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Cache Creek group and contiguous rocks, near Cache Creek, B.C. Shannon, Kenneth Robb 1982

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CACHE CREEK GROUP AND CONTIGUOUS ROCKS, NEAR CACHE CREEK, B.C.  By  KENNETH ROBB SHANNON B.Sc., UNIVERSITY OF BRITISH COLUMBIA, 1975  THESIS SUBMITTED IN PARTIAL FULFILLMENT, OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE (Department of G e o l o g i c a l  STUDIES Sciences)  We accept t h i s t h e s i s as conforming to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA APRIL, 1982 ©  KENNETH ROBB SHANNON  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  requirements f o r an advanced degree at the  the  University  of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and  study.  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may  be  department or by h i s or her  granted by the head o f  representatives.  my  It is  understood t h a t copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l not be allowed without my  permission.  Department of  GEOLOGY  The U n i v e r s i t y of B r i t i s h 1956 Main Mall Vancouver, Canada V6T 1Y3 D a t  DE-6  (3/81)  e  APRIL  26.  1982  Columbia  written  ii  ABSTRACT The Cache Creek Group i n the type area i s c h a r a c t e r i z e d  by  o c e a n i c rocks such as r a d i o l a r i a n c h e r t , fusulini'd limestone and pillow  basalt.  Three  divisions  have  been made i n the Cache  Creek Group i n t h i s study: 1) s t r u c t u r a l l y unit  i s the melange  (which has been i d e n t i f i e d as a subduction complex);  overlying  greenstone  Emplacement on  lowest  the  u n i t ; and 3) the Marble Canyon  of the Marble  Canyon Formation  u n d e r l y i n g melange u n i t  and  2)  Formation.  greenstone  emplacement  may  have  unit  i s b e l i e v e d to have o c c u r r e d i n  the E a r l y to M i d - J u r a s s i c along a shallow d i p p i n g t h r u s t This  an  caused  soft  sediment  fault.  deformation  f e a t u r e s i n the E a r l y to M i d - J u r a s s i c A s h c r o f t Formation. Felsic volcaniclastic the  volcanic  rocks  sediments  Cache Creek Group.  Late  These f e l s i c  T r i a s s i c age.  both with the western Preto  (1977)  (1961). Cache  and  associated  tuffs  rocks have been c a l l e d the  lithological  correlation  are  Pavilion  beds  described  Triassic  Group  melange  unit.  time the Cache Creek Group  by  as d e s c r i b e d by T r e t t i n  Blocks of N i c o l a ( ? ) Group t u f f s have been found Creek  of  The N i c o l a ( ? ) Group i s c o r r e l a t e d  b e l t of the N i c o l a Group as  the  and  are found mainly along the e a s t s i d e of  N i c o l a ( ? ) Group and based on probable  and  in  This indicates that and  Nicola(?)  the  i n Late  Group  were  a d j a c e n t to one another. Paleoenvironmental  and  geochemical  evidence  i n d i c a t e an  ocean i s l a n d or p l a t f o r m d e p o s i t i o n a l environment  f o r the  Creek  most  Group.  islands.  Tropical  shallow  seas  Lack of c o n t i n e n t a l sediments  covered  Cache  of these  i n d i c a t e s that the Cache  Creek Group was d i s t a n t  from any major land masses.  iv  Table of Contents ABSTRACT ACKNOWLEDGEMENTS INTRODUCTION L O C A T I O N AND A C C E S S P R E V I O U S WORK C A C H E C R E E K GROUP I ) MELANGE U N I T Ia) Bedded R a d i o l a r i a n C h e r t B l o c k s lb) Limestone Blocks Ic) Greenstone Blocks Id) N i c o l a ( ? ) Group B l o c k s AGE OF B L O C K S I N T H E M E L A N G E U N I T I I ) GREENSTONE U N I T AGE OF T H E G R E E N S T O N E U N I T I I I ) MARBLE CANYON FORMATION AGE OF T H E MARBLE CANYON FORMATION IV) SERPENTINITE C O R R E L A T I O N OF U N I T S N I C O L A C ? ) GROUP I) FELSIC TUFF UNIT I I ) VOLCANI C L A S T I C UNIT A G E OF T H E N I C O L A ( ? ) GROUP A S H C R O F T FORMATION RED CONGLOMERATE SANDSTONE U N I T C H E R T P E B B L E CONGLOMERATE U N I T A G E OF T H E C H E R T P E B B L E CONGLOMERATE KAMLOOPS GROUP STRUCTURAL GEOLOGY S T R U C T U R A L S T Y L E OF I N D U V I D U A L U N I T S PALEOENVIRONMENTAL RECONSTRUCTION T E C T O N I C MODELS AND H I S T O R Y ECONOMIC GEOLOGY CONCLUSIONS REFERENCES  UNIT  I  i i v i i 1 .3 3 .7 .7 11 14 17 17 18 21 29 29 33 34 37 38 38 39 41 43 45 46 48 48 50 50 57 59 63 65 69  V  List  of F i g u r e s  1.  Map  showing t e c t o n o s t r a t i g r a p h i c b e l t s of B.C.  4  2.  Map  showing  5  3.  General geology of f i e l d  4.  Summary s t r a t i g r a p h i c column area  5. 6. 7. 8. 9. 10.  l o c a t i o n of f i e l d  area  a r e a , from Shannon, 1981 showing  units in f i e l d 9  Photomicrograph of r a d i o l a r i a n c h e r t b r e c c i a , two north of Cache Creek, B.C  km 13  Rotated limestone block i n melange u n i t , on west s i d e of Bonaparte R i v e r , Cache Creek, B.C  13  I s o l a t e d limestone b l o c k , on Bonaparte Reserve of Cache Creek, B.C  16  north  R a d i a l s t r u c t u r e s i n l i m e s t o n e b l o c k t o west of Boston F l a t s  16  N i c o l a ( ? ) block from 3 km n o r t h of Cache Creek, B.C. Showing v o l c a n i c l a s t i c t e x t u r e  19  N i c o l a ( ? ) Group v o l c a n i c l a s t i c of Woodburn Ranch  rock from v i c i n i t y ;....19  11.  Cache Creek Group v o l c a n i c l a s t i c northwest of C a r g u i l e  12.  Photomicrograph of ashflow t u f f b l o c k i n Cache Creek Group melange u n i t from near Boston F l a t s  13.  8  rock from 3 km  20 ......20  Photomicrograph showing a u g i t e phenocryst a l t e r i n g to glaucophane, from agglomerate b l o c k i n melange unit  21  View l o o k i n g eastward a c r o s s Bonaparte V a l l e y to the north of Cache Creek, B.C. Dashed l i n e i n d i c a t e s contact of melange u n i t w i t h o v e r l y i n g greenstone u n i t  23  15.  B a s a l t p i l l o w s i n greenstone u n i t Carguile  24  16.  Trace element geochemistry of Cache Creek Group greenstones  26  A l k a l i c to t h o l e i i t i c p l o t of Y/Nb, Pearce and Cann, 1973  27  14.  17. 18.  3 km north of  adapted from  D i s c r i m i n a t i o n diagram, adapted from Pearce and  vi  Cann, 1973. F i e l d D = ocean i s l a n d or c o n t i n e n t a l basalt. F i e l d A+B = low potassium t h o l e i i t e s . F i e l d C+B = c a l c - a l k a l i b a s a l t  28  B a s a l t v o l c a n i c l a s t i c rock with f u s u l i n i d s . The f u s u l i n i d s are v i s i b l e as the round c l a s t s w i t h dark spots r a d i a t i n g out from t h e i r c e n t r e s . From west s i d e of Hat Creek V a l l e y t o the south of Medicine Creek  32  20.  Compound p i s o l i t i c t e x t u r e i n limestone from top of Cornwall H i l l s a t south end of map area  32  21.  Interbedded r a d i o l a r i a n limestone and t u f f near top of Cormwalls H i l l s  33  19.  22.  from  S e r p e n t i n i t e o u t c r o p showing t y p i c a l r e c e s s i v e nature from south s i d e of S c o t t i e Creek  35  N i c o l a ( ? ) v o l c a n i c l a s t i c rock from a l o n g the Hat Creek road a p p r o x i m a t e l y 8 km west of C a r q u i l e  42  P a v i l i o n bed v o l c a n i c l a s t i c rock from a l o n g r o a d s i d e approximately 6 km east of B i g Bar  42  A s h c r o f t Formation conglomerate on the Bonaparte Reserve n o r t h of Cache Creek, B.C  44  26.  S t e r e o p l o t of p o l e s t o bedding and f o l i a t i o n , Creek Group, f o l i a t i o n ( + ), bedding(X)  52  27.  S t e r e o p l o t of p o l e s t o bedding and f o l i a t i o n , N i c o l a ( ? ) Group, f o l i a t i o n ( + ), bedding(X)  53  28.  T e c t o n i c model f o r Cache Creek Group  60  29.  Geology  30.  F o s s i l and G e o l o g i c a l S t a t i o n Map  23. 24. 25.  of the Cache Creek a r e a , B.C  Cache  i n -peeHeetSpecx^A i n pee-k-et Sj«e\aA Colled-1«  vii  ACKNOWLEDGEMENTS I would l i k e invaluable  to  thank  assistance  encouragement d u r i n g participated  in  writing  Danner  the of  and  field this  thesis area.  as  well  and  thesis.  giving  advice  on  the  Orchard  o f t h e G e o l o g i c a l S u r v e y o f Canada.  Bonaparte Indian  and  of  from  public  access  was  categories at  was p r o v i d e d  U.B.C.,  including  by  Permission granted  s u p p o r t was p r o v i d e d  t o work  students Graham  Financial  by U . B . C , G e o l o g i c a l S u r v e y o f C a n a d a  and  B.C.  Hydro;. t h i s  i s g r a t e f u l l y acknowledged.  I would  like  t o t h a n k Hun K i m o f B.C. H y d r o f o r h i s s u g g e s t i o n s  during  preparation  support  the  Help i n  Parrish,  E r n i e P e r k i n s , E d M o n t g o m e r y a n d many o t h e r s .  Mike  by  by t h e g r a d u a t e Randy  editing  s e c t i o n of the  B a n d a n d t h i s was g r e a t l y a p p r e c i a t e d .  technicians  Nixon,  for  Travers  w i t h m i c r o f o s s i l s was k i n d l y g i v e n  in areas r e s t r i c t e d  and  Bill  structural  Assistance  variety  guidance  Marc B u s t i n c o n t r i b u t e d h i s s k i l l s i n  thesis.  a  J i m Monger  i n numerous d i s c u s s i o n s o f t h e t e c t o n i c h i s t o r y o f  the  as  W.R.  of t h i s t h e s i s .  1  INTRODUCTION Considerable  interest  has been d i r e c t e d towards the Cache  Creek Group because of the i m p l i e d terranes  proposed  by Danner  transport  of  stratigraphic  (1970) and Monger and Ross (1971).  Permian f u s u l i n i d s found i n l i m e s t o n e s of the Cache Creek are  Tethyan  in  origin  (Dunbar, 1932) with c o u n t e r p a r t s i n the  Permian of the Mediterranean south  China.  sea  area,  Japan,  water  fauna  and  may  d i s t a n c e from the Cache Creek 1981).  The more recent  have fauna  subduction melanges and a s s o c i a t e d  by  W. T r a v e r s  Group  (1978).  mechanism  Tethyan  subtropical  (W.R.  Subduction - of  Danner,  pers  for  fusulinids  fusulinids.  plates  clastic  would  and  the  Harper  Ranch  Assemblage  P r e l i m i n a r y d i s c o v e r i e s of subduction indicated  the  need  mapping of the Cache Creek Group and surrounding  by G r e t t e  (1978) and Ladd (1979).  Group  This  limestone.  To  the  east  i s a package of f e l s i c v o l c a n i c  rocks  with  some  silicified  These f e l s i c v o l c a n i c l a s t i c  Late T r i a s s i c  by G r e t t e  such  the j u x t a p o s i t i o n of the Cache Creek  thesis  a c o n t i n u a t i o n of r e g i o n a l mapping done e a r l i e r  Creek  comm,  complexes  oceanic  at the type l o c a l i t y at Cache Creek, B.C. is  and  i s l a n d a r c s has been made  complex f e a t u r e s by W. Travers (1978) regional  different  i n t e r p r e t a t i o n of f e a t u r e s i n the Cache  as  a  and  o r i g i n a l l y evolved a great  Creek Group thought to be t y p i c a l of s u b d u c t i o n  provide  Indochina  F u s u l i n i d s i n the Harper Ranch Assemblage 100 km  to the e a s t , i n p a r t of s i m i l a r age, belong to a cooler  Group  for rocks  mapping  t o the south  of  the  rocks and  sediments  and  Cache  immature minor  rocks have been dated as  (1978) and T r a v e r s  (1978) who  correlated  2  them  with  the  Nicola  Group  to  the e a s t .  suggests on the b a s i s of s i m i l a r age and felsic beds  volcaniclastic of T r e t t i n  rocks may  (1961).  Until  The present  lithology  study  that  these  be c o r r e l a t i v e with the P a v i l i o n the d e t a i l e d s t r a t i g r a p h y of the  N i c o l a Group i s known, the f e l s i c  volcaniclastic  rocks  will  be  r e f e r r e d to as the N i c o l a ( ? ) Group. Controversy has been generated over the o r i g i n of the Cache Creek  Group  and  i t s mechanism  of  forward by Monger (1977) and T r a v e r s of  this  emplacement (1978).  Work to the  present study was undertaken by G r e t t e some  of  these  south  (1978) and Ladd  (1979) i n an e f f o r t  to  problems  1) what was the environment of d e p o s i t i o n of  include:  solve  i n models put  problems.  Such  the  Cache Creek Group; 2) r e g i o n a l s t r u c t u r e and s t r a t i g r a p h y of  the  Cache Creek Group; 3) the nature of the r e l a t i o n s h i p between  the  Cache Creek Group and the N i c o l a (?)  of  juxtaposition  Group; and 4)  the  time  of the Cache Creek Group and N i c o l a ( ? ) Group.  The purpose of t h i s t h e s i s was t o t r y to p r o v i d e answers t o  the  above problems. A r e g i o n a l mapping p r o j e c t the  summer  (1:50,000) was undertaken d u r i n g  of 1980, near Cache Creek, B.C. and forms the b a s i s  of  this thesis.  the  Ashcroft  T h i s p r o j e c t was p a r t of r e g i o n a l remapping map  area  by  the  Geological  Survey of Canada.  E x t e n s i v e sampling of l i m e s t o n e s and c h e r t s of the  Cache  Group was undertaken i n the hopes of p r o v i d i n g more f o s s i l concerning the age of t h i s group.  of  Creek dates  3  LOCATION AND ACCESS The  area  mapped i s about 600 km , extending 2  from A s h c r o f t  Manor on the south to 20 M i l e House on the n o r t h and Valley The  on  the  west  to Bonaparte V a l l e y on the east  area l i e s on the western margin  which  consists  Hat  mainly  of  of  the  Creek  (Fig. 2).  Intermontane  unmetamorphosed  Belt  to  low-grade  in  age  metamorphic sediments and v o l c a n i c rocks  ranging  Mississippian  (Monger, 1981).  To the west a c r o s s the  F r a s e r R i v e r F a u l t system l i e s the Coast  P l u t o n i c Complex and t o  the east  t o Recent  i s the  Crystalline Belt Access  to  high-grade  (Fig.  metamorphic  the area  furnished  constructed new  roads.  in  the area  and important  outcrops.  during  altitudes  valleys.  Some  of the  New l o g g i n g this  study  roads and  Much of the map area i s  covered by overburden and the best exposures c u t s and stream  Omineca  i s good v i a Highways 1, 97 and 12, as  a r e o n l y a c c e s s i b l e by 4-wheel d r i v e .  were being  igneous  1).  w e l l as by numerous l o g g i n g and ranching latter  to  from  occur  Outcrops a r e more e a s i l y  along  road  seen a t lower  because of the sparse p l a n t cover of g r a s s , sagebrush  and c a c t u s .  Higher  a l t i t u d e outcrops a r e obscured  by f o r e s t s of  Ponderosa p i n e and Douglas f i r .  PREVIOUS WORK A. Selwyn the  study  (1872) was the f i r s t  geology  of  a r e a and named the Cache Creek Group a f t e r the small  v i l l a g e near the type first  t o d e s c r i b e the  geological  map  locality. of  G. Dawson  (1895a)  made the  the area and d i v i d e d the Cache Creek  F i g u r e 1.  Map  showing t e c t o n o s t r a t i g r a p h i c  b e l t s of  B.C.  Figure  2.  Map  showing  location  of  field  area  6  Group i n t o a lower u n i t of sedimentary rocks and greenstone an  upper  unit  and  predominantly of l i m e s t o n e , which he c a l l e d the  Marble Canyon Formation.  G. Dawson's reconnaissance mapping was  updated by D u f f e l l and McTaggart (1952) who  divided  the Cache  Creek Group i n t o an e a s t e r n , c e n t r a l and western b e l t . Most  of  the f e l s i c  volcanic  rocks and limestones along  Highway 1 between M a r t e l and Cache Creek were i n c l u d e d with  the  Cache  and  Creek  McTaggart  Group  (1952).  by  both  Dawson  These f e l s i c  (1895)  volcanic  and D u f f e l l  rocks  were  reassigned  from the Cache Creek Group t o the N i c o l a Group by G r e t t e Travers  (1978),  and Ladd  ( 1 978) and T r a v e r s as  a  steeply  relationship  west  (1979).  From f i e l d evidence G r e t t e  ('1978) d e f i n e d t h e Cache C r e e k - N i c o l a c o n t a c t dipping  NW-SE  trending  fault.  thrust  fault  o l d e r Cache Creek rocks being emplaced on top of N i c o l a Paleontological  and p a l e o - e n v i r o n m e n t a l  suggests  that  (1966, 1968, 1976). the Marble  W.R. Danner  Canyon  carbonate banks formed on a v o l c a n i c warm shallow t r o p i c a l waters.  Formation  with  rocks.  s t u d i e s o f Cache  Creek Group carbonate rocks i n t h e type area have by Danner  This  was i n agreement w i t h work done by Ladd (1979) who  a l s o suggested the c o n t a c t may be i n p a r t a  out  (1978),  been  carried  (pers comm, 1981) i s composed  of  t o sedimentary s u b s t r a t e i n  Ages of f u s u l i n i d s found  i n the  Cache Creek Group i n southern B r i t i s h Columbia range from Middle P e n n s y l v a n i a n t o Late Permian. A  preliminary  report  on  p u b l i s h e d by Monger (1981) and  the regional early  p r o j e c t have been p u b l i s h e d by Shannon  results (1981).  geology has been of  this  thesis  7  CACHE CREEK GROUP Work  completed  during  the summer of 1980  showed that  e a s t e r n and c e n t r a l b e l t s of the Cache Creek Group i n area, a  can be d i v i d e d  greenstone  greenstone  unit  unit  included  and  and  as  a  the  Marble  Canyon  Formation.  Marble Canyon Formation  fourth unit  of  the  field  area  appear to o v e r l i e Serpentinite  is  out  in  summarized  all in  u n i t s i s shown i n F i g . 4.  d i v i s i o n s of the  Cache  s t a r t i n g w i t h the lowest  Creek  Group  structural  divisions.  Fig. 3  s t r a t i g r a p h i c column i n d i c a t i n g the r e l a t i o n s h i p s litholog.ical  The  i n the Cache Creek Group and i s  d e s c r i b e d s e p a r a t e l y although i t crops Geology  type  i n t o three main d i v i s i o n s ; a melange u n i t ,  the melange u n i t p o s s i b l y along a t h r u s t c o n t a c t . is  the  the  of  and a  the  main  Below, each of the four is  described  separately  unit.  I) MELANGE UNIT Tectonic characterized  melanges by  pervasively  bodies  of  deformed  the i n c l u s i o n of t e c t o n i c a l l y mixed  or b l o c k s , which may a  are  sheared matrix  and  fragments  range up to s e v e r a l k i l o m e t r e s i n s i z e , (Hsu,  1968).  Sedimentary  are sheared o l i s t o s t r o m e s or d e b r i s flows which fragmented  rocks  mixed  by  sedimentary  embedded i n a p e r v a s i v e l y sheared matrix  (Hsu,  melanges  include  processes  blocks  that are  1974).  in  The  now  Cache  Creek melange u n i t c o n t a i n s a v a r i e t y of b l o c k s i n a p e r v a s i v e l y sheared m a t r i x .  Except  f o r the s e r p e n t i n i t e  bodies  which  are  f a u l t c o n t r o l l e d , most of the b l o c k s c o u l d have been emplaced by either  tectonic  or  sedimentary  processes.  Evidence  presented  8  [mm  L V  V  V  E  G  [v V V V V  E  N  D  KAMLOOPS GROUP (EOCENE) CHERT-PEBBLE CONGL. (L.-M. CRET.) ASHCROFT FM. (L. JURRASIC) NICOLA (?) GROUP (TRIASSIC) MARBLE CANYON FORMATION GREENSTONE UNIT MELANGE UNIT SERPENTINITE BEDDING, FOLIATION FAULT DEFINED, APPROX CONTACT DEFINED, APPROX .  K M.  2  ASHCROFTJ  S E C T I O N  F i g u r e 3.  A - A  1  G e n e r a l geology of f i e l d area, from Shannon, 1981  9  Kamloops Group  C h e r t Pebble Conglomerate Unit  Marble C a n y o n Fm  .Red  Conglomerate Unit  Greenstone Unit  NicolaC?) Group  Melange Unit  Figure area  4.  Summary  stratigraphic  column  showing  units  in  field  10  during  description  of  the  geology  i n d i c a t e s that both t e c t o n i c and  of  the  sedimentary  melange  blocks  p r o c e s s e s have been  i n v o l v e d i n the g e n e s i s of the melange u n i t . Best exposures Creek,  on  the  of the melange u n i t are i n the town of Cache  west  side  of the Bonaparte  outcrops are found along the Ashcroft  Manor  Bonaparte  melange  regions.  unit  The melange u n i t comprises chert,  tuff breccia argillite  in  variably  The  a  incompetency limestone  of  the  argillite  few  melange.  metres.  chert  or  although they may  show  only  greenstone,  matrix  of  range  Changes  Where  carbonaceous in  in  the  felsic  size  the  from  relative  the p h y s i c a l melange  is  cannot  normally  be  followed  for  T h i s i s a r e f l e c t i o n of the extreme As  the  proportion  of  chert  or  i n c r e a s e s , the competency of the melange a l s o  i n c r e a s e s and degree ribbon  may  or p h y l l i t e with few b l o c k s p r e s e n t , i t  of these r o c k s .  blocks  area  i s not exposed.  blocks  metres.  i s h i g h l y sheared and bedding that  unit  b l o c k s versus matrix g r e a t l y a f f e c t  characteristics predominantly  thesis  gabbro, s e r p e n t i n i t e and sheared  phyllite.  c e n t i m e t r e s to hundreds of of  from  are i n stream  b l o c k s of l i m e s t o n e ,  greywacke,  a  and  percentage  extending  W i t h i n the  N a t u r a l outcrops of the melange  radiolarian  Additional  i s exposed only i n these t o p o g r a p h i c a l l y low  b l o c k s as the r e c e s s i v e matrix u s u a l l y  more  Valley  t o 20 M i l e House; other exposures  v a l l e y s such as along lower Hat Creek. the  River.  of s h e a r i n g decreases.  Large  outcrops  of  limestone are u s u a l l y not e x t e n s i v e l y broken, be deformed.  L i t h o l o g i e s of b l o c k s i n the melange are rocks types common  11  in the Cache Creek Group but i n c l u d e some that the  N i c o l a C ? ) Group as w e l l .  u n i t are r a d i o l a r i a n c h e r t and  minor  greenstone,  (5-15%).  Numerous  present  in  occasionally normally  the  occurs  b l o c k s i n excess melange,  Most of the b l o c k s  (>50%), with some  of  felsic  vicinity  of  Cache  in  scattered  the  of  i n the melange  limestone  volcanic Creek  melange.  randomly  of 100 metres  geological  typical  (5-20%)  s e r p e n t i n i t e and N i c o l a ( ? ) Group blocks  blocks  elsewhere  are  m a t e r i a l ' are  but  only  appear  Radiolarian  chert  i n the melange with a few  across.  When  mapping  c o n t a c t s c o u l d not be f o l l o w e d  i n the  i n a normal  f a s h i o n because each block was not i n s t r a t i g r a p h i c c o n t a c t other b l o c k s . is  in  It i s d i f f i c u l t  t o determine i f a  small  with  outcrop  f a c t an outcrop or a recent s l i d e block because there i s  no g e o l o g i c a l c o n t i n u i t y between b l o c k s , and u n i t s  show  up  as  s c a t t e r e d knobs t o p o g r a p h i c a l l y . The  matrix  of  the  ribbon c h e r t and a r g i l l i t e mixed  ribbon  chert  melange u n i t  in varying proportions.  and a r g i l l i t e  incompetent and when deformed, with  thick  the matrix Ribbon ahd  sequences because  chert  of  i s formed of interbedded  or a r g i l l i t e  become  highly  of ribbon c h e r t a c t e d their  competence  i s the most frequent  Areas  with  alone are quite sheared.  Areas  independently  and  type of block  formed  from  blocks.  i n the melange  o f t e n forms the bulk of the outcrop.  Ia) Bedded R a d i o l a r i a n Chert  Blocks  Colours of the ribbon c h e r t s are v a r i a b l e a l t h o u g h black v a r i e t i e s probably  form over  90%  of  the  grey and  cherts.  Red,  12  green,  white  and  brown  varieties  are p r e s e n t ,  reflecting  i m p u r i t i e s such as i r o n and manganese.  commonly  forms  argillaceous undeformed  layers  1-5  partings. blocks  an  s i n g l e beds l a t e r a l l y . would pinch out,  On  cm  some  effort  thick of  was  Ribbon  separated  the  larger  chert  by  thin,  relatively  made t o t r a c e the extent of  A f t e r a few metres at best  as i s common  probably  for radiolarian  the c h e r t bed  chert  (Danner,  1970a). Locally,  the  cherts  contain  abundant  well  preserved  r a d i o l a r i a , u s u a l l y seen as c l e a r g l a s s y spheres l e s s mm i n diameter. ribbon for  In most modern i n t e r p r e t a t i o n s of the o r i g i n of  ribbon  Previously, provide  chert  subaqueous  sequences volcanic  the source of s i l i c a  (Davis,  1918).  (McBride  and  Folk,1979).  emanations  were  thought  f o r the  There i s s t i l l  of the rhythmic l a y e r i n g i n  theories  rely  on  pelagic deposition focused  around  bands (Davis,  an  (McBride and F o l k ,  diagenetic  of  and  to  2 cm i n s i z e  the c l a s t s  interbedded  sequences  as t o the method of  ribbon  cherts.  Current  1979).  Previous  theories  a l t e r a t i o n of the ribbon c h e r t  into  1918).  with  range  out two  the  composed of sub-rounded t o than  chert  to  a l t e r n a t i n g combination of t u r b i d i t e and  A chert b r e c c i a crops above  ribbon  controversy  formation  less  0.5  c h e r t , r a d i o l a r i a a r e thought t o be the source of s i l i c a  the  Creek,  than  kilometres  north  west of Highway 97. sub-angular  i n a matrix from  black  chert  of c h e r t to  r a d i o l a r i a n ribbon c h e r t .  of  Cache  The o u t c r o p i s  clasts,  usually  (Fig. 5).  Colours  gray.  This  unit  is  The v a r i e t y of c h e r t  13  F i g u r e 5. Photomicrograph of r a d i o l a r i a n c h e r t b r e c c i a , two n o r t h of Cache Creek, B.C.  Figure 6. Rotated limestone block i n melange u n i t , on west of Bonaparte R i v e r , Cache Creek, B.C.  km  side  14  clasts  i n the b r e c c i a and  such as limestone c o b b l e s be a s l i d e b r e c c i a . location  in  the  The study  l o c a l i z e d submarine  the occurrence  breccia unit area and  the  i s only found  interbedded  with  ribbon These  sometimes c o n t a i n shallow water f o s s i l s such  stratigraphy  would  support -a  t u r b i d i t e l i m e s t o n e s are Bonaparte  River  30) and  Flats  the  1 metre t h i c k .  either  the  radiolarian  as  turbidite  units.  Some  limestones appear to be composed of s o r t e d c l a s t i c  Fig.  other  as  chert  i n shallow water, or the limestone beds were emplaced i n  chert  which  i n one  i s probably best e x p l a i n e d by  are u s u a l l y l e s s than  f u s u l i n i d s , which i n d i c a t e that formed  lithologies  sliding.  c h e r t s and a r g i l l i t e beds  other  i n d i c a t e s t h a t t h i s b r e c c i a u n i t might  Limestone beds o c c a s i o n a l l y  limestone  of  2  km  turbidite found  origin.  along  the  of  fossil  the debris  Examples of east  side  these  of  n o r t h e a s t of 20 M i l e House ( s t a t i o n  south of Cache Creek j u s t to  the  west  of  the #4,  Boston  ( s t a t i o n #355, F i g . 30).  Ib) Limestone B l o c k s Limestone  b l o c k s commonly are i n t e c t o n i c c o n t a c t with  melange ( F i g . 6 ) . the  melange  However some b l o c k s grade i n t o the matrix  over  a  distance  gradat.ional c o n t a c t appears decrease  in  to be  these  usually  developed  <1 as  the amount of f i n e - g r a i n e d carbonate  edge of the block i n t o the m a t r i x . of  of  A  suggested  metre. a  the of The  progressive away from  the  interpretation  g r a d a t i o n a l c o n t a c t s i s t h a t the l i m e s t o n e b l o c k s are  l a r g e s l i d e b l o c k s which broke o f f i n shallow water and  slid  to  15  the  site  of d e p o s i t i o n as c o a r s e sediments with a f i n e g r a i n e d  carbonate c l o u d around them. contact  i s not  melange. comm,  present  In  most  cases  this  of  later  tectonism  because  Another i n t e r p r e t a t i o n proposed  1981)  is  that at l e a s t  l a r g e i n s i t u carbonate  by  W.R.  gradational  Danner  (pers  some of the limestone b l o c k s a r e  accumulations  such as a l g a l mounds.  c o n t a c t s of these mounds have been m o d i f i e d by l a t e r Some  of the  The  tectonism.  of the limestones i n the melange u n i t south of Cache Creek  have f i n e l y laminated s t r u c t u r e s which have been i n t e r p r e t e d  as  a l g a l l a m i n a t i o n s (Danner, 1976). Intensive  recrystallization  has  obliterated  t e x t u r e s i n many limestone b l o c k s , l e a v i n g mottled,  coarsely  crystalline  rock  a  with  grey  Limestone i s very r e s i s t a n t  the  climate  of  hillsides  i t may  form  comprises was  interior the  B.C.,  only  up t o 10% of some samples.  noticed  when  and  outcrop  white,  t o weathering i n  on  highly  (Fig. 7).  A fetid,  eroded Dolomite  bituminous  the l i m e s t o n e s were f r e s h l y broken.  the limestones i n the melange south  of  strange . columnar  that  radial  jointing  Cache  Creek  odor  Some of exibit  a  m o r p h o l o g i c a l l y looks  s i m i l a r to a spray of a r a g o n i t e c r y s t a l s except in  and  r a r e f u s u l i n i d s and  c r i n o i d columnals. arid  original  the columns  are  excess of 2 metres long i n p l a c e s and a r e composed of s p a r r y  calcite  ( F i g . 8 ) . Cathode-luminescence was attempted  zoning  could  be  observed  in  t o see i f  a c r o s s - s e c t i o n of the columns.  R e s u l t s showed no zoning a l t h o u g h the limestone d i d f l u o r e s c e l i g h t blue c o l o u r i n s t e a d of the u s u a l orange f o r c a l c i t e 1981).  a  (Koop,  The anomalous f l u o r e s c e n c e may be r e l a t e d to some c a t i o n  16  I  F i g u r e 7. I s o l a t e d limestone of Cache Creek, B.C.  Figure 8. Radial Boston F l a t s  b l o c k , on Bonaparte Reserve  structures  in  limestone  block  north  to west of  17  impurity  i n the c a l c i t e  s t r u c t u r e (Koop, 1981).  Ic) Greenstone B l o c k s Blocks  of  greenstone  are not common i n the melange u n i t .  Blocks up to s e v e r a l tens of metres most the  across  were  observed  were l e s s than ten metres i n l o n g e s t dimension. greenstones  Typically  the  structures. sheared  is  usually  blocks  are  Greenstones  and  up to 10 cm  dark  green  amygdaloidal  to  black.  some show p i l l o w  i n the melange u n i t tend to  f r e s h s u r f a c e s are r a r e .  Colour of  almost  and  but  be  highly  C a l c i t e and q u a r t z v e i n s  t h i c k commonly c r o s s c u t the b l o c k s .  Id) N i c o l a ( ? ) Group Blocks L i g h t green v o l c a n i c l a s t i c melange  u n i t , mainly  b l o c k s are s i m i l a r Nicola(?)  Group  the e a s t .  The  and  contain  scattered  in  the  i n the v i c i n i t y of Cache Creek, B.C.  Such  i n appearance and compostion to rocks of which  light a  b l o c k s occur  the  i s a d j a c e n t t o the Cache Creek Group on  green v o l c a n i c l a s t i c  variety  of  clasts  blocks  including  are  siliceous  felsic  volcanics,  quartz-eye p o r p h y r i e s , c h e r t and  f i n e - g r a i n e d sedimentary  ( F i g . 9).  b l o c k s are s i m i l a r to N i c o l a ( ? )  These v o l c a n i c l a s t i c  Group rocks c r o p p i n g out along Cache  Creek,  s i l t s t o n e and volcaniclastic  which  contain  the clasts  Bonaparte  south  of  of f e l s i c v o l c a n i c rocks,  r a d i o l a r i a n c h e r t ( F i g . 10). rocks  River  rocks  Cache  Creek  c o n t a i n o n l y mafic v o l c a n i c , and  Group  limestone  18  clasts  ( F i g . 11). Some of the l i g h t  have w e l l developed welded ash Welded  tuffs  have  been  green v o l c a n i c l a s t i c b l o c k s  flow  tuff  textures  (Fig.  found i n the N i c o l a Group by McMillan  (1978) a l t h o u g h such rocks have not been r e p o r t e d i n Creek Group. up  A l l the l i g h t  to s e v e r a l p e r c e n t .  Presence of p y r i t e  rocks ( M c M i l l a n , 1974) whereas  Cache  Creek  except  within  some  light  green  Partial alteration the  Nicola(?)  rubbly o u t c r o p s . blocks  range  has  is  ribbon  the  rare  i n the  cherts.  correlation  The  between  rocks.  t o c l a y s and c h l o r i t e has rendered  rocks  incompetent  and  they form  The v o l c a n i c and sedimentary  in  composition  v o l c a n i c greywackes. Creek  locally  v o l c a n i c l a s t i c b l o c k s i n the melange u n i t and  the N i c o l a ( ? ) Group v o l c a n i c l a s t i c  of  Cache  i s c h a r a c t e r i s t i c of  pyrite  preceeding e v i d e n c e s t r o n g l y supports the  the  green b l o c k s c o n t a i n p y r i t e ,  Nicola  Group  12).  from  tuffs  clasts  some  recessive in  these  and agglomerates t o  One of these b r e c c i a t u f f s n o r t h of  developed  rims of f i b r o u s b l u e - l a v e n d e r  around brown a u g i t e phenocrysts  (Fig.  Cache  glaucophane  13).  AGE OF BLOCKS IN THE MELANGE UNIT Fossil  dates  in  the  melange  unit  r a d i o l a r i a e x t r a c t e d from c h e r t s and limestone  blocks.  The  United  (Travers,  States  1978).  been  conodonts  o b t a i n e d from extracted  dates based on r a d i o l a r i a  from probable E a r l y Permian 1981,  have  (D. Jones,  Geological  written  Survey)  up  range  from  i n age  communication, t o Late T r i a s s i c  Ages of b l o c k s of l i m e s t o n e i n the melange a r e  mostly Late Pennsylvanian to E a r l y Permian  based  on  conodonts  Figure 10. N i c o l a ( ? ) Group v o l c a n i c l a s t i c Woodburn Ranch  rock  from v i c i n i t y  of  F i g u r e 12. Photomicrograph of a s h f l o w t u f f Group melange u n i t from near Boston Flats  block  i n Cache  Creek  21  F i g u r e 13. Photomicrograph showing a u g i t e phenocryst to glaucophane, from agglomerate block i n melange u n i t (M. Orchard, Canada).  written  communication,  1981, G e o l o g i c a l Survey of  T h e r e f o r e rocks i n the melange  unit  been d e p o s i t e d between Late Pennsylvanian Deposition  ceased  sometime  altering  appear  t o Late T r i a s s i c  i n the Late T r i a s s i c  Cache Creek Group rocks have been found  to  have time.  as no younger  i n the melange u n i t .  II) GREENSTONE UNIT The levels  greenstone with  best  unit  crops out mainly a t h i g h e r  exposures  along  topographic  r i d g e s above the Bonaparte  River V a l l e y e s p e c i a l l y on the west s i d e n o r t h of C a r q u i l e .  The  22  greenstone u n i t o v e r l i e s relatively  the melange  shallow clipping t h r u s t  Amygdaloidal b a s a l t distinctive  spotted  clast  volcaniclastic flows,  as  look  caused  by  small  i n an a p h a n i t i c  black  green  spherical  matrix.  size  (Fisher,  distribution  basalts  Other  Also  pumpellyite,  and  of  abrasive  lithologies  have  sometimes  abundant  with  a  lack  of  fragments,  stilpnomelane,  Opaque  stage  m i n e r a l s present  of  internal  multimodal  rounding of some c l a s t s  include basalt.  basalt  breccia,  Microscopically  plagioclase  phenocrysts  A u g i t e phenocrysts were brecciated  q u a r t z and c h l o r i t e .  mineral  of  These  slumping  appearance.  i n f i l l i n g s and a l t e r a t i o n products i n c l u d e  commonly i s a l a t e samples.  sorting,  flow  Degree  i s variable. submarine  0.1 to >10 mm i n l e n g t h .  observed  Amygdaloidal  poor  ( F i g . 15) and a p h a n i t i c  commonly  from  fragments  except f o r alignment  basalt  ranging  of  evidenced . by  1971).  pillowed  size  limestone.  rocks probably formed by  stratification clast  and  a  ( F i g . 14).  u s u a l l y c l a s t s are b a s a l t and  rounding  also  along  are v o l c a n i c l a s t i c rocks which appear t o be d e b r i s  deposits;  the  fault  possibly  i s the most common l i t h o l o g y ; i t has a  c h l o r i t e amygdules (<3 mm) common  unit  replacing  calcite,  The c h l o r i t e  calcite  in  some  i n c l u d e p y r i t e , hematite and  magnetite(?). Minor ribbon greenstone u n i t . 'and  c h e r t and p h y l l i t e a r e a l s o  Limestone i s p r e s e n t as i n t e r p i l l o w  c l a s t s i n basalt tuff b r e c c i a .  Carquile, during  f o r conodonts.  i n the infillings  Approximately 3 km north of  i n t e r p i l l o w limestones produced  processing  included  abundant  fish  The age of these t e e t h  teeth could  F i g u r e 14. View l o o k i n g eastward a c r o s s Bonaparte V a l l e y to the north of Cache Creek, B.C. Dashed l i n e i n d i c a t e s contact of melange u n i t with o v e r l y i n g greenstone u n i t  24  Figure 15. Carquile not  Basalt  pillows  in  greenstone u n i t  3 km n o r t h of  be determined and no conodonts were r e c o v e r e d . Major element geochemistry was not attempted on any samples  as extensive a l t e r a t i o n made a n a l y s e s others  on  the  Cache  Creek  Group  i n d i c a t e s that they s t r a d d l e (Souther, setting  1977). of  these  geochemistry. insensitive and  Y  Fig.  16.  ocean  An  done  i n northern B.C.,  e f f o r t t o i d e n t i f y the o r i g i n a l  tectonic  was  made  were  using  chosen  immobile  which  are  element relatively  to a l t e r a t i o n p r o c e s s e s ; these i n c l u d e T i , and  by  boundary  Elements  (Pearce  Cann,  1973).  L e v e l s of Nb and T i  floor  basalts  Work  alkaline-tholeiitic  rocks  the  suspect.  are  Results  are  substantially  Zr, Nb,  presented i n above  normal  b a s a l t and a c c o r d i n g to the Y/Nb r a t i o the samples  p l o t mainly i n the a l k a l i c t o t r a n s i t i o n a l  compositional  field  25  (Fig.  17).  When  (Fig.  18), the  plotted  samples  ocean i s l a n d f i e l d , distinctly  fall  the  mainly  except f o r sample  discrimination i n the " w i t h i n  103 which  d i f f e r e n t than the other samples.  anomalously e n r i c h e d ocean  on  floor  It  i s the only  p l a t e " or  appears  t o be  Sample 103 i s not  i n Nb or T i and appears s i m i l a r  basalt.  diagram  sample  to  normal  from the melange  u n i t ; a l l the other samples were from the greenstone u n i t or the Marble Canyon Formation. This  l i m i t e d evidence suggests that  greenstones enriched second  may  of  differences  two  distinct the  types.  ocean  Creek  ocean  floor  between  Cache  Canyon  are also  basalts  Group  The f i r s t  type,  variety.  The  island  has normal amounts of Nb and T i as compared  u n i t and Marble basalts  of  i n Nb and T i i s of type  average  be  the Cache  ( F i g . 16).  t o the  Geochemical  Creek greenstones of the greenstone  Formation  manifested  versus  normal  mineralogically.  ocean  floor  Clinopyroxene  phenocrysts a r e common i n the Cache Creek Group greenstones and in some samples the c l i n o p y r o x e n e s predominate over p l a g i o c l a s e . This  i s not  typical  of  normal  ocean  o l i v i n e and p l a g i o c l a s e are dominant, (Shilling,  1973).  Shilling  b a s a l t s a r e r e l a t e d to mantle.  hot  with  suggests spot  floor basalt  that  activity  rare  i n which  clinopyroxene  clinopyroxene-rich in  the  underlying  26  Nb(ppm) T i ( p p m ) Y(ppm)  SAMPLE MVS-80-3a  48  MVS-80-22  Zr(ppm)  17 100  26  172  37  15200  32  142  MVS-80-43a  29  17500  19  99  MVS-80-103  8  6800  38  25  MVS-80-171  77  28200  45  276  M V S - 8 0 - 19 l b  27  16800  42  111  38  16933  34  138  5  8350  30  92  32  16250  29  115  CACHE C R E E K GREENSTONE MEAN OCEAN-FLOOR B A S A L T MEAN OCEAN I S L A N D B A S A L T MEAN  (Pearce  and Cann, 1973)  (Values  a r e + maximum  pers  F i g u r e 16. greenstones  2  of 10%, Stanya  Horsky,  comm, 1 9 8 1 )  Trace element  geochemistry  of  Cache  Creek  Group  27  TRANSITIONAL  ALKALIC  „ —THOLEIITIC T  u  r  i  t  -  C 1 1 T 1  •  Carlsberg Ridge(OF)-  Palmer Ridge (OF)-  Hawali (01)-  Cache C r e e k * - * — •  •  •  •  i  0  Z  Madelra(OI)-  Flores (Ol)'  i  1  1  i  0.1  r—i—r—i—i I  1  r——r—r——i  1—i  i r 1  0  Y/Nb  Figure 17. Alkalic Pearce and Cann, 1973  to  tholeiitic  plot  of Y/Nb, adapted from  28  Ti/  I  00  Y.3  F i g u r e 18. D i s c r i m i n a t i o n diagram, adapted from Pearce and Cann, 1973. Field D = ocean i s l a n d or c o n t i n e n t a l b a s a l t . F i e l d A+B = low potassium t h o l e i i t e s . F i e l d C+B = calc-alkali basalt  29  AGE  OF THE GREENSTONE UNIT  D a t i n g the greenstone Fusulinid  limestone c l a s t s  northwest age  by  is difficult  because  of r a r i t y of  in a basalt v o l c a n i c l a s t i c  of C a r q u i l e have been a s s i g n e d an E a r l y to W.R.  fragment  Danner  found  (pers  in  a  comm,  limestone  1981). clast  A  greenstone u n i t was  1981).  These  rock 3 km Mid-Permian  single  in basalt  Cache. Creek has been i d e n t i f i e d as Upper Permian ( w r i t t e n communication,  fossils.  conodont  5 km south of by  M.  Orchard  two dates suggest that the  l i k e l y d e p o s i t e d i n the  Permian.  I l l ) MARBLE CANYON FORMATION The Marble Canyon Formation c r o p s out mainly along the east side  of  Hat  Mountains. be  Creek  valley  and  to  the n o r t h i n the P a v i l i o n  Areas u n d e r l a i n by the Marble Canyon  distinguished  on  air  limestone c l i f f s which sinkholes  and  the  photographs unit  tends  by to  the prominent form.  The McTaggart andesite,  in  white  Caves  and  the  local  circulation.  Marble  Canyon  Formation  as d e s c r i b e d by D u f f e l l  (1952) i s predominantly l i m e s t o n e with l e s s chert  and  argillite.  However  new  that  the  amount  than  and 10%  exposures along  l o g g i n g road c u t s i n the area mapped as Marble Canyon indicate  can  some t u f a s p r i n g s a r e found i n the Marble Canyon  Formation and are a r e f l e c t i o n of i t s importance groundwater  Formation  Formation  of m a t e r i a l other than limestone i s  30  substantially almost  g r e a t e r than  a l l limestone  such  Whiterock  Cliffs  Formation  i s composed  limestone  and  beds,  10%.  Except  as  Marble of  the  to  higher percentage be  itself  basaltic  radiolarian  weathering  t o p of  Canyon  in  Hills,  the Marble Canyon  argillite  abundance.  this  Cornwall  volcaniclastic  chert,  s e r p e n t i n e i n d e c r e a s i n g order of resistance  f o r l o c a l areas that are  rocks,  and  Because  of i t s  area the l i m e s t o n e forms a  of n a t u r a l outcrops, but i n r o a d - c u t s  seen that l i m e s t o n e  minor  i t can  forms l e s s than 50% of the Marble Canyon  Formation. The most common l i t h o l o g y among the l i m e s t o n e s grey and white m o t t l e d v a r i e t y  is a  which weathers l i g h t grey.  dark It i s  commonly c r o s s - c u t w i t h c o a r s e l y c r y s t a l l i n e c a l c i t e v e i n s up t o several  centimetres  i n width.  Other  varieties  limestone  with  black  stringers  limestone  with  small  rhombs of white-orange d o l o m i t e  mm) forming up to 10% of the almost  (graphite?)  i n c l u d e tan  rock.  Some  and  dolomitized  limestone  (0.1-0.2 has  been  completely c o n v e r t e d t o d o l o m i t e .  One  of  the more f o s s i l i f e r o u s rocks i n the Marble Canyon  Formation  is a  clastic  micrite,  fusulinids,  rock  with  c r i n o i d columnals  in a f i n e g r a i n e d t u f f a c e o u s ( ? ) matrix these c l a s t i c rocks a r e found (station shallow  #296, water  radiolarian indicates  F i g . 30). fossils  chert. transport  fragments  greenstone,  and other  f o s s i l debris  ( F i g . 19).  Occasionally  interbedded with r a d i o l a r i a n It  such  Abrasive of  of  the  i s unusual  as  fusulinids  rounding fossil  of  debris  chert  t o f i n d u n i t s with interbedded  with  some of the c l a s t s to  the  site  of  31  deposition.  Turbidite  t r a n s p o r t or d e b r i s flow of the shallow  water f o s s i l s would p r o v i d e a mechanism f o r t h e i r emplacement i n supposed deeper water  sediments.  Another d i s t i n c t i v e u n i t an  oolitic  Cornwall  to  pisolitic  Hills  selective  in  i n the Marble Canyon Formation  limestone  ( F i g . 20). these  which  Dolomitization  i s best exposed on has  been  highly  rocks sometimes r e p l a c i n g the c o r e s of the  o o l i t e s and sometimes the edges or even a few s e l e c t e d bands the  oolite.  is  These limestones p r o b a b l y  in  formed i n shallow, warm  and a g i t a t e d seas, as these c o n d i t i o n s are r e q u i r e d  for  oolite  formation. As  well  radiolarian  as  oolitic  limestone,  These  rocks  because  their  thin  even  of  oolitic  organisms.  Clasts  are  i n t e r b e d s of the r a d i o l a r i a n of  shallow  water  limestone and t u f f must  have  oolite  bedding  and  lack  of  l i m e s t o n e are found  clasts  been steep at t h i s l o c a l i t y .  facies benthic  i n the t u f f  The  i n the deep water  i n d i c a t e s t h a t t h e topgraphy  limestone b a s i n .  Hills  i n t e r p r e t e d as deep water  l i m e s t o n e sequence.  allow the shallow water o o l i t i c radiolarian  of t h i n bedded  limestone and t u f f a r e a l s o found on Cornwall  ( F i g . 21). of  outcrops  presence  radiolarian  on the  seafloor  Steep topography  d e b r i s to s l i d e  down  into  would the  32  Figure 19. B a s a l t v o l c a n i c l a s t i c 'rock with f u s u l i n i d s . The f u s u l i n i d s are v i s i b l e as the round clasts with dark spots radiating out from t h e i r c e n t r e s . From west s i d e of Hat Creek V a l l e y to the south of Medicine Creek  F i g u r e 20. Compound p i s o l i t i c t e x t u r e i n l i m e s t o n e from top Cornwall H i l l s at south end of map area  of  33  F i g u r e 21. Interbedded r a d i o l a r i a n top of Cormwalls H i l l s  limestone and t u f f from near  AGE OF THE MARBLE CANYON FORMATION Fusulinids  found  previously  i n l i m e s t o n e s of the Marble Canyon  Formation i n southern B.C., range to  l a t e Permian  (Danner  was reported by G r e t t e Canyon  Formation  t h i s map area.  Samples  determined Triassic  and N e s t e l l , (1978) of  1966).  in  the  Marble  Venables v a l l e y and to the south of  to M i d d l e Permian were  range  also  (W.R. Danner,  processed  from  probable  (M. Orchard,  written  Canyon  A Late Permian age  for fusulinids  Late  Formation near s t a t i o n  pers  range comm,  f o r conodonts  and ages  Pennsylvanian  to  communication,  c o l l e c t i o n s of r a d i o l a r i a o b t a i n e d from Marble  Mid-Pennsylvanian  Ages i n c o l l e c t i o n s made d u r i n g t h i s study  from E a r l y Permian 1981).  west  i n age from  ribbon  1981).  cherts  Late Two  i n the  #296 ( F i g . 30) gave  Early  34  Permian W.R.  dates  Danner  pelecypods Hills  (D. Jones,  has  collected  (pers  conodonts  comm,  in  communication, the  1981). an  these  are  1981).  shelled Halobia l i k e  Triassic  of the  Cornwall  age  limestones  These conodonts of  lookout  on.  the  as the Late T r i a s s i c .  provide  Canyon  Formation  youngest  a  appears  northeast to southwest;  of  written  clear  known  Cache  evidence  Creek  Group  Cordillera. was  mainly d u r i n g  from the Late P e n n s y l v a n i a n  In  basis  (M. Orchard,  D e p o s i t i o n of the Marble Canyon Formation Permian but extends  the  Hills  Cache Creek v o l c a n i s m i n t o the E a r l y  v o l c a n i c r o c k s i n the Canadian  the  on  t u f f s on Cornwall  Triassic  interbedded 1981).  communication,  Greenstone  Early  continuation  Triassic;  thin  i n l i m e s t o n e s northwest  have been a s s i g n e d  for  written  regional  perspective  to as young the  Marble  to become p r o g r e s s i v e l y younger  from  most of the o l d e r P e n n s y l v a n i a n to E a r l y  Permian l i m e s t o n e s occur i n the n o r t h e a s t , the M i d d l e Permian i s in the c e n t r a l p a r t of the map Triassic  i s found t o the  area  and  the  Late  Permian  to  southwest.  IV) SERPENTINITE S e r p e n t i n i t e i s found as i s o l a t e d outcrops of  the  Cache  Creek  Group.  s l i c k e n s i d e d s u r f a c e s and Serpentinite  usually  Normally  fractures  crops  out  i n a l l the u n i t s  there  throughout  are the  as a rubbly green  abundant outcrops.  t a l u s slope  35  ( F i g . 22) and commonly weathers  recessively.  Figure 22. Serpentinite outcrop showing nature from south s i d e of S c o t t i e Creek  Colour fractured fresher  varies  black.  unfractured  serpentine  Cross-cutting  cut  through  the  zones  common . i n out  outcrops.  usually  the s e r p e n t i n i t e s , o f t e n  in raised  relief  of  i s dark white  green  giving  a  North of 16 M i l e  <3 cm t h i c k a r e a l s o the chalcedony w i l l  coarse  mesh  to  serpentinite  s e r p e n t i n i t e s along an e a s t e r l y  Chalcedony and c a l c i t e v e i n s  Highly  green t o almost white whereas  a l t e r a t i o n products a r e q u i t e common. dykes  recessive  on amount of f r a c t u r i n g .  samples tend t o be l i g h t  relatively  almost  depending  typical  texture  diorite trend. quite weather t o the  36  A common a l t e r a t i o n product of the s e r p e n t i n i t e quartz,  carbonate  and  fuchsite  d i s t i n c t i v e orange-white fuchsite. and  (chromian-mica) rock which i s a  c o l o u r with b r i g h t  The quartz-carbonate  green  speckles  rock i s r e s i s t a n t to  be  erroneously  material  and  is  chalcopyrite Jack Creek the  map  Chromite  was  of  with  r a r e l y observed  outcrop  s e r p e n t i n i t e s was  serpentinite its  margins likely  highly indicate  that  this  was  an  d i s c o v e r y of s e r p e n t i n i t e s H. Kim  and  i n January, Creek cut.  i n the  Valley  to  s e r i e s of nature  It i s located  Hydro was along  and  Bonaparte  Canyon  of  Valley  east  the  Formation  side  so  A recent  examined by the  the  fault  Most of the  by  writer of  Hat  the south of M e d i c i n e Creek i n a l o g g i n g road  I t i s v a r i a b l y sheared to f r e s h s e r p e n t i n i t e  i n a sequence  limestone and b a s a l t i c v o l c a n i c l a s t i c r o c k s , t y p i c a l  Marble  aligned  emplacement  Marble  of  discrete  of h i g h f a u l t a c t i v i t y .  A. Penner of B.C. 1981.  south  serpentinite.  r e l a t e d to f a u l t a c t i v i t y .  area  2-3%  in s e r p e n t i n i t e s in  a  sheared  gossan  (1979) near Oregon  the  as  rock  with  o c c u r s as s m a l l  s e r p e n t i n i t e s are found along or near the probably  stained  j u s t to the  c r y s t a l s d i s s e m i n a t e d throughout occurrence  This  quartz-carbonate  but i n t h i n - s e c t i o n chromite  b o d i e s , together bounded  the  malachite  (W. M c M i l l a n , pers comm, 1981)  brecciated The  probably  as  and malachite d e s c r i b e d by Ladd  area.  the f i e l d  identified  of  weathering  tends to form r i d g e outcrops or c i r c u l a r knobs.  may  of  bodies i s a  Canyon Formation.  T h i s d i s c o v e r y means that  s e r p e n t i n i t e outcrops i s over 20 km  wide.  of  the  the b e l t of  37  CORRELATION OF UNITS S e v e r a l o u t c r o p s i n the f i e l d areas of Ladd(l979)  were v i s i t e d  Grette  and  so a c o r r e l a t i o n c o u l d be made with the  d i v i s i o n s of the Cache Creek Group e s t a b l i s h e d J.  (1978)  in  this  study.  G r e t t e d i v i d e d the Cache Creek i n t o three d i v i s i o n s , a lower  clastic J.  unit,  a mafic v o l c a n i c u n i t and an upper c l a s t i c  Ladd d i v i d e d the Cache Creek Group i n t o a melange  the  Marble  Canyon  Formation.  Areas  i n t e r p r e t e d by Ladd (1979) as l a r g e blocks  of  unit  greenstone  i n the melange  unit. and were unit.  The f o l l o w i n g c o r r e l a t i o n s are suggested:  Cache Creek Group  (Shannon,1981)  (Grette,1978)  (Ladd,1979)  1. Marble Canyon Fm—1. Upper C l a s t i c Unit 1. Marble Canyon Fm 2. Greenstone U n i t 2. Mafic V o l c a n i c U n i t - - 2 . Melange U n i t 3. Melange U n i t 3. Lower C l a s t i c Unit 3. Melange U n i t  38  NICOLA(?) GROUP The volcanic Triassic  Nicola(?)  Group rocks a r e p a r t of a package of f e l s i c  rocks and sediments  which  have  been  by . G r e t t e ( l 9 7 8 ) and Travers(1978)  by them with the N i c o l a Group t o the e a s t . out  immediately  adjacent to the Guichon  as f a r south as M e r r i t t Morrison,  1980).  (W.R. M c M i l l a n ,  dated  as  Late  and were c o r r e l a t e d Similar  rocks  crop  B a t h o l i t h and a r e found pers  comm,  1981 and  Rocks c a l l e d N i c o l a ( ? ) Group i n t h i s study a r e  c o r r e l a t e d with other N i c o l a Group rocks t o the east s t r i c t l y on lithostratigraphic detailed Nicola(?)  to  grounds.  outline  Group  the d i s t r i b u t i o n  rocks,  but  N i c o l a ( ? ) Group was d i v i d e d volcaniclastic  Mapping  was of  not  sub-units  for descriptive  into  a  felsic  sufficently i n the  purposes  tuff  unit  the  and a  unit.  I) FELSIC TUFF UNIT Best  exposures  of the f e l s i c  Cache Creek on C a t t l e V a l l e y Ridge Hill  along Highway 1.  light an  The f e l s i c  tuff  u n i t a r e t o the n o r t h of  and a l s o t o the south of Red tuff  u n i t c o n s i s t s mainly of a  green t u f f with augens of q u a r t z , p l a g i o c l a s e and c h e r t i n  aphanitic  evident  in  mica-chert  matrix.  some  the  recrystallization q u a r t z patches  of has  with  changed  highly  Undulatory  quartz  extinction  grains.  was  Extensive  the c h e r t g r a i n s t o metamorphic  sutured  boundaries.  Late  c a r b o n a t i z a t i o n has r e p l a c e d up t o 15% of the rock with  stage  calcite.  39  Thinly found  laminated limestones up t o s e v e r a l metres t h i c k a r e  with  observed  these  in  rocks.  these  Abundant  limestones  crinoid  which  columnals  were  are dark grey on a f r e s h  s u r f a c e and weather a l i g h t grey t o white.  Included within t h i s  u n i t a r e minor amounts of c o a r s e r v o l c a n i c l a s t i c d e b r i s .  II)  VOLCANICLASTIC UNIT The main exposures  of  McLean Lake and  Fig.  30).  green  The  of the v o l c a n i c l a s t i c u n i t a r e southwest  along  the  volcaniclastic  i n c o l o u r and i n c l u d e s  rocks  (mostly  lapilli  A characteristic quartz  "eyes"  Hat  Creek  unit  both  road  (station  is characteristically  pyroclastic  and  tuffs  i s their  due  products.  felsic  volcanic  intrusive  rocks,  rocks  and  common i n t h i s u n i t with Epiclastic  rocks  alteration  The blue green c o l o u r of the rocks i s  to the e x t e n s i v e c h l o r i t i z a t i o n .  amygdaloidal  nature;  i s extensive.  C h l o r i t e , p u m p e l l y i t e and s t i l p n o m e l a n e are found as and replacement  F i g . 23).  felsic  a r e very common and s i l i c i f i c a t i o n  chert,  fine-grained  limestone.  1-3% p y r i t e become  Clast l i t h o l o g i e s include sediments,  Pyritization  more  dominant  the N i c o l a ( ? ) i s e n t i r e l y sedimentary  Woodburn Ranch). volcanic  to  The change i n the N i c o l a ( ? )  sedimentary  i s very  i n most samples. higher  in  N i c o l a ( ? ) s e c t i o n and a t the c o n t a c t with the o v e r l y i n g sediments  blue  epiclastic  t u f f s and v o l c a n i c sandstones,  of the l a p i l l i  #19,  i s reflected  the  Jurassic  ( T r a v e r s , 1978, from  dominantly  i n d e p o s i t i o n of immature  40  volcanic  sandstones, s i l t s t o n e and m i n o r c l a y s t o n e  Nicola(?)  of the P a v i l i o n beds to the northwest ( T r e t t i n , 1 9 8 0 )  were examined i n an e f f o r t Fraser River.  sampled.  t o c o r r e l a t e N i c o l a C ? ) s t r a t a west to  Near B i g Bar, along the F r a s e r R i v e r about 50  km northwest of Cache  and  Colour,  Creek,  clast  green  south  of  volcanic  sandstones  l i t h o l o g y and amount of  p y r i t i z a t i o n were very s i m i l a r  out  upper  section.  Rocks  the  i n the  to N i c o l a ( ? )  Cache Creek ( F i g . 24).  were  silicification rocks  cropping  Conodonts r e c o v e r e d from  nearby limestone i n t e r b e d s gave a Late T r i a s s i c age (M. Orchard, w r i t t e n communication, 1981), which Nicola(?)  Group  rocks.  is  Because  of  N i c o l a ( ? ) rocks have been c o r r e l a t e d The  correlation  of  Nicola(?)  s i g n i f i c a n t as i t extends rocks  west  as  the  greenstone  unit  with  of  the  as  the  similarities  the  the  age  Pavilion  beds.  and the P a v i l i o n beds i s of  felsic  f a r as the F r a s e r R i v e r .  a f f i n i t y have been found with the  same  these  rocks area  the  Marble  volcaniclastic  No rocks of N i c o l a ( ? ) Canyon  Formation  or  Cache Creek Group between B i g Bar and  Cache Creek. Felsic volcaniclastic melange  blocks  in  the  Cache  Creek  u n i t have been c o r r e l a t e d with the N i c o l a ( ? ) G r o u p .  main p o i n t s of t h i s c o r r e l a t i o n are as f o l l o w s :  Group The  41  NICOLA(?) GROUP VOLCANICLASTICS  CACHE CREEK GROUP VOLCANICLASTICS  FELSIC VOLCANICLASTIC BLOCKS IN MELANGE  1. d i v e r s e l i t h o l o g y 1. b a s a l t , limestone including siltstone c l a s t s only. f e l s i c v o l c a n i c s and chert.  1. d i v e r s e l i t h o l o g y including siltstone f e l s i c v o l c a n i c s and chert.  2. c o n t a i n s f e l s i c v o l c a n i c u n i t s such as ash flow t u f f s and quartz-eye porphyries.  2. c o n t a i n s f e l s i c v o l c a n i c u n i t s such as ash flow t u f f s and quartz-eye porphyries.  2. c o n t a i n s no f e l s i c volcanic rocks.  3. u b i q u i t o u s p y r i t e 3. p y r i t e i n t h i s u n i t ranging from 1-3%. The  above  comparison  i s rare.  suggests  3. p y r i t e i s present i n a l l blocks u s u a l l y >2%.  t h a t the f e l s i c  volcaniclastic  b l o c k s a r e p a r t of the N i c o l a ( ? ) package and not the Cache Creek Group.  The occurrence  melange u n i t the  of N i c o l a ( ? ) b l o c k s i n  i s significant.  Nicola(?)  rocks  the Cache  Creek  Such a r e l a t i o n would suggest  were being d e p o s i t e d  that  i n t o the Cache Creek  melange u n i t as i t was forming.  AGE  OF THE NICOLA(?) GROUP No d i a g n o s t i c f o s s i l s  were  found  N i c o l a ( ? ) Group i n the t h e s i s a r e a . Cattle  Valley  abundant f i s h were  Ridge  the  units  of  (Travers,1978).  Ammonite  north  Cache A  fossils  Creek  of  Late  found  are Triassic  of the  T h i n l y bedded limestones on Cache  Creek produced  t e e t h d u r i n g conodont p r o c e s s i n g but no  found.  southeast  to  i n any  dated age  conodonts  i n N i c o l a ( ? ) sediments as based  Late  Triassic  on conodonts i s  F i g u r e 23. N i c o l a ( ? ) v o l c a n i c l a s t i c rock from Creek road approximately 8 km west of C a r q u i l e  Figure 24. P a v i l i o n bed v o l c a n i c l a s t i c approximately 6 km east of Big Bar  along  the  Hat  rock from along r o a d s i d e  A3  reported f o r N i c o l a l i m e s t o n e s by G r e t t e (1978). dated by Rb-Sr (Grette,1978) well. the  Limestones Nicola(?)  (M. Orchard,  i n d i c a t e d a Late  V o l c a n i c rocks  Triassic  age  of the P a v i l i o n beds which a r e c o r r e l a t e d  rocks  have  produced  w r i t t e n communication,  Upper  Triassic  volcanism  with  marine  1981).  limestones  present  E x t e n s i v e e r o s i o n d u r i n g the Late T r i a s s i c produced sediments  predominating  in  the  with  conodonts  N i c o l a ( ? ) Group rocks r e p r e s e n t a p e r i o d of e x t e n s i v e Triassic  as  upper  part  of  Late  locally.  the v o l c a n i c  the N i c o l a ( ? )  Group.  ASHCROFT FORMATION North  of  the  Bonaparte  Indian  Reserve w i t h i n the Cache  Creek Group i s a l a r g e area of brown t o siltstone.  Some  foliation.  No  areas  of  fossils  grey  conglomerate  and  f i n e r g r a i n e d sediment show a weak  were  found  in  these  rocks  but  on  l i t h o l o g i c a l grounds they a r e c o r r e l a t e d with the Lower J u r a s s i c Ashcroft  Formation  as  described  v i c i n i t y of A s h c r o f t , B.C. and sandstone  with no conglomerate,  of 20 M i l e House extending with the A s h c r o f t Clasts  Outcrops  by  Travers  (1978)  of w e l l f o l i a t e d  i n the siltstone  which occur t o the northwest  t o C l i n t o n are t e n t a t i v e l y  correlated  Formation.  i n the conglomerate  on the Bonaparte Indian r e s e r v e  44  are extremely v a r i a b l e i n s i z e although u s u a l l y not exceeding 10 cm i n diameter. felsic  Clast  intrusive  l i t h o l o g i e s are  rocks,  quartz-feldspar  a r g i l l a c e o u s sediments with minor gray mafic that  volcanic the  conglomerate  argillaceous were  rocks  sediment  incorporated  depositional site.  into  mostly  ( F i g . 25). is  quite  clasts the  are  porphyries  micritic  limestone  to and and  Well rounded c l a s t s  indicate  mature  of  but  some  the  q u i t e a n g u l a r ; perhaps they  conglomerate  Sand s i z e matrix  intermediate  material  close usually  to  the  exceeds  Figure 25. Ashcroft Formation conglomerate on the Bonaparte Reserve n o r t h of Cache Creek, B.C. 10%  of the rock and appears to be mostly q u a r t z .  calcite  s t r i n g e r s are common.  Cross-cutting  45  Siltstone conglomerate  and have  minor  argillite  interbedded  l o c a l l y developed s l a t y c l e a v a g e .  this foliation  i s p e r p e n d i c u l a r to bedding  subparallel.  Elsewhere  Formation  are  bedding.  in  mainly  conglomerate.  outcrop  the  of  Nicola(?)  felsic  and  i s usually Ashcroft  s i l t s t o n e s along Lower Hat Creek volcanics  s i d e up, t h i s  rocks.  would  sandstone  place  i t is  with  no  present a t low a n g l e s to sandstones  is stratigraphically  and  Sometimes  usually  Formation  sediments.  d e t e r m i n a t i o n on N i c o l a ( ? ) s i l t s t o n e s right  but  the  map area o u t c r o p s of A s h c r o f t  siltstone  Foliation  An  with  A  and  underneath  single  tops  i n d i c a t e s that the u n i t i s  Triassic  rocks  on  Jurassic  The most l i k e l y cause of such a s t r a t i g r a p h i c anomaly i s  that the J u r a s s i c  rocks have been f a u l t e d  i n t o p l a c e a g a i n s t the  Nicola(?).  RED CONGLOMERATE SANDSTONE UNIT A  few  outcrops  of  r e d conglomerate  v i s i b l e along and n o r t h of the lithology white  i s quite variable  f e l s i c volcanic  and q u a r t z , u s u a l l y are  subrounded  Abundant  bright  to  lower  Hat  and Creek  sandstone a r e Road.  Clast  i n c l u d i n g l i m e s t o n e , c h e r t , green to  r o c k s , a r g i l l a c e o u s sediments, s e r p e n t i n e  i n a s p a r r y white subangular  red c l a s t s  and are  calcite range  cement.  Clasts  up t o 20 cm a c r o s s .  distinctive  and  include  46  siltstone, Canyon  j a s p e r and red c h e r t .  Formation  on  An o u t c r o p c l o s e t o the Marble  the Hat  Creek  Road  contains  fusulinid  l i m e s t o n e c l a s t s ; another about 4 km west of  Carquile  contains  abundant c h r o m i t e - s e r p e n t i n e c l a s t s . The  c o r r e l a t i o n between Cache Creek bedrock type and c l a s t  lithology of  i n the conglomerate, the p o o r l y s o r t e d  coarse  nature  the d e p o s i t s , presence of minor c r o s s b e d d i n g and the l i m i t e d  extent of the u n i t a l l i n d i c a t e environment 1978).  an  alluvial  f o r the conglomerate u n i t  fan  (Friedman and Saunders,  Age of the red conglomerate sandstone  although  depositional  unit  i s unknown  i t appears t o u n d e r l i e a mid- Cretaceous c h e r t pebble  conglomerate a t s t a t i o n #271 ( F i g .  30).  CHERT PEBBLE CONGLOMERATE UNIT A c h e r t pebble conglomerate u n i t Creek.  Outcrops  strike.  G. Dawson (1895a) mapped the c h e r t pebble  unit  as  the  continue  both  to  i s found along  Eocene  i n c l u d i n g D u f f e l l and McTaggart  (1952) and Church  lithologies  conglomerate  Coldwater Formation of O l i g o c e n e age.  sandstones  and  age  to  conglomerates  i n the u n i t i t a l s o c o n t a i n s minor  The most common c l a s t  lithology  Hat  the south and n o r t h along  workers a s s i g n e d a T e r t i a r y or  Although  Lower  the  Subsequent Coldwater,  (1975). are  the main  siltstone  layers.  i n the conglomerates i s grey  to  47  black  chert  radiolaria.  pebbles Other  argillaceous  (usually  clasts  >50%)  include  sediments,, h i g h  rounded  chert  diameter.  and  grade  quartz  rocks,  rocks  (with  t u f f s and ash.  clasts,  usually  A  l e s s than 3 cm i n  rounded white ash c l a s t s  t h i s u n i t are anomalous during  volcanic  metamorphic felsic  visible  i s i n d i c a t e d by the preponderance of w e l l  Incompetent  volcanism  contain  aphanitic  s u t u r e d q u a r t z g r a i n s ) and d i s t i n c t i v e high l e v e l of m a t u r i t y  which  the  in  such  a  Cretaceous  mature  which  found throughout  sediment.  produced  Bridge Group t o the south and west has c o n t r i b u t e d  Likely  the Spences ash  t o the  with sparry  calcite  c h e r t pebble conglomerate. The  conglomerate  composing seen  often  cemented  up t o 5% of some samples.  that  thin  Fe-oxide  probably as a r e s u l t through  is  this  of  permeable  In t h i n - s e c t i o n  i t can  be  rims have formed around many c l a s t s , alteration unit.  composed c h i e f l y of small c h e r t  from  Most  groundwater  of  grains  the  and  flowing  sandstones  quartz  are  fragments.  Tops s t r u c t u r e s such as t r u n c a t e d c r o s s b e d d i n g i n d i c a t e that the beds  are  right  s i d e up.  mostly planar and massive thick  layers  of  Paleoenvironmental i n d i c a t o r s bedding  with  c o a r s e . sediments  little  include  cross-bedding;  and sand w i t h l o c a l  fining  upward sequences; l a r g e c a r b o n i z e d logs up t o 60 cm i n diameter; an absence of f i n e g r a i n e d sediments and l a c k of marine These a r e i n d i c a t i v e of b r a i d e d Saunders,  1978).  river  deposits  fossils.  (Friedman  and  48  AGE  OF THE CHERT PEBBLE CONGLOMERATE UNIT Previously  these  T e r t i a r y age based Duffell  and  continental  on l i t h o l o g i c a l  McTaggart,  1952  rocks  were  correlation  assigned  (Dawson,  and Church, 1975).  G. Rouse  Survey  (University  independantly  of B.C.) and W.S. Hopkins ( G e o l o g i c a l  of Canada) and a s s i g n e d a Late A l b i a n or Cenomanian  Correlation  with  the Eocene Coldwater  The c h e r t pebble  unit  the  i s probably c o r r e l a t i v e with  age.  Group and the Eocene Hat  Creek rocks i s t h e r e f o r e i n v a l i d .  south  1895,  Palynomorphs  c o l l e c t e d at s t a t i o n #280 ( F i g . 30) were examined by  an  Pasayten  conglomerate  Group  to the  (Monger, 1981).  KAMLOOPS GROUP The  Kamloops Group c o n s i s t s mainly  and v e s i c u l a r b a s a l t and a n d e s i t e . to  coloured  andesite  and  Clast  dacite  Kamloops Group crops out mainly Valley  but  also'  the map area. been  The l a h a r s have  sub-rounded c l a s t s which can exceed  a f i n e grained s i l t y m a t r i x .  assigned  an  t o the  occurs as i s o l a t e d  Eocene  age  black  by  east  lahars  sub-angular  30 cm i n diameter  lithologies  and  T h i s i s the youngest  of agglomerates,  set i n  include  glassy basalt. of  the  light The  Bonaparte  knobs s c a t t e r e d throughout  unit  i n the map area and has  Church  (1975)  based  on  49  radiometric  dating.  -  A  prominent  b a s a l t o u t c r o p n o r t h of the  Oregon Jack Creek road and west of the road l e a d i n g Cornwall  Hills  forestry  lookout  has  a  K-Ar  up  age  t o the  of  48 Ma  (W.R. Danner, pers comm, 1980). Chalcedony volcanic  and minor opal v e i n l e t s commonly  units  incompetent  observed areas  in c l i f f s  of  white  the  and vuggy c a v i t i e s l i n e d with s m a l l c r y s t a l s of  quartz and c a l c i t e a r e common. fairly  cross-cut  Some of the v o l c a n i c  units  are  and north of C a r q u i l e a few l a r g e caves were of  Kamloops  Group  volcanic  rocks.  r h y o l i t e c r o p p i n g out northwest  and north of White Rock c l i f f s  Large  of McLean Lake  are a l s o i n c l u d e d i n the Kamloops  Group and have been dated as Eocene (51 Ma)  by  Church  (1979).  T u f f s and ash u n i t s c o n t a i n i n g c l a s t s of s e r p e n t i n i t e were found in  the  Bonaparte also  Kamloops Group i n some outcrops t o the n o r t h e a s t of the Indian Reserve.  found  unconformably (Fig.  in  the  Minor  Kamloops  o v e r l i e Cache  sandstones Group.  Creek  Group  and  siltstones  Kamloops  Group  greenstones  30) but i n some p l a c e s they a r e i n f a u l t c o n t a c t .  at  are rocks #265  50  STRUCTURAL GEOLOGY There  are  two dominant s t r u c t u r a l  the o l d e s t s t r i k e s of  i n the map  area,  140 degrees and p a r a l l e l s the s t r i k e of  much  the C o r d i l l e r a .  It i s reflected  of map u n i t s (see F i g . with  this  Cretaceous northeast  trend  is a  rocks.  The  3).  A  by an elongate  pronounced  foliation  distribution  feature  reconized  younger  and i s r e f l e c t e d  trends  i n most pre-mid-  structural  by numerous l i n e a r  associated  trend  strikes  r i v e r v a l l e y s and  lakes. These two dominant s t r u c t u r a l later  one  that s t r i k e s north.  are thought t o have c o n t r o l l e d  f e a t u r e s are t r u n c a t e d  These north  striking  by  a  structures  the development of Eocene  basins  in the map area which formed i n grabens (eg. Hat Creek, Church, 1975). R e a c t i v a t i o n of f a u l t s has o c c u r e d throughout the region as evident  from the f a u l t j u x t a p o s i t i o n of o l d e r rocks  Cache Creek Group a g a i n s t younger rocks conglomerate and Kamloops Group. characteristic  of  the  units  such as the c h e r t  Faulted contacts in  this  f a u l t i n g has l e d to the development of  such as the  region  appear t o and  isolated  pebble be  extensive  fault  bounded  blocks.  STRUCTURAL STYLE OF INDUVIDUAL UNITS A  penetrative  deformation,  recognized  f o l i a t i o n and shear f a b r i c has a f f e c t e d  both  by Cache  a  micaceous Creek  and  51  N i c o l a ( ? ) Group r o c k s .  A planar  argillaceous  i s seen i n r a d i o l a r i a n c h e r t s , elsewhere  partings  f o l i a t i o n c o n s i s t i n g of a l i g n e d  the c h e r t s may  be h i g h l y b r e c c i a t e d as a r e s u l t  shearing.  absence of a  within  The  pronounced  near the Marble Canyon strain  effects  deformational  have  W h i l s t f u s u l i n i d s w i t h i n the  limestone  been  are  destroyed  north  as  a  most  result  of  the  of  post-  and  within Nicola(?)  Group  rocks  t u f f u n i t on C a t t l e V a l l e y Ridge,  of Cache Creek.  showing u n d u l a t o r y sericite  distorted,  recrystallization.  i s best seen i n the quartz-eye the  fabric  to a lack  entrance  i s due  mineral mainly  A m y l o n i t i c f a b r i c developed  to  planar  the Cache Creek Group limestones  of p l a t y m i n e r a l g r a i n s .  of the e x t e n s i v e  Quartz  e x t i n c t i o n occur  microcrystalline  augens (0.1-0.5 mm  i n an  quartz  aphanitic which  diam)  matrix  of  wraps around the  q u a r t z augens i n a f l a s e r t e x t u r e . In  both  foliations  the  are  strike direction exceptions almost  to  Cache  Creek  parallel of  degrees  Nicola(?)  ( F i g s . 26  this foliation orientation  and  to bedding  of l a r g e i s o c l i n a l  by  o r i e n t a t i o n of bedding  d i p s to the southwest except usually  dips  folds.  is  best  isoclinal  27).  The  This hypothesis  Minor  general by  the  i s supported  which i s predominantly  steep  and  w i t h i n anomalous zones i n which the  northeast.  folds.  and have a  explained  These  anomalous  i n t e r p r e t e d to be s t r u c t u r a l l y l o c a t e d i n the hinge large  Group  strike northeasterly,  p e r p e n d i c u l a r to the major s t r i k e d i r e c t i o n .  presence  bedding  and  or s u b - p a r a l l e l to bedding  140  c o n f o r m i t y of f o l i a t i o n  the  Group  Large  isoclinal  folds  zones  are  zones of the  (limb lengths i n  52  F i g u r e 26. S t e r e o p l o t of p o l e s t o bedding and f o l i a t i o n , Creek Group, f o l i a t i o n ( + ) , bedding(X)  Cache  53  Figure 27. Stereoplot of p o l e s to bedding N i c o l a ( ? ) Group, f o l i a t i o n ( + ) , bedding(X)  and  foliation,  54  excess of  1  Formation  by T r e t t i n  Slaty  km)  cleavage  Formation  also  have  been  reported  (1980) and W.B.  within  the  has  pronounced  a  Early  in  the  Marble  Canyon  T r a v e r s (pers comm, 1980). to  Mid-Jurassic  Ashcroft  northwest-southeast  W. T r a v e r s (.1978) r e p o r t e d a modal value of 136  strike,  degrees  strike  and a southwesterly d i p of 32 degrees.  W. T r a v e r s a l s o p r e s e n t s  evidence  f e a t u r e s i n the A s h c r o f t  of  soft  Formation. fractures  sediment  These in  soft  tight  deformation  sediment  fold  s t r u c t u r e s i n sandstone  deformation  features  hinges  layers.  and  include  thin  The presence  wispy of  s t r u c t u r e s i n the A s h c r o f t Formation  formation of the 140 degree  of  pull-apart  soft  sediment  indicates  that  f o l i a t i o n occured when the sediments  had not yet been l i t h i f i e d .  In  as  much  as  the  foliation  developed  Cretaceous  s t r a t a , development of the 140 degree  140  degree  i n m i d - J u r a s s i c s t r a t a and not i n post-midfoliation  then be p o s t - m i d - J u r a s s i c and pre-mid-Cretaceous. deformation  lack  structures  in  Soft  the A s h c r o f t Formation  must  sediment  suggest  that  the deformation was c l o s e t o m i d - J u r a s s i c time. Because of repeated r e a c t i v a t i o n of the f a u l t s the o r i g i n a l c o n t a c t s between  units  between  the  Group).  C l a s t s of  chert  are  Cache  found  Creek  been  modified  in volcanic  Cache  Cache  Creek  contact  Group  radiolarian  greywackes of the N i c o l a ( ? ) Group  The presence  i n N i c o l a ( ? ) sediments  Creek  of  clasts  of  Cache  Creek  i n d i c a t e s that the c o n t a c t between  the two u n i t s i s probably an unconformity the  (eg. the  Group melange u n i t and the N i c o l a ( ? )  presumably  south of Cache Creek. rocks  have  and at  least  melange r o c k s were being u p l i f t e d  locally  in Triassic  55  time.  The  best exposed c o n t a c t i s a steep f a u l t on the Woodburn  Ranch  south  sedimentary,  of  Cache  rocks  Creek  probably  with the melange u n i t , unconformably The  fact  Canyon  but  the  is  a  very  Nicola(?)  be a f a u l t e d one Bonaparte  s t r a t a abutt linear  Road,  trending  trend and  fault,  contact  both  Eocene  complexly  time.  faulted  fault  in tectonic in  more  North of  to the  dipping Nicola(?)  conglomerates  along  a  This feature  Along  Differing  the  Hat  orientation  of  To the south T r a v e r s (1978)  as an unconformity  and as a t h r u s t  unconformity.  interelationships  the Eocene Kamloops Group unconformably  vertical  area.  southwest  At s t a t i o n #265 ( F i g . 30)  the Cache Creek Group.  Marble  ( F i g . 30) N i c o l a ( ? ) rocks o v e r l i e  the t h r u s t i n g p o s t - d a t e s the  Such  or  found  c o n t a c t appears  a c r o s s the h i l l s i d e .  the u n i t s suggests a f a u l t c o n t a c t . the  Formation  Ashcroft  A s h c r o f t s i l t s t o n e s and sandstones.  reported  not  covered  i s probably a f a u l t .  near s t a t i o n #19  Formation.  are  factor  occur  history.  steeply  dipping  to  unit  be  most of the map  Reserve  depression  has a 140 degree Creek  significant  relationship  Canyon  greenstone  Group-Ashcroft  gently  Nicola(?)  seen  rocks  T h i s aspect w i l l  throughout  Indian  they  Group  the  i n the chapter on t e c t o n i c  The  are  u n i t or Marble  Nicola(?)  m o d e l l i n g f o r the a r e a . detail  nowhere  with r e s p e c t to  Formation  1978).  have an unconformable  on the greenstone that  unconformably  (Travers,  continue  into  immature sandstones  overlie  greenstones  of of  About 3 km to the n o r t h the c o n t a c t i s a  striking  n o r t h - s o u t h which c o n t a i n s s e r p e n t i n e  bodies c r o p p i n g out along the c o n t a c t .  The v a r i e d nature of the  56  stratigraphic  contacts r e f l e c t s  t h i s area between T r i a s s i c  the  deformational  and Eocene time.  history  of  57  PALEOENVIRONMENTAL RECONSTRUCTION The  association  of  radiolarian  ribbon  chert,  pillowed  b a s a l t , gabbro, u l t r a m a f i c rock and l i m e s t o n e suggest  an o c e a n i c  environment f o r d e p o s i t i o n  rocks.  variety  of  specific  of  Cache  enviroments  an  ocean  1973).  island  Group  has been proposed  mid-ocean r i d g e as w e l l as v o l c a n i c Geochemical evidence  Creek  seamounts  including a  (Monger,  and  environment.  or  c o n t i n e n t a l environment  calcareous  Together  a l a r g e oceanic  algae  i s l a n d or oceanic  water  suggest  the geochemistry  most l i k e l y d e p o s i t i o n a l Shallow  1977).  of high c o n c e n t r a t i o n s of Nb and T i suggest (Pearce and Cann,  The occurrence of abundant shallow water faunas  fusulinids  A  a  such  as  shallow  marine  and p a l e o n t o l o g y  suggest  plateau  environment  in  limestones  as the  site.  indicators  the  such  as  f u s u l i n i d s , o o l i t e s and a l g a l l a m i n a t i o n s show that most of the Cache  Creek  oceanic  p l a t e a u must have been covered by shallow  warm seas.  C o n d i t i o n s were t r o p i c a l  growth  large  of  Evidence  is  supported  Cache  f o r minor s u b - a r e a l exposure has been  Creek  plateau  v o l c a n i c and v o l c a n i c l a s t i c  was  mainly  reported  (Morrow, 1967). composed of mafic  rocks and l i m e s t o n e .  I n t e r m i x i n g of  l i m e s t o n e and mafic v o l c a n i c rocks i s common i n the Cache Group  in  southern B.C.  Creek  In n o r t h e r n B.C. the Cache Creek Group  u s u a l l y has d i s t i n c t areas of l i m e s t o n e and v o l c a n i c rocks little  the  banks (W.R. Danner, pers comm,  i n the Cache Creek Group near Dease Lake,, B.C. This  by  f u s u l i n i d s which p r o b a b l y grazed on algae and  other o r g a n i c d e b r i s on carbonate 1980).  as  i n t e r b e d d i n g of the two (Monger, 1977 ) .  with  58  Both  adjacent  to and w i t h i n the p l a t e a u were deeper water  areas of p e l a g i c d e p o s i t i o n . common  in  these  areas.  Argillite  Topographic  i t s margins l e d to the sedimentation debris-flow deposits into From  time to time  p l a t e a u and argillite  slid  The  Almost  such  as  were  most  on the p l a t e a u and  of both carbonate  water all  Cache  Creek  conodont  fauna  limestone b l o c k s  events  relief  surrounding  i n t o the deeper  sediments.  Permian  chert  and c h e r t  pelagic  sediments.  l a r g e b l o c k s of limestone were broken o f f the  melange u n i t of the similar  the  and  were  submarine t a l u s and  or  contain  (M. Orchard,  and  the  same  or  pers comm, 1981).  dislodged  earthquakes  slide deposits.  chert  the limestone b l o c k s i n the  Group  probably  hurricanes  radiolarian  by and  A similar  cataclysmic emplaced  explanation  as for  limestone b l o c k s interbedded with r a d i o l a r i a n c h e r t i n the Cache Creek  Group  in  northern  B.C.,  has been proposed  by J . Monger  (1977). Felsic rocks  t u f f s , agglomerates  characterize  mainly  are  flows  with  some  basaltic  the lower N i c o l a ( ? ) while the upper p a r t i s  water-lain  Limestones  and  found  volcanic  sediments  sporadically  c o n t a i n c r i n o i d s , brachiopods  (Travers,  throughout marine  the s e c t i o n  and  fossils.  This  sequence of rocks c o u l d have been d e p o s i t e d i n a maturing  island  arc  and other  1978).  s e t t i n g , where e x t e n s i v e e r o s i o n occurs as v o l c a n i s m wanes,  as proposed  by T r a v e r s (1978).  Granitic  rocks of the u n d e r l y i n g  comagmatic Guichon B a t h o l i t h would p r o v i d e for the system  (McMillan, 1976).  the  plutonic  roots  59  TECTONIC MODELS AND A model has forth  by  rocks  been developed  previous  (Ladd, 1979) collected  HISTORY  with  new  authors  i n an e f f o r t  (Monger, 1977), ( T r a v e r s ,  g e o l o g i c a l and  i n t h i s study.  to u n i t e models put  paleontological  1978)  and  information  In the model proposed here  the  older  are d i v i d e d i n t o four groups.  4) A s h c r o f t  Formation  3) N i c o l a ( ? ) Group ( I s l a n d  Arc)  2) Greenstone U n i t and Marble Canyon Formation  (Oceanic  1) Melange Unit  On arc.  occurs  (Subduction  F i g . 28 the oceanic  The  Marble  Plateau)  plateau  Canyon  plateau  i s shown as approaching  i s composed of the  Formation.  at the t r e n c h and  e v e n t u a l l y the melange.  greenstone  Formation  of  unit  into  the  a subduction  ocean  R a d i o l a r i a n c h e r t and  the  and  the  complex  o c c a s i o n a l arc d e b r i s slumps out  ocean; where i t i s i n c o r p o r a t e d  off  Complex)  to the  sediments  argillite  and  scraped  the ocean f l o o r are the main c o n s t i t u e n t s of the melange i n  the subduction  complex.  slid  off  rocks  from the N i c o l a ( ? )  rocks and deposited  Also  included  the nearby p l a t e a u and  out over the melange.  the N i c o l a ( ? ) v o l c a n i c and  blocks  minor v o l c a n i c and  island arc.  E a r l y to M i d - J u r a s s i c  are  Late  Ashcroft  Triassic  which  have  sedimentary Nicola(?)  Formation sediments are  These rocks are represented  sedimentary  rocks  south  of  by  Cache  60  SUBDUCTION POST  F i g u r e 28.  MID-JURASSIC  T e c t o n i c model f o r Cache Creek Group  61  Creek,  west  of  McLean  Lake  and  Reserve; and A s h c r o f t Formation of  west of the Bonaparte Indian  rocks south of Cache Creek, west  the Bonaparte Indian Reserve and a l o n g the  road.  The  Ashcroft  Formation  is  remanents of the e x t i n c t N i c o l a ( ? ) plutonic As over  the  ocean  plateau  the melange-arc u n i t  the  composed island  i s l a n d arc  collides  for  a  Mid-Jurassic  rocks  T h i s obduction may  as  Because t h i s deformation  c h e r t pebble  been  chert  pebble  two  opposing  the  two  quite  flat  half-grabens.  in  source  area.  Early  the  structural  has no obvious  conglomerate u n i t  140 degree and NS along  dramatic  block  effect i t must  Rocks  Along  trends  has  boundaries.  west of C a r q u i l e i n the which  r i v e r v a l l e y have now  originally  were  been t i l t e d  into  the upthrown center p o r t i o n of  h a l f - g r a b e n s are d i s c o n t i n u o u s pods of s e r p e n t i n i t e and  rocks from the N i c o l a (?).Group block  be the  rocks.  conglomerate u n i t .  d e p o s i t e d i n a broad  the map  discussed  brought a l l u n i t s i n t o c o n t a c t mainly has  of  o v e r l y i n g the N i c o l a ( ? ) Group rocks are  d e p o s i t i o n of these  effect  i t i s t h r u s t up  core  L a t e r block f a u l t i n g a l o n g the  This  associated  140 degree southwest d i p p i n g f o l i a t i o n common  mid-Cretaceous  predate  and  k i l o m e t e r s from the b a t h o l i t h i c  i n t h i s deformation section.  the  eroded  km,  the pre-mid-Cretaceous rocks throughout  on  arc  distance  in  geology  of  40  ( F i g 28c).  minimum  the predominant  involved  Creek  mainly  ( F i g 28b)  of  to  Hat  basement.  coming to a r e s t only a few of  Lower  faulting  has  continued  Kamloops Group rocks are l o c a l l y  and  Ashcroft  until  at  faulted  Formation.  This  l e a s t Eocene time against  Cache  as  Creek  62  Group  rocks.  63  ECONOMIC GEOLOGY M e t a l l i c mineral d e p o s i t s i n the map area i n c l u d e the Cache Creek,  S c o t t y Creek, Ferguson  occurrences found  as  ( D u f f e l l and  the  McTaggart,  1952).  The  chromite  chromite  is  small pods and d i s s e m i n a t i o n s i n s e r p e n t i n i t e s of the  Cache Creek Group. of  Creek and Cornwall Creek  Due t o the e r r a t i c  low-grade nature of  much  m i n e r a l i z a t i o n these occurrences have not been e x p l o r e d  in recent y e a r s . The Maggie Mine i s a low-grade deposit  with  equivalent  about  200  MT  of  reserves  copper-molybdenum g r a d i n g 0.4% copper  (B.C. Dept of Mines, G.E.M., 1971,  about 3 km n o r t h of C a r q u i l e . further  porphyry  examples  of  this  p  304), l o c a t e d  Regional geochemical  kind  of  sampling f o r  mineralization  have been  c a r r i e d out by Bethlehem Copper and other companies but  no  new  d i s c o v e r i e s have been made. Small  quartz  veins  i n Cache Creek Group and N i c o l a Group  rocks c a r r y minor amounts of c h a l c o p y r i t e , galena and s p h a l e r i t e throughout Flats,  the map a r e a .  South  of  Creek  near  Boston  ribbon c h e r t b l o c k s were found with m a l a c h i t e and a z u r i t e  coating  fracture  surfaces.  None  of  appear to be l a r g e enough t o warrant Altered serpentinites quartz,  carbonate  and  carbonate  rocks  literature  (Boyle, 1980).  fuchsite  and  these s m a l l  form  resistant  fuchsite  rock  may  gold  The  deposits  occurrences  furthur e x p l o r a t i o n .  which  tonnage low-grade gold d e p o s i t s .  and  Cache  outcrops  be hosts to l a r g e -  association i s documented  A grab sample  of  of  quartz,  of  quartz-  in recent carbonate  rock from west of McLean Lake gave v a l u e s of over  64  300  ppb  Au and  18 ppm  Ag.  However m i n e r a l i z a t i o n i s e r r a t i c  nearby o u t c r o p s c o n t a i n e d  no g o l d or  silver  sampling over l a r g e areas of q u a r t z , would  have  to  be  carried  out  values.  carbonate and  and  Detailed  f u c h s i t e rock  to l o c a t e g o l d and  silver-rich  zones. There i s good p o t e n t i a l in the N i c o l a ( ? ) volcanogenic 15 km  massive  south of  massive  sulphide d e p o s i t s .  Cache  Creek  chalcopyrite  (Albrechtsons, discovered c o u l d be  which  1981).  in  the  examined  at  New  Hill  appears  of  rocks  N i c o l a ( ? ) Group apparently  volcanogenic  areas of N i c o l a ( ? )  course for  Red  Group  rocks  contain  in  type  for  origin  rocks  were  mapping f o r t h i s p r o j e c t ; these  extensions  of  Red  Hill-type  massive  sulphide m i n e r a l i z a t i o n . G. Dawson pebble  (1895)  conglomerate  paleo-placer  coarse  unit  by  stratigraphy.  gravel  deposits  reports  (Coldwater  mineralization.  d e p o s i t c o u l d be done favourable  mentions  regional  which may  area  one  coal.  Estimates  of t o t a l r e s e r v e s  comm,  s t r a t i g r a p h y were not  i n the  chert  occuring this  geochemistry  as  kind  of  in  areas  of  be  focused  on  i n d i c a t e channel bottoms  and  gold.  on the west i s  contains  pers  for  S p e c i a l a t t e n t i o n should  which  (H. Kim,  of  gold  Formation)  Prospecting  c o u l d c o n t a i n p l a c e r accumulations of Adjacent to the map  of  Hat  Creek  Valley  the worlds t h i c k e s t s i n g l e d e p o s i t s  1980).  have exceeded 10 B i l l i o n  Tertiary  rocks  found i n the map  area  c o a l d e p o s i t s of the same type i s very  low.  with  of  tons  comparable  so the p o t e n t i a l f o r  65  CONCLUSIONS 1.  The Cache Creek Group rocks of the e a s t e r n and c e n t r a l  b e l t s i n southern B.C. divided  into  ( D u f f e l l and McTaggart,  1952),  a lower melange u n i t and a s t r u c t u r a l l y  can  be  overlying  greenstone u n i t and Marble Canyon Formation. 2.  Thinly  l a m i n a t e d c h e r t - a r g i l l i t e of t h e melange u n i t i s  i n t e r p r e t e d as r e p r e s e n t i n g a deeper water of  environment  because  lack of c a r b o n a t e (except as b l o c k s ) and evidence of p e l a g i c  s e d i m e n t a t i o n ( r a d i o l a r i a and t h i n rhythmic bedding of between  chert  layers).  Limestone  c o n t a i n f u s u l i n i d s and a l g a l provenance. clasts  of  Greenstone fusulinid  blocks i n the melange u n i t  s t r u c t u r e s i n d i c a t i n g shallow water  blocks  in  the  melange  unit  contain  l i m e s t o n e as w e l l as i n t e r p i l l o w carbonate  (but  no deeper ,water c h e r t - a r g i l l i t e ) ,  the  greenstone  in  argillite  relatively  indicating deposition  shallow  water.  T h e r e f o r e the  melange p r o b a b l y formed by b l o c k s of shallow water f a c i e s sliding  into  argillite  was predominant.  manner  deeper  would  be  water  talus  where  deposition  A term f o r melange melange.  of  Olistostrome  appear  to  have  occured.  rocks  chert  formed  sedimentary t r a n s p o r t of the c h e r t - a r g i l l i t e matrix not  of  and  in  would which  this  imply does  L a t e r tectonism has sheared the  melange u n i t and caused r o t a t i o n of blocks i n the melange. 3. such  evidence  from  immobile  elements  as Nb, Y and T i i n d i c a t e s that the Cache Creek greenstones  formed  partly  (Pearce Group  L i m i t e d geochemical  and  in Cann,  an  intra-plate  1973).  ocean  plateau  environment  Most greenstones i n the Cache  Creek  i n southern B.C. a r e h i g h l y e n r i c h e d i n Nb and T i compared  66  to normal ocean f l o o r b a s a l t s . ppm  Ti  were  concentrations indicating  Values up  recorded. of Nb  that  and  One  Ti  there may  sample  similar  to  this  environment  is  rocks  were a l k a l i c  to t r a n s i t i o n a l and  4.  o c c u r r i n g as b l o c k s several  Iceland  r a t i o s ( P e a r c e and Discovery  of  As  First,  the  to pressure  and  melange  which  r e s t of the  amphiboles  (Grette,  1978).  the  Triassic the  time.  is  radiolarian  Nicola(?)  Group.  occur  the  in  Most of  the  according  apparently  melange Creek  reported  Since  chert  Cache the  This  for  unit  has  Group  and  and  the  time  temperature c o n d i t i o n s s i m i l a r to  mineralogy  from  f u r t h u r evidence that  analogue  glaucophane they presumably have  the  they  clasts  the Bonaparte R i v e r  derived  basalts  magma source  rocks  by Late T r i a s s i c  i n t o the melange u n i t as l a t e r  probably  floor  tholeiitic  Cache  introduced  greywackes along  had  1973).  Nicola(?)  blueschist  Radiolarian  greenstone  modern  not  developed  5.  276  d e t r i t u s i n t o the Cache Creek melange.  the N i c o l a ( ? ) b l o c k s c o n t a i n  been s u b j e c t e d  A  i n the Cache Creek Group  shedding  and  Cann, 1973).  N i c o l a ( ? ) Group were juxtaposed was  ocean  (Schilling,  probable  implications.  Nicola(?)  of  Nb  have been more than one  for the Cache Creek Group greenstones.  to the Y/Nb  to 77 ppm  i s disputed  clasts  may  have  could fault  Group  by W.R.  Group.  Since  have  the  been  Cache  Nicola(?) Creek  c h e r t s and  were  come  blue  slices.  in  together Danner who  from  R a d i o l a r i a n c h e r t s are not  Nicola(?)  not  south of  units  contain  N i c o l a ( ? ) blocks have  found  Creek  two  to  provide by  Late  maintains  cherts  presently  Cache  are  Creek  in  the  known to Group  67  radiolarian  cherts  are as  young  as  Late T r i a s s i c  1978), the p o s s i b i l i t y e x i s t s that N i c o l a ( ? )  Group  (Travers,  radiolarian  c h e r t s may be d i s c o v e r e d . 6.  Superposition  of  the predominantly  Marble Canyon Formation-greenstone melange  unit  fault. the  u n i t and  Permo-Triassic  the P e r m o - T r i a s s i c  i s probably a l o n g a l a r g e s h a l l o w - d i p p i n g t h r u s t  Minimum displacement can be e s t i m a t e d by measuring  furthest  Fraser  River  greenstone at l e a s t  west  Cache  near  Moran)  to  melange type rocks (along the the easternmost  edge  of the  u n i t n o r t h of Cache Creek; t h i s p r o v i d e s a f i g u r e of  40 km displacement.  e x i s t e n c e of s i m i l a r Group  Creek  from  flat  i n the Marble  Trettin  lying thrust  Range  to  (1980)  has proposed  faults  the  i n the Cache Creek  the n o r t h .  An  alternative  e x p l a n a t i o n suggested by J . Monger (pers comm, 1981) i s that the areas of greenstone and limestone which appear melange  unit  a r e enormous  N i c o l a ( ? ) Group rocks above  should  the greenstone  blocks. be  found  If  to  this  sitting  Nicola(?)  Cache  Group  melange  unit  greywackes south of Cache Creek.  comm,  unconformably  unit.  derived  because However  1981), which  from  the  rocks a r e found i n N i c o l a ( ? ) However no l i m e s t o n e s of Cache  Creek Group o r i g i n have been found i n these rocks pers  then  unit.  R a d i o l a r i a n chert c l a s t s presumably Creek  the  rocks are observed on the Marble Canyon Formation  or the greenstone 7.  i s true  u n i t and Marble Canyon Formation  N i c o l a ( ? ) Group b l o c k s are found i n the melange no  overlie  i n d i c a t e s that  (W.R. Danner,  the melange u n i t was i n  contact with the N i c o l a ( ? ) Group i n the L a t e  Triassic  but the  68  Marble  Canyon  Formation d e b r i s to  the  Formation  was  not.  The  lack of Marble Canyon  i n the N i c o l a ( ? ) Group p r o v i d e s f u r t h e r support  suggestion  that  the  greenstone u n i t were emplaced of the N i c o l a ( ? ) v o l c a n i c  Marble  Canyon  Formation  and  in their p o s i t i o n a f t e r deposition  greywackes.  69  REFERENCES  Albrechtons, E.A. (1981) The geology of the S i l i c a Red H i l l area, near A s h c r o f t , B.C. Unpublished Lakehead U n i v e r s i t y , Thunder Bay, O n t a r i o , 56p.  Claim Group, BSc. T h e s i s ,  Boyle, R.W. (1980) The geochemistry of gold and G e o l o g i c a l Survey of Canada, B u l l e t i n 280, 584p.  i t s deposits.  Church, B.N. (1975) Geology of the Hat Creek Coal B a s i n . B.C. Ministry of Mines and Petroleum Resources, Geology i n B r i t i s h Columbia, p G99-G118. 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