Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Geology and mineralization of the stikine assemblage, Mess Creek area, northwestern British Columbia Holbek, Peter Michael 1988

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1988_A6_7 H64.pdf [ 16.49MB ]
Metadata
JSON: 831-1.0052696.json
JSON-LD: 831-1.0052696-ld.json
RDF/XML (Pretty): 831-1.0052696-rdf.xml
RDF/JSON: 831-1.0052696-rdf.json
Turtle: 831-1.0052696-turtle.txt
N-Triples: 831-1.0052696-rdf-ntriples.txt
Original Record: 831-1.0052696-source.json
Full Text
831-1.0052696-fulltext.txt
Citation
831-1.0052696.ris

Full Text

GEOLOGY AND MINERALIZATION OF THE S T I K I N E ASSEMBLAGE, MESS CREEK AREA, NORTHWESTERN, BRITISH COLUMBIA by PETER MICHAEL HOLBEK B.Sc,  The U n i v e r s i t y  of British  C o l u m b i a , 1980  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE  REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  in THE  FACULTY OF GRADUATE STUDIES  Department o f G e o l o g i c a l We a c c e p t t h i s  t h e s i s as conforming  to the required  THE  Sciences  standard  UNIVERSITY OF BRITISH COLUMBIA J u n e , 1988  ©  P e t e r M i c h a e l H o l b e k , 1988  In  presenting  degree  this  at the  freely available copying  of  department publication  of  in  partial  fulfilment  University of  British  Columbia,  for reference and study.  this or  thesis  thesis by  this  for scholarly  his  or  thesis  her  The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3  DE-6G/81)  V^V  J  I further agree  purposes  may It  be is  requirements  for  an  l^PJPs  advanced  that the Library shall make it that permission  for extensive  granted  head  by the  understood  that  for financial gain shall not be allowed without  Department  Our-  the  I agree  representatives.  permission.  Date  of  of  my  copying  or  my written  - ii  -  ABSTRACT  The S t i k i n e of  Assemblage  Mississippian  morphosed  and  greenstones. and  Original  tuffs,  Regional  time.  Four early  recumbent  style  felsic  phases  folding style  folding.  foliation. thermal  effects  crenulation  and  metamorphism  to  by  Creek a r e a .  stages  produced  and  of a  folds  produced Third  Late  phyllites  and  to  pyroclastics crystal-lithic  gabbroic lower  and  and  Triassic  Middle  Triassic including  trending  isoclinal,  trending  Potassium-argon  folding  was  penetrative  kink  synchronous axial  a  locally  fourth  phase  sediments  occurred  bank  parallel-  significantly  in Early Jurassic  plutonism  sills.  greenschist  recognised  easterly  phase  phase  of  are  meta-  and n o r t h e r l y t r e n d i n g  related to terrane c o l l i s i o n Three  Permian  northwesterly  first  cleavage.  overlying  Late  folding,  Second  breccias  consists  deformed,  mafic  sediments,  followed  and  were  deformation  of  The  metamorphism  affected  of  schists,  volcanic  between  phases  and c h e v r o n  altered,  lithologies  dynamothermal occurred  two  variably  graphitic  facies  t h e Mess C r e e k a r e a  mineralized  epiclastics,  ash  with  aged,  in  planar  outlasted pronounced  folding and  also  could  be  time.  within  and r u b i d i u m - s t r o n t i u m  the  Mess  dates  -  from  plutons  Middle  of  Triassic  Hickman  ages  Jurassic  age  syenitic  plutons,  deposits  the  for  for  batholith  quartz  quartz commonly  and  structurally  diorites  quartz  and  Two a g e s o f  and  cation  potassium  metasomatism,  and  to  Foliation-parallel alteration metals.  are  quartz  fracture bearing  veins  alteration albite, dolomite,  that  and  cut  mineralogy muscovite, barite  mineralogy arsenopyrite,  but  and  includes  all  barren  consists  hosts  gold  fabrics.  silicifiby  group  systems. with  this  of  precious  of  intense  silver  and  and  is  silver  Gangue  and  quartz,  manganiferous  phosphates.  sphalerite,  a  pre-kinematic  siderite,  chlorite,  galena,  been  sericitization,  ankerite,  lanthanide pyrite,  is  associated  and  fuchsite,  veins  characterized  deformation  includes  chalcopyrite,  conformable  which  commonly  by  a l t e r a t i o n have  generally  silicification  controlled  Cu-Au  hosted  hydrothermal  veins  alteration,  carbonatization,  generally  porphyry  is  assemblage,  volcanogenic  ubiquitous  Later  commonly  carbonate  attributed  Middle  quartz-carbonate  Widespread  quartz-muscovite-  a  to  ages.  identified. and  and  with  mineralization  alteration.  Early  Alkalic,  associated  silver  controlled  and a s s o c i a t e d  indicate  monzonites.  yield Early Jurassic  Gold  -  i i i  Ore  tetrahedrite, bismuth  -  tellurides,  electrum  and  w i t h i n v e i n s r a n g e from Hydrogen produced include H.  Precipitation  caused wall  by  a  pH  of  of  Sulphide  associated  changes Ca  and  quartz,  increase  concentrations  due  Na  with  within  host  and  addition  the  carbonates to  mineralization  and  rocks of  that K  and  sulphides  was  hydrolysis reactions  with  rocks. Potassium-argon  alteration  and  and  rubidium-strontium  mineralization yields  which c o i n c i d e with time  gold.  metasomatism  removal  -  massive to s p a r s e l y disseminated.  compositional the  iv  regional alkalic  Early  dating  Jurassic  plutonism  and  of ages,  possible  of t e c t o n i c a c c r e c t i o n of allochthonous terranes.  TABLE OF CONTENTS  PAGE NO.  ABSTRACT  i i v  TABLE OF CONTENTS L I S T OF TABLES  v i i  L I S T OF FIGURES L I S T OF PLATES  xi  ACKNOWLE DGEMENTS  xiv  FRONTISPIECE  xvi  CHAPTER 1: 1.1 1.2 1.3 1.4 1.5  General Statement L o c a t i o n and A c c e s s P h y s i o g r a p h y and V e g e t a t i o n P r e v i o u s Work P r e s e n t Work  CHAPTER 2: 2.1 2.2 2.3  2.4  2.5  3.3  1 3 3 6 9  REGIONAL GEOLOGY Tectonic Setting General Geology and S t r a t i g r a p h y S t r a t i f i e d Rocks 2.3.1 S t i k i n e Assemblage 2.3.2 S t u h u n i Group 2.3.3 Upper T r i a s s i c Sediments I n t r u s i v e Rocks 2.4.1 Hickman P l u t o n 2.4.2 Nighout Pluton 2.4.3 Yehiniko Pluton 2.4.4 Other P l u t o n i c Rocks Age a n d M e t a l l o g e n y  CHAPTER 3 : 3.1 3.2  INTRODUCTION  Summary  12 15 18 18 23 27 30 32 36 37 39 41  GEOLOGY OF STIKINE ASSSEMBLAGE Introduction Stratigraphy 3.2.1 S t r a t i g r a p h i c Summary 3.2.2 Argillaceous Schist 3.2.3 M a f i c P y r o c l a s t i c a n d E p i c l a s t i c U n i t 3.2.4 Felsic Pyroclastic Unit 3.2.5 Greenstone U n i t 3.2.6 A l t e r a t i o n U n i t s Structure 3.3.1 Introduction 3.3.2 S t r u c t u r a l Sequence 3.3.3 Stereonet Analysis  46 47 47 51 55 57 59 61 65 65 66 69  -  v i -  PAGE NO. 3.3.4 3.3.5 3.3.6  3.4  F o l d S e t s and D e f o r m a t i o n F a b r i c s Faults S t r u c t u r a l Comparison o f t h e Study Area w i t h o t h e r Exposures of t h e S t i k i n e Assemblage 3.3.7 Timing o f Deformation Metamorphism 3.4.1 M e t a m o r p h i c M i n e r a l o g y 3.4.2 C o n d i t i o n s o f Metamorphism 3.4.3 T i m i n g o f Metamorphism  70 75 76  78 81 92 94 97  3.5  Age o f t h e S t i k i n e A s s e m b l a g e 3.5.1 S t r a t i g r a p h i c E v i d e n c e 3.5.2 I s o t o p i c Ages  99 100 101  3.6  Chemistry 3.6.1 G e n e r a l S t a t e m e n t 3.6.2 Methods a n d Q u a l i t y C o n t r o l 3.6.3 M a j o r E l e m e n t C h e m i s t r y 3.6.4 T r a c e Element Chemistry  105 105 106 107 111  CHAPTER 4 : 4.1 4.2  4.3  4.4  Introduction Mineralization 4.2.1 F o l i a t i o n - P a r a l l e l Quartz Veins 4.2.2 Quartz-Breccia Veins 4.2.3 Carbonate-Sulphide Veins 4.2.4 Carbonate-Arsenopyrite Veins 4.2.5 Other V e i n Types 4.2.6 Sulphide Mineralogy Alteration 4.3.1 D e s c r i p t i o n and P e t r o g r a p h y 4.3.2 C h e m i c a l Changes A s s o c i a t e d with A l t e r a t i o n 4.3.3 C o n d i t i o n s and O r i g i n o f A l t e r a t i o n Comparison o f M i n e r a l i z a t i o n w i t h Other Deposits  CHAPTER 5: 5.1 5.2 5.3  ECONOMIC GEOLOGY 120 121 123 125 127 128 130 131 138 138 142 145 158  CONCLUSIONS Summary o f G e o l o g i c a l H i s t o r y o f t h e Study Area Tectonic Implications Mineral Exploration Potential  REFERENCES  164 168 171 176  -  v i i-  L I S T OF TABLES Page Table  2.1  I s o t o p i c Age D e t e r m i n a t i o n s f o r P l u t o n i c R o c k s o f t h e Hickman B a t h o l i t h  35  Table  3.1  Summary o f S t r u c t u r a l E l e m e n t s o f t h e S t i k i n e A s s e m b l a g e , Mess C r e e k A r e a  67  Table  3.2  Summary o f M e t a m o r p h i c M i n e r a l s a n d T e x t u r e s o f S t i k i n e Assemblage Rocks, Mess C r e e k A r e a  93  Table  3.3  R u b i d i u m - S t r o n t i u m Data f o r Rocks o f t h e S t i k i n e A s s e m b l a g e , Mess C r e e k A r e a  104  Table  3.4  Major Element Chemistry o f t h e S t i k i n e A s s e m b l a g e R o c k s , Mess C r e e k A r e a  108  Table  3.5  T r a c e Element Chemistry o f t h e S t i k i n e A s s e m b l a g e R o c k s , Mess C r e e k A r e a  109  Table  4.1  Summary o f M i n e r a l i z a t i o n a n d A l t e r a t i o n C h a r a c t e r i s t i c s , B J P r o s p e c t , Mess C r e e k Area  122  -  L I S T  O F  v i i i  -  F I G U R E S  Page o f S t u d y A r e a , Mess B r i t i s h Columbia  1.1  L o c a t i o n Map Northwestern  Figure  1.2  T o p o g r a p h y and M i n e r a l C l a i m s , B J P r o s p e c t , Mess C r e e k A r e a  Figure  1.3  L o c a t i o n Map f o r M a j o r M i n e r a l D e p o s i t s , N o r t h w e s t e r n B r i t i s h C o l u m b i a and Adjacent Parts of Alaska  11  Figure  2.1  Tectonic  14  Figure  2.2  R e g i o n a l Geology, S o u t h - C e n t r a l p a r t t h e T e l e g r a p h C r e e k Map S h e e t A r e a  Figure  2.3  S t r a t i g r a p h i c R e l a t i o n s o f P a l e o z i c and Mesozoic Rocks o f the S o u t h - C e n t r a l p a r t o f t h e T e l e g r a p h C r e e k Map S h e e t A r e a  21  Figure  2.4  D i s t r i b u t i o n of Late T r i a s s i c V o l c a n i c R o c k s R e l a t i v e t o t h e Cache C r e e k G r o u p i n the Canadian C o r d i l l e r a  24  Figure  2.5  S t r a t i g r a p i c Column f o r t h e U p p e r T r i a s s i c S e d i m e n t s , Mess C r e e k A r e a  29  Figure  2.6  D i s t r i b u t i o n o f P l u t o n i c Rocks o f t h e Hickman B a t h o l i t h , S t i k i n e R i v e r A r e a  33  Figure  2.7  Summary o f Age R e l a t i o n s h i p s f o r R o c k s and S e l e c t e d M i n e r a l D e p o s i t s o f t h e S t i k i n e Arch Area  43  Figure  3.1  S c h e m a t i c S t r a t i g r a p h i c Column o f S t i k i n e A s s e m b l a g e R o c k s , Mess Creek Area  49  Figure  3.2  G e n e r a l i z e d G e o l o g y o f t h e Mess Creek Area, Northwestern B r i t i s h Columbia  50  Figure  3.3  1:12,500 S c a l e G e o l o g y o f t h e W e s t e r n H e a d w a t e r s o f Mess C r e e k , T e l e g r a p h C r e e k Map S h e e t A r e a , N o r t h w e s t e r n B r i t i s h Columbia  Figure  3.4  Geological Cross Sections Creek Area  Features of the S t i k i n e  Creek,  4  Figure  Arch of  f o r t h e Mess  19  PojeneetV  X  - ix Page Figure  3.5  Summary o f F o l d S t y l e s and O r i e n t a t i o n s , Mess C r e e k A r e a  68  Figure  3.6  Contoured S t e r e o n e t P l o t s o f S t r u c t u r a l D a t a f r o m t h e Mess C r e e k A r e a  71  Figure  3.7  Schematic Diagram I l l u s t r a t i n g E f f e c t s of Superposed F o l d i n g  74  Figure  3.8  ACF, AKF, and QCM d i a g r a m s o f Metamorphic M i n e r a l Assemblages t h e Mess C r e e k A r e a  Figure  3.9  the  95 of  Some I s o b a r i c E q u i l i b r i u m C u r v e s f o r Metamorphic R e a c t i o n s i n t h e System SiO -MgO-CaO-H O-C0 2  2  98  2  Figure  3.10  Rubidium-Strontium I s o c h r o n Diagram f o r R o c k s o f t h e S t i k i n e A s s e m b l a g e , Mess Creek Area  103  Figure  3.11  H a r k e r V a r i a t i o n Diagrams Elements  112  Figure  3.12  A l k a l i e s - S i l i c a Plot of S t i k i n e A s s e m b l a g e R o c k s f r o m t h e Mess Creek Area  113  Figure  3.13  AFM  114  Figure  3.14  FeO-MgO-Al 0  Figure  3.15  Ti0 -Zr  Figure  3.16  A l 0 /TiO , A l 0 /lOOZr, v e r s u s MgO Diagrams  Figure  4.1  Composite V a n d e r v e e r Type Diagram showing s u l p h i d e m i n e r a l p a r a g e n e s i s f o r m i n e r a l i z a t i o n o f the BJ P r o s p e c t  137  Figure  4.2  I s o c h o n Diagrams D i s p l a y i n g C o m p o s i t i o n a l Changes a s s o c i a t e d w i t h a l t e r a t i o n , B J P r o s p e c t Mess C r e e k A r e a  144  Figure  4.3  C h e m i c a l and M i n e r a l o g i c a l Changes Associated with the T e l l u r i d e Vein, BJ P r o s p e c t  146  of Major  Diagram 2  2  3  T r i a n g u l a r Diagram  116  Diagram  118 100Zr/TiO  2  119  - x Page Figure  4.4  Phase R e l a t i o n s i n t h e System K 0-Na 0-Al 0 -Si0 -H 0.  152  Phase R e l a t i o n s i n t h e Systems Na 0-A1 0 - S i O -H 0-HC1 a n d K 0-A1 0 - S i O -H 0-HC1 a s a F u n c t i o n o f Log ( a + / + ) °g ( /a„+)  153  2  Figure  4.5  2  2  3  2  2  a  K  L  a  +  H a  a  H  n  d  - xi L I S T OF  PLATES Page  Plate  Plate  3.1a  Coarse clast-supported pyroclastic unit  breccia  of  felsic  3. l b  Fine bedding w i t h i n epiclastic unit  3. l c  V e s i c u l a r v o l c a n i c bombs w i t h i n pyroclastic/epiclastic unit  3. l d  Deformed f r a g m e n t a l - f r a g m e n t w i t h i n t r a n s i t i o n zone between m a f i c and felsic pyroclastic units  3.1e  M i c r o l i t h o n s t r u c t u r e (coarse c r e n u l a t i o n cleavage) i n f e l s i c p y r o c l a s t i c u n i t  3. I f  Folded a l t e r a t i o n reaction front u n a l t e r e d remnant w i t h i n m a f i c pyroclastic unit  3. l g  Warped c o n t a c t between m a s s i v e g r e e n s t o n e u n i t and f e l s i c f r a g m e n t a l u n i t  3.1h  F e l s i c ash fragment w i t h i n m a f i c pyroclastic unit displaying interference figure  3.2a  the  83  mafic p y r o c l a s t i c / the  Mafic  and  85  V i e w l o o k i n g s o u t h a c r o s s Wishbone G l a c i e r s h o w i n g c l i f f f a c e composed o f quartz-sericite-carbonate schist o v e r l a i n by a t h i n l a y e r o f g r e e n s t o n e  3.2b  View l o o k i n g northwest a c r o s s G l a c i e r s h o w i n g l a r g e zone od alteration  Wishbone sericitic  3.2c  Laminated c h l o r i t e s c h i s t with i s o c l i n a l f o l d s and a l a t e , c r o s s - c u t t i n g o x i d a t i o n zone  3.2d  Greenstone u n i t showing l a m i n a r t e x t u r e d e f i n e d by c o n c e n t r a t i o n s o f o l i v i n e and ilmenite  3.2e  T h i n e p i c l a s t i c beds w i t h i n t e r b e d carbonate layers i n mafic p y r o c l a s t i c epiclastic unit  3.2f  Weathered s u r f a c e of g r e e n s t o n e u n i t showing c o m p o s i t i o n a l layering defined concentration of p l a g i o c l a s e c r y s t a l s  by  - x i i-  Page Plate  Plate  Plate  3.3a  L a t e T r i a s s i c a r g i l l i t e and c h e r t b e d s o v e r l y i n g S t i k i n e Assemblage Rocks  3.3b  L a m i n a t e d a s h t u f f and a r g i l l a c e o u s with i s o c l i n a l fold  3.3c  Minor f o l d nose(s) i n f e l s i c schist units  3.3d  L_ l i n e a t i o n s p r o d u c e d by t h e i n t e r s e c t i o n o f two s e t s o f a x i a l p l a n e c l e a v a g e  3.3e  Chevron f o l d s i n f e l s i c  3.3f  Fe-carbonate impregnated in chlorite schist unit  3.3g  Refolded f o l i a t i o n , producing coarse crenulation cleavage i n f e l s i c pyroclastic unit  3.4a  Photomicrograph o f intense c r e n u l a t i o n cleavage i n f e l s i c p y r o c l a s t i c rock  3.4b  Photomicrograph showing second f o l d phase c l e a v a g e and p r i m a r y l a y e r i n g  3.4c  Photomicrograph rock  3.4d  Photomicrograph o f f e l s i c , l i t h i c ash t u f f with carbonate porpyroblasts  3.4e  Photomicrograph  3.4f  Photomicrograph o f q u a r t z - a l b i t e v e i n l e t c u t t i n g a mass o f a n t i g o r i t e  3 .4g  Photomicrograph greenstone  3.4h  Photomicrograph o f c h l o r i t e , t r e m o l i t e and o p a q u e s r e p l a c i n g o l i v i n e i n greenstone  3.5a  Photomicrograph o f c r e n u l a t i o n in sericite schist  87  tuff  tuff-sericite  c r y s t a l ash t u f f volcanic  of altered  89  imtermediate  of crystal-lthic  of albite  bombs  ash t u f f  porphyry  cleavage  91  -  xiii  -  Page 3.5b  Photomicrograph of c r e n u l a t e d muscovite s c h i s t  quartz-  3.5c  Photomicrograph showing m i c r o - k i n k in S crenulation cleavage  bands  2  Plate  Plate  3.5d  Photomicrograph o f crenulated muscovite s c h i s t  3.5e  Photomicrograph of i s o c l i n a l y f o l d e d quartz l a y e r i n s e r i c i t e s c h i s t  3.5f  Photomicrograph of i s o c l i n a l y f o l d e d q u a r t z l a y e r i n s e r i c i t e s c h i s t showing development o f a x i a l p l a n e r c r e n u l a t i o n cleavage  3.5g  Photomicrograph o f broad c r e n u l a t i o n cleavage i n c h l o r i t e - s e r i c i t e s c h i s t  3.5h  Photomicrograph discontinuities  3.7a  Quartz-carbonate greenstone u n i t  quartz-  showing c l e a v a g e i n c r y s t a l ash t u f f crackle breccia  in  3.7b  Banded c a r b o n a t e - s u l p h i d e v e i n  3.7c  Carbonate a l t e r a t i o n a l o n g planes i n mafic e p i c l a s t i c  3.7d  Altered l a p i l l i fragments  3.7e  Small stratbound sulphide lens i n t r a n s i t i o n zone f r o m m a f i c t o f e l s i c p y r o c l a s t i c rocks  3.7f  Ferruginous dolomite breccia M c l a u g h l i n zone  3.7g  Quartz-carbonate stockwork i n greenstone boulder within landslide debris  3.8a  3.8b  133  sample  foliation rock  t u f f with sulphide  from  Back s c a t t e r e d e l e c t r o n image f r o m scanning e l e c t r o n miscroscope showing p y r i t e formation along f o l i a t i o n planes, away from q u a r t z - c a r b o n a t e v e i n l e t Back s c a t t e r e d e l e c t r o n image f r o m scanning e l e c t r o n microscope showing muli-phase carbonate-sulphide g r a i n f r o m c a r b o n a t e a l t e r a t i o n zone w i t h i n greenstone u n i t  135  -  xiv  -  ACKNOWLEDGEMENTS  There and  a r e many  indirectly,  appreciated.  and  Dr.  to this  L t d . supported  both  C.  morally  Godwin  K.  Scott  interpretation  of  and W.  Spillsbury  Dr. H.  supervised  of  data.  least  Greenwood  Smit  and  Armstrong  related  suggestions  H.  o f Teck at  Dr. R.  the analyses  useful  much  the research  and d i r e c t i o n .  most  directly  are very  and f i n a n c i a l l y .  made that  efforts  concept,  performed and  their  both  the original  o f U.B.C.  geochronology  contributed,  P. F o l k  p r o v i d e d v a l u a b l e guidance and  who  thesis;  B. M e y e r s ,  Explorations initially,  people  for  and  P.  to the  Shipley  p r o v i d e d c o m p e t e n t and e n j o y a b l e a s s i s t a n c e i n t h e f i e l d . J . Knight  provided  scanning  electron  excursions help  in  obtaining  job  sections times.  in and  XRF  unpublished  the right  the  use  Cranston  thin  enjoyable tremendous facets  did a  of  first  polished  thin  going  at the  right  Anderson  helpful  a myriad  of the  and  a n d R.  were v e r y  f e l l o w graduate  was a  i n other  machines  d a t a and a n s w e r i n g  entertainment  of  J . Souther  o f Canada  Discussions with  and  a n d B.  the preparation  Survey  S. H o r s k y  results  E . Montgomery  kept  on  n o t t o m e n t i o n many  research.  D r s . J . Monger,  Geological  directions  microscope,  away from  geochemistry. rate  excellent  of the  i n providing  of questions.  s t u d e n t s p r o v i d e d much  and some v a l u a b l e i n s i g h t s .  In p a r t i c u l a r ,  -  stimulating deposits J.  and f r u i t f u l  and  J.  of northwestern  Mortinson.  V a n d e r H e y d e n a n d G. N i x o n many  useful  comments  Matysek,  K.  sounding  boards  G.  Hodge,  assisted  with  manuscript Godwin,  Shannon  H.  McDonald,  R.  on  volcanic  Simpson,  P.  the production  Greenwood, Marsden  rock D.  I would  Berman,  improved  of  geochemistry.  Heberlein  P.  P.  served  as  suggestions.  Thiersch  and E .  figures  Montgomery  and p l a t e s .  by c r i t i c a l  The  comments f r o m  C.  R.  L.  Armstrong,  D.  Heberlein, J .  and  R.  Britten.  To  a l l of  m e n t i o n e d a n d t o many who w e r e n ' t , Finally,  R.  p r o v i d e d c o m p u t e r p r o g r a m s and  a n d made many u s e f u l K.  B.C. were h a d w i t h  Parrish,  and e s p e c i a l l y  was g r e a t l y  H.  -  c o n v e r s a t i o n s on t h e n a t u r e o f g o l d  and t h e geology  Nelson  XV  like  those  thankyou.  t o thank  G.  Woodsworth  a n d L.  Werner, whose p a t i e n t e n c o u r a g e m e n t s o many y e a r s ago h e l p e d me make  i t through  to this  p o i n t , a n d my w i f e ,  t a u g h t me t h a t t h e r e i s more t o l i f e  than  rocks.  Carole,  who  - x v i  -  FRONTISPIECE  Oblique, westward l o o k i n g , a e r i a l view o f the c e n t r a l p a r t of t h e study area. Foreground shows rocks of the P a l e o z o i c S t i k i n e Assemblage. The t r a c e of t h e a n t i c l i n a l a x i s r e l a t e d to t h e f o u r t h phase o f f o l d i n g c r o s s e s through the c e n t e r of the photographed area. Potassium metasomatic (beige) and f e r r u g i n o u s carbonate (orange) a l t e r a t i o n zones can be seen i n outcrop areas. The r i d g e s t h a t t r e n d westwards composed o f Late T r i a s s i c sediments. Mt. Ambition  into  the i c e f i e l d are  Hickman can be seen i n t h e extreme r i g h t hand corner. Mtn. i s i n t h e center background.  - 1 -  CHAPTER 1:  INTRODUCTION  1.1 General Statement  This  report  mineralization  describes  of the BJ  the geology,  a l t e r a t i o n and  g o l d - s i l v e r prospect,  and the  i n t r u s i v e and s t r u c t u r a l h i s t o r y of the surrounding region. Objectives  of t h i s study were to evaluate the p o t e n t i a l of  mineralization on the BJ prospect, to develop c r i t e r i a t o guide  mineral  regional  e x p l o r a t i o n i s t s , both  on the prospect  and  scales, and to provide data useful to a regional  synthesis of t e c t o n i c a c t i v i t y .  Regional prospecting  stream  sediment  sampling  i n 1980 l e d to the discovery  mineralization  and  of precious  mineralization  Assemblage.  metal  (BJ prospect) along the western head waters  of Mess Creek, northwestern B r i t i s h Columbia. the  consequent  Initial  belong  to  the  Rocks hosting  Paleozoic  attempts to explore  Stikine  and evaluate the  mineralization were frustrated by complex structure, unknown stratigraphy  and a v a r i e t y of a l t e r a t i o n types.  A  better  understanding of the geology and geological history of the area  would  exploration.  significantly  contribute  to  cost  effective  -  Rocks  of  isolated  in  of ah  Stikine  a  500km  Columbia.  incomplete  understanding  Recent  work  has  deposits originally actually  the  1984).  Of  tectonic  potential  is  the  timing  north-south  trend  in  of  inaccessibility  the  has  base  occur  of  and  metamorphism  the  and  precious  within  Triassic  importance area  and  resulted  geology  that  to  the  of  in  S t i k i n e Assemblage  particular of  occur  exposures  shown  by  history  the  these  thought  hosted  Assemblage  Relative  o f many o f  Payne,  both  -  continuity  rocks are and  along  British  Assemblage. metal  Paleozoic  exposures  northwestern lack  the  2  (Nelson  in  determining  the  exploration  and  deformation  w i t h i n t h e S t i k i n e Assemblage r e l a t i v e t o m i n e r a l i z a t i o n deposition of overlying  It  was  required field  s e a s o n was  funding  rocks.  i n i t i a l l y p l a n e d t h a t two  t o meet t h e  consequent  loss  sufficient  field  objectives  of  from  work  specimens  collected  collected  during regional  preceeding  field  help  any  fill  to  had  season gaps  At been  allow  the  seasons would  above.  The  to curtailed  plummeting  revenue.  field  outlined  n e v e r r e a l i z e d due  resulting  and  the  metal time  conducted project  second  exploration prices  i t was and  and  felt  that  enough  hand  t o proceed.  Data  e x p l o r a t i o n by t h e a u t h o r f r o m  was  within  r e g i o n a l t e c t o n i c h i s t o r y and  incorporated into the  database  metallogeny.  and  be  this in  study  the to  defining  -  1.2  L o c a t i o n and The  (57  08'north,  edge  of  the  Stewart (Fig. to  study  and  a  area,  served  from  50'west - NTS:  Coast  Mountains,  plane the  to to  (Fig.  lakes  1.2).  the  Teck  The  area  in  6km the  1.3  P h y s i o g r a p h y and Topography o f ranging  drainage  easterly  the  fixed-wing  aircraft  the  recent  Schaft  This  airstrip  Provincial  Airlines  study  area  airstrip.  be  was  More  by  direct  achieved  by  small  southwest,  or  possibly  between  the  study  from  area  1,000  glacial  to  and  Mess  and  More  float to  Creeks  50km e a s t  displaying  orientation.  a  i s moderately 2,000m.  west.  retreat.  have e x p l o i t e d zones o f  weaknesses  Columbia  area.  Trans  of  of  Vegetation  bound t h e a r e a t o t h e s o u t h by  north  British  S t e w a r t - C a s s i a r highway p a s s e s  area.  provided  study  to  could  pass  eastern  Exploration Limited's  Creek  to  150km  Creek,  i s by  p r o j e c t by  Schaft  Lake,  the  elevations  region  Access  study  Round  small  the  B.C.  from the  approximately  24km n o r t h o f t h e  Terrace,  access  at  c l a i m groups  104G/2W), i s on t h e  of Telegraph  to the  airstrip  during  helicopter  on t h e B J m i n e r a l  130  Creek d e p o s i t , was  centered  Access  gravel  -  Access  90km s o u t h  1.1).  3  ice  with  fields  E x c e l l e n t exposure i s Both  structural  preferred  Large  rugged  glaciation or  north-south  and  lithological or  north-  - .4 -  Figure 1.1 Location Map of the Study Area, Mess Creek, Northwestern B.C.  Figure 1.2  1:50,000 scale topographic map showing BJ claim group.  - 6 -  Retreat  of glaciers  oversteepened  i n areas  of a l t e r a t i o n  has  slopes r e s u l t i n g i n recent l a n d s l i d e  produced activity.  Large, g r a v e l outwash p l a i n s cover t h e southern map area. Vegetation between  1200  i s alpine  and  1300m.  and A  sub-alpine  young  forest  with  treeline  o f spruce  and  s u b - a l p i n e f i r b l a n k e t s t h e lower e l e v a t i o n s a l o n g t h e Hess Creek  valley.  I n some  areas,  sub-alpine  f i r make passage  are  either  barren  are  reasonably  elevations, below  well-developed  1100m  predominately  altered  or  Higher  of  stunted  elevations  a l p i n e meadows.  between  over  level  growths  difficult.  or carpeted with  particularly  the  thick  Soils  t h e 1600 and 1100m bedrock.  valley  Overburden  bottoms  consists  of g l a c i a l l y derived material.  1.4 P r e v i o u s Work The  first  p u b l i s h e d g e o l o g i c a l work i n t h e r e g i o n was  c a r r i e d o u t by F.A. K e r r of  Canada,  Rivers  who  during  (1948a),  mapped areas the  late  f o r t h e G e o l o g i c a l Survey  along  1920's.  the Stikine Kerr  and I s k u t  (1948a  and  b)  r e c o g n i z e d a t h i c k sequence o f pre-Permian s t r a t a which was characterized  by  e x t e n s i v e l y deformed  volcano-sedimentary  r o c k s and separated from o t h e r u n i t s by u n c o n f o r m i t i e s . the  basis  (1948b)  of similar  correlated  s t r a t i g r a p h y and composition,  t h e pre-Permian  R i v e r a r e a w i t h exposures  rocks  On Kerr  of the Stikine  i n t h e Taku R i v e r a r e a .  He a l s o  noted abundant quartz v e i n s a s s o c i a t e d w i t h these r o c k s .  - 7  The  Geological  Survey  Operation  area  in  1956  Rocks  of  the  with  Telegraph  intermittently Paleozoic Monger units  rocks  More  areas within  Read  refinements  of  the  by  area J.  of  the  Souther  Permian of  an  1:50,000  by  examined (1972).  were i n v e s t i g a t e d by  subject  studies  the  1961).  were  MSc  scale  T e l e g r a p h C r e e k map  Mineral  on  the  within  B.C.  insignificant  Hydro, has  J.  carbonate thesis  by  mapping  of  sheet,  related  been  the  the  began  was  renewed low  1975)  done  of  gold in  grade  the  other  have  placed  relations  of  region.  in  the was  (Monger  and  geological  placer  river  richer  tonnage,  and  Stikine  of  the  assemblages  Cordilleran evolution  deposits  and  1977  g e o l o g y and  discovery  Placer  Exploration  of  exploration  with  to  Monger,  i n models  older rocks  River.  sheet  years  in  (Gabrielse,  tectonostratigraphic  1979;  renewed emphasis  large  14  work  (1983).  Price,  1920's  map  t h e s i s area  the  resumed  Stikine  recently,  feasibility  Definition  route  next  Canada  Biostratigraphy  (1966).  to damsite  the  the  n e a r G a l o r e C r e e k was  various  and  of  Creek  near the  (1977).  Pitcher  by  for  -  the gold  area  in  along  Stikine, mainly  fields  1950's w i t h  porphyry  copper  the  early Stikine  however,  used of  the  as the  an  were access  Klondike.  the  search  for  and  molybdenum  - 8 -  deposits. helped  Two  important  maintain  next two  discoveries  exploration  decades.  The  in  activity  Galore  the  i n the  Creek d e p o s i t s  mid  1950's  area  for  the  (Allen et a l . ,  1976), 24km west o f the t h e s i s area, were d i s c o v e r e d i n by  prospectors  Development  working  Company  for  Hudson  Limited.  Bay  Kennco  Exploration  Explorations  c a r r i e d out work on the d e p o s i t s from 1960  and Smelting Company L i m i t e d became the  in  Reserves  are  m i l l i o n tonnes g r a d i n g The  1.06%  et  0.40  Work was  Asarco,  Hecla  Ag and  billion  tons  0.12g/t Au  Exploration minimal u n t i l  grading  carried  Operating  0.30%  and  i n 1957  e v e n t u a l l y Teck E x p l o r a t i o n s L i m i t e d .  a r e one  Cu,  7.7g/t  Ag.  Nicholas  out by  Silver  reserves 1.09  g/t  region  was  i n c r e a s e s i n the p r i c e o f  base  in  Teck E x p l o r a t i o n s  125  by  0.034% Mo,  for  precious  and p r e c i o u s metals had  as  Current  1981).  when the  operators  Company L i m i t e d  ( F i n a n c i a l Post, Oct.  1980  Hudson  a l . . 1976)  g / t Au  discovered  Bik Syndicate.  Standard Mines NPL,  (Allen Cu,  S c h a f t Creek d e p o s i t was  B i r d of the  and  given  metals  the  a consequent a f f e c t on e x p l o r a t i o n .  Limited,  Dupont E x p l o r a t i o n Canada  and  o t h e r s were a c t i v e l y i n v o l v e d i n the r e g i o n d u r i n g  and  1981.  and  became  Highway 37  E x p l o r a t i o n slowed w i t h concentrated and  the  and  Limited  t o 1967.  Bay M i n i n g 1972.  1955  in  more  Iskut River.  declining  Ltd., 1980  copper p r i c e s  accessible Resurgence o f  areas  along  exploration  - 9 -  accompanied resulted 1987.  t h e advent  i n some  o f flow-through  significant  The n e a r e s t p a s t  new  to  the  northwest  mines). of  Figure  (Polaris  1.3  financing  and  d i s c o v e r i e s i n 1986 a n d  or present  a r e l o c a t e d 150km t o t h e s o u t h  share  precious metal  i n t h e Stewart  Taku  and  shows t h e m a j o r  producers  a r e a a n d 250km  Alaska  Juneau  Gold  d e p o s i t s and p r o s p e c t s  the region.  1.5 P r e s e n t Work A  regional,  Telegraph  Creek  Explorations consequent claim  map  sheet  prospecting along  work  subsequent  on  study,  claims  was  which  structure  on m i n e r a l i z a t i o n ,  the mineral  history  of  surrounding work,  the  showings  the  host  rocks.  approximately  sediment  headwaters proved  i n 1981.  of  and  o f the BJ  A  Creek. and  a  field  and  thesis,  was  lithology  and  of alteration  the exploration potential  and, t h e s t r u c t u r a l and  their  In conjunction with 110 s q u a r e  the Teck  sampling  o f Mess  the relationship  rocks,  by  encouraging  controls  and m i n e r a l i z a t i o n ,  in  undertaken  forms a p o r t i o n o f t h i s  determine:  of  program  i n the staking  undertaken  to  lithology  Stream  t h e western  designed  to  was  resulted  the  program  laboratory  exploration  L t d . i n 1980.  groups  Initial  mineral  and metamorphic  relationships  to  continuing regional  k i l o m e t e r s were mapped a t a  1:12,500 s c a l e o n a n d a r o u n d t h e B J c l a i m  groups.  -  Plutonic studies northwest  in  history the  of  of  the  Hickman  the  BJ  10  claim  -  area  was  determined  batholith, group,  best exposure of i n t r u s i v e - e x t r u s i v e  as  based  approximately this  and  area  on 15km  offers  the  intrusive-intrusive  relationships.  Laboratory determinations polished  section  work on  a  consisted variety  studies  and  of of  major rock  i s o t o p i c age  and  trace  samples,  element thin  determinations.  and  Figure 1.3 Major mineral deposits of Northwestern British Columbia and adjacent parts of Alaska.  12  -  -  CHAPTER 2: REGIONAL GEOLOGY  2.1  Tectonic Setting  The t h e s i s area i s l o c a t e d w i t h i n the S t i k i n e Arch the  western  edge  of  the  Intermontane  G a b r i e l s e , 1972; Monger e t a l . , t h e Coast P l u t o n i c Complex. t h e a r e a , shown i n F i g u r e the  Whitehorse  Trough,  1972)  Belt  (Wheeler  the  and  near i t s c o n t a c t w i t h  The main t e c t o n i c 2.1,  on  include:  Atlin  features of  the S t i k i n e Arch,"  Terrane  (Horst),  the  Quesnel Trough, and the Bowser and S u s t u t B a s i n s .  The S t i k i n e Arch i s a t r i a n g u l a r remained  tectonically  Mesozoic  (Souther,  Belt,  separating  Trough.  positive  1972) the  and  Bowser  shaped  area that  has  most  the  throughout transects  Basin  the  from  Intermontane  the  Whitehorse  M a t e r i a l eroded from the S t i k i n e Arch was  northwards  into  the Whitehorse  Trough  and  of  shed both  southwards  into  the Bowser B a s i n (Souther, 1971; E i s b a c h e r , 1974).  Triassic  and  Stuhini,  Jurassic  p l u t o n s and  coeval volcanics  of the  T a k l a and H a z e l t o n Groups a r e i n t e r p r e t e d t o be remnants o f magmatic a r c s (Monger and P r i c e , 1979) the S t i k i n e edge o f rocks  Arch, and  the  are  that  extend  Bowser B a s i n i n t o  underlain  by  t h a t form the c o r e o f  around  the northeastern  the Quesnel  Paleozoic  strata  Trough. of  the  \  These Stikine  - 13 -  Assemblage Stikine the  (Monger,  Arch  underwent  Permian  to  and  1972;  Read  edge  the Stikine  Coast P l u t o n i c  cherts rocks are from  ophiolite-like argillites  i n age  similar  Okulitch,  orogeny  1977).  Arch i s intruded  limestones,  distinct,  and  metamorphism  Tahltanian  Terrane, northeast  of  range  d e f o r m a t i o n and  by  rocks of the  On  during  (Souther,  i t s western  granitic  rocks  of  the  Complex.  The A t l i n composed  Pre-Middle T r i a s s i c  mid-Triassic  1971  is  1977).  of the Whitehorse  assemblages and  minor  from M i s s i s s i p p i a n  both aged  lithologically  rocks  of  ultramafics,  volcanics.  to Late  and  of the S t i k i n e  Trough,  These  Triassic  but  paleontologically, Assemblage  (Monger,  1977). Paleomagnetic, studies  have  paleontological  shown  Intermontane  Belt  that  are  most  of  (Monger  Monger  Saleenby,  Price,  1981;  forms t h e n o r t h e r n  part  island the  consisting arcs  (Monger  Intermontane  Cache  C r e e k Group  Late J u r a s s i c ,  of  (Atlin  as rocks  The  to  Monger, Stikine  Terrane or  the the 1977; Arch  Stikinia  1972), which i s a composite Triassic  1981)  Stikinia  had  that  and  amalgamated  age w i t h i n  Jurassic  u n d e r l i e s much o f  T e r r a n e ) by a t l e a s t of that  within  respect  1972;  1985).  Paleozoic,  and P r i c e ,  Belt.  with  of the S t i k i n e  stratigraphic  rocks  et al..  ( S t i k i n e B l o c k o f Monger e t a l . . terrane  the  allochthonous  North American c o n t i n e n t and  and  with  the  the Middle to  t h e Bowser  Basin  Figure 2.1  Tectonic elements of the northwestern Canadian Cordillera and relative locations of the Hickman and Hotialuh batholiths (after Souther, 1972).  15  -  -  contain f o s s i l i f e r o u s Cache Creek detritus (Eisbacher, 1974; Monger et a l . .  1978).  I f the Cache Creek rocks are  inter-  preted as a subduction complex f o r Upper T r i a s s i c volcanism, as suggested  by Monger and Price  (1979), then amalgamation  would have had to have taken place by Late T r i a s s i c .  The  c o l l i s i o n of S t i k i n i a with continental North America i s less well-defined,  but  Jurassic  Late  and  likely  along  the  Insular  Belts  began  place  Cretaceous  Templeman-Kluit, 1982). Complex  took  (Monger  and  the  Middle  Price,  1981;  Emplacement of the Coast Plutonic  suture by  between  at  between  the  Intermontane  and  least  Lower  Cretaceous  time  (Monger, 1982).  Right Lateral s t r i k e s l i p displacement along the Queen Charlotte Fault system produced resulting  in  late  faulting  an extensional environment  (graben  development  ?)  and  eruption of T e r t i a r y a l k a l i c volcanic rocks of the Edziza Complex (Souther, 1974 and 1984).  2.2  G e n e r a l Geology and S t r a t i g r a p h i c Summary  D i s t r i b u t i o n of the major rock units within the study region i s shown i n Figure 2.2.  A table of formations  s t r a t i g r a p h i c summary i s given i n Figure 2.3. stratigraphic  unit  in  the  study  region  The  i s the  and  oldest Stikine  - 16 -  Assemblage  (Monger,  pre-Mesozoic  1977)  rocks  in  younger r o c k u n i t s by the  Stikine  headwaters  Mess  F o r r e s t K e r r and Paleozoic  It  were mapped  Creek  at  the  Mountain  contacts  between  volcanics  are  determine  area.  is  the  either  and  briefly  sheet  they  separated  north  were  Stikine faults  end  not  or  west  Large of  the  within  the  exposures  examined.  Creek  of and  All  observed  and  Triassic  insufficiently  are mapped as  of  Mess  Assemblage  from  Rocks of  examined  t h e i r nature, although elsewhere  Creek map  includes a l l  in detail  Scud R i v e r d r a i n a g e s .  rocks  Zagoddetchino  the  essentially  a pronounced unconformity.  Assemblage of  which  exposed  i n the  to  Telegraph  unconformable  contacts  (Souther, 1972).  T r i a s s i c v o l c a n i c rocks with,  and  lithologically  i n the  similar  region are to,  the  correlative....  Takla  Group.  W i t h i n the S t i k i n e Arch area t h e s e r o c k s are r e f e r r e d t o the  Stuhini  Age  of  Late  the  Group Stuhini  Carnian  to  (Souther,  1972;  Souther  Group i s r e a s o n a b l y  Late  Norian  (Souther,  et  a l . . 1979).  w e l l determined 1971).  as  It  is  as not  c l e a r from f i e l d mapping whether o r not rocks o f the S t u h i n i Group have been i n t r u d e d by  the T r i a s s i c p l u t o n i c s u i t e  the  The  Hickman  radiometric similarity  batholith.  ages between 230 of  ages  between  and the  Triassic 220  Ma  Stuhini  plutons  of  yield  (Table 2.1).  The  v o l c a n i c s and  the  - 17 -  plutonic typical  rocks of  suggests  an  intrusion  arc-type  into  setting.  coeval  volcanics  and  intrusive-  Ages  e x t r u s i v e r e l a t i o n s h i p s o f the Hickman b a t h o l i t h are s i m i l a r to those of the Hotialuh b a t h o l i t h  (Anderson,  towards  the  the  northeastern  apex  of  1983)  Stikine  located  Arch  (Fig.  2.1) .  The  narrow  belt  of  sediments  ( F i g . 2.2)  that  lies  immediately west o f the study area does not have f o r m a t i o n a l status.  Fossils  indicate  Coarse  boulder  having  lithologies  which mid-  Upper T r i a s s i c  conglomerates similar  implies r e l a t i v e l y  of  most  basis  and  t o the T r i a s s i c p l u t o n i c  suite,  contacts of  are  and  erosion during  relationships  Group v o l c a n i c s are not  faulted  present  uplift  Contact  Stuhini  belt  age. clasts  rapid  this  (Norian) contain  t o L a t e T r i a s s i c time.  t h e s e sediments as  an  or  fieldwork,  p o o r l y exposed. these  sediments  between clear, On  the  appear  c o r r e l a t i v e w i t h , o r t o s l i g h t l y predate, the upper p a r t s o f Stuhini  The within  stratigraphy.  pronounced the  north-south  Telegraph  Creek  c o n t r a s t t o the east-west of  the  from  Stikine  h o r s t and  map  alignment sheet  is  of  lithologies  a  significant  o r i e n t a t i o n along t h e n o r t h edge  Arch.  The  graben  type  north-south  orientation  features related  results  t o the E d z i z a  - 18  Complex,  Mess Creek v a l l e y ,  features  may  north-south faults  been  and  caused  Hickman b a t h o l i t h . by  strike-slip faults.  These  variable u p l i f t  Initial  formation  along  of  these  c o u l d have r e s u l t e d from d i f f e r e n t i a l motion as  Stikine  Arch  accretion rock  have  -  of  was  forced  Stikinia.  units within  under  the  Deposition  narrow  Atlin of  structural  Terrane  various  the  during  sedimentary  depressions  along  the  margins o f the Hickman b a t h o l i t h suggests t h a t both v e r t i c a l and  lateral  motion  took  place  along  these  faults  over  c o n s i d e r a b l e l e n g t h s o f time.  2.3  S t r a t i f i e d Rocks  2.3.1  S t i k i n e Assemblage The  S t i k i n e Assemblage i s one  t o Upper P a l e o z o i c rocks 1977a).  These  lithologies, external  groups  gross  o f s i x groupings o f  i n the western C o r d i l l e r a are  defined  stratigraphy,  relationships.  The  by  faunal  Stikine  of  assemblages  and  Assemblage,  on the  northeast  Payne, 1983), and  i n an  area  about  This  Gabrielse,  edge o f the Bowser B a s i n ,  t h a t have been d e s c r i b e d i n the Taku R i v e r area Nelson and  northern  ( F i g . 2.1).  assemblage i n c l u d e s the A s i t k a Group (Lord, 1948; 1978)  which  region, i s  exposed i n windows o f younger m a t e r i a l around the o f the Bowser B a s i n  (Monger,  similarity  i n c l u d e s a l l p r e - T r i a s s i c rocks w i t h i n the study  and western p e r i p h e r y  mid-  and  rocks  (Kerr,  1948;  100km  south  -19 -  TERTIARY AND  QUATERNARY  E d z i z a V o l c a n i c s : b a s a l t flows and r e l a t e d p y r o c l a s t i c rocks  Tev  CRETACEOUS S u s t u t Group: c h e r t pebble conglomerate, g r a n i t e b o u l d e r conglomerate, sandstone, s i l t s t o n e ; nonmarine  Kss  JURASSIC  mT .  g r a n i t e , quartz-monzonite; medium t o c o a r s e - g r a i n e d , p i n k t o orange i n c o l o u r ; Yehiniko Pluton  1J  s y e n i t e , o r t h o c l a s e p o r p h y r y monzonite, p y r o x e n i t e G a l o r e Creek I n t r u s i o n s  amphibolite,  amphibolite  g n e i s s ; age u n c e r t a i n  p e r i o d o t i t e , gabbro; age u n c e r t a i n  TRIASSIC greywacke, s i l t s t o n e , c h e r t , g r a n i t e b o u l d e r conglomerate, p o l y m i c t i c v o l c a n i c conglomerate S t u h i n i Group and Unnamed Rocks: a n g i t e prophyry andesite, andesite t u f f , b r e c c i a , v o l c a n i c conglomerates, d e r i v e d e p i c l a s t i c r o c k s  Tsv  B i o t i t e hornblende q u a r t z d i o r i t e , g r a n o d i o r i t e , d i o r i t e , Hickman and Night-Out P l u t o n s  mT  Ld  PERMIAN limestone, b i o c l a s t i c limestone, phyllites, felsic tuff  < _l CQ Li)  Ul Ul < Ld Z  MISSISSIPPIAN M  c r i n o i d a l limestone, ferruginous maroon t u f f and p h y l l i t e  limestone,  MISSISSIPPIAN TO DEVONIAN MD  Ul  chlorite  f e l s i c t o mafic p y r o c l a s t i c rocks, p h y l l i t e , greenstone, q u a r t z - s e r i c i t e s c h i s t , c h l o r i t e s c h i s t , a r g i l l a c e o u s s c h i s t , limestone  LEGEND  FOR  FIGURE  2.2  -20*  Figure 2.2:  Regional  geological map of the Mess Creek-Stikine  River area. The detailed study area is outlined in the lower right hand corner. (Modified after Souther, 1972.)  PERIOD/ EPOCH QUATERNARY  DIAGRAMATIC SECTION k  * A A .  A V A A A A A A A" A A A A A A A n-ir AAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAflnAMll  INTRUSIVE ROCKS AGE  EDZIZA VOLCANICS  TERTIARY V r i i H i r n II « fl H « i S  CRETACEOUS  II "  LITHOLOGY -Basalt flow* and related pyroclastic rocks: minor rhyolite  UNCONFORMITY  n » f* A A A /  A A AA AAAA_A.A-A.A-- *  A A A A A A A A A A A A A A A AA A A A AA/ • • •  GROUP OR NAME  SUSTUT  Conglomerate , quartzose sandstone, arkose  •  UNCONFORMITY  JURASSIC  O co co <  YEHINIKO PLUTON  17616 Ma  H A Z E L T O N (?)  Auglte andesite flows, pyroclastic rocka,  LATE  .••*.* A* y*  ^  /A  o  <  Q.  sandstones/wackes  JNCONFORMITY/FAUL Siltstone, greywacke, chert.shale, volcanic conglomerate, granite boulder conglomerate JNCONFORMITY/FAUL1  PERMIAN  o o  maroon volcanic conglomerate, ash tuffs volcanic  HICKMAN PLUTON 230i16 NIGHTOUT Ma PLUTON  MID  UJ  tuffs, volcanic conglomerates, minor grey w a c k e  FAULT C O N T A C T  STUHINI  cc  N  Maroon 1o green lithic tuffs, c r y s t a l ash  Limestone, chloritic ash tuffs, minor chert  UNCONFORMITY ?  < o. p. CO CO CO CO  STIKINE ASSEMBLAGE  Limestone, chlorite phyllltes, greenstone, quartz sericite schist, lithic tuffs, argillite  DEVONIAN See Table 2.1.  Figure 2.3 Table of formations for the Mess Creek area, northwestern B.C.  -  of  Terrace  (Evenchick,  22  -  1980).  p r i m a r i l y on the widespread,  Correlation  is  based  f o s s i l i f e r o u s Permian limestone  common t o a l l a r e a s . Lithologies  of  the  Stikine  Assemblage  include  a r g i l l i t e s , c h e r t s , limestones, b a s a l t i c t o r h y o l i t i c flows, pyroclastics deformation  and  derived  i s variable  epiclastics.  depending  Metamorphism  upon  age  and  and  location.  I n s u f f i c i e n t work has been done t o s u b d i v i d e the Assemblage into  formations;  i t i s unlikely  t h a t i t i s composed  s i n g l e s t r a t i g r a p h i c succession w i t h i n a l l areas.  of  a  There i s  s u b s t a n t i a l evidence i n d i c a t i n g a s e p a r a t i o n between Permian and pre-Permian r o c k s . cally  widespread  500km, t y p i c a l whereas and  a  a  north-south  often intercalated  missing  limestones  limestone  Near the  s t r a t i g r a p h y between a  i s much l e s s  5km  Permian  strike  1977a),  suggests  study  area, 1,500m  and  Mississippian  distance  suggests  W i t h i n the study r e g i o n , pre-Permian  r o c k s a r e t y p i c a l l y metamorphosed t o m i d - g r e e n s c h i s t display  presumed  or  an  (Monger 1977a). T h i s r e l a t i o n s h i p , however, i s  c o m p l i c a t e d by f a u l t s .  and  of  continuous  w i t h v o l c a n i c r o c k s , which  seamount r e e f s .  over  unconformity  d i s t a n c e i n excess  o f m i o g e o c l i n a l d e p o s i t i o n (Monger,  Mississippian  d e p o s i t i o n on of  over  The Permian limestone i s geographi-  three known  or  more phases  Permian-aged  metamorphosed and deformed.  of rocks  deformation, are  facies whereas  commonly  less  - 23 -  Faunal Permian  ages  of the Stikine  t o Devonian.  Fauna  Assemblage  collected  range  from  from  t h e Permian  l i m e s t o n e near Scud R i v e r a r e s i m i l a r t o those  o f t h e same  age found i n n o r t h e r n C a l i f o r n i a and Nevada ( P i t c h e r , 1961). Devonian conodonts have been r e c o v e r e d from grey a l o n g F o r r e s t K e r r R i v e r and from study  area  (P. Read, p e r s .  strata  comm.,  limestones  12km south o f t h e  1984, and R. Anderson,  p e r s . comm., 1987, r e s p e c t i v e l y ) .  Rocks s t u d i e d i n d e t a i l  (Chapter  below  3) a r e s t r a t i g r a p h i c a l l y  limestone  and c o n s i s t  of a r g i l l i t e s ,  clastics,  and massive  greenstones.  the Mississippian  felsic  t o mafic  pyro-  R e l a t i o n s h i p s between  M i s s i s s i p p i a n and Devonian aged s t r a t i g r a p h y a r e n o t known. 2.3.2  S t u h i n i Group A  more  or less  continuous  belt  o f Upper  v o l c a n i c r o c k s runs t h e l e n g t h o f t h e c o r d i l l e r a  ( F i g . 2.4).  This b e l t  c o n s i s t s o f t h e N i c o l a Group i n southern  Columbia,  the Takla  Stuhini  Group  w i t h i n t h e Quesnel  Group w i t h i n t h e S t i k i n e  Group i n t h e Yukon T e r r i t o r y and  Takla  Group  rocks  (Preto, 1977; Souther, rocks  (Souther,  British  Trough, t h e  and t h e Lewis R i v e r 1977).  The N i c o l a  are characteristically  alkaline  1977) and although t h e S t u h i n i Group  are l i t h o l o g i c a l l y  calc-alkaline  Arch  Triassic  chemistry  similar (Souther,  they  tend  1979).  towards  more  Differences i n  c h e m i s t r y may r e f l e c t t e c t o n i c p o s i t i o n as o n l y t h e S t u h i n i Group o c c u r s west o f t h e Cache Creek r o c k s .  -24 "  FIGURE 2.4  D i s t r i b u t i o n o f Late T r i a s s i c v o l c a n i c rocks i n the Canadian C o r d i l l e r a , and t h e i r s p a t i a l r e l a t i o n s h i p t o t h e P a l e o z o i c Cache Creek Group; a p o s s i b l e s u b d u c t i o n complex f o r T r i a s s i c a r c v o l c a n i s m  - 25 -  Age Late  of  the  Triassic  Stuhini  Group  (Souther,  is fairly  1977)  and  well confined therefore  to  contact  r e l a t i o n s h i p s w i t h o t h e r u n i t s a r e important f o r determining the  Group  rocks  a t t a i n a t h i c k n e s s o f over 3,600m i n the Tulsequah map  sheet  area  Creek  map  tectonic  history  (Souther, sheet  area,  1971)  area  of  the  Stuhini  but o n l y 1,200m i n the Telegraph  (Souther,  1972).  W i t h i n the r e g i o n a l study  S t u h i n i v o l c a n i c s occur as a d i s r u p t e d f r i n g e  t h e Hickman b a t h o l i t h .  Approximately  maroon v o l c a n i c b r e c c i a s and the  area.  r i d g e south  of  the  600m o f p a l e green  conglomerates  Schaft  are  Creek d e p o s i t .  n o r t h o f the d e p o s i t , a u g i t e porphyry t h e sequence. Souther  (1972) noted  exposed  observed  rocks  t o the  west.  A  to on  Immediately  flows predominate i n  t h a t the v o l c a n i c s e a s t  of Mess Creek are l e s s massive and c o n t a i n more beds than  around  similar  sedimentary  distribution  was  i n a southwesterly d i r e c t i o n away from the Hickman  batholith.  The  thick  breccia  and  conglomerate  sequences  observed a l o n g the s o u t h - e a s t e r n and northwestern margins o f t h e Hickman b a t h o l i t h c o u l d have accumulated depressions  formed  coincidentally  with  i n trough-like uplift  of  the  batholith. Lithologically, augite  phenocrysts  S t u h i n i v o l c a n i c s are c h a r a c t e r i z e d by and  andesitic  s t r a t i g r a p h y o f the Group has region)  and  is  likely  composition.  not been d e f i n e d  subject  to  strong  Internal ( w i t h i n the  local  controls.  26  -  Lithologies correlate  exposed  well  S t i k i n e Arch (1972  and  within  with  those  by Anderson  -  the  study  reported  elsewhere  (1983), Schink  flows  pyroclastics  are  and  generally within  (1977) and  1971). In the area immediately  batholith,  region  grained,  reworked  to  fragment  breccias  and  massive,  dark  dark  light  to  sandstones; minor  supported,  heterolithic green  flows.  (4)  The  porphyry  lithic maroon  first  groups  coarse-  are  pillowed  (3)  wackes  pyroclastics,  three  (2)  flows;  tuffs,  (1)  Four  t o maroon v o l c a n i c  conglomerates;  augite  green  and  grey-green  coarse  material.  l i t h o l o g i c a l / d e p o s i t i o n a l groups are r e c o g n i z e d : grained,  Souther  e a s t o f the Hickman  v o l u m e t r i c a l l y subordinate  finer  the  to  andesitic,  and  volcanic  epiclastics  and  commonly  inter-  Stuhini  Group  layered.  Spilsbury stratigraphy  (1982)  which  describes  overlies  the  the  Schaft  Creek d e p o s i t  as  a  sequence o f f i n e g r a i n e d a n d e s i t e flows, a u g i t e p o r p h y r i t i c a n d e s i t e s , a n d e s i t i c l a p i l l i t u f f s and i n t e r c a l a t e d t u f f  and  volcanic  The  sandstone  upper p a r t of t h i s overlain  by  maroon  o v e r l a i n by  more  andesite  sequence i s weathered and subaerial  pyroclastics.  p y r o c l a s t i c s are p o s t - m i n e r a l i z a t i o n and are not  emplaced by  a thrust fault,  t h e J u r a s s i c H a z e l t o n Group.  flows.  unconformably The  maroon  t h e r e f o r e , i f they  they  likely  belong  to  - 27  A  thick  unit  of  -  volcanic  o v e r l i e s massive a u g i t e - b e a r i n g o f Round Lake, about 6km polymictic to  a  of  fragments  Stuhini  Group  Granitoid is  Hotailuh  by  and  that  at  intrusive  pyritic  least  some  activity  (1983)  Contact  for  the  in  area  relationships  i n t r u s i v e r o c k s are d i s c u s s e d  This  i n addition quartz of  the  demonstrably S t u h i n i aged  Anderson  batholith.  volcanics  2.3.3  post-dates  c l a s t s within  reported  c l a s t s , contains  indicating  area west  study a r e a .  a maroon m a t r i x and,  volcanic  diorite  conformably  greenstone i n the  southwest o f the  conglomerate has  variety  conglomerate  area.  volcanics  fringing  between  the  Stuhini  i n section  2.4.  Upper T r i a s s i c Sediments Sediments o f probable Upper T r i a s s i c age  a t h i n b e l t , one edge  of  the  thickness  t o t h r e e k i l o m e t e r s wide, a l o n g the western  study  of  are exposed as  this  area belt  (Fig. is  in  2.2). the  True  order  stratigraphic  of  1,000m.  sequence c o n s i s t s o f a r k o s i c sandstones, i n t e r c a l a t e d and  c h e r t s , maroon agglomerates, a r g i l l i t e s ,  and  granite  within the  the  the  boulder  interbedded  sequence  dipping  by  cherts  and  i s r i g h t s i d e up  were observed. obscured  conglomerates  but  argillites  Contacts on both s i d e s  icefields,  fault,  appear  marked  by  to  be a  shales  limey s i l t s o n e s  ( F i g . 2.6).  no  The  Load  casts  suggest  o t h e r top  that  indications  o f the b e l t , l a r g e l y tectonic. 50m  A  thick  steeply zone  - 28 -  of ankerite  cemented b r e c c i a ,  s e p a r a t e s the sediments  from  S t u h i n i v o l c a n i c s on the n o r t h e a s t e r n edge o f the b e l t .  At  the  is  southern  absent  and  the  volcanics. volcanics  end  of  the  study  sediments  area  may  the  breccia  conformably  On the western edge o f t h e b e l t , appear  t o be  thrust  shallow, w e s t e r l y d i p p i n g  Lithologies particularly  the  of  over  the  zone  overlie  augite-bearing  sediments  along  and  sheets.  1972)  the  granite  Upper  boulder  i n the Tulsequah  Lithological  a  fault.  Triassic  sequence,  conglomerate,  correlate  w e l l w i t h the base o f the J u r a s s i c s t r a t a mapped by (1971  the  and  similarity,  Souther  T e l e g r a p h Creek  the  absence  of  map  meta-  morphism, and a s i m i l a r degree o f deformation ( c o n s i s t i n g o f low amplitude, e a s t e r l y p l u n g i n g , open chevron f o l d s the  Triassic  However,  sequence),  fossil  collections  F o s s i l s were c o l l e c t e d Paul  Smith  Terebratulid  make  (pers.  this  indicate  from two comm.,  brachiopods  a  were  logical  correlation.  a  Norian  late  h o r i z o n s and  1981).  of  fine  Rhynchonellids  recovered  arkose a t t h e base  age.  identified  from  u n i t s a t t h e base o f the b o u l d e r conglomerate. bed  within  thin  and  shaley  A 30m  o f t h e sequence  by  thick  contained  i  abundant Norian reports  Monotis  (cf.  ( S u e s s i zone) age sedimentary  subcircularis)  indicating  (Westerman, 1973).  beds  containing  Souther  Monotis  a  late (1972)  that  are  -29 -  METERS Feldspar porphyry dacite flow (?)  A A A A A A A V ^ A A A A A A A A A A A A A A A A A A A A  fc  V V V V V V V V V V V V V V  vvvvvvvvvvvvvv  Sheared mafic rock (basalt or gabbro) THRUST  (?) Granitic boulder conglomerate with thin faiterbeds ol siltstone  Limey shale/slltstone Maroon volcanic' conglomerate  Friable shales with interbedded argillites  Maroon volcanic conglomerate  Grey quartz-feldspar, hornblende sandstone and greywackes, minor Interbedded maroon Dthlc tufts  Thin bedded shales and cherts  Arkose sandatones. Interbedded siltstones  AAAAAi AA AA AA AAA AA A A A A AAAAAi A A A A A .  kV"  Ankerite/quartz cemented breccia with maroon volcanic fragments  " *  Massive maroon tuff-breccias  Figure 2.5 Stratigraphic section of u n n a m e d Triassic sediments on  western edge of detailed study area.  -  overlain east  by S t u h i n i  of  the  conglomerates  30  -  Group v o l c a n i c s  study  area.  within  near  The  the  Ball  thin  Creek,  maroon  sedimentary  20km  volcanic  sequence  are  i n d i s t i n q u i s h a b l e from outcrops o f s i m i l a r l i t h o l o g y w i t h i n the  Stuhini  therefore  volcanics,  a  close  affinity  Hornblende g r a n o d i o r i t e are  similar  batholith. periphery source  in  appearance  o f t h e Hickman  ages  and  t h e two  to  phases  provide  batholith  of  stratigraphic  the  groups.  Hickman  i t as t h e  constraints  phases.  for  Similarly,  c l a s t s from t h e 218 t o 227 m i l l i o n  pluton,  of the Hotialuh  batholith  (Fig.  I n t r u s i v e Rocks  rocks  underlie  about  30  T e l e g r a p h Creek map sheet area and p l a y the tectonic  There i s a s t r o n g  and m e t a l l o g e n i c  percent  Telegraph  coincident  history  of the  region.  s p a t i a l a s s o c i a t i o n between r o c k s o f t h e  Creek  uplift  o f the  a significant role  S t i k i n e Assemblage and p l u t o n i c rocks w i t h i n and  rock  and  w i t h i n t h e base o f o n l a p p i n g Upper T r i a s s i c v o l c a n i c s .  Intrusive  in  source  implicate  o f some o f t h e p l u t o n i c  y e a r o l d Cake H i l l  2.4  between  common  c l a s t s i n t h e b o u l d e r conglomerates  Anderson (1983) d e s c r i b e s  2.1),  a  The presence o f these conglomerates around t h e  area,  minimum  suggesting  map  sheet  areas;  t h e Tulsequah  possibly  due t o  o f S t i k i n e Assemblage and p l u t o n i c  rocks  -  31  -  through younger s t r a t a .  P l u t o n i c r o c k s occur t o the north,  east  the  and  northwest  outcrops  of  granitoid  d e t a i l e d mapping. the  best  of  study  rocks  area.  occur  combination  cursory,  interpreted  but  in  within  two  the  small  area  of  Plutons o f t h e Hickman b a t h o l i t h p r o v i d e d of  ranges  in  i n t r u s i v e r e l a t i o n s h i p s f o r study. only  Only  data  light  of  are  age,  lithologies  and  Study o f these rocks  rendered  exhaustive  more  useful  studies  by  was when  Anderson  (1983) on the nearby, and s i m i l a r , H o t a i l u h b a t h o l i t h .  Souther roughly  circular  Hickman, map  (1972) used t h e term Hickman b a t h o l i t h f o r the  i n the  sheet.  pluton south  approximately  central  area  centered  on  Mount  o f the Telegraph  Creek  The term Hickman b a t h o l i t h i s h e r e i n extended  encompass the a d j o i n i n g p l u t o n s t o the n o r t h . batholith 2.6),  informally  pluton, have  would  an  the  exposed  a t the  Columbia and and  Nightout  be  composed  named, from  Yehiniko  Samples c o l l e c t e d 2.1)  then  pluton,  of  three  north to and  plutons  south,  the  Hickman  1,100  square  the  pluton,  from  the t h r e e p l u t o n s were dated l a b o f The  plutons  and  a  Middle  (Fig.  Nightout  of  and  kilometers.  University  i n d i c a t e a M i d d l e T r i a s s i c age  Yehiniko pluton.  Hickman  area  geochronolgy  about  The  to  of  (Table British  f o r the Hickman  Jurassic  age  for  the  - 32 -  2.4.1  Hickman P l u t o n  The  Hickman  approximately topography  pluton  is a  roughly  16km i n diameter,  About  one h a l f  intrusion,  which forms t h e most rugged  i n the region, with  elevation.  circular  peaks  i n excess  o f t h e area  o f 3,000m  of the pluton i s  covered by g l a c i a l i c e .  The less  pluton  mafic  medium  o u t e r phase  grained  interior,  i s zoned  from  a more mafic  (Souther,  hornblende  1972).  biotite  interior  to a  Rocks range  quartz  diorites  from  i n the  t o f i n e r g r a i n e d b i o t i t e hornblende g r a n o d i o r i t e s  towards t h e e x t e r i o r .  M a f i c m i n e r a l s make up from 10 t o 20  percent  volume  of  t h e rock  i n both  phases.  Accessory  m i n e r a l s i n c l u d e sphene, a p a t i t e and magnetite.  The Mount Hickman area i n t h e southwestern  part of the  p l u t o n i s u n d e r l a i n by u l t r a m a f i c r o c k s which form a n o r t h easterly  oriented  elliptical  Mount Hickman i t s e l f ,  shaped  body  6km  i n length.  i n t h e southern end o f t h e u l t r a m a f i c  body, c o n s i s t s o f h o r n f e l s e d v o l c a n i c and sedimentary of  p r o b a b l e Permian age.  intrusive  into  The u l t r a m a f i c body appears  t h e Hickman  pluton  and i s zoned  rare  biotite  at  t h e margin.  Foliated  t o be  from  o l i v i n e b e a r i n g p y r o x e n i t e c o r e through t o hornblende with  rock  an  gabbro  hornblende  -33 -  Figure 2.6. Distribution of the plutonic components of the Hickman batholith, and location of dated samples.  - 34 -  diorites  occur  around  the  margin  of  the  u l t r a m a f i c body.  F o l i a t i o n i s o r i e n t e d p a r a l l e l t o the c o n t a c t s . of  gabbro,  from  20  t o 200m i n s i z e ,  Small p l u g s  were a l s o observed  the n o r t h e r n edge o f the Hickman p l u t o n .  on  Dykes and p l u g s o f  m a g n e t i t e - r i c h s y e n i t e , p o s s i b l y r e l a t e d t o the G a l o r e Creek bodies  which  monzonites  occur  of  the  10km  to  Yehiniko  the  west,  pluton,  occur  and/or i n the  quartz northern  h a l f o f the p l u t o n .  Steep western  dipping  faults  bound  and e a s t e r n margins.  the  pluton  on  both  I n t r u s i v e c o n t a c t s between the  Hickman p l u t o n and  S t u h i n i v o l c a n i c s were not observed.  remnant o f S t u h i n i  v o l c a n i c s appears  its  northwestern  edge, but t h e  volcanics—consisting  of  andesitic fragmentals—and  its  t o cap  the  A  pluton  on  c o n t a c t between m i n e r a l i z e d  plagioclase  porphyry  flows  and  the Hickman p l u t o n i s obscured  by  dykes and s i l l s o f younger quartz monzonite.  Age  of  the  potassium-argon Ma  and  221±8 Ma  hornblende near  the  Hickman  pluton  been  d a t i n g as Middle T r i a s s i c . (Table 2.1)  center  of  the  r u b i d i u m - s t r o n t i u m date 87  Sr/  86  determined  by  Dates o f 209  15  were o b t a i n e d from b i o t i t e  separates, r e s p e c t i v e l y ,  assumed i n i t i a l  has  pluton  from a sample  ( F i g . 2.6).  A  Sr o f 0.7038.  collected  whole  i s c a l c u l a t e d as 233±23 Ma  and  rock  using  an  TABLE 2.1  SAMPLE Latitude Loneitude • 81-HAl7a 57"30' 131°03'  Radiometric Age Determinations f o r Plutons of the Hickman B a t h o l i t h and M i n e r a l i z a t i o n Within the Stikine Assemblage, Northwestern B.C.  LITHOLOGY Hornblende biotite granodiorite  UNIT/FORMATION OR GROUP Nightout Pluton  AGE (Ma) and error 3  METHOD  1  K-Ar  MINERAL Bi  INITIAL 87„ /86. Sr Sr  TIME SCALE  236±9  K-Ar  Hb  228±8  Rb-Sr  Bi  232±5  j AGE  (Ma)  0.7038  PERIOD  EPOCH  Hickman Pluton  K-Ar  Rb-Sr  Bi  209±15 •  160-  Hb  221±8  170-  Bi  216±4  0.7038  180•  WR  233±23  0.7038  190_  o  57"09'08" 130°58'10"  1  Siderite-quartz vein  Stikine Assemblage  BAJOCIAN  AALEN1AN TOARCIAN EARLY  K-Ar  Bi  172±6  Rb-Sr  Bi  170±16  0.7038  210-  WR  178±11  0.7038  220 -  PLIENSBACHIAN SINEMURIAN HETTANGIAN  K-Ar  Ms  192±7  230 -  J-0 -  TRL  81-HRC4  Yehiniko Pluton  BATHONIAN MIDDLE  200-  OISSV  57°25* 131°15'  Leucocratic quartz monzonite  CALLOVIAN  CC D  -  81-HAl9a  KIMMERIDGIAN OXFORDIAN  •  ASSI  57°l3' 131°l6'  Biotite hornblende granodiorite  AGE  TITHONIAN  150LATE  81-HAlOa  4  LATE  NORIAN  CARNIAN MIDDLE EARLY  LADINIAN ANISIAN SCYTHIAN  A l l analyses were performed by K. Scott, R.L. Armstrong and J . Harakal, Geochronology Lab,The University of B r i t i s h Columbia Bi = B i o t i t e , Hb = Hornblende, WR = Whole Rock, MS «= Muscovite (± fuchsite)' Decay constants a f t e r Steiger and Jager (1977) Geological Society of America, DNAG - 1983 Time Scale (Kent et a l . , 1984; Armstrong, 1982)  -  2.4.2  The  Nightout  Pluton  Nightout  pluton  36  -  forms  the  northern  part  Hickman b a t h o l i t h and i s b i s e c t e d i n t o n o r t h e r n and bodies  by  the  Yehiniko  the northern h a l f , in  the  southern  relatively  pluton.  Topography  near Nightout  portion.  homogeneous  the  southern  i s moderate  in  Mountain, but more rugged  Compositionally, with  of  the  lithologies  pluton  ranging  is  from  hornblende b i o t i t e quartz d i o r i t e t o g r a n o d i o r i t e , which i s c o m p o s i t i o n a l l y e q u i v a l e n t t o the o u t e r phase o f t h e Hickman pluton.  Distinctive  g r a i n s and  features  are  abundant  commonly c h l o r i t i z e d m a f i c s .  t h a t f e l d s p a r s a r e weakly t o moderately and  coarse  T h i n s e c t i o n s show altered to  sericite  carbonate.  I n t r u s i v e r e l a t i o n s h i p s o f the Nightout clear.  A  remnant  of  Stuhini  volcanics  pluton are lies  along  n o r t h e r n edge o f the southern body but c o n t a c t s a r e by e x t e n s i v e t a l u s . Mt.  sphene  Lacasse,  intruded flows.  and  an  apophysis  of  the  relatively  pluton  appears  metamorphosed p y r o x e n e - p l a g i o c l a s e  the  exposed  sharp  the  covered  On the e a s t s i d e o f S c h a f t Creek, below  However, abundant dyke  complicate  not  swarms o f  contacts.  intrusive  The  contacts  with  the  sediments o f Zagoddetchino Mountain ( F i g . 2.2).  have  porphyritic  quartz  Nightout  to  monzonite pluton  has  Paleozoic  -  Age  of  collected  the  from  the  Potassium-argon were  pluton,  from Samples  determined  body,  o f 236±9 Ma biotite  and  collected  and  Four  Hickman  r u b i d i u m - s t r o n t i u m age  from  Middle  228±8 Ma hornblende  from  an  samples Triassic.  (Table  apophysis  altered  for  on  (190±70 Ma)  yielded  a  t h a t , although  the  potassiumNightout  whole rock samples from  plutons  2.1)  separates,  Ages o f the Hickman and the  p l u t o n s a r e concordant. Nightout  is  and  s i d e o f S c h a f t Creek were t o o  argon d e t e r m i n a t i o n s .  the  -  southern  dates  determined  respectively. east  Nightout  37  both  whole  rock  concordant  w i t h t h e ages above, has e x c e s s i v e c a l c u l a t e d e r r o r .  2.4.3  Yehiniko Pluton  F l e s h c o l o u r e d , l e u c o c r a t i c q u a r t z monzonite t o g r a n i t e make  the  vaguely  Yehiniko  circular  batholith,  but  considerable (1972)  noted  Pluton  outline  distinctive. w i t h i n the  dykes, s i l l s  distances the  away  strong  and  pluton  center of the  has  the  main  patterns,  mass.  which  a  Hickman  o t h e r apophyses extend  from  joint  The  for  Souther  result  in  i m p r e s s i v e m o n o l i t h i c peaks, c h a r a c t e r i s t i c o f t h i s p l u t o n .  38  -  The  -  i n t r u s i o n i s c o m p o s i t i o n a l l y homogeneous, b e i n g composed  o f r o u g h l y equal amounts o f orange potassium plagioclase,  and  clear  to  smokey  quartz.  feldspar, Mafic  minerals  seldom t o t a l more than f i v e p e r c e n t by volume, w i t h predominating  over  constituent,  locally  volume.  is  grey  biotite  hornblende.  Magnetite  a  common  r e a c h i n g two  to three percent of  rock  A l a r g e p l u t o n west o f the S t i k i n e R i v e r ( F i g . 2.2)  i s l i t h o l o g i c a l l y i d e n t i c a l t o the Y e h i n i k o p l u t o n .  The  quartz monzonites are u n e q u i v o c a l l y i n t r u s i v e  a l l s u r r o u n d i n g r o c k s except f o r the Cretaceous and Sustut  conglomerates  monzonite  which  (Souther,  1972).  contain  clasts  Xenoliths  Tertiary  of  and  into  quartz  screens  of  g r a n o d i o r i t e w i t h i n t h e q u a r t z monzonite, between the n o r t h and  south  p a r t s of the Nightout  bodies  were  Schaft  Creek and  extensive  dyke  interdigitate rocks.  previously  the  swarms  of  Hickman  Near  the  by  Souther  that  S c h a f t Creek porphyry quartz plutonic  monzonite and  these  headwaters  and  Stuhini  Quartz monzonite i n t r u d e s a sedimentary  west o f Y e h i n i k o Lake. Jurassic  joined.  below  with  p l u t o n suggest  of  deposit, granite volcanic  package j u s t  These sediments are mapped as Lower  (1972),  but  they may  be  equivalent to  t h e Upper T r i a s s i c sediments d e s c r i b e d i n s e c t i o n 2.3.3.  -  Rubidium-strontium  39  whole  -  rock  and  biotite  potassium-  argon d e t e r m i n a t i o n s g i v e r e s p e c t i v e dates of 178+11 Ma 172±6 Ma Middle  (Table 2.1)  Jurassic  and  f o r the quartz monzonite, i n d i c a t i n g  age,  which  i s i n accordance  with  a  observed  geology.  2.4.4  Other P l u t o n i c Rocks  An e l o n g a t e p l u t o n o f r e l a t i v e l y homogeneous q u a r t z d i o r i t e occurs approximately the  detailed  study  area.  and  field  relations  plutonic  suite.  30km l o n g , was zone  with  the  The  all  Stikine  p l u t o n , which  Assemblage  and  to  be  along  southwestern  zone,  recrystallized, rarely  lithology Triassic  6km  wide  are  south  plutons.  Contacts  g r a d a t i o n a l over  foliated  margin  of  Stikine  the  by  of  the  but  Compositional  no  other  with a  forms  the  one  km  pluton.  Assemblage  disrupted, granitized  pyritized,  10km  gabbro o r s y e n i t e dykes and  absent.  rocks  contact  i s roughly  rocks,  Hickman  and  Assemblage the  the b a s i s o f  this  L i t h o l o g i c a l l y , t h i s pluton i s similar  foliation,  appear  On  correlated  not examined i n d e t a i l except f o r the c o n t a c t  Nightout  zonation,  (1972)  i t i s most l i k e l y p a r t o f t h e  d e t a i l e d study a r e a . to  f i v e kilometers east of  Souther  p l u t o n w i t h t h e Nightout p l u t o n .  hornblende  Stikine  wide  zone  Within  the  volcanics  are  (Souther, of  plugs  1972)  alteration  and were  - 40 -  observed.  Contacts  investigated.  with  Mesozoic  aged  rocks  were  not  The s m a l l e l i p t i c a l p l u t o n , 2km n o r t h e a s t o f  t h e study area  ( F i g . 2.2) has l i k e l y been severed  main i n t r u s i v e mass by f a u l t s . stream sediment geochemical  from t h e  Apart from sparse molybdenum  anomalies,  no m i n e r a l i z a t i o n was  observed t o be a s s o c i a t e d w i t h t h i s p l u t o n .  A lithologically  and c h r o n o l o g i c a l l y d i s t i n c t  plutonic  s u i t e i s formed by r e l a t i v e l y s m a l l a l k a l i c p l u t o n s , r a n g i n g from p o r p h y r i t i c s y e n i t e s t o magnetite that  occur  throughout  the  study  b i o t i t e pyroxenites,  region  (Souther,  Some o f t h e p l u t o n s o f t h i s s u i t e h o s t p o t e n t i a l l y  1972). economic  m i n e r a l d e p o s i t s , and d e p o s i t s hosted i n o t h e r r o c k s appear t o be g e n e t i c a l l y r e l a t e d t o t h i s p l u t o n i c s u i t e .  The G a l o r e Creek p r o s p e c t i s d e s c r i b e d by A l l e n e t a l . (1977) as t e n t a b u l a r t o manto shaped copper-gold d e p o s i t s , hosted with  by  altered  Triassic  s y e n i t e porphyry  dykes  occurs w i t h i n a b r e c c i a orthoclase  porphyry  (recalculated  t o new  indicating  mineralization.  and p l u g s .  an  and a s s o c i a t e d  The main  pipe associated with  syenite.  1968) on hydrothermal years  v o l c a n i c rocks  decay  Four  fine  constants  to  grained  potassium-argon from  White  b i o t i t e range from 178 t o 203 Early  deposit  Middle  Jurassic  dates et  al.,  million age  of  -  The  Red C h r i s d e p o s i t ,  Hotialuh  batholith,  composite 1977).  41 -  stock  l o c a t e d 35km southwest o f t h e  i s a porphyry  of altered  Host monzonites  volcanic rocks.  copper  hornblende  intrude Norian  Two potassium-argon  1977) , on hornblende  monzonite  deposit within a  monzonite  (Schink,  (Late T r i a s s i c ) age  determinations  and a  related  dates o f 210±7 Ma and 195±8 Ma r e s p e c t i v e l y ,  (Schink,  dyke,  give  i n d i c a t i n g an  E a r l y J u r r a s i c age.  2.5  Summary o f Age R e l a t i o n s h i p s and Metallogeny  T r i a s s i c p l u t o n s o f t h e Hickman b a t h o l i t h y i e l d concordant potassium-argon range  from  209 t o 236 Ma  and rubidium-strontium dates t h a t (Table 2.1) s u g g e s t i n g  C a r n i a n t o e a r l y Norian age. 2.7)  was o b t a i n e d  Hotialuh  from  batholith  roughly  an e a r l y  A s i m i l a r range o f dates ( F i g .  the T r i a s s i c  (Anderson,  plutonic  1983).  suite  Stuhini  of the  volcanics  range i n age from e a r l y C a r n i a n t o Late N o r i a n based on both isotopic 1972).  dates  (Anderson,  Unequivocal  1983) and f o s s i l  intrusive  ages  relationships  (Souther,  between  the  Hickman o r Nightout p l u t o n s and S t u h i n i v o l c a n i c s were n o t observed. the  Granodiorite boulders,  Hickman  sediments intrusion  pluton,  close  to  within the  lithologically  fossiliferous  Hickman  o f t h e p l u t o n took  place  pluton, prior  similar to  late  Norian  suggest  that  t o Norian  time.  - 42 -  Mapped r e l a t i o n s h i p s some  of  the  (Souther, 1972) i n d i c a t e t h a t a t l e a s t  Stuhini  volcanics  post  date  the  Norian  sediments.  Plutonic  rocks  that  have  clearly  intrusive  contacts  w i t h S t u h i n i v o l c a n i c s y i e l d potassium-argon dates o f 222±16 and of  218±12 Ma, from t h e K a t s e t s a the Stikine  from M c M i l l a n , the  Arch  stock  (recalculated  t o new  predate  that  the older  some  phases  volcanism,  source o f g r a n i t o i d c l a s t s w i t h i n  coeval  constants  while  (Schink, 1977).  o f t h e Hickman  or a l l of Stuhini  conglomerates,  decay  side  1974), and 210±9 Ma, from t h e Red s t o c k in"  south c e n t r a l S t i k i n e A r c h area  probable  on t h e e a s t e r n  volcanic  t h e younger  Triassic  and comagmatic w i t h t h e v o l c a n i c s .  I ti s  batholith  and were t h e  and sedimentary phases Anderson  may  be  (1983)  argues t h a t a l t h o u g h t h e H o t a i l u h b a t h o l i t h i n p a r t predates the  overlying  Stuhini volcanics,  i t i s the source area f o r  the v o l c a n i c s i n t h a t r e g i o n , w i t h t h e u l t r a m a f i c i n t r u s i v e s representing  feeders  relationships are  suggested  f o r the overlying  between v o l c a n i c s by  t h e presence  volcanics.  and t h e Hickman of  intrusive  Similar batholith  pyroxenites,  c l o s e temporal a s s o c i a t i o n o f i n t r u s i v e and e x t r u s i v e and  rocks,  t h e t h i c k accumulations o f coarse v o l c a n i c conglomerates  and b r e c c i a s a l o n g t h e margins o f t h e b a t h o l i t h .  9-  » •O  o CA  s> c to CJ CD  3 »• "  5T  c  CQ CD  "O _  DEVONIAN  CARBONIFEROUS MlUmiPrHAM  PERMIAN  TRIASSIC  JURASSIC  PEMNITLVANIAN  s3  CD CD  2 =>"  o o  CO  —^ 35  i  T i 11  s  ? .  <  Stikine Assemblage  ©  I  •I..  approx. 30 dates  Hotialuh batholith  S  8  IT O  Q.  ro  CD  s  o  CD^  12  Hickman batholith Stuhini Group Triassic sediments Galore Creek Intrusions  4 dates  BJ quartz-carbonate vein  12  Red Chris deposit Schaft Creek deposit © = Fossil Age  FIGURE 2.7  Summary o f age r e l a t i o n s h i p s f o r r o c k s and s e l e c t e d m i n e r a l d e p o s i t s o f t h e S t i k i n e A r c h a r e a , n o r t h w e s t e r n B.C. P o t a s s i u m argon d a t e s r e c a l c u l a t e d t o r e c e n t decay c o n s t a n t s ( S t e i g e r and J a g e r , 1977) by t h e method o f D a l r y m p l e , 1979). R e f e r e n c e s : (1) Anderson, 1983, (2) t h i s study, (3) N e l s o n and Payne, 1984 ,(4) P a n t a l e y e v 1973,(5) P. Read p e r s . comm., 1983,(6) Schink, 1977,(7) S o u t h e r , 1972 (8) White e t a l . ,  2  1  9  6  8  R a d i o m e t r i c D a t i n g Methods: (1) K-Ar h o r n b l e n d e (4) Rb-Sr b i o t i t e (5) Rb-Sr whole rock,  (2) K-Ar b i o t i t e  (3) K-Ar m u s c o v i t e  -  There  is  mineralization intrusives  a  -  notable  associated  within  44  absence  with  the  the Stikine  of  significant  Triassic  Arch  area.  o u t c r o p s near t h e S c h a f t Creek porphyry  suite  of  Granodiorite  deposit l e d to the  a s s o c i a t i o n o f t h e Hickman p l u t o n w i t h m i n e r a l i z a t i o n .  More  d e t a i l e d i n v e s t i g a t i o n r e l a t e d the genesis of the deposit t o quartz monzonites o f t h e Y e h i n i k o p l u t o n ( S p i l s b u r y , A potassium-argon  date o f 186±5 Ma on hydrothermal  1982). biotite  ( r e c a l c u l a t e d t o new decay c o n s t a n t s from Pantaleyev, 1973) from t h e d e p o s i t supports t h i s g e n e t i c i n t e r p r e t a t i o n .  Barr  e t a l . (1977) demonstrated  between E a r l y J u r a s s i c  a strong  association  ( P l e i n s b a c h i a n ) age a l k a l i c  porphyry  d e p o s i t s and Upper T r i a s s i c v o l c a n i c r o c k s a l o n g t h e l e n g t h of the C o r d i l l e r a .  I n many cases c h e m i s t r y o f t h e v o l c a n i c s  and i n t r u s i v e s suggest a comagmatic l i n k . age  between  the volcanics  these  intrusives  dated  minerals  events.  The  and i n t r u s i v e s  are l a t e  reflect Galore  The common gap i n  stage  cooling  Creek,  be  differentiates  ages  Red  may  or late  Chris  and  because  and  that  hydrothermal Schaft  Creek  d e p o s i t s a l l belong t o t h i s age and s t y l e o f m i n e r a l i z a t i o n . All  of  enriched  these  deposits,  i n precious  metals  deposits of the C o r d i l l e r a . metal  camps p e r i p h e r a l  particularly relative  Galore  Creek,  t o other  are  porphyry  Notably, t h e two major p r e c i o u s  t o t h e Bowser B a s i n — t h e  Toodoggone  -  camp  (Schroeter,  Stewart camp hosted  45  1982; F o r s t e r ,  intrusive-extrusive  Sinemurian  (176 - 205 Ma) age.  4)  1984) t o the e a s t ,  complexes  of  highly  rocks y i e l d e d  altered  Bajocian  Muscovite and f u c h s i t e  and s i l v e r b e a r i n g q u a r t z - s i d e r i t e v e i n  within  and t h e  ( A l d r i c k , 1986; Brown, 1986) t o t h e s o u t h — a r e  by  a gold  -  Stikine  a potassium-argon age o f 192±7 Ma  t o lower J u r a s s i c magmatic  activity.  from  (see Chapter  Assemblage  t h a t p r e c i o u s metal v e i n type m i n e r a l i z a t i o n  to  pyroclastic suggesting  i s also related  46  -  CHAPTER 3:  -  GEOLOGY OF THE STIKINE ASSEMBLAGE  3.1 I n t r o d u c t i o n  This  chapter  describes  the stratigraphy,  petrology,  s t r u c t u r e and c h e m i s t r y o f S t i k i n e Assemblage rocks exposed w i t h i n t h e study a r e a . exposed  in  uplifted,  throughout t h e S t i k i n e  Rocks o f t h e S t i k i n e Assemblage a r e generally Arch.  fault-bounded,  Lithologies  blocks  and t h e i n t e r 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 o f these b l o c k s a r e known i n o n l y a g e n e r a l way. blocks  is  described  largely herein  Mississippian and  Age d e t e r m i n a t i o n and c o r r e l a t i o n by  fossiliferous  underlie,  age l i m e s t o n e s  with  between  limestones. apparent  (Souther,  Rocks  conformity,  1972; Monger, 1970)  are considered t i m e - c o r r e l a t i v e with  these  limestones.  The base o f t h e s e c t i o n i s n o t exposed.  All  o f t h e r o c k u n i t s w i t h i n t h e study area have been  complexly deformed, metamorphosed and v a r i a b l y a l t e r e d . intensity unusual rocks  of  deformation  relative within  t o other  and  widespread  exposures  t h e Telegraph  Creek  r e l a t i v e t i m i n g o f t h e deformation  alteration  of Stikine map  sheet  interpreting  the g e o l o g i c a l  area.  and a l t e r a t i o n ,  history,  is  Assemblage  but a l s o  evaluation of the e x p l o r a t i o n p o t e n t i a l of the area.  The  and t h e  cause o f a l t e r a t i o n i s s i g n i f i c a n t , not o n l y as a f i r s t in  The  step  t o the  47  -  Map u n i t s  were d e f i n e d  compositional  and  i n the f i e l d  textural  the contact  contacts  is  commonly  arbitrary.  A  hampered  by  lack  probable  rapid  limits  the  area;  consequently,  understanding  of consistent  facies  quality  of  This,  complex  q u a l i t y and i n p l a c e s  3.2  fold  of the  areas,  field  contradictory;  o f map  places  even  geometry  severely  interpretations.  was i n t e r p r e t e d  specimens. data  is  markers and  i n turn,  stratigraphic  h e l p o f s t e r e o n e t s and o r i e n t e d  geologically  in  stratigraphic  changes. of  placement  and  S t r u c t u r a l data c o l l e c t e d i n t h e f i e l d the  Many  c o n t a c t s and/or a r e interbedded  approximate,  clear  on t h e b a s i s o f  similarities.  l i t h o l o g i e s have g r a d a t i o n a l within  -  with  As i n many  are variable  in  many problems remain.  Stratigraphy  3.2.1  S t r a t i g r a p h i c Summary  The  Stikine  Assemblage  i s composed  predominately o f  v o l c a n i c l a s t i c s with subordinate,  interbedded sediments and  minor  rocks  flow  unambiguous  and/or  intrusive  indicators  o f tops  ( F i g . 3.1).  were observed  No  and thus t h e  s t r a t i g r a p h i c sequence i s i n t e r p r e t e d t o be r i g h t s i d e up on the b a s i s o f s t r u c t u r a l c o n t i n u i t y w i t h a d e f i n e d Mississippian  contact  (Souther,  southwest o f t h e study a r e a .  1972) l o c a t e d  At the regional  appear t o be l e n t i c u l a r and s t r a t i g r a p h y  Permian1km  t o the  scale,  cannot be  units  followed  - 48  far  beyond  the  limits  of  -  the  mapped  area.  The  volcanic  sequence i s , f o r the most p a r t , bimodal c o n s i s t i n g o f e i t h e r rhyolitic display  or  basaltic  compositions.  evidence of mixing from two  Pyroclastic  units  or more sources.  Grain  s i z e of these rocks can change from coarse t o v e r y f i n e over short  distances,  Nomenclature follows  that  both  laterally  used  in  descriptions  of  Fisher  (1961),  and  of  and  vertically.  pyroclastic  Fisher  and  rocks  Schminke  (1984). Volcanic  and  sedimentary  i n t o seven u n i t s  on the b a s i s  characteristics  (Fig.  rocks  been  of t e x t u r a l and  3.2).  Two  non-stratigraphic  and  assemblages  indeterminable  with  have  of  subdivided  mineralogical  these  characterized  units  by  are  alteration  protoliths.  Chemical  a n a l y s e s support these groupings. The  lowest u n i t w i t h i n  the s t r a t i g r a p h i c s e c t i o n  s i l i c e o u s t o g r a p h i t i c a r g i l l i t e or a r g i l l a c e o u s intercalated overlain  by,  lithic and  characterized  by  interlayered  green  wackes  and  gradational a  wide and  ash  with,  variety  maroon  tuffs.  of  is a  s c h i s t with  This  mafic  unit  is  pyroclastics  fragment  types  Chlorite  schist,  beds.  and a  s u b - u n i t o f the m a f i c p y r o c l a s t i c s , i s interbedded w i t h the argillaceous  schist.  The  next o v e r l y i n g  unit  is felsic  composition and ranges from c o a r s e v o l c a n i c b r e c c i a s lapilli basic,  t u f f s to c r y s t a l - l i t h i c  ash  tuffs.  A dark  coarse t o f i n e g r a i n e d , t y p i c a l l y massive  in  through green,  unit  caps  - 49 -  *»  tt 9  - Shales, cherts, volcanic ssts, grits, boulder conglomerates Unconformity / Thrust  Mississippian  - Crinoidal limestone - Undifferentiated  o  -2  I volcanics  Unit 5 GRST Greenstone unit Gabbro sills  •Q  S « «l  ««  <0  - Unit 4 F V C S Felsic tuffs and breccias - Unit 3 PGST Hematitic schists, pyroclastics - Unit 2 CHST Massive chlorite schists - Unit 1 ARGL Meta-argillite, graphitic schist  Figure 3.1 Schematic stratigraphic column of Stikine Assemblage rocks, Mess Creek area, northwestern B.C.  - 50  Figure 3.2  -  G e n e r a l i z e d g e o l o g y of the M e s s C r e e k a r e a , n o r t h w e s t e r n B.C.  -  the sequence. be  an  All  may  also  contain  minor  been  metamorphosed  flow  and  rocks.  greenschist  3.3c).  sill,  lithologies  folding  -  T h i s uppermost u n i t , which i s i n t e r p r e t e d t o  intrusive  epiclastic  51  facies.  have Intense  has l o c a l l y  shearing  to  lower  r e l a t e d t o polyphase  o b l i t e r a t e d primary  textures  (Plate  Hydrothermal a l t e r a t i o n , c h a r a c t e r i z e d by s e r i c i t e -  carbonate-quartz  schist,  i s widespread.  At least  part of  t h i s a l t e r a t i o n appears t o be pre-deformation  and c o u l d have  served t o l o c a l i z e s t r a i n , thereby  f o r the higher  intensity  of  deformation  alteration affects felsic  3.2.2  accounting  i n this  area.  This  type  of  a l l u n i t s b u t i s most common w i t h i n t h e  rocks.  Argillaceous Schist  A r g i l l a c e o u s s c h i s t s and p h y l l i t e s form t h e base o f t h e s t r a t i g r a p h i c sequence, and a r e exposed i n t h e core  of the  l a r g e a n t i f o r m t h a t extends t h e l e n g t h o f t h e map area ( F i g . 3.3).  Although  r e g i o n a l l y widespread,  this  unit  i s not  demonstrably t i m e - s p e c i f i c enough t o use f o r c o r r e l a t i o n o f stratigraphy. approximately i s greater.  The  maximum  observed  thickness  200m but as t h e base i s not exposed  is  thickness  - 52 -  Argillite  i s intercalated  with  beds  and  lenses  f i n e - g r a i n e d v o l c a n i c l a s t i c rock, predominately mafic wackes sharp  similar  t o the overlying  and g r a d a t i o n a l , with  Apart  observed. black  from  pressure during  quartz  solution  rocks  Outcrops  carbonate  i s not  ranges  veinlets  and r e c r y s t a l l i z a t i o n  chlorite,  consists  carbonate, epidote  as a p a t i t e  of  rocks,  a  and v a r i o u s and z i r c o n  secondary  concentration  very  graphite,  p y r i t e g r a i n s a r e common.  riddled  resulting  i n dilatant  from zones  fine  as observed i n  grained  orthoclase,  oxides.  are also  quartz,  plagioclase,  Detrital present.  minerals Euhedral  I n s e c t i o n s taken from c r e n u l a t e d  compositional  of graphite  layering  and opaques  i s produced  along  3.5c). seen  Rare e l l i p t i c a l i n sections.  (Plate  fragments up t o 5mm i n s i z e can a l s o G r a p h i t e content v a r i e s from  p e r c e n t w i t h t h e average  a t about 5 p e r c e n t .  metamorphic m i n e r a l s were not observed section.  by  second-phase  c l e a v a g e s u r f a c e s between carbonate and q u a r t z l a y e r s  be  from  amounts o f  a r e commonly  of the argillaceous s c h i s t ,  section,  muscovite,  such  bedding  deformation.  Mineralogy thin  or  a r e both  more common.  depending upon t h e r e l a t i v e  q u a r t z and g r a p h i t e p r e s e n t . fine  layers,  of the argillaceous  t o p a l e grey  with  being  lithic  over a v e r t i c a l d i s t a n c e o f  the v o l c a n i c l a s t i c  Colour  Contacts  the l a t t e r  G r a d a t i o n a l c o n t a c t s can extend 30m.  unit.  of  2 t o 20  Pelitic-type  i n outcrop o r i n t h i n  - 53 -  Macro  fossils  were n o t observed  f o r conodonts were s i m i l a r l y b a r r e n . to  the intensity  o f deformation  and samples d i g e s t e d T h i s may be a t t r i b u t e d  and/or  t o t h e absence o f  fauna d u r i n g d e p o s i t i o n .  3.2.3  Chlorite Schist  Fine-grained, to  pale  green  metamorphic  laminated  chlorite  to thickly  schists  equivalents o f mafic  are  bedded, b l u e interpreted  ash t u f f s .  green t o be  These  tuffs  form p a r t o f t h e o v e r l y i n g m a f i c p y r o c l a s t i c / e p i c l a s t i c u n i t w i t h i n which they a r e i n t e r b e d d e d .  A t t h e south and n o r t h  ends  and  of  the  argillaceous  map  schist,  area,  within  the c h l o r i t e  adjacent  schists  t o the  are s u f f i c i e n t l y  homogeneous and t h i c k enough t o be mapped as d i s t i n c t These  units  are l e n t i c u l a r  strike;  a  feature  contrast  with  and p i n c h  possibly  the adjacent  out r a p i d l y  exaggerated  argillite  by  units. along  competency  during  deformation.  display  laminations  Maximum observed t h i c k n e s s i s 70m.  Outcrops  of this  within  compositional  3.3).  Quartz  and  bedding  outcrops from  unit  layers  typically presumed  and/or carbonate planes  occur  dominantly  are also  locally  layers p a r a l l e l common.  and r e f l e c t  chlorite  t o be bedding  (Plate  to foliation  Massive,  resistant  a m i n e r a l o g i c a l change  t o dominantly  epidote.  Near t h e  -  upper  and  lower  constituent  contacts,  and t h e rock  F i n e l i t h i c fragments, not obvious 10cm  long  schists.  i n outcrop.  occur  muscovite  takes  becomes  an  on a p h y l l i t i c  r e a d i l y apparent  elliptical,  fragments  -  54  appearance.  i n t h i n s e c t i o n , are  A n o t a b l e e x c e p t i o n i s where 3 t o finely  within  vesicular,  thickly  orange  bedded  weathering  chlorite-epidote  These fragments a r e w e l l p r e s e r v e d w i t h  fillings  o f f e r r u g i n o u s carbonate  frothy basaltic  important  vesicular  ( P l a t e 3 . 3 f ) , and resemble  bombs o f t h e type  commonly  a s s o c i a t e d with  s p a t t e r cones (McBirney and W i l l i a m s , 1979).  Thin  sections  of  chlorite,  epidote,  albite,  minus  talc?),  quartz,  the  schist  reveal  carbonate,  tremolite  and  fine  layers  of  muscovite  (plus o r  opaques.  Chlorite,  which can form up t o 35 p e r c e n t o f t h e s l i d e , occurs as f i n e wisps w i t h i n t h e m a t r i x  o r as c o a r s e  aggregates;  appear  rather  the  than  anomalous  latter  porphyroblasts.  berlin  blue  to  be  Matrix  elliptical  grains or  replaced  fragments  chlorite  interference colours  usually  has  indicating  a  high-magnesium ( p e n i n i t e ) composition.  Chemical have  analyses i n d i c a t e t h a t the rocks of t h i s  an unusual  composition  that  i s c h a r a c t e r i z e d by low  s i l i c a , h i g h i r o n and h i g h magnesium contents Compositions unit  a r e s i m i l a r t o those  supporting  the i n t e r p r e t a t i o n  unit  ( s e c t i o n 3.6).  o f t h e mafic o f a common  pyroclastic parentage.  - 55 -  I f chemistry by  o f these rocks has not been m o d i f i e d  d i a g e n e t i c and metsomatic processes  conclude  that  epiclastic  they  and  represent  minor  markedly  i t i s reasonable t o  f i n e - g r a i n e d , but proximal,  pyroclastic  detritus  derived  from  alkaline olivine basalts.  3.2.3  M a f i c P y r o c l a s t i c and E p i c l a s t i c U n i t  The  mafic  pyroclastic  and  epiclastic  unit  is  a  heterogeneous c o l l e c t i o n o f l i t h o l o g i e s t h a t i n c l u d e s coarse agglomerates, ash  tuffs.  part  d e b r i s flows, l a p i l l i t u f f s , l i t h i c wackes and The u n i t  o f t h e study  i s best  area  where  i n the  southwestern  steep  south-facing  i t forms  slopes.  Here,  although  some s t r u c t u r a l r e p e t i t i o n i s l i k e l y .  the  central  units  form  thickness  exposed  part  o f t h e map area  d i p slopes  i n this  a r e a an upper and a lower are  of the u n i t  material  be up t o 500m,  i s minimal  area.  Exposure i n as o v e r l y i n g  In the northern  l a y e r a r e exposed.  i n t e r p r e t e d t o be f o l d  northern  may  repetitions.  map  These l a y e r s  In general, the  exposures have a g r e a t e r p r o p o r t i o n o f e p i c l a s t i c while  the  southern  outcrops  are  predominatly  pyroclastic.  The  unit  i s c h a r a c t e r i z e d by h e t e r o g e n e i t y  of thinly  i n t e r b e d d e d f i n e - g r a i n e d p y r o c l a s t i c and e p i c l a s t i c m a t e r i a l (Plates chloritic  3.1b  and  3.2e).  Matrix  material  t o h e m a t i t i c and a r g i l l a c e o u s w i t h  ranges  from  corresponding  - 56 -  c o l o u r ranges green  o f dark green t o maroon and grey.  layers  are  frequently  i n d i v i d u a l beds v a r i e s from  interbedded.  30cm t o 10m.  Maroon and  Thickness  Coarse  fragmental  u n i t s a r e more common i n t h e c e n t r a l and southern map while map  fine  grained units  area.  tend  t o dominate  and more a r g i l l a c e o u s s t r u c t u r a l l y up s e c t i o n .  limestone  area,  and wackes become p r o g r e s s i v e l y f i n e r  of the section  area  i n t h e northern  On t h e v e r y n o r t h end o f t h e study  pyroclastics  of  mafic  grained  Near t h e top  (or bottom i f t h e sequence i s i n v e r t e d ) t h i n  lenses  appear  suggesting  marine  transgression.  The a l t e r n a t i n g maroon and green c o l o u r s c o u l d correspond t o changes  from  subaerial  to  submarine  depositional  environments.  Thin with  textural  orthoclase, oxides  sections  show  a  variation.  muscovite,  are a l l present  varied  mineralogy  Chlorite,  carbonate, i n variable  commensurate  epidote,  quartz,  albite,  graphite  proportions.  and  Textures  a r e o f t e n more n o t i c a b l e on weathered outcrop s u r f a c e s than they a r e i n t h i n s e c t i o n . v e r y conspicuous locations. microscopy  B r i g h t green micaceous spots are  w i t h i n maroon c o l o u r e d p h y l l i t e s  These spots were confirmed and  chrome-bearing  X-ray chlorite  diffraction  a t a few  (by scanning e l e c t r o n techniques)  (kammererite)  and  to  be  muscovite  ( f u c h s i t e ) which formed around and r e p l a c e d chromite g r a i n s .  57  -  -  Samples c o l l e c t e d f o r chemical a n a l y s e s from t h i s u n i t were  fine-grained  maroon  lithic  necessarily representative characterized s i m i l a r to section.  the  high  which  of the e n t i r e u n i t .  iron  and  magnesium,  c h l o r i t e s c h i s t discussed  are  not  Chemistry i s  and  low  i n the  silica,  preceeding  These samples are a l s o d i s t i n g u i s h e d by t h e i r h i g h  chromium  (300ppm)  combination rocks  by  tuffs  of  formed  reworking  and  nickel  textures as  of  a  and  result  basaltic  (200ppm)  chemistry of  both  values.  indicate  direct  pyroclastic  and  The  that  these  deposition  and  possibly  flow  material.  3.2.4  Felsic Pyroclastics  F e l s i c p y r o c l a s t i c s are the most abundant r o c k type i n the  area,  although  than d e p o s i t i o n . much  of  the  variable.  central  In  south  is a  function  of  exposure  T h i s u n i t forms a d i p s l o p e t h a t  the  maximum t h i c k n e s s and  this  ends o f  map  area.  east-central c o u l d be the  Thickness part  of  of the  i n excess o f 400m.  study  underlies  the  unit  is  study  area,  At the  north  area, where both  bottom o f the u n i t i s exposed, i t i s u s u a l l y  rather  the  top  l e s s than  and 150m  thick.  The  unit  i s primarily  l e s s e r l i t h i c ash t u f f s and  composed o f breccias.  a n g u l a r t o sub-rounded, p o o r l y  lapilli  t u f f s with  Fragments are  usually  t o moderately w e l l - s o r t e d  and  - 58 -  of  similar  lithologies.  pyroclastics,  reworked  with  supported  ( P l a t e 3.1a).  a crude  visible  layering  contrast  material  outcrops  but  In  to  i s minimal.  fragmental  mafic  Most  textures  o f the  are  clast  S t r a t i f i c a t i o n i s not o f t e n v i s i b l e  d e f i n e d by fragment  character  c o l o u r o r type) o c c u r s on some exposures. commonly grade  the  laterally,  (size,  Fragmental  rocks  and more r a r e l y v e r t i c a l l y ,  quartz-sericite-carbonate  schists.  This  is  into  attributed  p r i m a r i l y t o a l t e r a t i o n b u t c o u l d a l s o correspond t o changes i n fragment  The  s i z e and/or c o m p o s i t i o n .  felsic  structurally  pyroclastic  competent  unit  and massive  is  greenstone  c o n t a c t i s u s u a l l y sharp and u n d u l a t i n g . a r e a t h e greenstone thin  layer  mylonite strain folding.  decreasing  may  the  unit.  This  In t h e c e n t r a l map  of quartz-sericite  probably  the  less  Hydrothermal  deformation  Other  was  within  by  i s s e p a r a t e d from t h e f e l s i c r o c k s by a  (3 t o 20m)  zone  overlain  have  competency  produced  competent alteration  contributed of the  areas o f t h e f e l s i c  felsic  by  mylonite. localization  felsic prior to  This  rocks to  this  rocks  of  during  onset  of  process  by  even  u n i t may a l s o have been  further. affected  i n t h i s manner.  The mafic  lower c o n t a c t o f t h e f e l s i c pyroclastic  interdigitating.  unit This  is  p y r o c l a s t i c u n i t with the usually  transitional  area  gradational commonly  or  hosts  - 59 -  minor  sulphide  disseminated massive  pyrite  pyrite,  fragments  occurrences  sporadically  of  the  muscovite,  epidote,  felsic  carbonate,  orthoclase  and  late  grain  carbonate  size  zones  of  small  lenses  of  sphalerite.  Sulphide-rich  throughout  the  fragmentals  consists  is  felsic  re-crystallized  into  fine. fine  minor  Orthoclase  carbonate.  microveins  very  albite,  opaques.  f r i n g e d w i t h s e r i c i t e and some  to  from  ( P l a t e 3.7d).  Mineralogy quartz,  range  chalcopyrite  c h a l c o p y r i t e and  occur  pyroclastics  and  that  chlorite, is  often  With the e x c e p t i o n of  and  large  quartz  Fragments  masses  of  carbonate and i n d i s t i n g u i s h a b l e o x i d e s and  grains,  are  commonly  quartz,  sericite,  silicates.  Chemistry of the f e l s i c rocks i s not w e l l understood almost to  of  as  a l l o f the samples analyzed have undergone moderate  intense a l t e r a t i o n .  These samples are c h a r a c t e r i z e d  by  h i g h s i l i c a and potassium c o n t e n t s w i t h low i r o n , sodium and magnesium c o n c e n t r a t i o n s ( s e c t i o n  3.2.5  Greenstone  The  3.6).  Unit  greenstone  unit  forms  topographically  prominent  k n o l l s and r i d g e s over most o f the study a r e a , l a r g e l y owing to i t s greater resistance to erosion. ranges  from  20  to  140m  but  seldom  Thickness o f the u n i t  are both  the upper  and  -  lower c o n t a c t s exposed. over  the  central  60  The  part of  -  greenstone  the  map  forms a t h i n  area  veneer  with topographical  v a r i a t i o n s exposing the u n d e r l y i n g f e l s i c u n i t s and irregular Glacier  map  patterns.  (Figure 3 . 3 ) ,  cliff-forming, erosion.  Immediately  the greenstone  caused  by  near  but  it  the  could  of  Wishbone  i s characteristically  vertical  For the most p a r t ,  conformable,  north  causing  joints  greenstone  cross-cut  and  glacial  appears  to  be  stratigraphy  at  a  s h a l l o w angle i n the extreme n o r t h and south ends o f the  map  area.  Textures w i t h i n the greenstone range from weakly  foliated  hypidiomorphic  along  near  the  the  margins  center.  In  to  of  chlorite,  oxides.  epidote,  albite,  M a f i c phenocrysts,  distorted  to  distinguish  pyroxene.  Biotite  i s rarely  coarse-grained  thin  composed o f c o a r s e - g r a i n e d , p o r p h y r i t i c  section,  albite  carbonate  r e p l a c e d by  and  i t is  in a  matrix  iron-titanium  chlorite,  psuedomorphed observed  fine-grained,  are  hornblende  in thin  too from  section.  In  one s e c t i o n round masses o f c h l o r i t e and opaques pseudomorph what appears  t o have been o l i v i n e .  Coarse  albite  crystals  are t y p i c a l l y f r a c t u r e d , n o n - a l i g n e d and i n c i p i e n t l y  altered  t o v e r y f i n e g r a i n e d masses o f s e r i c i t e and carbonate, which i n d i c a t e s t h a t they are not p o r p h y r o b l a s t i c .  The  o r i g i n of the greenstone u n i t  i s ambiguous.  Fine-  g r a i n e d massive outcrops and g r a i n s i z e changes over 4 t o 5m  61  -  intervals coarsely On  are  suggestive  map  area,  changes  in  ilmenite  basalt  c r y s t a l l i n e texture  g l a c i a l l y polished  the  of  suggests  but  quantity  suggest  flows. an  outcrops, i n the  subtle  the  -  a  distinct and  layered  grain sill  Elsewhere,  the  intrusive origin.  west c e n t r a l p a r t  of  layering  defined  by  size  albite  and  of  (Plates  3.2d  and  e).  Chemical a n a l y s e s of t h i s u n i t d i s p l a y an e x t e n s i v e range of compositions a t t r i b u t e d t o both hydrothermal a l t e r a t i o n  and  original  inhomogeneity.  6.9  percent  (with  plausibly changes  T  i°  consistent  explained within  by  v a l u e s range from 0.62  2  A  l °3  v  2  crystal  correlative  a  l  u  e  ) '  s  this  settling  than  basalt  to  is  by  flows.  more  magmatic Chemical  s i m i l a r i t y among the greenstone, the m a f i c p y r o c l a s t i c s , the It  chlorite schist i s probable  sill  that  the  3.6)  suggests a g e n e t i c  greenstone  represents  t h a t i s comagmatic w i t h the m a f i c e x t r u s i v e  3.2.6  a  link.  gabbroic  rocks.  A l t e r a t i o n Units  Two units?  alteration i n part  significance many  (section  and  to  locations  assemblages  are  assemblages  mapped  t o emphasize them because o f mineral their  exploration,  protolith  was  but  The  former  s i g n i f i c a n t whereas the  as  separate  their  also  possible  because  unidentifiable.  quartz-muscovite-carbonate  carbonate-quartz-hematite. volumetrically  were  is  and  in The  ferruginous  widespread  and  later is restricted  t o narrow, s t r u c t u r a l l y c o n t r o l l e d zones.  - 62 -  Quartz-muscovite-carbonate intensely  within  developed  the f e l s i c  locally  greenstone u n i t . 60m  thick  and  within  schists  tuff  a r e developed  unit,  however,  a l l other  units  They occur as conformable as  large,  irregular  most  they a r e  except  the  l e n s e s from 1 t o  cross-cutting  zones,  p r i m a r i l y i n t h e n o r t h e r n p a r t o f t h e study a r e a ( F i g . 3.2). On t h e south s i d e o f Wishbone g l a c i e r , which c u t s a c r o s s the north-central equivalent  study  area,  thickness  a  200m  high  cliff  o f quartz-muscovite-carbonate  t h a t i s o v e r l a i n by a t h i n l a y e r o f greenstone In t h i s  (Plate  an  schist 3.2a).  area, remnants o f u n a l t e r e d rock, which a r e up t o  30m square, can be seen.  Foliation  remnants, t h e a l t e r e d s c h i s t s , bound t h e a l t e r e d zone. remnants, relative (Plate  exposes  which  and t h e u n a l t e r e d r o c k s t h a t  R e a c t i o n rims around t h e u n a l t e r e d  a r e d e f i n e d by  abundance,  carbonate  a r e deformed  3.1f) which  i s c o n s i s t e n t among the  suggests,  into  composition and  similar  although  style  folds  not unequivocally,  t h a t f o l d i n g post-dates the a l t e r a t i o n .  Outcrops and hand specimens o f t h e quartz-muscovitecarbonate distinctive  schist  are pale  bleached  usually obliterated. q u a r t z , muscovite, opaques.  Relative  grey  t o creamy  appearance.  Primary  yellow  with  textures  a  are  Mineralogicaly, the s c h i s t s consist of  carbonate,  albite,  proportions  of  and minor p y r i t e and  quartz,  carbonate  and  muscovite a r e v a r i a b l e , which i s l i k e l y  a r e f l e c t i o n o f the  protolith  form  composition.  Felsic  rocks  muscovite  and  63  -  -  q u a r t z - r i c h s c h i s t s t h a t are p a l e grey t o s i l v e r y - w h i t e extremely footing richer  friable. can  be  (On  steep  slopes  treacherous.)  i n carbonate,  more  The  of  more  competant,  mafic  and  from creamy y e l l o w t o p a l e orangey-brown. t h e carbonate, as determined dispersive  system  of  a  this  material, units  range  are  i n colour  The compostion  q u a l i t a t i v e l y u s i n g the  scanning  and  electron  of  energy  microscope,  is  h i g h l y v a r i a b l e , even w i t h i n the same sample, but i s u s u a l l y a  form  of  pyroclastic schists  iron-bearing rocks  with  fuchsite.  tend  bright  green  Typically,  rocks i s very  fine.  to  dolomite. form  The  maroon,  carbonate-quartz-muscovite  micaceous  spots  inferred  g r a i n s i z e w i t h i n a l l o f the Coarse  mafic  to  be  altered  g r a i n e d bands o f quartz  and/or  carbonate and p o r p h y r o b l a s t i c cubes of p y r i t e , up t o 2cm,  do  occur  to  locally.  pre-date  the  Formation later  of  phases  the  of  muscovite  deformation  s e c t i o n s d i s p l a y c r e n u l a t e d muscovite minimal  appears  as  most  thin  flakes or grains with  recrystalization.  Chemistry characterized magnesium  of by  and  this  high  silica  is  and  Ratios of  distinctive,  potash  from  3.6).  Zr  sodium,  a l t e r a t i o n samples a n a l y z e d are l i t h o l o g i c a l l y d i s t i n c t  2  and  low  that  (section  Ti0  and  and  suggest  the m a f i c u n i t s  iron.  unit  -  Origin  of this  conformable  hydrothermal  activity  g r e a t e r than  altered  zones  an area  entire  alteration  i s uncertain. associated  and a r e i n t e r p r e t e d  cross-cutting  the  -  lenses are s p a t i a l l y  silicification  pervade  64  with  t o have  zones o f  formed  related to mineralization. a r e more  problematical.  r o u g h l y 4 by 4km and extend  200m.  Some o f t h e  The a l t e r a t i o n  stratigraphic  and u n a l t e r e d  sequence.  rock  appears  The l a r g e  These  zones  t o depths o f  t o c u t through  Contacts  a r e commonly  from  between t h e  g r a d a t i o n a l but  l o c a l l y , they can be sharp.  F e r r u g i n o u s carbonate a l t e r a t i o n zones form r u s t y weathering the  quartz-muscovite-carbonate  carbonate both  areas a l o n g f a u l t s  and f r a c t u r e s .  alteration  typified  and  chemical  by  pervasive  ferro-magnesium  minerals,  reasons.  carbonate commonly  conversion o f ilmenite t o r u t i l e  from  Chapter 4.  These  zones  zones  are  replacement accompanied  Carbonate  f i n e - g r a i n e d massive  of coarse-grained  calcite.  The  unit f o r  of  by  the  ( o r anatase) and hematite.  Contacts are t y p i c a l l y g r a d a t i o n a l . v a r i a b l e and range  Unlike  the ferruginous  i s best-developed w i t h i n t h e greenstone  structural  fillings  conspicuous  botryoidal,  are discussed  textures are t o open  colloform i n more  space  ferroan  detail  in  -  3.3  -  65  Structure  3.3.1  Introduction  Four  phases  of  folding  are  recognized  S t i k i n e Assemblage rocks exposed w i t h i n the degree  and  intensity  of  deformation  within  folding  are  deformation  Arch.  interpreted  anticline.  which o v e r l i e the only  a  The  this  Stikine  minor  area  is  Assemblage  of  recumbent  structures  and  phases were  refolded  chevron f o l d s , and  a gentle  Late Stikine  single  study area.  phases  earlier  t r e n d i n g k i n k s and  undergone  Two  from  These  plunging  (Chapter 2), have  Stikine  fabrics.  into easterly northward  the  the  within  anomalous r e l a t i v e t o o t h e r exposures of rocks  within  phase  Triassic  sediments  Assemblage  volcanics  of  folding  and  are  describe  the  v i r t u a l l y f r e e of metamorphic e f f e c t s .  The  purpose  structural  of  i n t e r p r e t the  metamorphism,  structural other  this  section  characteristics,  mapping, and and  of  of  to  determined  relationships  alteration  s t y l e of the exposures  as  is  and  from  between deformation  mineralization.  study area i s then compared to the  Stikine  field  Assemblage  within  The that the  S t i k i n e Arch area.  Relative  ages  of  the  structural  determined from cleavage i n t e r s e c t i o n s  and  elements  were  cleavage-bedding  -  relationships, The  lack  of  or  a  well  from  66  -  folding  defined  of  linear  stratigraphy  and  markers p r e v e n t s a c l e a r understanding of  structures. stratigraphic  the  earlier  fold  morphologies, however, t h e i r o r i e n t a t i o n s r e l a t i v e t o structures  were  determined  from  stereonet  later  analysis,  and  approximate f o l d s t y l e s i n f e r r e d from minor s t r u c t u r e s .  3.3.2  S t r u c t u r a l Sequence  All  Paleozoic  moderate  to  structural 3.1.  rocks w i t h i n  intense  the map  deformation.  elements a s s o c i a t e d  F o l d s t y l e s and  area have undergone A  summary  of  the  w i t h each phase i s i n Table  o r i e n t a t i o n s are  summarized i n  Figure  3.5.  The trending  earliest fold  structures  (FI)  set, recognized  by  are  observed, but  with westerly  i s interpretted.  is  s e t has  been m o d i f i e d  superimposed  recumbent w i t h Mess Creek. coincident  an  it.  a l a r g e recumbent Morphology o f  a second f o l d  The  interpretted  second  fold  closure  to  set  (F2)  phase  this which  is  also below  Both phases are i s o c l i n a l i n s t y l e , w i t h  nearly  Penetrative  w i t h the  northwest and axial  second f o l d  planer  the  fold  east,  f o l d axes t r e n d i n g  respectively. associated  upon  by  planer  Map-scale f o l d hinges  o f t h i s phase are not  fold  northwesterly  r e f o l d i n g of a x i a l  cleavage, l i n e a t i o n s and minor f o l d s .  closure  a  north-northwest, foliation  phase i s the  dominant  (S2) rock  TABLE 3.1  PHASE  FOLD STYLE  Summary of Structural Elements of Stikine Assemblage Rocks, Mess Creek Area, Northwestern, B.C.  PLANAR  STRUCTURES  LINEAR  STRUCTURES  MINERAL GROWTH  ORIENTATION  SQI Compositional layering/bedding Similar; isoclinal S c a l e unknown R o o t l e s s minor f o l d s observed  S^: A x i a l foliation  planar  Similar; t i g h t to isoclinal Some r o o t l e s s m i n o r folds Sub-round t o angular h i n g e on m i n o r f o l d s  S2: A x i a l foliation  planar  Q  C h e v r o n t o K i n k Band F o l d s , low a m p l i t u d e open, p a r a l l e l f o l d s and warps  4  P a r a l l e l and open Folds are tighter t o t h e west  L^: I n t e r s e c t i o n S and S  between  1  L^: I n t e r s e c t i o n between S. and - mineral lineations L^: I n t e r s e c t i o n between S. and S^; c r e n u l a t i o n c l e a v a g e and p e n c i l lineations Lg: K i n k B a n d / C h e v r o n f o l d axes  AC j o i n t s east-west  oriented  muscovite, c h l o r i t e , e p i d o t e , a l b i t e and others  northwesterly  minor polygonalizat i o n o f f o l d e d sheet silicates carbonate growth  northnorthwesterly  east-west to northeasterly  northerly  - 68 -  F-j  Tight - Isoclinal (refolded?) Fold axes trended NE Axial planes dipped moderately NW Greenschist facies metamorphism  Large scale Fold - Thrust structure  Summary of fold styles and orientations within the Stikine Assemblage, M e s s Creek area, northwestern B.C.  -  f a b r i c i n the a r e a . chevron  folds  developed along  an  -  69  Phase 3 f o l d s range from k i n k bands and  to  broad  open  warps.  east-west  (F4)  orientation.  i s manifested  north  trending  with  this  They do  antiform.  phase.  direction.  not  are  The  significantly  f o u r t h phase of  as a l a r g e , open, There  Planar  are  no  fabrics  s t e e p e r d i p p i n g away from the study  and  folds  i n S2 cleavage and have v a r i a b l e t r e n d s , g e n e r a l l y  a l t e r the geometry o f mapped c o n t a c t s . folding  These  assymmetrical,  fabrics  become  associated  progressively  area i n a  southwesterly  T h i s c o u l d be caused by an i n c r e a s e i n  tightening  of  fourth  phase  folds  in  amplitude  a  westerly  direction.  3.3.3  Stereonet a n a l y s i s  Structural microcomputer. written  by  Woodsworth  data  were  plotted  Both p l o t t i n g  Pigage  (1986)  (1983).  Data  f o l i a t i o n s , l i n e a t i o n s , and  Distinction  between  and  on  stereonets  contouring  following plotted  the  by  programs were algorithm  include  poles  of to  f o l d axes.  first  and  second  phase  fold  axes  and m i n e r a l l i n e a t i o n s i n the f i e l d was  not u s u a l l y p o s s i b l e  and  on  t h e r e f o r e these  (Fig.  3.6),  with  a  which  maximum  data  shows a  are  plotted  relatively  concentration  of  a  single  diagram  homogeneous data points  at  set  155°/00°.  - 70  The  weaker  data.  concentration  F3  fold  axes  at  have  -  300°/08° might  a  maximum  azimuth of 075° with a 20° plunge. is  a f u n c t i o n of the d i p o f F2  due  to  FI  concentration  at  an  The  be  plunge  foliation  direction  surfaces.  A  plot  of poles to f o l i a t i o n  i s not p a r t i c u l a r l y  informative (Fig.  3.6).  two  F4  It  shows  considerable  This  square.  F3  data  The  virtually  f o l d s on was  of F3  earlier  taken  from  the  f o l d s and data  a  antiform warps.  i s seen i n  small  with  area  The  Figure  about  50m  average F3 f o l d a x i s p l o t s a t 075°/20° which i s  identical  to  poles to f o l i a t i o n s . circle,  limbs  d i s p e r s i o n caused by  e f f e c t s o f the 3.6d.  the  confirming  the  fold  L2 and that  F2  the  axis  c a l c u l a t e d from  f o l d axes l i e along a F3  fold  style  is  the  small  parallel  (Ramsey, 1967).  3.3.4  F o l d Sets and Deformation F a b r i c s  Outlines  of  phase  1  and  phase  2  folds  were  not  observed, with the e x c e p t i o n o f minor f o l d s , and most o f the information  about these  tectonic fabrics. and  phases i s d e r i v e d  from a n a l y s i s of  Because the major hinge areas o f phase 1  2 f o l d s were not known and phase 3 f o l d s were s m a l l  pervasive,  separation  of  the  homogeneous s t r u c t u r a l data was  map  area  into  not p o s s i b l e .  domains  and of  Figure 3.6  Contoured Stereonet Plots of Structural Data from the Mess Creek Area, Northwestern B.C.  72  -  -  Compositional l a y e r i n g can be it and  epiclastic  except  unit,  where  i s usually  i n the hinge  display  along  region  a  to  primary  3.8).  lineations  Ll  bedding  Most  plane  ( L l ) can be seen.  lineations  form  straight  r e g i o n s o f F2 similar  and  inhomogeneous  of  simple  phase 1 minor f o l d s  phases  outcrops  then  In t h i n  generally  rock SO/SI  section,  c l e a v a g e formed  from  intersect  lines  minor f o l d s , type  2  as  they  It  1967),  has  been r e f o l d e d  appear  t o be  by t h e  approximately  The the  folds  formed  is difficult  from phase 2 f o l d s  F2  to  by  discern  i n outcrop as  second  Where a  both first  phase, the  co-axial.  SI L2  over  indicating that  (Ramsey,  shear.  cross  o c c u r as f l a t t e n e d , r o o t l e s s i s o c l i n a l f o l d s . phase f o l d  layering,  (S0/S2) a t angles between 5 and 20 degrees.  lineations  hinge  folds.  bedding.  (S2), however i f the  can be seen t o be a c r e n u l a t i o n  (Plate  to  compositional  o f minor  foliation  intersection lineations  are  i t i s equivalent  parallel  only a single  fractures  Ll  but  i s b e s t developed and p r e s e r v e d i n the m a f i c p y r o c l a s t i c  Foliation  S2  found i n most u n i t s ,  two  Intersections  o f SI and S2 a x i a l p l a n e r cleavages o c c u r i n the hinge areas of F2 minor f o l d s and produce  a coarse crenulation  cleavage  (S2) w i t h attendant p e n c i l l i n e a t i o n s t h a t a r e e q u i v a l e n t L2 are  i n orientation. generally  co-linear  to  flattened either  figures defined lenses  or  Fragments w i t h i n  Ll  with or  L2.  the  the p y r o c l a s t i c axis  Large  of  scale  units  elongation interference  by bedding were not observed, but r a r e ,  fragments  of  felsic  ash  within  a  to  mafic  fine  matrix  - 73  appear 3.1h)  to  be  deformed  into  -  interference  patterns  which approximate a 31 type (Ramsey, 1967).  of pattern  previously  two  fold  described  axes  data.  i s small;  Figure  r e l a t i o n s h i p between the f i r s t and  Lithological  contact  foliations  and  with  illustrates  the  second phase f o l d s .  geometry  bedding  3.7  r e g i o n o f e i t h e r phase i s not the  F2  hinge may  and  the  indicates  The bands,  have  folds,  chevron and  northeasterly  plunge i n the  o f the a n t i f o r m . trend.  Kink  throughout the 1980)  Mapping suggests  kink  and  broad  40m.  of  warps.  On  the  eastern  band f o l d  east-northeasterly  opposite  The  former  t o a few metres, whereas  s i n g l e kink to  open  plunges are c o n t r o l l e d by the d i p of F2 Folds  The major hinge  t h i r d phase o f deformation i s c h a r a c t e r i z e d by  range from 2 t o  antiform,  F2  3.4)  range i n s i z e from m i c r o s c o p i c later  and.  (see  chevron  east  Fl  Mess Creek  cross sections: Figure  the  relationships  that  recognized.  l i e to  the  consistent  f o l d s are l a r g e s c a l e recumbent s t r u c t u r e s .  that  T h i s type  forms where recumbent f o l d s are r e f o l d e d and  a n g l e between the  between  (Plate  s i d e o f the axes  F4  generally  trends.  foliation  d i r e c t i o n on  the  Fold  surfaces.  the western  side  Conjugate kink bands s t r a d d l e an east-west bands  and  study  area  chevron and  folds  represent  along a n o r t h - s o u t h d i r e c t i o n .  are  shortening  pervasive (Wiess,  - 74  FIGURE 3.7  -  Schematic i l l u s t r a t i o n o f superimposed f o l d i n g o f t h e S t i k i n e Assemblage, Hess Creek area, northwestern, B.C. F^ and F_ a r e recumbent i s o c l i n a l f o l d phases w i t h s u b - p a r a l l e l a x i a l p l a n e s and s l i g h t l y d i v e r g e n t f o l d axes.  - 75 -  The f i n a l phase of f o l d i n g antiform This  plunging  fold  gently  in  north-northeast  direction.  has m o d i f i e d a l l p r e v i o u s s t r u c t u r e s .  Limbs are  planer to gently curving. having  been  sericite  (F4) i s expressed as an open  mostly  a  The  eroded.  s c h i s t s immediately  hinge  r e g i o n i s not  Mylonitization  of  3.3.5  greenstone  slip.  Faults  Rocks w i t h i n the map of  incompetent  below the competent  u n i t suggest t h a t t h i s f o l d formed by f l e x u r a l  exposed  faults  limited  and  offset  a r e a are a f f e c t e d by a m u l t i t u d e  fractures.  Relatively  are u b i q u i t o u s .  The  minor  greenstone  faults unit  with i n the  e a s t - c e n t r a l study area i s segmented by o r t h o g o n a l f r a c t u r e s which are are commonly open, up depths to  be  o f o f up t o 30m. caused  by  Potential particularly faults  are  extend  to  of  the  underlying  quartz-  schists.  for in  wide, and  These open f r a c t u r e s are presumed  instability  carbonate-muscovite  t o 2m  foliation  attenuated  difficult  to  fold  parallel hinges  recognize  thrust is  during  faults,  high.  field  These  mapping,  e s p e c i a l l y i n areas o f metasomatic a l t e r a t i o n ; consequently, s u b s t a n t i a l amounts of movement c o u l d o c c u r a l o n g f a u l t s be  undetected.  Faults  of  this  type  are  interpretted  and to  cause the p a r t i a l r e p e a t s o f f o l d e d s t r a t i g r a p h y i n the area n o r t h o f Wishbone G l a c i e r  ( F i g . 3.3).  - 76 -  Easterly faults  and  to  northeasterly  fractures  These f a u l t s ,  which  localized  A-C  by  Displacement  on  Northeasterly lateral  near  vertical  a r e common throughout the map commonly host m i n e r a l i z a t i o n ,  joints these  directed,  strike  trending,  slip  related  to  structures steeply  faults  fourth  appears  dipping  with  up  area.  could  phase  to  be  folds.  minimal.  normal and/or  to four  be  left  kilometers  of  l a t e r a l d i s p l a c e m e n t occur i n t h e western and n o r t h e r n p a r t s of  study  shuffled along  area  ( F i g 2.2).  slices  of Paleozoic  t h e Mess Creek v a l l e y  s t r u c t u r e s may  Related  structures  limestone (Souther,  into  may  have  younger  rocks  1971).  These  a l s o have been t h e l o c u s o f u p l i f t ,  same  bringing  t h e S t i k i n e Assemblage rocks up through Mesozoic s t r a t a .  3.3.6  S t r u c t u r a l Comparisons o f t h e Study Area w i t h o t h e r Exposures o f t h e S t i k i n e  Comparison  Assemblage  of the s t r u c t u r a l  style  between t h e study  a r e a and nearby exposures o f s t r a t i g r a p h i c a l l y s i m i l a r r o c k s reveals  some  difference  marked  i s i n t h e development  S t i k i n e Assemblage rocks  are  well  The  most  pronounced  of deformational  fabrics.  r o c k s immediately e a s t o f Mess Creek and  south o f S p a h l e r Creek  bedding p a r a l l e l rocks  differences.  foliation. preserved.  ( F i g . 2.2)  display  a  single,  Primary t e x t u r e s w i t h i n t h e s e Demonstrable  Permian  aged  77  -  -  v o l c a n i c l a s t i c rocks along the n o r t h s i d e o f Sphaler 12km  Creek,  southeast of Mess Creek, a l s o show a s i n g l e p e n e t r a t i v e  cleavage, u s u a l l y p a r a l l e l contain  mineral  t o bedding.  assemblages  A l l of these  compatible  with  rocks  greenschist  f a c i e s metamorphism.  Differences  in  deformation  style  are  S t i k i n e Assemblage rocks exposed i n u p l i f t s  exhibited  by  throughout  the  S t i k i n e Arch.  M i s s i s s i p p i a n l i m e s t o n e near the Scud R i v e r ,  15km  of the study a r e a , shows l i t t l e  northwest  deformation  (Pitcher,  limestones,  along the northwest  are  deformed  into  1961).  isoclinal  n o r t h e r l y t r e n d i n g axes (1984)  describe  near-isoclinal  However, p o s s i b l e Permian edge of  and  (Souther,  within  the  diapiric 1971).  north-northwesterly  folds  evidence  four  Stikine  trending  fault-bounded  age  Arch,  structures Nelson  of  and  with Payne  tight  to  blocks  of  S t i k i n e Assemblage rocks near the c o n f l u e n c e o f the Taku and Tulsequah Arch.  rivers,  the  w e s t - c e n t r a l edge o f the  contain  Payne, 1984).  The  east-central  mid-Pennsylvanian  block hosts  fusilinids  Deformation  study  (Nelson  o f the northernmost  which c o n t a i n s a l i t h o l o g i c a l s u i t e t h a t the  limestones  A l l of the b l o c k s are metamorphosed t o  greenschist facies.  of  Stikine  S t r a t i g r a p h i c c o n t i n u i t y e x i s t s w i t h i n the b l o c k s but  not between them. which  on  lower block,  i s s i m i l a r to that  area—including quartz-sericite  more i n t e n s e than the o t h e r b l o c k s  and  ( J . Nelson,  schists,  is  pers.comm.,  - 78 -  1985).  The  massive  Polaris-Taku  gold-silver  and  Tulsquah  Chief  s u l p h i d e d e p o s i t s occur w i t h i n these r o c k s .  3.3.7 Timing o f Deformation  Timing o f deformation  is critical  t e c t o n i c h i s t o r y o f t h e study a r e a .  t o understanding t h e  The r e l a t i v e t i m i n g o f  d e f o r m a t i o n t o metamorphism and a l t e r a t i o n can be determined from  the  analysis  relationships constraints  of  and to  rock  fabrics.  radiometric  be  Stratigraphic  dates  placed  on  some  within  deformed  of  allow the  temporal  def ormational  events.  Micro-fabrics  metamorphic m i n e r a l s were formed early  part  of  t h e second  3.4.3).  Evidence  indicate  that  thermal e f f e c t s . carbonate folding  within  phases  foliation  formed  and t h e  events  (section  synkinematic  crystals  o f deformation  prior  related  altered-unaltered  rock  t o t h e second  to this  formed from c r e n u l a t e d muscovite of  that  outlasted  The l a r g e areas o f quartz-muscovite-  alteration as  indicate  during the f i r s t  deformational  of s t r a i n  the l a t e r  rocks  grains.  phase  phase o f  i s commonly  Localized  c o n t a c t s suggests  that  some o f t h e a l t e r a t i o n o c c u r r e d p r i o r t o f o l d i n g .  folding  at least  - 79 -  A potassium-argon date on chrome-bearing muscovite from the  s e l v a g e s o f a c a r b o n a t e - s u l p h i d e v e i n y i e l d e d an age o f  192+7 Ma.  T h i s v e i n , and o t h e r s l i k e i t , a r e undeformed and  emplaced i n f r a c t u r e s  ( p o s s i b l y A-C j o i n t s r e l a t e d t o f o u r t h  phase f o l d s ) t h a t c u t a l l deformation f a b r i c s and kinkbands i n d i c a t i n g that E a r l y J u r a s s i c m i n e r a l i z a t i o n post-dates a l l but t h e l a s t phase o f deformation.  Upper T r i a s s i c  (Norian)  deformed  Paleozoic  oriented  chevron  folds. fault  rocks d i s p l a y folds  Therefore, emplaced,  sediments t h a t  and  these  prior  large  broad,  rocks  were  t o the t h i r d  overlie  intensely  amplitude,  open, likely  easterly  north  trending  deposited,  and f o u r t h  or  phase o f  f o l d i n g but a f t e r t h e e a r l y phases o f i s o c l i n a l f o l d i n g .  Absolute timing more d i f f i c u l t .  o f t h e e a r l y phases o f deformation i s  Differences  exposures o f P a l e o z o i c  i n t h e s t r u c t u r a l s t y l e among  r o c k s w i t h i n t h e S t i k i n e A r c h may be  a t t r i b u t e d t o one o r more o f t h e f o l l o w i n g :  (a) L o c a t i o n — d e f o r m a t i o n may be l o c a l i z e d by  proximity  t o a major s t r u c t u r e o r i n t r u s i v e complex.  (b) L i t h o l o g y — a l t e r e d , o r otherwise l e s s competant r o c k s w i l l become more s t r a i n e d than t h e competant r o c k s which surround them.  - 80 -  (c) A g e — p r e - P e r m i a n deformation r e s u l t e d i n an additional  fold  phase  Evidence f o r a pre-Permian  within  o r o g e n i c event  the older  rocks.  i s s l i g h t . Monger  (1977) has documented t h e disappearance o f a t l e a s t  1,500m  o f M i s s i s s i p p i a n s t r a t a over a 5km l o n g t r e n d j u s t south o f the study area, which suggests a profound pre-Lower Permian unconformity—although  the r e l a t i o n s h i p  i s complicated  by  faults.  I f t h i s was an e r o s i o n a l unconformity, t h e products  of  e r o s i o n a r e not observed  that  within  the rock record.  Although t h e v o l c a n i c rocks w i t h i n Permian s t r a t i g r a p h y a r e similar  t o those  associated  within  the Mississippian  limestones  Mississippian  are  quite  limestones a r e t y p i c a l  sections,  different.  the The  o f those d e p o s i t e d on  seamounts whereas t h e Permian l i m e s t o n e s a r e p l a t f o r m a l i n c h a r a c t e r (Monger, 1977). does n o t imply  an orogeny  v a r i o u s exposures structural  styles,  metamorphic  unequivocally,  b u t appear  that  a  growth single  f o r one.  Assemblage have t o have  The r e l a t i o n s h i p mineral  metamorphism took  so much as a l l o w  of the S t i k i n e  metamorphic event. and  T h i s change i n d e p o s i t i o n a l  shared  between  place during or a f t e r  The  differing t h e same  fold textures  suggests, episode  sites  of  although  not  dynamothermal  Permian time, b u t  p r i o r t o Upper T r i a s s i c time.  Souther period took  (1971)  of u p l i f t ,  defined  folding,  p l a c e between Middle  t h e T a h l t a n i a n orogeny  as a  metamorphism and i n t r u s i o n  that  and Upper  This  Triassic  time.  - 81  orogeny  accounts  for  mid-Triassic  time  west-central  British  Read  and  study  that  boundary  is  at  hiatus  recognized  1977).  supports,  for this  depositional  Cloumbia  Okulitch,  area  the  -  in  early  to  throughout  most  of  (Souther,  1971;  Deformational  the  orogenic  very  history  least,  event.  The  White,  the  of  upper  Tahltanian  1959; the time  Orogeny  appears t o be c o n f i n e d t o the S t i k i n e Terrane (Monger,  1977;  Read and  part  and  Okulitch,  could  form the  3.4  be  predominately  related to  the  i n the  amalgamation  western  of  blocks  which  terrane.  Metamorphism  Paleozoic history  of  Relative  of  possibly  overprinted  by  metamorphism outlasted  within  of  peak  metamorphism  these  study  metamorphism changes  syngenetic,  i s not  potassium  Triassic  lower  greenschist  metamorphism by  area  have a  t e x t u r a l changes  pre-Upper  overprinted  retrograde  the  and  metasomatism,  timing  Extensive,  largely  rocks  mineralogical  hydrothermal  and  1977)  strain  and  complex  incurred  and  by  deformation.  well  understood.  metasomatism  is  regional  dynamothermal  facies.  Deformation  metamorphic  features.  textures  are  L o c a l l y , prograde  e f f e c t s have been superimposed upon r e g i o n a l by  Early  Jurassic  hydrothermal  alteration.  -  82  -  PLATE 3.1  a)  Rhyolite breccia of f e l s i c p y r o c l a s t i c unit. elonation of c l a s t s p a r a l l e l to f o l i a t i o n .  b)  T h i n bedded r o c k s o f t h e m a f i c p y r o c l a s t i c / e p i c l a s t i c u n i t . Beds v a r y f r o m f i n e - g r a i n e d c h l o r i t e s c h i s t s t o l a p i l l i tuffs.  c)  C l o s e up p h o t o g r a p h o f t h e m a f i c p y r o c l a s t i c / e p i c l a s t i c u n i t showing a l a p i l l i t u f f l a y e r . Venticular, h e t e r o l i t h i c fragments s i t i n a c h l o r i t e - e p i d o t e m a t r i x . Note p r e s e r v e d v e s c u l a r fragment i n c e n t e r o f p h o t o , p o s s i b l y r e p r e s e n t i n g a s m a l l b a s a l t i c bomb. -  d)  E p i v o l c a n i c l a s t i c b r e c c i a t r a n s i t i o n a l from m a f i c pyroclastic to f e l s i c pyroclastic unit. The l a r g e fragment i s i t s e l f fragmental i n d i c a t i n g reworking o f volcanic material. Fragment shape which c o u l d r e p r e s e n t an i n t e r f e r e n c e f i g u r e p r o d u c e d by p o l y p h a s e folding. L e n s c a p i n b o t t o m l e f t c o r n e r i s 55mm i n diameter.  e)  Coarse felsic  f)  U n a l t e r e d remnant o f m a f i c e p i c l a s t i c m a t e r i a l i n quartz-muscovite-carbonate schist. Reaction haloes a r o u n d t h e remnant a r e more c a r b o n a t e - r i c h and a p p e a r t o be i s o c l i n a l l y f o l d e d .  g)  Greenstone-felsic pyroclastic contact. Contact i s s h a r p and u n d u l a t i n g . F e l s i c u n i t i s u n a l t e r e d but displays small-scale i s o c l i n a l folds in earlier f o l i a t i o n with a x i a l planes p a r a l l e l to the greenstone contact.  h)  Ash fragment i n m a f i c e p i c l a s t i c u n i t which d i s p l a y s a t y p e 31 (Ramsey, 1967) i n t e r f e r e n c e p a t t e r n i n d i c a t i n g two p h a s e s o f t i g h t f o l d i n g w i t h s m a l l a n g l e s b e t w e e n f o l d axes. V e r t i c a l s t r u c t u r e s a r e c a u s e d by l i g h t r e f l e c t i n g from water f l o w i n g over the o u t c r o p .  crenulation cleavage pyroclastic unit.  (microlithon  Note  structure)  in  P L A T E 3.1  - 84 -  P L A T E  3.2  a)  View a c r o s s Wishbone G l a c i e r showing c l i f f face composed of quartz-muscovite-carbonate s c h i s t o v e r l a i n by a t h i n l a y e r of greenstone. The appearance of a f l a t - l y i n g l a r g e i s o c l i n a l f o l d i s p a r t l y caused by t a l u s a l o n g the base of the c l i f f and an a c t u a l f o l d s t r u c t u r e c o u l d not be s u b s t a n t i a t e d . The greenstones e r i c i t e s c h i s t c o n t a c t d i s p l a y s s m a l l - s c a l e f o l d s on the r i g h t hand s i d e of the photograph.  b)  View l o o k i n g northwest a c r o s s the Wishbone G l a c i e r showing l a r g e zone of s e r i c i t i c a l t e r a t i o n . Area i n c e n t e r of photograph i s l a n d s l i d e d e b r i s . Note the stratabound nature of i n t e n s e s e r i c i t i c a l t e r a t i o n between m a f i c p y r o c l a s t i c u n i t and carbonate a l t e r e d greenstone (orange) i n l e f t c e n t e r of photograph.  c)  Laminated c h l o r i t e s c h i s t u n i t w i t h i s o c l i n a l f o l d e d quartz and c a l c i t e l a y e r s . Orange c o l o u r e d area r e f l e c t s l a t e oxidation feature.  d)  Greenstone u n i t showing laminar t e x t u r e d e f i n e d c o n c e n t r a t i o n s of o l i v i n e and i l m e n i t e .  e)  M a f i c p y r o c l a s t i c / e p i c l a s t i c u n i t showing t h i n beds of e p i c l a s t i c m a t e r i a l w i t h i n t e r b e d l a y e r s of carbonate (pale brown l a y e r 5cm above the top o f the hammer handle).  f)  Weathered s u r f a c e o f the greenstone u n i t showing composition changes d e f i n e d by c o n c e n t r a t i o n of plagioclase crystals.  by  subtle  PI A T F 3 ?  - 86 -  PLATE  3.3  a)  Unmetamorphosed, f o s s i l i f e r o u s Late T r i a s s i c (Norian) a r g i l l i t e and c h e r t on western edge of the study area. G r a n i t e b o u l d e r conglomerates forms the c l i f f outcrop i n the upper r i g h t c o r n e r of the photograph.  b)  Laminated ash t u f f and a r g i l l a c e o u s t u f f d i s p l a y i n g i s o c l i n a l f o l d s ( F ) and conjugate k i n k bands ( F ) . 1  c)  3  Shallow, n o r t h w e s t e r l y p l u n g i n g minor f o l d nose(s) i n f e l s i c t u f f - s e r i c i t i c alteration units. First fold phase f o l i a t i o n ( S ) has been r e - f o l d e d producing a " p e n c i l cleavage". 1  d)  L_ l i n e a t i o n s , produced by i n t e r s e c t i o n of two s e t s o f a x i a l p l a n a r cleavage (S. and S_), i n f e l s i c t u f f u n i t . Kink bands are r e l a t e d t o t h i r d phase of deformation and Fe-carbonate f i l l e d f r a c t u r e s may r e p r e s e n t A-C j o i n t s r e l a t e d t o the f o u r t h phase of deformation.  e)  Chevron f o l d i n g (F_) i n s t r o n g l y f o l i a t e d f e l s i c c r y s t a l - a s h t u f f . Quartz b l o b w i t h minor p y r i t e i s t y p i c a l o f m a t e r i a l i n f o l i a t i o n - p a r a l l e l quartz v e i n s .  f)  Fe-carbonate impregnated v o l c a n i c bombs (see P l a t e 3.1c) i n c h l o r i t e s c h i s t u n i t . Pen i s 14cm l o n g .  g)  R e - f o l d e d f o l i a t i o n , p r o d u c i n g coarse c r e n u l a t i o n cleavage t h a t has been r e - f o l d e d i n t o a chevron-type f o l d by t h i r d phase o f deformation.  PLATE 3.3  -  88 -  PLATE 3-4 Photomicrographs o f S t i k i n e Assemblage Rocks, Mess Creek Area, Northwestern, B.C.  a)  C a r b o n a t e - s e r i c i t e - r i c h fragment, showing p e r v a s i v e second phase f o l i a t i o n , i n f e l s i c t u f f u n i t . Note s t r a i n shadows around rounded p y r i t e g r a i n i n t h e upper l e f t c e n t r a l p a r t o f t h e photograph. S c a l e i s t h e same as P l a t e b.  b)  P e r v a s i v e S f o l i a t i o n (lower l e f t t o upper r i g h t ) a t a s m a l l angle t o c o m p o s i t i o n a l l a y e r i n g . Quartza l b i t e - c a r b o n a t e - r i c h l a y e r (lower) i n c o n t a c t w i t h a s e r i c i t e - c h l o r i t e - o p a q u e - r i c h l a y e r (upper).  c)  S e r i c i t e , c h l o r i t e , opaques, q u a r t z , a l b i t e , carbonate and e p i d o t e i n a f e l s i c ash t u f f . Quartz-carbonater i c h layer i s p a r a l l e l to f o l i a t i o n . S c a l e i s t h e same as i n P l a t e b.  d)  Carbonate p o r p h y r o b l a s t s ( ? ) and v e r y f i n e q u a r t z - r i c h e l i p t i c a l fragments i n f e l s i c ash t u f f . Scale i s the same as i n P l a t e b.  e)  Quartz and a l b i t e p h e n o c r y s t s and l i t h i c fragments i n a crystal-lithic tuff. M a t r i x i s composed o f c h l o r i t e , s e r i c i t e , q u a r t z , carbonate and opaques.  f)  Q u a r t z - a l b i t e v e i n l e t i n a mass o f a n t i g o r i t e from shear zone i n a l t e r e d greenstone u n i t .  g)  A l b i t e c r y s t a l s separated by rims o f c h l o r i t e , s e r i c i t e , b i o t i t e and opaques i n greenstone u n i t .  h)  S p r i g s o f t r e m o l i t e on t h e edge o f r e l i c o l i v i n e g r a i n i n greenstone u n i t . O l i v i n e i s mostly r e p l a c e d by c h l o r i t e , quartz and opaques. M a t r i x i s predominantly chlorite.  2  PLATE 3.4  -  90  -  PLATE 3.5 Photomicrographs o f Deformation Textures i n S t i k i n e Assemblage Rocks, Mess Creek Area, Northwestern, B.C.  a)  C r e n u l a t i o n cleavage developed i n s e r i c i t e ( t a l c ? ) r i c h layer i n quartz-sericite-carbonate schist. Cleavage d i s p l a y s minor o f f s e t s . Same s a c l e as t h a t o f P l a t e b.  b)  C r e n u l a t e d muscovite-quartz-carbonate s c h i s t . Crenulat i o n cleavage i s preserved i n muscovite whereas q u a r t z r i c h domains have r e c r y s t a l l i z e d . S c a l e b a r should read 0.1mm.  c)  Micro k i n k bands (F_) i n S cleavage muscovite-carbonate s c h i s t .  d)  Same rock as i n P l a t e c b u t a t g r e a t e r m a g n i f i c a t i o n . S. f o l i a t i o n i s s u b - v e r t i c a l , S_ c r e n u l a t i o n cleavage i s d i a g o n a l (lower r i g h t t o upper l e f t ) . S_ cleavage t r a c e s d e f i n e d by r e s i d u e o f i n s o l u b l e opaque m a t e r i a l . S c a l e b a r should read 0.1 mm.  e)  Isoclinal micro-fold (F ) of quartz-rich layer i n sericite-quartz schist. S c a l e i s t h e same as P l a t e c.  f)  Same specimen as P l a t e e, showing w e l l - d e f i n e d a x i a l p l a n a r c r e n u l a t i o n cleavage ( S ) . S c a l e i s t h e same as P l a t e c.  2  of quartz-  2  2  g)  Broad spaced c r e n u l a t i o n cleavage i n c h l o r i t e s e r i c i t e schist. S c a l e i s t h e same as t h a t i n P l a t e c.  h)  C r e n u l a t i o n w i t h cleavage d i s c o n t i n u i t i e s i n c r y s t a l ash t u f f . O r i g i n a l (S.) f o l i a t i o n t r e n d s d i a g o n a l l y a c r o s s photograph (lower l e f t t o upper r i g h t ) . An F. f o l d c l o s u r e appears t o be present i n t h e c e n t e r o f t h e photograph. S_ cleavage d e f i n e d by t h i n b l a c k l i n e s ( i n s o l u b l e opaques); some w i t h minor o f f s e t s . Scale i s the same as P l a t e c.  PLATE 3.5  -  3.4.1  92  -  MineralogyM i n e r a l assemblages were determined  and p o l i s h e d t h i n s e c t i o n a n a l y s i s . phases  was  scanning  done  with  electron  the  thin  V e r i f i c a t i o n of mineral  energy  microscope  p r i m a r i l y from  dispersive  or  X-ray  system  of  diffraction  a  where  appropriate.  Many o f the t h i n s e c t i o n s were o f specimens so  fine  that  grained  identified  The  only  the  main  mineral  could  predominant  mineral  assemblages  pyroclastic/epiclastic  units  and  their  The greenstone  are  mainly  and  composed  c h l o r i t e , e p i d o t e , a l b i t e , carbonate and opaques. was  be  optically.  i n t e r p r e t e d p r e c u r s o r s are i n T a b l e 3.2. mafic  phases  of  Tremolite  o n l y observed w i t h i n specimens t h a t p r e v i o u s l y c o n t a i n e d  olivine, unit.  and  in a  Biotite  single  is  w i t h i n the greenstone areas  of  these  specimen  rare.  Coarse  to  The  chlorite  but  other  the  chlorite  plagiclase  phenocrysts  are  distinguish  from  schist unit l i k e l y  pre-metamorphic  typically T a l c may  muscovite  fine  The  can  core  masses  of  be p r e s e n t but i s in  thin  c o n t a i n e d primary  minerals  schist  phenocrysts  a r e psuedomorphed by a l b i t e .  s e r i c i t e , carbonate and e p i d o t e . difficult  of  only  be  section. carbonate inferred.  The metamorphic m i n e r a l assemblage i n c l u d e s Mg-rich  chlorite  (indentified  epidote,  by  berlin  blue  interference colour),  a l b i t e , q u a r t z , carbonate and r a r e t r e m o l i t e .  TABLE 3.2 Summary of Mineral Changes due to Metamorphism, Stikine Assemblage Rocks, Mess Creek Area, Northwestern, B.C.  METAMORPHIC MAFIC  PRIMARY  TUFFS  MINERALS FELSIC  MINERALS (inferred)  GREENSTONE  TUFFS  Olivine  Tremolite Chlorite Magnetite Antigorite  Hornblende/ Augite  Chlorite  Chlorite Tremolite Carbonate  Chlorite  Biotite Carbonate  Plagiclase  Albite Chlorite Epidote Carbonate  Albite Chlorite Epidote Carbonate  Albite Muscovite Carbonate  Muscovite Quartz  Graphite  Quartz  Keolinite^" Calcite  1.  See S e c t i o n  Carbonate  4.3  TEXTURES OF SECONDARY  MINERALS  Pseudomorphs  Orthoclase  Quartz  ARGILLITE  Quartz  Quartz  Muscovite  Muscovite  Carbonate  Carbonate  Pseudomorphs, medium-grained euheral aggregates, fine-grained i r r e g u l a r masses Albite Muscovite Carbonate  Pseudomorphs, fine-grained i r r e g u l a r masses  Muscovite Quartz  Irregular  masses  Graphite Carbonate  Accicular Irregular  crystals masses  Quartz  Generally,  Carbonate  reduced  grain  Fine  sheath-like  Fine  to coarse anhedral  size  aggregates grains  - 94  The of  felsic  quartz,  -  t u f f u n i t i s c h a r a c t e r i z e d by an  muscovite,  carbonate,  albite  C h l o r i t e and e p i d o t e are l o c a l l y p r e s e n t . muscovite-carbonate  assemblage  metasomatism ( s e c t i o n 4.3), rich  assemblage  textures,  before  particularly  inconclusive  in  alteration  being of  metamorphism.  muscovite and  chlorite  folding  therefore  opaques.  quartz-  reflects  potassium  have been a  kaolinite  metamorphosed.  Mineral  muscovite  establishing  and  and  which may  and  The  likely  assemblage  the  and  chlorite,  relative  However,  are  timing  virtually  of .all  i s c r e n u l a t e d by the second phase o f both  alteration  and  metamorphism  preceeded t h i s event.  Argillaceous carbonate,  schists  ACF  indicate  muscovite, hematite),  epidote.  main metamorphic m i n e r a l and  AKF  that  metamorphosed  diagrams rocks within  of  assemblages are d i s p l a y e d  ( F i g . 3.8; the the  equivalent  Turner  (1968).  to  the The  Miyashiro,  S t i k i n e Assemblage  have  (Greenwood, 1976).  albite-epidote-amphibolite lower  1973),  and been  quartz-albite-epidote-biotite  s u b f a c i e s o f the g r e e n s c h i s t f a c i e s is  quartz,  C o n d i t i o n s o f Metamorphism  The on  of  g r a p h i t e and minor opaques ( p y r i t e +/-  a l b i t e , c h l o r i t e and  3.4.2  consist  temperature  boundary  This  facies for  of this  - 95 -  Q  calcite  dolomite  Figure 3.8 Mineral assemblages which define metamorphic grade of the Stikine Assemblage rocks, Mess Creek area, northwestern B.C. projected on ACF, AKF and QCM diagrams. Shaded areas show the common mineral assemblage of the quartz—albite-epidote-biotite subfacies of the greenschist facies (Greenwood, 1976) Stipled areas show the rare assemblage containing tremolite.  - 96 -  f a c i e s i s 300°C and i s r e c o g n i z e d by the absence o f z e o l i t e s (Winkler, 1974). is usually +  quartz  The upper boundary, i n t h e o r d e r o f 450°C,  i n d i c a t e d by the r e a c t i o n :  = biotite  assemblage (Winkler,  + almandine + H 0.  The  2  i s stable  over t h e range  from  albite-epidote  1 to 7  kilobars  of  chlorite  1974).  Composition  and  mineral  schist  unit  are  3.8).  The  occurence  mapping  c h l o r i t e + muscovite  but  best  could  assemblages  displayed of  not  talc  be  on  the  was  QCM  the  diagram ( F i g .  suspected  confirmed by  X-ray  t e c h n i q u e s , consequently t h i s phase i s o m i t t e d diagram.  However,  tremolite-carbonate Greenwood,  pers.  an  equilibrium  was  comm.,  1982).  in  thin  field  diffraction from t h e  assemblage  observed  from  of  QCM  quartz-  sections  (H.  formed  from  I f tremolite  e i t h e r of the r e a c t i o n s : 5 t a l c + 6 c a l c i t e + 4 quartz = 3 t r e m o l i t e + 6 C 0  + 2  2  H 0. 2  or 1 t a l c + 2 dolomite + 4 quartz = t r e m o l i t e + 4 C0  2  then a minimum temperature f o r a g i v e n P and X ( C 0 ) can be 2  determined  from  an  isobaive  T-X(C0 ) 2  diagram  ( F i g . 3.9a).  An upper temperature c o n s t r a i n t i s p r o v i d e d by t h e r e a c t i o n : 3 c a l c i t e + 2 quartz + t r e m o l i t e = 5 d i o p s i d e + 3 C 0 The  absence  stipled  area  o f both t a l c i n Figure  and  3.9b,  diopside, indicates  represented  2  +  H 0.  by  the  2  a temperature range  o f 420° t o 530° f o r X(C0 ) between 0.1 and  0.9.  -  Buffering within  of  the  pore  calc-silicate  increasing mechanism  X(C0 ) 2  97  -  fluid  rocks  (Fig.  f o r generating  by  metamorphic r e a c t i o n s  drive  3.9c) C0>  2  the  and rich  fluid  suggests fluids  towards  a  possible  during  prograde  metamorphism.  3.4.3  Timing o f Metamophism  T e x t u r a l evidence suggests t h a t metamophism took p l a c e during  the  early  stages  diminished during l a t e r synkinematic t o crenulation  cleavage  undulatory  quartz with  stages.  crumpled  heating  but  had  greatly  M i n e r a l growth was  largely  foliation.  earlier  A  silicates  pronouced with  only  Deformation twins w i t h i n carbonates  extinction  are u b i q u i t o u s .  slight  deformation  formation of e a r l y  minor p o l y g o n a l i z a t i o n . and  of  ( p r o g r e s s i v e subgrains)  within  These t e x t u r e s g e n e r a l l y d i s a p p e a r  (D.  Murphy,  pers.  comm.,  t h e r e f o r e deformation must have o u t l a s t e d thermal  1984)  and  effects.  REACTION L I S T isemblages on t h e l e f t a r e s t a b l e on t h e : high side of the Y-axis v a r i a b l e , or the high side of the X-axis v a r i a b l e f o r v e r t i c a l 1) : 2) : 3) : 4) : 5) : 6) : 7) i 8) : 9) : 0.1  0.2  0.3  0.4  0.5  0.6  X(C02) at P =  0.7  0.8  reactions  2 C02 + D i = Do + 2 aQz H20 + 3 C02 + S D i = 3 C C s s + 2 aQz + T r Wo + C02 » aQz + CCss 3 C02 + T c + 3 CCss = 3 Do + 4 aQz + H20 7 C02 + T r + 3 CCss - 5 Do + 8 aQz + H20 4 D i + Do + C02 + H20 = T r + 3 C C s s 2 H20 + 6 C02 + 3 T r - 6 C C s s + 4 aQz + 5 Tc 4 C02 + T r - 2 Do + 4 aQz + T c H20 + C02 + T r + Do = 3 C C s s + 2 Tc  0.9  2000 bars ID CO  Oil  0.J  0.3  0.4  0.5  X(C02) at P =  B Figure 3.9A. B.  T-X Q C  2  0.6  0.7  0.8  0.9  2000 b a r s  °-  C  1  °.2  0.3  0  >  4  0.5  XCC02) at P =  0.6  0.7  0.8  0.9  2000 b a r s  diagram for the system CaO-SiC^-COg-HgO at P*2 Kbars from G E O C A L C (Perkins et. a I., 1986).  Shaded.area indicates the stability field for the quartz-calcite-tremolite + dolomite assemblage with  diopside and talc absent.  C. Arrows show reaction path towards increasing X Q Q ^  pore fluid during prograde metamorphism.  if reactions buffer the  -  3.5 Age  of the S t i k i n e Assemblage rocks w i t h i n the  study area i s u n c e r t a i n . within  the  C o r r e l a t i o n of S t i k i n e Assemblage  Stikine  Permian and  Mississippian  also  f o r example,  exist;  Middle  -  of the S t i k i n e Assemblage  P r e c i s e age  rocks  99  Pennsylvanian  Arch  is  limestones. i n the  of  the  fusilinids  study  area  on  fossiliferous  However, o t h e r  Tulsequah map have  l i m e s t o n e s w i t h i n r o c k s t h a t are those  based  been  sheet  and  area,  recovered  lithologically  (Nelson  ages  from  similar  Payne,  to  1984) .  A r g i l l a c e o u s limestones a d j a c e n t t o the F o r r e s t K e r r R i v e r , 30km  southeast  conodonts  (P.  of  the  Read,  map  pers.  area,  contain  comm.,  1983).  Lower  Devonian  Stratigraphic  evidence i n d i c a t e s t h a t a M i s s i s s i p p i a n age i s most p r o b a b l e f o r r o c k s w i t h i n the t h e s i s a r e a .  Other methods f o r age with  regards  to absolute  and  conodonts,  unsuccessful. Jurassic  ages  from  the  Isotopic for  d e t e r m i n a t i o n were i n c o n c l u s i v e  age.  Attempts  appropriate dating  alteration  to obtain zircons lithologies,  methods and  indicate  mineralization.  were Early A  - 100  whole-rock  -  rubidium-strontium  isochron  on  altered  A  potassium-  u n a l t e r e d rocks g i v e s a date o f 201+16 Ma. argon  date  fuchsite  of  193±7  Ma  from  the  taken  was  obtained  selvage  from  of  a  and  muscovite  and  carbonate-sulphide  vein.  3.5.1  Stratigraphic  Evidence  Stratigraphy  of  the  M i s s i s s i p p i a n age  on  the b a s i s o f s t r a t i g r a p h i c  with  an  overlying,  Monger, with  1970)  thesis  fossiliferous  l o c a t e d 1km  Permian  area  fossils  has  limestone  also  occur  side  of  the to  west  the  Mess  stratigraphic  conformable  can  be  assumed.  Creek,  maintaining  relationships  in  direction  Permian  area,  along the  the  accordance  Creek,  contain Mississippian  of  limestones east  appropriate with  s t r u c t u r e c e n t e r e d w i t h i n the  Limestones,  pers.  study  limestone  I f t h i s contact i s then  the  area.  Anderson,  tuffs  Mississippian  north-trending a n t i c l i n a l  (R.  Calcareous  the  east of  12km  1972;  overlie  approximately to  (Souther,  west.  at  a  continuity  the  t o the west (Souther, 1972).  younging  assigned  to  immediately least  been  the map  southeast o f the head waters o f Mess  comm.,  assignment f o r the study a r e a .  (Visean t o Namurrian) 1988)  supporting  fossils  this  age  - 101 -  3.5.2 I s o t o p i c Dating Methods  Thirteen were c a r r i e d  whole  rubidium-strontium  out on a l t e r e d  from  t h e study  date  was o b t a i n e d  vein  rock  area  style  mineralization  according  to  A single  chromium muscovite  d e t e r m i n a t i o n s were performed U.B.C.  and u n a l t e r e d rocks  (Table 3.3).  from  the  determinations  (Table  potassium-argon associated with  2.1).  All  i n t h e geochronology  methods  collected  described  in  age  labs at Thorstad  (1983) .  Typically, can be used  Rb-Sr  determinations  t o determine  on m i n e r a l  separates  metamorphic ages, w h i l e whole rock  d e t e r m i n a t i o n s g i v e t h e o r i g i n a l age o f t h e rock.  On h i g h l y  a l t e r e d o r metasomatized r o c k s , as i s t h e case here, rock  Rb-Sr  determinations  give  the  alteration  r e f l e c t i n g p a r i t a l t o complete r e - e q u i l i b r a t i o n o f ratios.  whole age,  Sr: Sr  An i s o c h r o n c a l c u l a t e d by t h e York (1976) technique  of l e a s t squares r e g r e s s i o n g i v e s an age o f 201+16 Ma ( F i g . 3.10).  Potassium-argon  determinations  on  chromium  muscovite  g i v e s a date o f 192±7 Ma., i n d i c a t i n g an E a r l y J u r a s s i c age for mineralization. K-Ar  ages  suggests  Consistency  between t h e Rb-Sr and t h e  that the a l t e r a t i o n 87  are r e l a t e d .  The samples w i t h h i g h  Rb/  and m i n e r a l i z a t i o n 86 S r e x e r t t h e most  c o n t r o l on t h e s l o p e o f t h e i s o c h r o n and thus t h e a s s i g n e d  -  age.  the Early  isochron rocks. the  -  These samples were c o l l e c t e d  Telluride vein to  102  (section  i n the v i c i n i t y  4.2.1) which  i s apparently  Jurassic mineralization.  does  not i n d i c a t e  The p a u c i t y  o f the related  T h e r e f o r e t h e Rb-Sr  t h e metamorphic  age o f  these  o f i n t r u s i v e r o c k s o f t h i s age w i t h i n  a r e a makes i t u n l i k e l y t h a t  ages have been r e s e t  by a  r e g i o n a l thermal event.  The  a l t e r a t i o n and m i n e r a l i z a t i o n  ages a r e s i m i l a r t o  t h o s e o b t a i n e d from i n t r u s i v e phases a t t h e G a l o r e Creek and Schaft al.  f  (Fig.  Creek  1968)  porphyry  and  185+6  2.7), s u g g e s t i n g  may be a s s o c i a t e d  deposits, Ma  circa  198+7  (Panteleyev,  1973)  that  a l t e r a t i o n and  with s i m i l a r p l u t o n i c  Ma  (White e t  respectively mineralization  activity.  Figure 3.10 Rubidium s t r o n t i u m isochron indicating a 2 0 1 ± 1 6 M a date for metamorphic and metasomatically altered samples from the Stikine Assemblage, Mess Creek area n o r t h western B.C. Isochron calculated using a regression analysis after York (1967). R b - S r data is given in Table 3.3. 1  TABLE 3.3  R u b i d i u m - S t r o n t i u m Data f o r Rocks from t h e S t i k i n e Mess C r e e k A r e a , N o r t h w e s t e r n B . C .  Assemblage,  Sr  87 Sr/ 8 Sr  ppm Rb  Rb/Sr  226  8.7  0.038  0.111  0. 70406  130°57'10"  162  17.6  0.109  0.315  0. 70644  57°07'30"  130°59'00"  1883  61.0  0.032  0.094  0. 70594  Quartz-muscovite schist  57°09'08"  130°58'10"  195  33.9  0.173  0.502  0. 7064  81-BJ136b  Greenstone  57°09'50"  130°57'40"  65.7  68.5  1.043  3.02  0. 7127  81-BJ144a  Quartz-muscovite  57°11'30"  130°56'30"  119  21.5  0.181  0.524  0. 7064  81-BJ134a  Chlorite-muscovite carbonate s c h i s t  57°10'20"  130'57'45"  418  31.4  0.075  0.217  0. 7059  81-BJ173  Greenstone  57°10'50"  I S O ^ ' O S "  243  0.8  0.003  0.009  0. 7042  81-BJ181d.  Chlorite-quartz  57°06'40"  130°59'00"  165  49.2  0.298  0.864  0. 7078  81-BJ181e  Chlorite-muscovite schist  57°06'40"  130°59'00"  226  84.3  0.373  1.078  0. 7082  81-BJ181f  Muscovite-quartz schist  57°06'40"  130°59'00"  9.1  88.0  9.70  28.399  0. 7860  81-BJ181g  Chlorite  57°06'40"  130°59'00"  533  16.7  0.031  0.091  0. 7047  81-BJ188  Greenstone  57°10'20"  130°58'50"  173  4.4  0.025  0.074  0. 7061  SAMPLE I . D .  DESCRIPTION  LATITUDE  LONGITUDE  81-BJ23d  Chlorite  57°09'10"  130°57'15"  81-BJ24a  Quartz - c h l o r i t e muscovite s c h i s t  57°08'40"  81-BJ27  Metapelite  81-BJRC4  schist  schist  schist  schist  ppm Sr  '  - 105  3.6  -  Chemistry  3.6.1  General Statement  Chemical  compositions  the  study  the  lithological  area were determined  associated  map  with  according  units,  type of  alteration  chemical  or  rocks  clastic  classification  document to  plate is  chemical  classify  hampered  deposition.  changes  the  tectonic  inhomogeneity  schemes, such  from  chemically characterize  and  and  Classification and  to  to  alteration,  to  settling  o f S t i k i n e Assemblage rocks  by  as those  setting. metasomatic  caused  Therefore,  rocks  by  crystal  results  from  d i s c u s s e d below,  can  be m i s l e a d i n g and should be used w i t h c a u t i o n .  Virtually chemical loss  on  with  a  a l l o f the  modification. ignition minimum  v o l a t i l e s are C 0  rocks  Volatile  analyzed  show evidence  content,  as  2  2%  and  a  maximum  (carbonates), C  of  in either  range  21%.  The 2  Sulphur,  2+ caused  by  d e t e r m i n a t i o n o f LOI contents.  Major  by 10%  main (both which  s u l p h i d e o r s u l p h a t e m i n e r a l s , c o u l d be  s i g n i f i c a n t v o l a t i l e component i n the more a l t e r e d  Mass g a i n s  of  ( g r a p h i t e ) , and H 0  i n t e r g r a n u l a r and bound t o hydrous phases). occurs  indicated  (LOI) , i s g e n e r a l l y i n the of  of  the  o x i d a t i o n of  are i n s i g n i f i c a n t  element  analyses  F  plots.  samples.  3+ to  F  during  r e l a t i v e to v o l a t i l e  were  normalized  v o l a t i l e - f r e e b a s i s t o f a c i l i t a t e comparisons and use of c o n v e n t i o n a l chemical  a  to  a  a l l o w the  - 106 -  Sixty-three  rock  samples,  representing  thirty  sample l o c a t i o n s , were analyzed f o r major and t r a c e by X-ray f l u o r e s c e n c e methods.  one  elements  Results are discussed i n the  following sections.  3.6.2 Methods and Q u a l i t y C o n t r o l  Rock samples were c o l l e c t e d as square every  metre third  areas  o f unweathered  sample  c h i p s from two t o t e n outcrop.  was c o l l e c t e d  i n duplicate  chemical v a r i a n c e due t o sampling. collected samples,  from  adjacent  Approximately t o monitor  D u p l i c a t e samples were  outcrops  where  possible.  Rock  u s u a l l y from one t o t h r e e kg i n s i z e , were crushed  and  ground  t o -240 mesh.  The powdered samples were  and  l a b d u p l i c a t e s prepared  a t that  stage.  split  A l l elements,  except f o r g o l d , were a n a l y z e d on f o u r gram p r e s s e d powder pellets Brown  by X-ray  e t a l . (1973) .  performed procedures Horsky  fluorescence following  a t U.B.C. f o r major  Analyses  and data  r e d u c t i o n were  Equipment s p e c i f i c a t i o n s and o p e r a t i n g and t r a c e  e t a l . (1985) and Berman Acme  t h e technique o f  Analytical  elements (1979).  performed  by  Vancouver,  B.C., on lOg subsamples.  can be  found i n  Gold a n a l y s e s were  Laboratories  Limited  of  - 107 -  Analytical using  precision  was  the method o f Thompson and  Precision  a t the  90%  2  2  Na 0,  K 0,  2  T  2  and F e O  3  i0 '  '  M n 0  2  d u p l i c a t e samples  a  n  d  P  on  Howarth  confidence l e v e l  S i 0 ; + 5% f o r A 1 0 , CaO for  determined  t o t  lab duplicates  (1976  (n=19)  and  1978).  is +  ; + 7% f o r MgO;  2°5*  Variation  3%  for  and  10%  between  taken a t the sample s i t e i s approximately  t w i c e the a n a l y t i c a l v a r i a t i o n .  3.6.3  Major Element Chemistry and  Chemical provide 1971;  classification  consistancy i n  Cox  tectonic  et  classification  and  (Pearce  system  schemes  for  nomenclature  a l . . 1979)  setting  Classification  and  of  help  (Irvine  identify  Cann,  Irvine  volcanic  1975  and  and  rocks  Baragar,  original and  plate  1978).  Baragar  The  (1971)  is  l a r g e l y based on normative m i n e r a l c o n c e n t r a t i o n s c a l c u l a t e d from  major  element  classified  according to  determined  after  nomenclature sericite  abundances.  such  schist,  the as and  Rocks  this  system  method  of  K-rich picrite  of  (normative  Nixon  basalt basalt  the  for  study  mineralogy  (1985)) quartz  clastic  of  alteration  deposition)  (and/or of  these  unusual rocks.  yielded carbonate  for chlorite  These c l a s i f i c a t i o n s are i n a p p r o p r i a t e and r e f l e c t degree  chemistry  area  schist. the h i g h  caused  by  Nevertheless,  some  u s e f u l g e n e r a l chemical c h a r a c t e r i s t i c s can be d e r i v e d  from  e l e m e n t a l p l o t s used t o c l a s s i f y chemical d a t a .  TABLE 3.4  Sample  R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81 R81  1  -27 -78b -189a -189b -186 -181g -166b -126e -126f -136b -142 -143 -173 -176 -188 -126a -126b -144 -181f -190 -180 -184a -188C -188d -188f  . 2 Unit  ARGL PGST PGST PGST CHST CHST FVCS GRST GRST GRST GRST GRST GRST GRST GRST QMCS QCMS QMCS QCMS QMCS CALT CALT CALT CALT CALT  Average ARGL CHST QMCS CALT  -  Si0  Major Element Chemistry o f t h e S t i k i n e Assemblage Rocks, Mess Creek Area, Northwestern B.C., A n a l y t i c a l Techniques and P r e c i s i o n are Described i n Text  A 2  6 5 . 14 4 5 . 29 44 . 73 4 6 . 90 4 6 . 59 4 5 . 09 63 . 64 5 0 . 47 4 8 . 20 4 9 . 64 4 8 . 65 4 8 . 98 3 9 . 04 4 9 . 18 5 0 . 32 6 7 . 19 6 8 . 45 6 9 . 32 73 . 33 6 7 . 88 5 7 . 84 5 5 . 87 5 3 . 53 6 9 . 73 6 4 . 32  of field  l °3 2  17 . 65 1 5 . 65 14. 95 1 5 . 22 14. 15 13 . 99 1 5 . 06 1 5 . 68 14 . 88 17. 45 1 5 . 42 1 5 . 50 1 5 . 82 14 . 4 5 14 . 09 12 . 09 1 5 . 60 1 5 . 24 13 . 9 0 13 . 11 15. 91 1 8 . 58 1 6 . 16 1 2 . 36 13 . 90  FeO  6 . 00 10 .62 10 .33 9 .95 13 .26 13 . 37 7 . 64 14 . 83 14 .21 14 .21 15 .16 14 . 56 20 .96 13 . 67 16 . 10 4 . 86 4 .59 6 . 61 2 .46 6 . 58 8 .34 11 .75 13 .31 9 .24 9 . 06  and laboratory  MgO  2. 18 1 1 . 39 1 1 . 76 1 5 . 11 14. 90 1 5 . 85 6. 85 8. 30 8. 69 9. 59 9. 60 1 0 . 39 1 1 . 97 9. 18 7. 41 5. 55 3. 47 2. 95 4. 03 3 .78 4 .65 3 .60 3. 73 1. 34 1. 93  CaO  Na 0 2  2 .41 1. 84 4 .60 1 1 . 23 4 .10 1 1 . 83 6. 46 3. 73 6. 10 1. 78 7. 31 2 .21 3 .54 1. 79 4. 24 4. 11 7. 37 4. 4 1 2 .83 1. 8 5 5. 12 3 .06 4 .63 3 .46 2. 88 4 .58 7 .69 3 .74 3 .76 4 .17 5. 92 1. 64 2. 78 1. 79 2. 7 1 . 1. 32 0. 83 0. 23 6. 55 0. 76 8. 89 1. 46 4 .17 3 .88 7. 46 1. 25 2 .23 1. 21 4 .98 o. 8 1  duplicates  K 0  Ti0  3 .76 0. 35 0. 91 0. 98 1. 97 0. 86 0 .58 0. 33 0. 44 3 .93 1. 47 0 .82 0. 10 0. 49 0. 32 1. 72 2. 49 1. 7 1 4 .82 0. 5 5 2 .21 1. 74 3 .06 1. 82 2 .50  1. 00 1. 08 1. 33 0. 98 0. 89 0. 92 0 .66 2 .36 1. 97 1. 04 1. 87 1. 94 6. 68 1. 66 3 .66 0. 42 0. 59 0. 56 0. 28 0. 39 0. 66 0. 98 2 .22 1. 40 1. 97  2  2  MnO  P  0. 17 0. 10 0. 17 0. 17 0. 15 0. 12 0 .17 0. 17 0. 16 0. 17 0. 14 0. 15 0. 16 0. 09 0. 29 0. 17 0. 12 0. 13 0. 14 0. 17 0. 17 0. 17 0. 27 0. 17 0. 17  0. 24 0. 15 0. 20 0. 11 0. 15 0. 15 0. 11 0. 38 0. 37 0. 23 0. 36 0. 32 0. 61 0. 40 0. 53 0. 08 0. 27 0. 08 0. 03 0. 09 0. 12 0. 24 0. 33 0. 38 0. 3 1  2°5  Total  LOI  1 0 0 . 39 1 0 0 . 46 1 0 0 . 32 9 9 . 61 9 9 . 94 99 . 87 1 0 0 . 04 1 0 0 . 87 1 0 0 . 70 1 0 0 . 94 1 0 0 . 85 1 0 0 . 75 102 . 80 1 0 0 . 55 1 0 0 . 65 9 9 . 64 1 0 0 . 15 1 0 0 . 63 1 0 0 . 05 9 9 . 86 1 0 0 . 25 1 0 0 . 98 1 0 1 . 32 9 9 . 88 9 9 . 95  2 1 . 05 10 . 92 1 1 . 63 5. 59 5. 56 9. 61 1. 97 4 .33 1 1 . 46 4. 74 1 0 . 40 12. 71 5. 57 1 1 . 61 5. 17 9. 06 4 .90 12 . 47 3 .67 7 .72 14 . 60 7 .70 5. 80 8 .64 1 0 . 70  (see Appendix I ) .  Argillaceous s c h i s t u n i t , PGST - M a f i c p y r o c l a s t i c / e p i c l a s t i c u n i t , C h l o r i t e s c h i s t u n i t , FVSC - F e l s i c p y r o c l a s t i c u n i t , GRST - G r e e n s t o n e unit, Q u a r t z - m u s c o v i t e - c a r b o n a t e s c h i s t , QCMS - Q u a r t z - c a r b o n a t e - m u s c o v i t e schist, Carbonate a l t e r e d greenstone o r c h l o r i t e s c h i s t  TABLE 3 . 5  S e l e c t e d t r a c e element geochemistry  f o r rocks o f the S t i k i n e Assemblage, Mess Creek area, n o r t h e r n , B.C.  1  SAMPLE I.D. R81-27a R81-78b R81-126a R81-126b R81-126d R81-126e R81-126f R81-128a R81-136b R81-142 R81-143a R81-143b R81-144 R81-145b R81-166B R81-173a R81-175 R81-176a R81-180a R81-181a R81-181C R81-181d R81-181e R81-181f R81-181g R81-184 R81-186a R81-188 R81-188c R81-188d R81-188f R81-189 R81-190  ROCK TYPE ARGL PGST CQMS QCMS CHST CALT/GRST GRST ? CALT GRST GRST GRST QMCS GRST VFCS GRST CALT/GRST GRST ? QMCS QMCS CHST CHST QMCS CHST CALT/CHST CHST GRST CALT CALT CALT PGST QMCS  Nb  Zr  Y  Sr  £pm Rb  15 20 20 20 20  121 146 145 138 154  22 43 32 38 35  173 238 162 102 415  31 40 29 4 8  20 18 19  122 169 158  32 42 40  81 445 260  78 23 12  14  155  35  153  32  21  198  27  252  <1  20 18 17 14 24 18 17  99 114 99 110 271 64 110  26 39 26 18 <1 20 24  199 207 199 270 9 566 234  57 112 57 104 96 13 36  23  194  45  196  2  NI 13 208 45 62 32 20 23 3  23 8 22 110 4 33 11 3 5 5 11 11 58 4 63 5 4  15 17 18  See T a b l e 3.4 f o r d e f i n i t i o n o f r o c k  106 77 130  types.  24 25 32  1031 206 118 •  30 16 6  118  Cr  V  12 323 110 68 65 78 78 108 13 60 59 26 45 18 74 15 86 47 118 29 5 29 58 53 21 39 58 10 61 89 87 212  99 172 71 95 381 358 350 135 207 329 345 383 89 508 83 412 132 370 126 161 235 210 194 71 449 154 452 440 378 134 182 233  Ce  Nd  72 43 65 77 53 36 36  36 7 9 12 19 9 10  35 26 16 21 53 67 27 30 240 26 62 56 36 36 22 174 15 44 24 34 919 215 106 8 47  7 34 12 19 10 5 6 48 31 25 11 10 10 7 <1 48 5 14 18 14 15 <1 28 5 15  (PPb) Au 1 5  -  1 1 12 1  7 2 2  34 1 2 1 2 4 6 1 2 1 1  1 2  -  For t h e purposes field  duplicates  single  value  excessive discarded  and samples  MgO,  on  3.3).  negative  2  Outliers  a l t e r e d specimens. usefulness  of  classification  the from  fields.  an  these  been  analyses,  silica  and  along the  character  clusters  shown  ( F i g . 3.11),  between  bimodal  alkali-silica  of  normal  of  rock  a r e t h e more  plot  for  (non-potassic)  a  general  volcanic  rocks.  ( F i g . 3.12) w i t h t h e a l k a l i n e - s u b a l k a l i n e  area  cluster  (1971), shows t h a t rocks  within the b a s a l t  Samples w i t h i n t h e s u b a l k a l i n e f i e l d  most p a r t , v i s i b l y general  have  The two c l u s t e r s  d i v i d i n g l i n e o f I r v i n e and Baragar t h e study  to a  Cox e t a l . (1979) have demonstrated t h e  T h i s type o f p l o t  of  averaged  diagrams  correlations  demonstrate  compositions.  element  variation  2  axis  been  l a b o r a t o r y and  h i g h l y anomalous v a l u e s o r  Major  FeO, CaO, Na 0 and T i 0 .  silica  from  f o r lab duplicates)  Harker  typical  I I ) have with  (>+30%  (Table  graphically display  o f p l o t t i n g , data  (Appendix  error  -  110  altered.  classification  and  alkaline  a r e , f o r the  Rocks t h a t l i e o u t s i d e o f t h e  fields  suggest  extensive  chemical  m o d i f i c a t i o n i n v o l v i n g m o b i l i t y o f S i 0 , Na 0 and K 0 . 2  The  AFM  diagram  differentiate and Baragar, in  calc-alkaline 1971).  classifing  enrichment  ( F i g . 3.13)  rocks  trend  rocks  2  i s commonly from  tholeiites  T h i s p l o t i s not p a r t i c u l a r l y o f t h e study  of the a l k a l i e s  area,  but does  f o r the a l t e r e d  2  used  to  (Irvine effective show an samples.  -  I l l  -  P r e v i o u s l y r e p o r t e d analyses f o r S t i k i n e Assemblage v o l c a n i c rocks p l o t w i t h i n the c a l c - a l k a l i n e f i e l d o f the AFM (Souther, arc-type  1977)  and were i n t e r p r e t e d t o r e p r e s e n t an  (1977) demonstrated the use  triangular setting.  plot  2  study  and  3  counterparts.  The  area  origin  alumina  o f chemical  volcanic  rocks  by  tectonic  s u i t e s of  orogenic  belts  w i t h i n the  ( F i g . 3.14). due  to  fields  tholeiitic  indicating  rocks  A l t e r e d samples t r e n d  loss  of  Mg  and  p o i n t s i n d i c a t e s the  Fe.  overall  general  inconsistency area.  Chemistry  o f minor or t r a c e elements, p a r t i c u l a r l y  those  m o b i l i t y d u r i n g metamorphism o r a l t e r a t i o n ,  classifing  v o l c a n i c rocks  well-documented  (Pearce  and Winchester, 1978 elements  advantages  in  of  towards  The  t r e n d s w i t h i n the rocks o f the study  use  usually  of l i m i t e d  trace  3  average v a l u e s f o r the u n a l t e r e d u n i t s of  Trace Element  The  2  lower Fe/Mg r a t i o s than t h e i r  plot  apex  s c a t t e r o f data  3.6.4  classify  calc-alkalic  have more A 1 0  the  to  of an MgO-FeO-A1 0  T h i s i s based on o b s e r v a t i o n s l i k e those o f T i l l e y  (1950) t h a t  oceanic  island  setting.  Pearce  the  diagram  according  and  to t e c t o n i c setting  Cann, 1975;  and Holm, 1982).  for older,  classification chemically  G a r c i a , 1978; The use o f has  some  corrupted  for is  Floyd  'immobile' distinct terranes,  -112-  6 4 2 0 4 2  IT  0 -L  •i *  4 2 0 10  •  5 H  * o  A  -9-r  15  •  QMCS  •  GRST  •  PGST  io H  •  5  0CHST O  201510 • 5• 20-  2°5  ARGL  AFVCS  A  A 1  O  15 H  ft" '  ° o  n  10  40  50 60 % Si0  70  Figure 3.11 H a r k e r v a r i a t i o n d i a g r2a m s of m a j o r e l e m e n t geochemistry, Stikine Assemblage rocks, Mess Creek area, n o r t h w e s t e r n B.C. See Table 3.4 f o r e x p l a n a t i o n of legend.  CALT  F i g u r e 3.12 A l k a l i e s - S i l i c a p l o t of S t i k i n e R o c k s , Mess C r e e k A r e a . C l a s s i f i c a t i o n f i e l d s  Assemblage a f t e r C o x et  al_. (1979)  - 114 -  FeO t o t  Figure 3.13 AFM diagram for Stikine Assemblage rocks, Mess Creek area, n o r t h w e s t e r n B.C. Dashed line which sparates the tholeiitic field (upper) from the c a l c - a l k a l i n e field (lower) from Irvine and Baragar (1971).  -  including their types,  ease  secondary  115 -  large variation  o f measurement  processes  and r e l a t i v e  (Pearce,  their  use i s that a p p l i c a t i o n  basic  composition  by  partitioning  differentiating  i n order between  magma.  are not w e l l - s u i t e d setting.  However,  applied  i n c o n c e n t r a t i o n among magma  1974).  insensitivity  to  The d i s a d v a n t a g e s  to  s h o u l d be l i m i t e d  t o avoid fluid  unknown c h a n g e s  and  Therefore,  crystal  rocks  t o determine  phases  of plate  'immobile'  t h e parentage  caused in a  o f t h e study  for the determination the use o f  t o rocks of  tectonic  elements  of altered  area  c a n be  rocks  and  p o s s i b l y t h e degree o f a l t e r a t i o n .  Before their and  lack  Floyd  the so-called of mobility  (1977),  demonstrate and  Y  should  Pearce  the relative  among  others.  immobile  elements  c a n be  be e s t a b l i s h e d .  (1974),  and Pearce  immobility Although  Winchester  a n d Cann  o f t h e elements  these  elements  are s t i l l  addition Such  method Ti0  2  Zr,  Ti  have  processes,  s u s c e p t i b l e t o c o n c e n t r a t i o n changes by t h e  or subtraction o f other  changes  (1975)  may  l i m i t e d m o b i l i t y d u r i n g metamorphic o r a l t e r a t i o n they  used  c a n be d e d u c e d  o f Finlow-Bates  and Z r w i t h i n  a  from  rock-forming a Zr-Ti0  and Stumpfl rock  will  extent  o f magmatic d i f f e r e n t i a t i o n .  points  which  represent  magma w o u l d f o r m  (1981). vary  t h e products  2  components.  plot  T h e amounts o f  inversely  Therefore, of a  after the  with the  a series of  differentiating  a l i n e w i t h a n e g a t i v e s l o p e on t h e T i O v s  - 116 -  FeO Total  MgO  A 1  Figure 3.14 MgO - FeO (total) - A l 0 3 d i a g r a m for r o c k s of the S t i k i n e Assemblage, Mess C r e e k A r e a . S o l i d l i n e s divide t e c t o n i c e n v i r o n m e n t s ( a f t e r P e a r c e et a t , 1977). 2  2°3  - 117 -  Zr  diagram.  elements would  Dilution  due t o a d d i t i o n  drive  the  outlying  grouping  source.  to  by  towards  of  settling  the units  show  unit or  to  some  of  major  Al 0 /Ti0 , 2  3  2  units,  to and  3  trends that  the mafic  the f e l s i c  changes  Al O /100Zr  2  3.16) d i s p l a y among  from  A  possible pyroclastic  schists. may  different  spread  The  along  be  magma trends  o u t from t h e o r i g i n .  R a t i o s o f two r e l a t i v e l y i m m o b i l e effect  components  samples a  both  ( F i g . 3.15)  f o r the mafic  greenstone  or  o r away  lithology.  i s indicated  crystal  A l l of  radiating  of other  quartz-muscovite-carbonate  cluster  attributed  either  either  f o r the study area  2  d i f f e r e n t i a t i o n trend to  trend  The T i 0 ~ Z r p l o t  distinct  unit  concentration of  or subtraction  the plotted  the o r i g i n . shows  or  rock  minimize the  composition.  100Zr/TiO  suggest  elements  2  against  a comagmatic  a n d a d i s t i n c t magmatic  and q u a r t z - m u s c o v i t e - c a r b o n a t e  Plots  of  MgO ( F i g . relationship source f o r  alteration  units.  3 . 0 -  O ARGL  2 . 0  •  QMCS  •  GRST  •  PGST  AFVCS  Ti0 Wt.%  •  2  CALT  0CHST oo i  1 0 0  1 5 0  Zr (ppm) Figure 3.15.  Ti02-Zr diagram  f o r r o c k s of t h e  Stikine Assemblage, Mess C r e e k Area. D i s t r i b u t i o n t r e n d s with a negative slope i n d i c a t e t y p i c a l magmatic differentiation (Finlow-Bates and Stump, 1981). Trends towards o r away f r o m t h e origin reflect m u t u a l concentration or dilution due to s e c o n d a r y (alteration) processes.  2 5 0  -119-  O O X  o  • r-H  O ARGL  O O  *—I  X u  •  QMCS  •  GRST  •  PGST  A FVCS •  CALT  0CHST  3 0 -  O CO  2 0 -  CM 1 0 -  Figure 3.16 H a r k e r — t y p e v a r i a t i o n diagrams showing AlgOg/TiOg, A l 0 / 1 0 0 Z r a n d lOOZr/TiOg plotted against MgO f o r Stikine Assemblage Rocks of the Mess Creek Area. Segregation of the q u a r t z — m u s c o v i t e — c a r b o n a t e schist samples suggest t h a t these r o c k s were d e r i v e d f r o m the felsic pyroclastic unit. 2  3  - 120  -  CHAPTER 4. ECONOMIC GEOLOGY 4.1  Introduction  Gold and claim  group  s i l v e r m i n e r a l i z a t i o n was area  by  regional  stream  follow-up  work proved  returning  routine  sediment  values  of  alteration  types  survey.  with  75.4g/t  rock Au  over  noted  but  to  a  sampling  1.5m  wide  mineralization  relationships  m i n e r a l i z a t i o n , a l t e r a t i o n , l i t h o l o g y and  BJ  Initial  chip  A large v a r i e t y of  were  on the  consequent  geochemical  to  carbonate-sulphide vein. and  prospecting  encouraging up  discovered  among  s t r u c t u r e appeared  complex.  To date, i n s u f f i c i e n t work has been done t o formulate a specific  and  ization. of  the  predictive exploration  This  study  mineralization  general  geological  influenced, ization; alteration  the  documents the and  development the  r e l a t i v e to  tionists  discovery  mineralization. alteration  of  local  define  the  surface  may  mineral-  characteristics  characteristics  c o u l d a i d i n the e v a l u a t i o n  of  and  that  and  may  the those  mineral-  assist of  additional  known  strategy.  and  deposits  of e x p l o r a t i o n p o t e n t i a l and  development of e x p l o r a t i o n t o o l s and  and  explora-  mineralization of  or  dynamothermal  evaluation  of  with  and  in,  mineralization  plutonism  features  Comparisons  have r e s u l t e d  alteration  timing  metamorphism; and in  f o r the  a l t e r a t i o n i n order to: i d e n t i f y  processes t h a t  determine  model  the  -  4.2  -  121  Mineralization  A  variety  of  mineralization  around the p r o p e r t y and  the  primary  area.  types  not  the  (VMS)  exploration  deposits  focus  deposits  may  current  targets,  consist  presence  lapilli  be  of  tuffs;  of  crystal  ash  of massive p y r i t e and  it  but  are  Potential  for  VMS  stratabound  within  disseminated tuffs;  and  altered  chalcocite  2 to  8m  c h a l c o p y r i t e hosted by  long felsic  ( P l a t e 3.7e).  variety  of  showings (of v a r i a b l e and make  precious  target  fragments  zones  lenses  large  secondary  sulphide  a l t e r e d quartz  The  a  of  widespread, p a r t i a l l y  within  fragmental rocks  and  Volcanogenic massive  exploration.  i s i n d i c a t e d by:  alteration; felsic  of  within  A m a j o r i t y of the m i n e r a l i z a t i o n ,  m e t a l - b e a r i n g mesothermal s t y l e v e i n s . sulphide  occur  necessary  to  vein  types  and  the  o f t e n indeterminable  classify  veins  numerous  significance)  into  groups.  Five  groups o r v e i n t y p e s are d e f i n e d on the b a s i s o f morphology and  gangue and  of:  (1)  veins;  sulphide  mineralogy  foliation-parallel  quartz  (3) c a r b o n a t e - s u l p h i d e  arsenopyrite  veins;  groups  be  can  foliation-parallel  and  (5)  vague,  and  quartz  (Table  veins;  veins;  consist  quartz  breccia  D i s t i n c t i o n between  sometimes are  (2)  and  (4) carbonate-  others.  veins  4.1)  subjective.  commonly  deformed  The and  TABLE 4.1  M i n e r a l i z a t i o n C h a r a c t e r i s t i c s , BJ Prospect, Mess Creek Area, Northwestern B.C. GANGUE MINERALOGY  SULPHIDE MINERALOGY  Foliation parallel quartz veins  Quartz  Pyrite (Tetrahedrite, chalcopyrite, tellurides) Electrum  Silicification Sericitic Fuchsite Minor carbonatization  Foliation parallel, commonly folded discontinuous  Low  Quartz breccia veins  Quartz Fe-carbonate s i l i c i f i e d fragments  Pyrite Chalcopyrite Galena Tetrahedrite Sphalerite Arsenopyrite Hematite Gold  Silicifcation Sericitic CarbonatizatIon  Cross-cutting Structural control Stockworks Breccias  Variable 1 to 20 g/t Au: Ag - 1:1 to 1:1  Carbonate-sulphide veins  Ankerite, s i d e r i t e Manganiferous Fe-carbonates Quartz  Pyrite Sphalerite Chalcopyrite Freibergite Galena Arsenopyrite Gold  Fe-carbonates Sericitic Silicification Fuchsite Chlorite  Cross-cutting Fracture c o n t r o l l e d Tabular  Variable 0.5-50 g/t Au:Ag ~ 1:1 to 1:1  Arsenopyrite veins  Siderite Ankerite Quartz  Arsenopyrite Pyrite Sphalerite  Fe-carbonates Minor s e r i c i t e  Shear zones Lenticular Banded Brecciated  Low 0.1 to 2 g/t  Quartz A l b i t e veins  Albite Quartz Fe-carbonate  Pyrite ??  Weak, quartz carbonate  Irregular veins, plug?  Moderate to 7 g/t Au:Ag 1:3  Barite veins  Barite Jasper  Pyrite Chalcopyrite Tetrahedrite  Silicification Carbonatization  Narrow Sinuous Breccias  Moderate 3 - 7 g/t  VEIN TYPE  ALTERATION  MORPHOLOGY  GOLD GRADES  -  therefore  were  an  123  early  -  event,  possibly  related  to  dynamothermal metamorphism, whereas t h e o t h e r v e i n types a r e approximately  correlative  and g e n e t i c a l l y  related  t o an  E a r l y J u r a s s i c m i n e r a l i z i n g event.  4.2.1  F o l i a t i o n - P a r a l l e l Quartz  Foliation-parallel t h e study a r e a . within  quartz  veins  are ubiquitous within  They occur i n a wide v a r i e t y o f s i z e s and  a l l units  fracture  Veins  except  controlled  f o r t h e greenstone  cross-cutting  unit,  q u a r t z v e i n s occur.  where The  m a j o r i t y o f stratabound v e i n s appear t o be r e l a t e d , a t l e a s t temporally,  to  metamorphic-deformational  events.  These  v e i n s a r e from 0.5 t o 3m wide and 5 t o 50m l o n g and c o n t a i n traces of pyrite  and r a r e base metal  characteristically r u s t y weathering 2%  of vein  milky  and  Quartz i s  grained.  Euhedral,  coarse  carbonate c r y s t a l s u s u a l l y account  volume.  Weak  t o moderate  a l t e r a t i o n h a l o e s a r e common. envelopes  are  enrichment  o f precious  economically  sulphides.  deformed  significant,  sericite  L o c a l l y , v e i n s and a l t e r a t i o n  into  metals  intensity  for 1 to  isoclinal do o c c u r  contribute  folds.  Minor  and although, not  to soil  geochemical  anomalies.  The the  most s i g n i f i c a n t  Telluride  v e i n which  p a r t o f t h e study area  foliation-parallel i s located  ( F i g . 3.3).  quartz v e i n i s  i n the south-central  This vein i s f l a t - l y i n g ,  - 124  from  1 to  85m.  2m  thick  V e i n contacts  progressively  and  has  -  been  traced  for  approximately  are g r a d a t i o n a l w i t h w a l l rocks becoming  more  silicified  towards  the  vein  centre.  F o l i a t i o n of x e n o l i t h s w i t h i n the v e i n i s concordant w i t h that  of wall  vein.  Vein  rocks suggesting quartz  vitreous.  Fine  ranges  spots  of  'passive'  from  milky  rusty  and  sericitization  with  the  l i g h t . grey  and  carbonate  are  Alteration peripheral  wide haloes o f  patchy  Green muscovite, p o s s i b l y  to  weathering  d i s s e m i n a t e d throughout the v e i n . the v e i n c o n s i s t s of 3 t o 10m  emplacement of  silicification  development  f u c h s i t e , occurs  to  of  carbonate.  locally  as  unique  to  vein  selvages.  Sulphide property  and  sphalerite  mineralogy includes:  and  of  pyrite,  hessite  with  hematite, p y r r h o t i t e and noted  in  the  appear  to  vein.  Chip  amounts  field  be  of  morphologically assemblage  to  across  that  of  the  chalcopyrite,  tellurobismuthite,  T e l l u r i d e m i n e r a l s were  silvery single  the  metals.  stratabound,  indicates  traces  a  is  tetrahedrite,  bright,  restricted  precious  vein  electrum.  as  samples  the  sectile  location  vein  yielded  Although the  this  distinctive  i t i s unlikely to  be  w i t h the other f o l i a t i o n - p a r a l l e l quartz v e i n s .  spots  and  within  the  only vein  trace is  sulphide co-genetic  -  125 -  4.2.2 Q u a r t z - B r e c c i a V e i n s  Quartz-breccia steeply  veins  are  generally  d i p p i n g , and c o n t a i n a gangue mineralogy  by quartz w i t h minor carbonate are  cross-cutting,  common but not c r i t i c a l  or a l b i t e .  dominated  Breccia textures  t o the c l a s s i f i c a t i o n .  Large  a l t e r a t i o n envelopes  o f moderate t o i n t e n s e c a r b o n a t i z a t i o n  are c h a r a c t e r i s t i c .  Veins a r e t y p i c a l l y f r a c t u r e c o n t r o l l e d  and  well-defined  quartz-carbonate group.  with  sharp  stockworks  contacts,  are also  but  irregular  included  with  this  Vein trends are e a s t e r l y i n the northern part of the  map area and n o r t h e a s t e r l y i n t h e southern mineralogy pyrite,  i s typified  sphalerite  by  and  pyrite,  trace  part.  tetrahedrite,  amounts  of  Sulphide chalco-  arsenopyrite,  g a l e n a , hematite and g o l d .  Quartz much  and q u a r t z - b r e c c i a v e i n s  o f the prospect within  area  are distributed  b u t most  occur  Glacier.  On t h e n o r t h end o f t h e study area (Windy claim) a  current  surrounding  significant  showings  group o f e a s t e r l y  t h e area  of the  over  t r e n d i n g quartz v e i n s a r e t h e t a r g e t o f  exploration  (Folk,  1987).  These  p r i m a r i l y been exposed by hand-trenching the mafic p y r o c l a s t i c / e p i c l a s t i c u n i t , carbonate inferred grades  schists strike  t h e Wishbone  and greenstones.  over  have  and a r e hosted by  quartz-muscoviteThe main  l e n g t h o f 500m and widths  o f 7g/t o r more,  veins  v e i n has an  up t o 6m.  mineable widths,  Gold  a r e common  - 126 -  (Folk,  1988).  rare p y r i t i c alteration  Veins c o n s i s t  o f grey t o white  and s i l i c i f i e d w a l l envelopes  are  quartz with  rock fragments.  most  conspicuous  Carbonate within  the  greenstones.  Narrow t e t r a h e d r i t e intensely  carbonate  and g o l d  altered  b e a r i n g v e i n s w i t h i n the  greenstone  bluff  immediately  a d j a c e n t t o t h e n o r t h e a s t c o r n e r o f Wishbone G l a c i e r 3.2b)  a r e on  potential  strike  structure,  s t r i k e length  The  group.  This  t o the g l a c i e r ,  stockwork  belongs  stockwork  forms  a  with  a  (Plates  3.7a  and  g)  veins  relationships. that  t o the quartz-breccia a crackle  breccia  zone vein  within the  and c a r r i e s anomalous t o sub-ore grades o f  (0.1 t o 3.0g/t Au).  structure  and suggest  w i t h the McLaughlin Creek carbonate b r e c c i a  3.7f) probably  carbonate  veins  i n excess o f 3kms.  greenstone u n i t gold  t h e Windy  subparallel  quartz-carbonate  associated (Plate  with  (Plate  The  A t l e a s t two stages o f quartz and  are  indicated  stockwork  controls  is  by related  the carbonate b r e c c i a  McLaughlin Creek as w e l l .  cross-cutting to  the  same  and probably  - 127  4.2.3  Carbonate-Sulphide V e i n s  Carbonate-sulphide v e i n s south ends of rich  -  the  study area.  ( g r e a t e r than 10%  by  within  a  i n both  They are  volume) and  dominant gangue m i n e r a l . minerals  occur  the  typically  indicator  silver.  Other  vein  fuchsite  precious  gangue  and  is  common.  textures veins  caused  are  metal  minerals  chlorite.  quartz-sericite-rich by  and  include  Banding  disruption  a sub-type o f the includes,  sphalerite,  chalcopyrite,  of  of  order  and  breccia  that  these  Sulphide  abundance:  pyrite,  (friebergite),  and  t h i s vein  sericite,  veins.  tetrahedrite  exposure of  type  and  gold.  i s the  Rat  vein,  which i s hosted by quartz-muscovite-carbonate s c h i s t s on southwestern  side  of  G l a c i a l a c t i v i t y has roughly  varies  from  composed  of  vein 1  to  Wishbone  90  by  30m  well-exposed. 2m.  siderite  Glacier  (Fig.  the 3.3).  s t r i p p e d o f f the hanging w a l l l e a v i n g a  elliptical,  north-dipping  the  a  carbonate-rich,  layers,  of  brown  particularly  bands suggest  t r a c e amounts of galena, a r s e n o p y r i t e  best  the  i s generally  quartz,  quartz-breccia  in  Dark  values,  sulphide-rich  mineralogy  The  sulphide  A v a r i e t y o f d i f f e r e n t carbonate  single  of  and  have carbonate as  weathering manganiferous s i d e r i t e o r a n k e r i t e good  north  The and  outer  ferroan  section  of  Thickness margins o f  the  steeply  of  the  the  vein  dolomite w h i l e  the  vein are inner  - 128 -  part  of the v e i n c o n s i s t s  grey v i t r e o u s quartz altered,  c u t by  veinlets,  a  gangue. fine  and c o n t a i n  c h l o r i t e , muscovite, fuchsite  that  (section  3.7).  o f semi-massive Footwall  stockwork  patches  yielded  erratic  with  closely  ranging  from  74g/t  of s i d e r i t e  metal  spaced  and  pyrite  o f quartz  with  I t was t h e muscovite-  a potassium-argon  Precious  in a  rocks are carbonate  and clumps  and f u c h s i t e .  sulphides  date  content  chip  of  samples  Au t o 2g/t Au.  Gold  o f 194+6  Ma  the v e i n i s  yielding  values  to s i l v e r  ratios  v a r y , from about 1:1 t o 1:5.  Carbonate-sulphide part  o f the study  30cm),  sinuous,  rounded, indicates  v e i n s a r e exposed  area  but a r e u s u a l l y  and p o o r l y  that  more  g l a c i e r t h a t flows  veins  narrow  mineralized.  well-mineralized boulders of this  i n t h e southwest  An  than  abundance o f  up t o 87cm type  (less  occur  i n diameter below the  from t h e w e s t - c e n t r a l p a r t o f t h e study  area.  4.2.4 Carbonate-Arsenopyrite  Veins  C a r b o n a t e - a r s e n o p y r i t e v e i n s d i s p l a y f e a t u r e s common t o both q u a r t z - b r e c c i a and c a r b o n a t e - s u l p h i d e v e i n s , and may be genetically  related  to  either.  The  veins,  c r o s s - c u t t i n g and u s u a l l y hosted by shear zones,  which  are  are defined  by c o n t a i n i n g a r s e n o p y r i t e as t h e dominant s u l p h i d e m i n e r a l .  - 129 -  Gangue mineralogy quartz.  Only  boulders  i s mainly carbonate  two l o c a l i t i e s  indicate  discovered.  that  are currently  other  steep  Glacier, north  showings  slopes;  known b u t f l o a t remain  to  be  one on  The two showings a r e l o c a t e d  t h e south  the o t h e r on t h e south  ( F i g . 3.3).  Both  side  o f t h e Wishbone  s i d e o f t h e g l a c i e r t o the  veins  w i t h steep n o r t h e r l y d i p s .  have  east-northeast  trends  V e i n s range from 10cm t o 1.8m i n  t h i c k n e s s but other dimensions topography.  lesser  The showings and f l o a t samples a l l occur i n t h e  n o r t h e r n p a r t o f the map a r e a . on  ( s i d e r i t e ) with  a r e not known due t o rugged  P r e c i o u s metal enrichment  appears t o be l i m i t e d  w i t h t h e b e s t samples t o date c o n t a i n i n g from 0.5 t o 1.5g/t g o l d and n e g l i g i b l e  Veins  silver.  a r e banded  with  sulphide-rich breccias.  alternating  sulphide-poor  W i t h i n t h e s u l p h i d e - r i c h bands f i n e  rounded fragments o f s i l i c e o u s o r carbonate a  matrix  of very  sphalerite. fragments  fine  grained  The s u l p h i d e - p o o r and  lesser  dolomite matrix.  and  arsenopyrite,  bands  sulphide  material s i t i n  consist  fragments  pyrite  of in  and  siliceous a  ferroan  Narrow p y r i t e v e i n l e t s and c o a r s e r g r a i n e d  carbonate v e i n s c u t e a r l i e r b r e c c i a bands.  I t i s not c l e a r  whether t h e b r e c c i a t e x t u r e s a r e t e c t o n i c o r hydrothermal i n origin.  Vein  morphology  i s lenticular,  emplacement w i t h i n lens-shaped  possibly  owing t o  voids, or t o shearing  after  - 130  emplacement  or  to  a  -  combination  of  both.  Alteration  a s s o c i a t e d w i t h the v e i n s i s p r i m a r i l y carbonate w i t h patchy sericite.  Because of the low assay r e s u l t s from these v e i n s  no d e t a i l e d work was undertaken on t h e i r mineralogy.  4.2.5  Other V e i n Types  Two  other v e i n  significance  is  approximately This  body  exist  unknown.  An  800m s o u t h e a s t  is elliptical  morphology. quartz,  types  the p r o s p e c t but  albite-quartz  of  Rat  vein  i n p l a n and  may  have a  consists  dolomite  and  of  pyrite.  A  returned  a  6.3g/t  Au  assay  over  their occurs  ( F i g . 3.3). pipe-like  albite,  rutilated  weak t o  carbonate a l t e r a t i o n h a l o surrounds the zone. sample  body  the  Mineralogy  ferroan  on  moderate  A s i n g l e chip  the  maximum  2.8m  width.  Thin,  discontinuous  barite  veins,  widespread over the p r o s p e c t a r e a .  are  rare  Most occurrences c o n s i s t  o f white c o a r s e - g r a i n e d b a r i t e w i t h minor p y r i t e and t o be  late  features.  A  extreme w e s t - c e n t r a l map occurs  within  an  but  n o t a b l e e x c e p t i o n i s found  appear i n the  a r e a where a b a r i t e m a t r i x b r e c c i a  extensive  zone  of  carbonate  alteration.  The b a r i t e b r e c c i a v a r i e s from 1 t o 2m i n width and c o n s i s t s o f a n g u l a r carbonate and  j a s p e r o i d fragments  t o grey b a r i t e matrix.  A  c o n t a i n e d 2.9g/t Au.  15m  chip  w i t h i n a white  sample a c r o s s the  zone  - 131 -  4.2.6 S u l p h i d e Mineralogy  S u l p h i d e mineralogy chalcopyrite, hessite,  consists  sphalerite,  arsenopyrite,  telluorbiomuthite,  arsenopyrite,  chalcopyrite,  tetrahedrite,  galena,  pyrrhotite,  e l e c t r u m and g o l d .  hematite occur as o x i d a t i o n or  of pyrite,  Cuprite  and  r i n d s on c h a l c o p y r i t e and p y r i t e  respectively  tetrahedrite  (Bibby,  and  1981).  sphalerite  are  Pyrite, common _ t o  v i r t u a l l y a l l m i n e r a l i z a t i o n types w i t h i n t h e p r o s p e c t area. Arsenopyrite, usually Silver  galena  minor and  locality.  and  pyrrhotite  constituents  bismuth  with  tellurides  Sulphide contact  are  rare are  widespread  local  known  but  enrichments.  from  a  single  r e l a t i o n s h i p s are displayed  in a  composite Vandeveer'type diagram ( F i g . 4.1).  Most  of  associations,  the either  gold  and  silver  i n contact  with  occurs sulphide  in  sulphide  minerals  or  a d j a c e n t t o them i n both q u a r t z and carbonate gangue (Bibby, 1981).  The  tetrahedrite electrum.  principal  repository  (friebergite);  minor  for amounts  silver also  is  in  occur  as  - 132  -  PLATE 3.7 M i n e r a l i z a t i o n and A l t e r a t i o n F e a t u r e s i n S t i k i n e Assemblage Rocks, Mess Creek Area, Northwestern, B.C.  a)  Quartz-carbonate stockwork ( c r a c k l e b r e c c i a ) i n greenstone u n i t , McLaughlin Creek Zone.  b)  Carbonate s u l p h i d e v e i n showing p y r i t e - c h a l c o p y r i t e t e t r a h e d r i t e - m a n g a n i f e r o u s a n k e r i t e and q u a r t z muscovite-dolomite bands.  c)  P a r t l y carbonate a l t e r e d m a f i c e p i c l a s t i c rock. A l t e r a t i o n has p r e f e r e n t i a l l y t r a v e l l e d p a r a l l e l t o foliation.  d)  S u l p h i d e fragments (black) i n f e l s i c l a p i l l i t u f f . M a t r i x i s a l t e r e d t o s e r i c i t e - c a r b o n a t e and q u a r t z .  e)  Stratabound s u l p h i d e l e n s near the c o n t a c t between f e l s i c and m a f i c p y r o c l a s t i c r o c k s . S u l p h i d e l e n s has a p y r i t e - p y r r h o t i t e - r i c h bottom and a c o p p e r - r i c h top. M a l c h i t e s t a i n d e f i n e s a minor f o l d . Note e l l i p t i c a l j a s p e r o i d fragment i n c e n t e r r i g h t o f photograph. Photograph i s approximately 2m a c r o s s .  f)  Monomineralic Creek Zone.  g)  Quartz-carbonate stockwork i n greenstone b o u l d e r w i t h i n l a n d s l i d e r u b b l e i n Cauldron Creek area ( F i g u r e 3.3).  Fe-dolomite b r e c c i a from the McLaughlin  PLATE 3.7  -  134  -  PLATE 3.8 Back s c a t t e r e d e l e c t r o n images from the s c a n n i n g e l e c t r o n microscope. Specimens from S t i k i n e Assemblage Rocks, Ness Creek Area, Northwestern,  B.C.  F i n e q u a r t z v e i n l e t (bottom c e n t e r t o upper r i g h t ) and p y r i t e g r a i n s a l o n g f o l i a t i o n p l a n e s . P y r i t e formed from d i f f u s i o n o f s u l p h u r away from the v e i n . Bright l e n t i c u l a r s p o t s w i t h i n the v e i n a r e b a r i t e . F i n e c a r b o n a t e - s u l p h i d e fragment from carbonate a l t e r e d greenstone, McLaughlin Creek a r e a ( F i g u r e 3.3). Darker areas r e p r e s e n t s i x d i s t i n c t carbonate compositions r a n g i n g from r e l a t i v e l y pure s i d e r i t e , c a l c i t e and dolomite t o Fe-dolomite, F e - c a l c i t e and manganiferous siderite. B r i g h t e r s p o t s are s u l p h i d e s , s u l p h a t e s and phosphates i n c l u d i n g p y r i t e , galena, s p h a l e r i t e , a r s e n o p y r i t e , b a r i t e , xenotime and t e t r a h e d r i t e .  -A  »  £  40M  PLATE 3.8  - 136 -  Pyrite, widespread  the  abundant  and  euhedral  as  semi-massive  encapsulates intergrown  quartz  with  replace pyrite replacement areas  are  schist.  aggregates.  along  w i t h i n the  Pyrite  and carbonate  arsenopyrite.  with  gangue,  commonly  and i s r a r e l y  Minor amounts o f p y r r h o t i t e  c r a c k s and cleavage  extreme  fine  carbonate  grained  planes.  alteration.  pyrite  and subordinate branch  interpreted  reflect  crystal  to indicate  s u l p h u r moving from  is  t o euhedral  Hematite  o f p y r i t e a l s o occurs and i s p a r t i c u l a r l y  shows' v e r y selvages  mineral,  p o r p h y r o b l a s t s up t o 2cm occur  quartz-sericite-carbonate  in  sulphide  and occurs w i t h i n v e i n s as anhedral  disseminations Coarse  most  a  P l a t e 3.8a  distributed  structures; reaction  severe  along  these  front  vein  textures  and  either  t h e v e i n i n t o t h e w a l l rock o r  i r o n moving from t h e w a l l rock i n t o t h e v e i n . Arsenopyrite  usually  w i t h r a r e coarse  euhedral  A r s e n o p y r i t e appears of  the prospect  mineralized intergrown genetically  area.  than  and  pyrite.  Oxidation  locally.  Sphalerite i s less  still  widespread.  paragenetic  sequence  as i t i n f i l l s  chalcopyrite  Tetrahedrite as  to  than occurs  i t encloses  s p h a l e r i t e and a r s e n o p y r i t e .  associated  and s p h a l e r i t e .  common  aggregates.  i s common  i s usually  pyrite  grains  t o the northern part  Chalcopyrite  of  anhedral  grains within pyrite  tetrahedrite  later  as f i n e  t o be r e s t r i c t e d  structures with  occurs  to  a l l  and/or  I t i s paracracks within  cuprite  occurs  c h a l c o p y r i t e but late  grains  of  i n the pyrite,  - 137  Figure 4.1  -  Composite V a n d e v e e r diagram showing sulphide mineral paragenesls of  vein mineralization  on the B J p r o s p e c t , Mess Creek area, northwestern B. C .  Modified from Bibby (1981).  138  -  4.3  ALTERATION  4.3.1  D e s c r i p t i o n and  Two the  study  area:  a p r e - or syndeformational  by  a  sericitic  quartz-muscovite-carbonate  zone c h a r a c t e r i z e d by p e r v a s i v e carbonate  oxidation.  The  relative  partly,  by  composition  in  areas  o f the h o s t  where  alteration  zone are c o n t r o l l e d , a t rock.  mafic  schists  least  Consequently,  can be d i f f i c u l t t o d i f f e r e n t i a t e between the two types  carbonatereplacement  p r o p o r t i o n s o f the  m i n e r a l s w i t h i n the s e r i c i t i c  zone  assemblage;  a post d e f o r m a t i o n a l , m i n e r a l i z a t i o n r e l a t e d  oxide and  Petrography  predominant a l t e r a t i o n types have been d e f i n e d f o r  characterized and  -  are  it  alteration  altered  to  a  carbonate dominant assemblage.  Sericitic alteration and  occurs  as  (although  these  faults).  This  concentrated outcrop  both  alteration  within  p r e v i o u s chapter.  affected  stratabound  relationships  character  sericitic  i s widespread w i t h i n the map  of The  alteration ( F i g 3.1)  a l t e r a t i o n process.  the  two are  are  affects  felsic  this  and  cross-cutting often most  rocks.  alteration  the  volume  by  units  but  is  specimen  and  i s discussed  of  zones  complicated  Hand  most s i g n i f i c a n t  area  in  the  f e a t u r e s of  the  rock  that  it  has  and the i n t e n s i t y , or completeness of the  - 139 -  Mineralogy of the s e r i c i t i c a l t e r a t i o n i n c l u d e s quartz, muscovite, relic  and  carbonate  with  accessory minerals.  alteration this  assemblage  is  primary  relatively  Albite  but  or  minor  s u l p h i d e s , oxides  and  commonly occurs with  the  i t i s not  secondary  coarse-grained,  always  in  clear  origin.  interlocking  whether  Euhedral,  albite  crystals  w i t h i n quartz and/or carbonate v e i n l e t s i n d i c a t e t h a t a l b i t e was  stable  process. in  during  the  E p i d o t e and  areas  of  less  later  stages  c h l o r i t e may  persist  intense a l t e r a t i o n .  between s e r i c i t e and  of  the  alteration  as r e l i c  Replacement t e x t u r e s  c h l o r i t e do not u n e q u i v o c a l l y i n d i c a t e  the r e l a t i v e t i m i n g of metamorphism and s e r i c t i c Secondary veins. within  chlorite  grains  is  associated  with  some  alteration. late  quartz  There does not appear t o be any m i n e r a l o g i c a l zoning the  alteration,  remains c o n s i s t e n t but unaltered  within  q u a l i t a t i v e l y by  (1967) existing  alteration  mineralogy  i n abundance r e l a t i v e  to  a c c e s s o r y m i n e r a l s were  scanning e l e c t r o n microscopy  earth  attributes  rich  sericitic  element rare  non-enriched  of  Accessory minerals include a p a t i t e ,  z i r c o n and i l m e n i t e o r leucoxene.  carbonate  heavy-rare  does v a r y  o f the opaque and  polished thin sections. monazite,  i s , the  mineralogy.  Compositions determined  that  alteration  enriched  earth apatite  can  overgrowths.  enriched to  Monazite g r a i n s  monazite  hydrothermal  exhibit Vaslov with  co-  activity.  -  Very  fine  grains  throughout have  of  140 -  galena  and  barite  are  intensely s e r i c i t i z e d sections.  formed  from  lead  and barium  disseminated  These g r a i n s may  r e l e a s e d from  potassium  f e l d s p a r d u r i n g i t s c o n v e r s i o n t o muscovite.  Pyrite  throughout  disseminated  the  fine-grained  sericitic rounded  porphyroblasts.  zone  as  crystals  randomly to  coarse  occurs  euhedral  R u t i l a t e d quartz occurs w i t h i n t h e c o a r s e r  q u a r t z - a l b i t e v e i n s and i n d i c a t e s l o c a l t i t a n i u m m o b i l i t y .  Carbonate-oxide  a l t e r a t i o n i s a s s o c i a t e d w i t h f a u l t and  f r a c t u r e c o n t r o l l e d m i n e r a l i z a t i o n and o v e r p r i n t s a l l o t h e r deformation  and  alteration  features.  The  oxidation  r e a c t i o n s may be t e m p o r a l l y and/or g e n e t i c a l l y u n r e l a t e d t o the carbonate a l t e r a t i o n but because t h e o x i d a t i o n g i v e s t h e carbonate  alteration  features  are  a  usually  distinctive  orange  mapped  a  as  carbonate-oxide  alteration  envelope  veins or fractures.  or  around  stockworked  100m  greenstone  i n width.  More  typically  single occurs  zone. as  a  The  halo  or  In e x t e n s i v e l y v e i n e d  the a l t e r a t i o n  commonly,  c o l o u r t h e two  widths  zone can be up t o of the  alteration  zones v a r y from 2 t o 40m, o r f i v e t o t e n times t h e t h i c k n e s s of  the associated v e i n .  Mineralogy 4.2)  consists  ferrous  of of  the  carbonate,  or titaniferous  protolith.  Quartz  carbonate-oxide sericite,  oxides  usually  alteration albite,  and r e l i c  occurs  as  sulphides,  minerals  veinlets  (Table  or  o f the micro-  -  stockworks  and  only  141 -  rarely  occurs  within  the  matrix.  Development o f s e r i c i t e i s much more e v i d e n t  i n thin section  than  can  in  outcrop.  Carbonate  composition  v a r i a b l e even w i t h i n s i n g l e g r a i n s fracture  fillings  produced  i t i s relatively  1984).  Monazite  disseminations substantial rocks  homogeneous.  increases  (Table  same  pyrite,  may  of ilmenite  locally  as  secondary  as  i n t h e cerium  3.5). generally  assemblage  pyrrhotite,  be  minerals  very  grained,  as  found  within  spahalerite,  of  suggested  by  of altered  are  sparsely  and c o n s i s t o f  the veins,  galena,  (Hayes,  fine-grained  contents  Sulphide fine  Grains  ( t r e l l i s texture) are  the oxidation  occurs  and  disseminated, the  from  highly  ( P l a t e 3.8b), but w i t h i n  banded hematite and r u t i l e o r anatase probably  be  namely:  chalcopyrite  and  are varied  and  arsenopyrite.  Textures range  from  o f t h e carbonate  partial  coarse-grained large  (20  open  by  alteration  replacement space  800m)  of  filling  and  existing  minerals  i n stockwork  conspicous  zone  veins.  of  a l t e r a t i o n , which f o l l o w s a n o r t h e a s t e r l y t r e n d i n g in  the north-central  features. stockwork greenstone.  The n o r t h (Plate The  study  area,  displays  some  to A  carbonate structure unusual  o r f o o t w a l l s i d e i s a carbonate-quartz 3.7a)  south  which  side  grades  consists  into  of a  unaltered  monomineralic  - 142  carbonate  (Ca:Fe:Mg  coarse-grained 3.7f).  The  =  7:2:1)  botryoidal  stockwork  -  breccia  and  with  colloform  carries  fragments  carbonate  of  (Plate  geochemically anomalous  gold  and s i l v e r , whereas the carbonate b r e c c i a i s b a r r e n .  The not  orange  appear  weathering  to  localities,  be  and  and  areas  veinlets  supergene  alteration  feature.  In  green  rocks.  are  (Plate  Boundaries  commonly  3.3g).  either  No  orange-  between the quartz  discernable  does  numerous  outcrops show sharp t r a n s i t i o n s between  weathering green  a  carbonate-oxide  or  orange  carbonate  difference  mineralogy between the orange and green areas c o u l d be in  thin  s e c t i o n s which  control of t h i s the  oxidation  fluid  straddle  the  c o l o u r change.  c o l o u r a t i o n , which may  state  of  iron,  appears  p r e s s u r e and p e r m e a b i l i t y .  reflect t o be  a  in seen  Local  a change i n function  of  I t i s not known whether  the f l u i d s were ascending and hydrothermal or descending and meteoric.  4.3.2  Chemical Changes A s s o c i a t e d w i t h A l t e r a t i o n  Changes  i n the  can be used, changes,  material chemical  composition  of a l t e r e d  i n c o n j u n c t i o n w i t h m i n e r a l o g i c a l and  to  processes.  chemical  draw  inferrences  regarding  To a c c u r a t e l y determine that  took  compositions  place of  during  both  the  the  rocks  textural  alteration  the g a i n s and  l o s s e s of  alteration,  reliable  unaltered  and  altered  -  rocks are required. and  143 -  Additionally,  volume must a l s o  changes t o rock d e n s i t y  be c o n s i d e r e d .  Problems r e l a t i n g t o  t h i s procedure a r e summarized i n Meyer and Hemley (1967) and Riverin  (1977).  E s t i m a t e s o f t h e chemical compositon  of a  r o c k p r i o r t o a l t e r a t i o n a r e u s u a l l y made by a n a l y s i s o f t h e l e a s t a l t e r e d l i t h o l o g i c a l e q u i v a l e n t (Gresens, 1967). procedure of  i s tricky  probable  because that  This  f o r r o c k s w i t h i n t h e study area because  chemical  alteration  inhomogeneity  transgresses  the p r e - a l t e r a t i o n  within  rock  lithological  lithololgy  u n i t s and  contacts  i s n o t always  so  known.  Determination o f changes i n d e n s i t y o r volume can be made i f immobile elements diagram  (Grant,  Gresens'  can be i d e n t i f i e d and p l o t t e d on a isochon 1986),  carbonate-oxide likely  f o r samples from  alteration  solution to  greenstone  unit  t h e s e r i c i t i c and  zones a r e p l o t t e d  unaltered l i t h o l o g i c a l  diagrams o f F i g u r e 4.2. the  i s a graphical  (1967) volume-concentration e q u a t i o n s .  Major element data  most  which  against  their  e q u i v a l e n t s on isochon  The extreme chemical v a r i a b i l i t y o f  (section  3.6) and an almost  arbitrary  s e l e c t i o n of unaltered p r o t o l i t h f o r the s e r i c i t i c l y  altered  rocks  change.  prevents  a  meaningful  estimate  However, t h e i s o c h o n diagrams remain relative rocks. stockwork  elemental Destruction veins  changes of  within  between  primary  o f volume  useful  f o r displaying  altered  and u n a l t e r e d  rock  t h e carbonate  texture alteration  and  fine  indicate  - 144 -  5  10  15  20  Unaltered Greenstone  Figure 4.2  26  30  %  R81-188  An isochon diagram (Grant, 1986) for greenstone unit,  comparing fresh rock with three zones of progressive carbonate alteration.  Heavy lines show isochons for constant volume and  constant aluminium, dashed lines show changes in components.  -  possible  volume  change.  aluminium isochon K 0 2  and C 0  lines  145 -  Choosing  best  f i t or  ( F i g . 4.2) shows i n c r e a s e s o f S i 0 , 2  and decreases i n Na 0, FeO, MgO  2  and CaO w i t h i n  2  both t h e carbonate and s e r i c i t i c a l l y  Chemical  and  constant  corresponding  a l t e r e d rocks.  mineralogical  changes  in  s e r i c i t i c a l t e r a t i o n around t h e T e l l u r i d e v e i n and a r e l a t e d quartz  v e i n a r e shown  i n Figure  a l t e r a t i o n are c h l o r i t e study area.  Increases  4.3.  Host rocks  s c h i s t s i n t h e southern in Si0  for this  p a r t o f .the  and K 0 c o i n c i d e w i t h  intense  s e r i c i t i z a t i o n and r e l a t i v e d e p l e t i o n i n Na 0, MgO,  FeO and  2  2  2  CaO.  Secondary  peripheral  to  concentration  albite the  and  an  telluride  increase  vein  in  increases  carbonates the  and tends t o s t a b a l i z e t h e carbonate  components, CaO and MgO.  N  a 2  °  forming  Trends i n FeO c o n c e n t r a t i o n can be  l o c a l l y e r r a t i c due t o formation o f p y r i t e and s i d e r i t e .  4.3.3  C o n d i t i o n s and O r i g i n o f A l t e r a t i o n  M i n e r a l o g i c a l , chemical with  alteration  hydrothermal alteration  and  fluid(s)  took  understanding  can be  used and  place.  and t e x t u r a l changes a s s o c i a t e d to infer conditions  These  o f t h e proc e s s e s  related mineralization.  t h e nature under  inferences  allow  responsible  A l t e r a t i o n takes  of the  which a  the  better  for alteration place  through  f l u i d - r o c k i n t e r a c t i o n where t h e f l u i d and rock a r e i n i t a l l y out  of  chemical  equilibrium.  Unlike  metamorphism,  -  146 -  MINERALOGY QUARTZ MUSCOVITE CHLORITE ALBITE PYRITE CARBONATE  VEIN  VEIN  30  25 -  20 -  LU O DC III Q.  15  10 -  5  -  i 181 G  181 F  i  181 E 181 D 181 C 181 A  SAMPLE  Distance  10 m  FIGURE 4 . 3  C h e m i c a l and M i n e r a l o g i c a l Changes A s s o c i a t e d w i t h t h e T e l l u r i d e V e i n , B J P r o s p e c t , N o r t h w e s t e r n B.C.  147  -  -  a l t e r a t i o n i s u s u a l l y an open system where components may added o r s u b t r a c t e d (metasomatism). fluids  may  may  partial,  be  change w i t h leaving  (Rose and Burt, 1979; earlier  The  and  hydrothermal  r e a c t i o n s w i t h host  disequilibrium  mineral  Henley e t a l . . 1984).  alteration  complicating  time  Moreover,  assemblages  Metamorphism of  adds  an  additional  factor.  spatial  uniform  carbonate, that  extent  mineral  albite  chemical  although  and  and  intensity  equilibrium  this  types  of  formation  assemblage opaques  could  of  of  over  the  caused  quartz  large  by  hydrothermal  muscovite  fluid.  at  and  indicates  least  locally,  metamorphism.  A  by  carbonation.  from Na ,  +  the  quartz,  areas  later  c o n t r o l l e d by exchange o f c a t i o n s K , in  The more o r  were p r i m a r i l y caused  hydrolysis  and  sericitic  muscovite,  attained,  (Table 4.2)  reactions:  of  was  be  Changes i n mineralogy two  rocks  assemblages  a l t e r a t i o n suggests h i g h f l u i d t o rock r a t i o s . less  be  feldspars and  +  The  reaction  Ca  is  with  +  showing  H  +  the  h y d r o l y s i s o f a l b i t e i s as f o l l o w s : 3NaAlSi O 3  g  + K  +  + 2H  albite  +  =  KAl Si 0 3  3  1 ( )  (OH)  2  + 6Si0  muscovite  2  + 3Na  +  quartz  Any o f the f e l d s p a r compositions c o u l d be s u b s t i t u t e d i n f o r a l b i t e t o produce  a similar reaction.  Continued  hydrolysis  would produce k a o l i n i t e a c c o r d i n g t o the r e a c t i o n : KAl Si 0 (OH) 3  3  1 Q  muscovite  2  + H  +  + 3/2H 0 == 2  3/2Al Si 0 (OH) 2  2  5  kaolinite  4  +  K  +  - 148  -  The r e l a t i v e abundance o r a c t i v i t e s o f K these  reactions  to  the  chemical s t a b i l i t e s and  K  activites  +  left  or  and H  right,  will  respectively.  was  i s displayed  u n s t a b l e and  k a o l i n i t e ) and q u a r t z . fluid, (Fig  eventually  4.4).  stable near  graphically  decomposed This  driving  i n Figure  kaolinite,  for  4.4.  (or  have b u f f e r e d  the  albite-stable  temperature. feldspar  field albite  which i s  Stability  also  varies  of with  The r e a c t i o n curves f o r the K20-A1203-Si02-H20  ( F i g . 4.5)  show t h a t the t r a n s i t i o n from muscovite t o  requires  temperature.  and  +  muscovite  (Henley e t a l . . 1984)  that  muscovite  temperature.  kaolinite  form  r e a c t i o n may  i t i n t o the  i s approximately 5.5  system  to  H  initially  At 250°C the pH f o r muscovite + q u a r t z +  neutrality  The  f o r these r e a c t i o n s as a f u n c t i o n o f  T e x t u r a l evidence from t h i n s e c t i o n s suggests t h a t albite  drive  increasing  H  activity  +  A k a o l i n i t e r i c h assemblage  with  increasing  produced by  early  hydrogen o r potassium metasomatism c o u l d have been converted to  a muscovite  event.  assemblage  during  a  later  metamorphic  Muscovite and quartz r e a c t t o form a n d a l u s i t e  pyrophyllite  and/or  between  300  Hemley,  1975).  feldspar  rich  are  and  potassium  600°C Neither  observed  feldspar  depending andalusite indicating  on  at  aK /aH +  or  +  temperatures (Montoya  secondary  probable  metamorphic temperatures o f l e s s than 350°C.  and/or  and  potassium  alteration  or  - 149  Presence  of  dissolved  C0  -  within  2  the  hydrothermal  or  metamorphic f l u i d can c o n t r i b u t e t o hydrogen metasomatism by the f o l l o w i n g r e a c t i o n : C0  This  ==  2  HC0 ~ +  system and  C0 ,  such as:  will  be  3(MgFe) Al Si 0 (OH) 5  2  3  1 0  8  H  3  r e a c t i o n i s c o n t r o l l e d by  the 2  + H0  2  +  temperature  buffered  by  and  pressure  of  r e a c t i o n s which consume  + 15HC0 ~ + 13H  +2K  +  3  ==  +  chlorite  2KAL Si 0 (OH) 3  3  1 Q  + 15(MgFe)C0  2  muscovite  3  + 3Si0  ankerite  2  + 24H 0 2  quartz  Carbonation r e a c t i o n s c o u l d take p l a c e d u r i n g a l t e r a t i o n o r both. greenschist produce  C0  2  Harte and Graham (1975) have shown t h a t  f a c i e s metamorphism o f m a f i c igneous rocks  differing  chlorite,  metamorphism,  calcite  present  mineral and  assemblages,  ankerite,  depending on  d u r i n g metamorphism.  metamorphic  fluids  could  be  consisting  The  the  of  amount of  source f o r C0  graphite-water  will  2  within  reactions  decarbonation  r e a c t i o n s a t depth  the e x t e n s i v e  area t h a t r e c e i v e d carbonate a d d i t i o n and  the  intensity  that  not  typical  of  ( s e c t i o n 3.4.2).  or  addition within  f o r metamorphic  terranes.  the  study  However,  area,  A d d i t i o n a l l y , CO  is  will  - 150  -  remain a t r e l a t i v e l y low c o n c e n t r a t i o n s w i t h i n a metamorphic f l u i d i f pH i s b u f f e r e d ( K e r r i c h and F y f e , 1981).  Therefore  hydrogen metasomatism w i t h the a d d i t i o n o f carbonate i s more reasonably  caused  by magmatic r e l a t e d  alteration  processes  i n the Mess Creek area.  The  origin  area  remains  and  thin  of the  unclear.  sections  occurred  prior  therefore,  sericitic  to  Rock t e x t u r e s d i s p l a y e d i n indicate  the  that  second  which  is  and area  pyrite by  of  from  the  plagioclase,  assemblage  Grove  (1968).  has  outcrop  alteration and  carbonate-oxide District-scale  chlorite,  been  Grove  map  deformation  post-deformation.  a l t e r a t i o n w i t h a muscovite, carbonate  sericitic  phase  i s temporally d i s t i n c t  alteration  Stewart  a l t e r a t i o n w i t h i n the  mapped  quartz, in  attributes  the this  a l t e r a t i o n , which h o s t s many o f the m i n e r a l d e p o s i t s o f the region,  to a process  cataclasis,  involving  granitization,  dynamothermal metamorphism,  and  migrating  There  are  similarities  between  Grove  and  that  study  temporal  of  the  relationship  between  the area.  meteoric  waters.  alteration  mapped  by  However,  although  a  alteration  and  metamorphism  cannot be r u l e d out, a g e n e t i c r e l a t i o n s h i p i s r e j e c t e d remains moot) f o r the f o l l o w i n g reasons:  (but  - 151 -  Distribution appears  of s e r i c i t i c  localized  by  a  alteration combination  i s widespread but of  structure  and  lithology; i t i s d i f f i c u l t to explain t h i s distribution i n a r e g i o n a l metamorphic c o n t e x t . The  degree  o f hydrogen  and  carbonate metasomatism i s  u n c h a r a c t e r i s t i c o f g r e e n s c h i s t f a c i e s metamorphism. Both xenotime and monazite appear t o o c c u r as secondary phases.  These m i n e r a l s a r e regarded as u n s t a b l e d u r i n g  greenschist their  f a c i e s metamorphism  growth  with  rare-earth  c o n s i d e r e d most c h a r a c t e r i s t i c by V l a s o v (1967).  (Overstreet, element  1961)  and  enrichment  are  o f hydrothermal  systems  152  -  -  — I  T"  T=200*C P=500 bars  ALBITE D  PARAGONITE  O O  K-SPAR MUSCOVITE -  KAOLINITE  LOG(a +/a ) +  K  F i g u r e 4 . 4 P h a s e r e l a t i o n s in t h e s y s t e m  H  K 0-Na 0-Al203-Si02-HCI-H 0 2  2  2  in t h e p r e s e n c e o f q u a r t z a s a f u n c t i o n o f l0g(d^/a +) a n d log(a £/a,}) H  f o r unit a c t i v i t y o f H 0 a t 5 0 0 b a r s a r i d 2 0 0 ° C . 2  and Helgason (1985).  N  T a k e n from J a c k s o n  153 -  IOO -  i  i  i  1  1  0  1  2  3  4  L O  Figure 4.5  i 5  9 ( KCI HC|) m  /m  Phase relations in the systems I^O-AlgOjj-SiOg-HgO  Na 0-Al203-Si0 -H 0 2  2  2  as a function of temperature and  calculated activity ratios.  From Henley et al. ( 1 9 8 4 ) .  - 154  Potassium losses  and  gains  alteration type  metasomatism and  assemblage  deposits 1976),  deposits  (Ohomoto and  corresponding  elemental  quartz-muscovite-carbonate-albite  and  certain  q u a r t z v e i n systems  with  i s commonly  (Gilbert  Godwin,  Burt, 1979).  a  -  associated with  Lowell,  1974;  volcanogenic  Skinner,  1979;  (Casaderval and  W i t h i n the map  porphyry  Drummond  massive  Sillitoe,  and  sulphide 1978),  Ohmoto, 1977;  and  Rose  and  area, t h e r e are l a r g e volumes  of metasomatized rock w i t h few or no a s s o c i a t e d quartz v e i n s indicating  that,  alteration,  the  elsewhere. porphyry  although source  veins  of  the  are  associated  hydrothermal  with  fluids  lies  Zonation of a l t e r a t i o n assemblages, t y p i c a l of a  system, would be d i f f i c u l t  re-equilibriation distinction sulphide  during  between  related  assemblages observed  is  to  alteration  be  the a l t e r a t i o n  porphyry  and on  feasible.  spatially  zone.  regional  alteration not  to recognize following metamorphism volcanogenic the  Intrusive  associated  Therefore,  i t must e x i s t  basis  i f an  with  a t depth,  and  massive of  rocks the  intrusion  and  zoned  are  not  sericitic  i s related the  to  distinction  between porphyry and v o l c a n o g e n i c systems becomes i n d i s t i n c t (Britten, grained fragments  1981). felsic and  volcanogenic  Geological features, including  coarse-  fragmental  pyroclastic  small origin  rocks,  stratiform f o r the  sulphide  sulphide  sericitic  sulphide deposits i n l i t h o l o g i c a l l y  lenses,  alteration.  similar  and  favour  a  Massive  correlative  155  -  s t r a t i g r a p h y i n the Tulsequah 1984)  support t h i s  The  and  and  sulphide  the  veins.  assemblage  implies  a  quartz  and  genetic  reverse  (Nelson and  carbonate-oxide associated with  These between  Payne,  the  quartz,  conditions, at  and  alteration The  minerals  temperature  alteration  associations  relationship.  carbonate  physiochemical the  of  temporally  sulphide  R i v e r area  concept.  origin  spatially  -  least  solubility  is  carbonate a  and  similar  the  veins  co-precipitation  of  necessitates  special  theoretically,  due  coefficients  of  to  these  minerals.  Chemical very  changes  similar  to  related  changes  CaO  2  2  and  C0 .  These  2  combination  to  alteration  sericitic  are  alteration,  and FeO and g a i n s o f S i 0 , 2  changes  could  be  produced  by  a  hydrolysis-carbonation reaction:  3(MgAlFe) Si 0 5  4  1()  (OH) + 3 C a A l S i 0 8  2  3  chlorite 3  1 0  3  (OH) + 12C0 " + 5K  1 2  25H  +  3  +  epidote  = 5KAl Si O (OH) 3  carbonate  related  namely the l o s s o f Na 0, MgO, K0  to  2  muscovite  + 6Ca(MgFe)(C0 ) 3  2  + 6Si0  dolomite  2  + 3Fe  + 2  + 6Mg  +2  quartz  + 21H 0 2  Depending albite this  upon  c o u l d be  sort  section.  are  the  Na/K  ratio  of  the  hydrothermal  formed i n s t e a d o f muscovite. compatible  with  textures  fluid,  Reactions  observed  in  of  thin  - 156  Sudden  gas  hydrothermal deposition 1985).  loss  fluids  due  is a  -  to  adiabatic  mechanism  boiling  invoked  for  i n many epithermal d e p o s i t s (Meyers  carbonate  and  Hemley,  Textures a s s o c i a t e d with b o i l i n g such as b r e c c i a t i o n  are not commonly observed w i t h i n the m i n e r a l i z a t i o n BJ  prospect,  McLaughlin  except  Creek  phenomenon.  for  zone  the  which  Carbonate  may  carbonate could  also  well  be  situation  is  noted  where  of the  breccias be  of  a  seawater  the  boiling  precipitated  e n r i c h e d f l u i d s are c o o l e r than t h e i r host r o c k s . of  of  if  C0  2  T h i s type  convects  through  b a s a l t i c rocks o f the ocean f l o o r and carbonate i s d e p o s i t e d in  downward-flowing  1981).  An  "recharge  analogous  process  zones" may  (Kerrich  be  and  envisioned  Fyfe,  for  the  o r i g i n o f the o x i d a t i o n zones but i t i s not compatible w i t h t h e geometry o f the carbonate a l t e r a t i o n the time o f formation. that  metamorphic  fluids  K e r r i c h and undergoing  o r the geology  F y f e (1981)  demonstrate  C0 -forming 2  at  reactions  w i l l l a t e r r e v e r s e those r e a c t i o n s and p r e c i p i t a t e carbonate within wall  rock a l t e r a t i o n  zones.  I f the J u r a s s i c age  m i n e r a l i z a t i o n , i n d i c a t e d by a potassium-argon s e l v a g e muscovite, unlikely  source  t h e r e i s no  of  date on v e i n  i s c o r r e c t then metamorphic f l u i d s are an  for alteration  within  the  BJ  prospect  evidence of r e g i o n a l metamorphism i n t h i s  d u r i n g J u r a s s i c time.  as  area  - 157  Adjustment hydrolysis  can  i s g i v e n by the  The  of  (and  possibly, the  fluids  pressure  deposition  d i s s o c i a t i o n o f C0  2  + H0 2  ==  geothermal  carbon-bearing  therefore  to  hydrothermal  of  by and  carbonate  d i s s o l v e d i n water  2  reaction: C0  dominant  within  lead  1967).  Analyses  pH  reactions  temperature) (Holland,  of  -  other  HC0 " + 3  fluids  are  +  show  species  reactions  H  that  (Henley of  HC0  et_al.,  less  is  3  1984)  importance.  the and This  p r o c e s s i s suggested f o r the a l t e r a t i o n a t the Con  mine near  Yellowknife  by K e r r i c h and  carbonate  alteration  and  the  Fyfe  sericitic  produced by s i m i l a r p r o c e s s e s . of  the  two  (1981).  alteration Differences  a l t e r a t i o n t y p e s would be  structural  and  lithological  p o s s i b l e d i f f e r e n c e s i n the  Thus, the  controls  may i n the  caused by on  have  fluid  been  character lithology, flow,  r e l a t i v e amounts of HC1  and  and  C0  to  the  2  w i t h i n the a l t e r a t i o n f l u i d s .  Source  of  the  hydrothermal  fluids  related  carbonate a l t e r a t i o n i n the Mess Creek area i s not  evident  from f i e l d mapping.  f o r the  However, the E a r l y J u r a s s i c age  m i n e r a l i z a t i o n i n v i t e s comparison w i t h the C h r i s and as t h e r e i n the  s i m i l a r aged  Red  Galore Creek porphyry Cu-Au d e p o s i t s , p a r t i c u l a r l y i s no  evidence f o r a s i m i l a r age  immediate area.  associated  w i t h the Red  At the Red stock,  an  metamorphic event  Chris deposit, a l t e r a t i o n E a r l y J u r a s s i c hornblende  - 158 -  monzonite,  consists  carbonatization  of  potassium  i n d i c a t e d by t h r e e  orthoclase-albite-biotite, ankerite-quartz-sericite  metasomatism  alteration  and  assemblages:  albite-chlorite-calcite,  (Schink,  1977).  and  A n k e r i t e v e i n s and  b r e c c i a zones a r e noted w i t h i n a n d e s i t i c rocks p e r i p h e r a l t o the Red s t o c k . Temperatures the  Galore  of a l t e r a t i o n  Creek  deposits  and m i n e r a l i z a t i o n  were  within  i n t h e 450 t o 600°C  range  which produced an a l t e r a t i o n assemblage c o n s i s t i n g p r i m a r i l y o f o r t h o c l a s e , b i o t i t e and a n d r a d i t e - g r o s s u l a r garnet et  a l . , 1976).  Carbonate v e i n s  and a l t e r a t i o n  observed p e r i p h e r a l t o t h e d e p o s i t area  (Allen  zones a r e  (D. F o r s t e r ,  pers.  comm., 1988).  4.4  Comparison o f M i n e r a l i z a t i o n w i t h Other  M i n e r a l i z a t i o n o f t h e BJ p r o s p e c t common  with  Comparisons  other between  understood,  mesothermal the  deposits  study  could  has many f e a t u r e s i n vein-type  area lead  Deposits  and to  deposits.  other, more  better  efficient  exploration. Mineral alteration those  of  and  chemical  characteristics  on t h e BJ p r o s p e c t the  Mother  Lode  C a l i f o r n i a and v e i n d e p o s i t s the Canadian S h i e l d .  have  strong  deposits  of  veins  and  similarities to  in  north-central  i n Archean greenstone b e l t s o f  - 159 -  The Mother Lode i s a 1 t o 5km wide system o f en echelon quartz v e i n s which extends over a l e n g t h o f 190km, p r i m a r i l y along  t h e Melones  California minerals  zone,  a major  (Dodge and L l o y d , 1984).  i n quartz  mafic rocks.  veins  gold  i s contained  the  southern  part  g e n e r a l l y barren carbonate  mineralized  within  country  associated  rock  m i n e r a l i z e d country  by  t h e quartz  and t h e g o l d occurs and  break i n  carbonate-altered  p a r t o f t h e d i s t r i c t , most o f  of the d i s t r i c t  rock  tectonic  Gold and minor s u l p h i d e  a r e hosted  In t h e n o r t h e r n  the  of  fault  (Dodge  veins,  whereas i n  t h e quartz  veins are  w i t h i n enormous bodies carbonate-altered  and  Lloyd,  1984).  and The  rock, u s u a l l y greenstone, i s composed o f  ferro-magnesium carbonate and l e s s e r amounts o f s e r i c i t e (± f u c h s i t e ) , a l b i t e , quartz and s u l p h i d e s Gold vein  deposits  within  and a l t e r a t i o n  Mother  Lode  chemical  Archean greenstones have  mineralogy  and study  (Knopf, 1929).  area  t o that  described  mineralization.  changes a s s o c i a t e d w i t h  similar for  the  Additionally,  a l t e r a t i o n o f Archean g o l d  d e p o s i t s a r e s i m i l a r t o those documented f o r t h e study area. Pirie and  (1982) demonstrates w a l l r o c k  gains  of S i 0  and K 0,  2  2  l o s s e s o f MgO, FeO and Na 0 r e l a t e d t o v e i n - a s s o c i a t e d  alteration Ontario.  2  i n metavolcanic r o c k s Andrews  and Wallace  carbonate a l t e r a t i o n , greenschist localized,  facies intense  o f t h e Red Lake (1983)  note  that  i n t h e Red Lake d i s t r i c t , metamorphic  assemblages  Fe-carbonatization,  district, regional overprints  but  preceeds  silicification  s e r i c i t i z a t i o n associated with gold m i n e r a l i z a t i o n .  and  -  Both  the  Mother  mineralization setting,  differ  structural  Therefore,  Lode from  of  and  Archean  the  study  and  scale  controls  evolution  -  160  greenstone  area of  hydrothermal  in  mineralization.  systems  d i f f e r e n t areas c o u l d a l s o be q u i t e d i f f e r e n t . strong  similarity  between the  chemistry  tectonic  and  within  the  However, the mineralogy  of  t h e h o s t r o c k s , m i n e r a l i z a t i o n and a l t e r a t i o n o f t h e s e areas i n d i c a t e s a commonality o f hydrothermal  fluid  fluid-wallrock  of  interactions.  Studies  chemistry  the  and  carbonate-  q u a r t z - g o l d a s s o c i a t i o n , p a r t i c u l a r l y i n the s h i e l d d e p o s i t s (Dube  et  a l . . 1987;  Crockett,  1982)  carbonate  and  Kerrich  have gold  shown  is  is  by  can  with be  d e r i v e d from  2  at  1981;  deposition fluid  pressure  formation  C 0 / H 0 which i s i n i t i a l l y 2  that  for further discussion).  compatible  400°C and  Fyfe,  c o n t r o l e d by  r e a c t i o n s much more than s e c t i o n 3.3  and  and  Fyon of  pH  i n t e r a c t i o n g r a d u a l l y becomes o x i d i z i n g  redox  temperature  temperatures  r e d u c i n g but  quartz,  and  Alteration  a single  and  fluid  (see  mineralogy  from  200  with  a  through  to  high  water-rock  (Dube e t a l . ,  1987).  T h i s p r o v i d e s a reasonable e x p l a n a t i o n f o r why  d e p o s i t s of  this  metamorphic  type  terranes. likely  typically  occur  in  greenschist  D e p o s i t s which occur a t s h a l l o w depths  t o have m i n e r a l d e p o s i t i o n c o n t r o l l e d by p r e s s u r e and  temperature,  whereas  chemically  controlled  d e p o s i t i o n would occur a t g r e a t e r depths. such  are more  depths  would  metamorphic e f f e c t s .  likely  have  undergone  mineral  Rocks b u r i e d t o at  least  some  161  -  Deposits features  i n northwestern  B.C.  i n common w i t h t h e study  Juneau  (AJ) Gold  Polaris-Taku  Mine,  mine  and A l a s k a  area  t h e Golden  (locations  d e p o s i t s share, perhaps, scale  -  given  that  have  include the Alaska  Bear  deposit  i n Figure  and t h e  1.3).  These  a more common t e c t o n i c s e t t i n g and  of mineralization  with  t h e study  area  than  those  deposits previously discussed.  The gold  A l a s k a Juneau Mine has produced  (3 m i l l i o n  lowermost rocks  Jurassic  have  schist  ounces)  been  mafic  i s hosted  volcanics  regionally  facies  sphalerite,  and  (Miller,  veins  that  ranges  i n width  occur  from  and p h y l l i t e s .  1988).  within  30 t o 120m.  100,000kg o f  i n Triassic  metamorphosed  galena, t e t r a h e d r i t e  quartz  over  These  t o upper  Pyrite,  to  green-  pyrrhotite,  and g o l d a r e c o n t a i n e d i n a  5,000m  long  Individual  zone  that  quartz v e i n s ,  u s u a l l y l e s s than 1.5m i n width and 100m i n l e n g t h , a r e most numerous  within  or  ( M i l l e r , 1988).  near  the  mafic  metavolcanic  Intense b i o t i t e and Fe-carbonate  with  assemblage.  The m i n e r a l o g i c a l c h a r a c t e r i s t i c s o f t h e A l a s k a  deposit  although  the  overprints  are s i m i l a r presence  of  t o those biotite  the  alteration  associated  Juneau  veining  units  metamorphic  o f t h e study in  the  alteration  assemblage suggests h i g h e r m i n e r a l i z a t i o n temperatures. contrast  between  the s i z e  o v e r a l l s i z e o f t h e system  of  individual  veins  c o u l d have profound  area,  The  and t h e  implications  - 162 -  for  exploration.  L i k e t h e BJ p r o s p e c t ,  mineralization at  the A l a s k a Juneau mine i s l a t e r than r e g i o n a l dynamothermal metamorphism.  P l u t o n i c rocks  are not recorded  w i t h i n the  mine a r e a .  The Golden Bear d e p o s i t , a r e c e n t d i s c o v e r y by Chevron M i n e r a l s L t d . 100km west o f Dease Lake and 170km northwest of  t h e study  area,  has i n d i c a t e d  tonnes  grading  llg/t  hosted  by s c h i s t s and limestone  Mineralization  Au  (Franzen,  i s structurally  regional  metamorphism.  atization  and s e r i c i t i z a t i o n  c i f ication 1986).  1987).  o f 1.6  controlled  Alteration  Assemblage.  and  consists  post-dates of  within the s c h i s t s  mineralization  million  The d e p o s i t i s  of the S t i k i n e  w i t h i n t h e limestone  Detailed  reserves  (K. Shannon,  carbon-  and  pers.  characteristics  silicomm.,  of  the  Golden Bear d e p o s i t a r e n o t p a r t i c u l a r l y s i m i l a r t o those o f t h e study area, l i k e l y r e f l e c t i n g a d i f f e r e n c e i n s t r u c t u r a l and l i t h o l o g i c a l  The  P o l a r i s - T a k u mine  t h e study a r e a . the  mine  consists  1984).  quartz  deformed  greenstones  in  llg/t  of  i s situated  250km northwest o f  Past p r o d u c t i o n and remaining r e s e r v e s when  closed  approximately  altered,  controls.  1949 Au  (Smith,  and  700,000  1950).  quartz-carbonate  and metamorphosed  of the S t i k i n e  Alteration  totaled  i s widespread  of  Mineralization veins  pyroclastic  Assemblage  tonnes  (Nelson  within  r o c k s and and Payne,  and i s composed  o f Fe-  -  carbonate, (Bacon, areas  quartz,  1942). of  rocks  deformation  features  The  1950)  sericite  fractures  (Smith,  i d e n t i f i e d by Bacon stibnite.  -  and  local  fuchsite  About n i n e t y p e r c e n t o f p r o d u c t i o n came from  intersecting  greenstone  (Smith,  albite,  163  1950).  (Smith,  within  Mineralization  1950).  i s earlier  sill-like cuts a l l  Sulphide  (1942) i n c l u d e p y r i t e ,  widespread  the  a r s e n o p y r i t e and  quartz-albite-sericite or synchronous  minerals  with  alteration  dynamothermal  metamorphism ( J . Nelson, p e r s . comm., 1985).  The tectonic  P o l a r i s - T a k u mine history  controlled,  to that  appears  of the  post-deformation,  to  study  have  had  area.  a  similar  Structurally  greenstone  hosted  m i n e r a l i z a t i o n w i t h a s s o c i a t e d i n t e n s e carbonate  alteration  suggests a s i m i l a r ore g e n e s i s w i t h t h a t o f the study a r e a .  -  164 -  CHAPTER 5: CONCLUSIONS  5.1 Summary o f G e o l o g i c a l H i s t o r y  The g e o l o g i c a l h i s t o r y o f t h e study area i s determined from  observed  or  inferred  intrusive relationships.  structural,  stratigraphic  and  The key f e a t u r e s o f t h e Mess Creek  a r e a documented by t h i s study a r e reviewed i n t h e f o l l o w i n g section.  The  Stikine  Assemblage  is a  collection  r o c k s which form t h e basement o f S t i k i n i a , or  'suspect'  continental  terrane,  North  which  America  formed  (Monger,  of  an a l l o c t h o n o u s  to  the  1977).  west  of  Paleomagnetic  d a t a from Late T r i a s s i c r o c k s w i t h i n S t i k i n i a when those r o c k s formed  Palezoic  indicate  that  they were 13 t o 14° south o f t h e i r  p r e s e n t p o s i t i o n , p o s s i b l y near t h e p r e s e n t C a l i f o r n i a Oregon border the of  ( I r v i n g , 1981).  similarity  between M i s s i s s i p p i a n  the Stikine  California Permian  Assemblage  (Pitcher,  age  T h i s i s supported f u r t h e r by  Tethyian  fauna  and s p e c i e s  1960)—in  marked  fusilinids  from  found  limestones i n northern  contrast  found  in  to  exotic  Cache  Creek  limestones.  Pyroclastic  and  epivolcaniclastic  the M i s s i s s i p p i a n s t r a t i g r a p h y exposed compatible  with  an  arc-type  lithologies  within  i n t h e study area a r e  setting.  Local  basins,  - 165 -  presumably received  between  fine  receiving single  epiclastic  proximal  transition  preserved mark  volcanic  within  period(s)  material  debris  from  to  mafic  study  one  to  source  from  felsic  area.  volcanic  appear  from  pyroclastic  the  of  edifices,  while  another.  A  volcanism  is  Argillaceous  quiescence.  have  sediments  Large  areas  of  potassium metasomatism, d e f i n e d by a quartz-muscovitecarbonate  a l t e r a t i o n assemblage, were caused by s y n g e n e t i c ,  submarine (?) massive  geothermal  systems.  Related  sulphide deposits are p o s s i b l e .  sequence  is  capped  by  limestones  The  volcanogenic stratigraphic  deposited  on  emergent  seamounts (Monger, 1977).  Permian s t r a t i g r a p h y  was  likely  a b l y on the M i s s i s s i p p i a n r o c k s . precise  nature  deposited  disconform-  More work i s r e q u i r e d t o  determine  the  of  the P e r m i a n - M i s s i s s i p p i a n  contact.  Permian v o l c a n i c r o c k s are l i t h o l o g i c a l l y  similar  t o t h e M i s s i s s i p p i a n u n i t s but are g e n e r a l l y f i n e r g r a i n e d and  more  distal  carbonate  rocks  environment  Both  in  character.  suggest  The  widespread  deposition  in  a  Permian  platformal  (Monger, 1977).  the  Mississippian  and  Permian  rocks  r e g i o n a l l y metamorphosed t o lower g r e e n s c h i s t f a c i e s . deformation deformation phases  of  was  synchronous  significantly recumbant  with  outlasted  isoclinal  metamorphism,  thermal  folding  with  effects.  were Early but Two  northwesterly  - 166  trending  shallowly  easterly trending north-trending deformation  plunging  -  fold  k i n k bands and  parallel-type  exposed  in  axis  study  The  area  is  decreased s t r u c t u r a l competence caused by alteration.  Penetrative  both phases 10km  of  south o f  tentatively  the  study  correlated  Triassic  age.  metamorphism Triassic  a x i a l planar  isoclinal  folding. area,  with  by  the  before  by  of  attributed  to  foliation  This  accompanied  foliation  plutonic  is  cut,  r o c k s which pluton  regional Middle  intensity  e a r l y , widespread  Hickman  Therefore,  occurred  followed  chevron f o l d s , and by open, folds.  the  were  of  are  Middle  dynamothermal  Triassic  time.  Upper  (Norian) f o s s i l i f e r o u s sediments, which are unmeta-  morphosed,  unconformably  rocks  providing  limit  of  overlie  additional  regional  the  Stikine  constraints  metamorphism.  These  to  Assemblage  the  upper  Norian  time  sediments,  which i n c l u d e b o u l d e r conglomerates w i t h c l a s t s l i t h o g i c a l l y s i m i l a r t o the Hickman p l u t o n ,  were f o l d e d by the  third  and  f o u r t h phases o f deformation.  Plutonic logically Hotialuh Both  and  rocks  of  the  Hickman  chronologically  the  Hickman  w i t h , but  Chemical of  and  the  batholith  similar  b a t h o l i t h i n the e a s t e r n  associated rocks.  rocks  Hotialuh  Hotialuh  batholiths  between  batholith  rocks  lithoof  the  p a r t of the S t i k i n e Arch.  pre-date, e r u p t i o n  differences  to  are  are  of S t u h i n i  some o f  the  (calc-alkaline)  spatially volcanic plutonic and  the  - 167  S t u h i n i rocks (Anderson,  -  ( a l k a l i n e ) suggests d i f f e r e n t magmatic sources  1983).  Stuhini  v o l c a n i c rocks  in  A r c h area are Middle t o Late T r i a s s i c i n age and a r e unmetamorphosed and  the  Stikine  (Souther,  1971)  o n l y l o c a l l y deformed i n t o open  folds.  Tectonic  activity  within  the  Stikine  Arch  during  J u r a s s i c time was  concentrated a l o n g the n o r t h e r n edge where  r o c k s w i t h i n the  King Salmon a l l o c t h o n were metamorphosed,  deformed faults  and  transposed  (Monger,  1978;  along  southwest-verging  Thorstad,  1983).  Westerly  thrust trending  f o l d axes r e l a t e d t o t h i s deformation occur w i t h i n t h e Cache Creek Group r o c k s of the A t l i n  Terrane  t h e T r i a s s i c Kutcho formation.  The  bands and  chevron  (Souther,  east-west  1971)  and  oriented kink  f o l d s w i t h i n the S t i k i n e Assemblage rocks  and t h e o v e r l y i n g Late T r i a s s i c sediments o f the Mess Creek a r e a c o u l d be r e l a t e d t o t h i s d e f o r m a t i o n a l event. there  is  little  evidence  for  Jurassic  However,  or  younger  the  Yehiniko  related  porphyry  metamorphism w i t h i n o r near the study area.  The pluton,  G a l o r e Creek and and  various other  copper-molybdenum-gold Stikine  Arch  during  related  intrusions,  intrusions  deposits Early  were  to  and  emplaced  Middle  within  Jurassic  the time.  - 168  Potassium-argon structurally and  5.2  and  alteration within  ages  p l u t o n s and  rubidium-strontium  c o n t r o l l e d quartz  associated  Jurassic  and  -  which  coincide  dating  quartz-carbonate  the with  study area the  of veins,  give  Early  ages  of  alkalic  of  the  Stikine  r e l a t e d porphyry deposits..  Tectonic  Implications  Current  models  of  tectonic  evolution  A r c h r e l y h e a v i l y on the l a r g e r p l a t e t e c t o n i c model f o r the Cordillera. a  The  C o r d i l l e r a n model i n v o l v e s the a c c r e t i o n o f  " c o l l a g e of allocthonous  of  the  North  American  p l a t e motions  t e r r a n e s " t o the western margin  craton  by  convergent  ( P r i c e e t a l . . 1981;  Timing  of  terrane  accretion  events  or  features  that  Monger and  i s determined  either  link  or  and  transform  P r i c e , 1979).  from  geological  separate  adjacent  t e c t o n o s t r a t i g r a p h i c assemblages o r t e r r a n e s .  The three the to  Stikine terrane,  more e a s t e r l y t e r r a n e s :  Eastern  Assemblage, t o  emplacement  1981). with  or  This North  in  their  Cretaceous time  ( P r i c e , 1981).  occurs  extensive  right-lateral  coalesced  with  Cache Creek, Q u e s n e l l i a ,  present  between  primarily  had  form a composite t e r r a n e ,  composite t e r r a n e America  Stikinia,  locations  Jurassic  S t i k i n e A r c h and  displacement  on  collided  and  Evidence f o r t h i s  e x t e r n a l t o the  prior  (Price et a l . ,  i s thought t o have Middle  and  Middle  collision includes  strike-slip  fault  - 169 -  systems on t h e e a s t e r n margin o f the composite t e r r a n e which occurred (Price these  during  middle J u r a s s i c t o Middle  e t a l . , 1981). strike-slip  Cordilleran  The magnitude  fault  history  systems  renders  Cretaceous  time  o f displacement  on  (up t o 500km) so l a t e i n  tectonic  models  of  earlier  events s p e c u l a t i v e (Monger and P r i c e , 1979).  Dynaraothermal metamorphism o f S t i k i n e Assemblage r o c k s , within the  t h e study  area  took p l a c e  between Late  i n t r u s i o n o f t h e Hickman p l u t o n  i n Early-Middle and  T r i a s s i c time.  deformation  orogeny Early  marked  (Souther,  t o Middle  volcanics.  the  1971) t h a t Triassic  Permian .and  and r e l a t e d i n t r u s i o n s  T h i s p e r i o d o f metamorphism beginning  of  culminated  plutons  the  Tahltanian  i n the u p l i f t  and e r u p t i o n  of  of Stuhini  R e l a t i o n s h i p s between t h e T a h l t a n i a n orogeny and  t e r r a n e c o l l i s i o n remain u n c l e a r .  The  Cache Creek Group i s thought t o have been l i n k e d t o  S t i k i n i a by Late Triassic Group  rocks  rocks  consistent  T r i a s s i c time on t h e b a s i s t h a t uppermost of S t i k i n i a  (Monger with  a  possibly  i n Price collision  et  overlap  Cache  a l . , 1981).  between  Stikinia  Creek  This and  is more  e a s t e r l y t e r r a n e s d u r i n g t h e time o f t h e T a h l t a n i a n orogeny. However,  i f t h e Cache Creek Group  represents  a  subduction  complex f o r t h e S t u h i n i v o l c a n i c rocks, then i t i s u n l i k e l y that  Stikinia  collided  prior to Stuhini  with  volcanism.  t h e more  inboard  assemblages  - 170 -  Evidence within  the  southern  for  the  Stikine  British  northwesterly  Tahltanian  Arch  but  Columbia.  trending  orogeny  is  significantly  Anderson  foliation  caused  this  foliation  that  which  caused  has  a  isoclinal  folding  to  The  similar  so  documents  Early  T r i a s s i c p l u t o n s of the H o t i a l u h b a t h o l i t h . which  less  (1983)  within  widespread  a  Middle  compression  orientation  in  in  the  to  Stikine  Assemblage r o c k s , and c o u l d be r e l a t e d t o t e r r a n e c o l l i s i o n (Anderson,  1983).  Corroborating  continent c o l l i s i o n national  border  evidence  for  terrane-  c o u l d be p r e s e r v e d south o f the  where the  Sonoma orogeny  is  inter-  approximately  time e q u i v a l e n t w i t h the T a h l t a n i a n orogeny.  More d i r e c t evidence o f c o l l i s i o n between S t i k i n i a  and  North America  i s p r e s e r v e d i n Middle t o Late J u r a s s i c  rocks  and  Southwesterly  Atlin  events.  Terrane faults  (Monger, i n the  suggestive carbonate  of  1975)  King  and  Salmon  terrane  fragments  directed  southwesterly Assemblage  collision.  from  folds  Cache  in  the  verging  (Tipper,  Distinctive Creek  Group  1978)  are  chert  and  rocks  w i t h i n Middle t o Upper J u r a s s i c Bowser Lake Group which Terrane  indicates by  different  this  amalgamation  of  Stikinia  time  et  a l . , 1978) .  (Monger  and  thrust  occur  sediments the  A  Atlin  slightly  l i n e of r e a s o n i n g f o r t e r r a n e - c o n t i n e n t c o l l i s i o n  i s presented by Monger and P r i c e  (1979).  They p o i n t out the  d i s p a r i t y between the c o n f i g u r a t i o n o f the T r i a s s i c v o l c a n i c arcs  (Takla,  Stuhini,  Nicola)  and  their  associated  - 171  subduction  complex  (Cache  Creek  H a z e l t o n a r c and i t s proposed River  Formation.  This  -  Group)  and  the  Jurassic  subduction complex, the Bridge  reversal  i n arc-subduction  complex  p o l a r i t y i s b e s t e x p l a i n e d by c o l l i s i o n o f t h e S t i k i n e b l o c k w i t h the c r a t o n .  Accretion Jurassic  time  collision westerly evidence  of  the  Stikine  does not  exclude  within Stikinia, terrane,  before  t o support  Block w i t h  or  the  Jurassic  time.  such models would be  America  in  of  terrane  and  a more  However,  direct  l a r g e l y masked  by  cover.  Exploration Potential  Although alteration way,  possibility  between S t i k i n i a  younger events and Late Mesozoic  4.3  North  the  o f the  characteristics BJ p r o s p e c t  comparisons w i t h  of  mineralization  are known i n o n l y a  b e t t e r understood  and  general  d e p o s i t s and  their  g e o l o g i c a l s e t t i n g s a l l o w s the f o r m u l a t i o n o f a g e n e r a l i z e d g e n e t i c model.  T h i s , i n t u r n , can  e x p l o r a t i o n and  e v a l u a t i o n o f the  lead  t o more  p r o s p e c t and  efficient  surrounding  areas.  Two within  t e m p o r a l l y d i s t i n c t a l t e r a t i o n t y p e s are r e c o g n i z e d the  property  area.  quartz-muscovite-carbonate is  widespread  and  The  first,  + pyrite  c h a r a c t e r i z e d by  assemblage  pre-kinematic.  a  (sericitic),  Chemical  changes  172  -  -  associated with t h i s a l t e r a t i o n and  potassium  calcium.  (section  activity  4.3).  felsic  suggest  losses  This alteration  hydrothermal  the  and  The  of  i n c l u d e a d d i t i o n s of  magnesium,  i s attributed  r a t h e r then presence  tuff unit  and  of  small  hydrothermal  to  sulphide  possibly  temporally,  alteration. with  With a few  does  mineralization structural  not  exceptions,  serve  except  in  weaknesses  a  as  lenses  to  volcanogenic  possibilty.  spatially,  zones  these  of  a  guide sense  focus  the  to  barren  sericitic  gold-silver  where  later  and  sericitic  v e i n s are  Therefore,  regional  serve  sulphide  are  with  r e s p e c t t o p r e c i o u s metals.  alteration  within  Related  veins  associated  processes  caused by a submarine  system.  quartz  and  fragments  stratabound  massive s u l p h i d e d e p o s i t s a r e a d i s t i n c t  Foliation-parallel  iron  pre-metamorphic  t o metamorphic  t h a t t h i s e a r l y a l t e r a t i o n was  volcanogenic  sodium,  quartz  original  hydrothermal  activity.  The  second  controlled  zones  sericitization. alteration  but  previously structures commonly  type  of  of  c o n s i s t s of  carbonatization,  This  alteration  i s most  unaltered cut  alteration  noticeable mafic  silicification  overprints where  with  A-C  joints  and  sericitic  i t has  lithologies.  a l l deformation-related  coincident  fracture-  affected  Controlling  fabrics  and  are  associated  with  the  173  -  fourth  phase o f f o l d i n g .  consist and  of a variety  sulphides.  lenticular.  Veins r e l a t e d to t h i s a l t e r a t i o n  o f mixtures  Vein  o f quartz,  morphology  varies  Fe-carbonates  from  tabular  to  Textures range from massive t o banded and l e s s  commonly b r e c c i a t e d . sphalerite, galena,  -  Sulphide  tetrahedrite,  silver  mineralogy  includes  arsenopyrite,  and bismuth  tellurides,  pyrite,  chalcopyrite,  electrum  and  L a t e hypogene o x i d a t i o n l o c a l l y o v e r p r i n t s s u l p h i d e  gold.  minerals  w i t h a p y r r h o t i t e , hematite, and c u p r i t e assemblage.  Chemical include K 0,  C0  2  t h e l o s s o f MgO, and l o c a l l y Ce.  2  variable. sulphides slowly  cooling with  also  particularly allows  for  carbonate a l t e r a t i o n  2  2  Change i n c o n c e n t r a t i o n of  quartz,  due t o an i n c r e a s e  hydrothermal wall-rocks.  have  with  Na 0 and FeO, and g a i n s o f S i 0 ,  Co-precipitation was l i k e l y  reactions could  changes a s s o c i a t e d  fluid  and  i n t h e pH o f the hydrolysis  Oxidation-reduction  reactions  caused  to  This  considerable  carbonate  by  contributed  the sulphides.  o f CaO i s  mineral  form  vertical  deposition,  of vein  continuity  formation of  vein  mineralogy.  Potassium-argon and r u b i d i u m - s t r o n t i u m dates from associated for  vein  a l t e r a t i o n i n d i c a t e s a minimum E a r l y J u r a s s i c age  mineralization.  constraints.  This  age  Mineralization  i s supported  i s later  than  by  geological  o r synchronous  174  -  with  the  later  phases  o f deformation,  L a t e T r i a s s i c sediments. a thermal Jurassic  event  R e - s e t t i n g o f i s o t o p i c ages due t o  a single  ization i s possible. similar  Fyfe  how  d u r i n g prograde  deposits.  the  hydrothermal  a l t e r a t i o n and p r e c i o u s metal  Early  and  Phillips  can  mineralization  (1986) and  produce  chemistry  to  and  alteration  porphyry  (Schink,  deposit  sufficient  1983,  concordant  (1986)  reactions  of  with  the  quartz-carbonate-gold  extensive  zones  associated with 1977)  of  demonstrate  of  the  quartz-  Red  that  Chris alkalic  ( c f . Henely  and White, 1981).  m i n e r a l i z a t i o n on the  Creek and elswhere o f evidence  Kerrich  fluids  i n t r u s i v e r o c k s can produce s i m i l a r type f l u i d s  age  mineralogy  Kerrich  decarbonation  cause  the  ankerite-sericite  The  mineral-  metamorphism a t the g r e e n s c h i s t - a m p h i b o l i t e  Alternatively,  and E l l i s ,  fluids  Comparisons w i t h o t h e r d e p o s i t s shows  dewatering  transition  appropriate  of  i n a v a r i e t y of t e c t o n i c s e t t i n g s .  (1981),  demonstrate  origin  alteration  can be produced  facies  affected  intrusions.  r e l a t e d t o carbonate  and  which have  i s u n l i k e l y because o f the p a u c i t y o f  More than  that  -  age  of  alkalic  the  BJ  prospect  intrusions  i n the S t i k i n e Arch.  at  is  Galore  T h i s , and the l a c k  f o r an E a r l y J u r a s s i c metamorphic event  p r o s p e c t area, i m p l i c a t e s a moderate t o deep s e a t e d  i n the alkalic  - 175  intrusion  as  the  relationship  is  source  of  reflected  -  hydrothermal  on  a  fluids.  regional  scale  This by  the  s i m i l a r i t y between the g e o g r a p h i c a l d i s t r i b u t i o n o f p r e c i o u s metal and  d e p o s i t s along  the  the western  northwesterly  edge of the  trending b e l t  of  Stikine  alkalic  Arch  plutons  as  noted by B a r r e t a l . (1976).  R e g i o n a l e x p l o r a t i o n f o r mesothermal v e i n type d e p o s i t s should  focus  composition  on  pre-Middle  Jurassic  t h a t show evidence  of  mafic  o f a t l e a s t moderate  burial  (greenschist  f a c i e s metamorphism) and  observed  inferred  scale,  or  alkalic  mineralization  structure; importance.  lithological  will  controls  Structures with  spatial  plutons. be  rocks  At  primarily will  proximity the  property  controlled  be  of  to  by  secondary  associated alteration  warrant  attention.  Carbonate a l t e r a t i o n h a l o e s are t y p i c a l l y from 2  t o 20 times  the t h i c k n e s s o f a s s o c i a t e d v e i n s , and  contain  similar  a  Therefore,  sulphide  geochemical  based  assemblage exploration  as  the  commonly veins.  techniques  are  w e l l - s u i t e d t o search f o r m i n e r a l i z e d s t r u c t u r e s i n areas o f overburden.  - 176 -  REFERENCES ALDRICK, D. 1986. Geology o f the Stewart area, northwestern B. C., Unpub. PhD t h e s i s , Univ. o f B.C. ALLEN, D.G., PANTELEYEV, A., ARMSTRONG, A.T. 1976. G a l o r e Creek i n porphyry d e p o s i t s o f the Canadian C o r d i l l e r a . C. I.M. Spec. V o l . 15, pp. 402. AMLI, R. 1975. Mineralogy and r a r e e a r t h geochemistry o f a p a t i t e and xenotime from g l o s e r h e i a pegmatite, F r o l a n d , Norway. Am. M i n e r a l o g i s t , V o l . 60, pp. 607-620. ANDERSON, R.G. 1983. The H o t a i l u t h B a t h o l i t h , Cry Lake,. S p a t s i z i and Dease Lake map-areas n o r t h - c e n t r a l , B.C., Unpub. PhD t h e s i s C a r l t o n Univ. ARMSTRONG, R.L. 1984. Late T r i a s s i c E a r l y J u r a s s i c time s c a l e c a l i b r a t i o n i n B.C. Canada, i n Numerical D a t i n g o f the S t r a t i g r a p h i c Column. ODIN, G.S., E d i t o r . BARR, D.A., FOX, P.E., NORTHCOTE, K.E. and PRETO, V.A. 1976. The a l k a l i n e s u i t e porphyry d e p o s i t s : a summary i n Canadian Porphyry Deposits o f the Canadian C o r d i l l e r a , C.I.M. Spec. V o l . No. 16. BERMAN, R. 1977. The C o q u i h a l l a v o l c a n i c complex, S.W.B.C. Unpub. MSc. T h e s i s U.B.C. BIBBY, G.L. 1981. S u l p h i d e mineralogy o f the BJ c l a i m group northwestern, B.C., Unpub. G e o l . 428 Report, U n i v e r s i t y o f B.C. BOYLE, R.W. 1979. The geochemistry o f g o l d and i t s d e p o s i t s . G.S.C. B u l l . 280. BROWN, D. 1986. Geology o f the S i l b a k - P r e m i e r Mine, northwestern B.C. Unpub. MSc t h e s i s , Univ. o f B.C. BROWN, J . C , HUGHES, D.J. and ESSON J . 1973. New XRF data r e t r i e v a l techniques and a p p l i c a t i o n t o U.S.G.S. standard r o c k s . Chem. G e o l . V o l . 21, pp. 223-229. CASADERVAL and OHMOTO 1974. Sunnyside Mine, Eureka Mining D i s t r i c t , San Juan County, Colorado: Geochemistry o f Gold and Base metal Ore d e p o s i t i o n i n a v o l c a n i c environment. E.C. Geol., V o l . 72, pp. 1285-1320. COX,  K.G., BELL, J.D. and PANKHURST, R.J. 1979. The i n t e r p r e t a t i o n o f igneous r o c k s . George, A l l e n and Unwin Pub. London.  - 177 -  CURRIE, K.L. and FERGUSON, J . 1971. A study o f f e n i t i z a t i o n around t h e a l k a l i n e c a r b o n a t i t e complex a t C a l l e n d e r Bay, O n t a r i o , Canada. Can. J . E a r t h S c i . , V o l . 8, pp. 498-517. DALRYMPLE, G.B. 1979. C r i t i c a l t a b l e s f o r c o n v e r s i o n o f K-Ar ages from o l d t o new c o n s t a n t s , Geology, V. 7, pp. 558-560. DRUMMOND, A.D. and GODWIN, C.I. 1976. Hypogeme m i n e r a l i z a t i o n : an e m p i r i c a l e v a l u a t i o n o f a l t e r a t i o n zoning i n Porphyry D e p o s i t s o f t h e Canadian C o r d i l l e r a . C.I.M. Sepc. V o l . 15. DUBE, B., GUHA, J . and ROCHCLEAU, M. 1987. A l t e r a t i o n p a t t e r n s r e l a t e d t o g o l d m i n e r a l i z a t i o n and t h e i r r e l a t i o n s h i p t o CO /H_0 r a t i o s . Mineralogy and P e t r o l o g y V o l . 37, ppT 267-291. EISBACHER, G.H. 1974. E v o l u t i o n o f s u c c e s s o r b a s i n s i n t h e Canadian C o r d i l l e r a , i n Modern and A n c i e n t G e o s y n c l i n a l Sedimentation (R.H. Dott and R.H. Shaver, e d i t o r s ) . S o c i e t y o f Economic P a l e o n t o l o g i s t s and M i n e r a l o g i s t s , S p e c i a l P u b l i c a t i o n 19, pp. 274-291. 1977. M e s o z o i c - T e r t i a r y t e c t o n i c b a s i n models f o r t h e Canadian C o r d i l l e r a and t h e i r g e o l o g i c a l c o n s t r a i n t s . Canadian J o u r n a l o f E a r t h S c i e n c e s , V. 14, pp. 2414-2421. EVENCHICK, C A . 1979. S t r a t i g r a p h , s t r u c t u r e and metamorphism o f t h e Atna Peak area, B.C. Unpub. BSc t h e s i s , C a r l e t o n Univ. FINLOW-BATES, T. and STUMPFL, E.F. 1981. The behavior o f s o - c a l l e d immobile elements i n hydrothermally a l t e r e d rocks a s s o c i a t e d w i t h v o l c a n o g e n i c s u b m a r i n e - e x h a l i t i v e ore d e p o s i t s . Mineralium Deposita, V o l . 16, pp. 319-328. FISHER, R.V. 1961. Proposed c l a s s i f i c a t i o n o f v o l c a n i c l a s t i c sediments and r o c k s . G e o l . Soc. Amer. B u l l . 72, pp. 1409-1414. and SCHMINKE, H.U. 1984. P y r o c l a s t i c Rocks. FLOYD, P.A. and WINCHESTER, J.A. 1978. I d e n t i f i c a t i o n and d i s c r i m i n a t i o n o f a l t e r e d and metamorphosed v o l c a n i c rocks u s i n g immobile elements. Chem. Geol., V o l . 21, pp. 291-306.  - 178  -  FOLK, P. 1987. Geology and geochemistry of the BJ I n t e r n a l r e p o r t f o r Teck E x p l o r a t i o n s .  claims.  FORSTER, D.B. 1984. Geology, p e t r o l o g y and p r e c i o u s metal m i n e r a l i z a t i o n , Toodoggone r i v e r area, n o r t h - c e n t r a l B.C., Unpub. MSc t h e s i s , Univ. o f B.C. GABRIELSE, H. 1961. O p e r a t i o n S t i k i n e i n Current G e o l o g i c a l Survey o f Canada, Paper 61-1A.  Research  1978. O p e r a t i o n Dease. i n Current Research, P a r t A, G e o l o g i c a l Survey of Canada, Paper 78-1A, pp. 1-4. and MANSY, J.L. 1978. S t r u c t u r a l s t y l e i n n o r t h e a s t Cry Lake map-area, n o r t h - c e n t r a l B r i t i s h Columbia, i n Current Research, P a r t A, G e o l o g i c a l Survey o f Canada, Paper 78-1A, pp. 33-34. GARCIA, M.O. 1978. C r i t e r i a f o r the i d e n t i f i c a t i o n o f a n c i e n t v o l c a n i c a r c s . E a r t h S c i . Reviews, V o l . 14, pp. 147-166. GRANT, J.A. 1986. The isochon diagram - a simple s o l u t i o n t o Gresen's equation f o r metasomatic a l t e r a t i o n . Ec. Geol., V o l . 81, pp. 1976-1982. GREENWOOD, 1976. Unpub. c o u r s e notes f o r Geol. Metamorphic p e t r o l o g y . The Univ. o f B.C.  433:  GRESENS, R.L. 1967. Composition-volume r e l a t i o n s h i p s of metasomatism. Chem. Geol., V o l . 2, pp. 47-55. GROVEE, E.W. 1968. Geology and m i n e r a l d e p o s i t s o f the Stewart area, B.C., B.C. Dept. o f Mines, B u l l . #58. HARTE B. and GRAHAM, C M . 1975. The g r a p h i c a l a n a l y s i s o f g r e e n s c h i s t t o a m p h i b o l i t e f a c i e s m i n e r a l assemblages i n metabasites. J . P e r o l . 16, pp. 347-370. HAYES, T.S. 1984. G e o l o g i c a l s t u d i e s on the g e n e s i s o f the Spar Lake strata-bound c o p p e r - s i l v e r d e p o s i t , L i n c o l n County, Montana. Pub. PhD t h e s i s S t a n f o r d U n i v e r s i t y . HEMLEY, J . J . 1959. Some m i n e r a l o z i c a l e q u i l i b r i u m i n the system K.0-A1 O . - S J . - H O. Am J . S c i . V o l . 257, pp. 241-270. * * £  J  1  HENLEY, R.W., TRUESDELL, A.H. and BARTON, P.B. J r . 1984. F l u i d - m i n e r a l e q u i l i b r i a i n hydrothermal systems. S.E.G. Reviews i n Economic Geology, V o l . 1.  - 179 -  HOLLAND, H.D. and MALININ, S.D. 1967. The s o l u b i l i t y and occurrence o f non-ore m i n e r a l s i n Geochemistry o f Hydrothermal Ore D e p o s i t s , Barnes, H.L., E d i t o r J . Wiley & Sons. HOLM, P.E. 1982. N o n - r e c o g n i t i o n o f c o n t i n e n t a l t h o l e i i t e s u s i n g t h e T i - Y - Z r diagram. C o n t r i b s . t o Min. and P e t r . , V o l . 79 No. 3, pp. 308. HORSKEY, S., VANDERHEYDEN, P. and FLETCHER, K. 1985. U.B.C. l a b manual f o r XRF a n a l y s i s o f major elements. IRVINE, T.N. and BARAGAR, W.R.A. 1971. A guide t o t h e chemical c l a s s i f i c a t i o n o f v o l c a n i c r o c k s . Can. J . E a r t h S c i . , V o l . 8, pp. 523-545. IRVING, E., MONGER, J.W.H. and YOLE, R.W. 1980. New paleomagnetic evidence f o r d i s p l a c e d t e r r a i n s i n B r i t i s h Columbia, i n The C o n t i n e n t a l C r u s t and I t s M i n e r a l D e p o s i t s (D.W. Strangway, e d i t o r ) . G e o l o g i c a l A s s o c i a t i o n o f Canada, S p e c i a l Paper 20, pp. 441-456. JACKSON, K.J. and HELGASON, H.C. 1985. Chemical and thermodynamic c o n s t r a i n t s on t h e hydrothermal t r a n s p o r t and d e p o s i t i o n o f t i n . E c . G e o l . V o l . 80, pp. 1365-1378. KERR, T.A. 1948a. Lower S t i k i n e and western I s k u t r i v e r areas o f B.C., GSC Memoir 246. 1948b. Taku R i v e r map-area, B r i t i s h GSC Memoir 248.  Columbia,  KERRICH R. and FYFE W.S. 1981. The g o l d - c a r b o n a t e a s s o c i a t i o n : source o f C0_ and C0_ f i x a t i o n r e a c t i o n s i n Archean Lode d e p o s i t s . Chemical Geology, V o l . 33, pp. 265-294. KERRICK, D.M. 1974. Review o f metamorphic mixed v o l a t i l e (H 0-C0 ) e q u i l i b r i a . Am. Miner. V o l . 59, pp. 729-762. 2  2  KERRICH, R. and HODDER, R.W. 1982. Archean l o d e g o l d and base metal d e p o s i t s : chemical evidence f o r metal f r a c t i o n a t i o n i n t o independent hydrothermal r e s e r v o i r s . C.I.M. s p e c i a l V o l . 24, pp. 144-160. LOND, C.S. 1948. McConnel Creek map-area, C a s s i a r B r i t i s h Columbia. GSC - Mem. 251.  district,  LOWELL, J.D. and GILBERT, J.M. 1970. L a t e r a l and v e r t i c a l a l t e r a t i o n m i n e r a l i z a t i o n zoning i n porphyry o r e d e p o s i t s . Econ Geol. V o l . 65, pp. 373-408.  - 180 -  LORD, 1948. A s l t k a Group - McConnel Creek? McBIRNEY, A.R. and WILLIAMS, H. 1979. Volcanoloov . Freeman Cooper & Co., San F r a n c i s c o . MCMILLAN, W.J. 1974. Rey, 92I/SE-160. i n Geology, E x p l o r a t i o n and M i n i n g i n B r i t i s h Columbia, 1973. B.C. Dept. Energy, Mines and Petroleum Resources, pp. 181-184. MEYER C. and HEMLEY J . J . 1967. W a l l rock a l t e r a t i o n . I n Geochemistry o f hydrothermal o r e d e p o s i t s . H. L. Barnes Ed. H o l t R i e n h a r t and Winston, pp. 166-232. MIYASHIRO, 1973. Metamorphism and Metamorphic B e l t s . George a l i e n and Unwin Co. L t d . , London. MONGER, J.W.H. 1969. S t r a t i g r a p h y and s t r u c t u r e o f Upper P a l e o z o i c rocks, n o r t h e a s t Dease Lake map-area, B r i t i s h Columbia. G e o l o g i c a l Survey o f Canada, Paper 68-48, pp. 41. 1975. Upper P a l e o z o i c r o c k s o f t h e A t l i n Terrane, northwestern B r i t i s h Columbia and s o u t h - c e n t r a l Yukon. G e o l o g i c a l Survey o f Canada, Paper 74-47, pp. 63. 1975. C o r r e l a t i o n o f e u g e o s y n c l i n a l 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 i n t h e North American C o r d i l l e r a . Geoscience Canada, V o l . 2, pp. 4-10. 1977. Upper P a l e o z o i c r o c k s o f t h e Western C o r d i l l e r a and t h e i r b e a r i n g on C o r d i l l e r a n e v o l u t i o n . Can. J . E a r t h S c i . , V o l . 14, pp. 1832-1859. and PRICE, R.A. 1979. Geodynamic e v o l u t i o n o f t h e Canadian C o r d i l l e r a - p r o g r e s s and problems. Canadian J o u r n a l o f E a r t h S c i e n c e s , V o l . 16, pp. 770-791. 1980. Upper T r i a s s i c s t r a t i g r a p h y , Dease Lake and Tulsequah map-areas, northwestern B r i t i s h Columbia, i n Current Research, P a r t B, G e o l o g i c a l Survey o f Canada, Paper 80-1B, pp. 1-9. , PRICE, R.A. and TEMPLEMAN-KLUIT, D.S. 1981. T e c t o n i c a c c r e c t i o n and t h e o r i g i n o f t h e two major metamorphic and p l u t o n i c w e l t s i n t h e Canadian C o r d i l l e r a . Can. J . E a r t h S c i .  -  181  -  and SOUTHER, J.G. and GABRIELSE, H. 1972. E v o l u t i o n of the Canadian C o r d i l l e r a : a p l a t e - t e c t o n i c model. American J o u r n a l of Science, V o l . 272, pp. 577-602. MONTOYA, J.W. and HEMLEY, J . J . 1975. A c t i v i t y R e l a t i o n s and s t a b i l i t i e s i n a l k a l i f e l d s p a r and mica a l t e r a t i o n r e a c t i o n s . Econ Geol. V o l . 70, pp. 577-583. NELSON J . and PAYNE, J.G. 1984. P a l e o z o i c v o l c a n i c assemblages and v o l c a n o g e n i c massive s u l p h i d e d e p o s i t s near Tulsequah, B.C. J o u r n a l Can. E a r t h S c i . , V o l . 21 #3, pp. 379-381. NIXON, 1985.  U n i v e r s i t y o f B.C.  PhD  thesis.  OHOMOTO, H. and KERRICH, D. 1977. Devolitization i n g r a p h i t i c systems. Am. J . S c i . , V o l . 277, 1013-1044.  equilibria pp.  and SKINNER, B.J. 1983. The Kurocko and r e l a t e d v o l c a n o g e n i c massive s u l p h i d e d e p o s i t s : I n t r o d u c t i o n and summary of new f i n d i n g . In: Econ Geol Monograph #5. pp. 1-9. OVERSTREET, W.C. 1960. T h 0 i n monazite. 2  PANTELEYEV, A.  1973.  Metamorphic grade and abundance of USGS P r o f . Paper 400-B, pp. 55-57. B.C.D.M. Reports.  PEARCE, J.A. 1974. The Ti0_-K0-P05 Diagram: A method o f d i s c r i m i n a t i n g between o c e a n i c and non-oceanic b a s a l t s . E a r t h & P l a n . S c i . l e t t e r s , V o l . 24, pp. 419-426. and CANN, J.R. 1975. Tectonic s e t t i n g of v o l c a n i c rocks determined u s i n g t r a c e element a n a l y s e s . E a r t h and P l a n e t a r y S c i . l e t t e r s , V o l . 19, pp. 290-300. PERKINS, E.H., BROWN, T.H. and BERMAN, R.G. 1986. Three programs which c a l c u l a t e pressure-temperaturecomposition phase diagrams. Computers and Geosciences, V o l . 12, pp. 749-755. PITCHER, M.G. 1960. F u s u l i n i d s of the Cache Creek Group, S t i k i n e R i v e r area, C a s s i a r D i s t r i c t , B.C. Unpub. MSc t h e s i s , Brigham Young U n i v e r s i t y . PRETO, V.A. 1977. The N i c o l a Group: Mesezoic v o l c a n i s m r e l a t e d t o s i f t i n g i n southern B. C. GA.C Spec. Pap. No. 16, pp. 39-57.  - 182 -  PRICE, R.A., MONGER, J.W.H. and MULLER, J.E. 1981. C o r d i l l e r a n c r o s s s e c t i o n - C a l g a r y t o Vancouver, i n F i e l d Guides t o Geology M i n e r a l D e p o s i t s . G e o l o g i c a l A s s o c i a t i o n o f Canada, Annual Meeting, 1981, pp. 261-334. RAMSEY, 1967. F o l d i n g and F r a c t o r i n a i n Rocks. McGraw-Hill, New York, N.Y. READ, P., 1983. 1:50,000 s c a l e geology maps o f NTS 104B/15,16, Unpub. maps f o r B.C. Hydro and Power Authority. and OKULITCH, A.V. 1977. The T r i a s s i c unconformity o f s o u t h - c e n t r a l B r i t i s h Columbia. Can. J o u r . E a r t h S c i . V o l . 14 #4, pp. 606-638. RIVERIN, G. 1977. W a l l r o c k a l t e r a t i o n a t the M i l l e n b a c h mine, Noranda Que. Unpub. Ph.D. t h e s i s Queen's University. ROSE, A.W. and BURT, D.M. 1979. Hydrothermal a l t e r a t i o n i n Geochemistry o f hydrothermal ore d e p o s i t s . Barnes H.L., E d i t o r . John W i l e y and Sons, Publ. SALEEBY, 1985. Nature o r Am. J . Sc. SCHINK, E.A. 1977. Geology o f t h e r e d - c h r i s porphyry copper d e p o s i t northwestern B r i t i s h Columbia. Unpub. MSc t h e s i s Queen's Univ. SCHROETER, T.G. 1982. Toodoggone R i v e r (94E). I n G e o l o g i c a l f i e l d w o r k 1981, B. C. M i n i s t r y o f Energy, Mines and Petroleum Resources, Paper 1982-1, pp. 122-134. SILLITOE, 1978. SOUTHER, J.G. 1971. Geology and m i n e r a l d e p o s i t s o f the Tulsequah map-area, B r i t i s h Columbia. GSC Memoir 362. 1972. T e l e g r a p h Creek map-area, GSC Paper 71-44. 1977. V o l c a n i s m and t e c t o n i c environments i n the Canadian C o r d i l l e r a - a second look, i n V o l c a n i c Regimes o f Canada. GAC Spec. Pap. No. 16. , e t a l . 1979. Brew, D.A. and O k u l i t c h , A.V. (compilers) 1979. I s k u t R i v e r , B r i t i s h Columbia A l a s k a ; Sheet 104, 114 G e o l o g i c a l Survey o f Canada 1:1,000,000 G e o l o g i c a l A t l a s Map 1418A.  - 183 -  SPILSBURY, W. 1982. Geology o f the S c h a f t Creek porphyry Cu-Mo d e p o s i t , northwestern B r i t i s h Columbia. Unpub. Minex Paper Queen's U n i v e r s i t y . STEIGER, R.H. and JAGER, E. 1977. Subcommission on geochronology: Convention on t h e use o f decay constants i n geo- and cosmochronology. E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , V o l . 36, pp. 359-362. TEMPLEMAN-KLUIT, D.J. 1979. T r a n s p o r t e d c a t a c l a s t i t e , o p h i o l i t e and g r a n o d i o r i t e i n Yukon: evidence o f a r c c o n t i n e n t c o l l i s i o n . G e o l o g i c a l Survey o f Canada, Paper 79-14, pp. 27. THOMPSON, M. and HOWARTH, R.J. 1976. Duplicate analysis i n geochemical p r a c t i c e . A n a l y s t 101, pp. 690-709. 1978. A new approach t o the e s t i m a t e o f a n a l y t i c a l p r e c i s i o n . J . Geochem. E x p l . V o l . 9, pp. 23-30. TIPPER, H.W. 1978. J u r a s s i c b i o s t r a t i g r a p h y , Cry Lake maparea, B r i t i s h Columbia, i n Current Research, P a r t A, G e o l o g i c a l Survey o f Canada, Paper 78-1A, pp. 25-27. TURNER, F . J . 1968. Metamorphic Toronto.  P e t r o l o g y ; McGraw-Hill,  VANDERHEYDEN, P. 1982. T e c t o n i c and s t r a t i g r a p h i c r e l a t i o n s between t h e Coast P l u t o n i c Complex and Intermontane B e l t , w e s t - c e n t r a l , B.C., Unpub. Msc. T h e s i s U.B.C. VLASOV, K.A. 1966. Geochemistry o f r a r e elements. Academy o f S c i e n c e s , USSR. I s r a e l Program f o r S c i e n t i f i c Translations Ltd. WHEELER, J.O. and GABRIELSE H., 1972. The C o r d i l l e r a n S t r u c t u r a l Province i n V a r i a t i o n s i n t e c t o n i c s t y l e s i n Canada. G.A.C. Spec. Pap. 11, pp. 1-81. WHITE, W.H. 1959. C o r d i l l e r a n t e c t o n i c s i n B r i t i s h Columbia. Amer. Assoc. P e t r o l . G e o l . B u l l . V o l . 43, pp. 60-100. WHITE, W.H., HARAKAL, J . E . and CARTER, N.C. 1968. Potassium-argon ages o f some ore d e p o s i t s i n B r i t i s h Columbia. WIESS, L.E. 1972. Minor s t r u c t u r e s o f deformed r o c k s : A photographic a t l a s .  - 184 -  WINCHESTER, J.A. and FLOYD, P.A. 1977. Geochemical d i s c r i m i n a t i o n o f d i f f e r e n t magma s e r i e s and t h e i r d i f f e r e n t i a t i o n products u s i n g immobile elements, Chem. Geol., V o l . 20, pp. 325-343. WINKLER, H.G.F. 1974. P e t r o g e n e s i s o f metamorphic rocks (3rd e d i t i o n ) , S p r i n g e r - V e r l a g , New York, N.Y., pp. 320. YORK, D. 1976. The b e s t i s o c h r o n . E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , V o l . 2, pp. 479-482.  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0052696/manifest

Comment

Related Items