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Geology of the central part of the Callaghan Creek pendant, Southwestern B.C. Miller, Jack H.L. 1979

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GEOLOGY OF THE CENTRAL PART OF THE CALLAGHAN CREEK PENDANT, SOUTHWESTERN B.C. by JACK H.L. MILLER B.A.Sc, U n i v e r s i t y of B r i t i c h Columbia, 1977 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n THE FACULTY OF GRADUATE STUDIES i n the Department of Geological Sciences We accept t h i s thesis as conforming to the required standard: THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1979 ^ Jack H.L. M i l l e r , ]979 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f Geological Sciences The U n i v e r s i t y o f B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date May 4, ]979 BP 75-5 1 1 E ABSTRACT Callaghan Creek pendant, about 85 k north of Vancouver, B.C., is one of many northwesterly trending volcanic and volcanic-sedimentary pendants within the southern part of the Coast Plutonic complex. Rocks within this pendant have been correlated tentatively with the Gambier Group on the basis of lithologic s i m i l a r i t i e s with type sections of the Gambier rocks to the south. A crystal tuff unit in the Callaghan Creek sequence has been cut by what are thought to be genetically related hornblendite dykes for which a single K-Ar date on hornblende of 124 + 4 m.y. was obtained. Five major rock units were recognized in the Callaghan Creek pendant. Compositions range from a rhyodacite to more abundant andesites. Generally, these rock units dip steeply to the east, strike northerly to northwesterly, and appear to form a homoclinal succession with tops to the east. The envisaged depositional environment is of explosive volcanism in an arc environment characterized by calc-alkaline volcanism which probably extended along the length of the Coast Plutonic complex during Jurassic and Early Cretaceous time. Plutonic rocks, ranging in composition from quartz diorite to granodiorite and diorite, surround the Callaghan Creek pendant. Pleistocene to Tertiary rocks overlie and locally intrude the pendant and plutonic rocks. Seven mineral occurrences were recognized in the mapped area of the Callaghan Creek pendant, three of which, the Manifold, Warman and Discovery zones, are in production by Northair Mines Limited (N.P.L.). Minor produc-tion has come from three of the more southerly occurrences; the Silver Tunnel, M i l l s i t e and Tedi Pit zones of Van Silver Explorations Limited (now i n receivership). The Manifold, Warman and Discovery zones of Northair Mines and the Tedi Pit mineral occurrences of Van Silver Explorations show various structural and textural features indicating that a significant portion of the sulphides may have concentrated prior to regional metamorphism (greenschist facies) and emplacement of Coast Plutonic rocks. An apparent stratigraphic control, association with dacitic volcanics, local inter-calations with exhalites (carbonate and cherte) combined with textural data and systematic variations in assay values suggest that these occurrences are volcanogenic i n origin but have suffered considerable mobilization during subsequent metamorphism. i i CONTENTS Page 1. INTRODUCTION 1 1.1 LOCATION AND ACCESS 1 1.2 PHYSIOGRAPHY AND CLIMATE 1 1.3 MINING HISTORY 3 1.3.1 VAN SILVER EXPLORATION LIMITED (N.P.L.) PROPERTY 3 1.3.2 NORTHAIR MINES LIMITED (N.P.L.) PROPERTY 4 1.4 SCOPE OF THESIS 5 2. GEOLOGY OF THE CENTRAL PART OF THE CALLAGHAN CREEK PENDANT 6 2.1 REGIONAL GEOLOGY 6 2.2 CALLAGHAN CREEK PENDANT ROCKS 8 2.2.1 GREENSTONE 10 2.2.1.1 Marble 14 2.2.2 ANDESITIC AGGLOMERATE 16 2.2.3 ANDESITIC CRYSTAL TUFF 21 2.2.4 DACITIC AGGLOMERATE - matrix supported 30 2.2.4.1 Siliceous Siltstone 34 2.2.4.2 Dacitic Agglomerate - fragment supported 36 2.2.4.3 Tuffaceous Sandstones and Siltstones 37 i i i 2.2.5 ANDESITIC AGGLOMERATE 40 2.2.5.1 Epiclastic Volcanic Breccia 48 2.2.5.2 Arkosic Wacke 54 2.2.5.3 Andesitic Crystal Tuff 57 2.2.6 STRUCTURAL GEOLOGY 59 2.2.7 METAMORPHISM 64 2.3 PLUTONIC ROCKS 67 2.3.1 QUARTZ DIORITE 67 2.3.2 HORNBLENDE DIORITE , 7 2 2.3.3 GRANODIORITE 74 2.4 PLEISTOCENE TO TERTIARY ROCKS 76 2.4.1 OLIVINE BASALT 77 2.4.2 EQUIGRANUALR RHYODACITE 80 2.4.3 PORPHYRITIC RHYODACITE 84 2.4.4 EPICLASTIC BRECCIA 86 2.5 SUMMARY 3. MINERAL OCCURRENCES 90 3.1 INTRODUCTION 90 3.2 MINERAL OCCURRENCES IN THE VAN SILVER EXPLORATIONS LIMITED AREA 90 3.2.1 TEDI PIT SHOWING 90 3.2.1.1 Mineralogy and Textures 93 3.2.1.2 Paragenesis 97 3.2.1.3 Thermal Regime 98 iv 3.2.2 SILVER TUNNEL SHOWING 98 3.2.2.1 Mineralogy and Textures 99 3.2.2.2 Paragenesis 102 3.2.2.3 Thermal Regime 103 3.3.3 MILLSITE SHOWING 103 3.2.3.1 Stockwork-type Mineralization 105 3.2.3.2 Chalcopyrite-bearing Veins 105 3.2.3.3 Hematite Veins 107 3.2.3.4 Sphalerite and Galena-bearing Veins and Stringers 108 3.2.3.5 Summary 111 3.2.3.6 Thermal Regime 112 3.2.4 ZONE 4 113 3.2.4.1 Mineralogy and Textures 113 3.2.4.2 Paragenesis 116 3.2.4.2 Thermal Regime 118 3.2.5 CONCLUSIONS 119 3.3 NORTHAIR MINES PROPERTY 120 3.3.1 MINERALOGY AND TEXTURES 136 3.3.2 PARAGENESIS 141 3.3.3 THERMAL REGIME 143 3.3.4 GENETIC MODELS 144 3.3.4.1 Epigenetic Model: Hydrothermal Vein 144 3.3.4.2 Syngenetic Model: Distal Volcanogenic or or Exhalite Deposit 145 3.3.5 CONCLUSIONS 147 V 4. SUMMARY AND CONCLUSIONS 148 4.1 INTERPRETATION OF DEPOSITIONAL ENVIRONMENT OF THE CALLAGHAN CREEK PENDANT 148 4.2 METALLOGENY 151 4.3 ASPECTS PERTINENT TO MINERAL EXPLORATION 153 4.4 FUTURE WORK 154 BIBLIOGRAPHY 156 v i LIST OF APPENDICES A. 1 History of the Van Silver Property Area 160 A. 2 History of the Northair Mine Property 161 B. 1 Whole Rock Lithogeochemistry 163 B. 2 Trace Element Lithogeochemistry 169 C Age Dates 171 LIST OF TABLES 2. 1 Visual Estimates of Mineral Modes - Unit 1 12 2. 2 Visual Estimates of Mineral Modes - Unit 2 20 2. 3 Visual Estimates of Mineral Modes - Unit 3 24 2. 4 Visual Estimates of Mineral Modes - Unit 4, 4a and 4c 32 2. 5 Visual Estimates of Mineral Modes - Unit 5, 5a, 5b and 5c 42 2. 6 Visual Estimates of Mineral Modes - Unit 6a , 6b and 6 c 70 2. 7 Visual Estimates of Mineral Modes - Unit 7a , 7b, 7c and 7d 79 2. 8 Summary of Lithologies 89 3. 1 Visual Estimates of Northair Mine Mineral Modes - Warman Zone, 124 3. 2 Microprobe Analysis Results 130 B. 1 Whole Rock Geochemistry 165 B. 2 Trace Element Geochemistry ?V. 170 v i i LIST OF FIGURES 1.1 Location map 2 2.1 General tectonic chart of the Canadian Cordillera 7 2.2 Geology of the central part of the Callaghan Creek pendant 9 2.3 Pale tan, pale greyish-green and medium greyish-green greenstone 11 2.4 Photomicrograph of greenstone 11 2.5 Interbedded greenstone, quartz- and carbonate-rich layers from Unit la 15 2.6 Photomicrograph of specimen from skarn zone 15 2.7 Photomicrograph of chert from Unit la 17 2.8 Twinned carbonate porphyroblast 17 2.9 Fine grained matrix of andesitic agglomerate 19 2.10 Matrix-supported andesitic agglomerate 19 2.11 Porphyritic andesite fragment of Unit 3 23 2.12 Photomicrograph of plagioclase clast in Unit 3 23 2.13 Plagioclase phenocrysts in porphyritic andesite fragments within Unit 3 26 2.14 A pseudomorph of euhedral amphibole 27 2.15 Glass shards i n andesitic crystal tuff 28 2.16 Hand specimen of hornblende dyke 28 2.17 Photomicrograph of hornblende dyke 29 2.18 Matrix material of dacitic agglomerate 31 2.19 Dacitic agglomerate outcrop 31 2.20 Blocky outcrop of siliceous siltstone 35 2.21 Photomicrograph, of siliceous siltstone 35 v i i i 2. 22 Slabbed surface of massive arkosic wacke 38 2. 23 Chert fragment within arkosic wacke 38 2. 24 Weathered outcrop of andesitic agglomerate 41 2. 25 Gritty andesitic agglomerate matrix 41 2. 26 Weathered outcrop of andesitic agglomerate 44 2. 27 Jasper vein with magnetite-rich core 46 2. 28 Porphyritic andesite fragment of Unit 5 46 2. 29 Fresh surface of Unit 5a (Epiclastic Volcanic Breccia) 49 2. 30 Photomicrograph of porphyritic andesite fragment in Unit 5a 51 2. 31 Equigranular dacite fragment i n Unit 5a 53 2. 32 Photomicrograph of altered'glass fragments 53 2. 33 Carbonate clast in arkosic wacke 56 2. 34 Photomicrograph of arkosic wacke 56 2. 35 Andesitic crystal tuff hand specimen 58 2. 36 Area of structural analysis 60 2. 37 Equal area stereoplot of axes to fracture and foliation planes 63 2. 38 Pressure-temperature graph indicating the position of greenschist grade metamorphism 66 2. 39 Freshly broken surface of quartz diorite 69 2. 40 Photomicrograph of quartz diorite 69 2. 41 Slabbed surface of hornblende diorite 73 2. 42 Photomicrograph of hornblende diorite 73 2. 43 Slabbed surface of granodiorite 75 2. 44 Photomicrograph of granodiorite 75 2. ,45 Ropy surface of olivine basalt 78 2. 46 Photomicrograph of olivine basalt 78 ix 2.47 Fresh surface of equigranular rhyodacite 81 2.48 Photomicrograph of equigranular rhyodacite 81 2.49 Photomicrograph of flow banding in equigranular rhyodacite 82 2.50 Fresh surface of porphyritic rhyodacite 85 2.51 Photomicrograph of porphyritic rhyodacite 85 2.52 Weathered surface of epiclastic breccia 87 3.1 Location of five mineral occurrences 91 3.2 Detailed geological map of Tedi Pit 92 3.3 Curved cleavage traces in galena 95 3.4 Detailed geological map of Silver Tunnel 100 3.5 Detailed geological map of M i l l s i t e 104 3.6 Sphalerite- and pyrite-rich veins cross-cutting greenstone 109 3.7 Detailed geological map of Zone 4 114 3.8 Galena with inclusions of argentite and electrum 117 3.9 Detailed geological map of Northair Mines Limited (N.P.L.) porperty 121 3.10 Three producing zones within Northair mine 122 3.11 Cross-sections of the Warman zone, Northair mine (in pocket) 3.12 Megascopic appearance of tuffaceous sandstone 126 3.13 Graphs of modal percent chlorite, b i o t i t e and microcline from thin-sections around the Warman zone 128 3.14 Finely interlayered sulphides, carbonate, quartz and other si l i c a t e s 133 3.15 Trace element geochemistry of the northern traverse 134 3.16 Trace element geochemistry df:-:the southern travers 135 3.17 Deformation twins i n sphalerite 138 3.18 Curved cleavage traces in galena 138 3.19 Subhedral gangue laths intruding and protruding from sphalerite into galena 142 X 4.1 Sketch of the Cretaceous pendant rocks 149 B.l Geochemical sample location map 164 B.2 SiC>2 versus FeO (total)/MgO plot 166 B.3 Na20 and K20 versus SiC>2 plot 167 B.4 FeO (total) versus FeO (total)/MgO plot 168 x i ACKNOWLEDGEMENTS I wish to thank Dr. A.J. Sinclair for i n i t i a t i n g this project through the B.C. Ministry of Mines and Petroleum Resources with continuing support from Northair Mines Limited (N.P.L.) and the National Research Council of Canada. Dr. A.J. Sinclair provided encouragement, helpful discussions, suggestions and comments on the improvement of the f i n a l manuscript. I would like to thank Mr. M.P. Dickson, mine manager; Mr. W. Ash, chief engineer; and Mr. A. Boon, planning engineer of Northair Mines for their interest and encouragement. Dr. G. Woodsworth, Geological Survey of Canada; Dr. N.C. Carter, B.C. Ministry of Mines and Petroleum Resources; Dr. A.E. Soregaroli, Western Mines Limited; Drs. C. Godwin, W. Mathews, T. Brown, W.C. Barnes, R.L. Armstrong and H. Greenwood provided insight into various aspects of this manuscript. Norman Stacey prepared most of the figures and maps presented i n this thesis. Both Dennis Wetherell and David Meeks, students at the University of B.C., Department of Geology, aided in the evaluation of the opaque mineralogy. I benefited greatly from discussions with other members of and graduate students within the Geology department of the University of B.C. 1 CHAPTER 1  INTRODUCTION 1.1 LOCATION AND ACCESS Callaghan Creek pendant is along Brandywine and Callaghan Creeks, approximately 105 k. north of Vancouver, within the Vancouver Mining Division (Figure 1.1). The map-area is centred on latitude 50°07'N and 2 2 longitude 123°06'W (NTS 92J/3), covering about 26 square k (10 mi. ). Highway 99 and Brandywine Creek bound the area on the south while the plutonic rocks form the eastern, western and most of the northern boundaries. The minesite of Northair Mines Limited (N.P.L.), approximately 10 k (6 mi.) north of Highway 99 on the east side of Callaghan Creek at an elevation of 990 m., is the only operating mine in the area. Van Silver Exploration Limited (N.P.L.) which produced some concentrate in 1977 is now in receivership, but had a mil l s i t e about 1 k north of Highway 99 on the east side of Brandywine Creek. Access to most of the area is provided by numerous logging roads which are in use throughout the summer. 1.2 PHYSIOGRAPHY AND CLIMATE Callaghan Creek area has rugged topography typical of the Coast Mountains. The map-area has approximately 1100 m of r e l i e f with many northerly trending ridges and c l i f f s . An overmature forest of hemlock and balsam with some cedar and douglas f i r covers the area. Underbrush is scanty over most of the area but is thick near creeks. Treeline is at about 1300 metres above mean sea level. The region has a mild climate and receives an annual precipitation u r e 1.1 L o c a t i o n map w i t h the s t u d y a r e a i n a s t i p p l e d p a t t e r n . Highway 99 bounds the s t u d y a r e a on the s o u t h . 3 of 250 centimetres, mostly as snow. Snow usually stays on the ground from October to July. Temperature range from -30°C in the winter to 27°C in the summer. 1.3 MINING HISTORY The mining history of the map-area can be considered in two sections; one concerned with the Van Silver mineral occurrences and the other dealing with Northair mine. Detailed h i s t o r i c a l accounts for both areas can be found in Appendix A. 1.3.1 VAN SILVER EXPLORATION LIMITED (N.P.L.) PROPERTY This area f i r s t received attention in 1917 when Charles Camsell brie f l y described the geology of the area mentioning several mineral oc-currences . In 1923, a group of eight claims, known as the Blue Jack Group, were staked over what is known as the "Silver Tunnel" mineral occurrence. Astra group, consisting of six claims, was staked i n 1925 by Falconer and Associates. These claims were staked on a ridge between Brandywine and Callaghan creeks, north of the Blue Jack Group and may have covered the mineral occurrence now known as "Tedi P i t " . In 1932 the Blue Jack Group became the holding of a newly formed company, Blue Jack Mines Limited (N.P.L.). Price and Associates of Vancouver added more claims to the Astra Claim Group in 1934 and renamed the group of fourteen claims the Cambria Group. From 1937 to 1966, work in the area was done intermit-tently by various companies. Mr. M. Levasseur restaked a l l of the old showing in the early 1960's and formed a group of claims known today as the Van Silver Property. 4 This group consisted of 179 continuous claims which became the holding of Van Silver Explorations Limited (N.P.L.) in 1966. Geological mapping, and geophysical and geochemical studies have been undertaken on various scales intermittently to the present day. In 1975, rock from the Silver Tunnel was stockpiled and the following year construction of a small m i l l was initiated. The m i l l was completed in 1977 and went into production for a period of a few months. After Van Silver Exploration Limited (N.P.L.) went into receivership, Cominco Limited optioned the property in 1978 in order to re-evaluate Silver Tunnel and Tedi P i t . Some diamond d r i l l i n g and geological mapping were done but Cominco subsequently dropped their option. 1.3.2. NORTHAIR MINES LIMITED (N.P.L.) PROPERTY This area had not received any attention until 1969 when Dr. M.P. Warshawki obtained some positive geochemistry results on s i l t samples. Mr. A.H. Manifold aided Dr. Warshawki in follow-up geochemical studies which led to the staking of claims. In 1971 a mineralized outcrop was located (Discovery Zone). Further exploration was undertaken and miner ralized outcrop in the Manifold Zone was also discovered. Northair Mines Limited (N.P.L.) optioned the property in 1972 shortly after Mclntyre Mines had dropped the property. Underground and surface exploration from 1972 to 1974 proved the continuity of both the Warman and Manifold zones and resulted in Northair's decision to begin production. A m i l l plant was purchased in the summer of 1974 and completely i n -stalled by June of 1976 when production commenced. Production was from the 3500 and 3700 foot levels in the Manifold Zone and from the 3250 and 3500 foot levels in the Warman Zone. Discovery Zone was opened for production during the summer of 1977. Surface diamond d r i l l i n g , in 1977, proved the continuity of the Warman Zone to depth. Underground development on the 2800 foot level was begun'in early 1978 with the ore being intersected near the end of that summer. Production from raise and stope development began soon after the time of intersection. 1.4 SCOPE OF THESIS This project was undertaken as a combined f i e l d and laboratory study of the rocks in and around the central part of the Callaghan Creek roof pendant that includes the mineral deposits and occurrences of Northair Mines Limited (N.P.L.) and Van Silver Explorations Limited (N.P.L.) Specific objectives were: 1) to map the geology of the Callaghan Creek roof pendant volcanic rocks and the perimeter of surrounding plutonic rocks; 2) to describe individual rock units and interpret their significance 3) to describe and interpret mineralogical and textural features of mineral occurrences within the map-area; 4) to develop a genetic model for mineral deposits and occurrences; 5) to carry out limited K-Ar dating of volacanic and plutonic rocks in the map-area. From May to August 1977, mapping of the entire map-area was carried out on a scale of 1"=400', with some accompanying petrographic work the following winter. Detailed mapping of the Northair mine area and other specific parts of the 1977 map-area was undertaken from May to September 1978. 6 CHAPTER 2 GEOLOGY OF THE CENTRAL PART OF  THE CALLAGHAN CREEK PENDANT 2.1 REGIONAL GEOLOGY Callaghan Creek roof pendant l i e s within the Coast Plutonic Complex which forms the core of the Coast Mountains, the western-most of the two major belts of metamorphic and granitoid rock in the Canadian Cor-d i l l e r a , with the Omenica Crystalline Belt to the east, being the other. The Cordillera forms a 800 k. (500 mi.) wide segment of the Circum-Pacific Orogenic Belt. A generalized tectonic chart summarizing the evolution of the Canadian Cordillera for five western tectonic belts is shown in Figure 2.1. Generally, Cretaceous to Triassic pendant rocks in the Coast Plutonic Complex are remnants of volcanic and sedimentary rocks of volcanic island arcs and associated basins (Dickson, 1976). However, significant amounts of plutonic detritus i s also present i n some Lower Cretaceous to Upper Triassic rock units with their presence and extent dependent on the geographic location of the depositional site (Thompson, 1976). Up unt i l Mid Cretaceous a l l Mesozoic volcanism in the southern Coast Plutonic Complex had been submarine, but after this time small localized subaerial volcanic centres developed along the eastern margin of the Coast Plutonic complex and large successor basins formed in the west (Thompson, 1976). The Coast Plutonic Complex (Coast Crystalline Complex) i s a complex of gneisses and granitoid rocks with pendants and septae of metavolcanic and metasedimentary rocks which are variably metamorphosed from high amphibolite to low greenschist grade (Sutherland Brown, 1971). These pendants and septae characteristically have a northwesterly trending 7 PACIFIC OROGcN COLUMBIAN OROGEN Figure 2.1 Generalized tectonic chart of the Canadian Cordille (after Eisbacher, 1974) 8 foliation and were developed primarily between the Early Cretaceous and Early Tertiary (Sutherland Brown, 1971). Granitoid rocks range in com-position from diorite through quartz diorite to quartz monzonite, with the western intrusions being predominantly Cretaceous whereas eastern intrusions are primarily Early Cretaceous (Sutherland Brown, 1971). Contacts between roof pendants and septae with the surrounding plutonic rocks are sharp, commonly being narrow shear zones whose orientation subparallels the fo l i a t i o n of.the pendant or septa (Woodsworth,.personal communication, 1977). Callaghan Creek pendant is in the southern section of the Coast Plutonic Complex, about half way across i t s width. The pendant is a northwesterly-trending belt of metavolcanic and metasedimentary rocks about 46 k (28 mi.) long by 5 k (3 mi.) wide that was correlated with the Lower Cretaceous Gambier Group by Woodsworth and Roddick (1978). Regional geology of the area has been described by Woodsworth and Roddick (1978), Roddick and Woodsworth (1975), Green (1977) and Mathews (1958). In the following sections the Callaghan Creek pendant rocks, plutonic rocks and Pleistocence to Tertiary rocks w i l l be individually described. Metamorphism and structural geology of the map-area w i l l be discussed in the section dealing with the pendant rocks. At the end a f i n a l summary section w i l l be presented. 2.2 CALLAGHAN CREEK PENDANT ROCKS Lithologies mapped in and around the Callaghan Creek pendant are presented in Figure 2.2 with a more detailed map in Appendix B. Mapping for this study suggests that the strata of this pendant forms an east-facing homocline that has been metamorphozed to greenschist facies. Thus, the following sub-sections w i l l describe each individual pendant Figure 2.2 Geology of the central part of the Callaghan Creek pendant. This map is a reduced version of Map 1, contained in pocket, "a" marks Alexander F a l l s . 10 rock in the map-area, from oldest to youngest (west to east). Following the description of these rocks units a section on structural geology and another on metamorphism w i l l be presented. Visual estimates of the grain size and mode of minerals present were made from thin-sections which were used in conjunction with f i e l d notes to arrive at a f i n a l rock name. The rock names are consistent with the cl a s s i f i c a t i o n of volcanic rocks made by Strekeisen (1967) and the cla s s i f i c a t i o n of clastic volcanic rocks by Parsons (1968). 2.2.1 GREENSTONE (UNIT 1) Greenstone occurs in the western half of the map-area. This unit is generally moderately sheared and locally is strongly sheared. Shearing parallels the regional strike of schistosity but has variable dips. Intensity of shearing is more pronounced in the southern exposures. Rocks within this unit vary from a pale tan through pale to medium greyish-green colour (Figure 2.3). Colour variation between fresh and weathered surfaces are minor. Paler rocks are generally more schistose and, in places, chlorite-muscovite schists and muscovite schists are well developed in shear zones. The zones of strongly sheared rocks occur at intermittent i n -tervals and range up to a few metres in width. Pleistocene to Tertiary dykes intruded along some of the shear zones and have muscovite schist envelopes up to a few metres in width. Compositionally the rocks of this unit are andesitic (Table 2.1). Ghost-like fragments were observed loc a l l y in outcrop but were never re-cognized i n thin-section. Shapes, sizes and percentages of the frag-ments were impossible to estimate due to d i f f i c u l t i e s in their re-cognition. Since the fragments appear to be similar to the rest of the 11 F i g u r e 2.3 P a l e t a n , p a l e g r a y i s h - g r e e n and medium g r a y i s h - g r e e n g r e e n s t o n e ( U n i t 1 ) . P a l e t a n g r e e n s t o n e i s s t r o n g l y s h e a r e d compared to the o t h e r two r o c k f r a g m e n t s . F i g u r e 2.4 P h o t o m i c r o g r a p h o f g r e e n s t o n e ( U n i t 1 ) . E l o n g a t e q u a r t z g r a i n s , s e r i c i t e and m i n o r amounts o f c h l o r i t e o u t l i n e t h e f o l i a t i o n . A n h e d r a l t o s u b h e d r a l opaque g r a i n s a r e s p o r a d i c a l l y d i s s e m i n a t e d t h r o u g h o u t , ( c r o s s e d and u n c r o s s e d n i c o l s ) TABLE 2.1 VISUAL ESTIMATES OF MINERAL MODES-UNIT 1 (Percentages:maximum-minimum/average) Sericite Quartz Chlorite Plagioclase Opaques Carbonate Epidote c Feldspar-quartz Apatite Phlogopite Diopside Sphalerite Tremolite-actinolite Grossularite Number of thin-sections Unit 1 Greens tone 63-2 / 33 45-4 / 19 25-0 / 12 40-0 I l l a 16-5 / 10 25-0 / 9 14-0 / 3 20-0 / 3 1-0 /trace Unit la Marble 1-0 / 1 20-17 / 18 4-0 / 2 10-8 / 9 65 / 65 10-0 / 5 Unit la Skarn 35-5 / 20 5-0 / 2 b 10-1 / 5 15-14 / 15 15-0 / 8 30-20 / 25 22-10 / 21 18-0 / 9 trace 2 a; An2^-An2/An8 b; An 6 c; Identification impossible due to small grain size. 13 unit, where observed, i t is assumed that they are also andesitic in com-position . Chlorite and seri c i t e constitute at least 40% of the schists, where-as the more competent rocks contain 25% or less. In the latter rocks, chlo r i t e is the main phyllosilicate whereas the more sheared rocks have sericite and clays as the dominant platy mineral. Trains of opaque minerals, carbonate- and mica-rich bands, and alignment of micaceous minerals outline the f o l i a t i o n . A l l of the non-micaceous minerals ex-cept opaque minerals and epidote are slightly elongate parallel to the fol i a t i o n (Figure 2.4). Plagioclase composition was unobtainable due to the small size and altered nature of the crystals. It is assumed to be a l b i t i c in com-position because twinning, the refractive indices are less than balsam. Quartz occurs in anhedral ell i p s o i d grains which exhibit a strong ex-tinction . Depositional environment for this rock unit i s d i f f i c u l t to determine but i t is proposed that the rocks have a strong i f not complete vol-canic component since most of the other lithologies in the pendant are at least p a r t i a l l y volcanic in origin. These volcanics are primarily andesitic in composition, however minor input of other compositional types is not unreasonable. The badly sheared and schistose nature of the rocks is the result of considerable deformation unequalled in any other units within the study-area. This character was one of the primary, reasons for distinguishing units 1 and 2. Many intrusions of diorite were observed within the greenstone making i t hard to separate these two into mappable entities. Cross-sections of various mineral occurrences within ghe greenstone show i r -14 regular masses of greenstone interfingered with plutonic masses. These aspects give the impression that the greenstone has been extensively i n -truded by plutonic masses. 2.2.2.1 Marble (Unit la) Marble occurs in several pods within the greenstone unit in the southwestern section of the map-area. In a l l cases the marble is mod-erately to strongly sheared with impure carbonate layers showing the most pronounced development f o l i a t i o n . Pure carbonate layers, primarily consisting of calcite, are medium grained, sugary and recrystallized leaving very l i t t l e evidence of the regional f o l i a t i o n . This suggests that the thermal event which caused recrystallization was a post-defor-mational or at least a late syn-deformational event. In the northern pods of marble the shearing has been so extensive that no evidence of primary compositional layering remains. The southern pod however has interbedded greenstone and quartz-rich layers which range in width from 1 mm to 1 m (Figure 2.5). Quartz-rich layers are composed of more than 90% quartz and are white to pale grey or green. The quartz occurs in 0.5 mm anhedral blebs with irregular grain boun-daries and a sugary granulose texture. A l l of the quartz exhibits a strong undulatory extinction. The bedded nature and preponderance of quartz suggests that these quartz-rich layers may have once been layers of chert. Skarn minerals are present only within the southern-most pod; thus, the thin-section modes for this pod have been separated from those of the other marblepods in Table 2.1. Minerals such as diopside, tremolite-actinolite, grossularite and epidote are scattered erratically through-out the impure carbonate layers and locally form discontinuous lenses 15 F i g u r e 2.5 I n t e r b e d d e d g r e e n s t o n e , q u a r t z - r i c h and c a r b o n a t e - r i c h l a y e r s from U n i t l a . C a r b o n a t e - r i c h l a y e r s a r e w h i t e and the q u a r t z - r i c h l a y e r s a r e p a l e gray whereas t h e g r e e n s t o n e l a y e r s a r e d a r k g r a y i s h - g r e e n . Most l a y e r s a r e m i x t u r e s o f t h e s e t h r e e t y p e s . F i g u r e 2.6 P h o t o m i c r o g r a p h o f hand s p e c i m e n from s k a r n zone (Zone 4) i n U n i t l a . Mass o f a n h e d r a l d i o p s i d e ( p a l e g r e e n , r i g h t ) , q u a r t z and opaque g r a i n s w i t h m i n o r e p i d o t e ( p a l e y e l l o w -i s h g r e e n , r i g h t ) and a c t i n o l i t e l a t h s ( p a l e g r e e n , r i g h t ) , ( c r o s s e d and u n c r o s s e d n i c o l s ) 16 parallel to the bedding previously described (Figure 2.6). Significant amounts of sphalerite were also seen associated with the calc- s i l i c a t e minerals. Subhedral stubby laths of diopside, averaging 0.05 by 0.07 mm, and elongate subhedral laths of tremolite-actinolite, averaging 0.005 by 0.02 mm , exhibit a decussate texture. A l l of the skarn minerals occur in siliceous dirty carbonate layers and only trace amounts occur within the carbonate-rich layers. Within the northern marble pods extensive shearing has removed a l l megascopic signs of compositional layering, however lo c a l l y i t is s t i l l v i s i b l e in thin-section. Quartz-rich layers, containing minor amounts of opaque mineral grains, muscovite and trace amounts of chlorite, were seen in thin-section and interpreted to represent chert layers (Figure 2.7). Dark grey subhedral crystals of carbonate, (calcite) averaging 1.2 mm in diameter, are randomly scattered throughout a section of the western-most marble pod of the northerly group. Groundmass of anhedral carbonate, averaging 0.01 mm i n diameter, surrounds these crystals which are thought to be porphyroblasts. The depositional environment envisaged for the marble pods is a low energy environment. The presence of chert suggests that the marble was deposited as a deep water limestone with some interlayered chert. This environment existed within a regime dominated by volcanic rocks and so represents a possible interuption of volcanic activity with associated changes in energy lev e l . 2.2.2 ANDESITIC AGGLOMERATE (UNIT 2) Andesitic agglomerate occurs in the north-central section of the map-area. Regional f o l i a t i o n i s only slightly developed within this unit with the f o l i a t i o n being more developed in the matrix than the 17 Figure 2.7 Photomicrograph of quartz-rich layer (centre) from a northern marble pod of Unit l a . Fine grained granulose quartz (white to black) and minor amounts of carbonate (brown) and opaque grains (black, s l i g h t l y l a r g e r than quartz g r a i n s ) . (crossed n i c o l s ) Figure 2.8 Twinned carbonate porphyroblast (centre). Groundmass consists of anhedral carbonate, quartz (yellow to white) and opaque (black) grains. (crossed n i c o l s ) 18 fragments. Matrix is medium grey-green and fine grained, varying from 10 to 80 % with an average of about 30% (Figure 2.9). Subhedral plagioclase (An^ to An Q), anhedral quartz clasts, both averaging 0.02 mm in diameter, and o small l i t h i c fragments give the matrix a slightly gritty appearance. Schistosity i s outlined by trains of opaque grains and plates of chlorite and/or b i o t i t e . Chlorite, bio t i t e and epidote with minor amounts of plagioclase form diamond-shaped patches and probably represent the rem-nants of an amphibole. These patches may comprise up to 2% of the matrix. Several different fragment types occur in this unit and generally are supported by the matrix (Figure 2.10). Fragments vary from well rounded to sub-angular, commonly are ovoid and are up to 1 m in dia-meter (average about 7 cm ), Porphyritic andesite and dacite fragments were estimated in the f i e l d to 95% of the fragments. Andesitic fragments are only slightly more prevalent than are dacitic fragments. These fragments have a medium to dark grey-green gritty matrix which composes at least 70% of the fragments (Table 2.2). Clasts of subhedral plagioclase (An^Q to An Q) and anhedral quartz, averaging 1mm in diameter, are the major clasts i n these fragment types. Trace amounts of potassium feldspar were also seen forming clasts averaging less than 0.5 mm in diameter. Chlorite peppered with opaque grains form diamond-shaped patches, averaging 0.9 by 0.6 mm across, which contain a minor amount of plagio-clase. These patches, which are interpreted to be pseudomorphs after amphibole, constitute up to 5% of the fragment. Chlorite and opaque minerals also form elongate, very irregular patches which are probably pseudomorphs of glass shards. These shards comprise an average of 1% of the fragments. 19 Figure 2.9 Fine grained matrix of an d e s i t i c agglomerate (Unit 2). Clasts of quartz and plagioclase aid i n giving the matrix a g r i t t y megascopic appearance. A s l i g h t f o l i a t i o n i s developed from top r i g h t to bottom l e f t of the figure, (crossed n i c o l s ) Figure 2.10 Matrix supported a n d e s i t i c agglomerate (Unit 2). The rounded, p o r p h y r i t i c andesite fragment (centre) i s approximately 30 cm i n diameter. Other fragments are p o r p h y r i t i c andesite and dacites. This specimen i s from an exposure near the southern t i p of Unit 2 (Map 1). TABLE 2.2 VISUAL ESTIMATES OF MINERAL MODES-UNIT 2 (Percentages:maximum-minimum/average) Unit 2 Andesitic Agglomerate Mono minerallic clasts matrix fragments dacite andesite Plagioclase 37-12 / 28 a 35 / 35 Quartz 8-3 / 5 trace Biotite trace trace Potassium feldspar trace Groundmass Chlorite 30-23 / 26 22-5 / 15 10 / 10 Sericite 32-15 / 21 10-0 / 5 3 / 3 Plagioclase 20-10 / 15° Feldspar-quartz^ 28-0 / 13 25-15 / 20 20 / 20 Epidote 20-5 / 12 20-10 / 14 25 / 25 Opaques 7-5 / 6 7-2/5 2 / 2 Quartz • 5 / 5 10-0 / 3 Biotite 8-0 / 2 8-0 / 2 6 / 6 Carbonate 7-0 /3 N3 O Number of thin-sections a; An 3 4-An 2 g/An 3 0 c; An^-An^/A^ b; An. -An 0 0/An. n d; Identification impossible due to small grain size. 45 3o 4U 21 The other 5% of the rock fragments are composed of elongate irregu-lar patches of chlorite peppered with opaque grains. These patches average 0.02 by 0.008 mm and are probably remnants of glass fragments. Very few plagioclase crystals exhibit any signs of compositional zoning and most contain pervassive epidote and sericite, both in the fragments and matrix. Primary mafic minerals in fragments and matrix are replaced entirely by chlorite or less commonly biotite with an er-ratic chlorite rind. Bent albite twins and undulatory extinction in quartz are ubiquitous throughout the matrix and fragments and are evi-dence of deformation. Lack of bedding and the massive extensive nature of the andesitic agglomerate suggest that the unit i s a sequence of contemporaneous lahars (Parsons, 1968). These lahars or lahar occurred in a sedi-mentary environment dominated by andesitic to dacitic volcaniclastic debris. This environment differs from the environment envisaged for greenstone (Unit 1) only in that i t contains a stronger dacitic compon-ent than was seen in the greenstone. 2.2.3 ANDESITIC CRYSTAL TUFF (UNIT 3) Andesitic crystal tuff occurs within the north-central section of the map-area. This unit shows an extreme variation in apparent thickness from 100 to 1,000 m over a strike length of 1,000 m. Regional foliation is poorly developed within the core of the unit but becomes slightly more developed within a few metres of the contact with other units. In outcrop this unit i s pale grey with randomly oriented clasts of white plagioclase and black amphibole, both averaging 1 cm in length. Approximately 5% of the rock is composed of subangular to subrounded, slightly elongate l i t h i c fragments of porphyritic andesite which are 22 concentrated in the lower section of this unit and average 3 cm. in dia-meter (Figure 2.11). These rock fragments vary in shape from slightly elongate plates to crude spheres and can be distinguished from the sur-rounding matrix by minor differences in composition. The fragments average 35% broken plagioclase crystals and 5% broken amphibole crystals, as compared to a total amphibole and plagioclase content of 20% for the matrix. However, the ratio of plagioclase to amphibole in the fragment's matrix i s over 15 to 1 as compared to approximately 5 to 1 for the frag-ments . The upper central section of this unit, which is in contact with hornblende diorite (Unit 6b) and tuffaceous sandstones and siltstones (Unit 4c), contains a pod of andesite exposed over an area of 25 by 75 m This pod has a medium greyish brown weathered surface and a poorly developed regional f o l i a t i o n . Plagioclase laths do not show up on this weathered surface. Thin-sections of this rock contain strongly s e r i -citized plagioclase grains. An aphanitic, dark grey to black groundmass (Table 2.3) surrounds broken crystals of plagioclase and less abundant pseudomorphs of amphi-bole. Plagioclase clasts occur as glomeroporphyritic aggregates which exhibit compositional zoning within each segment of the aggregate. Albitization has occured to varying degrees and has in some cases completely altered plagioclase so that no evidence of the original com-positional zoning remains. Quartz becomes increasingly prevalent in the clasts and groundmass in the northeast section of this unit. These quartz clasts are anhedral and average 0.3 mm in diameter. This i n -crease in quartz content is sufficient in some areas to make the rocks close to a dacite in composition. 23 Figure 2.11 P o r p h y r i t i c andesite fragment ( l e f t of l^ns cap) w i t h i n a n d e s i t i c c r y s t a l t u f f (Unit 3). Lens cap i s about s i x cm i n diameter. Outcrop occurs 100 m southwest of a pod of Unit 4a i n the south ce n t r a l portion of Unit 4 (Map 1) . Figure 2.12 Photomicrograph of p l a g i o c l a s e c l a s t s i n a n d e s i t i c c r y s t a l t u f f (Unit 3). Same l o c a t i o n as fi g u r e above.(crossed n i c o l s ) TABLE 2.3 VISUAL ESTIMATES OF MINERAL MODES-UNIT 3 (Percentages:maximum-minimum/average) Monominerallic clasts Plagioclase Quartz Potassium feldspar Hornblende Groundmass Chlorite Epidote Sericite Plagioclase Opaques Quartz Carbonate d Feldspar-quartz Biotite Sphene Potassium feldspar Number of thin-sections Unit 3 Andesitic Crystal Tuff 47-26 / 37 a 20-0 / 6 3-0 /trace 10-0 / 1 25-0 / 12 15-3 / 11 20-0 / 8 25-0 / 8 b 12-3 / 7 20-0 / 7 7-0 / 1 10-0 / 1 5-0 / 1 2-0 /trace Unit 3 Hornblendite dyke 65-40 / 60 14-6 / 12 5- 0 / 4 11-8 / 9 2-0 / 1 C 6- 5 / 6 4-3 / 3 3- 2 / 2 4- 2 / 3 3 a; An 4 ( )-An 2 6/An 3 7 b; An,,-An„/An, 16 2 t c; An„-An„/An_ o z. J d; Identification impossible due to small grain size. 25 Thin-sections of porphyritic andesite fragments show that both am-phibole and plagioclase do not have a clastic appearance compared to the surrounding matrix (Figure 2.12 and 2.13). Plagioclase does occur in glomeroporphyritic aggregates but generally none of the laths composing the aggregate are broken. Pseudomorphs of amphibole (Figure 2.14) con-sisting of chlorite, epidote and opaque grains are euhedral in outline in these fragments whereas in the surrounding matrix they are subhedral. In outcrop, compositional variations marked by differences in am-phibole and plagioclase content were observed. These differences occur-red within distances of 10 cm and apparently were not associated with fragment versus matrix changes. Thus i t appears as though these com-positional variations are inherent in the rock. Plagioclase and amphibole crystals have broken, jagged surfaces and vary in their relative and absolute percentages in the matrix. Chlorite peppered with minute anhedral opaque mineral grains occur in extremely elongate, jagged patches and probably represent remnants of glass shards (Figure 2.15). These features suggest that this rock unit i s a crystal tuff rather than a flow. Further support for this conclusion i s given by the presence of fragments differing only in the percentages of plagioclase and amphibole and by the non-clastic nature of these two minerals. These fragments are interpreted as pieces of crystal-rich material which was collected in a magma chamber and then brecciated upon extrusion. Hornblendite dykes in the eastern central section of the map-area consists primarily of anhedral randomly oriented crystals of hornblende (Figure 2.16). This rock type cuts across stratigraphy at the southern tip of Unit 3 and shows very l i t t l e evidence of fol i a t i o n . Hornblende 2 6 Figure 2.13 Pl a g i o c l a s e phenocrysts i n p o r p h y r i t i c andesite fragments w i t h i n a n d e s i t i c c r y s t a l t u f f (Unit 3). Contrast these phenocrysts with the c l a s t s i n the previous f i g u r e . Same l o c a t i o n as Figure 2.11. 27 Figure 2.14 A pseudomorph of euhedral amphibole. Pseudomorph i s rimmed by opaque grains and consists of epidote (pale yellowish-green, bottom), c h l o r i t e (dark green, top) and p l a g i o -clase (white, top). Same l o c a t i o n as Figure 2.11. (crossed and uncrossed n i c o l s ) 28 Figure 2.15 Photomicrograph of glass shards i n a n d e s i t i c c r y s t a l t u f f (Unit 3). Arrows point to glass shards now con s i s t i n g of c h l o r i t e (green) and opaque grains (black). Specimen i s from an outcrop 80 m west of a pod of Unit 4a i n the south-central portion of Unit 4 Clap 1). Figure 2.16 Hand specimen of hornblende dyke. Specimen i s from the core zone of the eastern-most dyke (llap 1). Hornblende c r y s t a l s (black) are i n a f i n e r grained mottled matrix of hornblende, c h l o r i t e , s e r i c i t e , quartz, epidote and carbonate. -9 Figure 2.17 Photomicrograph of hornblende dyke. Same specimen as Figure 2.16. Anhedral hornblende grains occur wi t h i n a f i n e r grained groundmass.(crossed and uncrossed n i c o l s ) 30 laths, averaging 1.5 to 2.0 mm , have an irregular, jagged outline and occur within a finer grained mass of minerals (Figure 2.17). Table 2.3 contains the estimated mode of minerals for the hornblendite dyke. Hornblende-rich rounded, elongate to spherical shaped fragments, aver-aging 70% hornblende, have a matrix which averages 40% hornblende. Horn-blende within the matrix surrounding the fragments is slightly smaller in size than that of the fragments. Cores of the dykes were defined on the basis of grain size. Three areas with larger crystals were defined and assumed to be from the cores of dykes (Figure 2.2). Presence of hornblende and i t s cross-cutting nature suggests that these dykes may have been the feeder source for Unit 3 since i t is the only major unit containing appreciable amounts of amphibole. A K-Ar model age of 127 + 4 Ma was obtained on the hornblende in the dyke (Appendix C). True age may be greater i f partial release of argon occurred during metamorphism accompanying the emplacement of Coast Plutonic rocks. Thus Unit 3 i s thought to be Lower Cretaceous or older in age. 2.2.4 DACITIC AGGLOMERATE-MATRIX SUPPORTED (UNIT 4) Dacitic agglomerate occurs in the north central part of the map-area. Development of the regional foliation i s very slight within the unit and is more prevalent in the matrix than in the fragments. Cross-bedding and graded bedding observed in the basal section indicate that stratigraphic tops are facing east (085 degrees). Matrix i s medium grey-green, both on fresh and weathered surfaces, and varies from 20 to 70% (average - 50%) of the rock (Figure 2.18). Quartz, plagioclase (An^g) and minor amounts of potassium feldspar form slightly larger grains than the rest of the minerals (Table 2.4). These grains are anhedral and irregular in form. Diameter of quartz grains 31 Figure 2.18 Matrix material of d a c i t i c agglomerate (Unit 4). This outcrop occurs near the western edge of Unit 4 and has graded bedding (top right) and cross-bedding which i s not exemplified i n this photo (Map 1). Figure 2.19 D a c i t i c and r h y o d a c i t i c fragments wi t h i n d a c i t i c agglomerate (Unit 4). This water-worn outcrop i s on the eastern bank of Callaghan Creek, one km south of Alexander F a l l s . (Map 1) Lens cap i s about 6 cm i n diameter. Fragments are s l i g h t l y elongated i n a north-south d i r e c t i o n (top to bottom of photo) TABLE 2.4 VISUAL ESTIMATES OF MINERAL MODES-Units 4, 4a, and 4c (Percentages:maximum-minimum/average) Monominerallic clasts Quartz Plagioclase Potassium feldspar Groundmass Quartz Plagioclase Chlorite Sericite Opaques Epidote Potassium feldspar Sphene Carbonate Biotite Feldspar-quartz^ Number of thin-sections Unit 4 Dacitic Agglomerate Dacitic to matrix Rhyodacitic fragments 34 / 34 18 / 18a 2 / 2 41-40 / 40 25 / 25° 15 / 15 10 / 10 5-3 / 4 4-3 / 3 2 / 2 1 / 1 5 / 5 2 / 2 8 / 8 17 / 17 trace 13 / 13 Unit 4a Siliceous Siltstone 47-34 / 41 23-8 / 14 d 13-2 / 8 17-0 / 11 20-5 / 11 5-0 / 2 7- 0 / 4 1-0 /trace 8- 0 / 3 10-0 / 6 Unit 4c Siliceous Tuffaceous Siltstone Sandstone 27-24 / 25 10-6 / 8 b 40-33 / 37 32-29 / 30 e 5-2 / 3 19-16 / 18 9-7 / 8 24-22 / 23 24-17 / 19 15-5 / 10 11-5/7 Rhyolitic Tuff 15 / 15 25 / 25 20 / 20 25 / 25 15 / 15 15 / 15 2 a; An 2 8-An 6/An l g b; An3j-An^ c; An l g-An g/An 1 3 f; Identification impossible due to small grain size. d; An -An lo / An, 33 averages 0.3 mm. whereas those of the other two minerals average 0.2 mm. Anhedral elongate patches of chlorite peppered with minute anhedral grains of opaques are commonly observed in thin-section. These patches may be altered volcanic glass shards. Presence of these shards and the jagged form of the larger mineral grains indicate that the rock has not been re-worked extensively. The matrix supports three different compositional types of fragments; dacite (70%), rhyodacite (25%), and andesite (5%). Percentages are based on f i e l d estimates. Fragments are sub-angular and elongate with the elongated direction paralleling the regional f o l i a t i o n . Average diameter of the fragments i s 6 cm , but they have a wide range in size up to 30 cm. long. Generally, the andesite fragments are smaller and slightly more rounded than the other fragment types suggesting that the andesite fragments have undergone more weathering than have the other fragment types. Dacite and rhyodacite fragments are respectively, medium and light grey-green in colour, both in weathered outcrop and fresh surface (Figure 2.19). Both of these fragment types are very fine grained, slightly inequigranular and exhibit a sucrosic texture. Quartz, plagioclase (A^^.) and potassium feldspar form anhedral, jagged clasts, averaging 0.18 mm in diameter, which are encompassed within a finer grained mass of anhedral minerals. Table 2.4 gives the estimated mode of each mineral observed in thin-sections of these fragments. Irregular chlorite patches con-taining minute anhedral granules of epidote and opaque minerals are inter-preted as pseudomorphs of basic fragments. Some fragments observed in . fresh and weathered surfaces are dark grey-green but otherwise are com-parable in texture and grain size to the other fragment types. These 34 dark grey-green fragments are assumed to be andesitic in composition. Field and laboratory observations suggest that the environment of deposition was near a source of dacitic debris and minor amounts of an-desitic debris. Immature matrix and presence of some sedimentary tex-tures indicate that this unit has undergone l i t t l e reworking in a high to moderate energy environment since large clastic debris was seen in the unit. Plutonic fragments were not seen in this unit leading to the conclusion that plutonic rocks were not exposed i n the source area at the time of deposition. The massive cl a s t i c nature of the rock unit with minor sedimentary structures near the base implies that this unit consists largely of con-temporaneous mudflows or lahars (Parsons, 1968). Absence of andesitic crystal tuff and minor amounts of material andesitic in composition further suggest that the debris source was removed from the volcanic regime of Unit 3. 2.2.4.1 Siliceous Siltstone (Unit 4a) Silliceous siltstone occurs as elongate north-south pods, averaging 35 m in width and varying up to 80 m , throughout units 4 and 4c. Regional fo l i a t i o n i s well developed near the perimeter of each pod but becomes progressively less well developed near the core, to the extent that the core may show no evidence of foli a t i o n . Very finely dissemi-nated pyrite occurs throughout this unit and weathered outcrop surfaces have a limonite stain (Figure 2.20). This rock unit i s dark grey with a very fine grained to aphanitic texture. In thin-section, quartz, plagioclase (An^) and potassium feldspar form anhedral clasts averaging 0.08 mm in diameter, within a finer grained groundmass containing very minute specks of opaque 3 5 I Figure 2.20 Blocky outcrop of s i l i c e o u s s i l t s t o n e (Unit 4a). Out-crop occurs i n the western-most pod of Unit 4a (Map 1) Finely disseminated p y r i t e within this unit causes a t y p i c a l limonite covered weathered surface to develop. Figure 2.21 Photomicrograph of s i l i c e o u s s i l t s t o n e (Unit 4a). Thin-section i s from same outcrop as Figure 2.20. This rock i s composed of a mass of anhedral quartz (white), c h l o r i t e (dark green), plagioclase ( l i g h t gray to white) and opaque minerals (black). (crossed n i c o l s ) 36 minerals and approximately 12% quartz (Table 2.4). Quartz clasts are sli g h t l y larger than the other clast minerals (Figure 2.21). No sedi-mentary structures are apparent. Micaeous minerals and trains of opaque grains within the groundmass outline a foliation. Rare patches of chlorite.with minute granules of opaque minerals form irregular, sl i g h t l y elongate shapes, possibly representing remnants of mafic minerals or glass fragments. Carozzi (1960) concluded that some siliceous shales owe most of their s i l i c a to the alteration of volcanic ash. S i l i c a dissolves from the ash after long exposure in sea water and precipitates on decaying organic matter in a low energy regime. The organic matter becomes minute opaque grains scattered in the quartzose groundmass. This model seems appropriate for the formation of the siliceous siltstone described above. The low energy environment needed for deposition of the siliceous siltstone must represent a change in environment of deposition. In order for some of these siltstone pods to exist they must survive de-position of the dacitic agglomerate which may have had an associated erosional capacity. Since the siltstone pods do not contain any sand size debris i t must further be assumed that there was also a cessation in the deposition of the andesitic crystal tuff (Unit 3). 2.2.4.2 Dacitic Agglomerate-fragment supported (Unit 4b) Dacitic agglomerate occurs as a layer averaging 70 m in width, near the top of Unit 4 in the north-central section of the map-area. Regional fo l i a t i o n i s poorly developed within a few metres of the peri-phery and not at a l l in the rest of the unit. 37 Fragment types are identical to those described in Unit 4. Relative abundances of the fragment types are also very similar to those of Unit 4. Matrix is identical in grain size, texture and colour to the matrix supported dacitic agglomerate but averages only 10% of the rock. Frag-ments are subangular and elongate with an average diameter of 7 cm but may range up to 50 cm. Presence of larger fragments and less matrix than Unit 4 suggests that energy within the depositional environment is greater than that at time of deposition of Unit 4. Fragment types are similar in composition and relative abundance to Unit 4 implying that the epiclastic debris has come from the same provenance as the matrix supported dacitic ag-glomerate. 2.2.4.3 Tuffaceous Sandstones and Siltstones (Unit 4c) Interbedded tuffaceous siltstones and sandstones form a layer, averaging 200 m in width, in the central region of the map-area. They are interbedded with one another on varying scales from 1 cm to 50 m The f o l i a t i o n i s well developed in the siltstones and very poorly de-veloped in non-existent in the sandstones. Poorly developed graded bedding occurs within the sandstones indicating stratigraphic tops to the east. Arkosic wackes, which are pale grey to brown, coarse to fine grained, comprise 70% of this unit (Figure 2.22) but locally grade into sandy mudstones. Clasts, generally monominerallic, averaging 2.0 to 0.1 mm in diameter, are mainly subhedral to euhedral plagioclase (An^ to An.^) with some anhedral quartz fragments. Clasts of granulose quartz, i n -terpreted as- chert fragments, comprise 1% of the thin-sections examined (Figure 2.23). A l l of the quartz examined has an undulatory extinction. 38 Figure 2.22 Slabbed surface of massive arkosic wacke (Unit 4c). Specimen i s from the western edge of c e n t r a l portion of Unit 4c (Map 1 ) . Figure 2.23 Chert fragment wi t h i n arkosic wacke (Unit 4c). Same specimen as Figure 2.22. Chert fragment ( s l i g h t l y to the r i g h t of centre) i s now composed of granulose quartz. 39 Groundmass (Table 2.4) comprises, on the average, more than 20% of the sandstones. Chlorite peppered with minute opaque grains forms diamond shaped patches resembling an amphibole and some patches form extremely elongate shapes which may represent glass shards. However both of these types of patches comprise less than 1% of the rock. Twenty-five percent of this unit consists of a dark grey, s i l i -ceous siltstone which is identical to the rock described for Unit 4a. Rare rhy o l i t i c tuff layers, averaging 1 m in thickness, were observed scattered throughout this unit. Five percent of this tuff consists of rounded quartz eyes, averaging 0.3 mm in diameter, within a finer grained, well sheared groundmass (Table 2.4). Finely disseminated grains of pyrite form crude layers partially outlining the foliation. Patches of chlorite containing minute opaque grains form elongate i r -regular shapes, averaging 0.1 mm in diameter, possibly representing the remains of glass fragments. Proposed depositional environment is similar to that suggested for Unit 4a, except that the deposition of the dark grey siltstone has been interupted by influxes of epiclastic material. These influxes may have been the result of submarine mudflow or lahar activity. Clasts of the arkosic wackes formed from these lahars consist largely of fresh sub-hedral plagioclase leading to the conclusion that these rocks were only subjected to slight reworking. Also i t implies that the feldspars were exposed to weathering processes for only a short period of time. In order for this to occur the debris must have been eroded and deposited quickly, possibly from a very mountainous environment. Since the wackes include very l i t t l e except monominerallic material, the depositional site for the part of the flow observed in the map-area must have been 40 well removed from the start of the flow or represent the waning stages of a mudflow event. This hypothesis is further substantiated by the presence of the siliceous siltstone, the origin of which requires a low energy environment. 2.2.5 ANDESITIC AGGLOMERATE (UNIT 5) Andesitic agglomerate occurs in the northwestern section of the map-area and contains the mineral deposits of Northair Mines Limited (N.P.L.), the only metal producer in the map-area. Regional foliation is weakly developed but becomes pronounced in shear zones ranging up to 30 m in width. Sedimentary structures were not observed in this unit. Weathered surfaces are slightly paler than fresh dark grey-green surfaces and sur-face r e l i e f produced by weathering aids in recognition of fragments (Figure 2.24). Matrix i s medium to dark grey-green and fine grained varying from 20 to 95 % with an average of approximately 40%. Regional foliation is slightly better developed in the matrix than in most of the fragment types. It i s outlined by chlorite and trains of opaque mineral grains. Subhedral plagioclase clasts ( A ^ to An.^) > averaging 1 mm in diameter, and small fragments give the matrix i t s slightly gritty appearance (Figure 2.25). Opaque minerals, chlorite, epidote and plagioclase form anhedral masses which may locally resemble amphibole in cross-section. These patches comprise less than 1% of the matrix. Very rare elongate patches of chlorite peppered with opaque mineral grains are present and assumed to be altered remnant glass fragments. Biotite is developed locally within chlorite i n and to the east of Northair mine. Andesitic agglomerate matrix, west of the mine, is essentially devoid of biotite. Table 2.5 l i s t s a l l of the minerals seen within thin-sections of the matrix. 41 I Figure 2.24 Weathered outcrop of andesitic agglomerate (Unit 5). This outcrop i s approximately one k south of the Warman zone a d i t , j u s t east of Unit 5a (Map 1). One of the protruding fragments occurs at the base of the hammer. Figure 2.25 G r i t t y a n d e s i t i c agglomerate matrix. Specimen taken from outcrop shown i n above figure. Clasts are a l l plagioclase.(crossed n i c o l s ) TABLE 2.5 VISUAL ESTIMATES OF MINERAL MODES-l'nlts 5 5a. 5b and 5c (Percen Cages :maxlmuz>-i9lnlntum/avc rage) matrix Unit 5 Andesitic Agglomerate fragments Porphyritic Equlgranular Porphyritic matrix Equlgranular Unit 5a Unit 5b Unit 5c E p l c l a s t l c Volcanic Breccia Arkosic Andesitic fragments Wacke Crystal Porphyritic Equlgranular Equlgranular Tuff Monomlneralllc c l a s t s Plagioclase Andesite 40-0 / 20 a Andesite Daclte 20-10 / 15 b Daclte Andesite 45-30 / 36 c Andesite Daclte 45-25 / 23 d Quartz 7-3 / 5 8-0 / 1 8-3 / 5 Potassium feldspar trace Hornblende 10-0 / 2 Croundmass Plagioclase 56-13 / 33* 8-0 / 2 f 38-10 / 30 8 30-10 / 16 h 35-15 / 25 1 30-0 / 9> 45 / 45 k 23 / 23 1 30-15 / 26'° Epldote 32-3 / 17 75-13 / 38 20-7 / 15 7-5 / 6 18-5 / 12 3 - 2 / 3 5-1 / 3 6 / 6 8 / 8 10-0 / 3 20-3 / 10 Chlo r i t e 25-6 / 17 22-5 / 10 15-5 / 12 15-13 / 14 15-9 / 12 8 - 5 / 7 19-3 / 9 12 / 12 7 / 7 17-0 / 4 23-0 / 7 Feldspar-quart*" 20-0 / 7 25-0 / 10 20-10 / 16 35-15 / 25 45-15 / 29 20-12 / 16 35-0 / 19 13 / 13 17 / 17 20-8 / 16 25-10 / 17 Opaques 10-5 / 7 10-0 / 4 12-3 / 9 10-3 / 6 12-4 / 6 12-7 / 10 14-3 / 8 7 / 7 10 / 10 17-1 / 12 15-7 / 10 S e r i c i t e 18-0 / 5 7-0 / 4 15-0 / 8 15 / 15 12-2 / 5 18-12 / 14 20-2 / 8 5/5 14 / 14 20-3 / 15 21-0 / 6 Quartz 10-0 / 4 12-0 / 7 5 - 0 / 2 17-0 / 9 25-6 / 16 27-10 / 20 8-0 / I 16 / 16 38-12 / 19 B i o t i t e 13-0 / 4 8 - 0 / 3 20-0 / 7 trace trace 22-0 / 7 Carbonate 18-0 / 3 15-0 / 2 3-0 / 1 10-0 / 5 8-3/4 10-0 /5 20-0 / 5 trace 5 / 5 10-0 / 4 10-0 / 3 Hornblende 20-0 / 3 Sphene trace trace trace trace trace 5-0 / 1 1-0 /trace Totasslum feldspar Nuinbcr of thin-sections 11 6 4 2 3 4 6 1 1 1-0 / 1 4 5 a; An 2 4-An l 4/An 1 8 b; An^AnJ^ c; A n 1 8 - A n 1 2 / A n u d; An^-An^/An^ e; An^-An^/An^ f; Ang-An^/Anj g; Ang h; An^ 1; An^-An^/An^ J; An^-An^/Anj k; An^ 1; An^ a; Anj^-Ang/An^ n; I d e n t i f i c a t i o n Impossible due to small grain s i z e . 43 Five different fragment types occur in this unit and are generally supported by the matrix. These are: porphyritic andesite (70%), equigranular andesite (22%), porphyritic dacite ( 5 % ) , sandstones (2%) and equigranular dacite (1%). Percentages are based on visual f i e l d estimates. Fragments are ovoid, rounded, or more commonly sub-angular, and are up to 70 cm in diameter with a mode of approximately 4 cm (Figure 2.26). Porphyritic andesite fragments have a dark grey to grey-green, aphanitic to fine grained matrix which composes at least 50% of the fragment (Table 2.5). Subhedral plagioclase crystals (An_ to An„.) o Lh average 0.5 by 0.8 mm and are randomly oriented within the matrix. Composition and the absence of zoning in plagioclase suggest that these crystals have been extensively albitized. Minor amounts of epidote, plagioclase and quartz are contained in patches of chlorite with opaque grains concentrated near the perimeter. These patches are diamond shaped suggesting that they are pseudomorphs of amphibole. Other ex-tremely elongate patches of chlorite and disseminated opaque grains are thought to be altered glass shards. The presence of these possible shards indicates that these rock fragments could be altered tuffs, but the shards were recognized in only a few thin-sections, consequently i t is d i f f i c u l t to decide whether the majority of these fragments are altered tuffs or flows. Equigranular andesite is very fine grained to aphanitic and medium to dark grey-green. Subhedral plagioclase crystals (An^), averaging 0.05 mm in diameter, comprise about 30% of the rock and is only slightly larger than the other minerals (Table 2.5). Angular, spherical shaped porphyritic andesite fragments were observed within the equigranular 44 Figure 2.26 Weathered outcrop of a n d e s i t i c agglomerate (Unit 5). Outcrop i s ten m east of the 3700 p o r t a l i n the Manifold zone, Northair Mines (Map 1 ) . Bedding features are absent but v a r i a t i o n i n colour and shape of fragments are present. 45 andesite but only in trace amounts. These textures and the presence of very small amounts of glass shards indicate that the equigranular an-desite could be a tuff. Porphyritic dacite fragments have a medium grey-green, aphanitic matrix which constitutes at least 60% of the fragment (Table 2.5). Sub-hedral plagioclase (An^) and anhedral quartz, clasts have an average^, dia-meter of 0.2 mm. None of the plagioclase clasts show evidence of com-positional zoning suggesting complete albitization. In addition these phenocrysts apparently are not aligned in any regular way. Sandstone fragments are medium grey-green and identical in texture and grain size to the matrix of the andesitic agglomerate. No sedimen-tary features were seen in these fragments. None of the sandstone fragments were examined in thin-section but they are similar to the matrix of the agglomerate which is an immature sandstone. Presence of these fragments implies that previously deposited epiclastic rocks have been brecciated and redeposited. Equigranular dacite fragments are medium grey-green and aphanitic. This fragment type is identical in texture to the equigranular andesite but is apparently more siliceous, for this reason this fragment type was interpreted to be dacitic in composition. Previous work had identified a sixth fragment type, jasper, which, upon further f i e l d and polished section work was re-interpreted as magnetite-hematite veins. Figure 2.27 shows one of these veins with inclusions of plagioclase crystals, a magnetite-rich core with a hema-t i t e halo and no evidence of bedding. These features plus the presence of an epidote halo around the hematite indicates that i t is a vein. The 2800 foot level adit of Northair mine is cross-cut by a fresh Figure 2.28 P o r p h y r i t i c fragment w i t h i n Unit 5 almost e n t i r e l v replaced by epidote. Outcrop i s 600 m south of the Warman zone adi t (Map 1). 47 equigranular, northerly trending rhyodacite dykes with a quartz vein off-shoot which locally contains pockets of magnetite and hematite. This implies that these magnetite-hematite veins may be related in time to the magmatic event which formed the dyke. A few andesitic agglomerate fragments were observed forming within Unit 5. These fragments in Unit 5 contain the same fragment types and shapes as described previously except that the relative proportions are different. They are; porphyritic andesite (65%), equigranular andesite (15%), porphyritic dacite (10%), sandstones (5%) and equigranular dacite (5%). Degree of metamorphism of Unit 5 varies but generally epidote, chlorite and se r i c i t e are ubiquitous throughout fragments and matrix. However, development of epidote i s more intense within the fragments. Replacement of the fragments by epidote forms a continuum from epidote merely rimming the fragment to complete replacement (Figure 2.28). This character has been detailed in other rocks similar to the andesitic agglomerate by Roddick (1965). Andesite fragments appear to be more readily altered to epidote than the other compositional types. Biotite is more prevalent i n andesite fragments than in other fragments. Lack of bedding and the massive, extensive nature of Unit 5 in d i -cates that i t is a sequence of contemporaneous lahars (Parsons, 1968). The presence of agglomeratic fragments also makes i t reasonable to as-sume that previously l i t h i f i e d lahars have been broken up and incor-porated into later flows. Within the predominantly andesitic agglomerate unit are several layers of contrasting lithology such as: epiclastic volcanic breccia (Unit 5a), arkosic wackes with minor interbedded mudstones (Unit 5b). 48 andesitic crystal tuff (Unit 5c) and a detailed sequence in the mine area. Each of these rock types are described separately in the following sections although the sequence in the mine area is described in a sec-tion dealing with Northair mine. 2.2.5.1 Epiclastic Volcanic Breccia (Unit 5a) Epiclastic volcanic breccia form a layer of relatively uniform thickness, compared to the previously described units, which averages 35 m i n thickness. It l i e s within the lower section of the andesitic agglomerate (Unit 5) in the southeastern part of the map-area and on top of the andesitic crystal tuff (Unit 3) in the northeastern part. Regional f o l i a t i o n i s poorly developed in the matrix but is almost non-existent i n most fragments. Weathered surfaces easily delineate the fragment types because of weathering differences and colours. Fragments vary from a pale grey to dark grey against a medium grey matrix. On fresh surfaces the matrix and fragments are both a dark grey which makes fragments indistinguish-able. Weathered surfaces of the breccia generally are covered by a pale limonite stain which may become quite abundant in some areas due to pyrite-rich fragments. Black, aphanitic to fine grained matrix occupies 5 to 90% (average of about 15%) of the rock. Variations in the matrix grain size define bedding (Figure 2.29). Clasts of subhedral plagioclase (Ang to An^) average 0.2 mm i n diameter, and anhedral quartz, average 0.1 mm in dia-meter, comprise at least 40% of the matrix (Table 2.5). The remainder of the matrix consists of a mass of feldspar, quartz, sericite, chlorite, opaque minerals, carbonate and epidote a l l of which average less than 0.005 mm in diameter. Six fragment types were observed in this unit. 4 9 Figure 2.29 Fresh surface of Unit 5a. This block i s 660 m south of the Warman zone adi t (Map 1). Bedding (near the boot toes and oriented top to bottom i n the photo) i s marked by a bed of smaller, more cl o s e l y packed fragments than e x i s t s i n the r e s t of the rock surface. 50 In decreasing order of abundance, they are: porphyritic andesite, an-desitic crystal tuff, equigranular andesite, equigranular dacite, equi-granular and siliceous siltstone, and devitrified glass. The f i r s t three fragment types comprise 90% of a l l the fragments within the brec-cia. Each of the fragment types are represented in approximately the same relative proportions lat e r a l l y throughout the unit. Fragments of andesitic crystal tuff containing andesitic crystal tuff fragments, identical to those described for Unit 3, were also seen but they are rare (less than 1%). Fragments are subangular, slightly elongate and locally have an average diameter of 4 to 30 cm. Fragments, generally matrix supported, are unsorted with a perponderance of 4 cm fragments. Crude bedding is marked by variations in the percent matrix and frag-ment size (Figure 2.29). Porphyritic andesite fragments, which comprise 38% of the fragments, have a light grey, aphanitic groundmass surrounding subhedral plagioclase (An, to A 1 D) clasts (Figures 2.30). These clasts, averaging 0.2 by 0.25 mm, constitute at least 30% of this fragment type (Table 2.5). Approximately 3% of the plagioclase crystals are glomeroporphyritic aggregates. None of the plagioclase shows evidence of compositional zoning. Together with the low anorthite content this suggests that plagioclase has been extensively albitized. In some fragments the clasts show a slight alignment not coincident with the regional foliation i n -dicating that the fragments may have originated from flow rocks. Matrix around the fragments consists of a mass of minerals usually averaging less than 0.005 mm in diameter (Table 2.5). These minerals show a slight foliation due to alignment of sericite, chlorite and trains of opaque mineral grains. 51 Figure 2.30 Photomicrograph of porphyritic andesite fragment in Unit 5a. Thin-section is from the same location as Figure 2.29. Plagioclase is unzoned albite and contains many epidote grains. (crossed nicols) 52 Andesitic crystal tuff fragments are identical to those described for Unit 3 and comprise approximately 32% of the breccia fragments. As mentioned previously these fragments may contain porphyritic andesite fragments but they make up less than 1% of the andesitic crystal tuff fragments in the breccia. Equigranular andesite comprises 20% of the breccia fragments. These fragments are medium grey-green, equigranular and very fine grained to aphanitic. Subhedral plagioclase (An^) and anhedral quartz crystals, averaging 0.01 mm in diameter constitute at least 60% of this fragment type (Table 2.5). The rest of the fragment i s composed of finer grained masses of minerals which exhibit a slightly more definite f o l i a t i o n than the previous fragment types described. Equigranular dacite fragments, comprise 8% of the fragments, are light grey-green and aphanitic (Figure 2.31). Subhedral plagioclase (Ang) and anhedral quartz, both averaging 0.008 mm in diameter, forms at least 40% of this fragment type with quartz being the more abundant mineral (Table 2.5). Regional fo l i a t i o n development is slight in this fragment, similar to that of the porphyritic andesite fragments. Equigranular, tuffaceous, siliceous siltstone and devitrified glass fragments are approximately equally abundant, composing only 2% of the breccia fragments. Siltstone fragments have an average minimum diameter of 1 cm. These siltstone fragments are similar to siliceous siltstone (Unit 4a) which has already been described in detail. Glass fragment pseudomorphs averaging 0.08 mm in length and 0.03 mm in width and are angular in shape (Figure 2.32). These aspects suggest that the glass fragments are remnant shards, which now consist of a mass of chlorite peppered with anhedral opaque grains and trace amounts of other minerals. Chlorite is moderately aligned parallel to the fo l i a t i o n which makes this Figure 2.31 Equigranular dacite fragment i n Unit 5a. Same l o c a t i o n as Figure 2.29. F o l i a t i o n i s l s i g h t l y developed from top to bottom i n the photomicrograph. (crossed n i c o l s ) 54 fragment type the one which has the strongest foliation development. The widespread nature of this unit with heterolithologic non-vesi-cular fragments and crude betding indicates that this unit is an epi-c l a s t i c breccia or more specifically a laharic breccia (Parsons, 1968). Presence of significantly more quartz in the matrix than in the dominant fragment types suggests that foreign or reworked debris has been incor-porated into the matrix. Deposition of this relatively tabular body of uniformly thick brec-cia within an agglomerate environment which is locally bounded and inter-fingered with andesitic crystal tuff does not necessarily mark a signi-ficant change in the depositional environment. However the angular nature of the fragments in this unit does imply that the fragments were not extensively reworked and therefore this deposit must be near i t s source. Incorporation of andesitic crystal tuff and porphyritic andesite fragments in significant amounts suggests that considerable amount of the debris came from a similar or equivalent source area as the andesitic crystal tuff. The presence of angular and compositionally different debris further implies that a compositionally different provenance existed in the area. 2.2.5.2 Arkosic Wacke (Unit 5b) Arkosic wacke occurs i n the north-eastern section of the map-area within the basal part of Unit 5. Regional foliation is poorly developed throughout the unit. Graded bedding and cross-bedding occur but are poorly developed. Two separate locations indicated that stratigraphic tops are to the east. Arkosic wackes and minor mudstones which form this unit are pale to medium grey and coarse to aphanitic in grain size. Medium grained wackes 55 predominate. Monominerallic grains of anhedral quartz and subhedral to euhedral plagioclase (An 0 to An__.) comprise at least 40% of the wackes (Table 2.5). Minor irregular masses of granulose quartz (interpreted as chert fragments), irregular masses of seric i t e (interpreted as mud clasts) and anhedral carbonate clasts (interpreted as f o s s i l fragments) were also observed (Figure 2.33). The f i r s t two types of clasts average 0.3 mm in diameter. Carbonate clasts which average 0.5 mm in diameter were interpreted as f o s s i l remains because they consist entirely of carbonate which is unreasonable for calcareous muds. Feldspar clasts are fresh and euhedral suggesting very l i t t l e ex-posure to weathering (Figure 2.34) . This plus the fact that none of the clasts are rounded suggests that the epiclastic debris was probably de-rived from a mountainous environment. The f o s s i l fragments imply a water environment. The energy environment for deposition of the arkosic wackes is less than that existing during deposition of an agglomerate. It seems li k e l y that the arkosic wackes may then represent .waning stages of the agglom-eratic deposition (Lajoie, 1977). In general the amount of quartz con-tained in the andesitic agglomerate appears to be too low to account for the amount of quartz contained in the wacke. However, i f one only con-siders the matrix of the andesitic agglomerate and i t s quartz content plus the fact that matrix and wacke can have variations due to incor-poration of foreign debris i t seems entirely possible that the wackes and agglomerates could have formed from the same source area. Consideration must be given also to the idea that the wackes are found by an event entirely different from the one which formed the agglomerates. Since dacitic agglomerates do occur in the area i t also Figure 2.33 Photomicrograph of a carbonate c l a s t i n arkosic wacke (Unit 5b). Specimen i s from the southwestern t i p of the western-most patch of Unit 5b (Map 1). These carbonate grains occur near the centre of the photo but only the one on the r i g h t exhibits a well-defined c l a s t i c appearance. (crossed nicols) Figure 2.34 Photomicrograph of arkosic wacke (Unit 5b). Same l o c a t i o n as Figure 2.33. R e l a t i v e l y fresh p l a g i o c l a s e (twinned), undulatory quartz and opaque grains form monomineralic c l a s t s cemented by a f i n e r groundmass. (crossed n i c o l s ) 57 seems probable that this material could supply the quartz for the wackes quite easily. Determining which of these two suggestions is more appro-priate i s impossible on present evidence since the basal contact of the wackes i s not exposed and they both could give similar results. However in both cases, the required energy regime is less than that proposed for formation of agglomerates. 2.2.5.3 Andesitic Crystal Tuff (Unit 5c) Andesitic crystal tuff occurs in the northeastern section of the map-area within the andesitic agglomerate (Unit 5). Regional foliation is generally very poorly developed except along the western contact of the westerly pod which has slight to moderately developed f o l i a t i o n . Contacts between this unit and the hornblende diorite (Unit 6b) were not seen in the f i e l d . Sedimentary structures are completely absent in this rock unit. In fresh and weathered surfaces, this unit is similar in appearance to the andesitic crystal tuff described for Unit 3, except for the con-spicuous absence of fragments (Figure 2.35). In thin-section, however, andesitic crystal tuff fragments appear to comprise about 2% of the rock. These fragments are compositionally similar to the rest of the rock. Matrix is dark grey, aphanitic and contains b i o t i t e with very l i t t l e chlorite (Table 2.5) unlike the matrix of Unit 3 which contains no bio-t i t e . Subhedral plagioclase clasts, averaging 0.5 by 0.8 mm make up about 25% of the rock with about one quarter of this plagioclase occurring in glomeroporphyritic aggregates. Quartz occurs as anhedral clasts, aver-aging 0.5 mm in diameter, which exhibit undulatory extinction. Quartz also occurs in the groundmass as minute anhedral blebs but does not ap-58 Figure 2.35 Weathered surface of a n d e s i t i c c r y s t a l t u f f (Unit 5c) from western-most pod of Unit 5c (Map 1). Plagio-clase c l a s t s are subhedral and l o c a l l y consist of glomeroporphyritic aggregates. 59 pear to increase the quartz content enough to make this unit a dacite. Determination of exact proportions of quartz and plagioclase is very d i f f i c u l t due to the fine grain sizes involved. Biotite and trace amounts of chlorite around the perimeter form elongate jagged patches peppered with opaques. These are interpreted as the remnants of glass shards. Other patches of these same minerals containing minor feldspar-quartz grains have diamond shaped forms simi-lar to an amphibole. Both of these types of patches are relatively rare and probably compose less than 1% of this rock unit. Percentages of plagioclase and hornblende can vary over a distance of 8 cm from a total of 40 to 20%. This variation does not appear to be the result of a fragment in a matrix. Origin and implications presented for the andesitic crystal tuff (Unit 3) seem to be appropriate for this unit as well. However, since this unit is physically separated from and is not entirely identical to Unit 3, i t has been mapped separately as Unit 5c. 2.2.6 STRUCTURAL GEOLOGY This section examines the structural geology in the immediate v i c i -nity of Northair Mine (Figure 2.36); i t does not attempt to cover the entire map-area. Basically very l i t t l e i s known about the orientation of bedding, fractures and foliations in the regional area because of poor exposure and more time was spent mapping the Northair area. Furthermore, no significant differences were noted between foliation and fracture data in the v i c i n i t y of Northair and the rest of the map-area. It is therefore assumed that conclusions arrived at in the Northair "mine-area concerning structural features may be applied generally to the other 60 Figure 2.36 Stippled pattern marks area of structural analysis. 61 parts of the central section of the Callaghan Creek pendant. Interpretation of the structural features of the Northair area is d i f f i c u l t . Extreme irregularities in unit thickness and composition, gradational contacts, lack of outcrop in key areas and most importantly, the lack of well defined marker horizons a l l contribute to making this a d i f f i c u l t structure to interpret. Folding, on the scale of 1 m , was ob-served in the mineralized area of the Manifold Zone. The orientation of these folds relative to other measured structural features is unknown. Therefore, the orientation of fractures and foliation are the only fea-tures from which the regional stress f i e l d can be inferred. The map-area was originally divided into three separate domains. However, stereoplots of these domains showed no significant differences. In these domains, bedding orientations were variable but neither the fractures nor foliation were affected by these changes. These factors lead to the grouping of the map-area into one domain. Since the bedding ( S Q ) seemed to have very l i t t l e effect on the structure and has variable orientations, i t was deleted from the stereoplots. Generally, the Callaghan Creek pendant is a north-south homoclinal package with tops to the east. Callaghan Creek pendant rocks a l l have a penetrative foliation a l -though the degree to which i t i s developed varies. In most cases the f o l i a t i o n is more strongly developed near contacts with other pendant rocks. Air photo linears in the Northair mine-area, interpreted as faults may extend into plutonic rocks. Therefore i t appears as though there was a deformation event which extended in time from intrusion of plutonic rocks to after their s o l i d i f i c a t i o n . Another more plausable explanation is that the pendant rocks have been subjected to several 62 phases of deformation. The f i r s t phase of deformation being associated with plutonism and metamorphism, the penetrative foli a t i o n , and a later phase or phases which exploited weakness in the pendant rocks, such as contacts, creating shear zones and faults. At least part of this later deformation occurred after s o l i d i f i c a t i o n of the plutonic rocks. How-ever since the penetrative deformation generally parallels pendant rock contacts i t is d i f f i c u l t to distinguish these phases of deformation. Equal area stereoplots of the foliation and fractures were made and contoured (Figure 2.37). The contour intervals vary and are given on each plot, thus the plots are simplified to i l l u s t r a t e the general features needed for subsequent analysis. The plot of foliation (S^) defines a plane oriented at 174°/81°W. One set of fractures (F-^ ) defines a plane oriented at 173°/81°W., which is essentially p a r a l l e l to the foliation plane. This fracture set is assumed to be shear fractures due to their relation to the foliation and lack of extension fracture features. Mylonite zones and faults, in the mine area, identified by d r i l l i n g and underground work, are generally parallel to the f o l i a t i o n . Another group of fractures (F^) define a plane oriented at 079°/82° N. This plane is nearly perpendicular (87°) to the fo l i a t i o n . These frac-tures exhibit extensional features such as a plumose structure. The third group of fractures (F^) centres around a horizontal plane and, in the f i e l d , i s generally parallel to the orientation of the topo-graphy. These fractures or fracture sets are assumed to be "sheeting" caused by erosional unloading and/or glacial retreat. In order for this fracturing to occur the rock must be essentially isotropic (Hobbs et a l . , 1976) . This' requirement appears to be met by a l l units in the area under 63 Figure 2.37 Equal area stereoplot of axes to f o l i a t i o n and fracture planes. 64 consideration, based on f i e l d and laboratory observations. This frac-turing event is assumed to be unrelated to and later than the event causing the schistosity and other features. The direction of least stress (a^) i s perpendicular to the exten-sional fractures and generally oriented north-south based on i t s rela-tionship to the schistosity (Hobbs et a l , 1976). The intermediate and maximum stress directions (respectively and a^) are impossible to determine with available information but apparently are acting in an east-west direction. Two major faults identified in the map-area are oriented generally north-south and would f i t the stress regime above. Further confirmation that these faults are the result of the same proposed stress regime can be drawn from the presence of smaller scale north-south faults men-tioned above. 2.2.7 METAMORPHISM Based on microscopic examination, exact timing of metamorphism re-lative to deformation is not well defined. Bent albite twins and chlor-ite flakes, both metamorphic minerals, suggest that metamorphism is pre-deformation. In other cases, metamorphic minerals show no sign of de-formation or orientation parallel to the folia t i o n . However, the latter case i s more common than the former, implying that deformation i s generally a syn-metamorphic event or at least deformation and meta-morphism are not too widely separated in time. Slight variations in stable mineral assemblages occur between com-positionally distinct rock units (based on names assigned in this manu-script) . Stable assemblages, in this paper, implies that the minerals were observed in contact and appear to be in equilibrium. Assemblages 65 list e d below are generally those of the entire map-area. This l i s t was com-piled to alleviate the need for an exhaustive and repetitive l i s t of stable mineral assemblages for each unit. Stable assemblages are: Epidote-Plagioclase Epidote-Biotite Epidote-Calcite Epidote-Chlorite-Quartz Epidote-Muscovite-Quartz Epidote-Muscovite-Chlorite Epidote-Muscovite-Quartz-Albite Chlorite-Calcite-Quartz-Muscovite Chlorite-Calcite-Quartz Chlorite-Quartz Chlorite-Calcite Chlorite-Muscovite Albite-Quartz Biotite-Muscovite Biotite-Calcite Biotite-Calcite-Muscovite The ubiquitous presence of epidote (primarily clinozoisite), chlorite and muscovite i s diagnostic of greenschist grade metamorphism (Winkler, 1976). The extent of the pressure-temperature region containing the a-bove stable mineral assemblages i s given in Fig. 2.38. Temperatures of meta-morphism are roughly from 350°C to 550°C. Lack of appropriate pressure sensitive as opposed to temperature sensitive reactions makes i t impos-sible to estimate pressure. A zonal distribution of metamorphic minerals was not observed in the 10, Figure 2.38 Pressure-temperature graph with the stippled area representing the approximate l i m i t of greenschist grade metamorphism (after Winkler, 1976) . 67 map-area. However, a more detailed study of rock compositions and the mineralogy associated with each rock composition might provide more insight into metamorphic mineral zonation. 2.3 PLUTONIC ROCKS Three compositional types of plutonic rocks were recognized in the map-area, each of which w i l l be described in a separate section. Ages of each unit are unknown so that the order in which they are presented has no re-lative time significance. Visual estimates of the grain size and made of minerals present were made from thin-sections which were used in conjunction with f i e l d notes to arrive at a f i n a l rock name. The rock names are consistent with the classification of igneous rocks made by Strekeisen (1967) and Williams et a l . (1954). 2.3.1 QUARTZ DIORITE (UNIT 6A) Quartz diorite surrounds the Callaghan Creek pendant on the west and south. Within 30 to 50 m of the contact with the volcanics, the plutonic rocks may exhibit a f o l i a t i o n which i s less developed than that of the pendant rocks. Where the pendant rocks are strongly sheared and in con-tact with plutonic rocks, shearing is more strongly developed in the quartz diorite than i n other contact areas. The foliation i s generally parallel to that of the regional fo l i a t i o n in the pendant rocks. Contacts between the pendant and plutonic rocks are of two types. F i r s t , north-south contacts occur within well-defined areas forming de-pressions with very stronlgy sheared, almost schistose pendant rocks. The second type of contact i s generally east-west and very ill-defined where there i s a paucity of outcrop. Plutonic rocks on these contacts 68 show l i t t l e , i f any, evidence of f o l i a t i o n while the pendant rocks show moderate to weak folia t i o n . Rafts and inclusions were observed in the v i -cinity of east-west contacts but only rarely were inclusions seen near north-south contacts. Compositions within this unit vary from quartz diorite to diorite with the latter being in closer proximity to the pendant rocks. Quartz diorites are also more abundant than are diorites. Fresh and weathered surfaces are pale grey-green, interrupted by small patches of dark green minerals and/or epidote (Figure 2.39). Rare epidote veins containing minor amounts of quartz and chlorite occur throughout this unit. These veins are especially prevalent in the southwestern area. Granitic texture of the quartz diorite i s very obvious in outcrop and i s only sl i g h t l y disrupted by the development of foliation. Quartz diorite i s fine to medium grained with plagioclase (An to An _) Zo j o being the dominant mineral (Table 2.6). Anhedral plagioclase and quartz are the larger minerals, averaging 0.8 mm in diameter, with the mafic minerals occurring i n t e r s t i t i a l l y (Figure 2.40). Less than 1% of potassium feldspar was noted in stained rock slabs. These averaged 0.5 mm. in dia-meter. Quartz has an undulatory extinction and some albite twins within plagioclase are bent indicating subsequent deformation. Chlorite has re-placed a l l of the primary mafic minerals and biotite has replaced most of the chlorite in the southeastern rocks. Some patches of chlorite have shapes similar to that of an amphibole in cross-section. Alteration ranges from very slight to complete, where a l l of the plagioclase has been altered to s e r i c i t e , epidote and quartz. Complete alteration i s rare because most of the rock is only moderately altered, as evidence by ubiquitous small patches of epidote and sericite in the plagio-clase. None of the plagioclase crystals show evidence of zoning and the 69 Figure 2.39 Freshly broken surface of massive quartz d i o r i t e (Unit 6a). From an outcrop three k south of the Warman zone, near the pendant contact (Map 1). Figure 2.40 Photomicrograph of quartz d i o r i t e (Unit 6a). Same specimen as Figure 2.39. Plag i o c l a s e contains saussurite while qaurtz has an undulatory extinction.(crossed n i c o l s ) TABLE 2.6 VISUAL ESTIMATES OF MINERAL MODES-Units 6a, 6b and 6c (Percentages;maximum-minimum/average) Plagioclase Quartz Chlorite Epidote Sericite Carbonate Opaques Biotite Apatite Hornblende Sphene Zircon Orthoclase Number of thin-sections Unit 6a Quartz Diorite 45-0 / 32 a 23-7 / 16 25-2 / 16 20-0 / 11 15-2 / 9 35-0 / 7 8-0 / 3 15-0 / 3 3-0 / 1 8-0 / 1 5-0 / 1 1-0 /trace Unit 6b Hornblende Diorite 50-0 / 34b 18-2 / 7 20-0 / 9 45-0 / 13 8-0 / 5 3-0 / 1 8-3 / 5 11-0 / 2 2-0 / 1 45-7 / 23 1-0 /trace trace Unit 6c Granodiorite 33 / 33 C 22-20 / 21 1 / 1 10-7 / 9 4-3/3 2-1/2 12 / 12 2-1 / 1 17-15 / 16 2 a; An 0 0-An,/An„. 38 6 34 b; An 4 8-An g/An 3 9 c; An 3 8-An 8/An 3 ( ) 71 localized presence of albite suggests that albitization has been extensive in anothite-rich plagioclase. The nature of intrusion of quartz diorite can be inferred by using observations of the contact zones between the pendant and plutonic rocks. Contacts vary from north-south fault zones to poorly defined east-west con-tacts. These contacts may be consistent with the intrusion model. The grain size of the plutonic mass does not vary from the contact to outcrops which are hundreds of metres from the contact. These features suggest that intrusion of the quartz diorite was not completely the result of magmatic stoping but also the product of forceful injection and squeezing of a semi-solid plutonic mass through and past the pendant material. Inherent north-south weaknesses, either bedding, shear zones, faults or just a strong fol i a t i o n provided avenues for magmatic injection. On the other hand the more competent east-west contacts did not allow magmatic injections and therefore had to be eaten away by stoping or other processes which incor-porated more material into the plutonic mass. The fo l i a t i o n of quartz diorite, apparently coincident with the f o l i a t i o n of the pendant, further implies that one stress f i e l d existed for both, but the stress regime might have been initiated by the intrusion of the plutonic mass. Another interpretation of the deformational features in the quartz diorite, suggested by G. Woodsworth (personal communication, 1979), is that the quartz diorite has been subjected to the same metamorphic and deformational event as the pendant rocks. Paleozoic zircons and K-Ar age dates of about 160 m.y. have been obtained from a large quartz diorite body east of the pendant (Roddick et a l . , 1977). Assuming that this quartz diorite body is similar to the quartz diorite in the study-area, of this manuscript, suggests that the quartz diorite and pendant rocks are of 72 similar age. Therefore this later interpretation of the deformational features in the quartz diorite appears to be more appropriate than the f i r s t interpretation. 2.3.2 HORNBLENDE DIORITE (UNIT 6B) Hornblende diorite occurs as a pod within quartz diorite (Unit 6a) in the southwestern section of the map-area and also as a mass bordering the roof pendant in the northern and southwestern sections of the map-area (Figure 2.2). Contacts and development of foliation are identical to those described for the quartz diorite (Unit 6a). The protrusion of .plutonic rock into andesitic agglomerate (Unit 5) east of Northair mine is slightly sheared. This unit contains phases which vary in composition from hornblende diorite to hornblende quartz diorite with the former being more abundant. No f i e l d correlation could be made between the mafic content and distance from the pendant. In the southern pod of hornblende diorite, the pre-viously mentioned end member phases are in sharp contact; the change oc-curs over a distance of a few centimetres. Hornblende diorite i s medium grained and generally granitic in tex-ture although occasionally this texture is interrupted by fo l i a t i o n dev-elopment (Figure 2.41). Weathered and fresh surfaces are black to dark grey-green with patches of pale green. Plagioclase (Ang to An^g) and hornblende are the predominant minerals with the hornblende usually occur-ring i n t e r s t i t i a l l y (Figure 2.42). Table 2.6 presents estimates of mineral modes from thin-sections of this unit. P o i k i o l i t i c hornblende containing inclusions of quartz, plagioclase and biot i t e is the only ubiquitous primary mafic mineral. However, sig-nificant amounts of biotite occurs within the most northerly part of this 73 Figure 2.41 Slabbed surface of massive hornblende d i o r i t e (Unit 6b). From an exposure 150 m north of Alexander F a l l s (Map 1 ) . Plagioclase (white) with b i o t i t e and hornblende (both black) comprises most of the rock. Figure 2.42 Photomicrograph of hornblende d i o r i t e (Unit 6b). Same specimen as Figure 2.41. A r e l a t i v e l y fresh rock compared to Unit 6a. (crossed n i c o l s ) 74 unit. Generally, a l l plagioclase crystals exhibit compositional zoning. Some albite twins within plagioclase are bent and most quartz grains exhibit undulatory extinction. These two features become more intense as one approaches the pendant contact, indicating an increase in the degree of deformation. Alteration in the northern exposures of this unit is slight but elsewhere i t is moderate. Epidote veins containing minor carbonate and trace amounts of quartz occur in this unit. These veins may range up to 3 cm in width. Stock-work copper mineralization in the form of pyrite and minor chalcopyrite was observed in the stock located in the v i c i n i t y of Van Silver m i l l s i t e . A similar mode of emplacement i s proposed for this unit as was pro-posed for the quartz diorite (Unit 6a). K-Ar model age dating was conducted on hornblende diorite and gave ages of 90.0 +.3.2, 87.0 + 3.0 and 128 + 4 Ma (Appendix C). 2.3.3 Granodiorite (Unit 6c) Granodiorite abuts the Callaghan Creek roof .pendant volcanic rocks on the east in the northeastern section of the map-area. The contact follows a 10 m wide depression with strongly sheared volcanic rocks on the side and slightly deformed granodiorite on the other. This depression probably represents a fault or shear zone. Contacts with other plutonic rocks were not exposed in the map-area. Several granodiorite dykes, up to 1 m in width were seen cutting Unit 5 in the southeastern section of the map-area. This unit i s distinguished from the other plutonic rocks by anhedral patches of medium salmon pink perthite which interrupts the monotony of a pale grey-green, medium grained, leucocratic granitic rock (Figure 2.43). This potassium feldspar comprises approximately one f i f t h of the rock (Table 2.6). Biotite i s the only primary mafic mineral and generally is 75 Figure 2.43 Slabbed surface of massive granodiorite (Unit 6c). From an outcrop 50 m east of the contact with Unit 5 at the northern t i p of Unit 6c (Map 1). Rock has a g r a n i t i c texture with quartz ( l i g h t gray), plagioclase (white), p e r t h i t e (pink), c h l o r i t e (black) and epidote (green) comprising most of the rock. Figure 2.44 Photomicrograph of granodiorite (Unit 6c). Same l o c a t i o n as Figure 2.43. A l t e r a t i o n i s s l i g h t and comparable to that of Unit 6a. (crossed n i c o l s ) 76 rimmed by minor amounts of c h l o r i t e . This c h l o r i t e occurs i n i r r e g u l a r randomly oriented masses. None of the minerals e x h i b i t a preferred o r i e n -t a t i o n . A l t e r a t i o n . i s low to moderate wit h i n t h i s unit as evidenced by the minerals and modes presented i n Table 2.6. S a u s s u r i t i z a t i o n and a l b i t i -z a t ion have occurred i n p l a g i o c l a s e whereas clay minerals and s e r i c i t e are present i n p e r t h i t e (Figure 2.44). B i o t i t e l a t h s are s l i g h t l y bent and quartz has an undulatory e x t i n c t i o n i n d i c a t i n g that the rock has undergone some s t r e s s . Mode of emplacement of the granodiorite i s assumed to be i d e n t i c a l to other p l u t o n i c rocks previously described. The l i n e a r and well-defined nature of the contact with the pendant vo l c a n i c s implies that the grano-d i o r i t e might have been f a u l t emplaced. Relationships between the grano-d i o r i t e and other p l u t o n i c masses are impossible to determine since none of the contacts were exposed i n the map-area. 2.4 PLEISTOCENE TO TERTIARY ROCKS A separate sub-section f or each of the four Pleistocene to T e r t i a r y rock types recognized i n the map-area w i l l be described i n t h i s s e c t i o n . Ages of most of the units are uncertain so that they are presented i n order of r e l a t i v e abundance with the most abundant described f i r s t . F i e l d notes and v i s u a l estimates of the grain s i z e and mode of minerals present from t h i n - s e c t i o n provided the guidelines for the f i n a l rock name. The rock names are consistent with the work of Green (1977) and the c l a s s i f i c a t i o n schemes used by Strekeisen (1967) and Williams et a l . , (1954). 77 2.4.1 OLIVINE BASALT (UNIT 7A) Olivine basalt occurs in the central and southern regions of the map-area. These rocks have been described in detail by Green (1977) as part of a belt of olivine basalts within the Cheakamus River and Callaghan Creek valleys, which extend 22 k north from Garibaldi Station to Callaghan Lake. Green recognized the existence of several different flows. Here, only samples of the upper flow, exposed in the map-area, were examined. These flows are medium mauve-brown, vesicular, porphyritic and exhibit well defined columnar jointing. The base of this sequence is scoriaceous and commonly underlain by glacial t i l l . Smooth ropy surfaces, typical of pahoehoe basalts, were seen at the top of some of the flows (Figure 2.45). Vesicles comprise less than 10% of the rock (Table 2.7). Subhedral clasts of zoned plagioclase (An._ to An__), averaging 2 by 3 mm , are ran-4 J OU domly oriented and give the rock a porphyritic appearance. These clasts compose about 5% of the unit, while unzoned, euhedral plagioclase laths (An^Q to An^,.), averaging 0.2 by 0.8 mm , comprise another 10% (Figure 2.46). Less than 1% of these plagioclase grains form glomeroporphyritic aggregates. Anhedral crystals of olivine, averaging 0.6 mm in diameter constitute ap-proximately 13% of the rock. In some cases, these are large enough to give hand specimens a porphyritic appearance. Less than one-half percent of the olivine phenocrysts show evidence of zonation. Matrix consists of randomly oriented euhedral laths of plagioclase (An^Q to An^p), averaging 0.01 by 0.06 mm , with anhedral crystals of olivine, opaque grains and augite, about 0.01 mm in diameter. Olivine basalts i n the map-area are part of a thicker sequence of olivine basalt flows (Green, 1977). These flows occurred contemporaneously with the recession of continental ice sheets. A C ^ date of 34,200 years 78 Figure 2.45 Ropy surface of o l i v i n e b asalt (Unit 7a). Specimen from an outcrop along the eastern bank of Callaghan Creek d i r e c t l y west of Northair Mines (Map 1). Figure 2.46 Photomicrograph of o l i v i n e basalt (Unit 7a). Same l o c a t i o n as Figure 2.45. Large anhedral c r y s t a l s of o l i v i n e (pink, yellow, dark blue) and subhedral laths of l a b r a d o r i t e are cemented i n a f i n e r grained groundmass, pr i m a r i l y composed of andesine. (crossed n i c o l s ) TABLE 2.7 VISUAL ESTIMATES OF MINERAL MODES-Units 7a, 7b, 7c and 7d (Percentages:maximum-minimum/average) Unit 7a Unit 7b Unit 7c Olivine Equigranular Porphyritic Basalt Rhyodacite Rhyodacite Phenocrysts Plagioclase 1 5 / 1 5 Olivine 13-8 / l l Sanidine Quartz B i o t i t e Opaques Groundmass Plagioclase 35 / 35 c Olivine 20-17 / 18 Opaques 10 / 10 Augite 5-A / 5 Gas Cavities 10-3 / 6 Quartz B i o t i t e Carbonate Chlorite Sanidine Feldspar-quartz S e r i c i t e Number of thin-sections 2 22-18 / 20 4-0 / 2 52-45 / 49 6-2 / 4 10-0 / 5 25-15 / 20 20-16 / 19 15-0 / 7 13-10 / 11 7-0 / 4 1-0 /trace 15-0 / 5 e 1-0 /trace 50-0 / 19 2-0 / 1 44-0 / 29 8-2 / 5 3 Unit 7d E p i c l a s t i c Breccia matrix 20 / 20 14-10 / 12 10 / 10 5 / 5 35-28 / 32 23-20 / 21 2 U3 a; An 6 Q-An 4 5/An 5 2 f; An2g-An2/An^ b; An 1 4-An g/An 1 0 c; An 4 0-An 3 0/An 3 5 d; An i g-An 6/An 1 6 g;Identification impossible due to small grain s i z e . e; An l g-An 1 0/An 1 6 80 before present was obtained on pieces of wood trapped in the flows (Green, 1977) . 2.4.2 EQUIGRANULAR RHYODACITE (UNIT 7B) Equigranular rhyodacite occurs primarily as elongate north-south pods and less commonly as overlying blankets on the paleo-surface of pendant and plutonic rocks throughout the map-area. These pods occur in surface depres-sions and probably represent the surface expression of dykes f i l l i n g f i s -sures within both the volcanic and plutonic rocks. Regional f o l i a t i o n i s absent although sparsely spaced fractures occur throughout this unit forming cube-shaped blocks, 30 cm. on each side, of rhyodacite. In fresh and weathered surfaces, the rhyodacite i s pale pink to tan, fine grained to aphanitic and equigranular (Figure 2.47). Granophyric intergrowths of two minerals form crude spherules, averaging 0.4 mm in diameter, scattered throughout this unit . (Figure 2.48). These spherules might represent the remains of mineral grains which reacted with the sur-rounding magma. Quartz also occurs as anhedral blebs, averaging 0.01 mm in diameter, surrounding the spherules. Sanidine, albite, biotite, opaques minerals and trace amounts of carbonate (Table 2.7) also occur around the spherules as anhedral blebs slightly smaller than quartz. None of the elongate minerals show any evidence of a preferred orientation. In the v i c i n i t y of the Van Silver m i l l s i t e this unit has been brec-ciated and cemented by quartz bands (Figure 2.49). The rhyodacite frag-ments no longer have any plagioclase becasue they have been replaced by masses of randomly oriented seri c i t e and quartz. This alteration suggests that the quartz bands are actually veins. The bulk of this unit, however, does not show any evidence of alteration. Some of the biotite books are slightly bent i n d i c a t i n g that the SI Figure 2.47 Freshly broken surface of massive, blocky equigranular rhyodacite (Unit 7b). From an area on the eastern side of Callaghan Creek where Unit 7b crosses Northair Mines access road (Map 1). Figure 2.48 Photomicrograph of equigranular rhyodacite (Unit 7b). Same l o c a t i o n as Figure 2.47. Rock has a uniform texture except for a c r y s t a l of quartz, j u s t l e f t of centre, which has a reaction rim. (crossed n i c o l s ) 82 Figure 2.49 Photomicrograph of flow banding in equigranular rhyodacite (Unit 7b). From hte southernmost pod of Unit 7b, in the immediate vic i n i t y of Van Silver m i l l s i t e (Map 1). Specimen was taken near the perimeter of the rhyodacite pod. (crossed nicols) 83 mineral has undergone some strain after crystallization. Underground wor-kings in the Northair mine-area have encountered equigranular rhyodacite cutting andesitic agglomerate. These dykes have two types of contacts which are not mutually exclusive. F i r s t , there i s a well sheared contact which has a dark grey-green glassy appearance extending an average of 30 cm. into the volcanics. This glassy material contains flakes of biotite oriented par a l l e l to: the shearing. Away from the dyke the shearing decreases in inten-tensity but may s t i l l be v i s i b l e up to 5 cm. distance, although the shear zone generally averages 1 m. in idth. The second type of contact also has a slightly sheared halo around the dyke but has a banded or layered appear-ance within the dyke which is conformable with the contact. This layering may be present in the other type of contact but i t is never as well devel-oped as in this second type. Quartz-rich bands primarily contain quartz, whereas the other bands are identical to the rhyodacite in composition. Both contacts of the rhyodacite may contain angular fragments of the host rock, usually containing euhedral cubs of pyrite, which may vary up to 5 mm. in diameter. The fragments can vary up to many metres in diameter. Of the several dyke contacts observed there appears to be no definite position,, relative to the dyke, in which one type of contact appears. Grove (1974) took a sample from the Northair mine-area, which he interpreted as a "rhyolite glass", and obtained a whole rock K-Ar date of about 18 m.y. Detailed study of the mine-area shows that this glassy material i s part of a shear zone cross-cutting stratigraphy. Hand specimens of this glass-looking material at the pendant-dyke contact described earlier in this section. It i s therefore proposed that the date represents the age of shearing and and also maximum age of rhyodacite intrusion, since the dykes appear exploit weakness in the shear zones. 84 The types of contacts, presence of bent biotite and fracturing suggests a moderately forceful injection at low pressures for the rhyodacite. Presence of dykes leading up to blankets of rhyodacite exhibiting cubical fracturing also indicates that the paleo-surface on which the rhyo-dacite was deposited is very close to or the same as the surface existing at the present time. 2.4.3 PORPHYRITIC RHYODACITE (UNIT 7C) Porphyritic rhyodacite is sparsely scattered throughout the map-area and occurs as elongate pods. None of this material was seen cross-cutting any other lithologic units. This unit shows no evidence of regional f o l i a -tion but has sparsely-spaced fracture sets which create cubical blocks. This unit is pale pink to tan in fresh and weathered surface (Figure 2.50). It consists of an aphanitic groundmass of minerals (Table 2.7) with phenocrysts of quartz, plagioclase (average An.^) > sanidine and biotite (Figure 2.51). The phenocrysts comprise about 50% of the rock. Quartz phenocrysts occur as rounded eyes occasionally exhibiting a pseudohexagonal form. Plagioclase is zoned, subhedral and averages 0.8 by 1.6 mm., where-as sanidine is anhedral and averages 0.8 mm. in diameter. Sanidine, and rarely quartz, phenocrysts have a cloudy intergrowth of minerals forming rinds, averaging 0.05 mm. in width. These rinds are interpreted to re-present reaction of the phenocrysts with the surrounding groundmass. Biotite occurs in subhedral books, averaging 0.1 mm. in thickness and 0.8 mm. in diameter, some of which are bent. None of these phenocrysts shows any evidence of alignment. Porphyritic rhyodacite is assumed to have formed in a similar manner to that of the equigranular rhyodacite as they have similar megascopic at-tributes. This unit was seen directly overlying equigranular rhyodacite 85 Figure 2.50 Broken surface of massive p o r p h y r i t i c rhyodacite (Unit 7c). From the same l o c a t i o n as Figure 2.47. Figure 2.51 Photomicrograph of p o r p h y r i t i c rhyodacite (Unit 7c). Same specimen as Figure 2.50. Quartz phenocrysts (white, r i g h t side of photo) have a p a r t i a l l y resorbed boundary. Phenocrysts of plagioclase (top centre), orthoclase ( l e f t of centre) and b i o t i t e books (lower section) along with quartz form phenocrysts i n this unit.(crossed n i c o l s ) 86 indicating i t may be slightly younger. 2.4.4 EPICLASTIC BRECCIA (UNIT 7D) Epiclastic breccia occurs as one isolated pod in the southwestern sec-tion of the map-area.' It is cut by an equigranular rhyodacite dyke. The regional f o l i a t i o n i s conspicuously absent. Matrix is dark grey to black and aphanitic, constituting an average of approximately forty percent of ;the .rock .(Figure 2.52). Jagged, anhedral quartz clasts, averaging 1.0 mm in diameter, comprise up to 5% of the matrix. These clasts plus other small l i t h i c fragments five the matrix a gritty ap-pearance. Other minerals in the matrix, averaging less than 0.002 mm in maximum dimension, form anhedral grains grouped into irregular masses (Table 2.7). Fragments are subangular to angular and are composed of quartz diorite (60%) and basalt (40%). Quartz diorite fragments are identical to the quartz diorite of Unit 6a while the basalt fragments are similar to the basalt of Unit 7a. Basalt fragments d i f f e r s l i g h t l y from those of Unit 7a in that they have no large phenocrysts. This unit represents a Pleistocene to Tertiary epiclastic event. 2.5 SUMMARY Callaghan Creek pendant i s one of many northwesterly trending volcanic and volcanic-sedimentary pendants within the southern part of the Coast Plutonic Complex. The study-area was of the central section of this pen-dant. Five main units were recognized i n the map-area, some of which were further subdivided into less continuous sub-units. Surrounding plutonic rocks and overlying and cross-cutting Pleistocene to Tertiary rocks were also recognized and described. 87 Figure 2.52 Weathered surface of e p i c l a s t i c b r e c c i a (Unit 7d). From the only occurrence of Unit 7d, which i s on the west side of Callaghan Creek. White fragments are quartz d i o r i t e while the darker c l a s t s are b a s a l t . 88 Total apparent thickness of the Callaghan Creek pendant rocks is in ex-cess of 5,000 m (16,000 feet), assuming that no significant repetitions oc-cur in the sequence. This apparent homoclinal sequence generally strikes northerly with a vertical dip and "stratigraphic tops" to the east. Table 2.8 is a general summary of the relationships discovered in the study of the Callaghan Creek pendant. Formation names and associated thick-nesses have been taken from Roddick (1965). 89 TABLE 2.8 SUMMARY OF LITHOLOGIES Era Period or Epoch Formation and Thickness Unit Lithology Pleistocene |Garibaldi Group and Recent \ 700 m. 7a Olivine basalt Cenozoic Tertiary to Pleistocene Contact relations not known Possibly in part Garibaldi Group 7b, 7c, and 7d Equigranular and porphyritic rhyo-dacite, epiclastic breccia Unconformably overlies and intrudes pendant and plutonic rocks 6a, 6b,iQuartz diorite with and 6c \minor diorite, 'hornblende diorite |with minor hornblende jquartz diorite, 'granodiorite Unconformable (?) ; fault, intrusive Gambier Group 2000+ m. ,5, 5a, 15b, and ;5c Andesitic agglomerate, epiclastic breccia, arkosic wacke and mudstone, andesitic • crystal tuff Mesozoic Upper Jurassic to Cretaceous Conformably overlies Gambier Group 4, 4a, ; Dacitic agglomerate, 4b, and|siltstone and arkosic 4c -wacke Intercalated and conformably overlying Gambier Group •Andesitic crystal ;tuff Conformably overlying Gambier Group iAndesitic agglomerate Contact relations not known Gambier Group 11 and ; l a !Greens tone, minor i limestone and chert 90 CHAPTER 3  MINERAL OCCURRENCES 3•1 INTRODUCTION Five areas containing mineral occurrences were outlined, based on 1977 f i e l d mapping (Figure 3.1). Each of these areas w i l l be dealt with separ-ately in the following sections. The Northair property w i l l be examined in more detail since more time was spent in that area than the others. 3.2 MINERAL OCCURRENCES IN THE VAN SILVER EXPLORATIONS LIMITED AREA Of the five mineral occurrences seen in the map-area four of these oc-cur in the Van Silver property. These four occurrences w i l l be dealt with in order; Tedi Pit, Silver Tunnel, M i l l s i t e and Zone 4. 3.2.1 TEDI PIT SHOWING Tedi Pit mineral occurrence i s a small isolated patch of greenstone (Unit 1) within the Coast Plutonic Complex (Figure 3.2). This patch is i n -terpreted as part of the Callaghan Creek pendant since no apparent uncon-formity exists between Tedi Pit and the defined Callaghan Creek roof pen-t, dant. Rocks in the Tedi Pit area are moderately foliated and altered leaving no megascopic features indicative of i t s primary origin. As mentioned pre-viously, the rocks of Unit 1, based on thin-section modal analysis, were probably andesites. In Figure 3.2 there i s a small tadpole-shaped pod labelled "dacitic greenstone". This pod was not put on the larger map or described in the section on lithologic units in the Callaghan Creek pen-dant because of i t s small size. Also, the mineralogy is comparable to the 9 1 Figure 3.2 Detailed geological map of the Tedi Pit mineral occurrence. 93 greenstone, except an increase in quartz content, from 19 to 26%, and de-crease in chlorite, epidote and opaque mineral content. Therefore this com-position was assumed to be close to that of dacite. The strike of the da-cite greenstone and greenstone contact is approximately 170 degrees with a variable dip from 15° to 80° to the northeast. This orientation, however, is not very good because of poor contact exposure. The strike direction generally agrees with orientations obtained in the pendant rocks east of Tedi Pit but the dip i s shallower. The dacitic greenstone does not have as strong a f o l i a t i o n development as the greenstone. This makes this unit appear quite cometent and fresh . compared to Unit 1. 3.2.1.1 Mineralogy and Textures Mineralization at Tedi Pit has three main modes of occurrence: dis-seminated, banded (massive sulphides) and vein. The primary opaque minerals observed in polished section are, in decreasing order of abundance: pyrite, sphalerite, galena, chalcopyrite, tetrahedrite, argentite, electrum, bornite and ruby s i l v e r . Secondary chalcocite and covellite were also seen in polished section. Chalcocite is more abundant than tetrahedrite while cove-l l i t e is slightly less abundant than tetrahedrite. Pyrite is slightly more abundant relative to the other sulphides in the disseminated occurrences. Sulphides are concentrated in the greenstone, with only minor amounts of disseminated pyrite and gangue-sulphide veins in the dacitic greenstone. This suggests that economically important sulphides were originally con-centrated i n the greenstone and only remobilized, by veining, into the overlying dacitic greenstone. Pyrite i s ubiquitous through a l l three modes of mineral occurrence as anhedral to euhedral grains. Minor amounts of chalcopyrite, spahalerite, 94 gangue and, rarely, galena form anhedral inclusions within pyrite. Isolated, brecciated masses of pyrite appear to be cemented by galena, gangue minerals, and minor chalcopyrite and sphalerite. Sphalerite generally forms anhedral masses and occassionally minute disseminated anhedral blebs within gangue mineral grains. Sphalerite micro-vienlets, averaging less than 0.01 mm in width, were seen cutting chalco-pyrite, pyrite and gangue minerals. Exsolution blebs of chalcopyrite form both emulsion and crystallographic textures within the sphalerite. Defor-mation twinning is very common in the sphalerite and may locally have elon-gate exsolution laths of chalcopyrite along twin planes. Sparse, rounded, anhedral exsolution blebs of tetrahedrite were observed within sphalerite. Anhedral inclusions" of pyrite, chalcopyrite, galena and gangue minerals occur within sphalerite. Galena primarily occurs as anhedral masses which may be i n t e r s t i t i a l to gangue and pyrite, sphalerite or chalcopyrite but more usually galena occurs i n t e r s t i t i a l l y to these other minerals. Micro-veinlets (less than 0.01 mm in width) of galena were observed cross-cutting chalcopyrite, sphalerite and gangue. Galena has corroded and replaced pyrite, sphalerite and chal-. copyrite along grain boundaries and fractures producing jagged "tongues" of galena intruding upon these other sulphides. Sphalerite i s also replaced by galena along twin planes which may produce a well developed caries tex-ture. Bands of massive galena locally exhibit an internal banding caused by gneissic galena development. Also i n other areas where the galena i s not gneissic or massive, galena may have curved cleavage traces (Figure 3.3). Chalcopyrite occurs as anhedral masses, ordinarily i n t e r s t i t i a l to the other minerals, and as emulsion blebs and exsolution laths exhibiting a cry-stallographic texture in sphalerite. One small grain of bornite was seen 95 96 in contact with sphalerite and contained minute crystallographically oriented laths of chalcopyrite. Chalcopyrite is cut by microveinlets of secondary chalcocite (less than 0.01 mm in width) which may contain intermittent patches of randomly oriented covellite laths. Chalcopyrite locally has grain boundaries replaced by chalcocite which can contain covellite. This latter occurrence of chalcocite may exhibit a crude flame-like texture with chalcopyrite. Jagged "tongues" of chalcopyrite intrude and replace galena, pyrite and sphalerite along grain boundaries. This replacement results in a poorly developed caries texture. Deformation twins are not abundant but are common within chalcopyrite grains especially in massive sulphides. Tetrahedrite occurs as rounded exsolution blebs, averaging less than 0.01 mm in diameter within sphalerite and galena. It also forms mutual boundaries with chalcopyrite, pyrite and gangue. Argentite was seen in mutual contact with galena, sphalerite, chalco-pyrite and gangue minerals. Irregular blebs of electrum occur within the argentite and possibly are the result of exsolution. Electrum is in mutual contact with gaiena, sphalerite and gangue. Bornite occured as one rounded bleb within sphalerite in mutual con-tact with and containing exsolution lathes of chalcopyrite. The chalco-pyrite grain also contained exolution lathes of bornite crystallographically intergrown near the grain contact with bornite. Ruby sil v e r , chalcocite and covellite occur in trace amounts. Ruby silver occurred as one isolated grain in mutual contact with galena and gangue. Secondary chalcocite replaced chalcopyrite along grain boundaries and fractures. Covellite occurred in contact with chalcocite but was never seen in contact with any other opaque mineral. 9 7 3.2.1.2 Paragenesis Curved and rhombic cleavage traces in galena, deformation twinning in sphalerite and chalcopyrite and brecciated pyrite a l l suggest mechanical de-formation of the sulphides. The presence of galena, chalcopyrite and to a lesser degree, sphalerite, as a cement for brecciated pyrite grains probably indicates recrystallization and/or remobilization of these minerals. Galena forms a large number of replacement "tongues" and micro-veinlets in chalcopyrite and sphalerite. Chalcopyrite exhibits these features to a lesser degree in galena and sphalerite with very minor occurrences of sphalerite micro-veinlets cutting chalcopyrite. These features would be consistent with remobilization since galena is more readily remobilized than chalcopyrite and chalcopyrite is more readily mobilized than sphalerite under similar conditions ( G i l l , 1970). A grain of chalcopyrite containing minor amounts of galena cut by a veinlet of gangue and completely surrounded by galena was seen in polished section. Both the chalcopyrite grain and surrounding galena were cut by a gangue veinlet. These features further suggest remobilization. In veins the paragenetic sequence appears to be, from f i r s t to last: pyrite, sphalerite, galena and chalcopyrite. Tetrahedrite seems to be an exsolution product of galena. This paragenetic only represents the result of chemical remobilization of pre-existing sulphides. Minor secondary mineralization is locally present as chalcocite vein-lets and blebs replacing chalcopyrite. Covellite occurs within chalcocite and appears to replace only chalcocite. Sulphide layers i n banded ores may be thin, less than 1 mm . in width, to massive and are always parallel to the fol i a t i o n and compositional banding of the host rocks. Compositional banding and sulphide layers cru-98 dely par a l l e l one another around folds. This suggests either that the sul-phides are syngenetic in origin or that this area has been subjected to a complex history of deformation. For example, only one general direction of f o l i a t i o n i s apparent in the f i e l d and the foliation planes show no evi-dence of further deformation which would at least crenulate the f o l i a t i o n plane. 3.2.1.3 Thermal Regime Pyrite and sphalerite can only be i n equilibrium below 740°C (Stanton, 1972) and similarly chalcopyrite and pyrite can only be in equilibrium be-low 739°C (Yund and Kullerud, 1966). Galena and pyrite are in equilibrium-only below 716°C, but the presence of contaminants such as zinc (sphalerite) can depress this temperature to below 700°C (Brett and Kullerud, 1967). The presence of tetrahedrite and argentite in galena is indicative of tem-peratures above 350°-400°C (Hall and Czamanske, 1972). Hall and Czamanske (1972) also showed that minerals rich in silver and antimony form a solid solution in galena above these temperatures. The temperature imposed by these relationships probably represents a temperature above which most of the sulphides formed after remobilization. Bornite was seen with exsolution lathes of chalcopyrite and vice versa. This indicates that temperatures at this time of deposition were above 400°C (Brett, 1964). A l l of the above evidence from sulphide minerals suggests that tem-peratures of equilibriation from the remobilizing event were less than 700°C but more than 400°C, which is consistent with the proposed metamorphic grade of the pendant rocks. 3.2.2 SILVER TUNNEL SHOWING Silver Tunnel occurs within well sheared greenstone (Unit 1), pro-99 bably andesitic in composition (Figure 3.4). A dyke of equigranular rhyo-dacite, previously called a " f e l s i t e " in property reports by Van Silver Explorations Ltd., is in the area and is oriented approximately parallel to the regional north-south, vertical f o l i a t i o n . This dyke averages about 1 m and is shown in Figure 3.4, based totally on underground work and d r i l l holes done by Van Silver Explorations Ltd. Within the greenstone are local small outcrops of plutonic rocks which were not mapped out due to limitations in time and outcrop. 3.2.2.1 Mineralogy and Textures Opaque minerals primarily occur as veinlets cross-cutting the rhyo-dacite dyke or greenstone, as disseminations and as i n t e r s t i t i a l to massive sulphides loc a l l y banded parallel to the f o l i a t i o n . Van Silver Explorations Ltd. reports on the area state that mineral values are very erratic. Gen-erally economically important concentrations of sulphides are present in and within 50 m of the rhyodacite dyke. Pyrite, sphalerite, galena, chalcopyrite, magnetite, hematite and tetrahedrite were the only opaque minerals seen i n polished secti on. This l i s t of minerals is in their re-lative order of abundance, with the most abundant mineral pyrite li s t e d f i r s t . Pyrite occurs as anhedral to subhedral grains which may be locally brec-ciated and cemented by gangue minerals. Sphalerite, chalcopyrite, galena and tetrahedrite replace pyrite along fractures and grain boundaries. Pyrite i s the only opaque mineral within the rhyodacite dyke where i t oc-curs disseminated throughout and minute anhedral grains, averaging less than 0.02 mm in diameter. Within veins cross-cutting greenstone pyrite may loc a l l y be concentrated along the selvege. Inclusions of gangue minerals and rarely other sulphides occur within the pyrite. Inclusions 100 Figure 3.4 Detailed geological map of the Silver Tunnel mineral occurrence. 101 of other sulphides were not seen within the disseminated pyrite of the rhyodacite dyke. Sphalerite occurs as anhedral masses which exhibits strongly developed deformation twinning except in veins where the twinning is weak to absent. Chalcopyrite, galena and tetrahedrite replace sphalerite along grain boundaries and twin planes. Caries texture i s well developed between galena and sphalerite. Inclusions of other sulphides, comprising less than 1% of the sphalerite grains observed, and trace amounts of chalcopyrite in emulsion and crystallographic textures with sphalerite were seen in p o l i -shed section. Galena occurs as anhedral grains usually i n t e r s t i t i a l to the other opaque and gangue minerals. Five percent of the galena grains observed were composed of gangue and other sulphide inclusions. Tetrahedrite re-places galena along grain boundaries. Chalcopyrite primarily occurs as anhedral blebs in sphalerite and grains i n t e r s t i t i a l to pyrite, gangue minerals and sphalerite. Trace a-mounts of chalcopyrite occur as grains in a crystallographic and emulsion texture with sphalerite. Many of the chalcopyrite lathes forming the cry-stallographic texture are paral l e l to twin planes in sphalerite. Galena replaces chalcopyrite along grain boundaries. Magnetite and hematite were seen only in sulphide deficient gangue veins which were cross-cutting greenstone although some of these veins may contain jagged patches of sulphides. Magnetite occurs as anhedral, brec-ciated grains which are cemented by gangue minerals and, rarely, sphalerite. Anhedral inclusions of gangue minerals also occur in magnetite. Minute anhedral grains of hematite replace magnetite along fractures and grain boundaries. The lack of association between sulphides and magnetite-hema-tit e possibly suggests that they are the result of a different event than 102 the sulphides. Tetrahedrite occurs as anhedral blebs which are in mutual contact with pyrite, sphalerite, chalcopyrite and galena. 3.2.2.2 Paragenesis Pyrite was probably the f i r s t sulphide to form since i t is replaced by a l l the other sulphides and locally is brecciated. None of the other sul-phides are brecciated. Sphalerite is replaced by chalcopyrite, galena and tetrahedrite which means that i t probably formed second. Deformation twinning was only observed in sphalerite which also supports the positioning of sphalerite in this paragenetic sequence. Chalcopyrite formed after sphalerite which was followed by galena and then tetrahedrite, the posi-tioning being based on replacement relationships. Mutual inclusions of each mineral in each other mineral suggests that there is overlap in the formation of these minerals. This paragenetic sequence is not envisaged as the primary deposition of the sulphides but rather the sequence of the sulphides formation in re-sponse to remobilization. The presence of brecciated pyrite and twinned sphalerite plus the presence of these sulphides as patches strung-out para-l l e l to the fo l i a t i o n indicates that they have been strongly deformed. Cross-cutting veins with identical paragenetic sequences also suggest that the veins are remobilized products of original sulphides. Magnetite and hematite are d i f f i c u l t to position in the paragenetic sequence since they were only seen in contact with sphalerite. It should be noted that this sphalerite was untwinned. From the replacement relationships magnetite formed prior to both hematite and sphalerite. The exact relationship between hematite and sphalerite is unknown since they were never seen in contact with one another. In general, magnetite must 103 have formed prior to at least some part of the sphalerite formation and pos-sibly even as a completely separate early event prior to the formation of pyrite. 3.2.2.3 Thermal Regime The thermal regime envisaged for the Silver Tunnel mineral occurrence is similar to that of Tedi P i t . Thermal constraints of pyrite-sphalerite (Stanton, 1972), pyrite-chalcopyrite (Yund and Kullerud, 1966), galena-pyrite (Brett and Kullerud, 1967) and tetrahedrite-galena (Hall and Czamanske, 1972) a l l apply to the Silver Tunnel area. These constraints then suggest a temperature between 700°C and 400°C during remobilization. 3.2.3 MILLSITE SHOWINGS Most of the m i l l s i t e area is within greenstone (Unit 1) with patches of diorite of Unit 6a scattered throughout. One of these patches is out-lined in Figure 3.5. The greenstone i s strongly sheared with a north-south, approximately v e r t i c a l orientation. Several equigranular rhyodacite dykes, averaging less than 30 cm in width, are oriented parallel to this f o l i a -tion and are shown in Figure 3.5. Several different types of mineral occurrences were recognized in the m i l l s i t e area. Each of these w i i l be dealt with separately and then re-lationships between them w i l l be summarized at the end. The occurrences can be divided into four separate types, which are; 1/ stockwork-type copper mineralization with hornblende diorite (128 + 4 Ma; details in Appendix C), 2/ chalcopyrite-bearing veins cross-cutting greenstone, 3/ hematite-bearing cross-cutting greenstone, 4/ sphalerite and galena-bearing veins and stringers oriented parallel 104 Figure 3.5 Detailed geological map of the M i l l s i t e mineral occurrences. 105 to the f o l i a t i o n . 3.2.3.1 Stockwork-type Mineralization Mineralization occurs within a nose of hornblende diorite (Unit 6b) which i s completely surrounded by greenstone (Unit 1). Fractures criss-cross the host rock at various orientations with an average spacing of 20 cm. These fractures are primarily f i l l e d with epidote, minor amounts of quartz and carbonate and opaque minerals. Opaque minerals are concentrated in discontinuous bands near the selvage of the vein. Pyrite is the most abundant opaque mineral. This mineral usually occurs within the veins as bands and disseminations, but also occurs as disseminations within the host rock. The pyrite grains are anhedral and are brecciated locally within the vein. Chalcopyrite and gangue minerals cement the brecciated pyrite grains. Anhedral inclusions of gangue were seen in most pyrite grains. Chalcopyrite was the only other opaque mineral seen in polished sec-tion. This mineral was only seen in the veins as anhedral masses which usually formed crude bands near the selvage of the vein. Chalcopyrite re-places pyrite along fractures and grain boundaries. Gangue minerals formed prior to pyrite in the hornblende diorite. The veins were then introduced with brecciated pyrite being incorporated from the host rock and also being formed in the vein simultaneously with other gangue minerals. Formation of chalcopyrite followed by the for-mation of more gangue minerals then completed the stockwork-type mineral-ization event. 3.2.3.2 Chalcopyrite-bearing Veins Several chalcopyrite-bearing veins were seen within greenstone (Unit 1) 106 in the central region of the millsite area (Figure 3.5). These veins cut across the foliation at various angles and average 8 cm in width with chalcopyrite comprising 20% of the vein and gangue minerals the remainder. Coarsely crystalline quartz is the major component of these veins; white calcite, chlorite and potassium feldspar comprise the rest of the gangue minerals. Chalcopyrite plus carbonate, chlorite and potassium feldspar occur in sporadic patches usually near the vein selvage, and show no ap-parent inter-relationship with one another in their occurrence. Potassium feldspar is graphically intergrown with quartz. Chalcopyrite is the most abundant opaque mineral in these veins. It generally occurs as anhedral inclusions in pyrite and as massive clots within the vein. Minor amounts of disseminated chalcopyrite occur entirely within host rock clasts in the vein. However, the massive chalcopyrite, is not restricted in this way. Gangue veinlets transect massive chal-copyrite, averaging less than 1 mm in width, but show no definite trend in orientation. Trace amounts of finely disseminated chalcopyrite and sphalerite occur within these cross-cutting veinlets. Chalcopyrite with-in pyrite occurs as anhedral inclusions; chalcopyrite can also contain trace amounts of gangue inclusions. Pyrite i s the second most abundant opaque mineral in these veins. This mineral occurs in trace amounts as anhedral inclusions within chal-copyrite and as fine disseminations in the vein. Pyrite in the vein is anhedral and restricted to host rock clasts within the vein. Rare inclu-sions of gangue minerals occur scattered throughout most of the pyrite grains observed. Hematite, in trace amounts, locally has replaced some of the dissemi-nations and massive chalcopyrite along fractures and pyrite-chalcopyrite 107 boundaries. Hematite occurs as anhedral patches. Trace amounts of chalco-cite and covellite may interupt hematite and form fine layers between chal-copyrite and hematite. Covellite occurs as very fine irregularly oriented laths within the chalcocite. Chalcocite has completely replaced some chal-copyrite grains. Some of the chalcocite layers and grains have been re-placed by covellite along grain boundaries. Hematite, chalcocite and covel-l i t e are a l l thought to be secondary minerals. Chalcopyrite probably formed slightly after pyrite since chalcopyrite has replaced pyrite locally. The gangue minerals of the vein formed prior to and later than both of these sulphides. The secondary minerals formed in approximately this order, from f i r s t to last: hematite, chalcocite and covel l i t e . Overlap in these minerals formation with one another i s prob-able . 3.2.3.3 Hematite Veins Two hematite veins were seen in the northeastern section of the m i l l -site map-area within the greenstone (Figure 3.5). These veins were cross-cutting the fo l i a t i o n and average 5 cm in width. Coarse grained quartz with minor patches of chlorite and carbonate comprise 99% of the vein. Hematite, the other 1%, is concentrated along vein selvages in sporadically spaced patches. Hematite is the major opaque mineral in these veins. It occurs primarily as elongate laths within and on the edge of host rock clasts within the vein. Some of these laths form p a r t i a l radiating rosettes on the edge of the host rock. Minor amounts of hematite occur as laths on the edge of pyrite and chalcopyrite grains and occassionally form anhedral patches along fractures in pyrite and rinds around pyrite grains. 108 Trace amounts of pyrite, the next most abundant opaque mineral in these veins, i s the most abundant opaque mineral in the host rock. Pyrite in the host rock is finely disseminated and anhedral to subhedral in shape, but pyrite within the vein is sparsely disseminated and anhedral in shape. In the host rock and host rock clasts within the vein pyrite is replaced by chalcopyrite along fractures and grain boundaries. A l l of the pyrite grains observed contained trace amounts of anhedral inclusions of gangue minerals. Chalcopyrite i s the only other opaque mineral in the vein and host rock. The grains are anhedral and trace amounts are disseminated through-out the vein and host rock. Most of the chalcopyrite is within host rock or host rock clasts within the vein. A l l of the chalcopyrite grains ob-served contained minor amounts of anhedral inclusions of gangue minerals. Hematite must have formed later than chalcopyrite and pyrite, pos-sibly related to the later stages of the veining event. Pyrite formed prior to chalcopyrite in the host rock and has this same relationship in the vein. Both of the sulphides may have formed early in the veining event than hematite or are possibly even foreign clasts incorporated from the host rock. 3.2.3.4 Sphalerite and Galena-bearing Veins and Stringers Sphalerite and galena-bearing veins and stringers occur in well sheared greenstone (Unit 1), similar to the mineralized greenstone at S i l -ver Tunnel. This type of mineralization was never seen in unsheared, com-penent greenstone. In general the veins and stringers occur southeast of the hornblende diorite pod containing porphyry mineralization. Veins are sub-parallel to the fo l i a t i o n and are composed primarily of sphalerite and pyrite (Figure 3.6). Minor amounts of quartz, chlorite 109 Figure 3.6 Sph a l e r i t e - and p y r i t e - r i c h veins cross-cutting greenstone. 110 and carbonate also occur i n t e r s t i t i a l l y to the sulphides. Stringers always parallel the foliation but are erratic in their length and occurrence. About 80% of the stringers observed in the f i e l d were almost entirely composed of pyrite. Other stringers were composed of pyrite and sphalerite. Pyrite occurs as subhedral to anhedral grains in stringers and dis-seminated throughout the host rock. This mineral also occurs as anhedral grains concentrated near the vein selvage. A l l the other sulphides replace pyrite along fractures and grain boundaries. Inclusions of gangue minerals and minor amounts of sphalerite, chalcopyrite and galena inclusions occur within pyrite. Sphalerite occurs as anhedral masses scattered throughout the s t r i n -gers but may be concentrated along vein selvages. Chalcopyrite, galena and tetrahedrite are generally i n t e r s t i t i a l to sphalerite. Some chalcopy-r i t e grains, about 20% of that observed in polished section, occurs as emulsion blebs and rarely as crystallographic intergrowths in sphalerite. Sphalerite contains inclusions of a l l the sulphides except tetrahedrite. Deformation twinning i s conspicuous throughout a l l sphalerite grains ob-served. Chalcopyrite, galena and tetrahedrite replace sphalerite along fractures, grain boundaries and twin planes with galena and sphalerite exhibiting a well developed caries texture. Galena form i n t e r s t i t i a l grains which are anhedral in the stringers and anhedral to subhedral in the veins. Galena i s less abundant than chalcopyrite in the stringers. Inclusions of a l l the other sulphides oc-cur within galena. Bent cleavage traces, were observed in galena. Chalcopyrite occurs as i n t e r s t i t i a l anhedral masses to the other sul-phides and to a much lesser extent as emulsion blebs and crystallographic intergrowths in sphalerite. . Exsolution laths of chalcopyrite may form I l l along twin planes of sphalerite. Inclusions of a l l other sulphides occur within chalcopyrite. Irregular "tongues" of galena and tetrahedrite i n -trude and replace chalcopyrite along grain boundaries. Tetrahedrite occurs in veins and only in trace amounts within s t r i n -gers. Within the stringers and veins tetrahedrite occurs as anhedral blebs within galena and is in mutual contact with a l l the other sulphides. How-ever, i n the vein tetrahedrite can form anhedral masses containing i n -clusions of a l l the other sulphides. Along the perimeter of tetrahedrite, where i t is in contact with gangue minerals and rarely galena, minute grains of chalcopyrite may be present. In summary these minerals probably formed in the following order based on emplacement relationships in both the veins and stringers: pyrite, sphalerite, chalcopyrite, galena and tetrahedrite. Mutual inclusions of each mineral in each other mineral implies that there is overlap in this paragenetic sequence. 3.2.3.5 Summary Stockwork-type copper mineralization in the hornblende diorite (Unit 6b) was not seen in association with any of the other types of mine-r a l occurrences. A hematite vein was seen cross-cutting a chalcopyrite vein indicating that the hematite veins are younger. The strongly sheared volcanic rocks containing sphalerite and galena veins and stringers are not seen cross-cutting or being cross-cut by veins of hematite or chal-copyrite veins. However, gangue veins containing coarse grained quartz with minor calcite and chlorite were seen transecting the we l l sheared greenstone. Based on these observations i t i s proposed that the sphalerite-galena showings are the result of remobilization of sulphides previously e x i s t i n g 112 in the greenstone. The chalcopyrite and hematite veins also appear to be part of the remobilizing event. Chalcopyrite and pyrite i n the hornblende diorite may also contain re-mobilized opaque material. The K-Ar age date of 128 + 4 Ma on the horn-blende diorite containing the stockwork-type mineralizations indicates that this plutonic rock is similar in age to the pendant rocks. Therefore, i t seems lik e l y that the mineralizing event which formed the stockwork-type mineral occurrence was part of the remobilization event. 3.2.3. 6 Thermal Regime Thermal conditions envisaged for the M i l l s i t e showings cannot be re-lated to the mineralizing process prior to remobilization since remobili-zation has completely destroyed anything which can be recognized as part of the original mineralizing event or events. This means that the ther-mal event expounded upon in this section is only representative of the thermal conditions during remobilization or later processes. Stockwork-type copper mineralization occurs in epidote veinlets con-taining minor amounts of carbonate and traces of chlorite. This type of alteration veining has been characterized by Lowell and Gilbert (1970) within the propylitic zones of porphyry deposits. Temperatures which caused this alteration and deposition of opaque minerals are generally around 300°C. Assuming that this temperature is r e a l i s t i c and that the chalcopyrite veins in the greenstone are related to the porphyry copper mineralization, i t can be assumed that deposition for the chalcopyrite veins are around 300°C. Sphalerite-galena veins have sphalerite-pyrite (Stanton, 1972), galena-pyrite (Brett and Kullerud, 1967) and chalcopyrite-pyrite (Yund and Kullerud, 1966) which suggest that temperatures were l e s s than 700°C 113 at their time of deposition. The presence of tetrahedrite in galena is indicative of temperatures above 350-400°C (Hall and Czamanske, 1972). These temperatures mean that the sphalerite-galena veins were deposited between 700 and 350 to 400°C during the remobilization process. These temperature constraints are consistent with those of the Silver Tunnel and Tedi Pit mineral occurrences. 3.2.4 ZONE 4 Zone 4 mineral occurrence is entirely within a marble pod (Unit la) which i s surrounded by greenstone (Unit 1) on three sides and abutted on the east by quartz diorite (Unit 6a) (Figure 3.7). The mineralization i s concentrated i n the eastern half of the marble pod. Impure marble hori-zons which contain most of the ca l c - s i l i c a t e minerals such as diopside, tremoltie-actinolite, epidote and grossularite. These horizons contain most of the opaque minerals. The pure chert, marble and greenstone layers contain very minor amounts of cal c - s i l i c a t e and opaque minerals. 3.2.4.1 Mineralogy and Textures Generally, the opaque minerals occur in sporadic patches in or near the impure marble horizons. These opaque minerals w i l l be dealt with in their approximate order of relative abundance in the following paragraphs. The relative position of each of these minerals is based on f i e l d obser-vations and on examination of polished sections. Sphalerite forms anhedral masses, disseminations and patches within veins, greenstone and impure marble horizons. Within massive sphalerite, other sulphides such as chalcopyrite and galena occur i n t e r s t i t i a l l y . Anhedral inclusions of gangue minerals, galena, chalcopyrite, magnetite 114 Figure 3.7 Detailed geological map of the Zone 4 mineral occ entirely contained within Unit la. 115 and pyrite occur within sphalerite grains. Also rarely elongate laths of gangue minerals were seen protruding from the perimeter of sphalerite grains. Sphalerite forms elongate, irregular "tongues" which intrude and replace pyrite and magnetite along fractures. Pyrrhotite and chalcopyrite are replacing sphalerite along grain boundaries, locally showing a well developed caries texture and forming irregular intruding "tongues". Minor amounts of rounded exsolution blebs of chalcopyrite form emulsion tex-tures in sphalerite. Deformation twinning was also noted in some sphalerite grains. Magnetite occurs primarily within the greenstone-rich areas removed from where most of the other opaque minerals occur. This mineral occurs in veinlets and as disseminations in Zone 4. A l l of the magnetite is an-hedral and locally brecciated and cemented by gangue minerals. Discon-tinuous bands of brecciated magnetite were occassionally seen within the greenstone. Magnetite grains contain minor amounts of anhedral gangue inclusions. Pyrite, pyrrhotite, chalcopyrite and sphalerite replace magnetite along fractures and grain boundaries. Chalcopyrite occurs as anhedral grains which form disseminations in the gangue material and inclusions in galena, sphalerite, pyrrhotite and covellite. Less than 1% chalcopyrite occurs as exsolution blebs in sphalerite. Chalcopyrite contains inclusions of magnetite, pyrite, pyrrhotite, sphalerite, galena and gangue minerals. Elongate "tongues" of chalcopyrite intrude and replace sphalerite, pyrite and pyrrhotite along grain boundaries and fractures. Pyrrhotite occurs as anhedral masses containing inclusions of chal-copyrite, sphalerite, chalcopyrite, pyrite and gangue minerals but may also be cemented by these minerals. Some pyrite grains have shear and 116 tension gashes f i l l e d with gangue. Galena occurs as anhedral inclusions in sphalerite and may have mutual boundaries with chalcopyrite and pyrrhotite. Inclusions of argentite and electrum were seen on the perimeter of the galena inclusions (Figure 3.8). Covellite occurs as rounded anhedral blebs in late stage veinlets averaging less than 0.01 mm in width. Locally i t may replace chalcopy-r i t e along grain boundaries and may contain inclusions of chalcopyrite and gangue minerals. Argentite forms anhedral inclusions within galena and may have mutual boundaries with electrum, chalcopyrite, sphalerite and galena. Electrum occurs as anhedral blebs in argentite and has mutual con-tacts with galena, chalcopyrite, sphalerite and argentite. One speck of gold was identified tentatively. Elongate laths of gangue minerals occurred within sphalerite, chal-copyrite, pyrrhotite and covellite. These laths are conspicuously absent in pyrite and magnetite. 3.2.4.2 Paragenesis Lack of tremolite-actinolite and diopside laths in pyrite and magne-t i t e indicates that they formed prior to the deposition of the skarn minerals. Presence of crude magnetite bands in the greenstone also implies that some of the magnetite may have formed prior to the whole mineralizating event at part of the original deposition of the host rock. Based on replacement relationships, the f i r s t opaque mineral to form during the metasomatic event was magnetite, followed by pyrite and then sphalerite. This was followed by pyrrhotite and then chalcopyrite. Each of these sulphides contain inclusions of each other implying some 117 Figure 3.8 Galena (pale yellow) i n c l u s i o n has a myrmekitic boundary with s p h a l e r i t e (medium gray) and inclusions of argen-t i t e (pale gray) on ei t h e r side of chalcopyrite (medium yellow). Minute blebs of electrum (medium yellow) occur within the lower l e f t of the bottom grain of argentite (uncrossed n i c o l s ) 118 overlap in their formation. Since only trace amounts of galena were obser-ved in polished section i t is d i f f i c u l t to determine i t s exact time of for-mation in the paragenetic sequence. However, since i t only occurs as i n -clusions in sphalerite i t is assumed to have formed at least in later stages in formation of sphalerite. Also since i t contains no inclusions of chalcopyrite or pyrrhotite i t probably formed after these sulphides. Argentite i s contained only within galena and contains inclusions of elec-trum. Probably both argentite and electrum formed by exsolution. Covellite only occurs in late stage veins and as a replacement of chalcopyrite. Covellite contains inclusions of chalcopyrite but is not contained as inclusions in any other opaque minerals. This implies that covellite was the last opaque mineral to form as the later stages of the metasomatic event or as part of a secondary process. 3.2.4.3 Thermal Regime The thermal regime envisaged for the Zone 4 mineral occurrence is re-lated to both the formation of opaque and c a l c - s i l i c a t e minerals. Pyrite and magnetite were the f i r s t minerals to form but their time of formation relative to one another is questionable. In order for pyrite to form temperatures must have been below 740°C (Taylor, 1970). The occurrence of pyrite and magnetite primarily as disseminations in greenstone com-pared to the erratic location and massive nature of the other sulphides also suggests that pyrite and magnetite are the early part of or even prior to the metasomatic event. At the time of deposition of. covellite, temperatures must have been less than 507°C (Roseboom, 1966) otherwise digenite would have formed. Chalcopyrite inclusions in pyrrhotite and vice versa indicate that tem-peratures must have been less than 334°C (Yund and Kullerud, 1966). 119 Cubanite and pyrite are the stable mineral assemblage above this tempera-ture . Temperatures of formation for the ca l c - s i l i c a t e minerals must also be considered since they are in intimate association with most of the sul-phides. Schreyer (1977) estimates that skarn deposits are formed at low pressures, from 1 to 5 Kilobars. The presence of grossularite also i n d i -cates that the mole fraction of carbon dioxide i s less than 0.3 (Winkler, 1974). With these two constraints in mind, temperature estimates can be obtained from observed stable mineral assemblages. No wollastonite was seen in thin-section indicating that temperatures must have been less than 675°C (Winkler, 1976). In addition, a graph used by Winkler (1976) shows that quartz and zoisite, and grossularite and quartz, which were observed in contact, are stable below 630°C and 730°C respectively. The majority of the c a l c - s i l i c a t e minerals formed earlier than the sulphides, implying that most of the f i n a l equilibration of the sulphides occurred at tempera-tures less than 630 to 730°C. Equilibration of the sulphides occurred between 730 and 300°C 3.2.5 CONCLUSIONS Zone 4 has been described in section 3.2.4 as a skarn deposit within a marble (Unit l a ) . The erratic occurrence of ca l c - s i l i c a t e minerals, sulphides and oxides plus their massive to disseminated character is consistent with features of other metasomatic deposits. Sulphides are relatively undeformed which indicates that this mineral occurrence was formed during the later stages of deformation and metamorphism. Tedi Pit, Silver Tunnel and M i l l s i t e mineral occurrences have veins with similar mineralogies and paragenetic sequences. These three mineral occurrences also have showings of deformed sulphides in greenstone. 120 Therefore, i t is proposed that the veins are remobilized products of pre-existing sulphides within the greenstone. Temperature of equilibration for these sulphides i s between 700°C and 400°C which is consistent with temperatures envisaged for regional metamorphism of the pendant. Con-sequently, the remobilization event appears to be the result of regional metamorphism. 3.3 NORTHAIR MINES PROPERTY Northair mine i s the only producing mine in the map-area, milling 300 tons per day. Figure 3.9 is a detailed map of the mine-area showing the same rock units as described in the sections on lithologies for the whole area. Three ore zones are known on the Callaghan Creek property of Northair Mines, from north to south, the Discovery, Warman and Manifold zones (Figure 3.10). A l l zones are tabular in form, strike about N40°W and have nearly ve r t i c a l dips. Average thicknesses are about 2, 3 and 6 m respectively from north to south (Manifold, 1976). Ore grades d i f f e r pro-gressively from zone to zone. In general the southern (Manifold) zone is high in precious metals and low in base metals. The converse i s true for the Discovery zone, the Warman zone is intermediate in character. Similarly, the form of mineralization varies from north to south. In the Manifold zone sulphides are both disseminated and thickly layered in a siliceous carbonate layer and in the Discovery zone sulphides are layered and locally massive in form. Again the Warman zone is intermediate in character. The three zones appear to represent faulted segments of a single mineral-rich sheet. Such an interpretation is apparent underground be-LEGEND SYMBOLS GEOLOGIC CONTACTS: . DEFINED ASSUMED ~ FAULT + ' DIP AND STRIKE FOLIATION AREAS OF ABUNDANT OUTCROP PORTALS ROADS (Tw> LAKES ~JJS>i- TOPOGRAPHIC CONTOURS MAP UNITS __ GARIBALDI GROUP; 7b. RHYO-DACITE. __) COAST PLUTONIC COMPLEX; 6b.0IORITE. __ ANDESITIC AGGLOMERATE; 5a. EPICLASTIC VOLCANIC BRECCIA Bb.TUFFACEOUS SANDSTONES AND SILTSTONES; 5c. ANDESITIC CRYSTAL TUFF. _f] DACITIC AGGLOMERATE (MATRIX SUPPORTED); 4a, SILICEOUS, TUFFACEOUS SILTSTONE;4b. DACITIC AGGLOMERATES (FRAGMENT SUPPORTED); 4c, TUFFACEOUS SANDSTONES AND SILTSTONES. __ ANDESITIC CRYSTAL TUFF GEOLOGY OF THE NORTHAIR AREA -F £ E T 4 0 0 0 *f>0 _ l*X> I TOO ffiOOFCE MtTfltS OO 0 00 700 V » *00 V M Figure 3.9 Detailed geological map of Northair Mines Limited (N.P.L.) property Figure 3.10 Three producing zones within Northair mine. 123 tween the ends of the Warman and Manifold zones where small faulted seg-ments of the ore have been identified. However, a much more complex fault zone exists between the Warman and Discovery zones. This "single sheet" hypothesis is supported by the gradational characteristics of the ore, which is apparent i f a l l three zones are reconstructed to a single body. Characteristics of both the Discovery and Manifold zones extend to the respective adjacent parts of the Warman zone. Detailed examination of core from 12 exploratory d r i l l holes to the southwest of the Warman zone has established a local detailed s t r a t i -graphy that extends the length of, and parallels, the Warman zone. Several cross-sections were constructed perpendicular to this defined stratigraphy and are shown in Figure 3.11 (in pocket). The immediate footwall of the Warman zone is a layer of andesitic agglomerate, averaging 370 f t in thickness, which has a fine grained tuffaceous matrix containing approximately 70% large fragments as described for Unit 5 (section 2.2.5). Mineral modes estimated from thin-section are presented in Table 3.1. About 34 m southwest of the Warman zone is a 0.3 to 18 m thick, dacitic marker that is disrupted locally into fragments. These fragments are an-gular, equant and average 3 cm in diameter. The dacitic marker is medium to pale grey, with an aphanitic matrix which surrounds patches of epidote. Some of these epidote patches are crudely lath-like indicating that they may be pseudomorphs of plagioclase laths. Epidote patches comprise an average of less than 1% of the rock. Table 3.1 has visual estimates of the mineral modes for the andesitic agglomerate closest to the mineralized structure containing the dacitic marker acting as the boundary between the two andesitic agglomerate horizons. Rare elongate patches of chlorite peppered with minute opaque TABLE 3.1 VISUAL ESTIMATES OF MINERAL MODES-Rock types as defined i n the Warman zone, Northair mine (Percentages:maximum-minimum/average) Tuffaceous Sandstone matrix Andesitic Agglomerate Andesite fragments Southwest of Northeast of Southwest of Northeast of Dacite marker Dacite marker Dacite marker Dacite marker Dacite fragments Pla g i o c l a s e 30-17 / 25 a 34-14 / 24 b 25-0 / 7 C 40-5 / 29 d 10-0 / 5 e 12-0 / 3 f Carbonate 20-15 / 18 10-4 / 7 18-0 / 10 10-0 / 4 18-0 / 9 17-0 / 8 S e r i c i t e 25-0 / 14 36-14 / 25 53-2 / 27 33-1 / 11 32-2 / 18 72-0 / 41 Muscovite 10-0 / 3 5-0 / trace 1-0 / trace Opaques 10-7 / 8 3-1 / 2 15-0 / 4 2-1 / 2 8-0 / 4 15-2 / 9 Epido te 10-8 / 9 17-5 / 11 8-0 / 4 22-5 / 13 9-0 / 4 10-0 / 4 C h l o r i t e 15-0 / 7 16-2 / 9 8-0 / 1 3-0 / 1 8-0 / 2 3-0 / 1 Quartz 5-0 / 2 8-5 / 6 12-0 / 5 8-2 / 5 3-0 / 1 15-5 / 11 Peldspar-quartz 25-0 / 15 44-0 / 13 10-0 / 2 21-0 / 8 Leucoxcne trace ilema t i te trace Bio Li te 25-6 / 16 37-0 / 17 35-30 , / 33 60-12 / 69 40-0 / 15 M i c r o c l i n e 40-0 / 12 38-0 / 20 17-0 / 7 Sphene Number of thin-sections 3 2 3-0 / 9 trace 4 trace 7 3-0 / 4 1 a; An„ -An./An,. 24 4 14 g; I d e n t i f i c a t i o n b; An g-impossible &n^/An^ c; due to small Ang-An^/An^ grain s i z e d; An^2~An 5/An 9 e; A n l ( T 3 M n 8 f; An,. 6 125 mineral grains, possibly remnant glass fragments, within the dacite and the grain size of this rock suggest that i t may have been a tuff. Southeast of the andesitic agglomerate layers is a pale grey to green tuffaceous sandstone unit that contains rare subrounded fragments of sand-stone averaging 3 cm in diameter (Figure 3.12). The contact between the tuffaceous sandstone and the andesitic agglomerate i s gradational over about 1.5 m. This unit i s medium grained and exhibits no sedimentary structures. Mono-mineralic clasts comprise about 80% of the sandstone but rare clasts of granulose quartz were observed and interpreted to be chert. Estimated mineral modes for this unit have been tabulated from thin-section analyses in Table 3.1. Fragments are similar in appearance to the rest of the unit and are assumed to be sandstone although they were not examined in thin-section. The distribution of these fragments is erratic. One fragment of andesitic agglomerate containing dacitic marker frag-ments was seen in the core. This fragment was northeast of the i n i t i a l appearance of the dacitic marker and suggests that stratigraphic tops are to the northeast. A similar andesitic agglomerate containing the dacitic marker was observed in a single d r i l l hole on the southwest side of the Discovery zone, but this marker could not be traced because of lack of outcrop and other appropriately located d r i l l holes. Nevertheless, this one occurrence indicates that the stratigraphy immediately southwest of and parallel to the Warman zone extends over a total distance of at least 500 m. As yet, a comparable stratigraphy has not been recognized southwest of the Manifold zone because of the lack of new d r i l l holes and the deteriorated condition of boxes of d r i l l core from exploratory holes d r i l l e d several 126 gure 3.12 Megascopic appearance of the tuffaceous sandstone. 127 years ago. One cross-section of the Manifold zone drawn by L i t t l e (1974) shows a sequence of alteration zones. Potassium feldspar (microcline), and secon-dary biotite form an aureole that extends for approximately 30 m (90 ft) away from the main mineralized structure and biotite forms an aureole which extends approximately 50 m (150 ft) ( L i t t l e , 1974) . The presence of these aureoles was attributed to potassic hydrothermal alteration pro-duced by the veining event which was presumed to have formed mineralization in the Manifold zone. Samples were taken from 12 exploratory d r i l l holes and thin-sections were made from some of these samples. The modes presented in Table 3.1 are a summary of the results of thin-section examination. A graph (Figure 3.13) was also compiled, plotting the horizontal distance from the axis of the mineralized structure in the Warman zone, both to the southwest and northeast, to the sample versus visual estimates of the mineral's mode under consideration. This distance was measured in planes perpendicular to the strike of the stratigraphy (ie., northeast-southwest planes). A distinction between lithologies and fragment types were maintained in the plotting of the points in order to evaluate whether these aureoles were hydrothermal or metamorphic caused by varying compositions of the original rock. It is clear that the distinct mineralogical changes do occur at approximately the same distances from the axis of mineralization as the previously defined biotite and biotite-microcline aureoles. Furthermore, extreme variations do occur within the various fragment types and matrix at approximately equivalent distance from the mineralized structure. This fact in addition to the previous one implies that the biotite and micro-cline aureoles are not hydrothermal aureoles but are distinct composition-128 30 z o o j» R 20 m 3 o m z H 10 o o 2 H . m 0 E o o > a 4 * a o m z • • SOl a OS 0 H m 20-10 f « 0 Sso z -» o §20 o r; z m 10 XX ' 1 ' ' • _ - • M » 01 > u M 5 9 x 2 o o § V §. 8. 8. § * o O O Q Q ... o O , , , ^ B , r-1 I I 1 § I i i o D A N D E S I T I C F R A G M E N T ° " ° II 0 D A C I T I C F R A G M E N T 1 1 M A T R I X " M A T R I X A N D " 0 A N D E S I T I C F R A G M E N T o A II M A T R I X A N D " o DACITIC F R A G M E N T 11 T U F F A C E O U S S A N D S T O N E 1 1 II * a " a o II 01 y± *> X O a *> o 8 I 8 I 8 If S.W. ( F E E T ) , A N.E. AXIS OF MINERALIZED STRUCTURE**^  Figure 3.13 Graphs of the modal percent chlorite (top), b i o t i t e (centre), and microcline (bottor.) ,as estimated from thin-section, versus the estimated distance of the sample, southwest and northeast from the axis of the mineralized structure. 129 al zones which have been metamorphozed. Biotite and microcline are not uncommon minerals in greenschist grade metamorphic rocks (Mueller and Saxena, 1977) a fact which lends further support to the metamorphic hypo-thesis . Biotite and microcline aureoles identified in the Warman zone are identical to those described in the Manifold zone. If the Warman aureoles are attributed to compositional differences then these compositional zones may be extended to the Manifold zone. This relationship means that the stratigraphy defined for the Warman and Discovery zones can be ex-tended to the Manifold zone, over a total distance of at least 550 m. A whole rock K-Ar age of 74.2 + 2.5 m.y., from a sample within the biot i t e aureole, near the edge of the microcline aureole, was obtained by L i t t l e (1974) in the Manifold zone. This age was interpreted as repre-senting the age of mineralization. Based on this new interpretation of the origin of microcline and biotite aureoles presented in the previous paragraph, this age represents the time of fi n a l cooling after metamor-phism rather than the age of mineralization. This age i s probably a minimum age since the dated sample contains microcline. Microcline porphyroblasts seen in contact with albite grains near the perimeter of the layer containing microcline and biotite were interpreted to be in equilibrium with each other. A geothermometer based on the par-titioning of the albite component between plagioclase and a l k a l i feld-spar was presented by Stormer (1975) and further updated by Whitney and Stormer (1977). Microprobe analysis was done on one grain containing both albite and microcline in order to determine the amount of albite in plagioclase and microcline. The results of the analysis are presented in Table 3.2. In order to use the newer graphs and formulas presented by Whitney TABLE 3.2 MICROPROBE ANALYSIS RESULTSa A) MICROCLINE 1 2 3 4 5 Na 0.1018 0.0218 0.0244 0.0731 0.0332 Al 0.9817 0.9814 0.9891 0.9651 0.9660 Si 3.0134 3.0155 3.0107 3.0313 3.0303 K 0.8849 0.9608 0.9530 0.8892 0.9347 Ca 3.6 X 10~ •3 1.9 X 10 - 3 4.0 X 10~ •3 5.3 X 10" •3 3.9 X 10~ •3 Ba 3.6 X 10" •3 3.7 X 10"3 2.2 X 10" •3 3.2 X 10" 3 2.6 X 10" •3 Total 4.9891 4.9851 4.9835 4.9673 4.9707 B) PLAGIOCLASE 1 2 3 4 Na 0.9371 0.7369 0.8605 0.9730 Al 0.9845 0.9858 0.9891 0.9944 Si 3.0125 3.0108 3.0038 3.0024 K 0.0374 0.239 3 0.1331 0.0106 Ca 8.7 X 10"3 8.5 X 10~3 9, .9 X 10~3 0.0106 Ba 2.2 X 10~3 3.1 X 10"3 2. .0 X 10~3 1.2 X 10' Total 4.9825 4.9843 4.9984 4.9922 -3 a; Results are presented in cation form 131 and Stormer the activity rather than the mole fraction of albite in plagi-clase has to be known. Stormer (1975) assumed that the activity of albite in plagioclase was equal to the mole fraction, which in turn meant that plagioclase solid solution was assumed to be ideal. Since the activity is unknown from existing data i t is assumed to equal the mole fraction. Graphs presented by Whitney and Stormer, (1977) indicate the maximum and minimum equilibrium equilibriation temperatures for the microcline and albite analyzed, based on the available microprobe data. Temperatures at pressures of 1 kb can range from 320 to 500°C whereas 10 kb tempera-tures can range from 390 to 570°C. These temperatures are consistent with temperatures postulated for the regional metamorphic event. Thus the pre-sence of microcline and biotite does not neccesitate the introduction of potassium and high temperatures from a hydrothermal source, but may only be the result of regional metamorphism on layers of appropriate composition. Within the mine area are several different types of dykes besides the equigranular rhyodacite dykes already mentioned. These are; biotite 1am-prophyre, biotite-augite lamprophyre, micro-diorite and andesite. A l l of these rock types are slightly altered except for the microdiorite which is moderately altered suggesting that i t may be older than the other types. None of the dykes show any evidence of regional fol i a t i o n . Cross-cutting relationships between the dykes are rare since a l l of the dykes have a general north-south trend. Two dykes which apparently do cross one another based on d r i l l hole information were not exposed for observation in the c r i t i c a l area. None of the dykes mentioned in this paragraph resemble Pleistocene to Tertiary material observed elsewhere in the Callaghan Creek map-area. This fact plus the fact that the dykes are altered suggests that they are older than the Pleistocene to Tertiary material. 132 Scattered throughout the Manifold zone and in the eastern quarter of the Warman zone are mineralized carbonate-rich pods. These pods contain a fine grained sugary calcite (white) compared to coarser grained, white and pink calcite observed in other areas of the mine. Quartz- and bioti t e -rich layers, varying from less than 0.01 mm up to one cm in thickness (average 1 mm), can be seen paralleling finely layered sulphides (Figure 3.14). Locally these bands are folded on a scale of a few feet. Later veins, containing coarser-grained sulphides and gangue minerals cut across these bands. It is postulated that these banded carbonate pods were once a limestone containing chert and muddy layers plus layers of syngenetic sulphides. Upon later deformation and metamorphism these sulphides were remobilized locally into veins which here and there cross-cut the original syngenetic sulphides. Trace element analyses were made on samples collected along two separate east-west traverse lines on the eastern side of Callaghan Creek (details in Appendix B). The northern traverse line crosses the north-western tip of the Warman zone whereas the southern line i s about 600 m south of the Manifold zone portal. Purpose was to provide a preliminary investigation of the thickness and later a l extent of primary dispersion halos associated with mineralization of the Northair deposit. In addition, comparison could be made of trace element content of mineralized and un-mineralized parts of the volcaniclastic sequence. Results are shown in Figures 3.15 and 3.16. The trace elements in general, show significant variations between units which may reflect original compositional variations and/or the fragmental nature of most of the rock units. Nevertheless, lead, zinc, manganese, iron, calcium and strontium a l l show anomalous high values in 133 Figure 3.14 Finely i n t e r l a y e r e d sulphides (gray), carbonate (white), quartz (pale gray) and other s i l i c a t e s . 134 Figure 3.15 Trace element geochemistry of the northern traverse l i n e . The approximate position of Northair mine is denoted by "N". 135 Ag (ppm) i o 20 1 " — i — r A N' Pb ( p p m ) 1 0 120 Zn IOO (ppm) 80 60 100 Cu (ppm) so 1500 Mn (ppm) 1000 ~i 1—r "i 1—r LitHologic^ 4 c 5 5 o 5 Lithologic") * r - " £—' -Uni ts) 4c 5 5o 5 Figure 3.16 Trace element geochemistry for the southern traverse lin e . The projected relative stratigraphic position of Northair Mine is denoted by "N". 136 the v i c i n i t y of the Northair deposit along the northern traverse line . Potassium is anomalously low in this same area. Anomalous high values of zinc, manganese and potassium plus an anomalous low value of strontium oc-cur in the same approximate stratigraphic position as the Northair deposit along the southern traverse l i n e . The northern traverse line shows more significant anomalies in the stratigraphic position containing Northair than the southern traverse line . This suggests that the mineralized zone at Northair may not exist to the south. 3.3.1 MINERALOGY AND TEXTURES The opaque mineralogy for the Discovery, Warman and Manifold zones w i l l be dealt with in this section. An attempt was made to examine differences between the zones based on polished section and f i e l d exami-nation. Since much of the mineralogy and textures are uniform through-out a l l three zones, this section w i l l describe the mineralogy and tex-tures for the entire deposit, while peculiarities to a particular zone w i l l be mentioned in the appropriate places. The main ore minerals at Northair, in order of decreasing abundance are: pyrite, sphalerite, galena, chalcopyrite, tetrahedrite, argentite, bornite, ruby silver and electrum. Chalcocite and covellite are present as secondary minerals and are equivalent in abundance to argentite and bornite, respectively. Pyrite is the most abundant sulphide in a l l three ore zones at Northair mine. It occurs disseminated throughout the host andesitic ag-glomerate (Unit 5) and as a massive to disseminated sulphide in the ore horizon. Pyrite within the host rock is subhedral to euhedral in shape whereas grains in the ore horizon are subhedral to anhedral in shape and locally are brecciated. Sphalerite, chalcopyrite, galena, tetrahedrite, 137 argentite and gangue minerals corrode and replace pyrite but may also act as a cement for brecciated pyrite grains. Anhedral inclusions of sphal-erite, chalcopyrite, galena, tetrahedrite and gangue minerals comprise approximately 1% of a l l the pyrite grains observed. Sphalerite occurs as individual anhedral grains which may be inter-s t i t i a l to other sulphides or disseminated with volcaniclastic rocks within the ore zone. This mineral also occurs as massive layers and irregular patches with gangue minerals and other sulphides occurring i n t e r s t i t i a l l y . In general these layers average a few millimetres in thickness. Defor-mation twinning is ubiquitous in sphalerite grains, although i t is less well developed in material that can be definitely identified as veins cross-cutting the ore horizon. Less than 1% of the sphalerite grains ob-served contain chalcopyrite in emulsion and very rarely in crystallographic textures. Some of the chalcopyrite laths forming the crystallographic texture are oriented parallel to deformation twin planes (Figure 3.17). Chalcopyrite, galena, tetrahedrite and argentite corrode and replace sphalerite along grain boundaries and twin planes, locally forming jagged intruding "tongues". Pyrite, chalcopyrite, galena, tetrahedrite, angen-ti t e and gangue minerals form anhedral inclusions in sphalerite and com-prise approximately 2% of the sphalerite grains observed. Generally, galena is either massive or present as anhedral grains i n t e r s t i t i a l to gangue or sphalerite. Some of the massive galena forms bands with other sulphides occurring i n t e r s t i t i a l l y . These bands usually exhibit a gneissic texture and may be up to 4 cm in width. Curved and rhombic cleavages, fractures and the gneissic banding are present through-out the Northair deposit (Figure 3.18). Argentite and tetrahedrite re-place g/alena along grain boundaries, cleavages and fractures. Boundaries between sphalerite and galena exhibit a well developed caries texture. 138 Figure 3.18 Curved cleavage traces i n galena (white) and twinned s p h a l e r i t e (gray). (uncrossed n i c o l s ) 139 Galena contains inclusions of a l l the other primary sulphides. Chalcopyrite is slightly less abundant, relative to the other sul-phides, in the Warman and Manifold zones than in the Discovery zone. However, general characteristics of chalcopyrite's appearance and occurrence are similar in a l l three zones. Chalcopyrite occurs as anhedral masses and grains i n t e r s t i t i a l l y to sphalerite, galena and gangue minerals. Most of the chalcopyrite grains have a poorly developed deformation twin-ning and fracturing. Less than 1% of chalcopyrite occurs as emulsion blebs and crystallographic intergrowths in sphalerite. Pyrite, sphalerite, galena and gangue minerals occur as anhedral inclusions within chalcopy-r i t e . Galena and argentite replace chalcopyrite along grain boundaries and twin planes. Contacts between sphalerite and chalcopyrite may have a well developed caries texture. Tetrahedrite (including tennantite) occurs as anhedral inclusions in galena, usually along a grain boundary with another mineral. This mineral forms mutual boundaries with chalcopyrite and sphalerite. Locally tetra-hedrite appears to be replacing galena and pyrite along grain boundaries and fractures. Rounded anhedral grains of tetrahedrite and myrmekitic . intergrowth of galena and tetrahedrite suggests that at least some of the tetrahedrite, i f not at a l l , i s the result of exsolution. Argentite (including acanthite) only occurs in the Manifold zone as blebs and anhedral masses. These grains primarily occur away from the massive sulphides and are usually fine disseminations in a fine grained quartz-carbonate rock. This mineral also occurs as rounded anhedral blebs in galena and may possibly be the result of exsolution. Argentite replaces galena, pyrite and sphalerite along grain boundaries and frac-tures. Inclusions of argentite were observed within a l l the other major primary sulphides (the sulphides described in previous paragraphs) except 140 chalcopyrite. Bornite was not observed in the Discovery zone but was seen in both the other zones. In the Warman zone, bornite occurred as one anhedral grain in contact with chalcopyrite. In the Manifold zone, bornite occur-red as several rounded anhedral grains in galena and chalcopyrite. One grain of bornite was bounded on three sides by gangue minerals, while the other side formed a myrmekitic intergrowth with chalcopyrite. Ruby silver only occurs i n the Manifold zone as anhedral grains in mutual contact with sphalerite, argentite and galena. Rounded blebs of ruby silver which occurred within galena are thought to be the result of exsolution. Electrum (including a l l native gold and silver mixtures) was only seen in polished sections from the Manifold zone, however, electrum has been reported in individual grains with quartz-carbonate of the Warman zone (Manifold, 1976). Electrum occurs as individual anhedral grains dis-seminated in gangue minerals and a paler variety, possibly native silver, occurs as irregular grains within argentite and tetrahedrite. These paler grains are possibly the result of exsolution. Electrum has mutual grain contacts with galena and sphalerite. Stromeyerite has been reported in the Manifold zone in intimate as-sociation with argentite and gold (Manifold, 1976). Chalcocite is a secondary mineral replacing chalcopyrite, pyrite, galena, sphalerite and tetrahedrite along grain boundaries and fractures throughout the Northair deposit. Some of the chalcocite appears to be just coating mineral grains rather than replacing them. Covellite forms minute randomly oriented laths completely within chalcocite. These laths occur in sporadic patches in the chalcocite. U l Magnetite was not included in the opaque minerals of the ore zone be-cause i t primarily occurs as fine disseminations in the andesitic agglo-merate. These grains are anhedral and locally brecciated and replaced by pyrite and gangue minerals. Hematite occurs as exsolution laths in magnetite and as blebs and alongate laths replacing magnetite along grain boundaries and fractures. Gangue minerals within the ore horizon are generally anhedral in shape throughout the Northair deposit. Gangue minerals which are euhedral to subhedral in shape were seen in the massive ores of the Warman and Dis-covery ore zones. Gangue minerals do not transect pyrite but do cross-cut a l l of the other major sulphides, and locally appear to use sulphide grains as i n i t i a t i o n points for their growth (Figure 3.19). 3.3.2 PARAGENESIS Brecciation of pyrite, deformation twinning in both chalcopyrite and sphalerite, and rhombic and curved cleavages in galena suggest that the sulphides have undergone strain. However, sulphides which occur in veins generally lack strong deformational features and are coarser grained than the other sulphides. Rounded patches of sphalerite with an irregular rind of anhedral pyrite grains occur in massive, slightly gneissic galena. These patches have no definite orientation and appear to be mechanically mobilized clasts caught up in the flow of galena. These features plus textural sim i l a r i t i e s with sulphides of mineral occurrences in the Van Silver area strongly suggest that remobilization and recrystallization have occurred in the Northair deposit. Therefore, a paragenetic sequence can only be meaningfully developed for veins, chemically remobilized products of pre-existing sulphides. 142 Figure 3.19 Subhedral laths of gangue intruding and protruding from s p h a l e r i t e into galena. (uncrossed n i c o l s ) 143 In veins, brecciation of pyrite and replacement by most of the other sulphides indicates that i t was the f i r s t mineral to form. Further support for this conclusion is that, euhedral to subhedral laths of gangue minerals were not seen in pyrite but were seen in most of the other sulphides. After pyrite, sphalerite was deposited, followed by chalcopyrite and then galena, based on replacement relationships. Tetrahedrite and argentite occur as exsolution products in galena and may loc a l l y replace galena. 3.3.3 THERMAL REGIME The thermal regime envisaged for the deposition of sulphides before remobilization is impossible to estimate since sulphide relationships have been distorted by remobilization. However, temperatures can be es-timated for the thermal event which resulted in remobilization and w i l l be presented below. Inclusions of sphalerite, galena and chalcopyrite in pyrite appear to be in equilibrium. This means that a maximum temperature of formation can be estimated for these minerals. Pyrite and sphalerite are in e q u i l i -brium below 740°C (Stanton, 1972), chalcopyrite and pyrite are in e q u i l i -brium below 740°C (Yund and Kullerud, 1966) and galena and pyrite in the presence of other minerals such as sphalerite, are in equilibrium below 700°C (Brett and Kullerud, 1967). The presence of tetrahedrite in galena is indicative of temperatures around 350-400°C, since minerals rich in silver and antimony form a solid solution in galena above this temperature (Hall and Czamanske, 1972). This means that when exsolution of tetrahedrite occurred, temperatures must have been around 350-400°C. In summary the above relationships indicate that temperatures during remobilization reached more than 400°C but were less than 700°C. 144 3.3.4 GENETIC MODELS In the last few years controversy has arisen as to the origin of the Northair deposit. L i t t l e (1974) proposed an epigenetic hydrothermal model which was later supported by Manifold (1976). Manifold (1976) did not pro vide a new model but did l i s t factors which he f e l t were indicative of a hydrothermal origin. Miller and Sinclair (1978) proposed a dis t a l volcano genie or exhalative model as an alternative to the epigenetic model. Fur-ther support for the syngenetic model was again given by Miller and Sinclair (1978) and Miller et a l . (1979). Each model w i l l be summarized in the following sections and then factors which support each model w i l l be l i s t e d based on the various author's statements. A model w i l l be presented in a summary section which appears to be the most consistent with a l l the available data. 3.3.4.1 Epigenetic Model: Hydrothermal Vein L i t t l e (1974) studied polished sections and thin-sections taken from the Manifold zone. These lines were done so that they roughly occurred within one cross-section of the Manifold zone. The epigenetic model proposed was that of hydrothermal solutions, rich in potassium, calcium carbonate and s i l i c a , flowing through three closely spaced shear zones created by extensive fracturing and shearing related to regional metamorphism. These hydrothermal solutions were attributed to Coast Plutonic magmatic activity of upper Cretaceous age. Hydrothermal alteration in the form of an inner biotite-microcline core zone and an outer biotite zone were developed symmetrically about the shear zone. During hydrothermal alteration, quartz, calcite and sulphides were introduced in several pulses causing replacement relationships in sulphides and gangue minerals of the previous pulse or pulses. Once the 145 veins were formed, north-east striking faults displaced the veins into the three existing mineralized zones. A synthesis of the ideas presented by Manifold (1976) and L i t t l e (1974) which they feel support an epigenetic model are: 1/ Hydrothermal alteration zones of biot i t e and microcline are sym-metrically distributed around the mineral deposit. 2/ Distribution of sulphides suggests a zonal developement. 3/ Branching veins have been identified in both walls of the main mineralized structure. 4/ A f l a t lying quartz vein in the Manifold zone was cut-off sharply at the orebody with no evidence of movement after mineralization. 5/ The main mineralized zone is not conformable with the s t r a t i -graphy . 3.3.4.2 Syngenetic Model: Distal Volcanogenic or Exhalite Deposit Miller and Sinclair (1978) proposed a syngenetic model based on re-gional and local geological considerations plus surface and underground observations from a l l three ore zones. In idealized form the model is that of a local marine basin formed during a hiatus in explosive rhyo-dacitic to andesitic volcanism. Ore fluids were fed to the water-sediment interface from a pipe zone, not now identified, to contribute base and precious metals to the basin of chemical sedimentation. The sulphides were massive, massive to disseminated within fine grained sediments and banded to disseminated within limestone. This was followed by further deposition of agglomeratic material. The deposit was then deformed and metamorphozed to greenschist facies. During this event post-deforma-tional, sulphide-bearing quartz and/or carbonate veinlets formed by 146 mobilization of originally syngenetic material. The deposit was later disrupted by northerly trending faults, which broke the deposit into three zones and truncated the Discovery zone on the west. Data which Miller and Sinclair (1978 and 1979) feel support the syn-genetic model are: 1/ Quartz veins similar to those i n the mineralized zone, which are removed from known mineralized zones, are free of sulphides. 2/ Sulphides are strongly deformed. 3/ Pods of fine grained calcite and quartz in the Manifold zone and southeast end of the Warman zone resemble recrystallized limestone and chert. 4/ Layered sulphides parallel fine layers of carbonate, quartz and locall y , s i l i c a t e s , over distances of centimetres to metres. This parallelism i s also evident around folds. 5/ In the Warman zone the mineralized horizon is conformable to the surrounding stratigraphy. This also appears to be true in the Manifold and Discovery zones. 6/ Biotite and microcline inner zone and biotite outer zone to the southwest of the Warman zone represents compositional variations that parallels bedding. Thus, biotite and microcline are products of re-gional metamorphism of rock types of appropriate compositions. 7/ Only one sheet of mineralized structure may be present in the mine area since faults can be used to reconstruct the three ore zones into a single sheet. 8/ Remobilized veins cut across proposed syngenetic mineralized structure and generally contain coarser grained sulphides and gangue minerals. 1 4 7 9 / Final equilibriation temperatures of,the sulphide assemblages are consistent with regional metamorphic temperatures. 3.3.5 CONCLUSIONS Determination of the origin of the Northair deposit is complex based on available information. The interpretation of carbonate-quartz pods as metamorphozed limestone and chert is questionable. Also the biotite and biotite-microcline zones were not examined to the northeast of the War-man zone. However the remaining evidence appears to favour the syngene-t i c model. The realization that some material occurs in veins also aids in the explaination of some features mentioned by the proponents of the epigenetic model. It seems unreasonable to require that metals in these veinlets be derived elsewhere, particularly because similar veinlets else-where do not contain sulphides. Consequently, these veins can most lik e l y be attributed to local remobilization during regional metamorphism. Signs of deformation of sulphides are prevalent throughout the deposit which means that they have been subjected to some major deformational event. The epigenetic model would then require some major tectonic event to occur after the intrusion of the Coast Plutonic rocks or else they were deposited by some hydrothermal event prior to the intrusion of the Coast Plutonic rocks. Neither of these options are attractive since there is no evidence of a complex thermal and deformational history in the surrounding rocks. Consequently, the syngenetic model f i t s known information better than the hydrothermal model. I 148 CHAPTER 4 . SUMMARY AND CONCLUSIONS 4.1 INTERPRETATION OF DEPOSITIONAL ENVIRONMENT OF THE CALLAGHAN CREEK PENDANT This interpretation w i l l start generally at the oldest unit, the greenstone (Unit 1) and progress through time. Figure 4.1 is a conceptual model of the volcanic rocks of the map-area excluding Pleistocene to Tertiary material. The relative position of geological contacts generally agrees with the mapped contacts except features have been deleted to aid in the understanding of the depositional environments. Greenstone (Unit 1) was deposited in a deep water environment with local basins, low energy regimes, receiving limestones and cherts. Sedi-ments in the form of andesite agglomerate and then andesitic crystal tuffs could be deposited in a similar deep water environment. However, the presence of an andesitic crystal tuff makes the f i r s t appearance of volcanic-dominated debris. Interbedded sediments and andesitic crystal tuff layers, which were seen in the southern section of the contact be-tween units 2 and 3, indicate that this transition was gradual. Dacitic agglomerates (Unit 4) and other associated sediments have been deposited at apparently similar time stratigraphic positions to those of the andesitic crystal tuffs. The tuff apparently formed the edges of a basin or possibly even a channelway in which sediments were deposited. The idea of a channelway is attractive since i t would explain the large amount of coarse cl a s t i c debris, absence of andesitic crystal tuff hori-zons within the sediments and the topographical shape. The top of the dacitic agglomerate is covered by fine-grained sediments (Unit 4c) which VO 0 0-5 10 1-5 mis Figure 4.1 Sketch of the Cretaceous pendant rocks. The general orientation of contacts agree with actual contacts on the geological map (Map 1). Since units are approximately vertical i t is assumed that this sketch is a cross-section of the stratigraphy. 150 represent the waning stages of sedimentation. Faults in the Northair mine-area complicate the interpretation of the rock units. However, i t does seem that l e f t lateral displacement has off-set the epiclastic volcanic breccia. It is further assumed that l e f t l a t e r a l displacement has occurred on the fault truncating the Discovery Zone so that the s l i c e of arkosic wackes (Unit 5b) between the two most northeasterly faults is closer to being juxtaposed to the westerly slice of arkosic wackes. This seems a reasonable interpretation since i t matches units and bedding orientations. Andesitic agglomerate was deposited in the same depression or channel-way as the dacitic agglomerate. But this depositional environment was i n -terrupted, by a major event which disrupted the channelway and covered the entire map-area with an epiclastic volcanic breccia. Widespread deposition of andesitic agglomerate with associated interbedded sediments occurred with occasional interfingering with andesitic crystal tuffs. During quiescent periods, local basins could possibly form limestones and cherts which locally survived deposition of overlying agglomeratic material, depending on the erosional characteristics of the agglomerate. Location of a volcanic centre or centres based on the information available i s d i f f i c u l t since no distinct l a t e r i a l variations in s t r a t i -graphy were recognized. However, the general lack of very large clastic debris and the presence of crude layering and fine grained sediments suggests that a volcanic centre is less than a few kilometres away from this area of deposition (Lajoie, 1977). Age of the volcaniclastic sequence is somewhat uncertain. Litholo-gies and textures show a remarkable similarity to the lower volcanic mem-ber of the Gambier Group as exposed near the type area along Howe Sound, where Lower Cretaceous fo s s i l s have been found in an upper sedimentary 151 member (Woodsworth, personal communication, 1977). Similarly, Lower Cretaceous fossils have been found near Black Tusk Mountains in a sedimen-tary sequence, one member of which contains granitic cobbles and which seems to overly the volcaniclastic sequence unconformably (Mathews, 1958). Furthermore, mapping to date has not located any granitic fragments within the volcaniclastic rocks of the Callaghan Creek pendant. Consequently, i t seems f a i r l y certain that the volcaniclastic sequence is Early Cretaceous or older. This i s further supported by the minimum K-Ar model age of 124 + 4 m.y. obtained on the hornblende dyke (Miller and Sinclair, 1978). The general environment envisaged, i s of explosive volcanism in an arc environment characterized by calc-alkaline volcanism which probably extended along the length of the Coast Plutonic Complex during Jurassic and Early Cretaceous time. (Monger et a l . , 1972). The volcanism was the product of ongoing subduction of oceanic plate below the west coast of North America and produced many volcanic centres and basins. These basins were dominated by volcanic tuffs and flows or by epiclastic debris depen-ding upon location. Marginal and inter-arc basins are generally dominated by epiclastic debris. Since the Callaghan Creek pendant contains a sig-nificant proportion of andesitic crystal tuff, r the depositional environ-ment of the Callaghan Creek pendant must have been close to the arc and not in the epiclastic dominated regimes of marginal or inter-arc basins. 4.2 METALLOGENY Three distinct episodes of mineralization have been recognized in the area. An early phase of sulphide deposition appears to be syngenetic, based on the presence of extensive, thin, conformable layers of carbon-ate, chert and sulphides in the deposits at Northair mine. In fact the three ore zones at Northair (Discovery, Warman and Manifold) are part of 152 what was a single tabular sheet that is interpreted as an exhalite. (Ridler, 1976), which would classify the deposit into the dis t a l volcano-I genie class. Part of the Tedi Pit mineral occurrence also has a layered aspect with massive deformed sulphides (D.A. Soregaroli, personal communi-cation, 1978). This suggests that i t may also be syngenetic. Britannia copper-zinc deposits have been interpreted as volcanogenic deposits formed from hydrothermal and exhalite solutions related to daci-t i c volcanism (Payne, et a l . , 1972). The deposit was deformed by later shearing and faulting. The presence of this deposit is the Gambier Group and the dacitic marker with 100 feet of the mineralized zone at Northair suggests a similar type of origin for the deposit. Britannia deposits have recognizable feeder zones but Northair does not implying that the sulphides at Northair are more di s t a l from the volcanic vent than those at Britannia. A second period of mineralization produced sulphide-bearing quartz and/or carbonate veins and veinlets in a l l three ore zones at Northair and in the Tedi Pit mineral occurrence and possibly the Silver Tunnel and M i l l s i t e mineral occurrences in the Van Silver property. These veinlets cut deformed layered sulphides and themselves show l i t t l e evidence of pene-trative deformation. Apart from the sulphides these veinlets resemble quartz and/or carbonate veinlets associated with rocks elsewhere in the pendant which has been metamorphozed to greenschist facies. Consequently, sulphide-bearing veins and veinlets are thought to be a product of a thermal regime related to regional metamorphism and associated plutonism which may have occurred intermittently u n t i l about 90 Ma. Two other types of occurrences may relate to this second mineralizing episode: 1) Pyrite-chalcopyrite stockwork within hornblende diorite 153 (dated at 128 Ma., details in Appendix C) in the M i l l s i t e area, and 2) skarn mineralization at the Zone 4 mineral occurrence. A third period of mineralization is evidenced by sulphide-bearing veinlets cutting Pleistocene to Tertiary high level dykes in the Silver Tunnel occurrence of Van Silver Explorations Ltd. Origin of the metals is uncertain but i t is speculated that most or a l l of the sulphides may have been derived by local mobilization of earlier deposited sulphide con-centrations. The precise age of mineralization is unknoxm. 4.3 ASPECTS PERTINENT TO MINERAL EXPLORATION Recognition that Northair Mines Ltd. deposit is syngenetic has very important implications for future exploration within the Coast Plutonic Complex. It means that several mineralizing epochs may be present within pendants and septal of the Coast Plutonic Complex. Guidelines and factors to be considered for future mineral exploration are list e d below: 1) Sulphide-bearing veins or veinlets in pendants and septae of the Coast Plutonic Complex require a metal source, that in some cases could be a syngenetic sulphide concentration. 2) Detailed mapping of pendants and septae may provide indications as to which stratigraphic units could contain a syngenetic deposit. 3) Solomon (1976) makes note of the fact that most massive sulphide deposits appear to form clusters of deposits rather than one single depo-s i t . This generalization makes intuitive sense in that i f volcanic ac-t i v i t y and the depositional environment are conducive to the formation of one sulphide deposit, other sulphide deposits may occur. Therefore, once a mineralized horizon has been located other deposits may be found at other l o c a l i t i e s within that horizon. 154 4) Examination of pendant and/or septae between Northair and Britannia mines may provide insight into time-stratigraphic correlations. These correlations could aid in determining the stratigraphic relation-ships of these two deposits and could possibly identify one horizon which contains both deposits. 5) Basaltic marine to more acidic explosive t e r r e s t r i a l phases oc-curred during Cretaceous time (Sutherland Brown et a l . , 1971). Several massive sulphide deposits have b een related to the earlier basaltic phase of volcanism, but few to the more acidic phases. However, since both Britannia and Northair deposits are related to dacitic volcanism, i t im-plies that syngenetic metallogenic events are scattered over a broader stratigraphic and compositional range than previously recognized. 6) Rock geochemistry may enlarge the target area of volcanogenic-related deposits and increase the probability of finding mineral occur-rences (Thurlow et a l . , 1975 and Govett and Goodfellow, 1975). The pro-bability increases since primary dispersion halos in bedrock exist around most massive sulphide deposits, enlarging the size of the exploration tar-get. 4.4 FUTURE WORK In order to better understand the mineral occurrences and s t r a t i -graphic relationships within, and regional geological significance of the Callaghan Creek pendant more work must be done. Suggestions for future work are l i s t e d below. 1) Detailed underground and'surface mapping of the Northair deposit should be done in order to expand and further define the stratigraphy. The results would also aid in determining offsets and relationships of the 155 two major faults in this area. 2) Detailed surface mapping should be done on the mineral occurrences of the Van Silver Explorations Ltd., to delineate any inter-relationships and refine genetic models. 3) Detailed rock geochemistry in the Northair area would better de-fine the types and sizes of primary dispersion halos about the deposit. These results used in conjunction with the preliminary rock geochemistry done in this manuscript would provide a large enough data base to begin evaluation of chemical changes, primary or secondary, within pendant rocks. 4) Further detailed mapping of the Callaghan Creek pendant and sur-rounding septae and/or pendants may identify the feeder zone or zones for the Northair deposit. This information would help unravel the paleo-topography which existed during deposition of the pendant rocks. 5) Biotite and microcline zones should be further defined in the Manifold and Discovery zones relative to the detailed stratigraphy. These results would further support or deny that the biotite and microcline zones are the result of regional metamorphism of rocks with appropriate chemical compositions. 156 BIBLIOGRAPHY Brett, R. 1964. Experimental data from the Cu-Fe-S and their bearing on exsolution textures i n ores. Econ. Geol., vol. 59, pp.1241-1269. Brett, R. and Kullerud, G. 1967. The Fe-Pb-S system. Econ. Geol., vol. 62, pp. 354-369 Christopher, P.A., W..H. White and J.E. Harakal. 1972. K-Ar dating of the "Cork" (Burwash Creek) Cu-Mo prospect, Burwash Landing area, Yukon Territory. Can J. Earth Sci., vol. 9, pp. 918-921. Dickinson, W.R. 1976. Sedimentary basins developed during evolution of Mesozoic-Cenozoic arc-trench system in western North America. Can. J. 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Mtg., Oct. 13-15, Vancouver, B.C. Marton, A. S. 1978. Unpublished BSc thesis, Dept. of Geological Sciences, University of British Columbia. Mathews, W.H. 1958. Geology of the Mount Garibaldi Map-Area, South-western British Columbia, Canada. Geol. Soc. Amer., Bull, vol. 69, no. 2, pp. 161-178. Meeks, D. 1978. Unpublished Geol. 428 report. Dept. of Geological Sciences, University of British Columbia. Miller, J.H.L. and A.J. Sinclair. 1979. Geology of an area including Northair Mines Ltd.'s Callaghan Creek property. Geological f i e l d -work 1978, Paper 1979-1, B.C. Ministry of Mines & Energy, pp.124-131. Miller, J.H.L. and A.J. Sinclair. 1978. Geology of part of the Callaghan Creek roof pendant.. In Geological fieldwork 1977. B.C. Ministry of Mines and Petroleum Resources, pp. 96-102. Miller, J.H.L., A.J. Sinclair, D.G. Wetherell and A.H. Manifold. 1978. Mineral deposits i n the Callaghan Creek areas, southwestern B.C., (abstract). Can. Inst. Min. Metall. Bull., March, p. 129. Miller, J.H.L., A.J. Sinclair, A.H. Manifold and D.G. Wetherell. 1978. Mineral Deposits i n the Callaghan Creek area, southwestern B.C. Preprint and oral presentation, Can. Inst. Min. Metall., Ann. Gen. Mtg., April 23-27, Vancouver, B.C. Miyashiro, A. 1975. Volcanic rock series and tectonic setting. Ann. Rev. Eath Planet Sci., vol. 3, pp. 251-269. Monger, J.W.H., J.G. Souther and H. Gabrielse. 1972. Evolution of the Canadian Cordillera: A plate tectonic model. Am. J. Sci. 272, pp. 577-602. Mueller, R.F. 19 77. Chemical petrology: with applications to the ter r e s t r i a l planets and meteorites. Springer-Verlag, New York, N.Y. 394 p. Parsons, W.H. 1968. Criteria for the recognition of volcanic breccias: Review. Geol. Surv. Can., Mem. 115, pp. 263-304. 158 Payne, J.G., J.A. Bratt, and B.G. Stone. 1972. Deformed Mesozoic volcanogenic Cu-Zn deposits in the Brittania District, British Columbia. Unpublished manuscript. Ridler, R.H. 1976. Regional metallogeny and volcanic stratigraphy of the Superior Province: Canada. Geol. Surv., Paper 76-1A, pp. 399-405. Roddick, J.A. and G.J. Woodsworth. 1975. Coast Mountain Project: Pemberton (92J West Half) Map-Area, Bri t i s h Columbia. Geol. Surv. Can., Paper 75-1, Part A, pp. 37-40. Roseboom, E.H. 1966. An investigation of the system Cu-S and some natural copper sulphides between 25 and 700°C. Econ. Geol., vol. 61, pp. 641-672. Schreyer, W. 1976. Experimental metamorphic petrology at low pressures and high temperatures. In The Evolution of the Crystalline Rocks. Edited by D.K. Bailey and R. MacDonald. Academic Press, New York, N.Y., 484 p. Sinclair, A.J., H.R. Wynne-Edwards and A. Sutherland-Brown. 1978. An analysis of distribution of mineral occurrences in British Columbia. B.C. Ministry of Mines and Petroleum Resources, Bull. 68. Solomon, M. 19 76. "Volcanogenic" massive sulphide deposits and their host rocks - a review and an explanation. In Handbook of Strata-bound and Stratiform Ore Deposits. Vol. 6. Edited by K.H. Wolf. Elsevier S c i e n t i f i c Publishing Company, Amsterdam, Netherlands. 595 p. Stanton, R.L. 1972. Ore Petrology. McGraw-Hill Inc., New York, N.Y. 713 p. Steiger, R.H. and E. Jaeger. 1977. Subcommission on geochronology; convention on the use of decay constants i n geo- and cosmochronology. Earth Planet. Sci. Lett., vol. 36, no. 3, pp. 359-362. Stormer, J.C. 19 75. A practical two feldspar geothermometer. Amer. Mineral., vol. 60, pp. 751-761. Streckeisen, A.L. 1967. Classification and nomenclature of igneous rocks. N. Jb. Miner. Abb.., 107, 2 and 3, pp. 144-240. Sutherland-Brown, A., R.J. Cathro, A. Panteleyev and G.S. Ney. 1971. Metallogeny of the Canadian Cordillera. Can. Inst. Min. Metall., Bull., vol. 64, no. 709, pp. 37-61. Thompson, R.I. and A. Panteleyev. 1976. Stratabound mineral deposits of the Canadian Cordillera. In Handbook of Strata-bound and S t r a t i -form Ore Deposits, Vol 5. Edited by K.H. Wolf. Elsevier Scient-i f i c Publishing Company, Amsterdam, Netherlands. 319 p. 159 Thurlow, J.G., E.A. Swanson and D.F. Strong. 1975. Geology and li t h o -geochemistry of the Buchans polymetallic sulphide deposits, Newfoundland. Econ. Geol., vol. 70, pp. 130-144. Vokes, F.M- 1971. Some aspects of the regional metamorphic mobilization of preexisting sulphide deposits. Mineral. Deposita, vol. 6, pp. 122-129. Wetherell, D.G. 1977. Unpublished Geol. 428 report, Dept. of Geological Sciences, University of British Columbia. White, W.H., G.P. Erickson, K.E. Northsote, G.E. Dirom and J.E. Harakal. 1967. Isotope dating of the Guichon Batholith, B.C. Can. J. Earth Sci., vol. 4, pp. 677-690. Whitney, J.A. and J.C. Stormer. 1977. The distribution of NaAlSi30s between coexisting microcline and plagioclase and it s effects on geothermometric calculations. Amer. Mineral., vol. 62, pp. 687-691. Winkler, H.G.F. 1975. Petrogenesis of metamorphic rocks. Springer-Verlag, New York, N.Y. 329 p. Woodsworth, G.J., D.E. Pearson and A.J. Sinclair. 1977. Metal distribution patterns across the eastern flank of the Coast Plutonic Complex, south-central British Columbia. Econ. Geol., vol. 71, pp. 170-183. Woodsworth, G.J. and J.A. Roddick. 1977. Mineralization in the Coast Plutonic Complex of British Columbia south of latitude 55° N. Geol. Soc. of Malaysia, Bull. 9, p. 1-16. Yund, R.A. and G. Kullerud. 1966. Thermal s t a b i l i t y of assemblages in the Cu-Fe-S system. Jour. Petr., vol. 7, pp. 454-488. 160 APPENDIX A A.1 HISTORY OF THE VAN SILVER PROPERTY AREA 1917 Charles Camsell describes the geology of the Brandywine creek area and reports m i n e r a l i z a t i o n found i n lenses of quartz. M i n e r a l i z a t i o n was also reported on the east side of Highway 99 within a seven foot band of limestone. G.S.C. Summary Report. Part B, p. 21. 1923 E.L. Snow, H. Hogstrom and G.G. H e r r i o t t staked eight claims, c o n s t i t u t i n g the Blue Jack Group. Report of M i n i s t e r of Mines and Petroleum Resources, 1924, p. 243. 1924-1965 Intermittent work done i n the area, 1960-1964 M. Levasseur re-staked 179 claims on old showings between Brandywine and Callaghan creeks. Report of Minister of Mines and Petroleum Resources; 1926, p. 332, 310, 160, 210, F14, F53. 1978. 1978. 19 30, 1931, 1932, 19 34, 1936, L i t t l e , L i t t l e , 1966 These claims became the holdings of Van S i l v e r Explorations Limited (N.P.L.), a newly formed p u b l i c company headed by M. Levasseur. L i t t l e , 197? 196 7 Geological mapping, X-ray d r i l l i n g , magnetometer surveying and E.M. surveying were c a r r i e d out on the Van S i l v e r property. L i t t l e , 197* 1968 Sheep Creek Mines Limited (N.P.L.) optioned L i t t l e , 197? the property and underground workings were re-opened and 602 feet (3 holes) of diamond d r i l l i n g done. 1969 Bio-geochemical sampling and opening up of the S i l v e r Tunnel was conducted during the summer by Van S i l v e r Explorations Limited (N.P.L.). L i t t l e , 19 7? 19 70 A 100 pound sample was sent to Cominco Smelter i n T r a i l , B.C., from the S i l v e r Tunnel by Van S i l v e r Explorations Limited (N.P.L.). L i t t l e , 197! 161 1971 Noranda Mines Limited (N.P.L.) optioned L i t t l e , 1978. the property and conducted the following work; s o i l geochemistry, geophysics and 805 feet of d r i l l i n g 1973 Van Silver Explorations Limited (N.P.L.) L i t t l e , 1978. dr i l l e d 602 feet (two holes). 1974 Van Silver Explorations Limited (N.P.L.) L i t t l e , 1978. dr i l l e d sixteen holes in the Tedi Pit area (3,863 feet) and thirteen holes in the Silver Tunnel area (1,861 feet). 1974 Silver Tunnel was extended by Van Silver L i t t l e , 1978. Explorations Limited (N.P.L.) and the rock was stockpiled near the proposed m i l l s i t e . 1976 Construction of a small mill was started L i t t l e , 1978. by Van Silver Explorations Limited (N.P.L.) at the proposed m i l l s i t e . 1977 Work was completed on the mill and some L i t t l e , 19 78. of the stockpiled rock was milled. Later in the year Van Silver Explorations Limited (N.P.L.) went into receivership. 1978 Cominco did some diamond d r i l l i n g during personal observation, the summer and dropped the property in the f a l l . A . 2 HISTORY OF THE NORTHAIR MINE PROPERTY 1969 Dr. M.P. Warshawki obtained anomalous Dickson and McLeod, stream s i l t sample results while prospecting 1975. during the summer. In the later part of the year A.H. Manifold, head of Mining Technology at the British Columbia Institute of Technology, aided Dr. Warshawki i n follow-up geochemistry. 1970 Further follow-up geochemistry was done Dickson and McLeod, by these men and in September a large 19 75. piece of mineralized float was found and thirteen claims were staked around the general area. 19 71 During early summer mineralized structure Dickson and McLeod, was located, which was named the Discovery 19 75. zone. Trenching and s o i l sampling were conducted over the claims while more claims were added along the general trend of the structure. While running one of the claim 162 l i n e s another mineralized showing was found and i s now known as the Manifold zone. Late i n the year Mclntyre Mines Limited (N.P.L.) optioned the property. 1972 Mclntyre Mines Limited (N.P.L.) c a r r i e d out a s o i l geochemistry and trenching program but dropped the option at the end of the summer. D. McLeod, president of Northair Mines Limited (N.P.L.) optioned the property and diamond d r i l l e d 28 holes i n the l a t e r part of the year. 1973 An a d i t into the 3500 foot l e v e l of the of the Manifold zone and diamond d r i l l i n g was undertaken i n the Warman zone. Dickson and McLeod, 1975. Dickson and McLeod, 1975. 19 74 1975 An a d i t into the 3500 foot l e v e l of the Warman zone was completed. Results on the Manifold and Warman zones proved t h e i r c o n t i n u i t y . A f e a s a b i l i t y study was conducted i n the summer and r e s u l t e d i n the d e c i s i o n to purchase an e x i s t i n g m i l l . The mine was then upgraded i n preparation for the m i l l and the main haulage l e v e l at 3250 foot elevation was completed. Preparations were completed for production. Dickson and McLeod 1975. Dickson and McLeod, 1975. 1976 1977 Production commenced June 1, from a l l three l e v e l s at a m i l l i n g rate of 300 tons/day. Production from a l l three l e v e l s continued and the Discovery zone was put into production. Extensive diamond d r i l l i n g of the Warman zone was also conducted. Dickson and McLeod, 19 75. personal observation 19 78 Continued production from a l l four areas. Underground development on the 2800 foot l e v e l to i n t e r s e c t an area below the Warman zone was s t a r t e d . Ore was i n t e r -sected during l a t e summer and development work on r a i s e s and stopes were s t a r t e d and i s continuing to present. personal observation 163 APPENDIX B B.l WHOLE ROCK LITHOGEOCHEMISTRY Sixteen rock specimens, collected during the 19 77 f i e l d season were selected for major element analysis. Samples were selected in order to obtain a representative sample of the chemistry of the volcanic rocks in the map-area. Location of the samples are shown in Figure B.l. The main purpose of the whole rock lithogeochemistry was to classify the volcanic rocks. Table B.l contains the geochemical results for the sixteen samples. Sample number 13, has a 9.06 % loss on ignition and was therefore not considered in the following discussion. Sample number 8 was also not considered because of i t s high epiclastic content. Figure B.2 is a plot which distinguishes alkaline from subalkaline rocks (Miyashiro, 1975). The plot shows that a l l of the plotted rocks are within the subalkaline f i e l d . This means that these rocks can now be plotted to determine whether they are t h o l e i i t i c or calc-alkaline. An AFM diagram is commonly used to distinguish calc-alkaline rocks from t h o l e i i t i c rocks but w i l l not be used here because of the large variations in a l k a l i content. Instead two diagrams, used by Miyashiro (1975), w i l l be used since they are not dependent on a l k a l i contents for their classification. These diagrams are presented in Figures B.3 and B.4. The majority of the samples plot within the calc-alkaline f i e l d (CA) with a minority f a l l i n g in the t h o l e i i t i c f i e l d (TH). 164 TABLE B.l Sample Number SiO % ^ 3 to /o 1 54.04 19.20 7.33 2 53.19 18.58 7.61 3 58.89 17.58 6.71 4 63.76 16.30 4.30 5 55.92 17.96 5.81 6 52.95 18.07 7.46 7 53.23 18.41 7.79 8 59.35 16.59 6.04 9 63.90 16.74 4.59 10 56.67 20.25 5.06 11 56.25 20.28 8.53 12 55.16 19.07 8.11 13 41.54 18. 74 10. 22 14 51.38 21.41 7.46 15 63.23 16.42 4.06 16 70.64 14.71 1.75 WHOLE ROCK GEOCHEMISTRY MgO % CaO % Na 0 % K O % 4.18 7.33 3.977 1.983 4.48 5.69 3.779 2.886 2.50 4.28 2.514 2.450 1.92 3.39 5.484 0.842 3.06 5.33 6.018 0.791 3.75 5.55 5.212 1.073 5.20 5.08 4.033 2.159 3.22 2.28 5.533 0.898 2.57 1.47 5.119 1.905 2.75 4.37 4.373 1.336 1.55 6.51 2.631 0.283 2.71 4.45 4.104 1.612 7.26 5.58 0.566 2.889 3.57 5.56 2.951 2.843 2.31 4.44 3.463 1.685 0.56 2.40 0.334 4.225 TiO % MnO % L.I.O. 3 % Total % 0.790 0.170 1.38 100.38 0.845 0.168 2.11 99.34 0.643 0.199 2.74 98.50 0.426 0.160 2.51 99.09 0.574 0.137 3.56 99.16 0.754 0.248 3.73 98.80 0.776 0.123 2.18 98.99 0.703 0.149 3.07 97.83 0.504 0.108 2.29 99.20 0.610 0.091 2.68 98.19 0.663 0.215 2.23 99.14 0.792 0.161 2.92 99.10 1.083 1.026 9.06 97.96 0.796 0.137 3.36 99.47 0.457 0.075 3.22 99.36 0.275 0.136 3.82 98.85 ; Loss on ignition 166 70 — CVJ O CO 60 50 — F e O V MgO Figure B.2 S i 0 2 (%) versus FeO (total)/MgO (%) plot. This plot distinguishes calc-alkaline rocks from t h o l e i i t i c rocks (Miyashiro, 19 75). 167 50 60 70 80 90 SiCU Figure B.3 Na20 and K2O (%) versus S i 0 2 (%) plot. This plot distinguishes a l k a l i c from subalkalic rocks (Miyashiro, 19 75). 168 1 5 — 1 0 — O Li. 5 — F e 0 * / M g 0 Figure B.4 FeO (total) (%) versus FeO(total)/MgO (%) plot. This plot distinguishes calc-alkaline from t h o l e i i t i c rocks (Miyashiro, 1975). 169 B.2 TRACE ELEMENT LITHOGEOCHEMISTRY Fifety-nine rock samples collected from two east-west lines across the pendant on the eastern side of Callaghan Creek were analyzed for 11 trace elements. Purpose of this work was to determine whether Northair Mines Limited deposit had any recognizable trace element dispersion halo which would aid in future exploration. Sample locations are given in Figure B. l . For each major pendant rock unit (units 1 to 5) at least four samples were chosen. At each sample location three sights were sampled, two feet apart, across the strike of the stratigraphy. Rock chips of comparable size were taken from each sample site and mixed to form a composite locality sample, averaging 2 kilograms (4 lbs.). This sampling technique was chosen to standardize the size of the rock sample taken, while s t i l l making the sample representative within the limitations of time, outcrop, and size and weight of sample. Silver, copper, iron, lead and zinc were elements chosen for analysis because the Northair deposits contain these elements. Manganese was chosen because s o i l geochemistry had proven this element as a strong indicator of mineralization and fractures or shear zones. Other elements chosen for analysis were those which had showed anomalous behaviour in a sample line of the Manifold zone (personal communication, A. Soregaroli, 1978) . Results of the analysis are shown in Table B.2. 170 topic As Ea Ca uxbmr PP« PP» X 1 - 0 . 3 ' 425 2 .62 2 - 0 . 3 1500 1.73 3 - 0 . 3 1000 2 .18 4 - 0 . 3 1125 2 .41 5 - 0 . 3 940 2 .73 6 - 0 . 3 660 2 .03 7 - 0 . 3 825 1.71 8 - 0 . 3 1840 1.80 9 - 0 . 3 825 2 . 7 » 10 - 0 . 3 300 0 . 9 2 11 - 0 . 3 670 2 . 3 1 12 - 0 . 3 525 1.94 - 0 . 3 1650 2 .40 It 2 . 2 1250 1.26 15 - 0 . 3 1365 2 . 6 3 1« - 0 . 3 1275 0 . 9 6 17 - 0 . 3 1075 1.72 18 - 0 . 3 1100 1.94 19 0 . 8 1250 2 .19 - 0 . 3 1100 2 . 3 8 21 0 . 3 950 2 . 6 6 - 0 . 3 770 3 . 4 3 23 - 0 . 3 815 3 .97 24 - 0 . 3 975 1.02 - 0 . 3 750 1.33 26 - 0 . 3 460 1.80 27 - 0 . 3 1150 1.73 28 - 0 . 3 1400 1.35 29 - 0 . 3 950 2 .22 30 - 0 . 3 1000 1.84 31 - 0 . 3 750 0 . 5 7 32 - 0 . 3 765 0 . 4 9 33 - 0 . 3 280 1.71 34 - 0 . 3 1200 1.3* 35 - 0 . 3 900 1.82 37 - 0 . 3 650 3.11 38 - 0 . 3 925 2 . 0 3 39 - 0 . 3 725 4 . 1 1 40 - 0 . 3 550 4 . 0 9 41 - 0 . 3 790 2 . 5 3 42 - 0 . 3 200 3.94 43 - 0 . 3 800 2 . 3 8 44 - 0 . 3 950 3 .82 45 - 0 . 3 775 1.94 46 - 0 . 3 740 2 .46 47 - 0 . 3 650 0 . 3 6 48 0 . 3 600 1.47 49 - 0 . 3 250 1.70 50 - 0 . 3 800 0 . 5 7 91 - 0 . 3 175 0 . 4 7 52 - 0 . 3 475 0 . 6 0 53 - 0 . 3 900 2 .44 54 - 0 . 3 1400 1.54 55 - 0 . 3 950 1.71 56 - 0 . 3 890 0 . 9 6 57 0.4 900 1.29 58 - 0 . 3 500 3.05 59 - 0 . 3 750 2 .42 60 - 0 . 3 1000 1.68 61 - 0 . 3 850 2 .51 TAALE B.2 w e e n m E N T C H i g i g n s — Cu Fe K Ma pp. I I PP" 27 5.07 1.11 1200 35 4 .94 2.27 1144 31 5 .93 1.92 1434 21 3.29 1.93 1000 19 4 . 3 1 1.43 1840 23 4 .84 1.34 767 26 3 .46 2 .02 806 21 4 .69 1.46 800 24 5.32 1.66 1080 10 4 . 2 0 0 .55 720 8 3.24 1.25 680 24 3 .62 1.20 1090 16 5.04 2 .36 1086 2 5 .28 2 .81 1046 16 4 .64 2 .30 1128 34 3 .62 1.90 776 25 4 . 7 5 2 .31 1514 20 4 .57 1.46 915 26 4 . 9 0 3 .80 1100 9 6 .11 2 .45 1616 187 6 .36 3 .13 2726 60 5.24 2 .60 1452 2 3 .97 1.13 1924 15 4 . 0 1 1.71 682 23 4 . 5 1 2 .03 768 2 3.32 1.01 1268 5 3.10 1.42 1172 3 3.43 2.74 872 3 3.65 1.42 814 11 4 . 1 2 1.93 770 9 3 .26 1.26 620 12 2 .79 1.18 546 4 12.02 0 . 5 3 1362 10 2 .41 2 .75 560 2 2 . 22 1.49 392 9 5.64 1.38 1100 35 6.64 2.49 1040 10 6 .36 1.24 1184 a 6 . 2 2 0 . 7 2 1360 19 5.89 1.13 1140 8 7 .93 0 .41 1423 7 4 . 1 0 1.32 746 15 5.10 1.29 1004 35 4 . 2 3 1.11 674 94 5 .03 0 .81 836 3 1.06 1.40 138 38 6 .55 2 .33 1314 90 6 .82 0 . 8 2 1240 32 6 .99 3 .06 1214 4 4 .91 0 . 1 8 670 28 5.12 0 .80 780 8 2.96 2.71 680 29 6 .33 2 .93 1360 29 6.38 3.11 14 30 45 4 .56 1.60 684 29 5.24 4 .31 1006 46 4 .51 1.14 nio 35 4 .47 2 .25 940 13 4 .20 1.47 874 34 4 .33 1.28 920 Fb lb Sr Zo ppm PP» PfMl ppo 10 24 700 86 6 32 415 82 7 33 520 59 8 60 520 76 35 615 86 7 32 470 83 12 80 350 88 9 30 300 84 40 413 90 8 10 250 68 4 20 400 68 7 IS 920 70 4 46 370 98 5 52 500 88 11 58 700 78 4 36 410 82 9 42 560 82 6 26 470 67 8 108 613 104 4 92 365 88 22 88 350 164 17 60 590 ISO 14 22 800 89 3 40 440 74 8 64 380 82 10 19 275 88 42 570 74 4 38 350 86 a 20 450 56 4 23 420 68 4 17 300 58 14 IS 270 58 4 13 270 154 10 31 220 52 2 20 280 28 9 32 590 83 35 67 380 100 10 23 613 58 25 14 500 60 19 24 405 92 5 17 520 97 4 21 335 36 4 19 460 68 2 22 420 40 2 16 570 52 2 22 170 20 31 62 164 102 5 16 560 98 6 80 125 122 8 12 230 9 2 11 18 380 84 6 60 160 44 5 133 240 108 4 24 205 108 4 43 275 63 J 230 123 120 4 IS 275 90 4 24 325 74 4 27 290 66 4 28 370 76 a; Below d e t e c t i o n H a l t . 171 APPENDIX (NTS 92 J-3 Sample Number(s) and Reference(s) Lab No: AJ-lc material Date loerror Ref: MILLER ,J. ARMSTRONG, R. .0 4.72/.584/1. 19 - D 4.72/.584/1.18 •m 4.96/."581/1.167 ( Hb ) 127 ± 4 Ma ( ) + Ma ( ) + Ma ( ) + Ma Record No: Suite No: "o not reported Sample Name: Latitude: , O ' " (50 06 16 N . ,..) .. . UTM Zone v Sec. ', T. Longitude: i it (X Y* Z" or X" Y. Y 1) ,123 ~ 06 01 W (± ); -;'V E N; Province /. R. Co., State (NTS Map Area, Scale Location: Source Type: Rock: Geologic Unit: Geologic Age: Material Analyzed: A n a l y t i c a l Data: ( l i s t duplicate analyses or indicate n = 2, n = 3, etc.) K = 0.520 + 0.0004 *. , A ' r 4 0 * - 2 654 — ^' ' 40 K 20= " % ' ' A r . i n - l O ^ w ^ J t 45.6 %^Ar 4 U) 1= , % ; ( A r 4 0 * = xip-»cc/gm ) ; ( % Z A r 4 0 ) K 2 ° " % _ . . K ' %. ( A r40*:~~ 1 \ xlOj^cc/gm ) ; ( % E A r 4 0 ) 2 , K = % . 40*= - » ^ J . W ^ W Y I » , A N K 2O= - % M A r V " „ i n - 1 0 _ i %^Ar 4 U) Comment on Analyses: 2 ^ x i o " cc/gm ) xl0~ 1 0mol/gm) ; xl0~ 6 cc/gm ). xl0~ 10 ' mol/gm) xl0~ 6 - , . c/gm ) ; xl0~ mol/gm) xl0~ ^  cc/gm ) xl0~ 0 , , mol/gm) Interpretation: Collected by: Dated by: J- E- HARAKAL  Listed by: - - ' Date: 3-22-79 (name, institution) 172 (NTS 92 J 3 K-Ar Sample Number(s) and Reference(s)  Lab No: nGM Biotite  material Date la error Ref: _D 4. 72/.584/1. 19 -o 4. 72/.584/1. 18 -• 4.96/.581/1.167 ) 90 + 3-2 Ma ( ) + Ma ( ) + Ma ( ) V + Ma Record No: Suite No: D not reported Sample Name: Latitude: ; o • " (50 ., 07 49 , N UTM Zone Sec. Longitude: Or Y' Z" or X Y.Y') , 123 08 12 W . ( ± , -r,^ ) ; - E ' ~ r,-, N; Province (NTS ) Co., State Map Area, Scale Location: Source Type: Rock: Geologic Unit: Geologic Age: Material Analyzed: Biotite , quality fine A n a l y t i c a l Data: (list duplicate analyses^or indicate n = 2, n = 3, etc.) K = 6.49 6.48 (+ 0.2 K20= 1) %. %' ( A r 4 0 * = 23.289 .. , 10.392 _ g xlO cc/gm ) -10 xlO mol/gm) ' ( 91.2 %EAr4 0) K = K20= • %. . . . % . . xlO \ cc/gra ) m -10 ' xlO mol/gm) ( ' %EAr 4 0) K = K20= %'* ~40* (Ar4U'=-~. ^"frivol V^ .??',.vf- * 5 ' -xlO f- cc/gm ) # .xlO 1 0mol/gm)• ( . %EAr 4 0) K = K20= % % ; 40*= (Ar >~ xlO cc/gm ) xlO umol/gm)' ( - • - %ZAr4 0) Comment on Analyses:.^-;.;. — Interpretation: r.~::<.;7. '. •  - • -p Collected by: Dated by: J.E. HARAKAL ;" '  Listed by: _ ' Date: 2-20-79 (name, institution) 173 (NTS 92 J 3 ) K-Ar Sample Number(s) and Reference(s) material Date Lab No: DGM Hb Ref: MILLER. J . ARMSTRONG, R. decay constants: ~0 4. 72/.584/1. 19 -o 4. 72/.584/1.18 - O 4.96/.581/1.167 Record No: Suite No: D not reported Sample Name: ic error ( Hb ) 87.0 ± 3.0 Ma ( ) + Ma ( ) + Ma ( ) V + Ma Latitude: , o ' " ( 50 07 49 N UTM Zone Sec. • Longitude: (X Y' Z n or X" Y.Y') . , 123 08 ... 12 W (± . ) ; - E N;.-, Province (NTS ) Co., State Map Area, Scale Location: Source Type: Rock: Geologic Unit: Geologic Age: Material Analyzed: Hornblende, quality poor A n a l y t i c a l Data: (list duplicate analyses or indicate n = 2, n = 3, etc.) .40*_ Q i n AJ-U v - i - / y»' / An 93.8%2Ar ) .40* xl0~° cc/qm ) . , %EAr 4 0) K = 2.72 2.65 (+ 2.6%) %. K 20= # K = K 2 0 = = % K = % K 2 ° = %; K = . • K2O=; .40 *-xl0~ cc/gm )xl0~ "^mol/gm) ' ~ 6 g )xlO" mol/gm) r xl0~ cc/gm ) xl0~ 10 w mol/gm) xlO" ^  cc/gm ) xl0~ 1 0mol/gm)' .40*_ r xlO c /gm ) , %EAr 4 0) o.r* 40, %£Ar ) Comment on Analyses: Interpretation: Collected by: Dated by; J.E. HARAKAL  Listed by: Date: ?- \ 5-7Q (name, institution) (NTS 92 J 3 ) 174 K-Ar Sample Number (s) and Reference (s) material Date la error Lab No; AJS Hb decay constant: O 4.72/.584/1. 19 Ref: MILLER, J . _ , . „ • , «-«,,, L F T SINCLAIR, A. O 4. 72/. 584/1. 18 -• 4.96/.581/1.167 ( Hb ) 128 + 4 Ma ( ) + Ma ( ) + Ma ( ) - + Ma Record No: Suite No: D not reported Sample Name: Latitude: Longitude: (X Y* Z" or X Y.Y') o » " o I II ( 50 03 51 N , 123 08 10 W (± ); UTM Zone E N; Province Sec. ./. T.1 , R. ' ; • - - Co., State_ (NTS ) - Map Area, Scale Location: Source Type: Rock: Geologic Unit: Geologic Age: Material Analyzed: Hornblende, quality fine A n a l y t i c a l Data: (list duplicate analyses or indicate n = 2, n = 3, etc.) K = 0.495 0.494 *. ,,.40*. ^. J J 4 v-Wy»» / 4 n K20= % ' l A r " , l o n w 1 f t - 1 0 _ 1 / # r a ; w - ( 73.6 %^Ar 4 U) K = = % ; ( A r 4 0 * = , xlO-^cc/gm ) . { ^ 4 0 , I =0= ' * ; 7 A r 4 i J V - xlOj^cc/gm ) ; { % E A r 4 0 ) . . 2 • ... . • K20= -~ % ' l A r - „i r t-10_ n ; ( %ZAr 4 U) Comment on Analyses: - .... 2.554 xl0~ cc/gm ) 1.139 xl0~ •^mol/gm) ' xl0~ cc/gm . xlO" 10 , , , ' mol/gm) xl0~ ^  cc/gm ) xl0~ 10 , , x ' mol/gm) xl0~ ^  cc/gm ) xl0~ "^mol/gm) ' Interpretation: Collected by: "_ Dated by: j . R . H A R A K A L  Listed by: • Date: 3-22-79 (name, institution) 1 LEGEND PLEISTOCENE TO TERTIARY GARIBALDI GROUP', (a) OLIVINE BASALT; (b) EQUIGRANULAR RHYODACITE; (c) PORPHYRITIC RHYODACITE;(d) BRECCIA. CRETACEOUS TO UPPER JURASSIC COAST PLUTONIC COMPLEX; (a) QUARTZ DIORITE WITH MINOR DIORITE j (b) HORNBLENDE DIORITE WITH MINOR HORN-BLENDE QUARTZ DIORITEi (c) GRANODIORITE. GAMBIER GROUP (?) ANDESITIC AGGLOMERATE;(a) EPICLASTIC VOLCANIC BRECCIA ; (b) ARKOSIC WACKES WITH MINOR INTERBEDDED MUDSTONESJ ( C ) ANDESITIC CRYSTAL TUFF. DACITIC AGGLOMERATE, MATRIX SUPPORTED; (a) SILICEOUS SILTSTONEi(b) DACITIC AGGLOMERATE, FRAGMENT SUPPORTED} ( c ) TUFFACEOUS SANDSTONES AND SILTSTONES WITH MINOR INTERBEDDED RHYOLYTIC TUFF. ANDESITIC CRYSTAL TUFF; (x) HORNBLENDITE DYKE (I24±4m.y.) ANDESITIC AGGLOMERATE; GREENSTONE; ANDESITIC IN COMPOSITION; (a) MARBLE WITH MINOR INTERBEDDED CHERT AND GREENSTONE. MINERAL OCCURRENCES NORTHAIR MINES LIMITED 1 DISCOVERY ZONE 2 WARMAN ZONE 3 MANIFOLD ZONE VAN SILVER EXPLORATIONS LIMITED 4 SILVER TUNNEL 5 MILLSITE 6 TEDI PIT 7 ZONE 4 SYMBOLS / \ \ / \ \ / " S 6b :.<r. \ \ \ V / / \ \ \ \ / - - - v - : : k 5 d J : # : ; s 5 b .. ... . A. . .1. .}>..» \ \ V \ \ \ \ 6b \ \ ! \ l \ 7a N ,(4a): \ : > \ • \ \ \ ^ . : : : : \ 5b \ V J U si: :>»s.>^ . ZONE j f y . . . . . . . . .• •. • :;;h;V: :::;;;I::u::'-J:.-::: : ::y::::i:.v* 7- • •• • :/:::-v*f::;::Y;:: * I :• \\\-^\ • • • ' f f y ! ,' >TV. Ill r9o \ 4 /W ss* />• />/ s>J s**t J2 : 90° GEOLOGICAL BOUNDARY: DEFINED APPROXIMATE ASSUMED AREAS OF ABUNDANT OUTCROP LIMIT OF GEOLOGICAL MAPPING FAU L T A P P ROXIM ATE ASSUMED BEDDING PROSPECT, PORTAL WATERCOURSE L A K E S , PONDS ROADS: PAVED GRAVEL SCALE 2 KILOMETRES 0 5 10 1-5 MILES GEOLOGY BY J.H.L. MILLER AND A.J. SINCLAIR JANUARY 1979 V v6a / / 6a (Ia1 \ 7a : . \ . I .' II \ (7b 7a mm ^ V - J I : : : : : : : : : : : : : : : : : : V 5 SILVER / 6 b - : . \ \ J R A N C J r W i N E C R E E K ': / / ^ / TUNNEL/ mm 2 > S Gb ^ * ^ ^ * ELEVATION SW ^ (FEET) h3600 ' SECTION 1850 W 300 FEET 100 METRES o : C . - •• 1 •o.]C>;:?:: ° o<2: o; Y 3500' h 3400' K 3300' I" 3200' h 3100' 3000' r 2900' h 2800' h 2700' NE DDH 49-77 -.DDH 39-77 - ^ » 47-77 I m 7 7 mm*... SECTION 1550 W O-o-mm-.0/ •:o. . e_-0. ft* 100 200 300 FEET •Q:i 50 100 METRES A,§0? • o ; c> • LEGEND mm ANDESITIC AGGLOMERATE ELEVATION (FEET) Y 3700' Y 3600' Y 3500' I- 3400' h3300' 3200' I- 3100' h 3000' r 2900' NE DDH 51-77 DDH 37-77 SECTION 100 200 300 FEET •O.V --• W.o-f.O-o-P.o-O:' 50 J00 METRES C\A/ ELEVATION -(FEET) h 3600' H3500 Y 3300' h 3400" h 3200 r 3ioo' V 3000' H2900* V 2800' TUFFACEOUS SANDSTONE TUFF MARKER WARMAN ORE ZONE LOCATION MAP 400 800 FEET 0 100 200 METRES ROADS CONTOURS GRIDLINES • 

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