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UBC Theses and Dissertations

A petrographic study of granitization in the norite at Dinty Lake, Northern Saskatchewan McLellan, Robert Bryant 1940

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A PetrO'grapiiic Study o f G r a n d t i z a t i o n i n the N o r i t e a t D i n t y Lake, Northern Saskatchewan.  Robert Bryant  McLellan  A T h e s i s submitted i n P a r t i a l F u l f i l m e n t of The Requirements f o r the Degree of MASTER OF ARTS i n the Department of GEOLOGY  THE UNIVERSITY OP BRITISH COLUMBIA APRIL 1940.  Table of C o n t e n t s . Page I Introduction  1  (a) General Statement  1  (b) L o c a t i o n and Topography  2  lc)  3  P e t r o g r a p h i c Study and Acknowledgements  I I General Geology  4  (a) P r i n c i p a l Rock U n i t s  4  (b) S t r u c t u r e  5  I I I D i a m o n d - d r i l l Cores and T h i n S e c t i o n s  7  IV P e t r o g r a p h i c d e s c r i p t i o n  9-  of the Rock Types  (a) R e g i o n a l G r a n i t e Gneiss (b) H o r i t e and R e l a t e d Types  ^  1  9 10  (1) F o r i t e  10  (2) P y r o x e n i t e  IL  (3) Hybrid Types  12  ( c ) Pegmatites  14  (d) Lamprophyres  14  V Phenomena of G r a n i t i z a t i o n VI Process cf:Granitiza;tioh-. . .:  15 17  (a) The A n a r t h o s i t e Problem  18  (b) G r a n i t i z a t i o n of H o r i t e  19  £c) Accompanying E f f e c t s  21  VII Geologic H i s t o r y  22  V I I I Conclusions  24  IX B i b l i o g r a p h y  25  Illustrations E l a t e I. Map of the Main B o r e a l i s D e p o s i t .  Follows page  P l a t e I I S e c t i o n A c r o s s Main B o r e a l i s D e p o s i t . (Both reproduced from the r e p o r t of Dr. C O . on the D i n t y Lake N i c k e l D e p o s i t s } .  "  " Swanson  A P e t r o g r a p h i c Study of G r a n i t i z a t i o n i n the N o r i t e a t D i n t y Lake, Northern Saskatchewan,  Introduction (a) General  Statement The present work i a intended to c o n s i d e r , and  propose s o l u t i o n s f o r p e t r o g e n i c problems a r i s i n g from examination  the  of the D i n t y Lake N i c k e l D e p o s i t s , Saskatchewan, The fundamental problem i n v o l v e s the g r a n i t i z a t i o n  o f the n i c k e l i f e r o u 3 n o r i t e body, and d i v i d e s i t a e l f  into  t h r e e s p e c i f i c problems, namely to determine:  ( l ) the degree  to which the n o r i t e has been a l t e r e d ,  processes  c o n t r o l l i n g the g r a n i t i z a t i o n , and  (2) the  (3) the probable  nature  o f the o r i g i n a l ore body. Although regional granitic 1936,  ;  the sedimentary  g n e i s a was  o r i g i n of much of the  r e c o g n i z e d by A l c o c k  1  before  the known bodies of n o r i t e were considered to be  i n t r u s i v e i n t o the g r a n i t i z e d sediments.  I t was  not  until  a f t e r the D i n t y l a k e d e p o s i t s were d i s c o v e r e d i n 1936  that  t h e i r s t r u c t u r a l and m i n e r a l o g i c a l v a r i a t i o n s were a s c r i b e d to r e g i o n a l metamorphism. The p r o p e r t y was c o n s i d e r a b l e d e t a i l i n June, 1938 1  A l c o c k , P.J.,  examined i n  by Dr. C O .  Swanson.  The Geology of the Lake Athabaska R e g i o n i  Can. G e o l . Survey, Mem.  196,  p.10,  1936.  Trenching, and d i a m o n d - d r i l l i n g were the sampling  metho»ds,  and magnetic o b s e r v a t i o n s were taken to determine the extent of the ore body. H i a r e p o r t  1  on the d e p o s i t B s g i v e s c o n c l u s i v e  evl&eneemaf g r a n i t i z a t i o n . The group of c l a i m s c o n t a i n i n g the main d e p o s i t belongs  to the B o r e a l i s Mining  S y n d i c a t e , and adjacent  are h e l d by the G o n s i l i d a t e d Mining and Smelting  (b) L o c a t i o n and  claims  company.  Topography  D i n t y Lake i s s i t u a t e d a t the western edge o f the Eond-du-Lac map-area o f northern Saskatchewan. I t i s about 25 m i l e s to the n o r t h e a s t of G o l d f i e l d s and about 15 m i l e s fromhLake:.Athabaska i n t o which i t d r a i n s by way  o f the Beaver  E i v e r . D i n t y Lake measures about 2% m i l e s long and -§- m i l e wide. The a r e a to which the present problem i s c o n f i n e d i s about a q u a r t e r m i l e n o r t h of the l a k e . I t i s the l a r g e s t n o r i t e exposure i n the v i c i n i t y of the l a k e , having a width o f about 300 f e e t and extending about 1000  f e e t along i t s  north-south e l o n g a t i o n . The exposure caps a broad r i d g e a t an e l e v a t i o n of about 110 f e e t above D i n t y Lake. Other s i m i l a r , but s m a l l e r , n o r i t e bodies l i e along the same zone, the l a r g e s t being more than a h a l f m i l e to the n o r t h . ^ Swanson, CO., Sask.% J u l y 6,  "Report 1938.  on D i n t y Lake N i c k e l D e p o s i t s ,  -3The r e l i e f o f the area i a t y p i c a l o f the L a u r e n t i a n P l a t e a u r e g i o n , the edge o f which i s marked by Lake Athabaska. Howhere i s the r e l i e f g r e a t e r than 400 f e e t . P l a t - t o p p e d though m o d i f i e d by g l a c i a t i o n , suggest  hills,  a former p e n e p l a n e .  Drainage i s d i s o r g a n i z e d , and c o u n t l e s s l a k e s and swamps occupy the d e p r e s s i o n s . Dirnty Lake p a r t l y c r o s s e s and p a r t l y f o l l o w s the s t r i k e of the bedrock. S i n c e the physiography  i s largely  c o n t r o l l e d by g l a c i a t i o n , l o c a l m o d i f i c a t i o n s a r e not n e c e s s a r i l y guides  to the g e o l o g i c a l s t r u c t u r e .  (c) P e t r o g r a p h i c Study and Acknowledgments. During  the winter months o f 1939-40 the w r i t e r  devoted c o n s i d e r a b l e time to the examination drill  of diamond-  core samples from the p r o p e r t y . A 3 e t o f t h i n s e c t i o n s  made from the cores were s t u d i e d i n d e t a i l by means o f the p e t r o g r a p h i c microscope. TJhe w r i t e r wishes to express h i s indebtedness to Dr. G.O. Swanson f o r the use of the m a t e r i a l s and equipment, and f o r the many h e l p f u l suggestions  and f r e q u e n t words of  a d v i c e which were i n v a l u a b l e i n the undertaking work.  of t h i s  -4General Geology, (a) P r i n c i p a l Rock U n i t s . The u n d e r l y i n g bedrock of the area i s the r e g i o n a l g r a n i t e g n e i s s . I t c o n s i s t s of h i g h l y metamorphosed sediments v a r y i n g i n t e x t u r e from banded q u a r t z i t i e paragneiss to a ^rather b a s i c and .gneissic g r a n i t e or o r t h o g n e i s a . paragneiss is- u n i f o r m l y banded suggesting: an sedimentary  The  original  bedding:, but there are no h o r i z o n markers..The  more massive o r t h o g n e i s s has the c h a r a c t e r i s t i c s of an I n t r u s i v e rock i n c e r t a i n p a r t s but o t h e r specimens show a g r a d a t i o n i n t o s t r e a k e d and f o l i a t e d g n e i s s w i t h b a s i c c l o t s and  inclusions. The l a r g e s t and most n o t a b l e i n c l u s i o n s are  the  masses of p y r r h o t r t e - b e a r i n g n o r i t e . They range i n composi t i o n from b i a t i t e - r i e h n o r i t e to p y r o x e n i t e dense w i t h p y r r h o t i t e and through g n e i s s i c p o r t i o n s to h i g h l y f e l s p a t h i c types c a l l e d •'"anorthasites * f o r convenience. 1  These v a r i e t i e s  i n c l u d e many a l t e r e d and h y b r i d types b e l i e v e d due  to  processes of g r a n i t i z a t i o n . To the confusing mixtures  of  g r a n i t e g n e i s s and n o r i t e types the term "migmatites"  is  applied. A g r e a t many i r r e g u l a r pegmatite  d i k e s cut  g n e i s s and n o r i t e . Intruded i n t o a l l three are a  the  few  lamprophyre d i k e s of f r e s h massive m a t e r i a l w i t h dark mica phenoerysta. The economic value of the p r o p e r t y i s based on n i c k e l content o f the p y r r h o t i t e . Assays show t h a t even  the  -5the r i c h p a r t s o f the d e p o s i t c o n t a i n o n l y .2. to ,5 percent n i c k e l , and t h e r e f o r e connot he commercial o r e .  (h) S t r u c t u r e The r e g i o n a l s t r u c t u r e i s shown hy the conformable banding of  o f the p a r a g n e i a s . Ho such e x t e n s i v e  the i n t r i c a t e l y f o l d e d sedimentary  interpretation  g n e i s s has y e t been  worked out, however, f o r mapping, made d i f f i c u l t spread g l a c i a l d e p o s i t s and sand p l a i n s , i s s t i l l  by widevery  disjointed* In the v i c i n i t y o f D i n t y Lake the s t r u c t u r e i s f a i r l y u n i f o r m . The banded g n e i s s assumes a n o r t h - s o u t h s t r i k e w i t h a v a r i a b l e d i p to the west, and g e n e r a l l y conforms to the e l o n g a t i o n of the n o r i t e zone. The western p a r t of t h i s area has a steep d i p and i s g e n e r a l l y w e l l banded. Hear t h e o r e bodies and to the e a s t , however, the more massive g n e i s s i s i n t e r p r e t e d aa forming  structural  t e r r a c e s to which the n o r i t e a l s o conforms. This structure' i n v o l v e s f l a t d i p s to the west. The conformable nature o f the main n o r i t e body was  determined  II.  This l e a d s to the c o n c l u s i o n t h a t i t was o r i g i n a l l y a  concordant  by diamond d r i l l i n g  as shown i n P l a t e s I and  i n t r u s i v e , probably a s i l l . Numerous c r o s s - f a u l t s w i t h s m a l l o f f s e t s  cut  the g n e i s s and n o r i t e . Most of them are p r a c t i c a l l y  v e r t i c a l and s t r i k e west to northwest. Some of these a r e  -6occupied  by the pegmatite d i k e s which are o n l y a few  wide, w h i l e c o a r s e l y b r e c c i a t e d m a t e r i a l d e f i n e s Another s e t of f a u l t s s t r i k e s 40  no displacement i a apparent. The  i n j e c t i o n s be t r a c e d on the The  poorly  lamprophyre  d i k e s f o l l o w these f r a c t u r e s which cut a l l other Only by the s l i g h t l y magnetic p r o p e r t y  bedrock.  of the d i k e s can  these  surface.  s t r u c t u r e of the area i n q u e s t i o n  i s seen,  from t h i s o u t l i n e , to be q u i t e simple, w i t h very few which might complicate  others.  to 70 degrees  e a s t and d i p s s t e e p l y to the northwest. They are d e f i n e d and  the  feet  features  the r e c o n s t r u c t i o n of the o r i g i n a l  ore  body. In mapping the area Dr. Swanson s t r u c t u r a l f e a t u r e s such as the n o r i t e i t s e l f .  Personal  communication.  "'•sedimentation'*  1  found no  t r a c e of  structure within  -7D i a m o n d - d r i l l Gores and Thin S e c t i o n s . The specimens r e f e r r e d to i n t h i s study were s e l e c t e d as r e p r e s e n t a t i v e samples of the r o c k types i n the a r e a . They are taken from three of the twelve d i a m o n d - d r i l l h o l e s sunk i n and near the main B o r e a l i s d e p o s i t . A l l three h o l e s (D.D.H.I,2,3; P l a t e I I ) l i e i n the same v e r t i c a l east-weat p l a n e , and a r e arranged as shown hy t h e i r numbers. Prom the, s t r u c t u r a l r e l a t i o n s of the n o r i t e i t can r e a d i l y be seen t h a t w i t h t h i s arrangement the specimens r e p r e s e n t d i f f e r e n t s t r a t i g r a p h i c horizons i n their r e s p e c t i v e d r i l l h o l e s and f o l l o w no known s t r u c t u r a l or c o n s t r i c t i n g f e a t u r e s . Prom the 59 specimens a t hand 18 t h i n s e c t i o n s were c u t . They were s e l e c t e d to r e p r e s e n t the more  typical  r o c k s , and t h e i r d i s t r i b u t i o n i s i n d i c a t e d i n P l a t e I I . The f o l l o w i n g t a b l e g i v e s the index number, l o c a t i o n , and e s s e n t i a l nature of each t h i n s e c t i o n . The m i c r o s c o p i c examination  of theae t h i n s e c t i o n s  c o n s t i t u t e d the s o l e means of t e x t u r a l and q u a n t i t a t i v e d e t e r m i n a t i o n . The remaining megaseopically,  specimens proved  helpful  and g r a i n s o f s e v e r a l were examined under the  microscope i n r e f r a c t i o n o i l s as a check on t h e i r m i n e r a l composition.  -8Fa. D.D.H. D.L.  1** 1  Rook Type.  356*  Biotite granite,  ,fc  normal  n:  granite gneiss.  3  3  33  G n e i s s i c g r a n i t e , w i t h g a r . and q/tz..  6*  1  506"  Granitic gneiss,  7  3:  117£  Andesine r o c k , w i t h ehlor. and q^tz..  9*  1  609  Granitic gneiss, cataclastic.  sedimentary.  10  2  40  14*'  1  308i  18  1  21  1  166  24  3  85  30  1  215  A l t e r e d n o r i t e , w i t h s c a t t e r e d pyrrhotite, e t c .  35  1  251  A l t e r e d n o r i t e , w i t h amphihole and c h l o r i t e .  37  2.  40  2  172  A l t e r e d p y r o x e n i t e j w i t h p y r . and amph..  46  3  160  Contact p y r . - p y r o x e n i t e and g a r . gn..  57  2:  121  Mica lamprophyre, near upper c o n t a c t .  58  2  125  Mica lamprophyre, c e n t e r .  Garnet g n e i s s , t y p i c a l . Garnet g n e i s s , near p y r . i n c l u s i o n i n g r . . Contact p y r . - p y r o x e n i t e and g a r . gn..  55  Garnet g n e i s s , w i t h pyr.-pyx.  inclusion.  A l t e r e d n o r i t e , w i t h p y r r h o t i t e and m i c a .  Typical norite.  * S i t u a t e d w e l l "beyond the l i m i t o f the n o r i t e . A s i d e from the p e t r o g r a p h i c d i f f i c u l t i e s , the f a c t that the t h i n s e c t i o n s c o n s t i t u t e an i n f i n i t e s i m a l p a r t of the r o c k s which they r e p r e s e n t , i n d i c a t e s that they cannot be accurate q u a n t i t a t i v e guides to the rock  composition.  This i s e s p e c i a l l y true i n the present case where the r o c k s known to be heterogeneous and i r r e g u l a r l y a l t e r e d . Moreover,  the t h i n s e c t i o n s show wide v a r i a t i o n s even i n the same type of r o c k . This f e a t u r e , however, i s the e s s e n t i a l  characteristic  upon which t h i s study i s based, f o r the fundamental problem i s the i n t e r p r e t a t i o n of these v a r i a t i o n s .  P e t r o g r a p h i c D e s c r i p t i o n of the Rock Types, (a) R e g i o n a l G r a n i t e Gneiss As d e s c r i b e d i n g e n e r a l on a p r e c e d i n g page the g r a n i t e g n e i s s v a r i e s w i d e l y i n texture and composition i n d i f f e r e n t p a r t s . The v a r i a t i o n s are b e l i e v e d to be due to o r i g i n a l d i f f e r e n c e s i n the composition of the  partly  sedimentary  rocks but m a i n l y to d i f f e r e n c e s i n the degree o f g r a n i t i z a t i o n . As a b a s i s f o r comparisons,  the "normal" g r a n i t e g n e i s s  may  be d e s c r i b e d as the most h i g h l y r e c r y s t a l l i z e d rock showing the m i n e r a l c h a r a c t e r i s t i c s of an a l t e r e d  rock.  Of the f o u r r e p r e s e n t a t i v e t h i n s e c t i o n s of the r e g i o n a l g n e i s s , s e c t i o n Ho.9  appears  to be most h i g h l y  r e c r y s t a l l i z e d , but q u a r t z , the c h a r a c t e r i s t i c m i n e r a l of the sediments,  i s not p r e s e n t . S e c t i o n N o . l , then, i s taken as the  "normal" g r a n i t e g n e i s s . I t s composition compares f a i r l y c l o s e l y t a t h a t o f Ho.6  i n which a sedimentary  bedding i s  p r e s e r v e d . These r o c k s are composed e s s e n t i a l l y of q u a r t z Z0%)  and o r t h o c l a s e (40-60^) w i t h b i o t i t e  2.-8$)  as the common a c c e s s o r i e s . Small amounts of  r  (5-2.0#) and  garnet  magnetite  -10and p y r r h o t i t e are u s u a l l y present among the dark m i n e r a l s , A few g r a i n s of medium p l a g i o c l a s e and some s e r i c i t e f l a k e s occur w i t h the o r t h o c l a s e . The garnet i s a p i n k i s h v a r i e t y ,  probably  almandite, and commonly c o n t a i n s i n c l u s i o n s of q u a r t z , and magnetite.  The l a r g e r garnet c r y s t a l s are  biotite,  invariably  f r a c t u r e d , and i n both s e c t i o n s the f r a c t u r e s have a common o r i e n t a t i o n , i n d i c a t i n g s t r e s s c o n d i t i o n s . The  t e x t u r e of  the l i g h t m i n e r a l s i s a l l o t r i o m o r p h i c m i c r o c r y s t a l l i n e but the a c c e s s o r i e s u s u a l l y form l a r g e s t r e a k s or c l o t s .  The  other specimens of g r a n i t e g n e i s s d i f f e r from the "normal i n m i n e r a l p r o p o r t i o n s and  t e x t u r e . One  s e c t i o n shows an  abundance of q u a r t z and another very l i t t l e . G a t a e l a a t i c t e x t u r e s are common.  (b) N o r i t e and R e l a t e d Types; Cl)  Norite The l e a s t a l t e r e d n o r i t e i s a hypidiomorphic  fine  g r a i n e d to m i c r o g r a n u l a r r o c k . Hypersthene and a few g r a i n s of  e n s t a t i t e make up 65 p e r c e n t of i t , and  labradorite  (Ab4sAn55) about 15 p e r c e n t . Reddish-brown b i o t i t e  i s present  i n amounts up t o 12 p e r c e n t , and a s s o c i a t e d w i t h i t are a few g r a i n s of t i t a n i t e w i t h magnetite  C?)  r i m s . These  m i n e r a l s are a l l primary, f o r the f i r s t i n d i c a t i o n of a t i o n i s a s t r e a k a t one edge of the specimen where has reduced remnants.  alter-  sericite  the p l a g i o c l a s e to a few b a r e l y r e c o g n i z a b l e  -11An a l t e r e d n o r i t e specimen, though d i f f i c u l t d i s t i n g u i s h from the u n a l t e r e d  to  r o c k i n the hand specimen,  shows only a t e x t u r a l s i m i l a r i t y under the m i c r o s c o p e . t r a c e of pyroxene remains, but  i t i s replaced  by f i b r o u s u r a l i t e rimmed by c h l o r i t e . The s o d i c andesine and  No  isomorphously  plagioclase  is a  i s i n t e r s t i t i a l between the dark m i n e r a l s .  I t i s s l i g h t l y s e r i c i t i z . e d . B i o t i t e shows a tendency to concentrated i n s c h i s t o s e  s t r e a k s . Each of these m i n e r a l s  compares c l o s e l y i n abundance w i t h the i n the u n a l t e r e d  be  corresponding m i n e r a l s  norite.  (2.) P y r o x e n i t e The  n o r i t e grades i n t o p y r o x e n i t e by a decrease  i n the amount of f e l s p a r . In most specimens l a b r a d o r i t e i s completely s u b s t i t u t e d by p y r r h o t i t e . A s m a l l p r o p o r t i o n augite  of  i s a l s o developed* In the f r e s h p y r o x e n i t e b i o t i t e i s  the o n l y a c c e s s o r y m i n e r a l . A l t e r a t i o n products commonly present are amphibole, magnetite, and  garnet,  secondary b i o t i t e . A specimen o f  h i g h l y magnetic p y r o x e n i t e c o n s i s t s of f i b r o u s u r a l i t e enclosing  s c a t t e r e d p y r r h o t i t e and minor amounts of  and c h l o r i t e .  biotite  C3) H y b r i d Types The h i g h l y a l t e r e d types o f rock w i t h i n the n o r i t e body are r e p r e s e n t e d by the m a j o r i t y of the specimens. I t cannot be assumed from t h i s t h a t there i s n e c e s s a r i l y a preponderance of h y b r i d m a t e r i a l i n the body, y e t from field  the  r e l a t i o n s such types a r e found to p e r s i s t over l a r g e  p o r t i o n s o f the n o r i t e a r e a . Ho estimate of the p r o p o r t i o n of  u n a l t e r e d n o r i t e and p y r o x e n i t e has been made, but  b u l k of t h i s f r a y e d s i l l  the  i s probably a f f e c t e d by g r a n i t i z a t i o n .  Of the many h y b r i d types a t hand, the most common i s a migmatite  closely related  to the n o r i t e . There i s no  t r u l y r e p r e s e n t a t i v e t h i n a e c t i o n of t h i s , but powdered specimens under the microscope  were examined. They a r e r i c h i n  both s o d i c and medium p l a g i o c l a s e w i t h c o n s i d e r a b l e b i o t i t e and g a r n e t . The m i n e r a l r e l a t i o n s are shown by a t h i n s e c t i o n of  a more g r a n i t i c t y p e . The s o d i c f e l s p a r  c o n t a i n s a n d e s i n e - l a b r a d o r i t e as p o i k i l i t i c  (oligoclase) i n c l u s i o n s . Both  r e d d i s h and b l a c k garnet are present as s m a l l rounded g r a i n s . Magnetite  and b i o t i t e are a s s o c i a t e d w i t h them forming  g n e i s s i c c l o t s . A few pyroxene g r a i n s a l s o occur w i t h the g a r n e t Another t h i n s e c t i o n i s about 80 percent andesine w i t h s m a l l amounts of q u a r t z and a l b i t e . C h l o r i t e i s present as v e i n l e t s c r o s s i n g the whole specimen. When d e s c r i b i n g the fragmental m a t e r i a l of the  n o r i t e exposure, Cdoke  probably r e f e r r e d to. a migmatite type  x  c l o s e to the n o r i t e composition. He observes that -—  i s rather fine-grained, equigranular,  about the t e x t u r e and  and  **the r o c k  d i r t y gray,  g r a i n s i z e of l o a f sugar. In hand  specimen i t i s r e a d i l y mistaken f o r a f i n e - g r a i n e d , basic g r a n i t e , or gneiss. — Ahg§An|.g to Ab55An45, and  rather  The f e l d s p a r i s andesine,  on the whole I s f a i r l y f r e s h  •  I t s p r o p o r t i o n v a r i e s , i n d i f f e r e n t fragments, from about 30 percent o f the t h i n s e c t i o n to n e a r l y 100  percent'*. These  f e l s p a t h i c v a r i e t i e s have been c a l l e d a n o r t h o s i t e s . Garnet g n e i s s  I s another v a r i e t y of h y b r i d  found i n the n o r i t e body. I t c o n s i s t s m a i n l y of  commonly  plagioclase  and g a r n e t , w i t h the u s u a l a c c e s s o r y m i n e r a l s of the g n e i s s . Quartz i s abundant i n c e r t a i n specimens and mosaic p a t t e r n . A l k a l i f e l s p a r may  regional forms a  a l s o be present as i s o l a t e d  patches. There i s no g r a d a t i o n i n t o the garnet g n e i s s . The  from the n o r i t e or  contact  zones are very narrow,  a l t e r a t i o n products such as garnet and to a q u a r t e r  pyroxenite  s e r i c i t e are  confined  i n c h width a t the edge of the p y r o x e n i t e  In c o n t r a s t  to the f r e s h appearance of  masses.  the  m i n e r a l s i n the t y p i c a l n o r i t e , the b i o t i t e i n h y b r i d  types  i s u s u a l l y bleached, or p a r t l y a l t e r e d to> c h l o r i t e . S e r i c i t e 1  Cooke, H.C.,  G o l d f i e l d s A r e a , Sask., G e o l . Survey.  P r e l i m . Report, Paper 37-3,  (1937) p.  19.  Can.,  i s almost; i n v a r i a b l y present among the f e l s p a r s , and amphibole i s not r a r e as an a l t e r a t i o n product  of pyroxene,  (c) Pegmatites The v e i n s o r d i k e s which f o l l o w east-west c r o s s f a u l t s o f the area consist: o f quartz, and s o d a - r i c h f e l s p a r ( o l i g o c l a s e ) w i t h minor amounts o f garnet* m a g n e t i t e . Except  c h l o r i t e , and  f o r the s l i g h t c h l o r i t i z a t i o n  these  pegmatites appear to be u n a l t e r e d .  (d) Lamprophyres T h i n s e c t i o n s o f the lamprophyre d i k e m a t e r i a l show no e f f e c t s o f g r a n i t i z i n g s o l u t i o n s . T h i s  is.in  agreement w i t h t h e i r c r o s s c u t t i n g r e l a t i o n s h i p t o a l l o t h e r rocks i n the a r e a . The t e x t u r e and composition  o f the lamprophyre i s  3hown by two t h i n s e c t i o n s from a d i k e w i t h i n the n o r i t e body. The c e n t r a l p a r t has phenocrysts  of phlogopite,  potash  f e l s p a r , and magnetite. Some euhedral f e l s p a r c r y s t a l s a r e i n t e r m e d i a t e i n s i z e . Near the contact there i s o n l y a s l i g h t decrease  i n the s i z e o f the phenocrysts,  i s somewhat r i c h e r i n hornblende and m a g n e t i t e .  and the m a t r i x  Phenomena of G r a n i t i z a t i o n . The f o l l o w i n g a e c t i o n w i l l be devoted to a summary o f the p e t r o g r a p h i c evidence upon which the c o n c l u s i o n s of t h i s study are based. The  evidence  i s not a l l m i c r o s c o p i c ,  however, i n f a c t the main arguments have been observed  i n the  f i e l d ! . "That the g r a n i t e g n e i s s has i n t r u d e d the n o r i t e i s shown by the shape of the n o r i t e , by the development of h y b r i d r o c k s due  to r e a c t i o n between the n o r i t e and the granite,, and  by the presence of i s o l a t e d s l a b s or fragments of p y r r h o t i t e bearing n o r i t e a t some d i s t a n c e from the main c o n t a c t s * . 1  There i s a l s o abundant p e t r o g r a p h i c evidence  1  of  g r a n i t i z a t i o n throughout the a r e a . That the r e g i o n a l g r a n i t e g n e i s s was  developed  by the g r a n i t i z a t i o n of sediments needs  no support from the present  study, f o r the  r e l a t i o n s and m i n e r a l composition,  structural  along w i t h the widespread  and e r r a t i s c o c c u r e n c e p e p r e c l u d e any p o s s i b i l i t y o f an igneous o r i g i n . I n c o n f i r m a t i o n of the g r a n i t i z a t i o n p r o c e s s , however, t h i n s e c t i o n s o f the g r a n i t e g n e i s s , r e p r e s e n t i n g r o c k s more than 100 f e e t o u t s i d e the main c o n t a c t s , show m i c r o s c o p i c evidence. A t y p i c a l specimen of the r e g i o n a l g n e i s s aa d e s c r i b e d i n the preceding m i n e r a l composition  s e c t i o n has very n e a r l y the same  as another  specimen which s t i l l r e t a i n s  the handed appearance of a thin-bedded  1  Swanson, C O . ,  J u l y , 1938,  p.8.  sediment.  Report on D i n t y Lake N i c k e l D e p o s i t s , Sask.,  -16P e t r o g r a p h i e f e a t u r e s of the n o r i t e  complex,  which support the i d e a of g r a n i t i z a t i o n and h e l p to e x p l a i n the s t r u c t u r a l phenomena, i n c l u d e v a r i a t i o n s i n t e x t u r e and m i n e r a l r e l a t i o n s . At the c o n t a c t s between the garnet  gneiss  and p y r r h o t i t e - b e a r i n g : p y r o x e n i t e c e r t a i n a l t e r a t i o n  products  develop which are no doubt due a r e a r e q u i t e sharp i n two  to a r e a c t i o n . The  t h i n s e c t i o n s . One  contacts  of these  (No.  18)  shows garnet and pyroxene g r a i n s grouped i n g n e i s s i c f a s h i o n i n the g n e i s s , and g a r n e t rims developing around hyperathene g r a i n s o f the p y r o x e n i t e . B i o t i t e and magnetite are e x t e n s i v e l y developed  along the c o n t a c t zone and among the g n e i s s i c S e c t i o n No.  clots.  46 shows a sharp c o n t a c t between  p y r o x e n i t e and a coarse band o f andesine. Narrow s t r e a k s o f hypersthene,  g a r n e t , and b i o t i t e run p a r a l l e l to and near the  c o n t a c t . The hypersthene  i s a highly ferruginous v a r i e t y ,  some c r y s t a l s c o n t a i n i n g t a b u l a r i n c l u s i o n s . The p y r r h o t i t e i s g r a n u l a r and  interstitial,  and has i n c l u s i o n s and rims of  magnetite which appear to be r e l a t e d  to the b i o t i t e  There i s c o n s i d e r a b l e s e r i c i t e developed  flakes.  i n the f e l s p a r a r e a ,  but the process i s nowhere near completion. The f e l s p a r i s b a s i c andesine  and  c o n t a i n s no a c c e s s o r y m i n e r a l s .  An i n c l u s i o n of p y r r h o t i t e - b e a r i n g p y r o x e n i t e i n a s i m i l a r f e l s p a t h i c type i s r e p r e s e n t e d by s e c t i o n No.  21.  No  garnet i s p r e s e n t , but the evidence of a l t e r a t i o n c o n s i s t s of rims of f i b r o u s amphibole between the g r a i n s of and p y r r h o t i t e . The border of the i n c l u s i o n  hypersthene -cgai^e-. i r r l g g & l a r  and remnant g r a i n s of pyroxene are s c a t t e r e d through the g n e i s s . B i o t i t e i s abundant between the dark m i n e r a l s , and s e v e r a l f l a k e s of i t i n the t h i n s e c t i o n a r e bleached t o a p a l e green w i t h s t r e a k s of i r o n oxide d e p o s i t e d p a r a l l e l to the c l e a v a g e . Through a l l specimens of t y p i c a l garnet g n e i s s which are l o c a t e d w i t h i n the n o r i t e , t i n y rounded., g r a i n s o f pyroxene occur w i t h l a r g e r r g a r n e t c r y s t a l s and b i o t i t e  flakes.  The b i o t i t e i s more c l o s e l y a s s o c i a t e d w i t h pyroxene than w i t h garnet. The g e n e r a l c h a r a c t e r o f the migmatites  as d e s c r i b e d  i n a preceding s e c t i o n i s evidence of an advanced stage i n the g r a n i t i z a t i o n p r o c e s s . The development o f untwinned s o d i c p l a g i o c l a s e i n d i c a t e s the h i g h degree of r e g i o n a l metamorphism.  Process of G r a n i t i z a t i o n An i n t e r p r e t a t i o n of the p e t r o g r a p h i c d e t a i l s d e s c r i b e d above l e a d s to an a c c e p t a b l e e x p l a n a t i o n of the p r o c e s s e s c o n t r o l l i n g the g r a n i t i z a t i o n . The c o n c l u s i o n I s not a r r i v e d a t , however, without i n v e s t i g a t i n g more than p o s s i b i l i t y as to the o r i g i n a l nature of the n o r i t e  one inclusion.  Omitting any d i s c u s s i o n of the g r a n i t i z a t i o n of the r e g i o n a l sediments^-  assuming from the fragmentary  process was  a normal one - the d i s c u s s i o n w i l l be c o n f i n e d to  the n o r i t e changes.  evidence t h a t the  -18Ca)  The A n o r t h o s i t e Problem. Prom the i r r e g u l a r d i s t r i b u t i o n o f the p y r r h o t i t e ,  the l a r g e tongues of g n e i s s i c g r a n i t e , and masses o f h y b r i d rocks w i t h i n the ore body, the p o s s i b i l i t y of o r i g i n a l d i f f e r e n c e s i n composition i s suggested. The a r b i t r a r y boundaries  between some of the main rock types as shown i n  P l a t e I I suggest an o r i g i n a l banded s t r u c t u r e . The e x i s t e n c e of  primary a n o r t h o s i t i c l a y e r s might be taken as a p o s s i b l e  e x p l a n a t i o n of the p l a g i o c l a s e - r i c h r o c k s . In  d e s c r i b i n g the n o r i t e i n other p a r t s of the  r e g i o n , A l c o c k noted that "an i n t e r e s t i n g f e a t u r e i n connection  w i t h these rocks i s the occurrence of complementary  v a r i e t i e s , some dikes c o n s i s t i n g of l a b r a d o r i t e w i t h o n l y minor amounts of pyroxene and i r o n oxide and o t h e r s being made up almost  completely o f orthorhombie  pyroxenes'*'.  1  It i s  not c l e a r , however, whether both v a r i e t i e s occur i n the same •"dike*. The p o s s i b i l i t y of such a s i t u a t i o n i s worthy o f s e r i o u s c o n s i d e r a t i o n i n the present case, f o r a sill  composite  o f complementary v a r i e t i e s i s remotely c o n c i e v a b l e . The main s t r u c t u r a l argument i n f a v o r of the  a n o r t h o s i t e bands i s the rough correspondence  of the g n e i s s i c  h o r i z o n s i n three d r i l l h o l e s , and the i n j e c t i o n of tongues of 1  g n e i s s p a r a l l e l , i n g e n e r a l to the f l o o r o f the s i l l . The A l c o c k , P.J., Geology o f Lake Athabaska Region,  Can. G e o l . Survey, Mem. 196, (1936) p. 19.  Sask.,  -19evidence f o r t h i s , however, i s fragmentary, and pondence may  e a s i l y he  coincidental.  o c c u r r e n c e s of g n e i s s and  There are  The arguments are and  corres-  confusing  n o r i t e i n p l a c e s where the  are more c l o s e l y spaced, showing that d i s t a n c e s i s not  the  specimens  interpolation for  possible.  more c o n v i n c i n g of the p o s s i b l e ( l ) that  the  petrographic  sharp c o n t a c t between p y r o x e n i t e  andesine r o c k types i s the r e s u l t of an i n j e c t e d  i o c l a s e l a y e r i n t o a s t i l l hot  n o r i t e body, and  e x i s t e n c e together of c a l c i c and  sodic  that  i t i s not  r e f u t a t i o n of the f i r s t  basic plagioclase  i s not  The  of  There i s now  i n migma-  anorthosite.  of these arguments i s  and  i n any  the  case i t could  pyroxene going to form g a r n e t ,  thin sections, no  Horite no  reasonable argument, from the  to oppose the  anorthositic  s u p p o r t i n g e v i d e n c e . There are  variations.  no  The  possibility  labradorite  of  no  rocks r e p r e s e n t e d ,  there i s no g r a d a t i o n between such a type and  B e s i d e s , there i s more than one  study  idea of an o r i g i n a l n o r i t e  c r y s t a l s o r t i n g , to cause l a b r a d o r i t e - r i c h l a y e r s , h a s  and  the  mica.  (b) G r a n i t i z a t i o n  body which had  that  second i s f a u l t y i n that  labradorite  be developed from n o r i t e , the  of the  plag-  reasonable to assume a s e r i e s of such i n j e c t i o n s  of a n o r t h o s i t e i n t o a s i l l .  c h l o r i t e , and  (2)  plagioclase  t i t e i s the r e s u l t of g r a n i t i z a t i o n of the The  large  the  norite.  f e l s p a t h i c band to account f o r .  F u r t h e r evidence s u p p o r t i n g the homogeneous nature of the o r i g i n a l s i l l  i n c l u d e s the nature of the p l a g i o c l a s e  and the d i s t r i b u t i o n of the femic m i n e r a l s . The most c a l c i c p l a g i o c l a s e i s observed i n the u n a l t e r e d n o r i t e , and has a composition of Ab^QAngQ* As g r a n i t i z a t i o n e f f e c t s i n c r e a s e , f e l s p a r s of a more s o d i c composition a r e formed as shown by the h y b r i d types i n which the f e l s p a r s range from  labradorite,  A b ^ A n g g , to Andesine, Ab^An^g, w i t h a steady g r a d a t i o n . G n e i s s i c h y b r i d s r e p r e s e n t a l l stages, i n t r a n s i t i o n , but those more c l o s e l y i n contact w i t h p y r o x e n i t e have the more basic, felspars. That the g n e i s s has i n t r u d e d the n o r i t e i s a l s o i n d i c a t e d by the development of g n e i s s i c c l o t s of m o n o c l i n i c pyroxene,  b i o t i t e , and garnet by r e a c t i o n of the g r a n l t i z i n g  s o l u t i o n s on the n o r i t e . The a l t e r a t i o n i s d e f i n i t e l y shown by the phenomenon of rimming a t the g n e i s s i c c o n t a c t s as p r e v i o u s l y mentioned. T h e ~ g r a n i t i z a t i o n o f the n o r i t e complex i n v o l v e d c o n s i d e r a b l e a d d i t i o n of m a t e r i a l . Assuming s e c t i o n No. 37 to be t y p i c a l of the o r i g i n a l n o r i t e , i t can be seen that to produce  the migmatite  type such as No. 30 i t s composition  must have been changed a p p r e c i a b l y . To account f o r the f o r m a t i o n of garnet o f the alraandite v a r i e t y , brown b i o t i t e , and m o n o c l i n i c pyroxene from the o r i g i n a l combination of hypersthene  and l a b r a d o r i t e ,  very l i t t l e g a i n or l o s s o f m a t e r i a l i s n e c e s s a r y . The  -21abundanee of c h l o r i t e and amphibole, however, suggest the addition  of s i l i c a - * and water. S i n c e o r t h o c l a s e i s r a r e i n  the g r a n i t i z e d body, potash i s assumed to have been c o n f i n e d to the sedimentary g n e i s s . The presence of soda p l a g i o c l a s e i n c o n s i d e r a b l e q u a n t i t i e s may be a s c r i b e d l i q u i d a f t e r the r e a c t i o n  to r e s i d u a l  between the n o r i t e  alkali  constituents.  I t i s reasonable to assume, t h e r e f o r e ,  that the  Injection! of a c i d solutions  from the u n d e r l y i n g g r a n i t e  the o n l y important a d d i t i o n  of m a t e r i a l  was  i n the g r a n i t i z a t i o n  process.  (c) Accompanying E f f e c t s The  same f a c t o r s of temperature and pressure which  accompanied the r e g i o n a l  g r a n i t i z a t i o n , caused a rearrangement  of the p y r r h o t i t e . O r i g i n a l l y the s u l p h i d e probably o c c u r r e d as a primary m i n e r a l , being disseminated through p a r t s o f the n o r i t e w i t h a f a i r degree o f r e g u l a r i t y . The e f f e c t o f the granite  i n j e c t i o n was, no doubt, to concentrate the p y r r h o t i t e  from g r a n i t i z e d p a r t s ,  i n j e c t i n g then* i n t o  the complex i n the  form of t h i n seams. The  f o l d i n g which i s so evident throughout the  a r e a was undoubtedly a major f a c t o r i n the g r a n i t i z a t i o n p r o c e s s . By way o f f i s s u r e s and f r a c t u r e  zones the r e a r r a n g e -  ment of the s u l p h i d e s which i t caused, was f a c i l i t a t e d . The abundance of pegmatites which f o l l o w a d e f i n i t e s e t o f fractures  i s c o n c l u s i v e evidence that  the movement was  -22contemporaneous w i t h the g r a n i t i z a t i o n p r o c e s s . The c o a r s e l y c r y s t a l l i n e quartz;-f e l s p a r pegmatites which a r e c u t hy seams of s u l p h i d e s can o n l y be a s c r i b e d Injections  to f r a c t u r i n g and magmatic  as a l a t e stage i n the g r a n i t i z a t i o n p r o c e s s .  Geologic  History.  From the preceding d i s c u s s i o n events i n the development o f the n o r i t e can  the sequence of complex a t D i n t y Lake  be b r i e f l y summarized: The o r i g i n of the o r e body d a t e s  back to a pre-Cambrian, a time when t h i c k sediments covered the a r e a . The l e a s t metamorphosed remnants o f these, and the g e n e r a l composition of the r e s u l t i n g g n e i s s , i n d i c a t e they were l a r g e l y composed o f c o a r s e l y aluminous m a t e r i a l ,  that  fragraental and h i g h l y  probably i n the form o f a r g i l l a c e o u s  quartzites. The  norite  complex was then i n j e s t e d i n t o the  sediments as one member i n a s e r i e s of such i n t r u s i o n s r e g i o n . The n i c k e l - b e a r i n g  pyrrhotite  i n the  accompanied the o r i g i n a l  magma and was d e p o s i t e d among the m i n e r a l s of the n o r i t e . R e g i o n a l f o l d i n g f o l l o w e d t h i s development a f t e r the l a p s e of an undetermined p e r i o d injections into  of time, and g r a n i t i c  the sediments and the igneous bodies o f the  e n t i r e r e g i o n . This transformed the sediments l a r g e l y  into  a g r a n i t i c g n e i s s , but much of the o r i g i n a l bedding i s s t i l l  -23preserved  by coarse  banding.  The n o r i t e complex was  transformed  by the g r a n i t -  i z i n g s o l u t i o n s i n t o the f r a y e d l e n s e s which remain i n evidence  along a d e f i n i t e s t r a t i g r a p h i c h o r i z o n of  surrounding  the  g n e i s s . The remnants of n o r i t e which remain show  that a l t h o u g h  the s i l l was  c o n s i d e r a b l e p a r t of i t was  not e n t i r e l y a s s i m i l a t e d , a metamorphosed, w i t h the development  of migmatites and o t h e r g n e i s s i c h y b r i d s . The l e a s t a l t e r e d n o r i t e shows signs of hydrothermal a l t e r a t i o n . Tongues of garnet g n e i s s penetrated  the s i l l  to g r e a t d i s t a n c e s .  r e g u l a r d i s t r i b u t i o n of the s u l p h i d e s was in and  The  disturbed, resulting  the p r o d u c t i o n of dense p y r r h o t i t e - b e a r i n g p y r o n e n i t e seams of s u l p h i d e along b r e c c i a t e d zones. Pegmatite  were formed as a l a t e phase of the igneous a c t i v i t y , occupied  dike3  and  a s e t of c r o s s f a u l t s i n the r e g i o n . F u r t h e r movements a t a l a t e r time caused another  s e r i e s of f r a c t u r e s which was  accompanied by the i n j e c t i o n of  lamprophyre d i k e s . A small, amount of p y r r h o t i t e was rearranged, sheared  and was  d e p o s i t e d i n seams which cut the  again slightly  lamprophyres. Since the time of these developments, the  changes have been e r o s i o n , weathering, and glaciation.  extensive  only  -24-  Conolusion  The  n i c k e l - b e a r i n g nori.te body at D i n t y l a k e has  undergone a r a d i c a l t r a n s f o r m a t i o n .  Part  o f i t has been  a s s i m i l a t e d by g r a n i t i c i n t r u s i o n , while the remaining part has  s u f f e r e d v a r i o u s degrees o f a l t e r a t i o n .  The g r a n i t e  g n e i s s which has developed w i t h i n the borders o f the n o r i t e can be d i s t i n g u i s h e d regional gneiss.  i n i t s petrographic  features  from the  The e s s e n t i a l processes c o n t r o l l i n g the  g r a n i t i z a t i o n were the r e g i o n a l f o l d i n g and the i n t r o d u c t i o n o f a c i d emanations from the u n d e r l y i n g i n a l nature o f the d e p o s i t  granite.  The o r i g -  was a p y r r h o t i t e - b e a r i n g  norite  s i l l which, except f o r the d i s t r i b u t i o n o f p y r r h o t i t e , was e s s e n t i a l l y homogeneous throughout.  -25-  Bibllography.  A l c o c k , F . J . , The Geology of the Lake Athabaska Region: Can. G e o l . Survey, Mem.  Cooke, H.C,  196, CL936^  G o l d f i e l d s A r e a , Sask., G e o l . Survey.  P r e l i m . Report, Paper 37-5,  Swanson, CO.,  Can.,  (1937).;: :=>>-..  Report on D i n t y Lake N i c k e l D e p o s i t s , Sask.,  J u l y , (19381  Plate I MAP OF MAIN BORE A LI5 DEPOSIT I  |  Mort'fre. comptcx.  I  G-reunite  «• """"  Contours above.  show elevations Dt'wty Lake  and Hybrict RocJcs  Q-ne-iss  L, eLmproph-yre,  »5ccd<2  / inch =lOOf<ie-t  Plate E SECTION THROUGH DRILL-HOLES /V03.  I,Z,3.  MAIN 80REALIS SHOWING-  C  LOCATION  or  DEPOSIT  DRILL  CoR£ J/>£c/*/£/VS  1 Gran CC<z Q-nc/ss O  Th in- s e c ~tion Sptz a/n e «  Sca/e  iinch  = 200 A e t  

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