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Metallogeny of the Vancouver-Hope area, British Columbia Ditson, Gwendolen May 1978

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METALLOGENY OF THE VANCOUVER-HOPE AREA, BRITISH COLUMBIA GWENDOLEN MAY DITSON B.S., University of Southern C a l i f o r n i a , 1974 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Geological Sciences) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1978 (c) Gwendolen May Ditson, 1978 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of Brit ish Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Geological Sciences The University of Brit ish Columbia 2075 Wesbrook Place Vancouver, Canada V5T 1W5 D a t e May 24, 1978 ABSTRACT The study area i s characterized by complex terrane encompassing the junction of three major tectonic b e l t s : the Coast Plutonic Belt, the Intermontane Belt, and the Cascade Belt. Examination of the detailed tectonic framework was f a c i l i t a t e d by the construction of a time-space plot which i l l u s t r a t e s the salient features of the s i x small-scale tectonic belts within the area. Subsequent examination of metal deposits was f a c i l -i t a ted by the MINDEP inventory f i l e which supplied location and reference information. Detailed descriptive information on metal deposits was categorized and tabulated with respect to metals, deposit type, host rock formation and host rock type. This data was then integrated into the tectonic framework to outline a metallogenic model for the area. A s i m p l i s t i c model for the evolution of the major features i n the area involves eugeosynclinal and trench-like deposition from Upper Paleozoic u n t i l Jurassic-Cretaceous time when the developing Coast volcanic and plutonic arc collided with the established Intermontane arc on the east. Arc volcanism i n the Coast Plutonic Belt produced the i n i t i a l volcanogenic metal s u l f i d e accumulations i n the area which subsequently were remobilized into adjacent areas during c o l l i s i o n . The axis of c o l l i s i o n contains a major magmatic su l f i d e deposit which probably formed at this time as a result of c o l l i s i o n . Significant mineralization i s found also west of the c o l l i s i o n axis near the deep-seated Hozameen faul t along which gold-rich f l u i d s have formed veins near serpentine bodies. S i m i l a r l y , a large dissem-inated gold deposit occurs i n slate adjacent to the Hozameen fault i n the area of major vein mineralization. Subduction responsible for the Tertiary episode of plutonism and v o l -canism centered i n the Cascade Belt also produced small skarn, vein and porphyry deposits during a subsequent episode of remobilization mineralization. i v TABLE OF CONTENTS ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES i x LIST OF FIGURES x i ACKNOWLEDGEMENTS xiv CHAPTER 1. INTRODUCTION 1 General Statement 1 Definition of the Study Area 3 Methods 3 CHAPTER 2. GEOLOGY AND TECTONIC FRAMEWORK 5 Introduction 5 Time-Space Plot 8 Eagle Plutonic Belt 12 Units Within the Eagle Plutonic Belt 12 Deformation 13 Pasayten Fault 14 Ladner Trough 14 Stratigraphic Units 14 Deformation 16 Hozameen Fault 17 Hozameen Basin 18 Hozameen Group 18 Yale Intrusions 19 Deformation 19 Boundaries 19 V Cascade Belt 20 C-l : Crystalline Core Rocks 22 C-2: Shuksan Thrust Plate 24 C-3: Western Flanking Units 26 C-4: Vedder Mountain Wedge 28 Spuzzum Plutonic Belt 29 Metamorphic Rocks 30 Intrusive Rocks 34 Tertiary Volcanic Rocks 35 Coast Plutonic Belt 35 Pendant Rocks 36 Older Units of Unknown Age 36 Harrison Lake Sequence 37 Fire Lake and Gambier Groups; Pioneer Formation 39 Plutonic Rocks 42 Post-Plutonic Rocks 43 Summary and Discussion 44 CHAPTER 3. METAL DEPOSITS 47 Introduction 47 C l a s s i f i c a t i o n 51 Magmatic 51 Porphyry 51 Skarn 52 Volcanogenie 52 Vein 53 Shear 53 Disseminated and Massive 54 Major Mines and Related Occurrences 54 v i Britannia 54 Geologic Setting and Early Interpretations 54 Current Interpretations 55 Sulfide Occurrences Outside the Britannia Shear Zone 57 Northair 58 Description 58 Genesis 62 Other Deposits i n the Northair D i s t r i c t 64 Giant Mascot 64 Nature and Origin of Ultramafic Rocks 66 Mineralization 66 Occurrences Outside the Giant Mascot Ultramafite 69 Mining Camps Without Major Mines 69 Eagle Belt 71 Summit Camp 71 Jim Kelly Creek Camp 74 Ladner Gold Belt 76 23-Mile Camp 78 10-Mile Creek Camp 80 Harrison Lake D i s t r i c t 82 Fire Lake Camp 84 P i t t Lake 84 Sechelt Peninsula 87 Isolated Past Producers and Important Prospects 87 Zel 87 Gem 89 Other Deposits 89 Summary 90 v i i CHAPTER 4. COMPUTER STUDY 93 Introduction 93 Metal and Deposit Type Abundances 97 Possible Ore Controls 100 Deposit Type 100 Tectonic Belt 104 Mineralization Characterizing Tectonic Belts 112 Distribution of Metals and Deposit Types Among Tectonic Belts 114 Host Rock Formation 115 Distri b u t i o n of Deposit Types and Metals Among Host Rock Formations 117 Mineralization Characterizing Host Rock Formations 121 Eagle Plutonic Belt 121 Ladner Trough 121 Hozameen Basin 123 Cascade Belt 123 Spuzzum Plutonic Belt 123 Coast Plutonic Belt 123 Host Rock Type 126 Distribution of Metals and Deposit Types Among Host Rock Types 127 Mineralization Characterizing Host Rock Types 130 Intrusive Rocks 130 Volcanic Rocks 132 Sedimentary Rocks 134 Deposit Distribution Maps 134 Summary 137 CHAPTER 5. CONCLUSIONS AND METALLOGENY 139 v i i i REFERENCES CITED 143 APPENDIX A 149 APPENDIX B 156 i x LIST OF TABLES 2-1 Abbreviations used to id e n t i f y units on the Geologic Map 6 2-2 Brief descriptions of units outside the study area which are shown on the Geologic Map (Figure 2-1) but not discussed i n the text 7 2-3 K/Ar radiometric determinations on plutonic rocks i n and near the study area 11 2- 4 Summary of tectonic history 45 3- 1 Producing deposits 48 3-2 Abbreviations and symbols used i n deposit descriptions 50 3-3 Characteristics of deposits i n the Britannia D i s t r i c t 56 3-4 Characteristics of the Northair s u l f i d e bodies 61 3-5 Characteristics of deposits i n the Northair D i s t r i c t 65 3-6 Characteristics of deposits i n the Giant Mascot D i s t r i c t 70 3-7 Characteristics of deposits i n the Eagle Complex 72 3-8 Characteristics of deposits i n the Summit Camp 73 3-9 Characteristics of deposits i n the Jim Kelly Creek Camp 75 3-10 Characteristics of deposits i n the Ladner Gold Belt 77 3-11 Characteristics of deposits i n the 23-Mile Camp 79 3-12 Characteristics of deposits i n the 10-Mile Creek Camp 81 3-13 Characteristics of deposits i n the Harrison Lake D i s t r i c t 83 3-14 Characteristics of deposits i n the F i r e Lake Camp 85 3-15 Characteristics of deposits i n the P i t t Lake Area 86 3-16 Characteristics of deposits on the Sechelt Peninsula 86 3-17 Characteristics of isolated producers and important occurrences 88 X 3- 18 Summary of metallogenic history 92 4- 1 Grade and tonnage of major deposits 95 4-2 Deposit status based on history of exploration, development or production 98 4-3 Comparison of Coast Plutonic Belt densities of the present study area and of the C o r d i l l e r a of B r i t i s h Columbia 106 4-4 Characterization of tectonic belts 113 x i LIST OF FIGURES 1-1 Location of the study area r e l a t i v e to the tectonic belts of the Canadian C o r d i l l e r a 1- 2 Location of metal deposits i n the Vancouver-Hope area 2- 1 Geology of the Vancouver-Hope area 2-la Cross-section across the southeastern portion of the study area; plutons have been removed to c l a r i f y pre-intrusive structures 2-2 Time-space plot of the Vancouver-Hope area 2-3a Location of K/Ar radiometric determinations on plutonic rocks i n and near the study area 2-3b Location of K/Ar radiometric determinations from intrus i v e rocks i n a portion of the study area 2-4 Geologic map of the Skagit Region of Northern Cascades 2-5 Study areas of some p r i n c i p a l workers dealing with the metamorphic rocks of the Spuzzum Plutonic Belt 2- 6 A. Possible subduction zones i n the Canadian C o r d i l l e r a ; l a t e r transcurrent motion suggests oblique subduction B. Method of accretion of crustal blocks, resulting i n westward "jumping-out" of subduction zones 3- 1 P r i n c i p a l areas of mineral occurrences, Vancouver-Hope area 3-2 Relative positions pf the three main mineralized . , zones and faults at Northair Mines 3-3 Surface geology of the Giant Mascot Ultramafite 3-4 Di s t r i b u t i o n of metal deposits on the time-space plot 3- 4a Explanation of symbols on Figure 3-4 4- 1 Number of occurrences of each deposit type with respect to cha r a c t e r i s t i c metals 4-2 Total number of occurrences of each metal 4-3 Total number of occurrences of each deposit type \ s-(-pocket-) (-pockete). 10 Cpnn-k-p-t-) f^a-pGH^et Sr 31 46 49 60 67 (l>@ekat)7>?fl^ C4me1 91 96 99 101 x i i 4-4a Number of occurrences of copper, gold and s i l v e r with ' respect to deposit type 102 4-4b Number of occurrences of molybdenum, zinc, lead, iron and n i c k e l with respect to deposit type 103 4-5a Relative densities of copper, molybdenum, gold, s i l v e r , lead and zinc with respect to tectonic belts and subdivisions 108 4-5b Relative densities of n i c k e l , i r o n , antimony and tungsten with respect to tectonic belts and subdivisions 109 4-6a Relative densities of magmatic, porphyry, skarn and volcanogenic deposits with respect to tectonic belts and subdivisions 110 4-6b Relative densities of vein, shear, disseminated and massive deposits with respect to tectonic belts and subdivisions 111 4-7 Total number of occurrences i n each mineralized geologic unit of the study area 116 4-8 Number of occurrences of each deposit type with respect to host rock unit 118 4-9a Number of occurrences of copper, molybdenum, gold and s i l v e r with respect to host rock unit 119 4-9b Number of occurrences of lead, zinc, i r o n , antimony, tungsten and ni c k e l with respect to host rock unit 120 4-10a Number of occurrences i n host rock units of the Eagle Plutonic Belt, Ladner Trough, Hozameen Basin and Cascade Belt, with respect to metal content and deposit type 122 4-10b Number of occurrences i n host rock units of the Coast Plutonic Belt with respect to metal content and deposit type 124 4-11 Number of occurrences of each metal and deposit type with respect to intrusive ( I ) , volcanic (V) and sedimentary (S) host rock types 128 4-12 Total number of occurrences i n i n t r u s i v e , volcanic and sedimentary host rocks 129 4-13 Number of occurrences i n (a) intermediate to acid intr u s i v e rocks, (b) ultramafic rocks, and (c) dikes, with respect to metal content and deposit type 131 x i i i 4-14 Number of occurrences In (a) basic volcanic rocks and greenstones, (b) acid volcanic rocks, (c) t u f f , agglomerate and volcanic breccia', and (d) unclas s i f i e d and metamorphosed volcanic rocks, with respect to metal content and deposit type 133 4-15 Number of occurrences i n (a) c l a s t i c sedimentary rocks, (b) limestone, and (c) si l i c e o u s and unclas-s i f i e d sedimentary rocks, with respect to metal content and deposit type 135 x i v ACKNOWLEDGEMENTS I would l i k e to thank my advisor, Dr. A. J. Sinclair, for suggestion of the thesis topic and c r i t i c a l review of the manuscript. Dr. C. I. Godwin and Dr. J. G. Payne thoroughly reviewed the manuscript and provided valuable c r i t i c i s m and encouragement. Dr. R. L. Armstrong reviewed a por-tion of the manuscript and provided valuable information concerning the tectonic elements of the Cascade Belt. The B. C. Ministry of Mines and Petroleum Resources provided me with use of the a i r photo l i b r a r y , access to assessment reports, and information which was graciously supplied by Judy Winsby and George James. I am grateful to the MINDEP s t a f f for their cooperation and assistance. In p a r t i c u l a r , Jenny Stark assisted i n the tedious chore of data accumulation at the outset of the study and accompanied me during f i e l d investigations i n the summer of 1975. Lynn Gislason was an indispensable l i a s i o n between the computer and me; her s k i l l and patience were greatly appreciated. Several persons provided me with information and access to properties which I v i s i t e d i n 1975; t h e i r generosity with both t h e i r time and exper-ience i s gratefully acknowledged. S p e c i f i c a l l y , John Payne not only guided me around a portion of the Britannia orebodies, but provided me with a copy of the unpublished report regarding the volcanogenic origin- of Britannia and additional unavailable information on the regional geology of the area. Peter Christopher and Plen Dickson kindly guided me through underground workings at Giant Mascot and Northair, respectively. Funding was generously provided by Energy, Mines and Resources and the B r i t i s h Columbia Ministry of Mines and Petroleum Resources. It i s not possible to thank i n d i v i d u a l l y a l l the persons i n the Department of Geological Sciences who supplied me with moral support and X V encouragement. Outstanding personal contributions toward the completion of this thesis were made by JoAnne Nelson, Lee Pigage and Dita Runkle. Special thanks go to the departmental technicians for their sportive en-couragement and assistance. 1 1. INTRODUCTION GENERAL STATEMENT The objective of this study i s to define the metallogenic history of the southern end of the Coast Plutonic Belt and adjacent areas which include the northern t i p of the Cascade Belt and a small portion of the southwestern edge of the Intermontane Belt (Figure 1-1). Each of these major tectonic belts i s characterized by d i s t i n c t i v e geological features, but location of boundaries between belts i s d i f f i c u l t on the detailed scale of t h i s study. Metallogenesis i s approached from two viewpoints, f i r s t l y through des-c r i p t i o n of important i n d i v i d u a l deposits and groups of deposits, and secondly through s t a t i s t i c a l compilations of s p e c i f i c characteristics deter-mined for every deposit for which published descriptive information i s available. The second approach enables deposits of a l l sizes to be consid-ered i n order to obtain a more detailed view of metal d i s t r i b u t i o n s , and i s based on the hypothesis that small occurrences should not be ignored i n an area where large deposits are rare. Both these sections are preceded by a detailed examination of the geology and tectonic environment, presented on a geologic map, cross-section and time-space, plot (in pocket). The nature of the time-space plot w i l l be discussed i n d e t a i l i n Chapter Two. A simi l a r study of the adjoining Taseko Lakes-Pemberton area to the north (Woodsworth, et_ a l . , 1977) suggested that abundant vein deposits along the eastern edge of the Coast Plutonic Complex were formed by f l u i d s which might have originated i n plutonic rocks during cooling. However, such patterns are not readily apparent i n the area considered here. Of secondary importance to this study i s the evaluation of the MINDEP system as a quantitative approach to metallogenic studies. Details regarding the MINDEP system are discussed i n Chapter Four. gure 1-1. Location of the study area r e l a t i v e to the tectonic belts of the Canadian C o r d i l l e r a (after Sutherland Brown, et a l . , 1976). 3 DEFINITION OF THE STUDY AREA The boundaries of the study area enclose approximately 28,711 square kilometers, 18 percent covered by water and recent sediments. The o r i g i n a l boundaries at the outset of the study were contained within NTS sheets 92-G and 92-H, West Half, but were subsequently modified for three reasons (refer to Figure 1-2 for d e f i n i t i o n of NTS boundaries): 1) The northern boundary was extended to include the cluster of deposits southwest of Pemberton. One of these deposits, Northair, i s the only currently producing deposit i n the study area. 2) The southern portion of the eastern boundary was extended to include an area which contains few metal deposits, but whose geology i s valuable to an understanding of the tectonic history of the area. 3) The entire eastern boundary was modified to extend only so far as the main area of outcrop of the Nicola and Kingsvale Groups. The Nicola Group contains a large number of metal deposits which probably are not related to the Coast Plutonic Complex. METHODS Descriptive information on metal deposits was gathered through an extensive l i t e r a t u r e search. P r i n c i p a l sources of information include the Annual Reports of the B r i t i s h Columbia Minister of Mines, Geology,  Exploration and Mining i n B r i t i s h Columbia, and Assessment Reports for the Vancouver and New Westminister Mining D i s t r i c t s . A few private company reports were made available to the author. F i e l d investigations i n the summer of 1975 served to f a m i l i a r i z e the author with some of the deposits. Data were transferred onto coding forms and entered into the MINDEP data bank for storage and l a t e r r e t r i e v a l . Raw data output from t h i s data bank was an invaluable tool to the compilation process. Deposits are i d e n t i f i e d with reference to the NTS sheet i n which they occur. Since a l l sheets i n the study area are within the 92 g r i d , t h i s number has been dropped. Therefore, the i d e n t i f i c a t i o n number of a deposit i n the 92-H sheet, southwest quarter, w i l l be preceded by the l e t t e r s HSW. Figure 1-2 locates deposits i n the study area and the grids i n which they occur. 5 2. GEOLOGY AND TECTONIC FRAMEWORK INTRODUCTION Figure 1-1 i l l u s t r a t e s the position of the present study area r e l a t i v e to the s i x major sub-parallel belts of the Canadian C o r d i l l e r a (Sutherland Brown, et a l . , 1976). The general geology of the area, shown i n Figure 2-1 (see also Tables 2-1 and 2-2), has been compiled from numerous sources ( v i z . , Bostock, 1963; Roddick, 1965; Monger, 1970; Rice, 1960; Woodsworth, 1977; Roddick and Hutchison, 1973; Duffel and McTaggart, 1952; Richards and McTaggart, 1976; and Roddick and Okulitch, 1973). Two-thirds of the area i s underlain by intrusive rocks, most belonging to the Coast Plutonic Complex; sedimentary rocks dominate the southeastern section and occur with volcanic rocks i n scattered remnants throughout the Coast Plutonic Belt. A t r a n s i t i o n zone between western plutonic and eastern sedimentary terranes i s characterized by metamorphic rocks of unknown age which merge into the s t r u c t u r a l l y complex Cascades region to the south. Transecting the study area are the north-south-trending Fraser River Fault Zone''' and three other faults believed to have major horizontal and/or v e r t i c a l components. The author has divided the study area further into s i x tectonic sub-di v i s i o n s , which, from east to west, are the Eagle Plutonic Belt, the Ladner Trough, the Hozameen Basin, the Cascade Belt, the Spuzzum Plutonic Belt and the Coast Plutonic Belt. The Cascade Belt, due to i t s complexity, has been subdivided further into four b e l t s , referred to as C - l , C-2, C-3 and C-4. The time-space plot (Figure 2-2; described below) has used these tectonic divisions to present data not evident on the geologic map (Figure also referred to herein as the Straight Creek Fault Zone 6 TABLE 2-1. Abbreviations used to i d e n t i f y units on the Geologic Map (Figure 2-1). Units are arranged alphabetically within tectonic b e l t s ; see text for descriptions and ages. I. Eagle Plutonic Belt CQ Coquihalla Group N Nicola Group I I . Ladner Trough CQ Coquihalla Group CR Coast Plutonic Complex DC Dewdney Creek Group JM Jackass Mountain Group L Ladner Group P Pasayten Group I I I . Hozameen Basin CR Coast Plutonic Complex HZ Hozameen Group Qs Quaternary sediments IV. Cascade Belt C Cultus Formation CH Chilliwack Group CK Chuckanut Formation CR Coast Plutonic Complex D Darrington P h y l l i t e NK Nooksack Group •Qs Quaternary sediments SK Skagit Formation YA Yellow Aster C r y s t a l l i n e Complex Coast Plutonic Belt AP Agassiz P r a i r i e Formation av acid volcanic rocks BH Brokenback H i l l Formation BI Bowen Island Group {Billhook Creek Formation Mysterious Creek Formation Echo Island Formation bv basic volcanic rocks fCheakamus Formation CEH < Empetrum Formation (.Helm Formation CR Coast Plutonic Complex FL Fire Lake Group G Gambier Group GB Garibaldi Group gn gneiss HL Harrison Lake Formation K Kent Formation m metamorphic rocks ms metasedimentary rocks PI Pioneer Formation PN Peninsula Formation Qs Quaternary sediments s sedimentary rocks TI Twin Islands Group V. Spuzzum Plutonic Belt av acid volcanic rocks CR Coast Plutonic Complex gn gneiss ms metasedimentary rocks Qs Quaternary sediments SS Settler Schist TABLE 2-2. Brief"descriptions of units outside the study area which are shown on the Geologic Map (Figure 2-1) but not discussed in the text. Where possible, information was updated from Roddick and Okulitch, (1973). Symbol abv bv-1 bv-2 CW HU KL KVs KVv PRs PRv s,bv SB Name Coldwater Beds Hurley Formation Kamloops Group Kingsvale Group; sedimentary rocks Kingsvale Group; volcanic rocks Princeton Group; sedimentary rocks Princeton Group; volcanic rocks Spences Bridge Group Description plateau basalt and dacite flows; may be equivalent to Garibaldi Group andesite; minor amounts of dacite valley and plateau basalt sandstone, shale, conglomerate; coal seams argillite, limestone, tuff, conglomerate, andesite flows basalt and dacite arkose, conglomerate, greywacke basalt and andesite lavas; agglomerate, tuff, breccia basin conglomerate, sandstone and shale basalt, andesite and dacite lavas sedimentary and volcanic rocks andesite and dacite lava and pyroclastic rocks; minor amounts of basalt and rhyolite \ Age late Miocene or Pliocene lower Tertiary late or post-Miocene Eocene Upper Triassic Eocene and Oligocene Upper Cretaceous Upper Cretaceous Eocene Eocene mid-Eocene Lower Cretaceous Reference Roddick and Hutchison, 1973 Roddick and Hutchison, 1973 Rice, 1960 Duffel and McTaggart, 1952 Roddick and Hutchison, 1973 Duffel and McTaggart, 1952 Rice, 1960 Rice, 1960 Rice, 1960 Rice, 1960 Duffel and McTaggart, 1952 Rice, 1960 8 2-1). Both the geologic map and the time-space plot should be constantly referred to as i l l u s t r a t i o n s of events and relationships discussed through-out the text. TIME-SPACE PLOT The time-space plot (Figure 2-2) i s designed to diagrammatically i l l u s t r a t e events occurring i n a pa r t i c u l a r area at a part i c u l a r time i n order to c l a r i f y cause/effect relationships which are d i f f i c u l t to portray 2 on geologic maps or cross-sections. Events represented on the plot include: 1) Deposition 2) Intrusion (K/Ar dates are plotted as minimum ages; location and source of these dates are shown i n Figures 2-3a,b and Table 2-3) 3) Faulting (fault movement i s depicted along corresponding belt divisions or i n the affected belt i n an approximate east-west position according to units affected) 4) Folding (without s i g n i f i c a n t metamorphism) 5) Deformation (period of folding, f a u l t i n g and metamorphism which generally masks the o r i g i n a l character of rocks) A v e r t i c a l time axis i s presented to scale (except where noted) and i s divided according to Van Eysinga, 1975. The horizontal distance axis consists of two schematic northeast-southwest transects offset i n a north-south dire c t i o n between the Spuzzum Plutonic Belt and the Cascade Belt. Distance i s not to scale i n order to accommodate events i n the very narrow belts. Important aspects which cannot be portrayed on a time-space plot include the following: 1) True stratigraphic thicknesses are not shown i n order to i l l u s t r a t e the actual or possible duration of deposition or formation of a unit. G r i f f i t h s (1977) discusses the construction and application of time-space plots i n d e t a i l . Figure 2-3a. Location of K/Ar radiometric determinations on plutonic rocks i n and near the study area. Refer to Table 2-3 for b r i e f sample descriptions and sources of information. 10 Giant Mascot f ) \ Liltramattc Body. „. „ , I • j \ i M t H ,8S.iJ ,. Barr \ tatholiiVt K i '.Yale \Int.\ I 10 ' ^ .28fll\ kilometers ^/ CkilLick\ \ BatUilk j Canada " " U.S.A. Figure 2-3b. Location of K/Ar radiometric determinations from intrus i v e rocks i n a portion of the study area (after Richards and McTaggart, 1976, and McLeod, et a l . , 1976). TABLE 2-3. K / A r RADIOMETRIC DETERMINATIONS ON PLUTONIC ROCKS IN AND NEAR THE STUDY AREA; SEE FIGURE 2-3a,b FOR LOCATIONS. I d r n t l f l c a t l o n N u m h / T P l u t o n ( a ) Rock Type M n t c r l n l Analysed A R C (Mi) Rc fcrcncc CSC 62-56 Eagle Complex G r a n o d i o r i t e B l o t l t e 143 Leech, e£ a l _ . , 1963 CSC 65-8 Needle Peak G r a n i t e B l o t l t e 39 + 4 Wanless, ct a K , 1967 CSC 65-9 Eagle Complex C r a n o d l o r t t e B l o t l t e 9 8 - 6 CSC 65-10 p l u t o n on Hozameen F a u l t G r a n o d i o r i t e B l o t l t e 8 4 - 6 CSC 72-3 H e l l ' s Cate Quartz D l o r l t e Hornblende 4 0 - 4 Wanless, e t . d . , 1973 CSC 72-4 He 11'a Cate Quartz D l o r l t e B l o t l t e 4 4 - 3 " CSC 72-5 Scuzzy Quartz D l o r l t e B l o t l t e 7 0 - 4 CSC 72-6 SpuzEum Quartz D l o r l t e Hornblende 73 t 4 CSC 72-7 Spuzzum Quartz D l o r l t e B l o t l t e 7 4 - 4 CSC 72-8 Scuzzy Quartz D l o r l t e HornHlende 72 i 4 CSC 76-32 Coast P l u t o n i i Complex G r a n o d i o r i t e B l o t l t e 113 - 4 Wanless, et_ a l . , 1977 CSC 76-33 Coast P l u t o n i c Complex G r a n o d i o r i t e Hornblende 119 - 5 CSC 76-46 Coast P l u t o n i c Complex G r a n o d i o r i t e B l o t l t e 88.6 - 3.3 V CSC 76-47 Coast P l u t o n i c Complex G r a n o d i o r i t e Hornblende 97.5 - 4.5 II K A 126 Coast P l u t o n i c Complex G r a n o d i o r i t e B l o t l t e 99,95 Baadsgaard, e^ a l _ . , 1961 AK 24 H e l l ' s Gate G r a n o d i o r i t e B l o t l t e 35 AK 31 Mt. Barr Quartz D l o r l t e B l o t l t e 18 A K 43 Mt. B a r r Quartz D l o r l t e B l o t l t e 18 l a Spuzzum Quartz D l o r l t e B l o t l t e 103 i 5 Richards and White, 1970 lb Spuzzum Quartz D l o r l t e B l o t l t e 1 0 3 * 5 it 2a Spuzzum Quartz D l o r l t e B l o t I t e 79 t 4 " 2b Spuzzum Quartz D l o r l t e Hornblende 81 + 4 3 Spuzzum Quartz D l o r l t e B l o t l t e 83 + 4 Rlcharda and McTaggart, 1976 4a Y a l e G r a n o d i o r i t e B l o t l t e 59 i 3 Richards and White, 1970 4b Yale G r a n o d i o r i t e B i o t i t e 59 - 3 II 7 Y a l e 1 Quartz Monzonite B l o t l t e 41 + 2 9 S l i v e r Creek Stock Quartz D l o r l t e Hornb lende 35 i 2 10 C h l l l l w a c k Gabbro B i o t i t e 29 t 1 11 C h l l l l w a c k Quartz D l o r l t e B i o t i t e 28 Z 1 „ 12 C h l l l l w a c k Quartz Monzonite B l o t l t e 26 r I . 13 C h l l l l w a c k Quartz Monzonite B l o t l t e 26 i 1 14 C h l l l l w a c k Quartz Monzonite B l o t l t e 26 t 1 it 16a Mt. Ba r r Quartz D l o r l t e B i o t i t e '24 t 1 16b Mt. B a r r Quartz D l o r l t e B i o t i t e 24 i 1 17 Mt. Barr G r a n o d i o r i t e 1 B i o t i t e 21 t 1 18 Ht. B a r r Quartz D l o r l t e ' B i o t i t e 18 t 1 19 Mt. Ba r r Quartz Monzonite B i o t i t e 16 i 1 8H Spuzzum D l o r l t e Hornblende 89 - 2.8 Rlcharda and McTaggart, 1976 JHc 1 Gi a n t Mascot U l t r a m a f l t e Hornblendi'te Hornblende 95 t 4 McLeod, et_ a l . , 1976 JMc 2 Giant Mascot U l t r a m a f l t e Hornblende P y r o x e n l t e whole rock 1 1 9 * 4 • i JHc 3 Gi a n t Mascot U l t r a m a f l t e H o m b l e n d l t e Hornblende 104 - 4 JMc 4 GiaBt Mascot U l t r a m a f l t e H o r n b l e n d l t e Hornblende 108 - 4 " JMc 5 Spuzzum D l o r l t e Hornblende and pyroxene 89.6 - 3.1 JHc 6a Spuzzum T o n a l i t e B l o t l t e 79.4 - 2.5 " JHc 6b Spuzzum T o n a l i t e Hornblende 85.1 - 2.8 JH Spuzzum 76 Monger, 1970 482-1 Coast P l u t o n i c Complex Quartz D l o r l t e Hornblende 77.5 Woodsworth, 1977 482-2 Coast P l u t o n i c Complex Quartz D l o r l t e B l o t l t e 70.2 482-3 Coast P l u t o n i c Complex G r a n o d i o r i t e Hornblende 16.9 482-4 Const P l u t o n i c Complex G r a n o d i o r i t e B l o t l t e 84 " 482-5 Coast P l u t o n i c Complex G r a n o d i o r i t e Hornblende 75 " 482-6 Coast P l u t o n i c Complex D l o r l t e Hornblende 51.6 t l CB-1 Coast P l u t o n i c Complex B l o t l t e 158 White, 1968 CB-2 Const P l u t o n i c Complex B l o t l t e 95 C.B-3 Coast P l u t o n i c Complex Hornblende 97 GB-4 Coast P l u t o n i c Complex B l o t l t e 93 CB-5 Const P l u t o n i c Complex Amphlbole 97 CB-6 Const P l u t o n i c Complex B l o t l t e 90 GB-7 Coast P l u t o n i c Complex G r a n o d i o r i t e B l o t l t e 94 Mathews, 1968 CM-1 Coast P l u t o n i c Complex Quartz D l o r l t e Hornblende 148 - 5 M c K l l l o p , 1973 GM-2 Coast P l u t o n i c Complex Quartz D l o r l t e B l o t l t e 157 i 5 " M-19 Coast P l u t o n i c Complex D l o r l t e '' Hornblende 117 - 4 Caron, 1974 M-21 Coast P l u t o n i c Complex C r a n o d l o r l t e B i o t i t e 1 1 3 - 3 FT-1 Coast P l u t o n i c Complex whole rock 91 Roddick, et a l _ . , 1977 FT-2 Coast P l u t o n i c Complex Hornblende 103 i i description revised by Richards and McTaggart, 1976 12 2) Displacements along major faults cannot be shown, but time and place of major f a u l t i n g and units affected by f a u l t i n g are shown. Major horizontal movement might have juxtaposed units that o r i g i n a l l y were not side-by-side. 3) Relationships between units which are not conformable are not represented. Gaps between units i n the same str u c t u r a l belt might represent disconformities, angular unconformities, or the units might not be i n contact with each other, but but s p a t i a l l y separated within the same b e l t . EAGLE PLUTONIC BELT Units Within the Eagle Plutonic Belt Schistose basic volcanic rocks of the Nicola Group (N), granodiorite, to n a l i t e and gneiss of the Eagle Complex, and acid extrusions of the Coquihalla Group (CQ) are the main l i t h o l o g i c units i n the Eagle Plutonic Belt. Of these three units, the Eagle Complex i s by far the most widespread. Nicola greenstones are part of a large area of diverse submarine flows, flow breccias and shaley to limy sedimentary rocks east of the study area, but they occur intermittently i n the study area only within and around the borders of the Eagle Complex. Fo s s i l s i n the Nicola Group outside the study area are Upper T r i a s s i c (Rice, 1960). Coarse-grained, northwesterly-foliated granodiorite and tonalite (apparently of intrusive origin) make up the majority of the Eagle Complex, but pegmatite, gneiss and migmatite are common. Age constraints place intrusion between extrusion of Late T r i a s s i c Nicola Group, which i s intruded 3 and metamorphosed by the Eagle Complex (Cairnes, 1924), and deposition of Albian (uppermost Lower Cretaceous) Jackass Mountain conglomerates to the west, which contain cobbles of Eagle (?) granodiorite (Coates, 1974). Two samples of f o l i a t e d granodiorite along the Hope-Princeton highway have 3 An alternate hypothesis i s that of Anderson (1971), who believes intrusive rocks of the Eagle Complex were derived from the Nicola Group by anatectic melting. Metamorphic effects s p a t i a l l y associated with the Eagle/Nicola contact are interpreted by Anderson as effects of thermal gradients res-ponsible for the formation of the Eagle Complex, not products of intrusion. yielded K/Ar model ages of 148 Ma (Leech, et a l . , 1963) and 98 Ma (Wanless, et a l . , 1967). Subaerial Coquihalla volcanic rocks were deposited on an u p l i f t e d and eroded surface of granodiorite (Cairnes, 1924), and onto sedimentary rocks west of the granodiorite, thereby covering the f a u l t which forms the western boundary of the Eagle Plutonic Belt. R. G. Berman (personal communication, 1978) recognizes a 4,000-foot section of r h y o l i t i c flows and pyroclastic rocks intruded by andesitic to d a c i t i c bodies. These s t r a t i f i e d volcanic rocks are intruded by a massive d i o r i t i c plug which i s probably a late intrusive phase of the Coquihalla Group (Cairnes, 1924). Extrusion of the Coquihalla Group i s bracketed by three K/Ar determinations on dacite/ andesite, r h y o l i t e and d i o r i t e which yielded dates of 19.5+0.9, 20.9+0.7, and 22.1 + 0.8 Ma, respectively (R. G. Berman, personal communication, 1978). Deformation Monger (1970) states that the Eagle Complex, although f o l i a t e d , was not affected by major mid-Cretaceous compressive deformation evident i n rocks farther west. However, mid-Cretaceous u p l i f t of the Eagle Complex did occur along the Pasayten Fault. Large fa u l t s and folds i n the Eagle Complex were not recognized by Staatz, et a l . , (1971) i n studies south of the border; they concluded that mid-Cretaceous deformation did not extend east of the Pasayten Fault. On the other hand, Anderson (1971) described folded metasedimentary gneisses of the Eagle Complex which have "undergone the same deformational event" as rocks West of the Pasayten Fault, while more competent ton a l i t e does not exhibit folding. The 98 Ma date (Wanless, et a l . , 1967) i s also a contradiction to the supposed lack of mid-Cretaceous deformation. However, i f the Eagle Complex was unroofed and supplying sediment to a westerly basin i n Albian time (108-100 Ma), the significance of the 98 Ma radiometric date 14 i s not clear. If Monger and Staatz, et a l . , were f a m i l i a r only with granodiorite and ton a l i t e of the Eagle Complex, deformation recognized by Anderson has yet to be examined adequately. Certainly the contradictions are in d i c a t i v e of a poor understanding of the character and history of the Eagle Complex. Pasayten Fault Considerable v e r t i c a l and r i g h t - l a t e r a l movement i s assumed to have occurred along the steep westerly-dipping Pasayten Fault which forms the western boundary of the Eagle Plutonic Belt (Coates, 1974). Movement along the f a u l t produced c a t a c l a s t i c textures and increased intensity of f o l i a t i o n near the f a u l t i n rocks of the Eagle Complex. Small, unfoliated plugs near the f a u l t have been dated at 94 Ma (Staatz, et a l . , 1971). On the assump-ti o n that these plugs, i f present, would have been affected by movement of the Pasayten Fault, Staatz, et^ a l . , placed an upper l i m i t of 94 Ma on f a u l t movement. Rocks east of the Pasayten Fault are believed by Coates (1974) to be the source of Lower Cretaceous arkosic sediments i n the trough west of the f a u l t , thus f a u l t movement could have occurred as early as lowermost Cretaceous. LADNER TROUGH The fault-bounded Ladner Trough records a long history of sedimentation which i s important i n determining the timing of u p l i f t of adjacent areas. Detailed studies by Coates (1974) provide most of the data discussed below. Stratigraphic Units F o s s i l evidence indicates that deposition of the slaty Jurassic Ladner Group (L) might have begun as early as Sinemurian, and continued through mid-Bajocian. Deposition occurred along a basin which was open to the west 1 5 and receiving sediment from an easterly volcanic highland (probably Nicola). Sediments forming the eastern and western portions of the basin represent two different environments of sedimentation: eastern shallow-water to sub-a e r i a l , coarse-grained volcanic sediments with minor amounts of fine-grained marine turbidites and andesitic flows contrast with western deep-water pelagic sediments and tu r b i d i t e s . Easterly-derived arkosic sandstones toward the top of the western sequence indicate shallowing i n Bajocian time. The Upper Jurassic Dewdney Creek Group (DC) l i e s disconformably or with s l i g h t angular unconformity above the western part of the Ladner Group. Shallow-water marine sediments consisting of volcanic sandstone and sandy a r g i l l i t e were derived from an easterly volcanic source. Minor amounts of gra n i t i c detritus appear i n conglomerates near the base of the sequence. Minor a l l u v i a l sedimentation and volcanism was reported by Coates to have occurred between deposition of Dewdney Creek and Jackass Mountain Groups, but due to factors such as rare and indeterminate f o s s i l s , faulted contacts, and the r e s t r i c t e d extent of these units, they are not discussed further. Mixed marine and non-marine conglomerates and sandstones (Hauterivian to mid-Albian) of the Jackass Mountain Group (JM) l i e disconformably above the Dewdney Creek Group. The northern section i s described by Monger (1970) as dark, massive greywacke and interbedded conglomerate which may be partly non-marine. Coates described the southern sections as shallow marine sand-stones and conglomerates with l o c a l stagnant and non-marine portions. Throughout most of the sequence an easterly source i s indicated by increasing grain size toward the east. In addition, recognizeable detritus from Eagle and Nicola terranes was noted by Coates. Conglomerates record a sudden u p l i f t to the east i n early Albian time ( i . e . , movement along the Pasayten Fau l t ) ; westerly-derived sediments become evident near the top of the 16 Jackass Mountain Group. Non-marine Aptian-Albian Pasayten Group (P) conglomerate, sandstone and p e l i t e overlie and interfinger with dominantly marine Jackass Mountain Group rocks to the east. A sudden change to a high energy environment occurred i n Albian time, recorded by deposition of red beds, poorly sorted conglomerates and fanglomerates. Coates believed Albian sediments indicate both a westerly volcanic-sedimentary provenance and an easterly plutonic-metamorphic provenance; increasing proportions of westerly-derived sediments occur toward the top of the section. Other units of minor importance i n the Ladner Trough are volcanic rocks of the Coquihalla Group, Needle Peak pluton, and a small region of Nicola (?) volcanic rocks (Figure 2-1) along the Pasayten Fault. The southern area designated as Coquihalla volcanic rocks i s not correlated d e f i n i t e l y with the Coquihalla Group; i t unconformably overlies Lower Cretaceous sedimentary rocks and the Chuwanten Fault (see below), suggesting a Tertiary age. Needle Peak pluton i s a discordant intrusion of coarse granite and grano-d i o r i t e which has been dated at 39 Ma (Wanless, et_ a l . , 1967). Not much i s known of the small area of rocks which Rice (1960) mapped as Nicola Group, as he does not describe the occurrence i n d e t a i l . I t i s possible that this occurrence does not belong to the Nicola Group, as i t i s on the western ("wrong") side of the Pasayten Fault, but i t remains as Nicola i n this study for lack of contrary evidence. Metamorphism of rocks of the Ladner Trough i s s l i g h t , being confined to z e o l i t e or lowermost greenschist facies. Deformation The Chuwanten Fault i s an imbricate southwesterly-dipping thrust zone which probably i s related genetically to major f l e x u r a l - s l i p folding during Late Cretaceous compression. South of the border, Tabor, et a l . , (1968) report an 86 Ma dike offset by the Chuwanten Fault, indicating i n i t i a t i o n or renewal of movement after this time. Folding, however, may have begun as early as Cenomanian, as the Upper Albian Pasayten and Jackass Mountain Groups are the youngest units involved. An upper l i m i t for both folding and f a u l t i n g i s uncertain, but placed as lowermost Tertiary, since the Straight Creek Fault Zone truncates deformed Albian sedimentary rocks. A real upper l i m i t i s defined by the Eocene Needle Peak pluton which c l e a r l y 4 post-dates major structures. Hozameen Fault Just as the Pasayten Fault forms the eastern edge of the Ladner Trough, so the western edge i s defined by the Hozameen Fault. A major cr u s t a l break with probably mantle-derived, tectonically-emplaced serpentine (Misch, 1966) along i t s trace, exposures of the Hozameen Fault are v e r t i c a l to steeply westerly-dipping over thousands of v e r t i c a l feet i n some places (Staatz, et a l . , 1971), but f l a t t e n south of the United States-Canada border to blend with the easterly-directed Jack Mountain Thrust Prong (cf. Figure 2-4). Considerable v e r t i c a l movement i s presumed to have occurred, with the west side moving up r e l a t i v e to the east side. Movement along the Hozameen Fault i s related to major mid- to Late Cretaceous deformation involving Ladner Trough sedimentary rocks. Timing of the onset of movement i s not known, but i s probably recorded by westerly-derived, high-energy Pasayten sediments i n Albian time. An 84 Ma pluton on the trace of the f a u l t (Coates, i n Wanless, et a l . , 1967) gives an upper l i m i t to f a u l t movement. _ — The upper l i m i t proposed by Coates i s 84 Ma, the age of a small pluton that intrudes Ladner slates along the western boundary of the area. Although this pluton might c l e a r l y post-date structures here, i t does not necessarily post-date structures i n the rest of the b e l t , and i t contradicts the e v i -dence for l a t e r (post-86 Ma) movement along the Chuwanten Fault. 18 This upper l i m i t for the Hozameen Fault roughly coincides with the onset of movement along the Chuwanten Fault, perhaps indicating that easterly-directed compression (with consequent deformation and thrusting) was a pattern that persisted throughout Upper Cretaceous time, but the locus of thrusting shifted to the east i n mid-Upper Cretaceous. The Hozameen Fault i s truncated to the north along the Fraser River where the Straight Creek and Fraser River Fault Zones merge to form the eastern boundary of the Ladner Trough. The Straight Creek Fault, discussed i n d e t a i l below, i s an important feature of the Cascade Belt. HOZAMEEN BASIN  Hozameen Group The Hozameen Group (HZ) was formed i n an oceanic basin i n which chert, volcanic rocks, and limestone were deposited along with fine p e l i t i c rocks. Ribboned chert, generally associated with p e l i t e , i s abundant. Limestone lenses are rare, and most commonly are associated with b a s a l t i c , l o c a l l y pillowed greenstone. A paleogeographic reconstruction depicts a deep marine basin with volcanic islands and associated a t o l l s (Monger, 1977). Absence of f o s s i l s , and contacts which are either tectonic or with Upper Cretaceous or younger units or with metamorphic units, have obscured the age of the Hozameen Group. A Pennsylvanian-Permian age has been assigned tentatively based on l i t h o l o g i c s i m i l a r i t i e s with the Cache Creek Group (Monger, 1970); Lower to Middle T r i a s s i c has also been assigned on sim i l a r grounds with the Fergusson Group (Cameron and Monger, 1971). Lowermost greenschist facies regional metamorphism affected most of the Hozameen Group; metamorphic grade increases toward the western contact where almandine amphibolite grade rocks of the Hozameen Group appear to blend with the Custer Gneiss unit of that grade. 19 Yale Intrusions The f o l i a t e d stocks, s i l l s and dikes which intrude the western edge of the Hozameen Group are referred to as the Yale intrusions (McTaggart and Thompson, 1967). Rock types vary considerably, but b i o t i t e granodiorite i s most common. A l l types exhibit some degree of cat a c l a s i s , with sheared, mylonitized and gneissic v a r i e t i e s common. Planar structures i n intrusions p a r a l l e l those i n adjacent country rocks. The Paleocene to Eocene age of the Yale intrusions i s based on inclusions of Settler Schist, Hozameen Group, Custer Gneiss and Spuzzum intrusions, intrusion by the Chilliwack Batholith, and radiometric dates of 59 and 41 Ma (Richards and McTaggart, 1976). Deformation Deformational history of the Hozameen Basin i s summarized as follows: 1) Pre-Jurassic development of northwesterly-trending folds and faults (McTaggart and Thompson, 1967; Monger, 1970). 2) Minor northeasterly-trending folding and deformation associated with u p l i f t along the Hozameen Fault during mid-Cretaceous. 3) Northwesterly folding i n the southern portion related to Late Cretaceous Ladner Trough deformation (Monger, 1970). 4) Eocene shearing of the Yale intrusions, probably synchronous with major f a u l t i n g along the Fraser River and Straight Creek Fault Zones (McTaggart and Thompson, 1967). Folding associated with these f a u l t zones i s of l o c a l significance, and therefore not represented on the time-space plot. Boundaries The western boundary of the Hozameen Basin i s defined by the gradational metamorphic contact between Hozameen Group greenstones and amphibolite facies Custer Gneiss i n the southern and central portions, and by the Straight Creek Fault Zone i n the northernmost portion of the area. Neither the Hozameen Group nor the Yale intrusions occur west of these boundaries; both are cle a r l y truncated i n the Straight Creek Fault Zone by the Straight Creek 20 and Hope Faults. CASCADE BELT A s i m p l i f i e d view of Cascade structure i s that of a metamorphic core overlain by folded and faulted sedimentary rocks. The core was u p l i f t e d along a north-south axi s , u p l i f t increasing northward. Both core and flanking sedimentary rocks were intruded by Tertiary plutons and overlain by Tertiary volcanic rocks. A l l of these elements which Misch (1966) des-cribed i n d e t a i l for rocks south of the border, are present i n the study area. Information i n this section i s from Misch's 1966 report, except where noted; Figure 2-4 i l l u s t r a t e s the geology referred to south of the border. In a recent summary of Northern Cascades geology, Misch (1977) outlines three belts divided by the Straight Creek and Ross Lake (Hozameen) Faults; these belts represent fault-bounded c r y s t a l l i n e core flanked by easterly and westerly sedimentary bel t s . These divisions are retained i n this study, but further subdivisions are also made. Misch's eastern sedimentary belt ("East of the Hozameen Fault") has already been discussed as the Ladner Trough and Hozameen Basin which are cle a r l y separated by the Hozameen Fault i n the study area. South of the area (Figure 2-4) the continuation of the Hozameen Fault i s the Jack Mountain Prong, a shallow, easterly-directed thrust whose upper plate contains the Hozameen Group. The western contact of the Hozameen Group south of the area i s defined by the Jack Mountain Prong, but i n the study area i t i s grada-t i o n a l into the Custer Gneiss; Tertiary intrusions and volcanism have obliterated the connection between these features across the border. The central "East of the Straight Creek Fault" belt of Misch (referred to i n this study as C-l) i s composed of "core" rocks of the Skagit 21 Metamorphic Suite, whose eastern boundary south of the border i s the Hozameen Fault. In the study area, the equivalent of Skagit rocks, the Custer Gneiss, grades into the Hozameen Group (McTaggart and Thompson, 1967) along a "zone of shearing, metamorphism and intrusion," which Monger (1970) uses as a boundary for s t r u c t u r a l belts. Monger's boundary has been re-tained i n order to separate metamorphic core rocks from overlying Hozameen volcanic and sedimentary rocks. The western boundary of t h i s belt i s the Straight Creek Fault Zone, composed of the sub-parallel, graben-forming Hope and Straight Creek ( i . e . , Yale) Faults which merge with the Fraser River Fault Zone north of Boston Bar. Misch reports steep (60°) easterly dips and drag folds along the Straight Creek Fault, indicating d i p - s l i p movement, west side down. Right-l a t e r a l movement i s also suggested by drag folds and changes i n s t r u c t u r a l and metamorphic facies across the f a u l t . Recent correlation of the Hozameen Group with the Fergusson Group, west of the Fraser River Fault Zone and 190 kilometers north of the fault-truncated Hozameen Group, suggests considerable r i g h t - l a t e r a l movement (Cameron and Monger, 1971). Misch's western b e l t , "West of the Straight Creek Fault," i s sub-divided i n t e r n a l l y along the Shuksan and Church Mountain Thrust Faults. As the Church Mountain Thrust i s considered a shallow subsidiary of the Shuksan, only the l a t t e r i s considered a fundamental boundary i n this study. Between the Straight Creek and Shuksan Faults (subdivision C-2) are rocks of the Shuksan Metamorphic Suite, represented by the Darrington P h y l l i t e (D). This suite was brought up along the westerly-directed Shuksan Thrust, believed to be deep-seated because of associated sheared ultramafic rocks and s l i c e s of Yellow Aster basement (YA). West of the Shuksan Thrust, subdivision C-3 contains sedimentary units which are complexly folded and faulted ( i . e . , Church Mountain Thrust), but 22 are notably less-metamorphosed than Shuksan rocks. Units i n this belt are the Chilliwack Group (CH), Cultus.Formation (C), and Nooksack Group (NK). Misch described the Vedder Mountain metamorphic rocks (subdivision C-4) as a large s l i c e of pre-Devonian (Yellow Aster) basement. Misch included Vedder Mountain with other basement s l i c e s associated with the Shuksan Thrust, but because of i t s s i z e , post-Devonian age, and d i s t a l position from the f a u l t , i t i s placed as a separate tectonic unit i n this study. I t s eastern contact with C-3 sedimentary units i s a steeply-dipping f a u l t ; Monger (1970) believed a similar f a u l t l i e s to the west, buried i n alluvium. Descriptions of units within the Cascades, thei r deformational history and temporal relationships follow. C-l : C r y s t a l l i n e Core Rocks This subdivision represents the northern extension of the Cascade "core," described by McTaggart and Thompson (1967) as the Custer Gneiss. Banded, migmatitic, augen gneiss i s closely associated with coarse pegma-t i t i c bodies; amphibolite, metasedimentary and meta-ultramafic s c h i s t , marble, skarn and quartzite are present i n lesser amounts. In places the Yale intrusions are i d e n t i c a l i n appearance to portions of the Custer Gneiss. Almandine amphibolite facies metamorphism dominates Custer rocks, and granulite facies i s present l o c a l l y . McTaggart and Thompson believe the Custer Gneiss was formed by i s o -chemical metamorphism and migmatization of the Hozameen Group; the contact between units represents a migmatitic front which cuts across layering of Custer and Hozameen units at a low angle. Highly sheared and r e c r y s t a l l i z e d rocks i n the t r a n s i t i o n zone indicate that movement also occurred along the zone separating the two units. 23 Timing of gneiss formation i s not known accurately. Misch suggested that Skagit Metamorphism may be synchronous with formation of the Shuksan Suite (see below) which recent work by R. L. Armstrong (personal communica-t i o n , 1977) has shown to span the Late Jurassic to Lower Cretaceous i n t e r v a l . This age i s considerably younger than Misch's published estimate, determined on stratigraphic and s t r u c t u r a l grounds. Skagit Metamorphism i s assumed to extend from uppermost Jurassic through major mid-Cretaceous orogeny (R. L. Armstrong, personal communication, 1977). The Custer Gneiss i s overlain unconformably by Eocene Chuckanut (CK) conglomerate and sandstone which represent continental trough deposits between the Hope and Yale Faults. In the study area Chuckanut rocks con-s i s t e n t l y occur along the east side of the Hope Fault. I t i s debatable whether or not the Chuckanut Formation has been folded, for the geometry of the unit i n the study area may be a result of deposition along an active fa u l t zone. Just south of the border, Staatz, et_ a l . , (1972) report that the Chuckanut Formation has been gently folded, but only t i l t i n g was noted near the border. Oligocene Skagit (SK) volcanic rocks were deposited unconformably on Custer Gneiss; they cover the Custer/Hozameen contact and l a t e Eocene plutonic rocks south of the border, but are intruded by late Oligocene intrusive phases of the Chilliwack Batholith. The unit, which resembles the Coquihalla Group, consists of 5,000 feet of gently folded volcanic flows and pyroclastic rocks of andesitic to r h y o l i t i c composition. The Chilliwack composite batholith, composed of t o n a l i t e , granodiorite and quartz monzonite, i s a high-level intrusion i n which three main phases are recognized: Chilliwack b a t h o l i t h , Mt. Barr ba t h o l i t h , and S i l v e r Creek Stock (Richards and McTaggart, 1976). Hornfelsic contact aureoles are characteristic of these intrusions which cut across a l l e a r l i e r Cascade 24 structures. These young plutons (40-16 Ma i n the study area) generally are associated with volcanic rocks of si m i l a r ages ( i . e . , Skagit volcanic rocks); this association t y p i f i e s the Cascade Belt which extends southerly into northern C a l i f o r n i a . Development of the western boundary of the Custer Gneiss occurred during movement of the Straight Creek Fault. Misch bracketed movement between faulted Paleocene Chuckanut st r a t a and upper Eocene intrusions which cut the fau l t south of the border. However, Eocene Chuckanut strata i n the study area are cut by the f a u l t , contradicting Misch's estimate of an upper l i m i t to f a u l t movement. If Chuckanut strata were assumed to have been deposited during f a u l t movement, possibly as a consequence of movement, then an Eocene and Paleocene age could be envisioned, with no lower l i m i t other than mid-Cretaceous. C-2: Shuksan Thrust Plate The Shuksan Suite represents highly schistose rocks of the westerly-directed Shuksan thrust plate, confined between the Shuksan and Straight Creek f a u l t s . South of the border, t h i s suite consists of a thick meta-basalt sequence (Shuksan Greenschist) overlying graphitic p h y l l i t e s and schistose metagreywackes (Darrington P h y l l i t e ) . The upper unit has not been reported north of the border, but Misch's 1977 map of the Northwest Cascades implies the continuation of a Darrington/Yellow Aster assemblage north to an area which was previously described as Chilliwack/Yellow Aster (Monger, 1970; Roddick and Okulitch, 1973). 5 The Darrington unit (D) i s a terrigenous sequence of p h y l l i t e s and schistose metagreywackes which Misch believes to be derived from a c l a s t i c ^Monger's description of cherty p e l i t e s , limestone pods, r e l i c t volcanic textures i n amphibolites and possible altered Permian f u s i l i n i d s strongly suggests a Chilliwack assemblage, but the implications of Misch's 1977 map have been adopted here as they were by Richards and McTaggart (1976). 25 sequence which has no non-metamorphic equivalents i n the Cascades. South of the border, the overlying Shuksan Greenschist i s characterized by high pressure lower blueschist facies metamorphism; Brown (1977) estimates operative pressures of seven kilobars. The nature of metamorphism of the Darrington P h y l l i t e i n the study area i s not known, but assumed to be sim i l a r to that of the Shuksan Greenschist as described above. Deep-seated thrusting along the Shuksan Thrust brought up not only the Darrington, but also s l i c e s of basement material (Yellow Aster Complex) and ultramafic rocks. Along the east side of the Shuksan Thrust, Roddick and Okulitch (1973) show a large s l i c e of Yellow Aster (YA) which Monger (1970) described as coarse, l o c a l l y w e l l - f o l i a t e d amphibolites and d i o r i t e s , and massive, fine-grained amphibolites. Serpentinite lenses were also reported to p a r a l l e l f o l i a t i o n s i n amphibolitic rocks composed of f i f t y percent hornblende with epidote, sphene and plagioclase. Formation of basement material probably occurred i n S i l u r i a n and Ordovician, based on pebbles of Yellow Aster i n Devonian conglomerate and isotopic age determinations of zircons i n Yellow Aster rocks immediately south of the border (Mattinson, 1972). Emplacement of basement material i n this section occurred during Shuksan thrusting. Isotopic dates place metamorphism of the Shuksan Suite i n uppermost Jurassic and Lower Cretaceous; deposition i s believed to have occurred shortly before, i n Middle and Upper Jurassic (R. L. Armstrong, personal communication, 1977). These estimates comply with the r e s t r i c t i o n by Misch that "Shuksan Metamorphism pre-dates the mid-Cretaceous emplacement of the thrust plate and bears no genetic r e l a t i o n to that tectonic event." Movement along the Shuksan Thrust occurred i n mid-Cretaceous time. Time constraints are post-Valanginian and pre-Santonian, i n reference to faulted Nooksack Group rocks and Nanaimo Group sedimentary rocks which 26 overlie the f a u l t . Intense deformation accompanied thrusting near the f a u l t , and imbrication i s char a c t e r i s t i c . C-3: Western Flanking Units Sedimentary rocks dominate this section beneath the Shuksan plate. Chilliwack (CH), Cultus (C) and Nooksack (NK) rocks represent a long period of deposition which began i n Pennsylvanian and continued u n t i l major mid-Cretaceous orogeny, except for one i n t e r v a l of possible nondeposition around the Permo-Triassic boundary. The Chilliwack Group i s a sequence of c l a s t i c rocks, limestones and volcanic rocks. P e l i t e , s i l t s t o n e and fine-grained sandstone form the "base" of the unit along the Church Mountain Thrust (true base i s not exposed). The "base" contains l o c a l arenaceous shallow-water limestone pods with Lower Pennsylvanian crinoids. Coarse sandstone and conglomerate record a period of u p l i f t (after deposition of Pennsylvanian units) f o l -lowed by p e l i t e s , t u f f s and up to 2,000-foot sections of Lower Permian limestone. The top of the sequence contains arc-type eugeosynclinal v o l -canic rocks ranging from pillowed basalt to d a c i t i c pyroclastic rocks (Misch, 1977). Ribboned chert i s interbedded with volcanic rocks, generally s t r a t i g r a p h i c a l l y equivalent to or conformably overlying Pennsylvanian limestone. Monger (1970) states that this stratigraphic sequence i s applicable only to the area south of the Fraser River. Lowes (1972), who studied the area north of the Fraser River (see Figure 2-5, below), char-acterized the sequence as a varied sedimentary succession overlain by volcanic rocks, but he did not emphasize the presence of limestone. Monger states that the Chilliwack Group closely resembles the Hozameen Group l i t h o l o g i c a l l y , but the presence of a larger amount of The time-space plot shows the base of the Chilliwack Group extending into Devonian, as considerable Devonian limestone occurs south of the border (Danner, 1976). c l a s t i c material and evidence of near-shore deposition and subaerial erosion point to an environment of deposition that i s not known elsewhere i n south-western B r i t i s h Columbia. The disconformable contact between Chilliwack and Cultus units i s the result of either gentle upwarping (r e f l e c t i n g a deep-seated phenomena), or rapid accumulation of the uppermost volcanic rocks so that a shallow basin could not be maintained. The base of the Cultus Formation i s a t h i n , sporadic breccia layer containing clasts of underlying Chilliwack volcanic rocks. Above this breccia i s a sequence of f i n e , t u r b i d i t i c sediments which span the Late Tr i a s s i c to mid-Late Jurassic i n t e r v a l . The Cultus Formation i s a rather uniform section of alternating graded beds of p e l i t e , s i l t s t o n e and fine sandstone with rare coarser v a r i e t i e s , cherty p e l i t e s and limestone pods. The Upper Jurassic to lowermost Cretaceous Nooksack Group has been described only by Misch south of the border, although Monger's uppermost Cultus Formation i s temporally equivalent and l i t h o l o g i c a l l y s i m i l a r . The most recent maps by Roddick and Okulitch (1973) and Misch (1977) show an area of Nooksack Group west of the westernmost Cultus exposures, but the contact i s covered by alluvium. Deposited i n a trench environment, the Nooksack Group consists of rapidly-accumulated, volcanically-derived grey-wackes, si l t s t o n e s and slates with l o c a l conglomerate, t u r b i d i t e , clay and volcanic i n t e r c a l a t i o n s , characterizing a deep marine basin with l o c a l highs. The outstanding structural features of t h i s section are thrust faults and folds associated with Shuksan thrusting. The Church Mountain Thrust i s considered a shallow off-shoot of the Shuksan "root zone," u p l i f t i n g Chilliwack and Cultus rocks. Near the base of the Shuksan, s l i c e s of base-ment and serpentinized peridotite are imbricated with Chilliwack rocks of albite-epidote amphibolite facies metamorphism. The Cultus and Nooksack units occur below the Church Mountain Thrust; they are generally believed 28 to be autochthonous, simply because there i s no evidence that they have been transported s i g n i f i c a n t l y . Tight, northwesterly overturned folds r e f l e c t i n g thrust geometry were formed during thrusting; penetrative slaty cleavage and p h y l l i t i z a t i o n also formed, especially i n finer-grained rocks. The same time constraints have been placed on Church Mountain thrust movement as for the Shuksan; the possible time span for movement centered around mid-Cretaceous time. South of the Fraser River a second episode of folding was accompanied by reverse f a u l t i n g , both affecting the older, major thrust planes. This episode i s dated tentatively as Eocene, when the Chuckanut Formation was also folded s l i g h t l y . Metamorphism of Chilliwack and Cultus rocks i n this area occurred under moderate t o t a l pressures and high thermal gradients characterizing metamorphic conditions between prehnite-pumpellyite and blueschist facies (Beaty, 1972). North of the Fraser River, Lowes (1972) characterizes metamorphism of the Chilliwack Group as being d i s t i n c t l y higher grade than i n corre l a t i v e rocks to the south. An increase i n metamorphic facies occurs from west to east from greenschist to upper epidote amphibolite facies as the Shuksan Thrust i s approached. These higher grade rocks are garnetiferous and hornblende-rich schists. Monger noted that faults correlative with the Shuksan and Church Mountain Thrusts i n this northern area dip steeply to the east i n contrast with their r e l a t i v e l y f l a t - l y i n g counterparts to the south. C-4: Vedder Mountain Wedge Basement rocks on Vedder Mountain, southwest of Hope, belong to the Yellow Aster Complex of "ancient" continental crust (Misch, 1966). Misch 29 describes the area as an autochthonous f a u l t wedge of a "highly c r y s t a l l i n e , metamorphic-plutonic complex." Upper amphibolite facies metamorphism of Yellow Aster rocks i s accompanied by younger tectonic s l i c e s of a l b i t e -epidote amphibolite facies rocks which were dated at 250 Ma (lowermost Upper Permian), and believed by Misch to represent a younger metamorphic episode than that which affected the surrounding Yellow Aster Complex. More recent Rb/Sr dates by R. L. Armstrong (personal communication, 1977) show that Vedder Mountain "basement" was formed i n Upper Permian to Lower-most T r i a s s i c time; parent rocks are probably Pennsylvanian to Lower Permian. The western edge of Vedder Mountain i s buried i n alluvium, but i s probably a f a u l t , as the nearest outcrops to the west are of s l i g h t l y metamorphosed Jurassic volcanic rocks and intrusions of the Coast Plutonic Complex. SPUZZUM PLUTONIC BELT The Spuzzum Plutonic Belt i s named after the intrusions which dominate i t , but minor amounts of Tertiary volcanic rocks and metamorphic rocks of pre-Spuzzum age are also present. The belt i s delineated by the Fraser River Fault Zone and the Hope Fault on the east, the southernmost extension of the Spuzzum intrusions, the northerly extension of the Shuksan Thrust, and a hazy boundary to the west between Spuzzum and Scuzzy intrusions enclosing Paleozoic (?) pendant rocks, and the Coast Plutonic Complex with i t s much more varied assortment of pendants. In this belt Cascade and Coast Plutonic structures merge. A l l pre-Spuzzum units have been designated as either Custer Gneiss or Settler Schist; positive correlation i s not yet possible, but evidence w i l l be cited below which lends support to this suggestion. Units i n this study are labelled according to Roddick and Okulitch (1973). 30 Metamorphic Rocks Less than 30 percent of the Spuzzum Plutonic Belt i s composed of highly metamorphosed (amphibolite grade) pendant rocks which have been studied i n d e t a i l by various persons. Figure 2-5 shows the study areas of certain workers mentioned i n the following discussion. Referred to as Chilliwack Group on GSC Map 737A and as Hozameen Group by McTaggart and Thompson (1967) and Roddick and Hutchison (1969), Lowes (1972) suggests that this uniform sequence of aluminum-rich p e l i t i c schists and metamorphosed si l t s t o n e s and sandstones should be distinguished from the varied sequences of Chilliwack and Hozameen Groups. Localized meta-morphosed breccias and quartz pebble conglomerates, amphibole-bearing sc h i s t s , amphibolite and quartz feldspar porphyry dikes also characterize the Settler Schist (SS). Pigage (1976) suggests that o r i g i n a l rock types of the Settler Schist characterize a eugeosynclinal environment of shales and less common interbedded carbonate-rich layers, conglomerates, tuffs and sandstones or cherts. The type area of the Settler Schist i s east of Old Settler Mountain, southwest of Yale. As set out by Lowes, the Settler Schist i s confined by the Hope Fault on the east and the northward extension of the Shuksan Thrust on the west (discussed below), continuing northward to the area described by H o l l i s t e r (1969a,b) northwest of Boston Bar.^ Lowes concluded that Barrovian amphibolite facies metamorphism of unknown age was upgraded by another contact-metamorphic event resulting from intrusion of the Spuzzum Pluton. Pigage concluded that two metamorphic-^ H o l l i s t e r describes this area as dominated by greywacke, and reports some pillowed amphibolite. The long, narrow belt of northwest-trending serp-en t i n i t e i s correlated with the Hozameen Fault by Roddick and Hutchison (1969). This move also suggests that the pendant i s a Hozameen and Ladner combination, but t h i s idea has been abandoned for a more northerly Hozameen correlation, and Lowes believes the pendant to correlate with the Settler Schist. 31 Figure 2-5. Study areas of some p r i n c i p l e workers dealing with the metamorphic rocks of the Spuzzum P l u t o n i c B e l t . Refer to Table 2-1 for d e f i n i t i o n of abbreviations. 32 deformational events affecting the Settler Schist were continuing phases of the same Late Cretaceous orogeny during which the Spuzzum Pluton was emplaced. H o l l i s t e r considered metamorphism to be the result of one deep-seated prograde contact-metamorphic event occurring during intrusion of surrounding plutons. These c o n f l i c t i n g opinions are a consequence of g structural and metamorphic relations which have yet to be resolved. This study follows Lowes' assumption that an older event which pre-dates Spuzzum intrusion must have occurred prior to u p l i f t along the Shuksan Fault east of Harrison Lake (see discussion below). Regardless of when metamorphism occurred, i t i s generally considered to be deep-seated. H o l l i s t e r (1969a) estimated effe c t i v e pressures between 5.5 and 7.1 kilobars; Pigage (1976) estimated pressures between 5.5 and 8.0 kilobars (18-26 kilometers) and temperatures between 550-700°C. Information on the area northeast of Harrison Lake has been summarized from work by Reamsbottom (1974), who i d e n t i f i e d two conformable stratigraphic units which he called the Breakenridge and Cairn Needle Formations. The Breakenridge Formation i s composed of gneiss with amphibolite, minor mig-matite and skarn; the pre-metamorphic assemblage i s believed to be a mixture of greywacke, volcanic rocks and minor p e l i t e . The base of the overlying Cairn Needle Formation i s a stretched-pebble conglomerate which contains I t seems that the major d i f f i c u l t y l i e s i n the f a c t that a n d a l u s i t e appears to be a contact-metamorphic e f f e c t of the Spuzzum and Scuzzy i n t r u s i o n s ; Read (1960), H o l l i s t e r (1969a,b), Lowes (1972), and Pigage (1976) a l l noted the presence of c h i a s t o l i t e pseudomorphs i n the S e t t l e r S c h i s t near plutons. However, Pigage noted that pseudomorphs i n h i s area c o n t a i n products of r e g i o n a l k y a n i t e - s i l l i m a n i t e metamorphism, suggesting that t h i s higher pressure r e g i o n a l event followed i n t r u s i o n of the Spuzzum. S l i g h t t i l t i n g a f t e r i n t r u s i o n i s proposed to have caused t h i s i n c r e a s e i n pressure. H o l l i s t e r suggests that a n d a l u s i t e i s formed metastably under the same con d i t i o n s that formed k y a n i t e and s i l l i m a n i t e , and t h e r e f o r e r e q u i r e s only one episode of metamorphism w i t h i n c r e a s i n g temperature. These suggestions do not agree w i t h conclusions reached by Lowes that an e a r l y p e r i o d of deformation must have occurred before u p l i f t along the Shuksan Thrust and i n t r u s i o n of the Spuzzum pl u t o n . g r a n i t i c clasts and indicates s l i g h t u p l i f t before deposition of the Cairn Needle Formation. Above the conglomerate are meta-sedimentary schists (some p e l i t i c ) with minor c a l c - s i l i c a t e schist and limestone. P e l i t e s , conglomerate and limestone indicate a varied shallow marine environment. Reamsbottom correlated the Breakenridge with the Custer Gneiss and noted that the Cairn Needle merges to the south with the type area of Lowes' 9 Settler Schist which i s also probably part of the Skagit Metamorphic Suite. Granitoid clasts i n Cairn Needle conglomerates suggested to Reamsbottom that deposition may have occurred post-Coast Plutonic Complex, but Paleozoic conglomerates have also been known to contain such material. Age of these units i s therefore assumed to correspond to that of the Custer Gneiss. Reamsbottom delineated four phases of ess e n t i a l l y homoaxial pre-Late Cretaceous folding, which affected both units to the same degree. One of the l a t e r phases produced large, gneiss-cored, northwesterly-trending dome structures. Amphibolite facies Barrovian metamorphism was synchronous with folding before mid-Cretaceous f a u l t i n g . ^ The d i s t i n c t i o n of the southwestern boundary of the Spuzzum Belt l i e s i n Lowes' continuation of the Shuksan f a u l t into his area. Factors which led to his conclusion include the following: 1) The presence of rocks s i m i l a r to the Yellow Aster Basement Complex; 2) ultramafic rocks (some of which he likens to alpine-type dunites) whose contacts appear to be tectonic; 3) truncation of metamorphic isograds; and 9 I t i s interesting to note that the varied Cairn Needle assemblage includes limestone and appears to contrast with Lowes' uniform p e l i t i c sequence which has a notable lack of limestone. ^ C h i a s t o l i t e pseudomorphs were also recognized by Reamsbottom as a contact effect of Scuzzy intrusion. Whereas pseudomorphs i n Pigage's area contain s t a u r o l i t e , those i n Reamsbottom's area contain s i l l i m a n i t e , which does not require an increase i n pressure. 4) juxtaposed d i s s i m i l a r rock units. Unfortunately, Reamsbottom was not able to extend the trace of the Shuksan Thrust any further northward, so the f a u l t i s shown as being the eastern boundary of rocks mapped as Chilliwack, and i s not followed any further northward than are Chilliwack rocks. An important outcome of Lowes' work i s the implication that thrusting along the Shuksan i n t h i s area brought up rocks resembling schists of the Skagit Metamorphic Suite instead of the Shuksan Suite which forms the Shuksan plate to the south. The conclusion that this belt represents the northward continuation of the Cascade core axis at a much deeper st r u c t u r a l l e v e l i s a t t r a c t i v e . Intrusive Rocks The Giant Mascot body i s a large, crudely-zoned ultramafite located centrally within the Spuzzum pluton; isotopic ages place i t i n the Lower to mid-Cretaceous i n t e r v a l . I t has been suggested that the Giant Mascot body i s an early phase of Spuzzum a c t i v i t y (McLeod, 1975), but the r e l a t i o n -ship between ultramafic rocks and Spuzzum d i o r i t e and t o n a l i t e i s not known with certainty, other than the fact that the l a t t e r intrudes the former (Vining, 1977). I t i s interesting to note that the Giant Mascot body also l i e s at the southeastern end of a northwesterly-trending belt of ultramafic rocks which are believed to have been emplaced t e c t o n i c a l l y along the mid-Cretaceous Shuksan Thrust. Unfortunately, the connection between Giant Mascot and the Shuksan belt i s masked by the Spuzzum pluton. The Spuzzum and Scuzzy plutons are considered to be the easternmost extension of the Coast Plutonic Complex, and y i e l d Cretaceous K/Ar dates (see Figure 2-2) that correspond to the major pulse of Coast Plutonic intrusion. Richards and McTaggart (1976) show the Spuzzum as a zoned 35 intrusion of three d i o r i t i c phases surrounded by a l a t e r margin of t o n a l i t e (quartz d i o r i t e ) . The Scuzzy pluton was considered younger than the Spuzzum pluton (Roddick and Hutchison, 1969) because of a supposed genetic relationship between Scuzzy and Hell's Gate plutons (see below), but K/Ar dates have not been able to distinguish Scuzzy and Spuzzum plutons as separate intru s i v e events. The Scuzzy i s l i t h o l o g i c a l l y d i s t i n c t from the Spuzzum, composed of coarse granodiorite with less than f i v e percent mafic content, contrasting with the 15-25 percent mafic content of the Spuzzum. Hell's Gate pluton i s an Eocene to Oligocene fine-grained intrusion of granodiorite that i s truncated by the Straight Creek Fault. Tertiary Volcanic Rocks The only reference to Miocene-Pliocene acid volcanic rocks (av) appears i n Roddick and Hutchison (1973), who admit that the age of these rocks i s " l i t t l e more than a deflected guess." Unconformable on plutonic rocks and generally f l a t - l y i n g with l o c a l dips of 30° or l e s s , these volcanic rocks are remnants of a "once extensive cover of . . . r h y o l i t i c to d a c i t i c pyroclastics and flows." COAST PLUTONIC BELT F i f t y - f i v e percent of the study area consists of rocks of the Coast Plutonic B e l t , a tectonic province with about 20 percent non-plutonic rocks which occur as pendants or remnant units. Most pendant rocks are either highly deformed and metamorphosed or regionally altered during intrusion of plutonic rocks, although l o c a l unaltered areas are known. Cover units are dominantly volcanic and volcano-sedimentary, although a sedimentary record of erosion of the Coast Range i s preserved i n the southernmost portion of the belt. 36 Pendant Rocks Older Units of Unknown Age The oldest named units which occur as pendants i n the Coast Plutonic Belt are the Twin Islands (TI) and Bowen Island (BI) Groups. Except where noted, information concerning these units was obtained from Roddick (1965). The Twin Islands Group forms small pendants which commonly appear to grade into surrounding intrusive rocks through migmatitic zones. Rock types include granulite, amphibolite, micaceous quartzite, p h y l l i t e , schist and gneiss, with minor quantities of conglomerate, meta-andesite, rhyo-dacite and hornfels. Metamorphism i s generally high-grade ( i . e . , upper amphibolite), but examples of pendants containing small, scarcely-altered areas are reported. This group i s a ca t c h - a l l for rocks which have under-gone a period of intense metamorphism and therefore may include rocks of varying ages. Age of the group i s estimated as Pennsylvanian-Permian according to Roddick and Okulitch (1973). Highly metamorphosed cong-lomerates contain cobbles of plutonic rocks which must have been derived from an older plutonic terrane. At the northern end of Harrison Lake, rocks mapped by Roddick as Twin Islands Group correspond to a section of Reamsbottom's Cairn Needle Formation (Custer Gneiss), also of unknown age. A large pendant northeast of Squamish i s mapped as having Twin Islands Group i n the south and younger, less-deformed Gambier Group (G) i n the north (see below). The Bowen Island Group occurs on and near Bowen Island. I t i s dom-inated by massive, andesitic greenstone flows with minor interbedded sedimentary rocks, which are thinly-banded, cherty and tuffaceous. Meta-morphism i s up to greenschist facies. Several thousand feet of strata are thought to be present. The age of t h i s group i s unknown, but i s placed at 37 Lower to mid-Upper T r i a s s i c because Roddick believed i t to be older than the Cultus Formation and younger than the Twin Islands Group.''''' Roddick and Okulitch (1973) placed the Bowen Island Group i n the T r i a s s i c . Three unnamed units of unknown age are shown as "m," "ms," and "gn" on Figure 2-1, but do not appear on the time space plot (Figure 2-2). Many possibly are more highly metamorphosed equivalents of surrounding units. Only b r i e f descriptions are available for each as follows: m: Undivided metamorphic rocks including gneiss, s c h i s t , hornfels, metavolcanic rocks, quartzite, greywacke, s l a t e , a r g i l l i t e , migmatite, and agmatite (Bostock, 1963). ms: Metasedimentary rocks including micaceous quartzite, biotite-hornblende s c h i s t , schists bearing garnet, s t a u r o l i t e and possibly s i l l i m a n i t e (Roddick and Hutchison, 1973). gn: Gneissic units including granitoid gneiss, migmatitic complexes, and minor amphibolite and b i o t i t e schist (Roddick and Hutchison, 1973). Roddick and Okulitch (1973) correlated some of these pendants with the Twin Islands Group or Custer Gneiss. Harrison Lake Sequence A short i n t e r v a l of volcanism on the west side of Harrison Lake i n Bajocian (lowermost Middle Jurassic) time was followed by sporadic sedi-mentation through Hauterivian (mid-Lower Cretaceous) time. F o s s i l s have been of great importance i n determining ages of these units, a r a r i t y for Coast Plutonic Belt pendant rocks whose f o s s i l ages are generally indeter-minate. Information concerning these formations i s taken from Monger (1970), except where noted. Approximately 9,000 feet of intermediate to acid pyroclastic and flow rocks make up the Harrison Lake Formation (HL). Rock types include kerato-^The l a t t e r r e s t r i c t i o n i s based on the lesser degree of metamorphism, but he also suggests that i t may be a less-metamorphosed equivalent of the Twin Islands Group. 38 phyre, quartz-keratophyre, meta-andesite and dacite. Pyroclastic rocks include volcanic breccias with fragments up to one foot i n diameter and l i t h i c and c r y s t a l t u f f s ; flows are commonly porphyritic, massive, or l o c a l l y columnar jointed. Fossils indicate a Bajocian age, and possibly also Bathonian. This formation conformably overlies sandstone, black a r g i l l i t e and tuff labelled as Cultus Formation, but whose id e n t i t y and age are, i n f a c t , unknown. Contemporaneous volcanism sim i l a r to that of the Harrison Lake Formation occurred south of the border i n the Cascades (Misch, 1966). Conformably overlying the Harrison Lake Formation i s a series which includes the Echo Island, Mysterious Creek and Billhook Creek Formations, grouped together on the compilation map (Figure 2-1) for convenience as BME. Waning volcanism i s represented by nearly 3,000 feet of w e l l -s t r a t i f i e d , fine-grained tuff and minor agglomerate, sandstone, and a r g i l l i t e of the Echo Island Formation. Two to three thousand feet of uniform black calcareous a r g i l l i t e of the Mysterious Creek Formation ove r l i e Echo Island, and contain mid-Callovian f o s s i l s . These a r g i l l i t e s grade upward into the Billhook Creek Formation, composed of fine tuffs and volcanic sandstones with an apparant thickness of 1,800 feet. This gradational relationship implies the Billhook was deposited during upper Callovian; Brookfield (1973) also reports lower Oxfordian f o s s i l s . These three formations are found west of Long Island i n Harrison Lake as a conformable series which was mapped by Roddick on the adjacent western map sheet as the F i r e Lake Group (FL) which i s discussed below. Three thousand feet of poorly-sorted conglomerate (notably without gr a n i t i c pebbles) of the Kent Formation (K) i s sandwiched between two black argillaceous units south of Harrison Lake. A r g i l l i t e occurring conformably (?) below the conglomerate i s believed to be the mid-Callovian Mysterious Creek Formation; the section above i s referred to as the Agassiz P r a i r i e Formation (AP). Interbeds of sandstone, tuff and limestone are also present within this upper a r g i l l i t e sequence. If Oxfordian a r g i l l i t e s on the Cascade Peninsula can be considered to be Agassiz P r a i r i e Formation, the Kent Formation must also be Oxfordian, but Brookfield (1973) considered the Cascade Peninsula outcrop to be equivalent to the Billhook Creek Formation, i n which case both the Kent and the Agassiz P r a i r i e Formations can only be referred to as post-Oxfordian. Conglomerate with g r a n i t i c pebbles which resemble in t r u s i v e rocks occurring seven miles west of Harrison Lake, forms the base of the 1,260-foot thick Peninsula Formation (PN) which rests with angular unconformity on the Billhook Creek Formation. Arkosic sandstone forms the remainder, and Lowes (1972) reports layers of limestone. Berriasian and lower Valanginian f o s s i l s have been described. This formation may i n fact be the Nooksack Group, as they are temporally equivalent. Nooksack conglomerate on Vedder Mountain was mapped by Monger as possible Peninsula Formation because of s i m i l a r clast material. Conformable above the Peninsula Formation i s the 3,700-foot thick Brokenback H i l l Formation (BH) of Valanginian, Hauterivian, and possibly younger ages (the top i s faulted against older rocks). Tuff and agglomerate with minor amounts of sandstone and shale form a lower section overlain by bedded greywackes. Roddick (1965) mapped the westernmost extensions of the Peninsula and Brokenback H i l l Formations as F i r e Lake Group(FL). F i r e Lake and Gambier Groups; Pioneer Formation The F i r e Lake Group (FL) i s described i n d e t a i l by Roddick (1965). Berriasian f o s s i l s were located i n limestone of the lower member of the group, and i t includes Bathonian, Callovian and Oxfordian units described 40 above. The questionable extension up into Albian time i s a result of l i t h o l o g i c correlation with the Gambier Group. Lithologic divisions within the F i r e Lake Group are based on units of the large pendant northwest of Harrison Lake. A lowermost section of 12 fine-grained granulite and minor andesite, limestone and conglomerate i s overlain by a section of slate and a r g i l l i t e with minor amounts of grey-wacke. Above these units i s a thick greenstone member with some conglom-erate, quartzite and greywacke. Conglomerates contain appreciable g r a n i t i c d e t r i t u s , but some plutons are cross-cutting. The thickness of the group i s estimated at 15,000 feet. Metamorphism of a l l units i s s l i g h t except for the lowermost granulite unit which i s amphibolite facies. The Gambier Group i s characterized by andesitic to d a c i t i c volcanic and sedimentary rocks whose complexity, rapid facies changes and paucity of f o s s i l s make correlations between pendants d i f f i c u l t . However, the general character of volcanism has led to the designation of rocks i n an increasing number of pendants as Gambier Group. On Gambier Island, Gambier Group rocks unconformably ove r l i e Upper Jurassic plutonic rocks (McKillop, 1973); l a t e r plutons intrude pendant rocks. Roddick (1965) describes an approximately 6,000-foot section east of Gambier Island with three subdivisions l y i n g unconformably (in places v e r t i c a l l y ) on plutonic and metamorphic rocks. A basal conglomerate with g r a n i t i c cobbles i s overlain by andesitic flows and pyroclastic rocks of the lowermost d i v i s i o n . The middle unit consists of s l a t e , a r g i l l i t e , arkose and quartzite. Andesite and t u f f comprise the upper unit whose top has been removed by erosion. Albian ammonites were recovered from slaty _ Roddick (1965) defines granulite as "a feldspathic metamorphic rock having a r e l a t i v e l y even granular texture, s i m i l a r to an amphibolite, but containing less than 50 percent amphibole. Most of these rocks f a l l i n the amphibolite facies . . . not the granulite facies . . . ." 41 a r g i l l i t e i n this area. The large pendant north of t h i s section was described o r i g i n a l l y by James (1929) as the Britannia and Goat Mountain Formations. Here an almost 20,000-foot section whose sequence d i f f e r s s l i g h t l y from that to the south i s similar l i t h o l o g i c a l l y . The Cheakamus, Empetrum and Helm Formations (CEH) were described o r i g i n a l l y by Mathews (1958) as Upper Cretaceous sedimentary rocks north of Squamish, but recent reassignment of f o s s i l s found i n the Cheakamus 13 Formation implies a Lower Cretaceous age (Roddick, et a l . , 1977). Basal conglomerate of g r a n i t i c and greenstone pebbles si m i l a r to that of the Gambier Group, along with a Lower Cretaceous age and the fact that forma-tions are cut by l a t e r intrusive phases has led to the inclusion of these formations i n the Gambier Group. The sequence here i s not clear, as formations are i n f a u l t contact with each other, but there appears to be more than 20,000 feet of section. Several thousand feet of volcanic rocks are present and sedimentary rocks appear to contain an appreciably higher proportion of coarser-grained units than to the south. Limestone and limy sedimentary rocks also appear to be more common here. The Pioneer Formation, of Norian age, o r i g i n a l l y referred to a small, 1,000-foot section of variable greenstones (with minor amounts of rhyolite) north of the study area near Bralorne, but was extended southward on f o s s i l evidence by Roddick and Hutchison (1973) to a 5,000-foot sequence north of Pemberton. An unpublished map by Woodsworth (ca. 1975) extended the form-ation even further south to include two sub-parallel pendants north of Garibaldi. Roddick and Okulitch (1973) consider these same pendants as part __ — — — Green (1977) suggests that the Empetrum i s not part of this section, but pre-Cretaceous, as i t contains highly metamorphosed rocks, and dolomitic interbeds within the greenstone. 42 of the F i r e Lake Group, whereas Roddick, et_ a l . , 1977, and Woodsworth, 1977, consider them Gambier Group. The most recent correlation with the Gambier Group has been adopted i n this study, although i t i s by no means certain. No g r a n i t i c pebble conglomerates have been reported i n these northern pendants, and sedimentary rocks are a very minor component; limestone occurs l o c a l l y . The overwhelming majority of pendant rocks are intermediate to acid pyroclastic and flow rocks. The western pendant has yielded one reasonable K/Ar date of 124 + 4 Ma (see discussion of Northair Mine, Chapter Two). 1 4 Greenschist facies metamorphism affected the majority of Gambier Group rocks. Deformation i s l o c a l i z e d along northwesterly-trending zones of intense f o l i a t i o n , many of which are p y r i t i c . These f o l i a t e d zones are commonly referred to as "shear zones," although i n many i t i s questionable whether shear displacement has actually occurred. One such zone of major proportions i n the Britannia pendant w i l l be discussed i n d e t a i l i n Chapter Two. Plutonic Rocks Intrusive rocks representing the Coast Plutonic Complex (CR) i n the study area are most commonly reported to be quartz d i o r i t e or granodiorite, but other types of coarse-grained g r a n i t i c rocks (except syenite) are repre-sented i n lesser amounts. A northwesterly-trending f o l i a t i o n p a r a l l e l i n g pendant contacts i s common; contacts with pendants are sharp or gradational. Included with rocks designated as plutonic are migmatitic complexes containing over 50 percent plutonic rock. B r i t t l e deformation i s generally exhibited i n these rocks through f a u l t i n g and/or brecciation (Roddick, 1965). 1 4Green (1977) also considers these pendants pre-Cretaceous, s p e c i f i c a l l y , Jurassic, but does not state what c r i t e r i a led to this conclusion. 43 The e a r l i e s t record of intru s i v e a c t i v i t y occurs on Gambier Island and near the north end of Howe Sound; K/Ar dates are Upper Jurassic. A 30 m i l l i o n year gap occurs before the main pulse of plutonism i n upper Lower Cretaceous and Upper Cretaceous. One upper Paleocene date was obtained just outside the study area, south of Pemberton. Post-Plutonic Rocks Dominantly Eocene units exposed sporadically i n the Fraser River delta area consist of sedimentary and basic volcanic rocks labelled "s" and "bv," respectively (Figure 2-1). Sedimentary rocks include sandstone, shale and conglomerate (some t u f f and coal) which l i e unconformably on plutonic rocks and thicken to about 9,000 feet south toward the United States border. Shales become dominant to the south, indicating a northern source ( i . e . , Coast Range), but younger units thicken southward, indicating a more recent southern source. These continental floodplain deposits contain mostly Eocene f o s s i l s , but l a t e Campanian i s recorded north of Burrard I n l e t , and Roddick (1965) believed that younger, more southern units might be Oligocene. Rare basalt and tu f f interbeds i n the above-described sedimentary rocks are l o c a l l y thick enough to map as a separate unit. Fine-grained, porphyritic basalt i s l o c a l l y columnar-jointed, but o r i g i n as flows or s i l l s has not been determined. Dikes and rare pyroclastic rocks are also present. Quaternary, calc - a l k a l i n e Cascade volcanism extends from northern C a l i f o r n i a through Oregon and Washington, into B r i t i s h Columbia where i t appears as the Pleistocene to Recent Garibaldi Group (GB; Green, 1977). Basalt, andesite and dacite flows were extruded on the glaciated surface of the Coast Mountains. There i s evidence of extrusion contemporaneous with gl a c i a t i o n ; pre- and post-glacial lavas flowed along present valley floors which are s t i l l occupied by r i v e r s . 44 SUMMARY AND DISCUSSION A tectonic summary of the study area i s presented i n Table 2-4, and a generalized discussion of a plate tectonic model follows. The evolution of the Canadian C o r d i l l e r a has been described as the development of a series of Upper Paleozoic-Lower Mesozoic volcanic arcs off the coast of the continental craton, successively added to the craton through subduction (Monger, et_ a l . , 1972). As each arc c o l l i d e d with the craton, the related subduction zone ceased to function, and another one began to operate west of the arc. Figure 2-6 i l l u s t r a t e s this process and shows the locations of possible subduction zones i n the C o r d i l l e r a . To relate this model to the study area, one can view the mid-Cretaceous event discussed above as resulting from c o l l i s i o n between the P a c i f i c Plate, carrying a volcanic-plutonic arc (Coast Plutonic Complex), and the craton, to which the Omineca and Intermontane Belts have also been added. Meta-morphic core rocks of the Spuzzum and Cascade Belts mark the axis of compression, bounded by oppositely-verging thrusts (see Figure 2-la) , i l l u s t r a t i n g the compressive force which moved material up and away from the convergent zone. Subduction responsible for the Coast Plutonic Complex ceased after mid-Cretaceous c o l l i s i o n , although intermittent plutonism did occur through Miocene. Subduction responsible for Cascade volcanism i s a more recent phenomenon which overlaps the Coast Plutonic arc i n the study area, but does not continue far northward where plate interaction i s of a transcurrent nature. As suggested i n Figure 2-6A, subduction was followed by r i g h t - l a t e r a l transcurrent motion. This change i s i l l u s t r a t e d i n the study area by Upper Cretaceous compression followed by transcurrent movement i n Lower Tertiary along the Straight Creek/Fraser River Fault System. TABLE 2-4. SUMMARY OF TECTONIC HISTORY I. I I . TIME SPAN Pre-Devonian Upper Paleozoic/ Lower and Middle T r i a s s i c I I I . Permian/Triassic IV. Upper T r i a s s i c Lower and Middle Jurassic VI. Upper Jurassic VII. Lower Cretaceous VIII. mid-Cretaceous ( l i m i t s undefined) IX. Upper Cretaceous X. Tertiary EVENTS Formation of basement Marine eugeosynclinal deposition i n a basin which shallows westward (or, i f r i g h t - l a t e r a l offset i s considered, shallows to the south). Deformation Volcanism i n the Coast Plutonic Belt and extensively east of the study area forming the Intermontane Belt. Deposition of marine turbidites begins i n the southern section. Deep-water deposition In the Ladner Trough begins from a high source area to the east. Deposition continues i n the south, and a burst of acidic volcanism occurs on the eastern edge of the Coast Plutonic Belt, followed by deposition i n l o c a l basins of varying r e l i e f . Plutonism of unknown extent i n the Coast Plutonic Belt, and some deposition. Deformation and metamorphism begins along a north-south axis i n the Spuzzum and Cascade Belts. Deposition of trench-like sediments along t h i s axis begins. Shallow-water deposition of more easterly-derived sediments in the Ladner Trough and possible intrusion of the Eagle Complex. Considerable marine volcanism and sedimentation i n the Coast Plutonic Belt along with the beginning of intense plutonism and/or cooling of said plutons to the point where they have begun to retain argon to produce radiometric dates. A x i a l deformation continues, and the Giant Mascot Ultramafic body has also cooled s u f f i c i e n t l y to produce K/Ar dates. Trench-l i k e deposition along the metamorphic axis ceases by mid-Lower Cretaceous. Easterly-derived marine deposition continues i n the Ladner Trough, but becomes westerly-derived and non-marine by the close of Albian time, indicating considerable u p l i f t to the west, presumably of the Coast Plutonic Complex. The Eagle Complex i s also shedding debris into the Ladner Belt by Albian. XI. Pleistocene Major thrusting directed away from the central metamorphic axis brought up mantle-derived (?) ultramafic rocks and basement material. Genetically-related folding accompanied thrusting i n the Cascade Belt, Hozameen Basin and Ladner Trough. The Eagle Plutonic Belt was also u p l i f t e d at this time. Figure 2-la i l l u s t r a t e s this deformation episode, and includes l a t e r f a u l t i n g as w e l l . The majority of the Coast Plutonic Complex (and Spuzzum) K/Ar dates are clustered In thi s period, but by the end of Cretaceous time large-scale plutonism had ceased. Major deformation and thrusting i n a l l areas have also ceased by latest Cretaceous. The Coast Plutonic Belt records volcanism and sedimentation which began i n l a t e s t Cretaceous, recording,continued u p l i f t and erosion of theJCoast Mountains. One K/Ar date records l a t e cooling/intrusion of plutonic rocks. Major r i g h t - l a t e r a l move-ment along the Straight Creek/Fraser River Fault Zones and related (?) sedimentation and intrusion occurred before Oligocene. High-level plutons are concentrated i n the Cascade Belt, but are also scattered through-out the area; coeval volcanic rocks were extruded. Calc-alkaline volcanism occurred i n the Coast Plutonic Belt. UNITS INVOLVED (see Figures 2-1, 2-2) YA i n C-2 CH.HZ (TI?,BI?,YA i n C-4?) YA i n C-4 (TI?,BI?) PI.N C L C,D HL,BME CR.FL (AP?,K?) SS, Custer Gneiss D DC Eagle ? G,CEH,FL,PN,BH CR SS, Custer Gneiss D um NK JM,P Shuksan, Church Mountain, Hozameen, Pasayten Faults um Eagle CR, Spuzzum, Scuzzy s.bv.CR ' Straight Creek/Fraser River Fault Zone, CK, Yale Intrusions Hell's Gate, S i l v e r Creek, Chilliwack, Mt. Barr, Needle Peak av,SK,CQ GB °1 46 500 rnls t£2> GRANITIC ROCKS; INCLUDED SOLELY FOR REFERENCE B BLUESCHISI LOCALITIES CANADIAN CORDILLERA I V- PAL.-* \ FRAGMENTS OF OLD ISLAND ARCS \ ^ . C ° N r T | ! | N | T N T A L ' IN NORTHWESTERN BRITISH COLUMBIA? OCEANIC v: CRUST Figure 2-6. A. Possible subduction zones i n the Canadian C o r d i l l e r a ; l a t e r transcurrent motion suggests oblique subduction. Method of accretion of crustal blocks, r e s u l t i n g i n westward "jumping-out" of subduction zones. (Trans-current or normal plate interaction may be respon-s i b l e for c r u s t a l accretion.) (from Monger, et a l . , 1972) 47 3. METAL DEPOSITS INTRODUCTION Public records were examined for a t o t a l of 258 metal deposits i n the study area (Figure 1-2), but t h i r t y of these are not described adequately i n the available l i t e r a t u r e except for location and perhaps general com-modity data. Of the remaining 228 deposits, 86 percent are small occurrences that have never produced. A discussion of every deposit i s not necessary to give the reader an appreciation of mineralization which characterizes the study area. An alternative approach i s to present information only on deposits of the following three categories: 1) major mines and related occurrences 2) mining camps without major mines 3) isolated past-producers and important prospects Table 3-1 i s a compilation of production records from a l l deposits i n the study area for which such information i s available. Those producing deposits which are not included i n discussions of d i s t r i c t s and camps of the f i r s t and second categories outlined above w i l l be presented and d i s -cussed b r i e f l y i n the t h i r d section. Figure 3-1 shows locations of d i s t r i c t s , camps and indiv i d u a l deposits which w i l l be considered i n this chapter. Tabulation of the characteristics of these deposits i s presented with each discussion; abbreviations and symbols used i n these tables are defined i n Table 3-2. Discussion of deposits i n the categories outlined above w i l l acquaint the reader with about two-thirds of the deposits i n the area for which geological information i s available. The remaining deposits, generally the smallest and least known of the p u b l i c a l l y documented occurrences i n the study area, w i l l not be discussed. Mac No. Name Production Metals Produced Reference Time of Production G-3 Britannia G-5 Zel G-14 Lorraine G-23 Cambrian Chiefton G-24 King Midas G-25 Ashloo G-26 Money Spinner C--34 Viking 52,783,964 T Cu,Zn,Pb,Ag,Cd,Au BCDM G-36 Dandy HSW- 1 Canam HSW-2 Invermay HSW-4 Giant Mascot HSW-8 Empress HSW-11 Eureka-Victoria HSW-13 • Seneca HSW-15 Valley View HSW-16 Silver Chief HSW-18 Eureka HSW-25 Silver Daisy HSW-33 Anna HSW-34 Emancipation HSW-36 Aufeus HSW-42 B.B. (Rainbow) HNW-2 Providence HNW-3 Aurum HNW-11 Pipestem HNW-15 Ward J-45 Astra,Cambria J-51 Van S i l v e r J-130 Northair 70 T 1,566 T 95 T 15,047 T 200 lbs 1,500 T in dump and thousands of tons i n sight 198 T 16,000 T estimated present 55 T (includes G-26) 250,000 T estimated present 25 T ' 99 T 6,081,133 T 100 T 1 high-grade shipment 287 T 50 T 1 T 130 T lead concentrate and 1 carload zinc concentrate 23 T 28 T 1 carload 638 T 537 T 8 T 350 T 545 T 1,650 T 350 T 29 sacks of "selected" material shipped 67,100 T Cu.Zn.Ag Cu.Ag (Au)' Cu.Ag Cu,Ag,Au Au Cu.Ag Zn.Pb.Ag (Au) Ni.Cu Cu Zn,Cu,Ag,Au Cu.Ag Ag.Cu Pb.Zn.Ag (Au) Au,Ag,Pb,Zn Cu,Ag,Au Ag Au, Ag Cu,Au,Ag Au Pb,Cu,Ag (Au) Zn,Pb,Cd,Ag,Au MMAR BCDM BCDM BCDM BCDM BCDM MMAR BCDM MMAR GEM^ 1972, p. 104 MMAR MMAR BCDM GEM, 1974, p. 105-6 BCDM MMAR BCDM BCDM BCDM MMAR MMAR BCDM MMAR BCDM BCDM BCDM GEM, 1972, p. 104 BCDM BCDM BCDM BCDM MMAR Northair Mines Ltd. Annual Report, 1977 1 1905-1974 prior to 1890 1907,1917 1949,1952,1961,1963 1940 1932-39 1897 1916 1897 prior to 1947 1936,1941,1947 1933-1937, 1958-1974 1917 early 1870's 1962 1961 1926 1929,1956 1926 1916,1929 1920 1916-1941 1937-1941 1915 1879-1899 1930-1942 1935-1937 1905 1970 1934 1976-1977 Metals art l i s t e d i n decreasing order of amounts shipped i f such information i s available. B r i t i s h Columbia Department of Mines and Bureau of Economics and S t a t i s t i c s , V i c t o r i a , B r i t i s h Columbia ^Annual Reports of the B r i t i s h Columbia Minister of Mines Parentheses indicate very minor production; In the cases specified above less than 20 ounces of the metal was shipped. Geology, Exploration and Mining in B r i t i s h Columbia Figure 3-1. P r i n c i p a l areas of mineral occurrences, Vancouver-Hope area. Table 3-2. ABBREVIATIONS AND SYMBOLS USED IN DEPOSIT DESCRIPTIONS ac a c t i n o l i t e ml malachite ak ankerite Mn manganese stain am amphibole mo molybdenite an anhydrite Mo molybdenum ap arsenopyrite mr marcasite ar argentite po pyrrhotite at apatite pr pyrolusite Au native gold Pt pentlandite az azurite py pyrite ba barite qz quartz Bi native bismuth sb s t i b n i t e bo bornite SC specularite ca c a l c i t e sd s i d e r i t e cb carbonate sh scheelite cc chalcocite s i sphalerite c l c h l o r i t e sn spinel cp chalcopyrite sp sulfides cu cuprite SS s e r i c i t e Cu native copper St stro n t i a n i t e cv c o v e l l i t e t t tetrahedrite en enargite to tourmaline ep epidote ur uraninite fd feldspar wo wollastonite fm ferrimolybdite ( ) minor amount ga galena * producing deposit gt garnet + high dip angle gy gypsum — low dip angle hb hornblende frags fragments he hematite jm jamesonite ko k a o l i n i t e mg magnetite 51 CLASSIFICATION An i d e a l c l a s s i f i c a t i o n scheme for a metallogenic study concisely des-cribes each deposit i n genetic terms. Studies on a larger scale than t h i s one (e.g., Sutherland Brown, et_ a l . , 1971) generally deal only with pro-ducing deposits or important occurrences which have been described i n s u f f i c i e n t d e t a i l to be c l a s s i f i e d genetically with reasonable certainty. However, this study deals mainly with occurrences about which l i t t l e i s known; only three can be called major producing deposits. Restrictions imposed by i n s u f f i c i e n t data have resulted i n deposit c l a s s i f i c a t i o n s which are broadly defined and do not necessarily imply a s p e c i f i c o r i g i n . The c l a s s i f i c a t i o n scheme used i n t h i s study i s outlined below. Magmatic Magmatic deposits are i d e n t i f i e d by the presence of massive and/or disseminated copper and n i c k e l sulfides (commonly chalcopyrite and pyrrhotite, respectively) i n ultramafic host rocks. Sulfides are assumed to have been derived from the magma; therefore the i r age and genesis are similar to that of the host rock. Porphyry Porphyry deposits are low-grade accumulations of copper and/or molyb-denum sulfides genetically related to their intermediate to f e l s i c i n t r u s i v e host rocks, but they may also occur i n nearby country rocks. Metals such as s i l v e r , gold, zinc and iron are uncommonly present i n minor amounts. Sulfides (and rare iron oxides) occur as disseminations, i n quartz vein stockworks, or i n intrusive and/or pipe-like breccia bodies. Conventional de f i n i t i o n s of porphyry deposits (cf. Sutherland Brown and Cathro, 1976) describe mineralization associated with porphyritic g r a n i t i c rocks which were emplaced r e l a t i v e l y near the surface; sulfides formed during the late stages of emplacement and consolidation of the host intrusion. 52 Porphyry deposits of the present study include "conventional" porphyries as outlined above and occurrences of sulfides i n coarse, even-grained g r a n i t i c rocks which probably formed at greater depths than porphyritic g r a n i t i c rocks. Despite the difference i n character of host plutonic rocks, the genetic l i n k between su l f i d e deposition and late-stage plutonic events i s probably the same for porphyries i n coarse, even-grained and porphyritic, fine-grained host rocks. Skarn Skarn deposits are characterized by c a l c - s i l i c a t e mineral assemblages produced by contact metasomatism mainly i n calcareous rocks near intrusive bodies. Mineral assemblages are diverse and vary considerably within and among deposits. Chalcopyrite, magnetite and pyrrhotite are the most commonly reported minerals of economic inter e s t ; garnet, epidote and c a l c i t e are the most commonly recognized gangue minerals. Volcanogenic Volcanogenic deposits i n the study area were produced by submarine exhalative a c t i v i t y which closely followed eruption of ac i d i c pyroclastic rocks. Base metal mineralization i s dominated by p y r i t e , chalcopyrite, and/or sphalerite and galena; gold and s i l v e r enrichments are not uncommon. Quartz i s the dominant gangue mineral, but bari t e i s common; large concen-trations of anhydrite may occur near s u l f i d e s , but rarely within s u l f i d e bodies. Since most potential host rocks i n the study area have undergone deformation, recognition of volcanogenic deposits i s d i f f i c u l t , and this may account for the i d e n t i f i c a t i o n of only two deposits to date. Recent developments of the volcanogenic hypothesis (cf. Hodgson and Lydon, 1977) make i t clear that potential environments not requiring pyroclastic 53 volcanism''' also e x i s t , but detailed information necessary to recognize such environments i s seldom available. Vein C l a s s i f i c a t i o n of a deposit as a vein i s primarily based on the tabular, commonly discordant nature of the occurrence; an epigenetic, hydrothermal o r i g i n i s assumed for a l l veins, although i t i s possible that some tabular syngenetic deposits have been c l a s s i f i e d as veins. Since veins commonly are i n t e g r a l constituents of most deposit types, they are described as "veins" only when they appear to be isolated and/or unrelated to mineral-i z a t i o n which may be c l a s s i f i e d more s p e c i f i c a l l y . Most vein deposits are valued for their precious metal content, but many other metals can be present; quartz i s the most common gangue mineral. Shear 2 Shear deposits occur i n shear zones as small bodies or disseminations of sulfides that are not accompanied by gangue minerals such as quartz and c a l c i t e . P y r i t e , chalcopyrite, sphalerite and galena are the most commonly reported s u l f i d e s . This category may overlap somewhat with veins confined to shear zones, but veins are distinguished by being either (1) massive, well-defined, con-tinuous bodies and/or (2) small, discontinuous bodies with a considerable amount of gangue minerals. The d i s t i n c t i o n between vein and shear deposits i s made because the absence of gangue minerals i n shear deposits i s sug-gestive of an o r i g i n different to that of veins, whereas veins are commonly deposited from st r u c t u r a l l y - c o n t r o l l e d hydrothermal solutions, the o r i g i n of '''The ocean-floor r i f t i n g environment i s a well-known setting for volcanogenic deposits, but does not occur i n the study area. 2 The term "shear" i s imprecise, as i t does not always imply that shear d i s -placement has taken place. A preferred expression i s "a zone of intense f o l i a t i o n , " but the term shear zone i s retained since i t appears abundantly i n the l i t e r a t u r e . 54 shear deposits might be linked to development of the shear zone as a con-temporaneous feature. Development of intense f o l i a t i o n and r e c r y s t a l l i z a t i o n i n host rocks during the formation of a shear zone might cause migration of sparce s u l f i d e components from surrounding rocks into the shear zone where they might accumulate as coarse disseminations or aggregates. Disseminated and Massive These categories are used as descriptive terms for s u l f i d e accumulations which cannot be c l a s s i f i e d as any of the foregoing deposit types due to inadequate descriptive geological data. Therefore, deposits i n these categories probably include representatives of other deposit types whose mineralization i s disseminated or massive i n character. MAJOR MINES AND RELATED OCCURRENCES  Britannia Although only two volcanogenic deposits are reported i n the study area, the 53 m i l l i o n tons of ore produced from Britannia make this type of occurrence the most important of a l l . The other volcanogenic deposit, Seneca (HSW-13), produced 287 tons i n comparison. Intense deformation and a l t e r a t i o n superimposed on complex stratigraphy make interpretation of the geology of the Britannia area d i f f i c u l t . Although recent ideas on the o r i g i n of Britannia consider the deposit to be syngenetic, most published reports discuss an epigenetic o r i g i n . Geologic Setting and Early Interpretations Orebodies at Britannia are on both limbs and the crest of a major a n t i -c l i n e i n a large northwest-trending shear zone i n a pendant of Lower Cretaceous Gambier Group rocks i n the Coast Plutonic Belt. This zone of shear movement i s the locus of folding, f a u l t i n g and the development of 55 intense s c h i s t o s i t y and related a l t e r a t i o n and r e c r y s t a l l i z a t i o n during shear deformation. Because most su l f i d e veins p a r a l l e l f o l i a t i o n s i n the shear zone, early workers interpreted them as introduced along f o l i a t i o n s . Local bedded sulfides were interpreted as replaced sedimentary beds, and the position of ore s t r u c t u r a l l y below slate and dacite dike "hoods" was interpreted as a result of ore solutions being ponded below impermeable barriers. Brecciation, folding, shearing and s i l i c i f i c a t i o n were looked upon as ground preparations for ore solutions. The occurrence of bedded zi n c - r i c h sulfides i n sedimentary rocks and copper-rich sulfides i n v o l -canic rocks was interpreted as a r e f l e c t i o n of host rock preference, although an explanation of this preference was not presented. Schofield (1918, 1922, 1926) and James (1929) attributed the o r i g i n of orebodies to hydrothermal solutions related to intrusion of surrounding plutonic rocks. On the basis of temperature of formation of mineral assemblages, Irvine (1946) suggested that plutonic rocks might not be the source of mineralization, but did not propose an alternate source. Current Interpretations In 1969 and 1970, world-wide interest i n the volcanogenic model stim-ulated reinterpretation of many deposits hosted by acidic volcanic rocks, and Britannia was no exception. Sutherland Brown and Robinson (1970) des-cribed the relationship between ore deposits and stratigraphy at Britannia, and concluded that the ore was volcanogenic i n o r i g i n , dominated by the Keiko (stringer) variety. A detailed study by many Anaconda geologists who worked at the mine (Payne, et_ al., 1974) i s the basis for the following discussion. Orebodies are i n a d a c i t i c volcanic center dominated by a complex sequence of volcanic flows and pyroclastic rocks. During hiatuses i n d a c i t i c volcanism, andesitic sediments were supplied from nearby centers. TABLE 3-3, CHARACTERISTICS OF DEPOSITS IN THE BRITANNIA DISTRICT Mac NO. Name Type of Deposit Host Rock. Formation Host Rock Type M i n e r a l i z e d S t r u c t u r e Cangue M i n e r a l i z a t i o n C-3" B r i t a n n l a v o l c a n o g e n i c C-4 Bank of porphyry Vancouver G-6 McVlcar shear ( v o l c a n o g e n i c ? ) C-l 7 Venus porphyry C-21 Roy Group d i s s e m i n a t e d C-22 Ray Creek G-31 I r i s h M o l l y porphyry C-3 2 B u l l i o n d s l e porphyry G-43 Indian R i v e r shear Copper G-6 2 Horseshoe shear Roy massive G-85 C a l e d o n i a d i s s e m i n a t e d C-86 ABC Group shear G-89 SUN G-124 C h r i s t i n a porphyry C-l 25 Dal No.l d i s s e m i n a t e d C-126 McKlnnon disseminated Croup C-133 London G-152 CaBh porphyry Gambler Croup Coaat P l u t o n i c Complex Cambler Group Gambler Group Gambler Group Cambler Group Cambler Croup Gambler Group Gambler Group d a c l t l c v o l c a n i c rocks a n d e s l t l c t u f f and sedimentary rocks q u a r t z d l o r l t e to q u a r t z monzonite q u a r t z / s e r l c l t e s c h i s t massive bodies s t r i n g e r s b r e c c i a p i p e w i t h v e i n s , s t r i n g e r s , and m i n e r a l i z e d m a t r i x v e l n l e t s and ( w e l l - f o l i a t e d greenstone t u f f ) d i s s e m i n a t i o n s bedded s u l f i d e s q u a r t z porphyry a l t e r e d , s l l l c l f l e d , p o r p h y r i t i c , t u f f a c e o u s t a n d e s i t i c greenstone Gambler Croup green t u f f a c e o u s s c h i s t f r a c t u r e f i l l i n g s J o i n t s l e n s e s shears r e c r y s t a l l l z e d a p l l t e d i k e ? l e n s e s ; bunches s c l d p o r p h y r i t i c d i k e and limes tone Gambier Group v o l c a n i c rocks "replacements" l e n s e s a n d e s i t i c greenstone porphyry massive " v e i n " s c h i s t w e l l - f o l i a t e d , s c h i s t o s e greenstone d i s s e m i n a t i o n s b r e c c i a p i p e p a r t l y s c h i s t o s e greenstone "replacements" p a r a l l e l i n g and c h l o r i t e s c h i s t s c h i s t o s i t y Gambler Group f i s s i l e t u f f and s c h i s t Gambler Group s c h i s t Coast P l u t o n i c Complex ( I n d i a n q u a r t z d l o r l t e R i v e r I n t r u s i o n s ) Gambler Croup c h l o r l t e / s e r i c l t e s c h i s t d i s s e m i n a t i o n s v e l n l e t s i n J o i n t s s l l l c l f l e d shear zones w i t h v e l n l e t s an.ba.qz.gy qz.ca,ba q z . c l q« q* q* q* q« a l . p y . c p (ga.ar.po) cp.py ( t t . g a . s l ) he.mg.cl.cb.qz cp.py (mo,si) q* p y . c p . s l (ga) g a . s l cp,mo py (cp) py.cp cp ( s i ) py .cp c p . s l py.po (cp) cp.py ( s i ) PYiCp py.cp py .cp p y . c p . s l (ga) c p . s l . p y py.cp ( s i ) py.cp,sl tmo 57 During one hiatus, sulfides and related bodies of anhydrite were formed. Massive, bedded, z i n c - r i c h orebodies occur i n andesitic sedimentary rocks above or at the contact with a p a r t i c u l a r unit of coarse d a c i t i c t u f f below the sedimentary section. This coarse d a c i t i c tuff and the sedimentary rocks at the upper contact are host to copper and zinc sulfides i n stringers and massive bodies. Orebodies were deformed during a major episode of deformation which produced the shear zone and related f o l i a t i o n . Most orebody contacts are along or near l a t e major northwest-southeast f a u l t s . An hypothesis based on removal of cumulative r i g h t - l a t e r a l movement of some 8,000 feet along these faults allows a reconstruction of sulfides into two o r i g i n a l orebodies. If this i s correct, a large portion of massive lead-zinc-rich ore may have been eroded; this hypothesis explains why stringer-type copper sulfides are more abundant than normally would be expected to be associated with the present amount of massive zinc and copper-zinc ore. Sulfide Occurrences Outside the Britannia Shear Zone (Table 3-3) Descriptions of mineral occurrences i n the Britannia pendant are remin-iscent of early reports on the Britannia orebodies. Two deposits report massive mineralization: G-77 i s a massive chalcopyrite body with less abundant sphalerite; G-6 (McVicar) contains massive, bedded, sphalerite-rich ore with galena and stringer-type copper-zinc su l f i d e s . Other deposits hosted by schistose, andesitic, volcanic rocks commonly are described as disseminations, lenses and veinlets p a r a l l e l to schistose fa b r i c s ; sulfides include p y r i t e , chalcopyrite, sphalerite and rare galena. Figure 2-1 shows the location of these deposits near a poorly-defined shear zone sub-parallel to and east of the Britannia shear zone. Host rocks are undeformed d a c i t i c flows and pyroclastic units, many of which contain abundant disseminated pyrite (J. G. Payne, personal communication, 58 1978). James, 1929, considered the absence of ba r i t e , anhydrite and the "Britannia S i l l s " (dacite dikes) i n this area to be s i g n i f i c a n t indications of unfavorable conditions for mineralization. However, barite i s not abundant at Britannia, anhydrite i s leached readily from surface rocks, and the "Britannia S i l l s " are now believed to be post-ore. The most reasonable hypothesis regarding the o r i g i n of these deposits i s that they are the same age and type as the Britannia orebodies. Porphyry deposits i n the Britannia d i s t r i c t are either associated with the "Indian River intrusions" near the eastern shear zone (G-31,32,133), or near the Britannia shear zone, just outside the l i m i t s of the pendant (G-4,17,89). The Indian River intrusions are believed to be la t e acidic phases of the Coast Plutonic Complex which intrude pendant rocks (James, 1929). Copper and l o c a l molybdenum sulfides i n these porphyries are sparce. More abundant mineralization i s located i n intrusive breccia pipes i n plutonic rocks (G-4,89) at the southeastern end of the Britannia shear 3 zone. Age of mineralization corresponds to late stage a c t i v i t y of intruding plutons, i n Upper Cretaceous time. Northair High-grade vein mineralization at Northair was discovered i n 1969; production began i n 1976, and continues to make this mine the only operating one i n the study area. Reserves as of May, 1977, are estimated at 330,637 tons, averaging 0.4 ounces/ton gold, 4.6 ounces/ton s i l v e r , 2.7 percent lead and 4.0 percent zinc. Description Sulfides occur, i n three oner-to-f orty^-f oot-wide, northwesterly-trending, 3 Veins of massive chalcopyrite also occur i n plutonic rocks i n this v i c i n i t y (J, G. Payne, personal communication, 1978), but descriptions of s p e c i f i c l o c a l i t i e s are not available. 59 v e r t i c a l , more-or-less tabular sheets which appear to be offset by northerly-trending, sub-vertical f a u l t s (refer to Figure 3-2). Vein minerals include p y r i t e , sphalerite and galena, and minor amounts of chalcopyrite, native gold, pyrrhotite and various s i l v e r minerals (argen-t i t e , tetrahedrite, stromeyerite) i n a quartz-carbonate gangue. Quartz and c a l c i t e exhibit deformation textures; sulfides and gangue i n part appear to 4 be r e c r y s t a l l i z e d . No hydrothermal a l t e r a t i o n related to the vein has been recognized. The three s u l f i d e bodies, called (northwest to southeast) the Discovery, Warman and Manifold Zones, are distinguished from each other by metal r a t i o s , metal contents and textures, summarized i n Table 3-4. Enclosing rocks are considered equivalent to the Lower Cretaceous Gambier Group, although this correlation i s tenuous, as discussed i n Chapter Two. The southern portion of the pendant contains a 5,000-meter section of homoclinal, northerly-trending, v e r t i c a l or steeply east dipping, andesitic to r h y o l i t i c , frag-mental volcanic rocks including coarse agglomerates and fine-grained t u f f s ( M i l l e r , et: a l . , 1978). Where present, s c h i s t o s i t y and fau l t s commonly are sub-parallel to bedding i n volcanic rocks, so that northwesterly-trending veins cross-cut the str u c t u r a l grain of the host rock. A K/Ar date of 124 + 4 Ma was obtained from hornblende i n an intrusive rock believed to be a feeder for surrounding hornblendic c r y s t a l t u f f s s t r a t i g r a p h i c a l l y below mineralized agglomerates (J. H. M i l l e r , personal communication, 1977). However, the intrusion may post-date tuffaceous rocks. A whole rock K/Ar date of 74 Ma on f o l i a t e d greenstone adjacent to su l f i d e bodies ( L i t t l e , 1974) indicates that greenschist metamorphism of pendant rocks, intrusion of plutons, and/or vein emplacement might have occurred at ^Strained cleavage i n c a l c i t e and undulatory extinction i n quartz were noted by the wr i t e r ; sulfides and gangue minerals form an equilibrium texture with common 120° grain boundaries. s s s . Discovery s S S Zens S 1 «. War man Zone S f s / ^ — s <l Manhole! Zone s / s s \ s LEGEND — » mine, tuorWus^t — fault Sll 0 JSO iat /fs if* m«.t>ar> Figure 3-2. Relative positions of the three main mineralized zones and f a u l t s at Northair Mines (after Dickson and McLeod, 1975, and M i l l e r , et a l . , 1978). o TABLE 3-4. CHARACTERISTICS OF THE NORTHAIR SULFIDE BODIES Cu PbJ Zn Au As! Texture Discovery Zone ,55 5.43% 6.58% ,10 oz/T 1.18 oz/T massive ( l o c a l l y banded) and veinlets Warman Zone ,24 1.45% 2.39% ,68 oz/T .85 oz/T massive, disseminated and veins Manifold Zone .07 ,28% ,57% .28 oz/T 14.48 oz/T veins and disseminated (considerable quartz and carbonate gangue) from Manifold, 1976 "from M i l l e r , et a l . , 1978 62 t h i s time (or e a r l i e r ) . Genesis As sch i s t o s i t y and f a u l t i n g are p a r a l l e l to the large-scale outline of the pendant, they are believed to be results of the intrusion of surrounding plutonic rocks, and therefore mineralization which i s cut by these structures pre-dates intrusion i n the v i c i n i t y (M. P. Dickson, personal communication, 1975). Although Northair i s a tabular body which geometrically resembles a vein, metal and host rock associations are suggestive of a volcanogenic o r i g i n . Two major factors must be c l a r i f i e d before the volcanogenic hypo-: . thesis of o r i g i n can be applied with certainty. 1) Small-scale deformation of the vein should be demonstrated to be equivalent ( i . e . , p a r a l l e l ) to deformation of the host rock. 2) If sulfides (and gangue?) have not been transported f a r , they should be s p a t i a l l y related to a stratigraphic-time horizon i n the volcanic host rock. I f massive portions of the vein are o r i g i n a l syngenetic accumulations ( M i l l e r , et a l . , 1978), transportation could not have been great. If sulfides at Northair are not stratabound, but cross-cutting, as suggested by Manifold (1976), an epigenetic o r i g i n must be envisioned. However, i f su l f i d e mineralization was syn- or post-deformation synchronous with intrusion of the Coast Plutonic Complex, vein-forming hydrothermal solutions would be expected to follow s t r u c t u r a l trends of the host rock."' Since mineralization cross-cuts f o l i a t i o n s , an epigenetic vein would have to have been emplaced after deposition of the host rock and before defor-mation. I f host rocks are Lower Cretaceous, the available time i n t e r v a l for epigenetic mineralization i s minimal, since Coast Plutonic Complex K/Ar dates and Gambier Group deposition overlap i n the upper Lower Cretaceous. ^The conclusion that post-deformational hydrothermal f l u i d s would follow pre-existing planes of weakness i s based on the knowledge that basalt dikes i n the mine area that feed overlying Quaternary flows do follow s c h i s t o s i t y . 63 I t appears that i f one i s to consider epigenetic hydrothermal mineralization, the age of the host rock must be examined more closely. If host rocks are of the Upper T r i a s s i c Pioneer Formation, vein mineralization i s more easily reconciled with the available data. Two additional points of interest regarding a supposed volcanogenic o r i g i n are the following: 1) Carbonate i s not usually reported i n great quantities from volcanogenic deposits, and yet i t accounts for half the gangue at Northair. Perhaps the carbonate i s not a by-product of mineralization, but represents a calcareous horizon i n the host rock that may have helped l o c a l i z e sulfides ( M i l l e r , et a l . , 1978). 2) An environment d i s t a l from the source vent i s suggested by lack of stringer zones and very low copper values. This environment i s considerably different from that of other volcanogenic deposits i n the study area (Britannia, G-3; Seneca, HSW-13) which are copper-rich with abundant stringer mineralization. I t i s not possible at th i s time to do much more than speculate on the or i g i n of mineralization at Northair. Available information suggests to the writer that the deposit i s a vein, but the o r i g i n of that vein i s question-able, as i s the presence of syngenetic mineralization. Sulfides were probably o r i g i n a l l y volcanogenic accumulations, but u n t i l more data are presented to c l a r i f y certain relationships discussed above, the deposit cannot be categorized as volcanogenic i n nature. Formation of vein mineralization, i f epigenetic or remobilized syn-genetic, would have occurred i n Upper Cretaceous time during intrusion of surrounding plutons. I f sulfides are deformed syngenetic deposits, they would have formed i n Lower Cretaceous time, if_ host rocks belong to the Gambier Group. Unpublished data indicating the presence of disseminated sulfides i n bedded carbonate and the fact that portions of the deposit consist of multiple veins suggest to current investigators that the deposits cannot be consid-ered a vein, but a d i s t a l volcanogenic deposit ( S i n c l a i r , personal com-munication, 1978). 64 Other Deposits i n the Northair D i s t r i c t (Table 3-5) Occurrences i n the Northair D i s t r i c t are hosted by plutonic and meta-volcanic rocks; the l a t t e r are contained i n two northerly-trending pendants of Gambier (?) Group rocks surrounded by intrusive rocks (Figure 2-1). Veins, disseminations, shears, skarns and porphyries are present. The four deposits i n the western or Callaghan Creek pendant (J-45,51, 151,152) are mineralogically s i m i l a r to Northair, and therefore might be related genetically. Disseminated lead-zinc-copper mineralization i n stringers and disseminations i s accompanied uncommonly by quartz-carbonate gangue and may be l o c a l i z e d along shear zones i n andesitic greenstone hosts. One deposit (J-51, Blue Jack or S i l v e r Tunnel) i s possibly syngenetic, and has been deformed (Woodsworth, et a l . , 1977). D e f i n i t i o n of a mineralizing episode for the remaining deposits i s not feasible; both Lower Cretaceous deposition of host rocks and Upper Cretaceous intrusion of nearby plutons are potential mineralizing events. Mineralization i n and around the eastern pendant d i f f e r s considerably from that of the Northair pendant. Although both pendants are proposed to be of the same formation, the eastern pendant contains very l i t t l e known lead-zinc mineralization. Aside from one galena and barite vein i n green-stone (J-150), deposits i n the eastern pendant are either skarns i n pendant rocks (J-42,67), or porphyries i n intrusions (J-49,50,134). Skarn and porphyry deposits formed during intrusion of plutonic rocks i n Upper Cretaceous time. Giant Mascot Giant Mascot (also Pride of Emory, P a c i f i c Nickel) i s the only occurrence of magmatic n i c k e l and copper i n the area which ever produced; 6.0 m i l l i o n tons of ore were mined. TABLE 3-5. CHARACTERISTICS OF DEPOSITS IN THE NORTHAIR DISTRICT Mac No. Kane Type of Deposit Host Rock Formation Mineralized Host Rock Type Structure Attitude Gangue Mineralization .1-42 London 'skarn Coast Plutonic Complex Gambier(?)Group qu a r t z / s e r i c i t e s c h i s t ( w e l l - f o l i a t e d granodiorite) metabasalt skarn zone ca ep,mg,ca,qz cp.ml.py * J-45 Astra, Cambria disseminated Gambier(?)Group andesite; d i o r i t e stringers N35W.65SW qz.cb ga,sl,cp,py J-49 Azure porphyry Coast Plutonic Complex qu a r t z / s e r i c i t e s c h i s t ( w e l l - f o l i a t e d granodiorite) stringers and lenses qz cp.py (ral.az) J-50 Elk porphyry Coast Plutonic Complex granite fractures and shears s s , c l t q z ml,cp,mo,py * J-51 Blue Jack J-67 shear Gambier(?)Group muscovite/chlorite schist lenses, streaks and disseminations i n shear zone N-S.65W v a i l rock (qz,ca) ga,sl,py,cp,Au,tt Fitzsimmons skarn ep,cb,gt py.sl.cp (ga.mg) J-!30* Northair vein Gamb ier(?)Group pyr o c l a s t i c andesite vein N55W, + N qz, cb py.ga.sl.cp J-131 CI.JE vein Coast Plutonic Complex (?) vein qz cp J-132 CI.JE' disseminated Coast Plutonic Complex disseminations cp,ml J-134 RM porphyry meta-diorite shear zone NW cp.py J-150 (occurrence) vein Gambier(?)Group greenstone vein ba ga J-151 Kay disseminated Gambier(?)Group andesitic volcanic rocks velnlets and shear zones ga.sl (cp) J-152 ' TMC No.l disseminated Gambier(?)Group andesite; minor quartz d i o r i t e small fractures Cu,Ag,Zn 66 Nature and Origin of Ultramafic Rocks The Giant Mascot Ultramafite i s a unique e l l i p t i c a l , crudely-zoned body (Figure 3-3) which does not f i t into most existing c l a s s i f i c a t i o n schemes (cf. Naldrett and Cabri, 1976). The dominance of orthopyroxene i n ultramafic and n o r i t i c rocks and the presence of magmatic sulfides are the major features which distinguish the Giant Mascot Ultramafite from "Alaskan-type" zoned ultramafic intrusions. Several steeply-dipping, p i p e - l i k e cores of perid o t i t e and less common dunite are surrounded by substantial amounts of pyroxenite (hornblendic and b r o n z i t i c ) ; e r r a t i c zones of hornblendite occur along the periphery of the main ultramafic body. Norite and d i o r i t e are the major feldspathic i n t r u -sive rocks surrounding the ultramafic body. Similar pyroxenes i n ultramafic and d i o r i t i c rocks have led authors (Cockfield and Walker, 1933; Horwood, 1936; Aho, 1956; and Peach, i n Clark, 1969) to the conclusion that d i f f e r e n t i a t i o n of an orthopyroxene-rich magma produced progressively less mafic intrusive phases. K/Ar dates (McLeod, et a l . , 1976) indicate that ultramafic rocks (119-95 Ma) cooled shortly before d i o r i t i c phases (79-89 Ma). Cumulate textures suggested to McLeod (1975) that the o r i g i n a l d i f f e r e n t i a t i n g magma was crudely stratiform before re-emplacement as a " c r y s t a l mush." Mineralization P y r i t e , pentlandite, chalcopyrite, pyrrhotite and magnetite occur i n three types of orebodies: zoned, massive and v e i n - l i k e . Zoned orebodies of disseminated sulfides occur within the pipe structures referred to above. The presence of sulfides i s a function of rock type, as dunite and peridotite cores commonly contain s u l f i d e s , pyroxenites less commonly so, and horn-blendite rarely. Norite contains rare disseminated s u l f i d e s . Sulfide and 67 + + 4 -r + '-I- + fi- + •+ + + + + + • + + + + . + + + +- + + + + 4- H»K|^ + -tt' (+ +^ '-<';.^ "^f^ .*;v.S;-S'V "A t-I f + + + + + + + + + * + + + + -*- \<+N«? \\V » + + + +;+.+,+ ^ + +, •-0',U\\V i ,+ + + + + + ,+ + + •+ -+*i(• l.;'U I, + +'<• + P"l LEGEND |:: : ::-:-| D O I P T ' C O V C Q C D EZ3 H O M t U E M O l T t KAN OP • U f t F A C t G E O L O G Y AND M I N E R A L I Z A T I O N PACIFIC NICKEL MINES P V Q O « t M I T t J W . V J P V » 0 » • > • ! • « , E2E3 P c n i o o r i T C . S C A L E O P F " C C T t O O O SOOO 4 Q Q d 3 0 0 0 ONI MILK Figure 3-3. Surface geology of the Giant Mascot Ultramaflte (from Aho, 1956). 68 rock type relationships are not consistent; a s u l f i d e - r i c h rock type i n one orebody may be barren i n another. Nickel to copper r a t i o s are highest i n the cores of zoned orebodies, decreasing outwards as t o t a l s u l f i d e con-^ tent decreases. Massive orebodies are simi l a r mineralogically to zoned ones, but are irregular i n form, and commonly show evidence of movement or remobilization through brecciation, large-scale protoclastic textures, or flow-banding. Sharp contacts are chara c t e r i s t i c of massive orebodies, but some grade into zoned orebodies. Vein-like sulfides with lower n i c k e l to copper ratios than either zoned or massive orebodies occur i n a l l rock types, but are economic only where enriching larger orebodies. These veins can probably be attributed to late-stage mobilization of existing s u l f i d e bodies. The o r i g i n of mineralization at Giant Mascot remains as much of a dilema as the o r i g i n of the ultramafic host rocks. Cockfield and Walker (1933) favored a hydrothermal o r i g i n for the su l f i d e bodies; McTaggart (1971) favored a metasomatic o r i g i n for the pipes by fracture-controlled f l u i d s , and Aho (1956) proposed high-temperature metasomatic and magmatic origins for pipe and massive orebodies, respectively. Cairnes (1924), Horwood (1936) and McLeod (1975) favored a magmatic o r i g i n involving segregation and sub-sequent i n j e c t i o n of sulfides. McLeod (1975) supported his view by demon-strat i n g that pyroxene pairs from assorted rock types i n the ultramafic body equilibrated at a mean minimum temperature of 990°C. Although detailed knowledge of the processes involved i s lacking, a complex magmatic o r i g i n i s accepted here for the ultramafic body and i t s contained s u l f i d e s . Age of su l f i d e formation, 108 + 4 Ma (McLeod, 1975), corresponds to that of mineralized hornblendite i n one of the orebodies.^ I t i s important to consider the significance of this date (and others i n 69 Occurrences Outside the Giarit Mascot Ultramafite (Table 3-6) As mentioned i n Chapter Two, the Giant Mascot Ultramafite i s s p a t i a l l y associated with a belt of ultramafic rocks near the northern extension of the Shuksan Thrust. The largest ultramafic body i s on Old Settler Mountain, i n the southern portion of the b e l t . Described by Lowes (1972) as a t y p i c a l alpine-type ultramafite, i t i s mainly dunite and contains no sul f i d e s . Smaller bodies north of Old Settler Mountain, i n the Cogburn Creek area, are similar to Giant Mascot (HNW-38,39,40,41,42). Pyroxenite and hornblende-pyroxenite, mineralized sparingly by massive and disseminated p y r i t e , pyrrhotite, chalcopyrite and rare pentlandite, are closely associated with Spuzzum d i o r i t e i n these deposits. Orthopyroxene i s of secondary abundance compared to clinopyroxene i n these occurrences. S i m i l a r i t i e s to Giant Mascot suggest that mineralization at Cogburn Creek was contemporaneous with that at Giant Mascot. Other magmatic deposits commonly are associated s p a t i a l l y with major f a u l t s , implying an o r i g i n linked to movement along these deep-seated crustal breaks. HSW-5 and HNW-52 are near the Hope Fault, and outside the Giant Mascot D i s t r i c t , HNW-34, HSW-118 and HSW-125 are near the Hozameen Fault. Mineralization i s presumed to have occurred during f a u l t i n g when access to mantle (?) sources was obtained. MINING CAMPS WITHOUT MAJOR MINES Camps or d i s t r i c t s discussed i n t h i s section stand out as areas of r e l a t i v e l y high concentrations of mineral prospects. Regardless of pro-duction, i f any, they have generally boasted of enough mineral occurrences the Spuzzum Plutonic Belt) i n l i g h t of the fact that high pressure and temperature metamorphism discussed i n Chapter Two might have affected argon retention i n these rocks. Thus the reported age of the Giant Mascot U l t r a -mafite and i t s sulfides might be younger than the actual age which might pre-date metamorphism and/or intrusion of the Spuzzum and Scuzzy plutons. TABLE 3-6. CHARACTERISTICS OF DEPOSITS IN THE GIANT MASCOT DISTRICT Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Gangue Mineralization HSW-4 Giant Mascot magmatic HSW-5 Bea HSW-111 Suede HNW-38 AL HNW-39 occurrence HNW-40 occurrence HNW-41 occurrence HNW-42 occurrence HNW-45 Victo r HNW-52 Cit a t i o n magmatic magmatic magmatic magmatic magmatic magmatic magmatic magmatic Giant Mascot . Ultramaflte magmatic pe r i d o t i t e ; hornblende pyroxenite ; dunite p i p e - l i k e bodies ultramafic pyroxenite; p e r i d o t i t e fractured and s i l i c i f i e d Spuzzum Pluton mafic-rich rocks i n bands and lenses quartz d i o r i t e hornblende pyroxenite pyroxenite hornblende~pyroxenite amphibolite (?) pyroxenite amphibolite Spuzzum Pluton meta-quartz d i o r i t e p e r i d o t i t e (?) sc h i s t ; amphibolite near gabbro/pyroxenite contact massive; disseminated po.pt,cp.py disseminated po.cp.py massive py.po (cp.pt) pervas ive po.cp.py disseminated cp massive; disseminated py (po.cp) disseminated cp.po disseminated py.po,cp minor disseminated po, cp Cu.Ni.Zn O 71 to have attracted considerable exploration inte r e s t . Locations of a l l camps are shown i n Figure 3-1. Eagle Belt (Table 3-7) Two d i s t i n c t types of mineral occurrences are present i n the Eagle Belt. Copper, zinc and lead sulfides occur as disseminations (HNW-22,23) and i n a vein (HNW-24). Molybdenum and copper sulfides occur i n porphyry deposits i n breccia bodies (HNW-28,54) and a dike (HNW-31). Assuming the breccia bodies and dike are related to l a t e stages of plutonism i n the Eagle Complex, deposition of sulfides i s contemporaneous with the formation of t h i s complex i n Jurassic or Lower Cretaceous time. The age of copper-zinc-lead deposits i s more d i f f i c u l t to determine, as the mineral assemblage i s not char a c t e r i s t i c of s u l f i d e deposits associated with plutonic rocks, and the nature of non-plutonic rocks i n the v i c i n i t y i s uncertain. Summit Camp (Table 3-8) Fault-controlled mineralization of the Summit Camp on Treasure Mountain has been explored and worked intermittently since 1894 when the Eureka claim was located. Veins and stringer zones from one inch to f i v e feet wide con-t a i n p y r i t e , sphalerite, and galena, with minor amounts of tetrahedrite, pyrrhotite, chalcopyrite, s t i b n i t e , quartz, c a l c i t e and s i d e r i t e . The most common occurrences are thin s u l f i d e v e i n l e t s , with or without gangue, that occupy a much wider fracture zone composed of altered country rock with, perhaps, some gouge. Fault zones are nearly perpendicular to bedding, and sulfides are found e r r a t i c a l l y along them. Ten of the twelve deposits i n the Summit Camp occur i n Lower and Middle Jurassic Ladner Group volcanic and sedimentary rocks. The remaining two are i n Lower Cretaceous Pasayten sedimentary rocks. Distribution between these host rocks appears to be a function of the amount TABLE 3-7. CHARACTERISTICS OF DEPOSITS IN THE EAGLE COMPLEX Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure ' Width Attitude Gangue Mi n e r a l i z a t i o n HNW-22 Mag Group HNW-23 Ly,Ford, Snow,Dora HNW-24 Coldwater 1^-28 JM.SEC EKH-31 Gossan HNW-54 Mod Bar disseminated disseminated vein porphyry porphyry porphyry Eagle- Complex Eagle Complex Eagle Complex Eagle Complex Eagle Complex i n t r u s i v e b r e c c i a a l t e r e d porphyry a l t e r e d porphyry (quartz monzonite or quartz d i o r i t e ) fractures;veins disseminations zone of disseminations 150' a l t e r e d quartz monzonite vein limestone and r h y o l i t e near granodiorite fractures NW.50NE N40E.70NW bre c c i a g r a n i t i c , p b r p h y r i t i c dike intruding granodiorite Eagle Complex rhyodacite porphyry pipe (?) al t e r a t i o n halo around dike with stringers a l t e r e d area near breccia pipe with p h y l l i c a l t e r a t i o n qz (cb) qz qz py.cp.sl py.cp.sl py.sl.ga (cp) py,ga,sl,tt (cp) sl . g a mo (cp) py (cp.mo) (qz) py,cp.mo,cu,en,cc . N3 TABLE 3-8. CHARACTERISTICS OF DEPOSITS IN THE SUMMIT CAMP Mac No. Name Host Rock Type of Deposit Formation Host Rock Type Mineralized Structure Width Attitude Gangue Mineralization HSW-16 . Sil v e r Chief HSW-18* Eureka HSW-19 Southern No. 8 Fr. HSK-20 Bluebell HSW-21 Queen Bess HSW-22 Indiana ESW-23 Summit HSW-45 U.S. Rambler HSW-46 Blackjack HSW-47 Hall's Group ESW-66 Rainy HSW-85 Morning Star vein vein vein vein vein vein vein shear shear shear shear vein Pasayten Group Ladner Group Ladner Group Ladner Group Ladner Group Ladner Group Ladner Group Ladner Group Ladner Group Ladner Group Pasayten Group Ladner Group a r g i l l i t e , arkose and conglomerate a r g i l l i t e , breccia and conglomerate agglomerate and black a r g i l l i t e a r g i l l i t e , breccia and conglomerate fault zone l"-20' vein along fault 4"-12" massive breccia and agglomerate; t u f f and a r g i l l i t e t u f f , breccia'and a r g i l l i t e contact of porphyry and quartzite massive agglomerate, t u f f and a r g i l l i t e vein along dike vein bedded quartz velnlets vein fracture zone stringers vein along fault contacts of dike stringers i n 20' zone vein stringers coarse black dike quartzite with p y r i t i c bands a r g i l l i t e and conglomerate t u f f and massive andesite seam dike walls rusty bed bedded gouge seam shears and fractures vein stringers i n fracture zone 18" 4"-6" up to 19" 1"-1' l ' - 3 ' 6" l" - 6 " 17" 6'-8' 15" 2'-4' 10"-12" 20' N50E.65SE N70E.65SE N45E N70E N20E, +E N20E.50SE SW,N WSW SW.NW N65E, + N75E.70SE N60K N70E.70SE N33E qz,cb,sd qz.ca cb ,qz qz qz,gouge qz qz sl,ga,py,cp,tt (Mn) ga.sl.cp ga.sl.cp.py sb sl,ga,py (sp.Mn) sl.ga.py sp.py (Mn) py.sl.ga gouge, rock ga.sl.py frags (qz.cb) po.sp rock frags,? ? rock frags rock frags py.ga.sl py.ga.sl sl.ga py py.si sl,po,py,cp 3"-4" 5' E-W.40S N60E qz,rock frags ga,tt,cp 74 of f a u l t i n g , since of the f i v e recognized faults i n the camp, only one has been traced into the Pasayten Group. Two reports of host rock preference from different deposits i n t h i s camp c o n f l i c t as to whether a r g i l l i t e i s associated with r i c h or poor min-e r a l i z a t i o n . Host rock control, therefore, i s assumed to be minimal. Rock type hosts include quartzite, agglomerate, t u f f , breccia, conglomerate, arkose and a r g i l l i t e . Old reports commonly attribute the source of sulfides to a porphyritic dike which intrudes the Treasure Mountain f a u l t zone and commonly separates mineralized zones into hanging- and footwall portions. However, the main relationship between this dike and mineralization i s that both intruded the weak faul t zone; dike and sulfides commonly are independent of each other. Sulfides occur i n faults that offset the Chuwanten, defining th e i r age as post-86 Ma. The only known post-86 Ma events nearby that might be res-ponsible for mineralization are intrusion of the Needle Peak Pluton and extrusion of the Coquihalla Group (Figure 2-1). Jim K e l l y Creek Camp (Table 3-9) Aside from minor differences between mineral assemblages, prospects at Jim Kelly Creek are s i m i l a r to those of the Summit Camp on Treasure Mountain. Deposits i n fracture zones consist of veins and quartz stringers up to one foot wide i n zones up to 20 feet wide. Veins contain p y r i t e , galena, sphalerite, chalcopyrite, and minor amounts of tetrahedrite and chalcocite; quartz gangue i s reported i n every occurrence. The deposits are i n schistose metavolcanic rocks of the Nicola Group which were affected by Late Cretaceous movement along the Pasayten Fault. S i m i l a r i t i e s i n form and mineralogy between Jim Kelly Creek and Summit TABLE 3-9. CHARACTERISTICS OF DEPOSITS IN THE JIM KELLY CREEK CAMP Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Width Attitude Gangue Mineralization HSW-48 Gold Mtn. HSW-49 Superior HSW-50 John B u l l HSW-51 Marsellaise HSW-52 Spokane vein vein vein vein vein Nicola Group metavolcanic sc h i s t Nicola Group s c h i s t Nicola Group Nicola Group Nicola Group metavolcanic and minor sedimentary sch i s t s c h i s t s c h i s t vein 2"-12" N90E, S faults o f f s e t t i n g vein vein i n fracture zone 4'-6' N-S vein 6"-10" N7E.45NW fracture zone with stringers 3' fau l t zone 20* N68W.35SW cross-fractures qz gouge ga,py,cp,ap,tt minor qz, rock frags ga,py,cp,tt py.cp qz qz py.cp low grade \ 7 6 Camp suggest sim i l a r modes and time of formation. As the Coquihalla Group i s only four kilometers north of Jim Kelly Creek, i t i s suggested that volcanism provided heat and/or solutions and/or metals which migrated into fracture zones and deposited s u l f i d e - r i c h veins. Ladner Gold Belt (Table 3-10) Unlike most vein deposits i n the study area whose l o c a l i z a t i o n i s generally unpredictable, veins i n the Ladner gold belt occur consistently along the serpentine belt which marks the Hozameen Fault (Figure 2-1). East of the serpentine b e l t , slaty a r g i l l i t e of the Ladner Group i s the most common host for gold veins, but serpentine and greenstones of the Hozameen Group, which l i e s west of the serpentine b e l t , are also mineralized. A l l three rock types and quartz veins are intimately associated along the b e l t . Mineralization i n quartz veins consists of native gold, auriferous arsenopyrite, p y r i t e , uncommon pyrrhotite, and rare chalcopyrite. Gangue minerals other than quartz and rare c a l c i t e are not reported (with the exception of HSW-35). Wall rock fragments commonly make up a good portion of the vein as at the Emancipation property (HSW-34) where the content of massive, milky quartz decreases away from the vein through a wide (about two meter) zone of brecciated slate i n a groundmass of quartz. Quartz veins are not required to l o c a l i z e mineralization; a few prop-erties (HNW-3,27; HSW-60) report schistose (shear) zones of serpentine with sulfides and thin plates of native gold along f o l i a t i o n s . Auriferous zones of t a l c also occur. The prevailing hypothesis on the o r i g i n of sulfides has been that serpentinization of p e r i d o t i t e along the belt resulted i n formation of veins and auriferous zones by providing easy access to deep-seated magmatic solutions (Cairnes, 1929). In recent years, geologists working i n the area TABLE 3-10. CHARACTERISTICS OF DEPOSITS IN THE LADNER COLD BELT Mac No. Name. Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Gangue Mineralization HNW- 3 Au rum HNW-1* Roddick HNW-5 Emigrant HNW-6 Snowstorm HNW-7 Idaho HNW-8 Montana HNW-9 Rush-of-the Bull Fr. HNW-10 Cera HNW-11* Pipestem HNW-13 Home X HNW-U . Star HNW-25 Cem HNW-27 Brett HNW-35 Cold Cord HNW-36 Cold Coin HNW-37 Majestic HNW-^ 6 Hlllsbar HSW-34 Emancipation HSW-35 Morning HSW-44 St. Patrick HSW-60 Pacific Mines HSW-95 Montana HSW-116 Camp vein vein vein vein vein vein vein disseminated vein vein vein shear Ladner Croup Hozameen Group Ladner Croup Ladner Croup Ladner Group Hozameen Group Ladner Group Hozameen Croup Ladner Group Ladner Group Ladner Group Ladner Group Ladner Group Ladner Croup Ladner Group Hozameen Group (?) Ladner Group Hozameen Group Ladner Croup a r g l l l l t e s greenstone serpentine Hozameen Group Ladner Group slate andesitic greenstone andesitic greenstone slate s l l i c l f l e d . a c l d s i l l slate slate slate slate serpentine slate at contact with serpentine porphyritic dike ln slate slate slate greenstone feldepithic dikes slate greenstone near quartz d l o r l t e / serpentine contact d l o r l t e dike/serpentine contact ("white rock") greenstone slate veins; s i l l -fled zones talcose shears veins wall rock veins wall rock veins wall rock vein wall rock stockwork vein and wall rock stringers shear/vein veins shear veins stringers velnlets veins veins vein shears N50W.25SW N55W.80NE N80W.45NE N80W, + E-W NW.50SW N70V, + N16W.50SW q* qz rock frags Aufpy,po,ap (cp) 1 , 1 P°.ap,Au (py) q* rock frags P vtap,Au Au q r «P.Au q* r°ck fraga PX.ap qz.cb . rock frags P v. f lP. A u qz qz.ca rock frags Au.py Au py,ap,Au (cp (po) qz.ca (gy) ap.py (ga) Au,Ag,Zn values q« 78 have come to believe that major mineralized veins and shear zones are re-mobilizations of low grade (about 0.10 ounces/ton gold), disseminated, possibly syngenetic mineralization i n the Ladner Group (cf. Kayira, 1975). According to Montgomery, et^ al., 1977, p y r i t e , arsenopyrite, pyrrhotite, minor amounts of chalcopyrite and native gold occur i n a l b i t i z e d quartz-chlorite-carbonate schist which represents a coarse greywacke member of the dominantly argillaceous Ladner Group. Small quartz-carbonate-feldspar veinlets associated with mineralization cross-cut a l l formations including the Ladner and Hozameen Groups, and contained serpentine bodies ( S i n c l a i r , personal communication, 1977). Mode of o r i g i n i s not clear, but i f a syn-genetic model i s accepted, the age of mineralization before remobilization into quartz veins would be Lower to Middle Jurassic. Remobilization into veins and shears would have occurred during emplacement of the serpentine during major movement along the Hozameen Fault i n early Late Cretaceous, prior to 84 Ma. 23-Mile Camp (Table 3-11) The 23-Mile Camp i s characterized best by i t s d i v e r s i t y i n types of mineral occurrences. Most deposits occur i n Hozameen Group limestone, greenstone or dikes, but one i s i n Ladner Group slate and two are i n small plutons which intrude the Ladner Group. Hozameen-hosted deposits include four skarns (HSW-3,12,41,117), one disseminated occurrence (HSW-42; i n andesite), and two vein deposits (HSW-25,117). Ladner-hosted deposits include one copper-nickel occurrence (HSW-1), two vein deposits i n quartz d i o r i t e (HSW-2,27), and a breccia pipe made up of fragments of disrupted a r g i l l i t e (HSW-1). This breccia pipe, Canam, i s the fourth largest deposit i n the study area, with reserves estimated at eight m i l l i o n tons grading 0.61 percent copper; i t i s the only deposit to report uranium i n the study area. TABLE 3-11. CHARACTERISTICS OF DEPOSITS IN THE 23-MILE CAMP Xac No. Host Rock Mineralized Name Type of Deposit Formation Host Rock Type Structure Width Attitude Gangue Mineralization HSW-1* Canam porphyry Ladner Group s i l i c e o u s and argillaceous periphery of sedimentary rocks breccia pipe qz.ca.cl,to,ep,am,fd py, ,cp,po (mg.mo.sl, ga,ap,sh,ur) \ hornblendite lenses qz,ca,ak cp, ,po ( s i ) HSW-2* Invermay vein Invermay Stock altered quartz d i o r i t e "banded rock" lenses i n shear zone dark bands 1' '-6" variable qz to (qz) py, ,sl,ap,cp (py.jm) .cp HSW-3 Mammoth skarn Hozameen Group l i m e / s i l i c a t e b e l t i n . cherty sedimentary rocks and massive- greenstones 50' qz,ca,sd po, ,sh,sl,pr,mo,st HSW-12 D + J skara Hozameen Group chert, volcanic rocks and some limestone fractures 20' NW, + S gt,qz,ep,hb,wo,ac po, ,cp (sl,ap,ga,Cu) HSW-25* Sil v e r Daisy vein Hozameen Group "cherty member" lenses i n shear zone 2"-8" N65E-N20E qz, gouge po, ,sl,cp,ga,ap (tt) HSV-27 July vein Invermay Stock quartz d i o r i t e lenses i n shear zone 3' '-4' NE, + E qz, gouge, rock frags s i , ,ap,cp HSW-41 Defiance skarn limestone and diabase dike contact 12' -30' po HSW-42* disseminated B.B., Rainbow Hozameen Group andesite and granular quartzite jo i n t s j fractures NE.90 po, cp.ap.py.ga (jm) HSW-117 Star #1 vein hornblende andesite limes tone/greens tone vein contact 6' '-r N80E.80SE qz ap, ga ga (cp.po.sl) HSW-118 Forks magmatic pe r i d o t i t e (?) po HSW-125 Mammoth magmatic pyroxenite dikes less than 10' po, sl.cp 80 In contrast to the d i v e r s i t y of deposit types, a major s i m i l a r i t y i n deposits of this camp i s mineralogy. Chalcopyrite i s present i n ten of fourteen cases, sphalerite and pyrrhotite i n nine, galena and arsenopyrite i n seven. Mineralization i n the Ladner Group probably can be attributed to intrusion of the Invermay Stock. A smaller pluton two miles northwest of the Invermay Stock has been dated at 84 + 6 Ma. Since these two bodies are l i t h o l o g i c a l l y s i m i l a r , they are considered to be contemporaneous. Deposits i n the Hozameen Group cannot be dated as ea s i l y . An important point i s that the Ladner-Hozameen contact i s the Hozameen Fault, which i s cross-cut by the 84 Ma pluton discussed above. I f most deposits i n t h i s camp are related to the stocks as products of the same mineralizing event (due to mineralogical s i m i l a r i t i e s and proximity), a post-faulting age of 84 Ma or younger i s required. The 84 Ma age i s adopted i n this study. Ultramafic rocks and related mineralization most l i k e l y are related to pre-84 Ma thrusting along the Hozameen Fault, and therefore constitute an early episode of mineralization. 10-Mile Creek Camp8 (Table 3-12) Sulfides i n the 10-Mile Creek Camp occur i n lenses, veins, fractures and as disseminations. P y r i t e , pyrrhotite, chalcopyrite, sphalerite and arsenopyrite occur commonly with quartz, but c a l c i t e has been reported; magnetite, s t i b n i t e and galena are rare. One showing (HSW-82) i s i n quartz d i o r i t e , two minor ones (HSW-28,55) are i n porphyritic d i o r i t e dikes, and the other seven occurrences are contained i n Hozameen Group 9 greenstones or limestone (?). Q The large number of occurrences recognized i n this camp resulted from i n -tense exploration during a promotional swindle i n 1910; by 1911 interest i n the area had declined considerably. No production occurred i n this camp. ^Rocks and a l t e r a t i o n associated with mineralization have not been studied i n d e t a i l ; descriptions l i k e " s o f t , white, decomposed rock" are common. TABLE 3-12. CHARACTERISTICS OF DEPOSITS IN THE 10-MILE CREEK CAMP Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Width Attitude Gangue Mineralization HSW-9 B i l l l c a n Group HSW-14 Gold Coin HSW-28 Sunrise HSW-5 5 Steamboat Mtn. HSW-58 Utah ESW-82 North Star disseminated massive disseminated disseminated HSW-109 Skagit Giant massive HSW-121 occurrence HSW-122 occurrence HSW-123 occurrence vein vein massive Hozameen Group Hozameen Group sedimentary rocks and andesite disseminated Hozameen Group limestone (?) d i o r i t e disseminated Hozameen Group quartzite, a r g i l l i t e porphyritic d i o r i t e veins, stringers and lenses i n fractures lenses fractures near quartz d i o r i t e lenses, stringers and disseminations dike lens dike disseminated Hozameen Group ferruginous limestone stringers and disseminations Hozameen Group quartz d i o r i t e greenstone close to intrusive Hozameen Group andesitic greenstone greenstone Hozameen Group greenstone Hozameen Group limestone (??) Hozameen Group andesite veins 6 " - l ' disseminations injected (?) lens lens fissured zone 4'-6' veins 2"-10" vein l'-2.5' lens qz qz,ca qz qz qz,ca qz gt.ep qz ' (qz) • (qz) qz (at,sn) py,sl,po,cp,sb,ap,ga,jm p y . s l s i py.sl.ga p y . s l py,cp,po,ap py.cp py.cp ap,ga,sl,po sp po,py,cp Fy.mg py,cp,po,sb sl.ap py.po.ap mg 00 82 Skarnification i s commonly reported, but only one deposit (HSW-109) reports a skarn assemblage. P o s i t i v e i d e n t i f i c a t i o n of limestone i s rare, therefore, i t i s unlikely that this mode of o r i g i n can s a t i s f a c t o r i l y describe the entire d i s t r i c t . Dikes and other intr u s i v e rocks i n the area have been looked upon as mineralizing sources because they commonly contain disseminated s u l f i d e s . However, dikes may have picked up sulfides from pre-existing accumulations during intrusion. The undefined nature of massive and disseminated min-e r a l i z a t i o n i n th i s camp suggests that s u l f i d e deposits, l i k e t h e i r host rocks, have undergone deformation. The precise character of s u l f i d e bodies p r i o r to deformation i s not known. The association of copper-zinc mineralization i n greenstones might lead to speculation that massive, disseminated and vein deposits are related to syngenetic volcanic accumulations, but much more data are necessary. Age of mineralization i s either Paleozoic ( i f syngenetic) or mid-Cretaceous ( i f epigenetic or remobilized during deformation). Harrison Lake D i s t r i c t (Table 3-13) The Harrison Lake Formation contains abundant disseminated copper-zinc mineralization. Chalcopyrite, sphalerite, pyrite and rare galena and pyrrhotite occur as veinlets associated with fractures i n ca l c - a l k a l i n e , l o c a l l y p y r i t i c , pyroclastic volcanic rocks. Quartz gangue and/or s i l i c i -f i c a t i o n i s common. One report describes c a l c i t e gangue, and another reports barite. Some reports do not describe gangue minerals. Early descriptions of the Seneca volcanogenic deposit (HSW-13) are much l i k e those of other deposits i n the Harrison Lake Formation. Although work began on Seneca i n 1898, i t was not u n t i l 1971 that Geology, Exploration  and Mining i n B r i t i s h Columbia reported a stratiform lens of massive TABLE 3-13. CHARACTERISTICS OF DEPOSITS IN THE HARRISON LAKE DISTRICT Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Attitude Gangue Mineralization G-145 Rat G-154 Cleveland HSW-13 Seneca disseminated disseminated volcanogenic HSW-15* disseminated Valley View HSW-96 Luv HSW-103 IAM HSW-106 Fab HSW-112 Ascot HSW-113 Sku HSW-114 SF disseminated disseminated disseminated disseminated porphyry vein Harrison Lake Formation Harrison Lake Formation Harrison Lake Formation Agassiz P r a i r i e Formation Harrison Lake Formation Harrison Lake Formation Harrison Lake Formation Harrison Lake Formation Harrison Lake Formation Harrison Lake Formation volcanic brecciated, s i l i c i f i e d r h y o l i t e t u f f r h y o l i t e l a p i l l i t u f f and breccia greywacke metavolcanic rocks andesite flows and agglomerate • r h y o l i t e '. s i l i c i f i e d , p y r i t i z e d , fractured agglomerate andesite flows and breccia p y r i t i z e d , s e r i c i t i z e d andesite flows gossan veinlets fractures gossan fractures stringers i n breccia pipe stringers fractures a l t e r a t i o n halo around granite pluton qz qz,ca,ba (qz) ba qz qz (Cu and Zn traces) cp,sl,py,po,Bi,mg,cc py,cp,sl,cv,tt,ga,mr py.cp (1966 info) cp.bo.cc (1974 info) cp.sl.py sl.cp.ga py.cp.sl.cc py.cp.sl py qz cp.sl.py HSW-115 Top HSW-120 KU HSW-126 J No.6 vein disseminated disseminated Harrison Lake Formation Harrison Lake Formation Echo Island Formation Harrison Lake Formation s i l i c i f i e d , epidotized, blebs and veinlets p y r i t i z e d pyroclastics i n shear f e l s i c volcanic rocks sedimentary, tuffaceous porphyritic andesite and flow breccia shear which p a r a l l e l s 10' wide p y r i t i z e d t u f f band N70W.65SW qz,ca ga,cp,po sl.cp (py.po) - cp CO 84 sulfides interpreted as syngenetic mineralization. On this basis, other vein or disseminated showings with structure and mineralogy si m i l a r to that of Seneca might be re-interpreted as small volcanogenic manifestations. In t h i s interpretation, age of mineralization i n the d i s t r i c t would cor-respond to the mid-Jurassic age of the Harrison Lake Formation. Of course, concentration of sulfides by l a t e r hydrothermal f l u i d s flowing through the s u l f i d e - r i c h volcanic rocks also would be a p o s s i b i l i t y , but i n i t i a l min-e r a l i z a t i o n would be syngenetic, and there seems to be no evidence that implies a superimposed remobilizing event. Some vein stages of the volcano-genic system can continue beyond the period of host rock deposition; these would be s l i g h t l y younger than host rocks. F i r e Lake Camp (Table 3-14) The F i r e Lake Group i s dominantly sedimentary i n o r i g i n , but includes greenstones which contain f i v e of the s i x deposits reported i n the formation. Deposits i n greenstone are quartz veins with chalcopyrite and, commonly, native gold. Veins are not continuous but consist of lenses and gash veins i n a wider (possibly sheared) zone. The si x t h deposit i s contained i n a belt of brecciated sedimentary rocks which enclose lead-zinc mineralization i n quartz and c a l c i t e gangue. An o r i g i n by hydrothermal action along zones of weakness during intrusion of surrounding plutons i s most l i k e l y . Age of mineralization i s therefore Late Cretaceous. P i t t Lake (Table 3-15) Most deposits i n the P i t t Lake area are quartz veins i n intrusive rocks of the Coast Plutonic Complex; sim i l a r mineralization i s scattered through-out the Coast Plutonic Belt. The veins at P i t t Lake carry p y r i t e , chalco-p y r i t e , uncommon galena and pyrrhotite, and rare sphalerite and c o v e l l i t e . TABLE 3-14. CHARACTERISTICS OF DEPOSITS IN THE FIRE LAKE CAMP Mac No. Nane Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Width Attitude Gangue Mineralization G-26 Money Spinner vein G-27 Barkoola G-28 Blue Lead G-29 King No.l G-30 R i c h f i e l d G-36* Dandy vein vein vein vein vein v e i n In F i r e Lake Group porphyritic greenstone shear zone 3'-A' N10W.60SW F i r e Lake Group greenstone p a r a l l e l veins and lenses up to 2* i n 25' wide zone F i r e Lake Group (?) F i r e Lake Group F i r e Lake Group greenstone greenstone 4 p a r a l l e l lenses gash veins gash vein up to 18" N85E.45NE up to 36" 0-14" E-W.26N brecciated sedimentary F i r e Lake Group rocks vein qz qz qz qz qz Py,cp,Au,bo cp.Au cp.Au cp breccia b e l t 100'-200' py (ga.sl) qz,ca cement ga.sl (py) CO Ln TABLE 3-15. CHARACTERISTICS OF DEPOSITS IN THE PITT LAKE AREA Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Width Attitude Gangue Mineralization G-l Jubilee G-7 St. Paul G-20 Standard G-34* Viking G-82 St. John vein vein vein vein vein Coast Plutonic Complex Coast Plutonic Complex Coast Plutonic Complex d i o r i t e quartz d i o r i t e granodiorite stringer(s) vein fractures shear zone vein l'-1.5' N55W.90 2 " - l ' 2"-4" 2"-4" N25E.80NW N25E.80NW N90E.80S NW.90 qz qz py.cp py.cp py.ga.cp qz, ko (ca) rock frags py,po,cp (cv.sl) qz py.cp TABLE 3-16. CHARACTERISTICS OF DEPOSITS ON THE SECHELT PENINSULA Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Width Attitude Gangue Mineralization G-23 * Cambrian Chieftan skarn Gambler Group limestone fractures i n skarn gt, ep cp,py,mg,sl (ml,cc,cv) G-24* King Midas skarn Coast Plutonic Complex Gambier Group granite/granodiorite calcareous remnant irr e g u l a r , altered, s i l i c i f i e d contact zone ep,gt,ca,mg cp,py,Cu,sc. G-84 Sundown porphyry Cu.Mo cp (mo) cp,mo G-93 War porphyry Gambier Group Coast Plutonic Complex volcanic rocks, skarn, and hornfels granite stockworks shears qz G-94 Day skarn Gambler Group chert, limestone (near intrusions) v e i n - l i k e bodies along contact cp.py.mg.sl G-138 M.C. skarn Gambier Group limestone, dolostone shear ng,py.cp 87 Veins are r e l a t i v e l y narrow (two inches to one and one half feet) and are steep to v e r t i c a l ; no preferred orientation i s apparent. The o r i g i n of veins i n plutonic rocks i s attributed to la t e stage hydrothermal a c t i v i t y of host plutons i n Late Cretaceous time. Sechelt Peninsula (Table 3-16) Although skarns are uncommon i n the Coast Plutonic Belt, four skarn deposits occur on the Sechelt Peninsula. Deposits were formed i n limestone of the Gambier (?) Group during intrusion of surrounding plutons of the Coast Plutonic Complex. Characteristic skarn assemblages consist of garnet, epidote, magnetite, pyrite and chalcopyrite; some sphalerite, native copper and specularite have also been reported. Age of mineralization corresponds to plutonism i n mid-Cretaceous time. In addition to skarn mineralization, two porphyry occurrences appear i n t h i s area. They are t y p i c a l of most porphyry deposits of the Coast Plutonic Belt, consisting of disseminated copper and molybdenum sulfides i n plutonic (and rarely pendant) rocks. The age of porphyry mineralization probably i s equivalent to that of the plutonic rocks and skarns. ISOLATED PAST PRODUCERS AND IMPORTANT PROSPECTS Table 3-17 presents information on deposits with production records that were not discussed previously because of their isolated locations outside designated camps and d i s t r i c t s . The Zel and Gem deposits are included and discussed i n d i v i d u a l l y because they are the most accurately dated deposits i n th i s section. Zel A small muscovite granite pluton intrudes b i o t i t e granodiorite of the Coast Plutonic Complex 20 kilometers east of Squamish on the Zel property TABLE 3-17 . CHARACTERISTICS OF ISOLATED PRODUCERS AND IMPORTANT OCCURRENCES. Mac No. Name Type of Deposit Host Rock Formation Host Rock Type Mineralized Structure Width Attitude G-5 Zel G-14 Lorraine G-25 Ashloo HSW-8 Empress HSW-11 Eureka-Victoria HSK-33' Anna HSW-36 Aufeus HNW-1 Gem HNW-2 Providence porphyry shear vein skarn ve i n skarn ve i n porphyry vein Gangue Mineralization 83.4 Ma pluton muscovite granite (some pegmatite) Bowen Island Group basic dike (?) intrudes granodiorite Chilliwack Group limestone Chuckanut conglomerate Formation Chilliwack Group limestone Spuzzum pluton quartz d i o r i t e 34.2 Ma intrusion Harrison Lake Formation quartz monzonite porphyry veins and up to 2.51 disseminations two shears bands, lenses and stringers i n shear fracture zone shear . with veins" 1-12" 2"-2* disseminations and veins i n and around breccia pipe vein N35W.80N N85E.50S N77E.40S N77E.23S N82E.43S qz qz gt,ca,fd,ep sd,qz ep.gt qz,ca qz bo fcp,cv fmo py,cp,po,ml,az py.cp.po cp ,bo ,mg ,py, mo ,wo, az.ml py,tt,mr,ml,az cp,ml,az,cc ap.py.cp mo (py,po,cp,sh,sl,Bi) py.Au co co 89 (G-5). Chalcopyrite, bornite, c o v e l l i t e and molybdenite occur as dissem-inations, i n quartz veins and i n pegmatites related to the granite plug. A K/Ar date of 83.4 + 4.2 Ma was obtained from granite, and i s used to approximate the age of mineralization (G. J. Woodsworth, personal communi-cation, 1978). Gem Porphyry mineralization of the Gem deposit (HNW-1) i s related gene-t i c a l l y to a quartz monzonite porphyry breccia pipe. The pipe i s associated with a small g r a n i t i c plug which intrudes Settler Schist and Custer Gneiss. Molybdenite occurs as disseminations i n host rocks, i n quartz veins and i n massive molybdenite veins. Veins are randomly oriented i n a l l rock types, but are highly concentrated around the contact between the pipe and the granite into which the pipe intrudes. P y r i t e , pyrrhotite, chalcopyrite, scheelite, sphalerite and bismuthinite occur l o c a l l y i n quartz veins, and gold values up to 0.02 ounces/ton were reported i n 1938. Age of mineralization corresponds to intrusion of the quartz monzonite porphyry breccia pipe. A K/Ar date on b i o t i t e from the quartz monzonite indicates intrusion occurred at least 34.2 + 1.2 Ma (R. L. Armstrong, personal communication, 1978). Other Deposits The remaining deposits are skarns, veins and one shear. The formation of skarn deposits can be attributed with r e l a t i v e certainty to intrusion of plutons, but the age of veins and shears can only be estimated. Veins i n plutonic and non-plutonic rocks are probably results of intrusion of host or nearby plutons, but mineralization could have occurred at any time after formation of the host rock. Estimations of deposit ages are as follows: G-14 Lorraine Cretaceous ? 90 G-25 Ashloo HSW-8 Empress HSW-11 Eureka-Victoria HSW-33 Anna HSW-36 Aufeus HNW-2 Providence Upper Cretaceous ? late Oligocene or Miocene Miocene (21 Ma) late Oligocene or Miocene Upper Cretaceous (83 Ma) Upper Cretaceous ? Absolute ages assigned to HSW-11 and 36 are based on K/Ar dates on plutonic rocks less than one kilometer from the deposits. SUMMARY The metallogenic history of the study area as discussed i n this chapter i s presented i n Figure 3-4 and Table 3-18. Figure 3-4 i s a duplicate of the time-space plot of Figure 2-2 onto which mineralization of d i s t r i c t s , camps and i n d i v i d u a l producers has been superimposed. An explanation of the symbols used i n t h i s figure i s contained i n Figure 3-4a. In the case of the Britannia and Harrison Lake D i s t r i c t s , volcanogenic mineralization represents a l l occurrences except porphyries. Where more than one p o s s i b i l i t y exists as to the o r i g i n of a deposit, a l l p o s s i b i l i t i e s are indicated and accom-panied by question marks. If a dashed-line symbol i s not present for epigenetic occurrences, mineralization i s assumed to be about the same age as i t s host (e.g., veins i n the Coast Plutonic Complex). Table 3-18 describes the d i s t r i b u t i o n of metal deposits through time with respect to actual and/or potential causative events. Figure 3-4a. Explanation of Symbols on Figure 3-4. Vein Skarn Q Disseminated Shear ind i v i d u a l deposit group of deposits fj'W major mine Magmatic Volcanogenic ^ — ^ ^ Porphyry ^ Massive Q In the case of epigenetic mineralization: time of formation location i n host ro </ unit 1. Britannia D i s t r i c t 2. Northair D i s t r i c t 3. Giant Mascot D i s t r i c t 4. Eagle Belt 5. Summit Camp 6. Jim Kelly Creek Camp 7. Ladner Gold Belt 8. 23-Mile Camp 9. 10-Mile Creek Camp 10. Harrison Lake D i s t r i c t 11. Fi r e Lake 12. P i t t Lake 13. Sechelt Peninsula 14. Zel 15. Gem 16. Lorraine 17. Ashloo 18. Empress 19. Eureka-Victoria 20. Anna 21. Aufeus 22. Providence TABLE 3-18. SUMMARY OF METALLOGENIC HISTORY TIME SPAN EVENTS DISTRICTS, CAMPS AND DEPOSITS INVOLVED I. Pre-Devonian I I . Upper Paleozoic/ Lower and Middle T r i a s s i c I I I . Peraian/Triassic IV. Upper T r i a s s i c V. Lower and Middle Jurassic VI. Upper Jurassic VII. Lower Cretaceous VIII. mid-Cretaceous ( l i m i t s undefined) IX. Upper Cretaceous X. Tertiary deposition of volcanogenic sulfides i n the Hozameen Group ? deposition of syngenetic gold i n the Ladner Group ? deposition of volcanogenic sulfides i n the Harrison Lake Formation porphyry and vein mineralization during late stages of formation of the Eagle Complex magmatic s u l f i d e formation In Giant Mascot Ultramafite deposition of volcanogenic sulfides i n the Gambier Group deposition of volcanogenic sulfides i n the northern Gambier (?) Group ? vein formation near the Hozameen Fault and introduction of disseminated gold (?) Into the Ladner Group during movement of the Hozameen Fault formation of epigenetic disseminated, massive and vein deposits i n the Hozameen Group during deformation ? skarn, vein and porphyry mineralization i n the Coast Plutonic Complex and Spuzzum pluton during l a t e stages of plutonism skarn, vein, porphyry and disseminated mineralization i n the Hozameen Group related to intrusion of small pluton(s) ? porphyry mineralization associated with minor late plutonism i n the Spuzzum Plutonic Belt skarn and vein formation during intrusion i n the Cascade Belt vein mineralization i n fracture zones In the Ladner Trough and Eagle Plutonic Belt possibly related to extrusion of the Coquihalla Group ? 10-Mile Creek Camp ? Ladner Gold ? Harrison Lake D i s t r i c t Eagle Belt Giant Mascot D i s t r i c t Britannia D i s t r i c t Northair D i s t r i c t ? Ladner Gold Belt 10-Mile Creek Camp ? Sechelt Peninsula, Lorraine, Northair D i s t r i c t , P i t t Lake, Ashloo, Fire Lake, Providence, Aufeus, Zel 23-Mile Camp ? Gem Anna, Empress, Eureka-V i c t o r i a Summit Camp, Jim Kelly Creek Camp 4. COMPUTER STUDY 93 INTRODUCTION This chapter deals with the s t a t i s t i c a l aspects of mineral occurrences. The main concern i s to catalogue and analyse available information on si t e s at which metals have been concentrated and to draw conclusions r e l a t i v e to the genesis of these concentrations. In theory, the value of a computerized mineral deposits f i l e such as MINDEP i s that i t enables fast r e t r i e v a l and reorganization of large amounts of data which would be tedious to deal with manually (cf. Orr and S i n c l a i r , 1971). I f the data bank i s set up properly and programs are available for selective information r e t r i e v a l and organization, the time spent by the re-gional geologist or metallogenesist acquiring data i s minimal. After geol-ogical and related features of each deposit are entered into the system, deposits may be grouped easily on the basis of a wide variety of parameters. Evaluation of such data might lead to rapid appraisal of characteristics and controls of mineralization. The variables examined below are commodities ( s p e c i f i c a l l y metals), deposit type, tectonic setting, host rock formation and host rock type. Data are presented on histograms; numerical values are tabulated i n contin-gency tables i n Appendix A. Spatial d i s t r i b u t i o n and zonation of metals and deposit types are presented on maps produced d i r e c t l y from the computer on a Calcomp pl o t t e r . Commodities are reported i n the l i t e r a t u r e either as assays or by the presence of sulfides of the metal concerned.''' In some cases, mining claims were staked on the assumption that certain metals were present, although . "^An exception i s ir o n , which occurs i n nearly a l l deposits as pyrite (and rarely as s i d e r i t e and pyrrh o t i t e ) , but i s usually not reported unless there are concentrations of magnetite. 94 subsequent work has not v e r i f i e d these assumptions. Many such instances were noted i n the l i t e r a t u r e , and the unrecognized commodities were deleted from the data f i l e ; some errors i n th i s regard might s t i l l be present. Inaccurate and/or incomplete sources of information prevented system-a t i c evaluation of the r e l a t i v e importance of metals between and within deposits. Wherever possible, metals are l i s t e d i n order of abundance or economic importance, but s t a t i s t i c a l counts of metal occurrences consider each metal i n a deposit with equal emphasis. I t i s believed that the presence of a metal i s the primary concern, regardless of amount or concen-t r a t i o n , but where information i s available, metals with only trace assay values were deleted. On the other hand, metals have been included by the writer where a metal s u l f i d e has been reported to occur (commonly i n unknown amounts), but the contained metal was not included i n the descrip-tion of the occurrence by previous reporters. Deposits with production records (referred to as "producers") are distinguished on histograms i n order to compare viable economic occurrences with those that did not produce. Five deposits (Table 4-1) whose sizes greatly exceed the average deposit size i n the study area are distinguished also. Further description of deposit types on the basis of metal content i s presented i n Figure 4-1. These histograms i d e n t i f y metal associations i n each type of deposit, and can be referred to when c l a r i f i c a t i o n of metal and deposit type relationships i s required i n the subsequent discussion. Host rock formation refers to the unit i n which mineralization occurs, whether i t i s a formation, group, or named pluton; i t i s not specified for some deposits i n small units of unknown correlation, dikes, or small plutons of unknown age. However, host rock type applies to every deposit for which a description i s available. Zoning maps require a method of recognizing deposit s i z e , but since the TABLE 4-1. GRADE AND TONNAGE OF MAJOR DEPOSITS Cu Pb Zn Au Ag Ni Production Total Resources B r i t a n n i a 1 ' 2 1.1% .65% ,02oz/T .20oz/T 52,783,964 T G-3 Giant Mascot 1' 3.33% .77% 6,081,133 T 7,577,000 T HSW-4 No r t h a i r 4 ' 5 2.7% 4.0% .40oz/T 4.60oz/T 330,637 T J-130 Canam6 .61% 8,000,000 T HSW-1 Aurum7 .098oz/T 3,650,000 T HNW-3 '''Data calculated from production records. 2 B r i t i s h Columbia Department of Mines and Bureau of Economics and S t a t i s t i c s , V i c t o r i a , B r i t i s h Columbia 3 B r i t i s h Columbia Department of Mines and Bureau of Economics and S t a t i s t i c s , V i c t o r i a , B r i t i s h Columbia, and Christopher and Robinson, 1974 4 Data calculated from reserves estimate. ^Northair Mines Ltd., Annual Report, 1977 Pilcher and McDougall, 1976 ^Montgomery, et a l . , 1977 Y em 3<H 2<M 10-EL rorphurij n X=loo% 10J F e C o / V ; C»2n A . H o f l j C d Sk U flu ft Bi U x=ioo% 3 0 - 1 2oJ Fe C. Ni Cv Zn «< M. flj Cd So U ft. Pb B; V 1 0 - j 1 0 -jDisseminafce.d' 3-f i a s s iv e X=100% n r i n F* Co N; C» Zn A> rt. A , Cd S h W fl« th Rt U 2 0 - . 1 0 . Fe Co N; Cv2*t\i fl. ftj Cd W A« Pk B i U Skam X'ioo'/c 1 0 - . 2 0 . Vol canogemc 3 1 Skear F e C o N i C u 2 « f t s n . A 3 C J S b W / ) g P i . 8 « U F e C o N i C u Z w / U r M g C d S V ) U ftoPfc ft U F a C N i Cu2»/»«CI./»9CdSl. W f l . K U feC. Ni CuZn ftsl^flg C i S k U R«Pk 6\ 0 Figure 4-1. Number of occurrences of each deposit type with respect to characteristic metals. "X" i s the percent of t o t a l occurrences of each deposit type i n the study area for which metal content i s known. Triangles id e n t i f y major deposits of Table 4-1; stipples represent deposits with production records; blank bars represent a l l others (see Table 4-2). 9 7 dimensions of very few deposits are known, a rating system of the magnitude of deposits according to the status of exploration or production has been defined as a substitute (see Table 4-2). Magnitude I, the smallest, includes both showings and prospects because for many the d i s t i n c t i o n between them i s based on whether or not geochemical or geophysical surveys were made. These remote sensing techniques are employed commonly i n recent exploration programs, whereas older programs r e l i e d p r i n c i p a l l y on s u r f i c i a l mapping. Magnitude I I i s assigned to developed prospects, because although they have not produced, they have attracted more attention than showings and prospects. Magnitude I I I i s assigned to deposits which produced several thousand tons or less. The f i v e major deposits of Table 4-1 are of magni-tude IV. Each commodity i s examined f i r s t with respect to i t s d i s t r i b u t i o n among deposit types to determine i f metals occur p r e f e r e n t i a l l y i n any particular type. Subsequent studies examine distrib u t i o n s r e l a t i v e to tectonic s e t t i n g , host rock formation and host rock type. A f i n a l section examines the areal d i s t r i b u t i o n df metals and deposit types for regional zoning patterns which might relate to deposit genesis. METAL AND DEPOSIT TYPE ABUNDANCES Copper i s reported i n 73 percent of a l l deposits (Figure 4-2), but the percentage of deposits which produced copper (10 percent) i s the same as gold and s i l v e r , which are found i n 45 percent of a l l deposits. Zinc has been reported i n more cases than i t s common associate, lead, but the per-centage of producers for each (5.6 percent) are equal because deposits which produce one commonly produce the other. Molybdenum i s more common than the remaining reported metals. Very few deposits reporting molybdenum have proven economic, but the number of molybdenum producers i s approximately that of i r o n , arsenic and tungsten, which are much less common than molyb-TABLE 4-2. DEPOSIT STATUS BASED ON HISTORY OF EXPLORATION, DEVELOPMENT OR PRODUCTION Status History Magnitude Number of Deposits Showing Prospect Developed Prospect Past Producers no development or si g n i f i c a n t exploration, or no description of mineralization available geochemical or geophysical survey, and/or detailed mapping, or developed by open cuts or short adits considerable exploration and development, well-established camp f a c i l i t i e s ; rarely some ore has been m i l l tested II production record of several thousand tons or less I I I production record over several hundred thousand tons IV 152 55 20 30 4 Producers currently producing deposits IV 1 99 100-80 Percent 7^  Deposits 60 so-30-20-1 10' 1 Fe 'Co 'Ni ICulZn'Rs'Molftg'Cd'SD'w IfluWBi >U 25Z 2Z5 •200 -175 -150 125 -100 -75 -SO IS QX Numb Deposits Figure 4-2. Total number of occurrences of each metal (metal content i s known for 97.9% of a l l deposits i n the study area). Triangles i d e n t i f y major deposits of Table 4-1; s t i p p l e s represent deposits with production records; blank bars represent showings, pros-pects and developed prospects. 100 denum. The d i s t r i b u t i o n of major deposits (Figure 4-2) roughly r e f l e c t s general abundances and percentages of producers. S i m i l a r l y , the d i s t r i b u t i o n of producers r e f l e c t s the abundance of metal occurrences. Nickel i s an exception; the only deposit to produce was a major one. Figure 4-3 portrays the d i s t r i b u t i o n of deposits among the eight types found i n the area. Veins are by far the most common deposit type, and the most common type to go into production, as nineteen vein deposits are pro-ducers , whereas no other type includes more than three producers. Porphyries and disseminated deposits are about half as abundant as veins; skarns and shears each account for ten percent of a l l deposits. I t i s interesting to note that the two recognized volcanogenic deposits are producers, although the correlation i s probably not s i g n i f i c a n t , but more a r e f l e c t i o n of the lack of recognition of other deposits as volcanogenic; many disseminated, vein and shear deposits might, i n fact, be volcanogenic i n o r i g i n . Major deposits do not demonstrate close t i e s with any p a r t i c u l a r type of deposit, but are evenly distributed among most types. Magmatic and volcanogenic types are r e l a t i v e l y uncommon, but include major deposits. POSSIBLE ORE CONTROLS Deposit Type Figure 4-4a,b i l l u s t r a t e s the d i s t r i b u t i o n of the most common metals among deposit types. Metals reported i n less than f i v e percent of deposits are not shown because they lack a substantial data base and limited a v a i l -able information i s not d e f i n i t i v e . Each metal d i s t r i b u t i o n pattern can be compared to that of Figure 4-3; different d i s t r i b u t i o n patterns for metals r e l a t i v e to each deposit type suggest that the occurrence of the metal i s controlled by deposit type. Generalizations made from these distri b u t i o n s regarding metal sources are speculative, but are mentioned where appropriate. 101 80 70-1 Number QQ-\ oS 30-Z0-. 10AI: C ' CO ^ Co c QJ in > CO , -35 h30 Percent 1-25 o? Deposits .ST £ £ CO TO • 20 - 1 5 -10 -5" o — cy o CO o Figure 4-3. Total number of occurrences of each deposit type (deposit type i s known for 88.4% of a l l deposits i n the study area). Triangles i d e n t i f y major deposits of Table 4-1; s t i p p l e s represent dep-os i t s with production records; blank bars represent showings, prospects and developed prospects. 102 60-1 SO-c opper \-HO. c £ < tn cn 3 -> .<J Gold J I Sil ver h 3 M \-20-A •10-x=q3% Ql o SZ > ^ V £ l b g 2- (O 0_ crj ST! O QJ NT" CD >_ CO a) CO o c d . ca o u - P ca <2 s: a-1 o a) c <0 u CO Figure 4-4a. Number of occurrences of copper, gold and s i l v e r with respect; to deposit type. "X" i s the percent of t o t a l deposits of each metal for which deposit type i s known. Triangles i d e n t i f y major deposits of Table 4-1; stipples represent deposits with production records; blank bars represent showings, prospects and developed prospects. 103 10. I ror, 10-5A - <o <U Oj E 3 ^ s S-M o2 {F5S c£ CP o c O F i g u r e 4 - 4 b . Number o f o c c u r r e n c e s o f molybdenum, z i n c , l e a d , i r o n and n i c k e l w i t h r e s p e c t t o d e p o s i t t y p e . "X" i s t h e p e r c e n t o f t o t a l d e p o s i t s o f each m e t a l f o r w h i c h d e p o s i t t y p e i s known. T r i a n g l e s i d e n t i f y m ajor d e p o s i t s o f T a b l e 4 - 1 ; s t i p p l e s r e p -r e s e n t d e p o s i t s w i t h p r o d u c t i o n r e c o r d s ; b l a n k b a r s r e p r e s e n t s h o w i n g s , p r o s p e c t s and d e v e l o p e d p r o s p e c t s . 104 The d i s t r i b u t i o n of copper (Figure 4-4a) i s much the same as that of deposit types (Figure 4-3), r e f l e c t i n g the diverse and widespread occurrence of the metal. Gold and s i l v e r occur dominantly i n veins, but whereas gold i s sing-u l a r l y dominant i n veins, s i l v e r i s reported also i n other types of deposits. The r a t i o of s i l v e r occurrences to gold occurrences i n dissem-inated, shear, skarn and porphyry deposits i s 1.27, 1.30, 1.50 and 2.00, respectively. Molybdenum (Figure 4-4b) i s prominent i n porphyry deposits, suggesting that intrusive a c t i v i t y i s responsible for the concentration of molybdenum. Further support for this hypothesis comes from the fact that skarns are the only other type of deposit to report molybdenum with any s i g n i f i c a n t f r e -quency (five of 23 skarns i n the area report molybdenum). The d i s t r i b u t i o n of lead shows a dominance i n veins, and a conspicuous absence i n porphyry and magmatic deposits. Zinc i s almost as widespread as copper, generally occurring i n veins or disseminated deposits. Shears and skarns also report considerable zinc. Iron oxides are not reported commonly. Not enough data are present to generalize beyond the fact that they are reported most often i n skarns. Nickel i s reported as uncommonly as i s iro n , and i s r e s t r i c t e d to magmatic deposits. Ultramafic rocks are the most l i k e l y source of n i c k e l since they are n i c k e l - r i c h (Turekian and Wedepohl, 1961) and host most of the n i c k e l deposits i n the study area (see below). Tectonic Belt Relative densities of commodity occurrences are discussed by S i n c l a i r , et a l . , 1977. They are used here to examine relationships between tectonic environment and mineralization as characterized by metals and deposit types. 105 Relative densities indicate how densities within a pa r t i c u l a r sub-area (or belt) compare with those of the entire area. The mineral potential for each belt i s thereby outlined by abundances of metals and deposit types i n the belts. The procedure for determining r e l a t i v e densities i s as follows: 1) Individual belt densities are determined by dividing the number of occurrences of each metal or deposit type i n each belt by the area (a planimeter measurement) of each belt. 2) Belt densities are divided by those of corresponding metals and deposit types for the entire area. 3) Resulting r e l a t i v e densities are evaluated; those approaching 1.00 (1.90-1.10) are considered average, lower values indicate lower than average densities of occurrences, and higher values indicate a high concen-t r a t i o n r e l a t i v e to the entire area. Table 4-3 i s a comparison between Coast Plutonic Belt metal occurrence densities of the present study area and those of the B r i t i s h Columbia 2 Co r d i l l e r a . Values for many metals from the present study are two to three times greater primarily because a l l metals i n each deposit were counted i n this study, whereas S i n c l a i r , et a l . , 1977, counted only the first-reported metal. On this basis, the densities of copper, molybdenum and tungsten occurrences i n th i s study are probably representative of the entire C o r d i l l e r a , whereas cobalt, n i c k e l , arsenic, s i l v e r , lead and esp-e c i a l l y zinc occurrences are much denser; density values of antimony and gold are r e l a t i v e l y low i n the study area. Factors which might lead to distorted values include cover materials and exploration density. A l l u v i a l deposits ( i . e . , Fraser River delta) and si g n i f i c a n t bodies of water ( i . e . , Howe Sound, Harrison Lake) have been The Coast Plutonic Belt of the B r i t i s h Columbia C o r d i l l e r a includes the entire study area except the Eagle Plutonic Bel t , therefore the area of the Spuz zum Plutonic Belt was included wxth that of the Coast Plutonic Belt m calculating densities for the present study area which appear on Table 4-3. The Cascade Belt (Figure 1-1) was also included i n calculations of the B r i t i s h Columbia C o r d i l l e r a , but i t s effect i s assumed to be minimal. TABLE 4-3. COMPARISON OF COAST PLUTONIC BELT DENSITIES OF THE PRESENT STUDY AREA AND OF THE CORDILLERA OF BRITISH COLUMBIA1 Number of deposits; present study Deposits/1,000 Km2 present study Deposits/1,000 Km2 B.C. Cord i l l e r a Present study/ B.C. Cordillera Co 2 .12 .03 4.0 Ni 12 .70 .11 6.4 Cu 106 6.21 2.20 2.8 Zn 38 2.23 . 17 13.4 As 1 .06 .01 6.0 Mo 25 1.46 .52 2.8 Ag 44 2.58 .55 4.7 Sb 2 .12 .10 1.2 W 4 .23 .07 3.3 Au 38 2.23 2.05 1.1 Pb 17 1.00 .21 4.8 Cordilleran values are from S i n c l a i r , et a l . , 1977. 107 excluded from areal calculations; remaining g l a c i a l and a l l u v i a l cover i s not believed by the writer to be s i g n i f i c a n t i n affecting calculations (cf. S i n c l a i r , et a l . , 1977). The only major item not considered i s forest cover; i t undoubtedly varies between b e l t s , but i s not dealt with easily. Density of exploration could d i s t o r t values because the northern one-t h i r d of the area i s not easily accessible except for roads along the Fraser River and between Squamish and Pemberton. "The Coast and Spuzzum Plutonic Belts are probably the most affected by poor access, but prevailing opinions that plutonic terranes have low mineral potential have also con-3 tributed to low occurrence densities i n these bel t s . To check i f low density values i n plutonic terranes are r e a l , the Coast and Spuzzum Plutonic Belts were subdivided into areas underlain by plutonic rocks and areas underlain by pendant rocks. Resulting density values for the Coast Plutonic Belt are commonly high i n pendant rocks and low i n plutonic rocks, sug-gesting that perhaps densities are reflections of both exploration and min-. e r a l potential. Values for the Spuzzum Plutonic Belt are consistently low, with the exception of n i c k e l and magmatic values for i n t r u s i v e rocks. I t i s possible that low densities r e f l e c t poor exploration here, but mineral potential i s also expected to be low, as discussed below. Separate examination of each tectonic belt serves to describe each i n terms of metals and deposit types which characterize i t ; density d i s t r i -butions of i n d i v i d u a l metals and deposit types can then be studied to examine the behavior of each metal and deposit type across the area. Figures 4-5a,b and 4-6a,b show that intrusions of the Coast Plutonic Complex have a marked d i l u t i o n effect of density calculations. The area underlain by plutonic rocks with l i t t l e or no reported mineralization makes up such a 3 The fact that a good portion of the Coast Plutonic Belt as close as 20 miles to Vancouver has not been mapped i n any d e t a i l also has not encouraged prospecting. 108 E a c -2 _S l o n c li CL ca 3-2-i -3*7 3 M a. CO , c ml l l " i * >1/->C0 ca « o CO O c _£ CP (0 CO O £ f ~ 0) al 4) £ £ w - a N CO O — 1 =E 0J CX3 VJ "c o «J CO U J Gc opper e n u m G o l d ver H Lead Z i m o Figure 4-5a. Relative densities of copper, molybdenum, gold, s i l v e r , lead and zinc with respect to tectonic belts and subdivisions. Bar widths are proportional to belt areas. Only r e l a t i v e den-s i t i e s greater than two (dashed l i n e ) are considered s i g n i f i c a n t . Triangles i d e n t i f y major deposits of Table 4-1; stipples rep-resent deposits with production records; blank bars represent showings, prospects and developed prospects. 109 3 2-1 o o OS O 0 0 1°" i s (0 e «J a. -p <u CO 3 - — N _ p C O C Q i U S I N I 3 -I O-M (/"ICQ HP ca -a TO u o vi . OT ICO § «i £ o o f i «-£ - a to ;*2 CQ c O-o UJ Nick, Irov\ Figure 4-5b. Relative densities of n i c k e l , i r o n , antimony and tungsten with respect to tectonic belts and subdivisions. Bar widths are proportional to belt areas. Only r e l a t i v e densities greater than two (dashed li n e ) are considered s i g n i f i c a n t . Triangles i d e n t i f y major deposits of Table 4-1; stipples represent dep-; o s i t s with production records; blank bars represent showings, prospects and developed prospects. 110 5 H-3-2 1 * 2 " C O ° " o i a: -g g "5 I £ o CO -a c a) «1 I ° C Q C L . £ N M »^ o-ID. «" ! £ 5 Q3 <u - a co o tn ro O al £ CO CO C d5 ti ca D-3 5 -3 2 Skarn 10 9-8 7-6 -5 -V I 3 -z-1 -Vol cahoqeruo Figure 4-6a. Relative densities of magmatic, porphyry, skarn and volcanogenic deposits with respect to tectonic belts and subdivisions. Bar widths are proportional to belt areas. Only r e l a t i v e densities greater than two (dashed line) are considered s i g n i f i c a n t . Triangles i d e n t i f y major deposits of Table 4-1; stipples rep-resent deposits with production records; blank bars represent showings, prospects and developed prospects. I l l c o -tf t o - 4 J 0 i 0 1 • s so CD -a £ O -C O o c "5 g c o 1c - o -» „ a.« £ -e ' e l 3 £ , £ « i N • I =>a C O |</)£fl « i -a TO o CO O 7 ^ :±2 0) CP 3 ca o o '£ o V e) C -a La <1 cr< w UJ • Vein 5H «»• 3-1 H ear ]jissewi\r\a4iecl if 73 1 f • assivs Figure 4-6b. Relative densities of vein, shear, disseminated and massive deposits with respect to tectonic belts and subdivisions. Bar widths are proportional to belt areas. Only r e l a t i v e den-s i t i e s greater than two (dashed l i n e ) are considered s i g n i f i -cant. Triangles i d e n t i f y major deposits of Table 4-1; stipples represent deposits with production records; blank bars represent showings, prospects and developed prospects. large portion of the study area that a l l belts without s i g n i f i c a n t pluton-ism appear heavily mineralized i n comparison. Since this i s considered an important outcome of r e l a t i v e density calculations, values have not been recalculated to compensate. An alternative approach has been to regard as s i g n i f i c a n t only those values approaching or exceeding an a r b i t r a r i l y chosen value of 2.00. A metal or deposit type which i s reported rarely w i l l produce an ex-tremely high r e l a t i v e density value for the units i n which i t occurs; a difference of one or two samples w i l l cause an u n r e a l i s t i c v a r i a t i o n i n values. Such extreme cases include the following commodities and deposit types (numbers i n parentheses are numbers of occurrences); uranium (1), cadmium (1), cobalt (2), bismuth (2), arsenic (3), tungsten (6), antimony (7), volcanogenic (2), and massive (5). Relative densities are not consid-ered for the foregoing categories except as indicators of the presence of a metal or deposit type; uranium, cadmium, cobalt, bismuth and arsenic are not discussed further. Mineralization Characterizing Tectonic Belts Table 4-4 summarizes information derived from histograms of Figures 4-5a,b and 4-6a,b by characterizing each tectonic belt according to metals, deposit types and numbers of major deposits. The Hozameen Basin and Coast Plutonic Belt pendants have the highest potential for the greatest variety of metals and deposit types, but the concentration of producers and major deposits i n Coast Plutonic Belt pendants shows a much greater potential for large, producing deposits. The Ladner Trough also exhibits a variety of metal concentrations mainly i n veins and (associated?) shears; the number of producers here i s almost as high as i n Coast Plutonic Belt pendants. TABLE 4-4. CHARACTERIZATION OF TECTONIC BELTS Tectonic Belt Metals Deposit Type(s) Maj or Deposits Coast Plutonic Belt intrusions Coast Plutonic Belt pendant rocks Spuzzum Plutonic Belt intrusions Spuzzum Plutonic Belt pendant rocks Cascade Belt Hozameen Basin Ladner Trough Eagle Plutonic Belt Fe,Zn,Cu,Ag,Pb (Au) Ni 1 (Fe,Mo,Ag,Pb) Ni,Au,Pb,Fe,Ag,Zn (Cu) Au,Pb,Zn,Ag shear, disseminated, skarn (volcanogenic)^ magmatic skarn disseminated, skarn, magmatic (massive) vein, shear Relative densities of metals i n parentheses are nearly 2.00; other values are greater than 2.50. I "Deposit types i n parentheses have very high r e l a t i v e densities based on very few occurrences. 114 With the exception of r e l a t i v e l y abundant magmatic n i c k e l i n intrusions of the Spuzzum Plutonic Belt, t h i s subdivision, plus Coast Plutonic Belt intrusions, Spuzzum Plutonic Belt pendants, and the Eagle Plutonic Belt, feature low r e l a t i v e densities which are to be expected i n dominantly pl u t -onic or highly metamorphosed terranes. The Cascade Belt exhibits moderate r e l a t i v e metal occurrence densities; no metal values greatly exceed 2.00. Skarns overshadow a l l other types of deposits. Perhaps intense deformation i s p a r t i a l l y responsible for r e l a -t i v e l y low values i n this b e l t . D i s t r i b u t i o n of Metals and Deposit Types among Tectonic Belts In the preceding section an ov e r a l l pattern was determined which d i s -tinguished the Coast Plutonic Belt pendants, the Ladner Trough and the Hozameen Basin as areas of most abundant mineral occurrences. The Cascade Belt contains moderate occurrence densities, and the remaining plutonic and metamorphic belts have r e l a t i v e l y low occurrence densities. A few of the common metals (gold, lead, zinc, s i l v e r ; Figure 4-5a) exhibit s i m i l a r distributions which r e f l e c t t h i s pattern of abundance. Minor variations are as follows: gold and lead are more common i n the Hozameen Basin and Ladner Trough than i n pendants of the Coast Plutonic Belt, but zinc shows the opposite r e l a t i o n s ; s i l v e r i s almost equally abundant i n a l l three areas. The behavior of these metals suggests that tectonic environment was not very selective between them. In other words, both precious and base metals occur i n approximately the same manner i n a variety of tectonic environments. Iron oxide and tungsten (Figure 4-5b) behave much l i k e zinc except that both are notably low or absent from the Ladner Trough. Copper i s most common i n Coast Plutonic Belt pendants, and i s only s l i g h t l y enriched i n the Hozameen Basin. Antimony i s reported most commonly i n the Hozameen Basin or Ladner Trough and i s reported rarely i n Coast Plutonic Belt pendants. 115 Molybdenum Is not notably abundant In any belt. Relative abundances of nic k e l show s i g n i f i c a n t l y high values i n Spuzzum Plutonic Belt intrusions and the Hozameen Basin. Tectonic belts show greater correlation with deposit types (Figures 4-6a,b). Vein, volcanogenic and massive deposits are p a r t i c u l a r l y abundant i n the Ladner Trough, Coast Plutonic Belt pendants and Hozameen Basin, res-pectively. Shears, magmatic and disseminated deposits are each common i n two b e l t s , and skarns are common i n three. Porphyry deposits show no si g n i f i c a n t concentration i n any be l t . Host Rock Formation Figure 4-7 records the t o t a l number of deposits reported i n each mineralized unit of the study area; the Ladner, Hozameen and Gambier Groups, 4 and the Harrison Lake Formation stand out as the best-mineralized units. Two major deposits, Aurum (HNW-3) and Canam (HSW-1), and many producers i n the Ladner Group lend even more importance to i t as a host for mineralization. Considering the many occurrences i n the Hozameen Group, the lack of major deposits i s notable. The Gambier and Gambier? Groups together account for an abundance of mineralization (on a l l scales) exceeding that of the Ladner Group; therefore, the Gambier? Group pendants are worthy of close examin-ation. Like the Hozameen Group, the Harrison Lake Formation has yet to produce a major deposit, but unlike the Hozameen Group, mineralization i n the Harrison Lake Formation has warranted considerable recent attention. Major mineralization i n the Giant Mascot Ultramafite i s not only a unique occurrence i n the study area, but also among ultramafic-hosted mineral deposits throughout the world (Naldrett, 1973). _ The area underlain by Coast Plutonic intrusions i s so large that even un-common mineralization can amount to a large number of deposits which w i l l , consequently, overshadow a l l other units when compared on a scale of t o t a l occurrences. High numbers of occurrences i n some non-plutonic units may also be reflections of areal abundance. 116 Figure 4-7. Total number of occurrences i n each mineralized geologic unit of the study area (host units are known for 77% of a l l deposits i n the study area). Roman numerals i d e n t i f y tectonic belts (see Table 2-1). Triangles i d e n t i f y major deposits of Table 4-1; dense stipples represent deposits with production records; sparse stipples represent showings, prospects and developed prospects. 117 Di s t r i b u t i o n of Deposit Types arid Metals Among Host Rock Formations The d i s t r i b u t i o n of in d i v i d u a l metals and deposit types among host rock formations {Figures 4-8 and 4-9a,b) are s i g n i f i c a n t only i f they d i f f e r from that of t o t a l deposits (Figure 4-7). The abundant mineralization i n the Ladner Group i s a r e f l e c t i o n of vein deposits; other deposit types do not exhibit this degree of prominence i n any pa r t i c u l a r formation. The presence of shears i n the Gambier Group, disseminated deposits i n the Harrison Lake Formation, porphyries i n the Coast Plutonic Complex, and the apparent absence of volcanogenic deposits i n units other than those of Coast Plutonic Belt pendants i s notable. The only differences between d i s t r i b u t i o n patterns of t o t a l occurrences and of copper occurrences (Figure 4-9a) are that less than one half the Ladner Group deposits carry copper values. This i s a s i g n i f i c a n t l y low value when one considers that 73 percent of the deposits i n the study area contain copper. A major copper deposit, Canam (HSW-1), i n the Ladner Group stands out almost as a contradiction to these r e l a t i v e l y low copper values. Gold and s i l v e r behave s i m i l a r l y , both r e f l e c t i n g t o t a l abundances shown i n Figure 4-7, with minor exceptions. Coast Plutonic Belt intrusions show very low values for both, and gold occurrences are s l i g h t l y more abun-dant i n the Hozameen and Ladner Groups than are those of s i l v e r , which i n turn are more common than gold i n the Cascade Belt. The major d i s t i n c t i o n between lead and zinc (Figure 4-9b) i s that lead i s minor i n Coast Plutonic Belt pendants, but zinc i s r e l a t i v e l y abundant. Both metals are uncommon i n Coast Plutonic Belt intrusions, but are abundant i n both the Hozameen and Ladner Groups. The d i s t r i b u t i o n of molybdenum mirrors that of porphyry deposits, but although molybdenum occurrences are more abundant than any other metal i n Coast Plutonic Belt intrusions, the density of these occurrences i s not high. 3<h 20' 10-V I E L 43 V 4^ 4 I I I I V II V, em 3<h 2W V I in v 43 I V II Porphyry X«<tfV Lfe—J Shear X=83% 5-H 4=t ass/vg X=80% lioS £ 1-»<5 ^ ^ u tl <° O o TO Skarn X-87% Disseminated 1 X=<?0% 01 1-1.3 S-S'c j;.y2-is O ^ s g H - J } 3 >qmalic Jo 1°/ H c O -+> o n o o u a J ' " » n « - C x = J a i % \/oh canogemc. X= 100% C 2 H a Figure 4-8. Number of occurrences of each deposit typ percent of t o t a l deposits of each deposit numerals i d e n t i f y tectonic belts (see Tab Table 4-1; dense stipples represent depos represent showings, prospects and develop e with respect to host rock unit. type for which host rock unit i s le 2-1). Triangles identify major i t s with production records; spars ed prospects. "X" i s the known. Roman deposits of e stipples oo I l l 30J 20-1 10-V I V I V II c BY x=8a% Gold X=84% Moiybdenum lo. 43d 4S£ X=81% •5 3 .S ~u LC 5 £<3 8 <3 CO OE N —' in S =S CJ 1-2 i - S S t « « t ! £ 5-* 21*2 s I s 5 S»s-?--«.3 jTS-s 5^ oi c v 2 ul o — u <0 .3 C_> 3 C S HU Figure 4-9a. Number of occurrences of copper, molybdenum, gold and s i l v e r with respect t unit. "X" i s the percent of t o t a l deposits of each metal for which host ro known. Roman numerals i d e n t i f y tectonic belts (see Table 2-1). Triangles major deposits of Table 4-1; dense stipples represent deposits with product sparse stipples represent showings, prospects and developed prospects. o host rock ck unit i s ide n t i f y ion records; 120 III IV II L e a d x=<?i% is--m r r z mc X=<?0% JE3- X=7S% I imoh Tunqsien x=ieo% •5s - J <n J C K CI W 3 $J- u D cJ _5 to (o 3: <o ro J > g £ n o r 2 3 3 ^ - * t>5 " J s Nickel x=a6% eg -c o (0 i 3: s v <3 - P C O U l ••3 S*5.s^»u 3 o Figure 4-9b. Number of occurrences of lead, zinc, i r o n , antimony, tungsten and n i c k e l with respect to host rock unit. "X" i s the percent of t o t a l deposits of each metal for which host rock unit i s known. Roman numerals i d e n t i f y tectonic belts '(see Table 2-1), Triangles i d e n t i f y major deposits of Table 4-1; dense stipples represent deposits with production records; sparse stipples represent showings, prospects and developed prospects. 121 Mineralization Characterizing Host Rock Formations Host rock formations are discussed as members of the tectonic belts i n which they occur, thereby further c l a r i f y i n g occurrence d i s t r i b u t i o n s within tectonic be l t s . Figure 4-7 serves as an outline for discussion of r e l a t i v e abundances between formations. Figures 4-8 and 4-9a,b provide information on the more weakly mineralized units not discussed i n d e t a i l below. Eagle Plutonic Belt. Deposits i n the Eagle Plutonic Belt occur i n both the Nicola Group and the Eagle Complex (Figure 4-10a); no production has been recorded i n this belt. Considering the 99 percent dominance of plutonic outcrop over volcanic (Nicola) outcrop, the fact that the number of occur-rences are equal i n both units suggests that the Nicola Group i s w e l l -mineralized. In fact, mineralization on the Princeton Map Sheet (92H, East Half) i s reported to occur most commonly i n the Nicola Group (Rice, 1960). Only veins are reported i n the Nicola Group i n the study area, f i v e of them i n the Jim Kelly Creek Camp, whereas the Eagle Complex contains four different deposit types dominated by porphyries. Recognized metals do not vary much between units, but Nicola Group veins contain more gold, and porphyries i n the Eagle Complex contain molybdenum mineralization not found i n the Nicola Group. Ladner Trough. Of the seven"* formations i n the Ladner Trough, only the Ladner Group (Figure 4-10a) contains abundant mineral occurrences; the Pasayten Group, Needle Peak Pluton and Invermay Stock contain few deposits. The Ladner Group i s dominated by veins of the Ladner Gold Belt and Summit Camp, one-third of which are producers. However, the two major deposits, Canam (HSW-1) and Aurum (HNW-3), are porphyry and disseminated ^Only s i x units are recognized on the time-space plot (Figure 2-2), but a small mineralized pluton, the Invermay stock, i s an additional unit con-sidered i n this discussion. The age of this stock i s probably equivalent to the 84 Ma pluton two kilometers north, which straddles the Hozameen Fault. E-atjIe Plut-cmicBelt . Cc u inn I I I 8 deposits "3 £ n 8 depasih* t S -\ Eagle. Complex. AJicola Group Hozameen Basin JL <r as 24 deposits | 20 h 10 4$ E 5 5£ # 0 2 Group Figure 4-10a. Number of occurrences i n host rock units of the Eagle Plutonic Belt, Ladner Trough Hozameen Basin and Cascade Belt, with respect to metal content and deposit type ° Triangles i d e n t i f y major deposits of Table 4-1; stipples represent deposits with proauction records; blank bars represent showings, prospects and developed prospects J3 123 types, respectively. Precious metal occurrences are more dominant than base metals, and the only uranium occurrence i n the area i s found here (Canam). Hozameen Basin. Deposits i n the Hozameen Basin occur i n the abundant Hozameen Group (Figure 4-10a). A variety of deposit types i s present, con-centrated i n the 10-Mile and 23-Mile Creek Camps; veins are only s l i g h t l y more common than other types. The most commonly reported metal i s gold, but copper and s i l v e r are almost as common; zinc and lead are also reported with moderate frequence. The only production was from veins. Cascade Belt. Mineral occurrences are most common i n the Chilliwack and Mt. Barr batholiths, and the Chilliwack Group (Figure 4-10a). Other formations with few occurrences are Custer Gneiss, Cultus, Chuckanut and Skagit Formations. The Chilliwack and Mt. Barr batholiths are grouped together because they are simi l a r i n age, setting and mineralization. Deposits are either veins or porphyries; metals are copper, molybdenum, s i l v e r and gold. Skarns characterize the Chilliwack Group; copper and s i l v e r stand out as the most common metals. Minor production i n the Cascade Belt i s r e s t r i c t e d to the Chilliwack Group and Chuckanut Formation. Spuzzum Plutonic Belt. Mineralized units of this belt are the Scuzzy and Spuzzum plutons, and the Giant Mascot Ultramafite. Although the number of deposits i s small, the magmatic nickel-copper orebodies of the Giant Mascot Ultramafite form one of the major deposits i n the study area (HSW-4). Coast Plutonic Belt. The Twin Islands and Bowen Island Groups, and Echo Island, Agassiz P r a i r i e and Cheakamus Formations contain very few deposits. Figure 4-10b i l l u s t r a t e s mineralization i n the f i v e formations 124 s n a -E Coast Plutonic Complex 21 J a p o a i t i s . I" *3 T 20 QJ vn ui AA a - fa lev taro up .10 da JL 3 c 5 .yj 5 «! <=> 1 1 -jamDieir? Group -Q-1M jnyos'i-ls 10 .of IDS Harrison lake, formal ion IN cT /-7re /.a/re Figure 4-10b. Number of occurrences i n host rock units of the Coast Plutonic Belt with respect to metal content and deposit type. Triangles i d e n t i f y major deposits of Table 4-1; st i p p l e s represent dep-o s i t s with production records; blank bars represent showings, prospects and developed prospects. 125 discussed below. The Fire Lake Group contains only gold-copper veins i n the Fir e Lake Camp, but other units are more d i v e r s i f i e d i n their deposit content. Mineralization i n the Harrison Lake Formation most commonly i s disseminated, but minor production was from a vein and a volcanogenic deposit (Providence, HNW-2, and Seneca, HSW-13, respectively). Copper and zinc dominate other metals, although s i l v e r , gold and lead also occur. The Gambier Group i s divided into two sections because the two min-eralized pendants to the north (referred to as "Gambier? Group") have not been correlated p o s i t i v e l y with the Gambier Group. The number- of producers i n the southern pendants i s very low, but includes the major volcanogenic deposit at Britannia (G-3), whose presence alone c l a s s i f i e s i t s host as the best mineralized unit i n the entire study area. Vein deposits, which dom-inate the area i n number, are not reported from the Gambier Group i n the south. As l i t t l e as ten years ago, this would not have been the case, as Britannia was then considered a vein. I t i s possible that other deposit types (except porphyries) might be volcanogenic accumulations (especially McVicar, G-6) which have not yet been recognized as such. Copper i s by far the most commonly reported metal; zinc and s i l v e r also are reported f r e - ... quently. One or both of the northern pendants may be Tr i a s s i c or Jurassic, as discussed i n the previous chapter. The percentage of producers i s high, and one vein deposit i s major (Northair, J-130). Metal di s t r i b u t i o n s resemble those of Gambier Group pendants discussed above except for the more abundant occurrence of lead and the presence of antimony and tungsten. Porphyries are the most common deposits i n intrusions of the Coast Plutonic Complex; th i s i s reflected i n metal distri b u t i o n s by dominant copper and molybdenum. Moderate s i l v e r and gold reports are probably from 126 vein deposits which are the only other r e l a t i v e l y common type of miner-a l i z a t i o n . Production i s low. Host Rock Type Host rock types are known for 78 percent of the deposits i n the study area. Intrusive, volcanic and sedimentary rocks are well-represented, but metamorphic rocks are not discussed for two reasons: 1) Only 15 deposits (out of 203 total) report metamorphic host rocks; and 2) Eight of those 15 occurrences are described as metavolcanic or metasedimentary, and can therefore be classed as volcanic or sedimentary. If a metal or type of deposit i s associated genetically with a p a r t i -cular rock type, i t should be readily apparent, regardless of coincidental occurrences i n other types. Therefore, when more than one mineralized rock type i s reported for a deposit, each i s recorded and given equal weight. The three major rock types are subdivided further as follows: 1) Intrusive rocks which include^ a) intermediate to acid intrusions, b) ultramafic intrusions, and c) dikes of any composition. 2) Volcanic rocks which include a) basic volcanic rocks and greenstones ( i . e . , andesite, b a s a l t ) , b) acid volcanic rocks ( i . e . , r h y o l i t e , dacite), c) pyroclastic volcanic rocks ( i . e . , t u f f , agglomerate, breccia) of unspecified composition,7 and d) unclassified volcanic and metavolcanic rocks. 3) Sedimentary rocks which include a) c l a s t i c sedimentary rocks ( i . e . , shale, sandstone, conglomerate, breccia), b) limestone, and c) si l i c e o u s ( i . e . , chert, quartzite) and uncl a s s i f i e d sedimentary rocks. With the exception of dikes, mafic intrusions were not reported to host mineralization i n the study area. A pyroclastic rock whose composition i s known i s categorized by that composition. Metals and deposit types are f i r s t examined below to review t h e i r d i s t r i b u t i o n among the three major rock types (Figure 4-11). A l l histogram distrib u t i o n s i n this section are compared to mineralized rock type abun-dances for the study area shown i n Figure 4-12. The apparent concentration of mineral occurrences i n intrusive rocks i s misleading, because the amount of plutonic outcrop i s much greater than either volcanic or sedimentary g outcrop. I f densities of occurrences were determined for each rock type, values for plutonic rocks would be very low; volcanic and sedimentary rocks (especially basic volcanic rocks and c l a s t i c sedimentary rocks, Figures 4-14 and 4-15) would exhibit very high densities. Subsequent discussion of rock types uses the more detailed c l a s s i f i -cations described above to characterize mineralization i n each host rock and further examine the behavior of metals and deposit types i n the smaller categories. Figures 4-2 and 4-3 are used as indicators of general abundances for comparison of mineralization i n each rock type. Dis t r i b u t i o n of Metals and Deposit Types Among Host Rock Types Copper, molybdenum and n i c k e l exhibit predictable d i s t r i b u t i o n patterns (Figure 4-11). Copper occurrences are abundant i n every rock type, but n i c k e l and molybdenum occurrences are associated p r e f e r e n t i a l l y with i n t r u -sive rocks; other metals studied appear to occur p r e f e r e n t i a l l y i n volcanic and sedimentary rocks. Zinc, lead and antimony occurrences prefer volcanic over sedimentary rocks, zinc showing the most s i g n i f i c a n t preference. Gold, s i l v e r and iron oxides are more common i n sedimentary than volcanic rocks. Many vein occurrences are reported i n a l l rock types, but the density — Sixty-four percent of the study area i s underlain by Eagle Complex, Coast Plutonic Belt intrusions and Spuzzum Plutonic Belt intrusions; the remaining 36 percent i s occupied by both volcanic and sedimentary rocks, along with various plutons whose areas were not computed. 128 3 6 - V I 20-10-Vein 36-Porphuru r-VrtV X = 83% V lo- I Sli&ar 2 0 -1 0 -I V am X"-100% s-Ma5s'iv& X=60e/o 3 6 -3Jr-s-Vol X=ioo% Disse.mmai.ed MaamaVlC So-10-30-I 30 Copper X»83% X M o l u U enum X«88% Figure 4-11. I X=80% V 1 .A' SilvsY 10-Tor* X=<)0% 5 0 -hi-3 0 -20 1<H irmc X=80% (U y=ioo7o" 30-Lead ~Tvmy4;e,Y\ X*\D07* Number of occurrences of each metal and deposit type with respect to in t r u s i v e ( I ) , volcanic (V) and sedimentary (S) host rock types. "X" i s the percent of t o t a l deposits of each metal or deposit type for which host rock type i s known. Triangles i d e n t i f y major deposits of Table 4-1; stipples rep-resent deposits with production records; blank bars represent showings, prospects and developed prospects. 129 10. 80-7fl-60-50-HO-30-20-10-1 A 1*1 ~T~" a) 1 o ' :r» ? u c on Figure 4-12. Total number of occurrences i n i n t r u s i v e , volcanic and sedi-mentary host rocks (host rock type i s known for 73% of a l l deposits i n the study area). Triangles i d e n t i f y major deposits of Table 4-1; stipples represent deposits with production records; blank bars represent showings, prospects and devel-oped prospects. 130 of occurrences i n intrusive rocks i s very low. Sedimentary rocks favor vein mineralization s l i g h t l y more than volcanic rocks, but the l a t t e r host the only major vein deposit, Northair (J-130). Porphyry and Magmatic deposits are p a r t i c u l a r l y abundant i n the i r genetically associated intrusive host rocks. The occurrence of a major porphyry deposit, Canam (HSW-1), i n sedimentary rocks i s unusual. A preference by skarn deposits for sedimentary rocks i s predictable, as calcareous sedimentary rocks are commonly affected by contact metasomaT.. tism. The fact that the volcanogenic deposits, Britannia (G-3) and Seneca (HSW-13) are i n volcanic rocks i s almost a matter of d e f i n i t i o n , although d i s t a l sedimentary rocks are also potential hosts. With only two reported deposits of this type, further discussion i s not possible. Massive dep-osits also lack a s u f f i c i e n t data base for detailed analysis. Shear and disseminated deposits occur i n a l l rock types, but are most common i n volcanic rocks: the only disseminated deposit to produce, Astra (J-45), i s i n volcanic rocks. I t i s possible that these deposits are genetically related to volcanism, representing syngenetic accumulations. The presence of a major disseminated deposit, Aurum (HNW-3), i n sedimentary rocks i s unusual. Mineralization Characterizing Host Rock Types Figures 4-13 through 4-15 i l l u s t r a t e the d i s t r i b u t i o n of metals and deposit types among sp e c i f i c rock types characterizing i n t r u s i v e , volcanic and sedimentary rocks. The height of each histogram i s equivalent to the number of deposits i n each rock type so that values may also be estimated as percentages. Intrusive Rocks (Figure 4-13). The high percentage of porphyry deposits 131 Intermediate lo flc'id Jnt rusive Rock fa) (b) (c) Fe'Co'ff; WihflslT.fljCd'Sfc W flu PI, Bi U C & -o £ O E 3"> ~SZ Jc. -p <4 <o ro :T> to * — _ c QJ o c ro o Figure 4-13. Number of occurrences i n (a) intermediate to acid i n t r u s i v e rocks, (b) ultramafic rocks, and (c) dikes, with respect to metal content and deposit type. Triangles i d e n t i f y major deposits of Table 4-1; stipples represent deposits with production records; blank bars represent showings, prospects, and developed prospects. 132 i n intermediate to acid intrusive rocks has resulted i n an unusually high abundance of molybdenum occurrences i n these rocks. S i m i l a r l y , the high incidence of magmatic deposits i n ultramafic rocks correlates d i r e c t l y with the high proportion of n i c k e l occurrences i n ultramafic rocks, to the exclusion of a l l other metals except gold and s i l v e r . Vein and disseminated deposits i n intermediate to acid int r u s i v e rocks probably carry the variety of metals which i s not present i n ultramafic rocks. Occurrences which report dikes as the predominant mineralized host rock most commonly contain copper, gold and/or s i l v e r . Dikes do not show a preference for any part i c u l a r type of deposit. Volcanic Rocks (Figure 4-14). Metal abundances i n basic volcanic rocks resemble general abundances of metals i n the study area, except that basic volcanic rocks appear to contain an above average proportion of zinc occurrences and, to a lesser extent, lead. This trend i s even more evident i n a c i dic and pyroclastic volcanic rocks where zinc i s as common as copper. The number of lead occurrences i n th i s category i s close to that of the precious metals; normally lead i s only one-half to one-third as common as precious metals. The absence of n i c k e l and few reports of molybdenum i n a l l volcanic rocks i s to be expected i f concentrations of these metals originate with intru s i v e rocks. Antimony most often occurs i n volcanic (especially basic volcanic) rocks. Although many veins occur i n volcanic rocks, disseminated deposits are as common. The high proportion of deposits reporting vein, shear, d i s -seminated and massive deposits, and the presence of the only recognized volcanogenic deposits i n the study area suggest that occurrences i n volcanic rocks are dominantly of volcanogenic o r i g i n . Veins, disseminations and massive sulfides are characteristic of volcanogenic deposits, and shears might easily describe portions of a deformed volcanogenic deposit. Skarns 133 5 and Green si, oh&s Acid Volcanic Rocks (b) i}—i -10-- s -7t/ff, Aqalom&raie and Volcanic Breccia Unclassified and /Helamorphos&J Volcanic Rocks i i i -10-- 5 -Fe Co Ni Cu 2n flsfl, % CJ Si W /.»PA Bi U _ s. -o « O c 3 ^ O TO CO in (o c •a") o o Figure 4-14, Number of occurrences i n (a) basic volcanic rocks and green-stones, (b) acid volcanic rocks, (c) t u f f , agglomerate and volcanic breccia, and (d) unc l a s s i f i e d and metamorphosed volcanic rocks, with respect to metal content and deposit type. Triangles i d e n t i f y major deposits of Table 4-1; stipples represent deposits with production records; blank bars represent showings, prospects and developed prospects. 134 and porphyry deposits do not appear to favor volcanic rocks. Sedimentary Rocks (Figure 4-15). C l a s t i c sedimentary rocks report far less copper than intrusive and volcanic rocks, but gold and s i l v e r are reported i n more than half the deposits. Despite the importance of precious metals to c l a s t i c sedimentary rocks, only one major non-producing gold deposit, Aurum (HNW-3), i s present (cf. the two major producing deposits with precious metals i n volcanic rocks; Britannia, G-3, and Northair, J-130). Other sedimentary rocks, on the other hand, are dominated by copper. With the exception of two n i c k e l occurrences i n limestone, n i c k e l and molyb-denum are rare. Iron i s commonly reported i n limestone, and the only uranium occurrence i n the area i s i n c l a s t i c sedimentary rocks. Veins account for 74 percent of a l l deposits i n c l a s t i c sedimentary rocks, and many were producers, but disseminated and porphyry types host the two major deposits, Aurum (HNW-3) and Canam (HSW-1). Skarn mineral-i z a t i o n exceeds a l l other types i n limestone. DEPOSIT DISTRIBUTION MAPS Appendix B contains areal d i s t r i b u t i o n maps of deposit types and selected metals reproduced d i r e c t l y from Calcomp pl o t t e r output (cf. S i n c l a i r , et^ a l . , 1978). Outstanding physiographic features and tectonic belts are included for easy reference to Figure 1-2. Observations of deposit type distributions are as follows: 1) Magmatic deposits are noticeably clustered around Giant Mascot, as discussed previously. 2) Massive deposits (with one exception) are located i n the 10-Mile Creek Camp. 3) Shear deposits are clustered a) around Britannia and b) i n an area which combines deposits of two dominantly vein camps whose ages of mineralization are probably d i s s i m i l a r — Summit and Ladner Gold. Shears i n the Coast Plutonic Belt 135 CldSJlC S £(jima)rfc a r t f Rocks Limesi one Siliceous 3rid UncldssiPied S&dimaniaRock F « C o / V i C u 2 n Asd. • a tL - S-fljCjst wflu pb'oi'u c »- -a S S " 5 K l to » i n CO o _ EST in in .Co £ <n o- o V E =5 Figure 4-15. Number of occurrences i n (a) c l a s t i c sedimentary rocks, (b) limestone, and (c) s i l i c e o u s and u n c l a s s i f i e d sedimentary rocks, with respect to metal content and deposit type. Triangles i d e n t i f y major deposits of Table 4-1; stipples represent deposits with production records; blank bars rep-resent showings, prospects and developed prospects. 136 are Intimately associated with disseminated and porphyry deposits, whereas the eastern cluster of shears i s notably devoid of both disseminated and porphyry occurrences. The opposite relationship applies to shears and veins, as the eastern shear deposits are s p a t i a l l y related to veins which are not reported i n the Britannia area. 4) Veins dominate the eastern one-third of the area, but are rarely reported i n the Coast Plutonic Belt except at Northair, Fi r e Lake and P i t t Lake; no veins are reported west of 123° 30' west longitude. Vein deposits are not reported i n the v i c i n i t y of the known volcanogenic deposits, Britannia and Seneca. 5) Although porphyry deposits are evenly scattered among occurrences i n the eastern one-third of the area, they occur i n the Coast Plutonic Belt mainly i n an east-west-trending band from the Sechelt Peninsula to Harrison Lake. Porphyries are s l i g h t l y more dense around Britannia than elsewhere. With one exception, no vein deposits occur i n this band of porphyries. 6) Disseminated deposits i n the Coast Plutonic Belt occur i n an arc extending northwest to southeast through Northair, Britannia, Harrison Lake and the 10-Mile Creek Camp; they surround the Seneca deposit. 7) Skarns are most common i n the southeast corner of the area, and occur i n the Coast Plutonic Belt only near Northair, on the Sechelt Peninsula, and s l i g h t l y north of Vancouver. Metals do not generally exhibit d i s t r i b u t i o n s as marked as those of deposit types. To the contrary, most metal distr i b u t i o n s are simi l a r to that of the general abundance of deposits shown i n Figure 1-2, with minor deviations. Some observations that can be made are as follows: 1) The d i s t r i b u t i o n of ni c k e l i s si m i l a r to that of magmatic deposits. The cluster of n i c k e l deposits i s devoid of zinc, s i l v e r , gold, lead and molybdenum occurrences. 2) The d i s t r i b u t i o n of molybdenum i s si m i l a r to that of porphyries. Only one deposit contains both molybdenum and lead, Canam (HSW-1). 3) Copper, s i l v e r , gold and zinc are distributed according to the general abundance of deposits, only gold exhibiting a marked preference to eastern deposits. 4) Lead i s reported primarily i n the southeastern corner of the area and less commonly i n the Northair D i s t r i c t . Only scattered occurrences appear elsewhere, and no lead occurs west of 123° 30' west longitude. 137 The following information i s derived from multi-commodity occurrence distributions of Maps B-26 through B-30: 1) Where precious metals occur with molybdenum, s i l v e r i s invariably present. 2) Lead i s commonly reported with s i l v e r ; with one exception, s i l v e r i s absent from lead deposits only i n small showings or prospects which may not have assayed for s i l v e r . 3) Lead occurs most commonly with zinc east of Hope. 4) Gold occurs without s i l v e r only east of P i t t and F i r e Lakes. Commodity d i s t r i b u t i o n maps each present every occurrence of a com-modity according to deposit size and ranking among other metals i n each deposit. Examination of these maps reveals that d i s t r i b u t i o n patterns would have been considerably different for many metals had only f i r s t -reported (or first-ranked) commodities been portrayed. A first-ranked commodity map for molybdenum would imply that none i s present i n the Coast Plutonic Belt whereas, i n fact, molybdenum occurrences are more common i n intrusions of t h i s belt than are occurrences of other metals studied. Since zinc i s rarely reported as a first-ranked commodity, this r e l a t i v e l y common metal would not have shown up on such a map. Similar variations apply to lead, s i l v e r and copper; even inclusion of second-ranked commo-d i t i e s w i l l not always lead to satisfactory representation of the d i s t r i -bution of a metal (cf. lead, z i n c ) . SUMMARY A s t a t i s t i c a l examination of deposit characteristics i n the study area has led to the following observations: 1) Dominant metals, i n order of abundance of occurrences, are copper, gold, s i l v e r , zinc, lead and molybdenum. 2) Dominant deposit types, i n order of numerical abundances, are vein, porphyry and disseminated. 138 3) The d i s t r i b u t i o n of metals among major and producing deposits generally r e f l e c t s t o t a l metal abundances. 4) The d i s t r i b u t i o n of deposit types among major and producing deposits does not r e f l e c t t o t a l deposit type abundances. Porphyry, disseminated and magmatic deposit types are either uncommonly present or uncommonly pro-ducers, and yet each i s host to a major deposit. The most abundant deposits with the majority of producers i n the area are veins, and yet only one major deposit i s a vein. Volcanogenic deposits have only been recog-nized i n the area twice, and yet one of these deposits, Britannia, i s of colossal proportions r e l a t i v e to other occurrences i n the area. Additional discrepancies between major deposits and other factors include the following: a) Seventy-four percent of a l l deposits i n c l a s t i c rocks are veins, and yet the major deposits are disseminated (Aurum) and porphyry (Canam). b) Porphyries are singularly dominant i n intru s i v e rocks, and yet the only producing porphyry (Canam) i s i n sedimentary rocks. c) Disseminated and shear deposits dominate volcanic rocks, and yet the major, disseminated deposit i s i n sedimentary rocks (Aurum). 5) Molybdenum occurs generally i n porphyry deposits i n intr u s i v e rocks. 6) Nickel occurs generally i n magmatic deposits i n ultramafic rocks whose d i s t r i b u t i o n i s centered around the Giant Mascot Ultramafite. 7) Skarn deposits generally occur i n limestone. 8) Intermediate to acid intrusive rocks are poorly mineralized. 9) Pendant rocks i n the Coast Plutonic Belt are w e l l mineralized. 10) With the exception of the Cascade Belt, geologic units across the area with considerable volcanic rocks are well-mineralized by vein, shear, disseminated and massive deposits. 11) C l a s t i c sedimentary rocks also report considerable mineralization, but only the Ladner Group reports a s i g n i f i c a n t number of occurrences. 12) The most economically favorable host rock units i n the area are. the Gambier Group and the Ladner Group; each contain high numbers of occurrences and two major deposits. 139 5. CONCLUSIONS AND METALLOGENY The tectonic model presented b r i e f l y i n Chapter Two implies the presence of (at least) two episodes of subduction which resulted i n form-ation of the Cretaceous Coast Plutonic Complex and the Tertiary Cascade Belt. Intense plutonism i n Cretaceous time, c o l l i s i o n of the Coast Plutonic arc with the Intermontane arc i n mid-Cretaceous time, and considerable r i g h t - l a t e r a l movement along major fa u l t s i n Tertiary time have s i g n i f i -cantly disguised o r i g i n a l relationships i n the area. In this context, i t becomes d i f f i c u l t not only to unravel the tectonic his t o r y , but to relate the metallogenic history to the tectonic framework. Examination of major deposits, d i s t r i c t s of s i g n i f i c a n t concentrations of deposits, and deposits with production records has served to describe the dominant areas of interest and relate them to the tectonic evolution of the area. The results of the descriptive work i n Chapter Three are i l l u s t r a t e d on the time-space plot of Figure 2-2. The d i s t r i b u t i o n of min-e r a l i z a t i o n here implies that the great majority of deposits were formed (a) throughout the Coast Plutonic Belt and (b) s p a t i a l l y related to the Hozameen Fault during Cretaceous c o l l i s i o n and plutonism. This epoch of mineralization includes the f i v e major deposits found i n the study area. Less abundant mineralization occurred i n Oligocene-Miocene time. As a t t r a c t i v e as this model of two metallogenic epochs may be, i t i s i n part a b u i l t - i n result of the manner i n which this study was undertaken. Determination of the age of mineralization of many camps i s l i t t l e more than supposition; i f mineralization i s assumed to be epigenetic, i t i s also assumed to be the product of observed deformation or plutonism. These assumptions are believed by the author to be reasonable, although supportive evidence commonly i s lacking. 140 Major mineralization characterizing the Cretaceous episode includes: 1) volcanogenic copper-zinc su l f i d e deposition (Britannia) i n volcano-sedimentary rocks of the Coast Plutonic arc, 2) formation of a gold-silver-lead-zinc vein (?; Northair) i n volcanic pendant rocks of the Coast Plutonic Belt, 3) magmatic nickel-copper s u l f i d e formation (Giant Mascot) i n the a x i a l metamorphic core of the Spuzzum Plutonic Belt, 4) introduction of gold i n veins and disseminations (Ladner Gold) i n rocks adjacent to the deep-seated Hozameen Fault and serpentine b e l t , and 5) formation of a copper-rich breccia pipe (Canam) i n sedimentary rocks adjacent to the Hozameen Fault. Formation of copper-zinc s u l f i d e deposits (Harrison Lake D i s t r i c t ) p r ior to Cretaceous time occurred during a c i d i c volcanism of the Middle Jurassic Harrison Lake Formation. Mineralization might have occurred during deposition of the Hozameen Group i n Upper Paleozoic time, but too l i t t l e i s known about these deposits to put much emphasis on this suggestion. The application of s t a t i s t i c a l tabulations to information accumulated on metal occurrences i n the study -area has revealed some interesting r e l a -tionships. Although major deposits r e f l e c t the general abundance of metals i n the area, they do not correspond to the most, common deposit types. This i s unfortunately a poor r e f l e c t i o n of the c l a s s i f i c a t i o n scheme used i n this study, as a l l of the major deposits (except Canam) are located i n areas where they should be expected to occur on the basis of geology and surrounding metal occurrences. For this reason, a detailed knowledge of the geology and characteristics of i n d i v i d u a l occurrences has proved i n -valuable. The most notable results of the s t a t i s t i c a l study pertain to the control of host rock type over mineralization. Intrusive rocks are sing-u l a r l y characterized by molybdenum and n i c k e l s u l f i d e occurrences i n intermediate to acid v a r i e t i e s and ultramafic rocks, respectively. The 141 source of n i c k e l corresponds to i t s inherently n i c k e l - r i c h host rock, and since molybdenum occurrences are r e s t r i c t e d to intermediate to acid intrusive rocks, the source of this metal also i s assumed to be i t s host intrusion. C l a s t i c sedimentary rocks primarily contain vein deposits with pre-dominant precious metal (mainly gold) content. However, this abundance of deposits i s r e s t r i c t e d to the Ladner Group, s p e c i f i c a l l y along the serpentine belt of the Hozameen Fault. Gold deposits, therefore, are controlled by tectonic environment, not rock typei Other c l a s t i c sedimentary units i n the area (especially the s l a t y , t u r b i d i t i c Cultus Formation) are poorly mineralized. I t i s on th i s basis that a mid-Cretaceous epigenetic o r i g i n and not a Middle Jurassic syngenetic o r i g i n i s favored for the disseminated gold deposit i n the Ladner Gold Belt. A source for the gold i n this area can probably be related to deep-seated sources (sub-crustal?) which were tapped by the Hozameen Fault. The fact that gold occurrences are most prominent along the f a u l t where ultramafic rocks occur suggests a genetic relationship. Volcanic rocks are most commonly mineralized by shear, vein and disseminated deposits, which may also describe portions of volcanogenic deposits. Since (a) Britannia i s surrounded by shears which look si m i l a r to s u l f i d e occurrences i n the Britannia orebodies, and (b) Seneca i s surrounded by disseminated occurrences which are similar to portions of the Seneca deposit, a l l such occurrences are l i k e l y "volcanogenic-type" deposits. With the exception of molybdenum and n i c k e l , the predominant metals i n the area are copper, s i l v e r , gold, zinc and lead, i n decreasing order of abundance. Since this assemblage i s characteristic of volcanic rocks, i t i s suggested that i n the study area these metals, o r i g i n a l l y accumulated 142 i n volcanic rocks, were subsequently remobilized into epigenetic deposits. Integration of th i s information with the tectonic and metallogenic history of the area indicates that arc volcanism of the Coast Plutonic Belt i s primarily responsible for the o r i g i n a l accumulations of metals. Cretaceous c o l l i s i o n with the Cascade and Intermontane Belts remobilized these o r i g i n a l accumulations; Tertiary Cascade plutonism (and volcanism?) was also responsible for some remobilization. During the c o l l i s i o n epi-sode, access to sub-crustal sources through ultramafic intrusion and deep-seated f a u l t i n g introduced n i c k e l and gold accumulations along the c o l l i s i o n axis. Formation of molybdenum deposits, although d e f i n i t e l y correlated with plutonism, i s not r e s t r i c t e d to any part i c u l a r episode. Computer inventory f i l e s are potential assets to regional studies such as t h i s one, but i t s applications are limited. As a data storage bank for information necessary to acquaint one with mineral deposits i n a specified area, i t s potential i s indisputed, however, i t was necessary i n this study to do most tabulation manually. S t a t i s t i c a l analyses of such data require areas which are tailor-made to the problem under examination. For example, a detailed study of a small area with a high density of occurrences i s p r a c t i c a l i f the geology i s r e l a t i v e l y uncomplicated and applications are on a small scale. But i f large-scale problems are to be tackled, a much larger area should be examined to eliminate small-scale variations i n the large-scale picture. The conclusions reached i n this study are based on a very small population r e l a t i v e to the large-scale features discussed, and should be regarded i n this l i g h t . 143 REFERENCES CITED Aho, Aaro E. (1956): Geology and genesis of ultrabasic nickel-copper-pyrrhotite deposits at the P a c i f i c Nickel Property, southwestern B r i t i s h Columbia, Economic Geology, Vol. 51, p. 444-81. 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(1968): Granitic rocks of southwestern B r i t i s h Columbia, i n Guidebook for Geological F i e l d Trips i n Southwestern B r i t i s h Columbia, U.B.C. Geology Dept. Rept. No. 6, W. H. Mathews, ed., A p r i l , p. 13-17. Woodsworth, G. J. (1977): Pemberton (92J) map-area, Geol. Surv. Can. Open F i l e Map No. 482. Woodsworth, G. J . , Pearson, D. E., and S i n c l a i r , A. J. (1977): Metal d i s t r i b u t i o n patterns across the eastern flank of the Coast Plutonic Complex, south-central B r i t i s h Columbia, Ec. Geol., Vol. 72, p. 170-83. APPENDIX A STATISTICAL DATA BASE TABLE A-l. DISTRIBUTION.OF COMMODITY OCCURRENCES.INTO. DEPOSIT.TYPES r H r H - O veins 1 45 C13) 20 C9) 2 CD 1 44 C16) 2 2 CD 64 C18) 26 C9) shears 1 (1) 1 1 17 . C2) 12 CD . 1 13 C2) l CD 10 C2) 7 CD disseminated 1 1 31 CD 20 CD 1 1 14 CD 5 CD c l CD 10 9 1 CD massive 1 4 2 1 2 magmatic 1 Cl) 13 CD 13 CD 1 1 1 skarns 10 (2) 2 20 C4) 11 CD 5 C2) 15 C3) 1 10 CD 5 porphyries 3 CD • 37 C2) 5 33 C2) 14 (2) 1 7 (D 1 1 1 CD CD volcanogenic 1 CD 2 C2) 2 C2) 2 C2) 2 C2) 2 C2) unknown 2 2 15 9 1 9 8 5 "The lower number in parentheses is the number of commodity occurrences from deposits with production records; this number is included in the total count above it. TABLE A-2. NUMBER OF COMMODITY OCCURRENCES AND DEPOSIT TYPES IN EACH TECTONIC BELT OR BELT SUBDIVISION IN THE STUDY AREA' | togenic .ated 4J rH u u a § | •H .& togenic E -H 01 0) e oi CO Xi 01 ;> E CO | s j= c >•* u rt 01 E CJ > rH o U a c rH u e rt CO rt u rt •H 8 CO CO CO CO rt u y C u N rt 1 cn u cd u OO rH WO 3 o a r*l CO O > . £ CO •H T) « E o H Coast Plutonic Belt Intrusions -10,187 Km 2 1 32 (3) 5 (1) 19 (1) 9 (3) 7 (2) 1 i 21 (1) 8 (D 1 4 35 (2) Coast Plutonic Belt Pendants . 2,652 Km 10 (3) 59 (9) 32 (7) 4 (D 30 (9) 1 CD 3 C3) 25 (9) 15 (6) 1 7 9 (2) 2 (2) 13 (5) 14 (2) 19 (D 1 65 (12) Spuzzum Plutonic Belt Intrusions-3,097 Km 1 10 (1) 11 (1) 1 2 1 1 1 3 1 1 8 CD 2 2 1 1 14 (D Spuzzum Plutonic Belt Pendants -1,145 Km 1 1 4 (1) 1 CD 4 (1) 3 (1) 1 4 CD 1 6 (D Cascade Belt 1,619 Km2 3 (1) 2 15 (3) 6 6 (D 14 (3) 1 9 7 CD 1 4 7 (2) 7 (D 1 3 23 (3) Hozameen Basin 1,111 KE2 3 3 16 (1) 10 (1) 1 3 15 (1) 3 1 17 (1) 8 (D 2 1 4 5 (D 7 4 23 (D Ladner Trough 1,875 Km2 1 (1) 1 21 (7) 17 (5) 1 2 (1) 22 (9) 2 37 CH) 15 (6) 1 (1) 1 1 (D 34 (10) 7 2 45 (11) Eagle Plutonic Belt 1,787 Km2 1 1 18 6 5 9 1 10 6 1 5 2 7 2 17 Total.. -23,473 Km 20 (5) 2 19 (1) 176 (25) 77 (14) 3 (1) 41 (4) 104 (26) 1 7 (D 6 (3) 111 (24) 53 (14) 2 1 (1) 14 (1) 41 (2) 23 (4) 2 (2) 80 (19) 24 (2) 39 (1) 5 228 (31) 'The lower number in parentheses is the number of deposits with production records; this number is included in the total count above it. ' Areal calculations are included below each division name. \ TABLE A-3. DENSITIES (NUMBER OF DEPOSITS/100 III2) OF COMMODITY OCCURRENCES AND DEPOSIT TYPES IN EACH TECTONIC BELT OR BELT SUBDIVISION IN THE STUDY AREA' § p « *H 41 u u ti « •fc u V §• -J . & J S w & JI V 3 • § •a O fr E G M o a ! ti t> o 1 O a jj a 41 § 3 • S 1 & u ti « w n w a u N * 8 a S § 4J 8> 9 s o a 3 m i • > j: m S i 1 Coast Plutonic Bait Intrusions .05 .03 .81 (.08) .13 (.03) .48 (.03) .23 (.08) .18 (.05) .03 .03 .33 (.03) .21 (.03) .03 .10 .89 (.05) Coast Plutonic Belt Pendants .98 (.29) 5.76 (.88) 3.13 (.68) .39 (.10) 2.93 C.B8) .10 (.10) .29 (.29) 2.44 (.88) 1,46 (.59) .10 .68 .88 (.20) .20 1.27 (.49) 1.37 (.20) 1.86 (.10) .10 6.35 (1.17) Spuzzum Plutonic Belt Intrusions .08 .84 (.08) .92 (.08) .08 .17 .08 .08 .08 .25 .08 .08 .67 (.08) .17 .17 .08 .08 1.17 (.08) Spuzzum Plutonic Belt Pendants .23 .23 .90 (.23) .23 .90 (.23) .68 (.23) .23 .90 (.23) .23 1.36 (.23) Cascade Belt .48 (.16) .32 2.40 (.48) .96 .96 (.16) 2.24 (.48) .16 1.44 1.12 (.16) .16 .64 1.12 (.32) 1.12 (.16) .16 .48 3.68 (.48) Hozameen Basin - .70 .70 3.73 (.23) 2.33 (.23) .23 .70 3.50 (.23) .70 .23 3.96 (.23) 1.86 (.23) .47 .23 .93 1.17 (.23) 1.63 .93 5.36 (.23) Ladner Trough .14 (.14) • 14 2.90 (.97) 2.35 (.69) .14 .28 (.14) 3.04 (1.24) .28 5.11 (1.52) 2.07 (.83) .14 (.14) .14 .14 (.14) 4.70 (1.38) .97 .28 6.23 (1.52) Eagle Plutonic Belt .14 14 2.61 .87 .72 1.30 .14 1.45 .87 .14 .72 .29 1.01 .29 2.46 Total .22 (.06) .02 .21 (.01) 1.94 (.28) .85 (.15) .03 (.01) .45 (.04) 1.15 (.29) .01 ..08 (.01) .07 (.03) 1.22 (.26) .58 (.15) .02 .01 (.01) .15 (.01) .45 (.02) .25 (.04) .02 (.02) .88 (.21) .26 (.02) .43 (.01) .06 2.52 (.34) 'ho lower number i n parentheses i s the number of deposits with production records; this number i s included in the total count above i t . TABLE A-4. RELATIVE DENSITIES OF COMMODITY OCCURRENCES AND DEPOSIT TYPES IN EACH TECTONIC BELT OR BELT SUBDIVISION IN THE STUDY AREA* a p >balt . b V o. O. c rsehlc rlybdenum Liver 1 i ltlmony a u & g •o •o Lsmuth 1 | •rt I fr JS & e Leanogenlc a h 3 iseminated isive •3 - u a u M « a a * a Si -1 3 o 2 s 1 .c n • -o i •2 CoaBt Plutonic Belt Intrusions .23 .14 I, .42 .04) .15 (.03) 1.07 (.07) .20 C.07) . 15 (.04) .05 .20 1.18 (.07) .24 (.03) .12 .23 .35 (.02) Coast Plutonic Belt Pendants 4.45 (1.32) 2, (. .97 .45) 3.68 C.80) .87 (.22) 2.55 (.77) 1.25 C1.25) 4.14 (.4.14) 2.00 (.72) 2.52 0 . 0 2 ) 5.00 1.51 3.52 10.00 (.80)(10.00) 1.44 (..56) 5.27 (.77) 4.33 (.23) 1.67 2.52 (.46) Spuzzum Plutonic Belt. Intrusions •07. 4.00 (.38) (' .47 .04) .09 .38 .07 1.00 1.14 .20 .14 4.00 4.47 (.53) .38 .19 .31 .19 .46 (.03) Spuzzum Plutonic Belt Pendants 1.10 1.10 (.. .46 .12) 7. (7 .67 .67) .78 (.20) .56 (.19) .92 1.02 (.26) .53 .54 (.09) Cascade Belt 2.18 (.73) 1.52 1 (. .24 .25) 1.13 2.13 (.35) 1.95 (.42) 2.29 1.18 1.93 (.28) 1.07 1.42 4.48 (1.28) 1.27 (.18) .62 1.12 1.46 (.19) Rozaejeen Basin 3.18 3.33 1 (, .92 .12) 2.74 .27 7, .67 1.56 3.04 (.20) 8.75 3.29 3.25 (.19) 3.21 (.40) 3.13 .51 3.72 1.33 (.26) 3.79 15.50 2.13 (.09) ".adner Trough .64 (.64) .67 1 (. .49 .50) 2.76 (.81) 4 .67 .62 (.31) 2.64 (1.08) 3.50 4.19 (1.25) 3.57 (1.43) 14.00 (14.00) .93 .31 (.31) 5.34 (1.57) 3.73 .65 2.47 (.60) Eagle Plutonic Belt .64 .67 1 .35 1.02 1.60 1.13 14.00 1.19 1.50 .93 ' 1.60 1.16 1.15 • .67 .98 Total 1.00 (-27) 1.00 1.00 (.05) .1 ( .00 .14) 1.00 (.18) ( .00 .33) 1.00 (.09) l . o o (.25) 1.00 l.OO (.13) 1.00 (.50) 1.00 (.21) 1.00 (.26) 1.00 1.00 • (1.00) 1.00 (.07) 1.00 (.04) 1.00 (.16) 1.00 (1.00) 1.00 (.24) 1.00 (.08) 1.00 (.02) 1.00 1.00 (.13) ^ho lower number in parentheses i s the number of deposits with production records; this number i s included in the total count above i t . o u I o u S >> c a 3 I fr 0 00 g S • f l • o M u - V I V " > 0 E | S r i " e u 3 S «• M -« 3 u t Ti I N 1 3 * •t u 9 I '2 •o s a a « 1 M 3 o H Coast Plutonic Complex 2 l 34 (4) 7 (2) 19 % 12 <4> l 2 (2) 11 (3) ft ( l ) i 21 (1) 11 (2) ( i ) 3 ftl (4) Chilliwack and Ht. Barr 1 1 3 1 4 3 T 3 l 4 3 7 Batholltha Needle Peak Pluton 1 -* ' 1 1 Invermay Stock 2 (1) 2 (1) 2 (O 2 (1) i ( i ) 2 (1) 2 (1) Scuzzy/Spuzzum Plutons 3 (1) 1 1 (1) 2 1 (1) 1 1 (O -1 2 I (1) 3 (1) Eagle Cooplex 8 3 ft 3 1 3 3 4 i -1 2 8 Clant Mascot Ultramafite l O) 1 (1) ( i ) 1 (O Agassli P r a i r i e Formation 1 1 1 1 Boven Island Croup 1 (1) 2 (1) 1 (1) 1 (1) 2 Cheakamus Formation 1 1 1 1 1 Chilliwack Group 1 . (1) 8 (2) 2 2 (1) 6 (2) 1 3 1 5 (2) 3 1 9 (2) Chuckanut Formation * 1 (1) 1 <l> 1 (1) 1 (1) 1 (I) Cultus Formation 1 1 1 1 Custer Gneiss 1 1 2 2 - 2 - 3 f * 3 Echo Island Formation 1 1 1 . 1 Fire Lake Group 4 (1) 1 (1) 1 (1) 5 (2) 1 6 (2) 6 (2) Gambler Group 4 (1) 21 (2) 13 (2) 1 10 (2) 7 (2) 4 (1) 2 S (1) 1 (1) 7 3 i 21 (2) Cambler T Group 2 (1) 9 (4) 6 (3) 1 (1) 5 O) i ( i ) 2 (2) ft (3) 5 • (3) 2 . 2 .Ul 2 (1) 1 (1) 3 ( » 10 (4) Harrison Lake Formation 1 12 (1) 9 (1) 1 5 (2) ft (2) 3 (0 1 2 1 (1) 2 (1) 1 V " 14 (2) Hozameen Group 2 2 16 (3) 10 (1> 1 2 14 (3) 3 1 18 (3) 7 (1) i ft .9 (3) 1 6 J 24 (3) Ladner Croup 1 (1) 12 (5) 10 (3) 1 1 (0 16 (7V 2 21 (8) 11 (4) i to : . 1 U) • 21 (7) 3 2 27 (8) Nicola Group 6 3 5 1 8 4 :' 8 8 Pasayten Group 2 (1) 2 O) 1 (1) 1 (0 1 (1) 1 <D 1 2 (1) Skagit Formation 1 1 1 1 1 i 1 Twin Islands Group I 1 1 The lower number in parentheses i s the number of deposits with production records;.this number i s included'in the t o t a l count-above i t . .. . TABLE A-6. NUMBER OF COMMODITY OCCURRENCES"AND DEPOSIT TYPES - IN HOST ROCK TYPES IN THE STUDY AREA' iron cobalt nickel ;copper zinc arsenic ; molybdenum silver .cadmium antimony tungsten gold lead bismuth uranium magmatic porphyry skarn volcanogenic vein shear disseminated massive basic volcanic rocks; greenstone 6 38 24 3 20 4 2 21 14 1 1 2 1 15 9 15 3 (3) (8) (4) (7) (1) (2) (7) (4) (1) (1) (4) (2) (1) acid volcanic rocks 3 12 10 2 6 1 4 5 1 2 1 2 2 5 (1) (2) (2) (2) (2) (2) (2) pyroclastic volcanic rocks 2 9 13 2 8 3 8 6 1 6 1 7 (1) (1) (4) (5) (5) (4) (4) (1) unclassified volcanic rocks 13 4 1 6 7 4 3 6 5 2 dikes 9 4 2 8 2 7 2 4 1 4 1 3 (2) (1) (2) (2) (2) (1) (1) (1) intermediate to acid intrusive rocks 2 1 A6 14 1 28 22 1 1 2 19 11 1 28 2 16 2 9 W (2) (1) (1) (4) (3) (1) (1) (3) ultramafic rocks 1 1 15 15 1 4 6 14 2 3 1 (1) (2) (1) (1) (1) tl) clastic sedimentary rocks 2 21 10 1 2 24 2 29 10 1 1 2 28 1 6 (1) (7) (4) (9) (9) (6) (1) (1) (9) limes tone 8 2 22 11 1 4 19 1 1 14 6 1 19 3 1 1 (2) (4) (1) (1) (4) (2) (3) (1) unclassified sedimentary rocks 3 10 8 2 6 2 6 4 1 2 1 3 5 (1) (2) (1) (2) (2) (1) (1) (1) schist 6 2 1 2 1 2 1 1 3 unknown 2 2 26 14 5 15 22 9 5 12 2 1 2 (1) (1) (2) (3) (1) (3) The lower number in parentheses is the number of deposits with production records; this number is included in the total count above it. APPENDIX B DEPOSIT DISTRIBUTION MAPS 157 TABLE B - l . SYMBOL DEFINITIONS FOR DEPOSIT DISTRIBUTION MAPS Unless specified on the map, symbols used to designate deposit locations are defined by deposit type as follows: Vein Skarn Disseminated Shear Magmatic Volcanogenic Porphyry Massive Unknown Symbol size on a l l maps i s determined as follows: Magnitude (Table 4-2) Size I o I I E I I I • IV • CD o x Note: A l l maps i n this appendix are Xerox reductions of o r i g i n a l Calcomp ^ p l o t t e r output; resulting d i s t o r t i o n may have altered the accuracy of deposit locations. MAP B-2. D i s t r i b u t i o n of Shear Deposits X I—» o MAP B-3. D i s t r i b u t i o n of Disseminated Deposits MAP B-4. D i s t r i b u t i o n of Massive Deposits X MAP B-5. Distribution, of Magmatic Deposits MAP B-7. D i s t r i b u t i o n of Porphyry Deposits MAP B-8. D i s t r i b u t i o n of Volcanogenic Deposits X SI 1st rank LD 2nd rank MAP B-10. D i s t r i b u t i o n of Copper Occurrences (according to f i r s t , second or lower rank) jgg 1st rank 0 2nd rank X 3rd or lower rank . Distribution of Gold Occurrences (according to f i r s t , second or lower rank) MAP B-13. D i s t r i b u t i o n of a l l S i l v e r Occurrences (regardless of rank) g§ 1st rank • 2nd rank X 3rd or lower rank MAP B-14. Distribution of Silver Occurrences (according to f i r s t , second or lower rank) X •^1 MAP B-15. D i s t r i b u t i o n of a l l Zinc Occurrences (regardless of rank) gjg 1st rank Q 2nd rank X 3rd or lower rank MAP B-16. Distribution of Zinc Occurrences (according to f i r s t , second or lower rank) X MAP B-17. D i s t r i b u t i o n of a l l Lead Occurrences (regardless of rank) H 1st rank • 2nd rank X 3rd or lower rank MAP B-18. D i s t r i b u t i o n of Lead Occurrences (according to f i r s t , second or lower rank) X MAP B-19. D i s t r i b u t i o n of a l l Molybdenum Occurrences (regardless of rank) X ) HI 1st rank Q 2nd rank X 3rd or lower rank 92/GO MOLY MAP B-20. D i s t r i b u t i o n of Molybdenum Occurrences (according to f i r s t , second or lower rank) MAP B-21. D i s t r i b u t i o n of a l l Iron Occurrences (regardless of rank) 'MAP B-22. Distribution of Iron Occurrences (according to f i r s t , second, third or lower rank) / MAP B-24. D i s t r i b u t i o n of a l l Tungsten Occurrences (regardless of rank) X oo MAP B-25. D i s t r i b u t i o n of a l l Antimony Occurrences (regardless of rank) • Au + Ag X Au without Ag - j - Ag without Au 9 2 / G O GOLD/S ILVER 1 L MAP B-26. Distribution Relationships Between Gold and Silver Occurrences X \J] Mo + Cu X M o without Cu 92/GD MOLY/COPPER MAP B-27. D i s t r i b u t i o n Relationships.Between Molybdenum and Copper Oc currences • Mo + Au + Ag -f~ Mo + Ag only X Mo + Au only 92/GD MOLY/GOLD/SILVER MAP B-28. D i s t r i b u t i o n Relationships Between Molybdenum, Gold and S i l v e r Occurren ces • Pb + Ag . D i s t r i b u t i o n Relationships Between Lead and S i l v e r Occurrences X CO Pb + Zn X P b without Zn 00 MAP B-30. D i s t r i b u t i o n Relationships Between Lead and Zinc Occurrences 

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