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Geology of the Clinton Creek asbestos deposit, Yukon Territory Htoon, Myat 1979

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CO  GEOLOGY OF THE CLINTON CREEK ASBESTOS DEPOSIT, YUKON TERRITORY by MYAT|HTOON  B . S c , Rangoon A r t s and S c i e n c e s U n i v e r s i t y , 1967  A THESIS SUBMITTED I N PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE  in THE FACULTY OF GRADUATE STUDIES THE DEPARTMENT OF GEOLOGICAL SCIENCES  We a c c e p t t h i s t h e s i s as conforming to t h e r e q u i r e d  THE  UNIVERSITY  OF  standard  BRITISH  March, 1979  0  Myat Htoon, 1979  COLUMBIA  In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l  f u l f i l m e n t of  an  of  advanced degree at  the L i b r a r y I further for  shall  the U n i v e r s i t y  make i t  agree that  freely available for  permission for  Columbia,  I agree  r e f e r e n c e and  extensive copying of  this  thesis for  It  financial  i s understood that gain shall  written permission.  Department of  Geological  The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e V a n c o u v e r , Canada  Sciences  Columbia  V6T 1W5 M a r c h , 2 3 r d , 19 79.  not  for  that  study.  this  thesis  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  by h i s r e p r e s e n t a t i v e s . of  British  the requirements  or  copying or p u b l i c a t i o n  be a l l o w e d w i t h o u t  my  ii  ABSTRACT  C l i n t o n Creek a s b e s t o s d e p o s i t i s s i t u a t e d a t 77 k i l o m e t r e s northwest o f 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 o f O r d o v i c i a n to Devonian age (470 Ma, Rb-Sr date) covers most of the C l i n t o n Creek a r e a . The most prominent metamorphism o f the a r e a o c c u r r e d i n Permian time (245 to 278 Ma, K-Ar d a t e s ) . Based on 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 o f u l t r a m a f i c b o d i e s and c o u n t r y r o c k s i t i s suggested t h a t the u l t r a m a f i c r o c k s were emplaced p r o b a b l y d u r i n g 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 a l o n g w h i c h the a l p i n e u l t r a m a f i c b o d i e s o f C l i n t o n Creek 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 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 c o u n t r y r o c k s . D u r i n g 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 a r e a was 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 . The youngest undeformed and f r e s h b a s a l t i s p r o b a b l y o f S e l k i r k v o l c a n i c s equivalent. Three prominent 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 the o l d e s t and most complex phase o c c u r r e d d u r i n g the Permian, a l o n g 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 a r e c h a r a c t e r i s t i c s o f t h i s phase. The s t r u c t u r a l t r e n d (300* to 315') i s r o u g h l y 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 d e f o r m a t i o n s changes i n d i r e c t i o n o f f o l d axes o f t h i s phase (190* to 350") i s common. The second phase of d e f o r m a t i o n gave r i s e to l a r g e recumbent f o l d s w i t h t r e n d s 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. T h i r d phase o f d e f o r m a t i o n 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 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 c h r y s o t i i l e a s b e s t o s . Afew o t h e r u l t r a m a f i c 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 o f c h r y s o t i l e - f i b r e b u t not o f adequate q u a n t i t y to be mined. 'Mbst o f the u l t r a m a f i c b o d i e s a r e sheared o r m a s s i v e , and a r e d e v o i d o f known chrysotile-fibre. I n g e n e r a l , 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 p e r c e n t t h e r e i s no chance o f commercial 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 a r e 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 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 and o t h e r u n i t s seem to c a r r y o r e grade o r 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 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 m a i n l y s u p p o r t s 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 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 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 , a few e v i d e n c e 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 o f 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 o c c u r a t the end o f C r e t a ceous when 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 . These i n t r u s i o n s c o u l d have p r o v i d e d 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 s e r p e n t i n e a l o n g f r a c t u r e s . T h i s r e s u l t e d 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.  iii  A n a l y s i s o f i s o t o p i c dates o f t h e 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 g r o u p i n g o f igneous a c t i v i t y a t mid Cretaceous and l a t e s t C r e t a ceous time. Some i s o t o p i c dates o f igneous and metamorphic r o c k s r a n g i n g from 135 t o 230 Ma 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 Trench. The t r e n d s u g g e s t s ' t h a t the date a t the T i n t i n a Trench i s about 200 Ma, and 2'50 k i l o m e t r e s p e r p e n d i c u l a r d i s t a n c e from t h e t r e n c h i s 150 Ma. The apparent 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. However, more d a t a i s r e q u i r e d 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 g e o s u t u r e and v a n i s h e d ocean.  iv  CONTENTS  Page I  j  II  INTRODUCTION  1  1-1  PRELIMANARY  1-2  S C O P E OF  1-3  L O C A T I O N AND  1-4  C L I M A T E AND  1-5  PHYSIOGRAPHY  1- 6  HISTORY  GEOLOGY OF  STATEMENT  1  THESIS  OF  1  ACESS  3  VEGETATION  4  5  THE C L I N T O N C R E E K  DEPOSIT  THE C L I N T O N C R E E K A R E A  2- 1  INTRODUCTION  2-2  METAMORPHIC  ROCKS O F  CRYSTALLINE  PLATEAU  6  7  7  THE YUKON 7  Page 2-2-A  Regional S e t t i n g  2-2-B  C l i n t o n Creek  7  Area  a.  Carbonaceous  argillites  13  b.  Greenstone and q u a r t z - m u s c o v i t e chlorite schist  16  Q u a r t z - m u s c o v i t e s c h i s t and quarzite  18  Q u a r t z - m u s c o v i t e -• b i o t i t e  20  c. d.  and l i m y  12  schist  2-3  ULTRAMAFIC  2-3 -A  Regional  2-3'-B  Clinton  2-4  ACID INTRUSIVE ROCK  25  2-5  BASALT  26  2-6  STRUCTURE  27  2-6--A  Introduction  27  2-6'-B  Folds  29  2-6--c  Faults  44  2-6--D  Joints  48  2-6'-E  Regional  2-7  ISOTOPIC AGE  2-7-A  Introduction  ROCKS  22  Setting  22  Creek  Area  Structure  DETERMINATIONS  24  48  50 50  vi  Page 2-7-B  III  Isotopic Analyses  55  a.  Potassium-Argon  55  b.  Rubidium-Strontium  56  2-1-0.  Regional Synthesis  58  2- 7-D  Summary  66  CLINTON CREEK ULTRAMAFIC BODIES  68  3- 1  INTRODUCTION  68  3-2  PETROLOGY  69  3-2-A  Ultramafic  3-2-B  E a r l y Stage A l t e r a t i o n  72  a.  Serpentinization  72  b.  Rodingitization  84  c.  Blackwall  Rock Types  and  69  talc-carbonate  alteration 3-2-C  91  Late Stage A l t e r a t i o n  92  a.  Silica-carbonate  alteration  b.  Quartz-magnesite veins  92 103  3-3  STRUCTURE  103  3-4  ORIGIN  106  vii  Page IV  THE  CLINTON  CREEK  ASBESTOS  DEPOSIT  118  4-1  INTRODUCTION  118  4-2  CHRYSOTILE  118  4-2-A  Textures  4-2-B  VEINS  and S t r u c t u r e s  a.  Chrysotile-fibre  b.  Picrolite  120  veins  120  veins  Relationship with  123  Serpentine  Wall-rock 4-2-C  Chemistry  127 o f C h r y s o t i l e and  Antigorite  4-3  FRACTURES  129  AND  DISTRIBUTION  CHRYSOTILE-FIBRE  4-4  O R I G I N OF  4-4-A  Temperature Serpentine  4-4-B  4-4-C  Formation  VEINS  13 5  CHRYSOTILE VEINS of Formation  14 3  of  Minerals  14 3  of C h r y s o t i l e Veins  a.  Previous  ideas  b.  Evidence  from  C h r y s o t i l e Forming Chrysotile  OF  14 5 14 5  C l i n t o n Creek Solutions  Deposition  14 6  and 148  viii  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  C a s s i a r , 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, A l a s k a  157  5-2-G  Eagle, A l a s k a  158  5-3  FEATURES OF BARREN ULTRAMAFIC BODIES  159  5-4  GUIDES IN SEARCH FOR CHRYSOTILE ASBESTOS  VI  160  SUMMARY AND CONCLUSION  163  BIBLOGRAPHY  166  ix  APPENDIX A  Page 17 6  APPENDIX B  177  APPENDIX C  180  APPENDIX D  182  APPENDIX E  183  APPENDIX F  191  APPENDIX G  194  X  LIST OF TABLES  2-1  U n i t s i n the C l i n t o n Creek Area, Y.T.  2-2  S t r u c t u r a l Elements o f the C l i n t o n Creek  Page 9  Area  30  2-3  Potassium-Argon A n a l y t i c a l Data  52  2-4  Rubidium-Strontium Data f o r Analyzed Whole Rock Samples R e l a t i o n s h i p s o f I s o t o p i c Dates and I t s P e r p e n d i c u l a r D i s t a n c e from the T i n t i n a Trench i n the Yukon C r y s t a l l i n e P l a t e a u  2-5  4-1 4-2 4-3  53 60  A n a l y t i c a l Data f o r Eleven Oxides o f C h r y s o t i l e and A n t i g o r i t e  188  S t a t i s t i c a l Summary o f the E l e v e n Oxides o f 33 C h r y s o t i l e Samples  131  S t a t i s t i c a l Summary o f the E l e v e n Oxides o f 64 A n t i g o r i t e Samples  132  xi  LIST OF FIGURES  1- 1  L o c a t i o n o f the C l i n t o n Creek Asbestos Deposit  2- 1  Regional Geology  2-2  G e o l o g i c a l Map o f the C l i n t o n Creek Area  2-3  D i s t r i b u t i o n of the Yukon Metamorphic Complex and E q u i v a l e n t s i n Yukon T e r r i t o r y and A l a s k a  2-4  Page 2 8 -b-a-ck pocket 11  Generalized Distribution of Serpentinized U l t r a m a f i c Rocks i n Yukon T e r r i t o r y and A l a s k a  23  2-5  D i s t r i b u t i o n o f 73 L^ L i n e a t i o n s  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 o f Second Phase F o l d s  41  2-8  Poles to 75 (F^)  42 43  2-9  Poles to 123 L  2-10  Poles to 66 F a u l t s  2-11 2-12  Poles to 133 J o i n t s Geology o f the C l i n t o n Creek Area w i t h I s o t o p i c a l l y Dated Sample S i t e s  54  Plots of Sr/ Sr vs. R b / S r f o r Whole Rock Rb-Sr Analyses of the C l i n t o n Creek Area  57  2-13 2-14  2- 15  2  F o l i a t i o n s and A x i a l Planes Lineations  Histogram o f K-Ar and Rb-Sr Dates o f Igneous and Metamorphic Rocks of the Yukon C r y s t a l l i n e Plateau K-AR and Rb-Sr Dates of Igneous and Metamorp h i c Rocks o f the Yukon C r y s t a l l i n e P l a t e a u vs. P e r p e n d i c u l a r D i s t a n c e from the T i n t i n a Trench  3- 1  Modal C l a s s i f i c a t i o n o f U l r r a m a f i c Rocks  3-2  T-X Diagram i n S a t u r a t e d System MgO-SiO„H 0-C0 -CaO 2  2  47 49  63  65 70 79  xii  Page back pocket  3-3  Ore Grade Zones i n the Porcupine P i t  3-4  Cross S e c t i o n o f Porcupine S e r p e n t i n i t e Body Along 12W  3-5  Dehydration, C a r b o n a t i z a t i o n and S i l i c i f i c a t i o n o f 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-H 0 Tetrahedron  100  Ore B e a r i n g Porcupine, Creek and Snow Shoe S e r p e n t i n i t e Bodies  10 5  Cross S e c t i o n o f Porcupine U l t r a m a f i c Body Along 19W  10 8  Cross S e c t i o n o f Porcupine U l t r a m a f i c Body Along 20W  109  Cross S e c t i o n o f Porcupine U l t r a m a f i c Body Along 26W  110  Cross S e c t i o n o f Porcupine U l t r a m a f i c Body Along 24W  111  Cross S e c t i o n o f Porcupine U l t r a m a f i c Body Along 23W  112  Cross S e c t i o n o f Porcupine U l t r a m a f i c Body Along 10W  113  2  3-6 3-7 3-8 3-9 3-10 3-11 3-12 3- 13  95  Cross S e c t i o n o f Porcupine U l t r a m a f i c 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  C h a r a c t e r i s t i c s o f C h r y s o t i l e - f i b r e Veins  124  4-3 4-4  C h a r a c t e r i s t i c s o f P i c r o l i t e Veins Frequency Diagrams o f MgO, A I 2 O 3 , S i 0 2 and FeO (by wt. %) o f 64 A n t i g o r i t e Samples  128  4-5  4-6  Frequency Diagrams o f MgO, A ^ O o , S i 0 and FeO (by wt. %) o f 33 C h r y s o t i l e  133  2  Samples  134  Poles to 264 C h r y s o t i l e - f i b r e Veins  136  xiii  4-7  4-8 4-9  Poles to 125 C h r y s o t i l e - f i b r e Veins Showing Displacement Along the C o n t a i n i n g Fracture Poles to 139 C h r y s o t i l e - f i b r e Veins i n Joints  Page 138 139  Ore ( C h r y s o t i l e - f i b r e ) L e v e l 1410 f t .  Grade Zones a t  4-10  Ore ( C h r y s o t i l e - f i b r e ) L e v e l 1470 f t .  Grage Zones a t  4-11  Ore ( C h r y s o t i l e - f i b r e ) Grade Zones i n Cross S e c t i o n Along 17W  140  4-12  Poles to 105 F a u l t s i n and Adjacent to the Porcupine U l t r a m a f i c Body  144  4-13  Mechanics o f O r i g i n o f C h r y s o t i l e  Veins  14 7  4- 14  C h r y s o t i l e Forms Adjacent to S e r p e n t i n e but Not to O l i v i n e  150  5- 1  Asbestos B e a r i n g U l t r a m a f i c Bodies i n B.C., Y.T. and A l a s k a  153  back pocket' back pocket  xiv  L I S T OF PLATES  2-1  Carbonaceous a r g i l l i t e i n c o n t a c t quartz-muscovite schist  with  2-2  Dark, bedded l i m e s t o n e w i t h i n t h e naceous a r g i l l i t e u n i t  carbo-  2-3 2-4 2-5 2-6  Page 14 15  Lens o f marble i n the quartz-muscovite s c h i s t and q u a r t z i t e u n i t  19  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 muscovite s c h i s t  21  Columnar j o i n t e d b a s a l t o f S e l k i r k Volcanics  28  Tight i s o c l i n a l  f o l d s i n carbonaceous  argillite  32  2-7  G l e i t b r e t t s t r u c t u r e i n schistose rocks  33  2-8  R e l i c t of L j f o l d closures i n the enclosing a r g i l l i t i c sandstone C h e v r o n f o l d s shown b y y e l l o w s a n d s t o n e b e d s  34 38  C r e n u l a t i o n s r e l a t e d t o L2 f o l d muscovite s c h i s t  39  2-9 2-10 2-11 2-12 2- 13  F o l i a t i o n s F]_ a n d F schist  2  in  i n quartz-  quartz-muscovite  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 Porcupine p i t  40 45  Northerly trending v e r t i c a l fault with considerable displacement i n the Porcupine pit  46  3- 1  Serpentinized harzburgite  71  3-2  Serpentinized  73  lherzolite  X V  3-3 3-4  P a l e y e l l o w b r u c i t e formed d u r i n g pervasive, f i r s t main episode of s e r p e n t i n i z a t i o n Yellowish  white brucite  i n fractures  Page 76  between  picrolite  77  3-5  Chromite w i t h  3-6  Older rodingite  3-7  Older rodingite  3-8  Contact of older  3-9  Uralitized, chloritized rodingite  88  3-10  Serpentine dehydrated i n t o pyroxene  90  3-11  Talc-carbonate vein  93  3-12  Silica-carbonate  3-13  F i r s t stage of s i l i c a - c a r b o n a t e  3-14 3-15  O p a l 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 Quartz-magnesite vein of l a t e s i l i c a carbonate a l t e r a t i o n  3- 16  Ore  magnetite  82 85  (crossed  nicols)  r o d i n g i t e and  serpentinite  in serpentinite  a l t e r a t i o n a l o n g f a u l t zone  bearing Porcupine ultramafic  p l u n g i n g 10'  86  alteration  87  96 98 10 2 104  body  t o w a r d s 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  Cross-fibre  121  4-3  P i c r o l i t e vein  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  Long-fibre c h r y s o t i l e veins spaced f r a c t u r e s Serpentinite breccia  141 142  4-6  vein  in thin section  in thin section  126  i n widely  xvi  ACKNOWLEDGEMENT  This  t h e s i s was s u p e r v i s e d b y D r s .  S i n c l a i r and C . I .  G o d w i n , whose a d v i c e  K.C. M c T a g g a r t , A . J . and g u i d a n c e a r e g r e a t l y  appreciated. The  w r i t e r w i s h e s t o t h a n k D r . R.L. A r m 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 Harakel  for t h e i r help  i n i s o t o p i c d a t i n g ; K.C. S c o t t a n d J . i n Rb-Sr and K-Ar d a t i n g  processes;  and  G. G e o r g a k o p o u l o s 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 npreparation of thin  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 Asbestos Corp. L t d . i s a l s o g r e a t l y appreciated . The  w o r k was s u p p o r t e d  by t h e 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 , W h i t e H o r s e , Yukon T e r r i t o r y . ed  f i n a n c i a l l y by t h e U n i t e d N a t i o n s  United Nations,  The w r i t e r was  support-  D e v e l o p m e n t Programme,  New Y o r k .  Most o f a l l t h e w r i t e r l i k e s  t o thank again  t o D r . 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 guidance 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  thesis i s the geological  g a t i o n o f C l i n t o n Creek Asbestos a r e a i n Y u k o n T e r r i t o r y , Canada h e l d by C a s s i a r A s b e s t o s economic asbestos ant t o study  investi-  d e p o s i t and i t s s u r r o u n d i n g (Figure 1-1).  The d e p o s i t ,  Cooperation L t d . , i s the only  d e p o s i t i n Yukon T e r r i t o r y .  I t was  t h e d e p o s i t and t h e c o n t r o l s o f a s b e s t o s  known importforma-  t i o n b e f o r e 1978 when t h e m i n e was c l o s e d and t h e o p e n 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  u s e f u l i n t h e 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 mafic bodies w i t h asbestos  1-2  SCOPE OF  s t u d y m i g h t be of other  ultra-  mineralization.  THESIS  Purpose of the study 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°  NORTHWEST TERRITORIES  V...  I  YUKON  i TERRITORY 65° CLINTON * »  CREEK'  ^ D A W S O N  \  (  n  *o,  rt  \  I*  I  \  V V WHITEHORSE  100  X  4  B.\C.  50  100  200 km 150  FIG H : LOCATION OF THE CLINTON C R E E K ASBESTOS DEPOSIT  mil  3  is  t o develop genetic concepts that could guide  exploration  f o r c h r y s o t i l e asbestos,  T i n t i n a r e g i o n o f t h e Yukon.  e s p e c i a l l y i n the  The s e c o n d o b j e c t i v e i s t o  d e s c r i b e t h e geology o f t h e mine, t h e g e n e s i s and  to consider  core  M a p p i n g was d i f f i c u l t b e c a u s e o f l i m i t e d  w h i c h amount t o l e s s t h a n f i v e p e r c e n t  Because d r i l l records  of the deposit  t h e o r i g i n and emplacement o f u l t r a m a f i c  rocks of the area. outcrops  future  core  had been logged  of the area.  by a t l e a s t e i g h t  were i n c o n s i s t e n t and t h e w r i t e r r e l o g g e d  persons,  a l l the  t h a t c o u l d be d o c u m e n t e d . F i e l d w o r k was c a r r i e d o u t f r o m J u n e t o A u g u s t i n  1975  and 1 9 7 6 .  covers  During  these  periods  the property,  which  a b o u t one s q u a r e m i l e , was mapped a t a s c a l e o f one  inch to forty  f e e t , and a s e v e n t y - s q u a r e - m i l e  area  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  The  ACCESS  C l i n t o n Creek asbestos  l o n g . 140"23'W. F i g u r e  deposit  ( l a t . 64'23'N,  1-1) i s s i t u a t e d a b o u t 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 , Y u k o n T e r r i t o r y on C l i n t o n C r e e k , 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 river.  with Forty  S i x t y M i l e r o a d w h i c h c o n n e c t s Dawson C i t y  b a n k s p a s s e s 32 k i l o m e t r e s  t o the southeast  Mile  and F a i r -  o f t h e mine.  4  A gravel a i r - s t r i p  on t h e p r o p e r t y i s adequate  aeroplanes o f moderate s i z e . e a s t and t r e n d i n g r i d g e  The d e p o s i t o c c u r s o n a n o r t h -  ( e l e v a t i o n 545 m e t r e s ) some 155 m e t r e s  above t h e v a l l e y o f C l i n t o n  1-4  f o r commercial  Creek.  CLIMATE AND VEGETATION  The  a r e a l i e s w i t h i n t h e zone o f d i s c o n t i n u o u s  f r o s t and x s s u b j e c t t o severe c l i m a t i c c o n d i t i o n s w i n t e r months.  perma-  during  The t h i c k n e s s a n d n a t u r e o f p e r m a f r o s t a p p e a r  to vary depending on the type o f s o i l  o r rock water content  and t h e d i r e c t i o n t h a t t h e g r o u n d s u r f a c e f a c e s .  Precipita-  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 , m o s t o f w h i c h o c c u r s as r a i n i n June, J u l y and A u g u s t . b e t w e e n -56*  Celsius  i n w i n t e r a n d +32*  Temperatures celsius  Freeze-up u s u a l l y o c c u r s around l a t e September; 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. s n o w f a l l i s about one m e t r e .  i n summer. spring break-  The a v e r a g e a n n u a l  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 m e t r e s ) Black spruce, birch  are below t r e e  and p o p l a r a r e abundant.  w i l l o w a n d b a l s a m p o p l a r a r e l e s s common.  line.  Alpine  b u t s p a r s e g r o w t h e x t e n d s up t h e h i l l s i d e s .  fir,  In general,  heavy f o r e s t growth i s r e s t r i c t e d t o t h e main v a l l e y  s l o p e s a r e more h e a v i l y  range  floors,  South-facing  forested than north f a c i n g  slopes  5  which are covered  1-5  by t h i c k moss and s p a r s e  timber.  PHYSIOGRAPHY  C l i n t o n Creek d e p o s i t  lies  i n the Klondike  Plateau  which extends n o r t h w e s t w a r d 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  (Wahrhaftig,  i s b o u n d e d on t h e n o r t h e a s t  1965).  The K l o n d i k e  Plateau  by t h e T i n t i n a T r e n c h a n d t h e  s o u t h w e s t by t h e N i s l i n g R i v e r , a n d 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,  which escaped g l a c i a t i o n during 1968).  The K l o n d i k e  e t a l . , 1970) m o s t o f  the P l e i s t o c e n e  P l a t e a u i s marked by l o n g ,  (Prest, et a l . , irregular  m a i n and s p u r 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 dendritic 1,000  stream 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 b e t w e e n  a n d 1,350 m e t r e s e l e v a t i o n a n d p r o b a b l y  old uplifted erosion surface.  represent  C l i n t o n Creek has a  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 narrow v-shaped v a l l e y s w i t h steep hills  gradients.  an  gentle  occupy Dome-shaped  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 t h e  mapped a r e a .  Outcrops are scarce  found along  and n e a r r i d g e c r e s t s .  and most o f t h e s e  are  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 a n d i s c r e d i t e d  t o A r t A n d e r s o n , an I n d i a n t r a p p e r ; he was l i s t e d on  t h e p a y r o l l o f C l i n t o n Creek mine.  of 9 4 claims 1957-58. and  The p r o p e r t y  t h e f i r s t p h a s e o f e x p l o r a t i o n was  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  Plumb a n d D.R. B u d i n s k y . s u r f a c e diamond d r i l l i n g  consists  One a d i t was d r i v e n i n  T h i s w o r k was f o l l o w e d b y m a g n e t o m e t e r  drilling;  i n lb)63.  a n d two p l a c e r l e a s e s .  an " N o . l "  surveys completed by  N.W.  From 1963 t o 1 9 6 6 , u n d e r g r o u n d a n d as w e l l as g e o l o g i c a l and  mapping were c a r r i e d o u t .  geophysical  C o n s t r u c t i o n o f an a c c e s s  u n d e r t a k e n i n 1965 a n d 1966.  road  was  The m i n e b e g a n t o p r o d u c e i n  1967. B o t h t h e mine and t h e p r i m a r y s i t u a t e d a t a lower  c r u s h i n g p l a n t were  l e v e l than t h e m i l l and p l a n t s i t e .  b e l t conveyor c a r r i e s o r e from t h e primary tramway f e e d e r .  The o r e i s e l e v a t e d  crusher  A  t o the  152 m e t r e s b y a 1,600  m e t r e l o n g t r a m l i n e t o t h e p l a n t s i t e and was d e l i v e r e d a t 30 0 t o n s p e r h o u r .  The m i n e h a d p r o d u c e d o r e f o r e l e v e n  y e a r s w i t h an a v e r a g e w a s t e - t o - o r e r a t i o o f a b o u t 5.5 t o 1. Operations  c e a s e d i n 1978 when t h e o r e was e x h a u s t e d .  7  CHAPTER I I  GEOLOGY OF  2-1  THE  CLINTON CREEK AREA  INTRODUCTION  The  r e g i o n a l geology  o f map  t h e C l i n t o n C r e e k a r e a has (1961) and map.  The  Green  (1972).  F i g u r e 2-1  was  prepared  ( T a b l e 2-1)  (Tempelman-Kluit,  belong  19 7 4 ) .  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 Cretaceous The  to  Roddick  from  their to  Grandior-  earliest  y o u n g e s t u n i t , n o t i n c l u d e d i n F i g u r e 2-1  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 H o l o c e n e age. o f a l l u n i t s and  the  Ultra-  m a f i c r o c k s were p r o b a b l y emplaced i n P e r m i a n t i m e .  Tertiary.  includes  b e e n d e s c r i b e d by G r e e n and  o l d e s t rocks i n the area  Yukon Metamorphic Complex  s h e e t 12 84A w h i c h  is  Distribution  l o c a t i o n s o f s p e c i m e n s a r e shown i n ( F i g u r e  2-2) .  2-2  METAMORPHIC ROCKS OF  2-2-A  REGIONAL SETTING  THE  YUKON CRYSTALLINE PLATEAU  FIGURE 2-1: REGIONAL GEOLOGY. 1= G r i t and s l a t e ; 2= Q u a r t z - m i c a s c h i s t and q u a r t z i t e ; 3= 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 ; 4= 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 ; 5= B i o t i t e g r a n o d i o r i t e and q u a r t z monzonite; 6= Sandstone, s h a l e , conglomerate and lignite; 7= A l l u v i a l d e p o s i t s ; F= F o s s i l l o c a l i t y . ( M o d i f i e d 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  PALEOZOIC  Late Tertiary  Selkirk Group (?)  Basalt  Early Tertiary  Nisling Alaskite Group (?)  Biotite Granodiorite  Permian  Main phase o f metamorphism o f the C l i n t o n Creek a r e a . D e r i v e d from K-Ar dates o f m u s c o v i t e and h o r n b l e n d e , and Rb-Sr d a t e of whole r o c k .  Pensylvan i a n and/or Permian Devonian(?) or e a r l i e r Ordovician and earlier(?)  1:  64.9±2.3  245±8 255.8±22.3 278±10  Ultramafic Rocks  Yukon Metamorphic Complex  Carbonaceous a r g i l l i t e , limy a r g i l l i t e , limestone, sandstone Greenstone, q u a r t z - m u s c o v i t e chlorite s c h i s t , quartzmuscovite s c h i s t , q u a r t z muscovite-biotite schist, micaceous q u a r t z i t e and c r y s t a l l i n e limestone  I s o t o p i c ages a r e d i s c u s s e d i n Chapter I I , s e c t i o n s e v e n .  470  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 r e r e f f e r r e d t o as Yukon Complex ( T e m p l e m a n - K l u i t , 1974).  These r o c k s u n d e r l i e most  o f t h e a r e a b e t w e e n T i n t i n a and S h a k w a k - D e n a l i Yukon T e r r i t o r y  Metamorphic  faults i n  ( F i g u r e 2-3) a n d a r e e q u i v a l e n t w i t h t h e  B i r c h C r e e k 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 b y M e r t i e i n 1937.  The T e r r a n e h a s b e e n c a l l e d b y d i f f e r e n t names i n  d i f f e r e n t areas. D.D.  The f i r s t p e r s o n who mapped t h e a r e a was  C a i r n e s (1914) who a s s i g n e d t h e Y u k o n G r o u p t o P r e -  Cambrian.  Names s u c h a s " 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 " ,  " N a s i n a 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 terrane  (McConnell, 1905).  The K l o n d i k e s c h i s t ,  Nasina  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 t h e 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 t h e T e r r a n e near t h e Y u k o n - A l a s k a b o r d e r , and c o n t a i n large lenses of c r y s t a l l i n e bolite  l i m e s t o n e , s e r p e n t i n i t e and  (Green and R o d d i c k , 1972).  Metasediments,  just  amphiwest  o f t h e C l i n t o n Creek a r e a a c r o s s t h e 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 a s s e m b l a g e s 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 1974).  Rocks  r a t h e r t h a n an ( F o s t e r and K e i t h ,  o f t h e C l i n t o n Creek area resemble those o f t h e  E a g l e a r e a i n A l a s k a a n d f o r m p a r t o f t h e same  belt.  Ages o f r o c k s i n t h e Y u k o n C r y s t a l l i n e P l a t e a u from Pre-Cambrian  t o Cenozoic.  The P e l l y  gneiss, near the  west-central part of the Plateau south of the C l i n t o n y i e l d s a R b - S r age o f a b o u t 750 Ma  range  Creek  (R.L. A r m s t r o n g , p e r s o n a l  B.G FIGURE 2 - 3 : D I S T R I B U T I O N OF THE YUKON METAMORPHIC COMPLEX AND EQUIVALENTS I N THE YUKON TERRITORY AND ALASKA. ( A f t e r TempelmanK 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 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 the  C l i n t o n C r e e k a r e a h a v e y i e l d e d a R b - S r m o d e l age o f 470 Ma"*". However, i n an a r e a j u s t w e s t o f t h e Y u k o n 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  i n limestone a s s o c i a t e d w i t h metasedimentary a P a l e o z o i c age 19 7 2 ) ,  ( M e r t i e , 1937;  p r o b a b l y Devonian.  columnals  rocks indicate  D o u g l a s , e t a l . , 1970;  Green,  The y o u n g e s t i g n e o u s 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  Area  More t h a n 8 0 p e r c e n t o f t h e a r e a i s u n d e r l a i n by morphic rocks w i t h l i t h o l o g i c  characteristics similar  t h o s e o f t h e 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 2-3). units  The w r i t e r d i s t i n g u i s h e d t h e f o l l o w i n g  meta-  to  (Figure  lithologic  ( H t o o n , 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 f r o m d t o a:  1 2  a.  Carbonaceous 2  and l i m y a r g i l l i t e ( y o u n g e s t ) ,  b.  Greenstone  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 ,  d.  Quartz-muscovite-biotite schist  and q u a r t z - m u s c o v i t e - c h l o r i t e  : See C h a p t e r two s e c t i o n s e v e n . : Greenstone i s d e s c r i b e d i n Appendix  A  and  (oldest).  schist,  13  a.  C a r b o n a c e o u s and  limy  argillites  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 It  c o n s i s t mostly  limy a r g i l l i t e , stone.  of interbedded  b l a c k to dark  carbonaceous  gray  Carbonaceous a r g i l l i t e  limestone  ( P l a t e 2-1).  Limy a r g i l l i t e is  dull  and  Limestone,  normally  b l a c k and  is well  laminated but  f r a c t u r e s are coated or muscovite. very  limy  sand-  fragile,  c o n s t i t u t e s most o f to recognize.  than carbonaceous  i s found  rock between carbonaceous a r g i l l i t e stone.  and  Bedding i s d i f f i c u l t  i s r e l a t i v e l y harder  to brownish  argillite,  i s j e t black, very  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 this unit  valley.  and  as a  agrillite,  transitional  limestone or  sand-  highly fractured (Plate  2-2),  seldom t h i c k l y bedded.  Partings  and  f o r t h e most p a r t w i t h c a r b o n a c e o u s  Sandstone, o r d i n a r i l y b u f f to brownish  l i m y , i s uncommon b u t  locally  forms c o n s p i c u o u s  matter  and beds i n  argillite. 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 to  s i s t of q u a r t z , carbonaceous matter, c h l o r i t e , p y r i t e and Quartz percent  and  traces of epidote, a l b i t e  carbbnaceous matter  and  T h e r e a r e two  and  clay,magnetite, and  biotite.  u s u a l l y t o t a l more t h a n  20 p e r c e n t r e s p e c t i v e l y .  t u t e as much as 15 p e r c e n t rock.  sercite,  Clay minerals  sericite  generations  up  t o 10 p e r c e n t o f  o f q u a r t z , o r i g i n a l and  c r o s s a t a n g l e s o f a b o u t 120*  and  50  consti-  gers of metamorphic q u a r t z which c u t across the bedding. cleavages  con-  sericite  the  strinTwo  elonga-  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 t o p ) i n c o n t a c t with quartz-muscovite s c h i s t ( l i g h t coloured layers a t bottom).  15  0 i  im •  1  PLATE 2 - 2 : D a r k , b e d d e d l i m e s t o n e w i t h i n t h e carbonaceous a r g i l l i t e u n i t . Thin l a y e r s o f carbonaceous a r g i l l i t e a l s o occur between each limestone bed.  16  tion parallels  these cleavages.  by t h e r e p l a c e m e n t o f b i o t i t e . weakly  Most c h l o r i t e has  formed  Much o f t h e a r g i l l i t e  mylonitized. In  thin section limy a r g i l l i t e  q u a r t z , 35 p e r c e n t c a l c i t e ,  c o n s i s t s o f 35 p e r c e n t  20 p e r c e n t c l a y m i n e r a l s ,  10 p e r c e n t c a r b o n a c e o u s m a t t e r w i t h m i n o r s e r i c i t e , and c h l o r i t e . ceous  is  5 to  pyrite  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 -  argillite. Dark  g r a y l i m e s t o n e , w e a k l y f o l i a t e d and m e t a m o r p h o s e d ,  i s o f two t y p e s .  S a n d y 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 c a r b o n a c e o u s l i m e s t o n e h a s as much as 15 p e r c e n t carbonaceous matter.  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  o z o i s i t e are a l s o present. c e o u s m a t t e r and s e r i c i t e rich are  Limestone w i t h abundant  i s finely  Quartz  e l o n g a t e d i n t h e f o l i a t i o n and show h i g h l y  extinction.  carbona-  l a m i n a t e d whereas  l i m e s t o n e s a r e m a s s i v e t h i c k bedded.  clin-  quartz-  grains  undulose  Limy s a n d s t o n e , n o t abundant, grades i n t o  sandy  limestone.  b.  G r e e n s t o n e and q u a r t z - m u s c o v i t e - c h l o r i t e  schist  T h i s u n i t i s composed o f 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 chlorite  s c h i s t a n d m i n o r 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  schist.  The  rocks of t h i s u n i t are f i n e t o medium-grained  c o l o u r ranges from dark green to s i l v e r y - g r e e n . foliation varies  from poor t o w e l l .  Degree  Shearing i s not  and  of  pervasive.  17  Greenstone  i s g e n e r a l l y dark green, massive  foliated but locally well consists of a foliated sericite,  foliated.  In thin-section i t  mass o f q u a r t z , c h l o r i t e , e p i d o t e ,  c a l c i t e , a m p h i b o l e , p l a g i o c l a s e and opaque m i n e r a l s .  Q u a r t z 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 , carbon-  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 In  or obscurely  less sheared rock, p l a g i o c l a s e  (albite  of shearing.  to oligoclase)  occurs  w i t h a l e s s e r amount o f e p i d o t e g r o u p 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 . the  S h e a r i n g i n greenstone has l a r g e l y d e s t r o y e d  texture of the o r i g i n a l  rock.  I n r o c k s which 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 still  r e c o g n i z a b l e , even though  albite of  and s a u s s u r i t e .  ferromagnesium  v e r y few s p e c i m e n s are  preserved.  i n massive  t h e y have been a l t e r e d t o  Generally the o r i g i n a l  forms  minerals are not recognizable, but i n a amphibole  Actinolite,  pseudomorphs a f t e r  pyroxene  t h e common a m p h i b o l e ,  i s common  a l t e r e d greenstone but i s l e s s prominent i n  sheared g r e e n s t o n e where c h l o r i t e  takes i t s place.  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 Relict  crystal  Carbonate  to the f o l i a t i o n .  t e x t u r e s a n d m i n e r a l s s u g g e s t t h a t t h e g r e e n s t o n e was  originally  a b a s i c igneous rock.  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 , moderately 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  partings.  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 u a r t z a n d m u s c o v i t e a r e more a b u n d a n t t h a n i n g r e e n s t o n e .  18  Schistosity quartz.  i s mainly p a r a l l e l to layers of muscovite  Although  i t resembles greenstone,  pronounced s c h i s t o s i t y , a sedimentary In greenstone if  former  i t was  except  the h i g h q u a r t z content  and  for i t s  suggests  origin.  the f i e l d  i t is difficult  to d i s t i n g u i s h  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 , i s h i g h l y sheared.  between  especially  But a f t e r t h i n s e c t i o n  study,  found t h a t the southern p a r t of the study area 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 , h o w e v e r , t o draw a g e o l o g i c c o n t a c t b e t w e e n t h e 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 . greenstone  c.  and a r g i l l i t e  are  Quartz-muscovite  two  I n some p l a c e s ,  interbedded.  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 s c h i s t and m i c a c e o u s q u a r t z i t e .  quartz-muscovite  T h e s e a l t e r n a t e one w i t h  the  o t h e r and c o n t a c t s b e t w e e n them a r e g e n e r a l l y g r a d a t i o n a l . few  lenses of white to whxtish-gray c r y s t a l l i n e  limestone  also occur  ( P l a t e 2-3).  dominant.  I t i s g r a y t o d a r k 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 muscovite of  and  A  At the base of the u n i t q u a r t z i t e i s  i s well  foliated.  V a r i a t i o n of  size  q u a r t z g r a i n s b e t w e e n f o l i a t i o n p l a n e s i s n o t uncommon.  At higher levels quartz-muscovite l y , quartz-muscovite  s c h i s t i s prominent.  Local-  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: L e n s o f m a r b l e ( g r a y zone i n t h e m i d d l e ) 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 ite unit.  20  mica  f l a k e s grow a s 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 . I n 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  percent q u a r t z , about t e n percent muscovite, carbonaceous  80  about f i v e  m a t t e r a n d a b o u t one t o f i v e p e r c e n t  percent  calcite.  Most o f t h e q u a r t z g r a i n s a r e 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  matter.  matter p a r a l l e l In t h i n  Bands o f m u s c o v i t e  and  carbonaceous  the f o l i a t i o n of the rock. section, quartz-muscovite s c h i s t consists of  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 , calcite,  1 percent magnetite  iron-oxide, chlorite Quartz  1 to 4 percent  and r a r e l y t r a c e s o f a l b i t e ,  and c a r b o n a c e o u s  matter  (Plate 2-4).  i n post 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 .  Muscovite  layers a l t e r n a t e w i t h quartz l a y e r s ; muscovite i s  also scattered within quartz layers with i t s elongation parallel  to schistosity.  rich i n calcite,  albite,  Locally, schists are unusually 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 a n d p o i k i l o b l a s t i c a l l y encloses quartz grains, but generally i t f i l l s  fractures.  Generally s c h i s t o s i t y planes are sinuous.  d.  Quartz-muscovite-biotite schist  Quartz-muscovite-biotite schist unit rarely 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  bution of f l o a t .  crops out  m o s t l y by t h e d i s t r i -  Specimens a r e deeply 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 h a s w e l l - d e v e l o p e d  schistosi-  21  0 I  JAAM  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 . Foliation F]_ i s p a r a l l e l t o t h e 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 c u t s F]_ a t 6 0 " . N o t e t h e d e v e l o p m e n t o f p r e f e r r e d o r i e n t a t i o n o f muscov i t e p a r a l l e l s F 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 nicols.) 2  2  22  ty.  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 more t h a n 55  q u a r t z , a b o u t 30 p e r c e n t and  a b o u t one  i n a few  m u s c o v i t e , about 5 p e r c e n t  to ten percent  ation minerals. rocks  calcareous  M i n o r amounts o f g a r n e t of t h i s  and  ULTRAMAFIC ROCKS  2-3-A  Regional  limonitic  are  also  The  mafic  serpentinized equivalents  and  their  discontinuous  are i n t e r l a y e r e d w i t h metamorphic rocks U l t r a m a f i c bodies  stock-like bodies,  l i k e masses o c c u r  are  t h a t range i n s i z e  f e e t to s e v e r a l miles across.  The  by  ultra-  (Figure  o f the Yukon  2-4)  Crystal-  sill,dyke  f r o m a few  In g e n e r a l , the  and  hundred  larger stock-  near the T i n t i n a Trench, whereas the  smaller  found f u r t h e r from  number o f u l t r a m a f i c e x p o s u r e s i s much  e r t o the n o r t h w e s t i n the A l a s k a n ultramafic belt  Yukon  b e l t of sheared  f o u n d as  ones w h i c h a r e h i g h l y s e r p e n t i n i z e d , are trench.  contained  form a d i s t i n c t i v e u n i t i n the  Metamorphic Complex.  the  alter-  Setting  Ultramafic rocks  line Plateau.  biotite  unit.  2-3  rocks  percent  seems t o be  the T i n t i n a Trench  p a r t of the b e l t .  c o n t r o l l e d , at l e a s t i n  (Roddick,  The alignment,  196 7) w h i c h i s a m a j o r  w e s t 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  great-  north-  Pre-  23  FIGURE 2-4: GENERALIDED D I S T R I B U T I O N OF S E R P E N T I N I Z E D ULTRAMAFIC ROCKS I N YUKON TERRITORY AND ALASKA. E = eclogite locality; B = glaucophane occurrance. ( M o d i f i e d a f t e r F o s t e r , 19 74; G o d w i n , 1 9 7 5 ; TempelmanK l u i t , 1976.)  24  C a m b r i a n , P a l e o z o i c and  Mesozoic  sedimentary  n o r t h e a s t f r o m m e t a m o r p h i c r o c k s on b a s i s o f f i e l d o b s e r v a t i o n and most o f t h e u l t r a m a f i c b o d i e s  the southwest.  aeromagnetic data  the  (Veach,  ly72)  separate  beneath the s u r f a c e .  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  2-3-B  b e e n a s s i g n e d a P e r m i a n age  C l i n t o n Creek  The  distribution  dark  t h e y p r o d u c e c a n be from the a i r .  There i s a g e n e r a l l a c k of r o c k s a r e e x p o s e d and  green to orange w e a t h e r i n g recognized easily  or pyroxene.  Most of the b o d i e s  Identification  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 relict  t e x t u r e s and  l a y e r i n g was  found  are p r a c t i c a l l y  to f i n d  are  origi-  of u l t r a m a f i c rocks  p y r o x e n i t e was  surviving original minerals.  based No  and m u t u a l r e l a t i o n s h i p s o f t h e s e  on  original rocks  unknown.  S e r p e n t i n i t e ranges i n c o l o u r from dark to o l i v e  talus  from a d i s t a n c e o r  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  olivine  blocky  the  Rock t y 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 . completely  (1975).  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  heavy v e g e t a t i o n wherever these characteristic  by T e m p e l m a n - K l u i t  Area  a r e a i s shown i n F i g u r e 2-2.  nal  the  On  a r e b e l i e v e d t o be  masses o r l e n s e s t h a t a r e n o t c o n n e c t e d The  r o c k s on  g r e e n and  a l l stages  c o n d i t i o n s were o b s e r v e d .  greenish  from massive t o h i g h l y  black  sheared  S u g a r y t e x t u r e i s n o t uncommon.  as  25  Highly polished, f i s h scale serpentinite i n t h i n section are antigorite, chrysotile, brucite, chlorite, magnetite,  chrome s p i n e l and c h r o m i t e .  Several  kinds of s e r p e n t i n i t e are d i s t i n g u i s h e d : serpentinite, fine grained  talc,  fibre  idocrase, different bearing  d a r k g r e e n 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 s u g a r y 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 a r e 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 events 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 . o f i n t r u s i o n may be r e p r e s e n t e d diortie, but  dated  considered  The o l d e s t p e r i o d  by t h e K l o t a s s i n q u a r t z  by T e m p e l m a n - K l u i t  (1975) as l a t e  Triassic,  b y G o d w i n (1975) t o be m i d - C r e t a c e o u s ;  q u a r t z m o n z o n i t e was e m p l a c e d a b o u t m i d - J u r a s s i c ; aceous i n t r u s i o n s a r e t y p i f i e d by t h e C o f f e e  Pink  mid-Cret-  Creek  quartz  m o n z o n i t e ; and t h e y o u n g e s t p e r i o d i n v o l v e d t h e N i s l i n g alaskite  (Tempelman-Kluit,  that  Range  1975).  The g r a n o d i o r i t e o f t h e C l i n t o n C r e e k a r e a posed w i t h i n the area o f F i g u r e  2-2.  Two  i s not ex-  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 a n d t h e o t h e r  14 k i l o m e t r e s e a s t , a n d  a small stock  o f t h e C l i n t o n Creek  area  26 k i l o m e t r e s s o u t h e a s t  a r e shown on F i g u r e  c l o s e r t o the study  area.  2-1.  Several small bodies  Lithologically  the rocks  a r e even are s i m i -  26  lar  t o t h 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  zonite suite.  The r o c k ,  consists of quartz,  medium g r a i n e d  plagioclase  commonly w i t h n o r m a l z o n i n g ) , b l e n d e and m a g n e t i t e . rocks  biotite  mon-  granodiorite,  ( o l i g o c l a s e t o andesine  potash f e l d s p a r , b i o t i t e ,  Potash feldspar  (22 p e r c e n t )  horn-  i n some  i s f r e e f r o m a l t e r a t i o n b u t more commonly i s f a i n t l y  cloudy  i n t h i n s e c t i o n due t o d e v e l o p m e n t o f f i n e - g r a i n e d  clay minerals. hedral  Quartz  and i n t e r s t i t i a l  (14 p e r c e n t ) a n d o r t h o c l a s e to the plagioclase  a r e an-  (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 prisms, and  (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  b u t more commonly i t i s i n p l a t e s w i t h  has a l t e r e d i n p a r t t o c h l o r i t e .  formed as f l a k e s , w i t h  Biotite  well-formed ragged edges (17 p e r c e n t )  r a g g e d 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 h o r n b l e n d e and n o r m a l l y  alters to  chlorite.  2-5  BASALT  Two b a s a l t i c s e q u e n c e s a r e f o u n d i n t h e Y u k o n talline  Plateau.  The o l d e r i s t h e C a r m a c k s G r o u p o f B o s t o c k  (19 3 6 ) , w i d e s p r e a d i n t h e c e n t r a l p a r t o f t h e Y u k o n talline  Plateau.  Crys-  Crys-  The y o u n g e r 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 along Holocene ore P l e i s t o c e n e  t h e Yukon R i v e r , a r e  i n age ( B o s t o c k , 1 9 6 6 ) .  The  27  Selkirk are  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  roughly  British  equivalent  Columbia  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  ( C a m p b e l l and T i p p e r ,  Selkirk Volcanics p a r t of the study  area  1971).  a r e exposed i n t h e s o u t h - c e n t r a l  (Figure 2-2).  formed columnar j o i n t e d f l o w s a b l y on t h e m e t a m o r p h i c r o c k s .  These a r e f r e s h , unde-  (Plate 2-5), l y i n g  unconform-  The b a s a l t i s d e n s e , d a r k  gray w i t h phenocrysts o f o l i v i n e .  In t h i n s e c t i o n the rock  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 , pyroxene, o l i v i n e , m a g n e t i t e and g l a s s . groundmass m i n e r a l  P a l e brown a u g i t e o c c u r s  and as p h e n o c r y s t s .  a position interstitial  borders.  b o t h as a  I t usually  t o t h e p l a g i o c l a s e as s m a l l  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 h a v e more o r l e s s Much o f t h e g l a s s i s a l t e r e d t o  minor  occupies grains.  corroded  yellowish-brown  palagonite.  2-6  STRUCTURE  2-6-A  Introduction  Evidence o f a t l e a s t three phases o f deformation been observed.  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  have been deformed d u r i n g tight,  a second f o l d i n g ,  has folds  into small,  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 o p e n t h i r d p h a s e f o l d o f r e g i o n a l e x t e n t . s t r u c t u r e s have undergone l a t e r  faulting.  A l l of these  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 age  r e l a t i o n s h i p s was  d a t a was  done i n t h e f i e l d .  relative  Analysis of  such  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  stereographic projections.  The most p r o m i n e n t  feature  and of  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  to composition-  al  developed during  the  layering.  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  f i r s t p h a s e o f f o l d i n g as a r e s u l t o f t i g h t  and s h e a r i n g w h i c h foliation als  compression  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  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  miner-  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 which accompanied  folding.  This intense deformation  and m e t a m o r p h i s m h a s o b s c u r e d t h e o r i g i n a l succession. and b o t t o m s  Very  stratigraphic  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  h a v e b e e n made b e c a u s e  sedimentary  h a v e b e e n 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 .  tops  structures  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 for  plane  observe  t h e same r e a s o n . Certain  Creek  2-6-B  s t r u c t u r a l elements  area are l i s t e d  i n Table  observed i n the  Clinton  2-2.  Folds  Two  groups  of mesoscopic  f o l d s and r e l a t e d  f e a t u r e s have been observed i n the f i e l d .  Major  structural fold  (Figure  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 o r c o m p o s i t i o n a l l a y e r i n g  F^  A x i a l p l a n e s and a x i a l p l a n e c l e a v a g e o f e a r l i e s t i s o c l i n a l folds  L^  I n t e r s e c t i o n o f FQ and F ^ and f o l d axes o f e a r l i e s t i s o c l i n a l folds A x i a l p l a n e s and a x i a l p l a n e c l e a v a g e o f recumbent second f o l d s I n t e r s e c t i o n s o f F ^ w i t h F and F ^ , f o l d axes and c r 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 p l a n e o f t h i r d phase f o l d  L^  I n t e r s e c t i o n s o f F ^ w i t h F ^ , F ^ and the t h i r d f o l d  and a x i s o f  31  2-2)  r e p r e s e n t a t h i r d group.  been r e f o l d e d by  large  along L  scale  This  a x i a l planes.  shown i n P l a t e 2-6.  are q u i t e  folds  (L^)  g r o u p has An  are  example o f t h i s  to  (Plate  rocks.  Massive  (F^)  i s not  well  located;  are p r e s e r v e d i n  fold  closures  c o m p e t e n t r o c k s l i k e s a n d s t o n e and  limestone  small  foliation in the  rocks. fold  (F^)  phyllitic  and  associated  aligned minerals.  can  be  as h i g h  F., f o l i a t i o n s ,  as  L^  folds  are  (F^)  and  These are b e s t  seen Due  a r e a i n t o d i f f e r e n t domains respect  f o l d a x e s , w h i c h have been m o d i f i e d  fold  competent  a r g i l l i t i c sandstone u n i t s .  approxiamte homogeniety w i t h  p l a n e s o f L^  2-8).  to  unequal d i s t r i b u t i o n of outcrops i t i s  t o d i v i d e the  phase f o l d s , are  with  relatively  axes, i n t e r s e c t i o n of bedding  s c h i s t and  s c a r c i t y and  impossible  Lineations  dis-  (Plate  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  tightly  developed.  e v e r y w h e r e s h e a r e d and  relict  2-7)  massive greenstone were a l s o  i n these, f o l i a t i o n  the  deformation  C o m p o s i t i o n a l l a y e r i n g i s not  s e e n as  folded  sub-parallel  first  Gleitbrett structures  u n i t s l i k e q u a r t z i t e and  schistose  have  exposed i n  parallel  common, e s p e c i a l l y i n s c h i s t o s e  folded but,  (L^)  have, i n t u r n , been  f i r s t phase f o l d s  C l i n t o n Creek area.  is  a x e s and  first  f o l d along i t s axis.  O n l y a few  l i m b s and  2  The  shown i n F i g u r e  to f o l d system. by  2-5.  the  s e c o n d and  Most of the  s e t approach the  h o r i z o n t a l but  20*.  f o l d s and  T y p i c a l L^  s k e t c h e d i n the  of  field,  are  L^ third  axial the  dip  associated  shown i n F i g u r e  F^, 2-6.  32  0 I  IM I  P L A T E 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 c e o u s a r g i l l i t e , w h e r e F-j_ p a r a l l e l s F Q . A l t h o u g h 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: Gleitbrett structure i n schistose rocks. This s t y l e of deformation associates 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 b e t w e e n i r o n - s t a i n e d b e d s 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 sandstone. F o l d wavel e n g t h o f t h i s type 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 o f  crenulations  folds.  In w e l l  Associated (Plate axial  the  i n t e r s e c t i o n of  of  L  of  L  are  2  f o l d s and  i n t o two  or by  at  (F )  are  2  and  fold  axes o f  addition  shows t h e 900  This  axis fold  30* L  the  2  2-7.  plunge at mesoscopic  2-2),  (Figure  regional  of  j o i n t s and  L^  seen.  with  their  n o r t h and  of  L  or  F^  to  the are  2  small  2-11).  folds  Examples  Field  sketches  orientations,  (F ) 2  can  be  or  dip  (Figure  either  about  2-8).  fol20*  Lineations  westerly  folds with  div-  south i n which  Most a x i a l p l a n e s and  folds described  open a n t i f o r m fractures,  The  data of  i s about h o r i z o n t a l  i s shown on  2-9)  (Figure  2-9).  a b o v e , mapping lengths  of  6 00  2-2).  gentle  structures.  de-  observed.  Lineations  not  a b o u t 15*  recumbent  are  parallel  A x i a l planes  horizontal  2  folds  angle to F  (Plate  f o l d s are  southwesterly  L  (Plate  2 - 1 0 ) , axes o f  w i t h F^  (Figure  nearly  presence of  related  mentioned the  to  metres A  with  or  a large  structures,  i n Figure  2  folds.  (Plate  2  folds  i s generally  F^ L  related  domains  northeasterly  to  overturned L  shows d i f f e r e n t o r i e n t a t i o n s .  iations  In  F^  are  common i n t h i s g r o u p  overturned  refolded  illustrated  ided F  folds  are  lies  2  fine crenulations  or  2  (F )  Cheveron  i n some c a s e s .  planes of  1  2-10)  bedded u n i t s  foliation  2-11)  commonly  (Plate  and  Q  F^.  formed about a x i a l s u r f a c e d and  folds, F ,  Figure  2-2.  of  the  deforms the Figure and  2-8  trends  third  group,  previously suggest  that  northwesterly.  38  PLATE 2-9: L2 c h e v r o n 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 to a x i a l plane of the chevron f o l d .  39  0  01  M M  PLATE 2-10: Crenulations r e l a t e d to L fo! C r e n u l a t i o n cleavage p a r a l l e l s to a x i a l p i of small f o l d i n quartz-muscovite schist, the outcrop, F i s gently dipping.(Crossed nicols.) 2  2  40  PLATE 2 - 1 1 : F o l i a t i o n F1 and F in quartzmuscovite s c h i s t . L i s m a r k e d by t h e i n t e s e c t i o n o f F]_ and F 2  2  2  41  FIGURE 2-7:  F I E L D SKETCH OF SECOND PHASE FOLDS.  42  FIGURE 2-9:  POLES TO 123 L V L I N E A T I O N S .  44  2-6-C  Faults  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  both  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 m a j o r o n e s 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 m e t r e s h a v e b e e n i d e n t i f i e d .  o n l y as l i n e a m e n t s a c r o s s which placed. ities  Mesoscopic  Large  f a u l t s a r e seen  l i t h o l o g i c contacts are dis-  f a u l t s have been observed  i n many  local-  ( P l a t e 2-12, 2-13) i n t h e s t u 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 a n d r o a d c u t s . exposed  areas suggests  out t h e C l i n t o n Creek Lineaments graphs  The f r e q u e n c y o f f a u l t i n g  t h a t such  i n these  f a u l t i n g i s common  through-  area.  detected i n the f i e l d  a n d on a e r i a l  have been i n t e r p r e t e d as p r o b a b l e  faults.  photo-  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 t h e p r e s e n c e , o n t h e g r o u n d , of  m i n o r f a u l t s and b r e c c i a z o n e s ,  u n i t s and s t r u c t u r e s .  and d i s p l a c e d  I n r a r e cases, these lineaments  b e e n shown t o b e f a u l t l i n e s by d i a m o n d d r i l l i n g ( P l a t e 2-13) . 130*  lithologic have  and m i n i n g  S u c h 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  t o 160". C o m p a r i s o n o f F i g u r e 2-8 a n d 2-10 shows t h a t many o f  t h 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 . 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 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  cannot,  features.  A  h o w e v e r , be  Some  displace-  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  faults,  45  PLATE 2-12: Minor f a u l t d i s p l a c i n g r o d i n g i t e b o d y 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 p r o d u c e s s c a l e . )  46  PLATE 2-13: Northerly trending v e r t i c a l fault with considerable d i s p l a c e m e n t i n the Porcupine p i t . The f a u l t s u r f a c e i s c u r v e d . R e l a t i v e l y c l e a n 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 is a r g i l l i t e . (The h e i g h t o f the w a l l i s about 20 metres.)  47  FIGURE  2-10:  POLES  TO  66  FAULTS  48  but  g e n e r a l l y m a g n i t u d e o f movement i s unknown.  2-6-D  Joints  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 . graphic  p r o j e c t i o n o f measured j o i n t s  least five sets. ly,  another  One  (B)  and  tically,  a fourth  (E)  s t r i k e s 150"  s t r i k e s 000"  easterly  fifth  (A)  westerly, (D)  (Figure  t o 20*  a third  (C)  s t r i k e s 115"  s t r i k e s 060* and  dips  and  and  2-11)  dips  dips  A  indicates  almost  80*  dips  70*  vertically.  both  dips  ver-  southerly  Age  and  joints  p h a s e f o l d and trending  2-6-E  150*  is parallel  rocks  to the  and  a x i s of the  are  considered  to l i e i n chronological i s o t o p i c age  s e c t i o n s e v e n ) and  limestone  n o r t h w e s t of the  muscovite-biotite stone of the  one  T i n t i n a Trench.  of the  area are  fossil  evidence.  s i m i l a r to  C l i n t o n Creek area.  those  eight  Quartz-  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  a r e a y i e l d e d an O r d o v i c i a n  order  determina-  where a p r o b a b l e Devonian f o s s i l s were f o u n d , a b o u t kilometres  The  radiometric  greenage.  In  third  Structure  ( s e e c h a p t e r two,  argillite  the  i t s a x i a l plane.  s t a t e d p r e v i o u s l y , b a s e d m a i n l y on  tions The  115"(D) c o n t a i n  probably represents  Regional  The as  trending  a  r e l a t i o n s h i p of  j o i n t sets to d i f f e r e n t phases of deformation i s u n c e r t a i n . general,  at  vertical-  t o 90*  s t r i k e s 080* and and  stereo-  49  FIGURE 2-11: P O L E S TO 1 3 3 J O I N T S . ed i n t h e mine a r e n o t i n c l u d e d . )  (Joints  measur-  50  H o w e v e r , t h e c r o s s s e c t i o n ( F i g u r e 2-2) o f t h e s t u d y  area  reveals, the oldest rock, quartz-muscovite-biotite s c h i s t , a t t h e t o p and t h e youngest meta-sedimentary r o c k , and  limestone 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  2-7  ISOTOPIC AGE DETERMINATIONS  2-7-A  Introduction  fold.  C l i n t o n Creek i s i n t h e northwestern Yukon C r y s t a l l i n e P l a t e a u Yukon T e r r i t o r y  argillites  (Douglas  et al.,  portion of the 1970) i n t h e  ( F i g u r e 1 - 1 ) . The Y u k o n M e t a m o r p h i c C o m p l e x  (Tempelman-Kluit,  1974) c o n s i s t s o f m e t a s e d i m e n t a r y and m e t a -  v o l c a n i c rocks that are continuous  with the Birch  schists of Alaska  The m e t a m o r p h i c r o c k s  C l i n t o n Creek  ( F o s t e r , 1973).  near  ( F i g u r e 2-1) a r e s i m i l a r t o t h e r o c k s o f w e s t -  c e n t r a l Yukon where C a i r n e s Group.  Creek  (1914) f i r s t d e s c r i b e d Y u k o n  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  are recognized.  McConnell  divisions  (1905) d e f i n e d t h e P e l l y  which i s i n the northern p a r t of the Stewart  gneiss  R i v e r map  sheet,  the Klondike s c h i s t i n the Klondike g o l d - f i e l d which i s immediately  s o u t h o f Dawson C i t y and t h e N a s i n a q u a r t z i t e  occurs prominently  which  i n the northernmost p a r t o f the Stewart  51  R i v e r map  area.  A l l these  type  l o c a l i t i e s are j u s t south  southeast of the C l i n t o n Creek area. c o n t i n u a t i o n of the Nasina the C l i n t o n Creek area. been thought  q u a r t z i t e and  t o be o f P r e c a m b r i a n  R i v e r a t the A l a s k a Boundary  age.  t h a t i n d i c a t e a P a l e o z o i c age  However,  Tempelman-Kluit  and  echinoderm  columnals  Douglas, et a l . ,  (1976) has  speculated  equivalent to  B i g Salmon C o m p l e x  o f the P e l l y P l a t f o r m w h i c h a r e o f Upper  Paleo-  ( M u l l i g a n , 19 6 3 ) .  No  geochronometric  type area.  data e x i s t f o r Cairnes  T h e r e f o r e , e i g h t samples  ( T a b l e 2-3  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 q u a r t z i t e and  and  1976  also obtained  ( F i g u r e 2-12).  ( T a b l e 2-3)  was  the western  edge o f F i g u r e 2-12.  and to  2-4)  post-metamorphic  of  Nasina  One  Clinton sample  from a g r a n o d i o r i t e stock  p r o v i d e e s t i m a t e s o f t h e age  m o r p h i s m and  (1914)  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 r e e k a r e a d u r i n g 1975  to  limestones  a t 64'39.5'N,  ( M e r t i e , 1937;  p a r t s o f t h e E n g l i s h m a n ' s C o m p l e x and  z o i c age  into  j u s t west o f the Yukon  t h a t many o f t h e m e t a m o r p h i c u n i t s m i g h t be  ( F i g u r e 2-3)  the  Klondike schist  ( F i g u r e 2-1:  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  Green, 1972).  (1972) n o t e d  These metamorphic r o c k s g e n e r a l l y have  a s s o c i a t e d w i t h metasedimentary rocks  1970;  Green  and  These samples were  near  analysed  o f d e p o s i t i o n , major metaintrusion.  TABLE 2-3 POTASSIUM-ARGON ANALYTICAL DATA*  Sample b No."  Location  Rock u n i t  : Rock name  Lat.(N);  Long.(W)  SP 21A  64*27'  140'54'  Kb  MH 62  64*27.5'  140*4i:2*  Pzq: a m p h i b o l i t e  Mineral  40  dated  : b i o t i t e granodiorite  40  %K ± S  A  Ar  *"  Ar t o t a l  40. * Ar  u  -5 3 (10 cm STP/g)  biotite  5.60 ±.01  0.812  1.475  hornblende  0.152+.001  0.629  0.182  Apparent  Time  p  age(Ma)  64.9±2.3  Late Cref R taceous »°  278 +10  Permian Early  Mil 105  64*29'  140*45.5'  Pzq: quartz-muscovite schist  muscovite  6.06 +.06  0.910  6.31  245 +8  Early Permian  MH  64*24'  140*40'  P z g : greenstone  hornblendeactinolite  0.674±.009  0.898  0.542  191 +7  Early Jurassic  a. b. c. d. e. f. g.  122  A l l a n a l y s e s done i n Geochronology L a b o r a t o r y , Department 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 Columbia, K by K.L. S c o t t , A r by J . E . l l n r n k n l . See F i g u r e 2-12. 'S' i s one s t a n d a r d d e v i a t i o n o f q u a d r u p l i c a t e a n a l y s i s . ^ A r * means r a d i o g e n i c argon. 10 1 -10 1 Constants used i n model age c a l c u l a t i o n s : KX = 0.585*10" y r ~ ; KA - 4.72xl0~ y r ~ ; 40K/K = 0.0119 atom p e r c e n t . Time d e s i g n a t i o n a f t e r Armstrong (1978). Time d e s i g n a t i o n a f t e r Obradovich and Cobban (1974). fi  g  f  f  TABLE 2-4 RUBIDIUM-STRONTIUM DATA FOR ANALYSED WHOLE ROCK SAMPLES  Sample  Location  Rock u n i t : Rock name  Rb  Sr  (ppm)  (ppm)  &  Rb  8 7  /Sr  8 6 C  Sr^/Sr  8 6  No.  Lat.(N);  Long.(W)  MH 61  64*26.8'  140*41.3'  Pzq : q u a r t z - m u s c o v i t e schist  80.0  41.2  5.63  0.7279  MH 81A  64*25.4'  140*38.7'  Pzg : q u a r t z-mus c o v i t e chlorite schist  69.0  25.3  7.90  0.7330  "•MH 101  64*29.4'  140*45'  Pzg : greenstone  0.019  0.7080  MH 105  64*29'  140*45.5'  Pzq : q u a r t z - m u s c o v i t e schist  24.1  3.25  0.7188  •MH 112  64*24.7'  140*37.4'  Pzq : q u a r t z - m u s c o v i t e schist  63.3  5.89  0.7300  MH 112A  64*24.7*  140*37.4'  Pzqm: q u a r t z-mus c o v i t e biotite schist  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  131  1020  0.377  0.7065  a. b. c. d.  : b i o t i t e granodiorite  1.8 27.1 129 37.7  278  A l l a n a l y s e s done i n the Geochronology L a b o r a t o r y , Department 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 of B r i t i s h Columbia by K.L. S c o t t . See F i g u r e 2-12. One s t a n d a r d d e v i a t i o n e r r o r i n measurment i s (±2%). One s t a n d a r d 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 g r a n o d i o r i t e ; Pzu= serpentinite; Pza= a r g i l l i t e , l i m e s t o n e and sandstone; Pzg= greenstone and q u a r t z muscovite-chlorite schist; Pzq= quartz-muscovite s c h i s t ; Pzqm= q u a r t z - m u s c o v i t e 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  Isotopic  Analysis  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  s a m p l e s o f m e t a m o r p h i c r o c k a n d one s a m p l e o f i n t r u s i v e a r e g i v e n i n T a b l e 2-3.  rock  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 a n d one o f g r a n o d i o r i t e w e r e 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 r e g i v e n i n T a b l e 2-4.  a.  The morphic  Potassium-Argon  o l d e s t p o t a s s i u m - a r g o n d a t e o b t a i n e d f r o m meta-  r o c k s ( F i g u r e 2-12) i s E a r l y P e r m i a n  ( T a b l e 2-3:  MH 62 - 278±10 Ma) f o r h o r n b l e n d e s e p a r a t e d f r o m a m p h i b o lite  (Pzq).  The d a t e 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 m a i n  e p i s o d e o f metamorphism because h o r n b l e n d e i s t h e l e a s t  likely  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 cooling  (York and F a r q u h a r , 1972).  quartz-muscovite schist  A date f o rmuscovite  from  (Pzq), although muscovite i s less  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 P e r m i a n age ( T a b l e 2-3: MH 105 - 245±8 Ma) f o r m e t a m o r p h i s m .  The E a r l y  Jurassic  d a t e 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 ( T a b l e 2-3: 191±7Ma) f r o m g r e e n s t o n e age o f m e t a m o r p h i s m .  MH 122 -  ( P z g ) p r o v i d e s , a t b e s t , a minimum  In t h i n s e c t i o n t h i s hornblende  as r e l a t i v e l y c o a r s e r - g r a i n s a n d a c t i n o l i t e  as f i n e r  exists grains  mixed w i t h e p i d o t e , a product o f a l t e r a t i o n o f t h e hornblende.  56  Hence, t h e date  (191±7 Ma) may n o t be t h e 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 later retrogressive alteration. Biotite  g r a n o d i o r i t e (Kb), 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 s a m p l e d f r o m a s t o c k t h a t i n t r u d e d t h e m e t a morphic rocks  ( F i g u r e 2-12).  The b i o t i t e  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 2.3 M a ) .  This i s d i s t i n c t l y  the metamorphic r o c k s .  yielded a latest  ( T a b l e 2-3:  younger than  crystallization of  This rock 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 d a t e range o f dates Kluit,  f o r t h e N i s l i n g Range a l a s k i t e s u i t e  (Tempelman-  Rubidium-Strontium  Rubidium-strontium  analysis, listed  interpreted i n Figure  l i n e A"*") c a n be o b t a i n e d and  i s w i t h i n the  1975) .  b.  and  Sp 21A - 64.9±  2-13.  i n Table  An i s o c h r o n  2-4, a r e p l o t t e d ( F i g u r e 2-13:  f r o m two g r e e n s t o n e s a m p l e s  MH 122) and f o u r s c h i s t w h o l e r o c k  samples  (MH 101  (MH 6 1 , MH 81A,  MH 1 0 5 , MH 1 1 2 ) . The P e r m i a n age (255.8±22.3*Ma) i n d i c a t e d i s c o m p a r a b l e t o t h e m e t a m o r p h i c age d e f i n e d b y a r g o n a n a l y s i s ( T a b l e 2-3: further illustrated reference  1:  potassium-  245±8 t o 278+10 M a ) .  This i s  i n F i g u r e 2-13 b y l i n e B w h i c h i s a  l i n e drawn u s i n g t h e i n i t i a l  r a t i o i n d i c a t e d by  B e s t f i t l i n e ( l i n e A) i s d r a w n b y u s i n g L e a s t R e g r e s s i o n T r e a t m e n t , M o d e l I o f Y o r k (1967) .  Square  •740 - i  F I G U R E 2 - 1 3 : PLOT OF Sr/ Sr v s . R b / S r FOR WHOLE ROCK ANALYSES OF SAMPLES FROM THE CLINTON CREEK AREA, YUKON TERRITORY. L i n e A r e p r e s e n t s t h e b e s t f i t l i n e f o r C l i n t o n Creek data (MH 112A o m i t t e d ) and r e f l e c t s metamorphic r e s e t t i n g . L i n e B i s a r e f e r e n c e l i n e based on t h e o l d e s t 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. L i n e C i s model, p r o b a b l y minimum, d e p o s i t i o n age ( O r d o v i c i a n ) f o r s c h i s t s o f the C l i n t o n Creek a r e a 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  ( T a b l e 2-4:  and a s l o p e g i v e n by t h e o l d e s t m e t a m o r p h i c by p o t a s s i u m - a r g o n  (278+10 M a ) .  Initial  MH 101)  date determined  r a t i o s d e f i n e d by  l i n e s A a n d B a r e 0.7082 and 0.7080, r e s p e c t i v e l y , a n d a r e higher than the i n i t i a l Initial  r a t i o 0.7040 assumed f o r l i n e  r a t i o s o f 0^7040 t o 0.7060 w o u l d be e x p e c t a b l e f o r  P a l e o z o i c eugeosynclinal sediments. of  The h i g h i n i t i a l  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 ,  metamorphic  resetting  (Hart,  1962).  i s markedly d i f f e r e n t i s o t o p i c a l l y  samples 470 Ma of  A model date o f  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  0.7040 i s a s s u m e d .  whole  f o r one sam-  from the o t h e r s i x  a n a l y s e d ( T a b l e 2-4 a n d F i g u r e 2 - 1 3 ) . ( F i g u r e 2-13:  from t h e Yukon Metamorphic  Creek  and A r m s t r o n g , 1978, p e r s o n a l c o m m u n i c a t i o n ) . Rubidium-Strontium data f o r b i o t i t e  listed  dated  rocks  Complex n e a r t h e C a s i n o p o r p h r y  d e p o s i t , a b o u t 250 k i l o m e t r e s s o u t h - w e s t o f C l i n t o n  is  ratio  S u p p o r t f o r s u c h a n a g e comes f r o m a  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 m e t a m o r p h i c  (Godwin  ratios  extensive  An O r d o v i c i a n w h o l e - r o c k d a t e i s p o s s i b l e ple  C.  i n T a b l e 2-4.  (Rb-Sr)  granodiorite  (Sp 21A)  As t h e r o c k i s d i f f e r e n t f r o m o t h e r  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,  Regional Synthesis  C l i n t o n C r e e k d a t a may be c o m p a r e d t o r e g i o n a l i s o -  59  t o p i c d a t a ( K - A r a n d Rb-Sr) c o l l e c t e d by o t h e r w o r k e r s 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 .  from  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 b o u n d e d on t h e n o r t h e a s t b y t h e T i n t i n a T r e n c h a n d on t h e s o u t h w e s t by t h e ShakwakDenali fault.  Documentation  f o r dates 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 T a b l e 2-5 a r e p l o t t e d i n t h e  h i s t o g r a m o f F i g u r e 2-14. of igneous a c t i v i t y 120 Ma  a t 45 t o 75 Ma  (closed c i r c l e )  i g n e o u s and metamorphic range  In t h i s  figure distinct (open c i r c l e )  are apparent.  grouping  a n d 85 t o  In addition,  mixed  d a t e s s c a t t e r i n t h e 135 t o 2 05 Ma  (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  A p l o t o f t h e s e d a t e s b y s y m b o l o n t o F i g u r e 2-15  diamond). indicates  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 y o u n g i n g away f r o m t h e 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 t h e Yukon Although the trench i s s t i l l  Territory.  e n i g m a t i c , Roddick  (1967)  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 ment o f 400 k i l o m e t r e s a n d T e m p e l m a n - K l u i t  (1972)  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.  move-  noted  ment . t h a t m i g h t h a v e t r a n s c u r r e n t c o m p o n e n t . movement o c c u r r e d d u r i n g m i d - C r e t a c e o u s d u r i n g Eocene o r O l i g o c e n e t i m e  that  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 along steep southwest-dipping f a u l t s with v e r t i c a l  des-  time  displace-  The s e c o n d  t i m e and t h e t h i r d  (Tempelman-Kluit,  1976).  TABLE 2-5 RELATIONSHIPS OF ISOTOPIC DATES AND ITS PERPENDICULAR  DISTANCE FROM THE TINTINA TRENCH  OF THE YUKON CRYSTALLINE PLATEAU  Sample  Material  No.  Dated  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Rb-Sr Date(Ma) Metamorphic  Biotite Biotite Biotite Biotite Biotite Biotite Biotite Hornblende Biotite Whole r o c k Biotite Biotite Hornblende Biotite A n a l y s e s ave. Biotite Biotite Biotite Biotite Hornblende Biotite Biotite Biotite Biotite  Igneous  K-Ar  Date(Ma)  Metamorphic  Distance(km)  Reference  Igneous  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 II  I I I III  I I I I I I I I I  Table 2-5  (continued):  Sample  Material  No.  Dated  25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52  Rb-Sr Date(Ma) Metamorphic  Horblende Biotite Biotite A n a l y s e s ave. Biotite Hornblende Hornblende Hornblende Whole r o c k Biotite Biotite Muscovite Biotite Biotite Biotite Biotite Muscovite Biotite Muscovite Muscovite Biotite Horblende Biotite Muscovite Biotite Hornblende Hornblende Muscovite  Igneous  K-Ar Date(Ma) Metamorphic  Reference  Igneous 92  93 97.6 99.3 99.6 99 100.8 103  138 140 137 147 164 168 161 160 175 187 181 182 178 202 191 278 245  Distance(km)  117 137  104.5 121 64 121 94 123 210 122 128 127 121 12.5 229 88.5 202 93.5 92 97 97 46 101.5 101.5 106.5 106.5 42.5 14 14 j 14  I III I III I I I I III I I I I I I I I I I I I I I I I II II II  Table 2-5  (continued):  Sample  Material  No.  Dated  53 54 55 56 57 58 59 60 61 62 63 64 65 66 67  I: IV:  Biotite Biotite Hornblende Biotite Biotite Hornblende Hornblende Biotite Hornblende Biotite Biotite Biotite Hornblende Whole rock Whole r o c k  Rb-Sr Date(Ma) Metamorphic  255.8  Tempelman-Kluit and Wanless W. P e a r s o n (1977)  Igneous  165  (1975); I I :  K-Ar Date(Ma) Metamorphic  Distance(km)  Reference  Igneous  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  See c h a p t e r two, s e c t i o n seven;  I I I I I I I I I I IV IV I III II I I I : C.I. Godwin(1975);  to  10-i tt M  io M  §  N  5 H  m  Oi N 01  8  oft  o z  CTl  |  50  100 -I  l_  s ®  —  ?  j 150  515 » »  1  200  150  300  flu  DATE (Mo) FIGURE 2-14: HISTOGRAM OF K - A r AND R b - S r 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 T a b l e 2- 5.)  64  Distance-date trends are analysed f u r t h e r i n Table and F i g u r e 2-15. 85 t o 120 Ma  Igneous  r o c k d a t e s i n t h e 45 t o 75 Ma  g r o u p s i n t h e h i s t o g r a m o f F i g u r e 2-14  t o c l u s t e r n e a r 200 k i l o m e t r e s kilometres  ( F i g u r e 2-15:  ( F i g u r e 2-15:  l i n e B)  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  135  t o 230 Ma,  Otherwise  kilometres.  ( F i g u r e 2-15;  l i n e C:  o n X(S ) = 54.6; m i g r a t i o n r a t e = 0.5  number o f  = -0.627; slope(m)  - 0 . 1 9 9 ; s t a n d a r d d e v i a t i o n on Y ( S ) = 1 7 . 3 ; y  standard deviation  cm/yr).  L i n e C,  and 250 k i l o m e t r e s  f r o m t h e T r e n c h i s n e a r 150 Ma.  The  the  Younging  Thermal  (Dewey and B i r d ,  i n d u c e d magmatism e l s e w h e r e  (19 74)  p l a t e boundary  1970;  attributed to Benioff  (Godwin,  1975) .  t h a t l i n e C i n F i g u r e 2-15  igneous a c t i v i t y  to  zone m i g r a t i o n a t t h e r a t e o f 0.5  compatible with those s h i f t s  possibility  cm/yr.  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  B e n i o f f z o n e d by numerous w r i t e r s J a m e s , 19 71) .  perpen-  apparent  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 a b o u t 0.5  Foster  =  l i n e through the data suggests t h a t the date a t the  T i n t i n a T r e n c h i s a b o u t 200 Ma,  is  lines  h o w e v e r , show a d i s t i n c t y o u n g i n g t r e n d away  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 )  dicularly  100  and i g n e o u s r o c k s w i t h d a t e s r a n g i n g f r o m  from the T i n t i n a Trench  best f i t  and  s c a t t e r along both  f r o m n e a r t h e t r e n c h t o a d i s t a n c e o f 250 Metamorphic  and  appear  L i n e A)  respectively.  2-5  above a B e n i o f f zone  cm/yr  zone  Therefore, the  might r e f l e c t  migrating  i s an a t t r a c t i v e  one.  s u g g e s t e d t h a t the T i n t i n a Trench marked a f o r the j u x t a p o s i t i o n of markedly  different  250 '52  200  |63  ^AO 36BBB55 42*3 f  60  (50  45  D  o  JC too  t  B  (9 <  27  38  2«^  D  31  7  35  1(L*  53  30  .31 23  19,21,23,25  Oil  -©  50  80  •00  2*6 » , 6  0|  18  t\7  5  NIO  Q9_  O ° 13  14  "753  0| n  2  o  O" I,2,4,5L8  6  7  o  J_  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 a c t i v i t y around 60 Ma. Line B represents widespread igneous a c t i v i t y around 95 Ma. Line C represents a younging of dates away from, the Tintina Trench from early T r i a s s i c to early Cretaceous time. Number of points (n) used to define l i n e C i s 27. Correlation coefficient (r) for l i n e C i s -0.627. Sample nos., symbols and references are i n Figure 2-14 and Table 2-5 respectively. (Sample 51 and 67 excluded.)  66  t e r r a n e s on each f a u l t system.  side of the great length o f the T i n t i n a  H o w e v e r , more d a t a i s n e e d e d t o c o n f i r m t h e  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 s u t u r e and v a n i s h e d  2-7-D  r e p r e s e n t s an e x t i n c t  ocean.  Summary  The morphic  p r e - m e t a m o r p h i c age o f a s c h i s t o f t h e Y u k o n M e t a -  Complex n e a r C l i n t o n Creek  (470 Ma b y R b - S r ) .  i s possibly Ordovician  T h i s i s t e n o u s l y based  s a m p l e a n d an assumed i n i t i a l  ratio.  on one w h o l e  rock  H o w e v e r , t h e age i s  s u p p o r t e d b y u n p u b l i s h e d d a t a f r o m t h e C a s i n o a r e a and b y Tempelman-Kluit  (1976) who s u g g e s t e d  the Nasina  quartzite  and K l o n d i k e s c h i s t a r e P a l e o z o i c i n a g e , n a m e l y O r d o v i c i a n to  Mississippian. Potassium-argon  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  data  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  (278±10 Ma) f r o m K - A r a n a l y s i s o f h o r n b l e n d e .  Permian  Permian  metamorphism i n t h e 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 . morphic  The o l d e s t s i n g l e K - A r d a t e o n m e t a -  r o c k r e c o r d e d by T e m p e l m a n - K l u i t  ( T a b l e 2-5:  (1975) was 202 Ma  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 t h e map a r e a i s l a t e s t Cretaceous youngest  or earliest Tertiary.  This i s o t o p i c date i s the  i n t h e n o r t h w e s t e r n p a r t o f t h e Yukon  Crystalline  67  Plateau.  T h i s might  C o m p l e x , 70.3  Ma  were c l a s s i f i e d to  r e p r e s e n t equivalence to the  (Godwin,  1975).  as m i d - C r e t a c e o u s  P r e v i o u s l y these ( G r e e n , 1972)  intrusions  and e q u i v a l e n t  t h e C o f f e e C r e e k q u a r t z - m o n z o n i t e , 9 0 t o 100 Ma  Kluit,  Casino  (Tempelman-  1976) . W i t h i n t h e 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 Y u k o n  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  trend i n  i g n e o u s and m e t a m o r p h i c i s o t o p i c d a t e s away f r o m t h e Trench i s present.  Tintina  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 w e r e mapped w i t h i n t h e study  area  (Figure 2-2), o f which  contain c h r y s o t i l e asbestos.  f i v e b o d i e s a r e known t o  These a r e 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  extending  along almost  I n some  the e n t i r e l e n g t h o f T i n t i n a Trench.  places the b e l t reaches  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  bodies  form t h e lower 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 -  ified  allocthonous sheets  R i v e r areas  large ultramafic  (Tempelman-Kluit,  1977).  These  s h 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 folded with country rock. in  the P e l l y  quadrangle of  Some o f t h e u l t r a m a f i c  R i v e r and S t e w a r t  R i v e r areas  i n A l a s k a a r e o v e r l a i n by a u n i t  and t h e E a g l e consisting  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 ,  suite of rocks t y p i c a l of o p h i o l i t e  1:  rocks  1  that closely  See A p p e n d i x 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 .  a  resembles  69  r o c k s e q u e n c e s o f p r e s e n t day  o c e a n i c r i d g e s and  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 of  t h e o c e a n i c c r u s t and u p p e r m a n t l e  F o s t e r and  Keith  emplaced  fragments  (Coleman,  appears  t o be  1971).  the southeast e x t e n s i o n  t h e 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  3-2  PETROLOGY  3-2-A  U l t r a m a f i c Rock T y p e s  All  quadrangle.  of the u l t r a m a f i c rocks i n t h i s area are a t  75 p e r c e n t s e r p e n t i n i z e d and m o s t o f them a b o u t 95 serpentinized. from r e l i c t  The  n a t u r e o f o r i g i n a l r o c k was  s t r u c t u r e s and  t e x t u r e s , and  chemistry of the primary minerals. d e p o s i t a r e m a i n l y h a r z b u r g i t e and ite  least  percent  inferred  from the nature  Host rocks of the  and  asbestos  I h e r z o l i t e w i t h m i n o r dun-  ( F i g u r e 3-1) . Specimens of 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  c o n t a i n s e v e r a l of the f o l l o w i n g :  olivine,  gorite with r e l i c t  section  orthopyroxene  ( P l a t e 3-1), b a s t i t e pseudomorphs a f t e r p y r o x e n e ,  ite,  floor.  (1974) d e s c r i b e d t h e 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 of  sea  anti-  o l i v i n e n e t w o r k t e x t u r e , c h r o m i t e , magnet-  chrome-spinel, t a l c , magnesite,  According to microprobe  analyses  b r u c i t e and  (Appendix  C)  the  chrysotile. olivine  70  FIGURE 3-1: MODAL C L A S S I F I C A T I O N OF ULTRAMAFIC ROCKS ( a f t e r J a c k s o n , 1968 ) .  71  o i  •s'*><> ,  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 uns 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 pyroxenes. 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 granular o l i v i n e . (Crossed n i c o l s . )  72  network i s f o r s t e r i t i c enstatite  ( c ) ^ 7-91  (Fo  9^  E n  anc  _ „  0 0  ^  .) .  n  Orthopyroxene i s  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 lamellae of clinopyroxene.  The  most  significant  feature of the 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 which 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 t h e o l i v i n e g r a i n s , 0.1 cataclastic matrix. undulatory and  t o 1 mm  The  extinction.  1 t o 10 mm  l o n g , whereas  i n modal diameter,  o r t h o p y r o x e n e s a r e b e n t and O l i v i n e g r a i n s are h i g h l y  strongly fractured.  form a show  granulated  M o s a i c s o f u n s t r a i n e d much  finer-  grained o l i v i n e are f r e q u e n t l y observed e n c l o s i n g the pyroxene p o r p h y r o c l a s t s  (Plate  3-1).  Serpentinized l h e r z o l i t e c o n s i s t s of clinopyroxene, magnetite total  olivine,  ( P l a t e 3-2).  a b o u t 45 p e r c e n t .  clinopyroxene  Large anhedral  grains of  a l s o has  3-2-B  replaced  Early State  a.  sheared.  r e p l a c e d by b a s t i t e .  The  t o o r t h o p y r o x e n e i s a b o u t 4 t o 1.  is still  and  pyroxene  Some o r t h o p y r o x e n e shows s t r a i n e d  o l i v i n e g r a i n s are preserved, after olivine  orthopyroxene,  antigorite, bastite, chlorite  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 pyroxenes are p a r t i a l l y  ortho-  but  preserved.  olivine.  Alteration  Serpentinization  typical  A  few  ratio Very  serpentine  I n some s p e c i m e n s  of few  network chlorite  73  o  snn.  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 ot the o l i v i n e has been s e r p e n t i n i z e d . Serpentin i z a t i o n o f pyroxene i n the middle o f photog r a p h 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. (Crossed 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 all  u l t r a m a f i c bodies  i n the study area.  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 rock type.  The d e g r e e o f Generally, dunite  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 , a p p a r e n t l y b e c a u s e 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 than pyroxenes.  S e r p e n t i n e minerals"'' i n t h e C l i n t o n  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 . be two  absent.  Creek  L i z a r d i t e appears t o  Most s e r p e n t i n i z a t i o n i n t h i s area o c c u r r e d i n  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 . second stage, which w i l l  be d i s c u s s e d i n Chapter  The  I V , 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 , mostly  on f r a c t u r e s a n d f a u l t s u r f a c e s . Two t y p e s o f o l i v i n e a r e o b s e r v e d ,  fine grained  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 .  gran-  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  (Plate  3-1). largely  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 a n d i s 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 .  s e r p e n t i n i z a t i o n i s complete,  I n specimens where  the cores o f o l i v i n e are 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 c a n f o r m i n two w a y s :  i n one, t h e  volume r e m a i n s 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 in  1:  volume.  The c o n s t a n t v o l u m e r e p l a c e m e n t  model  (Thayer,  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 w o r k 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 of d i f f e r e n t serpentine minerals used here.  75  1966) i n v o l v e s  t h e r e m o v a l o f l a r g e amounts o f MgO a n d S i O  in 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 reaction possible of the type  ( T u n e r a n d V e r h o o g e n , 1960) :  F o r s t e r i t e + Water  5Mg  o  Serpentine + Solution  S i O . + 4H 0  I n 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  p y r o x e n e w i t h o u t any e x p a n s i o n textured tures  ( P l a t e 3-2).  Some  Creek u l t r a m a f i c body c o n t a i n s ,  2  ribbon-  H o s t e t l e r e t a l . (1966) a r g u e t h a t t h e  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 .  of S i 0  replaced  a n t i g o r i t e f i l l s w h a t a p p e a r s t o be e x p a n s i o n f r a c -  i n olivine.  brucite  being  The C l i n t o n  on t h e a v e r a g e , one p e r c e n t  ( 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 w o u l d 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 v o l u m e f o r v o l u m e but  t h a t t h e r e was some v o l u m e Scarfe  the  and W i l e y  increase.  (1967) a n d J o h a n n e s (1969) h a v e shown  breakdown t e m p e r a t u r e o f f o r s t e r i t e  t o serpentine  reaction,  F o r s t e r i t e + Water  2Mg Si0 2  4  + 3H" 0 2  Serpentine + Brucite  Mg Si 0 3  2  -2H 0 + Mg(OH) 2  i n the  0 L  -I  PLATE 3-3: Pale 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 episode o f s e r p e n t i n i z a t i o n . (Crossed n i c o l s . )  77  0 I  ( M M 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 . (Crossed n i c o l s . )  78  is  a little  a b o v e 400*C a t 2 k b ( F i g u r e 3 - 2 ) .  The s t a b i l i t y  of  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 l o w CC> c o n t e n t , a b o u t 0.5 m o l e 2  p e r c e n t CC> a t f l u i d p r e s s u r e 2  1969).  2 k b a n d 400"c  (Johannes,  A t h i g h e r CC> c o n t e n t o f t h e f l u i d p h a s e t h e b r e a k 2  down o f o l i v i n e o c c u r s b y t h e r e a c t i o n  Forsterite+Water+Carbon  2Mg Si0 2  4  Dioxide  (Figure 3-2):  Serpentine+Magnesite  + 2 H 0 + CC> -»»*-»• M g S i C > . 2 H 0 + MgCC> 2  2  3  2  7  2  3  S i n c e b o t h b r u c i t e a n d m a g n e s i t e a r e common i n t h e 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 c h a n g e d a n d became r i c h e r i n C 0 w e r e two s e p a r a t e e p i d o s e s  2  fluid  during the process, or there  o f a l t e r a t i o n , one y i e l d i n g  serp-  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 . O r t h o p y r o x e n e 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 of  e x p a n s i o n , by b a s t i t e w h i c h  preserves the morphological  f e a t u r e s o f t h e 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 magnetite  arranged e i t h e r along the cleavage planes o r  around t h e g r a i n .  From a c h e m i c a l p o i n t o f v i e w ,  e n t i n i z a t i o n o f orthopyroxene and,  the serp-  i n v o l v e s an i n c r e a s e i n w a t e r ,  s i n c e t h e r e a c t i o n a p p a r e n t l y goes o n a t c o n s t a n t  v o l u m e , 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 part o f the s i l i c a released i s probably  incorporated i n serpentine replacing the s i l i c a - p o o r  olivine,  79  FIGURE 3-2: T-X DIAGRAM I N THE SATURATED SYSTEM MgOSi0 -H 0-C0 -CaO (after: Greenwood, 1967; J o h a n n e s , 1969; and S k i p p e n , 1971). 2  2  2  80  w h e r e a s a n o t h e r p a r t may be c o m b i n e d uminum t o f o r m c a l c i u m - r i c h (see b e l o w ) . vives ized.  with  calcium  alumino-silicates of rodingite  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 -  i n rocks i n which o l i v i n e i s completely Experimentally  a t 2 kb w i t h  low X  C Q  Evans and Trommsdorff, phyllite  and a l -  serpentin-  e n s t a t i t e i s n o t s t a b l e below ( G r e e n w o o d , 196 3; J o h a n n e s , 19 7 0 ) ,  700*C  196 9;  b u t b r e a k s down t o a n t h o -  and f o r s t e r i t e .  E n s t a t i t e + Water  9Mg Si O 2  2  Anthophyllite  + 2H 0  g  2Mg^SigC> (OH)  2  22  + Forsterite  2  + 2Mg SiO 2  However, a n t h o p h y l l i t e a p p e a r s t o be a b s e n t i n t h e a r e a . T h e r e f o r e , i t i s assumed, a t l o w e r t e m p e r a t u r e and  higher  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 b r e a k down t o f o r s t e r i t e and t a l c  (Figure 3-2).  Anthophyllite  + W a t e r -*-»-•• F o r s t e r i t e + T a l c  5Mg S i 0 _ ( 0 H ) „ + 4H„0 -»-»-> 4Mg Si0„ + 9Mg S i 0 7 ^2 4 3 4 10 8o  Eventually,  2  2  o  with  water pressure, tine  2  2  (OH) „ 2  a drop o f t e m p e r a t u r e and a d d i t i o n o f f o r s t e r i t e a n d t a l c may b r e a k down t o s e r p e n -  (Evans and Trommsdorff,  reaction:  o  1970) a c c o r d i n g  to the following  81  F o r s t e r i t e + T a l c + W a t e r -*->-»- S e r p e n t i n e  6Mg Si0 2  4  + Mg Si 0 3  a r o u n d 450"C a t 2 The not  1 Q  (OH)  3  2  Most chromite  g r a i n s a r e rimmed by  is  apparently  a thin  surrounding  g r a i n s w i t h b l a c k rims This  and  o r may  n o t be  f i l l e d w i t h c h l o r i t e and  ( P l a t e 3-5),  adjacent  before  pervasive  chromite  t o m a g n e t i t e and  above t h e s t a b i l i t y  but  chromite.  this  chlorite  of  bordered  fractures cross antigorite  to a black margin.  suggest that a l t e r a t i o n producing occurred  of  generations  later antigorite-filled  c u t t i n g the c h l o r i t e halo  and  c h l o r i t e occurs  l i m i t of s e r p e n t i n e  at  vein-  This  may  magnetite  serpentinization. Alteration  Several d i f f e r e n t kinds  It  suggests t h a t both  g r a i n s commonly h a v e two  an e a r l y one  chromite  serpentine.  c h l o r i t e are a l t e r a t i o n products  Large chromite  the  f i n e - g r a i n e d halo of r a d i a t i n g  around u n a l t e r e d chromite.  l e t may  chromite  replace  grains or magnetite a f t e r  found o n l y around chromite  by m a g n e t i t e ,  Unaltered  Some  form a r i m or completely  c h l o r i t e w h i c h merges w i t h t h e  fractures:  2  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  w h i c h may  m a g n e t i t e and  ?  kb.  i s t r a n s l u c e n t dark r e d d i s h brown.  r e p l a c e d by  grain.  not  ->-»--> 5 M g S i 0 . 2 H 0  2  degree of a l t e r a t i o n of chromite  ( P l a t e 3-5),  is  + H0  2  r e l a t e d to the degree of s e r p e n t i n i z a t i o n .  chromite is  4  of  temperatures  (Cerny,  1968).  of s e r p e n t i n i t e are  distin-  82  0  PLATE 3-5: with black (PPL.)  .\e\n.  Brownish red, trunsluscent chromite 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 .  83  guished  i n the C l i n t o n Creek area.  Generally, fibre-bearing  s e r p e n t i n i t e c o n s i s t s of a n t i g o r i t e , b a s t i t e , chrysotile, picrolite, arily  p r o c h l o r i t e and  i t i s dark green,  texture. normally  c o m p a c t and  c o n s i s t s of a n t i g o r i t e ,  40 p e r c e n t  of the rock.  q u i t e common.  of serpophite.  f o r m s as much  C h l o r i t e and  This i s very dark,  v e i n l e t s o f t a l c and  and  chlorite.  brucite veins  are arranged  fish-scales.  The  One  age  of  antigorite,  along  sheared  Slabs of  are serpent-  i n an o v e r l a p p i n g manner a n a l o g o u s of the c h a r a c t e r i s t i c s of fibre.  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 w o u l d  h a v e o c c u r r e d when t h e u l t r a m a f i c b o d y f i r s t Pervasive  have t a k e n p l a c e i n Permian time  to  fish-scale  of 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 to  w i t h hydrous rock u n i t s .  80  magnet-  s i z e to a metre s i z e  i s lack of c h r y s o t i l e  are  nearly black  c h r y s o t i l e and  This occurs  S l a b - l i k e blocks of f i s t  serpentinite  as  Fine-grained, flaky antigorite i s  coated 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 .  mine.  chlorite,  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 mainly  some s e r p h o p i t e  inite  sugary  N e t w o r k s e r p e n t i n i t e c o n t a i n s more t h a n  r o c k w i t h a few  zone.  Ordin-  a somewhat  serpophite,  b r u c i t e i n which c h l o r i t e  r e p l a c e d by b r u c t i e i n p a r t .  ite.  magnetite.  Very f i n e g r a i n e d , dark g r e e n compact s e r p e n t i n i t e  m a g n e t i t e and  percent  has  serpophite,  deter-  probably  came i n c o n t a c t  serpentinization could  d u r i n g the main phase  metamorphism o f the C l i n t o n Creek a r e a  (Table  2-1).  of  84  b.  Rodingitization  Rodingite Shoe p i t s .  i s e x p o s e d o n l y i n t h e P o r c u p i n e and Snow  Two g r o u p s o f r o d i n g i t e a r e d i s t i n g u i s h e d o n t h e  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 , tion,  degree o f deformation  and n a t u r e  stage o f a l t e r a -  of contacts.  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 t h a t range i n l e n g t h from three metres t o twelve with thicknesses  o f 1 t o 1.5 m e t r e s  The  ( P l a t e 3-6) metres  (Plate 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 garnet, and  idocrase, prehnite, chlorite, diopside,  epidote  ( P l a t e 3-7).  Lack o f p r i m a r y r e l i c t  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 the o r i g i n a l ular  rock.  to precisely define  and d e f o r m a t i o n  s i m i l a r t o those i n the surrounding of metamorphism o f a d j a c e n t  that are  s e r p e n t i n i t e , and absence  serpentine  (Plate 3-8), suggest  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  uralitized  minerals,  However, p r e s e n c e o f p y r o x e n e , t h e t a b -  form, i n t e n s i t y o f s h e a r i n g  inization.  actinolite  serpent-  O r i g i n a l ferro-magnesium s i l i c a t e s were (actinolite)  and c h l o r i t i z e d  ( P l a t e 3 - 9 ) , and c a l -  cic  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 ,  and  hydrogarnet.  According  t o Coleman  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  2+  + 2H^0  epidote  (1967) t h e r e p l a c e -  to the f o l l o w i n g r e -  actions :  3 A n o r t h i t e + Ca  probably  Z o i s i t e + 2H  +  85  PLATE 3 - 6 : Older rodingite. Generally tabul i n t e n s e l y d e f o r m e d 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 . E x p o s e d i n Snow Shoe p  86  0  • \ f*M  •  PLATE 3-7: Older r o d i n g i t e : i s o t r o p i c grossul 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 epidote; pale or w h i t i s h c h l o r i t e . (Crossed nicols.)  87  R ODIN&IT E  0  -IM*!-  PLATE 3-8: Older r o d i n g i t e showing absence of 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  i  1  sMM  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 rodingite. Y e l l o w i s h green pyroxene at l e r t top 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 g r a y m i n e r a l s a r e 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 + 1 3 H 0 -*->--> H y d r o g a r n e t + 10H 2  or 1.5 A n o r t h i t e + 0 . 5 C a  2 Prehnite + 4Ca  + 1.5H 0  2 +  + Al C>  2 +  1 Prehnite + 0.5Al O  2  2  3  2  + 6H 0 + ^  2Hydrogarnet + 8H  2  Decomposition o f ferro-magnesium minerals for the formation  of prehnite, epidote  magnesium f o r i d o c r a s e .  Therefore,  + H  +  +  iron  and i d o c r a s e , and  during  o n l y c a l c i u m and w a t e r need t o be added. i n g i t e c o u l d be d e r i v e d f r o m c l i n o p y r o x e n e rocks  could y i e l d  3  rodingitization Calcium  f o r rod-  of ultramafic  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).  Cal-  c i u m h a s b e e n shown t o b e 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 of u l t r a m a f i c rocks The  ( P o l d e r v a a r t , 1955).  younger group o f r o d i n g i t e s i s m a i n l y  u i s h e d by t h e d e v e l o p m e n t o f t h e r m a l with serpentine,  metamorphism a t c o n t a c t s  l e s s pronounced f o l i a t i o n and  rodingitization.  disting-  non-pervasive  The c e n t r a l p a r t s o f t h e b o d i e s  are slightly  a l t e r e d gabbro b u t t h e margins c o n s i s t o f h y d r o g a r n e t , t a l c and c h l o r i t e . hydrated and  At the contacts  and c o n v e r t e d  chlorite  serpentine  Thus i t a p p e a r s t h a t  dykes o f gabbro were i n t r u d e d i n t o a l r e a d y peridotite.  has been de-  i n t o d i o p s i d e and l o c a l l y  ( P l a t e 3-10).  epidote,  into  talc  probably  serpentinized  90  Q I  I  5MM-  PLATE 3-10: Serpentine dehydrated i n t o pyroxene. 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 serpentine. 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  talc-carbonate  Blackwall alteration  was  1  t h e A i r F i e l d u l t r a m a f i c body p o s e d o v e r an a r e a  found only a t the margin  ( F i g u r e 2-2)  f o u r m e t r e s by  zone i s m o d e r a t e l y s h e a r e d .  alteration  where i t i s  ten metres.  The  Blackwall alteration  ex-  marginal zone i s  s u c c e e d e d t o w a r d s t h e 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 t a l c - c a r b o n a t e zone. the a l t e r a t i o n  In both zones, s e r p e n t i n e  c o n s i s t s of gray  a zone a b o u t 0.5  to greenish b l a c k rock  coarsely c r y s t a l l i n e chlorite t o 20 mm).  ite.  The  I t has  (1 mm  abrupt boundary w i t h the country  and  schist.  One  and  occurs  I t has  zone o r  a l s o a sharp  and  rock which i s calcareous-  In t h i n s e c t i o n , the b l a c k w a l l  Three t e x t u r a l  as b a n d o f f l a k y  varieties  type, .forms v e i n s i n a d j a c e n t as v e i n s i n f r a c t u r e s , and to the c o n t a c t w i t h country  chlorite crystals,  serpentinite.  is restricted rock.  serpentine  of c h l o r i t e  a n o t h e r as s m a l l e r g r a i n s m i x e d w i t h s e r p e n t i n e .  1:  thick,  tremolite  talc-carbonate  c o n s i s t s of c h l o r i t e , t r e m o l i t e , t a l c ,  opaque m i n e r a l s .  found.  metres  replaced highly fractured serpentin-  serpentinite i s sharply defined.  alteration  co-exists with  c h a r a c t e r i z e d by  t o 5 mm)  contact w i t h the adjacent  quartz-muscovite  a  minerals.  Blackwall alteration,  (4 mm  of  The  The  Tremolite  are  and third occurs  t o a zone c l o s e  silica  required for  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 almost massive, mainly dark c o l o u r e d c h l o r i t e - r i c h rocks t h a t f o r m 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 production  may h a v e come f r o m t h e q u a r t z - m u s c o v i t e  schist  and m a g n e s i u m f r o m t h e u l t r a m a f i c r o c k s . A talc-carbonate wall alteration  zone w h i c h l i e s  zone i s a b o u t 0.3 m e t r e s t h i c k ,  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 . ational with  adjacent  serpentinite.  t o the blackmoderately  I t i s more o r l e s s  The g r a d u a l  transition  grad-  occurs  t h r o u g h t h e development, i n t h e s e r p e n t i n i t e , o f t a l c and talc-carbonate veins serpentinite.  ( P l a t e 3-11) m o s t l y  i n shear surfaces o f  Pure t a l c - c a r b o n a t e i s r a r e other  than i n veins.  I n t h i n s e c t i o n t h e a v e r a g e mode o f t a l c - c a r b o n a t e m a g n e s i t e 50 p e r c e n t , w i t h minor c h l o r i t e Talc-carbonate  antigorite  25 p e r c e n t ,  talc  zone i s 20  percent  and c h r o m i t e . c o u l d be d e r i v e d d i r e c t l y  d o t i t e o r from s e r p e n t i n i t e .  from  peri-  Preservation of serpentine  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  primary  minerals  s u g g e s t t h a t i t was more  d e r i v e d from s e r p e n t i n i t e . of talc-carbonate  The s o u r c e  probably  o f CO^ f o r t h e f o r m a t i o n  seems t o h a v e b e e n c a l c a r e o u s  country  rocks.  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  along f r a c t u r e s .  C 0  3-2-C  Late Stage  a.  2  Alteration  Silica-carbonate alteration  S i l i c a - c a r b o n a t e rock  i s made l a r g e l y o f v a r y i n g amounts  93  PLATE 3-11: B r o w n i s h 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 m a g n e s i t e w i t h l e s s a n k e r i t e , dolomite,  chromite  and p i c o t i t e and r a r e m a r i p o s i t e ,  and  h u n t i t e {MgCa(CO^) }.  The  rock  4  O p a l i s n o t a s common a s q u a r t z .  f o r m s an a l t e r a t i o n  serpentinite bodies  zone a l o n g  thicker,more  along by  the margin o f the  ( F i g u r e 3-3, 3-4, P l a t e 3 - 1 2 ) .  small sheared s e r p e n t i n i t e bodies but  are completely  replaced,  The r o c k  i seasily  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 relationship with serpentinite.  o r i g i n a l rocks, the intensity of shearing, of r e p l a c i n g minerals  and i t s  Its variation i n ofthe  the grain  S i l i c a - c a r b o n a t e rock  derived  sheared 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 nature.  various  size  and t h e r e l a t i v e abundances o f q u a r t z  carbonate minerals.  ferent lenses  only  recognized  a p p e a r a n c e d e p e n d s upon d i f f e r e n c e s i n m i n e r a l o g y  and  Some  m a s s i v e ones a r e g e n e r a l l y r e p l a c e d  t h e i r sheared margins.  frequent  clacite  and s t r e a k s a r e g e n e r a l l y gray  from  The d i f -  and g r e e n o f  s h a d e s ; t h e s h e a r e d t e x t u r e may be a c c e n t u a t e d  v e i n i n g w i t h l i g h t - c o l o u r e d magnesite, dolomite  by  or quartz.  Weathering g e n e r a l l y a l t e r s the appearance o f s i l i c a carbonate rock, because ferroan-magnesite a l t e r e d by w e a t h e r i n g ,  leaving surface coatings of hydrated  f e r r i c - o x i d e s and s i l i c a . silica  o r dolomite i s  A r o c k w i t h more c a r b o n a t e  u s u a l l y g i v e s r i s e t o an o c h e r o u s s o i l  ( F i g u r e 3-3  a r o u n d 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 one  w i t h more s i l i c a  brown  rock.  than  fragments,  than 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  FIGURE 3-4: CROSS SECTION OF THE PORCUPINE S E R P E N T I N I T E BODY ALONG 12W. N o t e s i l i c a - c a r b o n a t e z o n e d i p p i n g 4 5 * . ( S e e l o c a t i o n a t F i g u r e 3-3.)  96  i  1  PLATE 3-12: North-western f a u l t contact o f the 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" t p w a r d s northwest. (Photograph taken l o o k i n g n o r t h e a s t . )  97  Stages of replacement carbonate  r o c k c a n be  a n t i g o r i t e and  from s e r p e n t i n e t o  generalized.  In the e a r l i e s t  network of i r r e g u l a r v e i n l e t s i s found  gorite.  stage  c h r y s o t i l e v e i n s a r e r e p l a c e d by q u a r t z  l e s s abundant magnesite, r a r e l y c a l c i t e  process  silica-  and  i n cracks giving  ( P l a t e 3-13).  The  a  replacement  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 -  Secondly,  b a s t i t e and  serpophite i n the core  (away  f r o m 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 , m a g n e s i t e and d o l - ; mite. maining It  F i n a l l y q u a r t z and m i n o r m a g n e s i t e r e p l a c e t h e r e serpentine minerals.  These s t a g e s p a r t i a l l y  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  overlap.  alteration  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 .  It is  thus c l e a r t h a t the development of the s i l i c a - c a r b o n a t e rock 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  chrysotile  vein  formation. T h e r e a r e two  stages of quartz formation.  The  early  stage quartz 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 rather r o u n d e d o u t l i n e s and ance. clear.  The  i n h a n d s p e c i m e n has  a milky  appear-  s e c o n d 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  I n some s p e c i m e n s , c a r b o n a t e  b e e n b r o k e n o f f and  g r a i n s appear t o have  i s o l a t e d w i t h i n patches  of the second  quartz i n d i c a t i n g that clear variety quartz c r y s t a l l i z e d t h a n m o s t o f t h e m a g n e s i t e and stage of s i l i c i f i c a t i o n  i t i s probable  that this  stage later  late  i s unrelated to s i l i c a - c a r b o n a t e  alteration. Secondary magnetite  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 stage of 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 occurred along c h r y s o t i l e veins. W h i t e v e i n s c o n s i s t o f q u a r t z and m a g n e s i t e pseudomorphs a f t e r c h r y s o t i l e . Chrysotile veins are l i g h t green.  99  incorporated i n ferro-magnesite hydrous-iron oxide. locally  Chromite  and i s a l s o t r a n s f o r m e d  into  remains mostly u n a l t e r e d b u t  i s a l t e r e d t o marip'osite.  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 h a s b e e n no a p p r e c i a b l e c h a n g e i n v o l u m e . The  average s i l i c a - c a r b o n a t e rock 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  ofr e -  p l a c e m e n t 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 zation  (Figure 3-5). The  to margin,  s i l i c a - c a r b o n a t e zone i s i t s e l f z o n e d .  t h e sequence o f a l t e r e d rock 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 , ate rock.  t a l c - c a r b o n a t e r o c k , and s i l i c a  2  grain boundries.  careous  carbon-  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 p r o c e e d s by  t r a n s p o r t i n g CC> i n w a r d and  From c o r e  from s u r r o u n d i n g rocks a l o n g  fratures  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 -  r o c k s i n a d j a c e n t f o r m a t i o n w e r e t h e s o u r c e o f CO,,. Quartz  and m a g n e s i t e a r e f o r m e d f r o m t h e r e a c t i o n o f  s e r p e n t i n e and CC> 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 2  an o p e n s y s t e m  ( F i g u r e 3-2, 3 - 5 ) :  S e r p e n t i n e + C a r b o n D i o x i d e -»-»-> Q u a r t z  M g S i 0 . 2 H 0 + 3CC> 3  2  7  2  2  2SiC>  2  + Magnesite  + 3MgCC>  3  + Water  + 2H 0 2  E v e n v e r y l o w CO„ v a l u e s o f t h e f l u i d p h a s e c a n l e a d  100  Si0  2  MgO  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 - C 0 - M g 0 - H 0 TETRAHEDRON. 9  9  0  101  to formation of magnesite i n serpentine Magnesite entine, having  and  talc  (Johannes,  q u a r t z c o u l d a l s o be  1969).  formed from  as an i n t e r m e d i a t e s t e p  (Figure  serp3-2,  3-5) .  Serpentine  2Mg Si 0 3  2  + C a r b o n D i o x i d e ->-»-»- T a l c + M a g n e s i t e  ,2H  0 + 8CC> -»-»-»• M g S i 0 2  3  4  2 2  + Water  . H 0 + 3MgCC> + 2  H 0  3  2  This r e a c t i o n takes place at s l i g h t l y higher C0 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  and m a g n e s i t e f r o m s e r p e n t i n e 1969).  (Greenwood, 1967;  Talc i s unstable w i t h i n c r e a s i n g C0  f l u i d p h a s e , and y i e l d s m a g n e s i t e and 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,  T a l c + Carbon D i o x i d e  Mg Si 0 3  4  2 2  . H 0 + 3C0 2  A b i g zone m i n e r a l s and  4  S  i  0  + 2  Johannes,  v a l u e s i n the  2  quartz according  + Magnesite  3  quartz  M  9  (14 m e t r e s a c r o s s )  C  0 3  +  H 2  + Water  °  of opal, r i c h i n clay  l i m o n i t e ( P l a t e 3 - 1 4 ) , a p p e a r s t o be  o f p r e s e n t day w e a t h e r i n g .  the  These o p a l i n e masses a r e  result mainly  r e s t r i c t e d t o n e a r s u r f a c e l o c a t i o n s and w e r e d e v e l o p e d the s i l i c a - c a r b o n a t e zones.  to  3-5):  Quartz  2  to  values  2  in  10  2  IN.  PLATE 3 - 1 4 : B l a c k c h u n k s o f 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 give r i s e to a unique l o o k i n g r u s t y zone a t t h e h i g h e s t l e v e l o f t h e P o r c u p i n e p i t . A d j a c e n t g r a y zone i s s e r p e n t i n i t e  103  b.  Quartz-magnesite  veins  Quartz-magnesite veins are the r e s u l t of l a t e carbonate  a l t e r a t i o n and a r e f o u n d i n s h e a r  f a u l t s throughout the u l t r a m a f i c bodies the country  rock.  quartz-carbonate b r u c i t e , dolomite  They c u t a c r o s s zones.  Magnesite,  or at contacts  o f them r e p l a c e s h e a r e d  q u a r t z and minor f i b r o u s  wide and m a i n l y  veins  The  consist of  and q u a r t z .  ( P l a t e 3-15) f o r m e r l y  w i t h p i c r o l i t e , braided a n t i g o r i t e , sheared  3-3  with  the previously described  (4 t o 50 mm) m a g n e s i t e c r y s t a l s  sheared  zones o r minor  and s e r p e n t i n e a r e t h e c h i e f m i n e r a l s .  v e i n s a r e 2 t o 12 c e n t i m e t r e s coarse  silica-  Many filled  chrysotile or  t a l c o s e gouge.  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  m e t r e s b y 350 m e t r e s ) h a s b e e n f a u l t e d a n d now c o n s i s t s o f three p a r t s , the large western Porcupine C r e e k body a n d e a s t e r n Snow Shoe body  body, t h e c e n t r a l  (Figure 3-6). F a u l t s  s e p a r a t i n g t h e 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 vertical  ( P l a t e 2-14).  down-thrown. argillite  A t each f a u l t ,  These b o d i e s  the western block i s  a r e s u r r o u n d e d by  and minor c a l c a r e o u s  schist.  limy-carbonaceous  The u p p e r g e n t l y  104  PLATE 3-15: Quartz-magnesite v e i n of l a t e s i l i c a carbonate a l t e r a t i o n . These v e i n s a r e a l w a y s s e e n to r e p l a c e s e r p e n t i n e along shear f r a c t u r e s i n the Porcupine p i t .  sew  40W  30W  20W  IOW  OOO  ICE  20 E  30E  o  15 S  FIGURE 3-6: ORE BEARING PORCUPINE, CREEK AND SNOW SHOE S E R P E N T I N I T E BODIES 1 = mme c r u s h e r . 2 = d r i l l - c o r e storage. 3 = d r i l l storage. F-F = f a u l t B.L. = b a s e l i n e . L  106  c o n v e x s u r f a c e o f t h e p o r c u p i n e b o d y p l u n g e s a b o u t 10" d i r e c t i o n south  55*west  ( P l a t e 3-16).  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 erly  ( P l a t e 3-12)  gillite lite the by  and  northwestern  that dips  ( F i g u r e 2-2).  At the  s e r p e n t i n i t e are h i g h l y sheared.  southeasterly  contact  diamond d r i l l i n g  45*  and  d i p s a b o u t 60*  ( F i g u r e 3-7,  3-8,  s c h i s t at this v i c i n i t y dips C r o s s s e c t i o n s b a s e d on  on  diamond d r i l l  of the 3-7,  data  The  middle part  southeast  3-9).  this  Relatively small, tight,  along  the  contact  3-12,  3-13).  long to the the  can  speculate  zone.  suggested f o l d  upper  are  s t y l e s (Figure  argillite  part (Figure  3-10,  distinct (Figure  t h a t the recumbent f o l d s  f a u l t i s probably  Argil-  outlines  recumbent f o l d s are  f i r s t phase o f d e f o r m a t i o n  fault  partly  r e s e m b l e s an o p e n f o l d  o f s i l i c a - c a r b o n a t e and  northwest contact  phase o f  3-4  One  defined  southerly.  t h a t resemble recumbent f o l d s o f v a r i o u s 3-11),.  as  of  I t i s also a  show t h a t t h e o u t l i n e o f t h e  S u p e r i m p o s e d on  ar-  argil-  o p e n p i t e x p o s u r e s and  u l t r a m a f i c mass c u r v e s and  3-8).  northwest-  fault,  contact w i t h a h i g h l y sheared s e r p e n t i n i t e contact lite  con-  i s almost p a r a l l e l to bedding i n the  i n that v i c i n i t y  and  The  in a  t h a t a f f e c t e d the  bearea,  r e l a t e d to the  second  broad kinds  ultra-  deformation.  ORIGIN  Most g e o l o g i s t s r e c o g n i z e  three  of  107  oi  iION.  PLATE 3-16: Ore-bearing Porcupine u l t r a m a f i c b o d y p l u n g i n g 10' t o w a r d s 235". (Photograph taken l o o k i n g south-westerly.)  8N  6N  4N  2N  0.0  4S  2S 100  6S 100 F t . 50 Mtrs . _J  5  U R FA C £  18 0 0 '  1600 '  1400  FIGURE 3-7: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 19W. Note southeast c o n t a c t d i p p i n g about 6 5 " . ( See l o c a t i o n at F i g u r e 3-3.)  -1  8 N  6N  4N  2N  O.O  2S  4S 100 0 L_  6S 100 Ft. 50Mtrs. I  ^4  1  1  18 0 0 '  -4  1600'  -4  1400'  -I  fe'  FIGURE 3-8: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 20W. N o t e s o u t h e a s t c o n t a c t d i p p i n g a b o u t 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  4S 100  6S  100 F t . 50 Mtrs .  S  a  f> /r  4  c  ,  18 0 0 '  1600 Fault  FIGURE 3-9: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 26W. Note s o u t h e a s t c o n t a c t d i p p i n g about 7 ( T . ( See l o c a t i o n a t F i g u r e 3-3.)  A  H  FIGURE 3-10: CROSS SECTION LOOKING NORTHEAST OF THE PORCUPINE S E R P E N T I N I T E BODY ALONG 24W. N o t e o u t l i n e o f c o n t a c t r e s e m b l e s r e c u m b e n t 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 S E R P E N T I N I T E BODY ALONG 23W. N o t e o u t l i n e o f c o n t a c t r e s e m b l e s r e c u m b e n t 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 S E R P E N T I N I T E BODY ALONG 10W. N o t e 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 a n d a r g i l l i t e resembles recumbent f o l d . ( S e e l o c a t i o n a t F i g u r e 3-3.)  8N  6N  4N  2N  O.O  2S  4S  6S  100  100  Fl.  50 Mtrs . —J  18 0 0 '  1600 '  MOO  S Nfo t e 9W. CR  S  ™ K I N G NORTHEAST OF THE PORCUPINE SERPENTINITE BODY ALONG 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 resembles recumbent f o l d . ( S e e l o c a t i o n a t F i g u r e 3-3.) ln^v fr^r L R  3  S  E  0  N  L 0 0  '  -J  115  mafic rocks.  Layered u l t r a m a f i c rocks are  m a g m a t i c d i f f e r e n t i a t i o n and  crystal settling  B r o w n , 1 9 6 7 ) , o r p e r h a p s , d e f o r m a t i o n and et al.,1971).  The  second k i n d , rocks of  complexes have been e x p l a i n e d researchers; somatic  some b e l i e v e  (Zavaritsky,  1960;  Bhattacharji  and  tures  and  s u c h as  textures  found i n both l a y e r e d  ( I r v i n e , 1967; i s recognized  Wager and i n the  and  two  and  Taylor  ture,  and  zoned u l t r a m a f i c  crust.  zoning,  structures  features  the  C l i n t o n Creek u l t r a m a f i c  (1972) s t a t e t h a t t h e t o the  rocks  alpine  f o r m e d by  at spreading centres  emplacement  i n t e r a c t i o n of of which bears  They d i s t i n g u i s h f o u r t y p e s :  (a)  bodies  tempera-  d i a p i r i c upwelling  of  w h i c h were s u b s e q u e n t l y  i n d e p e n d e n t l y emplaced onto the mantle slabs  The  below.  MacGregor  (b) m a n t l e s l a b s  disrupted  struc-  intrusions  thermal aureoles suggesting i n t r u s i o n at high  material  Noble,  None o f t h e s e  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  with  different  channel f i l l  t y p e u l t r a m a f i c b o d i e s i s due  continental  ultramafic  t h i r d k i n d of u l t r a m a f i c body, the  M o o r e s and  (Loney  C l i n t o n Creek u l t r a m a f i c b o d i e s .  type, which i s discussed  of a l p i n e  flow  McTaggart, 1971).  Brown, 1967).  author, therefore, believes to b e l o n g t o the  zoned  and  cumulate t e x t u r e s , c r y p t i c  graded b e d d i n g , slump s t r u c t u r e s are  solid  to  magmatic, o t h e r s meta-  W a l t o n , 19 51;  S m i t h , 1963;  due  (Wager  i n d i f f e r e n t ways by  t h e m t o be  1928;  s a i d t o be  c o n t i n e n t a l margins,  incorporated  mantle and  (c)  i n t o m e l a n g e s ; and  c o n f o r m a b l e 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  (d) re-  116  presenting  recrystallization  o f t y p e s a, b and u l t r a m a f i c rocks or  c.  and  deformation  Certain features  of the  of  occurrences  suggest that  C l i n t o n Creek area  fall  the  i n t o group c  d. Pronounced mosaic t e x t u r e s i n weakly  p e r i d o t i t e are tion  s a i d to r e s u l t from s y n t e c t o n i c  ( R a g a n , 1969) .  B o t h m o s a i c t e x t u r e and  l a t o r y e x t i n c t i o n are considered deformation  serpentinized  i n the pressure  and  t o be  recrystalliza-  s t r a i n e d undu-  c a u s e d by  solid  state  temperature c o n d i t i o n s of  the  ! upper mantle calcium  (Nicholas e t a l . , 1972).  ( A p p e n d i c C)  are  considered  c r y s t a l l i n e mantle residue liquid  (Dickey,  19 70) .  left  t o be  F o l i a t i o n may  subsolidus  t i o n of clinopyroxene L o n e y e t a l . , 1971;  characteristic  O r i g i n a l u l t r a m a f i c rocks  of  basalt during  surface.  release  With  resulted i n  i n orthopyroxene  H i m m e l b e r g and  and  have d e v e l o p e d  reactions probably lamellae  aluminium  a f t e r e x t r a t i o n of  ascent of mantle m a t e r i a l towards the of pressure  Very low  Loney, of the  exsolu-  (Ragan,  1967;  1963). area  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  are b e l i e v e d and  to  dunite.  Country rocks  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  limestone  w i t h the  to  and  f o r m an o p h i o l i t e .  u l t r a m a f i c r o c k s , can  by  considered  U l t r a m a f i c b o d i e s a b o u t 48 k i l o m e t r e s  of the C l i n t o n Creek area lites  be  Foster (1974). The a b s o l u t e age  i n Alaska  are  of formation  i n t e r p r e t e d as  of the  west  ophio-  ultramafic bodies  117  is  n o t known.  H o w e v e r , t h e i r minimum age  c a n be d e t e r m i n e d . almost  The  o f emplacement  oldest tight isoclinal  h o r i z o n t a l a x i a l planes  g i n s o f t h e u l t r a m a f i c body known f i r s t p h a s e d e f o r m a t i o n  folds  with  (F^) seem t o i n v o l v e t h e mar-  ( F i g u r e 3-11).  As  this oldest  o c c u r r e d w i t h the main  o f metamorphism, i n Permian time  (see T a b l e  2-1),  the  episode emplace-  ment o f t h e u l t r a m a f i c r o c k s c o u l d n o t be y o u n g e r t h a n  Permian.  A zone o f u l t r a m a f i c m a s s e s t o g e t h e r w i t h l e n s e s a m p h i b o l i t e and m a r b l e 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 allel  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  T e r r i t o r y border. porated  i n t o and  small bodies  Occurrences  r o c k s and  o f e c l o g i t e are r e p o r t e d near Ross R i v e r ( F o s t e r , 1974).  These d a t a suggest  c r u s t i n e a r l y P e r m i a n t i m e , and  an o p e n r i f t  that  i n con-  that ultramafic  a s s o c i a t e d l e n s e s o f h i g h grade m e t a m o r p h i t e s were  e m p l a c e d t e c t o n i c a l l y when t h e r i f t  closed.  The  q u e s t i o n were t h r u s t southwestward o v e r Yukon  1976).  Therefore  (Tempelman-  the s e r p e n t i n i z e d u l t r a m a f i c rocks  m i g h t 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 o n t o Yukon 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 which through  rocks i n  Crystalline  P l a t e a u at the time of the c l o s i n g of the t r e n c h Kluit,  rocks  of blue amphibole i n q u a r t -  i s p o s s i b l e t h a t t h e T i n t i n a f a u l t was  tinental  incor-  i n t e r l a y e r e d w i t h low grade metamorphic  along T i n t i n a Trench it  par-  Alaska-Yukon  T h e s e a m p h i b o l i t e s and m a r b l e s a r e  of greenschist f a c i e s . z i t e and  of  subsequent deformation  Crystalline  (Permian)  and  and m e t a m o r p h i s m 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 I V  THE CLINTON CREEK ASBESTOS DEPOSIT  4-1  INTRODUCTION  The C l i n t o n C r e e k m i n e , a b o u t 22 5 k i l o m e t r e s  south  o f t h e A r t i e C i r c l e , was t h e m o s t n o r t h e r l y o p e n p i t ( P l a t e 4-1) o p e r a t i o n i n C a n a d a .  I t i s a t an e l e v a t i o n o f 5 3 5 m e t r e s  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 The m i l l  i s s i t u a t e d on T r a c e H i l l  C l i n t o n Creek  (Figure 2 - 2 ) .  on t h e o p p o s i t e  side of  C l i n t o n C r e e k , a n d t h e o r e was t r a n s p o r t e d b y a m i l e - l o n g tramline.  The o r e t o w a s t e r a t i o a v e r a g e was 1:5 a n d t h e  average c h r y s o t i l e - f i b r e The t h r e e o r e - b e a r i n g  l e n g t h between  1.5 mm and 3.0  mm.  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 2 7 0 m e t r e s w i d e a n d 1 , 4 0 0 m e t r e s l o n g  (Figure  3-6).  The m a i n P o r c u p i n e o r e zone i s 1 3 5 m e t r e s w i d e , a n d  535 m e t r e s l o n g , and has been d r i l l e d t o a d e p t h o f 900 f e e t (Figure 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 ) ; C r e e k p i t ( m i d d l e ) ; Snow Shoe p i t ( l e f t ) . ( P h o t o g r a p h t a k e n l o o k i n g t o w a r d s 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 uished:  types o f c h r y s o t i l e  veins are d i s t i n g -  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  a.  Chrysotile-fibre  Chrysotile  veins.  veins  f i b r e v e i n s a r e o f two t y p e s :  and  s l i p - f i b r e veins.  the  Clinton  are  u n d e r s i x mm i n w i d t h .  cross-fibre  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  Creek mine c o n s i s t  of cross-fibre  chrysotile  I n some, c h r y s o t i l e  fibres l i e  perpendicular to the vein w a l l , but i n others the f i b r e s an  acute angle w i t h the w a l l  B show common v a r i a t i o n s  (Plate  of the f i r s t  i d u a l f i b r e s p a s s f r o m one w a l l perfect continuity.  4-2).  form  F i g u r e 4-1, A a n d  two t y p e s ; a n d i n d i v -  of the vein to the other  Many f i b r e - v e i n s  and  show p a r t i n g s .  with  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  B o t h i n c l i n e d and c e n t r a l  vein wall.  partings are 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 .  some s p e c i m e n s , p a r t i n g s d i v i d e d  the f i b r e s into  lenses  In (Figure  4 - 1 - C ) , a n d i n t h e s e t h e r e i s no c h a n g e 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  fibre  of the parting.  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 ,  ( F i g u r e 4-1-E). of  A few v e i n s a r e made up o f  the chrysotile  S l i p - f i b r e veins  p i c r o l i t e o r magnetite  ( F i g u r e 4-1-F) i n w h i c h m o s t  f i b r e s are almost p a r a l l e l t o the v e i n  occur i n conjunction with the c r o s s - f i b r e  wall,  o r i n zones where  121  0 I  -\MIV I  PLATE 4-2: Cross-fibre chrysotile vein i n thin section. Fibres l i e o b l i q u e l y to the w a l l of the v e i n . A d j a c e n t , g r a y 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 . (Crossed n i c o l s . )  A  B  E  F  FIGURE 4-1: CHRYSOTILE-FIBRE VEINS. A,B. F i b r e s o r i e n t e d p e r p e n d i c u l a r and i n c l i n e d t o v e i n w a l l s . C. I n c l i n e d p a r t i n g s d i v i d e d the f i b r e s b u t the f i b r e s do not change i n d i r e c t i o n on each s i d e o f the p a r t i n g . D. C e n t r a l p a r t i n g i s u s u a l l y f i l l e d w i t h magnetite. E. Composite v e i n i s made up o f f i b r e l e n s e s separated by magnetite, p i c r o l i t e o r a n t i g o r i t e . F. Slip-fibre vein. (P = p i c r o l i t e ; M = magnetite; S = n o n - f i b r e s e r p e n t i n e ; 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  intense.  F i b r e v e i n s may b e s t r a i g h t Some i n t e r s e c t Colours  separate veins  ( F i g u r e 4-2-B) o r d i v e r g e  of veins  i v i d u a l veins  a r e o f o n l y one c o l o u r .  readily  Adjacent fibres  (Figure  (Figure  4-2-A).  4-2-C).  range from l i g h t green t o dark green b u t i n d -  and a r e s o f t  Most o f t h e f i b r e s  l i k e s i l k b u t some  a r e h a r s h a n d do n o t s e p a r a t e  straight  o r curved  are p a r a l l e l .  easily into  chrysotile fine  fibres.  Some o f them a r e p e r f e c t l y  b u t u s u a l l y minute c o r r u g a t i o n s  are present  which  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 t h e v e i n ( F i g u r e 4-1-B).  Fine-grained  m a g n e t i t e o c c u r s as t h i n  sheets  or lenses which 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 , or p a r a l l e l t o f i b r e s fills  ( F i g u r e 4-2-D).  t h e acute angle a t low angle j u n c t i o n s  some v e i n j u n c t i o n s t h e r e m a g n e t i t e and s e r p e n t i n e . o f one v e i n w i l l  (4-2-E).  i s a confused mixture of f i b r e , At other  vein junctions the f i b r e  vein without  any d i s c o n t i n u i t y  (4-2-E a n d  A t some j u n c t i o n s f i b r e s o n one v e i n c u t a c r o s s  of another v e i n completely  b.  (Figure  the fibres  4-2-B).  P i c r o l i t e veins  P i c r o l i t e , non-fibrous sotile  At  b e n d a n d 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 of the other F) .  M a g n e t i t e commonly  chrysotile,  f i b r e , i s r e l a t i v e l y hard, pale  g r e e n , and has a s p l i n t e r y  fracture.  compared t o c h r y -  green t o y e l l o w i s h P i c r o l i t e veins  occur  124  B  D  FIGURE 4-2: CHARACTERISTICS OF CHRYSOTILE-FIBRE VEINS. A. Two f i b r e v e i n s c u t across each o t h e r a t d i f f e r e n t p o i n t s . B. F i b r e i n v e i n X c r y s t a l l i z e d i n an expansion f r a c t u r e which s e p a r a t e s v e i n Y p e r p e n d i c u l a r l y . C. Magnetite commonly f i l l s acute angle a t low angle j u n c t i o n D. Magnetite o c c u r s as thin; sheets o r l e n s e s i n f i b r e - v e i n s . E. F. F i b r e o f one v e i n bands and becomes o r i e n t e d p a r a l l e l to the f i b r e o f the o t h e r v e i n w i t h o u t 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 = n o n - f i b r e s e r p e n t i n e ) .  125  mostly along f a u l t surfaces, generally with f i b r e veins are mostly of s l i p - f i b r e , fillings.  Picrolite  and r a r e l y  as i s o l a t e d  fracture  a p p e a r s t o be c o n t e m p a r a n e o u s  l a t e r than c h r y s o t i l e f i b r e .  that  with or  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 a r e 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 t h e y 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 veins are usually only a small  fraction  o f a m i l l i m e t r e i n t h i c k n e s s b u t may r e a c h a s much a s s e v eral millimetres.  The b a n d i n g w h i c h i s f u r t h e r  emphasized  b y 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 b e t w e e n s u c c e s s i v e bands i s o r d i n a r i l y  sharp  are p e r f e c t l y s t r a i g h t ;  they mostly r e f l e c t the i r r e g u l a r -  ities  ( P l a t e 4-3).  V e r y few bands  i n t h e 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 o t e x t e n d a c r o s s t h e f u l l w i d t h o f e v 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 parallel  t o the vein w a l l s  displays delicate  ( P l a t e 4-3), a n d i n d i v i d u a l  o f p i c r o l i t e a r e f o u n d t o be composed o f t r a n s v e r s e w h i c h occupy  bands  fibres  a p o s i t i o n anywhere f r o m normal t o o b l i q u e t o  the margins o f t h e bands  ( P l a t e 4-3).  i t i o n o f e x t i n c t i o n from band t o band,  V a r i a t i o n i n t h e posi s due t o s l i g h t  ferences i n o r i e n t a t i o n of the fibres i n successive The  banding  dif-  bands.  c o n t a c t b e t w e e n t h e v e i n a n d w a l l r o c k may b e s h a r p o r  126  0  I  -1MMI  PLATE 4-3: l i g h t green, p a r a l l e l , sharp banding o f p i c r o l i t e , a t l e f t hand t o p , d i s p l a y s f i b r e l i k e forms w h i c h a r e t r a n s v e r s e t o b a n d i n g . P u r p l e 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 b o t t o m c o r n e r i s a n t i g o r i t e . (Crossed n i c o l s . )  127  gradual.  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 ,  a r e amorphous o r c r y p t o c r y s t a l l i n e . p i c r o l i t e v e i n s a r e amorphous. p i c r o l i t e veins are devoid is  some  Usually the smallest  Unlike chrysotile-fibre  of magnetite.  In places  veins,  magnetite  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  magnetite i n f i b r e veins  ( F i g u r e 4-3-A a n d B ) .  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  Commonly  ( F i g u r e 4-3-C) a n d  such p i c r o l i t e v e i n s a r e 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 the d i r e c t i o n o f major shear planes. such p i c r o l i t e - b e a r i n g shears reverse.  i s g e n e r a l l y normal r a t h e r  selvages  on c h r y s o t i l e - f i b r e v e i n s  and b r o w n i s h .  m i g h t b e due t o l a t e d e f o r m a t i o n vein, f o r there  Picrolite  a r e t h i c k o n one s i d e o f  f i b r e v e i n and t h i n o r a b s e n t o n t h e o t h e r  side.  This  e f f e c t s on t h e c h r y s o t i l e  a r e 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  has  b e e n d e f o r m e d and a l t e r e d t o p i c r o l i t e  and  E).  (Figure  fibre  4-3-D  F i g u r e 4-3-F shows c r o s s - f i b r e c h a n g e d t o s l i p -  f i b r e and t h e n t o p i c r o l i t e  4-2-B  or directly to p i c r o l i t e .  Relationship with Serpentine  The  Wall  Rock  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 rock i s  sharp 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 r e n o t uncommon.  than  C h r y s o t i l e - f i b r e si n contact with or close to p i c -  r o l i t e veins are invariably b r i t t l e  the  The s e n s e o f movement o n  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  coated w i t h magnetite 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  F  S  FIGURE 4-3: CHARACTERISTICS OF PICROLITE VEINS. A. P i c r o l i t e occurs as p a r t i n g i n c h r y s o t i l e - f i b r e v e i n . B. P i c r o l i t e forms a c o a t i n g on c h r y s o t i l e - f i b r e v e i n . C. P i c r o l i t e stops the c o n t i n u a t i o n of some f i b r e v e i n . D. P i c r o l i t e forms a pseudomorphs a f t e r deformed s l i p - f i b r e . E. P i c r o l i t e o c c u r s a t an acute angle t o f i b r e i n same v e i n . F. S u c c e s s i v e change o f 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  macroscopic s c a l e v e i n w a l l s match, b u t under t h e microscope t h e r e a r e minor e x c e p t i o n s . i n the veins are observed  Inclusions of wall  h e r e a n d t h e r e a n d 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 . abruptly against another a few c a s e s  4-2-C  A total gorite study  F i b r e v e i n s t h a t end  v e i n do n o t t a p e r i n w i d t h .  v e i n s t a p e r and f i n a l l y  Chemistry  rock  disappear  In  ( P l a t e 4-4).  o f C h r y s o t i l e and A n t i g o r i t e  o f 97 s p e c i m e n s o f c h r y s o t i l e  (64) w e r e c o l l e c t e d  anti-  from t h e C l i n t o n Creek area t o  their respective chemistries.  t h a t no o t h e r s e r p e n t i n e  (33) a n d  X - r a y a n a l y s i s showed  s p e c i e s were p r e s e n t .  Chemical  a n a l y s i s o f a l l s a m p l e s w e r e done u s i n g an ARL e l e c t r o n microprobe  (Model-SEMO) i n t h e D e p a r t m e n t o f G e o l o g i c a l  Sciences, University of B r i t i s h Mr.  G. G e o r g a k o p o u l o s .  oxides FeO,  Samples were a n a l y z e d  ( N a 0 , MgO, l ° f A  2  a n d NiO) .  2  Columbia w i t h a s s i s t a n c e o f  3  S i  °2'  K  2°'  Results are l i s t e d  C a 0  '  T i  °2'  i n Table  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 r e g i v e n i n a summary  (Table  f o r eleven C r  2°3'  4-1.''"  ° '  Means,stan-  4-2, 4 - 3 ) . F i g u r e 4-4 a n d 4-5 a r e h i s t o -  that are different s t a t i s t i c a l l y  1:  n  statistical  grams s h o w i n g 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 m a j o r  erals.  M  These h i s t o g r a m s  See A p p e n d i x E  oxides  i n t h e two s e r p e n t i n e  illustrate  the l i m i t e d  min-  composition-  130  O I  -&riM. 1  PLATE 4 - 4 : Tapered, l i g h t gray c h r y s o t i l e fibre vein. 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 periods of c h r y s o t i l e - f i b r e formation. A l s o note matching 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 E L E V E N O X I D E S OF  Oxides  Std.  Deviation(S)  Variance(S  0.0318  0.0101  0 .0001  3y . 6 4 1 7  0.4369  0.1y09  0. 8 3 5 1  0.2676  0. 0 7 1 6  40.4060  0.8466  0.7168  K 0 2  0 .0306  0.0152  0 . 0002  CaO  0 .0397  0.0230  0.0005  0.0336  0.0197  0.0004  0.3379  0.3130  0.0980  MnO  0.0312  0.0192  0.0004  FeO  2.12y7  0.6585  0.4336  NiO  0.2079  0.1255  0.0158  2  MgO A l  2°3  Si0  T10  2  2  Cr 0 2  3  SAMPLES  Arithmetic Means(X)  Na 0  33 C H R Y S O T I L E  )  132  TABLE  STATISTICAL  0  x  1 d  e  SUMMARY OF E L E V E N O X I D E S OF  64 ANTIGORITE  Means(X)  Std. Deviation(S)  Variance(S ) 2  0.0208  0.0113  0.0001  38.0282  0.6792  0.4613  0.9456  0.3603  0.1298  41.9354  0.9900  0.9802  K 0 2  0.0248  0.0148  0.0002  CaO  0.030U  0.0225  0.0005  0.0237  0.0174  0.0003  0.2961  0.2266  0.0513  MnO  0.0487  0.0418  0.0017  FeO  2.9778  0.7924  0.6279  NiO  0.1961  0.1405  0.0198  2  MgO A 1  2°3  sio  Ti0  2  2  Cr 0 2  3  SAMPLES  Arithmetic  s  Na 0  4-3  MEAN  (Y)  380262  0-9456  STD. DEVIATION (S)  0-6792  0-3603  0-99  0-7924  CLASS INTERVAL (CL)  1-65  0 0901  0-245  0-I98  20  i  4I-9354  201  2-9778  201  10  « cr  37 % MgO  38  oJ/W  39  l-O I-5 % A I 0 3 b y wt.  by wt.  ^ ^ ,™!i„„-™ "™? _? OF 64 ANTIGORITE SAMPLES. G  E  % S i 0 b y wt.  2  Q  Y  I  A  G  R  A  M  S  0  F  M <  3°'  %  2  A l  2°3'  S  i  0  ?  a  n  d F  e  0  w  t  FeO by wt.  - Percent)  MEAN (X)  39-6417  0-8851  40-4060  21297  STD DEVIATION (S)  0-4369  0-2676  0-8466  0-6585  00669  0-21  0165  CLASS INTERVAL (CL) Oil  FIGURE 4 - 5 : FREQUENCY DIAGRAMS OF MgO OF 3 3 CHRYSOTILE SAMPLES.  135  a l v a r i a t i o n of the major oxides ically  i n t h e two  t h a t are d i f f e r e n t  serpentine minerals.  The  histograms  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 i n Table  4-2  o f t h e two "F"  and  4-3.  Means and  serpentine minerals  statist-  summarized  v a r i a n c e s of each v a r i a b l e  a r e c o m p a r e d by  t e s t t o f i n d w h e t h e r o r n o t t h e two  " t " test  m i n e r a l s have  same c h e m i c a l  composition  ence l e v e l ) .  T h e s e t e s t s i n d i c a t e t h a t t h e means f o r  A^O^,  SiO^  minerals. minerals  and  could arise  fluid  factors.  be  are s i g n i f i c a n t l y  from s e v e r a l causes.  composition  o f t h e two  FRACTURES AND  Figure  4-6  two  serpentine  Conditions  m i g h t have been the  of  controlling  some c o n t r o l s u c h  to e x p l a i n the d i f f e r e n t  minerals  i f they  DISTRIBUTION OF  chemical  are i n e q u i l i b r i u m .  CHRYSOTILE F I B R E VEINS  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 of f i b r e v e i n s . the author  MgO,  the 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-  as t e m p e r a t u r e n e c e s s a r y  4-3  the  d i f f e r e n t f o r the  C e r t a i n l y t h e r e w o u l d seem t o be  composition  and  ( t e s t e d at the 9 5 percent c o n f i d -  C h e m i c a l d i f f e r e n c e b e t w e e n t h e two  f o r m a t i o n may t u r e and  FeO  il-  t o be m a i n l y  T h i s randomness i s b e l i e v e d due  to the curved  nature  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 c a n be  by  of the  veins  measured.  136  FIGURE 4-6:  POLES TO 264 CHRYSOTILE-FIBRE V E I N S .  137  Nevertheless,  i f concentrations of only three or four  cent are considered, 4-6): SE; S;  A. C.  and  f i v e d i s t i n c t g r o u p s c a n be  305*/35* t o 60" 340"/40" - NE  E.  and  240*/80* - SE.  F i g u r e 4-7  and  4-8  seen  - NE  and  SW;  SW;  D.  270*/45" t o 70"  - N  i n shear  z o n e s and  g r o u p D and  Ore  grade zones of the P o r c u p i n e  p i t ( F i g u r e 4-9,  the e l o n g a t i o n of the h i g h grade ore t h e t r e n d s o f g r o u p s B and  D.  E occur  f r o m 45"  joints.  4-10)  show  zones are i n a c c o r d  A cross-section (Figure  to  those  t o 27 c e n t i m e t r e s age  fibre  o f low  seems t o be  ( P l a t e 4-5).  with 4-11)  different  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 t h i c k e r than  B  in  p i t a l s o r e v e a l s t h a t the d i p s of  ore grade zones v a r y  and  with  shows t h a t f i b r e - v e i n s o f g r o u p s A,  C occur  and  (Figure  225*/70" t o 90"  C o m p a r i s o n o f F i g u r e 4-6  and  of the Porcupine  B.  per-  dips.  longer  Fracture spacing of  associated with longest  With higher  7  aver-  fracture density,  fibres  become s h o r t e r . Massive unsheared s e r p e n t i n i t e contains very fibre.  Zones o f p o l i s h e d f i s h - s c a l e  of f i b r e .  A l s o , f i n e l y crushed  d i s i n t e g r a t e s on gers  e x p o s u r e and  c a n be b r o k e n b e t w e e n t h e  are b a r r e n , even i f i t o c c u r s w i t h i n ore  are devoid of An  devoid  zones where s e r p e n t i n i t e  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) ite,  s e r p e n t i n i t e are  little  mostly  zones.  adjacent  fin-  Rare  to roding-  chrysotile-fibre.  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  f r a c t u r e s i n the country  rocks  ( F i g u r e 2-11)  as w e l l  as  of  -  138  FIGURE 4-7: POLES TO 125 CHRYSOTILE-FIBRE V E I N S SHOWING DISPLACEMENT ALONG THE CONTAINING FRACTURE.  139  FIGURE 4-8:  POLES TO 139 C H R Y S O T I L E - F I B R E VEINS I N JOINTS  100'  200  Ft  o  FIGURE 4-11: CHRYSOTILE-FIBRE ORE GRADE ZONES I N CROSS SECTION ALONG 17W. (See F i g u r e 3-3 f o r location.) 1= S e r p e n t i n i t e w i t h 0 t o 1 p e r c e n t 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 p e r c e n t f i b r e ; 3= S e r p e n t i n i t e w i t h 3 t o 7 p e r c e n t 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 p e r c e n t 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: Long-fibre chrysotile veins i n widely spaced f r a c t u r e s . This kind of v e i n i s planer and has a c o n s i s t a n t a t t i t u d e s . Usually the length of f i b r e s i s longer than the l e n g t h of the f i b r e s i n shear 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 S h o e 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 adjacent to rodingite.  143  fractures adjacent 4-12)  t o the Porcupine  with five concentrations  E closely parallel  shown i n F i g u r e allel  2-11.  (Figure  of chrysotile-fibre-veins  ( F i g u r e 4-6) p r e v i o u s l y m e n t i o n e d . and  u l t r a m a f i c body  F i b r e - v e i n s o f group  some o f t h e j o i n t  F i b r e - v e i n s o f group  some o f t h e f a u l t c o n c e n t r a t i o n s  D , 2  concentrations and  par-  shown i n F i g u r e 4-12.  G r o u p 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 coincides with  foliations F  w e s t and d i p n o r t h e a s t . quite parallel  2  ( F i g u r e 2-8) w h i c h s t r i k e  north-  Some g r o u p s o f f i b r e - v e i n s a r e n o t  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 d e g r e e s 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 t h e u l t r a m a f i c r o c k and the .country  rock.  Some o f t h e f i b r e - v e i n s c a n n o t 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 these  v e i n - f r a c t u r e s developed during  serpent-  inization . 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-.!  t h o u g h 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 , t h e main commercial c o n c e n t r a t i o n o f f i b r e i s cont r o l l e d by j o i n t s a n d f a u l t s n o t e d  above.  4-4  ORIGIN OF CHRYSOTILE VEINS  4-4-A  Temperature o f Formation o f Serpentine  Minerals  144  14 5  Temperatures of s e r p e n t i n i z a t i o n are r e p o r t e d to range f r o m a b o u t 400*C t o 100'C.  Cashman and W h e t t e n  (ly76)  proposed t h a t f o r m a t i o n of s e r p e n t i n e o c c u r r e d under conditions probably Wenner and  Taylor  l e s s than  100"C, b a s e d on  (1971) s u g g e s t e d  field  a temperature  P-T evidence.  range  85*C t o 185*C f r o m t h e e q u i l i b r i u m o f t h e a s s e m b l a g e a r d i t e and low  c h r y s o t i l e and  as 220 *C.  liz-  argue f o r a n t i g o r i t e f o r m a t i o n  T h i s i s b a s e d on  "^O/^O f r a c t i o n a t i o n  b e t w e e n 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 . perature  of  formation of c h r y s o t i l e  i s probably  data  T h i s low due  as  tem-  to i t s  chemical d i f f e r e n c e from other 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 of u l t r a m a f i c rocks 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 h a v e t a k e n p l a c e a t 4 80*C, (Aumento Laubat,  19 7 1 ) .  Experiments  perature of o l i v i n e  (Fo^)  indicate serpentinization  tem-  a t a w a t e r p r e s s u r e o f 1000  at-  m o s p h e r e s , i s a r o u n d 400'C (Bowen and 1952;  4-4-B  Hostetler et a l . ,  Formation  Tuttle,  Yoder,  of C h r y s o t i l e Veins  a.  Previous  The  formation of c h r y s o t i l e asbestos  ideas  The  a r e open space f i l l i n g  replacement.  o c c u r i n two  1949;  1967).  j e c t o f many d i s c u s s i o n s .  may  and  ways:  and  has  been the  p r i n c i p a l hypotheses of Fracture  sub-  origin  filling  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 a r e f i l l e d B a i n , 1932; B a d o l l e t , 1947; Laliberte, ii.  (Keep,  1929;  Gabrielse,1960; Tatarinov,  1967;  1972).  The v e i n s a r e f o r m e d as c r y s t a l g r o w t h p u s h e s t h e w a l l  a p a r t and t h e c r y s t a l s  grow f r o m s o l u t i o n s i n t r o d u c e d  at  the  c e n t r a l p a r t i n g of the f i b r e - v e i n s  Two  types of replacement are  i.  Veins c r y s t a l l i z e d during s e r p e n t i n i z a t i o n of the rock.  Chrysotile-fibre  (Taber, 1924).  distinguished:  forms outward  from p r e - e x i s t i n g  fractures,  through which waters passed during s e r p e n t i n i z a t i o n (Dresser, 1917; ii.  H a r v i e , 1923;  Graham, 1 9 4 4 ) .  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  serpentinized  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 1956;  Grubb,  1962).  Riordon placement  (Hendry,  (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 -  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 vein formation.  b.  Evidence from C l i n t o n  Creek  Evidence from the C l i n t o n Creek d e p o s i t m a i n l y supports the  fracture f i l l i n g  hypothesis.  Most o f the v e i n s have  s t r a i g h t clean-cut w a l l s which are not c h a r a c t e r i s t i c of r e placement v e i n s . on a m e g a s c o p i c  Most o f t h e f i b r e v e i n s have m a t c h i n g scale  ( F i g u r e 4-13-A).  I t thus appears  walls that  147  FIGURE 4-13: MECHANICS OF ORIGIN OF CHRYSOTILE VEINS. A. Matching w a l l s . B. Matching r e - e n t r a n t . C. Straight border i n c l u s i o n . D. B a r r e n f r a c t u r e s i n t e r s e c t e d by chrysotile-fibre vein. E. Miss-match w a l l s ( o n l y on microscopic s c a l e ) . F. D i r e c t l y r e p l a c e d 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 = b a r r e n 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 openings.  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 . S u c h 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 r e p l a c e m e n t s .  Some v e i n s  as f r a c t u r e f i l l i n g s  carry i n c l u s i o n s of wall-rock  w h i c h match t h e 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  wall-rock  Some i n c l u s i o n s , a l t h o u g h  ( F i g u r e 4-13-B).  a matching r e - e n t r a n t , s t i l l ders  than  show r e l a t i v e l y  ( F i g u r e 4-13-C) w h i c h s u p p o r t s  adjacent lacking  s t r a i g h t bor-  fracture 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 n o t 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 4-2-B).  F i b r e s s p l i t c l e a n l y from t h e v e i n w a l l s and t h i s  suggests f r a c t u r e f i l l i n g  r a t h e r than replacement.  Tight  f r a c t u r e s , w h i c h a r e contemporaneous w i t h o r e a r l i e r fibre  formation  Dilation off-set at inter-  secting veins  ( F i g u r e 4-2-B)  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  s u g g e s t s open space fracture  Although evidence of f r a c t u r e f i l l i n g r e p l a c e m e n t seems c o n v i n c i n g  and  few i n t e r s e c t i n g v e i n s  4-4-C  (Figure  filling. filling.  rather  than  and e x i s t s on a wide s c a l e ,  i n a few s p e c i m e n s h a v e m i s m a t c h e d w a l l s  acteristics  than  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 replacement.  veins  (Figure  (Figure  show p o s s i b l e r e p l a c e m e n t  4-13-E),  char-  4-13-F).  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  Deposition  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 w e r e  149  deposited  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  d u r i n g the e a r l y p e r v a s i v e  serpentinization.  t h e C l i n t o n C r e e k d e p o s i t has  formed  C h r y s o t i l e at  not been observed d i r e c t l y  contact w i t h o l i v i n e or pyroxene or country  rock but i t  is  by  i n v a r i a b l y separated  serpentine sotile  from these  ( F i g u r e 4-14).  f i b r e was  minerals  Therefore,  i n p r e v i o u s l y formed s e r p e n t i n e .  a l a y e r of  i t seems t h a t  p r e c i p i t a t e d o n l y on  in  d e p o s i t i o n e x p l a i n s why  f r a c t u r e s i n the  T h i s l e a d s t o the  Chrysotile has  t h e r e was  adjacent  chry-  the w a l l s of f r a c t u r e s  t h e s i s t h a t serpentine w a l l s are a requirement f o r tile  country  no  hypochryso-  chrysotile  as  c r o s s - c u t t i n g r e l a t i o n s h i p of the  formed  rock.  f i b r e a t the C l i n t o n Creek asbestos  d i f f e r e n t phases of f o r m a t i o n  in  i n d i c a t e d by  fibre veins.  deposit  some o f  I t has  the  been  suggested t h a t serpentine minerals, 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 85"C  d i s s o l v e d and  (Wenner and  redeposited  T a y l o r , 1971).  l u t i o n w o u l d seem t o be w i d e l y sources.  The  c o u l d have t a k e n  known a r o u n d t h e d e p o s i t .  p l a c e a t the end i n t r u d e d the  of the  nearest, but  (30 s q . k i l o m e t r e s )  northwest of the deposit.  Cret-  vicinity  I n t r u s i v e r o c k s , however, are The  so-  phase of m i n e r a l i -  un-  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 w e s t o f t h e mine a l a r g e body  as  r e q u i r e d warm a q u e o u s  and  a c e o u s when t h e a c i d i n t r u s i v e r o c k s of the C l i n t o n Creek area.  low  a v a i l a b l e f r o m a number b f  However, the main s o u r c e  zation probably  a t t e m p e r a t u r e s as  and  i s about t h i r t e e n k i l o m e t r e s  These i n t r u s i o n s are b e l i e v e d  to  150  FIGURE 4-14: CHRYSOTILE FORMS ADJACENT TO SERPENTINE, BUT NOT TO O L I V I N E . (Ch = chrysotile; F = fracture; 0 = Olivine; S = non-fibre serpentine).  151  have p r o v i d e d  a heat source  to generate thermal  waters.  r e a c t i o n o f warm aqueous s o l u t i o n w i t h t h e e x i s t i n g t i n e along  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  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 s y s t e m . o n l y r e a c t e d as an a g e n t i n t h e but  n e i t h e r a d d e d new  able  amount.  serpen-  chrysotile  Warm a q u e o u s s o l u t i o n  formation  of c h r y s o t i l e  e l e m e n t o r s u b t r a c t e d h a r d l y any  the p r e - e x i s t i n g elements of the  The  s e r p e n t i n i t e i n any  fibre, of  detect-  152  CHAPTER V  EXPLORATION FOR CHRYSOTILE ASBESTOS I N THE NORTHERN CORDILLERA  5-1  INTRODUCTION  The  writer visited,  f o r periods ranging  f r o m 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  occurrences.  C a s s i a r and K u t c h o d e p o s i t s i n t h e B r i t i s h  C o l u m b i a , Canex,  Caley  and T i n c u p  Creek and E a g l e  Lake d e p o s i t s i n Yukon T e r r i t o r y  and Dahl  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 ) .  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 f r o m w h i c h has  been p r o d u c t i o n .  some b a r r e n  ultramafic bodies.  These r e c o n n a i s s a n c e  exploration.  FEATURES OF CHRYSOTILE ASBESTOS BEARING ULTRAMAFIC BODIES  5-2-A  C a s s i a r , B.C.  there  The w r i t e r , i n a d d i t i o n , e x a m i n e d  w e r e c a r r i e d o u t i n an a t t e m p t t o d e f i n e g u i d e s  5-2  Of  visits  f o r asbestos  153  FIGURE 5-1: ASBESTOS BEARING ULTRAMAFIC BODIES I N B.C., Y.T. AND ALASKA. l = D a h l C r e e k ; 2=Eagle; 3=Canex; 4=Clinton Creek; 5=Caley; 6=Tin-cup; 7=Kutcho; 8=Cassiar.  154  Cassiar asbestos 5-1)  deposit  ( 5 9 ' 2 3 ' N , 129'46'W; F i g u r e  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 l u m b i a , 65  s o u t h o f Y u k o n B o r d e r and Watson Lake.  An  160  kilometres  k i l o m e t r e s southwest  o r e - b e a r i n g u l t r a m a f i c b o d y was  from  emplaced  i n t o t h e 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 G r o u p 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 lites  and  f l o w s and  a r g i l l a c e o u s q u a r t z i t e , and tuff.  of completely  The  o r e body o c c u r s  u l t r a b a s i c b o d y and  within a lenticular  d i p p i n g 30"  The  e n c l o s i n g s t r a t a form the e a s t e r n  limb  the southern  The  kilometres  t w o - t h i r d s i s narrow, sheared  The  o r e body i s i n t h e n o r t h e r n  s l a b and  has  a w i d t h o f 210  zone i s n o t known.  o f l e n s e s by s h e a r  t o 45"  s l a b i s 3.2  barren.  conjugate  The  metres.  metres of  the  orebody i s d i v i d e d i n t o a s e r i e s  zones o f low d i p .  s e r p e n t i n e between these  460  and  Depth of the f i b r e - b e a r -  f r a c t u r e s i n the r e l a t i v e l y shears.  C h r y s o t i l e occupies competent b l o c k s  B o t h h a n g i n g and  of  footwall  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 . hanging-wall  c o n t a c t c o n s i s t s o f a zone o f i n d u r a t e d  lite  r e f e r r e d t o as  locally  "alteration  z o i s i t e - q u a r t z - t r e m o l i t e rock w i t h l o c a l n e p h r i t e j a d e and  uvarovite garnet  w a l l c o n t a c t , mask by itic  slab  east.  of a n o r t h e r l y trending s y n c l i n e .  ing  volcanic  s e r p e n t i n i z e d p e r i d o t i t e folded conformably  w i t h t h e e n c l o s i n g r o c k s and  l o n g , and  interbedded  argil-  s c h i s t s , i s a reverse  argil-  z o n e " , composed o f i r r e g u l a r bodies  (Hewett, 1978).  a zone o f c r u s h e d  The  argillite  f a u l t t r e n d i n g 135*  and  The and  of  foot-  graph-  dipping  155  northeast.  The c o n t a c t o f t h e C a s s i a r b a t h o l i t h  i s within  2.5 k i l o m e t r e s o f t h e d e p o s i t .  5-2-B  K u t c h o , B.C.  Kutcho mountain  ( 5 9 ' 3 3 ' N , 129'58'W; F i g u r e  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 t a r y rock volcanic  (argillite, flows  sandstone, limestone)  (greenstone)  sedimen-  interbedded  correlative with the Sylvester  Group o f D e v o n i a n - M i s s i s s i p p i a n enclose  and  5-1) i s  age ( G a b r i e l s e , 1963).  These  a n u l t r a m a f i c b o d y a t l e a s t 19 k i l o m e t r e s l o n g a n d  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 to  dunite.  The b o d y s t r i k e s n o r t h w e s t e r l y  the east.  Dykes a n d i r r e g u l a r  and d i p s  intrusions of diorite  some g a b b r o c u t t h e s e r p e n t i n i t e body o r a r e m a r g i n a l The  Cassiar batholith  a granitic body.  spur  lies  serpentinized but the  serpentinized.  Three  zones have been l o c a t e d so f a r . zones w h i c h a r e p a r a l l e l  contact.  Fibresooccupy  carbonate  alteration  5-2-C  to i t .  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  other parts are wholely  a r a t e d by s h e a r  with  nine miles east of the area, but  P a r t s o f t h e body a r e p a r t l y  fibre-bearing  gently  C a n e x , Y...T.  conjugate  i s present.  joint  enechelon These a r e sep-  to the f o o t w a l l systems.  Silica-  156  The  Canex u l t r a m a f i c  (Figure  5-1, F i g u r e  2-2)  with  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 C l i n t o n Creek P o r c u p i n e o r e body. by  I t i s surrounded mostly  l i m y a r g i l l i t e a n d i n p a r t by g r e e n s t o n e .  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 MF-1 v e r t i c a l The  west o f the  The a r e a was  w i t h a Sharpe's  i n t e n s i t y f l u x g a t e magnetometre i n 1964.  r e s u l t o f t h i s m a g n e t i c 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 s h e e t a b o u t 80 m e t r e s t h i c k a n d a b o u t 600 m e t r e s l o n g , e a s t e r l y and d i p p i n g  a b o u t 30" s o u t h e r l y .  I t i s probably  conformable w i t h the o v e r l y i n g limy a r g i l l i t e s and  i s near the c r e s t o f a major a n t i c l i n a l  estimates  striking  on t h e w e s t .  structure.  o f t h e f i b r e c o n t e n t do n o t e x c e e d t h r e e  Visual  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 b e t w e e n t h e s e r p e n t i n i t e and a r g i l l i t e a t t h e s o u t h e r n  5-2-D  Caley,  The Figure  contact.  Y.T.  Caley asbestos occurrence  ( 6 4 ' 1 8 ' N , 140"l2'W;  5-1) i s s i t u a t e d a b o u t 32 k i l o m e t r e s  C l i n t o n Creek.  The d e p o s i t  lies  southeast of  i n a serpentinized  d o t i t e t h a t i s s u r r o u n d e d by q u a r t z - c a r b o n a t e r o c k . s t r i k e s n o r t h e r l y and d i p s  gently  eastward.  periIt  The b o d y i s  b o r d e r e d o n t h e n o r t h b y q u a r t z - s e r c i t e s c h i s t s a n d on t h e  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 appear t o trend n o r t h - e a s t e r l y .  The body i s a b o u t 1000 m e t r e s  l o n g a n d 400 m e t r e s w i d e , m o s t o f w h i c h i s composed o f quartz-carbonate  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  (400 m e t r e s b y 130 m e t r e s ) o f s e r p e n t i n i t e w i t h fibre.  The b o d y i s t r o u g h - l i k e a n d was f o u n d  w i t h i n 100 m e t r e s o f t h e s u r f a c e . lies  5-2-E  remnant  chrysotile  t o bottom  A large granitic  stock  five kilometres to the north.  Tincup  The  L a k e , Y.T.  Tincup  Lake asbestos  occurrence  F i g u r e 5-1) i s a l o n g t h e n o r t h e r n b o r d e r p e r i d o t i t e body.  ( 6 1 ' 1 8 ' N , 135'15'W;  of a serpentinized  The b o d y i s a b o u t 1.6 k i l o m e t r e s w i d e a n d  appears t o d i p a t a very h i g h angle probably with the surrounding  rock u n i t s .  The u l t r a m a f i c b o d y i s  composed o f d u n i t e , p e r i d o t i t e a n d p y r o x e n i t e . i n country  rocks c o n s i s t i n g of greenstone,  s t o n e and a r g i l l a c e o u s r o c k s . Ruby Range b a t h o l i t h l i e s  conformably  The l a r g e  I t i s enclosed  quartzite,  lime-  northwest-trending  j u s t t o the south o f the u l t r a m a f i c  body.  5-2-F  Dahl  The  Creek, A l a s k a  Dahl Creek asbestos  occurrence  ( 6 6 ' 5 6 ' 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 b o d y .  The  158  ore body has p r o m i n e n t shear and  z o n e s t r e n d i n g 320* t o 330*  d i p p i n g 10* t o 28* a n d 60* t o 90* n o r t h e a s t .  f i b r e s occur  i n j o i n t s adjacent  m a f i c body i s m o s t l y stone  t o shear  zones.  Longest The u l t r a -  i n contact with black argillaceous lime-  and minor s c h i s t .  Country rock c o n s i s t s o f limestone,  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 probable  e a r l y P a l e o z o i c age.  the country  Structural relationship of  r o c k t o t h e u l t r a m a f i c body seems  conformable.  A l t e r a t i o n was n o t o b s e r v e d .  5-2-G  Eagle,  The  Alaska  Eagle  asbestos  occurrence  (64*35'N, 142*30'W;  F i g u r e 5-1) i s a b o u t 90 k i l o m e t r e s w e s t o f t h e C l i n t o n C r e e k asbestos  mine.  An a s b e s t o s - b e a r i n g ,  highly serpentinized  p e r i d o t i t e body i s c u t by w i d e l y s p a c e d j o i n t s . appears t o extend tion.  The b o d y  a b o u t 1,000 m e t r e s i n a n e a s t - w e s t  The f i b r e - b e a r i n g zone i s e x p o s e d o v e r  a length of  a b o u t 500 m e t r e 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 erratic.  The n o r t h and s o u t h  direc-  zone i s  ends o f t h e 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 fibre.  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  contains l i t t l e  o r no f i b r e .  s p a c e d 25 t o 50 c e n t i m e t r e s  80 m e t r e s  long  Generally, fibre-veinsare apart, although  more c l o s e l y s p a c e d f i b r e - v e i n s a r e o b s e r v e d .  i n some p l a c e s Average  l e n g t h i s about 6 m i l l i m e t r e s and t h e l o n g e s t f i b r e  fibre  observed  159  is  20 m i l l i m e t r e s .  The  country rock of s i m i l a r C r e e k a r e a and  s e r p e n t i n i t e body i s e m p l a c e d i n l i t h o l o g y to t h a t of the  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.  Alteration  zones were not o b s e r v e d .  were noted  i n the v i c i n i t y  5-3  Clinton  Granodiorite bodies  of the u l t r a m a f i c  body.  FEATURES OF BARREN ULTRAMAFIC BODIES  Barren u l t r a m a f i c bodies w i t h i n the C l i n t o n a r e a , i n a d j a c e n t p a r t s o f Y u k o n , n o r t h e r n B.C. v i s i t e d by  the w r i t e r , d i f f e r  that contain asbestos.  i n some r e s p e c t s f r o m  or i n quartz-mica  r a t h e r than a t or near c o n t a c t s of a r g i l l i t e in argillite.  extremely  and A l a s k a , ,  and  l a r g e o r s m a l l compared t o the  unsheared;  s e r p e n t i n e , the r e s u l t of i n t e n s i v e  of  shearing. fractured  t h e d e g r e e o f s e r p e n t i n i z a t i o n d o e s n o t seem t o be fifty  percent.  are  fibre-bearing  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 bodies are not h i g h l y  than  greenstone  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  fish-scale  and  schist,  I n a d d i t i o n , most o f the b a r r e n ones  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 and  those  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 greenstone  or  Creek  more  160  5-4  GUIDES IN THE  a.  SEARCH FOR  Exposures of u l t r a m a f i c bodies  l a c k o f h e a v y v e g e t a t i o n and blocky be  CHRYSOTILE ASBESTOS  t a l u s they produce.  a r e i n d i c a t e d by  dark green to orange  weatherin  Both c h a r a c t e r i s t i c s can  easily  seen from a d i s t a n c e or from the 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 bodies  discussed  h e r e are emplaced a l o n g the c o n t a c t o f a r g i l l a c e o u s metas e d i m e n t s and  greenstone or s c h i s t , or wholely  laceous metasediments. and  A l l of these  in  interbedded  argilgreenstone  a r g i l l a c e o u s p a r t l y m e t a m o r p h o s e d s e d i m e n t s seem t o  o f D e v o n i a n - M i s s i s s i p p i a n age. u l t r a m a f i c bodies mica  On  the c o n t r a r y ,  be  barren  are s i t u a t e d w i t h i n greenstone or  quartz-  schist. c.  A l l d e p o s i t s o c c u r w i t h i n one  g r a n i t i c i n t r u s i o n s of probably  to nine miles  of  J u r r a s s i c or Cretaceous  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 h e a t source  f o r asbestos d.  formation.  S i g n i f i c a n t concentrations of c h r y s o t i l e  are c o n f i n e d t o u l t r a m a f i c bodies which are a t l e a s t  asbestos 75  percent serpentinized. 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 p e r p e n d -  i c u l a r or at high angle  to the d i r e c t i o n s of r e g i o n a l f o l d  a x e s seem t o be m o s t f a v o r a b l e s i t e s chrysotile  asbestos  deposit.  f o r development of  a  161  f.  Known c o m m e r c i a l d e p o s i t s and  chrysotile-fibre  l i e i n relatively small  metres) u l t r a m a f i c bodies a r e w i d e s p r e a d i n B.C., d e p t h c a n n o t be  Y.T.  estimated  and  a l l o w the  e n t l y t o f o r m an g. potentials  Alasaka.  from outcrop  which  unfortunately  area.  It is  probable  r e l a t i v e to deforming  stress,  s e r p e n t i n e body t o be  fractured s u f f i c i -  orebody.  R e l a t i v e l y unsheared u l t r a m a f i c bodies  have  Also fish-scale  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  shearing, i f a  criterion  f o r the  of economic c o n c e n t r a t i o n s of c h r y s o t i l e - f i b r e .  great m a j o r i t y of small s e r p e n t i n i t e bodies fish-scale  low  f o r the development o f c o n c e n t r a t i o n s o f good  quality chrysotile-fibre.  rence  of  (1,000 t o 2,000  compared t o l a r g e b o d i e s  t h a t t h e r e i s an o p t i m u m s i z e , that w i l l  occurrences  serpentinite.  In a l l cases,  occurThe  a r e composed  fibre-veinlets  of  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 b o u n d e d by  lenticular h.  shear  zones.  F r a c t u r i n g must Pe  openings f o r c h r y s o t i l e - f i b r e tions.  fairly  intense to provide  formation  i n ore grade  S t r u c t u r a l mapping i n s u r r o u n d i n g  country  adequate  concentra-  rocks  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 extensions  a c r o s s u l t r a m a f i c m a s s e s may  h i g h grade  quality-fibre.  i.  indicate potential  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 m a s s e s , and be  for  a u s e f u l guide  t o r such masses.  i n c e r t a i n cases  may  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 if  that post-dates  chrysotile-fibre  formation  and  s u p e r i m p o s e d on c h r y s o t i l e - f i b r e c a n r e d u c e i t s q u a l i t y  destroy i t completely.  or  163  CHAPTER V I  SUMMARY AND  The  CONCLUSION  m o s t a b u n d a n t r o c k s o f t h e C l i n t i n Creek: a r e a  t o t h e Yukon Metamorphic Complex w h i c h nate  sequence o t marine s e d i m e n t a r y  are o r i g i n a l l y  belong  an a l t e r -  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 m o d e l age f o r t h e s e r o c k s o f 470  Ma(Ordovic-  ian) by whole r o c k Rb-Sr d a t i n g .  documented  F o s s i l evidence,  by o t h e r s f r o m an a r e a j u s t w e s t o f t h e Y u k o n R i v e r n e a r border episode  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. o f metamorphism o c c u r r e d i n Permian.  Alaska  The m a i n  I t appears,  t h e r e f o r e , t h a t t h e r o c k s o f t h e a r e a were formed i n t h e m i 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 Devonian). Intensity  and s t y l e o f d e f o r m a t i o n  and u l t r a m a f i c b o d i e s s u g g e s t  i n the country  rocks  t h a t the u l t r a m a f i c rocks of the  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 , t h e time o f main metamorphism.  I t i s probable  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 f r o m t h e s t u d y area r e f l e c t s  a zone o f w e a k n e s s 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 t h e C l i n t o n Creek a r e a and p r o b a b l y o f t h e o t h e r s a l o n g and c l o s e t o t h e T i n t i n a Trench  some  w e r e em-  164  placed tectonically.  These were l a t e r  w i t h the country r o c k s .  The  metamorphosed  i n t r u d e d by a c i d  intrus-  ive rocks 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 time.  Colum-  nar j o i n t e d b a s a l t o f S e l k i r k youngest,  a r e a wa's  f o l d e d and  v o l c a n i c s e q u i v a l e n t i s the  undeformed, f r e s h rock o f the a r e a .  These  Selkirk  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 m o s t c o m p l e x p h a s e o c c u r r e d d u r i n g Permian,  a l o n g w i t h t h e i n i t i a l movement o f t h e T i n t i n a  Small, tight, i s o c l i n a l phase.  The  folds are c h a r a c t e r i s t i c of  s t r u c t u r a l t r e n d (300*  t o 315')  to the d i r e c t i o n of the T i n t i n a Trench.  Due  t o 010"  t o 100*.  i s common. The  r e c u m b e n t and t o ^90*  second  D i r e c t i o n of vergence phase o f d e f o r m a t i o n  isoclinal  i s roughly  parallel  to later  deformat-  v a r i e s f r o m 0 30*  gave r i s e t o l a r g e  The  t h i r d phase o f  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  ultramafic bodies bodies  Two  of these, the Porcupine  are mined f o r asbestos.  270" deformat-  scale.  Eighteen lenses of s e r p e n t i n i z e d ultramafic h a v e b e e n mapped.  trends  f o l d s w i t h trends v a r y i n g from  w i t h s o u t h e r l y vergence.  fault.  this  i o n o f t h e f o l d s o f t h i s p h a s e , l o c a l change i n a x i a l up  the  bodies  and Snow Shoe  A few  of  other  c o n t a i n a p p r e c i a b l e amount o f c h r y s o t i l e - f i b r e  a p p a r e n t l y n o t o f a d e q u a t e q u a n t i t y t o be m i n e d .  but  Most of  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  chrysotile-  fibre  massive  and  these were e x c e s s i v e l y sheared  w i t h o u t much f r a c t u r e s .  or very  Again, i f serpentinization i s less  165  t h a n 75 p e r c e n t mineralization. factors  t h e r e i s p r a c t i c a l l y no c h a n c e Fracturing  i s one o f t h e m o s t  i n control of mineralization.  f o r commercial important  F a i r l y intense  fractures  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 fibre  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 .  bearing serpentinized  ultramafic  or a t the contact of a r g i l l i t e to carry  argillite  unit  u n i t and o t h e r r o c k u n i t s  seem  o r e grade o r s u b s t e n t i a l  masses w i t h i n  Chrysotile-fibre  amount o f c h r y s o t i l e - f i b r e .  166  BIBLIOGRAPHY  A n h a e u s s e r , C.R., 1976, The N a t u r e o f C h r y s o t i l e A s b e s t o s Occurrences i n Southern A f r i c a : A Review: Ec. 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Zussman, 1 9 7 7 , An I d e a l i z e d Model f o r S e r p e n t i n e Textures A f t e r O l i v i n e : Cana. M i n e r a l . , v . 1 5 , p . 446-458. and J . Zussman, 1 9 7 5 , M i c r o b e a m X - r a y D i f f r a c t i o n P a t t e r n s of the Serpentine Minerals: Cana. M i n e r a l . , v . 1 3 , p . 244 -258. W i l l i a m s , H., a n d J . M a l p a s , 1 9 7 2 , S h e e t e d Dykes a n d 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 I g n e o u s C o m p l e x e s , B a y 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. S m y t h , 1 9 7 3 , M e t a m o r p h i c A u r e o l e s B e n e a t h 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 : Tectonic Implic a t i o n s w i t h W e s t e r n N e w f o u n d l a n d E x a m p l e s : Am. J o u r . S c i . , v . 2 7 3 , p. 5 9 4 - 6 2 1 . W i n k l e r , H.G.F., 1 9 7 4 , P e t r o g e n e s i s o f M e t a m o r p h i c R o c k s : 3 r d e d . , S p r i n g e r - V e r l a g , New Y o r k I n c . , 237 p . Y o d e r , H.S. J r . , 1 9 5 2 , The M g O - A l 2 O 3 - S i O - H 0 S y s t e m a n d t h e R e l a t e d M e t a m o r p h i c F a c i e s : Am. J o u r . S c i . , Bowen V o l . , p. 569-627. 2  Y o r k D., 1 9 6 7 , The B e s t v. 2, p . 4 7 9 - 4 8 2 .  Isochron:  2  Earth P l a . S c i . Lett.,  1969, L e a s t S q u a r e 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. - a n d R.M. F a r q u h a r , 1 9 7 2 , The E a r t h ' s Age a n d G e o c h r o n o logy: Pergamon, 178p.  176  APPENDIX A  Definition of  Greenstone  used i n t h i s  v o l c a n i c ' r o c k s and p e l i t i c  Greenstone  t h e s i s i s d e r i v e d from mafic  sedimentry rocks.  These a r e formed  i n t h e lower temperature p a r t o f t h e metamorphic Hornblende epidote. calcite  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 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  are also present.  sedimentary o r i g i n of  albite,  Greenstone  o f v o l c a n i c o r i g i n and  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  m i n e r a l s they c o n t a i n .  origin  conditions.  Greenstone  d e r i v e d from  c o n t a i n s more q u a r t z a n d m u s c o v i t e , l e s s  amount  sedimentary  chlorite,  a n d e p i d o t e , a n d 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 h a s  undergone c o n s i d e r a b l e used by Steinmann peridotite  s i n c e t h e t e r m was  first  (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  ( 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  related rocks tion  evolution  (Church, 1972).  A r e c e n t l y proposed  defini-  (G.S.A. P e n r o s e C o n f e r e n c e o n O p h i o l i t e s , 1972)  i s :  A completely developed o p h i o l i t e c o n s i s t s o f mafic to u l t r a m a f i c  r o c k s i n t h e f o l l o w i n g sequence from t h e  bottom w o r k i n g up: Ultramafic  complex c o n s i s t i n g o f h a r z b u r g i t e ,  z o l i t e and d u n i t e ,  usually with  a metamorphic  Ihertecton-  ite febric. Gabbroic complex o r d i n a r i l y w i t h and  sheeted dike  Mafic  v o l c a n i c c o m p l e x , commonly  rock  -ribbon -sodic  complex.  complex. pillowed.  types: cherts,  felsic  Most r e c e n t 1971;  textures  u s u a l l y l e s s deformed than t h e u l t r a m a f i c  Mafic  Associated  cumulus  shale,  minor  limestone  i n t r u s i v e and e x t r u s i v e  interpretations  rocks.  (Church, 1972; Coleman,  Dewey and B i r d , 1971) v i e w o p h i o l i t e s u i t e s a s 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 ,  b a s e d on t h e  c o n s i d e r a t i o n s , as s u m m e r i z e d by W i l l i a m s and 1.  Similarities  following  Smyth  (1973):  i n gross p h y s i c a l c h a r a c t e r i s t i c s  of  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  (LePichon,  2.  1969).  Transported on-land o p h i o l i t e i s rooted i n oceanic  l i t h o s p h e r e a t P a p u a , New 3. and  Guinea  Strong lothologic  ( D a v i e s and S m i t h ,  s i m i l a r i t i e s between  rocks of MacQuarie Ridge(Varne 4.  L o t h o l o g i c a l and  tholeiites  and p i l l o w  and  1971).  ophiolites  Rubenach,  1972).  chemical s i m i l a r i t i e s of  lavas of o p h i o l i t e suites  oceanic  (Aumento e t  a l . , 1971) . 5.  Models r e l a t i n g sea  t i o n of sheeted 6.  d i k e complexes  f l o o r spreading to the ( W i l l i a m s and  High pressure mineralogy  mentle depths  Malpas,  of peridotites  f o r conditions of c r y s t a l l i z a t i o n  forma1972).  requiring  (Medaris,  1972) . 7.  Common o c c u r r e n c e o f m e t a m o r p h i c t e c t o n i t e s i n  ophiolite peridotites, displaying textures l i k e prementally reproduced the mentle 8.  (Nicolas,  ex-  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 of 1969).  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 ( W i l l i a m s and M a l p a s ,  1972;  Aumento,  o f o c e a n i c c r u s t and  ophiolites  1972).  According to P l a t e Tectonic theory fragments  those  ( e g . Coleman,19 71)  upper mantle are emplaced  along  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 , w h e r e b y l i t h o s p h e r e i s o v e r t h r u s t onto  oceanic  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  Total  No. MHP  Number o f ions on the b a s i s o f 6 oxygens Si  Al  Al  Fe  Mg  En  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  Sample  Si02  (Diopside)  ^2^3  F e (  ^  Total  No.  No. o f i o n s on t h e b a s i s o f 6 oxygens Si  Al  Al  Fe  Mg  Ca  En  Di  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  Total  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  No.  I n 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 t a k e n as FeO.  No. o f ions on the b a s i s o f 4 oxygens . Si Fe Mg  (Fo) 100 Mg Mg + Fe  182  APPENDIX D  D E F I N I T I O N OF DIFFERENT SERPENTINE MINERALS USED HERE  Two d i f f e r e n t and  chrysotile  species of serpentine minerals,  are recorded i n the Clinton  antigorite  Creek area.  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 u s e d by t h e w r i t e r the  basis of  textures.  Antigorite  Antigorite  = Antigorite  pseudomorphs a f t e r  Feathery textured  olivine;  antigorite;  M o s a i c t e x t u r e d a n t i g o r i t e . ... Serpophite = Isotropic Bastite  antigorite.  = Antigorite  that retains.pyroxene's  ( a n t o g o r i t e pseudomorphs a f t e r  Chrysotile  Chrysotile  = Asbestiform  chrysotile.  Picrolite  = Non-asbestiform  chrysotile.  texture  pyroxene).  Under on  183  APPENDIX E  MICROPROBE ANALYSES OF  Chemical analyses of  CHRYSOTILE AND  33  c h r y s o t i l e s a m p l e s and  g o r i t e s a m p l e s w e r e done u s i n g an ARL ( M o d e l - SEMQ) a t t h e University  andalusite,  The  wallastonite, spessartite,  Si,  T i , Cr,  listed  Ca,  i n the  Mn,  Sciences,  following  orthoclase,  and  Table  Ni  for  forsterite,  wallstonite, rutile,  olivine  f o r Na,  respectively.  4-1.  anti"  the  Samples were a n a l y z e d  f a y l i t e and Fe  64  microprobe  standards used were j a i d e i t e ,  escoalite, K,  electron  Dept. o f G e o l o g i c a l  of B r i t i s h Columbia.  eleven oxides.  ANTIGORITE  Mg,  Results  Al, are  TABLE A N A L Y T I C A L DATA FOR  MgO  4-1  E L E V E N OXIDES  OF C H R Y S O T I L E  AND  sio2  CaO  Ti0  C r  K 0  ANTIGORITE  MnO  Sample No.  Na„0  CHOI  0.03  3y.oo  0.89  39.91  0.04  0.01  0.04  0.49  0.05  2.72  0.38  CH02  0.02  39.50  0.86  40.28  0.02  0.05  0.06  0.23  0.01  2.71  0.38  CH03  0.03  38.87  0.88  41.36  0.04  0.09  0.02  0.29  0.04  3.08  0.27  CH04  0.02  39.8y  0.79  39.48  0.05  0.01  0.03  0.03  0.07  2.77  0.45  CH05  0.03  38.99  0.86  41.99  0.01  0.07  0.01  0.48  0.02  2.87  0.52  CH06  0.02  39.6 8  0.30  41.13  0.03  0.02  0.01  0.21  0.02  3.62  0.2y  CH07  0.01  39.77  0.98  39.24  0.01  0.04  0.06  0.35  0.03  2.42  0.54  CH08  0.02  38.84  0.54  41.79  0.03  0.07  0.01  0.90  0.03  3.28  0.27  CH09  0.03  40.07  0.35  40.00  0.01  0.03  0.04  0.72  0.05  3.21  0.24  CH10  0.03  39.54  0.41  41.17  0.01  0.05  0.01  0.69  0.04  2.88  0.20  CH11  0.04  39.69  0.59  41.59  0.03  0.07  0.07  0.74  0.02  1.42  0.06  CH12  0.04  38.77  0.88  41.24  0.03  0.05  0.0b  0.63  0.01  1.19  0.11  •CHI 3  0.03  40.08  0.89  41.01  0.02  0.06  0.04  0.09  0.02  1.62  0.15  CH14  0.03  39.89  0.81  40.59  0.06  0.02  0.05  0.05  0.01  1.58  0.19  A l  2°3  2  2  2°3  FeO  NiO  T a b l e 4-1 ( c o n t i n u e d ) : -,°o  SiO.  40.22  0 . 86  0.03  39 .27  CH17  0.04  CH18  K 0  CaO  TiO,  C r  40.89  0.02  0.06  0.05  0.07  0. 87  40.11  0.06  0.03  0.05  40.07  0.62  39.77  0.03  0.04  0.03  39.45  0.73  40. 72  0.03  CH19  0.04  39.89  0.76  40.41  CH2 0  0.06  39 .56  0.68  CH21  0.03  39.57  CH2 2  0.05  CH2 3  Sample  Na 0  MgO  CH15  0.02  CH16  FeO  NiO  0.02  1.63  0.19  0.07  0.04  1.65  0. 11  0.04  0.11  0.04  1.53  0.01  0.01  0.01  0.07  0.06  1.51  0.12  0. 04  0.03  0.03  0.07  0.01  1.65  0.21  40.83  0.03  0. 03  0.02  0.06  0.01  1.49  0.04  0.64  40.42  0 .03  0.06  0.03  0.57  0.01  1.77  0.16  39.52  0.49  41.38  0. 05  0.07  0. 02  0.82  0.07  1.97  0.18  0.05  39.69  0.58  40.97  0 . 05  0.07  0.02  0. 59  0. 03  2.12  0.18  CH2 4  0.04  39.99  1.41  40.06  0.04  0. 02  0. 06  0.04  0.04  2.27  0. 17  CH25  0.03  40.19  1.01  40.35  0.03  0.02  0. 02  0.03  0.07  1.99  0.13  CH26  0.03  39. 84  1.08  40. 34  0. 02  0. 01  0.02  0.04  0.01  2.58  0.19  CH2 7  0.04  39 .83  1.05  39.44  0.01  0.03  0.01  0.04  0.03  2.52  0.07  CH2 8  0 .03  3y.l7  1.22  39.84  0 .02  0.02  0.08  0.07  0.04  2.02  0.12  CH2 9  0.02  39 .12  1.23  39.74  0.01  0.01  0.0b  0.04  0.01  1.92  0.21  No.  1  Al  1  6  2  2°3  MnO  T a b l e 4-1  (continued):  Sample No.  Na 0  MgO  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  2  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  T a b l e 4-1  (continued):  Sample No.  Na„0  MgO  Al O  PC11  0. 01  38. 40  1. 08  PC12  0. 02  38. 57  PC13  0. 01  PC14  SiO,  K 0  CaO  TiO,  Cr 0  42.52  0.04  0.07  0.04  1. 08  41.47  0.03  0. 08  38. 25  0. 95  41. 96  0.01  0. 01  37. 60  0. 38  42. 15  PC15  0. 04  38. 55  0. 62  PC16  0. 02  39. 12  PC17  0. 03  PC18  Mno  FeO  NiO  0. 31  0.03  3. 31  0.28  0.01  0.30  0.02  2.95  0.26  0.06  0.02  0.30  0. 05  2.78  0.30  0.01  0 .02  0.01  0.28  0.10  3. 73  0.16  43.75  0.01  ,0.07  0.02  0.07  0.05  2.71  0.09  0. 62  43.09  0.03  0.02  0.01  0.09  0.03  1.76  0.17  38. 57  1. 13  40.93  0.01  0. 01  0.01  0.36  0.08  2.79  0.11  0. 03  38. 71  1. 34  38.90  0.02  0.04  0.01  0.39  0.04  2.57  0.03  PC19  0. 01  38. 34  0. 36  41.68  0.03  0.02  0.02  0.02  0.07  2.90  0.12  PC20  0. 04  38. 11  1. 25  41.60  0.04  0.01  0.02  0.65  0.02  1.62  0.02  PC21  0. 05  38. 96  1. 11  39.78  0 . 05  0.03  0.01  0.48  0.02  2.36  0.10  PC22  0. 05  38. 07  1. 15  41.54  0.06  0.01  0.03  0.43  0.03  1.57  0.07  PC23  04 ti.  38. 13  0. 72  41. 70  0. 05  0. 02  0.01  0.49  0 .03  3.30  0.08  PC24  0. 01  38. 10  0. 97  43.21  0.01  0.01  0. 01  0.31  0.16  3.21  0.22  PC25  0. 01  36. 28  0. 99  42.52  0.01  0.5  0.01  0.26)  0.16  4.45  0.21  1  1  6  2  2  3  Table  4-1  (continued):  Sample No.  Na„0  MgO  PC26  0.01  37.08  0.87  PC27  0.03  37.25  PC28  0.01  PC29  K 0  CaO  TiO^  Cr 0  42.10  0.03  0.05  0.02  0.94  42.43  0.02  0.06  38.85  0.99  43.25  0.01  0.03  38.51  1.03  41.48  PC30  0.01  38.11  1.18  PC31  0.02  38.40  PC32  0.01  PC33  MnO  FeO  NiO  0.37  0.03  3.14  0.47  0.02  0.45  0.03  3.43  0.56  0.01  0.01  0.61  0.01  1.64  0.41  0.02  0.09  0.03  0.55  0.03  2.60  0.31  41.90  0.02  0.02  0.08  0.63  0.04  2.43  0.31  0.89  42.32  0.04  0.01  0.01  0.60  0.01  3.20  0.36  38.80  0.63  43.86  0.01  0.07  0.01  0.47  0.01  1.31  0.53  0.02  38.37  0.93  42.87  0.01  0.01  0.01  0.60  0.02  2.110.37  PC34  0.01  37.79  1.95  40.76  0.04  0.06  0.02  0.25  0.02  z.47  0.10  PC35  0.01  37.14  0.52  42.14  0.01  0.02  0.02  0.45  0.07  3.65  0.04  PC36  0.02  37.49  0.40  41.89  0.02  0.03  0.04  0.06  0.08  3.56  0.03  PC37  0.03  37.35  0.58  41.45  0.03  0.04  0.06  0.08  0.12  3.46  0.01  PC38  0.02  37.47  0.29  42.16  0.02  0.01  0.02  0.18  0.12  3.30  0.06  PC39  0.02  36.99  0.34  41.58  0.01  0.02  0.02  0.24  0.18  3.89  0.05  PC40  0.01  37.78  0.34  42.82  0.01  0.01  0.02  0.24  0.12  3.36  0.07  A 1  2°3  S  l  0  2  2  2  3  T a b l e 4-1  (continued-/.':  Sample No.  Na„0  MgO  PC41  0.01  37.09  1.21  PC42  0.04  37.38  PC43  0.03  PC44  sio2  K 0  CaO  T l 0  MnO  FeO  NiO  41.22  0.02  0.02  0.03  0.62  0.04  2.83  0.38  0.70  41.94  0.04  0.02  0.05  0.24  0.03  3.91  0.16  38.21  0.77  43.08  0.03  0.02  0.01  0.51  0.04  2.29  0.41  0.03  36.84  0.77  42.44  0.02  0.01  0.01  0.58  0.04  3.78  0.40  PC45  0.02  38.74  0.85  43.22  0.01  0.07  0.02  0.59  0.01  2.38  0.32  PC46  0.03  38.81  0.72  42.36  0.03  0.01  0.01  0.29  0.02  1.90  0.18  PC47  0.01  38.59  0.73  42.06  0.04  0.07  0.02  0.03  0.07  3.33  0.13  PC48  0.02  38.68  0.87  42.66  0.03  0.01  0.01  0.08  0.03  1.42  0.14  PC49  0.02  38.30  1.07  42.19  0.04  0.01  0.04  0.10  0.02  1.78  0.21  PC50  0.02  37.94  0.81  41.86  0.05  0.02  0.02  0.05  0.02  3.68  0.17  PC51  0.03  38.40  0.82  42.49  0.03  0.03  0.02  0.07  0.05  1.95  0.12  PC52  0.03  39.22  0.81  41.31  0.03  0.07  0.02  0.04  0.03  3.76  0.15  PC53  0.02  38.37  0.83  41.43  0.02  0.02  0.01  0.07  0.01  2.67  0.12  PC54  0.01  37.72  0.69  40.12  0.02  0.04  0.03  0.23  0.02  3.61  0.14  PC55  0.01  39.09  1.59  40.35  0.05  0.01  0.02  0.02  0.02  4.22  0.11  A 1  2°3  2  2  Cr 0 2  3  Table  4-1 ( c o n t i n u e d ) , :  Sample No.  Na„0  MgO  PC56  0.01  38.37  1.57  PC57  0.01  38.40  PC58  0.02  PC59  sio2  K 0  CaO  Ti0  40.87  0.02  0.03  0.02  1.58  40.76  0.02  0.04  39.03  1.5-9  39.17  0.01  0.01  38.03  1.59  42.66  PC60  0.02  38.22  1.48  PC61  0.01  38.07  PC62  0.04  PC63 PC64  MnO  FeO  NiO  0.06  0.03  3.78  0.18  0.03  0.07  0.01  4.00  0.12  0.02  0.01  0.03  0.01  4.04  0.14  0.02  0.03  0.03  0.03  0.03  2.45  0.12  42.89  0.02  0.02  0.03  0.01  0.03  1.71  0.13  0.87  41.88  0.04  0.01  0.01  0.33  0.03  2.81  0.37  38.02  0.94  41.86  0.03  0.02  0.01  0.17  0.02  3.58  0.17  0.02  36.42  1.24  40.05  0.06  0.01  0.05  0.60  0.04  3.92  0.49  0.02  36.81  1.37  42.27  0.02  0.05  0.01  0.74  0.01  3.81  0.33  A l  2°3  2  A l l a n a l y s e s done b y e l e c t r i n m i c r o p r o b e . Sample n o . 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 .  2  Cr 0 2  3  T o t a l i r o n i s r e p r e s e n t e d a s FeO. Sample n o . 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. potassium-argon  method a n d s e v e n s a m p l e s by  w h o l e r o c k method. schist,  Four samples were d a t e d by t h e  Samples i n c l u d e :  three o f greenstone,  rubidium-strontium  four of  quartz-muscovite  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 but  t h e g r a n o d i o r i t e s a m p l e 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 muscovite  schist.  f r o m an e i g h t f o o t l e n s i n q u a r t z -  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 t h e 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 British  Columbia. For m i n e r a l s e p a r a t i o n t h e r o c k s were crushed  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 fast  to a  electro-  m a g n e t i c d e v i c e was u s e d t o s e p e r a t e q u a r t z a n d f e l s i c als  from mafic m i n e r a l s .  miner-  F l a k y micas and p r i s m a t i c a m p h i b o l e s  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 .  Further separation of the  r e s i d i u m was done o n a s l o w e l e c t r o m a g n e t i c s e p a r a t o r . ly,  some s a m p l e s w e r e s e p a r a t e d  ing  was u s e d f o r f i n a l c l e a n i n g .  i n heavy l i q u i d s .  Final-  Hand p i c k -  19 2  Potassium absorption  analyses  were run  1  using a Techtron  AA4  i n d u p l i c a t e by  spectrophotometer  atomic  and  argon  2 analyses  by  spectrometer one KA  xsotope and  dilution 3 8  purity  Ar  standard deviation. = 0.585 x l 0 " y  The  1  0  _  u s i n g an spike.  AEI  MS  -  10  mass  E r r o r s reported are  constants  used  for  are:  1  e  KA  =  4 .72xl0"  1 0  y  - 1  p 4 0  K/K  =  0.0119 a t o m  percent. 3  In Sr  the whole rock  rubidium-strontium analyses  c o n c e n t r a t i o n s were determined  pressed gical  powder p e l l e t s  Survey  rock  by  u s i n g X-ray  standards  replicate  absorption  coefficients  were o b t a i n e d  scattering  measurments.  Rb/Sr r a t i o s  (la)  and  isotope using (60*  concentrations a precision composition  standard s e c t o r , 30  measured on  cm  is digitized  radius, solid  from  perimental  data  0.1194 and  a d j u s t e d so  automated  of  5%  Ka  The  H.  mass  Geolomass  of  prepared  National,  Data  aquisi-  u s i n g a NOVA c o m p u t e r . 86 88  NBS  to a standard  Sr/ SrC0  2%  spectrometer  U.S.  Faul.  of  Strontium  samples  i s of  and  Compton  (la).  unspike  source)  have been n o r m a l i z e d t h a t the  Mo  have a p r e c i s i o n  d e s i g n , m o d i f i e d by and  U.S.  for calibration;  i o n exchange techniques.  Bureau of Standard tion  was  analysis  fluorescence.  were used  , Rb  Sr 3  ratio  Exof  (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 sity of B r i t i s h Columbia. 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 of the U n i v e r s i t y of B r i t i s h Columbia. 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 were done by K.L. S c o t t of the U n i v e r s i t y of B r i t i s h Columbia.  193  gives  a °'Sr/  Amend S r r a t i o ratio  °°Sr r a t i o  o f 0.70800±2.  i s 0.00013  ( l a ) . Rb-Sr  c o n s t a n t o f 1.42x10 according  o f 0.71022±2  1  .  and t h e Eimer and  The p r e c i s i o n  of single  dates a r e based  The r e g r e s s i o n s  t o the technique o f York  (19 6 7 ) .  o n a Rb  Sr/ decay  are calculated  194  APPENDIX  G  PROCEDURES A P P L I E D FOR PRODUCING L E V E L PLANS WITH CHRYSOTILE-FIBRE  The C l i n t o n slices of usually of  DIFFERENT  CONCENTRATION ZONES  C r e e k o p e n p i t a s b e s t o s m i n e was m i n e d i n 30 f e e t t h i c k .  On e a c h s l i c e  information  c h r y s o t i l e - f i b r e content i n percentage are a v a i l a b l e i n  drill  holes logs  and r e c o r d s o f b l a s t h i l e s .  h o l e s were d r i l l e d w i t h i n fairly  As t h e b l a s t  five to ten feet distance,  i t is  r e l i a b l e t o draw i s o l i n e s o n 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 serpentinite.  I n t h i s manner  iso-  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 a n d s e v e n p e r c e n t w e r e d r a w n o n F i g u r e 3-3, 4-9 a n d 4-10.  

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