswap Complex near Azure Lake  21  1-7  Large P I i s o c l i n a l f o l d i n i n t e r l a y e r e d quartzite  22  1-8  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s of p o l e s to P0 c o m p o s i t i o n a l l a y e r i n g and P I a x i a l p l a n e s c h i s t o s i t y i n the Shuswap Complex (Azure Lake area)  25  1-9  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f P I minor f o l d s t r u c t u r e s i n the Shuswap Complex (Azure Lake area)  27  1-10  P2 minor f o l d i n i n t e r l a y e r e d  29  1-11  I s o c l i n a l P I minor f o l d r e f o l d e d  1-12  Equal a r e a s t e r e o g r a p h i c p r o j e c t i o n s of P2 minor f o l d s t r u c t u r e s i n the Shuswap Complex (Azure Lake area)  32  1-13  D i s t r i b u t i o n of p e l i t i c metamorphic m i n e r a l assemblages c o n s t r a i n i n g the l o c a t i o n of the i s o g r a d between the k y a n i t e - s i l l i m a n i t e and the s i l l i m a n i t e metamorphic zones  35  1-14  Large F l f o l d h i n g e i n i n t e r l a y e r e d p h y l l i t e and q u a r t z i t e  42  1-15  I s o c l i n a l F l minor f o l d s i n i n t e r l a y e r e d quartzite  s c h i s t and  43  1-16  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f p o l e s to F0 c o m p o s i t i o n a l l a y e r i n g i n the cover sequence (Azure Lake area)  46  1-17  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s of p o l e s t o F l a x i a l 48 p l a n e s c h i s t o s i t y i n the cover sequence (Azure Lake area)  s c h i s t and  s c h i s t and q u a r t z i t e around a P2 minor f o l d  30  ix  Figure  Figure  1-18  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s of F l minor f o l d s t r u c t u r e s i n the c o v e r sequence (Azure Lake a r e a )  51  1-19  F2 minor f o l d s i n i n t e r l a y e r e d p h y l l i t e and marble  52  1-20  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s of F2 minor s t r u c t u r e s i n the c o v e r sequence (Azure Lake a r e a )  54  1-21  I s o c l i n a l F l f o l d s i n s c h i s t and q u a r t z i t e a r e c o a x i a l l y r e f o l d e d around F2 f o l d s  56  1-22  Equal area stereographic p r o j e c t i o n s of s t r u c t u r a l elements i n the c o v e r sequence (Azure Lake a r e a )  58  1-23  F4 minor f o l d s d e v e l o p e d i n s l a b b y q u a r t z i t e s o f the Yankee B e l l e F o r m a t i o n  60  1-24  Schematic AFM p r o j e c t i o n s o f p e l i t i c m i n e r a l assemblages i n the Kaza Group f o r t h e d i f f e r e n t metamorphic zones i n the c o v e r sequence, A z u r e Lake, B r i t i s h Columbia  64  1-25  Experimental reactions defining pressure-temperature c o n d i t i o n s i n the c o v e r sequence d u r i n g r e g i o n a l metamorphism (Azure Lake a r e a )  70  2-1  Major s t r u c t u r a l elements of the Canadian C o r d i l l e r a  109  2-2  Metamorphic zones i n the Shuswap Complex, A z u r e L a k e , B r i t i s h Columbia  111  2-3  S t e r e o s c o p i c p r o j e c t i o n s of a n a l y z e d p e l i t i c assemblages c o n t a i n i n g k y a n i t e  116  2-4  S t e r e o s c o p i c p r o j e c t i o n s of a n a l y z e d p e l i t i c assemblages c o n t a i n i n g k y a n i t e and s i l l i m a n i t e  118  2-5  S t e r e o s c o p i c p r o j e c t i o n s of a n a l y z e d p e l i t i c assemblages c o n t a i n i n g s i l l i m a n i t e  120  2-6  Fe-Mg d i s t r i b u t i o n diagram f o r g a r n e t and b i o t i t e  121  2-7  P l o t o f (X.. )„ v s . (X„ ) _ , . T TJa M u s c o v i t e Ca P l a g i o c l a s e  122  2-8  C h e m i c a l z o n i n g p a t t e r n s of s e l e c t e d g a r n e t s  127  2-9  D i s p l a c e d e q u i l i b r i u m c u r v e s E4, E5 f o r p e l i t e assemblages, A z u r e Lake, B r i t i s h Columbia  159  Figure  2-10  D i s p l a c e d e q u i l i b r i u m c u r v e s (E9) f o r t h e assemblage muscovite-quartz-plagioclase-sillimanite with a(H 0) =1.0  162  2-11  I n t e r s e c t i o n o f e q u i l i b r i a E4 and E8 f o r s e v e r a l d i f f e r e n t r e d u c e d R^O a c t i v i t i e s  163  2-12  V a r i a t i o n s i n the P-T-a(H 0) p o s i t i o n o f t h e i n t e r s e c t i o n o f e q u i l i b r i a E4 and E8  165  2-13  I n t e r s e c t i o n of e q u i l i b r i a ( E l ) , (E4,E5), and (E8,E9) f o r the f i v e samples c o n t a i n i n g t h e assemblage muscovite-quartz-plagioclasestaurolite-garnet-A^SiO^  167  2-14  Displaced  171  2-15  D i s p l a c e d e q u i l i b r i u m c u r v e s E10 f o r a l l 12 a n a l y z e d p e l i t e samples  172  2-16  Calcareous reactant carbonate mineral  177  2-17  I s o b a r i c T-X(C0 ) diagram f o r t h e system CaO-MgOAl 0 -Si0 -H 0-C0  182  D i s p l a c e d e q u i l i b r i u m c u r v e s E17 i n an i s o b a r i c T-X(C0 ) diagram f o r samples 20, 224, and 2-312  188  2-19  Displaced  190  2-20  P o l y b a r i c Temperature-X(C0 ) d i a g r a m f o r t h e assemblage c a l c i t e - z o i s i t e - p l a g i o c l a s e tschermakitic amphibole-calcic pyroxene-quartz  193  2-21  P o l y b a r i c Temperature-X(C0 ) diagram f o r the assemblage calcite-muscovite-quartz-K-feldsparp l a g i o c l a s e - z p o s i t e i n sample 387  194  2-22  C o m p o s i t i o n s o f metamorphic f l u i d phase c o e x i s t i n g w i t h g r a p h i t e i n the sytem C-O-H a t P„ „ , = 7600 b a r s , T - 727 °C °  198  2-23  E x p e r i m e n t a l r e v e r s a l s and c a l c u l a t e d e q u i l i b r i a c u r v e s f o r E4 and E5  247  2-24  White m i c a c o m p o s i t i o n i n terms of f o u r end-member components  250  2-25  E x p e r i m e n t a l r e v e r s a l s f o r e q u i l i b r i u m E10 ( H a r i y a and Kennedy 1968)  253  2  2  and p r o d u c t assemblages f o r equilibria  2  2  2-18  p o s i t i o n of e q u i l i b r i u m E10 f o r sample 82  3  2  2  2  2  e q u i l i b r i u m c u r v e s E14 f o r samples 387 and 69 2  2  T  t  a  l  xi  Figure  3-1  Index map  of s o u t h - c e n t r a l B r i t i s h Columbia  277  3-2  G e o l o g i c s k e t c h map o f study a r e a , W e l l s Gray P r o v i n c i a l P a r k , B r i t i s h Columbia  278  3-3  I s o c h r o n diagram f o r b i o t i t e - w h o l e r o c k + h o r n b l e n d e i s o c h r o n s l i s t e d i n T a b l e 3-2  282  3-4  D e t a i l o f a r e a shown i n F i g u r e 3-3  283  xii  LIST OF PLATES  Plate  1-1 A) S c h i s t from t h e s i l l i m a n i t e zone, Shuswap Complex B) S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex  86  Plate  1-2 A) S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex B) S c h i s t from t h e s i l l i m a n i t e zone, Shuswap Complex  88  Plate  1-3 S c h i s t from t h e k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex  90  Plate  1-4 A) S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex B) S c h i s t from t h e s i l l i m a n i t e zone, Shuswap Complex  92  Plate  1-5 S c h i s t from the s i l l i m a n i t e zone, Shuswap Complex  94  Plate  1-6 A) S c h i s t from t h e s t a u r o l i t e - k y a n i t e zone, c o v e r sequence B) P h y l l i t e f r o m the g a r n e t - b i o t i t e zone, c o v e r sequence  96  Plate  1-7 A) P h y l l i t e from the g a r n e t - b i o t i t e zone, c o v e r sequence B) P h y l l i t e from the g a r n e t - b i o t i t e zone, c o v e r sequence  98  Plate  1-8 P h y l l i t e from t h e g a r n e t - b i o t i t e zone, c o v e r sequence  100  Plate  1-9 A) P I minor f o l d s i n i n t e r l a y e r e d s c h i s t and q u a r t z i t e , Shuswap Complex (Azure Lake area) B) F3 minor f o l d h i n g e i n p h y l l i t e  102  Plate  1-10 A) F3 minor f o l d h i n g e s i n p h y l l i t e B) Graded b e d d i n g i n f e l d s p a t h i c ' g r i t s ' o f the Kaza Group  104  Plate  2-1 A) S c h i s t from t h e s i l l i m a n i t e zone, Shuswap Complex B) S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex  265  Plate  2-2 A) S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex B) S c h i s t from the s i l l i m a n i t e zone, Shuswap Complex  267  xiii  Plate  2-3 S c h i s t from t h e k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex  269  Plate  2-4 S c h i s t from t h e s i l l i m a n i t e zone, Shuswap Complex  271  Plate  2-5 A) C o e x i s t i n g c a l c i c amphibole, c a l c i c p y r o x e n e , q u a r t z , and c a l c i t e from a d i s c o n t i n u o u s marble u n i t i n t h e k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex B) C o e x i s t i n g m u s c o v i t e , q u a r t z , and c a l c i t e from a s m a l l marble u n i t i n t h e k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex  273  Plate  4-1 Geology, A z u r e L a k e , B.C.  pocket  Plate  4-2 S t r u c t u r a l g e o l o g y , Azure Lake, B.C.  pocket  Plate  4-3 Geology, A z u r e Lake, B.C.  pocket  Plate  4-4 S t r u c t u r a l g e o l o g y , Azure L a k e , B.C.  pocket  xiv ACKNOWLEDGMENTS  This study has benefited from the support and comments of numerous people.  Although space doesn't permit recognition of a l l contributors,  several people have made my years here most enjoyable. I am indebted to Dr. H.J. Greenwood for his consistent i n t e r e s t and enthusiasm while supervising the study. progress was also h e l p f u l .  His patience during times of slow  Discussions with Dr. T.H. Brown were useful i n  debugging problems associated with the electron microprobe and the thermodynamics of f l u i d s and s o l i d s .  The s t r u c t u r a l i n t e r p r e t a t i o n was  improved by discussions with Dr. J.V. Ross. were Dr. R.L. Armstrong, Dr. P.B.  Other interested contributors  Read, Dr. R.B. Campbell, and Dr. B. Ryan.  B. H a l l , P. Marcello, and N. Duncan were able f i e l d assistants during the three summer seasons.  G.E. Montgomery and basement crew provided  technical advice both i n work and recreation. maze of a c t i v i t i e s i n the geochronology l a b .  K. Scott helped with the J . Nelson provided much  needed moral support and helped me survive through the p e r i l s of convoluted geologic arguments. F i e l d and laboratory expenses were covered by NRCC 67-4222 to Dr. H.J. Greenwood.  Lab expenses for the Rb-Sr geochronology were p a r t l y supported  by NRCC 67-8841 to Dr. R.L. Armstrong. was  During the course of this study I  supported by graduate research fellowships sponsored by the National  Science Foundation and the International Nickel Company.  1  GENERAL INTRODUCTION  The Shuswap Metamorphic Complex forms a metamorphic  c o r e complex  w i t h i n the Omineca C r y s t a l l i n e B e l t i n s o u t h e a s t e r n B r i t i s h Columbia. I t i s c h a r a c t e r i z e d by s i l l i m a n i t e - b e a r i n g p e l i t e s and p o l y p h a s e d e f o r mation.  Near Azure L a k e , B r i t i s h Columbia the margins o f t h e Complex  c o n t a i n a r a p i d metamorphic  t r a n s i t i o n from g a r n e t - b i o t i t e zone t o  s i l l i m a n i t e zone i n t h e B a r r o v i a n f a c i e s  series.  T h i s s t u d y p r e s e n t s the r e s u l t s o f a d e t a i l e d p e t r o l o g i c - s t r u c t u r a l i n v e s t i g a t i o n o f t h e n o r t h e a s t margin o f the Shuswap Complex n e a r Azure Lake, B r i t i s h Columbia.  I t p r o v i d e s a "window" on t h e d e f o r m a t i o n and  metamorphic m a r g i n a l r e l a t i o n s o f a h i g h grade metamorphic  c o r e complex.  The r e s u l t s o f t h i s s t u d y a r e p r e s e n t e d i n t h r e e complementary  papers.  These papers d i s c u s s r e l a t e d f a c e t s o f the m a r g i n a l r e l a t i o n s .  The  l a r g e s c a l e maps c o n t a i n e d i n t h e pocket ( p l a t e s 4-1 through 4-4) s h o u l d be used when r e a d i n g each o f the t h r e e p a p e r s . The f i r s t paper p r o v i d e s a g e n e r a l o v e r v i e w o f metamorphism and d e f o r m a t i o n o f the Shuswap Complex and the a d j a c e n t l o w e r grade metasediments.  D e f o r m a t i o n s t y l e s and t r e n d s , metamorphic  assemblages,  and the r e l a t i o n o f metamorphism t o d e f o r m a t i o n a r e p r e s e n t e d .  This  paper a l s o d i s c u s s e s t h e n a t u r e o f the c o n t a c t s e p a r a t i n g t h e Complex from the l o w e r grade metasediments.  The metamorphic  are then r e l a t e d t o the r e g i o n a l t e c t o n i c  and t e c t o n i c p a t t e r n s  framework.  The second paper p r e s e n t s a d e t a i l e d d i s c u s s i o n o f metamorphic c o n d i t i o n s w i t h i n the Shuswap Complex near Azure L a k e , B r i t i s h Columbia. 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 a r e combined w i t h l i n e a r r e g r e s s i o n t e c h n i q u e s to o u t l i n e p r o b a b l e s i l l i m a n i t e - f o r m i n g r e a c t i o n s i n t h e p e l i t i c  2  assemblages.  Pressure-temperature-a  c o n d i t i o n s f o r the p e l i t e s d u r i n g H  2°  metamorphism are e s t i m a t e d by a d j u s t i n g p u b l i s h e d e x p e r i m e n t a l m i n e r a l e q u i l i b r i a s t u d i e s f o r the e f f e c t s of s o l i d s o l u t i o n .  These e s t i m a t e d  c o n d i t i o n s are then used t o study b u f f e r i n g o f f l u i d phase  compositions  d u r i n g metamorphism by m i n e r a l assemblages i n p e l i t e and c a r b o n a t e The  units.  t h i r d paper p r e s e n t s the r e s u l t s o f Rb-Sr r a d i o m e t r i c d a t i n g  o f g r a n o d i o r i t i c i n t r u s i o n s i n the Azure Lake a r e a .  These i n t r u s i o n s  p o s t d a t e r e g i o n a l s t r u c t u r a l and metamorphic p a t t e r n s i n the s u r r o u n d i n g metasediments.  A Rb-Sr date of 163 + 7 Ma i n d i c a t e s t h a t the  d e f o r m a t i o n and metamorphism d e s c r i b e d i n the two e a r l i e r papers completed  by L a t e J u r a s s i c t i m e .  was  3  Metamorphic and S t r u c t u r a l R e l a t i o n s on the N o r t h e a s t M a r g i n of the Shuswap Metamorphic Azure Lake, B r i t i s h  Columbia  Lee C. P i g a g e Department of G e o l o g i c a l S c i e n c e s U n i v e r s i t y of B r i t i s h Vancouver, B r i t i s h V6T 1W5  Columbia  Columbia  Canada  Complex,  4  ABSTRACT  Four phases of d e f o r m a t i o n have been r e c o g n i z e d i n the Shuswap Complex and a d j a c e n t l o w e r grade metasediments of the c o v e r sequence. e a r l i e s t deformation  ( P l - F l ) c o n s i s t s of w e s t - v e r g i n g i s o c l i n a l  p l u n g i n g n o r t h and n o r t h w e s t . a x i a l plane s c h i s t o s i t y .  folds  These f o l d s a r e accompanied by a p e r v a s i v e  The second phase of d e f o r m a t i o n  (P2-F2) r e s u l t e d  i n l a r g e u p r i g h t f o l d s w i t h a shallow northwest or southeast The  The  t h i r d and f o u r t h phases of d e f o r m a t i o n c o n s i s t o f l a t e  plunge.  faults,  f r a c t u r e s , and b r i t t l e f o l d s which t r e n d n o r t h and n o r t h e a s t , r e s p e c t i v e l y . M i n e r a l assemblages on the n o r t h e a s t margin of the Complex range from g a r n e t - b i o t i t e t h r o u g h f i r s t s i l l i m a n i t e zones o f the B a r r o v i a n f a c i e s series.  Metamorphic grade i n c r e a s e s toward the southwest.  Regional  metamorphism i s a s s o c i a t e d w i t h the P l - F l phase of d e f o r m a t i o n .  Mineral  t e x t u r e s and i n c l u s i o n t r a i l p a t t e r n s i n d i c a t e t h a t metamorphic r e c r y s t a l l i z a t i o n o u t l a s t e d the P l - F l  deformation.  The Shuswap Complex i s s e p a r a t e d from the c o v e r sequence by a t e c t o n i c s l i d e r e l a t e d t o the geometry of major P l - F l i s o c l i n a l f o l d s .  Estimated  metamorphic c o n d i t i o n s on e i t h e r s i d e of the s l i d e zone i n d i c a t e  the  p r e s e n c e of a 100°C temperature  Similarly,  d i s c o n t i n u i t y across the s l i d e .  o r i e n t a t i o n s of P l - F l minor s t r u c t u r e s are d i s c o r d a n t a c r o s s t h i s S t r u c t u r a l d i s c o r d a n c e and the temperature  slide.  d i s c o n t i n u i t y are r e l a t e d to  complex movement a l o n g the s l i d e w i t h a t l e a s t p a r t o f the movement b e i n g rotational.  R o t a t i o n p r o b a b l y r e s u l t e d from r e a c t i v a t i o n o f t h e  slide  s u r f a c e d u r i n g the second phase (P2-F2) f o l d i n g . L a t e J u r a s s i c p l u t o n s c r o s s - c u t minor s t r u c t u r e s a s s o c i a t e d w i t h the P l - F l and P2-F2 d e f o r m a t i o n s and impose a c o n t a c t h o r n f e l s i c a u r e o l e on the  5  r e g i o n a l metamorphic assemblages. were t h e r e f o r e  R e g i o n a l d e f o r m a t i o n and metamorphism  completed by L a t e J u r a s s i c t i m e .  The l a r g e s c a l e  anticlinoria  and s y n c l i n o r i a i n the C a r i b o o Mountains are c o r r e l a t e d w i t h t h e P2-F2 deformation.  6 INTRODUCTION  The Shuswap Metamorphic Complex forms the c o r e of the Omineca C r y s t a l l i n e B e l t i n s o u t h e a s t e r n B r i t i s h Columbia, Canada ( f i g u r e 1-1).  It  i s d e f i n e d by the s i l l i m a n i t e i s o g r a d and i s c h a r a c t e r i z e d by p o l y p h a s e d e f o r m a t i o n (R.B. Campbell 1977). H a d r y n i a n (Windermere)  Metasediments r a n g i n g i n age from  t o l a t e T r i a s s i c a r e i n v o l v e d i n the d e f o r m a t i o n and  metamorphism (K.V. Campbell 1971; R.B.  Campbell and T i p p e r 1971).  Gneiss  domes c o r e d by r e a c t i v a t e d Hudsonian basement a r e r e g u l a r l y spaced a l o n g the e a s t e r n m a r g i n of t h e Complex (Ross 1968; Wanless and Reesor 1975). T h i s paper p r e s e n t s the r e s u l t s of a d e t a i l e d  structural-petrologic  s t u d y of the n o r t h e a s t margin of the Shuswap Complex n e a r A z u r e Lake, B r i t i s h Columbia. metamorphic  I t p r o v i d e s an o v e r v i e w of m a r g i n a l r e l a t i o n s of a  c o r e complex.  D e f o r m a t i o n s t y l e s and t r e n d s ,  metamorphic  assemblages, and the r e l a t i o n o f d e f o r m a t i o n t o metamorphism a r e p r e s e n t e d f o r the Complex and f o r the a d j a c e n t lower grade metasediments.  It is  shown t h a t t h e r e i s no d i s c e r n i b l e d i f f e r e n c e i n metamorphic  tectonic  and  p a t t e r n s a c r o s s t h e m a r g i n a l boundary a l t h o u g h t h e Complex i s s e p a r a t e d f r o m t h e l o w e r grade r o c k s by a s y n t e c t o n i c f a u l t zone. of metamorphic  A detailed  discussion  c o n d i t i o n s w i t h i n the Shuswap Complex near A z u r e Lake i s  p r e s e n t e d elsewhere ( P i g a g e 1978, t h i s volume). The A z u r e Lake a r e a i s o u t l i n e d i n f i g u r e s 1-2 and 1-3.  It is  l o c a t e d i n the C a r i b o o Mountains n o r t h of C l e a r w a t e r , B r i t i s h Columbia. T o t a l r e l i e f i n the a r e a i s a p p r o x i m a t e l y 1800 m (6000 f t ) .  Detailed  g e o l o g i c mapping (1 i n = 1000 f t ) was completed d u r i n g the summers o f 1972 and 1973.  I n 1975 mapping (1 i n = 0.5 mi) was extended t o t h e n o r t h w e s t  t o c o r r e l a t e the d e t a i l e d a r e a w i t h r e g i o n a l s t r a t i g r a p h y and  structure.  7  F i g u r e 1-1.  Major s t r u c t u r a l elements o f the Canadian C o r d i l l e r a .  F i g u r e s 2 and 3 a r e i n d i c a t e d by the p a r a l l e l o g r a m . Metamorphic Complex c o r r e s p o n d s to the r u l e d a r e a . Wheeler and G a b r i e l s e (1972).  Shuswap M o d i f i e d from  F i g u r e 1-2. R e g i o n a l geology o f the C a r i b o o M o u n t a i n s , B r i t i s h Columbia. The a r e a o f s t u d y i s j u s t n o r t h o f Azure Lake.  M o d i f i e d from Wheeler,  R.B. Campbell, Reesor, and Mountjoy (1972). LEGEND  JURASSIC r +++++,f + + ++ + t + +  r  UPPER  GRANODIONTE  TRIASSIC  TO QUARTZ  to MIDDLE JURASSIC  DOMINANTLY  UPPER UTS  Unnamed  s  D E V O N I A N (?) . . . .'| M  VOLCANIC-CLASTIC  ROCKS  TRIASSIC  I"  D  DIORITE  S  unit-BLACK PHYLLITE, ARGILLITE, MINOR  and MISSISSIPPIAN  Slide Mountain  Group-PILLOW BASALT, ARGILLITE, CHERT, CONGLOMERATE,  PRECAMBRIAN " P  € - E  and  Cariboo  C  LIMESTONE  LIMESTONE  CAMBRIAN  Group-INTERBEDDED  PHYLLITE, QUARTZITE,  PRECAMBRIAN P K €  |  Kaza  Group - INTERBEDDED MINOR  PHYLLITE,  MARBLE  UNKNOWN GRANITIC  GNEISS  OF UNKNOWN AGE  QUARTZITE,'GRIT',  MARBLE  9  121" W  I20"W  SILLIMANITE  STAUROLITE-KYANITE  GARNET  BIOTITE  F i g u r e 1-3. D i s t r i b u t i o n o f metamorphic  isograds i n the Cariboo Mountains, B r i t i s h  M o d i f i e d from Wheeler, C a m p b e l l , R e e s o r , and Mountjoy  (1972).  and  CHLORITE  Columbia. o  11  In  t o t a l , f i v e months were spent i n t h e Azure Lake a r e a . P r e v i o u s work c o n s i s t s o f t h e f o u r - m i l e r e g i o n a l c o m p i l a t i o n by  R.B. Campbell (1963, 1968). the  D e t a i l e d s t u d i e s on p o r t i o n s o f t h e Complex t o  west have been completed by K.V. Campbell (1971) and F l e t c h e r ( 1 9 7 2 ) .  GEOLOGIC SETTING  F i g u r e s 1-2 and 1-3 i l l u s t r a t e t h e r e g i o n a l geology a l o n g t h e n o r t h e r n m a r g i n o f t h e Shuswap Complex.  N o r t h w e s t - p l u n g i n g a n t i c l i n o r i a and  s y n c l i n o r i a o u t l i n e a g e n e r a l t r a n s i t i o n t o h i g h e r s t r u c t u r a l and s t r a t i g r a p h i c l e v e l s "down p l u n g e " t o t h e n o r t h w e s t (R.B. Campbell 1970). S t r u c t u r a l l y t h i s t r a n s i t i o n i s marked by t h e s u c c e s s i v e r e p l a c e m e n t o f i s o c l i n a l p o l y p h a s e f o l d s f i r s t by a t r a n s i t i o n zone o f u p r i g h t f o l d s and then by a b r i t t l e zone o f t i l t e d C o n c o m i t a n t l y metamorphic  faulted blocks with l o c a l  folds.  grade d e c r e a s e s r a p i d l y f r o m s i l l i m a n i t e zone t o  c h l o r i t e zone ( f i g u r e 1-3).  G e n e r a l l y metamorphic  grade i s h i g h e r i n  a n t i c l i n o r i a r e l a t i v e to adjacent s y n c l i n o r i a . The Azure Lake a r e a c o n s i s t s o f two s t r u c t u r a l - m e t a m o r p h i c p r o v i n c e s s e p a r a t e d by a c o m p o s i t e f a u l t zone which g e n e r a l l y d i p s a t moderate a n g l e s to  t h e n o r t h o r n o r t h e a s t ( f i g u r e 1-4).  Individual faults i n this  zone  formed t o g e t h e r w i t h o r l a t e r t h a n t h e r e g i o n a l metamorphism and p e n e t r a t i v e deformation w i t h i n the area. s t r u c t u r a l t r e n d and metamorphic  The p r o v i n c e s d i f f e r i n b o t h  grade.  Metamorphic grade i n t h e Azure Lake a r e a ranges from g a r n e t - b i o t i t e to  f i r s t s i l l i m a n i t e zones i n t h e B a r r o v i a n f a c i e s s e r i e s ( M i y a s h i r o 1961).  B o t h metamorphic ( f i g u r e 1-5).  grade and g r a i n s i z e i n c r e a s e toward t h e southwest  Since the s i l l i m a n i t e isograd i s generally coincident w i t h  F i g u r e 1-4.  D i s t r i b u t i o n o f the d i f f e r e n t s t r u c t u r a l domains i n the  Azure Lake a r e a .  P r o v i n c e 1 c o r r e s p o n d s t o the Shuswap Metamorphic  Complex, and p r o v i n c e 2 i s the a d j a c e n t lower grade c o v e r sequence.  F i g u r e 1-5.  D i s t r i b u t i o n o f metamorphic zones i n the A z u r e Lake a r e a .  The d e t a i l e d a r e a shown i n F i g u r e 1-13 i s c i r c l e d .  14  the fault zone separating the two provinces, the Shuswap Complex corresponds to province 1.  Province 2 consists of the adjacent lower grade  metasediments; i n the following discussion province 2 i s referred to as the cover sequence.  STRATIGRAPHY  The stratigraphic framework and correlations for the Azure Lake area are based on studies by Holland (1954), Sutherland Brown (1957, 1963), and R.B. Campbell (1963, 1968).  Recent work i n the McBride area (see  figure 1-2) by R.B. Campbell, Mountjoy, and Young (1973) has c l a r i f i e d stratigraphic problems r e s u l t i n g from poor exposure and complex relations i n the other areas.  The stratigraphic column presented i n  table 1-1 i s based upon type sections from the McBride area. mapped informally  near  structural  Units  Azure Lake are included i n the table for  comparison. The detailed area of study contains Hadrynian metasediments of the Kaza and Cariboo Groups.  The sequence represents miogeoclinal shelf  deposits i n a shallow to deep marine environment (R.B. Campbell, Mountjoy, and Young 1973).  Textural relations and facies changes i n the McBride  area suggest a northeastern cratonic source for the sediments.  Original  stratigraphic thicknesses i n the Azure Lake area cannot be r e a d i l y estimated because of intense folding and f l a t t e n i n g during deformation. Kaza Group The Kaza Group (Sutherland Brown 1963) i s the oldest unit exposed i n the Cariboo Mountains.  It consists largely of feldspathic g r i t s with  intercalated quartzites, gray to green p h y l l i t e s , and minor marble.  Its  Table  1-1.  Stratigraphy  f o r t h e Azure Lake and M c B r i d e a r e a s .  McBRIDE  AREA  AZURE  C a m p b e l l , Mountjoy, Young (1973)  YANKEE  BELLE  interbedded  and  < X  sandstone  limestone  minor  and  marker-silvery  phyliite  phyliite +  white  limestone  WIATIOI  massive  limestone  conglomerate  Lower to  with  black  minor  o  <i  phyliite  phyliite  limestone to  or o  Middle lensoid,  alternating  TIOls  argillaceous  u.  and  transitional  Cunningham  Fm  Middle resistant, dark  rust-weathering,  gray  phyliite  Lower silvery  green  phyliite  interlayered limestone ;  AAC  minor  shale  A R I BOO  phyllitic  limestone  gray  FM  Upper gray  with  u.  limestone  with  dolostone  massive  O  FM  q u a r t z i t e and  CUNNINGHAM  shale,  Upper  or < o  BELLE  interlayered  or  ISAAC  DR  >  limestone, dolostone,  dark  study)  p h y l i i t e ; minor  or e>  BOO  ( W I N ID E R I  <  dno  rr  YANKEE  siltstone,  FM  siltstone, and  (this  AREA  dolostone  CUNNINGHAM  LU  FM  l i m e s t o n e -, m i n o r  sandstone  LU  Pigage  OUP  and  shale,  LAKE  with minor  quartzite  siltstone,  sandstone, a n d limestone  KAZA  GROUP  alternating gray  phyliite  limestone  KAZA  feldspathic and  or  'grits'  schist  and  minor  conglomerate  GROUP  interlayered phyliite  or  quartzitej calcareous  feldspathic  'grits' ,  schist, and  massive  minor  limestone  quartzite  and  16 t h i c k n e s s has been e s t i m a t e d t o exceed 3700 m (12000 f t ) w i t h t h e base unexposed ( S u t h e r l a n d Brown 1963). I n t h e Azure Lake a r e a t h e Kaza Group i s t h e o n l y u n i t t o o c c u r i n both s t r u c t u r a l provinces.  I n t h e Shuswap Complex ( p r o v i n c e 1) i t c o n s i s t s  o f i n t e r c a l a t e d massive q u a r t z i t e s and c o a r s e s c h i s t s . range from 2 cm t o more than 15 m i n t h i c k n e s s .  Individual units  G r i t s a r e uncommon  a l t h o u g h q u a r t z i t e s commonly c o n t a i n s c a t t e r e d w h i t e f e l d s p a r porphyroblasts.  D i s c o n t i n u o u s marble u n i t s up t o 30 m t h i c k a r e s p a r s e l y  d i s t r i b u t e d throughout hornblende  t h e sequence.  T h i n c a l c - s i l i c a t e bands c o n t a i n i n g  and garnet s c a t t e r e d i n a q u a r t z - p l a g i o c l a s e m a t r i x a r e common.  A m p h i b o l i t e bands o c c u r o n l y r a r e l y .  Southwest o f O v i s Creek t h e  sequence has been d i s t u r b e d by numerous pegmatite  intrusions.  I n t h e cover sequence t h e Kaza Group c o n s i s t s o f i n t e r l a y e r e d green q u a r t z i t e and s i l v e r y green p h y l l i t e . few cm t o g r e a t e r than 5 m i n t h i c k n e s s .  pale  I n d i v i d u a l u n i t s range from a  F e l d s p a t h i c g r i t s a r e common;  c l a s t s i n c l u d e c l e a r q u a r t z , b l u e o p a l e s c e n t q u a r t z , p l a g i o c l a s e , and r a r e microcline.  Many o f t h e g r i t h o r i z o n s a r e graded and p r o v i d e i n d i c a t o r s o f  s t r a t i g r a p h i c " t o p s " ( p l a t e 1-10B). o c c u r throughout variable.  t h e sequence.  Minor amounts o f micaceous marble  Thicknesses of marble u n i t s a r e h i g h l y  T h i n (5 cm) c a l c - s i l i c a t e bands c o n s i s t i n g o f hornblende and  g a r n e t i n a q u a r t z - p l a g i o c l a s e m a t r i x a r e common.  Rare t h i n a m p h i b o l i t e  bands a r e a l s o p r e s e n t .  Isaac  Formation The I s a a c F o r m a t i o n  Kaza Group.  ( S u t h e r l a n d Brown 1963) conformably  o v e r l i e s the  W i t h a measured t h i c k n e s s g r e a t e r than 1200 m (4000 f t ) i n t h e  M c B r i d e a r e a , t h i s u n i t c o n s i s t s dominantly o f c a l c a r e o u s gray  phyllite  i n t e r c a l a t e d w i t h s i l v e r y p h y l l i t e , micaceous gray l i m e s t o n e , and minor  17  q u a r t z i t e (R.B. C a m p b e l l , Mountjoy, and Young 1973). In t h e Azure Lake a r e a t h e I s a a c F o r m a t i o n has been i n f o r m a l l y d i v i d e d i n t o t h r e e l i t h o l o g i c a l l y d i s t i n c t members.  The t h r e e u n i t s i n t h e e a s t e r n  p a r t o f t h e a r e a a r e e s t i m a t e d t o have t h e f o l l o w i n g t h i c k n e s s e s :  lower  member (610-700 m), m i d d l e member (30-180 m), upper member (30-150 m) . A l t h o u g h n o t i n d i c a t i v e o f o r i g i n a l t h i c k n e s s , these e s t i m a t e s i n d i c a t e t h a t the lower u n i t i s s u b s t a n t i a l l y t h i c k e r than t h e o t h e r two. The l o w e r member c o n s i s t s d o m i n a n t l y o f f i n e - g r a i n e d s i l v e r y p h y l i i t e w h i c h i s c o l o r banded on a s c a l e o f 1-2 cm.  green  The l o w e r c o n t a c t has  been d e f i n e d as t h e t o p o f t h e l a s t m a s s i v e , p a l e green q u a r t z i t e o f t h e Kaza Group. unit.  Minor l i g h t t a n q u a r t z i t e s occur i n the lower p o r t i o n o f t h i s  I n t e r l a y e r e d w i t h t h e p h y l i i t e a r e brown  nodular marble, pale white  t o gray marble c o n t a i n i n g w h i t e c a l c i t e s t r i n g e r s , micaceous m a r b l e , and f i n e l y i n t e r b a n d e d  gray t o brown  p h y l i i t e and sandy r e d d i s h m a r b l e .  I n d i v i d u a l u n i t s a r e up t o 25 m t h i c k w i t h l a r g e v a r i a t i o n s i n t h i c k n e s s occurring along s t r i k e .  These c a l c a r e o u s l i t h o l o g i e s o c c u r m a i n l y i n t h e  lower p o r t i o n o f t h i s member. The m i d d l e member c o n s i s t s o f a f i n e - g r a i n e d gray t o b l a c k p h y l i i t e w h i c h weathers  t o a deep r u s t y - r e d c o l o r .  commonly forms sharp a n g u l a r r i d g e s .  T h i s u n i t i s r e s i s t a n t and  P y r i t e and p y r r h o t i t e a r e t h e o n l y  macroscopic m i n e r a l s . The upper member i s t r a n s i t i o n a l t o t h e o v e r l y i n g Cunningham Formation.  I t c o n s i s t s o f t h i n l y banded s i l v e r y p h y l i i t e a l t e r n a t i n g w i t h  p i n k - w e a t h e r i n g sandy marble.  I n d i v i d u a l l a y e r s a r e 0.2-1.0 cm t h i c k .  The upper c o n t a c t w i t h t h e Cunningham F o r m a t i o n has been d e f i n e d as t h e base o f t h e f i r s t m a s s i v e , gray marble  unit.  18 Cunningham Formation The Cunningham Formation (Holland 1954) thick at the type section.  i s over 550 m (1800 f t )  I t consists dominantly of limestone with lesser  amounts of dolostone, shale, s i l t s t o n e , and sandstone (R.B. Campbell, Mountjoy, and Young 1973).  In the Azure Lake region the middle portion of  the formation consists of gray, massive to slabby marble with minor discontinuous micaceous partings.  Lower and upper parts contain slabby,  brown-weathering marble interlayered with abundant p h y l l i t e bands. Individual p h y l l i t e layers are from 0.5 to 15 cm thick. dolomitic layers are common throughout the formation.  Boudinaged Dolomitic  layers  are up to 3 m thick; they are t y p i c a l l y highly fractured with coarse white c a l c i t e f i l l i n g  fractures.  The marker horizon indicated i n the maps  (plates 4-3 and 4-4) consists of a s i l v e r y p h y l l i t e  (5 cm - 6  m) overlain  by a d i s t i n c t i v e massive creamy white marble (6 m). Yankee Belle Formation Conformably overlying the Cunningham Formation i s the Yankee Belle Formation (Holland 1954). than 900 m (2900 f t ) thick.  In the McBride area the Yankee B e l l e i s more The unit consists mainly of alternating beds  of s i l t s t o n e , quartzite, limestone, and shale and Young 1973).  (R.B.  Campbell, Mountjoy,  In the Azure Lake area i t contains interlayered s i l v e r y  p h y l l i t e , slabby creamy-colored quartzite, and gray to brown micaceous marble.  Quartzite units are more common near the base of the formation.  Intrusions Two sets of intrusions have been recognized i n the cover sequence. The e a r l i e s t occur only as s i l l s and dykes.  These early intrusions have  undergone a l l of the deformation and contain the same f o l i a t i o n s as surrounding metasediments.  Rock types range from fine-grained  felsic  19  a p l i t e s t o h o r n b l e n d e - b i o t i t e metabasic  intrusions.  The second s e t o f i n t r u s i o n s o c c u r s as h o r n b l e n d e - b i o t i t e q u a r t z d i o r i t e t o g r a n o d i o r i t e s t o c k s on t h e n o r t h e r n edge o f t h e Azure Lake area.  Abundant p l a g i o c l a s e p h e n o c r y s t s i n an u n f o l i a t e d , medium-grained  m a t r i x g i v e a d i s t i n c t i v e appearance t o t h e s e s t o c k s .  L e s s e r amounts o f  h o r n b l e n d i t e and f i n e - g r a i n e d w h i t e a p l i t e a r e t y p i c a l l y a s s o c i a t e d w i t h the i n t r u s i o n s .  These s t o c k s have imposed a h o r n f e l s i c c o n t a c t  metamorphic a u r e o l e on r e g i o n a l metamorphic assemblages i n t h e metasediments.  E a r l y s t r u c t u r e s a r e c r o s s - c u t by t h e s t o c k s ; t h e  e a r l i e s t r e c o g n i z e d s t r u c t u r e s i n t h e s t o c k s a r e F3 f r a c t u r e s (see s e c t i o n on d e f o r m a t i o n ) .  Rb-Sr (Pigage 1977) and K-Ar (Wanless e_t a l . 1965)  r a d i o m e t r i c d a t i n g g i v e c o n s i s t e n t L a t e J u r a s s i c d a t e s f o r emplacement. W i t h i n t h e Shuswap Complex t h e o n l y r e c o g n i z e d i n t r u s i o n s a r e c o a r s e , u n f o l i a t e d q u a r t z - m i c r o c l i n e - p l a g i o c l a s e ± muscovite pegmatites. p e g m a t i t e b o d i e s a r e e s p e c i a l l y abundant i n t h e a r e a southwest Creek.  These  of Ovis  Modal amounts o f t h e d i f f e r e n t m i n e r a l s a r e h i g h l y v a r i a b l e w i t h i n  t h e same p e g m a t i t e  intrusion.  DEFORMATION/METAMORPHISM  Both p r o v i n c e s a r e polydeformed w i t h metamorphism c o n t i n u i n g through more than one d e f o r m a t i o n phase.  The f o l l o w i n g s e c t i o n s d i s c u s s  d e f o r m a t i o n and metamorphic e p i s o d e s f o r each o f t h e p r o v i n c e s s e p a r a t e l y . The geometries o f t h e d e f o r m a t i o n e p i s o d e s a r e p r e s e n t e d , and t h e phases o f d e f o r m a t i o n a r e t h e n r e l a t e d t o metamorphic c o n d i t i o n s .  Coexisting  m i n e r a l assemblages a r e used t o e s t i m a t e p r e s s u r e - t e m p e r a t u r e c o n d i t i o n s d u r i n g metamorphism.  Through t h i s d e t a i l e d a n a l y s i s i t i s shown t h a t  d e f o r m a t i o n and metamorphic p a t t e r n s i n t h e two p r o v i n c e s a r e s i m i l a r .  20 Furthermore, e s t i m a t e d metamorphic c o n d i t i o n s a l l o w d i s c u s s i o n o f r e l a t i v e d i s p l a c e m e n t a l o n g the f a u l t zone s e p a r a t i n g the two p r o v i n c e s . D e f o r m a t i o n and metamorphic c o n d i t i o n s f o r the Shuswap Complex a r e discussed f i r s t .  D i f f e r e n t d e f o r m a t i o n e p i s o d e s i n the Complex a r e  d e s i g n a t e d as P1-P3  i n o r d e r t o d i s t i n g u i s h them from r e c o g n i z e d phases of  deformat i o n i n the c o v e r sequence Shuswap D e f o r m a t i o n  ( P I , P2,  (Fl—F4).  P3)  Three phases o f d e f o r m a t i o n have been r e c o g n i z e d i n t h e Shuswap Complex near Azure Lake.  Minor s t r u c t u r e s a s s o c i a t e d w i t h each  deformation  phase were d i s t i n g u i s h e d by s t y l e and o r i e n t a t i o n of minor f o l d s ,  relation  o f c l e a v a g e s t o minor f o l d s , and r e f o l d i n g of e a r l i e r minor s t r u c t u r e s by later folds.  Minor s t r u c t u r e s a s s o c i a t e d w i t h the two e a r l i e r  deformation  phases (PI and P2) a r e p r e s e n t over the e n t i r e a r e a and c o a x i a l l y g e n t l y northwest and s o u t h e a s t .  plunge  A l a t e , b r i t t l e f o l d and f r a c t u r e p a t t e r n  (P3) t r e n d i n g n o r t h t o n o r t h e a s t i s o n l y l o c a l l y p r e s e n t . The e a r l i e s t r e c o g n i z e d minor s t r u c t u r e s a r e P I i s o c l i n a l recumbent f o l d s i n the c o m p o s i t i o n a l l a y e r i n g PO.  P I minor f o l d s a r e p r e s e r v e d  o n l y i n q u a r t z i t e and c a l c - s i l i c a t e u n i t s .  They a r e commonly r o o t l e s s w i t h  t h i c k e n e d h i n g e zones and g r e a t l y a t t e n u a t e d l i m b s ( f i g u r e 1-6).  These  f o l d s a r e accompanied by a p e r v a s i v e P I a x i a l p l a n e s c h i s t o s i t y which t h e dominant f o l i a t i o n i n the Complex.  forms  The s u b p a r a l l e l o r i e n t a t i o n o f  P I and PO and the absence of P I minor f o l d s i n the s c h i s t s i n d i c a t e t h a t PO i s a c t u a l l y t r a n s p o s e d p r i m a r y bedding. F i g u r e 1-7  i l l u s t r a t e s the problems i n h e r e n t i n u s i n g minor f o l d  vergences t o d e l i n e a t e m a c r o s c o p i c The c l i f f exposure  f o l d p a t t e r n s i n the Shuswap Complex.  c o n t a i n s an i s o l a t e d f o l d nose w i t h a h a l f - a m p l i t u d e  g r e a t e r than 15 m and a h a I f - w a v e l e n g t h of o n l y 3m.  A sequence of f o l d s  Figure Lake.  1-6.  I s o c l i n a l P i minor  f o l d i n t h e Shuswap C o m p l e x n e a r A z u r e  F o l d i s o u t l i n e d by q u a r t z i t e  traced from a photograph.  in schist.  The l i n e  drawing  is  22  F i g u r e 1-7.  Large P I i s o c l i n a l f o l d i n i n t e r l a y e r e d s c h i s t and q u a r t z i t e .  The l i n e drawing i s t r a c e d  from a photograph.  23 on this scale i s not commonly seen i n outcrop.  Consequently minor f o l d  vergences may not be consistent even when considering a small area. Repetition of interlayered schist and quartzite units by large PI i s o c l i n a l folds i n the Azure Lake area could not be unravelled because of the absence of suitable continuous marker horizons. Just north of Azure River the PO compositional layering along the northeast margin of the Complex consistently dips toward the southwest. This discordance with the northeast-dipping PI s c h i s t o s i t y suggests a large PI synform.  The northern limb of this synform has been cut off by  the fault bounding the Complex.  The calculated o r i e n t a t i o n of the fault  plane as determined from the surface trace i s 142/36E.  This o r i e n t a t i o n  i s subparallel to the PI s c h i s t o s i t y i n this area and suggests that the f a u l t represents a major tectonic s l i d e (Fleuty 1964)  formed either  during PI deformation or with tightening of PI structures during the P2 deformation.  The s l i d e and adjacent synform are o f f s e t by the l a t e r  north-trending f a u l t which truncates the metamorphic isograds and s t r u c t u r a l trends i n the Complex and cover sequence.  Other s l i d e s may  be  present within the Complex but were not detected. The Shuswap Complex i n the Azure Lake area was  divided into three  homogeneous s t r u c t u r a l domains ( l a , l b , l c ) based upon the o r i e n t a t i o n of the PI s c h i s t o s i t y (figure 1-4).  The domains are bounded by n e a r - v e r t i c a l  f a u l t s which do not v i s i b l y o f f s e t regional metamorphic assemblages. Domain lb appears to be t r a n s i t i o n a l between l a and l c . Figure 1-8 contains stereographic projections of poles to PO compositional layering and PI s c h i s t o s i t y for each of the three domains. The d i f f e r e n t projections a l l show the general northwest s t r i k e for PO PI planar structures. predominantly  Planar structures i n domains l a and l c dip  northeast and southwest, respectively. The composite  and  F i g u r e 1-8  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f p o l e s t o PO c o m p o s i t i o n a l l a y e r i n g and P I a x i a l p l a n e s c h i s t o s i t y i n t h e Shuswap Complex  (Azure  Lake a r e a ) .  Top row: P o l e s t o PO c o m p o s i t i o n a l l a y e r i n g Domain l a - 250 p o i n t s , 0.4-2-4-8-12%  p e r 1% a r e a ; maximum 13%  Domain l b - 70 p o i n t s Domain l c - 280 p o i n t s , 0.4-2-4-8% p e r 1% a r e a ; maximum 8%  Bottom row: Poles t o P I a x i a l plane  schistosity  Domain l a - 316 p o i n t s , 0.3-2-4-8-12% p e r 1% a r e a ; maximum 18% Domain l b - 46 p o i n t s Domain l c - 105 p o i n t s , 0.9-2-4-8-12% p e r 1% a r e a ; maximum 15%  P,  -axial  plane  schistosity  F i g u r e 1-9  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f P I minor f o l d s t r u c t u r e s i n the Shuswap Complex (Azure Lake a r e a ) .  Top row: Domain l a - p o l e s t o P I minor f o l d a x i a l p l a n e s 115 p o i n t s , 0.9-4-8-12-16% p e r 1% a r e a ; maximum 20% Domain l b - P I minor f o l d  structures  d o t s - p o l e s t o a x i a l p l a n e s , 17 p o i n t s t r i a n g l e s - f o l d a x e s , 27 p o i n t s Domain l c - p o l e s t o P I minor f o l d a x i a l p l a n e s 77 p o i n t s , 1.3-4-8-12-16% p e r 1% a r e a ; maximum 17%  Bottom row: Domain l a - P I minor f o l d axes and l i n e a t i o n s 160 p o i n t s , dashed l i n e  i n d i c a t e s average P I a x i a l p l a n e  Domain l c - P I minor f o l d axes and l i n e a t i o n s 112 p o i n t s , dashed l i n e i n d i c a t e s average P I a x i a l p l a n e Composite diagram o f PO and P I p o l e s t o p l a n a r s t r u c t u r e s 12% p e r 1% a r e a t o PO c o m p o s i t i o n a l l a y e r i n g (8% p e r 1% a r e a f o r domain l c ) 12% p e r 1% a r e a f o r P I minor f o l d a x i a l p l a n e s 12% p e r 1% a r e a f o r P I a x i a l p l a n e  schistosity  28 p r o j e c t i o n i n f i g u r e 1-9 shows t h e o v e r l a p and  o f PO and P I p l a n a r  structures  demonstrates t h e i s o c l i n a l n a t u r e o f t h e f o l d i n g . F i g u r e 1-9 i l l u s t r a t e s p r o j e c t i o n s o f P I minor f o l d e l e m e n t s .  P I minor f o l d axes p l u n g e g e n t l y t o t h e n o r t h w e s t and s o u t h e a s t .  Most  In  domains l a and l c t h e dashed l i n e s c o r r e s p o n d t o t h e mean P I a x i a l p l a n e orientation. surface.  P I minor f o l d axes have v a r i a b l e p l u n g e w i t h i n t h i s P I a x i a l  S i m i l a r p l u n g e v a r i a t i o n s i n o t h e r t e r r a i n s have been a t t r i b u t e d  t o d i f f e r e n t i a l f l a t t e n i n g o f f o l d s d u r i n g d e f o r m a t i o n (Ramsay 1962a). the Azure Lake a r e a t h i s inhomogeneous s t r a i n i s a l s o e v i d e n t nesoscopic s c a l e ( p l a t e 1-9A).  In  on t h e  The f l a t t e n i n g p r o b a b l y o c c u r r e d e i t h e r  during l a t e P I f o l d i n g or w i t h t i g h t e n i n g of P I f o l d s during  t h e P2  deformation. The  P2 d e f o r m a t i o n i s d e l i n e a t e d by u p r i g h t t i g h t t o open minor f o l d s .  M i n o r f o l d s a r e common b o t h i n s c h i s t s and q u a r t z i t e s . c r e n u l a t i o n c l e a v a g e i s a x i a l p l a n a r t o P2 minor f o l d s .  A pervasive  P2  In schists this  P2 c l e a v a g e forms a s t r o n g c r i n k l e l i n e a t i o n o f P I s c h i s t o s i t y s u r f a c e s . F i g u r e 1-10 i l l u s t r a t e s a t y p i c a l P2 minor f o l d . I n some i n s t a n c e s  P I minor f o l d s a r e r e f o l d e d around P2 f o l d s .  The  r e s u l t i n g i n t e r f e r e n c e p a t t e r n corresponds t o Ramsay's t y p e 3 (Ramsay 1967)  for c o a x i a l deformation.  F i g u r e 1-11 i l l u s t r a t e s t h e t y p i c a l  i n t e r f e r e n c e p a t t e r n f o r t h e Complex i n t h e Azure Lake Stereographic  area.  p r o j e c t i o n s o f P2 minor s t r u c t u r e s f o r t h e t h r e e  domains a r e p r e s e n t e d i n f i g u r e 1-12. A x i a l p l a n e s a r e n e a r l y and  vertical  l i n e a t i o n s ( f o l d axes and i n t e r s e c t i o n s of P2 and P I s c h i s t o s i t i e s )  p l u n g e g e n t l y n o r t h w e s t and s o u t h e a s t . P2 minor f o l d s from domains l a and l c have o p p o s i n g v e r g e n c e s and d e f i n e a l a r g e P2 a n t i f o r m w i t h a h i n g e zone c e n t e r e d i n domain l b (see  F i g u r e 1-10.  P2 minor f o l d i n i n t e r l a y e r e d s c h i s t and q u a r t z i t e .  Stippled area i s q u a r t z i t e . milky white quartz lenses. photograph.  I r r e g u l a r pods i n s c h i s t a r e c o a r s e , The l i n e drawing i s t r a c e d from a  30  F i g u r e 1-11.  I s o c l i n a l P I minor f o l d r e f o l d e d around a P2 minor  Hammer h a n d l e i s p a r a l l e l t o the a x i a l p l a n e of the P2 f o l d . l i n e drawing i s t r a c e d from a photograph.  fold. The  F i g u r e 1-12  Equal area stereographic  p r o j e c t i o n s o f P2 minor f o l d s t r u c t u r e s i n  the Shuswap Complex (Azure Lake a r e a ) .  Top row: P2 minor f o l d axes and l i n e a t i o n s Domain l a - 212 p o i n t s , 0.5-4-8-12% p e r 1% a r e a ; maximum 20% Domain l b - 33 p o i n t s Domain l c - 117 p o i n t s , 0.9-4-8% p e r 1% a r e a ; maximum 1 1 %  Bottom row: p o l e s t o P2 minor f o l d a x i a l p l a n e s and c r e n u l a t i o n c l e a v a g e Domain l a - 191 p o i n t s , 0.5-4-8-12% p e r 1% a r e a ; maximum 12% Domain l b - 60 p o i n t s Domain l c - 109 p o i n t s , 0.9-4-8-12% p e r 1% a r e a ; maximum 15% average o r i e n t a t i o n 140/50 SW  33 p l a t e 4-4).  The s l i g h t d i f f e r e n c e s i n o r i e n t a t i o n of P2  schistosities  from domains l a and l c i n d i c a t e t h a t the P2 a n t i f o r m i s a c o n v e r g e n t f a n structure.  The c l o s e a s s o c i a t i o n o f the v e r t i c a l f a u l t s i s o l a t i n g  domain  l b w i t h the h i n g e zone o f t h e P2 a n t i f o r m s u g g e s t s t h a t the f a u l t s a r e l a t e f r a c t u r e s formed d u r i n g t h e P2 d e f o r m a t i o n . D i s p l a c e m e n t a c r o s s t h e s e f a u l t s appears t o be m i n i m a l s i n c e l i t h o l o g i e s a r e s i m i l a r and metamorphic grade does n o t v a r y a c r o s s them. L o c a l l y a minor P3 d e f o r m a t i o n has produced f r a c t u r e s and a n g u l a r f o l d s w i t h r u p t u r e d h i n g e zones. northeast. Shuswap  F r a c t u r e s and f o l d s t r e n d n o r t h t o  P e g m a t i t e i n t r u s i o n s a l s o c o n t a i n t h e s e P3 minor s t r u c t u r e s .  Metamorphism  The Shuswap Complex near Azure Lake c o n t a i n s m i n e r a l assemblages r a n g i n g from k y a n i t e t h r o u g h f i r s t s i l l i m a n i t e zones i n the B a r r o v i a n f a c i e s series.  Three d i s t i n c t metamorphic zones may be d i s t i n g u i s h e d u s i n g  the p e l i t i c m i n e r a l assemblages ( f i g u r e 1-5).  These zones d e f i n e a g e n e r a l  i n c r e a s e i n metamorphic grade toward the southwest.  M i n e r a l assemblages f o r  t h e s e zones a r e : K y a n i t e zone kyanite-garnet-biotite-muscovite-quartz-plagioclase-ilmenite ± staurolite K y a n i t e - S i l l i m a n i t e zone sillimanite-garnet-biotite-muscovite-quartz-plagioclase-ilmenite ± kyanite ± s t a u r o l i t e S i l l i m a n i t e zone sillimanite-garnet-biotite-muscovite-quartz-plagioclase-ilmenite ± staurolite M i n o r amounts o f t o u r m a l i n e , a p a t i t e , z i r c o n , and opaque d u s t ( g r a p h i t e ? )  34 are accessory The  minerals  i n each of the assemblages.  i s o g r a d s u r f a c e s e p a r a t i n g the k y a n i t e - s i l l i m a n i t e  s i l l i m a n i t e zones has  and  a V-shaped p r o f i l e on the r i d g e j u s t n o r t h e a s t  of  O v i s Creek ( f i g u r e 1-5).  The  "V" marks a steep v a l l e y w h i c h i n t e r r u p t s  the r i d g e a t t h a t p o i n t .  The  v a l l e y therefore provides  o f the i s o g r a d s u r f a c e .  F i g u r e 1-13  a cross s e c t i o n  shows t h a t the p o s i t i o n of  i s o g r a d i n the v a l l e y i s f a i r l y t i g h t l y c o n s t r a i n e d by the of the p e l i t i c  assemblages.  The  compositional  distribution  a t t i t u d e o f the i s o g r a d c a l c u l a t e d  from t h i s s u r f a c e t r a c e i s 132/20NE. b o t h the PO  the  This o r i e n t a t i o n i s s u b p a r a l l e l to  l a y e r i n g and the P I s c h i s t o s i t y i n the same a r e a .  A d e t a i l e d d i s c u s s i o n of p r o b a b l e metamorphic r e a c t i o n s and  estimated  p r e s s u r e - t e m p e r a t u r e c o n d i t i o n s d u r i n g metamorphism i s p r e s e n t e d  elsewhere  (Pigage  1978,  t h i s volume).  B r i e f l y , t e x t u r a l r e l a t i o n s demonstrate t h a t  aggregates o f f i b r o l i t e - b i o t i t e - m u s c o v i t e - i l m e n i t e have formed a t expense of g a r n e t , s t a u r o l i t e , and k y a n i t e .  Estimated  c o n d i t i o n s f o r the Complex i n the Azure Lake a r e a a r e : T = 705 + 40°C, a^ Q = 0.5  +  Q*^ •  the  metamorphic P = 7600 + 400  These e s t i m a t e s were d e r i v e d  bars,  from  the mutual i n t e r s e c t i o n of s e v e r a l d i s p l a c e d e q u i l i b r i a i n v o l v i n g s t a u r o l i t e , g a r n e t , p l a g i o c l a s e , m u s c o v i t e , q u a r t z , and A ^ S i O ^ sillimanite).  (kyanite,  The metamorphic g r a d i e n t n o t i c e d i n the f i e l d mapping i s not  observed i n the c a l c u l a t e d p r e s s u r e - t e m p e r a t u r e p o s i t i o n s of the d i s p l a c e d e q u i l i b r i u m curves.  Apparently  t h i s g r a d i e n t i s s m a l l and  i s masked by  a n a l y t i c a l e r r o r and l o c a l d i s e q u i l i b r i u m . Metamorphism may  be r e l a t e d i n time to the P I and P2  deformations  through the use of m i n e r a l r e a c t i o n t e x t u r e s and i n c l u s i o n t r a i l The  patterns.  d i f f e r e n t t e x t u r e s o u t l i n e a sequence of r e a c t i o n s t h a t have been  p a r t i a l l y preserved  by growth p a t t e r n s i n m i n e r a l s .  T a b l e 1-2  summarizes  F i g u r e 1-13.  D i s t r i b u t i o n o f p e l i t i c metamorphic m i n e r a l assemblages  c o n s t r a i n i n g the l o c a t i o n o f the i s o g r a d between the k y a n i t e - s i l l i m a n i t e and the s i l l i m a n i t e metamorphic zones.  36 the o b s e r v a t i o n s c o n c e r n i n g m i n e r a l growth and d e f o r m a t i o n .  Textural  r e l a t i o n s l e a d i n g to t h i s table are discussed i n the f o l l o w i n g s e c t i o n s . Garnet p o r p h y r o b l a s t s from a l l t h r e e metamorphic zones i n t h e Complex o u t l i n e two s t a g e s o f growth. w i t h abundant i n c l u s i o n s .  F i r s t s t a g e g a r n e t s form l a r g e ragged g r a i n s  I t i s these g a r n e t s which a r e b r e a k i n g down t o  form f i b r o l i t e - b i o t i t e - m u s c o v i t e - i l m e n i t e a g g r e g a t e s . of  Since  replacement  s t a g e one g a r n e t s i s more e x t e n s i v e w i t h i n c r e a s i n g metamorphic g r a d e ,  t h e s e g a r n e t s a r e n o t commonly p r e s e r v e d southwest  of Ovis  Creek.  I n c l u s i o n t r a i l s i n f i r s t g e n e r a t i o n g a r n e t s p r o v i d e a means o f r e l a t i n g garnet growth t o the P1-P2 d e f o r m a t i o n phases. inclusions define straight  U s u a l l y the  ( p l a t e 1-1A) o r S-shaped ( p l a t e 1 - l B ) t r a i l s .  In both cases i n c l u s i o n s t r a i l s a r e r o t a t e d r e l a t i v e t o t h e e x t e r n a l P I s c h i s t o s i t y although continuous w i t h i t . a c r e n u l a t i o n c l e a v a g e ( p l a t e 1-2A).  O c c a s i o n a l l y the t r a i l s preserve  Since the c r e n u l a t i o n planes w i t h i n  t h e garnet a r e c o n t i n u o u s w i t h t h e e x t e r n a l P I s c h i s t o s i t y , t h e e a r l i e r c r e n u l a t e d s u r f a c e s r e p r e s e n t PO c o m p o s i t i o n a l l a y e r i n g . These i n c l u s i o n p a t t e r n s i n d i c a t e n u c l e a t i o n and growth o f s t a g e one g a r n e t s d u r i n g and a f t e r t h e P I d e f o r m a t i o n (Zwart 1960a, 1960b).  Relative  r o t a t i o n o f garnet porphyroblasts i n the s c h i s t s probably r e s u l t e d  from  f l a t t e n i n g e i t h e r d u r i n g l a t e P I f o l d i n g o r d u r i n g P2 d e f o r m a t i o n (Ramsay 1962a; P o w e l l and Treagus 1970). Second s t a g e g a r n e t s t y p i c a l l y form c l e a r , i d i o b l a s t i c r i m s ragged stage one g a r n e t c o r e s ( p l a t e 1 - l B ) .  around  Where f i r s t s t a g e g a r n e t s  a r e uncommon, t h e second g e n e r a t i o n g a r n e t s occur as s m a l l i d i o b l a s t i c g r a i n s ( p l a t e 1-2B).  Commonly f i b r o l i t e  and i l m e n i t e g r a i n s a r e p a r t l y t o  c o m p l e t e l y e n c l o s e d by second s t a g e g a r n e t s ( p l a t e 1-3).  Second s t a g e  g a r n e t s a l s o form e u h e d r a l o u t l i n e s a g a i n s t t h e f i b r o l i t e  aggregates  T a b l e 1-2.  R e l a t i o n o f m i n e r a l growth t o phases o f d e f o r m a t i o n i n the  Shuswap Metamorphic Complex, Azure Lake, B r i t i s h Columbia.  P2  P| SYNPOSTTECTONIC  SYNPOSTTECTONIC  BIOTITE MUSCOVITE PLAGIOCLASE GARNET KYANITE STAUROLITE SILLIMANITE ILMENITE  ^™ — • — M M  ^  ^ ™  ^  ™™  m  ™  m  38 (plate 1-3).  Therefore second generation garnet growth occurred after  the i n i t i a l formation of the f i b r o l i t e aggregates.  A paucity of  inclusions i n second stage garnets makes i t d i f f i c u l t to r e l a t e their growth to the deformations. Inclusion t r a i l s i n kyanite and s t a u r o l i t e are similar to those f o r garnet (plate 1-4A).  Relic s t a u r o l i t e and kyanite grains are enclosed by  muscovite or f i b r o l i t e aggregates. grains partly enclosing garnet.  Kyanite forms large p o i k i l o b l a s t i c  In some instances kyanite grains are  warped or kinked by P2 microfolds.  Kyanite and s t a u r o l i t e growth occurred  a f t e r i n i t i a l nucleation of stage one garnets but before the formation of fibrolite  aggregates.  Fibrolite-biotite-muscovite-ilmenite aggregates p a r t l y to completely enclose garnet, s t a u r o l i t e , and kyanite.  Individual f i b r o l i t e needles are  randomly oriented although aggregates are elongate i n the PI and P2 schistosities.  In some instances the aggregates are folded and warped by  P2 microfolds (plate 1-4B). These d i f f e r e n t textures indicate growth of the major metamorphic minerals during and a f t e r the PI deformation and before or during the P2 deformation.  The formation of f i b r o l i t e aggregates apparently was  i n i t i a t e d a f t e r PI but before the P2 deformation phase.  Since second  stage garnets formed a f t e r the i n i t i a l growth of f i b r o l i t e  aggregates,  garnet growth may have continued during the P2 deformation. Narrow elongate grains of b i o t i t e and muscovite define both the PI and P2 s c h i s t o s i t i e s .  Grains are r e c r y s t a l l i z e d to form polygonal arcs around  P2 microfolds and crenulations. In the sillimanite-bearing zones randomly oriented b i o t i t e i s intimately intergrown with f i b r o l i t e  aggregates.  Muscovite also occurs as coarse, equant flakes which are randomly  39  oriented.  Commonly t h e s e f l a k e s c o n t a i n r e l i c k y a n i t e and  g r a i n s ( p l a t e 1-5).  staurolite  When a s s o c i a t e d w i t h f i b r o l i t e a g g r e g a t e s ,  m u s c o v i t e g r a i n s a r e i n t e r l o c k i n g w i t h ragged m a r g i n s .  At  individual  higher  metamorphic grades b i o t i t e - f i b r o l i t e aggregates form a t t e n u a t e d  trails  through the c o a r s e m u s c o v i t e f l a k e s ( p l a t e 1-5). The m i c a t e x t u r e s i n d i c a t e a l o n g p e r i o d o f c o n t i n u e d recrystallization.  growth and  Polygonal arc textures r e q u i r e continued  t h e P I and P2 d e f o r m a t i o n s .  growth t h r o u g h  M u s c o v i t e growth c o n t i n u e d a f t e r  formation of f i b r o l i t e aggregates,  the  j u d g i n g from the r e p l a c e m e n t t e x t u r e s  v i s i b l e a t h i g h e r metamorphic grades. Shuswap Summary The  Shuswap Complex near A z u r e Lake c o n t a i n s two r e g i o n a l l y developed  c o a x i a l phases of d e f o r m a t i o n . deformations  Minor s t r u c t u r e s a s s o c i a t e d w i t h both  plunge g e n t l y n o r t h w e s t and s o u t h e a s t .  the e a r l i e r P I d e f o r m a t i o n  Folds associated with  are i s o c l i n a l w i t h s h a l l o w l y d i p p i n g a x i a l  surfaces.  P2 minor f o l d s are u p r i g h t w i t h s t e e p l y d i p p i n g a x i a l  surfaces.  A l a r g e P2 a n t i f o r m i s p r e s e n t  area.  i n the w e s t e r n p a r t of the mapped  A l o c a l l y d e v e l o p e d l a t e f r a c t u r i n g and b r i t t l e f o l d i n g event  w i t h n o r t h t o n o r t h e a s t t r e n d s was  also  recognized.  T e x t u r a l r e l a t i o n s and i n c l u s i o n t r a i l p a t t e r n s i n d i c a t e t h a t r e g i o n a l metamorphism began d u r i n g the P I d e f o r m a t i o n i n t o the P2 d e f o r m a t i o n .  The  and p r o b a b l y  extended  s u b p a r a l l e l o r i e n t a t i o n o f mapped i s o g r a d s  and the P I s c h i s t o s i t y s u b s t a n t i a t e s a s s o c i a t i o n of metamorphism w i t h PI deformation.  the  P e l i t i c metamorphic assemblages range from k y a n i t e  t h r o u g h f i r s t s i l l i m a n i t e zones of the B a r r o v i a n f a c i e s s e r i e s . c o n d i t i o n s are estimated  t o be P = 7600 b a r s , T = 705°C, a„  n  Garnet i n c l u s i o n p a t t e r n s i n d i c a t e two s t a g e s o f growth.  =  Metamorphic 0.5. I n a more  40 detailed study of mineral zoning patterns and textural r e l a t i o n s (Pigage 1978, this volume), i t i s shown that the two growth periods may be related to a sequence of continuous and discontinuous reactions during a single prograde metamorphism. Q u a l i t a t i v e l y removing the folding effects of the P2 antiform i n the Azure Lake area shows that the PI s c h i s t o s i t y and metamorphic isograds were o r i g i n a l l y subhorizontal.  The increase i n metamorphic grade i s  therefore at least p a r t l y related to increasing depth of b u r i a l , but not necessarily to the stratigraphy. It i s suggested that the fault zone separating the Shuswap Complex from the adjacent cover sequence i s a tectonic s l i d e related to the PI f o l d geometry.  Formation of the fault zone i s probably related to  tightening of PI folds either late during the PI deformation or with P2 folding. Two coaxial deformation phases followed by a l o c a l l y developed fracturing event were also described for portions of the Shuswap Complex to the west (K.V. Campbell 1971; Fletcher 1972).  Fletcher considered the  regional metamorphism to have culminated after the second deformation. This i s l a t e r than the time i n t e r v a l suggested i n t h i s paper.  This  discrepancy i s p a r t l y related to the fact that he considered f i b r o l i t e aggregates to have formed after the growth of second stage garnets. Cover Deformation ( F l , F2, F3, F4) Four phases of deformation ( F l to F4) were recognized i n the cover sequence near Azure Lake.  Relative ages of the deformation phases have  been determined from refolded minor structures and cross-cutting cleavages.  Minor structures associated with each of the four phases are  present in varying i n t e n s i t y over the entire Azure Lake area.  41 Overturned i s o c l i n a l F l f o l d s a r e the e a r l i e s t r e c o g n i z e d i n the c o v e r sequence.  structures  M a j o r and minor f o l d s a r e accompanied by a  p e r v a s i v e F l a x i a l p l a n e s c h i s t o s i t y w h i c h forms t h e major metamorphic f o l i a t i o n i n the c o v e r sequence.  Minor f o l d s g e n e r a l l y plunge moderately  (30°) t o the n o r t h . F o l d s t y l e s o f F l minor f o l d s change s i g n i f i c a n t l y as t h e Shuswap Complex i s approached a l o n g a n o r t h - s o u t h t r a v e r s e .  I n the n o r t h e r n p a r t  of t h e Azure Lake a r e a F l minor f o l d s i n q u a r t z i t e u n i t s have l a r g e c o n c e n t r i c h i n g e zones w i t h no n o t i c e a b l e t h i c k e n i n g o f i n d i v i d u a l u n i t s ( f i g u r e 1-14).  FO p r i m a r y b e d d i n g ( c o l o r banding) i s r e a d i l y v i s i b l e i n  p h y l l i t e s and i s commonly a t an a c u t e a n g l e t o the F l s c h i s t o s i t y . Near t h e Shuswap Complex F l minor f o l d s i n the q u a r t z i t e u n i t s a r e i s o c l i n a l w i t h t h i c k e n e d , V-shaped h i n g e zones ( f i g u r e 1-15).  Fold limbs  a r e t h i n n e d t o the e x t e n t t h a t r o o t l e s s f o l d c o u p l e t s a r e common.  FO  p r i m a r y b e d d i n g i s no l o n g e r v i s i b l e i n the p h y l l i t e s ; F l minor f o l d s i n the p h y l l i t e s have been d e s t r o y e d by extreme f l a t t e n i n g w i t h d i s r u p t i o n o f the h i n g e zones.  The FO c o m p o s i t i o n a l l a y e r i n g i n t h e d i f f e r e n t  units  now r e p r e s e n t s t r a n s p o s e d p r i m a r y b e d d i n g . T h i s change i n F l f o l d s t y l e i s accompanied by an i n c r e a s e i n metamorphic grade a l o n g t h e same n o r t h - s o u t h t r a v e r s e .  The metamorphic  t r a n s i t i o n ranges from b i o t i t e - g a r n e t zone t o s t a u r o l i t e - k y a n i t e zone i n t h e B a r r o v i a n f a c i e s s e r i e s ( M i y a s h i r o 1961).  Isograds are not e a s i l y  d e f i n e d because b u l k c o m p o s i t i o n s o f the I s a a c and Cunningham F o r m a t i o n s p r e c l u d e development o f t h e c l a s s i c a l p e l i t e m i n e r a l assemblages. Metamorphic assemblages marking t h i s t r a n s i t i o n a r e p r e s e n t e d i n a subsequent s e c t i o n . S e v e r a l m a c r o s c o p i c F l f o l d s a r e d e f i n e d by the d i s t r i b u t i o n o f  Figure  1-14.  Large F l f o l d h i n g e i n i n t e r l a y e r e d p h y l l i t e and q u a r t z i t e .  F o l d i s l o c a t e d i n the n o r t h e r n p a r t o f the Azure Lake a r e a ( c o v e r sequence).  Dark u n i t s a r e p h y l l i t e s .  subhorizontal.  F l a x i a l plane s c h i s t o s i t y i s  The l i n e drawing i s t r a c e d from a photograph.  F i g u r e 1-15. quartzite.  I s o c l i n a l F l minor f o l d s i n i n t e r l a y e r e d s c h i s t and Stippled unit i s quartzite.  outcrop i s f o r s c a l e .  Hammer on r i g h t s i d e o f  F o l d s a r e l o c a t e d i n the cover sequence near  the Shuswap Complex, Azure L a k e , B r i t i s h Columbia. drawing i s t r a c e d  from a photograph.  The  line  44 l i t h o l o g i e s i n the A z u r e Lake a r e a . t r a c e s of the F l f o l d s .  most n o t i c e a b l e  F o r m a t i o n and  ( i n pocket) i n d i c a t e s a x i a l  The major f o l d s are c o m p l i c a t e d by numerous  p a r a s i t i c f o l d s on l i m b s and The  P l a t e 4-2  i n h i n g e areas of the l a r g e r s t r u c t u r e s .  f o l d s are the l a r g e s y n c l i n e c o r e d by the Cunningham  the a n t i c l i n e o u t l i n e d by the K a z a - I s a a c c o n t a c t  n o r t h e r n p a r t of the a r e a .  Both the s t r a t i g r a p h i c s u c c e s s i o n  i n the and  graded  b e d d i n g w i t h i n f e l d s p a t h i c g r i t s of the Kaza Group j u s t i f y the use t h e d e s c r i p t i v e terms s y n c l i n e and folds. map  a n t i c l i n e f o r these macroscopic  S i n c e the F l f o l d s plunge m o d e r a t e l y t o the n o r t h , the  pattern represents  viewed down-plunge.  a general  of  lithologic  c r o s s - s e c t i o n of the f o l d s t r u c t u r e when  D i s t r i b u t i o n of the f o l d s i n d i c a t e s t h a t the F l  s t r u c t u r e s are west-verging.  The  s y n c l i n e and  a n t i c l i n e are b o t h o f f s e t  some 6 km a l o n g a l a r g e r i g h t - l a t e r a l F3 f a u l t w h i c h r u n s t h r o u g h c e n t r a l p a r t of the A z u r e Lake The  area.  cover sequence c o n t a i n s  ( f i g u r e 1-4).  the  f i v e s t r u c t u r a l l y homogeneous domains  Domain 2e i s i s o l a t e d from the o t h e r s by the l a r g e F3  mentioned above.  Domain 2d i s s e p a r a t e d from the o t h e r s because  F3 f o l d i n g a p p r e c i a b l y Boundaries separating  scatters s t r u c t u r a l information  for that  fault  intense area.  the o t h e r domains c o r r e s p o n d t o a x i a l t r a c e s  of  macroscopic F l f o l d s . Figures FO  1-16  compositional  domains.  and  1-17  present stereographic  p r o j e c t i o n s of p o l e s t o  l a y e r i n g and F l a x i a l p l a n e s c h i s t o s i t y i n the d i f f e r e n t  Both FO and  F l planar  m o d e r a t e l y t o the n o r t h .  The  s t r u c t u r e s t r e n d e a s t - w e s t and  summary p r o j e c t i o n comparing the  f o r the d i f f e r e n t domains ( f i g u r e 1-22)  dip orientations  i l l u s t r a t e s the s u b p a r a l l e l  o r i e n t a t i o n s of FO and F l . Stereographic fold  p r o j e c t i o n s o f p o l e s t o F l a x i a l p l a n e s and F l minor  axes are i l l u s t r a t e d i n f i g u r e 1-18.  F l minor f o l d axes have  F i g u r e 1-16  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f p o l e s t o FO c o m p o s i t i l a y e r i n g i n t h e cover sequence (Azure Lake a r e a ) .  Domain 2a - 51 p o i n t s Domain 2b - 374 p o i n t s , 0.3-5-10-15-20% p e r 1% a r e a ; maximum average 90/32 N Domain 2c - 163 p o i n t s , 0.6-5-10-15-20% p e r 1% a r e a ; maximum average 72/26 N Domain 2d - 80 p o i n t s Domain 2e - 30 p o i n t s  F i g u r e 1-17  Equal a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f p o l e s t o F l a x i a l  plane  s c h i s t o s i t y i n t h e cover sequence (Azure Lake a r e a ) .  Domain 2a - 78 p o i n t s , 1.2-5-10-15-20% p e r 1% a r e a ; maximum 23% average 76/43 N Domain 2b - 446 p o i n t s , 0.2-5-10-15-20% p e r 1% a r e a ; maximum 29% average 86/33 N Domain 2c - 167 p o i n t s , 0.6-5-10-15-20% p e r 1% a r e a ; maximum 30% average 64/28 N Domain 2d - 28 p o i n t s Domain 2e - 32 p o i n t s  axial  plane  schistosity  49 v a r i a b l e plunge  w i t h i n the F l a x i a l p l a n e .  This pattern  probably r e s u l t s  from inhomogeneous f l a t t e n i n g of F l minor f o l d s (Ramsay 1962a) w h i c h o c c u r r e d e i t h e r l a t e i n the F l d e f o r m a t i o n o r w i t h t i g h t e n i n g o f F l f o l d s d u r i n g the F2 d e f o r m a t i o n .  S i n c e domain 2a c o n t a i n s the  f l a t t e n e d F l f o l d s (see above d i s c u s s i o n northwest plunge of F l minor s t r u c t u r e s least disturbed  least  on f o l d s t y l e s ) , the n o r t h to i n t h i s domain r e p r e s e n t s  p l u n g e d i r e c t i o n of F l f o l d s t r u c t u r e s  the  i n the A z u r e Lake  area. The  F2 d e f o r m a t i o n i s c h a r a c t e r i z e d  mesoscopic f o l d s .  by l o c a l l y d e v e l o p e d  In micaceous u n i t s F2 minor f o l d s a r e accompanied by  a x i a l plane c r e n u l a t i o n around F2 f o l d s and  cleavage.  Refolding  of F l minor  structures  d i s r u p t i o n of the F l s c h i s t o s i t y by the F2  c l e a v a g e b o t h denote the younger r e l a t i v e age F o l d s t y l e s v a r y depending on l i t h o l o g y .  an  crenulation  of the F2 d e f o r m a t i o n phase. I n marble and  p h y l l i t e units  F2 f o l d s a r e t y p i c a l l y V-shaped w i t h s l i g h t l y t h i c k e n e d h i n g e zones ( f i g u r e 1-19).  Minor f o l d s are not w e l l developed i n q u a r t z i t e s ; t h e y  concentric  w i t h e x t e n s i v e f r a c t u r i n g i n the h i n g e zone.  w h i t e q u a r t z s t r i n g e r s are abundant i n a r e a s of i n t e n s e These s t r i n g e r s are p a r a l l e l to F2 a x i a l p l a n e s .  are  Opaque p e g m a t i t i c F2  folding.  F2 minor f o l d s  c o n s i s t e n t l y have southwest v e r g e n c e . F i g u r e 1-20 structures.  presents stereographic projections  Structural orientations  discussed separately.  i n domain 2e are d i s t i n c t and w i l l  I n a l l o t h e r domains F2 a x i a l p l a n e s  a p p r o x i m a t e l y e a s t - w e s t and  dip steeply  to the n o r t h .  minor f o l d axes p l u n g e m o d e r a t e l y n o r t h w e s t . not  o f F2 minor  coaxial with e a r l i e r F l  be  trend  Lineations  and  These f o l d o r i e n t a t i o n s  structures.  F2 minor f o l d s i n domain 2e are c o a x i a l w i t h the e a r l i e r F l  are  F i g u r e 1-18  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f F l minor f o l d s t r u c t u r e s i n the c o v e r sequence (Azure Lake a r e a ) .  A l l domains - s o l i d c i r c l e s :  Domain 2a  Domain 2b  - open t r i a n g l e s :  F l minor f o l d axes  - f o l d axes  26 p o i n t s  - a x i a l planes  15 p o i n t s  - f o l d axes  92 p o i n t s  - a x i a l planes  73 p o i n t s  great c i r c l e :  Domain 2c  Domain 2e  86/33 N - maximum f o r F l s c h i s t o s i t y  - f o l d axes  38 p o i n t s  - a x i a l planes  39 p o i n t s  great c i r c l e :  Domain 2d  poles to F l a x i a l planes  74/26 N - maximum f o r F l s c h i s t o s i t y  - f o l d axes  7 points  - a x i a l planes  8 points  - f o l d axes  19 p o i n t s  - a x i a l planes  18 p o i n t s  F|  -minor  fold  structures  52  F i g u r e 1-19.  F2 minor f o l d s i n i n t e r l a y e r e d p h y l i i t e and m a r b l e .  areas o f these f o l d s c o n t a i n The l i n e drawing i s t r a c e d  Hinge  an F2 a x i a l p l a n e c r e n u l a t i o n c l e a v a g e .  from a photograph.  Figure  1-20  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s o f F2 minor s t r u c t u r e s i n t h e cover sequence (Azure Lake a r e a ) .  All  domains - s o l i d c i r c l e s :  p o l e s t o minor f o l d a x i a l p l a n e s and  c r e n u l a t i o n cleavage 2a - 2d  - open t r i a n g l e :  2e  - solid triangle: - open t r i a n g l e :  Domain 2a  Domain 2b  Domain 2c  Domain 2d  F2 l i n e a t i o n s , F2 l i n e a t i o n s ,  F2 minor f o l d axes  p o l e s t o F2 c r e n u l a t i o n c l e a v a g e  - f o l d axes  30 p o i n t s (300/40)  - a x i a l planes  50 p o i n t s (97/85 N)  - f o l d axes  172 p o i n t s (302/22)  - a x i a l planes  180 p o i n t s (114/85 N)  - f o l d axes  96 p o i n t s (296/22)  - a x i a l planes  91 p o i n t s (98/56 N)  - f o l d axes - a x i a l planes  Domain 2e  F2 minor f o l d axes  - f o l d axes  30 p o i n t s  - a x i a l planes  34 p o i n t s  55 structures. Figure  1-21  F2 minor f o l d s plunge g e n t l y n o r t h and have e a s t v e r g e n c e . i l l u s t r a t e s the i n t e r f e r e n c e p a t t e r n f o r F l and  F2 f o l d s f o r  t h i s domain. F3 minor s t r u c t u r e s are o n l y l o c a l l y developed i n the Azure Lake area.  N o r t h - p l u n g i n g minor f o l d s are accompanied by an a x i a l p l a n e  c r e n u l a t i o n cleavage or f r a c t u r e cleavage.  Some f o l d s a l s o have  gashes f i l l e d by q u a r t z ( q u a r t z i t e u n i t s ) or c a l c i t e F3 f o l d s are most e x t e n s i v e l y developed i n p h y l l i t e s . c o n c e n t r i c and have west v e r g e n c e .  P l a t e 1-9B  tension  (marble u n i t s ) . They a r e  generally  i l l u s t r a t e s an F2  crenulation  c l e a v a g e warped around an F3 minor f o l d ; t h i s g i v e s a r e l a t i v e age F3  for  the  deformation. F3 minor f o l d s c o n s i s t e n t l y o c c u r near s t e e p l y d i p p i n g ,  trending f a u l t s . small  north-  R i g h t - l a t e r a l d i s p l a c e m e n t a l o n g the f a u l t s i s g e n e r a l l y  (up t o 200 m).  v e r t i c a l movement.  S l i c k e n s i d e s on f a u l t s u r f a c e s The  s p a t i a l proximity  i n d i c a t e near-  of F3 minor f o l d s t o t h e s e  f a u l t s , the s u b p a r a l l e l o r i e n t a t i o n of b o t h s t r u c t u r e s , and sense of movement f o r f o l d s and  the  f a u l t s a l l suggest t h a t the F3  opposing deformation  phase i s c h a r a c t e r i z e d by a c o n j u g a t e f o l d - f a u l t system. As mentioned p r e v i o u s l y , the l a r g e f a u l t o f f s e t t i n g F l m a c r o s c o p i c f o l d s appears t o be an F3 s t r u c t u r e . a r e 158/27E and 96/60N. and  Measured a t t i t u d e s of t h i s  T h i s f a u l t a l s o t r u n c a t e s metamorphic  surface isograds  s t r u c t u r a l t r e n d s i n the Shuswap Complex j u s t n o r t h e a s t of O v i s Creek.  Apparent r i g h t - l a t e r a l d i s p l a c e m e n t a l o n g t h i s f a u l t i s a maximum of 6  1/2  km. F i g u r e 1-22  p r e s e n t s the s t e r e o g r a p h i c  p r o j e c t i o n of F3 minor  s t r u c t u r e s from a l l domains of the cover sequence. are s u b p a r a l l e l w i t h F3 minor f o l d a x i a l p l a n e s .  Measured f a u l t  surfaces  F3 minor f o l d s i n domain  56  F i g u r e 1-21. refolded  I s o c l i n a l F l f o l d s i n s c h i s t and q u a r t z i t e a r e c o a x i a l l y  around F2 f o l d s .  cover sequence.  Outcrop i s l o c a t e d i n domain 2e i n the  P h y l i i t e units are s t i p p l e d .  The l i n e drawing i s t r a c e d  from a photograph.  Note hammer f o r s c a l e .  Figure  1-22,  E q u a l a r e a s t e r e o g r a p h i c p r o j e c t i o n s of s t r u c t u r a l  elements i n the  cover sequence (Azure Lake a r e a ) .  Top  row:  L e f t - F3 minor f o l d s t r u c t u r a l - open t r i a n g l e : - open square:  e l e m e n t s , a l l domains  F3 l i n e a t i o n s ,  90 p o i n t s  p o l e s to F3 f a u l t s u r f a c e s  - solid circle:  3 points  p o l e s to F3 a x i a l p l a n a r s u r f a c e s  R i g h t - F4 minor f o l d s t r u c t u r a l - open t r i a n g l e : - solid circle:  Bottom  F3 minor f o l d axes  142 p o i n t s  e l e m e n t s , a l l domains  F4 l i n e a t i o n s ,  F4 minor f o l d axes  20 p o i n t s  p o l e s to F4 p l a n a r s u r f a c e s  28 p o i n t s  row:  L e f t - Composite diagram of F0 and F l p o l e s t o p l a n a r s u r f a c e s from domains 2a, 2b, and - horizontal ruling: - vertical ruling:  2c.  F l a x i a l plane s c h i s t o s i t y  F0 c o m p o s i t i o n a l l a y e r i n g (20%  R i g h t - S t r e s s a n a l y s i s f o r box abbreviations:  (20%  °i  >  a  contour)  contour)  f o l d near Twin S p i r e s . 2  >  CT  3  c  o  m  P  r  e  s  s  i  f l - F l a x i a l plane  v  e  s t r e s s axes,  schistosity,  a p l , ap2 - a x i a l p l a n e o r i e n t a t i o n s o f the fold.  box  cn  oo  59 2d verge e a s t ; i n t h i s r e g i o n f o l d i n g r a t h e r t h a n f a u l t i n g has been t h e dominant F3 d e f o r m a t i o n  style.  S i n c e F3 f a u l t d i s p l a c e m e n t  i s l a r g e r than F3 f o l d movement i n the  A z u r e Lake a r e a , the net e f f e c t o f the F3 d e f o r m a t i o n i s to c o u n t e r a c t t h e northwest  plunge o f F2 s t r u c t u r e s .  I n most of the A z u r e Lake a r e a F4 minor s t r u c t u r e s c o n s i s t o f n e a r v e r t i c a l northeast-trending fractures.  Near Twin S p i r e s these f r a c t u r e s  a r e a x i a l p l a n a r to a n g u l a r , V-shaped f o l d s w i t h r u p t u r e d h i n g e Conjugate box  zones.  f o l d s a r e common i n s l a b b y q u a r t z i t e u n i t s of the Yankee  B e l l e Formation  ( f i g u r e 1-23).  F i g u r e 1-22  depicts a stress analysis for  one of the box f o l d s t r u c t u r e s n e a r Twin S p i r e s (Ramsay 1962b). expected  from the b r i t t l e f o l d p a t t e r n , the major compressive  l i e s i n the F0-F1  As  s t r e s s (a^)  surface.  Cover Metamorphism P e l i t i c m i n e r a l assemblages i n the cover sequence o u t l i n e a metamorphic t r a n s i t i o n from g a r n e t - b i o t i t e through s t a u r o l i t e - k y a n i t e zones i n the B a r r o v i a n f a c i e s s e r i e s . toward  the s o u t h .  Metamorphic grade and g r a i n s i z e i n c r e a s e  P a r a g o n i t e , m a r g a r i t e , and m u s c o v i t e  d i s t i n g u i s h e d u s i n g x ^ r a y d i f f r a c t i o n peaks suggested (1971).  I n carbonate  were  by C h a t t e r j e e  assemblages x-ray t r a c e s were r u n on  insoluble  residues. A l l metamorphic assemblages i n the cover sequence have been s u b j e c t e d t o a l a t e r e t r o g r a d e metamorphism.  Porphyroblasts of garnet, b i o t i t e ,  and c h l o r i t o i d a r e p a r t i a l l y to c o m p l e t e l y a l t e r e d t o a f i n e - g r a i n e d , i n t e r l o c k i n g matte o f s e r i c i t e and c h l o r i t e . rimmed by f i n e - g r a i n e d s e r i c i t e .  K y a n i t e and s t a u r o l i t e  The random o r i e n t a t i o n o f  these  are  F i g u r e 1-23.  F4 minor f o l d s developed i n s l a b b y q u a r t z i t e s o f the  Yankee B e l l e F o r m a t i o n . n e a r Twin S p i r e s .  F o l d s a r e l o c a t e d i n the c o v e r sequence  The l i n e drawing i s t r a c e d from a photograph.  61 a l t e r a t i o n r i m s i n d i c a t e s t h a t t h e r e t r o g r a d i n g o c c u r r e d a f t e r the main t e c t o n i c a c t i v i t y f o r the Azure Lake a r e a ; r e t r o g r a d i n g was  definitely  l a t e r than the F2 and p r o b a b l y l a t e r than the F3 d e f o r m a t i o n I s o g r a d s f o r the r e g i o n a l metamorphic t r a n s i t i o n d e f i n e d because t h e I s a a c and Cunningham Formations  phase.  a r e not  easily  have b u l k  compositions  w h i c h p r e c l u d e development of the c l a s s i c a l p e l i t e assemblages. I s a a c Formation  The  t y p i c a l l y c o n t a i n s p a r a g o n i t e - b e a r i n g assemblages.  B i o t i t e i s n o t a b l y absent  from the p h y l l i t e s .  G u i d o t t i (1968) has shown  t h a t p a r a g o n i t e t y p i c a l l y o c c u r s i n h i g h l y aluminous r o c k s w h i c h o n l y r a r e l y c o n t a i n b i o t i t e and p l a g i o c l a s e . C a l c a r e o u s c o m p o s i t i o n s Cunningham F o r m a t i o n  i n the  a l s o l i m i t development o f p e l i t e m i n e r a l o g y .  In the  subsequent d i s c u s s i o n of metamorphic zones, m i n e r a l assemblages from the Kaza Group a r e p r e s e n t e d f i r s t s i n c e t h i s u n i t does c o n t a i n t h e  pelite  i n d e x m i n e r a l s t y p i c a l of B a r r o v i a n metamorphism. Table 1-3  c o n t a i n s m i n e r a l assemblages i n the Kaza Group f o r the  d i f f e r e n t metamorphic zones.  F i g u r e 1-4  o f the zones i n the A z u r e Lake a r e a . Thompson 1957)  shows the a p p r o x i m a t e l o c a t i o n s  Schematic AFM  p r o j e c t i o n s (J.B.  o f t h e d i f f e r e n t assemblages a r e shown i n f i g u r e  1-24.  The g a r n e t - b i o t i t e zone has d i f f e r e n t c h a r a c t e r i s t i c s i n the n o r t h e r n and s o u t h e r n p o r t i o n s o f the cover sequence.  I n the n o r t h o n l y  t h e q u a r t z i t e u n i t s c o n t a i n the t h r e e phase assemblage c h l o r i t e - b i o t i t e garnet (muscovite-quartz). chlorite.  P h y l l i t e s t y p i c a l l y contain only b i o t i t e -  T h i s d i f f e r e n c e i s r e l a t e d t o b u l k c o m p o s i t i o n as shown  s c h e m a t i c a l l y i n f i g u r e 1-24. t h e s e assemblages i s a l b i t e .  The p l a g i o c l a s e f e l d s p a r c o e x i s t i n g w i t h I n the g r i t s the l a r g e f e l d s p a r  p o r p h y r o c l a s t s a r e a l b i t e , and the m a t r i x p l a g i o c l a s e r e t a i n s o r i g i n a l c o m p o s i t i o n of An^^-An^^.  an  62  Table 1-3.  Metamorphic mineral assemblages in the cover sequence, Azure Lake, British Columbia.  Kaza Group Garnet-Biotite zone (North) chlorite-muscovite-quartz  ± biotite ± garnet ± albite  Garnet-Biotite zone (South) chlorite-biotite-garnet-muscovite-quartz-plagioclase calcite-muscovite-quartz-plagioclase-carbon-pyrite/pyrrhotite ± chlorite Staurolite-Kyanite zone chlorite-biotite-garnet-muscovite-quartz-plagioclase ± staurolite ± kyanite calcite-muscovite-quartz-carbon-pyrite/pyrrhotite ± chlorite  ± plagioclase  Isaac Formation Garnet-Biotite zone chlorite-muscovite-quartz  ± paragonite  chlorite-muscovite-quartz  ± garnet ± chloritoid ± paragonite  calcite-muscovite-quartz  ± paragonite ± margarite  calcite-muscovite-quartz-chlorite-plagioclase ± biotite ± hornblende ± garnet ± clinozoisite Cunningham Formation Garnet-Biotite zone calcite-muscovite-quartz  ± plagioclase ± paragonite ± margarite  calcite-muscovite-quartz-dolomite  iplagioclase  calcite-muscovite-quartz-biotite ± garnet ± hornblende ± plagioclase ± clinozoisite ± chlorite  63 I n the s o u t h b o t h p h y l l i t e and q u a r t z i t e u n i t s w i t h i n the Kaza Group c o n t a i n l a r g e g a r n e t s c o e x i s t i n g w i t h b i o t i t e and c h l o r i t e .  Figure  1-24  shows t h a t t h i s r e s u l t s from the s y s t e m a t i c change o f c h l o r i t e and b i o t i t e t o more magnesian c o m p o s i t i o n s d u r i n g prograde metamorphism. t r e n d has a l s o been n o t e d by A t h e r t o n (1968).  T h i s same  T h i s t r a n s i t i o n i s not  c o n s i d e r e d an i s o g r a d s i n c e the t o p o l o g y o f the AFM p r o j e c t i o n has not changed ( J . B . Thompson 1957). has  P l a g i o c l a s e i n the s c h i s t s and q u a r t z i t e s  c o m p o s i t i o n s r a n g i n g from An2^-An^Q. The t r a n s i t i o n t o the s t a u r o l i t e - k y a n i t e zone i s marked by the l o c a l  appearance of s t a u r o l i t e and/or k y a n i t e w i t h the above assemblage. f u l l assemblage i s shown i n f i g u r e  The  1-24.  Carbonate u n i t s i n the Kaza Group o c c u r o n l y i n t h e h i g h e r t e m p e r a t u r e p a r t o f t h e g a r n e t - b i o t i t e zone and i n t h e s t a u r o l i t e - k y a n i t e zone.  The  metamorphic assemblage i s the same i n b o t h zones and i s i n d i c a t e d i n T a b l e 1-3. Both the I s a a c and Cunningham Formations o c c u r e n t i r e l y w i t h i n the g a r n e t - b i o t i t e zone.  Metamorphic assemblages f o r t h e s e two f o r m a t i o n s a r e  p r e s e n t e d i n T a b l e 1-3.  Common a c c e s s o r y m i n e r a l s f o r p h y l l i t e  assemblages a r e a p a t i t e , t o u r m a l i n e , z i r c o n , and p y r i t e / p y r r h o t i t e . R u t i l e , c a r b o n , and p y r i t e / p y r r h o t i t e are a c c e s s o r y m i n e r a l s i n the c a l c a r e o u s assemblages.  The carbon phase i s not c a l l e d g r a p h i t e because  i t s c r y s t a l l i n e form has n o t been v e r i f i e d .  P y r i t e and/or p y r r h o t i t e a r e  b o t h p r e s e n t i n t h e d i f f e r e n t assemblages.  The f o l l o w i n g s e c t i o n c o n t a i n s  s e v e r a l comments on t h e d i f f e r e n t assemblages. P e l i t i c assemblages i n t h e I s a a c F o r m a t i o n i n d i c a t e A l - r i c h b u l k c o m p o s i t i o n s ( G u i d o t t i 1968).  C h l o r i t o i d p o r p h y r o b l a s t s o c c u r o n l y i n one  s t r a t i g r a p h i c i n t e r v a l i n the l o w e r member of the I s a a c F o r m a t i o n : i t s  64  GARNET-BIOTITE  GARNET-BIOTITE  Bio  F i g u r e 1-24. Schematic AFM p r o j e c t i o n s o f p e l i t i c m i n e r a l assemblages i n the Kaza Group f o r the d i f f e r e n t metamorphic zones i n t h e c o v e r sequence, Azure Lake, B r i t i s h Columbia.  T r i a n g l e corresponds to p h y l l i t e / s c h i s t ,  and c i r c l e r e p r e s e n t s q u a r t z i t e .  65 r e s t r i c t e d occurrence  i s r e l a t e d to h i g h - A l , high-Fe bulk  compositions  (Hoschek 1967). M a r g a r i t e i s r e s t r i c t e d t o c a l c a r e o u s assemblages i n b o t h  formations.  Within calcareous u n i t s margarite i s u s u a l l y subordinate to paragonite. Green hornblende g a r b e n s c h i e f e r a r e common i n c a l c a r e o u s  phyllites.  Hornblende h a s t y p i c a l l y been a l t e r e d t o aggregates o f c h l o r i t e , q u a r t z , c a l c i t e , opaques, and c l i n o z o i s i t e .  M a r g i n a l zones between c a l c a r e o u s and  p e l i t i c assemblages have sharp b o u n d a r i e s  w i t h no a p p a r e n t r e a c t i o n .  Because o f t h e numerous d e f o r m a t i o n sequence, i t i s i m p o r t a n t  phases p r e s e n t i n t h e cover  t o r e l a t e t h e n u c l e a t i o n and growth o f  metamorphic m i n e r a l s t o t h e d i f f e r e n t d e f o r m a t i o n e p i s o d e s .  T a b l e 1-4  summarizes t h e v a r i o u s o b s e r v a t i o n s on m i n e r a l t e x t u r e s and i n c l u s i o n p a t t e r n s i n t h e c o v e r sequence.  trail  These t e x t u r e s a r e d i s c u s s e d i n t h e  following sections. Porphyroblasts of garnet, c h l o r i t o i d , b i o t i t e , hornblende, and k y a n i t e a l l have s i m i l a r i n c l u s i o n p a t t e r n s and t e x t u r e s .  staurolite, Inclusion  t r a i l s a r e p l a n a r o r s l i g h t l y S-shaped (see p l a t e s 1-6A, 1-6B, 1-7A).  These  t r a i l s a r e continuous w i t h the e x t e r n a l F l s c h i s t o s i t y although r o t a t e d relative to i t .  Q u a r t z - r i c h p r e s s u r e shadows w i t h i n t h e F l s c h i s t o s i t y  a r e common around these p o r p h y r o b l a s t s .  I n one i n s t a n c e a k y a n i t e g r a i n i s  f r a c t u r e d by t h e F3 c r e n u l a t i o n c l e a v a g e . These d i f f e r e n t t e x t u r e s p l a c e m i n e r a l growth d u r i n g and a f t e r t h e F l d e f o r m a t i o n phase (Zwart 1960a, 1960b).  Rotation of the i n c l u s i o n  r e l a t i v e t o t h e e x t e r n a l F l s c h i s t o s i t y r e s u l t e d from f l a t t e n i n g 1962a; P o w e l l and Treagus 1970).  trails  (Ramsay  F l a t t e n i n g probably occurred w i t h  t i g h t e n i n g of F l folds e i t h e r l a t e during F l deformation  o r w i t h F2 f o l d i n g .  W i t h i n c r e a s e d f l a t t e n i n g toward t h e s o u t h (see s e c t i o n on  deformation)  66  Table 1 - 4 .  R e l a t i o n o f m i n e r a l growth t o phases o f d e f o r m a t i o n i n the  cover sequence, A z u r e L a k e , B r i t i s h Columbia.  B i o t i t e ( p ) r e f e r s to  p o r p h y r o b l a s t i c b i o t i t e , and b i o t i t e ( m ) t o m a t r i x b i o t i t e .  F  SYNCHLORITE MUSCOVITE BIOTITE (p) BIOTITE (m) GARNET CHLORITOID STAUROLITE KYANITE  l  F  POST- SYN-  2 POST- SYN-  F  3 POST- SYN-  F  4 POST-  67 b i o t i t e porphyroblasts ( p l a t e 1-7B).  form e l o n g a t e augen w i t h i n t h e F l s c h i s t o s i t y  B i o t i t e a l s o o c c u r s as narrow, e l o n g a t e  grains intermixed  w i t h m u s c o v i t e and c h l o r i t e i n t h e m a t r i x o f s c h i s t s and q u a r t z i t e s . f o r m o c c u r s o n l y i n t h e h i g h e r grade zones n e a r t h e Complex.  This  Biotite  g r a i n s a r e r e c r y s t a l l i z e d t o form p o l y g o n a l a r c s around F2 m i c r o f o l d s and crenulations. M u s c o v i t e and c h l o r i t e t y p i c a l l y occur as narrow e l o n g a t e the m a t r i x .  flakes i n  These g r a i n s d e f i n e t h e F l , F 2 , and F3 s c h i s t o s i t i e s .  R e c r y s t a l l i z e d g r a i n s form p o l y g o n a l a r c s around F2 and F3 m i c r o f o l d s and c r e n u l a t i o n s ( p l a t e 1-8).  O c c a s i o n a l l y f i n e - g r a i n e d narrow m u s c o v i t e  f l a k e s form s t r o n g l y c r e n u l a t e d p o l y g o n a l a r c s around F l m i c r o f o l d s . some i n s t a n c e s these f i n e micas have been t r a n s p o s e d w i t h t h e dominant F l s c h i s t o s i t y .  until  These m u s c o v i t e s p r e d a t e  In  concordant the F l  s c h i s t o s i t y and may be s u b p a r a l l e l t o t h e o r i g i n a l b e d d i n g FO. E l e c t r o n m i c r o p r o b e x - r a y scans f o r Na show t h a t p a r a g o n i t e i s i n t i m a t e l y i n t e r g r o w n w i t h m u s c o v i t e a l o n g t h e 001 d i r e c t i o n . p a r a g o n i t e g r a i n s a r e up t o 10 micrometres t h i c k .  Typically  I t i s assumed t h a t t h e  few c a l c a r e o u s u n i t s c o n t a i n i n g m u s c o v i t e and m a r g a r i t e have a s i m i l a r intergrowth texture. C h l o r i t e a l s o o c c u r s as l a r g e equant t o e l o n g a t e twinning.  flakes with lamellar  These l a r g e g r a i n s d e f i n e the F2-F3 s c h i s t o s i t i e s o r a r e  randomly o r i e n t e d .  I n many i n s t a n c e s t h e randomly o r i e n t e d g r a i n s c o n t a i n  s p a r s e t o abundant k i n k bands. The m i c a t e x t u r e s o u t l i n e a c o n t i n u e d sequence o f growth and r e c r y s t a l l i z a t i o n extending  from t h e F l through t h e F3  deformations.  M u s c o v i t e and c h l o r i t e were s t a b l e through a l l t h r e e d e f o r m a t i o n s . was s t a b l e o n l y d u r i n g t h e F l and F2 d e f o r m a t i o n s .  Textures  i n the  p o r p h y r o b l a s t i c m i n e r a l s i n d i c a t e t h a t the r e g i o n a l metamorphism  Biotite  68 c u l m i n a t e d d u r i n g and a f t e r the F l d e f o r m a t i o n . Cover Metamorphic C o n d i t i o n s M i n e r a l assemblages i n the cover sequence s t r a d d l e the  transition  from c h l o r i t o i d - b e a r i n g assemblages to s t a u r o l i t e - b e a r i n g assemblages. Broad l i m i t s on metamorphic c o n d i t i o n s are p r o v i d e d by p u b l i s h e d e x p e r i m e n t a l s t u d i e s and oxygen i s o t o p e thermometry.  Figure  1-25  i l l u s t r a t e s the experimental r e a c t i o n s p e r t i n e n t to t h i s d i s c u s s i o n . Q i s assumed e q u a l t o Prr-otal" FMQ  or NNO  solid buffers.  Where a p p l i c a b l e f ^  The A l S i 0 2  5  was  b u f f e r e d by  diagram by Holdaway (1971) was  s e l e c t e d because i t i s most c o m p a t i b l e w i t h r e c e n t c a l o r i m e t r y (Anderson, Newton, and K l e p p a  1977).  Ganguly (1969) has shown t h a t the d i f f e r e n t r e a c t i o n s m a r k i n g the breakdown of c h l o r i t o i d t o form s t a u r o l i t e a l l o c c u r w i t h i n a narrow temperature  interval.  temperature  range f o r the t h r e e r e a c t i o n s i n v o l v i n g c h l o r i t o i d and/or  staurolite.  T h i s i s c o n f i r m e d i n f i g u r e 1-25  R e a c t i o n (1) was  by the narrow  reversed using n a t u r a l minerals (with  c o m p o s i t i o n s w h i c h a r e p r o b a b l y s i m i l a r t o t h o s e from t h e A z u r e Lake a r e a ) (Hoschek 1969).  The o t h e r two r e a c t i o n s used Fe-endmember c o m p o s i t i o n s .  S i n c e Fe-Mg p a r t i t i o n i n g between c h l o r i t o i d and s t a u r o l i t e i s almost (Albee 1972), s o l i d s o l u t i o n would not a p p r e c i a b l y d i s p l a c e t h e s e e x p e r i m e n t a l l y determined  curves.  E s t i m a t e d metamorphic  based on t h e s e r e a c t i o n s range from 540° t o 580° C.  1.0  two  temperatures  Experimental  curves  f o r the s t a b i l i t y l i m i t s o f m a r g a r i t e - q u a r t z and p a r a g o n i t e - q u a r t z are b o t h g e n e r a l l y c o m p a t i b l e w i t h these t e m p e r a t u r e s .  More d e t a i l e d a n a l y s i s  w i l l not be p o s s i b l e u n t i l c o m p o s i t i o n s of c o e x i s t i n g m a r g a r i t e , p a r a g o n i t e , and p l a g i o c l a s e a r e known. The c o e x i s t e n c e o f k y a n i t e w i t h s t a u r o l i t e i n t h e K a z a Group p r o v i d e s  F i g u r e 1-25.  Experimental reactions defining  pressure-temperature  c o n d i t i o n s i n the cover sequence d u r i n g r e g i o n a l metamorphism (Azure Lake area).  P„ H^O  n  = P  Al Si0 2  5  m  ^ n • Total  R e a c t i o n s are from the f o l l o w i n g r e f e r e n c e s :  system  Margarite reactions  (Holdaway  1971)  ( C h a t t e r j e e 1976)  P a r a g o n i t e + Quartz = H i g h - a l b i t e + A^SiO,. + Vapor ( C h a t t e r j e e 1972) 1)  C h l o r i t o i d + S i l l i m a n i t e = S t a u r o l i t e + Q u a r t z + Vapor (Richardson  2)  C h l o r i t e + M u s c o v i t e = S t a u r o l i t e + B i o t i t e + Q u a r t z + Vapor (Hoschek  3)  1968)  1969)  C h l o r i t o i d + Quartz = S t a u r o l i t e + Almandine + Vapor (Ganguly  1969)  P a r a l l e l o g r a m o u t l i n e s e s t i m a t e d metamorphic c o n d i t i o n s f o r the Shuswap Metamorphic Complex i n the Azure Lake a r e a (Pigage 1978, t h i s Abbreviations:  volume).  Ab-high a l b i t e , A n - a n o r t h i t e , A n d - a n d a l u s i t e , K y - k y a n i t e ,  S i l l - s i l l i m a n i t e , L a w s - l a w s o n i t e , Ma-margarite,  Pa-paragonite,  Q t z - q u a r t z , Z o - z o i s i t e , A l s - A ^ S i O , - , V-vapor(t^O) .  70  71  a minimum pressure l i m i t of 4.5 kilobars for the cover sequence. pressure l i m i t i s much less t i g h t l y controlled.  An upper  Chatterjee (1976) has  calculated an upper s t a b i l i t y l i m i t of 7 to 8.6 k i l o b a r s for the assemblage margarite-quartz (see figure 1-25).  This upper l i m i t would  s h i f t to higher pressures with margarite s o l i d solution and lower pressures with reduced E^O a c t i v i t i e s .  An upper l i m i t of 9 kilobars seems  reasonable e s p e c i a l l y when considering possible e f f e c t s of reduced H^O a c t i v i t i e s i n calcareous assemblages. O'Neil and Ghent (1975) have completed oxygen isotope analysis of s i m i l a r metamorphic  assemblages from the Esplanade Range, B r i t i s h Columbia.  Mineral assemblages i n the Esplanades range from c h l o r i t o i d - b i o t i t e through s t a u r o l i t e - b i o t i t e zones.  Using the c a l i b r a t i o n by Bottinga and  Javoy (1973), they arrived at consistent temperatures of 490° C for the garnet zone and 540° C for the s t a u r o l i t e - b i o t i t e zone.  These temperatures  are similar to the estimates presented i n figure 1-25. Cover Summary The cover sequence near Azure Lake contains evidence of four phases of deformation (F1-F4). moderately northward.  I s o c l i n a l , west-verging F l macroscopic folds plunge These e a r l i e s t structures are accompanied by a  pervasive a x i a l plane s c h i s t o s i t y .  F2 minor folds plunge gently northwest  and consistently have southwest vergence.  The F2 folds are accompanied by  a steeply dipping a x i a l plane crenulation cleavage. are only l o c a l l y developed.  F3 structures consist of a north-trending  conjugate f o l d - f a u l t system. faults offset metamorphic Shuswap Complex.  F3 and F4 structures  Minor F3 structures are n e a r - v e r t i c a l .  F3  isograds i n both the cover sequence and the  F4 structures consist of fractures and angular folds  with ruptured hinge zones.  These structures consistently trend northeast.  72 Mineral assemblages i n the d i f f e r e n t units outline a t r a n s i t i o n from garnet-biotite zone into the staurolite-kyanite zone i n the Barrovian facies s e r i e s . the Kaza Group.  C l a s s i c a l p e l i t e mineralogy i s developed largely within The Isaac Formation i s highly aluminous and commonly  develops paragonite-bearing assemblages.  The calcareous composition of  the Cunningham Formation also precludes development of p e l i t e mineralogy. Oxygen isotope thermometry of other similar rocks and published experimental studies place broad l i m i t s on metamorphic conditions within the cover sequence.  Estimated temperatures range from 490° C (garnet-biotite zone)  to 580° C (staurolite-kyanite zone).  Pressure l i m i t s are less constrained;  they range from 4.5 to 9 k i l o b a r s . Textural r e l a t i o n s and i n c l u s i o n t r a i l patterns indicate that the regional metamorphism began during the F l deformation. into the F2 deformation.  B i o t i t e was  stable  R e c r y s t a l l i z a t i o n of muscovite and c h l o r i t e  during the F3 deformation indicates that lower greenschist facies conditions prevailed during that deformation. affected by a l a t e retrograde metamorphism.  A l l assemblages have been The major v i s i b l e e f f e c t of  retrograding i s p a r t i a l to complete a l t e r a t i o n rims of f i n e c h l o r i t e and/ or s e r i c i t e around porphyroblastic minerals. These s t r u c t u r a l and metamorphic t r a n s i t i o n s outline a large scale asymmetry associated with the F l deformation.  F l folds have undergone more  extensive f l a t t e n i n g closer to the Shuswap Complex.  Increasing metamorphic  temperatures near the Complex allowed the various rock units to behave i n a more ductile fashion, r e s u l t i n g i n increased f l a t t e n i n g and i n t e n s i t y of deformation.  This asymmetry i s substantiated by the 5 to 1 thickness r a t i o  for the Isaac Formation on the north and south limbs of the F l syncline containing the Cunningham Formation.  73 COVER-COMPLEX CORRELATION  Lack o f s t r a t i g r a p h i c c o n t i n u i t y between t h e cover sequence and t h e Shuswap Complex means t h a t e a r l y metamorphic and d e f o r m a t i o n each p r o v i n c e cannot be d i r e c t l y c o r r e l a t e d .  events i n  I n the f o l l o w i n g d i s c u s s i o n  the two p r o v i n c e s a r e c o r r e l a t e d through s i m i l a r i t i e s i n t h e metamorphicd e f o r m a t i o n r e l a t i o n s w i t h i n each p r o v i n c e .  I t i s shown t h a t t h e r e i s no  d i s c e r n i b l e d i f f e r e n c e i n t h e metamorphic and d e f o r m a t i o n p a t t e r n s a c r o s s t h e f a u l t zone s e p a r a t i n g t h e p r o v i n c e s . C o r r e l a t i o n o f metamorphic and d e f o r m a t i o n events does n o t i m p l y strict  t i m e - e q u i v a l e n c e f o r these events i n b o t h p r o v i n c e s .  It is  r e c o g n i z e d t h a t d e f o r m a t i o n and metamorphism a r e d i a c h r o n o u s when developed over a l a r g e a r e a .  However, i t i s assumed t h a t metamorphic and t e c t o n i c  events are approximately time-equivalent w i t h i n a f a i r l y r e s t r i c t e d area. T a b l e 1-5 l i s t s t h e d i f f e r e n t metamorphic and d e f o r m a t i o n events i n t h e Shuswap Complex and t h e c o v e r sequence.  The two p r o v i n c e s must have  assumed t h e i r p r e s e n t g e o m e t r i c c o n f i g u r a t i o n b e f o r e t h e F3 d e f o r m a t i o n phase because t h e l a r g e F3 f a u l t i n t h e c e n t r a l p a r t o f t h e a r e a c o n t i n u e s u n d i s t u r b e d through b o t h t h e Complex and t h e cover sequence. S i m i l a r d e f o r m a t i o n s t y l e s and s t r u c t u r a l t r e n d s i n d i c a t e t h a t F3 and F4 i n t h e cover sequence must b o t h c o r r e l a t e w i t h t h e P3 d e f o r m a t i o n phase i n the Complex.  I n b o t h p r o v i n c e s t h e s e d e f o r m a t i o n phases c o n s i s t o f l a t e  f r a c t u r e s and b r i t t l e f o l d s w i t h n o r t h and n o r t h e a s t t r e n d s .  F3 and F4  c o u l d be d i f f e r e n t i a t e d i n t h e cover sequence b u t were combined when mapping i n t h e Shuswap Complex. Comparison o f t h e e a r l i e r metamorphic and d e f o r m a t i o n events i n T a b l e 1-5 shows s t r i k i n g s i m i l a r i t i e s between t h e two p r o v i n c e s . metamorphism  The r e g i o n a l  i n b o t h domains i s a s s o c i a t e d l a r g e l y w i t h t h e e a r l i e s t phase  74  Table  1-5.  Correlation  o f d e f o r m a t i o n and metamorphism  Shuswap C o m p l e x a n d t h e c o v e r  sequence, Azure Lake, B r i t i s h  SHUSWAP  P3 DEFORMATION  between  the  Columbia.  COVER F4  DEFORMATION  F  DEFORMATION  3  LATE JURASSIC INTRUSIONS P  2  DEFORMATION  REGIONAL P|  METAMORPHISM  DEFORMATION  F  2  DEFORMATION  REGIONAL F|  METAMORPHISM  DEFORMATION  75 of d e f o r m a t i o n .  I n b o t h cases metamorphic r e c r y s t a l l i z a t i o n appeared t o  o u t l a s t the f i r s t deformation.  Metamorphic grade i n b o t h p r o v i n c e s ' •  i n c r e a s e s i n t h e same g e n e r a l d i r e c t i o n ,  and metamorphic assemblages  a c r o s s t h e f a u l t zone s e p a r a t i n g t h e p r o v i n c e s a r e r o u g h l y e q u i v a l e n t . The second d e f o r m a t i o n phase i n b o t h p r o v i n c e s have s i m i l a r and f o l d i n g  styles.  near-vertical  I n b o t h p r o v i n c e s t h e minor f o l d s  a x i a l plane surfaces.  trends  are upright with  Furthermore v e r g e n c e s o f minor  a s s o c i a t e d w i t h t h e second d e f o r m a t i o n have t h e same o r i e n t a t i o n  folds  across  the f a u l t zone s e p a r a t i n g t h e two p r o v i n c e s . Because o f these s i m i l a r i t i e s I c o n s i d e r t h e s t r u c t u r a l and metamorphic p a t t e r n s t o be c o n t i n u o u s a c r o s s t h e f a u l t zone s e p a r a t i n g t h e two p r o v i n c e s .  T h e r e f o r e t h e P I and P2 d e f o r m a t i o n s  c o r r e l a t e d w i t h t h e F l and F2 d e f o r m a t i o n s metamorphic assemblages i n each p r o v i n c e  i n t h e Complex a r e  i n t h e cover sequence.  Regional  a r e a s s o c i a t e d w i t h t h e same  metamorphic event. The f a u l t zone s e p a r a t i n g t h e two p r o v i n c e s i s c o n s i d e r e d t o be a tectonic slide related of F2-P2 minor f o l d s  t o t h e P I f o l d geometry.  The c o n s i s t e n t vergence  a c r o s s t h e f a u l t zone suggests t h a t i n i t i a l  f o r m a t i o n o f t h e s l i d e preceded  t h e F2 d e f o r m a t i o n .  Comparison o f  e s t i m a t e d metamorphic c o n d i t i o n s i n each p r o v i n c e near t h e s l i d e shows a temperature  d i s c r e p a n c y o f r o u g h l y 100° C a c r o s s t h e f a u l t zone.  e s t i m a t e d s e p a r a t i o n a c r o s s ; t h i s slide..may.be temperature  An  c a l c u l a t e d from t h i s  gap ;using e s t i m a t e d metamorphic temperature  gradients f o r  the Azure Lake a r e a . A rough e s t i m a t e o f t h e metamorphic temperature  g r a d i e n t was  c a l c u l a t e d by measuring t h e t h i c k n e s s o f t h e g a r n e t - b i o t i t e zone. I s o g r a d s were assumed t o be p a r a l l e l t o t h e F l s c h i s t o s i t y .  The  resulting  E s t i m a t e i s a maximum v a l u e because t h e n o r t h e r n boundary o f t h e g a r n e t b i o t i t e zone may be l o c a t e d n o r t h o f t h e mapped a r e a . zone was assumed t o encompass t h e temperature 580° C.  The g a r n e t - b i o t i t e  range between 490° C and  The c a l c u l a t e d g r a d i e n t i s 15° C/km; t h i s g r a d i e n t i s comparable  t o t h e r e c e n t l y c a l c u l a t e d metamorphic temperature (P. Thompson 1976).  gradient f o r the Alps  Using t h i s gradient the separation recorded along  t h e t e c t o n i c s l i d e i s on t h e o r d e r o f 7 km; i t i s r e a s o n a b l e t o c o n s i d e r t h e s e p a r a t i o n as b e i n g 10 km o r l e s s .  A c t u a l displacement along the  s l i d e i s p r o b a b l y much l a r g e r because t h e s l i d e s u r f a c e i s a p p r o x i m a t e l y p a r a l l e l t o t h e metamorphic i s o g r a d s . A l t h o u g h t h e F l ( c o v e r sequence) and P I (Shuswap Complex) d e f o r m a t i o n phases have been c o r r e l a t e d , t h e o r i e n t a t i o n s o f p l a n a r and l i n e a r s t r u c t u r e s a s s o c i a t e d w i t h t h i s d e f o r m a t i o n i n each p r o v i n c e a r e discordant.  T h i s d i s c o r d a n c e may be r e l a t e d t o movement a l o n g t h e  t e c t o n i c s l i d e s e p a r a t i n g t h e two domains.  I n i t i a l development o f t h e  s l i d e s u r f a c e d u r i n g t h e P l - F l d e f o r m a t i o n would j u x t a p o s e two p r o v i n c e s w i t h s l i g h t angular discordance.  As a zone o f weakness t h e s l i d e would be  r e a c t i v a t e d d u r i n g r e f o l d i n g a s s o c i a t e d w i t h t h e P2-F2 d e f o r m a t i o n . D i f f e r e n t i a l response o f t h e s l i g h t l y d i s c o r d a n t p r o v i n c e s t o t h e P2-F2 d e f o r m a t i o n would cause r o t a t i o n a l o n g t h e r e a c t i v a t e d s l i d e s u r f a c e . The d i s c o r d a n c e o f P l - F l minor s t r u c t u r e s a c r o s s t h e s l i d e i s t h e r e f o r e r e l a t e d t o complex movement d u r i n g b o t h t h e P l - F l and P2-F2  phases o f  deformation. The 100° C temperature  d i s c o n t i n u i t y across the t e c t o n i c  slide  measures o n l y t h e d i s p l a c e m e n t and r o t a t i o n t h a t has o c c u r r e d a f t e r t h e metamorphic c u l m i n a t i o n .  S i n c e r e g i o n a l metamorphism i s a s s o c i a t e d m a i n l y  w i t h t h e P l - F l d e f o r m a t i o n , t h e temperature  discontinuity i s related  77 l a r g e l y to displacement  d u r i n g t h e P2-F2 r e a c t i v a t i o n o f t h e s l i d e s u r f a c e .  T h i s d i s p l a c e m e n t has been e s t i m a t e d as b e i n g g r e a t e r than 10 km based on the metamorphic temperature  g r a d i e n t c a l c u l a t e d from the g a r n e t - b i o t i t e  zone i n the Azure Lake a r e a . R e c e n t l y F l e t c h e r and Greenwood (1978) have d e s c r i b e d m a r g i n a l r e l a t i o n s f o r the Shuswap Complex j u s t west of the A z u r e Lake a r e a . n o t e d a m y l o n i t e zone between the garnet and  They  staurolite-kyanite  metamorphic zones but c o n s i d e r e d the metamorphism t o p o s t d a t e movement a l o n g the m y l o n i t e .  C a l c u l a t e d temperature  metamorphic zones v a r y from 25° C/km k y a n i t e zone).  gradients for t h e i r  ( b i o t i t e zone) t o 120°  C/km  (staurolite-  Yet t h e i r d e t a i l e d e q u i l i b r i u m s t u d i e s d e t e c t e d no  e v i d e n c e f o r a temperature s i l l i m a n i t e zones.  g r a d i e n t w i t h i n the s t a u r o l i t e - k y a n i t e  and  Based on the g e o l o g i c r e l a t i o n s i n the Azure Lake a r e a ,  t h i s v a r i a t i o n i n temperature  g r a d i e n t s might e q u a l l y w e l l r e s u l t from  post-metamorphic d i s p l a c e m e n t  a l o n g the m y l o n i t e zone.  REGIONAL TECTONICS  I n the p r e v i o u s s e c t i o n i t was  shown t h a t metamorphism and  d e f o r m a t i o n a r e c o n t i n u o u s a c r o s s the margin of the Shuswap Complex.  In  t h i s s e c t i o n the r e l a t i o n of Azure Lake d e f o r m a t i o n s t r u c t u r e s t o the r e g i o n a l metamorphic-deformation framework i s d i s c u s s e d . The predominant r e g i o n a l s t r u c t u r e s i n the C a r i b o o Mountains are l a r g e northwest-plunging  a n t i c l i n o r i a and s y n c l i n o r i a .  These l a r g e s t r u c t u r e s  f o l d an e a r l i e r s c h i s t o s i t y t h a t i s s u b p a r a l l e l t o c o m p o s i t i o n a l l a y e r i n g ( S u t h e r l a n d Brown 1963;  R.B.  Campbell, Mountjoy, and Young 1973).  f e a t u r e t o g e t h e r w i t h the northwest  This  t r e n d of these l a r g e s t r u c t u r e s  suggests t h a t the a n t i c l i n o r i a and s y n c l i n o r i a c o r r e l a t e w i t h the P2-F2  phase o f d e f o r m a t i o n i n t h e Azure Lake a r e a .  The n e a r - v e r t i c a l  faults  w h i c h bound many o f t h e a n t i c l i n o r i a and s y n c l i n o r i a p r o b a b l y r e p r e s e n t movement a l o n g t h e s t e e p l y d i p p i n g P2-F2 a x i a l p l a n e s u r f a c e s . W i t h i n t h e Azure Lake a r e a q u a r t z d i o r i t e t o g r a n o d i o r i t e i n t r u s i o n s c r o s s - c u t F l and F2 s t r u c t u r e s and impose a c o n t a c t a u r e o l e on t h e r e g i o n a l metamorphic assemblages. 1977)  An Rb-Sr date o f 163 ± 7 Ma (Pigage  f o r t h e s e i n t r u s i o n s i s c o n s i s t e n t w i t h an e a r l i e r K-Ar date o f  148 ± 14 Ma completed by t h e G e o l o g i c a l Survey o f Canada (Wanless et a l . 1965; r e c a l c u l a t e d from t h e r e p o r t e d date u s i n g new decay c o n s t a n t f o r 40.K ( B e c k i n s a l e and Gale 1 9 6 9 ) ) .  T h e r e f o r e r e g i o n a l metamorphism and  d e f o r m a t i o n f o r both t h e Shuswap Complex and t h e c o v e r sequence i n t h e Azure Lake a r e a o c c u r r e d b e f o r e t h e L a t e J u r a s s i c emplacement o f t h e stocks. Younger b i o t i t e - w h o l e r o c k ± hornblende Rb/Sr d a t e s f o r t h e s e s t o c k s i n d i c a t e s p o s t - i n t r u s i o n i s o t o p i c r e s e t t i n g (Pigage 1977). was  This r e s e t t i n g  t e n t a t i v e l y a s c r i b e d t o t h e Eocene t h e r m a l event noted f o r p o r t i o n s o f  the Shuswap Complex f u r t h e r s o u t h (Medford 1975).  Ross (1974) has shown  t h a t t h i s t h e r m a l event i s c o n s i s t e n t l y a s s o c i a t e d w i t h n o r t h - t o n o r t h e a s t t r e n d i n g b r i t t l e f o l d and f r a c t u r e s t r u c t u r e s .  S i n c e n o r t h - t r e n d i n g F3  f r a c t u r e s a r e t h e e a r l i e s t s t r u c t u r e s r e c o g n i z e d i n t h e s t o c k s from t h e Azure Lake a r e a , t h e F3 and F4 d e f o r m a t i o n s a r e t e n t a t i v e l y  correlated  w i t h t h i s Eocene t h e r m a l event. E s t i m a t e d metamorphic p r e s s u r e s f o r t h e Shuswap Complex i n t h e Azure Lake a r e a r e q u i r e some 25 km o f o v e r l y i n g m a t e r i a l .  Yet the p r e -  C r e t a c e o u s s t r a t i g r a p h y i n t h e a r e a accounts f o r a maximum o f o n l y about 12 km o f o v e r l y i n g sediments.  Extensive tectonic thickening i s required  t o o b t a i n t h e n e c e s s a r y metamorphic p r e s s u r e s .  79 CONCLUSIONS AND SUMMARY  Both low and h i g h grade metasediments a l o n g t h e n o r t h e a s t margin o f the  Shuswap Complex n e a r A z u r e Lake c o n t a i n f o u r r e c o g n i z e d phases o f  deformation.  The e a r l i e s t d e f o r m a t i o n phase c o n s i s t s o f w e s t - v e r g i n g  i s o c l i n a l f o l d s plunging north to northwest. the  R e g i o n a l metamorphism i n  Azure Lake a r e a i s a s s o c i a t e d w i t h t h i s e a r l i e s t d e f o r m a t i o n .  Mineral  textures indicate that r e c r y s t a l l i z a t i o n outlasted deformation. The second phase o f d e f o r m a t i o n r e s u l t e d i n l a r g e u p r i g h t f o l d s w i t h a shallow northwest plunge.  M a j o r a n t i c l i n o r i a and s y n c l i n o r i a i n t h e  C a r i b o o Mountains a r e a s s o c i a t e d w i t h t h i s d e f o r m a t i o n phase. L a t e J u r a s s i c p l u t o n s c r o s s - c u t minor s t r u c t u r e s a s s o c i a t e d w i t h t h e s e f i r s t two phases o f d e f o r m a t i o n . D e f o r m a t i o n and metamorphism were t h e r e f o r e completed by L a t e J u r a s s i c . The t h i r d and f o u r t h phases o f d e f o r m a t i o n c o n s i s t o f f r a c t u r e s and b r i t t l e f o l d s w h i c h t r e n d n o r t h and n o r t h e a s t , r e s p e c t i v e l y .  These  d e f o r m a t i o n s a r e t e n t a t i v e l y c o n s i d e r e d t o be T e r t i a r y based on t h e i r o r i e n t a t i o n and i s o t o p i c r e s e t t i n g o f m i n e r a l s from t h e L a t e J u r a s s i c plutons. M i n e r a l assemblages on t h e margin o f t h e Shuswap Complex range from g a r n e t - b i o t i t e t h r o u g h f i r s t s i l l i m a n i t e zones w i t h metamorphic i n c r e a s i n g towards t h e southwest.  grade  The margin o f t h e Complex i s a t e c t o n i c  s l i d e which i s r e l a t e d t o t i g h t e n i n g o f major f o l d s from t h e e a r l i e s t d e f o r m a t i o n phase. of  Metamorphic m i n e r a l assemblages i n d i c a t e t h e p r e s e n c e  a 100° C temperature gap between t h e Complex and a d j a c e n t l o w e r grade  metasediments a c r o s s t h i s s l i d e .  T h i s temperature gap i s r e l a t e d t o  movement i n v o l v i n g r o t a t i o n w i t h r e a c t i v a t i o n o f t h e t e c t o n i c s l i d e d u r i n g the  second d e f o r m a t i o n phase.  D i s c o r d a n c e i n e a r l i e s t d e f o r m a t i o n minor  80 s t r u c t u r e s between t h e Complex and a d j a c e n t metasediments i s a l s o caused by complex movement a l o n g t h i s f a u l t zone d u r i n g t h e f i r s t two d e f o r m a t i o n episodes.  ACKNOWLEDGEMENTS  T h i s paper r e p r e s e n t s p a r t o f a Ph.D. t h e s i s completed a t t h e U n i v e r s i t y o f B r i t i s h Columbia.  Dr. H.J. Greenwood p r o v i d e d  i n t e r e s t and enthusiasm w h i l e s u p e r v i s i n g t h e s t u d y .  continued  Brian Hall,  Pat M a r c e l l o , and Norm Duncan were a b l e f i e l d a s s i s t a n t s d u r i n g t h e summer seasons.  The s t r u c t u r a l p r e s e n t a t i o n has been improved  through  d i s c u s s i o n s w i t h Dr. J.V. Ross, Dr. P.B. Read, and Dr. R.B. Campbell. J . N e l s o n p r o v i d e d much needed m o r a l support and l i s t e n e d p a t i e n t l y t o c o n v o l u t e d g e o l o g i c argument. F i e l d and l a b o r a t o r y expenses were covered by NRRC 67-4222 t o Dr. H.J. Greenwood.  D u r i n g t h e course o f t h i s s t u d y I was supported by  graduate r e s e a r c h f e l l o w s h i p s from t h e N a t i o n a l S c i e n c e F o u n d a t i o n (NSF) and t h e I n t e r n a t i o n a l N i c k e l Company (INCO).  81  SELECTED REFERENCES  ALBEE, A.L. 1972. Metamorphism o f p e l i t i c s c h i s t s : r e a c t i o n r e l a t i o n s of c h l o r i t o i d and s t a u r o l i t e . G e o l o g i c a l S o c i e t y o f America B u l l e t i n , 83, pp. 3249-3268. ANDERSON, P.M., NEWTON, R.C., and KLEPPA, O.J. 1977. The e n t h a l p y change o f the a n d a l u s i t e - s i l l i m a n i t e r e a c t i o n and the A ^ S i O ^ diagram. American J o u r n a l of S c i e n c e , 277, pp. 585-593. 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A T e r t i a r y t h e r m a l event i n s o u t h - c e n t r a l B r i t i s h Columbia. Canadian J o u r n a l o f E a r t h S c i e n c e s , 11, pp. 1116-1122. SUTHERLAND BROWN, A. 1957. Geology o f t h e A n t l e r Creek a r e a , C a r i b o o D i s t r i c t , B r i t i s h Columbia. B r i t i s h Columbia Department o f Mines and P e t r o l e u m R e s o u r c e s , B u l l e t i n 38, 105 p. . '. 1963. Geology o f the C a r i b o o R i v e r a r e a , B r i t i s h Columbia. B r i t i s h Columbia Department o f Mines and P e t r o l e u m R e s o u r c e s , B u l l e t i n 47, 60 p. THOMPSON, J.B., JR. 1957. The g r a p h i c a l a n a l y s i s o f m i n e r a l assemblages i n p e l i t i c s c h i s t s . American M i n e r a l o g i s t , 42, pp. 842-858. THOMPSON, P.H. 1976. I s o g r a d p a t t e r n s and p r e s s u r e - t e m p e r a t u r e d i s t r i b u t i o n s d u r i n g r e g i o n a l metamorphism. 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 , 57, pp. 277-295.  84  WANLESS, R.K. and REESOR, J.E. 1975. P r e c a m b r i a n z i r c o n age o f o r t h o g n e i s s i n the Shuswap Metamorphic Complex, B r i t i s h Columbia. Canadian J o u r n a l o f E a r t h S c i e n c e s , 12, pp. 326-332. WANLESS, R.K., STEVENS, R.D., LACHANCE, G.R., and RIMSAITE, R.Y.H. 1965. Age d e t e r m i n a t i o n s and g e o l o g i c a l s t u d i e s . G e o l o g i c a l Survey o f Canada, Paper 64-17, P a r t 1, pp. 15-16. WHEELER, J.O., CAMPBELL, R.B., REESOR, J.E., and MOUNTJOY, E.W. 1972. S t r u c t u r a l s t y l e o f t h e s o u t h e r n Canadian C o r d i l l e r a . I n Guidebook f o r E x c u r s i o n A-01 - X-01. 2 4 t h I n t e r n a t i o n a l G e o l o g i c a l Congress, M o n t r e a l , Quebec, 118 p. WHEELER, J.O. and GABRIELSE, H. 1972. The C o r d i l l e r a n s t r u c t u r a l province. I n V a r i a t i o n s i n t e c t o n i c s t y l e s i n Canada. E d i t e d by R.A. P r i c e and R.J.W. D o u g l a s . G e o l o g i c a l A s s o c i a t i o n o f Canada, S p e c i a l Paper 11, pp. 1-81. ZWART, H.J. 1960a. C h r o n o l o g i c a l s u c c e s s i o n o f f o l d i n g and metamorphism i n the c e n t r a l P y r e n e e s . G e o l o g i s c h e Rundschau, 50, pp. 203-218. . 1960b. R e l a t i o n s between f o l d i n g and metamorphism i n t h e c e n t r a l Pyrenees. G e o l o g i e en Mijnbouw, 39e, pp. 163-180.  PLATE  A)  1-1  S c h i s t from the s i l l i m a n i t e zone, Shuswap Complex.  S t a u r o l i t e ( s ) and  garnet(G) a r e surrounded by equant, p o r p h y r o b l a s t i c m u s c o v i t e w i t h fibrolite(m+  f).  Inclusion t r a i l s  i n garnet are s t r a i g h t ,  (x-nicols)  B)  S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex.  s t a g e g a r n e t c o n t a i n s S-shaped i n c l u s i o n t r a i l s . r i m ( o u t e r margin) c o n t a i n s o n l y a few s c a t t e r e d  Second s t a g e g a r n e t inclusions.  p a r t l y surrounded by p o r p h y r o b l a s t i c m u s c o v i t e - f i b r o l i t e K y a n i t e ( K ) i s common i n the s c h i s t m a t r i x , (x-nicols)  First  Garnet i s  aggregate(M + F ) .  PLATE  A)  1-2  S c h i s t from t h e k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex.  Quartz  i n c l u s i o n s o u t l i n e a r e l i c c r e n u l a t i o n c l e a v a g e i n t h i s l a r g e s t a g e one garnet.  Opaque i n c l u s i o n s a r e c o n t i n u o u s w i t h the e x t e r n a l P I s c h i s t o s i t y  although rotated r e l a t i v e to i t .  F i b r o l i t e aggregates o c c u r i n t h e l o w e r  p o r t i o n of. the p h o t o m i c r o g r a p h , (plane l i g h t )  B)  S c h i s t from t h e s i l l i m a n i t e zone, Shuswap Complex. I d i o b l a s t i c  second s t a g e g a r n e t s ( g ) a r e e n c l o s e d by p o r p h y r o b l a s t i c m u s c o v i t e w i t h minor f i b r o l i t e ( m + f ) .  The l a r g e m u s c o v i t e g r a i n s have a random  o r i e n t a t i o n and i n t e r l o c k i n g g r a i n m a r g i n s , (x-nicols)  PLATE  1-3  S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex. and s t a u r o l i t e ( s ) are p a r t l y e n c l o s e d by aggregates.  Garnet  fibrolite-muscovite-ilmenite  K y a n i t e ( k ) i s abundant i n the s c h i s t m a t r i x .  Arrow p o i n t s  to a r e a where f i b r o l i t e i s p a r t l y e n c l o s e d by second s t a g e g a r n e t . s t a g e garnet rims are e u h e d r a l a g a i n s t the f i b r o l i t e  A)  B)  (plane l i g h t )  (x-nicols)  aggregates.  Second  I m m  PLATE  A)  1-4  S c h i s t from t h e k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex.  inclusion t r a i l s i n kyanite(k)  Straight  and s t a u r o l i t e ( s ) a r e r o t a t e d r e l a t i v e t o  the e x t e r n a l P I s c h i s t o s i t y . M i n o r g a r n e t i s a l s o p r e s e n t i n t h e photomicrograph. (plane l i g h t )  B)  S c h i s t from the s i l l i m a n i t e zone, Shuswap Complex.  Photomicrograph  shows a l a r g e f i b r o l i t e - b i o t i t e - m u s c o v i t e - i l m e n i t e aggregate i n t h e s c h i s t matrix. cleavage. (x-nicols)  F i b r o l i t e i s warped and f o l d e d by t h e P2 c r e n u l a t i o n  I m m  i I  m m  PLATE  Schist  1-5  from the s i l l i m a n i t e zone, Shuswap Complex.  muscovite(M) i s randomly o r i e n t e d i n the s c h i s t m a t r i x .  Porphyroblastic Fibrolite-  b i o t i t e aggregates form a t t e n u a t e d w i s p y t r a i l s through the m u s c o v i t e (arrows).  R e l i c s t a u r o l i t e ( s ) i s e n c l o s e d by f i b r o l i t e o r m u s c o v i t e .  Arrow i n second g e n e r a t i o n g a r n e t shows where f i b r o l i t e has been e n c l o s e d by the g a r n e t .  A)  B)  (plane l i g h t )  (x-nicols)  94  B  I  m m  PLATE  A)  Schist  from the s t a u r o l i t e - k y a n i t e  g a r n e t ( g ) c o n t a i n s S-shaped i n c l u s i o n to the e x t e r n a l F l s c h i s t o s i t y . matrix.  1-6  Sample i s from the Kaza  zone, cover sequence.  Skeletal  t r a i l s w h i c h are r o t a t e d  relative  K y a n i t e ( k ) i s p r e s e n t i n the s c h i s t Group,  (plane l i g h t )  B)  P h y l i i t e from the g a r n e t - b i o t i t e  S-shaped i n c l u s i o n the  Slightly  t r a i l s i n i d i o b l a s t i c garnets are -rotated r e l a t i v e to  external F l schistosity.  garnets.  zone, cover sequence.  Q u a r t z p r e s s u r e shadows o c c u r near the  The s l i g h t w a r p i n g o f the F l s c h i s t o s i t y i s due t o the F2  crenulation cleavage.  The arrow p o i n t s t o a s m a l l r e t r o g r a d e r i m o f  s e r i c i t e + c h l o r i t e around the g a r n e t . of the I s a a c F o r m a t i o n , (plane l i g h t )  Sample i s from the l o w e r member  96  B  i  i I mm  PLATE  A)  1-7  P h y l l i t e from the g a r n e t - b i o t i t e zone, cover sequence.  Biotite  porphyroblasts c o n t a i n s t r a i g h t i n c l u s i o n t r a i l s which are s l i g h t l y r o t a t e d r e l a t i v e t o the e x t e r n a l F l s c h i s t o s i t y .  Warping o f the F l  s c h i s t o s i t y i s due t o the F2 d e f o r m a t i o n . Sample i s from the Kaza Group i n the n o r t h e r n p a r t of the Azure Lake a r e a , (plane  B)  light)  P h y l l i t e from the g a r n e t - b i o t i t e zone, cover sequence.  Biotite  forms p o r p h y r o b l a s t i c augen concordant w i t h the F l s c h i s t o s i t y .  Warping  o f the F l s c h i s t o s i t y i s caused by the F2 d e f o r m a t i o n . Sample i s from a p h y l l i t e u n i t w i t h i n the Cunningham F o r m a t i o n , (plane l i g h t )  I  m  m  i  i I  m  m  PLATE  1-8  P h y l i i t e from the g a r n e t - b i o t i t e zone, cover sequence. c l e a v a g e r e f o l d s the e a r l i e r F l s c h i s t o s i t y . Formation. (plane  light)  F2 c r e n u l a t i o n  Sample i s from the I s a a c  100  I  m  m  PLATE  A)  1-9  P I minor f o l d s i n i n t e r l a y e r e d s c h i s t and q u a r t z i t e , Shuswap  Complex (Azure Lake a r e a ) .  F o l d a x i s f o r a s i n g l e f o l d has a v a r i a b l e  plunge a l t h o u g h the a x i a l p l a n e has a c o n s t a n t o r i e n t a t i o n .  This i s  r e l a t e d t o d i f f e r e n t i a l f l a t t e n i n g o f t h e P I minor f o l d s .  B)  F3 minor f o l d h i n g e i n p h y l l i t e .  P e n c i l i s p a r a l l e l t o the  o r i e n t a t i o n o f the F2 c r e n u l a t i o n c l e a v a g e which i s warped around t h e F3 f o l d h i n g e .  P e n c i l and hammer a r e f o r s c a l e .  PLATE  A)  F3 minor f o l d h i n g e s i n p h y l i i t e .  a subvertical  B)  1-10  Hinge a r e a s a r e accompanied by  F3 a x i a l p l a n e c r e n u l a t i o n c l e a v a g e .  Graded bedding i n f e l d s p a t h i c ' g r i t s ' of the Kaza Group.  Fractures  r u n n i n g from lower l e f t to upper r i g h t aire p a r a l l e l to the F l a x i a l plane s c h i s t o s i t y .  These beds a r e o v e r t u r n e d and form the lower l i m b  of a l a r g e F l a n t i c l i n e .  104  Metamorphic  Conditions  i n the Shuswap Metamorphic  Complex,  A z u r e Lake, B r i t i s h  Columbia  Lee C. Pigage Department of G e o l o g i c a l S c i e n c e s U n i v e r s i t y of B r i t i s h Vancouver, B r i t i s h V6T 1W5  Columbia  Columbia  Canada  106 ABSTRACT  P e l i t i c m i n e r a l assemblages i n the Shuswap Metamorphic Complex n e a r Azure Lake, B r i t i s h Columbia are c h a r a c t e r i s t i c of the k y a n i t e t h r o u g h f i r s t s i l l i m a n i t e zones of the B a r r o v i a n f a c i e s s e r i e s .  Mineral textures  p a r t i a l l y p r e s e r v e a sequence of r e a c t i o n s i n v o l v i n g the breakdown o f g a r n e t , s t a u r o l i t e , and k y a n i t e t o form aggregates o f muscovite-ilmenite.  M i c r o p r o b e a n a l y s e s have been combined w i t h  r e g r e s s i o n techniques The  fibrolite-biotite-  t o o u t l i n e probable  linear  sillimanite-forming reactions.  r e g r e s s i o n s show t h a t r e a c t i o n t e x t u r e s a r e p r o b a b l y p r e s e r v e d  because  of the e x h a u s t i o n o f r u t i l e as a r e a c t a n t phase. Several experimentally studied mineral e q u i l i b r i a are adjusted f o r s o l i d s o l u t i o n e f f e c t s and used t o e s t i m a t e metamorphic c o n d i t i o n s f o r the p e l i t e assemblages.  Mutual i n t e r s e c t i o n of these e q u i l i b r i a r e s u l t i n the  consistent estimated  conditions:  a  = 0.5.  a  P = 7600 ± 400 b a r s , T = 705 ± 40°C,  i s v e r y s e n s i t i v e to thermochemical u n c e r t a i n t i e s ,  a n a l y t i c a l e r r o r s , and  the c h o i c e of s o l i d s o l u t i o n models f o r d i f f e r e n t  m i n e r a l s ; i t v a r i e s between 0.25  and 1.0  depending upon the s e l e c t e d  parameters. Comparison of p u b l i s h e d e x p e r i m e n t a l  e q u i l i b r i a s t u d i e s w i t h carbonate  m i n e r a l assemblages from the Azure Lake a r e a shows t h a t the c a r b o n a t e assemblages i n i t i a l l y b u f f e r e d f l u i d phase c o m p o s i t i o n s  to high X  values cu  near 0.75  d u r i n g metamorphism.  i n composition occurrences  The  f l u i d phase t h e r e f o r e was  throughout a l l r o c k types d u r i n g metamorphism.  2  not homogeneous Local  o f z o i s i t e r e p l a c i n g p l a g i o c l a s e i n c a r b o n a t e assemblages i s  i n t e r p r e t e d t o r e s u l t from the l a t e i n f l u x of IL^O-rich f l u i d s t o the c a r b o n a t e s from the e n c l o s i n g p e l i t e s and q u a r t z i t e s .  107  C a l c u l a t i o n s o f t h e c o m p o s i t i o n o f the f l u i d phase c o e x i s t i n g w i t h graphite  show t h a t CH^, CO^, and JL^O a r e the major s p e c i e s p r e s e n t a t t h e  e s t i m a t e d metamorphic c o n d i t i o n s . p e l i t e assemblages were b u f f e r e d  Oxygen f u g a c i t i e s f o r b o t h c a r b o n a t e and t o v a l u e s near FMQ oxygen b u f f e r .  108 INTRODUCTION  The Shuswap Complex i n s o u t h e a s t e r n B r i t i s h Columbia i s a metamorphic c o r e complex w i t h i n t h e Omineca C r y s t a l l i n e B e l t ( f i g u r e 2-1) .  It is  c h a r a c t e r i z e d by upper a m p h i b o l i t e f a c i e s metamorphism and p o l y p h a s e d e f o r m a t i o n (R.B. Campbell 1977).  Near Azure L a k e , B r i t i s h Columbia t h e  n o r t h e a s t margin o f t h e Complex c o n t a i n s t h e t r a n s i t i o n from k y a n i t e t h r o u g h f i r s t s i l l i m a n i t e metamorphic ( M i y a s h i r o 1961).  series  T h i s study p r e s e n t s t h e r e s u l t s o f a d e t a i l e d  i n v e s t i g a t i o n o f metamorphic Lake a r e a .  zones o f t h e B a r r o v i a n f a c i e s  c o n d i t i o n s w i t h i n t h e Complex i n t h e Azure  Mass-balance c a l c u l a t i o n s u s i n g l i n e a r r e g r e s s i o n t e c h n i q u e s  have been used t o t e s t p r o b a b l e s i l l i m a n i t e - f o r m i n g r e a c t i o n s i n t h e pelitic units.  P u b l i s h e d e x p e r i m e n t a l r e a c t i o n s t u d i e s were a d j u s t e d f o r  s o l i d s o l u t i o n e f f e c t s and used t o e s t i m a t e p r e s s u r e - t e m p e r a t u r e - a c t i v i t y (H^O) c o n d i t i o n s f o r t h e p e l i t e s d u r i n g metamorphism.  These  conditions  were then a p p l i e d t o c a r b o n a t e - b e a r i n g assemblages t o s t u d y t h e b u f f e r i n g of  f l u i d phase c o m p o s i t i o n s by m i n e r a l assemblages d u r i n g metamorphism. The A z u r e Lake s t u d y a r e a i s i n d i c a t e d i n f i g u r e s 2-1 and 2-2.  R.B. Campbell (1963, 1968) c o m p i l e d t h e r e g i o n a l g e o l o g i c map.  Detailed  s t u d i e s on p o r t i o n s o f t h e Complex t o t h e west have been completed by K.V. Campbell (1971) and F l e t c h e r (1972).  I conducted t h e f i e l d work f o r  t h i s s t u d y d u r i n g t h e summers o f 1972, 1973 and 1975. D e t a i l e d g e o l o g i c r e l a t i o n s between t h e Complex and s u r r o u n d i n g low grade r o c k s a r e d i s c u s s e d elsewhere (Pigage 1978, t h i s volume). the  Briefly,  Complex c o n s i s t s o f i n t e r l a y e r e d s c h i s t s and q u a r t z i t e s b e l o n g i n g t o t h e  H a d r y n i a n (Windermere) Kaza Group ( S u t h e r l a n d Brown 1963).  M i n o r marble and  r a r e a m p h i b o l i t e u n i t s a r e s c a t t e r e d throughout t h e Kaza Group i n t h e  109  F i g u r e 2-1.  Major s t r u c t u r a l elements o f the Canadian C o r d i l l e r a .  Shuswap Complex i s i n d i c a t e d by the r u l e d a r e a . f i g u r e 2-2 i s c i r c l e d .  The  The l o c a t i o n o f  M o d i f i e d from Wheeler and G a b r i e l s e  (1972).  110 study a r e a .  The Complex i s s e p a r a t e d from lower grade r o c k s t o t h e n o r t h -  e a s t by a composite  f a u l t zone.  Metamorphic grade a d j a c e n t t o t h e Complex  decreases r a p i d l y t o g a r n e t - b i o t i t e zone i n the g r e e n s c h i s t f a c i e s . The Complex i t s e l f c o n t a i n s two r e c o g n i z e d c o a x i a l phases o f d e f o r m a t i o n ; minor and major s t r u c t u r e s plunge g e n t l y n o r t h w e s t and southeast. deformation.  R e g i o n a l metamorphism was synchronous w i t h b o t h phases o f D e f o r m a t i o n and metamorphism a r e r e s t r i c t e d t o t h e t i m e  i n t e r v a l between L a t e T r i a s s i c and L a t e J u r a s s i c (K.V. Campbell 1971; P i g a g e 1977).  METHOD OF STUDY  F i g u r e 2-2 i l l u s t r a t e s t h e l o c a t i o n s o f 20 samples (12 p e l i t e s and 8 c a r b o n a t e s ) s e l e c t e d f o r a n a l y s i s o f major m i n e r a l s . t h e s e samples a r e g i v e n i n T a b l e s 2-1 and 2-2. through 2-18) were a c c o m p l i s h e d e l e c t r o n microprobe  E s t i m a t e d modes o f  Analyses  ( T a b l e s 2-3  u s i n g a t h r e e - c h a n n e l , automated ARL SEMQ  a t t h e U n i v e r s i t y o f B r i t i s h Columbia.  p o t e n t i a l was c o n s t a n t a t 15 kV.  Beam diameter  Accelerating  (2-35 micrometers) and  specimen c u r r e n t (0.02-0.05 microamperes) were v a r i e d t o p r o v i d e maximum counts w i t h minimum specimen damage.  Count r e a d i n g s f o r a f i x e d  i n t e r v a l were n o r m a l i z e d t o an averaged beam c u r r e n t . 20 second c o u n t i n g i n t e r v a l was used.  time  F o r most elements a  With f l u o r i n e and c a r b o n a t e  a n a l y s e s , c o u n t i n g t i m e s o f 120 and 40 seconds, r e s p e c t i v e l y , improved t h e counting s t a t i s t i c s . A n a l y z e d s y n t h e t i c and n a t u r a l m i n e r a l s from t h e U n i v e r s i t y o f B r i t i s h c o l l e c t i o n were used as s t a n d a r d s  (see Appendix 2-3).  c o r r e c t e d f o r dead t i m e , d r i f t , and background.  A l l r e a d i n g s were  F l u o r i n e and c a r b o n a t e  a n a l y s e s were computed u s i n g a l e a s t squares l i n e a r r e g r e s s i o n curve f i t t o  F i g u r e 2-2.  Metamorphic  B r i t i s h Columbia.  zones i n the Shuswap Complex, Azure Lake,  Samples s e l e c t e d f o r e l e c t r o n m i c r o p r o b e a n a l y s i s  of c o e x i s t i n g m i n e r a l s are shown.  112 the s t a n d a r d s .  F o r a l l o t h e r elements count r e a d i n g s were c o r r e c t e d f o r  m a t r i x e f f e c t s u s i n g t h e computer program EMFADR V I I ( R u c k l i d g e and G a s p a r r i n i 1969). S e v e r a l g r a i n s o f each m i n e r a l i n a probe mount were a n a l y z e d w i t h r e p e a t e d counts on each g r a i n .  D i f f e r e n t m i n e r a l s were i n v e s t i g a t e d i n  c l o s e c l u s t e r s t o t a k e i n t o account p o s s i b l e l o c a l d i f f e r e n c e s i n composition.  A l l m i n e r a l s were checked f o r c o n c e n t r i c and s e c t o r z o n i n g ;  where z o n i n g was p r e s e n t  ( p l a g i o c l a s e , g a r n e t , c a l c i c amphibole) the g r a i n  edges were c o n s i d e r e d t o r e p r e s e n t the c o m p o s i t i o n i n e q u i l i b r i u m w i t h t h e r e s t o f t h e m i n e r a l assemblage. Mean c o m p o s i t i o n s and sample v a r i a n c e s f o r each g r a i n were c a l c u l a t e d from t h e spot a n a l y s e s .  I n most i n s t a n c e s s e p a r a t e g r a i n s i n t h e same  s l i d e had mean c o m p o s i t i o n s  t h a t were n o t s i g n i f i c a n t l y d i f f e r e n t ;  these  mean a n a l y s e s were then combined t o form an o v e r a l l mean and s t a n d a r d Sample v a r i a n c e s a s s o c i a t e d w i t h t h e mean c o m p o s i t i o n s used t o weight  f o r each g r a i n were  t h e l a t t e r c a l c u l a t i o n ( B e v i n g t o n 1969).  F e r r o u s - f e r r i c r a t i o s and water content cannot be determined e l e c t r o n microprobe.  with the  I r o n was computed as FeO o r Fe^O^ depending on t h e  mineral being considered.  Water content i n hydrous m i n e r a l s was c a l c u l a t e d  from s t o i c h i o m e t r i c c o n s t r a i n t s i n t h e s t r u c t u r a l f o r m u l a e . f o r R^O  error.  Standard e r r o r s  were computed by a Monte C a r l o approach assuming n o r m a l l y  d i s t r i b u t e d random e r r o r s i n t h e o t h e r a n a l y z e d o x i d e s  (Anderson 1976) .  PELITIC MINERAL ASSEMBLAGES  P e l i t i c m i n e r a l assemblages i n t h e Azure Lake a r e a may be d i v i d e d i n t o t h r e e d i s t i n c t metamorphic zones ( f i g u r e 2-2).  D i s t r i b u t i o n o f these zones  i n d i c a t e s a g e n e r a l i n c r e a s e i n metamorphic grade toward  t h e southwest.  113 M i n e r a l assemblages f o r each of t h e s e zones a r e : Kyanite  Zone  kyanite-garnet-biotite-muscovite-quartz-plagioclase-ilmenite ± staurolite K y a n i t e - S i l l i m a n i t e Zone Sillimanite-garnet-biotite-muscovite-quartz-plagioclase-ilmenite ± kyanite ± staurolite S i l l i m a n i t e Zone sillimanite-garnet-biotite-muscovite-quartz-plagioclase-ilmenite ± staurolite M i n o r amounts o f t o u r m a l i n e , (graphite?)  a p a t i t e , z i r c o n , and f i n e opaque d u s t  a r e p r e s e n t i n each of the assemblages.  These assemblages a r e  i l l u s t r a t e d i n the p r o j e c t i o n s of f i g u r e s 2-3 t h r o u g h 2-5.  A l l projections  were c a l c u l a t e d f o l l o w i n g t h e approach o u t l i n e d by Greenwood (1975b).  TESTS OF EQUILIBRIUM  I n v e s t i g a t i o n of r e g i o n a l metamorphic assemblages u s i n g  equilibrium  c o n s t a n t s n e c e s s a r i l y assumes e q u i l i b r i u m c o n d i t i o n s d u r i n g metamorphism. D i f f e r e n t c r i t e r i a f o r e q u i l i b r i u m i n c l u d e homogeneity of  mineral  c o m p o s i t i o n s , n o n - v i o l a t i o n of the Gibbs phase r u l e , s y s t e m a t i c of elements between c o e x i s t i n g m i n e r a l s , r e l a t i o n s (Zen 1963).  partitioning  and e q u i l i b r i u m t e x t u r a l  P r o j e c t i o n ( f i g u r e s 2-3 t h r o u g h 2-5) and element  d i s t r i b u t i o n diagrams ( f i g u r e s 2-6 and 2-7) f o r p e l i t i c assemblages from the Azure Lake a r e a a r e u s e f u l i n d i s c u s s i n g t h e s e v a r i o u s  equilibrium  tests. E l e c t r o n m i c r o p r o b e spot a n a l y s e s of s e v e r a l g r a i n s f o r each  mineral  w i t h i n t h e same s l i d e i n d i c a t e t h a t m i n e r a l s a r e g e n e r a l l y homogeneous. P l a g i o c l a s e g r a i n s show t h e most v a r i a b i l i t y  (see T a b l e 2-7).  This  small  114 s c a l e v a r i a t i o n i n a n o r t h i t e c o n t e n t has a l s o been n o t e d i n o t h e r r e g i o n a l l y metamorphosed t e r r a i n s (Evans and G u i d o t t i 1966; F l e t c h e r and Greenwood 1978). P e l i t i c assemblages from t h e Azure Lake a r e a may be d e s c r i b e d  by t h e  t e n component system K 0-Na 0-CaO-Al 0 -Si0 -MgO-FeO-MnO-Ti0 -H 0. 2  2  2  3  2  2  2  Two a l t e r n a t i v e t e t r a h e d r a l p r o j e c t i o n s a r e used t o i l l u s t r a t e phase r e l a t i o n s and Mg-Fe-Mn p a r t i t i o n i n g f o r c o e x i s t i n g m i n e r a l s i n t h e d i f f e r e n t metamorphic zones.  Figures  2-3a, 2-4a, 2-5a a r e t h e AFM  p r o j e c t i o n (J.B. Thompson 1957) w i t h MnO as t h e f o u r t h c o r n e r o f t h e tetrahedron.  T h i s p a r t i c u l a r p r o j e c t i o n assumes t h a t q u a r t z , m u s c o v i t e ,  H 0 , i l m e n i t e , a l b i t e , and a n o r t h i t e a r e p r e s e n t i n e x c e s s o r behave as 2  species with f i x e d chemical p o t e n t i a l s .  A l t e r n a t i v e l y Rumble (1974)  suggested t h a t H 0 s h o u l d be i n c l u d e d i n t h e p r o j e c t i o n s i n c e i t may n o t 2  have a u n i f o r m c h e m i c a l p o t e n t i a l f o r a l l samples. incorporated appropriate  T h i s has been  i n f i g u r e s 2-3b, 2-4b, 2-5b by p r o j e c t i n g from t h e A l S i O ^ polymorph r a t h e r than from H- 0. 2  2  In b o t h p r o j e c t i o n s g a r n e t i s t h e o n l y m i n e r a l w h i c h p l o t s away from the  (A,H)FM p l a n e o f t h e t e t r a h e d r o n .  T i e - l i n e s between c o e x i s t i n g m i n e r a l s  are g e n e r a l l y s u b p a r a l l e l i n d i c a t i n g s y s t e m a t i c between phases.  p a r t i t i o n i n g o f Mg-Fe-Mn  Assemblages i n t h e k y a n i t e and s i l l i m a n i t e zones a r e a t  l e a s t b i v a r i a n t i n both p r o j e c t i o n s . i n the intermediate  C o e x i s t e n c e o f k y a n i t e and s i l l i m a n i t e  zone r e q u i r e s u n i v a r i a n c e  i f e q u i l i b r i u m was a t t a i n e d .  C o e x i s t i n g m i n e r a l s i n t h e HFM diagram do n o t c o n t a i n c r o s s i n g r e l a t i o n s and i n d i c a t e t h a t  tie-line  a^ ^ may have been u n i f o r m f o r a l l p e l i t e  samples. F i g u r e 2-6 a l s o i l l u s t r a t e s t h e r e g u l a r p a r t i t i o n i n g o f Mg-Fe between c o e x i s t i n g garnet and b i o t i t e .  P a r t i t i o n i n g c o e f f i c i e n t s f o r each o f t h e  F i g u r e 2-3. S t e r e o s c o p i c p r o j e c t i o n s o f a n a l y z e d  pelitic  assemblages  containing kyanite. A)  M o d i f i e d AFM p r o j e c t i o n w i t h MnO as the f o u r t h c o r n e r o f t h e tetrahedron.  B)  P r o j e c t i o n onto the components MnO-FeO-MgO-H 0.  C)  Projected  2  phase r e l a t i o n s between A l S i C > , m u s c o v i t e , p l a g i o c l a s e , 2  5  and K - f e l d s p a r i n t h e subsystem K 0 - N a 0 - C a O - A l 0 - S i 0 - H 0 . 2  Abbreviations:  2  2  3  2  2  Ab-albite, An-anorthite, B t - b i o t i t e , Cel-celadonite,  I l m - i l m e n i t e , Gt-garnet,  K y - k y a n i t e , M a - m a r g a r i t e , Ms-muscovite,  Or-orthoclase, Pa-paragonite,  Sil-sillimanite,  St-staurolite.  116  An Ab  F i g u r e 2-4.  Stereoscopic p r o j e c t i o n s of analyzed  c o n t a i n i n g k y a n i t e and  pelitic  assemblages  sillimanite.  A ) , B ) , C) and a b b r e v i a t i o n s are the same as i n f i g u r e  2-3.  118  Samples 82,223,367, 492,2-376  MnO  - > MgO  MnO  MgO  Samples 82,223,367, 492,2-376  MgO  FeO  FeO  An Ab  Si"AKy  Samples 82,223,367, 492,2-376  Cel.Or  Projected Qtz H,0  from  Cel.Or  F i g u r e 2-5. containing  A ) , B ) , C)  Stereoscopic  p r o j e c t i o n s of a n a l y z e d  pelitic  assemblages  sillimanite.  and a b b r e v i a t i o n s  a r e the same as i n f i g u r e 2-3.  120  1.20 ^2H3 • . 398 A  0)  1.10 A  o  • 74  _  9 2  ^ • 82  2-376  q  J*  m  373  "l2l  1.00 A Y =0.293 + 0.115 X (X = 0.0073) 0.90 6.00  6.50  7.00  8.00  7.50  (Fe/Mg) Garnet  F i g u r e 2-6. Fe-Mg d i s t r i b u t i o n diagram g a r n e t and b i o t i t e .  "Best f i t "  l i n e a r e q u a t i o n was c a l c u l a t e d r e c o g n i z i n g t h a t b o t h v a r i a b l e s a r e s u b j e c t t o e r r o r (Mark and Church 1977). A = (sample v a r i a n c e o f y ) / ( s a m p l e v a r i a n c e o f x) t r i a n g l e - k y a n i t e zone; c i r c l e - k y a n i t e - s i l l i m a n i t e s q u a r e - s i l l i m a n i t e zone.  zone;  122  .gure 2-7. 5  P l o t o f (£ )„ . v s . (X„ )„, . , TJa' M u s c o v i t e Ca'Plagioclase T  v  .  "Best f i t "  l i n e a r e q u a t i o n was c a l c u l a t e d r e c o g n i z i n g t h a t b o t h v a r i a b l e s a r e s u b j e c t to e r r o r (Mark and Church 1977). X = ( v a r i a n c e of y ) / ( v a r i a n c e o f x) t r i a n g l e - k y a n i t e zone; c i r c l e - k y a n i t e - s i l l i m a n i t e square - s i l l i m a n i t e zone.  zone;  123 t h r e e metamorphic zones o v e r l a p on the diagram; temperature g r a d i e n t s cannot be d i s t i n g u i s h e d . F i g u r e s 2-3c,  2-4c,  2-5c  d e p i c t phase r e l a t i o n s between A 1 S 1 0 2  5  m u s c o v i t e - p l a g i o c l a s e - ( K - f e l d s p a r ) i n the subsystem K 2 0 - N a 2 0 - A l 0 2 - S i 0 2 - H 0 . 2  T i e - l i n e s between K - f e l d s p a r  (samples 2-376, 398,  2-13)  and o t h e r  a r e d o t t e d because phase r e l a t i o n s are p r o b l e m a t i c a l . o n l y as t h i n s e l v a g e s  (approximately  some of the p l a g i o c l a s e  grains.  minerals  K-feldspar  occurs  20 micrometers t h i c k ) p a r t l y e n c l o s i n g  Microprobe analyses  show t h a t i t i s more  p o t a s s i c t h a n m u s c o v i t e i n the same s l i d e (see T a b l e s 2-4, p o t a s s i c composition  2  contrasts sharply with K-feldspar  2-8).  This  compositions  r e p o r t e d i n s t u d i e s on the prograde development of K - f e l d s p a r by r e a c t i o n s or by p a r t i a l m e l t i n g G u i d o t t i , Herd, and T u t t l e 1973; K - f e l d s p a r was  (Evans and G u i d o t t i 1966; T r a c y 1978).  subsolidus  Lundgren  1966;  I n these s t u d i e s prograde  c o n s i s t e n t l y more s o d i c than the c o e x i s t i n g m u s c o v i t e .  G u i d o t t i , Herd, and T u t t l e (1973) n o t e d t h a t p o t a s s i c K - f e l d s p a r o n l y i n r e t r o g r a d e v e i n l e t s t r a n s e c t i n g the r e g i o n a l K - f e l d s p a r s i l l i m a n i t e assemblages.  occurred +  Because of these c o n s i d e r a t i o n s , I c o n c l u d e  t h a t the K - f e l d s p a r s e l v a g e s i n the A z u r e Lake a r e a a r e a  retrograde  a l t e r a t i o n of p l a g i o c l a s e and a r e not p a r t of the assemblage formed d u r i n g prograde r e g i o n a l metamorphism. F i g u r e s 2-3c,  2-4c,  2-5c  and 2-7  i l l u s t r a t e the  systematic  p a r t i t i o n i n g of Na between p l a g i o c l a s e and m u s c o v i t e . i n d i c a t e the i n v e r s e r e l a t i o n between a n o r t h i t e content and p a r a g o n i t e  c o n t e n t of c o e x i s t i n g m u s c o v i t e .  The  diagrams  of p l a g i o c l a s e  A g a i n the  different  metamorphic zones do not have d i s t i n g u i s h a b l e element p a r t i t i o n i n g (figure The  2-7). above c o m p o s i t i o n a l r e l a t i o n s a l l support  c h e m i c a l e q u i l i b r i u m d u r i n g r e g i o n a l metamorphism.  the assumption of M i n e r a l grains are  124  homogeneous on the s c a l e of a probe s e c t i o n . . D i f f e r e n t p r o j e c t i o n s t h a t the Gibbs phase r u l e has not been v i o l a t e d . p a r t i t i o n i n g diagrams show a s y s t e m a t i c coexisting minerals.  Projections  indicate  and  p a r t i t i o n i n g of elements between  I n c o n t r a s t , t h i n s e l v a g e s of K - f e l d s p a r  enclosing p l a g i o c l a s e probably represent a retrograde  partly  a l t e r a t i o n of  the  e a r l i e r r e g i o n a l metamorphic assemblage.  MINERAL TEXTURES  T e x t u r a l r e l a t i o n s w i t h i n the p e l i t e s deomonstrate t h a t some of c o e x i s t i n g m i n e r a l s a r e not i n t e x t u r a l e q u i l i b r i u m .  the  Aggregates of  f i b r o l i t i c s i l l i m a n i t e - i l m e n i t e - b i o t i t e - m u s c o v i t e appear t o have formed a t the expense of g a r n e t , s t a u r o l i t e , and k y a n i t e . sequence of r e a c t i o n s i n various  These t e x t u r e s o u t l i n e a  t h a t have been p a r t i a l l y p r e s e r v e d by growth  minerals.  Garnet p o r p h y r o b l a s t s of growth ( f i g u r e 2-8  and  i n a l l t h r e e metamorphic zones o u t l i n e two p l a t e 2-18).  T y p i c a l l y they c o n t a i n an even, s p a r s e , opaque d u s t i n g . porphyroblasts  stages  F i r s t s t a g e g a r n e t s form l a r g e ,  ragged g r a i n s w i t h abundant q u a r t z , p l a g i o c l a s e , m i c a , and  opaque i n c l u s i o n s .  Individual  are p a r t l y to c o m p l e t e l y e n c l o s e d by a g g r e g a t e s of  intergrown f i b r o l i t e , ( p l a t e s 2-1,  patterns  2-3).  c o a r s e m u s c o v i t e , x e n o b l a s t i c i l m e n i t e , and  biotite  Breakdown of g a r n e t to form these a g g r e g a t e s i s more  e x t e n s i v e w i t h i n c r e a s i n g metamorphic grade.  F i r s t stage garnets are  commonly p r e s e r v e d southwest of O v i s Creek ( f i g u r e 2-2) . kyanite porphyroblasts  not  S t a u r o l i t e and  form s i m i l a r r e l i c t g r a i n s w i t h i n a g g r e g a t e s of  m u s c o v i t e of f i b r o l i t e - m u s c o v i t e .  F i b r o l i t e c o a r s e n s t o form s i l l i m a n i t e  p r i s m s w i t h i n c r e a s i n g metamorphic grade. Second s t a g e g a r n e t s form c l e a r , i d i o b l a s t i c r i m s around ragged, f i r s t  125 s t a g e garnet c o r e s . p l a t e 2-1B).  These r i m s c o n t a i n o n l y minor i n c l u s i o n s ( f i g u r e  2-8,  Where f i r s t s t a g e g a r n e t s a r e uncommon, second g e n e r a t i o n  g a r n e t s form s m a l l i d i o b l a s t i c p o r p h y r o b l a s t s .  Fibrolite, biotite,  and  i l m e n i t e a r e p a r t l y t o c o m p l e t e l y e n c l o s e d by second stage r i m s ( f i g u r e p l a t e 2-3). fibrolite  Second stage garnet growth succeeded  2-8,  f o r m a t i o n of the  aggregates.  Chemical z o n i n g p a t t e r n s i n garnet a l s o r e f l e c t two s t a g e s of T r a v e r s e s a c r o s s s e l e c t e d g a r n e t s are shown i n f i g u r e 2-8. g a r n e t c o r e s a r e c o m p o s i t i o n a l l y homogeneous.  First  growth. stage  Second g e n e r a t i o n rims a r e  c o n c e n t r i c a l l y zoned w i t h s p e s s a r t i n e c o n t e n t d e c r e a s i n g outward. Almandine c o n t e n t v a r i e s i n v e r s e l y w i t h s p e s s a r t i n e . I n most samples pyrope and g r o s s u l a r c o n t e n t remain f a i r l y c o n s t a n t . pyrope are a l s o c o n c e n t r i c a l l y zoned.  I n sample 367 g r o s s u l a r and  Zoning p a t t e r n s i n s m a l l second  s t a g e g a r n e t s a t h i g h e r metamorphic grades a r e s i m i l a r but a r e l i m i t e d ... in  range. T h i s z o n i n g i s s i m i l a r t o the "normal" z o n i n g p a t t e r n d e s c r i b e d f o r  metamorphic g a r n e t s from p e l i t i c s c h i s t s (Harte and Henley 1966; and many others).  Hollister  (1966) suggested a f r a c t i o n a t i o n - d e p l e t i o n model t o  e x p l a i n t h e d i s t i n c t i v e c o n c e n t r i c Mn-zoning.  R e c e n t l y i t has been  suggested t h a t the z o n i n g r e s u l t s from c o n t i n u o u s g a r n e t - f o r m i n g r e a c t i o n s d u r i n g prograde metamorphism ( T r a c y , Robinson, and A.B. T r z c i e n s k i 1977) .  Thompson  I n k y a n i t e - and s i l l i m a n i t e - b e a r i n g s c h i s t s  assumes i n c r e a s e d importance i n m o d i f y i n g the o r i g i n a l growth p a t t e r n (Anderson and O l i m p i o 1977; Woodsworth 1977).  A.B.  1976;  diffusion zoning  Thompson,  T r a c y , L y t t l e , and J.B. Thompson (1977) have f u r t h e r argued t h a t i n t e r n a l c h e m i c a l and i n c l u s i o n d i s c o n t i n u i t i e s i n g a r n e t s from Vermont r e s u l t e d from r e s o r p t i o n o f garnet t h r o u g h a d i s c o n t i n u o u s r e a c t i o n i n v o l v i n g g a r n e t  F i g u r e 2-8.  Chemical  zoning patterns of s e l e c t e d garnets.  Spot a n a l y s e s were determined w i t h the e l e c t r o n m i c r o p r o b e .  Brief  d e s c r i p t i o n s of the g a r n e t s a r e g i v e n below:  A)  Sample 74.  F i r s t g e n e r a t i o n garnet w i t h numerous i n c l u s i o n s  e n c l o s e d by a second g e n e r a t i o n r i m c o n t a i n i n g f i b r o l i t e  B)  Sample 2-376.  inclusions,  S m a l l f i r s t g e n e r a t i o n garnet c o r e c o n t a i n i n g  opaque dust surrounded  by l a r g e second g e n e r a t i o n g a r n e t r i m .  127  mol %  GARNET  74  F i g u r e 2-8  C)  (continued).  Sample 367.  Large f i r s t g e n e r a t i o n g a r n e t w i t h narrow second  generation garnet r i m . Chemical zoning i n v o l v e s g r o s s u l a r pyrope as w e l l as almandine and s p e s s a r t i n e .  D)  Sample 40.  S m a l l second g e n e r a t i o n garnet from southwest o f  O v i s Creek.  GARNET  40  mol  130 as a r e a c t a n t phase.  S i n c e garnet was a p r o d u c t phase i n prograde  c o n t i n u o u s r e a c t i o n s a t b o t h h i g h e r and lower t e m p e r a t u r e s , t h e d i s c o n t i n u i t i e s may have formed d u r i n g a s i n g l e prograde metamorphic episode. The sharp change i n i n c l u s i o n d e n s i t y between stage 1 and s t a g e 2 g a r n e t s from t h e Azure Lake a r e a suggests t h a t each g e n e r a t i o n o f growth was formed through a s e p a r a t e metamorphic r e a c t i o n . p a t t e r n i s compatible w i t h homogenization  The o v e r a l l z o n i n g  of f i r s t generation garnets  concomitant w i t h t h e f o r m a t i o n o f f i b r o l i t e a g g r e g a t e s .  Concentric  z o n i n g i n second g e n e r a t i o n g a r n e t s r e s u l t e d from subsequent  growth  a c c o r d i n g t o a c o n t i n u o u s g a r n e t - f o r m i n g r e a c t i o n d u r i n g prograde metamorphism.  The suggested sequence of r e a c t i o n s may be due t o a s i n g l e  prograde metamorphic e p i s o d e . M u s c o v i t e i n t h e f i b r o l i t e aggregates t y p i c a l l y forms c o a r s e , equant, randomly o r i e n t e d f l a k e s . margins  I n d i v i d u a l g r a i n s a r e i n t e r l o c k i n g w i t h ragged  ( p l a t e s 2-1, 2-2, 2-3, 2-4). F i b r o l i t e c o n t e n t i n aggregates  varies  i n v e r s e l y w i t h t h e modal amount o f m u s c o v i t e ; aggregates i n q u a r t z i t i c p e l i t e s commonly c o n t a i n m a i n l y m u s c o v i t e . biotite-fibrolite  At h i g h e r metamorphic grades  aggregates form a t t e n u a t e d t r a i l s through c o a r s e  m u s c o v i t e . g r a i n s ( p l a t e 2-4). P l a g i o c l a s e commonly forms e l o n g a t e augen conformable w i t h t h e regional schistosity.  G r a i n s a r e r a r e l y twinned.  I n many i n s t a n c e s g r a i n s  a r e c o n c e n t r i c a l l y zoned w i t h a narrow r i m o f more c a l c i c c o m p o s i t i o n . S i n c e p l a g i o c l a s e i s t h e o n l y major C a - b e a r i n g phase b e s i d e s garnet i n t h e p e l i t e s , z o n i n g i s p r o b a b l y r e l a t e d t o g a r n e t breakdown. These t e x t u r e s d e s c r i b e t h e i n i t i a l breakdown o f g a r n e t , s t a u r o l i t e , and k y a n i t e t o form aggregates o f f i b r o l i t e - m u s c o v i t e - b i o t i t e - i l m e n l t e .  131 Second stage g a r n e t growth o c c u r r e d a t t h e expense o f p r e v i o u s l y formed f i b r o l i t e aggregates.  Replacement t e x t u r e s w i t h i n aggregates a t h i g h e r  metamorphic grades a l s o i m p l y t h a t m u s c o v i t e growth c o n t i n u e d beyond formation of the f i b r o l i t e .  METAMORPHIC REACTIONS  D e s c r i b e d t e x t u r a l r e l a t i o n s support t h e f o l l o w i n g  sillimanite-  forming r e a c t i o n s : 8 g a r + 9 mus = 14 s i l l •+ 3 b i o + 1 3 q t z , 12 s t a u + 9 mus + 7 q t z = 58 s i l l  +' 3 b i o +' 12 H 0 , .  (2)  2  1 ky = 1 s i l l .  (3)  These r e a c t i o n s a r e b a l a n c e d f o r t y p i c a l metamorphic m i n e r a l c o m p o s i t i o n s i n t h e system K ^ O - F e O - M g O - A l ^ - S K ^ - ^ O  (KFMASH) (A.B. Thompson 1976a).  Q u a r t z , m u s c o v i t e , and ^ 0 have been added where n e c e s s a r y . and  R e a c t i o n s (1)  (2) a r e c o n t i n u o u s i n t h e system KFMASH; they o c c u r over an i s o b a r i c  temperature i n t e r v a l because o f Mg-Fe p a r t i t i o n i n g .  These r e a c t i o n s do  n o t account f o r g r o s s u l a r c o n t e n t i n g a r n e t , p a r a g o n i t e c o n t e n t i n m u s c o v i t e , or T l c o n t e n t i n b i o t i t e .  A d d i t i o n a l phases needed t o i n c o r p o r a t e t h e s e  elements a r e p l a g i o c l a s e and i l m e n i t e . M u s c o v i t e i s r e q u i r e d as a r e a c t a n t phase i n r e a c t i o n s (1) and ( 2 ) . T e x t u r e s i n d i c a t e t h a t c o a r s e m u s c o v i t e i s a p r o d u c t phase w i t h i n t h e f i b r o l i t e aggregates and i s r e p l a c i n g k y a n i t e and s t a u r o l i t e .  T h i s apparent  d i s c r e p a n c y may be e x p l a i n e d by l o c a l c a t i o n exchange r e a c t i o n s and/or changes i n c o m p o s i t i o n , o f t h e f l u i d phase. discussed  Both p o s s i b i l i t i e s a r e  later.  S i m i l a r s i l l i m a n i t e - f o r m i n g r e a c t i o n s have been d e s c r i b e d from o t h e r r e g i o n a l l y metamorphosed t e r r a i n s ( C h a k r a b o r t y and Sen 1967; Y a r d l y 1977). T e x t u r a l d e s c r i p t i o n s f o r garnet breakdown i n p e l i t e s from Connemara,  132 I r e l a n d are s i n g u l a r l y comparable ( Y a r d l e y 1977).  Reactions  (1) and  (2)  c o n t r a s t w i t h the commonly observed r e a c t i o n i n v o l v i n g the breakdown of s t a u r o l i t e and m u s c o v i t e t o form g a r n e t , b i o t i t e , and (A.B.  sillimanite  Thompson 1976a; C a r m i c h a e l 1970).  LINEAR REGRESSION (Table  The use of l i n e a r r e g r e s s i o n t e c h n i q u e s  2-19)  t o s o l v e the mass-balance  c o n s t r a i n t s i m p l i e d by p o s s i b l e metamorphic r e a c t i o n s has been p r e v i o u s l y o u t l i n e d (Greenwood 1968; P i g a g e 1976). for  R e i d , Gancarz, and A l b e e 1973;  1973;  B r i e f l y , the method uses a l e a s t squares approach t o t e s t  l i n e a r dependencies among s e t s of m i n e r a l s  assemblages.  Gray  ( v e c t o r s ) i n one  or more  T e x t u r a l r e l a t i o n s and o t h e r c o n s t r a i n t s are needed t o  s e l e c t p r o b a b l e r e a c t i o n s from among t h e d i f f e r e n t p o s s i b l e mass-balance regression  equations.  A p a r t i c u l a r mass-balance e q u a t i o n  i s considered  s i g n i f i c a n t i f the  r e s i d u a l d i f f e r e n c e between the o b s e r v e d and m o d e l l e d c o m p o s i t i o n s s m a l l e r than the combined p r e c i s i o n e s t i m a t e s  f o r the m i n e r a l and  I n an e a r l i e r study u s i n g l i n e a r r e g r e s s i o n (Pigage  is the model.  1976), s m a l l e r r o r  l i m i t s were shown t o be e s s e n t i a l t o a s s e s s the r e l i a b i l i t y of a l e a s t s q u a r e s model.  Elements o c c u r r i n g i n s m a l l amounts commonly f a l l w i t h i n  e r r o r l i m i t s r a t h e r than p r o v i d i n g a d d i t i o n a l c o n s t r a i n t s on the  regression  coefficients. I have m i n i m i z e d t h i s problem by w e i g h t i n g  each mass-balance  equation  a c c o r d i n g t o the i n v e r s e of the v a r i a n c e of the mean f o r a p a r t i c u l a r s e t of analyses  ( R e i d , Gancarz, and A l b e e  considered  negligible.  I n t h i s way  i m p o r t a n c e i n the r e g r e s s i o n model.  1973).  Inter-element  covariances  minor elements assumed i n c r e a s e d  were  133 The s t a n d a r d w e i g h t e d  l e a s t squares approach assumes t h a t t h e  independent v a r i a b l e s i n t h e r e g r e s s i o n e q u a t i o n a r e e n t i r e l y f r e e o f e r r o r . T h i s approach i s v a l i d when a n a l y z e d m i n e r a l s a r e b e i n g modelled of end-member c o m p o s i t i o n s .  i n terms  I n m o d e l l i n g metamorphic r e a c t i o n s , however,  m i n e r a l a n a l y s e s among t h e independent v a r i a b l e s u s u a l l y have e r r o r s o f about t h e same magnitude as t h e dependent v a r i a b l e .  In t h i s s i t u a t i o n the  problem becomes n o n l i n e a r and must be s o l v e d i t e r a t i v e l y . Provost  A l b a r e d e and  (1977) have d e s c r i b e d an a l g o r i t h m f o r s o l v i n g weighted  least  squares problems w h i c h r e c o g n i z e s e r r o r s i n b o t h t h e dependent and independent v a r i a b l e s .  T h i s a l g o r i t h m was used t o t e s t f o r p o s s i b l e  metamorphic r e a c t i o n s , among t h e Azure Lake p e l i t e assemblages.  Examination  of r e g r e s s i o n c o e f f i c i e n t s and r e s i d u a l s from t h i s approach i n d i c a t e s t h a t i t g i v e s r e s u l t s s i m i l a r t o those r e s u l t i n g from s t a n d a r d weighted  linear  regression techniques. A r e g r e s s i o n model was c o n s i d e r e d s i g n i f i c a n t , i f t h e modelled c o m p o s i t i o n f o r each a n a l y z e d m i n e r a l i n t h e r e g r e s s i o n e q u a t i o n was w i t h i n the t w o - s i d e d c o n f i d e n c e i n t e r v a l c a l c u l a t e d from t h e e s t i m a t e d errors f o r that mineral.  standard  A l l c o n f i d e n c e i n t e r v a l s were c o n s t r u c t e d a t t h e  95% p r o b a b i l i t y l e v e l ( a = 0.05).  A p p r o p r i a t e t - f a c t o r s were s e l e c t e d  from s t a t i s t i c a l t a b l e s (Guenther 1965, p. 2 9 4 ) . T e x t u r a l r e l a t i o n s i n p e l i t i c u n i t s o f t h e Shuswap Complex suggest t h a t garnet and s t a u r o l i t e were b r e a k i n g down t o form b i o t i t e - m u s c o v i t e i l m e n i t e - f i b r o l i t i c s i l l i m a n i t e aggregates.  The r e g r e s s i o n approach was  used t o model s t a u r o l i t e and garnet i n terms o f t h e o t h e r m i n e r a l s c o e x i s t i n g w i t h them.  Zn was e x c l u d e d from t h e mass-balance e q u a t i o n s  because o t h e r metamorphic s t u d i e s i n d i c a t e t h a t Zn remains i n r e l i c s t a u r o l i t e i n i n c r e a s i n g c o n c e n t r a t i o n s w i t h t h e p r o g r e s s i v e breakdown o f m a t r i x s t a u r o l i t e ( G u i d o t t i 1970; Woodsworth 1977).  A f l u i d phase  134 c o n s i s t i n g o f R^O was assumed t o be p r e s e n t .  Q u a r t z , H^O, and s i l l i m a n i t e  were c o n s i d e r e d t o be s t o i c h i o m e t r i c and f r e e o f e r r o r (Albee and Chodos 1969; Ghinner, S m i t h , and Knowles 1969; Kwak 1971). The r e g r e s s i o n models o f s t a u r o l i t e and garnet s h o u l d i d e a l l y use c o m p o s i t i o n s o f c o e x i s t i n g m i n e r a l s a t t h e time o f i n i t i a l formation.  fibrolite  Based on t h e t e x t u r a l i n t e r p r e t a t i o n p r e s e n t e d e a r l i e r ,  would c o r r e s p o n d t o m i n e r a l c o m p o s i t i o n s i n e q u i l i b r i u m w i t h f i r s t t i o n garnet r i m s .  this genera-  S y s t e m a t i c p a r t i t i o n i n g o f Mg and Fe between second  g e n e r a t i o n g a r n e t rims and b i o t i t e  ( f i g u r e 2-6)indicates that the v a r i o u s  homogeneous m i n e r a l s have a d j u s t e d t h e i r c o m p o s i t i o n s t o remain i n near e q u i l i b r i u m w i t h t h e l a t e r s t a g e two garnet r i m c o m p o s i t i o n s .  Consequently  c o m p o s i t i o n s i n e q u i l i b r i u m w i t h f i r s t g e n e r a t i o n g a r n e t s have n o t s u r v i v e d and cannot be used f o r t h e r e g r e s s i o n s t u d i e s . W h i l e r e c o g n i z i n g t h i s problem, I have chosen t o model s t a u r o l i t e and garnet breakdown u s i n g r i m c o m p o s i t i o n s f o r a l l m i n e r a l s .  Major  priority  has t h e r e f o r e been p l a c e d on u s i n g e q u i l i b r i u m c o m p o s i t i o n s f o r c o e x i s t i n g minerals.  The. s i g n i f i c a n c e o f t h i s c h o i c e cannot be f u l l y a s s e s s e d .  c o m p o s i t i o n s d i f f e r m a i n l y i n Fe and Mn c o n t e n t .  The b i o t i t e  Garnet  inclusion  w i t h i n garnet from sample 74, however, has a c o m p o s i t i o n v e r y s i m i l a r t o m a t r i x b i o t i t e i n t h e same sample (see T a b l e 2-5).  Regression equations  must be r e g a r d e d as i n t e r p r e t i v e r a t h e r than s t r i c t l y  quantitative.  S e v e r a l d i f f e r e n t p o s s i b l e r e g r e s s i o n models aire l i s t e d i n T a b l e 2 1 9 • —  E q u a t i ons R—1 t h r o u g h R—9 use t h e same m i n e r a l c o m p o s i t i o n s f o r comparative purposes  (sample 82).  and/or g a r n e t t o form  A l l t h e models i n v o l v e t h e breakdown o f s t a u r o l i t e sillimanite.  R e a c t i o n s R - l and R-2 model g a r n e t and s t a u r o l i t e i n terms o f edge c o m p o s i t i o n s of c o e x i s t i n g phases.  R e s i d u a l s a r e much l a r g e r than p e r m i t t e d  135  T a b l e 2-19. R e g r e s s i o n e q u a t i o n s f o r p e l i t i c m i n e r a l assemblages, Shuswap Metamorphic Complex, Azure Lake, B r i t i s h  Equation R - l .  Columbia.  Sample 82 - r e g r e s s i o n model o f g a r n e t .  REGRESSION  SIGMA  COEFFICIENTS SILL QTZ 17.321 18.557 0.401 0.470  INFORMATION  PERTAINING  RESIDUALS ELEMENT SI + 4 ALO FE + 2 HN*2 HG*2 CA +2 NA+ 1 K* 1 H+ 1 TI*4 BA + 2 P*0 ERROR  RATIO  (X  H20 11.100 0. 277  BOS -6.712 0. 1*49  BIO 1.153 0.012  PLAG 0.711 0.008  ILH 0.123 0. 005  TO THIS P I T :  - X*)  MUS -0.000 -0.000 0. 040 0.0 -0.144 0.0 0. 209 1.217 -0.000 -0.009 0.0 19 0.005  BIO 0. 000 0.000 -0.035 -0.006 0. 128 0.0 -0.012 -0.423 0. 000 0.008 -0.000 -0.001  PLAG 0.000 0. 000 0.0 0.0 0.0 0. 009 -0.006 -0.000 0.0 0.0 0.0 0.0  (RESIDUAL / PERMITTED  ELEMENT MUS SI*4 0. 000 AL*3 0. 000 FE + 2 8. 296 0. 0 HN*2 MG + 2 33.998 CA*2 0. 0 NA* 1 18.932 K* 1 83.676 H+1 0. 000 TI*4 4. 230 BA + 2 16.987 F*0 1. 974  BIO 0.000 0. 000 3. 170 6.561 12.992 0.0 1.808 19 .980 0. 000 1.616 0.651 0.251  CORRELATION COEFFICIENTS SILL 1.000 QTZ 0. 977 1.000 H20 0. 995 0.984 MUS -0.996 -0.984 BIO 0. 848 0.827 PLAG -0.177 -0.199 ILH 0.662 0.66 1 SILL QTZ  ERROR  PLAG 0.000 0.000 0.0 0.0 0.0 2. 157 1.073 0. 237 0.0 0.0 0.0 0.0  1.000 -0.998 0.841 -0. 164 0.668 H20  ILH 0.0 0. 000 -0.002 -0.001 0.002 0. 0 0. 0 0.0 0.0 0. 003 0.0 0.0  GAR -0.000 -0.000 0.02 0 0.061 -0.127 -0.010 0.0 0.0 0.0 -0.000 0.0 0.0  ) ILH 0.0 0. 000 0.223 0. 685 0. 406 0.0 0.0 0. 0 0.0 0. 278 0.0 0.0  1.000 -0.864 0. 165 -0.6 56 HUS  GAS 0. 000 0.000 2.364 21.758 12.917 2.710 0.0 0.0 0.0 0. 16 1 0.0 0.0  1.000 -0.153 0.392 BIO  1.000 -0.100 PL AS  1.000 ILH  GAR 1. 000  136  Table 2-19 ( c o n t . ) . E q u a t i o n R-2.  Sample 82 - r e g r e s s i o n model o f s t a u r o l i t e .  DEGRESSION COEFFICIENTS SILL QTZ 10.383 -1. 316 SIGBA 0.014 0. 056  H20 2. 337 0. 019  NUS 1. 254 0.012  BIO 1. 109 0. 007  PLAG 0.069 0. 004  IL (1 0. 119 0. 006  NPOHH AT ION PERTAINING TO T BIS F I T : RESIDUALS ELEMENT SI*4 AL*3 FE+2 BN + 2 BG + 2 CA + 2 NA*1 K* 1 H* 1 TI*4 BA*2 F*0 EB ROB  RATIO  ELEBENT SI + 4 AL»3 FE*2 BB*2 HG + 2 CA*2 NA* 1 K*1 H* 1 TI*4 BA»2 F+ 0  (X - X*) BUS -0.000 -0.000 0.014 0.0 -0.012 0. 0 0. 140 0. 046 -0.000 -0.003 0.010 -0.052  BIO 0.000 0.000 -0.065 -0.001 0.055 0.0 -0.040 -0.083 0. 000 0.013 -0.000 0.026  PL AG 0.000 0.000 0.0 0.0 0.0 0.003 -0.002 -0.000 0.0 0.0 0.0 0.0  (RESIDUAL / PERBITTED BUS 0.000 0.000 2.981 0.0 2. 823 0.0 12.641 3. 182 0. 000 1. 348 9. 201 19.153  ILB 0.0 0.000 -0.004 -0.000 0.001 0.0 0. 0 0.0 0.0 0.005 0.0 0.0  STAU -0.000 -0.000 0.322 0.008 -1 .567 -0.016 0.0 0.0 -0.000 -0.26 2 0.0 0.0  ERROR )  BIO 0.000 0.000 5.867 1.606 5.557 0.0 6.220 3.913 0.000 2.652 1.815 12.563  PLAG 0.000 0.000 0.0 0.0 0.0 0.712 0. 370 0.005 0.0 0.0 0.0 0.0  ILB 0.0 0.000 0. 416 0. 169 0. 175 0.0 0.0 0.0 0. 0 0. 460 0.0 0.0  STAO 0.000 0.000 10.745 3.138 24.426 5.264 0.0 0.0 0.000 9.714 0.0 0.0  CORRELATION COEFFICIENTS SILL 1. 000 QTZ -0.209 1.000 U20 0. 527 0.469 nos -0.570 -0.405 BIO 0. 272 0.061 PL AG -0.118 -0.182 ILB -0.144 -0.007 SILL QTZ  1.000 -0.764 0. 181 -0.066 -0.061 H20  1.000 -0.705 0. 130 0.414 nos  1 .000 -0.138 -0.652 BIO  1.000 0.085 PLAG  1 .000 ILH  STAU •1. 000  137  Table 2-19 ( c o n t i n u e d ) . E q u a t i o n R-3.  Sample 82 - R e g r e s s i o n model o f s t a u r o l i t e :  garnet  i n c l u d e d i n model.  REGRESSION  SIGMA  COEFFICIEHTS SILL QTZ 9.915 -1. 583 0.045 0.054  INFORMATION  MUS - 1 . 031 0. 012  BIO 0.914 0.009  PLUG -0.045 0.005  IL H 0.095 0. 006  P E R T A I N I N G TO T H I S F I T :  RESIDUALS  (X - X « )  ELEMENT MUS SI*4 0.000 AL*3 0.000 0.009 FE»2 0.0 MN»2 -0.008 NG»2 0.0 CA*2 NA*1 0. 196 K*1 0.045 H* 1 0.000 TI*4 -0.002 BA*2 0.010 F»0 -0.052 EBBOR  H20 2. 272 0.016  BATIO  ELEMENT SI + 4 AL*3 FE»2 HN*2 HG*2 CA*2 NA* 1 K* 1 H»1 TI»4 BA»2 P»0 CORRELATION SILL QTZ H20 H0S BIO PLAG ILH GAB  BIO -0.000 -0.000 -0.041 0.001 0.037 0.0 -0.056 -0.080 -0.000 0.008 -0.000 0.026  (BESIOUAL HQS 0. 000 0.000 1. 869 0.0 1. 908 0.0 17.746 3.068 0.000 0.810 9. 173 19.192  PLAG 0.000 0.000 0.0 0.0 0.0 -0.003 0.002 0.000 0.0 0.0 0.0 0.0  ILN 0.0 -0.000 -0.002 0.000 0.000 0.0 0.0 0.0 0.0 0. 003 0.0 0.0  GAR -0.000 -0.000 -0.007 0.00 3 0.011 0.013 0.0 0.0 0.0 0.000 0.0 0.0  STAU 0.000 0.000 0.246 -0.006 -1.288 -0.027 0.0 0.0 0. 000 -0.192 0.0 0. 0  GAR 0.000 0.000 0. 860 1 .098 1. 170 3.824 0.0 0.0 0.0 0.050 0.0 0.0  STAU 0.000 0.000 8. 196 2.510 20. 0 76 8.751 0.0 0.0 0. 000 7. 101 0.0 0.0  / P E B H I T T E D EBROB )  BIO 0.000 0.000 3.690 1.059 3.766 0.0 8.757 3.784 0.000 1.598 1.815 12.626  PLAG 0.000 0.000 0.0 0.0 0.0 0. 768 0.410 0.004 0.0 0.0 0.0 0.0  ILH 0. 0 0.000 0. 254 0. 108 0. 115 0.0 0. 0 0.0 0.0 0.269 0.0 0.0  COEFFICIENTS 1.000 -0.215 1 .000 0. 4 5 * 0.425 -0.590 -0.413 0.412 0. 189 -0.011 -0.104 -0.070 0.016 -0.316 -0.187 SILL QTZ  1.000 -0.638 0. 163 -0.152 -0.065 -0.032 B20  1.000 -0.818 0.002 0.266 0.493 H0S  1.000 0.138 -0.314 -0.664 BIO  1.000 0.299 -0.530 PLAG  1.000 -0.240 ILH  GAR 0.248 0. 009  STAU -1.000  138 T a b l e 2-19 ( c o n t i n u e d )  E q u a t i o n R-4. Sample 82 - R e g r e s s i o n model o f  garnet:  anorthite  i n c l u d e d i n model.  REGRESSION C O E F F I C I E N T S SILL ANOR 19.948 -0. 733 SIGH* 0.470 0.028 INFORHATION  PERTAINING  RESIDUALS  U2 0 13.515 0. 343  BUS •8.020 0. 185  BIO 1.24 8 0.015  PLAG 3.252 0. 097  ILI 0. 1«8 0.006  TO T H I S F I T :  (X - X*)  ELEBENT DOS SI»4 0.000 AL*3 0.000 FE*2 0.024 HN*2 0.0 HG»2 -0.130 CA*2 0.0 NA*1 -0.004 K»1 1.254 H«1 0.000 TI*4 -0.006 BA*2 0.019 F+0 0.007 ERROR RATIO  QTZ 17.945 0.450  BIO -0.000 -0.000 -0.019 -0.006 0. 105 0.0 0.000 -0.394 -0.000 0.005 -0.000 -0.001  PLAG -0.000 -0.000 0.0 0.0 0.0 0.000 0.000 -0.000 0.0 0.0 0.0 0.0  (RESIDUAL / PERMITTED  ELEHENT MUS SI*4 0.000 AL*3 0.000 FE+2 4.979 MN»2 0.0 NG + 2 30.629 CA*2 0.0 NA + 1 0.386 K*1 86.181 H»1 0.000 Tim 2. 864 BA»2 17.160 F»0 2.646  BIO 0.000 0.000 1.723 6.943  ILH 0.0 -0.000 -0.001 -0.001 0. 001 0.0 0.0 0.0 0.0 0.002 0.0 0.0  GAR 0.000 0.000 0.010 0.059 -0.096 -0.000 0.0 0.0 0.0 -0.000 0.0 0.0  ERROR )  10.603 0.0 0.033 18.643 0.000 0.991 0.595 0.305  PLAG 0.000 0.000 0.0 0.0 0.0 0.000 0.084 0.935 0.0 0.0 0.0 0.0  CORRELATION C O E F F I C I E N T S SILL 1.000 AN0B -0.757 1.000 QTZ 0. 949 -0.610 H20 0.994 -0.781 HUS -0.995 0.782 BIO 0.875 -0.691 PLAG 0.775 -0.973 ILB 0.656 -0.513 SILL ANOR  1.000 0.948 •0. 948 0.820 0.624 0.636 QTZ  ILH 0.0 0.000 0.135 0. 808 0. 370 0.0 0.0 0.0 0.0 0. 190 0.0 0.0  1.000 -0.998 0.870 0.802 0.663 H20  GAR 0.000 0.000 1.187 21.272 9.739 0.000 0.0 0.0 0.0 0.091 0.0 0.0  1.000 -0.889 -0.803 -0.651 BUS  1.000 0.710 0.420 BIO  1.000 0.527 PLAG  1.000 ILH  GAB -1.000  139 Table 2-19 ( c o n t i n u e d ) .  E l a t i o n R-5. S a ^ l e 82 - Regression „ B  d e  l of s t a u r o l i t e :  anorthite  I n c l u d e d i n model.  REGRESSION  SIGMA  COEFFICIENTS SILL ANOR 10.446 -0.109 0.04* 0.003  INFORMATION RESIDUALS ELEMENT S I +4 AL*3 FE*2 MN+2 MG*2 CA+2 NA»1 K*l H+l TI*4 BA»2 F*0 ERROR RATIO  H20 2.443 0.019  MUS -1.318 0.012  BIO 1. 120 0. 00 7  PLAG 0.396 O.OU  PERTAINING TO THIS F I T :  ILM 0.115 0.006  (X - X * l MUS 0.000 0.000 0.014 0.0 -0.013 0.0 -0.000 0.071 0.000 -0.003 0.011 -0.050  BIO -0.000 -0.000 -0.063 -0.001 0.056 0.0 0.000 - 0 . 122 -0.000 0.013 -0.000 0.025  PLAG -0.000 -0.000 0.0 0.0 0.0 0.000 0.000 -0.000 0.0 0.0 0.0 0.0  (RESIDUAL / PERMITTEO  ELEMENT MUS SI*4 0.000 AL*3 0.000 FE»2 3.027 MN*2 0.0 MG+2 2.990 CA»2 0.0 NA*1 0.02 0 K*l 4.900 H*l 0.000 TI*4 1.369 8A»2 9.577 F»0 18.598 CORRELATION SILL ANOR OTZ H20 MUS BIO PLAG ILM  QTZ -1.726 0.056  BIO 0.000 0.000 5.725 1.621 5.656 0.0 0.010 5.791 0.000 2.588 1.816 11.722  COEFFICIENTS 1 .000 0.158 1 .000 0.286 0.158 0.520 -0.312 0.554 0.365 0.260 -0.215 0.159 -0.914 0. 133 0. 119 SILL ANOR  STAU 0.000 0.000 0.311 0.008 -1.579 -0.000 0.0 0.0 0.000 -0.253 0.0 0.0  ERROR .  PLAG 0.000 0.000 0.0 0.0 0.0 0.000 0.003 0.039 0.0 0.0 0.0 0.0  1.000 0.351 -0.26* -0.029 -0.184 0.045 OTZ  ILM 0.0 -0.000 -0.004 -0.000 0.001 0.0 0.0 0.0 0.0 0.005 0.0 0.0  ILM 0.0 0.000 0. 390 0.164 0.171 0.0 0.0 0.0 0.0 0.431 0.0 0.0  1.300 -0.781 0.204 0.342 -0.072 H20  STAU 0.000 0.000 10.381 3.136 24.612 0.000 0.0 0.0 0.000 9.387 0.0 0.0  1 .000 -0.701 -0. J99 0.404 MUS  1.000 0.235 -0.642 BIO  1.000 -0.130 PLAG  1.000 ILM  STAU -1.000  140  Table 2-19 (continued)  Equation R-6.  Sample 82 - Regression model of s t a u r o l i t e :  anorthite  and garnet included i n model.  REGRESSION COEFFICIENTS SILL ABOB 8.330 -0.206 siam o.osi 0.003  QTZ -3. 116 o.osi  R20 2.085 0.010  BOS -0.273 0.022  BIO 0. 23 5 0.019  PLAG 0.082 0. 007  ILH 0.063 0.005  GAR 1.002 0.019  INFORHATION PERTAINING TO THIS F I T : RESIDUALS ELEHEHT SI HI AL»3 Tt*2 a»*2  NG»2 CA«2 NAM N«1 H*1 TIM BA»2 T*0  EBBON BATIO ELEHENT SIM AL»3 FE»2 NN»2 HG«2 CJ.2 NA«1 K»1 HO TIM BA»2 F»0  (X - X*) H0S 0.000 0.000 0.000 0.0 -0.000 0.0 -0.000 0.062 0.0 -0.000 0.011 -0.051  BIO -0.000 -0.000 -0.002 0.001 0.002 0.0 0.000 -0.107 0.0 0.000 -0.000 0.025  PL AG -0.000 -0.000 0.0 0.0 0.0 -0.000 0.000 -0.000 0.0 0.0 0.0 0.0  ILH 0.0 -0.000 -0.000 0.000 0.000 0.0 0.0 0.0 0.0 0.000 0.0 0.0  GAB -0.000 -0.000 -0.005 0.0*0 0.007 -0.000 0.0 0.0 0.0 0.000 0.0 0.0  STAU 0.000 0.000 0.043 -0.019 -0.205 0.000 0.0 0.0 0.0 -0.022 0.0 0.0  STAU 0.000 0.000 1.450 8. 007 3.198 0.000 0.0 0.0 0.0 0. 816 0.0 0.0  (BESID0AL / PEBHITTED EBBOB ) BOS 000 ,000 ,088 0 080 0 018 233 0 025 »37 810  BIO 0.000 0.000 0.168 0.870 0. 15* 0.0 0.008 5.078 0.0 0.0«7 1.816 12.03*  COBBELATION COEFFICIENTS SILL 1.000 ANON 0.«02 1.000 0TI -0.060 0.317 B20 0.5*0 0.318 NOS -0.762 -0.50* BIO 0.757 0.511 FLAG 0.720 0.*11 ILI -0.002 0.236 CAN -0.7M -0.63* SILL ANOI  PL AG 0.000 0.000 0.0 0.0 0.0 0.000 0.003 0.034 0.0 0.0 0.0 0.0  ILI 0.0 0.000 0.030 0.227 0.012 0.0 0.0 0.0 0.0 0.020 0.0 0.0  GAB 0.000 0.000 0.615 1*.161 0.75* 0.000 0.0 0.0 0.0 0.023 0.0 0.0  1.000 0.332 0.453 0.4*7 0.*08 0.120 0.506 QT»  1.000 -0.699 0.673 0.67* -0.059 -0.627 H20  1.000 -0.997 -0.950 0.092 0.930 •as  1.000 0.9«* -0.09* -0.933 BIO  1.000 -0.087 -0.880 PLA8  1.000 -0.1*7 ILH  1.000 HAN  STA0 -1.000  141  T a b l e 2-19 ( c o n t i n u e d ) .  E q u a t i o n R-7.  Sample 82 - R e g r e s s i o n model o f g a r n e t :  a n o r t h i t e and  r u t i l e i n c l u d e d i n model.  REGRESSION COEFFICIENTS SILL ANOR 1.0*2 0. 170 SIGMA 0.005 0.002  OTZ 1.722 0.007  H20 0.057 0.00 3  RUT -2.120 0.009  MUS -0.185 0.003  BIO 0.159 0.003  PLAG 0.055 0.002  ILN 1.0*5 0.004  GAR -I .000  INFORMATION PERTAINING TO THIS F I T : RESIDUALS  (X  ELEMENT MUS SI»* 0.000 0.000 AL*3 -0.000 FE*2 MN»2 0.0 MG*2 0.000 CA-»2 0.0 NA*1 -0.000 K*l 0.061 H-l 0. 000 TI»* 0.000 BA*2 0.011 F»0 -0.051 ERROR RATIO  PL AG -0.000 -0.000 0.0 0.0 0.0 0.0 0.000 -0.000 0.0 0.0 0.0 0.0  (RESIDUAL / PERMITTED ERROR  ELEMENT MUS SI** 0.000 AL«3 0.000 FE*2 0.0*5 MN»2 0.0 MG*2 0.039 C««2 0.0 NAU 0.018 K»l *.22* H»l 0.000 Tl»* 0.000 BA-2 "».*35 F»0 18.812 CORRELATION SILL ANOR OT I H20 RUT MUS BIO PLAG ILM  BIO -0.000 -0.000 0.001 -0.001 -0.001 0.0 0.000 -0.107 -0.000 -0.000 -0.000 0.025  BIO 0.000 0.000 0.086 0.787 0.075 0.0 0.008 5.069 0.000 0.000 1.816 12.039  COEFFICIENTS 1.000 0.*19 1 .000 0.158 -0.160 0.771 -0.126 0.387 -0.082 0.835 0.162 0.667 -0.1*1 0.*26 -0.282 0.*56 0.097 SILL ANOR  PL AG 0.000 0.000 0.0 0.0 0.0 0.0 0.003 0.03* 0.0 0.0 0.0 0.0  1 .000 0.335 -0 . 1 11 0. 000 -0.180 -0.275 0.136 OTZ  ILM 0.0 -0.000 0.00* -0.006 -0.001 0.0 0.0 0.0 0.0 -0.300 0.0 0.0  GAR 0.000 0.000 -0.00* 0.053 0.005 0.0 0.0 0.0 0.0 0.000 0.0 0.0  1 ILM 0.0 0.000 0.3 73 5.061 0.1*5 0.0 0.0 0.0 0.0 0.000 0.0 0.0  GAR 0.000 0.000 0.*63 18.863 0.5*0 0.0 0.0 0.0 0.0 0.000 0.0 0.0  1.000 0.211 -0.485 0.3T3 0.**7 -0.2*3 M20  1.000 -0.5*1 0.588 0.292 -0.873 RUT  1.000 -0.927 -0.573 0.6*1 MUS  1.000 0.501 -0.700 BIO  1.000 -0.3*3 PL AG  .000  ILN  142  T a b l e 2-19 ( c o n t i n u e d ) . Equation  R-8.  Sample 82 - R e g r e s s i o n  model o f s t a u r o l i t e : a n o r t h i t e and  r u t i l e i n c l u d e d i n model.  REGRESSION COEFFICIENTS SILL ANOR 9.232 -0.026 SIGflA 0.039 0.002 |  H20 2. 106 0.009  RUT -2. 397 0.031  BUS -0.341 0.015  BIO 0.295 0.012  PLAG 0. 102 0.005  ILH 1.213 0.015  INFOBHATION PERTAINING TO THIS F I T : RESIDUALS ELEHENT SI*» AL»3 FE»2 HN»2 no*2  C»»2 NA»1 K»1 H«1 TI»4 BA*2 P*0 ERROR RATIO ELEMENT  (X - X*) BUS 0.000 0.000 0.000 0.0 -0.000 0.0 -0.000 0.061 0.0 -0.000 0.011 -0.051  BIO -0.000 -0.000 -0.000 0.000 0.000 0.0 0.000 -0.107 0.0 0.000 -0.000 0.025  PL AG -0.000 -0.000 0.0 0.0 0.0 -0.000 0.000 -0.000 0.0 0.0 0.0 0.0  (RESIDUAL / PERMITTED ERROR  -0.000 -0.000 0.000 0.000 0.0 0.0 0. 0 0.0 0.000 0.0 0.0  STAU 0.000 0.000 0.001 -0.001 -0.005 0.000 0.0 0.0 0.0 -0.000 0.0 0.0  )  PLAG 0.000 0.000 0.0 0.0 0.0 0.000 0.003 0.034 0.0 0.0 0.0 0.0  ILH 0.0 0.000 0.015 0.322 0.006 0.0 0.0 0.0 0.0 0.000 0.0 0.0  STAU 0.000 0.000 0.037 0.572 0.078 0.000 0.0 0.0 3.0 0.000 0.0 0.0  CORRELATION COEFFICIENTS SILL 1.000 ANOR -0.31B 1.000 QTX 0. 100 -0.73* B20 0.293 -0.386 ROT 0. 370 -0.532 BUS -0.46* 0.656 BIO 0. *«7 -0.692 PLAG 0. 388 -0.769 ILH -o. * o a 0.582 SILL ANOB  1.000 -0.011 -0.123 0. 127 -O.1»8 -0.158 0. 136 QTI  1. o o o 0.408 -0.563 0.H95 0.502 -0.9*5 H20  1.000 -0.81B 0.829 0.691 -0.926 BOT  AL»3 PE»2 HR»2 MG»2 CA»2 NA»1 K»1 B«1 TI»» Bi»2  r»o  HUS 0.000 0.000 0.003 0.0 0.002 0.0 0.018 V. 229 0.0 0.000 9.U35 18.812  ILH o.d  BIO 0.000 0.000 0.005 0.078 0.005 0.0 0.008 5.069 0.0 0.000 1.816 12.039  sim  I  QTZ -1. 336 0.01K  1.000 -0.988 -0.853 0.895 aos  1.000 0.835 -0.907 BIO  1.000 -0.756 PLAG  STAU -1.000  143  T a b l e 2-19 ( c o n t i n u e d ) . E q u a t i o n R-9.  Sample 82 - R e g r e s s i o n model o f s t a u r o l i t e :  anorthite,  r u t i l e , and garnet i n c l u d e d i n model.  8EGBESSI0H COEFFICIEHTS SILL A HOB 9.262 -0. 020 SIGHA 0.043 0.001  QTZ -1.280 0.055  H20 2. 107 0.009  BUT -2.471 0.054  GAB 0.032 0.019  BOS -0.315 0.015  BtO 0. 297 0.012  PLAS 0. 103 0.005  ILH 1. 280 0. 027  STA0 -1. 000  INPOBHATION PEBTAIHIHG TO TBIS F I T : BESIDUALS  ( I - !•)  ELEMENT GAB SI.1 0. 000 0.000 AL*3 0.000 FE»2 BN»2 -0.000 0.000 HG»2 C»»2 -0.000 HAH 0.0 K.I 0.0 HO 0.0 TI»1 0.000 BA*2 0.0 F»0 0.0 ER BOB BATIO ELEOEST SI»4 »L.3 FE«2  BOS 0.000 0.000 0.000 0.0 0.000 0.0 -0.000 0.061 0.000 0.000 0.011 -0.051  BIO -0.000 -0.000 -0.000 0.000 -0.000 0.0 o.ooo  -0.107 -0.000 -0.000 -0.000 0.025  PLAG -0.000 -0.000 0.0 0.0 0.0 0.000 0.000 -0.000 0.0 0.0 0.0 0.0  ILB 0.0 -0.000 -0.000 -0.000 0.0 0.0 0.0 0.0 -0.000 0.0 0.0  STAU 0.000 0.000 0.000 -0.000 0.000 -0.000 0.0 0.0 0.000 0.000 0.0 0.0  o.ooo  (BESIDUAL / PEBBITTED EBBOB ) BUS 0.000 0.000 0.000 0.0 0.000 0.0 0.018 1. 221 0.000 0.000 9.135 18.812  BIO 0.000 0.000 0.000 0.000 0.000 0.0 0.008 5.069 0.000 0.000 1. 816 12.039  PLAG 0.000 0.000 0.0 0.0 0.0 0.000 0.003 0.031 0.0 0.0 0.0 0.0  ILK 0.0 0.000 0.000 0.000 0.000 0.0 0.0 0.0 0.0 0.000 0.0 0.0  STAU 0.000 0.000 0.000 0.000 0.000 0.000 0.0 0.0 0.000 0.000 0.0 0.0  COBBELATIoa COEPFICIEHTS SILL 1.000 ANOB 0.215 1 .000 QTZ -0.286 0.565 H20 0.292 -0.136 B0T -0.1»0 -0.860 GAB -o. mo -0.870 BOS -0.470 0.212 BIO 0.155 -0.201 PLAG 0. 391 -0.286 ILH 0.121 0.876 SILL ABOB  1.000 0. 029 -0.518 -0.602 0.026 -0.012 -0.062 0.555 QTZ  1.000 0.185 -0.061 -0.565 0.197 0.S03 -0. 204 B20  1.000 0.815 -0.369 0.373 0.311 -0.975 BUT  1.000 0.123 -0.125 -0. 104 -0.818 GAB  n»»2  «Ci2 CA»2 »AO HO HO TI.U BA»2 P.O  GAB 0. 000 0.000 0.000 0. 000 0.000 0.000 0.0 0.0 0.0 0.000 0.0 0.0  1.000 -0.988 -0.853 0.410 BUS  1.000 0. 835 -0.4 15 BIO  1.000 -0.346 PLAG  1.000 ILH  144  Table 2-19 ( c o n t i n u e d ) .  E q u a t i o n R-10.  Sample 2-376 - R e g r e s s i o n model o f g a r n e t :  anorthite  and r u t i l e i n c l u d e d i n model.  8E5RESSION COEFFICIENTS SILL ANOB 1. 003 0. 197 SIGN* 0. 007 0.003 INPORHATION PERTAINING RESIDDALS ELEMENT sim  AL»3 FE*2 MN*2 HG*2 CA»2 Ni»1 K• 1 H*1 TI*1 BA*2 F-tO ERROR RATIO ELEMENT SI*4 AL + 3 PE*2 MN»2 na*2  CA*2 NA+ 1 K*1 H+1 Tint BA*2 P*0  QTZ 1.716 0. 007  H20 0. 063 0. 002  RUT -2. 1 37 0. 5 16  HUS -0. 199 0. 002  BIO 0. 172 0. 001  PLAG 0. 06 1 0. 001  TO THIS P I T :  (X - X«) NOS 0.000 0. 000 -0.000 0.0 0. 000 0.0 -0.000 0.058 0.0 -0.000 0. 006 -0.020  BIO -0.000 -0.000 0.00 1 -0.000 -0.002 -0.000 0.000 -0.065 0.0 0.000 -0.001 0.088  PLA3 -0.000 -0.000 0.0 0.0 0.0 -0.000 0.000 -0.000 0.0 0.0 0.0 0.0  ILH 0.0 -0.000 0. 077 -0.023 -0.000 -0.ooo 0.0 0.0 0.0 0.000 0.0 0.0  GAR 0.000 0.000 -o.ooi 0.014 0.003 0.000 0.0 0.0 0.0 -0.000 0.0 0.0  (RESIDUAL / PERHITTED ERROR ) MUS 0.000 0. 000 0.060 0.0 0.111 0.0 0. 005 5.579 0.0 0.000 11.152 22.667  BIO 0.000 0.000 0. 177 0.642 0. 218 0.000 0.005 5.453 0.0 0.000 4. 37 2 14.329  CORRELATION COEPPICIENTS SILL 1.000 ANOR -0.535 1.000 QTZ -0.086 -0.175 H20 0. 159 -0.041 RUT 0.019 -0.005 HUS -0.162 0.049 BIO 0. 280 -0.037 PLAG 0. 399 -0.058 ILH -0.059 0.006 SILL ANOB  PLAG 0.000 0.000 0.0 0.0 0.0 0.000 0.005 0.055 0.0 0.0 0.0 0.0  ILN 0.0 0.0 00 2. 9 06 11.732 0.060 0.000 0.0. 0.0 0.0 0. 000 0.0 0.0  GAR 0.000 0.000 0.690 9.395 0.637 0.000 0.0 0.0 0.0 0.000 0.0 0.0  1.000 0.318 -0.018 -0.141 -0.074 0. 108 0.021 QTZ  1.000 0. 039 -0.755 0.260 0.710 -0.045 H20  1.000 -0.131 0. 166 0.102 -0.851 RUT  1.000 -0.822 -0.845 0.166 HUS  1.000 0.629 -0.209 BIO  1.000 -0.126 PLAS  ILH 1. 053 0. 007  SAR -1 .000  145  T a b l e 2-19 ( c o n t i n u e d ) .  Equation R - l l .  Sample 40 - R e g r e s s i o n model o f g a r n e t :  a n o r t h i t e and  r u t i l e i n c l u d e d i n model.  B EGB ESSION COEFFICIENTS SILL ABOB 1.044 0.130 SIGHA 0.004 0.003  OTZ 1.671 0.005  H20 0.025 0.002  BUT -2..148 0.310  BOS -0. 166 0.002  BIO 0. 158 0.001  PLAG 0.052 0.001  ILB 1.063 0.003  GAB •1. 000  IHPOBHATION PERTAINING TO THIS F I T : BESIDUALS ELEHENT sim  »L»3 FE»2 »B»2 HG»2 CA»2 NAtl N»1 H*1 TI*4 BA»2 F*0 ERROE RATIO ELEHENT SI*4 AL*3  (X - X*) BUS 0.000 0.000 -0.000 0.0 0.000 0.0 -0.000 0. 000 0.0 -0.000 0.001 -0.010  BIO -0.000 -0.000 0.000 -0.000 -0.000 0.0 0.000 -0.001 0.0 0. 000 -0.005 0.113  PLAG -0.000 -0.000 0.0 0.0 0.0 0.0 0.000 -0.000 0.0 0.0 -o.ooo 0.0  ILB 0.0 -0.000 0.000 -0.000 -0.000 0.0 0.0 0.0 0.0 0.000 0.0 0.0  GAB 0.000 0.000 -0.000 0.062 0.000 0.0 0.0 0.0 0.0 -0.000 0.0 0.0  (BESIDUAL / PEBBITTED ERBOB ) BIO 0.000 0.000 0.014 0. 104 0.017 0.0 0.005 0.099 0.0 0.000 4 .005 12.356  PL AG 0.000 0.000 0.0 0.0 0.0 0.0 0.000 0.001 0.0 0.0 0.077 0.0  ILH 0.0 0.000 0.041 0.413 0.013 0.0 0.0 0.0 0.0 0.000 0.0 0.0  GAB 0.000 0.000 0.033 8.203 0.011 0.0 0.0 0.0 0.0 0.000 0.0 0.0  COBRELATION COEFFICIENTS SILL 1.000 ABOB -0.719 1.000 QTZ 0. 388 -0.469 H20 0.531 -0.034 BUT 0. 110 -0.011 BUS -0.585 0.049 BIO 0. 399 -0.040 PLAG 0.264 -0.092 ILH -0.181 0.019 SILL ANOB  1.000 0.266 -0.059 0.034 -0.204 -0.244 0. 101 QTX  1.009 0.042 -0.56S 0. 164 0.364 -0.064 H20  1.000 -0.248 0.280 0.122 -0.629 BOT  rz*2  BN + 2 HG»2 CA*2 NAU K»1 H*1 TI»» BA»2 F»0  BUS 0. 000 0.000 0.002 0.0 0.001 0.0 0. 005 0. 062 0.0 0.000 1.503 3. 861  1.000 -0.890 -0.535 0.412 HOS  1.000 0.439 -0.470 BIO  1.000 -0.202 PL AS  .000 ILB  146  T a b l e 2-19 ( c o n t i n u e d ) .  Equation  R-12.  Sample 40.- R e g r e s s i o n  model o f s t a u r o l i t e :  anorthite  and r u t i l e i n c l u d e d i n model.  REGRESSION COEFFICIENTS SILL ANOR 9. 1 93 -0. 022 SIGN* 0.019 0. 000  QTZ -1. 5 7 8 0.016  H20 2. 037 0.003  ROT -2.127 0.0 16  NOS -0.287 0.003  BIO 0. 275 0.003  Pl»G 0.090 0. 002  ILN 1. 299 0.006  STAU -1.000  INFOBHATION PERTAINING TO THIS PIT: RESIDUALS ELEMENT  SI*0 AL» 3 FE»2 «N »2 NG»2 CA»2 NA* 1 K« 1 H» 1 TI»9 BA«2  P»0  ERROR RATIO ELEMENT SI » U AL»3 PE*2  (X -  X»)  HQS -0. 000  -0. 000 0. 000 0. 0 0. 000 0. 0 -0. 000 - 0 . 001 0 . 000 0. 000 0 . 001 -0. 002  BIO  0. 000 0.000 -0.000 0.000 -0.008 0.0 0.000 0.003 -0.000 -0.000 -0.005 0. 028  PLAG 0.000 0.000 0.0 0.0 0.0 0.000 0.000 0.000 0.0 0.0 0.000 0.0  ILH 0. 0 0. 000 -0. 000 0. 000 -0. 001 0. 0 0. 0 0. 0 0. 0 -0. 000 0. 0 0. 0  STAO -0.000 -0.000 0.000 -0.000 0.004 0.0 0.0 0.0 0.000 0.000 0.0 -3.017  (RESIDUAL / PERBITTED ERROR ) BIO 0.000 0.000 0.006 0.069 0. 345 0.0 0.009 0.250 0.000 0.000 3.972 3.072  PLAG 0.000 0.000 0.0 0.0 0.0 o.ooo 0.000 0.002 0.0 0.0 0.076 0.0  ILH 0. 0 0.000 0.011 0. 185 0. 185 0.0 0.0 0.0 0.0 0.000 0.0 0.0  STAU 0.000 0.000 0.023 0.979 0. 477 0.0 0.0 0.0 0.000 0.000 0.0 9.72 9  CORRELATION COEFFICIENTS SILL 1.000 AMOR -0.199 1 .000 QTZ -0.737 0. 195 H20 0. 206 -0.297 BUT 0.079 -0.179 BOS -0.299 0.565 BIO 0. 219 -0.986 PL AG 0.195 -0.980 iLn -0.103 0.237 SILL ANOR  1.000 0.119 -0.051 0.053 -0.135 -0.199 0.069 QTZ  1.000 0.051 -0.435 0. 197 0. 302 -0.063 H20  1 .000 -0.339 0.371 0. 183 -0.789 BUT  fl««2  HG»2 CA»2 NA * 1 K» 1 H« 1  T l »9 3A»2  r*o  HUS 0.000 0. 000 0 . 001 0.0 0.019 0.0 0. 009 0. 156 0. 000 0. 000 1 . 985 0. 957  1.000 -0.917 -0. 577 0.999 HUS  1.000 0.496 -0.495 BIO  1.000 -0.242 PLAG  .000 ILN  147  Table 2-19 ( c o n t i n u e d ) . E q u a t i o n R-13.  Sample 223 - R e g r e s s i o n model o f g a r n e t :  a n o r t h i t e and  r u t i l e i n c l u d e d i n model.  REGRESSION SIGMA  COEFFICIENTS SILL ANOR 0. 972 0.181 0.004 0. 003  INFOBHATION  H20 0.028 0. 00 1  BUT -2.065 0.0 10  HUS -0. 165 0. 001  BIO 0. 156 0. 00 1  PLAG 0.053 0. 00 1  23IL 1. 023 0.004  PERTAINING TO THIS FIT:  RESIDUALS ELEHENT SItU AL*3 FE»2 H»»2 HG»2 CA*2 NA»1 K»1 a»i TI»4 B» »2 F*0 ERROR RATIO ELEHENT SI»4 AL»3 FE»2 HN»2 nG»2 CA»2 NA* 1 K»1 H»1 TI*4 BA»2 P»0  QTZ 1.685 0.006  ( I - X») HUS 0.0 0.0 -0.000 0.0 0. 001 0.000 -0.000 0.0*5 0.000 0. 000 o.ooi -0. 056  BIO 0.0 0.0 0.001 -0.000 -0.002 -0.000 0.000 -0.006 -0.000 -0.000 -0.001 0.067  PLAG 0.0 0.0 0.0 0.0 0.0 -0.000 0.000 -o.ooo 0.0 0.0 -0.000 0.0  (RESIDUAL / PERHITTED HUS 0.0 0.0 0.032 0.0 0.098 0.000 0. 042 1.018 0. 000 0.000 3.187 20.317  BIO 0.0 0.0 0.112 0.851 0.161 0.000 0.007 1.498 0.000 0.000 1.416 22.566  COBBELATION COEFFICIENTS SILL 1.000 ANOR -0.641 1 .000 QTZ 0. 140 -0.337 H20 0.391 -0.039 BUT 0.081 -0.012 nus -0.156 0.059 BIO 0. 318 •0.018 PLAG 0.059 -0.181 ILH -0.093 0.014 SILL ANOR  ILH 0.0 0.0 0.020 -0.003 -0.001 0.0 0.0 0.0 0. 0 -0.000 0. 0 0.0  GAB 0.0 0.0 -9.001 0.082 0.000 0.000 0.0 0.0 0.0 0.0 3.0 0.0  EBROR )  PL AG 0.0 0.0 0.0 0.0 0.0 0.000 0.011 0.043 0.0 0.0 0. 134 0.0  ILH 0.0 0.0 1.245 5.286 0.226 0.0 0.0 0.0 0. 0 0.000 0.0 O. 0  GAR 0.0 0.0 0.589 28.288 9. 182 o.ooo 0.0 0.0 0.0 0.0 0.0 0.0  1.000 0.175 -0.033 0.008 -0.121 -0.313 0.039 QTZ  1.003 0. 042 -0.548 0. 177 0.214 -0.04S H20  1 .000 -0.230 0.259 0.068 -0.899 RUT  1.000 -0.895 -0.323 0. 267 HUS  1.000 0. 265 -0. 303 BIO  1.000 -0.079 PL AG  GAR -1. 000  148 e r r o r l i m i t s f o r s e v e r a l major elements. Mg,  Fe, Na,  and K are e s p e c i a l l y n o t i c e a b l e .  c o e f f i c i e n t s between v a r i o u s m i n e r a l s standard  Large e r r o r s i n the b a l a n c i n g The  large correlation  i s r e f l e c t e d i n the  d e v i a t i o n s i n the r e g r e s s i o n c o e f f i c i e n t s .  large  These l a r g e v a l u e s  r e l a t e d t o the o c c u r r e n c e of s p e c i f i c elements i n o n l y a few  i n the b i o t i t e c o e f f i c i e n t s i n c e t h e s e two m i n e r a l s b a l a n c e the  errors  regression  f o r potassium.  E q u a t i o n R-3  i n c l u d e s g a r n e t i n the s t a u r o l i t e model.  s t i l l quite large.  Residuals  are  Garnet appears as a p r o d u c t phase w h i c h i s i n g e n e r a l  agreement w i t h the commonly r e p o r t e d 1976a).  are  minerals.  E r r o r s f o r the m u s c o v i t e c o e f f i c i e n t , f o r example, are m i r r o r e d by  equation  of  s t a u r o l i t e - o u t r e a c t i o n (A.B.  Thompson  However, t h i s ^ e q u a t i o n c o n f l i c t s w i t h observed g a r n e t breakdown  t e x t u r e s i n the Azure Lake p e l i t e s . Many of the p l a g i o c l a s e g r a i n s i n Azure Lake p e l i t e s e x h i b i t r e v e r s e c o n c e n t r i c zoning.  I n e q u a t i o n s R-4,  R-5,  and R-6  a n o r t h i t e has  been  i n c l u d e d i n the r e g r e s s i o n models t o accommodate a, changing f e l d s p a r composition during r e a c t i o n . with this addition.  The  Residuals  f o r Na and Ca become n e g l i g i b l e  g a r n e t r e g r e s s i o n model (R-4)  improves  c o n s i d e r a b l y because i n c l u s i o n of a n o r t h i t e a l l o w s f o r b a l a n c i n g g r o s s u l a r c o n t e n t of the g a r n e t . R-5,  and R-6.  the  A n o r t h i t e i s a r e a c t a n t phase i n  T h i s c o n t r a d i c t s the observed c o m p o s i t i o n a l  zoning  R-4, in  plagioclase. Mg,  Mn,  and K r e s i d u a l s s t i l l denote l a r g e imbalances f o r some of  major c o n s t i t u e n t s .  E q u a t i o n R-6  a n o r t h i t e reduces the r e s i d u a l s . c o n t r a d i c t i o n t o the E q u a t i o n s R-7,  i s s i m i l a r t o R-3  the  a l t h o u g h i n c l u s i o n of  Garnet remains as a p r o d u c t phase i n  textures. R-8,  and R-9  show t h a t r e s i d u a l s f o r b o t h g a r n e t  and  s t a u r o l i t e r e g r e s s i o n models are reduced s i g n i f i c a n t l y by the a d d i t i o n of  149 r u t i l e as a p a r t i c i p a t i n g phase. only s l i g h t l y compositions  Major element r e s i d u a l s a r e w i t h i n or  above p e r m i t t e d e r r o r l i m i t s .  Mn  i n modelled  garnet  i s c o n s i s t e n t l y lower than a n a l y z e d Mn-content.  T h i s i s at  l e a s t p a r t l y r e l a t e d to the d i f f i c u l t y of a n a l y z i n g garnet r i m because of the c o n c e n t r i c z o n i n g . c o n s t i t u e n t s l i k e Ba and F.  B a l a n c e i s s t i l l poor f o r l e s s e r  Because these elements a r e p r e s e n t  amounts, they c o u l d be r e a d i l y b a l a n c e d  i n small  by s m a l l c o n c e n t r a t i o n s i n  u n a n a l y z e d phases ( t o u r m a l i n e or f l u i d p h a s e ) . may  compositions  C o n t i n u e d K imbalance  i n d i c a t e i n c r e a s e d m o b i l i t y of K r e l a t i v e t o the o t h e r elements b e i n g  c o n s i d e r e d or c o n t i n u e d adjustment of mica c o m p o s i t i o n s  t o lower  temperatures  during cooling. A n o r t h i t e i s a product  phase i n e q u a t i o n R-7.  This equation i s  c o n s i s t e n t w i t h b o t h t e x t u r e s and p l a g i o c l a s e z o n i n g i n the Azure Lake pelites.  I n c l u d i n g r u t i l e i n e q u a t i o n R-9  a r e a c t a n t phase.  has caused garnet  A g a i n t h i s i s c o n s i s t e n t w i t h the t e x t u r a l  A n o r t h i t e i s a r e a c t a n t phase i n e q u a t i o n s  R-8  and R-9,  t o appear as interpretation.  but p a r t i c i p a t e s i n  the suggested r e a c t i o n s o n l y t o a minor e x t e n t . The R-9  c o n s i d e r a b l e improvement i n r e s i d u a l s f o r e q u a t i o n s  R-8,  and  suggests t h a t r u t i l e must be i n c l u d e d as a p a r t i c i p a t i n g r e a c t a n t phase.  T h i s i s a l s o supported  by t h e correspondence between r e g r e s s i o n e q u a t i o n s  the observed t e x t u r e s and p l a g i o c l a s e z o n i n g . minor elements may The  R-7,  be  Problems w i t h b a l a n c i n g of  r e l a t e d t o u n a n a l y z e d phases or t o i n c r e a s e d m o b i l i t y .  r e g r e s s i o n equations  are dehydration  r e a c t i o n s and a r e c o n s i s t e n t w i t h  an o v e r a l l i n c r e a s i n g metamorphic grade toward the southwest. R u t i l e o c c u r s o n l y as s c a t t e r e d i n c l u s i o n s i n p o r p h y r o b l a s t i c k y a n i t e and garnet  and  i n the Azure Lake s c h i s t s .  Lack of r u t i l e i n the s c h i s t  s u g g e s t s t h a t r e a c t i o n t e x t u r e s a r e p a r t l y p r e s e r v e d because o f  the  matrix  150  exhaustion of a v a i l a b l e  rutile.  R e a c t i o n s R-10 through R-13 show t h a t s i m i l a r r e a c t i o n r e l a t i o n s a r e r e v e a l e d when r e g r e s s i o n models a r e c a l c u l a t e d f o r o t h e r samples c o n t a i n i n g s t a u r o l i t e and/or garnet w i t h s i l l i m a n i t e .  INTERPRETATION  The z o n i n g and i n c l u s i o n p a t t e r n s i n g a r n e t s i m p l y two p e r i o d s o f growth w i t h t h e second o c c u r r i n g a f t e r i n i t i a l f o r m a t i o n o f f i b r o l i t e aggregates.  Second s t a g e growth r e s u l t e d from a c o n t i n u o u s  r e a c t i o n d u r i n g p r o g r a d e metamorphism.  garnet-forming  Any growth z o n i n g p a t t e r n s i n  s t a g e one g a r n e t s have been d e s t r o y e d by homogenization  through  diffusion.  The h i a t u s between f i r s t and second g e n e r a t i o n g a r n e t s may be e x p l a i n e d by r e s o r p t i o n o f garnet through a d i s c o n t i n u o u s garnet breakdown r e a c t i o n . T h i s garnet breakdown r e a c t i o n has been modelled compositions using l i n e a r r e g r e s s i o n techniques.  f o r Azure Lake m i n e r a l Regression modelling of  garnet and s t a u r o l i t e breakdown r e a c t i o n s i n d i c a t e s t h a t r u t i l e i s r e q u i r e d as a r e a c t a n t phase i n t h e s i l l i m a n i t e - f o r m i n g r e a c t i o n s .  Reaction  t e x t u r e s i n t h e s c h i s t s . a r e p a r t l y p r e s e r v e d because o f e x h a u s t i o n o f m a t r i x rutile.  T h i s sequence o f r e a c t i o n s may be e x p l a i n e d by a s i n g l e prograde  metamorphism. Muscovite equations.  i s r e q u i r e d as a r e a c t a n t i n a l l o f t h e above r e g r e s s i o n  T e x t u r e s i n d i c a t e t h a t c o a r s e , equant m u s c o v i t e  phase w i t h i n t h e f i b r o l i t e aggregates staurolite.  Carmichael  i s a product  and t h a t i t r e p l a c e s k y a n i t e and  (1969) has suggested  t h a t t e x t u r a l r e l a t i o n s between  m i n e r a l s a r e c o n t r o l l e d by l o c a l c a t i o n exchange r e a c t i o n s ( i o n i c r e a c t i o n s ) . The " g e n e r a l " metamorphic r e a c t i o n r e s u l t s from t h e summation o f two o r more d i f f e r e n t l o c a l r e a c t i o n s .  The l o c a l r e a c t i o n s a r e c o u p l e d by i o n i c  151  diffusion  so t h a t the system i s c l o s e d t o mass t r a n s f e r on the s c a l e o f a  thin section.  H i s example o f the l o c a l replacement o f k y a n i t e by m u s c o v i t e  concomitant w i t h the f o r m a t i o n of s i l l i m a n i t e i n nearby m u s c o v i t e g r a i n s i s d i r e c t l y a p p l i c a b l e t o s c h i s t s from the A z u r e Lake a r e a . o v e r a l l , d e c r e a s e i n modal m u s c o v i t e due may be accompanied  I n t h i s case an  t o s t a u r o l i t e o r g a r n e t breakdown  by the l o c a l f o r m a t i o n of c o a r s e m u s c o v i t e around k y a n i t e .  S i m i l a r i o n i c r e a c t i o n s would account f o r the replacement of o t h e r phases by m u s c o v i t e . A l t e r n a t i v e l y , c o a r s e m u s c o v i t e may  r e s u l t from a change i n  metamorphic c o n d i t i o n s a t some i n d e t e r m i n a t e time a f t e r the f o r m a t i o n o f the f i b r o l i t e aggregates.  E u g s t e r (1970) and Kwak (1971) have shown t h a t i o n i c  r e a c t i o n s r e l a t i n g m u s c o v i t e and the a l u m i n o s i l i c a t e polymorphs  are very  s e n s i t i v e t o s l i g h t changes i n c o n c e n t r a t i o n s of i o n i c s p e c i e s (K+ and d i s s o l v e d i n the f l u i d phase.  A s m a l l change i n f l u i d c o m p o s i t i o n d u r i n g  metamorphism would cause m u s c o v i t e t o l o c a l l y r e p l a c e k y a n i t e sillimanite.  H+)  and/or  Any such m u s c o v i t e - f o r m i n g r e a c t i o n c o u l d not be a s i m p l e  r e t r o g r a d i n g a c c o r d i n g t o the p r o b a b l e r e a c t i o n s o u t l i n e d by the r e g r e s s i o n e q u a t i o n s s i n c e newly formed r u t i l e was not observed.  With  r e g a r d t o t h i s l a t t e r model i t i s i n t e r e s t i n g t o n o t e t h a t imbalance of K i n the r e g r e s s i o n e q u a t i o n s may be r e l a t e d t o i n c r e a s e d m o b i l i t y of K r e l a t i v e t o the o t h e r major elements c o n s i d e r e d .  Observed  textures  s u b s t a n t i a t e the l a t e r replacement of o t h e r metamorphic m i n e r a l s by c o a r s e m u s c o v i t e i n d i c a t i n g t h a t a t l e a s t p a r t of the m u s c o v i t e t e x t u r e s may r e l a t e d to t h i s  be  model.  F l e t c h e r and Greenwood (1978) have d i s c u s s e d metamorphic t e x t u r e s i n s c h i s t s from the Shuswap Complex j u s t n o r t h w e s t of the Azure Lake a r e a . They argue t h a t two metamorphic e p i s o d e s a r e r e q u i r e d t o e x p l a i n the observed t e x t u r a l and z o n i n g p a t t e r n s .  I n t h e i r suggested sequence  of  152  r e a c t i o n s s i l l i m a n i t e i s the l a s t metamorphic m i n e r a l t o c r y s t a l l i z e . I n c o n t r a s t I have attempted area may  t o show t h a t s i m i l a r t e x t u r e s i n the A z u r e Lake  be e x p l a i n e d by a sequence of r e a c t i o n s d u r i n g a s i n g l e prograde  metamorphism. aggregates  W i t h t h i s i n t e r p r e t a t i o n the f o r m a t i o n o f  preceded  growth of second g e n e r a t i o n g a r n e t s .  fibrolite Muscovite  t e x t u r e s a r e p r o b a b l y p a r t l y r e l a t e d t o changes i n f l u i d c o m p o s i t i o n d u r i n g l a t e s t a g e s o f t h e same metamorphism.  METAMORPHIC CONDITIONS  The d i s c u s s i o n i n t h e s e c t i o n on e q u i l i b r i u m t e s t s has shown t h a t m i n e r a l assemblages i n the A z u r e Lake a r e a appear t o have reached e q u i l i b r i u m d u r i n g metamorphism.  chemical  I t i s therefore reasonable to estimate  metamorphic c o n d i t i o n s by comparing Azure Lake p e l i t i c assemblages t o p u b l i s h e d e x p e r i m e n t a l s t u d i e s on m i n e r a l e q u i l i b r i u m . The thermodynamic parameters  AG^,  A S ^ , and  AV^_ have been used t o  d e s c r i b e t h e l o c a t i o n o f each e x p e r i m e n t a l e q u i l i b r i u m c u r v e i n p r e s s u r e temperature  space.  A l l thermodynamic parameters f o r t h e d i f f e r e n t  e q u i l i b r i a have been reduced  to a common r e f e r e n c e s t a t e o f 298.15 K  1 bar t o t a l pressure to f a c i l i t a t e c a l c u l a t i o n s .  Appendix 2-2  and  contains a  d i s c u s s i o n o f the assumptions and e q u a t i o n s used i n r e d u c i n g e q u i l i b r i a t o the reference s t a t e .  I n t e r n a l c o n s i s t e n c y of thermodynamic p a r a m e t e r s f o r  each e x p e r i m e n t a l e q u i l i b r i u m was (Gordon 1973).  confirmed u s i n g l i n e a r  inequalities  Where p o s s i b l e , e n t r o p i e s o f r e a c t i o n ( AS^) were s e l e c t e d  t o be c o n s i s t e n t w i t h p r e v i o u s l y t a b u l a t e d v a l u e s (Robie and Waldbaum 1968) . Approximate e r r o r l i m i t s on each c a l c u l a t e d e q u i l i b r i u m were d e r i v e d from the p e r m i t t e d range i n  AG  v a l u e s a t the s e l e c t e d r range was e s t i m a t e d from t h e s i m p l e x of c o n s i s t e n t  c a l c u l a t e d u s i n g l i n e a r i n e q u a l i t i e s (Gordon 1973).  As  .  The p e r m i t t e d A G  r AG  r and  AS  values  153  At l e a s t t h r e e independent e x p e r i m e n t a l e q u i l i b r i a s o l v e f o r p r e s s u r e , temperature, following four e q u i l i b r i a  and a c t i v i t y of H^O.  are r e q u i r e d to I have used the  t o e s t i m a t e metamorphic c o n d i t i o n s f o r the  Shuswap Complex i n the Azure Lake a r e a : 1 Kyanite = 1 S i l l i m a n i t e  (El)  6 F e - s t a u r o l i t e + 11 Quartz = 23 K y a n i t e + 4 Almandine + 3 H 0  (E4)  1 P a r a g o n i t e + 1 Quartz = 1 A n d a l u s i t e + 1 H i g h - A l b i t e + 1 H 0  (E7)  1 G r o s s u l a r + 2 K y a n i t e + 1 Quartz = 3 A n o r t h i t e  (E10)  2  2  E q u i l i b r i u m c o n s t a n t s were used t o c o n s i d e r s o l i d s o l u t i o n e f f e c t s and v a r i a t i o n s i n H 0  a c t i v i t y when c a l c u l a t i n g the d i s p l a c e d p o s i t i o n s  2  of the e q u i l i b r i u m c u r v e s .  The d i f f e r e n t e q u i l i b r i u m c o n s t a n t s are.  defined as: K  E4  =  ( a  Almandine (a  K  E7  a  ^^(P  )  Fe-staurolite  )6  Albite H 0 a  2  a_ Paragonite 3 K  E10  =  ( a  Anorthite a  )  Grossular  Other phases i n these r e a c t i o n s were c o n s i d e r e d t o be pure and s t o i c h i o m e t r i c ( a c t i v i t y = 1). E x p r e s s i o n s r e l a t i n g c o m p o s i t i o n t o a c t i v i t y a r e needed f o r each of the above components i n o r d e r t o use the e q u i l i b r i u m c o n s t a n t s t o d i s p l a c e the e x p e r i m e n t a l e q u i l i b r i u m c u r v e s .  The  f o l l o w i n g s e c t i o n d i s c u s s e s the  a c t i v i t y models f o r these d i f f e r e n t components.  154  Garnet: An i o n i c m i x i n g model f o r almandine and g r o s s u l a r a c t i v i t i e s i n the expressions  results  (Greenwood 1977) :  a Almandine = ( vAlmandine  *x„ ) "Fe  ^G r o s s u l,a r = ( Y' G r o s s uil a r  * P  v  r  A 1  r  X  Ca>  3  (A)  C5)  3  where t h e X's a r e t h e mole f r a c t i o n s o f t h e atoms on t h e e i g h t - f o l d  sites.  T h i s model assumes t h a t A l i s t h e o n l y t r i v a l e n t c a t i o n i n t h e o c t a h e d r a l site  (see T a b l e 2-3). R e c e n t l y Ganguly and Kennedy (1974) proposed a p r e l i m i n a r y model f o r  n o n i d e a l garnet  s o l i d s o l u t i o n i n v o l v i n g t h e f o u r components almandine,  g r o s s u l a r , p y r o p e , and s p e s s a r t i n e . grossular-pyrope  More d e t a i l e d s t u d i e s a l o n g t h e  b i n a r y j o i n a r e i n g e n e r a l agreement w i t h t h e i r model  (Hensen, Schmid, and Wood 1975; Wood 1977). ' ' f o r Azure Lake garnet c o m p o s i t i o n s  Calculated  v_ values ' Grossular n  u s i n g t h i s model range from 1.5 t o 1.7  ( f o r 500-700° C ) . The c a l c u l a t e d y ... ,. f o r t h e same temperature Almandine 1  range i s a p p r o x i m a t e l y  1.02.  Staurolite: Thermodynamic parameters f o r e q u a t i o n s  (E4 and E5) have been d e r i v e d  u s i n g t h e f o r m u l a F e ^ l g S i ^ O ^ O H ) f o r F e - s t a u r o l i t e (Ganguly 1972). N a t u r a l s t a u r o l i t e s c o n s i s t e n t l y c o n t a i n t w i c e as much h y d r o x y l as t h i s f o r m u l a  ( G r i f f e n and Ribbe 1976).  content  This compositional difference  can be accounted f o r t h r o u g h t h e c o u p l e d s u b s t i t u t i o n s : Al(VI) + H where D  +  = S i ( I V ) , Fe(IV) =  • (IV) + 2 H , and A l ( V I ) = • ( V I ) + 3 H  denotes a vacancy i n t h e s i t e .  coordination of the s i t e being  +  The Roman numerals r e f e r t o t h e  considered.  F o l l o w i n g K e r r i c k and Darken (1975), t h e a c t i v i t y o f F e - s t a u r o l i t e i s d e f i n e d by t h e r e l a t i o n :  +  155  a  where  Fe-staurolite = Te  , X. , Al n  ( X  Fe  )  *  (X  A1>  *  (  S  S i  )  ( 6 )  and X.,. r e f e r t o the mole f r a c t i o n s o f each of t h e s e Si  elements i n the s t r u c t u r a l f o r m u l a (note t h a t i n t h i s model v a c a n c i e s a r e i n c l u d e d i n the t o t a l s i t e p o p u l a t i o n ) . T h i s model assumes i d e a l m i x i n g on the d i f f e r e n t s i t e s .  H y d r o x y l i s i m p l i c i t l y i n c l u d e d through the  d i f f e r e n t coupled s u b s t i t u t i o n s .  The model i s a d m i t t e d l y s i m p l i f i e d  s i n c e n a t u r a l s t a u r o l i t e s have A l and Fe d i s t r i b u t e d over b o t h 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 ( G r i f f e n and Ribbe  1976).  E x p r e s s i o n (6) c o n t r a s t s w i t h e a r l i e r p u b l i s h e d  models where  the a c t i v i t y of F e - s t a u r o l i t e i s e q u a l t o the mole f r a c t i o n of Fe r a i s e d t o the second power (Ganguly 1972; F l e t c h e r and Greenwood 1978).  Including  the terms f o r A l and S i has the g e n e r a l e f f e c t of l o w e r i n g the calculated Fe-staurolite activity.  T h i s i s o b a r i c a l l y d i s p l a c e s the  c a l c u l a t e d e q u i l i b r i u m to higher temperatures.  Comparison of d i s p l a c e d  e q u i l i b r i u m c u r v e s (E4, E5) f o r A z u r e Lake s t a u r o l i t e c o m p o s i t i o n s i n d i c a t e s t h a t i n c l u d i n g the terms f o r A l and S i i s o b a r i c a l l y i n c r e a s e s the e q u i l i b r i u m temperature by about 30°  C.  Plagioclase: A c t i v i t i e s f o r a l b i t e and a n o r t h i t e i n p l a g i o c l a s e have been c o n s i d e r e d as, b e i n g e q u a l t o the mole f r a c t i o n s of N a A I S i 0 and 3 8 o  CaAl2Si20g. (1972).  A c t i v i t y c o e f f i c i e n t s were taken from the s t u d y by  Orville  The r e s u l t i n g e x p r e s s i o n s f o r p l a g i o c l a s e c o m p o s i t i o n s from the  Azure Lake a r e a a r e : a..,,.. = 1.0 * X , . Albite Albite t  A1  a. = 1-276 Anorthite  * X. Anorthite  v  (7) ' (8)  156  Muscovite: B i n a r y s o l i d s o l u t i o n between muscovite ( E u g s t e r e t a l 1972). 1972)  and p a r a g o n i t e i s n o n i d e a l .  The asymmetric b i n a r y s o l u t i o n model (Eugster e t a l .  i s f u r t h e r c o m p l i c a t e d by the u b i q u i t o u s presence  component i n metamorphic w h i t e micas. have handled  of c e l a d o n i t e  F l e t c h e r and Greenwood (1978)  t h i s problem by assuming a q u a t e r n a r y n o n i d e a l m i x i n g model  w i t h m u s c o v i t e , p a r a g o n i t e , K c e l a d o n i t e , and Na c e l a d o n i t e as components. A l l Margules W-parameters were c o n s i d e r e d zero except f o r the parameters d e s c r i b i n g the m u s c o v i t e - p a r a g o n i t e t h e q u a t e r n a r y m i x i n g model may W-parameters f o r Na-K  binary j o i n .  i n t e r a c t i o n a r e i d e n t i c a l f o r the  excess  muscoviteSolid  solution  the c e l a d o n i t e component a l o n g each b i n a r y j o i n from muscovite  p a r a g o n i t e i s c o n s i d e r e d i d e a l (W-terms = 0 ) . G  Alternatively  be c o n s t r u c t e d assuming t h a t the  p a r a g o n i t e and K c e l a d o n i t e - N a c e l a d o n i t e b i n a r y j o i n s . toward  two  excess  .and  Appendix  F u l l expressions f o r  Y„ . u s i n g the l a t t e r s o l u t i o n model a r e p r e s e n t e d i n Paragonite  2-2.  Three d i f f e r e n t s e t s of M a r g u l e s W-parameters have been suggested the m u s c o v i t e - p a r a g o n i t e 1975;  or  Blencoe 1977).  join  (Eugster et: a l . 1972;  C a l c u l a t e d e q u i l i b r i u m curves  C h a t t e r j e e and  polymorphs from Blencoe  Froese  (E8) f o r sample 82 .  u s i n g the d i f f e r e n t parameters d i f f e r by a maximum of o n l y 15° C. subsequent computations  for  All  use the 8 kbar volume d a t a f o r s y n t h e t i c 2M^ (1977).  P a r a g o n i t e a c t i v i t y i s r e l a t e d t o mole f r a c t i o n by the e q u a t i o n ( K e r r i c k and Darken 1975) : 2 a  Paragonite  T h i s corresponds paragonite.  =  ^Paragonite * ^ a  * ^Al^  2 *  t o the f o r m u l a N a A l S i C > ( O H ) 3  3  1 0  M i x i n g on the S i s i t e i s accounted  2  ( 8 )  for stoichiometric f o r by c o u p l e d  substitutions  157 f o r A l i n the o c t a h e d r a l s i t e .  y. . i Paragonite  p r e s e n t e d above ( a l s o see Appendix  s c a l c u l a t e d by the scheme  2-2).  The above a c t i v i t y e x p r e s s i o n s have been used i n the e q u i l i b r i u m c o n s t a n t s t o d i s p l a c e e q u i l i b r i u m c u r v e s E4, E5, E8, E9, E10, and  Ell.  The d i s p l a c e d curves c o r r e s p o n d t o the e q u i l i b r i a f o r c o e x i s t i n g m i n e r a l c o m p o s i t i o n s i n the Azure Lake a r e a . d i s c u s s e d i n Appendix  2-2.  The method of c a l c u l a t i o n i s  Thermodynamic parameters  c a l c u l a t i o n s a r e p r e s e n t e d i n T a b l e s 2-21 d i s c u s s the r e s u l t s f o r the d i f f e r e n t  and 2-22.  used t o the The f o l l o w i n g s e c t i o n s  equilibria.  Kyanite-Sillimanite T h i s t r a n s i t i o n i s independent  of the a c t i v i t y of H^O,  p r o v i d e s an i m p o r t a n t r e s t r i c t i o n on the p o s s i b l e c o n d i t i o n s d u r i n g metamorphism.  and t h e r e f o r e  pressure-temperature  S i n c e b o t h k y a n i t e and  sillimanite  c o n t a i n o n l y minor i m p u r i t i e s , s o l i d s o l u t i o n d i s p l a c e m e n t of the t r a n s i t i o n i s n e g l i g i b l e (Albee and Chodos 1969; C h i n n e r , Smith, and Knowles 1969). Two  different petrogenetic  c u r r e n t l y i n the l i t e r a t u r e . and B e l l  g r i d s f o r the A l ^ S i O ^ polymorphs a r e  E x p e r i m e n t a l s t u d i e s by R i c h a r d s o n , G i l b e r t ,  (1969) p l a c e the i n v a r i a n t t r i p l e p o i n t a t a h i g h e r p r e s s u r e and  temperature than the g r i d p r e s e n t e d by Holdaway (1971).  The major d i f f e r e n c e  i n the two s t u d i e s i s the p o s i t i o n o f the a n d a l u s i t e - s i l l i m a n i t e transition.  Recent c a l o r i m e t r i c s t u d i e s a r e c o n s i s t e n t w i t h the Holdaway  i n t e r p r e t a t i o n (Anderson, Newton, and K l e p p a 1977).  A c c o r d i n g t o Holdaway  (1971), the k y a n i t e - s i l l i m a n i t e t r a n s i t i o n does not appear to be s i g n i f i c a n t l y a f f e c t e d by the presence of f i b r o l i t e i n p l a c e of s i l l i m a n i t e . . . I have used i n t e r n a l l y c o n s i s t e n t thermodynamic parameters  f o r the  158 d i f f e r e n t A l ^ S i O ^ t r a n s i t i o n s from.the c o m p i l a t i o n by H e l g e s o n ejc a l . (1978). grid.  These parameters a r e c o n s i s t e n t w i t h t h e Holdaway  petrogenetic  E r r o r l i m i t s f o r each t r a n s i t i o n a r e based on e x p e r i m e n t a l  studies  by Newton (1966a, 1966b), R i c h a r d s o n , B e l l , and G i l b e r t (1968), R i c h a r d s o n , G i l b e r t , and B e l l  (1969), and Holdaway (1971).  Staurolite-Quartz-Garnet-Al^SiO^ The (E4).  upper s t a b i l i t y l i m i t o f s t a u r o l i t e + q u a r t z i s d e f i n e d by r e a c t i o n  T h i s e q u i l i b r i u m has been e x p e r i m e n t a l l y  c a l i b r a t e d by Ganguly (1972).  R i c h a r d s o n (1968) has a l s o s t u d i e d t h i s r e a c t i o n u s i n g s i l l i m a n i t e of k y a n i t e .  instead  H i s suggested r e a c t i o n c o e f f i c i e n t s a r e s l i g h t l y d i f f e r e n t  because he assumed a d i f f e r e n t c o m p o s i t i o n f o r F e - s t a u r o l i t e .  Calculated  thermodynamic parameters 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  brackets  from b o t h s t u d i e s r e q u i r e t h e r e a c t i o n c o e f f i c i e n t s and s t a u r o l i t e c o m p o s i t i o n p r e s e n t e d by Ganguly (see Appendix 2-2). C a l c u l a t e d p o s i t i o n s o f t h e assemblage s t a u r o l i t e - g a r n e t - q u a r t z Al„SiCv ( k y a n i t e , s i l l i m a n i t e ) f o r P _ = P ^_ ., a r e i n d i c a t e d i n 2 5 H 0 Total TT  m  2  figure  2-9.  The d i f f e r e n t curves, have a l l been d i s p l a c e d t o c o r r e s p o n d t o  m i n e r a l c o m p o s i t i o n s from t h e Azure Lake a r e a .  Y.. „. i s s m a l l and Almandine  has been s e t t o 1.0 ( i d e a l s o l u t i o n ) because o f t h e t e n t a t i v e n a t u r e o f the s t a u r o l i t e s o l u t i o n model. c a l c u l a t i o n s (Eugster  FMQ oxygen b u f f e r has been assumed f o r a l l  and Wones 1962).  D i f f e r e n t samples i n t h e Azure Lake a r e a a l l c l u s t e r i n a narrow pressure-temperature i n t e r v a l i n f i g u r e  2-9.  E r r o r l i m i t s due t o  thermodynamic u n c e r t a i n t y f o r each c u r v e a r e a p p r o x i m a t e l y ± 15° C.  The  dashed l i n e i s t h e c a l c u l a t e d e q u i l i b r i u m curve f o r sample. 82 assuming t h a t the a c t i v i t y o f ^ 0 = 0.5.  I t shows t h a t t h e e q u i l i b r i u m c u r v e f o r t h i s  159  500  600  700  800  TEMPERATURE, °C  F i g u r e 2-9.  D i s p l a c e d e q u i l i b r i u m c u r v e s E4, E5 f o r p e l i t e  Azure L a k e , B r i t i s h Columbia.  a^.  Q  = 1.0.  is staurolite-quartz-garnet-A^SiO^. samples. 82 w i t h a  assemblages,  The e q u i l i b r i u m assemblage  Numbers on curves denote t h e  Dashed l i n e c o r r e s p o n d s t o the d i s p l a c e d c u r v e f o r sample H  Q  = 0.5.  Al SiO,- t r a n s i t i o n s a r e from Holdaway (1971) . 2  160  assemblage i s not a p p r e c i a b l y <  d i s p l a c e d t o lower t e m p e r a t u r e s f o r  P,T o t a l '  Muscovite-Quartz-Plagioclase-Al^SiO^ The m i n e r a l  assemblage m u s c o v i t e - q u a r t z - p l a g i o c l a s e - A l ^ S i O ^  s i l l i m a n i t e ) provides another e q u i l i b r i u m which i s u s e f u l f o r metamorphic p r e s s u r e and  temperature c o n d i t i o n s .  The  (kyanite, estimating  c o m p o s i t i o n s of  m u s c o v i t e and p l a g i o c l a s e can be used w i t h thermodynamic models of s o l u t i o n t o c a l c u l a t e d i s p l a c e m e n t of c u r v e s (E8, E 9 ) . determination  solid  Experimental  of the p r e s s u r e - t e m p e r a t u r e l o c a t i o n of c u r v e (E7) has  completed by Ivanov and G u s y n i n (1970) and parameters f o r the A l ^ S i O ^ and  Chatterjee  (1972).  been  Thermodynamic  the h i g h - a l b i t e t o l o w - a l b i t e t r a n s i t i o n s  were combined w i t h the e x p e r i m e n t a l r e a c t i o n t o o b t a i n  the  equilibrium  curves: 1 P a r a g o n i t e + 1 Quartz = 1 K y a n i t e ,  S i l l i m a n i t e + 1 Low  Albite (E8,  These r e a c t i o n s c o r r e s p o n d more c l o s e l y t o m i n e r a l  E9)  assemblages i n the Azure  Lake a r e a . P r e v i o u s s t u d i e s u s i n g t h i s e q u i l i b r i u m have used e i t h e r h i g h (Ghent 1975)  or low a l b i t e (Pigage 1976)  R e c e n t l y J.B.  albite  as the s t a h l e f e l d s p a r phase.  Thompson, Waldbaum, and H o v i s (1974) suggested a thermo-  dynamic model i n v o l v i n g a temperature-dependent g r a d u a l t r a n s i t i o n between low and h i g h a l b i t e . feldspars.  These d i f f e r e n t models were d e s i g n e d f o r N a — r i c h '  E x t r a p o l a t i o n to intermediate  problematical  u n t i l more i n f o r m a t i o n  of C a - b e a r i n g p l a g i o c l a s e f e l d s p a r s .  p l a g i o c l a s e compositions i s  i s a v a i l a b l e on thermodynamic  properties  C o n s e q u e n t l y I have performed a l l  c a l c u l a t i o n s u s i n g e i t h e r h i g h or low a l b i t e as the s t a b l e f e l d s p a r  species.  161 H i g h a l b i t e r e q u i r e s H^O a c t i v i t i e s g r e a t e r than 1.0 f o r e q u i l i b r i u m assemblages t o be c o n s i s t e n t w i t h r e a c t i o n s has  ( E l , E4, and E 5 ) .  Low . a l b i t e  t h e r e f o r e been used as t h e p r e f e r r e d s t a b l e phase i n a l l subsequent  calculations. F i g u r e 2-10 i l l u s t r a t e s t h e d i s p l a c e d c u r v e s f o r e q u i l i b r i u m  (E9).  C o e x i s t i n g m u s c o v i t e and p l a g i o c l a s e c o m p o s i t i o n s from t h e t w e l v e a n a l y z e d p e l i t e samples were used t o c a l c u l a t e t h e d i s p l a c e d e q u i l i b r i u m c u r v e s . P  _ H^O TT  and  was e q u a l t o P„ ., f o r a l l c a l c u l a t i o n s . Total n  Except f o r samples 492  74, t h e d i f f e r e n t c u r v e s f a l l w i t h i n a narrow 30° temperature i n t e r v a l .  Comparison o f t h e c a l c u l a t e d c u r v e s w i t h sample l o c a t i o n s from f i g u r e 2-2 demonstrates t h a t t h e e q u i l i b r i u m c u r v e s do n o t have a temperature g r a d i e n t  systematic  r e l a t e d t o i n c r e a s i n g metamorphic grade.  Apparently  the metamorphic g r a d i e n t n o t i c e d i n t h e f i e l d mapping i s masked by s c a t t e r from a n a l y t i c a l e r r o r and l o c a l d i s e q u i l i b r i u m .  The o u t l y i n g  c u r v e s (74, 492) p r o b a b l y a l s o r e p r e s e n t l o c a l d i s e q u i l i b r i u m o r i m p e r f e c t a n a l y s i s of c o e x i s t i n g The  minerals.  s t i p p l e d a r e a i n f i g u r e 2-10 i s t h e d i s p l a c e d e q u i l i b r i a  w h i c h were a l s o shown i n f i g u r e 2-9. (E5)  With P„' equal t o P  (E4, E5) equilibria  n  and (E9) i n t e r s e c t a t p r e s s u r e s between 2.5 and 5.2 kbar and  temperatures from  675 t o 705° C.  These c o n d i t i o n s r e p r e s e n t much lower  p r e s s u r e s than t h e i n t e r s e c t i o n o f e q u i l i b r i a ( E l ) and (E5) o r (El) and (E9) w h i c h a l s o o c c u r i n t h e same samples.  These w i d e l y d i f f e r i n g i n t e r s e c t i o n  p o i n t s i n d i c a t e t h a t P^ ^ was n o t e q u a l t o P f Mutual coexistence  o  t  a  i d u r i n g metamorphism.  of e q u i l i b r i u m (El) with displaced  equilibria  (E4, E5) and (E8, E9) t h e r e f o r e r e q u i r e s reduced H^O a c t i v i t i e s . 2-11  i l l u s t r a t e s s e v e r a l c a l c u l a t e d curves f o r e q u i l i b r i a  different ^ 0 activities.  Figure  (E4) and (E8) a t  M i n e r a l c o m p o s i t i o n s from sample 82 have been  16 2  500  600  700  800  900  TEMPERATURE,  F i g u r e 2-10.  D i s p l a c e d e q u i l i b r i u m curves  muscovite-quartz-plagioclase-sillimanite correspond  t o t h e a n a l y z e d samples.  1000  °C  (E9) f o r t h e assemblage with a  u  =1.0.  Numbers  The s t i p p l e d a r e a r e p r e s e n t s t h e  d i s p l a c e d e q u i l i b r i a (E4,E5) ( s t a u r o l i t e - q u a r t z - g a r n e t - A ^ S i O ^ . ) from i f i g u r e 2-9.  The A l S i 0 . t r a n s i t i o n s a r e from Holdaway 9  c  (1971).  163  Figure  2-11.  reduced R^O  I n t e r s e c t i o n o f e q u i l i b r i a E4 and E8 f o r s e v e r a l d i f f e r e n t activities.  S o l i d s o l u t i o n displacements correspond to  c o m p o s i t i o n s f o r the subassemblage  garnet-staurolite-muscovite-quartz-  plagioclase-kyanite  The heavy l i n e marks the e q u i l i b r i u m  coexistence  from sample 82.  o f t h i s subassemblage f o r a^  l e s s than  1.0.  164 used t o d i s p l a c e t h e e q u i l i b r i a f o r s o l i d s o l u t i o n e f f e c t s .  K y a n i t e was  used as t h e s t a b l e A l ^ S i O ^ polymorph I n these p a r t i c u l a r c a l c u l a t i o n s .  The  heavy l i n e i n t h e diagram marks the c o e x i s t e n c e of the sub-assemblages f o r equilibria  (E4) and (E8) w i t h a f l u i d phase h a v i n g an rl^O a c t i v i t y  than o r e q u a l t o 1.0.  T h i s e q u i l i b r i u m was generated  of d i s p l a c e d curves f o r e q u i l i b r i a  less  from t h e i n t e r s e c t i o n  (E4) and (E8) a t s p e c i f i e d H^O  activities.  S i n c e sample 82 c o n t a i n s b o t h k y a n i t e and s i l l i m a n i t e , metamorphic c o n d i t i o n s f o r t h i s sample a r e d e f i n e d by t h e p o i n t i n p r e s s u r e - t e m p e r a t u r e a  „ space where t h e heavy e q u i l i b r i u m l i n e p i e r c e s the k y a n i t e - s i l l i m a n i t e 2  t r a n s i t i o n plane.  T h i s o c c u r s a t P = 7.6 k b a r , T = 705  C, and a  = 0.5. 2°  These e s t i m a t e d metamorphic c o n d i t i o n s a r e s u b j e c t t o e r r o r because o f v a r i a t i o n s i n m i n e r a l c o m p o s i t i o n s and e r r o r s i n c a l c u l a t e d thermodynamic parameters.  I have examined b o t h o f t h e e f f e c t s of these u n c e r t a i n t i e s  on t h e i n f e r r e d p r e s s u r e , temperature,  and a  f o r sample 82.  The  l a r g e s t v a r i a t i o n i n m i n e r a l composition occurs i n a n o r t h i t e content of the p l a g i o c l a s e . W i t h sample 82, a 10 mole % i n c r e a s e i n a n o r t h i t e c o n t e n t s h i f t s the i s o b a r i c i n t e r s e c t i o n of e q u i l i b r i a and  Aa  (E4) and (E8) by  AT = +4.5° C  = +0.05. The e s t i m a t e d metamorphic c o n d i t i o n s a r e not s e n s i t i v e  to v a r i a t i o n s i n m i n e r a l c o m p o s i t i o n .  C o n v e r s e l y t h e range o f p l a g i o c l a s e  c o m p o s i t i o n s b o t h between o r w i t h i n t h e d i f f e r e n t samples can be e x p l a i n e d by s m a l l l o c a l v a r i a t i o n s i n f l u i d  composition.  Thermodynamic parameters f o r t h e t r a n s i t i o n between h i g h and low a l b i t e have been t a k e n from c a l o r i m e t r i c s t u d i e s by Hemingway and R o b i e (1977).  E r r o r s a r e on t h e o r d e r o f ± 1100 c a l o r i e s and r e s u l t i n a l a r g e  temperature  e r r o r b r a c k e t f o r e q u i l i b r i u m (E4) w i t h low a l b i t e .  The e f f e c t  of t h i s l a r g e e r r o r b r a c k e t on the: e s t i m a t e d metamorphic c o n d i t i o n s i s shown i n f i g u r e 2-12.  Curve B i s t h e e q u i l i b r i u m l i n e r e p r e s e n t i n g the.  i n t e r s e c t i o n of e q u i l i b r i a  (E4) and (E8) u s i n g t h e t a b u l a t e d thermodynamic  165  F i g u r e 2-12.  V a r i a t i o n s i n the P-T-a^ ^ p o s i t i o n of the i n t e r s e c t i o n o f  e q u i l i b r i a E4 and E8. the subassemblage  I n t e r s e c t i o n of these e q u i l i b r i a corresponds to  garnet-staurolite-muscovite-quartz-plagioclase-kyanite.  V a r i a t i o n r e s u l t s from thermochemical e r r o r s i n the thermodynamic parameters f o r the h i g h a l b i t e t o l o w i a l b i t e t r a n s i t i o n . the l i n e shown i n F i g u r e 2-11.  Curve B i s  Curves A and C c o r r e s p o n d t o the upper  and lower temperature u n c e r t a i n t y l i m i t s f o r e q u i l i b r i u m E8, r e s p e c t i v e l y .  166 parameters f o r the t r a n s i t i o n between h i g h and as the c a l c u l a t e d l i n e shown i n f i g u r e 2-11.  low a l b i t e .  I t i s the same  Curve A i s the same  e q u i l i b r i u m u s i n g the upper temperature l i m i t f o r e q u i l i b r i u m ( E 8 ) ,  and  c u r v e C i s the c a l c u l a t e d e q u i l i b r i u m f o r the lower temperature l i m i t . The  major change i n the i n f e r r e d metamorphic c o n d i t i o n s i s i n the  of R^O  w h i c h v a r i e s from 1.0  t o a p p r o x i m a t e l y 0.24.  Temperature  activity and  p r e s s u r e e s t i m a t e s f o r the i n f e r r e d metamorphic c o n d i t i o n s are w i t h i n ± 20°  C and  ± 325 b a r s , r e s p e c t i v e l y f o r the e n t i r e e r r o r range i n  e q u i l i b r i u m (E8).  A c t i v i t y of H^O  i s v e r y s e n s i t i v e t o e r r o r i n the  thermodynamic p a r a m e t e r s , w h i l e temperature and extensively with substantial error F i g u r e 2-13  p r e s s u r e do not  brackets.  i l l u s t r a t e s the c a l c u l a t e d d i s p l a c e d e q u i l i b r i u m c u r v e s  f o r the assemblage  staurolite-garnet-plagioclase-muscovite-quartz-Al^SiO^  (kyanite, s i l l i m a n i t e ) .  The  d i s c u s s e d w i t h f i g u r e 2-11.  c u r v e s were generated by the method T h e r e f o r e i n t h i s diagram P  i s l e s s than H  ]?Total w i t h a curve.  The  R  change  ^ decreasing  2°  w i t h i n c r e a s i n g t o t a l p r e s s u r e a l o n g each  f i v e a n a l y z e d samples c o n t a i n i n g t h i s assemblage form  c l o s e c l u s t e r s of e q u i l i b r i u m c u r v e s .  two  These p i e r c e the k y a n i t e - s i l l i m a n i t e  t r a n s i t i o n p l a n e a t the p o i n t s P = 7600 b a r s , T = 705° C and P = 7750 b a r s , T = 710  C.  I n b o t h cases a  n  i s approximately  M u t u a l i n t e r s e c t i o n of e q u i l i b r i a ( E l ) w i t h e s t i m a t e d metamorphic p r e s s u r e s and respectively.  0.5. (E4 and  E8)  results i n  temperatures of 7600 b a r s and  705° C,  Combined e r r o r s f o r the d i f f e r e n t e q u i l i b r i a g i v e e s t i m a t e d  t o t a l e r r o r s of ± 400 b a r s and  ± 40°  C f o r these estimated c o n d i t i o n s .  The  range i n temperature e r r o r r e s u l t s l a r g e l y from thermochemical e r r o r i n the t r a n s i t i o n between low and h i g h a l b i t e . C a l c u l a t i o n of a f o r the f i v e samples c o n t a i n i n g H0 n  staurolite results  2  in  v a l u e s around 0.5.  T a b l e 2-20  lists'the'HO  a c t i v i t y r e q u i r e d to b r i n g  167  600  700 TEMPERATURE,  Figure  2-13.  Intersection of e q u i l i b r i a  f o r the f i v e samples c o n t a i n i n g 0  a l o n g each c u r v e .  °C  ( E l ) , (E4,E5), and (E8,E9)  the assemblage m u s c o v i t e - q u a r t z -  plagioclase-staurolite-garnet-Al SiCv. P  800  P„ _ decreases w i t h  increasing  !68  Table 2-20.  Calculated a  R  Q  required f o r e q u i l i b r i a  (E8, E9) t o pass  through t h e e s t i m a t e d metamorphic c o n d i t i o n s :  P  = 7600 Total  b a r s , T = 705° C.  Sample  a ^0  Paragonite  3 7 3  0.55  3.37  121  0.54  3.37  3 6 7  0.53  3.50  8 2  0.49  3.34  98  0.56  3.17  492  0.63  3.25  223  0.54  3.43  2-376  0.49  3.43  2-1  0.49  3.46  7 4  0.36  3.19  5 9  0.48  3.38  4 0  0.53  3.35  3  3  169  t h e c a l c u l a t e d c u r v e f o r e q u i l i b r i a (E8, E9) f o r each sample through the i n f e r r e d metamorphic p r e s s u r e  (7600 b a r s ) and temperature  (705° C ) .  i s a l s o l i s t e d i n t h e t a b l e t o g i v e an i n d i c a t i o n o f t h e Paragonite c o r r e c t i o n a p p l i e d to the paragonite a c t i v i t i e s f o r the c a l c u l a t e d  curves.  For a l l t w e l v e samples t h e IL^O a c t i v i t e s range between 0.35 and 0.63 w i t h a mean v a l u e v e r y c l o s e t o 0.5.  I t must be remembered t h a t t h i s v a l u e i s  s u b j e c t t o l a r g e e r r o r because o f t h e s e n s i t i v i t y o f a ^ ^ t o  thermochemical  e r r o r and t h e p a r t i c u l a r s o l i d s o l u t i o n models used. Plagioclase-Garnet-Quartz-A^SiO,. The sub-assemblage p l a g i o c l a s e - q u a r t z - g a r n e t - k y a n i t e , s i l l i m a n i t e has been suggested  as a p o t e n t i a l geothermometer-geobarometer (Ghent 1976),  These m i n e r a l s a r e r e l a t e d through r e a c t i o n (E10, E l l ) .  As a s o l i d - s o l i d  r e a c t i o n i t has t h e advantage o f b e i n g independent o f a  . Uncertainties  i n t h e e x p e r i m e n t a l l o c a t i o n o f t h i s curve and i n t h e c h o i c e o f n o n i d e a l m i x i n g models f o r p l a g i o c l a s e and garnet s o l i d s o l u t i o n c o n t r i b u t e t o u n c e r t a i n t y i n t h e p r e s s u r e s and temperatures  i n f e r r e d from t h i s  equilibrium. Hays (1967) and H a r i y a and Kennedy (1968) c a l i b r a t e d r e a c t i o n ( E l O ) e x p e r i m e n t a l l y u s i n g end-member c o m p o s i t i o n s a t p r e s s u r e s between 20 and 35 kbar w i t h p i s t o n c y l i n d e r a p p a r a t u s . moderately  Although experimental b r a c k e t s are  s m a l l a t t h e s e h i g h p r e s s u r e s , e x t r a p o l a t i o n o f maximum and  minimum a l l o w e d s l o p e s t o lower p r e s s u r e s r e s u l t s i n a l a r g e i s o b a r i c temperature  u n c e r t a i n t y ( a p p r o x i m a t e l y ± 375° C a t 10 k b a r ) i n t h e p o s i t i o n  of t h e r e a c t i o n (see f i g u r e 2-25).  To f u r t h e r r e s t r i c t t h i s  temperature  u n c e r t a i n t y , I have r e q u i r e d r e a c t i o n (ElO) t o be 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 from n i n e i n d e p e n d e n t l y s t u d i e d r e a c t i o n s i n t h e system C a O - A l 0 - S i 0 - H 0 . 2  3  2  2  C o n s i s t e n c y was v e r i f i e d u s i n g i n e q u a l i t i e s  170 and l i n e a r programming f o l l o w i n g the approach o u t l i n e d by Gordon (1973). A l l r e a c t i o n s were s t u d i e d u s i n g o u t e r l i m i t s of e x p e r i m e n t a l u n c e r t a i n t y . D e t a i l s c o n c e r n i n g e r r o r l i m i t s and e x p e r i m e n t a l b r a c k e t s used f o r each of the r e a c t i o n s a r e g i v e n i n Appendix 2-2.  By i n c l u d i n g t h e s e o t h e r  r e a c t i o n s the i s o b a r i c temperature u n c e r t a i n t y i n r e a c t i o n (E10) i s reduced t o a p p r o x i m a t e l y ± 60° C (10 k b a r ) (see f i g u r e 2-25).  This  c o r r e s p o n d s t o a p r e s s u r e u n c e r t a i n t y of ± 1.0 kbar i n the l o c a t i o n of the equilibrium reaction.  The c u r v e suggested by H a r i y a and Kennedy (1968)  i s a p p r o x i m a t e l y i n the c e n t e r o f t h i s r e s t r i c t e d p r e s s u r e - t e m p e r a t u r e space and has been used i n a l l f u r t h e r F i g u r e 2-14  calculations.  compares the d i s p l a c e d p r e s s u r e - t e m p e r a t u r e p o s i t i o n s o f  e q u i l i b r i u m (E10) f o r sample 82 w i t h t h r e e d i f f e r e n t s o l i d s o l u t i o n models. The s t a b l e A l ^ S i O ^ polymorph f o r the c a l c u l a t i o n s was k y a n i t e . c o r r e s p o n d s t o i d e a l s o l u t i o n i n b o t h g a r n e t and p l a g i o c l a s e .  Curve A Nonideal  p l a g i o c l a s e - i d e a l g a r n e t i s r e p r e s e n t e d by c u r v e B, and n o n i d e a l p l a g i o c l a s e — n o n i d e a l g a r n e t c o r r e s p o n d s t o c u r v e C.  I n a l l cases the c a l c u l a t e d c u r v e  o c c u r s a t h i g h e r p r e s s u r e s than the e r r o r p a r a l l e l o g r a m around the mutual i n t e r s e c t i o n of e q u i l i b r i a  ( E l , E4, and E8) f o r the same sample.  Ghent  (1975, 1976) a l s o noted t h a t e s t i m a t e s u s i n g t h i s e q u i l i b r i u m g i v e c o n s i s t e n t l y h i g h e r p r e s s u r e s f o r a s p e c i f i e d temperature.  The  preliminary  n a t u r e of t h e g a r n e t m i x i n g model s u g g e s t s t h a t use o f t h i s r e a c t i o n as a pressure-temperature i n d i c a t o r i s l i m i t e d without a d d i t i o n a l study of garnet thermochemistry. F i g u r e 2-14  a l s o i n d i c a t e s the h i g h s e n s i t i v i t y of t h i s e q u i l i b r i u m t o  u n c e r t a i n t i e s i n e x p e r i m e n t a l e r r o r and m i n e r a l c o m p o s i t i o n s . u n c e r t a i n t y b r a c k e t s f o r thermochemical e r r o r (±1.0  Isothermal  k b a r ) are. t h e  e x p e r i m e n t a l u n c e r t a i n t y i n the c a l c u l a t e d p r e s s u r e - t e m p e r a t u r e p o s i t i o n  I 7 I  F i g u r e 2-14.  D i s p l a c e d p o s i t i o n of e q u i l i b r i u m  i s the s t a b l e A ^ S i O ^ polymorph.  Curve B r e p r e s e n t s i d e a l  s o l u t i o n , and curve C c o r r e s p o n d s t o  nonideal garnet-nonideal plagioclase  solid solution.  e n c l o s e s the e s t i m a t e d metamorphic c o n d i t i o n s of e q u i l i b r i a E l , (E4, E 5 ) , and (E8, E 9 ) . from Holdaway  (1971).  Kyanite  Curve A corresponds t o i d e a l s o l i d  s o l u t i o n f o r b o t h g a r n e t and p l a g i o c l a s e . garnet-nonideal plagioclase  ElO f o r sample 82.  Parallelogram  from the i n t e r s e c t i o n  Al Si0 2  5  t r a n s i t i o n s are  400  F i g u r e 2-15.  500  600 700 TEMPERATURE, °C  800  D i s p l a c e d e q u i l i b r i u m curves ElO f o r a l l 12 a n a l y z e d p e l i t e samples.  calculated with kyanite stable. t r a n s i t i o n s a r e from Holdaway  900  A l l curves  P a r a l l e l o g r a m i n d i c a t e s e s t i m a t e d metamorphic c o n d i t i o n s .  (1971).  Al  173 of t h e end-member c a l i b r a t e d c u r v e .  The l a r g e r u n c e r t a i n t y  o f ± 1.3 k b a r  r e p r e s e n t s t h e s h i f t i n p o s i t i o n o f the e q u i l i b r i u m c u r v e w i t h a change i n p l a g i o c l a s e c o m p o s i t i o n o f ± 10 mole % a n o r t h i t e c o n t e n t .  Local  e q u i l i b r i u m o r p a t c h y z o n i n g i n p l a g i o c l a s e would have a s i g n i f i c a n t e f f e c t on the c a l c u l a t e d p r e s s u r e s and temperatures f o r t h i s e q u i l i b r i u m . Calculated f i g u r e 2-15.  c u r v e s f o r a l l t w e l v e p e l i t e s samples a r e shown i n  Because o f l i m i t e d i n f o r m a t i o n  on s o l i d s o l u t i o n models,  i d e a l s o l u t i o n was assumed f o r b o t h p l a g i o c l a s e and g a r n e t . A l l c a l c u l a t i o n s used k y a n i t e  as t h e s t a b l e A l ^ S i O ^ polymorph.  Using  s i l l i m a n i t e i n t h e e q u i l i b r i u m c a l c u l a t i o n s would i s o b a r i c a l l y d e c r e a s e the c a l c u l a t e d t e m p e r a t u r e o f t h e e q u i l i b r i u m c u r v e .  The A z u r e Lake  samples show a l a r g e s c a t t e r o f a p p r o x i m a t e l y 100° C i n t h e e s t i m a t e d equilibrium position for reaction  (ElO).  As w i t h t h e o t h e r  t h e r e i s no s y s t e m a t i c temperature g r a d i e n t  equilibria,  i n the c a l c u l a t e d p o s i t i o n o f  the e q u i l i b r i u m c u r v e s when compared t o t h e r e g i o n a l metamorphic  gradient.  I n summary, t h i s e q u i l i b r i u m c o n s i s t e n t l y r e s u l t s i n h i g h p r e s s u r e e s t i m a t e s f o r a g i v e n temperature when compared t o o t h e r e q u i l i b r i a a l t h o u g h i t i s c o n s i s t e n t when e r r o r b r a c k e t s a r e t a k e n i n t o I t s use as a r e l a t i v e e s t i m a t o r  o f metamorphic c o n d i t i o n s  i t s s e n s i t i v i t y to small variations i n plagioclase  consideration.  i s l i m i t e d by  compositions.  Summary Metamorphic c o n d i t i o n s  f o r t h e Shuswap Complex i n t h e Azure Lake a r e a  are e s t i m a t e d t o be P = 7600 ± 400 b a r s , T = 705 ± 40° C, a H  &pprox.).  = 0.5 2°  These e s t i m a t e s r e s u l t from t h e mutual i n t e r s e c t i o n o f  several e q u i l i b r i a i n v o l v i n g garnet, s t a u r o l i t e , p l a g i o c l a s e , muscovite, quartz,  and A l ^ S i O ^ .  The d i f f e r e n t e q u i l i b r i a have been t h e r m o d y n a m i c a l l y  d i s p l a c e d f o r s o l i d s o l u t i o n and reduced a  _ effects,  a  i n the twelve  174 a n a l y z e d p e l i t e samples ranges between 0.35 and 0.63 w i t h a mean o f 0.5. These a  e s t i m a t e s a r e approximate because o f t h e extreme s e n s i t i v i t y o f 2° c a l c u l a t e d v a l u e s t o thermochemical e r r o r s ; e r r o r b r a c k e t s f o r a s i n g l e n  H  sample r e s u l t i n a range o f a  „ between 0.25 and 1.0. 2° F l e t c h e r and Greenwood ( i n p r e s s ) have p r e s e n t e d e s t i m a t e d metamorphic H  c o n d i t i o n s o f P = 7000 ± 1500 b a r s , T = 680 ± 30° C, a„• = 0.8 (approx.) 2° H  f o r t h e Shuswap Complex j u s t n o r t h w e s t o f t h e A z u r e Lake a r e a .  Their  estimated conditions overlap w i t h the conditions presented here. t h e same e q u i l i b r i a were used i n b o t h s e t s o f c a l c u l a t i o n s .  Many o f  Differences  i n t h e r e s u l t i n g e s t i m a t e d metamorphic c o n d i t i o n s a r e r e l a t e d t o d i f f e r e n t s o l i d s o l u t i o n , models f o r s e v e r a l m i n e r a l s .  The s o l u t i o n model f o r  s t a u r o l i t e appears t o be t h e major f a c t o r i n t h e d i f f e r e n t e s t i m a t e s . The s t a u r o l i t e s o l u t i o n model used i n t h i s paper i n c r e a s e s e s t i m a t e d t e m p e r a t u r e s by 30° C when compared t o t h e model used by F l e t c h e r and Greenwood. I t i s i n t e r e s t i n g t o compare these e s t i m a t e s t o those c a l c u l a t e d from the d i s t r i b u t i o n o f Fe-Mg between g a r n e t and b i o t i t e (A.B. Thompson 1976b). A.B. Thompson's g a r n e t - b i o t i t e geothermometer c o n s i s t e n t l y g i v e s temperatures near 530° C f o r Azure Lake m i n e r a l c o m p o s i t i o n s .  Similarly  t h e e x p e r i m e n t a l l y c a l i b r a t e d geothermometer p r e s e n t e d by F e r r y and Spear (1977) r e s u l t s i n temperatures near 550° C.  I n b o t h cases t h e e x c e e d i n g l y  low temperatures a r e p r o b a b l y r e l a t e d t o a d d i t i o n a l components i n t h e participating  phases.  CALCAREOUS ASSEMBLAGES  D i s c o n t i n u o u s marble u n i t s up t o 30 in. t h i c k a r e s p a r s e l y d i s t r i b u t e d throughout t h e Kaza Group i n t h e A z u r e Lake a r e a .  T e x t u r a l l y these u n i t s  range from m a s s i v e , f i n e - g r a i n e d , f l i n t y , b l u e - g r a y o u t c r o p s t o m e d i u m -  175 c o a r s e , o f f - w h i t e , f r i a b l e a g g r e g a t e s of c a l c i t e .  L o c a l brownish i r o n  s t a i n i n g from o x i d i z e d s u l f i d e g r a i n s i s u b i q u i t o u s . form s t r e a k y l a y e r s and n o d u l e s w i t h i n marble.  S i l i c a t e minerals  Inequant m i n e r a l s  ( m u s c o v i t e , b i o t i t e , c a l c i c amphibole) a r e p o o r l y a l i g n e d p a r a l l e l t o t h e dominant r e g i o n a l s c h i s t o s i t y . Marginal  r e a c t i o n zones between marble and e n c l o s i n g p e l i t e o r  q u a r t z i t e u n i t s a r e m i n i m a l a l t h o u g h some marbles c o n t a i n c a l c i c amphibole i n t h i n marginal selvages.  P l a g i o c l a s e i n m a r g i n a l zones i s p a r t l y t o  c o m p l e t e l y r e p l a c e d by z o i s i t e . pegmatitic  One marble u n i t c o n s i s t e n t l y  contains  v e s u v i a n i t e i n t e r g r o w n w i t h z o i s i t e i n t h e m a r g i n a l zone.  M i n e r a l assemblages were determined by c o m b i n i n g t h i n s e c t i o n e x a m i n a t i o n w i t h x - r a y powder d i f f r a c t i o n s t u d y o f i n s o l u b l e K-feldspar  was v e r i f i e d by s t a i n i n g i n s o l u b l e r e s i d u e s w i t h  residues. sodium  cobaltinitrite. C a l c a r e o u s metamorphic assemblages i n the t h r e e p e l i t e  metamorphic  zones a r e as f o l l o w s : Kyanite  Zone  calcite-muscovite-quartz-K-feldspar-plagioclase-(zoisite) K y a n i t e - S i l l i m a n i t e Zone calcite-muscovite-quartz-plagioclase  ± b i o t i t e ± K-feldspar  c a l c i t e - q u a r t z - c a l c i c amphibole-plagioclase  - (zoisite)  ± garnet ± b i o t i t e  ± c a l c i c pyroxene - ( z o i s i t e ) S i l l i m a n i t e Zone c a l c i t e - q u a r t z - p l a g i o c l a s e ± K-feldspar  ± muscovite - ( z o i s i t e )  c a l c i t e - q u a r t z - p l a g i o c l a s e ± c a l c i c amphibole ± c a l c i c pyroxene ± b i o t i t e ± K-feldspar  ± scapolite - (zoisite)  176  Z o i s i t e i s i n c l u d e d i n p a r e n t h e s e s i n the above assemblages because i t t y p i c a l l y o c c u r s as a l o c a l a l t e r a t i o n of p l a g i o c l a s e g r a i n s . p y r r h o t i t e , sphene, and  Graphite,  a p a t i t e are l o c a l l y a c c e s s o r y m i n e r a l s i n each of  t h e s e assemblages. The  sequence of m i n e r a l  described  assemblages w i t h i n the Azure Lake a r e a may  by the f o l l o w i n g r e a c t i o n s :  1 muscovite + 1 c a l c i t e + 2 quartz = 1 K-feldspar + 1 H0  + 1 C0  2  5 phlogopite  + 1 anorthite (E14)  2  + 6 c a l c i t e + 24 q u a r t z = 3 t r e m o l i t e + 2 H 0 2  + 6  + 5 K-feldspar  + 3 C0  (E17)  2  3 anorthite + 1 calcite + 1 H 0 These r e a c t i o n s are c o n t a i n e d  FeO,  n  w i t h i n s u b s e t s of the seven component  2  temperature or X  (E19)  2  system K 0 - A l 0 - M g O - S i 0 - C a O - C 0 - H 0 . 3  (E18)  = 2 z o i s i t e + 1 CC>  2  2  2  ).  2  A l l are i s o b a r i c a l l y  univariant  A d d i t i o n a l components such as TiO„,  and N a 0 cause the r e a c t i o n s t o become m u l t i v a r i a n t . 2  I s o g r a d r e a c t i o n s u r f a c e s w i t h i n the c a r b o n a t e u n i t s a r e d e f i n e d because of s c a n t y o u t c r o p and units.  compositional  (A-D)  r e a c t i o n assemblage o c c u r s over a g e o g r a p h i c a r e a . t o 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 of the m i n e r a l s and n a t u r e of most of the r e a c t i o n s .  f o r these  by p l o t t i n g p r o d u c t and  assemblages f o r each r e a c t i o n ( C a r m i c h a e l 1970).  An assemblage map  poorly  d i f f e r e n c e s between the  Approximate l o c a t i o n s of the r e a c t i o n s s u r f a c e s  are i n d i c a t e d i n f i g u r e 2-16  not  2  R^O  3 anorthite + 1 c a l c i t e = 3 meionite (scapolite)  2  C0  (E16)  1 tremolite + 3 c a l c i t e + 2 quartz = 5 diopside + 1  (varying i  be  reactions  reactant  I n each example the This i s r e a d i l y r e l a t e d t o the  multivariant  f o r r e a c t i o n (E19)  was  i n c l u d e d s i n c e t h i s r e a c t i o n assemblage i s l o c a l l y p r e s e n t throughout  177  F i g u r e 2-16.  C a l c a r e o u s r e a c t a n t and p r o d u c t assemblages f o r c a r b o n a t e  mineral e q u i l i b r i a .  Carbonate l a y e r s w i t h i n the Kaza Group a r e  indicated i n black. A)  E q u i l i b r i a E13, E14  178  F i g u r e 2-16.  C a l c a r e o u s r e a c t a n t and p r o d u c t assemblages f o r c a r b o n a t e  mineral e q u i l i b r i a .  Carbonate l a y e r s w i t h i n t h e Kaza Group a r e  indicated i n black. B)  E q u i l i b r i a E15, E16  179  Figure  2-16.  Calcareous reactant  mineral e q u i l i b r i a . indicated i n black. C)  Equilibrium  E17  and p r o d u c t assemblages f o r c a r b o n a t e  Carbonate l a y e r s w i t h i n the Kaza Group a r e  180  Figure  2-16.  C a l c a r e o u s r e a c t a n t and p r o d u c t assemblages f o r c a r b o n a t e  mineral e q u i l i b r i a . indicated i n black. D)  E q u i l i b r i u m E18  Carbonate l a y e r s w i t h i n the Kaza Group a r e  181  the Azure Lake  area.  The r e l a t i v e i s o b a r i c T-X  arrangement  of r e a c t i o n s (E13, E 1 4 ) ,  (E15, E16) , E17, E18, and E19 f o r h i g h grade metamorphic been o u t l i n e d by H e w i t t s i m i l a r T-X  (1973b) and F e r r y (1976) .  c o n d i t i o n s has  F i g u r e 2-17  is a  diagram c o n s t r u c t e d f o r a t o t a l p r e s s u r e of 7600 b a r s .  T h i s p r e s s u r e was chosen t o be c o n s i s t e n t w i t h e s t i m a t e s p e l i t e assemblages.  from the  S e v e r a l r e a c t i o n s around the d i f f e r e n t  i n v a r i a n t p o i n t s have not been i n c l u d e d .  isobaric  I t i s i m p r a c t i c a l to discuss a  complete Schreinemaker's a n a l y s i s because of u n c e r t a i n e q u i l i b r i u m r e l a t i o n s between t s c h e r m a k i t i c and t r e m o l i t i c amphiboles.  The  progressive  sequence of r e a c t i o n s w i t h i n c r e a s i n g temperature i n f i g u r e 2-17 i s c o n c o r d a n t w i t h the s e q u e n t i a l change of m i n e r a l assemblages i n c r e a s i n g metamorphic  with  grade i n o t h e r r e g i o n a l l y metamorphosed t e r r a i n s  (P. Thompson 1973; F e r r y 1976). The p r e s s u r e - t e m p e r a t u r e - X  p o s i t i o n s of the c u r v e s i n f i g u r e 2-17  were c a l c u l a t e d u s i n g the methods o u t l i n e d e a r l i e r f o r the p e l i t e e q u i l i b r i a (see Appendix 2-2) . parameters  A G^ and  A S^ f o r each e x p e r i m e n t a l  using l i n e a r i n e q u a l i t i e s experimental  I n t e r n a l c o n s i s t e n c y of the  (Gordon 1973).  s t u d i e s and thermodynamic  thermodynamic  e q u i l i b r i u m was  verified  T a b l e 2-21 l i s t s the r e l e v a n t  parameters f o r the d i f f e r e n t  equilibria. Reactions  (E13) and (E15) were e x p e r i m e n t a l l y s t u d i e d u s i n g s a n i d i n e as  the p a r t i c i p a t i n g a l k a l i f e l d s p a r ( H e w i t t 1973b, 1975; Hoschek 1973). F i e l d o b s e r v a t i o n s f o r the same e q u i l i b r i a t y p i c a l l y r e p o r t m i c r o c l i n e (A.B. Thompson 1975; F e r r y 1976). the T-X^Q  positions  The d o t t e d l i n e s i n f i g u r e 2-17  illustrate  o f e q u i l i b r i a (E14) and (E16) w i t h maximum m i c r o c l i n e  as the s t a b l e a l k a l i f e l d s p a r phase.  Thermodynamic parameters f o r the  182  J  I  1  I  1  \  Figure 2-17.  Isobaric  SiC^-H^O-CC^.  P  1  1  1  L  Me  T - X  xotal  =  QQ  diagram f o r t h e system CaO-MgO-A^O^-  '^®® b a r s .  Dotted  l i n e s represent e q u i l i b r i u m  r e a c t i o n s u s i n g m i c r o c l i n e ( r a t h e r than s a n i d i n e ) as the s t a b l e K - f e l d s p a r . A b b r e v i a t i o n s a r e t h e same as l i s t e d i n T a b l e 2 - 2 2 .  Dol - dolomite.  Thermodynamic parameters f o r t h e d i f f e r e n t r e a c t i o n s a r e l i s t e d i n Table 2 - 2 1 .  183  sanidine-maximum m i c r o c l i n e data  t r a n s i t i o n were c a l c u l a t e d from  (Hemingway a n d R o b i e l 9 7 7 ) .  temperatures,  and r e a c t i o n  with reaction  (E17).  temperature  i s not  calorimetric  Both r e a c t i o n s are d i s p l a c e d to  (E16)  changes r e l a t i v e  T h i s new s e q u e n c e o f  compatible with f i e l d  temperature  reactions with  higher  position  increasing  o b s e r v a t i o n s and s u g g e s t s  t h e r e may b e p r o b l e m s w i t h u s i n g maximum m i c r o c l i n e a s t h e s t a b l e K - f e l d s p a r phase f o r  t h e s e p r e s s u r e and t e m p e r a t u r e  Greenwood ( 1 9 7 5 a )  has suggested that  fluid  compositions.  to have a s i g n i f i c a n t and p e l i t e  units  effect  continuous  reactions  O n l y s m a l l amounts o f  on f l u i d  c a p a c i t y of  sections w i l l  show t h a t  carbonate e q u i l i b r i u m  calculated a  buffered  its  Since the d i f f e r e n t space,  conditions  units.  own f l u i d  the  equilibria  thermodynamically  E14  =  example  of  following  thermodynamically  displac  calculated  This indicates that  each rock  type  c o m p o s i t i o n d u r i n g m e t a m o r p h i s m and was p r e s e n t  i n the  are at  rocks.  least  bivariant  i n d e p e n d e n t l y e s t i m a t e d p r e s s u r e and assemblages were used to  ( E 1 7 ) , and ( E 1 9 ) . displaced for  equilibrium constant approach.  K  carbonate  temperature  solve for  a  u  _ in  the  A n a l y z e d carbonate samples c o n t a i n r e a c t i o n assemblages f o r (E14),  d e f i n e d as  The  lower than  calcareous e q u i l i b r i a  from the p e l i t e  carbonates.  values for  A  t h a t no h o m o g e n e o u s , p e r v a s i v e f l u i d  in P-T-X  Interlayered  2°  curves are c o n s i s t e n t l y  _ from the e n c l o s i n g p e l i t e  effectively  buffering  r e a c t i o n are needed  the c a l c a r e o u s assemblages.  H  u  involving  from the A z u r e Lake a r e a p r o v i d e an e x c e l l e n t  the b u f f e r i n g  a  composition.  triclinic  conditions.  c o e x i s t i n g metamorphic m i n e r a l s have a h i g h c a p a c i t y f o r metamorphic  that  These c a l c a r e o u s e q u i l i b r i a  solid solution effects The a p p r o p r i a t e  using  equilibrium  follows: fa ) * (a ) * /a J * fa 1 Anorthite^ ^K-feldspar ^ H 0 ^ CO^ 7  J  2  (a  Muscovite  ) *  (a  Calcite  )  were  the constants  are  184  h  u  «  Dio side  ( a  * V  ) 5  *  (  P  ( a  C0  ) 3 2  3  ^Tremolite'* * ^ C a l c i t e ^ a  K  E 1 9  (a ) ^Zoisite  =  2  7  fa v  * (a ) CO '  ) Anorthite'  3  * fa ) * fa ^Calcite'  )  Expressions r e l a t i n g mole f r a c t i o n to a c t i v i t y are needed for the above components i n order to evaluate the equilibrium constants.  Solution  models for the components are discussed i n the following section. Calcic pyroxene, C a l c i t e : Solid solution i n both c a l c i c pyroxene and c a l c i t e was  considered  ideal with a c t i v i t y being related to the mole f r a c t i o n of the appropriate component.  Nonideality i n c a l c i t e i s i n s i g n i f i c a n t for the Ca-rich  compositions l i s t e d i n Table 2-10  (Gordon and Greenwood 1970).  Substitution i n c a l c i c pyroxene was considered to be only on the Mg-site. The resulting a c t i v i t y expressions are: a  Calcite  =  X  Calcite  Diopsxde  ( 1 0 )  Hg  Calcic amphibole: The a c t i v i t y of tremolite i n c a l c i c amphibole i s less obvious.  The  following expression has been adopted for tremolite a c t i v i t y (Kerrick and Darken 1975): a  Tremolite = < •  where X q  X  > * <  X C  /  *  *  (  X 0  /  ^  represents the mole f r a c t i o n of vacancies i n the twelve-  coordinated A s i t e .  The X  term has not been included i n t h i s expression  because substitution of A l for S i i s coupled to substitutions on the other  185  s i t e s (Ferry 1976;  Skippen and Carmichael  1977).  This coupled  substitution approach i s s t r i c t l y v a l i d only i f Mg/Fe r a t i o s do not change with increased tetrahedral A l content.  This model i s reasonable f o r  a c t i n o l i t e because tetrahedral A l i s i n s i g n i f i c a n t , but the model may inadequate for tschermakitic amphiboles.  Saxena and Ekstrom (1969)  have shown that i n c a l c i c amphiboles Fe-content tetrahedral A l content. Table 2-14.  be  increases with increasing  The same trend i s also present i n the analyses i n  Including a term for X  would decrease tremolite a c t i v i t y  and therefore increase the calculated temperature for equilibrium (E17) at constant t o t a l pressure and X  . LU  2  Muscovite: Activity-mole f r a c t i o n r e l a t i o n s for white micas were described previously, r  J  a,, M u s c o v i.t e  Muscovite "  i s calculated i n a manner analogous to paragonite:  Muscovite * V (  Y Muscovite „ . i s very close to  *  (  X  A / *  ( X  0H  ) 2  ( 1 3 )  1.0.  Feldspar: A c t i v i t y r e l a t i o n s for anorthite were discussed i n connection with the pelites.  K-feldspar a c t i v i t i e s were considered as equal to the mole  f r a c t i o n of K A l S i 0 o  o  i n the analyzed a l k a l i feldspar.  Calculations  involving equilibrium (E14) used maximum microcline as the preferred stable a l k a l i feldspar phase. was  Consequently the a c t i v i t y c o e f f i c i e n t for K-feldspar  calculated from the Margules G-excess term (J.B. Thompson 1967,  with Margules W-parameters from the study of the microcline-low solvus by Bachinski and Muller (1971). aK-feldspar =  albite  The resulting expressions  Y Microcline * X K-feldspar  eqtn  are: (14)  80)  186 RTlnv„. -* . 'Microcline  = (X ) albite'  2  * (W„. „ + 2 * X. Microcline ^-feldspar  ^Albite^Microcline^  *  ( 1 5 )  A c t i v i t y c o e f f i c i e n t s f o r c o m p o s i t i o n s l i s t e d i n T a b l e 2-12  are n e a r l y  1.0. Zoisite: Mossbauer s t u d i e s by D o l l a s e (1973) have demonstrated t h a t f e r r i c i r o n p r e f e r e n t i a l l y o r d e r s i n t o o n l y one o f the t h r e e A l - s i t e s i n the s t r u c t u r a l formula  (13 oxygen b a s i s ) .  Consequently  zoisite activity i s  r e p r e s e n t e d by t h e e x p r e s s i o n :  Zoisite " where Fe, Mg, structural  ( 1  -  ( F e  +  M  S  +  < >  M n ) )  16  and Mn a r e the number o f atoms o f each s p e c i e s i n the  formula.  These a c t i v i t y e x p r e s s i o n s have been s u b s t i t u t e d i n t h e e q u i l i b r i u m constants to d i s p l a c e e q u i l i b r i a effects.  (E14), (E17), and  (E19) f o r s o l i d  The e q u i l i b r i a were c a l c u l a t e d f o r d i f f e r i n g a  solution  contents at  TI  H0 2  t h e p r e s s u r e e s t i m a t e d from t h e p e l i t e assemblages. correspond  t o the e q u i l i b r i a f o r c o e x i s t i n g m i n e r a l c o m p o s i t i o n s i n the  Azure Lake a r e a . different  The d i s p l a c e d c u r v e s  The  following sections discuss  the r e s u l t s f o r t h e  equilibria.  C a l c i t e - Q u a r t z - C a l c i c a m p h i b o l e - C a l c i c pyroxene The p r e s s u r e - t e m p e r a t u r e - X e x p e r i m e n t a l l y determined  p o s i t i o n of e q u i l i b r i u m (E17) has been  by S l a u g h t e r , K e r r i c k , and W a l l (1975).  Their  curve i s c o n s i s t e n t w i t h t h e c a l c u l a t e d p o s i t i o n o f t h e r e a c t i o n a c c o r d i n g t o Skippen  (1971).  E x p e r i m e n t a l s t u d i e s by Metz (1970) b r a c k e t  r e a c t i o n a t h i g h e r temperatures  f o r a g i v e n p r e s s u r e and X  . This co of the n a t u r a l 2  i n c o n s i s t e n c y i s a p p a r e n t l y due t o u n s p e c i f i e d F-content  the  187 t r e m o l i t e used i n h i s experiments  (P. Metz,' p e r s o n a l communication 1977).  I n t e r n a l l y c o n s i s t e n t thermodynamic parameters were d e r i v e d from the study by S l a u g h t e r e t a l . (1975) and a r e l i s t e d i n Table  2-21.  The e q u i l i b r i u m assemblage c a l c i t e - q u a r t z - c a l c i c a m p h i b o l e - c a l c i c pyroxene o c c u r s i n s c a t t e r e d o u t c r o p s over p o r t i o n s of the s i l l i m a n i t e k y a n i t e - s i l l i m a n i t e metamorphic zones.  Grain boundaries  are  and  sharp;  c o e x i s t i n g m i n e r a l s appear t o be i n t e x t u r a l e q u i l i b r i u m ( p l a t e 2-5A). T a b l e s 2-10,  2-14  and 2-15  c o n t a i n microprobe  a n a l y s e s f o r the e q u i l i b r i u m  assemblage from t h r e e samples (224, 20, 2-312). C a l c i c pyroxenes v a r y m a i n l y i n Fe/Mg r a t i o : . . No z o n i n g o r inhomogeneity was  detected during a n a l y s i s .  C a l c i c amphiboles range from  a c t i n o l i t e s t o f e r r o - t s c h e r m a k i t i c hornblendes g r a i n s c o n t a i n patchy t o c o n c e n t r i c z o n i n g .  chemical  (Leake 1968).  T a b l e 2-14  A l l amphibole  c o n t a i n s two  spot  a n a l y s e s f o r each sample; these a n a l y s e s r e p r e s e n t the f u l l range of analyzed compositions.  The major v a r i a t i o n i s i n s u b s t i t u t i o n of  tetrahedral A l for S i .  A l - r i c h amphiboles a l s o c o n t a i n i n c r e a s e d amounts  of Na, K, and Fe.  I n examples of c o n c e n t r i c z o n i n g , g r a i n r i m s c o n t a i n e d  more aluminum. F i g u r e 2-18  i l l u s t r a t e s the c a l c u l a t e d T-X  e q u i l i b r i u m curves f o r L  2  the d i s p l a c e d e q u i l i b r i a c o r r e s p o n d i n g t o samples 224, 20, and 2-312.  An  assumed t o t a l p r e s s u r e of 7600 b a r s i s c o n s i s t e n t w i t h the p r e s s u r e e s t i m a t e d from the p e l i t e assemblages.  S o l i d curves correspond  to the  e q u i l i b r i u m assemblage u s i n g the a c t i n o l i t i c c o m p o s i t i o n s , and d o t t e d  curves  r e p r e s e n t the c a l c u l a t e d e q u i l i b r i u m u s i n g t s c h e r m a k i t i c amphibole compositions. C a l c u l a t e d r e a c t i o n assemblage c u r v e s with, a c t i n o l i t e s a l l r e q u i r e X  v a l u e s near 0.75  t o be c o n s i s t e n t w i t h p r e v i o u s l y e s t i m a t e d  188  F i g u r e 2-18.  D i s p l a c e d e q u i l i b r i u m curves E17  diagram f o r samples 20, 224, and 2-312.  P  i n an i s o b a r i c T-X  xotal  e q u i l i b r i u m assemblage i s c a l c i c a m p h i b o l e - c a l c i c calcite.  bars.  =  using  Dotted l i n e s correspond  same e q u i l i b r i u m u s i n g t s c h e r m a k i t i c amphibole compositions:. l i n e s r e p r e s e n t e r r o r margins on e s t i m a t e d metamorphic (from p e l i t i c assemblages) a t 7600 b a r s .  The  pyroxene-quartz-  S o l i d l i n e s r e p r e s e n t d i s p l a c e d e q u i l i b r i u m E17  a c t i n o l i t i c amphibole c o m p o s i t i o n s .  _  t o the Dashed  temperature  189 metamorphic c o n d i t i o n s . buffered  t o low  The  f l u i d c o m p o s i t i o n appears t o have been  ^ (high'  e q u i l i b r i u m assemblage.  ) v a l u e s n e a r the T-X  maximum by  the  I n c o n t r a s t 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  u s i n g t s c h e r m a k i t i c c o m p o s i t i o n s i n d i c a t e t h a t the c o e x i s t i n g f l u i d a  n  values ranging Tschermakitic  from 0.5  to  0.2.  amphibole c o m p o s i t i o n s r e q u i r e i n v o l v e m e n t of  p l a g i o c l a s e i n the a m p h i b o l e - f o r m i n g r e a c t i o n . zoning  has  P a t c h y and  concentric  i n the Azure Lake amphiboles suggest t h a t t s c h e r m a k i t i c amphibole  growth o c c u r r e d  after i n i t i a l  a c t i n o l i t i c amphibole.  formation  of c a l c i c pyroxene from  C a l c u l a t e d temperature-X  p o s i t i o n s of C U  d i s p l a c e d e q u i l i b r i u m c u r v e s i n f i g u r e 2-18  the  2  i n d i c a t e that  amphiboles p r o b a b l y formed i n response t o i n c r e a s e d a  tschermakitic i n the f l u i d phase.  Calcite-Quartz-Muscovite-Plagioclase-K-feldspar Reaction  (E13)  has been e x p e r i m e n t a l l y  c o m p o s i t i o n s by H e w i t t (1973b). calcite-muscovite-quartz terrains.  He  c a l i b r a t e d f o r end-member  suggested t h a t the r e a c t a n t  assemblage  should occur only r a r e l y i n s i l l i m a n i t e - b e a r i n g  The Azure Lake a r e a i s of i n t e r e s t because the f u l l  reaction  assemblage s t r a d d l e s the k y a n i t e - s i l l i m a n i t e t r a n s i t i o n zone.  All  c a l c u l a t e d e q u i l i b r i u m c u r v e s have used maximum m i c r o c l i n e as  the  preferred stable a l k a l i feldspar.  C a l o r i m e t r i c d a t a from Hemingway and  R o b i e (1977) were used t o i n c o r p o r a t e m i c r o c l i n e i n r e a c t i o n Combined e r r o r s of ± 1600 temperature b r a c k e t curve.  The  (E14).  c a l o r i e s i n the c a l o r i m e t r i c d a t a r e s u l t i n a  of ± 45°  C i n the c a l c u l a t e d p o s i t i o n of the e q u i l i b r i u m  p o s i t i o n of the most s t a b l e c u r v e would be somewhere between  the p o s i t i o n s c a l c u l a t e d f o r s a n i d i n e and maximum m i c r o c l i n e s i n c e s t a b l e a l k a l i f e l d s p a r presumably has an i n t e r m e d i a t e (see f i g u r e 2-17).  degree of  the  ordering  190  F i g u r e 2-19.  D i s p l a c e d e q u i l i b r i u m curves E14 = 0.5.  The  69.  e q u i l i b r i u m assemblage i s c a l c i t e - m u s c o v i t e -  quartz-K-feldspar-plagioclase. represent  f o r samples 387 and  The  two dashed curves f o r sample 69  the range i n m u s c o v i t e c o m p o s i t i o n s i n 69 determined by  microprobe a n a l y s i s .  Parallelogram o u t l i n e s estimated  c o n d i t i o n s from p e l i t e assemblages. Holdaway (1971).  metamorphic  A^SiO,- t r a n s i t i o n s are from  191  T a b l e s 2-10, 2-11, 2-12, and 2-13 m i n e r a l s f o r two samples assemblage.  c o n t a i n a n a l y s e s of c o e x i s t i n g  (387, 69) w h i c h i n c l u d e the complete r e a c t i o n  Muscovite compositions contain extensive celadonite  component w i t h m i n i m a l p a r a g o n i t e c o n t e n t . sample 387 a r e homogeneous.  Coexisting minerals i n  S l i d e 69, however, shows e v i d e n c e of  r e t r o g r a d e adjustment of m i n e r a l c o m p o s i t i o n s . K - f e l d s p a r contains extensive s e r i c i t e .  Muscovite g r a i n s d i s p l a y a patchy zoning  o f c e l a d o n i t e and m u s c o v i t e components. than p y r r h o t i t e .  The s u l f i d e i s p y r i t e r a t h e r  T a b l e 2-13 c o n t a i n s two spot a n a l y s e s f o r m u s c o v i t e s  from sample 69; t h e s e r e p r e s e n t the most m u s c o v i t i c and c o m p o s i t i o n s i n the probe F i g u r e 2-19  typically  celadonitic  sample.  i l l u s t r a t e s c a l c u l a t e d p o s i t i o n s of the d i s p l a c e d  e q u i l i b r i u m (E14) f o r samples 387 and 69.  Two  c u r v e s a r e shown f o r 69;  t h e s e c o r r e s p o n d t o the m u s c o v i t i c and c e l a d o n i t i c c o m p o s i t i o n s i n T a b l e 2-13.  F l u i d c o m p o s i t i o n s were s e t t o a  = a H  2°  = 0.5 w h i c h r e s u l t s i n C  °2  the maximum temperature p o s s i b l e f o r t h i s r e a c t i o n .  Both samples  s l i g h t l y lower temperatures t h a n those e s t i m a t e d from p e l i t e  indicate  assemblages.  Low temperatures c o u l d r e s u l t e i t h e r from r e t r o g r a d e adjustment o f m i n e r a l c o m p o s i t i o n s o r from i n a d e q u a t e s o l i d s o l u t i o n models f o r the phases involved.  The v i s i b l e r e t r o g r a d i n g i n sample 69 s u p p o r t s the former  interpretation. Calcite-Zoisite-Plagioclase Carbonate samples from a l l t h r e e p e l i t e metamorphic  zones c o n t a i n  p l a g i o c l a s e g r a i n s w h i c h a r e p a r t l y t o c o m p l e t e l y r e p l a c e d by z o i s i t e ^ . T h i s replacement t e x t u r e i s e s p e c i a l l y n o t i c e a b l e near the m a r g i n a l c o n t a c t s of c a r b o n a t e u n i t s w i t h e n c l o s i n g p e l i t e s o r q u a r t z i t e s . F i g u r e 2-17  shows t h a t the e q u i l i b r i u m r e a c t i o n assemblage  calcite-  192  p l a g i o c l a s e ( a n o r t h i t e ) - z o i s i t e denotes h i g h  i n the c o e x i s t i n g  Q  fluid  phase. Sample 20 c o n t a i n s complete r e a c t i o n assemblages f o r b o t h e q u i l i b r i u m curves  (E17) and :(E19).  S i n c e the c a l c u l a t e d d i s p l a c e d curve  (E17) f o r the  t s c h e r m a k i t i c amphibole i n sample 20 i n d i c a t e s H ^ O - r i c h f l u i d s , i t seems r e a s o n a b l e t o c o n s i d e r t h a t patchy A l - r i c h amphibole z o n i n g concomitantly w i t h a l t e r a t i o n of p l a g i o c l a s e to z o i s i t e . s i m p l i f i e d system r e p r e s e n t e d by f i g u r e 2-17  developed  I n the  the i n t e r s e c t i o n of these  c u r v e s generates an i s o b a r i c i n v a r i a n t p o i n t .  two  Both c u r v e s become p o l y v a r i a n t  through s o l i d s o l u t i o n w i t h a d d i t i o n of the components N a 0 and 2  FeO.  T h e i r i n t e r s e c t i o n i s no l o n g e r i s o b a r i c a l l y i n v a r i a n t , but i t s t i l l marks the j o i n t c o e x i s t e n c e of b o t h r e a c t i o n assemblages f o r a g i v e n p r e s s u r e . The  i n t e r s e c t i o n may  be regarded as a " d i s p l a c e d i n v a r i a n t p o i n t " a l t h o u g h  no l o n g e r i n v a r i a n t . F i g u r e 2-20  i l l u s t r a t e s the temperature-X „ 2  curve generated by  the  C U  mutual i n t e r s e c t i o n of e q u i l i b r i a been t h e r m o d y n a m i c a l l y phases.  (E17) and  (E19).  Both e q u i l i b r i a have  d i s p l a c e d f o r s o l i d s o l u t i o n e f f e c t s of p a r t i c i p a t i n g  T h i s diagram i s p o l y b a r i c s i n c e i t shows the i n t e r s e c t i o n f o r  s e v e r a l reasonable t o t a l pressures.  The r e s u l t s show t h a t the  d i s p l a c e d c u r v e s i n t e r s e c t a t T = 710°  C and X  e s t i m a t e d from the p e l i t e assemblages.  = 0.25  n C U  f o r the p r e s s u r e  2  T h e r e f o r e reduced  ( i . e . r e t r o g r a d i n g ) i s not r e q u i r e d t o produce replacement by z o i s i t e i n the a m p h i b o l e - b e a r i n g  two  assemblages.  temperature of p l a g i o c l a s e  Rather z o i s i t e c o u l d  have formed a t the same e s t i m a t e d metamorphic c o n d i t i o n s w i t h an i n f l u x o f H^O-rich f l u i d s .  E n c l o s i n g p e l i t e and q u a r t z i t e u n i t s of the Kaza Group  p r o v i d e a ready s o u r c e of H 0 - r i c h . f l u i d s . 2  The u b i q u i t o u s o c c u r r e n c e  of  z o i s i t e a t margins of marble u n i t s I n d i c a t e s t h a t t h i s i n f l u x of f l u i d s o c c u r s t o a l i m i t e d e x t e n t throughout  the Azure Lake. a r e a .  Limited  800 Sample  20  o o  LU  700  -t  7,6 kbar V  Sill Ky  ^- 7,0 kbar  <  a:  6.0 kbar  UJ ^  600  -I  5 . 0 kbar  LU  4 . 0 kbar (I kbar * IO  500 0.0  0.1  0.2  xco F i g u r e 2-20.  P o l y b a r i c Temperature-X  5  kPa) 0.3  2  diagram f o r t h e assemblage  c a l c i t e - z o i s i t e - p l a g i o c l a s e - t s c h e r m a k i t i c a m p h i b o l e - c a l c i c pyroxenequartz.  The curve marks t h e p o l y b a r i c i n t e r s e c t i o n o f e q u i l i b r i a E17  and E19 f o r sample 20. Dashed l i n e s r e p r e s e n t e r r o r margins on the metamorphic t e m p e r a t u r e e s t i m a t e d 7600 b a r s .  from t h e p e l i t i c assemblages a t  194  800  o  700  Sample  387  Sill  -4  Ky  o  LU  3  A 7.6 kbar m  QC  < tr  y 7.0  600  UJ CL  .  LU  ^ 5 . 0  500  kbar  6.0 kbar kbar  * 4.0 kbar (I kbar = l 0  400 0.0  0.1  5  kPa)  0.2  0.3  CO*  Figure 2 - 2 1 .  P o l y b a r i c Temperature-X-,-  diagram f o r t h e assemblage  calcite-muscovite-quartz-K-feldspar-plagioclase-zoisite  i n sample  387.  Curve marks t h e p o l y b a r i c i n t e r s e c t i o n o f e q u i l i b r i a E14 and  E19.  Dashed l i n e s r e p r e s e n t e r r o r margins on e s t i m a t e d  temperature ( p e l i t i c assemblages) a t 7600 b a r s . i s from Holdaway  (1971).  A^SiO,-  metamorphic transition  195 e x p e r i m e n t a l d a t a (Holdaway 1972)  concerning  clinozoisite-zoisite  s t a b i l i t y r e l a t i o n s a l s o support f o r m a t i o n of z o i s i t e a t t h e s e e s t i m a t e d pressure-temperature Similarly and  conditions.  the c o e x i s t e n c e of r e a c t i o n assemblages f o r e q u i l i b r i a  (E14)  (E19) i n sample 387 a l s o r e p r e s e n t s a " d i s p l a c e d i n v a r i a n t p o i n t " i n  T-X  space.  As w i t h the p r e v i o u s example, s o l i d s o l u t i o n makes the  2  i n v a r i a n t p o i n t generated by t h e i r i n t e r s e c t i o n p o l y v a r i a n t .  Figure  2-21  i l l u s t r a t e s the p o l y b a r i c t r a c e of t h i s " d i s p l a c e d i n v a r i a n t p o i n t " .  For  an e s t i m a t e d p r e s s u r e of 7600 b a r s , . t h e i n t e r s e c t i o n of c u r v e s (E14) (E19) o c c u r s a t T = 620° C, X  = 0.12.  and  T h e r e f o r e the mutual c o e x i s t e n c e  of r e a c t i o n assemblages f o r b o t h e q u i l i b r i a o c c u r s a t a temperature some 80° C lower than the temperature e s t i m a t e d from the p e l i t e  assemblages.  F o r m a t i o n of z o i s i t e i n the m u s c o v i t e - b e a r i n g assemblages o c c u r s as a r e t r o g r a d e r e a c t i o n as the metamorphic assemblages a r e c o o l i n g .  This  r e t r o g r a d i n g i s c o n s i s t e n t w i t h the e a r l i e r s u g g e s t i o n of lower r e a d j u s t m e n t o f m i n e r a l c o m p o s i t i o n s f o r t h e same assemblage.  temperature As w i t h  sample 20, the e n c l o s i n g p e l i t e and q u a r t z i t e u n i t s were a ready s o u r c e o f the r e q u i r e d H^O-rich  fluids.  Summary C a l c u l a t e d d i s p l a c e d e q u i l i b r i u m c u r v e s f o r the assemblage c a l c i t e quartz-actinolite-calcic  pyroxene  show t h a t carbonate u n i t s c o n t a i n i n g t h i s  assemblage b u f f e r e d c o e x i s t i n g f l u i d c o m p o s i t i o n s t o a a c t i v i t y i s much lower than a  i n surrounding p e l i t e s  n  =0.25.  This  and i n d i c a t e s t h a t  H0 2  each r o c k type e f f e c t i v e l y b u f f e r e d i t s own  f l u i d c o m p o s i t i o n d u r i n g the  i n i t i a l s t a g e s of metamorphism. P a t c h y o r c o n c e n t r i c z o n i n g t o t s c h e r m a k i t i c amphiboles  and  alteration  of p l a g i o c l a s e t o z o i s i t e denote an i n f l u x of H 0 - r i c h f l u i d s i n t o the o  196  carbonate u n i t s . a  A  H  2°  C a l c u l a t e d d i s p l a c e d e q u i l i b r i a f o r sample 20 show t h a t  = 0.75 i s r e q u i r e d f o r c o e x i s t e n c e  o f z o i s i t e and p l a g i o c l a s e w i t h  the amphibole r e a c t i o n assemblage a t temperature and p r e s s u r e estimated  from the p e l i t e assemblages.  C a l c u l a t e d d i s p l a c e d e q u i l i b r i a f o r the assemblage quartz-plagioclase-K-feldspar estimated  conditions  calcite-muscovite-  c o n s i s t e n t l y g i v e t e m p e r a t u r e s l o w e r than  metamorphic c o n d i t i o n s .  S i m i l a r l y the c a l c u l a t e d c o e x i s t e n c e o f  z o i s i t e w i t h t h i s assemblage i n sample 387 r e q u i r e s r e t r o g r a d e conditions.  These r e s u l t s i n d i c a t e t h a t m i n e r a l  assemblage have homogeneously r e a d j u s t e d  metamorphic  compositions f o r t h i s  t o lower t e m p e r a t u r e c o n d i t i o n s  during i n i t i a l stages o f c o o l i n g . I n summary, a t l e a s t some o f the c a r b o n a t e u n i t s i n i t i a l l y  buffered  c o e x i s t i n g f l u i d c o m p o s i t i o n s through c o n t i n u o u s metamorphic r e a c t i o n s . I n f l u x o f H ^ O - r i c h f l u i d s from s u r r o u n d i n g metamorphism was r e s p o n s i b l e  pelites or quartzites late i n  f o r development o f z o i s i t e - b e a r i n g assemblages.  FLUID COMPOSITIONS  E s t i m a t e d metamorphic c o n d i t i o n s f o r p e l i t e assemblages i n d i c a t e t h a t X  = 0.5 (approx.) f o r the c o e x i s t i n g f l u i d phase.  i n v o l v i n g carbonate assemblages i n the p r e v i o u s existence of a binary  CO2-H2O  fluid.  Calculations  s e c t i o n assumed t h e  The o c c u r r e n c e o f g r a p h i t e  (?) i n  p e l i t e s and g r a p h i t e - p y r r h o t i t e i n c a r b o n a t e s means t h a t a d d i t i o n a l s p e c i e s i n the system C-O-H-S must be c o n s i d e r e d  when d i s c u s s i n g metamorphic  fluid  compositions. Ohmoto and K e r r i c k (1977) have c a l c u l a t e d c o n c e n t r a t i o n s  of d i f f e r e n t  gas s p e c i e s i n the system C-O-H-S over a wide range o f metamorphic temperatures and p r e s s u r e s .  They assumed c o e x i s t e n c e  o f t h e f l u i d phase  197  with graphite-pyrite-pyrrhotite.  None o f t h e s u l f u r s p e c i e s  considered  i n t h e i r c a l c u l a t i o n s (S0„,C0S,S , S ,H,,S) o c c u r r e d i n c o n c e n t r a t i o n s Z  g r e a t e r than 1 mole %.  Z  o  Z  S i n c e p y r i t e i s o n l y r a r e l y encountered i n t h e  Shuswap Complex i n t h e Azure Lake a r e a , g e n e r a l i t y i s n o t l o s t by c o n s i d e r i n g o n l y t h e s p e c i e s i n t h e system C-O-H when d i s c u s s i n g t h e Azure Lake assemblages. F i g u r e 2-22 i l l u s t r a t e s mole f r a c t i o n s o f major s p e c i e s c o e x i s t i n g w i t h g r a p h i t e i n t h e system C-O-H.  Temperature and p r e s s u r e were s e t t o  727° C and 7600 b a r s , r e s p e c t i v e l y t o be c o n s i s t e n t w i t h metamorphic c o n d i t i o n s .  estimated  The s p e c i e s C0^, CO, H^O, H , and CH^ were 2  c o n s i d e r e d t o compose t h e t o t a l p r e s s u r e o f the f l u i d . t h e e q u i l i b r i u m c o n s t a n t approach o u t l i n e d by F r e n c h  Calculations followed  (1966).  The d i a g r a m  shows t h a t f l u i d c o m p o s i t i o n s were c a l c u l a t e d f o r s p e c i f i e d oxygen fugacities.  A c t i v i t y c o e f f i c i e n t s f o r t h e d i f f e r e n t s p e c i e s were computed  u s i n g Redlich-Kwong e q u a t i o n s o f s t a t e ( R e d l i c h and Kwong 1949) appendix 2-2) .  H  2  (see  f u g a c i t y c o e f f i c i e n t s were e x t r a p o l a t e d from e q u a t i o n s by  Shaw and Wones (1964).  Log K - e q u i l i b r i u m c o n s t a n t s r e l a t i n g t h e d i f f e r e n t  s p e c i e s a r e from JANAF t a b l e s ( S t u l l and Prophet 1971). The  diagram shows t h a t o n l y t h e t h r e e s p e c i e s C o , ^ 0 , and CH^ o c c u r 2  i n s u b s t a n t i a l amounts.  C 0 ~ and H 0 - r i c h f l u i d c o m p o s i t i o n s 2  2  over a narrow range o f oxygen f u g a c i t i e s . c o n t a i n e i t h e r CH^ o r C 0  2  e x i s t only  Furthermore H 0 - r i c h 2  fluids  as the secondary s p e c i e s .  I t has a l r e a d y been demonstrated t h a t some o f t h e carbonate buffered f l u i d compositions  to high X  assemblages  v a l u e s d u r i n g metamorphism.  uu  2  F i g u r e 2-22 i l l u s t r a t e s t h a t t h e assumption o f a f l u i d c o n s i s t i n g dominantly  o f H 0 and C 0 2  2  temperature and p r e s s u r e .  i s reasonable  f o r t h e e s t i m a t e d metamorphic  The diagram a l s o shows t h a t c o e x i s t e n c e o f a  198  F i g u r e 2-22.  Compositions o f metamorphic f l u i d phase c o e x i s t i n g w i t h  g r a p h i t e i n the system C-O-H  a t 'j; - ^ ^600 b a r s , T=727 °C. P  =  ot  a  were c a l c u l a t e d f o r a range o f oxygen f u g a c i t i e s .  Compositions  199 CO^-rich f l u i d with graphite buffers oxygen fugacities to values equivalent to those of the FMQ oxygen buffer It was shown i n the discussion on the p e l i t e s that the calculated a  n H  i n the p e l i te assemblages i s very sensitive to thermochemical  error  2°  and s o l i d solution models used for d i f f e r e n t phases.  Therefore a is F^O  only approximate and may range from 0.25 to 1.0 (in case of extreme e r r o r s ) . Ohmoto and Kerrick (1977) have shown that graphitic p e l i t e s i n a closed system buffer  ^ to the maximum possible value during metamorphism.  buffering i s accomplished reactions.  This  through continuous and discontinuous dehydration  Figure 2-22 i l l u s t r a t e s that the maximum 5L  i s approximately  2° 0.85  for estimated metamorphic conditions near Azure Lake with ...the remainder  of the f l u i d phase consisting of equal amounts of CH^ and CO^.  Since  probable reactions for Azure Lake p e l i t e assemblages are dehydration reactions, X^ ^ should reasonably be buffered to this maximum value. This value i s within the error l i m i t s of the calculated X^ ^ for the p e l i t e s . Coexistence of a f l u i d phase consisting largely of U^O with graphite buffers oxygen fugacities to values between the MW and FMQ oxygen buffers. SUMMARY  P e l i t i c assemblages i n the Shuswap Complex near Azure Lake, B r i t i s h Columbia contain the metamorphic t r a n s i t i o n from kyanite through s i l l i m a n i t e zones of the upper amphibolite f a c i e s .  first-  Textures indicate that  garnet, s t a u r o l i t e , and kyanite were replaced by fibrolite-muscoviteb i o t i t e - i l m e n i t e aggregates.  Regression analysis of coexisting mineral  rim compositions show that r u t i l e i s probably a reactant phase i n the reactions involving the breakdown of garnet and s t a u r o l i t e to s i l l i m a n i t e bearing assemblages.  Reaction textures are partly preserved because of  200 the e x h a u s t i o n of a v a i l a b l e r u t i l e i n the m a t r i x .  Concentric  zoning,  growth p a t t e r n s , and replacement t e x t u r e s a r e r e l a t e d t o c o n t i n u o u s  and  d i s c o n t i n u o u s metamorphic r e a c t i o n s d u r i n g a s i n g l e p r o g r a d e metamorphic episode. The mutual i n t e r s e c t i o n of s e v e r a l e x p e r i m e n t a l l y s t u d i e d e q u i l i b r i a i n v o l v i n g garnet, s t a u r o l i t e , muscovite,  p l a g i o c l a s e , q u a r t z , and A l ^ S i O ^  r e s u l t e d i n a c o n s i s t e n t e s t i m a t e of metamorphic c o n d i t i o n s : P = 7600 ± 400 b a r s , T = 705 ± 40° C, a  _ = 0.5  u  (approx.).  Several  i n t e r e s t i n g o b s e r v a t i o n s r e s u l t i n g from the d e t a i l e d c a l c u l a t i o n s a r e : 1.  The e s t i m a t e d temperature and p r e s s u r e were e s s e n t i a l l y determined  by the i n t e r s e c t i o n of the k y a n i t e - s i l l i m a n i t e t r a n s i t i o n ( E l ) w i t h the e q u i l i b r i a marking the upper s t a b i l i t y l i m i t o f s t a u r o l i t e + (E4, E 5 ) .  E q u i l i b r i u m ( E l ) i s independent of a  quartz  _ and r e a c t i o n s (E4,  . 2° v a l u e s a r e determined by e q u i l i b r i a  E5)  do not s h i f t s i g n i f i c a n t l y f o r reduced a  H  2.  Estimated a  n  mark the upper s t a b i l i t y l i m i t o f p a r a g o n i t e + q u a r t z .  a  (E8, E9) w h i c h must be  H  2°  c o n s i d e r e d a " g u e s s t i m a t e " because i t i n c l u d e s a l l the d i f f e r e n t e r r o r s a s s o c i a t e d w i t h s o l i d s o l u t i o n models f o r m u s c o v i t e and p l a g i o c l a s e as w e l l as thermochemical e r r o r s . 3.  The assemblage p l a g i o c l a s e - g a r n e t - q u a r t z - A l ^ S i O ^ (E10, E l l )  c o n s i s t e n t l y r e s u l t s i n p r e s s u r e e s t i m a t e s h i g h e r than e s t i m a t e s u s i n g the other e q u i l i b r i a .  The use of t h i s assemblage as a r e l a t i v e geobarometer-  geothermometer i s a l s o l i m i t e d by the h i g h s e n s i t i v i t y of c a l c u l a t e d curve p o s i t i o n s to s l i g h t v a r i a t i o n s i n p l a g i o c l a s e composition. 4.  Although  a r e g i o n a l metamorphic g r a d i e n t i s e v i d e n t from the  r e g u l a r d i s t r i b u t i o n of m i n e r a l assemblages i n the f i e l d , c a l c u l a t e d e q u i l i b r i u m curves do not c o n f i r m t h i s g r a d i e n t .  A p p a r e n t l y s c a t t e r from  a n a l y t i c a l e r r o r and c h e m i c a l z o n i n g overwhelm the expected  gradient  201 distribution. 5.  From s t r a t i g r a p h i c arguments metamorphic p r e s s u r e s cannot have  exceeded 4 k i l o b a r s (  12km).  Yet e s t i m a t e d metamorphic p r e s s u r e s  the e q u i l i b r i a c a l c u l a t i o n s a r e g r e a t e r than 7 k i l o b a r s (  from  27km).  E x t e n s i v e t e c t o n i c t h i c k e n i n g i s r e q u i r e d t o s a t i s f y b o t h the s t r a t i g r a p h i c and thermodynamic d a t a . A d e t a i l e d l o o k a t carbonate m i n e r a l e q u i l i b r i a i n d i c a t e t h a t c o n t i n u o u s r e a c t i o n s i n c a l c a r e o u s assemblages i n i t i a l l y b u f f e r e d c o e x i s t i n g f l u i d compositions to high a the f l u i d phase, w h i l e i t may homogeneous throughout  v a l u e s near 0.75.  Therefore  have been c o n t i n u o u s , cannot have been  a l l r o c k t y p e s d u r i n g metamorphism.  Local  o c c u r r e n c e s of z o i s i t e r e p l a c i n g p l a g i o c l a s e i n carbonate  assemblages  r e s u l t e d from the l a t e i n f l u x of FL^O-rich f l u i d s i n t o the  marbles.  S u r r o u n d i n g p e l i t e and q u a r t z i t e u n i t s p r o v i d e d a ready source f o r the fluids.  C a l c u l a t i o n s a l s o show t h a t p a r t o f the z o i s i t e formed d u r i n g  the r e t r o g r a d e readjustment  of m i n e r a l c o m p o s i t i o n s t o lower  temperatures.  C a l c u l a t i o n s f o r t h e f l u i d phase c o e x i s t i n g w i t h g r a p h i t e i n the system C-O-H  show t h a t CH^,  C O 2 , and H^O  a r e the major s p e c i e s p r e s e n t a t  t h e e s t i m a t e d metamorphic c o n d i t i o n s . F l u i d s c o e x i s t i n g w i t h p e l i t e assemblages were p r o b a b l y b u f f e r e d t o h i g h amounts of CH^ and C 0  2  ^ v a l u e s near 0.85  making up the remainder.  coexisted w i t h a f l u i d c o n t a i n i n g mainly C0  2  Carbonate assemblages  and F^O.  Oxygen f u g a c i t i e s  f o r b o t h s e t s o f assemblages were b u f f e r e d t o v a l u e s near FMQ buffer.  w i t h equal  oxygen  202  ACKNOWLEDGMENTS  T h i s paper r e p r e s e n t s p a r t o f a PhD t h e s i s completed a t t h e U n i v e r s i t y o f B r i t i s h Columbia.  I am i n d e b t e d t o Dr. H.J. Greenwood f o r  s u p e r v i s i n g t h e s t u d y w i t h c o n t i n u e d i n t e r e s t and enthusiasm.  Discussions  w i t h Dr. T.H. Brown were u s e f u l i n debugging problems a s s o c i a t e d w i t h t h e e l e c t r o n microprobe and t h e thermodynamics  o f f l u i d s and s o l i d s .  P. M a r c e l l o , and N. Duncan a s s i s t e d w i t h t h e f i e l d work.  B. H a l l ,  J . Nelson kept  my i n t e r e s t and e n t h u s i a s m f o r t h e p r o j e c t a t a s u i t a b l e l e v e l . F i e l d and l a b o r a t o r y expenses were d e f r a y e d through NRCC 67-4222 t o Dr. H.J. Greenwood.  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E d i t e d by W.S. MacKenzie and J . Zussman. Manchester U n i v e r s i t y P r e s s , Manchester,. E n g l a n d , pp. 218-248. THOMPSON, P.H. 1973. M i n e r a l zones and i s o g r a d s i n "impure" c a l c a r e o u s r o c k s , an a l t e r n a t i v e means o f e v a l u a t i n g metamorphic grade. 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 , 42, pp. 63-80. TRACY, R . J . 1978. H i g h grade metamorphic r e a c t i o n s and p a r t i a l m e l t i n g i n p e l i t i c s c h i s t , w e s t - c e n t r a l M a s s a c h u s e t t s . American J o u r n a l of S c i e n c e , 278, pp. 150-178. TRACY, R.J., ROBINSON, P., and THOMPSON, A.B. 1976. Garnet c o m p o s i t i o n and z o n i n g i n t h e d e t e r m i n a t i o n o f temperature and p r e s s u r e o f metamorphism, c e n t r a l M a s s a c h u s e t t s . American M i n e r a l o g i s t , 61, pp. 762-775. TRZCIENSKI, W.E., JR. 1977. Garnet z o n i n g - p r o d u c t o f a c o n t i n u o u s r e a c t i o n . Canadian M i n e r a l o g i s t , 15, pp. 250-256. ULBRICH, H.H. and MERINO, E. 1974. An e x a m i n a t i o n o f s t a n d a r d e n t h a l p i e s of f o r m a t i o n o f s e l e c t e d m i n e r a l s i n t h e system Si02-Al20.j-Na20K2O-H2O. American J o u r n a l o f S c i e n c e , 274, pp. 510-542. WHEELER, J.O. and GABRIELSE, H. 1972. The C o r d i l l e r a n s t r u c t u r a l province. In V a r i a t i o n s i n t e c t o n i c s t y l e s i n Canada. E d i t e d by R.A. P r i c e and R.J.W. Douglas. G e o l o g i c a l A s s o c i a t i o n o f Canada, S p e c i a l Paper 11, pp. 1-81. WOOD, B . J . 1977. 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 o f t h e m i x i n g p r o p e r t i e s o f s o l i d s o l u t i o n s w i t h p a r t i c u l a r r e f e r e n c e t o g a r n e t and c l i n o p y r o x e n e s o l u t i o n s . I n Thermodynamics i n geology. E d i t e d by D.G. F r a s e r . D. R e i d e l P u b l i s h i n g Co., H o l l a n d , pp. 11-27. r  W00DSW0RTH, G.J. 1977. H o m o g e n i z a t i o n o f zoned garnets schists. Canadian M i n e r a l o g i s t , 15, pp. 230-242.  from p e l i t i c  YARDLEY, B.W.D. 1977. The n a t u r e and s i g n i f i c a n c e o f t h e mechanism o f s i l l i m a n i t e growth i n t h e Connemara S c h i s t s , I r e l a n d . Contributions to M i n e r a l o g y and P e t r o l o g y , 65, pp. 53-58. ZEN,  E-AN. 1963. Components, phases, and c r i t e r i a o f c h e m i c a l i n r o c k s . American J o u r n a l o f S c i e n c e , 261, pp. 929-942.  equilibrium  1973. Thermochemical parameters o f m i n e r a l s from oxygenb u f f e r e d h y d r o t h e r m a l e q u i l i b r i u m d a t a : method, a p p l i c a t i o n t o a n n i t e and almandine. 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 , 39, pp. 65-80.  212  APPENDIX  2-1  Modes 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  t  T a b l e 2 - 1 . Assemblages and modes f o r p e l i t e m i c r o p r o b e s a m p l e s .  373  Specimen Metamorphic Zone Quartz (qtz) Plagioclase K-feldspar  (plag)  (mus)  40 Sill  Ky-Sill  Sill  20  30  2  25  30  20  50  25  30  10  30  25  20  17  25  10  15  10  5  15  15  20  15  10  X  X  X  20  10  20  15  15 35  17 15  35 30 5  3 X  (sill) X  X  X  10  15  35  15  14 25 15  35  20  25  35  10  30  5  5  5  2  10  6  X  2  3  15  8  ?  7  5  3  23 12  5 X  30 3  2 X  X  X  X  X  (zrcn)  X  X  X  X  (ap)  X  X  X  5 X in  in  in  Rutile (rut)  Apatite  59 Sill  Ky-Sill  10  (tour)  74  Ky-Sill  3  Tourmaline  2-13  Ky-Sill  X  Ilmenite (ilm)  2-376  Ky-Sill  2  Sillimanite  223  Ky-Sill  Staurolite  (ky)  492  Ky  10  (stau)  398  Ky  5  Zircon  82  Sill  Garnet (gar)  Kyanite  367  (K-sp)  B i o t i t e (bio) Muscovite  121  X  2  X  X  15  4  7  X  X  X  X  X  X  X  X  X  X  X  X  in X  X  3  X  X X  X  X - present in - inclusion  ro  T a b l e 2-2.  Assemblages  and modes f o r c a r b o n a t e m i c r o p r o b e samples.  387  Specimen  219  224  2-375  494  69  20  2-312  Ky  Ky-Sill  Ky-Sill  Ky-Sill  Ky-Sill  Sill  Sill  Sill  Calcite (cc)  80  85  85  50  50  89  75  90  Quartz ( q t z )  7  2  7  30  25  1  10  3  Muscovite (mus)  5  3  Metamorphic  Zone  X  5  B i o t i t e (bio) C a l c i c amphibole  5  3  (amph)  C a l c i c pyroxene (pyrx)  5  Garnet (gar)  X  Plagioclase K-feldspar  (plag) (K-sp)  Z o i s i t e (zo) Scapolite  2  X  5  4  1  4 2  X  X  Sphene (sph)  X  P y r r h o t i t e (po)  2  X X  X  X  X  X  X  X  X  X X  X  (py) (ilm)  2  4  (scap) X  Ilmenite  X  15  X  X  5  2 10  5  8  4  Graphite (gra)  Pyrite  10  X X  X - present  ro  T a b l e 2-3.  Garnet a n a l y s e s from p e l i t i c  samples.  Estimated standard e r r o r s a r e given i n parentheses.  121  373  Specimen  Analyses sio  2  Ti0  2  367  82  edge  core  edge  core  edge  core  edge  core  39  1  11  1  14  1  23  1  37.91  (0.05)  -  37.85  37.05 (0.07)  37.88  (0.08)  36.42  -  37 74 (0.05)  37. 40  -  20.57 (0.03)  19.59  21.50  (0.04)  21.49  21.55  (0.04)  21.18  21 49 (0.03)  21 37  34.55 (0.04)  32.92  34.97 (0.07)  33.48  34.18 (0.06)  30.15  36 22 (0.06)  34 84  MnO  1.19 (0.01)  3.36  1.67 (0.04)  1.99  1.38 (0.05)  4.35  1 04 (0.02)  2 70  MgO  2.75 (0.02)  2.16  2.87 (0.02)  3.11  2.90 (0.01)  1.24  2 81 (0.02)  2 97  2°3 FeO*  A 1  CaO Total  2.44 (0.06) 99.41  3.30 99.18  -  36.51  -  2.41 (0.04) 100.47  0.02 (0.01)  3.00 100.95  3.49 (0.08) 100.03  6.42 99.76  0 01 (0.004)  2 18 (0.02) 101 49  0.02  2 22 101 52  formulae on the b a s i s o f 12 oxygens Si  3.057 (0.004)  3.080  2.971 (0 006)  2.972  2.941 (0.006)  3.004  2 996 (0.004)  Al  1.955 (0.003)  1.879  2.032 (0 004)  2.009  2.046 (0.004)  2.025  2 010 (0.003)  2.004  0 001 (0.0002)  0.001  2 011  2.005  -  -  -  -  1.955  1.879  2.032  2.009  Ti  0.001 (0.0006) 2.047  2.025  2.975  Fe  2.330 (0.003)  2.240  2.345 (0 005)  2.221  2.303 (0.004)  2.046  2 404 (0.004)  2.318  Mn  0.081 (0.0007)  0.232  0.113 (0 003)  0.134  0.094 (0.003)  0.299  0 070 (0.001)  0.182  Mg  0.331 (0.002)  0.262  0.343 (0 002)  0.368  0.348 (0.001)  0.150  0 332 (0.005)  0.352  Ca  0.211 (0.005)  0.288  0.207 (0 003)  0.255  0.301 (0.007)  0.558  0 185 (0.002)  0.189  3.053  2 991  3.041  2.953  3.022  3.008  2.978  3.046  molecular percent end-members f Almandine Spessartine Pyrope Grossular  76  78  74  78  75  77  67  80  3  8  4  4  3  10  2  6  11  9  11  12  12  5  11  12  8  10  7  9  9  18  * t o t a l i r o n as FeO t - c a l c u l a t e d using weighted l i n e a r r e g r e s s i o n a n a l y s t - L.C. Figage  T a b l e 2-3 ( c o n t i n u e d ) . 492  398  Specimen  Analyses Si0  2  Ti0  2  A1 0 2  2-376  core  edge  core  edge  core  edge  14  1  18  1  16  1  15  37.37 (0.03)  3  223  edge  37.80 0.02  38 05 (0.06) 0.01 (0.003)  37 93  37. 54 (0 05)  37 76  0 55  0 01  37 91 (0.04) 0 02 (0.004)  core 1 37 95 0 01  21.16 (0.06)  21.30  21. 37 (0.02)  21 07  21. 17 (0 04)  21 11  20 84 (0.03)  20 64  34 44  35 38 (0.04)  33 41  35.81 (0.06)  34.98  36. 06 (0.06)  34 95  35 01 (0 05)  MnO  2.65 (0.03)  3.28  1.49 (0.06)  2 57  1 46 (0 02)  2  57  0 75 (0.01)  3 72  MgO  2.76 (0.02)  3.11  3.01 (0.03)  3 09  2 92 (0 01)  2  99  3 03 (0.02)  2 90  FeO*  CaO Total  1.40 (0.04) 101.15  1.43 101.92  1 57 (0.07) 101. 56  formulae Si  2.990 (0.002)  Al  1.996 (0.006)  2.994  1 39 101 55  2 33 101 21  2 51 (0.04) 100 44  2 12 100 75  on the b a s i s o f 12 oxygens  3 014 (0.005) (0.002)  3 019  3 005 (0.004)  1 995  1 997 (0.004)  1.988  1 995  -  0.001  0 0006 (0.0002)  0 033  1.996  1.989  1 996  2 028  Ti  2 36 (0 03) 100 46  3 005  3 030 (0.003)  3.034  1 980  1 963 (0.003)  1.945  -  0 0005  0 001 (0.0002)  0.001  1 997  1 980  1 964  1.946  Fe  2.397 (0.004)  2.318  2 389 (0.004)  2 316  2 344 (0.003)  2 292  2 365 (0.003)  2.234  Mn  .0.180 (0.002)  0.220  0 100 (0.004)  0 172  0 099 (0.001)  0 173  0 051 (0.0007)  0.252  Mg  0.329 (0.002)  0.368  0 355  (0.004)  0 365  0 348 (0.001)  0 354  0 361 (0.002)  0.346  Ca  0.120 (0.003)  0.122  0 133 (0.006)  0 118  0 202 (0.003)  0 198  0 215 (0.003)  0.182  2 993  3 017  2 992  3.014  3.026  3.028  2 977  molecular Almandine Spessartine Py rope Grossular  2 971  percent end-members t 74  79  77  80  78  78  76  79  6  7  3  6  3  6  2  8  11  12  12  12  12  12  12  12  4  4  5  4  7  7  7  6  * t o t a l i r o n as FeO t - c a l c u l a t e d using weighted l i n e a r r e g r e s s i o n analyst - L.C. Pigage  ro 03  T a b l e 2-3 ( c o n t i n u e d ) .  Specimen  2-13  Analyses Si0  2  Ti0  2  74  59  40  edge  core  edge  core  edge  core  edge  18  1  14  1  52  1  30  37.42 (0.03)  -  37. 70 0.01  38.03 (0.12) 0.02 (0.004)  38 43  37. 61 (0 02)  37 66  0 02  0 03  37.11 (0 04)  core 1 36 83  0.01 (0 002)  20.58 (0.05)  20. 95  20.82 (0.07)  19 84  20. 56 (0 006)  21 03  21.53 (0 02)  21 64  34.10 (0.05)  34. 30  33.40 (0.10)  30 13  34 59 (0 02)  33 33  36.72 (0 05)  36 24  MnO  1.69 (0.01)  2.62  2.37 (0.04)  6 30  1.27 (0 01)  4 34  1.04 (0 05)  2 22  MgO  2.42 (0.01)  2.93  3.02 (0.01)  3 33  2 97 (0 006)  3 23  3.03 (0 01)  2 85  CaO  2.44 (0.02)  2.28  2.71 (0.02)  1 98  2 10 (0 01)  1 59  1.67 (0 03)  A1 0 2  3  FeO*  Total  98.65  100. 79  formulae Si Al  3.047 (0.002)  3.013  100 02  100.37  99 10  101 21  101.11  on the ba s i s o f 12 oxygens  3.037 (0.010)  3.083  3.044 (0.002)  3.001  2.965 (0.003)  2.952  1.961 (0.0006)  1.975  2.027 (0.002)  2.044  1.973  1.960 (0.007)  1.876  -  0.001  0.001 (0.0002)  0.001  -  0.002  0.0006 (0.0001)  1.974  1.974  1.961  1.877  1.961  1.977  2.028  1.974 (0.005)  Ti  1 30 101 08  2.044  Fe  2.322 (0.003)  2.292  2.231  (0.007)  2.022  2.342 (0.001)  2.221  2.454 (0.003)  2.428  Mn  0.117 (0.0007)  0.177  0.160 (0.003)  0.428  0.087 (0.0007)  0.293  0.070 (0.003)  0.150  Mg  0.294 (0.001)  0.349  0.360 (0.001)  0.398  0.358 (0.0007)  0.384  0.361 (0.001)  0.340  Ca  0.213 (0.002)  0.195  0.232 (0.002)  0.170  0.182 (0.0009)  0.136  0.143 (0.003)  0.112  2.946  3.013  2.983  3.018  2.969  3.034  3.028  3.030  molecular percent end-members t Almandine Spessartine Pyrope Grossular  80  79  76  74  67  78  73  82  4  6  5  14  3  10  2  5  12  11  10  12  12  13  12  13  8  6  8  6  6  4  * t o t a l i r o n as FeO t - calculated using weighted l i n e a r r e g r e s s i o n analyst - L.C. Pigage  218 Table 2-4.  Muscovite analyses from p e l i t i c samples.  Estimated standard errors are given i n parentheses.  Specimen 2  22  20  ses  13  28  16  sio  2  45. 17 (0.03)  46.03 (0.06)  46 17 (0.13)  46. 85 (0.08)  45 80 (0.05)  T10  2  0.60 (0.01)  0.70 (0.01)  0 65 (0.01)  0. 69 (0.01)  0. 59 (0.01)  36.1 1 (0.07)  35.95 (0.03)  35 55 (0.06)  36 20 (0.06)  36 32 (0.02)  1. 18 (0.01)  1 13 (0.01)  1 21 (0.02)  1 06 (0.004)  0.99 (0.01)  0 71 (0.02)  0 71 (0.01)  0 64 (0.01)  0.52 (0.01)  0 27 (0.01)  0 41 (0.01)  0 34 (0.005)  2°3 FeO«  A 1  1.02 (0.005)  -  MnO  -  MgO  0.66 (0.006)  CaO  0.01  BaO  0.26 (0.01)  (0.002)  47.39 (0.09) 0.62  (0.01)  36.70 (0.07)  (0.01)  0.70  -  0.01  0.35 (0.003)  (0.004)  0.50 (0.01)  Na 0  1.27 (0.006)  1.17 (0.01)  1 02 (0.01)  1 21 (0.02)  1 58 (0.02)  1.56 (0.03)  K0  9.18 (0.01)  9.40 (0.02)  9 77 (0.02)  9 42 (0.04)  9 11 (0.03)  8.59 (0.07)  F  0.05 (0.003)  0.05 (0.001)  0 04 (0.002)  0 06 (0.003)  0 04 (0.002)  0.03 (0.002)  4.45 (0.004)  4.50 (0.004)  4 49 (0.008)  4 55 (0.005)  4 51 (0.003)  2  2  H 0» 2  Subtotal less 0=F Total  99 80  100.03  98.78  101 31  99 99  4.60 (0.006) 101.51  0.02  0.02  0 02  0 03  0 02  0.01  98.76  100.01  99 78  101 28  99 97  101.50  formulae on the b a s i s of 24 (O.OH.F) Si  6 055 (0.004)  6. 102 (0.008)  6 1 38 (0.017)  6 130 (0 010)  6 069 (0 007)  6 155 (0 012)  A1(IV)H  1 945 (0.004)  1 .898 (0.002)  1 862 (0.003)  1 870 (0 003)  1 931 (0 001)  1 845 (0 004)  A1(VI)H  3 760 (0.007)  3.718 (0.003)  3 707 (0.006)  3 712 (0 006)  3 742 (0 002)  3 772 (0 007)  Ti  0 060 (0.001)  0.070 (0.001)  0 065 (0.001)  0 068 (0 001)  0 059 (0 001)  0 061 (0 001)  Fe  0 114 (0.0006)  0. 131 (0.001)  0 126 (0.001)  0 132 (0 002)  0 117 (0 0004)  0 108 (0 001)  Mg  0. 132 (0.001)  0. 138 (0.002)  0. 141 (0.004)  0. 138 (0 002)  0 126 (0.002)  0.101  4.066  4.057  4.039  4 050  4 044  4 .042  -  0.001  Ca  0.001  (0.0003)  Ba  0.014  (0.0005)  Na K  -  -  -  (0 002)  (0 0006)  0. 02 1 (0 0005)  0 018 (0.0003)  0.025 (0 0005)  0.263 (0.003)  0. 307 (0 005)  0 406 (0.005)  0. 393 (0 008)  1 .657 (0.003)  1 572 (0 007)  1 540 (0.005)  1 .423 (0 012)  1.9 34  1 900  1 964  1 .842  0.018 (0.0002)  0.014  0.330 (0.002)  0. 301 (0.003)  1.570 (0.002)  1 .590 (0.003)  1.915  1.909  (0.0005)  F  0.021  0.017 (0.0008)  0. 025 (0 001)  0 017 (0.0008)  0.012 (0 0008)  OH  3.979 (0.004)  3.979 (0.004)  3.983 (0.007)  3 975 (0 004)  3 983 (0.003)  3.988 (0 005)  0.92  0.92  0.92  0 .92  0 .93  0.93  0.54  0.51  0.53  .0 .51  0.52  0.48  Na/£  0.17  0. 16  0.14  0.16  0 .21  0.21  OH/4  0.99  1.00  0 .99  1 .00  1.00  AKVD/Z Mg/(Mg  +  Fe)  (0.001)  0.021  (0.0004)  0.99  * - t o t a l Iron as FeO standard e r r o r  for H 0  of other elements using Monte Carlo approach. - t o t a l standard e r r o r f o r A l Is d i v i d e d p r o p o r t i o n a l l y between the two s i t e s , a l y s t - L.C. Pigage  2  c a l c u l a t e d from standard e r r o r s  219  Table 2-4 ( c o n t i n u e d ) .  Specimen  223  2-376  2-13  74  59  Analyses  14  31  26  23  19  sio  2  Ti0  2  A1 0 2  45.72 (0.09)  3  FeO*  46.22 (0 08)  0.62 (0.02)  0.75 (0 01)  0.70 (0 02)  35.74 (0.09)  35.60 (0 04)  35.53 (0 08)  1. 10 (0.01)  1.18 (0 01) -  -  MnO  45.46 (0.04)  MgO  0.68 (0.02)  CaO  0.02 (0.004)  BaO  0.18 (0.01)  0.65 (0 01) 0.24 (0 005)  44.78 (0.07)  40 29  45.92 (0.05)  46.19 (0.03)  0.56 (0.01)  0.75 (0.02)  35.25 (0.03)  35.39 (0.11)  36.29 (0.03)  1.20 (0.01)  1.11 (0.01)  0.66 (0.005)  1.29 (0 02)  1.91 (0.01)  0.01 (0 002)  0.01 (0.003)  0.65 (0 01)  0.72 (0.004)  0.68 (0.01)  0.01 (0 002)  0.01 (0.004)  0.01 (0.005)  0.32 (0 01)  0.32 (0.009)  0.35 (0.01)  -  0.60 (0.003) 0.26 (0.004)  Na 0 2  1.17 (0.02)  1.11 (0 003)  1.02 (0 01)  0.89 (0.004)  1.14 (0.01)  1.32 (0.01)  K0  9.64 (0.03)  9.36 (0 03)  9.46 (0 03)  9.92 (0.03)  9.37 (0.02)  9.13 (0.02)  F  0.06 (0.003)  0.04 (0 001)  0.05 (0 002)  0.07 (0.002)  0.04 (0.002)  0.07 (0.003)  H0//  4.47 (0.007)  4.45 (0 003)  4.49 (0 006)  4.41 (0.004)  4.46 (0.007)  2  2  Subtotal less 0=F Total  99.40  98.84  99.75  98.95  99.12  4.51 (0.003) 100.23  0.03  0.02  0.02  0.03  0.02  0.03  99.37  98.82  99.73  98.92  99.10  100.20  formulae on the basis of 24 (O.OH.F) 6.096 (0 004)  Si  6.101 (0.012)  6.095 (0.005)  6.143 (0.011)  6.049 (0.009)  6.142 (0.007)  A1(IV)1  1.899 (0.005)  1.905 (0.002)  1.857 (0.004)  1.951 (0.002)  1.858 (0.006)  1.904 (0 002)  A1(VI)1  3.722 (0.009)  3.721 (0.004)  3.709 (0.009)  3.660 (0.003)  3.720 (0.011)  3.741 (0 003)  Ti  0.062 (0.002)  0.076 (0.001)  0.070 (0.002)  0.067 (0.0005)  0.056 (0.001)  0.074 (0 002)  Fe  0.123 (0.001)  0.132 (0.001)  0.143 (0.002)  0.216 (0.001)  0.134 (0.001)  0.123 (0 001)  -  Mn Me  -  -  -  0.001 (0.0002)  0.001 (0.0003)  0.135 (0.004)  0.130 (0.002)  0.129 (0.002)  0.145 (0.0008)  0.136 (0.002)  0.118 (0 0006)  4.042  4.059  4.052  4.089  4.046  4.056  -  -  Ca  0.003 (0.0006)  0.001 (0.0003)  0.001 (0.0006)  0.001 (0.0007)  Ba  0.009 (0.0005)  0.013 (0.0003)  0.017 ( 0.0005)  0.017 (0.0005)  0.018 (0.0005)  0.013 (0 0002)  Na  0.303 (0.005)  0.289 (0.0008)  0.263 (0.003)  0.233 (0.001)  0.296 (0.003)  0.338 (0 003)  K  1.641 (0.005)  1.601 (0.005)  1.604 (0.005)  1.709 (0.005)  1.599 (0.003)  1.537 (0 003)  1.956  1.903  1.885  1.960  1.914  1.888  F  0.025 (0.001)  0.017 (0.0004)  0.021 (0.0008)  0.030 (0.0008)  0.017 (0.0008)  0.029 (0 001)  OH  3.975 (0.006)  3.983 (0.003)  3.979 (0.005)  3.970 (0.004)  3.983 (0.006)  3.971 (0 003)  AKVD/5T  0.92  0.92  0.92  0.90  0.92  0.92  Mg/(Mg + Fe)  0.52  0.50  0.47  0.40  0.50  0.49  Na/JT  0.15  0.15  0.14  0.12  0.15  0.18  OH/4  0.99  1.00  0.99  0.99  1.00  0.99  * - total Iron as FeO # - H 0 calculated from structural formula assuming A (0,OH,F); standard error for HjO calculated from standard 2  of other elements using Monte Carlo approach. 1 - total standard error for Al la divided proportionally between the two sltea. analyst - L.C. Pigage  220 Table 2-5.  B i o t i t e a n a l y s e s from p e l i t i c  samples.  E s t i m a t e d s t a n d a r d e r r o r s are g i v e n i n p a r e n t h e s e s .  Specimen  373  121  36 7  82  398  Analyses  25  25  24  11  24  sio  2  35.23 (0.07)  35.65  (0, .03)  (0.01)  2.02  (0. .02)  1.90  T102  19.48 I ( 0 . 0 3 )  19. 14 ( 0 . 0 3 )  "2°3 FeO*  18.84  19.41 ( 0 . 0 4 )  (0. .02)  0.03  (0. .001)  MnO  0.02  (0.002)  MgO  9.69  (0.02)  CaO  0.01  (0.002)  BaO  0.08 (0.003)  Na20  0.22  (0.002)  0.32  2° F  8.91  (0.03)  0.25  (0.003)  H 2 0#  3.80 ( 0 . 0 0 5 )  K  Subtotal less  0=F  Total  10.00  (0 . 0 3 )  -  36. 73  (0. 0 6 )  36. 81 ( 0 . 0 8 )  492 13  3 5 . 71 ( 0 . 0 4 )  3 6 . 2 7 (0. 15)  1. 96  (0. .02)  2 . 18  (0.02)  1. 93  (0.01)  19. 59  (0. .05)  19. 50  (0.06)  19. 24  (0.03)  19.39  (0. .03)  18. 72  (0. .01)  19. 00  (0.04)  19. 34  (0.02)  18.80  (0. ,03)  0 . 02 10. 36  2 . 0 2 (0. ,02)  (0. ,001)  0 . 01 ( 0 . 0 0 3 )  0 . 06  (0.002)  0 . 0 2 (0. ,002)  (0, ,02)  9 . 80  9 . 45  (0.01)  9 . 9 5 (0, ,03)  (0.02)  0. 01 (0. .002)  0 . 01 ( 0 . 0 0 2 )  0 . 0 1 (0, .002)  0. 12  (0 .003)  0 . 20  (0.002)  0 . 14  (0.004)  0 . 2 1 (0. .01)  (0 . 0 0 3 )  0, ,29  (0 .01)  0 . 36  (0.01)  0 . 21 ( 0 . 0 0 3 )  0 . 3 5 (0. .01)  8.83  (0 . 0 2 )  9. .03  (0 . 0 3 )  8. 65  (0.05)  9 . 06  (0.01)  8 . 5 9 (0 .01)  0.22  (0 . 0 0 3 )  0. .21 (0 .003)  0 . 24  (0.002)  0 . 23  (0.003)  0.21  3. ,94  3. 92  (0.005)  3. 84  (0.003)  3.89 (0 .008)  0.  18 (0. .003)  3 . 8 6 (0 .003)  (0 . 0 0 5 )  98.66  99.43  100. .98  100. 67  99. 22  0.11  0.09  0. .09  0 . 10  0 . 10  0.09  98.55  99.34  100 .89  100. 57  99. .12  99.62  f o r m u l a e on t h e b a s i s o f  24  (0 .002)  99.71  (O,0H,F)  5.390 (0.011)  5.391 (0.005)  5.450 (0.009)  5.478 (0.012)  5.429  Al(IV)l  2.610 (0.004)  2.609 (0.004)  2.550 (0.007)  2.522  2.571 (0.004)  2.54  0.898 (0.003)  0.877  (0.001)  0.889  0.244  (0.002)  0.221  (0.001)  0 . 2 2 8 (0. .002)  A1(V1)«  0.841  (0.001)  0.863 (0.001)  0.876 (0.002)  Tl  0.219  (0.001)  0.230 (0.002)  0.219 (0.002)  (0.008)  (0.006)  5 . 4 5 3 (0. 023)  SI  7 (0. ,004) (0. .001) (0. .004)  Fe  2.484 (0.005)  2.383 (0.003)  2.323 (0.001)  2.365  (0.005)  2.459 (0.003)  2.364  Mn  0.003 (0.0003)  0.004  (0.0001)  0.003 (0.0001)  0.001  (0.0004)  0.008 (0.0003)  0 . 0 0 3 (0. .0003)  Mg  2.210  2.254  (0.007)  2.292 (0.004)  2.174  (0.004)  2.142 (0.002)  2 . 2 3 0 (0. .007)  5.713  5.682  (0.005)  5.757  5.734  5.707  5.714  0.002 (0.0003)  0.002  (0 .0003)  0.008 (0.0002)  0.012  (0 . 0 0 0 6 )  0.062 (0.0009)  0.102  (0 .003)  1.647  (0. .002)  Ca  0.002 (0.0003)  -  0.002 (0.0003)  -  Ba  0.005 (0.0002)  0.011  (0.0002)  0.007 (0.0002)  0.012  Na  0.065  (0.0006)  0.094  (0.0009)  0.083 (0.003)  0.  K  1.739  (0.006)  1.703 ( 0 . 0 0 4 )  1.709 ( 0 . 0 0 6 )  1.642 ( 0 . 0 0 9 )  1.757  1.811  1.808  1.801  1.758  1.829  F  0.121 (0.001)  0.105 (0.001)  0.099 (0.001)  0 . 113 ( 0 . 0 0 0 9 )  0.111 (0.001)  0. 100 (0 . 0 0 1 )  OH  3.879 (0.005)  3.895 (0.003)  3.901 ( 0 . 0 0 5 )  3.887  3.889  (0.003)  3 . 9 0 0 (0 . 0 0 8 )  (0.0001)  104 ( 0 . 0 0 3 )  (0.005)  (0.002)  1.763  Tl/£  0.04  0.04  0.04  0.04  0.04  0.04  Fe/Z!  0.43  0.42  0.41  0.42  0.43  0.41  Mg/JI  0.38  0.39  0.40  0.38  0.38  0.39  0.47  0.49  0.50  0.48  0.47  0.49  Na/2  0.03  0.05  0.04  0.05  0.03  0.05  K/2  0.87  0.85  0.85  0.82  0.88  0.82  0H/4  0.97  0.97  0.98  0.97  0.97  0.98  Mg/(Mg +  Fe)  * - total  i r o n as FeO  # - H 0 c a l c u l a t e d from s t r u c t u r a l 2  formula assuming A (O.OH.F);  e r r o r s o f o t h e r e l e m e n t s u s i n g Monte C a r l o 1 - t o t a l standard error analyst - L . C . Plgage  standard e r r o r  f o r H^O c a l c u l a t e d  approach.  f o r A l i s d i v i d e d p r o p o r t i o n a l l y b e t w e e n t h e two s i t e s ,  from s t a n d a r d  22  T a b l e 2-5 ( c o n t i n u e d ) .  B i o t i t e a n a l y s e s from p e l i t i c  Specimen  223  2-376  2-13  74  74-lncl  Analyses  22  27  13  18  4  sio  2  T10  2  A1 0 2  35.88 ( 0 . 0 6 )  3  FeO«  35.48 ( 0 . 0 3 )  35.65 (0.05) (0.003)  34.81 2.52  (0.07) (0.005)  35.56 ( 0 . 0 6 )  2.23  (0.02)  2.15  2.84  (0.04)  2.30  (0.02)  2.06  (0.02)  (0.03)  19.00  (0.01)  18.80  (0.02)  18.95  (0.19)  19.22  (0.03)  19.40  (0.03)  18.68  (0.04)  18.72  (0.03)  19.45  (0.02)  18.99  (0.04)  18.10 ( 0 . 1 5 )  18.54  (0.07)  18.88 ( 0 . 0 7 )  0.01  (0.002)  0.03  (0.003)  0.04  (0.002)  (0.03)  9.75  (0.02)  9.26  (0.02)  9.76  (0.01)  CaO  0.01  (0.001)  0.01  (0.002)  0.02  (0.002)  -  BaO  0.09  (0.004)  0.11  (0.002)  0.19  (0.003)  0.15  Na 0 2  0.32  (0.003)  0.28  (0.003)  0.31  (0.01)  0.26  K 0  8.73  (0.01)  8.82  (0.03)  8.76  (0.03)  F  0.32  (0.003)  0.27  (0.002)  0.27  3.82  (0.004)  3.80  (0.003)  3.80  l e s s 0=F  (C.06)  19.11  (0.002)  Total  18  35.71  (0.04)  0.02  Subtotal  35.49 ( 0 . 1 5 )  (0.02)  10.22  2  40  11  1.76  MgO  H OI  59  19.43  MnO  2  9  samples.  98.59  99.28  (0.01)  0.02  (0.004)  0.01  (0.002)  10.20 ( 0 . 0 9 )  0.12  9.63  (0.02)  9.89  (0.05)  -  0.01  (0.005)  0.02  (0.002)  (0.005)  0.18  (0.02)  0.14  (0.01)  0.14  (0.01)  (0.003)  0.27  (0.005)  0.36  (0.004)  0.35  (0.01)  9.13  (0.01)  9.40  (0.05)  8.65  (0.03)  8.30  (0.03)  (0.002)  0.24  (0.003)  0.28  (0.02)  0.21  (0.003)  0.32  (0.009)  (0.004)  3.79  (0.004)  3.83  (0.02)  3.84  (0.005)  3.79  (0.006)  98.89  98.49  98.64  99.67  98.70  0.13  0.11  0.11  0.10  0.12  0.09  0.13  99.15  98.48  98.78  98.39  99.55  98.55  98.57  f o r m u l a e on t h e b a s i s  o f 24 ( 0 , 0 H , F )  5. ,439 ( 0 . 0 0 8 )  5.346 ( 0 . 0 1 1 )  5.365 ( 0 . 0 2 3 )  5,.430  (0.009)  5.405 (0, ,009)  2.589 ( 0 . 0 0 4 )  2. .561  (0.0015)  2.654  (0.003)  2.635 ( 0 . 0 2 6 )  2, .570 ( 0 . 0 0 4 )  2.595 (0, ,004)  (0.002)  0.846 (0.001)  0, .855  (0.0005)  0.749  (0.001)  0.741  (0.007)  0,.875 ( 0 . 0 0 1 )  0.880 (0, .001)  Tl  0.200 (0.002)  0.256 (0.002)  0. .247  (0.003)  0.291  (0.0006)  0.323 (0.005)  0,.263 ( 0 . 0 0 2 )  0.235 (0..002)  Fe  2.361  (0.005)  2.388 ( 0 . 0 0 4 )  2, .482  (0.003)  2.439 ( 0 . 0 0 5 )  2.288 ( 0 . 0 1 9 )  2..358 ( 0 . 0 0 9 )  2.400 (0..009)  Mn  0.003 (0.0003)  0.001  (0.0003)  0.,004  (0.0004)  0.005 (0.0003)  0.015  (0.001)  0..003  (0.0005)  0.001  (0 .0003)  Mg  2.303 (0.007)  2.217  (0.005)  2. ,106 ( 0 . 0 0 5 )  2.235 ( 0 . 0 0 2 )  2.299 ( 0 . 0 2 0 )  2 .183  (0.005)  2.241  (0 .011)  5.751  5.708  5,,694  5.719  5.666  5 .682  -  SI  5.423 ( 0 . 0 0 9 )  5.411  A1(IV)I  2.577 ( 0 . 0 0 5 )  A1(VI)1  0.884  (0.005)  5.757  -  Ca  0.002  (0.0002)  0.002  (0.0003)  0, ,003  (0.0003)  0.002  (0.001)  0..003  (0.0003)  Ba  0.005  (0.0002)  0.007 (0.0001)  0.,011  (0.0002)  0.009 ( 0 . 0 0 0 3 )  0.011  (0.001)  0 .008  (0.0006)  tia  0.094  (0.0009)  0.083 ( 0 . 0 X 9 )  0..092  (0.003)  0.077 (0.0009)  0.079 (0.001)  0 . 106 ( 0 . 0 0 1 )  0.103  (0,.003)  K  1.683  (0.002)  1.716  1,.705  (0.006)  1.789  1.813  (0.010)  1 .678 ( 0 . 0 0 6 )  1.609  (0,.006)  1..795  1.720  1.784  (0.006)  1,.811  1.808  (0.002)  1.875  1.905  0 .101  (0.001)  0.154  3,.899  (0.005)  3.846 (0..006)  0.153  (0.001)  0 .130  (0.001)  0.117  3.847 ( 0 . 0 0 4 )  3.870 ( 0 . 0 0 3 )  3..870  (0.004)  3.883 ( 0 . 0 0 4 )  0.03  0.04  0 .04  0.05  0.06  0.,05  0.41  0.42  0..44  0.43  0.40  0, .41  0.42  0.40  0.39  0 .37  0.39  0.41  0, ,38  0.39  0.49  0.48  0 .46  0.48  0.50  0,.48  0.48  0.05  0.04  0 .05  0.04  0.04  0,.05  0.05  0.84  0.86  0 .85  0.89  0.91  0.,84  0.80  0.96  0.97  0 .97  0.97  0.97  0.,97  0.96  z E E  Mg + F e )  * - total i r o n as  0.130  FeO  # - H 0 calculated from structural fornula assuming 4 (O.OH.F); atandard arror for HjO calculated from standard errors of 2  other elements using Monte Carlo approach. 1 - total standard error for Al Is divided proportionally between the two sites, analyst - L.C. Pigage  (0..004)  (0.010)  3.866 ( 0 . 0 2 0 )  0.134  F OH  (0.001)  (0.001)  0.008 (0,.0006)  0.04  T a b l e 2-7. P l a g i o c l a s e a n a l y s e s from p e l i t i c  samples.  Estimated standard e r r o r s are given i n parentheses. Specimen  373  Analyses  32  367  398 23  25  36  28  19  61 22 (0.18)  60 60 (0.19)  58. 19 (0.13)  61. 60 (0.07)  63.54 (0.07)  63.96 (0.17)  24 25 (0.12)  26 30 (0.10)  26.35 (0.08)  23. 98 (0.04)  22.73 (0.04)  23.49 (0.04)  CaO  5 74 (0.12)  6 41 (0.11)  8.09 (0.04)  5 94 (0.04)  4.39 (0.03)  4.74 (0.03)  Na 0  8 19 (0.08)  7 69 (0.04)  6.84 (0.03)  8 46 (0.03)  9.19 (0.03)  8.75 (0.03)  K0  0 07 (0.004)  0 07 (0.002)  0.06 (0.002)  0 07 (0.003)  0.08 (0.004)  0.05 (0.002)  Si0  2  A1 0 2  3  2  2  BaO Total  0 02 (0.004) 99 49  0 01 (0.003)  0.01 (0.002) 99.54  101 08  0.01 (0.003) 100 05  99.94  0.01 (0.003) 101.00  formulae on the b a s i s of 8 oxygens 2.795 (0.007)  Si  2 729 (0.008)  2 663 (0.008)  2.611 (0.006)  2 735 (0.003)  2.809 (0.003)  Al  1 274 (0.006)  1 362 (0.005)  1.39 3 (0.004)  1 255 (0.002)  1.184 (0.002)  1.210 (0.002)  4 003  4 025  4.004  3 990  3.993  4.005  0 274 (0.006)  0 302 (0.005)  0.389 (0.002)  0 283 (0.002)  0.208 (0.001)  0.222 (0.001)  0.788 (0.003)  0.741 (0.003)  0.005 (0.0002)  0.003 (0.0001)  Ca Na K Ba  0 708 (0.007)  0 655 (0.003)  0.595 (0.003)  0 728 (0.003)  0 004 (0.0002)  0 004 (0.0001)  0.003 (0.0001)  0 004 (0.0002)  tr  tr  tr  0 986  0 961  0.987  molecular Anorthi te Albite  27 7 71 9  33 8 66 .1  1 015  tr  tr  1.001  0.966  percent end-members t 39.2 60.2  26 8  20.0  22.5  72 6  79.4  76.0 0. 3 17-25  Orthoclase  0 4  0 4  0.3  0 4  0.5  Range (An)  20 -33  23 -35  35-41  21 -30  20-25  Zoning  reverse  reverse  reverse  reverse  15-33  19-32  17-22  16-20  range (An)  t r - less than 0.0005 t - calculated  using weighted l i n e a r r e g r e s s i o n  analyst - L.C. Pigage  ro ro  OJ  T a b l e 2-7 ( c o n t i n u e d ) .  P l a g i o c l a s e a n a l y s e s from p e l i t i c  samples.  Specimen  223  2-376  2-13  74  59  40  Analyses  12  19  31  10  33  22  2 A1 0 S i 0  2  3  59.37 (0 11)  61 .24 (0  25.03 (0 07)  24.31 (0 04)  11)  60.24 ( 0 . 10)  60.37 (0 18)  60.98 (0 10)  62.90 (0 07)  24.76 ( 0 . 0 5 )  25.13 (0 08)  24. 10 (0 02)  23.67 (0 03)  CaO  7. 18 (0 11)  5.74  (0 06)  6. 50 ( 0 . 0 4 )  7.31  (0 07)  5.33 (0 03)  5.08 (0 02)  Na 0  7.71  (0 05)  8.16  (0 03)  7.91  (0.03)  7.20  (0 17)  8.46  (0 02)  8.88  (0 003)  K 0 2  0.07  (0 003)  0.08  (0 003)  0.09  (0.006)  0.05  ( 0 005)  0.09  (0 003)  0.06  (0 003)  BaO  0.02  (0 00A)  -  -  0.01  (0 002)  99.53  99.50  2  Total  99. 38  100.06  98.96  100.60  f o r m u l a e on t h e b a s i s o f 8 o x y g e n s Si  2.665 (0 005)  2 728 (0 005)  2 693 (0 004)  2 683 (0 008)  2 732 (0 004)  Al  1.324  1 276 (0 002)  1 305 (0 003)  1 316 (0 004)  1  4 004  3 998  3 999  4 005  3 997  (0 004)  3.989  273 (0 001)  2 769 (0 00 3) 1 228 (0 002)  Ca  0. 345 (0 005)  0 274 (0 003)  0 311 (0 002)  0 348 (0 003)  0 256 (0 001)  0 240 (0 001)  Na  0.671  0 705 (0 003)  0 686 (0 003)  0 620 (0 015)  0 735 (0 002)  0 758 (0 0003)  K  0.004 (0 0002)  0 005 (0 0002)  0 005 (0 0003)  0 003 (0 0003)  0 005 (0 0002)  0 003 (0 0002)  1.020  0 984  1 002  0 971  0 996  1 001  (0 004)  Ba  m o l e c u l a r p e r c e n t end-members Anorthite  32.9  27.9  30.9  33.5  26.4  23. 7  Albite  66.5  71.4  68.6  66.0  73.6  75.8  Orthoclase  0.4  0.5  0.5  0.3  0.5  0. 3  Range (An)  33-38  22-29  26-34  33-38  24-30  23-26  reverse  reverse  21-25  20-32  Zoning range  (An)  t r - l e s s t h a n 0.0005 ^ - calculated using weighted a n a l y s t - L.C. P i g a g e  linear  regression ^  ro  225  Table 2 - 8 .  K - f e l d s p a r a n a l y s e s from p e l i t i c  samples.  Estimated standard errors are given i n parentheses.  Specimen  398  2-376  2-13  Analyses  2  7  5  Si0  2  A1 0 2  3  64.46 (1.39)  64.81 (0.24)  64.50 (0.34)  19.24 (0.26)  18.22 (0.07)  17.75 (0.07)  CaO  0.02 (0.00)  0.01 (0.004)  0.13 (0.09)  Na 0 2  0.22 (0.03)  0.20 (0.009)  0.18 (0.004)  K0  15.04 (0.68)  BaO  0.31 (0.02)  2  Total  98.85  15.74 (0.16) 0.25 (0.005) 99.75  15.51 (0.14) 0.50 (0.01) 99.29  formulae on the basis of 8 oxygens SI  2.983 (0.064)  3.011 (0.011)  3.021 (0.016)  Al  1.049 (0.015)  0.998 (0.004)  0.980 (0.004)  4.032  4.009  4.001  Ca  0.001 (0.000)  tr  0.007 (0.005)  Na  0.020 (0.003)  0.018 (0.0008)  0.016 (0.0004)  K  0.888 (0.038)  0.933 (0.009)  0.927 (0.008)  Ba  0.006 (0.0004)  0.005 (0.0001)  0.009 (0.0002)  0.915  0.956  0.959  molecular percent end-members t Anorthite  0.1  -  0.7  Albite  2.2  1.9  1.7  97.0  97.6  96.7  0.7  0.5  0.9  Orthoclase Celsian  tr - less than 0.0005 analyst - L.C. Pigage t - calculated using weighted linear regression  Table 2-9. I l m e n i t e a n a l y s e s from p e l i t i c  samples.  Estimated standard e r r o r s are given i n parentheses. Specimen  373  121  367  82  398  Analyses  5  9  11  6  8  Ti0  51.77 (0.08)  2  A1 0 2  3  FeO*  0.15 (0.11) 45.33 (0.12)  51.66 (0.17) 0.01 (0.007) 44.29 (0.12)  52.52 (0.21)  52.76 (0.11)  0.02 (0.006)  0.06 (0.008)  46.90 (0.08)  46.67 (0.09)  53.22 (0.25)  492 11 52.76 (0.11)  0.06 (0.05)  0.15 (0.11)  45.21 (0.22)  46.45 (0.17)  ZnO  na  0.03 (0.003)  0.03 (0.006)  0.04 (0.05)  0.04 (0.007)  0.06 (0.006)  MnO  0.85 (0.01)  0.39 (0.01)  0.51 (0.02)  0.25 (0.01)  1.38 (0.03)  0.33 (0.02)  MgO  0.06 (0.002)  0.04 (0.01)  0.05 (0.003)  0.07 (0.02)  0.03 (0.004)  0.10 (0.04)  0.09 (0.02)  0.02 (0.01)  CaO Total  98.16  96.51  -  100.05  99.85  0.01 (0.004) 99.95  _  99.64  formulae on the basis o f 6 oxygens Ti  1.999 (0.003)  2.022 (0.007)  1.995 (0.008)  2.003 (0.004)  2.014 (0.009)  2.005 (0.004)  Al  0.009 (0.007)  0.001 (0.0004)  0.001 (0.0004)  0.004 (0.0005)  0.004 (0.003)  0.009 (0.007)  1.996  2.007  2.018  2.014  2.008  2.023  Fe  1.947 (0.005)  1.928 (0.005)  1.981 (0.003)  1.971 (0.004)  1.903 (0.009)  1.954 (0.004)  Zn  na  0.001 (0.0001)  0.001 (0.0002)  0.001 (0.002)  0.001 (0.0003)  0.002 (0.0002)  Mn  0.037 (0.0004)  0.017 (0.0004)  0.022 (0.0009)  0.011 (0.0004)  0.059 (0.001)  0.014 (0.0009)  Mg  0.005 (0.0002)  0.003 (0.0008)  0.004 (0.0002)  0.005 (0.002)  0.002 (0.0003)  0.008 (0.003)  0.005 (0.001)  0.001 (0.0005)  1.954  2.009  -  Ca  1.989  1.988  0.001 (0.0002) 1.966  1.978  molecular percent end-members t  Ilmenite Zn Ti 0 2  2  6  0.1  0.2  97.7  98.9  98.7  96.3  0.1  0.1  0.1  0.1  0.1  98.2  Pyrophanlte  1.9  0.9  1.1  0.5  3.0  0.7  Geikiellte  0.2  0.2  0.2  0.3  0.1  0.7  0.1  tr  tr  na - not analyzed t - calculated using weighted linear regression * - total iron as FeO tr - leas than 0.05Z  analyst - L.C. Pigaga  ro  T a b l e 2-9 ( c o n t i n u e d ) .  223  Specimen  11  Analyses TiO, 2 A1,0, 2 3 FeO* ZnO MnO MgO  52.22 (0.11) 0.02 (0.003) 46.45 (0.17)  Total  samples.  2-376  2- 13  74  59  40  9  9  1  5  8  52.29 (0.21)  51. 23 (0.12)  49.62  0.17 (0.14)  0 02 (0.01)  0.02  46.07 (0.27)  44 29 (0.16)  44.99  52.73 (0.06) 0.04 (0.002) 44.13 (0.09)  52.84 (0.20) 0.02  (0.004)  46.87 (0.10)  0.03 (0.006)  0.06 (0.007)  0 15 (0.06)  0.06  0.06 (0.009)  0.06 (0.005)  0.31 (0.006)  0.27 (0.02)  0 76 (0.03)  1.78  1.18 (0.009)  0.18 (0.004)  0.14 (0.02)  0.03 (0.003)  0 03 (0.01)  0.02  0.03 (0.004)  0.32  0.01 (0.003)  0 05 (0.02)  -  _  CaO  I l m e n i t e analyses from p e l i t i c  96.70  96 53  98.90  99.17  0.01  (0.004)  (0.02)  -  100.29  98.18  formulae on the b a s i s of 6 oxygens 1.998 (0.004)  Ti Al  Fe  2.003 (0.008)  2.010 (0.005)  1.966  2.027 (0.002)  1.997  (0.008)  0.001  0.002 (0.0001)  0.001  (0.0002)  2.029  1.998  0.001 (0.002)  0.010 (0.008)  0.001  1.999  2.013  2.011  (0.0006)  1.967  1.977 (0.007)  1.962 (0.012)  1.933 (0.007)  1.982  1.886  0.002  0.002 (0.0003)  0.002 (0.0002)  0.079  0.051  0.008 (0.0002)  0.002  0.002 (0.0003)  Zn  0.001  (0.0002)  0.002 (0.0003)  0.006 (0.002)  Ma  0.013  (0.0003)  0.012  0.034 (0.001)  Mg  0.011  (0.002)  0.002 (0.0002) 0.001  Ca  (0.0009) (0.0002)  0.002 (0.0008) 0.003 (0.001) 1.978  1.979  0.001 2.065  (0.004) (0.0004)  1.970 (0.004)  0.024 (0.002)  (0.0002)  1.942  molecular percent end-members t 0.1  0.1 98.4  98.7  98.9  97.7  0.1  0.1  0.4  0.1  0.1  Pyrophanite  0.7  0.6  1.7  2.6  0.4  Geikielite  0.5  0.1  0.1  1.2  Ilmenite Zn Ti 0 2  2  6  0.1 0.1  96.4  0.1 97.3  3.9  tr  * - t o t a l i r o n as FeO t - calculated using weighted l i n e a r regression t r - lese than 0.05Z analyst - L.C. Flgage  ro ro -4  T a b l e 2-10. C a l c i t e a n a l y s e s f r o m c a r b o n a t e s a m p l e s . Estimated standard e r r o r s a r e given i n parentheses.  Specimen  387  219  224  2-375  494  69  20  Analyses  30  29  32  29  29  33  26  24  0.05 (0.002)  2.15 (0.006)  0.74 (0.01)  2.76 (0.01)  1.37 (0.006)  0.05 (0.002)  0.65 (0.01)  0.53 (0.006)  2.48 (0.01)  0.98 (0.007)  0.65 (0.01)  0.34 (0.009)  0.52 (0.01)  0.71 (0.005)  0.02 (0.002)  FeC0  3  MgC0  0.54 (0.008)  1.32 (0.005)  0 . 30 (0.006)  MnCOj  0.01 (0.002)  0.11 (0.002)  0.68 (0.003)  3  CaCO, Total  99.53 (0.08) 100.13  95.04 (0.16)  97.63 (0.22)  98.62  99.35  0.38 (0.002) 94.81 (0.33) 100.43  97.21 (0.22) 100.27  99.98 (0.11)  0.14 (0.002)  2-312  0.09 (0.002)  97.80 (0.32)  97.59 (0.09)  100.70  98.93  98.73  molecular percent end-members Siderite  0.1  1.9  0.6  2.4  1.2  tr  0.6  0.5  Magnesite  0.6  1.6  0.4  2.9  1.2  0.8  0.4  0.6  tr  0.1  0.6  0.3  0.6  tr  0.1  0.1  99.3  96.4  98.4  94.4  97.0  99.2  98.9  98.8  Rhodochrosite Calcite  t r - less than 0.05 analyst - L.C. Figage  ro ro  00  T a b l e 2-11. P l a g i o c l a s e a n a l y s e s f r o m c a r b o n a t e  samples.  Estimated standard errors are given i n parentheses.  Specimen  387  219-rim  Analyses  6  22  Si0  60.22 (0.18)  2  A1 0 2  25.90 (0.12)  3  219-core 1  2-375  44.19 (0.06)  62.53  44.65 (0.09)  36.41 (0.05)  24.05  36.64 (0.04)  CaO  7.06 (0.06)  19.08 (0.06)  5.43  Na 0  7.35 (0.06)  19.43 (0.04)  0.36 (0.01)  8.28  0.49 (0.02)  K0  0.20 (0.01)  0.01 (0.003)  0.05  BaO  0.01 (0.005)  0.01 (0.002)  2  2  Total  100.74  -  100.05  100.35  69-A 7  19  63.07 (0.13) 23.27 (0.25) 3.83 (0.12) 8.50 (0.08) 0.23 (0.02) 0.02 (0.01)  0.01 (0.002) 101.23  98.92  69-B  20  5  22  55.92 (0.61)  51.39 (0.28)  27.33 (0.25)  31.24 (0.23)  8.97 (0.27)  13.39 (0.25)  5.65 (0.20)  3.68 (0.12)  0.10 (0.02)  0.06 (0.004) 0.01 (0.004)  97.97  99.77  formulae on the basis of 8 oxygens Si  2.661 (0.008)  2.037 (0.003)  2.757  2.037 (0.004)  2.807 (0.006)  Al  1.349 (0.006)  1.978 (0.003)  1.250  1.970 (0.002)  1.220 (0.013)  4.010  4.015  4.007  4.007  4.027  Ca  0.334 (0.003)  0.942 (0.003)  0.256  0.950 (0.002)  0.183 (0.006)  Na  0.630 (0.005)  0.032 (0.0009)  0.708  0.043 (0.002)  0.733 (0.007)  K  0.011 (0.0006)  0.001 (0.0002)  0.003  0.001 (0.0001)  0.013 (0.001)  Ba  tr  -  -  tr  0.975  0.975  0.967  0.994  tr 0.929  2.552 (0.028)  2.336 (0.013)  1.470 (0.013)  1.674 (0.012)  4.022  4.010  0.439 (0.013)  0.652 (0.012)  0.500 (0.018)  0.324 (0.011)  0.006 (0.001)  0.003 (0.0002)  0.945  0.979  tr  molecular percent end-members t A  M  n  ° M  r  t  t  h  i  t  e  e  3 4  6  Orthoclase  4  -° -  6  1.1  96-7  25.7  '  72.5  4.3  2.0  -  3  3  95.9  2  7 8  0  7  .'o  1.4  46.2  66.7  53.2  33.1  0.6  0.3  tr - less than 0.0005 t - calculated using weighted linear regression analyst - L.C. Pigage PO  ro  230  Table 2-12. K - f e l d s p a r a n a l y s e s from carbonate  samples.  Estimated standard errors are given i n parentheses.  Specimen  387  69  20  Analyses  23  16  16  Si0  o  z Al 0 CaO  65.22 (0.07)  64.85 (0.09)  64.73 (0.06)  18.27 (0.03)  18.01 (0.07)  18.95 (0.01)  0.01 (0.002)  0.04 (0.005)  0.05 (0.003)  Na 0  0.81 (0.02)  0.79 (0.02)  0.68 (0.003)  K„0  14.64 (0.02)  14.74 (0.03)  15.00 (0.03)  BaO  0.66 (0.06)  0.34 (0.02)  0.86 (0.02)  2  Total  99.61  98.77  100.27  formulae on the basis of 8 oxygens SI  3.014 (0.003)  3.018 (0.004)  2.983 (0.003)  Al  0.995 (0.002)  0.988 (0.004)  1.029 (0.0005)  4.009  4.006  4.012  Ca  tr  0.002 (0.0002)  0.002 (0.0001)  Na  0.073 (0.002)  0.071 (0.002)  0.061 (0.0003)  K  0.863 (0.001)  0.875 (0.002)  0.882 (0.002)  Ba  0.012 (0.001)  0.006 (0.0004)  0.016 (0.0004)  0.948  0.954  0.961  molecular percent end-members t Anorthite  0.1  0.2  0.3  Albite  10.3  9.1  6.2  Orthoclase  87.6  89.5  92.0  1.3  0.7  1.9  Celslan  tr - less than 0.0005 t - calculated using weighted linear regression analyst - L.C. Pigage  231  Table 2-13. M u s c o v i t e and b i o t i t e a n a l y s e s from c a r b o n a t e  samples.  Estimated standard e r r o r s a r e given i n parentheses.  Specimen  387  219  69 -A  69 -B  Specimen  219  Analyses  17  35  1  1  Analyses  22  sio  2  Ti0  2  A1 0 2  49. 82 (0.07) 0. 12 (0.007) 31. 60 (0.04)  3  46. 11  49. 36  Si0  2  0.83 (0.02)  0. 10  0. 31  Ti0  2  33.28 (0.05)  36. 60  32. 55  0. 15  0. 08  1.87 (0.008)  0. 12 (0.003)  FeO *  46.88 (0.05)  -  MnO 2.95 (0.02)  1.34 (0.01)  CaO  0.04 (0.003)  0.04  BaO  0. 17 (0.O06)  0.19 (0.003)  Na 0  0. 22 (0.003)  0.32 (0.003)  2  10.66  10. 80 (0.05)  K 0 2  F H 0 # 2  l e s s OEF Total  2  (0.03)  FeO *  19.38 (0.03) 0.02 (0.002)  2.41  MgO  9.44 (0.02)  -  0.01  CaO  0. 12 (0.009)  0. 24  0. 09  BaO  0.09 (0.006)  0. 32  0. 23  Na 0  0.12 (0.004)  10.93  10. 92  K 0  9.10 (0.05)  2  2  0. 21  0. 21  F  4. 22 (0.005)  4.42 (0.004)  4. 42  4. 47  H 0  99. 87  100. 64  0. 30  0.06  0.09  0..09  100. 48  99.92  99. 78  100. 55  formulae on the b a s i s  18.13 (0.07)  0. 79  0. 15 (0.002)  99.98  3  MnO  0. 72 (0.006)  100. 78  Subtotal  (0.003)  2.63 (0.02)  A1 0  -  MgO  35.52 (0.07)  0.54 (0.004) 2  t  Subtotal l e s s 05F Total  3.65 (0.005) 98.74 0.23 98.51  formula on the b a s i s  o f 24 (O.OH.F) 6.478  Si Al(IV) 1  Si  6.548 (0.009)  6.265 (0.007)  6.120  Al(IV) H  1.452 (0.002)  1.735 (0.003)  1.880  1.522  o f 24 (O.OH.F)  5.448 (0.011) 2.552 (0.010) 0.726 (0.003)  A l ( V I ) 11  3.442 (0.004)  3.506 (0.005)  3.845  3.513  Tl  0.012 (0.0007)  0.083 (0.002)  0.010  0.031  Al(VI) 1 Ti  Fe  0.013 (0.0003)  0.209 (0.0009)  0.017  0.009  Fe  2.486 (0.004)  Mn  0.003 (0.0003)  Mg  2.159  -  -  0.578 (0.004)  0.267 (0.002)  0.156  0.472  4.028  4.025  -  Mn Mg  -  0.303 (0.002)  (0.005)  5.677  4.045  4.065  Ca  0.006 (0.0004)  0.006 (0.0004)  -  0.001  Ca  0.020 (0.001)  Ba  0.009 (0.0003)  0.010 (0.0002)  0.012  0.005  Ba  0.005 (0.0004)  Na  0.056 (0.0008)  0.083 (0.0008)  0.082  0.059  Na  0.036 (0.001)  1.811 (0.008)  1.817 (0.005)  1.851  1.828  K  1.781 (0.010)  1.882  1.916  1.945  1.893  F  0.299 (0.002)  0.063 (0.0008)  0.088  0.087  F  0.262 (0.002)  OH  3.701 (0.004)  3.937 (0.004)  3.912  3.913  OH  3.738 (0.004)  AKVI)/S!  0.85  0.86  0.95  0.87  T i / ^  0.05  Mg/(Mg + Fe)  0.98  0.56  0.90  0.98  0.44  Na/X  0.03  0.04  0.04  0.03  Fe/S Mg/SI  0.93  0.98  0.98  0.98  Mg/(Mg + Fe)  0.46  K  OH/4  total H 0 2  i r o n as FeO  calculated  from s t r u c t u r a l formula assuming 4 (OH.F); standard  u s i n g Monte C a r l o 5 - t o t a l standard e r r o r analyst  - L.C. Pigage  approach. f o r A l Is divided  proportionally  between the two s i t e s  1.842  0.38  Na/2  0.02  K/2  0.89  OH/4  0.93  232  Table 2-14.  C a l c i c amphibole a n a l y s e s from c a r b o n a t e samples.  A - T s c h e r m a k i t i c amphibole , B - A c t i n o l i t i c  B  A  rseB  A  1  1  1  1  B  A 1  2- 312  20  494  2- 375  224  Speciimen  amphibole  B 1  A 1  B 1  B  A 1  1  2  50.26  54.43  42.88  49.45  50.34  54.89  42.38  55.91  52.00  Ti02  0.13  -  0.58  0.31  0.15  0.05  0.21  0.04  0.05  -  A1203  6.65  0.84  16.54  7.96  6.75  1.51  13.58  0.94  5.14  1.14  FeO*  9.90  sio  55.25  18.74  18.01  14.31  13.52  13.71  18.14  16.91  10.52  MnO  0.48  0.58  0.09  0.11  0.30  0.28  0.08  0.12  0.05  MgO  10.52  12.81  7.55  12.41  12.85  (4.69  9.08  13.25  15.27  17.34  CaO  12.20  12.38  12.27  12.57  12.46  12.21  12.70  16.90  0.01  12.71  11.98  NajO  0.49  0.07  0.96  0.51  0.47  0.09  0.88  0.05  0.49  K20  0.28  0.02  0.69  0.28  0.21  0.03  1.13  0.03  0.24  F  0.16  0.16  0.15  0.15  0.10  0.10  0.13  0.13  0.43  H20J Subtotal l e s s 0=F Total  12.39  0.11  0.43  1.98  1.99  1.96  1.99  2.01  2.04  1.92  2.04  1.86  1.89  101.89  101.29  100.69  99.75  99.27  100.10  99.51  101.88  98.26  98.77  0.07  0.07  0.06  0.06  0.04  0.04  0.05  0.05  0.18  0.18  101.82  101.22  100.63  99.69  99.23  100.06  99.46  101.83  98.08  98.59  formulae on the b a s i s o f 24 (0.0H.F) Si  7.318  7.906  6.323  7.207  7.346  7.898  6.401  7.989  7.547  7.924  Al(IV)  0.682  0.094  1.677  0.793  0.654  0.102  1.599  0.011  0.453  0.076  Al(VI)  0.459  0.050  1.197  0.574  0.507  0.154  0.819  0.148  0.426  0.117  Tl  0.014  -  0.064  0.034  0.016  0.005  0.024  0.004  0.005  -  Fe  2.282  2.188  2.084  1.744  1.650  1.650  2.292  2.021  1.277  1. 187  Mn  0.059  0.071  0.011  0.014  0.037  0.034  0.010  0.015  0.006  0.001  Mg  2.284  2.774  1.660  2.696  2.795  3. 151  2.045  2.823  3.  304  3.707  5.098  5.083  5.016  5.062  5.005  4.994  5.190  5.011  5.018  5.012  Ca  1.903  1.927  1.957  1.916  1.965  1.959  1.939  1.908  1.899  1.952  Na  0. 138  0.020  0.274  0.144  0.133  0.025  0.258  0.014  0.138  0.031  K  0.052  0.004  0.130  0.052  0.039  0.006  0.218  0.005  0.044  -  2.093  1.951  2.361  2.112  2.137  1.990  2.415  1.927  2.081  1.983  F  0.074  0.074  0.070  0.069  0.046  0.046  0.062  0.059  0.  197  0.195  OH  1.926  1.926  1.930  1.931  1.954  1.954  1.938  1.941  1.803  1.805  Si/8  0.91  0.99  0.79  0.90  0.92  0.99  0.80  1.00  0 94  0.99  Fe/Z  0.45  0.43  0.42  0.34  0.33  0.33  0.44  0.40  0 25  0.24  Mg/r  0.45  0.55  0.33  0.53  0.56  0.63  0.39  0.56  0 66  Mg/(Mg + Fe)  0.50  0.56  0.44  0.61  0.63  0.66  0.47  0.58  0  72  0.76  Ca/2  0.95  0.96  0.98  0.96  0.98  0.98  0.97  0.95  0 95  0.98  0.91  1.00  0.64  0.89  0.86  1.00  0.58  1.00  0 92  1.00  0.96  0.96  0.96  0.97  0.98  0.98  0.97  0.97  0 90  0.90  a/i  1  0H/2  *  - t o t a l Iron as FeO  # - HjO c a l c u l a t e d from s t r u c t u r a l 1 -  Q Is  formula assuming 2 ( O H , F ) .  the mole f r a c t i o n of vacancy i n the A - s l t e .  a n a l y s t - L . C . Pigage  0.74  233  Table 2-15.  C a l c i c pyroxene a n a l y s e s from carbonate  samples.  Estimated standard e r r o r s are given i n parentheses.  Specimen  224  20  2-312  Analyses  68  11  16  Si02  52.59 (0.02)  Ti02  -  A1203  0.29  FeO*  (0.004)  12.53 (0.03)  52.97 (0.10)  54.16  (0.04)  0.03  (0.003)  0.71  (0.02)  0.33  (0.01)  11.42 (0.05)  6.98  (0.01)  0.04  (0.002)  MnO  0.62  (0.004)  MgO  9.92  (0.02)  11.44 (0.05)  13.44  (0.03)  CaO  23.94  (0.01)  24.37 (0.04)  24.64  (0.03)  Na 2 0  0.07  Total  99.96  (0.001)  0.13 (0.003)  0.18 (0.008) 101.25  0.09  (0.005)  99.68  formulae on the b a s i s o f 6 oxygens 2.007 (0.0008)  Si  1.983  (0.004)  0.001  (0.0001)  2. 015  Ti  -  Al  0.013  Fe  0.400 (0.001)  Mn  0.020  (0.0001)  0.004  Mg  0.564  (0.001)  0.6 39 (0.003)  0. 745  1.033  0. 977 0. 982  (0.001)  0. 006  (0.0004)  (0.002)  0.997  -  0.031 (0.0009)  0. 014  (0.0004)  0. 358 (0.002)  0. 217  (0.0003)  (0.0001)  Ca  0.979  (0.0004)  0.978 (0.002)  Na  0.005  (0.0001)  0.013  (0.0006)  0. 001 (0.0001)  0.984  0.991  0. 988  Fe/Z. Mg/5~  0.40  0.35  0.22  0.57  0.62  0. 76  Mg/(Mg + Fe)  0.59  0.64  0.77  *  (0.001)  - total  i r o n as FeO  a n a l y s t - L . C . Pigage  (0.002)  T a b l e 2-16. Z o i s i t e a n a l y s e s from c a r b o n a t e s a m p l e s . Estimated standard errors are given i n parentheses. men  387  224  494  20  2-312  ses  74  8  29  17  18  Si0 Ti0  40.06 (0.03)  2  -  2  A1 0 2  3  2°3* MnO F e  MgO  0 16 (0 005)  32.79 (0.02)  F H 0# 2  Total  28 82 (0 17)  39.28 (0 02) 0.06 (0 007) 29.89 (0 06)  39.61 (0.04) 0.01 (0.003)  1.30 (0.01)  7 59 (0 18)  6.09 (0 06)  7.20 (0.08)  0.14 (0 00 3)  0.03 (0.002)  -  0 04 (0 005)  0.03 (0 002)  0.03 (0.002)  24.44 (0 02)  24.46 (0.02)  0.01 (0.003)  0 02 (0 002)  0.01 (0 001)  0.01 (0.002)  1.96 (0.002)  1.93 (0 005)  1.97 (0 002)  1.97 (0.002)  100 64  99.06  101.91  0.02 (0.004) 31.70 (0.04)  0 14 (0 01) 23 36 (0 06)  39.75 (0.05)  28.89 (0.02)  -  0.07 (0.002)  24.17 (0.02)  CaO  38 58 (0 06)  24.01 (0.02) 0.01 (0.002) 1.95 (0.002) 98.74  102.21  formulae on the basis of 13 (0,0H,F) Si  3.052 (0.002)  Al  2.944 (0.002)  Ti Fe Mn  0.004 (0.001) -  2.975 (0.005)  2 981 (0.002)  3.006 (0 003)  3.053 (0 004)  2.619 (0.015)  2 673 (0.005)  2.584 (0 002)  2.869 (0 004)  0.009 (0.0003)  0 003 (0.0004)  0.001 (0 0002)  0.001 (0 0002)  0.440 (0.010)  0 348 (0.003)  0.411 (0 005)  0.075 (0 0006)  0.009 (0.0007)  0 009 (0.0002)  0.002 (0 0001)  -  0.005 (0.0006)  0 003 (0.0002)  0.003 (0 0002)  2.948  3.082  3 036  3.001  2.945  Ca  1.973 (0.002)  1.930 (0.005)  1 987 (0.002)  1.989 (0 002)  1.976 (0 002)  F  0.002 (0.0007)  0.005 (0.0005)  0 002 (0.0002)  0.002 (0 0005)  0.002 (0 0005)  0.998 (0.001)  0.995 (0.003)  0.998 (0.001)  0.998 (0 001)  0.998 (0 001)  1.00  0.85  0 88  0.86  0.97  Mg  OH  -  * - t o t a l i r o n as F e 0 2  -  3  # - H 0 calculated from s t r u c t u r a l formula assuming 1 (0H,F); standard error f o r H 0 calculated from standard errors 2  2  of other elements using Monte Carlo approach analyst - L.C. Pigage  ro OJ  235  T a b l e 2-17.  Sphene a n a l y s e s from carbonate  samples.  Estimated standard e r r o r s are given i n parentheses.  Specimen  387  2-375  494  20  2-312  Analyses  20  13  7  17  4  sio Ti0  2  2  A1 0 2  32.58 (0.03)  30.33 (0.05)  30.45 (0.08)  30.52 (0.04)  31.28 (0.08)  25.00 (0.04)  38.18  37.69 (0.18)  35.84 (0.23)  30.20 (0.69)  10.03 (0.01)  3  0.01 (0.002)  2°3* MnO F e  -  MgO  0.02 (0.002)  CaO  29.14  Na 0  -  2  F  (0.03)  0.79 (0.009)  2  Subtotal  99.65  l e s s 0=F Total  1.79 (0.04)  1.96 (0.10)  3.34 (0.13)  6.03 (0.37)  0.40 (0.02)  0.31 (0.03)  0.29 (0.002)  0.29 (0.04)  0.03 (0.003)  0.07 (0.004)  0.01 (0.002)  -  -  29.17 (0.08) 0.01 (0.003)  2.08 (0.02)  H 0#  (0.06)  0.25 (0.003) 0.25 (0.008) 100.41  0.01 (0.002)  27.92 (0.22)  -  28.95 (0.03) 0.01 (0.002)  0.32 (0.01) 0.24 (0.02) 98.96  0.48 (0.01) 0.40 (0.02) 99.85  0.04 (0.01) 29.48 (0.08)  0.89 (0.01) 0.69 (0.07) 98.90  0.88  0.11  0.13  0.20  0.37  98.77  100.30  98.83  99.65  98.53  formulae on the b a s i s o f 5 (0,0H,F) Si  1.033 (0.001)  0.983 (0.002)  0.997 (0.003)  0.989 (0.001)  1.014 (0.003)  Ti  0.596 (0.001)  0.931 (0.001)  0.928 (0.004)  0.873 (0.006)  0.736 (0.017)  Al  0.375 (0.0004)  0.068 (0.002)  0.076 (0.004)  0.128 (0.005)  0.230 (0.014)  Fe  tr  0.010 (0.0005)  0.008 (0.0007)  0.007 ( t r )  0.007 (0.001)  -  0.001 (0.0001)  0.002 (0.0001)  Mn Mg  0.001 (0.0001) 0.972  Ca  0.990 (0.001)  Na  -  -  -  1.010  1.014  1.013 (0.003)  0.980 (0.008)  0.001 (0.0002)  0.990  1.014  -  tr tr  0.002 (0.0005)  1.008  0.975  1.005 (0.001)  1.023 (0.003)  0.001 (0.0001)  0.980  1.006  1.023  F  0.209 (0.002)  0.026 (0.003)  0.033 (0.001)  0.049 (0.001)  0.091 (0.001)  OH  0.168 (0.002)  0.053 (0.002)  0.052 (0.004)  0.086 (0.004)  0.148 (0.015)  0.377  0.079  0.085  0.135  0.239  0.61  0.92  0.92  0.87  0.75  Ti/2!  t o t a l i r o n as P e j O j # - HjO c a l c u l a t e d  from s t r u c t u r a l  standard e r r o r t r - l e s s than 0.0005 a n a l y s t - L.C. Pigage  formula assuming (OH + F) » ( A l + Fe + Mn + Mg) (Higgins and Ribbe 1976);  for H 0 calculated 2  from standard e r r o r s  o f other elements u s i n g Monte C a r l o technique,  T a b l e 2-18.  S c a p o l i t e a n a l y s i s from c a r b o n a t e  samples.  Estimated standard e r r o r s are given i n parentheses.  Specimen  20  Analyses  12  f o r m u l a on t h e b a s i s o f 27 oxygens 45.91 (0.09)  Si  7.006 (0.014)  A1203  28.12  (0o04)  Al  5.057 (0.007)  CaO  18.19  (0.05)  Na 0 2  2.79  (0.01)  K 0  0.16  (0.006)  co # 2  4.80  (0o005)  Total  99.97  Si0  2  2  12.063 Ca  2.974 (0.008)  Na  0.825 (0.003)  K  0.031 (0.001) 3.830  C  Ca/(Ca + Na)  1.000 (0.001)  0.78  # - C 0 c a l c u l a t e d from s t r u c t u r a l f o r m u l a a s s u m i n g 1 CO^ ( E v a n s , Shaw, and Haughton 1969); 2  standard e r r o r f o r C 0 c a l c u l a t e d from s t a n d a r d e r r o r s o f o t h e r elements 2  Monte C a r l o  approach  a n a l y s t - L.C. P i g a g e  using  237 APPENDIX  2-2  A l l c a l c u l a t i o n s o f m i n e r a l e q u i l i b r i a have been done w i t h the thermodynamic parameters AG ,  AS^., and AV .  r  internally  r  These parameters a r e  c o n s i s t e n t r e p r e s e n t a t i o n s of e q u i l i b r i a w h i c h have been  experimentally determined.  The  thermodynamic d a t a have been reduced  a common r e f e r e n c e s t a t e of 298.15 K and  to  1 bar t o t a l p r e s s u r e t o f a c i l i t a t e  comparison between t h e d i f f e r e n t r e a c t i o n s .  The f o l l o w i n g s e c t i o n s o u t l i n e  the g e n e r a l e q u a t i o n s and assumptions used i n d e r i v i n g and m a n i p u l a t i n g thermodynamic  the  parameters.  C o n s i d e r the g e n e r a l e q u i l i b r i u m r e a c t i o n En.  A. + £ m .  i  B.=0  (A  J  where the A^ r e f e r to s o l i d s p e c i e s and B.. to v o l a t i l e s p e c i e s .  Each n^  and m_. i s p o s i t i v e f o r r e a c t i o n p r o d u c t s and n e g a t i v e f o r r e a c t a n t s . this equilibrium, a general expression r e l a t i n g r e f e r e n c e temperature temperature  T^, and p r e s s u r e P  r  For  the AG o f r e a c t i o n a t the  to the AG of r e a c t i o n a t any  other  T and p r e s s u r e P i s ( U l b r i c h and Merino 1974) :  AG (T,P) = r  E  i  n  H  i  A.i VV (  +  E  m  j B.< r' r> J 3 H  T  P  +  E  n  i  Ji  C  p T  dT  U  F  r  A. I  (A2)  238 By i n s p e c t i o n i t i s o b v i o u s t h a t A H ( T , P ) = E n. H  (T ,P )  (A3)  A S ( T , P ) = £ n. S _ ( T , P ) + E m S ( T , P ) j j  (A4)  Ac  (A5)  r  r  r  r  r  A  r  A  1  r  H  r  r  r  r  c <T ,P ) . B.  r  r  J  By d e f i n i t i o n AH  r  = AG  r  r  1  ( T , P ) = £ n. c ( T , P ) + E m l ^A. j r  r  ( T ^ ) + Z m  + T AS  r  r  F  a t a g i v e n p r e s s u r e and t e m p e r a t u r e .  S u b s t i t u t i n g t h e s e two s e t s o f r e l a t i o n s i n t o e q u a t i o n (A2), t h e r e l a t i o n then becomes Ac  J  T r ^T  OP /T) dT + E n. I V. r i Jp i r  (Ac  T r  P  f  1  P  dT r  (A6)  dP  A  p  A d o p t i n g the e m p i r i c a l M a i e r - K e l l e y heat c a p a c i t y f u n c t i o n c  = a + b T + c T ~  P  and i n t e g r a t i n g from T  2  t o T, e q u a t i o n (A6) becomes  AG (T,P) = A G ( T , P ) - ( T - T ) A S ( T , P ) + A a r  r  r  r  r  r  + (Ab /2)(T -T ) - Ac 2  r  - Ab  r  2  r  r  r  r  J  ^P  P  A  r  2  r  V.  r  dP + E m. i j JP J  r  r  ( T - T ) + (Ac /2) (1/T - 1/T ) r  (T-T )  (1/T - 1/T ) - A a T l n ( T / T )  2  r  r  pP  I  B  r  V_ j  dP  r  (A7)  239 The c o e f f i c i e n t s a, b, c f o r the c^ terms were o b t a i n e d from a p r e p r i n t of the r e c e n t c o m p i l a t i o n by H e l g e s o n e t a l . (1978).  These were m o d i f i e d  f o r t h e a l p h a - b e t a q u a r t z t r a n s i t i o n by T.H. Brown ( p e r s o n a l communication, 1977). The volumes o f s o l i d s p e c i e s a r e assumed t o be independent o f pressure, r e s u l t i n g i n the expression OP En. i J X  A P  V. i  dP = ( A V ( T , P ) ) (P - P ) A  r  r  .  r  (A8)  The d e f i n i t i o n o f f u g a c i t y c o n v e n i e n t l y a l l o w s the e x p l i c i t e v a l u a t i o n o f the p r e s s u r e i n t e g r a l f o r t h e v o l a t i l e  Z m j  j "P  V r  B  dP = Z m J j  species  R T ln(f  (T,P)/f j  (T,P ) .  B  (A9)  r  j  F u g a c i t i e s f o r E^O and CO^ were c a l c u l a t e d u s i n g t h e Redlich-Kwong equation of corresponding  s t a t e s ( R e d l i c h and Kwong 1949).  c o n t a i n s two a d j u s t a b l e c o e f f i c i e n t s .  This  equation  These c o e f f i c i e n t s were e m p i r i c a l l y  d e r i v e d by a n o n l i n e a r l e a s t squares r e g r e s s i o n t o t a b u l a t e d f r e e energy v a l u e s f o r t h e pure gas s p e c i e s a t d i f f e r e n t p r e s s u r e s and  temperatures.  The c o e f f i c i e n t s were assumed t o be l i n e a r f u n c t i o n s o f temperature f o r t h e r e g r e s s i o n (T.H. Brown, p e r s o n a l communication 1978). for  were taken from Burnham, H o l l o w a y , and D a v i s  Free energy v a l u e s (1969); CC^ f r e e  energy v a l u e s were computed from f u g a c i t y c o e f f i c i e n t s r e p o r t e d by Shmulovich and Shmonov (1975).  I n b o t h cases t h e l e a s t s q u a r e s r e s i d u a l s  were l e s s than 100 c a l o r i e s . F u g a c i t i e s f o r CO and CH^ were a l s o determined u s i n g t h e R e d l i c h Kwong e q u a t i o n .  The c r i t i c a l temperature and p r e s s u r e o f t h e a p p r o p r i a t e  s p e c i e s was used t o c a l c u l a t e the f u g a c i t y c o e f f i c i e n t .  E q u a t i o n s by Shaw  and Wones (1964) were e x t r a p o l a t e d t o c a l c u l a t e f u g a c i t i e s f o r H . 0  240 For o x y g e n - b u f f e r e d d e h y d r a t i o n r e a c t i o n s , t h e I^O f u g a c i t y was c a l c u l a t e d u s i n g the method o u t l i n e d by Zen ( 1 9 7 3 ) . d i f f e r e n t gas s p e c i e s i s assumed.  I d e a l m i x i n g o f the  Oxygen f u g a c i t i e s f o r s o l i d b u f f e r s  were c a l c u l a t e d from the e q u a t i o n s g i v e n i n Huebner ( 1 9 7 1 ) . V o l a t i l e s were assumed t o be i d e a l m i x t u r e s o f r e a l g a s e s .  With t h i s  assumption the f u g a c i t y f o r each s p e c i e s B.. i s p r o p o r t i o n a l t o t h e mole f r a c t i o n o f B. i n t h e v o l a t i l e phase  f  B  (P,T) = j  f° (P,T) J  .  (AlO)  where f° (P,T) i s the f u g a c i t y of pure B. a t the p r e s s u r e P and temperature j T of i n t e r e s t . 3  D i s p l a c e m e n t o f the r e a c t i o n c u r v e due t o s o l i d s o l u t i o n i s c a l c u l a t e d by i n c l u d i n g an a d d i t i o n a l term d e s c r i b i n g t h e change i n f r e e energy o f each s o l i d s p e c i e s r e s u l t i n g from s o l u t i o n .  The form o f t h i s term i s  r e a d i l y d e r i v e d by r e c a l l i n g t h e r e l a t i o n f o r the m o l a r f r e e energy of a species i n s o l i d y  A  i  solution  = V°  A  i  + R T In a  A  i  .  (All)  For a l l i s o l i d s p e c i e s i n t h e r e a c t i o n , t h i s a d d i t i o n a l term assumes the form R T ln(JI a " i ) i i  .  (A12)  A  The s o l u t i o n models r e l a t i n g c o m p o s i t i o n t o a c t i v i t y f o r each s p e c i e s A^ a r e d i s c u s s e d i n the main p a r t o f t h i s paper. s p e c i e s A^ i s 1.0.  The a c t i v i t y f o r each pure  I f a l l s o l i d s p e c i e s a r e pure, term  (A12) i s z e r o .  S u b s t i t u t i n g e x p r e s s i o n s ( A 8 ) , ( A 9 ) , ( A l O ) , and (A12) i n t o e q u a t i o n (A7) , t h i s e q u a t i o n assumes the form  241 AG (T,P) = A G ( T , P ) r  r  r  - (T-T ) A S ( T , P ) + A a  r  r  r  r  + (Ab /2) ( T - T ) - A c 2  2  r  - Ab  r  r  r  r  (1/T - 1/T.) - A a  r  T ln(T/T )  (T-T ) + (Ac /2) (1/T - 1/T ) 2  r  (T-T )  r  r  + AV (T ,P ) i A  r  r  (A13)  2  r  r  (P-l) + E m j  R T ln(X  R  r  f°(T,P)) j j  + R T ln( n a i ) i i n  A  Note t h a t f o r the chosen r e f e r e n c e p r e s s u r e P r  =1 r  b a r , f ^ = P_ = 1 . B. B. 3  At  3  equilibrium AG (T,P) = 0 r  ,  and e q u a t i o n (A13) may be s o l v e d i t e r a t i v e l y f o r temperature T a t a s p e c i f i e d p r e s s u r e P.  (A14)  Table 2-21.  Thermodynamic parame  ters for selected mineral  U n i t s a s s o c i a t e d w i t h the d i f f e r e n t parameters a r e : cm  A V  r,s  (cal/bar)  3  Ac Pr Aa  j K  l  r  _ J K~  3  Ab *10 Ac * 1 0 " r AG  (cal K )  - 1  5  * 10  2  J K * 10" J  3  5  (cal K  (cal)  j K" r  1  (cal  o * 1(T)  ( c a l K * 10  r  AS  9  K" ) 1  )  equilibria.  Ml  if iii  i |  Mi  iiiii  - I lie I  M  M I'lilS  i LI  .  S i i i i ! ISiij  i \\ H I ifiii« i PP!1111 I!. js I i !i 1 1I i II P I .  i  !  35 = § = 1 J  +  +  a s  i  1  1  1  =• i! il i i I«ii ii ii if Ii il tl i i i i i i\ } !! !l il 11! 1! IIII il !I, iiiii,  JIlMfl  5  ;- si;!!! If!!, If ?! 111!, 1! I! IS 111!, i!!! mi ih!!!  , j  Mmdiiiiiimitiniiiii i i i I i i i i i i I i i i 11 i ! A i A i i if i i 8  8  +  o  o  =~  °~  =~  a"  5  5  o"  1  o  °~ +  e <  1  a 3  o  »~  "* +  -<  a-  a  O-l  sa M  3 -  5  -  &2  CD-  O-  S -  + 3  + 3  1  b k  M  -a  ^  7  EC  +  +  . O-  *  +  +  N  +  +  +  +  +  *  *  *  +  2s  2  -  +  —  +  +  +  11  +  +  *  *  +  1 : «  244 Table 2-22. Volume and h e a t c a p a c i t y d a t a f o r s e l e c t e d m i n e r a l s .  C Mineral  Volume @  Carbon Dioxide  CO  2  Steam H0 2  Corundum (Co) A 1  2°3  o-Quartz (Qtz) Si0  2  C a l c i t e (Cc) CaC0  3  Fe-Staurolite  (Fe-stau)  Fe Al Si 0 (0H) 2  9  4  Gehlenite  (Ge)  Ca Al Si0 2  2 3  2  ?  Z o i s i t e (Zo) Ca Al Si 0 (OH) 2  3  3  Andalusite  1 2  (And)  Al„Si0„ Kyanite (Ky) Al Si0 2  5  Sillimanite Al Si0 2  (Sill)  5  Almandine (Aim) Fe Al Si 0 3  2  3  1 2  Grossular (Gr) Ca Al Si 0 3  2  3  1 2  b * 10  24464.98  44.22  8.79  -8.62  (584.727)  (10.57)  (2.1)  (-2.06)  24464.98  30.54  10.29  (584.727)  (7.3)  (2.46)  25.575  115.02  11.80  -35.06  (0.61126)  (27.49)  (2.82)  (-8.38)  22.688  69.94  2.5292  -19.27385  (0.54226)  (16.716)  (0.6045)  (-4.60656)  36.934  104.52  21.92  -25.94  (0.88274)  (24.98)  (5.24)  (-6.2)  223.38  866.59  154.56  -239.41  (5.3389)  (207.12)  (36.94)  (-57.22)  90.236  266.69  33.47  -63.26  (2.1567)  (63.74)  (8.0)  (-15.12)  51.5615  -141.9035  (12.3235)  (-33.91575)  51.53  172.845  26.3282  -51.84838  (1.2316)  (41.311)  (6.2926)  (-12 . 39 2 06)  44.09  173.18835  28.5202  -53.8987  (1.05378)  (41.39301)  (6.8165)  (-12.8821)  49.90  167.46  30.922  -48.84423  (1.19264)  (40.024)  (7.3905)  (-11.67405)  115.27  476.926  45.411  -120.73246  (2.7551)  (113.988)  (10.8535)  (-28.85575)  125.3  471.32  32.9427  -130.89958  (2.9947)  (112.648)  (7.8735)  (-31.28575)  (1967)  (1972) (1976)  (cal/bar) 1  K"  $ - J mol"  1  K"  & - J mol"  1  K * 10"  1  2  ( c a l mol" * 10 5  3  1  0  (118.278)  (1972)  # - J mol"  c * 10  494.875  4 - C h a t t e r j e e and Johannes (1974)  @ - cm  $  136.52  1 - Robie, Bethke, and Beardsley  6 - Newton and Goldsmith  3  (3.263)  2 - Robie and Waldbaum (1968)  5 - Chatterjee  - a + b*T + c*T"  a II  Ref(vol)  Volume r e f e r e n c e s  3 - Ganguly  p  K~')  ( c a l mol" ( c a l mol"  1  1  K~  2  * 10 ) 3  K * 10" ) 5  T a b l e 2-22 ( c o n t i n u e d ) . C  = a + b*T + c*T  -2  P  Mineral  Volume @  Wollastonlte  (Wo)  CaMgSi.O, 2 0  Tremolite ( T r ) Ca Mg Si 0 (OH) 2  5  g  Muscovite  2 2  2  (Mus)  KAl AlSi O (OH) 2  3  Paragonite  1 0  2  (Pa)  NaAl AlSi 0 (OH) 2  3  1 Q  2  Phlogopite (Phi) KMg AlSi 0 3  3  1 ( )  (OH)  2  A n o r t h i t e (An) CaAl Si O 2  2  g  H i g h - A l b i t e (H-ab) NaAlSi,0_ 3 o Low-Albite  (L-ab)  NaAlSi 0 3  g  3  S  -5 c * 10  111.46  15.06  -27.28  (0.95435)  (26.64)  (3.6)  (-6.52)  66.09  221.21  32.80  -65.86  (1.5795)  (52.87)  (7.84)  (-15.74)  272.92  787.52  239.72  -187.535  (6.5229)  (188.222)  (57.294)  (-44.822)  140.81  408.19  110.37  -106.44  (3.3654)  (97.56)  (26.38)  (-25.44)  131.98  407.65  102.51  -110.62  (3.1545)  (97.43)  (24.5)  (-26.44)  149.91  420.95  120.42  -89.96  (3.583)  (100.61)  (28.78)  (-21.5)  100.79  269.53  57.32  -70.67  (2.4089)  (64.42)  (13.7)  (-16.89)  100.43  258.15  58.16  -62.80  (2.4003)  (61.7)  (13.9)  (-15.01)  100.07  258.15  58.16  -62.80  (2.3917)  (61.7)  (13.9)  (-15.01)  109.05  267.06  53.97  -71.34  (2.6063)  (63.83)  (12.9)  (-17.05)  108.72  267.06  53.97  -71.34  g  (2.5984)  (63.83)  (12.9)  (-17.05)  (Me)  340.524  S a n i d i n e (Sa) KAlSi.0  b * 10  39.93  CaSiO. Diopside (Di)  Ref(vol)  o  J a M i c r o c l i n e (Mi) KAlSi 0 3  Meionite  Ca.Al,Si,0„,C0, 4 6 6 24 3  (8.1387)  Volume r e f e r e n c e s 1 - Robie, Bethke, and Beardsley 2 - Robie and Waldbaum  (1967)  (1968)  3 - Ganguly (1972) 4 - C h a t t e r j e e and Johannes (1974) 5 - Chatterjee  (1972)  6 - Newton and Goldsmith  @ - cm  (1976)  (cal/bar)  // - J m o l " K  _ 1  $ - J mol" K  - 2  1  1  (cal mol" * 10  & - J mol" K * 10" 1  5  3  1  K  _ 1  )  (cal mol  - 1  K  - 2  * 10 )  (cal mol" K * 10 1  3  - 5  )  246 Fe-s t a u r o l i te-Quar t z-Almand i n e - A l S iO 2  The upper s t a b i l i t y l i m i t of F e - s t a u r o l i t e + q u a r t z i s denoted by t h e general r e a c t i o n : F e - s t a u r o l i t e + Quartz = Almandine + A l S i C > 2  5  + H 0  (unbalanced)  2  T h i s r e a c t i o n has been e x p e r i m e n t a l l y s t u d i e d f o r s i l l i m a n i t e 1968)  and k y a n i t e (Ganguly  1972).  (Richardson  C o e f f i c i e n t s i n the balanced  depend upon t h e c o m p o s i t i o n assumed f o r F e - s t a u r o l i t e .  .  reaction  Ganguly (1972)  s y n t h e s i z e d s t a u r o l i t e from t h e b u l k c o m p o s i t i o n F e A l g S i ^ 0 - j ( O H ) . 2  2  R i c h a r d s o n (1967) r e p o r t e d t h a t h i s attempts t o s y n t h e s i z e s t a u r o l i t e from t h e same b u l k c o m p o s i t i o n c o n s i s t e n t l y r e s u l t e d i n a m i x t u r e of s t a u r o l i t e + quartz. approximated  E l e c t r o n microprobe  analyses of h i s s t a u r o l i t e s  the composition F e ^ l ^ S i ^ ^ ( ^ ( O H ) , , .  The l a t t e r  composition  i s more c o m p a t i b l e w i t h t h e h y d r o x y l c o n t e n t of n a t u r a l s t a u r o l i t e ( G r i f f e n and Ribbe  1976).  I n d e r i v i n g thermodynamic parameters  f o r e q u i l i b r i a E4 and E5, I  have used t h e same b a l a n c e d r e a c t i o n c o e f f i c i e n t s ( i . e . s t a u r o l i t e formulae) f o r b o t h e x p e r i m e n t a l s t u d i e s .  S i n c e t h e two r e a c t i o n s a r e  r e l a t e d by t h e k y a n i t e - s i l l i m a n i t e t r a n s i t i o n , i t s h o u l d be p o s s i b l e t o d e r i v e parameters  f o r each r e a c t i o n which d i f f e r by t h e AG  r  and A S of r  the k y a n i t e - s i l l i m a n i t e t r a n s i t i o n m u l t i p l i e d by t h e A l S i O ^ r e a c t i o n 2  coefficient.  T h i s c o n s t r a i n t s h o u l d e l i m i n a t e a number o f p o s s i b l e  s t a u r o l i t e f o r m u l a e and b a l a n c e d Thermodynamic parameters  reactions.  were d e r i v e d f o r b a l a n c e d r e a c t i o n s  c o r r e s p o n d i n g t o t h e s t a u r o l i t e formulae F e A l g S i ^ 0 ^ ( O H ) , 2  Fe  1 < 5  Al Si 0 9  4  2 2  (OH) , 2  F e ^ g ^ S ^ O ^ O H ) , and F 2  2  e i  Fe^l^Si^  ^ A l g ^ S i ^ O H )  y^0 (OH) 22  r  Heat c a p a c i t y c o e f f i c i e n t s f o r each of these s t a u r o l i t e f o r m u l a e were estimated u s i n g t h e approach  o u t l i n e d by Helgeson  et_ a l .  (1978) .  The o n l y  247  F i g u r e 2-23. E4 and E5.  E x p e r i m e n t a l r e v e r s a l s and c a l c u l a t e d e q u i l i b r i a curves f o r E x p e r i m e n t a l r e v e r s a l s are from Ganguly (1972) and  R i c h a r d s o n . (1968). i n Table  2-21.  Thermodynamic parameters  f o r E4 and E5 a r e  listed  248 s t a u r o l i t e f o r m u l a and b a l a n c e d r e a c t i o n c o n s i s t e n t w i t h t h e c o n s t r a i n t s imposed by t h e k y a n i t e - s i l l i m a n i t e t r a n s i t i o n and t h e e x p e r i m e n t a l b r a c k e t s corresponded Fe2AlgSi^022(OH).  t o t h e f o r m u l a p r e s e n t e d by Ganguly (1972) -  F i g u r e 2-23 i l l u s t r a t e s t h e c a l c u l a t e d  equilibrium  c u r v e s E4 and E5 and t h e e x p e r i m e n t a l b r a c k e t s when u s i n g t h e Ganguly s t a u r o l i t e f o r m u l a and b a l a n c e d  reaction.  M u s c o v i t e A c t i v i t y Model Activity-mole.fraction  r e l a t i o n s f o r m u s c o v i t e and p a r a g o n i t e  components i n metamorphic w h i t e micas a r e c o m p l i c a t e d by t h e u b i q u i t o u s presence of c e l a d o n i t e component and n o n i d e a l i t y o f t h e Na-K i n t e r a c t i o n a t l e a s t a l o n g t h e m u s c o v i t e - p a r a g o n i t e j o i n ( E u g s t e r e t a l . 1972).  Any  a c t i v i t y model f o r w h i t e micas s h o u l d a t l e a s t c o n s i d e r t h e s e two e f f e c t s . I n t h i s paper t h e s e problems have been handled by f i r s t computing  an i d e a l  a c t i v i t y based upon an i d e a l s i t e m i x i n g model ( K e r r i c k and Darken 1975) and then m u l t i p l y i n g t h e i d e a l a c t i v i t y by an a c t i v i t y c o e f f i c i e n t d e r i v e d from t h e s t u d i e s by E u g s t e r e_t al_. (1972) and B l e n c o e (1977).  The  r e s u l t i n g expressions are Paragonite  Paragonite * ( N a > * ( A l X  X  ) 2  * W (  (A 15)  2  (A16) where the X's r e f e r t o mole f r a c t i o n s o f t h e i n d i c a t e d s p e c i e s .  These  e q u a t i o n s c o r r e s p o n d t o t h e s t o i c h i o m e t r i c formulae NaA^AlSi^O^QtOH) ^ and KA^AISI-JO^QCOH) ^ f o r p a r a g o n i t e and m u s c o v i t e , r e s p e c t i v e l y . term Xg^ i s n o t i n c l u d e d  The  i n t h e a c t i v i t y e x p r e s s i o n s because s u b s t i t u t i o n  of t e t r a h e d r a l A l f o r S i i s c o u p l e d t o s u b s t i t u t i o n of b i v a l e n t (Mg, Fe) f o r o c t a h e d r a l A l .  cations  A p p r o p r i a t e y c o e f f i c i e n t s were c a l c u l a t e d f o r  the a n a l y z e d m u s c o v i t e c o m p o s i t i o n s by d e s c r i b i n g t h e excess f u n c t i o n s i n  249  terms o f asymmetric Margules parameters s t u d i e s by E u g s t e r e t a l .  ( J . B . Thompson 1967)  t a k e n from .  (1972) and B l e n c o e (1977).  As a f i r s t a p p r o x i m a t i o n A z u r e Lake m u s c o v i t e s can b e d e s c r i b e d by the f o u r component system K A l g S i ^ U j ^ O H ) paragonite, KAl(Mg,Fe)Si 0 (OH) 4  Na c e l a d o n i t e .  1 0  2  - muscovite, NaAlgSigOj^OH) ^ _  - K c e l a d o n i t e , and N a A l ( M g , F e ) S i 0 ( O H )  2  4  1 0  2  T h i s assumes t h a t Mg and Fe a r e e q u i v a l e n t when s u b s t i t u t i n g  for octahedral A l .  T i - c o n t e n t o f the m u s c o v i t e s was n o t c o n s i d e r e d .  These  components a r e i l l u s t r a t e d i n f i g u r e 2-24 w i t h X r e p r e s e n t i n g a n a n a l y z e d white mica.  From the diagram i t can be seen t h a t the mole f r a c t i o n o f each  component i s p r o p o r t i o n a l t o the a r e a o f the r e c t a n g l e o p p o s i t e t h e s p e c i f i e d component.  T h e r e f o r e the mole f r a c t i o n o f each component i s  g i v e n by: *Pa = ( a>*< - g,Fe X  1  X  N  ^us  )  = < " »a>^ - g,Fe> 1  (  A  1  7  )  (  A  1  8  )  (  A  1  9  )  M  X  1  X  M  ' ^ a c e l = < Ka>^ Mg,Fe X  X  )  ^ c e l = - Na * Mg,Fe> (1  X  )  "  (X  (  A  2  0  )  Excess f u n c t i o n s between these components have been e x p e r i m e n t a l l y d e t e r m i n e d o n l y f o r t h e Na-K i n t e r a c t i o n a l o n g the m u s c o v i t e - p a r a g o n t e binary j o i n .  I t seems r e a s o n a b l e t o assume t h a t the Na-K i n t e r a c t i o n  between the two c e l a d o n i t e end-members i s s i m i l a r .  S i n c e no f u r t h e r  i n f o r m a t i o n i s a v a i l a b l e , a l l o t h e r i n t e r a c t i o n Margules parameters between the d i f f e r e n t components a r e assumed t o b e zero ( i d e a l s o l u t i o n ) .  This  r e s u l t s i n the e x c e s s f r e e energy f u n c t i o n g i v e n i n e q u a t i o n (A21). G = X. 2L, (W 2L. + W X_ ) ex MUS T a Pa Mus Mus T a D  M  (A21) +  ^Kcel^Nacel^Pa^Sccel  +  ^Mus^acel^  where the W's a r e d e f i n e d as ( B l e n c o e 1977; E u g s t e r e t a l . 1972)  250  K-Celadonite KAI(Mg,Fe)Si 0 (0H) 4  i0  Na-Celadonite  NaAI(Mg,Fe)Si 0| /0H)  2  4  Muscovite  KAI Si 0, (OH) 3  3  0  Paragonite NaAI Si 0 (0H) 3  2  F i g u r e 2-24. White mica c o m p o s i t i o n components.  (  3  |0  2  2  i n terms o f f o u r end-member  Mole f r a c t i o n o f each component i s p r o p o r t i o n a l t o a r e a o f  ::.rectangle d i a g o n a l l y o p p o s i t e  from t h e component.  251  W„ = 3096.8 + 0.075 P ( b a r s ) + 0.1698 T (K) Pa W„ = 4305.9 + 0.0571 P ( b a r s ) + 0.3954 T (K) Mus To d e r i v e a p p r o p r i a t e e x p r e s s i o n s f o r y„ • and YT> -4. * * * 'Muscovite 'Paragonite  i t  v  i s e a s i e s t t o c o n s i d e r t h e g e n e r a l case w i t h t h e f o u r components X^, i = l , 4 . With t h e same assumptions c o n c e r n i n g t h e W parameters as o u t l i n e d f o r t h e mica system, e q u a t i o n (A21) becomes G  = X X (W X  £ x  1  2  1 2  1  + W X ) + X X (W X 21  2  3  4  1 2  3  + W X ) 21  4  .  (A22)  But G i s a l s o d e f i n e d by t h e r e l a t i o n ex G  ex  = E X. R T I n y. , l I 4  •  I n o r d e r t o d e r i v e an e x p r e s s i o n f o r o t h e r Yj_ from e q u a t i o n (A23). outlined f o r  ( i ti  The procedure  s  necessary  A 2 3  )  t o e l i m i n a t e the  followed i n doing t h i s i s  .  The p a r t i a l d e r i v a t i v e o f e q u a t i o n (A23) w i t h r e s p e c t t o X^ (X^ and X^ c o n s t a n t ) i s g i v e n by 9G  ex  „ „ , = R T In y  3 X 1  T  x  „ „ , - R T lnY  ^  (  A  2  4  )  ' ' 3 , 3*1,2  s i n c e dX^ = - d X . 2  P  X  By r e a r r a n g i n g terms t h i s becomes  R T lny  = R.T I n y,  9  9G - —— 1  S u b s t i t u t i n g (A25) i n t o (A23) e l i m i n a t e s Y  .  (A25)  T P Y  2  from e x p r e s s i o n (A23).  With  s i m i l a r s u b s t i t u t i o n s f o r X^ and X^, e q u a t i o n (A23) becomes, upon rearrangement R T In  YI  1  =  _ G  4 9G + E X. ex 2 l aX 1  .  e X  (A26)  T,P,X. .....  S u i t a b l e expressions f o r the p a r t i a l d e r i v a t i v e s o f G  a r e o b t a i n e d from  252  e q u a t i o n (A22).. : A f t e r s u b s t i t u t i n g these d e r i v a t i v e s i n t o (A26) , c o l l e c t i n g terms, and u s i n g for  t h e f a c t t h a t t h e f o u r components sum t o 1, t h e e x p r e s s i o n  is R T In y  = X W ( 1 - 2 X ) + 2V^^(l-XY)  - 2X X (W X  2  2  2 1  1  3  4  1 2  3  + W X > . 21  4  (A27) I n t h e f o u r component mica system t h i s e q u a t i o n becomes  R  T  l  n  ^Pa -  ^usM - ^ 1  2  R  T  l  n  %us  2  ^ M ^ a W  +  X  ( 1  -  2 X  MU8  ^ (A28)  ^Nacel^Kcel^Mus^Nacel  = P^MU8  1  )  +  2 W  ^Pa^Kcel^  +  Pa Pa Mu8 X  i  ( 1  - MuB X  )  (A29) ^Nacel^Kcel^Mus^Nacel a r e as d e f i n e d p r e v i o u s l y . 2  where W„ andW., Pa Mus  +  ^Pa^Kcel^  J  Gro s s u l a r - K y a n i t e-Quar t z-Anor t h i te E x t r a p o l a t i o n o f e x p e r i m e n t a l d a t a f o r e q u i l i b r i u m ElO t o l o w e r p r e s s u r e s r e s u l t s i n l a r g e u n c e r t a i n t i e s i n the p r e s s u r e - t e m p e r a t u r e p o s i t i o n o f t h i s c u r v e (see f i g u r e 2-25).  C h o o s i n g a b e s t f i t curve i s  d i f f i c u l t to j u s t i f y from t h e r e v e r s e d e x p e r i m e n t s . r e a c t i o n as a geobarometer-geothermometer r e q u i r e s  Y e t use o f t h i s s e l e c t i o n o f thermodynamic  parameters c o n s i s t e n t w i t h one o f t h e many p o s s i b l e c u r v e s .  The c h o i c e  i s e s p e c i a l l y c r i t i c a l since t h i s e q u i l i b r i u m i s s e n s i t i v e to a n a l y t i c a l e r r o r ( s e e f i g u r e 2-14). To f u r t h e r r e s t r i c t the u n c e r t a i n t y  i n d i c a t e d i n f i g u r e 2-25,  e x p e r i m e n t a l s t u d i e s o f e q u i l i b r i u m ElO were combined w i t h  experimental  r e s u l t s from n i n e i n d e p e n d e n t l y s t u d i e d r e a c t i o n s i n t h e system CaO-Al 0.j2  Si0 -H 0. 2  2  Reactions included  i n t h i s study are i n d i c a t e d w i t h  asterisks  200  J  I  I  400  600  800  TEMPERATURE,  I  1000  from t h e l i n e a r programming s t u d y i n t h i s p a p e r .  1200  1400  °C  F i g u r e 2-25. E x p e r i m e n t a l r e v e r s a l s f o r e q u i l i b r i u m E10 ( H a r i y a and Kennedy and minimum s l o p e s p e r m i t t e d by e x p e r i m e n t a l b r a c k e t s .  L  1968).  S o l i d l i n e s a r e maximum  Dashed l i n e s a r e maximum and minimum a l l o w e d s l o p e s  Dot-dash l i n e i s t h e p r e f e r r e d p o s i t i o n o f t h e c u r v e .  ro  01 OJ  Table 2-23.  E x p e r i m e n t a l u n c e r t a i n t i e s f o r s e l e c t e d exp  REACTION  REFERENCE  t a l reaction  APPARATUS  studies.  ERROR BRACKET ± T <°C)  + P (bars)  El  Newton (1966b) Richardson et a l . (1968)  pstn c y l gas app  10 5  400 100  E2  Newton (1966a) Richardson et a l . (1969) Holdaway (197lT^  pstn c y l gas app cold seal  15 5 5  5 Z 100 1.5 Z  E3  Holdaway (1971) Weill In Holdaway (1971)  cold seal calorlmetry  5 20  1.5 Z  E10  Harlya and Kennedy (1968) Hensen et a l . (1975)  pstn c y l pstn c y l  5, 15 5  1000 1000  E20  Newton and Kennedy (1963) Newton (1966c)  pstn c y l pstn c y l  10 10  500 400  E21  Newton (1966c) Newton (1966c) Boettcher (1970)  cold seal pstn c y l cold seal  5 10, 20 5  50 200 50  E22  Newton (1966c) Newton (1966c) Boettcher (1970) Huckenholz et a l . (1975)  cold seal pstn c y l cold seal gas app  5 10 5 5  50 400 50 50  E23  Newton (1965) Newton (1965) Boettcher (1970) Huckenholz e_t a l .(1975)  cold seal pstn c y l cold seal gas app  5 10 5 5  50 400 50 2 Z  E24  Huckenholz et a l .(1975) Huckenholz et a l .(1975)  cold seal gas app  5 5  50  Newton (1965) Newton (1965) Boettcher (1970)  cold seal pstn c y l cold seal  5 15 5  50 400 50  E25  2 X  r o c n - A  255  i n T a b l e 2-21.  S i n c e o n l y seven of the t e n e q u i l i b r i a are  linearly  independent, the a l g e b r a i c r e l a t i o n s between the r e a c t i o n s can be used t o r e s t r i c t the u n c e r t a i n t y  i n the p r e s s u r e - t e m p e r a t u r e p o s i t i o n of  T h i s r e s t r i c t i o n was o u t l i n e d by Gordon (1973).  completed u s i n g the l i n e a r programming approach Experimental brackets  a s e t of i n e q u a l i t y c o n s t r a i n t s .  f o r each r e a c t i o n formed  In addition s i x equality constraints  r e l a t e d the thermodynamic parameters AH  r  and  AS  of the d i f f e r e n t r e a c t i o n s .  r  Outer l i m i t s o f e x p e r i m e n t a l e r r o r were used i n c o n s t r u c t i n g inequalities. used.  contains  the e r r o r l i m i t s used i n the l i n e a r programming.  o b j e c t i v e f u n c t i o n c o n s i s t e d of the AH  or AS r  T h i s f u n c t i o n was permitted  values.  for reaction  ElO.  r  b o t h maximized and m i n i m i z e d to f i n d the f u l l range i n Maximum and minimum v a l u e s a r e :  AH (max) = 76366 J o u l e s  AH (min) = 32995 J o u l e s  r  r  AS (max) = 186.86 J m o l " r  1  K"  A S ( m i n ) = 147.74 J m o l "  1  r  (These v a l u e s a r e reduced to the s t a n d a r d r e f e r e n c e and  the  I n most cases the e r r o r l i m i t s suggested by the a u t h o r s were  T a b l e 2-23 The  ElO.  p r e s s u r e 1 bar.)  1  K  temperature 298.15 K  These v a l u e s c o r r e s p o n d t o the dashed c u r v e s  i l l u s t r a t e d i n f i g u r e 2-25.  I n c l u d i n g the n i n e o t h e r r e a c t i o n s causes a  s i g n i f i c a n t d e c r e a s e i n the t o t a l u n c e r t a i n t y a s s o c i a t e d w i t h r e a c t i o n S i n c e the c u r v e suggested by H a r i y a and f i g u r e 2-25) brackets,  .  _ 1  Kennedy (1968) (dot-dash l i n e i n  i s a p p r o x i m a t e l y i n the c e n t e r  t h i s c u r v e was  ElO.  of the r e s t r i c t e d u n c e r t a i n t y  used i n a l l f u r t h e r c a l c u l a t i o n s .  256  APPENDIX  2-3  257 Table 2-24.  Standards used f o r e l e c t r o n microprobe a n a l y s i s .  Number i n p a r e n t h e s e s i c o r r e s p o n d s t o r e f e r e n c e number i n m i c r o p r o b e standards c o l l e c t i o n , G e o l o g i c a l Sciences, U n i v e r s i t y of B r i t i s h Columbia. ab(20)  albite  an(102)  anorthite  and(26)  andalusite  angl(32)  anorthite  ben(35)  benitoite (California)  cc(76)  calcite  dol(10)  dolomite  en(81)  enstatite  fa(104)  fayalite  fo(22)  forsterite  gr(83)  g r o s s u l a r (New Y o r k )  jd(41)  j a d e i t e (Burma)  ky(4)  kyanite (British  l a b (97)  l a b r a d o r i t e (Oregon)  mus(49)  muscovite M  or(28)  o r t h o c l a s e OR-1  phl(24)  fluorophlogopite  py(84)  pyrope  (synthetic)  qtz(36)  quartz  (synthetic)  rho(88)  r h o d o c h r o s i t e (New Mexico)  rut(13)  rutile  si(ll)  siderite  sp(15)  spessartine  wi(l)  w i l l e m i t e (New J e r s e y )  wo(21)  w o l l a s t o n i t e (New Y o r k )  (Oregon) (synthetic) (Brazil) glass  (Cumberland) (Austria) (synthetic) (synthetic) (synthetic)  Columbia)  (synthetic)  (synthetic) (Greenland) (Brazil)  Table 2-25.  Standards used f o r garnet a n a l y s e s .  Si  Ti  Al  Fe  Mn  Mg  Ca  373  wo(21)  rut(13)  and(26)  fa(104)  sp(15)  fo(22)  wo(21)  121  gr(83)  py(84)  py(84)  gr(83)  367  gr(83)  py(84)  py(84)  gr(83)  py(84)  gr(83)  Specimen  .i  82  gr(83)  py(84)  II  398  gr(83)  py(84)  n  .1  py(84)  gr(83)  en(81)  wo(21)  492  wo(21)  and(26)  II  2-376  gr(83)  py(84)  II  py(84)  gr(83)  II  fo(22)  wo(21)  II  fo(22)  angl(32)  II  fo(22)  wo(21)  py(84)  gr(83)  2-13  wo(21)  and(26)  n  74  qtz(36)  and(26)  i,  59  wo(21)  and(26)  40  gr(83)  py(84)  ..  Table 2-26.  Specimen All Specimen All  Table 2-27. Specimen  Standards used f o r m u s c o v i t e and b i o t i t e  analyses.  Si  Ti  Al  Fe  Mn  Mg  Ca  Ba  Na  phl(24)  rut(13)  mus(49)  fa(104)  sp(15)  phi(24)  wo(21)  ben(35)  ab(20)  K  F  phi(24)  phi(24)  Mn  Mg  Ca  F  sp(15).  fo(22)  wo(21)  phl(24)  Standards used f o r s t a u r o l i t e a n a l y s e s . Si  Ti  Al  Fe  • Zn  373  wo(21)  rut(13)  and(26)  fa(104) w i ( l )  82  and(26)  492  and(26)  223  and(26)  en(81)  40  and(26)  en(81)  en(81) 11  en(81)  Table 2-28.  S t a n d a r d used f o r p l a g i o c l a s e a n a l y s e s . Si  Al  Ca  Na  K  Ba  373  ab(20)  angl(32)  angl(32)  ab(20)  or(28)  ben(35)  121  or(28)  ky(4)  wo(21)  367  or(28)  l a b (97)  lab(97)  82  or(28)  and(26)  wo(21)  398  or(28)  and(26)  wo(21)  492  or(28)  and(26)  wo(21)  223  or(28)  and(26)  wo(21)  2-376  or(28)  ky(4)  wo(21)  2-13  ab(20)  angl(32)  angl(32)  "  74  qtz(36)  and(26)  angl(32)  n.a.  59  ab(20)  angl(32)  angl(32)  ben(35)  40  or(28)  and(26)  wo(21)  387  ab(20)  and(26)  wo(21)  219  or(28)  ky(4)  wo(21)  2-375  or(28)  and(26)  wo (21)  II  69  or(28)  an(102)  an(102)  II  20  or(28)  an(102)  an(102)  II  Specimen  i b l e 2-29. Specimen 398  " " " " "  "  "  ii  »  II  "  ir  S t a n d a r d s used f o r K-feldspar analyses. Si  Al  Ca  Na  K  or(28)  an(102)  an(102)  ab(20)  or(28)  Ba ben(35)  2-376  6r(28)  ky(4)  wo (21)  II  2-13  ab(20)  an(102)  an(102)  II  II  II  387  ab(2Q)  and(26)  wo(21)  II  II  II  69  or(28)  an(102)  an(102)  II  ii  II  20  or(28)  an(102)  an(102)  II  ii  II  II  II  Table 2-30. Specimen 373  Standards used f o r i l m e n i t e a n a l y s e s . Ti  Al  Fe  Zn  Mn  Mg  Ca  rut(13)  and(26)  fa(104)  wi(l)  sp(15)  fo(22)  wo(21)  2-375  "  ky(4)  "  n.a.  "  fo(22)  all others  "  and(26)  "  wi(l)  "  en(81)  Table 2-31. Specimen All  Standards used f o r c a l c i t e a n a l y s e s . Ca  Fe  Mn  Mg  cc(76)  si(ll)  rho(88)  dol(10)  to  T a b l e 2-32.  Standards used f o r c a l c i c amphibole a n a l y s e s .  Specimen 224  Si  Ti  Al  Fe  Mn  Mg  Ca  Na  K  wo(21)  rut(13)  and(26)  fa(104)  sp(15)  en(81)  wo(21)  jd(41)  or(28)  "  en(81)  2-375  "  "  ky(4)  494  "  "  ky(4)  "  "  en(81)  20  "  "  and(26)  "  "  en(81)  2-312  "  "  and(26)  "  "  fo(22)  11  F 224  phl(24)  2-375 494 20 2-312 Table 2-33.  Standards used f o r c a l c i c pyroxene a n a l y s e s .  Specimen 224 20 2-312  Si  Ti  Al  Fe  Mn  Mg  Ca  Na  wo(21)  rut(13)  and(26)  fa(104)  sp(15)  fo(22)  wo(21)  jd(41)  " "  "  " 11  " 11  " "  " "  en(81) fo(22)  Table 2-34.  Standards used f o r z o i s i t e a n a l y s e s .  Specimen 387  T a b l e 2- 35.  Si  Ti  Al  Fe  Mn  wo(21)  rut(13)  and(26)  fa(104)  sp(15)  and(26)  II  II  .  • •  Mg  Ca  F  fo(22)  wo(21)  phl(24) 11  en(81)  224  II  . I I  494  II  II  ky(4)  II  II  en(81)  II  II  20  II  II  and(26)  II  II  en(81)  II  II  2-312  II  II  and(26)  II  II  fo(22)  II  II  W ;  Standards used f o r sphene a n a l y s e s . Si  Ti  Al  Fe  Mn  Mg  Ca  Na  F  387  wo(21)  rut(13)  and(26)  fa(104)  sp(15)  fo(22)  wo(21)  jd(41)  phi(24)  2-375  wo(21)  ti  ky(4)  II  II  en(81)  wo(21)  jd(41)  II  494  wo(21)  II  ky(4)  II  II  en(81)  wo(21)  jd(41)  II  20  wo(21)  II  and(26)  ii  II  en(81)  wo(21)  jd(41)  II  2-312  qtz(36)  ii  and(26)  II  II  fo(22)  angl(32)  ab(20)  II  Specimen  T a b l e 2- 36. Specimen 20  Standards used f o r s c a p o l i t e a n a l y s e s .  Si  Al  Ca  Na  K  Ba  or(28)  an(102)  an(102)  ab(20)  or(28)  ben(35)  PLATE  A)  S c h i s t from the s i l l i m a n i t e  and g a r n e t ( G )  2-1  z o n e , Shuswap C o m p l e x .  Staurolite(s)  a r e s u r r o u n d e d by e q u a n t , p o r p h y r o b l a s t i c m u s c o v i t e  fibrolite(m + f).  Inclusion  trails  i n garnet  are  with  straight,  (x-nicols)  B)  S c h i s t from the k y a n i t e - s i l l i m a n i t e  stage garnet  contains  (outer margin) partly  z o n e , Shuswap C o m p l e x .  S-shaped i n c l u s i o n t r a i l s .  Second stage garnet  c o n t a i n s o n l y a few s c a t t e r e d i n c l u s i o n s .  s u r r o u n d e d by p o r p h y r o b l a s t i c m u s c o v i t e - f i b r o l i t e  Kyanite(K)  is  common i n  (x-nicols)  the s c h i s t  matrix,  First  Garnet  rim  is  aggregate(M + F ) .  265  B  PLATE  A)  2-2  Schist from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex.  Quartz  inclusions outline a r e l i c crenulation cleavage i n this large stage one garnet.  Opaque inclusions are continuous with the external PI s c h i s t o s i t y  although rotated r e l a t i v e to i t . F i b r o l i t e aggregates occur i n the lower portion of the photomicrograph, (plane l i g h t )  B)  Schist from the s i l l i m a n i t e zone, Shuswap Complex.  second stage garnets(g) are enclosed by porphyroblastic minor f i b r o l i t e ( m + f ) .  muscovite with  The large muscovite grains have a random  orientation and interlocking grain margins, (x-nicols)  Idioblastic  I mm  B  i  i I mm  PLATE  2-3  S c h i s t from the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex. and s t a u r o l i t e ( s ) are p a r t l y e n c l o s e d by aggregates.  Garnet  fibrolite-muscovite-ilmenite  K y a n i t e ( k ) i s abundant i n the s c h i s t m a t r i x .  Arrow p o i n t s  to a r e a where f i b r o l i t e i s p a r t l y e n c l o s e d by second s t a g e g a r n e t . s t a g e garnet rims a r e e u h e d r a l a g a i n s t the f i b r o l i t e  A)  B)  (plane l i g h t )  (x-nicols)  aggregates.  Second  269  B  Imm  PLATE  Schist  2-4  from the s i l l i m a n i t e zone, Shuswap Complex.  muscovite(M) i s randomly o r i e n t e d i n the s c h i s t m a t r i x .  Porphyroblastic Fibrolite-biotite  aggregates form a t t e n u a t e d w i s p y t r a i l s through the m u s c o v i t e ( a r r o w s ) . R e l i c s t a u r o l i t e ( s ) i s e n c l o s e d by f i b r o l i t e o r m u s c o v i t e .  Arrow i n  second g e n e r a t i o n g a r n e t shows where f i b r o l i t e has been e n c l o s e d by garnet.  A)  B)  (plane l i g h t )  (x-nicols)  271  B  i  i I  m m  PLATE  A)  Coexisting  2-5  c a l c i c amphibole ( a ) , c a l c i c pyroxene ( p ) , q u a r t z ( q ) , and  c a l c i t e ( c ) from a d i s c o n t i n u o u s marble u n i t i n t h e k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex, (plane l i g h t )  B)  Coexisting  m u s c o v i t e (m), q u a r t z ( q ) , and c a l c i t e (c) from a s m a l l  marble u n i t i n the k y a n i t e - s i l l i m a n i t e zone, Shuswap Complex, (x-nicols)  273  B i  J  I mm  274  Rb-Sr Dates f o r G r a n o d i o r i t e I n t r u s i o n s on the N o r t h e a s t M a r g i n of t h e Shuswap Metamorphic  Complex,  Cariboo Mountains, B r i t i s h Columbia*  Lee C. P i g a g e Department of G e o l o g i c a l S c i e n c e s U n i v e r s i t y of B r i t i s h Columbia Vancouver, B.C.  V6T  1W5  Canada  * p u b l i s h e d as a Note i n Canadian J o u r n a l o f E a r t h S c i 14,  1690-1695.  275  ABSTRACT  Whole r o c k Rb-Sr dates of 138 ± 12 Ma  ( a l l f i v e whole r o c k s )  and  163 ± 7 Ma were o b t a i n e d f o r g r a n o d i o r i t e s t o c k s i n W e l l s Gray P r o v i n c i a l Park, Cariboo Mountains, b i o t i t e K-Ar  B r i t i s h Columbia.  date of 143 ± 14 Ma determined  G e o l o g i c a l Survey o f Canada.  These d a t e s b r a c k e t the p r e v i o u s l y by  the  Two b i o t i t e - whole r o c k ± hornblende  of 119 ± 11 Ma and 77 ± 20 Ma i n d i c a t e i s o t o p i c r e s e t t i n g . 8 7  Sr-  8 6  dates  Initial  S r r a t i o s v a r y from 0.7061 ± 0.0001 t o 0.7103 ± 0.0002 f o r r o c k  and m i n e r a l d a t e s . When combined w i t h f i e l d r e l a t i o n s , t h e s e d a t e s r e s t r i c t r e g i o n a l d e f o r m a t i o n and metamorphism i n t h i s a r e a t o the time i n t e r v a l between Upper T r i a s s i c and Upper J u r a s s i c .  The r e s e t t i n g event was  probably  Eocene, as shown i n o t h e r areas a l o n g r e g i o n a l s t r i k e t o t h e n o r t h and south.  276 INTRODUCTION  Metamorphic r o c k s b e l o n g i n g t o the H a d r y n i a n t o lower P a l e o z o i c Kaza and C a r i b o o Groups b o r d e r t h e n o r t h e a s t margin o f t h e Shuswap Metamorphic Complex i n t h e C a r i b o o M o u n t a i n s , B r i t i s h Columbia  (Campbell 1963, 1968).  D e t a i l e d mapping i n W e l l s Gray P r o v i n c i a l P a r k ( F i g . 3-1, 3-2) has o u t l i n e d a complex, p o l y p h a s e h i s t o r y w i t h f o u r d e f o r m a t i o n a l and two metamorphic e p i s o d e s (Pigage  1978).  N o r t h - p l u n g i n g i s o c l i n a l F^ s t r u c t u r e s  are accompanied by a p e r v a s i v e a x i a l p l a n e s c h i s t o s i t y .  F^ minor f o l d s  and a s s o c i a t e d c r e n u l a t i o n c l e a v a g e a r e c o r r e l a t e d w i t h l a r g e s c a l e a n t i c l i n o r i a and s y n c l i n o r i a d e s c r i b e d by S u t h e r l a n d Brown (1963) and Campbell e t a l . (1973). towards  the west.  F  3  These s t r u c t u r e s plunge n o r t h w e s t and v e r g e  and F^ s t r u c t u r e s a r e l o c a l l y d e v e l o p e d as f r a c t u r e s ,  f a u l t s , and a n g u l a r f o l d s w i t h r u p t u r e d h i n g e zones.  These s t r u c t u r e s  t r e n d n o r t h and n o r t h e a s t , r e s p e c t i v e l y . R e g i o n a l metamorphic assemblages r a p i d l y i n c r e a s e from l o w e r g r e e n s c h i s t f a c i e s i n t h e n o r t h e r n p a r t o f F i g . 3-2 t o upper a m p h i b o l i t e f a c i e s a t t h e margin o f t h e Shuswap Complex.  Rotated planar i n c l u s i o n  t r a i l s i n garnet and c h l o r i t o i d i d e n t i f y t h e p e r v a s i v e r e g i o n a l metamorphism as s y n - t o p o s t - F ^ , c o n t i n u i n g i n t o F^.  Fine grained s e r i c i t e - c h l o r i t e  a l t e r a t i o n o f g a r n e t r e p r e s e n t s l a t e r e g r o g r a d e metamorphism.  SCOPE OF STUDY  F i e l d e v i d e n c e c o n f i r m s t h a t g r a n o d i o r i t e s t o c k s i n t h e a r e a were emplaced between d e f o r m a t i o n e v e n t s F  2  and F .  This dates i n t r u s i o n a f t e r  the p e r v a s i v e r e g i o n a l d e f o r m a t i o n and metamorphism.  D a t i n g o f these  F i g u r e 3-1.  Index map  o f s o u t h - c e n t r a l B r i t i s h Columbia.  s t u d y a r e a ( F i g u r e 3-2)  i s outlined.  Shuswap Metamorphic Complex.  Detailed  Ruled a r e a r e p r e s e n t s the  M o d i f i e d from Campbell  (1973).  Figure 3-2.  Geologic sketch map of study area, Wells Gray P r o v i n c i a l  Park, B r i t i s h Columbia. indicated by c i r c l e s .  Samples collected for Rb-Sr dating are Triangle marks location of sample c o l l e c t e d by  the Geological Survey of Canada for K-Ar dating (Wanless e_t a l . 1965) . Geology modified from Pigage (1978) and Campbell (1963, 1968). l i n e s outline permanent snow and i c e f i e l d s .  Dotted  279  intrusions should therefore place a minimum age on the regional ^-y^2 events.  A maximum age for F-^ !^ deformation i s provided by the -  involvement of Upper T r i a s s i c p h y l l i t e s i n a l l of the deformational history (Brown 1968; Campbell 1971). Previous dating of these intrusions consists of a b i o t i t e K-Ar  date  of 143 ± 14 Ma for the largest granodiorite pluton (Wanless et a l . 1965). (Using K-Ar decay constants of Beckinsale and Gale (1969) t h i s date becomes 148 Ma.)  During 1975 I collected several samples (grapefruit-  sized or larger) from offshoots or s a t e l l i t e s of the large stock for Rb-Sr dating.  Sample locations are indicated i n F i g . 3-2 and l i s t e d i n Table  3-1.  Brief notes on samples and a n a l y t i c a l methods are presented i n Appendix 3-1.  RESULTS AND  INTERPRETATION  Table 3-1 l i s t s a n a l y t i c a l results for f i v e whole rock and three mineral separate samples.  Calculated ages and i n i t i a l r a t i o s are  presented i n Table 3-2 and i l l u s t r a t e d i n Figs. 3-3 and Whole rock samples do not l i e on a single isochron.  3-4. Sample AP2  controls the calculated whole rock dates because a l l other samples are 87 clustered near the  86 Sr/  Sr coordinate.  If AP2 i s not considered i n the  calculations, the r e s u l t i n g Paleozoic dates are not consistent with involvement of T r i a s s i c strata i n the F^-F^ events.  When a l l whole rock  samples are included, the calculated errorchron has an i n i t i a l r a t i o of 0.7084 ± 0.0003 with a slope corresponding to a date of 138 ± 12 Ma. errorchron i s probably not v a l i d because the samples come from  This  two  different granodiorite stocks which appear to have s i g n i f i c a n t l y d i f f e r e n t  TABLE 3-1.  Rb-Sr d a t a f o r a l l a n a l y z e d samples.  Sample  Latitude  Longitude  Material  HBL1  52°32.5'  120°05.2'  rock  259  83  0.930  0.7105  hornblende  234  38  0.469  0.7092  10  528  707  94  28  517  Sr (ppm)  biotite GDI  52°33.1'  120°06.3'  rock biotite  Rb (ppm)  8 7  Rb/  8 6  Sr  159 0.386 53.9  ^Sr/  8 6  !  0.8814 0.7110 0.8019  API  52°33.1'  120°06.3'  rock  449  110  0.708  0.7102  GD2  52°33.5'  120°09.7'  rock  1003  91  0.262  0.7067  AP2  52°33.5'  120°09.7'  rock  135  260  5.60  0.7191  NOTE: A n a l y t i c a l e r r o r s : Rb-Sr r a t i o , 2% ( l a ) ; S r / d e s c r i p t i o n s and a n a l y t i c a l methods. 8 7  8 6  S r , 0 .00013 ( l a ) . See A p p e n d i x f o r sample  TABLE 3-2. I n t e r c e p t s and apparent  Samples used i n c a l c u l a t i o n  ages f o r whole r o c k and m i n e r a l s e p a r a t e d a t a l i s t e d i n T a b l e 3-1.  Intercept ± 2  0  ( Sr/ Sr) 8 7  8 6  Apparent age 1 2 a (Ma BP)  Whole r o c k WR1: a l l whole r o c k samples  0.708410.0003  138112  WR2: GD2 and AP2  0.706110.0001  16317  M l : GDl-bt and GDI-rock  0.710310.0002  119111  M2: H B L l - b t , H B L l - h b l , and H B L l - r o c k  0.709110.0013  77120  B i o t i t e - whole r o c k  NOTE: x_. = 1.42 X 10 Rb  1 1  /year.  oo  282  F i g u r e 3-3.  I s o c h r o n diagram f o r b i o t i t e - w h o l e r o c k + h o r n b l e n d e  i s o c h r o n s l i s t e d i n Table  3-2.  R. i s the i n i t i a l l  8 7  Sr- ^Sr 8  ratio.  283  0.720  i  0.715  H  0.710  T  0.705  119  ±11 Ma  0.7103 ± 0 . 0 0 0 2  77  ±20  0.7091 ±  WR  163  ± 7 Ma  WR2  l38±l2Ma  Ma  0.7061 ± 0.0001 0.7084  8 7  0.700  F i g u r e 3-4.  Rb/  8 6  ±0.0003  Sr  - 1 —  —I 0.0  4.0  2.0  are i n d i c a t e d w i t h t r i a n g l e s .  8.0  6.0  D e t a i l o f a r e a shown i n F i g u r e 3-3.  Mineral separate points  C i r c l e s i n d i c a t e whole r o c k p o i n t s .  S o l i d l i n e s a r e b i o t i t e - w h o l e rock + h o r n b l e n d e d a t e s . are whole rock c a l c u l a t e d  0.0013  dates.  Dashed l i n e s  284 initial  87 S r - 86 Sr r a t i o s .  The two p o i n t i s o c h r o n f o r samples GD2  and  has an i n t e r c e p t of 0.7061 ± 0.0001 and a s l o p e c o r r e s p o n d i n g t o an of 163 ± 7 Ma.  AP2  age  T h i s d a t e i s p r o b a b l y more r e p r e s e n t a t i v e because the  samples were c o l l e c t e d from t h e same l o c a t i o n .  These two whole r o c k d a t e s  b r a c k e t the K-Ar d a t e determined by the G e o l o g i c a l Survey o f Canada. V a r i a b i l i t y o f i n i t i a l r a t i o s i s l i k e l y the r e s u l t of u n e q u a l  assimilation  of s m a l l amounts o f r a d i o g e n i c S r - r i c h c o u n t r y r o c k . B i o t i t e - whole r o c k ± hornblende i s o c h r o n s a r e i n d i c a t e d by l i n e s i n F i g s . 3-3 and 3-4.  solid  The younger dates (119 ± 11 Ma and 77 ± 20  i n d i c a t e p o s t - i n t r u s i o n d i s t u r b a n c e of Rb-Sr.  Ma)  The 77 ± 20 Ma d a t e i s a  maximum age f o r e i t h e r the event c a u s i n g i s o t o p i c r e s e t t i n g o r the time of f i n a l c o o l i n g below the t h r e s h o l d temperature f o r Rb or Sr m i g r a t i o n . S e v e r a l workers f u r t h e r s o u t h i n the Shuswap Complex have r e c o g n i z e d the presence of an Eocene t h e r m a l event t h a t caused r e s e t t i n g of and Rb-Sr d a t e s (Ryan 1973; Medford 1975).  K-Ar  Recent s t u d i e s f u r t h e r n o r t h  have a l s o produced T e r t i a r y d a t e s ( P a r r i s h 1976).  The younger m i n e r a l  dates from W e l l s Gray P a r k suggest t h a t t h i s same event may have p a r t i a l l y r e s e t i s o t o p i c ages.  A maximum age o f 77 ± 20 Ma f o r r e s e t t i n g i s  c o m p a t i b l e w i t h the 40-50 Ma d a t e s encountered t o the n o r t h and s o u t h .  CONCLUSIONS  A whole r o c k Rb-Sr date of 163 ± 7 Ma f o r a g r a n o d i o r i t e - a p l i t e p a i r from W e l l s Gray P r o v i n c i a l P a r k i s o n l y s l i g h t l y o l d e r t h a n a p r e v i o u s K-Ar date (143 ± 14 Ma) o b t a i n e d from t h e same s u i t e o f intrusions.  When combined w i t h f i e l d r e l a t i o n s , t h e s e d a t e s c o n s t r a i n the  r e g i o n a l F' -F 1  9  d e f o r m a t i o n and metamorphism t o the time i n t e r v a l between  285 Upper T r i a s s i c and Upper J u r a s s i c . B i o t i t e Rb-Sr d a t e s a r e younger than t h e whole r o c k d a t e s .  In other  areas t o t h e n o r t h and s o u t h  s i m i l a r d i s t u r b e d d a t e s have been a t t r i b u t e d  to an  The HBL1 b i o t i t e age (77 ± 20 Ma) i s  Eocene t h e r m a l event.  consistent with t h i s  interpretation.  ACKNOWLEDGEMENTS  D u r i n g t h i s s t u d y I was supported by an INCO ( I n t e r n a t i o n a l N i c k e l Company) graduate r e s e a r c h f e l l o w s h i p . NRCC ( N a t i o n a l Research  F i e l d expenses were d e f r a y e d  by  C o u n c i l o f Canada) grant 67-4222 t o H.J. Greenwood.  A n a l y t i c a l work was s u p p o r t e d i n p a r t by NRCC g r a n t 67-8841 t o R.L. Armstrong.  Ms. K. S c o t t h e l p e d g r e a t l y w i t h l a b t e c h n i q u e s and q u i r k s o f  the mass s p e c t r o m e t e r .  D i s c u s s i o n s w i t h B. Ryan and R.L. Armstrong  sharpened my i d e a s c o n c e r n i n g r a d i o m e t r i c age d a t i n g .  286 SELECTED REFERENCES  BECKINSALE, R.D. and GALE, N.H. 1969. A reappraisal of the decay constants and branching r a t i o of ^K. Earth and Planetary Science Letters, 6, pp. 289-294. BROWN, A. 1968. McBride area (93H), B r i t i s h Columbia, s t r u c t u r a l study. Geological Survey of Canada, Paper 68-1, part A, pp. 20-21. CAMPBELL, K.V. 1971. Metamorphic petrology and s t r u c t u r a l geology of the Crooked Lake area, Cariboo Mountains, B r i t i s h Columbia. PhD thesis, University of Washington, Seattle, WA, 192p. CAMPBELL, R.B. 1963. Quesnel Lake (east h a l f ) B r i t i s h Columbia. Geological Survey of Canada, Map 1-1963. . 1968. Canoe River, B r i t i s h Columbia. of Canada, Map 15-1967.  Geological Survey  . 1973. Structural cross-section and tectonic model of the southeastern Canadian C o r d i l l e r a . Canadian Journal of Earth Sciences, 10, pp. 1607-1620. CAMPBELL, R.B., MOUNTJOY, E.W., and YOUNG, F.G. 1973. Geology of McBride map-area, B r i t i s h Columbia. Geological Survey of Canada, Paper 72-35. 104p. HUSTER, E. 1974. The h a l f - l i f e of natural R b measured as difference between the isotopes of and 85jfo (abstract). International Meeting for Geochronology, Cosmochronology, and Isotope Geology. Paris, France, August 1974. 87  McINTYRE, G.A. , BROOKS, C , COMPSTON, W., and TUREK, A. 1966. The s t a t i s t i c a l assessment of Rb-Sr isochrons. Journal of Geophysical Research, 71, pp. 5459-5468. MEDFORD, G.A. 1975. K-Ar and f i s s i o n track geochronometry of an Eocene thermal event i n the Kettle River (west h a l f ) map area, southern B r i t i s h Columbia. Canadian Journal of Earth Sciences, 12, pp. 836-843. PARRISH, R.A. 1976. Geology and geochronology of the Wolverine Metamorphic Complex near Chase Mountain, Aiken Lake map area, B r i t i s h Columbia. MSc thesis, University of B r i t i s h Columbia, Vancouver, B.C. PIGAGE, L.C. 1978. Metamorphism and deformation on the northeast margin of the Shuswap Metamorphic Complex, Azure Lake, B r i t i s h Columbia. PhD thesis, University of B r i t i s h Columbia, Vancouver, B.C.  287 RYAN, B.D. 1973. Geology and Rb-Sr geochronology o f t h e A n a r c h i s t Mountain a r e a s o u t h c e n t r a l B r i t i s h Columbia. PhD t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B.C. 256p. SUTHERLAND BROWN, A. 1963. Geology o f t h e C a r i b o o R i v e r a r e a , B r i t i s h Columbia. B r i t i s h Columbia Department o f Mines and P e t r o l e u m R e s o u r c e s , B u l l e t i n 47, 60 p. WANLESS, R.K., STEVENS, R.D., LACHANCE, G.R., and RIMSAITE, R.Y.H. 1965. Age d e t e r m i n a t i o n s and g e o l o g i c a l s t u d i e s . G e o l o g i c a l Survey o f Canada, Paper 64-17, p a r t 1. pp. 15-16. YORK, D. 1969. L e a s t squares f i t t i n g o f a s t r a i g h t l i n e w i t h c o r r e l a t e d e r r o r s . E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , 5, pp. 320-324.  288 APPENDIX Analytical  3-1  Methods  Rb and Sr c o n c e n t r a t i o n s were determined by X - r a y f l u o r e s c e n c e u s i n g U n i t e d S t a t e s G e o l o g i c a l Survey (USGS) s t a n d a r d s  for  calibration.  R e p l i c a t e a n a l y s e s i n d i c a t e t h a t Rb-Sr r a t i o s have a p r e c i s i o n o f 2% ( l a ) . Sr i s o t o p e d a t a were measured on a s o l i d - s o u r c e mass s p e c t r o m e t e r N a t i o n a l Bureau of S t a n d a r d s (NBS) c o l l e c t i o n and r e d u c t i o n .  S r C 0 , SRM 3  987  to a  and  86 Sr-  Sr r a t i o of 0.71022 f o r NBS  standard  ( t h i s i s e q u i v a l e n t t o a v a l u e of 0.7080 f o r the Eimer 87  Amend Sr i s o t o p e s t a n d a r d ) .  U.S.  design w i t h o n - l i n e d i g i t a l data  E x p e r i m e n t a l measurements were n o r m a l i z e d 87  adjusted to correspond  of  The p r e c i s i o n of a s i n g l e  and  86 Sr-  Sr  measurement i s 0.00013 ( l a ) . Slopes and e r r o r s o f i s o c h r o n s were computed u s i n g the p r o c e d u r e o f M c l n t y r e e t a l . (1966) f o r f i t s w i t h more than two p o i n t s . i s o c h r o n s were computed u s i n g the method o f Y o r k (1969). have 95% c o n f i d e n c e l i m i t s . c o n s t a n t o f 1.42  X 10  - 1 1  Two  Isochron e r r o r s  Dates r e p o r t e d a r e based on a Rb  /year  point  decay  (Huster 1974).  Petrographic Descriptions HBL1  - Medium-grained  Hornblendite  P o i k i l i t i c h o r n b l e n d e (70%) e n c l o s e s a l l o t h e r m i n e r a l s . i s zoned w i t h brown c o r e s and b l u e - g r e e n commonly i n t e r s t i t i a l . ( 2 % ) , and opaques ( 5 % ) .  rims.  Biotite  (20%) i s  A c c e s s o r y m i n e r a l s i n c l u d e sphene ( 3 % ) , a p a t i t e Sphene i s t y p i c a l l y a s s o c i a t e d w i t h the opaques.  GDI - Medium-grained H o r n b l e n d e - B i o t i t e Quartz Subhedral  Hornblende  Diorite  p l a g i o c l a s e (67%) occurs w i t h l e s s e r amounts of q u a r t z  h o r n b l e n d e ( 8 % ) , and b i o t i t e  (7%).  P l a g i o c l a s e t y p i c a l l y has  complex  (15%),  289 t w i n n i n g and c o n c e n t r i c normal z o n i n g ( A n ^ - A ^ ^ ) . interstitial  clots.  E p i d o t e (3%) w i t h brown p l e o c h r o i c c o r e s and  rims i s i n t e r g r o w n w i t h b i o t i t e and h o r n b l e n d e . interstitial  grains.  clear  Quartz forms a n h e d r a l ,  S e r i c i t e a l t e r a t i o n of p l a g i o c l a s e i s minor;  c h l o r i t e a l t e r a t i o n i s not p r e s e n t . a p a t i t e , z i r c o n , and  M a f i c m i n e r a l s form  A c c e s s o r y m i n e r a l s i n c l u d e sphene,  opaques.  API - F i n e - g r a i n e d A p l i t e Equant, a n h e d r a l q u a r t z (30%) and p l a g i o c l a s e (55%) a r e the major minerals.  Myrmekite i s a s s o c i a t e d w i t h minor m i c r o c l i n e ( 1 0 % ) .  m i n e r a l s p r e s e n t a r e g a r n e t , e p i d o t e , and opaques. intergrown w i t h vermicular quartz.  Other  E p i d o t e i s commonly  P l a g i o c l a s e i s l o c a l l y a l t e r e d to  sericite. GD2  - Medium-grained B i o t i t e G r a n o d i o r i t e  S u b h e d r a l p l a g i o c l a s e l a t h s (45%) are l o c a l l y r e p l a c e d by s e r i c i t e epidote.  A vague c o n c e n t r i c z o n i n g i s e v i d e n t i n p l a g i o c l a s e .  amounts o f q u a r t z ( 3 0 % ) , m i c r o c l i n e ( 1 0 % ) , b i o t i t e form a n h e d r a l , i n t e r s t i t i a l g r a i n s . sphene, t o u r m a l i n e , and  and  Smaller  ( 5 % ) , and e p i d o t e  (5%)  Accessory minerals i n c l u d e garnet,  zircon.  AP2 - F i n e - g r a i n e d A p l i t e Equant, a n h e d r a l q u a r t z ( 3 0 % ) , p l a g i o c l a s e ( 3 5 % ) , and m i c r o c l i n e (30%) are the major m i n e r a l s .  P l a g i o c l a s e and m i c r o c l i n e show a n t i p e r t h i t i c  and p e r t h i t i c t e x t u r e s , r e s p e c t i v e l y .  A slight s e r i c i t e dusting i s  c o n s i s t e n t l y present i n p l a g i o c l a s e . Minor minerals i n c l u d e muscovite ( 2 % ) , e p i d o t e ( 3 % ) , and g a r n e t .  Epidote t y p i c a l l y contains vermicular quartz.  

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