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Geology of the guano-guayes rare earth element bearing Skarn property, Pelly Mountains, Yukon Territory Chronic, Felicie Jane 1979

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GEOLOGY OF THE GUANO-GUAYES  RARE EARTH ELEMENT BEARING SKARN PROPERTY  PELLY MOUNTAINS, YUKON TERRITORY by F e l i c i e Jane C h r o n i c B . A ; . w i t h d i s t i n c t i o n , The U n i v e r s i t y o f C o l o r a d o A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES THE 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 t o t h e r e q u i r e d s t a n d a r d The U n i v e r s i t y o f B r i t i s h C o lumbia May, 1979 © F e l i c i e Jane C h r o n i c , 1979 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 W e s b r o o k P l a c e V a n c o u v e r , C a n a d a V6T 1W5 D E - 6 B P 7 5 - 5 1 1 E i i The Guano-Guayes Area Viewed from the North A b s t r a c t The Guano-Guayes p r o p e r t y , i n t h e P e l l y M o u n t a i n s o f t h e Yukon T e r r i -t o r y , c o v e r s a r a r e e a r t h element (REE) b e a r i n g c o n t a c t metamorphic a u r e o l e w h i c h d e v e l o p e d around a s y e n i t e s t o c k d u r i n g M i s s i s s i p p i a n t i m e (319 + 10 Ma p h l o g o p i t e K-Ar d a t e , 333 + 10 Ma Rb-Sr s k a r n m i n e r a l i s o c h r o n ) . S e d i -mentary r o c k s c o n s i s t o f s e v e r a l hundred metres o f O r d o v i c i a n d a r k g r a y s h a l e w h i c h a r e f a u l t e d upward a d j a c e n t to 450 m o f S i l u r i a n i n t e r b e d d e d impure c a l c i t e and d o l o m i t e m a r b l e s and q u a r t z i t e s o v e r l a i n by a t l e a s t 500 m o f S i l u r a i n q u a r t z i t e . S e d i m e n t a r y r o c k s a r e on the s t e e p l y , w e s t - d i p p i n g l i m b o f a r e g i o n a l a n t i c l i n e ( t h e a x i s b e a r s 162 degrees and p l u n g e s 24 de-gre e s s o u t h ) . The s y e n i t e , a t t h e s o u t h e a s t end o f a n o r t h w e s t - t r e n d i n g b e l t o f s y e n i t e s t o c k s and a s s o c i a t e d v o l c a n i c r o c k s , c o n s i s t s o f 40 t o 90 p e r c e n t o r t h o c l a s e i n l a t h s up t o s e v e r a l cm l o n g , and o f up to 60 p e r c e n t m a f i c m i n e r a l s now m o s t l y a l t e r e d to b i o t i t e . R are e a r t h element v a l u e s o f s y e n i t e , when n o r m a l i z e d to c h o n d r i t i c v a l u e s , have a c r u s t a l p a t t e r n w i t h magnitude s l i g h t l y h i g h e r t h a n t h a t o f c r u s t a l r o c k s . D i k e s , b e l i e v e d to be c o g e n e t i c w i t h s y e n i t e , i n t r u d e s e d i m e n t a r y r o c k s w i t h i n and inear t h e co n -t a c t metamorphic a u r e o l e . These d i k e s a r e d a r k - c o l o u r e d and o r i g i n a l l y c o n t a i n e d up to 25 p e r c e n t z i r c o n (now p a r t l y a l t e r e d to s e c o n d a r y m i n e r a l s ) . Z i r c o n i s e n r i c h e d i n t o t a l REE and r e l a t i v e l y e n r i c h e d i n l i g h t REE com-pa r e d to s y e n i t e , p r o b a b l y due to s e l e c t i v e p a r t i t i o n i n g o f REE. REE p a t -t e r n s i n s k a r n and s e d i m e n t a r y r o c k s s u g g e s t t h a t f l u i d s c i r c u l a t e d t h r o u g h s y e n i t e and c a r r i e d t r a c e amounts o f REE fr o m i t i n t o t he s k a r n . There was no s i g n i f i c a n t movement o f REE fr o m d i k e s i n t o s k a r n o r s e d i m e n t a r y r o c k s . i i i i v C o n t a c t metamorphic r o c k s c a n be d i v i d e d i n t o t h r e e u n i t s : q u a r t z -m u s c o v i t e h o r n f e l s , d a r k g r e e n d i o p s a d e - c a l c i t e - p h l o g o p i t e - t r e m d l i t e - s p h e n e s k a r n , and l i g h t g r e e n d i o p s i d e - c a l c i t e - p h l o g o p i t e s k a r n . Depth a t t i m e o f i n t r u s i o n o f s y e n i t e , as e s t i m a t e d from r e g i o n a l g e o l o g i c c o n t r a i n t s , was around 1 t o 2 km ( c i r c a 500 b a r s ) . Parageneses and t e x t u r e s o b s e r v e d i n t h i n s e c t i o n i n c o n t a c t metamorphic r o c k s i n d i c a t e t h a t p r o g r a d e metamor-phism a t t h i s p r e s s u r e r e a c h e d a maximum t e m p e r a t u r e o f 450 to 540 degrees C, w i t h h e a t b e i n g t r a n s f e r r e d f r o m t h e i n t r u s i v e d o m i n a n t l y by f l u i d s . The mole f r a c t i o n o f C ^ i n metamorphic f l u i d s , i n c r e a s e d By t h e l i b e r a t i o n o f CT>2 d u r i n g p r o g r a d e metamorphic r e a c t i o n s , was moderate. L a r g e amounts o f Fe, Mg, and p o s s i b l y S i 0 2 , were added to t h e s k a r n . R e t r o g r a d e meta-morphism i n v o l v e d s i g n i f i c a n t a d d i t i o n o f w a t e r t o t h e system, p r o v e n by t h e appearance o f s e c o n d a r y e p i d o t e , c h l o r i t e , and, l a t e r , s e r p e n t i n e . Ex ten-: . s i v e r e t r o g r a d e metamorphism accompanied by l a r g e - s c a l e m i g r a t i o n o f e l e - : ments t h r o u g h s y e n i t e ended 206 +15 Ma ago ( s y e n i t e w h o l e - r o c k i s o c h r o n ) and the l a s t r e s e t t i n g event t o o k p l a c e between 156 + 5 Ma (K-Ar d a t e on b i o t i t e - a l t e r e d a r f v e d s o n i t e ) and 128 + 25 Ma ( s y e n i t e m i n e r a l i s o c h r o n ) . P e t r o l o g y , geochronometry, and r a r e e a r t h element s t u d i e s p r e s e n t e d h e r e have c o n t r i b u t e d to an u n d e r s t a n d i n g o f t h e g e n e s i s o f s y e n i t e , s k a r n , and m i n e r a l i z e d d i k e s w i t h i n t h e Guano-Guayes a r e a . TABLE OF CONTENTS CHAPTER 1 : INTRODUCTION 1 1.1 THE GUANO-GUAYES PROPERTY 1 1.2 LOCATION, CLIMATE, AND PHYSIOGRAPHY 1 1.3 SCOPE OF THESIS 1 CHAPTER 2 : REGIONAL GEOLOGY 4 CHAPTER 3 : STRUCTURAL GEOLOGY OF THE,GUANO-GUAYES AREA 6 3.1 INTRODUCTION " 6 3.2 STRUCTURAL DATA 6 3.2.1 B e d d i n g 6 3.2.2 F r a c t u r e s 10 3.2.3 F a u l t i n g and B r e c c i a t i o n 10 3.3 SUMMARY AND INTERPRETATION OF STRUCTURE 12 CHAPTER 4 : DETAILED PETROLOGY OF THE GUANO-GUAYES AREA 15 4.1 INTRODUCTION 15 4.2 SEDIMENTARY PETROLOGY 15 4.2.1 S t r a t i g r a p h y 15 4.2.2 S t r a t i g r a p h i c C o r r e l a t i o n 19 4.3 IGNEOUS PETROLOGY 22 4.3.1 U n i t 16 : S y e n i t e 22 4.3.2 U n i t 17a : M e l a g r a n i t e D i k e s 25 4.3.3 U n i t 17b : M a f i c D i k e s 29 4.3.4 Whole Rock A n a l y s e s o f Igneous Rocks 33 4.3.5 R e l a t i o n s Between S y e n i t e and D i k e s 33 v v i 4.4 VEINS 34 4.5 CONTACT METAMORPHISM 37 4.5.1 Introduction 37 A . • " . ': 4-5LIII Unit A : Banded quartz-muscovite-hornfels 40 4.5.1.2 Unit B. : Dark green diopside-phlogopite-calcite-tremolite- 42 sphene skarn with rare garnet 4.5.1.3 Unit C : Pale green diopside-phlogopite-calcite skarn 51 4.5.2 Conditions of Metamorphism 53 CHAPTER 5 : GEOCHRONOMETRY OF THE GUANO-GUAYES PROPERTY 63 5.1 INTRODUCTION AND DATA 63 5.2 DISCUSSION 63 5.3 SUMMARY OF GEOCHRONOMETRY 67 CHAPTER 6 RARE EARTH ELEMENT DISTRIBUTION ON THE GUANO-GUAYES PROPERTY 6.1 INTRODUCTION 6.2 CHEMISTRY OF RARE EARTH: ELEMENTS 6.3 GEOCHEMISTRY OF RARE EARTH ELEMENTS 6,'4 RARE EARTH ELEMENTS OF TH'E GUANO-GUAYES PROPERTY 6.4.1 Introduction 6.4.2 Rose's F i e l d Test for Rare Earth Elements 6.4.3 Neutron A c t i v a t i o n Analyses f o r Rare Earth Elements 6.4.3.1 Introduction 6.4.3.2 Analysis of data 6.4.3.3 Conclusions CHAPTER 7 : CONCLUSIONS 88 . " ;•- Bibliography 93 Appendices Appendix A: Petrography • '; 97 68 68 68 72 77 77 78 78 78 78 86 v i i A l : T h i n S e c t i o n Modes o f R e c r y s t a l l i z e d S e d i m e n t a r y Rocks A2: T h i n S e c t i o n Modes of U n i t 16, S y e n i t e A3: T h i n S e c t i o n Modes o f U n i t 17a, M e l a g r a n i t e D i k e s , and U n i t 17b, M a f i c D i k e s A4: T h i n S e c t i o n Modes o f U n i t A, Q u a r t z - M u s c o v i t e H o r n f e l s A5: T h i n S e c t i o n Modes o f U n i t B,°Skarn A6: T h i n S e c t i o n Modes of U n i t C, S k a r n A7: P e t r o g r a p h i c P r o p e r t i e s o f Z i r c o n , A l l a n i t e , M o n a z i t e , M i n e r a l A, M i n e r a l B, and M i n e r a l C Observed i n Guano-Guayes A r e a Rocks A8: A n a l y s e s o f t h e C o m p o s i t i o n o f P h l o g o p i t e and G a r n e t A p p e n d i x B: C h e m i c a l A n a l y s e s ^ B l : A n a l y t i c a l D a t a and Method f o r Whole-Rock A n a l y s e s B2: A n a l y t i c a l D a t a and Method f o r N i c k e l A n a l y s e s B3: A n a l y t i c a l Method f o r Rare E a r t h Element A n a l y s e s and Comparison o f Rock-Type REE-Groups A p p e n d i x C: Geochronometry C I : Rb-Sr A n a l y t i c a l T e c h n i q u e and Data C2: K-Ar A n a l y t i c a l T e c h n i q u e and Data v i i f i L I S T OF TABLES 4.1 R e l a t i v e t i m e and t e c t o n i s m v e r s u s m i n e r a l growth f o r 39 Guano-Guayes a r e a i n t r u s i v e r o c k s , c o n t a c t metamorphic r o c k s , and v e i n s 5.1 Rb-Sr and K-Ar d a t e s o f r o c k samples from t h e Guano- 66 Guayes a r e a 6.1 S t a n d a r d REE v a l u e s i n ppm 74 6.2 Rare e a r t h element v a l u e s i n ppm and r e s u l t s o f f i e l d n 80 t e s t s f o r Guano-Guayes a r e a r o c k samples i x LIST OF FIGURES 1.1 Map showing the l o c a t i o n of the Guano-Guayes area i n 2 the Yukon T e r r i t o r y and the area mapped 2.1 Geologic s e t t i n g of the Guano-Guayes area 5 3.1 P i diagrams of geological structures, Guano-Guayes 7 area 4.1 Measured section of sedimentary rocks of the Guano- 16 Guayes area 4.2 Restored section across the P e l l y - C a s s i a r Platform 21 near the Guano-Guayes area 4.3 Stereogram of poles to dikes and veins 26 4.4 Pressure-temperature diagram for reactions involving 57 the observed parageneses serpentine + diopside and muscovite + quartz 4.5 T-X diagram at 500 bars f o r reactions involving 58 2 the observed paragenesis c a l c i t e + diopside + phlogo-p i t e + tremolite + sphene 5.1 Location map for samples used for geochronometry, 64 Guano-Guayes area 5.2 Rb-Sr isochrons of rocks from the Guano-Guayes area 65 6.1 Periodic chart of the elements 69 6.2 Comparison of r e s u l t s from f i e l d tests and neutron 79 a c t i v a t i o n analyses for REE 6.3 REE patterns for Guano-Guayes rock groups normalized 83 to chondritic meteorites 6.4 REE patterns for standard REE values normalized to 84 chondrites 7.1 Diagrammatic model of the formation of the Guano- 90 Guayes skarn X L I S T OF PLATES '•;<•. '.iThe Guano-Guayes A r e a Viewed from the N o r t h i i 3.1 S e d i m e n t a r y . b e d d i n g s t y l e and o s c i l l a t i o n 8 r i p p l e marks 3.2 B a n d i n g i n c o n t a c t metamorphic r o c k s 9 3.3 S h e a r i n g and b r e c c i a t i o n o b s e r v e d i n c o n t a c t 11 metamorphic r o c k s 3.4 F a u l t on t h e e a s t e r n s i d e o f t h e f i e l d a r e a 13 4.1 X e n o l i t h o f U n i t A, h o r n f e l s , e n c l o s e d i n 20 U n i t 16, s y e n i t e 4.2 Hand specimens o f U n i t 16, s y e n i t e 23 4.3 P h o t o m i c r o g r a p h s o f t h i n s e c t i o n s o f U n i t 16, 24 s y e n i t e 4.4 U n i t 17a, m e l a g r a n i t e d i k e s , i n t h e f i e l d 27 4.5 Hand specimens o f U n i t 17a, m e l a g r a n i t e d i k e s 28 4.6 P h o t o m i c r o g r a p h s o f t h i n s e c t i o n s o f U n i t 17a, 30 m e l a g r a n i t e d i k e s 4.7 Pseudomorphs a f t e r z i r c o n i n U n i t 17a, m e l a - 31 g r a n i t e d i k e s 4.8 U n i t 17b, m a f i c d i k e s , i n o u t c r o p and i n t h i n 32 s e c t i o n 4.9 F l u o r i t e - q u a r t z - m i c r o c l i n e - c a l c i t e v e i n s i n 35 hand s p e c i m e n and i n t h i n s e c t i o n 4.10 C a l c i t e - e p i d o t e - a c t i n o l i t e - q u a r t z v e i n s i n t h e 36 f i e l d and i n hand specimen 4.11 Q u a r t z - s i d e r i t e - d o l o m i t e v e i n s i n the f i e l d and 38 i n hand specimen 4.12 U n i t A, q u a r t z - m u s c o v i t e h o r n f e l s , i n t h i n 41 s e c t i o n x i 4.13 U n i t B, s k a r n , i n o u t c r o p 4.14 P h o t o m i c r o g r a p h s o f s k a r n U n i t B and c a l c i t e i n s k a r n U n i t B 4.15 P h o t o m i c r o g r a p h s d f p h l o g o p i t e , t r e m o l i t e , d i o p s i d e and c a l c i t e i n U n i t B s k a r n 4.16 G a r n e t f r o m U n i t B s k a r n i n hand specimen and i n t h i n s e c t i o n 4.17 R e t r o g r a d e a l t e r a t i o n i n s k a r n U n i t B 4.18 S k a r n U n i t B a f t e r l a t e - s t a g e s e r p e n t i n i z a -t i o n J 4.19 S k a r n U n i t C i n hand specimen and i n t h i n s e c t i o n 4.20 P h o t o m i c r o g r a p h s o f s k a r n U n i t C s e r p e n t i n e , d i o p s i d e , c a l c i t e , p h l o g o p i t e , and c h l o r i t e 4.21 P o o r c r o s s - f i b e r c h r y s o t i l e f i l l i n g s u b h o r i z o n t a l f r a c t u r e s i n s k a r n U n i t C x i i Acknowledgements I am g r a t e f u l to many p e o p l e f o r t h e i r generous a i d f o r and i n t e r e s t i n t h i s s t u d y o f t h e Guano-Guayes p r o p e r t y : Ab O l i v e r and Doug C r a i g o f t h e Department o f I n d i a n A f f a i r s and N o r t h e r n Development a p p r o v e d f u n d i n g f o r t h e t h e s i s and f o r a t a l k on t h e a r e a a t t h e N o r t h w e s t M i n i n g C o n f e r e n c e , 1977; they v i s i t e d t h e p r o p e r t y d u r i n g the f i e l d s e a s o n o f 1977. J i m M o r i n o f DIAND a l s o v i s i t e d the p r o p e r t y and t o g e t h e r we l o o k e d a t a number o f s y e n i t e b o d i e s i n t h e r e g i o n . A r c h e r - C a t h r o and A s s o c i a t e s L t d . s u p p o r t e d my f i e l d work g e n e r o u s l y and p r o v i d e d v e r y h e l p f u l i n s i g h t d u r i n g o u r d i s -c u s s i o n s o f t h e a r e a . Dr. C. I . Godwin o f The .''.University o f B r i t i s h Colum-b i a d i d and e x c e l l e n t j o b o f s u p e r v i s i n g my r e s e a r c h and w r i t i n g . Dr. K. C. M c Taggart, Dr. R. L. A r m s t r o n g , and Dr. H, J . Greenwood each r e a d and c r i t i -c i s e d p a r t s o f t h e m a n u s c r i p t . I r e n e M c l n t y r e , Graeme M c L a r e n , P a u l e t t e Bond, Kim C a r s w e l l , and J o a n Carne s u p p l i e d a g r e a t d e a l o f energy towards t h e c o m p l e t i o n o f t h e f i n a l copy o f t h e t h e s i s . To a l l t h e s e p e o p l e and to many o t h e r s who h e l p e d my work a t The U n i v e r s i t y o f B r i t i s h C olumbia I ex-t e n d my t h a n k s . CHAPTER 1: INTRODUCTION 1.1 THE GUANO-GUAYES PROPERTY M i n e r a l c l a i m s Guano 1 t h r o u g h 22 and Guayes 23 t h r o u g h 30 were s t a k e d d u r i n g t h e summer o f 1976 by A r c h e r - C a t h r o and A s s o c i a t e s L t d . f o r Ukon J o i n t V e n t u r e . S t a k i n g was based on t h e o c c u r r e n c e o f up t o a few p e r c e n t r a r e e a r t h o x i d e s i n s e v e r a l samples f r o m w i t h i n s k a r n w h i c h had formed n e a r t h e c o n t a c t between a s y e n i t e i n t r u s i v e and a s e c t i o n o f c a r b o n a t e and q u a r t z i t e r o c k s . I t was hoped t h a t a f o l l o w - u p s t u d y o f t h e r a r e e a r t h e l e m e n t (REE)"'' c o n c e n t r a t i o n and t h e g e o l o g y m i g h t l e a d t o d i s c o v e r y o f an u r a n i u m d e p o s i t s i m i l a r t o t h e M a r y - K a t h l e e n s karn-REE-uranium p r o p e r t y i n A u s t r a l i a ( W h i t t l e , 1 9 6 0 ) . 1.2 LOCATION, CLIMATE, AND PHYSIOGRAPHY The Guano and Guayes c l a i m s , c c e r i t r e d l a t l a t i t u d e 60°30' n o r t h and l o n g i t u d e 132°25" west a r e 50 km due s o u t h o f Ross R i v e r i n t h e Yukon T e r r i -t o r y . They-are i n t h e S a i n t Cyr Range o f t h e P e l l y M o u n t a i n s a t an e l e v a t i o n o f 1600 t o 2000 m (5000 t o 6000 f e e t ) above s e a l e v e l ( F i g . 1.1). The a r e a has been g l a c i a t e d and i s cc-erit-redl o v e r t h r e e c i r q u e s and t h e i r a s s o c i a t e d r i d g e s . C l a i m s and names f o r t o p o g r a p h i c f e a t u r e s t h a t a r e used" i n t h e t e x t a r e shown i n F i g . 1.1. Most o f t h e f i e l d a r e a i s above t i m b e r l i n e w h i c h i s n e a r 1700 m (5200 f e e t ) . About 25 p e r c e n t o f the a r e a i s o u t c r o p ; t h e r e s t i s e i t h e r t a l u s o r g r a s s y a l p i n e s l o p e s . i : 3 SCOPE OF THE THESIS I n November o f 1976 a p r o p o s a l was made t o D. C r a i g of t h e Department o f I n d i a n and N o r t h e r n Development, W h i t e h o r s e , f o r f u n d i n g o f a g e o l o g i c a l 1. "REE" i s used as an a b b r e v i a t i o n f o r " r a r e e a r t h e l e m e n t s . " 2 CONTOUR INTERVAL 100m 250m F i g . 1.1 Map showing the l o c a t i o n of the Guano-Guayes area i n the Yukon T e r r i t o r y and the area mapped, i n c l u d i n g topography, topographic names used i n the text, and claim l i n e s . s t u d y o f t h e c l a i m groups as th e y a r e t h e f i r s t known d i s c o v e r y o f a concen-t r a t i o n o f r a r e e a r t h e lements i n t h e Yukon T e r r i t o r y . The g o a l s o f t h e s t u d y were t o d e s c r i b e t h e R E E - b e a r i n g s k a r n , t o e v a l u a t e t h e . a r e a ' s ' e c o n o m i c i m p o r t a n c e w i t h r e s p e c t t o b o t h REE and::uranium p o t e n t i a l , and t o d e t e r m i n e t h e mode of f o r m a t i o n o f the s k a r n as c l o s e l y as p o s s i b l e . F i e l d work a t t h e c l a i m s l a s t e d f r o m J u l y 2 7 t h t h r o u g h September 1 s t , 1977. Work i n c l u d e d c o n s t r u c t i o n o f a t o p o g r a p h i c - c o n t o u r map, g e o l o g i c a l mapping, and t e s t i n g o f samples f o r REE u s i n g t h e f i e l d t e s t o f Rose ( 1 9 7 6 ) . D u r i n g t h e w i n t e r s o f 1977-78 and 1978-79 s e v e r a l d i f f e r e n t l a b o r a t o r y s t u d i e s were c o m p l e t e d on samples from t h e a r e a . N e u t r o n a c t i v a t i o n a n a l -y s e s o f n i n e REE were done on each o f 40 r o c k s by R.G.V. Hancock a t t h e SLOWPOKE F a c i l i t y , The U n i v e r s i t y o f T o r o n t o , O n t a r i o . O t h e r l a b o r a t o r y s t u d i e s , done a t The U n i v e r s i t y o f B r i t i s h C o l u m b i a , i n c l u d e d p o t a s s i u m -a r g o n and r u b i d i u m - s t r o n t i u m geochronometry, w h o l e - r o c k a n a l y s e s , t r a c e element a n a l y s e s , p e t r o l o g y o f 61 t h i n s e c t i o n s and q u a l i t a t i v e s c a n n i n g e l e c t r o n m i c r o s c o p e a n a l y s e s . CHAPTER 2: REGIONAL GEOLOGY Geology o f t h e r e g i o n around t h e Guano-Guayes p r o p e r t y i s i l l u s t r a t e d i n two p u b l i s h e d g e o l o g i c a l maps o f t h e Q u i e t Lake a r e a , i n w h i c h t h e p r o -p e r t y i s l o c a t e d . These a r e t h o s e o f Wheeler e t a l . (1960) and Tempelman-K l u i t ( 1 9 7 7 a ) . The t e c t o n i c s e t t i n g o f t h e a r e a has been d i s c u s s e d i n t h e l i t e r a t u r e by G a b r i e l s e and Wheeler ( 1 9 6 1 ) , R o d d i c k 0.9-67), Monger e t a l . ( 1 9 7 2 ) , Mon-ge r ( 1 9 7 5 ) , and Tempelman-Kluit (1976, 1 9 7 7 b ) . The p r o p e r t y i s i n t h e S t . C y r range o f t h e P e l l y M o u n t a i n s . I t l i e s w i t h i n t h e Omineca C r y s t a l l i n e c. B e l t o f Monger e t a l . ( 1 9 7 2 ) , n o r t h e a s t o f t h e c r y s t a l l i n e c o r e o f t h e b e l t . I t i s s e p a r a t e d from t h e Rocky M o u n t a i n B e l t by the n o r t h w e s t - t r e n d i n g T i n -t i n a F a u l t . From t h e Q u i e t Lake Map (.Tempelman-Kluit, 1 9 7 7 a ) , p a r t o f w h i c h i s r e -produced i n s i m p l i f i e d f o r m i n F i g . 2.1, r o c k s i m m e d i a t e l y e a s t o f t h e Guano-Guayes a r e a c o n s i s t o f s t e e p l y d i p p i n g Upper Cambrian and O r d o v i c i a n t o S i -l u r i a n b l a c k g r a p t o l i t i c s l a t e and g r a y c h l o r i t e - m u s c o v i t e - q u a r t z p h y l l i t e (u€0p and O S s ) . These a r e o v e r l a i n i n t h e Guano-Guayes a r e a by S i l u r i a n t o D e v o n i a n d o l o m i t e s and l o c a l graywacke (SDsd) w h i c h a r e c u t by M i s s i s s i p p i a n s y e n i t e ( M i ) . The s y e n i t e i s a t t h e s o u t h e a s t end o f a s o u t h e a s t - t r e n d i n g r e g i o n a l b e l t o f s y e n i t e s t o c k s . V o l c a n i c t u f f s , b r e c c i a s , and f l o w r o c k s , a l s o M i s s i s s i p p i a n (uDMv) c o v e r a l a r g e a r e a s u r r o u n d i n g t h e s y e n i t e s t o c k s . G e n e r a l pronounced s t r u c t u r a l t r e n d s o f t h e a r e a ( j f o l d axes and f a u l t t r a c e s ) a r e n o r t h w e s t e r l y , s u b p a r a l l e l to t h e s t r i k e o f t h e T i n t i n a F a u l t . The s t r a t i g r a p h y o f t h e a r e a has been s t u d i e d by Tempelman-Kluit e t a l . (1975) and Gordey and Tempelman-Kluit (1976) and w i l l be d i s c u s s e d i n C h a p t e r 4 w i t h i n t h e c o n t e x t o f t h e s t r a t i g r a p h i c s e c t i o n on t h e p r o p e r t y . 5 QTvs uODp l a t e Tertiary or Quaternary basaltic to r h y o l i t i c volcanic rocks and sandstone, conglomerate and shale Upper Trlassle to Jurassic b i o c l a s c i c limestone with interbedded •andy or s i l t y limestone, volcaniclas-t i c sandstone, and minor tuff Hlsslsslppiaa resistant, massive, equigranular me-dium to fine-grained syenite Upper Devonian to Mississippian chert, grayvackt, cherty to sandy and l a p i l l i t u f f , volcanic breccia and andesitic to trachytlc flow rocks ' Devonian amygdaloldal basalt, tuff, breccia, and minor calcarenlte and slate Lover Devonian to S i l u r i a n calcareous quartz siltstone and minor sandy dolomite tan thin-bedded dolomltlc siltstone and minor volcanic tuffs and breccias Ordovlclan to S i l u r i a n black g r a p t o l i t l c slate with minor basalt and volcanic breccia and rare dolomite lenses Upper Cambrian to Ordovlclan ch l o r i t e muscovite quartz p h y l l i t e v l t h minor ahalc, limestone, and ba-s a l t i c s i l l s and flows Proterozolc to Lower Cambrian c a l c l t e and dolomite marble and minor a r g i l l i t e , b i o t i t e achlst, and shaly quartzite 5 10 15. kilometers Fig. 2.1 Geologic setting of the Guano-Guayes area (lower center), modified after Tempelman-Kluit (1977a) CHAPTER 3: STRUCTURAL GEOLOGY OF THE GUANO-GUAYES PROPERTY 3.1 INTRODUCTION Sedi m e n t a r y r o c k s o f t h e Guano-Guayes a r e a a r e on t h e w e s t - d i p p i n g l i m b o f a r e g i o n a l f o l d ( c r o s s s e c t i o n s , Map 1 ) . S t r u c t u r a l d a t a d e f i n i n g t h i s a r e shown on Map 1. Two hundred and s e v e n t e e n b e d d i n g a t t i t u d e s and band a t t i t u d e s i n c o n t a c t metamorphic r o c k were measured a l o n g w i t h t h e o r i e n t a -t i o n s o f 136 f r a c t u r e s and 33 d i k e s , v e i n s , and m i n e r a l i z e d f r a c t u r e s . These d a t a have been c o m p i l e d i n t o f i v e p i diagrams w h i c h a r e d i s c u s s e d b e l o w . 3.2 STRUCTURAL DATA 3.2.1 B e d d i n g S e d i m e n t a r y b e d d i n g w i t h i n t h e a r e a was w e l l d e f i n e d everywhere e x c e p t f o r a few p l a c e s w i t h i n t h e c o n t a c t metamorphic a u r e o l e . F i g . 3.1a i s a p i d i a g r a m o f a t t i t u d e s o f 154 b e d d i n g p l a n e s . P o l e s to b e d d i n g d e f i n e a f o l d ' a x i s w h i c h b e a r s 164 degrees and p l u n g e s 24 degrees t o t h e s o u t h . S t r a t i g r a p h i c c r i t e r i a f o r y o u n g i n g d i r e c t i o n s were d i f f i c u l t t o f i n d due to metamorphism'u . I t i s c l e a r l y shown a t one l o c a l i t y by o s c i l l a t i o n r i p p l e marks ( P l a t e 3.1a), and a t a n o t h e r by graded s i l t s t o n e l a m i n a e . R i p -p l e marks and graded l a m i n a e b o t h i n f e r t h a t beds a r e r i g h t - s i d e up. P r o m i n e n t bands found i n c o n t a c t metamorphic u n i t s A, B, and C, e a s t o f t h e i n t r u s i v e c o n t a c t , p r o b a b l y r e p r e s e n t b e d d i n g . Bands o f u n i t s B and C have a s i m i l a r a t t i t u d e to s e d i m e n t a r y s t r a t a ( F i g s . 3.1a and 3.1b) w h i l e t h o s e o f u n i t A have a s l i g h t l y d i f f e r e n t o r i e n t a t i o n ( F i g . 3 . 1 c ) . Bands i n t h e s e u n i t s a r e i n d e n t i c a l i n t h i c k n e s s and w e a t h e r i n g p a t t e r n to s e d i -mentary beds s e e n e l s e w h e r e ( P l a t e s 3.1b and 3.2). A l l b e d d i n g and b a n d i n g i s e x p r e s s e d by v a r i a t i o n s i n g r a i n s i z e , c a l c i t e , i r o n , and/or m i c a c o n t e n t 6 F i g . 3.1 P i diagrams of geological structures, Guano-Guayes area: a) bed-ding attitudes snowing great c i r c l e g i r d l e and f o l d axis (2% contours); b) Units B and C skarn banding attitudes- C3% contours); c) sedimentary bedding atti t u d e s ( s o l i d l i n e s ) and Unit A banding attitudes (dashed l i n e s ; A and 8% contours r e s p e c t i v e l y ) ; d) fracture attitudes i ( .2.7% contours); e) dike and vein attitudes Plate 3.1b Bedding s t y l e i l l u s t r a t e d i n f l o a t of impure c a l c i t e marble Unit 7. 9 P l a t e 3.2 B a n d i n g i n c o n t a c t metamorphic r o c k s , p r o b a b l y a f t e r sedimentary-b e d d i n g , i s r e p r e s e n t e d h e r e i n a) U n i t A, q u a r t z - m u s c o v i t e h o r n f e l s and b) U n i t B, s k a r n . 1Q o f t h e d i f f e r e n t l a y e r s . 3.2.2 F r a c t u r e s P o l e s to f r a c t u r e s a r e c o m p i l e d i n the p i d i a g r a m o f F i g . 3 . I d . Two s e t s o f f r a c t u r e s a r e found i n t h e a r e a : one s e t w i t h p o l e s w h i c h p l o t i n t h e s o u t h w e s t q u a r t e r o f t h e s t e r e o g r a m and one s e t w i t h p o l e s i n t h e n o r t h -w e s t e r n and s o u t h e a s t e r n q u a r t e r s o f t h e s t e r e o g r a m . The f i r s t s e t o f f r a c -t u r e s d i p s s t e e p l y t o the e a s t and has a s t r i k e r o u g h l y p a r a l l e l to t h e f o l d a x i s w h i l e t h e second s e t i s a p p r o x i m a t e l y p e r p e n d i c u l a r to t h e f o l d a x i s . There i s no s i g n i f i c a n t d i f f e r e n c e i n o r i e n t i a i o n between f r a c t u r e s on t h e e a s t and w e s t s i d e s o f t h e bench s h e a r zone. Other f r a c t u r e s , w h i c h a r e s c a r c e , have s t r i k e s r o u g h l y p a r a l l e l to t h e f o l d a x i s b u t d i p s h a l l o w l y , from 30 d e grees to h o r i z o n t a l , and p r o b a b l y formed due to r e l i e f o f v e r t i c a l p r e s s u r e as t h e r o c k s c o n t r a c t e d w i t h coo-l i n g and t h e o v e r b u r d e n was removed. 3.2.3 F a u l t i n g and B r e c c i a t i o n H a l f w a y up t h e w e s t - f a c i n g f l a n k o f t h e c a r b o n a t e r i d g e i s a t o p o g r a -p h i c s h e l f , t h e "bench s h e a r zone," w h i c h s e p a r a t e s most o f U n i t A from o-t h e r m e t a s e d i m e n t a r y r o c k s t o t h e e a s t ( F r o n t i s p i e c e ) . B a n d i n g i n U n i t A has a s l i g h t l y d i f f e r e n t a t t i t u d e from b a n d i n g and b e d d i n g o f o t h e r r o c k s to t h e e a s t ( F i g . 3 . 1 c ) . T h i s i s p r o b a b l y t h e r e s u l t o f f a u l t i n g a l o n g t h e s h e l f . There i s o u t c r o p o n l y a t t h e s o u t h e r n and n o r t h e r n ends o f t h e s h e l f . U n i t A i n t h e s e two p l a c e s i s h i g h l y s h e a r e d ( P l a t e 3.3a) and, o c c a s i o n a l l y , f o l d e d . Movement a l o n g t h e bench s h e a r zone has r e s u l t e d i n a c l o c k w i s e i n c r e a s e i n t h e s t r i k e o f U n i t A by a b out 20 degrees and a d e c r e a s e i n i t s d i p by around t e n d e g r e e s . S l i c k e n s i d e s measured on a s h e a r s u f a c e a t t h e edge o f U n i t B have a b e a r i n g o f 331 degrees and a p l u n g e o f 47 degrees Plate 3.3b Outcrop of b r e c c i a of Unit B, skarn, which i s cemented by c a l c i t e . 12 n o r t h w e s t . They s u g g e s t t h e e a s t s i d e may have moved r e l a t i v e l y upwards. A few o u t c r o p s o f U n i t A a r e found e a s t o f t h e bench s h e a r zone, s u g g e s t i n g t h a t no major o f f s e t has o c c u r r e d . There i s no c l e a r e v i d e n c e o f when s h e a r i n g t o o k p l a c e . On t h e e a s t e r n m o s t s i d e o f t h e map a r e a t h e r e i s a r e v e r s e f a u l t b e -tween d a r k gray s h a l e and r e c r y s t a l l i z e d impure c a r b o n t e r o c k s ( P l a t e 3 . 4 ) . F a u l t gouge, d a r k g r e e n i s h gray and u n c o n s o l i d a t e d , o c c u r s on t h e s i d e o f t h e l o w e r e a s t e r n c i r q u e . The c a r b o n a t e r o c k s c o n t a i n much l e s s e v i d e n c e o f d e f o r m a t i o n t h a n t h e s h a l e ; t h e l a t t e r i s h i g h l y s h e a r e d and c o n t a i n s numerous s m a l l (5 mm l o n g by 1 mm w i d e ) t e n s i o n gashes f i l l e d w i t h s e r i c i t e , q u a r t z , and p y r i t e . T e n s i o n gashes c u t b e d d i n g a t a h i g h a n g l e and r o u g h l y p a r a l l e l t h e s t e e p l y e a s t - d i p p i n g f r a c t u r e s o f t h e c a r b o n a t e s e c t i o n on t h e o p p o s i t e s i d e o f t h e f a u l t . A p p a r e n t t h i n n i n g o f t h e c a r b o n a t e s e c t i o n to t h e n o r t h i s a r e s u l t o f .movement a l o n g t h i s f a u l t . P o s i t i v e i n d i c a t i o n s f o r a d i r e c t i o n o f movement a l o n g t h e . f a u l t were n o t s e e n . S i n c e t h e s h a l e p r e d a t e s t h e c a r b o n a t e s e c t i o n as f a r as i s known ( S e c t i o n 4 . 2 ) , t h e s i m p l e s t m o t i o n r e q u i r e d to p l a c e the two r o c k t y p e s i n t h e i r p r e s e n t r e l a t i v e p o s i -t i o n s i s e a s t s i d e r e l a t i v e l y , upward. The t i m e o f f a u l t i n g r e l a t i v e t o s k a r n f o r m a t i o n , b r e c c i a t i o n , and o t h e r s h e a r i n g i s unknown. S e v e r a l s m a l l a r e a s i n c o n t a c t metamorphic r o c k s e a s t o f t h e bench s h e a r zone a r e b r e c c i a t e d . These a r e a s c o v e r o n l y a few t e n s o f s q u a r e me-t r e s each. B r e c c i a s c o n s i s t o f a n g u l a r f r a g m e n t s o f c o n t a c t metamorphic r o c k i n a m a t r i x o f p u r e c o a r s e l y c r y s t a l l i n e c a l c i t e ( P l a t e 3.3b). 3.3 SUMMARY AND INTERPRETATION OF STRUCTURE Rocks o f t h e Guano-Guayes a r e a a r e on t h e w e s t - d i p p i n g l i m b o f a r e -g i o n a l a n t i c l i n e , t h e a x i s o f w h i c h b e a r s 162 degrees and p l u n g e s 24 degrees P l a t e 3.4 Steep f a u l t between U n i t 1 (dark gray s h a l e , to the east) and Units 2 through 15 (carbonate rocks and q u a r t z i t e s , to the west) photographed l o o k i n g southeast from the c r e s t of the carbonate r i d g e . 14 s o u t h . B e d d i n g d i p s s t e e p l y , m o s t l y around 65 degrees to t h e w e s t , and i s r i g h t , s i d e up. Three s e t s o f f r a c t u r e s i n c l u d e : 1) f r a c t u r e s w h i c h s t r i k e NNW r o u g h l y p a r a l l e l to t h e f o l d a x i s and d i p s t e e p l y to t h e e a s t , 2) v e r t i -c a l f r a c t u r e s w i t h a s t r i k e o f about 045 degrees w h i c h a r e p r o b a b l y t h e r e s u l t o f e x t e n s i o n p a r a l l e l to t h e f o l d a x i s , and 3) s u b - h o r i z o n t a l f r a c -t u r e s , u s u a l l y v e i n - f i l l e d , c aused by t h e r e l i e f o f v e r t i c a l s t r e s s . A s h e a r zone i n U n i t A, t h e c o n t a c t metamorphic u n i t c l o s e s t to s y e n i t e , forms a p r o m i n e n t bench h a l f w a y up t h e w e s t e r n s i d e o f t h e c e n t r a l r i d g e where i t i s c l o s e to c o n t a c t metamorphic r o c k . B e d d i n g a t t i t u d e s a r e d i f f e r e n t on o p p o s i t e s i d e s o f t h e s h e a r zone b u t t h e r e i s no e v i d e n c e f o r s i g n i f i c a n t o f f s e t a l o n g i t . B r e c c i a t i o n o f c o n t a c t metamorphic r o c k i s s e e n i n a few s m a l l a r e a s . A t t h e e a s t e r n edge o f t h e s e d i m e n t a r y s e c t i o n , d a r k gray s h a l e s have been f a u l t e d r e l a t i v e l y upward a l o n g a v e r t i c a l f a u l t . The w e s t e r n boun-dary o f t h e s e d i m e n t a r y s e c t i o n i s t h e c o n t a c t between i t and s y e n i t e . R e l a t i v e t i m i n g f o r d i f f e r e n t s t r u c t u r a l e v e n t s i n t h e a r e a c a n be e s -t a b l i s h e d to some e x t e n t by f i e l d o b s e r v a t i o n s . F r a c t u r e s u r f a c e s w i t h s i m i l a r o r i e n t a t i o n s a r e found i n s e d i m e n t a r y r o c k s , c o n t a c t metamorphic r o c k s , and s y e n i t e . Some f r a c t u r e s i n c o n t a c t metamorphic r o c k s and i n s y e n i t e a r e m i n e r a l i z e d , i m p l y i n g they formed d u r i n g o r soon a f t e r i n t r u s i o n o f s y e n i t e c a u s e d the c o n t a c t metamorphic e v e n t . C l a s t s i n l o c a l l y b r e c -c i a t e d a r e a s i n c o n t a c t metamorphic r o c k s a r e o f m e t a s o m a t i z e d r o c k s w h i l e c a l c i t e s u r r o u n d i n g them i s p u r e , i m p l y i n g t h a t l o c a l b r e c c i a t i o n t o o k p l a c e a f t e r i n i t i a l c o n t a c t metamorphism. F o r m a t i o n o f t h e bench s h e a r zone might have b e e n synchronous w i t h l o c a l b r e c c i a t i o n . P e t r o l o g i c a l e v i d e n c e f o r t h i s i s p r e s e n t e d i n C h a p t e r 4. CHAPTER 4 : DETAILED PETROLOGY OF THE GUANO-GUAYES AREA 4 . 1 INTRODUCTION , Rocks mapped i n the Guano-Guayes area include r e c r y s t a l l i z e d sedimen-tary rocks (Units 1 through 15), syenite and cogenetic dikes (Units 16, 17a, and 17b), and contact metamorphic rocks (Units,A, B, and C). Map 1 (back po-cket) shows the geology of the area. Sample locations are on Map 2 and modes estimated from t h i n sections are l i s t e d i n Appendices A l through A6. Table 4.1 contains information on r e l a t i v e time versus mineral growth and s t r u c t u -r a l events for igneous and contact metamorphic rocks. 4.2 SEDIMENTARY PETROLOGY The rocks described below were r e c r y s t a l l i z e d during regional or con-tact metamorphism. Areas w i t h i n them where o r i g i n a l mineralogy has been a l -tered by contact metamorphism are described i n Section 4 . 5 . 4.2.1 Stratigraphy Sedimentary rocks, mostly carbonate-rich, crop out on and east of the carbonate ridge. They can be divided into f i f t e e n d i s t i n c t u n i t s . A l l con-tacts, except the one between the two oldest units, are conformable. A mea-sured s e c t i o n i l l u s t r a t e s stratigraphy i n F i g . 4 . 1 . S t r a t i g r a p h i c a l l y , se-dimentary rocks are upright as determined from r i p p l e marks found i n Unit 12 (Plate 3.1),and from graded beds found i n Unit 3. St r a t i g r a p h i c units are described below from the base of the section upward. :. Unit 1, dark gray g r a p h i t i c shale, crops out on the eastern edge of the map area and i s at l e a s t 500 m thick. Laminations a few mm thick contain two percent p y r i t e i n 0.2 mm disseminated c r y s t a l s . Bedding attitudes are conformable with those to the west i n other rock u n i t s . A 12-meter-thick 15 16 Unit 16 15 14 13 12 11 10 9 7 6 5 4 Thickness >500 m 30 to 45 m De s c r i p t i o n syenite laminated to very t h i n l y bedded tan q u a r t z i t e laminated to very t h i n l y bedded shaly dolomite marble (? a l t e r e d to skarn) shaly dolomite marble (?"a l t e r e d to skarn) laminated to t h i n l y bedded l i g h t gray shaly c a l c i t e marble t h i c k l y bedded to laminated dark gray f o s s i l i f e r o u s shaly dolomite marble interbedded'tan limy shale and shaly c a l c i t e marble impure white q u a r t z i t e bedded white dolomite marble t h i n l y bedded gray shaly c a l c i t e marble massive interbedded white dolomite marble and q u a r t z i t e massive white q u a r t z i t e t h i c k l y bedded white dolomite marble laminated l i g h t gray shaly c a l c i t e marble l i g h t brown dolomite marble f a u l t gouge dark gray g r a p h i t i c shale F i g . 4.1 Measured s e c t i o n of sedimentary rocks of the Guano-Guayes 17 v e r t i c a l zone o f f a u l t gouge s e p a r a t e s t h i s u n i t f r o m t h o s e t o t h e w e s t . U n i t 1 has s t r o n g l y d e v e l o p e d a x i a l p l a n e f o l i a t i o n . Two hundred m e t r e s e a s t o f t h e map a r e a t h e s h a l e i s h i g h l y deformed and l o c a l l y metamorphosed t o p h y l l i t e . U n i t 2, l i g h t brown d o l o m i t e m a r b l e , 7 m e t r e s t h i c k , i s t h e sec o n d o l d -e s t u n i t r e c o g n i z e d . T h i s r o c k i s made up o f v e r y f i n e - g r a i n e d ( a v e r a g e 0.05 mm) d e c u s s a t e d o l o m i t e and c o n t a i n s s m a l l (2 mm a c r o s s ) c a l c i t e - r i m m e d t a b u l a r vugs w h i c h p a r a l l e l b e d d i n g . :. U n i t 3, l a m i n a t e d l i g h t g r a y s h a l y c a l c i t e m a r b l e , i s 68 m e t r e s t h i c k . G r a i n s i z e a v e r a g e s 0.05 mm. Fragments o f f o s s i l s a few mm a c r o s s compose up t o 30 p e r c e n t o f t h e volume o f t h e few u n l a m i n a t e d b eds. S h a l y t o - s i l t y , l a m i n a e , 5 mm t h i c k , i n some p l a c e s c o n t a i n up t o 3 p e r c e n t d i s s e m i n a t e d p y r i t e . a n d , i n one s e c t i o n , g r a d e d b e d d i n g . E v i d e n c e o f s m a l l - s c a l e s o f t - s e d i m e n t d e f o r -m a t i o n ( s l u m p i n g , p o s s i b l e b i o t u r b a t i o n ) i s common. U n i t 4, t h i c k l y bedded w h i t e d o l o m i t e marble,' i s 13 metr e s t h i c k . T h i s • \ u n i t " i s f i n e - g r a i n e d (0.05 MM) arid w e a t h e r s p a l e p i n k . U n i t 5, m a s s i v e w h i t e q u a r t z i t e , i s an 11 m e t r e - t h i c k c l i f f - f o r m i n g r o c k . I f i s f i n e - g r a i n e d (0.1 mm average) and c o n t a i n s m i n o r c a l c i t e and p e l i t i c m a t e r i a l . U n i t 5 has s h a r p c o n t a c t s w i t h o l d e r and younger s e d i m e n t a r y r o c k s . U n i t 6, m a s s i v e i n t e r b e d d e d w h i t e d o l o m i t e m a r b l e and q u a r t z i t e , i s 51 , |.metfes t h i c k . M a r b l e , s i m i l a r t o U n i t 4, c o n t a i n s a few q u a r t z i t e b e d s , each l e s s t h a n 1 m t h i c k , w h i c h a r e s i m i l a r t o U n i t 5. U n i t 7, t h i n l y bedded g r a y s h a l y c a l c i t e m a r b l e , i s 8 metr e s t h i c k . G r a i n s a v e r a g e 0.05 mm i n d i a m e t e r . Beds a r e about 3 cm t h i c k and composed of l a y e r s o f c a l c i t e m a r b l e s e p a r a t e d by s h a l e . U n i t 7 i s more r e s i s t a n t t o w e a t h e r i n g t h a n a d j a c e n t d o l o m i t e s . 18 U n i t 8, bedded-white d o l o m i t e m a r b l e , i s 154 metr e s t h i c k . I t i s f i n e -g r a i n e d ( a v e r a g e 0.1 mm) and co n t a i n s : 5 t o , l o c a l l y , 60 p e r c e n t p e l m a t o z o a n stems. S e v e r a l specimens were d i s s o l v e d i n d i l u t e a c e t i c a c i d b u t no m i c r o -f o s s i l s were f o u n d . Beds a r e s e v e r a l m e t r e s t h i c k . U n i t 9, impure w h i t e q u a r t z i t e , i s 2 metr e s t h i c k i n most p l a c e s . Q u a r t z g r a i n s a r e w e l l rounded and 0.3 mm i n s i z e e x c e p t where they have been r e c r y s -t a l l i z e d to form a g r a n o b l a s t i c p o l y g o n a l t e x t u r e w i t h m i c a s o r t r e m o l i t e r e -p l a c i n g o r i g i n a l i n t e r s t i t i a l c l a y s . U n i t 9 c r o p s o u t o v e r a l o n g d i s t a n c e a l o n g s t r i k e and c o n s e q u e n t l y i s a v a l u a b l e marker h o r i z o n . U n i t 10, i n t e r b e d d e d t a n l i m y s h a l e and s h a l y c a l c i t e m a r b l e , i s 12 me-t r e s t h i c k and f i n e - g r a i n e d ( a v e r a g e 0.1 mm). B e d d i n g i s e x t r e m e l y w e l l de-f i n e d by s h a l y l a y e r s . U n i t 1 1 , t h i c k l y bedded to l a m i n a t e d d a r k g r a y f o s s i l i f e r o u s s h a l y d o l o - m i t e m a r b l e , i s 21 metres t h i c k . F o s s i l fragments make up t e n to 30 p e r c e n t o f t h i s u n i t , t h e r e m a i n d e r b e i n g p e l i t i c m a t e r i a l and g r a p h i t e (15 p e r c e n t combined) and c a l c i t e . L a m i n a t i o n s a r e s e v e r a l mm i n t h i c k n e s s , and a r e common i n l e s s f o s s i l i f e r o u s s e c t i o n s . F o s s i l s i n c l u d e p e l m a t o z o a n stems, p e l e c y p o d s , c o e l e n t e r a t e s , and s t o n y b r y o z o a n s . One c o e l e n t e r a t e common i n U n i t 11 re s e m b l e s S y n a p t o p h y l l u m simpson ( C l a s s . Z o a n t h a r i a , Order Rugosa) o f S i l u r i a n to D e v o n i a n age w h i c h has been d e s c r i b e d i n t h e D e v o n i a n o f O n t a r i o (Moore e t a l . , 1 9 5 2 ) . M i c r o f o s s i l s were n o t found when samples o f U n i t 11 were d i s s o l v e d i n d i l u t e a c e t i c a c i d . U n i t 11 has been c o m p l e t e l y r e c r y s t a l -l i z e d and m i l d l y to s t r o n g l y deformed, d e s t r o y i n g a l l f o s s i l m i c r o s t r u c t u r e s . The b a s a l 50 cm o f U n i t 11 i s h i g h l y b r e c c i a t e d and cemented w i t h c a l c i t e . U n i t 12, l a m i n a t e d to t h i n l y bedded l i g h t g ray s h a l y c a l c i t e m a r b l e , a -b o u t 23 metres t h i c k , has an a v e r a g e g r a i n s i z e o f 0.05 mm. I t c o n t a i n s one p e r c e n t p y r i t e as p o r p h y r o b l a s t s w h i c h a r e each s e v e r a l mm a c r o s s . B e d d i n g 19 t h i c k n e s s e s v a r y f r o m s e v e r a l mm t o s e v e r a l cm. A few beds show o s c i l l a t i o n r i p p l e marks ( P l a t e 3.1). U n i t 13, s h a l y d o l o m i t e m a r b l e ( ? ) , r a n g e s f r o m one t o 24 metres i n t h i c k n e s s . The o r i g i n a l s e d i m e n t a r y n a t u r e o f U n i t 13 i s t o t a l l y masked by c o n t a c t metamorphism. I t i s now a c o a r s e - g r a i n e d p h l o g o p i t e - c a l c i t e t s k a r n . U n i t 14, l a m i n a t e d t o v e r y t h i n l y bedded s h a l y d o l o m i t e m a r b l e ( ? ) , i s 30 t o 45 m e t r e s t h i c k . B e d d i n g t h i c k n e s s e s v a r y f r o m s e v e r a l mm t o s e v e r a l cm. C o n t a c t metamorphism has a l t e r e d U n i t 14 t h r o u g h o u t t h e a r e a and i s d i s -c u s s e d i n S e c t i o n 4.5. U n i t 15, l a m i n a t e d t o v e r y t h i n l y bedded t a n q u a r t z i t e , t h e y o u n g e s t s e d i m e n t a r y u n i t i n t h e a r e a , i s a t l e a s t 500 m e t r e s t h i c k . I t c o n t a i n s e x t r e m e l y f i n e - g r a i n e d (0.01 mm) q u a r t z and m i c a s and minor s i d e r i t e . ^ B e d d i n g p l a n e s a r e s e v e r a l mm t o cm a p a r t . U n i t 15 i s h i g h l y s h e a r e d b u t p r o b a b l y o n l y s l i g h t l y d i s p l a c e d a l o n g t h e bench shear "zone ( S e c t i o n 3.2.3). I n t h e c e n t r a l c i r q u e , s y e n i t e i n t r u d e s U n i t 15 and c o n t a i n s l a r g e x e n o l i t h s o f U n i t 15 ( P l a t e 4 . 1 ) . C o n t a c t metamorphism has c a u s e d r e c r y s t a l l i z a t i o n o f a l l e x p o s u r e s o f t h e u n i t . 4.2.2 S t r a t i g r a p h i c C o r r e l a t i o n S t r a t i g r a p h i c u n i t s i n t h e f i e l d a r e a can be r o u g h l y c o r r e l a t e d w i t h o t h e r P e l l y M o u n t a i n s t r a t a d e s c r i b e d by T empelman-Kluit (1977b) . H i s schema-t i c c r o s s s e c t i o n o f t h e P e l l y - C a s s i a r P l a t f o r m i s r e p r o d u c e d i n F i g . 4.2. A l i n e has been drawn on h i s c r o s s s e c t i o n t h r o u g h t h e sequence o f r o c k s w h i c h most r e s e m b l e s t h e Guano-Guayes s e c t i o n . I n t h i s c o r r e l a t i o n , l o c a l U n i t 1 ( d a r k g r a y g r a p h i t i c ; s h a l e ) would be O r d o v i c i a n - arid U n i t s 2 t h r o u g h 15 (pure t o s h a l y c a r b o n a t e s and q u a r t z i t e s ) S i l u r i a n . T h i s c o r r e l a t i o n i s i n agreement w i t h t h e l i m i t e d f o s s i l d a t a f r o m t h e p r o p e r t y . I n t h e s t u d y a r e a , a f a u l t / a t t h e top o f t h e O r d o v i c i a n d a r k g r a y g r a p h i t i c s h a l e - c u t s o f f an u n d e t e r m i n e d 2 0 P l a t e 4.1 X e n o l i t h o f U n i t A, q u a r t z - m u s c o v i t e h o r n -f e l s e n c l o s e d i n U n i t 16, s y e n i t e . T h i s p h o t o g r a p h was t a k e n 200 m f r o m t h e c o n t a c t between h o r n f e l s and s y e n i t e . OMINECA CRYSTALLINE BELT YUKON CRYSTALLINE TERRANE SELWYN BASIN T R I A S S I C g " l,Vol § § c M I S S I S S I P P I A N ; b a r_it P=j_-_-j-SlV.VDEVONIAN g ^ ^ ^ T ^ b R D O V IC I AN c a l c sl^Sf"-*- 5 F i g . 4.2 R e s t o r e d s e c t i o n a c r o s s the P e l l y - C a s s i a r P l a t f o r m n e a r the Guano-Guayes a r e a from Tempelman-Kluit (19.76) i l l u s t r a t e s f a c i e s . r e l a t i o n s h i p s o f t h e main s t r a t i g r a p h i c u n i t s . Approximate t i m e l i n e s a r e shown by heavy d o t s . The heavy b a r marks a s e c t i o n s i m i l a r t b the one a t t h e Guano-Guayes p r o p e r t y . 22 amount o f t h e s e c t i o n . 4.3 IGNEOUS PETROLOGY A s y e n i t e s t o c k ( U n i t 16) and c o g e n e t i c d i k e s ( U n i t s 17a and 17b) i n -t r u d e s e d i m e n t a r y r o c k s d e s c r i b e d i n the p r e v i o u s s e c t i o n . 4.3.1 U n i t 16: S y e n i t e The s y e n i t e s t o c k c r o p s o u t o v e r r o u g h l y 35 s q u a r e km to t h e n o r t h and west o f t h e p r o p e r t y ( F i g . 2 . 1). I n hand specimen ( P l a t e 4.2) t h e r o c k c o n -t a i n s 60 to 90 p e r c e n t l i g h t g r a y , c a r l s b a d - t w i n n e d o r t h o c l a s e i n l a t h s 1 mm to 3 cm ( a v e r a g e 5 mm) l o n g . O r t h o c l a s e i s s u r r o u n d e d by g r e e n i s h - b l a c k masses o f b i o t i t e w i t h one p e r c e n t i r r e g u l a r to e u h e d r a l p y r i t e g r a i n s 0.5 to 3 mm a c r o s s o r , i n l e u c o c r a t i c s p e c i m e n s , by l i g h t t a n l i m o n i t i c s i d e r i t e . T h i n s e c t i o n s o f s y e n i t e ( A p p e n d i x A2) show t h e f e l d s p a r t o be o r t h o -c l a s e o r p e r t h i t e i n randomly o r i e n t e d l a t h s a v e r a g i n g 5 cm i n l e n g t h , a s s o -c i a t e d w i t h r e l i c t s o f 5 t o 20 p e r c e n t a e g i r i n e - a u g i t e o r a r f v e d s o n i t e i n i r r e g u l a r a n h e d r a l g r a i n s and w i t h , m i n o r e u h e d r a l a p a t i t e , sphene, z i r c o n , p y r i t e , and i l m e n i t e ( P l a t e 4 . 3 ) . Samples f r e e o f m a f i c m i n e r a l s c o n t a i n about t e n p e r c e n t a n h e d r a l t o e u h e d r a l s i d e r i t e . C h i l l i n g o f s y e n i t e a t t h e i n t r u s i v e c o n t a c t i s l i m i t e d t o a band a few cm w i d e where e q u i d i m e n s i o n a l o r t h o c l a s e and m a f i c g r a i n s a v e r a g e 1 mm i n d i a m e t e r . The c o n t a c t between s y e n i t e and metasedimenary r o c k s i s v e r t i c a l i n t h e v a l l e y w e s t o f t h e c e n t r a l c i r q u e , i n c l i n e d to t h e e a s t as i t c r o s s e s t h e back o f t h e c i r q u e , and h o r i z o n t a l b o t h a t t h e summit o f t h e c i r q u e and b e n e a t h m e t a s e d i m e n t a r y r o c k s o n t h e r i d g e t o t h e n o r t h w e s t (Map 1) . I f t h e r e has been no s i g n i f i c a n t p o s t - i n t r u s i o n d e f o r m a t i o n , t h e s e g e l a t i o n s s u g g e s t t h a t t h e exposed s y e n i t e i s near t h e r o o f o f t h e i n t r u s i v e body. A l t e r a t i o n o f s y e n i t e i s moderate to extreme. O r t h o c l a s e i s p a r t l y r e -23 b P l a t e 4.2 Hand Specimens o f U n i t 16, s y e n i t e , r e p r e s e n t e d b y: a) sample N3 and b) sample N5. On t h e l e f t , samples a r e s t a i n e d w i t h s odium c o b a l t i n i -t r i t e t o show K - f e l d s p a r ( y e l l o w ) , and p l a g i o c l a s e f e l d s p a r ( w h i t e ) , I n u n s t a i n e d s a m p l e s , on t h e r i g h t , b l a c k m a t e r i a l i s o r i g i n a l p y r o x e n e (N5) o r s e c o n d a r y b i o t i t e (N3) . 2A P l a t e 4.3 Photomicrographs (crossed n i c o l s ) of t h i n s e c t i o n s of representa-t i v e samples of U n i t 16, s y e n i t e ( a , sample N10) and l e u c o s y e n i t e b ) , sample M27), showing o r i g i n a l o r t h o c l a s e l a t h s p a r t l y a l t e r e d to a l b i t e , mafic minerals to b i o t i t e , and abundant secondary carbonates. 25 p l a c e d by p a t c h e s o f p l a g i o c l a s e o f v a r i a b l e c o m p o s i t i o n (An^ t o A n ^ ^ ) . Most m a f i c m i n e r a l s a r e c o m p l e t e l y r e p l a c e d by masses o f g r e e n p l e o c h r o i c f e l t e d b i o t i t e mixed w i t h s p a r s e g r a i n s o f p y r i t e o r m a g n e t i t e . F e l t e d b i o t i t e i s found a l o n g c l e a v a g e p l a n e s and as r i m s on o r t h o c l a s e i n m a f i c m i n e r a l - b e a r -i n g r o c k s . M u s c o v i t e p a r t l y r e p l a c e s o r t h o c l a s e i n l e u c o s y e n i t e . C a l c i t e o c c u r s as s m a l l amoeboid g r a i n s and q u a r t z as: f i n e g r a n o b l a s t i c p o l y g o n a l masses. B o t h c a l c i t e and q u a r t z were p r o b a b l y added to t h e r o c k d u r i n g a l -t e r a t i o n and a r e i n t e r m i x e d w i t h b i o t i t e and p l a g i o c l a s e i n p o l y g o n a l masses o f 0.05 mm g r a i n s . These masses a r e common between o r i g i n a l g r a i n s and i n s m a l l v e i n s f i l l i n g f r a c t u r e s a c r o s s them. E p i d o t e , a m i n o r a l t e r a t i o n m i -n e r a l , i s u s u a l l y found i n s m a l l w i d e l y s c a t t e r e d g r a i n s b u t i s a l s o s e e n i n d e c u s s a t e masses r e p l a c i n g p y r o x e n e . 4.3.2 U n i t 17a: M e l a g r a n i t e D i k e s M e l a g r a n i t e d i k e s are. s e e n o n l y i n c o n t a c t metamorphic r o c k , w h i c h t h e y i n t r u d e a l o n g b e d d i n g p l a n e s and f r a c t u r e s ( F i g . 4.3, P l a t e 4 . 4 ) . They range f r o m about f i v e cm to f i v e mm i n t h i c k n e s s and a r e u s u a l l y t r a c e a b l e f o r o n l y a few t e n s o f m e t e r s . D e n s i t y o f d i s t r i b u t i o n o f d i k e s i s u n c e r t a i n b e c a u s e o f s i m i l a r c o l o u r and w e a t h e r i n g o f m e l a g r a n i t e and h o s t r o c k s , b u t a l l major m e l a g r a n i t e d i k e s a r e shown on t h e g e o l o g i c a l map (Map 1 ) . I n hand specimen ( P l a t e 4 . 5 ) , d i k e s o f U n i t 17a a r e d a r k g r e e n i s h g r a y and c o n s i s t o f q u a r t z and o r t h o c l a s e i n e q u i d i m e n s i o n a l g r a i n s 1 t o 5 mm a c r o s s and abundant euhe-d r a l t a n z i r c o n 0.2 to 2 mm a c r o s s i n a g r e e n i s h - g r a y to b l a c k a p h a n i t i c ma-t r i x . M e l a g r a n i t e d i k e s a r e more r a d i o a c t i v e t h a n c o n t a c t metamorphic r o c k s , r a n g i n g from 300 to 1200 c o u n t s p e r second ( c p s ) . Background o v e r c o n t a c t metamorphic r o c k s i s 200 c p s . M i n e r a l s s e e n i n t h i n s e c t i o n (modes i n A p p e n d i x A3) a r e 10 to 60 p e r c e n t o r t h o c l a s e , as s i m p l e e u h e d r a l e q u i d i m e n s i o n a l c r y s t a l s a few mm a c r o s s , about 2 6 POLES TO ( FRACTURES \ c- -E E E I V E POLES TO O-BEDDING \ Fig. 4.3 Poles to dikes and veins plotted on a stereonet with poles to regional fractures and bedding for comparison, showing the variable orientation of different types of dikes and veins: 0: Unit 17a, melagranite dikes; R: Unit 17b, mafic dikes; M: fluorite-calcite-quartz-microcline veins; E: epidote-actinolite calcite-quartz veins; and C: siderite-dolomite-quartz veins. r 27 b P l a t e 4.4 U n i t 17a, m e l a g r a n i t e d i k e s , i n t h e f i e l d , a) c u t i r r e g u l a r l y a c r o s s d a r k g r e e n s k a r n o f U n i t B o r b) p a r a l l e l b a n d i n g i n U n i t B. 28 b P l a t e 4.5 Hand specimens o f U n i t 17a m e l a g r a n i t e d i k e s , showing a) t a n z i r c o n w i t h q u a r t z , o r t h o c l a s e , and d a r k g r e e n d i o p s i d e - h e d e n b e r g i t e b) abundant K - f e l d s p a r ( s t a i n e d y e l l o w by sodium c o b a l t i n i t r i t e , i n the sample on the l e f t ) , q u a r t z and p l a g i o c l a s e ( c o l o r l e s s ) and a r f v e d s o n i t e ( d a r k green) i n sample Q12A. The w h i t e m i n e r a l n e a r t h e t o p o f t h e r i g h t -hand sample i n b i s a l t e r e d z i r c o n . 2 9 15 p e r c e n t a n h e d r a l d i o p s i d e - h e d e n b u r g i t e o r a r f v e d s o n i t e , 5 to 70 ( a v e r a g e 20) p e r c e n t p o i k i l o b l a s t i c q u a r t z , and 3 to 15 p e r c e n t e u h e d r a l z i r c o n , as e q u i d i m e n s i o n a l g r a i n s up t o a few mm a c r o s s ( P l a t e 4 . 6 ) . I n some m e l a g r a n i t e d i k e s m i n e r a l s o c c u r i n l e n s e s r o u g h l y p a r a l l e l to t h e edges o f t h e d i k e s . T h i s c o u l d be bec a u s e o f i n t r u s i v e f l o w s t r u c t u r e , r e c r y s t a l l i z a t i o n o f some m i n e r a l s d u r i n g c o n t a c t metamorphism, o r a combi-n a t i o n o f t h e two. C o n t a c t s between d i k e s and s u r r o u n d i n g r o c k s a r e s h a r p . L i t t l e o r no t h e r m a l e f f e c t s were o v s e r v e d a t c o n t a c t s , b u t metamorphic r o c k s a r e e n r i c h e d i n i r o n and p o s s i b l y magnesium f o r s e v e r a l t e n s o f meters around each d i k e . M a f i c m i n e r a l s i n U n i t 17a a r e a l t e r e d to t r e m o l i t e - a c t i n o l i t e and l a t e r , r a r e l y , to f e l t e d g r e e n - p l e o c h r o i c b i o t i t e . Q u a r t z g r a i n s , r e c r y s t a l l i z e d :". i n t o p o i k i l o b l a s t i c amoeboid shapes up to s e v e r a l cm i n s i z e , c o n t a i n o r t h o -c l a s e c r y s t a l s ( P l a t e 4.6) w h i c h a r e p a r t l y r e p l a c e d by a l b i t e (An^) and o c -c a s i o n a l l y by a x i n i t e . Most z i r c o n i s a l t e r e d to pseudomorphs c o n t a i n i n g a l l a n i t e , m o n a z i t e , and a p i n k i s h - w h i t e b o t r y o i d a l m i n e r a l ( m i n e r a l C) ( P l a t e 4 . 7 ) . P r o p e r t i e s o f R E E - e n r i c h e d m i n e r a l s a r e l i s t e d i n A p p e n d i x A7. Grano-b l a s t i c p o l y g o n a l q u a r t z , c a l c i t e , b i o t i t e , and a l b i t e f orm v e i n l e t s c u t t i n g a l t e r e d m i n e r a l s . 4.3.3 U n i t 17b: M a f i c D i k e s M a f i c d i k e s i n t r u d e both, c o n t a c t metamorphic r o c k s and r e c r y s a l l i z e d s e d i m e n t a r y r o c k s . They a r e 10 t o 20 cm t h i c k and c a n be t r a c e d f o r o n l y a few t e n s o f m each. They a r e seen e a s i l y i n l i g h t - c o l o u r e d r e c r y s t a l l i z e d s e -d i m e n t a r y r o c k s ( P l a t e 4 . 8 ) , b u t a r e o v e r l o o k e d i n c o n t a c t metamorphic r o c k s u n l e s s a s c i n t i l l o m e t e r i s use d . I n hand specimen, m a f i c dikes- a r e d a r k g r e e n to b l a c k , a p h a n i t i c , and have a h i g h , s p e c i f i c g r a v i t y . T h e i r r a d i o a c t i v i t y ranges from 1000 to 9000 cps o v e r a h o s t r o c k b a c k g r o u n d o f 200 c p s . 30 i i 0.3mm P l a t e 4.6 P h o t o m i c r o g r a p h s ( c r o s s e d n i c o l s ) o f t h i n s e c t i o n s o f U n i t 17a, m e l a g r a n i t e d i k e s , showing: a) z i r c o n (zoned m i n e r a l i n top c e n t e r ) w i t h q u a r t z , o r t h o c l a s e p a r t l y a l t e r e d to t w i n n e d a l b i t e , and d i o p s i d e - h e d e n -b e r g i t e rimmed by a c t i n o l i t e (sample CC17) and b) s u b h e d r a l o r t h o c l a s e ( l o w e r l e f t ) , e n c l o s e d i n p o i k i l o b l a s t i c q u a r t z , a pseudomorph o f m i n e r a l C a f t e r z i r c o n ( t o p c e n t e r ) , and s e c o n d a r y g r e e n b i o t i t e (Sample P 1 B ) . 31 b J 0. 3mm P l a t e 4.7 Pseudomorphs ( p l a n e p o l a r i z e d l i g h t ) a f t e r z i r c o n i n U n i t 17a m e l a g r a n i t e d i k e s i n a) hand specimen o f sample Q12E and b) t h i n s e c t i o n o f sample P1B, c o n s i s t o f m i n e r a l C ( w h i t e i n hand specimen, i s o t r o p i c i n t h i n s e c t i o n ) and m o n a z i t e (brown m i n e r a l w i t h h i g h r e l i e f , l o w e r l e f t c o r n e r o f t h i n s e c t i o n ) . 32 b 0.1mm P l a t e 4.8 U n i t 17b, m a f i c d i k e s , i l l u s t r a t e d a) i n o u t c r o p , i n t r u d i n g m a r b l e o f U n i t 12 p a r a l l e l to AC j o i n t s ( t h e c l i f f f a c e i s r o u g h l y p a r a l l e l t o b e d d i n g - n o t e b l u e pack a t base o f d i k e f o r s c a l e ) and b) i n t h i n s e c t i o n (sample S5D). M i n e r a l s i n t h i n s e c t i o n a r e a c t i n o l i t e ( g r e e n ) , z i r c o n ( i s o t r o p i c g r a i n s w i t h p l e o c h r o i c h a l o e s i n a c t i n o l i t e ) , a l l a n i t e ( o r a n g e -y e l l o w , moderate r e l i e f , a t r i g h t ) and s t i l p n o m e l a n e ( l a r g e orange g r a i n , l o w e r l e f t ; p l a n e p o l a r i z e d l i g h t ) . 33 I n t h i n s e c t i o n (modes i n A p p e n d i x A 2 ) , m a f i c d i k e s a r e s e e n t o c o n s i s t o f 40 t o 70 p e r c e n t f e l t e d t o d e c u s s a t e a c t i n o l i t e g r a i n s 0.04 t o 0.2 mm i n d i a m e t e r , 15 t o 25 p e r c e n t z i r c o n and a l l a n i t e 0.01 t o 2 mm i n d i a m e t e r i n d i s s e m i n a t e d g r a i n s and masses, and m i n o r o r t h o c l a s e , q u a r t z , c a l c i t e , c l i n o -z o i s i t e , and s t i l p n o m e l a n e . One sample c o n t a i n s a 0.4 mm s k e l e t a l g r a i n o f d i o p s i d e - h e d e n b u r g i t e . Z i r c o n and a l l a n i t e p r o d u c e p l e o c h r o i c h a l o e s i n s u r r o u n d i n g a c t i n o l i t e ( P l a t e 4.8). C o n t a c t s between m a f i c d i k e s and h o s t r o c k s a r e s h a r p . Where d i k e s i n t r u d e r e c r y s t a l l i z e d s e d i m e n t a r y r o c k s , t h e r e i s no c o n t a c t metamorphic a u r e o l e . The f i n e g r a i n s i z e i n d i k e s s u g -g e s t s t h e y were c h i l l e d on i n t r u s i o n . Where m a f i c d i k e s i n t r u d e c o n t a c t metamorphic r o c k s t h e d i k e s c o n t a i n s m a l l amounts o f o r t h o c l a s e and q u a r t z , and s u r r o u n d i n g r o c k s a r e d a r k c o l o u r e d s u g g e s t i n g t h a t i r o n m i g h t have m i g r a t e d o u t w a r d from t h e d i k e s . The n a t u r e o f t h e o r i g i n a l d i k e r o c k f r o m w h i c h m a f i c d i k e s formed i s unknown-. The o c c u r r e n c e o f a r e l i c t d i o p s i d e - h e d e n b u r g i t e g r a i n i n one ma-f i c d i k e , s u g g e s t s t h a t t h e u b i q u i t o u s a c t i n o l i t e i s a r e p l a c e m e n t m i n e r a l ; 4.3.4 Whole-Rock A n a l y s i s o f Igneous Rocks Wh o l e - r o c k a n a l y s e s o f s y e n i t e and m e l a g r a n i t e d i k e s were c a r r i e d out u s i n g X - r a y : f l u o r e s c e n c e f o l l o w i n g p r o c e d u r e s e s t a b l i s h e d i n 1978 by G. N i x o n . R e s u l t s a r e shown i n A p p e n d i x B. S i l i c a c o n t e n t o f s y e n i t e i s 60 p e r c e n t , o r i n t e r m e d i a t e . M e l a g r a n i t e d i k e s a r e a c i d i c , w i t h 65 t o 71 p e r c e n t S K ^ . Whole r o c k a n a l y s e s o f m a f i c d i k e s were u n s u c c e s s f u l because no s t a n d a r d c o n t a i n i n g l a r g e amounts o f z i r c o n was a v a i l a b l e f o r c a l i b r a t i o n . 4.3.5 R e l a t i o n s between S y e n i t e and D i k e s The o r i g i n o f m a f i c and m e l a g r a n i t e d i k e s , t h e mechanism by w h i c h b o t h became e n r i c h e d i n R E E - b e a r i n g m i n e r a l s , and t h e i r r e l a t i o n s h i p t o each 34 o t h e r i s u n c e r t a i n . Some d i k e s a r e i n t e r m e d i a t e between t h e two, c o n t a i n -i n g abundant o r t h o c l a s e i n a groundmass o f a c t i n o l i t e and z i r c o n , s u g g e s t i n g t h a t t h e y a r e r e l a t e d . M e l a g r a n i t e d i k e s w h i c h c l o s e l y r e s e m b l e s y e n i t e i n o r t h o c l a s e t e x t u r e and m a f i c c o n t e n t b u t c o n t a i n s e v e r a l p e r c e n t z i r c o n a r e a l s o s e e n , s u p p o r t i n g t h e h y p o t h e s i s t h a t s y e n i t e and d i k e s a r e oogene-t i c . 4.4 VEINS Three k i n d s o f v e i n s a r e r e c o g n i z e d i n t h e a r e a : f l u o r i t e - q u a r t z - m i c r o -c l i n e - c a l c i t e v e i n s , c a l c i t e - e p i d o t e - a c t i n o l i t e - q u a r t z v e i n s , and q u a r t z -s i d e r i t e - d o l o m i t e v e i n s . None o f t h e s e was seen t o c u t a v e i n o f a n o t h e r t y p e . F l u o r i t e - q u a r t z - m i c r o c l i n e - c a l c i t e v e i n s ( P l a t e 4 . 9 ) , l e s s t h a n two cm t h i c k , c u t s y e n i t e and m e l a g r a n i t e d i k e s . They a r e r a r e ; o n l y a few, r e c o g -n i z e d by t h e p u r p l e c o l o u r o f t h e f l u o r i t e , were seen. I n t h i n • . s e c t i o n , q u a r t z and ^subhedral m i c r o c l i n e g r a i n s 1 mm a c r o s s ; m a k e . u p 80 p e r c e n t o f t h e veins-* g r o w i n g j;, i n w a r d t o f o r m comb s t r u c t u r e . A n h e d r a l f l u o r i t e and c a l c i t e f i l l s p a c es between g r a i n s b o t h i n v e i n s . and i n e n v e l o p e s around v e i n s t h a t a r e s e v e r a l mm t h i c k . M i c r o c l i n e i s p a r t l y a l t e r e d t o a l b i t e and m u s c o v i t e . F l u o r i t e - q u a r t z - m i c r o c l i n e - c a l c i t e v e i n s p r o b a b l y c r y s t a l l i z e d f r o m l a t e - m a g m a t i c v o l a t i l e - r i c h f l u i d s . E p i d o t e - a c t i n o l i t e - c a l c i t e - q u a r t z v e i n s ( P l a t e 4.10) a r e f o u n d only, i n s k a r n r o c k s . They a r e s paced a few cm t o s e v e r a l m a p a r t . They range f r o m 1 mm t o 5 cm i n t h i c k n e s s . W i t h i n t h e v e i n s , e p i d o t e o c c u r s as randomly o r i e n t e d l i g h t green, e l o n g a t e , twinned, t a b u l a r c r y s t a l s . Dark g r e e n a c i c u l a r c r y s t a l s o f a c t i n o l i t e grow i n w a r d f r o m t h e v e i n w a l l s . Q u a r t z and c a l c i t e f i l l s p a c e s between e p i d o t e and a c t i n o l i t e c r y s t a l s . A l l g r a i n s a r e s e v e r a l mm t o cm i n s i z e . V e i n w a l l s a r e c l e a r l y d e f i n e d . V e i n s f i l l s h a l l o w - d i p p i n g 35 0. 3 mm Plate 4.9 F l u o r i t e - q u a r t z - m i c r o c l i n e - c a l c i t e vein cutting Unit 17a, melagranite dike a) i n hand specimen (sample DD17) and b) i n t h i n section (sample E 14). In hand specimen, purple f l u o r i t e characterizes the vein. In t h i n section, microcline grows inward from the vein wall and the center of the vein i s f i l l e d with quartz (crossed n i c o l s ) . 36 * 0 1 2 3 cr P l a t e 4.10 C a l c i t e - e p i d o t e - a c t i n o l i t e - q u a r t z v e i n s , a) i n the f i e l d f i l l i n g f r a c t u r e s i n s k a r n U n i t B and b ) i n hand specimen (Sample DD23) a r e c h a r -a c t e r i z e d by l a r g e t w i n n e d c r y s t a l s o f g r e e n e p i d o t e . Q u a r t z and a c t i n o l i t e a r e common b u t a r e not i l l u s t r a t e d h e r e . 37 e x t e n s i o n f r a c t u r e s ( F i g . 4 . 3 ) . E p i d o t e - a c t i n o l i . t e - c a l c i t e - q u a r t z v e i n s formed d u r i n g c o o l i n g o f c o n t a c t metamorphic r o c k s . S i d e r i t e - d o l o m i t e - q u a r t z v e i n s ( P l a t e 4.11) a r e found i n a l l r o c k t y p e s o f t h e a r e a b u t a r e most common i n s y e n i t e where t h e y f i l l s u b h o r i z o n t a l t e n s i o n f r a c t u r e s w i t h i n a few tens o f meters o f i t s c o n t a c t w i t h metamor-phosed s e d i m e n t a r y r o c k s ( F i g . 4 . 3 ) . I n t h e s e a r e a s t h e v e i n s a r e b o u t 20. cm t h i c k and spaced t h e same d i s t a n c e a p a r t . I n t h e v e i n s , a n h e d r a l o r sub-h e d r a l q u a r t z (90 p e r c e n t o f t h e rock)_ e i t h e r grows i n w a r d f r o m v e i n edges i n comb s t r u c t u r e o r forms i r r e g u l a r l y r a d i a t i n g c l u s t e r s o f c r y s t a l s . The r e -m a i n i n g 19 p e r c e n t o f t h e r o c k i s composed o f e u h e d r a l rhomb-shaped s i d e r i t e and d o l o m i t e w h i c h i s a n h e d r a l o r forms c u r v e d coxcombs. C r y s t a l s o f a l l m i n e r a l s range from s e v e r a l mm t o s e v e r a l cm i n s i z e . V e i n s have s h a r p c o n -t a c t s w i t h h o s t r o c k . C a r b o n a t e m i n e r a l s i n t h e v e i n s p r o b a b l y o r i g i n a t e d f r o m c o n t a c t metamorphic r o c k s . The s o u r c e o f t h e q u a r t z I s n o t c e r t a i n b e cause o r i g i n a l q u a r t z i s n o t p r e s e n t i n s y e n i t e , t h e r e i s no f r e e q u a r t z i n c a l c s i l i c a t e r o c k s , and no e v i d e n c e has been s e e n f o r d i s s o l u t i o n o f t h e q u a r t z i t e o f U n i t 15. 4.5 CONTACT METAMORPHISM 4.5.1 I n t r o d u c t i o n S e v e r a l d i f f e r e n t t y p e s o f c o n t a c t metamorphic r o c k s a r e found e a s t o f t h e s y e n i t e on t h e c a r b o n a t e r i d g e i n an i r r e g u l a r zone up t o 600 m w i d e (Map 1 ) . These u n i t s , mapped i n t h e f i e l d , a r e : U n i t A, banded q u a r t z - m u s c o -v i t e h o r n f e l s ; U n i t B, d a r k g r e e n d i o p s i d e - p h l o g o p i t e - c a l c i t e - t r e m o l i t e - s p h e n e s k a r n w i t h r a r e g a r n e t ; and U n i t C, p a l e g r e e n d i o p s i d e - p h l o g o p l t e - c a l c i t e s k a r n . I n f o r m a t i o n on r e l a t i v e t i m e v e r s u s m i n e r a l growth and s t r u c t u r a l e v e n t s f o r t h e s e u n i t s i s c o m p i l e d i n T a b l e 4.1. 38 b Plate 4.11 Quartz-siderite-dolomite veins i n the f i e l d (a) commonly f i l l subhorizontal fractures near the roof of Unit 16, syenite (note rock hammer for scale; photograph taken on side of central c i r q u e ) . In hand specimen (b) minerals are coarse-grained; s i d e r i t e i s the darker of the two brown minerals. 39 Table 4.1 R e l a t i v e .time and tectonism versus mineral growth f or i n t r u s i v e Units"16 and 17, contact metamorphic Units A, B, and C, and veins, Guano-Guayes area, P e l l y Mountains, Yukon T e r r i t o r y . WIT Id: STE.VITE orthocla«e + perttiltt apatite • l d c r l t c a c K 1 r 1 ne-a U R 1 ie erfved*onlte magnetite plagioclase (albite) microcline • anidlne c a l c i t e dolomite quartz b i o t i t e pyrite muscovite flour!te ZlTCOS epidote L A T T . J t A C M A T I C V K I M S HIC3IE5T CKADC S K A H K K l K r t A T I M * ALTTJ-ATKIH I <•> z IS. •-C A J X I T I : V K I I 5 AI.TIJCATIU:; Jl U N I T 1 7 : D I R S o r t h o d u c aphene dlopside-nedenburglte diopside arfvedsonite magnetite plagioclase (alblte) ntc r o d Ine c a l c i t e quartz b i o t i t e pyrite and l l s o n l t e zircon a l l a n i t e ponazite mineral C a c t i n o l i t e a t i l ononelanc axinlte UNITS B t C: SKARS dlopalde garnet phlogopltc c a l c i t e t r c n o l l t e sphene apatite c i c r o c l i n t arfvedsonlte zircon a l l a n l t e epidote quarts c h l o r i t e nlneral k mineral ft serpentine magnetite USIT A: H0RNTE3-S quartz + feldspar euscovlte pyrite b l o c l t e s l d e r l t a rpldote tourmaline 40 4.5.1.1 U n i t A: Banded q u a r t z - m u s c o v i t e h o r n f e l s About 100 m o f l i g h t t a n , v e r y f i n e - g r a i n e d (0.01 mm) e x t r e m e l y w e l l -banded q u a r t z - m u s c o v i t e h o r n f e l s ( P l a t e 3.2a) a d j o i n s t h e s y e n i t e on t h e e a s t . Samples examined i n t h i n s e c t i o n ( A ppendix A4) c o n t a i n about 65 p e r -c e n t g r a n o b l a s t i c p o l y g o n a l q u a r t z (and f e l d s p a r ?) i n g r a i n s 0.01 mm a c r o s s , 26 p e r c e n t p a l e g r e e n p l e o c h r o i c v e r y f i n e - g r a i n e d (0.01 mm o r l e s s ) f e l t e d m u s c o v i t e ( o r p o s s i b l y p h l o g o p i t e ? ) , up t o 15 p e r c e n t a n h e d r a l t o s u b h e d r a l s i d e r i t e c r y s t a l s 0.03 mm i n d i a m e t e r , and up t o 5 p e r c e n t p y r i t e i n sub-h e d r a l c r y s t a l s u s u a l l y . l e s s t h a n 1 mm i n d i a m e t e r . T r e m o l i t e , i n s t e a d o f m i c a , i s seen i n one s e c t i o n . Bands a r e on t h e o r d e r o f a few cm i n t h i c k -ness and weather w i t h v a r y i n g amounts o f l i m o n i t e s t a i n so t h e y a r e c l e a r l y v i s i b l e i n o u t c r o p . They r e f l e c t v a r i a t i o n s i n g r a i n - s i z e and r e l a t i v e amounts o f m i c a , p y r i t e , and c a r b o n a t e ( P l a t e 4.12). These v a r i a t i o n s a r e a p p a r e n t l y r e l i c t s o f d e p o s i t i o n a l b e ds. U n i t A i s h i g h l y s h e a r e d a l o n g t h e bench s h e a r zone. I n r o c k s f r o m t h i s zone m u s c o v i t e i s p a r t l y a l i g n e d o r f o l i a t e d p a r a l l e l t o s h e a r s . No m a f i c o r m e l a g r a n i t e d i k e s were o b s e r v e d i n t r u d i n g U n i t A a l t h o u g h some a r e a s a l o n g t h e bench s h e a r zone,.where t h e r e i s no o u t c r o p , are'more r a d i o a c t i v e t h a n s u r r o u n d i n g o u t c r o p s o f U n i t A. The bench s h e a r zone i s n e a r t h e b a s e . o f U n i t A. Rocks c o m p o s i t i o n a l l y e q u i v a l e n t t o U n i t A o c c u r e a s t o f t h e s h e a r zone i n some p l a c e s (Map 1 ) . I n t h e s e l o c a t i o n s , t he c o n t a c t between U n i t A and s k a r n U n i t B i s - c l e a r l y ' , c o n -f o r m a b l e w i t h c o m p o s i t i o n b a n d i n g i n b o t h u n i t s . The c o n t a c t between U n i t A and s y e n i t e i s s h a r p and c u t s bands a t an a n g l e . Metamorphism o f U n i t A c o n s i s t e d o f r e c r y s t a l l i z a t i o n o f s e d i m e n t a r y U n i t 13 w i t h no s i g n i f i c a n t a d d i t i o n o r r e m o v a l o f components. 41 0 . 3mm Plate 4.12 Unit A, quartz-muscovite hornfels, i n th i n section (Sample 01A) shows banding (from l e f t to right) by a gradual decrease i n grain s i z e and an increase i n muscovite (higher birefringence) content. Opaque mineral i s p y r i t e . Note the poorly developed f o l i a t i o n of muscovite, possibly r e l a t e d to formation of the bench shear zone (crossed n i c o l s ) . 42/ 4.5.1.2 Unit B: Dark green diopside-phlogopite-calcite-tremolite-sphene skarn with rare garnet Dark green diopside-phlogopite-calcite-tremolite-sphene skarn with rare garnet, Unit B on Map 3, i s a 75 to 250 m thick c l i f f - f o r m i n g f i n e -grained rock with occasional composition banding. This unit outcrops on the western slope of the carbonate ridge and across the southern end of the r i d g e -crest to the top of the eastern cirque. Thickness of Unit B ranges from 50 to 240 m. In the f i e l d , Unit B i s d i v i s i b l e into two subunits, B l which i s banded and so f i n e l y c r y s t a l l i n e that mineral grains cannot be i d e n t i f i e d i n hand specimen and B2 which i s coarsely c r y s t a l l i n e with grains several mm to cm i n diameter (Plate 4.13). Bands i n Subunit B l are characterized by both v a r i a t i o n s i n c a l c i t e content, more calcareous bands weathering re c e s s i v e l y , and by t r e m o l i t e - c a l c i t e - f i l l e d fractures several mm wide which are oriented p a r a l l e l to c a l c i t i c bands. Occasionally bands contain-ing garnet were found which also p a r a l l e l e d c a l c i t i c bands. These bands were traceable for only a few m. Outcrops of Subunit B2 are rare.- This subunit i s usually represented i n the f i e l d by phlogopitic s o i l . Contacts between Subunits B l and B2 p a r a l l e l bedding i n the r e c r y s t a l l i z e d s ection to ;the :south, suggesting that these subunits might;reflect differences i n o r i g i n a l l i t h o l o g y . Thin sections of Unit B, described below and i n Appendix A4, show that although v a r i a t i o n s i n mineral content are^.common between specimens, d i f f e r -ent parageneses do not f a l l i nto geographically d i s t i n c t zones. Diopside i s generally colourless i n t h i n section and occurs i n masses of rounded to subhedral grains with 0.1 mm average diameter i n Subunit B l and 3 mm diameter i n Subunit B2 but i s euhedral where completely surrounded by c a l c i t e (Plate 4.14a). C a l c i t e usually forms amoeboid p o i k i l o b l a s t i c grains from several mm to 4 cm i n diameter with smaller marginal grains i n granoblastic polygonal or 43 Plate 4 . 1 3 Unit B , i n outcrop, i s d i v i s i b l e into two subunits-. a) subunit B ^ , green, fine-grained skarn with poorly developed bands (sample point 08C ) and b) subunit E^, coarse-grained phlogopitic skarn from near sample point P6C. 44 0. 1mm Plate 4.14 Photomicrographs of skarn Unit B include: a) sample P5C, con-t a i n i n g phlogopite (large anhedral grain, r i g h t of center), diopside (gran-ul a r mass i n lower l e f t and rhombs) and c a l c i t e which i s p o i k i l o b l a s t i c , one grain being larger than the f i e l d of view and b) sample 010, bent c a l c i t e which shows lamellar g l i d e twins formed during deformation (both photomicro-graphs with crossed n i c o l s ) . 45 d e c u s s a t e masses. L a r g e r c a l c i t e g r a i n s have u b i q u i t o u s g l i d e t w i n s and a r e o c c a s i o n a l l y b e n t ( P l a t e 4.14b). P h l o g o p i t e forms r a n d o m l y - o r i e n t e d p l a t y e u h e d r a l t o s u b h e d r a l p a l e brown p l e o c h r o i c c r y s t a l s commonly p o i k i l o b l a s t i c w i t h e n c l o s e d d i o p s i d e . T h e i r a v e r a g e d i a m e t e r i n S u b u n i t B l i s 0.2 mm. I n S u b u n i t B2 p h l o g o p i t e c r y s t a l s range f r o m 1 mm t o s l i g h t l y more t h a n 3 mm a c r o s s ( P l a t e 4.15a). G r a i n s a r e s l i g h t l y b e n t b u t n o t k i n k e d . No p h l o g o p i t e was s e e n i n U n i t B between p o i n t s 08) and P3 (Maps 1 and 3 ) , s u g g e s t i n g p o t a s s i u m c o n t e n t d r o p s o f f i n t h i s s e c t i o n o f t h e c o n t a c t metamorphic a u r e o l e . A p e t r o l o g i c a l i d e n t i f i c a t i o n o f p h l o g o p i t e was c o n f i r m e d by q u a l i t a t i v e a n a l y s i s o f s p e c -imens on an ETEC, a u t o s c a n s c a n n i n g e l e c t r o n m i c r o s c o p e w i t h an O.RTEC x - r a y a n a l y t i c a l u n i t ( A ppendix A 8 ) . T r e m o l i t e - a c t i n o l i t e ( P l a t e 4.15b) i s found as masses o f a c i c u l a r , commonly r a d i a t i n g , p a l e t o d a r k g r e e n p l e o c h r o i c c r y s t a l s . A v erage l e n g t h i s 0.1 mm. T r e m o l i t e - a c t i n o l i t e i s a s s o c i a t e d w i t h d i o p s i d e i n a l l samples b u t one. G a r n e t ( P l a t e 4.16), d a r k r e d d i s h - b r o w n i n hand specimen, i s seen i n a few t h i n s e c t i o n s i n S u b u n i t B l . I t i s s u b h e d r a l and e n c l o s e s e u h e d r a l d i o p s i d e . Most g a r n e t i s s l i g h t l y b i r e f r i n g e n t , p o s s i b l y due t o s t r a i n . G r a i n s , a v e r a g i n g 1 cm, r a n g e f r o m 0.2 mm t o more t h a n 2 cm i n d i a m e t e r . I n some specimens "grains w h i c h a r e a l m o s t c o l o u r l e s s a r e rimmed by p a l e y e l l o w s e c o n d -g e n e r a t i o n g a r n e t . The c o m p o s i t i o n o f g a r n e t was a l s o d e t e r m i n e d q u a l i t a -t i v e l y by t h e x - r a y s c a n n i n g e l e c t r o n m i c r o s c o p e and i s a s o l i d s o l u t i o n between g r o s s u l a r i t e and a n d r a d i t e , C a ^ ( A l , F e ) ^ S i ^ O ^ ^ ( A p p e n d i x A 8 ) . A l l g a r n e t g r a i n s a r e h i g h l y f r a c t u r e d , most f r a c t u r e s b e i n g r o u g h l y p a r a l l e l as though caused by s h e a r i n a c o n s t a n t d i r e c t i o n . F r a c t u r e s a r e f i l l e d w i t h c a l c i t e and o c c a s i o n a l l y e p i d o t e . 4 6 0. 1mm Plate 4.15 Photomicrographs of Unit B show: a) randomly oriented phlogopite i n c a l c i t e (sample P6C, subunit B^l crossed n i c o l s ) and b) a c i c u l a r tremo-l i t e with rhomb-shaped diopside (sample 012A, subunit B ; uncrossed n i c o l s ) 47 b 0. 3mm P l a t e 4.16 G a r n e t , s e e n r a r e l y i n U n i t B s k a r n , i l l u s t r a t e d a) i n hand specimen (sample DD26), i n t h i s case p a r t l y a l t e r e d t o l i g h t g reen e p i d o t e and b) i n t h i n s e c t i o n (sample Q13C, c r o s s e d n i c o l s ) , where i t d i s p l a y s low f i r s t - o r d e r b i r e f r i n g e n c e and z o n i n g . 4 8 O t h e r m i n e r a l s p r e s e n t i n U n i t B a r e sphene, a p a t i t e , p y r i t e , e p i d o t e , c h l o r i t e , m a g n e t i t e , s e r p e n t i n e , m i n e r a l A, and m i n e r a l B. Sphene, a p a t i t e and p y r i t e appear o n l y i n t r a c e amounts. The r e m a i n i n g m i n e r a l s were formed by r e t r o g r a d e a l t e r a t i o n o f s k a r n . E p i d o t e and c h l o r i t e a r e common t h r o u g h -o u t U n i t B. E p i d o t e o c c u r s i n t a b u l a r p r i s m a t i c c r y s t a l s and a n h e d r a l g r a i n s , 0.01 t o 0.3 mm a c r o s s , a s s o c i a t e d w i t h v e r y f i n e - g r a i n e d ( l e s s t h a n 0.1 mm) f e l t e d masses of c h l o r i t e i n g a r n e t o r g a r n e t - s h a p e d pseudomorphs ( P l a t e 4.17a) and i n o r d i s p e r s e d amongst g r a i n s o f t r e m o l i t e , d i o p s i d e and p h l o g o p i t e . C h l o r i t e a l s o o c c u r s i n l a r g e r (0.01 t o 3 mm) g r a i n s p a r t l y r e p l a c i n g p h l o g o p i t e ( P l a t e 4.17b). C h l o r i t e e i t h e r shows s t r o n g anomalous b l u e and brown f i r s t o r d e r b i r e f r i n g e n c e (Fe-Mg c h l o r i t e ) o r n o r m a l f i r s t o r d e r b i r e f r i n g e n c e ( M g - c h l o r i t e ) ( A l b e e , 1 9 6 2 ) . S e r p e n t i n e and m a g n e t i t e a r e common i n t h e n o r t h e r n o u t c r o p s o f U n i t B. S e r p e n t i n e forms masses o f f o l i a t e g r a i n s 0.01 t o 0.2 mm l o n g . Some s e r p e n t i n e i s a s s o c i a t e d w i t h m a g n e t i t e i n pseudomorphs and i n i r r e g u l a r p a t c h e s w h i c h mimic p y r o x e n e . D i s c o n t i n u o u s , s i n u o u s f r a c t u r e s i n s e r p e n t i n i z e d r o c k f i l l e d : w i t h poor c r o s s -f i b e r c h r y s o t i l e a v e r a g e 1 mm b u t a r e up t o s e v e r a l cm w i d e . M a g n e t i t e i n h i g h l y s e r p e n t i n i z e d a r e a s o f s k a r n o c c u r s a l o n g c l e a v a g e i n c h l o r i t i z e d p h l o g o p i t e ( P l a t e 4.17b) and as i r r e g u l a r f r a c t u r e f i l l i n g s t h a t r a n g e f r o m 0.5 t o s e v e r a l mm w i d e ( P l a t e 4.18a). I n one specimen, s e r p e n t i n e and mag-n e t i t e t o g e t h e r f o r m g e o m e t r i c a l shapes, s u g g e s t i n g f o r m a t i o n by a l t e r a t i o n o f a p r e e x i s t i n g m i n e r a l ( P l a t e 4.18b). M i n e r a l A and m i n e r a l B a r e see n i n s e r p e n t i n i z e d a r e a s o f U n i t B. . M i n e r a l A, found i n sample P7A, i s a s s o c i a t e d w i t h anomalous b l u e s e r p e n t i n e . G r a i n s o f m i n e r a l A a r e l e s s t h a n 0.2 mm a c r o s s and t h i n l y rimmed by a m i n e r a l w i t h h i g h b i r e f r i n g e n c e w h i c h r e s e m b l e s a c a r b o n a t e . M i n e r a l B, se e n i n sample A9, has p r o p e r t i e s i d e n t i c a l t o t h o s e o f t h e h u m i t e group e x c e p t t h a t i t has a s m a l l 2V. I t forms p r i s m a t i c - r a d i a l g r a i n s 0.5 mm l o n g w i t h w e l l - d e v e l o p e d a l b i t e - l i k e 49 0. 1mm Plate 4.17 Retrograde a l t e r a t i o n i n skarn Unit B includes: a) a l t e r a t i o n of garnet to epidote (high r e l i e f , anomalous blue) and c h l o r i t e (low r e l i e f , f i r s t order gray birefringence) i n sample 08E (crossed and uncrossed n i c o l s ) and b) replacement of phlogopite (high birefringence, lower l e f t ) by c h l o r i t e of both anomalous and normal f i r s t order birefringence (sample B3; crossed n i c o l s ) . The f i r s t - o r d e r gray mineral i s serpentine. 50 0. 3mm P l a t e 4.18 S k a r n U n i t B a f t e r l a t e - s t a g e s e r p e n t i n i z a t i o n seen a) i n hand specimen (sample K 1 7 ) , c o n t a i n i n g v e i n l e t s o f m a g n e t i t e and i n t h i n s e c t i o n b) (sample A9) where m a g n e t i t e and s e r p e n t i n e o c c a s i o n a l l y form pseudomorphs a f t e r an u n i d e n t i f i e d m i n e r a l ( c r o s s e d n i c o l s ) . 51 t w i n n i n g and ra g g e d g r a i n b o u n d a r i e s . P r o p e r t i e s o f t h e s e two m i n e r a l s a r e d e t a i l e d i n A p p e n d i x A6. Three o u t c r o p s , each one s e v e r a l t e n s o f m e t e r s s q u a r e o r l e s s , c o n s i s t o f b r e c c i a o f c o n t a c t m e t a s o m a t i z e d r o c k f r a g m e n t s i n a m a t r i x o f p u r e c a l -c i t e (Map 1 ) . Fragments a r e h i g h l y a n g u l a r and r a n g e f r o m s e v e r a l mm t o s e v e r a l cm i n d i m e n s i o n ( P l a t e 3.3a). B r e c c i a t i o n m i g h t be r e l a t e d t o f o r m -a t i o n o f t h e bench s h e a r zone. The c o n t a c t between U n i t B and U n i t A t o t h e west i s c o n f o r m a b l e and i s caused by a change i n o r i g i n a l l i t h o l o g y f r o m impure q u a r t z i t e ( U n i t A) t o c a r b o n a t e - ( U n i t B ) . L a r g e amounts of Fe, Mg, and p r o b a b l y S i G ^ were added t o U n i t B, e s p e c i a l l y near m e l a g r a n i t e and m a f i c d i k e s where d i o p s i d e becomes d a r k e r i n c o l o u r and a c t i n o l i t e o c c u r s i n s t e a d o f t r e m o l i t e . The c o n t a c t between U n i t B and p a l e g r e e n s k a r n o f U n i t C t o t h e e a s t i s s h a r p on t h e n o r t h e r n end o f t h e c a r b o n a t e r i d g e . To t h e s o u t h , U n i t C i s o n l y l o c a l l y d e v e l o p e d , U n i t B i s commonly i n s h a r p c o n t a c t w i t h r e c r y s t a l l l i z e d s e d i m e n t a r y rocks-.- I n many p l a c e s , t h e c o n t a c t between U n i t . B and.' (rocks to 'the e a s t , c u t s a c r o s s • r e l i c t s e d i m e n t a r y b e d d i n g p l a n e s . 4.5.1.3 U n i t C: P a l e g r e e n d i o p s i d e - p h l o g o p i t e - c a l c i t e s k a r n P r i n c i p a l m i n e r a l s o f U n i t C a r e c a l c i t e , p h l o g o p i t e , d i o p s i d e , c h l o r i t e , and s e r p e n t i n e . A l t h o u g h s i m i l a r t o U n i t B i n m i n e r a l o g y , U n i t C i s d i f f e r -e nt i n appearance i n t h e f i e l d . U n i t C i s a 50 t o 250 m t h i c k , c l i f f - f o r m i n g , v e r y p a l e g r e e n banded r o c k w i t h abundant s e r p e n t i n e - c a l c i t e - f i l l e d gashes p a r a l l e l t o bands ( P l a t e 4.19). U n i t C forms t h e s h a r p r i d g e - c r e s t e a s t o f o t h e r c o n t a c t metamorphic r o c k s , and c o v e r s a l a r g e a r e a on t h e e a s t e r n s i d e o f t h e r i d g e (Map 3 ) . T h i n s e c t i o n modes a r e i n A p p e n d i x A5. C a l c i t e g r a i n s , a v e r a g i n g 0.05 t o 0.1 mm b u t r a n g i n g up t o s e v e r a l mm i n d i a m e t e r , f o r m g r a n o b l a s t i c p o l y g o n a l masses and l a r g e amoeboid p o i k i l o -52 0. 3mm P l a t e 4.19 S k a r n U n i t C a) i n hand specimen and b) i n t h i n s e c t i o n ( c r o s s e d n i c o l s ) c o n t a i n i n g s m a l l s p h e r i c a l g r a i n s o f s e r p e n t i n e a r r a n g e d i n bands w h i c h mimic o r i g i n a l s e d i m e n t a r y b e d d i n g (sample P7D). 53 b l a s t i c g r a i n s . D o l o m i t e , o b s e r v e d o n l y i n one sample, o c c u r s as l a r g e . (2 mm) g r a i n s : s u r r o u n d e d and s e p a r a t e d from o t h e r m i n e r a l s by a c o r o n a o f f i n e r - g r a i n e d c a l c i t e . D i o p s i d e i s abundant (45 to 75 p e r c e n t o f t h e r o c k ) i n two specimens where i t forms 0.05 to 0.1 mm s u b - r a d i a l s l i g h t l y rounded c o l o u r l e s s p r i s -m a t i c g r a i n s ( P l a t e 4.20). P h l o g o p i t e forms l a r g e s u b h e d r a l 0.2 to. 3 mm u n o r i e n t e d g r a i n s . C h l o r i t e i s e i t h e r a s s o c i a t e d w i t h s e r p e n t i n e i n f e l t e d masses o r i t r e p l a c e s p h l o g o p i t e and i s i n t u r n r e p l a c e d by s e r p e n t i n e ( P l a t e 4 . 2 0 ) . S e r p e n t i n e o c c u r s i n a l l specimens and a c c o u n t s f o r t h e p a l e g r e e n t i n g e i n o t h e r w i s e w h i t e h o r n f e l s . G r a i n s a r e 0.03 to 0.1 mm l o n g and f e l t e d ; t h e l a r g e s t g r a i n s o c c u r where i t has r e p l a c e d p h l o g o p i t e and c h l o r i t e . S e r p e n -t i n e a l s o f i l l s e x t e n s i o n gashes, forms a c i c u l a r c r y s t a l s w h i c h r i m d i o p s i d e , and o c c u r s i n s m a l l rounded g r a n u l a r shapes s u g g e s t i n g r e p l a c e m e n t o f o l i v i n e ( P l a t e s 4.19 and 4.21). A p a t i t e i s t h e o n l y t r a c e m i n e r a l seen. A l l m i n e r a l s w i t h l a r g e g r a i n s i z e i n U n i t C a r e deformed, as i n U n i t B. O nly one phase o f d e f o r m a t i o n i s e v i d e n t . U n i t C i s t h e e a s t e r n m o s t c o n t a c t metamorphic u n i t i n t h e a r e a . I n t h e n o r t h e a s t , i t ends a g a i n s t O r d o v i c i a n d a r k gray g r a p h i t i c s h a l e w h i c h has been f a u l t e d upwards. I n t h e s o u t h e r n end o f t h e a r e a , I t was p o s s i b l e to map t h e c o n t a c t between U n i t C and r e c r y s t a l l i z e d s e d i m e n t a r y r o c k s . T h i s c o n t a c t c u t s a c r o s s b e d d i n g i r r e g u l a r l y . 4.5.2 C o n d i t i o n s o f Metamorphism I n t r u s i o n o f s y e n i t e ' i n t o a S i l u r i a n r e e f c a r b o n a t e r o c k and q u a r t z i t e s e c t i o n formed h o r n f e l s and s k a r n on what i s now the Guano-Guayes p r o p e r t y . 54 0. 3mm P l a t e 4.20 P h o t o m i c r o g r a p h s o f s k a r n U n i t C showing a ) a c i c u l a r s e r p e n t i n e r a d i a t i n g from d i o p s i d e ( g r a n u l a r , s e c o n d - o r d e r b i r e f r i n g e n c e ) , i n t o a l a r g e c a l c i t e g r a i n (sample P11A) and b) s e r p e n t i n e ( f i r s t o r d e r gray b i r e f r i n g e n c e ) rimming c h l o r i t e (anomalous b l u e and brown f i r s t o r d e r b i r e f r i n g e n c e ) w h i c h i s i n t u r n r e p l a c i n g p h l o g o p i t e ( h i g h s e c o n d - o r d e r b i r e f r i n g e n c e ) i n sample P9B ( b o t h w i t h c r o s s e d n i c o l s ) . 55 P l a t e 4.21 S u b h o r i z o n t a l f r a c t u r e s i n s k a r n U n i t C f i l l e d w i t h poor c r o s s - f i b e r c h r y s o t i l e ( n e a r p o i n t P 8 B ) . 56 S y e n i t e i s a c o a r s e - g r a i n e d r o c k o f o r t h o c l a s e l a t h s w i t h i n t e r s t i t i a l p y r o -xene o r amphibole and minor amounts o f a p a t i t e , z i r c o n , sphene, p y r i t e , and i l m e n i t e . C o n t a c t metamorphism, o f low to medium grade ( W i n k l e r , 1976), i n v o l v e d low p r e s s u r e s , h i g h t o low t e m p e r a t u r e s , and metasomatism. S t r u c t u r a l r e l a t i o n s between s y e n i t e and a s s o c i a t e d v o l c a n i c r o c k s e l s e w h e r e i n t h e S t . C y r range s u g g e s t t h a t s t o c k s were emplaced a t s h a l l o w d e p t h s . S y e n i t e has been o b s e r v e d g r a d i n g i n t o t r a c h y t e f l o w r o c k s w h i c h s u g g e s t s i n t r u s i o n as s h a l l o w as 600 m i n p l a c e s ( M o r i n , 1976). A s l i g h t l y g r e a t e r d e p t h o f i n t r u s i o n o f 1 t o 2 km i s h y p o t h e s i z e d f o r Guano-Guayes a r e a s y e n i t e b e c a u s e t h e top o f the s y e n i t e i n -t r u d e s s e d i m e n t a r y , n o t - v o l c a n i c , crocks•. A p r e s s u r e o f 500 b a r s , c o r r e s p o n d i n g to a d e p t h o f 1.7 km, i s used i n t h e f o l l o w i n g d i s c u s s i o n o f c o n t a c t metamorphic c o n d i t i o n s . E s t i m a t e s o f o t h e r c o n t a c t metamorphic c o n d i t i o n s can be made by use o f t h e r m o d y n a m i c a l l y - d e r i v e d r e a c t i o n c u r v e s i n v o l v i n g m i n e r a l s o b s e r v e d i n con-t a c t metamorphic r o c k - * u n i t s . U n i t A, q u a r t z - m u s c o v i t e h o r n f e l s , was formed a t a P-T-X grade b e low and to t h e l e f t o f t h e c u r v e f o r t h e r e a c t i o n : q u a r t z + m u s c o v i t e = a n d a l u s i t e + K - f e l d s p a r + R^O ( r e a c t i o n 25) shown i n F i g . 4.4. The maximum p o s s i b l e t e m p e r a t u r e f o r s t a b i l i t y o f q u a r t z + m u s c o v i t e a t l e s s t h a n 500 b a r s i s 540 degrees C. I n t h i s c a s e , X n must be co2 z e r o . I f X was above z e r o i n t h e r o c k s , maximum t e m p e r a t u r e o f s t a b i l i t y o f cu 2 U n i t A was as low as 450 degrees C. T h i s i s a p o s s i b i l i t y s i n c e some p h l o g o p i t e may be p r e s e n t i n t h e r o c k and t h e f o r m a t i o n o f p h l o g o p i t e r e l e a s e s C 0 2 - i n t o t h e s y s t e m . ( F i g . 4.5, r e a c t i o n s 31,and 3 3 ) . W h o l e - r o c k a n a l y s e s show t h a t t h e r o c k c o n t a i n s s i g n i f i c a n t s o d i u m ( A p p e n d i x B ) , p r o b a b l y as f i n e - g r a i n e d a l b i t e . T h i s w o u l d a l s o cause t h e a n d a l u s i t e - f o r m i n g r e a c t i o n t o t a k e p l a c e a t a l o w e r t e m p e r a t u r e ( H e w i t t , 1973). 57 4 0 0 , 500 6 0 0 Temperature i n degrees C Fi g . 4 . 4 P-T diagram for reactions 60 and 61 which define the upper l i m i t of s t a b i l i t y of serpentine ( 6 0 ) and of serpentine plus diopside ( 6 1 ) at Pf = PH2O (from Evans and Trommsdorff, 1 9 7 0 ) and for reaction 25 which defines the upper l i m i t of s t a b i l i t y of muscovite plus quartz at vari a b l e X c 0 2 ( s o l i d curves from Kerrick , 1 9 7 2 ; dashed curve extrapolated from s o l i d curves). Abbreviations used are: S serpentine Tc t a l c Q quartz Di diopside Fo f o r s t e r i t e And andalusite Tr tremolite Mu muscovite Kf K-feldspar 58 F i g . 4.5 T - X c o d i a g r a m a t 500 b a r s f o r r e a c t i o n s i n t h e systems l i s t e d b e l ow: 2 r e a c t i o n I t h r o u g h 7 I I - 14, 20 33 31 32 s y s t e m CaO-MgO- S10 2-C0 2 - H 2 0 -Ca0-MgO-Si0 2-CO 2-H 2Q-K 2O-Al 2O 3-TiO C a O - M g O - S i 0 2 - C 0 2 - H 2 0 - K 2 0 - A l 2 0 3 CaO-MgO-SiO -CO -H 0-K 0 - A l 2 0 3 CaO-MgO-S10 2-C0 2-H 0 - K 2 0 - A l 2 0 r e f e r e n c e : • S k i p p e n , 1974 Hunt and K e r r i c k , 1977 Hunt and K e r r i c k , 1977 Puhan and Johannes, 1974 H e w i t t , 1975 S o l i d c u r v e s a r e c a l c u l a t e d o r e x p e r i m e n t a l c u r v e s f o r 500 b a r s . R e l a t i v e p o s i t i o n s o f dashed curves, a r e e x t r a p o l a t e d from t h e i r p o s i t i o n s a t h i g h e r p r e s s u r e s . Open c i r c l e s a r e i n v a r i a n t p o i n t s , d i t i o n to t h o s e on t h e p r e v i o u s f i g u r e a r e : A b b r e v i a t i o n s used i n a d -Gr g r o s s u l a r Zo z o i s i t e Ca c a l c i t e Do d o l o m i t e Wo w o l l a s t o n i t e An a n o r t h i t e Ph Ru Sp p h l o g o p i t e r u t i l e sphene F i g . 4.5 Explanation on previous page 60 R e a c t i o n s i n v o l v i n g m i n e r a l s o b s e r v e d i n U n i t B a r e i l l u s t r a t e d i n F i g . 4.5. Arrows show two p r o g r a d e T-X p a t h s w h i c h w o u l d have b o t h cu 2 r e s u l t e d i n the p a r a g e n e s i s f o u n d . W i t h i n c r e a s i n g t e m p e r a t u r e , t h e s e r e a c -t i o n s c a u s e d t h e f o r m a t i o n o f t r e m o l i t e , c a l c i t e , p h l o g o p i t e , sphene, and d i o p s i d e . Each r e a c t i o n caused an i n c r e a s e i n X n . R e a c t i o n s p r o c e e d e d u n t i l a l l q u a r t z , d o l o m i t e , K - f e l d s p a r , and r u t i l e were used, b u t stopped.-b e l o w t h e c u r v e f o r t h e f o r m a t i o n o f f o r s t e r i t e ( r e a c t i o n 5) and b e l o w t h e c u r v e s f o r the f o r m a t i o n o f r u t i l e ( r e a c t i o n s 13, 14, and 1 5 ) . Maximum tem-p e r a t u r e r e a c h e d was between 450 and 525 degrees C. T h i s a g r e e s w i t h m a x i -mum t e m p e r a t u r e o f 450 t o 540 d e g r e e s C f o r U n i t A. I n U n i t C, T K ^ was not p r e s e n t , so t h e s p h e n e - f o r m i n g r e a t i o n s ( F i g . 4.5, r e a c t i o n s 11 and 12) d i d n o t t a k e p l a c e as i n U n i t B. O t h e r r e a c t i o n s were s i m i l a r t o t h o s e :6f U n i t B. The s c a r c i t y o f t r e m o l i t e s u g g e s t s t h a t most o f i t was used i n t h e f o r m a t i o n o f d i o p s i d e , ( r e a c t i o n s 2. and -33); ;:thus 5 t h e r o c k s wer.e< .heated t o a minimum of >l.400c>.degrees C 'based on 'the . formation:' o f d i o p s i d e and an X above 0.2 ( r e a c t i o n 2 ) . c u ^ G a r n e t i s seen i n s e v e r a l samples o f U n i t B. I t i s nowhere i n c o n t a c t w i t h p h l o g o p i t e . A t low p r e s s u r e g a r n e t forms o n l y a t v e r y l o w X ( l e s s c u 2 t h a n 0.1) from e x p e r i m e n t a l d a t a o f Gordon and Greenwood ( 1 9 7 1 ) . G a r n e t does n o t r e - e q u i l i b r a t e r e a d i l y so i t c a n o c c u r i n an a p p a r e n t l y i n c o m p a t -i b l e p a r a g e n e s i s ( H o l l i s t e r , 1 9 6 9 ) . There a r e two p o s s i b l e e x p l a n a t i o n s f o r the s i m u l t a n e o u s p r e s e n c e o f g a r n e t and p h l o g o p i t e . P h l o g o p i t e c o u l d have formed i n s k a r n i n r e s p o n s e t o t h e a d d i t i o n o f K and A l i n f l u i d s f r o m t h e s y e n i t e a f t e r g a r n e t had formed a t low X . A l t e r n a t i v e l y , g a r n e t may have c u ^ -formed i n l o c a l a r e a s of low X d u r i n g p r o g r a d e c o n t a c t metamorphism. The LU 2 l a t t e r method i s c o n s i d e r e d more l i k e l y b ecause of t h e w e l l - d i s p e r s e d , o c c a -s i o n a l l y r e l i c t sedlment'afy banded, o c c u r r e n c e ; o f p h l o g o p i t e and because K and A l c o u l d e a s i l y have been p r e s e n t i n c l a y s o r f e l d s p a r i n o r i g i n a l s e d i -61 mentary r o c k s . Minimum t e m p e r a t u r e s n e c e s s a r y f o r t h e f o r m a t i o n o f d i o p s i d e ( g r e a t e r t h a n 400 degrees C i f X was g r e a t e r t h a n 0.2) i m p l y t h a t f l u i d s were a f a c t o r i n t r a n s f e r r i n g h e a t f r o m t h e s y e n i t e . I f h e a t were t r a n s f e r r e d o n l y by c o n d u c t i o n t h r o u g h t h e r o c k s , t e m p e r a t u r e s w o u l d be e x p e c t e d t o have r a n g e d f r o m 460 degrees C t o 360 degrees C i n U n i t B and fr o m 360 t o 310 deg r e e s C i n U n i t C ( W i n k l e r , 1976 fr o m J a e g e r , 1957) . S i n c e d i o p s i d e i s seen t h r o u g h o u t b o t h u n i t s , movement t h r o u g h s k a r n r o c k o f f l u i d s h e a t e d by s y e n i t e i s r e q u i r e d i n a d d i t i o n t o c o n d u c t i o n as a mechanism f o r t r a n s f e r -r i n g h e a t . B e f o r e o f d u r i n g maximum grade c o n t a c t metamorphism, m e l a g r a n i t e and m a f i c d i k e s c o n t a i n i n g R E E - e n r i c h e d z i r c o n i n t r u d e d t h e c a r b o n a t e s e c t i o n . I r o n and magnesium d i f f u s e d i n t o n e i g h b o r i n g r o c k , f o r m i n g t h e d a r k g r e e n s k a r n o f U n i t B. REE m i n e r a l s a r e n o t fo u n d i n s k a r n r o c k s , i m p l y i n g REE d i d n o t m i g r a t e f r o m d i k e s . S i l i c a i n c a l c - s i l i c a t e r o c k s has s e v e r a l p o s s i b l e o r i g i n s . I t c o u l d have been: 1) a d e t r i t a l component i n o r i g i n a l s e d i m e n t a r y r o c k s , 2) t a k e n f r o m q u a r t z i t e o f U n i t A by s o l u t i o n s c o n v e c t i n g i n t o t h e c a l c a r e o u s s e c t i o n , o r 3) c a r r i e d b y . s o l u t i o n s o u t o f s y e n i t e and/or d i k e s i n t o s u r r o u n d i n g s k a r n . The l a s t mechanism i s c o n s i d e r e d u n l i k e l y b ecause s y e n i t e i s q u a r t z -poor and t h e t o t a l volume o f m e l a g r a n i t e d i k e s i s s m a l l . Growth o f e p i d o t e and c h l o r i t e d u r i n g r e t r o g r a d e metamorphism o f s k a r n r o c k s i s w e l l documented by r e p l a c e m e n t t e x t u r e s o b s e r v e d i n t h i n s e c t i o n . The two m i n e r a l s formed a f t e r w a t e r c o n t e n t o f the sys t e m had i n c r e a s e d and, p o s s i b l y , a f t e r t h e s k a r n had c o o l e d s l i g h t l y . E x a c t Pj_T-X c o n d i t i o n s o f e p i d o t e and c h l o r i t e f o r m a t i o n a r e u n c e r t a i n as o t h e r m i n e r a l s p r e s e n t i n e x p e r i m e n t a l l y documented r e a c t i o n s , n o t a b l y q u a r t z and f e l d s p a r , a r e a b s e n t 62 i n U n i t s B and C. R e t r o g r a d e metamorphism i n i n t r u s i v e r o c k s i n v o l v e d t h e a l t e r a t i o n o f o r t h o c l a s e t o a l b i t e and the a d d i t i o n o f H^O t o form e p i d o t e , g r e e n b i o t i t e i n s y e n i t e , and a c t i n o l i t e and s e c o n d a r y REE m i n e r a l s i n d i k e s . C a r b o n a t e m i n e r a l s , formed by p r e c i p i t a t i o n f r o m s o l u t i o n s from t h e s k a r n , were depo-s i t e d w i t h q u a r t z ( o f u n c e r t a i n o r i g i n ) i n g r a n o b l a s t i c p o l y g o n a l masses and v e i n l e t s i n i n t r u s i v e r o c k s . S e r p e n t i n i z a t i o n o f p a r t s o f U n i t s B. and C t o o k p l a c e a f t e r t h e f o r m a -t i o n o f r e t r o g r a d e e p i d o t e and c h l o r i t e . The s t a b i l i t y f i e l d o f s e r p e n t i n e e x t e n d s to v e r y low t e m p e r a t u r e s p r o v i d e d s u f f i c i e n t s i l i c a and w a t e r a r e p r e s e n t (Hemley e t a l . , 1977)., The P-T c o n d i t i o n s f o r t h e b e g i n n i n g o f f o r m a t i o n o f s e r p e n t i n e i n t h e s e r o c k s a r e u n c e r t a i n b e c a u s e i t i s n o t known i f f o r s t e r i t e was p r e s e n t i n them and r e a c t i o n s i n v o l v i n g t h e f o r m a -t i o n o f s e r p e n t i n e from d i o p s i d e a r e n o t documented e x p e r i m e n t a l l y . A c u r v e f o r t h e maximum p r e s s u r e - t e m p e r a t u r e s t a b i l i t y o f t h e p a r a g e n e s i s s e r p e n t i n e + d i o p s i d e ( s e e n i n U n i t C) i s shown i n F i g . 4.4. T h i s s u g g e s t s t h a t a t 500 kb s e r p e n t i n i z a t i o n must have t a k e n p l a c e below 380 d e g r e e s C. M a s s i v e s e r p e n t i n e pods i n U n i t B were o r i g i n a l l y s k a r n , n o t u l t r a m a f i c r o c k . S e r p e n t i n e o f u l t r a m a f i c o r i g i n c o n t a i n s 2000 to 3000 p a r t s p e r m i l -l i o n (ppm) n i c k e l (Abbey, 1977) b u t t r a c e element a n a l y s e s o f s e r p e n t i n e , s k a r n , and i n t r u s i v e r o c k s from t h e f i e l d a r e a r e v e a l e d o n l y a few ppm n i -c k e l i n each r o c k t y p e ( A p p e n d i x B ) . D e f o r m a t i o n c o n t i n u e d a f t e r f o r m a t i o n o f r e t r o g r a d e metamorphic mine-r a l s i n a l l r o c k s had ended. CHAPTER 5: GEOCHRQNOMETRY OF THE GUANO-GUAYES PROPERTY 5.1 INTRODUCTION':AND DATA A g e o c h r o n o m e t r i c s t u d y o f r o c k s o f t h e a r e a was u n d e r t a k e n t o a i d i n t h e i n t e r p r e t a t i o n o f l o c a l g e o l o g i c a l e v e n t s . B o t h Rb-Sr and K-Ar methods were us e d . R u b i d i u m - s t r o n t i u m g e o c h e m i s t r y was done by t h e a u t h o r , p o t a s s i u m a n a l y s e s by K. S c o t t and a r g o n a n a l y s e s and c a l c u l a t i o n s by J . H a r a k a l . One c o n t a c t metamorphic r o c k ( U n i t B sample P 6 C ) , f o u r samples o f s y e n i t e ( U n i t 16: samples M27, N3, N5 and N10) and a h o r n b l e n d e p o r p h y r y d i k e (sample N2A) w h i c h c r o s s c u t s the s y e n i t e were d a t e d . Sample l o c a t i o n s a r e shown on F i g . 5.1. Raw d a t a a r e l i s t e d , w i t h a n a l y t i c a l t e c h n i q u e s , i n A p p e n d i x C. Sample P6C,from U n i t B, i s an u n a l t e r e d c o a r s e - g r a i n e d p h l o g o p i t e - c a l c i t e s k a r n . U n i t 16 s y e n i t e samples a r e a l l m o d e r a t e l y a l t e r e d . O r t h o c l a s e i s p a r t l y r e p l a c e d i n a l l samples by a l b i t e and a l s o by m u s c o v i t e i n samples M27 and N5. B i o t i t e p a r t l y r e p l a c e s m a f i c m i n e r a l s i n sample N3 and r e p l a c e s them c o m p l e t e l y i n i sample 10, C a r b o n a t e m i n e r a l s - a r e p r e s e n t i n samples M27, N3, and N10. Secondary q u a r t z makes up 5 p e r c e n t of sample N10. E p i d o t e i s seen i n sample N3 r e p l a c i n g o r t h o c l a s e and may be p r e s e n t i n o t h e r s y e n i t e s a mples. Sample N2A, o f a p o r p h y r y d i k e s e e n o u t s i d e -of t h e mapped a r e a c o n t a i n s u n a l t e r e d h o r n b l e n d e p h e n o c r y s t s . The groundmass of t h e d i k e i s a l t e r e d t o c h l o r i t e , q u a r t z , c a l c i t e , and c l a y m i n e r a l s . Dates o b t a i n e d a r e l i s t e d i n T a b l e 5.1 and i s o c h r o n s a r e p l o t t e d on F i g . 5.2. C o n t a c t metamorphic sample P6C y i e l d e d a Rb-Sr m i n e r a l i s o c h r o n of 333:^10 Ma w i t h an i n i t i a l 8 7 S r / 8 6 S r r a t i o o f 0 . 7 1 0 5 + 2 . The K-Ar d a t e o b t a i n e d f r o m a p h l o g o p i t e s e p a r a t e o f t h e same r o c k i s 319 + 10 Ma. The Rb-Sr m i n e r a l i s o c h r o n f o r s y e n i t e sample N3 i s 128 + 25 Ma w i t h c o r r e s p o n d -i n g o r i g i n a l s t r o n t i u m i s o t o p i c r a t i o o f 0.7146 + 14. An impure s e p a r a t e 63 Fig. 5.1 Location map for samples used for geochronometric study, Guano-Guayes area, P e l l y Mountains, Yukon Territory. 65 0.820 0.810 0.800 0.790 0.780 w 0.770 oo. u ^ 0.760 0.710 0.700 Rb/ Sr F i g . 5.2 Rb-Sr isochrons. of rocks from the Guano-Guayes area, from: Unit B skarn mineral separates (circles-, 333 + 10 Ma), Unit 16 syenite whole-rock samples (squares, 206 + 15 Ma) and Unit 16 syenite mineral separates ( t r i a n g l e s , 128 + 25 Ma). 66 of amphibole (arfvedsonite) from t h i s same rock sample has a 156 + 5'Ma.K-Ar age. A whole-rock isochron of 206 + 15 Ma and an i n i t i a l r a t i o of 0.7099 + 12 was obtained from syenite samples . Dikes c u t t i n g syenite give a hornblende K-Ar date of 110 + 4 Ma. Table 5.1 Rb-Sr and K-Ar Dates of Rock Samples from the Guano-Guayes Area, P e l l y Mountains, Yukon T e r r i t o r y Unit Material Method Date I n i t i a l Ratio Age B mineral separates Rb-Sr 333 + 10 Ma 0.7105 + 0.0002 Miss i s s i p p i a n B phlogopite K-Ar 319 + 10 Ma M i s s i s s i p p i a n 16 whole-rock Rb-Sr 206 + 15 Ma 0.7099 + 0.001 Early Jurassic 16 arfvedsonite & b i o t i t e K-Ar 156 + 5 Ma Late Jurassic 16 mineral separates Rb-Sr 128 + 25 Ma 0.7146 + 0.0014 Early Cretaceous _ dike hornblende K-Ar 110 + A Ma Early Cretaceous 5.2 DISCUSSION M i s s i s s i p p i a n (333 ± 10 Ma mineral isochron i n F i g . 5.2 and 319 ± 10 Ma phlogopite K-Ar) dates for formation of contact metamorphic rocks imply a s i m i l a r date for i n t r u s i o n , s o l i d i f i c a t i o n , and c ooling of .the syenite which caused contact metamorphism. This date i s older than the maximum isochron of 304 ± 1 0 Ma for syenite stocks and associated v o l c a n i c rocks to the north (Mortensen, 1979, personal communication) which are b e l i e v e d to be of the same i n t r u s i v e episode, suggesting the syenite dates represent a l a t e r age of metamorphism. S i g n i f i c a n t l y younger dates from syenite samples are a r e s u l t of l a t e r a l t e r a t i o n . The 206 ± 5 Ma whole-rock isochron gives a maximum date for extensive metamorphism accompanied by large s c a l e migration of elements through the rock. . The 156 ± 5 Ma K-Ar airfvedsonite-biotite datcand the 128 + 25 Ma mineral isochron both i n d i c a t e the l a s t r e s e t t i n g event. Both of these 67 analyses are on al t e r e d material. The youngest date obtained from rocks: of the area i s 110/+ 4 Ma from unaltered hornblende from a 2 to 5 m wide fine-grained porphyry dike which cuts syenite 2 km from i t s periphery. 87 86 I n i t i a l Sr/ Sr from the syenite whole-rock isochron i s 0.7099 + 12. Since the corresponding date represents the f i r s t r e s e t t i n g event, the true i n i t i a l strontium i s o t o p i c r a t i o was somewhat l e s s . Crustal strontium i s o -topic r a t i o s are s i m i l a r , I n f e r r i n g that the syenite i n the Guano-Guayes- area probably had a c r u s t a l source. 5.3 SUMMARY OF GEOCHRONOMETRY Dates for several geologic events i n the Guano-Guayes area were obtained by using Rb-Sr and K-Ar geochronometry. Dates from contact metamorphic rocks of 333 + 10 Ma (Rb-Sr) suggest a M i s s i s s i p p i a n age f o r syenite i n t r u s i o n and skarn formation i n pre-Mississippian impure carbonate rocks. Large s c a l e a l t e r a t i o n of syenite involving extensive movement of radiogenic material en-/ ded at or more recently than Early Jurassic (206 + 15 Ma). Cooling of the syenite below the blocking temperature for b i o t i t e did not occur u n t i l Late Jurassic to Early Cretaceous time (156 + 5 to 128 + 25 Ma) or even l a t e r i f •only p a r t i a l r e s e t t i n g occurred. Hornblende porphyry dikes intruded the sy-^ 87 86 enite i n Early Cretaceous time (110'+. '4 Ma). I n i t i a l / Sr/,^Sr .o-f-. syenite i s poorly defined (0.7099 + 12 for the f i r s t r e s e t t i n g event), but i s high, sug-gesting the source of syenite melt was c r u s t a l . CHAPTER 6: RARE EARTH ELEMENT DISTRIBUTION ON THE GUANO-GUAYES PROPERTY 6.1 INTRODUCTION R a d i o a c t i v i t y i n r o c k s f r o m t h e a r e a was t h e o r i g i n a l r e a s o n f o r s t a k i n g t h e Guano and Guayes c l a i m s . S p e c t r o s c o p i c a n a l y s e s i n d i c a t e d t h a t a r e a s o f h i g h r a d i o a c t i v i t y a l s o c o n t a i n e d l o c a l e n r i c h m e n t s o f r a r e e a r t h e l e m e n t s . A r e a s o f h i g h REE c o n c e n t r a t i o n a r e n o t w e l l documented i n t h e Yukon T e r r i -t o r y . I n a d d i t i o n t o b e i n g u s e f u l i n i n d u s t r y , REE c a n be used as g e o c h e m i c a l i n d i c a t o r s of t h e p e t r o g e n e s i s o f a r o c k . I t i s p o s s i b l e , t h r o u g h n e u t r o n a c t i v a t i o n a n a l y s e s o f t h e i n d i v i d u a l r a r e e a r t h e lements i n r o c k s and an u n d e r s t a n d i n g o f REE c h e m i s t r y , n o t o n l y to d e l i n e a t e REE o c c u r r e n c e i n t h e a r e a b u t t o u n cover some o f t h e p r o c e s s e s by w h i c h t h e y were c o n c e n t r a t e d . 6.2 CHEMISTRY OF RARE EARTH ELEMENTS The f i r s t " r a r e e a r t h " was s e p a r a t e d f r o m an u n u s u a l b l a c k m i n e r a l f r o m Y t t e r b y , Sweden by Johan G a d o l i n a t The U n i v e r s i t y o f Abo i n 1794. T h i s was c a l l e d Y t t r i a , and was soon shown t o be a complex m i x t u r e o f o x i d e s o f s e v e r -a l e l e m e n t s . S e p a r a t i o n o f a l l t h e o x i d e s , u s i n g wet c h e m i s t r y , was a t t a i n e d 113 y e a r s l a t e r , e x c e p t f o r t h e element promethium w h i c h was n o t o b t a i n e d u n t i l 1947 ( M o e l l e r , 1 9 6 3 ) . The v e r y s i m i l a r c h e m i c a l and p h y s i c a l p r o p e r t i e s o f t h e r a r e e a r t h e lements made t h e i r s e p a r a t i o n d i f f i c u l t . I n o r d e r o f i n -c r e a s i n g a t o m i c number, the f i f t e e n r a r e e a r t h e l e m e n t s ( a l s o c a l l e d t h e l a n -t h a n i d e s ) a r e : lanthanum, c e r i u m , praseodymium, neodymium, promethium, samar-ium, europium, g a d o l i n i u m , t e r b i u m , d y s p r o s i u m , holmium, e r b i u m , t h u l i u m , y t t e r b i u m , and l u t e t i u m . REE c h e m i s t r y h i n g e s on t h e i r s i m i l a r a t o m i c and i o n i c s t r u c t u r e s . They a r e a subgroup o f " g r o u p ' I I I B i n .the p e r i o d i c t a b l e o f t h e e l e m e n t s { F i g . 6.1). 68 69 - - i 14 4a u 14 0 Offet 1 .1 H t um R E V T O C H A t T 2 0 He 4 00140 K 3 •! L i 4 W Be Atomic Wtiftit — Sn • H I 44 • • I I • 4 5 *) B 4 *1 c 7 * i N :| t -1 o » - 1 F 10 • Ne » t * . i-i • O i l i l 2-1 10 I I i-i lion 1-4 * J - I 14 00*7 -1 1-1 -1 n MM : « iinfii 1-T K 11 , 1-1 n *i Na 12 «-l Mg TraniMioa ElvfnrMl EICtF «*n 13 .1 A l 14 .1 s» IS o Ii . 4 17 +i a :| 18 o Ar S !} J : «t*r> 14 »0i C o u p ! 26 mu 10.711* UN )9 • * ! I* *i K 20 . J Ca 21 *1 Sc 22 .1 ^ ;> 23 .1 V ;> 14 .1 cr:> 25 *l M n : J 2* .1 Fe •> 27 •! C o " 2S -1 Ni " Cu •» 30 *} Zn 31 -j Ga 32 .1 Ge " 33 .1 A , 34 . . ^ 35 »i Br 34 o K r 14 04, -» H 40 M -i i-i 44 4 J * 47.40 -1-10-1 * i M«4U -«-|-l -l-ll-l 4 M 0 -l-ll-l 51 MT -•-14-1 M411 -i-ti-1 i t K -•-•*-! • J »«* -l-U-l tlH -l-ll-l 44 Tl - I - I I - ) n » T4 4]1* -l-ll-l i l ** -l-ii-* T4.W -1 -ll-T • ) 40 -l - l l-l • L-M-N 37 ,1 Rb 3» Sr 39 •} Y 40 , 4 Zr 41 *) N b " 42 • * M o 4J . 4 Tc *• 44 .) Ru 45 »1 Rh 4* . 1 Pd •* 41 .1A g 4 * .1 Cd 49 * J In 50 .1 Sn •• 51 .1 Sb -.J 52 . 4 S3 * i ' '•: 54 o Xe u •*', n-i-i I T * ; -U - t - f u«oi» -11-4-1 •i» -ll-IO-l 41 «OM -ll-ll-l -ii-n-i *t *06l -ll-IJ-1 101 0* -tl-ll-l 102401 -11-14 -1 10* 4 li-il-0 107 l o t -u-ia-i 111 40 -ll-ll-l 114 1 1 -ll-li-1 I I I 44 -ft-ll-4 Hi Tl - i l - i t - 4 I1T40 -14-14 I14«0«1 - I t . I I - 7 11 M - 1 1 - 1 1 ^ . M - N - O 55 . i Cs Ba 57" -J La 72 * 4 Hf 73 * i Ta 74 .* w 73 . 4 Rc 7* * j Os * 4 77 , j Ir " 7t *l Pi *4 79 . 1 A M " M *i H g " tl . 1 Tl •> S2 . 1 Pb •* *3 »J Bi •» S4 .1 Po «5 A l 86 a Rn Ul 40M -•»-«-« i r y* H l - l l i ) • w» -i«-«-i | T I 4* -11-10-1 IW«4% -51-11-1 rn is -31-11-1 I U 1 - I I - I M I W 1 -n-14-i 191.31 -ll-M-2 1*104 -11-14-1 -12-11- Xo » -J1-H-; 104 JT -Jl-ll- JOT 2 -U - l l-4 1 0 1 4 1 0 1 -12-l-i I W I - 1 1 - I I - * 1110) -11-11-7 tin* -ii-n-i - N - o - r Fr «t . J Ra *>•• A c * J 104 •4 105 106 tint 11401M -ll-l-l lint -u-4-i 1*11 •1-10-1 13611 - 1 I • 1 1 ••J t i -1 j -l o r o *L4*lh*ni4«t 5S * J C e ' 4 140 l l - X i - l - 1 59 41 Pr 140 W77I - H - l - l 60 *1 Nd 144 1 4 - 1 1-l - J tl . i Pm ti.ii -iyt-3 42 , 1 S m " I W 4 - 1 4 - 1 - 1 43 . 1 E u " l l l.M -11-1-1 44 ,} G d IJT.IJ - 1 J - 4 - 1 45 . » Tb 111 4114 -17-1-1 44 4-1 Dy I i? 10 -21-1-1 67 *1 Ho -«-l-l 48 . 1 Er I H 1 6 - J O 1 - 1 49 . J Tm 141 4141 - l l - l - J 70 * 1 Y b •> 1 7)04 -11-1-1 71 . 1 Lu |T4 » 7 - J l - 4 i 90 - 4 » l . 1 92 * i 93 . 1 M . 1 95 . 1 96 .) 97 . » 98 99 * J 100 * J 101 •! 102 103 O Th Pa •* u •; N P . - ; Pu ;« A m * 4 Cm Bk •* C f Es Fm Md-> No *> Lr 1110)1) 111 a m . •« • 4 1 1 7 0 4 i ? •>*> 11441 * 4 « 1 4 ) ( ll4?» ( 1 4 7 ) mn 11141 I l l T i ( 1 S B 1 ( 1 S 4 1 (340) •iOt-2 - H - . - l - 1 1 - 4 1 - J 4 - I - J - 1 V I - 1 -11-4-1 -IT-1 - 1 - 11-1-2 - W - l - 1 - l l - l - l - 11-1-1 - l l - * - l Nwniocn m p t t m l h n t t vt «Mtl «Hi«»btrj of tttou U4blc notopr Of* tkat rtcmvfil F i g . 6.1 P e r i o d i c chart of the elements (Weast, 1975) The elements i n group HI'S act as metals. The second to l a s t quantum l e v e l con-tains only S2 el e c t r o n s . These elements are each end-members of a d-type t r a n s i t i o n s e r i e s . In the d-type t r a n s i t i o n s e r i e s , the a d d i t i o n of e l e c -trons f or each of the following nine elements i s to the outermost d sub l e v e l . For example, looking at the d-type t r a n s i t i o n s e r i e s elements two l i n e s above lanthanum on the p e r i o d i c chart: atomic number 21 Scandium = Argon core + 3d^ + As^ , atomic number 22 Titanium = Argon core + 3d2 + ^ s2» atomic number 23 Vanadium = Argon core + 3d^ + 4s2> e t c . In t h i s s e r i e s the a d d i t i o n a l e l e c t r o n i n the inner o r b i t a l of each sub-sequent element causes a s l i g h t decrease i n the radius of atoms and ions with inc r e a s i n g atomic number. This i s because the elec t r o n s , when added to an 70 inner o r b i t a l , add a smaller r e p e l l i n g force than the a t t r a c t i n g force of the added proton. There i s a skip i n atomic number between lanthanum and the next member of i t s d-type t r a n s i t i o n s e r i e s . Elements of intermediate atomic numbers are members of an inner t r a n s i t i o n s e r i e s . -In t h i s s e r i e s , each a d d i t i o n a l e l e c t r o n goes into the f o r b i t a l s of the t h i r d quantum l e v e l inward. For the elements immediately following lanthanum i n atomic number, the rare earth elements, these are the 4f o r b i t a l s . There are seven of these f o r b i -t a l s f o r each element, each with a capacity for two electrons. The r e s u l t of f i l l i n g an inner o r b i t a l with electrons i s the same i n t h i s case as i t i s for the d-type t r a n s i t i o n s e r i e s , so when elements are arranged i n order of increasing atomic number t h e i r r a d i i decrease s l i g h t l y i n the same order. Scandium and yttrium, although not members of t h i s inner t r a n s i t i o n s e r i e s , have s i m i l a r properties, because they are also i n group IIIB and t h e i r i o n i c r a d i i are s i m i l a r to those of some REE. The radius of yttrium i s between those of holmium and dysprosium while the radius of scandium i s appreciably smaller than that of lutetium, the smallest REE. In REE studies, yttrium i s thus often included with REE while scandium i s r a r e l y considered s i m i l a r l y . Lanthanide elements have the same atomic ground state outer e l e c t r o n configuration as the group IIIB elements. With t h i s configuration, a dipos-i t i v e i o n i c state would be expected. Instead, the t r i p o s i t i v e state i s most common because of a combination of REE i o n i z a t i o n and hydration energies. Although the t r i p o s i t i v e state i s preferred by most of the f i f t e e n REE, a d i p o s i t i v e state i s also found for Ce, Nd, Sm, Eu, Tm, and Yb:y and a quad-r i p o s i t i v e state f or Ce, Pr, Nd, Tb, and Dy. Lanthanides can be divided into cerium (La through Lu) or l i g h t , and yttrium (Gd through Lu) or heavy 71 groups, based on differences i n the s o l u b i l i t i e s of t h e i r t r i p o s i t i v e s a l t s . REE are extremely powerful reducing agents with r e l a t i v e l y large atomic and i o n i c r a d i i , so they usually form r e l a t i v e l y simple-ionic bonds'.:\".Pure REE metals oxidize quickly i n both water and a i r , and even more r a p i d l y i f heated. Cerium-rich mixtures of these metals are pyrophoric, and a l l the metals w i l l i g n i t e and burn i f heated i n a i r . Rare earth elements, have many uses i n science and industry, but they are not used i n great volume because they are so d i f f i c u l t and expensive to sep-arate. Because of i t s pyrophoric nature Ce i s used i n an a l l o y with i r o n to make f l i n t s for l i g h t e r s . Samarium oxide i s used as a high-temperature pro t e c t i v e coating, and as an addit i v e with cobalt i n permanent magnets because i t i s strongly paramagnetic. D i f f e r e n t REE cations absorb l i g h t of; d i f f e r e n t wavelengths, from i n f r a r e d through u l t r a v i o l e t , with uniquely narrow absorption peaks, many of which are measurable to within an angstrom unit or l e s s . Their light-absorbing properties make REE extremely u s e f u l i n manufacturing many types of l i g h t f i l t e r s , i n c l u d i n g : u l t r a v i o l e t - a b s o r b -ing glass and p l a s t i c s f o r sunglasses and welders' lenses, infrared-absorbing glass, p r e c i s i o n o p t i c a l lenses and f i l t e r s , f i b e r o p t i c s , l a s e r glass rods, phototropLc glass, and glass f i l t e r plates which improve brightness and contrast i n colour t e l e v i s i o n sets. Europium i s used extensively as anactivator for the red phosphor i n colour t e l e v i s i o n tubes. REE also are used i n t i n t i n g glass and ceramic glazes, and i n inorganic pigments and coatings, producing yellow, salmon, green, v i o l e t , red, and turquoise hues. Cerium i s used i n abrasive compounds f or glass grinding and p o l i s h i n g . In metallurgy, i n the manufacturing of a l l o y s , cerium i s used for grain-growth c o n t r o l and gado-linium i s added to give higher ultimate and t e n s i l e strength to titanium. Cerium also i s used as a strong o x i d i z i n g agent and c a t a l y s t i n chemical 72 r e a c t i o n s . . The c r o s s s e c t i o n f o r t h e r m a l n e u t r o n c a p t u r e i s g r e a t e r f o r g a d o l i n i u m t h a n f o r any o t h e r element, so i t i s used, sometimes a l o n g w i t h . europium, whose c r o s s - s e c t i o n i s s l i g h t l y s m a l l e r , i n n u c l e a r r e a c t o r s h i e l d -i n g and c o n t r o l . S m a l l b u t s y s t e m a t i c c h e m i c a l and p h y s i c a l d i f f e r e n c e s between REE o f th e i n n e r t r a n s i t i o n s e r i e s i s t h e key t o t h e i r c h e m i s t r y . G e o c h e m i c a l s t u d i e s o f REE, a l o n g w i t h o t h e r s t u d i e s o f them, a r e a l s o b a s e d on t h e i r s l i g h t d i f f e r e n c e s and b r o a d s i m i l a r i t i e s . 6.3 GEOCHEMISTRY OF RARE EARTH ELEMENTS L a n t h a n i d e s e r i e s elements were o r i g i n a l l y c a l l e d " r a r e " b e c a u s e m i -n e r a l s c o n t a i n i n g them i n c o n c e n t r a t i o n a r e uncommon. The l a n t h a n i d e s a r e s i m p l y w i d e l y d i s s e m i n a t e d t h r o u g h o u t t h e e a r t h . REE c a t i o n s a r e found i n c r y s t a l l i n e compounds w i t h most e x i s t i n g a n i o n i c s p e c i e s . REE range i n A. abundance i n t h e c r u s t from 28.1 to 0.75 g p e r tonne, w i t h an a v e r a g e o f 9.28 g p e r tonne.- T h i s i s comparable to l e a d , a t 16 g p e r tonne and a r s e -n i c a t 5 g p e r tonne. The abundance o f s i l v e r , 0.1 g p e r tonne, i s much l o w e r t h a n t h a t o f any l a n t h a n i d e e x c e p t promethium, whose s h o r t h a l f - l i f e a c c o u n t s f o r i t s v i r t u a l absence i n t e r r e s t r i a l m a t t e r . When s t u d i e s o f REE c h e m i s t r y began, d i f f i c u l t y e n c o u n t e r e d i n s e p a r a t i n g t h e i n d i v i d u a l elements l e d p e o p l e to b e l i e v e t h a t g e o l o g i c a l systems had p r o b a b l y been i n s u f f i c i e n t to s e p a r a t e them t h r o u g h o u t t i m e . T h e i r abun-dances were assumed to be t h e same ( p r i m o r d i a l ) i n a l l r o c k s . E x p e r i m e n t a l s t u d i e s have s i n c e p r o v e n t h a t t h i s a s s u m p t i o n i s wrong. REE have f r a c t i o n -a t e d w i t h t i m e a c c o r d i n g to t h e i r s m a l l d i f f e r e n c e s . i n i o n i c r a d i u s and, f o r a few o f them, t h e i r o x i d a t i o n s t a t e s . I n n a t u r e , t h e o n l y common n o n t r i p o -s i t i v e s t a t e s f ound a r e +4 f o r Ce i n s e a w a t e r ( P i p e r , 1974) and +2 f o r Eu i n i g n e o u s r o c k s . (Nagasawa and S c h n e t z l e r , 1 9 7 1 ) . N a t u r a l f r a c t i o n a t i o n was d i s c o v e r e d i n 1935. I n t h a t y e a r , Noddack and Minami p u b l i s h e d a n a l y s e s o f REE i n m e t e o r i t e s and s h a l e s r e s p e c t i v e l y ( H a s k i n e t a l . , 1 9 6 6 ) . I n b o t h , odd-numbered e l e m e n t s were l e s s abundant t h a n even-numbered ones, r e f l e c t i n g the g r e a t e r r e l a t i v e abundance o f e v e n -numbered e l e m e n t s formed d u r i n g n u c l e o s y n t h e s i s . F u r t h e r c o m p a r i s o n o f a n a l y s e s o f t h e two r o c k t y p e s showed more major d i f f e r e n c e s between them: f i r s t , s h a l e s c o n t a i n e d more t o t a l REE t h a n m e t e o r i t e s and s e c o n d , s h a l e s were e n r i c h e d i n l i g h t ( L a t h r o u g h Eu) REE r e l a t i v e t o heavy (Gd t h r o u g h Lu) REE compared t o m e t e o r i t e s . F r a c t i o n a t i o n compared t o m e t e o r i t e s had o b v i -o u s l y t a k e n p l a c e d u r i n g the p r o c e s s e s t h a t l e d t o t h e f o r m a t i o n o f t h e s h a l e s . I f s h a l e s c o u l d be t a k e n as r e p r e s e n t a t i v e c r u s t a l r o c k s , t h i s meant t h a t REE had f r a c t i o n a t e d t h e same way as t h e e a r t h , l i g h t e r e l e m e n t s of t h e s e r i e s b e i n g r e l a t i v e l y c o n c e n t r a t e d i n t h e c r u s t , and p r o b a b l y de-p l e t e d i n t h e m a n t l e and deeper r o c k s . S i n c e t h i s d i s c o v e r y REE geochemi-c a l s t u d i e s have f o c u s e d on t h e i d e a t h a t t h e f r a c t i o n a t i o n o f REE r e f l e c t s the h i s t o r y o f the r o c k s i n w h i c h t h e y a r e f o u n d . I n t h e s e s t u d i e s t h e v a l u e s f o r REE i n c h o n d r i t ' i c ( s t o n y ) m e t e o r i t e s a r e used as an e s t i m a t e o f p r i m o r d i a l abundances o f REE. Many d i f f e r e n t methods o f p r e s e n t i n g d a t a a r e used i n REE s t u d i e s . T h e i r g e n e r a l i n t e n t i s t o s i m p l i f y d a t a so i n t e r p r e t a t i o n i s easy and l o g i -c a l . N u m e r i c a l methods i n c l u d e summing o f Ce and Y group v a l u e s o r c a l c u l a -t i o n :of v a r i o u s r a t i o s o f l i g h t REE f o r c o m p a r i s o n o f r e l a t i v e e n r i c h m e n t . These r a t i o s a r e u s e f u l f o r g e n e r a l c o m p a r i s o n o f r o c k s , b u t i n summing up d a t a f o r l i g h t and heavy REE groups some o f t h e d a t a i s l o s t , i n c l u d i n g anom-a l o u s v a l u e s f o r s i n g l e e l e m e n t s , w h i c h can be o f g r e a t i m p o r t a n c e . G r a p h i c a l methods a r e more a p p l i c a b l e t h a n n u m e r i c a l methods when . d a t a i s abundant: because t h e y c a n show a l l d a t a . I t i s e a s i e r t o com-74 pare graphs than to'compare l i s t s of numbers.". REE values represented i n ' •-graphs are'generally p l o t t e d with e i t h e r atomic number or atomic radius (same order, s l i g h t l y d i f f e r e n t spacing) along the h o r i z o n t a l axis and i n d i v i d u a l REE values on a l o g scale along the v e r t i c a l a x i s . A l i n e con-necting the points f o r the d i f f e r e n t elements i s c a l l e d the "REE pattern" of the rock. Not only simple values for REE i n parts per m i l l i o n are presented t h i s way but also values which have been normalized r e l a t i v e to a standard so that a pattern becomes a comparison between a sample and the standard. Many d i f f e r e n t normalizing values are used; most common are average values f o r c h o n d r i t i c meteorites. Others v-ih usage are averages f o r g r a n i t i c rocks, shales, c r u s t a l rocks and ocean water. Standard rock values are l i s t e d i n Table 6.1. Table 6.1 Standard REE values i n ppm Element 1: Chondrites 2: G r a n i t i c Rocks 3: Shales 4: Ocean La .32 55. 38. .0029 Ce .94 104. 80. .0013 Nd .60 47. 32. .0023 Sm .20 8. 5.6 .0042 Eu .075 1.1 1.1 .000114 Tb .050 1.1 . .77 Dy .31 6.2 4.4 .00073 Yb .19 4.3 2.8 .00052 Lu ' .031 • 6 8 . . . .50 .00012 Totals 2.72 227. 165. .0122 1. Average of 22 c h o n d r i t i c meteorites, Herrmann, 1971 2. Haskin et a l . , 1968 3. Average of Post-Archean A u s t r a l i a n sediments (an estimate of upper c r u s t a l v a l u e s ) , Nance and Taylor, 1976 4. Average f o r 100 m deep P a c i f i c Ocean Water, Goldberg et a l . , 1963. REE geochemical studies, with data presented as described, are used extensively i n attempts to unravel the past h i s t o r y of the earth and the solar system. This i s done by comparing and i n t e r p r e t i n g the REE patterns of 75 d i f f e r e n t r o c k types,. M a j o r a r e a s o f s.tudy i n y o l y i n g REE i n t e r p r e t a t i o n a r e d e s c r i b e d below. I n g e n e r a l , o n l y a v e r y s m a l l p r o p o r t i o n o f a n a l y z e d c h o n d r i t i c meteo-r i t e s have f l a t , u n f r a c t i o n a t e d REE p a t t e r n s w i t h i n c u r r e n t e x p e r i m e n t a l e r -r o r . Some f r a c t i o n a t e d m e t e o r i t i c REE p a t t e r n s can be e x p l a i n e d by c o m p a r i -s o n w i t h s i m i l a r t e r r e s t r i a l r o c k p a t t e r n s caused by s o l i d - l i q u i d f r a c t i o n a -t i o n . O t h e r f r a c t i o n a t e d m e t e o r i t i c REE p a t t e r n s a r e n o t f a m i l i a r and may be due to g a s - s o l i d f r a c t i o n a t i o n and d i f f e r e n t i a l m o t i o n (Evensen e t a l . , 1 9 7 8 ) . REE p a t t e r n s a r e used e x t e n s i v e l y i n a t t e m p t s to d e f i n e the o r i g i n o f b a s a l t i c magmas. O c e a n i c t h o l e i i t e s have REE p a t t e r n s v e r y s i m i l a r to chon-d r i t i c o n e s . T h i s may i m p l y t h a t i f c h o n d r i t e s a r e r e l a t i v e l y p r i m o r d i a l , so a r e o c e a n i c t h o l e i i t e s . A l l o t h e r b a s a l t s have more f r a c t i o n a t e d v a l u e s , en-r i c h e d i n l i g h t e r REE compared to c h o n d r i t e s ( F r e y e t a l . , 19 6 8 ) . Low-grade metamorphism o f b a s a l t s s i g n i f i c a n t l y changes t h e i r REE p a t t e r n s . L i g h t REE (La t h r o u g h Eu) become more m o b i l e as metamorphic grade i n c r e a s e s t h r o u g h z e o l i t e and e p i d o t e - b e a r i n g f a c i e s (Wood e t a l . , 1967; Ludden, 1 9 7 8 ) . Europium v a l u e s have been shown to d e c r e a s e s y s t e m a t i c a l l y r e l a t i v e to o t h e r REE i n t h e r e s i d u a l m e l t d u r i n g magmatic f r a c t i o n a l c r y s t a l l i z a t i o n o f a c i d i g n e o u s r o c k s ( T o w e l l e t a l . , 1965; F r e y e t a l . , 1 9 6 8 ) . T h i s i s p r o -b a b l y due t o r e d u c t i o n o f Eu to t h e d i v a l e n t s t a t e and i n c o r p o r a t i o n i n t o +2 c a l c i c f e l d s p a r i n t h e Ca s i t e . Only p e r i d o t i t e s w i t h h i g h - t e m p e r a t u r e m i n e r a l assemblages have REE v a l u e s w h i c h a r e d e p l e t e d i n l i g h t REE r e l a t i v e .to c h o n d r i t i c p a t t e r n s and a r e complementary t o c r u s t a l v a l u e s , as w o u l d be e x p e c t e d o f m a n t l e r o c k s . They a r e n o t , however, s i g n i f i c a n t l y d e p l e t e d i n t o t a l REE r e l a t i v e to chon-d r i t e s . P erhaps r o c k s from deeper w i t h i n t h e e a r t h , w h i c h a r e r a r e l y b r o u g h t to t h e s u r f a c e , a r e . 76 A n a l y s e s o f REE have been used e x t e n s i v e l y by R u s s i a n g e o l o g i s t s i n a t t e m p t s t o document magmatic d i f f e r e n t i a t i o n i n a l k a l i c i n t r u s i v e c o m p l e x e s . REE i n a l l complexes s t u d i e d f o l l o w e d a d i s t i n c t f r a c t i o n a t i o n t r e n d - w i t h s e q u e n t i a l i n t r u s i v e p h a s e s . The t r e n d , c o r r e l a t e d w i t h i n c r e a s i n g m a f i c c o n t e n t i n r o c k s , i s f r o m l o w e r t o h i g h e r t o t a l REE c o n t e n t , and f r o m more t o l e s s e n r i c h e d i n l i g h t e r (La t h r o u g h Lu) REE (Mineyev, 1 9 6 3 ) . A l l a l k a -l i c m a s s i f s c o n t a i n e d two-; to t e n times-more, t o t a l REE t h a n average-, c r u s t a l r o c k s . REE a r e t y p i c a l l y more c o n c e n t r a t e d i n c a r b o n a t i t e s . . (commonly found i n r i f t zones), t h a n i n any o t h e r r o c k t y p e e x c e p t p l a c e r s and l a t e r i t e s d e r i v e d f rom c a r b o n a t i t e s . One of t h e l a r g e s t REE d e p o s i t s o f t h e w o r l d i s t h e c a r -b o n a t i t e a t M o u n t a i n P a s s , C a l i f o r n i a ( O l s o n e t a l . , 1 9 5 4 ) . S t u d i e s o f c a r b o n a t i t e s show REE p a t t e r n s w i t h a s t r a i g h t - l i n e d i s t r i b u t i o n , t h e e l e -ments n o t b e i n g s p l i t n a t u r a l l y i n t o l i g h t e r and h e a v i e r g r o u p s , each w i t h d i f f e r e n t p a t t e r n s l o p e s , as seen i n n o r m a l c r u s t a l r o c k . REE p a t t e r n s o f s e d i m e n t a r y r o c k s a r e t h o u g h t t o be r e p r e s e n t a t i v e o f t h e c r u s t o f t h e e a r t h . They a r e r e a s o n a b l y c o n s t a n t between d i f f e r e n t s o u r c e a r e a s , and a r e e n r i c h e d i n t o t a l and i n l i g h t REE r e l a t i v e t o : ; c h o n d r i t e s . C omposite v a l u e s o f g r a n i t i c r o c k s r e s e m b l e t h i s " c r u s t a l " a v e r a g e a l t h o u g h L a i s r e l a t i v e l y e n r i c h e d and Eu i s d e f i c i e n t - a p a t t e r n w h i c h i s a l s o q u a l -i t a t i v e l y complementary t o b a s a l t i c v a l u e s . G e o c h e m i c a l s t u d i e s o f REE, f i r s t u n d e r t a k e n i n t h e mid 1930's, expanded s u d d e n l y i n t h e 1960's because o f t h e development o f r e l a t i v e l y s i m p l e a n a l -y t i c a l methods. These i n c l u d e X - r a y f l u o r e s c e n c e , i o n p r o b e , mass s p e c t r o -m e t r i c i s o t o p e d i l u t i o n , and t h e use o f s p a r k s o u r c e mass s p e c t r o m e t e r s . W i t h t h e i n c r e a s i n g a v a i l a b i l i t y o f even more a c c u r a t e n e u t r o n a c t i v a t i o n a n a l y s i s , REE s t u d i e s w i l l become more and more u s e f u l t o g e o l o g i s t s e v e r y -where. 77 6.4 RARE EARTH ELEMENTS OF THE GUANO-GUAYES PROPERTY 6.4.1 I n t r o d u c t i o n REE o f the Guano-Guayes a r e a were s t u d i e d u s i n g t h r e e s e t s o f d a t a : 1) a q u a l i t a t i v e f i e l d t e s t (Rose, 1976); 2) p e t r o g r a p h i c a l d e s c r i p t i o n s o f m i n e r a l s , and 3) n e u t r o n a c t i v a t i o n a n a l y s e s o f f o r t y l o c a l s a mples. REE s t u d i e s o f r o c k s from t h e a r e a were made w i t h two g o a l s i n mind: t o document t h e p o t e n t i a l f o r a m i n e a b l e d e p o s i t i n h o r n f e l s and s k a r n and t o d e f i n e t h e o r i g i n o f t h e r o c k . M i n e r a l o g y o f REE, d i s c u s s e d i n Chap t e r 4, was fo u n d t o be q u i t e s i m p l e . REE were o r i g i n a l l y c o n c e n t r a t e d i n 0.5 t o 5 mm e u h e d r a l z i r c o n c r y s t a l s making up two t o f i f t e e n p e r c e n t o f t h e volume o f s y e n i t e -r e l a t e d d i k e s . REE ( o r r a d i o a c t i v e ) m i n e r a l s a r e seen o n l y v e r y r a r e l y o u t -s i d e t h e d i k e s . Secondary REE m i n e r a l s ( a l l a n i t e , m o n a z i t e , and m i n e r a l C, a p a l e g r a y b o t r y o i d a l m i n e r a l ) a r e common i n d i k e s as pseudomorphs a f t e r z i r c o n . 6.4.2 Rose'e F i e l d T e s t f o r Rare E a r t h Elements Rose's (1976) f i e l d t e s t f o r r a r e e a r t h e l e m e n t s was used e x t e n s i v e l y w h i l e mapping. I t i s a c h r o m a t o g r a p h i c t e s t . A s m a l l amount o f powdered sample i s d i s s o l v e d i n c o n c e n t r a t e d HCL. A f i l t e r p a p e r , t r e a t e d i n advance w i t h one o f two o r g a n i c i n d i c a t o r ; a c i d s , i s w e t t e d w i t h t h e s o l u t i o n , r e s u l t -i n g i n a c o l o u r i n d i c a t i v e o f t h e p r e s e n c e o r absence o f REE. F i e l d t e s t s were marked q u a l i t a t i v e l y : - f o r no REE d e t e c t e d , + f o r a f a i n t i n d i c a t i o n o f REE, ++ f o r a d e f i n i t e i n d i c a t i o n o f REE, and +++ f o r an e x t r e m e l y s t r o n g i n d i c a t i o n o f REE. D e l i n e a t i o n o f a d e p o s i t , i f p r e s e n t , s h o u l d have been r e a l i z e d a c c o r d i n g t o t h e REE c o n c e n t r a t i o n s e n s i t i v i t y o f t h e t e s t as d e f i n e d by Rose. However, no g e n e r a l a r e a o f REE e n r i c h m e n t was e s t a b l i s h e d w i t h i t s u s e . F i e l d t e s t r e s u l t s were q u i t e u n s y s t e m a t i c . V a r i a t i o n s were common fr o m p l a c e t o p l a c e w i t h i n one r o c k : t y p e . More p o s i t i v e t e s t s c w e r e o b t a i n e d f r o m 78 some o f t h e a p p a r e n t l y u n a l t e r e d s e d i m e n t a r y r o c k s t h a n f o r most o f t h e s k a r n r o c k s . T h i s l e d t o s e r i o u s doubts as t o t h e i r v a l i d i t y . N e u t r o n a c t i v a t i o n a n a l y s i s samples were used t o check t h e s e t e s t s , and r e s u l t s o f t h e two a r e compared i n F i g . 6.2. I n t h i s f i g u r e , f i e l d t e s t r e s u l t s and n e u t r o n a c t -i v a t i o n a n a l y s e s have, i f a n y t h i n g , a n e g a t i v e c o r r e l a t i o n . 6.4.3 N e u t r o n A c t i v a t i o n A n a l y s i s f o r Rare E a r t h Elements 6.4.3.1 I n t r o d u c t i o n F o r t y r o c k samples f r o m t h e Guano-Guayes a r e a were each a n a l y z e d f o r n i n e r a r e e a r t h e lements ( L a , Ce, Nd, Sm, Eu, Tb, Dy, Yb, and Lu) by n e u t r o n a c t i v a t i o n a n a l y s i s by R.G.V. Hancock a t t h e SLOWPOKE R e a c t o r , t h e U n i v e r -s i t y o f T o r o n t o . Sample l o c a t i o n s a r e shown on Map 2. Rocks s e l e c t e d f o r a n a l y s e s r e p r e s e n t : s e v e n m e l a g r a n i t e and m a f i c d i k e s f r o m w i t h i n c o n t a c t metamorphic r o c k s , s i x s y e n i t e samples f r o m t h e main i n t r u s i v e body, 21 con-t a c t metamorphic r o c k s and s i x s e d i m e n t a r y r o c k s . These were chosen f o r f o u r r e a s o n s : 1) t o d e f i n e REE c o n t e n t s i n d i f f e r e n t r o c k t y p e s , 2) t o com-p a r e s e d i m e n t a r y r o c k s and s y e n i t e as p o s s i b l e s o u r c e s f o r REE c o n c e n t r a - f r : o t i o h s , 3) t o p r o v i d e a r e a s o n a b l y comprehensive g e o g r a p h i c a l d i s t r i b u t i o n , and 4) t o check t h e a c c u r a c y o f Rose's (1976) f i e l d t e s t f o r REE. A n a l y t i c a l r e s u l t s and e r r o r a r e g i v e n i n T a b l e 6.2. A n a l y t i c a l p r o c e d u r e i s i n Appen-d i x B. 6.4.3.2 A n a l y s i s o f d a t a REE a n a l y s e s were s e p a r a t e d i n t o groups on t h e b a s i s o f r o c k t y p e . , C a l c u l a t i o n s o f t . , , were used t o compare t h e groups w i t h , one a n o t h e r i n d e p e n d e n t ( A p p e n d i x B ) . T h i s t e s t e v a l u a t e s w h e t h e r the means o f t h e two groups i n q u e s t i o n a r e s t a t i s t i c a l l y d i f f e r e n t from one a n o t h e r w i t h r e s p e c t t o i n d i v i -d u a l REE c o n t e n t s . R e s u l t s f r o m the t e s t i n d i c a t e s t r o n g l y t h a t r o c k groups 79 Samples, Arranged i n Order of Decreasing REE Content F i g . 6.2 Comparison of REE f i e l d t e s t r e s u l t s by Rose's chromatographic method and REE from instrumental neutron a c t i v a t i o n analyses, Guano-Guayes properties, P e l l y Mountains, Yukon T e r r i t o r y . Table 6.2 Rare Earth Element values In ppn and resul t s of f i e l d tes ts . Guano and Guayes Propert ies , Pe l ly Mountains, Yukon T e r r i t o r y Unit Sample Rock Type La 5 8 C e (6 0 : : d , 2 Sm 63_ Eu ( " l b ) 2 66^ Dy 7 ° V b Lu Tota l F i e l d T 17b K30 Mafic Dike 4980. .8070. 4300. 930. 103. 170. 1066. 790. 71.6 20400. +++ 17b S5D Mafic Dike 4460. 6150. 3300. 450. 46.3 61. 397. 230. 16. 15100. 17b Mean Mafic Dike 4720. 7110. 3800. 690. 75. 116. 730. 510. 44. 17800. 17a 08A Melagranite Dike 410. 940. 380. 39.0 4.99 3.8 33. 30. 1.9 1840. + 17a 08F Melagranite Dike 610. 2660. 1000. 19.9 8.74 6.3 50. 21. 2.0 4380. 17a 09D Melagranite Dike 1860. 2950. 1400. 153. 8.2 11. 68. 42.6 3.3 6500. •H-t-17a 4 P1B Melagranite Dike 64.5 121. 64. 10.1 0.72 0.8 6.3 8.0 1.25 276. +++ 17a CC17 Melagranite Dike 806. 2300. 480. 166. 3.8 3.5 32.0 22.2 2.26 3820. . ~ 17a Mean Melagranite Dike 920. 2210. 815. 94. 6.4 6. 46. 29. 2.4 4130. 16 H21 Syenite 37. 79. 28. 5.89 0.32 0.9 10.6 9.3 1.07 172. +++ 16 H27 Syenite 77. 210. 89. 9.47 2.37 0.60 5.7 3.5 0.40 398. ++ 16 N3 3 Syenite 66. 180. 84. 8.03 1.45 0.79 6.7 4.4 0.56 352. ~ 16 N5 3 Syenite 39. 120. 69. 7.06 1.48 0.60 4.8 3-4 0.42 246. 16 N6 Syenite 47.5 214. 120. 7.42 1.80 1.2 9.6 4.0 0.61 406. — 16 N10 3 Syenite 64. 165. 48. 8.94 1.80 0.80 6.0 3.6 0.49 299. 16 . Mean Syenite 55. 160. 73. 7.80 1.54 0.82 7.2 4.7 0.59 311. B i 08D Skarn 60. 170. 120. 13.5 1.03 0.97 7.8 5.5 0.56 380. -1 B i 08E • Skarn 88. 200. 41. 22.5 1.19 0.81 . 7.5 7.0 0.66 369. +++ 1 B i 08K Skarn 30.9 65. 84. 8.97 0.85 0.8 6.7 4.9 0.48 202. +++ 1 B T 09B3 Skarn 18. 25. 22. 3.48 0.39 <0.15 1.13 <0.04 0.10 70. ++ 2 B , 010 Skarn 117. 165. 96. 15.4 6.9 1.4 12.3 10.8 1.16 426. ++ 1 B, 012A Skarn 17. 46. <7T 4.04 0.57 0.37 3.0 1.7 0.19 80. +++ 1 B , 012C Skarn 24. 60. 30. 4.08 0.76 0.39 3.2 1.6 0.21 124. +++ 1 B, PIC , Skarn 22. 60. 38. 4.44 0.62 0.47 2.9 1.7 0.25 . 130. +++ 1 B. P2A3 Skarn 18. 54. 20. 9.16 0.64 0.47 3.6 1.9 0.23 108. +++ 1 B, 4 P3D Skarn 580. 1540. 490. 38.2 10.9 2.6 24. 14. 1.3 2700. ++ 1 B, P5A3 Skarn 4. 25. 16. 1.54 0.51 0.37 1.0 0.5 0.26 49. +++ 1 B l P5C 3 Skarn 25. 49. 23. 2.78 0.59 0.28 2.1 1.1 0.16 104. -H+ Unit Sample Rock Type 5', La 58,. Ce <6(W So Eu ( 6 W 66^ Dy 7 0 Y b ? 1 L u T o t a l F i e l d ' B 2 P6C Skarn 12. .2 11. 27. 0.45 0.19 <0.1 <0.6 0.4 <0.05 52. +++ B l P7A Skarn 35. .5 58. 22. 2.34 0.26 0.3 1.7 3.4 0.54 124. +++ C P7D Skarn 3. .9 25. <5. 1.01 0.37 <0.1 0.8 0.3 0.11 45. ++ B l P8B Skarn 17. 34. 66. 15.6 0.64 0.5 4.2 4.1 0.53 203. + c P11A Skarn 12. 9.4 7. 0.56 <0.18 <0.1 <0.4 0.25 0.06 <16. +++ B l Q13C Skarn 69. 2 123. 11. 16.3 4.6 1.4 12.7 6.8 0.67 245. +++• B l DDI Skarn 11. 2 31. 5. - 8.25 0.8S 0.9 7.8 4.3 0.36 69. -B l DD235 Skarn 296. 336. 53. 8.35 2.8 . 1.8 24.0 31.6 2.93 756. -H-+ B & C Mean Skarn 32. 70. 35. 7.5 1.2 0.54 4.4 3.1 0.37 152. Test A A A 01A 04 B 4 Mean Hornfels Hornfels Hornfels 30. 900. 30. 53. 1860. 53. 17. 340. 17. 4.85 40.6 4.85 0.38 15.75 0.38 0.5 2.8 0.5 3.1 27. 3.1 2.3 15. 2.3 0.21 1.5 0.21 111. + 3200. 111. 13 9 11 8 2 R4E S8D U21 X2A X13A Mean Dolomite Quartz i te Dolomite Dolomite Dolomite Sedimentary rocks 4.5 4.4 6.6 6.6 3.5 5.1 5.3 12. 12. 15. 4.5 9.7 1.6 6. 5. <4. <4. <7. 1.60 0.89 1.36 2.26 0.50 1.29 0.30 0.40 0.34 0.37 0.17 0.30 0.2 <0.1 . 0.2 0.1 0.1 <0.1 1.2 1.0 2.0 2.4 0.7 1.5 1.3 1.1 0.8 1.3 0.3 1.0 0.16 0.15 0.10 0.13 0.07 0.12 16.2 + <26. 28. +++ <32. +++ <14. <26. 1 s 0.5 1. 2. 0.04 0.07 0.1 0.3 0.2 0.03 oo 1. Counting s t a t i s t i c a l standard dev ia t ion for a l l samples except d ikes . Counting s t a t i s t i c a l errors for dike samples are approximately 1 percent of a l l the values shown. 2. Accuracy for Nd and Tb values i s approximately 20 percent . 3. REE values shown are averages of two analyses . 4. REE analyses are questioned due to c o n f l i c t with p e n o l o g i c a l data and are not used i n th i s study. 5. REE values are anomalous to other samples i n the group, and are not used In c a l c u l a t i n g mean values . 82 a r e a n a l y t i c a l l y d i s c r e t e . C u m u l a t i v e p r o b . a b l i l i . t y graphs, were used to t e s t w h e t h e r o r n o t c o n t a c t metamorphic rocks- m i g h t c o n t a i n REE from more t h a n one subgroup. No n a t u r a l s u b d i v i s i o n s : were f o u n d . Mean t o t a l a n a l y z e d REE i s q u i t e d i f f e r e n t f o r each r o c k group as shown i n T a b l e 6.2. S y e n i t e - r e l a t e d d i k e s c o n t a i n one t o two o r d e r s o f magnitude more t o t a l REE t h a n s y e n i t e . C o n t a c t metamorphic r o c k s and s e d i m e n t a r y r o c k s c o n t a i n f o u r and twenty t i m e s , r e s p e c t i v e l y , l e s s REE t h a n t h e s y e n i t e . Com-p a r i s o n o f Guano-Guayes REE to t h a t o f s t a n d a r d s r e v e a l s t h e s y e n i t e c o n t a i n s t h r e e t i m e s as much t o t a l REE ak a v e r a g e g r a n i t e s - * l o c a l s t r a t a l e s s t h a n a f o u r t h as much as a v e r a g e s e d i m e n t a r y r o c k s and c o n t a c t metamorphic r o c k s around t h e same amount as a v e r a g e s e d i m e n t a r y r o c k s . REE q u a n t i t i e s i n t h e most e n r i c h e d r o c k s , the two d i k e g r o u p s , a r e around one p e r c e n t t o t a l a na-l y z e d REE. T o t a l REE, e s t i m a t e d from c o m p a r i s o n w i t h a n a l y s e s o f a l l REE i n r e p r e s e n t a t i v e c r u s t a l r o c k s , i s p r o b a b l y about 20 p e r c e n t more. T h i s i s too low a p e r c e n t a g e o f REE to be economic w i t h p r e s e n t N o r t h A m e r i c a n de-mands more t h a n met by t h e M o u n t a i n P a s s mine i n C a l i f o r n i a , where REE miner? r a l s c o n s t i t u t e around 30 p e r c e n t o f t h e r o c k i n a l a r g e c a r b o n a t i t e ( O l s o n e t a l . , 1 954). V i r t u a l l y no u r a n i u m was found i n samples f r o m t h e a r e a so no p o s i t i v e c o r r e l a t i o n between REE and uranium was e s t a b l i s h e d . The o c c u r r e n c e o f REE i n t h e Guano-Guayes p r o p e r t y i n f i n e - g r a i n e d z i r c o n and even f i n e r -g r a i n e d s e c o n d a r y m i n e r a l s d i s s e m i n a t e d i n a m a s s i v e d i k e r o c k r e n d e r s t h e i r p o s s i b l e s e p a r a t i o n e x t r e m e l y d i f f i c u l t , compounding t h e economic u n f e a s a -b i l i t y o f t h e a r e a . REE p a t t e r n s f o r Guano-Guayes. and s t a n d a r d r o c k s , showing v a r i a t i o n s w i t h i n t h e l a n t h a n i d e s.eires. between the d i f f e r e n t r o c k t y p e s , a r e i l l u s t r a t e d i n F i g s . 6.3 and 6.4. F i g . 6.3 shows t h e Guano-Guayes r o c k groups n o r m a l i z e d to c h o n d r i t e s . M a g n i t u d e s f o r a l l t y p e s a r e g r e a t e r t h a n c h o n d r i t e s , and a l l r o c k t y p e s a r e more e n r i c h e d i n l i g h t REE t h a n i n heavy REE compared to chon-83 T — n — i 1 — i i r r* B & c J__L I I La Ce (Nd) Sm Eu (Tb)Dy Yb Lu Element i n Order of Increasing Atomic Number Fig. 6.3 REE patterns f o r Guano-Guayes rock groups•normalized to chondritic meteorites. Error bars represent the standard error of the mean. Numbered patterns are f o r : 17a melagranite dikes B & C skarn 17b mafic dikes S sediments 16 syenite 84 \ T — i - i 1— I r—r i r 1 i t I 1 L J I 1 La Ce Nd Sm Eu Tb Dy Yb Lu Element i n Order of Increasing Atomic Number F i g . 6.4 REE patterns for standard REE values normalized to chondrites. Numbered patterns are f o r : 1 g r a n i t i c rocks (Haskin et a l . , 1968) 2 post—Archean A u s t r a l i a n sediments (Nance and Taylor, 1976) 3 100m deep P a c i f i c Ocean water CGoldberg et a l . , 1963) 85 d r i t e s V I f c h o n d r i t e s a r e t r u l y r e p r e s e n t a t i v e samples o f p r i m o r d i a l m a t e r -i a l s i m i l a r t o t h e o r i g i n a l c o m p o s i t i o n o f t h e u n f r a c t i o n a t e d e a r t h , and i f l i g h t REE have n o t been l o c a l l y c o n c e n t r a t e d by metamorphism, REE p a t t e r n s o f t h e s e r o c k s i l l u s t r a t e t h e g e n e r a l l y e x t e n s i v e f r a c t i o n a t i o n o f l a r g e - i o n e l e m e n t s i n t o t h e c r u s t . Note t h e n e g a t i v e d e f l e c t i o n o f t h e p a t t e r n s a t Ce f o r s e d i m e n t a r y r o c k s and s k a r n , not seen f o r s y e n i t e . T h i s c o u l d be due t o a s l i g h t d e p l e t i o n i n Ce i n o r i g i n a l s e d i m e n t s c a u s e d by t h e i r p r e c i p i t a -t i o n f r o m s e a w a t e r , w h i c h has a n e g a t i v e Ce peak when n o r m a l i z e d t o chon-d r i t e s ( F i g . 6.4). Comparison d f l o c a l r o c k s t o s h a l e s (an e s t i m a t e o f n o r m a l c r u s t a l r o c k s ) shows s i m i l a r p a t t e r n s i n b o t h F i g s . 6.3 and 6.4. The s y e n i t e and s k a r n p a t t e r n s a r e s i m i l a r t o n o r m a l c r u s t b o t h i n shape and i n m a g n i t u d e . S e d i -mentary r o c k s c o n t a i n r e l a t i v e l y l e s s l i g h t REE and a l s o l e s s t o t a l REE when compared t o c r u s t a l r o c k s . The s i m i l a r i t y between REE p a t t e r n shapes and magnitudes f o r s y e n i t e and c o n t a c t metamorphic r o c k s compared t o l o c a l s e d i -mentary r o c k s s u g g e s t s common a n c e s t r y f o r REE i n s y e n i t e and c o n t a c t meta-m o r p h i c r o c k s . T h i s s u p p o r t s t h e i d e a t h a t f l u i d s f r o m t h e s y e n i t e , c o n t a i n -i n g s i g n i f i c a n t amounts o f REE, permeated c o n t a c t metamorphic r o c k s , i n f l u -e n c i n g t h e i r REE p a t t e r n s . A l l i n t r u s i v e r o c k s , b o t h t h e g r a n i t e s t a n d a r d and Guano-Guayes r o c k s , have r e l a t i v e Eu d e p l e t i o n s . T h i s d e p l e t i o n i s most pronounced i n d i k e s . B o t h t h e e n r i c h m e n t i n l i g h t REE and t h e d e p l e t i o n i n Eu c a n c o i n c i d e as a r e s u l t o f f r a c t i o n a l c r y s t a l l i z a t i o n o f magmas: l i g h t e r l a r g e r REE i o n s p a r t -i t i o n i n t o t h e r e s i d u a l m e l t i n p r e f e r e n c e to t h e h e a v i e r REE and' d i v a l e n t +2 europium l e a v e s t h e m e l t e a r l y t o f i l l Ca s i t e s i n f e l d s p a r s (Higu'chi and Nagasawa, 1969). Metamorphic m o b i l i z a t i o n e a r i , c a u s e , c o n c e n t r a t i o n . . o f l i g h t REE b u t n o t a d e p l e t i o n o f Eu (Wood e t a l . , 1 9 7 6 ) . T h e r e f o r e t h e d i f f e r e n c e s i n p a t t e r n s between s y e n i t e and d i k e s i n f e r t h e d i k e s m i g h t have formed f r o m 86 r e s i d u a l m e l t w h i c h was a r e s u l t o f more e x t e n s i v e f r a c t i o n a t i o n t h a n t h a t w h i c h m i g h t have t a k e n p l a c e f o r t h e f o r m a t i o n o f the s y e n i t e . The e n r i c h -ment i n t o t a l REE i n b o t h v a r i e t i e s o f d i k e compared t o s y e n i t e may a l s o be a f u n c t i o n o f t h e h i g h z i r c o n c o n t e n t o f t h e d i k e s . REE have v e r y l a r g e p a r t -i t i o n c o e f f i c i e n t s f o r z i r c o n , r a n g i n g from 10 t o 400 f o r Ce a c c o r d i n g t o a n a l y s e s o f d a c i t e s (Nagasawa, 1970) . P a t t e r n s f o r d i k e s show r e l a t i v e en-r i c h m e n t i n l i g h t REE, n o t t h e r e l a t i v e e n r i c h m e n t i n heavy REE e x p e c t e d u s i n g Nagasawa's p a r t i t i o n c o e f f i c i e n t s f o r each e l e m e n t . The cause f o r t h i s c o n -f l i c t i n g b e h a v i o u r i n z i r c o n i s unknown. D i f f e r e n c e s i n p a t t e r n s between t h e two v a r i e t i e s o f d i k e c o u l d e i t h e r be due t o f r a c t i o n a t i o n w h i c h was more e x t e n s i v e f o r t h e f o r m a t i o n o f m a f i c d i k e s t h a n f o r m e l a g r a n i t e d i k e s o r due t o d i f f e r e n t m i n e r a l o g y and c onsequent e f f e c t on p a r t i t i o n c o e f f i c i e n t s . The i d e n t i f i c a t i o n o f m a f i c d i k e REE m i n e r a l s as z i r c o n i s u n c e r t a i n s i n c e g r a i n s a r e s m a l l and s i g n i f i c a n t l y m e t a m i c t . 6.4;'3.3 C o n c l u s i o n s S t u d i e s o f REE i n Guano-Guayes a r e a r o c k s have l e d t o s e v e r a l c l e a r c o n -c l u s i o n s as t o t h e i r o r i g i n and t h e economic f e a s a b i l i t y o f the a r e a : 1. The a r e a i n v e s t i g a t e d i s n o t ' e c o n o m i c . REE o c c u r i n c o n c e n t r a t i o n s o f around one p e r c e n t o n l y i n s y e n i t e - r e l a t e d d i k e s w h i c h c u t c o n t a c t metamor-p h i c r o c k s . They a r e c o n c e n t r a t e d i n f i n e - g r a i n e d z i r c o n and even f i n e r -g r a i n e d s e c o n d a r y s i l i c a t e s and p h o s p h a t e s . Q u a n t i t a t i v e s e p a r a t i o n o f m i n -e r a l s f r o m t h e r o c k and REE f r o m m i n e r a l s w o u l d be e x t r e m e l y d i f f i c u l t . No u r a n i u m above t r a c e amounts was f o u n d i n t h e a r e a . 2. REE a n a l y s e s ;bf r o c k samples group a c c o r d i n g t o c o r r e s p o n d i n g r o c k t y p e s : s e d i m e n t a r y r o c k s , c o n t a c t - a l t e r e d r o c k s , s y e n i t e , m e l a g r a n i t e d i k e s , and m a f i c d i k e s . These groups a r e s t a t i s t i c a l l y d i s t i n c t f r o m one a n o t h e r . 87 3. Syenite and contact metamorphic rock groups contain REE of approximate upper c r u s t a l magnitude and pattern, defining t h e i r source as concentration from within the upper crust of the earth. The Eu depletion i n igneous rocks suggests f r a c t i o n a l c r y s t a l l i z a t i o n of plagioclase may have•-taken place Before separation of the syenite melt from a parent magma. Group V, carbonate rocks, r e f l e c t t h e i r sea-water o r i g i n with some c r u s t a l contribution. 4. The syenite i n t r u s i v e stock was the source of f l u i d s which contained enough REE to s i g n i f i c a n t l y a l t e r REE quantities and patterns within contact meta-morphic rocks. 5. REE o r i g i n a l l y p a r t i t i o n e d into z i r c o n from syenite or syenite-related melt. Fractionated melt containing REE-bearing minerals then formed dikes c u t t i n g contact metamorphic rocks. No s i g n i f i c a n t movement of REE-containing f l u i d s from dikes into contact metamorphic rocks took place. Time of form-a t i o n and i n t r u s i o n of REE-enriched melt r e l a t i v e to formation and i n t r u s i o n of syenite melt i s uncertain, although dikes may be older as they are not observed crosscutting syenite. CHAPTER 7: CONCLUSIONS On t h e Guano and Guayes p r o p e r t i e s , i n t r u s i o n o f a s y e n i t e s t o c k and c o g e n e t i c d i k e s i n t o a s e c t i o n o f s e d i m e n t a r y r o c k s formed a c o n t a c t meta-m o r p h i c a u r e o l e t h a t ; c o n t a i n s an u n u s u a l l y h i g h c o n c e n t r a t i o n o f REE. S e d i m e n t a r y r o c k s c o n s i s t of a 430 m t h i c k s t r a t i g r a p h i c e x p o s u r e o f impure banded m a r i n e d o l o m i t e and l i m e s t o n e m a r b l e s w i t h r e e f f a u n a and a few t h i n q u a r t z i t e beds o v e r l a i n by a minimum s t r a t i g r a p h i c t h i c k n e s s o f 500 m o f banded q u a r t z i t e . Age of t h e s e c t i o n i s S i l u r i a n . The M i s s i s s i p p i a n s y e n i t e s t o c k i s a t t h e s o u t h end o f a r e g i o n a l c h a i n o f s y e n i t e s t o c k s and t r a c h y t i c t o a n d e s i t i c e x t r u s i v e r o c k s . Two t y p e s of d i k e s , m e l a g r a n i t e d i k e s and ma-f i c d i k e s , a r e c o g e n e t i c w i t h s y e n i t e and c o n t a i n h i g h c o n c e n t r a t i o n s o f REE-which a r e m a i n l y i n z i r c o n , s e c o n d a r y m o n a z i t e , a l l a n i t e and unknown-m i n e r a l C. B o t h t y p e s o f d i k e i n t r u d e c o n t a c t metamorphic r o c k s a l o n g b e d d i n g p l a n e s and f r a c t u r e s ; m a f i c d i k e s a l s o i n t r u d e / s e d i m e n t a r y r o c k s . C o n t a c t metamorphic r o c k s c o n s i s t o f banded q u a r t z - m u s c o v i t e h o r n f e l s and c a l c i t e - d i o p s i d e - p h l o g o p i t e + t r e m o l i t e , sphene, and g a r n e t s k a r n . R e t r o g r a d e a l t e r a t i o n has r e s u l t e d i n p a r t i a l r e p l a c e m e n t o f c a l c - s i l i c a t e m i n e r a l s and p h l o g o p i t e by e p i d o t e and c h l o r i t e f o l l o w e d by s e r p e n t i n i z a t i o n o f s k a r n where f u r t h e s t f r o m t h e i n t r u s i v e . The t h e s i s a r e a i s n o t known t o c o n t a i n economic q u a n t i t i e s o f u r a n i u m o r REE. Uranium was n o t found t o be abundant i n a s s o c i a t i o n w i t h REE as i n some d e p o s i t s . REE i n subeconomic amounts a r e c o n f i n e d t o z i r c o n and s e c o n -d a r y m i n e r a l s i n d i k e s . There a r e no l a r g e c o n c e n t r a t i o n s o f REE i n c o n t a c t metamorphic r o c k s . P r e s e n t - d a y g e o l o g y o f t h e a r e a r e s u l t e d f r o m t h e f o l l o w i n g sequence o f 88 89. events, from oldest to youngest: 1. A marine shallow-water layered carbonate sequence followed by layered quartzites was deposited during S i l u r i a n time (Sections 4.2.1 and 4.2.2). 2. The sequence was buried to a maximum depth of 1 to 2 km (Section 4.5.2). 3. A s y e n i t i c magma and a cogenetic melagranite zircon-enriched melt formed by f r a c t i o n a l c r y s t a l l i z a t i o n from melted c r u s t a l rocks. REE p a r t i t i o n e d from the parent magma of dikes (probably the syenite) and was concentrated : •.<. i n z i r c o n (Section 6.4.3.2). 4. Gentle a n t i c l i n a l f o l d i n g commenced along an axis which bears 162 degrees and plunges 24 degrees so that l o c a l rocks are on the west-dipping limb (Section 3.2.1). Syenite and cogenetic dikes (Section 4.3.4) intruded the car-bonate and quartzite section at a depth of 1 to 2 km (about 500 bars f l u i d pressure; Section 4.5.2) during the M i s s i s s i p p i a n Seagull Creek i n t r u s i v e and volcanic episode ( c i r c a 330 Ma from a Rb-Sr isochron and a K-Ar date; Section 5.2). 5. A contact metamorphic aureole ( F i g . 7.1) developed i n country rocks; maximum prograde conditions indicated by th i s metamorphism are: 1) about 500 bars f l u i d pressure, 2) temperature of 450 to 540; degrees C, .arid 3) moderate X^Q (Section 4.5.2). L i q u i d , mostly CO2 and H^O, moved through contact metamorphic and igneous rocks, carrying REE from syenite and depo-s i t i n g them i n contact metamorphic rocks (Sections 4.5.2 and 6.4.3.3). The syenite acted as a heat pump for c i r c u l a t i n g f l u i d s (Section 4.5.2). Whe-ther water was dominantly magmatic or meteoric i s unknown; however, f l u o r i n e , probably from l a t e magmatic f l u i d s , f i l l e d open spaces i n cooled i n t r u s i v e rocks with f l u o r i t e (Section 4.4). Iron and magnesium, added to metasedLmentary rocks near dikes, caused the dark green colour of Unit B (Sections 4.3.2 and 4.3.3).. There was no s i g n i f i c a n t movement of REE from dikes into surrounding 90 SEA L E V E L MISSISSIPPIAN VOLCANIC AND CLASTIC ROCKS SILURIAN MARINE SEDIMENTARY ROCKS, I TO 2 km F i g . 7.1 Diagrammatic model of the formation of the Guano-Guayes skarn during M i s s i s s i p p i a n and l a t e r time, i n v o l v i n g prograde and retrograde contact metamorphism of carbonate rocks and quartzites adjacent to a shoulder on the syenite stock. Prograde (PG) contact metamorphism i n v o l -ved the i n t r u s i o n of syenite and dikes, the formation of hornfels by heat and the formation of skarn by heat and a d d i t i o n of Fe, Mg, and possibly Si0~. Retrograde (RG) contact metamorphism included cooling of rock and ad d i t i o n of water, causing formation of epidote, c h l o r i t e and eventually serpentine. 91 r o c k s ( S e c t i o n 6.4.3.3). Some s i l i c a was o r i g i n a l i n t h e s e d i m e n t a r y s e c -t i o n and some was- p r o b a b l y added by s k a r n — f o r m i n g f l u i d s t h a t o b t a i n e d i t e i t h e r from t h e i n t r u s i v e s o f from t h e q u a r t z i t e ( S e c t i o n ' 4 . 5 . 2 ) . . 6. C o o l i n g accompanied by r e t r o g r a d e a l t e r a t i o n a f f e c t e d each r o c k t y p e d i f -f e r e n t l y . I n s y e n i t e , o r t h o c l a s e a l t e r e d t o a l b i t e and e p i d o t e ; p y r o x e n e and a m p h i b o l e s a l t e r e d t o b i o t i t e ( S e c t i o n 4.3.1). S i l i c a and c a r b o n a t e -r i c h c o n v e c t i o n f l u i d s , p r o b a b l y d e r i v e d from s u r r o u n d i n g s e d i m e n t s , formed l a t e q u a r t z - s i d e r i t e - d o l o m i t e v e i n s i n s u b h o r i z o n t a l f r a c t u r e s i n s y e n i t e ( S e c t i o n 4 . 4 ) . L a r g e - s c a l e a l t e r a t i o n i n v o l v i n g e x t e n s i v e movement o f f l u i d s i n s y e n i t e , some o f w h i c h was p r o b a b l y s y n c h r o n o u s w i t h s k a r n f o r m a -t i o n , ended 206 + 15 Ma ago o r more r e c e n t l y (Rb-Sr i s o c h r o n ; S e c t i o n 5.2). I n d i k e s , o r t h o c l a s e a l t e r e d to a l b i t e , e p i d o t e , and sometimes a c t i n o l i t e . P y r o x e n e s and o r i g i n a l a mphiboles were r e p l a c e d by a c t i n o l i t e , and l a t e r by b i o t i t e o r s t i l p n o m e l a n e . A l l a n i t e and m o n a z i t e grew a t t h e expense o f z i r -c o n. Q u a r t z r e c r y s t a l l i z e d f o r m i n g m i n e r a l bands p a r a l l e l to t h e edges, o f d i k e s ( S e c t i o n s 4.3.2 and 4.3.3). I n s k a r n , g a r n e t a l t e r e d to e p i d o t e , t r e -m o l i t e , and c h l o r i t e . P h l o g o p i t e was a l t e r e d p a r t l y o r c o m p l e t e l y to c h l o r i t e . C a l c i t e - t r e m o l i t e - q u a r t z - e p i d o t e v e i n s f i l l e d f r a c t u r e s i n s k a r n on b o t h ma-c r o s c o p i c and m i c r o s c o p i c s c a l e s ( S e c t i o n 4.5.2). 7. L o c a l l y , c o n t a c t metamorphic r o c k s were b r e c c i a t e d and cemented w i t h p u r e c a l c i t e ( S e c t i o n 3.2.3). Movement a l o n g t h e bench, s h e a r zone d i s p l a -ced U n i t A s l i g h t l y I ( S e c t i o n 3.2.3). 8. A d d i t i o n a l c o o l i n g and a d d i t i o n o f w a t e r to t h e c o n t a c t metamorphic s y s -tem, e s p e c i a l l y i n r o c k s most d i s t a n t from t h e s y e n i t e , caused growth o f s e r -p e n t i n e and sometimes m a g n e t i t e a t t h e expense o f d i o p s i d e and c h l o r i t e . C h r y s o -t i l e f i l l e d f r a c t u r e s i n r o c k , and sometimes r e p a l c e d t r e m o l i t e . Z i r c o n i n 9.2 most m e l a g r a n i t e d i k e s a l t e r e d t o m i n e r a l C ( S e c t i o n 4.5.2). 9. G e n t l e a n t i c l i n a l f o l d i n g c o n t i n u e d , r e s u l t i n g i n the f i n a l s t e e p l y w e s t - d i p p i n g p o s i t i o n o f s t r a t a ( S e c t i o n s 3.2.1 and 4.5.2). F i g . 7.1 i s a d i a g r a m m a t i c c r o s s s e c t i o n o f r o c k s o f t h e a r e a d u r i n g s k a r n f o r m a t i o n , showing development o f t h e metamorphic a u r e o l e n e a r the top o f a s h o u l d e r i n t h e s y e n i t e body. D u r i n g p r o g r a d e metamorphism, r o c k s n e a r t h e c o n t a c t were i n t r u d e d by d i k e s r e l a t e d £0 s y e n i t e ; movement o f f l u i d s a i d e d i n t r a n s f e r i n g . . h e a t from s y e n i t e and i n c a r r y i n g i o n s f r o m d i k e s and s y e n i t e i n t o c o n t a c t metamorphic r o c k s . R e t r o g r a d e metamorphism i n c l u d e d t h e a d d i t i o n o f w a t e r t o t h e s y s t e m , w i t h c o o l i n g , r e s u l t i n g i n e v e n t u a l s e r p e n t i n i z a t i o n o f some a r e a s o f s k a r n . B i h l l o g r a p h y 1. Abbey, S., 1977, S t u d i e s i n " s t a n d a r d s a m p l e s " f o r use i n t h e g e n e r a l a n a l y s i s o f s i l i c a t e r o c k s and m i n e r a l s : G e o l o g i c a l Survey o f Canada Paper 77-34, 31p 2. A l b e e , A. L., 1962, R e l a t i o n s h i p s between the m i n e r a l a s s o c i a t i o n , c h e -m i c a l c o m p o s i t i o n and p h y s i c a l p r o p e r t i e s o f t h e c h l o r i t e s e r i e s : A m e r i c a n M i n e r a l o g i s t 47, pp 851-870 3. Evans, B. . W., and Trommsdorff, V., 1970, R e g i o n a l metamorphism o f u l t r a -m a f i c r o c k s i n t h e c e n t r a l A l p s - parageneses i n t h e sys t e m CaO-MgO-SiO„-H„0: S c h w e i z e r i s c h e M i n e r a l o g i s c h e und P e t r o g r a p h i s c h e M i t t e i l u n g e n 50, pp 481-492 4. Evensen, M. M., H a m i l t o n , P. J . , and O'Nions, R. K., 1978, Rare e a r t h abundances i n c h o n d r i t i c m e t e o r i t e s : G e o c h i m i c a e t Cosmochimica A c t a 42, pp 1199-1212 5. F o r d , W. E., 1945, Dana's Textbook o f M i n e r a l o g y : John W i l e y and Sons, I n c . , New Y o r k , 851 p 6. F r e y , F. A., H a s k i n , M. A., P o e t z , J . A., and H a s k i n , L. A., 1968, Rare e a r t h abundances i n some b a s i c r o c k s : J o u r n a l o f G e o p h y s i c a l R e s e a r c h 73, pp 6085-6098 7. G a b r i e l s e , H., and Wheeler, J . 0., 1961, T e c t o n i c framework o f s o u t h e r n Yukon and n o r t h w e s t e r n B r i t i s h C o l u m b i a : G e o l o g i c a l Survey o f Ca-. nada Pa p e r 60-24, 37p 8. G o l d b e r g , E. D., K o i d e , M., S c h m i t t , R. A., and S m i t h , R. H., 1963, Rare e a r t h d i s t r i b u t i o n s i n t h e m a r i n e e n v i r o n m e n t : J o u r n a l o f G e o p h y s i c a l R e s e a r c h 68, pp 4209-4217 9. Gordey, S. 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C , eds., P h y s i c s and C h e m i s t r y o f t h e E a r t h , , 7, Pergamon P r e s s , Toronto 13. H a s k i n , L. A., F r e y , F. A., and Wildeman, T. R., 1968, R e l a t i v e and a b s o -l u t e : , t e r r e s t r i a l abundances o f ; t h e r a r e e a r t h s j- i n : . ' Ahrens,.- 1;.. H., ed. I n t e r n a t i o n a l S e r i e s o f Monogf aphs" i n • E a r t h - S c i e n c e -30",-pp 889-912' 14. Hemley, J . J . , Montoya, J.,W., C h r i s t , C. L., and H o s t e t l e r , P. B., 1977, ' ':- ' M i n e r a l e q u i l i b r i a i n t h e M g 0 - S i 0 2 - H 2 0 system: I : t a l c - c h r y s o t i l e -f o r s t e r i t e - b r u c i t e s t a b i l i t y r e l a t i o n s : A m e r i c a n J o u r n a l o f S c i e n c e 277, pp 322-351 93 94 15. Herrmann, A. G. , 19.71, The l a n t h a n l d e s , i n : Wedepohl, K. H., ed., Hand-book o f G e o c h e m i s t r y P a r t I I , ;y. IT-4 3 9 , pp 57-71 16. H e w i t t , D. A., 1973, S t a b i l i t y o f the. assemblage m u a c o v i t e - c a l c i . t e - q u a r t z : A m e r i c a n M i n e r a l o g i s t 58, pp 785-791 17. H e w i t t , D. A., 1975, S t a b i l i t y o f t h e assemblage p h l o g o p i t e - c a l c i t e -q u a r t z : A m e r i c a n M i n e r a l o g i s t 60, p 391-39.7 18. H i g u c h i , H., and Nagasawa, H., 1969, P a r t i t i o n i n g o f t r a c e elements b e -tween r o c k - f o r m i n g m i n e r a l s and h o s t v o l c a n i c r o c k 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 7, pp 281-287 19. H o l l i s t e r , L. S., 1969, C o n t a c t metamorphism i n t h e Kwoiek A r e a o f B r i t i s h C o l u m b i a : an end member o f t h e metamorphic p r o c e s s : G e o l o g i c a l So-c i e t y o f A m e r i c a B u l l e t i n 80, pp 2465-2496 20. Hunt, J . A., and K e r r i c k , D. M., 1977, The s t a b i l i t y o f sphene; e x p e r i m e n -t a l r e d e t e r m i n a t i o n and g e o l o g i c i n d i c a t i o n s : G e o c h i m i c a e t Cosmo-c h i m i c a A c t a 41, pp 279-288 21. J a e g e r , J . C , 1957, The t e m p e r a t u r e i n t h e n e i g h b o r h o o d o f an i n t r u s i v e s h e e t : A m e r i c a n J o u r n a l o f S c i e n c e 255, pp 306-318 22. K e r r i c k , D. M., 1972, 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 m u s c o v i t e + q u a r t z s t a b i -l i t y w i t h P T T n l e s s t h a n P ^ : A m e r i c a n J o u r n a l o f S c i e n c e 272, pp 946-958 H 2 ° t o t a l 23. Ludden, J . N., 1978, A r e t h e r a r e e a r t h , elements m o b i l e d u r i n g a l t e r a t i o n p r o c e s s e s : i n : G e o l o g i c a l A s s o c i a i o n o f Canada, M i n e r a l o g i c a l A s s o -c i a t i o n o f Canada, and G e o l o g i c a l A s s o c i a t i o n o f A m e r i c a J o i n t A n n u a l M e e t i n g A b s t r a c t s w i t h Programs, p 447 24. M i n e y e v , D. A., 1963, G e o c h e m i c a l d i f f e r e n t i a t i o n o f t h e r a r e e a r t h s : Geo-c h e m i s t r y U.S.S.R., 1963, pp 1129-1148 25. M o e l l e r , T., 1963, The C h e m i s t r y o f t h e L a n t h a n l d e s , R e i n h o l d P u b l i s h i n g C orp., New Y o r k , 117 p 26. Monger, J . W. H., 1975, C o r r e l a t i o n o f e u g e o s y n c l i n a l t e c t o n o s t r a t i g r a p h i c b e l t s i n t h e N o r t h A m e r i c a n C o r d i l l e r a : G e o s c i e n c e Canada 2, pp 4-10 27. Monger, J . W. H., S o u t h e r , J . 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V., 1965, Rare e a r t h d i s t r i b u t i o n s i n some r o c k s and a s s o c i a t e d m i n e r a l s o f t h e b a t h o l i t h o f S o u t h e r n C a l i f o r n i a : J o u r n a l o f G e o p h y s i c a l R e s e a r c h 70, pp 3485-3496 96 47. Weast, R. C , ed., 1975, Handbook o f C h e m i s t r y and P h y s i c s : C h e m i c a l Rubber Company P r e s s , C l e v e l a n d , Ohio 48. W h e e l e r , J . 0., Green, L. H., and R o d d i c k , J . A., 1960, Q u i e t L a k e , Yukon T e r r i t o r y : G e o l o g i c a l S u rvey o f Canada Map 7-1960 49. W h i t t l e , A. G., 1960, C o n t a c t m i n e r a l i z a t i o n phenomena a t the Mary K a t h l e e n Uranium D e p o s i t : Neues J a h r b u c h F u e r M i n e r a l o g i e , Abhun-gen 94, pp 798-830 50. W i n k l e r , H. G. F., 1976, P e t r o g e n e s i s o f Metamorphic Rocks: S p r i n g e r -V e r l a g , New Y o r k , 334p 51. Wood, D. A., G i b s o n , I . L., and Thompson, R. N., 1976, E l e m e n t a l mob* b i l i t y d u r i n g z e o l i t e . f a c i e s metamorphism o f t h e t e r t i a r y b a s a l t s o f e a s t e r n I c e l a n d : 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 55, pp 241-254 52.. Y o r k , D., 1967, The b e s t i s o c h r o n : 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 2, pp 479-482 97 Appendix A: Petrography 98 Ap p e n d i x A l : T h i n 2 S e c t i o n Modes of R e c r y s t a l l i z e d S e d i m e n t a r y Rocks U n i t 2 8 9 9 9 11 14 Sample X I 3 X2A S8D T32 T35 W21 R4E M i n e r a l D o l o m i t e 98 100 10 100 C a l c i t e 90 M a g n e s i t e 10 Q u a r t z 73 60 75 T r e m o l i t e 30 15 M u s c o v i t e 20 C l a y 5 t r G r a p h i t i c m a t t e r -i 8 G a r n e t 2 t r t r t r Z i r c o n 1 t r t r E p i d o t e t r t r T o u r m a l i n e t r L i m o n i t e 1 2 t r 1 The symbol " t r " d e n o t e s t h e p r e s e n c e o f a t r a c e o f t h e m i n e r a l . 2 Modes a r e e s t i m a t e d v i s u a l l y 99 A p p e n d i x A2: T h i n S e c t i o n Modes o f U n i t 16, S y e n i t e Sample E5 . E6 M21 M27 N5 . N6A N10 M i n e r a l O r t h o c l a s e 61 6P 40 65 92 20 60 P l a g i o c l a s e 14 1 77 45 t r 54 20 M i c r o c l i n e 5 M u s c o v i t e t r 10 5 t r t r C l a y t r E p i d o t e t r t r 5 1 A e g i r i n e - A u g i t e 5 A r f v e d s o n i t e 5 B i o t i t e 19 20 20 10 C h l o r i t e 12 t r 1 M a g n e t i t e 3 L i m o n i t e 2 2 1 t r t r C a l c i t e 2 t r 5 M a g n e s i t e 10 15 10 7 t r Q u a r t z 5 t r 5 Z i r c o n 1 t r 2 A p a t i t e t r t r t r Sphene 2 1 Leucoxene t r Unit Sample 0OA 08F 17a 011B P1B Q12A Q12E CC17 K30 09C 17b 09D S5D Mineral Quartz Orthoclase Pl a g i o c l a s e M i c r o c l i n e Muscovite A x i n i t e Epidote Arfvedsonite Di. -Hedenburgite B i o t i t e A c t i n o l i t e Stilpnomelane C h l o r i t e Magnetite Liraonite 5 60 15 t r 10 t r 68 10 tr 10 15 5 10 10 10 15 25 20 i t r 3 5 20 t r t r 10 20 32 15 10 A O t r 10 25 10 5 10 t r 38 15 10 30 t r 10 10 t r 70 20 42 t r t r t r t r 68 5 t r o o C a l c i t e Magnesite Zircon Monazite A l l a n i t e Mineral C tr 1 1 t r t r 2 3 10 10 4 1 15 8 t r 1 1 2 2 t r 6 6 t r 15 t r t r 15 35 20 4 5 3 15 10 10 15 Apatite Sphene Garnet t r t r 101 A p p e n d i x A4: T h i n S e c t i o n Modes o f U n i t A, Q u a r t z - M u s c o v i t e H o r n f e l s Sample F10 01A 01C 08C Q6A Q9A M i n e r a l Q u a r t z 80 50 70 78 60 60 M u s c o v i t e 20 30 18 35 29 P y r i t e t r 5 t r 5 1 B i o t i t e t r S i d e r i t e o r M a g n e s i t e 15 12 10 M i c r o c l i n e t r C l a y t r T r e m o l i t e 20 Z i r c o n . 2 . Appendix A5: Thin Section Modes of Unit B, Skarn (Page 1 of 2) Subunit B 1 B x B x ^ Hj_ * ± ^ B 2 B% * ± ^ ^ B± Sample A9 A l l BI B3 08D 08E 08K 09B 010 011B 012A 012C P1A Mineral C a l c i t e 50 40 35 2 15 35 15 5 30 10 50 Diopside 55 30 75 20 74 50 40 35 Phlogopite 2 10 2 5 10 68 10 45 t r Tremolite t r 15 15 20 Garnet t r 2 Sphene 3 t r t r t r 1 t r C h l o r i t e t r 2 10 t r 33 15 Epidote t r t r 70 t r 15 4 Serpentine 35 47 88 35 ' Dolomite 40 Mineral B 3 Quartz 5 Apatite Zircon t r t r 1 1 Limonite t r 10 10 t r 1 t r Magnetite 10 Appendix A5: Thin Section Modes of Unit B, Skarn (Page 2 of 2) Subunit Sample "1 PIC "1 P2A "1 P3D "2 P5A "2 P5C u l P6B "2 P6C "1 P7A "1 P8B "1. Q13C "1 DDI "1 DD23 Mineral C a l c i t e Diopside Phlogopite Tremolite Garnet Sphene 15 49 35 15 5 80 12 50 3 20 1 4 85 5 30 57 5 40 35 5 20 60 40 20 t r 20 55 33 36 30 5 55 10 30 30 t r C h l o r i t e Epidote Idocrase Serpentine Dolomite Mineral A t r 15 t r 20 50 15 t r t r Plagioclase Microcline Apatite Zircon Limonite Magnetite t r t r t r t r 35 39 t r t r 104 A p p e n d i x A6: T h i n S e c t i o n Modes o f U n i t C,'Skarn Sample P7D P8A P9B P11A M i n e r a l C a l c i t e D i o p s i d e P h l o g o p i t e D o l o m i t e C h l o r i t e S e r p e n t i n e 90 10 77 17 2 51 10 20 45 45 10 105 Appendix A7: Petrographic.-Properties of Zircon, A l l a n i t e , Monazite, Mineral A, Mineral B, and Mineral C Observed i n Guano-Guayes Area Rocks Zircon •5+ 1 Z r S i 0 4 (usually with Hf, often with Y, Th, U, Fe ; here with REE) see plates 4.5 and 4.6 hand specimen: tan, euhedral with pyramidal faces dominant hardness greater than 5.5 t h i n s e c t i o n : colourless to brown or opaque i f metamict; may. have zoning causes pleochroic halos- i n a c t i n o l i t e euhedral to granular and disseminated o p t i c a l properties: u n i a x i a l p o s i t i v e t h i r d order or greater birefringence very high p o s i t i v e r e l i e f length-slow p a r a l l e l e x t i n c t i o n A l l a n i t e (Ca, C e ) 2 ( F e 2 + , F e ^ ) A 1 2 0 ( S i ^ 0 ? ) ( S i 0 A ) (OH) 1 hand specimen: not observed t h i n section: l i g h t red-brown (ra r e l y green) pleochroic causes pleochroic halos : i n a c t i n o l i t e elongate grains often associated with mineral C and some-times associated with epidote twinning s i m i l a r to a l b i t e twinning two cleavage d i r e c t i o n s i n t e r s e c t i n g at about 90 degrees o p t i c a l properties: b i a x i a l p o s i t i v e or negative; 2V moderate to large f i r s t order birefringence moderate p o s i t i v e r e l i e f i n c l i n e d e x t i n c t i o n a x i a l plane perpendicular\to long axis of c r y s t a l " Monazite (Ce,La).P0A (Th, Nd and other rare earth elements present)"*" see plate 4.7 hand specimen: not observed 1. Shelley, "31975 106 t h i n s e c t i o n : l i g h t b r o w n i s h r e d p l e o c h r o i c c a u s e s p l e o c h r o i c h a l o s i n a c t i n o l i t e o p t i c a l p r o p e r t i e s : u n i a x i a l p o s i t i v e o r b i a x i a l p o s i t i v e w i t h s m a l l 2V f i r s t t o s e c o n d o r d e r b i r e f r i n g e n c e moderate to h i g h p o s i t i v e r e l i e f l e n g t h - s l o w e x t i n c t i o n i n c l i n e d , maximum 14 d e grees J 0. 3mm M i n e r a l A t h i n s e c t i o n above, c r o s s e d n i c o l s : M i n e r a l A s u r r o u n d e d by s e r p e n t i n e hand s p e c i m e n : n o t o b s e r v e d t h i n s e c t i o n : c o l o r l e s s rounded g r a i n s rimmed by l i m o n i t e o r c a r b o n a t e no c l e a v a g e , no t w i n n i n g o p t i c a l p r o p e r t i e s : b i a x i a l p o s i t i v e , 2V l a r g e h i g h f i r s t t o s e c o n d o r d e r b i r e f r i n g e n c e 107 L 0. 3mm M i n e r a l B t h i n s e c t i o n p h o t o m i c r o g r a p h above, c r o s s e d n i c o l s : m i n e r a l B i n s e r p e n t i n e hand s p e c i m e n : n o t o b s e r v e d t h i n s e c t i o n : c o l o u r l e s s p r i s m a t i c , r a d i a l t w i n n i n g v e r y w e l l d e v e l o p e d , s i m i l a r t o a l b i t e t w i n n i n g o p t i c a l p r o p e r t i e s : b i a x i a l n e g a t i v e , 2V 20 to 30 degrees o p t i c a x i a l p l a n e p a r a l l e l s t w i n n i n g f i r s t t o t h i r d o r d e r b i r e f r i n g e n c e moderate p o s i t i v e r e l i e f l e n g t h - f a s t e x t i n c t i o n i n c l i n e d a r o u n d 14 d e g r e e s maximum n o t e : M i n e r a l B r e s e m b l e s m i n e r a l s o f t h e H umite group e x c e p t i t s 2V i s too s m a l l . M i n e r a l C see p l a t e 4.7 hand specimen: t h i n s e c t i o n : g r a y i s h w h i t e , sometimes w i t h a r e d t i n g e b o t r y o i d a l r e p l a c e s REE e n r i c h e d z i r c o n no e f f e r v e s c e n c e i n c o l d d i l u t e HCI b l a c k o r opaque ( m e t a m i c t ) c a u s e s p l e o c h r o i c h a l o s i n a c t i n o l i t e r a d i a l t o f i b r o u s 108 o p t i c a l p r o p e r t i e s : moderate to h i g h , p o s i t i v e r e l i e f l e n g t h - f a s t n o t e : p r o p e r t i e s o b s e r v e d f o r m i n e r a l C r e s e m b l e t h o s e o f c h u r c h i t e (Ce,La) (P0 4)«2H 20 ( F o r d , 1945) 109 Appendix A8: Analyses of the Composition of Phlogopite and Garnet A Mg A l S i K K BaBa Fe Phlogopite K 2(Mg,Fe 2 +) ( S i 6 A l 2 O 2 0 ) . (OH)^ Two samples of phlogopite (09B, P6C) were analyzed q u a l i t a t i v e l y by Arvid L a c i s of The Department of Metallurgy, The U n i v e r s i t y of B r i t i s h Columbia on an ETEC autoscan scanning e l e c t r o n microscope with an ORTEC X-ray a n a l y t i c a l u n i t , producing the diagram above. The v e r t i c a l s c a le on the diagram i s l i n e a r , allowing comparison of r e l a t i v e amounts of elements present. The grains analyzed have e s s e n t i a l l y i d e n t i c a l compo-s i t i o n , with Mg/Fe much greater than 2/1, the composition d i v i d i n g phlo-gopite from b i o t i t e . The grains analyzed are unusual because they contain a s i g n i f i c a n t amount of Ba. 1. Shelley, 1975 110 013C - J V J A •1 \ DD29 V J A A . —• AISi Ca Ca Fe Garnet composition between grossularite and andradite C a 3 ( F e + 3 , A l ) 2 S i 3 0 1 2 1 Two samples of garnet were analyzed q u a l i t a t i v e l y by Arvid Lacis of the Department of Metallurgy, The University of B r i t i s h Columbia, on an ETEC autoscan scanning electron microscope equipped with an ORTEC X-ray a n a l y t i c a l unit, producing the above peaks. A l i n e a r v e r t i c a l scale on the peaks allows comparison of r e l a t i v e abundances of elements. Peaks for A l and Fe are of the same order of magnitude for both samples but show that sample Q13C contains r e l a t i v e l y more A l and less Fe than sample DD29. No compositional variations were found within i n d i v i d u a l grains. 1. Shelley,;1975 I l l Appendix B: Chemical Analyses Appendix B l : \ n a l y t l c a l Data and Method for Uhole-Rock Analyses Unit * 6 16 16 16 16 17a 17a 17a 17a Sample N3a H5 N5 dup N6 S10 «8A f)8F 08F dup P1B Oxide S10, 60.47 61.69 62.02 61.92 60.13 55.29 64.97 64.98 70.48 TIO, 0.60 0.56 0.55 0.53 0.66 0.32 0.91 0.89 0.33 L 17.58 18.24 18.00 15.98 16.30 11.71 5.82 5.71 5.83 Fe,0 6.53 2.81 2.85 7.52 8.54 6.53 11.13 11.07 11.61 L J MnO 0.07 0.05 0.05 0.08 0.09 0.13 0.26 0.26 0.14 HgO 0.99 0.67 0.59 0.85 1.03 5.11 3.96 3.91 1.84 CaO 1.50 3.91 3.93 1.37 1.47 10.55 9.27 9.22 3.50 Na,0 3.74 5.78 5.73 5.05 3.60 1.18 1.37 1.38 0.38 K,0 7.99 5.93 6.06 4.69 6.53 5.82 0.86 0.86 2.94 I P,0. 0.14 0.14 0.14 0.16 0.13 0.17 0.14 0.13 0.25 i. > H 20 0.61 0.54 0.54 0.87 1.43 2.52 0.60 0.59 1.21 REE 2 0.04 0.03 0.03 0.05 0.03 0.21 0.49 0.49 0.32 Total 100.25 100.34 100.48 99.07 99.94 99.53 99.77 99.47 98.81 1. Whole-rock analyaes run by X-ray fluorescence according to procedure standardized by C. T. Nixon i n 1978. His 1ZTA program was used to c a l c u l a t e values for matrix-corrected oxides on a hydrous basis. Low values for and NajO were recalculated using regression curves for lower values. 2 . T o t a l REE estimated from upper c r u s t a l abundances (Nance and Taylor, 1976) by comparing the t o t a l of a l l REE to the t o t a l of the nine REE analyzed here (Table 6.2). The following formula was thus derived: (sum of 9 REE analyzed here] x 10/9 • Total REE 3. Imtttat i s probably due to the presence of s i g n i f i c a n t amounts of zirconium. Standards with high Zr were not av a i l a b l e for c a l i b r a t i o n . 113 A p p e n d i x B2: A n a l y t i c a l D a t a and Method f o r v N i c k e l A n a l y s e s Sample D e s c r i p t i o n ppm n i c k e l 95%. c o n f i d e n c e . l i m i t N3 U n i t 16 s y e n i t e 2.6 2.2 :. i. N5 U n i t 16 s y e n i t e 4.9 2.2 N6 U n i t 16 s y e n i t e 4.3 2.2 08F U n i t 17a m e l a g r a n i t e dike.™ 9.7 2.1 P1B U n i t 17a m e l a g r a n i t e d i k e 10.9 2.1 CC17 U n i t 17a m e l a g r a n i t e d i k e " 19.6 2.1 P7A U n i t B s k a r n , s e r p e n t i n i z e d 7.3 2.1 P7D U n i t B s k a r n , s e r p e n t i n i z e d 1.0 2.2 P11A U n i t C s k a r n , s e r p e n t i n i z e d 2.1 2.2 DDI U n i t B s k a r n 1 1 . 8 2.1 1. N i c k e l a n a l y s e s were done by X-ray f l u o r e s c e n c e on p r e s s e d powder samples f o l l o w i n g s t a n d a r d p r o c e d u r e s e s t a b l i s h e d by R. Berman i n 1978 A p p e n d i x B3: A n a l y t i c a l Method f o r Rare E a r t h Element Analyses: and Comparison o f Rock-Type REE-Croups A n a l y t i c a l Method f o r Rare E a r t h Element A n a l y s e s The r a r e e a r t h elements L a , Ce, Sm, Eu, Dy, Yh, and L u were a n a l y z e d a t t h e U n i v e r s i t y o f T o r o n t o . They were i r r a d i a t e d i n t h e low f l u x SLOWPOKE-1 n u c l e a r r e a c t o r . Measurements: o f 1-vay a c t i v i t i e s were made w i t h a C a n b e r r a G e ( L i ) d e t e c t o r c o u p l e d through, a 452 ORTEC s p e c t r o s c o p y a m p l i f i e r to an 8100 s e r i e s , 4096 c h a n n e l C a n b e r r a a n a l y z e r . S t a n d a r d r e f e r e n c e m a t e r i a l s used f o r c a l i b r a t i o n were BCR-1, C o a l (_SRM 1632) and F l y Ash (SRM 1633) , from t h e U n i t e d S t a t e s N a t i o n a l Bureau o f S t a n d a r d s . D e t a i l e d a n a l y t i c a l p r o c e d u r e was as d e s c r i b e d by Hancock ( 1 9 7 6 ) . V a l u e s f o r Nd and Tb were c a l c u l a t e d by Hancock. Appendix B3: S t a t i s t i c a l comparison of rock-type REE groups. Cuano-Cuayes area. Pelly Mountains. Yukon Te r r i t o r y , using calculations of t l n d j ^ ' - a n d corresponding confidence l e v e l s . Units La Ce Sm Eu Dy Yb Lu Unit 17a, Melagranite Dikes compared to Unit 16, Syenite df = 8 'independent percent confidence l e v e l 3.39 99 to 99.9 5.81 >99.9 2.89 98 4.82 99 to 99.9 5.65 >99.9 5.91 >99.9 6.30 >99.9 Unit 16, Syenite, compared to Units B anc C, Skarn df - 28 'independent percent confidence l e v e l 1.68 80 to 90 3.45 99 to 99.9 0.12 <80 0.48 <80 2.02 90 to 95 1.03 <80 1.11 <80 Units B and C, Skarn compared to Sedimentary Rocks df •= 21 'independent percent confidence l e v e l 1.79 90 to 95 2.31 95 to 98 2.03 90 to 95 1.11 <80 1.67 80 to 90 1.59 80 to 90 1.87 90 to 95 Unit 16, Syenite, compared to Sedimentary Rocks df - 9 'independent percent confidence l e v e l 6.33 >99.9 6.32 >99.9 0.99 <80 4.00 99 to 99.9 5.30 >99.9 3.51 99 to 99.9 4.16 99 to 99.9 Unit 17b, Mafic Dikes, compared to Unit 17a, Melagranite Dikes df "4 'independent percent confidence l e v e l 7.44 99 to 99.9 5.50 99 to 99.9. 4.08 98 to 99 3.90 98 to 99 3.34 95 to 98 2.80 95 to 98 2.43 90 to 95 1. The formula used for t l n d e p e n d e n t . includes a correction for comparison of groups of di f f e r e n t variance. It i s : independent X - Y ^ < B , - 1 ) S V ; ( ° V 2 - 1 ) S Dv2j[j V] 2. The confidence l e v e l defines the amount of certainty that the difference between the Wo groups i s large i n r e l a t i o n to the standard deviation of the d i s t r i b u t i o n of differences between sample oeans ( s ^ ). 116 Appendix C: Geochronometry 117 A p p e n d i x C I : Rb-Sr A n a l y t i c a l T e chnique and Data Rb-Sr A n a l y t i c a l T e chnique Rb and S r c o n c e n t r a t i o n s were d e t e r m i n e d by r e p l i c a t e a n a l y s i s o f p r e s s e d powder p e l l e t s u s i n g X - r a y f l u o r e s c e n c e . . U.S. G e o l o g i c a l Survey r o c k i s t a n d a r d s were used f o r c a l i b r a t i o n ; mass a b s o r p t i o n c o e f f i c i e n t s were o b t a i n e d from Mo K<x Compton s c a t t e r i n g measurements. Rb/Sr r a t i o s have a p r e c i s i o n , o f 2% (1 <* ) and c o n c e n t r a t i o n s a p r e c i s i o n of.. 5% ( l o " ) . Sr i s o t o p i c c o m p o s i t i o n was measured on u n s p i k e d samples p r e p a r e d u s i n g s t a n d a r d i o n .exchange t e c h n i q u e s . The mass s p e c t r o m e t e r (60° s e c t o r , 30 cm r a d i u s , s o l i d s o u r c e ) i s o f U.S. N a t i o n a l B u r e a u o f S t a n d a r d s d e s i g n , m o d i f i e d by H. F a u l . Data a q u i s i t i o n i s d i g i t i z e d and automated u s i n g a 86 88 NOVA computer. E x p e r i m e n t a l d a t a have been n o r m a l i z e d to a S r / Sr r a t i o o f 0.1194 and a d j u s t e d so t h a t t h e NBS s t a n d a r d S r C o 3 (SRM987) g i v e s a 87 86 S r / Sr r a t i o o f 0.71022 + 2 and the Eimer and Amend Sr a r a t i o o f 0.70800 + 2. The p r e c i s i o n o f a s i n g l e 8 7 S r / 8 6 S r r a t i o i s 0.00013 (.1 <J ). -11 -1 Rb-Sr d a t e s a r e based on a Rb decay c o n s t a n t o f 1.42 x 10 y . The r e g r e s s i o n s a r e c a l c u l a t e d a c c o r d i n g to t h e t e c h n i q u e o f Y o r k (1967) . Appendix CI : Rb-Sr Data Sample Suite : Skarn adjacent to Seagull Creek syenite I n i t i a l 8 ? S r / 8 5 S r : O.710451.OO0I5 Age 1 : 332.8i9.7Ma ") 87 86 87 86 Sample Description Locality N Latitude W Longitude IS10 2 X K £ ppm Sr ppm Rb Rb/ Sr Sr/ Sr Number P6CWR Unit B skarn Guano-Guayes Property Pelly Mountains 61°30' '06" 132°24' 54" - - 106 572 15.599 0.7822 P6CPh Unit B skarn phlogopite separate Guano-Guayes Property Pelly Mountains 61°30' •06" 132°24' '54" - - 77 612 22.889 0,8220 P6CCc Unit B skarn c a l c i t e separate Guano-Guayes Property Pelly Mountains 61°30' '06" 132°24' '54" - — 348 3.75 0.03097 0.7106 1 Rb decay constant used - 1.4200 x 10 2 see F i g . 5.1 Appendix CI : Rb-Sr Data Sample Suite : Seagull Creek Syenite - Whole Rock Samples I n i t i a l 8 7 S r / 8 6 S r : 0.709871.00119 Age 1: 206.0114.7Ma Sample Number Description L o c a l i t y 87„. ,86„ 87„ ,86„ N Latitude W Longitude ZSi0 2 JKjO ppm Sr ppm Rb Rb/ Sr Sr/ Sr N3WR Unit 16 syenite N3AWR Unit 16 syenite N3BWR Unit 16 syenite N5WR Unit 16 syenite N10HR Unit 16 syenite M27WR Unit 16 syenite Cuano-Pelly Guano-Pelly Cuano-Pelly Guano-Pelly Guano-Pelly Guano-Pelly •Guayes Property Hjuntains •Cuayes Property Mountains •Cuayes Property Mountains -Guayes Property Mountains -Guayes Property Mountains -Guayes Property Mountains 6l"30'24" 132°26'47" 60 . 4 7 7.99 61°30'24" 132°26'47" 60.47 7.99 61°30'24" 132°26'47" 60.47 7.99 61°29'56" 132°25'27" 61.93 6.00 61°29'51" 132°25'02" 60.13 6.53 61°29 ,18" 132025'45" 61.01 6.63 160 159 152 4 34 50.4 79.4 193 192 196 119 195 19.4 3.505 0.7203 3.476 0.7201 3.749 0.7990 11.283 0.7061 0.7210 0.7139 0.7429 0.7102 87 -11 1 Rb decay constant used - 1.4200 x 10 2 see F i g . 5.1 Appendix CI : Rb-Sr Data Sample Suite : Seagull Creek Syenite - Mineral Separates I n i t i a l 8 7 S r / 8 6 S r : 6.71456±.00136 Age 1: 127.7i25.1Ma Sample Description L o c a l i t v N Latitude W Longitude ZS10. xx. o 2 ppm Sr ppm Rb 87„.,86 87. ,86. Rb/ s r S r ' S r N3WR Unit 16 syenite Guano-Guayes Property P e l l y Mountains 61°30' 24" 132°26'47" 60.47 7.99 160 193 3.505 0. .7206 N3Arf Unit 16 syenite b i o t i t e and arfvedsonite separate Guano-Guayes Property P e l l y Mountains 61°39' '24" 132°36'47" — 3.423 171 279 4.706 0. .7232 N3Kf Unit 16 syenite K feldspar separate Guano-Guayes Property P e l l y Mountains 61°30' '24" 132°36'47" - - 112 122 3.145 0. .7205 "87 " ~11 1 Rb decay constant used - 1.4200 x 10 2 see F i g . 5.1 3 percent K 121 A p p e n d i x C2: K-Ar A n a l y t i c a l Technique and Data K-Ar A n a l y t i c a l T e chnique K i s d e t e r m i n e d i n d u p l i c a t e by a t o m i c a b s o r p t i o n u s i n g a T e c h t r o n AA4 s p e c t r o p h o t o m e t e r and A r by i s o t o p e d i l u t i o n u s i n g an AEI MS — 10 mass s p e c -38 t r o m e t e r and h i g h p u r i t y A r s p i k e . E r r o r s r e p o r t e d a r e f o r one s t a n d a r d d e v i a t i o n . The c o n s t a n t s used a r e : K\} = 0.585 x 1 0 _ 1 y _ 1 K\p = 4.72 -x 1 0 ~ 1 0 y _ 1 4°K/K = 0.0119 atom p e r c e n t Sample Description Appendix C2: K-Ar Analytical teta Locality N3 P6C W Latitude S Longitude ZK N2A Dike cutting Unit 16 Cuano-Guayes Property 61°30'20" 132*26'44r syenite; '-- w - • Pelly Mountains hornblende separate Yukon T e r r i t o r y Unit 16 syenite; arfvedsonite + b i o t i t e separate Guano-Guayes Property 61°30'24" 132*26'4J" Pelly Mountains, Yukon T e r r i t o r y Unit B skarn; phlogopite separate Pelly Mountains Yukon T e r r i t o r y Guano-Cuayes Property 61°30'06" 132°24'54' 0.862 + 0.013 + 1.15Z 3.42 + 0.03 + 0.9Z 8.15 + 0.04 + 0.5Z A r * 4 0 / T o t a l A r 4 0 Ar* 4 O10- 5cc STtfg A r 4 0 / K 4 ° 70.0Z 86.1Z 92.8Z 3.900 x 10" 1 6.634 x 10~ 3 2.224 11.317 9.535 x 1 0 - 3 156 + 5 Ma Age 110 + 4 Ma 2.036 x 10 319 + 10Ma N3 N ) 1. see F i g . 5.1 2. Ar refers to radiogenic Ar 

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