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The metamorphism of the rocks of the Aldridge formation, Kimberley B.C Hoadley, John William 1947

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L C3 & J  THE METAMORPHISM OF THE ROCKS OF THE f  ALDRIDGE FORMATION KIMBERLEY, B.C.  BY  JOHN W. HOADLEY  A THESIS SUBMITTED IK PARTIAL FULFILMENT OF THE.REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE IN THEf DEPARTMENT ,OF GEOLOGY AND GEOGRAPHY  THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1947  ACKNOWLEDGMENTS  The w r i t e r acknowledges t h e a s s i s t a n c e by D r s . Gunning, Watson and Swans, on.  rendered  The t e c h n i c a l  .advice and a s s i s t a n c e g i v e n by Mr. J.A. Donnan was invaluable.  CONTENTS PAGE Abstract  : 1  .  Introduction  3  Object of the r e s e a r c h  3  P a r t 1. L o c a t i o n and G e n e r a l Geology ; W a l l r o c k a l t e r a t i o n of the S u l l i v a n Ore Body .* .Petrography of u n a l t e r e d s e d i m e n t a r y r o c k s P a r t 2.  5 6 7  -  M i n e r a l s o c c u r r i n g i n the r o c k s of the A l d r i d g e F o r m a t i o n cut by d r i l l h o l e 249' ;  9  P a r t 3. A l t e r a t i o n of the' r o c k s of the A l d r i d g e Formation G e n e r a l Statement . . . .• D e s c r i p t i o n of the s p o t t i n g V a r i a t i o n i n t e x t u r e of the spots B i o t i t e c o n t e n t and d i s t r i b u t i o n P y r r h o t i t e content Tourmaline c o n t e n t R u t i l e content C l i n o z o i s i t e content Chloritization Part  15 15 16 .'.. . 16 16 16 17 17 17  4. O r i g i n of New Formation O r i g i n of O r i g i n of O r i g i n of  Minerals.  •  of the b i o t i t e t o u r m a l i n e and s u l p h i d e s albite rutile  18 20 22 24  P a r t 5. Conclusions Bibliography Appendix  ;  25 27 28  15  ILLUSTRATIONS PAGE P l a t e 1. V e i n l e t of p y r r h o t i t e i n t h i n s e c t i o n 289A  53  2 . Lens of p y r r h o t i t e shown i n P l a t e 1  53"  3. Pronounced  54  s p o t t i n g i n t h i n s e c t i o n 264A  4. Large s p o t s i n t h i n s e c t i o n 340A. ."  54  5.. S i m i l a r t o P l a t e 4 -• c r o s s e d N i c o l s  55  6. Tourmaline aggregates i n t h i n s e c t i o n 160B-' low power-. 7. Tourmaline aggregates i n t h i n s e c t i o n 160B- ' h i g h power; F i g u r e 1. G e o l o g i c map  Illustrated  55 56  of S u l l i v a n Mine, and v i c i n i t y . . . . 57  s t r a t i g r a p h i c : s e c t i o n of d r i l l h h o l e 249.... i n envelope on.back c o v e r .  THE METAMORPHISM OF THE ROCKS OF THE •ALDRIDGE FORMATION KIMBERLEY B.C. BY J.W. HOADLEY  ABSTRACT The area near the S u l l i v a n Mine, K i m b e r l e y B.C., i s s  u n d e r l a i n Toy r o c k s o f the P u r c e l l s e r i e s w h i c h c o n s i s t sedimentary  f o r m a t i o n s o f l a t e Pre-Cambrian age, the A l d r i d g e  and the C r e s t o n .  Both a r e composed o f a r g i l l i t e ,  and q u a r t z i t e .  deposit i n c e r t a i n  favourable horizons i n the A l d r i d g e formation.  The o n l y known  r o c k s near the"mine a r e the P u r c e l l i n t r u s i v e s o f l a t e  Pre-Cambrian age. sills,  s i l t s tone,  -  The S u l l i v a n ore body i s a replacement  igneous  o f two  These i n t r u s i v e s o c c u r as l a r g e  a t a s m a l l angle t o t h e bedding —  sheets, or  of the P u r c e l l s e r i e s .  i  They a r e c h e m i c a l l y about the same as gabbro. The o b j e c t o f t h i s r e s e a r c h was t o determine induced i n the sedimentary  the changes  r o c k s o f the A l d r i d g e f o r m a t i o n near  the S u l l i v a n Mine by t h e i n t r u s i o n o f the P u r c e l l s i l l s ; t o compare the a l t e r a t i o n s found w i t h the a l t e r a t i o n s known t o be p r e s e n t i n t h e w a l l r o c k s o f the S u l l i v a n o r e body; and from '-this comparison,  determine  whether t h e r e I s any j u s t i f i c a t i o n  f o r r e l a t i n g the m i n e r a l i z a t i o n  o f the S u l l i v a n ore body t o the  i n t r u s i o n of the P u r c e l l  sills.  I n o r d e r t o o b t a i n the i n f o r m a t i o n r e q u i r e d t h e w r i t e r made a p e t r o g r a p h i c e x a m i n a t i o n o f t h i r t y - s i x t h i n s e c t i o n s o f specimens located  o f the core o f the S u l l i v a n Diamond D r i l l Hole 249  j u s t e a s t o f the mine.  through a s i x t y f o o t s i l l ,  The h o l e was d r i l l e d v e r t i c a l l y  and on i n t o t h e u n d e r l y i n g sediments  of the A l d r i d g e f o r m a t i o n . The r e s u l t s o b t a i n e d from t h i s e x a m i n a t i o n i n d i c a t e ^ , t h a t the sediments a d j a c e n t t o the s i l l have been s u b j e c t e d t o low grade t h e r m a l metamorphism, w h i c h has r e s u l t e d ment o f a pronounced  i n the d e v e l o p -  b i o t i t e s p o t t e d c o n t a c t zone.  Late  magmatic emanations, e i t h e r from the p a r t i a l l y c o n s o l i d a t e d sill,  o r from the p a r e n t magma chamber caused metasomatism i n  the s e d i m e n t a r y r o c k s o f the c o n t a c t zone, and the e f f e c t s o f the metasomatic  a c t i o n a r e super imposed upon the e f f e c t s o f  the t h e r m a l metamorphism.  Tourmaline, a l b i t e , p y r r h o t i t e ,  s p h a l e r i t e , sphene and r u t i l e a r e the main m i n e r a l s produced by the h y d r o t h e r m a l  action. of A comparison b o t w a o n the a l t e r a t i o n s found i n these W/T/i  s e d i m e n t a r y r o c k s examined, e«4 the a l t e r a t i o n p r e s e n t i n the S u l l i v a n ore body and i t s w a l l r o c k s , r e v e a l s a d i s t i n c t similarity.  T h i s s i m i l a r i t y , p l u s the f a c t t h a t the d r i l l  h o l e i s w i t h i n one h a l f m i l e o f the mine suggests a common • o r i g i n f o r the" magmatic  solutions.  T h e r e f o r e , the s o l u t i o n s  w h i c h produced  the S u l l i v a n Mine  ore body may have been g e n e t i c a l l y r e l a t e d t o the P u r c e l l intrusives.  INTRODUCTION O b j e c t o f the R e s e a r c h The  g e o l o g y o f the S u l l i v a n mine has been s t u d i e d i n  d e t a i l b y o f f i c e r s o f the G e o l o g i c a l Survey o f Canada, and by g e o l o g i s t s employed b y the owners, the C o n s o l i d a t e d and S m e l t i n g  Company.  Mining  The v a r i o u s workers a r e n o t i n complete  agreement regarding, the age o f t h e m i n e r a l i z a t i o n . H.M.A. R i c e  (1) b e l i e v e s t h a t the m i n e r a l i z a t i o n  occurred  d u r i n g cCretaceous o r e a r l y T e r t i a r y t i m e , a n d i s g e n e t i c a l l y r e l a t e d t o t h e g r a n i t e i n t r u s i v e s o f t h a t age. CO.- Swans on and H.C. Gunning ( 2 ) , f e e l t h a t t h e a s s i g n a t i o n o f the age o f m i n e r a l i z a t i o n t o t h e C r e t a c e o u s or T e r t i a r y p e r i o d i s open t o ' q u e s t i o n . be  They s u g g e s t , as an  a l t e r n a t i v e , that i t may related to the P u r c e l l I n t r u s i v e s A  t h a t a r e o f Pre-Cambrian age. I t was suggested t h a t a s t u d y o f the a l t e r a t i o n o c c u r r i n g i n t h e s e d i m e n t a r y r o c k s near one o f the P u r c e l l s i l l s , and a comparison o f t h i s a l t e r a t i o n w i t h t h a t found i n t h e w a l l of the S u l l i v a n ore body,might r e v e a l f u r t h e r regarding The  rock  information  t h e age o f t h e ore f o r m i n g s o l u t i o n s . w r i t e r , t h e r e f o r e , u n d e r t o o k a p e t r o l o g i c a l examin-  a t i o n o f specimens o f the core o f a diamond d r i l l l o c a t e d j u s t e a s t o f t h e S u l l i v a n mine.  hole,  The h o l e was d r i l l e d  v e r t i c a l l y t h r o u g h a s i x t y f o o t s i l l and c o n t i n u e d  on i n t o t h e  u n d e r l y i n g sediments f o r a p p r o x i m a t e l y f i v e hundred f e e t . • 1. R i c e , H.M.A. 1937, G.S.C. Mem. 207 2. Swanson, C O . and Gunning, H.C. 1945, Geology o f the S u l l i v a n Mine, C.I.M.M. V o l . 48, pp 645 - 667  4  The work c o n s i s t e d o f a d e t a i l e d p e t r o g r a p h i c e x a m i n a t i o n of t h i r t y - s i x t h i n s e c t i o n s and the i n t e r p r e t a t i o n o f the r e s u l t s o b t a i n e d from t h i s  examination.  The e x t r e m e l y f i n e - g r a i n e d n a t u r e o f the r o c k made i t d i f f i c u l t t o determine  and e s t i m a t e the r e l a t i v e amounts o f  the m i n e r a l s i n the t h i n s e c t i o n s . An i m p o r t a n t p a r t o f the i n t e r p r e t a t i o n was t o d e c i d e how much o f t h e a l t e r a t i o n was caused by r e c o n s t i t u t i o n o f o r i g i n a l m a t e r i a l and how much was due t o the i n t r o d u c t i o n o f m a t e r i a l from some o u t s i d e s o u r c e .  GENERAL  GEOLOGY  The S u l l i v a n mine i s l o c a t e d i n t h e s o u t h - e a s t  corner  of B r i t i s h Columbia, about one and one h a l f m i l e s n o r t h - e a s t of the town o f KImberley,  B.C.  The a r e a i n the v i c i n i t y o f K i m b e r l e y i s u n d e r l a i n by g e n t l y f o l d e d sediments o f t h e P u r c e l l s e r i e s , o f Pre-Cambrian age.  These sediments were i n t r u d e d by a l a r g e number o f s i l l s ,  known as /the P u r c e l l s i l l s ,  i n l a t e Pre-Cambrian t i m e .  The S u l l i v a n ore body i s a replacement  d e p o s i t , i n the  l o w e r member o f t h e P u r c e l l s e r i e s , c a l l e d the A l d r i d g e formation.  T h i s f o r m a t i o n i s an .assemblage o f t h i n bedded  q u a r t z i t e s , s i l t s t o n e s , and a r g i l l i t e s a p p r o x i m a t e l y 16000 feet thick. The  ore body conforms r o u g h l y w i t h the s t r i k e and d i p o f  the sediments,  and grades i n t o them.  The h o r i z o n s r e p l a c e d  r e p r e s e n t a s t r a t i g r a p h i c t h i c k n e s s o f about 200 f e e t . The  ore i s an i n t i m a t e , f i n e - g r a i n e d mixture o f g a l e n a ,  and s p h a l e r i t e , w i t h minor amounts o f p y r r h o t i t e , - p y r i t e , m a g n e t i t e , and j a m e s o n i t e ; the s c a n t gangue c o n t a i n s manganese g a r n e t , g a r n e t , t o u r m a l i n e , d l o p s i d e , a c t i n o l i t e , and b i o t i t e , with subordinate c a l c i t e . In  Some c a s s i t e r i t e i s p r e s e n t .  t h e v i c i n i t y o f the mine, t h e r e g i o n a l d i p i s e a s t ,  the r e g i o n as a whole b e i n g on the e a s t s i d e o f a broad a n t i c l i n e w h i c h has an a x i s l y i n g a few m i l e s west o f the area shown i n f i g .  1.  However, the r e g i o n a l d i p i s m o d i f i e d  by s e v e r a l g e n t l e warpings and by minor f o l d s w h i c h a r e f r e q u e n t l y quite sharp.  F i g u r e 1 p o r t r a y s the nature means of s u b s u r f a c e The area.  Kimberley  contours  of the g e n t l e warpings by  of the f o o t w a l l of the ore zone.  f a u l t i s one  of the major f e a t u r e s of the  As shown i n F i g u r e 1, i t s t r i k e s about E.W.  45 to 55° The  and  dips  N. S u l l i v a n f a u l t , t o g e t h e r w i t h a number of  similar  ones w h i c h form a w e l l defined, s e t , c o n s t i t u t e the o n l y important  fault structures.  Of t h e s e , the S u l l i v a n , E a s t  L o i s f a u l t s are shown on the The  other and  map..  P u r c e l l i n t r u s i v e s , l o c a l l y c a l l e d d i o r i t e s are  the  o n l y l a r g e i n t r u s i v e s known i n the immediate v i c i n i t y of the mine.  T y p i c a l l y they occur as l a r g e s i l l s  s m a l l angle  o r sheets  t o the bedding of the P u r c e l l s e r i e s .  them are a p p r o x i m a t e l y  uniform  i n composition,  c h e m i c a l l y about the same as Gabbro. some of the s i l l s  and  at a "  Many of are  In the upper p a r t o f -  there i s a graduation  to a type, t h a t i s  d e f i n i t e l y more a c i d . All  the l a r g e s i l l s  (see f i g u r e 1) near the S u l l i v a n  1  mine are accompanied by a c o n t a c t zone 100 f e e t o r so t h i c k s i n which the sediments have developed a s p o t t e d WALLROCK ALTERATION OF THE The  SULLIVAN ORE  f o r m a t i o n of the S u l l i v a n ore body was  by c o n s i d e r a b l e a l t e r a t i o n of the w a l l r o c k . w a l l r o c k a l t e r a t i o n may  character. BODY accompanied  Briefly,  this  be d e s c r i b e d as t o u r m a l i n i z a t i o n of  the f o o t w a l l sediments and a l b i t i z a t i o n and c h l o r i t i z a t i o n of the hanging w a l l members.  PETROGRAPHY OF THE UNALTERED SEDIMENTS In  o r d e r ' t h a t the a l t e r a t i o n i n the sediments i n the  v i c i n i t y of the S i l l s "may he p r o p e r l y a p p r e c i a t e d i t w i l l be n e c e s s a r y to g i v e a b r i e f d e s c r i p t i o n of the u n a l t e r e d sediments.  ,  " S t r i c t l y s p e a k i n g , the beds are not u n a l t e r e d s e d i m e n t s , as they have a l l s u f f e r e d more or l e s s  recrystallization.  However, t h e changes so produced have been s l i g h t i n compari s o n w i t h those caused by replacement and c o n t a c t metamorphism i n the sediments a d j a c e n t t o the ore body, and are i n g e n e r a l l e s s than the changes encountered i n the c o n t a c t zones o f the Purcell S i l l s . The beds are l a r g e l y composed o f s e r i c i t e f l a k e s JD1 to  .03 mm.  sizes.  mm.  i n d i a m e t e r , and q u a r t z g r a i n s o f s i l t y t o sandy  The  s e r i c i t e f l a k e s have random o r i e n t a t i o n s - and  e v i d e n t l y r e p r e s e n t c l a y e y m a t e r i a l t h a t r e c r y s t a l l i z e d under static conditions. i n o u t l i n e but new of  mm.  irregular  growth has not m a t e r i a l l y changed the s i z e  the c o a r s e r g r a i n s .  0.03 owe  The q u a r t z g r a i n s are u s u a l l y  However, the s m a l l e r ones, l e s s t h a n  i n d i a m e t e r , w h i c h are i n t e r g r d w n w i t h s e r i c i t e , .  t h e i r shapes and s i z e s e n t i r e l y t o r e c r y s t a l l i z a t i o n . L i t h o l o g i c types w h i c h range from a r g i l l i t e  form a l a r g e p a r t of the sediments,'and a linear series. argillltes  to s i l t s tone  can be a r r a n g e d  into  I t has been found c o n v e n i e n t t o c l a s s i f y as  those which are more than 75% s e r i c i t e , and as  s i l t s tones those which are more than 75%' q u a r t z o c c u r r i n g as  8 g r a i n s up t o .01 mm."  (3)  T h i s c l a s s i f i c a t i o n w i l l he adhered to t h r o u g h o u t t h i s report.  (3)  Swanson, C O .  and Gunning, H.C  1944 - Op. C i t :  9 MINERALS OCCURRING IN THE SECTION OF THE . ALDRIDGE FORMATION CUT BY DRILL HOLE 249. I n t h e f o l l o w i n g p a r a g r a p h s , the m i n e r a l s a r e l i s t e d a c c o r d i n g t o Dana's c l a s s i f i c a t i o n . SULPHIDES PYRRHOTITE:  F e ^ ^  P y r r h o t i t e i s very wide s p r e a d throughout a l l t h e sediments o f the A l d r i d g e f o r m a t i o n .  I t occurs  i n varying  amounts i n p r a c t i c a l l y a l l the t h i n s e c t i o n s examined. I t i s found as f r a c t u r e f i l l i n g and, o r , replacement of r  c e r t a i n favourable horizons  (see Appendix t h i n s e c t i o n 289A),  as c o n c e n t r a t i o n s o f i r r e g u l a r shaped g r a i n s i n t h e spots o f the s p o t t e d bands, and as s m a l l , more o r l e s s e v e n l y  distrib-  uted grains i n c e r t a i n h o r i z o n s . i/irhere a p y r r h o t i t e - r i c h l a y e r o r v e i n l e t occurs  i n or  near a s p o t t e d h o r i z o n , the c o n c e n t r a t i o n o f the p y r r h o t i t e i n the spots v a r i e s d i r e c t l y w i t h the d i s t a n c e from the p y r r h o t i t e - r i c h zones. The most common a s s o c i a t e s a r e b i o t i t e and c l i n o z o i s i t e . SPHALERITE  Zn S.  A b r i g h t orange y e l l o w v a r i e t y o f s p h a l e r i t e was i d e n t i f i e d i n most o f the t h i n s e c t i o n s o f specimens w i t h i n t e n f e e t of the c o n t a c t w i t h the S i l l .  taken  I n most cases  i t o c c u r r e d as v e r y minute g r a i n s w h i c h were o n l y p o s i t i v e l y i d e n t i f i e d w i t h the a i d o f a m i c r o c h e m i c a l  test f o r zinc.  However, t h i n s e c t i o n 154B c o n t a i n s a coarse b i o t i t e and  10 s p h a l e r i t e - r i c h zone i n -which the s p h a l e r i t e was large grains replacing c a l c i t e . p y r r h o t i t e , c l i n o z o i s i t e , and  I t was  found i n  a s s o c i a t e d w i t h some  chlorite.  OXIDES QUARTZ;  SlOg  T h i s i s the most abundant m i n e r a l i n the sediments of the P u r c e l l s e r i e s .  I t occurs as v e r y s m a l l i r r e g u l a r shaped'  i n t e r l o c k i n g g r a i n s g e n e r a l l y l e s s than .01 mm. Spots or c o n c e n t r a t i o n s  in  diameter.  of l a r g e r g r a i n s up t o .05 mm.  in  d i a m e t e r are common i n some of the beds. The  i n t e r l o c k i n g g r a i n s and the presence of many  i n c l u s i o n s i n d i c a t e t h a t the q u a r t z has been l a r g e l y recrystallized. RUTILE:  Ti0  2  There i s abundant development o f r u t i l e throughout the m a j o r i t y o f the t h i n s e c t i o n s examined.  I t most commonly  occurs as c l u s t e r s or aggregates of s h o r t s t u b b y  euhedral  c r y s t a l s , w h i c h o f t e n show good g e n i c u l a t e d t w i n n i n g . ' I t i s a l s o found as minute needles r e p l a c i n g b i o t i t e . There i s a marked i n c r e a s e i n t h e . c o n c e n t r a t i o n of  rutile  i n the spots and a l o n g the c o n t a c t s between a r g i l l a c e o u s and s i l t y layers.  I t appears t o be c l o s e l y a s s o c i a t e d w i t h the  b i o t i t e i n the spots and  i s not found i n the b l e a c h e d  zones.  CARBONATES CALCITE: i  CaCo, o  C a l c i t e occurs i n a p p r e c i a b l e amounts i n a number of the  s e c t i o n s examined.  I t i s always a s s o c i a t e d w i t h  chlorite  11 e i t h e r as v e i n f i l l i n g or as i r r e g u l a r patches i n the more h i g h l y c h l o r i t i z e d areas. SILICATES ALBITE:  .  There appears t o be a f a i r l y abundant development of A l b i t e i n the t h i n s e c t i o n s  studied.  I t o c c u r s as  grains' s c a t t e r e d throughout'the general f i l l i n g material. cases. 13°. 2V  The  A l b i t e twinning  was  matrix,  small  o r as  vein  observed i n a  maximum e x t i n c t i o n angle measured was  few  12-l/2 to  A b i a x i a l p o s i t i v e interference figure with a large  was  obtained  on a few  An attempt was  grains.  made t o determine the amount of  feldspar  p r e s e n t i n the s e c t i o n s by s e l e c t i v e s t a i n i n g of the  feldspar  grains.  included  Detailed explanation  i n the a p p e n d i x .  The  of the p r o c e s s used i s  r e s u l t s i n d i c a t e t h a t t h e r e was  g r e a t e r degree of f e ^ s p a t h i z a t i o n t h a n was unstained was in  sections.  The  the spots t h a n i n the g e n e r a l  revealed to the  apparent i n the  stained sections  a tendency f o r the c o n c e n t r a t i o n  a  showed t h a t  there  of f e l d s p a r t o be  ground mass.  One  greater  section  the presence of a s t r o n g l y f e f s p a t h i c l a y e r p a r a l l e l  bedding.  CORDIERITE: The  H  c  (MgFe), A L S i .  6  n  presence o f c o r d i e r i t e was  ' s u s p e c t e d i n some of  t h i n s e c t i o n s , but no d e f i n i t e proof was appendix t h i n s e c t i o n WOLLASTONITB One  Ca S i  obtained.  the  See  146A. 0  3  f i b r o u s g r a i n of w o l l a s t o n i t e was  identified in thin  12 s e c t i o n 340B. follows:  The  o p t i c a l p r o p e r t i e s were found to be  Index 1.60  as  -, B i r e f r i n g e n c e 0.010, o r i e n t a t i o n  l e n g t h slow, b i a x i a l n e g a t i v e w i t h 2V moderate t o l a r g e . The  c r y s t a l i d e n t i f i e d c o n t a i n e d numerous s m a l l  i n c l u s i o n s of  tourmaline.  CLINOZOISITE;  Ca^.lg  (OH)  (S10 ) 4  T h i s m i n e r a l i s common i n the t h i n s e c t i o n s examined.. I t i s g e n e r a l l y found i n t i m a t e l y a s s o c i a t e d w i t h p y r r h o t i t e and h i o t i t e and q u i t e o f t e n forms a r i m around g r a i n s o f the former m i n e r a l .  I t was  noted t h a t i t o c c u r r e d i n g r e a t e r  c o n c e n t r a t i o n i n the spots t h a n i n the m a t r i x , and  that'those  spots h i g h i n p y r r h o t i t e c o n t a i n e d more t h a n those  which  showed a d e f i c i e n c y of p y r r h o t i t e . EPIDOTE:  Ca  g  (Al  Pe) (OH)(SiQ ) 3  4  3  T h i s m i n e r a l i s found r e p l a c i n g m u s c o v i t e and. h i o t i t e i n some of the s p o t s .  I t i s commonly a s s o c i a t e d w i t h c l i n o z o i s i t e .  E p i d o t e i s much l e s s w i d e s p r e a d i n o c c u r r e n c e TOURMALINE;  than  clinozoisite.  A complex b o r o s i l i c a t e o f aluminum and  other  metals. Tourmaline i s of w i d e s p r e a d o c c u r r e n c e cut by d r i l l h o l e 249.  i n the sediments  I t i s commonly found as minute  e u h e d r a l c r y s t a l s which appear s l i g h t l y g r e e n i s h i n t h i n section.  A number of l a r g e r c r y s t a l s of p a l e y e l l o w  t o u r m a l i n e were encountered w h i c h showed marked  pleochroism,  w i t h maximum a b s o r p t i o n p a r a l l e l t o the a n a l i z e r . f r a c t u r e s were w e l l  Cross.  developed.  . Large Csievey, anhedra of t h i s y e l l o w p l e o c h r o i c -  13 t o u r m a l i n e were found i n some o f t h e more s p o t t e d hands. I n t h i n s e c t i o n s 160 A & B , these anhedra range up t o . 3 mm. i n s i z e and o c c u r w i t h i n t h e s p o t s , i n some c a s e s , as much as 25% o f the t o t a l area o f the s p o t .  On  occupying the.whole,  the c o n c e n t r a t i o n o f t o u r m a l i n e was found t o be g r e a t e r i n the spots than i n the f i n e - g r a i n e d ground mass. MUSCOVITE:  HpKAl (SiO.)  — — — — — —  ,  4 O  &  W e l l c r y s t a l l i z e d muscovite examined.  i s r a r e i n the s e c t i o n s  Where p r e s e n t , i t o c c u r s as l a r g e s i e v e y f l a k e s  up t o .4 mm. i n s i z e , a s s o c i a t e d w i t h e p i d o t e and c h l o r i t e . The. f i n e - g r a i n e d v a r i e t y s e r i c i t e i s second t o q u a r t z i n o r d e r o f abundance.  I t occurs as minute, e v e n l y  d i s t r i b u t e d , l a t h - s h a p e d g r a i n s , g e n e r a l l y l e s s than .01 mm. in length. I t was noted t h a t t h e r e i s a c o n s i d e r a b l y lower  con-  c e n t r a t i o n o f s e r i c i t e i n the spots t h a n i n t h e s u r r o u n d i n g matrix. BIOTITE:  H K g  (MgFe) Al(Si0 ) 3  4  B i o t i t e i s . the most common a c c e s s o r y m i n e r a l .  I t occurs  i n t h r e e d i s t i n c t ways; (a) As e q u i d i m e n t i o n a l g r a i n s , ' averaging  .04 - .06 mm. i n d i a m e t e r , more o r l e s s  d i s t r i b u t e d throughout comprises  some o f the beds.  evenly  I n some c a s e s , i t  2 5 % o f the m i n e r a l s p r e s e n t ; (b) as c o n c e n t r a t i o n s  of l a r g e r g r a i n s , up t o .2 mm. i n d i a m e t e r , i n more o r l e s s c i r c u l a r s p o t s , a s s o c i a t e d w i t h l a r g e g r a i n s o f q u a r t z and feldspar.  I n some c a s e s , the b i o , t i t e c l u s t e r s form a c e n t r a l  core i n the s p o t s , and a r e surrounded  by a r i n g o f b i o t i t e -  14 free quartz g r a i n s .  In o t h e r s , the whole spot c o n s i s t s of  c l o s e l y packed b i o t i - t e f l a k e s , w h i l e i n s t i l l  other  spots,  the h i o t i t e g r a i n s form a r i n g around the p e r i p h e r y of the spot l e a v i n g a more .or l e s s b l e a c h e d (c)  core of q u a r t z g r a i n s ;  I n s m a l l v e i n l e t s c o n t a i n i n g b i o t i t e g r a i n s more o r  l e s s o r i e n t e d w i t h t h e i r l o n g a x i s p a r a l l e l t o the l e n g t h of the v e i n l e t . spots.  The  v e i n l e t s cut a l l s t r u c t u r e s i n c l u d i n g the  In a l l cases the b i o t i t e i s more o r l e s s c h l o r i t i z e d .  CHLORITE;. Hg.(Fe,Mg) A l S i 0 2  The  7  sediments examined, have been c o n s i d e r a b l y  P a l e g r e e n i s h c h l o r i t e occurs  chloritized.  i n s m a l l v e i n l e t s and  r e l a t i v e l y l a r g e i r r e g u l a r patches.  in  I t i s commonly a s s o c i a t e d  w i t h c a l c i t e and p y r r h o t i t e . ' _SPHENE;  TITANOSILICATES CaTiSiO^5  T h i s m i n e r a l was  i d e n t i f i e d i n o n l y one  thin section.  I t o c c u r r e d w i t h a l b i t e i n a s m a l l v e i n l e t which c u t s a b i o t i t e - r i c h zone i n t h i n secti'on 241B. .04 mm. The  The  g r a i n s average  i n s i z e and e x h i b i t t y p i c a l diamond-shaped o u t l i n e s .  i n d e x was  1.80  + and  the b i r e f r i n g e n g e n c e  g r a i n s were o p t i c a l l y p o s i t i v e w i t h 2V=  20°  very h i g h .  1.  The  ,  I t i s thought t h a t some s m a l l i s o l a t e d g r a i n s w i t h h i g h i n d e x seen i n t h i n s e c t i o n 340A are p r o b a b l y p o s i t i v e d e t e r m i n a t i o n c o u l d be made.  sphene but  no  15 ALTERATION OF THE ALDRIDGE FORMATION The  development of the pronounced s p o t t i n g i s the most  n o t i c e a b l e change i n d u c e d i n the rocks of the A l d r i d g e f o r m a t i o n by the i n t r u s i o n of the P u r c e l l s i l l s .  Other  changes have o c c u r r e d which are e q u a l l y i m p o r t a n t but which  do  not m a t e r i a l l y a l t e r the megascopic c h a r a c t e r of the r o c k s . They a r e , t o u r m a l i n i z a t i o n , c h l o r i t i z a t i o n , c a r b o n a t i z a t i o n , and i n t r o d u c t i o n of the s u l p h i d e s , p y r r h o t i t e , and  sphalerite.  The f o l l o w i n g few pages w i l l be devoted t o a d e t a i l e d d e s c r i p t i o n of these and o t h e r changes. DESCRIPTION OF SPOTTING; The  s p o t t i n g i s c h a r a c t e r i z e d by the pronounced  ment of areas l a r g e l y composed o f coarse q u a r t z and  developbiotite.  The amount of b i o t i t e v a r i e s from almost 100$.to almost z e r o . The g r a i n s i z e o f the main m i n e r a l s o c c u r r i n g i n these  spots  i s c o n s i s t e n t l y c o a r s e r t h a n t h a t o f the same m i n e r a l s o c c u r r i n g i n the ground mass. The  spots are u s u a l l y r o u g h l y c i r c u l a r i n o u t l i n e 'and  g r a d u a l l y i n c r e a s e i n s i z e from a p p r o x i m a t e l y .2 mm,.in d i a m e t e r i n the beds near the c o n t a c t w i t h the s i l l maximum of 6 mm. sill.  - to a  i n d i a m e t e r i n the beds 500 f e e t below the  However, as the s i z e of the s p o t s i n c r e a s e ^ the  number o f spots per u n i t a r e a decreases  p r o p o r t i o n a l l y , so -that  the t o t a l area o c c u p i e d by spots i s a p p r o x i m a t e l y the same throughout  the s e c t i o n . (See s t r a t i g r a p h i c s e c t i o n ; i n appendix)  16 VARIATION IN TEXTURE AND COMPOSITION OF. THE SPOTS WITH REGARD TO THE FOLLOWING MINERALS. Biotite: The  0  d i s t r i b u t i o n o f t h e b i o t i t e w i t h i n the spots v a r i e s  considerably.  I n some cases the g r a i n s a r e c o n c e n t r a t e d i n  the c e n t r e o f t h e spots and a r e surrounded by a d i s t i n c t r i m of q u a r t z .  I n o t h e r cases the b i o t i t e i s c o n c e n t r a t e d around  the p e r i p h e r y o f t h e spot l e a v i n g a b a r r e n c e n t r a l c o r e . The l a t t e r type i s v e r y w e l l developed p l a t e s 45 and 5 ) .  i n specimens,340, (see  The g r a i n s f o r m i n g t h e o u t e r p o r t i o n o f the  r i m are n o t i c e a b l y f i n e r - g r a i n e d than .those o c c u r r i n g . c l o s e r to t h e c e n t r e .  The b i o t i t e r i m grades  'and shows d e f i n i t e r a d i a l arrangement.  i n t o t h e b a r r e n core : •  Pyrrhotite; There i s a d i s t i n c t tendency f o r the p y r r h o t i t e i n the s p o t t e d l a y e r s t o be c o n c e n t r a t e d w i t h i n t h e s p o t s .  The  amount of p y r r h o t i t e i n the spots appears t o v a r y Inverse;!y w i t h t h e d i s t a n c e between t h e spots and a p y r r h o t i t e - r i c h layer or vein. Tourmaline: There i s , i n g e n e r a l , a wide d i s t r i b u t i o n o f t o u r m a l i n e throughout  the r o c k s examined.  I n most o f the s p o t s t h e r e  appears to be a s l i g h t i n c r e a s e i n c o n c e n t r a t i o n .  I n some,  the i n c r e a s e i s very pronounced, i n which case, the t o u r m a l i n e assumes the r o l e o f the major c o n s t i t u e n t o f t h e spots.  T h i s i s b e s t i l l u s t r a t e d i n s e c t i o n s 160 A & B where  l a r g e s i e v e y g r a i n s of t o u r m a l i n e occupy a p p r o x i m a t e l y 2b%  17  See P l a t e s 26) and' . 1 .  of the s p o t s . Rutile;  R u t i l e i s p r o b a b l y t h e most common a c c e s s o r y m i n e r a l . It« - d i s t r i b u t i o n I s n o t c o n f i n e d t o the s p o t s b u t i s found i n g r e a t e r amounts i n the spots t h a n e l s e w h e r e .  Rutile  appears to be more c l o s e l y a s s o c i a t e d w i t h b i o t i t e t h a n w i t h any o t h e r m i n e r a l .  Minute n e e d l e s a r e f o u n d r e p l a c i n g b i o t i t e  a l o n g c l e a v a g e p l a n e s ; c l u s t e r s o f l a r g e r stubby c r y s t a l s a r e common i n t h e w e l l developed s p o t s , such as appear i n t h i n s e c t i o n 340, and a r e found i n t h e b i o t i t e r i m s and n o t i n the barren core.  See p l a t e s '& and ,5.  Clinozoisite: >,The ooourrenoe  of C l i n o z o i s i t e i s v e r y c l o s e l y a s s o c i a t e d  w i t h p y r r h o t i t e , thus i t , i s more commonly found i n t h e spots and i n the p y r r h o t i t e - r i c h zones.  V.c  ..... . 7.  Chloritization: C h l o r i t i z a t i o n i s n o t c o n f i n e d t o d e f i n i t e areas b u t i t was n o t e d t o be more pronounced where the c o n c e n t r a t i o n o f pyrrhotite  i shigh.  ^ 18 FORMATION OF THE  BIOTITE  Sediments of the type f o u n d i n the P u r c e l l s e r i e s  are  formed by pronounced c h e m i c a l and p h y s i c a l d e c o m p o s i t i o n p r e - e x i s t i n g l a n d masses. amount of b i o t i t e now detrital  of  I t i s t h e r e f o r e u n l i k e l y t h a t the  found i n the c o n t a c t zone c o u l d be of  origin.  A r g i l l a c e o u s sediments are n o t a b l y low i n l i m e  and  ; a.  soda, h i g h i n p o t a s s i w s magnesia and a l u m i n a , and u s u a l l y c o n t a i n some i r o n , g e n e r a l l y p r e s e n t as l i m o n i t e .  These  c o n s t i t u e n t s w i t h the p o s s i b l e e x c e p t i o n of i r o n , are  largely  r e c o n s t i t u t e d t o form s e r i c i t e and m i n e r a l s of the s e r p e n t i n e and c h l o r i t e groups.  Under c o n d i t i o n s of r i s i n g  temperature,  temporary s o l u t i o n would be i n i t i a t e d a t i s o l a t e d p o i n t s i n the r o c k .  With c o n t i n u e d e l e v a t i o n o f temperature  would g r a d u a l l y spread and would be f o l l o w e d by i z a t i o n and the p r o d u c t i o n of new Harker  minerals.  ( l ) , b i o t i t e i s v e r y o f t e n the f i r s t  product.  process  recrystall-  According to important  new  I t i s formed f r o m c h l o r i t e , s e r i c i t e , i r o n ore  r u t i l e o f the o r i g i n a l sediment.  and  As i t s f i r s t appearance t h i s  m i n e r a l i s i n numerous v e r y s m a l l elements, times rounded, but i t soon develops, w h i c h may  this  s h a p e l e s s , or some-  characteristic  flakes  have c r i s s - c r o s s o r p a r a l l e l arrangement.  T h i s , t h e r e f o r e , g i v e s a probable - e x p l a n a t i o n as to the source o f the b i o t i t e , but i t does not e x p l a i n why i t s development i n some l a y e r s i s v e r y pronounced w h i l e i n o t h e r s it is entirely (1)  lacking. Harker, A l f r e d  Metamorphism 2nd E d i t i o n P 49  19 B a r k e r s t a t e s t h a t the m i n e r a l formed a t any g i v e n depends upon the c o m p o s i t i o n o f the r o c k w i t h i n a v e r y r a d i u s about t h a t p o i n t .  point small  The l i m i t o f e f f e c t i v e d i f f u s i o n  thus i n d i c a t e d i s commonly a s m a l l f r a c t i o n of an i n c h .  It  may, t h e r e f o r e , be assumed t h a t m a t e r i a l d i s s o l v e d i n one t h i n bed would not be t r a n s p o r t e d by d i f f u s i o n from t h a t bed i n t o a n o t h e r ; and s o , w h i l e b i o t i t e ' might have been produced i n one l a y e r w h i c h c o n t a i n e d  the r e q u i s i t e m i n e r a l s ,  i t would not  have formed i n an a d j a c e n t bed w h i c h l a c k e d one o f the essential  original.components.  The i n c r e a s e  i n temperature need n o t have been g r e a t ,  i n d e e d , i t c o u l d n o t have been g r e a t , o t h e r w i s e t h e r e would have been a development o f the medium and h i g h e r s i l i c a t e s such as h y p e r s t h e n e , g a r n e t ,  temperatures!  e t c . However> a l t h o u g h  the r i s e i n temperature was not g r e a t , the d u r a t i o n o f the temperature e l e v a t i o n must have been q u i t e p r o l o n g e d . i s evident  This  from the f a c t t h a t the s p o t t i n g occurs hundreds o f  f e e t from the s i l l c o n t a c t .  I t i s thought t h a t the a c t u a l  s p o t t i n g may have r e s u l t e d , d u r i n g  t h i s prolonged e l e v a t i o n  i n t e m p e r a t u r e , due t o i s o l a t e d l o c a l i n c r e a s e s  i n the,amount  of s o l v e n t , g i v i n g r i s e t o s o l u t i o n of the b i o t i t e over s m a l l areas,'and d i f f u s i o n o f the d i s s o l v e d . m a t e r i a l towards a common c e n t r e where r e c r y s t a l l i z a t i o n t o o k place.,  Continued  a c t i o n would tend t o form a core o f l a r g e g r a i n s surrounded by an a r e a c o m p a r a t i v e l y  free of b i o t i t e .  Slight variations i n  any of the c o n t r o l l i n g f a c t o r s would have a d e c i d e d e f f e c t on t h i s tendency t o form s p o t s , and upon the shape o f the s p o t s .  In-those  spots which e x h i b i t an o u t e r r i n g of b i o t i t e  surrounding  a b a r r e n c o r e , there must have been s o l u t i o n a t  what i s now  the c e n t r e of the spot and d i f f u s i o n outward from'  this centre.  T h i s might -account f o r the r a d i a l arrangement  of the b i o t i t e n o t i c e d i n some s p o t s . I t has been n o t e d t h a t t h e r e i s a g r a d a t i o n a l change i n the s i z e o f the spots throughout the l e n g t h of the hole.  drill  Near the s i l l are numerous s m a l l s p o t s , whereas a t  the f a r t h e s t p o i n t from the s i l l , the spots are fewer i n number end c o n s i d e r a b l y l a r g e r i n diameter.  However, i t seems  t h a t the o v e r a l l a r e a l e x t e n t ^of the s p o t t i n g i s  approximately  the same throughout the l e n g t h of the . d r i l l h o l e . i n the number of spots per u n i t a r e a may  be due  The  t o the  t h a t near the c o n t a c t , s o l u t i o n and r e c r y s t a l l i z a t i o n  change fact was  i n i t i a t e d at a l a r g e number of p o i n t s , and t h a t the number of c e n t r e s of s o l u t i o n decreased as the d i s t a n c e from the increased.  Why  contact  there s h o u l d be' an i n c r e a s e i n the s i z e ' of the  spots as the d i s t a n c e from the s i l l  i n c r e a s e s i s not under-  stood. ORIGIN OF TOURMALINE AND The to  development o f b i o t i t e and  SULPHIDES  s p o t t i n g can be a t t r i b u t e d  r e c o n s t i t u t i o n under the i n f l u e n c e of low grade  thermal  metarnorphism. However, t h i s p r o c e s s  does not e x p l a i n the presence of  a p p r e c i a b l e amounts of t o u r m a l i n e , p y r r h o t i t e , and  i n some  c a s e s , s p h a l e r i t e , found throughout the sediments examined. Moreover, the q u a n t i t y of t o u r m a l i n e  present  appears t o be  too  21  g r e a t f o r I t to be merely r e c r y s t a l l i z e d d e t r i t a l m a t e r i a l and the p o s s i b i l i t y o f the p y r r h o t i t e and e s p e c i a l l y the s p h a l e r i t e b e i n g formed from o r i g i n a l m a t e r i a l i n the r o c k seems remote.  I t t h e r e f o r e , must be assumed t h a t m a t e r i a l  has been i n t r o d u c e d from o u t s i d e t o form these m i n e r a l s . i s thought  t h a t l a t e magnetic emanations from the  p o s s i b l y p a r t l y p'neumatolytic for this introduction.  It  sills,  i n c h a r a c t e r were r e s p o n s i b l e  Whether the t o u r m a l i n e and  the  s u l p h i d e s were formed contemporaneously i s not knowa. I t i s •known, however, t h a t the p y r r h o t i t e i s d e f i n i t e l y l a t e r  than  the s p o t t i n g . I n o r d e r to form these m i n e r a l s , the a s c e n d i n g s o l u t i o n s must have c o n t a i n e d a p p r e c i a b l e q u a n t i t i e s of boron, s u l p h u r and w a t e r , p l u s some z i n c and t i t a n i u m . The  s o l u t i o n s appear to have e n t e r e d a l o n g f r a c t u r e s  and a l o n g more permeable l a y e r s i n the s e d i m e n t s ,  and to have  p e n e t r a t e d e x t e n s i v e l y i n t o the s u r r o u n d i n g r o c k , g i v i n g t o s o l u t i o n and subsequent f o r m a t i o n of the new the more porous a r e a s .  Evidence  minerals i n  to support t h i s t h e o r y i s  found i n the f a c t t h a t i n the s p o t t e d zones b o t h and t o u r m a l i n e are found  rise  pyrrhotite  i n g r e a t e r c o n c e n t r a t i o n i n the  spots t h a n i n the ground mass.  I t was  a l s o noted t h a t where  a v e i n l e t of p y r r h o t i t e c u t s through a s p o t t e d l a y e r , o r where a p y r r h o t i t e - r i c h l a y e r occurs i n c o n t a c t w i t h a s p o t t e d l a y e r , the. percentage  of p y r r h o t i t e i n the spots i s i n v e r s e l y  p r o p o r t i o n a l t o the d i s t a n c e the spots are from the p y r r h o t i t e v e i n l e t or band.  The  t o u r m a l i n e c o n t e n t i n the spots does not  22  show any r e l a t i o n s h i p t o p y r r h o t i t e v e i n l e t s .  In fact i t i s  g r e a t e s t I n the spots i n s e c t i o n s 160 A & B w h i c h c o n t a i n little  o r no p y r r h o t i t e .  apparent c o n n e c t i o n and t o u r m a l i n e  There does not. appear t o he any  between the c o n c e n t r a t i o n s  of p y r r h o t i t e  i n any one l a y e r , and t h e d i s t a n c e o f the l a y e r  from the d i o r i t e  contact. ORIGIN OF ALBITE  D u r i n g t h e e x a m i n a t i o n o f the s e c t i o n s a o e r t a i n amount of a l b i t e was i d e n t i f i e d .  I n o e r t a i n i n s t a n c e s g r a i n s were  found t o occupy v e i n l e t s w h i c h were younger t h a n t h e s p o t t i n g . I n one case i t was found i n a s m a l l v e i n l e t a s s o c i a t e d sphene.  with  S e l e c t i v e s t a i n i n g i n d i c a t e d t h a t some s e c t i o n s were  quite h i g h l y f e l s p a t h i z e d . seers'r  A- o o r t a i n -amount o f t h i s a l b i t e i s . q u i t e p r o b a b l y t h e r e s u l t of r e c r y s t a l l i z a t i o n of d e t r i t a l f e l d s p a r but there seems t o be a d i o t i n o t p o s s i b i l i t y t h a t some o f i t may have been  introduced. H a r k e r ( l ) b e l i e v e s t h a t a r g i l l a c e o u s sediments  bordering  c e r t a i n b a s i c i n t r u s i o n s may have been a l b i t i z e d and c o n v e r t e d to a d i n o l e s by the a c t i o n o f j u v e n i l e l i q u i d s c a r r y i n g s o d i c compounds.  He p o s t u l a t e d t h a t s i n c e the igneous  rocks  r e s p o n s i b l e f o r t h e t r a n s f o r m a t i o n a r e themselves r i c h i n ' soda tha-% they have been a l b i t i z e d by the j u v e n i l e l i q u i d a f t e r t h e i r f i r s t c o n s o l i d a t i o n , and t h a t the same l i q u i d s o l u t i o n s have i n v a d e d the a d j a c e n t  r o c k , and have b r o u g h t about r a d i c a l  metasomatic changes. (1) H a r k e r , A l f r e d , Metsmorphism 2nd E d i t i o n P.128  23 The a l b i t i z e d a r g i l l a c e o u s r o c k s c o n t a i n o t h e r  minerals  i n v a r y i n g p r o p o r t i o n s , such as c h l o r i t e , e p i d o t e , " i r o n o r e " , sphene and r u t i l e .  A t Diwas  ;  actinolite,  Head, C o r n w a l l , the .  a d i n o l e s grade i n t o r o c k s composed e s s e n t i a l l y o f d r a v i t e . A comparison of the s e d i m e n t a r y rocks a d j a c e n t  t o the  P u r c e l l i n t r u s i v e w i t h the a d i n o l e s d e s c r i b e d by H a r k e r r e v e a l s o o r t a i n ' - p o i n t s of s i m i l a r i t y . In b o t h c a s e s , argillaceous. minerals.  the o r i g i n a l sediments were  notably  B o t h c o n t a i n a l b i t e and have s i m i l a r  Both are a s s o c i a t e d w i t h b a s i c igneous  accessory  intrusives.  The i n t r u s i v e s a s s o c i a t e d w i t h the a d i n o l e s are r i c h i n soda and i t has been p o s t u l a t e d t h a t t h e l i q u i d magmatic s o l u t i o n s r e s p o n s i b l e f o r t h i s i n c r e a s e i n soda content a l s o r e s p o n s i b l e f o r the a l b i t i z a t i o n o f the  were  adjacent  sedimentary rock. I t i s known t h a t g r a n o p h y r i c  r o c k s are a s s o c i a t e d  with  many of the P u r c e l l i n t r u s i v e s and t h a t these g r a n o p h y r i c are r i c h e r i n a c i d p l a g i o c l a s e t h a n t h e normal  rocks  type.  • I t i s , t h e r e f o r e , suggested t h a t the a l b i t e i n the sedimentary rocks  of the A l d r i d g e f o r m a t i o n  adjacent  t o the  p u r c e l l i n t r u s i v e s may a l s o be of magmatic o r i g i n , and t h a t the same magmatic s o l u t i o n s which caused the a l b i t i z a t i o n , were r e s p o n s i b l e f o r the i n c r e a s e i n soda content p o r t i o n s of the a d j a c e n t  intrusives.  of c e r t a i n '  2  4  ,  .  •  .  ORIGIN OF RUTILE The  w i d e s p r e a d d i s t r i b u t i o n of r u t i l e t h r o u g h o u t these  sediments c o u p l e d w i t h the f a c t t h a t i t i s a v e r y common d e t r i t a l mineral  i n a r g i l l a c e o u s sediments would' a a ova to  i n d i c a t e s t h a t i t i s due o r i g i n a l rock.  t o r e c r y s t a l l i z a t i o n of r u t i l e i n the  However, the f a c t t h a t sphene i s a s s o c i a t e d  w i t h a l b i t e i n v e i n l e t s , would soon to suggests t h a t  the  a s c e n d i n g s o l u t i o n s c a r r i e d a c e r t a i n amount of t i t a n i u m . Thus,' t h e r e  i s a p o s s i b i l i t y t h a t a p a r t of the r u t i l e  i s not a u t h o g e n i c , but has of t i t a n i u m b e a r i n g  r e s u l t e d from the  o f t o n a s s o c i a t e d w i t h p y r r h o t i t e and iates this  theory.  introduction  s o l u t i o n s a f t e r the r o c k s were  to low grade t h e r m a l metamorphism.  The  present  subjected  f a c t that i t i s quite  clinozoisite  substant-  25 CONCLUSIONS The  i n t r u s i o n of the P u r c e l l S i l l s has r e s u l t e d i n low  grade t h e r m a l metamorphism of the a d j o i n i n g beds of the Aldridge formation.  T h i s t h e r m a l metamorphism has  resulted  i n the f o r m a t i o n o f b i o t i t e i n a l a r g e number o f the  thin  beds by r e c o n s t i t u t i o n of o r i g i n a l m i n e r a l s i n the r o c k .  The  metamorphism caused the s p o t t i n g w h i c h occurs i n the c o n t a c t zone, but the r e a s o n f o r the i n c r e a s e i n the s i z e of the spots as the d i s t a n c e from the c o n t a c t i n c r e a s e s , i s not known. The  thermally metamorphosed r o c k s were f u r t h e r a l t e r e d  the a c t i o n of magmatic emanations from the a d j a c e n t I t i s thought  intrusive.  t h a t these emanations were e s s e n t i a l l y  t h e r m a l , but they may  by  hydro-  have been p a r t l y pneumato'lyti.c. . The  metasomatism r e s u l t e d i n the p r o d u c t i o n - of t o u r m a l i n e ( d r a v i t e ) a l b i t e , p y r r h o t i t e , s p h a l e r i t e , sphene, and p o s s i b l y some of the r u t l l e .  The  f o r m a t i o n of the new  m i n e r a l s was  by c h l o r i t i z a t i o n , c a r b o n a t i z a t i o n , and the  accompanied  widespread  p r o d u c t i o n of c l i n o z o i s i t e p l u s minor e p i d o t e . A comparison between the a l t e r a t i o n i n the w a l l r o c k s of the S u l l i v a n ore body and the a l t e r a t i o n found i n the sedimenta r y r o c k s of the A l d r i d g e f o r m a t i o n a d j a c e n t t o the sill,  r e v e a l s t h a t w h i l e the a l t e r a t i o n i n the w a l l r o c k s i s  much more pronounced t h a n t h a t found sill,  Purcell  the m i n e r a l o g y  essentially  i n the r o c k s near the  of the a l t e r a t i o n , i n both'cases  is  similar.  T h i s s i m i l a r i t y combined w i t h the f a c t t h a t the h o l e i s l e s s than h a l f a m i l e from the ore body may  drill Indicate  26 t h a t the magmatic s o l u t i o n s w h i c h caused the changes may have had. a common s o u r c e .  I f t h i s i s t r u e , and i f i t i s conceded  t h a t the a l t e r a t i o n s found i n the r o c k s near the s i l l  resulted  from the a c t i o n o f magmatic s o l u t i o n s t h a t o r i g i n a t e d  either  in  the s i l l ,  o r i n the p a r e n t magma chamber of the s i l l ,  it  may be p o s t u l a t e d t h a t the S u l l i v a n ore body i s g e n e t i c a l l y  r e l a t e d t o the P u r c e l l s i l l s .  /  then  27 BIBLIOGRAPHY  Harker, A l f r e d .  Me tamorphism second e d i t i o n 1939  R i c e , H.M.A.  1937, G.S.C. Mem. 207  Swans on,  CO. and Gunning, H.G.  1945. The Geology o f the S u l l i v a n Mine  T r a n s . C.I.M.M. V o l . 48 pp. 645-667  I  \  APPENDIX  28 DESCRIPTION OF THIN SECTIONS THIN SECTION 158  A  T h i s s e c t i o n appears to 'be normal s i l i c e o u s  argillite  g r a d i n g to a r g i l l a c e o u s s i l t s t o n e .  The main c o n s t i t u e n t s  are q u a r t z , s e r i c i t e , and b i o t i t e .  The  q u a r t z g r a i n s show  v e r y i r r e g u l a r o u t l i n e s and range from .01 - .02 mm. diameter. mm.  The  in  s e r i c i t e occurs as i n t e r s t i t i a l f l a k e s .02  i n s i z e , between g r a i n s of q u a r t z .  The  -  b i o t i t e appears  as r e l a t i v e l y l a r g e e q u i d i m e n t i o n a l g r a i n s .04 - .10 mm. d i a m e t e r and occupies  approximately  .04  25$ of the s l i d e .  in The  g r a i n s are g e n e r a l l y more o r l e s s c h l o r i t i z e d R u t i l e occurs as v e r y s m a l l s c a t t e r e d g r a i n s and aggregates o f c r y s t a l s . i n the b i o t i t e .  The  fine  I n p l a c e s i t appears as f i n e needles  s e c t i o n has been f r a c t u r e d , and  the  f r a c t u r e s subsequently  f i l l e d w i t h an i n t i m a t e m i x t u r e  c a l c i t e and c h l o r i t e .  P y r r h o t i t e occurs as  i r r e g u l a r g r a i n s up t o .05 mm  of  isolated  in size.  THIN SECTION 158 B  -~ .  T h i s s e c t i o n i s v e r y s i m i l a r t o 138 A but c o n t a i n s a g r e a t e r amount of b i o t i t e , a p p r o x i m a t e l y  20$ *.  There- i s one  vague b i o t i t e e n r i c h e d l a y e r . Vague s p o t t i n g i n the form of s l i g h t l y e n l a r g e d  biotite  and q u a r t z g r a i n s p l u s a c o n c e n t r a t i o n of p y r r h o t i t e i s discernable.  I n g e n e r a l , the p y r r h o t i t e i s more abundant  i n l a r g e r masses ( g r e a t e r than .2 mm.)  than i n 138 A..,  and  There  i s a vague s u g g e s t i o n of a c o n c e n t r a t i o n of p y r r h o t i t e i n  29 s t r e a k s p a r a l l e l t o the b e d d i n g . accessory  mineral.  R u t i l e i s the most abundant  Tourmaline and p o s s i b l y z i r c o n a r e p r e s e n t  i n v e r y s m a l l amounts. THIN SECTION 158 C S i m i l a r t o 138 A and B b u t showing g r a d a t i o n a l t h i n bedd i n g , some l a m e l l a e c o n t a i n q u a r t z up t o '.05 mm i n d i a m e t e r . The s e c t i o n c o n t a i n s f e l d s p a r ' o f . a p p r o x i m a t e l y o l i g o c l a s e composition.  albite-  I t c o u l d o n l y be d e t e c t e d where t h e  g r a i n s i z e was l a r g e enough t o o b t a i n a f i g u r e .  2V was found  t o be l a r g e - a p p r o a c h i n g 90°. I n some, cases i t i s p o s s i b l e t o see the c l e a v a g e by u s i n g o i l immersion.  R u t i l e i s the most abundant a c c e s s o r y  m i n e r a l , o c c u r r i n g e i t h e r as s h o r t p r i s m a t i c e u h e d r a l  crystals,  which sometimes show e x c e l l e n t g e n i c u l a t e d t w i n n i n g , or as long slender needles, of b i o t i t e .  .02 - .03 mm.  i n l e n g t h , i n the grains  They l i e i n random o r i e n t a t i o n on the c l e a v a g e  planes and can o n l y be seen d i s t i n c t l y i n b a s a l s e c t i o n s . S p h a l e r i t e occurs mm.  i n size..  as v e r y s m a l l e u h e d r a l  I t s presence was c o n f i r m e d  g r a i n s l e s s than .01 by a  micro-chemical  test f o r zinc. THIN SECTION 146 A • This i s a s e c t i o n of spotted s i l t s t o n e .  The m a t r i x i s  composed o f i r r e g u l a r q u a r t z and f e l d s p a r g r a i n s .02 - .04 mm i n d i a m e t e r w i t h v e r y minor amounts o f i n t e r s t i t i a l s e r i c i t e . The spots a r e r o u g h l y from 0.3 - 0.8 mm. averaging  c i r c u l a r i n o u t l i n e and range i n s i z e  They a r e composed of q u a r t z  .05 - .1 mm.,  grains  b i o t i t e f l a k e s up t o 0.1 mm.  and  50. s i e v e y g r a i n s o f muscovite showing p o i k i l o b l a s t i c The c h a d o c r y s t s  a r e , q u a r t z f e l d s p a r , and t o u r m a l i n e .  attempt, was made t o determine the type o f f e l d s p a r and the approximate p e r c e n t a g e . g r a i n s showed a l b i t e  twinning.  was found t o be 12-1/2 - 13°. positive,  w i t h a l a r g e 2V.  was e v i d e n t .  structure. An  present,  I f was noted t h a t ' a few The maximum e x t i n c t i o n angle These g r a i n s were ' o p t i c a l l y  Under o i l immersion 90° c l e a v a g e  These g r a i n s were c o n c l u d e d t o be a l b i t e .  The s e c t i o n a l s o c o n t a i n s a number o f f a i r l y l a r g e g r a i n s of what appeared t o be q u a r t z . most commonly c l o u d e d  These g r a i n s were  by minute i n c l u s i o n s .  The index  was  found t o be j u s t s l i g h t l y above t h a t o f balsam and g r e a t e r than the a l b i t e .  The b i r e f r i n g e n c e appeared t o be s l i g h t l y  h i g h e r t h a n t h a t o f the a l b i t e .  The l a t t e r showed a dark  grey i n t e r f e r e n c e c o l o r whereas the f o r m e r showed a l i g h t grey t o cream c o l o r , g i v i n g a b i r e f r i n g e n c e of .010.  approximately  A c a r e f u l check o f s e v e r a l g r a i n s proved t h a t the  m i n e r a l was b i a x i a l n e g a t i v e  w i t h 2V from 60° - 70°.  One o r  two g r a i n s e x h i b i t e d what was thought t o be a type o f r a d i a l twinning.  I t I s thought t h a t t h i s m i n e r a l may be  The s e c t i o n c o n t a i n s c o n s i d e r a b l e  tourmaline.  cordierite.  I t occurs  pale b l u e - g r e e n s h o r t s t u b b y - c r y s t a l s w h i c h show good outlines.  The l a r g e r g r a i n s show p l e o c h r o i s m  g r e a t e s t when p a r a l l e l t o the a n a l i z e r . common.  L a r g e s i e v e y anhedra o f c h l o r i t e  through t h i s s e c t i o n . clinozoisite.  with  euhedral  absorption  Cross f r a c t u r e s a r e o c c u r commonly  They are f r e q u e n t l y a s s o c i a t e d  The c l i n o z o i s i t e  as  i s also associated  with  with  31 m u s c o v i t e , where i t i s found r e p l a c i n g the muscovite cleavage planes. areas.  along  C a l c i t e i s f a i r l y abundant i n the c h l o r i t i z e d  R u t i l e i s p r e s e n t i n s m a l l amounts as an a c c e s s o r y  mineral. THIN SECTION 146 B T h i s s e c t i o n c o n s i s t s o f banded, b i o t i t e specked and spotted argillaceous s i l t s t o n e .  The main ground mass o f the  s l i d e i s composed o f a p p r o x i m a t e l y 50% q u a r t z g r a i n s a v e r a g i n g .01 - .02 mm. i n d i a m e t e r and 50% b i o t i t e g r a i n s a v e r a g i n g .02 - .04 mm. i n d i a m e t e r . random arrangement throughout  The spots o c c u r w i t h  the general matrix.  They a r e  r o u g h l y c i r c u l a r t o e l l i p s o i d a l i n o u t l i n e and range from a p p r o x i m a t e l y . 6 - 2 mm. i n d i a m e t e r .  They are f r e q u e n t l y  i s o l a t e d from one a n o t h e r b u t i n many cases  it'is'possible  to t r a c e a d i r e c t c o n n e c t i o n between two o r more s p o t s , giving a chainlike effect.  The spots q u i t e commonly e x h i b i t '  a c e n t r a l core o r c l u s t e r o f l a r g e b i o t i t e g r a i n s up t o .2 mm. i n diameter.  S u r r o u n d i n g t h i s core and s e p a r a t i n g i t from  the g e n e r a l b i o t i t e r i c h ground mass i s a b l e a c h e d r i m o f quartz g r a i n s .  I n p r a c t i c a l l y a l l cases the b i o t i t e g r a i n s  i n the spots have been more o r l e s s a l t e r e d and r e p l a c e d by clinozoisite.  The spots have n o t a b l y h i g h e r percentage o f '  p y r r h o t i t e t h a n the r e s t o f t h e s e c t i o n . common a c c e s s o r y m i n e r a l throughout  Tourmaline  i sa  the s l i d e b u t i t appears  i n g r e a t e r amounts and i n l a r g e r c r y s t a l s i n the spot's than i n the g e n e r a l ground mass.  32 The  s e c t i o n i s t r a v e r s e d by an i r r e g u l a r p y r r h o t i t e  r i c h band c o n t a i n i n g c l u s t e r s of b i o t i t e i n .a coarse ground mass.  silty  This l a y e r i s s i m i l a r t o the spots p r e v i o u s l y  d e s c r i b e d , except t h a t i t i s .continuous  a c r o s s the whole  w i d t h of the s e c t i o n , i s p a r a l l e l to the bedding p l a n e ,  and  c o n t a i n s a much h i g h e r c o n c e n t r a t i o n of p y r r h o t i t e than i s found i n any of the s p o t s .  A v e i n l e t of co.ar.se b i o t i t e  c r y s t a l s cuts a c r o s s a l l the s t r u c t u r e s i n c l u d i n g the  spots  and the p y r r h o t i t e r i c h l a y e r . THIN SECTION 155 A T h i s s e c t i o n i s c o n s i d e r e d t o be a r e l a t i v e l y pure s i l t s t o n e s i n c e i t c o n t a i n s p r a c t i c a l l y no s e r i c i t e .  The  m a t r i x c o n s i s t s of q u a r t z and f e l d s p a r g r a i n s w i t h a s m a l l percentage o f b i o t i t e e v e n l y d i s t r i b u t e d t h r o u g h o u t . s l i d e i s vaguely  The  s p o t t e d w i t h i r r e g u l a r shaped c l u s t e r s of  b i o t i t e g r a i n s , but no c l e a r l y marked b l e a c h e d  rimming  can  be seen. • Large s l e v e y f l a k e s of muscovite are common and a l a r g e percentage show replacement by c h l o r i t e and The  epidote.  b i o t i t e i n the spots i s more or less, r e p l a c e d by  and e p i d o t e and p o s s i b l y some c l i n o z o i s i t e .  The  chlorite  most  ".notable  f e a t u r e of t h i s s e c t i o n i s the presence of a l a y e r which c o n t a i n s a r e l a t i v e l y h i g h c o n c e n t r a t i o n of p y r r h o t i t e . p y r r h o t i t e appears to have e n t e r e d the s e c t i o n a l o n g transverse f r a c t u r e s .  Prom these f r a c t u r e s i t has  small spread  and permeated a c o n s i d e r a b l e amount o f the s u r r o u n d i n g stone. I t i s commonly found r e p l a c i n g b i o t i t e .  The  The  out  silt-  intro-  d u c t i o n of the p y r r h o t i t e appears t o have been accompanied  by.  33  the f o r m a t i o n of c h l o r i t e and c a r b o n a t e .  The  carbonate,  p r o b a b l y c a l c i t e , i s v e i n e d and r e p l a c e d by s p h a l e r i t e . dark o l i v e green m i n e r a l o c c u r s i n the p a r t s of the where p y r r h o t i t e i s p r e s e n t .  I t i s thought t o be  section  chloritoid.  I t o c c u r s as vague, rims on c a l c i t e g r a i n s and i n a few as i s o l a t e d aggregates  of v e r y s m a l l g r a i n s .  A  cases  Tourmaline  occurs as a minor a c c e s s o r y m i n e r a l . THIN SECTION 154 A In g e n e r a l , t h i s s e c t i o n i s c l a s s e d as a s p o t t e d s i l t y argillite.  The m a t r i x i s a p p r o x i m a t e l y 80%  i s l i t t l e d i s t i n c t quartz.  sericite.  There  The  spots average 1 mm.  in  diameter and occupy r o u g h l y 20%  of the t o t a l a r e a .  .They,are  c i r c u l a r i n o u t l i n e and e x h i b i t a b l e a c h e d r i m and r i c h c e n t r a l cores.  biotite  Some of the spots c o n t a i n ' u p t o 25%  0  p y r r h o t i t e and most have c o a r s e r q u a r t z g r a i n s t h a n i s found i n the s u r r o u n d i n g m a t r i x .  The p y r r h o t i t e i n the spots i s '.  v e r y commonly i n t i m a t e l y a s s o c i a t e d w i t h b i o t i t e , and i n g e n e r a l i t appears t h a t the p y r r h o t i t e has r e p l a c e d the b i o t i t e .  selectively  Q u i t e f r e q u e n t l y the spots c o n t a i n f a i r "  s i z e d c l u s t e r s o f c l i n o z o i s i t e g r a i n s and s h o r t stubby of  rutile.  Tourmaline  THIN SECTION 154 B The  crystals  i s p r e s e n t as an a c c e s s o r y m i n e r a l . .  ^  g r e a t e r p a r t o f t h i s s e c t i o n i s v e r y s i m i l a r to 154  The r o c k i s a s p o t t e d s i l t y a r g i l l i t e .  The m a j o r i t y of the  spots show'the b i o t i t e c o r e s , but a few are l a r g e l y composed of  coarse q u a r t z g r a i n s a v e r a g i n g 10 mm.  above s i l t y a r g i l l i t e  In diameter.  The  i s i n sharp c o n t a c t w i t h a l a y e r of  A.  34 b i o t i t e r i c h (35$) a r g i l l a c e o u s s i l t s t o n e w i t h q u a r t z g r a i n s .03 mm. i n s i z e ; h a v i n g a l a r g e r c o a r s e ' b i o t i t e and s p h a l e r i t e r i c h patch.  The s p h a l e r i t e occurs i n l a r g e i r r e g u l a r masses  and as s m a l l e r e u h e d r a l c r y s t a l s  (dodecahedrons). I t . ,  p e n e t r a t e s a l o n g c l e a v a g e planes i n the b i o t i t e g r a i n s and i n some p l a c e s appears t o almost e n t i r e l y r e p l a c e some o f the biotite grains. of  quartz.  I t a l s o occurs i n t e r s t i t i a l l y b e t w e e n g r a i n s  The s p h a l e r i t e e n r i c h e d area c o n t a i n s a c o n s i d e r -  a b l e , amount o f c a r b o n a t e , p r o b a b l y c a l c i t e .  I t i s commonly  found rimming the g r a i n s o f s p h a l e r i t e . THIN SECTIONS 160 A and B Both, t h i n s e c t i o n s show a f i n e g r a i n e d massive l a y e r and a specked o r s p o t t e d - l a y e r .  The l a t t e r has round  biotite  r i c h spots 1 ram. i n d i a m e t e r w i t h t h i n p a l e rims .04 mm. wide plus i n t e r s t i t i a l c r y p t o c r y s t a l l i n e m a t e r i a l s i m i l a r to that found i n the massive l a y e r .  The s p o t t i n g i s more pronounced  i n 160 B than 160 A. The massive c r y p t o c r y s t a l l i n e l a y e r i s almost  entirely  composed o f q u a r t z and s e r i c i t e g r a i n s .01 - .03 mm. i n , diameter.  The r a t i o o f the q u a r t z t o s e r i c i t e v a r i e s  from  1.2 t o 1.1. B i o t i t e o c c u r s as s c a t t e r e d g r a i n s , a v e r a g i n g .02 mm. i n size.  R u t i l e and t o u r m a l i n e a r e common a c c e s s o r y m i n e r a l s  o c c u r i n g as s c a t t e r e d e u h e d r a l c r y s t a l s , the former o f t e n showing 'good t w i n n i n g .  What i s thought  to be z i r c o n appears  as a v e r y minor a c c e s s o r y m i n e r a l . The s p o t s c o n t a i n b i o t i t e g r a i n s r a n g i n g from  .03 - .12 mm  35 i n s i z e , which, a r e more o r l e s s c h l o r i t i z e d -- the c h l o r i t e p e n e t r a t i n g a l o n g cleavage  planes.  Tourmaline i s found as a n a c c e s s o r y both s e c t i o n s .  I t occurs  m i n e r a l throughout  i n two d i s t i n c t ways.  I n the  massive c r y p t o c r y s t a l l i n e l a y e r i t appears as s m a l l i s o l a t e d euhedral occurs  g r a i n s g e n e r a l l y c o l o u r l e s s -to l i g h t g r e e n i s h .  It  i n the b i o t i t e cores o f the spots as l a r g e s i e v e y  anhedra up t o .2 - .3 mm.  i n s i z e , and f o r m i n g  i n some cases  as much as 25% o f the area of the s p o t s . C l i n o z o i s i t e and r u t i l e occur q u i t e a b u n d a n t l y as accessory minerals THIN SECTION 182 A  i n some o f the spots." '  J  •  '  ''  T h i s s e c t i o n c o n s i s t s of two p r e d o m i n a t e l y  s i l t y layers  s e p a r a t e d by a t h i n f i n e r - g r a i n e d h i g h l y a r g i l l a c e o u s l a y e r . The  s i l t y l a y e r s are b i o t i t e r i c h .  I n one l a y e r the  b i o t i t e i s l a r g e l y c o n f i n e d t o i r r e g u l a r s p o t s , w h i l e i n the' other , I t i s more o r l e s s e v e n l y d i s t r i b u t e d t h r o u g h o u t . 1  The  spots i n v a r i a b l y c o n t a i n c o a r s e r q u a r t z g r a i n s t h a n the surrounding  matrix.  A number o f the spots have, a c o n c e n t r a t i o n o f r u t i l e cry. stals  .02 - .04 mm.  i n size.  These r u t i l e g r a i n s show no  common o r i e n t a t i o n , b u t r a t h e r e x h i b i t complete random arrangement.• One p a r t o f the s e c t i o n has been h i g h l y c h l o r i t i z e d by s o l u t i o n s p e n e t r a t i n g a l o n g minute f r a c t u r e s .  W i t h i n the  v i c i n i t y o f these v e i n l e t s the b i o t i t e has been s e v e r e l y chloritized.  The a l t e r a t i o n appears t o have been accompanied  36 by the f o r m a t i o n of r u t i l e n e e d l e s , w h i c h are found a l o n g cleavage  planes  i n altered biotite.  The r u t i l e found i n the  c h l o r i t e does not resemble t h a t p r e v i o u s l y d e s c r i b e d . occurs i n l o n g a c l c u l a r  It  needles.  The a r g i l l a c e o u s l a y e r i s r e l a t i v e l y d e v o i d of s p o t t i n g , but i t i s c h a r a c t e r i z e d by the presence o f c o n s i d e r a b l e amounts o f s m a l l stubby r u t i l e c r y s t a l s w h i c h occur i n s m a l l aggregates i n s t r e a k s , more o r l e s s p a r a l l e l t o the b e d d i n g . The c o n c e n t r a t i o n o f the r u t i l e i s g r e a t e s t a l o n g the c o n t a c t s w i t h the s i l t y l a y e r s . THIN SECTION 182 B T h i s s e c t i o n shows banded s i l t y a r g i l l i t e g r a d i n g t o almost pure a r g i l l i t e .  S m a l l c l u s t e r s o r spots o f b i o t i t e  occur s c a t t e r e d throughout the h i g h l y a r g i l l a c e o u s .matrix. The s l i d e c o n t a i n s i r r e g u l a r areas of what appears t o be coarse r e c r y s t a l l i z e d q u a r t z g r a i n s .  They are more numerous,  and the g r a i n s of q u a r t z are. l a r g e r , i n the more a r g i l l a c e o u s l a y e r s , where t h e y occupy 50 - 75% of the t o t a l  area.  These areas o r spots are devoid of b i o t i t e and c o n t a i n o n l y v e r y s m a l l amounts of . s e r i c i t e .  The q u a r t z g r a i n s c o n t a i n  a l a r g e number o f s m a l l i n c l u s i o n s . Two i r r e g u l a r  streaks  of r u t i l e c r y s t a l s t r a v e r s e the s e c t i o n more o r l e s s p a r a l l e l to  the b e d d i n g .  There i s a s l i g h t amount o f c h l o r i t i z a t i o n  of the b i o t i t e c l o s e t o these  streaks.  THIN SECTION 182 C T h i s i s a s e c t i o n o f s i l t y a r g i l l i t e s i m i l a r t o "A "B", b u t l a c k i n g pronounced t h i n b e d d i n g and areas of  n  and '  37 r e c r y s t a l l i z e d quartz. The s e c t i o n shows a s l i g h t amount of normal s p o t t i n g , i . e . h i o t i t e r i c h core, with bleached  rim. Pyrrhotite grains  o c c u r i n some o f the s p o t s . THIN SECTION 190 T h i s i s , a s e c t i o n of m o t t l e d s i l t s t o n e m a i n l y composed of q u a r t z g r a i n s l e s s than .02,mm. i n d i a m e t e r . The m a t r i x c o n t a i n s a p p r o x i m a t e l y  15 t o 20 p e r cent  b i o t i t e , more o r l e s s e v e n l y d i s t r i b u t e d throughout as equidimentional grains averaging  .02 mm.,  w i t h a fe?; g r a i n s  up t o .1 mm. Several v e i n l e t s of c h l o r i t e approximately c u t the s e c t i o n .  .2 mm.  wide  The areas a d j a c e n t t o the v e i n l e t s are  intensely c h l o r i t i z e d , resulting i n several highly c h l o r i t i z e d bands s e p a r a t e d b y l a y e r s i n w h i c h the b i o t i t e i s :  only s l i g h t l y a l t e r e d . THIN SECTION 195"A T h i s s l i d e c o n s i s t s of two bands o f a r g i l l a c e o u s s i l t stone.  One i s b i o t i t e ' e n r i c h e d and c o n t a i n s l a r g e s p o t s of  b i o t i t e , coarse q u a r t z and p y r r h o t i t e .  I n sharp c o n t a c t w i t h  t h i s l a y e r i s a more a r g i l l a c e o u s band, n o t i c e a b l y d e f i c i e n t in biotite. The most prominent m i n e r a l i s t o u r m a l i n e .  I t occurs i n  t h r e e ways: as v e r y s m a l l g r a i n s g e n e r a l l y l e s s t h a n .01 mm. i n diameter,  f a i r l y e v e n l y d i s t r i b u t e d throughout the s e c t i o n :  as l a r g e i s o l a t e d p l e o c h r o i c g r a i n s : and as aggregates o f v e r y small grains.  38 THIN SECTION 195 B This i s fine  grained spotted s i l t s t o n e .  the m a t r i x v a r i e s from .01 - .04 mm.  The q u a r t z i n  i n diameter.  The s p o t s  are composed o f c o a r s e r q u a r t z g r a i n s a v e r a g i n g .05 - .1 mm. i n d i a m e t e r , and g r a i n s o f b i o t i t e more o r l e s s up t o .4 mm i n s i z e .  chloritized,  A few l a r g e , (up t o 1.5 mm.)  anhedra of mus'covite occur s c a t t e r e d throughout  sievey  the s e c t i o n .  The b i o t i t e i n the spots has been p a r t i a l l y r e p l a c e d by clinozoisite.  Subsequent t o t h e f o r m a t i o n of t h i s m i n e r a l a  l a r g e percentage' of the r e m a i n i n g b i o t i t e - has been h i g h l y chloritized.  The r e s u l t  i s t h a t a p p r o x i m a t e l y 50 p e r cent of  the spots are now composed o f an i n t i m a t e m i x t u r e of c h l o r i t e , c l i n o z o i s i t e , and coarse g r a i n e d q u a r t z . Tourmaline  i s the most common a c c e s s o r y m i n e r a l .  occurs as v e r y s m a l l s c a t t e r e d g r a i n s and as l a r g e  It  isolated  s i e v e y anhedra. THIN SECTION 195 C This argillaceous spotted s i l t s t o n e  has a m a t r i x  composed o f s e r i c i t e ' , q u a r t z , and b i o t i t e a v e r a g i n g .01 - .02 mm.  i n size.  The spots range from .2 - .6 mm.  show c e n t r a l cores o f b i o t i t e quartz g r a i n s .  surrounded  i n d i a m e t e r and  by a r i m o f coarse  I n some cases t h e s p o t s are j o i n e d t o g e t h e r  forming i r r e g u l a r  bands.  One v e i n l e t  containing large grains  of b i o t i t e and q u a r t z cuts a c r o s s t h e s e c t i o n a t an angle t o the b e d d i n g .  The b i o t i t e g r a i n s a r e more o r l e s s o r i e n t e d  p a r a l l e l t o the v e i n l e t .  They are c o n s i d e r a b l y c h l o r i t i z e d  and i n some cases r e p l a c e d by  clinozoisite.  39 P y r r h o t i t e i s found c o n c e n t r a t e d  i n the s p o t s and i s  always i n c l o s e a s s o c i a t i o n w i t h the b i o t i t e and replaces i t .  often  R u t i l e i s a l s o a common c o n s t i t u e n t of the  spots  and appears t o be more abundant i n the spots where c h l o r i t i z a t i o n and development o f c l i n o z o i s i t e i s more pronounced. THIN SECTION 210 (1)  A  T h i s s e c t i o n shows -three d i s t i n c t l y d i f f e r e n t bands:  c r y p t o c r y s t a l l i n e l a y e r composed o f q u a r t z and . s e r i c i t e i n e q u a l amounts.  G r a i n s i z e .01 - .02 mm.-  .02 - .04 and coarse s c a t t e r e d throughout.  (.04  - .10 mm.)  Rutile grains  f l a k e s of b i o t i t e  There i s a d e f i n i t e alignment  s e r i c i t e and r u t i l e g r a i n s p a r a l l e l to the (2) .3 mm.  are  of the  banding.  In sharp c o n t a c t w i t h the c r y p t o l a y e r i s a dark band wide which c o n t a i n s a h i g h percentage) o f p y r r h o t i t e  (10 - ) o c c u r r i n g as s c a t t e r e d g r a i n s .03 - .10 mm. This band i s a p p r o x i m a t e l y g r a i n s and 15%  sericite.  85% The  in size.  q u a r t z i n .02 - .04 mm.  size  l a t t e r occurs i n l a r g e r g r a i n s  than i n ( 1 ) . (3) band.  The  p y r r h o t i t e - r i c h l a y e r grades i n t o a c o a r s e l y s p o t t e d  The  m a t r i x i s s i m i l a r t o number 2.  s i z e up to a p p r o x i m a t e l y  3 mm.  The  i n diameter.  p y r r h o t i t e i n .considerable q u a n t i t y .  The  They c o n t a i n  percentage  as the d i s t a n c e from number 2 l a y e r i n c r e a s e s . the s p o t s i s more o r l e s s c h l o r i t i z e d . are p r e s e n t i n c o n s i d e r a b l e q u a n t i t y .  spots v a r y i n  decreases  The b i o t i t e i n  C l i n o z o i s i t e and  rutile  I n g e n e r a l the l a y e r  i s q u i t e s t r o n g l y t o u r m a l i n i z e d , but t h e r e i s a d i s t i n c t i n c r e a s e i n c o n c e n t r a t i o n of t h i s m i n e r a l i n the spots  as  40 compared t o the s u r r o u n d i n g  matrix.  I n some spots the amount  i s over 50$ of the t o t a l . A v e i n l e t o f q u a r t z and f e l d s p a r c u t s a l l layers..  The  f e l d s p a r i s thought t o be a l b i t e , b i a x i a l p o s i t i v e - 2V = l a r g e i n d e x 1.54.  Where the v e i n l e t c r o s s e s t h e p y r r h o t i t e - r i c h  layer, i t contains large grains of p y r r h o t i t e . ( A number o f g r a i n s o f a l b i t e were' i d e n t i f i e d throughout the s e c t i o n , and i t i s thought a c o n s i d e r a b l e  proportion  of the ground mass i s f e l d s p a t h i c , r a t h e r than p u r e l y  quartzose.  THIN SECTION 210 B The same s e r i e s  o f t h r e e . l a y e r s a r e observed here as i n  210 A. (1)  The c r y p t o c r y s t a l l i n e s e r i c i t e band i n t h i s case i s  vaguely  spotted.  There are o c c a s i o n a l muscovite s i e v e s up t o  2 mm. i n s i z e w i t h i n c l u d e d r u t i l e n e e d l e s , and s c a t t e r e d f e l d s p a r s i e v e s .1 mm. albite (2)  (3) quartz  probably  (+) 2V l a r g e . Dark'band 1.5 mm wide s i m i l a r t o one i n A c o n t a i n i n g  approximately quartz  i n d i a m e t e r w h i c h a r e most  10 - 12$ p y r r h o t i t e .  .02 - .05 mm. w i t h 10$ -  The remainder i s l a r g e l y  sericite.  The b i o t i t e s p o t t e d band has a f i n e s i l t y m a t r i x o f (.01 - .03) p l u s minor s e r i c i t e .  The b i o t i t e spots  c o n t a i n a c o n s i d e r a b l e amount o f t o u r m a l i n e . s m a l l g r a i n s (.01 mm.)  more o r l e s s e v e n l y  I t occurs as  distributed  throughout the spots and produces n o t i c e a b l e r i m s .  Some o f  the s m a l l e r spots show a g r e a t e r c o n c e n t r a t i o n o f t o u r m a l i n e and a much lower c o n c e n t r a t i o n of b i o t i t e t h a n i s observed i n  41 the l a r g e s p o t s . P y r r h o t i t e i s a s s o c i a t e d w i t h the b i o t i t e i n the One  spots.  a l b i t e g r a i n was . i d e n t i f i e d near a s p o t , but most of the  c o l o u r l e s s m i n e r a l w i t h the b i o t i t e i s q u a r t z . THIN SECTION 241  A  T h i s s e c t i o n i s composed of t h r e e w e l l d e f i n e d l a y e r s . A s i l t y a r g i l l a c e o u s band, made up of c r y p t o c r y s t a l l i n e s e r i c i t e p l u s 5 - 10% s c a t t e r e d q u a r t z g r a i n s .02 - .04 mm. diameter.  in  T h i s h i g h l y s e r i c i t e l a y e r grades I n t o a b i o t i t e  and p y r r h o t i t e - r i c h band w h i c h i n t u r n grades i n t o a c o a r s e l y spotted l a y e r . The  zone between the c r y p t o c r y s t a l l i n e s e r i c i t e l a y e r and  the b i o t i t e - r i c h l a y e r i s c h a r a c t e r i z e d by abundant r u t i l e g r a i n s w h i c h occur i n i s o l a t e d s t r e a k s p a r a l l e l to the banding.  The  q u a r t z and  general  ground mass i n the s p o t t e d l a y e r i s l a r g e l y /  s e r i c i t e , of a p p r o x i m a t e l y  .5 - .6 mm.  i n size.  T h e i r m o s t ^ s t r i k i n g f e a t u r e i s the h i g h c o n c e n t r a t i o n of p y r r h o t i t e , w h i c h amounts t o over 75% i n some c a s e s .  The  p y r r h o t i t e i s a l m o s t always i n t i m a t e l y a s s o c i a t e d w i t h biotite.  The  spots show some coarse  g r a i n s of a l b i t e .  (.1  - .4 mm)  I n some c a s e s , these g r a i n s are  sievey entirely  surrounded and e n g u l f e d by p y r r h o t i t e . The chlorite.  s e c t i o n i s cut by a v e i n l e t of p y r r h o t i t e and One  s i d e of t h e . v e i n l e t i s o c c u p i e d by p y r r h o t i t e ,  the o t h e r by c h l o r i t e p l u s a s m a l l amount of c a r b o n a t e .  Where  the v e i n l e t c r o s s e s the l a r g e r spots  spread  the p y r r h o t i t e has  out t o form l a r g e i r r e g u l a r masses w i t h i n the  spots.  42  .  THIN SECTION 241 B T h i s s e c t i o n i s v e r y s i m i l a r t o A.  There a r e two  c o a r s e l y s p o t t e d bands separated- by a n o n - s p o t t e d b i o t i t e - r i c h layer.  The m a t r i x i s q u a r t z and s e r i c i t e i n a p p r o x i m a t e l y 1:1  proportions.. The  spots are l a r g e —  up t o 2-4 mm.  They c o n s i s t o f  coarse g r a i n s of q u a r t z .05 - .1 .mm. i n d i a m e t e r , l a r g e f l a k e s of b i o t i t e  .05 -. .2 mm. and a c o n s i d e r a b l e amount o f coarse  pyrrhotite.  There i s a marked decrease i n the amount of  s e r i c i t e as compared t o the m a t r i x .  C l i n o z o i s i t e i s found  as an a c c e s s o r y m i n e r a l i n the s p o t s and i s o f t e n v e r y c l o s e l y associated with pyrrhotite.  Sphene occurs i n a v e i n l e t o f  a l b i t e which c u t s the b i o t i t e - r i c h l a y e r p a r a l l e l t o the banding.  I t was r e c o g n i z e d by i t s h i g h i n d e x , h i g h b i r e -  f r i n g e n c e , and diamond-shaped c r y s t a l o u t l i n e . p o s i t i v e , g r a i n size approximately R u t i l e and t o u r m a l i n e  2V=20 - b i a x i a l  .04 o r l e s s .  (some s i e v e y c r y s t a l s ) a r e a l s o  p r e s e n t as a c c e s s o r y m i n e r a l s . THIN SECTION 246 A Three d i s t i n c t l a y e r s are r e c o g n i z a b l e i n t h i s  section.  A m o t t l e d l a y e r composed o f numerous s m a l l spots o f q u a r t z g r a i n s i n a c r y p t o c r y s t a l l i n e s e r i c i t e m a t r i x occurs i n sharp c o n t a c t w i t h a p y r r h o t i t e - r i c h band c o n t a i n i n g about 10$ s c a t t e r e d p y r r h o t i t e i n a m a t r i x composed o f 50$ s e r i c i t e and 50$ q u a r t z g r a i n s . The  p y r r h o t i t e l a y e r grades i n t o one t h a t i s quit©  strongly spotted.  The s p o t s are l a r g e l y c o a r s e q u a r t z and  43 biotite grains.  Q u i t e commonly t h e b i o t i t e f l a k e s i n t h e  centre, o f t h e spots a r e c o n s i d e r a b l y l a r g e r t h a n those periphery.  on t h e  T h i s produces a n o t i c e a b l e rimming e f f e c t .  The most common a c c e s s o r y m i n e r a l i s r u t i l e .  It is  found s c a t t e r e d throughout t h e whole s l i d e , b u t is,most abundant a l o n g the contact' between l a y e r s 1 and 2-, and i n the spots. C l i n o z o i s i t e and p y r r h o t i t e a r e p r e s e n t spots.  i n most of the  Tourmaline occurs as a minor a c c e s s o r y  mineral.  THIN SECTION 246 B This s e c t i o n Is very w e l l spotted. consists of l a r g e , well-rounded,  In general, i t  b i o t i t e - r i c h spots up t o  3 ram. i n s i z e i n . a s l i g h t l y a r g i l l a c e o u s s i l t s t o n e >  matrix.  The most c h a r a c t e r i s t i c t h i n g about the s p o t t i n g i s the  h i g h c o n c e n t r a t i o n o f b o t h r u t i l e and c l i n o z o i s i t e i n the spots. The l a t t e r shows a tendency t o occur i n the c e n t r e o f the spots r e p l a c i n g some o f the b i o t i t e whereas t h e former i s q u i t e o f t e n f o u n d as a r i n g o f s m a l l c r y s t a l s around the p e r i p h e r y o f the spot.  However, t h i s i s n o t always the case.  The s e c t i o n i s s t r o n g l y t o u r m a l i n i z e d t h r o u g h o u t . THIN SECTION 264 A This s e c t i o n i s a f a i r l y uniform  argillaceous biotite  e n r i c h e d s i l t s t o n e w i t h an " A p l i t i c " t e x t u r e .  Both the q u a r t z  and the b i o t i t e g r a i n s average .01 - .02 mm. i n d i a m e t e r . R u t i l e , c l i n o z o i s i t e a n d ' t o u r m a l i n e a r e common a c c e s s o r y  min-  e r a l s and a r e found more o r l e s s e v e n l y d i s t r i b u t e d throughout  44 the s e c t i o n . THIN SECTION 264. B T h i s s e c t i o n i s w e l l handed w i t h l a r g e c l e a r l y d e f i n e d spots i n two o f the l a y e r s .  Other l a y e r s show an " a p l i t i c "  .texture s i m i l a r t o 264 A. The  " a p l i t i c " bands a r e n o t a b l e f o r the abundant  development o f very minute g r a i n s o f r u t i l e and t o u r m a l i n e . These minute c r y s t a l s g i v e t h e band a d u s t y appearance. Another cut  c h a r a c t e r i s t i c o f these l a y e r s i s t h a t they a r e  by one o r more v e r y narrow i r r e g u l a r b l a c k bands more o r  l e s s p a r a l l e l t o the b e d d i n g .  E x a m i n a t i o n under h i g h magnif-  i c a t i o n r e v e a l s t h a t these.bands c o n s i s t o f a c o n c e n t r a t i o n of  s m a l l r u t i l e c r y s t a l s l e s s t h a n .01 mm i n s i z e ,  extremely  f i n e g r a i n s o f t o u r m a l i n e a p p r o x i m a t e l y .002 mm. i n d i a m e t e r , and g r a n n u l a r c l i n o z o i s i t e i n c l o s e a s s o c i a t i o n w i t h the rutile  crystals.  One zone.  '  •  o f the " a p l i t i c " bands c o n t a i n s a p y r r h o t i t e - r i c h  The p y r r h o t i t e ' i s ' i n t i m a t e l y a s s o c i a t e d w i t h  clinozoisite.  S m a l l r u t i l e c r y s t a l s a r e s c a t t e r e d throughout  the l a y e r . I n g e n e r a l , the s p o t t e d laminae rounded aggregates  consist of large well-  o f coarse q u a r t z and b i o t i t e ,  approximately  2 mm. i n d i a m e t e r , p l u s v a r y i n g amounts o f r u t i l e , and  pyrrhotite,  clinozoisite. In some c a s e s , the spots are almost e n t i r e l y made up o f  biotite. ing  However, i t i s more common t o f i n d the b i o t i t e  form-  a t h i n p e r i p h e r a l r i n g , l e a v i n g . a more o r l e s s b a r r e n core  45 of q u a r t z  grains.  R u t i l e i s commonly found as c l u s t e r s , o f s m a l l grains  associated  w i t h the b i o t i t e .  dozen such c l u s t e r s .  One spot may have up t o a  They a r e n o t found i n the b a r r e n c o r e s .  One 'spotted band l o c a t e d near the p r e v i o u s l y p y r r h o t i t e - r i c h zone has spots which c o n t a i n percentage o f p y r r h o t i t e . associates  euhedral  described  a very high  C l i n o z o i s i t e and r u t i l e  o f the p y r r h o t i t e .  a r e common  "See p l a t e 3.  THIN SECTION 264 C This s e c t i o n i s very s i m i l a r i n a l l i t s f r a c t u r e s one  just described.  I t i s w e l l banded w i t h a l t e r n a t i n g  " a p l i t i c " *and s p o t t e d l a y e r s .  I t lacks  zone and the spots do not c o n t a i n pyrrhotite.  t o the A  the p y r r h o t i t e - r i c h  any a p p r e c i a b l e amount o f  They do, however, show a tendency towards  bleached rims. THIN SECTION 289 A T h i s s e c t i o n i s m o d e r a t e l y w e l l banded. a highly s e r i c i t i c argillaceous  "mottled" l a y e r i n t o a b i o t i t e - r i c h  s i l t s t o n e band, which i s c u t by two i r r e g u l a r  veinlets of.pyrrhotite. grains  I t grades from  I t a l s o c o n t a i n s numerous  scattered  of p y r r h o t i t e .  The  most n o t a b l e f e a t u r e s  veinlets.  o f the  s l i d e are. the  They a r e p a r a l l e l to' the b e d d i n g and appear t o  f o l l o w a s e t o f p a r a l l e l f r a c t u r e s , o r porous zones. the q u a r t z g r a i n s considerably The  pyrrhotite  closely associated  Some o f  w i t h the v e i n l e t s are  c o a r s e r than found e l s e w h e r e .  v e i n l e t s a r e v e r y i r r e g u l a r and tend t o p i n c h and  46 swell.  One of the beds near the v e i n l e t s show a .3 mm.  hand o f f s e t caused by p r e - m i n e r a l movement.  right  Upon e n c o u n t e r i n g  t h i s f e a t u r e , the p y r r h o t i t e f o l l o w s the j o i n t plane f o r a d i s t a n c e e q u a l t o the o f f s e t and then c o n t i n u e s a l o n g t h e same l a y e r as b e f o r e .  See p l a t e s 1 and 2.  THIN SECTION 289 B ' T h i s s e c t i o n i s c o a r s e l y s p o t t e d and banded w i t h s p o t s r a n g i n g up t o 4 mm. e x h i b i t markedly  In general, they  rounded o u t l i n e s , and a r e m a i n l y composed of  b i o t i t e and q u a r t z . entirely  i n diameter.  siltstone  I n some c a s e s , t h e b i o t i t e  i s almost,  a l t e r e d t o c h l o r i t e , w h i l e o t h e r s show v e r y  chloritization.  little  Some spots show a marked r e d u c t i o n i n g r a i n  s i z e around the b o r d e r s , g i v i n g a pronounced rimming e f f e c t . The percentage It  of p y r r h o t i t e i n the spots v a r i e s  i s almost always a s s o c i a t e d w i t h c l i n o z o i s i t e  greatly.  and r u t i l e .  The degree of c h l o r i t i z a t i o n o f the b i o t i t e i n the spots seems to be d i r e c t l y r e l a t e d t o the amount of c o n t a i n e d p y r r h o t i t e . THIN SECTION 315 A This s l i d e  shows w e l l s p o t t e d s l i g h t l y a r g i l l a c e o u s  stone i n which t h e spots range up t o 6 mm.  i n diameter.  siltThe  ground mass i s composed o f q u a r t z and b i o t i t e g r a i n s g e n e r a l l y l e s s t h a n .04 mm. i n d i a m e t e r .  The p r o p o r t i o n of q u a r t z t o  b i o t i t e i s a p p r o x i m a t e l y 60 - 40.  The ground mass c o n t a i n s  sparsely s c a t t e r e d grains of p y r r h o t i t e w i t h a s s o c i a t e d clinozoisite. There i s a- n o t a b l e l a c k o f b i o t i t e  i n the s p o t s .  there i s , i s concentrated i n the c e n t r e s .  What  The 'remainder i s  47 almost a l l q u a r t z g r a i n s over ory minerals.  .2 mm.  i n diameter  access-  There i s a d e c i d e d c o n c e n t r a t i o n of p y r r h o t i t e ,  e p i d o t e , and t o u r m a l i n e , i n p r a c t i c a l l y a l l the The  plus  spots.  e p i d o t e occurs as c l u s t e r s of s m a l l stubby occurs as  (a) s m a l l i s o l a t e d e u h e d r a l  crystals.  The  tourmaline  crystals,  and  (b) as a n h e d r a l c l o u d y masses or aggregates o f s m a l l  c r y s t a l s .which appear t o be r e p l a c i n g ; b i o t i t e . The  s p o t t e d band i s i n sharp c o n t a c t w i t h a h i g h l y  argillaceous layer.  T h i s l a y e r shows a c o n s i d e r a b l e amount o f  scattered r u t i l e crystals.  They do not s t o p a t  w i t h the s p o t t e d l a y e r , but c o n t i n u e 3 - 4  mm.  the'contact into  the  spotted l a y e r before f a d i n g out. THIN SECTION 315 B ' T h i s s e c t i o n i s made up of two d i s t i n c t bands.  The  c o n t a c t between them i s marked by a t h i n seam o f c h l o r i t e . On one was  s i d e i s a l a y e r of coarser a r g i l l a c e o u s s i l t s t o n e which  o r i g i n a l l y b i o t i t e enriched.  a l t e r e d and r e p l a c e d by The ance due  The b i o t i t e i s now  largely,  chlorite.  a r g i l l i t e l a y e r g r a d u a l l y assumes a m o t t l e d appearto the presence o f s m a l l c l u s t e r s o f q u a r t z g r a i n s  embedded i n a c r y p t o c r y s t a l l i n e s e r i c i t i c ground mass.  The  s i z e and number o f q u a r t z c l u s t e r s i n c r e a s e s as the d i s t a n c e from the c o n t a c t w i t h the s i l t y band i n c r e a s e s . The  a r g i l l a c e o u s matrix contains scattered r u t i l e  and i r r e g u l a r areas o f c a r b o n a t e .  The  crystals  percentage of r u t i l e  appears t o be g r e a t e s t near the c o n t a c t w i t h the s i l t y band.  48 THIN SECTION 540 A T h i s specimen i s c l a s s i f i e d as a v a g u e l y s p o t t e d siltstone.  The m a j o r i t y of the s l i d e c o n s i s t s o f a f i n e -  g r a i n e d m a t r i x o f q u a r t z g r a i n s w i t h a few i r r e g u l a r of b i o t i t e f l a k e s .  clusters  There i s a' pronounced development of  r u t i l e c r y s t a l s a s s o c i a t e d w i t h t h e b i o t i t e and r u t i l e . p a r t of the s l i d e has'been c a r b o n a t i z e d t o a. s l i g h t  One  extent.  S e v e r a l s m a l l b l u e - g r e y g r a i n s o c c u r i n the s e c t i o n . They have a v e r y h i g h i n d e x (1.80 t  ) and a r e e i t h e r p o s i t i v e  u n i a x i a l o r b i a x i a l p o s i t i v e w i t h - a low 2,V. f r i n g e n c e appeared t o be a p p r o x i m a t e l y the g r a i n s are l e s s than .03 mm. as a c c u r a t e .  The b i r e -  .030 - .040, but s i n c e  i n s i z e t h i s cannot be t a k e n  They show diamond shapes t o p y r a m i d a l o u t l i n e s  and may p o s s i b l y be sphene -- the c o l o u r does not seem t o be t h a t of .sphene p o s i t i v e l y i d e n t i f i e d i n s e c t i o n 241 B. The carbonated  area p r e v i o u s l y mentioned c o n t a i n s two  c a l c i t e g r a i n s which appear to be pseudomorphs.  The shape of  the o r i g i n a l c r y s t a l s i s o u t l i n e d by an u n i d e n t i f i e d mineral.  greenish  I t i s thought t h a t these g r a i n s may be pseudomorphs  a f t e r sphene.. THIN SECTION 340 B T h i s s e c t i o n appears t o be a r e l a t i v e l y pure s i l t s t o n e containing large well-rounded  spots up t o 5 mm. i n d i a m e t e r .  The s i l t y ground mass c o n t a i n s some a l b i t e w h i c h shows good t w i n n i n g . The spots show a d i s t i n c t tendency towards more o r l e s s b a r r e n cores surrounded by t h i n r i n g s of b i o t i t e .  I n some  49 cases the b i o t i t e has been b l e a c h e d and,.'partially r e p l a c e d by what i s thought to be The  epidote.  spots are c h a r a c t e r i z e d by c l u s t e r s ' o f s m a l l  c r y s t a l s a s s o c i a t e d w i t h t h e - b i o t i t e and by a•marked i n the c o n c e n t r a t i o n  of t o u r m a l i n e .  The  latter  rutile increase  generally  occurs i n i s o l a t e d e u h e d r a l c r y s t a l s up t o .04 mm. l o n g , !  i t was  but  a l s o f o u n d as minute i n c l u s i o n s i n a c o l o u r l e s s f i b r o u s  mineral.  This m i n e r a l was  properties.  Index 1.60  I,  found t o have the prismatic  0.010, l e n g t h s l o w , b i a x i a l n e g a t i v e , The  mineral  was  identified.  This  cleavage, birefringence 2 V moderate t o l a r g e .  i s thought to.be w o l l a s t o n i t e .  THIN SECTION 340  following  One  one  grain  C  specimen i s c l a s s i f i e d as an a r g i l l a c e o u s  siltstone.  I t resembles the more h i g h l y a l t e r e d p a r t s o f the ,one described.  The  s p o t t i n g i s not as pronounced, but  a l t e r a t i o n of the b i o t i t e and  the f o r m a t i o n  just  the  of r u t i l e i s  exactly similar. The-most i n t e r e s t i n g f e a t u r e of the b i o t i t e . now  I t has  i s the s e l e c t i v e a l t e r a t i o n  been s t r o n g l y b l e a c h e d , so t h a t i t i s  c o l o u r l e s s , and has been s e l e c t i v e l y r e p l a c e d  along  c l e a v a g e p l a n e s by v e r y t h i n n e e d l e - l i k e yellow-brown c r y s t a l s . They are thought to be n e e d l e s of THIN SECTION This  rutile.  415  s e c t i o n shows a v a g u e l y s p o t t e d p y r r h o t i t e - r i c h  a r g i l l a c e o u s s i l t s t o n e showing a g e n e r a l i n small evenly d i s t r i b u t e d grains.  enrichment of b i o t i t e  50 The  s p o t t i n g e f f e c t i s l a r g e l y due  t o more or l e s s  c i r c u l a r ' areas whiph have a marked i n c r e a s e .in the concent r a t i o n of p y r r h o t i t e .  The  p y r r h o t i t e i s v e r y n e a r l y always  a s s o c i a t e d w i t h c l i n o z o i s i t e w h i c h tends to form as an a u r e o l e around groups of p y r r h o t i t e g i v i n g the whole a circular The  outer  "spot"  outline.  c l i n o z o i s i t e occurs  as  g r a n u l a r aggregates which'  show a d i s t i n c t tendency to be e l o n g a t e d  p a r a l l e l to the  o v e r a l l banding. The  p e r i p h e r i e s of some of these  vague spots are marked  by a d i s t i n c t ' r i m of r u t i l e g r a i n s . The (albite).  spots c o n t a i n c l o s e g r a i n s The  of q u a r t z and f e l d s p a r  l a t t e r i s g e n e r a l i n l a r g e r and more  irregular grains. THIN SECTION 606  A  This s e c t i o n contains large well-rounded  spots i n a  biotite-rich, slightly argillaceous, siltstone. The  s p o t s . a r e l a r g e l y composed of coarse  g r a i n s of q u a r t z up to 2 mm.  irregular  i n d i a m e t e r and l a r g e i r r e g u l a r  g r a i n s of p y r r h o t i t e .3 - .6 mm. b i o t i t e i n the spots i s low and  in size.  The  percentage of  i s g e n e r a l l y o n l y found  c l o s e i y a s s o c i a t e d w i t h g r a i n s of p y r r h o t i t e which i n some cases appears t o r e p l a c e the b i o t i t e .  P r a c t i c a l l y a l l grains  of p y r r h o t i t e have a s s o c i a t e d c l i n o z o i s i t e . a l s o found a s s o c i a t e d w i t h  At t i m e s , ,±t i s  rutile.  There i s a g e n e r a l i n c r e a s e i n the c o n c e n t r a t i o n  and  51 s i z e o f the t o u r m a l i n e g r a i n s i n the spots as compared t o the s u r r o u n d i n g ground mass. THIN SECTION 606  B  This s l i d e i s very s i m i l a r  t o 606 A showing w e l l d e f i n e d  spots w i t h c o n c e n t r a t i o n of p y r r h o t i t e ,  rutile,  and  t o u r m a l i n e c e n t r e and a b a r r e n r i m of coarse q u a r t z . s p o t s are connected by i r r e g u l a r  The  s t r i n g e r s composed of  p y r r h o t i t e g r a i n s and a s s o c i a t e d c l i n o z o i s i t e , and o c c a s i o n a l .rutile.  These c o n n e c t i n g s t r i n g e r s are p a r a l l e l t o the  g e n e r a l f a i n t banding seen i n the arrangement of the g r a i n s on the m a t r i x .  biotite  52 SELECTIVE STAINING The was  f o l l o w i n g method of s e l e c t i v e s t a i n i n g of f e l d s p a r  employed. The  specimen t o be s t a i n e d was  i m a t e l y 1 mm.  i n thickness.  I t was  f i r s t ground t o approxt h e n e t c h e d w i t h hydroi  f l u o r i c a c i d f o r one  minute, washed, and  placed i n a  s o l u t i o n of a s o d i u m - s i l i c a t e f o r f i v e m i n u t e s . sodium s i l i c a t e was specimen was  The  removed by washing g e n t l y , and  then p l a c e d  hot excess  the  i n a b a t h of F u c h i a n dye.  A.fter  t e n or f i f t e e n minutes the c h i p was. removed, a l l o w e d  to  dry,  •and made i n t o a t h i n s e c t i o n i n the u s u a l manner. A number of s t a n d a r d s were r u n on specimens of  rocks  which were known t o c o n t a i n f e l d s p a r . The dye  t e s t s were s u c c e s s f u l , i n t h a t they proved t h a t  s t a i n e d f e l d s p a r , but had no e f f e c t on o,uartz, and  i t c o u l d be c o n c l u d e d t h a t any  s t a i n e d m a t e r i a l was  the that  most  probably f e l d s p a r . The  t e s t s i n d i c a t e d , however, t h a t I n one  rock a c e r t a i n  f e l d s p a r would r e a c t p o s i t i v e l y t o the s t a i n i n g w h i l e  in  a n o t h e r r o c k , the same f e l d s p a r under e x a c t l y the same t r e a t ment, would remain u n a f f e c t e d . t h a t w h i l e the method u s e d , may, determining  T h e r e f o r e i t must be  concluded  i n some cases h e l p i n  the presence of f e l d s p a r the f a c t t h a t the  does not r e a c t p o s i t i v e l y i s no guarantee t h a t i t does contain feldspar.  specimen not  53  P l a t e 1. P h o t o m i c r o g r a p h o f p y r r h o t i t e - r i c h l a y e r s  in thin  section  left-  289A. K a g . l 6 X . N o t e how p y r r h o t i t e f o l l o w s  hand o f f s e t .  P l a t e 2. P h o t o m i c r o g r a p h o f l e n s veinlet  shown i n P l a t e  of p y r r h o t i t e  1. I J a g . l 6 X .  connected  with  P l a t e 3. Photomicrograph of pronounced s p o t t i n g i n t h i n s e c t i o n 264A» Note c o n c e n t r a t i o n of b i o t i t e i n t h e c e n t r e and r i m of b i o t i t e - f - r e e quafctz and f e l d s p a r . Dark m i n e r a l i n ground mass i s b i o t i t e . I,Iag.l6X.  P l a t e 4. Photomicrograph of l a r g e s p o t s i n t h i n s e c t i o n 340A. Note pronounced c o n c e n t r a t i o n of b i o t i t e around the r i m of t h e l a r g e s p o t . The s m a l l b l a c k g r a i n s a r e c r y s t a l s of r u t i l e . I.:ag.l6X.  55  P l a t e 5. Photomicrograph showing same s p o t s seen i n P l a t e 4, hut taken w i t h crossed N i c o l a . Note i n c r e a s e i n g r a i n s i z e of q u a r t z w i t h i n the s p o t s . I»Iag.l6X.  P l a t e 6. Photomicrograph showing l a r g e g r a i n s of t o u r m a l i n e c o n c e n t r a t e d i n t h e spors i n t h i n s e c t i o n 160B. Tourmaline shows l i g h t t o dark grey and e x h i b i t s a g r a n n u l a r t e x t u r e . Mag.l6X.  P l a t e 7. Photomicrograph of t o u r m a l i n e g r a i n i n l a r g e r of two spots seen i n P l a t e 6. Predominant g r a n n u l a r m i n e r a l i s t o u r m a l i n e . B l a c k g r a i n s are r u t i l e . LIag.50X.  57  FIG.1.  GEOLOGIC MAP - SULLIVAN MINE.  A f t e r C O . Swan son' and H.C.Gunning Trans. C.I.M.M. 1945  STRATIGRAPHIC SECTION OF THE ALDRIDGE FORMATION CUT BY SULLIVAN LIBRARY DRILL HOLS 249. University of British Columbia I l l u s t r a t e d - b y photographs o f a v a i l a b l e specimens. Vancouver, Ca^oj t g r a p h s i l l u s t r a t e the t h i n b e d d i n g t h a t i s c h a r a c t e r i s t i c o f t h e s e sedimentary r o c k s . They a l s o show the g e n e r a l c h a r a c t e r of t h e s p o t t i n g and the g r a d u a l i n c r e a s e i n the s i z e o f the spots w i t h i n c r e a s e i n depth. p h o  0  FOOTAGE 134  138  Contact with s i l l .  No specimen a v a i l a b l e .  S i l l i c i o u s a r g i l l i t e . No v i s i b l e Prominent f r a c t u r e s .  spotting,  T h i n bedded s i l t s t o n e w i t h numerous soots.  small  146 Spotted a r g i l l a c e o u s s i l t s t o n e .  Vaguely s p o t t e d s i l t s t o n e .  153  Spotted s i l t s t o n e grading into a pyrrhotiter i c h layer. Vaguely s p o t t e d s i l t s t o n e .  Vaguely s p o t t e d  silty  argillite.  154  Biotite-rich argillaceous siltstone c o n t a i n i n g a p a t c h o f c o a r s e b i o t i t e and sphalerite.  Strongly spotted a r g i l l a c e o u s s i l t s t o n e ; s p o t s up t o 1 m.m. i n d i a m e t e r .  160  Argillaceous spotting.  s i l t s t o n e . Note absence o f  Spotted a r g i l l a c e o u s s i l t s t o n e .  132  195  I n t e r b e d d e d s i l t y and a r g i l l a c e o u s l a y e r s . The s i l t y l a y e r s a r e r i c h i n b i o t i t e and c o n t a i n numerous s m a l l s o o t s .  Uniformly spotted a r g i l l a c e o u s s i l t s t o n e . The s p o t s a r e l a r g e l y composed o f b i o t i t e f l a k e s , w h i c h i n some a r e a s , have a b l e a c h e d appearance caused by c h l o r i t i z a t i o n .  Fine-grained  210  S t r o n g l y s p o t t e d s i l t s t o n e . The s p o t s a r e l a r g e l y composed o f b i o t i t e and p y r r h o t i t e  Fine-grained  Silty  241  argillaceous siltstone.  argillaceous siltstone.  argillite.  S p o t t e d a r g i l l a c e o u s s i l t s t o n e . The spots c o n t a i n a h i g h percentage o f p y r r h o t i t e .  Silty  argillite.  Silty  argillite.  246 Well-spotted argillaceous s i l t s t o n e .  Argillaceous s i l t s t o n e .  264  Spotted p y r r h o t i t e - r i c h layer  I n t e r b e d d e d s p o t t e d and n o n - s p o t t e d beds. The s p o t s a r e l a r g e l y composed o f c o a r s e biotite flakes.  Highly  a r g i l l a c e o u s band.  Argillaceous s i l t s t o n e layer containing p a r a l l e l veinlets of pyrrhotite. Argillaceous s i l t s t o n e .  two  289  C o a t s e l y s p o t t e d s i l t s t o n e . Spots a r e l a r g e l y composed o f coarse q u a r t z and biotite.  S l i g h t l y argillaceous s i l t s t o n e containing c o a r s e i r r e g u l a r s p o t s which show b l e a c h e d rim e f f e c t . 315 Highly  340  415  606  argillaceous layer.  Very c o a r s e l y s p o t t e d s i l t s t o n e . The s p o t s have a core o f q u a r t z surrounded by a r i m of b i o t i t e f l a k e s .  Argillaceous s i l t s t o n e layer with large i r r e g u l a r s p o t s . The spots c o n t a i n l a r g e amounts o f p y r r h o t i t e .  Very coarsely spotted a r g i l l a c e o u s s i l t s t o n e . The spots a r e l a r g e l y composed o f c o a r s e q u a r t z g r a i n s and l a r g e i r r e g u l a r g r a i n s o f pyrrhotite.  

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