Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
DSpace
UBCV
Htoon, Myat
Master of Science - MSc
University of British Columbia
Clinton Creek asbestos deposit is situated at 77 kilometres northwest of Dawson City on Clinton Creek in Yukon Territory. Yukon Metamorphic Complex of Ordovician to Devonian age (470 Ma, Rb-Sr date) covers most of the Clinton Creek area. The most prominent metamorphism of the area occurred in Permian time (245 to 278 Ma, K-Ar dates). Based on intensity and style of deformation of ultramafic bodies and country rocks it is suggested that the ultramafic rocks were emplaced probably during the Permian period. Tintina fault is a weak zone along which the alpine ultramafic bodies of Clinton Creek and probably some of the others along and close to the Tintina Trench were tectonically emplaced. These were later folded and metamorphosed with the country rocks. During latest Cretaceous-earliest Tertiary time (64.9 Ma, K-Ar date) the area was intruded by acid intrusive rocks. The youngest undeformed and fresh basalt is probably of Selkirk volcanics equivalent. Three prominent phases of deformation were delineated. Probably the oldest and most complex phase occurred during the Permian, along with the initial movement of the Tintina fault. Small, tight, isoclinal folds are characteristics of this phase. The structural trend (300* to 315') is roughly parallel to the direction of the Tintina Trench. Due to later deformations changes in direction of fold axes of this phase (190* to 350") is common. The second phase of deformation gave rise to large recumbent folds with trends varying from 270" to 290' with southerly vergence. Third phase of deformation gave rise to antiform structure of regional scale. The Porcupine and Snow Shoe ultramafic bodies are mined for chrysotiile asbestos. A few other ultramafic bodies contain appreciable amount of chrysotile-fibre but not of adequate quantity to be mined. Most of the ultramafic bodies are sheared or massive, and are devoid of known chrysotile-fibre. In general, if serpentinization is less than 75 percent there is no chance of commercial mineralization. Fairly intense fractures are essential to provider adequate openings for chrysotile-fibre formation in ore grade concentrations. Chrysotile-fibre bearing serpentinized ultramafic masses within argillite unit or at the contact of argillite and other units seem to carry ore grade or substantial amount of chrysotile-fibre. Evidence of Clinton Creek asbestos deposit mainly supports formation of chrysotile-fibre as fracture filling. Although evidence of fracture filling rather than replacement seems convincing and exists on a wide scale, a few evidence indicates replacement characteristics on minor scale. The main phase of mineralization is believed to occur at the end of Cretaceous when acid intrusive rocks intruded the vicinity of the Clinton Creek area. These intrusions could have provided warm aqueous solution to react with the existing serpentine along fractures. This resulted deposition of chrysotile-fibre in an essentially closed system. Analysis of isotopic dates of the Yukon Crystalline Plateau shows a distinct grouping of igneous activity at mid Cretaceous and latest Cretaceous time. Some isotopic dates of igneous and metamorphic rocks ranging from 135 to 230 Ma show a distinct younging trend away from the Tintina Trench. The trend suggests that the date at the Tintina Trench is about 200 Ma, and 2'50 kilometres perpendicular distance from the trench is 150 Ma. The apparent horizontal rate of isotherm migration is about 0.5 cm/yr. However, more data is required to confirm the speculation that the Tintina Trench represents an extinct geosuture and vanished ocean.
CO GEOLOGY OF THE CLINTON CREEK ASBESTOS DEPOSIT, YUKON TERRITORY by M Y A T | H T O O N B . S c , Rangoon Ar t s and Sciences U n i v e r s i t y , 1967 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 accept t h i s t h e s i s as conforming to the req u i r e d standard T H E U N I V E R S I T Y OF B R I T I S H C O L U M B I A March, 1979 0 Myat Htoon, 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 o f G e o l o g i c a l S c i e n c e s The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 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 March, 23rd, 19 79. i i ABSTRACT C l i n t o n Creek asbestos deposit i s s i t u a t e d at 77 k i l o m e t r e s northwest of Dawson C i t y on C l i n t o n Creek i n Yukon T e r r i t o r y . Yukon Metamorphic Complex of Ordovician to Devonian age (470 Ma, Rb-Sr date) covers most of the C l i n t o n Creek area. The most prominent metamorphism of the area occurred i n Permian time (245 to 278 Ma, K-Ar dates). Based on i n t e n s i t y and s t y l e of deformation of u l t r a m a f i c bodies and country rocks i t i s suggested that the u l t r a m a f i c rocks were emplaced probably during the Permian p e r i o d . T i n t i n a f a u l t i s a weak zone along which the a l p i n e u l t r a m a f i c bodies of C l i n t o n Creek and probably some of the others along and c l o s e to the T i n t i n a Trench were t e c t o n i c a l l y emplaced. These were l a t e r f o l d e d and metamorphosed w i t h the country rocks. During l a t e s t C r e t a c e o u s - e a r l i e s t T e r t i a r y time (64.9 Ma, K-Ar date) the area was i n t r u d e d by a c i d i n t r u s i v e rocks. The youngest undeformed and f r e s h b a s a l t i s probably of S e l k i r k v o l c a n i c s e q u i v a l e n t . Three prominent phases of deformation were d e l i n e a t e d . Probably the o l d e s t and most complex phase occurred during the Permian, along w i t h the i n i t i a l movement of the T i n t i n a f a u l t . Small, t i g h t , i i s o c l i n a l f o l d s are c h a r a c t e r i s t i c s of t h i s phase. The s t r u c t u r a l trend (300* to 315') i s roughly p a r a l l e l to the d i r e c t i o n of the T i n t i n a Trench. Due to l a t e r deformations changes i n d i r e c t i o n of f o l d axes of t h i s phase (190* to 350") i s common. The second phase of deformation gave r i s e to l a r g e recumbent f o l d s w i t h trends v a r y i n g from 270" to 290' w i t h s o u t h e r l y vergence. Third phase of deformation gave r i s e to a n t i f o r m s t r u c t u r e of r e g i o n a l s c a l e . The Porcupine and Snow Shoe u l t r a m a f i c bodies are mined f o r c h r y s o t i i l e asbestos. Afew other u l t r a m a f i c bodies c o n t a i n appreciable amount of c h r y s o t i l e - f i b r e but not of adequate qu a n t i t y to be mined. 'Mbst of the u l t r a m a f i c bodies are sheared or massive, and are devoid of known c h r y s o t i l e - f i b r e . In general, i f s e r p e n t i n i z a t i o n i s l e s s than 75 percent there i s no chance of commercial m i n e r a l i z a t i o n . F a i r l y intense f r a c t u r e s are e s s e n t i a l to provider.adequate openings f o r c h r y s o t i l e -f i b r e formation i n ore grade concentrations. C h r y s o t i l e - f i b r e bearing s e r p e n t i n i z e d u l t r a m a f i c masses w i t h i n a r g i l l i t e u n i t or at the contact of a r g i l l i t e and other u n i t s seem to carry ore grade or s u b s t a n t i a l amount of c h r y s o t i l e - f i b r e . Evidence of C l i n t o n Creek asbestos deposit mainly supports formation of c h r y s o t i l e - f i b r e as f r a c t u r e f i l l i n g . Although evidence of f r a c t u r e f i l l i n g r a t h e r than replacement seems convincing and e x i s t s on a wide s c a l e , a few evidence i n d i c a t e s replacement c h a r a c t e r i s t i c s on minor s c a l e . The main phase of m i n e r a l i z a t i o n i s b e l i e v e d to occur at the end of Creta-ceous when a c i d i n t r u s i v e rocks intruded the v i c i n i t y of the C l i n t o n Creek area. These i n t r u s i o n s could have provided warm aqueous s o l u t i o n to r e a c t w i t h the e x i s t i n g serpentine along f r a c t u r e s . This r e s u l t e d d e p o s i t i o n of c h r y s o t i l e - f i b r e i n an e s s e n t i a l l y closed system. i i i A n a l y s i s of i s o t o p i c dates of the Yukon C r y s t a l l i n e P l a t e a u shows a d i s t i n c t grouping of igneous a c t i v i t y at mid Cretaceous and l a t e s t Creta-ceous time. Some i s o t o p i c dates of igneous and metamorphic rocks ranging from 135 to 230 Ma show a d i s t i n c t younging trend away from the T i n t i n a Trench. The trend suggests'that the date at the T i n t i n a Trench i s about 200 Ma, and 2'50 kilometres perpendicular d i s t a n c e from the trench i s 150 Ma. The apparent h o r i z o n t a l r a t e of isotherm m i g r a t i o n i s about 0.5 cm/yr. However, more data i s required to confirm the s p e c u l a t i o n that the T i n t i n a Trench represents an e x t i n c t geosuture and vanished ocean. i v CONTENTS Page I INTRODUCTION 1 1-1 PRELIMANARY STATEMENT 1 1-2 SCOPE OF THESIS 1 1-3 LOCATION AND ACESS 3 1-4 CLIMATE AND VEGETATION 4 j 1-5 PHYSIOGRAPHY 5 1- 6 HISTORY OF THE CLINTON CREEK DEPOSIT 6 I I GEOLOGY OF THE CLINTON CREEK AREA 7 2- 1 INTRODUCTION 7 2-2 METAMORPHIC ROCKS OF THE YUKON CRYSTALLINE PLATEAU 7 Page 2-2-A Regional S e t t i n g 7 2-2-B C l i n t o n Creek Area 12 a. Carbonaceous and limy a r g i l l i t e s 13 b. Greenstone and quartz-muscovite-c h l o r i t e s c h i s t 16 c. Quartz-muscovite q u a r z i t e s c h i s t and 18 d. Quartz-muscovite-• b i o t i t e s c h i s t 20 2-3 ULTRAMAFIC ROCKS 22 2-3 -A Regional S e t t i n g 22 2-3' -B C l i n t o n Creek Area 24 2-4 ACID INTRUSIVE ROCK 25 2-5 BASALT 26 2-6 STRUCTURE 27 2-6--A I n t r o d u c t i o n 27 2-6' -B Folds 29 2-6--c F a u l t s 44 2-6--D J o i n t s 48 2-6' -E Regional S t r u c t u r e 48 2-7 2-7-A ISOTOPIC AGE DETERMINATIONS I n t r o d u c t i o n 50 50 v i Page 2-7-B I s o t o p i c A n a l y s e s 55 a. Potassium-Argon 5 5 b. R u b i d i u m - S t r o n t i u m 56 2-1-0. R e g i o n a l S y n t h e s i s 58 2- 7-D Summary 66 I I I CLINTON CREEK ULTRAMAFIC BODIES 6 8 3- 1 INTRODUCTION 68 3-2 PETROLOGY 69 3-2-A U l t r a m a f i c Rock Types 69 3-2-B E a r l y Stage A l t e r a t i o n 72 a. S e r p e n t i n i z a t i o n 72 b. R o d i n g i t i z a t i o n 84 c. B l a c k w a l l and t a l c - c a r b o n a t e a l t e r a t i o n 91 3-2-C L a t e Stage A l t e r a t i o n 9 2 a. S i l i c a - c a r b o n a t e a l t e r a t i o n 9 2 b. Q u a r t z - m a g n e s i t e v e i n s 103 3-3 STRUCTURE 103 3-4 ORIGIN 106 v i i Page IV THE CLINTON CREEK ASBESTOS DEPOSIT 118 4-1 INTRODUCTION 118 4-2 CHRYSOTILE VEINS 118 4-2-A T e x t u r e s and S t r u c t u r e s 120 a. C h r y s o t i l e - f i b r e v e i n s 120 b. P i c r o l i t e v e i n s 123 4-2-B R e l a t i o n s h i p w i t h S e r p e n t i n e W a l l - r o c k 127 4-2-C C h e m i s t r y o f C h r y s o t i l e and A n t i g o r i t e 129 4-3 FRACTURES AND DISTRIBUTION OF CHRYSOTILE-FIBRE VEINS 13 5 4-4 ORIGIN OF CHRYSOTILE VEINS 14 3 4-4-A T e m p e r a t u r e o f F o r m a t i o n o f S e r p e n t i n e M i n e r a l s 14 3 4-4-B F o r m a t i o n o f C h r y s o t i l e V e i n s 14 5 a. P r e v i o u s i d e a s 14 5 b. E v i d e n c e f r o m C l i n t o n C r e e k 14 6 4-4-C C h r y s o t i l e F o r m i n g S o l u t i o n s and C h r y s o t i l e D e p o s i t i o n 148 v i i i Page V EXPLORATION FOR CHRYSOTILE ASBESTOS IN THE NORTHERN CORDILLERA 152 5-1 INTRODUCTION 152 5-2 FEATURES OF CHRYSOTILE ASBESTOS BEARING ULTRAMAFIC BODIES 152 5-2-A Cassiar, B.C. 152 5-2-B Kutcho, B.C. 155 5-2-C Canex, Y.T. 155 5-2-D Caley, Y.T. 156 5-2-E Tincup Lake, Y.T. 157 5-2-F Dahl Creek, Alaska 157 5-2-G Eagle, Alaska 158 5-3 FEATURES OF BARREN ULTRAMAFIC BODIES 159 5-4 GUIDES IN SEARCH FOR CHRYSOTILE ASBESTOS 160 VI SUMMARY AND CONCLUSION 163 BIBLOGRAPHY 166 i x Page APPENDIX A 17 6 APPENDIX B 177 APPENDIX C 180 APPENDIX D 182 APPENDIX E 183 APPENDIX F 191 APPENDIX G 194 X LIST OF TABLES Page 2-1 Units i n the Clinton Creek Area, Y.T. 9 2-2 Structural Elements of the Clinton Creek Area 30 2-3 Potassium-Argon A n a l y t i c a l Data 52 2-4 Rubidium-Strontium Data for Analyzed Whole Rock Samples 53 2-5 Relationships of Isotopic Dates and Its Perpendicular Distance from the Ti n t i n a Trench i n the Yukon C r y s t a l l i n e Plateau 60 4-1 A n a l y t i c a l Data for Eleven Oxides of Chrysotile and Antigorite 188 4-2 S t a t i s t i c a l Summary of the Eleven Oxides of 33 Chrysotile Samples 131 4-3 S t a t i s t i c a l Summary of the Eleven Oxides of 64 Antigorite Samples 132 x i LIST OF FIGURES Page 1- 1 Location of the Clinton Creek Asbestos Deposit 2 2- 1 Regional Geology 8 2-2 Geological Map of the Clinton Creek Area -b-a-ck pocket 2-3 D i s t r i b u t i o n of the Yukon Metamorphic Complex and Equivalents i n Yukon Ter r i t o r y and Alaska 11 2-4 Generalized D i s t r i b u t i o n of Serpentinized Ultramafic Rocks i n Yukon Te r r i t o r y and Alaska 23 2-5 D i s t r i b u t i o n of 73 L^ Lineations 35 2-6 F i e l d Sketch of F i r s t Phase Folds 36 2-7 F i e l d Sketch of Second Phase Folds 41 2-8 Poles to 75 (F^) F o l i a t i o n s and A x i a l Planes 42 2-9 Poles to 123 L 2 Lineations 2-10 Poles to 66 Faults 2-11 Poles to 133 Joints 43 47 49 63 2-12 Geology of the Clinton Creek Area with I s o t o p i c a l l y Dated Sample Sites 54 2-13 Plots of Sr/ Sr vs. R b / S r for Whole Rock Rb-Sr Analyses of the Clinton Creek Area 57 2-14 Histogram of K-Ar and Rb-Sr Dates of Igneous and Metamorphic Rocks of the Yukon C r y s t a l l i n e Plateau 2- 15 K-AR and Rb-Sr Dates of Igneous and Metamor-phic Rocks of the Yukon C r y s t a l l i n e Plateau vs. Perpendicular Distance from the Ti n t i n a Trench 3- 1 Modal C l a s s i f i c a t i o n of Ulrramafic Rocks 3-2 T-X Diagram i n Saturated System MgO-SiO„-H20-C02-CaO 65 70 79 x i i Page 3-3 Ore Grade Zones i n the Porcupine P i t back pocket 3-4 Cross Section of Porcupine Serpentinite Body Along 12W 9 5 3-5 Dehydration, Carbonatization and S i l i c i -f i c a t i o n of Serpentine During S i l i c a -carbonate A l t e r a t i o n Shown on S i 0 2 ~ C 0 2 -MgO-H20 Tetrahedron 100 3-6 Ore Bearing Porcupine, Creek and Snow Shoe Serpentinite Bodies 10 5 3-7 Cross Section of Porcupine Ultramafic Body Along 19W 10 8 3-8 Cross Section of Porcupine Ultramafic Body Along 20W 109 3-9 Cross Section of Porcupine Ultramafic Body Along 26W 110 3-10 Cross Section of Porcupine Ultramafic Body Along 24W 111 3-11 Cross Section of Porcupine Ultramafic Body Along 23W 112 3-12 Cross Section of Porcupine Ultramafic Body Along 10W 113 3- 13 Cross Section of Porcupine Ultramafic Body Along 9W 114 4- 1 C h r y s o t i l e - f i b r e Veins 122 4-2 Characte r i s t i c s of C h r y s o t i l e - f i b r e Veins 124 4-3 Characteristics of P i c r o l i t e Veins 128 4-4 Frequency Diagrams of MgO, AI2O3, S i 0 2 and FeO (by wt. %) of 64 Antigorite Samples 133 4-5 Frequency Diagrams of MgO, A ^ O o , S i 0 2 and FeO (by wt. %) of 33 Chrysotile Samples 134 4-6 Poles to 264 C h r y s o t i l e - f i b r e Veins 136 x i i i 4-7 Poles to 125 C h r y s o t i l e - f i b r e Veins Showing Displacement Along the Containing Fracture 4-8 Poles to 139 C h r y s o t i l e - f i b r e Veins i n Joints 4-9 Ore (Chrysotile-fibre) Grade Zones at Level 1410 f t . 4-10 Ore (Chrysotile-fibre) Grage Zones at Level 1470 f t . 4-11 Ore (Chrysotile-fibre) Grade Zones i n Cross Section Along 17W 4-12 Poles to 105 Faults i n and Adjacent to the Porcupine Ultramafic Body 4-13 Mechanics of Origin of Chrysotile Veins 4- 14 Chrysotile Forms Adjacent to Serpentine but Not to Olivine 5- 1 Asbestos Bearing Ultramafic Bodies i n B.C., Y.T. and Alaska Page 138 139 b a c k p o c k e t ' b a c k p o c k e t 140 144 14 7 150 153 x i v LIST OF PLATES Page 2-1 Carbonaceous a r g i l l i t e i n c o n t a c t w i t h q u a r t z - m u s c o v i t e s c h i s t 14 2-2 Dark, bedded l i m e s t o n e w i t h i n the c a r b o -naceous a r g i l l i t e u n i t 15 2-3 Lens o f marble i n the q u a r t z - m u s c o v i t e s c h i s t and q u a r t z i t e u n i t 19 2-4 Two s e t s o f f o l i a t i o n p l a n e s i n q u a r t z -m u s c o v i t e s c h i s t 21 2-5 Columnar j o i n t e d b a s a l t o f S e l k i r k V o l c a n i c s 28 2-6 T i g h t i s o c l i n a l f o l d s i n carbonaceous a r g i l l i t e 32 2-7 G l e i t b r e t t s t r u c t u r e i n s c h i s t o s e r o c k s 33 2-8 R e l i c t o f L j f o l d c l o s u r e s i n the e n c l o s i n g a r g i l l i t i c s andstone 34 2-9 Chevron f o l d s shown by y e l l o w sandstone beds 38 2-10 C r e n u l a t i o n s r e l a t e d to L2 f o l d i n q u a r t z -m u s c o v i t e s c h i s t 39 2-11 F o l i a t i o n s F]_ and F 2 i n q u a r t z - m u s c o v i t e s c h i s t 40 2-12 M i n o r f a u l t d i s p l a c i n g r o d i n g i t e body i n the P o r c u p i n e p i t 4 5 2- 13 N o r t h e r l y t r e n d i n g v e r t i c a l f a u l t w i t h c o n s i d e r a b l e d i s p l a c e m e n t i n the P o r c u p i n e p i t 46 3- 1 S e r p e n t i n i z e d h a r z b u r g i t e 71 3-2 S e r p e n t i n i z e d l h e r z o l i t e 73 X V Page 3-3 P a l e y e l l o w b r u c i t e formed d u r i n g p e r v a s i v e , f i r s t main e p i s o d e o f s e r p e n t i n i z a t i o n 76 3-4 Y e l l o w i s h w h i t e b r u c i t e i n f r a c t u r e s between p i c r o l i t e 77 3-5 Chromite w i t h m a g n e t i t e 82 3-6 O l d e r r o d i n g i t e 85 3-7 O l d e r r o d i n g i t e ( c r o s s e d n i c o l s ) 86 3-8 C o n t a c t o f o l d e r r o d i n g i t e and s e r p e n t i n i t e 87 3-9 U r a l i t i z e d , c h l o r i t i z e d r o d i n g i t e 88 3-10 S e r p e n t i n e d e h y d r a t e d i n t o pyroxene 90 3-11 T a l c - c a r b o n a t e v e i n i n s e r p e n t i n i t e 93 3-12 S i l i c a - c a r b o n a t e a l t e r a t i o n a l o n g f a u l t zone 96 3-13 F i r s t s t a g e o f s i l i c a - c a r b o n a t e a l t e r a t i o n 98 3-14 Opal zone i n c o n t a c t w i t h s e r p e n t i n i t e 10 2 3-15 Q u a r t z - m a g n e s i t e v e i n o f l a t e s i l i c a -c a r b o n a t e a l t e r a t i o n 104 3- 16 Ore b e a r i n g P o r c u p i n e u l t r a m a f i c body p l u n g i n g 10' towards 23 5' 10 7 4- 1 C l i n t o n Creek open p i t a s b e s t o s mine 119 4-2 C r o s s - f i b r e v e i n i n t h i n s e c t i o n 121 4-3 P i c r o l i t e v e i n i n t h i n s e c t i o n 126 4-4 Tapered c h r y s o t i l e - f i b r e v e i n 130 4-5 L o n g - f i b r e c h r y s o t i l e v e i n s i n w i d e l y spaced f r a c t u r e s 141 4-6 S e r p e n t i n i t e b r e c c i a 142 x v i ACKNOWLEDGEMENT T h i s t h e s i s was s u p e r v i s e d by Drs. K.C. McTaggart, A . J . S i n c l a i r and C. I . Godwin, whose a d v i c e and gui d a n c e a r e g r e a t l y a p p r e c i a t e d . The w r i t e r w i s h e s t o thank Dr. R.L. Arm s t r o n g f o r h i s d i s c u s s i o n and a d v i c e i n i s o t o p i c d a t i n g ; K.C. S c o t t and J . H a r a k e l f o r t h e i r h e l p i n Rb-Sr and K-Ar d a t i n g p r o c e s s e s ; and G. Georgakopoulos f o r h i s a s s i t a n c e i n m i c r o p r o b e a n a l y s i s . The t e c h n i c a l a s s i t a n c e o f B. C r a n s t o n i n p r e p a r a t i o n o f t h i n s e c t i o n s and m i c r o p r o b e s e c t i o n s i s g r e a t l y a p p r e c i a t e d . Co-o p e r a t i o n o f C a s s i a r A s b e s t o s Corp. L t d . i s a l s o g r e a t l y appre-c i a t e d . The work was s u p p o r t e d by the Dept. o f I n d i a n and N o r t h e r n A f f a i r s , White H o r s e , Yukon T e r r i t o r y . The w r i t e r was s u p p o r t -ed f i n a n c i a l l y by the U n i t e d N a t i o n s Development Programme, U n i t e d N a t i o n s , New York. Most o f a l l the w r i t e r l i k e s t o thank a g a i n t o Dr. K.C. McTaggart f o r h i s p a i n s t a k i n g t e a c h i n g and h i s g u i d a n c e i n E n g l i s h and w r i t i n g . 1 CHAPTER I INTRODUCTION 1-1 PRELIMINARY STATEMENT The s u b j e c t o f t h i s t h e s i s i s t h e g e o l o g i c a l i n v e s t i -g a t i o n o f C l i n t o n Creek A s b e s t o s d e p o s i t and i t s s u r r o u n d i n g a r e a i n Yukon T e r r i t o r y , Canada ( F i g u r e 1-1). The d e p o s i t , h e l d by C a s s i a r A s b e s t o s C o o p e r a t i o n L t d . , i s the o n l y known economic a s b e s t o s d e p o s i t i n Yukon T e r r i t o r y . I t was i m p o r t -ant t o s t u d y t h e d e p o s i t and the c o n t r o l s o f a s b e s t o s forma-t i o n b e f o r e 1978 when the mine was c l o s e d and the open p i t became i n a c c e s s i b l e . I t i s hoped t h a t t h i s s t u d y might be u s e f u l i n the e x p l o r a t i o n and u n d e r s t a n d i n g o f o t h e r u l t r a -m a f i c b o d i e s w i t h a s b e s t o s m i n e r a l i z a t i o n . 1-2 SCOPE OF THESIS Purpose o f t h e st u d y i s t w o f o l d . The f i r s t o b j e c t i v e 2 70° V . . . NORTHWEST TERRITORIES I YUKON i TERRITORY 65° C L I N T O N C R E E K ' I* I * » ^ D A W S O N ( rt*o, \ n \ \ V V X W H I T E H O R S E 4 B.\C. 100 50 100 150 200 km mil FIG H : LOCATION OF THE CLINTON CREEK ASBESTOS DEPOSIT 3 i s t o d e v e l o p g e n e t i c c o n c e p t s t h a t c o u l d g u i d e f u t u r e e x p l o r a t i o n f o r c h r y s o t i l e a s b e s t o s , e s p e c i a l l y i n the T i n t i n a r e g i o n o f t h e Yukon. The second o b j e c t i v e i s t o d e s c r i b e the geology o f t h e mine, the g e n e s i s o f the d e p o s i t and t o c o n s i d e r t h e o r i g i n and emplacement o f u l t r a m a f i c r o c k s o f the a r e a . Mapping was d i f f i c u l t because o f l i m i t e d o u t c r o p s w h i c h amount t o l e s s than f i v e p e r c e n t o f t h e a r e a . Because d r i l l c o r e had been lo g g e d by a t l e a s t e i g h t p e r s o n s , r e c o r d s were i n c o n s i s t e n t and the w r i t e r r e l o g g e d a l l the c o r e t h a t c o u l d be documented. F i e l d work was c a r r i e d o u t from June t o August i n 1975 and 1976. D u r i n g t h e s e p e r i o d s the p r o p e r t y , w h i c h c o v e r s about one square m i l e , was mapped a t a s c a l e o f one i n c h t o f o r t y f e e t , and a s e v e n t y - s q u a r e - m i l e a r e a around the d e p o s i t was mapped a t a s c a l e o f one i n c h t o 1,000 f e e t . 1-3 LOCATION AND ACCESS The C l i n t o n Creek a s b e s t o s d e p o s i t ( l a t . 64'23'N, l o n g . 140"23'W. F i g u r e 1-1) i s s i t u a t e d about 77 k i l o m e t r e s n o r t h w e s t o f Dawson C i t y , Yukon T e r r i t o r y on C l i n t o n Creek, e i g h t k i l o m e t r e s upstream from i t s c o n f l u e n c e w i t h F o r t y M i l e r i v e r . S i x t y M i l e r o a d w h i c h connects Dawson C i t y and F a i r -banks p a s s e s 32 k i l o m e t r e s t o the s o u t h e a s t o f t h e mine. 4 A g r a v e l a i r - s t r i p on the p r o p e r t y i s adequate f o r commercial a e r o p l a n e s o f moderate s i z e . The d e p o s i t o c c u r s on a n o r t h -e a s t and t r e n d i n g r i d g e ( e l e v a t i o n 545 metres) some 155 metres above the v a l l e y o f C l i n t o n Creek. 1-4 CLIMATE AND VEGETATION The a r e a l i e s w i t h i n the zone o f d i s c o n t i n u o u s perma-f r o s t and x s s u b j e c t t o s e v e r e c l i m a t i c c o n d i t i o n s d u r i n g w i n t e r months. The t h i c k n e s s and n a t u r e o f p e r m a f r o s t appear t o v a r y depending on the type o f s o i l o r r o c k w a t e r c o n t e n t and the d i r e c t i o n t h a t the ground s u r f a c e f a c e s . P r e c i p i t a -t i o n i s a p p r o x i m a t e l y 33 c e n t i m e t r e s p e r y e a r , most o f wh i c h o c c u r s as r a i n i n June, J u l y and August. Temperatures range between -56* C e l s i u s i n w i n t e r and +32* c e l s i u s i n summer. Freeze-up u s u a l l y o c c u r s around l a t e September; s p r i n g b r e a k -up i s e x p e c t e d i n l a t e A p r i l o r e a r l y May. The average a n n u a l s n o w f a l l i s about one metre. The h i g h e s t r i d g e s w i t h i n t h e mapped a r e a ( e l e v a t i o n 1,000 metres) are below t r e e l i n e . B l a c k s p r u c e , b i r c h and p o p l a r a r e abundant. A l p i n e f i r , w i l l o w and balsam p o p l a r a re l e s s common. I n g e n e r a l , heavy f o r e s t growth i s r e s t r i c t e d t o th e main v a l l e y f l o o r s , b u t s p a r s e growth extends up the h i l l s i d e s . S o u t h - f a c i n g s l o p e s a re more h e a v i l y f o r e s t e d than n o r t h f a c i n g s l o p e s 5 which a r e c o v e r e d by t h i c k moss and s p a r s e t i m b e r . 1-5 PHYSIOGRAPHY C l i n t o n Creek d e p o s i t l i e s i n the K l o n d i k e P l a t e a u which extends northwestward i n t o A l a s k a where i t i s c a l l e d Yukon-Tanana U p l i f t ( W a h r h a f t i g , 1965). The K l o n d i k e P l a t e a u i s bounded on the n o r t h e a s t by the T i n t i n a Trench and the southwest by t h e N i s l i n g R i v e r , and i s a s u b d i v i s i o n o f t h e Yukon C h r y s t a l l i n e P l a t e a u (Douglas, e t a l . , 1970) most o f w h i c h escaped g l a c i a t i o n d u r i n g the P l e i s t o c e n e ( P r e s t , e t a l . , 1968). The K l o n d i k e P l a t e a u i s marked by l o n g , i r r e g u l a r main and spur r i d g e s c h a r a c t e r i s t i c o f a h i g h l y d e v e l o p e d d e n d r i t i c s t r e a m p a t t e r n . C r e s t s o f most r i d g e s a r e between 1,000 and 1,350 metres e l e v a t i o n and p r o b a b l y r e p r e s e n t an o l d u p l i f t e d e r o s i o n s u r f a c e . C l i n t o n Creek has a g e n t l e g r a d i e n t compared t o i t s t r i b u t a r y streams w h i c h occupy narrow v-shaped v a l l e y s w i t h s t e e p g r a d i e n t s . Dome-shaped h i l l s a r e q u i t e p r o m i n e n t and v e g e t a t i o n i s t h i c h w i t h i n the mapped a r e a . Outcrops a r e s c a r c e and most o f t h e s e a r e found a l o n g and near r i d g e c r e s t s . 6 1-6 HISTORY OF THE CLINTON CREEK DEPOSIT The o r i g i n a l d i s c o v e r y was made i n 1957 and i s c r e d i t e d t o A r t Anderson, an I n d i a n t r a p p e r ; he was l i s t e d an " N o . l " on the p a y r o l l o f C l i n t o n Creek mine. The p r o p e r t y c o n s i s t s o f 9 4 c l a i m s and two p l a c e r l e a s e s . One a d i t was d r i v e n i n 1957-58. T h i s work was f o l l o w e d by magnetometer s u r v e y s and d r i l l i n g ; t h e f i r s t phase of e x p l o r a t i o n was completed i n lb)63. G e o l o g i c a l s t u d y was u n d e r t a k e n m a i n l y by N.W. Plumb and D.R. B u d i n s k y . From 1963 t o 1966, underground and s u r f a c e diamond d r i l l i n g as w e l l as g e o l o g i c a l and g e o p h y s i c a l mapping were c a r r i e d o u t . C o n s t r u c t i o n o f an a c c e s s r o a d was und e r t a k e n i n 1965 and 1966. The mine began t o produce i n 1967. B o t h the mine and the p r i m a r y c r u s h i n g p l a n t were s i t u a t e d a t a l o w e r l e v e l t han the m i l l and p l a n t s i t e . A b e l t conveyor c a r r i e s o r e from t h e p r i m a r y c r u s h e r t o the tramway f e e d e r . The o r e i s e l e v a t e d 152 metres by a 1,600 metre l o n g t r a m l i n e t o the p l a n t s i t e and was d e l i v e r e d a t 30 0 tons p e r hour. The mine had produced o r e f o r e l e v e n y e a r s w i t h an average w a s t e - t o - o r e r a t i o o f about 5.5 t o 1. O p e r a t i o n s ceased i n 1978 when the o r e was e x h a u s t e d . 7 CHAPTER I I GEOLOGY OF THE CLINTON CREEK AREA 2-1 INTRODUCTION The r e g i o n a l geology o f map s h e e t 12 84A w h i c h i n c l u d e s the C l i n t o n Creek a r e a has been d e s c r i b e d by Green and Roddick (1961) and Green (1972). F i g u r e 2-1 was p r e p a r e d from t h e i r map. The o l d e s t r o c k s i n the a r e a (Table 2-1) b e l o n g t o the Yukon Metamorphic Complex (Tempelman-Kluit, 19 7 4 ) . U l t r a -m a f i c r o c k s were p r o b a b l y emplaced i n Permian t i m e . G r a n d i o r -i t e p l u t o n s were i n t r u d e d i n l a t e s t C r e t a c e o u s t o e a r l i e s t T e r t i a r y . The youngest u n i t , n ot i n c l u d e d i n F i g u r e 2-1 i s b a s a l t , p r o b a b l y o f P l e i s t o c e n e o r Holocene age. D i s t r i b u t i o n o f a l l u n i t s and l o c a t i o n s o f specimens a r e shown i n ( F i g u r e 2-2) . 2-2 METAMORPHIC ROCKS OF THE YUKON CRYSTALLINE PLATEAU 2-2-A REGIONAL SETTING FIGURE 2-1: REGIONAL GEOLOGY. 1= G r i t and s l a t e ; 2= Quartz-mica s c h i s t and q u a r t z i t e ; 3= Greenstone and quartz-muscovite-chlorite s c h i s t ; 4= Serpentinized ultramafic rocks; 5= B i o t i t e granodiorite and quartz monzonite; 6= Sandstone, shale, conglomerate and l i g n i t e ; 7= A l l u v i a l deposits; F= F o s s i l l o c a l i t y . (Modified a f t e r Green, 1972.) 9 TABLE 2-1 UNITS IN THE CLINTON CREEK AREA, Y.T. ERA PEROID UNIT LITHOLOGY ISOTOPIC AGES"(Ma) CENOZOIC Late T e r t i a r y S e l k i r k B a s alt Group (?) E a r l y T e r t i a r y N i s l i n g A l a s k i t e Group (?) B i o t i t e G r a n o d i o r i t e 64.9±2.3 PALEOZOIC Permian Main phase of metamorphism of the C l i n t o n Creek area. Derived from K-Ar dates of muscovite and hornblende, and Rb-Sr date of whole rock. 245±8 255.8±22.3 278±10 Pensylva-nian and/or Permian U l t r a m a f i c Rocks Devonian(?) Yu- Carbonaceous a r g i l l i t e , or e a r l i e r kon limy a r g i l l i t e , l imestone, Me- sandstone O r d o v i c i a n t a - Greenstone, quartz-muscovite and mor- c h l o r i t e s c h i s t , q u a r t z -e a r l i e r ( ? ) p h i c muscovite s c h i s t , q u a r t z -Com- m u s c o v i t e - b i o t i t e s c h i s t , p l e x micaceous q u a r t z i t e and c r y s t a l l i n e limestone 470 1: I s o t o p i c ages are discussed i n Chapter I I , s e c t i o n seven. 10 Metasedimentary and m e t a v o l c a n i c r o c k s o f t h e Yukon C r y s t a l l i n e P l a t e a u a re r e f f e r r e d t o as Yukon Metamorphic Complex (Templeman-Kluit, 1974). These r o c k s u n d e r l i e most o f the a r e a between T i n t i n a and Shakwak-Denali f a u l t s i n Yukon T e r r i t o r y ( F i g u r e 2-3) and are e q u i v a l e n t w i t h the B i r c h Creek S c h i s t o f A l a s k a , o r i g i n a l l y mapped by M e r t i e i n 1937. The T e r r a n e has been c a l l e d by d i f f e r e n t names i n d i f f e r e n t a r e a s . The f i r s t p e r s o n who mapped t h e a r e a was D.D. C a i r n e s (1914) who a s s i g n e d t h e Yukon Group t o P r e -Cambrian. Names such as " P e l l y G n e i s s " , " K l o n d i k e S c h i s t " , " Nasina Q u a r t z i t e " were a l s o g i v e n t o v a r i o u s p a r t s o f t h i s t e r r a n e ( M c C o n n e l l , 1905). The K l o n d i k e s c h i s t , N a s i n a q u a r t z i t e and P e l l y g n e i s s c o v e r the n o r t h e r n and w e s t - c e n t r a l p a r t s o f the Te r r a n e near the Yukon-A l a s k a b o r d e r , and c o n t a i n l a r g e l e n s e s o f c r y s t a l l i n e l i m e s t o n e , s e r p e n t i n i t e and amphi-b o l i t e (Green and Roddick, 1972). M e t a s e d i m e n t s , j u s t west o f the C l i n t o n Creek a r e a a c r o s s the b o r d e r i n A l a s k a were c o n s i d e r e d t o be o f c o n t i n e n t a l assemblages r a t h e r t h a n an i s l a n d a r c o r o c e a n i c c r u s t a l assemblages ( F o s t e r and K e i t h , 1974). Rocks o f the C l i n t o n Creek a r e a resemble t h o s e o f t h e E a g l e a r e a i n A l a s k a and form p a r t o f the same b e l t . Ages o f r o c k s i n the Yukon C r y s t a l l i n e P l a t e a u range from Pre-Cambrian t o C e n o z o i c . The P e l l y g n e i s s , n e a r the w e s t - c e n t r a l p a r t o f the P l a t e a u s o u t h o f t h e C l i n t o n Creek y i e l d s a Rb-Sr age o f about 750 Ma (R.L. A r m s t r o n g , p e r s o n a l B.G FIGURE 2-3: DISTRIBUTION OF THE YUKON METAMORPHIC COMPLEX AND EQUIVALENTS IN THE YUKON TERRITORY AND ALASKA. ( A f t e r Tempelman-K l u i t , 1975.) 12 communication, 1978). Rocks w h i c h a r e l i t h o l o g i c a l l y e q u i v -a l e n t t o the N a s i n a q u a r t z i t e and K l o n d i k e s c h i s t , i n the C l i n t o n Creek a r e a have y i e l d e d a Rb-Sr model age o f 470 Ma"*". However, i n an a r e a j u s t west of the Yukon R i v e r n e a r t h e A l a s k a b o r d e r (64*39.5 N, 140*57.5 W) echinoderm c o l u m n a l s i n l i m e s t o n e a s s o c i a t e d w i t h metasedimentary r o c k s i n d i c a t e a P a l e o z o i c age ( M e r t i e , 1937; Douglas, e t a l . , 1970; Green, 19 7 2 ) , p r o b a b l y Devonian. The youngest igneous r o c k s r e c o r d e d i n t h i s T e r r a n e a r e Tertiary"*". 2-2-B C l i n t o n Creek A r e a More than 8 0 p e r c e n t o f the a r e a i s u n d e r l a i n by meta-morphic r o c k s w i t h l i t h o l o g i c c h a r a c t e r i s t i c s s i m i l a r t o those o f the K l o n d i k e s c h i s t and N a s i n a q u a r t z i t e ( F i g u r e 2-3). The w r i t e r d i s t i n g u i s h e d the f o l l o w i n g l i t h o l o g i c u n i t s (Htoon, 19 77) w h i c h a r e l i s t e d i n p r o b a b l e c h r o n o l o g i c o r d e r from d t o a: a. Carbonaceous and l i m y a r g i l l i t e ( y o u n g e s t ) , 2 b. Greenstone and q u a r t z - m u s c o v i t e - c h l o r i t e s c h i s t , c. Q u a r t z - m u s c o v i t e s c h i s t and q u a r t z i t e , and d. Q u a r t z - m u s c o v i t e - b i o t i t e s c h i s t ( o l d e s t ) . 1 : See Chapter two s e c t i o n seven. 2 : Greenstone i s d e s c r i b e d i n Appendix A 13 a. Carbonaceous and l i m y a r g i l l i t e s T h i s u n i t u n d e r l i e s the main C l i n t o n Creek v a l l e y . I t c o n s i s t m o s t l y o f i n t e r b e d d e d carbonaceous a r g i l l i t e , l i m y a r g i l l i t e , b l a c k t o dark gray l i m e s t o n e and l i m y sand-s t o n e . Carbonaceous a r g i l l i t e i s j e t b l a c k , v e r y f r a g i l e , c l e a v e s e a s i l y a l o n g p a r t i n g p l a n e s , and c o n s t i t u t e s most o f t h i s u n i t ( P l a t e 2-1). Bedding i s d i f f i c u l t t o r e c o g n i z e . Limy a r g i l l i t e i s r e l a t i v e l y h a r d e r t h a n carbonaceous a g r i l l i t e , i s d u l l t o b r o w n i s h and n o r m a l l y i s found as a t r a n s i t i o n a l r o c k between carbonaceous a r g i l l i t e and l i m e s t o n e o r sand-s t o n e . L i m e s t o n e , b l a c k and h i g h l y f r a c t u r e d ( P l a t e 2-2), i s w e l l l a m i n a t e d b u t seldom t h i c k l y bedded. P a r t i n g s and f r a c t u r e s are c o a t e d f o r the most p a r t w i t h carbonaceous m a t t e r o r m u s c o v i t e . Sandstone, o r d i n a r i l y b u f f t o b r o w n i s h and v e r y l i m y , i s uncommon but l o c a l l y forms c o n s p i c u o u s beds i n a r g i l l i t e . Carbonaceous a r g i l l i t e i n t h i n s e c t i o n i s seen t o con-s i s t o f q u a r t z , carbonaceous m a t t e r , s e r c i t e , c l a y , m a g n e t i t e , c h l o r i t e , p y r i t e and t r a c e s o f e p i d o t e , a l b i t e and b i o t i t e . Q u artz and carbbnaceous m a t t e r u s u a l l y t o t a l more t h a n 50 p e r c e n t and 20 p e r c e n t r e s p e c t i v e l y . C l a y m i n e r a l s c o n s t i -t u t e as much as 15 p e r c e n t and s e r i c i t e up t o 10 p e r c e n t o f the r o c k . There are two g e n e r a t i o n s o f q u a r t z , o r i g i n a l and s t r i n -g e r s o f metamorphic q u a r t z w h i c h c u t a c r o s s t h e b e d d i n g . Two c l e a v a g e s c r o s s a t a n g l e s o f about 120* and s e r i c i t e e l o n g a -14 I PLATE 2-1: Carbonaceous a r g i l l i t e ( b l a c k l a y e r s on top) i n c o n t a c t w i t h q u a r t z - m u s c o v i t e s c h i s t ( l i g h t c o l o u r e d l a y e r s a t bottom). 1 5 0 im • i 1 PLATE 2-2: Dark,bedded l i m e s t o n e w i t h i n the carbonaceous a r g i l l i t e u n i t . T h i n l a y e r s o f carbonaceous a r g i l l i t e a l s o o c c u r between each l i m e s t o n e bed. 16 t i o n p a r a l l e l s t h e s e c l e a v a g e s . Most c h l o r i t e has formed by the r e p l a c e m e n t o f b i o t i t e . Much o f t h e a r g i l l i t e i s weakly m y l o n i t i z e d . In t h i n s e c t i o n l i m y a r g i l l i t e c o n s i s t s o f 35 p e r c e n t q u a r t z , 35 p e r c e n t c a l c i t e , 20 p e r c e n t c l a y m i n e r a l s , 5 t o 10 p e r c e n t carbonaceous m a t t e r w i t h minor s e r i c i t e , p y r i t e and c h l o r i t e . T e x t u r e s a r e much l i k e t h o s e o f t h e c a r b o n a -ceous a r g i l l i t e . Dark gray l i m e s t o n e , weakly f o l i a t e d and metamorphosed, i s o f two t y p e s . Sandy l i m e s t o n e has up t o 35 p e r c e n t q u a r t z and carbonaceous l i m e s t o n e has as much as 15 p e r c e n t carbonaceous m a t t e r . S e r i c i t e , m a g n e t i t e and t r a c e s o f c l i n -o z o i s i t e a re a l s o p r e s e n t . Limestone w i t h abundant c a r b o n a -ceous m a t t e r and s e r i c i t e i s f i n e l y l a m i n a t e d whereas q u a r t z -r i c h l i m e s t o n e s a r e massive t h i c k bedded. Q u a r t z g r a i n s are e l o n g a t e d i n the f o l i a t i o n and show h i g h l y u n d u l o s e e x t i n c t i o n . Limy s a n d s t o n e , n o t abundant, grades i n t o sandy l i m e s t o n e . b. Greenstone and q u a r t z - m u s c o v i t e - c h l o r i t e s c h i s t T h i s u n i t i s composed of g r e e n s t o n e , q u a r t z - m u s c o v i t e -c h l o r i t e s c h i s t and minor amount o f q u a r t z - f e l d s p a r - m u s c o v i t e s c h i s t . The r o c k s o f t h i s u n i t are f i n e t o medium-grained and c o l o u r ranges from dark green t o s i l v e r y - g r e e n . Degree o f f o l i a t i o n v a r i e s from poor t o w e l l . S h e a r i n g i s n o t p e r v a s i v e . 17 Greenstone i s g e n e r a l l y dark g r e e n , massive o r o b s c u r e l y f o l i a t e d b u t l o c a l l y w e l l f o l i a t e d . I n t h i n - s e c t i o n i t c o n s i s t s o f a f o l i a t e d mass o f q u a r t z , c h l o r i t e , e p i d o t e , s e r i c i t e , c a l c i t e , amphibole, p l a g i o c l a s e and opaque m i n e r a l s . Quartz nowhere exceeds 25 p e r c e n t , c h l o r i t e , e p i d o t e , c a r b o n -a t e s and s e r i c i t e i n c r e a s e w i t h h i g h e r degree o f s h e a r i n g . I n l e s s s h e a r e d r o c k , p l a g i o c l a s e ( a l b i t e t o o l i g o c l a s e ) o c c u r s w i t h a l e s s e r amount o f e p i d o t e group m i n e r a l s , s e r i c i t e and c a r b o n a t e s . S h e a r i n g i n gre e n s t o n e has l a r g e l y d e s t r o y e d the t e x t u r e o f the o r i g i n a l r o c k . I n r o c k s w h i c h were n o t i n t e n s e l y s h e a r e d l a t h - l i k e pseudomorphs o f f e l d s p a r s a r e s t i l l r e c o g n i z a b l e , even though they have been a l t e r e d t o a l b i t e and s a u s s u r i t e . G e n e r a l l y the o r i g i n a l c r y s t a l forms o f ferromagnesium m i n e r a l s a r e not r e c o g n i z a b l e , b u t i n a v e r y few specimens amphibole pseudomorphs a f t e r pyroxene are p r e s e r v e d . A c t i n o l i t e , t he common amphibole, i s common i n massive a l t e r e d g r e e n s t o n e b u t i s l e s s p r o m i n e n t i n sheared g r e e n s t o n e where c h l o r i t e t a k e s i t s p l a c e . Carbonate tends t o be a r r a n g e d i n s t r e a k s p a r a l l e l t o t h e f o l i a t i o n . R e l i c t t e x t u r e s and m i n e r a l s s u g g e s t t h a t t h e gr e e n s t o n e was o r i g i n a l l y a b a s i c igneous r o c k . Q u a r t z - m u s c o v i t e - c h l o r i t e s c h i s t i s p a l e t o medium g r e e n , m o d e r a t e l y t o w e l l f o l i a t e d and l a c k s s h i n y micaceous p a r t i n g s . I t c o n s i s t s o f 40 t o 60 p e r c e n t q u a r t z , 15 p e r c e n t m u s c o v i t e , 10 p e r c e n t c h l o r i t e , 8 p e r c e n t e p i d o t e and t h e r e s t i s c a l c i t e . Q uartz and m u s c o v i t e a re more abundant t h a n i n g r e e n s t o n e . 18 S c h i s t o s i t y i s m a i n l y p a r a l l e l t o l a y e r s o f m u s c o v i t e and q u a r t z . A l t h o u g h i t resembles g r e e n s t o n e , e x c e p t f o r i t s pronounced s c h i s t o s i t y , the h i g h q u a r t z c o n t e n t s u g g e s t s a s e d i m e n t a r y o r i g i n . I n the f i e l d i t i s d i f f i c u l t t o d i s t i n g u i s h between greenstone and q u a r t z - m u s c o v i t e - c h l o r i t e s c h i s t , e s p e c i a l l y i f former i s h i g h l y s h e a r e d . But a f t e r t h i n s e c t i o n s t u d y , i t was found t h a t the s o u t h e r n p a r t o f the s t u d y a r e a i s u n d e r l a i n l a r g e l y by g r e e n s t o n e and the n o r t h e r n p a r t p r e -d o m i n e n t l y by q u a r t z - m u s c o v i t e - c h l o r i t e s c h i s t . I t i s impos-s i b l e , however, t o draw a g e o l o g i c c o n t a c t between th e two r o c k s on t h e b a s i s o f a v a i l a b l e i n f o r m a t i o n . I n some p l a c e s , greenstone and a r g i l l i t e a re i n t e r b e d d e d . c. Q u a r t z - m u s c o v i t e s c h i s t and q u a r t z x t e T h i s u n i t i s composed m a i n l y o f q u a r t z - m u s c o v i t e s c h i s t and micaceous q u a r t z i t e . These a l t e r n a t e one w i t h t h e o t h e r and c o n t a c t s between them are g e n e r a l l y g r a d a t i o n a l . A few l e n s e s o f w h i t e t o w h x t i s h - g r a y c r y s t a l l i n e l i m e s t o n e a l s o o c c u r ( P l a t e 2-3). A t the base o f t h e u n i t q u a r t z i t e i s dominant. I t i s gray t o dark g r a y , medium t o c o a r s e g r a i n e d w i t h minor m u s c o v i t e and i s w e l l f o l i a t e d . V a r i a t i o n o f s i z e o f q u a r t z g r a i n s between f o l i a t i o n p l a n e s i s n o t uncommon. A t h i g h e r l e v e l s q u a r t z - m u s c o v i t e s c h i s t i s p r o m i n e n t . L o c a l -l y , q u a r t z - m u s c o v i t e s c h i s t becomes v e r y c o a r s e - g r a i n e d and 19 PLATE 2-3: Lens o f marble (gray zone i n t h e middle) i n q u a r t z - m u s c o v i t e s c h i s t and q u a r t z i t e u n i t . 20 mica f l a k e s grow as l a r g e as f o u r m i l i m e t r e s i n d i a m e t e r . In t h i n s e c t i o n q u a r t z i t e c o n s i s t s o f more t h a n 80 p e r c e n t q u a r t z , about t e n p e r c e n t m u s c o v i t e , about f i v e p e r c e n t carbonaceous m a t t e r and about one t o f i v e p e r c e n t c a l c i t e . Most o f the q u a r t z g r a i n s are e l o n g a t e d and i n t e r l a y e r e d w i t h carbonaceous m a t t e r . Bands o f m u s c o v i t e and carbonaceous m a t t e r p a r a l l e l t h e f o l i a t i o n o f the r o c k . In t h i n s e c t i o n , q u a r t z - m u s c o v i t e s c h i s t c o n s i s t s o f 50 t o 6 0 p e r c e n t q u a r t z , 35 p e r c e n t m u s c o v i t e , 1 t o 4 p e r c e n t c a l c i t e , 1 p e r c e n t m a g n e t i t e and r a r e l y t r a c e s o f a l b i t e , i r o n - o x i d e , c h l o r i t e and carbonaceous m a t t e r ( P l a t e 2-4). Quar t z i n p o s t metamorphic f r a c t u r e s c u t s t h e f o l i a t i o n . M u s c o v i t e l a y e r s a l t e r n a t e w i t h q u a r t z l a y e r s ; m u s c o v i t e i s a l s o s c a t t e r e d w i t h i n q u a r t z l a y e r s w i t h i t s e l o n g a t i o n p a r a l l e l t o s c h i s t o s i t y . L o c a l l y , s c h i s t s a r e u n u s u a l l y r i c h i n c a l c i t e , a l b i t e , g r a p h i t e and/or c h l o r i t e . Carbonate i n p l a c e s o c c u r s as l a r g e c r y s t a l s and p o i k i l o b l a s t i c a l l y e n c l o s e s q u a r t z g r a i n s , b u t g e n e r a l l y i t f i l l s f r a c t u r e s . G e n e r a l l y s c h i s t o s i t y p l a n e s a r e s i n u o u s . d. Q u a r t z - m u s c o v i t e - b i o t i t e s c h i s t Q u a r t z - m u s c o v i t e - b i o t i t e s c h i s t u n i t r a r e l y c r o p s o ut and i t s d i s t r i b u t i o n was d e t e r m i n e d m o s t l y by t h e d i s t r i -b u t i o n o f f l o a t . Specimens are d e e p l y weathered and r u s t y . I t i s medium t o f i n e - g r a i n e d and has w e l l - d e v e l o p e d s c h i s t o s i -21 0 J A A M I 1 PLATE 2 - 4 : Two s e t s o f f o l i a t i o n p l a n e s a r e common i n q u a r t z - m u s c o v i t e s c h i s t . F o l i a t i o n F]_ i s p a r a l l e l t o the e l o n g a t i o n o f m u s c o v i t e and f o l i a t i o n F 2 c u t s F]_ a t 60". Note t h e development o f p r e f e r r e d o r i e n t a t i o n o f musco-v i t e p a r a l l e l s F 2 shear zones w h i c h i s i n i -t i a l l y o r i e n t e d p a r a l l e l t o F]_. ( C r o s s e d n i c o l s . ) 22 t y . In t h i n s e c t i o n i t c o n s i s t s o f more t h a n 55 p e r c e n t q u a r t z , about 30 p e r c e n t m u s c o v i t e , about 5 p e r c e n t b i o t i t e and about one t o t e n p e r c e n t c a l c a r e o u s and l i m o n i t i c a l t e r -a t i o n m i n e r a l s . M i n o r amounts o f g a r n e t a r e a l s o c o n t a i n e d i n a few r o c k s o f t h i s u n i t . 2-3 ULTRAMAFIC ROCKS 2-3-A R e g i o n a l S e t t i n g U l t r a m a f i c r o c k s form a d i s t i n c t i v e u n i t i n the Yukon Metamorphic Complex. The d i s c o n t i n u o u s b e l t o f s h e a r e d u l t r a -m a f i c r o c k s and t h e i r s e r p e n t i n i z e d e q u i v a l e n t s ( F i g u r e 2-4) are i n t e r l a y e r e d w i t h metamorphic r o c k s o f t h e Yukon C r y s t a l -l i n e P l a t e a u . U l t r a m a f i c b o d i e s are found as s i l l , d y k e and s t o c k - l i k e b o d i e s , t h a t range i n s i z e from a few hundred f e e t t o s e v e r a l m i l e s a c r o s s . In g e n e r a l , t h e l a r g e r s t o c k -l i k e masses o c c u r near th e T i n t i n a T r e n c h , whereas the s m a l l e r ones w h i c h are h i g h l y s e r p e n t i n i z e d , are found f u r t h e r from the t r e n c h . The number o f u l t r a m a f i c e x posures i s much g r e a t -e r t o the n o r t h w e s t i n the A l a s k a n p a r t o f t h e b e l t . The u l t r a m a f i c b e l t seems t o be c o n t r o l l e d , a t l e a s t i n a l i g n m e n t , by the T i n t i n a Trench (Roddick, 196 7) w h i c h i s a major n o r t h -west t r e n d i n g s t r u c t u r e , s e p a r a t i n g unmetamorphosed P r e -23 FIGURE 2-4: GENERALIDED DISTRIBUTION OF SERPENTINIZED ULTRAMAFIC ROCKS IN YUKON TERRITORY AND ALASKA. E = e c l o g i t e l o c a l i t y ; B = glaucophane o c c u r r a n c e . ( M o d i f i e d a f t e r F o s t e r , 19 74; Godwin, 1975; Tempelman-K l u i t , 1976.) 24 Cambrian, P a l e o z o i c and Mesozoic s e d i m e n t a r y r o c k s on t h e n o r t h e a s t from metamorphic r o c k s on the s o u t h w e s t . On the b a s i s o f f i e l d o b s e r v a t i o n and aeromagnetic d a t a (Veach, ly72) most of the u l t r a m a f i c b o d i e s are b e l i e v e d t o be s e p a r a t e masses o r l e n s e s t h a t are not connected b e n eath the s u r f a c e . The time o f emplacement o f the u l t r a m a f i c r o c k s i s u n c e r t a i n b u t has been a s s i g n e d a Permian age by Tempelman-Kluit (1975). 2-3-B C l i n t o n Creek A r e a The d i s t r i b u t i o n o f u l t r a m a f i c b o d i e s w i t h i n t h e mapped a r e a i s shown i n F i g u r e 2-2. There i s a g e n e r a l l a c k o f heavy v e g e t a t i o n wherever these r o c k s are exposed and t h e c h a r a c t e r i s t i c d a r k green t o orange w e a t h e r i n g b l o c k y t a l u s they produce can be r e c o g n i z e d e a s i l y from a d i s t a n c e o r from the a i r . Rock ty p e s i n c l u d e s e r p e n t i n i t e , h a r z b u r g i t e , i h e r z o l i t e , d u n i t e , and p y r o x e n i t e . Most o f t h e b o d i e s a r e c o m p l e t e l y s e r p e n t i n i z e d , so i t i s v e r y h a r d t o f i n d o r i g i -n a l o l i v i n e o r p yroxene. I d e n t i f i c a t i o n o f u l t r a m a f i c r o c k s as h a r z b u r g i t e , i h e r z o l i t e , d u n i t e and p y r o x e n i t e was based on r e l i c t t e x t u r e s and s u r v i v i n g o r i g i n a l m i n e r a l s . No o r i g i n a l l a y e r i n g was found and m utual r e l a t i o n s h i p s o f t h e s e r o c k s are p r a c t i c a l l y unknown. S e r p e n t i n i t e ranges i n c o l o u r from d a r k g r e e n i s h b l a c k t o o l i v e green and a l l s t a g e s from massive t o h i g h l y s h e a r e d c o n d i t i o n s were o b s e r v e d . Sugary t e x t u r e i s n o t uncommon. 25 H i g h l y p o l i s h e d , f i s h s c a l e s e r p e n t i n i t e i n t h i n s e c t i o n a r e a n t i g o r i t e , c h r y s o t i l e , b r u c i t e , c h l o r i t e , t a l c , i d o c r a s e , m a g n e t i t e , chrome s p i n e l and c h r o m i t e . S e v e r a l d i f f e r e n t k i n d s o f s e r p e n t i n i t e a re d i s t i n g u i s h e d : f i b r e b e a r i n g s e r p e n t i n i t e , f i n e g r a i n e d dark green s e r p e n t i n i t e , mesh s e r p e n t i n i t e and sugary t e x t u r e d s e r p e n t i n i t e . 2-4 ACID INTRUSIVE ROCKS There are a t l e a s t f o u r d i s t i n c t p l u t o n i c e v e n t s t h a t a f f e c t e d t h e Yukon C r y s t a l l i n e P l a t e a u . The o l d e s t p e r i o d o f i n t r u s i o n may be r e p r e s e n t e d by the K l o t a s s i n q u a r t z d i o r t i e , d a t e d by Tempelman-Kluit (1975) as l a t e T r i a s s i c , b u t c o n s i d e r e d by Godwin (1975) t o be m i d - C r e t a c e o u s ; P i n k q u a r t z monzonite was emplaced about m i d - J u r a s s i c ; m i d - C r e t -aceous i n t r u s i o n s a r e t y p i f i e d by the C o f f e e Creek q u a r t z monzonite; and the youngest p e r i o d i n v o l v e d the N i s l i n g Range a l a s k i t e (Tempelman-Kluit, 1975). The g r a n o d i o r i t e o f the C l i n t o n Creek a r e a i s not ex-posed w i t h i n the a r e a o f F i g u r e 2-2. Two l a r g e s t o c k s , one 10 k i l o m e t r e s n o r t h w e s t and the o t h e r 14 k i l o m e t r e s e a s t , and a s m a l l s t o c k 26 k i l o m e t r e s s o u t h e a s t o f t h e C l i n t o n Creek a r e a a r e shown on F i g u r e 2-1. S e v e r a l s m a l l b o d i e s a r e even c l o s e r t o the s t u d y a r e a . L i t h o l o g i c a l l y t h e r o c k s are s i m i -26 l a r t o th o s e o f t h e K l o t a s s i n g r a n o d i o r i t e and q u a r t z mon-z o n i t e s u i t e . The r o c k , medium g r a i n e d b i o t i t e g r a n o d i o r i t e , c o n s i s t s o f q u a r t z , p l a g i o c l a s e ( o l i g o c l a s e t o a n d e s i n e commonly w i t h normal z o n i n g ) , p o t a s h f e l d s p a r , b i o t i t e , h o r n -b l e n d e and m a g n e t i t e . P o t a s h f e l d s p a r (22 p e r c e n t ) i n some r o c k s i s f r e e from a l t e r a t i o n but more commonly i s f a i n t l y c l o u d y i n t h i n s e c t i o n due t o development o f f i n e - g r a i n e d c l a y m i n e r a l s . Q u a r t z (14 p e r c e n t ) and o r t h o c l a s e a r e an-h e d r a l and i n t e r s t i t i a l t o the p l a g i o c l a s e (40 p e r c e n t ) . P l a g i o c l a s e i s p a r t l y a l t e r e d t o s a u s s u r i t e and s e r i t e . Hornblende (5 p e r c e n t ) r a r e l y o c c u r s i n f a i r l y w e l l - f o r m e d p r i s m s , b u t more commonly i t i s i n p l a t e s w i t h ragged edges and has a l t e r e d i n p a r t t o c h l o r i t e . B i o t i t e (17 p e r c e n t ) formed as f l a k e s , w i t h ragged edges and as i r r e g u l a r and d i s -c o n t i n u o u s f r i n g e s on hornblende and n o r m a l l y a l t e r s t o c h l o r i t e . 2-5 BASALT Two b a s a l t i c sequences are found i n t h e Yukon C r y s -t a l l i n e P l a t e a u . The o l d e r i s the Carmacks Group o f B o s t o c k (19 3 6 ) , w i d e s p r e a d i n the c e n t r a l p a r t o f t h e Yukon C r y s -t a l l i n e P l a t e a u . The younger i s t h e S e l k i r k V o l c a n i c s . These, exposed a t s t r e a m banks a l o n g t h e Yukon R i v e r , a re Holocene ore P l e i s t o c e n e i n age ( B o s t o c k , 1966). The 27 S e l k i r k l a v a s a r e t h e p r o d u c t o f l o c a l f i s s u r e e r u p t i o n s and are r o u g h l y e q u i v a l e n t t o P l i o c e n e P l a t e a u Lavas o f C e n t r a l B r i t i s h Columbia (Campbell and T i p p e r , 1971). S e l k i r k V o l c a n i c s a re exposed i n t h e s o u t h - c e n t r a l p a r t o f the s t u d y a r e a ( F i g u r e 2-2). These are f r e s h , unde-formed columnar j o i n t e d f l o w s ( P l a t e 2-5), l y i n g unconform-a b l y on the metamorphic r o c k s . The b a s a l t i s dense, dark gray w i t h p h e n o c r y s t s o f o l i v i n e . I n t h i n s e c t i o n t h e r o c k i s seen t o c o n s i s t o f l a b r a d o r i t e , p y r o x e n e , o l i v i n e , minor m a g n e t i t e and g l a s s . P a l e brown a u g i t e o c c u r s b o t h as a groundmass m i n e r a l and as p h e n o c r y s t s . I t u s u a l l y o c c u p i e s a p o s i t i o n i n t e r s t i t i a l t o t h e p l a g i o c l a s e as s m a l l g r a i n s . E u d h d r a l o l i v i n e p h e n o c r y s t s have more o r l e s s c o r r o d e d b o r d e r s . Much o f the g l a s s i s a l t e r e d t o y e l l o w i s h - b r o w n p a l a g o n i t e . 2-6 STRUCTURE 2-6-A I n t r o d u c t i o n E v i d e n c e o f a t l e a s t t h r e e phases o f d e f o r m a t i o n has been o b s e r v e d . The e a r l i e s t h i g h l y s h e a r e d i s o c l i n a l f o l d s have been deformed d u r i n g a second f o l d i n g , i n t o s m a l l , t i g h t , recumbent f o l d s w h i c h i n t u r n have been r e f o l d e d by 28 29 an open t h i r d phase f o l d o f r e g i o n a l e x t e n t . A l l o f t h e s e s t r u c t u r e s have undergone l a t e r f a u l t i n g . Measurements o f l i n e a r and p l a n a r s t r u c t u r e s and d e t e r m i n a t i o n o f r e l a t i v e age r e l a t i o n s h i p s was done i n the f i e l d . A n a l y s i s o f such d a t a was a i d e d by e x a m i n a t i o n o f m i c r o s c o p i c s t r u c t u r e s and s t e r e o g r a p h i c p r o j e c t i o n s . The most p r o m i n e n t f e a t u r e o f most u n i t s o f t h e a r e a i s f o l i a t i o n p a r a l l e l t o c o m p o s i t i o n -a l l a y e r i n g . T h i s p e n e t r a t i v e s t r u c t u r e was d e v e l o p e d d u r i n g the f i r s t phase o f f o l d i n g as a r e s u l t o f t i g h t c o m p r e s s i o n and s h e a r i n g w h i c h f o r c e d o r i g i n a l b e d d i n g and a x i a l p l a n e f o l i a t i o n i n t o near p a r a l l e l i s m . P l a t y and p r i s m a t i c m i n e r -a l s d e v e l o p e d a l o n g f o l i a t i o n p l a n e s i n r e s p o n s e t o meta-morphism w h i c h accompanied f o l d i n g . T h i s i n t e n s e d e f o r m a t i o n and metamorphism has o b s c u r e d the o r i g i n a l s t r a t i g r a p h i c s u c c e s s i o n . Very few d e t e r m i n a t i o n s o f s t r a t i g r a p h i c t o p s and bottoms have been made because s e d i m e n t a r y s t r u c t u r e s have been d e s t r o y e d by s e v e r e d e f o r m a t i o n . F a c i e s changes and u n c o n f o r m i t i e s , i f p r e s e n t , a r e i m p o s s i b l e t o o b s e r v e f o r the same r e a s o n . C e r t a i n s t r u c t u r a l elements o b s e r v e d i n t h e C l i n t o n Creek a r e a a r e l i s t e d i n Table 2-2. 2-6-B F o l d s Two groups o f mesoscopic f o l d s and r e l a t e d s t r u c t u r a l f e a t u r e s have been o b s e r v e d i n the f i e l d . M a j or f o l d ( F i g u r e 30 TABLE 2-2 STRUCTURAL ELEMENTS OF THE CLINTON CREEK AREA Symbol S t r u c t u r a l Element FQ Bedding or compositional l a y e r i n g F^ A x i a l planes and a x i a l plane cleavage of e a r l i e s t i s o c l i n a l f o l d s L^ I n t e r s e c t i o n of FQ and F^ and f o l d axes of e a r l i e s t i s o c l i n a l f o l d s A x i a l planes and a x i a l plane cleavage of recumbent second f o l d s I n t e r s e c t i o n s of F^ wi t h F and F^, f o l d axes and cr e n u l a t i o n s a s s o c i a t e d w i t h recumbent second f o l d s F^ A x i a l plane of t h i r d phase f o l d L^ I n t e r s e c t i o n s of F ^ wi t h F^, F^ and and a x i s of the t h i r d f o l d 31 2-2) r e p r e s e n t a t h i r d group. The f i r s t f o l d s (L^) have been r e f o l d e d a l o n g L 2 axes and have, i n t u r n , been f o l d e d by l a r g e s c a l e f o l d a l o n g i t s a x i s . Only a few f i r s t phase f o l d s (L^) a r e exposed i n t h e C l i n t o n Creek a r e a . T h i s group has p a r a l l e l t o s u b - p a r a l l e l l i m b s and a x i a l p l a n e s . An example o f t h i s f i r s t d e f o r m a t i o n i s shown i n P l a t e 2-6. G l e i t b r e t t s t r u c t u r e s ( P l a t e 2-7) are q u i t e common, e s p e c i a l l y i n s c h i s t o s e r o c k s . M a s s i v e u n i t s l i k e q u a r t z i t e and massive g r e e n s t o n e were a l s o t i g h t l y f o l d e d b u t , i n t h e s e , f o l i a t i o n (F^) i s n o t w e l l d e v e l o p e d . C o m p o s i t i o n a l l a y e r i n g i s not everywhere s h e a r e d and d i s -l o c a t e d ; r e l i c t f o l d c l o s u r e s are p r e s e r v e d i n r e l a t i v e l y competent r o c k s l i k e sandstone and l i m e s t o n e ( P l a t e 2-8). Most of such s t r u c t u r e s were d e s t r o y e d i n l e s s competent s c h i s t o s e r o c k s . L i n e a t i o n s a s s o c i a t e d w i t h L^ f o l d s are seen as s m a l l f o l d a x e s , i n t e r s e c t i o n o f b e d d i n g (F^) and f o l i a t i o n (F^) and a l i g n e d m i n e r a l s . These are b e s t seen i n p h y l l i t i c s c h i s t and a r g i l l i t i c s a n d s t o n e u n i t s . Due t o the s c a r c i t y and unequal d i s t r i b u t i o n o f o u t c r o p s i t i s i m p o s s i b l e t o d i v i d e the a r e a i n t o d i f f e r e n t domains o f a p proxiamte homogeniety w i t h r e s p e c t t o f o l d system. L^ f o l d a xes, w h i c h have been m o d i f i e d by the second and t h i r d phase f o l d s , a r e shown i n F i g u r e 2-5. Most o f t h e a x i a l p l a n e s o f L^ f o l d s e t approach the h o r i z o n t a l b u t the d i p can be as h i g h as 20*. T y p i c a l L^ f o l d s and a s s o c i a t e d F^, F., f o l i a t i o n s , s k e t c h e d i n the f i e l d , are shown i n F i g u r e 2-6. 32 0 I M I I PLATE 2-6: T i g h t i s o c l i n a l f o l d s i n c a r b o n a -ceous a r g i l l i t e , where F-j_ p a r a l l e l s F Q . A l -though c o n t i n u i t y o f some l a y e r s i s w e l l p r e s e r v e d , i n many p l a c e s l a y e r s a r e c u t i n t o s h o r t segments. 33 PLATE 2-7: G l e i t b r e t t s t r u c t u r e i n s c h i s t o s e r o c k s . T h i s s t y l e o f d e f o r m a t i o n a s s o c i a t e s m a i n l y w i t h f i r s t phase o f f o l d i n g . Note b e d d i n g s u r f a c e between i r o n - s t a i n e d beds and s i l i c e o u s beds. 34 PLATE 2-8: R e l i c t o f L]_ f o l d c l o s u r e s i n t h e e n c l o s i n g a r g i l l i t i c s a n d s t o n e . F o l d wave-l e n g t h o f t h i s t y pe i s r a r e l y g r e a t e r than two m e t r e s . 35 36 FIGURE 2-6: F I E L D SKETCH OF F I R S T PHASE FOLDS. 37 In the second group of f o l d s , F Q , and are de-formed about a x i a l s u r f a c e d F^. Cheveron f o l d s ( P l a t e 2-9) and c r e n u l a t i o n s ( P l a t e 2-10) are common i n t h i s group of f o l d s . In w e l l bedded u n i t s o verturned L 2 f o l d s are observed. A s s o c i a t e d f o l i a t i o n (F 2) l i e s a t a l a r g e angle to F or F^ ( P l a t e 2-11) i n some cases. i s g e n e r a l l y p a r a l l e l t o the a x i a l planes of the o verturned f o l d s . L i n e a t i o n s L 2 are commonly f i n e c r e n u l a t i o n s ( P l a t e 2-10), axes of s m a l l f o l d s or i n t e r s e c t i o n of F^ or F^ w i t h F^ ( P l a t e 2-11). Examples of L f o l d s r e f o l d e d by L f o l d s are not seen. F i e l d sketches 1 2 of L 2 f o l d s and r e l a t e d s t r u c t u r e s , w i t h t h e i r o r i e n t a t i o n s , are i l l u s t r a t e d i n F i g u r e 2-7. A x i a l planes (F 2) can be d i v -ided i n t o two domains ( F i g u r e 2-2), n o r t h and south i n which F 2 shows d i f f e r e n t o r i e n t a t i o n s . Most a x i a l planes and f o l -i a t i o n s (F 2) are n e a r l y h o r i z o n t a l or d i p e i t h e r about 20* n o r t h e a s t e r l y or 30* southwesterly (Figure 2-8). L i n e a t i o n s and f o l d axes of L 2 plunge at about 15* w e s t e r l y (Figure 2-9). In a d d i t i o n to the mesoscopic f o l d s d e s c r i b e d above, mapping shows the presence of L 2 recumbent f o l d s w i t h l e n g t h s of 6 00 to 900 metres (Figure 2-2). A r e g i o n a l g e n t l e open a n t i f o r m of the t h i r d group, w i t h r e l a t e d j o i n t s and f r a c t u r e s , deforms the p r e v i o u s l y mentioned s t r u c t u r e s . The data of F i g u r e 2-8 suggest t h a t the a x i s of L^ i s about h o r i z o n t a l and trends n o r t h w e s t e r l y . T h i s f o l d i s shown on F i g u r e 2-2. 38 PLATE 2-9: L2 chevron f o l d s shown by y e l l o w sandstone beds i n carbonaceous a r g i l l i t e . F o l i a t i o n p l a n e s F2 i n a r g i l l i t e a r e p a r a l l e l t o a x i a l p l a n e o f the chevron f o l d . 3 9 0 0 1 M M PLATE 2 - 1 0 : C r e n u l a t i o n s r e l a t e d t o L 2 fo! C r e n u l a t i o n c l e a v a g e p a r a l l e l s t o a x i a l p i o f s m a l l f o l d i n q u a r t z - m u s c o v i t e s c h i s t , t h e o u t c r o p , F 2 i s g e n t l y d i p p i n g . ( C r o s s e d n i c o l s . ) 40 PLATE 2-11: F o l i a t i o n F1 and F 2 i n q u a r t z -m u s c o v i t e s c h i s t . L 2 i s marked by t h e i n t e s e c t i o n o f F]_ and F 2 -41 FIGURE 2-7: FIELD SKETCH OF SECOND PHASE FOLDS. 42 FIGURE 2-9: POLES TO 123 L V LINEATIONS. 44 2-6-C F a u l t s Rocks o f t h i s a r e a have been f a u l t e d e x t e n s i v e l y b o t h d u r i n g and a f t e r t h e t h r e e phases o f d e f o r m a t i o n d e s c r i b e d above. Many f a u l t s show s m a l l d i s l o c a t i o n s o f o n l y a few c e n t i m e t r e s b u t major ones w i t h d i s p l a c e m e n t o f p r o b a b l y 20 to 30 metres have been i d e n t i f i e d . Large f a u l t s a r e seen o n l y as l i n e a m e n t s a c r o s s w h i c h l i t h o l o g i c c o n t a c t s a re d i s -p l a c e d . M e s o s c o p i c f a u l t s have been o b s e r v e d i n many l o c a l -i t i e s ( P l a t e 2-12, 2-13) i n the stu d y a r e a , p a r t i c u l a r l y i n mine w a l l s and r o a d c u t s . The f r e q u e n c y o f f a u l t i n g i n t h e s e exposed a r e a s s u g g e s t s t h a t such f a u l t i n g i s common t h r o u g h -out the C l i n t o n Creek a r e a . Lineaments d e t e c t e d i n the f i e l d and on a e r i a l photo-graphs have been i n t e r p r e t e d as p r o b a b l e f a u l t s . Such an i n t e r p r e t a t i o n i s c o n f i r m e d by the p r e s e n c e , on t h e ground, of minor f a u l t s and b r e c c i a zones, and d i s p l a c e d l i t h o l o g i c u n i t s and s t r u c t u r e s . I n r a r e c a s e s , t h e s e l i n e a m e n t s have been shown t o be f a u l t l i n e s by diamond d r i l l i n g and m i n i n g ( P l a t e 2-13) . Such e v i d e n c e i n d i c a t e s ; ' t h a t many f a u l t s t r e n d 130* t o 160". Comparison o f F i g u r e 2-8 and 2-10 shows t h a t many o f th e f a u l t s o f t h e a r e a a r e p a r a l l e l t o F^ f o l i a t i o n s . A group o f n o r t h e a s t e r l y d i p p i n g f a u l t s c a n n o t , however, be r e l a t e d t o any o t h e r s t r u c t u r a l f e a t u r e s . Some d i s p l a c e -ment o f l i t h o l o g i c u n i t i s e v i d e n t on some o f t h e s e f a u l t s , 45 PLATE 2-12: M i n o r f a u l t d i s p l a c i n g r o d i n g i t e body s u r r o u n d e d by s e r p e n t i n i t e , i n t h e P o r -c u p i n e p i t . (Hammer produces s c a l e . ) 4 6 PLATE 2-13: N o r t h e r l y t r e n d i n g v e r t i c a l f a u l t w i t h considerable displacementin the Porcupine p i t . The f a u l t surface i s curved. R e l -a t i v e l y clean and l i g h t rock on the l e f t i s s e r p e n t i n i t e and dark and d i r t y l o o k i n g rock on the r i g i i t i s a r g i l l i t e . (The height of the w a l l i s about 20 metres.) 4 7 FIGURE 2-10: POLES TO 66 FAULTS 48 b u t g e n e r a l l y magnitude o f movement i s unknown. 2-6-D J o i n t s J o i n t s have been o b s e r v e d i n a l l o u t c r o p s . A s t e r e o -g r a p h i c p r o j e c t i o n o f measured j o i n t s ( F i g u r e 2-11) i n d i c a t e s a t l e a s t f i v e s e t s . One (A) s t r i k e s 150" and d i p s almost v e r t i c a l -l y , a n o t h e r (B) s t r i k e s 000" t o 20* and d i p s 80* t o 90* b o t h e a s t e r l y and w e s t e r l y , a t h i r d (C) s t r i k e s 080* and d i p s v e r -t i c a l l y , a f o u r t h (D) s t r i k e s 115" and d i p s 70* s o u t h e r l y and a f i f t h (E) s t r i k e s 060* and d i p s v e r t i c a l l y . Age r e l a t i o n s h i p o f j o i n t s e t s t o d i f f e r e n t phases o f d e f o r m a t i o n i s u n c e r t a i n . I n g e n e r a l , j o i n t s t r e n d i n g 115"(D) c o n t a i n the a x i s o f the t h i r d phase f o l d and p r o b a b l y r e p r e s e n t s i t s a x i a l p l a n e . The one t r e n d i n g 150* i s p a r a l l e l t o the T i n t i n a Trench. 2-6-E R e g i o n a l S t r u c t u r e The r o c k s a r e c o n s i d e r e d t o l i e i n c h r o n o l o g i c a l o r d e r as s t a t e d p r e v i o u s l y , based m a i n l y on i s o t o p i c age d e t e r m i n a -t i o n s (see c h a p t e r two, s e c t i o n seven) and f o s s i l e v i d e n c e . The a r g i l l i t e and l i m e s t o n e o f t h e a r e a a r e s i m i l a r t o t h o s e where a p r o b a b l e Devonian f o s s i l s were found,about e i g h t k i l o m e t r e s n o r t h w e s t o f the C l i n t o n Creek a r e a . Q u a r t z -m u s c o v i t e - b i o t i t e s c h i s t , q u a r t z - m u s c o v i t e s c h i s t and g r e e n -stone o f t h e a r e a y i e l d e d an O r d o v i c i a n r a d i o m e t r i c age. 49 FIGURE 2 - 1 1 : POLES TO 133 J O I N T S . ( J o i n t s m e a s u r -e d i n t h e m i n e a r e n o t i n c l u d e d . ) 50 However, the c r o s s s e c t i o n ( F i g u r e 2-2) o f the s t u d y a r e a r e v e a l s , t h e o l d e s t r o c k , q u a r t z - m u s c o v i t e - b i o t i t e s c h i s t , a t the top and t h e youngest meta-sedimentary r o c k , a r g i l l i t e s and l i m e s t o n e a t t h e bottom. Hence, t h e a r e a i s i n t e r p r e t e d as a p a r t o f a g i g a n t i c o v e r t u r n e d f o l d . 2-7 ISOTOPIC AGE DETERMINATIONS 2-7-A I n t r o d u c t i o n C l i n t o n Creek i s i n t h e n o r t h w e s t e r n p o r t i o n o f t h e Yukon C r y s t a l l i n e P l a t e a u (Douglas e t a l . , 1970) i n the Yukon T e r r i t o r y ( F i g u r e 1-1). The Yukon Metamorphic Complex (Tempelman-Kluit, 1974) c o n s i s t s o f metasedimentary and meta-v o l c a n i c r o c k s t h a t a r e c o n t i n u o u s w i t h the B i r c h Creek s c h i s t s o f A l a s k a ( F o s t e r , 1973). The metamorphic r o c k s near C l i n t o n Creek ( F i g u r e 2-1) are s i m i l a r t o the r o c k s o f west-c e n t r a l Yukon where C a i r n e s (1914) f i r s t d e s c r i b e d Yukon Group. W i t h i n t h i s group d i f f e r e n t l i t h o l o g i c d i v i s i o n s a re r e c o g n i z e d . M c C o n n e l l (1905) d e f i n e d the P e l l y g n e i s s w h i c h i s i n the n o r t h e r n p a r t o f t h e S t e w a r t R i v e r map s h e e t , t h e K l o n d i k e s c h i s t i n the K l o n d i k e g o l d - f i e l d w h i c h i s im-m e d i a t e l y s o u t h o f Dawson C i t y and the N a s i n a q u a r t z i t e w h i c h o c c u r s p r o m i n e n t l y i n the no r t h e r n m o s t p a r t o f t h e S t e w a r t 51 R i v e r map a r e a . A l l t h e s e type l o c a l i t i e s a re j u s t s o u t h and s o u t h e a s t o f t h e C l i n t o n Creek a r e a . Green (1972) noted t h e c o n t i n u a t i o n o f t h e N a s i n a q u a r t z i t e and K l o n d i k e s c h i s t i n t o the C l i n t o n Creek a r e a . These metamorphic r o c k s g e n e r a l l y have been tho u g h t t o be o f P r e c a m b r i a n age. However, l i m e s t o n e s a s s o c i a t e d w i t h metasedimentary r o c k s j u s t west o f the Yukon R i v e r a t the A l a s k a Boundary ( F i g u r e 2-1: a t 64'39.5'N, 140 * 57.5'W) c o n t a i n c r i n o i d o s s i c l e s and echinoderm c o l u m n a l s t h a t i n d i c a t e a P a l e o z o i c age ( M e r t i e , 1937; Douglas, e t a l . , 1970; Green, 1972). Tempelman-Kluit (1976) has s p e c u l a t e d t h a t many of t h e metamorphic u n i t s might be e q u i v a l e n t t o p a r t s o f the Englishman's Complex and B i g Salmon Complex ( F i g u r e 2-3) o f the P e l l y P l a t f o r m which are o f Upper P a l e o -z o i c age ( M u l l i g a n , 19 6 3 ) . No g e o c h r o n o m e t r i c d a t a e x i s t f o r C a i r n e s (1914) type a r e a . T h e r e f o r e , e i g h t samples (Table 2-3 and 2-4) o f the metamorphic r o c k , e q u i v a l e n t l i t h o l o g i c a l l y t o N a s i n a q u a r t z i t e and K l o n d i k e s c h i s t , were c o l l e c t e d i n t h e C l i n t o n Creek a r e a d u r i n g 1975 and 1976 ( F i g u r e 2-12). One sample (Table 2-3) was a l s o o b t a i n e d from a g r a n o d i o r i t e s t o c k near the w e s t e r n edge of F i g u r e 2-12. These samples were a n a l y s e d t o p r o v i d e e s t i m a t e s o f the age o f d e p o s i t i o n , major meta-morphism and post-metamorphic i n t r u s i o n . TABLE 2-3 POTASSIUM-ARGON ANALYTICAL DATA* Sample b Location Rock unit : Rock name Mineral No." Lat.(N); Long.(W) dated %K ± S 40 A *" Ar 40. *u Ar Apparent 40 -5 3 p Ar t o t a l (10 cm STP/g) age(Ma) Time SP 21A 64*27' 140'54' Kb : b i o t i t e grano-d i o r i t e b i o t i t e 5.60 ±.01 MH 62 64*27.5' 140*4i:2* Pzq: amphibolite MH 122 64*24' 140*40' Pzg: greenstone 0.812 hornblende 0.152+.001 0.629 1.475 0.182 Mil 105 64*29' 140*45.5' Pzq: quartz-muscovite muscovite 6.06 +.06 0.910 6.31 s c h i s t hornblende- 0.674±.009 0.898 0.542 a c t i n o l i t e 64.9±2.3 Late Cre-f R taceous »° 278 +10 Early 245 +8 191 +7 Permian Early f Permian Early f J u r a s s i c a. A l l analyses done i n Geochronology Laboratory, Department of Geological Sciences, The University of B r i t i s h Columbia, K by K.L. Scott, Ar by J.E. llnrnknl. b. See Figure 2-12. c. 'S' i s one standard deviation of quadruplicate a n a l y s i s . d. ^ A r * means radiogenic argon. 10 1 - 1 0 1 e. Constants used i n model age c a l c u l a t i o n s : KXfi = 0.585*10" yr~ ; KAg - 4.72xl0~ y r ~ ; 40K/K = 0.0119 atom percent. f. Time designation a f t e r Armstrong (1978). g. Time designation a f t e r Obradovich and Cobban (1974). TABLE 2-4 RUBIDIUM-STRONTIUM DATA FOR ANALYSED WHOLE ROCK SAMPLES& Sample L o c a t i o n Rock u n i t : Rock name Rb Sr R b 8 7 / S r 8 6 C S r ^ / S r 8 6 ' No. La t . ( N ) ; Long.(W) (ppm) (ppm) MH 61 64*26.8' 140*41.3' Pzq : quartz-muscovite s c h i s t 80.0 41.2 5.63 0.7279 MH 81A 64*25.4' 140*38.7' Pzg : q uart z-mus c o v i te-c h l o r i t e s c h i s t 69.0 25.3 7.90 0.7330 "•MH 101 64*29.4' 140*45' Pzg : greenstone 1.8 278 0.019 0.7080 MH 105 64*29' 140*45.5' Pzq : quartz-muscovite s c h i s t 27.1 24.1 3.25 0.7188 •MH 112 64*24.7' 140*37.4' Pzq : quartz-muscovite s c h i s t 129 63.3 5.89 0.7300 MH 112A 64*24.7* 140*37.4' Pzqm: q uart z-mus c o v i t e -b i o t i t e s c h i s t 37.7 22.5 4.85 0.7365 MH 122 64*24' 140*40' Pzg : greenstone 122 127 2.78 0.7209 Sp 21A 64*27' 140*54' Kb : b i o t i t e g r a n o d i o r i t e 131 1020 0.377 0.7065 a. A l l analyses done i n the Geochronology Laboratory, Department of Geological Sciences, The U n i v e r s i t y of B r i t i s h Columbia by K.L. S c o t t . b. See Figure 2-12. c. One standard d e v i a t i o n e r r o r i n measurment i s (±2%). d. One standard d e v i a t i o n e r r o r i n measurment i s (±.00015). OJ FIGURE 2-12: GEOLOGY OF THE CLINTON CREEK AREA. Kb= b i o t i t e granodiorite; Pzu= serpent i n i t e ; Pza= a r g i l l i t e , limestone and sandstone; Pzg= greenstone and quartz-muscovite-chlorite s c h i s t ; Pzq= quartz-muscovite s c h i s t ; Pzqm= quartz-muscovite-b o i t i t e s c h i s t ; •= K-Ar and Rb-Sr sample s i t e ; = geological contact. 55 2-7-B I s o t o p i c A n a l y s i s Potassium-Argon a n a l y s e s f o r m i n e r a l s from t h r e e samples o f metamorphic r o c k and one sample o f i n t r u s i v e r o c k are g i v e n i n Ta b l e 2-3. F i v e w h o l e - r o c k samples o f s c h i s t , two o f g r e e n s t o n e and one o f g r a n o d i o r i t e were a n a l y s e d f o r r u b i d i u m - s t r o n t i u m and s t r o n t i u m i s o t o p i c c o m p o s i t i o n ; r e s u l t s a re g i v e n i n T a b l e 2-4. a. Potassium-Argon The o l d e s t p o t a s s i u m - a r g o n date o b t a i n e d from meta-morphic r o c k s ( F i g u r e 2-12) i s E a r l y Permian (Table 2-3: MH 62 - 278±10 Ma) f o r ho r n b l e n d e s e p a r a t e d from amphibo-l i t e ( P z q ) . The date p r o b a b l y c l o s e l y r e p r e s e n t s t h e main e p i s o d e o f metamorphism because hornblende i s the l e a s t l i k e l y m i n e r a l t o s u f f e r argon l o s s d u r i n g l a t e r r e h e a t i n g o r slow c o o l i n g (York and F a r q u h a r , 1972). A dat e f o r m u s c o v i t e from q u a r t z - m u s c o v i t e s c h i s t ( P z q ) , a l t h o u g h m u s c o v i t e i s l e s s r e t e n t i v e t h a n h o r n b l e n d e , s u p p o r t s a Permian age (Table 2-3: MH 105 - 245±8 Ma) f o r metamorphism. The E a r l y J u r a s s i c date f o r a h o r n b l e n d e - a c t i n o l i t e m i x t u r e (Table 2-3: MH 122 -191±7Ma) from greenstone (Pzg) p r o v i d e s , a t b e s t , a minimum age o f metamorphism. I n t h i n s e c t i o n t h i s h o r n blende e x i s t s as r e l a t i v e l y c o a r s e r - g r a i n s and a c t i n o l i t e as f i n e r g r a i n s mixed w i t h e p i d o t e , a p r o d u c t o f a l t e r a t i o n o f t h e h o r n b l e n d e . 56 Hence, the date (191±7 Ma) may not be the age o f metamor-phism, b u t a r e s u l t o f p a r t i a l o r t o t a l argon l o s s d u r i n g l a t e r r e t r o g r e s s i v e a l t e r a t i o n . B i o t i t e g r a n o d i o r i t e ( K b ) , s a u s u r u t i z e d b u t w i t h f r e s h b i o t i t e , was sampled from a s t o c k t h a t i n t r u d e d t h e meta-morphic r o c k s ( F i g u r e 2-12). The b i o t i t e y i e l d e d a l a t e s t C r e t a c e o u s - e a r l i e s t T e r t i a r y date (Table 2-3: Sp 21A - 64.9± 2.3 Ma). T h i s i s d i s t i n c t l y younger than c r y s t a l l i z a t i o n o f the metamorphic r o c k s . T h i s r o c k i s m i n e r a l o g i c a l l y s i m i l a r t o N i s l i n g Range g r a n o d i o r i t e , b u t t h e date i s w i t h i n the range o f d a t e s f o r the N i s l i n g Range a l a s k i t e s u i t e (Tempelman-K l u i t , 1975) . b. R u b i d i u m - S t r o n t i u m R u b i d i u m - s t r o n t i u m a n a l y s i s , l i s t e d i n Ta b l e 2-4, are p l o t t e d and i n t e r p r e t e d i n F i g u r e 2-13. An i s o c h r o n ( F i g u r e 2-13: l i n e A"*") can be o b t a i n e d from two g r e e n s t o n e samples (MH 101 and MH 122) and f o u r s c h i s t whole r o c k samples (MH 61, MH 81A, MH 105, MH 112). The Permian age (255.8±22.3*Ma) i n d i c a t e d i s comparable t o the metamorphic age d e f i n e d by p o t a s s i u m -argon a n a l y s i s ( T a b l e 2-3: 245±8 t o 278+10 Ma). T h i s i s f u r t h e r i l l u s t r a t e d i n F i g u r e 2-13 by l i n e B w h i c h i s a r e f e r e n c e l i n e drawn u s i n g the i n i t i a l r a t i o i n d i c a t e d by 1: B e s t f i t l i n e ( l i n e A) i s drawn by u s i n g L e a s t Square R e g r e s s i o n Treatment, Model I o f York (1967) . •740 - i FIGURE 2-13: PLOT OF Sr/ Sr vs. R b / S r FOR WHOLE ROCK ANALYSES OF SAMPLES FROM THE CLINTON CREEK AREA, YUKON TERRITORY. Line A represents the best f i t l i n e for C l i n t o n Creek data (MH 112A omitted) and r e f l e c t s metamorphic r e s e t t i n g . Line B i s a reference l i n e based on the oldest K-Ar date (278 Ma.) and i n i t i a l r a t i o i n d i c a t e d by MH 101. Line C i s model, probably minimum, deposition age (Ordovician) f o r sc h i s t s of the C l i n t o n Creek area based on MH 112A and an assumed low i n i t i a l ^ S r / ^ o s r . 58 the r u b i d i u m - p o o r g r e e n s t o n e sample (Table 2-4: MH 101) and a s l o p e g i v e n by the o l d e s t metamorphic date d e t e r m i n e d by p o t a s s i u m - a r g o n (278+10 Ma). I n i t i a l r a t i o s d e f i n e d by l i n e s A and B are 0.7082 and 0.7080, r e s p e c t i v e l y , and a r e h i g h e r than the i n i t i a l r a t i o 0.7040 assumed f o r l i n e C. I n i t i a l r a t i o s o f 0^7040 t o 0.7060 would be e x p e c t a b l e f o r P a l e o z o i c e u g e o s y n c l i n a l s e d i m e n t s . The h i g h i n i t i a l r a t i o s o f l i n e s A and B p r o b a b l y r e f l e c t w i d e s p r e a d , e x t e n s i v e metamorphic r e s e t t i n g ( H a r t , 1962). An O r d o v i c i a n w h ole-rock d a t e i s p o s s i b l e f o r one sam-p l e i s markedly d i f f e r e n t i s o t o p i c a l l y from the o t h e r s i x samples a n a l y s e d (Table 2-4 and F i g u r e 2-13). A model date o f 470 Ma ( F i g u r e 2-13: l i n e C) i s o b t a i n e d i f an i n i t i a l r a t i o of 0.7040 i s assumed. S u p p o r t f o r such an age comes from a whole r o c k i s o c h r o n o f 465 Ma o b t a i n e d f o r metamorphic r o c k s from t h e Yukon Metamorphic Complex near the C a s i n o p o r p h r y d e p o s i t , about 250 k i l o m e t r e s south-west o f C l i n t o n Creek (Godwin and A r m s t r o n g , 1978, p e r s o n a l communication). R u b i d i u m - S t r o n t i u m d a t a f o r b i o t i t e g r a n o d i o r i t e (Sp 21A) i s l i s t e d i n T a b l e 2-4. As t h e r o c k i s d i f f e r e n t from o t h e r d a t e d (Rb-Sr) r o c k s i n o r i g i n and t i m e , i t i s n o t i n c l u d e d i n ; c a l c u l a t i n g t h e i s o c h r o n s i n F i g u r e 2-13. 2-1-0, R e g i o n a l S y n t h e s i s C l i n t o n Creek d a t a may be compared t o r e g i o n a l i s o -59 t o p i c d a t a (K-Ar and Rb-Sr) c o l l e c t e d by o t h e r w o r k e r s from the n o r t h e r n p a r t o f Yukon C r y s t a l l i n e P l a t e a u . The a r e a c o n s i d e r e d , shown i n F i g u r e 2-3, i s bounded on the n o r t h e a s t by the T i n t i n a Trench and on t h e southwest by the Shakwak-D e n a l i f a u l t . Documentation f o r d a t e s d i s c u s s e d here i s i n T a b l e 2-5. The 67 i s o t o p i c d a t e s i n Table 2-5 are p l o t t e d i n the h i s t o g r a m o f F i g u r e 2-14. In t h i s f i g u r e d i s t i n c t g r o u p i n g of igneous a c t i v i t y a t 45 t o 75 Ma (open c i r c l e ) and 85 t o 120 Ma ( c l o s e d c i r c l e ) a r e a p p a r e n t . I n a d d i t i o n , mixed igneous and metamorphic d a t e s s c a t t e r i n the 135 t o 2 05 Ma range (open and c l o s e d s q u a r e s ) ; t h r e e a d d i t i o n a l d a t e s , p o s s i b l y e x t e n d t h i s d i s t r i b u t i o n t o 280 Ma (open diamond). A p l o t o f t h e s e dates by symbol onto F i g u r e 2-15 i n d i c a t e s t h a t t h e r e may be a g e n e r a l p a t t e r n o f youn g i n g away from the T i n t i n a T r e n c h , a major s t r u c t u r e i n the Yukon T e r r i t o r y . A l t h o u g h the t r e n c h i s s t i l l e n i g m a t i c , Roddick (1967) des-c r i b e d i t as a t r a n s c u r r e n t f a u l t w i t h r i g h t l a t e r a l move-ment o f 400 k i l o m e t r e s and Tempelman-Kluit (1972) n o t e d t h a t t h e r e o c c u r r e d t h r e e s e p a r a t e p e r i o d s o f movement. The e a r l i e s t r e c o r d e d movement o c c u r r e d i n E a r l y T r i a s s i c time a l o n g s t e e p s o u t h w e s t - d i p p i n g f a u l t s w i t h v e r t i c a l d i s p l a c e -ment .that might have t r a n s c u r r e n t component. The second movement o c c u r r e d d u r i n g mid-Cretaceous time and t h e t h i r d d u r i n g Eocene o r O l i g o c e n e time (Tempelman-Kluit, 1976). TABLE 2-5 RELATIONSHIPS OF ISOTOPIC DATES AND ITS PERPENDICULAR DISTANCE FROM THE TINTINA TRENCH OF THE YUKON CRYSTALLINE PLATEAU Sample M a t e r i a l Rb-Sr Date(Ma) No. Dated Metamorphic Igneous K-Ar Date(Ma) Metamorphic Igneous Distance(km) Reference 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 B i o t i t e B i o t i t e B i o t i t e B i o t i t e B i o t i t e B i o t i t e B i o t i t e Hornblende B i o t i t e Whole rock B i o t i t e B i o t i t e Hornblende B i o t i t e Analyses ave. B i o t i t e B i o t i t e B i o t i t e B i o t i t e Hornblende B i o t i t e B i o t i t e B i o t i t e B i o t i t e 48.9 50.8 51.7 52.7 51.6 58 58 55.4 55.7 58.4 64.9 65 67.3 67.6 70.3 89.1 85.2 93.8 93.7 92 91.5 92 94.4 95 216 216.5 196.5 217 215 236.5 256 216 164.5 143 14 215.5 190 200.5 121 133.5 234.5 149 104 127 103 103.5 205 123 I I I I I I I I I I I I I I I I I I I I I I I I I I I Table 2-5 (continued): Sample M a t e r i a l Rb-Sr Date(Ma) No. Dated Metamorphic Igneous 25 Horblende 26 B i o t i t e 27 B i o t i t e 28 Analyses ave. 29 B i o t i t e 30 Hornblende 31 Hornblende 32 Hornblende 33 Whole rock 34 B i o t i t e 35 B i o t i t e 36 Muscovite 37 B i o t i t e 38 B i o t i t e 39 B i o t i t e 40 B i o t i t e 41 Muscovite 42 B i o t i t e 43 Muscovite 44 Muscovite 45 B i o t i t e 46 Horblende 47 B i o t i t e 48 Muscovite 49 B i o t i t e 50 Hornblende 51 Hornblende 52 Muscovite K-Ar Date(Ma) Distance(km) Metamorphic Igneous Reference 92 104.5 I 93 121 I I I 97.6 64 I 99.3 121 I I I 99.6 94 I 99 123 I 100.8 210 I 103 122 I 128 I I I 117 127 I 137 121 I 138 12.5 I 140 229 I 137 88.5 I 147 202 I 164 93.5 I 168 92 I 161 97 I 160 97 I 175 46 I 187 101.5 I 181 101.5 I 182 106.5 I 178 106.5 I 202 42.5 I 191 14 I I 278 14 I I 245 j 14 I I Table 2-5 (continued): Sample M a t e r i a l Rb-Sr Date(Ma) K-Ar Date(Ma) No. Dated Metamorphic Igneous Metamorphic Igneous Distance(km) Reference 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 B i o t i t e B i o t i t e Hornblende B i o t i t e B i o t i t e Hornblende Hornblende B i o t i t e Hornblende B i o t i t e B i o t i t e B i o t i t e Hornblende Whole rock Whole rock 165 255.8 160 160 165 164 166 174 174 174 190 176 177 180 199 182 135.5 141.5 165 134 135.5 131 81.5 165 224 81.5 81.5 130 128 14 I I I I I I I I I I IV IV I I I I I I to I : Tempelman-Kluit and Wanless (1975); I I : IV: W. Pearson (1977) See chapter two, s e c t i o n seven; I I I : C.I. Godwin(1975); 10-i § 5 H o z tt M io M N m Oi N 01 8 50 100 - I l _ | s ® ? — j 1 150 oft 515 » » 200 CTl flu 150 300 DATE (Mo) FIGURE 2-14: HISTOGRAM OF K-Ar AND Rb-Sr DATES OF IGNEOUS AND METAMORPHIC ROCKS OF THE YUKON CRYSTALLINE PLATEAU. (Numbers w i t h i n h i s t o g r a m r e f e r t o d a t e l i s t i n g o f Ta b l e 2-5.) 64 D i s t a n c e - d a t e t r e n d s are a n a l y s e d f u r t h e r i n T a b l e 2-5 and F i g u r e 2-15. Igneous r o c k d a t e s i n t h e 45 t o 75 Ma and 85 t o 120 Ma groups i n the h i s t o g r a m o f F i g u r e 2-14 appear t o c l u s t e r near 200 k i l o m e t r e s ( F i g u r e 2-15: L i n e A) and 100 k i l o m e t r e s ( F i g u r e 2-15: l i n e B) r e s p e c t i v e l y . O t h e r w i s e d a t e s f o r l i n e A and B i n F i g u r e 2-15 s c a t t e r a l o n g b o t h l i n e s from near the t r e n c h t o a d i s t a n c e o f 250 k i l o m e t r e s . Metamorphic and igneous r o c k s w i t h d a t e s r a n g i n g from 135 t o 230 Ma, however, show a d i s t i n c t y o u n g i n g t r e n d away from the T i n t i n a T r e n c h ( F i g u r e 2-15; l i n e C: number o f d a t a ( n ) = 27; c o r r e l a t i o n c o e f f i c i e n t ( r ) = -0.627; slope(m) = -0.199; s t a n d a r d d e v i a t i o n on Y(S ) = 17.3; s t a n d a r d d e v i a t i o n y on X(S ) = 54.6; m i g r a t i o n r a t e = 0.5 cm/yr). L i n e C, t h e b e s t f i t l i n e t h r o u g h the d a t a s u g g e s t s t h a t t h e d a t e a t t h e T i n t i n a T r ench i s about 200 Ma, and 250 k i l o m e t r e s perpen-d i c u l a r l y from the Trench i s near 150 Ma. The a p p a r e n t h o r i z o n t a l r a t e o f i s o t h e r m m i g r a t i o n i s about 0.5 cm/yr. Younging o f i n t r u s i v e e v e n t s have been r e l a t e d t o B e n i o f f zoned by numerous w r i t e r s (Dewey and B i r d , 1970; James, 19 71) . Thermal zone m i g r a t i o n a t the r a t e o f 0.5 cm/yr i s c o m p a t i b l e w i t h those s h i f t s a t t r i b u t e d t o B e n i o f f zone i n d u c e d magmatism e l s e w h e r e (Godwin, 1975) . T h e r e f o r e , t h e p o s s i b i l i t y t h a t l i n e C i n F i g u r e 2-15 might r e f l e c t m i g r a t i n g igneous a c t i v i t y above a B e n i o f f zone i s an a t t r a c t i v e one. F o s t e r (19 74) s u g g e s t e d t h a t the T i n t i n a Trench marked a p l a t e boundary f o r the j u x t a p o s i t i o n o f markedly d i f f e r e n t 2 5 0 2 0 0 '52 (50 o JC too (9 < 50 B | 6 3 60 ^AO 36BBB55 42*3 f 4 5 7 D 38 D 3 5 t27 2«^ 3 11(L* 5 3 30 .31 Oil 19,21,23,25 2*6 »,6 18 0 | 5 - © 23 t\7 14 NIO Q9_ O ° n 13 0 | 2 6 7 o o "753 O" I,2,4,5L8 80 J _ •00 150 200 DISTANCE (km) 250 300 350 FIGURE 2-15: K-Ar AND Rb-Sr DATES OF IGNEOUS AND METAMORPHIC ROCKS OF THE YUKON CRYSTALLINE PLATEAU VS. PERPENDICULAR DISTANCE FROM THE TINTINA TRENCH. Line A represents widespread igneous activity around 60 Ma. Line B represents widespread igneous activity around 95 Ma. Line C represents a younging of dates away from, the Tintina Trench from early Triassic to early Cretaceous time. Number of points (n) used to define line C is 27. Correlation coefficient (r) for line C is -0.627. Sample nos., symbols and references are in Figure 2-14 and Table 2-5 respectively. (Sample 51 and 67 excluded.) 66 t e r r a n e s on each s i d e o f the g r e a t l e n g t h o f the T i n t i n a f a u l t system. However, more d a t a i s needed t o c o n f i r m the s p e c u l a t i o n t h a t t h e T i n t i n a Trench r e p r e s e n t s an e x t i n c t s u t u r e and v a n i s h e d ocean. 2-7-D Summary The pre-metamorphic age o f a s c h i s t o f t h e Yukon Meta-morphic Complex near C l i n t o n Creek i s p o s s i b l y O r d o v i c i a n (470 Ma by R b - S r ) . T h i s i s t e n o u s l y based on one whole r o c k sample and an assumed i n i t i a l r a t i o . However, t h e age i s s u p p o r t e d by u n p u b l i s h e d d a t a from the C a s i n o a r e a and by Tempelman-Kluit (1976) who s u g g e s t e d the N a s i n a q u a r t z i t e and K l o n d i k e s c h i s t a re P a l e o z o i c i n age, namely O r d o v i c i a n t o M i s s i s s i p p i a n . 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 a n a l y t i c a l d a t a f u r t h e r i n d i c a t e a major r e g i o n a l metamorphism b e f o r e o r i n E a r l y Permian t i m e ; t h e most s i g n i f i c a n t date i s E a r l y Permian (278±10 Ma) from K-Ar a n a l y s i s o f h o r n b l e n d e . Permian metamorphism i n the Yukon C r y s t a l l i n e P l a t e a u has n o t been documented p r e v i o u s l y . The o l d e s t s i n g l e K-Ar date on meta-morphic r o c k r e c o r d e d by Tempelman-Kluit (1975) was 202 Ma (Table 2-5: sample no. 4 9 ) . A s m a l l g r a n o d i o r i t e s t o c k i n the map a r e a i s l a t e s t C r e t a c e o u s o r e a r l i e s t T e r t i a r y . T h i s i s o t o p i c date i s the youngest i n the n o r t h w e s t e r n p a r t o f the Yukon C r y s t a l l i n e 67 P l a t e a u . T h i s might r e p r e s e n t e q u i v a l e n c e t o the C a s i n o Complex, 70.3 Ma (Godwin, 1975). P r e v i o u s l y t h e s e i n t r u s i o n s were c l a s s i f i e d as mid-Cretaceous (Green, 1972) and e q u i v a l e n t t o the C o f f e e Creek q u a r t z - m o n z o n i t e , 9 0 t o 100 Ma (Tempelman-K l u i t , 1976) . W i t h i n the c e n t r a l and n o r t h e r n p a r t o f t h e Yukon C r y s t a l l i n e P l a t e a u a f a i r l y w e l l d e f i n e d younging t r e n d i n igneous and metamorphic i s o t o p i c d a t e s away from the T i n t i n a T r ench i s p r e s e n t . 68 CHAPTER I I I CLINTON CREEK ULTRAMAFIC BODIES 3-1 INTRODUCTION E i g h t e e n u l t r a m a f i c b o d i e s were mapped w i t h i n the stu d y a r e a ( F i g u r e 2-2), o f w h i c h f i v e b o d i e s a r e known t o c o n t a i n c h r y s o t i l e a s b e s t o s . These are a p a r t o f a d i s -c o n t i n u o u s b e l t o f u l t r a m a f i c and a s s o c i a t e d r o c k s e x t e n d i n g a l o n g a l m o s t the e n t i r e l e n g t h o f T i n t i n a Trench. I n some p l a c e s the b e l t r e a c h e s a w i d t h o f 60 k i l o m e t r e s ( F i g u r e 2-4). I n P e l l y and S t e w a r t R i v e r a r e a s l a r g e u l t r a m a f i c b o d i e s form the lo w e r s t r u c t u r a l u n i t o f a s e r i e s o f s t r a t -i f i e d a l l o c t h o n o u s s h e e t s (Tempelman-Kluit, 1977). These sh e e t s have been t h r u s t o v e r P a l e o z o i c r o c k s and l a t e r f o l d e d w i t h c o u n t r y r o c k . Some o f the u l t r a m a f i c r o c k s i n t he P e l l y R i v e r and S t e w a r t R i v e r areas and the E a g l e q u a d r a n g l e i n A l a s k a are o v e r l a i n by a u n i t c o n s i s t i n g o f g a b b r o i c r o c k s , p i l l o w l a v a s and c h e r t y a r g i l l i t e s , a s u i t e o f r o c k s t y p i c a l o f o p h i o l i t e 1 t h a t c l o s e l y resembles 1: See Appendix B f o r d e f i n i t i o n o f o p h i o l i t e . 69 r o c k sequences o f p r e s e n t day o c e a n i c r i d g e s and sea f l o o r . O p h i o l i t e s a r e r e g a r d e d as t e c t o n i c a l l y emplaced fragments o f t h e o c e a n i c c r u s t and upper mantle (Coleman, 1971). F o s t e r and K e i t h (1974) d e s c r i b e d the u l t r a m a f i c r o c k s i n Yukon T e r r i t o r y w h i c h appears t o be the s o u t h e a s t e x t e n s i o n of the zone o f u l t r a m a f i c r o c k s o f t h e E a g l e q u a d r a n g l e . 3-2 PETROLOGY 3-2-A U l t r a m a f i c Rock Types A l l o f the u l t r a m a f i c r o c k s i n t h i s a r e a are a t l e a s t 75 p e r c e n t s e r p e n t i n i z e d and most o f them about 95 p e r c e n t s e r p e n t i n i z e d . The n a t u r e o f o r i g i n a l r o c k was i n f e r r e d from r e l i c t s t r u c t u r e s and t e x t u r e s , and from t h e n a t u r e and c h e m i s t r y o f t h e p r i m a r y m i n e r a l s . Host r o c k s o f t h e a s b e s t o s d e p o s i t are m a i n l y h a r z b u r g i t e and I h e r z o l i t e w i t h minor dun-i t e ( F i g u r e 3-1) . Specimens o f s e r p e n t i n i z e d h a r z b u r g i t e i n t h i n s e c t i o n c o n t a i n s e v e r a l o f the f o l l o w i n g : o l i v i n e , o r t h o p y r o x e n e ( P l a t e 3-1), b a s t i t e pseudomorphs a f t e r pyroxene, a n t i -g o r i t e w i t h r e l i c t o l i v i n e network t e x t u r e , c h r o m i t e , magnet-i t e , c h r o m e - s p i n e l , t a l c , m a g n e s i t e , b r u c i t e and c h r y s o t i l e . A c c o r d i n g t o m i c r o p r o b e a n a l y s e s (Appendix C) the o l i v i n e 70 FIGURE 3-1: MODAL CLASSIFICATION OF ULTRAMAFIC ROCKS ( a f t e r J a c k s o n , 1968 ) . 71 o •s'*><,> i J PLATE 3-1: S e r p e n t i n i z e d h a r z b u r g i t e w i t h un-s t r a i n e d mosaic o l i v i n e s u r r o u n d i n g l a r g e r py-r o x e n e s . Ribbon t e x t u r e d a n t i g o r i t e r e p l a c e s f i n e - g r a i n e d g r a n u l a r o l i v i n e . ( C r o s s e d n i c o l s . ) 72 network i s f o r s t e r i t i c ( F o 0 0 _ n „ .) . Orthopyroxene i s e n s t a t i t e ( E n c ) ^ 7-91 9^ a n c ^ g e n e r a l l y e x h i b i t s abundant e x s o l u t i o n l a m e l l a e o f c l i n o p y r o x e n e . The most s i g n i f i c a n t f e a t u r e o f t h e h a r z b u r g i t e i s i t s t e c t o n i c f a b r i c i n w h i c h o r t h o p y r o x e n e forms p o r p h y r o c l a s t s 1 t o 10 mm l o n g , whereas the o l i v i n e g r a i n s , 0.1 t o 1 mm i n modal d i a m e t e r , form a c a t a c l a s t i c m a t r i x . The o r t h o p y r o x e n e s are bent and show u n d u l a t o r y e x t i n c t i o n . O l i v i n e g r a i n s a r e h i g h l y g r a n u l a t e d and s t r o n g l y f r a c t u r e d . Mosaics o f u n s t r a i n e d much f i n e r -g r a i n e d o l i v i n e a r e f r e q u e n t l y o b s e r v e d e n c l o s i n g t h e o r t h o -pyroxene p o r p h y r o c l a s t s ( P l a t e 3-1). S e r p e n t i n i z e d l h e r z o l i t e c o n s i s t s o f o r t h o p y r o x e n e , c l i n o p y r o x e n e , o l i v i n e , a n t i g o r i t e , b a s t i t e , c h l o r i t e and m a g n e t i t e ( P l a t e 3-2). L a r g e a n h e d r a l g r a i n s o f pyroxene t o t a l about 45 p e r c e n t . Some o r t h o p y r o x e n e shows s t r a i n e d e x t i n c t i o n , o t h e r s a r e s l i g h t l y b e n t and s h e a r e d . A few pyroxenes a r e p a r t i a l l y r e p l a c e d by b a s t i t e . The r a t i o o f c l i n o p y r o x e n e t o o r t h o p y r o x e n e i s about 4 t o 1. V ery few o l i v i n e g r a i n s a r e p r e s e r v e d , b u t t y p i c a l s e r p e n t i n e network a f t e r o l i v i n e i s s t i l l p r e s e r v e d . I n some specimens c h l o r i t e a l s o has r e p l a c e d o l i v i n e . 3-2-B E a r l y S t a t e A l t e r a t i o n a. S e r p e n t i n i z a t i o n 73 o s n n . PLATE 3-2: S e r p e n t i n i z e d l h e r z o l i t e . A l l o t the o l i v i n e has been s e r p e n t i n i z e d . S e r p e n t i -n i z a t i o n o f pyroxene i n the m i d d l e o f ph o t o -graph seems t o have t a k e n p l a c e a t c o n s t a n t volume. ( C r o s s e d n i c o l s . ) 74 S e r p e n t i n i z a t i o n i s a p e r v a s i v e a l t e r a t i o n common t o a l l u l t r a m a f i c b o d i e s i n the s t u d y a r e a . The degree o f s e r p e n t i n i z a t i o n v a r i e s w i t h r o c k t y p e . G e n e r a l l y , d u n i t e i s more s e r p e n t i n i z e d t h a n h a r z b u r g i t e o r I h e r z o l i t e , ap-p a r e n t l y because o l i v i n e i s more s u s c e p t i b l e t o a l t e r a t i o n t han p y r o x e n e s . S e r p e n t i n e minerals"'' i n t h e C l i n t o n Creek a r e a a r e a n t i g o r i t e and c h r y s o t i l e . L i z a r d i t e appears t o be a b s e n t . Most s e r p e n t i n i z a t i o n i n t h i s a r e a o c c u r r e d i n two main e p i s o d e s . The f i r s t was p a r t i a l t o complete r e -placement o f ferromagnesium s i l i c a t e s by a n t i g o r i t e . The second s t a g e , w h i c h w i l l be d i s c u s s e d i n Chapter IV, was t h e f o r m a t i o n o f a n t i g o r i t e , c h r y s o t i l e , p i c r o l i t e and b r u c i t e , m o s t l y on f r a c t u r e s and f a u l t s u r f a c e s . Two ty p e s o f o l i v i n e a re o b s e r v e d , f i n e g r a i n e d g r a n -u l a t e d o l i v i n e and u n s t r a i n e d , mosaic o l i v i n e . The former g e n e r a l l y i s r e p l a c e d by r i b b o n t e x t u r e d a n t i g o r i t e ( P l a t e 3-1). The l a t t e r r e s i s t s s e r p e n t i n i z a t i o n l o n g e r and i s l a r g e l y r e p l a c e d by l a m e l l a r a n t i g o r i t e . I n specimens where s e r p e n t i n i z a t i o n i s complete, the c o r e s o f o l i v i n e a r e r e -p l a c e d by s e r p o p h i t e . S e r p e n t i n i z a t i o n can form i n two ways: i n one, the volume remains c o n s t a n t and i n t h e o t h e r t h e r e i s a change i n volume. The c o n s t a n t volume r e p l a c e m e n t model (Thayer, 1: S e r p e n t i n e m i n e r a l s were i d e n t i f i e d by s i n g l e c r y s t a l x - r a y work and x - r a y powder d i f f r a c t i o n t e c h n i q u e s . See Appendix D f o r the d e f i n i t i o n o f d i f f e r e n t s e r p e n t i n e m i n e r a l s used h e r e . 75 1966) i n v o l v e s the removal o f l a r g e amounts o f MgO and SiO i n s o l u t i o n , the s e r p e n t i n i z a t i o n r e a c t i o n p o s s i b l e b e i n g o f the type (Tuner and Verhoogen, 1960) : In some t h i n s e c t i o n s a n t i g o r i t e appears t o have r e p l a c e d pyroxene w i t h o u t any e x p a n s i o n ( P l a t e 3-2). Some r i b b o n -t e x t u r e d a n t i g o r i t e f i l l s what appears t o be e x p a n s i o n f r a c -t u r e s i n o l i v i n e . H o s t e t l e r e t a l . (1966) argue t h a t the development o f b r u c i t e i n d i c a t e d volume i n c r e a s e . The C l i n t o n Creek u l t r a m a f i c body c o n t a i n s , on the average , one p e r c e n t b r u c i t e ( P l a t e 3-3, 3-4). A l o s s o f MgO r a t h e r t h a n a g a i n o f S i 0 2 would m i n i m i z e an i n c r e a s e i n volume. The w r i t e r c o n c l u d e s t h a t s e r p e n t i n i z a t i o n was p a r t l y volume f o r volume b u t t h a t t h e r e was some volume i n c r e a s e . S c a r f e and W i l e y (1967) and Johannes (1969) have shown the breakdown temperature o f f o r s t e r i t e t o s e r p e n t i n e i n t h e r e a c t i o n , F o r s t e r i t e + Water S e r p e n t i n e + S o l u t i o n 5Mg o S i O . + 4H 0 F o r s t e r i t e + Water S e r p e n t i n e + B r u c i t e 2 M g 2 S i 0 4 + 3H"20 M g 3 S i 2 0 -2H 20 + Mg(OH) 0 L - I PLATE 3-3: P a l e y e l l o w b r u c i t e formed d u r i n g p e r v a s i v e , f i r s t main e p i s o d e o f s e r p e n t i n i z a -t i o n . ( C r o s s e d n i c o l s . ) 77 0 ( M M -I I PLATE 3-4: Y e l l o w i s h w h i t e b r u c i t e p r o b a b l y formed d u r i n g second main e p i s o d e o f s e r p e n t i -n i z a t i o n , u s u a l l y i n f r a c t u r e s between p i c r o -l i t e . ( C r o s s e d n i c o l s . ) 78 i s a l i t t l e above 400*C a t 2 kb ( F i g u r e 3-2). The s t a b i l i t y o f b r u c i t e i s l i m i t e d by t h e c o m p o s i t i o n o f t h e f l u i d phase, b e i n g s t a b l e o n l y a t v e r y low CC>2 c o n t e n t , about 0.5 mole p e r c e n t CC>2 a t f l u i d p r e s s u r e 2 kb and 400"c (Johannes, 1969). A t h i g h e r CC>2 c o n t e n t o f t h e f l u i d phase the b r e a k -down o f o l i v i n e o c c u r s by the r e a c t i o n ( F i g u r e 3-2): F o r s t e r i t e + W a t e r + C a r b o n D i o x i d e S e r p e n t i n e + M a g n e s i t e 2 M g 2 S i 0 4 + 2H 20 + CC>2 -»»*-»• Mg 3Si 2C> 7. 2H 20 + MgCC>3 S i n c e b o t h b r u c i t e and magnesite a re common i n the C l i n t o n Creek u l t r a m a f i c body, e i t h e r t h e a l t e r i n g f l u i d changed and became r i c h e r i n C 0 2 d u r i n g the p r o c e s s , o r t h e r e were two s e p a r a t e e p i d o s e s o f a l t e r a t i o n , one y i e l d i n g s e r p -e n t i n e and b r u c i t e and t h e o t h e r s e r p e n t i n e and m a g n e s i t e . Orthopyroxene g e n e r a l l y i s r e p l a c e d , w i t h o u t any s i g n o f e x p a n s i o n , by b a s t i t e w h i c h p r e s e r v e s the m o r p h o l o g i c a l f e a t u r e s o f the o r i g i n a l g r a i n , and by minute c r y s t a l s o f ma g n e t i t e a r r a n g e d e i t h e r a l o n g the c l e a v a g e p l a n e s o r around the g r a i n . From a c h e m i c a l p o i n t o f vi e w , the s e r p -e n t i n i z a t i o n o f o r t h o p y r o x e n e i n v o l v e s an i n c r e a s e i n w a t e r , and, s i n c e the r e a c t i o n a p p a r e n t l y goes on a t c o n s t a n t volume, a l o s s o f s i l i c a , as w e l l as s m a l l amounts o f c a l c i u m and aluminum. A p a r t o f t h e s i l i c a r e l e a s e d i s p r o b a b l y i n c o r p o r a t e d i n s e r p e n t i n e r e p l a c i n g the s i l i c a - p o o r o l i v i n e , 79 FIGURE 3-2: T-X DIAGRAM IN THE SATURATED SYSTEM MgO-S i 0 2 - H 2 0 - C 0 2 - C a O ( a f t e r : Greenwood, 1967; Johannes, 1969; and S k i p p e n , 1971). 80 whereas a n o t h e r p a r t may be combined w i t h c a l c i u m and a l -uminum t o form c a l c i u m - r i c h a l u m i n o - s i l i c a t e s o f r o d i n g i t e (see b e l o w ) . E n s t a t i t e r e s i s t s s e r p e n t i n i z a t i o n and s u r -v i v e s i n r o c k s i n wh i c h o l i v i n e i s c o m p l e t e l y s e r p e n t i n -i z e d . E x p e r i m e n t a l l y e n s t a t i t e i s not s t a b l e below 700*C a t 2 kb w i t h low X C Q (Greenwood, 196 3; Johannes, 196 9; Evans and Trommsdorff, 19 7 0 ) , b u t b r e a k s down t o antho-p h y l l i t e and f o r s t e r i t e . E n s t a t i t e + Water A n t h o p h y l l i t e + F o r s t e r i t e 9 M g 2 S i 2 O g + 2H 20 2Mg^SigC> 2 2 (OH) 2 + 2Mg 2SiO However, a n t h o p h y l l i t e appears t o be absent i n the a r e a . T h e r e f o r e , i t i s assumed, a t lo w e r t e m p e r a t u r e and h i g h e r c o n t e n t o f w a t e r , a n t h o p h y l l i t e c o u l d break down t o f o r s t e r -i t e and t a l c ( F i g u r e 3-2). A n t h o p h y l l i t e + Water -*-»-•• F o r s t e r i t e + T a l c 5Mg Si o0_ o(0H)„ + 4H„0 -»-»-> 4Mg oSi0„ + 9Mg S i 0 (OH) „ 7 8 2 2 2 2 ^2 4 3 4 10 2 E v e n t u a l l y , w i t h a drop o f te m p e r a t u r e and a d d i t i o n o f wa t e r p r e s s u r e , f o r s t e r i t e and t a l c may break down t o s e r p e n -t i n e (Evans and Trommsdorff, 1970) a c c o r d i n g t o the f o l l o w i n g r e a c t i o n : 81 F o r s t e r i t e + T a l c + Water -*->-»- S e r p e n t i n e 6 M g 2 S i 0 4 + M g 3 S i 4 0 1 Q (OH) 2 + H 20 ->-»--> 5 M g 3 S i 2 0 ? . 2H 20 around 450"C a t 2 kb. The degree o f a l t e r a t i o n o f c h r o m i t e i s a p p a r e n t l y not r e l a t e d t o the degree o f s e r p e n t i n i z a t i o n . U n a l t e r e d c h r o m i t e i s t r a n s l u c e n t dark r e d d i s h brown. Some c h r o m i t e i s r e p l a c e d by an opaque b l a c k m a t e r i a l u s u a l l y m a g n e t i t e ( P l a t e 3-5), w h i c h may form a r i m o r c o m p l e t e l y r e p l a c e t h e g r a i n . Most c h r o m i t e g r a i n s o r m a g n e t i t e a f t e r c h r o m i t e g r a i n s are rimmed by a t h i n f i n e - g r a i n e d h a l o o f r a d i a t i n g c h l o r i t e w h i c h merges w i t h the s u r r o u n d i n g s e r p e n t i n e . I t i s found o n l y around c h r o m i t e g r a i n s w i t h b l a c k r i m s b u t not around u n a l t e r e d c h r o m i t e . T h i s s u g g e s t s t h a t b o t h m a g n e t i t e and c h l o r i t e a r e a l t e r a t i o n p r o d u c t s o f c h r o m i t e . Large c h r o m i t e g r a i n s commonly have two g e n e r a t i o n s o f f r a c t u r e s : an e a r l y one f i l l e d w i t h c h l o r i t e and b o r d e r e d by m a g n e t i t e , and l a t e r a n t i g o r i t e - f i l l e d f r a c t u r e s c r o s s c u t t i n g the c h l o r i t e h a l o ( P l a t e 3-5), t h i s a n t i g o r i t e v e i n -l e t may o r may not be a d j a c e n t t o a b l a c k m a r gin. T h i s may s u g g e s t t h a t a l t e r a t i o n p r o d u c i n g c h l o r i t e and m a g n e t i t e o c c u r r e d b e f o r e p e r v a s i v e s e r p e n t i n i z a t i o n . A l t e r a t i o n o f c h r o m i t e t o m a g n e t i t e and c h l o r i t e o c c u r s a t t e m p e r a t u r e s above the s t a b i l i t y l i m i t o f s e r p e n t i n e (Cerny, 1968). S e v e r a l d i f f e r e n t k i n d s o f s e r p e n t i n i t e are d i s t i n -82 0 .\e\n. PLATE 3-5: B r o w n i s h r e d , t r u n s l u s c e n t c h r o m i t e w i t h b l a c k m a g n e t i t e and p a l e c o l o u r c h l o r i t e . (PPL.) 83 g u i s h e d i n the C l i n t o n Creek a r e a . G e n e r a l l y , f i b r e - b e a r i n g s e r p e n t i n i t e c o n s i s t s o f a n t i g o r i t e , b a s t i t e , s e r p o p h i t e , c h r y s o t i l e , p i c r o l i t e , p r o c h l o r i t e and m a g n e t i t e . O r d i n -a r i l y i t i s dark g r e e n , compact and has a somewhat sugary t e x t u r e . Very f i n e g r a i n e d , dark green compact s e r p e n t i n i t e n o r m a l l y c o n s i s t s o f a n t i g o r i t e , s e r p o p h i t e , c h l o r i t e , m a g n e t i t e and b r u c i t e i n w h i c h c h l o r i t e forms as much as 40 p e r c e n t o f the r o c k . F i n e - g r a i n e d , f l a k y a n t i g o r i t e i s r e p l a c e d by b r u c t i e i n p a r t . C h l o r i t e and b r u c i t e v e i n s are q u i t e common. Network s e r p e n t i n i t e c o n t a i n s more than 80 p e r c e n t o f s e r p o p h i t e . T h i s i s v e r y d a r k , n e a r l y b l a c k r o c k w i t h a few v e i n l e t s o f t a l c and c h r y s o t i l e and magnet-i t e . F i s h - s c a l e s e r p e n t i n i t e c o n s i s t s m a i n l y o f a n t i g o r i t e , some s e r p h o p i t e and c h l o r i t e . T h i s o c c u r s a l o n g s h e a r e d zone. S l a b - l i k e b l o c k s o f f i s t s i z e t o a metre s i z e are c o a t e d w i t h s h i n i n g , p o l i s h e d a n t i g o r i t e . S l a b s o f s e r p e n t -i n i t e a re a r r a n g e d i n an o v e r l a p p i n g manner analogous t o f i s h - s c a l e s . One o f t h e c h a r a c t e r i s t i c s o f f i s h - s c a l e s e r p e n t i n i t e i s l a c k o f c h r y s o t i l e f i b r e . The age o f s e r p e n t i n i z a t i o n i s not p o s s i b l e t o d e t e r -mine. However, the i n i t i a l s e r p e n t i n i z a t i o n would p r o b a b l y have o c c u r r e d when the u l t r a m a f i c body f i r s t came i n c o n t a c t w i t h hydrous r o c k u n i t s . P e r v a s i v e s e r p e n t i n i z a t i o n c o u l d have t a k e n p l a c e i n Permian time d u r i n g t h e main phase of metamorphism o f t h e C l i n t o n Creek a r e a (Table 2-1). 84 b. R o d i n g i t i z a t i o n R o d i n g i t e i s exposed o n l y i n the P o r c u p i n e and Snow Shoe p i t s . Two groups o f r o d i n g i t e a re d i s t i n g u i s h e d on the b a s i s o f age d e t e r m i n e d by r e l i c t m i n e r a l s , s t a g e o f a l t e r a -t i o n , degree o f d e f o r m a t i o n and n a t u r e o f c o n t a c t s . The o l d e r group c o n s i s t s o f i s o l a t e d t a b u l a r b o d i e s ( P l a t e 3-6) t h a t range i n l e n g t h from t h r e e metres t o t w e l v e metres w i t h t h i c k n e s s e s o f 1 t o 1.5 metres ( P l a t e 2-3). The o l d e r r o d i n g i t e , i n t h i n s e c t i o n , c o n s i s t s o f g a r n e t , i d o c r a s e , p r e h n i t e , c h l o r i t e , d i o p s i d e , a c t i n o l i t e and e p i d o t e ( P l a t e 3-7). Lack o f p r i m a r y r e l i c t m i n e r a l s , e x c e p t p y r o x e n e , makes i t i m p o s s i b l e t o p r e c i s e l y d e f i n e the o r i g i n a l r o c k . However, presence o f p y r o x e n e , t h e t a b -u l a r form, i n t e n s i t y o f s h e a r i n g and d e f o r m a t i o n t h a t a re s i m i l a r t o tho s e i n the s u r r o u n d i n g s e r p e n t i n i t e , and absence o f metamorphism o f a d j a c e n t s e r p e n t i n e ( P l a t e 3-8), su g g e s t t h a t t h e b o d i e s were b a s i c dykes emplaced b e f o r e s e r p e n t -i n i z a t i o n . O r i g i n a l ferro-magnesium s i l i c a t e s were p r o b a b l y u r a l i t i z e d ( a c t i n o l i t e ) and c h l o r i t i z e d ( P l a t e 3-9), and c a l -c i c p l a g i o c l a s e was r e p l a c e d by i d o c r a s e , p r e h n i t e , e p i d o t e and h y d r o g a r n e t . A c c o r d i n g t o Coleman (1967) t h e r e p l a c e -ment p r o c e s s c o u l d o c c u r a c c o r d i n g t o the f o l l o w i n g r e -a c t i o n s : 2+ + 3 A n o r t h i t e + Ca + 2H^0 Z o i s i t e + 2H 85 PLATE 3 - 6 : O l d e r r o d i n g i t e . G e n e r a l l y t a b u l i n t e n s e l y deformed and u s u a l l y c o l o u r e d p u p l i on f r a c t u r e s u r f a c e s . Exposed i n Snow Shoe p 86 0 • \ f*M • PLATE 3-7: O l d e r r o d i n g i t e : i s o t r o p i c g r o s s u -l a r g a r n e t ; b l u e i d o c r a s e ; p u r p l i s h and g o l d e n e p i d o t e ; p a l e o r w h i t i s h c h l o r i t e . ( C r o s s e d n i c o l s . ) 87 R ODIN&IT E 0 - I M * ! -PLATE 3-8: O l d e r r o d i n g i t e showing absence o f metamorphism a t c o n t a c t w i t h s e r p e n t i n e . ( C r o s s -ed n i c o l s . ) 88 o s M M i 1 PLATE 3-9: U r a l i t i z a t i o n and c h l o r i t i z a t i o n i n r o d i n g i t e . Y e l l o w i s h green pyroxene a t l e r t t o p c o r n e r was r e p l a c e d by a d j a c e n t p a l e c o l o u r c h l o r -i t e and p r i s m a t i c a c t i n o l i t e . The r e s t i s o t r o p i c and gray m i n e r a l s are s e r p e n t i n e . ( C r o s s e d n i c o l s . ) 89 2+ + 4 Z o i s i t e + 0.5 Ca + 13H 20 -*->--> Hyd r o g a r n e t + 10H or 1.5 A n o r t h i t e + 0 . 5 C a 2 + + 1.5H 20 1 P r e h n i t e + 0 . 5 A l 2 O 3 + H + 2 P r e h n i t e + 4 C a 2 + + Al 2C> 3 + 6H 20 + ^ 2Hydrogarnet + 8H + D e c o m p o s i t i o n o f ferro-magnesium m i n e r a l s c o u l d y i e l d i r o n f o r the f o r m a t i o n o f p r e h n i t e , e p i d o t e and i d o c r a s e , and magnesium f o r i d o c r a s e . T h e r e f o r e , d u r i n g r o d i n g i t i z a t i o n o n l y c a l c i u m and w a t e r need t o be added. C a l c i u m f o r r o d -i n g i t e c o u l d be d e r i v e d from c l i n o p y r o x e n e o f u l t r a m a f i c r o c k s d u r i n g s e r p e n t i n i z a t i o n (Barnes and O ' N e i l , 1969). C a l -cium has been shown t o be r e l e a s e d d u r i n g s e r p e n t i n i z a t i o n o f u l t r a m a f i c r o c k s ( P o l d e r v a a r t , 1955). The younger group o f r o d i n g i t e s i s m a i n l y d i s t i n g -u i s h e d by the development o f t h e r m a l metamorphism a t c o n t a c t s w i t h s e r p e n t i n e , l e s s pronounced f o l i a t i o n and n o n - p e r v a s i v e r o d i n g i t i z a t i o n . The c e n t r a l p a r t s o f t h e b o d i e s a r e s l i g h t l y a l t e r e d gabbro b u t the margins c o n s i s t o f h y d r o g a r n e t , e p i d o t e , t a l c and c h l o r i t e . A t the c o n t a c t s s e r p e n t i n e has been de-h y d r a t e d and c o n v e r t e d i n t o d i o p s i d e and l o c a l l y i n t o t a l c and c h l o r i t e ( P l a t e 3-10). Thus i t appears t h a t p r o b a b l y dykes o f gabbro were i n t r u d e d i n t o a l r e a d y s e r p e n t i n i z e d p e r i d o t i t e . 90 Q 5MM-I I PLATE 3-10: S e r p e n t i n e d e h y d r a t e d i n t o p yroxene. G r a y i s h , g r e e n i s h and i s o t r o p i c m i n e r a l s a r e s e r p e n t i n e . Second o r d e r i n t e r f e r e n c e c o l o u r m i n e r a l s are pyroxene. (Crossed n i c o l s . ) 91 c. B l a c k w a l l and t a l c - c a r b o n a t e a l t e r a t i o n B l a c k w a l l a l t e r a t i o n 1 was found o n l y a t t h e margin o f t h e A i r F i e l d u l t r a m a f i c body ( F i g u r e 2-2) where i t i s ex-posed o v e r an a r e a f o u r metres by t e n metres. The m a r g i n a l zone i s m o d e r a t e l y s h e a r e d . B l a c k w a l l a l t e r a t i o n zone i s succeeded towards the i n t e r i o r o f t h e u l t r a m a f i c body by a t a l c - c a r b o n a t e zone. I n b o t h zones, s e r p e n t i n e c o - e x i s t s w i t h the a l t e r a t i o n m i n e r a l s . B l a c k w a l l a l t e r a t i o n , a zone about 0.5 metres t h i c k , c o n s i s t s o f gray t o g r e e n i s h b l a c k r o c k c h a r a c t e r i z e d by c o a r s e l y c r y s t a l l i n e c h l o r i t e (1 mm t o 5 mm) and t r e m o l i t e (4 mm t o 20 mm). I t has r e p l a c e d h i g h l y f r a c t u r e d s e r p e n t i n -i t e . The c o n t a c t w i t h t h e a d j a c e n t t a l c - c a r b o n a t e zone o r s e r p e n t i n i t e i s s h a r p l y d e f i n e d . I t has a l s o a sharp and a b r u p t boundary w i t h t h e c o u n t r y r o c k w h i c h i s c a l c a r e o u s -q u a r t z - m u s c o v i t e s c h i s t . I n t h i n s e c t i o n , t h e b l a c k w a l l a l t e r a t i o n c o n s i s t s o f c h l o r i t e , t r e m o l i t e , t a l c , s e r p e n t i n e and opaque m i n e r a l s . Three t e x t u r a l v a r i e t i e s o f c h l o r i t e are found. One o c c u r s as band o f f l a k y c h l o r i t e c r y s t a l s , and a n o t h e r as s m a l l e r g r a i n s mixed w i t h s e r p e n t i n e . The t h i r d type, .forms v e i n s i n a d j a c e n t s e r p e n t i n i t e . T r e m o l i t e o c c u r s as v e i n s i n f r a c t u r e s , and i s r e s t r i c t e d t o a zone c l o s e t o the c o n t a c t w i t h c o u n t r y r o c k . The s i l i c a r e q u i r e d f o r 1: B l a c k w a l l a l t e r a t i o n zone c o n s i s t s o f h i g h l y f o l i a t e d t o a l m o s t m a s s i v e , m a i n l y dark c o l o u r e d c h l o r i t e - r i c h r o c k s t h a t form t h i n , s h a r p l y d e f i n e d , and n e a r l y c o n t i n u o u s r i n d s about u l t r a m a f i c b o d i e s . 92 i t s p r o d u c t i o n may have come from the q u a r t z - m u s c o v i t e s c h i s t and magnesium from the u l t r a m a f i c r o c k s . A t a l c - c a r b o n a t e zone w h i c h l i e s a d j a c e n t t o the b l a c k -w a l l a l t e r a t i o n zone i s about 0.3 metres t h i c k , m o d e r a t e l y s h e a r e d , and b u f f t o p a l e g r e e n i s h . I t i s more o r l e s s g r a d -a t i o n a l w i t h s e r p e n t i n i t e . The g r a d u a l t r a n s i t i o n o c c u r s t h r o u g h the development, i n the s e r p e n t i n i t e , o f t a l c and t a l c - c a r b o n a t e v e i n s ( P l a t e 3-11) m o s t l y i n s h e a r s u r f a c e s o f s e r p e n t i n i t e . Pure t a l c - c a r b o n a t e i s r a r e o t h e r t h a n i n v e i n s . I n t h i n s e c t i o n the average mode o f t a l c - c a r b o n a t e zone i s magnesite 50 p e r c e n t , a n t i g o r i t e 25 p e r c e n t , t a l c 20 p e r c e n t w i t h minor c h l o r i t e and c h r o m i t e . T a l c - c a r b o n a t e c o u l d be d e r i v e d d i r e c t l y from p e r i -d o t i t e o r from s e r p e n t i n i t e . P r e s e r v a t i o n o f s e r p e n t i n e mesh t e x t u r e i n t a l c - c a r b o n a t e and l a c k o f p e r i d o t i t e t e x t u r e s o r any p r i m a r y m i n e r a l s s u g g e s t t h a t i t was more p r o b a b l y d e r i v e d from s e r p e n t i n i t e . The so u r c e o f CO^ f o r the f o r m a t i o n o f t a l c - c a r b o n a t e seems t o have been c a l c a r e o u s c o u n t r y r o c k s . Abundance o f v e i n s o f t a l c - m a g n e s i t e i n s e r p e n t i n i t e might r e s u l t from a l o c a l i n c r e a s e i n X a l o n g f r a c t u r e s . C 0 2 3-2-C L a t e Stage A l t e r a t i o n a. S i l i c a - c a r b o n a t e a l t e r a t i o n S i l i c a - c a r b o n a t e r o c k i s made l a r g e l y o f v a r y i n g amounts 93 PLATE 3-11: Brownish and g r e e n i s h t a l c - c a r b o n a t e v e i n s i n g r a y i s h and i s o t r o p i c s e r p e n t i n e s . ( C r o s s -ed n i c o l s . ) 94 o f q u a r t z , c h a l c e d o n y , o p a l and magnesite w i t h l e s s a n k e r i t e , d o l o m i t e , c h r o m i t e and p i c o t i t e and r a r e m a r i p o s i t e , c l a c i t e and h u n t i t e {MgCa(CO^) 4}. Opal i s not as common as q u a r t z . The r o c k forms an a l t e r a t i o n zone a l o n g the mar g i n o f t h e s e r p e n t i n i t e b o d i e s ( F i g u r e 3-3, 3-4, P l a t e 3-12). Some s m a l l s h e a r e d s e r p e n t i n i t e b o d i e s a re c o m p l e t e l y r e p l a c e d , b u t t h i c k e r , m o r e massive ones are g e n e r a l l y r e p l a c e d o n l y a l o n g t h e i r s h e a r e d m a r g i n s . The r o c k i s e a s i l y r e c o g n i z e d by i t s pseudomorphic c h a r a c t e r a f t e r s e r p e n t i n e and i t s f r e q u e n t r e l a t i o n s h i p w i t h s e r p e n t i n i t e . I t s v a r i a t i o n i n appearance depends upon d i f f e r e n c e s i n m i n e r a l o g y o f the o r i g i n a l r o c k s , t h e i n t e n s i t y o f s h e a r i n g , t h e g r a i n s i z e o f r e p l a c i n g m i n e r a l s and the r e l a t i v e abundances o f q u a r t z and c a r b o n a t e m i n e r a l s . S i l i c a - c a r b o n a t e r o c k d e r i v e d from s h e a r e d s e r p e n t i n i t e r e t a i n s a l e n t i c u l a r n a t u r e . The d i f -f e r e n t l e n s e s and s t r e a k s a re g e n e r a l l y g r a y and green o f v a r i o u s shades; t h e she a r e d t e x t u r e may be a c c e n t u a t e d by v e i n i n g w i t h l i g h t - c o l o u r e d m a g n e s i t e , d o l o m i t e o r q u a r t z . W e a t h e r i n g g e n e r a l l y a l t e r s t he appearance o f s i l i c a -c a r b o n a t e r o c k , because f e r r o a n - m a g n e s i t e o r d o l o m i t e i s a l t e r e d by w e a t h e r i n g , l e a v i n g s u r f a c e c o a t i n g s o f h y d r a t e d f e r r i c - o x i d e s and s i l i c a . A ro c k w i t h more c a r b o n a t e t h a n s i l i c a u s u a l l y g i v e s r i s e t o an ocherous s o i l ( F i g u r e 3-3 around 2 N, 9 W) c o n t a i n i n g o n l y a few s i l i c i o u s f r a g m e n t s , one w i t h more s i l i c a t han c a r b o n a t e w e a t h e r s t o a w h i t e and brown r o c k . FIGURE 3-4: CROSS SECTION OF THE PORCUPINE SERPENTINITE BODY ALONG 12W. Note s i l i c a - c a r b o n a t e zone d i p p i n g 45*. (See l o c a t i o n a t F i g u r e 3-3.) 96 i 1 PLATE 3-12: N o r t h - w e s t e r n f a u l t c o n t a c t o f t h e P o r c u p i n e u l t r a m a f i c body i s w e l l marked by r u s t y l o o k i n g q u a r t z - c a r b o n a t e zone d i p p i n g 45" tpwards n o r t h w e s t . (Photograph taken l o o k i n g n o r t h e a s t . ) 97 Stages o f r e p l a c e m e n t from s e r p e n t i n e t o s i l i c a -c a r b o n a t e r o c k can be g e n e r a l i z e d . I n the e a r l i e s t s t a g e a n t i g o r i t e and c h r y s o t i l e v e i n s are r e p l a c e d by q u a r t z and l e s s abundant m a g n e s i t e , r a r e l y c a l c i t e i n c r a c k s g i v i n g a network o f i r r e g u l a r v e i n l e t s ( P l a t e 3-13). The r e p l a c e m e n t p r o c e s s i s found t o be e a s i e r f o r c h r y s o t i l e t h a n f o r a n t i -g o r i t e . S e c o n d l y , b a s t i t e and s e r p o p h i t e i n t h e c o r e (away from f r a c t u r e s ) a r e r e p l a c e d w i t h q u a r t z , magnesite and d o l - ; m i t e . F i n a l l y q u a r t z and minor magnesite r e p l a c e the r e -m a i n i n g s e r p e n t i n e m i n e r a l s . These s t a g e s p a r t i a l l y o v e r l a p . I t seems p o s s i b l e t h a t d u r i n g a l t e r a t i o n , t h e a l t e r a t i o n p r o d u c t s were not n e c e s s a r i l y d e p o s i t e d t o g e t h e r . I t i s thus c l e a r t h a t t h e development of t h e s i l i c a - c a r b o n a t e r o c k i s l a t e r than s e r p e n t i n i z a t i o n and c h r y s o t i l e v e i n f o r m a t i o n . There a r e two s t a g e s o f q u a r t z f o r m a t i o n . The e a r l y s t a g e q u a r t z i n t h i n s e c t i o n i s f i n e - g r a i n e d w i t h r a t h e r rounded o u t l i n e s and i n hand specimen has a m i l k y appear-ance. The second s t a g e q u a r t z i s c o a r s e - g r a i n e d and g e n e r a l l y c l e a r . I n some specimens, c a r b o n a t e g r a i n s appear t o have been b r o k e n o f f and i s o l a t e d w i t h i n p a t c h e s o f t h e second s t a g e q u a r t z i n d i c a t i n g t h a t c l e a r v a r i e t y q u a r t z c r y s t a l l i z e d l a t e r than most o f the magnesite and i t i s p r o b a b l e t h a t t h i s l a t e s t a g e o f s i l i c i f i c a t i o n i s u n r e l a t e d t o s i l i c a - c a r b o n a t e a l t e r a t i o n . Secondary m a g n e t i t e formed d u r i n g s e r p e n t i n i z a t i o n i s 98 PLATE 3-13: F i r s t s t age o f s i l i c a - c a r b o n a t e a l t e r a t i o n o c c u r r e d a l o n g c h r y s o t i l e v e i n s . White v e i n s c o n s i s t o f q u a r t z and magnesite pseudomorphs a f t e r c h r y s o t i l e . C h r y s o t i l e v e i n s a r e l i g h t g r een. 99 i n c o r p o r a t e d i n f e r r o - m a g n e s i t e and i s a l s o t r a n s f o r m e d i n t o h y d r o u s - i r o n o x i d e . Chromite remains m o s t l y u n a l t e r e d b u t l o c a l l y i s a l t e r e d t o ma r i p ' o s i t e . The p r e s e r v a t i o n o f c h r y -s o t i l e v e i n s , and l a r g e r t e x t u r e s and s t r u c t u r e s i n d i c a t e . t h a t t h e r e has been no a p p r e c i a b l e change i n volume. The average s i l i c a - c a r b o n a t e r o c k c o n s i s t s o f about 60 p e r c e n t of. c a r b o n a t e s , 35 p e r c e n t o f q u a r t z w i t h some c h r o m i t e , i r o n o x i d e s and m a r i p o s i t e . The p r o c e s s o f r e -placement i s m a i n l y d e h y d r a t i o n o f s e r p e n t i n e and c a r b o n a t i -z a t i o n ( F i g u r e 3-5). The s i l i c a - c a r b o n a t e zone i s i t s e l f zoned. From c o r e t o m a r g i n , t h e sequence o f a l t e r e d r o c k i s : s e r p e n t i n i t e w i t h some c a r b o n a t e s , t a l c - c a r b o n a t e r o c k , and s i l i c a c a r b o n -a t e r o c k . I t i s c o n s i d e r e d t h a t a l t e r a t i o n proceeds by t r a n s p o r t i n g CC>2 i n w a r d from s u r r o u n d i n g r o c k s a l o n g f r a t u r e s and g r a i n b o u n d r i e s . I t i s p o s s i b l e t h a t l i m e s t o n e and c a l -c areous r o c k s i n a d j a c e n t f o r m a t i o n were the s o u r c e o f CO,,. Quartz and magnesite a re formed from the r e a c t i o n o f s e r p e n t i n e and CC>2 a c c o r d i n g t o t h e f o l l o w i n g e q u a t i o n i n an open system ( F i g u r e 3-2, 3-5): S e r p e n t i n e + Carbon D i o x i d e -»-»-> Quartz + Ma g n e s i t e + Water M g 3 S i 2 0 7 . 2 H 2 0 + 3CC>2 2SiC> 2 + 3MgCC>3 + 2H 2 0 Even v e r y low CO„ v a l u e s o f t h e f l u i d phase can l e a d 100 S i 0 2 M g O FIGURE 3-5: DEHYDRATION, CARBONATIZATION AND S I L I C I F I -CATION OF SERPENTINE DURING SILICA-CARBONATE ALTERATION SHOWN ON S i 0 9 - C 0 9 - M g 0 - H 0 0 TETRAHEDRON. 101 t o f o r m a t i o n o f magnesite i n s e r p e n t i n e (Johannes, 1969). M a g n e s i t e and q u a r t z c o u l d a l s o be formed from s e r p -e n t i n e , h a v i n g t a l c as an i n t e r m e d i a t e s t e p ( F i g u r e 3-2, 3-5) . S e r p e n t i n e + Carbon D i o x i d e ->-»-»- T a l c + M a g n e s i t e + Water 2 M g 3 S i 2 0 ,2H 0 + 8CC>2 -»-»-»• M g 3 S i 4 0 2 2 . H 2 0 + 3MgCC>3 + H 20 T h i s r e a c t i o n t a k e s p l a c e a t s l i g h t l y h i g h e r C 0 2 v a l u e s and h i g h e r t e m p e r a t u r e than d i r e c t a l t e r a t i o n t o q u a r t z and magnesite from s e r p e n t i n e (Greenwood, 1967; Johannes, 1969). T a l c i s u n s t a b l e w i t h i n c r e a s i n g C 0 2 v a l u e s i n the f l u i d phase, and y i e l d s magnesite and q u a r t z a c c o r d i n g t o the f o l l o w i n g r e a c t i o n ( F i g u r e 3-2, 3-5): T a l c + Carbon D i o x i d e Quartz + M a g n e s i t e + Water M g 3 S i 4 0 2 2 . H 2 0 + 3C0 2 4 S i 0 2 + 3 M 9 C 0 3 + H 2 ° A b i g zone (14 metres a c r o s s ) o f o p a l , r i c h i n c l a y m i n e r a l s and l i m o n i t e ( P l a t e 3-14), appears t o be t h e r e s u l t o f p r e s e n t day w e a t h e r i n g . These o p a l i n e masses are m a i n l y r e s t r i c t e d t o near s u r f a c e l o c a t i o n s and were d e v e l o p e d i n the s i l i c a - c a r b o n a t e zones. 1 0 2 IN. PLATE 3 - 1 4 : B l a c k chunks of o p a l s u r r o u n d e d by l i m o n i t i c i r o n - o x i d e s g i v e r i s e t o a unique l o o k i n g r u s t y zone a t the h i g h e s t l e v e l o f the P o r c u p i n e p i t . A d j a c e n t gray zone i s s e r p e n t i n i t e 103 b. Q u a r t z - m a g n e site v e i n s Q u a r t z - m a g n e s i t e v e i n s a re the r e s u l t o f l a t e s i l i c a -c a r b o n a t e a l t e r a t i o n and a r e found i n shear zones o r minor f a u l t s t h r o u g h o u t the u l t r a m a f i c b o d i e s o r a t c o n t a c t s w i t h t h e c o u n t r y r o c k . They c u t a c r o s s the p r e v i o u s l y d e s c r i b e d q u a r t z - c a r b o n a t e zones. M a g n e s i t e , q u a r t z and minor f i b r o u s b r u c i t e , d o l o m i t e and s e r p e n t i n e a re the c h i e f m i n e r a l s . The v e i n s a re 2 t o 12 c e n t i m e t r e s wide and m a i n l y c o n s i s t o f c o a r s e (4 t o 50 mm) magnesite c r y s t a l s and q u a r t z . Many o f them r e p l a c e s h e a r e d v e i n s ( P l a t e 3-15) f o r m e r l y f i l l e d w i t h p i c r o l i t e , b r a i d e d a n t i g o r i t e , s h e a r e d c h r y s o t i l e o r sheared t a l c o s e gouge. 3-3 STRUCTURE The u l t r a m a f i c body, o r i g i n a l l y a s i n g l e mass (150 0 metres by 350 metres) has been f a u l t e d and now c o n s i s t s o f t h r e e p a r t s , the l a r g e w e s t e r n P o r c u p i n e body, the c e n t r a l Creek body and e a s t e r n Snow Shoe body ( F i g u r e 3-6). F a u l t s s e p a r a t i n g the t h r e e p a r t s s t r i k e n o r t h e r l y and d i p n e a r l y v e r t i c a l ( P l a t e 2-14). A t each f a u l t , t he w e s t e r n b l o c k i s down-thrown. These b o d i e s a r e surrounded by l i m y - c a r b o n a c e o u s a r g i l l i t e and minor c a l c a r e o u s s c h i s t . The upper g e n t l y 104 PLATE 3-15: Quartz-magnesite v e i n o f l a t e s i l i c a -c a r b o n a t e a l t e r a t i o n . These v e i n s are always seen t o r e p l a c e s e r p e n t i n e a l o n g s h e a r f r a c t u r e s i n the P o r c u p i n e p i t . s e w 4 0 W 3 0 W 2 0 W IOW OOO ICE 2 0 E 3 0 E 15 S o FIGURE 3-6: ORE BEARING PORCUPINE, CREEK AND SNOW SHOE SERPENTINITE BODIES 1 = mme c r u s h e r . 2 = d r i l l - c o r e s t o r a g e . 3 = d r i l l s t o r a g e . F-F = f a u l t B.L. = base l i n e . L 106 convex s u r f a c e o f t h e p o r c u p i n e body p l u n g e s about 10" i n a d i r e c t i o n s o u t h 55*west ( P l a t e 3-16). The n o r t h w e s t e r n con-t a c t o f the P o r c u p i n e body i s a f a u l t t h a t d i p s 45* n o r t h w e s t -e r l y ( P l a t e 3-12) and i s a l m o s t p a r a l l e l t o b e d d i n g i n t h e a r -g i l l i t e i n t h a t v i c i n i t y ( F i g u r e 2-2). A t t h e f a u l t , a r g i l -l i t e and s e r p e n t i n i t e are h i g h l y s h e a r e d . The m i d d l e p a r t o f t h e s o u t h e a s t e r l y c o n t a c t d i p s about 60* s o u t h e a s t as d e f i n e d by diamond d r i l l i n g ( F i g u r e 3-7, 3-8, 3-9). I t i s a l s o a f a u l t c o n t a c t w i t h a h i g h l y s h e a r e d s e r p e n t i n i t e c o n t a c t zone. A r g i l -l i t e and s c h i s t a t t h i s v i c i n i t y d i p s s o u t h e r l y . C r o s s s e c t i o n s based on open p i t exposures and p a r t l y on diamond d r i l l d a t a show t h a t the o u t l i n e o f the upper p a r t o f the u l t r a m a f i c mass c u r v e s and resembles an open f o l d ( F i g u r e 3-7, 3-8). Superimposed on t h i s s u g g e s t e d f o l d are o u t l i n e s t h a t resemble recumbent f o l d s o f v a r i o u s s t y l e s ( F i g u r e 3-10, 3-11),. R e l a t i v e l y s m a l l , t i g h t , recumbent f o l d s a r e d i s t i n c t a l o n g the c o n t a c t o f s i l i c a - c a r b o n a t e and a r g i l l i t e ( F i g u r e 3-12, 3-13). One can s p e c u l a t e t h a t the recumbent f o l d s be-l o n g t o t h e f i r s t phase o f d e f o r m a t i o n t h a t a f f e c t e d t h e a r e a , the n o r t h w e s t c o n t a c t f a u l t i s p r o b a b l y r e l a t e d t o the second phase o f d e f o r m a t i o n . 3-4 ORIGIN Most g e o l o g i s t s r e c o g n i z e t h r e e b road k i n d s o f u l t r a -107 o ION. i i PLATE 3-16: O r e - b e a r i n g P o r c u p i n e u l t r a m a f i c body p l u n g i n g 10' towards 235". (Photograph t a k e n l o o k i n g s o u t h - w e s t e r l y . ) 8 N 6N 4N 2N 0.0 2S 4S 6S 100 100 Ft. 50 Mtrs . _ J 5 U R F A C £ 18 0 0 ' -1 1 6 0 0 ' 1 4 0 0 FIGURE 3-7: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 19W. Note southeast contact dipping about 65". ( See location-at Figure 3-3.) 8 N 6N 4 N 2N O.O 2S 4S 6S 100 0 L_ 100 Ft. 50Mtrs. I ^ 4 18 0 0 ' -4 1 1 f e ' 1 6 0 0 ' -4 1 4 0 0 ' - I FIGURE 3-8: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 20W. Note so u t h e a s t c o n t a c t d i p p i n g about 60*. ( See l o c a t i o n a t F i g u r e 3-3.) 8 N 6N 4N 2N O.O 100 4S 6 S 100 Ft. 50 Mtrs . S a f> /r 4 c , 18 0 0 ' A 1 6 0 0 H Fault FIGURE 3-9: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 26W. Note southeast contact d i p p i n g about 7(T. ( See l o c a t i o n at F i g u r e 3-3.) FIGURE 3-10: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 24W. Note o u t l i n e o f c o n t a c t resembles recumbent f o l d . ( See l o c a t i o n a t F i g u r e 3-3.) FIGURE 3-11: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 23W. Note o u t l i n e o f c o n t a c t resembles recumbent f o l d ( See l o c a t i o n a t F i g u r e 3-3.) FIGURE 3-12: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 10W. Note o u t l i n e o f c o n t a c t o f s i l i c a c a r b o n a t e and a r g i l l i t e r e s e m b l e s recumbent f o l d . ( See l o c a t i o n a t F i g u r e 3-3.) 8 N 6N 4 N 2N O.O 2S 4S 6S 100 100 Fl. 5 0 M t r s . — J 18 0 0 ' - J 1 6 0 0 ' MOO ' ln^vRfr^r3L CRSSf S E ™ 0 N L 0 0 K I N G NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 9W. Note o u t l x n e o f c o n t a c t o f s i l i c a - c a r b o n a t e and a r q i l l i t e r e s e m b l e s recumbent f o l d . ( See l o c a t i o n a t F i g u r e 3-3.) 115 m a f i c r o c k s . L a y e r e d u l t r a m a f i c r o c k s a r e s a i d t o be due t o magmatic d i f f e r e n t i a t i o n and c r y s t a l s e t t l i n g (Wager and Brown, 1967), o r p e r h a p s , d e f o r m a t i o n and s o l i d f l o w (Loney e t a l . , 1 9 7 1 ) . The second k i n d , r o c k s o f zoned u l t r a m a f i c complexes have been e x p l a i n e d i n d i f f e r e n t ways by d i f f e r e n t r e s e a r c h e r s ; some b e l i e v e them t o be magmatic, o t h e r s meta-s o m a t i c ( Z a v a r i t s k y , 1928; W a l t o n , 19 51; T a y l o r and N o b l e , 1960; B h a t t a c h a r j i and S m i t h , 1963; McTaggart, 1971). s t r u c -t u r e s and t e x t u r e s such as cumulate t e x t u r e s , c r y p t i c z o n i n g , graded b e d d i n g , slump s t r u c t u r e s and c h a n n e l f i l l s t r u c t u r e s are found i n b o t h l a y e r e d and zoned u l t r a m a f i c i n t r u s i o n s ( I r v i n e , 1967; Wager and Brown, 1967). None o f t h e s e f e a t u r e s i s r e c o g n i z e d i n the C l i n t o n Creek u l t r a m a f i c b o d i e s . The a u t h o r , t h e r e f o r e , b e l i e v e s the C l i n t o n Creek u l t r a m a f i c r o c k s t o b e l o n g t o the t h i r d k i n d o f u l t r a m a f i c body, the a l p i n e t y p e , w h i c h i s d i s c u s s e d below. Moores and MacGregor (1972) s t a t e t h a t t h e emplacement o f a l p i n e t ype u l t r a m a f i c b o d i e s i s due t o t h e i n t e r a c t i o n o f two o r more l i t h o s p h e r i c p l a t e s , a t l e a s t one o f w h i c h b e a r s c o n t i n e n t a l c r u s t . They d i s t i n g u i s h f o u r t y p e s : (a) b o d i e s w i t h t h e r m a l a u r e o l e s s u g g e s t i n g i n t r u s i o n a t h i g h tempera-t u r e , (b) mantle s l a b s formed by d i a p i r i c u p w e l l i n g o f mantle m a t e r i a l a t s p r e a d i n g c e n t r e s w h i c h were s u b s e q u e n t l y and i n d e p e n d e n t l y emplaced onto the c o n t i n e n t a l m a r g i n s , (c) d i s r u p t e d mantle s l a b s i n c o r p o r a t e d i n t o melanges; and (d) c o n formable b o d i e s i n r e g i o n a l l y metamorphosed t e r r a n e s r e -116 p r e s e n t i n g r e c r y s t a l l i z a t i o n and d e f o r m a t i o n o f o c c u r r e n c e s o f t y p e s a, b and c. C e r t a i n f e a t u r e s s u g g e s t t h a t t h e u l t r a m a f i c r o c k s o f the C l i n t o n Creek a r e a f a l l i n t o group c o r d. Pronounced mosaic t e x t u r e s i n weakly s e r p e n t i n i z e d p e r i d o t i t e are s a i d t o r e s u l t from s y n t e c t o n i c r e c r y s t a l l i z a -t i o n (Ragan, 1969) . B o t h mosaic t e x t u r e and s t r a i n e d undu-l a t o r y e x t i n c t i o n a r e c o n s i d e r e d t o be caused by s o l i d s t a t e d e f o r m a t i o n i n the p r e s s u r e and t e m p e r a t u r e c o n d i t i o n s o f t h e ! upper mantle ( N i c h o l a s e t a l . , 1972). Very low a luminium and c a l c i u m (Appendic C) are c o n s i d e r e d t o be c h a r a c t e r i s t i c o f c r y s t a l l i n e mantle r e s i d u e l e f t a f t e r e x t r a t i o n o f b a s a l t l i q u i d ( D i c k e y , 19 70) . F o l i a t i o n may have d e v e l o p e d d u r i n g a s c e n t of mantle m a t e r i a l towards the s u r f a c e . W i t h r e l e a s e o f p r e s s u r e s u b s o l i d u s r e a c t i o n s p r o b a b l y r e s u l t e d i n e x s o l u -t i o n o f c l i n o p y r o x e n e l a m e l l a e i n o r t h o p y r o x e n e (Ragan, 1967; Loney e t a l . , 1971; Himmelberg and Loney, 1963). O r i g i n a l u l t r a m a f i c r o c k s o f t h e a r e a a r e b e l i e v e d t o have been I h e r z o l i t e , h a r z b u r g i t e , p y r o x e n i t e and d u n i t e . C ountry r o c k s c o n s i s t o f g r e e n s t o n e , some c h e r t , a r g i l l i t e and l i m e s t o n e and w i t h the u l t r a m a f i c r o c k s , can be c o n s i d e r e d t o form an o p h i o l i t e . U l t r a m a f i c b o d i e s about 48 k i l o m e t r e s west o f t h e C l i n t o n Creek a r e a i n A l a s k a a r e i n t e r p r e t e d as o p h i o -l i t e s by F o s t e r (1974). The a b s o l u t e age o f f o r m a t i o n o f the u l t r a m a f i c b o d i e s 117 i s n o t known. However, t h e i r minimum age o f emplacement can be d e t e r m i n e d . The o l d e s t t i g h t i s o c l i n a l f o l d s w i t h a l m o s t h o r i z o n t a l a x i a l p l a n e s (F^) seem t o i n v o l v e t h e mar-g i n s o f the u l t r a m a f i c body ( F i g u r e 3-11). As t h i s o l d e s t known f i r s t phase d e f o r m a t i o n o c c u r r e d w i t h the main e p i s o d e o f metamorphism, i n Permian time (see T a b l e 2-1), the emplace-ment o f the u l t r a m a f i c r o c k s c o u l d n o t be younger t h a n Permian. A zone o f u l t r a m a f i c masses t o g e t h e r w i t h l e n s e s o f a m p h i b o l i t e and marble t r e n d n o r t h w e s t e r l y c l o s e t o and p a r -a l l e l t o t h e T i n t i n a f a u l t where i t c r o s s e s the A l a s k a - Y u k o n T e r r i t o r y b o r d e r . These a m p h i b o l i t e s and m arbles are i n c o r -p o r a t e d i n t o and i n t e r l a y e r e d w i t h low grade metamorphic r o c k s o f g r e e n s c h i s t f a c i e s . O c c u r r e n c e s o f b l u e amphibole i n q u a r t -z i t e and s m a l l b o d i e s o f e c l o g i t e a r e r e p o r t e d near Ross R i v e r a l o n g T i n t i n a T r e n c h ( F o s t e r , 1974). These d a t a s u g g e s t t h a t i t i s p o s s i b l e t h a t the T i n t i n a f a u l t was an open r i f t i n con-t i n e n t a l c r u s t i n e a r l y Permian t i m e , and t h a t u l t r a m a f i c r o c k s and a s s o c i a t e d l e n s e s o f h i g h grade metamorphites were emplaced t e c t o n i c a l l y when the r i f t c l o s e d . The r o c k s i n q u e s t i o n were t h r u s t southwestward o v e r Yukon C r y s t a l l i n e P l a t e a u a t the time o f the c l o s i n g o f the t r e n c h (Tempelman-K l u i t , 1976). T h e r e f o r e the s e r p e n t i n i z e d u l t r a m a f i c r o c k s m ight r e p r e s e n t r o c k s t h a t were t h r u s t onto Yukon C r y s t a l l i n e P l a t e a u b e f o r e o r d u r i n g t h e main metamorphism (Permian) and w h i c h t h r o u g h subsequent d e f o r m a t i o n and metamorphism became i n t i m a t e l y - m i x e d w i t h the r o c k s i n w h i c h they were emplaced. 118 CHAPTER IV THE CLINTON CREEK ASBESTOS DEPOSIT 4-1 INTRODUCTION The C l i n t o n Creek mine, about 22 5 k i l o m e t r e s s o u t h o f the A r t i e C i r c l e , was t h e most n o r t h e r l y open p i t ( P l a t e 4-1) o p e r a t i o n i n Canada. I t i s a t an e l e v a t i o n o f 535 metres on P o r c u p i n e H i l l w h i c h o v e r l o o k s C l i n t o n Creek ( F i g u r e 2 - 2 ) . The m i l l i s s i t u a t e d on Trace H i l l on the o p p o s i t e s i d e o f C l i n t o n Creek, and t h e o r e was t r a n s p o r t e d by a m i l e - l o n g t r a m l i n e . The ore t o waste r a t i o average was 1:5 and the average c h r y s o t i l e - f i b r e l e n g t h between 1.5 mm and 3.0 mm. The t h r e e o r e - b e a r i n g u l t r a m a f i c b o d i e s o u t l i n e d by diamond d r i l l i n g , was 270 metres wide and 1,400 metres l o n g ( F i g u r e 3 - 6 ) . The main P o r c u p i n e o r e zone i s 135 metres w i d e , and 535 metres l o n g , and has been d r i l l e d t o a depth o f 900 f e e t ( F i g u r e 3 - 7 ) . 4-2 CHRYSOTILE VEINS 119 PLATE 4-1: C l i n t o n Creek open p i t a s b e s t o s mine. P o r c u p i n e p i t ( r i g h t ) ; Creek p i t ( m i d d l e ) ; Snow Shoe p i t ( l e f t ) . (Photograph t a k e n l o o k i n g towards southwest.) 120 4-2-A T e x t u r e s and S t r u c t u r e s Two d i f f e r e n t t y p e s o f c h r y s o t i l e v e i n s a re d i s t i n g -u i s h e d : c h r y s o t i l e - f i b r e v e i n s and p i c r o l i t e v e i n s . a. C h r y s o t i l e - f i b r e v e i n s C h r y s o t i l e f i b r e v e i n s a r e o f two t y p e s : c r o s s - f i b r e and s l i p - f i b r e v e i n s . The m a j o r i t y o f t h e f i b r e v e i n s i n the C l i n t o n Creek mine c o n s i s t o f c r o s s - f i b r e c h r y s o t i l e and are under s i x mm i n w i d t h . I n some, c h r y s o t i l e f i b r e s l i e p e r p e n d i c u l a r t o t h e v e i n w a l l , b u t i n o t h e r s t h e f i b r e s form an a c u t e a n g l e w i t h the w a l l ( P l a t e 4-2). F i g u r e 4-1, A and B show common v a r i a t i o n s o f the f i r s t two t y p e s ; and i n d i v -i d u a l f i b r e s pass from one w a l l o f the v e i n t o the o t h e r w i t h p e r f e c t c o n t i n u i t y . Many f i b r e - v e i n s show p a r t i n g s . Those may be i n c l i n e d ( F i g u r e 4-1-C) o r p a r a l l e l ( F i g u r e 4-1-D) t o the v e i n w a l l . B o t h i n c l i n e d and c e n t r a l p a r t i n g s a re f i l l e d commonly w i t h m a g n e t i t e and l e s s commonly w i t h p i c r o l i t e . I n some specimens, p a r t i n g s d i v i d e d the f i b r e s i n t o l e n s e s ( F i g u r e 4-1-C), and i n t h e s e t h e r e i s no change i n d i r e c t i o n o f f i b r e s on each s i d e o f the p a r t i n g . A few v e i n s are made up o f f i b r e l e n s e s s e p a r a t e d by a n t i g o r i t e , p i c r o l i t e o r m a g n e t i t e ( F i g u r e 4-1-E). S l i p - f i b r e v e i n s ( F i g u r e 4-1-F) i n wh i c h most o f t h e c h r y s o t i l e f i b r e s a re a l m o s t p a r a l l e l t o the v e i n w a l l , o c c u r i n c o n j u n c t i o n w i t h the c r o s s - f i b r e o r i n zones where 121 0 -\MIV I I PLATE 4-2: C r o s s - f i b r e c h r y s o t i l e v e i n i n t h i n s e c t i o n . F i b r e s l i e o b l i q u e l y t o t h e w a l l o f the v e i n . A d j a c e n t , gray and i s o t r o p i c m i n e r a l i s a n t i g o r i t e . ( C r ossed n i c o l s . ) A B E F FIGURE 4-1: CHRYSOTILE-FIBRE VEINS. A,B. Fibres oriented perpendicular and i n c l i n e d to vein walls. C. Inclined partings divided the f i b r e s but the f i b r e s do not change i n d i r e c t i o n on each side of the parting. D. Central p a r t i n g i s usually f i l l e d with magnetite. E. Composite vein i s made up of f i b r e lenses separated by magnetite, p i c r o l i t e or a n t i g o r i t e . F. S l i p - f i b r e vein. (P = p i c r o l i t e ; M = magnetite; S = non-fibre serpentine; Ch = c h r y s o t i l e - f i b r e . ) 123 d e f o r m a t i o n has been i n t e n s e . F i b r e v e i n s may be s t r a i g h t o r c u r v e d ( F i g u r e 4-2-A). Some i n t e r s e c t ( F i g u r e 4-2-B) o r d i v e r g e ( F i g u r e 4-2-C). C o l o u r s o f v e i n s range from l i g h t green t o dark green b u t i n d -i v i d u a l v e i n s are o f o n l y one c o l o u r . Most o f t h e f i b r e s s e p a r a t e r e a d i l y and are s o f t l i k e s i l k b u t some c h r y s o t i l e v e i n s a r e h a r s h and do not s e p a r a t e e a s i l y i n t o f i n e f i b r e s . A d j a c e n t f i b r e s a r e p a r a l l e l . Some o f them are p e r f e c t l y s t r a i g h t b ut u s u a l l y minute c o r r u g a t i o n s a r e p r e s e n t w h i c h g i v e r i s e t o a c h a t o y a n t and banded appearance o f the v e i n ( F i g u r e 4-1-B). F i n e - g r a i n e d m a g n e t i t e o c c u r s as t h i n s h e e t s o r l e n s e s w h i c h a r e o r i e n t e d p a r a l l e l o r i n c l i n e d t o the w a l l , o r p a r a l l e l t o f i b r e s ( F i g u r e 4-2-D). M a g n e t i t e commonly f i l l s t h e a c u t e a n g l e a t low a n g l e j u n c t i o n s ( 4 - 2 - E ) . A t some v e i n j u n c t i o n s t h e r e i s a c o n f u s e d m i x t u r e o f f i b r e , m a g n e t i t e and s e r p e n t i n e . A t o t h e r v e i n j u n c t i o n s the f i b r e o f one v e i n w i l l bend and become o r i e n t e d p a r a l l e l t o t h e f i b r e o f t h e o t h e r v e i n w i t h o u t any d i s c o n t i n u i t y (4-2-E and F) . A t some j u n c t i o n s f i b r e s on one v e i n c u t a c r o s s the f i b r e s o f a n o t h e r v e i n c o m p l e t e l y ( F i g u r e 4-2-B). b. P i c r o l i t e v e i n s P i c r o l i t e , n o n - f i b r o u s c h r y s o t i l e , compared t o c h r y -s o t i l e f i b r e , i s r e l a t i v e l y h a r d , p a l e green t o y e l l o w i s h g r e e n , and has a s p l i n t e r y f r a c t u r e . P i c r o l i t e v e i n s o c c u r 124 B D FIGURE 4-2: CHARACTERISTICS OF CHRYSOTILE-FIBRE VEINS. A. Two f i b r e veins cut across each other at d i f f e r e n t points. B. Fibre i n vein X c r y s t a l l i z e d i n an expansion fracture which separates vein Y perpendicularly. C. Magnetite commonly f i l l s acute angle at low angle junction D. Magnetite occurs as thin; sheets or lenses i n fi b r e - v e i n s . E. F. F i b r e of one vein bands and becomes oriented p a r a l l e l to the f i b r e of the other vein without d i s c o n t i n u i t y . ( Ch = c h r y s o t i l e ; M = magnetite; S = non-fibre serpentine). 125 m o s t l y a l o n g f a u l t s u r f a c e s , g e n e r a l l y w i t h f i b r e v e i n s t h a t a r e m o s t l y o f s l i p - f i b r e , and r a r e l y as i s o l a t e d f r a c t u r e f i l l i n g s . P i c r o l i t e appears t o be contemparaneous w i t h o r l a t e r t han c h r y s o t i l e f i b r e . V e i n s range i n w i d t h from m i c r o s c o p i c t o e i g h t c e n t i m e t r e s . A l t h o u g h some o f t h e v e i n s are h a r d and compact, o t h e r s a r e s o f t due t o a h i g h c o n t e n t o f uncombined w a t e r , f o r they t e n d t o l o s e w e i g h t and crumble a f t e r b r i e f exposure t o t h e atmosphere. D e l i c a t e bands o r l e n s e s o f p i c r o l i t e p a r a l l e l i n g t h e w a l l s o f c h r y s o t i l e v e i n s a r e u s u a l l y o n l y a s m a l l f r a c t i o n o f a m i l l i m e t r e i n t h i c k n e s s but may r e a c h as much as sev-e r a l m i l l i m e t r e s . The banding which i s f u r t h e r emphasized by s l i g h t d i f f e r e n c e s i n c o l o u r and p a r t i n g between s u c c e s s -i v e bands i s o r d i n a r i l y s h a r p ( P l a t e 4-3). V e r y few bands are p e r f e c t l y s t r a i g h t ; t h ey m o s t l y r e f l e c t t h e i r r e g u l a r -i t i e s i n the v e i n w a l l , w h i c h i s s l i g h t l y wavy. The b a n d i n g does n ot ex t e n d a c r o s s the f u l l w i d t h o f ev e r y v e i n , b u t i s c o n f i n e d t o one s i d e o f t h e v e i n . Under m i c r o s c o p e p i c r o l i t e d i s p l a y s d e l i c a t e b a n d i n g p a r a l l e l t o the v e i n w a l l s ( P l a t e 4-3), and i n d i v i d u a l bands o f p i c r o l i t e are found t o be composed o f t r a n s v e r s e f i b r e s w h i c h occupy a p o s i t i o n anywhere from normal t o o b l i q u e t o the margins o f the bands ( P l a t e 4-3). V a r i a t i o n i n t h e pos-i t i o n o f e x t i n c t i o n from band t o band, i s due t o s l i g h t d i f -f e r e n c e s i n o r i e n t a t i o n o f the f i b r e s i n s u c c e s s i v e bands. The c o n t a c t between the v e i n and w a l l r o c k may be sharp o r 126 0 - 1 M M -I I PLATE 4-3: l i g h t green, p a r a l l e l , sharp banding of p i c r o l i t e , a t l e f t hand top, d i s p l a y s f i b r e -l i k e forms which are t r a n s v e r s e to banding. Purple band i s c h r y s o t i l e - f i b r e . Gray and i s o t r o p i c m i n e r a l a t r i g h t hand bottom corner i s a n t i g o r i t e . (Crossed n i c o l s . ) 127 g r a d u a l . Not a l l p i c r o l i t e v e i n s have a banded n a t u r e , some are amorphous o r c r y p t o c r y s t a l l i n e . U s u a l l y the s m a l l e s t p i c r o l i t e v e i n s a r e amorphous. U n l i k e c h r y s o t i l e - f i b r e v e i n s , p i c r o l i t e v e i n s a r e d e v o i d o f m a g n e t i t e . I n p l a c e s m a g n e t i t e i s found as i n c l i n e d p a r t i n g s o r c o a t i n g i n c o n t r a s t t o m a g n e t i t e i n f i b r e v e i n s ( F i g u r e 4-3-A and B ) . Commonly f i b r e v e i n s end a b r u p t l y a t p i c r o l i t e v e i n s ( F i g u r e 4-3-C) and such p i c r o l i t e v e i n s a re g e n e r a l l y s l i c k e n s i d e d and l i e a l o n g t h e d i r e c t i o n o f major shear p l a n e s . The sense o f movement on such p i c r o l i t e - b e a r i n g shears i s g e n e r a l l y normal r a t h e r than r e v e r s e . C h r y s o t i l e - f i b r e s i n c o n t a c t w i t h o r c l o s e t o p i c -r o l i t e v e i n s a r e i n v a r i a b l y b r i t t l e and b r o w n i s h . P i c r o l i t e s e l v a g e s on c h r y s o t i l e - f i b r e v e i n s a re t h i c k on one s i d e o f the f i b r e v e i n and t h i n o r absent on the o t h e r s i d e . T h i s might be due t o l a t e d e f o r m a t i o n e f f e c t s on t h e c h r y s o t i l e v e i n , f o r t h e r e are some i n d i c a t i o n s t h a t c h r y s o t i l e f i b r e has been deformed and a l t e r e d t o p i c r o l i t e ( F i g u r e 4-3-D and E ) . F i g u r e 4-3-F shows c r o s s - f i b r e changed t o s l i p -f i b r e and then t o p i c r o l i t e o r d i r e c t l y t o p i c r o l i t e . 4-2-B R e l a t i o n s h i p w i t h S e r p e n t i n e W a l l Rock The c o n t a c t o f c h r y s o t i l e - f i b r e and w a l l r o c k i s sha r p and g e n e r a l l y p l a n a r , b u t minor c r e n u l a t i o n s a re not uncommon. The w a l l may be i n d i r e c t c o n t a c t w i t h f i b r e o r c o a t e d w i t h m a g n e t i t e o r s l i c k e n s i d e d p i c r o l i t e . On a 128 S F FIGURE 4-3: CHARACTERISTICS OF PICROLITE VEINS. A. P i c r o l i t e occurs as par t i n g i n c h r y s o t i l e - f i b r e vein. B. P i c r o l i t e forms a coating on c h r y s o t i l e - f i b r e vein. C. P i c r o l i t e stops the continuation of some f i b r e vein. D. P i c r o l i t e forms a pseudomorphs afte r deformed s l i p - f i b r e . E. P i c r o l i t e occurs at an acute angle to f i b r e i n same vein. F. Successive change of c r o s s - f i b r e to s l i p - f i b r e and then to p i c r o l i t e . ( P = p i c r o l i t e ; .Ch = c h r y s o t i l e - f i b r e ; S = non-fibre serpentine ) . 129 m a c r o s c o p i c s c a l e v e i n w a l l s match, but under t h e m i c r o -scope t h e r e a re minor e x c e p t i o n s . I n c l u s i o n s o f w a l l r o c k i n t he v e i n s a r e o b s e r v e d here and t h e r e and some o f t h e s e fragments match t h e a d j a c e n t w a l l . F i b r e v e i n s t h a t end a b r u p t l y a g a i n s t a n o t h e r v e i n do not t a p e r i n w i d t h . In a few cases v e i n s t a p e r and f i n a l l y d i s a p p e a r ( P l a t e 4-4). 4-2-C C h e m i s t r y o f C h r y s o t i l e and A n t i g o r i t e A t o t a l o f 97 specimens o f c h r y s o t i l e (33) and a n t i -g o r i t e (64) were c o l l e c t e d from the C l i n t o n Creek a r e a t o stud y t h e i r r e s p e c t i v e c h e m i s t r i e s . X-ray a n a l y s i s showed t h a t no o t h e r s e r p e n t i n e s p e c i e s were p r e s e n t . C h e m i c a l a n a l y s i s o f a l l samples were done u s i n g an ARL e l e c t r o n m i c r o p r o b e (Model-SEMO) i n the Department o f G e o l o g i c a l S c i e n c e s , U n i v e r s i t y o f B r i t i s h Columbia w i t h a s s i s t a n c e o f Mr. G. Georgakopoulos. Samples were a n a l y z e d f o r e l e v e n o x i d e s ( Na 20, MgO, A l 2 ° 3 f S i ° 2 ' K 2 ° ' C a 0 ' T i ° 2 ' C r 2 ° 3 ' M n ° ' FeO, and NiO) . R e s u l t s a re l i s t e d i n T a b l e 4-1.''" Means,stan-d a r d d e v i a t i o n s and v a r i a n c e s a re g i v e n i n a s t a t i s t i c a l summary (Table 4-2, 4-3). F i g u r e 4-4 and 4-5 a r e h i s t o -grams showing c o m p o s i t i o n a l v a r i a t i o n o f t h e major o x i d e s t h a t a r e d i f f e r e n t s t a t i s t i c a l l y i n the two s e r p e n t i n e min-e r a l s . These h i s t o g r a m s i l l u s t r a t e t he l i m i t e d c o m p o s i t i o n -1: See Appendix E 130 O - & r i M . I 1 PLATE 4 - 4 : Tapered, l i g h t gray c h r y s o t i l e -f i b r e v e i n . Note c r o s s - c u t t i n g v e i n , s u g g e s t i n g d i f f e r e n t p e r i o d s o f c h r y s o t i l e - f i b r e f o r m a t i o n . A l s o note m a t c h i n g w a l l s . (Crossed n i c o l s . ) 131 TABLE 4-2 S T A T I S T I C A L SUMMARY OF ELEVEN OXIDES OF 33 CHRYSOTILE SAMPLES O x i d e s A r i t h m e t i c M e a ns(X) S t d . D e v i a t i o n ( S ) V a r i a n c e ( S ) N a 2 0 MgO A l 2 ° 3 S i 0 2 K 2 0 CaO T 1 0 2 C r 2 0 3 MnO FeO NiO 0.0318 3y .6417 0. 8351 40.4060 0 .0306 0 .0397 0.0336 0.3379 0.0312 2.12y7 0.2079 0.0101 0.4369 0.2676 0.8466 0.0152 0.0230 0.0197 0.3130 0.0192 0.6585 0.1255 0 .0001 0.1y09 0. 0716 0.7168 0 . 0002 0.0005 0.0004 0.0980 0.0004 0.4336 0.0158 132 TABLE 4-3 S T A T I S T I C A L SUMMARY OF ELEVEN OXIDES OF 6 4 ANTIGORITE SAMPLES 0 x 1 d e s A r i t h m e t i c M e a ns(X) S t d . D e v i a t i o n ( S ) V a r i a n c e ( S 2 ) N a 2 0 0.0208 0.0113 0.0001 MgO 38.0282 0.6792 0.4613 A 1 2 ° 3 0.9456 0.3603 0.1298 sio 2 41.9354 0.9900 0.9802 K 2 0 0.0248 0.0148 0.0002 CaO 0.030U 0.0225 0.0005 T i 0 2 0.0237 0.0174 0.0003 C r 2 0 3 0.2961 0.2266 0.0513 MnO 0.0487 0.0418 0.0017 FeO 2.9778 0.7924 0.6279 N i O 0.1961 0.1405 0.0198 MEAN ( Y ) 380262 STD. DEVIATION (S) 0-6792 CLASS INTERVAL (CL) 1-65 2 0 i 10 « cr 201 37 38 % MgO by wt. 39 oJ/W 0-9456 0-3603 0 0901 201 4I-9354 0-99 0-245 2-9778 0-7924 0-I98 l-O I-5 %AI 2 03by wt. %Si0 2 by wt. % FeO by wt. ^ G ^ E , ™ ! i „ „ - ™ Q " ™ ? Y _ ? I A G R A M S 0 F M < 3 ° ' A l 2 ° 3 ' S i 0 ? a n d F e 0 w t - P e r c e n t ) OF 64 ANTIGORITE SAMPLES. MEAN (X) STD DEVIATION (S) CLASS INTERVAL (CL) 39-6417 0-4369 Oil 0-8851 0-2676 0 0 6 6 9 FIGURE 4 - 5 : FREQUENCY DIAGRAMS OF MgO OF 3 3 CHRYSOTILE SAMPLES. 40-4060 0-8466 0-21 21297 0-6585 0165 135 a l v a r i a t i o n o f the major o x i d e s t h a t are d i f f e r e n t s t a t i s t -i c a l l y i n the two s e r p e n t i n e m i n e r a l s . The h i s t o g r a m s i l -l u s t r a t e the l i m i t e d c o m p o s i t i o n a l ranges t h a t are summarized i n T a b l e 4-2 and 4-3. Means and v a r i a n c e s o f each v a r i a b l e o f the two s e r p e n t i n e m i n e r a l s a r e compared by " t " t e s t and "F" t e s t t o f i n d whether o r n o t t h e two m i n e r a l s have th e same c h e m i c a l c o m p o s i t i o n ( t e s t e d a t t h e 9 5 p e r c e n t c o n f i d -ence l e v e l ) . These t e s t s i n d i c a t e t h a t the means f o r MgO, A^O^, S i O ^ and FeO a r e s i g n i f i c a n t l y d i f f e r e n t f o r the two m i n e r a l s . C h e m i c a l d i f f e r e n c e between th e two s e r p e n t i n e m i n e r a l s c o u l d a r i s e from s e v e r a l c a u s e s . C o n d i t i o n s o f f o r m a t i o n may be t h e p r i n c i p a l e x p l a n a t i o n , i n t h a t tempera-t u r e and f l u i d c o m p o s i t i o n might have been the c o n t r o l l i n g f a c t o r s . C e r t a i n l y t h e r e would seem t o be some c o n t r o l such as t e m p e r a t u r e n e c e s s a r y t o e x p l a i n the d i f f e r e n t c h e m i c a l c o m p o s i t i o n o f t h e two m i n e r a l s i f they are i n e q u i l i b r i u m . 4-3 FRACTURES AND DISTRIBUTION OF CHRYSOTILE FIBRE VEINS F i g u r e 4-6 shows a n e a r l y random d i s t r i b u t i o n o f a t -t i t u d e s o f f i b r e v e i n s . T h i s randomness i s b e l i e v e d by the a u t h o r t o be m a i n l y due t o t h e c u r v e d n a t u r e o f the v e i n s a l o n g w h i c h a t t i t u d e s i n many d i r e c t i o n s can be measured. 136 FIGURE 4-6: POLES TO 264 CHRYSOTILE-FIBRE VEINS. 137 N e v e r t h e l e s s , i f c o n c e n t r a t i o n s o f o n l y t h r e e o r f o u r p e r -c e n t a r e c o n s i d e r e d , f i v e d i s t i n c t groups can be seen ( F i g u r e 4-6): A. 305*/35* t o 60" - NE and SW; B. 225*/70" t o 90" -SE; C. 340"/40" - NE and SW; D. 270*/45" t o 70" - N and S; and E. 240*/80* - SE. Comparison o f F i g u r e 4-6 w i t h F i g u r e 4-7 and 4-8 shows t h a t f i b r e - v e i n s o f groups A, B and C o c c u r i n s h e a r zones and group D and E o c c u r i n j o i n t s . Ore grade zones o f t h e P o r c u p i n e p i t ( F i g u r e 4-9, 4-10) show the e l o n g a t i o n o f t h e h i g h grade o r e zones a r e i n a c c o r d w i t h the t r e n d s o f groups B and D. A c r o s s - s e c t i o n ( F i g u r e 4-11) o f t h e P o r c u p i n e p i t a l s o r e v e a l s t h a t the d i p s o f d i f f e r e n t o r e grade zones v a r y from 45" t o 70*. F i b r e s i n s t e e p l y d i p p i n g v e i n s are g e n e r a l l y l o n g e r and t h i c k e r t h a n those o f low d i p s . F r a c t u r e s p a c i n g o f 7 t o 27 c e n t i m e t r e s seems t o be a s s o c i a t e d w i t h l o n g e s t a v e r -age f i b r e ( P l a t e 4-5). W i t h h i g h e r f r a c t u r e d e n s i t y , f i b r e s become s h o r t e r . M a s s i v e unsheared s e r p e n t i n i t e c o n t a i n s v e r y l i t t l e f i b r e . Zones o f p o l i s h e d f i s h - s c a l e s e r p e n t i n i t e are d e v o i d o f f i b r e . A l s o , f i n e l y c r u s h e d zones where s e r p e n t i n i t e d i s i n t e g r a t e s on exposure and can be b r o k e n between the f i n -g e r s are b a r r e n , even i f i t o c c u r s w i t h i n o r e zones. Rare s e r p e n t i n i t e b r e c c i a s ( P l a t e 4-6) m o s t l y a d j a c e n t t o r o d i n g -i t e , a re d e v o i d o f c h r y s o t i l e - f i b r e . An a t t e m p t was made t o c o r r e l a t e d i f f e r e n t k i n d s o f f r a c t u r e s i n the c o u n t r y r o c k s ( F i g u r e 2-11) as w e l l as 138 FIGURE 4-7: POLES TO 125 CHRYSOTILE-FIBRE VEINS SHOWING DISPLACEMENT ALONG THE CONTAINING FRACTURE. 139 FIGURE 4-8: POLES TO 139 CHRYSOTILE-FIBRE VEINS IN JOINTS 100' 200 F t o FIGURE 4-11: CHRYSOTILE-FIBRE ORE GRADE ZONES IN CROSS SECTION ALONG 17W. (See Figure 3-3 f o r l o c a t i o n . ) 1= S e r p e n t i n i t e w i t h 0 to 1 percent f i b r e ; 2= S e r p e n t i n i t e w i t h 1 to 3 percent f i b r e ; 3= S e r p e n t i n i t e w i t h 3 to 7 percent f i b r e ; 4= S e r p e n t i n i t e w i t h more than 7 percent f i b r e ; 5= S i l i c a - c a r b o n a t e rock; 6= A r g i l l i t e . 141 PLATE 4-5: L o n g - f i b r e c h r y s o t i l e v e i n s i n w i d e l y spaced f r a c t u r e s . T h i s k i n d o f v e i n i s p l a n e r and has a c o n s i s t a n t a t t i t u d e s . U s u a l l y t h e l e n g t h o f f i b r e s i s l o n g e r than the l e n g t h o f t h e f i b r e s i n s h e a r zones. 142 PLATE 4-6: S e r p e n t i n i t e b r e c c i a i n Snow Shoe p i t . I t o c c u r s u s u a l l y i n c r u s h e d s e r p e n t i n i t e zone o r a d j a c e n t t o r o d i n g i t e . 143 f r a c t u r e s a d j a c e n t t o the P o r c u p i n e u l t r a m a f i c body ( F i g u r e 4-12) w i t h f i v e c o n c e n t r a t i o n s o f c h r y s o t i l e - f i b r e - v e i n s ( F i g u r e 4-6) p r e v i o u s l y mentioned. F i b r e - v e i n s o f group D 2, and E c l o s e l y p a r a l l e l some o f the j o i n t c o n c e n t r a t i o n s shown i n F i g u r e 2-11. F i b r e - v e i n s o f group and p a r -a l l e l some o f the f a u l t c o n c e n t r a t i o n s shown i n F i g u r e 4-12. Group A, t h e h i g h e s t c o n c e n t r a t i o n o f f i b r e - v e i n s g e n e r a l l y c o i n c i d e s w i t h f o l i a t i o n s F 2 ( F i g u r e 2-8) wh i c h s t r i k e n o r t h -west and d i p n o r t h e a s t . Some groups o f f i b r e - v e i n s a re n o t q u i t e p a r a l l e l t o s e t s o f f r a c t u r e s b u t d i f f e r by f i v e t o t e n degrees b o t h i n s t r i k e and d i p . T h i s may be due t o t h e d i f f e r e n c e i n p h y s i c a l p r o p e r t i e s o f the u l t r a m a f i c r o c k and the .country r o c k . Some o f t h e f i b r e - v e i n s cannot be c o r -r e l a t e d w i t h any o f t h e f r a c t u r e s d e s c r i b e d above and i t i s p o s s i b l e t h a t t h e s e v e i n - f r a c t u r e s d e v e l o p e d d u r i n g s e r p e n t -i n i z a t i o n . The above f a c t s l e a d t h e w r i t e r t o b e l i e v e t h a t al-.! though c h r y s o t i l e - f i b r e c h r y s t a l l i z e d i n many k i n d s o f f r a c -t u r e s , the main commercial c o n c e n t r a t i o n o f f i b r e i s con-t r o l l e d by j o i n t s and f a u l t s n o t e d above. 4-4 ORIGIN OF CHRYSOTILE VEINS 4-4-A Temperature o f F o r m a t i o n o f S e r p e n t i n e M i n e r a l s 144 14 5 Temperatures o f s e r p e n t i n i z a t i o n a r e r e p o r t e d t o range from about 400*C t o 100'C. Cashman and Whetten (ly76) proposed t h a t f o r m a t i o n o f s e r p e n t i n e o c c u r r e d under P - T c o n d i t i o n s p r o b a b l y l e s s than 100"C, based on f i e l d e v i d e n c e . Wenner and T a y l o r (1971) s u g g e s t e d a temperature range o f 85*C t o 185*C from the e q u i l i b r i u m o f t h e assemblage l i z -a r d i t e and c h r y s o t i l e and argue f o r a n t i g o r i t e f o r m a t i o n as low as 220 *C. T h i s i s based on "^O/^O f r a c t i o n a t i o n d a t a between c o - e x i s t i n g s e r p e n t i n e and m a g n e t i t e . T h i s low tem-p e r a t u r e f o r m a t i o n o f c h r y s o t i l e i s p r o b a b l y due t o i t s c h e m i c a l d i f f e r e n c e from o t h e r s e r p e n t i n e m i n e r a l s . However, s e r p e n t i n i z a t i o n o f u l t r a m a f i c r o c k s a t the M i d - A t l a n t i c r i d g e i s b e l i e v e d t o have t a k e n p l a c e a t 4 80*C, (Aumento and L a u b a t , 19 71). E x p e r i m e n t s i n d i c a t e s e r p e n t i n i z a t i o n tem-p e r a t u r e o f o l i v i n e ( F o ^ ) a t a water p r e s s u r e o f 1000 a t -mospheres, i s around 400'C (Bowen and T u t t l e , 1949; Yoder, 1952; H o s t e t l e r e t a l . , 1967). 4-4-B F o r m a t i o n o f C h r y s o t i l e V e i n s a. P r e v i o u s i d e a s The f o r m a t i o n o f c h r y s o t i l e a s b e s t o s has been t h e sub-j e c t o f many d i s c u s s i o n s . The p r i n c i p a l h y p otheses o f o r i g i n a r e open space f i l l i n g and r e p l a c e m e n t . F r a c t u r e f i l l i n g may o c c u r i n two ways: 146 i . F l u i d s d e p o s i t c h r y s o t i l e i n open f r a c t u r e s o r i n f r a c -t u r e s t h a t a r e o p e n i n g as t h e y are f i l l e d (Keep, 1929; B a i n , 1932; B a d o l l e t , 1947; G a b r i e l s e , 1 9 6 0 ; T a t a r i n o v , 1967; L a l i b e r t e , 1972). i i . The v e i n s a r e formed as c r y s t a l growth pushes the w a l l a p a r t and the c r y s t a l s grow from s o l u t i o n s i n t r o d u c e d a t the c e n t r a l p a r t i n g o f the f i b r e - v e i n s (Taber, 1924). Two t y p e s o f r e p l a c e m e n t a r e d i s t i n g u i s h e d : i . V e i n s c r y s t a l l i z e d d u r i n g s e r p e n t i n i z a t i o n o f t h e r o c k . C h r y s o t i l e - f i b r e forms outward from p r e - e x i s t i n g f r a c t u r e s , t h r o ugh w h i c h w a t e r s p a s s e d d u r i n g s e r p e n t i n i z a t i o n ( D r e s s e r , 1917; H a r v i e , 1923; Graham, 1944). i i . V e i n s formed by r e p l a c e m e n t o f a l r e a d y s e r p e n t i n i z e d w a l l r o c k by s o l u t i o n s t h a t p a s s e d a l o n g t i g h t c r a c k s (Hendry, 1956; Grubb, 1962). R i o r d o n (1955) b e l i e v e d t h a t , a t T h e t f o r d , b o t h r e -placement and f r a c t u r e f i l l i n g p l a y e d major r o l e s i n c h r y -s o t i l e - f i b r e v e i n f o r m a t i o n . b. E v i d e n c e from C l i n t o n Creek E v i d e n c e from the C l i n t o n Creek d e p o s i t m a i n l y s u p p o r t s the f r a c t u r e f i l l i n g h y p o t h e s i s . Most o f the v e i n s have s t r a i g h t c l e a n - c u t w a l l s w h i c h a r e n o t c h a r a c t e r i s t i c o f r e -placement v e i n s . Most o f the f i b r e v e i n s have m a t c h i n g w a l l s on a megascopic s c a l e ( F i g u r e 4-13-A). I t t h u s appears t h a t 147 FIGURE 4-13: MECHANICS OF ORIGIN OF CHRYSOTILE VEINS. A. Matching walls. B. Matching re-entrant. C. St r a i g h t border i n c l u s i o n . D. Barren fractures i n t e r s e c t e d by c h r y s o t i l e - f i b r e vein. E. Miss-match walls(only on microscopic s c a l e ) . F. D i r e c t l y replaced i n t e r s e c t i n g veins. (Ch = c h r y s o t i l e ; S = non-fibre serpentine; Ba = barren f r a c t u r e ) . 148 the f i b r e s f i l l e d p r e - e x i s t i n g o p e n i n g s . Some f i b r e s seem t o have t h e shape o f t e n s i o n gashes o f S shaped f r a c t u r e s . Such v e i n s a r e more e a s i l y e x p l a i n e d as f r a c t u r e f i l l i n g s t h a n as r e p l a c e m e n t s . Some v e i n s c a r r y i n c l u s i o n s o f w a l l - r o c k w h i c h match the r e - e n t r a n t s o f s i m i l a r shape i n t h e a d j a c e n t w a l l - r o c k ( F i g u r e 4-13-B). Some i n c l u s i o n s , a l t h o u g h l a c k i n g a m a tching r e - e n t r a n t , s t i l l show r e l a t i v e l y s t r a i g h t b o r -d e r s ( F i g u r e 4-13-C) w h i c h s u p p o r t s f r a c t u r e f i l l i n g . Most i n t e r s e c t i o n s o f c r o s s c u t t i n g v e i n s do not show w i d e n i n g , c h a r a c t e r i s t i c o f r e p l a c e m e n t , b u t show m a t c h i n g w a l l s ( F i g u r e 4-2-B). F i b r e s s p l i t c l e a n l y from the v e i n w a l l s and t h i s s u g g e s t s f r a c t u r e f i l l i n g r a t h e r than r e p l a c e m e n t . T i g h t f r a c t u r e s , w h i c h are contemporaneous w i t h o r e a r l i e r t han f i b r e f o r m a t i o n c o n t a i n no c h r y s o t i l e ( F i g u r e 4-13-D) and thus argue a g a i n s t r e p l a c e m e n t . D i l a t i o n o f f - s e t a t i n t e r -s e c t i n g v e i n s ( F i g u r e 4-2-B) suggests open space f i l l i n g . Tapered v e i n s ( P l a t e 4-4) a l s o s u p o o r t s f r a c t u r e f i l l i n g . A l t h o u g h e v i d e n c e o f f r a c t u r e f i l l i n g r a t h e r t h a n r e p l a c e m e n t seems c o n v i n c i n g and e x i s t s on a wide s c a l e , v e i n s i n a few specimens have mismatched w a l l s ( F i g u r e 4-13-E), and few i n t e r s e c t i n g v e i n s show p o s s i b l e r e p l a c e m e n t c h a r -a c t e r i s t i c s ( F i g u r e 4-13-F). 4-4-C C h r y s o t i l e Forming S o l u t i o n s and C h r y s o t i l e D e p o s i t i o n The w r i t e r b e l i e v e s t h a t t h e c h r y s o t i l e f i b r e s were 149 d e p o s i t e d i n f r a c t u r e s , i n s e r p e n t i n i t e , t h a t was formed d u r i n g the e a r l y p e r v a s i v e s e r p e n t i n i z a t i o n . C h r y s o t i l e a t the C l i n t o n Creek d e p o s i t has not been o b s e r v e d d i r e c t l y i n c o n t a c t w i t h o l i v i n e o r pyroxene o r c o u n t r y r o c k b u t i t i s i n v a r i a b l y s e p a r a t e d from t h e s e m i n e r a l s by a l a y e r o f s e r p e n t i n e ( F i g u r e 4-14). T h e r e f o r e , i t seems t h a t c h r y -s o t i l e f i b r e was p r e c i p i t a t e d o n l y on the w a l l s o f f r a c t u r e s i n p r e v i o u s l y formed s e r p e n t i n e . T h i s l e a d s t o the hypo-t h e s i s t h a t s e r p e n t i n e w a l l s a r e a r e q u i r e m e n t f o r c h r y s o -t i l e d e p o s i t i o n e x p l a i n s why t h e r e was no c h r y s o t i l e formed i n f r a c t u r e s i n the a d j a c e n t c o u n t r y r o c k . C h r y s o t i l e f i b r e a t t h e C l i n t o n Creek a s b e s t o s d e p o s i t has d i f f e r e n t phases o f f o r m a t i o n as i n d i c a t e d by some o f the c r o s s - c u t t i n g r e l a t i o n s h i p o f t h e f i b r e v e i n s . I t has been s u g g e s t e d t h a t s e r p e n t i n e m i n e r a l s , e s p e c i a l l y c h r y s o t i l e c o u l d be d i s s o l v e d and r e d e p o s i t e d a t t e m p e r a t u r e s as low as 85"C (Wenner and T a y l o r , 1971). The r e q u i r e d warm aqueous so-l u t i o n would seem t o be w i d e l y a v a i l a b l e from a number b f s o u r c e s . However, the main s o u r c e and phase o f m i n e r a l i -z a t i o n p r o b a b l y c o u l d have t a k e n p l a c e a t t h e end o f t h e C r e t -aceous when the a c i d i n t r u s i v e r o c k s i n t r u d e d the v i c i n i t y o f the C l i n t o n Creek a r e a . I n t r u s i v e r o c k s , however, a r e un-known around th e d e p o s i t . The n e a r e s t , b u t s m a l l , exposed g r a n o d i o r i t e i s about f i v e k i l o m e t r e s west o f the mine and a l a r g e body (30 s q . k i l o m e t r e s ) i s about t h i r t e e n k i l o m e t r e s n o r t h w e s t o f t h e d e p o s i t . These i n t r u s i o n s a r e b e l i e v e d t o 150 FIGURE 4-14: CHRYSOTILE FORMS ADJACENT TO SERPENTINE, BUT NOT TO OLIVINE. (Ch = c h r y s o t i l e ; F = f r a c t u r e ; 0 = O l i v i n e ; S = n o n - f i b r e s e r p e n t i n e ) . 151 have p r o v i d e d a h e a t s o u r c e t o g e n e r a t e t h e r m a l w a t e r s . The r e a c t i o n o f warm aqueous s o l u t i o n w i t h the e x i s t i n g s e r p e n -t i n e a l o n g f r a c t u r e s gave r i s e t o d e p o s i t i o n o f c h r y s o t i l e f i b r e i n an e s s e n t i a l l y c l o s e d system. Warm aqueous s o l u t i o n o n l y r e a c t e d as an agent i n the f o r m a t i o n o f c h r y s o t i l e f i b r e , b u t n e i t h e r added new element o r s u b t r a c t e d h a r d l y any o f the p r e - e x i s t i n g elements o f t h e s e r p e n t i n i t e i n any d e t e c t -a b l e amount. 152 CHAPTER V EXPLORATION FOR CHRYSOTILE ASBESTOS IN THE NORTHERN CORDILLERA 5-1 INTRODUCTION The w r i t e r v i s i t e d , f o r p e r i o d s r a n g i n g from two days t o two weeks, t h e f o l l o w i n g a s b e s t o s o c c u r r e n c e s . C a s s i a r and Kutcho d e p o s i t s i n the B r i t i s h C o lumbia, Canex, C a l e y and Ti n c u p Lake d e p o s i t s i n Yukon T e r r i t o r y and Dahl Creek and E a g l e d e p o s i t s i n A l a s k a , U.S.A. ( F i g u r e 5-1). Of t h e s e , t h e C a s s i a r d e p o s i t i s t h e o n l y one from w h i c h t h e r e has been p r o d u c t i o n . The w r i t e r , i n a d d i t i o n , examined some b a r r e n u l t r a m a f i c b o d i e s . These r e c o n n a i s s a n c e v i s i t s were c a r r i e d o u t i n an at t e m p t t o d e f i n e g u i d e s f o r a s b e s t o s e x p l o r a t i o n . 5-2 FEATURES OF CHRYSOTILE ASBESTOS BEARING ULTRAMAFIC BODIES 5-2-A C a s s i a r , B.C. 153 FIGURE 5-1: ASBESTOS BEARING ULTRAMAFIC BODIES IN B.C., Y.T. AND ALASKA. l = D a h l Creek; 2=Eagle; 3=Canex; 4 = C l i n t o n Creek; 5=Caley; 6=Tin-cup; 7=Kutcho; 8 = C a s s i a r . 154 C a s s i a r a s b e s t o s d e p o s i t (59'23'N, 129'46'W; F i g u r e 5-1) i s s i t u a t e d i n n o r t h e r n B r i t i s h C o lumbia, 65 k i l o m e t r e s s o u t h o f Yukon B o r d e r and 160 k i l o m e t r e s southwest from Watson Lake. An o r e - b e a r i n g u l t r a m a f i c body was emplaced i n t o the D e v o n i a n - M i s s i s s i p p i a n S y l v e s t e r Group composed o f s e v e r a l hundred f e e t o f a l t e r n a t i n g , t h i n bedded b l a c k a r g i l -l i t e s and a r g i l l a c e o u s q u a r t z i t e , and i n t e r b e d d e d v o l c a n i c f l o w s and t u f f . The o r e body o c c u r s w i t h i n a l e n t i c u l a r s l a b o f c o m p l e t e l y s e r p e n t i n i z e d p e r i d o t i t e f o l d e d c o n f o r m a b l y w i t h the e n c l o s i n g r o c k s and d i p p i n g 30" t o 45" e a s t . The u l t r a b a s i c body and e n c l o s i n g s t r a t a form the e a s t e r n l i m b o f a n o r t h e r l y t r e n d i n g s y n c l i n e . The s l a b i s 3.2 k i l o m e t r e s l o n g , and the s o u t h e r n t w o - t h i r d s i s narrow, sheared and b a r r e n . The o r e body i s i n the n o r t h e r n 460 metres o f the s l a b and has a w i d t h o f 210 metres. Depth of t h e f i b r e - b e a r -i n g zone i s n o t known. The orebody i s d i v i d e d i n t o a s e r i e s o f l e n s e s by s h e a r zones o f low d i p . C h r y s o t i l e o c c u p i e s c o n j u g a t e f r a c t u r e s i n the r e l a t i v e l y competent b l o c k s o f s e r p e n t i n e between the s e s h e a r s . Both h a n g i n g and f o o t w a l l c o n t a c t s o f t h e s e r p e n t i n i t e body a r e h i g h l y s h e a r e d . The h a n g i n g - w a l l c o n t a c t c o n s i s t s o f a zone of i n d u r a t e d a r g i l -l i t e l o c a l l y r e f e r r e d t o as " a l t e r a t i o n zone", composed o f z o i s i t e - q u a r t z - t r e m o l i t e r o c k w i t h l o c a l i r r e g u l a r b o d i e s o f n e p h r i t e j a d e and u v a r o v i t e g a r n e t (Hewett, 1978). The f o o t -w a l l c o n t a c t , mask by a zone of c r u s h e d a r g i l l i t e and graph-i t i c s c h i s t s , i s a r e v e r s e f a u l t t r e n d i n g 135* and d i p p i n g 155 n o r t h e a s t . The c o n t a c t o f the C a s s i a r b a t h o l i t h i s w i t h i n 2.5 k i l o m e t r e s o f the d e p o s i t . 5-2-B Kutcho, B.C. Kutcho mountain (59'33'N, 129'58'W; F i g u r e 5-1) i s u n d e r l a i n by a e u g e o s y n c l i n a l assemblage o f marine sedimen-t a r y r o c k ( a r g i l l i t e , s a n d s t o n e , l i m e s t o n e ) and i n t e r b e d d e d v o l c a n i c f l o w s (greenstone) c o r r e l a t i v e w i t h t h e S y l v e s t e r Group o f D e v o n i a n - M i s s i s s i p p i a n age ( G a b r i e l s e , 1963). These e n c l o s e an u l t r a m a f i c body a t l e a s t 19 k i l o m e t r e s l o n g and 1.6 k i l o m e t r e s w i d e , composed o f s e r p e n t i n i z e d p e r i d o t i t e and d u n i t e . The body s t r i k e s n o r t h w e s t e r l y and d i p s g e n t l y t o t he e a s t . Dykes and i r r e g u l a r i n t r u s i o n s o f d i o r i t e w i t h some gabbro c u t the s e r p e n t i n i t e body o r are m a r g i n a l t o i t . The C a s s i a r b a t h o l i t h l i e s n i n e m i l e s e a s t o f t h e a r e a , b u t a g r a n i t i c spur comes w i t h i n one m i l e o f t h e s e r p e n t i n i t e body. P a r t s o f t h e body a r e p a r t l y s e r p e n t i n i z e d b u t t h e o t h e r p a r t s a r e w h o l e l y s e r p e n t i n i z e d . Three e n e c h e l o n f i b r e - b e a r i n g zones have been l o c a t e d so f a r . These a r e sep-a r a t e d by sh e a r zones w h i c h a r e p a r a l l e l t o the f o o t w a l l c o n t a c t . F i b r e s o o c c u p y c o n j u g a t e j o i n t systems. S i l i c a -c a r b o n a t e a l t e r a t i o n i s p r e s e n t . 5-2-C Canex, Y...T. 156 The Canex u l t r a m a f i c ( F i g u r e 5-1, F i g u r e 2-2) w i t h some c h r y s o t i l e a s b e s t o s o c c u r r e n c e i s a s e r p e n t i n i z e d p e r i d o t i t e body l o c a t e d about 4 k i l o m e t r e s west o f the C l i n t o n Creek P o r c u p i n e o r e body. I t i s su r r o u n d e d m o s t l y by l i m y a r g i l l i t e and i n p a r t by g r e e n s t o n e . The a r e a was s u r v e y e d by C a s s i a r A s b e s t o s C o r p o r a t i o n w i t h a Sharpe's MF-1 v e r t i c a l i n t e n s i t y f l u x g a t e magnetometre i n 1964. The r e s u l t o f t h i s magnetic s u r v e y and g e o l o g i c a l mapping i n d i c a t e t h a t t h e s e r p e n t i n i z e d u l t r a m a f i c mass i s a sheet about 80 metres t h i c k and about 600 metres l o n g , s t r i k i n g e a s t e r l y and d i p p i n g about 30" s o u t h e r l y . I t i s p r o b a b l y c o n f o r m a b l e w i t h t h e o v e r l y i n g l i m y a r g i l l i t e s on t h e wes t . and i s near the c r e s t o f a major a n t i c l i n a l s t r u c t u r e . V i s u a l e s t i m a t e s o f the f i b r e c o n t e n t do not exceed t h r e e p e r c e n t and most f i b r e - v e i n s a r e s h o r t , r a r e l y e x c e e d i n g s i x m i l l i m e t r e s . A s i l i c a - c a r b o n a t e a l t e r a t i o n zone l i e s between the s e r p e n t -i n i t e and a r g i l l i t e a t the s o u t h e r n c o n t a c t . 5-2-D C a l e y , Y.T. The C a l e y a s b e s t o s o c c u r r e n c e (64'18'N, 140"l2'W; F i g u r e 5-1) i s s i t u a t e d about 32 k i l o m e t r e s s o u t h e a s t o f C l i n t o n Creek. The d e p o s i t l i e s i n a s e r p e n t i n i z e d p e r i -d o t i t e t h a t i s surrounded by q u a r t z - c a r b o n a t e r o c k . I t s t r i k e s n o r t h e r l y and d i p s g e n t l y e a s t w a r d . The body i s b o r d e r e d on the n o r t h by q u a r t z - s e r c i t e s c h i s t s and on the 157 s o u t h by b l a c k , a r g i l l a c e o u s l i m e s t o n e and s l a t e w h i c h ap-pear t o t r e n d n o r t h - e a s t e r l y . The body i s about 1000 metres l o n g and 400 metres w i d e , most o f wh i c h i s composed o f q u a r t z - c a r b o n a t e a l t e r a t i o n w i t h an u n a l t e r e d c e n t r a l remnant (400 metres by 130 metres) o f s e r p e n t i n i t e w i t h c h r y s o t i l e f i b r e . The body i s t r o u g h - l i k e and was found t o bottom w i t h i n 100 metres o f the s u r f a c e . A l a r g e g r a n i t i c s t o c k l i e s f i v e k i l o m e t r e s t o t h e n o r t h . 5-2-E T i n c u p Lake, Y.T. The T i n c u p Lake a s b e s t o s o c c u r r e n c e (61'18'N, 135'15'W; F i g u r e 5-1) i s a l o n g the n o r t h e r n b o r d e r o f a s e r p e n t i n i z e d p e r i d o t i t e body. The body i s about 1.6 k i l o m e t r e s wide and appears t o d i p a t a v e r y h i g h a n g l e p r o b a b l y c o n f o r m a b l y w i t h the s u r r o u n d i n g r o c k u n i t s . The u l t r a m a f i c body i s composed o f d u n i t e , p e r i d o t i t e and p y r o x e n i t e . I t i s e n c l o s e d i n c o u n t r y r o c k s c o n s i s t i n g o f g r e e n s t o n e , q u a r t z i t e , l i m e -s t o n e and a r g i l l a c e o u s r o c k s . The l a r g e n o r t h w e s t - t r e n d i n g Ruby Range b a t h o l i t h l i e s j u s t t o the so u t h o f the u l t r a m a f i c body. 5-2-F Dahl Creek, A l a s k a The Dahl Creek a s b e s t o s o c c u r r e n c e (66'56'N, 156'54'W; F i g u r e 5-1) i s i n a s e r p e n t i n i z e d u l t r a m a f i c body. The 158 o r e body has prominent shear zones t r e n d i n g 320* t o 330* and d i p p i n g 10* t o 28* and 60* t o 90* n o r t h e a s t . L o n g e s t f i b r e s o c c u r i n j o i n t s a d j a c e n t t o shear zones. The u l t r a -m a f i c body i s m o s t l y i n c o n t a c t w i t h b l a c k a r g i l l a c e o u s l i m e -s t o n e and minor s c h i s t . C o u n t r y r o c k c o n s i s t s o f l i m e s t o n e , m i c a - s c h i s t , g r a p h i t e - m i c a - s c h i s t , and c h l o r i t e - s c h i s t a l l o f p r o b a b l e e a r l y P a l e o z o i c age. S t r u c t u r a l r e l a t i o n s h i p o f the c o u n t r y r o c k t o the u l t r a m a f i c body seems c o n f o r m a b l e . A l t e r a t i o n was not o b s e r v e d . 5-2-G E a g l e , A l a s k a The E a g l e a s b e s t o s o c c u r r e n c e (64*35'N, 142*30'W; F i g u r e 5-1) i s about 90 k i l o m e t r e s west o f the C l i n t o n Creek a s b e s t o s mine. An a s b e s t o s - b e a r i n g , h i g h l y s e r p e n t i n i z e d p e r i d o t i t e body i s c u t by w i d e l y spaced j o i n t s . The body appears t o ext e n d about 1,000 metres i n an e a s t - w e s t d i r e c -t i o n . The f i b r e - b e a r i n g zone i s exposed o v e r a l e n g t h o f about 500 metre s , b u t m i n e r a l i z a t i o n w i t h i n t h i s zone i s e r r a t i c . The n o r t h and so u t h ends o f the m i n e r a l i z e d p a r t appear t o c o n t a i n the h i g h e s t c o n c e n t r a t i o n s o f c h r y s o t i l e -f i b r e . A zone i n t h e c e n t r e a p p r o x i m a t e l y 80 metres l o n g c o n t a i n s l i t t l e o r no f i b r e . G e n e r a l l y , f i b r e - v e i n s a re spaced 25 t o 50 c e n t i m e t r e s a p a r t , a l t h o u g h i n some p l a c e s more c l o s e l y spaced f i b r e - v e i n s a r e ob s e r v e d . Average f i b r e l e n g t h i s about 6 m i l l i m e t r e s and the l o n g e s t f i b r e o b s e r v e d 159 i s 20 m i l l i m e t r e s . The s e r p e n t i n i t e body i s emplaced i n c o u n t r y r o c k o f s i m i l a r l i t h o l o g y t o t h a t o f t h e C l i n t o n Creek a r e a and i s p r o b a b l y o f m i d d l e P a l e o z o i c age. A l t e r a t i o n zones were not o b s e r v e d . G r a n o d i o r i t e b o d i e s were n o t e d i n the v i c i n i t y o f the u l t r a m a f i c body. 5-3 FEATURES OF BARREN ULTRAMAFIC BODIES B a r r e n u l t r a m a f i c b o d i e s w i t h i n the C l i n t o n Creek a r e a , i n a d j a c e n t p a r t s o f Yukon, n o r t h e r n B.C. and Alaska,, v i s i t e d by the w r i t e r , d i f f e r i n some r e s p e c t s from t h o s e t h a t c o n t a i n a s b e s t o s . These b a r r e n b o d i e s have been emplaced w h o l e l y i n g r e e n s t o n e o r i n q u a r t z - m i c a s c h i s t , r a t h e r t h a n a t o r near c o n t a c t s o f a r g i l l i t e and g reenstone or i n a r g i l l i t e . I n a d d i t i o n , most o f the b a r r e n ones a r e e x t r e m e l y l a r g e o r s m a l l compared t o the f i b r e - b e a r i n g b o d i e s . ...Larger b o d i e s :are ^ g e n e r a l l y r e l a t i v e l y unsheared; and s m a l l e r b o d i e s commonly a r e composed c o m p l e t e l y o f f i s h - s c a l e s e r p e n t i n e , the r e s u l t o f i n t e n s i v e s h e a r i n g . G e n e r a l l y l a r g e r u l t r a m a f i c b o d i e s a r e not h i g h l y f r a c t u r e d and t h e degree o f s e r p e n t i n i z a t i o n does n o t seem t o be more tha n f i f t y p e r c e n t . 160 5-4 GUIDES IN THE SEARCH FOR CHRYSOTILE ASBESTOS a. Exposures o f u l t r a m a f i c b o d i e s a r e i n d i c a t e d by l a c k o f heavy v e g e t a t i o n and dark green t o orange w e a t h e r i n b l o c k y t a l u s they produce. Both c h a r a c t e r i s t i c s can e a s i l y be seen from a d i s t a n c e o r from th e a i r . b. A l l f i b r e - b e a r i n g s e r p e n t i n i z e d b o d i e s d i s c u s s e d here a r e emplaced a l o n g t h e c o n t a c t o f a r g i l l a c e o u s meta-sediments and g r e e n s t o n e o r s c h i s t , o r w h o l e l y i n a r g i l -l a c e o u s metasediments. A l l o f t h e s e i n t e r b e d d e d g r e e n s t o n e and a r g i l l a c e o u s p a r t l y metamorphosed sediments seem t o be o f D e v o n i a n - M i s s i s s i p p i a n age. On t h e c o n t r a r y , b a r r e n u l t r a m a f i c b o d i e s a r e s i t u a t e d w i t h i n g r e e n s t o n e o r q u a r t z -m ica s c h i s t . c. A l l d e p o s i t s o c c u r w i t h i n one t o n i n e m i l e s o f g r a n i t i c i n t r u s i o n s o f p r o b a b l y J u r r a s s i c o r C r e t a c e o u s age These i n t r u s i o n s a r e b e l i e v e d t o have c o n t r i b u t e d a heat s o u r c e f o r a s b e s t o s f o r m a t i o n . d. S i g n i f i c a n t c o n c e n t r a t i o n s o f c h r y s o t i l e a s b e s t o s are c o n f i n e d t o u l t r a m a f i c b o d i e s w h i c h a r e a t l e a s t 75 p e r c e n t s e r p e n t i n i z e d . e. U l t r a m a f i c l e n s e s whose e l o n g a t i o n i s perpend-i c u l a r o r a t h i g h a n g l e t o t h e d i r e c t i o n s o f r e g i o n a l f o l d axes seem t o be most f a v o r a b l e s i t e s f o r development o f a c h r y s o t i l e a s b e s t o s d e p o s i t . 161 f . Known commercial d e p o s i t s and o c c u r r e n c e s o f c h r y s o t i l e - f i b r e l i e i n r e l a t i v e l y s m a l l (1,000 t o 2,000 metres) u l t r a m a f i c b o d i e s compared t o l a r g e b o d i e s w h i c h are w i d e s p r e a d i n B.C., Y.T. and A l a s a k a . u n f o r t u n a t e l y depth cannot be e s t i m a t e d from o u t c r o p a r e a . I t i s p r o b a b l e t h a t t h e r e i s an optimum s i z e , r e l a t i v e t o d e f o r m i n g s t r e s s , t h a t w i l l a l l o w the s e r p e n t i n e body t o be f r a c t u r e d s u f f i c i -e n t l y t o form an orebody. g. R e l a t i v e l y unsheared u l t r a m a f i c b o d i e s have low p o t e n t i a l s f o r the development o f c o n c e n t r a t i o n s o f good q u a l i t y c h r y s o t i l e - f i b r e . A l s o f i s h - s c a l e s h e a r i n g , i f a dominant c h a r a c t e r i s t i c , i s a n e g a t i v e c r i t e r i o n f o r the o c c u r -rence o f economic c o n c e n t r a t i o n s o f c h r y s o t i l e - f i b r e . The g r e a t m a j o r i t y o f s m a l l s e r p e n t i n i t e b o d i e s a r e composed o f f i s h - s c a l e s e r p e n t i n i t e . I n a l l c a s e s , f i b r e - v e i n l e t s occupy f r a c t u r e s , i n more o r l e s s m a s s i v e s e r p e n t i n i t e b l o c k s bounded by l e n t i c u l a r s h ear zones. h. F r a c t u r i n g must Pe f a i r l y i n t e n s e t o p r o v i d e adequate openings f o r c h r y s o t i l e - f i b r e f o r m a t i o n i n o r e grade c o n c e n t r a -t i o n s . S t r u c t u r a l mapping i n s u r r o u n d i n g c o u n t r y r o c k s may i n d i c a t e p a r t i c u l a r i n t e n s i t i e s o f r e g i o n a l f r a c t u r e s whose e x t e n s i o n s a c r o s s u l t r a m a f i c masses may i n d i c a t e p o t e n t i a l f o r h i g h grade q u a l i t y - f i b r e . i . S i l i c a - c a r b o n a t e a l t e r a t i o n i s commonly a s s o c i a t e d w i t h s e r p e n t i n i z e d u l t r a m a f i c masses, and i n c e r t a i n c a s e s may be a u s e f u l guide t o r such masses. However, t h i s i s u s u a l l y 162 an a l t e r a t i o n t h a t p o s t - d a t e s c h r y s o t i l e - f i b r e f o r m a t i o n and i f superimposed on c h r y s o t i l e - f i b r e can reduce i t s q u a l i t y o r d e s t r o y i t c o m p l e t e l y . 163 CHAPTER VI SUMMARY AND CONCLUSION The most abundant r o c k s o f t h e C l i n t i n Creek: a r e a b e l o n g t o the Yukon Metamorphic Complex wh i c h a r e o r i g i n a l l y an a l t e r -n ate sequence o t marine s e d i m e n t a r y and v o l c a n i c r o c k s . The w r i t e r o b t a i n e d a model age f o r t h e s e r o c k s o f 470 Ma( O r d o v i c -i a n ) by whole r o c k Rb-Sr d a t i n g . F o s s i l e v i d e n c e , documented by o t h e r s from an a r e a j u s t west o f t h e Yukon R i v e r near A l a s k a b o r d e r i n d i c a t e d a P a l e o z o i c age, p r o b a b l y Devonian. The main e p i s o d e o f metamorphism o c c u r r e d i n Permian. I t appe a r s , t h e r e f o r e , t h a t the r o c k s o f the a r e a were formed i n the mi d d l e P a l e o z o i c ( O r d o v i c i a n t o D e v o n i a n ) . I n t e n s i t y and s t y l e o f d e f o r m a t i o n i n the c o u n t r y r o c k s and u l t r a m a f i c b o d i e s s u g g e s t t h a t the u l t r a m a f i c r o c k s o f t h e a r e a were emplaced i n t h e c o u n t r y r o c k s p r o b a b l y d u r i n g t h e Permian p e r i o d , the time o f main metamorphism. I t i s p r o b a b l e t h a t t h e T i n t i n a f a u l t a.few k i l o m e t r e s away from the st u d y a r e a r e f l e c t s a zone o f weakness a l o n g w h i c h the a l p i n e - t y p e u l t r a m a f i c b o d i e s o f the C l i n t o n Creek a r e a and p r o b a b l y some o f the o t h e r s a l o n g and c l o s e t o the T i n t i n a Trench were em-164 p l a c e d t e c t o n i c a l l y . These were l a t e r f o l d e d and metamorphosed w i t h the c o u n t r y r o c k s . The a r e a wa's i n t r u d e d by a c i d i n t r u s -i v e r o c k s i n l a t e s t C r e t a c e o u s - e a r l i e s t T e r t i a r y t i m e . Colum-nar j o i n t e d b a s a l t o f S e l k i r k v o l c a n i c s e q u i v a l e n t i s the y o u n g e s t , undeformed, f r e s h r o c k o f t h e a r e a . These S e l k i r k v o l c a n i c r o c k s were e x t r u d e d a t Holocene o r P l e i s t o c e n e ( B o s t o c k , 1966) . Three main phases o f d e f o r m a t i o n were d e l i n e a t e d . P r o b a b l y t h e o l d e s t and most complex phase o c c u r r e d d u r i n g t h e Permian, a l o n g w i t h the i n i t i a l movement o f t h e T i n t i n a f a u l t . S m a l l , t i g h t , i s o c l i n a l f o l d s a r e c h a r a c t e r i s t i c o f t h i s phase. The s t r u c t u r a l t r e n d (300* t o 315') i s r o u g h l y p a r a l l e l t o the d i r e c t i o n o f t h e T i n t i n a T r e n c h . Due t o l a t e r d e f o r m a t -i o n o f t h e f o l d s o f t h i s phase, l o c a l change i n a x i a l t r e n d s up t o 010" i s common. D i r e c t i o n o f vergence v a r i e s from 0 30* t o 100*. The second phase o f d e f o r m a t i o n gave r i s e t o l a r g e recumbent and i s o c l i n a l f o l d s w i t h t r e n d s v a r y i n g from 270" t o ^90* w i t h s o u t h e r l y v e r g e n c e . The t h i r d phase o f deformat-i o n gave r i s e t o a n t i f o r m s t r u c t u r e o f r e g i o n a l s c a l e . E i g h t e e n l e n s e s o f s e r p e n t i n i z e d u l t r a m a f i c b o d i e s have been mapped. Two o f t h e s e , the P o r c u p i n e and Snow Shoe u l t r a m a f i c b o d i e s are mined f o r a s b e s t o s . A few o f o t h e r b o d i e s c o n t a i n a p p r e c i a b l e amount of c h r y s o t i l e - f i b r e b u t a p p a r e n t l y not o f adequate q u a n t i t y t o be mined. Most o f the u l t r a m a f i c b o d i e s a r e e s s e n t i a l y d e v o i d o f known c h r y s o t i l e -f i b r e and t h e s e were e x c e s s i v e l y s h e a r e d o r v e r y massive w i t h o u t much f r a c t u r e s . A g a i n , i f s e r p e n t i n i z a t i o n i s l e s s 165 tha n 75 p e r c e n t t h e r e i s p r a c t i c a l l y no chance f o r commercial m i n e r a l i z a t i o n . F r a c t u r i n g i s one o f the most i m p o r t a n t f a c t o r s i n c o n t r o l o f m i n e r a l i z a t i o n . F a i r l y i n t e n s e f r a c t u r e s are e s s e n t i a l t o p r o v i d e adequate openings f o r c h r y s o t i l e -f i b r e f o r m a t i o n i n o r e grade c o n c e n t r a t i o n s . C h r y s o t i l e - f i b r e b e a r i n g s e r p e n t i n i z e d u l t r a m a f i c masses w i t h i n a r g i l l i t e u n i t o r a t the c o n t a c t o f a r g i l l i t e u n i t and o t h e r r o c k u n i t s seem t o c a r r y o re grade o r s u b s t e n t i a l amount o f c h r y s o t i l e - f i b r e . 166 BIBLIOGRAPHY Anhaeusser, C.R., 1976, The Nature o f C h r y s o t i l e A s b e s t o s O c c u r r e n c e s i n S o u t h e r n A f r i c a : A Review: Ec. G e o l . , v. 71, p. 96-116. Armstrong, R.L., 1978, P r e - C e n o z o i c P h a n e r o z o i c Time S c a l e -Computer F i l e o f C r i t i c a l Dates and Consequences o f New I n - P r o g r e s s Decay-Constant R e v i s i o n s : i n Cohee, G.V., and M.F. G l a e s s n e r , ed., C o n t r i b u t i o n s t o t h e G e o l o g i c Time S c a l e : Am. A s s o c . P e t r o l . G e o l o g i s t , S t u d i e s i n Geology, No. 6, p. 73-91. 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T a y l o r J r . , 1960, C o u e l a t i o n o f t h e u l t r a -m a f i c Complexes o f S o u t h e a s t e r n A l a s k a w i t h Those o f Other P a r t s o f N o r t h America and the World: _in P e t r o g r a p h i c P r o v i n c e s , Igneous and Metamorphic Rocks: I n t e r n a t . G e o l . Cong., 2 1 s t , Norden 1960, p t . 8 p. 188-197. O b r a d o v i c h , J.D., and W.A. Cobban, 1975, A Time S c a l e f o r the L a t e C r e t a c e o u s o f the Western I n t e r i o r o f N o r t h A m e r i c a : G e o l . A s s o c . Cana. Spec. Paper 13, p. 31-54. Page, N.J., 1967, S e r p e n t i n i z a t i o n C o n s i d e r e d as a C o n s t a n t Volume Metasomatic P r o c e s s : A D i s c u s s i o n : Am. M i n e r a l . , v. 52, p. 545-549. 1968, Ch e m i c a l D i f f e r e n c e s Among t h e S e r p e n t i n e " P o l y -morphs": Am. M i n e r a l . , v. 53, p. 201-215. 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Geochem., Sp. v. 4, 95 p. S k i p p e n , G.B., 1971, E x p e r i m e n t a l Data f o r R e a c t i o n s i n S i l i c e o u s M a r b l e s : J o u r . G e o l . , v. 79, p. 4 57. Steinmann, F., 1905, G e o l o g i s c h e Beobachtungen i n den A l p e n I I : D ie S c h a r d t ' s c h e U b e r f a l t u n g s t h e o r i e und d i e g e o l -o g i s h e Bedautung der T i e f s e e a b s a t z e und der o p t h i o l i t h i s -chen M a s s e n g e s t e i n e . B e r . Nat. Ges. F r e i b u r g , I , Bd. 16, 44-65. Taber, S., 19 24, The O r i g i n o f V e i n s o f F i b r o u s M i n e r a l s : Ec. G e o l . , v. 19, p. 475-486. T a t a r i n o v , P.M., and B.R. Artemov, 1967, C h r y s o t i l e A s b e s t o s D e p o s i t s o f t h e U.S.S.R.: M i n i s t r y o f Geology, U.S.S.R. Tempelman-Kluit, D.J., 1972, Geology and O r i g i n o f the F a r o , Vangorda, and Swim Concordant Z i n c - L e a d D e p o s i t s , C e n t r a l Yukon T e r r i t o r y : Cana. G e o l . S u r v . B u l l . 20 8, 7 3 p. 174 1974, Reconnaissance Geology o f A i s h i h i k Lake, Sang and P a r t o f S t e w a r t R i v e r Map-Areas, West C e n t r a l Yukon: Cana. G e o l . S u r v . Paper 73-41, 97 p. 19 76, The Yukon C r y s t a l l i n e T e r r a n e : Enigma i n the Canadian C o r d i l l e r a : G e o l . Soc. Am. B u l l . , v. 87, p. 1343-1357. and R.K. Wanless, 1975, Potassium-Argon Age Determina-t i o n s o f Metamorphic and P l u t o n i c Rocks i n t h e Yukon C r y s t a l l i n e T e r r a n e : Cana. J o u r . E a r t h S c i . , V. 12, p. 1895-1909. Thayer, T.P., 1966, S e r p e n t i n i z a t i o n C o n s i d e r e d as a C o n s t a n t -Volume Metasomatic P r o c e s s : Am. M i n e r a l . , v. 51, p. 685-709. T u r n e r , F . J . and J . Verhoogen, 1960, Igneous and Metamorphic P e t r o l o g y : 2nd ed., M c G r a w - H i l l , New Y o r k , 694 p. Vance, J.A., and M.A. Dungan, 1977, F o r m a t i o n o f P e r i d o t i t e s by D e s e r p e n t i n i z a t i o n i n t h e D a r r i n g t o n and S u l t a n A r e a s , Cascade M o u n t a i n s , Washington: G e o l . Soc. Am. B u l l . , v. 88, p. 1497-1508. Varne, R., and M.J. Rubenach, 1972, Geology o f Macquarie I s l a n d and I t s R e l a t i o n s h i p t o Oceanic C r u s t : i n Hayes D.E., ed., A n t a r c t i c Oceanology 11: A n t a r c t i c Research S e r . A u s t r a l i a n - N e w Zealand S e c t o r , v. 19, p. 98-109. Veach, N.J., 1972, Aeromagnetic S u r v e y , E a s t A l a s k a Range, E a g l e , A l a s k a : A l a s k a Dept. Nat. R e s o u r c e s , G e o l . and Geophys. Surveys 24 map, s c a l e 1:63,360. Wager, L.R. and G.M.Brown, 1968, L a y e r e d Igneous Rocks: O l i v e r and Boyd, E d i n b u r g h and London, 588 p. W a h r h a f t i g , C , 1965, P h y s i o g r a p h i c D i v i s i o n s o f A l a s k a : U.S. Dept. I n t e r i o r , G e o l . S u r v . P r o f . Paper 482,52 p. Wenner, D.B. and H.P.J. T a y l o r , 1971, Temperatures o f Serpen-t i n i z a t i o n o f U l t r a m a f i c Rocks-Based on 0 I 8 / 0 I 6 F r a c -t i o n a t i o n Between C o e x i s t i n g S e r p e n t i n e and M a g n e t i t e : C o n t r . M i n e r a l , and P e t r o l , v. 32, p. 165-185. W h i t e , W.H., G.P. E r i c k s o n , K.E. N o r t h c o t e , G.E. Dirom, and J.E. H a r a k a l , 1967, I s o t o p i c D a t i n g o f the Guichon B a t h -o l i t h , B.C.: Cana. J o u r . E a r t h S c i . , v. 4, p. 677-690. 17 5 W i c k s , F . J . , 1977, S e r p e n t i n e T e x t u r e s and S e r p e n t i n i z a t i o n : Cana. M i n e r a l . , v. 15, p. 459-488. and E.J.W. W h i t t a k e r , 1975, A R e a p p r a i s a l o f the S t r u c -t u r e s o f t h e S e r p e n t i n e M i n e r a l s : Cana. M i n e r a l . , v. 13, p. 227-243. E.J.W. W h i t t a k e r , and J . Zussman, 1977, An I d e a l i z e d Model f o r S e r p e n t i n e T e x t u r e s A f t e r O l i v i n e : Cana. M i n e r a l . , v. 15, p. 446-458. and J . Zussman, 1975, Microbeam X-ray D i f f r a c t i o n P a t t e r n s o f t h e S e r p e n t i n e M i n e r a l s : Cana. M i n e r a l . , v. 13, p. 244 -258. W i l l i a m s , H., and J . Ma l p a s , 1972, Sheeted Dykes and B r e c c i a t e d Dyke .Rocks w i t h i n T r a n s p o r t e d Igneous Complexes, Bay o f I s l a n d s , Western Newfoundland: Cana. J o u r . E a r t h S c i . , v. 9, p. 1216-1229. and W.R. Smyth, 1973, Metamorphic A u r e o l e s Beneath O p h i o l i t e S u i t e s and A l p i n e P e r i d o t i t e s : T e c t o n i c I m p l i -c a t i o n s w i t h Western Newfoundland Examples: Am. J o u r . S c i . , v. 273, p. 594-621. W i n k l e r , H.G.F., 1974, P e t r o g e n e s i s o f Metamorphic Rocks: 3rd ed., S p r i n g e r - V e r l a g , New Yo r k I n c . , 237 p. Yoder, H.S. J r . , 1952, The MgO-Al2O3-SiO 2-H 20 System and the R e l a t e d Metamorphic F a c i e s : Am. J o u r . S c i . , Bowen V o l . , p. 569-627. York D., 1967, The B e s t I s o c h r o n : E a r t h P l a . S c i . L e t t . , v. 2, p. 479-482. 1969, L e a s t Square F i t t i n g o f a S t r a i g h t L i n e w i t h C o r r e l a t e d E r r o r s : E a r t h P l a . S c i . L e t t . , v. 5, p. 320-324. - and R.M. F a r q u h a r , 1972, The E a r t h ' s Age and Geochrono-l o g y : Pergamon, 178p. 176 APPENDIX A D e f i n i t i o n o f Greenstone Greenstone used i n t h i s t h e s i s i s d e r i v e d from m a f i c v o l c a n i c ' r o c k s and p e l i t i c s e d i m e n t r y r o c k s . These are formed i n t h e l o w e r t e m p e r a t u r e p a r t o f the metamorphic c o n d i t i o n s . Hornblende has been r e p l a c e d by a c t i n o l i t e , c h l o r i t e , and e p i d o t e . Q u a r t z , a l b i t e and minor b i o t i t e , m u s c o v i t e and c a l c i t e a re a l s o p r e s e n t . Greenstone o f v o l c a n i c o r i g i n and se d i m e n t a r y o r i g i n a r e d i s t i n g u i s h e d by t h e r e l a t i v e amount o f m i n e r a l s they c o n t a i n . Greenstone d e r i v e d from s e d i m e n t a r y o r i g i n c o n t a i n s more q u a r t z and m u s c o v i t e , l e s s c h l o r i t e , a l b i t e , and e p i d o t e , and g e n e r a l l y no a c t i n o l i t e . 177 APPENDIX B THE OPHIOLITE ASSEMBLAGES The d e f i n i t i o n and i n t e r p r e t a t i o n o f o p h i o l i t e has undergone c o n s i d e r a b l e e v o l u t i o n s i n c e t h e term was f i r s t used by Steinmann (1905) i n r e f e r r i n g t o an a s s o c i a t i o n o f p e r i d o t i t e ( s e r p e n t i n i t e ) , gabbro, d i a b a s e , s p i l i t e and r e l a t e d r o c k s (Church, 1972). A r e c e n t l y proposed d e f i n i -t i o n (G.S.A. Penrose C o n f e r e n c e on O p h i o l i t e s , 1972) i s : A c o m p l e t e l y d e v e l o p e d o p h i o l i t e c o n s i s t s o f m a f i c t o u l t r a m a f i c r o c k s i n the f o l l o w i n g sequence from t h e bottom w o r k i n g up: U l t r a m a f i c complex c o n s i s t i n g o f h a r z b u r g i t e , I h e r -z o l i t e and d u n i t e , u s u a l l y w i t h a metamorphic t e c t o n -i t e f e b r i c . G a b b r o i c complex o r d i n a r i l y w i t h cumulus t e x t u r e s and u s u a l l y l e s s deformed than the u l t r a m a f i c complex. M a f i c s h e e t e d d i k e complex. M a f i c v o l c a n i c complex, commonly p i l l o w e d . A s s o c i a t e d r o c k t y p e s : - r i b b o n c h e r t s , s h a l e , minor l i m e s t o n e - s o d i c f e l s i c i n t r u s i v e and e x t r u s i v e r o c k s . Most r e c e n t i n t e r p r e t a t i o n s (Church, 1972; Coleman, 1971; Dewey and B i r d , 1971) view o p h i o l i t e s u i t e s as b e i n g 178 t r a n s p o r t e d o c e a n i c c r u s t and m a n t l e , based on the f o l l o w i n g c o n s i d e r a t i o n s , as summerized by W i l l i a m s and Smyth (1973): 1. S i m i l a r i t i e s i n g r o s s p h y s i c a l c h a r a c t e r i s t i c s o f o p h i o l i t e s u i t e s w i t h g e o p h y s i c a l models o f o c e a n i c c r u s t and mantle ( L e P i c h o n , 1969). 2. T r a n s p o r t e d o n - l a n d o p h i o l i t e i s r o o t e d i n o c e a n i c l i t h o s p h e r e a t Papua, New Guinea (D a v i e s and S m i t h , 1971). 3. S t r o n g l o t h o l o g i c s i m i l a r i t i e s between o p h i o l i t e s and r o c k s o f MacQuarie R i d g e ( V a r n e and Rubenach, 1972). 4. L o t h o l o g i c a l and c h e m i c a l s i m i l a r i t i e s o f o c e a n i c t h o l e i i t e s and p i l l o w l a v a s o f o p h i o l i t e s u i t e s (Aumento e t a l . , 1971) . 5. Models r e l a t i n g sea f l o o r s p r e a d i n g t o t h e forma-t i o n o f s h e e t e d d i k e complexes ( W i l l i a m s and Malpas, 1972). 6. H i g h p r e s s u r e m i n e r a l o g y o f p e r i d o t i t e s r e q u i r i n g mentle depths f o r c o n d i t i o n s o f c r y s t a l l i z a t i o n ( M e d a r i s , 1972) . 7. Common o c c u r r e n c e o f metamorphic t e c t o n i t e s i n o p h i o l i t e p e r i d o t i t e s , d i s p l a y i n g t e x t u r e s l i k e t h o s e ex-p r e m e n t a l l y r e p r o d u c e d under c o n d i t i o n s r e p r e s e n t a t i v e o f t h e mentle ( N i c o l a s , 1969). 8. S i m i l a r metamorphic m i n e r a l assemblages i n o c e a n i c r o c k s a t mid-ocean r i d g e s compared w i t h t h o s e o f o p h i o l i t e s ( W i l l i a m s and Malpas, 1972; Aumento, 1972). A c c o r d i n g t o P l a t e T e c t o n i c t h e o r y (eg. Coleman,19 71) fragments o f o c e a n i c c r u s t and upper mantle a r e emplaced a l o n g 179 c o n t i n e n t a l edges by a p r o c e s s o f o b d u c t i o n , whereby o c e a n i c l i t h o s p h e r e i s o v e r t h r u s t onto the c o n t i n e n t a l margin. APPENDIX C MICROPROBE ANALYSES OF PYROXENES AND OLIVINE ORTHOPYROXENE ( E n s t a t i t e ) Sample SIO^ ^"2°3 T o t a l Number of ions on the b a s i s of 6 oxygens En No. S i A l A l Fe Mg MHP 14 55.30 3.00 5.2 34.50 98.50 1.91 0.09 0.03 0.16 1.77 91.7 MHP 33 56.74 0.31 5.7 37.14 99.89 1.95 0.01 - 0.16 1.91 91.9 APPPNDIX C (Cont.) CLINOPYROXENE (Diopside) Sample Si02 ^ 2 ^ 3 F e (^ T o t a l No. of ions on the basis of 6 oxygens En D i No. S i A l A l Fe Mg Ca MHD 39 53.91 2.32 2.11 17.7 23.10 99.14 1.96 0.04 0.06 0.06 0.96 0.90 49.9 46.7 MHD 99 52.52 4.07 1.83 16.7 24.23 99.35 1.91 0.09 0.08 0.06 0.90 0.94 47.5 49.6 OLIVINE ( F o s t e r i t e ) Sample Si0„ FeO MgO T o t a l No. of ions on the ba s i s of 4 oxygens (Fo) -. 100 Mg No. S i Fe Mg Mg + Fe MHO 31 41.56 11.19 47.76 100.41 1.014 0.228 1.738 88.3 MHO 66 40.9 7.4 50.8 99.1 0.997 0.151 1.846 92.4 In a l l c a l c u l a t i o n s t o t a l i r o n i s taken as FeO. 182 APPENDIX D DEFINITION OF DIFFERENT SERPENTINE MINERALS USED HERE Two d i f f e r e n t s p e c i e s o f s e r p e n t i n e m i n e r a l s , a n t i g o r i t e and c h r y s o t i l e a r e r e c o r d e d i n t h e C l i n t o n Creek a r e a . Under t h e s e two s p e c i e s d i f f e r e n t names a r e used by the w r i t e r on the b a s i s o f t e x t u r e s . A n t i g o r i t e A n t i g o r i t e = A n t i g o r i t e pseudomorphs a f t e r o l i v i n e ; F e a t h e r y t e x t u r e d a n t i g o r i t e ; M osaic t e x t u r e d a n t i g o r i t e . .. S e r p o p h i t e = I s o t r o p i c a n t i g o r i t e . B a s t i t e = A n t i g o r i t e t h a t r e t a i n s . p y r o x e n e ' s t e x t u r e ( a n t o g o r i t e pseudomorphs a f t e r p y r o x e n e ) . C h r y s o t i l e C h r y s o t i l e = A s b e s t i f o r m c h r y s o t i l e . P i c r o l i t e = N o n - a s b e s t i f o r m c h r y s o t i l e . 183 APPENDIX E MICROPROBE ANALYSES OF CHRYSOTILE AND ANTIGORITE Chem i c a l a n a l y s e s o f 33 c h r y s o t i l e samples and 64 a n t i " g o r i t e samples were done u s i n g an ARL e l e c t r o n m i c r o p r o b e (Model - SEMQ) a t the Dept. o f G e o l o g i c a l S c i e n c e s , t h e U n i v e r s i t y o f B r i t i s h Columbia. Samples were a n a l y z e d f o r e l e v e n o x i d e s . The s t a n d a r d s used were j a i d e i t e , f o r s t e r i t e , a n d a l u s i t e , w a l l a s t o n i t e , o r t h o c l a s e , w a l l s t o n i t e , r u t i l e , e s c o a l i t e , s p e s s a r t i t e , f a y l i t e and o l i v i n e f o r Na, Mg, A l , S i , K, Ca, T i , C r , Mn, Fe and N i r e s p e c t i v e l y . R e s u l t s a r e l i s t e d i n the f o l l o w i n g T able 4-1. TABLE 4-1 ANALYTICAL DATA FOR ELEVEN OXIDES OF CHRYSOTILE AND ANTIGORITE Sample Na„0 No. MgO A l 2 ° 3 s i o 2 K 2 0 CaO T i 0 2 C r 2 ° 3 MnO FeO N i O CHOI 0.03 3 y . o o CH02 0.02 39.50 CH03 0.03 38.87 CH04 0.02 39.8y CH05 0.03 38.99 CH06 0.02 39.6 8 CH07 0.01 39.77 CH08 0.02 38.84 CH09 0.03 40.07 CH10 0.03 39.54 CH11 0.04 39.69 CH12 0.04 38.77 •CHI 3 0.03 40.08 CH14 0.03 39.89 0.89 39.91 0.04 0.86 40.28 0.02 0.88 41.36 0.04 0.79 39.48 0.05 0.86 41.99 0.01 0.30 41.13 0.03 0.98 39.24 0.01 0.54 41.79 0.03 0.35 40.00 0.01 0.41 41.17 0.01 0.59 41.59 0.03 0.88 41.24 0.03 0.89 41.01 0.02 0.81 40.59 0.06 0.01 0.04 0.49 0.05 0.06 0.23 0.09 0.02 0.29 0.01 0.03 0.03 0.07 0.01 0.48 0.02 0.01 0.21 0.04 0.06 0.35 0.07 0.01 0.90 0.03 0.04 0.72 0.05 0.01 0.69 0.07 0.07 0.74 0.05 0.0b 0.63 0.06 0.04 0.09 0.02 0.05 0.05 0.05 2.72 0.38 0.01 2.71 0.38 0.04 3.08 0.27 0.07 2.77 0.45 0.02 2.87 0.52 0.02 3.62 0.2y 0.03 2.42 0.54 0.03 3.28 0.27 0.05 3.21 0.24 0.04 2.88 0.20 0.02 1.42 0.06 0.01 1.19 0.11 0.02 1.62 0.15 0.01 1.58 0.19 T a b l e 4-1 (continued) : Sample Na 0 MgO Al-,°o No. 1 1 6 SiO. K 20 CaO TiO, C r 2 ° 3 MnO FeO NiO CH15 CH16 CH17 CH18 CH19 CH2 0 CH21 CH2 2 CH2 3 CH2 4 CH25 CH26 CH2 7 CH2 8 CH2 9 0.02 0.03 0.04 0.03 0.04 0.06 0.03 0.05 0.05 0.04 0.03 0.03 0.04 0 .03 0.02 40.22 39 .27 40.07 39.45 39.89 39 .56 39.57 39.52 39.69 39.99 40.19 39. 84 39 .83 3 y . l 7 39 .12 0 . 86 0. 87 0.62 0.73 0.76 0.68 0.64 0.49 0.58 1.41 1.01 1.08 1.05 1.22 1.23 40.89 40.11 39.77 40. 72 40.41 40.83 40.42 41.38 40.97 40.06 40.35 40. 34 39.44 39.84 39.74 0.02 0.06 0.03 0.03 0. 04 0.03 0 .03 0. 05 0 . 05 0.04 0.03 0. 02 0.01 0 .02 0.01 0.06 0.03 0.04 0.01 0.03 0. 03 0.06 0.07 0.07 0. 02 0.02 0. 01 0.03 0.02 0.01 0.05 0.05 0.04 0.01 0.03 0.02 0.03 0. 02 0.02 0. 06 0. 02 0.02 0.01 0.08 0.0b 0.07 0.07 0.11 0.07 0.07 0.06 0.57 0.82 0. 59 0.04 0.03 0.04 0.04 0.07 0.04 0.02 0.04 0.04 0.06 0.01 0.01 0.01 0.07 0. 03 0.04 0.07 0.01 0.03 0.04 0.01 1.63 1.65 1.53 1.51 1.65 1.49 1.77 1.97 2.12 2.27 1.99 2.58 2.52 2.02 1.92 0.19 0. 11 0.01 0.12 0.21 0.04 0.16 0.18 0.18 0. 17 0.13 0.19 0.07 0.12 0.21 T a b l e 4-1 ( c o n t i n u e d ) : Sample Na 20 MgO A l 2 ° 3 S i 0 2 K 2 ° C a 0 T i 0 2 C r 2 ° 3 M n 0 F e 0 N i 0 No. CH30 0. 03 40.00 0.91 39.61 0.04 0. 05 0.03 0.89 0.02 1. 80 0.27 CH31 0. 04 39.98 0.99 38.29 0.06 0. 06 0.04 0.90 0 . 05 1.22 0.12 CH32 0. 03 39.97 1.08 39. 02 0.03 0. 04 0.02 0.19 0.01 1.86 0. 07 CH33 0. 03 40.26 1.32 40.43 0 . 02 0. 01 0.01 0.58 0.04 1.40 0.17 PC01 0. 01 37.19 0.86 42 . 83 0. 01 0. 01 0.01 0.02 0.06 3.58 0.01 PC02 0. 01 37.93 0. 53 42. 34 0.01 0. 01 0.01 0. 02 0.11 3. 81 0.02 PC03 0. 01 37.65 0. 85 42.56 0.01 0. 01 0.05 0.02 0.12 4.09 0.02 PC04 0. 01 38.20 0 . 52 42. 81 0.01 0. 01 0 . 02 0.03 0. 12 3 .56 0.01 PC05 0. 04 37.15 1.29 41.74 0.01 0. 01 0.02 0.69 0. 03 2.77 0.33 PC06 0. 03 37.92 1. 38 41.45 0.01 0. 01 0.08 0.81 0. 02 2.90 0.33 PC07 0. 02 38.78 0.75 42.62 0. 04 0. 05 0.03 0.26 0.10 1.95 0.20 PC08 0. 02 37.40 0.94 42.71 0.01 0. 02 0. 04 0.41 0.03 2.84 0.16 PC09 0. 03 38.12 0.97 42.13 0.01 0. 06 0.08 0.35 0.01 2.91 0.24 PC10 0. 01 37.58 1.15 41.81 0.06 0. 04 0.03 0.27 0.06 3.18 0.14 Table 4-1 ( c o n t i n u e d ) : Sample Na„0 MgO A l O No. 1 1 6 SiO, K 20 CaO TiO, C r 2 0 3 Mno FeO NiO PC11 0. 01 38. 40 1. 08 PC12 0. 02 38. 57 1. 08 PC13 0. 01 38. 25 0. 95 PC14 0. 01 37. 60 0. 38 PC15 0. 04 38. 55 0. 62 PC16 0. 02 39. 12 0. 62 PC17 0. 03 38. 57 1. 13 PC18 0. 03 38. 71 1. 34 PC19 0. 01 38. 34 0. 36 PC20 0. 04 38. 11 1. 25 PC21 0. 05 38. 96 1. 11 PC22 0. 05 38. 07 1. 15 PC23 ti. 04 38. 13 0. 72 PC24 0. 01 38. 10 0. 97 PC25 0. 01 36. 28 0. 99 42.52 41.47 41. 96 42. 15 43.75 43.09 40.93 38.90 41.68 41.60 39.78 41.54 41. 70 43.21 42.52 0.04 0.03 0.01 0.01 0.01 0.03 0.01 0.02 0.03 0.04 0 . 05 0.06 0. 05 0.01 0.01 0.07 0. 08 0.06 0 .02 ,0.07 0.02 0. 01 0.04 0.02 0.01 0.03 0.01 0. 02 0.01 0.5 0.04 0.01 0.02 0.01 0.02 0.01 0.01 0.01 0.02 0.02 0.01 0.03 0.01 0. 01 0.01 0. 31 0.30 0.30 0.28 0.07 0.09 0.36 0.39 0.02 0.65 0.48 0.43 0.49 0.31 0.26) 0.03 0.02 0. 05 0.10 0.05 0.03 0.08 0.04 0.07 0.02 0.02 0.03 0 .03 0.16 0.16 3. 31 2.95 2.78 3. 73 2.71 1.76 2.79 2.57 2.90 1.62 2.36 1.57 3.30 3.21 4.45 0.28 0.26 0.30 0.16 0.09 0.17 0.11 0.03 0.12 0.02 0.10 0.07 0.08 0.22 0.21 T a b l e 4-1 ( c o n t i n u e d ) : S a m ple Na„0 No. MgO A 1 2 ° 3 S l 0 2 K 2 0 CaO T i O ^ C r 2 0 3 MnO FeO N i O PC26 0.01 37.08 PC27 0.03 37.25 PC28 0.01 38.85 PC29 0.03 38.51 PC30 0.01 38.11 PC31 0.02 38.40 PC32 0.01 38.80 PC33 0.02 38.37 PC34 0.01 37.79 PC35 0.01 37.14 PC36 0.02 37.49 PC37 0.03 37.35 PC38 0.02 37.47 PC39 0.02 36.99 PC40 0.01 37.78 0.87 42.10 0.03 0.94 42.43 0.02 0.99 43.25 0.01 1.03 41.48 0.02 1.18 41.90 0.02 0.89 42.32 0.04 0.63 43.86 0.01 0.93 42.87 0.01 1.95 40.76 0.04 0.52 42.14 0.01 0.40 41.89 0.02 0.58 41.45 0.03 0.29 42.16 0.02 0.34 41.58 0.01 0.34 42.82 0.01 0.05 0.02 0.37 0.06 0.02 0.45 0.01 0.01 0.61 0.09 0.03 0.55 0.02 0.08 0.63 0.01 0.01 0.60 0.07 0.01 0.47 0.01 0.01 0.60 0.06 0.02 0.25 0.02 0.02 0.45 0.03 0.04 0.06 0.04 0.06 0.08 0.01 0.02 0.18 0.02 0.02 0.24 0.01 0.02 0.24 0.03 3.14 0.47 0.03 3.43 0.56 0.01 1.64 0.41 0.03 2.60 0.31 0.04 2.43 0.31 0.01 3.20 0.36 0.01 1.31 0.53 0.02 2.110.37 0.02 z.47 0.10 0.07 3.65 0.04 0.08 3.56 0.03 0.12 3.46 0.01 0.12 3.30 0.06 0.18 3.89 0.05 0.12 3.36 0.07 T a b l e 4-1 (continued-/.': Sample Na„0 No. MgO A 1 2 ° 3 s i o 2 K 20 CaO T l 0 2 C r 2 0 3 MnO FeO NiO PC41 0.01 37.09 PC42 0.04 37.38 PC43 0.03 38.21 PC44 0.03 36.84 PC45 0.02 38.74 PC46 0.03 38.81 PC47 0.01 38.59 PC48 0.02 38.68 PC49 0.02 38.30 PC50 0.02 37.94 PC51 0.03 38.40 PC52 0.03 39.22 PC53 0.02 38.37 PC54 0.01 37.72 PC55 0.01 39.09 1.21 41.22 0.02 0.70 41.94 0.04 0.77 43.08 0.03 0.77 42.44 0.02 0.85 43.22 0.01 0.72 42.36 0.03 0.73 42.06 0.04 0.87 42.66 0.03 1.07 42.19 0.04 0.81 41.86 0.05 0.82 42.49 0.03 0.81 41.31 0.03 0.83 41.43 0.02 0.69 40.12 0.02 1.59 40.35 0.05 0.02 0.03 0.62 0.02 0.05 0.24 0.02 0.01 0.51 0.01 0.01 0.58 0.07 0.02 0.59 0.01 0.01 0.29 0.07 0.02 0.03 0.01 0.01 0.08 0.01 0.04 0.10 0.02 0.02 0.05 0.03 0.02 0.07 0.07 0.02 0.04 0.02 0.01 0.07 0.04 0.03 0.23 0.01 0.02 0.02 0.04 2.83 0.38 0.03 3.91 0.16 0.04 2.29 0.41 0.04 3.78 0.40 0.01 2.38 0.32 0.02 1.90 0.18 0.07 3.33 0.13 0.03 1.42 0.14 0.02 1.78 0.21 0.02 3.68 0.17 0.05 1.95 0.12 0.03 3.76 0.15 0.01 2.67 0.12 0.02 3.61 0.14 0.02 4.22 0.11 Table 4-1 (continued),: Sample Na„0 No. MgO A l 2 ° 3 s i o 2 K 20 CaO T i 0 2 C r 2 0 3 MnO FeO NiO PC56 0.01 38.37 PC57 0.01 38.40 PC58 0.02 39.03 PC59 0.01 38.03 PC60 0.02 38.22 PC61 0.01 38.07 PC62 0.04 38.02 PC63 0.02 36.42 PC64 0.02 36.81 1.57 40.87 0.02 1.58 40.76 0.02 1.5-9 39.17 0.01 1.59 42.66 0.02 1.48 42.89 0.02 0.87 41.88 0.04 0.94 41.86 0.03 1.24 40.05 0.06 1.37 42.27 0.02 0.03 0.02 0.06 0.04 0.03 0.07 0.02 0.01 0.03 0.03 0.03 0.03 0.02 0.03 0.01 0.01 0.01 0.33 0.02 0.01 0.17 0.01 0.05 0.60 0.05 0.01 0.74 0.03 3.78 0.18 0.01 4.00 0.12 0.01 4.04 0.14 0.03 2.45 0.12 0.03 1.71 0.13 0.03 2.81 0.37 0.02 3.58 0.17 0.04 3.92 0.49 0.01 3.81 0.33 A l l a n a l y s e s done by e l e c t r i n m i c r o p r o b e . T o t a l i r o n i s r e p r e s e n t e d as FeO. Sample no. w i t h CH r e p r e s e n t s c h r y s o t i l e . Sample no. w i t h PC r e p r e s e n t s a n t i g o r i t e . 191 APPENDIX F METHODS USED FOR RADIOMETRIC AGE DETERMINATIONS E l e v e n samples from t h e C l i n t o n Creek a r e a have been d a t e d by r a d i o m e t r i c methods. Four samples were d a t e d by t h e pot a s s i u m - a r g o n method and seven samples by r u b i d i u m - s t r o n t i u m whole r o c k method. Samples i n c l u d e : f o u r o f q u a r t z - m u s c o v i t e s c h i s t , t h r e e o f g r e e n s t o n e , two o f q u a r t z - m u s c o v i t e - b i o t i t e s c h i s t , one o f g r a n o d i o r i t e and one o f a m p h i b o l i t e . A l l b u t the g r a n o d i o r i t e sample was c o l l e c t e d w i t h i n t h e mapped a r e a . A m p h i b o l i t e was c o l l e c t e d from an e i g h t f o o t l e n s i n q u a r t z -m u s c o v i t e s c h i s t . A l l samples were a n a l y s e d i n t h e K-Ar l a b o r a t o r y and the Rb-Sr l a b o r a t o r y o f t h e U n i v e r s i t y o f B r i t i s h Columbia. F o r m i n e r a l s e p a r a t i o n the r o c k s were c r u s h e d t o a s t a g e where i n d i v i d u a l m i n e r a l s were f r e e . A f a s t e l e c t r o -magnetic d e v i c e was used t o s e p e r a t e q u a r t z and f e l s i c m i n e r -a l s from m a f i c m i n e r a l s . F l a k y micas and p r i s m a t i c amphiboles were s e p a r a t e d on v i b r a t i n g t a b l e . F u r t h e r s e p a r a t i o n o f the r e s i d i u m was done on a slow e l e c t r o m a g n e t i c s e p a r a t o r . F i n a l -l y , some samples were s e p a r a t e d i n heavy l i q u i d s . Hand p i c k -i n g was used f o r f i n a l c l e a n i n g . 19 2 P o t a s s i u m a n a l y s e s 1 w e r e r u n 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 g o n 2 a n a l y s e s by x s o t o p e d i l u t i o n u s i n g an A E I MS - 10 mass 3 8 s p e c t r o m e t e r and 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 u s e d a r e : KA = 0.585 x l 0 " 1 0 y _ 1 e KA = 4 . 7 2 x l 0 " 1 0 y - 1 p 4 0 K / K = 0.0119 atom p e r c e n t . 3 I n t h e w h o l e r o c k r u b i d i u m - s t r o n t i u m a n a l y s e s , Rb and S r c o n c e n t r a t i o n s w e r e 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 S u r v e y r o c k s t a n d a r d s w e r e u s e d 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 w e r e o b t a i n e d f r o m Mo Ka Compton s c a t t e r i n g m e a s u r m e n t s . R b / S r r a t i o s h a v e a p r e c i s i o n o f 2% ( l a ) a n d c o n c e n t r a t i o n s a p r e c i s i o n o f 5% ( l a ) . S t r o n t i u m i s o t o p e c o m p o s i t i o n was m e a s u r e d on u n s p i k e s a m p l e s p r e p a r e d u s i n g s t a n d a r d i o n e x c h a n g e 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 d e s i g n , m o d i f i e d by H. F a u l . D a t a a q u i s i -t i o n i s d i g i t i z e d and a u t o m a t e d u s i n g a NOVA c o m p u t e r . E x -8 6 8 8 p e r i m e n t a l d a t a h a v e b e e n n o r m a l i z e d t o a S r / S r r a t i o o f 0.1194 and a d j u s t e d s o t h a t t h e NBS s t a n d a r d S r C 0 3 (SRM987) 1: P o t a s s i u m a n a l y s e s w e r e done by K.L. S c o t t o f 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 . 2: A r g o n mass s p e c t r o m e t e r a n a l y s e s w e r e done by J . H a r a k e l o f 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 . 3: R u b i d i u m - s t r o n t i u m w h o l e r o c k a n a l y s e s w e r e done by K.L. S c o t t o f 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 . 193 g i v e s a °'Sr/ °°Sr r a t i o o f 0.71022±2 and t h e E i m e r a nd Amend S r r a t i o o f 0.70800±2. The p r e c i s i o n o f s i n g l e S r / r a t i o i s 0.00013 ( l a ) . R b - S r d a t e s a r e b a s e d o n a Rb d e c a y c o n s t a n t o f 1.42x10 1 . 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 t o t h e t e c h n i q u e o f Y o r k (19 6 7 ) . 194 APPENDIX G PROCEDURES APPLIED FOR PRODUCING LEVEL PLANS WITH DIFFERENT CHRYSOTILE-FIBRE CONCENTRATION ZONES The C l i n t o n Creek open p i t a s b e s t o s mine was mined i n s l i c e s o f u s u a l l y 30 f e e t t h i c k . On each s l i c e i n f o r m a t i o n o f c h r y s o t i l e - f i b r e c o n t e n t i n p e r c e n t a g e a r e a v a i l a b l e i n d r i l l h o l e s l o g s and r e c o r d s o f b l a s t h i l e s . As t h e b l a s t h o l e s were d r i l l e d w i t h i n f i v e t o t e n f e e t d i s t a n c e , i t i s f a i r l y r e l i a b l e t o draw i s o l i n e s on c e r t a i n p e r c e n t a g e o f c h r y s o t i l e - f i b r e i n the s e r p e n t i n i t e . I n t h i s manner i s o -l i n e s o f one p e r c e n t , t h r e e p e r c e n t and seven p e r c e n t were drawn on F i g u r e 3-3, 4-9 and 4-10.
Thesis/Dissertation
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Geological Sciences
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Geology of the Clinton Creek asbestos deposit, Yukon Territory
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