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The Geology and ore deposits of the Howards Pass Area, Yukon and Northwest Territories : the origin of… Morganti, John Michael 1979

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THE GEOLOGY AND ORE DEPOSITS OF THE HOWARDS PASS AREA, YUKON AND NORTHWEST TERRITORIES:  THE ORIGIN OF BASINAL SEDIMENTARY  STRATIFORM SULPHIDES DEPOSITS  by JOHN MICHAEL MORGANTI B.A., B . S c , Western Washington State University, Bellingham, 1969 M.Sc, Washington State University, Pullman, 1972 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Dept., Geological Sciences) We accept t h i s thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA September, 1979  ^cJJohn Michael Morganti , 1979  In p r e s e n t i n g t h i s  thesis  an advanced degree at  further  fulfilment  of  the  requirements  the U n i v e r s i t y of B r i t i s h Columbia, I agree  the L i b r a r y s h a l l make it I  in p a r t i a l  freely  available  for  this  thesis  f o r s c h o l a r l y purposes may be granted by the Head of my Department  of  this thesis for  It  financial  of  gain s h a l l not  Geological Sciences  The U n i v e r s i t y o f B r i t i s h Columbia 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5  or  i s understood that copying or p u b l i c a t i o n  written permission.  Department  that  reference and study.  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f  by h i s r e p r e s e n t a t i v e s .  for  be allowed without my  i  ABSTRACT  Economically exist  important  sedimentary-type  stratiform  Zn-Pb  deposits  in the Lower S i l u r i a n basinal facies of the Selwyn Basin along  Yukon-Northwest T e r r i t o r i e s border.  the  Three major similar deposits have been  defined to date, and are referred to c o l l e c t i v e l y as the Howards Pass deposits. The  Pre-Mesozoic  history  three major basin systems. 'Grit Unit' was  deposited  of the  Howards Pass area  was  led to  by  During the Late Hadrynian to Early Cambrian the as a c l a s t i c wedge with a western source  I n i t i a l l y deep water turbidites were deposited but continued the basin  dominated  shallow water deposition.  During  area.  filling  in of  the Late Cambrian to  Early Devonian the Rabbitkettle and Road River groups were deposited in the Selwyn Basin.  The  Selwyn Basin is defined by shallow water carbonates  the east and a general deep water environment to the were  succeeded  by  hemipelagic  and  pelagic  west.  The  on  carbonates  organic-rich sediments  occasional terrigenous material deposited by geostrophic currents.  with  Within  the Selwyn Basin the Ordovician to the Early S i l u r i a n Howards Pass formation contains three major facies from east to west; a slope f a c i e s , a base of  slope facies and a chert basin f a c i e s .  in sub-basins  in the base of slope f a c i e s .  The  Howards Pass deposits occur  The t h i r d major basin system in  the region was associated with u p l i f t to the west and is represented by the Earn Group.  In this  later basin t u r b i d i t y  currents associated with  sub-  marine fans deposited c l a s t i c material derived from the uplifted centre of the Selwyn Basin and Earn Group.  underlying rocks.  Major barite deposits occur in the  ii The individual Howards Pass deposits consist of complex saucer shaped bodies containing laminated to massive sulphides occurring in the Lower Silurian active member of the Howards Pass formation. characterized  by  galena and pyrite.  simple  sulphide mineralogy,  The deposits are  predominantly  sphalerite,  The sulphides in the deposits may be divided into six  textural types which aid in characterizing the sulphides geologically and metallurgically.  Types I,  II,  and III  consist of laminated sulphides,  types IV and V consist of laminated to massive sulphides and type VI consists of late diagentic concretionary sulphides.  Types I thru V are as-  sociated with specific lithofacies in the active member. The Howards Pass deposits show characteristics common to stratiformsedimentary deposits such as conformity with bedding, no obvious association with volcanic rocks, similar age of the three major associated depos i t s , single-stage Pb isotope systematics and association with organic-rich sedimentary rocks. sits and other  In contrast differences between the Howards Pass depo-  stratiform-sedimentary  deposits, include deposition in a  starved basin sedimentary environment, a lack of any associated feeder zone within 10 km, a lack of massive pyrite associated with the deposits, relatively  low Ag and Cu associated with the deposits and a lack of bedded  barite near the deposits. This datum suggests that the Howards Pass deposits are unique, and therefore a model is proposed which is relevant to the geologic setting. The most important part of the model is the synsedimentary deposition of Zn and Pb sulphides within sub-basins occurring at the base of slope of the eastern edge of the Selwyn Basin.  The formation of biogenetic sulphide  from sea water sulphate is suggested by the sulphur isotope data.  This  data also supports the existence of an ideal cycle of the active member  i ii and suggest a possible sub-basin  evolution during an individual cycle.  origin of the metals in the deposit  is not clear, but  The  the association of  volcanic t u f f s near the shale-out at the eastern margin of the Selwyn basin suggests that warm f l u i d s may grated down slope and possibly  The  collected  compaction f l u i d s may  basins and concentrated  have been expelled onto the  floor,  in the topographically low sub-basins, have been expelled d i r e c t l y  into the  mior sub-  during brine evolution.  abundant evidence  for slumping and  l a t e r folding and the  l i t y of both ordinary and more radiogenic Pb  location of Zn and  possibi-  leads to the conclusion that  post-depositional mobilization of both sediment and in the f i n a l  sea  sulphide was  important  Pb.  Exploration for Howards Pass-type deposits, based on the above model, should emphasize the sedimentary nature of the deposits. graphic  exploration should be aimed at defining major,  starved basins.  The  Regional  strati-  platform-marginal,  importance of defining the paleogeography, such as the  base of slope and s p e c i f i c sub-basins,  appears to be c r i t i c a l .  This method  emphasizes the petroleum methodology of looking for traps, although present case these are paleogeographic  sulphide traps.  in the  iv TABLE OF  CONTENTS Page  ABSTRACT  ,  1  PREFACE  xix  ACKNOWLEDGMENTS CHAPTER  xx  I INTRODUCTION  PURPOSE  AND  1  SCOPE OF THE PRESENT STUDY  1  METHODS OF STUDY  1  LOCATION AND  3  ACCESS  TOPOGRAPHY AND  CLIMATE  3  LOCAL GEOGRAPHY HISTORY AND  7  PREVIOUS  ROCK CLASSIFICATION CHAPTER  GEOLOGIC USED  INVESTIGATIONS  IN THE PRESENT STUDY  II - GEOLOGY  INTRODUCTION  7 8 10  .  10  LOCAL GEOLOGY  13  STRATIGRAPHY  15  Map  Unit  2 ( 'Grit  Unit  Map  Unit  7a (Lower  Map  Unit  7b-l (Massive  Map  Unit  7b-2 (Wavy Banded  Map  Unit  7b-3 ( T r a n s i t i o n  Map  Unit  10a (Howards  1  )  15  Siltstone  Unit)..  Limestone  17  Formation)  Limestone  Formation)..  Formation)  Pass  Unit  Formation)  29 29  10a-l ( P y r i t i c  Siliceous  Shale  Member) Map  Unit  Map U n i t Member) Map U n i t  23 28  Introduction Map  19  31 10a-2 ( C a l c a r e o u s 10a-3 (Lower  Mudstone Member)  Cherty  32  Mudstone  10a-4 ( A c t i v e Member)  35 37  V  Page Facies  1 (Basal  Facies)  Facies 2 (Light Fac i es )  Grey  3 (Graded  Facies  4 (Thin  Facies  Basal  Limestone  Bedded  Facies)  5 (Cherty  Mudstone)  7 (Whitish  Facies  8 (Grey Chert  Unit  10a-5 (Upper  Map  Unit  10b ( F l a g g y  44  45  Facies  Map  Cherty 48  Grey  Zn-Pb Mudstone)  Facies)  Siliceous Mudstone  47  Mudstone  51 55  Member)  Formation)  55 59  ORANGE WEATHERING MEMBER  62  FETID  67  LIMESTONE  ZONE  Map  Unit  10c (Upper  Map  Unit  18b-l ( I r o n  Creek  Map  Unit  1 8 b - 2 (Yara  Peak  Map  Unit  18b-3 ( C h e r t  III  CORRELATION  CORRELATION  AND  Chert  Formation) Formation) Formation)  Pebble Conglomerate)... SEDIMENTATION  OF UNITS  SEDIMENTATION  68 71 78 85 90 90 95  Introduction  95  Lower  96  Units  Howards Pass Upper  CHAPTER  Facies)...  Calcareous  F a c i e s 6 ( T h i n Bedded Mudstone Fac i es )  CHAPTER  Limestone 43  Facies  Mudstone  41  Formation  Units  98 109  Summary  120  IV - Zn-Pb DEPOSITS  123  INTRODUCTION  123  vi Page DESCRIPTION  OF TEXTURAL TYPES  125  Textural  Type  1  125  Textural  Type  II  131  Textural  Type  III  138  Textural  Type  IV  140  Textural  Type V  145  Textural  Type  145  VI  DISCUSSION  150  SUMMARY  156  CHAPTER  V  STRUCTURE  157  INTRODUCTION  157  PRE-FRANCONIAN  STRUCTURES  157  PALEOZOIC STRUCTURES  158  CRETACEOUS  164  STRUCTURES  SUMMARY CHAPTER  VI  170 GEOCHEMISTRY  INTRODUCTION  171  AND METHODS  DISCUSSION Zinc  171 183  and Lead  183  Copper  191  Silver  196  Cadmium  •  196  Molybdenum  198  Cobalt  198  and N i c k e l  Manganese  201  Barium  204  and Vanadium  Iron Calcium  205 and Magnesium  206  vii Page P o t a s s ium Organic  206  Carbon  (C(  o r  g))  207  Sulphur  208  Phosphate  208  Silica  and  Alumina  209  M i c r o c hemi s t r y  210  SUMMARY  CHAPTER  VII  213  SULPHUR  ISOTOPES  215  INTRODUCTION  215  METHODS AND R E S U L T S  216  DISCUSSION Origin  19 of  Sulphur  Mechanism Sulphide  of  Sulphide  222 Reduction  222  Deposition  227  SUMMARY  CHAPTER  232  VIII  LEAD  ISOTOPES  233  INTRODUCTION  233  METHODS  235  RESULTS  236  DISCUSSION  238  SUMMARY  243  CHAPTER  IX  DISCUSSION  246  INTRODUCTION MODEL FOR THE DEPOSITS  246 ORIGIN  OF THE  HOWARDS  A C L A S S I F I C A T I O N FOR S T R A T I F O R M Z n , Pb C u , Ag AND Ba D E P O S I T S : E X P L O R A T I O N I S T S VIEW  PASS246  - SEDIMENTARY AN 259  vi i i Page METALLOGENY  OF THE EASTERN  YUKON  REFERENCES  274  282  APPENDIX  A.  PLATE LOCATION MAP  APPENDIX  B.  MINERAL  APPENDIX  C.  LOCATION OF STRATI GRAPH IC SECTIONS  311  LOCATION OF MINERAL TERRITORIES  312  APPENDIX D. APPENDIX  E.  CHEMICAL  308  IDENTIFICATION  METHODS  309  DEPOSITS IN THE  METHODS AND DATA FOR  CHAPTER  VI  313  ISOTOPE ANALYTICAL METHOD  321  APPENDIX  F.  SULPHUR  APPENDIX  G.  LEAD  ISOTOPE ANALYTICAL METHOD  323  tx  L O C A T I O N OF  FIGURES  1-1  Location  1-2  L o c a t i o n map o f t h e v a r i o u s c o n s t i t u t e t h e Howards Pass  I- 3  map o f t h e H o w a r d s P a s s  Photograph Howards  showing  Pass  Page deposits....  claim groups claims  the general  which  topography  5 of the  area  6  II- 1  Major  11-2  Reconstruction of part of the northern Cordillera Composite s t r a t i g r a p h i c section f o r the ' G r i t Unit 'with approximate s c a l e  16  Composite siltstone  strati graphic unit  section  18  Composite limestone  stratigraphic formation  section  11-3 11-4 11-5 11-6 11—7 11-8  11-9 11-10 11-11  tectonic  4  features  of t h e Yukon  11 12  f o r the lower of the massive 21  Composite s t r a t i g r a p h i c section banded limestone formation P h o t o g r a p h o f t h e u p p e r member banded limestone formation  f o r t h e wavy 24 o f t h e wavy 27  Composite s t r a t i g r a p h i c s e c t i o n of t h e Howards Pass formation showing the various members  30  Photograph of a specimen m u d s t o n e member  33  of the  S t r a t i g r a p h i c column showing w i t h i n t h e a c t i v e member Detailed holes  sections  calcareous  an i d e a l  cycle 38  of the active  member  in drill  1 2 , 18 a n d 19  11-12  Detailed  11-13  Spacial d i s t r i b u t i o n of the basal facies in the XY a r e a Photograph of t h e t h i n bedded calcareous m u d s t o n e f a c i e s o f t h e a c t i v e member  46  Photograph of t h e t h i n bedded f a c i e s o f t h e a c t i v e member  cherty  49  Specimen of laminated mudstone  grey  11-14 11-15 11-16  lithologic  39 log of d r i l l  whitish  hole  36  40 42  mudstone Zn-Pb 53  X  Page 11-17 11-18  11-19  11-20 11-21  1-22 1-23 1-24 1-25 1-26 1-27 1-28  1-29  1-30 1-31  I- 32 II- 1 11-2  Photograph of the grey c h e r t a c t i v e member Composite siliceous formation  facies  of the 56  s t r a t i g r a p h i c s e c t i o n o f t h e upper mudstone member o f t h e Howards Pass 58  Specimen o f a broken l i m e s t o n e c o n c r e t i o n o c c u r r i n g i n t h e upper s i l i c e o u s mudstone member  60  Composite s t r a t i g r a p h i c s e c t i o n mudstone f o r m a t i o n from DDH 38  61  f o r the f l a g g y  P h o t o g r a p h o f t h e orange w e a t h e r i n g u n i t f l a g g y mudstone f o r m a t i o n  of t h e 63  Worm burrows o c c u r r i n g i n t h e orange w e a t h e r i n g u n i t o f t h e f l a g g y mudstone f o r m a t i o n  65  Composite s t r a t i g r a p h i c chert formation  section  69  Composite s t r a t i g r a p h i c Creek f o r m a t i o n  section  f o r t h e upper f o r t h e Iron 72  Graded beds t y p i c a l of d i s t a l t u r b i d i t e s o c c u r r i n g i n t h e I r o n Creek f o r m a t i o n  74  S t r a t i g r a p h i c s e c t i o n f o r t h e Selwyn b a r i t e h o r i z o n i n t h e XY a r e a  76  Laminated horizon  barite  from t h e Selwyn  Composite formation  stratigraphic  Mountains  Mountain  barite 77  section  o f t h e Yara Peak 80  P h o t o m i c r o g r a p h o f a greywacke Peak f o r m a t i o n  from  t h e Yara 81  P h o t o m i c r o g r a p h o f t h e c a r b o n a c e o u s wacke o c c u r r i n g i n t h e I r o n Creek f o r m a t i o n  82  Turbidite formation  84  sequences and c h e r t  p r e s e n t i n t h e Y a r a Peak pebble conglomerate  Composite s t r a t i g r a p h i c s e c t i o n pebble conglomerate u n i t Biostratigraphic correlation Howards Pass a r e a  f o r the chert  of u n i t s  87 i n the  L i t h o f a c i e s t i m e - s l i c e i n t e r p r e t a t i o n f o r the e a s t e r n Selwyn B a s i n d u r i n g d e p o s i t i o n o f t h e wavy banded l i m e s t o n e f o r m a t i o n  93  99  xi Page 111-3  111-4  111-5  111-6 111-7  111-8  111-9  111-10  111-11  General l i t h o f a c i e s t i m e - s l i c e i n t e r p r e t a t i o n of t h e e a s t e r n Selwyn B a s i n d u r i n g d e p o s i t i o n the Howards Pass f o r m a t i o n  100  C o m p o s i t e s t r a t i g r a p h i c s e c t i o n s of the Pass f o r m a t i o n a c r o s s the base of s l o p e facies  101  Diagram showing s p a c i a l r e l a t i o n s h i p s between b a s i n and the edge of the B a s i n d u r i n g the lower P a l e o z o i c a r e a General cycle  trends  within  active  member  110  General l i t h o f a c i e s f o r the upper c h e r t map-area  117  time-slice interpretation f o r m a t i o n i n the Nahanni  General l i t h o f a c i e s t i m e - s 1 i c e i n t e r p r e t a t i o n f o r the Iron Creek f o r m a t i o n i n the Nahanni map-area  114  P h o t o g r a p h showing the I r o n Creek f o r m a t i o n o v e r l y i n g l i m e s t o n e of the c a r b o n a t e sequence on the n o r t h e a s t s i d e of the South Nahanni River  115  Lithofacies time-slice interpretation for Yara Peak f o r m a t i o n and the c h e r t p e b b l e c o n g l o m e r a t e i n the Nahanni map-area  118  I I I - 13  Facies i n t e r p r e t a t i o n and Earn groups based f a n model  I V- 3  idealized  102  General l i t h o f a c i e s t i m e - s l i c e i n t e r p r e t a t i o n f o r the f l a g g y mudstone f o r m a t i o n i n the Nahanni map-area  Submarine  I V- 2  an  the  107  111-12  IV- 1  Howards  fan  environmental  the  model  119  f o r the upper Road on the submarine  River 122  Map of the Howards Pass p r o p e r t y showing the l o c a t i o n of the XY, ANN IV and OP d e p o s i t s and t h e a p p r o x i m a t e o u t l i n e of r e l a t e d sub-basins  124  Sample of type I  126  laminated  Photomicrograph framboid  of  sulphide a well  of  textural  preserved  pyrite 129  xi i Page I V -4 IV-6 IV - 7 IV -8 IV-9 I V - 10 I V -11 I V - 12 IV -13 IV -14 IV-15  IV-16 IV-17 I V - 18 I V -19 V- l V-2 V-3  Photomicrograph py r ite  of modified  framboids  of  Photomicrograph type II  of microfolds in t e x t u r a l  13 2 133  Photomicrograph showing massive t e x t u r a l type II Photomicrograph of pyrite t e x t u r a l type II Sphalerite concentrated textural type III  pyrite  in 134  cube o c c u r r i n g in 136  in fold  hinge  of 137  Photomicrograph of a flow f o l d s occurring in textural type III  139  Photomicrograph of whitish grey showing t e x t u r a l type IVa  142  Photomicrograph of t e x t u r a l type buckshot texture  Zn-Pb  mudstone  IVa showing 143  Photograph of p i l l a r s t r u c t u r e s in the whitish grey Zn-Pb mudstone f a c i e s  144  Sulphide filled Zn-Pb mudstone  146  cleavage  in the whitish  grey  Photomicrograph of mineral segregation of sulphide in the cleavage in t e x t u r a l type IVb  147  Photomicrograph type V  148  of massive  sulphide in textural  D e t a i l e d s e c t i o n of the w h i t i s h grey mudstone f a c i e s Major steps format ion  in the process  Zn-Pb 149  of diagenetic  pyrite 153  A p o s s i b l e model f o r the e v o l u t i o n of the w h i t i s h grey Zn-Pb mudstone f a c i e s  154  Spiral structure occurring in the thin cherty mudstone f a c i e s  159  bedded  S c h m i d t s t e r o g r a m b a s e d on 382 p o l e s t o in t h e Howards Pass area S t r u c t u r a l e v o l u t i o n of the Howards t h r o u g h t ime  Pass  cleavage 167 area 170  xi i i Page VI-1  L o c a t i o n o f diamond and 36  drill  holes  12, 18, 19 172  VI - 2  ( a , b , c , ) Element abundance compared s t r a t i g r a p h i c s e c t i o n from DDH-12  to  173175  VI-3  ( a , b , c , ) Element abundance compared s t r a t i g r a p h i c s e c t i o n from DDH-18  to  176178  VI-4  ( a , b , c , ) Element abundance compared s t r a t i g r a p h i c s e c t i o n from DDH-19  to  179182  VI-5  Matrix of c o r r e l a t i o n p a i r s f o r DDH-12  coefficients  Matrix of c o r r e l a t i o n p a i r s o f DDH-18  coefficients  Matrix of c o r r e l a t i o n p a i r s f o r DDH-19  coefficients  VI-6 VI-7  f o r element 185 f o r element 186 f o r element 187  VI-8  (a,b) Mean (x) element a c t i v e member  VI - 9  Pb + Zn v s . Zn:Pb r a t i o i n t h e a c t i v e member showing t h e g e n e r a l t r e n d o f d e c r e a s i n g Zn:Pb r a t i o w i t h i n c r e a s i n g Pb + Zn  190  Zinc content lithology  192  VI-10 VI-11 VI-12  compared  Pb+Zn c o n t e n t lithology Lead c o n t e n t lithology  content  for facies  to a c t i v e  compared  to a c t i v e  in the.  member member 193  compared  to a c t i v e  member 194  VI -13  C o p p e r - z i n c - l e a d diagram sedimentary d e p o s i t s  VI-14  Organic  carbon  compared  f o r stratiform-  195  t o Cu w i t h r e g r e s s i o n  line  197  VI-15  Cd compared  VI-16  Organic  t o Zn w i t h  carbon  compared  regression line  199  t o Ni w i t h r e g r e s s i o n  line  200  VI-17  CaO compared  VI-18  S e c o n d a r y e l e c t r o n and X-ray s c a n n i n g p h o t o g r a p h s o f Fe, S, Zn and Pb i n f r a m b o i d a l pyrite Microprobe t r a v e r s e across dewatering s t r u c t u r e in t h e w h i t i s h g r e y Zn-Pb mudstone f a c i e s . . . .  VI-19  188189  t o Mn w i t h  regression line  203  211 212  xi v Page VI- 20 VII- 1 V11 - 2 V11 - 3  Microprobe t r a v e r s e across lamination t h i n bedded c h e r t y mudstone f a c i e s Average sulphur  <5 -^S v a l u e s in petroleum  Distribution Howards Pass  f o r seawater t h r o u g h time  of sulphur deposits  Sulphur isotope values t h e a c t i v e member  isotope  in the 214  s u l p h a t e and  data  217 from t h e 220  f o r associated facies in 221  VII - 4  Reaction  VII- 5  Diagram showing r e l a t i o n s h i p o f H 2 S t o s u b - b a s i n c o n d i t i o n s at 25 t o 50°C  VIII- 1  VIII- 2  scheme f o r JJ. d e s u l f u r i c a n s .  Graph o f Pb/ P b plotted against 206ph/204pb s t a c e y and Kramers' two s t a g e e v o l u t i o n curve 2 0 7  225 231  2 0 4  lead 239  Graph o f Pb/ P b plotted against 206pb/204p| showing S t a c e y and Kramers' ( 1 975) two s t a g e l e a d e v o l u t i o n c u r v e 2 0 8  2 0 4  :)  VIII -3  Data  240  points f o r recently deposited m e t a l l i f e r o u s  sediments  244  I X -1  Density  IX- 2  S e d i m e n t a r y e x h a l a t i v e model f o r t h e Howards Pass d e p o s i t s P l a n view o f t h e model f o r t h e f o r m a t i o n o f t h e Howards Pass Zn-Pb d e p o s i t s  253  IX-4  Formation  254  IX-5  I n t e r p r e t a t i o n f o r the o r i g i n in t h e a c t i v e member  IX-3  IX-6  Plan  of ore forming  of b r i n e  view o f major  brines  250  in sub-basin  slump  of the i d e a l  252  cycle 256  i n t h e XY Zn-Pb  deposit  257  I X- 7  Diagramatic  IX-8  Stratiform-sedimentary sulphide deposits grouped by age Generalized synsedimentary model f o r t h e formation of sub-class I s t r a t i f o r m - s e d i m e n t a r y deposits  266  G e n e r a l i z e d d i a g e n e t i c model f o r f o r m a t i o n o f sub-class I stratiform-sedimentary deposits..  267  IX-9  I X-10  e v o l u t i o n o f t h e XY s u b - b a s i n . . . .  258  212  XV  Page IX-11  IX-12 IX-13 IX-14  G e n e r a l i z e d s y n s e d i m e n t a r y model f o r the f o r m a t i o n f o r s u b - c l a s s II s t r a t i f o r m - s e d i m e n t a r y deposits  270  G e n e r a l i z e d d i a g e n e t i c model o f f o r m a t i o n f o r s u b - c l a s s II s t r a t i f o r m - s e d i m e n t a r y d e p o s i t s  272  Water e s c a p e c u r v e s d e p t h s of b u r i a l  f o r various  and 273  Ordovician-Silurian siliceous North  temperatures  mudstones of  America  276  IX-15  Late  IX-16  Late S i l u r i a n to M i d d l e Devonian p a l e o c o n t i n e n t a 1 map C o m p a r a t i v e s t r a t i g r a p h y of t h e Howards Pass and M a c M i l l a n Pass a r e a  280  A-l  Location  map  308  C-l  Location in t e x t  of s t r a t i g r a p h i c  IX-17  D-1  Ordovician  pa 1 e o c o n t i n e n t a 1 map  showing  t h e map  277  areas  sections  278  discussed  L o c a t i o n map o f Zn, Pb and Ba o c c u r r e n c e s Yukon and Northwest T e r r i t o r i e s  311 i n the 312  xvi LIST OF  TABLES  Table  Page  II — 1  Table  III — 1  Summary o f r e g i o n a l s t r a t i g r a p h i c in t h e e a s t e r n Yukon  111 - 2 IV-1 VI-1  VI- 2 VII-  1  V11 - 2 VIII- 1 IX- 1 I X- 2 IX- 3  IX-4 I X- 5  E-l  of u n i t s  from  t h e Howards  Pass  area....  14  correlation 92  Major d e p o s i t i o n a l e n v i r o n m e n t s f o r t h e s t r a t i g r a p h i c u n i t s i n t h e Howards Pass a r e a  121  Point counts f o r s u l p h i d e m i n e r a l s types I thru V  127  of t e x t u r a l  Mean (x) element c o n t e n t s f o r v a r i o u s e l e m e n t s in column at l e f t f o r t h e s t r a t i g r a p h i c u n i t s shown at t h e top o f t h e t a b l e  184  T r a c e e l e m e n t r a t i o s from the Howards Pass a r e a  202  Sulphur isotope r a t i o s deposits  stratigraphic  f o r t h e Howards  units in Pass 218  Values f o r the p a r t i t i o n i n g s u l p h u r spec i e s  of s u l p h u r  between 228  Lead i s o t o p e r a t i o s o f s u l p h i d e m i n e r a l s Howards Pass d e p o s i t s  f o r the 237  T a b l e showing c h a r a c t e r i s t i c s o f p r o x i m a l , and s e d i m e n t a r y s u l p h i d e d e p o s i t s General s i z e deposits  distal 249  of s t r a t i f o r m - s e d i m e n t a r y s u l p h i d e 261  T a b l e of f e a t u r e s a s s o c i a t e d with s u b - c l a s s I type s t r a t i f o r m - s e d i m e n t a r y d e p o s i t s  265  T a b l e of f e a t u r e a s s o c i a t e d w i t h s u b - c l a s s II type s t r a t i f o r m - s e d i m e n t a r y d e p o s i t s  269  T a b l e of f e a t u r e s a s s o c i a t e d with s u b - c l a s s I I I type s t r a t i f o r m - s e d i m e n t a r y d e p o s i t s  275  Methods used s amp l e s  313  in chemical  analysis  o f Howards  Pass  E-2  ( a , b ) Data f o r c h e m i c a l d r i l l h o l e (DDH) 12  analyses  in core  from  314315  E-3  (a,b) Data f o r c h e m i c a l d r i l l h o l e (DDH) 18  analyses  in core  from  316317  E-4  ( a , b , c ) Data f o r c h e m i c a l from d r i l l h o l e (DDH) 19  analyses  in core  318320  xvi i Page 6-1  Lead i s o t o p e p a r a m e t e r s the p r e s e n t r e s e a r c h  and  constants  used i n 325  xvni LIST OF PLATES I  Regional Geologic ( s c a l e 1:32, 160)  Map  - Howards Pass  II  Geologic  Map  - XY a r e a  III  Geologic  Map  - ANN IV a r e a  IV  Geologic  Map  - OP a r e a  (scale  1:4800)  (scale  (scale  _ , , ITT fuckFL In P o c k e t y , - „ p c c > ir  1:4800)... I-rr-fVH****  1:4800)  In- Pockety.  xix PREFACE  "What now seems to be needed i s a substantial standing of primary  ores.  One possible approach  increase in our underin this endeavour i s to  accept, as a working  hypothesis, that  rocks  the relevant conditions f o r the s t a b i l i t y  and, provided  ores are no more or no less  than  of ore  minerals are observed, that they may have formed in a l l the ways that "ordinary" rocks have formed.  The ores themselves  as  aggregates  natural  polycrystalline  are then seen quite simply  conforming  physical metallurgy and "materials science".  with  the principles of  I f such an assumption  i s cor-  rect t h e i r development, pattern of d i s t r i b u t i o n , and physiochemical characteristics  should conform  s i l i c a t e s and carbonates.  quite systematically with that of the associated The problem then becomes part of petrogenesis i n  i t s broadest sense."  from ORE PETROLOGY by R.L. Stanton, 1972  XX  ACKNOWLEDGMENTS  I am very much indebted  to Professor W. C. Barnes, my thesis  super-  visor, f o r continued discussions during research on the Howards Pass deposits.  His continued  deposits has guided  emphasis the author  consideration of important environments.  Throughout  Barnes has provided  on sedimentalogical from overgeneralized  aspects  of the Zn-Pb  concepts  to detailed  aspects of mineral deposition in the sedimentary the preparation  of the manuscript  Professor  invaluable guidance, assistance and encouragement f o r  which I am most g r a t e f u l . I am also indebted to the members of my thesis committee, Professors C. I. Godwin, A. J . S i n c l a i r ,  D. Perry  and R. V. Best  throughout the course of my thesis research and for c r i t i c a l thesis  for their reviews  help  of the  manuscript.  I am grateful  f o r the beneficial  discussions I had with  Drs. A. E.  Soregaroli, M. Barnes, J. W. Murray, J. V. Ross, H. R. Wynne-Edwards, B. Ryan andT.H. Brown and graduate students at U. B. C , especially R. Lett, B. Cooper and G. Ashley and R. 01 sen.  Professors H. J. Greenwood and H. R.  Wynne-Edwards  during  provided  while the manuscript  encouragement  periods  of low productivity  was in preparation.  Economic support for the thesis research was supplied mostly by Placer Development Ltd., including f i e l d  support  and laboratory funds.  Funds f o r  microprobe studies and one year teaching assistantship were provided by the Geological Sciences Department of the University of B r i t i s h Columbia. sonal  and research  expense were p a r t i a l l y  defrayed  Per-  by the James Coates  Memorial award donated by Redstone Mines Limited during 1973-74.  xx i Placer Development personnel critical  also helped the present research by their  discussions and constant encouragement; most notable of these are  D. C. Rotherham, D. A. Howard, I. Borovic, B. Ainsworth, A. D. Drummond, E. A. Scholz, L. Adie, A. Spat, E. A. Lawrence, J. Hylands, E. Lonergan and A. Clendenan. J.  Taylor  Technical  assistance was provided  and C. Sawyer helped  Goddard, P. Pacor, J . Libal the figures. ing  by other Placer employees.  in the typing  of early manuscripts;  H.  and A. Kemp assisted in preparation of many of  I am also grateful to the l i b r a r y s t a f f at Placer for obtain-  those hard to find a r t i c l e s which seem a l l too common. Drs. H. L. Hosmer, H. C. F e r r e i r a , R. L'Lesperance and Mr. R. Peterson  of the United States Steel Corporation have provided many stimulating discussions.  Their personal experience with ore deposits throughout the world  provided information not obtainable in journals. The thesis topic was o r i g i n a l l y Drummond and D. C. Rotherham.  suggested  by A. E. Soregaroli, A. D.  Dr. Soregaroli acted as thesis advisor dur-  ing the i n i t i a l thesis research. Many stimulating discussions occurred study  in the thesis f i e l d  sedimentary ore deposits.  area; these  throughout  the course  of the  contributed much to my thinking on  Most i n f l u e n t i a l  were D. F. Sangster, W. Krebs,  K. Dawson, N. Campbell, C. Smith, I. Borovic, P. Lasnica, R. Macqueen, K. Pride, J . Caja, L. M i l l e r  and many others who v i s i t e d  the author  in the  field. During support  the preparation  of the manuscript  from my fiancee Cheryl.  patience and understanding.  I have received continual  To her go my sincerest thanks f o r her  1  CHAPTER I  INTRODUCTION  PURPOSE AND The  SCOPE OF THE  PRESENT STUDY  purpose of the report investigation is to construct an explora-  tion oriented ore genesis model for sedimentary-type stratiform sulphide deposits, based  primarily on  a detailed investigation of the Howards  Pass Zn-Pb deposits in the Summit Lake area Territories.  The  summer of 1972. and  deposits  of the Yukon and  in the Summit Lake area  L i t t l e geologic information was  therefore the  geologic  Northwest  were found  in the  available for the area,  framework, a description of the  posits and the origin of the deposits are a l l considered  Zn-Pb  in the  de-  present  research. The Zn-Pb  emphasis in the present  sulphide  formation  and  thesis is on the relationship between  sedimentation;  therefore,  stratigraphic relationships are thought most important.  the  vertical  Lateral facies  relationships are also considered and appear relevant in the search for the  Howards Pass  type  deposits.  Because  of  the  large  size  of  Howards Pass deposits and the early stage of exploration, lateral within  the  deposits  is not  considered  in d e t a i l .  Thus, the  the  zoning present  thesis does not represent an exhaustive description of the deposits, but an  overall  view aimed at defining key  the exploration for similar deposits.  parameters thought  important  To this end the present  in  research  uses a multidisciplinary approach. Many of the ideas presented extent, been presented 1979)  and  in the present thesis have, to a large  by the author previously (Morganti, 1975;  have been tested extensively by d r i l l i n g  Pass and by exploration in the surrounding  region.  1977a;  programs at Howards  2 METHODS OF STUDY In  the course of the present study many methods of  were used.  investigation  A l l of these were oriented toward the understanding of the  origin of the Zn-Pb deposits in the hope of constructing an exploration oriented model of ore deposition. used  to  define s p a t i a l ,  Surface mapping at various scales was  stratigraphic  Data were obtained by mapping 780 km^ of  this  and  also completed  the data base.  drill  Detailed  mapping  at a  Detailed logging by the author of  core at a scale of 1:120  Many fresh  cross-sections are based  I.  in the areas of Zn-Pb mineralization  (Plates II, III and IV) (Appendix A). 10,670 m of diamond  relationships.  at a scale of 1:31,680, and part  information i s presented as Plate  scale of 1:4800 was  structural  samples were collected  also formed part of from  on both surface mapping and  the core; and  drill  core data.  Representative samples from each l i t h o l o g i c unit were examined by  semi-  quantitative x-ray d i f f r a c t i o n methods described by Schultz (1964) (Appendix B), owing to limitations of optical grain size of the rocks.  methods because  of the fine  Many samples of the l i t h o l o g i c units and sul-  phides were examined microscopically.  Other methods were also used and  detailed descriptions of these methods are presented with the data, but b r i e f mention of these techniques is made here.  Cores from three d r i l l  holes which had intersected the mineralized formation were analyzed for various trace and major elements. atomic  absorption spectrometry  were completed  Over 3000 quantitative analyses by  and/or  x-ray  fluorescence spectrometry  and organic carbon and carbonate measured by loss on i g -  nition.  Detailed  chemical  completed  on material  studies  using the electron-microprobe were  from the Zn-Pb deposits; again, distributions of  3 both trace and  major elements were studied.  studies were completed cationic  and  Lead  and  sulphur isotope  in an effort to locate possible sources for the  anionic components of the ore minerals.  A l l these data  were collected with the s p e c i f i c goal of developing an exploration model for the Howards Pass deposits. LOCATION AND ACCESS The Howards Pass area (Lat. 62°27'N., Long. 129°12' W.) 20  km  northeast  of Summit  Lake and  Northwest T e r r i t o r i e s border  straddles the  (Fig. 1-1).  The  is centered  Yukon T e r r i t o r y  area extends 40 km  -  from  the Pelly River to five km southeast of Yara Peak (Fig. 1-2). Access  was  initially  Lake, a distance of 258 main camp.  by  km,  float  plane  from  Watson Lake to Summit  and by helicopter from Summit Lake to the  Winter access i s by ski plane from Watson Lake to camp or by  a winter road originating from Mile 101  on the Nahanni Range Road bet-  ween Watson Lake and the town of Tungsten. was constructed in 1973 and  A 520 m dry weather a i r s t r i p  improved in 1974.  It is suitable for small  a i r c r a f t such as Otter, Twin Otter and Twin Bonanza. TOPOGRAPHY AND  CLIMATE  Topography of the Selwyn Mountains in the area of Howards Pass consists  of broad  peaks.  glaciated  valleys,  rolling  and  Elevation of the study area ranges from 1100  River to 1986 m at Yara Peak (Fig. 1-2). wide and  hills  U-shaped due  area studied in detail  steep alpine-type m near the Pelly  Major valleys above 1000 m are  to Pleistocene alpine g l a c i a t i o n .  Much of the  consists of gently r o l l i n g h i l l s with sparse pe-  l i t i c rocks cropping out, and barren glaciated peaks carved from coarsegrained sedimentary  rocks (Fig. 1-3).  Most of the study area i s above  4  Figure 1-1. Location map f o r the Howards Pass deposits, showing Howards Pass, the Yukon-Northwest T e r r i t o r i e s border, Tungsten and Watson Lake.  Figure 1-2. Location map of the various claim groups which constitute the Howards Pass claims. The main claim groups are the XY, DON, ANNIV and OP.  6  Sugar Mtn.  Yara Peak  Figure 1-3. The Howards Pass area, showing the rounded peaks and the lack of trees above 1400 m. Photograph taken looking east in the XY area.  7  the 1400  m tree l i n e in the region, and dense spruce forests and willow  shrubs are present only in large valleys below 1400 m elevation. Climate  in the area  i s typical  of this  portion of the Yukon and  Northwest T e r r i t o r i e s with wet cool summers and extremely cold winters. The f i e l d season runs from mid-June to mid-September in an average year. Snow thickness at base camp (elevation 1503 based  on three years of observations, and  from October to May.  m)  ranges  temperatures  Temperatures during the f i e l d  from  2 to 5 m  averaged  season averaged  -15°C 7°C  to 10°C with moderate shower a c t i v i t y frequent in the afternoons. LOCAL GEOGRAPHY Names given to geographic shown in Figure 1-2. will  features in the Howards Pass area  Henceforth  are  in this report claim groups (Fig. 1-2)  be referred to as areas, such as the XY, DON,  ANNIV and OP areas,  while the term Howards Pass area refers to the whole group of claims. The  surrounding areas referred to are located r e l a t i v e to the various  above claim groups. Plate 1.  The  The  Howards Pass map-area refers  Nahanni map-area or map  by the 4 mi. topographic map HISTORY AND The  sheet refers to the area covered  (Fig. A - l ) .  in 1972  deposits were discovered by  Canex-Placer  following a regional stream sediment geochemical  pling program that began in 1966. geochemical  area in  PREVIOUS GEOLOGIC INVESTIGATIONS  Howards Pass Zn-Pb  personnel  to the  sampling  had  1971,  follow-up stream  delineated several anomalous areas  "black shales" that extended king commenced in 1972  By  sam-  sediment overlying  f o r 40 km along the regional s t r i k e .  over the geochemical l y anomalous areas and  phide showings were subsequently discovered by prospecting. The  Stasul-  present  8 study began in 1973 1975,  and  field  work was  concluded  during the summer of  during which time 10,670 m of diamond d r i l l i n g  were completed  on  the property. Prior to the present study of the Howards Pass area, geologic i n vestigations were of a regional nature.  The  Nahanni map-sheet (105-1)  was mapped by the Geological Survey of Canada during the early 1960s and a geologic map  and  legend was  published in 1967  (Green  et a l . , 1967).  Their mapping consisted of aerial  photograph interpretation  spaced  The  zoic  regional check traverses. pelites  of  the  Howards  Pass  published map  area  into  unit  widely  grouped a l l Paleo18b,  host  for  the  (1967) summarized  the  Howards Pass deposits.  Subsequently,  geology  correlated the rock units defined by Green et  of the Yukon and  Gabrielse  and  a l . (1967) with other units in the region.  Mapping projects similar to  that completed by the Geological Survey of Canada  in the Nahanni  area  included the Sekwi Mountain area (Blusson, 1971), Flat River (Gabrielse et a l . , 1973)  and Coal River (Gabrielse and Blusson, 1969).  provide general  regional data, but the method used appears to be better  suited to areas with predominatly recessive, study.  low  In 1977  These maps  colour  limestone l i t h o l o g i e s rather than  contrast, basinal  facies  considered  in  the this  the Geological Survey of Canada began a mapping project  in the area on a scale of 1:50,000, this project includes 1/5  of Plate I  in the XY area. ROCK CLASSIFICATION USED IN THE PRESENT STUDY The and  general  sedimentary  rock  classification  Sloss (1953) has been adopted here although  modified according to Blatt et a l . (1972).  proposed  by  Krumbein  t h e i r terminology  was  "Mudstone" is preferred as a  9 general  term because of grain  nable in terms of f a b r i c .  size implications, while shale is d e f i -  " A r g i l l i t e " , a term used extensively by some  for mudstone, i s more correctly pient metamorphism, especially  used for a mudstone hardened by in Precambrian  terrains  (Blatt  1972) and should not be used for diagenetically altered  inci-  et a l . ,  varieties.  In  the present report, "shale" refers to mudstone which i s f i s s i l e parallel to bedding.  The Lower Paleozoic rocks in the Howards Pass area contain  only minor amounts of shale. leading,  f o r as defined  The term "black  by Swanson  shale" is somewhat mis-  (1961) i t i s not  restricted  to a  single l i t h o l o g i c type of carbonaceous mudstone, but includes other dark coloured, fine-grained rocks.  Demonstrating the range of material con-  sidered to be c l a s s i f i e d as black shale are examples such as the "Chattanooga shale" which i s c h i e f l y a s i l t s t o n e (Conant and Swanson, 1961), the g r a p t o l i t i c black shale in the Vinini  Formation in Nevada, U.S.A.,  which i s siliceous mudstone (Ketner and Smith, 1963), the Kupfershiefer of Germany and the Green River Formation of the i n t e r i o r of the U.S.A., which are marlstones (Wedepohl, 1964; Bradley, 1931), and Pennsylvanian black shale in western Indiana, U.S.A., which i s intermediate in compos i t i o n beween claystone and coal  (Zanger et. a l . , 1963).  In this report  "black shale" is used only as a general term since the s p e c i f i c  use of  the term has varied to a great degree in depositional environments and chemical c h a r a c t e r i s t i c s , both of which are of great importance in considering contained ore deposits.  In the present report mudstone, s i l t -  stone and shale with appropriate modifiers are preferred.  10 CHAPTER II GEOLOGY INTRODUCTION The  Howards  Paleozoic basinal  Pass  Zn-Pb  deposits  occur  facies of the Selwyn Basin  in unmetamorphosed  Lower  in the northern Canadian  C o r d i l l e r a within the Yukon and western Northwest T e r r i t o r i e s .  The nor-  thern part of the C o r d i l l e r a can be divided into two major tectonic elements separated by the T i n t i n a Trench ( F i g . 11-1). geologic and physiographic displacement  ( F i g . 11-2)  East of this major  discontinuity, with an estimated (Tempelman-Kluit, 1977),  450  km of  are Precambrian to  Tertiary sedimentary and minor metasedimentary rocks which have been i n truded by Mesozoic g r a n i t i c Trench  plutons.  To the southwest of the T i n t i n a  are metasedimentary and meta-igneous  Tertiary  intrusions  (Gabrielse, 1967).  rocks  cut by  Mesozoic to  Rocks to the southwest of the  trench are not considered further in this report. The  Selwyn Basin  has been defined as a major Paleozoic  tectono-  stratigraphic feature to the east of the T i n t i n a Trench, and consists of unmetamorphosed pelites Mississippian in  and limestones ranging in age from Cambrian to  (Gabrielse, 1967).  Ordovician-Si1urian  Zn-Pb deposits at Howards Pass occur  carbonaceous and  edge of the eastern side of the basin.  siliceous  mudstones  near the  Rocks of the Selwyn Rasin uncon-  formably overlie Hadrynian to possibly Cambrian argillaceous and quartzose  rocks with  minor  limestone  informally  Unit"  (Roddick and Green, 1961;  young  as Mississippian (?) are intruded  some of which  have  alpine g l a c i a t i o n  associated  Green  referred  to as the  and Roddick, 1962).  Rocks as  by Cretaceous g r a n i t i c  tungsten mineralization.  "Grit  rocks,  Pleistocene  has carved out the present topography, with  granitic  n  Figure 11-1 Major tectonic features of the Yukon and western Northwest T e r r i t o r i e s , showing the relative location of the Selwyn Basin (from Gabrielse, 1967).  12  Figure II-2. Reconstruction of part of the northern C o r d i l l e r a , showing the original outline of the .Selwyn Basin. Also shown are the Mackenzie Platform, Cassiar Platform and Yukon Cataclastic Complex (modified from Tempelman-Kluit, 1979).  13 intrusions,  coarse-grained  clastic  forming most of the sharp  alpine type  rocks underling lower r o l l i n g h i l l s study  regional  and  detailed  Sheet (Green et a l . , 1967) The  terminology  sedimentary peaks and  rocks  limestones  fine-grained  and low mountains.  mapping was  and  clastic  In the present  confined to the Nahanni  Map-  (Appendix A).  used  in this  report follows the Code of  Strati-  graphic American Commission on Stratigraphic Nomenclature (in Blackadar, 1972;  Hedberg, 1976).  lithologic used  The units are rock-strati graphic units based  characteristics.  in the Howards Pass  Two  separate  region.  First,  identification numbers and  systems  letters  Green et a l . (1967) are used with s i g n i f i c a n t sub-divisions and local  informal names used by many geologists working  Roberts, 1978)  and f i r s t proposed  fold stratigraphic nomenclature  by Morganti  (1975).  on are  used  by  second,  in the area (e.g. Using this two-  a unit would be presented, for example,  as 18b-l (Howards Pass formation (Table I I - l ) ) . LOCAL GEOLOGY The most important geologic aspects pertaining to the Howards Pass Zn-Pb deposits are stratigraphy, sedimentation and structure.  As  will  be evident throughout this report the Howards Pass deposits are synsedimentary; thus, subsequent the  Zn-Pb deposits  as  structural evolution of the area has  well  as  the  other  sediments.  nature of the deposits indicate that regional and local the best exploration guides in the area.  The  affected  stratiform  stratigraphy are  14  Table I I - l . Table of units from the Howards Pass area. in the table are informal.  PERIOD  Green 1967  et al  This report based on m a j o r units proposed by G r e e n e t a l . , 1967  A l l units  This report - local informal usage ( M o r g a n t i , 1975 ).  PENNSYLVANIAN  MISSISSIPPI 18b-3  CHERT  !8b-2  VARA  PEAK  IRON  CREEK  DEVONIAN  SILURIAN  PEBBLE  CONGLOMERATE  FORMATION  FORMATION  10c  UP^E!"1!!H1'RT~^  10b  FLAGGY  10a  HOWARDS  MUDSTONE F O R M A T I O N  18b  PASS  FORMATION  ORDOVICIAN  7b-3  TRANSITION WAVY  CAMBRIAN  MASSIVE LOWER  ->ADRYNIAN  BANDED  FORMATION LIMESTONE  LIMESTONE  SILTSJQ2E  FORMATION  FORMATION  JINIJ  15 STRATIGRAPHY MAP-UNIT 2 ('GRIT UNIT') The oldest rocks studied in the Howards Pass area are fine-grained clastic  rocks (with minor limestone) mapped by Green et a l . (1967) as  Map Unit 2 and in the present study l i t h o l o g i c a l l y correlated with the 'Grit Unit and  of Gabrielse (1967).  1  are overlain  unconformably  These rocks show intense deformation  by the Paleozoic formations.  mapped as 'Grit Unit' occur to the southwest The  generalized section  Outcrops  of the Howards Pass area.  ( F i g . II-3) presented here i s tentative due to  the reconnaissance nature of the traverses made over these rocks, and to typically  recessive outcrops which only l o c a l l y form steep slopes where  capped by more resistant units. The commonest rock types, in order of decreasing abundance, are i n tercalated  maroon and green  to buff mudstones to s i l t s t o n e s ,  brown mudstones and s i l t s t o n e s and minor limestone. Howards Pass area.  with minor sandstones,  The base of this The lowest  unit  rocks noted  was  dolomitic limestone.  in the  ( F i g . 11 -3)  which are overlain by  These are overlain  calated maroon and green mudstones and siltstones majority of the 'Grit Unit' near Howards Pass.  phyllites  not observed  in the section  are dark grey to brown mudstones to siltstones orange weathering  green  grey to  which  by  inter-  constitute a  In areas where the unit  is t h i n , green rocks overlie the maroon rocks, but at thicker sections this  sequence can be repeated up to f i v e times.  A limestone conglo-  merate overlies the brightly coloured pelites and l o c a l l y the 'Grit Unit'. are  slightly  The conglomerate  rounded  occurring  i s the top of  contains grey limestone clasts which in an  orange  weathering  dolomitic  16  lower s i l t s t o n e unit-orange dolomitic s i l t s t o n e .unconformity  weathering  (?)  Discontinuous l i g h t green p h y l l i t e unit Conglomeratic limestone with grey limestone clasts in an orange weathering dolomitic limestone matrix. Maroon and green pelite-dusky red to l i g h t green mudstone, minor light grey, s i l v e r weathering shale, with minor siltstone near contacts. T y p i c a l l y green mudstone overlies maroon mudstone. Mudcracks and cross-beds are present l o c a l l y . Contacts between maroon and green mudstone are gradational in colour without apparent other l i t h o l o g i c changes.  Grey shale and  slate.  Grey siltstone and shale with abundant graded beds.  i-  Dolomitic limestone, l o c a l l y dolostone which weathers orange, but i s various shades of grey in fresh outcrops. Grey mudstone, shale and  siltstone.  Base of section near Summit Lake.  Figure 11-3. Composite s t r a t i graphic section for the 'Grit Unit' with approximate scale. The section is based on locals between Howards Pass and Summit Lake, southeast of the eastern edge of Plate I.  limestone matrix. the unit  i s an  17  Locally, clasts of the dolomitic matrix suggest that  intraformational  occur throughout  the top 100  faults and are thought  conglomerate.  Pale  m of the unit, but  to have been produced  pressure associated with these structures  by  green  phyllites  are associated an  with  increase in water  (Higgins, 1971).  possible that the p h y l l i t e s constitute a stratigraphic  It is also  unit  (Gabrielse,  1967), but no evidence for this was found in the Howards Pass area. MAP-UNIT 7a (LOWER SILT STONE UNIT) Map-unit  7a, here informally called the lower s i l t s t o n e unit, con-  s i s t s of a sequence of dolomitic the XY camp ( F i g . II-4). served sented.  in stream  beds  siltstones  exposed  8 km  southeast of  Only a few outcrops of the unit have been ob-  and  therefore no  thickness estimates  are  pre-  The unit consists of s i l t s t o n e and minor amounts of sandstone,  both of which contain abundant c a l c i t e and dolomite cement.  Spatial re-  lationships between the s i l t s t o n e and sandstone have not been observed, but the local  occurrence of these sandstone  occur as lenses within the s i l t s t o n e massive,  showing  little  evidence  lenses show a weakly developed bedding.  in  float  ( F i g . II-4).  of  bedding,  along s t r i k e  The  they  s i l t s t o n e s are  whereas  the  sandstone  low angle (less than 10°) tabular cross-  Locally, minor amounts of dark  associated with s i I t y dolomite.  bodies suggests that  to pale green  mudstone are  These green mudstone beds can be traced  for over 10 m.  Illite  and  abundant a l b i t e  served in thin section suggest that the beds are altered  ob-  tuffs.  Siltstone consists of quartz, K-feldspar and muscovite in order of decreasing  abundance,  rounded grains.  with  quartz  and  K-feldspar occurring  Quartz t y p i c a l l y shows overgrowths.  as  sub-  Muscovite occurs  18  Massive limestone formation • massive grey weathering limestone, unconformity (?)  Orange weathering dolomitic s i l t s t o n e to s i l t y dolomite with lenses ( ? ) of dolomitic s i l t s t o n e to sandstone occurring l o c a l l y .  —  Pale green t u f f f l o a t  Orange weathering dolomitic siltstone to s i l t y dolomite with lenses. ( ? )  unconformity (?) Grit Unit • l i g h t green p h y l l i t e unit  Figure II-4. Composite stratigraphic section for the lower s i l t stone unit. The t u f f horizon does not outcrop, but can be traced in f l o a t . Section i s based on area 0.5 km southeast of the southeast corner of Plate I. Scale i s approximate.  19  both as randomly oriented grains and as grains aligned sub-parallel to cleavage i n thin section forming a microscopic slaty cleavage not evident  i n outcrop.  muscovite.  Sandstones  show the same mineralogy  but with  Calcite and dolomite cement constitute up to 5 to 10% of the  rock with the higher values occurring in the sandstone. simple  less  cement  bonds  (Dapples,  1967) between  quartz  C a l c i t e forms and K-feldspar  grains; t h i s c a l c i t e i s in part replaced by later stage dolomite. stage r e c r y s t a l l i z a t i o n of muscovite, minor chert and clay  Late  accompanied  development of slaty cleavage. The has  contact between the lower  s i l t s t o n e unit  and the 'Grit Unit'  not been seen by the author, although angular discordance and the  lack of intense folds similar to that found in the 'Grit Unit' are evident  suggest  with  low angular  (1970).  an unconformity.  Using  discordance  A pre-Franconian has been  the stratigraphic  regional  proposed  by  sequence of this  unconformity  Douglas  et a l .  report, the uncon-  formity should occur between the lower s i l t s t o n e and the overlying massive limestone formations, but no evidence f o r or against this proposal could be found, as the contact i s everywhere covered. tion of the lower  siltstone  and major east-west  Map  Sheet  correla-  i s tentative owing to the lack of f o s s i l s  facies changes that occur in unit.  similar rocks occur in the Sekwi Formation Sekwi  Regional  to the north  Lithologically  of Early Cambrian aqe in the  (Blusson, 1971; W.  J. Crawford,  Oral  Commun., 1976). MAP UNIT 7b-l (MASSIVE LIMESTONE FORMATION) Map unit 7b-l i s informally termed the massive limestone formation and i s mappable on a regional scale. grey, m i c r i t i c  The formation consists of massive  s i l i c e o u s limestone which crops out in the northeastern  20 part of the XY map  area (Plate I ) . Although outcrops are abundant along  ridge tops, valley  occurrences are poorly exposed.  There  i s no  type  section f o r the unit owing to the discontinuous and spotty nature of the outcrops, although an idealized section is proposed  ( F i g . 11-5).  It i s  estimated that the formation i s 100 to 300 m thick, although folding  may  account for some of this thickness. Contacts between the massive  limestone and  overlying  wavy banded  limestone are faults in the XY map area (Plate I I ) , although gradational contacts between these two area.  Continuous  formations are present northeast of the  deposition i s further supported  l a r i t y between the massive  by  lithologic  DON  simi-  limestone and the thick microsparite beds of  the lower member of the wavy banded limestone. Two  major rock types are present within the formation ( F i g . 11-5).  Over 90% of the outcrops consist of generally massive microspar grading l o c a l l y into micrite.  Minor occurrences of biomicrite occur as l e n t i c u -  lar masses in the lower part of the formation.  The  massive  microspar  constitutes most of the lower 50 m and a l l upper portions of the formation,  and  rough,  i s easily  elephant  identified  hide-like  by  surfaces.  noted in this rock type is parallel darker d e t r i t a l  i t s massive  laminae 2 mm  thick  (1) and  to 1 cm thick.  sedimentary  showing  structure  Two  These quartz-rich carbonatypes of c a l c i t e concretions  Minor light calcite-quartz l e n t i c u l a r concretions 2 to 5 rrm  20 mm  to more than  10  cm  Gradational  contacts and minor folding  soon  deposition of  after  main  outcrops  bedding which is weakly defined by  ceous laminae are t y p i c a l l y irregular. occur:  The  grey  the  long  occur  parallel  to  bedding.  indicate that these were formed  surrounding  limestone,  before  complete  21  t '  i ' 1  i s "1k  Wavy banded limestone formation consisting of intercalated microsparite and micrite  i-  Upper unit - grey weathering, poorly bedded microspar and micrite, with micrite occurring as isolated patches.  »  i  in ro CM  Lower unit - grey weathering, weakly bedded microspar with patches of micrite, also present are lenses of biomicrite up to 75m across.  unconformity (?) Lower siltstone unit - orange weathering dolomitic siltstone.  Figure 11-5. Composite stratigraphic section of the massive limestone formation. Based on c l i f f s north of Don Creek (Location 7b-l, Appendix C).  22 1ithification. ym.  (2)  spherical  Grain  Coarse-grained concretions  across; bedding before  sizes within these  concretions  (150 ym to 500 ym) c a l c i t e  and veins.  These  concretions  i s draped over them indicating  1ithification.  are less than 10  The two types  have similar origins although  higher  in semi-  are 5 to 20 cm  that they  of concretions  the s l i g h t l y  occurs  were  present  are considered to  clay content  of the  smaller concretions may have hindered crystal enlargement during neomorphism. less  The greater extent of deformation  evidence  of crystal  noted in the concretions  enlargement may be explained  by the greater  strength associated with larger crystal size (Fuchtbauer, veins  are abundant  i n the unit, and appear  with  1974). C a l c i t e  to cut a l l sedimentary  features. Many of the micrite laminae are a r g i l l a c e o u s . The micrite appears dark in thin section with grain sizes generally less than 10 ym across, and  occurs  microspar  as patches within  a silicic  grains are 5 to 40 ym across,  microspar  (Folk, 1962).  showing t r i p l e  junctions and  serrated edges suggestive of neomorphism (Bathurst, 1975). s t i t u t e s 90% of the microspar amounts of organic  with  matter and clay.  approximately  The  C a l c i t e con-  10% quartz  and trace  Locally the microspar-micrite i s  intercalated with argillaceous microspar  laminae up to 2 cm thick,  al-  though most are less than 1 cm thick. These contain up to 30% clay, the rest being microspar  microspar  and minor amounts of organic  matter.  The mixed  and micrite contain up to 30% i n t r a c l a s t s , some of which show  deformed twin lamellae. The of  lower 50 m of the massive limestone  calcarenite (packstone  formation  of Dunham, 1962) showing  contain  poorly  lenses  developed  23 bedding.  The  grain-supported limestone contains up to 60%  which appear to be Some of  the  indicating  composed  fragments  show attached  1 Unification  in the u n i t .  The  of f o s s i l  and  possibly  calcite  oolith  and/or  intraclasts fragments.  dolomite  had occurred before the clasts  cement  were deposited  matrix i s similar to micrite noted elsewhere  in the  formation, with microspar and quartz grains common. MAP  UNIT 7b-2  The  (WAVY BANDED LIMESTONE FORMATION)  wavy banded  limestone  formation  is a  c l a s t i c deposit which shows characteristic texture in the upper part.  The  regionally  significant  "chain-link" outcrop surface 1 i t h o l o g i c a l l y with  unit is correlated  part of the Rabbitkettle Formation to the south and  east (Gabrielse et  a l . , 1973). Rocks of the wavy banded limestone crop out the XY area, and northern edge  in areas  are present along the edge of the DON  of the ANNIV and OP areas (Plate I ) . The  surrounding  area  and  the  unit i s e s t i -  mated to be 250 to 300 m thick (Plates I - IV), although i t is apparently thickened to over 500 m by minor folding which i s pervasive throughout the upper member of the formation.  As  discussed previously,  lower part of the unit i s i n t e r d i g i t a t e with the massive mation.  limestone for-  The upper contact with the transition formation i s gradational  over 10 to 30 The  the  m.  wavy banded  limestone  i s divided  into  two  informal members  (Fig. 11-6) based on the amount of argillaceous material in some beds, as expressed at outcrops in the thickness and evenness of bedding.  The  lower member consists of intercalated microspar and m i c r i t e , and shows even  bedding,  whereas  the  upper  member  consists  of  intercalated  24  —  — V 7  1  Transition formation - laminated mudstone  1  i !  -1  -  I  - 1  —  Upper member - intercalated l i g h t grey microsparite and micrite and calcareous mudstone, laminae are 1 to 5 cm thick. The top 50 m shows a c h a r a c t e r i s t i c chain link structure. Carbonate content of the mudstone laminae decreases up section. Green t u f f occurs in lower 30 m of member.  _l  i—  — 1  ' i ' l ' ) 1 L  1  1  1  1  1  Lower member - intercalated light grey microspar and dark grey micrite beds which are 5 to 40 cm thick.  1  J  j  ^  )  /  Massive limestone - light grey weathering massive microsparite.  Figure 11-6. Composite s t r a t i graphic section for the wavy banded limestone formation. Based on exposures on a h i l l southeast of the XY area (Location 7b-2, Appendix C). Scale i s approximate.  25  siliceous  micrite  structure. The  and a r g i l l a c e o u s  A gradational  contact  micrite  separates  beds  micrite  and m i c r i t e .  beds  over  10  Most  cm  beds  thick  a  "chain-link"  t h e s e two members.  l o w e r member o f t h e wavy b a n d e d l i m e s t o n e  microsparite  showing  c o n s i s t s of interbedried  a r e 5 t o 30 cm t h i c k  showing  an  apparent  Textures i n d i c a t i v e o f bottom current d e p o s i t i o n  with  graded  some  bedding.  have n o t been n o t e d .  P e t r o g r a p h y o f t h e l o w e r member shows t h a t t h e d a r k g r e y m i c r i t e b e d s (type  III M of Folk,  Besides  1959) l o c a l l y c o n t a i n  m i c r i t i c c a l c i t e with  grain  i n t h e same s i z e r a n g e c o n s t i t u t e throughout t h e rock. of t r a c e thin  of p e l l e t s .  s i z e s up t o 10 ym, c l a y s and  quartz  up t o 10% and a r e d i s t r i b u t e d  The f i n e g r a i n e d  amounts o f o r g a n i c  trace quantities  material  evenly  n a t u r e o f t h e m i c r i t e and  presents  give  a brownish  tint in  the darker  micrite  t h e rock  sections. Light  grey microspar  beds a r e i n t e r c a l a t e d  b e d s i n t h e l o w e r member. primary depositional microspar contains  T h e s e b e d s a r e 5 t o 40 cm t h i c k  structures.  5% q u a r t z  matter.  junctions  show  enfacial  (Bathurst,  1975) d u r i n g  major difference  junctions,  T h e c a l c i t e and q u a r t z  a r e 10 t o  According  with  an i n t e r l o c k i n g  mosaic  L e s s t h a n 2% o f t h e t r i p l e  indicating  aggrading  neomorphism  diagenesis. between t h e m i c r o s p a r  l o w e r member a r e t h e l o w c l a y and o r g a n i c spar.  indicate that the traces of  showing t r i p l e j u n c t i o n s .  grains  and show no  and o n l y  and a r e t y p i c a l l y e q u i g r a n u l a r ;  of c a l c i t e grains  The  X-ray diffractograms  95% c a l c i t e with  mixed l a y e r e d c l a y s and o r g a n i c 40 ym a c r o s s  with  and t h e m i c r i t e  matter contents  in the  i n the micro-  t o S p r y ( 1 9 6 9 ) i m p u r i t i e s s u c h a s c l a y and q u a r t z  recrystal1ization.  Thus, while t h e "purer" m i c r i t e beds undergo r e -  hinder  26  c r y s t a l l i z a t i o n producing microspar, impurities in the clay rich micrite recrystal1ization.  inhibit  that the original also sharp.  The  sharp  contacts  between beds  contacts between clay-rich and clay-poor micrite were  A green aquigene tuff breccia occurs  the upper member of the wavy banded limestone. ash and l a p i l l i  are over 2 mm  ding in the limestone. glass shards.  indicate  The  across and  in the lower 30 m of  In hand specimen coarse  are elongate  parallel  to bed-  In thin section the t u f f shows abundant  best outcrops  of this  rock  type  are 7 km  relict  north of  Yara Peak where the t u f f is 12 m thick. The terized  upper member of the wavy banded limestone formation by  is charac-  "chain l i n k " structure which consists of intercalated  light  grey micrite and calcareous mudstone, and appears wavy owing to varying bedding with  thickness.  micrite beds  lateral  variation.  Bedding is in general thinner than the lower member, ranging  from  1 to  5  cm  thick,  and  showing  Many of the beds show a weak grading.  tions the micrite consists of 70 to 80%  c a l c i t e with  rapid  In thin sec-  grains generally  less than 10 pm across, although some grains are up to 20 ym across. Grey to tan micrite.  calcareous mudstone  These beds are 5 mm  thin laminae. micrite  laminated  beds  is interbedded  The mudstone beds generally drape over the discontinuous forming  and 45-65% clay. the  clay  the  to 3 cm thick and consist of 5 to over 50  a  "chain-link" structure  (Fig.II-7).  section the calcareous mudstone contains 20-30% c a l c i t e ,  cate  of  In  thin  15-25% quartz  X-ray d i f f r a c t i o n patterns from selected samples i n d i consists of mixed  I M Q clay  and  2M  amounts of organic matter darken some laminae, and trated in the cleavage.  muscovite.  Minor  l o c a l l y are concen-  Trace amounts of cubic pyrite  are  the mudstone and are much more abundant than in micrite beds.  present in  27  Figure II-7. Photograph of the upper member of the wavy banded limestone formation. The wavy nature of the bedding i s the result of the intersection of bedding and cleavage and constitutes the "chainlink" structure referred to in the text. The pencil near the top of the photograph i s f o r scale.  28 Mineral sequence.  species in the upper member vary progressively through the  Quartz  near the top.  increases from 10% in the micrite at the base to 30%  The calcareous mudstone also shows a progressive decrease  in carbonate content at the top of the member.  Thus, the combination of  progressive increase in the relative abundance of mudstone and the decrease  in carbonate  defines a transitional  contact  with  the overlying  t r a n s i t i o n formation. MAP-UNIT 7b-3 The  (TRANSITION FORMATION)  transition  intercalated  formation consists of laminated mudstone and minor  limestone, which  the Howards Pass formations.  separates  the wavy banded  This informal unit  limestone and  i s mappable on a re-  gional scale and i s therefore given formational status. T e x t u r a l l y , the unit i s similar to the wavy banded limestone; the main difference being the lower carbonate content. onal  As the name implies, the unit i s gradati-  between the underlying limestones and the overlying  mudstone.  carbonaceous  The lower contact with the wavy banded limestone i s gradati-  onal over 1 to 10 m, and i s based  on the c a l c i t e content.  Rocks having  less than 50% c a l c i t e are placed in the t r a n s i t i o n formation.  The upper  contact with the Howards Pass formation i s also gradational, over 0.5 to 5 m, and i s based on the organic matter content.  The unit ranges  10 to 80 m in thickness and i s d i s t i n c t i v e on a regional scale  from (Plate  I). The  formation  laminated mudstone. (1)  consists  predominantly  of brown to grey  Three basic types of laminae  pale grey s i l i c e o u s  laminae,  pale grey calcareous laminae.  (2)  weathering  have been recognized:  brown c l a y - r i c h laminae  The laminae  and (3)  are 1 to 10 mm thick; most  29 are over 5 mn thick and are both calcareous and more abundant near the base of the unit.  Clay-rich laminae tend to occur in beds consisting of  5 to 50 laminae.  Sedimentary structures other than parallel  lamination  are rare, with only a few graded beds evident near the base of the unit. X-ray diffractograms indicate a large range in mineral contents with 15 to 65% quartz, 20 to 45% 2 M muscovite, 0 to 45% c a l c i t e and  up to 10%  pyrite. MAP-UNIT 10a  (HOWARDS PASS FORMATION)  INDR0DUCTI0N The  Howards Pass formation  contains a l l economically  Zn-Pb deposits in the Howards Pass area.  The unit is given informal f o r -  mational  status, because of regional mappability and  cance.  The  Howards Pass  formation  consists  (Fig.  11-8).  The  economic  of highly  siliceous mudstones with minor chert and limestone. of surface outcrops and d r i l l  carbonaceous,  core allows d i v i s i o n into d i s t i n c t members  active member, which contains the Howards Pass Zn-Pb The  formation  homogeneous, consisting of carbonaceous mudstones, most of  which are s i l i c e o u s . unit  signifi-  Detailed study both  deposits, i s further subdivided into l i t h o l o g i c f a c i e s . is moderately  significant  consisting  of  An exception i s the active member, a heterogeneous intercalated  carbonaceous  mudstone,  limestone  and  chert, with some mudstone containing up to 50% Zn+Pb. Mapping (Morganti, 1976) is  of  regional extent  tinuously  has shown that the Howards Pass formation  (Plate  in a l i n e a r belt  I).  The  active member occurs discon-  about 10 km wide for approximately  between Flat Lakes and the Itsi Mountains along a 300° azimuth.  220  km  Within  30  10b (flaggy mudstone formation) 10a-5 (upper siliceous mudstone member) laminated, siliceous carbonaceous mudstone with abundant limestone concretions, and a graptolite zone 1 m thick occurring near the top of the member.  10a-4 (active member) - intercalated mudstone, limestone and chert with economically s i g n i f i c a n t amounts of Zn and Pb with a poorly preserved graptolite horizon.  Irlrlrl-.  131  10a-3 (lower cherty mudstone member) massive, carbonaceous s i l i c e o u s mudstone with blocky fracture and up to 12% C( )  =1  10a-2 (calcareous mudstone member) calcareous carbonaceous mudstone with 0.2 m graptolite zone.  10a-l ( p y r i t i c silceous shale) - s i l i c e o u s carbonaceous f i s s i l e shale with common pyrite concretions. 7b-3 (transition formation) Figure 11-8 - Composite stratigraphic section of the Howards Pass formation showing the various members. Numbers refer to Geological Survey of Canada nomenclature (Green et a l . , 1967). Based on data from DDH 18, 19, 36, 32 and 80 i n the XY area (Plate I I ) .  31  the Howards Pass area, the active member i s limited to the XY, ANNIV and OP areas  (Morganti,  deposition in small onal  1975).  Lateral thinning  isolated sub-basins,  of the member  elongate  s t r i k e , within the larger Selwyn Basin  parallel  suggests  to the regi-  in which the Howards Pass  formation was deposited. MAP-UNIT 10a-l The  pyritic  (PYRITIC SILICEOUS SHALE MEMBER)  siliceous shale member i s s t r a t i g r a p h i c a l l y the lowest  carbonaceous rock unit to occur in the Paleozoic section in the Howards Pass area. thickness  The member i s 2 to 10 m thick, and i s generally uniform in over distances  less than 0.5 km.  features are well developed f i s s i l i t y  Its two most  and abundant, 1 to 10 mm,  cular pyrite concretions which define the lamination. sists  of interlaminated  carbonaceous  shale. Some of the pyrite concretions cretions the  distinctive  shale  lenti-  The member con-  and p y r i t i c  carbonaceous  are folded; and a l l pyrite con-  weather to limonite pods which a i d in the i d e n t i f i c a t i o n of  member at surface.  which parallel  Other  structures noted  include  quartz  veins  bedding and are termed "pseudo beds" in the present re-  port. The  pyritic  pyrite, with  siliceous  shale member contains quartz, muscovite and  minor dolomite;  and i s the oldest  section to contain over 1% organic carbon. mineral  unit  in the Paleozoic  Quartz i s the most abundant  in the shale; x-ray diffractograms indicate 40 to 60% quartz in  samples studied.  Muscovite constitutes 35 to 50% of the shale, and in  thin section i s aligned parallel  to bedding.  Pyrite ranges from  than 5 to 10%, most of which occurs as fine grained concretions.  less  (less than 0.1 mm)  These d i f f e r from concretions which are ubiquitous  in the  32 rest  of the Howards Pass formation because the pyrite i s fine grained  and more abundant than the  concretions are  in other members in the formation, and  elongate  parallel  to bedding.  Trace  because  amounts of  c a l c i t e and dolomite occur as segregations. The  upper contact with the overlying calcareous mudstone member i s  sharp and marked by a decrease in pyrite content, and an increase in carbonate content. dational mation  and and  The lower contact with the t r a n s i t i o n formation i s gra-  demonstrates a continuity the  underlying  limestones;  thought to be an unconformity MAP-UNIT 10a-2 The  previously  Howards Pass this  contact  forwas  (S.L. Blusson, Oral Commun., 1975).  (CALCAREOUS MUDSTONE MEMBER)  calcareous mudstone member consists  carbonaceous mudstone. cretions.  between the  of massive,  calcareous,  Calcite occurs as cement and as microscopic con-  The unit has been i d e n t i f i e d in outcrop and d r i l l  XY, ANNIV and OP areas.  core in the  Rocks in the member are dark grey where fresh  and pale brown where weathered. Although most of the member i s massive, rare poorly defined bedding and p y r i t e - c a l c i t e microconcretions are present. are  defined by  variable  carbonate  content  less than 5% to 40% CaC03 based on the HC1 calcareous beds individual and  pyrite content.  The  laminae  Poorly developed  ranging  from  an  estimated  reaction f i e l d t e s t .  show a variation  beds  in organic  Within matter  most diagnostic structures in the calcareous  mudstone member are what are  descriptively  beds ( F i g . II-9), which consist  of thin  termed  "feathery" c a l c i t e  calcite-cemented concretions,  many of which contain pyrite cores. The concentrations range up to 5 rrm in  diameter  and  are  elongate  parallel  to  cleavage  and microfaults,  giving a feathery appearance to the beds containing them. faults show displacement up to 15 mm,  These micro-  and curve over distances of a few  33  Figure I I - 9 . Specimen of the calcareous mudstone member of the Howards Pass formation. Shown are the laminated nature, the high content of organic matter and a feathery c a l c i t e bed. In this instance the c a l c i t e concretions contain pyrite cores. This particular mudstone contains 2 0 % carbonate.  cm  sometimes coalescing downward within 3 to 5 cm  formed before 1 i t h i f i c a t i o n  (Fairbridge, 1946).  indicating that they  The  occurrence  of car-  bonate l o c a l l y associated with the microfaults suggests that the elongation  of the concretions  (Berner, 1968). cretions  The  suggests  is due  to growth  parallel  to migration  paths  lack of disturbed laminae associated with the con-  that  physical  rotation  of  the  concretions  did  not  occur. Another structure typical cite  "pseudo-beds".  of the calcareous mudstone member is c a l -  These are veins, ranging  cm which parallel bedding.  in thickness from 1 to 3  Within the total thickness of the member, 10  to 25 "pseudo-beds" have been observed  The  veins consist mostly of f i b -  rous c a l c i t e and minor fibrous quartz; the long axes of the fibres perpendicular to the veins f i l l e d  with  vein walls and  white sparry  also bedding.  calcite  cut  Late stage  a l l the  are  calcite  above structures.  These veins are abundant and range from 5 nm to 1 cm across, and in some cases the crystal  terminations are v i s i b l e .  Minerals i d e n t i f i e d by x-ray d i f f r a c t i o n  in the calcareous mudstone  member include c a l c i t e , quartz, muscovite, pyrite and dolomite. and mountain leather were i d e n t i f i e d at outcrops. dark colour. interstitial  crystals  10 urn across, although c a l c i t e grains noted  the  rock  in quartz and  local  carbonaceous matter, and  their  in thin section are elongate  i s elongate  irregular  Individual grains range from 1 to  segregations are up to 0.2 mm  which ranges from 1 to 10 ym and  and gives the rocks  constitutes 5 to 3 5 % of the rock, occurring as  masses surrounded by organic matter.  Quartz,  in minor amounts in the ANNIV area  Organic matter is also important Calcite  Gypsum  parallel  across.  All  to bedding.  across, constitutes 20 to 50% of  p a r a l l e l , to bedding.  Quartz also occurs in  elongate lenses 100 ym to 10 mm long perpendicular to bedding, and i s associated with ptygmatic  folds.  Muscovite  ranges from 20 to 30%, with  the flakes parallel to bedding, however, the unit i s n o n - f i s s i l e . Pyrite  in minor  amounts  up to 3%, i s associated  spatially,  both  as disseminated  associated  with  carbonate  pyrite  masses  blebs  (Zangerl  and as cores  with  calcite  et a l . , 1969)  of c a l c i t e  microcon-  cretions. MAP-UNIT 10a-3 (LOWER CHERTY MUDSTONE MEMBER) The  lower  cherty mudstone member consists  bedded, s i l i c e o u s throughout  carbonaceous mudstone.  of monotonous, poorly  The unit  has been  observed  the Howards Pass area with only slight l i t h o l o g i c change. To  the northeast, near the South Nahanni River, the member contains up to 20% carbonate, where as to the southwest, near Summit Lake, a carbonaceous bedded chert i s the major rock type. member i s 20 to 90 m thick.  In the Howards Pass area the  T y p i c a l l y , outcrops are dark grey to black  and massive with blocky to conchoidal fracture. Sedimentary structures are sparse and include weakly defined lamination, abundant quartz "pseudo-beds" and pyrite dual  laminae  are 2 to 10 mm thick and d i f f e r  pyrite content.  member i s quartz "pseudo-beds".  in quartz, carbonate and vari-  The most obvious structure in the  These are similar to those occurring in  calcareous mudstone member except  over c a l c i t e .  Indivi-  Contacts between laminae are uneven, with lateral  ation over a few centimeters common.  the  concretions.  f o r the predominance of quartz  They are also more abundant; up to 30% quartz "pseudo-  beds" have been found  over a stratigraphic  thickness of 70 m.  These  are generally parallel  to bedding  with fibrous quartz elongate  perpen-  dicular to the walls, and are 5 mn to 2 cm thick, but vary considerably along t h e i r length. slightly crystal  T y p i c a l l y they have a geopetal  wavy, bases  and serrate tops  terminations.  contemporaneous  throughout  the lower  the unit.  Pyrite  cretions observed  are related  to quartz  the veins  formation.  displace microfaults, nodules  are common  cherty mudstone member, constituting  about 1% of  Pyrite  may occur alone, but approximately are surrounded  a high angle to bedding.  Unlike similar  nated throughout  the unit.  and  long.  90% of the con-  by fibrous quartz which i s elongate at structures in the calcareous  mudstone member these do not occur in localized  up to 20 mm  sharp,  Penecontemporaneous microfaults l o c a l l y displace  some of the veins, but occasionally suggesting  which  fabric with  Individual  zones but are dissemi-  concretions are 2 to 10 mn wide  The s i m i l a r i t y  between fibrous  quartz  in the  nodules and veins suggests similar modes of formation. The general limits  mineralogy  of the lower  cherty mudstone  way because of a high organic carbon microscopic  identification  content  tuting  (Appendix  B).  Quartz  known in a  (4 to 12%) which  and the p o s s i b i l i t y  minor minerals which would be below the 5% limit detection  i s only  of identifying  f o r x-ray  diffraction  i s the most abundant mineral, consti-  between 40 and 80% of the rock.  Approximately  60% occurs as  grains 2 to 10 pm across, associated with organic matter, and 40% occurs in  the "pseudo-beds".  The most obvious  mineralogical feature of the  lower cherty mudstone i s the low clay content compared to most mudstones (Pettijohn,  1975).  Muscovite  analyzed.  Calcite  constitutes  constitutes  10 to 25% of the samples  5 to 15% of the lower  10 to 30 m  of  the unit.  Bitumen  i s associated with  pyrite in quartz veins, and  shows a cubic outline with conchoidal fracture. The  lower  contact  with  the calcareous mudstone member  i s tran-  s i t i o n a l over 10 to 25 m, and i s distinguished by an increase in carbonate content and concomitant  decrease in s i l i c a  down section.  The upper  contact with the active member i s sharp. MAP-UNIT 10a-4 (ACTIVE MEMBER) The  active  member  consists  sequence of intercalated and  easily  possibly  rhythmic,  carbonaceous mudstone, cherty mudstone, chert  limestone and l o c a l l y  sulphides.  of a r e p e t i t i v e ,  contains economically  significant  Zn and Pb  Because of i t s heterogeneity, the member i s d i s t i n c t i v e and  i d e n t i f i e d , both  at outcrops  and in d r i l l  core.  The unit i s  established as a member because i t i s advantageous to recognize i t as a specially developed geographically  part of the Howards Pass formation.  restricted  member  that  appears  Since i t i s a  to terminate  on  all  sides (?) i t may be a l e n t i l , but in the present thesis the term member is thought to be suitable. Detailed logging of diamond d r i l l the member  into  nine  1ithologically  cores has allowed sub-division of homogeneous facies  ( F i g . 11-10).  Eight of these are repeated up to 8 times v e r t i c a l l y within the member (Figs. 11-11, 11-12). an  idealized  In the present thesis the member i s presented as  cycle, a composite  each facies occurs only once. sections of the member will Walton, 1962); rarity.  in f a c t ,  sequence of the l i t h o l o g i e s  in which  This ideal cycle does not imply that a l l  show a complete cycle (Wells, 1960; Duff and  a complete  cycle  in the active  member  is a  Weller (1956) distinguished two categories of cycle: those re-  ferred to as " t y p i c a l " , "normal", etc., which might be expected to be of  38  Grey Chert - Light grey laminated chert Whitish grey Zn-Pb Mudstone - Light grey laminated chert with up to 50% Zn + Pb present as sphalerite and galena. Water escape structures are common.  Thin Bedded Cherty Mudstone - Laminated siliceous mudstone with up to 12% organic carbon (LOI). Some laminae contain framboidal pyrite and/or sphalerite with trace amounts of galena. Slump structures are abundant.  -X  -  —  x •- t i i i T -  —  Xi  i  i —- — A  - X I 1 1, 1 1 1 y - y - y -  Cherty Mudstone - Dark grey to black s i l i c e o u s carbonaceous mudstone showing weak lamination; 'pseudo-beds' are abundant. Mixed Cherty Mudstone and Limestone - Mixed cherty mudstone and light grey basal limestone. Contacts between l i t h o l o g i e s are sharp and cross-cutting. Thin Bedded Calcareous Mudstone - Laminated calcareous carbonaceous mudstone with up to 5% organic carbon (LOI). Some laminae contain framboidal pyrite and/or sphalerite with traces of galena. Slump structures are abundant.  — i — > — I— I— I —T I —  I —  T~~T i — r I  i  i  '  I I I I ' ' I t  l -  Graded Limestone - Laminated limestone with carbonaceous matter at the top of laminae. Light Grey Basal Limestone - Light grey laminated limestone with up to 35% muscovite.  I  i  '  Figure 11-10. Stratigraphic column showing an ideal cycle within the active member, with the eight c y c l i c a l facies noted in the member i d e n t i f i e d by local informal name. No scale implied.  39  DDH 18  udstone  Member  2  SiWcco  4  6 7 4  5 9 4  2  6 7  rr  LU CD  ui  2 2 7 6 2  4  6  Fault  2 4  2  UJ  7  O <  >  6  Lower  (1)  Cherty  (6) C h e r t y  Basal  (2) L i g h l G r e y B a s a l L i m e s t o n e (3) G r o d d e d  Limestone  (4) T h i n B e d d e d C o l c a r e o u s Mudstone (5) M i x e d  Mudstone Member  Mudstone Cherty  Mudstone  (8) W h h i s h G r e y Z n - P b  Mudstone  (7)  (9)  Thin Bedded  Grey Chert  L i m e s t o n e a n d Mudstone  Figure 11-11. Detailed sections of the active member in d r i l l holes 12, 18 and 19. Numbers represent the individual facies of the active member. Note that the presence of a complete ideal cycle of the active member i s rare in these d r i l l holes.  40  UPVCR  SILICEOUS  2  B A S A L »cltS~ LOWER CMfRTY | HUDSTDW •  Figure 11-12. Detailed l i t h o l o g i c log of d r i l l hole 36, showing repeditive nature of facies occurring in the active member. Bedding i s 90° to core axis, and total length of active member i s 70.82 m. Numbers refer to active member facies: 1) basal, 2) l i g h t grey basal limestone, 3) graded limestone, 4) thin bedded calcareous mudstone, 5) mixed cherty mudstone and limestone, 6) cherty mudstone, 7) thin bedded cherty mudstone, 8) whitish grey Zn-Pb mudstone and 9) grey chert f a c i e s .  41  common occurence and those, l i k e the "idealized standard" here referred to as the ideal cycle which may be rarely developed, but which some c h a r a c t e r i s t i c order of the l i t h o l o g i c a l units.  express  Duff et a l . (1967)  have correctly suggested that a t h e o r e t i c a l , or in the present context, an ideal cycle, i s one to which the observed sedimentary sequence can be referred, and through which the observed sedimentary successions can be understood.  This  ideal  cycle  theoretical  considerations  vironments  and experimental  i s one which  and from  can be constructed from  accumulated  evidence.  Such  data  from  modern en-  i s the case of the ideal  cycle of facies occurring in the active member.  Research aimed at con-  struction of a "modal" or most typical  cycle i s s t i l l  i n progress. To  date, wherever the facies of the ideal  cycle have been found  in t h e i r  suggested sequence, t h e i r contacts are gradational; i n contrast, where the same facies are found out of the proposed sequence the contacts are generally sharp. ideal  cycle  Furthermore, i t i s the author's experience that the  order i s most common  of any sequence  which  includes a l l  elements of the cycle. FACIES 1 (BASAL FACIES) The basal facies i s a highly contorted and l o c a l l y f o l i a t e d sense of Hobbs et a l . , 1976) carbonaceous facies  i t i s not repeated  (in the  mudstone.  Unlike the other  higher i n the member.  Its d i s t r i b u t i o n  appears to be important; because i t appears l o c a l l y to contain the s l i p zone of a major slump; to date, the facies has only been observed in the XY area, where i t occurs only in d r i l l (Fig. 11-13) and i s 10 cm to 2 m thick. carbonaceous  s i l i c e o u s mudstone with  s l i g h t l y carbonaceous  chert.  holes southwest  of Yara  Peak  The facies consists of massive  lenses and laminae  of contorted,  The s i m i l a r i t y between the lenses and the  H 45  \  I,-  r>  H 19  O YARA  j  H 71  O  I NAME  PEAK  NO PEAK  SUGAR MTN  / /  v.. • —  X  <:  V  \  XY  \  CAMPj I  \  I  I  \ 0  1_  \  625  metres  Figure 11-13. Spacial d i s t r i b u t i o n of the basal facies in the XY area. Location of some d r i l l holes are shown f o r location reference. The stippled area represents the basal facies as seen in d r i l l core, and may be more widespread than i s indicated (see Plate I I ) .  43 laminae and the abundance of flow folds (de S i t t e r , 1958) the lenses are disrupted laminae. light  indicate that  Locally, the facies i s f o l i a t e d , with  grey chert lenses occurring in the plane of the f o l i a t i o n which  parallels  bedding  of nearby  units.  appears to be the result of bedding  At  least  part  of  the  foliation  plane slippage formed during later  folding. X-ray  diffractograms indicate  a similar mineralogy  to the under-  lying lower cherty mudstone member, but quartz i s more abundant, up to 75%  locally.  tinents.  Muscovite  and  organic carbon  (4 to 6%)  are minor  con-  Pyrite i s present in amounts up to 3%, but d i f f e r s t e x t u r a l l y  from that of the underlying unit, because the nodules are broken and/or elongate parallel to the plane of the f o l i a t i o n . Contacts with the underlying lower cherty mudstone and  the other  overlying facies of the active member are in general sharp; although in two  instances fragments  of limestone up to 3 cm in diameter were found  within the basal f a c i e s . FACIES 2 (LIGHT GREY BASAL LIMESTONE FACIES) The  light grey basal limestone facies consists of laminated  laceous limestone.  The  argil-  facies occurs from one to f i v e times within the  active member, most commonly occurring near the base,  just  above the  basal facies in the XY area and at the base of the member northeast of Yara  Peak  in the  XY  (Plates III and IV).  area  (Plate  II) and  in the ANNIV  and  OP  areas  Individual facies are 70 cm to 11 m thick.  The limestone consists of 60 to 70% c a l c i t e , 20 t o 35% 2M  muscovite  and minor amounts of quartz, with traces of pyrite and organic matter. Calcite occurs as microspar and micrite with the l a t t e r being associated  44 with clays.  The microspar grains are 5 to 30 urn across, the same size  range as quartz.  Micrite grains are less than 10 urn in diameter.  bonaceous matter  and associated pyrite microconcretions  clay-rich laminae.  in the  Laminae are 500 ym to 15 mm thick and are defined by  variations in c a l c i t e and clay content.  Other structures evident in the  facies are s t y l o l i t e s and c a l c i t e veins. the limestone and may be parallel gle.  occur  Car-  S t y l o l i t e s are abundant within  to lamination or cut i t at a high an-  Quartz and organic matter are contained in the s t y l o l i t e seams. Contact with the basal facies  in the southwestern  part of the XY  area i s sharp, although clasts of limestone do occur in the basal facies in a few instances.  In the northeast part of the XY area and in the  ANNIV and OP areas the contact between the limestone and the lower cherty mudstone member i s gradational over 1 to 5 cm.  The upper contact  with the graded limestone facies i s gradational over 1 to 30 cm. FACIES 3 (GRADED LIMESTONE FACIES) The  graded  limestone facies i s a laminated  with intercalated  argillaceous  carbonaceous limestone laminae.  limestone  The thicker  laminae  (>5mm) appear inversely graded because of upward decreasing proportions of carbonaceous matter. and ANNIV areas. graded  limestone  The graded  As with  limestone i s present in both the XY  the other facies  i s repetitive  and occurs  in the active member the up to 5 times  within the  member, with individual occurrences being 25 cm t o 2 m thick. The main rock type in the facies i s laminated limestone with laminae 100 ym to 7 mm thick.  These laminae  contain microspar  which  con-  s i s t s of c a l c i t e grains up to 10 ym across and quartz grains which are s l i g h t l y smaller.  Thin sections show the microspar to have a brown t i n t  45 indicating minor amounts of organic matter (Greensmith, portion  of organic  laminae.  matter  increases  near  1978); the pro-  the top of most  microspar  Patches of c a l c i t e grains 100 to 400 um across contain grains  up t o 20 ym.  T r i p l e junction grain boundaries  ganic matter suggest  and the lack of brown or-  that oxidation and recrystal1ization have produced  these  patches.  stone  indicate 50 to 60% c a l c i t e , 25 to 30% muscovite and 10 to 20%  quartz. basal  X-ray diffractograms of samples from the graded  Thus the main compositional  limestone  and the graded  differences between the light  limestone  facies  lime-  grey  are the increase in  quartz and a slight increase in carbonaceous matter in the l a t t e r . The  contacts with the light grey basal limestone and the thin bed-  ded calcareous mudstone facies are gradational over 5 t o 40 cm. trast,  contacts  with  a l l other  facies  In con-  in the member are r e l a t i v e l y  sharp. FACIES 4 (THIN BEDDED CALCAREOUS MUDSTONE FACIES) The  thin bedded calcareous  mudstone facies  consists of laminated  carbonaceous mudstone containing 20 to 40% c a l c i t e . peated  up to five times  the ANNIV area.  The facies i s re-  in the member in the XY area and four times in  In the XY area i t i s usually the lowest facies in the  section to contain  laminated  sulphides.  The facies  i s 2 cm to 10 m  thick, and may vary in thickness by 100% within 200 m along  strike.  Individual laminae are 200 ym to 5 mm thick and d i f f e r in colour as a result and  of varying amounts of pyrite, organic matter, c a l c i t e and Zn  Pb sulphides  least  (Fig. 11-14).  These  1 m, but poor exposures prevent  demonstration  of t h e i r  between d r i l l  holes  laminae are traceable study  of t h e i r  continuity, and laminae  160 m apart.  full  over at  extent or  can not be correlated  X-ray diffractograms indicate that  46  Figure 11-14. Photograph of the thin bedded calcareous mudstone facies of the active member. The laminae are the result of variations in amounts of c a l c i t e , organic matter, quartz, p y r i t e , sphalerite and galena.  47 the facies contains 20 to 40% c a l c i t e , 40 to 55% quartz and 10 to 20% muscovite,  with minor dolomite ( ? ) .  Calcite  occurs as microspar  with  crystals ranging from 1 to 40 pm in diameter.  In thin  is  masked by carbonaceous  microcrystal1ine and i s to a large extent  matter.  Accessory  minerals  because of organic matter  could  not be i d e n t i f i e d  section, quartz  i n thin  section  (1 to 5% organic carbon); but polished sec-  tions indicate that sulphides are most abundant within the carbonaceous mudstone occur  laminae.  in laminae  Within from  this  pyrite  facies  sphalerite  and galena  separate, but minor mixing  tend to  of a l l three  sulphides i s common. Structures i d e n t i f i e d  in the facies  "pseudo-beds", microfolds, spiral  include pseudo-graded  structures (Fairbridge,  volute lamination, pull-aparts, decollement poraneous  microfaults.  Pseudo-graded pyrite,  of framboidal  genesis  (Love, 1965; Sweeney and Kaplan,  mentioned above are a l l typical  which  1946),  i s believed to form 1973).  of sediments  con-  structures and penecontem-  lamination consists  grading  laminae,  of a  size  during d i a -  The other structures  that have slumped and have  rapidly lost associated water (Williams, 1963). Contacts with other facies within the active member are gradational to  sharp.  Gradational  contacts with the underlying graded  limestone  facies are from 5 mm to 5 cm, and with the overlying thinbedded  cherty  mudstone facies  i n the  are 1 to 10 cm.  Contacts  with  other  facies  active member are sharp. FACIES 5 (CHERTY MUDSTONE) The cherty mudstone facies i s a greyish black monotonous s i l i c e o u s ,  48  carbonaceous member.  mudstone which i s repeated up to 9 times within the active  It i s most t y p i c a l l y found overlying the thin bedded calcareous  mudstone f a c i e s .  In a few  instances in d r i l l  core argillaceous lime-  stone i s intercalated with mudstone, but the sharp contact between the two  cross-cuts the laminae  onal juxtaposition.  of the limestone, indicating  post-depositi-  The facies ranges in thickness from 50 cm to 7 m.  Mineralogically the facies i s the same as the lower cherty mudstone member.  The distinguishing characteristics of the cherty mudstone facies  i s the presence of abundant quartz "pseudo-beds" which may  occur up to  15 times in 1 m of stratigraphic thickness and l o c a l l y constitute 10 to 15% of the lithology.  The  presence of microfolding i s suggested by the  occurrence of folded "pseudo-beds" and i s t y p i c a l l y more intense than in the lower cherty mudstone member. FACIES 6 (THIN BEDDED CHERTY MUDSTONE FACIES) The  thin bedded cherty mudstone facies consists of rhythmic  (Gross  et a l . , 1963; Muller and Blaschke, 1969)  intercalated laminae of chert,  carbonaceous  visible  mudstone  (with or without  galena) and minor micrite.  pyrite,  sphalerite  or  Colours range from very light grey (N 8) or  l i g h t grey (N 7) to greyish black (N 2) and dark yellowish orange (10 YR 6/6)  and  emphasize the  There are two  variants:  laminated  nature  of the  facies  in the XY area a laminated siliceous  ceous mudstone i s dominant compared to the ANNIV and OP moresiliceous laminated cherty carbonaceous variants occur in a l l three Zn-Pb deposits. importance phides.  because  i t contains s i g n i f i c a n t  Stratigraphic  ( F i g . 11-15).  thicknesses ranges  carbona-  areas where a  mudstone i s dominant. The  facies i s of economic  amounts of Zn from  Both  5  cm  and  to 6  m;  Pb  suli t is  49  Figure 11-15. Photograph of the thin bedded cherty mudstone facies of the active member. The laminae are the result of variations in quartz, organic matter, pyrite, sphalerite and galena content. Microfolds and faults evident in the specimen are the result of minor slumping, concretion growth and later regional deformation.  50 thickest  in the XY area, although i t i s repeated more commonly in the  ANNIV area where i t occurs up to 8 times in the member. The  XY thin bedded cherty mudstone facies variant consists of i n -  tercalated laminae of siliceous carbonaceous mudstone (many of which are sulphide  bearing) chert  and  occasional  carbonaceous  laminae are 300 ym to 1 cm thick and average 500 ym. laminae  in the facies are siliceous carbonaceous  limestone.  The  The most abundant  mudstones, containing  60 to 70% quartz, 20 to 35% muscovite and 4 to 12% organic carbon.  Ap-  proximately 37% of the 356 laminae examined in polished section contain sulphides and some consist of massive sulphide. are dominated two.  In general, the laminae  by sphalerite or pyrite with only minor mixing of these  The black chert and limestone laminae do not contain sulphides or  more than 1% organic carbon.  The  laminae are rhythmically interlayered  (Reineck and Singh, 1975), but to date no repetitive sequence has been found. poraneous  Structures observed faults,  include  intraformational  microscopic  breccias,  folds,  spiral  penecontem-  structures,  con-  volute lamination, pull-aparts and decollement structures, a l l of which indicate  slumping.  slumping was  The  abundance  of these  structures  indicate  that  common and occurrences of the facies without these struc-  tures are rare. The  ANNIV  carbonaceous  variant  of the facies  consists mostly  cherty mudstone and carbonaceous  contain abundant sulphides. thick, thicker than those  Individual  in the  XY  of  intercalated  chert laminae; either  laminae  variant.  are 500 X-ray  ym to 1.5  diffraction  may cm and  chemical analyses show the rhythmites to contain 65 to 90% quartz, and up to 10% muscovite,  with the  remaining  rock  made up  of  sphalerite,  51 pyrite and galena.  Organic carbon constitutes up to 3% of the rock.  Thus, the ANNIV variant type.  ( i . e . rhythmites) i s more siliceous than the XY  The sulphides occur in the carbonaceous  stitute  massive  examined  sulphide as i n the XY  i n polished  section  laminae, but do not con-  variant.  Of the 220  68% contain greater than  laminae  5% sulphide.  Unlike the XY variant, the ANNIV variant shows abundant mixing of Fe, Zn and  Pb  sulphides  i n individual  laminae.  Structures i n d i c a t i v e of  slumping, which are abundant in the XY variant ANNIV  variant,  where  stylolites,  many  are not present in the  of which  contain  sphalerite,  galena and organic matter, were the only structures noted. Contacts with the thin bedded cherty mudstone and thin bedded c a l careous mudstone facies are gradational  over 1 mm to 5 cm.  In the for-  mer the contact is marked by an increase in lamina d e f i n i t i o n , whereas the l a t t e r i s marked by a decrease in carbonate content.  A l l other con-  tacts are sharp. FACIES 7 (WHITISH GREY Zn-Pb MUDSTONE FACIES) The whitish grey Zn-Pb mudstone facies i s a laminated cherty rock containing up to 70% sulphides. The r e l a t i v e l y low chert content necessitates the use of the term mudstone (Blatt  et a l . , 1972).  The term  sulphide mudstone could also be used, but the presence of less than 5% pyrite leads the present author to conclude that the term whitish grey Zn-Pb mudstone facies s u f f i c i e n t l y describes the facies at present.  The  high Zn and Pb content makes the facies the most economically s i g n i f i cant in the area; and constitutes 80% of the 11 original led to the staking of the XY, ANNIV and OP claims. observed  in d r i l l  cores, but also  occurs  as  showings which  The facies i s best  resistant  outcrops at  52 showings in the area (Plates II, III and IV). to 9 times and i s 1 cm to 12 m t h i c k .  The  facies is repeated  up  Both repetition and thickness are  greatest in the XY area. The mineralogy  of the facies is simple.  X-ray d i f f r a c t i o n studies  indicate that quartz, sphalerite and galena are the only major minerals present with only minor amounts of pyrite and l o c a l l y c a l c i t e . organic carbon constitutes less than 0.2% nearly a l l planktic organic matter was  Overall,  of the f a c i e s , suggesting that  oxidized above the chemocline or  during sulphate reduction. Sedimentary diagenetic structures are common and well displayed in the f a c i e s , and  include lamination, "pseudo-beds", c a l c i t e nodules,  abundant penecontemporaneous water escape-structures ture of Lowe, 1975).  Lamination  to organic matter, quartz and  and  ( i e . p i l l a r struc-  i s defined by variation in colour due  sulphide content; laminae are 100  to  500  urn thick and occur in beds 500 urn to 2 cm thick, each consisting of 5 to 50  laminae  (Fig. 11-16). Laminae are  traceable over  considerably in thickness because of d i f f e r e n t i a l also variable, but beds" are present  can be  traced over a few  50  cm,  compaction.  meters.  Quartz  in the f a c i e s , occuring up to four times  s t r a t i graphic section.  Locally these veins are terminated  but  vary  Beds are "pseudoin 1 m of  by  penecon-  temporaneous microfaults. The  most obvious  structures in the facies are cross-cutting veins  containing massive sphalerite and galena with minor pyrite (Fig. 11-16); and range in width from 500 pm to 1 cm, varying by a factor of f i v e over a few centimetres. locally  are  Internally  The  veins are irregular and sinuous  anastomosing where not the  modified  by  axial  veins show structures similar to the  in outline and plane  cleavage.  p i l l a r structures  53  Figure 11-16. Specimen of laminated whitish grey Zn-Pb mudstone. Light grey laminae contain chert, sphalerite and galena with minor organic matter. The dark grey laminae are similar except f o r a r e l a t i v e l y higher organic carbon content. Water escape structure at right contains massive sphalerite and galena.  described by Lowe (1975, 1976). tures demonstrates mation  The matching  that d i f f e r e n t i a l  of the p i l l a r structures.  of beds across the struc-  compaction  is associated with  for-  Terminations of the structures at the  base of the facies are sharp, and where the facies is greater than 25 cm thick  massive  sulphide commonly occurs  graphic top of the facies the veins may lying  facies.  axial  plane cleavage i s not evident.  been observed  The  at the base.  At the  protrude a few mm  into the over-  veins cut the facies at nearly right The  pillar  strati-  angles where  structures have only  in the whitish grey Zn-Pb mudstone and are considered to  be related to the occurrence of a high sulphide content.  According to  Lowe (1976), p i l l a r structures are the result of rapid f l u i d escape from fine-grained sediments and are therefore penecontemporaneous. Quartz "pseudo-beds" and limestone nodules are present with f a c i e s , occurring up to 8 times in 1 m of section.  The  "pseudo-beds" show f l a t  bottoms and serrate tops due to upward crystal  growth, and are l o c a l l y  terminated by the modified p i l l a r beds" cross-cutting  structures; no instances of "pseudo-  modified p i l l a r structures have been noted.  Lime-  stone nodules are poorly developed in the f a c i e s , and even though coarse c r y s t a l s of c a l c i t e with a radiating structure occur, ghost  structures  are well displayed, indicating that the nodules formed after the unmodified p i l l a r structures. Most contacts between the whitish grey Zn-Pb mudstone facies other facies in the member are sharp. with the grey chert and contact  with  with  Exceptions to this are contacts  the thin bedded cherty mudstone f a c i e s .  the grey chert the contact i s marked by  sulphide and a slight increase in carbonaceous  matter.  an  The  increase in  55 FACIES 8 (GREY CHERT FACIES) The grey chert facies consists of laminated medium light grey (N 6) to medium dark grey (N 4) chert.  The facies i s repeated up to 4 times  within the member; i t i s 5 cm to 1 m thick in the XY area and up to 2 m thick in the ANNIV and OP areas.  Individual  thick, and are separated by dark carbonaceous thick  ( F i g . 11-17).  laminae are 500 pm to 8 mn laminae  less than 100 pm  Locally, the lamination has been destroyed by re-  c r y s t a l l i z a t i o n of the chert.  This type of destruction  thought to be a result of c h e r t i f i c a t i o n  of bedding i s  (Park and Croneis, 1969).  mineralogy of the facies i s extremely simple;  The  quartz constitutes 95 to  99%, secondary c a l c i t e up to 5% and organic carbon up to 0.5% l o c a l l y . Except  f o r the lack of laminated  sulphides, the grey chert  facies i s  mineralogically the same as the whitish grey Zn-Pb mudstone f a c i e s . The only structures noted in the f a c i e s , other than lamination, are common stylolites.  They are rectangular to sutured in style  1968), both parallel  (Park and Schot,  and perpendicular to lamination and contain quartz  and organic matter. Contacts with a l l other facies of the active member are sharp except with the whitish dational tent.  grey Zn-Pb mudstone.  Here the contact i s gra-  over 2 to 4 cm and i s marked by an increase in sulphide conThe contact with the upper  sharp, although distinguishing  siliceous  mudstone member i s also  between the grey chert  facies  and dark  grey chert i n the overlying unit i s not always easy. MAP-UNIT 10a-5 (UPPER SILICEOUS MUDSTONE MEMBER) The upper  s i l i c e o u s mudstone, the uppermost member of the Howards  Pass formation, d i r e c t l y overlies the active member in the XY, ANNIV and  56  Figure 11-17. The grey chert facies of the active member. The laminae are the result of variation of chert (quartz) and organic matter content. The specimen contains up to 1% organic carbon. S t y l o l i t e s and veins present in the specimens are quartz f i l l e d .  57 OP  areas.  Outside of these three areas the member overlies the  cherty mudstone member.  lower  Within the Howards Pass area the member i s 25  to 120 m thick compared to 20 to 65 m thick regionally.  It consists of  interlaminated dark grey (N 3) to greyish black (N 2) mudstone and grey (M 7) to medium grey (N 5) chert.  light  In areas where the member over-  l i e s the active member i t can be divided  into lower, middle  and  upper  units ( F i g . 11-18). The  lower unit consists of laminated carbonaceous  mudstone and  mi-  nor intercalated medium grey chert; the mudstone contains abundant limestone concretions. The dominant rock type in the unit i s a laminated, s i l i c e o u s carbonaceous The  carbonaceous  mudstone which contains 20% grey chert laminae.  laminae are 200 um  to 8 mm  thick and contain 2 to 4%  organic carbon whereas the chert laminae are 500 contain only trace amounts of organic matter.  ym to 5 mm  The  thick  chert laminae  and have  quartz veins or "pseudo-beds" overlying them commonly where microfolding was most intense.  Laminated medium grey (N 5) to medium dark grey (M 4)  chert 3 to 16 cm thick i s intercalated with the carbonaceous  mudstone.  The chert beds constitute 10 to 15% of the unit; and are in gradational contact with the mudstone. following types: cretions 3 to 40  in the mudstone consists of the  (1) elongate coarsely c r y s t a l l i n e cm  carbonaceous  long perpendicular to bedding, with  banded internal structure; to 10 cm  Carbonate  long, parallel  radiating  or  (2) l i g h t grey; bedded microspar c l a s t s 5 mm  to bedding.  the lower 10 m of the unit.  con-  The  l a t t e r are found only within  The laminated carbonaceous  mudstone is bent  around both types of carbonate, but more so around the bedded types.  58  flaggy mudstone formation - buff to dark grey intercalated laminae of carbonaceous and non-carbonaceous mudstone.  upper unit - laminated carbonaceous mudstone with graptolite horizon (F) approximately 15 m from the upper contact. middle unit - laminated carbonaceous mudstone with intercalated l i g h t grey cherty mudstone laminae, f e t i d coarse c r y s t a l l i n e carbonate concretions are abundant, frequently with radiating structure. The unit shows abundant microfolds which may be related to the limestone concretions.  o  V-  'i  lower unit - laminated carbonaceous mudstone with intercalated light grey cherty mudstone, f e t i d coarse c r y s t a l l i n e limestone concretions are abundant, frequently with radiating or banded structure, medium grey laminated chert and c a l c i l u t i t e clasts are also present. Galena and sphalerite micro-concretions occur l o c a l l y near the base of the unit.  active member - intercalated chert, laminated and massive carbonaceous mudstones and 1imestone. Figure 11-18. Composite stratigraphic section of the upper s i l i c e o u s mudstone member of the Howards Pass formation. The section is based on data from d r i l l holes 18, 36 and 39 in the XY area.  59 The middle unit of the member i s similar to the lower, being mainly composed of laminae of carbonaceous mudstone and light grey chert, but lacks  the laminated grey chert beds.  Coarsely c r y s t a l l i n e  spherical  carbonate concretions 5 to 20 cm in diameter only occur in the middle u n i t , and show mostly radial internal structures ( F i g . 11-19). The upper unit of the member i s composed of laminated carbonaceous mudstone, and ranges from 10 to 30 m thick with individual laminae being 500 ym to 4 mm thick. chert.  Approximately 20% of the laminae are light grey  The upper unit does not show the intense bending of laminae no-  ted in the lower two units.  A regionally s i g n i f i c a n t  1 m thick  grap-  t o l i t e zone occurs 15 m below the top of the unit, and i s a good marker horizon for c o r r e l a t i o n .  In areas not overlying the active member the  upper s i l i c e o u s mudstone member i s similar to the upper unit the active member and s t i l l Contacts units is  between  overlying  contains the graptolite zone.  the upper  siliceous  are sharp, although the upper contact  mudstone member and other with the flaggy mudstone  interdigitate. MAP-UNIT 10b (FLAGGY MUDSTONE FORMATION) The  flaggy  mudstone formation i s a regionally  distinctive  which overlies the Howards Pass formation and marks a major the depositional environment  of the Selwyn Basin.  map-unit 10, the formation i s used in an informal into two units: tid tion  unit  change in  As with a l l units of sense.  It i s divided  a lower, generally orange weathering member, and a fe-  limestone zone  (Hedberg, 1976) ( F i g . 11-20). The l i t h o l o g i c  forma-  has been observed in an 80 km radius from Howards Pass except to  60  Figure 11-19. Specimen of a broken limestone concretion occurring in the upper s i l i c e o u s mudstone member of the Howards Pass formation. Most of the concretions show a radiating structure similar to that evident in the specimen, although banded structures are also evident in many of the concretions.  61  Upper c h e r t f o r m a t i o n , c o n t a i n i n g c a l c a r e o u s , carbonaceous chert with c l a y c l a s t s . 1 1 1  Bo  Carbonaceous f e t i d burrows.  limestone  with  abundant  I n t e r c a l a t e d carbonaceous mudstone and noncarbonaceous mudstone with l o c a l s i l t s t o n e lenses containing b a r i t e c o n c r e t i o n s .  Dark g r e y , carbonaceous mudstone, are 0.5 t o 3 cm t h i c k .  laminae  I n t e r c a l a t e d laminae of carbonaceous and non-carbonaceous mudstone. B u f f weathering q u a r t z - m u s c o v i t e siltstone. I n t e r c a l a t e d laminae of carbonaceous and non-carbonaceus mudstone. L a m i n a t e d , carbonaceous mudstone. I n t e r c a l a t e d carbonaceous and n o n - c a r b o n a ceous mudstone. S l i g h t l y c a l c a r e o u s , carbonaceous and non-carbonaceous mudstone.  I n t e r c a l a t e d laminae of carbonaceous and non-carbonaceous mudstone.  Laminated,  carbonaceous mudstone.  Howards Pass formation - upper s i l i c e o u s mudstone member, laminated carbonaceous mudstone.  Figure 11-20. Composite s t r a t i g r a p h i c s e c t i o n f o r the mudstone formation from d r i l l hole 38 and the northeast Peak ( P l a t e II, L o c a t i o n 10b in Appendix C ) .  flaggy s i d e of  Yara  62 the northeast where a facies change occurs 10 km from Yara Peak. Within the Howards Pass claim groups the formation i s exposed in the XY, ANNIV, DON and OP areas.  Locally the XY area, a few outcrops appear similar to  flagstone, from which the formation derives i t s name. ORANGE WEATHERING MEMBER The orange weathering member consists of orange weathering mudstone to s i l t s t o n e intercalated with minor carbonaceous mudstone.  Quartz, the  most abundant mineral constitutes 50 to 70% of the mudstone, and muscovite up to 45%.  P y r i t e , c a l c i t e and traces of barite and gypsum con-  s t i t u t e the remaining minerals.  The regional stratigraphic thickness i s  r e l a t i v e l y uniform compared to units in the Howards Pass formation. The estimated thickness i s 60 to 200 m in the XY area, 75 to 300 m in the ANNIV area and 80 to 300 m in the DON and OP areas. To date, no systema t i c variation can be demonstrated, although thicknesses over 75 m are present only overlying the sub-basins in which the active member of the Howards Pass formation was deposited. unit are greyish orange moderate  brown  Outcrops of the orange weathering  (10 YR 7/4) through l i g h t brown (5 YR 5/6) to  (5 YR 3/4), and fresh  samples  are dark  grey  (N 3) to  light brown (5 YR 5/6). Intercalated laminae of light coloured mudstone and dark grey carbonaceous 11-21).  mudstone  constitute  approximately  70% of the unit ( F i g .  Sedimentary structures include lamination, burrows,  dolomitic  s i l t s t o n e and mudstone clasts and p i l l a r water escape structures a l l which have been overprinted by l a t e r cleavage. are easy to recognize because coloured s l i g h t l y  of  A l l the above structures  of a colour contrast between the light  carbonaceous and dark carbonaceous  intercalated mud-  63  Figure 11-21. Outcrop of the orange weathering unit of the flaggy mudstone formation. The orange weathering areas consist of quartz and muscovite with minor dolomite and pyrite. The darker grey areas are discontinuous laminae of carbonaceous mudstone.  64 stones in the member.  Laminae 5 mm to 2 cm thick make up the member and  typically  mudstone bases  show light  and carbonaceous  mudstone  Light grey rounded dolomitic quartzose s i l t s t o n e clasts occur the member, constituting up to 3% by volume.  tops.  throughout  Uncommon dark grey  lenti-  cular mudstone clasts are present and are bent, suggesting that the mud in the clasts was not l i t h i f i e d  when later deposited in the s i l t s t o n e .  The mudstone clasts are similar to carbonaceous mudstone in the member, but  the s i l t s t o n e  exotic.  clasts  are s u f f i c i e n t l y  different  to be  termed  Many thin beds and laminae that contain 2 to 3% carbonaceous  matter also contain burrows p a r a l l e l t o bedding three-dimensional  geometry  indicative  ( F i g . 11-22), which show  of simple  t o highly  organized  mining or feeding of the nereites-facies (Seilacher, 1967). Two types  of concretions  are present  in the member.  Coarsely  c r y s t a l l i n e limestone concretions 5 cm to 1.5 m in diameter  are found  within the lower 25 m of the member, but most are found  i n an interval  10 to 25 m above the base of the member, forming a stratigraphic zon.  hori-  Many are similar to those present in the upper part of the Howards  Pass formation  in that they  are f e t i d  and contain a radial  or banded  internal structure. Most of the concretions are spherical, but some are elongate parallel to bedding. in  Pyrite i s abundant throughout  the form of pyritohedrons, cubes and spherical  the member;  concretions.  Ir-  regular oblate concretions represent 80% of the pyrite; many have rims of fibrous c a l c i t e  and quartz which may i n turn be rimmed by gypsum.  S l i g h t l y elongate pyrite concretions are perpendicular to bedding. Dish  structures (Middleton, 1967; Lowe, 1975) are common in the  orange weathering  member, and consist  of strongly curved  dishes and  65  Figure 1 1 - 2 2 . Worm burrows in the orange weathering unit of the flaggy mudstone formation. The burrows are t y p i c a l l y parallel to lamination indicating nereites, deep water f a c i e s .  66 closely spaced h a i r - l i n e p i l l a r s .  The e l u t r i a t i o n of carbonaceous mat-  ter emphasizes the structures by t h e i r colour contrast.  The dish struc-  tures are outlined by the upturned edges of discontinuous 500 um to 1 cm thick carbonaceous  laminae.  These structures do not occur in the lower  2 or 3 m of the member nor in those which are over 1 cm thick.  intercalated  Dish structures  carbonaceous  are l o c a l l y  beds  d i f f i c u l t to  recognise because of overprinting by the later regional cleavage. . Lens shaped  bodies of fine  to medium grained orange  weathering  s i l t s t o n e and laminated carbonaceous mudstone are contained in the member.  The former which  consist  of fine-grained  quartz-muscovite  silt-  stone with only traces of organic matter, are 2 to 15 m thick and up to 150 m in length. These  lenses are present in the XY and ANNIV areas  where the member overlies areas where the active member was deposited. Lenticular bodies of laminated carbonaceous have been traced in d r i l l ly. are  mudstone 5 to 40 m thick  holes for over 500 m, and are common regional-  None of the sedimentary structures noted in the rest of the member present in the carbonaceous mudstone. The  contact between the orange weathering member and the Howards  Pass formation i s generally sharp, although l o c a l l y the lower 1 to 3 m of  the orange weathering member i s more carbonaceous  than i s t y p i c a l .  Intercalation of the orange weathering member and the Howards Pass formation over 3 to 7 m in d r i l l ing  of the two units.  core further suggests a local  interfinger-  The upper contact with the upper chert formation  is also sharp or i s gradational over less than 0.5 m.  67 FETID LIMESTONE ZONE The f e t i d limestone zone i s a discontinuous limestone at the top of the flaggy mudstone formation. The zone in the XY,  ANNIV and  OP  present author  areas  and  locally  has  identified  to the  southwest  Howards Pass area although i t i s mappable only in the XY area. is thickest near Yara Peak (Plate II) and the  regional s t r i k e .  l o c a l l y , and  In the Yara  thins  rapidly  this  The  of  unit  to zero along  Peak area the zone i s 20 m thick,  in the ANNIV and OP areas a maximum thickness of 5 m  was  observed. Detailed  descriptive data  plete owing to poor exposure,  for the f e t i d  limestone  but  description  a general  zone i s incomi s possible.  The limestone i s greyish black (N 2) on fresh surfaces, and weathers to darkgrey faces.  (N 3).  A strong f e t i d  odour i s characteristic at broken sur-  Bioturbation structures are abundant in the zone and are similar  in morphology to those burrows found in the rest of the flaggy mudstone formation, except abundant.  that they  are  larger,  up  to 2 cm  across, and  more  These feeding traces do not follow bedding as they do in the  rest of the formation, but instead have a random orientation. of any noticeable bedding of bedding by burrowing  in the zone may  The lack  be the result of destruction  animals.  The mineralogy of the zone i s simple, consisting of c a l c i t e , pyrite and  muscovite  and  grains 0.2 to 1 mm  only  minor  quartz.  Coarsely  crystalline  across constitute 90% of the limestone.  thin section shows organic matter  sparite  Limestone in  (1 to 4%) disseminated throughout,  is similar in appearance t e x t u r a l l y to the coarse c r y s t a l l i n e  and  limestone  68 limestone  concretions  siliceous mudstone.  present elsewhere in the formation  and the upper  Pyrite i s present in quantities up to 5%, occurring  as cubes and pyritohedrons 0.1 to 0.5 mm in diameter. the underlying mudstone i s sharp, although underlying mudstone increases up-section  The contact with  the carbonate  content  toward the contact  in the  over 3 m.  The contact with the overlying upper chert formation i s also sharp. The discontinuous nature regionally and the l e n t i c u l a r shape l o c a l ly of the f e t i d limestone zone suggest the development of local ments favourable to i t s deposition. fetid  limestone  zone and the f e t i d  environ-  The s i m i l a r i t y of textures of the limestone  concretions  stratigraphi-  c a l l y below raises the question of a sedimentary or a diagenetic o r i g i n for the zone.  The presence of bedding  locally  and bioturbation i n d i -  cates that a sedimentary origin i s more probable. MAP-UNIT 10c (UPPER CHERT FORMATION) The  upper chert  formation  consists of a sequence  of dark  grey  weathering chert and mudstone, showing characteristics of both the Road River  group  11-23).  (see chapter  III) and Earn  (Campbell,  1967)  (Fig.  It contains laminated cherts and mudstones which are similar to  the Road River group and also local Group.  Group  The unit  i s best  current marks typical  exposed on the northeast  (Appendix C) and i s also exposed l o c a l l y from just Nahanni River to Summit Lake and from the Itsi west to Tungsten.  Regionally, the formation  of the Earn  slope of Yara  Peak  west of the South  Mountains in the northi s 50 t o 400 m thick; i n  the Howards Pass area i t i s 110 to 400 m thick. The  formation contains chert and siliceous mudstone, both of which  are greyish black (N 2) and weather to a l i g h t e r medium dark grey (N 4 ) .  69  Iron Creek formation - massive carbonaceous mudstone to s i l t s t o n e . unconformity  mm l  I I  I  ~ — r — T'  — r  [  I  n" i T i T  Upper chert containing carbonaceous chert with beds ranging from 2 to 10 cm, but is l o c a l l y massive. Siliceous carbonaceous mudstone with cherty mudstone occurring l o c a l l y . Minor bulbous f l u t e casts are present in s i I t y portions.  Lower chert containing carbonaceous chert with beds ranging from 2 to 10 cm thick.  S l i g h t l y calcareous, carbonaceous chert with clay clasts l o c a l l y . Flaggy mudstone formation ( f e t i d limestone unit) containing dark grey f e t i d limestone with abundant burrows.  Figure 11-23. Composite s t r a t i graphic section for the upper chert formation, from the northeast side of Yara Peak (Location 10c in Appendix  70 The  cherts are thin  bedded, ranging  from 2 to 10 cm thick and show  l i t t l e internal  lamination except  to  Chert textures are evident in thin section despite par-  3 cm thick.  t i a l masking by organic matter. quartz  and up to 20% mixed  f o r rare light grey chert laminae 0.5  X-ray diffractograms indicate 75 to 95%  lMp. i l l ite  and 2M muscovite, with  c a l c i t e which exceeds 10% only i n the lower 15 m of the unit. to  2% organic carbon i s present  formation mica  i s similar to the cherts except  relative  illite  in the formation.  to quartz.  minor  Only 0.3  The mudstone in the  f o r the greater abundance of up to 40% mixed I M Q  The mudstone contains  and 2M muscovite and only 40 t o 60% quartz.  Beds are 1 t o 5 cm  thick and do not contain light grey chert laminae.  Weakly graded mud-  stone to s i l t s t o n e  i s present  where the formation  same areas contain bulbous flutes associated with The  top 10 to 30 m of the formation  stone which contains from 20 to 35% c a l c i t e . 10 to 30 cm thick with  i s thinnest.  These  siltstone.  consists of calcareous mudBeds of this lithology are  no other sedimentary structures evident.  The  c a l c i t e i s very fine-grained (less than 5 ym in diameter). Contacts sharp.  between the upper chert  The lower contact with  although within approximately  formation  and other  units are  the orange weathering member i s sharp,  1 to 2 m of the contact the proportion of  carbonaceous matter in the lower unit i s greater than t y p i c a l .  In areas  where the f e t i d limestone zone occurs, the contact between the chert and the limestone i s extremely formation  sharp.  The upper contact with the Iron Creek  i s sharp and i s marked by the occurrence  vious graded bedding in the upper unit.  of mudstone and ob-  Regional mapping indicates that  71 this contact i s an unconformity with a slight angular discordance which in some areas accounts for the top 5 to 40 m of the upper chert  forma-  t i o n being absent. MAP-UNIT 18b-l (IRON CREEK FORMATION) The Iron Creek formation i s an informal map unit consisting of s i l ver-grey weathering mudstones to fine-grained  sandstones showing  quitous graded beds in the Howards Pass area.  The formation i s present  regionally, facies  although outside  changes  occur.  the  immediate  Howards  Within the area the formation  Pass  area  ubi-  major  i s 100 to 350 m  thick. The type l o c a l i t y  f o r the formation  (Plate II) which has an orange coloured cuts through the formation. formal  units:  The  is Iron Creek in the XY area valley bottom where the creek  formation  i s subdivided  into six i n -  a lower carbonaceous mudstone, lower graded beds, car-  bonaceous wacke, the Selwyn Mountains barite horizon, upper graded beds and upper carbonaceous mudstone (Fig. 11-24).  The most s i g n i f i c a n t unit  regionally i s the Selwyn Mountains barite horizon. The  lower and upper carbonaceous mudstone units  consist  of dark  grey (N 3) to greyish black (N 2) mudstone, the lower being 10 to 40 m thick and the upper 20 to 45 m thick in the Howards Pass area.  Beds are  1 to 10 cm thick, and are weakly graded from s i l t s t o n e at the base to mudstone at the top.  In a few instances bulbous loaded f l u t e casts are  found  the  in f l o a t  from  unit.  X-ray analyses  indicate  that  quartz  ranges from 30 to 60% and mixed IMQ i l l i t e and 2M muscovite from 40 to 60%.  Traces of plagioclase (?) are indicated by x-ray d i f f r a c t i o n , but  72  Yara Peak formation - brown weathering mudstone to siltstone with abundant graded beds. unconformity Carbonaceous mudstone - s i l i c e o u s , _ carbonaceous mudstone to coarse s i l t s t o n e with abundant graded beds. Upper graded beds containing carbonaceous mudstone to coarse s i l t s t o n e with abundant graded beds. Selwyn Mountains barite 11-28 f o r d e t a i l s ) . Carbonaceous wacke.  horizon (See F i g .  Lower graded beds containing carbonaceous mudstone to coarse s i l t s t o n e with abundant graded beds.  Massive carbonaceous mudstone unconformity Upper chert formation - carbonaceous chert with local patches of carbonaceous mudstone.  Figure 11-24. Composite stratigraphic section for the Iron Creek formation, from Iron Creek in the XY area (Location 18b-l in Appendix C).  the low intensity of these peaks precludes positive i d e n t i f i c a t i o n .  The  unit contains less than 1% organic carbon. The lower and upper graded beds are light grey (N 7) to medium dark grey  (N 4), depending  on the grain  size  and  related  Beds are 1 to 15 cm thick, averaging about 4 cm.  carbon content.  As the name implies,  the units are characterized by wel1-developed graded beds and l o c a l l y exhibit f l u t e casts, tool  (Fig. 11-25)  mark casts, flame structures and  load casts at the bases of the graded beds.  T y p i c a l l y , the beds have  bases rich in coarse s i l t - s i z e chert grains, grading upward through fine s i l t to carbonaceous mudstone tops.  At the tops of some beds d i s c o n t i -  nuous light grey chert laminae are present. Carbonaceous wacke ranges from 1 to 5 m thick i s up to 20 m thick in the OP area. are dark grey  (N 3).  grains 100 pm to 2 mm stone matrix.  in the XY area, but  Both fresh and weathered  The wacke i s characterized  by  samples  subangular chert  in diameter, contained within a carbonaceous mud-  The matrix consists mostly of quartz and clays with 0.5  to 10% organic carbon. To the northwest of the OP area this unit grades l a t e r a l l y into a conglomerate. Barite occurs sporadically throughout the Howards Pass area at the same stratigraphic horizon in the formation and i s therefore a s i g n i f i cant  regional  marker  separate stratigraphic the Tom  horizon.  Because  of  i t s regional  position from the bedded  Pb-Zn-Ag deposit  barite  extent  horizon  and  hosting  in the MacMillan Pass area, the barite occur-  ring in the Iron Creek formation is given the informal name Selwyn Mountains barite weathers  horizon.  to a  light  The  horizon crops out as a resistant  greyish  yellow colour  which  i s easily  unit  and  distin-  74  Figure 11-25. Graded beds typical of d i s t a l turbidites occurring in the Iron Creek formation. These distal t u r b i d i t e s generally only show intervals A, B and E of the Bouma sequence.  guished.  In the Howards Pass area the horizon occurs in the XY,  DON,  ANNIV and OP areas and ranges from 0 to 12 m thick in the XY area, but is less than 1 m thick in the ANNIV area.  The  horizon l o c a l l y exceeds  25 m in thickness, but regionally most stratigraphic  sections examined  is  in diameter which  represented by barite concretions less than 1 cm  occur in carbonaceous mudstone over a 50 cm to 5 m stratigraphic thickness.  In areas where the barite horizon is more obvious, the barite i s  laminated and contains limestone concretions and carbonaceous chert beds (Fig. 11-26). 2  cm  thick  laminae  In the areas of laminated barite the laminae are 2 nm to  and  are  ( F i g . 11-27).  intercalated  with  thinner  carbonaceous  Some of the thicker laminae are size graded, with  thin carbonaceous tops.  The  lower parts of the laminae  90% BaS04 and decrease upwards in barite content. with b a r i t e .  Pyrite concretions less than 1 cm  up to 5% of the organic rich b a r i t i c usually associated with the pyrite.  structures,  in diameter  constitute  laminae; i n t e r s t i t i a l  c a l c i t e is  of  beds, which contain limestone lenses and  grey  bedded  limestone occurs as  laminae  occur in beds  structures, convolute bedding  a l l indicative  grey carbonaceous coarsely c r y s t a l l i n e  contain 50 to  Clay varies inversely  The b a r i t i c  10 cm to 20 m thick which show spiral de'collement  mudstone  internal  spherical  carbonate.  rounded clasts  slumping  of  and  these  concretions of dark In addition,  2 to 5 cm  light  across  and  elongate lenses which are 25 cm to 2 m thick and up to 10 m in length in the  plane  of bedding.  large limestone bodies. have occurred. and was  Laminae of b a r i t i c Thus, two  mudstone wrap around  stages of carbonate  these  deposition may  F i r s t , limestone was deposited with the b a r i t i c mudstone  involved in the slumping  carbonate concretions developed.  of these beds; secondly, after  slumping  76  Upper graded beds with coarse s i l t s t o n e to mudstone showing abundant graded beds. Laminated barite intercalated with minor b a r i t i c carbonaceous mudstone. The laminated barite contains limestone clasts and concretions.  Thin bedded carbonaceous chert  VI!I!I!I/  i . i . i . i i  Intercalated laminated barite to highly b a r i t i c mudstone and laminated b a r i t i c mudstone with abundant barite concretions. Limestone clasts and concretions occur in the laminated barite. Locally s i l t s t o n e beds occur near the base of the unit.  Thin bedded carbonaceous chert with beds 1 to 8 cm thick. Carbonaceous wacke containing chert c l a s t s with a carbonaceous mudstone matrix.  Figure 11-26. Stratigraphic section f o r the Selwyn Mountains barite horizon, taken from the XY area (Location Ba in Appendix C).  77  Figure 11-27. Laminated barite from the Selwyn Mountains barite horizon. Light laminae contain more than 90% barite and darker laminae consist of b a r i t i c laminae with organic matter.  78  Carbonaceous mudstone beds 10 cm to 3 m thick containing barite concretions 2 mm b a r i t i c beds.  abundant  to 1 cm in diameter are intercalated  with the  Some of the larger concretions show a rosette structure,  although most are elongate in the plane of the bedding. ceous mudstone beds are identical  These carbona-  to the carbonaceous mudstones  which  occur regionally at the same stratigraphic horizon, even in areas where laminated barite  i s not present.  The  carbonaceous mudstone does not  show any of the slump structures evident in the laminated barite beds, suggesting that the gravitational the  i n s t a b i l i t y which caused slumping in  laminated barite did not cause similar structures in the mudstone. Carbonaceous chert beds 0.5 to 5 m thick are associated with the  laminated b a r i t i c beds. to  Laminae within the chert beds range from 0.5 cm  3 cm thick and contain no v i s i b l e  internal  sedimentary structures.  The thickness of the chert beds are d i r e c t l y proportional  to the thick-  ness of laminated barite in the deposits examined. MAP-UNIT 18b-2 The  (YARA PEAK FORMATION)  Yara Peak formation  i s an informal  unit  that  i s present re-  gionally and consists of brown-weathering c l a s t i c sediments which overl i e the grey weathering units described e a r l i e r .  The formation is at  least 100 to 200 m thick in the Howards Pass area and forms the top of the  stratigraphic  characteristic  section  in most of the area  of the Yara Peak  formation  (Plate  I).  The  i s i t s weathering  colour,  which ranges from brown (5 YR 3/4) to dusky brown (5 YR 2/2). samples range greatly in colour, from moderate yellow brown (10 YR to dark grey (N 3).  main  Fresh 5/4)  79 The typical slate, found  rock types present in the Yara Peak formation are diverse and, of a flysch assemblage (Lajoie, 1970), include mudstone, shale,  siltstone  and sandstone.  The best exposures  to date are southwest of the DON area  (Plate I ) .  of the formation  and west of the OP area  In these the formation may be sub-divided into four informal  units, designated A through  D ( F i g . 11-28).  Regional  facies  changes  make the four-fold d i v i s i o n applicable only to the Howards Pass area. Unit A forms the lower 50 to 70 m of the formation and comprises a sequence of thin graded beds of s i l t s t o n e to mudstone and, l o c a l l y , mudstone and associated s l a t e .  The graded  beds are 1 to 5 cm thick of  coarse s i l t s t o n e grading upwards into f i n e r mudstone.  The graded  beds  are similar to those in the Iron Creek formation except for the presence of the quartz grains, the proportion of organic matter state of Fe.  The Yara  and the valence  Peak formation contains monocrystal1ine  quartz  grains ( F i g . 11-29) compared to chert grains i n the Iron Creek formation (Fig. 11-30). Yara  The ratio of organic matter to clay i s also lower in the  Peak formation than  slate occur l o c a l l y  in the underlying units.  in unit A; f o r example, in the XY area they  s t i t u t e 10 to 15% of the unit. vious bedding.  of the unit  developed  flute  con-  The mudstone i s massive and lacks ob-  Slate i s associated with the mudstone but shows clay  minerals aligned parallel beds  Mixed mudstone and  there  to the regional cleavage. are abundant  flame  structures and poorly  casts and load casts which are best pyrite  Within the graded  observed  over 4 cm thick.  Lenticular  present throughout  the unit with t h e i r long axis parallel  in beds  concretions 1 to 5 cm long are  These weather to limonite and are common in the unit.  to bedding.  80  chert pebble conglomerate - dark brown, weathering chert and shale clast mudstone matrix conglomerate. nconformity UNIT D - Brown weathering mudstone to greywacke showing large scale graded beds; greywacke i s more abundant than mudstone. UNIT C - Brown weathering mudstone to greywacke showing abundant graded beds with s i l t s t o n e and mudstone more abundant than greywacke.  UNIT B - Brown weathering s l i g h t l y carbonaceous mudstone to fine-grained sandstone with abundant graded beds; same as unit B except greater proportion of s i l t s t o n e and sandstone, also noted are occasional greywacke beds.  UNIT A - Brown weathering s l i g h t l y carbonaceous mudstone to fine-grained sandstone with abundant graded beds.  unconformity Iron Creek formation - Grey weathering massive carbonaceous mudstone.  Figure 11-28. Composite stratigraphic section of the Yara Peak formation from a ridge southwest of Don Creek (Location 18b-2 in Appendix C).  81  Figure 11-29. Photomicrograph of a greywacke from the Yara Peak formation. The clasts are predominatly quartz grains; the matrix cons i s t s of mudstone. The quartz grains are similar to those in the 'Grit Unit'.  82  Figure 11-30. Photomicrograph of carbonaceous wacke occurring in the Iron Creek formation. The clasts are predominantly chert; the matrix consists of carbonaceous mudstone. The chert clasts are similar to chert occurring in the basinal facies of the Howards Pass formation.  83 Unit B i s 70 to 120 m thick and consists of thin graded beds with minor greywacke lenses and s l a t e .  The graded beds have fine sandstone  to coarse s i l t s t o n e bases and grade upward to f i n e r mudstone at the top. Sedimentary structures include flame structures and groove casts.  Len-  t i c u l a r massive greywacke beds 10 cm to 2 m thick are interbedded with the finer-grained beds and constitute less than 10% of the unit. Quartz grains are up 2.5 cm in diameter, but average 0.5 to 2 mm; quartz s i l t and clay constitute the matrix of the greywacke. The greywacke beds are traceable  f o r up to 150 m along s t r i k e , but eventually  pinch out. In  two instances where greywacke beds have been traced, they are found to turn into the cleavage; here they can be traced across bedding for up to 25 m forming c l a s t i c Unit  dikes.  C i s 50 to 130 m thick and consists  of intercalated  fine-  grained graded beds and greywackes; the l a t t e r making up 30 to 50% of the unit.  The graded beds are similar to those found in units A and B.  The greywacke beds are also similar to those found i n unit B, but are traceable  over 500 m and occur at the base of the f i n e r graded beds.  Flute casts  and groove casts  are common at the base of the greywacke  beds. To the south of the XY area, six measurements indicate  local  current  directions  were  on in-place  from the west  casts  to southwest.  Partial Bouma sequences are present in the unit (Fig. 11-31). Unit D, the uppermost unit in the Yara Peak formation i s 30 to 110 m thick and consists  of intercalated greywackes, quartzose sandstones  and minor siltstones and mudstones.  Beds range from 3 cm thick in the  mudstones to over 5 m in the greywackes. found  locally,  and include  Complete Bouma sequences are  coarse greywackes  ( d i v i s i o n A) with bases  84  PELAGIC SHALE  (B)  HORIZONTAL LAMINATION CURRENT RIPPLE & CONVOLUTE LAMINATION  HORIZONTAL LAMINATION  tvcr»i^>accostTO  BEDDING  Figure 11-31. Turbidite sequences present in the Yara Peak formation and the chert pebble conglomerate; A) ideal Bouma cycle, B and C) partial cycles from the Yara Peak formation, D) partial cycle from the chert pebble conglomerate. Not drawn to scale.  85 containing groove and f l u t e casts which indicate a western source, a l though only a few measurements were obtained.  Quartz-rich cross-bedded  s i l t s t o n e and sandstone are found in d i v i s i o n C.  The mudstones at the  top of the sequences are similar to those present in unit A at the base of the formation. The Yara Peak formation i s bounded by unconformities. contact  The lower  i s l o c a l l y conformable, but 1 km northeast of the DON area the  formation  overlies the lower graded beds of the Iron Creek formation,  suggesting an unconformity. The chert pebble conglomerate unconformably overlies the Yara Peak formation, l o c a l l y d i r e c t l y overlying unit A. MAP-UNIT 18b-3 (CHERT PEBBLE CONGLOMERATE) The chert pebble conglomerate i s an informal in  the Howards Pass  (Walker and Mutti, locally  intercalated  area and consists  1973) with chert,  unit over 400 m thick  of disorganized  quartz and minor  conglomerates shale  clasts,  with brown weathering mudstones and sandstones.  The unit contains complex  facies relationships and has not been studied  in d e t a i l , and i s therefore considered an informal  unit.  The unit weathers brown (5 YR 3/4) to dusky brown (5 YR 2/2) and at a distance appears similar to the underlying Yara Peak formation, except that the outcrops of the conglomerate appear rubbly.  The conglomerate  was studied mainly to the southwest of Howards Pass where i t i s contained in a syncline which  extends  f o r approximately 35 km along  (Plate I ) , although the unit does occur elsewhere.  strike  The top of the con-  glomerate was not observed in the Howards Pass area, but i s similar to the chert pebble conglomerate in the Canol Formation near MacMillan Pass (Smith, 1978) where i t underlies  the Tom Ba-Pb-Zn-Ag deposit,  similar to the Earn Group to the west.  and i s  86 In the Howards Pass area the best exposures are to the west of the OP area, where a stratigraphic sequence has been developed which applies to the unit  in the syncline south of Howards Pass.  Elsewhere  a l l the  sub-units described occur, but t h e i r interrelationships cannot be demonstrated. pebble chert  The  conglomerate, similar  i s similar consisting  to that  noted  in a l l the subdivisions of the chert of  siliceous  mudstone,  siltstone  in the greywackes of the Yara  and  Peak  for-  can be subdivided into five  sub-  (A thru E) based on clast type and grain size (Fig. 11-32).  All  mation. units  matrix  The chert pebble conglomerate  of these sub-divisions are present in the OP area, but regionally only partial  sections occur suggesting l a t e r i a l facies  changes.  Sub-unit A i s the s t r a t i g r a p h i c a l l y lowest recognizable d i v i s i o n of the chert  pebble conglomerate;  i t i s 10 to 40 m thick and  terized by up to 20% l e n t i c u l a r carbonaceous maining  80% of the clasts consist  mudstone c l a s t s .  of sub-rounded  parallel  appear  to bedding  to be  supported.  found elsewhere  The  The re-  black to white chert  and minor quartz ranging from 1 to 10 cm in diameter. the clasts  i s charac-  On cut surfaces  mudstone clasts  in the unit and  are aligned  represent the only  sedimentary structures. Sub-unit B i s 25 to 40 m thick  in the OP  area and  consists  pebbly mudstone containing pebbles 5 nm to 2 cm in diameter. dark  grey chert  clasts  constitute 80  to 90%  light grey chert pebbles make up the remainder.  of the  of a  Black to  pebbles, whereas  Pebbles are  sub-rounded  and equant with the pebble:matrix r a t i o being approximately 2:3,  which  is lower than other sub-units. The matrix consists of s l i g h t l y carbonaceous mudstone to s i l t s t o n e .  87  Top of the s t r a t i g r a p h i c Howards Pass a r e a .  s e c t i o n in  the  SUB-UNIT E - L i g h t grey to white c l a s t , c h e r t pebble conglomerate with no bedding evident.  SUB-UNIT D - L i g h t brown weathering i n t e r c a l a t e d quartz a r e n i t e to sub-greywacke and greywacke sandstone with weakly graded b e d s . •»•>•..*•.. •'.,„,...r SUB-UNIT C - Brown w e a t h e r i n g , black c h e r t . c l a s t pebble conglomerate, with massive lower part and upper t h i c k graded b e d s . L o c a l l y upper part grades i n t o brown mudstone.  o in oo » o • &»T> -o, •staler  •o ' Q U |  SUB-UNIT B - F i n e black c l a s t chert pebble conglomerate. SUB-UNIT A - Chert and shale c l a s t conglomerate nconformity YARA PEAK FORMATION - Mudstone to greywacke showing abundant graded beds.  Figure 11-32. Composite s t r a t i g r a p h i c s e c t i o n f o r the chert conglomerate u n i t , from a r i d g e southeast of the OP area ( L o c a t i o n Appendix C ) .  pebble 18b-3,  88 Sub-unit  C i s 300 t o 350 m t h i c k and i s d i s t i n g u i s h e d , by  black c h e r t pebbles which equant; 30%.  a r e 0.5 t o 10 cm i n d i a m e t e r ,  b l a c k c h e r t c o n s t i t u t e s 70 t o 8 0 % and l i g h t  abundant  sub-rounded  g r e y c h e r t 20 t o  The l o w e r p a r t o f t h e s u b - u n i t i s m a s s i v e and d o e s n o t show  or i m b r i c a t i o n . pebbles,  shows  bedded.  These  The u p p e r weak  and  bedding  part contains a greater proportion of oblate  imbrication modified  by  cleavage  and  is crudely  b e d s a r e 10 t o 40 m t h i c k and a r e p o o r l y g r a d e d ,  the tops o f t h e beds a r e s t i l l f i n e  although  conglomerate.  S u b - u n i t D o c c u r s o n l y l o c a l l y w e s t o f t h e OP a r e a and has n o t been identified  elsewhere.  I t i s 20 t o 150 m t h i c k and c o n s i s t s o f  v e r y c o a r s e l i t h i c a r e n i t e and i n t e r c a l a t e d g r e y w a c k e .  bedded  Quartz grains are  1 t o 3 mm i n d i a m e t e r w i t h o n l y m i n o r c h e r t g r a i n s p r e s e n t e x c e p t  in the  greywacke. In t h e OP  area the top of the chert pebble  conglomerate,  and t h e  h i g h e s t s t r a t i g r a p h i c u n i t i n t h e Howards P a s s a r e a , i s s u b - u n i t E, w h i c h i s o v e r 200 m t h i c k .  The s u b - u n i t c o n s i s t s o f m a s s i v e c o n g l o m e r a t e  90 t o 9 5 % l i g h t  grey  arenite  chert clasts.  and d a r k  to white  6/4) due t o t h e p r e s e n c e constitutes  chert pebbles,  with  o n l y minor  The s u b - u n i t w e a t h e r s  of iron oxides  10% o f t h e c o n g l o m e r a t e .  light  in the siltstone  No o b v i o u s  bedding  with quartz  brown (5YR  matrix  which  or imbrication  is present. Regional  facies  conglomerate. conglomerates siltstones  Within  changes the  a r e abundant  and g r e y w a c k e s  same e a s t w a r d  fining  are  syncline while  evident  in  mentioned  to the east  o c c u r a t t h e same  the  chert  previously they  are less  pebble  (Plate I ) , abundant;  stratigraphic level.  This  a l s o o c c u r s t o t h e s o u t h and o n l y s a n d s t o n e s  occur  at t h i s s t r a t i g r a p h i c l e v e l near  Tungsten.  89  The chert pebble conglomerate t y p i c a l l y overlies the Yara Peak formation, and appears to be the culmination of the upwards coarsening observed in that formation.  The  is  pebble conglomerate  indicated by the chert  throughout  the stratigraphic  stone; although local tact.  presence of an unconformity at the base  section, including  faults may  overlying  various units  the wavy banded lime-  also bring these two  units  into  con-  90 CHAPTER III CORRELATION AND SEDIMENTATION CORRELATION OF UNITS The  problem of biostratigraphic  area has been accentuated may  correlation  by the sparseness  provide better biostratigraphic  in the Howards Pass  of megafossils.  control  i n the future, but t h i s  method i s just beginning to be used in the area. lithologic  Conodonts  In the present  correlation was the method used, although  study  graptolite  fossil  assemblages provided further control within the Howards Pass formation. In the present study the term group i s used informally f o r the Rabbitkettle and Road River strata. tion  status, but confusion  detailed 1975,  At present these are considered of formahas resulted  stratigraphy available  1977a, 1979).  in part because of the more  in the Howards Pass  The informal  area  (Morganti,  use of groups and formations  in the  present work appears j u s t i f i e d because of stratigraphic hierarchy. lack of detailed  biostratigraphy in the area at present makes, in the  view of the present stratigraphic  The  units.  author,  a strong  case  against the use of time-  As more d e f i n i t e biostratigraphic correlation i s  completed, new, more regional,  names will  obviously be formally  pro-  posed. The  oldest units i n the Howards Pass area  are the fine  grained  e l a s t i c s and p h y l l i t e occurring below the Franconian unconformity; are correlated with the 'Grit (1973).  these  Unit' as described by Gabrielse et  They stated that the l i t h o l o g i c a l  al.  c h a r a c t e r i s t i c s of the 'Grit  Unit' and i t s stratigraphic relationships with Lower Cambrian rocks suggest correlation with the Hadrynian  Kaza, Miette and Windermere strata  occurring farther south in the Canadian C o r d i l l e r a .  The same assemblage  91 is  recognized  in  the  Flat  Frances Lake map-area  River  (Blusson,  area  1966)  (Gabrielse and  as  et  a l . , 1973)  far west as  and  the T i n t i n a  Trench in the Finlayson Lake map-area (Green et a l . , 1960). The  lower  Franconian  siltstone  unit  unconformity.  The  (map  unit  general  7a)  also  lithology  occurs  and  below  relative  the  strati-  graphic position of the unit suggest that i t correlates with the Sekwi Formation  (Blusson, 1971;  siltstone  in contrast  Gabrielse et a l . , 1973), but the former is a  to the  latter  which  is a  dolomitic  limestone.  Furthermore this correlation i s tentative because of the limited amount of exposure of the unit and  the lack of f o s s i l s .  consists of orange weathering s i l t y dolomite  The  Sekwi  whereas the more westerly  lower s i l t s t o n e is an orange weathering dolomitic s i l t s t o n e . change, related to al.(1973), and may The  the  easterly source  explain this  massive limestone,  was  Formation  proposed  by  A facies  Gabrielse  et  discrepancy.  wavy banded  limestone  and  transition  for-  mations are a l l correlated with the Rabbitkettle Formation as defined by Gabrielse et a l . (1973).  This correlation is based on lithology, f o s s i l  data and the tracing of the unit from the Coal River to the Pelly River by (Gabrielse and Blusson, 1969). present  The  presence of three informal forma-  tions  in the  study  indicates that  given  informal group status  (Table I I I - l ) .  Rabbitkettle should  the Broken Skull  based on evidence  presented by Gabrielse et a l . (1973).  Howards Pass, flaggy mudstone and  be  Further correlation of the  Rabbitkettle and  The  formation  the  to  the  a l l or  east  part  can  be made  of the  upper  chert formations are equivalent to the Road River Formation as described by Gabrielse et a l . (1973). and  megafossils  found  in  This correlation is supported the  Howards Pass  area  by  lithology  (Fig. I I I - l ) .  The  92  Table I I I - l . Summary of regional stratigraphic correlation in the eastern Yukon. Regional units are shown in column at right. The use of formations as presented in the present thesis would elevate the Road River and Rabbitkettle formations to group status.  PERIOD  •This r e p o r t b a s e d on m a j o r u n i t s proposed by Green e t a l .  R e g i o n a l uni ts w h i c h c o r r e l a t e w i t h the l o c a l s e c t i o n , some o f w h i c h meet group r e q u i r e m e n t s  This report - local informal usage ( M o r g a n t i , 1975)  PENNSYLVANIAN  MISSISSIPPI 18b-3 18b-2  CHERT PEBBLE CONGLOMERATE YARA PEAK FORMATION EARN GROUP  DEVONIAN  18b-1  IRON CREEK FORMATION  10c  UPPER CHERT FORMATION  10b  FLAGGY MUDSTONE FORMATION  SILURIAN  ROAD RIVER FORMATION (GROUP) 10a  HOWARDS PASS FORMATION  ORDOVICIAN  CAMBRIAN  HADRYNIAN  7b-3  TRANSITION  7b-2  WAVY BANDED LIMESTONE  FORMATION  7b-1  MASSIVE LIMESTONE  7a  LOWER SILTSTONE UNIT  2  'GRIT UNIT'  RABBITKETTLE FORMATION (GROUP)  FORMATION  FORMATION ^  SEKWI  FORMATION  'GRIT UNIT'  cc Ul  o  _J  TIME  FOSSIL  ROCK UNIT  (RANGE)  COUVINIAN  I  EMSIAN  o >  UJ Q  SIEGENIAN  DOWNTONIAN LUDLOVIAN WENLOCKIAN _J CO  t  GEDINNIAN  FETID oo Ul  fc  cr >o  2  or  l-  UPPER SILICEOUS MUDSTONE  < <  Q: UI UJ  CARADOCIAN  o  > o Q  u o  Q O  UJ  i  ACTIVE  MEMBER  o  e to  2 _J O (O (CALCAREOUS  MUDSTONE  to Q  LLANDEILIAN  I  LLANVIRNIAN ARENIGI AN  O  tr  LLANDOVERIAN  ASHGILLIAN  LIMESTONE  TRANSITION  ZONE  o TREMADOCIAN  Figure I I I - l . Biostratigraphic correlation of units in the Howards Pass area using known worldwide ranges of i d e n t i f i e d genera. The Early S i l u r i a n age for the active member is for a l l three Zn-Pb deposits in the area. Fossil locations are marked on Plates I I , III and IV.  o X  94 i d e n t i f i c a t i o n of the better preserved f o s s i l s were made by the present author, but a suite of f o s s i l s collected from the Cyrotograptus  zone in  the XY area and sent to Dr. C.R. Stelk (Stelk, written commun. to A.D. Clendenan, 1974) confirm the Lower S i l u r i a n age of the upper s i l i c e o u s mudstone member of the Howards Pass formation.  The present f o s s i l  data,  although preliminary in nature, does allow placement of the Howards Pass formation  and i t s contained  graphic framework. present  Zn-Pb  deposits  i n a useful  time-strati-  The Road River i s given informal group status in the  report because  of the presence  of three  regionally  mappable  units within i t as previously defined, as well as the importance of the ability  to trace the unit containing the Howards Pass Zn-Pb deposits.  Correlation of the Road River with the Whittaker  Formation  to the east  has been proposed by Gabrielse et a l . (1973). The  Iron Creek and Yara Peak formations  and the chert pebble  con-  glomerate unit can be traced to the MacMillan Pass area where they have been  correlated  with  the Canol  Formation,  but major  facies  changes  between the formation at the type l o c a l i t y in the A r c t i c make this later correlation questionable of the chert pebble Group  1970).  The d i s t i n c t i v e  lithology  conglomerate i s also similar to that of the Earn  in the Glenlyon  formations  (Mackenzie,  map-area  (Campbell,  1967).  Thus  the three  i n the Howards Pass area may be better correlated with the  Earn Group. Mapping i n the Howards Pass region has s i g n i f i c a n t l y  refined the  stratigraphic section there (Morganti, 1975, 1976, 1977a).  It i s pro-  posed that the Rabbitkettle and Road River formations be given informal group status, and that term Earn Group be used in the Howards Pass area  95 for the Middle Devonian to Mississippian (?) units. help define locations  in the stratigraphic  This would not only  section but also allow f o r  l i t h o f a c i e s time-slice reconstructions to be made, as has been done in this study with the Howards Pass formation. The age of the active member  i s tentatively thought to be Early S i l u r i a n  fossil  evidence presented here.  sedimentary  rate of deposition  The f o s s i l  in age, based on the  data also indicate that the  f o r the Howards Pass formation in the  Howards Pass area was in the range of 1 to 6 mm/1000 y r s . , depending on assumptions made concerning the percent compaction.  SEDIMENT AT ION INTRODUCTION The sedimentary environments which evolved in the Paleozoic in the eastern Yukon area are complex,  and in this report are presented in a  separate section because of economic  ramifications.  The major  strati-  graphic-tectonic feature in the area i s the Selwyn Basin which, based on data presented .here, was in existence  from the Cambrian  to the Early  Devonian, and not Late Devonian to Mississippian as previously proposed (Gabrielse, 1967; Green et a l . , 1967). poorly upper  preserved Monograptus chert  formation.  This i s based on the presence of  ( c f . M_j_ Yukonensis) near the top of the  Sedimentary  sulphides  Selwyn Basin during the Lower S i l u r i a n  were  deposited  in the  in the Howards Pass formation.  Post-Road River sediments were deposited in a different basin than the Selwyn Basin and included fine to coarse e l a s t i c s derived from a westerly source.  A later basin had a different geometry than the Selwyn Basin  and the associated Zn-Pb deposits have no direct genetic link with the Howards Pass deposits.  96 LOWER UNITS The and  'Grit Unit' consists of a lower unit with abundant graded beds  an upper unit with abundant shallow water structures.  The depth of  water during deposition of the lower graded beds i s unknown, but s i m i l a r turbidites  are generally  (Walker, 1969).  considered  to  have  formed  The upper part of the unit contains  for  shallow  and  intra-formational conglomerates.  in deep  abundant evidence  water deposition, including mudcrack casts,  water deposition suggest f i l l i n g  This  cross-bedding  sequence of deep to shallow  of the basin.  'Grit Unit' i s not clear from the present  water  The source area f o r the  study, but Gabrielse  (1967),  in summarizing the unit regionally, stated that the source was c r y s t a l line and probably  lay to the west or southwest, and that the unit was  deposited as a c l a s t i c wedge. The Sekwi  lower s i l t s t o n e appears to be a c l a s t i c basinward facies of the  Formation which, in the Sekwi Mountain map-area (Blusson  1971),  consists of dolomites and sandy, s i l t y dolomites and limestones.  Simi-  lar  shelf carbonate-basinal  described by Selley (1970). three  factors acting  terrigenous  facies relationships have been  These conditions can be brought  singly or in concert.  Low input  about by  of terrigenous  sediment to the shoreline may be due to low runoff or, i f the hinterland i s low-lying, low sediment a v a i l a b i l i t y . very gentle seaward gradient i t w i l l and  T h i r d , i f the shoreline has a  have an extremely broad t i d a l  zone  an extremely wide development of the facies. belts p a r a l l e l i n g the  shore. broad  Regional tidal  relationships in the Sekwi  zone may  be at least  in part  clastic-carbonate relationship ( F r i t z , 1976).  Formation indicate that a the reason  f o r the mixed  97 The  depositional environment of the massive limestone formation i s  speculative due to poor exposures, but the abundance of micrite suggests deposition below wave base (Bathurst, 1975). s i l material by  currents  Lenses of transported  fos-  in the lower part further suggests deposition i n i t i a l l y was with  a  reef  or bioherm  source,  possibly  to the east  (Gabrielse et a l . , 1973).  The upper part of the unit contains m i c r i t e ,  suggesting  activity;  l i t t l e current  this  and the high  indicate deposition below wave base (Selley, 1970). form to the east shallowing  - basin  content  The carbonate plat-  to the west geometry and possible  of the depositional that  silica  formation  suggest  deposited  in the Selwyn Basin.  environment  the unit  eastward  f o r the massive  limestone  had a geometry similar to the units  Therefore  the massive limestone may mark  the beginning of the existence of the Selwyn Basin. The wavy banded limestone i s the f i r s t formation the typical  geometry of the Selwyn Basin  to d e f i n i t e l y show  (Gabrielse, 1967).  member consists of graded micrite beds typical  of proximal  rhythmites of the basin-slope  (1974).  facies of Hoffman  The lower limestone  He suggested  that the facies i s "deep water", but the lack of wave related in  the wavy banded limestone only  wave base.  The overlying  indicates that  deposition  features was below  upper member consists of laminated micrites  which l o c a l l y show penecontemporaneous folds and are more typical distal-limestone rhythmite facies (Hoffman, 1974).  of the  These laminae in the  upper member are l o c a l l y graded and show spiral  structures suggestive of  clastic  The laminae may  deposition  result of distal  and subsequent  slumping.  be the  t u r b i d i t y current deposition, sedimentation or basinal  currents, although the formation  of microspar has obscured the original  98 nature  of the laminae.  I f , as has been suggested  (Gabrielse et a l . ,  1973), the source area for the formation was to the east, then the proximal  facies overlain  basin deepening Broken Skull  by a distal  or eastward  Formation.  facies could be a result  of either  shelf migration ( i . e . , transgression) of the  The roughly synchronous nature of the format-  ions (Gabrielse et a l . , 1973)  and the same location of facies changes in  the massive limestone suggest  that the basin deepened during the late  Cambrian (Fig. Ill-2)The  transition  formation i s the result of a depositional  environ-  ment similar to that in which the wavy banded limestone was deposited, except f o r a higher silicate/carbonate r a t i o . quartz over carbonate  suggest  The dominance of clay and  that the r e l a t i v e rate of s i l i c a t e input  increased gradually, or that the Selwyn Basin continued to subside below the carbonate-compensation  depth.  HOWARDS PASS FORMATION The  Howards Pass formation marks the beginning  of "black  shale"  deposition in the Selwyn Basin, and because of i t s economic  importance  is  regionally  considered  in some d e t a i l .  The formation  i s subdivided  into three major facies (Morganti, 1977), from west to east, these are: a chert basin f a c i e s , a base of slope facies and a slope facies ( F i g . Ill-3), s t i l l  further east, near the south  Nahanni River, are shallow  water shelf and l o c a l l y reef limestone facies of the Whittaker  Formation  (Gabrielse et a l . , 1973). The Howards Pass formation i s thickest in the area  of Howards  III-4). lamination  Pass,  where the base  Characteristics  such  of slope  as the high  and slow deposition rate of less  facies  organic than  occurs  matter  (Fig.  content,  6 mm/1000 y r s . are  99  Figure III-2. Lithofacies time-slice interpretation f o r the eastern Selwyn Basin during deposition of the wavy banded limestone format i o n . The area shown i s the Nahanni map sheet.  100  Figure 111-3. Lithofacies time-slice interpretation for the eastern Selwyn Basin during deposition of the Howards Pass formation in the Nahanni map-area. Arrows indicate the direction of sediment transport.  Figure III-4. Composite stratigraphic sections of the Howards Pass formation across the base of slope facies in the Howards Pass area. These sections show a general thickening of the formation in the area of the Howards Pass sub-basins (section C).  102  typical  of a starved basin  (Lineback,  1968,  1969;  Conant and  Swanson,  1961). Pelagic  deposition in the  eastern  Selwyn Basin  was  preceded  basinward migration of the top of the slope due in part to local velopment (Fig. III-5).  formation  and  reef de-  This migration was on the order of 10 km, based  on the difference in location limestone  by  of the contacts between the wavy banded  Broken  Skull  Howards Pass formation and Whittaker  Formation  and  that between  the  Formation.  Within the three basinal f a c i e s , the slope facies i s characterized by a thin sequence of calcareous mudstones similar in appearance to the calcareous mudstone member in the Howards Pass area.  This lithology has  been found from 6 km to 20 km east of Yara Peak (Fig. Ill-3) and fingers with  the Whittaker  Formation  to the east.  f a c i e s , blocks of al1ochthonous limestones  Within  inter-  the  up to 30 m across and  slope 10 m  thick are present up to 5 km from the reef. The presence of rudites and poorly preserved f o s s i l s suggests fore-reef  (Wilson, 1975;  Krebs,  that t h i s material has come from the 1976a).  These blocks have apparently  rolled or s l i d down the slope as is evidenced by the lack of s i g n i f i c a n t associated slump structures. In the Howards Pass area, laminated, s i l i c e o u s , highly carbonaceous mudstone defines the  base of slope facies  Selwyn Basin (Fig. III-3).  An  of the Ordovician-Silurian  extreme thickening of the formation i s  associated with this f a c i e s , suggesting a weakly developed base of the slope.  This trough  is most clearly  developed  trough at the in areas  sub-basin development where the active member occurs (Fig. Ill-4). sub-basins  are elongate  sub-parallel  of The  to the trend of the major facies  HOWARDS  SOUTH  BROKEN  PASS  NAHANNI  S K U L L RIVER  RIVER  REEF  CARBONATE  PLATFORM SHORE  BASINAL  CLASTICS  I  ~  10  km  1  RESTRICTED  DURING WAVY  SHELF  DEPOSITION O F BANDED  FORMATION  LIMESTONE  f-^, ^  I  'SHFI F CARBONATES — (BROKEN SKULL FM.)  Figure III-5. Diagram showing spacial relationships between the basin and the edge of the Selwyn Basin during deposition of the wavy banded limestone formation and the Howards Pass formation. Not drawn to scale.  104  changes in the changes.  area, and  define a trend  sub-parallel to major facies  This suggests that the origin of the sub-basins is d i r e c t l y or  i n d i r e c t l y related to the formation  of the regionally s i g n i f i c a n t facies  changes.  West of Howards Pass, near Summit Lake, chert  rock  in the  type  black,  but  to  cherts with blebs,  Howards Pass formation.  the  north  near  Mount  only traces of organic  barely  radiolarian  visible  in  tests in thin  hand section.  The  Sheldon  chert  specimens,  major  i s dark grey to  equivalent  carbon occur.  This  is the  varicoloured  Abundant white chert  appear  to  be  replaced  suggests that mainly pelagic  sediments were deposited on the basin f l o o r . Only minor amounts of terriginous sediments were deposited starved  Selwyn Basin  and  nels, canyons or fans  regional mapping has  (Silver and Todd, 1969)  the Ordovician-Silurian Selwyn Basin. The bonate environment  not  in the  indicated any  chan-  along the eastern edge of  extensive  in the Whittaker Formation  shallow  water car-  (Gabrielse et a l . ,  1973)  could have prohibited s i g n i f i c a n t terriginous material from entering the basin from the east (Fig. 111 —5) The  large amount of thickening  Howards Pass (Conant and  formation  i s not  Swanson, 1961).  in the base of slope facies of the  typical  This may  of be  most due  black  shale  to either the  deposits fact  that  most black shales described in the l i t e r a t u r e are intracratonic (Heckel , 1969), whereas the Selwyn Basin may  be platform-marginal,  thickening  of a f a u l t  i s due  to the  presence  or that  bounded trough  local  (Weeks,  1952). Similar 1974) ness  platform  marginal  graptolitic  shales  are less than one-third the thickness with changes  reported.  The  coincident  in Nevada  (Churkin,  no s i g n i f i c a n t thick-  alignment  of  regional  facies  105 change, major faults in the Proterozic units and the Howards Pass subbasins  suggest  that d i f f e r e n t i a l  fluenced sedimentation.  The  movement  in the  basement  lack of coarse e l a s t i c s near the edges of  the sub-basins further suggests that the rate of subsidence basins was  rocks i n -  in the  sub-  slow, and possibly that reactivation of the basement did not  produce fault scarps in the sub-basins. The  regional  facies  distribution,  within the  Howards Pass  for-  mation, ( F i g . 111-3) of slope, base of slope and chert basin are typical of an  increase of water depth  toward the basin f l o o r  (Selley, 1976).  While there has been general agreement that marine carbonaceous shales with a sparse or non-existent benthic fauna have formed in stagnant bottom  conditions, opinions have varied  deposition.  At one  widely  on  the  extreme, i t has been suggested  probable  depth  of  that many carbona-  ceous shales in the geologic past have been deposited in extremely  shal-  low water, no more than a metre deep, with benthic algae acting as baffles  restricting  water movement  1961; Hal lam, 1967).  (Twenhofel,  1939;  Conant and  Swanson,  An alternative view has been for a deep water o r i -  gin ranging from several hundred to several thousand metres, at the bottom of marine basins (Wodnough, 1937).  The  l a t t e r deep water depositi-  onal model i s supported by modern analogies such fornia (Calvert, 1964;  1966)  and the Black Sea  as the Gulf of C a l i -  (Ross and Degens, 1974).  In the Howards Pass area allochthonous blocks of limestone are present 5 km  down the slope from  the  nearest  carbonate  buildup from  appear to be derived.  This type of submarine talus suggests  over 5°  If the slope was  (King, 1948)  slopes of  consistent over the 18 km  the reef front to the base of slope a water depth to 1600 m i s indicated.  which they  of approximately  from 500  106  Evidence suggestive of water depth during deposition of the base of slope facies of the formation carbonaceous mudstones with benthic  f o s s i l s , both  includes the association of g r a p t o l i t i c  well  suggestive  preserved  of deposition below wave base.  dence against the "shallow water - algal presence of hydrodynamically  lamination and the lack of  aligned  b a f f l e model" consists of the  graptolites  undirectional bottom currents (Moors, 1969). conflicting above.  with  was  presented  by the preserva-  in the active member which indicates that the member compensation depth of 4,500 m (Hudson,  to 5,400 m (PettiJohn, 1975).  base of slope  indicate weak  Thus there i s no evidence  The shallow l i m i t s of water depth i s suggested  deposited above the carbonate  1967)  which  the proposed water depth of 500 to 1600 m  tion of limestone  Evi-  facies  This deep limit applies only to the  since the lack of carbonate  in the radiolarian  chert in the basin f l o o r faces could be a result of deposition below the compensation depth.  The above data and considerations suggest  Ordovician-Silurian  Selwyn Basin  had a deep water base  that the  of slope and  basin f l o o r . All  three major Howards Pass Zn-Pb deposits  member which in turn was deposited The  active member contains  nature, but the ideal breaks in sedimentation generalized quartz  trends  increase  occur  only in the base of slope  recurring facies  related to slumping.  up-section,  including  a carbonate  facies.  which may be c y c l i c a l in  cycle i s not often developed,  ( F i g . III-6),  in the active  in part because of  The ideal cycle shows four a  sphalerite-galena and  decrease  up-section  and an  organic matter maximum in the middle. The occurrence of limestone in a deep water environment i s not common, but may be related to sulphate reduction in the sub-basins.  I f the  107  Figure III-6. General trends within an ideal active member cycle. A. sphalerite + galena content, B. carbonate content, C. organic carbon content, D. quartz content. Facies of the active member are shown by numbers; 1) light grey basal limestone, 2) graded limestone, 3) thin bedded calcareous mudstone, 4) mixed cherty mudstone and limestone, 5) cherty mudstone, 6) thin bedded cherty mudstone, 7) whitish grey Zn-Pb mudstone and 8) grey chert. Scale not implied.  108 sub-basins were closed by a chemocline, which seems probable, two models for limestone and  production are possible, both  sulphate.  The  occurrence  of which  of c a l c i l u t i t e s  require bacteria  occurring in deep water  environments at the expense of sulphate in salt lakes, in the Dead Sea and  in ancient evaporite deposits has been documented thoroughly  1963;  Neev and Emery, 1967;  Schmalz, 1969).  Specifically,  c a l c i t e in the Dead Sea sulphate by  sulphate  environment  of  product  Friedman, 1965;  the  Sanders and Friedman,  Neev, (1963) found  that  (Neev, 1969;  low-magnesium  forms as a result of the breakdown of calcium  reducing  bacteria,  sub-basin.  particularly  Hydrogen  sulphide,  in the the  reducing  intermediate  in gypsum degradation, can evolve on the sea f l o o r from gypsum  in violent eruptions (Butlin, 1953). The  lack of any  remaining  suggests that sulphate was of s o l i d  sulphate minerals  in the active member  not present in a solid form.  calcium sulphate, calcium carbonate  calcium and sulphate ions in sea water.  can  In the absence  still  be  formed from  In the laboratory Zobell (1958)  studied sulphate reduction by Desulfovibrio using soluble compounds such as MgSO^ or Na2S04. tack  the  sulphate  Under these laboratory conditions the bacteria ation  directly  in  solution  (Friedman,  1972).  The  generalized equation for sulphate reduction under these conditions i s : 2CH 0 + S0 = 2  where 2CH 0 represents 2  2H 0 + S  4  =  2  organic matter  (Richards, 1965;  a l . , 1972), or the more general form presented by Berner 2CH 0 + S0 = 2  2HC0 - +  4  3  Nissenbaum et (1971):  HS 2  with the high HCO3- ion concentration possibly bringing about tation al.,  of dissolved C a  1968).  The  + +  as  CaC0  3  (Feely and  Kulp,  change in pH as a result of bacterial  1957;  precipi-  Presley et  sulphate  reduc-  109 tion depends upon the nature of the organic source (Berner, 1971). ever there is some suggestion that the overall ments and in anaerobic waters cause a slight  How-  reaction in marine  sedi-  increase in pH (Emery and  Rittenberg, 1952; Kaplan et a l . , 1963; T i s s o t and Welte, 1978). S i m i l a r l y , deamination of nitrogenous organic matter, which occurs largely through the agency  of biological  processes in the presence or  absence of dissolved oxygen, leads to the development  of ammonia.  With-  in aerobic environments the ammonia may build up to considerable levels and may  sometimes exceed  1955) and hence may  concentrations of 10-3  M, (Rittenberg  et a l . ,  raise the pH of the environment.  Consideration of the ideal cycle of the active member suggests that pH could be very important.  The  inverse relationship of carbonate and  organic matter and the inverse relationship between carbonate and chert suggests that pH could be a controlling  factor  (Fig. 111-6).  Experi-  mental work has shown that the deposition of SiO2 and CaC03 i s pH dependent and that at higher pH CaCOg is' preserved while at lower pH chert i s preserved (Freidman and Sanders, 1978). UPPER UNITS The  flaggy mudstone occurs throughout the Nahanni map-area  I) and i s everywhere tures  similar in thickness and in the sedimentary  present, except  in the  Howards Pass  (Plate struc-  area where the formation  thickness increases to over 75 m ( F i g . I l l - 7 ) -  Regional  distribution  indicates that the formation was deposited to within 3 km of the carbonate front to the east, and that this distance i s uniform along s t r i k e . T h i s , combined with the nereites facies trace f o s s i l s  (Seilacher,  and laminated nature of the sediments indicate a deep water at the time of deposition.  1967)  environment  Alternating laminae of quartz-muscovite  mud-  no  Figure III-7. General lithofacies time-slice interpretation for the flaggy mudstone formation in the Nahanni map-area. The unit i s characterized by regional homogeneity and the lithology is identical over thousands of knr. Area with vertical lines indicates thickness of the formation greater than 75 m.  Ill  stone and non-terrigenous the  formation  carbonaceous mudstone and local thickening of  where there  apparently  Howards Pass area, are suggestive 1972). These are deposited transport  sediments  were sub-basins  (Bouma and H o l l i s t e r , 1973).  to topographic  currents which can  contours  i n deep  The occurrence of minor distal  abundant burrows and pelagic deposits mudstone beds are in general  as in the  of contourites ( H o i l i s t e r and Heezen,  by contour or geostrophic  parallel  such  water  turbidites,  in the form of the carbonaceous  supportive  of the deep water  contourite  mode of deposition (Stow and L o v e l l , 1979). The sediments of the flaggy mudstone blanketed  the eastern  Selwyn  Basin  and at least  partially  f i l l e d i n basin i r r e g u l a r i t i e s such as at the base of the slope. The  paleogeographic d i s t r i b u t i o n  of the upper chert  formation i s  similar to that of the flaggy mudstone (Fig. III-8), although the unconformity at the base of the Iron Creek formation interpretation.  hinders  paleogeographic  The uniformity of thickness of the upper chert suggests  that the trough at the base of the slope had been f i l l e d deposition of the flaggy mudstone. in the cherts, and minor small  by the end of  The presence of sparse radiolarians  scale sole marks in the mudstone suggest  that the unit was deposited by a combination of pelagic and hemipelagic sedimentation  and weak local  turbidity  cribed by Bramlette (1946, 1961).  currents, similar to that  des-  The d i s t r i b u t i o n of the flaggy mud-  stone and the upper chert formations  may be s i g n i f i c a n t .  has been found east of the South Nahanni River.  Neither  unit  This d i s t r i b u t i o n could  be the result of either a facies change or removal of the units from the east side of the river by erosion.  Although detailed geologic mapping  has not been completed in this inverval to the east, the proposal the flaggy mudstone and the upper chert formations ments and contourites  suggests that  these  that  contain pelagic sedi-  lithologies  would  not have  112  Figure 111-8. General l i t h o f a c i e s time-slice interpretation for the upper chert formation in the Nahanni map-area. Within the map sheet the formation is l i t h o l o g i c a l l y uniform with only r e l a t i v e l y minor thickness variations.  113 been deposited on the carbonate is  platform, and therefore a facies change  suggested. The Earn Group, which consists of the Iron Creek and Yara Peak for-  mations  and  the  chert  pebble  conglomerate  in  the  Nahanni  map-area  ( 1 0 5 - 1 ) , contains c l a s t i c sequences and marks a major change in the type of  deposition in the eastern Yukon.  The  Iron Creek  formation  is the  f i r s t major c l a s t i c unit in the Paleozoic sequence to have been obviously deposited by t u r b i d i t y currents (Kuenen and M i g l i o r i n i , 1950; Walker, 1973).  In the Howards Pass area the formation consists predominantly  of  coarse s i l t s t o n e to mudstone deposited as graded beds, and is similar to distal  t u r b i d i t e sequences, with abundant s i l t  and mud  compared to sand  and the presence of only Bouma A, B and E d i v i s i o n s , on the fringes of submarine fans the  relative  (Nelson  amount of  and  Nil sen, 1974).  sand  increases  clasts 2 to 5 rrm across l o c a l l y occurs  To  and  a  the west of the OP conglomerate with  (Fig. I l l - 9 ) .  The  area chert  conglomerate  contains a mudstone matrix and is similar to upper fan deposits (Walker, 1976).  To  the  Delorme Formation  east, the  formation  overlies  the  (Fig. 111-10); here the formation  limestones consists of  grained mudstone and chert and i s similar to the hemipelagic formation.  of  the  fine-  upper chert  This regional facies pattern is suggestive of a small  sub-  marine fan originating just west of the OP area near the Pelly River and grading  eastward into d i s t a l  deposits. in - and  turbidites  (Walker, 1967) and  hemipelagic  This d i s t r i b u t i o n implies a source to the west and a reversal  basin polarity between the times Iron Creek formations.  provenance between the that this unit was  Iron  The  of deposition of the Howards Pass  distinct  Creek  and  differences in lithology  underlying  formations  and  indicate  not deposited in the Selwyn Basin as defined in this  114  «  *  <*  - KHOUCTBCS  Figure 111-9. General l i t h o f a c i e s time-slice interpretation for the Iron Creek formation in the Nahanni map-area. This interpretation is based mainly on the grain size d i s t r i b u t i o n within the formation. Two general features are evident and include a source area to the west of the OP area and two small chert basins along the margin of the coarse grained fan complex.  115  Figure 1 1 1 - 1 0 . Photograph showing the Iron Creek formation overlying limestones of the carbonate sequence on the east side of the South Nahanni River looking northeast. In this area the Iron Creek formation consists of laminated mudstone with minor graded beds.  116 thesis.  The presence of clasts of radiolarian chert in the Iron Creek  formation, furthermore, suggests that the source material may have been the central  part of the Selwyn Basin, where the Howards Pass formation  consists of radiolarian chert. The depositional  environment  for the Selwyn Mountains barite hori-  zon i s important because of the local association of Pb, Zn and Ag. The presence of minor amounts of barite in this horizon regionally has been demonstrated  (Morganti, 1976) and may be equivalent  taining  barite  eastern  British  nodules  and diagenetic barite  Columbia.  Surface  grab  to sediments  further  samples  south  from  con-  in north-  this  horizon  regionally contain over 5000 ppm Ba which suggests the presence of a Ba rich  time  associated basins  horizon  regionally.  with carbonaceous  on the sea f l o o r .  laminated barite  The  chert  presence  suggests  In areas  of laminated  deposition  of drastic  in local sub-  thickening  rocks  (Weeks, 1952). local  of the  (e.g. at the 0R0, GHMS and NOR claims, Appendix D),  rapid termination along one edge and penecontemoraneous underlying  barite  suggest  that  these  local  folds  basins are f a u l t  in  the  bounded  The faults could have channeled Ba-rich f l u i d s into the  basins making the faults  important in both the source of Ba and  the concentration of Ba. The delicate lamination and abundance of slump structures in the barite further suggest a synsedimentary origin for the laminated b a r i t e . The Yara Peak formation and chert pebble conglomerate the  attributes  1970):  of flysch  sequence  (Dzulynski  and Smith,  have most of 1963; Hsu,  (1) the succession i s made up of alternating shales, mudstones  and s i l t s t o n e s , with sandstones; sandstones are greywackes;  (2)  in the Yara Peak formation the  (3) graded beds and sole marks are common;  117  (4)  slump deposits are present;  rocks are absent; absent  and  (8)  (7) no  (5)  f o s s i l s are rare;  (6)  large scale c r o s s - s t r a t i f i c a t i o n  volcanic  is virtually  features suggestive of sub-aerial conditions are  present. Regional occur  in the  (Fig.  III-ll)  This  mapping  formation,  and  indicates a  distribution  development  (Plate  the  demonstrated  source  suggests Nelson  that d i s t i n c t  regional d i s t r i b u t i o n  westerly  further  (Normark, 1974;  I) has  area  deposition  of  facies  lithologies  f o r these  sediments.  associated  with  and Nil sen, 1974).  The  general  gional grain size d i s t r i b u t i o n indicates that the fan head was  area in the chert pebble conglomerate indicate a southwesterly inconsistency may  be  explained  (Potter and Petti John, 1977). fined, but the p o s s i b i l i t y  by  local  current  re-  west of  the OP area, although a few paleocurrent features found south of the  This  fan  DON  source.  perturbations  To date, only one major fan has been de-  of multiple fans  ( F i g . 111-12) is possible  and would explain the various chert pebble conglomerate sub-units. The  lithology of the c l a s t s  in the Yara Peak and  mations indicates either a different  source area or a different  material.  In the Yara  Peak formation  than  grains, but  the  chert  similar  Iron Creek forsource  quartz grains are more abundant  regional  spacial  distribution  of  l i t h o l o g i e s indicate that the fan systems for both units originated in approximately  the same area.  The difference between the dominant clasts  can be explained by continued u p - l i f t and erosion of the sedimentary quence to the west of the Howards Pass area. earlier,  the  Howards Pass  formation  se-  I f , as has been proposed  and/or the  upper chert  formation  constituted the source material for the Iron Creek formation, continued u p - l i f t would eventually cause stripping off of the Paleozoic strata and  113  Figure I I I - l l . Lithofacies time-slice interpretation for the Yara Peak formation and the chert pebble conglomerate in the Nahanni maparea. The grain size d i s t r i b u t i o n indicates a general source area to the west of the OP area and major sediment transport to the east ( i n d i cated .by arrows).  11  BASIN FLOOR  Figure 111-12. Submarine fan environmental model, showing generalized location of channels, fan and outer fan. No scale i s implied (modified from Nelson and Kulm, 1973).  120  exposure and erosion of the 'Grit Unit' which contains quartz clasts and F e , both c h a r a c t e r i s t i c of the Yara Peak formation. + 3  abundant  chert  clasts  continued u p l i f t may  in the  chert  The occurrence of  pebble conglomerate suggests  that  have eventually exposed the sediments undelying the  Grit Unit (Green et a l . , 1967). SUMMARY The  general  depositional history of the Howards Pass area, and  of  the Nahanni map-area in general, during the Paleozoic consisted of three main stages sediments  (Table  in a  111-2).  starved  The  basin  first with  was  deposition of carbonaceous  shallow  water  carbonates  on  its  eastern margin, with minor amounts of terrigenous sediments originating from the east.  Sub-basin deposits which host the Howards Pass deposits  occur only in the base of slope f a c i e s . flaggy mudstone was by a combination  Subsequent deposition of the  of pelagic sedimentation  genous material deposited by basinal currents. tion was pelagic  The  and  terri-  upper chert forma-  deposited in a similar manner, but with a greater proportion of sedimentation  last stage preserved  with  some deposition as distal  in the area was  plexes, which developed  the formation  turbidites.  of c l a s t i c  The  fan com-  to the west of the Howards Pass area with  transport of sediment from west to east.  These rocks record the  the  uplift  and erosion of the central part of the underlying Selwyn Basin sediments and older rocks and deposition in fan complexes which, in general, show a  coarsening  upward  sequence  ( F i g . 111-13).  The  third  stage  is not  considered to be part of the Selwyn Basin, but constitutes deposition in a subsequent basin.  121  T a b l e 111-2 - Major d e p o s i t i o n a l environments f o r the s t r a t i g r a p h i c u n i t s i n the Howards Pass a r e a . Note t h a t two s e p a r a t e d e p o s i t i o n a l b a s i n s o c c u r , the O r d o v i c i a n - E a r l y Devonian Selwyn B a s i n and the p o s t E a r l y Devonian f l y s c h b a s i n .  STRATIGRAPHIC UNIT  MAJOR TYPE OF DEPOSITION  CHERT PEBBLE CONGLOMERATE  YARA PEAK FORMATION  TURBIDITE DEPOSITION (submarine fan r e l a t e d d e p o s i t i o n )  IRON CREEK FORMATION  UPPER CHERT". FORMATION DEPOSITION BY MIXED GEOSTROPHIC AND TURBIDITY CURRENTS WITH VARYING AMOUNTS OF PELAGIC SEDIMENTATION FLAGGY MUDSTONE FORMATION  HOWARDS PASS FORMATION  STARVED BASIN DEPOSITION  TRANSITION FORMATION  TRANSITIONAL  WAVY BANDED LIMESTONE FORMATION  BASINAL LIMESTONE DEPOSITION  122 ROCK  CHERT  UNIT  FACIES  SEQUENCE  INTERPRETATION  INNER FA~N  PEBBLE  F-U(?)  CONGLOMERATE UNIT  CHANNEL  FILL  CHANNELLED F- U  PORTION OF SUPRAFAN L08E3  YARA  C-U  PEAK  z  FORMATION CHANNELLED C- U  < u. 1  ii  a  2 Z  o  sMoarH  w  F-U F-U  UJ CQ Q  SMOOTH PORTION OF  IRON  C-U  CREEK  FORMATION  F-U  _l  z SUPRAFAN LOBES  < < cc  u.  CL  in  4-  C-U C- U  UPPER  CHERT  F-U  FORMATION  OUT ER FAN  B AS IN  FLOOR  C-U  Figure II1-13. Facies interpretation of the upper Road River and Earn groups based on the submarine fan model of Walker and Mutti (1973). The Earn group consists of the Iron Creek and Yara Peak formations and the chert pebble conglomerate; and was deposited in a basin overlying the e a r l i e r Selwyn Basin.  123 CHAPTER IV  Zn-Pb DEPOSITS  INTRODUCTION All  significant  Zn-Pb  sulphide  discoveries at  Howards Pass have  been in the active member of the Howards Pass formation. Zn-Pb deposits have been i d e n t i f i e d , and deposits  (Fig. IV-1).  These  are  include the XY,  stratiform and  saucer-shaped Zn-Pb sulphide deposits with sive sulphides.  local  Three main ANNIV and  stratabound areas  OP  complex  containing mas-  Texturally the deposits are similar to one another and  for descriptive purposes are subdivided into six textural types, f i v e of which occur within s p e c i f i c facies of the active member. These deposits also show similar geometry and  association with  of slope facies of the eastern based  on  hand  specimen  and  Selwyn Basin.  microscopic  sub-basins The  textural types  properties, but  mineralogical differences are evident between them. laminated, sulphide-rich carbonaceous mudstones.  in the base  chemical  are and  Type I consists of  Sulphides are found in  only some of the carbonaceous laminae, which are intercalated with similar  laminae containing  only trace amounts of sulphides.  Laminae  are  only s l i g h t l y folded and in sulphide-rich laminae can be traced l a t e r a l l y with no change in sulphide concentration.  Type II contains sulphide  rich laminae similar to those  open to closed microfolds  are  abundant; and  areas. the  many of  of type  these  f o l d s show fracturing  Sphalerite and trace amounts of galena  fold  hinges.  Type  I or II.  i n the  hinge  are more concentrated  III also consists of laminated  folding is more intense than in types 1958)  I, but  in  sulphides, but  Flow folds (de  Sitter,  are common, and sulphides associated with them are massive and  not as obviously associated with s p e c i f i c laminae as in types  are  I and I I .  Figure IV-1. Map of the Howards Pass property showing the locations of the XY, ANNIV and OP deposits and the approximate outline of the original related sub-basins.  ro  125 Type  IV  i s sub-divided  macroscopic  laminated  laminated mudstone.  into  two  sphalerite Type IVb  sub-types; and  galena  sub-type  IVa  occurring in a  cleavage  that cross-cut mudstone laminae.  massive sphalerite, galena and  of  siliceous  i s associated with type IVa and consists  of massive sphalerite and galena occurring in dewatering later  consists  pyrite.  Type VI  structures and  Type V consists i s of l i t t l e  of  economic  consequence and consists of isolated sphalerite and/or galena associated with pyrite concretions, or galena occurring along microfault planes or in  stylolite  present  seams  chapter  deposits.  not  associated with  describes the  textural  other types  textural  types.  The  occurring  in the  three  Because of the f a c i e s - s p e c i f i c nature of the textural  the combination  of the description  of the textural  types and  types,  the  des-  c r i p t i o n of the active member (Chapter II) provides a general description of the Howards Pass deposits. sits  has  the  Thus, the description of the depo-  same emphasis on vertical  than on lateral  stratigraphic  sequences rather  variations.  DESCRIPTION OF TEXTURAL TYPES TEXTURAL TYPE I Type I consists of laminated sulphides ( F i g . IV-2) and laminated carbonaceous mudstones.  interbedded  To date, this type has been observed  only within the thin bedded cherty mudstone and thin bedded calcareous mudstone facies of the active member.  The  major sulphide minerals i n -  clude pyrite, sphalerite and minor galena, in order of decreasing abundance (Table IV-I). Pyrite occurs as framboids, a t o l l s (pyrite type B of Blanchard H a l l , 1942)  and as cubes.  and  Framboids which constitute 90% of the pyrite  126  Figure IV-2. Sample of laminated sulphide of textural type I. The specimen contains alternating laminae of carbonaceous mudstone with varying amounts of pyrite, sphalerite and minor galena.  127  TABLE IV-1  POINT COUNTS FOR SULPHIDE MINERALS OF TEXTURAL TYPES I THRU V TEXTURAL TYPE  PYRITE (%)  SPHALERITE (%)  I I  15.9 21.2 16.0  4.0 5.1 10.2  II II  13.9 9.1 13.4  III III [II til III  1  IV IV IV IV V V V V V  GALENA (%)  CHALCOPYRITE (%)  GANGUE (%)  TOTAL COUNTS NO.  0.1 0.1 0  79.8 63.6 73.7  758 711 293*  17.1 17.2 13.3  0.3 0 0  68.7 73.1 73.3  709 871 730  26.6 25.9 26.0 12.3 9.2  8.8 22.2 20.0 55.3 50.6  0 0 0 2.9 2.2  63.6 51.9 53.6 29.3 37.7  730 769 731 624 741  0.4 1.4 0.8 0  32.8 39.0 33.9 51.9  3.5(13.8)** 7.1(7.1) 2.4(7.6) 7.7(7.7)  49.6 45.3 55.3 40.3  690 644 838 856  15.2 1.2 2.0 0.4 0.4  30.3 53.9 40.3 22.3 27.1  19.0 41.3 44.6 20.2 23.9  35.1 3.5 3.2 57.0 64.3  564 748 650 703 723  1.1 0 0.3 0.2 0.4  * not enough space was present on section for 600 counts ** pits present i n section which may represent plucked galena  128  observed, range in size from 5 to 50 ym, and are well preserved so that the individual IV-3).  cubes forming the "raspberry" texture are v i s i b l e ( F i g .  These cubes are less than 1 ym in diameter and occur in a matrix  of organic matter, Slate.  a  feature also  Locally, framboids  noted  by  Love  (1965) in the Marl  are present in attached groups  ( F i g . IV-4)  which are usually found associated with the hinges of open f o l d s .  These  attached groups contain 2 to 6 individual framboids sharing common boundaries.  The tiny internal cubes are preserved in most instances; a few  groups lack the internal similar  to that  (1970).  texture, but do have a highly pitted surface  described as  pyrite"  at  Mt.  Isa by  McDonald  Atoll-texture pyrite consists of grains 10 to 30 ym across and  constitutes 5% of the pyrite cross  "dirty  section  with  their  in type I; the grains have an  centres  Atoll-texture  pyrite  i s invariably  Similar a t o l l  texture pyrite  containing  associated with  has been  mudstones, including  and  in the Marl  1942)  and  present as disseminated cubes 0.1  or  quartz.  framboidal  pyrite.  reported from  bearing carbonaceous Hall,  sphalerite  Slate  other base metal  those at Mt.  (Love, 1962).  to 0.5  mm  octagonal  Isa (Blanchard Pyrite  i s also  across constituting  5% of  the pyrite in type I. These cubes are not t y p i c a l l y associated with the framboidal pyrite laminae. Sphalerite, the dominant base metal (Table IV-1)  appears  in some laminae  sulphide in the textural  as disseminated grains which are  t y p i c a l l y elongate with t h e i r major axis cleavage. length. in  They range  from  9 to 50  type  ym  in the plane of the regional in width  and  20  to 200  ym in  Approximately 80 to 90% of the sphalerite occurs as free grains  quartz  and  organic matter  and  10  to  20%  as  simple  intergrowths  129  Figure I V - 3 . Photomicrograph of a well preserved pyrite framboid. The internal structure is shown by the arrangement of individual pyrite cubes less than 1 um across.  130  Figure IV-4. Photomicrograph of modified framboids of pyrite. Evidence of alteration includes destruction of internal texture and combination of individual framboids into masses.  131 (Kraft,  1967;  Amstutz,  1962)  partially  rimming  framboidal  pyrite.  Sphalerite in the deposits has a metallic luster even though i t contains l i t t l e iron.  Galena  i s present only in trace amounts and is associated  with isolated grains of sphalerite. mon;  Simple  intergrowths are most com-  with sphalerite being the most abundant phase. Some of the organic matter  reflected  light  with a crystal  in this textural  similar to those of shungite structure similar to, but  type has properties in  (Marmo, 1960), a mineral  not as well ordered  as, gra-  phite. TEXTURAL TYPE II Type II consists of laminated sulphides which are similar to type I, but contain greater amounts of Zn and complex (Figs. IV-5, IV-6). of type type  I, but the  II i s present  Pb,  and  i s more s t r u c t u r a l l y  The sulphide mineralogy i s the same as that  proportions are different in the  thin  bedded  bedded calcareous mudstone f a c i e s .  (Table IV-1).  Textural  cherty mudstone and  Approximately  70%  the  of the  thin  samples  examined of this textural type (p250) are in the thin bedded cherty mudstone f a c i e s . Pyrite occurs as framboids, a t o l l s and irregular masses. constitute spherical  55  to  60%  outline but  massive i n t e r i o r s .  of  the  pyrite,  with  lacking the internal  most  showing  d e t a i l , having  Most of the altered framboids  Framboids  the  typical  only pitted  are in groups of  two  to f i v e which coalesce into masses in which part of the outlines of the original  framboids  are s t i l l  distinguishable  (Fig. IV-7). Atoll  is associated in minor amounts with framboidal served,  indicating  that  the  atolls  were  pyrite  pyrite, and i s well pre-  more  resistant  or  formed  132  Figure IV-5. Textural type II consists of laminated sulphides showing open f o l d s . Individual laminae shown are generally rich in pyr i t e and/or pyrite intercalated with carbonaceous mudstone. Scale is in cm.  133  Figure IV-6. Photomicrograph of microfold in textural type I I . Note that mobilized sulphides are l o c a l l y associated with the hinges of the folds although the laminated nature of sulphides is s t i l l evident.  134  II.  Figure IV-7. Photomicrograph of massive pyrite in textural type The outline of the individual pyrite framboids is s t i l l v i s i b l e .  135 later.  Irregular masses of pyrite and occasional cubes constitute 40 to  45% of the pyrite in this textural  type.  boids in cubes and masses of pyrite  The abundance of r e l i c t  ( F i g . IV-8) suggests that most or  possibly a l l of the pyrite occurring in textural tion product of framboidal  fram-  type II i s an a l t e r a -  pyrite.  Sphalerite occurs as disseminated grains in individual carbonaceous mudstone laminae. axial  In the XY area the grains are elongate parallel to  plane cleavage, but in the less disturbed ANNIV and OP deposits  the sphalerite grains are close to equidimensional.  Grains are 5 to 60  pm across, although some elongate grains in the XY deposit are up to 200 pm long. tion  The grains are disseminated, although the control by lamina-  i s obvious.  In some cases elongate sphelerite grains in the XY  deposit are in end-to-end contact, combining  to form elongate masses up  to 500 pm long in the plane of the cleavage.  In general, sphaleriterich  laminae in type II have more sphalerite than type I; samples not showing obvious microfolds have laminae containing 40 to 50% sphalerite whereas those of type I contain less than 25%.  Massive sphalerite up to 100 pm  across  fold  i s associated with microscopic  hinges  (Fig. IV-9).  The  increase in the sphalerite in these hinge zones may be a result of both structural thickening of the sphalerite-rich laminae  (Ramsey, 1967) and  a higher concentration of sphalerite r e l a t i v e to other minerals in the hinge  zones.  suggests tation  The association  mobilization  of higher  sphalerite  of Zn and Pb during slumping  of sphalerite grains during l a t e r  gional cleavage formation.  folding  with  slump  and only  folds  reorien-  associated with re-  Sphalerite i s not t y p i c a l l y intergrown with  136  Figure IV-8. Photomicrograph of a pyrite cube occurring in textural type I I . The presence of r e l i c t framboids (outlined in ink) suggests that the cube is a result of alteration of framboids. The abundance of r e l i c t framboids in the active member further suggests that most, or possibly a l l , of the pyrite in the member was o r i g i n a l l y framboidal in nature.  137  Figure IV-9. Sphalerite may be concentrated in the hinge areas of microfolds occurring in textural type I I I . In the specimen shown the mobilization of zinc r e l a t i v e to the p y r i t i c laminae i s evident.  138 other sulphides away from microscopic fold hinges.  The minor amount of  sphalerite-pyrite intergrowth that does occur shows sphalerite p a r t i a l l y surrounding  framboidal  sphalerite  pyrite.  contains modified  In the microfold hinge areas  framboids  in a buckshot  massive  (Amstutz,  1962)  texture. Galena  occurs  in trace amounts as  irregular  grains 10  across and these show simple intergrowths with sphalerite. only been  identified  in the microfold hinges  in the  to 200 Galena  same laminae  um has as  sphalerite. TEXTURAL TYPE III Type locally  III  consists  related  to  of  laminated  laminae,  microfolds ( F i g . IV-10).  The  but  are  to  massive  also  sulphides which  structurally  sulphide mineralogy  controlled  are by  i s similar to that of  types I and II except for a greater abundance of galena and the presence of trace amounts of chalcopyrite (Table IV-I).  Textural type III occurs  in the thin bedded cherty mudstone f a c i e s . Pyrite occurs as irregular masses; approximately half of these are modified framboids  enough that  internal  cubes are not  identifiable.  These  range in size from 10 to 70 um but are commonly in coalesced  masses over 100 broken.  the  The  um  second  across.  Near microfold hinges  major form  of p y r i t e ,  irregular  associated with microfolds and i s 0.1 to 2 mm across. elongate in the plane of cleavage.  The  some framboids  are  masses, i s only Some of these are  characteristic  "dirty  pyrite"  texture and colloform-1ike edges suggest that these too are formed from a l t e r a t i o n of framboidal p y r i t e .  139  Figure IV-10. Flow folds which are typical Dashed lines outline some of the f o l d s .  of textural  type I I I .  140  Sphalerite occurs as individual irregular masses 150 to over  grains 10 to 60 um across and as  1000 um in diameter.  Individual  grains  constitute approximately 30 to 35% of the sphalerite in type III and are associated  with  specific  laminae.  Some of these  are associated with  shungite and pyrite with simple intergrowths of pyrite-sphalerite being most common.  Most of the sphalerite occurs as large (greater than 100  pm) irregular masses associated with microfolds. These irregular masses occur only in slump folds and are not elongate parallel in  type  II.  Also, massive sphalerite  to cleavage as  does not show confinement  to  s p e c i f i c laminae as in types I and II, but may cut lamination at various angles in fold hinges.  Intergrowths with galena and pyrite are common,  t y p i c a l l y with the l a t t e r minerals occurring as inclusions. Galena  and chalcopyrite are present in minor amounts, galena being  more abundant than type  in types I and II and chalcopyrite being  III (Table IV-1).  across only in the hinge with sphalerite.  unique to  Galena  occurs as irregular grains 10 to 50 pm  areas  of microfolds, where i t i s intergrown  The few grains of chalcopyrite noted in this textural  type are also intergrown with sphalerite in fold hinges. TEXTURAL TYPE IV Textural  type IV can be divided  into two sub-types,  IVa and IVb.  Sub-type IVa consists of laminated sphalerite and galena with the i n d i vidual grains being disseminated in the laminae.  Sub-type IVb, in con-  t r a s t , consists of massive sphalerite and galena with minor pyrite in cross-cutting  veins.  The two sub-types  scale of a hand specimen.  are always associated on the  141 Textural  type  IVa consists  of mesoscopically laminated sulphides  in laminated chert. This sulphide mudstone i s by d e f i n i t i o n the whitish grey Zn-Pb mudstone f a c i e s .  Microscopic investigations have shown that  while the sulphides appear laminated to the unaided laminae  contain microscopically  equant grains 3 to 45 these  minerals  occur  disseminated  urn across as  free  sphalerite  (Fig. IV-11).  grains and  most complex  type  of intergrowth  and  galena  Approximately  40%  are  intergrowths are simple, but most have complex The  eye the individual  60%  intergrown.  or buckshot  i s a buckshot  as of  Some  textures.  texture in which  individual  sphalerite grains 20 to 40 ym across contain up to 30 or 40  blebs  galena  of  ( F i g . IV-12)  intergrowths in granitic rocks.  in  a  manner  similar  to  myrmekitic  Up to 80% of the galena in sub-type IVa  is intergrown in this manner; the rest occurs as free grains. Pyrite in sub-type IVa occurs in a manner similar to that of types I, II and I I I , consisting of framboidal pyrite in a few of the more carbonaceous laminae in the f a c i e s ; i t appears i n 0.5 to 1% of the laminae, compared to 10 to 20% in types I and I I . Textural  type IVb consists of massive  traces of massive crosscut These  pyrite occurring in 500  laminae, and  veins  specifically  occur  represent f l u i d  only  in the  sphalerite and ym to 1 cm  escape  whitish grey  associated with textural  type  wide veins that  structures Zn-Pb  IVa.  galena, with  ( F i g . IV-13).  mudstone  Within  and  are  these veins,  irregular massive grains of sphalerite 100 ym to more than 1 mm across. Galena grains 50 to more than 500 ym Elongation  of these  two  minerals  long appear in a similar manner.  in the  plane  of the  vein  give the  142  Figure IV-11. Photomicrograph of whitish grey Zn-Pb mudstone showing textural type IVa. At this scale (microscope) the sulphides are disseminated, but in hand specimen the sulphides appear laminated.  143  Figure IV-12. Photomicrograph of individual sphalerite grain in textural type IVa. Galena grains less than 2 ym across occur in a buckshot texture within the sphalerite grain.  144  Figure IV-13. Photograph of whitish grey Zn-Pb mudstone with p i l l a r structures and sulphide concretions. These sulphide f i l l e d structures are irregular and anastomosing which suggest that they are the result of compaction related to f l u i d escape.  145 veins  a streaky  viously  modified  concentrated IV-15).  later  the  is  cleavage  edges  laminae  through  the  they noted  most  prominent  (Fig.  and/or  occurs in trace  suggests t h a t  traced  which  in  IV-14).  the  amounts  g r a i n s 5 t o 80 urn a c r o s s .  containing  is  by  at  Pyrite  irregular grains  appearance  centre  i n the  those  veins  Generally, of  the  galena vein  The p i t t e d s u r f a c e t y p i c a l  are  altered  in  sub-type  framboids. IVa  obis  (Fig.  s u b - t y p e and c o n s i s t s o f in  these  The framboidal  can,  in  veins where the massive p y r i t e  not p o s s i b l e where the  in  some  occurs,  pyrite  instances  be  although  v e i n s have been m o d i f i e d by l a t e r  this  cleavage.  TEXTURAL TYPE V Type  V consists  of  approximately  intergrown  massive s p h a l e r i t e  and  no  shows  galena  obvious  texture  is  common, w i t h  (Fig.  150  pm  galena. Zn-Pb the the  across  Textural  mudstone  sulphides whitish  sulphides occurred  is type  facies  5 to  20  typically II  pm s p h a l e r i t e  grey  (Fig.  shows  of  mudstone IV-17),  Minor  Both  at  spiral  slumping. facies  suggesting  blebs  irregular  intergrown  is t y p i c a l l y  and  indicative  IV-16).  of  complexly  (Table  with  the  textures In  appear that  some to  across  Buckshot in  the  instances related  slumping  larger  sphalerite whitish  (Fairbridge,  be  and  massive p y r i t e  the  base of  IV-I),  sphalerite  massive g r a i n s 20 pm t o 1 mm a c r o s s .  galena masses 200 pm t o 1 mm a c r o s s . to  proportions  and galena with minor p y r i t e  lamination  occur as i r r e g u l a r  equal  and  the  40 and  grey  1946)  in  veins  in  type  V  to water  escape  sphalerite  100 pm  simultaneously.  TEXTURAL TYPE Type VI  VI  c o n s i s t s of c o n c r e t i o n s of galena  and/or  146  Figure IV-14. S u l f i d e f i l l e d cleavage i n the w h i t i s h grey Zn-Pb mudstone. In c o n t r a s t to those p i l l a r s t r u c t u r e s formed d u r i n g compact i o n these show s t r a i g h t c o n t a c t s and i n the f i e l d show a coherent s t r i k e p a r a l l e l t o the r e g i o n a l s t r i k e of c l e a v a g e . Note the s e g r e g a t i o n o f s p h a l e r i t e and galena i n the c l e a v a g e .  147  Figure IV-15. Photomicrograph of mineral s e g r e g a t i o n in t e x t u r a l type IVb. Galena (Gn) occurs i n s e g r e g a t i o n s p a r a l l e l to cleavage and i n c o n t a c t with s i l i c a t e s . T h i s p a r t i c u l a r specimen shows cleavage m o d i f i e d t e x t u r a l t y p e IVb.  148  Figure IV-16. Photomicrograph of massive s u l p h i d e in t e x t u r a l type V. T h e r e i s no evidence of lamination in t h i s t e x t u r a l t y p e . Note t h a t buckshot t e x t u r e i s common with both s p h a l e r i t e i n galena and galena in sphalerite.  149  Grey chert facies with abundant s t y l o l i t e s  Massive sphalerite and galena in p i l l a r structures (textural type IVb).  Laminated whitish grey Zn-Pb mudstone with intercalated laminae of chert and carbonaceous chert with laminated sphalerite and galena, (textural type IVa). •  'Massive Zn-Pb sulphides with local development of spiral structures indicating that slumping has occurred (textural type V). Thin bedded cherty mudstone facies  Figure IV-17. Detailed section of the whitish grey Zn-Pb mudstone facies showing relationship between textural types IVa, IVb and V. Section i s based on DDH-66 in the XY area (Plate I I ) .  150 to  2 cm a c r o s s ,  This textural  most  of  which  are  a s s o c i a t e d with  type VI c o n s i s t s of massive galena or s p h a l e r i t e seams  or  as  above the f i r s t upper  concretions.  These  s i l i c e o u s mudstone  member,  the  which have p a r t i a l l y  a r e s i m i l a r to the  small  pyrite  occur  types  textural  the  In the a c t i v e member  in fractures  always  o c c u r r e n c e of one of t e x t u r a l  and/or sphalerite  Pass  concretions.  type occurs not only i n the a c t i v e member, but a l s o in  lower 10 m of the upper s i l i c e o u s mudstone member.  lite  pyrite  and s t y l o -  stratigraphically  I through V.  type  In  c o n s i s t s of  replaced pyrite  the  galena  c o n c r e t i o n s which  c o n c r e t i o n s found throughout  the  Howards  formation. The  spotty  stratigraphic location further  of  nature  control the  this  textural  suggest t h a t the  sulphide,  suggests t h a t  migrating  of  the  above metal  f l u i d s of d i a g e n e t i c  type  and  the  lack  of  strict  s u l p h i d e s may be d i a g e n e t i c .  previously  deposited  was s u p p l i e d by l a t e  Zn-Pb stage,  The  sulphide, vertically  origin.  DISCUSSION The grouping of geous i n two ways: dual  types.  six  textural  into  mudstone  and  differences which  defined  ranges  in  types.  laminated the  into  for for  six  textural  types  p r o p o s a l s of o r i g i n  is  advanta-  of the  quick c h a r a c t e r i z a t i o n  indivi-  of s u l p h i d e s  p u r p o s e s , only the former use i s c o n s i d e r e d h e r e .  types  of  allows  has allowed  origin-related  consisting  sulphides  (1) It  (2) It  for metallurgical  the  thin  the  Howards Pass  Textural  types  I,  sulphides occurring bedded  between  these  from  nonfolded  calcareous  textural in  type  types I  to  d e p o s i t s may be grouped II  in  and the  mudstone are  in  flow  The  III  thin  are  bedded  facies.  structural folds  in  similar,  The  cherty main  complexity,  type  III,  and  151 in  sulphide  content  grain  and f i n e s t  phide  content  phide  (Morganti,  ing  size  of  associated  grain  1973).  regional  these  structures).  slump  Stanton,  1972;  in  metamorphism,  suggests  tion and  the  complexity  (Vokes, Gorman  phides  by  1969) (1968)  slumping  and III  timing  and g r a i n  Howards that  using  of  and not for  in  higher  further  50  metallic  massive  sul-  complexity  provides  1 0 0 ° metal  the  solid  d e p o s i t s have  inter-  sulphide  ym t h i c k .  as The  at  with  indicative  no evidence with and  for  compaction.  of  solu-  Stanton  modification some  of  increasing  proposed by  least  sul1970;  movement would be i n  temperatures. that  for  (McDonald,  slumping  state  are  etc.).  associated  during  des-  structures,  textures  but  slump-  sulphides  s i z e change as evidence  deposits,  mainly  of  detailed  mobilized  presence of  indicates  of  sul-  the  metal  slumping.  initial  These r e s u l t s  bacterial"  containing  (spiral  mobilization  l e s s than  sulphide  formation  in  in o r i g i n .  suggest t h a t  types  at  in  and a m u l t i - e l e m e n t (1970),  in  the  a  similar  ( F e , Z n , Cu) s u l p h i d e s i n the form of  II  recent some of  and Bubela  laboratory  solution.  I,  on  least  For example, Lambert  s u l p h i d e bands  Farrand  textural  evidence and o b s e r v a t i o n s  and o b s e r v a t i o n  produced monomineralic  were up t o tained  Pass  occurred  s u l p h i d e s are d i a g e n e t i c  (1970)  The  i s suggested by experimental  sediments. the  of  sul-  II  the  structures  1973).  s u l p h i d e was formed b e f o r e The  of  sulphide  highest  in s t r u c t u r a l (Chapter  lowest  with the  on metamorphosed s t r a t i f o r m  Lambert,  low temperatures  III  the  which o c c u r r e d d u r i n g metamorphism  remobilization  structural  having  locally  Much  related  I  to type  size,  folding  sulphide mobilization  phide r e m o b i l i z a t i o n  At  grain  later  with  type  The i n c r e a s e  Previous i n v e s t i g a t i o n s preted  amount;  s i z e grading  and c o a r s e s t  and a l s o  criptions  and  These  at  laminae  experiment,  framboids.  53°C  ob-  152  A diagenetic data  of  Garrels  seawater.  (1971)  Investigations  for  the  and C h r i s t  s t a b l e i n normal by Berner  origin  framboidal  (1965)  which  of  and proposed f o r  mackinawite  outer  rim  (FeSi_ )  or  x  (FeS2)  (Fig.  r e p l a c e d by  suggested t h a t boids.  If  pyrite, atoll  pyrite  the  textures  similar  to  originated  during  early  that  framboids  of  framboids,  indicating a later types  IV  of  with  Zn-Pb  history  laminae  textured  and  (Fig.  may be the with  subsequent griegite  The author  pyrite  would  result  of  framboidal  framboidal  pyrite  has  showing a  pyrite Where  the  result.  alteration pyrite  It of  is  this  in carbonaceous  and suggests a l l  two  the  fram-  supports  sphalerite  former  an  always  or  three  galena  is  surround  the  origin.  mudstone  IV-19a)  for-  pyrite associated  latter.  texture  and V c o n s i s t of  of the  initial  d i s s o l v e d subsequently and  atoll  and a s s o c i a t e d massive s u l p h i d e s (types  diagenetic  1977).  from a modern bog c o n s i s t i n g of  diagenesis.  with  grey  not  laboratory  sulphur to form  from the  c o r e were  atolls  intergrown  whitish  Atoll  (FeS)  The o c c u r r e n c e o f s p h a l e r i t e and galena  is  Textural  the  is  (Elverhol,  surrounding a core of  a typical  The a s s o c i a t i o n o f  mode or o r i g i n . laminae  pyrite  i n v o l v e s the  elemental  IV-18).  rim r e p l a c e d by m a r c a s i t e texture.  pyrite  hydrotroilite  p y r i t e may be d e r i v e d  observed framboidal  "raspberry"  that  Mesozoic sediments  phase with b a c t e r i a l  or p y r i t e  with framboidal recently  indicates  supported by  by Berner (1969) and Sweeney and Kaplan (1973) have shown  r e a c t i o n of t h i s (Fe3S4)  is  T h i s has been demonstrated in the  t h a t the marine formation of framboidal mation  pyrite  laminated IVb and V)  facies,  facies  (Fig.  whereas  and  are  IV-19).  type  IVb  sulphides  IVa)  and o n l y occur i n  the  associated  the  Type is  (type  IVa  with  is associated  a s s o c i a t e d with  water  153  Pyrite  FeS  2  Figure IV-18. Major steps i n the process of d i a g e n e t i c p y r i t e f o r m a t i o n . Although p y r i t e can form d i r e c t l y from H S and F e i n modern s e d i m e n t s , framboids form only d u r i n g the FeS s t a g e . ( B e r n e r , 1971, Sweeny and K a p l a n , 1973; Howarth, 1979). 2 +  2  154  Stage 1 - b r i n e f o r m a t i o n and i n i t i a l Zn and Pb d e p o s i t i o n ; formation o f t e x t u r a l type I V a .  Stage 3 - f l u i d escape due to c o m p a c t i o n , f o r mation o f t e x t u r a l type IVb.  Stage 2 - i n i t i a l compaction a n d / o r slumping due to gravitational instab i l i t y , formation of t e x t u r a l type V.  D.  Stage 4 - C r e t a c e o u s c l e a v a g e f o r m a t i o n which m o d i f i e d most p i l l a r s t r u c t u r e s and formed s u l phide f i l l e d c l e a v a g e , format i o n o f t e x t u r a l type IVb.  Figure IV-19. A p o s s i b l e model f o r the e v o l u t i o n of the w h i t i s h grey Zn-Pb mudstone. Stage I - b r i n e d e p o s i t i o n , stage 2 - compaction a n d / o r s l u m p i n g , stage 3 - f l u i d e s c a p e , stage 4 - Cretaceous cleavage formation.  155 escape  structures  phide at All  the  these  base of  of  compared to  ing  a  ling  and type  some i n d i v i d u a l  framboidal  types  pyrite  of  a  10  to  15  are  constant  factor  mentation  rate  in  rate  of  iron  fold  only  influx  and the  s u b - b a s i n s during  This  orders  of  magnitude  areas.  The s y n g e n e t i c  documented  in  Red  the  Sea  the  conclusion that  textural brines  type and  by  facies  al.,  is  whitish  modified related  further  type VI  150  the  the  the  the  r a t e assum-  in the whitish  deposition  surrounding  (Degens  mudstone  et  and  by  local  rate  is  non-brine has been 1972)  reasoning  leads  and  associated  deposited  compaction  thick  grey  al.,  syngenetically  slumping  sedi-  s u b - b a s i n depo-  The above  Zn-Pb  of  rate-control-  increase of  rate  t o extreme d e n s i t y c o n t r a s t s .  suggested  The  laminae  relative  is  2 +  Lake K i v u  grey  by  IV-19c).  s i l i c e o u s sediments  1975).  sections  due  by to  Deposiof  the  part of the s u b - b a s i n s .  transgresses stata  This relationship  1968)  at  sul-  nodules.  to  analogous to  of  Zn in  (Bignell,  i n the c e n t r a l - d o w n s l o p e  Textural types.  instability  brines  of  Fe  where  s u l p h i d e s c o u l d have been  subsequently  gravitational tion  IV  the  is  those  environment  pools  20  the  deposition  1975)  than  deposition  brine  and the Red Sea b r i n e to  (Bignell,  faster  in  suggested  Zn-Pb mudstone and a s s o c i a t e d limestone the  (Fig.  i n c r e a s e in sedimentation  in  in  facies  every  increase  formation.  sition  the  massive  carbonaceous mudstones suggests  pyrite the  in  the  c r o s s c u t by c a l c i t e  in the  d e p o s i t i o n , and a s i m i l a r  V represent  beds  laminae  every 2 t o 5 laminae  possibility  sediment  IV-19b)  sulphide textural  occurrence  the  (Fig.  and o v e r l i e s  the  other  a l s o occurs at White P i n e , M i c h i g a n  and above some v o l c a n o g e n i c d e p o s i t s  (Govett  textural  (Ensign  et  and G o o d f e l l o w ,  156  1975)  and i s a r e s u l t  liferous material. ic  of  pyrite  by  sphalerite  cates  that  sulphide was  mudstones. own r i g h t ,  in  compaction r e l a t e d  and galena as  the  free  p a s s i n g through m e t a l -  The  active  member  rare,  2  pyrite  fluids.  above the  H S was  and t h a t  concretions occurring  Even though type its  fluids  At Howards P a s s , t h i s was most l i k e l y  upward m i g r a t i o n  available  o f upward m i g r a t i n g  VI  late  replacement further  the  in  diagenet-  only  the  indi-  sulphide  carbonaceous  may not be of economic i n t e r e s t  a s s o c i a t i o n with the o t h e r t e x t u r a l  of  in  its  types may prove to be  an ore guide f o r p r o s p e c t i n g . SUMMARY The area  economically  occur  in  three  significant distinct  Zn-Pb  sulphides  stratiform  deposits  b a s i n s where the a c t i v e member was d e p o s i t e d . divided into i n the  six textural  a c t i v e member.  carbonaceous mostly to  mudstones  slumping.  and  types  show  Textural  subsequent  compaction m o d i f i e d  OP d e p o s i t s , between  although  deposits.  the  Thus,  IV  result by  type VI c o n s i s t s of l a t e d i a g e n e t i c The s u l p h i d e t e x t u r e s  II,  increasing  types  Zn-Pb mudstone and c o u l d be the  I,  later  textural three  Howards occur  in  sedimentary occur in  sub-  structural  facies  laminated  complexity  i n the w h i t i s h  due grey  synsedimentary d e p o s i t i o n and cleavage  formation.  Textural  of  the  six  i n the XY, ANNIV and textural  types  vary  study supports the  stratigraphic  d e p o s i t s formed in the  same e n v i r o n -  ment, and t h a t v a r i a n t s o f the same ore g e n e s i s model apply t o a l l deposits.  Pass  s u l p h i d e c o n c r e t i o n s and n o d u l e s .  proportions  evidence i n d i c a t i n g t h a t the  to  and III  and m i n e r a l s are s i m i l a r  the  which  and V o c c u r of  the  The s u l p h i d e s can be sub-  types which are r e l a t e d  Textural  in  three  157 CHAPTER V STRUCTURE INTRODUCTION Secondary s t r u c t u r e s  present  in the Howards Pass area  tory  of l o c a l  penecotemporaneous f o l d i n g and f a u l t i n g  tion  folding  and  section  faulting,  and igneous  complex, although gional the  scale  'Grit  has  Unit'  low  intrusion.  the  grade The  structural  predominance of  resulted (Plate  in  I).  metamorphism  fairly  faulting flat  For the  and p o s t l U n i f i c a at  these  massive rocks  are:  lying  limestone  i n the  formation,  Howards Pass  t u r e s which a f f e c t  all  which  Paleozoic  r e g i o n to  strata  rocks in the  affect  of  of  the  the  the  area  is  on a  re-  occurring  above  structures  types of  rocks  structures  varying  base  and open f o l d s  sake of c l a r i t y  Pre-Franconian,  the  history  s u b - d i v i d e d i n t o t h r e e age groups which show d i f f e r e n t tion;  record a h i s -  are  deforma-  underlying  which  the  affect  most  degrees and Mesozoic s t r u c -  region.  PRE-FRANCONIAN STRUCTURES Low grade metamorphism and open f o l d i n g 'Grit  Unit'  1967).  to  the  Regionally  southwest pervasive  t h e u n i t are a r e s u l t i n the Sekwi deformation  formation  formation  is  G a b r i e l s e et  slaty  indicates  Howards Pass  cleavage  that t h i s  1973),  and  area  local  from  regional  although  in  rocks of  (Green  u n i t was not  affected  the  the  d i s c o r d a n c e observed c o u l d a l s o be due to  (Douglas  Howards  al.,  within  by  two u n i t s .  et  Pass area  faulting.  the  structures  the base of the massive mapping  et  phyllite  The l a c k of these  i s an unconformity between  unconformity at  inferred al.,  the  of t h i s d e f o r m a t i o n .  and t h a t t h e r e  P r e - F r a n c o n i a n angular  of  have a f f e c t e d  A  limestone  al., the  the  1970; angular  158 PALEOZOIC SFRUCfURES Structures  formed  because  some have  Howards  Pass a  these  structures  Paleozoic area  produced  deposits,  record  little  structural  during  known are  and a few  local  Paleozoic  barite  part  the  of  poorly  understood  faults  of  which are  also  history  structures  of  to  that  folds  important  base metals  and  owing  penecontemporaneous  regional  economically  deposits,  tectonic  The major  local  are  redistribution  and the  overprinting. include  the  in  because the  later  the  they  area,  in  Howards  a s s o c i a t e d with  yet  Cretaceous  were formed in  the  the Pass  sedimentation  of the Earn Group. Abundant  evidence  for  Howards Pass formation the  active  slumping occurs in  and in  the  member two d i s t i n c t  microscopic  intralaminar  slumping of  parts  types  active  t u r e s are most obvious i n the  most  are  s u l p h i d e s , which  clasts onal  (Fig. V-l)  of  pyrite  brecciation  folds  folds  (Fairbridge,  slumping occur: in  the  XY  In  deformed  occurred  during  the  horizon.  In  mesoscopic and  deposit,  The s m a l l e r  both  facies  by the  megascopic  s c a l e slump s t r u c -  spiral  and  and  indicate  local  Many  of  subsuperfical  which show t h i c k e n i n g  Abundant  that  slumping and  decollement  emplacement  structures.  slumping.  intralaminar 1963)  of  t h i n bedded c h e r t y mudstone and t h i n b e d -  i n a mudstone matrix  (Williams, 1946)  and,  member  barite  present and these p o s t - d a t e the  are  show evidence of  volute  of  member.  ded c a l c a r e o u s mudstone f a c i e s . structures  active  Selwyn Mountains  slumping  of the  the  microscopic  complete  intraformational  i n the hinge  slide  intraformati-  the  include  of  confolds  areas.  Many of the m i c r o f o l d s i n the a c t i v e member have a p o o r l y developed axial  plane  slaty  cleavage.  These  folds  are  open  to  closed  and  are  159  Figure V-l. S p i r a l s t r u c t u r e o c c u r r i n g i n the t h i n bedded c h e r t y mudstone f a c i e s of the a c t i v e member. T e x t u r e s such as t h i s are common i n the XY Zn-Pb d e p o s i t and i n d i c a t e i n t r a l a m i n a e slumping contemporaneous with d e p o s i t i o n .  160 found  in  above.  the  same f a c i e s  as the  intraformational  The cleavage shows convergent fans  microfolds.  The  redistribution relative phides  cleavage  and  slump f o l d s d e s c r i b e d  (Ramsay, 1967)  associated microfolds  of Zn and Pb s u l p h i d e s in t e x t u r a l  age of  in the  cleavage and f o l d s  folding  and the  is  lack  this  cleavage  pre-lithification  Williams rapid  et  al.  loading;  environment  folds  (1969).  is  probable  a  cutting  The  of  sul-  limestone  in  structures  a  formed by  sulphide-depositing  l i k e t h a t of the Howards Pass d e p o s i t s .  In the ANNIV and OP d e p o s i t s the to  and III.  has been documented by  They suggested t h a t these is  the  The cleavage a s s o c i a t e d  not common, but  a mechanism t h a t  to  caused much  by involvement  n o d u l e s , s u g g e s t i n g an e a r l y d i a g e n e t i c o r i g i n . with  have  types II  indicated  of  related  lesser  degree.  above s t r u c t u r e s  An e x p l a n a t i o n  of  this  may be  are  present,  that  the  but  lower  o r g a n i c carbon and high SiO2 contents i n the t h i n bedded c h e r t y mudstone facies  of  the  ANNIV  and OP a r e a s ,  aspect of  slump c o n t r o l  posed  Boswell  by  may have  by mud chemistry  (1961).  The  is  inhibited not  gravitational high f l u i d  instability  content  of  the  s u l p h i d e - r i c h muds would producing  high  fluid  s e d i m e n t a t i o n and the tive tectonic related  to  associated  with  in  effect  act  pressures and nature  crustal  slumping was m i n i m a l .  base  metal  The  rapid  slumps  deposition,  deposition  loading.  of  1963)  dense  sediment  The  rate  slow  p o s s i b i l i t y of earth  (Williams,  and  deposited  of d e p o s i t i o n , both o f which suggest  movements  pro-  of a combination o f  as a r a p i d l y  q u i e s c e n c e , suggest t h a t the  rapid  intraformational  result  carbonaceous muds.  This  new and was f i r s t  a s s o c i a t i o n of  with the s u l p h i d e d e p o s i t s appears to be the  slumping.  as  of  of  rela-  tremors  cause  of  161  In  the  tribution active  XY d e p o s i t the  of  the  member  sediment a l l The the  and  locally  local  a basal  variations  asymmetry o f the  only  the  in  slip  the  of  Yara  minor  sub-basin is  and the f o l i a t e d  Peak  the  active  intraformational  the  thickness  of  This  which  down s l o p e .  slid  is  member  is  thin  base  the  of  the  overlying  hole d a t a . (5  slump s t r u c t u r e s .  interpreted  sub-basin is thick  to  Near  grey basal  15  To  m)  the  and  central  limestone  (50  to  be a block  The a c t i v e to  80 m)  member  of  in  and c o n t a i n s  the  facies  the  active  southern  abundant  Slump f e a t u r e s  (e.g.  spiral  and decollement  member part  whitish  Zn-Pb mudstone compared to the a c t i v e member or the northern sub-basin.  redis-  basal f a c i e s occur where t h e r e i s u s u a l l y 30 t o 50 m of  a c t i v e member.  the  zone at  d e f i n e d by d r i l l  part of the s u b - b a s i n , s l i d e c l a s t s of l i g h t  has  s u b - b a s i n , apparent  suggest megascopic slumping of the a c t i v e member.  northeast  shows  member,  asymmetry of  of  grey  part of  structures)  the are  more abundant in the s o u t h e r n , d o w n - s l o p e , p o r t i o n of the a c t i v e member, and here Where  a l s o the  the  member  than where i t areas the  basal is  missing,  o v e r l i e s the  away from the  member  movement  Small  Mountains  barite  deposits  upper  member  is  is  highly  s i l i c e o u s mudstone 3 times  The asymmetry of the  i n by the  foliated. is  thicker  thicker  than  a c t i v e member and  upper s i l i c e o u s mudstone where proposed proposed, is  suggestive  of  major  slump  1971).  s c a l e , intralaminae  Selwyn  active  a c t i v e member and 2 t o  displacement  (Lewis,  the  the  sub-basin.  suggested f i l l i n g  active  zone of  barite where  slump s t r u c t u r e s are a l s o abundant  horizon.  BaS04  These  constitutes  occur from  only 50  to  in  the  95%  of  in  the  laminated the  rock.  162 Spiral of  and decollement s t r u c t u r e s are abundant and p o s t - d a t e  the  that in  barite.  Microscopic-scale redistribution  barite  instability  deposits.  and  shock  have  caused  important lift  to  the b a r i t e  west,  Faults, vity  unconformities  nated  occurred in  by  the  to  block  faulting  (?).  laminated  induced  faults  and  been  similar  to  gravitational  important.  overlying  are  slaty  time and  those  Peak  indicate time.  include  associated  formations  have  been  tectonic  up-  a s s o c i a t e d with d e p o s i t i o n  cleavage  interval  The  l e s s dense mud  slumping may a l s o  to M i s s i s s i p p i a n (?)  barite  along  to in  the the  and c h e r t  suggest t h a t the  occur  in  (Appendix D)  barite  related  during  Locally,  present  deposits the  4  faults  tectonic  acti-  Faults considered  those with  which  are  termi-  laminated  by u n c o n f o r m i t i e s  o c c u r in the  edges and i n  wavy  and  of part  and f a c i e s  faults  Middle-Devonian facies  Selwyn Mountains  barite.  underlying  Howards Pass map-  the  changes barite  GHMS, NOR  explain  the  to are  and  local  changes between  banded  compaction. limestone.  Early  0R0 rapid  them.  Minor  faults  These  have  due  Missis-  associated  horizon.  were penecontemporaneous with  differential  the  the  of  deposits).  These show a maximum displacement of 200 m and are a p p a r e n t l y  sippian  are  and Yara  have  ( S . G . = 4.5)  roughly 3 0 0 ° and terminated  Iron Creek  area.  this  unconformities,  Faults s t r i k i n g  may  both  example at the 0R0 and NOR b a r i t e  from M i d d l e - D e v o n i a n  have  deposits  h o r i z o n was d e p o s i t e d d u r i n g  locally  (for  barite  slumping  Shock  barite  and  deposits  the  of b a r i t e  slumping.  because the the  In  induced  higher s p e c i f i c g r a v i t y  to  BaS0  noted f o r ZnS and PbS i n the Howards Pass d e p o s i t s was not observed  the  may  of  emplacement  with  These  faults  bedded  barite  thickening These  features  sedimentation  striking dolomitic  of  300°  and also  alteration  163 up t o  3 m wide  formation.  is  noted higher  needed  in the  age  formation fact  of  to  slaty  cannot  be  t h a t the major  90°  across  north.  cleavage  in  do not  not  cut  the  Howards  Pass  known and more d e t a i l e d  their  the  demonstrated,  relationship  but  basal the  100  to  m of  associated  the  in-  faults  The s l a t y defined  cleavage s t r i k e s  bodies  of the s l a t y c l e a v a g e . only  of  the  265°  formation  to 2 8 5 ° ,  noted  and  follow  in the mudstone.  d i p s 75  up to  The a t t i t u d e i s d e f i n e d by p a r a l l e l structure  Peak  cleavage suggest  massive mudstone  Yara Peak  Yara  structures,  Cretaceous cleavage c r o s s - c u t s t h i s  Poorly  the  is  understand  in the bottom 100 m of the  micas and i s  but  section.  a p r e - c r e t a c e o u s age. to  them,  The age of these f a u l t s  vestigation  The  a s s o c i a t e d with  150 m  the  strike  alignment  Greywacke  of  dikes  up to 75 m long f o l l o w the c l e a v a g e , and show i r r e g u l a r  to s t r a i g h t  con-  tacts.  from  they  The  originated, clastic  were s t i l l  The  suggest  formation  Alterman,  1973).  high pore-water formation  impermeable  greywacke  beds  mudstone b o d i e s .  The  these  of  the  features  300°  of high f l u i d  o c c u r r e n c e of that  into  abnormal (Rubey  these  fracture  Conditions  Hubbert, favouring  include  (1)  beds to  the  in  the  Yara  The s l a t y  cleavage,  features  pore-fluid  and  while  1962).  which  a s s o c i a t i o n with  p r e s s u r e s over an  but  this  1959;  turbidity  the  development  cleavwould  current  et of  al.,  de-  in  the  1969;  abnormally  of d e p o s i t s such as the Yara  presence of  r e t a r d escape of  Williams  Peak  unrealistically  p r e s s u r e s were i n v o l v e d  pressures which are t y p i c a l  pelite  formed  u n c o n s o l i d a t e d (Maxwell,  variant  cleavage  Peak  that  the maintenance  long t i m e . posits  traceable  indicate  c o u l d be a  require  are  o c c u r r i n g below the  dikes  greywackes age  dikes  compactible  and  relatively  pore f l u i d s ;  (2)  interbeds  164 of  less  compactible,  f l u i d s ; and (3) unit  than  Alps  chert  that  c l e a v a g e are  of  questionable.  sity  of  (Williams, The  is  For example, slaty  not  to  pore w a t e r .  experimental  deformation  as  reservoirs  t h i c k n e s s of a r a p i d l y  escape of  in contrast,  greywackes  pebble conglomerate  have shown that weak  tening;  permeable  a great t o t a l  such as the  greater  more  The  implications studies  interval  of  unconformities,  was  relatively  the Howards Pass a r e a .  1974)  French  t h e r e was caused by 25%  by  intensity  faults  and  tectonically  of  slaty  coarse  active.  f o r the c o a r s e e l a s t i c s i n d i c a t e s t h a t the major  Boucot  slaty  flatinten-  cleavage  1977).  abundance  occurred  of  i n the  clastic  ments i n the Earn Group suggest t h a t the Middle Devonian to an (?)  a rate  s t u d i e s have suggested t h a t the  indicated  the  overlying  produce l o a d i n g at  detailed  cleavage  deposited  for  throughout  et and  al., is  called  source  o c c u r r e d west  T h i s Middle Devonian to M i s s i s s i p p i a n (?)  the  1974;  Mississippi-  A western  uplift  sedi-  Cordilleran  Poole, the  1972;  Antler  belt  (Burchfiel  Stewart  orogeny  in  and  and  Poole,  Nevada  and  uplift  Davis,  1972;  of  1972;  Churkin,  parts  of  Cali-  fornia. CRETACEOUS STRUCTURES Mesoscopic faults  are  the  and macroscopic f o l d s , result  of  regional  Cretaceous deformation  fracture  cleavage,  and a s s o c i a t e d  and  igneous  intrusion. Mesoscopic dant  in  the  Howards Pass  range from 0.5 be  open to  and megascopic (Turner  to  area.  and W e i s s , 1963)  Mesoscopic f o l d s  over 100 m and amplitudes  i s o c l i n a l , but  in  general  the  o f 0.5 smaller  folds  are  have wavelengths t o 25 m. folds  are  abunthat  These may c l o s e d and  165 locally  isoclinal  whereas  the  larger  f o l d s have wavelengths  that  0.5  typically  to  2 km, and are  plane f a u l t s the  lack  of  between  the 5°  folds  folds  (Plate buted  open.  Megascopic  local  in  In  the  from  bedding  mudstone and Howards Pass formation  fracture  thickening  in f o l d  to  and  cleavage  and the  and  transition  305°;  the XY a r e a ,  Howards  Within  Pass  fold  thickening  bedded c h e r t y  of  o c c u r r e n c e of  hinges  plunge  have  are  most  and  indicate  planes  evident  formations.  ranges  longitudinal  axial  from 4 5 °  hinges,  of  mudstone  area  the  been  bedded  with  the  northwest  to  drillhole The Zn-Pb  d i s p l a c e d by these  calcareous  resultant  in  of  s e c t i o n s based on  s u l p h i d e s have been  thin  facies,  have  that  The t r e n d  i n d i c a t e an average plunge o f 5 t o 1 5 ° northwest.  IV). by  The  associated with,  upper c h e r t  southeast.  deposits  are  ranges from 290  information  open.  differential  regional  Howards P a s s ,  more  f o l d mechanism.  Mesoscopic the  are  range from 2 t o 10 km and amplitudes  flaggy  significant  a flexural-slip  parallel,  the  ones  locally  redistri-  mudstone  concentration  folds  and  of  thin  associ-  ated Zn and Pb s u l p h i d e s . Megascopic on the  1:30,000  315°  with  fold  studied  west.  axial in  folds  are  responsible for  s c a l e map  (Plate  planes  dipping  detail  in  the  80  I). to  the  major  Regional 85°  XY area  to  fold  the  they  may be c l o s e d  Tungsten and i n the A regional s e c t i o n , but  Itsi  fracture  near  trends  northeast.  outlines  are  major  intrusive  ( P l a t e I)  centres  290  One  shows a 1 0 ° plunge to the  A l l megascopic f o l d s i n the Howards Pass area  although  formation  to  such  north-  are open,  such as  near  Mountains. cleavage a f f e c t s  all  units  in the  stratigraphic  i s most obvious i n the Yara Peak and Iron Creek  formations  166 and i n the w h i t i s h tion.  The c l e a v a g e s t r i k e s  northeast (Fig. it  grey Zn-Pb mudstone f a c i e s of the Howards Pass  and  V-2).  290 t o 3 1 5 ° , a v e r a g i n g 3 0 0 ° ,  is  distinct  from the  The  relative  age of  c r o s s - c u t s slump f o l d s  scopic  nor megascopic f o l d s ,  faults. filled  In  the  whitish  with s p h a l e r i t e  mesoscopic  folds.  they  planar  whereas planar  straight  the  sulphide  but  is  cleavage  cut  Zn-Pb  escape  by  filled  and (2)  and  faults  are  (1)  strike  approximately  faults  cut  all  300°  rock  and are  in  common  units  local  over  (Plate  I).  The presence of m u l t i p l e  show movement orientation features,  that of  at to  km long  and  contain  along  these  postdates  both  or t h a t the  fault the  suggests  parallel  faults  of  differ  from  earlier  of  same  of  the  Zn and Pb  cleavage. Pass  area  northeast.  up  to  in  25  the  m wide  divergent  strike  but  forces  the  that  faults parallel  produced  formed along planes of weakness  the  strike  t o 4 5 ° suggests of  and  These  folds  zones and  and c l e a v a g e ,  the  the  sharp  Some of these  fault  of  that  have  The e f f e c t s  zones  Most  in  is  intervals  cleavage  the  vertical  zones.  folds that  gouge  cleavage hinges  Howards  to  cross  i n the  redistribution  the  and  irregular  IV-14).  dips  showing r e l a t i v e movement  recurred  the  and mesoscopic and m i c r o s c o p i c  are  movement  facies  t u r n d i s p l a c e d by c r o s s - f a u l t s . 20  deformed by meso-  longitudinal  s i z e in the  steep  faults  slickensides  not  described  occur  throughout  with  is  attributed  a c o a r s e n i n g of s u l p h i d e g r a i n  Strike  because  structures  structures  veins  s u l p h i d e s are:  can be bracketed  late  c o n t a c t s and are c l o s e l y spaced ( F i g .  c l e a v a g e on the  locally  mudstone  contacts  filled  and  85°  occurs  and i s most abundant  sulphide  d i p s 75 t o  c l e a v a g e which  stylolites  grey  These water  have  the  and galena  penecontemporaneous  area,  and  slaty  forma-  both  provided by  167  Figure V - 2 . Schmidt stereogram based on 382 p o l e s to cleavage in the Howards Pass a r e a . Two major s t r i k e d i r e c t i o n s are e v i d e n t , 3 0 0 ° and 270°. The 3 0 0 ° cleavage i s a f r a c t u r e cleavage whereas the 2 7 0 ° cleavage shows both f r a c t u r e and s l a t y c l e a v a g e .  168 the  cleavage  cleavage found  (Spencer,  are  cut  outside  tensive  factor  the  faults  suggests  that  dikes  Both the  associated  Howards Pass  with  facies  of  e s t a b l i s h e d elsewhere  vertical  parallel  scopic f o l d s . V e r t i c a l m.  In  tural  all  the  to  the XY area the  series  of  development  of  mesoscopic faults  area  (Plate  zontal  fault  faults  northwest  80  the  be  most  'Grit an  strike  have been  joints  060°  important faults,  as  frac-  (Plates  and have  with  plane  to  (Plate  mega-  ranges from 5 t o 20 struc-  producing a s t e p In  the  ANNIV  cross-faults  is  area also  II). i n a small  faulting  area  in  t h e XY  includes a nearly  slickensides  indicating  c l e a v a g e by t h i s is  I  nearly  a s s o c i a t e d with  member.  related  identified  thrust  cm t h i c k  amount of movement along t h i s  ex-  Unit'  and macroscopic f o l d s ,  active  movement and displacement of f r a c t u r e  tigraphic  some of the  the  the  may  s i d e downthrown,  blocks  Evidence f o r  plane  in  intrusions  c r o s s - f a u l t s d i v i d e the XY s u b - b a s i n i n t o  structural  II).  faults  approximately  e v i d e n t , but no o r d e r l y s t e p p i n g occurs Late t h r u s t  faults  fracture  i n the Howards Pass area  AC e x t e n s i o n  displacements of of  Cretaceous  s e p a r a t i o n along these f a u l t s  b l o c k s which have the  like  "basement"  These c r o s s - f a u l t s s t r i k e dips,  the  and the  ( C l o o s , 1955).  t u r e c l e a v a g e and l o n g i t u d i n a l IV).  with  faults  The a s s o c i a t i o n of  l o c a t i o n and o r i e n t a t i o n  Late c r o s s - f a u l t s c u t  thru  area.  strike  changes and major  reactivation  i n the  i s well  by  1969).  fault  unknown because i t  reverse  plane.  cuts  hori-  The  no s t r a -  markers.  SUMMARY The found f o r  tectonic other  history  areas  in  in the  the  Howards Pass  western  area  Cordillera.  is  Most  similar of  the  to  that  tectonic  169 events  have a f f e c t e d  Paleozoic  Era  two  the major  During the O r d o v i c i a n to tectonically neous  Howards Pass  stable  deposits  sedimentary-tectonic E a r l y D e v o n i a n , the  and c o n s i s t e d of a  slumping caused much of  i n the Zn-Pb d e p o s i t s and major  the  small  Subsequent orogeny b e g i n n i n g  an u p l i f t  to the west  the  stages of  tern  United  faults,  by  Devonian a f f e c t e d sissippian locally  and  the  A  igneous Howards  Cretaceous  have they  in  the  orogeny  intrusion.  redistributed  All  the  dominant.  basin.  Penecontemporaof  metals  and upgrading in  Middle Devonian  shed d e t r i t u s  to  produced tectonism  displaced  major after  the  deposits,  east; wes-  folds the  The Mid-Devonian the  the  produced  A n t l e r Orogeny i n the  Pass d e p o s i t s .  tectonism  were  scale redistribution  Pass which  Cretaceous  During  Selwyn B a s i n may have been  starved  which c o i n c i d e with the  States.  followed  of Howards  V-3).  regimes  southwest t r a n s p o r t  XY a r e a .  later  (Fig.  and Early  to  Mis-  but  only  the Zn-Pb c o n c e n t r a t i o n s w i t h i n them.  o PERIOD  TO  TO 3>  3»  STRUCTURAL AND IGNEOUS PRODUCTS  T7  FAULTS Cross  faults  Strike  faults  Thrust  faults  FOLDS Microscopic  folds  Mesoscopic  folds  Megascopic  folds  CLEAVAGE Fracture Slaty  1. 4  y  cleavage  Cleavage  I ocal regional  V).  SLUMPS STRUCTURES PHYLLITIC TEXTURE UNCONFORMITY VOLCANIC FLOWS VOLCANIC TUFFS INTRUSIVE ROCKS  Figure V-3. S t r u c t u r a l e v o l u t i o n of the Howards Pass area through t i m e . Bars i n d i c a t e time o f f o r m a t i o n of s t r u c t u r e s and igneous a c t i v i t y . Time of Zn-Pb m i n e r a l i z a t i o n and t o p of the s t r a t i g r a p h i c s e c t i o n are shown f o r comparison. The v o l c a n i c flows and t u f f s contemporaneous with the Zn-Pb m i n e r a l i z a t i o n are not w i t h i n the Howards Pass area ( P l a t e I ) , but o c c u r near the s h a l e - o u t near the South Nahanni R i v e r .  171 CHAPTER VI  GEOCHEMISTRY  INTRODUCTION AND METHODS Rock geochemistry of the Howards Pass and other vestigated the  i n an attempt  Howards  three into  Pass  deposits.  complete d r i l l intervals  to c h a r a c t e r i z e  cores  Three  formations  the sediments  approaches  were  from t h e XY d e p o s i t  was i n -  associated  attempted.  ( F i g . VI-1)  with  First,  were  l e s s than 3.2 m long and analyzed f o r twenty-one  split  elements  (Mo, C u , Z n , P b , C d , N i , C o , A g , Mn, V, B a , F e , C a , Mg, K, C ( o r g ) , C 0 , 2  P, S , SiO2> AI2O5) by v a r i o u s q u a n t i t a t i v e (Appendix E ) ; the data pared to l i t h o l o g y .  were  recalculated  and s e m i - q u a n t i t a t i v e t o 3.2 m i n t e r v a l s  the  individual  bedded c h e r t y examined The  facies.  Third,  by e l e c t r o n  microprobe  grains  are only  and across were  (Appendix  relative  marized  three  graphically  structures  analyzed  E).  using  The data ways.  (Figs.  VI-2  data  scanning  Zn-Pb mudstone f a c i e s  were  on chemical were  images  VI-4).  Second,  1970) and other  stratiform  element  VI-7),  drill  the v a l i d i t y  are  for  elements  shales ( e . g .  deposits  and  sum-  lithologies  statistical  distributions  although  association  with  on black  between  individual  holes  means  Zn-Pb  are  VI-6,  element  the  data  and t r e n d s .  variation,  are c o r r e l a t e d  T h i r d , elementary  ( F i g . VI-5,  of  used and  for  and S c o t t , 1973) (Table V I - 1 ) .  ships  samples  variations  from the t h r e e  t h e data  used to a i d i n determining  helped c h a r a c thin  beam t r a v e r s e s  thru  data  the  and show only  obtained  First,  grey  •analyzed are compared t o p u b l i s h e d chemical Vine and T o u r t e l o t ,  com-  f o r Z n , P b , F e , C a , Mg, K, Si and A l .  Two t e c h n i q u e s were used to o b t a i n laminae  laminated  mudstone and the w h i t i s h  probe data  when  Second, samples of the v a r i o u s f a c i e s i n the a c t i v e  member were a l s o analyzed by the same methods; t h i s terize  methods  (Lambert  techniques  interrelation-  of t h i s  approach  Figure VI-1. holes were used f o r  L o c a t i o n of diamond d r i l l holes 12, 18, 19 and 36. c h e m i c a l - 1 i t h o l o g i c a l analyses d i s c u s s e d in the t e x t .  Core  from  these  to  1  to*  io*  10*  log V (ppm)  log P b (ppm)  log Z n (ppm)  DDHI2  to* &  10*  io*  to*  B*ipr« iff*  io°  to*  io*  la^w*  to*  7  log Bo (ppm) id* to*  to'  Figure VI-2a. Element abundance ( Z n , P b , C d , V, Ba) compared t o s t r a t i g r a p h i c s e c t i o n from DDH 12. USMS = upper s i l i c e o u s mudstone, AM = a c t i v e member, LCMS = lower c h e r t y mudstone member, C a l c . MS = c a l c a r e o u s mudstone member. T o t a l length of core i s 180 m.  to*  Figure VI-2b. Element abundance (Ag, C u , N i , C o , Mn) compared to s t r a t i g r a p h i c s e c t i o n from DDH 12. USMS = upper s i l i c e o u s mudstone member, AM = a c t i v e member, LCMS = lower c h e r t y mudstone member, C a l c . MS = c a l c a r e o u s mudstone member. T o t a l length of core i s 180 m.  -p.  Figure VI-2c. Element abundance ( K 0 , F e , caO, MgO, C ( ) , S , P) compared to s t r a t i g r a p h i c s e c t i o n from DDH 12. USMS = upper s i l i c e o u s mudstone member, ,AM = a c t i v e member, LCMS = lower c h e r t y mudstone member, C a l c . MS = c a l c a r e o u s mudstone member. C U ) r e f e r s ' t o o r g a n i c c a r b o n . T o t a l length of core i s 180 m. 2  o r g  ODH 18  log Zn (ppm)  log Pb (ppm)  bgCd(ppm)  log V (ppm)  log Bo (ppm)  Figure VI-3a. Element abundance ( Z n , Pb, C d , V, Ba) compared to s t r a t i g r a p h i c s e c t i o n from DDH 18. FMS = f l a g g y mudstone f o r m a t i o n , USMS = upper s i l i c e o u s mudstone member, AM = a c t i v e member, LCMS = lower c h e r t y mudstone member, C a l c . MS = c a l c a r e o u s mudstone member. T o t a l length of core i s 198 m.  DOH 18  log Aa (ppm)  log Cu (ppm)  log Ni (ppm)  log Cot ppm)  log Mn (ppm)  Figure. V I - 3 b . Element abundance (Ag, C u , N i , Co, Mn) compared to s t r a t i g r a p h i c s e c t i o n from DDH 18. FMS = f l a g g y mudstone f o r m a t i o n , USMS = upper s i l i c e o u s mudstone member, AM = a c t i v e member, LCMS = lower c h e r t y mudstone member, C a l c . MS = c a l c a r e o u s mudstone member. T o t a l l e n g t h of core i s 198 m.  Figure VI-3c. Element abundance ( K 2 C , F e , CaO, MgO, C ( ) , S , P) compared to s t r a t i g r a p h i c s e c t i o n from DDH 18. FMS = f l a g g y mudstone f o r m a t i o n , USMS = upper s i l i c e o u s mudstone member, AM = a c t i v e member, LCMS = lower cherty mudstone member, C a l c . MS .= c a l careous mudstone member. C(%) r e f e r s to o r g a n i c c a r b o n . T o t a l length of core i s 198 m. 1  o r g  log Zn (ppm)  log Pb (ppm)  log Cd (ppm)  log V (ppm)  log Bo (ppm)  Figure VI-4a. Element abundance (Zn, Pb, C d , V, Ba) compared to s t r a t i g r a p h i c s e c t i o n from DDH 19. FMS = f l a g g y mudstone f o r m a t i o n , USMS = upper s i l i c e o u s mudstone member, AM = a c t i v e member, LCMS = lower c h e r t y mudstone member, C a l c . MS = c a l c a r e o u s mudstone member, PSSh = p y r i t i c s i l i c e o u s shale member, TZ = t r a n s i t i o n f o r m a t i o n , WB = wavy banded l i m e s t o n e f o r m a t i o n . T o t a l length of core i s 225 m.  log A g ( p p m )  log C u ( p p m )  l o g Ni ( p p m )  log C o ( p p m )  l o g M n (ppm)  Figure VI-4b. Element abundance (Ag, C u , N i , C o , Mn) compared to s t r a t i g r a p h i c s e c t i o n from DDH 19. FMS = f l a g g y mudstone f o r m a t i o n , USMS = upper s i l i c e o u s mudstone member, AM = a c t i v e member, LCMS - lower c h e r t y mudstone member, C a l c . MS = c a l c a r e o u s mudstone member, PSSh = p y r i t i c s i l i c e o u s s h a l e member,.TZ = t r a n s i t i o n f o r m a t i o n , WB = wavy banded l i m e s t o n e f o r m a t i o n . T o t a l length of core i s 225 m.  DDHI9  K,OfW i  FMS  i  F«(t)fW  CoO(%)  MgOft) v  i  r*  «  ' ' '  •  t »  C(%) •  r  i  «  - p d — - - ,  v  m  *  —, i  w  * i  m  r  iv  i  *-> USMS  AM  > •—j  [  r  LCMS  Calc.MS  PSSh I  TZ  -4  >  4  -1  Figure VI-4c. Element abundance ( K 2 O , F e , CaO, MgO, C ( q ) ) compared to s t r a t i g r a p h i c s e c t i o n from DDH 19. .FMS = f l a g g y mudstone f o r m a t i o n , USMS = upper s i l i c e o u s mudstone member, AM =• a c t i v e member, LCMS = lower c h e r t y mudstone member, C a l c . MS = c a l c a reous mudstone member, PSSh = p y r i t i c s i l i c e o u s s h a l e member, TZ = t r a n s i t i o n f o r m a t i o n , WB - wavy banded limestone f o r m a t i o n . C(%) r e f e r s to organic c a r b o n . T o t a l length of core i s 225 m. o r  Figure VI-4d. Element abundance ( S , P, S i 0 , AI2O3) compared to s t r a t i g r a p h i c s e c t i o n from DDH 19. FMS = f l a g g y mudstone f o r m a t i o n , USMS = upper s i l i c e o u s mudstone member, AM = a c t i v e member, LCMS = lower cherty mudstone member, C a l c . MS = c a l c a r e o u s mudstone member, PSSh = p y r i t i c s i l i c e o u s s h a l e member, TZ = t r a n s i t i o n f o r m a t i o n , WB = wavy banded l i m e s t o n e f o r m a t i o n . T o t a l length of core i s 225 m. 2  ^ ro  183 may be  questioned on the  1971),  which  was  grounds o f  not  strictly  Kolmogorov-Smirnov t e s t  (Winkler  sample d i s t r i b u t i o n and  showed t h a t  and Ba)  random  approximate  elements  a  in  (Zn,  lognormal  practice  the  and H a y s , 1975)  with t h e o r e t i c a l  trace  and Brown, 1957)  sampling  (Koch and L i n k ,  present  study.  was used to compare the  distributions  for  goodness of  P b , Mo, C u , C d , N i ,  distribution  whereas major elements  (Ahrens,  fit  C o , A g , Mn, V  1954;  ( F e , C a , K, Mg, C (  and Si02) more c l o s e l y approximate a normal  The  o r  Aitchison  g),  P, AI2O3  distribution.  DISCUSSION ZINC AND LEAD Zn and  Pb are  relative  both  (1970),  and to  to  highly  concentrated  units  in  the  Howards  Howards Pass area  h i g h e s t Zn and Pb c o n c e n t r a t i o n s occur  the v i s u a l  the  Pass  formation  and  Tourtelot  carbonaceous mudstones analyzed by Vine  other  mean Zn content  in  of 1.23% w h i l e  generalization  that  (Table V I - 1 ) .  The  in the a c t i v e member, which has a  of Pb i s 0.35%.  T h i s data  confirms  that the Zn and Pb c o n t e n t s of the a c t i v e mem-  b e r are the only c o n c e n t r a t i o n s i n the f o r m a t i o n t h a t c o u l d be c o n s i d e r ed of ore g r a d e . There  is a definite  a s s o c i a t i o n of Zn and Pb with l i t h o l o g y  in  the  a c t i v e member, which i s best demonstrated by comparing data  from samples  taken  Zn: Pb  also  from each of the vary  Zn: Pb r a t i o  between with  facies  lithologies  in  the member  and  i n c r e a s i n g grade  show a (Fig.  (Fig.  general  VI-9).  VI-8). trend  To further  this  r e l a t i o n s h i p between Zn-Pb content and l i t h o l o g y  ber,  samples from DDH-36 were c o l l e c t e d and analyzed c  of  ratios  decreasing investigate  in the a c t i v e memon a 0 . 3  m inter-  184 Table V I - 1 . Mean ( x ) element contents f o r v a r i o u s elements i n column at l e f t f o r the s t r a t i g r a p h i c u n i t s shown at the top of t h e table. P u b l i s h e d chemical content averages f o r black s h a l e s and noncarbonaceous shales are shown f o r c o m p a r i s o n . C o n c e n t r a t i o n of S i 0 2 f o r average black s h a l e i s taken from P e t t i j o h n (1975). Numbers l i s t e d under heading " S t r a t i g r a p h i c U n i t s " r e f e r s t o N used i n c a l c u l a t i n g the mean c o n c e n t r a t i o n , f o r example, next to f l a g g y mudstone the terms 1 0 / 3 r e f e r s t o the use o f N=10 to determine mean f o r a l l elements and compounds except S i 0 and AI2O3, f o r which N=3. 2  Units  0  ul T3 3  2 >* o> o>  a  U.  Upper Siliceous 70, Mudstone 38 u  c  \2  ao\  CO  CA 3  >.  a>  c o  i_  U  93  NJ  £.  93  ° §  a> •>  11  u <  c o  93 <U <=  3 O 93  O  O  VI T3  O  a  =  u  5  O  JC  CT>  co 7>  01  O  93  <u 3 Z u  M C  CO  .2  y « c °  «> r -  §>cO c: v <u c  c  o  3 >  a. co  c g Average Shole (Green 1959)  !  Stratigraphic  2 •— i2 <3 \L cn—  —  S. »  ° "2 % 5  < aJ  2  9  2 4  21  16  8  1 0  1 0  I  3  Cu  2 6  61  5 7  6 0  6 0  17  2 4  7 0  3 8  4 5  Zn  2 5  9 8 6  3 5  1 0 4  2 0 0  2 0 0  1 6 0  2 0  17  2 0  2 0  2 0  Mo  Pb  197  3 4 6 3  11-9  6 2  8  Cd  0-  2  1 2 2 9 5  Ni  2 7  9 3  7  Co  1 7  14  18  Ag  •3  7  2 - 4 7  4  162  4  •78  '12a  4 7 8  7  1  5  0  •  0 1  — — —  4  1 4 6  117  3 9  4 3  5 0  21  6 8  14  1 5  14  17  1 0  1 2  1 9  •9  •18  • 2 7  <l  113  1 9 8  1 5 9  150  271  1-55  • 0 7  •9  Mn  1 9 8  112  2 0 0  V  1 0 8  3 8 4  5 1 6  1091  6 0 3  1 6 0  Ba  8 6 2 1  1316  4 5 3  8 1 3  1 0 6 1  2 2 1 4  1 8 2 5  3 0 0  8 0 0  2 0 1  1  - 9 6  2 - 4 5  1  2-11  2  4 - 3  5 1 7  9  31  5-51  14-29  7-  6 3  9 - 0 5  2  0 - 7 4  3 - 7 9  4  14  3 - 2 5  0 - 9  3  3 - 6 4  4 - 3 5  3 - 7 3  I-03  1 1 5  1 4 - 5 3  8 - 9 5  9 - 9 8  Felt) Ca  0  2-51  8 9  2  17-63  2 5  MgO  2 - 8 8  0 - 6 8  K  3  1-67  0-  I - 0 2  4 - 9 0  4 - 4 9  6 - 5 0  6-  6  1 0 - 7 3  6 - 0 5  2  0  C(org C  0  2  po 2  5  s  •  9 2  0 2  113  1  2 S  7 - 7 4  Si  o  2  S 2 - 6 7  2 3  II  0 - 2 2  7  1-64  6 9  •  5 2 9  2  9 5  3 - 7 8  0  6 4 - 7 9  4 8  - 6 7  •  9 4  3 0 2  2-62  6  8 4  9 3 6 3 - 9 0  •211  1-6  8  41  5 7 - 3 9  9 7  • 3 6 3  4-81  • 3 5 4  •77  • 8 2  7- I I  5 7 0 5  1 5 0  9  0  6  5 4 - 7 2  2  0  1  6 7 0 0  1 3 0  1 3 0  4  5 8 0  4 - 7 2  7-3  2  8 5 0  3 1  5  3 - 3 7  1-9 3-20  — — — — — — — —  3 - 2  1 3 2 3  5 1 - 0 3  •  6 5  14-74  1 5  12  —  1  c c  185  Cu  Zn  Pb  Cd  A,  So  Fell) CoO MgOl  C% C 0  2  iLoir  Mo Cu Zn  Pb  -•2794-8147 406a-07«9i  Ag  Ba Felt!  ••327d--5705f  MgO|.  -2850--2575  ! K,0  c%  (LOI1  CO,  Figure VI-5. M a t r i x of c o r r e l a t i o n c o e f f i c i e n t s f o r element p a i r s f o r DDH 12. Sign before c o e f f i c i e n t i n d i c a t e s d i r e c t i o n of slope of r e gression l i n e . C(LOI) r e p r e s e n t s o r g a n i c carbon C02(|_0I) r e p r e s e n t s  CO3 -. 2  1  Cu  Zn  Pb-  Cd  Co  A  9  Bd  Felt) CoO MgO  K  2°  C%  Si 0, 2°J A,  (LOI)  Mo Cu  0002^3670-3481 -•06831-2596 •  Zn Pb  Cd -3898)--4874  Co Ag -45aa-6297 —27981-2624:  -0102-04671  CoO MgO >-•378M-4637  C  V.  (LOI)  C0  2  :LOD  SiO,  Figure VI-6. M a t r i x of c o r r e l a t i o n c o e f f i c i e n t s f o r element p a i r s f o r DDH 18. Sign b e f o r e c o e f f i c i e n t indicates d i r e c t i o n of slope of regression line. C(|_oi) represents organic carbon, ^ 2 ( L O I ) represents C O 3 " .  c  2  1  Cu Mo  •2137  Cu  Zn  Pb  Cd  • 0 9 0 8 - 0 6 0 8 •1065  Ni  Co  A,  Mn  •2587 • 2 4 2 0 •1842 -•1839 •HOI  Zn  •7697 •8369 --0940 - 1 5 4 6 •3055 •1619 •6336 - 1 7 9 7 -1268 •1990 Cd  Bd  Felt) C o O  MgO  K 0 2  C% C 0 , P 0 (LOI) (LOI) 2  -097!  •0893 -1149  •1808 -•1507 -1679 - 0 3 1 6 •2093 - 1 8 5 0 -3160  •3211 Mn  •0822 -1764 -0311  -2006  -•1593 -0153 - 2 0 8 C •3603 -2127 - 2 7 6 5  - 2 7 2 5 •0204 - 0 7 5 2 - 2 1 8 6 •5314 •5457 • 4 9 4 6 - 3 3 3 9 •2576  -•I960 • 5125 •3276 •2691 - 0 6 8 1  •0881 - 3 8 4 8 •0186  •4157 - 3 2 7 0 • 3020 1153  - 3 5 9 6 -1338 - 0 9 9 6 •8261 V  -  - 1 5 9 5 - 0 3 9 8 - 3 9 9 3 •0518  •2726 •4965 •0432 •1785 Ag  Al.,0,  - 0 5 9 7 - 2 1 0 9 •0876 •1549 - 2 2 6 4 -3187 - 0 3 9 9 - 0 4 4 4 - 1 7 6 0 -1378 -1691 -3116  •1457 - 0 7 2 5 -4821 •7164 Co  Si  •2933 - 1 8 3 7 - 1 3 5 0 - 1 4 7 6 •2957 - 2 7 5 4 •2546 •3050 •1425  - 0 6 7 2 - 0 5 0 6 •3979 •2775 •0192 - 2 5 4 7 •0892 •1218 Ni  s  5  • 4 8 5 6 •2754 •2199 •0394 •6248 - 3 1 9 3 —1874 •0775 - 1 4 4 3 •0337 •2950 •0529 -1541  1881  Pb  V  -2107 - 2 6 8 5  •1699 • 2051 •4239  •5613 • 0 8 5 5 - o a i - 6 0 2 0 -2671 •3223 - 2 1 3 3 •3291 - 3 4 5 6 -•3230  -1043 - 3 9 8 3 - 3992 •76 8 9 -1972 - 0 0 9 2 - 7 6 2 6 - 3 2 2 5  —3388 - 0 2 6 2 - 3 3 7 0 -1299 • 4 0 4 5 •4886 -•2911 - 2 0 4 0 •1927 -1927 •3157 Ba  •034 5 -•2B65 • 8 4 4 3 •5567 -1160 - 2 1 0 8 •1609 — 1611 •0801 •5392 Fell) - 2 2 4 3 •0222 •0298 •3039 - 2 5 9 8 - 0 9 4 5 • 6 0 6 0 •1284 -•0089 CaO  - 2 2 7 4 - 4 9 2 2 -3811 MgO  '946  -•0642 -1215 -•8142 —»728  • 6 4 3 2 • 0 8 4 0 -1306 •1644 -•1052 - 0 3 6  K 0 2  •2234 - 3 3 8 9 •0361  C%  (LOI)  •6235  •0158 •1705  •9167  - 4 2 6 5 0 6 5 3 • 3165 •2770  •1490  C 0 - 0 5 1 5 - 2577 - 7 5 4 4 - 2 8 4 4 (LOI) 2  P 0 2  5  -1751 •0982  s  •0061  -0402 -0252 Si 0  2  •0404  Figure VI-7. M a t r i x of c o r r e l a t i o n c o e f f i c i e n t s f o r element p a i r s f o r DDH 19. Sign b e f o r e c o e f f i c i e n t i n d i c a t e s d i r e c t i o n of slope of regression line. C(|_OI) represents organic carbon C02(i_0I) represents C O 3 " . 2  188  Ag  Ba  Mn Mo Co  Ni  Cu  Cd  Pb  Zn  Figure IV-8a. Comparison of mean (x) element content values f o r f i v e samples from each of 10 rock c a t e g o r i e s r e p r e s e n t i n g f a c i e s of the a c t i v e member and a s s o c i a t e d r o c k s . Rock l i t h o l o g i e s are represented by numbers; (1) upper s i l i c e o u s mudstone member, 2-9 represent f a c i e s of the a c t i v e member (2) grey c h e r t , (3) w h i t i s h grey Zn-Pb mudstone, (4) t h i n bedded c h e r t y mudstone, (5) c h e r t y mudstone, (6) t h i n bedded c a l c a r e o u s mudstone, (7) graded l i m e s t o n e , (8) l i g h t grey basal l i m e stone, (9) basal f a c i e s and (10) lower c h e r t y mudstone member.  189  Figure IV-8b. Comparison of mean (x) element content values f o r f i v e samples from each of 10 rock f a c i e s of the a c t i v e member and a s sociated rocks. F a c i e s are represented by numbers; (1) upper s i l i c e o u s mudstone member, 2-9 represent f a c i e s of the a c t i v e member 2) grey chert, 3) w h i t i s h grey Zn-Pb mudstone, 4) t h i n bedded cherty mudstone, 5) c h e r t y mudstone, 6) t h i n bedded c a l c a r e o u s mudstone, 7) graded limestone, 8) l i g h t grey basal l i m e s t o n e , 9) basal f a c i e s and 10) lower c h e r t y mudstone member.  190  Pb+  Zn  (%)  Figure VI-9. Pb+Zn vs Zn:Pb r a t i o i n the a c t i v e member showing the general t r e n d of d e c r e a s i n g Zn:Pb r a t i o with i n c r e a s i n g Pb+Zn. Fields of t e x t u r a l types are p l o t t e d f o r comparison.  191 val.  The most obvious r e l a t i o n s h i p s are t h a t the  light  grey basal  lime-  stone and graded limestone f a c i e s c o n t a i n only t r a c e s of Zn and Pb (<500 ppm Zn and <100 contains  the  ppm Pb)  highest  and t h a t the w h i t i s h  concentrations  of  grey Zn-Pb mudstone f a c i e s  these  metals  (>10%  Zn and  >5%  P b ) ; t h e t h i n bedded c h e r t y mudstone and t h i n bedded c a l c a r e o u s mudstone facies  contain  varying  concentrations  range from 2 t o 15% Zn and 0.5 relationships  visually  samples  VI-8),  and d e t a i l e d  of  are  the  sampling of  ( F i g s . VI-10, VI-11,  by  Cu: (Zn+Pb) deposits sis,  deposit  (1972).  and,  some d e g r e e ,  ( F i g . VI-13)  that  the  but  active  core from d r i l l  in  general,  and V I - 1 1 ) .  supported  The  in  by  member  h o l e 36  stratiform  Howards  Pass  These  analyses facies  in  the  of  (Fig.  XY area  d e p o s i t s has been  deposits  Zn: Pb from other  s u p p o r t i n g one of the major  Howards Pass d e p o s i t s c o n s t i t u t e  (Chapter  Pb,  VI-12).  Stanton to  and  further  various  Comparison of Zn: Pb: Cu r a t i o s gested  Zn  t o 4% Pb ( F i g s . VI-10  grade-1ithofacies typical  of  differ  "similar"  sug-  in  both  stratabound  p r o p o s a l s of t h i s  a new s u b - c l a s s  the-  of Zn-Pb  IX).  COPPER The Cu c o n c e n t r a t i o n w i t h i n the Howards Pass formation ly  uniform  (Figs.  concentration shales.  VI-3,  of the  sits  (Lambert,  formation, 1976;  deposits  McArthur R i v e r  VI-4),  and  is  similar  to  of 50 ppm reported by Vine and T o u r t e l o t  The Cu content  rest  copper  VI-2,  in  of the  a c t i v e member  an a t y p i c a l  situation  is for  K r e b s , 1976b); f u r t h e r m o r e , the  (Lambert,  Howards  Pass  1976), Mt.  Isa  area  similar  (Bennet,  the  to  t h e r e are to  1967),  relativeaverage  (1970) f o r  stratiform  similar  is  that  Cu  black of  the  Zn-Pb depono  those  satellite found  or Lady  at  Loretta  192  8  10  za ma  IS  20  28  Figure VI-10. Z i n c content compared to a c t i v e member lithology based on d e t a i l e d l i t h o l o g i c l o g of core from d r i l l hole 36 compared t o 0.328 m samples analyzed f o r Z n . T h r e e major zones of high Zn are r e l a t e d t o the presence of w h i t i s h grey Zn-Pb mudstone f a c i e s . Total l e n g t h of a c t i v e member i s 70.82 m, bedding i s 9 0 ° to core a x i s . Numbers r e f e r t o a c t i v e member f a c i e s : 1) b a s a l , 2) l i g h t grey basal limestone, 3) graded l i m e s t o n e , 4) t h i n bedded c a l c a r e o u s mudstone, 5) mixed c h e r t y mudstone and l i m e s t o n e , 6) c h e r t y mudstone, 7) t h i n bedded c h e r t y mudstone, 8) w h i t i s h grey Zn-Pb mudstone and .9) grey chert f a c i e s .  193  Figure VI-11. Lead + Zn content compared t o a c t i v e member l i t h o logy based on d e t a i l e d l i t h o l o g i c l o g of core from d r i l l hole 36 compared t o 0.328. m samples analyzed f o r Zn + P b . Three major zones of high Zn + Pb are r e l a t e d t o the presence o f w h i t i s h grey Zn-Pb mudstone facies. T o t a l length o f a c t i v e member i s 70.82 m, bedding i s 9 0 ° to core a x i s . Numbers r e f e r t o a c t i v e member f a c i e s : 1) b a s a l , 2) l i g h t grey basal l i m e s t o n e , 3) graded l i m e s t o n e , 4) t h i n bedded c a l c a r e o u s mudstone, 5) mixed c h e r t y mudstone and l i m e s t o n e , 6) c h e r t y mudstone, 7) t h i n bedded c h e r t y mudstone, 8) w h i t i s h grey Zn-Pb mudstone and 9) grey c h e r t f a c i e s .  194  10 m LOWCB CMtRTY MUOSTONC  Figure VI-12. Lead content compared t o a c t i v e member l i t h o l o g y based on d e t a i l e d l i t h o l o g i c l o g o f core from d r i l l h o l e 36 compared t o 0.328 m samples analyzed f o r P b . Three major zones of high Pb are r e l a t e d to the presence of w h i t i s h grey Zn-Pb mudstone f a c i e s . T o t a l length of a c t i v e member i s 70.82 m, bedding i s 9 0 ° t o c o r e a x i s . Numbers r e f e r t o a c t i v e member f a c i e s : 1) basal, 2) l i g h t grey basal l i m e s t o n e , 3) graded l i m e s t o n e , 4) t h i n bedded c a l c a r e o u s mudstone, 5) mixed c h e r t y mudstone and l i m e s t o n e , 6) c h e r t y mudstone, 7) t h i n bedded c h e r t y mudstone, 8) w h i t i s h grey Zn-Pb mudstone and 9) grey chert f a c i e s .  195  Pb  Figure VI-13. C o p p e r - z i n c lead diagram with the f o l l o w i n g p l o t t e d : Howards P a s s , s t r a t i f o r m - s e d i m e n t a r y d e p o s i t s ( S t a n t o n , 1972) and the general t r e n d of temperature decrease in a b r i n e ( S a t o , 1972; L a r g e , 1977; W i l l i a m s , 1978). The use of t h i s model suggests t h a t the low copper cont e n t in the Howards Pass d e p o s i t s c o u l d be the r e s u l t of a low temperature ore forming f l u i d .  196 (Loudon et C( g) o r  ated  at  al.,  1975).  rg.005 l e v e l  There  is  a positive correlation  between  of s i g n i f i c a n c e suggesting that the Cu i s  with o r g a n i c matter  g r a i n s i n d i c a t e t h a t at  (Fig.  least  VI-14),  although o c c a s i o n a l  Cu and associ-  chalcopyrite  part of the Cu occurs as a s u l p h i d e .  SILVER The s i l v e r content  of the Howards Pass formation  is  similar  to  that  of other carbonaceous mudstones (Table V I - 1 ) , with means f o r the members ranging from 0.18  t o 2.47  ppm, compared to  p o r t e d by Vine and T o u r t e l o t occur  i n the  active  member,  a s s o c i a t e d with  Howards Pass d e p o s i t s are  tiform  deposits,  such  as  Mt.  Isa  Meggen  (Mathias  1976),  again  sits.  S e l e c t e d s u r f a c e samples from the  and  (Dornsiepen,  a geochemical  ppm A g , but  to  date  s i g n i f i c a n c e of these  not  similar  is  stra-  Tom  (Freberg,  from these other  to  depo-  c o n t a i n up  contain  available  of  McArthur  Iron Creek formation  enough data  al-  1975),  and  6 ppm Ag and samples from the Yara Peak formation  0.5  (up t o 4 ppm)  The Ag content  Clark,  1976)  difference  1 ppm r e -  Zn and Pb v a l u e s ,  anomalously low compared to  (Lambert,  indicating  high  has been n o t e d .  River  to  1976),  l e s s than  (1970). The h i g h e s t Ag values  though no d i s c r e t e A g - b e a r i n g mineral the  slightly  less  than  indicate  the  results.  CADMIUM Cadmium i s h i g h l y c o n c e n t r a t e d i n the a c t i v e member, which c o n t a i n s a mean value o f 620 ppm, with 1000 t o 1600 mudstone f a c i e s . less  than  Other  5 ppm and are  samples from bituminous  members similar Pierre  in  the  to the Shale  shows a high degree of c o r r e l a t i o n  ppm in the w h i t i s h  Howards 1.4  Pass  grey Zn-Pb  formation  ppm Cd mean reported  (Tourtelot  with Zn ( f o r  et  al.,  1964).  example DDH 12 r  contain for  84  Cadmium =  .837  Figure VI-14. Organic carbon (C%) r e s s i o n l i n e , showing p o s i t i v e c o r r e l a t i o n  compared to Cu (ppm) with r e g between o r g a n i c carbon and C u .  198 where  r.Q05=0.27  Zn i n  the  Howards Pass formation may be e x p l a i n e d by the s u b s t i t u t i o n of Cd in  the  sphalerite deposits  structure  up t o  the 1.66%  (Fig.  1.4%  VI-15)).  (Walkita  The  a s s o c i a t i o n of  and S c h m i t t ,  Cd has been found  in  1972).  Cd with  In  sphalerite,  maximum r e p o r t e d by Mason and B e r r y  the  Howards Pass  which  is  close  to  from 8 t o  24  (1968).  MOLYBDENUM The  Mo content  ppm with  higher  variability  at  the  weak c o r r e l a t i o n  by  .Q05  Bertine  organic  datum  is  not  Pass formation  the  makes  o r  g);  any  anoxic  waters  where  the  major  factor  in  of Mo with the  low  iron  The  generalizations  example  slow  noted  s u l p h i d e to  be  between  There  in  important  r =  a  .275  of  Mo onto  sediment  and  a l s o found in  Fe and Mo in  suggests that t h i s mechanism was not  is  experimentally  absorption  Bertine  high  tentative  i n DDH 18,  Mo d e p o s i t i o n  humic a c i d s .  correlation  member.  stratigraphy.  for  in  ranges  active  T h i s a s s o c i a t i o n was a l s o  2700 ppm Mo i n marine  although  formation  compared to  between Mo and C (  is  from  concentrations  (1972)  coprecipitation ments,  Howards Pass  obtained  .267).  =  matter  found up to  the  values low  and t h e r e f o r e  (where r  of  some the  the  sedi-  Howards  important.  COBALT AND NICKEL Cobalt  and Ni  abundances i n the  of b l a c k s h a l e s (Vine and T o u r t e l o t ,  Howards Pass formation 1970).  w i t h i n the  Nickel  range of t y p i c a l  typical  The means of Co content  the v a r i o u s members of the formation are r e l a t i v e l y from 14 t o 19 ppm.  are  homogeneous, ranging  on the other hand i s more v a r i a b l e , but black  shales.  for  Correlation  shows Ni  still  related  t o o r g a n i c carbon and other elements a l s o a s s o c i a t e d with o r g a n i c carbon (Figs.  VI-5,  VI-6,  VI-7,  VI-16)  such as V, Cu and Mo.  The high  affinity  /  199  1500  3000  4500 Zn (ppm)  6000  7500  9000  Figure VI-15. Cd (ppm) compared to Zn (ppm) with r e g r e s s i o n l i n e , showing p o s i t i v e c o r r e l a t i o n between Zn and C d . No s p e c i f i c Cd mineral has been found which suggests t h a t Cd i s s u b s t i t u t e d in the s p h a l e r i t e structure.  200  Figure ression line  VI-16. Organic carbon (C(%)) compared to Ni (ppm) with r e g showing p o s i t i v e c o r r e l a t i o n between o r g a n i c carbon and N i .  201 for  Ni  to  occur  by Burns et carbonates  in metal 1 o r g a n i c complexes has been d i s c u s s e d at  al.  (1972).  in the  to the c r i t i c a l The  (e.g.,  ratio  for  pyrite,  various the  members  Co:Ni of  the  and are  is  in  ratios  ratios, Howards  Pass  l e s s than  1.  Co: Ni  ratios  have been  used ex-  and S c o t t ,  from  is  Lambert  and  ratio  may be the  Scott's  result  reasoning  mean are  of a g r e a t e r  s i t i o n of s u l p h i d e s by the v o l c a n i c - r e l a t e d ore  minerals  comments can 1973).  values  similar  Table for  the  throughout  in c o n t r a s t t o the McArthur  are  this  deposit  some general  formation, This  is close  -267).  =  (Lambert  with  here  stratiform  calculated  associated  correlation  greater  than  l e s s than 1 away from the Zn-Pb s u l p h i d e s (Lambert  Using  mal  indicator  rock  R i v e r d e p o s i t in which the but  but  Rankama and Sahama, 1950), but  that  formation  hand,  s p e c i f i c sulphide minerals  as an environmental  shows  other  Howards Pass f o r m a t i o n ,  be made c o n c e r n i n g whole VI-2  on the  value f o r s i g n i f i c a n c e (ir .rj05  Co: Ni  tensively  Cobalt  length  relative  1 in the  and S c o t t ,  constancy  p r o p o r t i o n of c o n t r o l  sedimentary environment  rather  ores, 1973).  of  Co: Ni  on the depo-  than by p r o x i -  fluids.  MANGANESE Manganese x=  89  ppm i n  member,  concentrations the  similar  Tourtelot,  lower  to  1970),  an  in  cherty  the  mudstone to  average  of  and much lower  150 than  which average 6700 ppm (Green, 1959). correlation .826 where r unstable,  of  Mn with  Ca ( F i g .  .QO5 = . 2 8 3 ,  only  in  a  VI-5,  Fig. VI-17).  reducing  Howards Pass x=  ppm f o r that  of  Within  Formation  200  ppm in  black  range the  shales  active  (Vine  and  non-carbonaceous s h a l e s ,  the Howards Pass  V I - 6 , VI-7)  is  formation  significant  (r  T h i s i s p o s s i b l e , where fe^^  environment  from  (Garrels  and  Christ,  = i  s  1965).  Table VI-2. T r a c e element r a t i o s from s t r a t i g r a p h i c u n i t s in the Howards Pass a r e a , part of t a b l e shows data f o r Co:Ni r a t i o s , lower part i s f o r Ba: V r a t i o s .  Upper  Co/Ni DDH-18  DDH-19  0.70  0.52  upper s i l i c e o u s mudstone  0.13  0.15  0.16  active  0.18  0.22  0.28  0.09  0.11  0.09  Stratigraphic  Unit  FLAGGY MUDSTONE FORMATION  DDH-:  HOWARDS PASS FORMATION  member  lower c h e r t y  mudstone  c a l c a r e o u s mudstone  0.13  pyritic  0.36  siliceous  shale  0.40  TRANSITION FORMATION  Ba/V FLAGGY MUDSTONE FORMATION  78.57  82.10  upper s i l i c e o u s mudstone  2.26  3.99  active  0.92  1.05  4.50  0.89  0.57  0.74  HOWARDS PASS FORMATION  lower  member cherty  mudstone  1.76  c a l c a r e o u s mudstone pyritic  siliceous  13.84  shale  TRANSITION FORMATION Average black s h a l e 2 . 0 0 ,  6.73 Average s h a l e 6.15  (Table  VI-1).  203  Figure VI-17. CaO (%) compared to Mn showing p o s i t i v e c o r r e l a t i o n between CaO and Mn.  (ppm)  with  regression  line  204 rhe  low Mn content  the  Mn content  Oral  a s s o c i a t e d with the  a s s o c i a t e d with  Commun., 1976;  rifting  regions  the  Howards Pass  Meggen  deposit  Gwosdz and K r e b s , 1977)  (Bonatti,  deposits is (Krebs  unlike  and Gwosdz,  and hydrothermal  activity  in  1975).  BARIUM AND VANADIUM Barium and V are area in  but  the  o c c u r only Howards locally  while  few  a  trace  area.  contains  grab  approximately  in  Pass  horizon  concentrated  1% B a .  some areas  amounts w i t h i n For  example,  laminated  samples  in  taken  the  barite  from  the  of  Selwyn  Iron  Nahanni  Howards Pass  deposits  the  the  Creek  The Howards Pass f o r m a t i o n ,  formation  Mountains  with  map-  barite  up to  30% B a ,  formation  average  in c o n t r a s t ,  contains  l e s s than 2000 ppm Ba and r e g i o n a l l y  i s a Ba-poor u n i t ,  even though com-  parison  (1970)  it  with  Vine  and T o u r t e l o t ' s  times the Ba in an average black drill the high  core  and  Howards in  the  surface  Pass  chip  samples  formation,  barite  horizon  shale.  data  shows  to  contain  Comparison of Ba a n a l y s e s  show t h a t  increasing  up  and dropping  Ba i s  section  relatively  until  substantially  it  in  3  from  low  in  reaches  a  the Yara Peak  formation. The barite  Howards  deposits  when compared to other  typically phides, 1978)  Pass  or  have  as  averages  either  to  the  unique  in  their  lack  stratiform  Zn-Pb d e p o s i t s .  directly  a s s o c i a t e d with  the Tom d e p o s i t s  marginal  (Dornsiepen, The  in  barite  are  (Morganti,  sulphide  bodies,  1975; as  the  associated  Other d e p o s i t s the  Dawson, in  of  Zn-Pb  1977;  sul-  Carnes,  case  of  Meggen  1500  ppm V and  1976).  Howards more  Pass  than  formation 150  ppm  of  locally the  contains  typical  up to  black  shale  (Vine  and  205 Tourtelot, lower  1970).  cherty  1000  (  the  Vanadium  a  example, r f o r V : C (  f o r  the  (Morganti,  shows  s u g g e s t i n g t h a t V i s present mineral  formation  mudstone member  ppm V .  C(org)  Within  highest  )  are  1977a) with an average  significant  o r g  values  positive  in  the  of  over  correlation  with  i n DDH 18 i s 0.542 where r.005=.283)  i n o r g a n i c complexes, s i n c e no V - c o n t a i n i n g  has been i d e n t i f i e d .  Fischer  (1973) observed t h a t V can a l s o be  c o n c e n t r a t e d by r e d u c t i o n i n the  presence of o r g a n i c matter or b i o g e n e -  tically  generated  the  Fischer  (1973)  although  H2S,  and  in  the  present  association  study  of  indicates  V and  P noted  by  an a s s o c i a t i o n with  organic matter. There tive  i s a general  trend  of i n c r e a s i n g Ba u p - s e c t i o n above the a c -  member and d e c r e a s i n g V,  determining contrast,  facing  is  masked by  Ba: V r a t i o s  Ba: V r a t i o s  appear  may prove to  where v i s u a l  but  stratigraphic  to  be an  the  use  of  individual  elements  lateral  variations  in  be more  consistent  (Table  important  the  stratigraphic  r e l a t i o n s h i p s are not  for  units.  In  VI-2);  guide  in  thus areas  clear.  IRON Total to  2.51%  2.0%  iron in  average  the for  content various black  i n the  Howards  members shales  (Table  reported  Pass  formation  VI-1) by  which  Vine  ranges is  from  similar  and T o u r t e l o t  1.92  to  the  (1970).  The Howards Pass d e p o s i t s are unique i n t h a t the Zn-Pb s u l p h i d e s are a s s o c i a t e d with massive p y r i t e centrations  typical  1976b; V o l k s , 1976). major the  difference  or p y r r h o t i t e  of s t r a t i f o r m  and lack the high i r o n  Zn-Pb d e p o s i t s  (Lambert,  C o n s i d e r i n g Howards Pass formation  between  p r o p o r t i o n s of Fe or  the  active  pyrite,  but  member and other is  textural;  the  1976;  not con-  Krebs,  as a whole,  members i s active  the  not  in  member  is  206 the  only  member  FeS2 content similar  where  framboidal  c a l c u l a t e d from the  pyrite  is  dominant.  Fe a n a l y s e s and the  i n d i c a t e that nearly a l l  the  i r o n occurs i n  In  all  pyrite  cases,  content  are  pyrite.  CALCIUM AND MAGNESIUM The  mean  CaO content  formation  is  Tourtelot  (1970),  lated  greater  limestones  but  of  than  the  this  is  rather  than  the  various  average in to  part an  members  of  2.1%  due to  of  Howards  reported  the  abundance  the  by  Vine  presence of  of  calcareous  fically  and  intercamudstone.  The h i g h e s t CaO content and a l s o the most limestone occurs i n the member.  Pass  active  W i t h i n the a c t i v e member the l i m e s t o n e i s not a s s o c i a t e d s p e c i with the  idealized  Zn-Pb s u l p h i d e s .  c y c l e of  the  active  Comparison of CaO vs l i t h o l o g y of an  member  (Fig.  VI-8)  shows a  general  de-  c r e a s e upward i n c a l c i u m c o n t e n t . The MgO content that  of the  cates, that  in  average b l a c k  based on the  these  the  elements  shale.  Pass  formation  are  clay minerals  2  gy mudstone formation  in  2  and MgO suggests t h a t  quantities.  low  and A l 2 ^ 3 *  MgO, K 0  present  is  compared  to  Most Mg appears to be in p h y l l o s i l i -  a s s o c i a t i o n of  verse r e l a t i o n s h i p of C 0 in substantial  Howards  The r e l a t i v e l y  compared to  the  (Grim,  dolomite  which suggests 1968); t h e is  not  high MgO content  Howard Pass  present  in the  formation  is  in-  flag-  the  re-  s u l t of a h i g h e r p h y l l o s i l i c a t e content and d o l o m i t i c cement. POTASSIUM The average similar  to  Tourtelot, values;  for  that 1970)  potash  (K 0) 2  reported (Table  example,  to  VI-1),  in the  content be  o f the  typical  of  although there  Howards Pass black is  shales  a large  a c t i v e member x = 0.69%  formation  K 0 2  (Vine  is and  range of mean whereas  in  the  207 lower  c h e r t y mudstone member  3.24%  K 0  in  average  2  shales  present  is  all  by a  strong  Further  check  for  any  d e p o s i t , where originated 1967).  tuff  Up to formation, 1974).  12% o r g a n i c based  on  grained  estimation  of  organic  is  map  area  typical  highest lower than  of  black  values  cherty the  stratiform deposit less  (Plate  than  for  deposits. contain 0.5%  loss  K 0 2  c o n s i s t e d of  in  the  Mt. to  deposit  Isa have  (Bennet,  formation.  (Dean,  l e s s than 0.5%  and/or  traces  C(  for  the  o r  g)  example, contains  over  found in  content  For example, than in  1%  in  which of  x=  host  o r  g)  sediments  be  in  of  for  o n l y major  1% C (  o r  g)  Pass  rocks  (Lambert, the  (1970).  area is  associated  in  the  are  The  in  the  much h i g h e r with  other  McArthur  River  1976) Red  mudstones.  whereas x-= 4.95%  This  s h a l e s " in  shales",  rock u n i t  and T o u r t e l o t  6.50%.  near  "black  given  Howards  "black C(  t  ignition  i s the  the  g)  r e s e n  colour  should  C(  carbon  between  550°C  by Vine  less  the  at  on  dark  cause  which  carbon  in  Howards Pass  shales analyzed o r  2  the  can  mudstone member,  organic  by  P  s  of  carbon  I)  ^  0  carbon content  The Howards Pass f o r m a t i o n , the  that  K 0  T h i s was done  (1967)  Howards Pass  (C( rg))  estimation  pyrite  most  )l  carbon  S i n c e an o r g a n i c  fine  areas.  by Bennet  No such beds were found i n the o r g  VI-7)  2  2  (1924)  supported  of the K 0 content  same source as Zn and Pb f o r  (C(  is  (Fig.  any high K 0  noted  shown that  This  correlation  Clarke's  beds are c o n s i d e r e d by some workers  2  from the  as  has  or m i c a s .  check f o r  beds  i s c l o s e to  (1968)  examination  high K 0 t u f f  ORGANIC CARBON  of  clays  detailed  This  Grim  positive  K 2 O s t a i n i n g t e c h n i q u e s to to  3.9%.  shales.  a s s o c i a t e d with  study  and A l 2 O 3 •  for  x=  Sea  and  there  brine  is  pools  208 (Sweeney organic  and K a p l a n ,  1973).  carbon content  Thus,  more t y p i c a l  the  Howards  of h i g h l y  than those sediments a s s o c i a t e d with other  Pass  formation  has  carbonaceous b l a c k  stratiform  an  shales  ore d e p o s i t s .  SULPHUR Sulphur  is  most  abundant  members, with means o f 2.95 tions  of  sphalerite  in  the  and 2.62%  and galena  active  and  respectively.  and the  s u l p h u r could occur i n  cording  to  Smith and B a t t s  organic  matter.  pyrite  pyrite  In the  and o r g a n i c  (1977), may c o n s t i t u t e  cherty  mudstone  The high c o n c e n t r a -  presence of  high c o n c e n t r a t i o n s of S in the a c t i v e member. stone the  lower  explains  the  lower c h e r t y mudsulphur w h i c h , a c -  up t o  3 wt.%  of  the  PHOSPHATE The mean P 2 O 5 c o n t e n t s of the members of the Howards Pass range from 0.2% t o 0.15%  for  Howards  1.17%, and are  carbonaceous  Pass  formation  any other element. by  a  high  VI-3c),  and  graptolite of  P2O5  shales  reported  phosphate  shows  content the  compared highest  zone near the  concentration  has  shown t h a t d i a g e n e t i c  Deposition  of  to  P2O5  of  the  has been  phosphate  occur r e a d i l y , of  top  upwelling  the  tion will  by  higher than the McKelvey  no s i g n i f i c a n t  (Freas  the  rest  of  concentration member.  the  phosphate at  the  in  sediment-water  the with  formation  (Fig.  a s s o c i a t e d with  great  response to interface  the  Cook  the  study  importance  and E c k s t r o m , 1968).  probably  of  characterized  C l a s s i c a l l y , in  c o n s i d e r e d of  In  correlation  phosphatization, c a l c i t i z a t i o n and are  average  (1967).  The upper s i l i c e o u s mudstone member i s  shows  phosphorites,  i n general  formation  in  (1970)  and s i l i c i f i c a changes of pH. does not  appear  209  to  be s i g n i f i c a n t ,  (Trudinger, usually  1976)  but  the  o r g a n i c matter  and a g e n e r a l l y reducing environment  a s s o c i a t e d with  specific  presence of  C( g)-P205  high  phosphate  a s s o c i a t i o n in  o r  (Cook,  the  bacteria  ( S e n i n , 1970)  1970).  Howards Pass  t h a t d i a g e n e t i c d e p o s i t i o n may have been  and/or  The  lack  formation  are of  a  suggest  important.  SILICA AND ALUMINA T h e means f o r  SiO2 content o f the members of the Howards Pass  mation range from 48 t o 93% (Table VI-1)  and the mean f o r the  i s 64.8%, which i s s i m i l a r to 55 t o 64% r e p o r t e d by C l a r k Paleozoic chert  which  1978);  was  phides.  to  deposited the  Si0  carbonate,  2  as  S i 0 2 i n the  amorphous  content  Howards Pass  silica  reflects  (Friedman  the  carbonaceous m a t t e r ,  formation  (1924) f o r  51  formation  is  and S a n d e r s ,  proportions  of  phyllosilicates  chert  and  sul-  For example, the lower S i 0 2 content o f 50% in the a c t i v e member  because of  grey  Most of the  therefore  relative  is  shales.  for-  chert  relatively  more carbonate and s u l p h i d e .  f a c i e s contains  over 99% S i 0  2  compared to  T h u s , the the  whitish  light grey  Zn-Pb mudstone which c o n t a i n s 50 t o 60% Si02> suggesting t h a t the change between away  the  from  constant  two the  is  because of a change i n the  sub-basins,  Si02:C( g)  +  o r  The Al2O3 content t h a t of o t h e r black  sedimentation  carbonate of the  2  phyllosilicate  that  of  :  continued  Howards Pass formation  shales and to  For the Howards Pass formation  +  Si0  other  ZnS + PbS with  +  essentially  sulphide is  ratio;  ratios.  low compared to  mudstones i n  the  area.  x =0.67% AI2O3 compared to an average of  13.23% reported by Vine and T o u r t e l o t  (1970).  The s i g n i f i c a n t  positive  210 correlation Al2O3  between  occurs  in  A l 2 O 3 and K 0 and the  lack  2  micas  and  clays,  which  are  of f e l d s p a r  rare  in  the  suggest t h a t Howards  Pass  formation. MICROCHEMISTRY The tures  chemistry  and  of  individual  individual grains  microprobe.  Nine elements  Si  Within  and A l .  predominantly  the  scopic count this  in  study for  for  bedded  for,  cherty  XY d e p o s i t  textural  type but  the  water  escape s t r u c -  investigated  by  Z n , Pb, F e , S , K, C a , Mg,  mudstone but  facies,  a l s o to  occurs as monomineralic  type of  I  is  not  Pb i n t h e  shows t h a t it  did  not  Pb  is  indicate  known i f  samples.  the  carbonaceous mudstones (Macqueen et was found  in  occurs  sulphides.  complexes  these  degree  al.,  Howards Pass f o r m a t i o n ;  galena  have  If  and  chemical  altered,  appears t h a t  with  ac-  the  pyrite  enough Pb data  for  in  of  to Pb.  similar  no such a s s o c i a t i o n  Zn and Pb p r e v i o u s l y e x i s t e d  s i n c e been  to  framboidal  contains  1975), but it  Micro-  Probe i n v e s t i g a t i o n  pyrite  visual  laminae.  Z i n c and Pb have been reported a s s o c i a t e d with o r g a n i c matter  in  Zn o c c u r s  a lesser  enough  a s s o c i a t e d with  d i s c r e p a n c y between  the  electron  T h i s supports the m i c r o s c o p i c o b s e r v a t i o n t h a t most  concentrations  VI-18),  account  the of  textural  (Fig.  s u l p h i d e were  were analyzed  thin  modified  i n monomineralic ZnS l a m i n a e ,  in F e - r i c h laminae. sphalerite  of  laminae,  in  metals  all  Zn and Pb  metal1-organic forming  sul-  phides. Microprobe  traverses  s t r u c t u r e s which are f i l l e d er  concentrations  the w h i t i s h  of  across  tectonically  with t e x t u r a l  type  Z n , P b , Fe and S than  grey Zn-Pb mudstone f a c i e s  (Fig.  modified  IVb  are  water  escape  s u l p h i d e s show g r e a t -  found in o t h e r  VI-19).  parts  of  Local i n c r e a s e s  in  211  c.  d.  Figure VI-18. Microprobe scanning images of framboidal pyrite grains, a. Fe Ka x - r a y s showing o u t l i n e of f r a m b o i d s , b. S Ka x - r a y s showing o u t l i n e of f r a m b o i d s , c . Si Ka x - r a y s showing s i l i c a t e s s u r r o u n d i n g p y r i t e and d . Pb Ka x - r a y s showing t h a t minor amounts of Pb occur i n the framboidal pyrite. L a r g e s t framboid i s 45 pm a c r o s s .  Figure VI-19. Microprobe t r a v e r s e across dewatering s t r u c t u r e s in the w h i t i s h grey Zn-Pb mudstone f a c i e s , showing chemical d i f f e r e n c e s between cleavage and sedimentary l i t h o l o g i e s . Numbers at l e f t r e f e r to l i t h o l o g i e s ; 1) t e x t u r a l . type II, 2) t e x t u r a l type IVa, 3) t e x t u r a l type IVb. T o t a l l e n g t h o f t r a v e r s e i s 7.0 mm. :  213 K, Mg and Al i n d i c a t e the presence of c l a y s i n t h i s parison narrow  of  data  for  Zn and Pb ( F i g .  d i s c r e t e bands i n  of c a l c i t e ,  is  structures,  but  only  where  present  variation  microprobe s t u d i e s are  along the  cleavage  is  i n the w h i t i s h  is  show that  massive s p h a l e r i t e .  also concentrated  a c r o s s laminae chemical  the  VI-19)  complex  (Fig.  textural  type.  galena  Com-  occurs  C a l c i u m , i n the  c o n t a c t s of the  present.  form  water escape  Microprobe  traverses  grey Zn-Pb mudstone i n d i c a t e VI-20),  and  that  in  more  that  detailed  warranted.  SUMMARY The geochemical ciated  deposits  differs Chemical  from  data  indicate  that  stratigraphic sulphides,  (3)  deposits,  section, l a c k of  the  deposits  are:  homogeneity  of  (2)  that  V concentration  ratios  in the  underlying  the  a s s o c i a t e d with the Zn-Pb d e p o s i t s . differentiate  the  Howards  tary sulphide deposits.  part  throughout  lower  Pass  cherty  of  elsewhere.  low Ba content  Fe content section  throughout  containing  in the  Zn-Pb  i n the s u l p h i d e d e p o s i t s ,  the  Howards Pass  mudstone member,  Zn-Pb d e p o s i t s  and  (7)  formation,  (6)  lack  lack  These chemical c h a r a c t e r i s t i c s  deposits  asso-  deposition  deposits  (1)  of  and the  base metal  similar  i n c r e a s e i n Ag content  (5)  beds  environment  apparently  including  c o n s i s t e n c y of Co: Ni  tuff  the  Howards Pass formation  for  of  (4)  high-K20  that  proposed  characteristics  and near to the  from' the  from other  stratiform  of  of Cu help  sedimen-  Figure VI-20. Microprobe t r a v e r s e across l a m i n a t i o n in the t h i n bedded cherty mudstone f a c i e s , showing v a r i a t i o n s i n chemistry with Zn and Pb. Data i s s e m i - q u a n t i t a t i v e with i n c r e a s i n g c o n c e n t r a t i o n towards the r i g h t . Numbers r e f e r to l i t h o l o g i e s ; 1) carbonaceous mudstone, 2) s i l i c e o u s mudstone, 3) s p h a l e r i t e r i c h mudstone, 4) s p h a l e r i t e - g a l e n a r i c h mudstone, 5) s p h a l e r i t e - g a l e n a - p y r i t e r i c h mudstone. T o t a l length of t r a v e r s e i s 8.2 mm.  215 CHAPTER VII  SULPHUR ISOTOPES  INTRODUCTION The o r i g i n posits base  is  important  metals  phur.  of the  is  s u l p h u r component of  because  related  to  3 2  = 95.02%,  S  3  i s o t o p i c composition of used as an  formation larly its  of  indicator  valuable  minerals  1976).  generally  approximately  6  valence  4.55%,  =  36  so t h i s  is  The  not  in  the  its  terms  is  of  of  most  in  natural  the  The  mode of  it  particu-  ability  to  retain  not a l l ,  the  post-  it  take  is  contained  place  isotope  abundance  ratio  345/325  between  deposits  Sulphur  of  abun-  and as such may  Howards Pass  variation  of sul-  o.014%.  =  which  may  the  important.  range  it  deposit  of  s u l p h u r and the  apparent  exchange  10% and when r e f e r r i n g samples  state  s u l p h u r t h a t makes  is  the  s  ranges widely  g r a d e s , but  are  variations of  ^  n a  the  two  t re  is  U  to d i f f e r e n c e s of i s o t o p e abundance common  practice  to  use  the  "del"  where:  s  (o/oo) = ( 3 4 s / 3 2 ) S  s  a  m  ( S/32s)  the  standard  s  of  context  34  gives  4  source of  isotopic  considered  between  34  Some  isotopes.  notation  present  high metamorphic  unmetamorphosed,  ratios  the  processes a f f e c t i n g  at  principal  3  An a t t r i b u t e  i n the  and  fixation,  i s o t o p e s with the f o l l o w i n g  = 0.76%,  of  therefore  i s o t o p i c composition throughout most, i f  depositional (Sangster,  3s  Howards Pass Zn-Pb de-  and  availability  s u l p h u r i n nature  sulphide.  original  are  the  Sulphur has four s t a b l e  dances:  be  precipitation  the  permil (Thode  difference et  a !., -  in  1961).  p  1  e  - ( 3 4 / 3 2 ) standard y IQOO S  S  standard  isotope The  ratio  between  generally  a  accepted  sample  and  standard  a is  216  troilite  from  the  o f 22.22 o/oo  (Thode,  In n a t u r e , isotopic  Canyon  Diablo meteorite,  of  about for  forms  100  of s u l p h u r  o/oo  for  t o assume t h a t t h e y h a v e b e e n u n i f o r m ( T h o d e and  associatied  with  varied  widely (Fig.  +IO0/00  (1958)  N  for  ancient that  over  geologic  showing  Thus,  that  (1968,  stratabound marine  the  Based  -1).  V11  1965).  oceans  show  related, Sangster  V11 - 1 ) .  Monster,  day  S.  reasonable in the past  a l l present  34  &  constant  1966)  34  a  32  S/  show an o v e r a l l  remarkably  Kaplan,  has  S  ratio  1970)..  the d i f f e r e n t  values  which  Values  oceans  The  ( T h o d e and 6 34S v a l u e  and  Monster, of  1965;  seawater  on t h e  same m e t h o d s u s e d  1971)  approximately  coeval  of  S  are  it  is time  evaporites Holser  and  sulphate  has  +30o/oo  and  by T h o d e e t a l .  seawater  sulphate  are  made a s t r o n g c a s e f o r t h e d e r i v a t i o n o f  s u l p h i d e d e p o s i t s from c o e v a l seawater  i f seawater  and  study of marine  between  and  seas  34  6  a t any p a r t i c u l a r  time,  petroleum  for  range  sulphate  i s the  source  sulphate (Fig.  of sulphur  for  the  basis  of  s u l p h i d e s t h e s e may be u s e d as a r o u g h age d a t i n g t e c h n i q u e . METHODS AND  RESULTS  Samples  f o r sulphur  lithology drill  cores  isotope study  from  were c o l l e c t e d  t h e Howards P a s s  formation,  on  the  and  include  the  w h i t i s h g r e y Zn-Pb m u d s t o n e , t h e t h i n b e d d e d c h e r t y m u d s t o n e and t h e t h i n bedded c a l c a r e o u s mudstone f a c i e s . to  the  U n i v e r s i t y of A l b e r t a where t h e y  compositions (Appendix These  T h e s e w e r e e x a m i n e d , c r u s h e d and  F).  data  (S = 3 . 6 8 % ) ,  were a n a l y z e d  u s i n g a N i e r - t y p e d o u b l e - i n l e t gas  s o u r c e mass  The r e s u l t s o f t h e a n a l y s e s a r e p r e s e n t e d show  that  galena  s p h a l e r i t e = 19.68  has 0/00,  a  mean  for S  6 *^S  (S = 3.30%) and  isotopic  spectrometer  in Table of  pyrite  sent  15.17  V11-1.  0/00  217  PERIOD  QUATERNARY TERTIARY CRETACEOUS JURASSIC TRIASS IC PERMIAN  CARBONIFEROUS DEVONIAN SILURIAN OROOVICIAN CAMBRIAN  21.50  21.75  22.C0  22 2 5  22.50  Figure V I I - 1 . Average 6 ^ 4 $ values f o r seawater s u l p h a t e f o r g e o l o g i c time ( s o l i d l i n e ) and s u l p h u r i n petroleum (dashed l i n e ) . Fractionation fact o r average = 13.8 (modified from Thode et a l . , 1958).  218  Table  VII-1.  Sulphur i s o t o p e r a t i o s  Sample No.  6 34  s  f o r the Howards Pass d e p o s i t s .  ( /oo) 0  Galena  Sphalerite  HP-S-1 HP-S-2 HP-S-3 HP-S-4 HP-S-5 HP-S-6 HP-S-7 HP-S-8 HP-S-9 HP-S-10 HP-S-11 HP-S-12 HP-S-13 HP-S-14 HP-S-15 HP-S-16 HP-S-17 HP-S-18 HP-S-19 HP-S-20 HP-S-21 HP-S-22 HP-S-23 HP-S-24  22.3 17.6 11.1 17.9 18.2 10.7 17.7 11.9 13.0 12.0 11.3 12.6 13.6 20.4 11.8 13.3 8.5 14.8 19.3 17.3 19.3 17.7 13.2 18.5  26.2 21.2 15.0 21.9 22.1 16.9 21.6  21.6 16.8  23.0 14.8 22.4  X  15.17 3.68  19.68 3.30  15.6? 9.0'  S  Barite  from f l a g g y mudstone  Standard NBA 1.1  Pyrite  22.7 23.5 21.1 17.0 4.1  18.1 20.1 15.3 16.6  19.6 1.4 21.0  24.6 15.8 19.4  -3.2 16.6  21.3  formation  23.7 24.6  219 15.69  o / o o (S = 9.04%).  formation  An a n a l y s i s o f b a r i t e  produced a value o f  t h a t o f S i l u r i a n seawater  6 ^  sulphate  from t h e f l a g g y mudstone  = 23.7 o / o o which i s very c l o s e to ( H o l s e r and K a p l a n , 1966).  DISCUSSION A histogram o f t h e i s o t o p i c data modal  distribution  other  hand shows a wide  bution. 1972)  This  between  pyrite  f o r data  from  sphalerite  shows a d i s t i n c t b i -  and g a l e n a .  Pyrite  range of values and only a weak bimodal  and the abundance framboidal  and t h e o t h e r  ( F i g . VII-2)  pyrite  of d i s e q u i l i b r i u m and the other  sulphides  have  a separate  textures  sulphides origin  on the distri-  (Stanton,  suggest  and/or  that  time of  formation. Sphalerite the  most  i s the major  important  phase to c o n s i d e r .  were s t r a t i g r a p h i c a l l y (  x = 15.37 o / o o ) ,  the  whitish  grey  Two  sphalerite  s u l p h i d e phase i n t h e d e p o s i t s and i s thus Isotopic  grouped, f o r the t h i n  authors which (1)  (Thode,  must  sphalerite  the t h i n bedded c h e r t y mudstone ( x = 17.96 o/oo) and Zn-Pb mudstone  samples  from  of  ( x = 22.56  textural  isotopic  1970, H o e f s ,  type  o/oo) facies  (2)  sphalerite  has been  1973).  There  nature  of the s u l p h i d e and (3)  ( F i g . VII-3).  V are not i n c l u d e d  effects  be c o n s i d e r e d i n the o r i g i n  source o f t h e s u l p h u r ,  formation als.  theory  for  bedded c a l c a r e o u s mudstone  they may have formed subsequent t o the other The  values  i n the f a c i e s .  discussed  are three  of the Howards  because  by  basic Pass  various problems  sulphide;  of the processes o p e r a t i v e  the formation  of the s u l p h i d e  during miner-  In the present d i s c u s s i o n s u l p h u r i s o t o p e s and other g e o l o g i c data  are used t o e v a l u a t e  each of t h e t h r e e  steps.  SULPHUR ISOTOPE DATA FOR HOWARDS PASS -Estimated seawater sulphate Barite Sph  •i—h  Hill II  Gn  till  I I I  Py  IIII I i 26  I  i 24  t  I • III  I I 20  1 llllll  H—I I  ie  i 12  4  I  I  -4  c f S %'oo M  6 5  5  >  O  z  o z Iii z> a u  3 o UJ  tr a.  P  TTJI j <f" S  5  INTERVAL -17 OBSERVATIONS  s i ± cf^S INTERVAL  5 8  T  24 OBSERVATIONS  Figure VI1-2. D i s t r i b u t i o n of sulphur isotope data from the Howards Pass d e p o s i t s , a. I n d i v i d u a l a n a l y s e s p l o t t e d r e l a t i v e to S i l u r i a n seawater s u l p h a t e , b. Frequency d i s t r i b u t i o n f o r i s o t o p i c data from s p h a l e r i t e and g a l e n a .  cr u.  221  Figure VII-3. Sulphur i s o t o p e values f o r a s s o c i a t e d f a c i e s i n the a c t i v e member. I s o t o p i c values are p l o t t e d with a s s o c i a t e d a c t i v e member f a c i e s . Squares represent samples with s i g n i f i c a n t amounts of t e x t u r a l types V a n d / o r V I . F a c i e s of the a c t i v e member are shown by number: 1) l i g h t grey basal l i m e s t o n e , 2) graded l i m e s t o n e , 3) t h i n bedded c a l c a r e o u s mudstone, 4) mixed c h e r t y mudstone and l i m e s t o n e , 5) c h e r t y mudstone, 6) t h i n bedded c h e r t y mudstone, 7) w h i t i s h grey Zn-Pb mudstone and 8) grey c h e r t . Within the i d e a l c y c l e t h e r e i s a general t r e n d of g r e a t e r 6 34$ values proceeding up s e c t i o n w i t h i n the c y c l e .  222 ORIGIN OF THE SULPHUR Three major  sources of  s u l p h a t e are  p o s s i b l e in  sulphide deposits:  magmatic s u l p h u r , s u l p h u r leached from nearby rock or sediments and s e a water  sulphate  deposits  (Hoefs,  similar  contemporaneous not  be  1973).  to those at seawater,  v o l c a n o g e n i c , or  1977).  The  lack  of  In  from geothermal a combination  evidence  hydrothermal)  in  of  the  an  the  Howards  seawater  s u l p h a t e was the major on other  sedimentary  source f o r  the  high o r g a n i c  which  (Hoefs,  may or 1973;  source f o r  Pass  stratiform  s u l p h u r may be S04= from  two  external  high s u l p h u r c o a l s have demonstrated the ( > 90%)  of  emanations,  for  or  investigations  case  Howards P a s s , the  magmatic  topic  the  formation sulphide.  source of s u l p h u r (Smith and B a t t s ,  Faure,  sulphur  (i.e.  suggests  that  Detailed  iso-  carbon environments  seawater  may  sulphate  such as  i s the  major  1977).  MECHANISM OF SULPHATE REDUCTION The r e d u c t i o n of s u l p h a t e to n i c or b i o l o g i c a l nant the  process i n latter  ments  organic  The former  hydrothermal  i s the major  (Berner,  sedimentary  reduction.  1971;  pile  ore  deposits  in  of 1:31 ,680  1975).  (Morganti,  1976)  1974)  Regional  a l t e r a t i o n which would be s u g g e s t i v e of system in the Howards Pass area in  most  cases where a model  and Ohmoto,  of  (Plate large  inorga-  1974)  sulphate  reduction  by  or by r e a c t i o n  mapping of  ( P l a t e I)  of  i n modern sedimentary  chemical  compounds above 80°C ( O r r ,  compounds ( B o n a t t i ,  (Rye  C i r c u l a t i o n of marine  result  result  has been proposed as the  process o p e r a t i n g  1974).  could  s u l p h i d e may be the  over 700  while  environ-  through  reaction with km  domi-  2  the with  inorganic at  a scale  shows no evidence of  hydrothermal  such a hydrothermal  circulation  I).  T h i s i s s i g n i f i c a n t , because  scale  circulation  has  been  pro-  223 posed,  using  system i s 1974;  1976)  D and  obtainable  Sheppard  rounding  the  et  area  by f i e l d  Howards  alteration Plate  in the  area  is  wavy  generally faults  banded  I.  limestone  deposits.  Furthermore  composition  of  the  host  lower  cherty that  and  introduced.  not  material  material  to the  were  have  to  scale  of  1:4800  core  has  only  possible alteration  the  of  are  in  For example,  veins  Thus,  are  is  sulphide  alteration with  alteration all  ages  to the  which  are  of  from the  no evidence  (Bonatti,  of  has  present  the been  within  reflect the  those  the  calcacutting  siliceous.  This  surrounding  areas  for  the  case i f 1975;  are  strike  origin  present  predominantly  faults  zones  v e i n s which cut  such as would be the  the  the  c a l c a r e o u s , while  was d e r i v e d  there  deposits within  associated  are  sur-  2  any  sulphide mineralization  those t h a t  member  not  km  (Morganti,  hydrothermal  These  and v e i n s  rare:  190  Taylor,  indicated  a s s o c i a t e d with  predominantly  formation  produced  at  system" f o r  faults,  mudstone  suggests  a  are  rock.  reous mudstone member are the  group  no evidence  the Howards Pass formation  1974;  the  c o n s i d e r e d to be u n r e l a t e d  a s s o c i a t e d with these  circulation  of  formation.  l e s s than 5 m a c r o s s ,  the  (Rye and Ohmoto,  diamond d r i l l  The  of  mapping  weak d o l o m i t i c  and are t h e r e f o r e  found  of  evidence  Detailed  or a " f e e d e r  in  the  claim  logging  ratios,  techniques  1971).  Pass  covered  noted  H isotopic  al.,  and d e t a i l e d  evidence of  in  C,  addition  deep  of  circulation  Spooner  and  Fyfe,  core,  using  1973). Regional both  mapping  quantitative  (Bennett,  1967)  and d e t a i l e d  chemical  indicate  v o l c a n i s m in the  (Plate  The  only  and  t h a t t h e r e are  evidence of I).  analyses  investigations  the  diagnostic  chemical  of  staining  no t u f f a c e o u s  Howards evidence  drill  horizons  Pass formation of  techniques  tuffaceous  i n the  or  other  map-area  horizons  in  the  224 Paleozoic stone,  stratigraphic  section  wavy banded limestone  significant  that  there  are  in  the  map area  and f l a g g y minor  but  gradient in  the  still  there  is  dark  green  reduction activity  of of  Pass  no evidence of  map a r e a .  sulphate  to  anaerobic  Many s t u d i e s sulphur  factor  (Kaplan  effectiveness  fractionation of  these  scheme ( F i g . V I I - 4 ) with the  and  final  6 34  (1958), (1973).  in  these  Kaplan  (Zobell,  and  siltmay be in  the  the South Nahanni high  low,  geothermal of  the  sulphur chemical  the  notably  1958;  It  reduction  vanishingly  metabolic  forms such as  McReedy, 1975),  could  of s u l p h i d e .  Rittenberg,  1964;  fractionation  fractionation  Kaplan  of 25 o/oo  et is  al., far  of  1963).  less  than  of 74 o / o o at 25°C and i s a measure of  bacteria  in  reaching  equilibrium.  shows t h a t the f r a c t i o n a t i o n  The  the  general  occurs in several  steps  S  showing the possible  lower  basalt  low temperatures  i n the formation  maximum b i o l o g i c a l  the t h e o r e t i c a l  and  have been made concerning m i c r o b i a l  isotopes  The normal  chemical  sulphate-reducing b a c t e r i a ,  D e s u l f o v i b r i o and Desulfotomaculum become an important  is  the  an abnormally  S i n c e at  sulphide  tuffs  s h a l e - o u t at  which c o u l d have caused shallow Howards  in  mudstone f o r m a t i o n s  Howards Pass formation w i t h i n 1 km of the River,  is  steps  have  Rittenberg  combined e f f e c t . been  discussed  (1964),  Large s u l p h u r i s o t o p e e f f e c t s  Kemp are  The  by and  isotope  Harrison Thode  effects  and  Thode  (1958),  Rees,  a s s o c i a t e d with the  reaction  s t e p s which i n v o l v e the b r e a k i n g of s u l p h u r - o x y g e n bonds; t h e c o n v e r s i o n of APS (adenosine to  hydrogen  these  5'  sulphide.  indicated  -  phosphosulphonate)  The assignment  in f i g u r e  VI1-4  is  of  to  sulphite  values  of 25  only an approximation  and of o/oo and  to  sulphite each  of  represents  CELL WALL ENZYME AND METABOLITES  ®  ATP SULPHURYLASE  2 +  APS REDUCTASE  10)  ( 3%o)  EXTERNAL SULPHATE  H Fe  +  A T P  INTERNAL SULPHATE  t25%o)  APS  ®  (25%o)  SULPHITE  HYDROGEN SULPHIDE  Figure VII-4. R e a c t i o n scheme f o r D. d e s u l f u r i c a n s . The various sulphur s p e c i e s are shown t o g e t h e r with enzymes and m e t a b o l i t e s r e q u i r e d to promote r e a c t i o n s to the r i g h t . The numbers i n b r a c k e t s are the i s o t o p e e f f e c t s a s s i g n e d to the i n d i v i d u a l r e a c t i o n steps (based on data from Rees, 1973).  cn  226 a  combination  of  the  s t u d i e s and t h e o r e t i c a l  information  available  consideration  (Thode,  Proposed models f o r duction which  of  sulphate  are  first  H a r r i s o n et of  the  dent  of  reactant  low s u l p h a t e uptake  is  concentrations  only.  by  utilizable  Such a s t e a d y - s t a t e  limiting  and Monster poraneous 15 o/oo  al.,  At  consumption  of  most  system i n which the  of m i c r o b i a l  factors,  carbon  a  system  the  Pass  the  that to  the  uptake  sulphate  at  the  rate  of  concentration  of  (Berner,  formation,  sulphur reduction  of  (Thode et  sulphide  the  1971;  but  Rickard,  with  final  car-  sulphate  has been a p p l i e d al.,  1958;  within  a  in  petroleum  seawater  closed  basin  sulphate. could  i s o t o p i c c o m p o s i t i o n equals the  would  sulphate be  the  (Sangster, limiting  1976;  factor.  Thode contem-  in 6 ^^s Only  account  for  a  iso-  Rees, 1973). a  by  major  original  Such  to  Harrison  with  s u l p h i d e was d e p l e t e d  contemporaneous  S04=  sulphate  as  The  2  concentrations  such  indepen-  and summarized by Thode and Rees (1970).  t o p i c composition of seawater such  suspensions  production.  and found t h a t  compared to  sequences  than 10~ M.  indicates  higher  Howards  (1965) compared 6 34$  seawater  stage c e l l  values g r e a t e r  re-  concentrations.  order with respect  organic  the  1958)  reaction  species  resting  s u l p h u r a s s o c i a t e d with petroleum d e p o s i t s and Thode et  produced in the  system i s reasonable f o r a high o r g a n i c  sulphide  The above model  for  first  some other  such as  sulphur  isotope  Rees, 1973).  assumed  ( C a s p e r s , 1957) is  limited  ultimately  to  inorganic  hydrogen s u l p h i d e p r o d u c t i o n was  by D e s u l f o v i b r i o  bon environment  have  concentration  rate plateau  bacteriologically 1973).  respect  r a t e of  sulphate  o f the  of sulphate  Desulfovibro  with  the  1970;  isotopic fractionation  (1957) observed t h a t ,  bacterium,  existence  by  order  al.  the  from  In  system  227 would  have a h i g h e r  H2S/SO4  ratio  than  an o r g a n i c  carbon l i m i t i n g  case  because most of the SO4 would be consumed. SULPHIDE DEPOSITION Sakai the  (1968)  sulphur  isotopic  presented  in sulphide  fractionation  data  that  indicate  phases forming  factors.  and  various  sulphur s p e c i e s .  summarized by Ohmoto  more  reasonable  (Table V I I - 2 ) .  (1972)  temperatures  for  the composition o f  in equilibrium  Ohmoto (1972)  and produced an i s o t o p i c geothermometer between  that  was a f f e c t e d  quantified  these  f o r the p a r t i t i o n i n g  These d a t a , for 150°C, sediments  T h e i n t i m a t e intergrowth  factors  of s u l p h u r  presented by Sakai have  by  been  (1968)  extrapolated  Campbell  of s p h a l e r i t e  by  et  to  al.  (1978)  and galena  i n the  Howards Pass d e p o s i t s i n d i c a t e s t h a t e q u i l i b r i u m may have been approached d u r i n g large  their  formation.  range of p y r i t e  The l a c k  isotopic  values  of an "ore stage" suggest t h a t  pyrite  pyrite  and the  may not have  been i n e q u i l i b r i u m with the other two s u l p h i d e s p e c i e s . The major f a c t o r s which c o n t r o l minerals the  forming  fractionation  the s u l p h u r i s o t o p i c composition i n  i n e q u i l i b r i u m are: between  (1)  temperature,  sulphur-bearing  s p e c i e s , (2)  which  determines  6 ^^S, which  c o n t r o l l e d by the source of the sulphur and (3)  the p r o p o r t i o n s  d i z e d and reduced s u l p h u r s p e c i e s i n s o l u t i o n .  The lack  thermal  activity  was low, p o s s i b l y 2 5 ° to 5 0 ° C ,  source was c o n s t a n t ,  p o s s i b l y seawater  the  o f seawater result  of o x i -  o f evidence o f  d u r i n g d e p o s i t i o n of the Howards Pass d e p o s i t s suggests  t h a t the temperature  tive  is  sulphate.  If  this  sulphate  were so then  and t h a t the s u l p h u r  or an immediate fractionation  derivawould be  o f the p r o p o r t i o n s o f o x i d i z e d and reduced sulphur s p e c i e s .  TABLE  VI1-2  VALUES FOR THE PARTITIONING OF SULPHUR BETWEEN SULPHUR SPECIES  25°C  A HS  50°C  100°C  150°C  0  0  0  0  73.5  64  50  39  A ZnS  +1.5  +0.6  -0.8  -0.9  A PbS  -8.2  -7.4  -6.0  -5.1  +4.2  +3.3  +1.6  +0.8  2  A S0  2 4  A FeS  2  "  Taken from Ohmoto (1972, F i g .  1.).  229  Three f u r t h e r assumptions be  must be made i f i s o t o p i c c o m p o s i t i o n  a f u n c t i o n o f t h e p r o p o r t i o n s o f t h e o x i d i z e d and reduced  species:  (1) That  deposition. al., and  there  This i s supported  1969) and geochemical B i s c h o f f , 1977),  assumed  that  within  constant.  sphalerite  and galena  by e v i d e n c e  modelling  the interval (2) That  reasonable  i f seawater  source (Rees, Based  from  sulphide  t h e Red S e a (Brooks e t  o f sulphide  brines unless  deposition  t h e sulphur  (Shanks i t is  t h e pH was  i s o t o p i c composition o f  since formation  of the deposits.  h a d an e s s e n t i a l l y c o n s t a n t  sulphur  i n t h e pH d u r i n g  o f low temperature  have n o t changed  lack o f any metamorphism  source  change  b u t i s q u e s t i o n a b l e f o r Howards P a s s  reasonably  the  was l i t t l e  is to  isotopic  i s supported by  (3) That  t h e sulphur  composition,  which i s  sulphate o r a constant derivative i st h e sulphur  1973).  o n Ohmoto's  (1972)  original  c a l c u l a t i o n s , Campbell  et  al.  ( 1 9 7 8 ) h a v e shown t h a t t h e f o l l o w i n g r e l a t i o n s h i p s a r e a p p l i c a b l e t o a sedimentary  environment.  5 3 l + S  i  * hS 3k  =  + AH S_i - C A = _ S 0  2  H 2  S(1 - XH S)] 2  ( 1 )  w i t h , f o r a n o r i g i n a l homogeneous s u l p h a t e s o u r c e w h e r e 6 S ^ s 3 4  6  3 L T  S04  =  A  R  E  E  1 ted,  3  +  ^  c a n be t r a n s f o r m e d t o  u a  (S ' S )-(6  an<  3 1 +  i  S< = «. = A _ \ 4 - S0 -H2S+ H S-S-j -) S 0; N  X  0  u  C  X  P  H<> = —  c  2  4  (2)  2  A  S04-H S 2  For  a sedimentary  environment  where t h e t h r e e  above assumptions  apply,  e q u a t i o n (2) may be s i m p l i f i e d t o calc. XH S  :  =  2  A  (3)  : —  S04-H S 2  w h e r e XL| $ i s t h e m o l e f r a c t i o n H S a s s u m i n g H S and S 0 4 2  2  2  =  are the  230 significant observed  S s p e c i e s (Nissembaum et  mineral  and  ( 6  S -j )  3 4  m  al.,  calc.  n  1972), is  for  ( 6 the  3 4  S -j ) m  is for  n  calculated  the  mineral  species. The  three  groups  i n t o the a p p r o p r i a t e  of  isotopic  data  (Fig.  formulae suggest that  VII-3)  when  p o s s i b l y the  substituted  idealized  active  member c y c l e r e c o r d s the e v o l u t i o n of the s u b - b a s i n , and shows a general increase crease sub-  in  in  the XLJ^S  XL^S d u r i n g suggests  a  development general  of  a cycle.  increase  in  The  the  general  isolation  b a s i n i n which the a c t i v e member was d e p o s i t e d , s i n c e the  nature  of the s u b - b a s i n i s a measure of i s o l a t i o n  (Calvert,  al  if  sphalerite  seawater  should be much more  sulphate.  If  it  is  depleted  assumed t h a t  in  the  the  reducing  (Fig.  the s u b - b a s i n was a system open to sulphate during  reduction,  source  of  1964).  A comparison of s u l p h a t e source i s o t o p i c compositions shows t h a t  in-  3 4  S  VII-5) bacteri-  than  sub-basin  the  was  a  system c l o s e d with r e s p e c t t o s u l p h a t e then a more reasonable comparison is  obtained between the c a l c u l a t e d and observed v a l u e s . Comparison  position  of  of  the  values  XLJ^S  s u l p h i d e s from the  obtained  1978) suggest t h a t  than  those  this  difference  of  these  may be  other two d e p o s i t s . f0£  in  low  equilibrium.  more  the  isotopic  (Kaplan et  al.,  thoroughly related  to  brines  studied the  deposits.  o c c u r r e n c e of  The  et  reducing for  in  the  (1977)  the  by  magnetite-hematite  The Howards Pass d e p o s i t s , on the other  hand, show no e v i -  dence of the presence of F e  3 +  buffered  obtained  reason  magnetite  by Shanks and B i s c h o f f  may be  com-  1969; Campbell  Howards Pass s u b - b a s i n s were more  As demonstrated  temperatures  the  Howards Pass d e p o s i t s and those  from the Red Sea and the S u l l i v a n Mine al.,  from  during sulphide  formation.  .231  50°C  25°C  X H S = 1.0  XH«S«"|.0  2  Sph = +24.6%«J  XH S Z  =0.75  Sph =+8.6 % o  XH S*0.50 2  sph= -r.4%oi  Totally Closed  Sph= + 22.3%©  XH S * 2  0.75  8 m  Sph =+4.12 % o  XH S 2  = 0.50  sph =- U 3 % o  at  M O  a «  a « w U e  s-l  tn «i  w C»  to  -a  •o — a> *•  •"5 XH,S  = 0.25  Sph=-23.4%ol  XHJS = 0  S04 "»+24%ol 2  A AAA  XH S 2  = 0.25  c •  x  .c o CO  2  S04 "=+24%o 2  UJ «  4> VI O « w  o  . in  •o  .5  »•  o  o i  c  ut 3 UJ  o  VI  -O 3 CO  X  e o u (O s  sph* -32.63%o  XH S = 0  O <D w <J C  Totally open no sphalerite formed.  F i g u r e VII-5Diagram showing r e l a t i o n s h i p of X^„s c o n d i t i o n s at 25° C and 50°C, assuming a seawater sulpriate s u l p h u r o f 24.0 o / o o . A l l examples are based on c a l c u l a t i o n s t h a t s p h a l e r i t e i s the major s u l p h i d e mineral f o r m i n g . The f o r 50° C more c l o s e l y approximate the data from Howards Pass f o r 25° C. t  o  sub-basin source f o r and assume X H 2 s value tfran those  232 SUMMARY Sulphur  i s o t o p i c and g e o l o g i c data  tion  that  seawater  Pass  deposits.  sedimentary Howards of  sulphate, by  (2)  that bacterial correct, (Thode was  the  and  the  phide the  sulphate  reduction  Rees,  of 1970)  deposition,  of  of  ^2$  (4)  enrichment  during  which  is  s u b - b a s i n . Grouping of  for  direct  of  by  for of  a the  reduction  (3)  deep  (Orr,  HS 2  system  sulphate  circulating  1976)  from in  of  If  deposits sulphate  Geologically  relative  during  sul-  isolation  the  t h i n bedded c a l c a r e o u s mudstone, the t h i n bedded c h e r t y mudstone and  the  tions in  grey Zn-Pb mudstone f a c i e s and  turn  progressive  supports  restriction  a model  sequence i n the a c t i v e  indicate of  postulating  member.  the the  indicates  of  that  whitish  i s o t o p i c data by l i t h o l o g y  oil  which  X^s  of  suggests  mechanism.  sulphide.  estimation  a l s o an e s t i m a t i o n  Howards  deposition  probable  in  restricted  an  the  of any evidence of a geo-  a most  formation  sugges-  possible  methane,  > 80°C  noted  in  bacterial  reduction  The l a c k  is  are  during  by b i o g e n i c  sulphate  allow  (1)  temperature  suggests a  factor  assumptions  include:  sediments.  sulphide  generation  present  reduction  suggestive  lack  that  and  c o n s i s t e n t with the  source of  sulphide  methane  underlying  limiting  reasonable  These  abiogenic  system  of  the  such as  deposits.  waters i n the thermal  was  Four models  environment  Pass  reduction  sulphate  are  increasingly  reducing c o n d i -  sub-basins.  This  existence  of  an  reasoning  ideal  cycle  233 CHAPTER VIII  LEAD ISOTOPES  INTRODUCTION The r a d i o a c t i v e decay of uranium and thorium to lead as well topic for  variations  of  lead  an understanding  of  in  uranium-free  the  genesis  of  ores ore  lead method was used on samples from the lead  is  Th/Pb  any  lead  such t h a t  from a mineral no  of  great  deposits.  radiogenic  Only the common  a low value lead  has  of  been  Such phases are galena and other  such as p y r i t e  and s p h a l e r i t e  and a l s o some f e l d s p a r s and m i c a s .  of the mass s p e c t r o m e t e r .  gress  was  made,  techniques isotope  investigations  geologic  the  to  ( R i c h a r d s , 1971; Natural  generation  238y  }  235u  a n (  j  rapid  of  2  232j  0 Pb 6  n  i n the ^ Pb  not  fractionation lighter  evolution  the  and 208pb as the  7  small to  new  differences  natural  in  1968; of  lead  isotopes  Faure,  lead  1977).  result  from  end products  mass between  variations  new have  ionic chemistry,  physicochemical  such as s u l p h u r ( L o v e l e s s , 1 9 7 5 ) .  lead  seems to  of  stable  pro-  in  application  field  Because of i t s  era  Kanasewich,  isotopes  the  develop-  spectrometric  S a n g s t e r , 1976;  p r o c e s s e s which cause i s o t o p i c  elements  1960;  lead in  a  in  sulphides  continued  of  i s o t o p i c c o m p o s i t i o n of  respectively.  susceptible  started  few y e a r s of  1959  refinement  Farquhar,  Stacey and K r a m e r s , 1975;  mass and r e l a t i v e l y is  past  interpretation  of  variations  the  1960s  and  (1938) with the  time t o  interpretations  Over the  the  period  early  (Russell  1974).  models  caused another  lead  in  and mathematical  Doe and S t a c e y ,  atomic  but  Since that  and/or  generated  phase formed.  ment  Common  U/Pb  s i t u s i n c e the  The use of common leads dates back to N i e r  iso-  importance  Howards Pass d e p o s i t s .  phase with  significant  are  as the  of  high  isotopes,  or  biochemical  in  many of  To d a t e ,  attempts  the to  234 interpret  common lead  isotope  abundances  types of lead models, d i s c u s s e d (1)  Single-stage the  tion  Appendix G f o r  (see  the  ratios  index  of  the  isotopes  radioactive  models o f  earth began with a s i n g l e  (  list  of  radioactive  2 3 8  U/  decay.  Pb,  2 0 4  based  of  isotopic  primeval  b  a  lead  and that  isotopes  5u/204p  Withdrawal  lead  symbols)  parent 2 3  been  on two  main  evolution  as-  below.  (ordinary)  sume t h a t  have  n  some l e a d ,  the  to  232  d  isotopic  only changes  the  T n  stable  /204  uranium  composi-  P b  )  a  r  in  daughter due  e  and thorium  to from  the s i n g l e - s t a g e source by f l u i d s or other means i s not excluded so long as the s i n g l e stage the is,  radioactive the  1974).  source i s  parent  examples  volcanogenic  hosted  O s t i c et a l . ,  1967);  these  isotopes  source of the f l u i d s The b e s t  from  of  enough so t h a t the  are  not  significantly  ordinary  l e a d s are  deposits  1957;  of  are  hot  a  perfect  fit  conditions,  isotopically  Richards, 1971).  as m u l t i p l e  distrubed;  (Doe and S t a c e y ,  and  reworking  (Armstrong,  posits. tion  Thus,  for  T h i s mixing  the  shown to  model. be  1968)  The  evident  source  would  apply to leads  small in  (Shaw,  processes such  of lead from very l a r g e volumes of r o c k ,  that  for  even  materials  may be done through  so-called single-stage  lead model  1959;  seem best e x p l a i n e d by the  heterogeneous  under s i n g l e - s t a g e c o n d i t i o n s .  tionary  within  Russell,  way t h a t a s i n g l e - s t a g e system i s approached; subduction i s cess  that  although s i n g l e - s t a g e c o n d i t i o n s are approached  single-stage  several  involving  those c o n t a i n e d  (Stanton  those d e p o s i t s t h a t most c l o s e l y approach i t , mixing  ratios  i s an " i n f i n i t e - r e s e r v o i r "  stratiform  d e p o s i t s , they  departures  large  i n such a  such a p r o -  volcanogenic s t r a t i f o r m only  More r e c e n t l y ,  has been proposed to b e t t e r f i t  approximate  de-  an  evolu-  a "two-stage"  evolu-  the v o l c a n o g e n i c  lead  235 data  1975).  (Stacey and Kramers,  various posits  parameters and  troilite  and comparison with  various  development  T h e i r model  feldspars.  The  new  of lead from a p r i m o r d i a l 4.57  l e a d , beginning at  lead  single-stage  though  model  imperfect,  stage, until  of  an  the  lead  chrons  2 0 7  Pb/  Differentiation  the  lead  Kramers'  age  of  If  the  chrons means the  solution  order m u l t i s t a g e  leads  are  2 0 6  information  a  on the  two-stage  Pb/  the  initial  Ga.  of  Either  model,  age of  2 0 4  even  formation  of  formed  38u/204p  the  from  process to be  along s t r a i g h t  lines  c a l l e d secondary i s o -  mineralization  lead  varying  that  first  ratio  D  lie  for  simplest  the  lead  is  known  may be  ap-  calcu-  secondary i s o -  successive approximations.  Higher  may have been  associ-  U/Pb and T h / P b r a t i o s  and may  lengths of time ( F a u r e ,  1977).  systems having d i f f e r e n t  have r e s i d e d i n these systems f o r  In  2  of the equation f o r the  one of  The  single-stage  P b ratios)  age  lead.  process.  caused the  soure m a t e r i a l  nature is  3.7  modified  excess r a d i o g e n i c  is  P b versus  1968).  the  processes brought  approximately  lead i s o t o p e data t h a t  The t r a n s c e n d e n t a l  ated with s e v e r a l  and  occurred that  is  2 0 4  (Kanasewich,  proximately, lated.  event  conformable  postulates  i s o t o p i c c o m p o s i t i o n evolved by a  The r e s u l t  p l o t s of  de-  from  ages).  contain  anomalous  some l a t e r  changed. (in  (model-lead  Anomalous leads  example  Stacey  data  c o m p o s i t i o n , assumed to be t h a t  Ga.  provides v a l u a b l e  of the Pb m i n e r a l s (2)  or  for  model  about the c o n d i t i o n s of a second stage at the  i s based on new values  METHODS Lead and s t o r e d  samples were c o l l e c t e d in  plastic  from  sample bags f o r  drill three  p l e s were broken and sub-samples were taken  cores months.  from  the  XY d e p o s i t  S u b s e q u e n t l y , sam-  only from the  inner  parts  of  236 the c o r e s .  (Doe,  1970;  U n i v e r s i t y of A l b e r t a of  the  analytical  sphalerite  and  Doe and D e l e v a u x , 1972).  f o r a n a l y s i s of the  method  pyrite  are  given  separates  in  were  These were sent t o  lead i s o t o p i c r a t i o s .  Details  Appendix  galena,  G.  dissolved  Briefly,  using  various  acids,  loaded on a R e - f i l a m e n t  and analyzed on a s o l i d s o u r c e , 9 0 ° s e c t o r ,  radius,  mass spectrometer  single  P h y s i c s at  filament  the U n i v e r s i t y  a n a l y s i s and the on N . B . S . # 981 analysis  of A l b e r t a .  resultant  raw data  the  housed i n  Fifteen  the  Department  12" of  scans were made f o r each  processed by computer.  Pb standard were completed b e f o r e  Fifteen  and a f t e r  runs  each sample  (Kuo and F o l i n s b e e , 1974).  For  interpretation,  the  l e a d , two stage and m u l t i p l e son and R u s s e l l ,  1967;  lead  data  were  compared  to  stage models to check f o r  Kanasewich, 1968;  Koppel  the  model  and S a a g e r ,  ordinary  fit  (Slaw-  1976),  and  a l s o compared to g e o l o g i c data as another c h e c k . RESULTS Data obtained from the Two types textural of  IV,  o c c u r r i n g in the  synsedimentary  To  check the  gram.  When a l l  The lead  origin.  whitish  for  data  the  Samples HP 3 , 4 ,  were  applicability plotted  lead data  suggests t h a t  were  of the  calculated  by  2 0 7  plotted  an anomalous  s l o p e and i n t e r c e p t line  are  on a  lead  2 0 7  of  Pb/  2 0 4  Pb  to  are  textural  2 0 6  Pb/  2 0 4  Pb  manner a weak l i n e a r  P b versus using  from  an anomalous  versus  interpretation  computer  from  member.  data  in t h i s  2 0 6  5 and 6 are  7 and 8 are  the  Pb/  2,  V111-1.  grey Zn-Pb mudstone, and  from s u l p h i d e c o n c r e t i o n s in the a c t i v e  model,  tern  presented in T a b l e  of s u l p h i d e s were sampled; samples HP 1,  type  type V I ,  lead a n a l y s e s are  2 0 6  the  may be Pb/  2 0 4  lead diapat-  applicable.  P b anomalous  least-squares  cubic  TABLE V I I I - 1 Lead Isotope R a t i o s of S u l p h i d e M i n e r a l s  Mineral  206  HP-Pb-1  Galena  18.6930 ± .0112  15.7365 ± .0093  38.8640 ± .0229  HP-Pb-2  Pyrite  18.6722  15.6902  38.8395  HP-Pb-3  Galena  ± .0211 18.4046 ± .0281  ± .0176 15.6635 ± .0236  ± .0434 38.6610 ± .0576  HP-Pb-4  Pyrite  18.6109 ± .0211  15.6707 ± .0176  38.4602 ± .0434  HP-Pb-5  Galena  18.6765 ± .0210  15.7358 ± .0174  38.8275 ± 0.429  HP-Pb-6  Sphalerite  18.6248 ± .0119  15.6723 ± .0099  38.6791 ± .0244  HP-Pb-7  Galena  18.7944 ± .0283  25.6947 ± .0238  38.7028 ± .0582  HP-Pb-8  Pyrite  18.6320 ± .0171  15.7095 ± .0141  38.8386 ± .0348  The n o r m a l i z a t i o n  The a b s o l u t e  factors  isotope  are:  ratios  207  P b  206 207 208  P b  P b  P b  of N . B . S .  16.9371  /204 /204 /204  P b  P b  P b  p b  /204  P b  208  P b  /204  Deposits  Sample No.  P b  /204  f o r the Howards Pass  P b  X 1.00315 X 1.00383 X 1.00585  # 981 s t d / are: 15.4913  36.7213  238 method tary  (York,  lead  1969).  Data  and those  from samples b e l i e v e d to c o n t a i n synsedimen-  containing  both  synsedimentary  onary lead were used.  The whole data  error  95% c o n f i d e n c e ± 0 . 1 3 5 1 ) ;  do  of  not  estimate appear  206ph/204p to  fit  verify  to  c|-j g a  L)  an  (at  show  a  linear  line  lead  and  concreti-  show an unacceptable standard  trend  on  the  synsedimentary  the  207ph/204pD  versus  T h u s , the present l e a d i s o t o p i c data do not  r a m >  anomalous  lead  model,  although  more  data  are  data  appear  required  to  this.  The  lead  isotopic  data  from  the  Howards  Pass  deposits  were  also  compared to the two stage model developed by Stacey and Kramers  (1975).  F i g u r e s V111-1 and VII1-2 are  present  work.  Only the  sidered  since  sulphides. ratios  is  they  data  show  The mean  plotted  isochron  lead  replotted  from  less  2 0 7  Pb/  i n d i c a t i n g a time of  much younger than  the  ratios  2 0 4  Pb  data  synsedimentary  heterogeneity  isotopic  on the  the  from t h e i r  for  versus  than  the 2  age of m i n e r a l i z a t i o n  later  are  con-  diagenetic  synsedimentary  06ph/204pb  Pb m i n e r a l i z a t i o n  the  sulphides  the  four  for  (t ), m  diagram of  indicated  187  lead  show an Ma,  which  by other  evi-  dence. DISCUSSION Three of  explanations  common leads  age and model  (Oversby,  age are  Manitouwadge, but A those f o r the  are  p o s s i b l e f o r the 1974).  small  for  age d i s c r e p e n c y in the  The d i f f e r e n c e s the  oldest  (A)  deposits  between at  accepted  Barberton  stage  Howards Pass d e p o s i t s .  model  and  i n c r e a s e s s u b s t a n t i a l l y f o r younger samples such as This  d i s c r e p a n c y at  younger ages  was one of the main reasons f o r Stacey and Kramers (1975) developing two  use  which  has  reduced,  but  not  eliminated,  this  the  error.  239  Figure VIII-1. Graph of Pb/ P b plotted against Pb/0 P b showing Stacey and Kramers' two stage lead e v o l u t i o n c u r v e . Upper diagram shows, a d e t a i l p l o t of the Howards Pass d a t a , c i r c l e s represent synsedimentary s u l p h i d e s , squares i n d i c a t e data from c o n c r e t i o n a r y sulphides. P o i n t s along Stacey and Kramers lead e v o l u t i o n cure are shown by x. 2 0 7  2  4  2 0 4  2 0 6  240  .a  a.  350  o  CM CL  00  O  CM  h-300.  90  20-0  150 206  204  Pb  Figure VI11-2. Graph of 08pb/204 plotted against Pb/Pb showing Stacey and Kramers' (1975) two stage lead evolution curve. Upper diagram shows a d e t a i l p l o t of the Howards Pass d a t a , c i r c l e s r e p r e s e n t synsedimentary s u l p h i d e , squares i n d i c a t e data from c o n c r e t i o n a r y s u l p h i d e s , X r e p r e s e n t s p o i n t s on the lead e v o l u t i o n c u r v e . 2  2 0 6  P b  2 u 4  241  Using the two-stage  model, e r r o r s between accepted age and model age  for  deposits  l e s s than 500 Ma range from 12 t o 15% (N=3), as compared t o 55%  for  Howards  the  difference  Pass  can be  deposits.  explained  It  by  thus  the  appears  inherent  that  only  A value,  part  but  it  of  the  must  be  remembered t h a t the growth curve i s based on v o l c a n o g e n i c d e p o s i t s . second  possible explanation  crepancy i s t h a t the more data w i l l  for  the  lead m o d e l - g e o l o g i c model  l e a d s are anomalous; as mentioned  adequately  answer t h i s  question.  volcanic  black  association 1977).  The  s h a l e s are  (Stanton 2 3 8  U/  2 0 4  more r a d i o g e n i c  and R u s s e l ,  Pb  1959)  (u) f o r the  than  age  dis-  previously,  only  A third  d i s c r e p e n c y c o u l d be a more r a d i o g e n i c Pb s o u r c e .  reason f o r  That  those  of  for  the  the  V2-  2  P b  •a  = 206p /204 b  time e l a p s e d  Using t h i s genic 1976).  The  Howards  Pass  since  P b  r  a  t  x  i  o  a  t  removal =  sulphide  heterogeneity is  equation:  e 8*  T  procedure v>2  massive  Pass  2  t  i  m  e  t  d i x G ) , T]_ = time of beginning of the =  (1976,  ° Pb A  2  arc  4  e 8 l-  where a  island  Howards  l e a d s was c a l c u l a t e d f o r the mean lead using the f o l l o w i n g 206  the  l e a d s from non-  has been shown by Gulson  source m a t e r i a l  The  similar  of  9.89,  to  which  the that  Cooper and R i c h a r d s , 1969), and i s mation and l o c a l U-Pb  X  l  =  1.55125  second stage  a common lead  deposits of  ^  variations.  is  concretionary noted  in  lead  than  1976;  evolution  for  p o s s i b l y due to  its  most  Koppel  sulphide  most  (Appen-  y  sample from  higher  (Sangster,  irj-10 -l  x  t  source. volcano-  and  lead  and  Sagger,  data  from  sediments  (Doe,  1970;  various  ages of  for-  242 Comparison Sea  deeps  review,  of  the  suggests that  1976).  the  lantis nated  three  II  mode of  II  (Degens and Ross,  brines  as o v e r f l o w  those  formation  are  the  brines  from the  1969).  result in  of  the  Atlantis  At  found is  the  Red  possible.  In  in  brine  (Brooks  1969)  Atlantis  II  et  al.,  indicate  that  Deep,  lead  II  and b a t h i m e t r y ,  from the A t l a n t i s  II  terogeneity  Lead  They f u r t h e r  reflected  the  Chain thought  in the  isotopic  data  lead  have  Atlan-  (Cooper  is  present  Chain and D i s c o v e r y deeps are  (1969)  composition of  proposed t h a t  increasing contribution  and in pro-  brines  overflow  brine  Chain Deep and f i n a l l y  proposed t h a t the  At-  origi-  compared to the  homogeneous  Deep moved through the  the D i s c o v e r y Deep.  is  et  The o v e r f l o w b r i n e s  Based on chemical  Cooper and R i c h a r d s  it  v o l c a n i c emanations  Deep.  although  g r e s s i v e l y more heterogeneous.  II,  Chain and D i s c o v e r y deeps  1969).  from the  Atlantis  present,  a d i s t a n c e of up t o 6 km and are d i l u t e  Richards, the  with  deeps to be s t u d i e d were the  Deep and t h a t  travelled tis  similar  leads  b r i n e s and a s s o c i a t e d b r i n e d e p o s i t s ( B i g n e l l  The f i r s t  and D i s c o v e r y deeps that  a  Pass  the Red Sea b a s i n c o n t a i n s over twenty s u b - b a s i n s , many of which  contain metalliferous al.,  Howards  into  i n c r e a s e of l e a d he-  of lead from the  sedi-  ments. The trend;  lead  that  geneous than  i s o t o p i c data  i s , the that  from  i s o t o p i c data  from the  the  Howards  from t e x t u r a l  proposed b r i n e  The c o n c r e t i o n s were formed d u r i n g l a t e r times  and i n a system where  between rain  the  eastern  source a r e a .  area  show a  similar  type VI  i s more  hetero-  deposit  limited  of  textural  type  d i a g e n e s i s , probably at  Pb and U were m o b i l e .  Selwyn B a s i n and the The  Pass  Another  various  similarity  Red Sea i s a Precambrian  terrigenous  material  that  did  IV.  enter  terthe  243 Selwyn B a s i n appears to  have o r i g i n a t e d  to  the  ments i n r e s t r i c t e d  b a s i n s , such as the B a l t i c  drain  terrains,  Precambrian  ratios,  especially  Tilton,  1966).  regional  Data  lead  and  m.y.  for  nodules the  Sea or the  sediments  (Chow,  sedi-  Red Sea which  radiogenic  lead 1965;  Howards Pass d e p o s i t s are  data  the  Red S e a .  (Reynolds from  the  Shield rather  than to  common c h a r a c t e r i s t i c  is  the  ages A = 189 m.y.  the  lead  to  Another  Red Sea  lead model  grained  from the  proximity  deposit.  the  fine  highly  Typically,  isotopic Hart  and  compatible with  i s o t o p i c zoning proposed by Kuo and F o l i n s b e e (1974),  may be due t o Anvil  in  contain  east.  age for  A large  and Dasch, Howards  the  between  the  Howards  d i s c r e p a n c y between  the  geologic  and  d e p o s i t s and A =  500  the  Howards Pass  age  discrepancy is  1971)  Pass  d i s t a n c e from  but  (Fig.  deosits  VI11-3). is  more  also  evident  This  suggests  similar  to  Pass  i n Mn that  sedimentary  leads than to v o l c a n o g e n i c l e a d s . SUMMARY Lead i s o t o p i c data  are compatible with other  Pass d e p o s i t s .  The p r e l i m i n a r y  two types:  (1)  synsedimentary lead data  stage model  curve and  (2) l a t e  very heterogeneous d i s t r i b u t i o n  data  stage  data  from the  Howards  presented here can be d i v i d e d plot  near the Stacey-Kramer two  diagenetic  of lead p l o t s .  s u l p h i d e s which show a  The r e l a t i o n  between  Howards Pass data and the lead growth curve i s s i m i l a r to those of gic  sediments and Red Sea b r i n e  genic  deposits  such  suggests t h a t the  as  the  sediments  Kuroko type  lead i s d e r i v e d mainly  p r o p o r t i o n of m a n t l e - d e r i v e d  lead.  Kuo and F o l i n s b e e (1974) f u r t h e r  into  and not  (Sato  to  those  of  the  pela-  volcano-  and S a s a k i , 1973).  This  from sediments, with an unknown  Regional  lead zoning as presented by  suggests t h a t m a t e r i a l  d e r i v e d from  the  244  Mn nodules (Reynolds ond Oascft. 1971)  155  f  Oceanic basalts » metalliferous sediments. Red Sea Cooper and Richards (1969) • basalt. Red Sea Delevoux and Oo* (1974) s sediments. Red Sea » metalliferous sediments. East Pacific Rise (Dasch et ot, 1971) • conformable ore deposits 17.S  J_  no  193  3001  tvo-stoge  growth curves,  380  SO  Figure VI11-3. Lead i s o t o p i c data p o i n t s f o r r e c e n t l y d e p o s i t e d metalliferous sediments (Red Sea and East P a c i f i c R i s e ) . The two-stage growth curves are f o r d i f f e r e n t u v a l u e s . Note t h a t lead data give negat i v e ages even though they are from conformable d e p o s i t s . Numbered p o i n t s r e p r e s e n t data from conformable d e p o s i t s (from Koppel and S a a g e r , 1976).  Precambrian S h i e l d c o u l d have been a major Pass d e p o s i t s .  source of lead  in the  Howards  246. CHAPTER IX  DISCUSSION  INTRODUCTION The data  presented in the present r e s e a r c h l e a d s the author to  c l u d e t h a t the  Howards Pass Zn-Pb d e p o s i t s are  sedimentary-type ment  of  stratiform  possible  ore  genesis  s i m i l a r d e p o s i t s elsewhere chapter  presents  Howards  Pass  allowed  f o r the  sification chapter  an  models  oriented  (Morganti,  1975;  Furthermore,  a  ore  exploration In  of  this  model  for  the  published  data  has  exploration-oriented  deposits.  regional  for  part,  genesis  review  stratiform  some c o n s i d e r a t i o n i s given to  toward  1977a; 1979).  c o n s t r u c t i o n of a t h r e e - f o l d  sedimentary-type  other  T h i s has a l s o l e d to the d e v e l o p -  exploration-oriented  deposits.  of  deposits.  unique compared to  con-  At the  clas-  end of  metallogeny  in the  the eas-  t e r n Yukon. MODEL FOR THE ORIGIN OF THE HOWARDS PASS DEPOSITS The g e n e r a t i o n four c r i t i c a l  a s p e c t s (White,  t u e n t s must e x i s t ; persed in phosed,  of an ore d e p o s i t t h a t (1)  in  sediments, in  a s s o c i a t e d with magmas, in the (2)  ments  in  at  least  D i s s o l u t i o n of part  in  rocks of the environment. by p h y s i c a l selective  and/or  (Anderson,  1978).  of  change  or  the  ore  (3)  Brine migration  differentials.  the  in  the  migrates  and  in  new  formed  related of  elethe  controlled  d e p o s i t i o n by  response to into  dis-  metamor-  interstices  Mineral  has  consti-  previously  in d i r e c t i o n s  (4)  constituents fluid  rocks being  constituents,  hydrous phase in  certain as  ore  mantle,  the  chemical  precipition  chemical  A source f o r  the most commonly e n v i s i o n e d sources are metals  products of w e a t h e r i n g ,  ore d e p o s i t s .  and/or  1968):  i n v o l v e s a hydrous f l u i d  physical  environments  247 In the Howards Pass d e p o s i t s , two major sources of metal gically tion  possible:  (Berner,  (1)  1975)  Howards  providing  1977a), or  (2)  Unit'  high temperature  with  the  the  T h e r e i s no experimental  fluid  required  the  (greater (i.e.  formation. because brine  1977)  T h u s , the  (150  to  of  fluid  with  200°C  first  crustal  vent  brine  migration  the  or  I),  reasoning, migration  to  the Howards Pass  Shanks  (Tissot  'Grit  exhaled  outside  covered by  Plate  the formation  vertical  of  of a  migration  or  of  an o u t l e t  of  heat  to  the  if  heated  problem locate  Howards of  the  an area  formation.  Pass  of  of  1977)  rich  and  the  Zarkharov,  as would be  usually  main  re-  occurs because  commonly a s s o c i a t e d  question  There  is  i n the  brines  where  the  no evidence  of  Howards Pass map for  must have been e x p e l l e d to  the  area. centre  heat  flow  did  is  supply metals  map  high  present  1975).  surface  exhalation  at  a metal  1973;  1978)  flow  located.  Zn-Pb d e p o s i t s they the  (Nixon,  movement  the  of  and B i s c h o f f ,  (Fischer,  migration, was  formation  centres  Such f l u i d  centre  reasonable  and W e l t e ,  a n d / o r deepening brine  more  the  subsidence and e l e v a t e d  of the  the is  basin  from  suggesting t h a t  outside  for  away  exhalation  formation  surface  required to  source.  considering  (Plate  source appears  a c r o s s bedding  brine  area  such as the  area  b r i n e or the  according  flow  with b a s i n formation In  1975,  evidence f o r movement of the q u a n t i t i e s  latter  temperature  not  q u i r e d in the of  advec-  (Morganti,  50°C) brines  o u t s i d e of the  with  in sediments s i m i l a r to those which formed the Howards Pass  the  and  brines  f o r such a model of b r i n e development,  of  nature  itself,  Selwyn B a s i n ,  than  very low ( l e s s than 5 0 ° C ) temperature such a b r i n e  formation  temperature  rocks u n d e r l y i n g  of the Howards Pass map-area I).  low  Pass  are g e o l o -  Following  the  a s s o c i a t e d with during  above brine  deposition  of  248  Comparison o f the graphic  control  Pass f o r m a t i o n graphic  on ore  deposition  dominating  source of the b r i n e s ,  empirical  importance of b r i n e (Table  IX-1)  shows t h a t  if  sulphide d e p o s i t i o n .  exhaled at  would be o u t s i d e and based  the  relatively  Howards  on d e s c r i p t i o n s  1976; T a t s u m i , 1970;  of  This high  Pass  position  from a d e n s e , low temperature  of metals  (Anderson,  experimentally  1975,  Turner  (1969)  brines  do e x i s t  in  the in  isolated bodies.  1967;  natural  1977)  although the  may be s i m i l a r reasonable  to  seawater  Sato,  1972)  (Fig.  IX-1).  source area  for  in  response  Gustafson,  to  have  systems and t h a t  the  which  (Degens  may  have  gravitational  Pass  would be  (Wolf,  been  shown  deposits.  as  Shanks  Howards  Pass  Red Sea b r i n e s Thus,  u p - s l o p e from the seawater,  dense  differences 1969;  the  of the  that  can e x i s t  and R o s s ,  (Turner,  chloride  O b s e r v a t i o n s by  suggest  formed  compared to forces  has  such b r i n e s  i n mineralogy  Howards  a brine  is  l a c k of Cu  That  demonstrated  physical evolution  Pass d e p o s i t s , s i n c e denser b r i n e s , slope  pools  Red Sea b r i n e s  of  estimate  deposits  brine.  than  general  those  ore  denser  and those  the  p a l e o t o p o g r a p h i c lows suggest de-  However, d i f f e r e n c e s the  This  are  Red Sea b r i n e  c h e m i s t r y between  deposits,  1978)  (Ellis,  suggests t h a t  i n the Howards Pass d e p o s i t s , the  of the d e p o s i t s to  and B i s c h o f f ,  Howards  1977).  and the confinement  in  the  ( g r e a t e r than 5 0 ° C )  area.  stratiform  K r e b s , 1976b; L a r g e ,  T h e simple mineralogy  brines  source vs p a l e o g e o -  r e p r e s e n t s an end-member group of d e p o s i t s with paleogeo-  control  temperature  relative  the  Howards  migrate  1973;  most  down-  Turner  and  1978).  T h e only evidence of a p o s s i b l e h i g h heat f l o w d u r i n g d e p o s i t i o n of the  Howards  Pass  formation  c o n s i s t s of  minor  amounts  of  tuff  within  1  Table IX-1. T a b l e showing c h a r a c t e r i s t i c s of p r o x i m a l , deposits. The t a b l e suggests the r e a l i t i v e importance of b r i n e the l o c a l i z a t i o n of ore d e p o s i t s , even though d i s c r e p a n c i e s do s o n , 1975; Lambert and S a t o , 1974; L a r g e , 1977; Lydon, 1978; Sato, 1972.  CHARACTERISTIC  PROXIMAL  Metal  Cu-rich (with be p r e s e n t i n  content.  Pb  is  zone Iron  sulphides  and  oxides  Z o n i ng  Sulphur  or  by  Zn m a y quantities,  Setting  isotopes  DEPOSIT  P b - Z n r i c h , Cu p o o r may h a v e e c o n o m i c A g .  SEDIMENTARY  DEPOSIT  Zn-Pb  low  low  rich,  Cu a n d  Ag.  low.  a distinct  alteration  No d i s t i n c t  footwall  alteration  zone.  pipe.  No e v i d e n c e o f a n y wall alteration.  foot  Pyrite dominant, pyrrhotite absent. M a g n e t i t e may b e i n hanging wal1.  S p h a l e r i t e and g a l e n a major sulphides only minor p y r i t e , no magneti t e .  P i p e l i k e o r mushroom shaped g e n e r a l l y massive and c r o s s - c u t t i n g . Banding only in hanging w a l l .  Well  Laminated  Good z o n i n g , Cu i s concentrated toward f o o t w a l l . Zn/Cu ratio i n c r e a s e s u p w a r d , Pb o c c u r s i n hanging wall of deposit.  Generally zonino.  Toward the top o f a p i l e of m a s s i v e p y r o c l a s t i cs , f r a g m e n t a l v o l c a n i cs and l a v a s .  Within  P y r i t e and sulphides.  pyrrliotite-dominant Magnetite often in  footwal1.  Form  Geologic  Au, Ag); economic  generally  Underlain  Alteration  DISTAL  DEPOSIT  d i s t a l and sedimentary s u l p h i d e source and paleogeogeography i n occur (based on data from AnderM o r g a n t i , 1979; S a n g s t e r , 1972,  Phanerozoic  ore  decrease  a  in  exhibit  hanging  stratigraphic  wall.  wall .  distinct  metal  from  are  either show a  footwall  variable distinct to  None  evident.  Sediments; only volcanics present up s l o p e .  sedimentary  or  blanket  shape.  pile.  S values  increase  S  from to  lacks  mixed  volcanic  8  and  shaped.  and e r r a t i c , 34  footwall  distinct  banded, s t r a t i f o r m ,  blanket  hanging  are  Distinct increase in i$34s i n c r e a s i n g up section within cyclic evolution of the sub-bas i n .  250  01  r  _i 0.95  i  1  1——i  i  i  i  1  •  1  1  1 1 '  1.00 OENSITY, g / c c  1  1——i !  1  1  1  r  '  1.05  Figure IX-1. D e n s i t y of ore forming b r i n e s , a) Comparison of dens i t y of v a r i o u s b r i n e s , 0.5m s o l u t i o n would approximate seawater (from E l l i s , 1967). b) T h r e e b r i n e types a c c o r d i n g t o Sato (1972) the low temp e r a t u r e dense b r i n e (type I) would most c l o s e l y approximate a b r i n e moving along the sea f l o o r or trapped in a s u b - b a s i n .  251 km of the Howards out,  shale-out  Pass.  where  formation out of  near the  South Nahanni  These v o l c a n i c s suggest a  hot  brines  of the  could  have  brines  (Figs.  (Degens  solutions sion,  IX-2 and  (Turner,  Ross,  1973)  plain  density the  and/or  generally  an i d e a l i z e d  active  heat  and  flow  at  B r i n e s exhaled at in  the  the  s u b - b a s i n s at studies  experimental  show t h a t once a b r i n e  the  thermal  stratification  member c y c l e .  generation type  (Fig.  contents  IX-4)  which may  tion.  Sulphur i s o t o p e data  Anderson  Zn and Pb s u l p h i d e s  (1978)  s u l p h i d e was generated  those b r i n e s  has  at  the  of  in  the  of M i s s i s s i p p i V a l l e y  must  have  had a low  sul-  of d e p o s i -  Howards Pass d e p o s i t s suggest  site  in  steps to  reviewed  t h a t s u l p h u r was added at the s i t e from the  ex-  proceeding up s e c t i o n  D e p o s i t i o n of  1978).  d e p o s i t s and concluded t h a t and t h e r e f o r e  salt  i s c o n f i n e d in a d e p r e s -  of b r i n e s r e s p o n s i b l e f o r the f o r m a t i o n  phur content  the  (Lydon,  Red Sea  Howards Pass s u b - b a s i n s , upgrading can o c c u r  i n c r e a s i n g metal  formation  shale-  with  the s u b - b a s i n s may have o c c u r r e d , p o s s i b l y through i n t e r m e d i a t e sulphide  with  the base  on the  modelling  of  shale-  contemporaneously  Evidence from  1969)  and 12 km northeast  exhaled  confined  and I X - 3 ) .  such as those of the  due to  high  Howards Pass s u b - b a s i n s .  c o u l d move down s l o p e u n t i l slope  been  River  d e p o s i t i o n , perhaps  that  biogeni-  cally. T h e above model  a p p l i e s to  sulphide deposits ( e . g . member c o u l d be the  the  XY, ANNIV and O P ) .  result  of the  suming  cycle  of  the  the  X^ s o  active  and  member  pH were  of  the  of b r i n e  The d e p o s i t i o n a l (Fig.  major  Howards Pass  The c y c l i c i t y  interaction  t i o n of the s u b - b a s i n environment. ideal  formation  Ill-6)  controlling  of the  type  active  supply and e v o l u -  trends  noted i n  can be e x p l a i n e d factors  in  the  by a s -  deposition  Shale out and /or Sea  Level  Fault I  Figure IX-2. Sedimentary e x h a l a t i v e model f o r the Howards Pass d e p o s i t s . Deep m i g r a t i n g f l u i d s move t o and up s h a l e - o u t a n d / o r f a u l t and migrate down s l o p e , where they are trapped i n s u b - b a s i n s . B r i n e moving down s l o p e would be a Zn r i c h , Cu p o o r , low temperature high d e n s i t y b r i n e (type I of S a t o , 1972).  253  Figure IX-3. Plan view of the model f o r the f o r m a t i o n of the Howards Pass Zn-Pb d e p o s i t s . B r i n e s are exhaled along the s h a l e - o u t at the edge of the Selwyn Basin with a s s o c i a t e d b a s i c v o l c a n i c m a t e r i a l ( l i n e pattern). These b r i n e s migrate down slope (arrows) because of t h e i r dens i t y and c o l l e c t i n the s u b - b a s i n s at the base of the slope where d e p o s i tion occurs.  P~=3> DENSE BRINE MOVING DOWN SLOJ  NORMAL SEAWATER  OVERSPILL  SLOPE  MOST SALINE HIGHEST TEMPERA-' TURE SOLUTION  T !  * .-pAblN U B  Figure IX-4. Formation of b r i n e i n s u b - b a s i n . B r i n e f i l l s in s u b - b a s i n from below with continuous f l o w e v e n t u a l l y forming a s t a b l e s t r a t i f i c a t i o n b r i n e with more dense b r i n e concent r a t i n g at base of s u b - b a s i n (Based on data from T u r n e r , 1969, adapted to geology of the Nahanni map-area).  255 within  the  controlled  sub-basins. to  The  a large  pH of  extent  i n the  pH d r o p ,  brine  with  CaC03 and p r e c i p i t a t i o n be the  result  associated  of  both  cooling  subsequently  f o l d s and f a u l t s . major  implied  contorted scale  slumps  reduction  and  by  slumping  IX-5).  cause  II,  III  and IV)  Consideration  of  and  the  active  These and  starved slope,  should be basins  chert  A of  and were  regional  but  subsequently no such  all  large  have  been  (see c r o s s - s e c t i o n s  IX-7).  above model  for  finding  early  (Appendix  I)  showing  shelf  Specific  anomalous (Zn and Pb) s u b - b a s i n s at  the  Regional  at  facies.  and  To date,  deposits,  aimed  basin  deposits  later,  member  IX-6).  similar  d e p o s i t s has economic i m p l i c a t i o n s . deposits  dissolution  p o s s i b l y mixing  1972).  slumping,  (Fig.  in  (Fig.  the  both  Sulphide deposition could  g e o m e t r i c a l l y m o d i f i e d by l a t e r f o l d i n g and f a u l t i n g on P l a t e s  formation  to CaCC>3 p r e s e r v a t i o n .  could  Sato,  much of  found  ammonia  part of the XY s u b - b a s i n was upgraded by  and f a u l t i n g  been  up,  compaction,  of  sediments may have been  pH change  1978;  F o r example,  have  build (Fig.  (Anderson,  by f o l d i n g  pH f a v o r a b l e  o f Si02  modified  original  by s u l p h i d e a n d / o r  of which can cause a r i s e associated  the  origin  the  Howards  exploration-plays  Paleozoic (or  targets  platform  reef),  f o r such marginal  slope,  should be  Pass  base  of  geochemical l y  the base of s l o p e . The importance  of  paleogeography i s o b v i o u s ; and may i n d i c a t e t h a t the c h a s i n g of p o s s i b l e s u l p h i d e t r a p s would be more rewarding than d e f i n i n g base metal s o u r c e s . Once the s u b - b a s i n environment attempt  to  sub-basin  define since,  grade in  the  has been d e f i n e d ,  trends case of  are of higher grade than the  rest  and the  the  location  XY d e p o s i t ,  of the  deposit.  initial of it  drilling  slumps appears  should  within that  the  these  c  B  C a C O j or  Si0  [min.  pH  XH S 2  2  max}  5 6  7  INTERPRETATION 8 Opening of sub-basin and/or d e s t r u c t i o n of chemocline.  J  V  7"V ^  3  /  I n t e r m i t t e n t deposition of sulphide (evolution and upgrading of b r i n e ) .  /\  /  \  \  / I  \  \  / -A I s o l a t i o n of sub-basins (sedimentary l i p and/or chemocline develops).  Figure IX-5. I n t e r p r e t a t i o n f o r the o r i g i n of the ideal c y c l e in the a c t i v e member. The i d e a l c y c l e i s shown at the l e f t with numbers r e f e r r i n g to i n d i v i d u a l f a c i e s : 1) l i g h t grey basal l i m e s t o n e , 2) graded l i m e s t o n e , 3) t h i n bedded c a l c a r e o u s mudstone, 4) mixed c h e r t y mudstone and l i m e s t o n e , 5) c h e r t y mudstone, 6) t h i n bedded c h e r t y mudstone, 7) w h i t i s h grey Zn-Pb mudstone, 8) grey chert f a c i e s . Column A shows r e l a t i v e p r o p o r t i o n s of CaC03 and S i 0 . Column B shows the X ^ ^ s based on the s u l p h u r i s o t o p i c d a t a . Column C shows probable pH f o r b r i n e and sediment (Anderson, 1975, 1978; B e r n e r , 1971). The i n t e r p r e t a t i o n column e x p l a i n s the events a s s o c i a t e d with these t r e n d s . The diagram i s schematic and no s p e c i f i c numbers are i m p l i e d . 2  metres Figure IX-6. Plan area d e l i n e a t e s up-graded t i o n of t r a n s p o r t , .heavy holes and peaks are shown  view of the proposed major slump i n the XY Zn-Pb d e p o s i t . C r o s s - h a t c h e d slump a r e a , s t i p p l e d area d e l i n e a t e s slump s o u r c e , arrows show d i r e c dashed l i n e shows o u t l i n e of XY s u b - b a s i n . The l o c a t i o n of some d r i l l for location reference.  cn  258  Figure IX-7. Diagrammatic e v o l u t i o n of the XY s u b - b a s i n , a) O r i g i nal d e p o s i t i o n of synsedimentary Zn and Pb in s u b - b a s i n s , b) major l a r g e s c a l e slumping o f the a c t i v e member i n the XY area a f t e r d e p o s i t i o n of the a c t i v e member, p o s s i b l y d u r i n g i n i t i a l d e p o s i t i o n of the upper s i l i c e o u s mudstone member, c) Cretaceous f o l d i n g and f a u l t i n g of the s u b - b a s i n . The d e t a i l e d e v o l u t i o n i s more complex than shown, but t h e s e t h r e e events have produced the major c h a r a c t e r i s t i c s of the XY d e p o s i t , w h i l e a and c have been important i n a l l t h r e e d e p o s i t s .  259 A  CLASSIFICATION  DEPOSITS:  present  oriented  ore  deposits tion, the  investigation  g e o l o g i c model  research  mentary  STRAT I FORM-SEDIMENT ARY  i s the  the  are  not  exploration  attempt i s made at ploring for  aimed  Howards that  efficiency  classification  has to  Pass  Raybould,  conformable  and S a t o ,  exploration  of  the  to  some extent  the  the  likely  sulphide  the  date,  in  stratiformother  of  sedisimilar  basis for  explora-  deposits.  deposit  of  somewhat  here,  do  (Sangster, similar not  show  to  1970;  the  such an  of  volcanic  a  Here in  of an ex-  and Mannard,  obvious  Kuroko Lambert  1974)  and Lamarche,  processes because  and S c o t t ,  Pass  deposits  1974;  with  volcanic-exhalative  Howards  Stan-  such as the  Ishahara,  their  (e.g.  sulphide  and t e m p o r a l l y ,  Sangster  in  satisfactory  confusion  (McAllister  spatially  1972;  lack  Examples  (Walker  submarine  which a i d s  stratiform  rocks.  New Brunswick  result  the  caused general  enclosing  a s s o c i a t e d , both  deposits  are  a valid  in a framework  of submarine v o l c a n i s m . Such d e p o s i t s are  sidered  Ba  result  d e p o s i t s which may a i d  By d e f i n i t i o n  Kidd Creek  deposit  intimately  which  AND  exploration  One  for  stratiform  stratiform  1933);  1978).  with  1974),  Bathurst  are most  an  deposits.  even though a l l  d e p o s i t s of Miocene age i n Japan ( T a t s u m i ,  are  Aq  specific types.  (Lindgren,  the  Cu,  may be o b t a i n e d by c o n s i d e r a t i o n  setting  classifying  interpretation  are  Pb,  constructing  Although s t i l l  Ore d e p o s i t s must be c l a s s i f i e d  1972;  at  identical,  done by a n a l o g y .  better  is  realization  deposits  is  for  tectono-stratigraphic  ton,  Zn,  AN EXPLORATIONISTS VIEW  The  this  FOR  1976).  deposits,  association  and  with  and 1972) they  products stratiform Deposits are  con-  submarine  260  volcanic  rocks,  but are sedimentary-type  stratiform  sulphide  deposits.  E x a m p l e s o f t h i s c l a s s i n c l u d e Howards P a s s , S u l l i v a n , t h e Z a m b i a n C o p p e r Belt  and t h e Mt. I s a a r e a  deposits.  General  characteristics  of this  c l a s s o f d e p o s i t s a r e l i s t e d below. (1)  The d e p o s i t s surrounding  are g e n e r a l l y conformable sedimentary  with t h e bedding  of the  r o c k s , and a r e t a b u l a r t o l e n t i c u l a r i n  shape. (2)  Those d e p o s i t s o c c u r r i n g i n metamorphosed sedimentary  r o c k s show  s u l p h i d e t e x t u r e s i n d i c a t i v e o f metamorphism. (3)  The d e p o s i t s  show  no  obvious  association  with  volcanic  or  plutonic rocks. (4)  Deposits  o f t h e same a g e and s h o w i n g t h e same  f r e q u e n t l y occur grouped (5)  The d e p o s i t s , basin,  when  although  into metallogenic  grouped,  individual  occur  deposits  characteristics  provinces.  i n one m a j o r may o c c u r  sedimentary  within  separate  sub-basins. (6)  M o s t o f t h e d e p o s i t s show o r d i n a r y Pb i s o t o p e  systematics.  (7)  In g e n e r a l ,  with  sedimentary  the deposits  lateral but  and i n g e n e r a l dimensions  a l l deposits  carbonaceous  rocks.  Much o f t h e w o r l d ' s deposits  are associated  Z n , Pb and Cu i s won f r o m the deposits  are large.  of this class of deposits  stratiform-sedimentary The t h i c k n e s s e s and  vary widely  (Table  a r e , however, t a b u l a r i n shape, and t h e i r  are small r e l a t i v e t o t h e i r l a t e r a l dimensions.  When g r o u p e d  d e p o s i t s show t h e p r e s e n c e o f m e t a l l o g e n i c e p o c h s ( F i g .  IX-8).  IX-2),  thicknesses by a g e , t h e  T a b l e IX-2. General s i z e of s t r a t i f o r m - s e d i m e n t a r y s t i t u t e the major world d e p o s i t s of t h i s c l a s s .  sulphide  deposits.  These  deposits  DEPOSIT  AREAI- EXTENT  THICKNESS  REFERENCES  Zambian Copper Belt  Overall 3 . 5 x l 0 km . Individual Deposits > 3 km  Variable 50 cm - 10 cm  Mendelsohn, 1961; F l e i s c h e r et a l . , 1976  Overall 5 x l 0 km . Individual Deposits 10 km  8 - 30 m  Smith, 1976; Johnson and Croy, 1976  16 km'  1 - 8 m  White and W r i t e , 1954 , Ensign et a l . , 1968  15 m  H a r r i s o n , 1974  ?  3  2  West Texas Oklahoma  3  2  2  White P i n e , Mi ch i gan B e l t Super Group (U.S.A.)  = 1.4 km  Grinnel Formation, A l b e r t a , Canada  3 2 Overall 1x10' km . Individual occurrences < 5 km  30 cm - 5  Kupferschiefer Germany  Overall 1 . 2 x l 0 k m . Deposits) 100 km  30 - 50 cm  Wedepohl, 1971; Rentzsch, 1974  1 -• 50 m  Bennett, 1967; Mathias,, and C l a r k , 1975  up to 130 m  Lambert, 1976  Mt. I s a , Aust.  ni  Morton et a l . , 1973  2  3  2  Individual  2  Major Trough ~ e.OxlO' km . Individual Deposits 0.5 km 1  2  2  McArthur Ri v e r , Aust.  H.Y.C. 1.5 km  Dshezkazgan (U.S.S.R.)  not given  up to 700 in  Assanov et a l . , 1974  Tom-Jasen (Yukon-NWT, Cdn.)  0.4 km  2  up to 60 m  Smith, 1978  Sul1i van ( B . C . , Canada)  2.5 km  2  up to 25 m  Freeze 1966, Ethier et a l . , 1976  Howards Pass (Yukon, N.W.T.)  Base of S l o p e " 750 km . deposits 25 km2  2  2  Individual deposits up to 60 m.  PERIOD  TRIASSIC  PERMIAN PENSYLVANIAN MISSISSIPPIAN DEVONIAN  SILURIAN  ORDOVICIAN  CAMBRIAN  HADRYNIAN  HELIKIAN  |==  — 10 l NUMBER  20 i  30 1  OF DEPOSITS  Figure IX-8. Stratiform-sedimentary s u l p h i d e d e p o s i t s grouped by age. Two m e t a l l o g e n i c epochs are e v i d e n t ; the P r o t e r o z o i c and the Permian. Blank bars represent s u b - c l a s s I d e p o s i t s , h o r i z o n t a l l i n e s r e p r e s e n t s u b - c l a s s II, v e r t i c l e l i n e s represent s u b - c l a s s III deposits.  263 S t r a t i form-sedimentary three also  type  sulphide  s u b - c l a s s e s based on sedimentary has t e x t u r a l  these t h r e e cratonic  and geochemical  (2)  turbidite  environment;  this  s u b - c l a s s e s are:  basin  and  (3)  b a s i n environments. T h i s c l a s s i f i c a t i o n has both an ore g e n e s i s and an e x p l o r a t i o n  divided  (1)  classification define  shallow  platform-marginal important  into  intrastarved  implications  from  s t a n d p o i n t . The three s u b - c l a s s e s  are best s t u d i e d from a r e g i o n a l  viewpoint  be d i f f e r e n t i a t e d  of j u s t  by examination  can be  i m p l i c a t i o n s which may f u r t h e r  s u b - c l a s s e s . The three  basin,  deposits  and to a great the  extent may not  s u l p h i d e d e p o s i t s by them-  s e l v e s . The occurrence of s i m i l a r c h a r a c t e r i s t i c s of the d e p o s i t s w i t h i n a s u b - c l a s s suggests t h a t they have roughly s i m i l a r  origins.  S u b - c l a s s 1 c o n s i s t s of s u l p h i d e d e p o s i t s in shallow water, transgressive posits  sequences.  such as those  Zambian  Copper  Cordillera,  in  Belt,  White  Included the  the  Pine  in  sub-class 1  Kupferschiefer  Redstone  (U.S.A.)  of  significant  E u r o p e , Creta  occurrences  and McArthur  are  and  River  usually  Spar  de-  (USA),  Lake  in  (Australia).  the the  These  deposits: (1)  Always occur i n  carbonaceous sedimentary  t h a t formed in s h a l l o w - w a t e r (2)  Frequently (rote  overlie  red  or  near-shore  rich  in  pyrite  environments.  hematite-stained  sedimentary  rocks  faule).  (3)  U s u a l l y occur i n e v a p o r i t e - b e a r i n g  (4)  O f t e n occur near major f a u l t  (5)  U s u a l l y are their  rocks  zones and basement  zoned with r e s p e c t to t h e i r  zoning can be q u a l i t a t i v e l y  scheme.  sedimentary sequences. lineaments.  C u , Pb and Zn c o n t e n t ;  d e s c r i b e d by a simple  zoning  264 Table  IX-3  summarizes the c h a r a c t e r i s t i c s f o r the major  deposits i n c l u d -  ed i n s u b - c l a s s 1. The are the  three fault  (Renfro, (1969)  most c o n s i s t e n t related  1974)  and  brines  the  proposed t h a t  brines  In  debit  produces a c o a s t a l  fluid  migration;  model,  algae and r e d u c t i o n  of  an  model  is  to  this  climate  The  precipitated  as  Copper B e l t  result  diagenetic  d e p o s i t s formed i n t h i s the  epigenetic  phide  rich  model  horizons.  of  way  sulphides Africa  of  (Renfro,  1974;  of  phide d e p o s i t s which are not s t r i c t l y s u l p h i d e may be the phide m i n e r a l s  result  of  t h i s way i s White P i n e , Michigan 1  deposits  may  form  later  diagenetic  acts  of  as a  Van  Eden,  best  re-  1974). of  1976).  In  permiates  sul-  form base metal  sul-  or  replacement  original of  sul-  example of a d e p o s i t formed al.,  to  example  in d e t a i l . The  activity  or  a  is  evaporation  Lee and G l e n i s t e r ,  (Ensign et  syngenetically  1976;  sulphides  (Brown, 1978). The c l a s s i c  at  i n the ascending f l u i d s  stratiform  biogenic  metals  model,  to  mat  through a q u i f e r s  the  Smith  destruction  c o n s i d e r e d the  movement of f l u i d s Replacement  large  leads  algal  model  1968).  in t h i s  bacterial  (Caia,  are  a  which  s u l p h a t e . The H2S laden  deposits  al.,  same f a u l t  with  d u c t i o n membrane t h a t causes the t r a c e metals be  et  volcanism d e p o s i t e d  environment  the  deposits  sabkha d i a g e n e t i c  (Ensign  related arid  sabkha  sulphide  1969), the  sub-class I  the a s s o c i a t e d Cu d e p o s i t  deposit  time.  models f o r  a s s o c i a t e d with  Isa,  c o n s i d e r e d a replacement Sabkha  (Smith,  epigenetic  i n nearby s h a l e s at Mt.  the  general  1968).  diagenetically  in  Thus s u b - c l a s s (Figs.  IX-9,  IX-10). Exploration for this or  intracratonic  basins  s u b - c l a s s of d e p o s i t s should focus on with  associated  red  beds  and  interior  evaporite  se-  T a b l e IX-3. T a b l e of f e a t u r e s a s s o c i a t e d with s u b - c l a s s I type s t r a t i f o r m - s e d i m e n t a r y dep o s i t s (Assanov et a l . , 1974; Ensign et a l . , 1968; F l e i s c h e r et a l . , 1976; H a r r i s o n , 1974; Johnson and C r o y , 1976; Jung and K n i t z s c h k e , 1976, Kirkham, 1974; K r e b s , 1976a, Mathias and C l a r k , 1975; Murray, 1975; R e n t z s c h , 1974; Wedepohl, 1971).  DEPOSIT  SHALLOW WATER CONGLOMERATE  KUPFERSCHIEFER (Germany) CRETA (U.S.A.) DZHEZKAZGAN (U.S.S.R.)  X  ZAMBIAN Cu BELT  X  REDSTONE N.W.T. (Canada) BELT-GRINNELU. S.A.-CANADA WHITE PINE (U.S.A) Mt. ISA-HILTON (Aust.) McARTHUR RIVER (Aust. )  MUDCRACKS  CROSS-BEDS  SHALLOW-WATER MARINE CARBONATES  DOLOMITE  EVAPORITES  RED BEDS  Figure IX-9. G e n e r a l i z e d synsedimentary model f o r the formation of s u b - c l a s s I s t r a t i f o r m sedimentary d e p o s i t s . B r i n e m i g r a t i o n due to compaction or a thermal high cause m i g r a t i o n through red beds i n t o s h a l e s where d e p o s i t i o n occurs in s u b - b a s i n s . Zoning i s evident i n f a u l t c o n t r o l l e d d e p o s i t on r i g h t . r\3  Figure IX-10. G e n e r a l i z e d d i a g e n e t i c model of formation f o r s u b - c l a s s I s t r a t i f o r m s e d i m e n t a r y d e p o s i t s . Deposit on l e f t formed by brine, m i g r a t i o n through red beds i n t o carbonaceous muds t o n e s , d e p o s i t on r i g h t formed by l a t e r a l m i g r a t i o n . In both cases zoning i n d i c a t e s m i g r a t i o n path.  *  ro  268 quences.  Specific  areas  d u r i n g d e p o s i t i o n of the Sub-class thick  II  turbidite  of  interest  appear  sequences c o n s i s t i n g of  to  (Germany),  Tom-Jason  conglomerate.  Examples  (Canada),  c h a r a c t e r i s t i c s of t h i s  be near basement  highs  host b e d s .  stratiform-sedimentary  siltstone  to  deposits  are  associated  graded beds which  of  Sullivan  sub-class (Canada).  II  contain  include  The  major  with fine  Meggen defining  group are:  (1) They are always a s s o c i a t e d with t u r b i d i t e s (2) T h e y are f r e q u e n t l y  of f l y s c h sequences.  a s s o c i a t e d with a major  penecontemporaneous  fault. (3) They are f r e q u e n t l y really  barite  a s s o c i a t e d with b a r i t e  deposits  with  relatively  and in f a c t minor,  but  many are in  some  c a s e s , economic Zn and P b . This  s u b - c l a s s has not  been as e x t e n s i v e l y  studied  as s u b - c l a s s type  and as more s i m i l a r d e p o s i t s are d i s c o v e r e d more c r i t e r i a be d e f i n e d . T a b l e IX-4  lists  examples of s u b - c l a s s II  will  I  hopefully  d e p o s i t s and  their  di s t i nqui shi ng character!' s t i c s . Models f o r the as  for  sub-class  I,  d e p o s i t s may be the ascending to  a heat  from  sive  but  source at  of t h i s two  result  through the  compaction  IX-11).  origin  group of d e p o s i t s are  appear  most  First,  a s s o c i a t e d f a u l t s . These f l u i d s depth  fluids  instead  (Hodgson and Lydon,  (Morganti,  of  as obvious some of  of s y n g e n e t i c s u l p h i d e d e p o s i t i o n from  1977b;  A second p o s s i b l e o r i g i n f o r  sulphides  relevant.  not  laminated  1977)  Godwin  et  fluids  may o r i g i n a t e or al.,  may  the  due  originate  1979)  (Fig.  d e p o s i t s which c o n t a i n mostly massulphides  is  that  sulphate  that  T a b l e IX-4. T a b l e of f e a t u r e s a s s o c i a t e d deposits ( D o r i e p e n , 1976; Dawson, 1977; E t h i e r K r e b s , 1976b; S m i t h , 1978).  DEEP WATER CONGLOMERATE  with s u b - c l a s s et a l . , 1976;  DEPOSIT  GRADED BEDS  SILTSTONE & SANDSTOME  SULLIVAN, ( B . C . )  X  X  X  MEGGAN, (Germany)  X  X  X  X  X  X  X  DRIFTPILE,  X  X  X  X  TOM-JASON, (Yukon)  X  X  X  X  ORO, (Yukon)  X  X  X  NOR, (N.W.T.)  X  X  X  GHMS, (N.W.T.)  X  X  (B.C.)  X  CHERT (R)=RADIOLARIAN  X  RAMMELSBERG, (Germamy) X  II type s t r a t i f o r m - s e d i m e n t a r y F r e e z e , 1966; Fredberg, 1976,  ASSOCIATED FAULTS  X  BARITE  minor  X  X X  ?  X X  X  X  X (R)  X  X  X (R)  X  X  X (R)  X  X  F i g u r e IX-11. G e n e r a l i z e d synsedimentary model f o r the formation f o r s u b - c l a s s II stratiform-sedimentary d e p o s i t s . Shallow source d e p o s i t s ( l e f t ) c o n t a i n only b a r i t e , w h i l e deeper source d e p o s i t s c o n t a i n Zn-Pb and Ag with b a r i t e ( r i g h t ) .  o  271 was  originally  compaction zones  fluids  model  et  al.,  1978; Dozy,  Exploration  specific  III  b a s i n s . To d a t e , concentrations  deposits the Howards  which  are  though t h e present  thesis  III  lack  deposits,  applicability  the  o f these  has shown  defining  is  ( F i g . IX-13) deposits  to  very  deposits  and a l s o  exploration  metals  model  type  diagenesis.  reduced  similar  to  to  the model  and W e l t e ,  by the  search  for  1978).  should focus on major  guided  the  (Jackson and B e a l e s ,  similar  (Tissot  these  Late  flysch  for  graben  and submarine fan geometry.  Sub-class  study  during  provide  This  1970)  f o r s u b - c l a s s II  with  structures  could  1974).  escape f o r o i l m i g r a t i o n  sequences  was reduced  for M i s s i s s i p p i Valley  Anderson,  fluid  barite  ( F i g . IX-12)  (Carpenter  general 1967;  syngenetic  that  occur  in  major  Pass d e p o s i t s  known  to  occur  has examined of  comparison  characteristics the  following  platform-marginal  starved  are the o n l y major  sulphide  in  this  environment.  the key parameters with  other  elsewhere  Even  of sub-class  deposits  makes  the  t e n t a t i v e . The present  characteristics  are  important  in  the s u b - c l a s s :  (1) G r a p t o l i t i c  o r g a n i c - r i c h mudstones are a s s o c i a t e d with the s u l -  phide d e p o s i t s . (2) Paleogeographic sits  interpretation  shows t h a t  occur i n the base o f s l o p e f a c i e s  sub-class  o f an  III  depo-  platform-marginal  basin. (3) T h e s u l p h i d e deepwater stone  deposits  starved  and c h e r t ,  sub-basin  are l i m i t e d  basins. both  environment.  to s u b - b a s i n s w i t h i n  Sulphides  o f which  are a s s o c i a t e d  with  are not common away  larger lime-  from the  F i g u r e IX-12. G e n e r a l i z e d d i a g e n e t i c model of formation f o r s u b - c l a s s II stratiformsedimentary d e p o s i t s . M i g r a t i o n of l a t e stage compaction f l u i d s migrate along sandstone a q u i f e r s and m i n e r a l i z e synsedimentary b a r i t e d e p o s i t .  HYDROCARBONS GENERATED (SCHEMATIC)  WATER ESCAPE CURVE FOR MONTMORILLONTTE RICH MUD (SCHEMATIC) water available for migration  B iochsmJcd CH,, H S 2  Stage I dehydration 8. lattice water stability zone Stage II dehydration Stage M dehydration  1  WATER CONTENT OF SHALES FOR MONTMORILLONTTE RICH MUDS % WATER turfoct 50  80  sediment  Pore 81 excess interlayer water expulsion Lattice water stability zone Interlayer water expulsion by random collapse of montmorillonite-lllite layers krterloyer wal«r expulsion by IntsrtoyiftQ of illile loyers  ordered  Deep burial water loss Interlayer water expulsion complete conversion toilite  Stage TV dehydration  Figure IX-13. Water escape curves f o r various temperatures and depths of b u r i a l . These curves are u s e f u l i n r a p i d l y d e p o s i t e d sediments, but may not be a p p l i c a b l e to s t a r v e d b a s i n s (data from Powers, 1967; B u r s t , 1969; Chapman, 1972). E x p u l s i o n of ore forming f l u i d s could o c c u r d u r i n g Stage II d e h y d r a t i o n of Stage I i f a high geothermal gradient i s p r e s e n t .  274 (4) The  rate  of  deposits is  deposition  for  the  relatively  thick  starved  basin  slow, l e s s than 10 mm/1000 y r s .  (5) T h e s u l p h i d e d e p o s i t s are not a s s o c i a t e d with anomalous amounts of  pyrite  compared  to  that  found  in  associated  sedimentary  rocks. Specific characteristics are  presented i n T a b l e The  the  general  present  movements  are  d e p o s i t s of s u b - c l a s s  for  the  s u b - c l a s s III  deposits,  in  sub-basins.  Sulphide  b r i n e s c o u l d be due to pH change, mixing and  key in  sedimentary such a  for  should  basins.  Such b a s i n s  Central  Nevada  (Fig.  matter (Figs. facies,  and  of  (Twenhofel, IX-15,  presented  to  in  the  for  mudstone  major  climatic  1939;  Ryan  prime  regional  the  and  both  of  1974;  in  locating  of  the  deposition Berry  and  and/or  the  base  geochemical  of  slope  facies,  anomalies  of the major b a s i n f o r  the  location  should a i d  s u b - c l a s s III  1977)  such of  se-  organic  Wilde,  of  in  contain  Ross,  aid  1977;  starved  which  may  Cita,  objective  O r d o v i c i a n - S i l urian  sequences ( C h u r k i n ,  control  these  locating  platform-marginal  geocline,  reconstructions  the  should be aimed at  example  Ouachita  from  sulphidation.  I X - 5 ) . The  locate  deposition  in  crustal  I X - 1 6 ) . Once such a b a s i n has been found d e f i n i t i o n  especially  potential  be  deposits  (Table  exist,  Paleopole  because  sub-basins  do  organic-rich  IX-14).  quences  s u b - c l a s s III  environments  search  graptolitic  as  proposes t h a t b r i n e s d e r i v e d by compaction or  trapped  Exploration  III  H-5.  model  study,  noted in i n d i v i d u a l  1978) of  the  possible  in e v a l u a t i o n  of  the  Zn-Pb d e p o s i t s .  METALLOGENY OF THE EASTERN YUKON Aho (1969) v i n c e ; over the  suggested t h a t the  eastern  Yukon i s  past 10 y e a r s h i s g e n e r a l i z a t i o n s  a Zn-Pb and W p r o -  have proven  essential-  Table deposits.  IX-5.  Table  of  features  PYRITE CONTENT OF HOST ROCKS' DEPOSIT  ol lo  GRAPTOLITES  associated  with  PYRITE CONTENT OF DEPOSIT  sub-class  III  SUB-BASIN  type  stratiform-sedimentary  BASE OF SLOPE FACIES  MIXED LIMESTONE AND CHERT  XY  X  2-5  2-5  X  X  X  ANNIV  X  2-4'  2-4  X  X  X  OP  X  2-4  2-4  X  X  X  ITSI  X  5  5  X  X  X  PAB-HUG  X  1-4  1-4  X  X  X  276  Figure IX-14. O r d o v i c i a n - S i l u r i a n s i l i c e o u s mudstones of North America. Dash l i n e s show areas of o r g a n i c r i c h mudstones s i m i l a r to those d e p o s i t e d i n the Selwyn-Basin during the same time p e r i o d . (Based on data from R o s s , 1977; P a t t e r s o n , 1961; B e r r y , 1970). These s i l i c e o u s mudstones are prime t a r g e t areas f o r e x p l o r a t i o n f o r Howards Pass type d e p o s i t s .  Figure IX-15. Late O r d o v i c i a n p a l e o c o n t i n e n t a l map, using X path and Y p a t h . 'S(N) i s the south (north) geographic pole determined from apparent p o l a r wandering paths (from Morel and I r v i n g , 1978). At t h i s time Howards Pass (X) was not f a r from the e q u a t o r . The c l o s e n e s s to the p a l e o - e q u a t o r may be s i g n i f i c a n t s i n c e sediments near the equator tend to c o n t a i n h i g h e r organic carbon.  ro  Figure IX-16. Late S i l u r i a n to Middle Devonian p a l e o c o n t i n e n t a l map, using X path and Y path. S(N) i s the apparent p o l a r wandering paths (from Morel and I r v i n g , 1978). Note t h a t d u r i n g t h i s time the Howards Pass area was s t i l l near the e q u a t o r .  ro oo  279 ly  correct,  lished  but  whereas  models  1975;  Smith,  (Morganti,  for  individual  1978;  Dawson  deposits and  models have not been presented based on r e g i o n a l It are  i s evident  related  which  to  show a  stratigraphy. close  intrusions,  on these  deposits.  and Yara  Peak  the  and  although  rich  throughout  to the  difficult  and  the  Pass  is  Itsi  overall  environments.  unit  in  Pass  the  W deposits,  with  in  Cretaceous  the  area  Iron and  MacMillan  Cretaceous r e g i o n a l  extent  the  area  have some c o n t r o l  occur  The a s s o c i a t i o n of  regional  are  appears to  Howards  a s s o c i a t e d with t h r e e major of these p o t e n t i a l l y  because of Mountains  applicable, section  local  structure  r e p o r t e d on l i m i t e d  facies the  with  stratigraphic graben  this  Creek  locally  Pass  area.  cleavage i n  units  c o p p e r - r i c h veins and  suggests a  lateral  Zn-Pb a n d / o r b a r i t e o c c u r r e n c e s i n the  logic correlation is  pub-  secretion  veins.  The major specifically  of  to  veins  the  conglomerate  parallel  sediments  o r i g i n f o r the  1978)  geologic  association  stratigraphy  t h a t c o n t a i n over 150 ppm C u . copper  temporal  Tetrahedrite-quartz  pebble  T h e s e v e i n s occur  Exceptions  spatial  formations  chert  Dick,  been  t h a t most s u l p h i d e and s u l p h a t e d e p o s i t s in t h i s  granitic  above  have  in  stratigraphic  the  MacMillan  there  (Smith,  (Fig.  IX-17).  economically s i g n i f i c a n t  changes.  relatively  horizons  e a s t e r n Yukon  For  example,  section  minor Pass 1978).  between  area  is  Tungsten Howards  while  different  Recently  the  due to a  Dawson  f o s s i l c o l l e c t i o n s from the MacMillan Pass  Litho-  horizons  d e s c r i b e d at  modification,  are  (1977)  area.  " . . . A limestone bed immediately u n d e r l y i n g the Pb-Zn-Ba h o r i z o n on the PETE c l a i m s c o n t a i n s l a t e Devonian conodonts ( B . E . B . Cameron, p e r s . comm., 1976). A limestone bed about 100 m. s t r a t i g r a p h i c a l l y below w i t h e r i t e - b a r i t e beds on the BAR c l a i m s c o n t a i n s e a r l y to  280  PERIOD  STRATIGRAPHIC SECTION AT HOWARDS PASS  STRATIGRAPHIC SECTION AT MACMILLIAN PASS ( a f t e r Smith. 1978)  MINERAL DEPOSITS (see appendix D for l o c a t i o n s )  uni t ' 3 barite  top of section i n the Howards Pass area  M i s s i s s i p p i an  horizon  Pete (Ba)  unit 2 barite  'cKerf pebble conalomerate unit  horizon  Tom-Jasen (Ba, Zn, Pb, Ag), Tea ( B a ) .  horizon  GHMS ( B a ) , 0R0 ( B a ) , NOR ( B a , P b ) , Moose (Ba).  Yara Peak fm. Iron Creek fm. f£SS3 Selwyn Mtns. bari te hori zon  Devoni an  upper chert fm.  flaggy mudstone fm. Si l u r i an Howards Pass fm.  .  unit 1 VVVM  barite  Road River fm. MacPass graben established bottom of section in the MacPass area  active member XY (Zn, P b ) , ANNIV (Zn, Pb), OP (Zn, P b ) . ITSI ( Z n ) , PAB-HUG (Zn)  Ordovi ci an  Howards Pass fm.  t r a n s i t i o n fm.  Cambri an  Figure Millan  Pass  deposits.  IX-17. area  Comparative s t r a t i g r a p h y showing  stratigraphic  of  the  position  of  Howards Pass Zn-Pb  and Mac-  and/or  barite  281 M i d d l e Devonian conodonts (Cameron, p e r s . comm., 1976). In the same a r e a , but 1 km. to the south noted l a t e Devonian c o r a l s i n r e e f a l carbonates u n d e r l y i n g b a r i t e b e d s . A l a t e Devonian age of these b a r i t e beds i s i n d i c a t e d . Limestone beds w i t h i n the t h i c k TEA b a r i t e sequence c o n t a i n D e v o n o - M i s s i s s i p p i a n conodonts and a brachiopod t e n t a t i v e l y a s s i g n e d to the same broad range by Comeron ( p e r s . comm., 1976). Carbonized wood of i n d e t e r m i n a t e genus was c o l l e c t e d a few metres below m i n e r a l i z a t i o n beds at TOM by Sangster (1971), and s i m i l a r m a t e r i a l was found at about the same h o r i z o n at JASON by C L . Smith ( p e r s . comm., 1976). These d e p o s i t s may be M i s s i s s i p p i a n , as may the widespread nodular and l a m e l l a r b a r i t e occurences higher in the Canol F o r m a t i o n , but d e f i n i t i v e fossil evidence i s l a c k i n g . "  Further reported  fossil  by Carne  information  on the M a c M i l l a n  Pass area  was  recently  (1979).  " . . . N o f o s s i l s or t r a c e f o s s i l s were seen in rocks of Unit 1" (same nomenclature as F i g . IX-17 page 280). "An ammonite was c o l l e c t e d i n 1976 by J . A . Morin from a d e n s e , b l a c k , n o n - c a l c a r e o u s mudstone which u n d e r l i e s beds of Unit 1 about 1 km. east of the detailed study area ( J . A . M o r i n , p e r s . comm., 1976. The f o s s i l was subsequently i d e n t i f i e d as P o n t i c e r a s c f . P. tschernyschewi (Hozapfel) of Upper Devonian ( F r a s n i a n ) a g e . . . "  Thus the  age of the TOM b a r i t e d e p o s i t  More the  Howards  include age. of  recently  map-area  conodonts  There  the  Pass  fossils  have  been  (S.P.  Palmatelepsis  appears  from the  glabra  conodonts were e x t r a c t e d  are  to  mapping  several  indicates  that  different the  written of  from  Comm.,  lenses have a l s o been observed in the  Earn Group 1979).  (Upper  from grey  These  position  Howards Pass mudstones  horizons.  The  weathering  area, which  author's carbona-  pebble c o n g l o m e r a t e ,  brown weathering  in  Devonian)  stratigraphic  carbonaceous  stratigraphic  conodonts are  the  Famennian  as to the  ceous mudstone which occur w i t h i n the c h e r t  tion.  from  Earn Group in the  because the similar  collected  Gordey,  to be disagreement  f o s s i l s collected  should be F r a s n i a n or y o u n g e r .  Yara Peak  similar Forma-  These areas are  of  weathering  poor exposure.  from  chert  grey  lenses  carbonaceous mudstones  rocks  h o r i z o n , which that  would  Pass a r e a .  (2)  Dawson, Oral  and the  the  the  f o s s i l s are  presented  Pass  then  barite  problem, but  in  the  present  Howards  Pass  All  both  the  is  Pass  areas  correlated  conodont  would be u s e f u l data  with  in  the  sulphide  to  a  the Pass  eroded Howards as i s  Gordey and  Barite data  Horizon  collected  in s o l v i n g  supports the  the  are  or  Iron Creek f o r m a t i o n ,  More  Thus,  fossils  then the M a c M i l l a n  Selwyn Mountain  control  thesis.  areas  the  formation,  the  deposits  stratiform.  major  higher,  observed by the  The Howards  The  of s u b - c l a s s reason  for  sedimentary-tectonic d e p o s i t s are  Zn-Pb  this  correlation  horizons  great  extent  Ba  horizons  and/or  Selwyn Mountains  and MacMillan  little  in  the  different  present  are  Pass  understood, b a r i t e  author  Pass d e p o s i t s d e f i n e  b a r i t e d e p o s i t s with or without  typical  Pass  the  formation  conglomerate  from the  available  h o r i z o n s and a s t r a t i g r a p h i c a l l y  the  Peak  If  in  IX-17). Within  zon.  pebble  horizon.  the  Howards Pass and M a c M i l l a n (Fig.  Yarrow  (1)  problems  G e o l o g i c a l Survey of Canada ( S . P .  from areas of good s t r a t i g r a p h i c stratigraphic  exist:  proposed h e r e ,  chert  Comm., 1979),  MacMillan  the  stratigraphic  hosts the Tom d e p o s i t ,  proposed by members of the K.  of  as i s  overlie If  cause  Two p o s s i b i l i t i e s  pebble conglomerate,  barite  may  in  these  barite hori-  horizons  are  while  all  s u b - c l a s s III,  Zn and Pb (Ag)  the  have c h a r a c t e r i s t i c s  II. the  Zn-Pb  features  province are  is  present  a s s o c i a t e d with the  not in  starved  clear.  the  Three  region.  Selwyn B a s i n ,  separate  The  Howard  the  Selwyn  283. Mountains b a r i t e formation MacMillan basins be  Pass  in  producing  general. metal  its  The  rich  in  the  metals,  although  advection  needed i n t h i s  in it  the is  important  a s s o c i a t e d with  Iron Creek  likely  sulphide by  that  deposition  or  of  model field.  for  the  Howards  Pass  carbon  1971;  than  during  deposits,  to  in  1972,  is  Thus  of  de-  in  Richard,  deposits  metals  as has been suggested e a r l i e r  sediments  adsorption.  of the  the  (Rashid,  organic  (Berner,  chelation origin  Paleozoic  in  complexing  demonstrated  the  appears  sulphides  metal-organic  been  case of  in the in  of  the  the  evolution  L o c a l l y o r g a n i c matter  has  more  of  metals  important  be  effectiveness  generation the  to  a s s o c i a t i o n with  sediments  here  concentrating  may be more  appear  migration.  because of  o r g a n i c matter i s  the  fluid  considered  important  it  All  Degens, 1974), but  region  than  area.  and r e l a t e d  posits  in the  and the Tom-Jason d e p o s i t s are a s s o c i a t e d with a graben in  important  1974;  h o r i z o n i s a s s o c i a t e d with t u r b i d i t e s  the more 1973)  while  in the Yukon,  as  source  of  consideration  of  more  a  research  is  284  REFERENCES Aho, A . , 1969, Base metal v . 62, p. 7 1 - 8 3 .  p r o v i n c e o f Yukon:  C a n . 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C , 1954, The White Pine copper d e p o s i t , Ontonagon County, Michigan: E c o n . G e o l . , v . 49, p. 675-716. W i l l i a m s , E . , 1963, Convolute f o l d s and movement in water logged g r a n u l a r sediments iR S.W. Carey e d . , Syntaphral t e c t o n i c s and diagenesis: U n i v e r s i t y of T a s m a n i a , H o b a r t , p. 11-15. W i l l i a m s , N . , 1978, S t u d i e s of the base metal s u l f i d e d e p o s i t s at McArthur R i v e r , Northern T e r r i t o r y , A u s t r a l i a : I. The Cooley and Ridge d e p o s i t s : E c o n . G e o l . , v . 73, p. 1005-1035. W i l l i a m s , P . F . , 1977, F o l i a t i o n : p h y s i c s , v . 3 9 , p. 305-328.  a review  and d i s c u s s i o n :  Tectono-  W i l l i a m s , P . F . , C o l l i n s , A . R . , and W i l t s h i r e , R . G . , 1969, Clevage and penecontemporaneous deformation s t r u c t u r e s i n sedimentary r o c k s : J . G e o l . , v . 7 7 , p. 415-425. W i l s o n , J . L . , 1975, Carbonate f a c i e s V e r l a g , New Y o r k , 471 p.  in geologic h i s t o r y :  W i n k l e r , R . L . , and Hays, W . L . , 1975, W i n s t o n , New Y o r k , 889 p .  Statistics:  Wolf,  K . H . , 1976, Handbook of s t r a t a - b o u n d v.1-6: E l s e v i e r , Amsterdam.  Holt,  Springer-  Rinehard  and s t r a t i f o r m  and  ore d e p o s i t s ,  Woolnough, W . G . , 1937, Sedimentation in barred b a s i n s , a source rock o i l : Amer. A s s . P e t r o l . G e o l . , B u l l . , v . 21, p. 1101-1157. Y o r k , D . , 1969, correlated  Least squares f i t t i n g of a s t r a i g h t errors: Earth P l a n e t . S c i . L e t t e r ,  l i n e with v . 5, p. 320-324.  of  309  Zakharov, Y . Y . , 1977, D e p o s i t s of f o s s i l and C o . , New Y o r k , 270 p.  fuels,  v . 6:  G.K. Hall  Z a n g e r l , P . , R a i n e r , D . , and R i c h a r d s o n , E . , 1963, The p a l e o e c o l o g i c a l h i s t o r y of two Pennsylvanian black s h a l e s : F i e l d i a n a - G e o l . Mem. v . 4 , 352 p. Z o b e l l , C . E . , 1958, Ecology of s u l f a t e - r e d u c i n g M o n t h l y , v . 22, p. 12-29.  bacteria:  Producers  310  APPENDIX A- PLATE LOCATION MAP  F i g u r e A - l . L o c a t i o n map showing the map areas f o r P l a t e s and IV in the Nahanni map-area.  I,  II,  III  311 Appendix B  MINERAL IDENTIFICATION METHODS  The method of is  semi-quantitative  present  study  that  studied  by methods  of  Schultz  described  by  mineral (1964).  Carroll  identification Clay  (1970).  samples from d r i l l  cores were analyzed by x - r a y  aluminum  mount.  1962).  pack-type  L o c a t i o n and i n t e n s i t y  corded.  Klug  and  in  (1964)  operator  Inconsistency nation  of  greater erally  found t h a t  repeated  s a m p l i n g , sample p r e p a r a t i o n ,  by the  the  of  all  clay  to  using an  and r e -  derive  ± 10%.  the  If  Minerals  present  indicated  p r e c i s i o n of  a  sample, the  analyses  that  machine response and  has the  minerals.  than 15% of the is  affect  interpretation  due to  a broad  carbon compounds in  greatest  mineral  x-ray effect  is  the  its  i n amounts of  increase the  in  interpreta-  on the in  mudstones. C u b i t t  (1975)  but  because of the general  present  The those  x-ray  diffraction  recommended  by  which enhanced basal was  placed  nature  on  a  of the  methods  Carroll  reflections glass  slide  of the and  an  amount  percent  to  be a  gen-  or  less  undetectresult  reduced the  of  error  h i s m o d i f i c a t i o n s were not used  used to  (1970).  has  determi-  determination  a few  background b e l i e v e d  varia-  determinations.  present  p r e c i s i o n of  t o 6% by complex sample p r e p a r a t i o n ,  ry  rock  Alexander,  are not c o n s i s t e n t l y d e t e c t e d . M i n e r a l s with l e s s than 5% were able  further  s t r i p chart  standards  the  percentages.  Schultz  tion  diffractometer  was measured from the of  were  Representative  procedure;  Sample data was compared with t h a t  mineral  tions  (McCreery's  minerals  used i n  study. identify  Samples  were  clay  prepared  phyllosilicates. diffractograms  minerals in  are  a way  A sample s l u r -  made  after  drying  312  overnight hour  in  a desiccator.  in a f u r n a c e ;  after  Samples were  c o o l i n g to  then  heated  at  500°C  for  room temperature  in  a desiccator,  another d i f f r a c t o g r a m was made of the s l i d e . The major c l a y mineral fractogram peak minerals tion the  present  noted was at were  limited  approximately to  illite  (Figure 4,  peak  (IMQ)  being more d i f f u s e  C a r r o l l , 1970;  G r i m , 1968).  the  dif-  possible clay  a n d / o r m u s c o v i t e . The d i s t i n c -  between the m i n e r a l s was based on the i l l ite  1 0 ° . Thus,  one  sharpness of than  the  the  muscovite  8.1° (2M)  peak, peak  APPENDIX C  LOCATION OF STRATIGRAPHIC SECTIONS  Figure C-l. L o c a t i o n of s t r a t i g r a p h i c s e c t i o n s d i s c u s s e d i n t e x t . Identification is G . S . C . nomenclature, and r e f e r s to the composite s t r a t i g r a p h i c s e c t i o n s presented in chapter Ba denotes b a r i t e s e c t i o n ( F i g . 1 1 - 2 6 ) .  by II.  Figure D - l . L o c a t i o n map Yukon and Northwest T e r r i t o r i e s mark s p e c i f i c l o c a t i o n s .  of Z n , Pb and Ba o c c u r r e n c e s in the r e f e r r e d to in the t e x t . Triangles  APPENDIX  TABLE  ELEMENT  E-l.  E.  CHEMICAL METHODS AND DATA FOR CHAPTER VI  Methods used i n chemical  METHOD  analyses oF Howards Pass sampl  DETECTION  PRECISION  LIMIT (ppm)  Mo  AAS  1  ± 10%  Cu  AAS  2  ±  5%  Zn  AAS  2  ±  5%  Pb  AAS  2  ±  5%  Cd  AAS  0.2  ±  5%  Ni  AAS  2  ±  5%  Co  AAS  2  ±  5%  Ag  AAS  0.02  ± 10%  Mn  AAS  2  ±  V  AAS  10  ± 15%  Ba  AAS  400  ± 20%  Fe  AAS  2  ± 10%  Ca  AAS  500  ± 15%  Mg  AAS  500  ± 15%  K  AAS  500  ± 15%  Na  AAS  200  ± 15%  P  AAS  500  ± 10%  S  LECO  500  ± 10%  L0I(550°C)  300  ± 15%  L0I(1050°C)  500  ± 15%  XRF  0.5%  ± 10%  XRF  0.1%  ± 15%  C  (org)  C  (C0 =)  5%  3  Si0  2  A1 0 2  3  AAS = atomic a b s o r p t i o n  spectrometry  LOI = l o s s on i g n i t i o n XRF = x - r a y s p e c t r o c h e m i s t r y  (flourescence)  Table E-2a. Data f o r chemical i n t e r v a l from s u r f a c e ( i n f e e t ) .  analyses on core from d r i l l  22-30 30-10 10-50 50-57 01-90 90-100 100-110 110-120 120-130 130-110 110-112 112-115 115-150 150-152 152-151 151-157 157-159 159-163 163-167 167-169 169-171 171-173 173-176 176-181 181-181 181-189 189-191 191-195 195-197 198-201 201-205 205-210 210-211 211-218 210-223 223-227 227-220 220-231 231-233 233-235 235-239 239-211 211-216 216-217 217-219 219-250 250-260 260-270  Mo 23 33 29 37 5 7 5 16 6 7 15 10 5 7 10 2 13 0 11 10 9 7 10 11 21 11 23 11 31 30 51 11 18 25 26 20 26 16 5 35 21 75 65 10 21 35 62 63  Cu 91 88 58 69 51 39 39 60 58 51 00 91 71 83 59 101 61 59 38 61 59 75 30 31 36 32 18 81 12 53 58 29 29 37 13 58 11 70 85 72 72 196 113 210 210 85 125 170  Zn 120 100 150 160 230 230 120 070 190 760 1700 5000 1300 2000 2000 15100 2800 2500 3300 6200 1320 18800 1580 2300 1110 1700 3000 19600 16200 l l 000 31800 31600 29200 13600 UOOO 7800 I OOOO 161000 100000 36 000 50000 26100 15500 10200 15700 13300 16600 10500  Pb 90 110 60 60 30 30 30 7100 120 170 1030 1650 110 120 770 53000 110 290 370 750 70 2100 510 180 200  no  110 II300 1700 OOOO 6000 12600 8000 13100 5900 3800 5000 176000 27200 26100 10200 7100 2000 2900 2100 3100 1000 5700  Cd l .0 .9 2 .0 3 .0 .7 .7 .7 38 0 3 .0 I .0 100 0 100 0 100 0 100 0 100 0 100 0 100.0 100.0 100 0 100.0 100 0 100 0 100 0 100 0 100 0 100 0 100 0 200,0 100 0 100.0 100 0 100.0 100 0 200 0 100 0 100.0 100 0 700 0 100 0 100 0 200.0 100.0 100 0 100 0 100 0 100.0 65. 0 1fi.O  (DDH)  12,  CaO  MgO  K 0  shown with  I  PPM Depth(ft)  hole  Ni 97 130 111 125 82 77 GO 52 68 01 105 110 120 112 100 120 111 HO 95 120 90 95 101 81 100 71 95 80 86 98 108 50 62 72 00 85 100 68 75 91 63 129 90 110 120 76 127 200  Co  Ag  Mn  11 19 11 11 8 8 11 10 10 12 25 21 17 21 22 19 21 21 20 20 21 23 21 26 22 32 15 30 37 35 29 22 23 27 23 23 28 11 15 16 21 37 23 27 36 20 10 10  l .17 l .10 1 .01 .92 .25 .18 . 15 .90 .36 .31 .18 .10 .11 .16 .62 1 .67 .52 .11 .39 .17 .23 6 .00 .10 .27 1 .00 .61 1 .23 2 .10 .51 1 .00 1 .21 .03 .88 1 .35 1 01 1 06 1 28 11 00 7 00 6 00 1 16 5 00 1 18 2 11 1 59 1 21 3 00 5 00  90 102 171 192 29 17 112 170 108 210 137 107 03 91 111 117 120 220 115 102 103  no 120 135 101 117 76 103 180 163 210 160 350 310 260 205 123 167 122 158 380 99 196 12 111 175 109 51  V 530 550 660 500 300 210 190 270 130 130 210 220 300 200 200 320 330 210 270 100 250 310 300 110 520 560 1020 520 110 . 610 630 210 310 160 520 530 610 350 350 730 450 1070 1100 1350 1160 810 1320 2050  Ba 6200 5600 3500 3300 1700 1200 1300 200 1000 1600 1500 1900 1600 1100 1100 800 900 1100 900 900 500 800 700 700 000 500 700 100 100 900 1300 100 500 400 600 600 400 400 500 600 300 500 400 100 100 300 200 500  depth  * Fe(t) 3.30 3.70 2.03 2.03 .29 .43 .62 2.71 1.30 1.05 1.59 1.89 1.36 1.63 1.95 5.50 1.86 1.34 .99 1.52 1 .62 2.15 1.30 1.35 1 .53 1.99 1.05 5.05 2.21 3.60 2.57 1.82 2.37 3.20 3.50 2.50 2.20 4.00 3.25 1.39 1 .67 2.03 1.72 7.90 7.20 1.15 1.41 1.90  .98 2 .66 12 .01 9 .10 7 .04 7 .11 15 .96 19 04 13 72 19 00 0 82 9 30 8 26 26 10 78 10 00 3 92 16 94 10 92 8 40 5 04 5 18 1 34 1 62 6 02 3 36 2 66 6 86 7 00 6 30 9 66 31 16 29 40 16 94 23 24 10.06 5 88 6 02 3 64 8 82 35 70 9 94 29 12 9 . 10 0 54 2 0 . 50 1 1 . 31 7. 81  fl  1.25 1.07 1.75 3.35 .79 .73 .57 .11 .42 .39 .35 .39 12.04 .71 .73 .60 .55 .36 .19 .21 .21 .18 .19 .16 .21 .19 .31 .19 .11 .15 .23 .21 .21 .23 .28 .26 .21 .08 .15 .26 .31 .16 .21 .19 .16 .10 .21 .37  2  1.66 4.49 3.65 3.34 2.23 2.57 1.60 .21 1.75 l .31 l .51 1.68 1 .07 1.91 1.61 1.46 1.63 1.15 .06 1.20 .01 .09 .82 .80 .91 .67 1 .15 .60 .43 .62 1.01 .36 .55 .50 .65 .71 .71 .22 .12 .82 .31 .48 .53 .62 .48 .34 .62 1.32  C(LOI) 6.7 8.6 6.4 11.5 7.2 6.4 5.6 1.9 4.8 1.1 3.2 4.7 2.2 2.0 2.7 5.3 4.3 3.5 2.8 4.9 2.9 3.6 3.2 3.1 3.4 3.6 4.6 5.1 1.1 1.9 4.9 1.6 2.5 2.0 3.4 3.7 5.3 .1 1.0 5.1 2.1 1.9 5.2 7.6 7.0 3.1 7.4 9.9  P 0 ?  5  .643 .371 1.177 .934 2.279 1.061 1.805 .210 2.180 1.807 .199 .179 2.157 2.038 2.036 1.626 2.290 1.189 1.626 2.155 1.027 1.637 1.591 1.321 2.500 .010 .689 .279 .170 .110 .172 .229 .251 .222 .309 .160 .202 .133 .316 .710 .536 2.153 .992 1.333 .580 .758 .735 2.213  S .30 .20 .31 .44 .50 .60 .42 2 .32 1 .21 1 .21 1 .36 2 .02 1 .10 1 .70 1.78 4 .00 1 .70 1 .52 .92 1 .66 1 .32 2 06 1 00 1 02 1 01 1 86 1 18 1 00 2 61 1 00 3 71 1 02 1 00 1 00 1 06 3 02 2 52 1 00 4 00 3 50 1 22 1 00 2 18 1 00 1 00 87 2 32 2 64  Table E-2b. Data f o r chemical i n t e r v a l from s u r f a c e ( i n f e e t ) .  analyses on core from d r i l l  hole  (DDH)  12,  shown with  PPM Depth 2/0-200 280-290 290-300 300-310 310-320 320-330 330-310 340-350 350-360 360-370 370-380 380-390 390-400 400-410 410-420 420-430 430-440 440-450 450-460 460-470 470-480 480-490 490-500 500-510 510-520 520-530 530-540 540-550 550-560 560-570 570-580 580-590 590-600 600-610 610-620  (ft)  Mo 31 22 25 36 36 46 38 50 44 46 21 16 19 31 27 37 35 12 45 29 23 30 21 35 47 42 26 29 28 21 39 42 43 50 32  Cu 72 50 54 52 60 65 52 59 66 63 60 50 61 50 57 64 84 44 63 83 74 75 46 38 52 42 52 58 59 58 50 48 60 110 43  Zn 4500 1000 2400 3300 3300 3000 1220 123 122 1830 3900 1740 1700 4 300 2500 3800 2010 2400 230 930 66 95 550 130 340 460 210 270 56 280 460 450 420 930 760  Ph  Cd  8900 620 110 220 540 460 400 96 84 70 280 1640 360 380 420 30 200 130 360 600 50 66 27 20 5 13 20 20 28 77 70 73 20 16 400  15 4 10 17 18 17 10  18 14 6 7 31 12 3 11 7 2 11 1 1 4 1 2 4 2 1 15 2 3 3 6 3  0 5 5 1 2 0 0 6 1 3 4 7 0 0 6 5 0 4 0 1 1 5 0 4 7 0 0 9 1 0 7 1 2 9 4  depth  %  Ni  Co  l\g  Mn  V  Ba  fe(l)  146 140 140 150 154 143 166 146 170 143 122 15? 158 166 154 82 195 72 181 270 180 200 104 60 02 74 74 68 60 155 128 132 23 89 108  12 12 11 11 10 13 13 14 12 12 11 11 12 11 12 17 12 18 14 12 14 13 16 18 16 17 16 15 15 10 16 17 16 16 17  4.00 1.10 1.05 1.22 1 .24 1.02 1.27 1.09 1.13 1 .42 1.27 1.67 1.15 1.15 1.11 1.30 1.33 1.26 1.56 2.08 1.62 1.62 .90 .69 .70 .55 .78 .87 1.00 1.11 2.50 .77 1.01 1.96 .64  102 63 93 70 73 111 93 147 84 54 73 51 106 64 90 189 63 77 154 53 151 97 129 159 142 175 160 163 188 60 135 135 189 167 166  1030 1020 1150 1530 1530 1330 1370 1360 1700 1950 1390 1170 1000 1480 1240 720 1520 550 1370 1700 1440 1410 540 440 530 400 510 550 520 1420 1300 800 760 1130 690  600 1000 600 1000 900 500 600 600 800 1000 600 900 800 1000 1400 3000 1500 800 1500 2200 2000 2900 8200 8600 6500 4400 4100 3800 3400 1400 2500 3700 2900 3000 3100  2 2 2 1 2 2 2 2 1 2 2 2 2 1 1 2 3 2 2 2 2 2 2 2 3 2 2 2 1 2 2 2 2 2  31 38 11 98 00 27 35 80 33 15 28 75 46 89 93 24 12 73 78 70 42 90 70 51 69 15 66 33 48 85 06 67 14 18 70  CaO 7 2 5 3 3 6 4 9 4 2 3 1 5 2 4 15 2 7 9 2 10 6 9 17 16 17 13 9 12 2 10 11 20 19 12  94 94 74 64 22 0? 90 38 48 66 64 96 74 24 34 54 94 28 10 94 64 44 66 08 24 50 72 94 41 38 76 62 44 18 18  MgO  K  .42 .58 .52 .47 .45 .60 .66 .62 .79 .76 .63 .63 .58 .51 .60 5.51 .60 .65 .63 .74 .66 .71 2.77 2.96 4.55 5.10 4.54 3.76 6.35 .52 3.66 2.07 4.37 3.04 2.98  2 3 3 3 2 3 3 3 3 4 3 3 3 3 3 3 3 3 3 3 3 3 4 4 3 3 3 4 3 3 2 4 2 3 4  >°  ;  59 98 65 07 95 41 55 07 94 13 72 94 70 12 60 31 55 40 55 79 41 72 66 42 89 36 74 01 98 10 95 27 90 07 03  C(L0!) 6.7 6.3 5.9 6.3 6.9 7.0 6.7 7.2 9.3 8.9 7.3 6.6 5.5 6.7 5.1 2.8 7.2 2.9 5.9 7.2 5.7 7.7 4.5 3.3 3.5 3.1 3.0 3.1 3.2 6.2 3.9 4.9 3.7 3.5 3.4  P 0 2  &  .492 .275 .218 .247 .170 .263 .309 .307 .488 .275 .376 .279 .192 .236 .241 .247 .250 .275 .309 .392 .346 .296 .256 .213 .190 .160 .131 .200 .160 .236 .176 .311 .215 .147 .389  S  2 2 2 2 2 2 2 2 2 2 2 3 2 2 2 1 3 3 2 2 2 2 2 1 2 2 1 1 1 2 1 1 1 1 1  80 70 32 42 26 56 70 96 80 30 58 16 86 18 14 08 26 02 94 84 54 92 40 92 08 10 54 14 08 14 42 84 04 20 70  Table E-3a. Data f o r chemical i n t e r v a l from s u r f a c e ( i n f e e t ) .  analyses on core from d r i l l  hole  (DDH)  18,  PPM Depth 86-90 90-100 100-110 110-120 120-130 130-110 140-150 150-160 160-170 170-180 130-190 190-200 200-210 210-220 220-230 230-240 240-250 250-260 260-270 270-280 280-290 290-300 300-310 310-320 320-330 330-340 340-350 350-360 360-370 370-380 380-390 390-400 400-410 410-420 420-430 130-441 141-443 143-444 446-419 449-453 153-154 454-158 458-463 163-167 467-170 470-173 173-178 478-179 179-183  (ft)  Mo I I I I l l l 2 13 8 15 7 3 8 7 1 2 1 3 6 7 11 8 10 13 11 20 15 16 12 9 15 11 18 9 12 28 28 16 23 70 25 9 15 13 13 23 21 16  Cu 27 30 44 14 16 22 32 20 51 90 63 98 90 136 94 71 61 66 75 74 78 51 30 35 55 58 40 30 28 110 40 36 28 29 60 52 47 108 63 22 19 90 15 29 32 21 50 12 31  Zn 42 37 27 26 24 22 24 40 55 290 54 70 37 330 330 58 900 260 640 55 2900 3300 710 . 900 1310 2200 1470 370 3400 5300 3000 2300 2700 3300 720 800 21900 81600 52000 1800 15500 90000 19100 38400 80800 14500 84800 68000 24800  Pb 3 6 4 2 3 2 8 2 38 33 26 34 40 70 30 50 40 30 32 71 200 162 120 520 350 185 180 128 62 1770 150 79 65 1830 320 410 17800 11800 15400 500 120 32000 9900 10600 23600 6600 16100 32800 8600  2 2 2 2 2 2 2 2 2 5 2 3 2 6 2 2 2 3 C  I 1 8 8 2 2 3 6 5 1 9 13 8 6 7 8 2 2 237 283 158 12 62 298 79 121 296 51 210 201 80  1 0 0 7 1 7 6 5 1 3 0 3 1 0 0 5 2 1 0 0 0 0 0 0 0 0 0 0 0 0 0  depth  %  Ni  Cd  shown with  18 31 28 28 20 12 25 27 112 121 106 144 133 • 131 127 116 105 100 112 106 98 102 63 60 77 80 79 71 76 82 70 60 65 92 81 80 93 100 73 58 156 78 39 60 47 39 65 60 64  Co 12 25 17 18 16 25 20 18 30 16 20 14 17 19 20 14 12 12 14 16 10 9 9 9 10 7 10 5 4 12 6 7 5 7 8 8 8 8 9 13 17 10 16 14 12 17 14 13 13  Ag  -  -  -  2.00 .75 .58 .48 .45 .40 .50 .32 2.00 2.00 2.00 2.00 4.00 4.00 4.00 2.00 1.50 .96 .82 .84 .62 1.10 1.21 .80 1.93 .60 1.26 .83 1.00 4.00 4.00 1.52 2.00 2.00 4.00 4.00 4.00 4.00 4.00 4.00 6.00 2.00  Mn  V  Ba  111 250 171 270 176 350 250 173 207 176 206 89 155 147 191 55 51 60 73 195 77 52 119 180 300 77 230 109 45 260 75 82 55 58 87 92 116 109 157 280 112 320 530 300 250 370 410 370 250  120 130 130 110 110 120 100 130 180 200 250 240 220 310 200 240 150 150 170 180 520 650 400 470 580 490 550 620 630 510 500 160 190 770 510 600 900 660 180 390 1250 500 170 320 260 170 370 370 360  10000 10000 11500 11700 9500 7600 5100 3800 3600 1900 1100 1500 1500 1100 1200 2000 1800 2300 1900 1900 1100 1600 900 1000 1200 1300 1000 900 900 400 700 300 100 800 300 100 800 100 800 500 1100 700 300 100 500 300 400 300 500  Fe(t)  2 l 2 I 4 l l 3 2 2 2 2 2 l l l l l 2  l 2  2 l  2 2 2 8 7 l 2 4 l 2 l 8 4 2 2  99 77 24 53 71 45 95 85 70 46 44 62 32 98 80 46 25 97 43 72 19 90 87 20 09 87 95 63 72 38 05 82 49 77 27 30 13 00 00 51 30 60 11 08 61 90 30 56 18  MgO  CaO 3 6 1 5 4 7 6 4 6 12 19 7 13 10 14 8 8 8 9 19 8 5 8 3 14 4 11 3 1 18 9 6 3 3 7 4 3 5 14 7 10 37 22 15 28 20 22 16  08 44 20 88 20 14 44 20 16 18 46 11 86 50 14 12 68 68 38 71 68 71 54 78 98 76 98 61 12 76 66 30 22 61 12 18 92 70 71 00 70 50 52 12 96 56 02 54 24  1.60 2.71 2.30 3.32 2.48 3.74 3.56 2.99 2.87 .73 .79 .65 .57 .62 .55 .55 .45 .37 .34 .31 .28 .31 .24 .32 .36 .26 .28 .26 .39 .42 .34 .22 .21 .31 .28 .31 .28 .21 .18 .11 .32 .15 .16 .19 .13 .13 .19 .22 .21  K 0  C(L01)  P  3.94 3.55 4.13 3.72 3.89 3.46 3.43 3.60 3.74 1.73 1.68 1.78 1.21 1.32 1 .60 1.81 1.84 1.79 1.64 1.28 1.02 1.02 .87 1.08 1.08 1 .23 1.09 1.30 1.62 1.23 1 .02 .87 .97 1.39 1.36 1.26 1.19 1.23 .81 .43 1.61 .82 .19 .58 .54 .29 .50 .56 .57  .6 .9 .3 .8 .5 1.5 1.1 1.2 5.9 6.3 5.4 7.8 6.3 6.7 5.9 7.0 7.6 5.1 5.6 5.1 5.6 5.5 2.9 2.2 4.0 3.6 5.0 5.7 6.8 4.0 3.9 3.1 3.6 5.4 '4.7 5.3 5.6 1.1 7.8 8.3 3.2 10.2 6.3 .6 3.3 3.6 4.3 2.9 4.3  .073 .087 .076 .080 .069 .076 .064 .048 .073 1.706 1.621 1.811 1.903 1.926 1.793 .854 .813 .813 .813 .802 .866 .829 .760 .845 .341 1.218 1.310 .632 .135 .332 .465 .909 .627 .858 1.150 .875 .195 .302 .172 .211 .309 .220 .208 .277 .261 .316 .288 .213 .252  ?  2°5  S 42 2 10 53 1 29 93 3 34 83 1 15 2 56 1 32 1 56 1 86 1 72 1 86 1 38 1 56 1 09 1 02 1 50 1 78 2 80 1 07 91 90 2 06 82 94 50 80 2 48 1 30 84 68 94 2 34 •1 24 3 82 4 00 4 00 1 92 3 42 4 00 2 20 4 00 1 00 4 00 4 00 1 00 1 08  Table E-3b. Data f o r chemical i n t e r v a l from s u r f a c e ( i n f e e t ) .  analyses on core from d r i l l  hole  (DDH)  18,  shown with  PPM Depth 103-185 185-100 108-190 190-195 195-490 498-503 503-506 506-5)0 510-513 513-516 516-517 517-522 522-526 526-531 531-533 533-536 536-540 540-550 550-560 560-570 570-500 500-590 590-600 600-610 610-620 620-630 630-640 640-650 650-660 660-670 670-680 680-690 690-700 700-710 710-720 720-730 730-735  ( f t ) Mo 21 21 22 17 20 14 30 14 27 I'l 21 43 65 42 23 11 15 17 15 18 37 40 33 10 30 25 25 13 9 0 10 2 3 2 3 2 3  Cu 32 20 61 31 28 32 32 22 50 130 29 90 151 00 136 69 65 60 60 60 61 62 60 65 69 71 68 14 03 88 63 58 63 68 40 41 43  Zn 23700 22600 55600 31600 1300 26100 10000 2600 13000 18000 9000 6100 16300 7100 700 3800 1620 2300 640 300 2600 1920 450 870 400 60 136 83 130 290 44 25 32 30 24 29 20  Ph 0600 6200 12600 7300 680 23400 0200 OOOO 7100 3000 630 1210 2300 3000 590 217 212 167 108 156 00 70 96 66 61 56 16 36 10 33 20 20 30 33 27 26 26  depth  %  Cd  Ni  Co  75.0 71.0 150.0 82.0 6.0 151.0 37.0 8.0 43.0 57.0 31.0 33.0 18.0 25.0 1.7 16.3 7.0 10.7 4.7 3.0 20.5 18.1 5.2 11 .6 5.8 1.0 1.1 .2 .7 1.4 .2 .2 .2 .2 .2 .2 .3  64 62 60 60 51 55 01 60 95 128 70 90 124 153 160 160 1 70144 145 147 157 164 185 196 200 197 1