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The Lost Horse intrusives, Copper Mountain, B.C. Richardson, Paul William 1950

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/fro  fl?  Cap  .I  THE LOST HORSE INTRUSIVES COPPER MOUNTAIN, B.C.  Paul W i l l i a m  A T h e s i s submitted  Richardson  i n P a r t i a l F u l f i l m e n t of  the Reauirements f o r the Degree of MASTER OF APPLIED SCIENCE i n the Department of GEOLOGY  THE UNIVERSITY OF BRITISH COLUMBIA May, 1950  e, '9-.ro  THE LOST HORSE  I N T R U S I V E S  COPPER MOUNTAIN, B.C.  ABSTRACT  The L o s t Horse i n t r u s i v e s are minor p l u t o n i c occurring The  bodies  t o the n o r t h and n o r t h e a s t of Copper Mountain, B.C.  rocks of the i n t r u s i v e s were c l a s s i f i e d by megascopic  examination.  I t was f e l t  that m i c r o s c o p i c examinations  rocks might b r i n g out r e l a t i o n s h i p s which were megascopically.  Such was the case.  of the  obscure  The nine specimens  examined, which were d i v i d e d m e g a s c o p i c a l l y  i n t o s i x types,  were found t o c o n s i s t of only three d i s t i n c t rock t y p e s . The obscured  i d e n t i t y of the three rock types had been  by weathering  alteration.  Now  and hydrothermal  that  and by d i f f e r e n t types of  hydrothermal  the changes brought about by  weathering  a l t e r a t i o n are r e c o g n i z e d , fewer., rock  types w i l l appear .on the d e t a i l e d maps and, i n a d d i t i o n , of a l t e r a t i o n may be o u t l i n e d .  zones  PO REWARD  The specimens s t u d i e d i n t h i s t h e s i s were c o l l e c t e d d u r i n g the summer of 1949 when the w r i t e r was employed a t Copper Mountain, B.C. by the Granby C o n s o l i d a t e d Smelting, and Power Company, L i m i t e d .  Mining,  The l a b o r a t o r y work  was c a r r i e d out d u r i n g the winter of 1949-1950 at the U n i v e r s i t y of B r i t i s h Columbia. Thanks are due to Mr. K e i t h C. Pahrni and Mr. J . Harvey Parliament  f o r t h e i r advice d u r i n g the f i e l d season and  Dr. H.C. Gunning, Dr. K. Dep. Watson, and Dr. L. D o l a r Mantuani f o r t h e i r h e l p i n c a r r y i n g out the l a b o r a t o r y work and i n w r i t i n g the manuscript.  Thanks are a l s o due to Mr. J.A.  Donnan f o r p r e p a r i n g the t h i n s e c t i o n s .  CONTENTS Page Foreward Abstract Introduction Copper Mountain Area Introduction ' Wolf Creek Formation Lost Horse I n t r u s i v e s Copper Mountain Stock, V o i g t and Smelter Lake Stocks D e s c r i p t i o n of Methods  1 2 2 2 3 3 6  .  ...  6  R e s u l t s of the D e t a i l e d D e s c r i p t i o n s Definitions Comparison of the I n v e s t i g a t e d specimens  9 9 10  Alteration  13  Conclusions  18  References  19  Appendix  A-l-A-33  TABLES  Figure 1 Figure 5 Figure 6  Figure 7  -  -  Page  Table of M i n e r a l V a r i a t i o n i n the Copper Mountain Stock  5  Table of the Modal Composition of the Lost Horse I n t r u s i v e s Table of Range i n Compositions of A u g i t e D i o r i t e and A u g i t e Syenite  ..  12  Table of A l t e r a t i o n and Replacement i n the T e n ' I n v e s t i g a t e d Specimens ...  15  ILLUSTRATIONS Figure 2 Figure 3  Figure 4  -  -  11  Page following  Graph of Chemical V a r i a t i o n i n the Copper Mountain Stock  5  Graph of Modal Composition versus P o s i t i o n i n the Copper Mountain . Stock  5  Fuming Box  Map of the Copper Mountain Area  8  at end of t h e s i s .  INTRODUCTION During  the summer of 1949  the w r i t e r was  engaged i n  d e t a i l e d mapping of an area n o r t h of Copper Mountain, B.C.  In  the area were many exposures of the Lost Horse i n t r u s i v e s which are minor p l u t o n i c bodies  i n v a d i n g the Wolf Greek v o l c a n i c s .  The L o s t Horse i n t r u s i v e s are thought to be g e n e t i c a l l y to  the Copper Mountain stock and  t h e r e f o r e to the  related  important  copper m i n e r a l i z a t i o n of the r e g i o n . In the f i e l d  the rocks of the Lost Horse i n t r u s i v e s  were mapped by megascopic examination. f i e l d work d u r i n g the 1950  I t was  felt  that the  season would be g r e a t l y aided by a  m i c r o s c o p i c examination  of the major rock t y p e s .  microscopic examination  c o u l d l e a d to one  of two  Such a. results.  E i t h e r the s u b d i v i s i o n s , which were e s t a b l i s h e d m e g a s c o p i c a l l y , could be f u r t h e r s u b d i v i d e d , or some s u b d i v i s i o n s c o u l d be combined. It  can be seen t h a t a r e l a t i v e l y s m a l l amount,of  m i c r o s c o p i c work would g r e a t l y i n c r e a s e the speed accuracy  of the f i e l d work.  and  2  H  II  -  The Copper Mountain Area ( l )  A - Introduction. The  Copper Mountain area l i e s  120 miles east of  Vancouver, B.C., and 10 miles south of P r i n c e t o n , B.C. The  o l d e s t rocks i n the area c o n s i s t e n t i r e l y of  v o l c a n i c m a t e r i a l which V i c t o r Dolmage t e n t a t i v e l y c o r r e l a t e s w i t h the N i c o l a s e r i e s of T r i a s s i c age. The v o l c a n i c rocks have been named the Wolf Creek f o r m a t i o n .  I t i s thought a t  the present time t h a t the beds have a n o r t h e r l y s t r i k e and gentle dips to the west. In the Copper Mountain a r e a , two or three r a t h e r l a r g e a u g i t e d i o r i t e stocks i n t r u d e the v o l c a n i c s . The l a r g e s t of these i n t r u s i v e s i s the Copper Mountain s t o c k .  To  the n o r t h and n o r t h - e a s t of the Copper Mountain s t o c k l i e the L o s t Horse I n t r u s i v e s . and  These i n t r u s i v e s appear t o be small  i r r e g u l a r and t o be made up of s e v e r a l d i s t i n c t rock t y p e s . I n t r u d i n g these  felsite, to  pegmatite,  late Tertiary.  stocks and minor plutons are many  and a n d e s i t e dykes which range i n age down The n o r t h end of the area i s covered by l a v a  flows of Eocene o r l a t e r age. B - Wolf Creek The  Formation. Wolf Creek v o l c a n i c s are made up of t u f f s ,  and b r e c c i a s . In n e i g h b o u r i n g  They form the country rock throughout  the a r e a .  areas, t r u e sediments have been observed  s e r i e s which have a i d e d the c o r r e l a t i n g of these rocks M Numbers i n brackets r e f e r to r e f e r e n c e s .  flows,  i n the  with  3  Dawson's N i c o l a s e r i e s of T r i a s s i c  age.  Throughout the area the s t r u c t u r e i s v e r y obscure because of the p a u c i t y of r e c o g n i z e a b l e the n o r t h e a s t  P a r a l l e l to  c o n t a c t of the Copper Mountain s t o c k the v o l c a n i c s  have been sheared occur i n t h i s  bedding.  and f r a c t u r e d .  The Copper Mountain  orebodies  zone.  C - L o s t Horse I n t r u s i v e s The Lost Horse i n t r u s i v e s occur to the n o r t h and northeast  of the Copper Mountain s t o c k between i t and the V o i g t  and Smelter Lake s t o c k s .  The L o s t Horse i n t r u s i v e s are  i r r e g u l a r i n o u t l i n e and are p o o r l y exposed. d i s t i n c t types.  One  There are two  i s a l i g h t , a c i d augite d i o r i t e .  The  other • i s a p i n k i s h grey^ b i o t i t e monzonite or s y e n i t e . Near d e p o s i t s of ore m i n e r a l s ,  the i n t r u s i v e s are  impregnated with s m a l l amounts of p y r i t e and c h a l c o p y r i t e , and the f e l d s p a r s are e x t e n s i v e l y a l t e r e d to s e r i c i t e . these  rocks were m i n e r a l i z e d by s o l u t i o n s which, a c c o r d i n g to  Dr. Dolmage, a p p a r e n t l y The composition the compositions stocks  In places  came from the Copper Mountain  stock.  of the Lost Horse i n t r u s i v e s i s so s i m i l a r to of the Copper Mountain, V o i g t , and Smelter Lake  that the Lost Horse i n t r u s i v e s may be c l o s e l y r e l a t e d  to them i n time as w e l l as i n o r i g i n . D - The Copper Mountain Stock. The Copper Mountain stock i s e l l i p t i c a l The major a x i s , extending  i n plan.  northwest, i s f i v e miles l o n g and  the minor a x i s i s three miles l o n g .  The Copper Mountain ore  4 d e p o s i t s l i e immediately s i d e of the  stock.  the west and  Other d e p o s i t s of ore minerals  south contacts of the  The composition  o u t s i d e the c o n t a c t of the  northeast l i e outside  stock.  stock i s d i v i d e d i n t o t h r e e zones.  I t ranges i n  from an outer zone of syenogabbro to an i n n e r core  of n e a r l y pure f e l d s p a r pegmatite. i n f i g u r e s 1, 2, and 3. compositional  The  The  s t o c k has  v a r i a t i o n may  be  the f o l l o w i n g three  peculiarities:  (1)  Both quartz and f e l d s p a t h o i d s are  (2)  Large a p a t i t e c r y s t a l s are abundant.  (3)  Abnormal amounts of o r t h o c l a s e occur with the and The  abrupt  seen  dioritic  absent.  gabbroic  phases.  contacts of the i n t e r m e d i a t e and  and can be mapped i n the f i e l d  i n n e r zones are  (see f i g u r e 3 ) .  Within  the three zones, however, there are v a r i a t i o n s which are gradual to permit  too  mapping the v a r i o u s phases of which each i s  composed. S u i t e s of minerals  from s e v e r a l periods of contact  metasomatism have been r e c o g n i z e d around and first  s u i t e occurs  s t o c k and  i n the sheared  does not penetrate  sulphides were d e p o s i t e d .  The  minerals  and  Vast amounts of b i o t -  small amounts of c o p p e r - i r o n second stage, which d e p o s i t e d  e p i d o t e , z o i s i t e , s c a p o l i t e , and andesine, m e t a l l i c minerals  The  zone to the n o r t h e a s t of the  the gabbro.  i t e , a u g i t e , and p l a g i o c l a s e and  i n the s t o c k .  c o n t a i n s few  i s of no economic importance.  cut and b l e a c h b i o t i t i z e d r o c k s .  The  or no  These  l a s t stage i s  FIGURE 1 Table of M i n e r a l V a r i a t i o n i n the Copper Mountain Stock ( A f t e r D>. Dolmage) Percent O Jf M i n e r a l s Present B i o t i t e Magne Plagioclase Ortho- A u g i t e clase tite  Position  Outer Zone  Syenogabbro to Syenodiorite  50 (Lab-And)  10-15  50 ( O l i g . A n d - O l i g )  12-20  2-11  4  25  10,12  3-4  30-40  Other Minerals  IntermedSyenodiorite iate to Zone Monzonite  50 ( O l i g o c l a s e )  25  15  Small  Small  Hornblende  55 (Afc-Olig)  35  7  Small  Small  Hornblende  Inner Zone  30 ( A l b i t e )  Small  -  Pegmatite  60 Includin g M i c r o c l i ne  Penninite  W S  *ft  h.  6  r e s p o n s i b l e f o r most of the ore d e p o s i t i o n . green b i o t i t e , and  i r o n and  i n the b i o t i t i z e d r o c k s .  Orthoclase,  copper i r o n s u l f i d e s form v e i n l e t s  This stage of metasomatism  has  e f f e c t e d a wide zone w i t h i n the i n t r u s i v e as w e l l as the surrounding  and n o r t h e a s t  1  V o i g t and  Stocks.  Smelter Lake stocks  occur  to the  north  of the Copper Mountain stock r e s p e c t i v e l y .  area between the two great  alte  volcanics .  B - V o i g t and Smelter Lake The  albite,  thickness  stocks  i s covered by T e r t i a r y lavas of  beneath which the stocks  Unlike  probably  are n e a r l y u n i f o r m  and  i n composition.  c o n s i s t of dark grey, medium grained augite  no  join.  the Copper Mountain stock, the V o i g t  Smelter Lake stocks  The  diorite  They  or  s y e n o d i o r i t e composed e s s e n t i a l l y of p l a g i o c l a s e , augite, and hornblende w i t h s m a l l amounts of o r t h o c l a s e and Accessories  are a p a t i t e and magnetite.  The  biotite.  p l a g i o c l a s e ranges  from andesine to l a b r a d o r i t e . The  m i n e r a l i z a t i o n i n and around these stocks  differs  from the Copper Mountain m i n e r a l i z a t i o n i n t h a t the opaque minerals  are hematite, magnetite, and  p y r i t e r a t h e r than  bornite. I l l - D e s c r i p t i o n of Methods. A standard descriptions.  petrographic  microscope was  used f o r a l l  In some s l i d e s the  o r t h o c l a s e was  very  to d i s t i n g u i s h from the p l a g i o c l a s e .  The  use  difficult  of o i l s of known  7  refractive altered  index was  that grains  As a r e s u l t , the the  attempted but immersed i n the  sodium c o b a l t i n i t r i t e  (2).  Rosiwal analyses  The  a c i d and The  are  o i l were not  potassium f e l s p a r was  s l i d e s with h y d r o f l u o r i c  facilitates  the f e l d s p a r s  so  transparent.  recognized by  etching  then s t a i n i n g them w i t h  s t a i n i n g of s l i d e s a l s o  (3).  f o l l o w i n g i s a b r i e f summary of the  procedure  used i n s t a i n i n g s l i d e s . (1)  The  minerals are  ^2)  The  cover g l a s s  with (3)  identified qualitatively. i s removed and  The  under s i d e of the  glass from the HP  glass  The  of the  s l i d e i s covered w i t h The  c e l l u l o i d protects  s l i d e i s set i n a l e a d t r a y and  box  above a one  f o r 40  the  to 50 seconds.  tray i s HP  i s heated to 65° G by p l a c i n g the box  bottom  s i x inches  h a l f i n c h bunsen flame.  A f t e r being removed from the fuming box,  to 40  placed  i n the  the  covered w i t h concentrated sodium c o b a l t i n i t r i t e 30  the  fumes.  i n a l e a d fuming box  (5)  balsam i s cleaned o f f  gasoline.  c e l l u l o i d d i s s o l v e d i n acetone.  (4)  the  seconds.  The  section is  solution for  s t a i n i s v e r y g e n t l y washed o f f  the  s l i d e w i t h water. (6)  The  s e c t i o n i s d r i e d f o r 24 hours and  then a cover  glass  i s cemented on top of the s t a i n e d r o c k s e c t i o n w i t h a c o l d s o l u t i o n of balsam i n x y l o l .  The  balsam becomes hard i n about  a week. The  s t a i n i n g treatment c o l o r s potassium  feldspar  8  yellow, roughens and darkens p l a g i o c l a s e , and does not  affect  quartz at a l l . The  concentrated sodium c o b a l t i n i t r i t e  prepared by adding 15 m i l l i l i t r e s 25 m i l l i l i t r e s  of water to 12.5  of g l a c i a l a c e t i c a c i d  grams of Go  and 20 grams of sodium n i t r i t e .  The  l e a d o n e * s i x t e e n t h of an i n c h t h i c k . The modal compositions by means of Rosiwal a n a l y s e s . the percentages  solution is  (N0 ) 3  2  . 6  and H0 g  l e a d box i s made of sheet (Figure 4).  of the s l i d e s were obtained  S l i d e S-^^  was  t e s t e d twice  and  of the main minerals were found t o be as  follows: Before Staining  After Staining  Augite  19,2%  Labradorite  51.0$  50.8$  Orthoclase  18.5$  21.2$  In counted  18.7%  a d d i t i o n to the i n c r e a s e i n amount of o r t h o c l a s e  after staining, this  comparison shows that the  analyses can be repeated w i t h f a i r a c c u r a c y . the appendix,  Rosiwal  Consequently,  in  the amounts of the minerals present i n each  s l i d e have been given to the n e a r e s t p e r c e n t . Although a Rosiwal a n a l y s i s can give the modal composition of a s l i d e a c c u r a t e l y , a s l i d e i s not a p e r f e c t sample of a rock specimen and a specimen i s not a p e r f e c t sample of a body of rock.  Consequently,  the author does not  wish t o emphasize the exact modal compositions specimens.  of the  Only general comparisons and c o n c l u s i o n s are  justified,  F I G U R E  -4* - F U M I N G  B O X  9  IV  R e s u l t s of the D e t a i l e d D e s c r i p t i o n s .  A - Definitions. The  v a r i o u s rocks of the Copper Mountain area have  been g i v e n code symbols.  The v o l c a n i c s are designated by V  plus a s u b s c r i p t , the dykes by D plus a s u b s c r i p t , and the various p l u t o n i c i n t r u s i v e s by S plus a s u b s c r i p t . Horse i n t r u s i v e s are a l l S r o c k s .  The L o s t  The numerical s u b s c r i p t s  do not s i g n i f y a n y t h i n g g e o l o g i c a l l y ; each time a new rock i s encountered  the next unused s u b s c r i p t i s assigned to i t .  The  l e t t e r a f t e r the s u b s c r i p t i n d i c a t e s the number of the specimen. F o r example, Sg g s i g n i f i e s  t h a t the rock i s the second  spec-  men of the rock type S^. The  rock types i n v e s t i g a t e d i n t h i s t h e s i s and t h e i r  d e f i n i t i o n s are as f o l l o w s : (1)  S]_ -  Massive  coarse g r a i n e d grey green  feldspathic  w i t h a u g i t e and b i o t i t e . (2)  -  L i g h t g r e e n i s h t o green medium g r a i n e d to coarse grained f e l d s p a t h i c rock with some pale augite.  It is like  green  but has a d e f i n i t e  greenish  color. (3)  S  -  L i g h t g r e e n i s h to white monzonite of medium t o  0 coarse g r a i n e d g r a n i t i c t e x t u r e and massive character.  I t contains mostly f e l d s p a r and  p r a c t i c a l l y no m a f i c s . (4)  Sg -  G r e y i s h green t o p i n k i s h s y e n i t e w i t h a f a i r amount of mafics, but l e s s than 15%. i s medium t o coarse g r a i n e d  granitic.  The t e x t u r e  10  (5)  S  (6)  SJ_Q-  -  Very l i g h t a c i d a u g i t e B i o t i t e monzonite.  diorite. P i n k i s h grey with o r t h o c l a s e ,  p l a g i o c l a s e , and numerous s m a l l f l a k e s of b i o t i t e . (7)  S - Q - F a i n t l y pink to p i n k i s h medium grey, coarse g r a i n e d monzonite w i t h about 10$ a u g i t e and 1 or 2% b i o t i t e  B - Comparison of the i n v e s t i g a t e d The  Specimens.  composition of a l l the specimens are l i s t e d i n  f i g u r e s 5 and 6.  I t may be seen t h a t f o u r d i s t i n c t  types of  rock are r e p r e s e n t e d . / - S „ - Specimens S~ S,,,-., S,, „, S._ . , ^ s o O-ii On o-0 o-B and Sg__^ are s i m i l a r to each o t h e r . f e l d s p a r i s very close  of the  to the a n d e s i n e - l a b r a d o r i t e boundary.  These rocks f i t i n t o the group Sg. classified  The composition  Specimen S^  B  was  i n the f i e l d as S^ r a t h e r than Sg because of the  l i g h t c o l o r of the a u g i t e .  In the hand specimen, S_ . 6—A  a p p a r e n t l y c o n t a i n s a great deal of o r t h o c l a s e but micros c o p i c a l l y i t i s seen to be t y p i c a l , Sg. the f e l d s p a r i s caused  by i r o n s t a i n .  t h a t p o s s i b l y the rock type S S  &  - Specimens  s i m i l a r to each o t h e r . Specimen Sg_^ appeared  x  g  I t may be concluded  does not e x i s t .  S _ , S 5  The pink c o l o r i n  A  g  ^,and S  1 Q  _  A  a l s o are  The rocks a l l f i t i n t o the group Sg. d i f f e r e n t m e g a s c o p i c a l l y because of  extensive a l t e r a t i o n to epidote.  S ^ Q _ ^ looked i n the hand  specimen as i f i t contained a c o n s i d e r a b l e amount of orthoc l a s e and some b i o t i t e . l a t t e r was p o s s i b l y  The former was i r o n s t a i n and the  chlorite.  FIGURE 5 Table of the Modal Composition of the Lost Horse I n t r u s i v e s . Rock SpeType cimen s  l  S  l-A  S  3  S  3-A  S  3  S  3-B  S  3  S  3-C  5  S  5-A  S  3  S  5-B  S  3  S  6-A  S  5  S  9-A  S  10-A  S  ll-A  s  S  l l  Aug.  %  Plag  Como Plag  19  51  27  73  A n  40-45  21  76  A n  47-52  31  67  A n  55-60  19  76  A n  5-10  17  82  An  15  82  A n  50  5  92  A n  10  16  77  An  15  1%  26 Quartz «  % Ortho  " 55 A n  A n  Biotite  %  Magne+Ue Hematite  21  4*  4*  --  —  <4  —  —  <*  -—  —  --  4 5  •  --  —  --  1 Q  50  %  48  —  1 *  % Apatite  --  < 1/2  < 1/2  1/2  % Sphene —  < 1/2  —  1  2  --  1  l/2  1/2  2i"  1  1/2  1/2  1/4  1*  1/4  --  2  1  3  2  —  ---  <* 2*  —  4*  4*  --  ll  —  FIGURE 6 Table  o f Range i n C o m p o s i t i o n s  Rock Type  Specimens  S : AugiteDiorite  ^3-A^3-B 3-C' 5-B  3  5 Augite syenite S  :  S  S  S  S  S  B  Percent Augite  Percent Plagio  15-31  67,82  5-A 10-  5-19 A  and A u g i t e  Comp. Plagio.  Percent Percent Percent H e m a t i t e A p a t i t e Sphene  An  6-A  9-A  of Augite^ D i o r i t e  76-92  An An  Percent Magnetite  Syenite  o-ii  o -<i  A A s-is  1 -2  0-2t  o -<i  2 - 3  1  n  4 5  5  1 Q  -  -2  13  S  - Specimen S  n  . was  c o l l e c t e d near the  margin of the Copper Mountain s t o c k and S  - Specimen S  n  The  syenogabbro.  i s an augite monzonite. However,  A  X X  XX  as may  n n  is typical  outer  be seen i n t a b l e I I I , the rock i s s i m i l a r to  S^^.  main d i f f e r e n c e i s that there i s twice as much o r t h o c l a s e  i n S,.  „ as i n S, . i""#*  In a d d i t i o n there i s s l i g h t l y over  percent quartz i n S-J_-J__ .  No  a  g e n e r a l i t i e s can be made on  one two  specimens c o l l e c t e d over a mile apart but the author wishes to point out the s i m i l a r i t y as being v e r y  interesting.  V Alteration. I t may  be concluded  from  the previous s e c t i o n t h a t  the L o s t Horse i n t r u s i v e s are made up of two a u g i t e d i o r i t e and a u g i t e s y e n i t e .  main kinds of rock,  M e g a s c o p i c a l l y i t appeared  that there were other rock types p r e s e n t .  The  reasons f o r  t h i s i s the v a r i a t i o n i n the c o l o r of the a u g i t e and presence  of d i f f e r e n t types of a l t e r a t i o n . The  reasons  a u g i t e i s obscure apparent  the  f o r the v a r i a t i o n i n the c o l o r of'the  but the d i f f e r e n t types of a l t e r a t i o n were  m i c r o s c o p i c a l l y (Figure 7). I  n  s  3 _ a > 3-B> S  a  n  d  S  3-C>  o  r  better, i n typical  Sg,  there i s moderate a l t e r a t i o n to c l a y m i n e r a l , s e r i c i t e , a little  carbonate,  is S ,  was  3  augite.  and a l i t t l e  mistaken  f o r S5  differs  epidote.  Specimen Sg g, which  because of the l i g h t  g r e a t l y i n appearance from  because the f e l d s p a r s are s t a i n e d w i t h red i r o n  c o l o r of the typical oxide.  S3  14  Specimen S,_ ^ i s t y p i c a l Sg. products.are c l a y mineral and s e r i c i t e . a l l y had the same composition as S  c  r  The main  alteration  Specimen S  , but the main  originsecondary  minerals are epidote and c l i n o z o i s i t e r a t h e r than c l a y mineral. Specimen S _ ^ 1 0  than k a o l i n i z e d  has dark green a u g i t e and e p i d o t i z e d r a t h e r feldspar.  15 FIGURE 7 Table of A l t e r a t i o n an6V Replacement i n the Ten Specimens. Rock Type S  VA S  S  3  A l t e r a t i o n and Replacement  Specimen  l  S  S  S  S  3-B  3-C  5"B  6-A  5-A  Investigated  Augite Plag.  -  Orthoclase  Unaltered Partly altered sericite.  -  Cloudy.  Augite  -  Plag.  -  P a r t l y a l t e r e d to c l a y mineral and a l i t t l e c l i n o z o i s i t e P a r t l y r e p l a c e d by carbonate P a r t l y to e p i d o t e and s e r i c i t e  Augite  -  Plag.  -  Augite  -  Plag.  -  Augite  -  Plag.  -  Augite  -  Plag.  -  Augite  -  Plag.  -  to f i n e g r a i n e d  About 10% a l t e r e d t o c h l o r i t e ( ? ) and/or s e r p e n t i n e ( ? ) P a r t l y altered to clay mineral, s e r i c i t e , and some c l i n o z o i s i t e . Some p y r i t e i s p r e s e n t . About 5%-10% a l t e r e d to clay m i n e r a l , carbonate,and s e r i c i t e . E x t e n s i v e l y a l t e r e d to c l a y m i n e r a l , carbonate, and s e r i c i t e . R e l a t i v e l y u n a l t e r e d , some c l a y mineral. Moderate amounts of c l a y m i n e r a l , sericite, clinozoisite,and chlorite. More than 50% r e p l a c e d by c h l o r i t e and carbonate - not c l a y mineral. E x t e n s i v e l y a l t e r e d to s e r i c i t e , c l i n z o i s i t e , e p i d o t e , and a l i t t l e clay mineral. I t i s also stained red. Some p y r i t e i s p r e s e n t . P a r t l y to c l a y m i n e r a l , carbonate, and c l i n o z o i s i t e . E x t e n s i v e l y , t o . c l a y m i n e r a l . Some s e r i c i t e , c l i n o z o i s i t e , a n d epidote Some c h a l c o p y r i t e i s p r e s e n t .  16  S  5  S  Augite  S-A  Flag.  S  Augite  10-A  Flag.  S  l l  S  Augite Flag. Ortho.  ll-A  -  H e a v i l y r e p l a c e d by the ground-. mass, carbonate, and a l i t t l e clay mineral. E x t e n s i v e l y to s e r i c i t e , epidote, clinozoisite,and chlorite. Some p y r i t e i s present. Relatively unaltered, a l i t t l e c l i n o z o i s i t e and c h l o r i t e . P a r t l y a l t e r e d to c l i n o z o i s i t e , s e r i c i t e , epidote,and c l a y mineral. There i s a l i t t l e i r o n s t a i n . Relative unaltered. S l i g h t l y t o s e r i c i t e ' a n d e"pidote. P a r t l y t o s e r i c i t e and c l a y mineral.  Note; The f i n e g r a i n e d m a t e r i a l c a l l e d "Clay M i n e r a l " i s undoubtedly p a r t l y v e r y f i n e grained s e r i c i t e . Every specimen examined has been s e r i c i t i z e d to some extent.  P o s s i b l y v a r i a t i o n s i n i n t e n s i t y of s e r i c i t i z a t i o n  could be r e c o g n i z e d i f a great d e a l of m i c r o s c o p i c work were done but s e r i c i t i z a t i o n can not be seen i n the hand specimen. In some of the r o c k s , f o r example S apparent secondary m i n e r a l i s c l a y m i n e r a l . for  ^, the most  I n other r o c k s ,  example Sg_^, the dominant secondary mineral i s e p i d o t e .  In specimen S These types in  &  g  ^,'the  oxide,  of a l t e r a t i o n and replacement can be r e c o g n i z e d  the hand specimens.  different  f e l d s p a r i s s t a i n e d pink with i r o n  Consequently, w i t h the knowledge t h a t • •  secondary minerals may be r e c o g n i z e d  i n various  rock types, i t should be p o s s i b l e to map zones of a l t e r a t i o n and  replacement.  17  A c c o r d i n g t o V i c t o r Dolmage, epidote and z o i s i t e were d e p o s i t e d i n the second stage o f contact metasomatism and a l s o s i m u l t a n e o u s l y w i t h the ores i n the v o l c a n i c s and i n the pegmatite dykes. (zoisite  P o s s i b l y the e p i d o t e and c l i n o z o i s i t e  ?) of the Lost Horse i n t r u s i v e s had the same o r i g i n .  The hematite which s t a i n e d the f e l d s p a r s of Sg_^ probably o r i g i n a t e d i n the Voigt o r Smelter Lake stocks which d e p o s i t e d hematite d u r i n g t h e i r p e r i o d s of m i n e r a l i z a t i o n . Inside the e a s t e r n c o n t a c t of the Copper Mountain stock, the l a t e f e l s i t e poikiloblastic biotite  dykes caused the growth of i n syenogabbro.  These dykes a l s o occur  to the n o r t h of the stock among the L o s t Horse  intrusives.  Consequently, c o n s i d e r a t i o n should a l s o be given to the possi b i l i t y that the dykes have e f f e c t e d p a r t of the a l t e r a t i o n of the L o s t Horse  intrusives.  18  CONCLUSIONS I t has been e s t a b l i s h e d by m i c r o s c o p i c  examination  t h a t the humber of d i s t i n c t rock types of the L o s t Horse i n t r u s i v e s i s l e s s than was i t was  o r i g i n a l l y thought.  In a d d i t i o n  observed that d i f f e r e n t types of a l t e r a t i o n were  dominant i n d i f f e r e n t outcrops and t h a t the types of a l t e r a t i o n c o u l d be r e c o g n i z e d i n the hand Simple  specimens.  l a b o r a t o r y t e s t s w i l l prove  or absence of o r t h o c l a s e .  The  the  presence  etching with hydrofluoric  a c i d and c o v e r i n g w i t h sodium c o b a l t i n i t r i t e may  be  carried  out on f a i r l y smooth rock c h i p s and then the f e l d s p a r s examined with a hand lens to determine stained.  whether they have been  The a u g i t e d i o r i t e and the a u g i t e s y e n i t e can  probably be d i s t i n g u i s h e d , when the rock c o l o r i s not d e f i n i t e l y green or d e f i n i t e l y white, by immersing  very f i n e l y  crushed f e l d s p a r i n an o i l w i t h r e f r a c t i v e index of n -  1.54. With the knowledge of the d i s t i n c t r o c k types  of the types of a l t e r a t i o n and w i t h the use of the  and  simple  l a b o r a t o r y methods o u t l i n e d above, the mapping of the L o s t Horse i n t r u s i v e s w i l l be simple and a c c u r a t e .  Furthermore,  zones of d i f f e r e n t types of a l t e r a t i o n w i l l probably be established.  19  REFERENCES (1)  Dolmage, V. (1934) Geology and Ore Deposits of Copper Mountain, B r i t i s h Columbia: G e o l . Survey, Canada, Memoir 171.  (2)  K e i t h , M.L. (1939) Selective S t a i n i n g to F a c i l i t a t e Rosiwal A n a l y s i s : American M i n e r a l o g i s t , v o l , 24, pp. 561-565.  (3)  L a r s e n , E.S. (1935), The Rosiwal Method and the Modal Determination of Rocks: American M i n e r a l o g i s t , v o l . 20, pp. 260-273.  (4)  R i c e , H.M.A. (1947), Geology and M i n e r a l Deposits of the P r i n c e t o n Map Area, B r i t i s h Columbia: Geol. Survey, Canada, Memoir 243.  (5)  Rogers, A.F., and K e r r , P.F. (1942), McGraw-Hill, New York.  (6)  T y r r e l l , G.W. (1948), The P r i n c i p l e s of P e t r o l o g y : Methuen, London.  (7)  W i n c h e l l , A.N. (1947), Elements of O p t i c a l Mineralogy, Part I I , d e s c r i p t i o n s of M i n e r a l s ; John W i l e y and Sons, New York.  O p t i c a l Mineralogy:  A-1  Specimen S - ^ I  (2500 N, 13,600 E)  Megascopic D e s c r i p t i o n . The r o c k  i s medium t o f i n e g r a i n e d h o l o c r y s t a l l i n e  w i t h a medium d a r k , g r e e n i s h grey c o l o r and a f a i n t p i n k t i n g e . The t e x t u r e i s g r a n i t i c .  The composition i s 30$ dark  green  a u g i t e , 60$ g r e e n i s h grey to p i n k i s h grey f e l d s p a r , '5$ f i n e g r a i n e d b i o t i t e , and some very f i n e , b l a c k , m e t a l l i c m i n e r a l . On weathered s u r f a c e s , the a u g i t e i s l i g h t e r green and the f e l d s p a r i s p i n k i s h white.  On each s i d e of  f r a c t u r e s , the r o c k has been bleached f o r one s i x t e e n t h of an inch. II  The a u g i t e i s l i g h t e r green and the f e l d s p a r i s white.  Microscopic Description  • (a) M i n e r a l s 1 - A u g i t e - Pale green, stubby, opt  eight-sided crystals;  2V - 55°, no ple©chroism, l e n g t h slow, maximum  e x t i n c t i o n angle i s 45°, maximum b i r e f r i n g e n c e i s .024  - -.027, n = 1.67  - 19$ of the rock - S i z e ranges - Subhedral  from l / 2 mm - 2 mm.  t o e u h e d r a l ; some c r y s t a l s a r e broken and  rounded. - The a u g i t e i s u n a l t e r e d . 2 - L a b r a d o r i t e - C o l o r l e s s , r e l i e f low, n g r e a t e r than balsam, shows p o l y s y n t h e t i c twinning,  maximum  e x t i n c t i o n angle i n s e c t i o n s p e r p e n d i c u l a r to (010)  A - 2  i s 3 0 ° . The Pc i s A n  5 g  51% of the r o c k The g r a i n average  i s s e r i a t e , r a n g i n g up to one mm.  size  is  The  .5 mm.  The c r y s t a l s are mostly euhedral w i t h the l e n g t h two to three times the width. The c r y s t a l s are zoned.  The outer rim i s always  u n a l t e r e d , whereas the i n t e r i o r may o r may not he partly altered  to f i n e g r a i n e d s e r i c i t e .  O r t h o c l a s e - S l i g h t l y pink, n l e s s than balsam, some simple twinning, s t a i n s  yellow with sodium  cobaltinitrite. 21% of the rock The average Subhedral  size  i s 5 mm.  to a n h e d r a l , s l i g h t l y e l o n g a t e .  The c r y s t a l s are cloudy but the a l t e r a t i o n i s not as i n t e n s e as i n the i n t e r i o r of the Pc c r y s t a l s . B i o t i t e - P l e o c h r o i c from dark r e d d i s h brown.  l i g h t yellow to medium  The a b s o r b t i o n i s maximum when  the cleavage i s p a r a l l e l t o the p o l a r i z e r . 4k% of the rock The g r a i n  ranges  from  Subhedral  to a n h e d r a l .  .1 t o .8 mm.  Unaltered. Magnetite  - Opaque, b l a c k , white  under r e f l e c t e d l i g h t .  pebbly s u r f a c e  - % % of the rock - The g r a i n ranges from m i c r o c r y s t a l i i n e up t o .5  mm.  A p a t i t e - C o l o r l e s s , n s 1.63, i n t e r f e r e n c e  6 -  c o l o r s are f i r s t  order blue grey.  End s e c t i o n s  are hexagonal and the c r y s t a l s a r e l e n g t h f a s t . -  Accessory.  - The c r y s t a l s are v e r y s m a l l . - Euhedral hexagonal prisms  terminated  with  dipyramids. (b)  Mutual R e l a t i o n s . The  texture i s p o i k i l i t i c w i t h the o r t h o c l a s e as  the o i k o c r y s t s and the other minerals as c h a d a c r y s t s .  In  some places the o r t h o c l a s e cuts i n t o the a u g i t e and p l a g i o clase.  Some l a b r a d o r i t e  i s e n c l o s e d i n a u g i t e and some a u g i t e  i s enclosed i n l a b r a d o r i t e . Magnetite, occurs'.throughout.  B i o t i t e cuts augite and l a b r a d o r i t e I t occurs  i n and cuts a l l the  other minerals but some g r a i n s are v e r y i r r e g u l a r and f i l l between a u g i t e and p l a g i o c l a s e c r y s t a l s . (c)  Composition  i  Augite  ii  Labradorite  - 51$  iii  Orthoclase  - 21$  iv  Biotite  v  Magnetite  vi  Apatite  19$  Accessory  A-4  (d)  The t e x t u r e i s P o i k i l i t i c . Prom the composition, the term Monzonitie may be used.  (e)  The rock i s a Syenogabbro.  Specimen S _^ 3  I  Megascopic D e s c r i p t i o n The  r o c k i s medium g r a i n e d h o l o c r y s t a l l i n e w i t h a  g r e y i s h green c o l o r . ion  (10,200N, 8700 E)  The t e x t u r e i s g r a n i t i c .  i s 2 5 % medium green augite and 75% l i g h t  The  composit-  grey f e l d s p a r .  There i s a t h i n c o a t i n g of brown hydrous i r o n  oxide  along f r a c t u r e s . II  Microscopic Description (a) 1  Minerals - A u g i t e - Pale green, stubby, e i g h t s i d e d c r y s t a l s ; no pleochroism, maximum e x t i n c t i o n angle i s 45°, n = 1.67 -  27% of the rock  - The g r a i n s i z e i s s e r i a t e , r a n g i n g down from - Subhedral  1  mm.  to euhedral, now mostly rounded and  corroded. - The g r e a t e r p a r t of the o r i g i n a l a u g i t e c r y s t a l s r e t a i n t h e i r i n t e r f e r e n c e c o l o r s but  are p a r t l y  a l t e r e d to c l a y m i n e r a l and a l i t t l e  clinozoisite  and are p a r t l y r e p l a c e d by carbonate  and f e l d s p a r  matrix.  still  A-5  2 -  Andesine  - C o l o r l e s s , low  r e l i e f , n g r e a t e r than  balsam, e x h i b i t s coarse p o l y s y n t h e t i c twinning, optically positive. 2,  the composition  - 73$ of the  From s e c t i o n s p e r p e n d i c u l a r to i s An^Q__^  rock.  - There are two d i f f e r e n t modes: (1)  Euhedral c r y s t a l s 1 - 3 mm  (2)  Anhedral  crystals  which form a matrix.  .05 mm The  i n size i n size  former comprise  the s e c t i o n , the l a t t e r comprise - The  Andesine  but the edges of the anhedral g r a i n s  are s e r i c i t i z e d  (?).  The  c o n t a c t s of the groundmass  w i t h the augite were s t a i n e d s l i g h t l y yellow sodium c o b a l t i n i t r i t e , sericite  a l t e r e d from  andesine.  Magnetite  - Opaque, black, shines white  reflected  light.  - Occurs  - The  under  i n v e r y minor amounts  - Grain s i z e i s about .1  4 -  f e l d s p a r caused  In a d d i t i o n , most of the epidote  i n the s l i d e has 3 -  by  i n d i c a t i n g the f o r m a t i o n of  or narrow rims of potassium  by r e a c t i o n .  of  43$.  groundmass i s l e s s a l t e r e d than the  phenocrysts  30$  mm.  c r y s t a l s are anhedral and bordered by  hematite.  Hematite - Almost opaque; i t transmits l i g h t of a deep r e d c o l o r . - Accessory  A-6  - Grain s i z e i s l / 4 to 1  mm.  - O r i g i n a l l y subhedral to e u h e d r a l ; now most of the grains are more or l e s s 6 -  corroded.  Sphene - P l e o c h r o i c medium t o dark brown, h i g h  relief,  high birefringence. - Accessory - The average - Occurs  s i z e i s .05 to .1  mm.  as subhedral t o euhedral rhombs.  - Unaltered. 7 -  Epidote - P l e o c h r o i c c o l o r l e s s  - f e r e n c e c o l o r s are second  to yellow; i n t e r -  order reds and greens,  n = 1.75 -  4% of the rock  - The c r y s t a l s range i n s i z e from  .2 to .6  mm.  - The epidote occurs i n anhedral c r y s t a l s as an a l t e r a t i o n product of andesine 8 -  and maybe of a u g i t e ,  Carbonate - C o l o r l e s s , change of r e l i e f of  the stage, h i g h b i r e f r i n g e n c e .  - P i l l s a veinlet  .02 mm wide, and occurs as a very f i n e  grained replacement 9 -  on r o t a t i o n  i n andesine  and a u g i t e ,  C h l o r i t e - L i g h t green, low r e l i e f , v e r y low b i r e f r i n g e n c e , one cleavage.  - Occurs  as a v e r y f i n e , sparse a l t e r a t i o n product of  "augite. (b)  Mutual R e l a t i o n s The t e x t u r e i s p o r p h y r i t i c w i t h phenocrysts  and andesine  s e t i n a groundmass of m i c r o c r y s t a l i i n e  of a u g i t e andesine.  A-7  In a d d i t i o n to r e p l a c i n g the a u g i t e , the groundmass has p a r t l y r e p l a c e d the andesine  phenocrysts  i n d i c a t i n g t h a t the groundmass  might be more sodic. than the phenocrysts. (c)  (d)  Composition. 1 - Augite  - 27$  2 - Andesine  - 73$  (1) Phenocrysts  - 30$  (8) Groundmass  - 43$  3 - Magnetite  - Accessory  4 - Hematite  - Accessory  5 - Apatite  - Accessory  6 - Sphene  - Accessory  The t e x t u r e i s m i c r o p o r p h y r i t i c • M e g a s c o p i c a l l y , i t appears  (e)  granitic.  The rock i s an Augite D i o r i t e . an Augite D i o r i t e  Microscopically, i t i s  Porphyry.  Specimen S _ 3  B  (3750 N, 12,800 E)  I - Megascopic D e s c r i p t i o n . - The rock i s medium t o f i n e g r a i n e d h o l o c r y s t a l l i n e with a l i g h t composition  g r e y i s h green c o l o r . The t e x t u r e i s g r a n i t i c . i s 30$ medium green a u g i t e and 70$ l i g h t  The  grey  feldspar. On weathered s u r f a c e s the f e l d s p a r i s s l i g h t l y  pink  but, on the o u t s i d e , there i s a t h i n c o a t i n g of l i g h t brown oxides.  F r a c t u r e s i n s i d e the rock are coated w i t h dark brown  A-8  hydrous o x i d e s , II - Microscopic D e s c r i p t i o n , (a)  Minerals.  1  - A u g i t e - Very pale green, almost  colorless,  stubhy  e i g h t - s i d e d c r y s t a l s ; o p t i c a l l y p o s i t i v e , 2 V » 60°, maximum e x t i n c t i o n angle i s 45°, n = 1.67 - 21$ of the rock - The s i z e ranges from  .1 t o 1  mm.  - Anhedral t o euhedral p r i s m a t i c c r y s t a l s . - The a u g i t e i s a l t e r e d to the e x t e n t of about 10$ a l o n g cleavages and cross f r a c t u r e s and i n i r r e g u l a r patches  to a brown m i n e r a l with low r e l i e f and low  birefringence. 2 -  Andesine  T h i s might be b a s t i t e .  - L a b r a d o r i t e - C o l o r l e s s , low r e l i e f ,  n g r e a t e r than balsam, shows p o l y s y n t h e t i c twinning. A s e c t i o n p e r p e n d i c u l a r t o X shows that the composition ranges  from A n ^ on the rims t o A n  g  i n the c e n t r e s . - 76$ of the rock. - The g r a i n i s s e r i a t e up t o 2 mm w i t h most of the c r y s t a l s l / 2 to 1  mm.  - The c r y s t a l s are subhedral t o almost  euhedral  prismatic. - The p l a g i o c l a s e i s a l t e r e d e x t e n s i v e l y t o c l a y mine r a l and s e r i c i t e .  Although  the d i f f e r e n c e i n  composition of the c e n t r e s and rims i s o n l y 5 t o 10$  A  A , n  i n some cases the centres are almost  a l t e r e d while the rims are u n a l t e r e d . clinozoisite Magnetite Occurs  completely  Some  i s present.  - Opaque, b l a c k , white  in reflected  light  i n v e r y minor amounts  .05 - .1 mm  i n sizw.  The c r y s t a l s  are a n h e d r a l and bordered w i t h  iron  stain. Pyrite  - Opaque, yellow i n r e f l e c t e d l i g h t , the  c r y s t a l s have square Occurs  outlines.  i n very minor amounts.  .05 - .1 mm i n s i z e . The c r y s t a l s are euhedral w i t h square are bordered.with  iron  Apatite - Colorless, colors, uniaxial,  o u t l i n e s and  stain.  n = 1.63, low i n t e r f e r e n c e  o p t i c a l l y negative,  1% of the rock g r a i n s i z e ranges The c r y s t a l s  from  .05 - .5  mm.  are subhedral to e u h e d r a l .  Unaltered. Sphene - P l e o c h r o i c medium t o dark brown, h i g h r e l i e f , h i g h b i r e f r i n g e n c e ; 2V = 25°, o p t i c a l l y positive. 2% of the rock Grain size  i s .1  mm.  Anhedral t o s u b h e d r a l .  (b)  Mutual R e l a t i o n s . The  rock i s e q u i g r a n u l a r .  have s l i g h t l y i r r e g u l a r boundaries  The f e l d s p a r c r y s t a l s and a p p a r e n t l y grew u n t i l  they were i n c o n t a c t w i t h each o t h e r . include plagioclase c r y s t a l s  The a u g i t e  crystals  and so may be l a t e r than the  initiation,of feldspar crystallization. c r y s t a l s have very i r r e g u l a r boundaries  However, the a u g i t e and completed  c r y s t a l l i z a t i o n before the f e l d s p a r , and were then by the l a t e l i q u i d s which were r i c h e r i n the a l b i t e than the e a r l y p l a g i o c l a s e (c)  crystals.  Composition. •1 - Augite  21%  2 - Andesine-Labradorite  76%  3 - Magnetite  Accessory  4 - Pyrite  Acces sory  5 - Apatite  1%  6 - Sphene  2%  (d)  The  texture i s g r a n i t i c  (e)  The  rock i s , A u g i t e  Diorite.  their  corroded molecule  A - 1 1  Specimen S _ 3  (10,900 N, 7100 E)  G  I - Megascopic D e s c r i p t i o n . The  rock i s medium t o f i n e grained  with a l i g h t g r e e n i s h grey c o l o r . The  composition  light  holocrystalline  The t e x t u r e i s g r a n i t i c .  i s 30$ medium t o dark green a u g i t e and 70$  grey t o white f e l d s p a r . On weathered s u r f a c e s the a u g i t e i s l i g h t e r  and the f e l d s p a r i s white. hydrous i r o n  green  F r a c t u r e s have f i l m s of brown,  oxides.  II - Microscopic D e s c r i p t i o n , (a)  Minerals  1 -  Augite  - Very pale green,  stubby, e i g h t s i d e d  c r y s t a l s , o p t i c a l l y p o s i t i v e , 2V = 60°, maximum e x t i n c t i o n angle  i s 45°, n = 1.67.  - 31$ of the rock. - The g r a i n s i z e i s s e r i a t e . - The a u g i t e i s subhedral  I t ranges down from 1  mm.  to e u h e d r a l .  - The a u g i t e i s a l t e r e d to the extent of 5$ t o 10$ to c l a y mineral, carbonate, 2 -  and c l i n o z o i s i t e .  L a b r a d o r i t e - C o l o r l e s s , low r e l i e f , n g r e a t e r  than  balsam, does not s t a i n yellow w i t h sodium c o b a l t i n itrite.  S e c t i o n s p e r p e n d i c u l a r to Z show a compos-  i t i o n of A n 55-60 c i  - There are two modes of occurrence: )1) Phenocrysts  w i t h an average s i z e of 1 mm.  make up 51$ of the r o c k .  These  ( 2 ) Groundmass w i t h an average makes up 16$ of the  s i z e of .1 mm.  This  rock.  The  phenocrysts  are subhedral to almost  The  edges are corroded by the groundmass.  groundmass i s composed of anhedral  euhedral. The  plagioclase  c r y s t a l s which are i r r e g u l a r l y intergrown. these groundmass c r y s t a l s  cut i n t o the  Since  phenocrysts,  they might be of d i f f e r e n t composition or they might be m a t e r i a l which r e c r y s t a l l i z e d from the edges of the phenocrysts. i a the prooonroo o£—bhc  carbonate  solutions- which havo a l t o r o d the rock. The  l a b r a d o r i t e has been a l t e r e d to c l a y m i n e r a l ,  carbonate, and  sericite  to such an e x t e n t that i t i s  very d i f f i c u l t  to recognize a l b i t e twinning.  Along  i r r e g u l a r zones, the c o l o r l e s s minerals have been s t a i n e d yellow w i t h sodium c o b a l t i n i t r i t e  indicating  i n t r o d u c t i o n of a small amount of potassium  feldspar -  or c o n c e n t r a t i o n s of v e r y f i n e g r a i n e d s e r i c i t e . Magnetite  - Black, opaque, white  under r e f l e c t e d  pebbled s u r f a c e  light,  v e r y minute amounts. The  g r a i n s i z e i s about  .01  mm.  The  g r a i n s have a s l i g h t r e d d i s h t i n g e i n d i c a t i n g  that they might be p a r t l y a l t e r e d to hematite. A p a t i t e - C o l o r l e s s , n «• 1.63,  low i n t e r f e r e n c e  colors, u n i a x i a l , o p t i c a l l y negative.  A-13  - 1$ of the  rock  - The  g r a i n s i z e ranges from  - The  c r y s t a l s are subhedral to e u h e d r a l .  5 -  Sphene - P l e o c h r o i c high  medium to dark brown, h i g h  relief,  rock  c r y s t a l s are  - Subhedral 6 -  mm.  birefringence.  - l / 2 $ of the - The  .25 t o .5  .05 mm  i n size  to euhedral rhombs.  Carbonate - C o l o r l e s s ,  change of r e l i e f  of the stage, extreme  on  rotation  birefringence.  - The  g r a i n s i z e ranges  down from 1  mm.  - The  c r y s t a l s are anhedral with i r r e g u l a r boundaries.  - The  carbonate  occurs i n narrow f r a c t u r e s  with  f e l d s p a r and a l s o r e p l a c i n g the other m i n e r a l s . (b)  Mutual The  Relations. large  subhedral a u g i t e and l a b r a d o r i t e  crystals  are a p p a r e n t l y set i n a f i n e g r a i n e d groundmass of anhedral labradorite  crystals.  The  groundmass cuts i n t o and  the l a r g e r c r y s t a l s .  This  l i q u i d of p l a g i o c l a s e  composition  plagioclase,  either a late  residual  or r e c r y s t a l l i z a t i o n of the  perhaps by s t r e s s as i n d i c a t e d  of f e l d s p a r c r y s t a l s i n the (c)  suggests  corrodes  by wavey e x t i n c t i o n  groundmass.  Composition. 1 - Augite  -  31$  2 - Labradorite  -  67$  A-14  (d)  (1) Phenocrysts  -  51%  (2) Groundmass  -  16$  5 - Magnetite  - Accessory  4 - Apatite  -  5, - Sphene  - l/2$  The  1$  texture i s m i c r o p o r p h y r i t i c .  Megascopically i t i s g r a n i t i c . (e)  The  rock i s a Gabbro. This rock, although i t i s a gabbro, i s very  much l i k e S _^ 3  which was  Specimen S  named an A u g i t e  Diorite.  (13,500 N, 7000 E )  I - Megascopic D e s c r i p t i o n The  rock i s medium to f i n e grained h o l o c r y s t a l l i n e  w i t h a l i g h t g r e e n i s h white c o l o r . granular. light  The  composition  The  texture i s equi-  is.20$ l i g h t  green a u g i t e and  grey t o white f e l d s p a r .  augite.  80$  I r o n s t a i n occurs around the  In a d d i t i o n , there are very minor amounts of epidote  and c h a l c o p y r i t e . There i s no apparent  change on the weathered s u r f a c e .  II - Microscopic D e s c r i p t i o n (a)  Minerals.  1 - A u g i t e - Almost c o l o r l e s s , t i n t e d s l i g h t l y stubby, angle  green,  e i g h t s i d e d c r y s t a l s , maximum e x t i n c t i o n  i s 45°.  n -  1.67.  A-15 19$ of the rock. The  g r a i n s i z e i s s e r i a t e up t o ljg- mm.  The  c r y s t a l s are subhedral  P a r t l y a l t e r e d to c l a y mineral and c l i n o z o i s i t e . Some carbonate  i s present which may be r e p l a c i n g  augite. Albite - Colorless,  low r e l i e f , n l e s s than balsam,  shows p o l y s y n t h e t i c  tjtfinning.  Sections perpendicular  to Z show a composition of Ang_^Q.  This  was  confirmed by the use of maximum e x t i n c t i o n angles i n sections  normal t o (010) and the use of combined  a l b i t e and c a r l s b a d  twinning.  76$ of the rock There are two modes of occurrence: (1) Phenocrysts  w i t h a s i z e of i to 1 mm.  These  make up 40$ of the rock. (2) Groundmass w i t h an average This  s i z e of .1 t o .2  mm.  makes up 36$ of the rock.  The  phenocrysts  a r e subhedral to almost  euhedral.  The  edges are corroded by the groundmass.  The  groundmass c r y s t a l s are a n h e d r a l and i r r e g u l a r l y intergrown. The  f e l d s p a r has been p a r t l y a l t e r e d t o s e r i c i t e ,  c l i n o z o i s i t e , e p i d o t e , and c l a y m i n e r a l . chlorite  Some  i n the groundmass may have r e s u l t e d  the replacement  of f e l d s p a r .  from  A-1  Hematite - Almost opaque but i t t r a n s m i t s deep red  light.  A c c e s s o r y i n v e r y small amounts .01 t o .02 mm  i n size.  The c r y s t a l s are anhedral and are s c a t t e r e d s p a r s e l y through the s l i d e . A p a t i t e - C o l o r l e s s , n = 1.63, low i n t e r f e r e n c e colors. 2jg% of the r o c k . The c r y s t a l s range i n s i z e from The c r y s t a l s are anhedral  .02 mm to .5  mm.  to s u b h e d r a l .  Sphene - P l e o c h r o i c medium to dark brown, h i g h r e l i e f , high b i r e f r i n g e n c e . V/o of the r o c k . The c r y s t a l s are  mm  to -g- mm  i n size.  The sphene i s subhedral to euhedral  i n elongated  rhombs.  .  .  .  E p i d o t e and C l i n o z o i s i t e - E p i d o t e i s p l e o c h r o i c c o l o r l e s s to yellow; c l i n o z o i s i t e  is colorless.  E p i d o t e has b r i g h t second order i n t e r f e r e n c e c o l o r s ; c l i n o z o i s i t e has i n t e r f e r e n c e c o l o r s r a n g i n g from anomalous blue to f i r s t n =  order y e l l o w .  Both have  1.7  Together  they make up  of the r o c k .  The c r y s t a l s are up t o .25 mm  i n size.  The epidote and c l i n o z o i s i t e are anhedral o c c u r r i n g as an a l t e r a t i o n product  of f e l d s p a r .  A-17 7 -  Ghlorite.(?) - Light  green, low r e l i e f ,  very low  birefringence, - Occur as s m a l l , scarce  c r y s t a l s i n the groundmass.  They have a r a d i a t i n g h a b i t . (b)  Mutual  Relations.  (1) The l a r g e augite f i n e grained  and a l b i t e c r y s t a l s occur i n a  groundmass of f e l d s p a r .  (3) The f i n e  grained f e l d s p a r may have been d e r i v e d from the c o a r s e . (2) Some l a r g e f e l d s p a r c r y s t a l s show f r a c t u r i n g and r o t a t i o n of the fragments, p o s s i b l y i n d i c a t i n g , protoclastic (c)  (d)  structure.  Composition. 1 - Augite  - 13$  2 - Albite  - 76$  (1) Phenocrysts  - 40$  (2) Groundmass  - 36$  3 - Hematite  - Accessory  4 - Apatite  - 2|-$  5 - Sphene  - 1$  The texture  i s either microporphyritic  granitic, later partly recrystallized. (e)  The r o c k i s an A u g i t e  Syenite.  or primary  A-18  Specimen Sg _ I  g  (13,750 N, 7000 E )  - Megascopic D e s c r i p t i o n The  green c o l o r .  rock i s medium to f i n e g r a i n e d w i t h a l i g h t The t e x t u r e i s e q u i g r a n u l a r .  grey  The composition  i s 20$ medium green a u g i t e and 80$ l i g h t grey f e l d s p a r . On weathered s u r f a c e s , the f e l d s p a r i s l i g h t covered w i t h a t h i n c o a t i n g of hydrous i r o n oxide.  grey  The  surface i s p i t t e d where the a u g i t e has weathered o u t . II  - Microscopic Description, (a)  Minerals  1 -  A u g i t e - Very pale green,  stubby, e i g h t s i d e d  c r y s t a l s , two cleavages at r i g h t a n g l e s , the maximum e x t i n c t i o n angle i s 4 5 ° , n = 1.67. - 17$ of the rock - The c r y s t a l s are up t o 1 mm i n s i z e . - The c r y s t a l s are subhedral to euhedral p r i s m a t i c . - The a u g i t e i s r e l a t i v e l y u n a l t e r e d .  There has been  some f o r m a t i o n of c l a y m i n e r a l . 2 -  Andesine  - C o l o r l e s s , low r e l i e f , n g r e a t e r than  that of balsam, shows p o l y s y n t h e t i c t w i n n i n g . S e c t i o n s p e r p e n d i c u l a r to Z give a composition of An45. - 82$ of the rock - There are two modes: (l)  Subhedral  c r y s t a l s 1 t o 4 mm i n s i z e .  A-19  (2)  Anhedral  crystals  .02 t o .1 ram i n s i z e  which form a groundmass.  The former make up 48$  of the rock; the l a t t e r make up 34$. The  groundmass corrodes the andesine  phenocrysts.  The  central  are much more  zones of the phenocrysts  highly altered mass.  than the outer zones o r the ground-  A l t e r a t i o n products are s e r i c i t e ,  mineral,clinozoisite, some replacement  and c h l o r i t e .  clay  There has been  by carbonate.  Hematite - Almost opaque but i t t r a n s m i t s a l i t t l e deep r e d l i g h t . A c c e s s o r y , v e r y minor amounts. .02 to .04 mm i n s i z e . The hematite crystals  occurs as very  scattered  sparse_anhedral  throughout.  Apatite - Colorless,  n = 1.63, l o w i n t e r f e r e n c e r  colors. 1$  of the rock  .2 to .5 mm i n s i z e . The  c r y s t a l s are subhedral t o a n h e d r a l .  Sphene - P l e o c h r o i c medium t o dark brown, h i g h r e l i e f , high birefringence. | j $ of the rock. .2 t o .5 mm i n s i z e . The  sphene i s subhedral to euhedral i n elongated  rhombs.  A-20  6 -  C h l o r i t e - P l e o c h r o i c c o l o r l e s s to g r e e n i s h brown, one cleavage, maximum a b s o r p t i o n p a r a l l e l t o the p o l a r i z e r , low b i r e f r i n g e n c e with some anomalous b l u e .  - Occurs i n v e r y minor amounts near carbonate i n feldspar, (b)  Muttial R e l a t i o n s . The l a r g e a u g i t e and andesine c r y s t a l s  a p h a n i t i c groundmass of p l a g i o c l a s e f e l d s p a r . -  occur i n an  The groundmass  has i r r e g u l a r l y invaded the edges of the-andesine and seems to have rounded the a u g i t e c r y s t a l s  phenocrysts  to a c e r t a i n  extent. :  (c)  Composition. 1 - Augite  - 17$  2 - Andesine  - 82$  (1) Phenocrysts  48$  (2)  34$  Groundmass  3 - Hematite  - Accessory  4 - Apatite 5 - Sphene (d)  The texture i s e i t h e r m i c r o p o r p h y r i t i c or a l t e r e d granitic.  (e)  The rock i s an A u g i t e D i o r i t e The rock, then, i s S3 not Sg  A-21  Specimen  Sg_  (12,300 N, 6,700 E)  A  I - Megascopic D e s c r i p t i o n . The  rock i s medium to f i n e g r a i n e d h o l o c r y s t a l l i n e  with a l i g h t f l e s h pink c o l o r .  The  texture i s g r a n i t i c .  rock i s 20$ dark green a u g i t e , 5% magnetite, feldspar.  The  and 75% l i g h t  pink  Throughout the rock there i s v a r i a t i o n i n the deep-  ness of the p i n k c o l o r .  In a d d i t i o n , the f e l d s p a r on a sawn  surface of the hand specimen d i d not s t a i n yellow when t r e a t e d w i t h sodium c o h a l t i n i t r i t e .  The  last  two f a c t s i n d i c a t e that  the f e l d s p a r i s p l a g i o c l a s e c o l o r e d w i t h f i n e l y  divided  hematite. II - Microscopic Description, (a) M i n e r a l s . 1 -  A u g i t e - Very pale green, almost  colorless,  e i g h t s i d e d c r y s t a l s , the maximum e x t i n c t i o n i s 45, n •  stubby angle  1.67.  '- 15% of the rock - The  c r y s t a l s are up to l l mm  i n size  - The  c r y s t a l s are subhedral t o euhedral i n o u t l i n e .  - The  a u g i t e i s over 50$ a l t e r e d and r e p l a c e d by  c h l o r i t e and carbonate, not c l a y m i n e r a l . 2 -  Andesine pink, low  - Labradorite - Colorless, a s l i g h t  tint  of  r e l i e f , n g r e a t e r than that of balsam, shows  p o l y s y n t h e t i c twinning.  S e c t i o n s p e r p e n d i c u l a r to Z  give a composition of An,- . n  A-22  82$ of the  rock  The  grain  is seriate  from very s m a l l up to 2  The  average s i z e i s i to 1  mm.  The f e l d s p a r  i s anhedral to s u b h e d r a l .  The  are a l t e r e d  crystals  mm.  to the extent that  a l b i t e twinning i s d i f f i c u l t  to see.  the  Alteration  products are s e r i c i t e , c l i n o z o i s i t e , e p i d o t e , and a little  clay mineral.  replacement by  There i s a l s o c o n s i d e r a b l e  carbonate.  Magnetite - Black, opaque, white w i t h a pebbled surface under r e f l e c t e d lif  0  of the  Subhedral The  light.  rock to anhedral  crystals.  c r y s t a l s are f r a c t u r e d  Chlorite  occurs i n the f r a c t u r e s .  c r y s t a l s were about Pyrite  along p a r t i n g  .2 mm  The  planes.  original  across.  - Opaque, very l i g h t  yellow under r e f l e c t e d  light. A c c e s s o r y , very minor i n amount. The  size  i s .1  mm.  The  c r y s t a l s are a n h e d r a l .  Apatite - Colorless, hexagonal  n = 1.63,  low  birefringence,  outlines.  l i $ of the rock, •g- to 1 mm The  i n size  apatite  c r y s t a l s are subhedral to e u h e d r a l .  A-23  6 -  Sphene - P l e o c h r o i c medium to dark brown, h i g h  relief,  high birefringence. - %fo of the -  .2 mm  - The  rock  in size.  sphene occurs i n subhedral to euhedral  elongated  rhombs. 7 -  C l i n o z o i s i t e - C o l o r l e s s to n e u t r a l , i n t e r f e r e n c e c o l o r s are anomalous blue to f i r s t $ of the  order y e l l o w .  rock  - The  s i z e ranges  from  minute up to  mm.  - The  c l i n o z o i s i t e occurs i n anhedral c r y s t a l s as  a l t e r a t i o n product of p l a g i o c l a s e .  The  an  crystals  occur  mostly i n clumps, i n which a s m a l l amount of epidote also occurs. 8 -  Carbonate - C o l o r l e s s , change of r e l i e f of - The  rotation  the stage, h i g h b i r e f r i n g e n c e . carbonate  i s a replacement  mineral, e s p e c i a l l y  i n a u g i t e , and occurs i n s m a l l anhedral (b)  oh  crystals.  Mutual R e l a t i o n s Previous to the a l t e r a t i o n , the textures and  boundaries (b)  were those of normal igneous  rocks.  Composition 1 - Augite  -  15$  2 - Andesine-Labradorite  -  82$  3 - Magnetite  _ i-|$  4 - Apatite  - i-|-$  5 - Sphene  - -|r$  crystal  A-24 (c)  The t e x t u r e , i n s p i t e of the a l t e r a t i o n , i s g r a n i t i c .  (d)  The  rock i s an Augite  The  Diorite.  d i f f e r e n c e from Sg i s o n l y i n the  alteration.  Instead of e x t e n s i v e change to c l a y m i n e r a l , the main changes were more than o r d i n a r y amounts of carbonate  i n the a u g i t e  and major changes of the f e l d s p a r to c l i n o z o i s i t e .  Specimen S  y —A  n  h  (13,600 N, 9800 E)  I - Megascopic D e s c r i p t i o n . The grey c o l o r .  rock i s medium grained w i t h a l i g h t g r e e n i s h The  texture i s equigranular.  The composition i s  10$ to 15$ l i g h t green a u g i t e , 50$ to 70$ l i g h t grey f e l d s p a r , and the remainder products.  epidote and o t h e r u n r e c o g n i z a b l e  Some yellow m e t a l l i c The  alteration  i s present.  weathered s u r f a c e i s much l i k e the i n t e r i o r of  the specimen but i s covered with a very t h i n  carbonate  evaporation residue. II - Microscopic Description, (a)  Minerals.  1 -  A u g i t e - Almost c o l o r l e s s ,  perhaps a s l i g h t t i n t  of  green, mostly stubby c r y s t a l s , two 'cleavages a t r i g h t angles, 2V = 60°, o p t i c a l l y p o s i t i v e , n = - 5$ of the  rock  - Normally the c r y s t a l s are about some of a l e n g t h of 1.5 - The  1.68.  mm  .5 mm  i n size  and a width of .2  but mm.  a u g i t e looks as i f i t were once euhedral but i t  A-25  now h e a v i l y corroded and r e p l a c e d by the f i n e g r a i n e d groundmass, by carbonate, and by a s m a l l amount of clay mineral. Albite  - Colorless,  low r e l i e f , n l e s s than that of  balsam, shows p o l y s y n e h e t i c twinning. normal t o (010) i n d i c a t e  Sections  a composition of A n ^ .  92% of the rock There are two modes: (1) Anhedral to almost euhedral c r y s t a l s | to 2 mm  i n size.  (2) Groundmass in  of anhedral c r y s t a l s  .02 to .1 mm  size.  The index of r e f r a c t i o n of the l a r g e  crystals  and the groundmass are almost e x a c t l y the same. The a l b i t e , e s p e c i a l l y the l a r g e c r y s t a l s , has been extensively altered  and r e p l a c e d by s e r i c i t e ,  c l i n o z o i s i t e , e p i d o t e , and carbonate.  The l a r g e  a l b i t e c r y s t a l s have been p a r t l y a l t e r e d and r e p l a c e d by the groundmass. Magnetite  - Black, opaque, white i n r e f l e c t e d  light.  Accessory .05 to .1 mm  i n size  The anhedral c r y s t a l s are intergrown w i t h the p y r i t e . Pyrite  - Opqque, p y r i t e  yellow i n r e f l e c t e d  Accessory .05 to .1 mm  i n size.  A n h e d r a l , intergrown w i t h  magnetite.  light.  A-26  - Near the intergrown magnetite  and p y r i t e  crystals  i s some l i m o n i t e s t a i n and maybe some hematite. 5 -  A p a t i t e - C o l o r l e s s , n = 1.63, low b i r e f r i n g e n c e .  - 2$ of the rock - Ranges i n s i z e from  .02 t o . 5  mm.  - The c r y s t a l s are anhedral w i t h i r r e g u l a r 6 -  outlines.  Sphene - P l e o c h r o i c medium t o dark brown, h i g h r e l i e f , high b i r e f r i n g e n c e .  - 1$ of the rock -  .1 t o .2 mm i n s i z e .  - The c r y s t a l s are anhedral and bordered 7 -  by c h l o r i t e .  Carbonate - C o l o r l e s s , change of r e l i e f on r o t a t i o n of the stage, extreme b i r e f r i n g e n c e .  - The carbonate  occurs as anhedral c r y s t a l s  the l a r g e and s m a l l a l b i t e (b)  c r y s t a l s and the a u g i t e .  Mutual.Relations. The l a r g e a u g i t e and a l b i t e  c r y s t a l s occur i n a f i n e  grained groundmass of a l b i t e . (c)  replacing  Composition 1 - Augite  5$  2 - Albite  92%  (1) Phenocrysts  -  47$  (2) Groundmass  -  45$  3 - Magnetite  Accessory  4 - pyrite  Accessory  5 - Apatite  2$  6 - Sphene  1$  A-27  (d)  The  t e x t u r e i s m i c r o p o r p h y r i t i c or a l t e r e d  (e)  The  rock i s an A u g i t e S y e n i t e .  This rock, Sg_^,  i s the same as S  a l t e r a t i o n , however, i s d i f f e r e n t . the presence  The  r  .  granitic.  The  green c o l o r i s due  to  of r a t h e r l a r g e amounts of e p i d o t e .  Specimen S._ 1U-A  (13,800 N, 10,100 E)  I - Megascopic D e s c r i p t i o n . The rock i s f i n e to medium g r a i n e d w i t h a l i g h t g r e e n i s h grey c o l o r . a u g i t e , 50$ l i g h t other a l t e r a t i o n The  The  composition i s 20$ dark  grey f e l d s p a r , and the remainder  green epidote  and  products.  presence  of megascopic epidote i n d i c a t e s t h a t ,  although the f e l d s p a r and a u g i t e appear f r e s h i n the hand specimen, m i c r o s c o p i c a l l y the rock w i l l Pe found to be extensively altered. The  f e l d s p a r s on weathered s u r f a c e s are  slightly  pink and the s u r f a c e s are covered w i t h a t h i n c o a t i n g of hydrous i r o n o x i d e s . II - M i c r o s c o p i c D e s c r i p t i o n , (a) M i n e r a l s 1 -  A u g i t e - Very pale green, stubby c r y s t a l s w i t h  two  cleavages at r i g h t a n g l e s , the maximum e x t i n c t i o n angle i s 45°, n = - 16$ of the rock.  1.67.  A-28  In g e n e r a l the g r a i n s i z e i s | m m t o 1 mm tout a few crystals The  range down t o a v e r y s m a l l s i z e .  c r y s t a l s are s u b h e d r a l .  The borders are corroded  and so the c r y s t a l s were probably euhedral o r i g i n a l l y . Except f o r the i r r e g u l a r borders, the a u g i t e i s relatively'unaltered.  There i s some a l t e r a t i o n to  c h l o r i t e and c l i n o z o i s i t e . Albite  - Oligoclase - Colorless,  very l i t t l e  low r e l i e f , n a  l e s s than balsam, shows p o l y s y n t h e t i c  twinning. 77$  of the rock  There are two modes of o c c u r r e n c e : (1) Phenocrysts  which are subhedral t o e u h e d r a l ,  are 1 mm t o 2 mm i n s i z e , and make up 39$ of the rock. (2)  Groundmass made up of anhedral c r y s t a l s  .03  mm t o . l'mm i n s i z e comprising 38$ of the rock. - The a l b i t e i s p a r t l y a l t e r e d  to c l i n o z o i s i t e ,  s e r i c i t e , e p i d o t e , and c l a y m i n e r a l .  The f i n e  g r a i n e d f e l d s p a r does not cut i n t o the edges of the coarse grained f e l d s p a r as much as i n the p r e v i o u s l y d e s c r i b e d rock. phenocrysts  The index of r e f r a c t i o n of the  is a little  h i g h e r than t h a t of the  groundmass. Some areas i n the groundmass were s t a i n e d yellow by sodium c o b a l t i n i t r i t e .  However,  these were so i r r e g u l a r that i t i s assumed that  A-29  s e r i c i t e , not o r t h o c l a s e , was 3 -  Magnetite -  2-gfo  - Opaque, white  of the  g r a i n s i z e ranges  - The  c r y s t a l s are a n h e d r a l .  The  larger  mm.  crystals  fragments.  A p a t i t e - C o l o r l e s s , n = 1.63,  low b i r e f r i n g e n c e .  rock  - Up t o 2 mm - The  light.  from v e r y s m a l l t o i  - The  - 3% of the  5 -  in reflected  rock  have been broken i n t o 4 -  stained.  i n size  a p a t i t e occurs i n subhedral  crystals.  Sphene - P l e o c h r o i c medium to dark brown, h i g h r e l i e f , high birefringence. - 2% of the  6 -  rock  - The  g r a i n s i z e i s .1 mm  t o .2  mm,  - The  c r y s t a l s are anhedral to s u b h e d r a l .  Carbonate - C o l o r l e s s , changes r e l i e f  on r o t a t i o n  of the stage, extreme b i r e f r i n g e n c e . - Occtirs as anhedral c r y s t a l s i n v e i n l e t s .  In these  v e i n l e t s a l s o occur anhedral c r y s t a l s w i t h n2-nj= & n = (b)  1.64.  Mutual R e l a t i o n s . The  l a r g e a u g i t e and a l b i t e c r y s t a l s occur i n a  groundmass of f i n e g r a i n e d a l b i t e . have been d e r i v e d from (c)  .010  The  groundmass appears  the l a r g e c r y s t a l s .  Composition 1 - Augite  -16%  to  A-30  2 - Albite  - 77$  ( l ) Phenocrysts  39$  (2) Groundmass  38$  3 - Magnetite 4 - Apatite  - 3$  5 - Sphene  - 2$  (d)  The  texture  i s microporphyritic  (e)  The  rock i s an Augite  or a l t e r e d g r a n i t i c .  Syenite.  This r o c k has dark green a u g i t e and e p i d o t i z e d than k a o l i n i z e d f e l d s p a r .  Otherwise, the r o c k i s i d e n t i c a l t o  Sg  Even the p r o p o r t i o n s  augite  c r y s t a l s , and the a l b i t e groundmass are the same.  Specimen S  rather  of the l a r g e a l b i t e c r y s t a l s , the  11-A  (14,250 N, 9700 E )  I - Megascopic D e s c r i p t i o n . The  rock i s f i n e t o medium grained h o l o c r y s t a l l i n e  w i t h a medium dark p i n k i s h green c o l o r . granitic.  The texture i s  The composition i s 20$ dark green a u g i t e ,  40$ l i g h t  p i n k o r t h o c l a s e , 30$ l i g h t green zoned p l a g i o c l a s e , and 5$ biotite. On weathered s u r f a c e s , the a u g i t e and  the o r t h o c l a s e  II - Microscopic (a) 1 -  is lighter  green  and p l a g i o c l a s e are l i g h t e r i n c o l o r .  Description,  Minerals. Augite  - S l i g h t l y p l e o c h r o i c pale  green to pale  p i n k i s h green, stubby, e i g h t s i d e d c r y s t a l s ,  A-31  o p t i c a l l y p o s i t i v e , 2V • 60°, maximum e x t i n c t i o n angle i s 45°. 15$  of the r o c k .  The  g r a i n s i z e ranges  The  a u g i t e i s subhedral to e u h e d r a l .  The  c r y s t a l s are almost u n a l t e r e d but are  from  .25 mm  to 2.5  mm.  invaded  a l o n g f r a c t u r e s to a s l i g h t extent by o r t h o c l a s e . Andesine  - L a b r a d o r i t e - C o l o r l e s s , low r e l i e f , n  g r e a t e r than t h a t of balsam, shows zoning and p o l y s y n t h e t i c twinning.  S e c t i o n s p a r a l l e l to Z i n d i c a t e  that the composition  grades  from A n ^  to An^Q  (n  would here be l e s s than balsam) and t h a t the , average  composition i s  An^.  26$  of the  rock  The  s i z e ranges from  The  c r y s t a l s are euhedral w i t h s l i g h t l y  .5 mm  to 2  mm. corroded  edges. The  p l a g i o c l a s e i s s l i g h t l y a l t e r e d to s e r i c i t e  c l a y mineral, e s p e c i a l l y i n d e f i n i t e  zones.  Orthoclase - S t a i n e d yellow w i t h sodium trite,  and  cobaltini-  low r e l i e f , n l e s s than t h a t of balsam,  exhibits microperthitic textures. 48$ of the rock. The g r a i n s i z e ranges The  from  .2 mm  to 1  c r y s t a l s are anhedral and f i l l  and l a b r a d o r i t e c r y s t a l s . are very i r r e g u l a r .  mm.  between the a u g i t e  T h e i r mutual  boundaries  The a l t e r a t i o n products are f i n e  g r a i n e d s e r i c i t e and  c l a y m i n e r a l . The a l b i t e of the m i c r o p e r t h i t e i s unaltered, Quartz  - Colorless,  low r e l i e f , n g r e a t e r than that  of balsam, u n i a x i a l , o p t i c a l l y p o s i t i v e ,  1% of the rock The s i z e ranges  from  .1 mm t o .5 mm.  The quartz i s anhedral f i l l i n g between o r t h o c l a s e crystals  and o c c u r r i n g e n c l o s e d i n a u g i t e c r y s t a l s .  Unaltered B i o t i t e - P l e o c h r o i c n e u t r a l to dark r e d d i s h brown w i t h maximum a b s o r p t i o n when the cleavage to the p o l a r i z e r .  is parallel  The i n t e r f e r e n c e f i g u r e  i s biaxial  w i t h a s m a l l 2V. 4k% of the rock. The s i z e ranges  down from 1 mm.  The c r y s t a l s are subhedral to very i r r e g u l a r a n h e d r a l . The b i o t i t e i s r e l a t i v e l y u n a l t e r e d but on the borders w i t h o r t h o c l a s e a l i t t l e  c h l o r i t e has  developed. Magnetite  - Opaque, b l a c k , white  i n reflected  light.  4-|$ of the rock. The s i z e ranges  down from  .5 mm.  The c r y s t a l s are anhedral t o s u b h e d r a l . throughout  -They occur  but are mainly i n the o r t h o c l a s e .  Apatite - Colorless,  n = 1.63, low b i r e f r i n g e n c e .  A-33  - ]_-§•$ of the rock - The a p a t i t e c r y s t a l s are -g- Mm to 2 mm i n s i z e . - The c r y s t a l s are anhedral t o subhedral i n o u t l i n e , (b)  Mutual R e l a t i o n s . The  subhedral t o euhedral a u g i t e and p l a g i o c l a s e  crystals f i l l e d  between with anhedral o r t h o c l a s e c r y s t a l s  make up a normal g r a n i t i c t e x t u r e . (c)  Composition 1 - Augite  - 15$  2 - Andesine-Labradorite  - 26$  3  - 48$  - Orthoclase  4 - Quartz  -  5 - Biotite  - 4|$  6 - Magnetite  - 4|$  7  -l|$  - Apatite  (d)  The t e x t u r e i s g r a n i t i c .  (e)  The rock i s an A u g i t e Monzonite. This rock i s very much l i k e  much o r t h o c l a s e and there i s a l i t t l e  1$  except  there i s too  quartz p r e s e n t .  Another  d i f f e r e n c e i s the g r a n i t i c t e x t u r e i n s t e a d of the monzonitic texture i n S . n  P.WR.  C O P P E R  M O I N T A I N B R I T I S H  GcnTcur  Interval  250  Feet  M I J Y I N G  A R E A  C O L U M B I A 1 I n c h t o 1 0 0 0 Vend  

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