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Geologic setting, mineralization, and aspects of zoning at the Berg porphyry copper-molybdenum deposit,… Panteleyev, Andrejs 1976

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GEOLOGIC SETTING, MINERALIZATION, AND ASPECTS OF ZONING AT THE BERG PORPHYRY COPPER-MOLYBDENUM DEPOSIT, CENTRAL BRITISH COLUMBIA  by B.Sc,  Andrejs Panteleyev 1964, M . S c , 1969, University of British Columbia  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Geological Sciences  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA  APRIL, 1976  fc^  Andrejs Panteleyev  In p r e s e n t i n g t h i s t h e s i s  in p a r t i a l  an advanced degree at the U n i v e r s i t y the L i b r a r y I further  s h a l l make i t f r e e l y  f u l f i l m e n t o f the requirements of B r i t i s h C o l u m b i a ,  a v a i l a b l e for  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  I agree  r e f e r e n c e and copying of  this  of t h i s t h e s i s f o r  It  i s understood  thesis  of  The U n i v e r s i t y  of B r i t i s h Columbia  2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5  Date  &&M£  10 (97b  or  publication  f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my  w r i t ten pe rm i ss i o n .  Department  that c o p y i n g or  that  study.  f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department by h i s r e p r e s e n t a t i v e s .  for  i ABSTRACT  Berg copper-molybdenum deposit i s i n mountainous t e r r a i n of the Tahtsa Range i n west-central B r i t i s h Columbia.  It is  a type example of Lowell and G u i l b e r t ' s (1970) model of porphyry copper deposits.  The deposit i s i n thermally metamorphosed and  hydrothermally  a l t e r e d Middle J u r a s s i c v o l c a n i c rocks and T e r t i a r y quartz d i o r i t e adjacent to a weakly mineralized Eocene stock.  The stock i s about  2,100  feet i n diameter and c o n s i s t s of four major quartz monzonitic phases. Unmineralized v o l c a n i c and sedimentary s t r a t a of the Cretaceous  Skeena  Group crop out east of the deposit.  Hydrothermal a l t e r a t i o n and sulphide minerals are arranged i n concentric, annular zones around the composite stock.  From the i n t e r i o r  outward pervasive a l t e r a t i o n zones are p o t a s s i c , p h y l l i c , and p r o p y l i t i c . A r g i l l i c alteration i s rare.  A b i o t i t i c a l t e r a t i o n zone that surrounds  the stock i s l a r g e l y a thermal aureole but i s also p a r t i a l l y of hydrothermal o r i g i n .  A multistage v e i n stockwork i s superimposed on the  pervasively a l t e r e d rocks.  E a r l y v e i n s , many with a l t e r a t i o n  envelopes,  were deposited from s a l i n e f l u i d s at temperatures i n excess of 400 degrees centigrade.  Later veins were deposited from cooler, less s a l i n e f l u i d s  and commonly have retrograde a l t e r a t i o n margins.  A gypsum-filled sub-  h o r i z o n t a l f r a c t u r e cleavage cuts a l l a l t e r a t i o n minerals and v e i n s .  The  molybdenite zone follows c l o s e l y the i n t r u s i v e contact where a quartz stockwork i s well developed. a l t e r a t i o n zone.  Chalcopyrite i s most abundant i n the b i o t i t i c  P y r i t e forms a broad halo that extends outward f o r at  l e a s t 2,000 feet from the stock.  Minor elements In p y r i t e are  concentrated i n disseminated p y r i t e from well-mineralized copper zones.  Leaching and supergene mineralization zoning i n the deposit.  cause pronounced v e r t i c a l  In the leached capping copper has been removed t o  a depth of 125 feet but molybdenum remains and i s l o c a l l y concentrated i n limonite.  In the supergene zone,which o v e r l i e s the e n t i r e deposit and i s  up to 300 feet t h i c k , copper i s enriched by a factor of 1.25 times primary grade.  Supergene m i n e r a l i z a t i o n  i s a contemporary ongoing process that  was i n i t i a t e d a f t e r Pleistocene g l a c i a t i o n .  iii •  TABLE OF CONTENTS Page  ABSTRACT  1  CHAPTER I - INTRODUCTION GENERAL STATEMENT  1  SCOPE AND PURPOSE OF THE STUDY  .  2  LOCATION AND ACCESS  2  WEATHER  A  HISTORY OF EXPLORATION  ....  5  PHYSIOGRAPHY  8  GLACIATION  9  CHAPTER II - GEOLOGY REGIONAL GEOLOGY OF TAHTSA RANGE INTRODUCTION  11  BEDDED ROCKS  14  Stratigraphic Relationships Hazelton Group (Middle Jurassic: Map 1, Unit 1)  i  14 15  Skeena-Group (Lower Cretaceous and ? Younger: Units 2 to 4) INTRUSIVE BODIES  16 20  Quartz Diorite  20  Quartz Monzonite Porphyry  22  Minor Intrusions  23  STRUCTURE  24  GEOLOGY OF BERG DEPOSIT INTRODUCTION  26  iv Page CHAPTER II - GEOLOGY (continued) GEOLOGY OF BERG DEPOSIT (continued) BEDDED ROCKS  31  INTRUSIVE ROCKS  35  Quartz Diorite (Map 2, Unit 2)  38  Quartz Monzonite Stock and Dykes (Map 2, Units 3 to 5)  39  Quartz Monzonite Porphyry Phase (QPM, Unit 3) . . .  39  Sericitized Quartz Plagioclase Porphyry Phase (QPP; Map 2, Unit 4) Plagioclase Biotite Quartz Porphyry (PBQP; Map 2, Unit 5)  42  Quartz Monzonite-Granodiorite or Quartz-Bearing Monzodiorite Dyke (hornblende quartz feldspar porphyry, hbde QFP; Map 3, Unit 6)  43  44  Basic Dykes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  45  Chemical Composition  50  Distribution and Geometry (Map 2)  50  Age of Intrusions .•  56  BRECCIAS .'•  58  Intrusive Pebble Breccia Pipe  59  Other Breccias (Observed Only in Diamond-Drill Core) .  60  STRUCTURE  Breccia 1  60  Breccia 2  61  Breccia 3  62  Breccia 4  62 63  V '-. CHAPTER III  Page - HYDROTHERMAL ALTERATION  INTRODUCTION  68  DEFINITION OF ALTERATION FACIES AND ZONES  70  POTASSIC ALTERATION  .  .  70  PHYLLIC ALTERATION  71  PROPYLITIC ALTERATION  72  ARGILLIC ALTERATION  74  BIOTTTIC ALTERATION  74  VEINS  ;  ORIGIN OF HYPOGENE ALTERATION AND ZONING  81 85  PRINCIPLES . . .  85  HYDROTHERMAL PROCESSES IN THE FORMATION OF BERG DEPOSIT . . .  90  CHAPTER IV - MINERALIZATION INTRODUCTION  99  PRIMARY MINERALIZATION AND LATERAL ZONING  100  SECONDARY MINERALIZATION AND VERTICAL ZONING  108  INTRODUCTION  108  EXTENT OF LEACHING AND SUPERGENE ENRICHMENT .  112  MINERALOGY AND PROCESSES OF FORMATION  117  Zone of Oxidation and Sulphide Leaching  117  Zone of Supergene Enrichment  125  CHAPTER V - MINOR ELEMENTS IN PYRITE INTRODUCTION  134  UNIVARIATE ANALYSIS  140  vi Page  CHAPTER V - MINOR ELEMENTS IN PYRITE ( c o n t i n u e d ) BIVARIATE ANALYSIS  156  MULTIVARIATE ANALYSIS  164  MINOR ELEMENT ZONING IN THE DEPOSIT  170  INTRODUCTION  170  UNIVARIATE MINOR ELEMENT ZONING  174  ZONING OF FACTORS (MULTIVARIATE ANALYSIS)  181  CHAPTER VI - SUMMARY AND CONCLUSIONS  186  BIBLIOGRAPHY . .  199  .  LIST OF APPENDICES A  CHEMICAL ANALYSES OF QUARTZ MONZONITE PORPHYRIES  B  ALTERATION:  ..  211  CATALOGUING OF CORE AND ESTIMATION OF ALTERATION  INTENSITY  212  C  CLAY SEPARATION TECHNIQUE  214  D  FLUID INCLUSION DATA  216  E  MINOR ELEMENTS IN PYRITE:  F  ELEMENTS DETECTED IN BERG PYRITE  220  G  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM)  224  H  DATA PARAMETERS AND COMPUTED CHI SQUARE VALUES  233  I  VARIMAX FACTOR MATRIX, DISSEMINATED PYRITE  234  J  VARIMAX FACTOR MATRIX, VEIN PYRITE  235  SAMPLE VARIABILITY  218  vil "'•  Page LIST OF TABLES  1  Mineralogical Composition of Intrusive Rocks, Berg Deposit  51  2  Chemical Compositions and Norms  52  3  Potassium-Argon Ages, Berg Deposit .  57  4  Partial Analyses of Iron Ores and Berg Ferricrete  120  5  Analytical Precision (For Logged Data)  138  6  Comparison of Spectrographs and Atomic Absorption Analyses of Pyrite Concentrates (All Analyses In PPM)  7  Summary - Means and Standard Deviations of A l l Analyses  8  Calculated t and F Probability of Vein Pyrite Versus Disseminated Pyrite (Based on L o g V a l u e s of A l l Available Data) . . . . . .  9 10 11 12  139 145  148  F and t Tests - Ni In Pyrite  149  Summary of t and F Tests For A l l Elements (Significance of Host Rock Type) Correlation of Paired Variables 2 R and F Ratios For A l l Data of A l l Pairs of Variables Having  151 158  Significant Correlation 13  Characteristic Co and Ni Concentrations In PPM  14  Successive Q-Mode Varimax Factor Components - Disseminated Pyrite .  160 163  166  15  Q-Mode Varimax Factor Scores - Disseminated Pyrite  167  16  Successive Q-Mode Varimax Factor Components - Vein Pyrite  168  17  Vertical Variation of Minor Elements in Pyrite  173  18  Spectrographs Analysis of Pyrite - Elements For Which Concentrations Were Determined .... Minor Element Content of Chalcopyrite (In PPM)  221 222  19  viii Page LIST OF FIGURES 1  Berg Property location map  3  2  Geology of Tahtsa Range  3  Air photo interpretation of fracture trends. Measurement of 87 most prominent photo linears in bedrock in Berg map-area. .  25  4  Geology - Berg Deposit  29  5  Geologic cross sections (view looking northerly)  30  6  Subdivision of Hazelton Group volcanic succession at Berg  .  12  Deposit  33  7  Mineralogical composition of intrusive rocks, Berg Deposit  53  8  Generalized alteration zones, Berg Deposit  77  9  Mineral assemblages in thermally metamorphosed andesitic, quartz diorite, and quartz monzonite. Average rock compositions from Nockolds, 1954  93  10  Primary minerals - pyrite  103  11  Pyrite-chalcopyrite ratio  104  12  Primary minerals - Cu  105  13  Primary minerals - Mo  106  14  Primary Cu and MoS grade in relation to distance from main 2  intrusive contact  109  15  Vertical zoning of Cu and KoS^ grades in diamond-drill cores . . .  111  16  Trend surface elevation marking start of gypsum in fractures . . .  114  17  Trend surface isopach map, strongly oxidized rocks (Cu leached).  115  18  Trend surface isopach map, supergene Cu mineralization  116  19  Mineral stability fields at 25° C, 1 ATM. A. Cu-Fe-S-O-H modified from Garrels (1960); B. Mo-Fe-S-O-H after Barakso and Bradshaw (1971); C. Fe-S-O-H in presence of K , after Brown (1971). Field of weathering after Sato (1960) Stability fields in Cu-H 0-C0 -0 -S system (including chalcopyrite) at 25° C and 1 ATM +  20  2  126  2  127  ix  'V.  Page LIST OF FIGURES  (continued)  21  Mineral compositions showing possible phase relationships  22  Primary and supergene copper minerals.  130  Zones underlain by  >.4% Cu.  132  23  Ni and Zn content of pyrite.  24  Pb and Ag content of pyrite  143  25  Frequency distributions of As, Co, and Ti  144  26  BImodal distribution containing vein and disseminated pyrite  27  populations (Normal curves fitted to the data) Distribution of Ni in pyrite. Data grouped according to host rock.  Normal curve fitted to L°gjg data.  A, C, D are fitted normal curves.  142  147 150  28  Cumulative probability.  Minor elements i n disseminated p y r i t e . .  29  Linear least squares regression line Y = a + bX for Co:Ni (A) and Pb:Zn (B)  155  157  30  Cobalt-nickel scatter diagram showing pyrite according to source  161  31  Co-NI ratios of pyrite  162  32  Zoning of minor elements in pyrite (As, B i , Ti)  175  33  Zoning of minor elements in pyrite (Co, N i , Co + N i , Co/Ni)  34  Zoning of minor elements in pyrite (Pb, Zn, Ag, Mn)  177  35  Composite of maximum minor element values  179  36  Contoured plan of Q-mode factor values  182  37  Composite of factors 1 to 4  184  38  Berg Deposit - idealized geological sections  192  > X + SD  ....  176  LIST OF PLATES FRONTISPIECE: 1  Berg deposit, view looking northerly  8,103 peak with unconformity between Hazelton Group volcanic rocks (MJ, Map 1, Unit 1) and overlying Skeena Group volcanic rocks (LK, Map 1, Unit 4)  18  X Page LIST OF PLATES (continued) 2  Skeena Group rocks about 2 miles east of 8,103 peak  18  3  Panoramic view of Berg prospect, view to north and east . . .  28  4 and 5  Embayed skeletal myrmekitic quartz phenocrysts containing oligoclase inclusions in quartz monzonite porphyry . . .  6 and 7 Quartz monzonite porphyry (QMP; Map 2, Unit 3)  46  8  Quartz monzonite porphyry (QMP; Map 2, Unit 3)  47  9  Quartz monzonite porphyry dyke (part of QMP; Map 2, Unit 3)  47  10  Sericitized quartz plagioclase porphyry (QPP; Map 2, Unit 4)  48  11  Typical sericitized quartz plagioclase porphyry (QPP;. Map 2, Unit 4)  v  40  12  Plagioclase biotite quartz porphyry (PBQP; Map 2, Unit 5) .  13  Hornblende quartz feldspar porphyry (hbde QFP; Map 2, Unit 6)  48 49  49  14  Potassic alteration in quartz monzonite porphyry (DDH.6) . .  78  15  Phyllic (quartz-sericite-pyrite) alteration of quartz monzonite porphyry (DDH 25) Potassic alteration of b i o t i t i c volcanic rocks (DDH 43)  78  16  (quartz-orthoclase veined biotite hornfels)  79  17  Propylitic alteration of b i o t i t i c volcanic rocks (DDH 16) .  79  18  Potassic alteration of b i o t i t i c volcanic rock (DDH 43) . . . .  80  19  Propylitic alteration-in l a p i l l i tuff (DDH 68) with ~bleached fracture margins Subhorizontal gypsum-bearing fracture cleavage crosscutting pyrite and chalcopyrite grains (DDH 28) Electron microprobe beam scan of Berg limonite ('Berg X') showing Mo concentration in rim  20 21, 22, and 23  80 84 124  xi ACKNOWLEDGMENT Fieldwork for this study was done while the writer was employed by Kennco Explorations, (Western) Limited.  The late Dr. J . A. Gower stimu-  lated the writer's interest in the deposit and suggested many research possibilities.  George 0. M. Stewart and other Kennco field geologists  familiarized the writer with geology of the deposit.  The most beneficial  contribution to this study was the supervision in the f i e l d , enthusiasm, and sustained interest by the late Charles S. Ney.  Dr. A. D. Drummond has  kindly kept the writer informed of results from recent exploration at the deposit. At the University of British Columbia research was supervised by the late Drs. W. H. White and J . A. Gower.  Preparation of this dissertation  began under the direction of Dr. A. E. Soregaroli and was later assumed by Dr. A. J . Sinclair." -The writer"is indebtedto Dr. Sinclair for  initially  supervising the investigation of pyrite geochemistry and later undertaking the role of thesis supervisor.  Dr. C. I.  Godwin made many suggestions for  improvement of earlier manuscripts. At Queen's University, Kingston, Ontario, where the writer spent one academic session, Dr. W. D. McCartney acted as graduate advisor and Mr. Leo Mes provided invaluable instruction and assistance in the spectrochemical laboratory. Mr. Harley Goddard of Kennco Explorations,  (Western) Limited  analysed a number of rock and pyrite specimens and Messrs. N. Colvin and P. Ralph of the British Columbia Department of Mines and Petroleum Resources provided some mineral identifications and analyses.  xii Assistance with computerized s t a t i s t i c a l analyses was given by Messrs. A.L.C. Fox and D. G. Cargill at the University of British Columbia and trend surfaces were generated by Mr. A. F. Bowman of the British Columbia Department of Mines and Petroleum Resources.  Mr. A. Bentzen  assembled equipment and instructed the writer in use of the microscopic heating apparatus. Preparation of this thesis was greatly facilitated by the efforts of the following members of the British Columbia Department of Mines and Petroleum Resources:  photography by Mr. R. E. Player; drafting by Messrs.  M. Calloway and J . Armitage; and typing by Ms. L. Mott.  The final manu-  script was typed by Mrs. Rosalyn J . Moir. The writer gratefully acknowledges a National Research Council of Canada Studentship for 1967/68; a National Research Council of Canada Postgraduate Scholarship for 1968-70; and financial assistance from Kennco Explorations, (Western) Limited during the winter of 1970/71.  Expenses  for spectrographs analyses at Queen's University were defrayed by National Research Council of Canada Grant A-4240 to W. D. McCartney. Finally I extend my gratitude to the members of ray family who patiently endured my long studentship and without whose optimism and encouragement I might never have completed this project.  LEAF x i i i OMITTED IN PAGE NUMBERING.  FRONTISPIECE:  Berg d e p o s i t , view l o o k i n g n o r t h e r l y . Pale c o l o u r e d r i d g e i n c e n t r e o f photo i s q u a r t z monzonite porphyry s t o c k . The m i n e r a l i z e d zone i s d e f i n e d by d r i l l a c c e s s r o a d s . E a s t ward d i p p i n g H a z e l t o n Group p y r o c l a s t i c r o c k s form r i d g e s on the n o r t h . Berg camp a t e l e v a t i o n o f 5,100 f e e t i s a t lower l e f t o f photograph. (Photo:  T. S c h r o e t e r ,  xiv  September,  1974)  GEOLOGIC SETTING, MINERALIZATION, AND ASPECTS OF ZONING AT THE BERG PORPHYRY COPPER-MOLYBDENUM DEPOSIT, CENTRAL BRITISH COLUMBIA  CHAPTER I INTRODUCTION GENERAL STATEMENT Berg prospect Is a copper-molybdenum deposit in the Canadian Cordillera that closely resembles the ' t y p i c a l ' porphyry copper deposit described in the idealized model of Lowell and Guilbert (1970) and the s t a t i s t i c a l composite model of De Geoffroy and Wignall (1973). Copper and molybdenum sulphides are associated with a small Tertiary quartz monzonite porphyry stock that intrudes Mesozoic volcanic rocks. bodies.  The stock has a number of intrusive phases and associated breccia Hypogene mineralization Is present as (1)  fracture-controlled  and disseminated pyrite and chalcopyrite; (2) a quartz stockwork with pyrite, molybdenite, and chalcopyrite; and, less commonly, (3) quartz and quartz-carbonate veins containing pyrite, sphalerite, galena, chalcopyrite, and sulphosalts.  Sulphide zoning i s evident within a  broad annulus of hydrothermally altered rocks about a weakly mineralized intrusive core.  Weathering has produced a leached capping underlain by  a laterally extensive supergene copper zone. Hypogene copper and molybdenum sulphides below the supergene zone are locally of ore grade.  Geological  reserves are In the order of 400 million tonnes containing 0.3 per cent copper and .05 per cent molybdenite at a 0.25 per cent copper cutoff grade.  2 SCOPE AND PURPOSE OF THE STUDY This study describes regional setting, detailed geology, and style of mineralization at Berg deposit.  Documentation of the type and  abundance of ore and alteration minerals, as well as an investigation of minor element content of pyrites, were undertaken with emphasis placed on defining distributions and systematic variations (zoning) in the area of economic interest. Interpretation of mineralogical and minor element distribution patterns might aid in defining and understanding processes of ore formation in porphyry copper environments, as well as refining existing porphyry copper models and thus improving their potential for practical applications. LOCATION AND ACCESS Berg deposit is in Omineca Mining Division in west-central British Columbia at latitude 53 degrees 49 minutes north, longitude 127 degrees 25.5 minutes west (Figures 1 and 2).  It lies in Tahtsa Range  approximately midway between Tahtsa, Nanika, and Kidprice Lakes in the northwestern corner of Whitesail map-area (NTS 93E/14W).  Except for some  habitation at Kemano to the southwest and Ootsa Lake to the east, the closest centres of commerce are Houston, 53 a i r miles to the northeast and Smithers, 68 miles to the north.  The property is about 365 air miles  north of Vancouver. The area of economic interest i s on moderate to steep, south and west-facing slopes in generally rugged, mountainous terrain.  The  claims group containing Berg deposit l i e s between elevations of 4,500 and 6,800 feet, mostly to the north of the east fork of Bergeland Creek.  Figure 1 BERG PROPERTY LOCATION M A P  4 Access by personnel during much of the early exploration phase was by helicopter from bases at Smithers and Houston, but later a 26-mile bulldozer road was built to the camp from Twinkle Lake on the Tahtsa Lake Forest Access road.  The access road trends along the northern flank  of Sibola Peak and then follows Kidprice Creek to its headwaters where i t crosses a 5,700-foot pass and descends to camp at an elevation of 5,100 feet. During the early stages of exploration most d r i l l equipment and supplies were brought to the property on sleds with a bulldozer but work on the access road has upgraded i t to the point where, since 1970, i t i s almost always possible during summer months to reach the property with a four-wheel-drive vehicle and occasionally with a two-wheel-drive  vehicle.  Access for about six winter months i s restricted to vehicles capable of travel in snow, but winter travel requires prudence because of avalanche hazards.  Spring thaw and resulting breakup render the property inaccessible  by road for up to one month.  Alternate access routes from the north and west  may be feasible If mining development continues.  WEATHER The weather, typical of mountainous terrain along the east flank of the Coast Mountains, i s unsettled with rapid changes. cool summers are punctuated with numerous showers.  Short, generally  Midsummer temperatures  of 21 degrees Celsius and more, are common but hail or sleet storms of short duration can occur on any day.  The region i s in the rain shadow of the  Coast Mountains and thus has only light precipitation of about 15 to 20 inches per year.  However, r a i n f a l l can accumulate very rapidly during  5 short, violent storms.  In winter, snow i s generally only a few feet deep  on the valley floors and open sidehills but deeper snow accumulations, d r i f t s , and avalanche areas on northern and eastern slopes give rise to small permanent snowfields that sustain numerous small glaciers.  Possibly  the most adverse weather conditions for work in the area are caused by high winds that occasionally reach gale and hurricane force.  Company  records also show that dense fog sometimes enveloped the area for days at a time and reduced v i s i b i l i t y to tens of feet.  HISTORY OF EXPLORATION Prospecting in the Whitesail map-area has been continuous since arrival of settlers in the early 1900's and has resulted in the discovery of a number of lead-zinc-silver, s i l v e r , gold-tungsten, copper, and more recently, copper-molybdenum and molybdenum deposits.  In 1913, 'Kid' Price  found placer gold and i t s source veins on Sibola Peak and precipitated a small rush to the area in 1914.  From 1915 to the late 1920's a number of  lead-zinc-silver and copper deposits were located, the most notable being the Emerald Glacier deposits on Sweeney Mountain, approximately 8.5 miles southeast of Berg property. Prospecting activity declined during the 1930's but was renewed during 1943-47 by discoveries of gold-tungsten mineralization on LIndquist Peak (Duffel, 1959).  General activity in the area increased after 1947  when the Aluminum Company of Canada Ltd. (Alcan) started engineering studies for i t s Kitimat project and the Geological Survey of Canada initiated a programme of systematic regional mapping.  6 The Francois-Tahtsa Lake access road built by Alcan, and the raised level in a number of lakes provided access to many new regions and prompted a period of renewed exploration and property development in the early 1950's.  During this time the Lead Empire Syndicate located claims  on lead-zinc-silver veins along what i s now the northern boundary of the Berg deposit and some mineral production was attained from the Emerald Glacier mine. The main brunt of exploration activity and an appreciation for the tremendous mineral potential of the area began in the early 1960's when exploration philosophy became oriented toward large tonnage deposits amenable to open-pit mining.  Highly mobile, helicopter-assisted exploration  teams with geochemical and geophysical f a c i l i t i e s , and assisted by a recently published geological map (Duffel, 1959, Geological Survey bf Canada, Map 1064A), found a large number of significant deposits and occurrences of copper-molybdenum and molybdenum. These include: Berg, Huckleberry, Whiting Creek, Ox Lake, Red Bird, Coles Creek, Lucky Ship, Troitsa, Bergette, Nanika, and others (see Carter, 1974). The property name 'Berg' is derived from local geographic features, Bergeland Creek and Bergeland Mountain.  Evidence of Berg deposit had been  known for a long time because a large, brightly coloured capping* most of which i s above treeline, marks the mineralized zone.  Exploration pits pre-  dating the original staking in 1961 were found on a quartz-molybdenite vein in the centre of the Berg property.  Claims were located in the late  1940's by the Lead Empire'Syndicate northeast of the colour anomaly on—  -  fissure veins with lead-zinc-copper-silver minerals that are peripheral to the zone of copper-molybdenum mineralization.  <;  7 Berg prospect was f i r s t staked (28 mineral claims) in 1961 to cover the prominent capping developed on and around a small stock that i s the locus of a strong geochemical anomaly.  Stream sediment samples at the confluence  of the north fork and Bergeland Creek, about 2 miles downstream from the deposit, are said to have returned values as high as 47,000 ppm copper and 600 ppm molybdenum (H. Goddard, 1974, personal communication).  In spite of a  strong geochemical expression, prospecting results were discouraging.  Only  minor surface expression of sulphides i s apparent in the form of widespread molybdenite in quartz veins and some local concentrations of secondary copper minerals along borders of basalt dykes.  In 1963 geologists with experience  in southwestern United States recognized the presence of a leached capping and the profound effects of surface leaching.  Increased exploration  expenditure in 1964 enabled bulldozer trenching and diamond d r i l l i n g that demonstrated the presence of supergene minerals, a feature not common in the Canadian Cordillera.  Subsequent work revealed that rocks are leached, in  places, to depths of 100 feet or more and are underlain by an extensive 'blanket' of supergene copper enrichment. D r i l l i n g during 1965 and 1966 delineated two main mineralized zones.  A northeast zone contains primary (hypogene) and some supergene  mineralization, and a southeast zone has widespread supergene mineralization. At the end of the 1966 field season the property consisted of 108 mineral claims on which there had been a total of 12,371 feet of diamond d r i l l i n g in 23 holes.  During 1967 a 12,000-foot d r i l l programme tested the south-  east zone on a widely spaced grid and three holes explored areas peripheral to the main area of interest.  From 1968 to 1970 the property was dormant  but metallurgical testing was done on composite samples of d r i l l core.  8 In 1971 three holes were drilled in the northeast zone.  At the end of  the 1971 exploration programme a total of 49 diamond-drill holes of mainly NQ and BQ core had been drilled with a total footage of 26,184 feet.  In 1972 exploration and development of the property were taken  over by Placer Development Limited (now Canex Placer Limited) under agreement with Kennco Explorations, (Western) Limited.  Since that time  (to 1975) 25 d r i l l holes of NQ core totalling 23,239 feet and 19 d r i l l holes of PQ core totalling 6,049 feet have been completed. The writer was f i r s t introduced to Berg prospect in 1966 and spent three months at the property in 1967 logging d r i l l core, studying rock alteration, and mapping regional geology.  Most of the materials and data  for this study were collected during that time. solved a number of stratigraphic problems.  Two separate v i s i t s in 1969  An 11-day stay during the 1971  d r i l l programme and a one-day v i s i t in 1974 permitted additional sampling, re-acquainted the writer with many of the field problems, and kept the writer abreast of recent developments.  PHYSIOGRAPHY Berg deposit is in the Tahtsa Ranges, a 10 to 15-mile-wide belt of mountains within the Hazelton Mountains (Holland, 1964).  The Hazelton  Mountains l i e along the eastern flank of the Kitimat Ranges of the Coast Mountains and form part of the Skeena Arch, a northeasterly trending area that was tectonically positive and was a locus for intrusive activity throughout much of the Mesozoic.  Duffel (1959) referred to the Tahtsa  Ranges as 'transitional ranges* because they represent a transitional zone between the rugged, predominantly granitic Coast Mountains to the  9 west and the r o l l i n g h i l l region of sedimentary and volcanic rocks that underlie the Nechako Plateau to the east. The Tahtsa Ranges are further subdivided into east-west to northeasterly trending ranges called, from north to south, the Tahtsa, Sibola, Whitesail, and Chikamln Ranges.  These are separated by major  valleys whose bottoms range in elevation from 2,600 to 3,100 feet and which are occupied by long lakes.  From north to south these are  Morice, Nanika, Tahtsa, Troitsa, Whitesail, and Eutsuk Lakes.  A l l drain  eastward into waterways of the Skeena or Fraser River drainage systems. The highest peak in the Tahtsa Ranges i s an unnamed 8,103-foot peak east of Nanika Lake, about 2.5 miles north-northeast of the Berg camp. A number of other mountains and ridges 7,000 feet and more in elevation occur as serrate peaks formed by cirque glaciation.  Many of the highest  and most rugged peaks are underlain by granitic cores.  Mountain flanks  and valley walls generally have more subdued, glacially rounded profiles with small benches, dissected plateau-like areas, and hanging valleys at various elevations.  GLACIATION The Tahtsa Ranges have undergone extensive glaciation.  According  to Tipper (1971), multiple glaciation i s probable over much of central British Columbia.  In the Berg area there is evidence for three types of  glaciation: a continental or mountain ice sheet, valley glaciation, and alpine cirque glaciation. During the main (Wisconsin) glaciation and possibly a second ice advance that was localized in north-central British Columbia (Fraser  10 glaciation), ice from the Coast Mountains flowed northeasterly and easterly along the existing major valleys into the Nechako Plateau. As ice depths increased, glaciers overrode valley walls and a l l but the highest peaks were glaciated.  In Berg area there i s ample evidence from  erratic boulders on small, dissected plateaus and beveled ridge crests to show that ice reached elevations of at least 5,500 feet. During deglaciation (circa 15,000 B.P. and later, as shown by Prest, 1970) valley glaciation, or surges during wasting and overall recession of the ice sheet, further modified valley walls.  Evidence of  valley glaciation i s preserved as terraces and ridges along sidehills bounding the larger valleys.  The ridges were f i r s t thought to be slump  structures but their occurrence from ridge crests to valley floors, lateral continuity over hundreds of feet, subparallel alignment along topographic contours, and development on slopes devoid of s o i l indicate that they are of glacial origin and may be poorly developed lateral moraines and lateral channels. Cirque glaciation has been the dominant influence in sculpturing present topography above 5,000 feet.  Small active cirque glaciers and  snowfields are found on eastern and northern slopes at elevations above 6,000 feet.  At present, cirque glaciers are wasting and receding so that  most cirques, alpine valleys, and gullies are mantled by recently deposited debris from terminal and recessional moraines, and by thin fluvioglacial deposits.  11  CHAPTER II  GEOLOGY REGIONAL GEOLOGY OF TAHTSA RANGE  INTRODUCTION Berg deposit i s about 8 miles east of the Coast Plutonic Complex in a region of bedded Jurassic and Cretaceous volcanic and sedimentary rocks intruded by a number of Jurassic, Cretaceous, and Tertiary stocks (Carter, 1974).  Mapping by Duffel (1959) provided a geological framework for the area  but i t is undergoing considerable revision as a result of recent work. Duffel's 'Hazelton Group' includes rocks of pre-Middle Jurassic to Early Cretaceous age.  Current work in the Whitesail Lake and other map-areas to  the north, mainly by geologists of the Geological Survey of Canada (Tipper, 1972; Richards, 1974), has resulted in Hazelton Group rocks being subdivided into Lower and Middle Jurassic units and has shown that Cretaceous sedimentary and volcanic rocks constitute a mappable unit that is more widespread than previously recognized.  Recent mapping In Tahtsa Lake v i c i n i t y by D. G.  Maclntyre (1974, personal communication) has resulted in a more precise description of the boundary between Hazelton Group and Cretaceous volcanic rocks.  Considerable refinement of intrusive history has been done with  potassium-argon dating (Carter, 1974).  A revised geological map of the  area i s shown on Figure 2. Geological mapping of about 20 square miles surrounding Berg deposit by the writer and C. S. Ney in 1967 and 1969 i s shown on Map 1, cross sections, Map 1A, and Map 2.  On the basis of this mapping, bedded  FIGURE 2  GEOLOGY  OF  TAHTSA  RANGE  BASED ON D U F F E L , 1959, M A P 1064A (WHITESAIL LAKE) AND UNPUBLISHED REVISIONS B Y N. C. C A R T E R , H. TIPPER. A . P A N T E L E Y E V , A N D O. MaclNTYRE  SCALE-MILES  SCALE-KILOMETRES  INTRUSIVE ROCKS TERTIARY MIDDLE TO UPPER EOCENE  MIDDLE EOCENE  ~ I COAST PLUTONIC COMPLEX: ____] GRANITIC ROCKS (MAY BE OLDER IN PART)  QUARTZ MONZONITE PORPHYRY, SOME ^^Bl=ELSiTE I N T R U S I O N S ; Cu AND M o BEARING STOCKS  CRETACEOUS AND TERTIARY UPPER CRETACEOUS -  PALEOCENE  ' B U L K L E Y INTRUSIONS' (IN PART): MAINLY PORPHYRITIC QUARTZ MONZONITE. M o - C u , AND Mo—W—BEARING STOCKS  JURASSIC LOWER A N D MIDDLE JURASSIC •OMINECA INTRUSIONS' (IN PART): GRANODIORITE, QUARTZ DIORITE, SYENITE  BEDDED ROCKS QUATERNARY PLEISTOCENE A N D RECENT IX-  I A L L U V I U M , GLACIAL OUTWASH, TILL, MORAINE  CRETACEOUS 'SKEENA GROUP' LATE LOWER CRETACEOUS AND ? YOUNGER G R E Y W A C K E , SILTSTONE, C O N G L O M E R A T E ; INCLUDES UNITS OF ANDESITE, DACITE, RHYOLITE FLOWS. BRECCIA, TUFF, AND R E L A T E D INTRUSIONS  PCRPHYRITIC SUUVOLCANIC  JURASSIC HAZELTON GROUP MIDDLE JURASSIC (MAY INCLUDE SOME LOWER CRETACEOUS) GREEN, ROCKS  GREY,  MAROON  VOLCANIC  BRECCIA,  TUFF,  FLOWS; SOME  SEDIMENTARY  LOWER JURASSIC I G R E E N , RED, PURPLE VOLCANIC BRECCIA, CONLOMGERATE. G R E Y W A C K E ; SOME INTERI C A L A T E D SEDIMENTARY ROCKS  TRIASSIC AND EARLIER , \ f ^ GNEISS COMPLEX  13 rocks were subdivided into three lithologically similar units:  a basal  volcanic unit consisting of mainly pyroclastic and volcanic-source sedimentary rocks (Map 1, unit 1) overlain by a series of porphyritic volcanic flow rocks (unit 2); a locally derived sedimentary, largely greywacke, unit forming an eastward-thickening prism or clastic wedge (unit 3); and an upper volcanic unit of porphyritic,  intermediate to  siliceous flows, breccias, and tuffs (unit 4). On Whitesail Lake map (1064A) a l l these rocks are shown as Hazelton Group and are described as '(mainly) Middle Jurassic' volcanic rocks.  However, the possibility that Lower Cretaceous rocks are included  in this map unit i s suggested (Duffel, 1959). C. S. Ney observed an angular discordance between volcanic rocks and overlying sedimentary rocks at the head of Kidprice Creek, south of Berg deposit.  Thus, classification of these rocks as Hazelton Group became suspect  and subsequent mapping In the Berg area revealed a gentle angular unconformity between volcanic rocks of the upper and lower map units (Map 1, units 4 and 2) at the pinchout of the intervening sedimentary unit (unit 3). Age relationships were established in 1972 when ammonites collected earlier from sedimentary rocks (unit 3) by the writer were identified by H. Tipper as Cleoniceras of Albian stage (late Lower Cretaceous).  Recent regional  mapping by the Geological Survey of Canada suggests that Cretaceous sedimentary and volcanic rocks may be equivalent, respectively, to the Brian Boru and Red Rose Formations of Sutherland Brown (1960), and are part of an extensive draping of Cretaceous rocks over Lower and Middle Jurassic Hazelton Group rocks that extends from Hazelton to south of Tahtsa Lake in Smithers and Hazelton map-areas.  They are now classified  as part of the newly resurrected 'Skeena Group* (Richards, 1974).  14  BEDDED ROCKS STRATIGRAPHIC RELATIONSHIPS Volcanic rocks of the Hazelton Group are seen throughout the entire western half of Berg map-area (Map 1).  In the eastern half they  underlie Cretaceous vesicular-amygdaloidal, in places trachytoid, feldspathic volcanic flows, sedimentary rocks, and brecciated porphyritic flows.  Originally a l l volcanic rocks exposed in the west and underlying  Albian sedimentary rocks in the centre of the map-area were considered to be part of the Hazelton Group. units:  These rocks were divided into two sub-  a thick lower pyroclastic unit (Map 1, unit 1) and an overlying  thinner flow unit (unit 2).  However, recent mapping by D. G. Maclntyre  (1974, personal communication) has shown unequivocably that vesicularamygdaloidal feldspathic volcanic rocks to the south near Tahtsa Lake overlie Hazelton Group pyroclastic rocks with pronounced angular unconformity and are therefore part of a younger volcanic-sedimentary succession rather than part of the Hazelton Group.  The relationship  between these two older map units (units 1 and 2) i s obscured in Berg map-area by snowfields and quartz diorite intrusions.  Although no d i s -  cordance i s obvious between map units 1 and 2, the vesicular-amygdaloidal feldspathic (Cretaceous) volcanic rocks (unit 2) dip more gently eastward than underlying Hazelton Group pyroclastic rocks and rocks to the west (unit 1).  This was rationalized during i n i t i a l mapping as being due to  flattening of a fold limb in Berg map-area.  However, i t is now concluded  that Cleoniceras-bearing (Albian) sedimentary strata (unit 3) overlie conformably or disconformably the feldspathic amygdaloidal lavas (unit 2) and are in turn overlain by intermediate to acidic volcanic rocks, mostly breccias (unit 3).  15 HAZELTON GROUP (MIDDLE JURASSIC: Map 1, Unit 1) Volcanic rocks of the Hazelton Group comprise a predominantly pyroclastic assemblage about 5,500 feet thick that underlies the mineralized area, Bergeland Creek valley, and ridges to the west.  The rocks  are grey, green, maroon, and purple t u f f , tuff breccia, and lesser units of volcanic flows, flow breccia, and tuffaceous or epiclastic sedimentary rocks.  Base of the unit i s not exposed but oldest strata are thick beds  of flow breccia, massive flows, and tuff that pass into a sequence of thinly bedded shale, chert, and tuffaceous siltstone and sandstone. These well-bedded sedimentary rocks are seen mainly in the lower reaches of the north fork of Bergeland Creek.  They are overlain by the principal  ridge forming pyroclastic members in Berg area.  These are massive to  sorted and graded, coarse to fine-grained tuff with some units of massive, rarely amygdaloidal flows and thin units of flow and tuff breccia and reworked tuffaceous sedimentary members.  Younger beds may be, in part,  subaerial but are mainly shallow marine (intertidal or l i t t o r a l ) .  A  number contain well-developed accretionary l a p i l l i , mud pellets, and one locality with oscillation ripple marks is known.  Many of the originally  porous, coarsely fragmental rocks have a limy or ferruginous matrix.  silt-sized  Near the top of the sequence a few cobble beds with reworked  volcanic sandstone matrix and volcanic clasts were noted.  None was seen  to contain any clasts of intrusive rocks; exotic rocks are mainly chert and a few pieces of crystalline limestone. Based on some partial analyses by Church (1972), Hazelton Group volcanic rocks from Sibola Peak, Berg deposit, and other nearby areas are andesite or basaltic andesite.  Regional alteration is of the sub-greenschist  16 facies (Richards, 1974) but In Berg map-area no prehnite nor pumpellyite and only one locality with zeolites were noted.  Epidote, chlorite, calcite,  tremolite, montmorillonite, albite, K-feldspar, and sericite are widespread in the map-area.  Also small amounts of garnet, tourmaline, amphi-  bole, scolecite, and other minerals are present in xenoliths within quartz diorite.  The latter minerals are of apparent hydrothermal origin and formed  in broad propylitic zones or small skarn zones associated with intrusive rocks.  SKEENA GROUP (LOWER CRETACEOUS AND ? YOUNGER; Map 1 , Units 2 to 4) Skeena Group rocks underlie the eastern part of Berg map-area. They can be subdivided into three map units:  a lower volcanic unit  (unit 2), an intervening sedimentary unit (unit 3), and an upper volcanic unit (unit 4). Rocks of the lower volcanic unit (unit 2) generally occur along a north-south-trending belt, up to 1% miles wide, through the centre of Berg map-area (Map 1).  Best outcrop exposures are on steep slopes east  of the main granitic intrusions and west of Kidprice Creek. of about 2,000 feet of strata i s present.  A maximum  The rocks were classified in  the f i e l d and later from partial chemical analyses as andesite to trachyandesite.  Flows are commonly vesicular and amygdaloidal and are, therefore,  mainly subaerial but may locally be subaqueous as in two l o c a l i t i e s they contain thin lenses of limestone.  Small amygdules and vesicules contain  abundant chlorite as radiating fibrous spherulites as well as calcite, quartz, and montmorillonite.  Calcite with crystalline and chalcedonic  quartz is common in larger vugs and cavities.  17 The tase of the rock unit i s not well exposed in Berg map-area but south of Tahtsa Lake i s marked by a purple conglomerate member (D. G. Maclntyre, 1974, personal communication).  Based on this observation,  two small outliers of boulder conglomerate unconformably capping the ridge northwest of Berg camp are mapped as Cretaceous rocks. Sedimentary rocks (unit 3) crop out in most of the eastern half of Berg map-area where they form a clastic wedge that overlies feldspathic trachytoid vesicular-amygdaloidal flow rocks of the Cretaceous lower volcanic unit (unit 2).  About 1 mile east of Berg camp sedimentary strata  are intruded and thermally metamorphosed by quartz d i o r i t e .  At i t s  maximum extent in the southeast corner of the Berg map sheet the clastic wedge i s at least 1,600 feet thick.  The pinchout can be traced along the  northern boundary of the area mapped and just east of 8,103 peak (see cross sections, Map 1A). Sedimentary units are predominantly sandstone with abundant feldspar grains and small rock fragments in a fine-grained micaceous matrix. Abundance of detrital mica i s a useful field criterion for recognizing Cretaceous sedimentary rocks in Smithers and Hazelton map-areas (H. Tipper, 1972, personal communication).  Beds are massive, poorly sorted deposits  whose monotony i s broken rarely by conglomerate members and units of thinly bedded shale and graded siltstone that show load casts, rip-up clasts, and slump structures.  Large spherical concretions about 1 foot in diameter  are common in some beds.  One cherty shale member contains a few specimens  of ammonite Cleoniceras which establishes an Albian age for the strata. The top of the unit i s marked by a 50-foot succession of thinly bedded to lamellar siltstone and shale beds.  These are overlain by a distinctive  18  PLATE 1:  8,103 peak w i t h u n c o n f o r m i t y between H a z e l t o n Group v o l c a n i c r o c k s (MJ, Map 1, u n i t 1) and o v e r l y i n g Skeena Group v o l c a n i c r o c k s (LK, Map 1, u n i t 4 ) . A p p r o x i m a t e l y 500 f e e t o f s t r a t a a r e shown.  PLATE 2:  Skeena Group r o c k s about 2 m i l e s e a s t o f 8,103 peak. Albian sedimentary s t r a t a (Map 1, u n i t 3) a r e o v e r l a i n by eastwardt h i n n i n g p r i s m s and beds o f v o l c a n i c r o c k s (Map 1, u n i t 4 ) . The conformable ( d i s c o n f o r m a b l e ?) c o n t a c t i s marked by a columnar f e l d s p a r p o r p h y r y s i l l . A p p r o x i m a t e l y 1,200 f e e t o f s t r a t a a r e shown.  19 red bed conglomerate that Is a maximum of about 20 feet thick, and red to purple siltstone lenses.  The red bed conglomerate forms a persistent  marker unit in the northeast corner of the map-area and can' be regarded as either the top of the sedimentary unit or, perhaps better, as the basal conglomerate of the overlying volcanic unit.  The conglomerate  contains cobble to boulder-sized clasts of volcanic rocks in a ferruginous, gritty sand matrix. Late Lower Cretaceous and possibly younger volcanic rocks of the Skeena Group upper volcanic unit (Map 1, unit 4) are seen in two areas.  The largest is In the northeast corner of the map sheet, V$ to r  2 miles east of 8,103 peak where volcanic rocks (unit 4) appear to l i e conformably on Albian sedimentary beds (unit 3) and are separated from them by a well-jointed feldspar porphyry s i l l that intrudes along the top of the red bed unit (Plate 2).  The volcanic rocks form a flat-topped  ridge with basal, dark-coloured, bedded volcanic flow rocks and an overlying pile of massive, pale-coloured breccias.  Basal beds are lenses or  discontinuous, rapidly eastward-thinning prisms of coarse-grained tuffaceous sandstone subsequently overlain by brown siltstone and shale, a coarse volcanic breccia member, porphyritic tuff breccia, and, purple to mauve and grey, aphanitic and porphyritic flow members.  The top of the volcanic  unit is composed of cream-coloured breccia about 400 feet thick.  Total  thickness of volcanic rocks in unit 4 i s about 700 feet. A second area in which volcanic rocks of the upper unit (unit 4) are seen i s a steep ridge forming the crest and summit of 8,103 peak and on a ridge to the northeast.  There, about 350 feet of porphyritic grey to  grey-green volcanic breccia and flows s i t unconformably on well-bedded, more steeply dipping, purplish Hazelton Group pyroclastic rocks (Plate 1).  On the ridge leading north from 8,103 peak, purple pyroclastic rocks of the Hazelton Group are intruded by a dyke swarm of glassy, black to mauve, and cream-coloured rocks averaging about 5 to 10 feet in thickness that may be feeders for overlying Cretaceous volcanic rocks.  The  abundance of coarse-grained volcanic breccias and glassy dykes may indicate the proximity of a volcanic centre In the vicinity of 8,103 peak. Partial chemical analyses of lithologically similar volcanic rocks overlying Cretaceous sedimentary strata in Sibola Range about 6 miles east of Berg area indicate that the composition of these volcanic rocks i s predominantly dacite and rhyolite, with lesser andesite (Church, 1972).  This contrasts with the andesitic to basaltic composition of  Hazelton Group volcanic rocks.  INTRUSIVE BODIES Intrusive rocks have been grouped into three map units (Map 1): a quartz diorite/diorite stock and related intrusions; a small multiphase mineralized stock of quartz monzonite porphyry; and minor intrusions of various probable affinities and ages.  QUARTZ DIORITE Quartz diorite forms the largest intrusive body mapped, a northsouth -trending stock at least 2,000 feet wide in the centre of Berg maparea.  The body has steep walls and forms the core of Tahtsa Range.  The  intrusion has been traced by the writer at least 4 miles to the south of Berg camp where i t widens to about 9,000 feet along the southern edge of  21  Berg map sheet.  The stock was mapped by Duffel (1959) as 'gabbro' which  'closely resembles many of the diorites associated with the main mass of the coast intrusion.'  More detailed mapping has shown the rock to be a  fine-grained, locally porphyritic, biotite hornblende quartz diorite or diorite.  A minor hornblende-rich contact phase is found where brecciated  microporphyritic andesite has been metasomatized along the intrusive contact. About 1 mile south-southeast of camp, the core of the quartz diorite intrusion i s composed of a porphyritic, pink, s e r i c i t e - r i c h granodiorite and quartz monzonite.  The quartz monzonite phase is por-  phyritic and has a gradational contact zone about 100 feet wide within quartz diorite.  The porphyritic phase i s seen as a 600-foot-wide zone  of rusty, hydrothermally altered rock surrounded by less altered, jointed quartz diorite typical of the main intrusive mass. Small intrusions of biotite hornblende diorite and hornblende diorite/quartz diorite related to the main intrusion are found to the north of and peripherally around the stock.  These smaller intrusions  occur as small stocks and dykes that penetrate Hazelton Group and younger strata as jagged intrusive plugs without any appreciable disruptive effects on bedding.  The largest of the peripheral bodies intrudes west  of the Berg camp and i s found along an east-northeast trend coaxial with the main mineralized quartz monzonite porphyry. Thermal metamorphic effects due to intrusion of the main diorite mass are evident as zones of purplish brown biotite hornfels formed across widths of up to 400 feet (commonly 100 feet or less) from the contact. Small areas and local patches of coarsely recrystallized, amphibole and biotite-bearing metasomatized rocks have a ' d i o r i t i z e d ' look.  Along the  22 north and northeast contact local patches of garnet-epidote skarn have developed in calcite-bearing amygdaloidal flow volcanics of Cretaceous volcanic units. Quartz diorite intrusions cut and metamorphose Albian sedimentary rocks but are intruded, altered, and mineralized by quartz monzonite porphyry. Potassium-argon dating by Carter (1974) shows that the quartz diorite intrusion i s equivalent in age to younger phases and s a t e l l i t i c stocks of the Coast Plutonic Complex.  Quartz diorite may be as young as about 47  million years and appears to be significantly younger than the 76.7±2.5 million year old intrusions on Sibola Peak 10 miles to the east.  QUARTZ MONZONITE PORPHYRY The most economically significant Intrusive body in the map-area i s a small composite stock of quartz monzonite porphyry about 2,100 feet in diameter that intrudes pyroclastic rocks near the northwest margin'of the quartz diorite intrusion (Map 2).  A l l phases of quartz monzonite are  hydrothermally altered and mineralized. The main mass of the quartz monzonite stock i s roughly equidimensional at surface with f a i r l y regular contacts.  Exceptions are along  the south and southwest contact and at depth where dykes and s i l l - l i k e bodies project into or along volcanic strata.  The main intrusive mass  i s a composite of at least three phases of coarse-grained biotite quartz feldspar porphyry that are intruded by at least one distinctly crosscutting phase of porphyry, namely hornblende quartz feldspar porphyry. This porphyry forms a northeasterly trending dyke that bisects the main quartz monzonite mass and intrudes hornfels and quartz diorite to the  northeast.  The main phases of quartz monzonite have not been observed  to intrude quartz diorite and are separated from i t by a screen of hornfelsed volcanic rock about 300 feet wide.  Quartz diorite close to  quartz monzonite i s strongly altered and mineralized.  An intrusive  breccia body that i s similar to quartz monzonite in composition and alteration intensity underlies a large area about 1,500 feet southeast of the quartz monzonite stock. Potassium-argon dating by Carter (1974) of biotite from the quartz monzonite stock, altered quartz diorite, and whole rock specimens from the mineralized hornfels surrounding the stock indicates Eocene ages with a mean value of about 50 million years.  MINOR INTRUSIONS A number of minor intrusions of various types have been mapped as shown on Map 1.  The two largest are coarse-grained, strongly  jointed feldspar porphyry s i l l s that are emplaced at the top of the Albian sedimentary succession in the eastern part of the map-area.  The  more northerly s i l l i s up to 50 feet thick and has intruded along the contact between sedimentary and volcanic rocks (Map 1, units 3 and 4). Small outliers of the feldspar porphyry can be seen to the west of the rhyolite mass where they overlie red bed conglomerate (uppermost part of unit 3).  A second, larger body of feldspar porphyry forms a dip-  slope capping of approximately 0.'5 square mile in area, about 1.5 miles east of Berg camp. feet.  The thickness of this s i l l may be as much as 150  Age of feldspar porphyries has not been determined but they may  be intrusive equivalents of extrusive Cretaceous volcanic rocks.  A  24 Tertiary age cannot be ruled out as thin feldspar porphyry dykes, possibly equivalent to the s i l l s , intrude the quartz diorite stock. Massive white to cream-coloured, weakly layered, microporphyritic rhyolite dykes, similar to brecciated rhyolite south of 'Sanfts' Creek, form small irregular intrusions on the ridge southwest of the camp and are associated with numerous glassy dykes northeast of 8,103 peak.  They are  „ probably intrusive equivalents of, and possibly feeders for, Cretaceous rhyolite flow and breccia members. The most abundant type of dyke in the region i s biotite feldspar or quartz feldspar porphyry.  These form small dykes commonly 5 to 50 feet,  rarely exceeding 100 feet, in thickness.  They are found in a l l the main  map units except volcanics of the youngest map unit (Map 1, unit 4) and are believed to be related to the main Tertiary quartz monzonite intrusion. Miocene (and younger ?) basalt and possibly some andesite dykes intrude a l l major rock units throughout the map-area.  They are commonly  1 to 10 feet wide although dykes up to 80 feet in width are known. are abundant at surface but are not concentrated in any one area.  Dykes A  greater than average number of thin basalt dykes has been intersected in d r i l l holes in the mineralized zone.  STRUCTURE Bedded rocks in the map-area form an easterly dipping panel, commonly with 10 to 30-degree dips.  Folding is weakly developed as  large-scale undulations and flexures of strata about north to northnortheasterly fold axes.  In a few areas slump folds, bed crenulations,  FIGURE 3 :  A i r photo i n t e r p r e t a t i o n of fracture trends. Measurement of 87 most prominent photo l i n e a r s i n bedrock i n Berg map-area.  26 and chaotic blocks with contorted strata are associated with small-scale de'collements.  Such de'collement structures are seen on the west flank of  8,103 peak (Plate 2). Fracture patterns, as shown on Figure 3, indicate predominance of east-northeast and north to northeasterly trends.  Where fault  displacements or offsets can be measured, the most significant movements are, at most, a few hundred feet in magnitude and appear to have taken place along northwesterly breaks.  Age of faulting i s uncertain but Miocene  basalt dykes that commonly invade the most intensely fractured zones rarely show any significant offsets.  This implies that post-Miocene movements  may have been minor relative to those during Cretaceous or Early Tertiary time. Structural controls on the emplacement of intrusive bodies are suggested by north-south elongation of the main quartz diorite stock and alignment of small diorite intrusions along the northern extension of the stock.  Subsidiary, possibly younger, northeasterly trending structures  or zones of weakness appear to have controlled emplacement of subsidiary quartz monzonite intrusions and younger dykes that bisect them.  The  youngest structural breaks are northwesterly zones that are invaded by basalt dykes and may offset younger ridge-forming porphyry dykes that cut the main stock.  GEOLOGY OF BERG DEPOSIT INTRODUCTION Geology of the mineralized zone at Berg deposit was studied extensively and described by George 0. M. Stewart (1967).  Stewart,  27  aided by some bulldozer trenches and a few diamond-drill holes, mapped highly weathered surface exposures.  His interpretation of general geology,  major map units, and locations of intrusive contacts i s s t i l l essentially valid.  Stewart described five main map units: hornfelsed and hydrothermally  altered Hazelton Group volcanic and sedimentary rocks; a diorite/quartz diorite stock thought to be a s a t e l l i t e of the Coast Plutonic Complex; a composite quartz monzonite porphyry stock about which copper-molybdenum mineralization i s localized; a crosscutting 'quartz l a t i t e ' post-ore dyke phase; and an intrusive breccia pipe.  Recent diamond d r i l l i n g in previously  untested areas, principally in the core and near margins of the quartz monzonite stock, indicates that a number of porphyry phases can be distinguished and internal intrusive relations are more complex than f i r s t thought.  Recent revisions of Stewart's mapping are shown on Map 2 and  illustrated in Figures 4 and 5. Surface exposures are limonite-stained, deeply weathered, crumbly outcrops that are leached by oxidation and acid groundwaters.  Slopes are  generally devoid of vegetation and are mantled by slide debris and talus. The centre of the mineralized area is underlain by a quartz monzonite porphyry stock generally containing 2 per cent and less sulphide minerals. This stock is a roughly equidimensional plug about 2,100 feet in diameter and has a bulbous northwesterly trending lobe in the southwest.  It  is  transected by a splayed northeasterly trending porphyry dyke that forms a spine-like ridge.  Porphyritic intrusive rocks weather pale to yellow  brown and form an elongated northeasterly trending mound in the centre of a broad, west-facing embayment in a prominent north-trending ridge. A broad horseshoe-shaped low-weathering area that opens Into Bergeland Creek tributary on the southwest surrounds the somewhat more  PLATE 3 :  Panoramic v i e w o f B e r g p r o s p e c t , view t o n o r t h and  east.  NJ 00  FIGURE GEOLOGY  4 -  BERG  DEPOSIT  [—20,000 N  •  •ib'tf  DRILL HOLE -VERTICAL v  DRILL HOLE - INCLINED  r><o ~  Scale  «  ' ' i - 'VoOL-  7 ' . ij.' v:- <• v  1  c  '  I ' .' V.<-, - > •  C qtz monz-granodi or •j qtz bearing monzodi L(hbde Q F P ) qtz monzonite qtz d i o r i t e hornfels ,volcanics  30  ] Scale 0 1  •  feet  800 I  breccia -qtz monz - granodi or qtz bearing monzodiorite (hbde Q F P ) qtz monzonite  QMP  qtz diorite hornfels  31 r e s i s t a n t porphyry  stock.  T h i s i s the zone o f s t r o n g l y f r a c t u r e d ,  m i n e r a l i z e d , and a l t e r e d v o l c a n i c r o c k s .  Rapid  erosion of a l t e r e d  rocks  a b e t t e d by p e r c o l a t i o n o f a c i d i c groundwater t h a t removes gypsum from f r a c t u r e s has p r o b a b l y been more i m p o r t a n t  than g l a c i a l s c o u r i n g i n  development o f l o w - l y i n g a r e a s about the s t o c k . zones have r e l i e f o f about 700 and a r e o c c u p i e d by northwest  (Map  'Red'  The most h i g h l y eroded  f e e t r e l a t i v e t o the porphyry  Creek on the s o u t h e a s t and  ridge crest  'Pump' Creek on  the  2).  Rocks c o n t a i n i n g e c o n o m i c a l l y s i g n i f i c a n t s u l p h i d e m i n e r a l s extend  outward f o r a t l e a s t 2,000 f e e t beyond the q u a r t z monzonite c o n t a c t  and a d j o i n i n g d e e p l y eroded  v o l c a n i c rocks.  Rocks w i t h s u l p h i d e m i n e r a l s  a r e marked by dark brown l i m o n i t e - s t a i n e d o u t c r o p s . q u a r t z monzonite s t o c k t h e s e a r e v o l c a n i c and n o r t h e a s t and e a s t , q u a r t z d i o r i t e . t y p e and a l t e r a t i o n . t o about 30 degrees  sedimentary  r o c k s and  the t o the  Topography r e f l e c t s changes i n r o c k  S l o p e s a r e r e l a t i v e l y g e n t l e near the s t o c k , on f l a n k i n g h i l l s i d e s , and  l i m o n i t e - s t a i n e d zone s t e e p e n and  To the n o r t h o f  steepen  a t the o u t e r edge o f t h e  a b r u p t l y t o about 45 d e g r e e s .  s p a r s e l y m i n e r a l i z e d v o l c a n i c r o c k s on the n o r t h and  Weakly a l t e r e d  quartz  diorite  on the e a s t form r i d g e c r e s t s t h a t tower over the m i n e r a l i z e d zone. Maximum r e l i e f i s a p p r o x i m a t e l y and  1,800  f e e t on the r i d g e t o the n o r t h  2,400 f e e t on the r i d g e t o the e a s t o f the q u a r t z monzonite s t o c k .  BEDDED ROCKS  Host r o c k s f o r i n t r u s i o n s and m i n e r a l d e p o s i t s a r e M i d d l e J u r a s s i c H a z e l t o n Group v o l c a n i c r o c k s (Maps 1 and are m a i n l y  2, u n i t 1 ) .  These  coarse t o medium-grained t u f f s o f a n d e s i t i c c o m p o s i t i o n  as  32 w e l l as s u b o r d i n a t e f l o w r o c k s , b r e c c i a s , e p i c l a s t i c v o l c a n i c s v o l c a n i c s o u r c e sandstones s h a l e and  siltstone.  or  'greywackes'),  and minor amounts o f marine  O u t s i d e the a r e a o f m i n e r a l i z a t i o n v o l c a n i c r o c k s  a r e dark g r e y , g r e y - g r e e n ,  p u r p l e , and r e d i n c o l o u r w i t h  f r a g m e n t a l t e x t u r e s and w e l l - d e f i n e d b e d d i n g . the v o l c a n i c r o c k s a r e r e c r y s t a l l i z e d  obvious  C l o s e r to i n t r u s i o n s  t o dark grey-brown and  r o c k s i n which o r i g i n a l fragments a r e seen as r e l i c t obliterated  (reworked  black  c l a s t s or are  totally  i n homogeneous-looking h o r n f e l s .  The v o l c a n i c s u c c e s s i o n s t r i k e s a p p r o x i m a t e l y n o r t h - s o u t h is tilted  eastward  a t about 30 d e g r e e s .  There i s no apparent  by f a u l t i n g o r o t h e r s t r u c t u r a l c o m p l i c a t i o n s . s e c t i o n measured a l o n g B e r g e l a n d of  Creek and  Thus, an  and  repetition  east-west  the r i d g e immediately  north  Berg d e p o s i t r e p r e s e n t s a r e a s o n a b l y t r u e g e o l o g i c c r o s s s e c t i o n w i t h  younger r o c k s o r  ' t o p s ' t o the e a s t .  A generalized succession subdivided  i n t o s i x u n i t s r e p r e s e n t i n g about 5,000 f e e t of s t r a t a i s shown i n F i g u r e 6.  O l d e s t r o c k s are on the west and a r e shown as map  Rocks o f map and  grey-green,  and  intercalated  A.  u n i t A form a 1 , 0 0 0 - f o o t - t h i c k sequence o f g r e y  f i n e - g r a i n e d t o weakly p o r p h y r i t i c a n d e s i t e s , f l o w b r e c c i a s , f i n e - g r a i n e d sedimentary  layers.  The  tuffs,  and f l o w s a r e seen a l o n g the n o r t h bank o f upper Bergeland o v e r l i e about 1,000  tuff breccias,  Creek  and  f e e t o f t h i n l y bedded s h a l e , s i l t s t o n e , c h e r t , and  t u f f a c e o u s sediments exposed f u r t h e r downstream.  Unit B c o n s i s t s of a  1 , 3 0 0 - f o o t - t h i c k p i l e o f t u f f s , minor b r e c c i a s , and i n c l u d i n g three p a i r e d u n i t s of purple l a p i l l i mauve ash t u f f .  unit  a few f l o w  t u f f o v e r l a i n by grey  P u r p l e members a r e made up of p a l e grey and  s i z e d p o r p h y r i t i c fragments c o n s t i t u t i n g from  units  cream  10 to 30 per cent o f  and  lapillithe  Figure 6.  Subdivision of Hazelton Group Volcanic Succesiion at Berg Deposit  TUFFS. TUFFACEOUS SEDIMENTS. FLOWS  FLOWS, FLOW BRECCIAS  iii  BRECCIA  TUFFS  TUFFS. BRECCIAS MINOR FLOWS  FLOWS. FLOW BRECCIAS SEDIMENTS  TUFFS. BRECCIAS, FLOWS SHALE, SILTSTONE. CHERT. TUFFACEOUS SEDIMENTS  SECTION INTRUDED BY MINERALIZED QUARTZ MONZONITE PORPHYRIES  34 r o c k i n a dense v i t r i c lithic  groundmass.  O v e r l y i n g g r e y and mauve r o c k s a r e  t u f f s i n which t h e r e I s abundant s o r t i n g o f fragments.  a r e graded  Most beds  and t h e r e i s much a l t e r n a t i o n between beds c o n t a i n i n g e i t h e r  f i n e ash o r c o a r s e ash and l a p i l l i  fragments.  The t h r e e p a i r e d u n i t s  a r e s u c c e s s i v e l y t h i n n e r ; t h e o l d e r b e i n g over 200 f e e t i n t h i c k n e s s , the m i d d l e  150 f e e t , and the upper o n l y 60 f e e t  w i t h i n t h e s e map u n i t s a r e 1 i n c h t o a few f e e t  thick.  I n d i v i d u a l members  i n thickness.  Above t h e  p a i r e d p u r p l e - g r e y u n i t s a r e m a i n l y dark p u r p l e , mauve, and g r e y , packed, l i t h i c  lapilli  l i m e s t o n e fragments.  loosely  and ash t u f f s t h a t c o n t a i n a few c r y s t a l l i n e The top o f u n i t B i s taken t o be a 4 0 - f o o t - t h i c k  s u c c e s s i o n o f massive f i n e - g r a i n e d f l o w v o l c a n i c s .  Map u n i t C c o n s i s t s o f about 600 f e e t lithic  tuffs.  o f r e d , p u r p l e , and grey  The s u c c e s s i o n i s made up o f t h i n l y bedded l a p i l l i  w i t h fragments up t o 5 c e n t i m e t r e s i n s i z e , 0.5 t o 1.5-centimetre b e i n g most common i n an ash m a t r i x .  fragments a r e c i n d e r y and p e l l e t e d a c c r e t i o n a r y l a p i l l i a s u b a e r i a l accumulation.  fragments  These t u f f s a r e v e r y porous w i t h  packed fragments i n a r e l a t i v e l y homogeneous n o n s o r t e d  in  tuffs  ash m a t r i x .  loosely  Some  probably deposited  Some beds c o n s i s t o f reworked t e p h r a w i t h  a l i m y mud m a t r i x and formed i n an a p p a r e n t l y s h a l l o w subaqueous environment. U n i t D c o n s i s t s o f about 300 f e e t o f p a l e and medium grey v o l c a n i c b r e c c i a w i t h fragments up t o 5 c e n t i m e t r e s i n s i z e .  T h i s u n i t i s o v e r l a i n uncon-  f o r m a b l y by a t h i n c a p p i n g o f C r e t a c e o u s b o u l d e r conglomerate r i d g e northwest  o f the camp.  U n i t E i s a 300-foot  on t h e  succession o f  'greenstone'  f l o w s and f l o w b r e c c i a s which i s o v e r l a i n by u n i t F, a heterogeneous assemblage o f t u f f s , f i n e - g r a i n e d t u f f a c e o u s sediments i n c l u d i n g l i m y s i l t s t o n e s , v o l c a n i c sandstones, in  stratigraphic thickness.  and f l o w s t o t a l l i n g a t l e a s t 500 f e e t  35 Rocks o f u n i t s B, a l t e r e d , and m i n e r a l i z e d .  C, and The  upper p a r t o f A have been i n t r u d e d ,  r o c k s have been d e s c r i b e d as  However t h e r e has been c o n s i d e r a b l e metasomatism and, ' h o r n f e l s ' i s used i n an i n f o r m a l s e n s e .  'hornfels.*  t h u s , the  At Berg d e p o s i t ,  term  Sutherland  Brown (1967) d i s t i n g u i s h e d between b i o t i t i c h o r n f e l s i n a t h e r m a l and h y d r o t h e r m a l l y  metasomatized r o c k s , he  r e c r y s t a l l i z e d q u a r t z , b i o t i t e , and hydrothermally  a l t e r e d rocks  termed s k a r n ,  K-feldspar.  He  containing  further subdivided  i n t o a t h i r d group o f m o t t l e d ' g r e i s e n - l i k e '  ( q u a r t z s e r i c i t e ) r o c k s . However, o r i g i n of b i o t i t e cannot always a s c r i b e d on  aureole  be  the b a s i s o f appearance t o e i t h e r p u r e l y c o n t a c t metamorphism  or metasomatism and  the term ' h o r n f e l s ' w i l l be  f o r purely d e s c r i p t i v e purposes.  retained i n this thesis  Thus, b i o t i t e h o r n f e l s r e f e r s t o a l l  the m a s s i v e , d a r k , f i n e - g r a i n e d metamorphosed r o c k s s u r r o u n d i n g intrusions.  While some e p i d o t e  c a l c a r e o u s beds a l o n g  and  r a r e garnet  occurs  Berg  in altered  the q u a r t z d i o r i t e c o n t a c t or i n pendants i n  quartz  d i o r i t e , no s k a r n assemblages a r e p r e s e n t w i t h i n Berg d e p o s i t .  INTRUSIVE ROCKS  Two  d i s t i n c t i v e i n t r u s i v e bodies  d i f f e r i n composition,  t e x t u r e , shape, and  a r e seen a t Berg d e p o s i t .  They  e f f e c t on i n t r u d e d r o c k s .  The  older rock i s a f i n e - g r a i n e d b a s i c quartz d i o r i t e m i n e r a l i z a t i o n and has hornfels.  recrystallized  i n t r u s i v e contact  continuous  inherent  i n t r u d e d r o c k s i n t o a dense, compact  Q u a r t z d i o r i t e i s p a r t o f a l a r g e i n t r u s i v e body a t l e a s t  f e e t wide t h a t extends f o r a t l e a s t The  t h a t has no  without  5 m i l e s to the south  o f Berg d e p o s i t .  i s s t e e p l y d i p p i n g , somewhat s e r r a t e d i n p l a n ,  known o f f s h o o t s or p r o j e c t i o n s .  2,000  but  36 The younger i n t r u s i o n i s a composite  s t o c k o f q u a r t z monzonite  porphyry not more than o n e - h a l f m i l e i n d i a m e t e r . i s m i n e r a l i z e d t o some degree and  a d j o i n i n g v o l c a n i c r o c k s and  d i o r i t e a r e a l t e r e d and m i n e r a l i z e d e x t e n s i v e l y . monzonite s t o c k i s p l u g - l i k e and by dykes, s i l l s ,  and  Every i n t r u s i v e  The  i r r e g u l a r apophyses.  l a r g e and  quartz  southwest  Quartz monzonite does not  i n t r u d e q u a r t z d i o r i t e , b u t has a l t e r e d and m i n e r a l i z e d i t . types a r e c u t by one  quartz  c o r e o f the  i s f l a n k e d to the s o u t h and  phase  a number of s m a l l e r porphyry  Both  rock  dykes r e l a t e d  t o q u a r t z monzonite.  Age not c e r t a i n .  and g e n e t i c r e l a t i o n s h i p s between I n t r u s i v e r o c k t y p e s P o r p h y r i t i c q u a r t z monzonite i s found  i n a zone a  are  few  hundred f e e t wide w i t h i n q u a r t z d i o r i t e 2 m i l e s south of Berg d e p o s i t . The  zone i s w i t h i n the c e n t r e o f and widest" p a r t o f the q u a r t z  i n t r u s i o n and  appears  t o have g r a d a t i o n a l c o n t a c t s w i t h q u a r t z  Thus, p o r p h y r i t i c q u a r t z monzonite may  diorite.  be a more h i g h l y d i f f e r e n t i a t e d  phase o f a p a r e n t q u a r t z d i o r i t e magma. porphyry  diorite  The m i n e r a l i z e d q u a r t z monzonite  and q u a r t z d i o r i t e a t Berg d e p o s i t might be  oogenetic.  D e s c r i p t i o n o f i n t r u s i v e r o c k s i n Berg map-area a t a r e g i o n a l s c a l e has been done by D u f f e l  (1959) and  a t the p r o p e r t y by Kennco  g e o l o g i s t s ( S t e w a r t , 1967), S u t h e r l a n d Brown (1967), and more r e c e n t l y Canex P l a c e r g e o l o g i s t s .  Nomenclature used  i n t h i s study i s a m o d i f i -  c a t i o n o f the d e s c r i p t i v e c l a s s i f i c a t i o n used by Canex P l a c e r g e o l o g i s t s (1974, p e r s o n a l communication).  I t i s based  l a r g e l y on diamond  i n the c o r e of the q u a r t z monzonite s t o c k s i n c e  Quartz d i o r i t e was  drilling  1972.  mapped by D u f f e l as gabbro.  Along  the r o c k i n p l a c e s c o n t a i n s l e s s than 10 per cent q u a r t z and  the c o n t a c t  Is m e l a n o c r a t i c  37 due  t o an abundance o f h o r n b l e n d e .  i s t h a t o f b a s i c andesine  However, average  plagioclase  composition  ( A n , ^ ) ; q u a r t z c o n t e n t s l i g h t l y exceeds 10  c e n t ; and b i o t i t e accompanies h o r n b l e n d e  as a m a f i c c o n s t i t u e n t .  per  The  rock  i s b e t t e r c l a s s i f i e d as q u a r t z d i o r i t e and has been so d e s c r i b e d by i n v e s t i g a t o r s subsequent  to D u f f e l .  The m i n e r a l i z e d s t o c k o f q u a r t z monzonite p o r p h y r y c o n s i s t s o f a t l e a s t two d i s t i n c t  types of porphyry.  b a s i s of texture, mineralogy,  The  two a r e d i s t i n g u i s h e d on  f r a c t u r e i n t e n s i t y , degree o f a l t e r a t i o n ,  and most r e a d i l y by d i f f e r e n c e s i n t h e i r w e a t h e r i n g outcrop.  characteristics in  The younger p o r p h y r y dyke i s l e s s a l t e r e d and  r i d g e c r o s s c u t t i n g the main mass o f  From f i e l d  forms a r e s i s t a n t  porphyry.  o b s e r v a t i o n s Kennco g e o l o g i s t s  (Stewart, 1 9 6 7 )  the main mass q u a r t z - m o n z o n i t e - p o r p h y r y - a n d - t h e - c r o s s c u t t i n g - d y k e l a t i t e porphyry.  S u t h e r l a n d Brown ( 1 9 6 7 )  and m i c r o s c o p i c e x a m i n a t i o n s and  q u a r t z - b e a r i n g monzonite p o r p h y r y .  the main s t o c k and  between the  on the b a s i s o f f i e l d  c l a s s e d r o c k s as q u a r t z monzonite  Brown r e c o g n i z e d the p r e s e n c e in  the  inferred  Both Stewart  and  called  -quartz—— mapping  porphyry  Sutherland  o f more than one phase o f q u a r t z monzonite that i n t e r g r a d a t i o n a l r e l a t i o n s h i p s  exist  phases.  Recent  drilling  m i n e r a l i z e d s t o c k (Map  by Canex P l a c e r L i m i t e d has r e v e a l e d t h a t  the  2) i s composed o f two phases o f q u a r t z monzonite,  c a l l e d i n t h i s r e p o r t , q u a r t z monzonite porphyry s e r i c i t i z e d quartz p l a g i o c l a s e porphyry  (QPP,  Map  (QMP;  Map  2, u n i t  2, u n i t  4 ) , as w e l l  a t h i r d phase o f q u a r t z monzonite o r q u a r t z - b e a r i n g monzonite p l a g i o c l a s e b i o t i t e quartz porphyry  (PBQP; Map  2, u n i t  5).  3 ) , and  called  The phases  as  are most apparent on and  proportion  of minerals  p o i n t c o u n t s and (QFP; on  Map  the b a s i s o f t e x t u r e . are s l i g h t  examination of rocks  2, u n i t 6)  that crosscuts  the b a s i s o f m i n e r a l o g y and  and  Differences  i n type,  amount,  o n l y by  careful  are r e c o g n i z e d  in thin section.  the q u a r t z  texture.  The  porphyry dyke  monzonite s t o c k  is distinct  D e s c r i p t i o n s o f r o c k types  d e t e r m i n e d from p o i n t counts on p h e n o c r y s t s i n l a r g e s t a i n e d s l a b s m a t r i x i n t h i n s e c t i o n are g i v e n below, summarized i n T a b l e 1, i l l u s t r a t e d by  a ternary p l o t i n Figure  QUARTZ DIORITE (Map  2, U n i t  as and  and  7.  2)  Quartz d i o r i t e i s a p a l e g r e y , f i n e t o medium-grained r o c k i n w h i c h p l a g i o c l a s e , h o r n b l e n d e , and  b i o t i t e are  Specimens range i n c o m p o s i t i o n from d i o r i t e d i o r i t e i s most common. a r e randomly o r i e n t e d and  very  i n a m a t r i x of h o r n b l e n d e , f i n e - g r a i n e d  f i n e a n h e d r a l g r a i n s of q u a r t z  and  crystals. (An,_  r  HZ-DO  o  ) .  orthoclase.  t o 5 m i l l i m e t r e s and  specimens from n e a r the i n t r u s i v e c o n t a c t and  to g r a n o d i o r i t e but  quartz  L a t h s o f p l a g i o c l a s e about 1 m i l l i m e t r e i n s i z e  c r y s t a l s o f h o r n b l e n d e are up  quartz  the most o b v i o u s components.  contain  biotite,  Some s u b h e d r a l  more i n s i z e .  A  l e s s than 10 p e r  have weak o r i e n t a t i o n o f p l a g i o c l a s e l a t h s and  few cent  hornblende  P l a g i o c l a s e i s n o r m a l l y zoned b a s i c a n d e s i n e to l a b r a d o r i t e C h l o r i t e formed a f t e r h o r n b l e n d e and  Other a l t e r a t i o n minerals M a g n e t i t e , sphene, and  l e s s commonly b i o t i t e .  include s e r i c i t e , epidote,  a p a t i t e are a c c e s s o r y  and  minerals.  calcite. In the zone o f  m i n e r a l i z a t i o n near q u a r t z monzonite, c h a l c o p y r i t e , p y r i t e , some molybdenite, by  q u a r t z v e i n i n g , and  t o t a l replacement o f o r i g i n a l m a f i c  f i n e - g r a i n e d f e l t e d b i o t i t e are  common.  minerals  39 QUARTZ MONZONITE STOCK AND DYKES (Map 2, U n i t s 3 t o 5) QUARTZ MONZONITE PORPHYRY PHASE (QMP, U n i t 3)  Quartz monzonite porphyry quartz porphyry.  i s a grey t o p i n k , c o a r s e ,  I t c o n t a i n s about 45 p e r c e n t p h e n o c r y s t s  two-feldspar  of mainly  o l i g o c l a s e - a n d e s i n e (An^g)» q u a r t z , b i o t i t e , and some o r t h o c l a s e i n a fine-grained quartz feldspar matrix. white  P l a g i o c l a s e phenocrysts are chalky  t o cream, g r e y , b u f f , and g r e y - g r e e n  subhedral blocky laths 2 to 8  m i l l i m e t r e s , a v e r a g i n g about 5 m i l l i m e t r e s , i n s i z e .  Quartz and g r a p h i c  q u a r t z - o l i g o c l a s e forms l a r g e , rounded, d e e p l y embayed, s k e l e t a l g r a i n s a v e r a g i n g 4 t o 6 m i l l i m e t r e s , i n a few cases up t o 1 c e n t i m e t r e , i n s i z e . O r t h o c l a s e i s seen as s c a t t e r e d p o i k i l i t i c  t o myrmekitic  phenocrysts  about 5 m i l l i m e t r e s i n s i z e and as s p a r s e , squat megacrysts up t o 2 c e n t i metres i n l e n g t h .  A few g r a i n s have r i m s o f p l a g i o c l a s e around o r t h o c l a s e .  B i o t i t e as t a b u l a r books 6 m i l l i m e t r e s i n l e n g t h and 4 m i l l i m e t r e s i n c r o s s s e c t i o n i s the s o l e m a f i c c o n s t i t u e n t . was  A s m a l l amount o f hornblende  that  o r i g i n a l l y p r e s e n t i s now t o t a l l y r e p l a c e d by b i o t i t e and s e r i c i t e .  The m a t r i x i s an a l l o t r i o m o r p h i c g r a n u l a r i n t e r g r o w t h o f g r a i n s o f p l a g i o c l a s e , s l i g h t l y i n excess  .04-millimetre  o f e q u a l amounts o f s i m i l a r l y  s i z e d q u a r t z and o r t h o c l a s e .  In t h i n s e c t i o n q u a r t z p h e n o c r y s t s a r e v e r y d i s t i n c t i v e w i t h a myrmekitic  o r g r a p h i c appearance.  G r a i n s a r e s t r o n g l y corroded w i t h deep  embayraents and c o n t a i n i n c l u s i o n s o f s m a l l o l i g o c l a s e ? g r a i n s . boundaries  Grain  appear t o be r e s o r b e d r e s u l t i n g i n r e a c t i o n rims o f m i c r o -  c r y s t a l l i n e quartz.  Large g r a i n s a r e s u t u r e d composite  c r y s t a l s that  appear t o be cumulates o f a number o f s m a l l e r g r a i n s , o r may s i m p l y be f r a c t u r e d megacrysts.  P l a g i o c l a s e phenocrysts are strongly s e r i c i t i z e d  PLATES 4 and 5:  Embayed s k e l e t a l myrmekitic q u a r t z phenocrysts containing o l i g o c l a s e i n c l u s i o n s i n q u a r t z monzonite p o r p h y r y .  41 and  locally argillic.  C r y s t a l s a r e s t r o n g l y zoned i n an  normal manner but t w i n n i n g i s l a r g e l y o b s c u r e d p l a g i o c l a s e determinations are d i f f i c u l t . d e t e r m i n a t i o n s p l a g i o c l a s e appears Hornblende which was r e p l a c e d by biotite  On  by a l t e r a t i o n  and  the b a s i s of a  few  t o be o l i g o c l a s e - a n d e s i n e (An^g).  o r i g i n a l l y p r e s e n t i n s m a l l amounts i s t o t a l l y  fine-grained felted b i o t i t e .  i s a l s o s c a t t e r e d throughout  Fine-grained  the m a t r i x .  s e r i c i t e , b i o t i t e , c h l o r i t e , c a l c i t e , and  z i r c o n are accessory minerals.  secondary  In a d d i t i o n to  opaque m i n e r a l s , some  k a o l i n i t e and m o n t m o r i l l o n i t e a r e a l t e r a t i o n p r o d u c t s . and  oscillatory-  Sphene, a p a t i t e ,  Quartz v e i n s and g y p s u m - f i l l e d  f r a c t u r e s a r e common.  A dyke phase o f a s i m i l a r q u a r t z monzonite porphyry d i s p l a y s c h i l l e d c o n t a c t s and porphyry  t o i n t r u d e q u a r t z monzonite  and p o s s i b l y p l a g i o c l a s e b i o t i t e q u a r t z porphyry  d r i l l holes.  The dyke r o c k c o n t a i n s about 40  grained phenocrysts and  can be seen  of p l a g i o c l a s e  commonly  (An.jQ_.33)  w  i n a number o f  t o 45 per cent *  t  n  coarse  b i o t i t e , some q u a r t z  o r t h o c l a s e , i n a f i n e - g r a i n e d matrix of mainly  q u a r t z and o r t h o c l a s e .  Q u a r t z m e g a c r y s t s up t o 1 c e n t i m e t r e i n s i z e a r e the l a r g e s t g r a i n s seen. M a t r i x I s a d i s t i n c t i v e p i n k i s h grey t o o r a n g e - t i n t e d grey o r brown c o l o u r and  i s considerably less altered  B i o t i t e and looking.  p l a g i o c l a s e phenocrysts  Secondary b i o t i t e and  than i n o t h e r porphyry  are a l s o l i t t l e  a l t e r e d and  phases. fresh  o t h e r a l t e r a t i o n m i n e r a l s are o f minor  abundance but f i n e - g r a i n e d d i s s e m i n a t e d magnetite  i s more abundant  in  c o n t a c t s and weak  o t h e r porphyry  phases.  In a d d i t i o n t o c h i l l e d  a l t e r a t i o n , s t r o n g magnetic response  and  than  p a u c i t y o f ore m i n e r a l s s e t  t h i s r o c k type a p a r t from o t h e r q u a r t z monzonite porphyry  phases.  42 SERICITIZED QUARTZ PLAGIOCLASE PORPHYRY PHASE (QPP; Map 2, Unit 4)  This phase of quartz monzonite i s a medium-grained porphyry, the f i n e s t grained of a l l the types of porphyry recognized at Berg deposit. The rock i s strongly s e r i c i t i z e d , l e u c o c r a t i c buff to grey, r a r e l y grading to medium brown i n colour. mainly plagioclase (^30-32^  I t contains about 35 per cent phenocrysts, some quartz.  Orthoclase phenocrysts are  notably rare or absent as are large grains of b i o t i t e .  Grain s i z e of  plagioclase and quartz phenocrysts v a r i e s from 1 millimetre to a maximum of 5 millimetres, 2 to 3 m i l l i m e t r e s being the average.  Fine-grained  plagioclase phenocrysts are equant subhedral c r y s t a l s that are evenly d i s t r i b u t e d to produce a rock with homogeneous appearance.  Coarser  phenocrysts vary i n s i z e and are rounded, thereby giving a s e r i a t e texture to the porphyry.  Quartz grains average 2 millimetres i n s i z e and are  strongly corroded.  In t h i n section matrix can be seen to be composed of very f i n e granular intergrowth from .01 to .03 millimetre i n s i z e of plagioclase, orthoclase, and quartz.  Plagioclase i s s l i g h t l y more abundant than ortho-  -tfit  clase and appears to be^same composition as phenocrysts (^n3o-32^*  Q  u a r t z  content i s v a r i a b l e , probably due to d i f f e r e n t degrees of s i l i c i f i c a t i o n . Where abundant, quartz i n the matrix i s an accumulation of rounded, possibly overgrown grains.  Quartz veins are common.  S e r i c i t e i s abundant and  pervasive; I t replaces both p l a g i o c l a s e and orthoclase. Together with k a o l i n i t e , l e s s e r c h l o r i t e , and montmorillonite, s e r i c i t e comprises up to 10 per cent and more of the rock.  I t has formed mainly a f t e r feldspars  but i s also found with p y r i t e , c h l o r i t e , and c a l c i t e replacing primary b i o t i t e (and hornblende ? ) .  Almost a l l b i o t i t e now seen i n the rock i s  43  present in the matrix as scattered, fine-grained secondary biotite.  Where  abundant, fine-grained biotite imparts a brownish cast to the matrix of the rock. Strong s e r i c i t i z a t i o n , medium-sized phenocrysts, absence of orthoclase phenocrysts, and lack of large biotite grains readily set this phase apart from other phases of quartz monzonite.  PLAGIOCLASE BIOTITE QUARTZ PORPHYRY (PBQP; Map 2, Unit 5) This rock type has less quartz and more plagioclase than the two quartz monzonite phases (units 3 and 4) and straddles the boundary of quartz monzonite and quartz-bearing monzonite fields (Figure 7 ) . Hand specimens are relatively homogeneous in appearance with grey to pinkish grey or brown matrix in which evenly^ distributed fine and medium-grained phenocrysts form about 40 per cent of the rock. clase phenocrysts are pale grey i n colour and are of two sizes.  PlagioLarger  ones 4 to 7 millimetres, averaging 5 millimetres, in size comprise about 80 per cent of the feldspar phenocrysts; smaller ones are 1 to 2 m i l l i metres in size.  Quartz phenocrysts are corroded grains 3 millimetres  and smaller in size.  Orthoclase i s seen as rare phenocrysts that are  the same size or smaller than surrounding plagioclase grains. crystals orthoclase forms rims or mantles on plagioclase.  In a few  Biotite i s  unaltered looking, fresh euhedral platelets or short, stubby books about 2 millimetres in cross section.  These contrast markedly with elongate  coarse books of biotite in quartz monzonite porphyry (QMP) and highly sericitized biotite in quartz plagioclase porphyry.  44 In t h i n s e c t i o n , m a t r i x i s seen t o c o n t a i n grains  o f m a i n l y p l a g i o c l a s e , some o r t h o c l a s e ,  .02-millimetre-sized  and l e s s e r q u a r t z .  Plagio-  c l a s e i n m a t r i x and p h e n o c r y s t s i s m o d e r a t e l y s e r i c i t i z e d b u t t w i n n i n g , m a i n l y as a l b i t e and combined C a r l s b a d - a l b i t e a f f e c t e d by a l t e r a t i o n .  types,  i s common and n o t much  C r y s t a l s a r e zoned i n an o s c i l l a t o r y - n o r m a l manner  commonly w i t h f o u r t o s i x c y c l e s .  Measured p l a g i o c l a s e c o m p o s i t i o n ranges  from b a s i c o l i g o c l a s e t o andesine ^^ 28-34^* n  Qv^zH  mafic minerals i n  t h i s r o c k type a r e about t w i c e as abundant as i n q u a r t z monzonite porphyry (QMP) and s e r i c i t i z e d secondary b i o t i t e  quartz p l a g i o c l a s e porphyry  The amount o f  i s reduced but i s compensated by the p r e s e n c e o f i n c r e a s e d  amounts o f f i n e - g r a i n e d h o r n b l e n d e . from 2:1 t o 5:1.  (QPP).  A l l fine-grained  i n the matrix a r e c h l o r i t i z e d  B i o t i t e to hornblende r a t i o  varies  o r i g i n a l b i o t i t e and h o r n b l e n d e  t o some degree.  grains  Hornblende i s r e p l a c e d  e x t e n s i v e l y by b i o t i t e o r c h l o r i t e , s e r i c i t e , c a l c i t e , and opaque  minerals.  QUARTZ MONZONITE-GRANODIORITE OR QUARTZ-BEARING MONZODIORITE DYKE ( h o r n b l e n d e q u a r t z f e l d s p a r p o r p h y r y , hbde QFP; Map 3, u n i t 6)  T h i s v a r i e t y o f quartz f e l d s p a r porphyry i s a pale  t o medium grey  c o a r s e p o r p h y r y t h a t s u p e r f i c i a l l y i s s i m i l a r t o q u a r t z monzonite phases o f the m i n e r a l i z e d  stock  that i t intrudes  ( u n i t s 3 to 5 ) . Large phenocrysts  o f cream t o p i n k i s h b u f f p l a g i o c l a s e , as w e l l as q u a r t z , sparse o r t h o c l a s e , contacts, and  make up about 35 p e r c e n t o f the r o c k .  the rock i s c h i l l e d  smaller  b i o t i t e , and v e r y Near i n t r u s i v e  and has s m a l l p h e n o c r y s t s commonly 2 m i l l i m e t r e s  o f p l a g i o c l a s e , quartz,  medium grey m i c r o c r y s t a l l i n e m a t r i x .  mafic minerals,  and some o r t h o c l a s e  ina  In the main mass o f porphyry equant  rounded p h e n o c r y s t s o f p l a g i o c l a s e a r e 5 t o 7 m i l l i m e t r e s  i n size.  Strongly  c o r r o d e d and r e s o r b e d q u a r t z g r a i n s average 6 m i l l i m e t r e s  i n s i z e , but are  45 up to 1.2 centimetres i n some large cumulate g r a i n s . i n t e r s p e r s e d s p o r a d i c a l l y throughout  Orthoclase c r y s t a l s are  the rock as a few, squat, euhedral mega-  c r y s t s up to 1.8 centimetres i n s i z e . and e x t e n s i v e l y replaced by epidote.  Most o r t h o c l a s e phenocrysts' are a l t e r e d Mafic minerals are present as large  elongate books of b i o t i t e up to 7 m i l l i m e t r e s i n length and small l a t h s of hornblende.  Large grains of sphene are common as w e l l as patches and  clots,  5 m i l l i m e t r e s and more i n s i z e , of f i n e l y matted needles of epidote. The most obvious d i f f e r e n c e between t h i s rock type and other phases of porphyry i s seen i n the matrix.  Quartz i s r e l a t i v e l y sparse, ranging from  6 to 12 per cent i n specimens examined.  The matrix i s mostly p l a g i o c l a s e ,  p o i k i l i t i c almost i n t e r s e r t a l o r t h o c l a s e , and f i n e - g r a i n e d hornblende, b i o t i t e , opaque and a l t e r a t i o n minerals.  Hornblende i s abundant, w e l l i n excess of  b i o t i t e , and t o t a l mafic content of the rock i s about 20 per cent. P l a g i o c l a s e phenocrysts are only s l i g h t l y a l t e r e d .  They are com-  bined c r y s t a l s that d i s p l a y complex twins and simple normal zoning with r a r e l y more than three or four c y c l e s . to an observed maximum of An^«  A n o r t h i t e content ranges from An-j^  Secondary b i o t i t e i s present but i n minor  amounts compared to quartz monzonite p o r p h y r i e s .  Hornblende i s seen as  small to medium-sized r e l i c t c r y s t a l s p a r t i a l l y or t o t a l l y replaced by c h l o r i t e , epidote, c a l c i t e , or f i n e - g r a i n e d b i o t i t e .  Overall,  secondary  b i o t i t e s e r i c i t e , quartz v e i n s , and gypsum are weakly developed and epidote, c h l o r i t e , and c a l c i t e are main a l t e r a t i o n m i n e r a l s .  BASIC DYKES Dykes, other than those r e l a t e d to quartz monzonite porphyry, are a l l s i m i l a r , common l o o k i n g , medium to dark grey, homogeneous, f i n e - g r a i n e d  46  PLATES 6 and 7:  Q u a r t z monzonite p o r p h y r y (QMP; Map 2, unit 3). One specimen s t a i n e d w i t h sodium c o b a l t i n i t r a t e . Scale i s i n centimetres.  47  PLATE 8:  T  M i l l ! III "3  PLATE 9:  Q u a r t z monzonite p o r p h y r y (QMP; Map 2, u n i t 3 ) . S t a i n e d p o l i s h e d specimen.  M l ! MM ! A  M i l  .5  MM l l l l l l l l l  Mill  7  II MM M i l MM M i l M i l l m i 1 Q  n.  1  Q u a r t z monzonite porphyry dyke ( p a r t o f QMP; Map 2, u n i t 3 ) . Specimen on r i g h t s t a i n e d w i t h sodium c o b a l t i n i t r a t e . Scale i s i n centimetres.  48  PLATE 10:  PLATE 11:  S e r i c i t i z e d q u a r t z p l a g i o c l a s e porphyry (QPP; Map 2, u n i t 4). Specimen on l e f t i s v e i n e d by q u a r t z and I s dark grey due t o abundant f i n e - g r a i n e d b i o t i t e . S p e c i men on r i g h t has p e r v a s i v e q u a r t z f l o o d i n g along f r a c t u r e s . Unstained p o r t i o n ( l e f t specimen) i s t y p i c a l o f most d r i l l c o r e . Scale i s i n centimetres.  T y p i c a l s e r i c i t i z e d quartz p l a g i o c l a s e p o r p h y r y (QPP; Map 2, u n i t 4). Sodium c o b a l t i n i t r a t e s t a i n shows p e r v a s i v e d i s t r i b u t i o n of s e r i c i t e i n matrix.  PLATE 12:  Plagioclase b i o t i t e quartz porphyry (PBQP; Map 2, unit 5). Specimen on r i g h t stained with sodium c o b a l t i n i t r a t e .  PLATE 13:  Hornblende quartz feldspar porphyry (hbde QFP; Map 2, unit 6 ) . Dyke rock of quartz monzonite-granodiorite or quartz-bearing monzodiorite composition.  50 andesite or b a s a l t .  They form t h i n s t e e p l y d i p p i n g s h e e t s g e n e r a l l y 10  or l e s s i n t h i c k n e s s .  A number c o n t a i n s up  to 5 p e r c e n t s m a l l  phenocrysts  o f p l a g i o c l a s e but more commonly a r e massive w i t h s m a l l amygdules o f In t h i n s e c t i o n b a s i c dyke r o c k s a r e f i n e - g r a i n e d f e l t e d growths o f p l a g i o c l a s e and hornblende and  feet  calcite.  to t r a c h y t o i d I n t e r -  w i t h abundant a c c e s s o r y , opaque m i n e r a l s  a l t e r a t i o n p r o d u c t s , m a i n l y c h l o r i t e and  calcite.  CHEMICAL COMPOSITION  Chemical porphyry Map  Map  o f r e p r e s e n t a t i v e samples o f q u a r t z monzonite  2, u n i t  3) and  p l a g i o c l a s e b i o t i t e q u a r t z porphyry  2, u n i t 5 ) , determined  by wet  c h e m i c a l s i l i c a t e a n a l y s e s , a r e g i v e n In  T a b l e 2.  (QMP;  compositions  A n a l y t i c a l r e s u l t s and  quartz porphyry  c a l c u l a t e d norms f o r p l a g i o c l a s e  c o r r e s p o n d v e r y c l o s e l y t o D a l y ' s and Nockold's  (PBQP;  biotite  average  q u a r t z monzonite o r a d a m e l l l t e whereas q u a r t z monzonite i s more a k i n t o granite.  T h i s i s p r o b a b l y due  metasomatism and  SiO^  due  DISTRIBUTION AND  The up o f two  through o r t h o c l a s e  to quartz v e i n i n g .  GEOMETRY (Map  2)  r o u g h l y e q u i d i m e n s i o n a l c o r e o f the m i n e r a l i z e d s t o c k i s made  phases: q u a r t z monzonite porphyry  b i o t i t e quartz porphyry ( u n i t A)  t o i n c r e a s e d amounts o f K^O  (unit 5).  (unit  3) and  plagioclase  S e r i c i t i z e d quartz plagioclase  forms i r r e g u l a r b o d i e s a d j a c e n t t o the c o r e i n the southwest.  t h r e e phases a r e t r a n s e c t e d by a n o r t h e a s t e r l y t r e n d i n g hornblende f e l d s p a r porphyry  dyke ( u n i t 6) which i s the o n l y porphyry  intrudes quartz d i o r i t e separated  porphyry  (unit 2).  All  quartz  phase t h a t  O l d e r q u a r t z monzonite p o r p h y r i e s a r e  from q u a r t z d i o r i t e by a s c r e e n of h o r n f e l s e d v o l c a n i c r o c k s .  TABLE 1.  MINERALOGICAL COMPOSITION OF INTRUSIVE ROCKS, BERG DEPOSIT Mean v a l u e s o f modal a n a l y s e s , not r e c a l c u l a t e d t o 100 p e r cent  MAP 2 - U n i t 3 QMP N=8 Phenocrysts Orthoclase Quartz Plagioclase Matrix  Unit 4 Sericitic QPP N=4  Unit 5  Unit 6  PBQP N=4  hbde QFP N=4  Unit 2 Qtz d i o N=9  3.1 6.4 27.3 54  5.7 25.9 65  0.8 5.3 28.1 59  0.2 5.1 26.0 63  --  26.1 27.1 35.6 7.5 3.6  25.8 26.7 32.2 5.2 10.1  26.7 15.1 41 .4 13.3 3.7  20.2 10.4 43.0 19.9 6.0  5.3 12.6 61 .2 16.8 4.1  Total Orthoclase Quartz Plagioclase Mafics Accessories (including Mafics  Plagioclase  sericite) bio  An  30±  bio (sericitized) 30-32±  bio  >hbde  31±3  hbde  38±4  >bio  variable hbde > b i o 50±3  TABLE 2.  CHEMICAL COMPOSITIONS AND NORMS  2  3  4  5  70.73  67.76  67.41  69.67  72.60  0.53  0.55  0.51  0.56  0.37  16.36  16.39  15.76  14.74  13.96  1 O x i d e s R e c a l c u l a t e d to 100-  sio T i 0  2  2  2°3 Fe 0 A 1  1 .21  1 .78  1 .93  1 .23  0.87  FeO  0.80  0.92  1.96  2.29  1.68  MnO  0.02  0.07  0.06  0.06  0.06  MgO  1.09  1.62  1 .43  1 .00  0.52  CaO  1 .07  2.59  3.54  2.47  1 .34  Na 0  2.89  3.39  3.45  3.37  3.10  K 0  5.30  4.93  3.76  4.61  5.50  0.30  0.18  0.19  0.20  0.18  1 .32  2.18  1 .15  0.54  0.53  4.53  -- ' --  --  2  3  2  2  O x i d e s a s Determined _ 2°5 H 0 P  2  so  3  1 .92  co  2  0.02  BaO  0.12  CuO  0.38  —  --  V  M o l e c u l a r NormQuartz Orthoclase Albite Anorthite Pyroxene Magnetite Ilmenite Unassigned 1. 2. 3. 4. 5.  30.5 31 .2 25.9 3.2 3.0 1.4 0.3 4.5  24.7 29.1 30.4 7.7 4.8 2.0 0.1 1 .2  21 .7 22.5 31 .3 16.6 5.1 2.0 0.7 0.1  24.8 27.2 28.3 11.1 4.7 1 .9 1.1 0.9  29.2 32.2 26.2 5.6 3.0 1 .4 0.8 1.6  B e r g q u a r t z monzonite porphyry (Map 2, u n i t 3 ) , NC-67-10 (DDH 1 9 ) , S. M e t c a l f e , a n a l y s t , 1968. B e r g p l a g i o c l a s e b i o t i t e q u a r t z p o r p h y r y (Map 2, u n i t 5 ) , NC-67-11 (DDH 1 ) , S. M e t c a l f e , 1968. Average q u a r t z monzonite, 20 a n a l y s e s , D a l y , 1933. Average a d a m e l l i t e , 121 a n a l y s e s , N o c k o l d s , 1954. Average c a l c - a l k a l i c g r a n i t e , 72 a n a l y s e s , N o c k o l d s , 1954.  FIGURE  7  MINERALOGICAL INTRUSIVE  COMPOSITION OF  ROCKS,  O  • T • A  BERG  DEPOSIT  M o p 2, U n i t  Qtz Dio QMP Q M P dyke ser QPP PBQ P hbde QFP  • average composition Classification  Modified  from A. Streckeisen , 1967  Or  2  54 Quartz monzonite porphyry forming  (unit  3) i s found  as a s u b c i r c u l a r mass  t h e s o u t h e r n and s o u t h e a s t e r n p o r t i o n o f t h e m i n e r a l i z e d p l u g .  porphyry  i s thought  possibly  t h e most voluminous phase p r e s e n t .  t o be a s m a l l , v e r t i c a l , p l u g - l i k e body t h a t i s Vertical d r i l l  27, and 34) c o l l a r e d a few f e e t from the c o n t a c t pass porphyry.  The c o n t a c t i s sharp but appears  holes  Rocks near  (DDH 19,  i n and out o f  to undulate  and p r o t r u d e  ward i n p l a c e s , and l o c a l l y s p l a y s t o form a r b o r e s c e n t dyke and projections.  The  out-  sill-like  the c o n t a c t a r e h i g h l y a l t e r e d by I n t e n s e  sericiti-  z a t i o n and q u a r t z v e i n i n g , and h o r n f e l s a t the c o n t a c t i s b r e c c i a t e d i n places.  P l a g i o c l a s e b i o t i t e q u a r t z porphyry abundant than q u a r t z monzonite porphyry  less  and forms a s h e l l up t o 600 f e e t  t h i c k about t h e n o r t h e r n h a l f o f t h e s t o c k . drilling  ( u n i t 5) i s s l i g h t l y  On t h e b a s i s o f l i m i t e d diamond  i n t r u s i v e c o n t a c t s w i t h h o r n f e l s appear t o be v e r t i c a l and simple  w i t h few ( p o s s i b l y no) r e l a t e d dykes and b r e c c i a s . . H o r n f e l s a d j a c e n t t o p l a g i o c l a s e b i o t i t e q u a r t z porphyry quartz v e i n i n g . in  I s b l a c k , b i o t i t e - r i c h r o c k w i t h some  R e l a t i o n s h i p to s e r i c i t i z e d  t h e southwest I s u n c e r t a i n and p o s s i b l y  quartz p l a g i o c l a s e  porphyry  complex.  S e r i c i t i z e d q u a r t z p l a g i o c l a s e porphyry  ( u n i t 4) i n t r u d e s as  an i r r e g u l a r mass o r group o f c o a l e s c i n g b o d i e s p e r i p h e r a l t o t h e main s t o c k on t h e southwest.  The l a r g e s t p o r t i o n o f t h i s r o c k type appears t o  form a n o r t h w e s t e r l y t r e n d i n g dyke, o r p o s s i b l y a l a c c o l i t h , h o l e 13 (Map 2 ) .  i n the v i c i n i t y  of  drill  in  t h e v i c i n i t y o r n o r t h e a s t o f d r i l l h o l e s 7, 30, and 31 f l a n k e d by s p l a y i n g  e l a b o r a t e dykes and s i l l s , and  17.  The i n t r u s i o n may have a s m a l l p i p e - l i k e  core  two o f which a r e i n t e r s e c t e d by d r i l l h o l e s 15  Two o t h e r a r e a s i n which s e r i c i t i z e d  quartz p l a g i o c l a s e  porphyry  may be p r e s e n t a r e a t t h e n o r t h margin o f t h e s t o c k by d r i l l  h o l e 1 and  in  t h e main mass o f q u a r t z monzonite porphyry  In  t h e v i c i n i t y o f d r i l l h o l e 1, ' h y b r i d i z e d ' r o c k s r e s e m b l i n g  p l a g i o c l a s e porphyry  were noted  ( u n i t 3) n e a r d r i l l h o l e 69.  i n a b r e c c i a t e d body i n h o r n f e l s near  the c o n t a c t w i t h p l a g i o c l a s e b i o t i t e q u a r t z p o r p h y r y . h o l e 69 a p o o r l y d e f i n e d and l i t t l e  understood  q u a r t z f e l d s p a r porphyry  the t h r e e o t h e r porphyry  Near d i a m o n d - d r i l l  metasomatized b r e c c i a zone  may c o n t a i n zones o r fragments o f q u a r t z p l a g i o c l a s e  A hornblende  quartz  porphyry.  dyke ( u n i t 6) c r o s s c u t s  phases and i s l o c a t e d , a t l e a s t  i n p a r t , along  the q u a r t z monzonite p o r p h y r y - p l a g i o c l a s e b i o t i t e q u a r t z porphyry Exact shape o f t h e i n t r u s i o n i s u n c e r t a i n . ized or  s t o c k , hornblende  contact.  In the c e n t r e o f the m i n e r a l -  q u a r t z f e l d s p a r porphyry  forms a s t e e p - w a l l e d dyke  n o r t h e a s t e r l y e l o n g a t e d p l u g up t o 225 f e e t wide w i t h a l o b e t o t h e  south.  D i s t a l p a r t s o f the i n t r u s i o n a r e t a b u l a r , d y k e - l i k e s h e e t s w i t h  c h i l l e d margins. extremity.  The dyke s p l a y s i n t o t h r e e branches a t i t s southwest  I n t h e n o r t h e a s t i t i s o f f s e t by f a u l t s and may change i n t o  a number o f s u b p a r a l l e l dykes, two o f which a r e seen a t s u r f a c e i n q u a r t z diorite  (unit 2 ) .  I n t e r n a l c o n t a c t r e l a t i o n s h i p s between phases a r e n o t known m a i n l y because s u r f a c e exposures No d i s t i n c t  a r e poor and diamond d r i l l i n g  c o n t a c t s have been r e c o g n i z e d i n d r i l l  main q u a r t z monzonite phases.  i s limited.  c o r e between t h e t h r e e  T h i s may be because d i f f e r e n c e s a r e s u b t l e ,  r o c k t y p e s a r e i n t e r g r a d a t i o n a l , o r a l t e r a t i o n and metasomatism mask o r i g i n a l t e x t u r a l and c o m p o s i t i o n a l d i f f e r e n c e s . c o n t a c t s s i m p l y may n o t be i n t e r s e c t e d by d r i l l i n g some e v i d e n c e  On t h e o t h e r hand, to date.  There i s  from outcrop d a t a t h a t c o n t a c t s o f p l a g i o c l a s e b i o t i t e  quartz  56 porphyry  ( u n i t 5) w i t h q u a r t z monzonite porphyry  o t h e r p l a c e s d r i l l - h o l e d a t a suggest  ( u n i t 3) a r e s h a r p .  t h a t c o n t a c t s may be metasomatized  b r e c c i a zones, e s p e c i a l l y where c o n t a c t s t r e n d n o r t h w e s t e r l y . q u a r t z f e l d s p a r porphyry phases i n d r i l l seen  c o n t a c t s a r e known.  hornblende  other  The o n l y r o c k  t h a t has c h i l l e d margins i s a q u a r t z monzonite p o r p h y r y  included i n unit  The  dyke ( u n i t 6) can be d i s t i n g u i s h e d from  c o r e s b u t no sharp  In  type  dyke t h a t i s  3.  AGE OF INTRUSIONS  R e l a t i v e ages o f i n t r u s i v e phases cannot  be determined  unequiv-  o c a b l y as o n l y two r o c k types have been demonstrated t o c r o s s c u t o t h e r phases. diorite  Hornblende q u a r t z f e l d s p a r porphyry  ( u n i t 6) i n t r u d e s q u a r t z  ( u n i t 2) and a l l t h r e e main q u a r t z monzonite phases ( u n i t s 3 t o 5 ) .  A t l e a s t one phase o f q u a r t z monzonite dyke i n t r u d e s q u a r t z monzonite porphyry  o f t h e main s t o c k ; both r o c k types a r e i n c l u d e d i n u n i t  because o f t h e i r s i m i l a r c o m p o s i t i o n and t e x t u r e . to be p l a g i o c l a s e b i o t i t e q u a r t z porphyry q u a r t z p l a g i o c l a s e porphyry i s not a c e r t a i n t y . sericitized  Dykes o f what appear  ( u n i t 5) i n t r u d e s e r i c i t i z e d  ( u n i t 4) b u t t h i s c l a s s i f i c a t i o n o f the dykes  These few observed  q u a r t z p l a g i o c l a s e porphyry  monzonite p o r p h y r y ,  3, Map 2,  r e l a t i o n s h i p s and t h e presence o f b r e c c i a fragments i n q u a r t z  as w e l l as c o n s i d e r a b l e g e o l o g i c a l i n t u i t i o n ,  suggest  the f o l l o w i n g sequence from o l d e s t t o youngest:*  *Recent d r i l l i n g (A. D. Drummond, 1975, p e r s o n a l communication) has r e v e a l e d t h a t fragments o f q u a r t z monzonite porphyry ( u n i t 3) a r e found i n s e r i c i t i z e d q u a r t z p l a g i o c l a s e porphyry ( u n i t 4 ) . The b r e c c i a fragments of s e r i c i t i z e d q u a r t z p l a g i o c l a s e porphyry ( u n i t 4) r e f e r r e d t o above a r e i n t r u d e d i n t o q u a r t z monzonite porphyry ( u n i t 3) i n a ' v o l c a n i c neck.' A l s o p l a g i o c l a s e b i o t i t e q u a r t z porphyry ( u n i t 5) c o n t a i n s fragments s a i d t o be q u a r t z monzonite porphyry ( u n i t 3) and s e r i c i t i z e d q u a r t z p l a g i o c l a s e porphyry (unit 4 ) .  TABLE 3.  POTASSIUM-ARGON AGES, BERG DEPOSIT (N. C. C a r t e r , 1974)  Sample  No.  Material  Rock Type  Location  whole  NC-67-12  DDH 20  biotite  hornfels  NC-67-11  DDH  1  p l a g i o c l a s e b i o t i t e quartz  NC-67-13  DDH  9  mineralized quartz  NC-67- 9  DDH 70  dyke q u a r t z monzonite  NC-67-10  DDH 19  q u a r t z monzonite b i o t i t e  NC-67- 8  13,000E 21,000N  quartz  diorite  porphyry  diorite porphyry porphyry  Sampled  Age  (m.y.)  52.0±3  rock  biotite  52.0±2  biotite  49.9+2.1  biotite  48.0±3  biotite  47.0±3  chloritized  biotite  Mean  46.8±1.5  49.0+2.4  58 (Map 2 , u n i t  1.  quartz d i o r i t e  2.  q u a r t z monzonite porphyry  2)  i n c l u d i n g dykes w i t h  margins t h a t may be c o n s i d e r a b l y younger  chilled  3.  s e r i c i t i z e d quartz p l a g i o c l a s e porphyry  4.  p l a g i o c l a s e b i o t i t e q u a r t z porphyry  (PBQP, u n i t  5.  hornblende  (hbde QFP, u n i t  q u a r t z f e l d s p a r porphyry  (1974) u s i n g potassium-argon  r a n g i n g from  4)  ( s e r QPP, u n i t  A b s o l u t e ages o f r o c k s a t Berg d e p o s i t have been by C a r t e r  3)  (QMP, u n i t  dating of b i o t i t e .  5) 6)  determined Results  52.0 t o 46.8 m i l l i o n y e a r s w i t h a mean o f 49.0+2.4 m i l l i o n  years are l i s t e d  i n Table 3.  No r e s o l u t i o n o f i n t r u s i v e e v e n t s o r s t a g e s  i s p o s s i b l e as a l l ages determined o f t h e mean age.  are within l i m i t s of a n a l y t i c a l  Age o f q u a r t z d i o r i t e i s n o t r e l i a b l e as b i o t i t e  was c h l o r i t i z e d and y i e l d e d o n l y 2.64 per c e n t p o t a s s i u m .  Quartz  error sampled diorite  might be c o n s i d e r a b l y o l d e r b u t b i o t i t e has been r e s e t o r c r y s t a l l i z e d d u r i n g i n t r u s i o n o f q u a r t z monzonite b o d i e s . f e l d s p a r porphyry  (Map 2 , u n i t 6)  Age o f hornblende  quartz  i s needed t o p l a c e an upper l i m i t on  emplacement o f q u a r t z d i o r i t e and q u a r t z monzonite i n t r u s i o n s  (units 2 to  5).  BRECCIAS  In t h i s t h e s i s the term  ' b r e c c i a ' i s used  t o d e s c r i b e fragmented  r o c k s i n which fragments can be demonstrated t o be d i s p l a c e d r e l a t i v e to their original position.  Intensely fractured rocks surrounding  the stock  at Berg d e p o s i t have been d e s c r i b e d as ' c r a c k l e zones' o r ' c r a c k l e b r e c c i a s ' but a r e n o t i n c l u d e d i n t h i s d i s c u s s i o n because r o c k s a r e s h a t t e r e d i n s i t u  59 and  fragments d i s p l a y i n s i g n i f i c a n t d i s p l a c e m e n t .  of b r e c c i a i n b e d r o c k ,  Only one  l a r g e body  an i n t r u s i v e b r e c c i a p i p e , i s known t o crop  A number o f o t h e r b r e c c i a b o d i e s have been i n t e r s e c t e d t h e i r geometry i s not known and  origin i s speculative.  out.  i n d r i l l h o l e s but Newly formed,  thin  s u r f i c i a l d e p o s i t s of ferruginous concretionary b r e c c i a s ( f e r r i c r e t e ) mantle s m a l l a r e a s but  these a c t i v e l y  forming d e p o s i t s a r e d i s c u s s e d  elsewhere.  INTRUSIVE PEBBLE BRECCIA PIPE  The  c e n t r e o f the i n t r u s i v e b r e c c i a p i p e i s about 2,500 f e e t  the s o u t h e a s t o f Berg camp. mately  1,900  The b r e c c i a mass i s e l l i p t i c a l  f e e t a l o n g i t s l o n g e r e a s t - s o u t h e a s t a x i s and  I t i n t r u d e s q u a r t z d i o r i t e and o f the zone o f m i n e r a l i z a t i o n . to y e l l o w , and  i n plan, approxiabout 500  f e e t wide.  p y r i t i c v o l c a n i c r o c k s a t the o u t e r edge Outcrops  are d e e p l y weathered, p a l e cream  c o n t r a s t s h a r p l y w i t h s u r r o u n d i n g d a r k e r brown o u t c r o p s .  B r e c c i a , i n t e r s e c t e d -for 521  f e e t i n d i a m o n d - d r i l l h o l e 21, i s  r e l a t i v e l y u n i f o r m i n appearance w i t h a cream to l i g h t i s composed o f a p p r o x i m a t e l y  grey c o l o u r .  e q u a l amounts o f s t r o n g l y m i l l e d  It  fragments,  f i n e l y comminuted groundmass, and p e r v a s i v e a l t e r a t i o n m i n e r a l s . are subangular  to  Fragments  t o subrounded g r a i n s commonly 1 to 4 m i l l i m e t r e s i n s i z e  o f q u a r t z , f e l d s p a r , and a few r o c k fragments. l a r g e r than 1 c e n t i m e t r e , 3.2  c e n t i m e t r e s b e i n g the l a r g e s t seen.  fragments a r e q u a r t z monzonite porphyry, not r e c o g n i z e d e l s e w h e r e ,  Some r o c k fragments a r e  one  or a n d e s i t e , and  o r more p o r p h y r i t i c s p e c i e s  siltstone.  to b u f f , f i n e l y comminuted mass of q u a r t z and a l k a l i spersed a l t e r a t i o n minerals.  Both m a t r i x and  Rock  M a t r i x i s a cream feldspars with  inter-  fragments a r e e x t e n s i v e l y  60 a l t e r e d by c a r b o n a t e , chlorite.  clays  (mainly m o n t m o r i l l o n i t e ) , s e r i c i t e ,  and  P y r i t e , much o f which i s p r e s e n t as s m a l l e u h e d r a l g r a i n s i n  the m a t r i x , c o n s t i t u t e s about 3 per cent o f the r o c k .  In fragments as w e l l  m a t r i x c h a l c o p y r i t e i s minor and molybdenite  Sulphide  i s rare.  a c c e s s o r y m i n e r a l s i n c l u d i n g a p a t i t e , z i r c o n , t o p a z , r u t i l e , and sphene, c o n s t i t u t e 4 t o 6 per c e n t of the r o c k , m a i n l y  The b r e c c i a p i p e i s thought by v e n t i n g o f v o l a t i l e s r e l a t e d  t o magma i n t r u s i o n ;  o f a few myrmekitic  i n the m a t r i x .  Abundance o f  possibly  quartz f e l d s p a r porphyry). p o s t - d a t e s a t l e a s t one m o l y b d e n i t e were seen  porphyry  quartz grains i n d i c a t e that C. S.  S u t h e r l a n d Brown (1967) have  t h a t the b r e c c i a p i p e i s a l a t e s t r u c t u r e r e l a t e d i n t r u s i v e phase(s)  Ney  suggested  t o emplacement o f young  'quartz l a t i t e p o r p h y r y '  (now  However, the b r e c c i a may  be o l d e r .  called  hornblende Brecciation  p e r i o d o f m i n e r a l i z a t i o n as q u a r t z v e i n l e t s  i n a milled breccia  formed  the v o l a t i l e s b e i n g o f  the b r e c c i a i s r e l a t e d g e n e t i c a l l y to the m i n e r a l i z e d s t o c k . (1969, p e r s o n a l communication) and  possibly  to be e x p l o s i v e i n o r i g i n and  e i t h e r magmatic o r p h r e a t i c e x p l o s i o n o r i g i n . fragments and p r e s e n c e  and  with  fragment.  OTHER BRECCIAS (OBSERVED ONLY IN DIAMOND-DRILL CORE)  BRECCIA 1  A s h a t t e r b r e c c i a i s seen o n l y -in the bottom 20 f e e t o f diamondd r i l l h o l e 35.  T h e r e f o r e , the e x t e n t o f t h i s b r e c c i a i s not e s t a b l i s h e d .  T h i s b r e c c i a i s composed o f abraded  a n g u l a r fragments up  to 5 c e n t i m e t r e s  i n s i z e o f a l t e r e d v o l c a n i c r o c k s i n a p u l v e r i z e d m a t r i x t h a t forms not more than 10 p e r cent o f the r o c k .  A l t e r a t i o n minerals are s i m i l a r  t h o s e i n the i n t r u s i v e b r e c c i a p i p e a l t h o u g h q u a r t z f l o o d i n g i s more  to  61 abundant.  A l t e r a t i o n i s n o t as i n t e n s e as many o f t h e l a r g e r  have weakly a l t e r e d  c o r e s surrounded  by more a l t e r e d r i m s .  fragments  P y r i t e as  f i n e to medium-sized g r a i n s c o n s t i t u t e s about 8 p e r c e n t o f t h e r o c k examined.  C h a l c o p y r i t e and m o l y b d e n i t e  are r a r e but i r r e g u l a r g r a i n s  o f s p h a l e r i t e , t e t r a h e d r i t e , and t r a c e s o f g a l e n a were noted B r e c c i a t i o n p o s t - d a t e s d e p o s i t i o n o f molybdenite veinlets.  i n the matrix.  i n f r a c t u r e s and q u a r t z  The b r e c c i a may be a l a t e formed d i a t r e m e  i n a weakly  vented  zone o f l i m i t e d gas s t r e a m i n g .  BRECCIA 2  B r e c c i a s i n which fragmented c o u n t r y r o c k s a r e e n g u l f e d i n a magmatic m a t r i x a r e developed porphyry  a l o n g t h e main c o n t a c t o f q u a r t z monzonite  phase, a d j a c e n t t o r e l a t e d dykes, and p o s s i b l y w i t h p a r t s o f the  s e r i c i t i c q u a r t z p l a g i o c l a s e porphyry  intrusion(s).  O r i g i n i s n o t from  c o l l a p s e o r removal o f magma s u p p o r t b u t r a t h e r by h y d r a u l i c ramming d u r i n g magma p u l s a t i o n s t h a t cause b r e c c i a t i o n and i n v a s i o n o f b r e c c i a t e d c o u n t r y r o c k s by magma.  T h i s a p p a r e n t l y takes p l a c e most commonly a t Berg d e p o s i t  where dykes s p l a y outward from the main i n t r u s i v e body. envelopes  a few f e e t  B r e c c i a zones  t o t e n s o f f e e t t h i c k s u r r o u n d i n g porphyry  form  dykes.  G e n e r a l l y volume o f i n t r u s i v e r o c k i n b r e c c i a d e c r e a s e s p r o g r e s s i v e l y outward from m a s s i v e i n t r u s i v e dyke c o r e s as p r o p o r t i o n , s i z e , and a n g u l a r i t y o f c o u n t r y r o c k fragments i n c r e a s e . o f b r e c c i a were n o t e d  Examples o f t h i s  i n d i a m o n d - d r i l l h o l e s 14, 25, and 35.  type  Similar  b r e c c i a , b u t l a c k i n g a massive i n t r u s i v e c o r e , was seen i n a 180-foot drill  intercept  assimilated  i n d i a m o n d - d r i l l h o l e 71.  fist-sized  In t h i s b r e c c i a weakly  fragments o f m i n e r a l i z e d b i o t i t e h o r n f e l s a r e  c o n t a i n e d i n an a p p r o x i m a t e l y  e q u a l amount o f s p a r s e l y m i n e r a l i z e d q u a r t z  62 monzonite p o r p h y r y m a t r i x . at  least  two  generation  p e r i o d s , one  M o l y b d e n i t e m i n e r a l i z a t i o n took p l a c e before  and  during  the o t h e r a f t e r b r e c c i a t i o n .  q u a r t z m o l y b d e n i t e v e i n l e t s are seen i n t r a n s p o r t e d  Early  breccia  fragments whereas younger q u a r t z m o l y b d e n i t e v e i n l e t s c r o s s c u t b o t h h o r n f e l s fragments and  q u a r t z monzonite  matrix.  BRECCIA 3  B r e c c i a s w i t h i n the s t o c k are p o o r l y documented; t h e i r and  composition  are u n c e r t a i n .  Apparently  q u a r t z monzonite p o r p h y r y ( u n i t 3) and porphyry and  origin  b r e c c i a s are most common i n  sericitic  quartz  ( u n i t 4) whereas p l a g i o c l a s e b i o t i t e q u a r t z  plagioclase  porphyry  (unit  dyke r o c k s a r e not known to be b r e c c i a t e d except n e a r f a u l t s .  5) One  b r e c c i a has been i n t e r s e c t e d i n d i a m o n d - d r i l l h o l e 69 where a s t r o n g l y altered  ' h y b r i d i z e d ' zone a t l e a s t 90  feet t h i c k contains porphyry f r a g -  ments i n the h a n g i n g w a l l o f a l t e r e d s e r i c i t i c Canex P l a c e r g e o l o g i s t s suggested that a present  (1974, P.  quartz  p l a g i o c l a s e porphyry.  G. Beaudoin, p e r s o n a l  'neck' o f s e r i c i t i c  quartz  communication) have  p l a g i o c l a s e p o r p h y r y may  w i t h i r l j ^ u a r t z monzonite porphyry phase i n t h i s  be  vicinity.  BRECCIA 4  Tectonic b r e c c i a s are present; and  northeasterly trending f a u l t s .  most are r e l a t e d to  northwesterly  These b r e c c i a s , as seen i n a number o f  d i a m o n d - d r i l l c o r e s , a r e crushed o r s i l i c i f i e d  zones, some w i t h  gouge.  to a few  F a u l t - r e l a t e d b r e c c i a s are only inches  w i d t h and  form s t e e p l y d i p p i n g  tabular bodies.  tens  abundant  of feet i n  A number of such b r e c c i a  zones are bounded or i n t r u d e d by massive b a s i c dykes.  STRUCTURE  O u t c r o p s a t Berg d e p o s i t a r e so h i g h l y a l t e r e d , l e a c h e d , and disintegrated observations  t h a t few s t r u c t u r a l f e a t u r e s can be measured. and measurements can be made o n l y from d r i l l  o f t h i s i s h i g h l y f r a c t u r e d and c r u s h e d .  Detailed  c o r e and much  F o r these r e a s o n s  structural  d a t a a r e m i n i m a l and a d d i t i o n a l i n f o r m a t i o n from l a r g e d i a m e t e r core o r underground o p e n i n g s i s d e s i r a b l e and i s b e i n g  drill  c o l l e c t e d by Canex  Placer Limited.  I n t r u s i v e rocks  forming  have been d e s c r i b e d i n a p r e v i o u s  s m a l l s t o c k s , p l u g s , dykes, and s i l l s section.  I n t r u s i o n s were f o r c e f u l l y  emplaced i n t o g e n e t i c a l l y u n r e l a t e d h o s t r o c k s .  There was l i t t l e  d i s r u p t i o n o f the m o d e r a t e l y eastward d i p p i n g h o m o c l i n a l v o l c a n i c and l o c a l l y d e r i v e d sedimentary r o c k s . without  apparent  succession of  Beds were t r u n c a t e d  any d i s c e r n i b l e development o f f o l i a t i o n o r f o l d i n g .  i n t r u s i v e r o c k s uiais made by s h o u l d e r i n g a s i d e c o u n t r y some magmatic s t o p i n g , and a s s i m i l a t i o n a l o n g w i t h  Room f o r  rocks, b r e c c i a t i o n ,  intense  fracturing,  metasomatism, and e x t e n s i v e r e c r y s t a l l i z a t i o n near t h e s t o c k .  On t h e  b a s i s o f s t r u c t u r e and s t y l e o f emplacement o f p o r p h y r i e s ,  Sutherland  Brown (1969) c l a s s i f i e d Berg d e p o s i t as a 'simple  deposit;'  porphyry  more r e c e n t l y (1974, 1975) he has d e s c r i b e d i t as t y p i c a l o f a c l a s s of porphyry d e p o s i t s c a l l e d  ' p h a l l i c porphyry d e p o s i t s . '  E v i d e n c e o f s t r u c t u r a l c o n t r o l s f o r emplacement o f i n t r u s i v e bodies  was searched  f o r d u r i n g r e g i o n a l mapping; none was f o u n d .  trending mainly n o r t h e a s t e r l y or northwesterly and  appear t o be o f minor  importance.  cause o n l y s m a l l  Faults offsets  64  Fracturing deposit This  but  o f r o c k s i s widespread In the a r e a o f the  i s most c o n c e n t r a t e d a d j a c e n t to the main i n t r u s i v e  c o r r e s p o n d s to the  f r a c t u r e s have reduced the r o c k to a  b r e c c i a ' o f 1 to 3 - c e n t i m e t r e fragments (Ney,  sulphide  include grains  1972).  Early  r e t i c u l a t e q u a r t z stockworks, f r a c t u r e s  o r v e i n l e t s , and  Younger f r a c t u r e s  filled  g r a i n s , gangue, and  contact.  zone o f b e s t copper-molybdenum m i n e r a l i z a t i o n  which numerous g e n e r a t i o n s o f  fractures  Berg  in  'crackle  generation  filled  with  fractures with a l t e r a t i o n envelopes.  w i t h gypsum c r o s s c u t  a l t e r a t i o n mineral grains  early fractures,  sulphide  as a s u b h o r i z o n t a l  fracture  cleavage.  The f r a c t u r e s up  c l e a v a g e i s a c l o s e l y spaced s e t o f p a r a l l e l h a i r l i n e to 1 m i l l i m e t r e  c h i p c l e a v a g e , and  t h i c k that has  sheet f r a c t u r e s  ( A l l e n , 1971).  per  f o o t are most common a t Berg d e p o s i t ,  100  o r more f r a c t u r e s per  interconnect  f o o t are known.  dominant.  e f f e c t on  r o c k s they c r o s s c u t  the  invasion  quartz v e i n i n g ,  The  as f o l l o w s :  w i t h the  low  sequence o f events r e s u l t i n g i n  (1) i n t r u s i o n s o f p o r p h y r i e s accompanied (2) e a r l y f r a c t u r i n g and  quartz  veining  zone; (3) widespread h y d r o t h e r m a l a l t e r a t i o n , a d d i t i o n a l  b r e c c i a t i o n , and  (4) development o f s u b h o r i z o n t a l filling  subhorizontal  visible alteration  o t h e r than b e i n g f i l l e d  of hydrothermal f l u i d s ;  to form a c r a c k l e d  although  and  Thus, f r a c t u r e c l e a v a g e appears to be much  younger than o t h e r f r a c t u r e s . f r a c t u r i n g would be  fractures  In d e t a i l f r a c t u r e s s p l a y  Cleavage f r a c t u r e s have no  temperature m i n e r a l gypsum.  Twenty to 30  poker  a l t h o u g h r o c k s w i t h as many as  r e s u l t i n g i n a r e t i c u l a t e pattern,  f r a c t u r e s are  by  been c a l l e d s h e e t i n g ,  ( p o s s i b l y at a much l a t e r  some f r a c t u r i n g o f i n t r u s i v e r o c k s ; f r a c t u r e c l e a v a g e and date).  and  gypsum f r a c t u r e  65 The  presence of s u b h o r i z o n t a l f r a c t u r e cleavage  fracture f i l l i n g ( B a r r , 1966;  with  gypsum  i s known i n a number of d e p o s i t s i n the Canadian  Allen,  1971;  South America (Howell  Godwin, 1975)  and M o l l o y ,  Cordillera  as w e l l as e l s e w h e r e i n N o r t h  1960;  L o w e l l and  G u i l b e r t , 1970).  and A  number of t h e o r i e s have been proposed to e x p l a i n o r i g i n o f sheet f r a c t u r e cleavage  i n p o r p h y r y d e p o s i t s but no s i n g l e e x p l a n a t i o n seems s a t i s f a c t o r y  nor can be a p p l i e d t o B e r g d e p o s i t .  The  problem i s t h r e e f o l d :  e x p l a i n the s u b h o r i z o n t a l f r a c t u r e c l e a v a g e , of  gypsum i n these  f r a c t u r e s , and  secondly  firstly  to  to e x p l a i n p r e s e n c e  t h i r d l y to e x p l a i n the h i g h f r e q u e n c y  of  fracture.  Allen  (1971) has  d e p o s i t s i n which sheet  developed  a model f o r the G a l o r e  Creek copper  f r a c t u r e s a r e formed a l o n g w i t h c o n c o m i t a n t depo-  s i t i o n o f gypsum as a consequence o f near s u r f a c e h y d r a t i o n o f  anhydrite.  In s i t u h y d r a t i o n o f gypsum i s accompanied by a 63-per-cent i n c r e a s e i n volume r e s u l t i n g i n f r a c t u r e s p a r a l l e l d i c u l a r to s t r e s s r e l i e f . of The  to the t o p o g r a p h i c  s u r f a c e , perpen-  F r a c t u r e s a r e f u r t h e r opened by m e c h a n i c a l f o r c e  c r y s t a l l i z a t i o n as gypsum i s r e d e p o s i t e d from s a t u r a t e d m e t e o r i c s o l u t i o n s . model i s a t t r a c t i v e f o r the d e p o s i t s s t u d i e d by A l l e n as r o c k s a t depth  c o n t a i n a n h y d r i t e up  to 20 per cent by volume as a p e r v a s i v e r o c k c o n s t i t u e n t .  At s h a l l o w depths where sheet hydrated  to gypsum.  a n h y d r i t e i s found  The  anhydrite i s t o t a l l y  model i s not c o n v i n c i n g f o r Berg d e p o s i t where  i n o n l y s m a l l amounts mainly  with quartz or c a l c i t e . filled  f r a c t u r i n g i s most I n t e n s e ,  as a v e i n c o n s t i t u e n t  These a n h y d r i t e - b e a r i n g v e i n s are cut by  f r a c t u r e s but a n h y d r i t e r a r e l y shows any e f f e c t s o f  together  gypsum-  hydration.  Other i n v e s t i g a t o r s d i s c u s s a l t e r n a t e o r i g i n s o f f r a c t u r e c l e a v a g e t h a t p l a c e l i t t l e o r no  emphasis on h y d r a t i o n o f a n h y d r i t e as a c a u s a t i v e  66 process.  Suggested mechanisms o f c l e a v a g e development i n c l u d e  b r e c c i a t i o n , c h e m i c a l b r e c c i a t i o n , and  Godwin (1973) has accompanied by  development o f s u b h o r i z o n t a l  no young b r e c c i a body has  c l e a v a g e can be why  v e i n e d by veined. has  t o the  f r a c t u r e c l e a v a g e caused  been r e c o g n i z e d Also  been used t o r e l a t e v e r t i c a l s h e e t i n g Similar  to which the  i n t r u s i v e s t o c k are s t r o n g l y  C h e m i c a l b r e c c i a t i o n as d i s c u s s e d  to e x p l o s i v e  by and  late  Sawkins and associated  Sillitoe  (Phillips,  t o the  1972;  of h y d r a u l i c  what P h i l l i p s At  the  be  fracture.  groundwater.  of  explain sub-  fracturing  d i r e c t i o n o f s t r e s s r e l i e f i n the p r e s e n c e o f a  r o c k s by  (1972) d e s c r i b e s  D i f f e r e n t i a l s t r e s s could  fluid be  emplacement of i n t r u s i v e r o c k s or magma i n as a p r o c e s s i n v o l v i n g n o n p e n e t r a t i v e  same time pore p r e s s u r e i n i n t r u d e d  penetrative  bodies  I t suggests that  formed by near s u r f a c e  Shearman e t a l . , 1972).  developed i n i n t r u d e d  cleavage  deposit.  h o r i z o n t a l f r a c t u r e c l e a v a g e may perpendicular  (1971)  l a t e development  p o s s i b l y most p r o m i s i n g t h e o r y advanced to  f r a c t u r e cleavage i s that  and  b r e c c i a t i o n , the mechanism i s  the v e r y widespread and  t h i r d and  and  flat-lying  but  The  explain  o n l y weakly f r a c t u r e d  c e r t a i n f r a c t u r e s p r o x i m a l to b r e c c i a  f r a c t u r e c l e a v a g e a t Berg  by  stage  cleaved  p o s s i b l y adequate to e x p l a i n i s i n a d e q u a t e to e x p l a i n  be  However, a t B e r g  the mechanism does not  gypsum whereas i n t r u s i v e r o c k s are  to b r e c c i a p i p e s .  b r e c c i a t i o n might  air-rock interface.  genetically related.  a l t e r e d rocks close  fracturing.  suggested that explosive  r e f l e c t i o n o f shock waves from the deposit  hydraulic  explosive  r o c k s would be  increased  fluids. by  f l u i d s such as h y d r o t h e r m a l s o l u t i o n s or m a g m a t i c a l l y h e a t e d Hydraulic  f r a c t u r i n g would take p l a c e  i n stressed  rocks  67 s u r r o u n d i n g the i n t r u s i v e s t o c k as h y d r o t h e r m a l f l u i d volume i n c r e a s e d .  T h i s has  f l u i d s were generated  r e c e n t l y been r e f e r r e d  magmafract p r o c e s s ' by W.  Burnham (Annual R e p o r t ,  L a b o r a t o r y , 1975,  i n which c r y s t a l l i z a t i o n  p. 627)  r e s u l t s i n r e l e a s e o f water and  t o as a  and  'hydro-  1974-1975, G e o p h y s i c a l o f w a t e r - s a t u r a t e d magma  a c o n c u r r e n t l a r g e volume I n c r e a s e .  68  CHAPTER  III  HYDRO-THERMAL ALTERATION  INTRODUCTION Alteration patterns at Berg deposit, as defined by changes in non-sulphide mineralogy in diamond-drill cores, are grossly similar to those in porphyry copper models described by Lowell and Guilbert (1970) and Rose (1970).  Refinements by Guilbert and Lowell (1974) and Carson  and Jambor (1974) embellished older models and made them more appropriate for Berg and other Cordilleran deposits where volcanic rocks are hosts for major portions of the mineralized systems.  These are the wallrock or  combined wallrock-intrusion porphyry copper type deposits of Titley (1972). This study Is concerned primarily with hypogene alteration types and zoning patterns.  At Berg deposit the distinction between rocks  with solely hypogene or hypogene and supergene alteration is indicated clearly in d r i l l core by fractures f i l l e d with gypsum that mark the limit to which ground waters have circulated.  Supergene alteration has taken  place only near surface where gypsum is leached.  In the zone with  gypsum-healed fractures, ground water flow following hydrothermal activity has been minimized and a l l alteration can be assumed to be hydrothermal and hypogene. Supergene alteration caused by weathering, oxidation, and leaching by acidic solutions i s extensive and has resulted in a thick leached capping containing mainly quartz, limonite, s e r i c i t e , chlorite, and clay minerals.  Thin section and X-ray diffraction analyses of  clay-sized minerals in the capping reveal marked increases in amounts of  69 k a o l i n i t e , s e r i c i t e , and  c h l o r i t e compared t o r o c k s s u b j e c t e d o n l y  to  hypogene a l t e r a t i o n .  A t Berg d e p o s i t zones w i t h q u a r t z - o r t h o c l a s e and a l t e r a t i o n a r e developed monzonite s t o c k and biotitic rocks.  quartz-sericite  c e n t r a l l y i n the weakly m i n e r a l i z e d  quartz  a r e surrounded by a l t e r a t i o n a u r e o l e s c o n t a i n i n g ,  c u p r i f e r o u s r o c k s , then, p y r i t i c  chlorite-calcite-epidote-bearing  Q u a r t z - s e r l c i t e - p y r i t e zones o c c u r e x t e n s i v e l y a l o n g  c o n t a c t o f the q u a r t z monzonite s t o c k and  first,  the  intrusive  c l a y - b e a r i n g zones a r e  developed  l o c a l l y i n p o s i t i o n s i n t e r m e d i a t e between t h e i n t r u s i v e c o r e and  pyritic  periphery.  Q u a n t i t i e s and sections of d r i l l logs.  a s s o c i a t i o n s of a l t e r a t i o n minerals  c o r e were r e c o r d e d  i n d e s c r i p t i v e and  A l l d i a m o n d - d r i l l core a v a i l a b l e to 1971  w r i t e r with p a r t i c u l a r regard f o r :  was  in  10-foot  graphic  catalogued  drill by  quartz, orthoclase, b i o t i t e ,  ( m u s c o v i t e ) , m a g n e t i t e , c a l c i t e , e p i d o t e , a n h y d r i t e , and gypsum. m i n e r a l s were i d e n t i f i e d l a t e r in' t h e l a b o r a t o r y by X - r a y (Appendix C ) . per  L o c a t i o n o f gypsum was  f o o t o f core was  recorded.  noted  and  sericite Clay  diffraction  number o f c l e a v a g e f r a c t u r e s  L i m o n i t e m i n e r a l s , where p r e s e n t , were  d e s c r i b e d i n terms o f c o l o u r , abundance, and on l i m o n i t e c o l o u r was  the  character.  An e s t i m a t e  made o f the p r o p o r t i o n s o f g o e t h i t e and  jarosite.  S i g n i f i c a n t d i f f e r e n c e s i n appearance o f d i a m o n d - d r i l l core hand specimens were used t o d e f i n e v a r i o u s a l t e r a t i o n types and intensities.  A s t a n d a r d i z e d c a t a l o g u i n g p r o c e d u r e enabled  i n t e n s i t i e s to be ranked and of  thereby  contoured  were used t o d e f i n e hypogene z o n i n g p a t t e r n s  and  alteration  alteration  q u a n t i f i e d (Appendix B ) .  a l t e r a t i o n i n t e n s i t i e s were p l o t t e d and  based  Ranked v a l u e s  on a g e o l o g i c p l a n  (Figure 8).  and  70 DEFINITION OF ALTERATION FACIES AND  ZONES  Diagnostic a l t e r a t i o n minerals used t o d e f i n e a number o f a l t e r a t i o n Burnham, 1962; recognized and  argillic  and m i n e r a l a s s o c i a t i o n s can  types, o r f a c i e s  Meyer and Hemley, 1967).  a t Berg d e p o s i t  ^  (Creasy,  1959,  A l l commonly used types  1966;  are  ( F i g u r e 8) i n c l u d i n g p o t a s s i c , p h y l l i c ,  f a c i e s as w e l l as a b i o t i t i c a l t e r a t i o n f a c i e s  be  propylitic,  (biotite hornfels).  B i o t i t i c a l t e r a t i o n i s more c l o s e l y a s s o c i a t e d w i t h c h a l c o p y r i t e c o n c e n t r a t i o n s than a r e o t h e r a l t e r a t i o n t y p e s .  Because o f t h i s important  relationship, i t  i s c o n s i d e r e d h e r e s e p a r a t e l y r a t h e r than p a r t o f the p o t a s s i c zone as done by some a u t h o r s .  A l t e r a t i o n e f f e c t s a r e most o b v i o u s  i n v o l c a n i c rocks  t h e q u a r t z monzonite s t o c k , c l o s e to the i n t r u s i v e c o n t a c t . q u a r t z monzonite v a r i e s i n i n t e n s i t y i n d i f f e r e n t the s t o c k . (Map  Most i n t e n s e l y a l t e r e d r o c k  2, u n i t 3) and  sericitized  zones and  surrounding  A l t e r a t i o n of r o c k types  types a r e q u a r t z monzonite porphyry  q u a r t z p l a g i o c l a s e porphyry  (Map  2, u n i t  Most s u b t l e a l t e r a t i o n i s i n p l a g i o c l a s e b i o t i t e q u a r t z porphyry (Map u n i t 5) and hornblende q u a r t z c o n t a c t s i n the southern  within  f e l d s p a r porphyry  p a r t o f the s t o c k and  (Map  2, u n i t 6 ) .  the n o r t h w e s t e r l y  f r a c t u r e o r b r e c c i a zones a r e the most h i g h l y a l t e r e d  4).  3,  Intrusive trending  zones w i t h i n the  stock.  POTASSIC ALTERATION  Potassic  ( q u a r t z - o r t h o c l a s e ) a l t e r a t i o n can be found  within  the  m i n e r a l i z e d s t o c k where i t appears to be r e s t r i c t e d  to q u a r t z monzonite  porphyry  (A. D. Drummond,  (Map  2, u n i t 3 ) .  However, r e c e n t d r i l l i n g  1975,  p e r s o n a l communication) i n d i c a t e s t h a t s e r i c i t i z a t i o n i s more widespread than o r i g i n a l l y  thought and p o t a s s i c a l t e r a t i o n might not be as  as shown i n F i g u r e  8.  extensive  71 O r t h o c l a s e , q u a r t z , s e r i c i t e , and minerals  t o g e t h e r w i t h a n h y d r i t e and  b i o t i t e a r e main a l t e r a t i o n  l e s s e r amounts o f s u l p h i d e  c h l o r i t e , m a g n e t i t e , k a o l i n i t e , and m o n t m o r i l l o n i t e .  Potassic alteration  i s seen as a p e r v a s i v e p i n k c o l o u r a t i o n i n the r o c k m a t r i x o r t h o c l a s e f l o o d i n g ( P l a t e 14).  caused  by  In t h i n s e c t i o n i t i s seen as a v e r y  f i n e - g r a i n e d mosaic o f o r t h o c l a s e - q u a r t z - p l a g i o c l a s e - s e r i c i t e . examined ( a l l from d r i l l h o l e  minerals,  1 and  In specimens  6) about 5 per c e n t o r t h o c l a s e appears  t o have been added d u r i n g o r t h o c l a s e metasomatism, g e n e r a l l y r e p l a c i n g p l a g i o c l a s e o r r a r e l y as o r t h o c l a s e r i m s on p l a g i o c l a s e p h e n o c r y s t s . s t r o n g l y a l t e r e d r o c k s q u a r t z v e i n s exceed phenocrysts  proximal  colour.  10 p e r c e n t and p l a g i o c l a s e  t o q u a r t z v e i n s a r e s e r i c i t i z e d and,  a r g i l l i z e d ; a l t e r e d p l a g i o c l a s e has  i n rare  cases,  a c h a r a c t e r i s t i c p a l e green to b u f f  Where q u a r t z v e i n s a r e l e s s than  10 per cent o f the r o c k volume,  p l a g i o c l a s e c r y s t a l s are u n a l t e r e d or s l i g h t l y clouded phenocrysts  In most  i n appearance.  Mafic  ( o r i g i n a l l y b i o t i t e and h o r n b l e n d e ) i n s t r o n g l y a l t e r e d r o c k s  r e p l a c e d t o t a l l y by f i n e - g r a i n e d , f e l t e d b i o t i t e and magnetite, sulphide minerals, a n d - c h l o r i t e .  are  l e s s common s e r i c i t e ,  In weakly a l t e r e d zones o f  p o r p h y r y , o n l y hornblende i s r e p l a c e d by secondary b i o t i t e and b i o t i t e phenoc r y s t s a r e e i t h e r p a r t i a l l y r e p l a c e d o r remain as e u h e d r a l  crystals.  PHYLLIC ALTERATION  Phyllic  ( q u a r t z - s e r i c i t e - p y r i t e ) a l t e r a t i o n of rocks i s e a s i l y  r e c o g n i z e d by a b l e a c h e d Bleaching  c h a l k y weathered appearance ( P l a t e 15).  i s caused by thorough q u a r t z - s e r i c i t e a l t e r a t i o n o f p l a g i o c l a s e ,  s e r i c i t e , and minerals  and  q u a r t z a l t e r a t i o n o f o r t h o c l a s e , and breakdown o f  t o dominantly s e r i c i t e and  c h l o r i t e , and  pyrite.  l e s s e r amounts o f b i o t i t e ,  M a g n e t i t e i s absent  but p y r i t e and  mafic quartz,  s m a l l amounts o f  72 hematite  are present.  In t h i n s e c t i o n r o c k s w i t h p h y l l i c  alteration  appear as a f i n e - g r a n u l a r , mosaic i n t e r g r o w t h o f q u a r t z - s e r i c i t e among relict,  s e r i c i t i z e d , and weakly k a o l i n i z e d  shredded ents.  g r a i n s o f secondary  f e l d s p a r phenocrysts.  b i o t i t e and minor c h l o r i t e a r e m a f i c  In s e r i c i t i z e d q u a r t z p l a g i o c l a s e p o r p h y r y  g r a i n e d b i o t i t e i s l o c a l l y abundant  medium brown c o l o u r t o the r o c k m a t r i x  to  be p r e s e n t a t Berg d e p o s i t by D a h l and N o r t o n  The  ( P l a t e 10).  Topaz, f i r s t  southwestern  altered  i s discontinuous  i n plagioclase  (Figure 8).  Phyllic  a l t e r a t i o n c r o s s e s the q u a r t z monzonite c o n t a c t i n the south and  southeast  outward f o r a few metres i n t o h i g h l y f r a c t u r e d v o l c a n i c r o c k s .  A s m a l l zone w i t h p h y l l i c a l t e r a t i o n was  a l s o i n t e r s e c t e d a t depth i n d r i l l  h o l e 1 a l o n g the n o r t h e r n boundary o f the s t o c k . a r e c o m p l i c a t e d , however, because more than one emplaced.  alter-  most e x t e n s i v e l y  i n t r u s i v e c o n t a c t s and  b i o t i t e q u a r t z porphyry which i s l i t t l e  is  reported  assemblages.  around the n o r t h e a s t c o n t a c t n e a r e s t q u a r t z d i o r i t e and  and extends  fine-  (1967) , i s a minor  zone o f p h y l l i c a l t e r a t i o n i s d e v e l o p e d  a l o n g t h e s o u t h e r n and  2, u n i t 4)  constitu-  (up t o 6 p e r c e n t ) and imparts a t a n  to  ation mineral i n p h y l l i c  (Map  Scattered,  P h y l l i c a l t e r a t i o n i s developed  Relationships i n this  area  i n t r u s i v e phase p r o b a b l y  p e r i p h e r a l l y to p o t a s s i c  a l t e r a t i o n but the zone o f p h y l l i c a l t e r a t i o n encroaches  p o t a s s i c zones.  A h i g h l y i r r e g u l a r c o n t a c t f o l l o w i n g i n t e r c o n n e c t e d zones of i n t e n s e f r a c t u r i n g and b r e c c i a t i o n l o c a l l y  isolates  ' i s l a n d s ' of rocks with p o t a s s i c  alteration.  PROPYLITIC ALTERATION  P r o p y l i t i c a l t e r a t i o n coincides with strongly p y r i t i z e d v o l c a n i c r o c k s and q u a r t z d i o r i t e p e r i p h e r a l t o e i t h e r p h y l l i c a l t e r a t i o n zones i n  73 quartz monzonite porphyry or biotite hornfels formed along the Intrusive contact (Figure 8 ) .  Presence of sulphide minerals, mainly pyrite, was the  sole criterion used to distinguish rocks with hydrothermal propylitic alteration from those having greenschist regional metamorphism. Propylitic alteration i s recognized by an overall green colouration in rocks caused by abundant and pervasive chlorite and epidote. Locally propylitized rocks have a mottled appearance due to bleached borders of fractures and veins (Plates 17 and 19).  Where fractures are  abundant, crosscutting, and interconnected, propylitic rocks are pervasively bleached to a pale grey-green to olive drab colour.  Possibly the  best indicator of propylitic alteration and most reliable criterion for distinguishing propylitized rocks from chloritic biotite hornfels is presence of calcite.  Invariably, abundant calcite coincides with rocks in  which chlorite exceeds biotite in abundance and epidote as well as magnetite are common.  In addition to the chlorite, calcite, and magnetite above,  albitized plagioclase, sericite, epidote, and pyrite are abundant along with lesser quantities of montmorillonite, kaolinite, dolomite, tremolite, gypsum, r u t i l e , leucoxene, and hematite.  Detailed examination of propylitized  rocks reveals three common mineral associations:  (1) chlorite-epidote-calcite  (widespread), (2) chlorite-epidote-tremolite (in basic volcanic rocks), and (3) chlorite-kaolinite-dolomite (localized in three small zones of a r g i l l i c alteration).  Bleached margins of quartz-pyrite veins consist of very fine-grained mixtures of calcite-gypsura-montmorillonite as well as chlorite-albite and possibly sericite.  Bleached vein margins in the propylitic zone are dis-  tinguished from phyllic alteration by sparseness of sericite.  74 P r o p y l i t i c a l t e r a t i o n i s a l s o found porphyry  (Map  i n hornblende quartz f e l d s p a r  2, u n i t 6 ) , the youngest phase o f the q u a r t z monzonite  However, u n l i k e v o l c a n i c r o c k s and  quartz d i o r i t e  p e r i p h e r a l t o the composite s t o c k , q u a r t z  i n the p r o p y l i t i c  stock. zone  f e l d s p a r p o r p h y r y i s o n l y weakly  pyrltized.  ARGILLIC ALTERATION  Argillic  (clay) a l t e r a t i o n Is recognized  abundant m o n t m o r i l l o n i t e in  and k a o l i n i t e .  t h r e e zones ( F i g u r e 8 ) .  The  tens o f metres i n w i d t h , but l i m i t e d subsurface  zones appear t o be  t h e i r extent  information.  One  southwestern contact of s e r i c i t i z e d The  Argillic  occur  to a  few  to  altered (Map  2, u n i t  p r o p y l i t i c a l t e r a t i o n zones In  southeast  The  two  the  and  In a l l t h r e e zones c o n t a i n i n g c l a y m i n e r a l s ,  a l t e r a t i o n f a c i e s a c c o r d i n g to Creasey  o f the  argillic  (1966), i s not e v i d e n t .  c l a y - b e a r i n g r o c k s a t Berg d e p o s i t might be r e g a r d e d  Therefore,  s i m p l y as c l a y - b e a r i n g ,  alteration.  BIOTITIC ALTERATION  Biotitic i n t e n s e l y developed  a l t e r a t i o n , a l s o r e f e r r e d t o as b i o t i t e h o r n f e l s , i s most i n v o l c a n i c rocks adjacent  to p h y l l i c o r p o t a s s i c  a l t e r a t i o n zones formed i n q u a r t z monzonite ( F i g u r e 8 ) . c o i n c i d e s with  4).  o t h e r zones a r e i n  o f the composite s t o c k  o f the main r e q u i r e m e n t s  aluminous s u b f a c i e s o f p r o p y l i t i c  the  q u a r t z p l a g i o c l a s e porphyry  p r o p y l i t i z e d v o l c a n i c r o c k s n o r t h and  s t r o n g c a l c i u m l e a c h i n g , one  small, limited  i s p o o r l y documented due  p o s i t i o n p r e d i c t e d by porphyry copper models.  t h e q u a r t z d i o r i t e contact..  r o c k s a r e known to  zone i s a s s o c i a t e d w i t h  a r g i l l i c zones l i e between p h y l l i c and  along  a t Berg by p r e s e n c e o f  Biotitic  zones o f most i n t e n s e copper m i n e r a l i z a t i o n .  alteration  This intimate  75  association of copper sulphides with a zone of b i o t i t i c alteration is characteristic of many porphyry deposits and, therefore, makes recognition and definition of b i o t i t i c alteration zones a useful product of alteration studies in ore search. Rocks with b i o t i t i c alteration at Berg deposit are andesitic metavolcanic rocks which are easily recognized by their dark brown to black colour and velvety hornfelsic texture.  B i o t i t i c alteration is also  seen in quartz diorite which has a spotted 'salt and pepper' appearance where i t i s biotitized near quartz monzonite.  As much as 50 per cent  biotite is present in some altered rocks but most commonly biotite content is 20 to 35 per cent. are:  Other alteration minerals associated with biotite  quartz, orthoclase, plagioclase, s e r i c i t e , anhydrite, epidote,  chlorite, magnetite, and minor calcite, clay minerals, and r u t i l e .  Chlorite  from the b i o t i t i c zone at Berg is a magnesian clinochore, leuchtenberglte (Dahl and Norton, 1967). The zone of b i o t i t i c alteration can be regarded as a transitional zone between potassic (quartz-orthoclase) peripheral propylitic alteration zone.  or phyllic alteration and the  Biotite hornfels can be classified  as part of either the potassic or propylitic alteration facies, depending on which alteration minerals accompany biotite.  Classification of b i o t i t i c  rocks into zones of either potassic or ;propylltic alteration is not always obvious, as pointed out by Titley (1972), and depends on whether potash metasomatism can be demonstrated to have taken place.  At Berg deposit in  the southern half of the quartz monzonite stock and along part of the northern contact, biotite hornfels flanks rocks with phyllic alteration. The b i o t i t i c rocks contain epidote, chlorite, magnetite, and traces of clay  76 m i n e r a l s and  c a l c i t e , but no a d d i t i o n o f p o t a s h  i s evident.  Biotitic  i n t h i s zone, t h e r e f o r e , a r e c o m p a t i b l e w i t h t h e p r o p y l i t i c f a c i e s and is:  rocks  alteration  the a l t e r a t i o n z o n i n g sequence from q u a r t z monzonite c o r e outward  p o t a s s i c ( q u a r t z - o r t h o c l a s e - s e r i c i t e ) , then p h y l l i c , and  p r o p y l i t i c i n t h e b i o t i t e h o r n f e l s , a normal z o n i n g  Along  finally  sequence.  the n o r t h e a s t c o n t a c t o f the q u a r t z monzonite s t o c k i n  the s c r e e n o f h o r n f e l s e d v o l c a n i c r o c k s between q u a r t z monzonite and diorite intrusions  (and p o s s i b l y a l s o a l o n g the n o r t h w e s t e r n  monzonite c o n t a c t ) , p h y l l i c a l t e r a t i o n i s p o o r l y developed In t h e s e zones b i o t i t i c  quartz  quartz  or i s absent.  rocks a d j o i n i n t r u s i v e rocks with p o t a s s i c a l t e r a t i o n  and a r e v e i n e d by q u a r t z - o r t h o c l a s e - a n h y d r i t e , q u a r t z - o r t h o c l a s e , and c l a s e v e i n s ( P l a t e s 16 and  18).  In such zones b i o t i t i c v o l c a n i c rocks a r e  l a c e d by a q u a r t z v e i n stockwork t h a t i s w e l l m i n e r a l i z e d w i t h Mineralogy The  molybdenite.  o f t h i s v e i n i n g i s c o m p a t i b l e w i t h the p o t a s s i c a l t e r a t i o n  alteration  ortho-  z o n i n g sequence i s :  facies.  p o t a s s i c ( v e i n and p e r v a s i v e q u a r t z -  o r t h o c l a s e ) i n q u a r t z monzonite, p o t a s s i c ( o r t h o c l a s e v e i n e d  biotitic  a l t e r a t i o n ) i n h o r n f e l s e d v o l c a n i c r o c k s n e a r the i n t r u s i v e s t o c k and  grading  outward t o p r o p y l i t i c i n q u a r t z d i o r i t e and v o l c a n i c r o c k s f u r t h e r from  the  q u a r t z monzonite c o n t a c t .  The p r e s e n c e might be r e s t r i c t e d  of p o t a s s i c f a c i e s  (orthoclase-veined) b i o t i t i c  t o t h a t zone i n which v o l c a n i c r o c k s have been,  t h e r m a l l y metamorphosed by q u a r t z d i o r i t e and, stockwork and b i o t i t i c hydrothermal Elsewhere  t o q u a r t z monzonite.  a l o n g the q u a r t z d i o r i t e c o n t a c t where h y d r o t h e r m a l  more remote from q u a r t z monzonite, b i o t i t e h o r n f e l s t h a t was  biotite,  to rocks o f p r o p y l i t i c  aspect.  first,  then o v e r l a p p e d by a q u a r t z  alteration related  t h e q u a r t z d i o r i t e c o n t a c t has degenerated,  rocks  f l u i d s were formed a l o n g  m a i n l y by c h l o r i t i z a t i o n o f  Figure 8  1  Quartz-K  felds-biotite-  GENERALIZED ALTERATION ZONES, BERG DEPOSIT  :4V::v:J Bi'ofjfe Qtz •  sericite  sericite-pyrite  Hypogene  Alteration Determined From Drill  Core  Argillic Propylitic \  • diamond drill site •/.•••.••.vV..-.  h-20.000 N  ilili • i f f ^"7  / /  N  7000 SCALE - FEET  0  300 SCALE-METRES  ?  |  |  breccia  j  |  qtz bearing monzodi.  |  |  qtz monzonite  |  |  qtz diorite  |  |  hornfels .volcanics  PLATE 14. P o t a s s i c a l t e r a t i o n i n quartz monzonite porphyry (DDH 6 ) . Pervasive pink appearance i s from orthoclase f l o o d i n g i n m a t r i x . H a i r l i n e f r a c t u r e s contain gypsum. Quartz g r a i n s are grey, p l a g i o c l a s e grains are pale grey to white.  PLATE 15.  Phyllic (quartz-sericite-pyrite) alteration o f q u a r t z monzonite porphyry (DDH 2 5 ) . The small v e i n l e t s contain quartz. Subhedral p l a g i o c l a s e c r y s t a l s are chalky; quartz g r a i n s a r e grey; s c a t t e r e d b l a c k m i n e r a l s a r e b i o t i t e . Q u a r t z v e i n s a t bottom o f sample c o n t a i n molybdenite. Scale i s i n m i l l i m e t r e s .  PLATE 1  Potassic a l t e r a t i o n of b i o t i t i c v o l c a n i c rocks (DDH 43) (quartz-orthoclase veined b i o t i t e h o r n f e l s ) . The ribboned quartz-molybdenite vein has an orthoclase envelope. Micro veinl e t s are quartz bearing and some have s l i g h t l y s e r i c i t i z e d margins (brown). Note lack of bleaching on larger vein margins. Scale i s i n millimetres.  I 111111111IIIII MM PLATE 17.  llllilll  11II M i l I M 111III MM  MM  MM  MM  P r o p y l i t i c a l t e r a t i o n of b i o t i t i c volcanic rock (DDH 26). Mottled appearance i s from bleached margins on p y r i t i c quartz veins and f r a c t u r e s . Pervasive (brown-green) a l t e r a t i o n consists of chlorite-calcite-gypsura-clay minerals i n chlori t i c b i o t i t i z e d rock (black). Scale i s i n millimetres.  PLATE 18,  Potassic a l t e r a t i o n of b i o t i t i c v o l c a n i c rock (DDH 4 3 ) . An o r t h o c l a s e v e i n i s c u t by a quartz-anhydrite vein containing fine-grained b i o t i t e . Note l a c k o f a l t e r a t i o n e n v e l o p e s on veins. Scale i s i n centimetres.  Illl PLATE 19.  l l l l i l i M I I I I I IMIIIIM  P r o p y l i t i c a l t e r a t i o n i n l a p i l l i t u f f (DDH 68) with bleached f r a c t u r e margins. Bleaching i s from a l t e r a t i o n t o c a l c i t e - g y p s u m - c l a y m i n e r a l s and/or s e r i c i t e b o r d e r i n g p y r i t i c , q u a r t z b e a r i n g f r a c t u r e s . Scale i s i n m i l l i m e t r e s .  81 VEINS V e i n s are found mineralized  zone.  throughout the h y d r o t h e r m a l l y  altered  They form a stockwork o f s m a l l v e i n l e t s  and  (mainly  b e a r i n g q u a r t z v e i n s ) t h a t surrounds the composite Berg s t o c k .  sulphide-  The  vein-  stockwork i s most c l o s e l y a s s o c i a t e d w i t h q u a r t z monzonite p o r p h y r y  and  p l a g i o c l a s e b i o t i t e q u a r t z porphyry a l t h o u g h  I t i s imposed on h o r n f e l s e d  r o c k s and  f e l d s p a r p o r p h y r y and b a s a l t  dykes.  a l l I n t r u s i v e phases except  The  quartz  zone w i t h h i g h e s t d e n s i t y o f v e i n s i s found  within  and h o r n f e l s e d r o c k s near the main i n t r u s i v e c o n t a c t s . decreases  more r a p i d l y inward than outward from the  The  Abundance o f v e i n s  contact.  a l t e r a t i o n f a c i e s d e s c r i b e d i n p r e c e d i n g pages r e p r e s e n t  l a r g e p e r v a s i v e a l t e r a t i o n zones.  V e i n s , on the o t h e r hand, a r e  p a r t l y synchronous w i t h p e r v a s i v e a l t e r a t i o n p r o c e s s e s . cases  intrusive  superimposed on p e r v a s i v e l y a l t e r e d r o c k s and  only  They a r e i n many  reflect  changes i n  h y d r o t h e r m a l f l u i d s t h a t passed through and were c o n f i n e d to f r a c t u r e s and o t h e r channelways.  Hydrothermal f l u i d s from which some v e i n m i n e r a l s were  d e p o s i t e d caused l i t t l e rocks without  a l t e r a t i o n o f e n c l o s i n g r o c k s and v e i n s c u t  appreciable a l t e r a t i o n e f f e c t s .  In o t h e r host r o c k s r e a c t i o n s  w i t h f l u i d s i n f r a c t u r e s r e s u l t e d i n a l t e r a t i o n e n v e l o p e s i n which adjacent mainly  v e i n margins i n which r e l i c t  rock-forming  primary  s e r i c i t e , and  o t h e r v e i n s have and  quartz, c h l o r i t e , clay  gypsum ( P l a t e 19).  metasomatism (most o b v i o u s l y o r t h o c l a s e - q u a r t z ) has are c a l l e d envelopes.  Still  to  t e x t u r e s are m a i n t a i n e d ,  m i n e r a l s a r e broken down to m a i n l y  m i n e r a l s , carbonate,  borders  minerals  to v e i n s were metasomatized o r r e c r y s t a l l i z e d and made over  q u a r t z , K - f e l d s p a r , s e r i c i t e , and b i o t i t e .  bleached  host  Thus, where s i g n i f i c a n t  taken p l a c e , a l t e r e d v e i n  Where r e t r o g r a d e breakdown of  rock-forming  82 constituents has taken place but original textures remain, altered vein borders are referred to as alteration margins. In zones of extensive fracturing away from the stock, bleached margins on veins result in a mottled appearance or coalesce to form large bleached zones.  In general, alteration envelopes are most abundant on  veins within the stock and along Its contacts where the quartz stockwork i s best developed.  Veins with alteration envelopes decrease in abundance  away from the composite stock and are exceeded by veins with bleached margins.  Bleached alteration margins are most noticeable in pyritic  hornfelsic and propylitic rocks. A l l three vein types (with alteration envelopes, without envelopes, and with bleached margins) can be found in the same rock. in sequence as a staged vein series.  They have formed  The sequence is complicated to decipher .  and cannot be resolved completely without additional detailed study.  The  following sequence from oldest to youngest Is suggested. Stage 1  A.  Quartz-pyrite-chalcopyrite-molybdenite veins with alteration envelopes of quartz-sericite (common), chlorite (less common), or K-feldspar (rare).  B.  Quartz-pyrite-chalcopyrite-molybdenite veins without envelopes.  The above associations are modified by presence of other minerals including chlorite, anhydrite (purple and clear), epidote, carbonate, clay minerals, and magnetite. Stage 2  Quartz-molybdenite (or molybdenite alone) veins without envelopes.  83 Stage 3  Quartz-pyrite veins with or without envelopes, many with bleached margins.  Veins may also contain  chalcopyrite, rare epidote, and magnetite. Stage 4  Quartz-carbonate (common) and quartz-anydritecarbonate (rare) veins, many with bleached margins. These inay contain pyrite, chalcopyrite, sphalerite, tetrahedrite, galena, and epidote.  Anydrite is partially  to completely hydrated (hemihydrite to gypsum). Stage 5  Gypsum-filled fractures.  Crosscutting relationships permit at least five periods of Stage 1 veining to be postualted (A. D. Drummond, 1975, personal communication). However, as a rule, Stage 1 veins display complex relationships and suggest that Stage 1 veins have f i l l e d a previously crackled zone rather than generated a sequential, crosscutting stockwork system.  Stage 1 veins  generally consist of massive quartz intergrowths although many have cockscomb structures and vugs with drusy lining.  In some veins vugs are f i l l e d with  anhydrite; in others, cavities are open and quartz crystals are overgrown by fine-grained chlorite.  Stage 2 veins are massive and composed of compact,  fine-grained quartz or are ribboned with granulated quartz grains interspersed by bands of fine-grained molybdenite.  Stage 3 veins are ubiquitous  and are possibly the most abundant veins in the stockwork.  Except where they  are clearly crosscutting, Stage 3 veins are indistinguishable from Stage 1 or any other quartz-pyrite veins.  Stage 4 veins up to 3 millimetres in width  have been noted in diamond-drill core but are rare overall.  In pyritic rocks  surrounding the composite stock a number of quartz-carbonate-pyrite-sphaleritegalena-tetrahedrite veins up to a few feet in width are known to occur.  Stage  5 gypsum-filled fractures are part of the subhorizontal fracture cleavage  34  PLATE 20.  Subhorizontal gypsum-bearing f r a c t u r e cleavage c r o s s c u t t i n g p y r i t e and c h a l c o p y r i t e g r a i n s (DDH 28). The sulphide-bearing f r a c t u r e cuts an older q u a r t z - e p i d o t e - p y r i t e - c h a l c o p y r i t e v e i n (top r i g h t ) . Length of bar s c a l e i s 2.5 centimetres.  85 t h a t c r o s s c u t s a l l p r i m a r y a l t e r a t i o n and o r e m i n e r a l s and p o s s i b l y l o n g a f t e r v e i n s o f Stages  formed  1 t o 4.  ORIGIN OF HYPOGENE ALTERATION AND ZONING  PRINCIPLES  V a r i o u s a l t e r a t i o n and ore m i n e r a l assemblages o c c u r i n zones c e n t r e d on and e n v e l o p i n g t h e composite  Berg s t o c k .  Zones a r e d e f i n e d by  m i n e r a l assemblages i n which p r e - e x i s t i n g m i n e r a l s have and new m i n e r a l s  re-equilibriated  (most s i g n i f i c a n t l y o r e m i n e r a l s ) a r e added.  i n essence, a response  t o temperature,  p r e s s u r e , and c h e m i c a l g r a d i e n t s  caused by (1) t h e emplacement and presence c r y s t a l l i z a t i o n o f t h e s t o c k , (3)  Zoning i s ,  o f magma, (2) t h e c o o l i n g and  g e n e r a t i o n and f l o w o f h y d r o t h e r m a l  fluids  i n and around t h e s t o c k , (4) i n t r o d u c t i o n , t r a n s p o r t , and d e p o s i t i o n o f m e t a l s and o t h e r s u b s t a n c e s  by h y d r o t h e r m a l  f l u i d s , and (5) r e a c t i o n s i n  f l u i d s o r between f l u i d s and r o c k s i n and o u t s i d e t h e s t o c k .  The p r e r e q u i s i t e f o r a l t e r a t i o n and m i n e r a l i z a t i o n was emplacement o f a magma a l t h o u g h  t h e f u l l r o l e and p r o d u c t s o f magmatism i n t h e  a l t e r a t i o n - m i n e r a l i z a t i o n process i s contentious. most s i g n i f i c a n t  P o s s i b l y the s i n g l e  c o n t r i b u t i o n o f magma i s the s u p p l y o f h e a t .  from 700 t o 900 degrees  Temperatures  c e n t i g r a d e a r e c a l c u l a t e d from Ab-Or-Q-^O s o l i d u s  c u r v e s f o r g r a n o d i o r i t e o r q u a r t z monzonite s t o c k s w i t h which most copper d e p o s i t s a r e a s s o c i a t e d (Theodore and B l a k e , 1975). degrees 1975)  750 t o 300  c e n t i g r a d e was e s t i m a t e d f o r q u a r t z monzonite i n t r u s i o n s  comparable t o t h e one a t Berg d e p o s i t .  w i t h temperatures  from ambient t o 150 degrees  o f emplacement and geothermal  gradients.  Country  porphyry  (Whitney,  r o c k s were c o o l e r  c e n t i g r a d e depending on depths  86 Magmas may contain up to 14 or 15 per cent R^O (Burnham, 1967; Holland, 1972) but in shallow environments as in porphyry copper deposits from 2 to 6 per cent H 0 in magma can be expected (Holland, 1972). 2  Whitney  (1975) assumes 3 to 4 per cent to be present although as much as 8 per cent H^O might be necessary to f a c i l i t a t e extensive brecciation such as at Casino deposit (Godwin, 1975).  Magmas lose volatile components during ascent and  contain from h to 1 per cent H 0 when crystallized (Holland, 1972). 2  Thus,  during crystallization magmas liberate fluids equivalent to 1 to 5 per cent of the magma's weight. Fluids liberated late in the magmatic stage (juvenile fluids ?) have been long considered to be the source and transporting agent of metals (Bowen, 1933; Fenner, 1973; Emmons, 1933; Lindgren, 1937).  Similar ortho-  magmatlc models of porphyry copper deposits are s t i l l used (Nielsen, 1968; Holland, 1972) and passage of magmatic fluids outward from crystallizing stocks with attendant mineralization and alteration in margins of stocks and their surrounding rocks i s thought to be the main ore-forming process in many porphyry deposits (Fournier, 1967; Rose, 1970; Lowell and Guilbert, 1970; Whitney, 1975). Evolution of vapour during crystallization would result in a zone of high water activity surrounding the stock and in an overlying cupola.  If  vapour i s evolved rapidly in magma, fluid pressures may exceed lithostatic pressures and brecciation may take place or cracks may be propagated (Nielsen, 1968; Whitney, 1975).  Connate and meteoric waters in country rocks would not  be expected to flow against the temperature gradient and into the zone of high water pressure (Whitney, 1975).  However, stable isotope data (Sheppard,  Nielsen, and Taylor, 1969, 1971; Taylor, 1973) suggest that meteoric hydro-  87 thermal solutions are present in outer alteration zones (most notably zones of phyllic alteration) and do invade at least marginal parts of cooling stocks. Therefore, mixing of juvenile fluids and groundwater in porphyry copper deposits.  .evidently takes place  Models with convective flow of such mixed  source hydrothermal fluids were described by White, Muffler, and Truesdell, 1970; Cathles and Norton, 1974; Whitney, 1975; and Norton, 1975. Metals introduced by hydrothermal fluids are deposited in intrusive rocks or near intrusive contacts.  Source of metals i s uncertain; i t may be  the stock i t s e l f , a larger reservoir of magma at depth, or intruded rocks. The efficiency of concentration of metallic elements during crystallization of a wet magma i s well documented (Ringwood, 1955; Burnham, 1967; Holland, 1972).  Estimates of heavy metal concentrations in hydrothermal fluids range 4  from dilute to concentrated solutions (1-10 p. 335).  ppm, Barnes and Czamanske, 1967,  In porphyry copper deposits heavy metal concentrations of less than  100 ppm are suggested by Roedder (1971) and 1,000 to 2,000 ppm copper by Rose (1970).  At Berg deposit the crystalline core ( a l l except quartz feldspar  porphyry) contains about 1,500 ppm copper and country rocks contain about 75 ppm copper (the average copper content of six samples of volcanic rocks from outside the hydrothermally altered zone).  Thus considerable metal-bearing  hydrothermal fluid has passed through the margin of the stock in order to produce the large zone containing in excess of 0.2 per cent copper. Fluid pressures are dependent on depth of magma emplacement, cooling rate, and composition.  Fluid pressures in excess of hydrostatic  pressure or even exceeding lithostatic pressure (250 to 285 bars/km) must exist at least briefly in many porphyry deposits as suggested by boiling of hydrothermal fluids (Roedder, 1967 and 1971) and explosive brecciation.  Tops  88 of stocks with porphyry copper deposits are commonly 1.5 to 3 kilometres in depth (Lowell and Guilbert, 1970; S i l l i t o e , 1973).  Processes of mineralization  can extend into plutonic roots at depths of 8 kilometres ( S i l l i t o e ,  1973) but  maximum depths near 4.5 kilometres is suggested by Whitney (1975) for porphyry copper deposits associated with porphyritic quartz monzonite intrusions as this is the depth at which vapour is f i r s t liberated in quantity.  Roedder (1971) suggested a depth of 4.2 kilometres for  mineralization at the Bingham plutonic porphyry copper deposit.  Most other  porphyry deposits are believed to form at depths under 3.2 kilometres (Cox, Gonzales, and Nash, 1975) and may be as shallow as 450 metres (Nielsen, 1968).  Relief of 900 metres at Berg deposit suggests that this i s the  minimum depth at which the intrusion was emplaced. Temperatures of ore-forming fluids are best estimated from fluid inclusion homogenization temperatures which are generally higher than 250 degrees centigrade and can be as high as 725 degrees centigrade (Roedder, 1971).  Many porphyry deposits, especially those with potassic alteration  have highly saline fluid inclusions and temperatures are greater than 500 degrees centigrade (Roedder, 1971; Dawson, 1972; Moore and Nash, 1974). Others, commonly with widespread phyllic and a r g i l l i c alteration, have less saline fluids and are cooler with temperatures from 300 to 400 degrees centigrade (Nash and Theodore, 1971; Nash and Cunningham, 1974; Cox, et a l . , 1975).  Corroborating temperature estimates of 450 to 600 degrees centigrade  (Beane, 1974) and 790 to 382 degrees centigrade (Batchelder and Blake, 1975) are available from thermodynamic data applied to biotite compositions. Temperatures of 310 to 550 degrees centigrade (Field, Jones, and Bruce, 1971) and 300 to 600 degrees centigrade (Field, 1973) are estimated from sulphur Isotope measurements of equilibrium chalcopyrite-anhydrite pairs.  89 Changes in physic-chemical conditions in pregnant hydrothermal solutions result in deposition of ore and alteration minerals (Holland, 1967; Barnes and Czamanske, 1967; Barton and Skinner, 1967; Helgeson, 1970; Holland, 1972).  Possibly most important is cooling of fluids by outward  and upward flow along a geothermal gradient outward from a crystallizing stock, adiabatic expansion during i n i t i a l and second or multiple boiling (Roedder, 1971), heat exchange and reactions with wallrocks, or mixing and dilution with meteoric fluids (Barnes and Czamanske, 1967; Toulmin and Clark, 1967; Rose, 1970).  Not a l l components in solutions need be pre-  • cipitated nor diluted as a result of cooling.  For example, salinity may  increase as a result of boiling and i f vapour-dominated hydrothermal systems are recharged with condensate, sulphate and s i l i c a may be concentrated (White, et a l . , 1970; Roedder, 1971). In addition to cooling and dilution of hydrothermal f l u i d s , redox reactions during hydrothermal alteration change and buffer solute and gas concentrations resulting in decreased solubilities of metal-bearing complexes (Raymahashay and Holland, 1969; Helgeson, 1970).  Limiting conditions for  aqueous phases, f02» fS2» pH, and temperature can be deduced from mineral stability diagrams such as those of Barnes and Czamanske, 1967, page 351, and Meyer and Hemley, 1967, p. 220.  There is evidently delicate interplay  between f0£ and fS^ in early potassic alteration stages (K-feldspar,  sericite,  b i o t i t e , anhydrite, sulphide, magnetite) as well as stockworks with quartzsulphide and quartz-sulphide-sulphate veins.  Precipitation of magnetite  and anhydrite w i l l decrease f0£ and increase fS^ whereas oxidation of -2 sulphur-bearing complexes decreases a ^ S , deposition (Barnes and Czamanske, 1967).  aHS, aS  and leads to sulphide  90  O x i d a t i o n of hydrothermal f l u i d s a l s o s i m u l t a n e o u s l y r e l e a s e s H  +  i o n s l e a d i n g t o d e c r e a s e i n pH  (Barnes and Czamanske, 1 9 6 7 ) .  Presence  o f a c i d i c h y d r o t h e r m a l f l u i d s d u r i n g a l t e r a t i o n has been d i s c u s s e d  by  Hemley and J o n e s , 1 9 6 4 ; Meyer and Hemley, 1 9 6 7 ; and H o l l a n d , 1 9 7 2 . g r a d i e n t s and consequent  changes  pH  i n i n t e n s i t y o f hydrogen metasomatism a r e  c o n s i d e r e d t o cause a l t e r a t i o n z o n i n g (Hemley and J o n e s , 1 9 6 4 ; H e l g e s o n , 1970),  metal zoning (Holland, 1 9 7 2 ) ,  (Meyer and Hemley, 1 9 6 7 ) . of H  +  r e l a t i v e t o OH  Korzhinshii et a l . ,  (1957).  1961;  Zoning may  and changes  i n f l u i d s during  also result  d u r i n g i n f i l t r a t i o n p r o c e s s e s as d e s c r i b e d Hydrolysis e q u i l i b r i a studies  Hemley, e t a l . ,  o b s e r v e d a l t e r a t i o n sequence  (Meyer and Hemley, 1 9 6 7 ) .  by  (Helmey, 1 9 5 9 ; Hemley,  of p o t a s s i c - p h y l l i c - a r g i l l i c  f a c i e s as a r e s u l t  t o hydrogen  ion ratios  Changes i n h y d r o t h e r m a l f l u i d s w i t h time are  documented a t Endako d e p o s i t  (Drummond and Kimura,  1 9 6 9 ; Dawson, 1 9 7 2 ) and  (Grant and N i e l s e n , 1 9 7 5 ) where v e i n a l t e r a t i o n e n v e l o p e s i n a  s t a g e d stockwork  show the same t r e n d from p o t a s s i c t o p h y l l i c and  a l t e r a t i o n t h e r e b y s u g g e s t i n g s i m i l a r changes hydrogen  mobility  1 9 7 0 ) can be used t o e x p l a i n the commonly  o f d e c r e a s i n g temperature and p o t a s s i u m o r sodium  a t Yandera  from i n c r e a s e d  cooling  i o n r a t i o s as i n p e r v a s i v e a l t e r a t i o n  argillic  i n temperature and a l k a l i t o zones.  HYDROTHERMAL PROCESSES IN THE FORMATION OF BERG DEPOSIT  With the p r e c e d i n g d e s c r i p t i o n o f a l t e r a t i o n f a c i e s a t Berg d e p o s i t and d i s c u s s i o n o f p r i n c i p l e s i n mind, a l t e r a t i o n z o n i n g a t Berg d e p o s i t be i n t e r p r e t e d  i n terms o f d e c r e a s i n g temperature outward  d i f f e r e n c e s i n b u l k r o c k c o m p o s i t i o n , and changes  The  can  from the s t o c k ,  i n hydrothermal  fluids.  composite s t o c k i s surrounded by b i o t i t e - b e a r i n g m e t a v o l c a n i c  r o c k s ( h o r n f e l s ) t h a t extend up t o 6 0 0 f e e t from the c o n t a c t .  The  larger  91 quartz diorite stock has similar biotite hornfels along i t s intrusive contact but hornfels there is commonly 100 feet or less in width.  Conductive thermal  effects of igneous intrusions have been described by Lovering, 1955; Jaeger, 1959, 1964; and Whitney, 1975. Based on their models and earlier calculations on a small stock (Panteleyev, 1969) , temperature at the contact of a stock the size of Berg intrusion containing quartz monzonite magma at 800 degrees centigrade would be 400 to slightly in excess of 500 degrees centigrade. Temperatures would decrease outward from the contact but the limit to which purely conductive heat transfer would cause biotite hornfels to form is uncertain.  Heat flow models are imprecise and allow great latitude in  determinations of conductive heat flow.  For example, at Copper Canyon,  Nevada, a granodiorite stock was suggested to impose temperatures by conduction of only 150 degrees centigrade (Steiger and Hart, 1967) whereas Winkler (1965, pages 61-63) suggested temperatures equal to 60 per cent of magma temperature could be conducted for up to 200 feet from a stock the size of that at Berg deposit.  In any case, even i f thermal conduction i s as  effective as stated by Winkler, the extensive zone of biotite.hornfels surrounding Berg deposit could not have formed solely by thermal metamorphism due to conduction alone.  It must have been expanded by more efficient heat  transfer involving outward flowing hydrothermal fluids in the manner discussed by Rose (1970).  The entire zone containing biotite is referred to either as  a biotite hornfels or a b i o t i t i c alteration zone because products of contact metamorphism (purely conductive heating) cannot be distinguished in the f i e l d from those of hydrothermal alteration.  In this case presence of a heated  f l u i d that abetted heat transfer i s regarded to be the onset of hydrothermal alteration regardless of whether mass transfer occurred. Imposition of heat on the different rocks at Berg deposit (quartz monzonite, andesite, quartz diorite) results in a number of zoned alteration  92 assemblages that reflect differences in bulk rock composition as illustrated (Figure 9) by ACF and A'KF diagrams (Winkler, 1965).  The expected alteration  assemblages under the same temperature conditions w i l l be quartz-biotitechlorite-epidote (biotite hornfels) in altered andesite and quartz diorite closest to the quartz monzonite stock, and quartz-sericite-biotite-chloriteepidote-kaolinite (K-feldspar stable, plagioclase degenerative alteration) quartz monzonite.  in  There is no justification for placing biotite hornfels  within the potassic (potassium-silicate) facies as no evidence for widespread potash enrichment can be found and none is necessary to produce the observed b i o t i t i c zone (biotite hornfels).  Chloritic rocks outside the zone in which  biotite recrystallized belong to the propylitic facies.  Presence of pyrite  can be used to delineate the area subjected to hydrothermal activity and to distinguish the propylitic zone from rocks with (sub) greenschist facies regional metamorphism. The foregoing discussion is used to explain observed zoning that can be related to the simplest possible (idealized)  geologic situation -  Increase in temperature within a closed chemical system.  In addition to re-  equilibriation of minerals due simply to elevated temperature, chemical reactions take place involving fluids.  Pervasive changes in rocks can be  interpreted to result from hydrolysis reactions which are most evident in feldspars.  In the core of the stock K-feldspar is unaltered; in the margin  of the stock, throughout the quartz plagioclase porphyry, and in highly fractured zones within the stock K-feldspar is sericitized; and at the extremity of the sheet-like quartz plagioclase intrusion in the southwest K-feldspar i s sericitized and a r g i l l i c .  Plagioclase in the core of the stock  Is unaltered or contains minor montmorillonite and in the periphery of the stock i s kaolinized.  These changes can be interpreted on the basis of  C Figure 9.  tremolite  p  F  Mineral Assemblages In Thermally Metamorphosed Andesite, Quartz Diorite, and Quartz Monzonite. Average Rock Compositions From Nockolds , 1954 .  94 feldspar s t a b i l i t i e s in a regime with outward decreasing temperature and increasing ratio hydrogen ion activity with respect to potassium ion activity as illustrated in the now familiar hydrolysis equilibria studies of Hemley (1959), and Hemley, et a l . (1961, 1970). Fluids in staged fractures resulted in deposition of a series of veins and fracture-associated alteration zones that suggest the fluids changed during the alteration sequence.  The sequence of veins and fractures  reveals that they, i n i t i a l l y had l i t t l e effect on host rocks and fluids were evidently in equilibrium with minerals present.  Later veins and fractures  superimposed local conditions of disequilibrium on areas of pervasive alteration and older fracture-controlled alteration, each younger stage causing retrogressive breakdown of rock-forming and older alteration minerals. Early veins (Stage 1 and 2) are vuggy, ribboned, or mass^ive and commonly contain molybdenite.  Vuggy and massive coarsely granular quartz  veins that contain anhydrite commonly have orthoclase associated with them whereas ribboned and finely granular quartz veins rarely have orthoclase envelopes.  Most Stage 1 and 2 veins are bereft of alteration envelopes or  bleached margins and crosscut host rocks without apparent alteration effects. Therefore early veins and fractures formed under conditions in which biotite and feldspars were stable - probably at elevated temperatures during hornfelsing.  Where alteration envelopes are present about Stage 1 veins, the  envelopes are s e r i c i t i c or have s i l i c i f i e d metasomatic selvages containing orthoclase. Most younger veins (Stage 3 and 4) alter enclosing rocks and therefore have alteration envelopes or bleached margins.  Such alteration  can be interpreted in terms of localized hydrolysis reactions and feldspar-  95 mafic mineral instability in a manner similar to pervasive alteration zoning. At Berg deposit minerals adjacent to f l u i d - f i l l e d fractures or veins were unstable and recrystallized to form s i l i c i f i e d s e r i c i t i c alteration envelopes (Plate 10), or degenerated to form bleached a r g l l l i c  (quartz-clay-chlorite-  carbonate-gypsum) vein margins or formed combined s e r i c i t i c envelopes with a r g l l l i c margins.  The sequence orthoclase-sericite-clay minerals has not  been recognized in any altered vein margin.  This suggests that quartz-  orthoclase metasomatism of Stage 1 veins and Stage 1 and 2 veins that lack alteration envelopes did not progress into nor were overlapped in the same vein by retrogressive sericite/clay alteration such as that in Stage 3 and 4 veins.  Evidently early (Stage 1 and 2) and late (Stage 3 and 4)  vein-forming processes were distinct and mutually exclusive.  Additional  support for presence of unique solutions during various vein stages and changes during the vein sequence i s provided by vein mineralogy as was described in preceding paragraphs. The nature of fluids involved in alteration processes can be deduced from examination and heating of fluid inclusions.  In this study  20 samples of various vein types were examined i n detail and 20 of the better f l u i d inclusions from four samples of molybdenite-bearing Stage 1 veins were heated on a Unitron-500 microscope heating stage. Fluid inclusions are abundant in a l l quartz veins and can also be seen in anhydrite and pale-coloured zones in sphalerite.  Fluid inclusions  commonly are less than 2 microns and rarely up to 20^A in size.  In quartz  they are particularly abundant and occur as two or three-phase negative crystal cavities, spheres, ovoids, or irregularly shaped bodies of primary and secondary origin as defined by Roedder (1967).  In anhydrite fluid  96 i n c l u s i o n s a r e t h i n r o d - l i k e bodies i n c l u s i o n s along  cleavage  that probably  i n t e r s e c t i o n s and c o n t a i n o n l y l i q u i d  a r e two phase w i t h minute vapour b u b b l e s . sphalerite" crystals f l u i d  formed as secondary  In outer  growth zones o f  i n c l u s i o n s were seen as n e g a t i v e  Two-phase i n c l u s i o n s a r e p r e s e n t  or r a r e l y  crystal  cavities.  i n s p h a l e r i t e b u t i n some samples the vapour  b u b b l e c o n t a i n s a s m a l l amount o f l i q u i d CC^.  D e t a i l e d e x a m i n a t i o n o f q u a r t z r e v e a l s t h a t two and three-phase fluid in  i n c l u s i o n s are present  i n quartz  from Stage 1 v e i n s .  t h r e e - p h a s e i n c l u s i o n s i s h a l i t e which forms s m a l l c u b i c  g e n e r a l l y s m a l l e r than 2 p e r cent by volume. c o n t a i n minute t a b u l a r c r y s t a l s  The s o l i d  phase  crystals  I n a d d i t i o n a few samples  (gypsum ?) and equant opaque g r a i n s  (sulphides  o r h e m a t i t e ? ) . Stage 2 v e i n s commonly c o n t a i n two-phase i n c l u s i o n s b u t t h r e e - p h a s e i n c l u s i o n s might be p r e s e n t . t a i n o n l y two-phase i n c l u s i o n s a l t h o u g h  Stage 3 and 4 v e i n s appear t o contwo s p e c i e s o f l i q u i d a r e p r e s e n t  ( b r i n e and CO^) i n s p h a l e r i t e from Stage 4 v e i n s .  From these d a t a  D) i t can be c o n c l u d e d  f l u i d s were s a t u r a t e d o r  that i n i t i a l l y vein-forming  c l o s e t o s a t u r a t i o n by NaCl and t h a t s a l i n i t y had d e c r e a s e d were  (Appendix  when younger v e i n s  deposited.  Volume o f vapour i n Stage 1 and 2 v e i n s v a r i e s from 1 t o 70 p e r cent.  Vapour volumes v a r y w i d e l y even i n the same v e i n o r v e i n specimen  although  most f l u i d  variability ing  i n c l u s i o n s c o n t a i n 10 t o 30 p e r cent vapour.  and h i g h vapour content  are considered  i f h o m o g e n i z a t i o n temperatures a r e . e q u a l  t h e r e f o r e s u s t a i n e d o r repeated  for  (Roedder, 1967 and 1971) and  Evidence f o r b o i l i n g a l s o  t h a t h y d r o t h e r m a l f l u i d s were m a i n t a i n e d  sustained  periods.  for b o i l -  b o i l i n g e v i d e n t l y took p l a c e d u r i n g a t  l e a s t e a r l y v e i n development a t Berg d e p o s i t . implies  t o be e v i d e n c e  Such  «t h y d r o s t a t i c  pressure  97 The veins include:  20  fluid  i n c l u s i o n s examined from f o u r specimens o f Stage 1  fourteen i n c l u s i o n s i n quartz  from t h r e e  quartz-anhydrite-  molybdenite-pyrite-chalcopyrite-bearing veins i n well-mineralized b i o t i t e h o r n f e l s , and  six fluid  i n c l u s i o n s from t e r m i n a t e d  vuggy, c o a r s e l y c r y s t a l l i n e q u a r t z - m o l y b d e n i t e porphyry with fluid  strong p h y l l i c  quartz c r y s t a l s i n a  v e i n from q u a r t z  monzonite  (quartz-sericite-pyrite) alteration.  i n c l u s i o n s ranged from 5 to 15yn  c o n t a i n i n g about 10 p e r cent vapour.  , most b e i n g Only one  10 t o 12y^  Size of  i n size  o f the 20 f l u i d i n c l u s i o n s  contained a r e a d i l y v i s i b l e h a l i t e c r y s t a l .  A d d i t i o n a l i n c l u s i o n s are  b e l i e v e d t o : c o n t a i n minute s a l t c r y s t a l s but  they were so s m a l l t h a t  p r e s e n c e c o u l d not be confirmed  with  be i n t i m a t e d from a b e r r a t i o n s and walls of f l u i d  inclusions.  the a v a i l a b l e a p p a r a t u s and  anomalous s p o t s o f l i g h t  Upon h e a t i n g 18 o f the 20 f l u i d  not homogenized a t temperatures up  to 406  transmittance  o f 406  degrees c e n t i g r a d e and  degrees c e n t i g r a d e and  centigrade or higher. i n c l u s i o n with  One  12/A  probably  two-phase n e g a t i v e  at  this was  c l o s e r to 500  crystal cavity  10 p e r cent vapour from an a n h y d r i t e - b e a r i n g  homogenized a t 392+15 degrees c e n t i g r a d e . i n c l u s i o n s are present  on  i n c l u s i o n s were  T h e r e f o r e , Stage 1 v e i n s appear t o have been d e p o s i t e d at  w e l l i n excess  their  could only  temperature a r e d u c t i o n i n vapour volume of o n l y about 10 p e r cent achieved.  and  temperatures degrees  fluid  Stage 1 v e i n  T h i s i n d i c a t e s t h a t secondary  i n Stage 1 v e i n s or t h a t a c o n s i d e r a b l e decrease  in  temperature m i g h t have taken p l a c e d u r i n g development o f Stage 1 v e i n s . A n o t h e r two-phase f l u i d  i n c l u s i o n t h a t i s a s s o c i a t e d w i t h a number o f h i g h  temperature i n c l u s i o n s i n a Stage 1  quartz-anhydrite-molybdenite-pyrite-  c h a l c o p y r i t e v e i n appears to be primary c e n t i g r a d e and  i s probably  but homogenized at 284+2 degrees  secondary o r a r e s u l t o f n e c k i n g  down.  98 Stage 5 g y p s u m - f i l l e d f r a c t u r e s do not have any  apparent  e f f e c t s on h o s t r o c k s o r m i n e r a l s a l o n g f r a c t u r e s e l v a g e s . to  have been d e p o s i t e d as open-space f i l l i n g  e v e n from deep d r i l l h o l e s t h a t a n h y d r i t e was hydrated  t o gypsum.  temperatures  and  Gypsum appears  t h e r e i s no  first  alteration  suggestion  precipitated  and  then  F r a c t u r e f i l l i n g by gypsum t h e r e f o r e took p l a c e a t  below 57 degrees c e n t i g r a d e because a t h i g h e r  temperature  a n h y d r i t e i s p r e c i p i t a t e d by i t s e l f o r a l o n g w i t h gypsum from aqueous solution  ( H o l l a n d , 1967).  The w i d e s p r e a d presence in  o f gypsum i n l a t e - s t a g e c l e a v a g e f r a c t u r e s  the m i n e r a l i z e d zone and a l l but  the youngest i n t r u s i v e phase o f the  composite s t o c k might be because s o l u b i l i t y o f gypsum (and c a r b o n a t e ) aqueous s o l u t i o n d e c r e a s e s w i t h i n c r e a s i n g temperature and pressure  ( H o l l a n d , 1967).  Thus gypsum was  in  decreasing  p r o b a b l y d e p o s i t e d by  heating  of  c i r c u l a t i n g and  upwelling sulphate-bearing f l u i d s during l a t e cooling  of  the s t o c k .  a s s o c i a t i o n o f these l a t e - f o r m i n g g y p s u m - f i l l e d f r a c t u r e s  The  w i t h the zone o f m i n e r a l i z a t i o n and at  i n t r u s i o n i s p o s s i b l y the b e s t  Berg d e p o s i t t h a t c o n v e c t i v e f l o w i n v o l v i n g m e t e o r i c  hydrothermal  f l u i d s has  M u f f l e r , and T r u e s d e l l  evidence  sulphate-bearing  taken p l a c e as d e s c r i b e d i n the model o f White, (1970).  99 CHAPTER IV MINERALIZATION INTRODUCTION  Widespread copper-molybdenum m i n e r a l i z a t i o n i s a s s o c i a t e d w i t h r o c k s i n t r u d e d by q u a r t z monzonite.  Drill  indicated  r e s e r v e s o f 394 m i l l i o n tons g r a d i n g 0.32 p e r cent copper per cent molybdenite  u s i n g a 0.25 p e r cent copper  geological and 0.054  equivalent cut-off  grade have been e s t i m a t e d by Canex P l a c e r L i m i t e d (1974, P. G. Beaudoin, p e r s o n a l communication).  A c o n s i d e r a b l y s m a l l e r mining  reserve i s  i n d i c a t e d because o f h i g h s t r i p p i n g r a t i o s over much o f the d e p o s i t .  P y r i t e and c h a l c o p y r i t e a r e t h e most abundant s u l p h i d e m i n e r a l s and  o c c u r p r i m a r i l y i n f r a c t u r e s , i n q u a r t z v e i n s , and as d i s s e m i n a t i o n s .  Molybdenite  i s contained mainly i n quartz v e i n s .  s u l p h i d e s a r e found 'Chalcocite' important  i n an enrichment  Secondary  copper  b l a n k e t o v e r most o f the d e p o s i t .  ( p r o b a b l y m a i n l y d i g e n i t e ) and c o v e l l i t e a r e the most  secondary  copper m i n e r a l s .  They o c c u r as t h i n c o a t i n g s on  p y r i t e and c h a l c o p y r i t e and a r e d e p o s i t e d i n a l a r g e , w e l l - d e f i n e d zone of  supergene enrichment.  l e a c h e d and secondary copper  Near s u r f a c e s u l p h i d e m i n e r a l s are e x t e n s i v e l y  copper m i n e r a l s a r e p r e s e n t  o x i d e s o r carbonates  Primary  and n a t i v e  o f copper  copper.  o r e m i n e r a l s a r e most abundant i n an asymmetrical  zone o f b i o t i t i c h o r n f e l s s u r r o u n d i n g grades  i n s m a l l amounts as  the q u a r t z monzonite s t o c k .  and molybdenum a r e found  in biotitic  annular Best  quartz d i o r i t e i n  the n o r t h e a s t s e c t o r o f the d e p o s i t , weakest m i n e r a l i z a t i o n i s a l o n g the western in  margin o f the i n t r u s i o n .  i n t e n s i t y away from  Copper-molybdenum m i n e r a l i z a t i o n d e c r e a s e s  the main q u a r t z monzonite c o n t a c t .  Outward  from  100 the c o n t a c t , p y r i t e i n c r e a s e s t o form a p y r i t i c h a l o about the zone o f copper-molybdenum m i n e r a l i z a t i o n , then d e c r e a s e s a b r u p t l y . q u a r t z monzonite s t o c k copper c o n t a c t and  r a r e l y exceed  S p h a l e r i t e w i t h p y r i t e and  0.15  Within  and molybdenum grades d e c r e a s e p e r cent copper  some t e n n a n t i t e and  and  0.05  the  away from  p e r cent  the  molybdenite.  g a l e n a a r e found  i n veins  w i t h i n and p e r i p h e r a l t o the p y r i t i c h a l o as w e l l as i n s m a l l l a t e - f o r m i n g q u a r t z and  q u a r t z c a r b o n a t e v e i n l e t s i n the main copper-molybdenum zone.  D i s t r i b u t i o n o f p r i m a r y m i n e r a l s i s not r e a d i l y seen due  to weathering  and  s u l p h i d e l e a c h i n g by a c i d i c s o l u t i o n s .  r o c k s a r e b l e a c h e d , crumbly masses commonly s t a i n e d and l i m o n i t e i n an e x t e n s i v e c a p p i n g . o r l e a c h e d t o a maximum depth  i n outcrop At s u r f a c e ,  cemented  by  Sulphide minerals are s t r o n g l y corroded  o f about 125  a r e d e p o s i t e d below the o x i d i z e d and  feet.  Secondary copper  l e a c h e d r o c k s i n a zone o f supergene  copper m i n e r a l i z a t i o n w i t h a maximum t h i c k n e s s of about 300  feet.  combined e f f e c t s o f o x i d a t i o n , l e a c h i n g , and supergene enrichment a pronounced v e r t i c a l z o n i n g t o the d e p o s i t t h a t o v e r l a p s , and degree, mask p r i m a r y  zoning p a t t e r n s .  minerals  The impart  to a l a r g e  V e r t i c a l zoning i s i l l u s t r a t e d i n  F i g u r e 15 w h i c h shows copper d e p l e t i o n and molybdenum c o n c e n t r a t i o n i n the s t r o n g l y o x i d i z e d zone n e a r s u r f a c e , copper enrichment approximately  a t the p r e s e n t water t a b l e , and  depth below t h e  beginning  primary m i n e r a l i z a t i o n a t  'gypsum l i n e , ' the e l e v a t i o n below which f r a c t u r e s  t i g h t l y cemented by gypsum and  t h e r e has been minimal  are  groundwater  circulation.  PRIMARY MINERALIZATION AND  Primary  LATERAL ZONING  (hypogene) ore m i n e r a l s are p r e s e n t m a i n l y  c h a l c o p y r i t e , and m o l y b d e n i t e .  as  pyrite,  In a d d i t i o n to the t h r e e main ore m i n e r a l s ,  101 m a g n e t i t e , s p h a l e r i t e , t e n n a n t i t e , and g a l e n a  are present  as a r e t r a c e  amounts o f a r s e n o p y r i t e , p y r r h o t i t e , s c h e e l i t e , i l m e n i t e , h e m a t i t e , and rutile. to  B o r n i t e has been r e p o r t e d  10 m i c r o n - s i z e d  i n c l u s i o n s i n p y r i t e b u t does n o t c o n t r i b u t e  cantly to ore value.  Gold and s i l v e r a s s a y s ,  composite samples o f d r i l l is anticipated.  (Owens, 1968) i n minute amounts as 2 signifi-  as d e t e r m i n e d f r o m a few  c o r e , a r e low and o n l y minor c r e d i t  for silver  Zoning p a t t e r n s , as d e f i n e d by v a r i a b l e amounts o f t h e  main o r e m i n e r a l s , a r e i l l u s t r a t e d  i n F i g u r e s 10, 11, 12, 13, and 14.  These p a t t e r n s a r e based on a l l i n f o r m a t i o n a v a i l a b l e t o 1971 and some "selected  data  from more r e c e n t d r i l l i n g .  No v e r t i c a l z o n i n g  can be  demonstrated i n p r i m a r y m i n e r a l i z a t i o n w i t h i n 1,000 f e e t o f s u r f a c e b u t deeper d r i l l i n g  s u g g e s t s t h a t m o l y b d e n i t e grades i n c r e a s e a t depths  greater  than 1,500 f e e t whereas copper grades d e c r e a s e below 2,000 f e e t from s u r f a c e (P. G. B e a u d o i n , 1975, p e r s o n a l  P y r i t e Is present averaging euhedral  communication).  as f r a c t u r e - c o n t r o l l e d and d i s s e m i n a t e d  about 1 m i l l i m e t r e i n s i z e as w e l l as more c o a r s e l y  grains  crystalline  g r a i n s and a g g r e g a t e s i n a number o f s u c c e s s i v e g e n e r a t i o n s o f  p y r i t e and q u a r t z - p y r i t e v e i n s .  Chalcopyrite i s intimately associated  p y r i t e b u t i s f i n e r g r a i n e d and commonly p r e s e n t millimetre grains.  as d i s c r e t e 0.1 t o 0.3  A s i g n i f i c a n t p r o p o r t i o n i s found as 10 t o 50-mlcron  inclusions i n pryite.  Some b l e b s o f c h a l c o p y r i t e 10 m i c r o n s and s m a l l e r i n  s i z e a r e s c a t t e r e d throughout and t o t a l l y e n c a p s u l a t e d commonly m a g n e t i t e .  with  Such c h a l c o p y r i t e may be d i f f i c u l t  i n p y r i t e and l e s s t o l i b e r a t e by con-  v e n t i o n a l m i l l i n g o f o r e . M o l y b d e n i t e i s most commonly found as f i n e grained  f l a k e s w i t h i n s e v e r a l generations  a l s o occurs  as v e r y  of quartz-bearing  f i n e grains or 'paint' i n ribboned  veinlets.  It  q u a r t z v e i n s , as  c r y s t a l s a l o n g q u a r t z v e i n s e l v a g e s , and l e s s commonly i n f r a c t u r e s w i t h  102 p y r i t e and/or c h a l c o p y r i t e . e n g u l f e d and  mechanically  Some c o a r s e c r y s t a l s o f m o l y b d e n i t e  t r a n s p o r t e d i n gypsum.  D i s t r i b u t i o n of p y r i t e represented c a l c u l a t e d over  long d r i l l  as mean volume per  i n t e r c e p t s i s shown i n F i g u r e 10.  i n q u a r t z monzonite a v e r a g e s 2 per cent o r l e s s by volume and p r o g r e s s i v e l y outward everywhere except d e p o s i t where the  i n the n o r t h e a s t  Pyrite increases  sector of  the main q u a r t z monzonite c o n t a c t .  The  p y r i t e h a l o e n v e l o p e s the  b e s t copper-molybdenum m i n e r a l i z a t i o n w i t h b e s t grades  to  a p y r i t e content  o f about 2 to 3 p e r  corresponding  in b i o t i t i c hornfels  in biotitized decreases  adjacent  q u a r t z d i o r i t e i n the  north-  p r o g r e s s i v e l y away from the-main  i n t r u s i v e c o n t a c t i n an i n v e r s e manner to p y r i t e . p y r i t e to p y r i t e i s i l l u s t r a t e d  zone  cent.  C h a l c o p y r i t e i s most c o n c e n t r a t e d  C h a l c o p y r i t e content  little  f e e t o r more from  of  the q u a r t z monzonite s t o c k and  the  P y r i t e i n c r e a s e s to a maximum o f  about 6 p e r cent o r more i n the p y r i t e h a l o about 500  e a s t zone.  cent  z o n i n g symmetry i s i n t e r r u p t e d by a zone w i t h  p y r i t e i n b i o t i t i c quartz d i o r i t e .  to  are  Relationship of chalco-  as a p y r i t e - c h a l c o p y r i t e r a t i o i n F i g u r e  11.  C h a l c o p y r i t e exceeds p y r i t e i n abundance o n l y i n q u a r t z d i o r i t e o f the w e l l mineralized northeast  s e c t o r and  d r i l l h o l e a t the s o u t h e r n  i n a low p y r i t e zone e n c o u n t e r e d i n a . s i n g l e  c o n t a c t o f the q u a r t z monzonite i n t r u s i o n .  ward from the i n t r u s i v e c o n t a c t p y r i t e - c h a l c o p y r i t e r a t i o o f 4:1 the s t a r t o f the p y r i t e h a l o and Within is any  a r a p i d i n c r e a s e i n amount o f  the p y r i t e h a l o p y r i t e - c h a l c o p y r i t e r a t i o exceeds 10:1  g r e a t e r than 50:1.  Out-  signifies pyrite.  and  locally  P y r i t e - c h a l c o p y r i t e r a t i o remains f a i r l y c o n s t a n t  g i v e n zone even where t o t a l volume o f s u l p h i d e s v a r i e s .  in  103  105  FIGURE 12  PRIMARY  MINERALS  4  breccia qtz bearing monzodi. qtz monzonite qtz diorite hornfels .volcanics  106  T  107 Chalcopyrite and molybdenite concentrations expressed as per cent copper and molybdenite are shown in Figures 12 and 13.  The annular pattern  of mineralization and intimate relationship of copper-molybdenite mineralization with intensely fractured and hydrothermally altered rocks along the quartz monzonite contact are evident.  The pattern and zoning trends are  remarkably consistent throughout the mineralized area.  Areas underlain by  20 feet and more of 0.4 per cent copper with the larger zones of - 0 . 2 per cent copper are shown.  The -0.4 per cent copper grade is an arbitrary value  used to indicate zones of better grade mineralization.  Twenty feet i s taken  to be the minimum thickness of rock from which a bench of ore could be developed.  *  In plan view small areas underlain by rocks with better copper  grades cluster around the quartz monzonite stock or are localized in b i o t i t i c quartz diorite In the northeast sector.  Grades of copper and molybdenite when averaged over long d r i l l ~ intercepts and plotted in .relation to distance from the main quartz monzonite :  contact (Figure 14) document behaviour of chalcopyrite and molybdenite more explicitly.  Both copper and molybdenum decrease in intensity in a regular  manner away from the quartz monzonite contact but two separate regimes are evident: hornfels and quartz diorite.  Quartz diorite is superior to hornfels  as a host for copper and molybdenum sulphides, even though in many localities i t - i s some distance from the quartz monzonite stock.  The same grade i s -  developed in quartz diorite twice as far from the quartz monzonite contact as hornfels.  Conversely, at the same distance from the quartz monzonite  contact grades of copper and molybdenite in quartz diorite are about double those in hornfels.  Best grades of copper discovered to date are in quartz  diorite, but some of the higher values shown in Figure 14 (marked by ?) may  108  not be r e p r e s e n t a t i v e as to 25 per  10  they a r e based on poor core r e c o v e r i e s ( f r o m  cent).  14  Trends o f copper-molybdenum m i n e r a l i z a t i o n shown i n F i g u r e are s i m i l a r but  some d i f f e r e n c e s a r e i n d i c a t e d .  Best m i n e r a l i z a t i o n has  taken p l a c e i n h o r n f e l s n e a r the q u a r t z monzonite s t o c k . concentrated  Copper i s most  at a s l i g h t d i s t a n c e from the main c o n t a c t whereas molybdenum  m i n e r a l i z a t i o n s t r a d d l e d the i n t r u s i v e c o n t a c t and m o l y b d e n i t e i s maximized along i t .  Copper v a l u e s e x h i b i t two  q u a r t z monzonite h a v i n g  distinct  o n l y about o n e - h a l f  A s i m i l a r o b s e r v a t i o n was  l e v e l s of concentration  the copper c o n t e n t  noted i n b r e c c i a bodies  of-hornfelsv  o u t s i d e the main  intrusive  mass where ore grades d e r i v e d m a i n l y from w e l l - m i n e r a l i z e d h o r n f e l s ments were d i l u t e d  with  i n p r o p o r t i o n to the amount o f q u a r t z monzonite  fragmatrix  present.  These p a t t e r n s i z a t i o n was  (Figure 14)  i n d i c a t e that molybdenite  superimposed on the main i n t r u s i v e c o n t a c t  d i m i n i s h i n a r e g u l a r manner away from the c o n t a c t . m o l y b d e n i t e i s f r a c t u r e i n t e n s i t y and  quartz v e i n i n g .  zone and  The  rock  grades  main c o n t r o l f o r  Copper g r a d e s ,  the o t h e r hand, d i m i n i s h a b r u p t l y w i t h i n i n t r u s i v e r o c k s and to f r a c t u r e i n t e n s i t y appear to be  mineral-  on  in addition  i n f l u e n c e d more than m o l y b d e n i t e  by  composition.  SECONDARY MINERALIZATION AND  VERTICAL ZONING  INTRODUCTION  V e r t i c a l zoning  d e f i n e d by p r o g r e s s i v e changes i n m i n e r a l o g y  o r e t e n o r w i t h depth i s _ a _ r e s u l t  o f o x i d a t i o n , s u l p h i d e l e a c h i n g , and  and super-  QTZ  MONZ  1  HORNFELS  r  .  »  QTZ 1  »  T  D/OR/TE  ~i  r  r  .5-  .5-  Cu  .4-  .3— qtz monz hornfels > qtz diorite  .2—  ••  F i g u r e 14  t PRIMARY IN  r  1 .14  < > z-  i  T  1  o  —  1 IOOO'  r  MoS  IO  O z  —  MAIN  2  GRADE  DISTANCE  INTRUSIVE  CONTACT  2  AO %  .06  FROM  r  TO  < 5  -  •08  i  2000'  <M Ok  .12  r  ~i  Cu and MoS  RELATION  •  MoS  2  —  I  -  INCREASING  04  —  •02  —  MAIN  i  r——o 200  i 200'  1  1 oOO'  1  1 IOOO  ; i  QMP  1  I4O0'  DISTANCE  FROM  CONTACT  "* ' 2O0O  r  FEET  o  110 gene p r o c e s s e s .  A t s u r f a c e , I n s u b c r o p , and a t r e l a t i v e l y s h a l l o w depths  abundance o f s u l p h i d e m i n e r a l s and o r e v a l u e a r e reduced due and l e a c h i n g by a c i d i c s o l u t i o n s . whereas molybdenum i s immobile Hansuld, 1966).  I n t h i s environment  ( G a r r e l s , 1954;  to o x i d a t i o n  copper i s m o b i l e  S a t o , 1960;  Titley,  1963;  Thus, when s u l p h i d e m i n e r a l s break down copper i s d e p l e t e d  b u t molybdenum remains and may  be c o n c e n t r a t e d .  F i g u r e 15 i l l u s t r a t e s v e r t i c a l  z o n a t i o n as d e f i n e d by o r e t e n o r .  Copper i s c o n s i s t e n t l y d e p l e t e d from r o c k s near s u r f a c e e x c e p t near b a s i c dykes where copper o x i d e s and h y d r a t e d copper c a r b o n a t e s a r e d e p o s i t e d ( f o r example, d i a m o n d - d r i l l h o l e 2 3 ) . behaviour.  Molybdenum i s more v a r i a b l e I n i t s  M o l y b d e n i t e g r a d e s o f o u t c r o p s commonly compare w i t h t h o s e o f  primary m i n e r a l i z a t i o n  ( f o r example, d i a m o n d - d r i l l h o l e 7 4 ) .  a r e a s o f s t r o n g l y o x i d i z e d r o c k s , molybdenum i s i n the form o f and complexes where i t was  In c e r t a i n molybdates  w i t h f e r r i c h y d r o x i d e as w e l l as m o l y b d e n i t e i n q u a r t z v e i n s p r o t e c t e d from l e a c h s o l u t i o n s .  o x i d i z e d r o c k s w i l l be d i s c u s s e d  Supergene  Mineralogy of s t r o n g l y  i n more d e t a i l i n a s u c c e e d i n g s e c t i o n .  copper m i n e r a l i z a t i o n r e s u l t i n g i n enrichment o f p r i m a r y  grade o r e t a k e s p l a c e below the zone o f o x i d a t i o n i n the zone  containing  groundwater.  leach  Copper  c o n t a i n e d i n downward p e r c o l a t i n g a c i d i c  s o l u t i o n s r e p l a c e s c h a l c o p y r i t e and p y r i t e as s o l u t i o n s become n e u t r a l i z e d at depth f o r m i n g s e c o n d a r y copper s u l p h i d e s and o x i d e s .  Enrichment  p r i m a r y copper grade a v e r a g e s about 25 per cent ( t h a t i s , 1:25 ment f a c t o r ) and i s maximized  n e a r the top o f the groundwater  of  to 1 e n r i c h table  immedi-  a t e l y below zones o f o x i d i z i n g p r i m a r y m i n e r a l i z a t i o n as i n d i a m o n d - d r i l l h o l e 23.  I n c r e a s e i n i n t e n s i t y o f enrichment w i t h depth shown by diamond-  d r i l l h o l e 19 i s o n l y apparent and r e f l e c t s i n c r e a s i n g p r i m a r y grade as the  VERTICAL ZONING OF Cu andMoS GRADES IN DIAMOND DRILL CORES 2  112 i n t r u s i v e contact  i s approached.  p r i m a r y grade d i m i n i s h e s  Away from the c o n t a c t  (at g r e a t e r  depth)  as does t h e amount o f supergene copper e n r i c h m e n t .  EXTENT OF LEACHING AND  SUPERGENE MINERALIZATION  Maximum t h i c k n e s s o f the s t r o n g l y o x i d i z e d zone w i t h l e a c h i n g i s about 125 f e e t ; the supergene  zone i s up t o 300  sulphide  feet thick.  Base o f the s t r o n g l y o x i d i z e d zone i s c l e a r l y shown by marked  increases  i n copper grade and amount o f s u l p h i d e m i n e r a l s , p r e s e n c e o f s e c o n d a r y copper s u l p h i d e s , and minor amounts o f n a t i v e copper, as w e l l as a d e c r e a s e i n the amount o f l i m o n i t e and a n o t i c e a b l e change i n l i m o n i t e c o l o u r from yellow-brown o r orange t o d a r k brown.  Base o f supergene copper m i n e r a l i z a t i o n  i s c l e a r l y marked i n d r i l l h o l e s by the 'gypsum l i n e ' - the l i m i t water c i r c u l a t i o n below which f r a c t u r e s a r e t i g h t l y cemented  Depth o f s t r o n g o x i d a t i o n w i t h  and 18.  by gypsum.  s u l p h i d e l e a c h i n g and  of the supergene copper zone i s i l l u s t r a t e d  o f ground-  thickness  as i s o p a c h maps i n F i g u r e s  The e l e v a t i o n below which gypsum i s p r e s e n t  ( t h e gypsum  17  surface)  t h a t d e f i n e s the s t a r t o f p r i m a r y m i n e r a l i z a t i o n a t depth i s shown I n F i g u r e 16.  The i s o p a c h s  and gypsum s u r f a c e a r e trend s u r f a c e maps computed  u s i n g double F o u r i e r s e r i e s a n a l y s e s method d e s c r i b e d by James (1966).  o f i r r e g u l a r l y spaced d a t a a f t e r a  Data i n p u t from 54 l o c a t i o n s were u t i l i z e d  u s i n g a wavelength o f 2,200 o r 2,300 f e e t and 25 terms i n s e r i e s r e p r e s e n t i n g a second harmonic s u r f a c e . topographic  The waveform generated approximates t h e p r e s e n t  p r o f i l e a t Berg d e p o s i t  (shown i n F i g u r e 16) t o which  - o f o x i d a t i o n and supergene m i n e r a l i z a t i o n a r e r e l a t e d . 2,200 f e e t i s c o m p a t i b l e w i t h  the depth  A wavelength o f about  the d i m e n s i o n s o f the i n t r u s i v e system,  of h y d r o t h e r m a l a l t e r a t i o n and m i n e r a l i z a t i o n , and t o p o g r a p h i c  relief.  zone The  _  ~  113 'goodness o f f i t ' o f t r e n d s u r f a c e s g e n e r a t e d a r e about 63, c e n t , thus a c h i e v i n g an a c c e p t a b l e smoothing o f t h e o b s e r v e d  70, and 88 p e r  and g e o l o g i c a l l y u s e f u l degree o f  data.  Contours r e l a t i v e t o s e a l e v e l marking the s t a r t o f gypsum i n f r a c t u r e s d e f i n e a 'gypsum p l a n e . ' unequiyocably  T h i s s u r f a c e i s shown i n F i g u r e 16, and  d e f i n e s the base o f groundwater c i r c u l a t i o n below which .  o x i d a t i o n and supergene e f f e c t s a r e m i n i m a l and c o n f i n e d t o a few narrow zones o f i n t e n s e f r a c t u r i n g o r f a u l t i n g .  Depth o f gypsum s o l u t i o n i s a  f u n c t i o n o f groundwater f l o w p a t t e r n s and degree o f a c i d i t y .  Flow p a t t e r n s  i n bedrock a r e i n f l u e n c e d a t B e r g d e p o s i t mainly by topography, major and s u b s i d i a r y s u r f i c i a l drainage intensity of fracturing. drilling  p a t t e r n s w i t h i n the c i r q u e - l i k e b a s i n , and  The zone o f gypsum l e a c h i n g d e f i n e d by diamond  forms a n o r t h e a s t e r l y e l o n g a t e d  to the northeast  roughly p a r a l l e l  depression  t o present  that r i s e s i n e l e v a t i o n  topography.  The zone o f deepest  gypsum l e a c h i n g i s c o a x i a l w i t h m i n e r a l i z e d i n t r u s i o n s p a r a l l e l t o 'Red' and 'Pump' Creeks b u t p e r p e n d i c u l a r major d r a i n a g e  t o the north f o r k o f Bergeland  Creek, t h e  system.  A t r e n d s u r f a c e i s o p a c h map-of o x i d i z e d r o c k s from which copper is  leached  -  i s shown i n F i g u r e 17 and one o f supergene copper m i n e r a l i z a t i o n  i s shown i n F i g u r e 18. i n the s o u t h e a s t  S i m i l a r t r e n d s a r e apparent w i t h maximum  and e a s t s e c t o r s o f t h e m i n e r a l i z e d  thicknesses  zone a l o n g - t h e  monzonite c o n t a c t and i n h o r n f e l s a d j o i n i n g quartz d i o r i t e .  quartz  Strongest  o x i d a t i o n and most advanced l e a c h i n g a r e seen i n r o c k s i n the v i c i n i t y o f 'Red'  Creek and i t s branches where the d e e p l y  conveys away s u r f a c e r u n o f f and s h a l l o w allowing intense oxidation.  i n c i s e d creek  efficiently  groundwaters from f l a n k i n g s l o p e s  Deep o x i d a t i o n takes p l a c e where a c i d i c s o l u t i o n s  from o x i d i z i n g p y r i t e - r i c h r o c k s p e n e t r a t e  the most h i g h l y f r a c t u r e d zones i n  FIGURE  TREND  SURFACE  ELEVATION START  16  MARKING  OF GVPSUM  IN  FRACTURES  Elevations  in feet  ASL  87.6 % sum of squorei contribuI ion  I  I  breccia  |  qtt bearing monzodio. qtz monzonite  |  qtz diorite  I  volcanics , hornfels  21000 N  FIGURE  18  TREND SURFACE ISOPACH M A P , SUPERGENE Cu MINERALIZATION  Thrcknau in f»*t  O 19000 N 63-4 Y, turn of iquorai contribution  I -17000 N  I  breccia  |  qtz bearing monzodio. qtz monzonite  cyst)  |  qtz diorite  |  volcanic* , hornfela  117 h o r n f e l s between q u a r t z monzonite and q u a r t z d i o r i t e  intrusions.  Diurnal,  p e r i o d i c , and s e a s o n a l f l u c t u a t i o n s i n groundwater f l o w and c h e m i s t r y f a c i l i t a t e deep, complete o x i d a t i o n and s u l p h i d e l e a c h i n g .  The s o u t h e a s t e r l y  e x t e n s i o n o f t h e d e e p l y o x i d i z e d zone may be l o c a l i z e d by i n c r e a s e d permeability i n northwest-southeast-trending  zones o f b r e c c i a t i o n and  faulting.  Supergene copper m i n e r a l s a r e found  i n a zone t h a t i s more wide-  spread than t h e zone o f i n t e n s e s u l p h i d e l e a c h i n g . the supergene zone i s d e v e l o p e d  along the e a s t e r n p a r t o f the m i n e r a l i z e d  zone between t h e major i n t r u s i o n s .  A westward-projecting  by t h i c k supergene zones i n two d r i l l  F i g u r e 18 i s exaggerated  copper-bearing  indicated  (Map 2, u n i t 3 ) . T h i c k n e s s o f  m i n e r a l i z a t i o n i n q u a r t z d i o r i t e shown i n  as v a l u e s p l o t t e d are v e r t i c a l d r i l l hole  c e p t s on s l o p e s t h a t commonly approach 45 d e g r e e s . F i g u r e 18 i s almost  lobe  h o l e s i n the i n t r u s i v e s t o c k i s  c o i n c i d e n t w i t h q u a r t z monzonite p o r p h y r y the zone w i t h supergene copper  Maximum t h i c k n e s s o f  inter-  The p a t t e r n shown i n  e n t i r e l y a r e s u l t o f downslope m i g r a t i o n o f a c i d i c  l e a c h s o l u t i o n s generated  by o x i d a t i o n o f weakly c u p r i f e r o u s  p y r i t e - r i c h r o c k s i n t h e p y r i t e h a l o and i n t e r a c t i o n w i t h a r e l a t i v e l y s t a b l e water t a b l e i n the zone o f i n t e n s e f r a c t u r i n g . of  secondary  copper  zone  s u l p h i d e s i n q u a r t z monzonite i s c o i n c i d e n t w i t h  h a v i n g most advanced s e r i c i t e - q u a r t z - p y r i t e a l t e r a t i o n monzonite porphyry  The t h i c k e s t  and s e r i c i t i z e d  (mainly  zones  quartz  q u a r t z p l a g i o c l a s e p o r p h y r y , Map 2,  u n i t s 3 and 4 ) .  MINERALOGY AND PROCESSES OF FORMATION ZONE OF OXIDATION AND SULPHIDE LEACHING Breakdown o f s u l p h i d e m i n e r a l s near s u r f a c e has r e s u l t e d i n a l e a c h e d capping c o n s i s t i n g o f m a i n l y  quartz, s e r i c i t e , clay minerals,  118 l i m o n i t e , and o p a l i n e s i l i c a .  Limonite  i s composed p r i m a r i l y o f amorphous  f e r r i c hydroxide  [ h y d r o g o e t h i t e , FeCOH)^], g o e t h i t e (FeOOH), and  hematite  with l o c a l l y developed  (Fe^)  Other m i n e r a l s observed  jarosite  [K(Fe,  minor  A1) (S0^) (0H) ]. 3  2  &  i n s m a l l amounts i n the zone o f o x i d a t i o n a r e :  c u p r i t e , t e n o r i t e , n a t i v e copper, m a l a c h i t e , a z u r i t e , b r o c h a n t i t e , c h a l c h a n t h i t e , f e r r i m o l y b d i t e , p o s s i b l y akaganeite  (molybdenum-bearing  b e t a l i m o n i t e ) , and b l a c k amorphous iron-manganese o x i d e s formed l e a d - z i n c - b e a r i n g carbonate v e i n s .  from  Owens (1968) has r e p o r t e d d e l a f o s s i t e .  F r e s h l y d e p o s i t e d l i m o n i t e i s amorphous ' a c t i v e ' h y d r o g o e t h i t e which changes w i t h time t o a more s t a b l e amorphous v a r i e t y -  'inactive'  h y d r o g o e t h i t e o r c r y s t a l l i n e g o e t h i t e (McAndrew, Wang, and Brown, 1975). Most l i m o n i t e observed variety.  i n outcrop  G r a n u l a r , c o a g u l a t e d and  i s a pervasive or s u r f i c i a l pulverulent caked,  s e e n i n p i t s and f r a c t u r e s a t d e p t h . s i n t e r e d c r u s t s are p r e s e n t but absent.  b o t r y o i d a l or f l a t  Some r e l i e f - t y p e l i m o n i t e and  c e l l u l a r boxwork and sponges a r e r a r e o r  A c c o r d i n g t o t h e , t e r m i n o l o g y o f Locke (1926) and B l a n c h a r d  most l i m o n i t e s t u d i e d would be c l a s s i f i e d as f r i n g i n g exotic  c r u s t s are  (1968),  (contiguous) or  ( t r a n s p o r t e d ) types i n which a s p e c i f i c s o u r c e o f i r o n cannot  identified.  Indigenous  l i m o n i t e s would be expected  h i g h c h a l c o p y r i t e - p y r i t e r a t i o s but none was brown, r e s i n o u s are present.  F l u f f y , f i b r o u s s t a r - s h a p e d and  i n quartz d i o r i t e  observed.  ' p i t c h l i m o n i t e s ' w i t h h i g h copper  be with  Instead, reddish  (and molybdenum) c o n t e n t  f l a k e - l i k e l i m o n i t e i s found  i n and p r o x i m a l t o b a s i c / ( r e d u c i n g ) dykes a l o n g w i t h amorphous, b l a c k , copper-bearing oxides  ( t e n o r i t e ?, m e l a c o n i t e  ?).  J a r o s i t e i s p r e s e n t i n v a r i o u s amounts throughout deposit.  I t i s most prominent a t s u r f a c e and  much o f the  s h a l l o w depths a l o n g  the  119 e a s t e r n margin o f the q u a r t z monzonite s t o c k and a l o n g the m i n e r a l i z e d q u a r t d i o r i t e contact.  L o c a l l y j a r o s i t e I s the dominant l i m o n i t e c o n s t i t u e n t .  Zones w i t h j a r o s i t e  i n excess  o f g o e t h i t e a r e c o i n c i d e n t w i t h t h e most  i n t e n s e l y o x i d i z e d and l e a c h e d r o c k s .  J a r o s i t e n o r m a l l y accompanied by  f e r r i m o l y b d i t e imparts a y e l l o w c o l o u r t o the capping. l e s s i n t e n s e l y l e a c h e d r o c k s away from the j a r o s i t i c  A t depth and i n  zone c o l o u r o f  l i m o n i t e changes p r o g r e s s i v e l y from yellow-brown t o orange, brown, and dark brown c h a r a c t e r i s t i c o f g o e t h i t e .  The most abundant a c c u m u l a t i o n  of limonite i s f e r r i c r e t e , a  r e l a t i v e l y homogeneous d e p o s i t o f f e r r i c h y d r o x i d e .  Ferricrete i s trans-  p o r t e d amorphous h y d r o g o e t h i t e and g o e t h i t e p r e c i p i t a t e d on s u r f a c e o r i n overburden  as s o f t , p o r o u s ,  friable limonite.  F e r r i c r e t e d e p o s i t s commonly  c o n t a i n p l a n t and r o c k fragments and o t h e r d e t r i t u s .  Some f e r r i c r e t e  forms  a m a t r i x i n s o i l and t a l u s d e p o s i t s r e s u l t i n g I n cemented s o i l and b r e c c i a l i k e deposits.  A t Berg  f e r r i c r e t e i s being deposited a c t i v e l y i n creek  g u l l i e s and a l o n g the base o f s l o p e s where groundwater d i s c h a r g e s .  Such  d e p o s i t s mantle much o f t h e lower s l o p e s a l o n g the n o r t h f o r k o f B e r g e l a n d Creek and l o c a l l y a r e f i v e f e e t , and g r e a t e r , i n t h i c k n e s s o v e r hundreds o f square  feet.  P a r t i a l chemical analyses o f l i m o n i t e s are l i s t e d  i n Table  A n a l y s e s show c o n c e n t r a t i o n o f - c o p p e r but v a l u e s o f molybdenum; and  o t h e r m e t a l s a r e low.  i r o n ores and g o e t h i t i c and  elsewhere.  4.  manganese,  I n b u l k , B e r g f e r r i c r e t e c l o s e l y resembles  ' s o f t o r e ' e x p l o i t e d a t Steep Rock ( J o l l i f f e ,  bog 1955)  I t i s h i g h e r i n i r o n c o n t e n t and has l e s s i m p u r i t i e s than  l i m o n i t i c i r o n ores d e p o s i t e d as e r o s i o n and t e r r e s t r i a l w e a t h e r i n g such as those b e i n g e v a l u a t e d i n I r a q (Skocek,  e t a l . , 1971).  products  However,  120 TABLE 4 PARTIAL ANALYSES OF IRON ORES AND ( i n per cent) 1 Berg Ferricrete (massive)  BERG FERRICRETE  2 Berg Ferricrete Crusts (newly d e p o s i t e d )  3 Steep Rock Fe Ore  4 Wadi Husainiya Iraq  ;  *  Fe t o t a l S P Mn A1 0 2  Cr T10  3  2  CaO MgO  sio  55.24 1 .24 0.043 0.08 0.25  39.8 4.6 0.08 0.001 0.3  0.003 0.010  0.001 0.01  0.05 0.05  0.12 0.01 1.0  2  Moisture L o s s on i g n i t i o n Note:  57.0 0.04 0.020 0.20 0.81  38.3 0.065 0.014 10.8  --  .009 1.59  —  0.32 0.27 3.1  •  7.0 7.6  20.9  6.3 0.41 15.3 5.5  --  -- = not r e p o r t e d  1 - A s s a y , Steep Rock I r o n Mines, c o u r t e s y o f A. W. J o l l i f f e , 1968. 2 - P. R a l p h , a n a l y s t , B r i t i s h Columbia Department o f Mines and P e t r o l e u m R e s o u r c e s , 1974. 3 - A n t i c i p a t e d average grade, H. M. R o b e r t s and M. W. B a r t l e y , Ec. G e o l . , V o l . 38, 1943, pp. 1-24. 4 - Average o f f i v e samples, V. Skocek, e t a l . , Ec. G e o l . , V o l . 66, 1971, pp. 986-994.  GEOCHEMICAL. DETERMINATIONS, BERG FERRICRETES ( i n ppm) 1 Cu Mo Zn Pb Ag Ni Co Mn .  2875 115 39 32 3.4 12 18 38  2  3  461 333 100 100 5 100 50 10  270 300 —  ----  1 - H. Goddard, a n a l y s t , Kennco E x p l o r a t i o n s , (Western) L i m i t e d , 1968. 2 — P. Ralph and R. H i b b e r s o n , a n a l y s t s , B r i t i s h Columbia Department o f Mines and Petroleum R e s o u r c e s , 1974. _3--_A..-Mariano, a n a l y s t , Ledgemont L a b o r a t o r y , 1968.  121 d e s p i t e s i m i l a r i t i e s i n c o m p o s i t i o n , a p p e a r a n c e , and  possibly  origin  w i t h some commercial i r o n d e p o s i t s , B e r g f e r r i c r e t e i s too l i m i t e d quantity  and  too h i g h  i n sulphur  c o n t e n t t o be  of present  in  economic  interest.  Molybdenum i s an i m p o r t a n t c o n s t i t u e n t deposit.  o f l i m o n i t e at Berg  I t s p r e s e n c e i n the c a p p i n g i n n o n s u l p h i d e m i n e r a l s  i s an  i m p o r t a n t i n d i c a t o r o f p r i m a r y s u l p h i d e m i n e r a l i z a t i o n at d e p t h . molybdenum i s c o n c e n t r a t e d  i n the  zone o f o x i d a t i o n and  those o f hypogene zones i n u n d e r l y i n g These o b s e r v a t i o n s  rocks  a r e i n marked c o n t r a s t  and  Orlov  (1974) who  the  zone o f o x i d a t i o n i n molybdenum and  t o d a t a p r e s e n t e d by  Ney,  D.  copper-molybdenum  noted e a r l y d u r i n g  L. Norton, and  -'15 p e r  'Berg-X.'  Studies  1 to 2 p e r  consistent with observations - percent  cent  made by  Orlov  copper deposit.  molybdenum.  1965)  who  generally crusts  Mariano (1967) found 5  'Berg-X' and  Carpenter  r e p o r t , Kennecott Copper C o r p o r a t i o n ,  P o k a l o v and  l e a c h i n g and  lacquer-like limonite  zones  These r e s u l t s  are  r e p o r t s up  report  i n l i m o n i t e from a number o f S o v i e t  s t a t e s t h a t up  an average o f 1.26 deposits.  s u c h l i m o n i t e s accumulate i n o x i d i z e d  to  C. W i l s o n (unpublished to 7 per  i n l i m o n i t e s i n a number o f porphyry d e p o s i t s ,  (1974) who  to  widespread  (1968) who  molybdenum i n l i m o n i t e at Questa; a l s o J .  molybdenum i s p r e s e n t  from  deposits.  e x p l o r a t i o n at Berg  by N o r t o n and  cent molybdenum i n s e l e c t c r u s t s o f  with limonite containing  ••- --  Pokalov  G.O.M. Stewart found enrichment to be  r e l a t e d to v i t r e o u s , b r i t t l e , violet-brown, r e f e r r e d t o as  15.  s t a t e t h a t molybdenum i s c o n s i s t e n t l y d e p l e t e d  d e p l e t i o n n e a r s u r f a c e was Si  grades exceed  as shown i n F i g u r e  Molybdenum enrichment accompanying s u l p h i d e  C.  Locally  7.5 :  cent  and  per cent molybdenum  If sufficient  amounts o f  r o c k s , molybdenum enrichment would  122 take p l a c e .  I t a p p a r e n t l y has t a k e n p l a c e a t Questa where, a c c o r d i n g  to Carpenter  (1968), b o t h  c h e m i c a l and m e c h a n i c a l  concentration result  i n s o i l s w i t h 1 p e r cent r e s i d u a l molybdenum and gossans  (presumably  from s u l p h i d e - b e a r i n g v e i n s ) h a v i n g g r e a t e r than 27 p e r cent molybdenum content.  I d e n t i t y o f molybdenum-bearing s u b s t a n c e s only p a r t i a l l y resolved.  a t Berg d e p o s i t i s  F e r r l m o l y b d l t e i s common and t o g e t h e r w i t h  molybdenum-bearing f e r r i c h y d r o x i d e  might c o n s t i t u t e a c o n s i d e r a b l e  p r o p o r t i o n o f t o t a l molybdenum i n the c a p p i n g .  Some molybdenum may a l s o  be p r e s e n t i n j a r o s i t e which a c c o r d i n g t o P o k a l o v  and O r l o v (1974) may  c o n t a i n up t o 1.75 p e r cent molybdenum, p r o b a b l y as minute i n c l u s i o n s o f MoO^. related  I n a d d i t i o n , a s e r i e s o f molybdenum-bearing f e r r i c  hydroxides  t o f e r r l m o l y b d l t e have been d e s c r i b e d by C a r p e n t e r  suggested  (1968) and  t o be p r e s e n t a t Berg by Barakso and Bradshaw (1971).  These  a r e v a r i o u s pH dependent, amorphous t o v e r y f i n e - g r a i n e d , orange-brown f e r r i c molybdate h y d r a t e phases h a v i n g d i f f e r e n t b r i t t l e , wine-coloured  Fe:Mo r a t i o s .  The  'Berg-X' i s p r o b a b l y an a l t o g e t h e r d i f f e r e n t and  r a r e r l i m o n i t e compound.  P r e l i m i n a r y i n v e s t i g a t i o n s by Norton and  M a r i a n o (1967) i n c l u d i n g e l e c t r o n m i c r o s c o p i c , d i f f r a c t i o n , and m i c r o probe a n a l y s e s suggest c r y s t a l l i t e s o f Mo0  t h a t 'Berg-X' may be, i n p a r t , 0.2 m i c r o n - s i z e d  (tentatively called  2  m i n e r a l , p r o b a b l y Fe MoO^,. 2  No o t h e r n a t u r a l o c c u r r e n c e s o f Mo0 a r e 2  known b u t J a g e r , e t a l . (1959), N o r t o n Pokalov  by  and Mariano (1967), as w e l l a s  and O r l o v (1974) s y n t h e s i z e d Mo0  laboratories.  S i b o l a i t e ) as w e l l as a s p i n e l  E l e c t r o n microprobe  2  a t low temperatures i n  a n a l y s i s o f 'Berg-X' l i m o n i t e c r u s t s  t h i s w r i t e r r e v e a l e d p e r i o d i c , i n t e r m i t t e n t molybdenum  took p l a c e d u r i n g d e p o s i t i o n o f banded l i m o n i t e c r u s t s .  enrichment Zoning o f  123 molybdenum i s e v i d e n t  w i t h i n some i n d i v i d u a l l i m o n i t e l a y e r s i n d i c a t i n g  p r o g r e s s i v e l y c h a n g i n g r a t e s o f molybdenum i n c o r p o r a t i o n d u r i n g of limonite.  Similar observations  deposition  o f p e r i o d i c molybdenum enrichment i n  l i m o n i t e a t Questa have been made by C a r p e n t e r  Behaviour o f s u l p h i d e minerals  (1968).  under o x i d i z i n g c o n d i t i o n s and  r e s u l t i n g p r o d u c t s a r e summarized and i l l u s t r a t e d  i n Figure  19.  In  p o r p h y r y d e p o s i t s c o n d i t i o n s i n the zone o f o x i d a t i o n commonly v a r y pH  3 t o 6 and o x i d a t i o n p o t e n t i a l (Eh) o f 0.4 t o 0.8 v o l t  More a c i d i c c o n d i t i o n s w i t h  (Sato,  from  1960).  pH 1.6, and l e s s , a r e p o s s i b l e ; o x i d i z i n g  v e i n s a t Questa have measured pH o f 1 t o 1.5 ( C a r p e n t e r ,  1968).  At Berg  d e p o s i t Barakso and Bradshaw (1971) r e p o r t pH o f 3.1 t o 5.9 and Eh from 0.4 t o 0.9 v o l t i n waters from s t r e a m s , s p r i n g s , and d r i l l - h o l e  discharge.  Waters as a c i d as pH 2.8 were measured d u r i n g p r o l o n g e d summer d r y s p e l l s . Eh o f 0.9 v o l t i m p l i e s the p r e s e n c e o f b a c t e r i a (probably f e r r o b a c i l l i ) according  t h i o b a c i l l i and  t o Baas B e c k i n g , e t a l . (1960).  Under h i g h l y o x i d i z i n g c o n d i t i o n s such as a t Berg and o t h e r porphyry deposits a l l s u l p h i d e m i n e r a l s except r a r e sulphide by n o n r e a c t i v e  d i s s o l v e (that i s , are leached)  g r a i n s where they a r e p r o t e c t e d  quartz  gangue.  Under m i l d e r  c o n d i t i o n s such as w e a t h e r i n g o f zones w i t h  from l e a c h s o l u t i o n s  o x i d i z i n g and l e s s a c i d i c little  pyrite  content,  m o l y b d e n i t e remains s t a b l e and o n l y copper and/or i r o n s u l p h i d e are  leached.  Oxidation  of s u l p h i d e s , abetted  b a c t e r i a , generates f e r r o u s o r f e r r i c sulphate  minerals  t o some degree by o x i d i z i n g and s u l p h u r i c a c i d s o l u t i o n s .  Copper as cuprous i o n i s m o b i l e under a c i d i c c o n d i t i o n s and i s removed i n aqueous s o l u t i o n s .  I r o n p r e c i p i t a t e s through h y d r o l y s i s as f e r r i c  h y d r o x i d e and forms l i m o n i t e , a m i x t u r e o f m a i n l y h y d r o g o e t h i t e goethite.  and  Hematite i s a minor l i m o n i t e c o n s t i t u e n t a t Berg d e p o s i t .  Under  PLATES 21, 22, and 23:  E l e c t r o n microprobe beam scans o f B e r g l i m o n i t e ('Berg X') showing Mo c o n c e n t r a t i o n i n r i m .  125 highly acidic oxidizing conditions  (pH l e s s than 3)  and dependent  a c t i v i t i e s o f p o t a s s i u m , s u l p h u r , and i r o n , j a r o s i t e i s s t a b l e  1971).  A t Berg d e p o s i t j a r o s i t e i s w i d e s p r e a d  limonite constituent.  on  (Brown,  and l o c a l l y i s t h e dominant  I t s p r e s e n c e c o i n c i d e s w i t h zones o f i n t e n s e l y  l e a c h e d r o c k s , p r o b a b l y where p o t a s s i u m i s a v a i l a b l e by d e g r a d a t i o n o f potassic alteration minerals.  The w i d e s p r e a d  d i s t r i b u t i o n and p e r s i s t e n c e  o f j a r o s i t e i n the c a p p i n g under m o d e r a t e l y a c i d i c c o n d i t i o n s i s e x p l a i n e d by Brown  (1971)  as b e i n g due t o s l u g g i s h r e a c t i o n r a t e s .  r e l e a s e d from s o l u t i o n o f m o l y b d e n i t e i s immobile  Molybdenum  under a c i d i c  conditions  and i s taken up by f e r r i m o l y b d i t e , l i m o n i t e , and i n s o l u b l e i r o n and molybdenum o x i d e s as d i s c u s s e d e a r l i e r ,  ZONE OF SUPERGENE ENRICHMENT  Supergene enrichment by s e c o n d a r y copper m i n e r a l s t a k e s p l a c e a t o r below the water  t a b l e where downward m i g r a t i n g a c i d i c oxygenated  s o l u t i o n s c o n t a i n i n g cuprous i o n a r e r e d u c e d and n e u t r a l i z e d .  leach  Secondary  copper m i n e r a l s s e l e c t i v e l y r e p l a c e p r e - e x i s t i n g s u l p h i d e m i n e r a l s o r under c e r t a i n c o n d i t i o n s i n the t r a n s i t i o n  zone between the o x i d i z i n g and p r i m a r y  s u l p h i d e zone p r e c i p i t a t e as n a t i v e c o p p e r , copper o x i d e s , o r c a r b o n a t e s . N a t i v e copper and o x i d e m i n e r a l s may a l s o form i f groundwater f l u c t u a t i o n s expose  table  secondary copper s u l p h i d e m i n e r a l s and o x i d a t i o n  t a k e s p l a c e when the water  table i s depressed.  R e a c t i o n s and p r o d u c t s o f t h e supergene i n a s i m p l i f i e d manner i n an Eh-pH diagram showing o f common m i n e r a l s , as shown i n F i g u r e 20 as i n d i c a t e d by p a t h s A — >  B, B — >  .  p r o c e s s can be i l l u s t r a t e d mineral s t a b i l i t y  fields  Three p r o c e s s e s can be e n v i s i o n e d  A, and A —>• C.  More a c i d i c  conditions  A  Figure 19 MINERAL STABILITY FIELDS AT 25°C , 1 AIM. Cu-Fe-S-O-H MODIFIED FROM GARRELS(1960 ) 8. Mo-Fe-S-O-H AFTER BARAKSO AND BRADSHAW(T971) C. Fe-S-O-H IN PRESENCE OF K+, AFTER BROWN (1971) FIELD OF WEATHERING AFTER SATO (1960)  I  1—;  2  I  '  1 4  1 6  .  i  1—:  pH  8  I  L  1 10  1 12  Figure 20 STABILITY FIELDS IN Cu - H 0 -C0 - 0 -S SYSTEM (INCLUDING CHALCOPYRITE) AT 25°C AND 7 ATM 2  2  2  MODIFIED FROM GARRELS (1960) ARROWS INDICATE PATHS OF SOLUTIONS IN THE ZONE OF OXIDATION AND SUPERGENE ENRICHMENT  128 t h a n t h o s e s u g g e s t e d by Sato (1960) and i n porphyry d e p o s i t s .  shown In F i g u r e 20 p r o b a b l y  Thus p o i n t s A and  the diagram. A t o B i s the r e s u l t  B may  be  shifted  to the l e f t  and  r e p l a c e d by  first  takes p l a c e .  are i n c r e a s i n g . the  rimmed  ' c h a l c o c i t e . ' . Near the w a t e r t a b l e n e u t r a l i z e d s o l u t i o n s i n  sulphide minerals  and  Pre-existing  c h a l c o p y r i t e (or b o r n i t e ) , l a t e r p y r i t e , are  the p r e s e n c e o f oxygen may reduction  in  of downward p e r c o l a t i n g l e a c h s o l u t i o n s  e n t e r i n g a r e l a t i v e l y s t a b l e zone o f groundwater s a t u r a t i o n . sulphide minerals,  occur  form t e n o r i t e o r c u p r i t e and  Path B t o A i s the r e s u l t  n a t i v e copper i f  o f i n s i t u r e a c t i o n s where  r e a c t w i t h pore waters whose a c i d i t y and  oxidation p o t e n t i a l  T h i s i s the case where the w a t e r t a b l e i s b e i n g  zone o f o x i d a t i o n i s e n c r o a c h i n g  depressed  on e x i s t i n g s u l p h i d e m i n e r a l s ,  or  groundwater f l o w p a t t e r n s change r e s u l t i n g i n a d d i t i o n s o f l e a c h s o l u t i o n s . As  a c i d i t y increases  in  the p r e s e n c e of copper i o n s .  s t a r t i n g with  c h a l c o c i t e , and  leached  from c o p p e r - i r o n  Secondary copper s u l p h i d e s  copper c o n t e n t ,  exceed pH  buffer solutions. 8.3  and,  and  n a t i v e copper.  (Sato, 1960).  will  other  at depth where h y d r o l y s i s  C u p r i t e , b r o c h a n t i t e , t e n o r i t e , and  i s high.  that  takes p l a c e ,  zone o f w a t e r s a t u r a t e d  ' f l u f f y ' l i m o n i t e as w e l l as m a l a c h i t e  concentration  rocks  Most commonly n e u t r a l i z i n g  s i g n i f i c a n t n e u t r a l i z i n g p o t e n t i a l and  mineralization.  with  Path A to C  a l o n g b o r d e r s o f b a s i c dykes or  e q u i l i b r i a r e a c t i o n s take p l a c e i n the  form w i t h  deposited  Solutions i n presence of c a l c i t e  i f hydrolysis of s i l i c a t e minerals  r e a c t i o n s take p l a c e i n l i m e s t o n e , rocks with  are  sulphides  ideally: a n i l i t e , digenite, djurleite,  p o s s i b l y copper o x i d e s  pH w i l l range from 6 to 10  C0„  are  f o l l o w e d where l e a c h s o l u t i o n s e n c o u n t e r r e a c t i v e h o s t  n e u t r a l i z e and not  sulphur  c o v e l l i t e , f o l l o w e d under i d e a l c o n d i t i o n s by m i n e r a l s  successively higher  is  i r o n and  and  primary  n a t i v e copper a z u r i t e where  may  129 At Berg d e p o s i t p r o c e s s e s  d e s c r i b e d by a l l t h r e e s o l u t i o n paths  shown i n F i g u r e 20yare t a k i n g p l a c e s i m u l t a n e o u s l y the d e p o s i t .  Path B t o A t a k e s p l a c e i n the p y r i t i c h a l o where p r o p y l i t i c  p y r i t e - r i c h rocks are o x i d i z i n g . 'B*  i n different parts of  I n i t i a l conditions are described  as o x i d a t i o n b e g i n s i n m i n e r a l i z e d  r o c k s exposed by e r o s i o n .  by a r e a As  o x i d a t i o n proceeds s o l u t i o n s and p r o d u c t s f o l l o w the p a t h toward 'A.' Path B t o A also describes  on-going processes  w i t h i n the supergene zone as  e r o s i o n proceeds r e s u l t i n g i n a downward m i g r a t i n g encroachment o f o x i d a t i o n mineralization.  groundwater t a b l e and  (weathering) c o n d i t i o n s upon the zone o f p r i m a r y  Path A t o B i s f o l l o w e d by c o n c e n t r a t e d  s o l u t i o n s generated by o x i d a t i o n they i n t e r a c t w i t h  (point  acidic  leach  'A') which m i g r a t e downslope  until  the r e l a t i v e l y s t a b l e groundwater t a b l e i n t h e l o w - l y i n g ,  h i g h l y f r a c t u r e d a r e a around the q u a r t z monzonite s t o c k . leach s o l u t i o n s with  groundwaters r e s u l t s i n m i g r a t i o n  t o B ( l e s s a c i d i c , more r e d u c i n g  conditions).  Interaction of  o f s o l u t i o n s from A  Path A t o C i s f o l l o w e d  l o c a l l y where l e a c h s o l u t i o n s e n c o u n t e r c a l c i t e - b e a r i n g dykes and a r e rapidly neutralized.  T h i s takes p l a c e b o t h above and below the water  t a b l e and a c c o u n t s f o r copper enrichment by o x i d e i n t h e zone o f s u l p h i d e some b r o c h a n t i t e )  l e a c h i n g and p r e v a l e n c e  i n andesite  and carbonate  minerals  o f c u p r i t e (together  with  dykes below the water t a b l e .  Secondary copper s u l p h i d e m i n e r a l s  l o o s e l y d e s c r i b e d a t Berg  d e p o s i t as ' c h a l c o c i t e ' a r e i d e n t i f i e d by X-ray d i f f r a c t i o n by Owens (1968) and  t h i s w r i t e r as c o v e l l i t e and d i g e n i t e .  o f c h a l c o c i t e and d e l a f o s s i t e .  Owens (1968) a l s o r e p o r t s  traces  D i g e n i t e and c o v e l l i t e a r e both found as  p a r t i a l replacement rims on c h a l c o p y r i t e and p y r i t e .  Complete replacement  o f s m a l l c h a l c o p y r i t e g r a i n s up t o 100 m i c r o n s i n s i z e was seen by Owens (1968) b u t g e n e r a l l y replacement r i m s a r e l e s s than 10 microns t h i c k and  130  cove/lite blaubleibender covellite anilite digenite djurleite chalcocite cha/copyrife bornite  cv bbcv .an di dj cc cp bn  ....Cui.jS -  CuS CU1.4S  Cu ].75 S Cui./ S-Cu S Cu].o S C1/2S CuFeS2 Cu FeS4 65  h79  0  5  MINERAL COMPOSITIONS SHOWING POSSIBLE PHASE RELATIONSHIPS MODIFIED FROM RUNNELS , 7969 Figure 21  131 commonly a r e n o t more than t a r n i s h .  I n specimens examined by t h e w r i t e r  c o v e l l i t e i s more abundant than d i g e n i t e whereas Owens (1968) r e p o r t s d i g e n i t e i n excess o f c o v e l l i t e .  M i n e r a l a s s o c i a t i o n s found  ( F i g u r e 21)  a r e c h a l c o p y r i t e - p y r i t e - c o v e l l i t e and c h a l c o p y r i t e - c o v e l l l t e - d i g e n i t e pyrite  (a non-equilibrium  are compatible  assemblage).  The o b s e r v e d supergene assemblages  w i t h phase r e l a t i o n s s u g g e s t e d by s t u d i e s i n system  Cu-Fe-S and Cu-S (Roseboom, 1966; Runnels, 1969; Morimoto and Koto, 1971;  and B a r t o n ,  1973) and a r e c o n s i s t e n t w i t h  enrichment i s i n i t s i n i t i a l s t a g e s copper m i n e r a l d e p o s i t i o n w i t h 25 p e r c e n t by  the b e l i e f t h a t supergene  at Berg d e p o s i t .  R e s u l t o f supergene  an i n d i c a t e d enrichment f a c t o r o f 1.25 o r  i s shown i n F i g u r e 15.  In p l a n  ( F i g u r e 22) zones u n d e r l a i n  20 f e e t o r more o f 0.4 p e r cent copper i n the supergene zone o v e r l a p  e x t e n s i v e l y zones o f p r i m a r y o r ' p r o t o r e ' w i t h thereby  0.2 p e r cent  copper and  c o n s i d e r a b l y expand o r e r e s e r v e s .  O r i g i n o f the supergene copper enrichment zone i s by contemporary on-going processes.  Supergene m i n e r a l i z a t i o n i s b e l i e v e d t o be a s i n g l e  s t a g e p o s t - g l a c i a l phenomenon t h a t began a f t e r F r a s e r or, at e a r l i e s t , during deglaciation. simple is  o r more p r o b a b l e  (Wisconsin) g l a c i a t i o n  It i s difficult  topography, c o u l d have s u r v i v e d  g l a c i a t i o n i f i t was p r e - P l e i s t o c e n e o r an i n t e r g l a c i a l  Berg d e p o s i t . and  other  a l t e r n a t i v e s t o how the enrichment b l a n k e t , which  so i n t i m a t e l y r e l a t e d t o p r e s e n t  a common m i n e r a l  to e n v i s i o n  feature.  repeated  Hematite,  i n m u l t i p l e s t a g e supergene zones, i s g e n e r a l l y absent a t  A s h o r t d u r a t i o n o f enrichment i s suggested by m i n e r a l o g y  i n c i p i e n t replacement t e x t u r e s o f s e c o n d a r y s u l p h i d e m i n e r a l s .  Further-  more, the p r e s e n c e o f Cretaceous r o c k s on r i d g e s i n B e r g map-area (Map 1) makes i t d o u b t f u l t h a t Berg d e p o s i t was exhumed by e r o s i o n p r i o r t o  132  FIGURE 22.  PRIMARY AND MINERALS — BY ^ . 4 % Cu  SUPERGENE COPPER ZONES UNDERLAIN  PRIMARY 1  J  SUPERGENE  f—20,000 N  breccia  Scale I  |  Q bearing monzodi]  I  1 qtz monzonite  |  |  qtz diorite  |  |  hornfels .volcanics  tz  133 Pleistocene  glaciation.  ice-marginal  positions  Economic M i n e r a l s not  earlier  Thus, as deduced from a map showing  speculative  (V. K. P r e s t , 1970, pp. 706, 707, i n : Geology and  o f Canada), supergene p r o c e s s e s were p r o b a b l y  initiated  t h a n 10,000 t o 12,000 B.P.  Ten  thousand y e a r s f o l l o w i n g g l a c i a t i o n i s ample time f o r  observed supergene e f f e c t s t o be d e v e l o p e d and t h e 1 2 5 - f o o t - t h i c k zone t o form i n t h e h i g h l y f r a c t u r e d , s t r o n g l y d i s s e c t e d deposit.  Lovering  (1948) c a l c u l a t e d t h a t a t San Manuel t o t a l  o f 3.5 t o 5 p e r cent  p y r i t e could  i n 40,000 t o 47,000 y e a r s . States  take p l a c e  zones i n p o r p h y r y d e p o s i t s )  oxidation  t o depths o f 500 t o 600 f e e t  than t h a t o f weathered  have complete o x i d a t i o n o f 5 p e r cent  to a depth o f 100 f e e t i n a few t e n s o f y e a r s r e p o r t , Kennecott Copper C o r p o r a t i o n ) . i n which e x t e n s i v e  a t Berg  A l s o , l e a c h dumps i n t h e s o u t h w e s t e r n  (whose p o r o s i t y i s n o t much g r e a t e r  deposits  terrane  leached  leached  Titley  United crackled pyrite  (D. N o r t o n , 1966, u n p u b l i s h e d (1975) has d e s c r i b e d  porphyry  and supergene enrichment zones a r e  f o r m i n g where m i n e r a l i z a t i o n i s as young as 1.11 m i l l i o n  years.  134 CHAPTER V  MINOR ELEMENTS IN PYRITE INTRODUCTION Minor element content of pyrite was investigated in order to: (i)  Define concentration levels of minor elements in pyrite from a porphyry copper-molybdenum deposit,  (ii) (Iii)  Test i f zoning of minor elements in pyrite i s evident. Relate zoning patterns and concentration ranges of minor elements in pyrite to mineralogical zoning (particularly the zone of primary copper sulphides).  (iv)  Test i f host rock compositions and different paragenetic types of pyrite influence the character or quantity of minor elements in pyrite.  Pyrite was selected because i t i s the most abundant sulphide mineral in porphyry copper deposits, is ubiquitous throughout mineralized areas, and i s treated relatively easily to obtain a clean concentrate. Representative samples from almost every d r i l l hole and a few surface exposures were taken to give maximum possible geologic coverage of the area. Pyrite was classified according to location, host rock, texture, mineral associations, and paragenesis.  Clean concentrates or hand-picked  pyrite grains were analysed by emission spectrograph^.  The method,  procedure, and calibrated curves used to Interpret analytical results were available to the author at Queen's University as part of a routine  135 analytical f a c i l i t y .  The a t t r a c t i o n of t h i s a n a l y t i c a l method over others  i s that only small amounts of p y r i t e are needed f o r a n a l y s i s .  This i s a  major consideration when minerals are sparse and f i n e grained, as i n porphyry copper deposits, and only small samples, such as s p l i t diamondd r i l l core, are a v a i l a b l e .  A n a l y t i c a l r e s u l t s (Appendix G) were treated s t a t i s t i c a l l y using e x i s t i n g computer programmes and the U n i v e r s i t y o f B r i t i s h Columbia Computing Centre's I.B.M. 360, Model 67 computer.  Conventional s t a t i s t i c a l  methods were applied using u n i v a r i a t e , b i v a r i a t e , and m u l t i v a r i a t e procedures.  S t a t i s t i c a l r e s u l t s were interpreted on the basis o f surface  mapping and diamond-drill information.  One hundred p y r i t e samples were selected as a representative sample s e t , from approximately 24,000 feet of diamond-drill core from 45 h o l e s .  A l l d r i l l holes without highly oxidized rocks were sampled  and, where p o s s i b l e , two or more samples were taken at d i f f e r e n t  depths.  A l l major types o f host rock, ore mineral a s s o c i a t i o n s , a l t e r a t i o n , and paragenetic types o f p y r i t e were sampled.  The sample set of one hundred p y r i t e s consists o f seventy-eight specimens o f disseminated or f r a c t u r e - c o n t r o l l e d f i n e l y dispersed sulphides (hereafter c o l l e c t i v e l y referred to as 'disseminated* p y r i t e ) , and twentytwo v e i n specimens. Of the seventy-eight disseminated p y r i t e s , forty-seven were taken from h o r n f e l s , nine from quartz d i o r i t e , eighteen from quartz monzonite, and four from peripheral v o l c a n i c rocks.  Vein p y r i t e was mainly  from quartz veins with various sulphide and gangue associations.  In  a d d i t i o n to p y r i t e , f i v e chalcopyrite and one s p h a l e r i t e samples were analysed to determine the e f f e c t s of contamination by these minerals i n pyrite.  136 The samples do not constitute a random sample set because the diamond d r i l l i n g programme tested specific areas with economic mineral potential rather than random areas.  Bias i s , thus, introduced into the  s t a t i s t i c a l basis of the data by a preponderance of samples from the zone of copper-molybdenum mineralization.  There i s proportionally less  representation of pyrite from the barren core, p y r i t i c halo, and weakly mineralized peripheral rocks.  However, any weakness introduced into the  s t a t i s t i c a l basis of this study by non-random sampling i s possibly overshadowed by having a maximum of information from the mineralized zone. Pyrite-bearing core and hand specimens were c l a s s i f i e d , described' in d e t a i l , and selected portions of the samples were marked and chipped off or cut out with a diamond saw.  Clean pyrite concentrates were prepared  in a sequence of steps involving crushing, screening, panning, heavy l i q u i d , and electromagnetic techniques.  A l l concentrates were examined under a  binocular microscope and a few polished grain mounts were prepared.  If a  concentrate was unacceptable due to contamination, pyrite was selected for analysis by hand picking pyrite grains. analysis by one or both of two methods.  Samples were prepared for  The standard method utilized  pulverized and homogenized pyrite concentrate and a direct electrodeloading method utilized crushed, hand-picked pyrite grains. Each sample electrode was volatilized with a DC constant current arc in a 2-metre Jarrell-Ash emission spectrograph, using a two-stage procedure developed by Mr. Leo Mes (Analyst, Department of Geological Sciences, Queen's University).  Spectra were recorded on film and line  intensities of diagnostic wavelengths of specific elements, as well as a palladium reference l i n e , were read with a NSL Spec Reader micro-  137 densitometer (Appendix F) .  Transmittance measurements were converted  to intensity ratios using 0.01 per cent palladium as an internal reference standard.  Concentrations of elements in parts per million  were obtained by referring the calculated intensity ratios to working curves calibrated with prepared pyrite standards.  Preparation of  standards and working curves used in this method are discussed in detail by Gosh-Dastidar (1970), and the analytical method is summarized by Dawson (1972) and Dawson and Sinclair (1974). One hundred and thirty-five analyses were performed u t i l i z i n g a total of one hundred pyrite samples.  In the case of multiple analyses,  mean values were used as analytical results.  Duplicates were run on a  routine basis to check r e l i a b i l i t y of the spectrographs method, homogeneity of samples, and to provide replicate pairs of analyses for computation of analytical error. Sample variability  (Appendices E and G) i s readily evident; some  can be explained by analytical (including sampling) error but precision (Table 5) and accuracy-(Table 6) of - the spectroscopic-method used are sufficient for zoning to be demonstrated. Calculation of analytical (including sampling) error from paired analyses was done with a computer programme written by A.C.L. Fox based on the procedure described by Garrett (1969).  Comparison between 27 samples  prepared from pyrite concentrates and 13 from hand-picked pyrite grains indicates values of B i , Co, N i , and Cu from hand-picked grains are about only one-half as precise as those from pyrite concentrates; but are about the same for Ag and Zn.  Analytical values of Pb and Mo from hand-picked  pyrite appear to be more precise than those from concentrates, probably  138 because the possibility of contamination was minimized.  In any case,  there appears to be no extreme difference in precision between analyses of pyrites from concentrates or hand-picked grains and analytical data are treated as one data set.  A summary of the calculated analytical  precision i s given in Table 5.  Precision i s computed using log values  of the analytical results and i s given as a per cent at 95 per cent confidence l e v e l . Accuracy, or the.relation of pyrite analyses to their true values, i s d i f f i c u l t to appraise.  An independent check of spectrographs  results by atomic absorption (AA) analyses of the same pyrite concentrates i s shown in Table 6. TABLE 5.  ANALYTICAL PRECISION (FOR LOGGED DATA)  Pyrite Concentrates No. of Paired Precision* Analyses (%) Bi Co Ni Cu Pb Zn Ag Mo  19 27 27 10 27 27 7 23  • - •  29.9 5.8 5.4 9.5 23.3 17.1 57.6 98.8  .  Hand-picked Pyrite No. of Paired Precision* Analyses (%) 10 13 13 10 13 10 13 10  74.0 14.2 9.3 13.7 8.2 14.3 59.0 29.5  ALL DATA No. of Paired Analyses As Bi Co Ni Cu Pb Zn Ag Ti Mo Mn  10 29 40 40 20 40 37 40 20 33 25  *Two standard deviations.  Analytical Precision 8.9 31.4 8.7 6.5 11.6 18.5 17.1 58.4 14.2 81.0 33.7  (%)*  139  TABLE 6.  COMPARISON OF SPECTROGRAPHIC AND ATOMIC ABSORPTION ANALYSIS* OF PYRITE CONCENTRATES (ALL ANALYSES IN PPM)  Sample No.  Mo  Cu  Zn  Pb  15-187 Spec 1 Spec i i AA  6 1 11  500 490 470  16 21 50  29-226 Spec AA  6 1  330 415  37-480 Spec i Spec i i AA  0 1 1  198 102 122  Ag  Ni  Co  Mn  Bi  20.5 12 22  2.5 2.5 4.0  168 142 160  115 93 117  5 5 12  2 4 5  53 60  18.5 18  8.0 4.7  62 60  620 520  5 9  1.5 5  80 52 44  20.5 16 21  1.5 1.0 2.1  850 1000 1000  560 600 415  5 5.5 45  3 7.5 5  *Atomic absorption analyses performed by Mr. H. Goddard, Kennco Explorations, (Western) Limited, 1968.  Comparison o f r e s u l t s shows roughly the same hierarchy as a n a l y t i c a l p r e c i s i o n — correspondence between the two a n a l y t i c a l methods i s best f o r Co, N i , Cu, and Pb; i s f a i r f o r Zn, B i , and Ag; and i s poor f o r Mo and Mn. In Berg p y r i t e a number of minor elements are c o n s i s t e n t l y present and are u s e f u l i n zoning s t u d i e s .  Their usefulness i s based on several  requirements i n c l u d i n g : (I)  . . elements must be incorporated i n some manner in.the p y r i t e s t r u c t u r e and cannot be contaminants from included grains of other minerals.  (ii)  the a n a l y t i c a l method must be s e n s i t i v e with a s u f f i c i e n t l y low detection l i m i t to allow trace concentrations to be determined,  (iii)  enough samples must contain detectable amounts o f minor elements to provide a representative, s t a t i s t i c a l l y meaningful data s e t .  (iv)  a n a l y t i c a l p r e c i s i o n must be s u f f i c i e n t l y high that v a r i a b i l i t y • can be a t t r i b u t e d to actual differences i n element rather than a n a l y t i c a l e r r o r .  concentrations  140 The f o l l o w i n g elements i n Berg p y r i t e t o t a l l y or p a r t i a l l y s a t i s f y the conditions l i s t e d above: Mo, T i , and Mn.  As, B i , Cu, Co, N i , Pb, Zn, Ag,  This assemblage can be ranked I to V i n order of  suspected value and r e l i a b i l i t y of the data.  I. II.  Co and N i :  a l l conditions mentioned above are s a t i s f i e d .  Pb, Zn, Ag, B i , and Mn:  may be affected by contamination and  have l e s s a n a l y t i c a l p r e c i s i o n than Co and N i . III.  As:  high detection l i m i t (300 ppm).  Provides a small sample  group as only 30 out of 100 analyses have detectable As. IV.  Cu and Mo:  are affected severely by contamination.  Mo  has  a n a l y t i c a l problems with Fe interference and poor p r e c i s i o n . Both elements may be u s e f u l , however, because hand-picked samples from veins and possibly a few disseminated samples may be accurate. V. ~  T i : a unique constituent. Judging from i t s e r r a t i c d i s t r i b u t i o n i t i s undoubtedly present as included grains.  However, T i may  be u s e f u l , regardless of i t s source, as an i n d i c a t o r of genetic type of p y r i t e , zone of copper mineralization, and host rock. Zirconium was detected i n a few samples and might be useful element i n other p y r i t e studies. samples; Cr and V i n about 5.  another  Sn was detected i n only 10  Cd and Sb were found only where there was  sphalerite or t e t r a h e d r i t e contamination.  UNIVARIATE ANALYSIS  A set of numerical data, such as p y r i t e analyses, can be simply yet l u c i d l y represented and described by r e l a t i v e frequency  histograms.  141  Histograms, i f properly drawn, enable a visual appraisal of data and allow rapid comparison of variables.  The apparent concensus of long  standing arguments about which distribution functions best describe minor element data i s summarized by Shaw (1961) who states:  "The  concentration of a camouflaged trace element in a crystallizing rock under conditions of chemical equilibrium w i l l correspond closely to a lognormal law' (a camouflaged trace element is a minor element that i s incorporated in the crystal lattice of a mineral). Histograms illustrating distributions of minor elements in Berg pyrite are shown i n Figures 23, 24, and 25. A normal curve, using the observed mean and standard deviation is fitted to the transformed data in Figure 23.  The mathematical expression for such i d e a l , Gaussian  (normal) distributions and tables of numerical constants necessary for their calculation are taken from Dixon and Massey (1969).  A l l data are  summarized in Table 8 which gives the number of analyses, means (measure of central tendency), and standard deviations (measure of dispersion of the data).  Both arithmetic and logarithmic values are given for  comparison. It i s evident in a few histograms ( e . g . , Figure 25) that some minor element distributions might contain more than one population. Arsenic appears to be bimodal and Co could contain three populations. The two apparent populations of As might be simply due to sampling error for the sample set contains only 33 analyses.  Three populations  of Co appear to be present and appear to be due to pyrite from different host rocks.  Populations of Co from vein pyrite and two types of d i s -  seminated pyrite (one from quartz monzonite, the other from hornfels and  PERCENTAGE  v  ?  g  PERCENTAGE  * s *  3  S  8  8  0  •  czo cso  O  C8t>  H m  CM  oot ooroos  Ml  009  o z  PYR  z oTI  a a3 3 m  K> CO  oot  Zn  O  001  cn  KJJ  ill /  rcz  8  m  fH  00^  8 § g 8.  008 OOo0001-  Z  o 2  PERCENTAGE  g  y  y  PERCENTAGE  y  z N 3  * • • •  g£§  o"  a  ^  • 6"  PERCENTAGE  -4  ?_  0 OS 001 OSI 001  ocz  ooc oct oor osr-  •o  r  •  •  •  •  o c  ZD  m  PERCENTAGE  8  PERCENTAGE  8  4-  aoro nro £060 ttCl  1=»  — <* M • •  PS  8«f  Z  8-3  S-,  a-  — Crt M % m  B  a  X  144  -25  N X S I  -20  -15  X  As 33 2.826 (670ppm) 0.2645 0.066  -10  "IT  CN  m  CN  8!  CM  co  rt  n  • rt  1-25  r  Co N 100  20  X 2.307(203ppm)  S 0.703 I 0.176  H5  H • H •  10  <D1.  O  ——  1  Oi  CN  CN  CN  Hornfels Veins Qtz.Monzonite Qtz Diorite  rt  Ti N 62  r-20  X 2.053(U3ppm)  S 0730 I 0.183 • Diss. M Veins  hio  ~5 O  <b co CN cS • ~  Q  *»o <-'  - uP p > cs 1 CK  ~  n  CN  CK  o  CN  r> O rt  FIGURE 25 FREQUENCY DISTRIBUTIONS OFAs.Co.andTi LOG (PP™) 10  TABLE 7.  SUMMARY - MEANS AND STANDARD DEVIATIONS OF ALL ANALYSES  No. of Element  Samples  Arithmetic (ppm) Mean  Std. Dev.  Logarithmic L o g Mean  1 0  (ppm)  Std. Dev.  2.860  (725)  0.343  0.551  (3.6)  0.738  354  2.307  (203)  0.703  156  200  1.886  ( 77)  0.587  55  263  194  2.257  (181)  0.461  Pb  93  84  104  1.613  ( 41)  0.602  Zn  92  59  82  1.518  ( 33)  0.462  Ag  93  13.0  17.3  0.481  (3.0)  0.847  Mo  75  13.0  20.0  0.3741 (2.4)  1.0335  Ti  62  2.053  (113)  0.730  Mn  89  0.0001 (1.0)  0.960  As  34  1237  Bi  96  Co  100  406  Ni  100  Cu  12.4  256 5.5  2528 21.9  225 10.5  146 quartz d i o r i t e ) appear to be d i f f e r e n t populations.  T i distribution i s  not r e a d i l y explained; the two apparent populations are composed of p y r i t e from veins and a l l host rock types.  One a t t r i b u t e of Berg minor element data shown by frequency d i s t r i b u t i o n s i s that v e i n p y r i t e generally has lower concentrations of elements than disseminated p y r i t e .  Thus, an hypothesis can be tested  using t and F t e s t s that one cause of polymodal d i s t r i b u t i o n s i s mixing of v e i n p y r i t e and disseminated p y r i t e , both d i s t i n c t populations. Figure 26 shows N i d i s t r i b u t i o n i n which v e i n and disseminated p y r i t e i s d i f f e r e n t i a t e d and tested by t and F t e s t s .  Table 8 summarizes t and F  t e s t s of v e i n versus disseminated p y r i t e f o r a l l elements determined.  -  The r e s u l t s summarized i n Table 8 are d e f i n i t i v e .  p r o b a b i l i t i e s of Co, N i , Cu* Zn, T i , and p o s s i b l y Pb, Ag, Mo,  F and t and Mn are  s u f f i c i e n t l y low that i t can be assumed populations of v e i n p y r i t e are d i s t i n c t from those of disseminated p y r i t e .  The only exceptions are As  and B i which are the only two o f ' a l l elements determined  that are believed  to be incorporated i n pyrite.by_anion .substitution_.rather_than. cation s u b s t i t u t i o n , i n c l u s i o n i n l a t t i c e defects, or l o c a t i o n i n i n t e r s t i t i a l s i t e s (see Appendix E ) . Polymodal d i s t r i b u t i o n s r e s u l t i n g from mixing of p y r i t e from d i f f e r e n t rock types are evident f o r c e r t a i n elements; f o r example, Co i n Figure 25.  A more subtle i n d i c a t i o n of polymodal populations can be  seen i n Figure 26 where the d i s t r i b u t i o n function of Ni i n disseminated p y r i t e i s much greater In amplitude than the normal curve f i t t e d to the data.  I t can be assumed, therefore, that a number of ( p a r t i a l l y ?)  coincident populations are present.  Figure 27 shows the d i s t r i b u t i o n of  ~  Figure 2 6 Bimodal Distribution containing Vein a n d Disseminated Pyrite Populations. x Disseminated  •15  Ni log (ppm) Vein Disseminated 74 N 22 2.06 X 1.14 0.36 S 0.66 1 0  1-0  7. x Veins  0.31  0.89  Vein: Disseminated t value 6.26 t probability 0 . 0 0 0 F probability 0 . 0 0 0  1.48  2.06  2.63  TABLE 8.  CALCULATED t AND F PROBABILITY OF VEIN PYRITE VERSUS DISSEMINATED PYRITE (BASED ON LOG  VALUES OF ALL AVAILABLE DATA)  S.D.  N  Disseminated X  2.898  0.242'  24  2.808  0.272  .87  .46  22  0.532  0.746  66  0.697  0.595  .16  .36  Co  22  1.296  0.730  74  2.572  0.333  .00  .00  Ni  22  1.143  0.659  74  2.060  0.358  .00  .00  Cu  19  1.889  0.522  33  2.459  0.252  .00  .00  Pb  20  1.423  0.872  69  1.643  0.498  .00  .29  Zn  20  1.260  0.582  68  1.560  0.389  .02  .04  Ag  20  0.664  0.508  69  0.922  0.426  .29  .05  Mo  20  0.381  0.494  51  0.808  0.639  .22  .00  Ti  20  1.389  0.729  39  2.375  0.496  .04  .00  Mn  20  0.275  0.447  48  0.515  0.493  .65  .04  N  Vein X  As  6  Bi  Lement  S.D.  F Prob.  -t prol  00  149 Ni i n disseminated p y r i t e (the disseminated p y r i t e p o r t i o n of Figure 26) with separate p l o t s of p y r i t e from d i f f e r e n t sources.  An hypothesis can be tested that the polymodal d i s t r i b u t i o n of N i i n disseminated p y r i t e i s due to a number of populations representing p y r i t e from d i f f e r e n t host rocks,  t and F t e s t s comparing d i s t r i b u t i o n s  of p y r i t e from h o r n f e l s , quartz monzonite, and d i o r i t e are summarized i n Table 9 and i l l u s t r a t e d i n Figure 26.  Vein p y r i t e s are also compared  to p y r i t e from other host rocks.  -  TABLE 9. F AND t TESTS - Ni IN PYRITE (No. of Samples: Hornfels, 47; D i o r i t e , 9; Quartz Monzonite, 18; Veins, 22) Source Hornfels: Quartz Monzonite Hornfels: D i o r i t e Quartz Monzonite: D i o r i t e Hornfels: Veins Quartz Monzonite: Veins D i o r i t e : Veins  F Probability 0.03 0.01 0.27 0.01 0.00 0.00  t Probability 0.37 0.10 0.01 0.00 0.00 0.00  The F and t tests indicate with a high confidence l e v e l (99 per cent or greater) that Ni i n v e i n p y r i t e i s a d i s c r e t e population compared to Ni i n disseminated p y r i t e from any of the three host rock types.  The  p o s s i b i l i t y of disseminated p y r i t e containing two or more populations of Ni i s not nearly so c e r t a i n .  A 90-per-cent  t and 99-per-cent F p r o b a b i l i t y  allows the conclusion that hornfels and d i o r i t e may  contain d i s t i n c t  populations of N i i n p y r i t e , but p y r i t e from h o r n f e l s and quartz monzonite cannot be distinguished and may be part of the same population.  A summary  o f t and F t e s t s of a l l elements from p y r i t e i n d i f f e r e n t rock types Is given i n Table 10.  All Disseminated Pyrite N 74 X 2.06 S 036 I 0.15  A Hornfels N 47 X 2.06 S 0.41  C Quartz Monzonite N 18 X 1.98 S 0.25  D Diorite N 9 X 2.20 S 0.17  Veins N22 X 1.14 S 0.66  FIGURE 27  DISTRIBUTION OF Ni IN PYRITE. DATA GROUPED ACCORDING TO HOST ROCK. A,C,D ARE FITTED NORMAL CURVES.  151 TABLE 10. SUMMARY OF t AND F TESTS FOR ALL ELEMENTS (SIGNIFICANCE OF HOST ROCK TYPE)  Element  No. o f . Samples*  t Prob.  F Prob.  Element  HORNFELS : QUARTZ MONZONITE As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  17 46 47 47 22 45 45 45 34 33 45  : ; : !. : : : !. :: ! :  2 18 18 18 9 16 16 16 15 5 16  .02* .08 .00** .37 .33 .00** .02* .78 .21 .07 .45  .41 .58 .69 .03* .78 .31 .01** .35 .88 .28 .77  2 18 18 18 9 16 16 16 15 5 16  : 5 .: 8 : 9 :• 9 •: 2 : 8 :: 7 :: 8 : 6 i 1 : 8  .14 .20 .00** .01** .62 .67 .70 .06 .53  .45 .91 .09 .27 .69 .35 .81 .92 .96  .20  .39  As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  17 46 47 47 22 45 45 45 34 33 45  : 5 : 8 : 9 : 9 : 2 : 8 : 7 : 8 : 6 : 1 : 8  6 22 22 22 19 20 20 20 20 20 20  : 17 : 46 : 47 t 47 : 22 >. 45 : 45 : 45 t 34 : 33 : 45  .35 .62 .00** .00** .00** .78 .18 .12 .05* .00** .17  .75 .13 .00** .00** .00** .00** .00** .13 .22 .07 .67  VEINS : QUARTZ MONZONITE As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  HORNFELS : DIORITE As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  F Prob.  VEINS : HORNFELS  QUARTZ MONZONITE : DIORITE As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  No. o f Samples* t Prob.  6 22 22 22 19 20 20 20 20 20 20  i  : : : ,t : : : : ,: :  2 18 18 18 9 16 16 16 15 5 16  .26 .07 .00** .00** .00** .03* .01** .15 .01** .00** .09  .46 .48 .00** .00** .06 .00** .40 .72 .37 .09 .55  VEINS : DIORITE  .74 .86 .20 .10 .86 .02* .08 .03* .14  .85 .80 .05 .01** .60 .80 .04* .58 .88  .03*  .46  As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  6 : 22 : 22 •: 19 !• 20 ! 20 : 20 : 20 ! 20 ! 20 ! 20 !  5 8 9 9 2 8 7 8 6 1 8  .49 .84 .15 .00** .69 .87 .22 .17 .01**  .93 .53 .00** .00** .76 .12 .71 .70 .56  .00**  .65  •Number o f samples v a r i e s because only samples with detectable ( i . e . measurable) minor element concentrations can be compared.  152 Conclusions drawn from t and F tests (Tables 8, 9, and  10)  are: (1)  Vein p y r i t e i s part of a separate population from the set of a l l disseminated p y r i t e on the basis of Co, N i , Cu, Zn, T i , and p o s s i b l y Pb, Ag, Mo, and Mn;  but not As and B i .  However, except on the basis  of Co and N i , v e i n p y r i t e cannot be distinguished with any c e r t a i n t y from disseminated p y r i t e i f disseminated p y r i t e i s further subdivided i n t o smaller groups according to host rock type.  Large sample sets  from each type of host rock could possibly overcome t h i s problem.  (2)  Only a few elements i n disseminated p y r i t e can be shown to c o n s t i t u t e separate populations on the basis of host rock composition.  For  example, f o r Zn there Is a 98-per-cent or greater t and F p r o b a b i l i t y that p y r i t e from h o r n f e l s i s d i s t i n c t from that i n quartz monzonite. S i m i l a r high p r o b a b i l i t i e s f o r Ni and Zn i n d i c a t e that separate populations of p y r i t e - a r e present i n hornfels and quartz d i o r i t e . Also, Co i n p y r i t e from quartz d i o r i t e i s d i s t i n c t from that i n quartz monzonite.  In a number of other cases, .separate populations  are i n f e r r e d by low F p r o b a b i l i t i e s but t p r o b a b i l i t i e s are high, and v i c e versa.  Thus, no generalization can be made on the basis  of t and F tests about populations of minor elements i n dissemianted p y r i t e from d i f f e r e n t host rocks.  Polymodal d i s t r i b u t i o n s may,  but"  need not be, caused by mixing samples from d i f f e r e n t host rocks. Each element must be looked at on an i n d i v i d u a l b a s i s .  Graphic d e s c r i p t i o n , interpretation, and r e s o l u t i o n of polymodal data i s p o s s i b l e , using cumulative p r o b a b i l i t y p l o t s .  The technique has  been long known to b i o l o g i s t s and sedimentologists (Harding, 1949; Cassie,  153 1950,  1954,  1963; H a r r i s , 1958;  and others) but has only r e c e n t l y been  applied on a routine basis to geochemical data (Tennant and White, L e p e l t l e r , 1969; Bolviken, 1971; Woodsworth, 1972;  S i n c l a i r , 1974;  1959; and  Parslow, 1974). Form of cumulative p r o b a b i l i t y curves can be used to determine I f d i s t r i b u t i o n s are normal, lognormal, or polymodal.  A second use i s  resolution of polymodal data i n t o components (constituent populations) and d e f i n i t i o n of parameters of constituent populations.  Use of p r o b a b i l i t y  p l o t s i s discussed i n d e t a i l and c l e a r l y i l l u s t r a t e d by S i n c l a i r (1974). In t h i s study cumulative p r o b a b i l i t y p l o t s are used as a supplement to other u n i v a r i a t e procedures  of data a n a l y s i s .  I f a l l Berg minor element  data are p l o t t e d on a cumulative p r o b a b i l i t y plot (except arsenic f o r which there i s i n s u f f i c i e n t data), the following r e s u l t s are apparent: (1)  B i , Co, N i , Cu, Pb, Zn d i s t r i b u t i o n s appear to be polymodal, each consisting of at l e a s t two lognormal populations.  (2)  Ag and Mo have s i n g l e , lognormally d i s t r i b u t e d populations.  (3)  T i has a s i n g l e , normally d i s t r i b u t e d population, or the d i s t r i b u t i o n i s a complex, polymodal mixture of lognormal  populations.  Interpretation of polymodal cumulative p r o b a b i l i t y curves  suggest  that bimodal populations of Co, N i , Cu, and Pb consist of one large group of samples with generally higher values than the smaller population.  This  i s r e a d i l y interpreted to be a r e s u l t of mixing disseminated and v e i n pyrite. Two  Zinc d i s t r i b u t i o n i s polymodal but i s d i f f i c u l t to i n t e r p r e t .  populations of about equal proportions appear to be present, but the  two are p a r t l y coincident and mask each other.  Bismuth and manganese can  be interpreted to c o n s i s t of two populations - one with detectable amounts of metal, the other with amounts below the a n a l y t i c a l detection l i m i t .  154 Normal d i s t r i b u t i o n of titanium i s anomalous.  On the basis of i t s  e r r a t i c behaviour i t i s suspected that T i i s present i n included mineral g r a i n s .  Normal d i s t r i b u t i o n of a n a l y t i c a l r e s u l t s might,  therefore, be one c r i t e r i o n of contamination i n minor element studies.  Resolution of polymodal data i n t o component populations using .cumulative p r o b a b i l i t y p l o t s i s not necessary i n t h i s study since type of p y r i t e , i t s source, geological s i g n i f i c a n c e , mean and variance of each sample group, and the proportions of a l l component populations are known from sampling.  However, the method can be i l l u s t r a t e d and con-  c l u s i o n s from other univariate procedures can be double checked.  F and  t t e s t s as w e l l as histograms show, with the exception of B i , that v e i n and disseminated p y r i t e s are d i s t i n c t and, with very few exceptions, disseminated p y r i t e appears to constitute s i n g l e populations of minor elements regardless of host rock.  Disseminated p y r i t e (Figure 28) appears to approximate s i n g l e , lognormally d i s t r i b u t e d , measured- populations of Cu, Pb, Ag, and possibly Mo, B i , and Mn.  A second population of B i , Mn,  and Mo can be postulated  i f samples with less than detectable amounts of these elements are considered.  Exceptions are Co, N i , and Zn which appear polymodal i n the  cumulative p r o b a b i l i t y p l o t , but t h i s was  indicated e a r l i e r on the basis  of t and F tests which suggested the following:  Co i n p y r i t e from d i o r i t e  and quartz monzonite; Ni and Zn i n p y r i t e from h o r n f e l s and d i o r i t e ; and Zn i n p y r i t e from hornfels and quartz monzonite are d i s t i n c t populations. Thus, p r o b a b i l i t y plots are a powerful a n a l y t i c a l method, i n this case capable of r e s u l t i n g i n s i m i l a r conclusions as t and F tests i n conjunction with frequency d i s t r i b u t i o n data.  CUMULATIVE  PROBABILITY  FIGURE 2 8  M I N O R E L E M E N T S IN D I S S E M I N A T E D P Y R I T E  156 A t h i r d , small population  containing high N i and low Co values  i s suggested i n histograms but i s c l e a r l y shown i n p r o b a b i l i t y p l o t s . The population  i s made up of only f i v e samples but they are a l l from the  p y r i t i c halo zone.  Further sampling might r e v e a l that p y r i t e - r i c h rocks  p e r i p h e r a l to the zone of copper-molybdenum m i n e r a l i z a t i o n are represented by N i - r i c h p y r i t e that constitutes a separate  population.  BIVARIATE ANALYSIS  B i v a r i a t e analysis including c o r r e l a t i o n and simple regression was undertaken to examine r e l a t i o n s h i p s between paired v a r i a b l e s . C o r r e l a t i o n describes the i n t e r a c t i o n or a s s o c i a t i o n of variables without casual e f f e c t .  Correlation c o - e f f i c i e n t s were computed f o r a l l p a i r s o f  v a r i a b l e s (Table 11). The data were treated, f i r s t c o l l e c t i v e l y , and then subdivided into groups according to source of p y r i t e to see i f any trends or s i g n i f i c a n t differences between various types o f p y r i t e are apparent. Simple ( l i n e a r ) regression examines the interdependent r e l a t i o n ships of paired variables and can be used to measure the amount or degree of v a r i a t i o n i n a variable due to v a r i a t i o n i n the other v a r i a b l e . proportion  of t o t a l v a r i a t i o n or measure of v a r i a t i o n explained  The  by the  interdependence of the variables compared to the t o t a l v a r i a t i o n i s c a l l e d 2 R .  Table 12 l i s t s R  2  and F r a t i o s (variance r a t i o s ) f o r pairs of v a r i a b l e s  with s i g n i f i c a n t c o r r e l a t i o n as l i s t e d i n Table 11. From the preceding tables i t i s apparent that the greatest  amount  of a s s o c i a t i o n at s t a t i s t i c a l l y s i g n i f i c a n t l e v e l s i s between Co and N i and a l s o Pb and Zn.  A least squares regression l i n e described by the  equation Y » a + bX can be calculated f o r the paired variables as shown i n Figure 29.  FIGURE 29  LINEAR LEAST SQUARES REGRESSION LINE Y=a+bX For Co-Ni(A) & Pb= Zn(B) 3.300-  Co:Ni 2950-  a = 0420  b=i.ooi e =0.364  2600-  Ff->(X735 2.250  1.900-  Co log ppm  1550  1.200  0.850r-  05001  o o o o  CO  o  B 2400r-  Ni log ppm  DETECTION LIMIT'  Zn=Pb a b e R  2  =0.679 =0.524 =0.342 =0.457  o .8  a  o .8  o o  8 oo  o o  o o  TABLE 11.  CORRELATION OF PAIRED VARIABLES  A l l Data N - 100 Var. As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  As 1.000 -0.1500 0.0827 0.2143 -0.1670 0.2261 0.1543 0.0717 -0.2260 -0.5396 0.2790  Bi  1.0000 -0.0489 0.0026 -0.0896  0.4951  0.3254 0.5107 0.1196 0.1457 0.0538  Co  Ni  Cu  Pb  Zn  Ag  Mo  Ti  Mn  1.0000 0.8574 0.6342 0.1438 0.3568 0.3455 0.3066 0.4502 0.2936  1.0000 0.5356 0.1745 0.3619 0.2066 0.2490 0.3681 0.3301  1.0000 -0.1522 0.1749 0.1422 0.1892 0.5816 -10.0186  1.0000 0.6762 0.5229 0.2564 0.0740 0.3862  1.0000 0.4437 0.1867 0.2330 0.3962  1.0000 0.5285 0.0946 0.2400  1.0000 0.2055 0.0614  1.0000 0.1477  1.0000  Hornfels and Quartz D i o r i t e N - 56 Var. As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  As  Bi  Co  Ni  Cu  Pb  Zn  Ag  Mo  Ti  Mn  1.0000 -0.2342 0.1080 0.1953 0.2595 -0.1129 0.0013 0.0118 -0.2950 -0.1479 0.2526  1.0000 -0.1338 0.0435 -0.3998 0.4801 0.2294 0.4215 0.1794 0.4864 0.0260  1.0000 0.5314 0.4382 0.1740 0.2538 0.3849 0.3192 -0.2577 0.1968  1.0000 -0.0988 0.1469 0.1999 0.0827 0.2056 -0.0980 0.2053  1.0000 0.0520 0.0206 0.4806 0.1358 -0.2966 0.0104  1.0000 0.6335 0.5696 0.3998 0.2349 0.3484  1.0000 0.4510 0.2568 0.4308 0.3091  1.0000 0.5971 0.1960 0.3077  1.0000 -0.0562 0.1901  1.0000 -0.0546  1.0000  TABLE 11.  CORRELATION OF PAIRED VARIABLES (continued)  Quartz Monzonite N - 18 Var.  Ti  Mn  1 .0000 0.2334 0.1434  1.0000 0.3759  1.0000  Ag  Mo  Ti  Mn  1.0000 0.3015 -0.1655 0.2029  1.0000 0.1782 -0.0111  1.0000 0.0452  1.0000  Bi  Co  Ni  Cu  Pb  Zn  Ag  1.0000 -0.4595 -0.1865 -0.3645 0.1528 -0.3599 0.2298 -0.1584 -0.8157 -0.0158  1.0000 0.7992 0.2566 0.3603 0.3310 0.4931 0.5021 0.3616 0.4083  1.0000 -0.2042 0.4926 0.4328 0.5741 0.3179 -0.2986 0.4048-  1.0000 -0.1257 -0.2084 0.0887 0.3146 0.6492 .-0.0553  1.0000 0.5215 0.6861 0.1031 -0.7887 0.4306  1.0000 0.2650 -0.0380 -0.3107 0.3398  1.0000 0.6777 •0.6585 0.3731  As  Bi  Co  Ni  Cu  Pb  Zn  1.0000 -0.2943 0.3568 0.5479 0.2950 -0.7512 0.1834 0.5528 0.3719 -0.7326 -0.4897  1.0000 -0.0941 -0.1753 -0.0496 0.6052 0.6813 0.7868 0.0660 -0.0978 0.0643  1.0000 0.8745 0.4397 -0.0275 0.2621 0.3512 0.2993 -0.0200 0.0761  1.0000 0.5351 -0.0702 0.1282 0.1665 0.2742 -0.0314 -0.0103  1.0000 -0.3390 0.1338 0.1437 0.0647 0.4562 -0.3954  1.0000 0.7222 0.5481 0.2008 -0.3402 0.3567  1.0000 0.7470 0.3383 -0.1174 0.2185  As  As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  Mo  Veins N - 22 Var. As Bi Co Ni Cu Pb Zn Ag Mo Ti Mn  In  160 TABLE 12.  R  AND  F RATIOS FOR ALL DATA OF ALL PAIRS OF VARIABLES HAVING SIGNIFICANT CORRELATION  Variables  F Ratio  Co : Ni Pb : Zn  272 75.8  Co Ni Cu Pb Ag BI Pb Ag  : : : : : : : :  Cu Cu Ti Ag Mo Ag Bi Zn  Level of S i g n i f i c a n c e :  R  2  0.735** 0.457* 0.402 0.287 0.338 0.273 0.279 0.261 0.246 0.197  35.7 21.3 19.A 34.3 27.9 31.8 29.3 22.1  * • 95 per cent; ** • 99 per cent  A regression p l o t of Co as a function of Ni i s useful as a further means of discriminating between types'of p y r i t e , as shown i n Figure 30. P y r i t e from d i f f e r e n t sources f a l l s i n t o separate f i e l d s on the diagram. Vein p y r i t e and disseminated p y r i t e are the most d i s t i n c t types.  Within  the group of disseminated p y r i t e , samples from peripheral volcanic rocks, -  quartz d i o r i t e , quartz monzonite, and many samples from hornfels occur i n separate f i e l d s , although p y r i t e .from h o r n f e l s shows wide dispersion. Overlap of some v e i n and disseminated. pyrite_is_.to be. expected., s i n c e , the group of 'disseminated' p y r i t e i n the sample set includes both disseminated  -  and f r a c t u r e - c o n t r o l l e d p y r i t e and the d i s t i n c t i o n between fracture-controlled and v e i n p y r i t e i s e n t i r e l y a r b i t r a r y .  As a generalization, most of the  -disseminated p y r i t e i n the field-of-mixed v e i n and disseminated p y r i t e i n Figure 30 i s from the p y r i t i c halo, and the majority of p y r i t e i n the disseminated f i e l d i s from the zone of copper-molybdenum mineralization.  Differences i n amounts of Co and Ni i n p y r i t e appear to be proportional to amounts of these elements i n the host rocks.  In general,  Co and N i contents decrease with increasing a c i d i t y of igneous rocks ( P r i c e , 1972).  S i m i l a r l y o r i g i n a l temperatures  decrease from r e l a t i v e l y  FIGURE 30  COBALT-NICKEL SCATTER DIAGRAM S H O W I N G PYRITE ACCORDING TO S O U R C E 100  10  Ni  1 0 0 ppm  SOURCE OF PYRITE  1000  1000  + x • • • •  100  T A  Hornfels Diorite Qtz. Monzonite Qtz.Monz.Dyke Veins Volcanic Rocks Mean Values  162 high temperatures i n basic v o l c a n i c s , lower ones i n intermediate and a c i d i c i n t r u s i o n s , and considerably  cooler ones i n hydrothermal v e i n s .  Thus, differences i n amount o f Co and N i seen i n Figure 30 appear t o correspond to changes i n host rock composition and might a l s o be influenced by temperatures at which p y r i t e c r y s t a l l i z e d . Cobalt-nickel r a t i o s (Figure 31) i n p y r i t e from veins and quartz monzonite are s i m i l a r and these are d i s t i n c t from p y r i t e i n h o r n f e l s , d i o r i t e , and possibly regional v o l c a n i c s , which are s i m i l a r .  The mean  cobalt-nickel r a t i o f o r 96 samples with detectable amounts o f both elements i s 3.8. Price (1972) noted that t h i s r a t i o i s s t a t i s t i c a l l y  indistinguishable  from the mean c o b a l t - n i c k e l r a t i o o f p y r i t e from the large Endako and Casino porphyry deposits but i s d i s s i m i l a r to p y r i t e s from smaller porphyry deposits at Tchentlo Lake and Molymine, B r i t i s h Columbia, which have cobalt-nickel r a t i o s o f 31 and 27 r e s p e c t i v e l y .  Co/Ni N=96 X=3.80 S =3.00 I =0.75  40  VEINS  20  N  ~!.  8  „  X = 2.40 S = 2.10  0  3.0  6.0  9.0  X  FIGURE 31  1  10 •  in, -  3D  %  C o - N i RATIOS OF PYRITE  QTZ. MONZONITE N =  20  6.0  X-  9.0  r-, HORNFELS, DIORITE, VOLCANICS  10  N  0  1.5 3.0 4.5 6.0 7.5  o  =  9.0 10.512.0  6  0  163 Some Ni enrichment i s evident i n vein p y r i t e (Co/Ni compared to disseminated p y r i t e (Co/Ni - 4.28). stage crosscutting  features,  2.40)  Since most veins are l a t e  l a t e magmatic-hydrothermal f l u i d s from which  p y r i t e c r y s t a l l i z e d were enriched i n n i c k e l as i s the case i n many other hydrothermal and advanced magmatic environments ( P r i c e , 1972). implies may  that n i c k e l - r i c h . p y r i t e from the periphery of the p y r i t i c halo  have formed during l a t e mineralization  discussion of zoning, page  as well (see Figure 33  characterize  and  174).  Generally, use of c o b a l t - n i c k e l r a t i o s and quantities  due  This  to  p y r i t e types or sources within i n d i v i d u a l deposits i s l i m i t e d  to large v a r i a t i o n s i n minor element concentrations.  are consistent  Where differences  and s u f f i c i e n t l y large, such as between vein and  disseminated  p y r i t e at Berg deposit, concentration ranges and means of Co and Ni  are  c h a r a c t e r i s t i c and p y r i t e from unknown sources can be c l a s s i f i e d into fundamental-groups.  P r i c e (1972) has concluded that amounts of Co and N i , and l e s s e r extent c o b a l t - n i c k e l r a t i o s , are useful i n d i s t i n g u i s h i n g  to a  different  types of p y r i t e from g e n e t i c a l l y d i s t i n c t mineral deposits, namely: syngenetic (sedimentary), hydrothermal (including porphyry, v e i n , skarn), and massive sulphide.  Characteristic amounts of Co and  and  Ni  determined by P r i c e are shown i n Table 13. TABLE 13.  CHARACTERISTIC Co AND  Ni CONCENTRATIONS IN  (After P r i c e , Syngenetic Co Ni Co/Ni  41 65 .63  1972)  Hydrothermal 141 121 1.17  PPM  Massive Sulphide 486 56 8.7  164 Mean concentrations of Co (203 ppm) and n i c k e l (77 ppm) of Berg p y r i t e are comparable to hydrothermal p y r i t e .  Mean values of Co  (374 ppm) and N i (415 ppm) i n disseminated p y r i t e can be distinguished with any certainty only from syngenetic p y r i t e .  Furthermore, when  only vein p y r i t e i s considered (Co - 20, N i - 14 ppm),  mean concentrations  are most comparable to syngenetic p y r i t e but are also s i m i l a r to hydrothermal (low temperature) lead-zinc deposits p y r i t e i n Tasmanian granites  ( P r i c e , 1972)  and disseminated  ( L o f t u s - H i l l s and Solomon, 1967).  Therefore,  any genetic c l a s s i f i c a t i o n of mineral deposits u t i l i z i n g b i v a r i a t e analysis and based on Co and N i content of p y r i t e (and possibly any other p a i r of elements) i s , at best, tenuous.  MULTIVARIATE ANALYSIS M u l t i v a r i a t e s t a t i s t i c a l analysis defines r e l a t i o n s h i p s between a number of v a r i a b l e s or between samples f o r which three or more variables are measured.  Factor analysis i s a technique by which measured v a r i a b l e s are  combined i n N-dimensional space i n t o l i n e a r combinations of new v a r i a b l e s (factors) by a mathematically sophisticated extension of c o r r e l a t i o n -analysis.  Relationships between v a r i a b l e s are defined by R-mode analysis  and those between samples or sample s i t e s by Q-mode a n a l y s i s .  In t h i s study  Q-mode factor analysis i s applied to the seven most frequently detected elements i n the sample set - B i , Co, N i , Pb, Zn, Ag, and Mn, as w e l l as Cu i n vein pyrite. 1964  The technique has been described by Imbrie and Van Andel,  and Klovan, 1968,  and Webb, 1969,  and applied to geochemical data by Nichol,  Wilson and Sinclair-, 1969,  Garrett,  and Dawson and S i n c l a i r , 1974.  Treatment o f p y r i t e geochemical data by Q-mode f a c t o r analysis accomplishes three main purposes:  165 (1)  The number of v a r i a b l e s i s reduced since the measured quantities are combined into multivariable  (2)  Associations  'factors.'  and i n t e r r e l a t i o n s among v a r i a b l e s are often r e a l i z e d  that are not apparent on the basis of i n t u i t i v e or subjective data examination. (3)  The data generated are quantified and can be p l o t t e d on a map  and  contoured-to reveal zoning patterns and areas of i n t e r e s t .  Data f o r f a c t o r analysis are divided i n t o two groups - disseminated and vein p y r i t e - and the two separately  (Appendix H).  are p l o t t e d representing account f o r 96.3  fundamental  groups are  treated  Sixty-one sample s i t e s of disseminated p y r i t e seventy-four analyses (Appendix I ) .  Six factors  per cent of the variance but the four f a c t o r s that explain  81 per cent of the variance are considered to be the most s i g n i f i c a n t . These four f a c t o r s define d i s t i n c t zoning patterns and a d d i t i o n a l factors simply duplicate observed patterns -  and are redundant or are simply  that cannot be r e l a t e d to any geological cause or process.  The  varimax f a c t o r components computed are l i s t e d i n Table 14 and of the four f a c t o r s p l o t t e d , i n Table  'noise*' ' -  successive  the scores  15.  A l l four f a c t o r s , i n a general way,  outline annular zones centred  on the quartz monzonite stock and have value maxima roughly with-the-zone of copper-molybdenum mineralization. s i m i l a r to those of i n d i v i d u a l elements but may  coincident  Zoning patterns" are  be more s i g n i f i c a n t i n  d e f i n i n g zoning trends as factors integrate behaviour of a number of elements.  However, the geological s i g n i f i c a n c e of f a c t o r s i s not always  obvious and explanations or interpretations are subjective and may speculative.  No outstanding relationships between s p e c i f i c f a c t o r s and  or waste, such as that found at Endako (Dawson and S i n c l a i r , 1974) evident.  be  are  ore  TABLE 14.  Factor F1 F2 F3 FA F5 F6  F1 F2 F3 FA F5  SUCCESSIVE Q-MODE VARIMAX FACTOR COMPONENTS - DISSEMINATED PYRITE  Components  % of Var.  25.3 -Ag, Co, (Mn, Zn, PbjNi) +BI 21.0 - B i , Mn, N i , Pb +(Co, Zn, Ag) 16.7 -Mn +Bi, Zn, (Ag, Pb) 13.8 -Ag, (Mn, B i , Pb, Zn) +Ni. Co •13.2 - B i , Co, Ag +Zn, Pb, N i , (Mn) 6.3 -Zn, (Mn, B i , Co) :2b, (Ag) cum. 96.3  F1  25.0  F3  -Ag, Co, (Mn, Pb, Zn, Ni) +Bi -Mn, B i , N i , (Pb) +(Co, Ag) -Mn +Bi, Zn, Pb, (Ag, Ni) - B i , Ag, Co +Zn, Pb, (Mn) -Ag, (Mn, Pb, Bi) +Co, N i , (Zn) cum.  F2 F3 FA  FT F2  21.1 17.3 13.9 13.8 91.1  Components  Factor  F1 F2  -Co, Ag, Zn, Pb, (Mn, Ni) +Bi - B i , N i , Mn, (Pb, Zn) + (Co) -Co. N i . (Mn) +Zn, Pb, (Ag, B i ) - B i , Ag, (Co) •tifa. (Zn, Ni)  -Ni, -Co. +Bi, ;Bi, +Zn,  % of Var. 25.2 25.0 15.7 1A.9 cum. 80.8  B i , Pb, Ag, Co, Mn, Zn 32.A N i . (Mn) 18.3 Pb, Zn (Co, Ni) 17.3 Mn, (Pb) cum. 68.0  -Pb. Mn. Zn, N i , Ag, (Co, B i ) 3A.0 -Co, (Mn, Ni) 21.1 +Bi, (Pb, Ag, Zn) cum. 55.1  TABLE 15.  Q-MODE VARIMAX FACTOR SCORES - DISSEMINATED PYRITE  Variable  Factor 1  Factor 2  Factor 3  Factor 4  Bi Co Ni Pb Zn Ag Mn  0.910 -1.3576* -0.388 -0.909 -1.171 -1.341* -0.441  -1.875* 0.265 -1.178 -0.882 -0.276 -0.008 -1.077  0.152 -1.551* -1.395* 0.949 1.230 0.414 -0.203  -1.284 -0.623 0.278 -0.089 0.476 -1.257 1.754*  Variance per cent  25.2  25.0  15.7  14.9  Cumulative variance per cent  25.2  50.2  65.9  80.8  •Denotes important  component factor.  TABLE 16. SUCCESSIVE Q-MODE VARIMAX FACTOR COMPONENTS - VEIN PYRITE  Factor F1 F2 F3 F4 F5 F6  % of Var.  Components -(Cu) +Pb, Zn, Ag, ( B i , - B i , Mn, (Ag) +Ni, Co, (Cu, Pb, -Mn, (Pb, Zn) +Bi, Cu. A R . -Mn, Co, (Ni, Ag, +Zn, Pb -Cu. Zn, Mn +(Co, N i , B i , Ag, -Zn, Co +Pb, (Cu, N i , Mn,  Factor Fl  Mn, Co, Ni)  29.3  Zn)  23.7 16.2  F3  Cu)  14.3  F4  F2  9.9  F3 F4 F5  29.6 30.5 18.8 10.2 89.1  4.3 F1  Ag)  F2  F2  -(Cu) +Pb. Zn, Ag. B i . (Mn, Co) - ( B i , Pb, Mn) +Co, N i , (Cu, Ag, Zn) -Mn, (Co, Pb) +Cu, B i , (Ag, Zn) ^Cu, Mn, (Zn, Ag) +(Co, Pb, Ni) cum.  Pb)  cum. 97.7  F1  % of Var.  Components  -(Cu) +Pb, Zn, Ag, B i , (Mn, Co, Ni) - B i , Mn, (Ag) +Ni. Co, (Cu, Zn, Pb) -Mn. Pb, (Ni) +Bi, Cu, Ag, (Co) -Mn, Co, Ag, N i , +Pb, Zn -Cu, Mn, Zn +(Co, B i , N i , Ag) cum.  F3 29.4  -(Cu) +Pb, Zn, Ag, B i , (Mn, Co) - ( B i , Mn, Pb) +Ni, Co, (Cu, Ag, Zn) -Mn, (Co, N i , Pb) +Cu, B i , (Ag, Zn) cum.  30.1 30.7 18.6 79.4  23.5 17.0  F 1  F2 15.2 9.9  +Bi, Pb. Zn. Ap. (Mn) - ( B i , Mn, Pb) •»Ki« Co. (Cu, Ag, Zn)  30.9 30.6 cum. 61.5  95.0 CO  169 • Factor 1 i s characterized by high (negative) scores of Co  and  Ag with moderate contributions from Zn and Pb, and minor contributions Mn and N i .  The only element that does not contribute to the  f a c t o r value i s B i and,  from  (negative)  thus, the f a c t o r can be interpreted as a measure  of the amount of cation s u b s t i t u t i o n i n p y r i t e . measure of B i with moderate contributions  Factor 2 i s l a r g e l y a  from N i , Mn,  and Pb  scores.  I t compliments Factor 1 i n as much as the most important factor components are those elements least s i g n i f i c a n t i n Factor 1; Factor 2 also indicates the amount of minor element s u b s t i t u t i o n i n p y r i t e , but because B i i s the main component i n the f a c t o r value, the f a c t o r may of anion s u b s t i t u t i o n .  be a measure of the. amount  I f indeed B i has a closer geochemical a f f i n i t y  i n p y r i t e with anions rather than c a t i o n s , Factor 2 might indicate zones that supplied sulphur during  mineralization.  Factor 3 i s composed of two pronounced c o r r e l a t i o n was  a n t i t h e t i c p a i r s of elements whose  observed i n a preceding section, c o b a l t - n i c k e l  as a negative f a c t o r component and  lead-zinc as a p o s i t i v e one.  The  f a c t o r i s possibly the most i n t e r e s t i n g from a zoning point of view as high (positive)  f a c t o r values with high lead-zinc and low c o b a l t - n i c k e l  are found mainly i n quartz monzonite and the quartz monzonite contact.  i n hornfels or quartz d i o r i t e near  The high content of lead and zinc i n p y r i t e  from i n t r u s i v e rocks was noted e a r l i e r i n discussion of univariate minor element data.  Thus, lead and zinc i n Factor 3 may  be postulated  to  represent a hydrothermal c o n t r i b u t i o n by quartz monzonite, whereas cobaltn i c k e l might be a contribution of elements to p y r i t e from country rocks (volcanics and quartz d i o r i t e ) . Factor 4 contains high ( p o s i t i v e ) manganese scores and modest (negative) B i and Ag scores.  High f a c t o r values are found i n a series  o f i s o l a t e d zones that encompass the quartz monzonite stock but are  located  170 at some distance from the contact.  Highest (negative) factor values occur  i n b i o t i t e - b e a r i n g hornfels and quartz d i o r i t e .  Factor 4 i s p o s s i b l y the  best i n d i c a t o r of a l l four f a c t o r s o f the l i m i t s of the zone containing i n excess of 0.2 per cent copper. Factor analysis o f v e i n p y r i t e (Table 16) includes values of copper (Appendix J ) .  Two groups of elements account f o r most variance i n  v e i n p y r i t e - Pb-Zn-Ag (and Bi) and Co-Ni.  Two other f a c t o r s , one composed  l a r g e l y of Mn, the other of Cu, account f o r much of the remaining v a r i a t i o n . Together, these four f a c t o r s account f o r 89 per cent of t o t a l variance. Factors of v e i n p y r i t e are not the same as those of disseminated p y r i t e (Table 14), probably because the two types of p y r i t e are o f d i f f e r e n t origins.  Certainly combinations o f elements from vein p y r i t e In f a c t o r s  provide g e o l o g i c a l l y f a m i l i a r and geochemically acceptable associations (e.g. N i and Co; B i , Pb, Zn, Ag), but otherwise very l i t t l e i s revealed about zoning of v e i n p y r i t e because of the e r r a t i c d i s t r i b u t i o n of the small group of samples. MINOR ELEMENT ZONING IN THE DEPOSIT INTRODUCTION Zoning, a systematic v a r i a t i o n i n space, of minor elements i n p y r i t e i s evident i n p l o t s of u n i v a r i a t e and f a c t o r analysis data.  Con-  centrations of impurity elements and high f a c t o r scores generally occur near the contact of the quartz monzonite stock although the most intense concentration of a l l elements i s i n p y r i t e from quartz d i o r i t e i n the w e l l mineralized northeast zone.  Coincidence of high factor values and  i n d i v i d u a l element concentrations with the zone of copper-molybdemum m i n e r a l i z a t i o n i s remarkably consistent.  Concentrations decrease away  171 from the i n t r u s i v e contact, both w i t h i n the stock and intruded rocks. F i v e specimens of weakly a l t e r e d p e r i p h e r a l v o l c a n i c rocks with only traces of p y r i t e do not f i t the zoning p a t t e r n .  These few samples suggest that  zoning of minor elements i n p y r i t e i s confined to the main zone o f mineralized and hydrothermally a l t e r e d rocks, p o s s i b l y a maximum of two thousand feet from the quartz monzonite contact.  Zoning patterns o f most i n d i v i d u a l elements are centred on the quartz monzonite stock and are s i m i l a r .  Consistent patterns of d i f f e r e n t  elements and factors i n disseminated p y r i t e may indicate that a s i n g l e , all-encompassing  hydrothermal system p r e v a i l e d during the main stages of  mineralization.  The v a r i a b l e most commonly considered to regulate i n c o r -  poration of minor elements i s temperature, and zoning i s interpreted to be a response to temperature gradients.  Undoubtedly there has been i n t e r p l a y  of numerous other v a r i a b l e s during sulphide deposition.  These include:  a v a i l a b i l i t y of elements — both metals and complexing ions; concentrations of elements and t h e i r p a r t i t i o n i n g between f l u i d and s o l i d phases (Rose, 1970); rates of p r e c i p i t a t i o n , m o b i l i t y (of elements) governed by f l u i d migration patterns, permeability, and d i f f u s i o n r a t e s ; confining pressure, p a r t i a l pressures of components i n hydrothermal f l u i d s - p a r t i c u l a r l y  those  containing sulphur; changes i n m i n e r a l i z i n g s o l u t i o n s caused by i n t e r a c t i o n with ground water and w a l l rock r e a c t i o n s ; and many others. Berg p y r i t e data were examined to see i f there i s any r e l a t i o n between quantity o f p y r i t e and amount of minor elements i n p y r i t e . concluded  I t was  that the zoning observed r e f l e c t s differences i n absolute amounts  of impurity elements and i s not caused by d i l u t i o n of a constant quantity of elements by d i f f e r e n t amounts o f p y r i t e .  Numerous studies have intimated  172 that d i f f e r e n t paragenetic stages may elements.  have d i f f e r e n t contents of impurity  This fact has already been i l l u s t r a t e d i n t h i s study by  comparison of v e i n and disseminated p y r i t e .  Therefore, zoning patterns  considered here are based on analyses of c a r e f u l l y selected disseminated p y r i t e of the same paragenetic type and from rocks of apparently s i m i l a r origin.  Except f o r a few samples from the supergene zone, most samples  analysed are from primary m i n e r a l i z a t i o n below the zone of oxidation. Regional metamorphism i s low grade and m i n e r a l i z a t i o n has undergone a uniform post-depositional h i s t o r y .  C r e d i b i l i t y of zoning patterns i s based on the premise that minor element concentrations are not e r r a t i c at d i f f e r e n t depths but vary as a function of distance from the stock, and t h e r e f o r e , one or two samples per d r i l l hole are representative of a large area.  V e r t i c a l zoning of primary  sulphide minerals and hypogene rock a l t e r a t i o n was not recognized over depths of a few hundred feet but may be present over greater depths. Presumably minor element d i s t r i b u t i o n s behave i n a s i m i l a r manner.  The abundance of minor elements was  found to be f a i r l y consistent  *  with depth - i f specimens of s i m i l a r rock and a l t e r a t i o n types were compared.  Table 17 i l l u s t r a t e s v a r i a b i l i t y of minor element concentrations  at d i f f e r e n t depths.  The specimens from d r i l l hole 71 are a l l from hornfels  but were selected to represent maximum v a r i a t i o n i n type and amount of rock alteration.  In comparison,  specimens from d r i l l holes 16 ( d i o r i t e ) and 23  ( b i o t i t e hornfels) are representative specimens from d r i l l holes with uniform rock type and a l t e r a t i o n throughout  the length of the hole.  As a group,  p y r i t e from d r i l l hole 71 shows considerable v a r i a t i o n but specimens from s i m i l a r a l t e r a t i o n zones are comparable.  As most p y r i t e i n t h i s study  was  taken from b i o t i t e hornfels of a s u p e r f i c i a l l y s i m i l a r type, the amount of  TABLE 17. Sample ( d r i l l hole and footage) B i o t i t e Hornfels 71-420 71-667 71-738 Brecciated Hornfels 71-533 71-569 S e r i c i t e Hornfels 71-869 71-915 Diorite 16-495 16-600  B i o t i t e Hornfels 23-328 23-434  VERTICAL VARIATION OF MINOR ELEMENTS IN PYRITE  Bi  As  Co  Ni  Pb  Zn  Ag  Mo  Ti  Mn  N N N  N 1.0 1.0  720 950 560  230 140 168  1 7 1  8 9 18  4.0 7.0 2.5  N 28 N  55 8 450  N 20 N  N 530  1.0 17.0  430 400  330 98  64 36  20 19  5.5 9.0  26 10  10 64  N 6  1050 400  26.0 12.0  305 435  107 74  63 105  30 34  18.0 19.0  31 14  380 G  N 5  N N  N N  380 353  172 154  25 24  26 31  8.0 3.5  8 2  G G  5.5 7.5  N 575  N N  615 640  55 67  13 24  10 28  6.5 7.0  N 6  40 270  N 12  N denotes l e s s than detection l i m i t ; G denotes greater than detection l i m i t .  174 v e r t i c a l v a r i a t i o n indicated by hole 71 i s p o s s i b l y the maximum that would be expected. It i s concluded that zoning patterns can be reproduced at d i f f e r e n t depths i f zones are defined by large, yet s t a t i s t i c a l l y meaningful,  contour  i n t e r v a l s such as values greater than the mean of a l l analyses (>X) greater than the mean plus one standard d e v i a t i o n ( > X  + s.d.).  and  Samples from  d i f f e r e n t depths might change the d e t a i l e d configurations of zones i f d i f f e r e n t a l t e r a t i o n zones were intersected but usually general patterns are not affected.  For example, i f each analysis from hole 71 was plotted successively,  only about one-third would cause any change i n the p o s i t i o n of zone contours and most of the changes would be due to e r r a t i c behaviour of Mo, T i , and  Mn.  UNIVARIATE MINOR ELEMENT ZONING Zoning of i n d i v i d u a l minor element concentrations i n p y r i t e i s shown i n Figures 32, 33, and 34.  Zoning patterns are s i m i l a r , with concentration  maxima seen as annular zones about the quartz monzonite stock near the i n t r u s i v e contact.  Zones are not symmetrical about the stock as concentration  contours bulge i n t o d i o r i t e to the east and northeast of the quartz monzonite i n t r u s i o n , and continuity of contours i s disrupted i n the southwest by i r r e g u l a r masses of quartz monzonite.  This i s s i m i l a r to the  d i s t r i b u t i o n of copper.  Co, N i , Pb, Zn, Ag, Mo, and Mn are concentrated i n p y r i t e near the quartz monzonite i n t r u s i v e contact with concentration maxima most common i n the northeast zone of m i n e r a l i z a t i o n i n hornfels and quartz diorite.  C o b a l t - n i c k e l r a t i o s have maximum values i n hornfels about 500  feet from the contact.  Four samples i n the south suggest that n i c k e l  content increases outward from the zone of c o b a l t - n i c k e l highs and p y r i t e  SOURCE OF PYRITE o HORNFELS • QUARTZ MONZONITE A  QUARTZ DIORITE  ZONING OF MINOR ELEMENTS IN PYRITE FIGURE 32  176  FIGURE 33.  ZONING OF MINOR ELEMENTS IN PYRITE  IZZ  178 south of t h i s zone contains n i c k e l i n excess of cobalt over distances of a few hundred f e e t .  Bismuth d i s t r i b u t i o n i s much l i k e that of other  elements with high values found i n a zone p r o j e c t i n g out i n t o the p y r i t i c halo to the south.  Bismuth (and p o s s i b l y lead, z i n c , and s i l v e r ) may  be  concentrated there i n p y r i t e related to north-south-trending structures. Detectable a r s e n i c (>300 ppm) copper-bearing  i s found i n a l l samples outside the main  zone but small zones c o n s i s t i n g of a few samples with  detectable a r s e n i c are coincident with the highest grades of copper within the area of copper mineralization.  A d d i t i o n a l sampling may reveal  that arsenic i s most abundant i n p y r i t e from the p y r i t i c halo and weakly mineralized p e r i p h e r a l volcanic rocks and therefore u s e f u l as a pathfinder element.  Titanium concentrations are e r r a t i c and highest values (those  above the d e t e c t i o n l i m i t ) are associated with i n t r u s i v e rocks or t h e i r contacts.  Values of T i below the mean of the sample group are found within  zones of copper m i n e r a l i z a t i o n .  Concentration- maxima o f - s i n g l e elements or-small -groups of elements do not coincide exactly with best copper or molybdenum grades, but zones of best mineralization are c l e a r l y defined when a l l concent r a t i o n highs are superimposed (Figure 35).  Ovchinnikov  (1967) states:  'An increase i n the quantity of the 'host' mineral i s accompanied by a simultaneous  increase i n the r e l a t i v e concentration of the impurity  elements i n i t . '  Although this may be true i n massive, p y r i t i c deposits,  i n t h i s study and perhaps porphyry deposits i n general, highest concent r a t i o n s of minor elements i n p y r i t e are intermediate between the p y r i t i c halo and the sparsely mineralized i n t r u s i v e core.  At Berg deposit con-  centration maxima of minor elements i n p y r i t e are not coincident with maximum amounts of the host p y r i t e .  Instead, highest minor element  179  180 concentrations are more c l o s e l y related to the amounts o f copper and molybdenum minerals present within a zone containing 2 to 4 per cent pyrite. A consistent zoning sequence i s not evident.  This may be,  i n part, because inhomogeneous s t r a t i f i e d rocks are mineralized and rock compositions may have influenced composition of p y r i t e .  Possibly  minor element d i s t r i b u t i o n s i n p y r i t e from homogeneous host rocks might display zoning sequences.  There i s some suggestion o f t h i s i n d i o r i t e  of the northeast copper zone where maxima of manganese, s i l v e r , and cobalt are c l e a r l y p e r i p h e r a l to highest N i , B i , Pb, and Zn values. A most noteworthy aspect o f zoning of minor elements i n p y r i t e i s that minor elements do not imitate sulphide mineral zoning patterns i n porphyry deposits. When Pb, Zn, Ag, and Mn minerals are found they most commonly occur i n late-stage v e i n l e t s p e r i p h e r a l to the main zone of i n t r u s i o n , a l t e r a t i o n , and Cu-Mo m i n e r a l i z a t i o n .  However as minor elements  i n p y r i t e Pb, Zn, Ag, and Mn appear to be concentrated i n p y r i t e from the ~ ore zone, i n t r u s i v e rocks, or rocks near the i n t r u s i v e contact; whereas maxima o f As, Co, and N i form p e r i p h e r a l highs i n the p y r i t i c halo.  Depletion o f minor elements or low element concentrations do not appear to have any defined patterns with the exception o f manganese. Manganese lows are found only i n areas with low concentrations of other minor elements i n p y r i t e or areas with only few elements.  Zones with  low manganese content (less than the detection l i m i t ) border zones of high concentrations of other minor elements.  Manganese lows may be  p o t e n t i a l l y u s e f u l , as i n a l l cases observed, manganese lows border zones with best copper grades.  181 ZONING OF FACTORS (MULTIVARIATE ANALYSIS)  Contoured p l o t s of factor values are shown i n Figure 36. Factors have values ranging from 1 to -1 and are i n t e r p r e t e d as follows:  large negative values are caused by large amounts of negative  v a r i a b l e s and small amounts of p o s i t i v e v a r i a b l e s .  S i m i l a r l y , large  p o s i t i v e values imply large amounts of p o s i t i v e v a r i a b l e s and small amounts of negative variables i n the f a c t o r s .  Factor 1 (negative) values define a broad, asymmetrical  girdle  about the quartz monzonite stock that coincides c l o s e l y with the most highly a l t e r e d and mineralized rocks.  Highest (negative) f a c t o r values  are associated with rocks containing about 3 to 4 per cent p y r i t e and occur i n an area bounded by p o s i t i v e factor values that correspond to weakly mineralized rocks of the barren i n t r u s i v e core and p y r i t i c halo. Factor 2 has a s i m i l a r zoning r e l a t i o n s h i p as Factor 1.  Highest (negative)  f a c t o r values occur i n areas of copper"mineralization and are" flanked by positive factor values.  ~  Factor maxima l i e i n areas with l e s s p y r i t e (about  2 per cent) than those of Factor 1, and define smaller zones more c l o s e l y related to i n t r u s i v e contacts p a r t i c u l a r l y quartz d i o r i t e .  I f Factor 2 i s ,  indeed, an i n d i c a t o r of anion s u b s t i t u t i o n i n p y r i t e , i t may be more c l o s e l y a l l i e d to a v a i l a b i l i t y of sulphur i n the m i n e r a l i z i n g process.  Thus, i t  would appear that the quartz d i o r i t e contact may have been a source area f o r sulphur during p y r i t e formation.  Factors 1 and 2, because of their  s i m i l a r zoning patterns and close r e l a t i o n s h i p to the zone of coppermolybdenum m i n e r a l i z a t i o n , may be made up of f a c t o r components contributed by the hydrothermal system and mineralizing processes.  182  CONTOURED PLAN OF Q - M O D E FACTOR VALUES FIGURE 36  183 'Zones of Factor 3 and 4 values do not correspond to any constant amount of p y r i t e and are more transgressive to p y r i t e contours.  Factor 3  c l e a r l y e x h i b i t s mutually exclusive, a n t i t h e t i c - z o n i n g r e l a t i o n s h i p s between lead-zinc and c o b a l t - n i c k e l , but zoning r e l a t i o n s h i p s to coppermolybdenum m i n e r a l i z a t i o n are not consistent.  In the eastern part of  the mineralized zone, p o s i t i v e factor values (high l e a d - z i n c , low cobaltn i c k e l ) define very c l o s e l y the quartz monzonite contact and the adjoining zone of molybdenum-copper m i n e r a l i z a t i o n , whereas high negative values define the p y r i t i c halo i n hornfels and d i o r i t e .  In southwest and  west part8 of the mineralized zone, high p o s i t i v e values again define the quartz monzonite contact but highest negative values correspond with copper-molybdenum m i n e r a l i z a t i o n i n h o r n f e l s .  Zones of Factor 4 values are the l e a s t continuous of the four f a c t o r s and are seen as i s o l a t e d areas with negative f a c t o r values ( B i , Ag component) spread around the quartz monzonite stock.  Most areas are i n  copper-bearing h o r n f e l s with only a very few sample s i t e s w i t h i n i n t r u s i v e rocks.  The zone of m i n e r a l i z a t i o n defined i s the copper zone, i n most  cases adjoining the s h e l l of copper-molybdenum m i n e r a l i z a t i o n .  The outer  edge of areas with negative factor values defines approximately the f u r t h e s t l i m i t of 0.2 per cent, and greater, copper m i n e r a l i z a t i o n and i s coincident with the s t a r t of the p y r i t i c halo.  Factors 3 and 4, i n view of t h e i r somewhat transgressive r e l a t i o n to zones of s i m i l a r p y r i t e content, yet consistent a s s o c i a t i o n with s p e c i f i c rock types, may  represent factors whose components are (partly) derived from  country rocks during mineralization; i n t h i s case, lead-zinc from quartz monzonite, c o b a l t - n i c k e l from hornfels and quartz d i o r i t e , and bismuth-silver from h o r n f e l s .  185 •Zoning patterns o f factors are generally s i m i l a r to those of i n d i v i d u a l minor elements with factor maxima concentrated i n an annulus about the quartz monzonite stock roughly coincident with the zone of copper and molybdenum sulphides (Figure 37).  Composite highest f a c t o r  values (-0.5) shown i n Figure 37 c l e a r l y coincide with the zone o f best copper-molybdenum m i n e r a l i z a t i o n .  Factor zoning patterns, while s i m i l a r  to those of i n d i v i d u a l minor elements or composites of minor element concentrations, appear to be more useful i n more p r e c i s e l y o u t l i n i n g the copper-molybdenum ore zone.  186 t. ,  CHAPTER VI  SUMMARY AND CONCLUSIONS  The Berg deposit i s a large tonnage low-grade copper-molybdenum deposit whose p o t e n t i a l was appreciated only a f t e r the profound e f f e c t s of near-surface o x i d a t i o n and weathering were recognized.  Prospecting  i n d i c a t i o n s of copper-molybdenum mineralization were provided by the presence of some.molybdenite-bearing  veins i n a quartz stockwork and by  secondary copper minerals i n margins of basic dykes.  The p o s s i b i l i t y of  i n t e r e s t i n g copper-molybdenum mineralization was suggested by h i g h l y anomalous s i l t and water geochemical r e s u l t s and leached capping appraisals but considerable diamond d r i l l i n g was required to demonstrate the presence of economically s i g n i f i c a n t hypogene copper-molybdenum and supergene copper minerals.  The p o s s i b i l i t y of s i g n i f i c a n t supergene m i n e r a l i z a t i o n had been  l a r g e l y overlooked because of the presence of g l a c i e r s and a h i s t o r y of extensive and-multiple g l a c i a t i o n throughout  the area.  The deposit i s located i n a predominantly v o l c a n i c terrane that has been intruded by many small stocks and plutons. a t r a n s i t i o n a l zone between the granitoid-metamorphic  The area i s part of Coast P l u t o n i c  Complex on the west and weakly deformed v o l c a n i c and sedimentary  rocks  of the Nechako Plateau (part of the Intermontane Belt) on the east.  Bedded rocks i n Berg map-area are present i n two major timerock u n i t s - Middle J u r a s s i c Hazelton Group and Cretaceous Skeena Group. Skeena rocks were not recognized i n the area p r i o r to t h i s study.  Hazelton rocks are subaqueous and i n part subaerial a n d e s i t i c p y r o c l a s t i c rocks with subordinate volcanic flows and l o c a l l y derived  187 sediments\  Subaerial members are recognized by t h e i r maroon colour or 'red  bed' appearance and by the presence of accretionary l a p i l l i and p e l l e t e d tephra.  About 5,500 feet o f the bedded sequence i s exposed i n Berg map-  area and has been subdivided into s i x l i t h o l o g i c a l l y d i s t i n c t u n i t s .  Skeena rocks o v e r l i e Hazelton rocks i n the eastern h a l f of Berg map-area.  Skeena rocks were divided i n t o three map u n i t s - a lower volcanic  unit of f e l d s p a t h i c andesitic to trachyandesitic flows and b r e c c i a s ; a sedimentary u n i t composed mainly of bedded micaceous sandstone containing beds with Clepniceras, an Albian (late Lower Cretaceous) ammonite; and an upper v o l c a n i c unit of andesitic to r h y o l i t i c flows, b r e c c i a , and t u f f . The oldest Skeena unit i s poorly exposed i n Berg map-area where i t s contact with Hazelton rocks i s intruded, f a u l t e d , or obscured by snowfields.  Closer  to Tahtsa Lake the contact i s known to be an angular unconformity and the base of the Skeena succession i s marked by conglomerate 1974, personal communication).  (D. G. Maclntyre,  The sedimentary unit forms a c l a s t i c wedge  that pinches out westward and thickens eastward where i t has a thickness of at least 1,600 feet along the eastern boundary of the map-area.  The upper-  most v o l c a n i c u n i t appears to conformably o v e r l i e sedimentary rocks except where the c l a s t i c wedge has pinched out i n the area of 8,103-foot peak. There Cretaceous rocks of the younger v o l c a n i c map unit can be seen to rest unconformably on l i t h o l o g i c a l l y s i m i l a r Hazelton v o l c a n i c rocks. Intrusive rocks i n Berg map-area consist o f two main bodies. The older and l a r g e r i n t r u s i o n i s a steep-walled elongate stock of quartz d i o r i t e that has been traced southward f o r 6 miles to Tahtsa Lake.  The  younger i n t r u s i o n i s a c y l i n d r i c a l quartz monzonite stock about 2,100 feet i n diameter that has intruded, a l t e r e d , and mineralized enclosing Hazelton rocks and part of the quartz d i o r i t e stock.  188 • The quartz monzonite i n t r u s i o n i s a composite  stock i n which four  i n t r u s i v e phases have been recognized on the basis of c r o s s c u t t i n g r e l a t i o n ships and presence o f fragments of one rock type i n another.  Five K-Ar age  determinations by Carter (1974) date the stock as Eocene (49.0+2.4 m.y.). No closer r e s o l u t i o n of the i n t r u s i v e sequence nor duration between c r y s t a l l i z a t i o n of the i n t r u s i v e phases i s possible as the dates are i n d i s t i n g u i s h able s t a t i s t i c a l l y . The four i n t r u s i v e phases are c l a s s i f i e d (from oldest t o youngest) on a l a r g e l y d e s c r i p t i v e basis as: plagioclase porphyry  quartz monzonite porphyry  (QMP); quartz  (QPP); plagioclase b i o t i t e quartz porphyry  quartz feldspar porphyry (QFP).  (PBQP); and  C l a s s i f i c a t i o n based on compositions as  determined by modal determinations and two f u l l s i l i c a t e analyses r e v e a l that quartz monzonite porphyry and quartz plagioclase porphyry are equivalent i n composition to quartz monzonite, plagioclase b i o t i t e quartz porphyry i s equivalent i n composition to quartz monzonite or quartz-bearing monzonite, quartz f e l d s p a r porphyry i s equivalent i n composition to quartz monzonite/ granodiorite or quartz-bearing monzodiorite according to a c l a s s i f i c a t i o n based on Streckeisen (1967).  Intrusive rocks are grey and r a r e l y pink when fresh or cream to orange or b r i c k pink when weathered.  They are a l l characterized by  abundant strongly zoned plagioclase phenocrysts, rare p o i k i l i t i c K-feldspar megacrysts (absent i n QPP), large s k e l e t a l quartz grains, and coarse-grained elongate books of b i o t i t e .  The phenocrysts together with a very fine  granular to m i c r o c r y s t a l l i n e matrix make up a s l i g h t s e r i a t e crowded porphyry that can be likened to 'quench type' porphyries i n other highl e v e l intrusions and some volcanic rocks.  Differences between the various  phases are most obvious on the basis of texture.  M i n e r a l o g i c a l differences  189 are s l i g h t but can be documented by determining abundances of quartz, plagioclase, and K-feldspar, degree of feldspar a l t e r a t i o n , b i o t i t e hornblende r a t i o s , and presence of magnetite and sphene.  A b r e c c i a pipe intrudes Hazelton rocks and quartz d i o r i t e southeast of the composite stock.  I t i s a polymictic m i l l e d b r e c c i a that i s  explosive i n o r i g i n and Is r e l a t e d g e n e t i c a l l y to the composite stock. Breccia i s mineralized with p y r i t e but postdates development of molybdenumbearing quartz stockwork.  A gypsum-filled subhorizontal fracture cleavage cuts a l l rocks except quartz p l a g i o c l a s e porphyry and basalt dykes.  The cleavage i s a  l a t e feature r e l a t i v e to quartz veining and copper-molybdemum m i n e r a l i z a t i o n that has been documented i n a number of other porphyry deposits.  Its origin  at Berg deposit i s uncertain but might be related to hydraulic f r a c t u r e as described by P h i l l i p s (1972) and Shearman et a l . (1972).  Beneath weathered rocks and a zone of supergene a l t e r a t i o n a number of d i f f e r e n t hypogene a l t e r a t i o n assemblages are present i n and around the composite stock.  Pervasive alteration-types recognized are:  (1) potassic ( q u a r t z - K - f e l d s p a r - b i o t i t e - s e r i c i t e - c h l o r i t e ) w i t h i n the core of the stock; (2) p h y l l i c ( q u a r t z - s e r i c i t e - p y r i t e ) around much of the margin of the stock; and  (3) p r o p y l i t i c (chlorite-epidote-carbonate)  i n p y r i t i c rocks surrounding the e n t i r e stock.  A r g i l l i c alteration i s  absent or i s very r e s t r i c t e d i n i t s d i s t r i b u t i o n . a l t e r a t i o n i s developed of b i o t i t e h o r n f e l s .  In a d d i t i o n , b i o t i t i c  adjacent to the composite stock as an annular zone  Most of the b i o t i t i c zone belongs to the p r o p y l i t i c  f a c i e s but a small part i n the northeast belongs to the potassic f a c i e s .  Superimposed on pervasively altered rocks are at l e a s t four stages of sulphide-bearing veins and a l a t e stage gypsum-bearing f r a c t u r e cleavage.  190 Many e a r l y veins o f the quartz stockwork (Stages 1 and 2) have l i t t l e e f f e c t on w a l l rocks although some veins have metasomatic quartz-orthoclase selvages or s e r i c i t i c a l t e r a t i o n envelopes.  Younger veins (Stages 3 and 4)  generally have a l t e r a t i o n envelopes or bleached margins i n which r e t r o gressive metamorphic reactions have taken place, most commonly b i o t i t e and feldspars are degenerated  to fine-grained mixtures of q u a r t z - s e r i c i t e -  chlorite-carbonate-clay minerals.  A l t e r a t i o n zones are centred on and encompass the composite stock.  The various a l t e r a t i o n assemblages can be interpreted to r e s u l t  from temperature  gradients i n the stock and outward from i t s contact;  differences i n bulk composition between quartz monzonite and the quartz d i o r i t e and a n d e s i t i c country rocks; changes i n hydrothermal  f l u i d s with  time as the i n t r u s i v e system cooled; and changes i n hydrothermal  fluids  due to flow o f j u v e n i l e f l u i d s outward from the stock, p o s s i b l e i n t e r action with meteroic or connate f l u i d s , and flow of mixed source f l u i d s upward along the margins of the stock as modelled by Norton ( 1 9 7 5 ) T h e core of the i n t r u s i o n contains an average 1,500 ppm copper and country rocks contain about 75 ppm copper, thus, large quantities of hydrothermal solutions must have passed through the margin of the stock and adjacent country rocks i n order to produce the large zone containing greater than 0.2 per cent copper.  The extensive zone of b i o t i t i c a l t e r a t i o n surrounding the stock ( b i o t i t e hornfels) cannot have formed s o l e l y by thermal metamorphism through conduction of heat from the stock.  The zone had to be expanded  by convective heat transfer by outward flowing f l u i d s .  However, there i s  no evidence except where some orthoclase veins are present i n the northeast t o suggest that the zone o f b i o t i t i c a l t e r a t i o n had any potassium  —  191 enrichment.  Therefore, most o f the b i o t i t i c zone cannot be included i n  the zone of potassic a l t e r a t i o n and b i o t i t e hornfels i s a contact a l t e r a t i o n type.  I t could have formed i n a n d e s i t i c rocks s o l e l y i n response to  increased temperature and i s equivalent to the albite-epidote f a c i e s o f contact metamorphism.  Data from a study o f a few two and three-phase f l u i d i n c l u s i o n s from Stage 1 veins from quartz monzonite with p h y l l i c a l t e r a t i o n and b i o t i t e hornfels i n d i c a t e that hydrothermal f l u i d s , at least i n e a r l y v e i n stages, were highly s a l i n e and at temperatures well i n excess of 406 degrees c e n t i grade.  There i s no evidence that Stage 1 and 2 quartz veins i n the p h y l l i c  zone were deposited from c o o l e r or l e s s saline f l u i d s .  Younger veins con-  t a i n two-phase i n c l u s i o n s and probably were formed from cooler and l e s s saline s o l u t i o n s .  Some evidence f o r b o i l i n g i s suggested by f l u i d i n c l u s i o n s i n Stage 1 and 2 v e i n s .  The b o i l i n g was sustained or repeated and hydrothermal  f l u i d s were probably maintained under conditions of h y d r o s t a t i c pressure. Recurrent b o i l i n g might have occurred during emplacement of each vapoursaturated phase of the stock and i t i s possibly during periods of b o i l i n g that successive periods or stages of f r a c t u r i n g and vein f i l l i n g "took place.".  Interaction of j u v e n i l e and meteoric solutions has not 'been proven.  Possibly the best evidence for.a convective hydrothermal regime  involving groundwater i s the presence and confinement of gypsum to l a t e subhorizontal fracture cleavage i n the zone of mineralization.  Gypsum  p r e c i p i t a t e s from aqueous s o l u t i o n as temperature increases and, thus, inflowing sulphate-bearing groundwater that was heated during l a t e cooling of the composite stock might be the dominant factor i n gypsum deposition.  192 FIGURE 38  BERG DEPOSIT Idealized Geological Sections SECTION 9800 E  6000'  (LOOKING WEST)  5000' 1525m  1Z000N  19,000 N  SECTION A-A'  4000'  21000N  6000'  SEE FIGURE 4  (LOOKING NORTHWEST) .t t '  ++++  ±+*+$ + + +  5000' 1525m  +++ + + + + +++>**;  ++++++  /'+ + + + + + + + + + + + * • + * * * * „<f+++++++ + + + + + + * * * * * * * , .  • , *• > -'  F++++++++++++++*«*********!  0  v>l " - - 1 /  1  - /J/  300 SCALE-METRES  0 1=  1000 SCALE-FEET  I ;.*;*;*. -.j Chalcocite blanket 1  1 i 0.2% Co (primary) Intrusive Breccia  o o o  t t t ±  ±  Q F Porphyry PBQ Porphyry  Porphyritic Q M r  1  :','oi.' Qfz Diorite  QP Porphyry  Gyptum Surface Marks Commencement of G y p s u m - F i l l e d Fractures at Depth  HazeltonGroup volcanic rocks  193 .Mineralization at Berg deposit i s assocaited with a l l rocks of the composite stock except the youngest phase (quartz feldspar porphyry) and r e s u l t e d i n deposition of p y r i t e , chalcopyrite, and molybdenite i n an area approximately  7,000 feet i n diameter.  Zones with these minerals are  centred on the weakly mineralized stock and surround i t as concentric, p a r t l y overlapping s h e l l s or c y l i n d e r s i n which one mineral dominates. This r e s u l t s i n l a t e r a l zoning of primary ore minerals.  Molybdenite  is  most abundant along the contact of the stock where a quartz stockwork i s best developed.  Chalcopyrite i s most abundant at the outer edge of the  molybdenite zone about 100 to 200 feet from the quartz monzonite contact as f r a c t u r e f i l l i n g i n b i o t i t e h o r n f e l s and i n quartz d i o r i t e along the northeast part of the mineralized zone.  Best copper grades are found i n  quartz d i o r i t e where intergranular permeability has produced  disseminated  as w e l l as f r a c t u r e - c o n t r o l l e d m i n e r a l i z a t i o n . P y r i t e i n the i n t r u s i v e core i s 2 per cent or l e s s and increases outward to an average of about 6 per cent i n the p y r i t i c halo that surrounds the chalcopyrite zone. Oxidation and leaching during weathering and attendant supergene processes have r e s u l t e d i n development of pronounced v e r t i c a l zoning i n the deposit (Figure 38).  An extensive leached capping has formed to a  depth of 125 feet and a zone of supergene copper enrichment (with an enrichment f a c t o r of 1.25) 300 f e e t .  i s developed  to a maximum thickness of around  The depth l i m i t to which supergene processes have been e f f e c t i v e  i s marked by presence of gypsum i n f r a c t u r e s . This datum which c l e a r l y marks the l i m i t of primary sulphides i n diamond-drill holes i s c a l l e d the •gypsum l i n e . ' In the leached capping under a c i d i c o x i d i z i n g conditions (measured pH 2.8  - 5.9  and Eh 0.4  - 0.9 v o l t s ) p y r i t e , chalcopyrite, and  194 some molybdenite are leached.  Copper has been removed; molybdenum i s  immobile and present i n ferrimolybdite and a number of poorly  defined  limonite compounds that, where abundant, cause molybdenum enrichment; and i r o n i s p r e c i p i t a t e d l o c a l l y or redeposited (goethite and j a r o s i t e ) .  elsewhere as limonite  Berg deposit i s one of the rare deposits i n the  Canadian C o r d i l l e r a that contains economically s i g n i f i c a n t supergene sulphides.  The deposit might be unique i n that supergene enrichment i s  probably a post-Pleistocene  phenomenon.  Economically important supergene enrichment has taken place where highly fractured (crackled) rocks are leached of gypsum allowing an i n f l u x of leach s o l u t i o n s .  Solutions are reduced and neutralized i n the zone of  groundwater saturation where replacement of primary sulphides by and chalcocite (mainly digenite) takes place.  covellite  In margins of basic dykes  and i n a t h i n zone at the top of the water table where supergene sulphides are being oxidized during f l u c t u a t i o n s of the air-groundwater i n t e r f a c e , native copper, copper oxides, carbonates, and possibly traces of hematite are  deposited.  Origin of the supergene zone i s by contemporaneous ongoing processes that were i n i t i a t e d , at earliest", during deglaciation following Fraser g l a c i a t i o n ( c i r c a 10,000 years B.P.).  I t i s most u n l i k e l y on  basis of mineralogy and i n c i p i e n t replacement textures observed that  the an  older, mature enrichment blanket has survived alpine g l a c i a t i o n .  Minor elements i n p y r i t e display l a t e r a l zoning around the composite stock i n a manner s i m i l a r to a l t e r a t i o n and sulphide  zoning.  Elements found to be most u s e f u l are Co and N i , moderately useful are Zn, Ag, B i , and Mn,  and p o s s i b l y u s e f u l are As, Cu, Mo,  and T i .  Pb,  195 Data were examined and compared e a s i l y by p l o t t i n g histograms. These i n f e r r e d that minor elements are lognormally d i s t r i b u t e d and are polymodal.  Another e f f e c t i v e method of data presentation i s using cumulative  p r o b a b i l i t y paper.  P r o b a b i l i t y p l o t s are e f f e c t i v e i n resolving and des-  c r i b i n g polymodal populations.  One cause of polymodal data as indicated  by histograms, t and F t e s t s , and cumulative p r o b a b i l i t y curves i s mixing of v e i n and disseminated p y r i t e .  There i s an i n d i c a t i o n that the i d e n t i t y  and quantity of some minor elements i s influenced by host rock but t h i s has not been demonstrated to be a general p r i n c i p l e .  Associations between paired v a r i a b l e s were demonstrated using c o r r e l a t i o n and simple regression analyses.  Most s i g n i f i c a n t c o r r e l a t i o n  and i n t e r r e l a t i o n s h i p s are between Co-Ni and Pb-Zn.  Cobalt-nickel r a t i o s  and regression p l o t s show wide ranges i n p y r i t e from Berg deposit.  Use of  such p l o t s might enable d i f f e r e n t types of p y r i t e from the same deposit to be grouped but genetic c l a s s i f i c a t i o n of mineral deposits based on cobaltn i c k e l and probably other element r a t i o s or quantities i s tenuous.  Associations between samples based on multiple elements were -demonstrated using Q-mode f a c t o r a n a l y s i s .  Four factors accounted f o r 81  per cent of t o t a l sample v a r i a b i l i t y and were considered to be g e o l o g i c a l l y meaningful.  Two f a c t o r s might be related to amount of minor element sub-  s t i t u t i o n i n p y r i t e — o n e measuring t o t a l cation substitution and the second measuring anion s u b s t i t u t i o n i n the p y r i t e l a t t i c e .  The remaining two  f a c t o r s are interpreted to represent areas with s i g n i f i c a n t concentration o f c e r t a i n minor elements from host rocks or hydrothermal f l u i d s .  Contoured concentrations of i n d i v i d u a l and composite minor elements and f a c t o r values reveal zoning i n which p y r i t e with highest minor element  196 concentrations coincides with the zone of best copper mineralization and only modest amounts of p y r i t e .  This refutes Ovchinnikov's (1967) statement  that highest concentrations of minor elements i n a host mineral w i l l where that mineral i s most abundant.  occur  Instead, i t appears that minor elements  are most abundant i n zones of best m i n e r a l i z a t i o n , that i s , zones where other metal sulphides are abundant i n a d d i t i o n to p y r i t e .  This observation  Is i n accord with studies by Kurz, Brownlow, and Park (1975).  Thus, a high  degree of contamination of p y r i t e by impurity elements might be u s e f u l as a guide to ore and can be a favourable i n d i c a t i o n of ore p o t e n t i a l .  Comparisons between Berg deposit and the ' t y p i c a l ' porphyry copper deposit of Lowell and Guilbert (1970) are generally v a l i d .  Of the 40  c r i t e r i a used to define the i d e a l i z e d ' t y p i c a l ' porphyry copper deposit, Berg prospect i s equivalent i n 30 categories, and p a r t i a l l y s a t i s f i e s another f i v e c r i t e r i a .  It i s not equivalent to f i v e categories and  these  are:  1.  Host rocks at Berg deposit are Middle J u r a s s i c v o l c a n i c s , not Precambrian to Cretaceous sediments and metasedimentary rocks.  2.  Diameter of the mineralized i n t r u s i o n at Berg deposit i s smaller (2,100 feet as opposed to 4,000 by 6,000 f e e t ) .  3.  A l t e r a t i o n patterns are not equivalent, e s p e c i a l l y with respect to b i o t i t i c a l t e r a t i o n ( b i o t i t e h o r n f e l s ) .  A l t e r a t i o n i s more  equivalent to models revised by Guilbert and Lowell (1974) i n which importance of volcanic rocks are stressed. 4.  'Typical' porphyry copper deposits have 70 per cent of ore i n i n t r u s i v e rocks and 30 per cent i n country rocks. deposit these quantities are reversed.  At Berg  -  197 5.  (Grade of copper a t Berg deposit i s about one-half that of ' t y p i c a l * porphyry deposits (0.4 versus 0.8 per cent copper i n the supergene zone; 0.2 versus 0.45 per cent copper i n the hypogene zone).  Molybdenite at Berg deposit i s 3.5 times more  abundant than that i n ' t y p i c a l ' porphyry deposits (.055 versus .015 per cent molybdenite).  In the terminology o f T i t l e y (1972), porphyry deposits i n southwestern United States (those described by Lowell and G u i l b e r t , 1970) are 'intrusion porphyry copper deposits;' the Berg deposit t y p i f i e s a number of deposits i n the Canadian C o r d i l l e r a that can be c a l l e d 'wall rock porphyry deposits.'  Sutherland Brown (1969) described Berg deposit as a 'simple'  type porphyry deposit because annular zones of a l t e r a t i o n and m i n e r a l i z a t i o n are regular and p e r s i s t e n t and symmetrically arranged around a p l u g - l i k e intrusive core.  More r e c e n t l y (1974) he has c l a s s i f i e d i t morphologically  as a 'phallic-type' porphyry deposit, one i n which a simple steep-walled plug penetrates host rocks.  A model suggested by t h i s study i s an orthomagmatic one i n which an inherently copper-molybdenura-rich  stock of quartz monzonite composition  has intruded, a l t e r e d , and mineralized enclosing volcanic rocks and part of a quartz d i o r i t e stock. :  During f i n a l c r y s t a l l i z a t i o n of the stock a  :  w a t e r - r i c h f l u i d phase evolved and migrated i n t o e a r l y c r y s t a l l i z e d parts :  of the i n t r u s i v e body and intensely fractured w a l l rocks.  Onset o f hydro-  thermal a c t i v i t y Is regarded to be when convective heat exchange i n v o l v i n g a f l u i d took place between the c r y s t a l l i z i n g stock and country rocks. i n i t i a l hydrothermal  The  f l u i d was l a r g e l y heated connate or meteoric waters  whose flow was c o n t r o l l e d by intergranular and fracture permeability and  198 resulted i n a pervasive zone of b i o t i t e hornfels around the stock. Extensive flow of hydrothermal f l u i d s along the margin of the stock  was  sustained by successive emplacement and c r y s t a l l i z a t i o n of at l e a s t four major Intrusive phases. .The  bulk of a l t e r a t i o n and sulphide minerals are  fracture controlled and were deposited during emplacement of the l a t t e r i n t r u s i v e phases.  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(1961): Some Preliminary Observations on the T h e o r e t i c a l Geochemistry of Molybdenum under Supergene Conditions, A r i z . Geol. S c i . Digest, V o l . 4, pp. 103-116. -•Toulmin, P. and Clark S. P. (1967): Thermal Aspects of Ore Formation, i n Geochemistry of Hydrothermal Ore Deposits, H. B. Barnes, e d i t o r , pp. 437-464, Holt, Rinehart, and Winston, Montreal. White, D. E. (1968): Environment of Generation of Some Base-Metal Ore Deposits, Econ. Geol., V o l . 63, pp. 301-335. White, D. E., M u f f l e r , L.J.P., and Truesdell, A. H. (1970): Vapour-dominated Hydrothermal Systems Compared with Hot-water Systems, Econ. Geol., V o l . 66, pp. 75-97. Whitney, J . A. (1975): Vapour Generation i n a Quartz Monzonite Magma: A Synthetic Model with Application to Porphyry Copper Deposits, Econ. Geol., V o l . 70, pp. 346-358.  210 Wilson, J;D.S. and S i n c l a i r , A. J . (1969): Q-mode Factor Analysis Applied to Mineral Exploration Data, i n Proc. of Symposium on Decision-making i n Mineral Exploration I I , UBC Extension Dept., pp. 244-257. Winkler, H.G.F. (1965): Petrogenesis of Metamorphic Rocks, Springer-Verlag New York Inc., New York, 220 pp. Woodsworth, G. J . (1971): A Geochemical Drainage Survey and i t s Implications for Metallogenesis, Central Coast Mountains, B r i t i s h Columbia, Econ. Geol., V o l . 66, pp. 1104-1120.  APPENDIX A  CHEMICAL ANALYSES OF QUARTZ MONZONITE PORPHYRIES  DDH 19 (126 - 300 feet)  QMP  sio  2  DDH 1 (626 - 640 feet; 645 - 672 feet) PBQP  67.54  62.50  A1 0  3  15.62  15.12  Fe 0  3  1.16  1.64  0.76  0.85  0.30  0.18  CaO  1.02  2.39  MgO  1.04  1.49  0.51  0.51  3  1.92  4.53  MnO  0.02  0.06  Na 0  2.76  3.13  5.06  4.55  H 0+  1.32  2.18  H 0-  0.31  0.95  co  2  0.02  0.01  BaO  0.12  CuO  0.38  2  2  FeO P  2°5  Ti0  so  2  2  K  2° 2  2  M0O3  PbO 99.86  100.09  Samples submitted by N. C. Carter, 1967. Analyses by S. Metcalfe, A n a l y t i c a l Laboratory, B r i t i s h Columbia Department o f Mines and Petroleum Resources, 1968.  212 APPENDIX B  ALTERATION:  CATALOGUING OF CORE AND  ESTIMATION OF ALTERATION INTENSITY  A l l d r i l l core a v a i l a b l e to 1971 d r i l l holes) was examined i n d e t a i l .  (26,184 feet i n 49 diamond-  A l t e r a t i o n minerals and  their  abundances from 10-foot i n t e r v a l s were noted; these include:  quartz  (veins and pervasive s i l i c i f i c a t i o n ) , b i o t i t e , c h l o r i t e , s e r i c i t e (including muscovite), magnetite, c a l c i t e , gypsum, orthoclase, epidote, and clay minerals.  Less common a l t e r a t i o n minerals include anhydrite,  tremolite, hematite, dolomite, sphene, and r u t i l e .  In supergene zones  limonite was described according to colour, abundance, and texture.  Differences i n appearance of cores and hand specimens were used i n i t i a l l y to define s i g n i f i c a n t grades or ranks of a l t e r a t i o n intensity.  Various a l t e r a t i o n types are c l e a r l y associated with c e r t a i n  sulphide mineral concentrations.  Later, examination of t h i n sections and  laboratory studies (C. L. Dahl and D. Norton, 1967, private report, Kennecott Copper Corporation) described rock types more completely. From these f i e l d and laboratory descriptions, standardized core logging procedures and a l t e r a t i o n i n t e n s i t y ranking were devised and followed throughout t h i s study.  A l t e r a t i o n i n t e n s i t i e s were i n i t i a l l y described on a r e l a t i v e scale and l a t e r q u a n t i f i e d corresponding to: moderate ™ 5, and strong = 7.  trace = 1, weak = 3,  For b i o t i t e , s e r i c i t e , c h l o r i t e  epidote), and quartz, weak, moderate, strong correspond t o :  (including  l e s s than  10 per cent, 10 to 25 per cent, more than 25 per cent of the rock volume. Quantity of b i o t i t e , s e r i c i t e , and c h l o r i t e could be estimated using colour  213 index.  Quartz was measured as volume of quartz veins and amount o f  pervasive s l l i c i f i c a t i o n estimated from scratching core with a k n i f e . Amount of c a l c i t e was estimated by observing and l i s t e n i n g to response of u n s p l i t d r i l l core to 5 per cent HCI sprayed on a 10-foot s e c t i o n of core. ... Magnetite content was estimated from response of a suspended magnet to s p l i t core.  Abundances of other minerals were recorded as number of grains  or veins per 10-foot section of core.  Clay minerals (less than 2-micron-sized f r a c t i o n i n crushed diamond-drill core) were separated from 46 representative specimens using a water suspension and c e n t r i f u g i n g technique (Appendix C).  A satisfactory  separation of various-sized f r a c t i o n s was attained, thus enabling cation by X-ray d i f f r a c t i o n and comparison of d i f f e r e n t - s i z e d Untreated, g l y c o l a t e d , and heated specimens were X-rayed  identifi-  fractions.  to i d e n t i f y and  estimate abundances of s e r i c i t e ( l o A ) , k a o l i n i t e (7A) and c h l o r i t e (14A) i n the manner described by C a r r o l l  (1970).  Ranked values of a l t e r a t i o n I n t e n s i t i e s of a l l abundant hydrothermal minerals were averaged over the entire d r i l l hole i n v e r t i c a l holes or averaged over long i n t e r c e p t s i n angle holes.  Contoured  rank values  define concentrations o f i n d i v i d u a l and related a l t e r a t i o n minerals and define zoning patterns (Figure 8).  214 APPENDIX C  CLAY SEPARATION TECHNIQUE  The  <2 micron-sized f r a c t i o n from crushed d r i l l core was  separated f o r q u a l i t a t i v e X-ray d i f f r a c t i o n determination of clay mineral content.  The technique developed by C. Pharo, D. G. C a r g i l l ,  and the w r i t e r i s a simple routine procedure that r e s u l t s i n quick and e f f e c t i v e separation and recovery of fine-grained m a t e r i a l s . The technique i s based on Stokes Law and uses both gravity s e t t l i n g and centrifuging i n water suspension.  Material used i n t h i s study was  approximately 5 grams of assay pulp (-100 mesh, 60 per cent -200 mesh crushed d r i l l  core).  REDUCTION OF SAMPLE SIZE Sample s i z e can be reduced by gravity s e t t l i n g i n a water suspension.  Assuming a mean sample s p e c i f i c gravity of 2.65 and with  a 5-centimetre suspension depth, s e t t l i n g times f o r various-sized f r a c t i o n s are as follows: P a r t i c l e Diameter in Suspension  Time Required  Time Required  Microns  @ 20° C  @ 25° C  22 seconds 2 minutes 20 seconds 37 minutes 30 seconds  20 seconds 2 minutes 5 seconds 33 minutes 20 seconds  < 50 <20 < 5  In  t h i s study a 22-second s e t t l i n g time to recover the  sized f r a c t i o n was used.  <50-micron-  215 RECOVERY OF < 2 MICRON-SIZED FRACTION FROM SUSPENSION  The water suspension containing <50-micron-sized f r a c t i o n was centrifuged to r e t r i e v e the  <2-micron-sized f r a c t i o n .  Centrifuging  time (t min) i s a function of centrifuge speed (RPM) and can be c a l c u l a t e d from the following r e l a t i o n which i s a modification of Stokes Law:  63.0 x 1 0 ^  twin  log  1 0  J  j  (Nm) ( D ) ( A S )  I  »  ~" ^ f ? ' j  Z  U  }  < £ ^  f  P  .-icenrrlfuae vessel  rotation  where: R • radius of r o t a t i o n to top of sediment S «• radius o f r o t a t i o n to top of suspension Nm - RPM  t\ « v i s c o s i t y i n poises (.00958) DL< • p a r t i c l e diameter ( i n microns) A S = d i f f e r e n c e i n s p e c i f i c gravity between p a r t i c l e s and solvent  Times used i n t h i s study: <2 micron f r a c t i o n @ 1000 RPM - 3.5 minutes @ 1250 RPM - 2 minutes 55 seconds <5 micron f r a c t i o n @  \  660 RPM - 1 minute 18 seconds  APPENDIX  D.  F L U I D I N C L U S I O N DATA H0M0GENIZATION  SPECIMEN  MINERALOGY  VEIN STACE  HOST  TEMPERATURE  PHASES  SHAPE  ABUNDANCE  (in 71-632 A, B, C  Qtz-MoS -py  1  Quartz  Irregular,  Many  ovoid  cp-anhya  2  ( L , V) and 3 ( L , V,  V  -  1 t o 70%, S -  S)  NaCl,  25-442  1 or 2  Qtz-MoS,  Quartz  Rare  Round  Many  Irregular  2  Calcite  Amygdule  Calcite  Rare  Rod-like,  12-191  Gyps-py-  4  Gypsum  Rare  Rod-like  tetrahed-gal-  ovoid  2  ( L , V) and 3  V  - 1 t o 7 0 % , 2 0 % common  1  12->406 1-392+15  ( L , V)  S HS22.6.A  ( L , V,  S) 6-  NaCl  (L), L  (C0  2  and b r i n e )  N.D. N.D.  1 (L)  (Selenite)  sphal 30-363  Gyps-carbonate-  4  Sphalerite  HS-M1 MS-M2  Qtz-MoS  2  •  Qtz-carbonate-  Few i n p a l e growth  sphal-gal-py  Qtz-calcite-  2  ( L , V) V  cavities  L  (C0  Negative X l  2  - 10 t o 2 0 %  N.D.  and b r i n e )  1 or 2  Quartz  Many  Irregular  2  ( L , V ) , some 3 ( L , V , S )  N.D.  4  Quartz  Few  Negative x l  1  ( L ) and r a r e 2  N.D.  ( L , V)  cavities  py-sphal-gal  1-583  zones  4  Selenite  Rare  Rod-like  selenite-py  1  ( L ) , very  V  - 0 t o 2%  rare 2  ( L , V)  N.D.  sphal-gal  3-72A  Quartz-MoS.  1 or 2  Quartz  Many  Negative x l  2  ( L , V) and 3  cavities  V  - 20 t o 5 0 % , S -  ( L , V, S)  N.D.  NaCl,  opaque 3-72B  Qtz-(carbonate?)py  3  Quartz  Many  Negative x l cavities  C)  1-248+2  opaque Anhydrite  °  2 and 3 phases indeterminable  - details  N.D.  406  HOMOGENIZAXICN SPECIMEN  71-655  MINERALOGY  V E I N STAGE  Qtz-anhydrite-  1?-  HOST  ABUNDANCE  (in  Ellipsoid  2  (1, V), V  Rare  Rod-like  1  (W  Few  Ellipsoid,  Quartz  Rare  Anhydrite  • •  py-cp-carbonate  Qtz-anhydrite-  71-718  MoS  1  Quartz  round  -cp-py-  carEonate-chlorite Anhydrite 71-677A  71-677B  Qtz-cp-pyMoS_-chlorite  1  Qtz-anhydrite-  1  py-MoS HS-Sanfts  vein  • Quartz  Quartz  Quartz  Gyps-tetrahed-py-  2  (L, V), V  Many  Irregular, ellipsoids , negative xl cavities  1  ( L ) , mainly  and  Many  Negative  Qtz-chalcedony  Many  x l  cavities,  ellipsoid  3  ( L , V, S)  N.D.  N.D.  - 20 t o 3 0 % 2  (L, V),  N.D.  ( L , V, S)  S  - minute  NaCl x l s  2  ( L , V ) , some  3 ( L , V, S)  N.D.  minute NaCl x l s N.D.  Indeterminable  N.D.  None  4  recognized  cp HS-22.6.B  ( L , V) a n d ? 3 - 5 t o 40%  ° C)  ( m i n u t e < 1y* )  gal-sphal 12-191  2 V  Cubes  ovoid, 4  • 5 t o 10%  Few  2  Qtz-carbonate-py-  TEMPERATURE  PHASES  SHAPE  Geode  Quartz  Rare  (in  xlline  Elongate  core)  1 V?  (L) and 2 ( L , V?)  liquid Rare  ( i n rim) Ovoid  N.D.  - 0 t o 1% ( V may b e C0 ) 2  1 (L)  >3  218 APPENDIX E  MINOR ELEMENTS IN PYRITE:  SAMPLE VARIABILITY  The quantity and composition of minor elements (trace elements) i n p y r i t e are c o n t r o l l e d by both the environment of formation and the supply of elements.  Four mechanisms are commonly used to explain the  manner by which elements are incorporated i n p y r i t e . +2 (i)  S u b s t i t u t i o n or proxy of c e r t a i n elements f o r Fe  -2 and S  in  true s o l i d s o l u t i o n , (ii)  Accommodation of elements i n t e r s t i t i a l l y between l a t t i c e s i t e s or at s i t e s o f l a t t i c e defects and along growth surfaces,  (iii) (iv)  Adsorption, Inclusion as minute discrete grains of other mineral phases. The wide v a r i e t y of minor elements and t h e i r ranges of concen-  t r a t i o n are summarized by Fleischer (1955).  There are numerous other  studies reported i n the l i t e r a t u r e but a p a r t i c u l a r l y l u c i d summary of minor elements i n p y r i t e s from a variety of environments i s by M i t c h e l l (1968).  He s t a t e s :  'From a consideration of metal-sulphur bond lengths  i n sulphides, stereochemistry of bonds, and experimentally investigated sulphide phase e q u i l i b r i a , i t i s concluded ( M i t c h e l l , 1968) that T i , V, Cr, Mn, Co, N i , Cu, Zr, Mo, Nb, and Sn can replace i r o n and that As, Se, Te, Sb, and B i can replace sulphur at l a t t i c e s i t e s i n p y r i t e .  The  degree of replacement v a r i e s from trace amounts (Mo) to complete replacement (Co). The incorporation of Zn, Ga, Au, Hg, Pb, Th, and U occurs at defect s i t e s i n the l a t t i c e . '  [Also] ... 'Of. the o v e r a l l trace element  219 assemblage only broad generalizations can be made.  A l l the p y r i t e s  are seen to contain T i , V, Cr, Mn, Co, N i , Cu, Zn, As, and Se.  The  hydrothermal p y r i t e s t y p i c a l l y contain Ag and Sn ....'  The a n a l y t i c a l procedure used i n t h i s study provides  an  i n d i c a t i o n as to the manner i n which elements are incorporated i n p y r i t e (assuming they are not from included g r a i n s ) . uses a two-stage e x c i t a t i o n of samples.  The s p e c t r o g r a p h s method  A short duration f i r s t stage  involves a low-intensity burn i n a i r that releases s o - c a l l e d v o l a t i l e elements Sb, As, Cd, Ag, Sn, and Zn. higher i n t e n s i t y bum  The second stage i s a longer,  i n an argon-oxygen atmosphere that i s used to  determine more r e f r a c t o r y (non-volatile) elements Cr, Co, Cu, Mn, N i , T i , V, and Zr.  Mo,  I t i s evident from M i t c h e l l ' s (1968) conclusions  and other studies that, with the possible exception of Sn, v o l a t i l e elements are those that are incorporated i n p y r i t e by anion s u b s t i t u t i o n , adsorption, and accommodation i n i n t e r s t i t i a l and l a t t i c e defect s i t e s . The n o n - v o l a t i l e elements are cations that substitute f o r i r o n i n l a t t i c e sites.  Two l e v e l s of e x c i t a t i o n energy can be used i n the a n a l y t i c a l  procedure because bond strengths of the v o l a t i l e elements are weaker than those of cations proxying f o r i r o n i n the p y r i t e l a t t i c e .  For a more thorough discussion of p y r i t e geochemistry, one' i s referred to an e x c e l l e n t compendium by Price (1972).  220 APPENDIX F  ELEMENTS DETECTED IN BERG PYRITE  Line s p e c t r a of a large number of elements were checked i n a group of s i x t e e n p y r i t e concentrates c o n s t i t u t i n g an o r i e n t a t i o n sample set.  The samples were examined i n i t i a l l y only on a q u a l i t a t i v e b a s i s .  The following elements were detected i n one or more samples.  Undoubtedly,  some are contaminants from admixed gangue and sulphide g r a i n s : Al Sb As Ba Cd Ca Cr  Co Pb Mg Mn Mo Ni Si  The following were not detected.  Ag Sr Sn Ti V Zn Zr These may be present but i f so,  concentrations are below spectrographic detection l i m i t s : Be B Ce Cb Ga Ge  Au La Pt Re Sc Se  Te Th W U Yb Y  Detection l i m i t s of the spectrographic method used are approximately i n the 0.1 to 1000 ppm range, but each element behaves i n d i v i d u a l l y and has a c h a r a c t e r i s t i c upper and lower l i m i t of detection.  Characteristic  wavelengths and 'index p o i n t s ' of elements f o r which standards were a v a i l a b l e are shown i n Table 18.  The 'index point' i s simply a concen-  t r a t i o n convenient f o r describing c a l i b r a t i o n curves.  Commonly maximum  and minimum detection l i m i t s of elements shown are approximately 10 times and .10 of the 'index points.*  221 TABLE 18. SPECTROGRAPHIC ANALYSIS OF PYRITE ELEMENTS FOR WHICH CONCENTRATIONS WERE DETERMINED  Standard Reference Line:  Element  Wavelength  X Sb As Ba Be Bi B Cd Ca Cr Co Cu Ga Ge  2598.0 2860.5 2780.2 4554.0 4130.6 3130.4 3067.7 2497.7 3261.2 3158.9 4254.3 3453.4 3273.9 2943.6 3039.1  Index Point ppm 370 3200 1800 4.2 330 11 12.5 92 49 2100 18 27 12.5 24 46  Pd 3421.2  I  Element  Wavelength A  Index Point ppm  Pb Mg Mn Mo Ni Ag Sr  2833.0 2779.8 2798.0 3170.3 3414.7 3382.8 4Q77.7 3464.5 3175.0 3361.2 2942.0 3185.3 3345.0 3345.5 3273.1  65 720 54 96 27 4 2.4 225 32 32 1500 100 32 210 57  Sn Ti V Zn Zr  Contamination of p y r i t e concentrates by gangue and sulphide inclusions i i s i n e v i t a b l e . S i to 1 percent, A l to 0.5 per cent, and some Sr, Ba, Mg, Ca, and Zr were detected and are believed to be due to quartz, feldspar, c h l o r i t e , c a l c i t e , or gypsum, and zircon i n c l u s i o n s . Gangue minerals are not considered to be serious contaminants i f they are present i n minute q u a n t i t i e s since most elements introduced are not contained i n the p y r i t e l a t t i c e . Contamination of p y r i t e by other sulphide minerals i s the main source of concern.  The main sulphide contaminant i s c h a l c o p y r i t e .  Polished  sections show that chalcopyrite i s intimately intergrown with p y r i t e i n the copper-molybdenum zone as minute 'encapsulated' grain boundaries and as f i l l i n g s i n micro-fractures.  grains within p y r i t e P y r i t e i n peripheral  volcanic rocks, the p y r i t i c halo zone, and c r y s t a l s from a l l types of veins generally have n e g l i g i b l e chalcopyrite intergrowths.  Five chalco-  p y r i t e samples from d i f f e r e n t areas within the deposit were analysed to determine e f f e c t s o f chalcopyrite contaminations.  Results are shown i n  Table 19.  TABLE 19. Sample No. 1 2 3 4 5 Note:  MINOR ELEMENT CONTENT OF CHALCOPYRITE (IN PPM)  Pb  Zn  Ag  Mn  12 38 23 10 23  180 365 680 16 620  35.0 43.0 1.0 20.0 14.5  .5 8.0 52.0 21.0 26.0  Mo  1.0 12.0 1.0  Sb, As, B i , Co, N i , and Cd were not detected. detection l i m i t .  Ti  Sn  164 DL 38  14.0 5.0  4  8.0  ---  --- means l e s s than  From these data, assuming a maximum chalcopyrite content of 1 per cent i n a p y r i t e concentrate,  i t appears that the only s i g n i f i c a n t  contribution to the a n a l y t i c a l r e s u l t s by chalcopyrite w i l l be copper and possibly minor amount of zinc (e.g., 6.8 ppm i n sample 3). Ag, Mn, Pb, and T i present below the detection  as contamination i n p y r i t e from chalcopyrite w i l l be limit.  Sphalerite i s the second most abundant sulphide contaminant. It i s found mainly i n the vein and b r e c c i a specimens and a few samples from outside the copper-molybdenum zone.  Analysis of a s i n g l e sample of  zoned, pale to medium brown sphalerite gave the following r e s u l t s : Pb As Cu Ag Mn  1000 6300 6800 250 2350  ppm ppm ppm ppm ppm  Ti Sb Cd Fe  80 990 22,000 10,000  ppm ppm ppm ppm  Note:  B i , Co, N i , Mo, and Sn were not detected.  223 Sphalerite with t h i s composition would contribute a number of elements i n s i g n i f i c a n t amounts to a n a l y t i c a l r e s u l t s f o r p y r i t e .  However,  based on t h i s and other analyses of mixed p y r i t e - s p h a l e r i t e g r a i n s , Cd appears to be always present and i s , thus, useful as an i n d i c a t o r of s p h a l e r i t e contamination.  Every p y r i t e analysis containing Cd  (seven  from the t o t a l 100 samples) also contains high values of Zn and commonly Mn, Pb, and Ag.  In a l l these seven cases i t i s assumed that s p h a l e r i t e  i s present and only a n a l y t i c a l values of B i , Co, N i , Mo, and Sn ( i f present) were u t i l i z e d .  Other p o t e n t i a l contaminants are molybdenite, galena, t e t r a h e d r i t e , and c o v e l l i t e , but these can be avoided by c a r e f u l sample s e l e c t i o n and hand p i c k i n g of p y r i t e grains.  APPENDIX G. As  Sample HORNFELS 1-260  620  Mn  Bi  Co  Ni  Cu  Pb  Zn  Ag  Mo  Ti  1.0  728 740 900  106 106 108  500 460 C  92 52 97  216 134 120  14.0 10.0 8.5  8 2 12  210 245 C  416 370  62 45  300 C  52 107  26 21  4.0 5.5  46 20  230 485  1100  820  C  46  35  3.0  C  C  1150  770  C  12  18  4.0  C  310  7.5  3-267 4-220  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM)  3.0  5-248  5.0 13.0 10.0 1.0  8-271  510  16.0  .760  162  C  140  95  18.0  C  C  7.0  8-490  820  18.0  1320  405  C  102  68  49.0  C  355  11.5  10-253  48.0  740  114  C  52  55  7.0  C  600  12-430  10.5 7.0  785 590  78 67  C C  15 10  23 17  12.5 4.5  54 83  480 390  4.0 5.0  410  44  C  15  33  5.0  6  310  4.0  355  50  C  20  28  2.5  1  142  16  370  12  8  3.0  600  172  C  92  82  17.0  12-597 13-385  700 9.0  13-693 14-432  NOTE:  11.0  C. 190  C  C  A blank space denotes not detected; C denotes greater than maximum detection l i m i t .  Sn  Cd  APPENDIX G.  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued Zn  Ag  Ti  Mo  Mn  Cu  Pb  C C  13 8  31 29  3.5 35.0  35  650  22  46  7.0  115 93  168 142  500 490  21 12  16 21  2.5 2.5  3.0  70  128  100  13  15  1.5  18-232  1.0 1.5  260 325  60 60  240 c  12 21  16 46  2.5 3.0  19-465  9.0 18.0  460 570  244 265  160  75 110  36 36  3.5 4.5  20-295  4.5  600  260  68  84  7.0  22-197  448  44  215  11  13  7.5  6  475  23-328  980 600 385 485  6.8 60 34 58  C C  9 17 12 21  10 230 12 8  5.5 8.0 8.0 3.5  5 1  64 50 29 20  1.0 2.0  650 630  70 63  630 C  25 23  33 22  8.0 6.0  19 1  300 240  10.0 5.0  25-165  21.5  70  47  196  19  12  2.0  4  26-437  11.0 10.0  188 180  32 31  181  28 64  17 51  8.0 12.0  1 4  395  5.0 9.0  Sample  As  HORNFELS (continued)  14-727  14-1163  400  15-187 17-105  23-434  •  600 450  Bi  Co  Ni  5.0 8.0  700 820  128 175  2.0  420  2.0 4.0  C  640 640  C  63 11  148 215  5.0 12.0  C  6 1  560 500 C  7.0  1 6  385  4.0 5.0  17 35  395  C C  5.0 9.5  315  18.5  C  APPENDIX G. Sample  As  Bi  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued  Co  Ni  Cu  Pb  HORNFELS (continued) 1200 26-437 500  3.0 2.5  55 64  17 21  38 10  30 26  27-584  400  55.0  120  74  C  c  C  28-410  300  1.5  390  86  360  48  34  620  62  330  19  1200  550  C  32-277  640  132  33A-558  2050 1280 4.5  35-367  500  35-376 36-582  400 450  37-480  43-281  450  63-141  630 1400  5.0 4.0  Mn  7 6 C  11.0  22  385  53  8.0  6  100  92  28  7.5  c  265  8.0  C  42  13  4.0  C  29  4.0  114 90  880 760  52 44  20 18  7.0 6.5  295  106  C  41  32  7.5  12  C  52.0  670  54  C  58  42  16.0  C  640  4.5  375  70  C  20  15  9.0  C  610  19.0 9.0  550 392  108 94  C C  58 37  27 25  20.0 11.0  86 31  3.0 7.5  560 640  850 1000  198 102  21 16  80 52  1.5 1.0  C  285  66  C  57  41  84.0  4.0 7.0  790 570  310 245  540 400  82 98  36 37  9.0 2.5  2.0  34-316  7 7  Ti  C  29-226 30-325  Mo  Ag  Zn  C  C  47 43  C C  11.5  4.0  C C C  C  9.0  450 210  92.0 81.0  APPENDIX G. Sample  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued  As  Bi  Co  Ni  Cu  Pb  65-129  3050 2290 C C  3.0 3.0 3.5 2.5  340 295 350 275  78 88 100 83  430 390 590 430  320 260 235 220  C C C C  68-74  300  24.0  140  28  103  72  720  230  C  1.0  430  330  17.0  400  71-667  1.0  71-738  HORNFELS (continued)  Ti  Mn  17.0 9.5 8.0 5.0  C C 800 610  140 146 110 152  44  8.0  625  1  8  4.0  55  C  64  20  5.5  26  10  98  360  36  19  9.0  10  64  6.0  950  140  280  7  9  7.0  28  8  20.0  1.0  560  168  C  1  18  2.5  71-420 71-533 71-569  530  Zn  Ag  Mo  Sn  41 54 28 30  7.0  450  71-869  1050  26.0  305  107  C  63  30  18.0  31  380  71-915  400  12.0  435  74  600  105  34  19.0  14  C  5.0  18.0 16.5  1140 570  1150 800  C C  79 29  24 11  96.0 29.0  17 11  610 405  5.0  72-400  Cd  )IORITE  4-446  850  C  445  200  C  C  C  C  C  C  9-155  1190  3.5  600  140  c  67  182  50.0  C  C  8.5 8.0  to >4  APPENDIX G.  Sample DIORITE continued  As  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued  Bi  Co  Ni  Cu  Pb  Zn  Ag  Mo  Ti  Mn  Sn  5.0 18.0  9-430  300  34.0  1040  .285  C  C  100  86.0  C  C  9-724  950  7.5  820  148  C  124  33  29.0  24  C  18.0  10-510  500 400  3.0 4.0  560 510  214 225  C C  192 173  620 367  21.0 18.5  94 86  C C  16.0 9.5  10-803  660  71  C  76  32  19.0  27  C  7.0  16-495  380  172  510  25  26  8.0  8  C  5.5  16-600  300 405  144 164  215 C  16 32  24 37  2.0 4.5  1 8  C C  5.0 15.0  450  130  C  380  C  17.0  7  680  10.6.6  17.0  C  4.0  12.0  t  QUARTZ MONZONITE  1-547  7.5  300  106  c  116  10  20.0  15  C  5-552  5.0  610  225  c  116  118  20.0  C  C  450  91  540  34  20  4.0  36  960  . 76 88 90  50 52 48  325 270  64 16 59  16 13 12  3.0 3.0 2.5  6 7 6  500 530  6-350 6-449  11.0 11.0 11.0  C  11.0 4.0  C ro ro CO  APPENDIX G.  Sample  As  QUARTZ MONZONITE continued  Bi  13.0  6-724 7-235  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued  Cu  Pb  Zn  Ag  Ti  Mo  Mn  Co  Ni  225  104  C  78  49  11.5  C  C  4.0  290  112  C  148  208  25.0  33  C  21.0  C  C  C  3  C  20  C  C  10-683  89.0  77  25  250  11-404  9.5  104  92  C  30  20  5.5  13-134  21.0  90  74  360  21  27  2.5  17-290  2.0  90  47  132  35  44  1.5  3  C  4.0  20-512  3.5  310  122  420  122  69  3.0  4  320  8.0  40.0 34.0  216 216  194 184  55 94  30 73  48 37  0.5 4.5  1 30  500 C  5.0 8.5  24-541  40.0 56.0  160 120  132 84  C C  270 196  38 85  39.0 13.0  C C  20.0 38.0  25-396  21 .0  164  120  180  430  148  17.0  27-358  27.0  86  46  C  C  C  31-337  1.5 2.0  256 230  132 122  175 325  80 270  330 510  3.0 6.0  34-368  2.0  325  140  C  58  260  13.0  21-502  1325 1110  c  Sn  Cd  34  C  C C  6  172  13  C  670 C  87  C  4  5.0 9.5  C ro so  APPENDIX G.  Sample  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued  As  Bi  Co  Ni  1030 900  54.0 38.0  390 332  220 205  C C  212 141  50 42  65.0 29.0  180  50  116  41  18  3.5  35.0  10  8  67  380  72  18.0  72.0  21  17  600  45  16  17.5  23-545  9  8  590  1  9  4.0  52  24-355  9  13  102  1  6  0.5  260  25-165  1  1  15  1  1  0.5  9 4  QUARTZ MONZONITE continued 69-463  Cu  Pb  Ag  Zn  Mo  Ti  51 88  Mn  C C  15.0 12.5  VEIN 1-596 12-191  500  14-261  C  5 C 7.5  144  26-437  850  3.0  60  19  24  28  7  4.5  30-363  900 700  29.0 50.0  29 14  54 56  C 430  360 440  C 215  27.0 34.0  1.0  13  11  30  14  7  1.5  8  6.5  24.0  64  9  180  136  148  36.0  5  4.0  83  loo  122  53  15  8.0  33A-558 35-627 37-390  900  C C  20  7 to  o  APPENDIX G.  Sample  As  VEIN continued 43-355  Bi  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued  Co  Pb  Cu  Ni  Ag  Zn  Mo  Mn  Ti  C  1  1  600  19  8  2.5  148.0  20  6  20  410  300  80.0  11  1.5  5  5  6  290  13  1.5  3  C  69-480  272  34  140  1  14  3.0  6  90  70-515  74 77  54 80  500 305  16 15  34 31  4.0 3.0  38 24  174 122  106  260  600  30  26  3.0  6  71-804  225  72  134  10  7  8.0  174  M.24.6  1  1  60  70  9  1.5  8  15 9  24 18  30 50  290 415  520 C  12.0 3.0  5 18  5 5  53 C  210 450  122 205  3.5 7.0  12 1  17 59  33  24  144  57  34  4.0  3  140  8.0  2400 1300  940 550  42 74  390 350  154 104  11.0 13.0  6 1  C 5  30.0 40.0  68-68  400  2.0  71-580  Fissure  1960 2100 22.0 26.0  M3 3.22.7  C  7  9.5 20.0  6 6  1.0 8.0  13.5 5.0  C . C  3.0 3.0  11 11 84  VOLCANIC ROCKS 3.25.7  Cd  235  7.0  63-251  Sn  APPENDIX G.  ANALYTICAL RESULTS - MINOR ELEMENTS IN PYRITE (IN PPM) - continued  Sample  As  Bi  Co  Ni  Cu  VOLCANIC ROCKS continued 1.8.6  350  2.0  920  570  650  42  128  600  2.0  880  680  C  84  39.0 29.0  550 395  400 360  300" 350  Pb  Mo  Ti  Mn  1.0  148  24.0  173  1.0  220  52.0  130 97  78 98  27.0 25.0  230 215  38.0 34.0  Major  12  180  35.0  164  Major  38  365  43.0  14-1003  Major  23  680  1.0  1  26-437  Major  10  16  20.0  12  71-677  Major  23  620  14.5  1  3.21.6 3.24.6  Zn  Ag  6 5  Sn  Cd  5.0  14.0  28  C  8.0  5.0  5  38  53.0  56  21.0  34  CHALCOPYRITE 1-596 i  10-510  4  26.0  8.0  SPHALERITE 30-363  6300  6800 also:  Sb 990 ppm Fe 1% Cd 2.2%  Major  Major  250  80  2350  N>  233  APPENDIX II  DATA PARAMETERS AND COMPUTED O i l SQUARE VALUES-  ~~ATP~ANT EL EY EV — F A C T O R OATA P A R A M E T E R S VARIABLE  MEAN  STAN  CHI  OEV  A3.5098 .  34.9593  -Z9TTATJT5 15.6186  58.1317  35.4500  CU  200 . 2 9 9 9  215.7057  2 5 . 5140  PB  sfc.649<;  133.1234  25.7593"-  ZN  45.3499  73.26*1  21.5763  AG  10.300C  1 7 . 98C1  35.1719  5.0592  47.9430  Rfl 2.8700 TRANSFORMED CATA P A R A M E T E R S VARIABLE MEAN ;  STAN  CHI  DEV  0.5056  0.7160  28.7609  1 .3046  0.7460  6.7097  NI  1.1044  0 . 6594  5.9948  CU  1w9999  0.5653  15.1119  ~PTT  1.4226  0.8496  1 8.3775  ZN  1.2603  0.5674  12.6403  AG  0 .6644  0.4952  BI  A . P A N T E L g Y E V — PACTOR CATA PARAMET ERS VARIABLE  ANALYSIS--/VARIABLES—MARCH MEAN  -CTJ-  STAN  9.8410  BI DISSEMINATED PYRITE  4S  Si  7.8990 49.9290  0.4354'  0.2750"  N - 61  06 1972-  Ttr NI  N - 20  VAR I A P . L E S — M A R C H  15.8750  BI VEIN PYRITE  ANALYSIS — 8  /S5  Ub ivf<:  CEV  CHI  12.4378  55.1237  312 . 4 6 7 3  14.2432  NI  189.2782  213.124 5  49.7227  PB  76.6718  83.7e64  30.8166  bb . 4 9 T 5 ~  B 7 .6576  4B.4221  14.5852  18.2134  40.6231  12.5966  41 . 3 4 1 6  "TTT AG  7. 3655 T R A N S F O R M t C CATA P A R A M E T E R S VAK 1 ArBrTf~~  SI AN  MEAN  LEV  CHI  0.6784  0.5514  28.4411  CO  2 .5909  0.3326  12.8796  -rrr  -2T09T5  PB ZN  BI  -A-trMN  -07379T-  5.3034  1.7C48  0.3903  6.5861  1.6188  0.3841  5.3026  99  - 0 7 ^ 5 26  J . 4 562  0.5792  0.4999  5 5 . 8327  -C.m  -  APPENDIX I  VARIMAX FACTOR MATRIX, DISSEMINATED PYRITE  "TTPAfftliTffYf V ^ T T C T r r f T ^ X A T V V r ? ~ - 7 A T I n r S - " - VJTPTH 0 6 197T"  VARIMAX FACTOR MATRIX 3 4 2 1 CCM.M. X ID Y 0.3509 0.2281 C.1461 -0.846C C. 9122 1CC8 HI 26 2C26 -0.0685 0.7709 0.1519 0.1252 0.6377 1C06 H326 2060 -0.0829 -0.0137 -0.7158 -0.1071 0.5310 1117 H422 15CE C . 3 1 4 5 0.1360 C . 9 C 8 2 -0.0633 C.946 2 4 F524 066 1911 ~Hfl2T~ T C 9 T T9TT3 ^3 =rrr65vr- - t m " 3 T 8 - - U . 2 3 3 3 •^Tjr65r5— -0.7623 -0.5966 C . 9 6 47 -0.2675 1112 H849 1 9C3 6 - 0 . 6 844 -0.7370 -0.3141 C.6650 - C . 0481 1067 H102 2006 7 0 . 1443 -0.3-999 0.3514 0.6645 -C.4737 919 H124 2032 8 0.3950 0.3201 0.8319 C. E569 -C.0743 917 H125 2042 9 0.2384 -0.2641 0.4C44 0.7941 -C.CC78 80 8 H133 1942 10 0.7489 U.1U510T0T98 — U . I i i i U.M4H 1 U . 6 4 26 H 1 ib 195/ T T 0 . 7 2 0 7 0 .2122 C . 1 5 8 3 C. 7779 -0.4341 1C89 H144 1637 12 -C.1936 0 . 1154 -C.6027 0.4168 -0.0528 1108 HI 4 7 18 37 13 -0.2175 0.8711 0.2C74 0.8949 0.2142 1135 H141 1 £37 14 0.0953 0.3327 - C . 03CC C.7764 0.8C9B 836 hl51 1763 15 0 . 4 9 C 9 0.1270 -0.0316 0.9196 0.8133 771 HI 71 1810 16 (' . 2 5 6 3 —0.7663 04 2 I t 8 f.SAsr- I T - TTTET C . 0 2 5 6 0 .7679 -C.3557 C , 7237 960 1791 H194 18 0. 0831 0.5719 - 0 . 5405 -0.2203 0 ,9587 922 1823 H202 19 -0.5395 -0.155 3 0.8690 -0.2322 1C07 c 56C8 H221 2C75 0.3573 20 0.3234 0 . 6887 -C.3975 c .7418 F2 3A 1049 1777 0.0672 21 -0.1339 0.1112 c ,9964 0.2117 H251 980 1766 0.9598 22 -0.1312 .0.U/B1 , 6583 H264 1 7 38 0.4897" — C . b 6 0 0 580 -nr -C.3388 0.e573 H284 0.1122 1812 0.8645. - 0 . 0 4 6 6 906 24 -0.1277 0.9265 H292 -0.0801 1797 0.8856 -0.0671 881 25 C.21C8 0 .2212 H3C3 - C . 7133 1653 . C . 8665 - 0.514 1 880 26 0.2882 0 . 53*7 H322 -0.6268 1768 0.7754 0.1166 933 27 -0.1657 H335 0.7030 -0.5078 1765 C . 8235 - 0 . 2 C99 1C2 8 28 —U.6521 -a.lB^y — ' J . 267H - C. UC59 - C . 8 8 9 0 IHJ3 ~ Z 9 - H343 1U33 H3 5A 0.3158 C.0521 0.0620 1810 30 1058 - 0 .9286 H365 0.1712 -0.0721 1793 31 1C80 0 • 5 £ 5 -0.12R8 F.374 C . 1 7 5 C C . 5557 C . C789 1735 32 1C79 <-.:49c 0.02C9 H432 -0.5017 0.2889 C.3184 197C 33 icei C.5818 H631 -C.3021 -0.5651 -0.3275 1919 34 631 - C . U452 H6 8U -U.2412 C . /216 1535 0.43/1 / 1'J -0.2650 T T H71A -0.3135 -0.7667 1797 0.2325 0.8105 931 -C.5492 36 H724 ^0.3904 -C.52C9 16C7 - 0 . 2e37 C. 8058 110 5 -0.0381 37 D915 0 . 1459 G . 2 6 S 5 1965 -0.8591 0.8334 1093 -0.4273 38 0543 -0.5874 1977 -0.6587 C.1245 0.9775 11C7 -0.0572 39 C972 -0.4747 19£6 -0:6261 - C . 1432 0.6412 1132 40 1 ',' . 4 1 4 1 , ' ('.2432 If 7 3 2f26 -D.774C L.3584 -4T0.4689 0.1476 - 0 . 6 2 92 -0.0129 C.6377 1C79 2C4E 0803 42 0.5C56 0.6516 0.0727 - C . 4528 0.8946 1949 D16A 1193 43 0.0497 -0.6650 0.2037 0.0497 0.4887 0154 44 icce 2CC7 -0.5029 0 .1435 - 0 . 84 05 C.1129 C. 5926 0555 45 e86 1914 0 . 7266 0 . 42e7 0.2293 -C.3713 0.9022 1R94 0635 46 1049 C.3462 -0.14/2 18S4 C.9334(j.a /84 C649 1C53 0 .5955 C. 7046 -0.2724 1894 0 . 2058 C.9677 Q677 1C76 48 -O.C970 0.4955 0.4633 1872 -0.7073 0.9698 C723 49 805 0.1436 C.2689 -0.2481 1 821 0 . 854 9 0.88 5 3 0114 50 1C6 0.0324 0 . 2720 -0.15C3 193C 0. 9189 C.9420 0131 51 794 C.4483 0.5223 1809 0.6411 0.9858 01 72 52 77 0 0 .2930 0.6B49 —C.349C Terr — C r F G T B 53 "7J2TJ5~ •0.0435 -0.6898 C . 0 5 4 4 , 0 . 8 9 5 8 C215 975 1699 54 0.0238 -0.7595 0.5151 0.8499 Q245 981 1 796 55 -0.3514 -0.4000 C.7072 0.8156 025 3 980 1764 56 0.6442 o .4653 0.0052 C.5688 0.7370 0313 857 1840 57 -0.094B -0.0802 0.2411 C.4771 C. 491 9 - 0 . 1788 0343 1033 1835 58 C T T B T T - - 0 . 2 7 3 3 " -=OTTC73C . 1:594'" - 0 . 4 4 3 8 ~ rwr - T 8 7 5 ~5T" ~E6V4 0 .6931 -0.4258 0.7695 1959 -0.4468 60 HS18 -0.2445 0 .0666 C.0006 C.9291 219C -U. 3TT561 HS32 -0.8684 14.933 15.677 VAP IANCF -0.2189 24.947 55.807 40.874 -0.4131 8 0 . 7 54 25.197 2 5 . 1 9 7 ^fA^TTfWfTv^SCTTjrTr^^ NG • 1 2 3  -U.l'4 84 '  "11  -r  C.8.5 3 0750 9 6 C9 . 134 0 ..3 C4 E 57 60 4  1'  A  H1U .5  -0.3634  U. 142 /  5  0.3180  -o.o/H'r  6 9196S x  -  CUM.VAR.  VARIMAX FACTOR SC OR F MATRIX FACTOR VAKIAULE 81  cn M  pn  -7»r AG MN  9C9 5 356' 388)', 416 1 0 --14 . 41.U  C. -1. -0.  -c.wu --iTnnv  C.l ,23 - 1. 5509 -1.395? 0.9V90 —1V23C0" 0 . 4 1 39 -0.2025 r  1 .. 8 0 --02 6 22.4 37177702-.16.8-471950. 1781 0 -0 . 801 -0B. K21 •-C.-4755 ~0? :0 706715' -11 .27 5 6 6 0 . .537 -1 0.769  235  APPENDIX  VARIMAX  A.PANTELEYEV—FACTOR  VARIMAX  NO 1 2 3 4 6 7 8 9 10 11 12 13. 1A 15 16 17 18 19 20  FACTOR  IO V159 VJ21 V142 V235 V243 V251 V264 V33A V356 V373 V433 V632 V686 V694 V705 V715 V713 VHS1 VHS2 VHS3  J  FACTOR MATRIX, V E I N  PYRITE  A N A L Y S I S — 8 VARI A B L E S — K A R C H 06 1 9 7 2 -  KATRIX  X 1C09 922 1C78 1049 981 SRC 980 10? 8 1058 1079 K 8 l 631 1017 . <=81 931 930 93? 1035 111 5 512  Y 2004 2017 1837 1777 1796 17 f t 1738 1765 1P1C 1735 1 .7C ' 1919 1535 1825 1854 1798 I79t 22<2 2178 1877 c  CCMM. 1 - 0 . 1569 C.e831 0.3321 0.9922 0.369.1 C.7618 -0.8168 C.S283 0.934f -0.9547 -0.6771 0.9666 C . -5378- - . 0 . 1 1 1 6 -0 .3705 C.9831 C . <=274 0.370C 0.8426 -0.1931 0 . 9 2 lb " - 0 . 3 5 6 4 0 . 9 36 2 C.9148 0.2259 0.9664 -0.59C7 0.7914 -C.2982 C.8769 -0.1503 0.8366 C.  6260  C.7957 C.8023 C . "5316 VAR I ANCE C CM.VAR.  A.PANTELEYEV—FACTOR ANAL.VS I S - -8 VAR I M A X F A C T O R S C O R E M A T R I X  -0.3411 0 .6591 0.2 221 29.593 29.593  3 0.0191 0.4681 0.7544 0.3592  -0.1049 -0.6211 0 . 19C9 -0.2348 0.1330 0.8644  - 0 .0278 -0.1718 -0.1418 -0.8875 0.2C83 0 . 1027  - 0 . /049 - C . 1X39 -C.4369 0.6507 0.82C6 0.8490  0 .4468 -0.0251 -0.8454 0.0543 0 . 2 94 8 0 .2788  o . r o 11 -0.8112 -0.4871 0.3473 30.521 60.1 14  -0.5285 -0.0158 C.3475 -0.6849 18.809 78.923  V A R I A B L E S — M A R C H 06  FACTOR VAR I A f l L E  81 CO NI. CU pe ZN AG MN  2 0.8576 -C.2500 0.0708 C.CC68  1.1872 0.3202 0 .061.1 -C.5821 1 .607 4 1.240 3 1.2493 0.6687  4 0.3502 0.1347 -0.2268 -0.3635 0.1070 0.3047 0.9321 0.C542  -n.3307  0.2915 .  -0  1972—  1.0534 -C.2424 -0.1691 1.3282 - 0 . 15C6 0.3754 0.6263 -2.1136  . ~dOO<£  0.1449 0.0994 -0.5409 10.210 89.133  2  -C.6399 1. 8 5 1 7 1 .8628 0 . 6 5 26 - 0 . 1436 0.2182 0.3739 -0.1075  'i'i'i'i  -0.1038 0.C990 0.1269 -0.1665 -0.1245  0.0484 C.6007 0.2145 -2.0786 0.4573 -0.7314 -0.1881 -1.5791  

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