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The alteration and mineralization of the poplar copper-molybdenum porphyry deposit West-Central British.. Mesard, Peter Morris 1979-03-22

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THE ALTERATION AND MINERALIZATION OF THE POPLAR COPPER-MOLYBDENUM PORPHYRY DEPOSIT WEST-CENTRAL BRITISH COLUMBIA by PETER MORRIS MESARD B.S. (Magna cum laude) Fort Lewis College A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF - MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Geological Sciences We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December 197 9 (c) Peter Morris Mesard, 1979 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Depa rtment The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 View of the study area taken from the west. Tagetochlain Lake is seen on the right, and the access road to the property is on the left. The center of the deposit is situated under the stand of fir trees in the forground. ABSTRACT The Poplar copper-molybdenum porphyry deposit, located 270 km west of Prince George, is centered in a late Upper Cretaceous differentiated calc-alkaline stock, which intruded Lower and Upper Cretaceous sedimentary rocks . The stock is capped by late Upper Cretaceous volcanic flow rocks. The lower Cretaceous Skeena Group consists of intermediate tuff, siltstone, and interbedded sandstone, which steeply dip to the south. This unit is unconformably overlain by a moderately sorted polylithic pebble conglomerate belonging to the Upper Cretaceous Kasalka Group. The Poplar Stock, which hosts mineralization, includes a border phase of hornblende quartz monzodiorite porphyry which grades in to a central biotite quartz monzonite porphyry. The stock is intruded by several post-ore dyke units, which include porphyritic dacite, porphyritic rhyolite, felsite, and andesite. Ootsa Lake porphyritic volcanic flow rocks overly the deposit, and are dacite in composition. Pre-ore, and post-ore rock units have been K-Ar dated, and are within analytical error of each other, having a mean age of 74.8 ±2.6 Ma. The deposit is covered extensively with glacial till and alluvial sediments. Therefore the majority of geologic information was obtained from logging the drill core from 34 diamond drill holes, twelve of which were logged in detail using a computer compatible logging format. Information logged in this manner was used in statistical studies , and for producing computer generated graphic logs and plots of various geologic parameters, along two cross-sections through the deposit. Alteration zoning at the Poplar porphyry consists of a 600 m by 500 m potassic alteration annulus which surrounds a 300 m by 150 m argillic alteration core. These are enclosed by 750 m wide phyllic alteration zone, which is itself bordered by a low intensity propylitic alteration zone. Phyllic alteration is defined by the occurence of sericite, and is the most abundant type of alteration present. Potassic alteration, recognized by the occurence cf secondary K-feldspar and/or secondary biotite, is most closely associated with chalcopyrite and molybdenite. At least two episodes of alteration are recognized at the Poplar porphyry. The first was contemporaneous with mineralization, following intrusion and crystallization of the Poplar Stock. This episode consisted of potassic alteration in the center of the deposit, which surrounded a 'low grade1 core, and graded out to phyllic and propylitic alteration facies at the periphery. The second alteration event took place after the intrusion of the post-ore dykes and consisted mainly of hydrolytic alteration of pre-existing alteration zones which were adjacent to more permeable centers, such as faults, contacts, and highly jointed areas. This alteration event is responsible for the anomalous central argillic zone, and the alteration of dykes, in addition to probably intensifying and widening the phyllic alteration halo surrounding the deposit. Chalcopyrite and molybdenite were deposited in the potassic zone at approximately 375° C and less than 250 bars, with relatively low oxygen, and relatively high sulfer, activities and moderate pH. As the potassic alteration zone was invaded by more acidic solutions feldspars were altered sericite and clay, and chalcopyrite was destroyed to form pyrite and hematite. Copper was removed from the system. Statistical studies include univariant one-way and two-way correlation matrices, and multivariant regression analysis. Statistical correlations generally support empirical correlations made in the field. These include positive correlations between various potassic alteration facies minerals, and these minerals and chalcopyrite and molybdenite. Multivariant regression analysis was used to determine which alteration minerals were best suited for indicating chalcopyrite and molybdenite. These minerals are quartz, biotite, magnetite, sericite, K-feldspar, and pyrite. Large error limits and poor correlation statistics in the results from these studies are attributed to deviations from normal distributions for all minerals. A possible cause of this may have been the multistage alteration events that the deposit has undergone V ACKNOWLEDGMENTS There are numerous individuals who offered support, discussion, and advice during the course of this study. Dr. C. I. Godwin first suggested the study, financially supported it, and was a source of advice, ideas, and enthusiasm, from the beginning. Dr. A. Sinclair visited me in the field, and cleared up many misconceptions dealing with statistics. Dr. 1. Brown was very helpful in discussing concepts and ideas, and provoking much thought about hydrothermal geochemistry. A grant from the British Columbia Ministry of Mines supported many of the field expenses. Dr. N. C. Carter, in particular was very helpful;. B. Bowen, of Utah Mines Ltd., participated in a number of discussions and provided company information dealing with the deposit. Mr. E. Montgomery helped in logistics and in offering technical advice about draughting and photography. I owe a great deal to Ms. Linda Mah who typed both the rough draft, and did a nice job of typing the final copy into the computer. Mr. and Mrs. Miles Shelford, of Francois Lake, British Columbia, were most generous, and were sources of encouragement during the field portion of this study. Finally, Ms. R. Wegner was very helpful in preparing the figures, plates, and captions for the final draft, and for demonstrating rare good humour during the final stages of the writing of this thesis. vi TABLE OF CONTENTS FRONTISPIECE - ii ABSTRACT ...iiACKNOWLEDGMENTS , ....V TABLE OF CONTENTS . . . vi LIST OF FIGURES X LIST OF PLATES xii LIST OF TAELES xiv LIST OF MAPS XV CHAPTER I: INTRODUCTION 1 1.1 Location1.2 Access 2 1.3 Physiographic Setting 3 1.4 History And Development ............................ 5 1.5 Scope Of Study .... , 7 CHAPTER II REGIONAL GEOLOGIC SETTING 9 2.1 Regional Tectonic Setting .......................... 9 2.2 Regional Geology ......................, 11 vii CHAPTER III GEOLOGY OI THE POPLAR PORPHYRY DEPOSIT ........ 15 3.1 General Statement .................................. 15 3.2 Poplarlog 16 3.3 Geologic Maps And Cross-sections ................... 19 . 3. a Rock Units 24 3.4.1 Overview3.4.2 Pre-Intrusive Bocks ........................... 25 Skeena Group . 25 Kasalka Group 27 Correlation Of Pre-Intrusive Rock Units .. 29 3.4.3 Mineralized Intrusive Rocks ..................... 30 General Statement ........................ 30 Hornblende Quartz Monzodiorite ........... 31 Biotite Quartz Monzonite ................. 34 3.4.4 Post-Ore Dykes 39 General Statement Porphyritic Dacite Dykes 39 Felsite Dykes 42 Porphyritic Rhyolite Dykes 42 Andesite Dykes .. 44 3.4.5 Extrusive Rocks Ootsa Lake Group 44 Correlation Of Extrusive Rocks 47 3.5 K-Ar Age Determinations ............................ 47 3.6 Comparison Of The Poplar Porphyry To Other Porphyry Deposits Of West-Central British Columbia 48 3.7 Structure ........................................... 51 CHAPTER IV MINERALIZATION AND ALTERATION OF THE POPLAR viii PORPHYRY DEPOSIT 54 4.1 General Statement .................................. 54 4.2 Distribution Of Alteration And Mineralization Zones At The Poplar Porphyry 58 4.3 Sulfide Mineralogy ................................. 64 4.3.1 Chalcopyrite 64.3.2 Molybdenite 7 4.3.3 Bornite .. 70 4.3.4 Covellite 71 4.3.5 Tetrahedrite4.4 Alteration Mineralogy ............................... 72 4.4.1 Potassic Alteration ........................... 72 4.4.2 Phyllic Alteration 84 4.4.3 Argillic Alteration 94.4.4 Propylitic Alteration 7 4.4.5 Secondary Alteration .......................... 99 4.5 Chemical Aspects Of Mineralization And Alteration Zoning 101 4.5.1 General Statement 104.5.2 Discussion ..................................... 101 4.6 Environment Of Ore Deposition ...................... 112 4.7 Evolution Of Mineralization And Alteration Zoning At The Poplar Porphyry ...................... ..115 CHAPTER V GEOSTATISTICS OF THE POPLAR PORPHYRY 117 5.1 General Statment 115.2 Correlations Eetween Variables ..................... 119 5.2.1 Two-Way Correlation Matrix 115.2-2 One-way Correlation Matrix 126 ix 5.3 Multivariant Analysis 128 5.3.1 General Statement5.3.2 Multivariant Equation For Chalcopyrite And Molybdenite 130 5.3.3 Estimation Of Error In Multivariant Equations 132 5.4 Summary Of Geostatistics 134 CHAPTER VI CONCLUSIONS 136 BIBLIOGRAPHY - . 139 APPENDIX A Analytical Data 152 APPENDIX B Poplarlog 155 APPENDIX C Computer Programs Used In This Study ............174 APPENDIX D Thin Section Descriptions .178 X LIST OF FIGURES Figure 1.1 Location Of The Poplar Porphyry ................ 2 Figure 1.2 Major Physiographic Subdivisions .......4 Figure 2.1 Regional Tectonic Setting ......................10 Figure 3.1 Typical Zonations In Porphyry Deposits .........17 Figure 3.2 Geology Of The Central Portion Of The Study Area ,20 Figure 3.3 Computer Generated Cross-section Of Geology Along Line A-A ......................................... 22 Figure 3.4 Computer Generated Cross-secticn Of Geology Along Line B-B* .23 Figure 3.5 Supplmentary Cross-section Along C-C*..Back Pocket Figure 3.6 Supplmentary Cross-section Along D-D*..Back Pocket Figure 3.7 Supplmentary Cross-section Along E-E*..Back Pocket Figure 3.8 Supplmentary Cross-section Along F-F(..Back Pocket Figure 3.9 Ternary Diagram Showing The Compositional Fields Of The Nanika And Bulkley Intrusions ................... 50 Figure 3.10 Aerial Phcto Lineaments In The Study Area .....52 Figure 4.1 Computer Generated Cross-secticn Showing Mineralization And Alteration Along Line A-A1 ........... 60 Figure 4.2 Computer Generated Cross-section Showing Mineralization And Alteration Along Line B-B* ........... 61 Figure 4.3 Mineralization And Alteration Of The Central Portion Of The Study Area ........................62 Figure 4.4 Bar Graph For Chalcopyrite ..................... 65 Figure 4.5 Bar Graph For Molybdenite ......................68 xi Figure 4.6 Graphic Log Of Potassic Alteration In Drill Core 74 Figure 4.7 Bar Graph For K-feldspar ....................... 78 Figure 4.8 Bar Graph For Biotite 80 Figure 4.9 Graphic Log Of Phyllic Alteration In Drill Core 85 Figure 4.10 Bar Graph For Sericite ........................ 87 Figure 4.11 Bar Graph For Quartz .......91 Figure 4.12 Bar Graph For Pyrite .......................... 93 Figure 4.13 Bar Graph For Clay «... ....96 Figure 4.14 Univariant Stability Relationships In The System A1Z03 - (K20-Na20)-Si02-H20 104 Figure 4.15 Schematic Diagram Of Fluid Pathlines Adjacent To A Cooling Intrusion .106 Figure 4.16 Log A(S2)-vs-Log A(02) Diagram For The System Cu-Fe-0 -S .......................113 Figure 5.1 Positive Correlation Cluster Based On Alteration Facies 12Figure 5.2 Ranked Intensity Of Chalcopyrite Verse Log Percent Chalcopyrite ................................... 134 Figure B.1 Poplarlog Coding Form Used In The Field ........157 Figure B.2 Model Of Alteration Facies In Porphyry Deposits 170 Figure B.3 Model Of Mineral Facies In Porphyry Deposits ...173 LIST OF PLATES Plate 3.1 Skeena Group Rocks .............................. 26 Plate 3.2 Kasalka Group Conglomerate ...28 Plate 3.3 Hornblende Quartz Monzodiorite .33 Plate 3.4 Biotite Quartz Mcnzonite ........................36 Plate 3.5 Intrusive Breccia ............................... 38 Plate 3.6 Porphyritic Dacite Dykes ........................ 40 Plate 3.7 Porphyritic Rhyolite ............................ 43 Plate 3.8 Ootsa Lake Group Volcanic Flow Rocks 46 Plate 4.1 Photomicrograph Of Chalcopyrite And Magnetite ...67 Plate 4.2 Photomicrograph Of Molybdenite Selvage ........... 70 Plate 4.3 Photomicrograph Of Intergrown Bornite And Chalcopyrite ...........................................71 Plate 4.4 Example Of Potassic Alteration .................. 73 Plate 4.5 Example Of Potassium Feldspar Envelopes .........75 Plate 4.6 K-feldspar Alteration Of Plagioclase Phenocrysts ,76 Plate 4.7 Secondary Biotite Alteration .79 Plate 4.8 Photomicrograph Of Secondary Biotite.Re placing Primary Biotite ...81 Plate 4.9 Phototmicrograph Of Coexisting Chalcopyrite And Magnetite 82 Plate 4.10 Sericite Envelopes Around Veinlets And Fractures ,. ........................................ .............84 Plate 4.11 Examples Of Phyllic Alteration ...88 Plate 4.12 Photomicrograph Showing Selective Alteration Of Zoned Plagioclase 89 xiii Plate 4.13 Example Of Argillic Alteration .,.97 Plate 4.14 Photomicrograph Of Propylitic Alteration .......99 xiv LIST OF TABLES Table 2.1 Major Volcanic And Sedimentary Bock Units Of West-Central British Columbia ................a......... 12 Table 2.2 Major Plutonic Bock Units Of West-Central British Columbia ........................... ... .................. 13 Table 4.1 Alteration And Ore Minerals Becorded At The Poplar Porphyry 56 Table 4.2 Alteration Facies At The Poplar Porphyry ........58 Table 5.1 Fifteen Hydrothermal Minerals Used In Statistical Analysis ....120 Table 5.2 Two-Way Correlation Matrix .................122 Table 5.3 Mineral Correlations Based On Alteration Facies .125 Table 5.4 One-Way Correlation Matrix ...127 Table B.1 Comment Codes Used On Poplarlog .................158 Taile B.2 First Type Modifier Used With Poplarlog .........160 Table B.3 Second Type Modifier Used With Poplarlog 162 Table B.4 Silicate Carbonate And Sulfate Alteration Minerals ..................166 Table B.5 Mode And Degree Of Mineralization And Alteration 167 Table B.6 One Letter Codes For Estimated Volume Percent Of Minerals ,..................168 Table B.7 Checklist Of Alteration Mineral Abundances ...... 169 Table B.8 Sulfide And Oxide Minerals 171 Table B.9 Checklist Of Sulfide And Oxide Abundances ....... 172 XV MAPS MAP A Back Pocket MAP B .......Back Pocket 1 CHAPTER I INTRODUCTION 1.1 Location The Poplar copper-molybdenum porphyry deposit, centered near 54<>01«N, 126°58» W (N.T.S. 93L/3E; 93E/15W), is located in west-central British Columbia approximately 270 km west of Prince George and 50 km south-southwest of Houston, in the Omineca Mining Division (Fig. 1.1). The deposit is situated near the centre of the northeast shore of Tagetochlain (local name Poplar) Lake. 1.2 Access Access to the Poplar porphyry by motor vehicle is made from Highway 16, one km west cf Houston, via the Morice River, Owen Lake, and Tahtsa Reach forest access roads to the southeast end of Tagetochlain Lake. A poorly developed dirt road parallels the north-east shore cf the lake and terminates at a core shack and abandoned drill camp on the property. The total distance from Houston is 80 km. Access to the deposit can also be made by helicopter from a helicopter base in Smithers or by float plane which can land on Tagetochlain Lake, adjacent to the property. 2 Figure 1.1: Location of the Poplar porphyry deposit; west-central British Columbia. 3 1.3 Physiographic Setting The study area lies within the Interior Plateau, approximately 20 km east of its boundary with the Coast Mountains. Major physiographic subdivisions of west-central B.C. are shown in Figure 1.2 (after Carter, 1974; and Holland, 1S78). The deposit is located in the west-central portion of the Nechako Plateau, an area of low relief that is largely undissected by erosion (Holland, 1964}; elevation generally ranges frcm 1225 m to 1530 m. This portion of the plateau forms a reentrant into the Hazelton Mountains and is bounded to the north and west by the Bulkley Ranges, and to the south by the lahtsa Ranges. Intense glaciation in the area has resulted in the development of many subparallel, northeast trending linear lakes (e.g. Morice, Nanika, and Whitesail Lakes). This orientation indicates a northeast tc eastward movement of advancing ice that originated from higher elevations in the Coast Range to the west (Duffell, 1959). Tagetochlain Lake, however, trends almost normal to this direction and evidence presented in Section 3.7 suggests a structurally controlled origin for the lake and adjacent valley. Duffell (1959) estimates that the glacial ice had a minimum thickness cf 1345 m because all peaks in the area were covered ty ice. R 10 to 25 km wide physiographic "transition zone" lies Figure 1.2: Major physiographic subdivisions of west-central British Columbia (after Carter, 1974; and Holland, 1978). 5 between the Nechako Flateau and the Coast Ranges (Duffell, 1959), and is characterized by small mountain ranges ( e. g. Sitola, Tahtsa, and flhitesail Ranges) trending northeast to east, normal to the regional northwest trend of the Canadian Cordillera. Locally, the deposit is situated in a northwest trending valley which parallels Tagetochlain Lake. The area is characterized by moderately rolling topography which ranges in elevation from 840 m at lake level to 1110 m at the western portion of the study area, and rises to 1626 m on Poplar Mountain, 6.5 km to the northeast. Two small streams, Canyon Creek and East Creek, cress the area and flow into Tagetochlain Lake. Local erosional relief varies from less than 1 m to over 10 m, locally forming steep cliffs. Vegetation includes grasses, wildflowers, and stands of aspen, spruce, and pine trees. Open meadows comprise roughly 60 percent of the land area, and are utilized by local ranchers for cattle grazing. Average annual precipitation averages 75 to 100 cm, but this study was carried out during 1978, an unusually dry and warm field season marked by only eight days of inclement weather. 1.4 History and Develop,pent Evidence of staking and limited assessment work prior to 1970 was discovered in Canycn Creek during the course of field mapping. However, nothing was found to identify the former developers. 6 The most recent history and development of the property began in the fall of 1970 with the initial staking of six claims by F. Onuchi and C. Critchlow (prospectors under contract to El Paso Mining and Milling Co. Ltd.), following the discovery of geochemical anomalies in silt and soil samples. During the summer of 1971 additional soil geochemical surveys led to the staking of 36 additional claims, which were recorded by F. Onuchi and M. Callaghan (Critchlow, pers. comm., 1978). That fall H. Jones of El Paso Mining and Milling Co. Ltd. commenced limited geologic mapping and extensive soil geochemical surveys (Jones, 1972). Copper and silver anomalies discovered by these surveys were investigated in the spring for 1972 by the excavation of four trenches. Based on the discouraging results from these investigations El Paso Mining and Milling Co. Ltd. transferred all claims on the property to the original prospectors in March of 1973 (Jones, 1972; and Critchlow, pers. comm., 1$78). Critchlow brought A. Schmidt of Hudson Bay Oil and Gas Co. Ltd. in tc examine the area during the summer of 1973 and additional claims were staked that fall (Critchlow, pers. comm., 1S78). Most of the claims were restaked by Critchlow during June of 1974, after many had lapsed. In August he drilled a hole near the south end of Canyon Creek and discovered "encouraging mineralization" (Critchlow, pers. comm., 1978). T. Schroeter, Resident Geologist at Smithers for the British Columbia Ministry of Mines, investigated the find and following his suggestion the 7 property was offered to several mining companies. The property was optioned by Utah Mines Ltd. on October 2, 1974. Exploration and development of the property commenced in the fall of 1^74; work included induced polarization and ground-magnetic geophysical surveys and the drilling of four BQ sized diamond drill holes, totalling 937 m (Schmidt, 1975; Witherly, 1S75) . Between 1S75 and 1977 additional exploration and development included geologic mapping, soil and silt geochemical surveys, geophysical surveys, and the drilling of 36 NQ sized diamond drill holes, totalling 7344 m in depth. 1.5 Scope of Study Nine weeks were spent on the property, during the course of this study, examining and irapping the surficial geology and logging the subsurface geology from drill core from 34 diamond drill holes. Particular attention was paid to logging the core along two cross-sections through the deposit (Map ft :Sections A-A' and B-B'). Detailed logging involved the use of a computer compatible data format, which was adopted to aid in statistical studies 8 involving a large number of geologic variables and to facilitate computer plotting of drill hole information. Wore detailed descriptions cf this logging format are given in Chapter III and Appendix E. 9 CHAPTER II REGIONAI GEOLOGTC SETTING 2. 1 JRiojial_T_§ctonic Sett lncj Regional tectonic elements of west-central British Columbia are shewn in Figure 2.1; included are the Coast Geanticline, the Hazelton Trough, the Nechako Trough and Bowser Basin, the Skeena Arch and tie Pinchi Geanticline. The Poplar porphyry deposit is situated on the southern flank of the Skeena Arch, which was a northeast to easterly trending positive feature frcm lower Middle Jurassic to Upper Jurassic (Tipper and Richards, 1976). White (1959) first recognized the Skeena Arch as a salient in the northwest trending folds of the Cordillera. The crest of the arch is marked by a concentration of small stocks and batholiths (Carter, 1974). Various origins for the Skeena Arch have been proposed, including: (1) a reactivated Precambrian basement feature (Carter, 1974); (2) a Jurassic volcanic arc, possibly controlled by basement features (Eisbacher, 1977) and; (3) an interarc high formed synchronously with andesitic vclcanism (Monger, et al., 1972). The Skeena Arch separates the Bowser Easin to the north, frcm the Nechako Trough to the south. These basins are interpreted as intra-continental successor basins filled with Figure 2.1: Regional tectonic setting of the Poplar porphyry in west-central British Columbia. 11 Middle to Opper Jurassic flysch and deltaic deposits derived from two paleo-topographic highs; the Pinchi Geanticline and the Skeena ftrch (Eistacher, 1977; Carter, 1974; and Tipper and Richards, 1976). 2.2 Regional. Geclogy The Poplar porphyry deposit is situated within the Intermontane Belt in west-central Eritish Columbia, approximately 30 km east of the boundary with the Coast Crystalline Complex. Stratified volcanic and sedimentary rocks, ranging in age from lower Mesozoic to Paleocene (Tipper and Richards, 1976b) underlie the Intermontane Belt of west-central Eritish Cclumtia. Major geologic formations of this region are compiled and summarized in Tables 2.1 and 2.2 (after Duffell, 1959; Carter 1974; Maclntyre, 1976; Tipper and Richards, 1976b; and flocdsworth, 1979). The Coast Crystalline Complex of west-central British Columbia is underlain by a central gneiss complex composed of banded amphibclite gneisses, plutonic rocks and minor schists, and skarn and marble (Woodsworth, 1979). This complex is in part derived from migtratization of the Paleozoic Gamsby Group, which consists of felsic and mafic tuff, epiclastic volcanic rocks, and limestone and associated skarn. The rocks of this group have all been metamorphosed to at least the greenschist facies (Woodsworth, 1979). Many satellites of the Coast TABLE 2.1 VOLCANIC AND SEDIMENTARY STRATIGRAPHY OF WEST-CENTRAL BRITISH COLUMBIA Epoch Oligocene or later Latest Upper Cretaceous to Oligocene Upper Cretaceous to Paleogene Early Upper Cretaceous Lower Cretaceous Lower to Middle Jurassic Group Endako unconformity Ootsa Lake Sustut Formation Ref unconformity Kasalka unconformity Skeena unconformity Hazelton Brothers Peak Local unconformity Tango Creek Swing Peak Mt. Baptiste Smithers Nilkitwa Telkwa Upper Triassic Takla Description Flat lying basaltic flows and related tuffs and breccia Mainly acidic flows with minor basalt, andesite, tuff, breccia, and rare (basal) conglomerate Acidic ash-fall tuffs and thick conglomerate bodies Feldspathic to chert-pebble-bearing arenites, mudstone and polymictic conglomerate Thick succession of flows and coarse clastic rocks (lahars) Rhyolite, subordinate andesitic pyroclastic and flow rocks, and basal pebble conglomerate Greywacke, sandstone, shale, conglom erate, minor to major coal seams, and basaltic to rhyolitic breccia, tuffs, and flows Greywacke, lithic sandstone, silt-stone, shale, tuff, volcanic breccia, pebble conglomerate, and silty limestone Interbedded shale, greywacke, andesite to rhyolite tuff and breccia, minor limestone Clastic, pyroclastic, and flow rocks Basaltic to andesitic volcanic rocks pelitic sedimentary rocks, minor carbonate rocks +References: 1) Tipper and Richards(1976); 2) Maclntyre(1976); 3) Duffell(1959); 4) Carter(1976); 5) Eisbacher(1974) to TABLE 2.2 INTRUSIVE ROCKS OF WEST-CENTRAL BRITISH COLUMBIA Age(Ma) 47-54 49-53 49-55 47-56 43-51 7 0-84 104* 133-155 173-206 Epoch Eocene Eocene Eocene Eocene Middle Eocene Upper Cretaceous to Tertiary Upper Cretaceous Upper Cretaceous Upper Jurassic to Lower Cretaceous Middle to Upper Jurassic Upper Triassic to Lower Jurassic Intrusive Suite Alice Arm Goosly Lake Babine Nanika Coast Crystalline Complex Intrusions Mt. Bolom Bulkley Kasalka Kitsault Francois Lake Topley Ref' 4 4 4 4 4 5 4 5 4,5 4,5 Description Small stocks of quartz monzonite porphyry which host major molybdenum deposits, including B.C. moly Porphyritic gabbro and synenomonzonite, representing centers of volcanism(?) Small plugs, dykes, and dyke swarms of fine grained biotite feldspar porphyry ranging from granodiorite to quartz diorite Small plutons of quartz monzonite to granite; hosts major copper-molybdenum deposits Quartz diorite, granodiorite, quartz monzonite; forms satellitic stocks east of, and marginal to, a central migmatitic gneiss Porphyritic biotite-hornblende granophyre Stocks and small batholiths of porphyritic granodiorite and quartz monzonite; hosts copper-molybdenum and molybdenum-tungsten deposits Porphyritic latite-andesite, porphyritic dacite, diorite Quartz diorite, augite porphyry porphyritic andesite, dacite Porphyritic quartz monzonite, diorite, quartz diorite, and granodiorite intrusions nf batholit deposit  of batholithic size; Hosts Endako molybdenum Quartz diorite to quartz monzonite; occupies core of Skeena Arch References: 1) Tipper and Richards( * Maclntyre determined this K-Ar date ceous age for this suite. 1976); 2) Maclntyre(1976); 3) Duffell(1959); 4) Carter (1976); 5) Eisbacher(1974) is incompatible with other geologic constraints and suggests an Upper Creta-14 Crystalline Complex forcibly of the Intermontane Eelt and by ultrametamorphism cf the c 1970; and Carter, 1S74). intrude stratified Mesozoic rocks are thought tc have been generated entral gneiss complex (Hutchinson, Carter (1974; and 1S76) has defined fcur intrusive rock suites, in west-central Eritish Columbia, which host copper only, copper-molybdenum, and molybdenum only mineralization. The individual suites are characterized and distinguished from one another by differences in age, type of mineralization, host rock composition, and location (Carter, 1974, and 1976). The setting of the Poplar porphyry with respect to Carter's classification scheme is discussed in Section 3.6. 15 CHAPTER III GEOLOGY OI THE POPLAR PORPHYRY DEPOSIT 3. 1 GENERAL STATEMENT Prior to the initiation of fieldwork it was known that the majority of geological information would have to be obtained frcm drill core. It further was decided that detailed logging of core frcm two cross-sections through the previously defined center of the deposit wculd form the major portion of the study. Drill core from other holes would be logged in less detail to facilitate extrapolation of geologic features in three dimensions. During the course of field study core from 12 holes totalling 2643 m was logged in detail, and core from 22 others totalling 6657 m was logged in less detail. Emphasis on information from drill core made it desirable to leg the core in such a manner that the data obtained would be quantitative and therefore valid for statistical analyses. This required that the measurements and methods used to log the core and record the data te as consistent and accurate as possible. At the same time the methods had to be flexible enough to accomodate any observed geologic feature that was considered pertinent. In addition it was desired that the information be amenable tc computer processing. 16 A logging format therefore was designed by modifying previous computer compatible logging formats (c.f. Blanchet and Godwin, 1972; Godwin, et al., 1977; and Wilton, 1978), and is referred tc as "Poplarlog". 3.2 Poplarlog Poplarlog is the name given to a 80 column drill core logging format, designed tc be compatible with the 80 columns of a standard computer card. Appendix B contains a blank Poplarlog coding format and a detailed description of its use. Also in Appendix E are tables with the meaning of symbols and codes that were used in filling cut the form. The majority of these symbols and codes as well as the diagrams cn which they are based, are taken from Godwin (1976), Elanchet and Godwin (1972) and Godwin, et al. (1977). Poplarlog was designed using the Lowell and Guilbert (1970) model of a 'typical' porphyry deposit as a basis, a simplified version of which is shown in Figure 3.1. The major characteristic of this model include: (1) concentric shells of alteration and mineralization centered around a porphyritic calc-alkaline stock, (2) occurrence cf characteristic minerals and/or mineral assemblages cf alteration and mineralization in each 17 Vns CHLORI-POTASSIC MODEL OF ALTERATION ZONATION Vns MODEL OF MINERALIZATION PROPYLITIC chlorite,tpidol«,olbit«,eorbonoti ARGILLIC cloyi, quortl PHYLLIC tfriclt* , quartz , pyrltt POTASSIC K-f«ld»por , biotite CHLOR I-POTASSIC chiori t • , K- ftldi por , »«ricit• Vni Vti MVI vtini vtinlett mi Cr 0 v «in I e tt Ont ditstminotlont (after Lowell and Guilbert, 1970) Figure 3.1: (a) Typical zonation of alteration facies in a porphy ry deposit; (b) model for "modes" of occurrence of alteration and economic minerals in a porphyry deposit. These models formed the basis for the development of Poplarlog. 18 particular shell, and (3) concertric variation in the style of occurrence of mineralization and alteration, frcm disseminated and pervasive at the center grading tc veins at the periphery cf the deposit. Every porphyry deposit, however, is urique, therefore the ceding fcritat has been designed to accomodate deviations from the typical deposit. Variables thought tc be the most valuable in describing the Ecplar porphyry deposit include: (1) position cf a described interval cf cere in x,y,z space , (2) 2cne cf enrichoent (i. e. hypegene, supergene, oxide, supergene sulfide), (3) original (pre-alteraticn) reck type; with descriptive and gualifyirg latels to record differences in texture and cr mineralogy which could later te used as criteria tc fern subdivisions cf reck units. (4) unusual or specific textural features present in the cere, and (5) sulfide, oxide and silicate alteration and economic 19 uineials present; their style cr "mode" cf occurrence, intersity, ard position within the Lowell and Guilrert (1S70) model. Ihree iieter depth intervals (roughly equal to two five foot core tcx lengths) were used to describe the core. However, in a fe* holes the nature cf the cere was extremely homogenous and a 6 in (20 ft) interval *as used to expedite logging. Shorter intervals viere used when afcrupt changes in the nature of the core were crserved. 3.2 Geological,Map and Cress-sections fciap fi (1:2500 cr 1 cm = 25 m) shews the geology cf the Icplar pciphyry depesit. The sap area, approximately 1800 m north-south ard 2100 n east-west, encompasses an area of 3.8 km2. Erill holes legged ir detail (i. e., 3 m intervals) are shewn as clcsed circles, these logged in less detail are shown as open circles. Figure 3.2 is a map of the central portion of the deposit. Cross-secticns A-A' and B-E * are through these holes logged in detail. Crcss-secticn A-A* trends east-west through eight holes, and is 1500 ir long; section E-E * trends 035° azimuth and includes four holes, ever a distance of 625 m. The geology of these sections, tasec cn computer clefs cf drill hole information are sho«n in Figures 3.3 and 3.4. These sections ;20 s s s s s vS.S W >9 -\ 3b / \ \ v \ \ \ ~ s / o-l-~—,2-V\ 1 14 o 28 / A- ©^6-0.-\ s . s 5—" \ \ \ \ V 3b N 4b xx. / \ / / Figure 3.2: Geology of the central portion of the study area (legend identical with Map A), scale= 1:5000. Rock units are: (1) Skeena Group; (2) Kasalka. Group; (3a) hornblende quartz raon-zodiorite, (3b) biotite quartz monzonite; (4a) porphyritic da cite, (4b) felsite; (5) porphyritic rhyolite; (6) andesite; (7) Ootsa Lake Group. 21 Figures 3.3 and 3.4: Computer generated cross-sections of geolo gy along lines A-A' and B-B' on Map A, respectively. LEGEND FOR COMPUTER GENERATED CROSS-SECTIONS OF THE POPLAR PORPHYRY Geology Rockunit Andesite Rhyolite dyke Felsite dyke Dacite dyke Biotite quartz monzonite porphyry - intrusive breccia Skeena Group Interval of core which could not be identified in the field; usu ally due to intense alteration. CROSS-SECTION SYMBOLS : ground surface overburden-bedrock contact -.—1 :— ' : geologic contact A, A/ 'W a A/ A. a\> fault, or faulted contact Tl 28 top of drill hole 28, on cross-section 1 Symbol o o • ® 616.35 642.75 663.15 I L I i i ELEVATION ABOVE SEA LEVEL (METRES) 635.55 721.94 748.34 774.74 801.14 827.54 853.34 880.34 _l I I I I I I I I I I I l ill 306.74 333.14 _J L_ cr %/•» fcO V/"» NJ"> A ^ OJ OJ cr ~D i— .OT —1 Q " i I 1 i 1—=» k U ro •CD ro m Q 1 1 o CD -< ID i— i o CD i— \ i i—i m —i i—» 04 CJO ro OJ ID GODC PLOT# 01637120. C3_ „ ^ ^ t<B RO„ ELEVRTION flBByE SER LEVEL (METRES) ; 616.35 632.75 669.15 695.55 721.94 738.34 774.74 801.14 827.54 853.94 890.34 906.74 933 —J 1 1 1 1 1 1 1 I -J I I I i i i i i i i III | \ cn. —i CD O cn a) cu' NJ / / / / CT \ \ \ \ cn CO" Jx cn Q -;o •LCJ ~J to ol rnw_ X I mpr" of —KD VK«/» ^ VIS VA Q VA,y> * VA VA in VA VA vA sA VA CM <A VA Q 3ca m -cu. co oi *A V\ K IA Ift^^^^^^WVN^V) VnVt VAV»V\V\V\ V^\rtV\ Vf> lA V* VA VA \A V\V>VAV>V» V\ WA v«\ AA VA sA vA \A\T» . NJ CM cr ^ 1 S V, ^ V VV"£ * ^ VA cr VA Vs \AV CO 5-cn fO cn Ol Ol a-CD cn cn" cn g" cn cn o-NJ 24 are plotted at a scale cf 1:1320 (1 cm=13.2 m) , which is the smallest size that plotting cculd te dene while retaining adequate resolution letween intervals. Supplementary cress-sections C-C, r-C, I-E* and F-F' (Figs. 2.5, 2.6, 3.7,and 2.8) are based on drill holes logged in less detail. These sections trend east-west with lengths cf SOC ir, 70C m, 400 m, and SCO m respectively, and are drawn at a scale cf 1:2500, ccnpstitle with Map A. 2. ii Jock_Uj3its 2.4.1 C vervie v> The Ecplar ccpper-ttclybdenum porphyry deposit is centered in a late Cpper Cretaceous coipcsiticnally zoned porphyritic calc-alkaline stock which has intruded upper Mesczcic vclcaniclastic ard epiclastic sedinentaiy recks. Mineralization and alteration were synchronous with emplacement and therefore the deposit is considered tc te paramagmatic (after White, et al., 1S6£). The deposit is cut ty several post-<-mineralization dykes ard is capped t] felsic volcanic flew recks. 25 3.4.2 Ire-Jn tiive_|cckg iii €Ej_ 6 tcuj Skeena Group recks (Unit 1) consist cf thinly tedded dark grey to light tar green crystal and lapilli (aquagene?) tuff and siltstone, and their contact metamorphosed equivalents, with locally intertedded rcedium grained sandstone lenses up to one meter thick (Elate 3.1). The unit forms an east-west trending telt through the study area (Map S), ranging frcm 60 tc 725 m wide. Bedding is defined ty sharp changes in eclour and texture, with planar tut locally undulating tedding surfaces that dip between 55° and 80° to the southeast. Upper and lewer contacts cf this unit are covered so that its tctal thickness is unknewn, but assuming an average dip cf 7C° ard a rcn-repeated section, there is a maxiffium 845 to cf stratigrapnic section present. Tuffaceous rocks are highly siliceous. Crystal tuff consists cf trcken guartz crystals ranging in size frcm 0.1 tc 0.25 rrm in a chlcritic matrix. Clcts of chlorite, clay, and spherulitic guartz are protably pseudomorphic after hornblende and biotite. lithic lapilli range frcn 4 nm tc 3 cm in size. Most rocks cf this unit have undergone varying degrees of 26 Plate 3.1: Skeena Group rocks (Unit 1, left to right) :_ (a) sili ceous ash tuff, iron staining from weathered pyrite veinlets; (b) thinly bedded siltstone, lighter patches are lenses of coar ser material? (c) crystal tuff. Scale is in centimeters. 27 contact Betamerphisa and/or hydrothermal alteration. Eifferences in permeability between sandstone lenses and the tuff probably account for an apparent stratigraphic control to hydrothermal alteration. Sandstone is intensely altered, but adjacent tuff teds are net. KasalkGroup Kasalka Group recks (Dnit 2) are found in a 300 m by 500 m salient cf pre-intrusive recks in the southeast portion of the study area (hap A). This unit, composed of reddish brown weathering pclylithic conglomerate, lies unconformably over Skeena Group rocks. Ihe contact is nowhere exposed and bedding in the conglomerate is undeterminable; however, cutcrcps of the Kasalka and Skeena Groups are found less than 10 m apart and neither unit grades towards the contact, therefore the contact appears to be sharp. Ihe conglomerate (Plate 3.2) consists of 85 percent rounded to sutangular clasts of felsic to intermediate tuff, and andesite, guartz, and banded chert. Lithic clasts are the most abundant and largest, ranging from one to five cm in diameter. Quartz clasts are mere rounded and are 0.25 to one cm in diameter. Barker tuff fragments appear identical to some of the Skeena Group recks. The matrix consists cf less than two mm grains of chert and guartz. The rock is cemented by silica, pyrite, specular and earthy hematite, and limonite. 28 Plate 3.2: Kasalka Group conglomerate (Unit 2). Clasts shown co sist of rhyolitic (?) and intermediate tuffs, and quartz. Scale is marked in centimeters. 29 3- <4. 2. 3 Correlation cf Pre-Intr usive Bock Units Tipper and Eichards (1967a) have described the upper portion of the Hazeltcn Greup as including an assemblage of greywacke, lithic sandstone, siltstone, tuffaceous shale, tuff, volcanic breccia and a poorly sorted pebble conglomerate. This unit was thought by Bcwen (1974, 1975, and 1976), and Mesard et al. (1979) to underlie the study area (Map A). However, with information obtained from recent regional mapping to the immediate south and southeast of Tagetochlain Lake by Woodsworth (1979, and pers. comm. 1978) the lower volcaniclastic and epiclastic unit (Unit 1) is assigned here to the Lower Cretaceous Skeena Group. The Skeena Group nas been described by Tipper and fiichards (1976a) to consist of greywacke, sandstone, shale, conglomerate and volcanic strata (Table 2.1). The upper conglomerate unit (Unit 2) is now assigned to the basal portion of the Upper Cretaceous Kasalka Group, which has been defined by Maclntyre (1976) in the Tahtsa Lake area, approximately 30 km south cf Tagetochlain Lake. Maclntyre (1S76) described this unit as a poorly sorted pebble conglomerate containing rounded to subangular clasts of oxidized Hazelton and Skeena Group rocks in a sandy matrix cemented with iron oxide and silica. The occurrence of the Kasalka Group conglomerate in the study area is the furthest location north of Tahtsa Lake that this unit has been observed. 30 3.4-3 Mineralized Intrusive Bocks General Statement Prior to the present study a number of porphyritic intrusive rocks, related tc mineralization and alteration, were identified by Utah Mines Ltd. geologists (Bowen, 1975, 1976 and pers. comm. 1S78). However, through the detailed logging of core during the course of this study, it is concluded that the textural and mineralogical differences previously attributed to different intrusive rocks are mainly due to the varying effects of hydrothermal alteration. The majority of mineralization and alteration at the Poplar porphyry deposit occurs within a late Upper Cretaceous guartz monzcdiorite tc guartz mcnzonite stock (Units 3a and 3b). Older rocks also host sulfide mineralization; younger rocks are barren except for rare occurrences of pyrite.. Therefore the major mineralization - alteration event is genetically related to this intrusive stock. Hornblende guartz monzodiorite (Unit 3a) , although mapped as a separate unit, is probably a hybrid border phase of the biotite guartz monzonite porphyry stock (Unit 3b). Widespread and variable alteration of all rock units (except Ootsa Lake Group volcanic rocks, unit 7) makes hand specimen and thin section examination difficult.. Commonly, only pseudomorphs after plagioclase and mafic minerals are available 31 for the interpretation of original texture and to estimate original mineral abundances. Groundmass minerals were often totally obliterated. Ambiguous relationships between alteration minerals compounded these difficulties. Hock descriptions which follow ignore alteration effects and are based on samples which have undergone the least amount of alteration. Bock names are taken from the classification of Streckeisen (1967) and the International Onion of Geological Sciences, I.U.G.S. (1973). Hornblende Quartz Monzodiorite Hornblende guartz monzodiorite (Unit 3a) is found at the surface in both the southern and western portions of the study area (Map A). The southern occurrence is bounded on the south by Tagetochlain Lake, and is found in intrusive contact with Kasalka Group rocks (Unit 2) to the north. The western occurrence forms a north-south trending outcrop pattern which is in gradational contact with the biotite guartz monzonite porphyry (Unit 3b) to the east, and in presumed intrusive contact (?) with Skeena Group rocks (Unit 1) to the west. However, this western contact is covered by Ootsa Lake Group volcanic rocks, (Unit 7) and therefore the exact nature of the contact is unknown. Fresh hornblende guartz monzodiorite, in hand sample, is 32 pale to dark grey and weathers pale tan to brown. The rock is porphyritic, with plagioclase and hornblende phenocrysts ranging in long dimension frcm one to eight mm and from one to 20 mm, respectively. Phenocryst packing varies from 10 to 80 percent, and phenocryst size varies inversely with abundance (Plate 3.3 ). The grcundmass is aphanitic to microcrystalline and ranges from ligbt to dark grey in colour. Thin sections of this unit show it to be composed of five to 20 percent euhedral to subhedral hornblende with an average length of 1.5 mm and a range of 0.1 mm to 20 mm. Seriate euhedral to subhedral plagioclase crystals ranging in size from 0.01 to eight mm, comprise from 10 to 70 percent of the rock. Plagioclase (about An33) is commonly glomeroporphyritic and zoned, and locally contains inclusions of quartz and zircon. Quartz, ranqing from one to 10 percent, occurs as resorbed 0. 1 to one mm subhedral crystals and anhedral infillings between plagioclase crystals in the groundmass. Orthoclase comprises about 15 percent of the rock, occurring as clouded equigranular anhedral crystals in the groundmass. Magnetite comprises approximately five percent of the rock, occurring as discrete grains in the groundmass or as inclusions in hornblende crystals. Euhedral books of primary oiotite, one to two mm across, range frcm less than one to five percent of the rock and are less abundant than hornblende. 33 Plate 3.3: Textural variations within the hornblende quartz mon zodiorite (Unit 3a). The sample on the left contains minor chal copyrite, the others are barren. 34 Whole rock major element analyses and C-I.P.W. norms of this unit is listed in Table A. 2 (Appendix A). These data will be discussed in more detail in Section 3.6. A K-Ar model age of 76.2 ± 2.7 Ma was determined from a hornblende separate from this unit (Table A.1 in Appendix A). This age is not statistically distinguishable from that of the biotite guartz monzonite porphyry, discussed below. This is a major criterion for interpreting the genetic relationship between these two units ( Section 3.5). Biotite puartz Monzonite Porphyry Biotite guartz monzonite porphyry (Unit 3b) underlies the northeast guarter of the study area (Map A), and comprises the most abundant rock type in the cross-sections (Figs. 3.3, 3.4, 3.5, 3.6, 3.7,and 3.8). This unit is bordered to the south and east by Skeena Group rocks; to the west it is in gradational contact with the hornblende diorite. Boundaries to the north and northeast have not been mapped. Contacts between the biotite guartz monzonite and Skeena Group rocks generally are intrusive but locally are faulted forming steeply sheared inliers of Skeena Group rocks within the intrusion (Figs. 3.3 and 3.4). Rocks on both sides of this contact have generally teen altered to such an extent that the original texture is totally obliterated which makes 35 identification of the rock type difficult. This intense alteration is due to abundant fractures and veins near the contact and the effect these fractures had on the localization of hydrothermal fluids. Contacts with the hornblende quartz monzcdiorite are gradational and are nowhere observed in outcrop. The contact is arbitrarily defined by a 1:1 hornblende to biotite ratio. Biotite quartz monzonite porphyry is light grey to black when fresh, and weathers reddish crown (Plate 3.4). One to seven mm euhedral biotite phenocrysts are diagnostic, comprising three to 15 percent of the rock. Euhedral to subhedral plagioclase phenocrysts range from two to eight mm across and comprise five to 80 percent of the rock. Size and packing of plagioclase phenocrysts is variable, even over short distances, and has a profound effect on the intensity and type of alteration present (discussed further in section 4.4.2). Hornblende phenocrysts form up to eight percent of the rock. The aphanitic groundmass is dark to pale grey to pink. Exotic fragments of Skeena Group (?) rocks ranging from one to 10 cm across were locally observed. Microscopically, the porphyritic texture varies from hiatal to seriate. Rare fresh plagioclase (about fin35) has normal and oscillatory zoning and is locally glomeroporphyritic. The groundmass is composed of 0.05 to 0.5 mm equidimensional 36 Plate 3.4: Biotite quarts monzonite porphyry (Unit 3b). This shows the compositional and textural variation within the unit. Plagioclase abundance and its susceptibility to alteration had the most effect on the variation in appearance. Plagioclase abun dance and intensity of alteration increases from left to right. 37 anhedral orthoclase and quartz, comprising 10 to 15 percent and 10 to 20 percent of the rock, respectively. Orthoclase forms local myrmekitic textures with guartz or plagioclase. Magnetite is commonly present as minute disseminations. Minor euhedral to subhedral apatite is also observed. Biotite guartz monzonite porphyry very locally consists of an intrusive breccia (Plate 3.5). The breccia consists of fragments of biotite porphyry and Kasalka Group(?) rocks which comprise 40 to 80 percent of the rock. Fragments are angular to subrounded, vary in size from 0.5 to 5 cm across and are rotated and generally matrix supported. The matrix is black to grey and varies from aphanitic to porphyritic with one to eight mm zoned and glomeroporphyritic plagioclase phenocrysts and one to two mm biotite phenocrysts. The groundmass of the matrix is composed of 25 percent 0.05 to 1.5 mm euhedral to subhedral biotite, and 50 percent subhedral to anhedral plagioclase 0.05 to one mm in length. The remainder consists of fine grained quartz, orthoclase, magnetite and apatite. Normative mineral abundances for the biotite guartz monzonite porphyry are listed in Table A.2 (in Appendix A). Two concordant late Upper Cretaceous K-Ar model ages for this unit, have been determined from biotite separates to be 76.9 ± 2.3 Ma and 73.7 ± 2.5 Ma (Table A.1 in Appendix A). 38 C M Plate 3.5: Intrusive breccia phase of the biotite quartz monzo nite (Unit 3b) . The clasts consist of both fragments of the por-phyritic phase of Unit 3b, and of Kasalka Group rocks (Unit 2). The matrix consists of 25% biotite. Chalcopyrite veinlet runs vertically through the sample one centimeter from the left edge. 39 3.4.4 Post^Ore Dykes 3.4.4. 1 General Statement Several north to northwest trending dykes intrude all previously described rock units (Map A and Fig. 3.2). The dykes do not contain any sulfides but are generally altered, especially at their contacts. This strongly indicates a second post-mineralization alteration event, and will be discussed in more detail in Section 4.4.5. There are four lithologically distinct dyke units; from oldest to youngest these are: porphyritic rhyodacite, felsite, porphyritic rhyolite, and andesite. Relative ages are defined by cross-cutting relationships. Porphyritic Dacite Dykes Porphyritic dacite (Unit 4a) occurs in faulted and intrusive contact with all other rock units except Kasalka Group rocks. The unit is found in three separate areas (Map A): (1) just east of the contact between Ootsa Lake Group volcanic rocks and the hornblende diorite, in the western portion of the study area, (2) in contact with a porphyritic rhyolite dyke (Unit 5), where both dyke units intrude mineralized biotite porphyry in the center of the study area, and (3) as one of many dyke units which occur between the biotite quartz monzonite porphyry and Skeena Group rocks in the eastern portion of Map A . Porphyritic dacite (Plate 3.6) is characteristically red to 40 Plate 3.6: Porphyritic dacite (Unit 4a). The drill core sample on the left shows pilotaxitic texture and contains xenoliths. The middle sample is a quartz latite-andesite from outcrop and is correlated with the dacite. The sample on the right shows the unit as it was most commonly observed, with biotite phenocrysts. 41 purple in colour, with a fine grained pilotaxitic texture. Amygdules, one to 20 mm across contain quartz and calcite. Bounded quartz "eyes" are locally observed. Fine to medium qrained euhedral plaqioclase, biotite, and hornblende phenocrysts comprise up to 25, 10 and five percent of the rock respectively. Zoned and glomeroporphyritic plagioclase (about An28) ranges from one to 10 mm across and have been partially resorbed. Biotite is one to five mm in diameter. Hornblende is one to five mm in length and has generally been altered to chlorite. The groundmass of the porphyritic dacite consists of mostly 0.1 ram laths of plagioclase with lesser anhedral grains of quartz and orthoclase. Fine grained apatite is an accessory mineral. Whole rock analyses of two samples of this unit are presented in Table A.2; one sample is from outcrop, the other from drill core. The former is classified as a quartz latite-andesite and the latter as a dacite (after Strechenisen, 1967). Tie term porphyritic dacite is preferred as a field name, and is used here to describe both rock types. One K-rAr model age of 72.2 ± 3.0 Ma has been determined for this unit from a biotite separate taken frcm drill core (Table A.2 in Appendix A). This date is important because it places an upper limit on the age of the mineralizing event at the Poplar porphyry. Field evidence, including chilled contacts and 42 paucity of sulfide mineralization, also indicates that this unit is younger than the mineralizing event which accompanied the intrusion of the biotite quartz monzodiorite porphyry. Felsite Dykes Light pink to tan aphanitic dykes (Unit 4b) less than two meters thick were noted in drill core . This unit resembles chilled portions of the porphyritic dacite dyke and is probably equivalent to it. However, locally this unit may'be the chilled equivalent to the porphyritic rhyolite. Porphyritic Bhyolite, Dykes Steeply dippinq porphyritic "quartz eye" rhyolite dykes (Unit 5) are the most abundant type of dyke rock in the study area (Map A.), and are found in faulted or intrusive contact with all other rock units except the Kasalka Group. Contacts with the porphyritic rhybdacite are qenerally chilled, but are locally gradational. Dykes of this unit generally trend northwesterly and are concentrated in areas marked by aerial-photograph lineaments which probably reflect fault zones. Porphyritic rhyolite (Plate 3.7) is characteristically white to tan with distinctive one to five mm embayed quartz phenocrysts ("eyes") comprising 10 percent of the rock. Chloritized biotite patches, one to five mm across are locally observed; one to two mm argillized plagioclase phenocyrsts are rare,. The aphanitic groundmass consists of 0.05 to 0.2 mm eguidimensional 43 Plate 3.7: Porphyritic rhyolite (Unit 5). Embayed quartz "eyes" are the most distinctive feature of this unit. Greenish spots are chlorite patches after biotite. The sample on the right has been stained to show K-feldspar in the groundmass. 44 eguigranular guartz and orthoclase. Andesite Dykes Dark grey andesite dykes (Unit 6) were intersected in a few drill holes. This unit is highly magnetic and consists of two percent altered, subhedral plagioclase and guartz phenocrysts 0.5 to 1.0 mm in diameter. The eguigranular groundmass consists of 95 percent subhedral plagioclase and three percent anhedral quartz, 0.1 to 0.2 mm in diameter. Locally the texture is amygdaloidal and pilotaxitic. A few 0.5 mm pseudomorphs of chlorite after hornblende (?) are also observed. 3.4.5 Extrusive Bocks ——————— i. , y. •• Ootsa Lake Group Ootsa Lake Group volcanic flow rocks (Unit 7) cap the hill immediately west of the deposit (Map A). From aerial photographs the lower contact of this unit, both near the deposit and on hills 1.5 km north and northwest of the map area, lie at approximately the same elevation; therefore, the lower contact of this unit is horizontal. Although the contact is obscured in the study area the flat attitude requires an unconformable contact with underlying units. Ootsa Lake Group volcanics also crop out topographically much lower, in Canyon Creek (Map A), and probably were emplaced by block faulting (see Section 3.7)•. 45 These rocks have not been dated isotopically, but are post-intrusive since they overlie and are not displaced by the major east-west trending fault which cross-cuts the deposit in Map A, yet protrudes from both sides of volcanic cover on aerial photographs. Outcrop of Ootsa Group rocks is characterized by subparallel cleavage that produces platey rubble which is pink, grey, or brown in colour (Plate 3.8). The rock is porphyritic, with lateral variations in phenocryst size; phenocrysts of coarse grained plagioclase and hornblende occur in the southwest, but become finer grained and impart a pilotaxitic texture to the rock in the northwest portion of Map A. Mineral content consists of 15 to 25 percent seriate plagioclase phenocrysts ranging from 0.5 to five mm in long dimesion, and up to 10 percent hornblende phenocrysts ranging from one to five mm in length. Plagioclase phenocrysts locally are pink due to inclusions of hematite, and can resemble orthoclase. The groundmass consists of 0.1 to 0.3 mm plagioclase laths and slightly larger and less abundant subhedral to anhedral quartz and anhedral orthoclase. Minor apatite is also observed. A whole rock analysis from a coarse grained porphyritic 46 Plate 3.8: Ootsa Lake Group volcanic flow rocks (Unit 7). The coarse grained porphyritic sample on the left comes from the southwestern portion of Map A. The middle sample shows pilotaxi-tic texture, and comes from Canyon Creek. The sample on the right comes from the northwest, and shows pilotaxitic texture, as in dicated by fine grained chloritized hornblende phenocrysts. 47 flow rock from this unit is presented in Table A.2 (Appendix A). The rock is classified as a dacite (after Strecheison, 1967). To the writer's knowledge there are at present no published data on the chemical composition of Ootsa Lake Group rocks. Therefore, no comparison can be made between "typical" Ootsa Lake Group rocks and the volcanic flow rocks found in the study area. Correlation of Extrusive Bocks Duffell (1959) described Ootsa Lake Group volcanic rocks as consisting of "... mainly acid flows with minor amounts of basalt, andesite, tuff, breccia, and rare conglomerate...." (Table 2.1). Tipper and Eichards (1967a, and 1976b) have mapped Upper Cretaceous volcanic rocks in the Tagetochlain Lake area as belonging to both the Endako and Ootsa Lake Groups (Table 2. 1) . After examining the volcanic flow rocks in the study area (Map A), Eichards (pers. . comm. , 1978) believed them to belong to the Ootsa Lake Group. 3.5 K-Ar Age Determinations Four K-Ar model ages were obtained at the Poplar porphyry (Table A.1, Appendix A): two from biotite separates of the biotite quartz monzonite porphyry (Unit 3b), one from a biotite separate of the dacite (Unit 4a), and a hornblende separate from the hornblende quartz monzodiorite (Unit 3a). All aqes are indistinguishable from each other within analytical error limits. The mean age of these dates is 74.8 ±2.6 Ma. 48 Because the age obtained from the post-mineralization dacite dyke is essentially the same as for mineralized rock units, the age of the mineralizing event can be considered geologically synchronous with the intrusion of the biotite quartz monzonite porphyry stock. White, et al (1968) have used the term "paramagmatic" to describe deposits which are epigenetic and can be shown by geological and/or radiometric evidence to be an integral feature of a magmatic event. 3.6 Comparison of the Poplar Porphyry to Other Porphyry Deposits  of West-Central British Columbia. There are a number of porphyry deposits located in west^ central British Columbia (Christopher and Carter, 1976)". Carter (1974, and 1976) has separated the intrusive rocks which host these deposits into fcur intrusive rock suites. Each suite is unique in one or more of the following: geographic distribution, type of contained mineralization, host rock composition, and K-Ar model age for intrusion. > These four intrusive rock suites form crude north-south trending belts. These belts consist of the following: the molybdenum bearing Alice Arm intrusions of Eocene age, on the west; copper and molybdenum bearing intrusions of the Upper Cretaceous Bulkley intrusions and Eocene Nanika intrusions, in the center; and copper bearing Babine intrusions of Eocene age, to the east. 49 Based on geographic location and type of contained mineralization, the Poplar Porphyry deposit cannot belong to either the Alice Arm or the Babine intrusive suites. However, intrusions of both the Bulkley and Nanika suites host copper-molybdenum porphyry deposits, and both types are known to occur within 50 km of the Poplar porphyry. The huckleberry, Ox Lake, Nadina , and Duck Lake intrusions are members of the former, and the Lucky Ship, Berg, Nadina Mountain, Goosley, and Morice Lake intrusions belong to the latter. The Nanika intrusive suite, however, is Eocene in age, and the Bulkley intrusions are Upper Cretaceous. A comparison between these ages and those obtained from the Poplar porphyry (Table A.1, Appendix A; and Section 3.5) indicates that all dated rock units at the Poplar porphyry were intruded during the Bulkley intrusive event. Further support of this classification is presented in Figure 3.9, which shows the normative compositional fields of the Bulkley and Nanika intrusions plotted on a ternary guartz-orthoclase-plagioclase diagram taken from Carter (1974, and 1976). Also shown on Figure 3.9 are the normative compositions of the hornblende quartz monzodiorite porphyry (Unit 3a) and the biotite quartz monzonite porphyry (Unit 3b). Hornblende quartz monzodiorite lies within the Bulkley compositional field and the biotite quartz monzonite porphyry lies on the boundary of this field. The latter is more potassium rich than most Bulkley rocks but is less siliceous than the Nanika compositional field. 50 QZ Figure 3.9: Orthoclase-Plagioclase-Ouartz ternary diagram show ing the compositional fields of the Nanika (N) intrusions, and the Bulkley (B) intrusions (after Carter, 1974, and 1976). Square is whole rock analysis of hornblende quartz monzodiorite, and circle is whole rock analysis of quartz monzonite from the Poplar porphyry. 51 From these criteria (geographical location, contained mineralization, K-Ar model age, and host rock composition) the Poplar porphyry is classified here as a Bulkley intrusion.. 3. 7 Structure Eegionally, the study area (Map A) lies just east of an area referred to as a "Transition Zone" between the Intermontane and Coast Crystalline tectonic belts (Woodsworth, 1979; and Duffell, 1959). The area surrounding Tahtsa (and probably Tagetochlain Lake) has been described by Maclntyre (1976) as containing major structural elements including "... high angle normal and reverse faults, which bound uplifted, down faulted, and tilted blocks". Woodsworth (1979, and pers..comm., 1979) identified major low angle thrust faults, southwest of the study area, with probable northeast movement -a direction normal to the trend of the Coast Crystalline Complex. The dominant structural trend in the study area is north-northwest, which parallels the trend of the eastern margin of the Coast Crystalline Complex; the uplift of which most likely dominated the structural regime in the area (Maclntyre, 1976). Due to a paucity of outcrop in the study area faults could be identified only in canyons and traces were extrapolated from drill core information. Aerial photograph interpretation was used to define larger structures (Fig. 3,^10). . Outcrop distribution, the dilational nature of dykes, the orthogonal nature of drainage patterns, and the alignment of these pattens 52 53 with major aerial photograph lineaments also were used to tentatively identify faults in the study area. . The regionally discordant trend of Tagetochlain Lake also is likely due to structural control, as can be seen in Figure 3.10 (Woodsworth, pers. comm. 1979; and Tipper and Hichards 1976a). Jointing, although common in drill core, is observed in outcrop only in Canyon Creek and East Creek canyons. Joint sets are spaced from centimeters to meters apart, forming a blocky to parallel pattern in Canyon Creek. Locally abundant, one to five cm, quartz-pyrite veins in Canyon Creek parallel the dominant north to northwesterly trend of jointing. This indicates the importance of jointing for localization of hydrothermal solutions during mineralization of the Poplar porphyry, and is evidence for directional permeability of these solutions (discussed in Section 4.5). 54 CHAPTER IV MINERALIZATION AND ALTERATION OF THE POPLAR PORPHYRY DEPOSIT 4.1 General Statement The major problem in deciphering and interpreting the geology of the Poplar porphyry deposit was distinguishing the textural and mineralogical changes in the rock due to variations within the original rock from those changes due to the effects of hydrothermal and supergene alteration. Early in the course of field study it was determined that the majority of variations in the appearance of the core was due to widespread alteration which varied in type, intensity, and mode of occurrence rather than differences in the original rock type. The effect of this variation is most discernible in the biotite porphyry (Plate 3.4). To define alteration and mineralization zoning at the Poplar porphyry the mode of occurrence (degree of dispersion, e. g. veins, patches, envelopes, or pervasive) and intensity (on ranked scale of abundance from nil = 0 to most intense = 9; see Appendix B) of twelve silicate, carbonate, sulfate, oxide, and sulfide alteration minerals, and four sulfide ore minerals were recorded for each 3 m depth interval (Table 4.1). The "intensity" of a particular mineral is used here to mean the volumetric abundance of the mineral, and implies no connotation to the physical conditions (i. e. pressure-^temperature) of the mineral's formation. Separate scales were used to rank the 55 intensity of different mineral groups. Silicate, carbonate, and sulfate minerals were ranked on one scale, and sulfide and oxide minerals ranked using another scale (Table B.6, Appendix B). Separate scales were used because the former group of minerals generally occurred in greater abundance than the latter, and to maintain resolution between differences in intensity in the sulfide-oxide group smaller intervals were used to rank their intensity. For example, a 3 m interval of core which contained 1235 chalcopyrite and 12% K-feldspar would be described as being "Very High" in chalcopyrite and given a rank of 8 while the K-feldspar would be described as "Fair" and given a rank of 3. The occurrence and relative abundances of these minerals, in every interval of core, was compared to a "checklist" of those abundances expected in any one of nine particular hypogene mineralization and alteration facies in the Lowell and Guilbert (1970) model, as modified by Blanchet and Godwin (1976) (See Tables B.7, and B.9 in Appendix B). A major problem encountered by using this approach was that two or more minerals, characteristic of separate and mutally exclusive alteration zones, according to the "checklist", were commonly observed in a single interval of core. 56 T&BLE 4,1 Alteration And Ore Minerals Recorded At The Poplar Porphyry Using Poplarlog Alteration Minerals Ore Minerals Quartz Chalcopyrite K-feldspar Bornite Biotite Chalcopyrite Sericite (muscovite) Molybdenite Chlorite Clay Epidote Carbonate Anhydrite-gypsum Pyrite Hematite Magnetite This problem reduced the effectiveness of the "checklist" method of defining alteration zones. Examples of conflicting mineral assemblages which may be found in a particular interval include: (1) vein minerals may be incompatible with pervasive alteration, (2) supergene mineral assemblages may be superimposed on hypogene assemblages, (3) incomplete alteration reactions are represented, (4) metastable mineral assemblages may occur, and (5) assemblages represent multiple alteration events. 57 There were, however, definite but more general mineral associations, observed at various intervals of occurrence in drill core, that parallel the Lowell and Guilbert (1970), Blanchet and Godwin (1972) , and Godwin (1976) alteration and mineralization zones.„ These zones are defined here as the potassic, phyllic, argillic, and propylitic facies of alteration, and the chalcopyrite-molybdenite zone of mineralization. This classification has no genetic connotation and refers only to the occurrence of the diagnostic mineral(s) defined for each facies. Each zone is characterized by a diagnostic mineral, or minerals, which define a particular facies; associated minerals are also commonly present, but are not considered diagnostic since they occur in more than one facies (Table 4.2). 58 TABLE 4.2 ALTERATION FACIES AT THE POPLAR PORPHYRY DEPOSIT, AND THEIR DIAGNOSTIC AND ASSOCIATED MINERALOGY. IN ORDER OF DECREASING ALTERATION GRACE. Mineralogy Facies (underlined minerals are diagnostic) Potassic K-feldspar. biotite. magnetite, guartz carbonate Phyllic sericite. guartz, pyrite, carbonate, hematite, gypsum Argillic clay, carbonate, guartz, gypsum Propylitic epidote, chlorite, carbonate 4.2 Distribution Of Alteration. And Mineralization, Zones At The Poplar,, Porphyry The distribution of alteration and mineralization zones at the Poplar porphyry is shown in plan on Map B and Figure 4.3, and in cross-section along lines A-A» and B-B• on Figures 4.1 and 4.2, respectively. Alteration and mineralization zones are defined by plotting the abundances of individual diagnostic minerals, from drill hole data, on computer generated cross-sections. Intervals that are above background levels of ranked abundance were used to determine the distribution of a particular facies. , Because some phyllic alteration was recorded 59 . Figures 4.1 and 4.2: Computer generated cross-sections of alter ation and mineralization along lines A-A1 and 3-B\ respectively LEGEND FOR COMPUTER GENERATED CROSS-SECTIONS OF THE POPLAR PORPHYRY Chalcopyrite Abundance Volume Percent 0 0.25%(trace) < 0.25% 0.25-0.5% 0.5-1.0% 16.0% Ranked Intensity Symbol 0 -1 a 2 S 3 Y 4 6 1.0-2.0% 5 *'E 2.0-4.0% 6 n 7 e 4.0-8.0% 7 R ."• X 8.0-16.0% s 9 •v CROSS-SECTION SYMBOLS ground surface overburden-bedrock contact geologic contact A, A/ "V A, A, A/ A/A, l\j fault, or faulted contact Yl 28 toP of dri11 hole 28, on cross section 1 EL^/HUON ABOVE SEA LEVAL (METFRS) _ nne „ _ 616.35 642.75 663.15 695.55 ^21.94 748.34 774.74 801.14 827.54 853.94 880.34 906.74 933.14 ~ ' ' » _J I I I I I I I I I I I I I I I I I fO O o ro M ru ID CO LO O co LO to (O CO CO Lo' to LO CO « CD CD 6 Ln' CO LO io" CD & o Lo' CD cn cn CO cn to cn cn to Ln" (Jl to cn • to cn ro ro Lo" «o cn 3 cn o ^3 ro to" CO m —Icn !±-LO CD co r--o gg <4f X-I ™" cog —ico t—I is-1 £ CO Lo' cn co ro CO X) m o CO m a rn co o —< DO O m m I rn a co X) ~n CD i—i O to cn cn Ln* cn CO to to cn ro-© CO ro-o cn ro-o ro-o to •o Ln' ro-ro co • . CO XI n ZD :z: a ZD x Gl m •D ! ZD O ZD "D ZT m xi ZD o Lo" ro t—a —i CO -J' ro-M o co ro co • . cn co ro -U cn io' co ro-H ro Lo' ro-LO o CO LO ro -co co ro • co CD cn co ro-<o io" ro ro 4» CO ro ro" 6 ro OK ..i i y 1111111111 II!! 11111111111111 III i y 111111111111111111 CO ro CO ON •o CO rs CM •II 11 1111111111111111 i P*?03"! I I P I I I I I I III I I I I O.l. v •2K 5 prm 4 23 5? 4 2TK X A X 3 PN Kl 4JU / / / II I'1 ,1" LJ v N V ^ v v \ \ \, \ \ \ \ \ V V; ^ \ \ \ \ \ \ \. \ \. \. \. ^ ^ \ \ \ \ \ v v ^ ^ \ \ \ X to fN MI in r 111111111111111111111111111 ii iii! 11 III 11 III 1111 CO i i 1—i i 1 1 1 1—i 1 1 1 1 1 1 1 r~ t>e*088 t«es& bS'Lze -brioe trwx W&L WIZL ss'ssg si'699 tS3^13W) "13A3~1 B3S 3r\Q8ti N0I18A3~]3 '221Z.£910 #101d 3Q03 62 Figure 4.3: Mineralization and Alteration of the central portion of the Poplar porphyry deposit (see Map B for more detail; le gend identical with Map B). Scale= 1:5000. Horizontal lines= chalcopyrite zone (C) ; vertical lines= molybdenite zone (M) ; right sloping lines= biotite zone (B); left sloping lines= K-feldspar zone (K); ph= phyllic zone; a= argillic zone; pr= pro-pylitic zone. 63 in almost every interval of core, potassic alteration was given priority when both facies were present in an interval of core. Zoning so defined avoids the complexity, noted in Secton 4. 1, caused when diagnostic minerals of more than one facies occur together in the same interval of core. Zoning is shown on Map A to consist of a 600 m by 500 m ring of potassic alteration associated with chalcopyrite and molybdenite mineralization. The potassic annulus surrounds a 300 m by 150 m central core consisting mostly of phyllic and argillic alteration. A 750 m wide east-west trending peripheral zone, consisting largely of phyllic alteration at depth and phyllic and argillic alteration near the surface, encompasses the potassic alteration zone. Fresh rocks are locally observed within this peripheral zone; however, most have undergone argillic to phyllic alteration. Outside the peripheral zone, rocks are generally fresh but locally propylitized. A portion of the potassic alteration annulus is truncated by an east-west trending fault (Map A). The offset portion was not intersected north of the fault by any drill hole. Therefore, its location is unknown, and offset along the fault is undetermined. This zonation is atypical for porphyry deposits in general (Fig. 3.1). Since the Poplar porphyry consists of an argillic core which is lower in 'alteration grade* than the potassic annulus which surrounds it, a second alteration event likely 64 took place. This is discussed in more detail in Section 4.4.5. 4.3 Sulfide Mineralogy Chalcopyrite and lesser molybdenite are the most abundant economic minerals present at the Poplar porphyry. Bornite, covellite, and tetrabedrite are minor and seldom observed in hand samples. Traces of chalcocite, sphalerite and galena were also observed. 4.3.1 Chalcopyrite Chalcopyrite at the Poplar porphyry is associated with the potassic zone, encompassing the central low grade core (Figs. 4. 1, 4.2,and 4.3,; and Map B). High grade chalcopyrite zones also occur in holes 34 and 39, and are thought by Bowen (pers. comm. 1978) to be part of a deeper or separate ore body. Chalcopyrite commonly occurs as 0.5 to 3 mm rounded to stellated disseminations, and is less abundant as veins and veinlets, which may also contain quartz (Fig..4.4). Numerous intervals hosted chalcopyrite in several separate modes of occurrence (i. e., as veins and disseminations, or as patches and veins, etc.). &s observed in polished section, disseminations of chalcopyrite are generally the result of dilation or 160H 16CH 140-4 140H 120H 120 H 100 100 80- 80H o c ca cr 60H ^ 40H 60H 40-2CH 20-1 6 7 8 1 2 3 7 8 CHALCOPYRITE intensity CHALCOPYRITE mode Figure 4.4: Bar graphs of the ranked intensity of chalcopyrite, and its mode"of"occurrence recorded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mod increases from 1= veins to 9= disseminated (see Appendix B for more detail). 66 intersections of microveinlets, and less commonly as isolated grains, commonly in altered mafic minerals (Plate 4.1). Chalcopyrite occurs with disseminated pyrite grains, and occurs as 0.01 to 0.05 mm inclusions in magnetite. During the course of field work a strong positive empirical relationship between- the abundance of chalcopyrite mineralization and of biotite and K-feldspar alteration was observed. This relationship was especially discernible where alteration facies changed over short intervals.. Statistical studies (Chapter V) emphasize these relationships, all of which have been described in the literature (Norton, 1972; Creasey, 1966; and Carson and Jamb-or, 1977). 4.3.2 Molybdenite It is difficult to estimate molybdenite intensity in hand sample because of its generally low abundance. However, a definite spatial zonation of molybdenite is shown in Sections A" A' and B-B" (Figs. 4.1, 4.2, and 4.3; and Map B). Molybdenite, like chalcopyrite, is spatially associated with potassic alteration minerals, but also has a strong empirical correlation with quartz veins. Molybdenite is largely restricted to guartz veins (Fig. 4.5), and is commonly either "ribboned" (see Wallace, et al., 1978), which consists of alternating layers of guartz and 67 Plate 4.1: Photomicrograph (30 X) showing anhedral grains of disseminated chalcopyrite (yellow) with very small spots of mag netite (white) located on the site of a chloritized (?) biotite phenocryst. 160 H 140 H 210 H po ison 100- 150H 80H >> o c « 60H 120-90-40- 60H 20H 30H 1 2 3 4 56789 MOLYBDENITE intensity 1 234 56789 MOLYBDENITE mode Figure 4.5: Bar graphs of the ranked intensity of molybdenite, and its mode of occurrence, corded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mode creases from 1= veins to 9= disseminated (see Appendix B for more detail). 69 coarse grained molybdenite, or occurs in a dark coloured mixture of guartz and very fine grained molybdenite (Plate 4.2). 4.3.3 Bornite Bornite, only rarely observed in drill core, occurs as fine grained disseminations, associated with chalcopyrite and locally with specular hematite. It occurs in polished section as rims around tetrahedrite inclusions in chalcopyrite and between chalcopyrite and hematite grains (Plate 4.3).. 4-3.4 Covellite Chalcopyrite and bornite ae observed in drill core to be very locally tarnished with a blue to purple iridescent coating of covellite. In polished section covellite is in contact with chalcopyrite along grain boundaries and fractures. 4.3.5 Tetrahedrite Tetrahedrite was identified only once in a hand sample of drill core. However, in polished section tetrahedrite appears to be more widespread. It is found as borders on, and inclusions in, chalcopyrite (Plate 4.3). The presence of tetrahedrite indicates that silver might be a recoverable by product at the Poplar porphyry. 70 Plate 4.2: Photomicrograph (30 X) of a molybdenite selvage in a quartz vein; the edge of a molybdenite vein in the lower left cor ner . 71 Plate 4.3: Photomicrograph (12 5 X) showing intergrown bornite (violet) and chalcopyrite (yellow) dissemination with small rim of tetrahedrite on the upper right edge. 72 4.4 Alteration Mineralogy 4.4.1 Potassic Alteration Numerous names and mineralogical definitions have been given for the potassic alteration assemblages found in porphyry deposits throughout the world (g. v. Creasey,,1959 and 1966; Burnham, 1962; Lowell and Guilbert 1970; Rose, 1972; and Gustafson and Hunt, 1S75). Based on chemical equilibria studies by Hemley (1959) and Hemley and Jones (1964), Jambor and Beaulne (1978) have defined potassic alteration at the Highland Valley, British Columbia, as consisting of secondary K-feldspar and/or secondary biotite, exclusive of all minerals considered essential constituents of other alteration facies (i. e., sericite, and kaolinite). The assemblages K-feldspar ± biotite, and biotite ± K-feldspar are observed in the field to be associated closely with chalcopyrite and lesser molybdenite. Other minerals commonly observed in this facies are magnetite, carbonate (mainly calcite) and quartz (Plate 4.4). A typical interval of potassic alteration in drill core is shown graphically in Figure 4.6, which is a bar graph of mineral abundances recorded for each 3 m interval of drill core. Salmon pink orthoclase is the only potassium feldspar observed in the deposit (Plates 4.5, and 4.6)., The majority of secondary K-feldspar occurs as envelopes around veins of quartz, 73 Plate 4.4: Example of potassic alteration. Magnetite vein is sur rounded by a K-feldspar envelope which grades out to pervasive secondary biotite. A later chalcopyrite vein can be seen offsett ing the magnetite vein. B 1 3? rvi ht>Ji K-SPAP R TOT T Tp MUSCOVITE CLAY CARBONATE ANHYDRITE PYPITE CHALCOPY MOLYBDENITE 74 ~??„ 30 AO *0 fO T0 11<"» ! ?0 ! 3" 1 Al I AO 1 fcO 1 70 ! 90 1 PO ~510" 710 ?30 741 _? 51 7r>0 770 ? 00 7^0 IPO ~VO0~ 310 316 ? 71 '3n 3 fti 170 3 <?0 7 Q-1 Ano "6 10' A ?1 ift n itO A 50 A57 4 70 4 RO 411 5 00 r jo HHMf'M HHtlOiM UMHn0 N MM un^ *j MUM HD M~" MM HO5 M M. u u n o •.( MMMO'M HHir" M H!l'-»ni MM UH-3 w UMWOOn MMHns M UMM°"M liMur'S ij~ D XPCV* p yon vy PHpn q p p^P" ri r pMpoiic" P'jpniic T nrrnr pnnpnc D n p*1 q c f>npi»H P] pr"»c Pl_ PP^F n-ipD n c P'IPf oc nv pnn F P'J pn;t F ~ PMPPRP D *j P o n p D * J P O (\ c P RPHF FL F'l c o^pprycr-p 7 pp or poppqp pnppRP nnpof^F ** * ** * ***** ***** ***** ***** ***** •-#**— *** * * * * * * *** * ** * *. ** * * ** "•****" ** #* ** ** ***** ***** ***** ********* * ****** * * * * ***** ***** ** * ** ** ** ** ** * + * ***** "~* "* * * ** ** ** * * " ** ** " ** * ** * T*** ***** ** **** ****** * ***** ********* *** ********* '"*** **• *** ** * * + * ******** * '" ******** *"' * ****** ******* ****** * ******* **** **** ***** ***** ** ** ** *»-*** ** * * ** ** *•* ** ""**•'** ** * * ** ** ** ** *•/.- * ** ** ** ** ** * * ** ** * * **** ** * * **** ** * * **** ** * * * * * * ' ** * * * * ***** **** ** * * * ** ***** **** ** * * * * ** ** ** * * * * *• ** ** * ** • +** *** ** * * *** *** ** * * + * ** ** * * * ** ** ** * * * * ** * **** *•• * * * *** **** *•« ***** **** * * * ***** • **** **' * ********* **** **** *** ** *•* ***** **** • *** **** *** ** *** ******* **** ** ** * ******* *+** ** ** * ******* ** ** ** ** ** ******* ** ** ** ~ ** ******** *** *** * * *** ******** *** ** * * * * ** ****** ** ** ** * ****** ** ** ** *** * ***** ** ** ** *** ******* ** ** ** *•* ******* ** ****** • * ** ** *** * **« ** ****** * ** ***** ** ******. * ** *** ** ** ***** * * ** ** * ****** ****** ** " * ****** * ***** ** * ****** '*•*** **** *** * ****** ***** * *** ***** *•** ******** * *** *** **» * • * ******** «*** * + * ** * * ** ****** ** + *'-**' * ****** ** * ** * ****** • * ** * ** ***** * * * * ** * * ** * ** ***** * ***** **** ** ** ** ****** **** *.* ** ** ****** ** * * ** ****** * ** ***** ****** ***** ** **** ** *** * * ***** ** **** ** ***** ******* ** *** ** ******* ** *** ** ****** ******* ** ** ** •* ****** ******* ** ** *** * Figure 4.6: Graphic log of mineral intensity (from zero to nine stars) for all minerals recor ded on Poplar log. This interval is from drill hole 24 and represents a typical interval of potassic alteration (i. e. K-feldspar, and biotite) . -j 75 1 W 1 w iff J 0 1 i 2 4 6 8 I l I 1 10 12 14 1 j C M Plate 4.5: Examples of potassium feldspar envelopes (left to right). K-feldspar surrounds a quartz vein and grades out into a green sericite envelope; K-feldspar envelope surrounding a quartz -chalcopyrite vein is developed in previous pervasive secondary biotite alteration; and a similar sample to the middle one, which has been stained to show the nature of the K-feldspar (yellow) alteration. Plagioclase is white. 76 r 4 Plate 4.6: K-feldspar alteration of plagioclase phenocrysts in an envelope surrounding a quartz-chalcopyrite vein. Scale is in cen timeter . 77 chalcopyrite and carbonate, and as combinations of veins and pervasive occurrences (Fig. 4.7). There is no empirical correlation between vein material or width, and width of the associated envelope. One mm to five cm envelopes are well defined in intervals which also contain pervasive secondary biotite. Pervasive secondary biotite imparts a dusty brown to jet black colour to the rock, depending on the intensity of biotite alteration (Plate 4.7); envelopes and patches are observed less often (Fig. 4.8). In general, biotite is most abundant in intevals of low vein and fracture densities.. Biotite patches, locally associated with chalcopyrite disseminations, consist of one to three cm wide spots, pseudomorphic after mafic xenoliths. Pervasive biotite occurs as 0.05 mm to 0.2 mm subhedral to anhedral pseudomorphs after primary biotite and hornblende (Plate 4.8). Opaque minerals (pyrite, chalcopyrite, magnetite, etc.) are commonly associated with the latter type of occurrence. Magnetite is most commonly observed as 0.1 to 2 mm euhedral to subhedral disseminated grains and in rare quartz-magnetite ± pyrite ± chalcopyrite ± hematite veins. Magnetite is intimately associated with chalcopyrite, in both disseminations and veins (Plate 4.9). Magnetite and hematite are both found as intergrowths or pseudomorphs after primary mafic minerals and 80n 7CH 60H 50-40 >, 30-1 o c a> => 20H cr a> >-"~ ioH 160H 140H 120H 100-80H 60-40-20" 3 4 5 6 7 8 9 3 4 5 6 7 8 K-FELDSPAR intensity K-FELDSPAR- mode Figure 4.7: Bar graphs of the ranked intensity of K-feldspar, and its mode of occurrence, re corded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mode in creases from 1= veins to 9= disseminated (see Appendix B for more detail). 00 79 Plate 4.7: Dusty dark brown secondary biotite near the bottom of the sample is overprinted by a K-feldspar envelope (middle of sample) adjacent to a split molybdenite vein (metallic grey in upper portion of sample). 40-1 80 H 35 H 70H 30H 60H 25H 5CH >» CJ c <u cr 2 OH 15H 40H 30' 10- 20H 10-7 8 9 7 8 9 BIOTITE intensity BIOTITE mode Figure 4.8: Bar graphs of the ranked intensity of biotite, and its mode of occurrence, recor ded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mode in creases from 1= veins to 9= disseminated (see Appendix B for more detail). 00 o 81 Plate 4.8: Photomicrograph (12 5 X) showing dark irregular grains of secondary biotite replacing primary biotite phenocryst. Opaque grains are magnetite (?). 82 Plate 4.9: Photomicrograph (30 X) showing irregular dissemina tions of chalcopyrite (yellow) and magnetite (white). 83 associated with secondary biotite. Potassic alteration, was in general the earliest alteration event at the Poplar porphyry. This is discernible where the diagnostic mineral (s) of more than one alteration facies are observed together. Cross-cutting relationships of veins and envelopes and replacement textures (Section 4.4.2) indicate that phyllic and argillic facies are superimposed on rocks that have undergone previous potassic alteration (Plate 4.10). Locally, however, potassic and phyllic alteration are synchronous (i. e., a guartz vein with a K-feldspar envelope grading into a sericite envelope; Plate 4.5). 4.4.2 Phyllic alteration Phyllic alteration is the most abundant alteration facies observed at the Poplar porphyry deposit (Map B; and Figs. 4.1, 4.2, and 4.3); affecting to some extent, almost every interval of core. Sericite, pyrite and guartz are the most commonly observed mineral cf this facies (Fig..4.9); pervasive carbonate alteration also is commonly observed in thin section. Sericite is in equilibrium with K-feldspar or kaolinite along univariant lines in temperature-pH space (Hemley and Jones, 1964). Under other than univariant conditions these minerals are mutually exclusive, consequently sericite alone is diagnostic of this alteration facies. The term sericite is used 84 Plate 4.10: Green and brown sericite envelopes from numerous veinlets and fractures impart a pervasive alteration to the rock Note that a small portion which had undergone previous potassic alteration remains. Ci^MricpTH5nrKT'Y''c OUA°TJ K-SP4» RinTITP MUSCOVITE CLAY CARBONXTE ANHYORlTE PYRITE CH4LCOPV MOLYBDENITE 1 3' ^ 7n S«n «• on 7^n pp QFUp no ncyp p | n p e< F nj_ poqp r»• I PP " r 7*11 7_v) 770 7 RO **90 o nn 010 H7T ? ?0" 940 Rc1 B"»0 P q'i "rt 90 901 OI0 0 ?i 030 040 Q50~ 9^0 9 30 1 r no Tf 04" p M D D n p PI or»n c D i_ o r» n F 0| ppf^c P ( ppq c o nnp q F ' f-norj PF-" PI or>;»c P| Ppn.F pn pn ap P1PPP.F pnpn'n C — P1POr\c pnppnp onppnc rrorqc D1Ri>qc P^PMl!" pn onq p on 00 q p pp PDrt C pn PP nc npp^c p^pTTqP POPf'TF pnpnqc pn DP ^ c nnpt'ir P»| Ppq F rinop'ii! ** 4* ** ** * * *** ***** * * *** ** + * *c •** *TV **** * * *•* ** * * *fr ** ** ** * * ** ** ** * * ** ** ** **** **** ** ** **** ~**ir*~ *** *** ** ***** *** ** ** *• *** ** •* •** * ** *" * >Y * ***** ***** *****" ***** * * ** * * * * * * * * ** ** ** ** ** ** ** *•* ** •* **** **** *** *** *** *** *** ** • ** ** * * **** *** *** *** * "'•"•"** **** •*• * ***** ***** **** **** ***** ***** **** ***• * * ** * * * **** ™* *** ***** ***** * * ** **** **** **** ** ** ** * ** *** ***** "*"* * * * * * * * * * * * ***** ***** ****** *** *** * * ** ** »* * * ** ** ** ** ***** —** * **~~ *** ** ***** *** * • *• * **** ~*v • ** *** *** *** *•* ** ** Figure 4.9: Graphic log of mineral intensity (from zero to nine stars) for all minerals recor ded on Poplar log. This interval is from drill hole 32 and represents a typical interval of phyllic alteration. 00 86 here to describe fine grained secondary muscovite, after Hurlbut (1971), Jambor and Delabio (1978), and Lowell and Guilbert (1970). The mineral is identified in hand specimen by lightly scatching the surface of a sample with a needle; a resultant "sieen" is indicative of sericite. Clay minerals on the other hand, produce a dull earthly scratch. If both minerals are present distinction is difficult. h binocular microscope facilitated field identification. Sericite occurs as a pervasive alteration with less commonly observed envelopes and patches (Fig. 4.10). Pervasive sericite alteration occurs; as (1) pseudomorphic replacement after biotite and hornblende phenocrysts and is commonly associated with pyrite, carbonate, and chlorite; (2) as an alteration of fine grained biotite, plagioclase, and orthoclase in the groundmass, which imparts a pervasive bleaching to the rock, and (3) as a light green to white selective alteration of plagioclase phenocrysts. The latter type of occurrence has the greatest affect on the alteration intensity recorded, since the volumetric intensity of alteration is dependent on the original plagioclase abundance in the rock. Plagioclase and biotite phenocrysts and are the most susceptible to phyllic alteration (commonly altered in an otherwise fresh rock) followed by plagioclase, biotite and K-feldspar in the groundmass (Plate 4.11). In zoned plagioclase sericite selectivly alters particular zones, either singularly or with associated carbonate and clay (Plate 4.12).. Envelopes of sericite, quartz, and 16CH 640H 140- 560 A 120H 480 H 100H 400H 80H 320-^ >> o c. CT 0> 60-40H 240H 160-20- 80 H 6 7 8 9 SERICITE intensity S ER I C J T E 6 7 8 9 mode Figure 4.10: Bar graphs of the ranked intensity of sericite, and its mode of occurrence, re- " corded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mode in creases from 1= veins to 9= disseminated (see Appendix B for more detail). 88 Plate 4.11: Three examples of phyllic alteration. Left: sericiti-zation of biotite phenocrysts (brown, linonite patches) and pla gioclase phenocrysts (bleached); middle: extreme pervasive pyrite -sericite-quartz bleaching. Pyrite and quartz veinlets cross the sample, sericite bleaches plagioclase phenocrysts and groundmass; right: sericite envelope affects only plagioclase phenocrysts, around a K-feldspar envelope and quartz vein. 89 Plate 4.12: Photomicrograph (30 X) shov/ing selective alteration of zoned plagioclase along specific compositional zones. Fine grained material consists of sericite and carbonate. Highly bi-refringent mineral at lov;er left is hornblende. 90 pyrite range in width from less than one mm up to tens of centimeters. Quartz and quartz-pyrite veins are most commonly associated with sericite envelopes. Greenish one to 15 mm patches of sericite, generally with guartz surrounding a pyrite nucleus are formed from the alteration of mafic phenocrysts or xenoliths. In thin section sericite generally is less abundant then had been recorded in the field, and is more commonly associated with clay and carbonate than had been thought during core logging. Quartz is the most widespread and abundant alteration mineral in the deposit, and occurs at least locally, with all other alteration minerals; however, it is most commonly observed with sericite and pyrite. Quartz is largely confined to veins, combinations of veins and patches, and patches and envelopes (Fig. 4.11). Quartz veining is the most important criterion affecting the distribution and mode of occurrence of other alteration minerals; veins of quartz are commonly surrounded by K-feldspar and/or sericite envelopes. Locally quartz extends outwards from veins tc form pervasively silicified rock. Quartz also occurs in veins containing pyrite, molybdenite, chalcopyrite and locally specularite and magnetite. Pyrite is the most abundant and widespread sulfide at the Poplar porphyry and is observed in almost all invervals of core. Pyrite has a bimodal mode of occurrence. Figure 4.12 400-140 + 3 5CH 120H 300H 100 1 250->> o 80 200-Z3 cr <x> GOH - 4CH 150H 100-20-i 50-6 7 8 6 7 8 QUARTZ intensity QUARTZ mode Figure 4.11: Bar graphs of the ranked intensity of quartz, and its mode of occurrence, re ded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mode i creases from 1= veins to 9= disseminated (see Appendix B for more detail). 9Z illustrates that pyrite occurs either as patches, and combinations of patches and veins, or as disseminations. Pyrite is ccmmonly observed on the sites of altered mafic minerals and less commonly as patches replacing mafic xenoliths. Pyrite may contain intergrowths cf both chalcopyrite and bornite. Specular hematite is associated with both phyllic and potassic alteration. However, because magnetite is much more abundant in potassic alteration, hematite is probably an oxidized product of magnetite in the phyllic alteration facies which is observed to have been superimposed on previous potassic alteration. Hematite occurs as one mm disseminations, and with guartz and calcite in veins. Calcite and lesser siderite and dolomite were observed in drill core, mainly as veins and veinlets and less commonly as pervasive alteration of plagioclase phenocrysts, with clay and sericite. Carbonate veins are associated with pyrite and minor chalcopyrite. Pervasive calcite alteration observed in thin section is associated with sericite, clay and chlorite occurring as subhedral to anhedral crystals and patches on altered plagioclase and hornblende phenocrysts. Carbonate observed in thin section shows it to be more abundant than had originally been thought during the field study. In particular carbonate is strongly associated in thin section with sericite and clay. Gypsum and lesser anhydrite, is widespread and locally 160H 160H MO-MO-120 H 120H 100H 100-o c Q) cr a> 80 H 60-40 H 20-80-60-40H 20--| 234567 8 9 PYRITE intensity 234 56789 PYRITE mode Figure 4.12: Bar graphs of the ranked intensity of pyrite, and its mode of occurrence, recor ded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mode in creases from 1= veins to 9= disseminated (see Appendix B for more detail). 94 abundant in the deposit, occuring in veins, averaging one cm wide. Although gypsum is widespread, and found within the potassic zone, it is most strongly associated with phyllic alteration. Gypsum is characteristically white to pink and varies from a dull massive translucent variety to a rare clear euhedral variety, with crystals up to five cm across. Veins of gypsum are commonly vuggy and locally associated with quartz and calcite. Pyrite is a commonly associated mineral. Phyllic alteration is closely associated with veins and fractures, and although sericite generally occurs as a pervasive alteration it is almost always associated with quartz, gypsum or pyrite veining, or barren fractures. . Much of pervasive sericitic alteration is the result of overlapping envelopes. Some of the most intense phyllic alteration occurs on both sides of the contact between biotite porphyry and Skeena Group rocks. 4.4.3 Argillic Alteration Argillic alteration is restricted in distribution and only locally is intensely developed. Clay is the diagnostic mineral of this facies; however no distinction could be made in the field between different clay minerals. Carbonate and quartz are associated minerals in the argillic facies. The most abundant and continuous occurrence of clay is found in the upper portion of drill hole 23 and in intervals of extremely sheared rock in drill hole 3 (Map B). 95 Clay is indentified in hand sample by a tackiness to the tongue, an argillaceous odor, the lack of a sheen when scratched with a needle, and by a pock-marked appearance in drill core due to its removal by drilling fluids (Fig. 4.13). Plagioclase phenocrysts were the most susceptible to argillic alteration (Plates 4.13). Clay forms extremely fine grained patches of low birefringence and low relief. Limonite may locally occur as a dark brown to opaque high relief stain with clay minerals to form a dusty or clouded appearance in thin section. Samples of drill core, selected from intervals where clay was recorded on Poplarlog in the field were analyzed by X-ray diffraction techniques to ascertain the type of clay minerals present (c. f. Godwin, 1976). Kaolinite was identified in every sample analyzed; illite was detected in only one sample. Sericite, biotite, and chlorite were locally recorded in addition to kaclinite. No pyrophyllite was detected. 4. 4. 4 Propylitjc, Alteration Propylitic alteration was never observed in drill core, nor was it obvious in surface samples, because of its low intensity and limited occurrence. Epidote is the diagnostic mineral of this facies^ but chlorite, carbonate and albitized plagioclase are also observed. 60H 45- 120H 100H <_> c a> z> cr a> 30H 80H 60 H 15 40H 20H 7 8 9 6 7 8 9 CLAY intensity C L AY mode Figure 4.13: Bar graphs of the ranked intensity of clay, and its mode of occurrence, recorded for each 3m interval of core. Intensity increases from 1= trace to 9= extreme; mode increases from 1= veins to 9= disseminated (see Appendix B for more detail). Plate 4.13: Argiilic alteration from the central argiilic zone, bleached to kaolinite. Greenish biotite remains fresh. in the biotite quartz monzonite Phenocrysts of plagioclase are patches are sericite. Note that 98 Epidote occurs in hornblende phenocrysts and as 0.1 to 0.5 mm subhedral intergrowths with albitized plagioclase phenocrysts (Plate 4.14) . Chlorite is the most abundant propylitic alteration mineral, but it is also observed in other facies (i. e. argillic) and is therefore not diagnostic. It occurs as intergrowths in biotite and hornblende developed parallel to original cleavage or along rims. 4. 4. 5 Secondary, Alteration The general paucity of clay minerals in drill core compared to locally moderate to high abundances in surficial rocks, and the localization of clay in zones of relatively high permeability near fault zones suggests that much argillic alteration is secondary, and possibly supergene, in origin. The close spatial relationship between this central argillic alteration zone and the major north-northwest trending Canyon Creek fault is further evidence for a secondary origin to this alteration due to a locally higher permeability. However the differentiation of clays derived by supergene processes from clays derived from hypogene processes is difficult (Rose, 1970; Creasy, 1966; and Godwin, 1976). The general lack of intense argillic alteration at the periphery of the deposit, and its occurrence at the center, 99 Plate 4.14: Photomicrograph (30 X) of propylitic alteration in the hornblende quartz monzodiorite. Highly birefringent mineral is epidote in altered plagioclase grain. Groundmass is largely chlorite and clay. 100 surrounded by a potassic alteration zone, is contrary to alteration zonation observed at the other deposit and described in the literature (i. e. Lowell and Guilbert, 1970; Drummond and Godwin, 1976; Eose, 1970; and Helgeson 1972). This is especially so, since no supergene sulfide or oxide minerals are present with the intense argillic alteration. Therefore this central argillic alteration zone was formed either by a late stage hydrothermal event which affected only those locations adjacent to areas of higher permeability such as the Canyon Creek fault; or from supergene processes which would have used the same permeable channels. Based only on the distribution of alteration facies which are present in rocks which host mineralization at the Poplar porphyry this second alteration event could be either supergene or hypogene in origin. However, since many post-ore dykes are also altered {i. e. sericitization of plagioclase phenocrysts in the porphyritic dacite, and chloritization of biotite in the porphyritic rhyolite) the solutions which altered these rocks must have been relatively warm and had a relatively low pH. Since traces of unoxidized and unaltered pyrite and chalcopyrite are observed in the central argillic core of the deposit the second alteration event was most likely not supergene in origin, or secondary copper minerals would be expected (i. e. covellite, chalcocite, cuprite, etc.). Therefore this alteration episode is considered to be hypogene in nature and may in fact be related to the intrusion of the dykes themselves which would have locally raised the temperature of the Poplar Stock, or to the overlying Ootsa Lake Group volcanics, which cap the deposit. 101 4.5 Chemical Aspects of Mineralization and Alteration Zoning 4.5.1 General Statement The three criteria for determining the stability of a mineral or mineral assemblage in an agueous system are: pressure, temperature and chemical potential (or activity ratio) of all components (Gibbs, 1873). In this section the zonation observed at the Poplar porphyry will be discussed in terms of these variables. 4. 5. 2 Discussion The generalized chemical reactions which best characterize the mineralogy of specific alteration zones, based on minerals observed in hand and thin section and the distribution of these zones, include: (4.1) Plagioclase +K+ = Orthoclase • (Na«-,Ca+ + ) (4.2) Annite + Mg++ = Phlogopite + Fe++ (4.3) Orthoclase + H+ = Sericite + Quartz + K+ (4.4) Plagioclase + H* + CC2 + K+ = Sericite + Carbonate + Na+ + Quartz (4.5) Muscovite • H+ = Kaolinite + K+ (4.6) Anorthite • H+ + CCL = Kaolinite 102 + Carbonate + Quartz (4.7) Anorthite + COz * Quartz + Na+ = Albite + Carbonate (4.8) Hornblende + CO^ = Chlorite + Carbonate (4.9) Anorthite + H+ = Epidote + H20 + Quartz These chemical reactions are generalized and are used only to help account for many of the mineral relationships observed in hand sample and thin section. Products of the reactions are observable alteration minerals (i. e. carbonate and sericite after plagioclase), and reactants can be identified locally from pseudomorphs (i. e. chlorite after hornblende) , or as a remaining part of a primary mineral which did not react (see detailed thin section descriptions in Appendix D). Microprobe analyses of biotites was beyond the scope of this study, however rections (4.2) is probable for the deposit based on studies of biotites frcm North America porphyry deposits by Beane (1974). Reactions (4.1) and (4.2) occur within the potassic alteration facies; (4.3) and (4.4) occur within the phyllic facies; (4.5) and (4.6) characterized the argiilic facies and (4.7) , (4.8) ' and (4.9) define the propylitic facies; • -103 The rections (4.3) to (4.6) and (4.9) are hydrolytic reactions (Hemley, 1964) , that is, they involve the consumption of H+ and the consequent release of a cation (ii e. K+,Ca++,Na+). Numerous authors (e. g,. Helgeson, 1970; Lowell and Guiibert, 1970; Hemley, 1959; Hemley and Jones, 1964; and Rose, 1970), have suggested that the typical potassic to phyllic to argillic to propylitic alteration observed at many porphyry deposits are due to various degrees of hydrolytic alteration. Helgeson (1970) has suggestd that alteration patterns at porphyry deposits are compatible with acidic solutions entering the margin of a pluton and reacting with host and country rocks, becoming less acidic with distance travelled inwards towards the core. As the fluid rises, due to thermally induced gravitational instability (Norton and Knight, 1977), it cools and may precipitate sulfides (Helgeson, 1964), thereby reducing solution pH, which promotes further acidic attack at shallow depths producing phyllic and argillic alteration zones above the deposit as well as along its margins (Helgeson, 1970). Implicit in this and similar models (i. e. Norton, 1972; Norton and Knight, 1977; Norton and Knapp, 1977; Villas and Norton, 1977; Cathles, 1977; Cunningham, 1978) is that fluid flow is free and permeability is symmetrical and isotropic. Figure 4.14 is a mineral stability diagram after Hemley and Jones (1964), Hemley (1959), and Hemley, Meyers, and Richter 104 Figure 4.14: Univariant stability relations in the system Al„0_.-(K20, Nao0)- SiO,- H20 (after Hemley, et al., 1960). Circled numbers represent chemical equations; possible mechanisms are dis-•cussed in the text, to inhibit a fluid from entering the Kaolinite Stability field. Total pressure= 1 kb. 105 (1961); with the 'direction' that a fluid packet, belonging to on the fluid pathline in Figure 4.15, takes from potassic to argiilic alteration facies indicated by an arrow. Superimposed on the diagram are numbered reactions (4.3) to (4.6). k schematic diagram of a porphyry type hydrothermal system with convective path lines, after Norton and Knight (1977), is shown in Figure 4.15. Numbered reactions (4.3) to (4.6) are placed at appropriate positions along the path lines to produce the alteration zoning observed at 'typical' porphyry deposits. The lack of hydrothermal argiilic alteration at the Poplar porphyry may be due to one or more of the following reasons (Fig. 4. 14) : (1) the original groundwater may not have had a sufficiently low pH to bring plagioclase or K-feldspar into the kaolinite stability field; (2) isotropic permeability along faults and joints may have restricted groundwater to certain areas of the deposit; and (3) the temperature of the intrusion and surrounding rocks may have been high enough to keep feldspar in the muscovite stability field (Fig. 4. 14) for most of the hydrothermal event, and then a rapid cooling and guick cessation of thermally induced hydrologic flow, with the majority of the deposit spending little or any of its time in the kaolinite stability field, until the second alteration event. Reactions (4.1), (4.4) and (4.7) involve potassium and/or 106 Figure 4.15: Schematic diagram of fluid pathlines adjacent to a hot porphyry type intrusion (after Norton,, and Knight, 1977) . Circled numbers refer to chemical equations referenced in the text and Figure 4.14; dotted lines are isotherms. 107 sodium metasomatism. Alternatively (4.4), (4.6), (4.7) and (4.8) may involve an increase in f (C02). . The high relative alkali activity of the solution, implicit in (4.1), (4.4) and (4.7), may in part be due to the release of these cations into solution during hydrolytic alteration. Norton (1977, Fig. 4) shows that depending on rock permeability and initial position of a "fluid packet" with respect to the intrusion, some fluid would indeed invade the already formed potassic zone after travelling through rocks that had undergone hydrolytic alteration. However, mass balance calculatins by Helgeson (1970), indicate that the actual molality of cations in solution remains essentially constant, and that the high alkali activities are instead due to a decrease of up to two orders of magnitude of hydrogen ion. This finding has been substantiated by Hemley and Jones (1964) who show that the stability of a particular mineral is a function of the "activity ratio" (i. e. a (Na+)/a (H+)) rather than the activity of a species alone. Therefore alkali metasomatism may occur either by a rise in the alkali activity due to cation release during hydrolytic alteration, or more likely, a decrease in a(H*) in solution during this alteration. Another source of alkalis for potassic or propylitic alteration (4.1), (4.2) and (4.7), could be the intrusive itself. Alkalis, water and silica are partitioned to the latest volatile rich phase of a crystallizing granitic magma (Jahns and Burnham, 1969; Hyndman, 1972; Burnham, 1967; and Carmichael, et 108 al., 1974). This fluid has been shown to make a substantial contribution to a hydrothermal system (Taylor, 1974; and Forester and Taylor, 1974). Fracturing of a chilled and impermeable brittle shell which encloses a crystallizing water saturated magma, either by P(HaO) exceeding lithostatic pressure plus tensile strength, or by outside tectonic influence, could initiate boiling, and the consequent release of alkali rich fluids along fractures and microveinlets producing alkali deuteric alteration. Boiling also promotes sulfide deposition, since it raises solution pH, and concentrates aqueous species (Cathles, 1977; Cunningham, 1978). Particular characteristics of alteration and mineralization zoning at the Poplar porphyry deposit are compatible with some of these features. Ignoring the central phyllic and argiilic zone (Section 4.2) because it is likley a secondary alteration feature (Section 4.4.5), the Poplar porphyry consists of an annular potassic alteration zone around a 'barren* core surrounded by a zone of phyllic and lesser argiilic alteration (c. f. Fig. 4.3). The high biotite abundance in the mineralized intrusive breccia, of the biotite porphyry (Section 3.4.3), suggests that the last phase of the crystallizing biotite porphyry was alkali and volatile rich (Section 4.4.1). Therefore the majority of potassic alteration is probably pneumatolytic in origin. 109 However, local reversals in the sequence of alteration (Section 4.4.1) suggests that some potassic alteration may be derived from later hydrogen ion depleted hydrothermal solutions (c. f. Helgeson, 1970; and Norton, 1977; above). Villas and Norton (1977), and Norton (1977) suggest that phyllic alteration takes place simultaneously with potassic alteration, at a lower temperature, outside the potassic zone. This probably took place in highly fractured and permeable Skeena Group rocks (Section 3.4.2 and 3.7) during the hydrothermal event. As the intrusion cooled large scale fracturing occurred due to thermal contraction. Permeability was enhanced along these fractures (Section 4.1 and 4.4.2) and meteoric waters flowed inward towards the centre of the deposit, hydrolytically altering both fresh rocks and those which underwent previous potassic alteration (Section 4.4.2)and produced the alteration patterns observed at the Poplar porphyry (Section 4.2). As the intrusion cooled, isotherms, and consequently phyllic alteraction collasped around the centre of the deposit as the lower stability limit of K-feldspar and plaqioclase was reached (Fig. 4.14; and Hemley and Jones, 1964). Those areas of the deposit which were not fractured, would be unaffected by hydrolytic alteration, and therefore the original potassic alteration minerals would remain (Section 4.1 and 4.4.1). The occurrence of a breccia pipe in many porphyry deposits is generally thought to be an expression of an explosive release of a vapor dominated phase above a shallow crystallizing stock. 110 This brecciation has an enormous influence on the localization of copper and molybdenum mineralization (Cunningham, 1978; Cathles, 1977) , and symmetrical hypogene zoning influenced by the greater permeability (Norton, 1977). If however, the excess pressure (P (H20) > P(Lith) + Tensile Strength) is '"tapped" by local fracturing events during emplacement and cooling of the stock, the pressure necessary for the development of a breccia pipe might not materialize. Consequently the alteration patterns observed would be controlled by much more directional permeability (faults, fractures, shear zones) about the intrusion. The locally faulted contact between the Poplar Stock and Skeena Group rocks (Section 3.4.3) may have aided such pressure release. Variables such as the healing and opening of fractures, multiple intrusive events and regional tectonics could further affect the circulation patterns of the hydrothermal system, and consequently the alteration patterns observed. Variation in the texture (i. e. plagioclase phenocryst abundance and packing, Section 4.4.2) and bulk composition of the altered host and country rock also has a profound affect on the intensity of a particular alteration facies. Reactions (4.2) and (4.8) are dependent on the activity of ferrous iron and the activity ratio of a(Fe++)/a(Mgt+). The oxidation potential of the system would have a major influence on this ratio since Fe+ + can be oxidized to Fe+++, while Mg has no equivalent trivalent state. Also the oxidation of Fe+ + 111 coupled with a sulfate-sulfide reduction could supply additional sulfide ion to the system. Precipitation of magnetite from solution would further tend to favour the right hand side of equation (4.2). The occurrence of magnetite within the ore zone of the Poplar porphyry and its association (along with chalcopyrite) with secondary biotite (Section 4.4.1) is compatible with these chemical relationships. Carbonate is an abundant alteration product in most samples of phyllic and argillic alteration at the Poplar porphyry (Section 4.4.2 and 4.5.2, reactions (4.4), and (4.6), (4.8)).. Because of the close association of altered plagioclase with calcite, the Ca++ released from plagioclase during hydrolytic alteration is probably the cation reactant for the carbonate (Section 4.4.2). Locally high fracture density in the host and country rocks makes the deposit locally susceptible to a second alteration event. The zonation at the Poplar porphyry includes a central zone of argillic and phyllic alteration which borders Canyon Creek fault. This zone is either secondary hypothermal or supergene in origin (Section 4.4.5). In addition, this zone occurs in an area bounded by a potassic alteration annulus and is suggestive of a "low-grade core" similar to that found in the Lowell and Guilbert (1970) model, because of a negligible amount of either supergene or hypogene mineralization. 112 4.6 Environment of Ore Deposition Mineral assemblages found in alteration and mineralization zones at the Poplar porphyry would, by themselves, place little constraint on the actual pressures and temperatures of formation and the chemical characteristics of the ore forminig splutions. However, work at other porphyry deposits , with similar potassic zone alteration and mineralization , can be used to place some limits on the environment of ore formation based on fluid inclusion (Roedder, 1971), stable isotope (Shepard et al. ,1971), and biotite geothermometry (Beane, 1974) studies. A temperature of 375°C, and a pressure of 250 bars (approximately equivilent to 2.5 Km of hydrostatic head) for potassic alteration and chalcopyrite mineralization at the Poplar porphyry is compatible with these studies. Chalcopyrite is the only copper bearing mineral observed in the deposit, except for traces of bornite, covellite and tetrahedrite, and is found almost exclusively in the potassic alteration zone (Map B), associated with magnetite. Figure 4.16 is a Leg a(Oz)-vs-Log a(Sz) diagram for the Cu-Fe-S^-02 system, at 250 bars and 375°C. The chalcopyrite-magnetite field is shown cross-hatched. This diagram indicates that potassic facies alteration and chalcopyrite mineralization occurred in an area ranging from -34 to -26 Log a (02) and from -13 to -4 Log a(Sz). 113 -10 H CO cr CD LU o >— X o -15H C3 O -20 -25 To -25 -20 -15 -10 LOG fl (SULFUR GRSh Figure 4.16: A Log a(S2).-vs- Log a(02) diagram for the system Cu-Fe-02-S2, at 375 C and 250 bars. TN= tenorite, CU= cuprite, C0= native copper, CC= chalcocite, CP= chalcopyrite, CV= covellite, BN= bornite, MG= magnetite, HM= hematite, P0= pyrrhotite, and PY= pyrite. The cross-hatched area is the stability field of magne-tite-chalcopyrite, found in the potassic zone of the Poplar por phyry. Arrow indicates direction of solution movement from po tassic to phyllic alteration facies. 114 The phyllic alteration assemblage contains no copper bearing minerals , but does contain a pyrite ± hematite assemblage (Section 4„4. 2). If copper was removed from the system (Fig- 4. 16) then pyrite and hematite would coexist along the join dividing their respective fields. The arrow in Figure 4.16 indicates the direction a solution would move from being in equilibrium with chalcopyrite-magnetite in the potassic facies to reaching equilibrium with pyrite ± hematite in the phyllic facies; both a(S^) and a(02) increase. If copper was present as the solution changed as described above then chalcocite+hematite, covellite+pyrite, or covellite+hematite should be precipitated as stable phases and observed in the phyllic alteration zone , which they are not. This suggests that chalcopyrite was removed by the same solutions which produced phyllic alteration minerals, rather than reacting to form another copper sulfide. Equation 4.10 may indicate a possible mechanism which may explain what happened. (4.10) CuFeS2 + 4H+ + 2C1- = CuCl" + Fe +++ + 2HZS As the solutions became more acidic rocks which had undergone previous potassic alteration and contained K-feldspar, plagioclase; and chalcopyrite were hydrolytically attacked. K-feldspar and plagioclase were altered to sericite or clay ± carbonate, and chalcopyrite was removed. The H S and Fe*++ released in reaction 4.10 may have been redeposited as pyrite ± 115 hematite ± chalcopyrite(?) in the phyllic alteration facies. 4,. 7 Evolution of Mineralization and alteration Zoning at the Poplar Porphyry In summary a model for the evolution of the Poplar porphyry deposit includes: A) Intrusion of a guartz monzonite stock, of the Late Cretaceous Bulkley intrusive suite, into Lower Cretaceous marine and volcanogenic sedimentary rocks of the Skeena Group, with concomitant fracturing and faulting of country rocks., B) Chilling of an impermeable monzodiorite shell around a cupola of the stock in contact with country rocks. Within this shell a water saturated alkali rich melt developes. C) Local fracturing of the shell, due to either excess vapor pressure, or an external tectonic event, initiates open but directional flow between intrusive and country rock, developing a convective hydrothermal system. Potassic alteration is formed early in the alteration sequence from late stage magmatic fluids, high in alkali metals (and/cr low in H+) concomitant with deposition of copper and mclybdenum sulfide. Fluids which are involved in hydrolytic alteration at the periphery of 116 the ore deposit convect inwards along localized fractures towards the central potassic alteration zone, reacting with wall rock, raising its pH and temperature along its path; eventually coming into equilibrium with the potassic alteration facies. As the stock cools, peripheral meteroic waters travel further through previously hydrolytically altered rocks, without raising its pH or temperature; subsequently the phyllic and lesser argiilic alteration zones collapse around the central potassic alteration zone. Continuous fracturing and healing of conduits, alternately enhances and inhibits the wall rock from reacting with hydrothermal solutions, leaving some higher"alteration grade" potassic - chalcopyrite - molybdenite zones unaffected by hydrolytic alteration. Seduction of stock temperature and the gradual diminution of the hydrothermal system. While the hydrothermal system was in its last stages numerous dykes were intruded followed by a second "lower grade" alteration event which overprinted most previous alteration zones that were within, or adjacent to, permeable areas (i. e. the central argiilic alteration zone). Holocene glaciation and removal of any cap or supergene mineralized horizons. 117 CHAPTER V GEOSTATISTICS OF THE POPLAR PORPHYRY 5.1 General Statement One of the most valuable characteristics of the Poplarlog format (Section 3.1, and Appendix B) for logging drill core is that geologic information is amenable to statistical analyses. Major advantages of statistical treatment of the large amount of data obtained at the Poplar porphyry include: the determination of geological variables which are most valuable for describing systematic spatial variations within the deposit; numerical results which may either verify or alter previously developed relationships based on field observations; and to indicate relationships not readily apparent from normal field observation. In particular, the determination of the type and strength of relationships among chalcopyrite, molybdenite, and alteration mineral abundances can be assessed statistically. In this chapter the results and interpretation of statistical analyses, consisting of linear correlations, and multivariant analysis, are presented. In addition to analytical statistical studies numerous computer programs have been designed to produce graphic illustrations of the spatial distribution and correlation between geologic variables (i. e. HISTLOG and CPY; Appendix C). 118 Over 1000 quantitative observations of 21 separate variables were made during the course of detailed loggiing of drill core along cross-sections A-A * and B-B* (Fig. 3.3,and 3.4;and Map A). These data were reduced to 739 observations by excluding data from unmineralized rock units such as post-ore dykes. Twenty-one variables that were examined in detail are listed and described in Appendix B; but for the purpose of this chapter the variables of most interest are the ranked intensities of 14 hydrothermal minerals (Table 5.1). Two computer packages, available at the Computer Science Centre at the University of British Columbia, were used in this study; TEP and MIDAS. TEP is an acronym for •Triangular Regression Package', the major purpose of which is regression analysis (Le and Tenisci, 1978). The major subroutines of TRP that were used, and their purpose are: INMSDC, for producing means, standard deviations, and simple correlation coefficients; SIMREG, for producing univariant linear regressions; and STPSEG, for multivariant regression analysis. MIDAS, or 'Michigan Interactive Data Analysis System' was used to calculate one-way correlations. Each of these subroutines are shown in Appendix D as they were used in a Fortran computer programs which were written by the author. 119 5. 2 Correlations Between, Variables 5. 2. 1 Two-way Correlation Matrix "Two-way" correlations is a term applied when all observations have equal weight in the correlation equation (Equation 5.1) (Le and Tenisci, 1978). (5.1) = "5, WL (Xi - X) (Yf - Y) ^. H; (X; - 1)2 Hi (Y; - Y)* where: r = w; x: x" = Y Y 1/2 correlation coefficient = weight of the i+K observation = value of the itk observation of X sample mean of X = value of the i*'*' observation of Y = sample mean of Y 120 TABLE 5.1 Fifteen Hydrothermal Minerals Osed in Statistical Analysis of Alteration and mineralization at Poplar Porphyry Deposit. ALTERATION MINERALS guartz K-feldspar biotite sericite chlorite clay epidote carbonate gypsum pyrite hematite magnetite ORE MINERALS chalcopryite bornite molybdenite Table 5.2 shows the correlation matrix, and the means and standard deviations of 14 economic and alteration minerals observed at the Poplar porphyry. The standard deviation of most minerals is as large or larger than their mean. This is because the number zero was recorded in the field when a particular mineral was absent in an interval of core; therefore zero does no represent a missing observation, but instead a numerical value. Except for quartz, 121 sericite, and pyrite which occur to some extent in most intervals of core, zero is the most frequently recorded value for any mineral, hence the standard deviation calculated accounts for this skewness towards zero. Correlations which disregard observations of zero in the correlation equation (5. 1) are discussed in detail in Section 5.2.2. Correlation coefficients that are statistically significant have been underlined in Table 5.2 by either a single or double line, indicating significance at the 99.0 percent and 99.9 percent confidence levels, respectively. Based on 739 observations a minimum departure from zero of 0.094 for the 99.0 percent confidence level, and 0.127 for the 99.9 percent confidence level, is required for significance (Dixon and Massey, 1969). The term "statistically significant" means that correlation coefficients with values above those calculated for a specific confidence level are significantly different from zero (i. e. there is a definite correlation) at the probability of the confidence level. Geologically significant correlations, with few exceptions, support correlations based on field observations (Chapter IV) and are shown classified by facies in Table 5.3. Alteration relationships defined by these correlation groupings" aire 'not only very similar to those in the field, but statistically substantiate the alteration facies of Lowell and Guilbert 7 l*i*-V CONTROL CARD NO. 1 ** INMSDC **** INMSCC **** INMSDC **** INMSDC **** INMSDC **** INMSDC **** INMSDC ** CONTROL CARD NOo 1 FORMAT CARDS ; -(30X,6 <1X,F1.0 ),1X,3(1X,F1.C>,5X,7(lXtFl.O) 1 CQRRELLATICN MATRIX QUARTZ 1.60C6 QUARTZ K-SPAR BICT IT SERICT CHLQRT CLAY EPIDO CARBS GYPSUM PYRITF HTPATT CHALPY BORNIT PAGNTT FCLY K-SPAR BIOTIT SERICT CHLCRT CLAY -O.0872 -0.0825 0.1139 -;lo 1'519" -0.0660 -0.0422 1.0000 0.4316 -0^306 -0.0080 -0.0651 0.0366 1.0000 -0.3002 n.O<fl -0.1108 0.0287 1.0000 -0.0333 0.3315 -0.087 2 1.0000 0.0288 -0.0034 l.COOO -0.0134 EPIDOT 1.0000 CARBS -0.0416 0 .0691 3646 -0.0078 -0.0611 -0.2215 -0.0600 0.0592 -0.0144 0.1281  -0.0975 0.0648 -0.1245 -0.0317 -0.0614 -C.1506 -0.0105 -0.0162 0.0920 -0.0162 0.0533 -0.0372 -0.1778 -0.0220 ST* -0.0204 «HfK -0.1260  0.1970 -0.0127 Q.122Q. -0.1966 0.0288 0-0364 -0.016E -0.0133 -0.6510 0.C148 0.0162 -0.0165 0.0125 -0.0052 1.0000 -0.3389  -0.2594  -16.1453 0.1117 0.010 5 -0.2634  0.1577 0-1376 •0.0063 0.1134 -Q.2182 -0.0429 0.C127 -0.0339 -0.C364 0.0407 -0.0129 0.0750 0.1740 0 .0550 GYPSUM PYRITE HEMATT 1.OOOO Op 3095 1.0000 -U. 14Hb -0.0981 -0. 0852 -0-1517 -0.C816 -0. 0867 1.0000 -p. 3008 0.0280 -0. C54S 0.00 86 -p. 2753 0.08 59 -o. 1271. -0.10 87 CORRELATION MATRIX CHALPY BORNIT MAGNTT HOLY I CHALPY 1.0000 0.0139 C". 2474. BCRNIT 1.0000 -0.0119 -0.078S MAGNTT MCLY 1.0000 -0,1264 1.0000 NAME MEAN STANDARD DEVIATION QUARTZ I 4.40054 2.09446 K-SPAR BIOTIT SERICT CHLORT CLAY EPIDOT CARBS GYPSUM PYRITE HEMATT CHALPY BCRNIT MAGNTT MCLY 1.62111 0.703654 4.70907 2.39520 1.66508 1.98928 0.224763E 0.338295 0.270636E -01 C.347700 C.932277 02 C.735712E-01 1.76049 1.13261 3.09202 1.74165 1.89744 1.97263 0.489851 1.45467 0.243572E -01 1.09611 1.60505 G.170928 0.510149 1.02842 1.45886 1.45874 739 OBSERVATIONS TOTAL 739 OBSERVATIONS ARE COMPLETE 738 DEGREES CF FREEDGE 123 Figure 5.1: A positive correlation "cluster", based on alter ation facies between minerals which are significantly correlated. Divisions between potassic, phyllic, and argillic facies are shown. 124 (1970). Figure 5.1 is a Correlation 'Cluster* diagram showing mineral correlations grouped according to alteration facies. One significant correlation which was not identified in the field is carbonate - pyrite. A correlation which was expected to be significant, but cannot be shown here to be so, is sericite - pyrite. The significant negative correlation (-0.1284) between molybdenite and magnetite is anomalous, since both are positively correlated with K-feldspar (Table 5.2), and both occur within the potassic alteration zone. However, molybdenite is largely restricted to guartz veins , and quartz is negatively correlated with magnetite. Therefore, the relationship between molybdenite and magnetite, may be due to the absence of magnetite near quartz veins, rather than its true spatial relationship to just molybdenite alone. The most useful correlation for the economic evaluation of the deposit are those that not only define alteration facies, but also establish which minerals are the most useful in predicting the occurrence and abundance of chalcopyrite and molybdenite. Chalcopyrite is correlated positively with potassic alteration minerals, and negatively with phyllic alteration minerals (Table 5.2). Molybdenite, less well defined in terms of facies relationships, is correlated positively with the potassic alteration facies minerals K-feldspar and biotite, and with quartz in the phyllic alteration facies. It is 125 TABLE 5.3 Correlations Between Minerals Based on Alteration Facies1 FACIES MINERAL +CORRELATION -CORRELATION Potassic K-feldspar biotite biotite chalcopyrite magnetite molybdenite chalcopyrite molybdenite K-feldspar sericite pyrite hematite sericite clay hematite magnetite Phyllic sericite carbonate chalcopyrite K-feldspar quartz clay . carbonate hematite quartz sericite gypsum pyrite molybdenite chalcopyrite magnetite K-feldspar biotite gypsum quartz pyrite pyrite sericite molybdenite gypsum quartz hematite magnetite K-feldspar magnetite chalcopyrite molybdenite clay carbonate Argiilic clay sericite gypsum biotite pyrite carbonate hematite chalcopyrite magnetite sericite gypsum pyrite This table is a summary of analytical results shown in Table 5.2 126 correlated negatively with pyrite and hematite in the phyllic alteration facies, and with magnetite in the potassic alteration facies, 5,2.2 One-way Correlation Matrix One-rway correlation is calculated using Equation (5. 1) ; if a principle variable X , is zero for a particular observation, i, that observation is excluded from the regression; the secondary variable, Y , is considered regardless of its value for a particular observation. The purpose of such a calculation is to distinguish those correlations which occur between variables because both, though unrelated, maintain mutual values of zero in a number of observations, and are consequently assigned a correlation coefficient that may not indicate their true spatial relationship. The one-way correlation matrix (Table 5.4) is nonsymmetrical, indicating that two variables have different correlation coefficients, depending on which is chosen as the principle variable, X . This shows that the inter-dependence of the two minerals is unequal (i. e. .the occurrence of mineral A is a more dependent on the occurrence of mineral B, than vice versa). For example, Tahle 5.4 shows that although chalcopyrite does not correlate significantly with occurrence of the principle variable K-feldspar; K-feldspar does significantly correlate with the occurrence of the principle variable chalcopyrite. TABLE 5.4 One-way Correlation Matrix of Alteration and Economic Minerals Quartz K-feldspar Biotite Sericite Chlorite Clay Epidote Carbonate Gypsum Pyrite Hematite Chalcopyrite Bornite Magnetite Molybdenite N3 b r99.0 Quartz 1.0 -.146 -.1297 1.567 . 0387 -.092 -• 057 -.106 .1017 • 3897 -.054 -.095 .010 -.1932 .0769 692 0.098 K-feldspar .0459 1.0 • 3439 -.045 -.085 -.055 -• 005 -.058 -.143 -.008 -.099 -.029 -.064 0.063 +.109 286 0.151 Biotite -.137 .2082 1.0 -.1949 • 2625 0.1212 .-• 0985 -.0498 .3327 .2055 -.078 .0511 -.0519 -.2073 .1069 133 0.223 Sericite .114 -.3104 -.2745 2.0 .0745 •1111 0. 0 • 1191 -.0832 .0701 • 1162 -.2054 .0244 -.2437 -.0438 727 0.095 Chlorite 0.0 -.0848 .967 -.4698 +.106 -.1446 0. 0 -.536 • 9670 .6926 -.1501 -.6954 0.0 -.2583 0.0 12 0.695 Clay .0474 .0040 .1826 .4113 -.0602 1 .0 0. 0 -.0534 -.0379 -.1189 -.1083 .1083 -.1116 -.0951 -.0156 112 0.2iZ Epidote 1.0 1.0 1.0 1.0 1.0 1 .0 I. 0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1 1.000 Carbonate .0331 -.0699 -.0744 • 1982 0.0332 .0448 0. 0 1.0 -.2372 -.1016 .0886 .0686 .0421 .1433 .0079 484 0.115 Gypsum -.0520 -.0818 .0806 .0299 • 2272 - .0446 0. 0 -.2492 1.0 • 2947 .1360 -.0059 0.0 -.1398 .0363 230 0.170 Pyrite • 3156 -.2555 -.0723 .0735 .0154 - • ir,27 -. 0357 -.1894 .2912 1.0 .0672 -.2241 -.226 -.1882 -.2017 646 0.101 Hematite -.0411 -.1401 0.1052 .0646 .0473 - .1533 0. 0 .1445 0.1456 .0325 1.0 -.0936 .0039 -.0029 .0062 184 0.188 Chalcopyrite .0610 : .1279 .1027 -.2535 -.0769 -• 1627 -. 0156 -.0902 .2018 -.0584 • 1288 1.0 -.0276 .2263 .1170 439 0.122 Bornite -.1471 .3388 -.1677 -.2275 0.0 .2190 0. 0 -.3962 0.0 .3797 -.1862 -.4467 1.0 -.1299 -.1690 16 0.623 Magnetite -.1475 -.0113 0.1114 -.4473 -.1036 • 3072 0. 0 .0623 -.0354 -.1289 -.1196 .1688 .0028 1.0 -.1069 109 0.256 Molybdenite • 1704 .0116 .0097 -.0046 .0358 .0144 0700 -.0376 -.0466 .0549 .0153 • 2841 -.0858 -.0479 1.0 312 0.145 Underlined correlation coefficient are statistically significant. a) N • number of observations of a particular variable in Equation (5.1). Equal to the number of non-zero observations b) r^j - minimum correlation coefficient, for the number of observations, N, at the 99.0 percent confidence level. Calculated from 0 Lxon and Massey (1969) 128 Results from the one-way correlation matrix (Table 5.4) in general corraborate results on the mineralogy of alteration facies presented in Sections 4.3, and 4.4. Quartz and sericite correlate positively with each other, and negatively with potassic alteration facies minerals and chalcopyrite. Chalcopyrite correlates significantly with K-feldspar, gypsum, hematite, and magnetite and negatively with sericite and chlorite. Molybdenite is positively correlated with quartz, and chalcopyrite. Inconsistencies between results from one-way (Table 5.4) and two-way (Table 5.2) correlation matrices include the lack of a significant positive correlation between K-feldspar and biotite, and between these minerals and chalcopyrite and molybdenite in the one way correlation matrix. The lack of a significant positive correlation between pyrite and sericite is also apparent in Table 5.4. 5.3 Multivariant Analysis 5.3.1 General Statement Univariant linear analysis (linear correlation between one dependent and one independent variable) is useful in evaluating what effect, if any, one variable has on another. Correlation coefficients presented in Section 5.2 are measures of this dependence between twc variables. However, this approach is restricted since most geologic variables are the result of interactions between numerous other variables (Davis, 1973). Multivariant analysis allows one to consider changes in several properties of a system simultaneously, in order to sort out the 129 major factors determining the relative worth of variables. (5.2) I = A,X(1) • A2 X (2) + . . ... • AMX(N) • K where: Y = dependent variable A; = coefficient of the i+K independent variable Xf = ifk independent variable K = a constant that is egual to the Y-intercept cn the regression hyperplane The multivariant regressions were performed using the subroutine STREG from the TRP statistical computer package (Le and Tenisci, 1S78). Both frontwards and backwards stepwise regression techniques were employed, with equal results (Equation 5.3 and 5.4). In backwards stepwise regression all independent variables are included in the equation (5.2) at the first step; a multivariant equation is calculated with a minimum variance in Y for those variables. Each variable is then tested for significance by computing the probability of obtaining an absolute value of the coefficient 'A' greater than the one calculated, if the variable X made no significant contribution. The greater this probability, the less significant X is to the 130 equation. If this probability is greater than 0.05 (five percent) the variable is eliminated from the equation. The least significant variable is dropped from the equation at each step and a new eguation is calculated by minimizing the variance between the remaining variables. This routine is carried out until each independent variable left in the equation has an associated probability of less than 0.05. 5.3.2 Multivariant Equations for Chalcopyrite and Molybdenite Multivariant equations (5.3 and 5.4) are presented for the dependent variables chalcopyrite or molybdenite versus the independent variables guartz, K-feldspar, gypsum, pyrite, and magnetite. Molybdenite was an independent variable in the chalcopyrite equation (5.3), and chalcopyrite was an independent in the molybdenite equation (5.4). (5.3) Chalcopryite = 0.78 quartz +1.5 biotite * 0.24 magnetite + 0.25 molybdenite - 0.07 sericite - 0.20 pyrite + 1.59 r2 = 0.229 S.E. = 1.415 E.I. (5.4) Molybdenite = 0.12 quartz + 0.05 K-feldspar • 0.23 chalcopyrite - 0.11 pyrite -0.20 magnetite + 0.52 r2 = 0.149 S.E. = 1. 350 E.I 131 Where: r2 = multiple correlation coefficient; equal to the proportion of the variance of the dependent variable, Y, accounted for by the regression line. S.E. = standard error; the estimate of the variance of the dependent variable Y, about the regression hyperplane (Le and Tenisci, 1978). Units of standard error are the "ranked abundance" used in logging drill core ( Appendix B)• E.I. Means Banked Intensity. (see Section Equation (5.3) indicates that the empirical relationship between chalcopyrite and the potassic and phyllic alteration facies is substantiated when the effects of the other variables are taken into account. The notable exclusion of K-feldspar from the equation is because its associated probability was greater than five percent. Even though K-feldspar and chalcopyrite are correlated positively at the 99 percent confidence level (Secions 5.2.1 and 5.2.2) K-feldspar is interdependent on the variables in the equation and forms a linear combination of the other independent variables (Le and Tenisci, 1978). Therefore K-feldspar does not contribute significantly to reducing the variance of the dependent variable (chalcopyrite). 132 The multivariant equation for molybdenite. (Equation 5.4) is also consistent with previous observations (Sections 4.4,and 5.2.1) that molybdenite is associated with the potassic alteration facies, and negatively related to pyrite of the phyllic alteration facies. The absence of biotite from the equation (Equation 5,. 4) is surprising since there is a significant positive correlation between molybdenite and biotite (Table 5.2). fl similar STPREG programme was run in which biotite was forced into the equation, with the result that K-feldspar was forced out; signifying the strong interdependnce between K-feldspar and biotite. As with K-feldspar in the chalcopyrite equation (Equation 5.3), this does not necessarily mean that biotite is a poor "indicator" of molybdenite, but only that the inclusion of biotite into the equation does not account for any more variance of molybdenite than K-feldspar does singularly. 5. 3. 3 Estimation of,, Error in Multivariant Equations The standard error of the multivariant equations in (5.3) and (5.4) is given in units of Ranked Intensity. Ranked intensity of alteration and ore minerals is discussed in Sections 3.2, and 4.1, and Appendix B. The reason for using this ranking was to normalize all mineralogic variables so as to retain resolution between small absolute changes in sulfide, and oxide mineral abundance, and to compare these with larger absolute changes in the abundance of silicate, 133 carbonate, and sulfate minerals. Although this ranking normalizes the changes in different minerals, it is difficult to understand the actual numerical value of the error. Figure 5.2 shows the absolute values of error associated with the standard erros for chalcopyrite and molybdenite. The ranking scale used for estimating abundances of chalcopyrite and molybdenite in the field is geometric (Appendix 6, Table B,.6, and therefore it should be noted that the absoulte value cf the error increases with the value of chalcopyrite and molybdenite in eguations (5.3) and (5.4)., 5.4 Summary of Geostatistics A simple two-way correlation matix of 15 hydrothermal minerals from the Poplar porphyry demonstrates that statistical analyses supports empirical observations made in the field regarding alteration zoning and facies, and helps define relationships which were not readily apparent. A one-way correlation technique was used to help show (1) which mineralogical variable was more the dependent one in a given correlation, and (2) to help remove correlations that were significant only because two minerals were both absent in a number of given observation. Finally, a stepwise multivariant regression technique was used to determine which variables were the most important for Figure 5.2: A graph of ranked intensity of chalcopyrite (as re corded on Poplarlog and used in the multivariant regression equation) versus the value of the midpoint of each rank in log percent chalcopyrite. The error limits associated with a stan dard error of 1.4 2 ranked intensity units are shown as dashed lines. 135 estimating the ranked intensity of chalcopyrite and molybdenite when all the other variables were considered together. The error associated with such estimations are fairly large. However, the equations serve to qualify the observation that certain alteration minerals can be used as a tool in estimating potential ore grade. 136 CHAPTER VI CONCLUSIONS This study was undertaken to define and map petrologic units, and mineralization and alteration zones at the Poplar porphyry copper-molybdenum porphyry deposit. Due to sparse outcrop in the study area most of the field portion of the study involved the logging of diamond drill core. A computer-compatible logging format was used to expedite this work. The following aspects of this study have been presented: (1) the deposit is gentically and spatially related to a zoned calc-alkaline stock which ranges from hornblende quartz monzodiorite to biotite quartz monzonite in composition. The stock intruded the Lower Cretaceous Skeena Group, and the Upper Cretaceous Kasalka Group. These units consist of volcaniclastic and epivolcaniclastic, and clastic sedimentary rocks, respectively. (2) Four K-Ar model ages have been determined and indicate that mineralization and alteration were geologically synchronous with intrusion* The term paramagmatic is used to describe this relationship. These ages range from 72.2 Ma to 76.9 Ma, placing 137 the event in late Upper Cretaceous time. (3) Two mineralized zones and four alteration zones are defined. Chalcopyrite and molybdenite are the two most abundant economic minerals; minor amounts of other sulfide ore minerals are locally present. Potassic, phyllic, argiilic, and propylitic alteration facies are defined based on the occurrence of the diagnostic minerals K-feldspar and/or biotite, sericite, clay, and epidote respectively. Chalcopyrite and molybdenite are most closely associated with the potassic alteration facies. Chalcopyrite occurs in an annular ring with potassic alteration which surrounds a core of argiilic alteration and is bordered to the outside by an area of high- to low-intensity phyllic alteration. (4) Argiilic alteration occurs in two areas; at the center of the deposit, and in a mere restricted area in a portion of drill core which is intensely fractured. Both areas occur within the larger potassic alteration zone. The central argiilic zone occurs in rock that is sparsely mineralized, and is due to secondary alteration of a central "low grade core" because of local intense fracturing and consequent increased permeability. (5) Based on the type of mineralization contained at the 138 Poplar porphyry, its age and its geographic location, it is considered here to belong to the Bulkley intrusive epoch, after Carter (1974,and 1976). (6) Statistical analysis of mineralogical features from 12 drill holes logged in detail, show that most hypotheses made in the field, dealing with mineralization and alteration associations, were substantiated by statistical correlations. This was especially useful in defining alteration facies, and their relationship with molybdenite and chalcopyrite. Multivariant regression analyses are used to show which minerals have the greatest effect on the observed values of chalcopyrite and molybdenite. However, certain inconsistencies in regression analysis indicate that statistical testing must be viewed in context of real field observations, or else misleading exploration parameters may be developed. The resolution of incompatibilities between field observation and statistical analysis can lead to a better understanding of the actual relationships between mineral variables. 139 BIBLIOGRAPHY Beane, R.E. ,1974. Biotite Stability in the.Porphyry Copper Environment: Econ. Geol. v. 69, pp.241-256. Blanchet, P.H. and Godwin, CI, 1972. "Geology System" for Computer and Manual Analysis of Geologic Data from Porphyry and Other Deposits: Econ. Geol. v. 67, pp. 796-813. Bowen, B., 1975. Geological and Geophysical Report on the Poplar Groups 1,2,3,5 and 6 Omineca Mining Division: E.c. Ministry of Mines Assessment Report no. 5679. Bowen, B., 1976. Geological, Geophysical, Geochemical and Drilling Report on the Poplar Groups 1 to 7 Omineca Mining Division: B.c. Ministry of Mines Assessment Report no. 6065. Burnham, C.W., 1962. Facies and Types of Hydrothermal Alteration: Econ. . Geol. v.. 57, pp. 768-784. Burnham, C.W., 1967. Hydrothermal Fluids of the Magmatic 140 Stage: in "Geochemistry of Hydrothermal Ore Deposits," ed- H. L. Barnes, Holt, Einehart, Winston, pp. 34-76. Carmichael, I.S., Turner, F.J. And Verhoogen, J., 1974. "Igneous Petrology," McGraw-Hill, inc., 739 p.. Carson, D.J.T., and Jambor, J.L., 1977. Phyllic Overprinting: A Fundamental Cause of Variations in Zoning at Porphyry Copper Deposit: Geol- Ass. Can. / Min. Assoc- Can., abstr., v. 2 pp. 11. Carter, N.C., 1974. Geology and Geochronology of Porphyry Copper and Molybdenum Deposits in West-Central British Columbia: Univ. of British Columbia, Ph.D. Thesis, unpub. 326 p. Carter, N.C., 1976.. Eegional Setting of Porphyry Deposits in West- Central British Columbia: in "Porphyry Deposits of the Canadian Cordillera," ed. A. Sutherland-Brown, Can. Inst. Min. Met. Spec.. 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"Statistics and Data Analysis in Geology": John Wiley and Sons, Inc. 550 p. Dixon, W.J. , and Massey, F.J., 1969. "Introduction to Statistical Analysis" McGraw-Hill, Inc. 638 p. Drummond, A.D., and Godwin, C.I. , 1976,. An Empirical Evaulation of Alteration Zoning: in "Porphyry Deposits of the Canadian Cordillera," ed. A.. Sutherland-Brown, Can. Inst. Min. Met.. Spec. Vol. 15, Harpells Press Coop pp. 52-71. Duffell, S., 1959. Whitesail Lake Map-Area British Columbia: Geol, Surv. Can. Mem. 299, 119 p. Eisbacher, G.H., 1977. Mesozoic - Tertiary Basin Models for the Canadian Cordillera and their Geological Constraints: Can. Jour. Earth Sci. v. 14 pp. 2414-2421. Forester, R.W., and Taylor, H.P., 1972. Oxygen and Hydrogen Isotope Data on the Interaction of Meteoric Groundwaters with a Gabbro-diorite Stock, San Juan 143 Mountains, Colorado: Internat. Geol. Cong., 24th, Montreal sec.10, Geochemistry, pp. 254-263. Gibbs, J.W., 1873. A Method of geometrical Representation of the Thermodynamic Properties of Substances by Means of surfaces: Trans.. Conn. Acad., v.2 p. p.309-342 Godwin, C.I., 1S76. Geology of Casino Porphyry Copper -Molybdenum Deposit, Dawson Range, Y.T.: University of British Columbia, Ph.D thesis, unpub., 245 p. Godwin, C.I., Hindson, R.E., and Blanchet, T., 1977. GEOLOG; A Computer-Based Scheme for Detailed Stratigraphy, Especially as Applied to Data from Drill Holes in Coal Exploration or Development: Can.. Inst. Min. Met., Bull., v. 70, pp. 1-10. Gustafson, L.B., 1978. . Some Major Factors of Porphyry Copper Genesis: Econ. Geol. v. 73 pp,. 600-607. Gustafson, L.B., and Hunt, J.P., 1975. The Porphyry Copper Deposit at El Salvador, Chile: Econ,. Geol. v. 70 pp. 856-912. 144 Helgeson, H.C., 1964,. "Complexing and Hydrothermal Ore Deposits": Pergamon Press Inc. 128 p. Helgeson, H.C, 1970. A Chemical and Thermodyanmic Model of Ore Deposition in Hydrothermal Systems: Min.. Soc. Am. Spec. Pap. 3, pp. 155-186. Hemley, J.J., 1959. Some Mineralogical Eguilibria in the System K^O-Alz03-SiOz-H^O. Am. Jour. Sci, v. 257 pp. 241-270. Hemley, J.J., and Jones, W.R., 1964 . Chemical Aspects of Hydrothermal Alteration with Emphasis on Hydrogen Metasomatism: Econ. Geol. v. 59 pp. 538^569. Hemley, J,. J., and Meyer, C. , and Eichter, D.H., 1961., Some Alteration Reactions in the System NazO-A1X03-SiOz-Hj,0: 0. . S. Geol. Surv., Prof. Paper 424-D, pp. 338-340. Holland, S.S., 1964. "Landforms of British Columbia A Physiographic Outline": Brit. Col. Ministry Min. Pet. Res., Bull. 48, 138 p. 145 Holland, S.S., 1976, "Landforms of British Columbia A Physiographic Outline": Brit. Col. Min, Mines and Pet.. Res., Bull.. 48, 138 p. Hurlbut, C.S., 1971. "Dana's Manual of Mineralogy": John Wiley and Sons, Inc. 579 p. Hutchinson, W.W., 1970. Metamorphic Framework and Plutonic Styles in the Prince Rupert Region of the Central Coast Mountains: Can. Jour.. Earth Sci. v. 8, pp. 523-548. Hyndman, D.W., 1972. "Petrology of Igneous and Metamorphic Rocks": McGraw-Hill, Inc. 533 pv. International Onion of Geological Sciences, 1973. Plutonic Rocks - Classification and Nomenclature Recommended by I.D.G.C. Subcommission on the Systematics of Igneous Rocks: Geotimes, v. 18, pp. 26-30. Jahns, R.H., and Burnham, W.C., 1969: Experimental Studies in Pegmatite Genesis; I. A Model for the Derivation and Crystallization of Granitic Pegmatites: Econ. 146 Geol- v. 64 pp 843-864. Jambor, J.L., and Beaulne, J. M., 1978,. Sulfide Zones and Hydrothermal Biotite Alteration in Porphyry Copper-Molybdenum Deposits, Highland Valley, British Columbia: Geol. Sur. Can. Pap. 77-12, 25 p. Jones, H.M., 1972. Geological-Geochemical Report on the Poplar Mineral Claims, Tagetochlain Lake Area: Brit. Col. Ministry Mines Petrol. Res. Assessment Report no. . 3665. Le,C, and Tenisci, T., 1978. UBC TRP, Triangular Regression Package: Univ. Brit. Col. Computing Center, 197 p. Lowell, J.D., and Guilbert, J.M., 1970. . Lateral and Vertical - Alteration •* Mineralization Zoning in Porphyry Ore Deposits: Econ. Geol. v.65, pp. 373-403. Maclntyre, D.G., 1976. Evolution of Upper Creteacous Volcanic and Plutonic Centers and Associated Porphyry 147 Copper occurrences, Tahtsa Lake Area, British Columbia: Univ. West. Ontario, Ph.p.. Thesis, unpub. 149 p. Mesard, P,.M., Godwin, C.I., and Carter, N.C., 1979. Geology of the Poplar Porphyry Copper - Molybdenum Deposit: Brit. Col. Ministry Min, and Pet. Res. Fieldwork 1S78, pp. 138-143. Monger, J.W.H., Souther, J.G., and Gabrielse, H., 1972. Evolution of the Canadian Cordillera, A Plate Tectonic Model: Am. Jour. Sci. v.272, pp. 577-602. Moore, W.J.,1978. Chemical Characteristics of Hydrthermal Alteration at Bingham, Utah: Econ* Geol. v.73, pp. 1260-1269. Norton, D., 1972. Concepts Relating Anhydrite Deposition to Solution Flow in Hydrothermal Systems: Internat. Geol. Cong., 24th, Montreal, Sec. 10, Geochemistry, pp. 237-244. Norton, D>., 1978. Source lines, Source regions, and 148 Pathlines for fluids in Hydrothermal Systems Related to Cooling Elutons: Econ. Geol. v.73 pp.21-28. Norton, D., and Knapp, R., 1977. Transport Phenomena in Hydrothermal Systems; The Nature of Porosity: Am. Jour. Sci., v. 277, pp. 913:936. Norton, D., and Knight, J., 1977. Transport Phenomena in Hydrothermal Systems; Cooling Plutons: Am. Jour. Sci., v. 277, pp. 937-981. Roedder, E.,1971. Fluid Inclusion Studies on the Porphyry Type Ore Deposits at Bingham, Utah, Butte, Montana, And Climax, Colorado: Econ. Geol., v. 66 pp. 98-120. Rose, A.W., 1970. Zonal Relations of Wallrock alteration and Sulfide Distribution at Porphyry Copper Deposits: Econ. Geol., v. 65, pp. 920-936. Schmidt, A.J., 1974. 1974 Drilling Report on the Poplar r i Lake Property: Brit. Col. Ministry Min. Pet. Res. Assessment Report no. 5360. 149 Schmidt, A.J., 1975. 1975 Drilling Report on the Poplar i Lake Property : Brit. Col. Ministry Min. Pet. Res., Assessment Report no. 5586. Sheppard, S. M(. F. , Nielsen, R. L., and Taylor, H. P., 1971. Hydrogen and Oxygen Isotope Ratios in Minerals from Porphyry Copper Deposits: Econ. Geol. v. 66, pp. 515-542. Streckeisen, A., 1967. Classification and Nomenclature of Igenous Rocks: Neues Jahrb. Mineral. Abhandl., v. 107, pp. 144-240, Taylor, H.P., 1974. The Application of Oxygen and Hydrogen Isotope Studies to Problems of Hydrothermal Alteration and Ore Deposition: Econ. Geol., v. 69, pp. 843-883. Tipper, H.W., and Richards, T. A., 1976a. Geologic Map of Smithers Map Sheet: Geol. Sur. , Can. Open File Map 351. Tipper, H.W., and Richards, T.A.., 1976b. Jurassic 150 Stratigraphy and History of North-Central British Columbia: Geol, Surv. Can. Bull. 270, 73 p. Villas, B.N., and Norton, D., 1977. Irreversible Mass Transfer between Circulating Hydrothermal Fluids and the Mayflower Stock: Econ. Geol., v.72, pp. 1471-1504. Wallace, S.E. , Mackenzie, W.B., Blair, E.G. , and Muncaster, N.K., 1978. Geology of the Urad and Henderson Molybdenite Deposits, Clear Creek County, Colorado, with a Section on a Comparison of these deposits with those at Climax, Colorado: Econ. Geol., v. 73, pp. 325-368. . White, W.H., 1959. Cordilleran Tectonics in North America: Amer. Assoc. Pet. Geol., Bull., v. 43, pp. . 60-100. White, W.H., Harakal, J.E., and Carter, N.C., 1968. Potassium- Argon Ages of Some Ore Deposits in British Columbia: Can. Inst. Min. Met. Bull., v. 61, pp. 1326-1334. 151 Wilton, D.H.C, 1978. A genetic Model for the Sustut Copper Deposit, North-Central British Columbia: Univ. Brit. Col. M.Sc. Thesis, unpubl., 215 p. Witherly, K.E., 1975. 1974 Geophysical Report on the Poplar Lake Property: Brit. Col. Ministry Min. Pet. Res. assessment Report no. 5361. Woodsworth, G.J., 1979. Geology of Whitesail Lake Map Area, British Columbia:in Current Research, Part A, Geol. Surv. Can., Paper 79-1A, pp. 25-29. APPENDIX A Analytical Da TABLE A.l POTASSIUM-ARGON ANALYTICAL. DATA3 FROM THE POPLAR PORPHYRY DEPOSIT, D.C. Sample No. Location Rock unit;'3 Mineral 40Ar* d ' 40„ *d Ar Apparent6 or Name Lat, (N) ; Long. (W) rock name da ted %K1S° 40Ar total (10_5cm3STP/g) age (Ma) Time G76TR22 54°01'126°50' 3b: biotite quartz bioti te 7. 14±0.07 0. 878 2.080 73.7±2.5 Late Cretaceous monzonite POPLAR LAKE 54<,01'126°50 3b: biotite quartz biotite 7. 00i0.04 0. 915 2.139 76.912.3 Late Cretaceous monzonite PC-36 54o01,126°50' 4a: porphyritic biotite 5. 97510.29 0. 846 1. 683 72.213.0 Late Cretaceous dacite PT-115 54°01'126o501 3a: hornblende hornblende 5. 87510.05 0. 794 1.780 76.212.7 Late Cretaceous quartz monzodiorite aAll analyses in the Geochronology Laboratory, Department of Geological Sciences, The University of British Columbia bRock units correspond to Map A C"S" is one standard deviation of quadruplicate analyses Ar " indicates radiogenic argon eDecay constants used: Xr- 0.501 x 10~10yr_1f Xfl = 4.90 x 10~10yr'"1, 4°K/K ° 1.167 x 10~4 fTime designed after Obradovich and Cobban, 1975 to TABLE A-2 CHEMICAL ANALYSIS .(% OXIDE WEIGHT PERCENT) AND C.I.P.W. NORMS OF IGNEOUS ROCKS FROM THE POPLAR PORPHYRY Sample: Rock unit PT51: 8 PT60: 5 Oxide Si02 64. ,76 61. ,60 M2°3 15. ,38 15. ,16 Fe2°3* 8. ,89 4. ,91 MnO 0. ,09 0. ,09 MgO 1. ,33 2. ,09 CaO 2. 43 3. .84 K20 2. ,67 2. ,92 P2°5 0. ,27 0. ,414 Na20 4. ,89 3. ,93 Ti02 0.37 0. ,54 L.O.I+ 2. ,94 4. ,103 TOTAL 98. 97 99. ,58 PT115: 3 30/132: 4 36/375: 5 62.33 66.10 • 59.75 16.59 16.55 15.62 5.55 5.41 4.98 0.12 0.05 0.12 2.60 1.69 1.91 3.75 3.38 5.40 2.70 2.31 2.87 0.30 0.31 0.40 3.94 4.29 2.32 0.624 0.515 0.525 1.94 1.64 7.29 100.29 102.26 101.18 quartz 19.47 15.18 13.70 15.99 16.63 orthoclase 16.36 17.74 15.83 13.02 17.22 albite 42.7 34.73 34.05 36.97 21.13 anorthite 10.84 15.32 16.52 14.07 23.51 magnetite 2.73 ' 2.97 3.07 2.88 2.95 illmenite 0.73 1.05 1.18 0.93 1.01 apatite 0.59 0.99 0.69 0.69 0.95 corundum 0.70 0.0 0.88 1.06 0.0 * All Fe as Fe^ ^L.O.I. = Loss On Ignition 155 APPENDIX B POPLARLOG The Computer Compatible Drillcore Logging Format Used In This Study. B.1 Introduction The development cf Poplarlog, as a computer compatible coding format for the logging of drill core, came about as a necessity to assure that geologic information be recorded in a standardized manner, and that each interval of core be examined for the same geologic parameters. Poplarlog was developed on the knowledge that the Poplar porphyry had an extensive alteration halo (Schmidt, 1978, pers. comm.; Bowen, 1976; and Carter, 1978, pers. comm.), and that outcrop made up less than one percent of the surface area on the property. Hany ideas and suggestions on the format of Poplarlog were offerred by colleagues who has previously used other computer compatible logging systems (Wilton, 1978, and pers. comm., 1978 and Mortensen, pers. comm., 1978). The major part of Poplarlog was formulated along the lines of a previously developed coding format for porphyry ccpper deposit designed by Blanchet and Godwin (1972), and C. I. Godwin (pers. comm. , 1 978> and 1 976). Most of the codes used during this study and described in Section B.3 and B.4 are taken directly from Blanchet and Godwin (1S72) . 156 B. 2 Description, and Coding A clank Poplarlog drillcore logging form is shown in Figure B.1. The characteristics and headings of the form will be describd from left to right. (1) Visual Log; This space was used to plot the attitudes with respect to drill core of veins, faults, fractures, rock unit contacts, bedding, foliation, and any other planar or linear feature. Paragenetic relationships between veins was also recorded. The appropriate symbol was plotted adjacent to the portion of a particular depth interval being described. (2) Comments, Column 1: Column one was used to record one letter codes denoting discontinuous geologic features, or as a one letter "flag", used to denote lines which were used for criteria other than formatted geologic information. The comment codes used in Column one on Poplarlog are shown in Table B.I. HOLE NUMBER II V A G L Depth to Bottom of Interva 7 Minjzn Zone 14—H TM y a p t Ie r ROCK TYPE 1M1TMTTH o u 15116 Oualr. Descr. 17 na |i9i?oizr OPLARLOG II Figure B.l PAGE OF h If a. TEXTURE DO Pol TAR I T X ft I I 0Z H I Al TF RATION K F H I B I H I M U H I C L H I C Y H I MINERALS E P H I C B H I ALT 1 H I ALT 2 H I SUM ALT H I P Y P H T H M H PT C P ,H PT MINERALIZATION B N HPT C C H.PT M O HPT M H HPT M N HPT M N H PT SUM ORE H PTZN 158 TABLE B.1 One Letter Comment Codes Used with Poplarlog (Column One) 1 Letter Code Meaning Bottom of hole-recorded with hole number and date; used as a flag in determining the end of a hole. Comment - to denote lines used for comments about the drill core in addition to, and sublimenting, normal coding; usually used to describe a particular geologic feature in more detail. Dykes - used to denote the bottom of an interval consisting of a dyke uni,t. . Contact - used to denote contacts between rock units, superseded by D (=dyke) where appropriate. Sample - sample taken at a particular depth (which was recorded in column 76-80). Zone of faulting, fracture, or a shear zone. Top of hole - recorded with hole number and date; used as a flag in denoting the top of a hole. (3) Depth to the bottom of the interval described on that .line; Columns 2-5: usually in 10 foot (3 m) intervals, or less if geologic features changed (i. e. contact between rock units) (4) Ore Zone; Columns 6-8: used to define which ore zone 159 that particular interval was in (i. e. hypogene (HYP), supergene sulfide (SOS), or supergene oxide (SUX)). (5) Type Modifier and Bock Name; Columns 9-14: used in conjunction with each other to name the rock unit being described (Coumns 11-14) using four letter code names which were developed as new units were intersected in drill core. Column 9 was used to record a one letter "flag", unique to each rock unit, to facilitate the rapid visual identification of the rock type in each interval (Table B.2). Column 10 was used to qualitatively describe with a one letter code the "condition" of the core with respect to the stability of biotite ( determined to be a diagnostic mineral, sensitive to various types of alteration (Table B.3). (6) Colour; Column 15-16: a gualitative estimate of the Colour Index. DK-dark, >50% mafics; MD-medium, 25-30% mafics and; LT-light, <25% mafic minerals. Includes both primary and secondary minerals. (7) Mafics; Columns 17-18: consists of a two letter (or letter and symbol) code for the type of mafic minerals present, and their relative abundance. HB-hornblende only; B<-hornblend greater than biotite; B>-biotite greater than hornblende and; Bl-biotite only. Biotite and hornblende were the only mafic minerals observed at the Poplar porphyry. Table B.2 First Type Modifiers and Coded Names Used With Poplarlog (Columns 9, and 11-14) Rock Unit ' Skeena(1) Quartz Monzodiorite(3a) Quartz Monzonite(3b) Intrusive Breccia(3b) Quartz Latite-Andesite(4a) Felsite Dykes(4b) Porphyritic Rhyolite(5) Andesite Field Name Hornfels Hornblende Diorite Biotite Porphyry Breccia Feldspar Porphyry Felsite Rhyolite Tracyte Type Modifier II B F F Q T 4 Letter Code HORN DIOR PPBF BRXX PPFL FELS PPFQ TRAC Comments used for any country rock observed in drill core - not necessarily hornfels meta morphosed . PP=Poplar porphyry BF=biotite-feldspar porphyry Sub-unit of quartz monzonite FL-feldspar porphyry Sub-unit of quartz latite andesite FQ=Feldspar-quartz porphyry T=Tracyte; originally named tracyte in field, later changed to andesite, but code kept to maintain consistency 161 (8) Qualifying Descriptor; Columns 19-21: a "catchall" heading used to denote unusual features in the core, or changes in the nature of the core which were too minor to describe under a new interval. Examples include; CNA-a change in alteration type; XEN-xenoliths; and PAT-patches.. 162 TABLE B.3 Second Type Modifier Used With Poplarlog (Column 10) Type Modifier D Dark - Secondary biotite is observed in the interval described. N Normal - Biotite books are present, and thought to be original phenocrysts. rock is fresh or has undergone minor alteration. L Light - Original biotite books have been altered to pseudomorphis of chlorite or sericite. 0* Obliterated - Biotite books are not observed and the texture is obliterated by alteration (generally phyllic). Identification of rock type is difficult and questionable., X* Extremely obliterated -The original texture has been destroyed by alteration. Bock type in doubt. •For both designations the original rock type could be ascertained by correlation by gradational changes to fresh either up or down the drill core. rock 163 (9) Texture; Columns 22-30: a general heading which is subdivided into seven subheadings. Originally intended for recording criteria to be used in correlating sedimentary rocks from drill core. These criteria include; (a) grain size mode, (b) maximum grain size, (c) open or closed packing of grains, (d) degree of sorting, and (e) and (f) particular textural features which were determined in the field to be important criteria for correlation. Most of these headings were never used because of the high intensity to which most of the Skeena rocks were altered, and the textural nature of the unit itself, made such observations difficult, and too infrequent to be of any use. However, the subheadings Texture I, and Texture II were used to denote unusual or distinguishing textures encountered in the drill core such as FL for flow lineation or pilotaxitic texture, cr AG for amygdaloidal texture,. (10) Alteration Minerals; Columns 31-54: this heading consists of the 16 subheadings listed in Table B.4. Each of 10 mineral subheadings consist of two columns (except for clay, and SUM ALT which are discussed below); the first of which (H) is used for a one numeral code describing "how" the mineral occurs, i. e. its relative dispersion (Table B.5, taken from Blanchet and Godwin); 1S72). The second column (I) is used for a one letter code describing the "intensity", or percentage by volume, of the mineral (Table B. 6). 164 The last subheading under Alteration Minerals on Poplarlog, SUM ALT, columns 52-54, was used to "summarize alteration" for that interval and to place that interval of core in one of 10 alteration zones in the Lowell and Guilbert Model of porphyry deposits, modified by Blanchet and Godwin (1972).. Columns 52 and 53 (H and I) were used to summarize both how the alteration occurred (its degree of dispersion), and its intensity (volume percent). Column 54 was used to place the interval described in one of the 10 alteration facies of Lowell and Guilbert (1970) based on criteria found in Table B.7 (taken from Blanchet and Godwin, 1972), which is a "checklist" of relative intensities of silicate, and carbonate alteration minerals versus the 10 alteration facies. Figure B.1 is a cross-section through a typical porphyry deposit showing the spatial relationship of 10 alteration facies (taken from Blanchet and Godwin 1972). (11) Mineralization; Columns 55-75: similar to the method for describing the degree of dispersion and intensity of silicate, carbonate, and sulfate alteration minerals; the mode of occurrence and intensity of 7 sulfide and oxide minerals in each interval of core was recorded in appropriate columns (Table B.8). However, because the degree of intensity to which oxide and sulfide minerals occur is generally a great deal less than that of alteration minerals, a geometric scale of abundances was used. Therefore the notation "PT" was used in the columns to describe intensity of mineralization, and distinguish it from the scale used to record intensities of alteration (Table B.6). 165 The method used to record degree of dispersion of sulfide and oxide .minerals is exactly the same as for alteration minerals as shown in Table B.5. The subheading SUM ORE is exactly analogous to the summary columns for alteration minerals, previously described in the previous sub-section (9),. The checklist of relative mineral abundance versus mineralization facies taken from Blanchet and Godwin (1972) is shown in Table B.9. A corresponding cross-section through a typical porphyry deposit showing the spatial relationship between these facies is shown in Figure B.2. (12) Sample Depth; Columns 76-80: These columns were used to record the depth at which samples were taken(c. f. .'S' in column 1; Table B. 1). 166 TABLE B.4 Silicate, Carbonate and Sulphate Alteration Minerals (Columns 31-51) Poplarlog Abbreviation QZ KF Bl MO CH CY EP CB ALT 1 {finer al Quartz Potassium Feldspar biotite muscovite chlorite clay Comments ALT 2 epidote carbonate Anhydrate-Gypsum miscellaneous alteration seldom used Column 43 was in tended to distin guish kaolinite from montmorillonite. it was never used. seldom used includes calcite siderite, and dolomite. Was used for these minerals after fieldwork indicated their importance used for seldomly observed minerals. 167 TABLE B. 5 Mode And Degree Of Mineralization And Alteration. V,E,D,P Refer To Modes Of Occurrence: Veins, Envelopes, Disseminations, And Pervasive, Respectively (from Blanchet And Godwin, 1972). Mode of Oc Mineralization rurrence Degree of Dispersion Mode of Occurrence Alteration Assemblages Veins and macro - veins including stockwork and gouge V V 1 2 J 4 5 6 7 8 ' 9 V or v j V veins Veins, veinlets, fracture fillings Sc minor disseminations D «* V E< V or P«V veins and moderate envelopes or minor pervasive Veinleta and some disseminations t> < V E * V or P<V envelopes and veins equal or veins and moderate pervasive Veinlets with moderate disseminations r s v E> V or PSV vp+iv envelopes with some veins or pervasive with moderate veins Veinlets and disseminations more or less equal 0 • V E or P « V •ip+^v 8 8 envelopes or pervasive equal to veins Disseminations and moderate veinlets 0 2 V P < E or P>V — P + — E ! -^P + —V 8 8*88 pervasive with some envelopes or moderate veins Disseminations with some veinlets f-°-.+ fv 0 > V P* E or P>V ip + if i±P+J2-V 8 T 8 j 8 r* 6 pervasive and envelopes or w;th some veins Mostly dissemination with minor veinlets or micro-vein- D ao V 1 6 , P>E or P»v I — p+ ir; 8 8 pervasive with some envelopes or minor veins Disseminations 0 D l P I P 1 i P pervasive 168 TABLE B.6 One Letter Codes for Estimated Volume Percent of Silicate, Carbonate and Sulfate Alteration Minerals, and for Sulfide and Oxide Mineralization, from Poplarlog "Alterat ion" Onec Letter "Mineralization" Mineral Abundances Code Mineral Abundances >60% X-extremely high >16% 50-60% V-very high 8-1655 40-50% H-high 4-8% 30-40% A-above medium 2-4% 20-30% M-medium 1-2% 15-20% B-below medium 0-5-1% 10-15% f-fair 0.25-0-5% 5-10% L-low <0.25% 2-5% E-extremely low «0.25% <1% T-trace Trace NIL hlank-none NIL 169 TABLE B. 7 Checklist of Relative Alteration Minerals Abundances Versus Alteration Facias in Porphyry Deposits (taken frcm Blanchet and Godwin 1972) Alteration Facie* Fresh Rock Propylitic Montmorillonitic Intermediate Argiilic KF - Stable Sericitic < = Phyllic) Advanced Argiilic Potaaaic 'Chlori-Potaeeic' S ilicic (Quartt Flooding) Quartz QZ I / i \ / A \ \ K-spar KF Biotite Bl Orig.KFJ stable Mus covite Sericite MU.MS Orig.BI 'A Mg- rich! Clays CY Kaolin KA I I /1 \ \ \ \ / • /I I I '.'</ I /! i i i IMontmor-illonite MM s Chlorite CL Epidote EP Carbon' ates CB Other and/or and/pr and/or and/or / // / AB Remark* Also Adularia, / ' ^ Sprite Z£ /.'PP AB=Albite ZE = Zeolite(s) TO TO= tourmaline PP - pyrophyilite AH= anhydrite I diagnostic t abundant a / / / j commonly present k moderate • / / infrequently present L minor = y 170 FIGDEE B.2 Model of Alteration Facies in porphyry Deposits after Lowell and Suilbert (1970), (taken from Blanchet and Godwin, 1972). \ I / // ,2,-3/4/5/6/ 1 ' 1 !// /' 1/ ' 1/ ' v\ \ \ M \l MM \\\\ Fresh Roch Propy litie M oiMmonllonitic Inter me dio 11 Artjillic KF -Stoolt Sc rici1>C ( Phfl.ic) Advortced Argillic Ii \ A! \ K V \ I A / \ I \ / \ e—V-W A 1 -Chlori - Polo«*ic - S ktorn 171 TABLE B.8 Poplarlog Abbreviation Sulfide and Oxide Minerals (Columns 55-72) Mineral Comments PY Pyrite HM hematite CP chalcopyrite BN bornite CC chalcocite MO molybdenite magnetite added in the field MN2 covellite, tetrahedrite only rarely used MN3 galena, etc. Only rarely used 172 TABLE B.9 Checklist of Relative Sulfide and Dxide Mineral Abundances Versus Mineralization Facies in Porphyry Deposits [taken from Blancet and Godwin, 1972). Mineralization Zones Pyrite PY Chalco pyrite CP Molyb denite Wolframite Covellite Digenite WF, CV.DG Chalcocite CC Hematite Magnetite Galena-Sphalerite GX (Gold-Silver occurrence) Pyrrhotite PR Native Copper Shx oud Peripheral Shell Low Pyrite Shell Deep Ring Pyrite Shell Ore Shell L-o-*'-Grade Core Deep Core / /// J J J A / / / / ' J /i i i / /// 'A i i /i i /// / / i / JI A / 1/ dia-gnostic & abundant frequently present U substantial = / / // usually present h. moderate a/// sometimes present k minor s. / / infrequently present h. trace to minor -S 173 FIGO.EE B. 3 Model of Sulfide, Oxide Mineral Facies in Porphyry Deposits after Lowell and Guilbert (1970) (taken from Blanchet and Godwin, 1972). Compare with Table B. 9, and Figure 3.1. / I Shroud , "~ —^2 r- Peripherol Shell / ,^ , — 3 ^— -V Low Pyrite Shell ' ' N \ \ / / ^vi--^Vv^5-\ * r Pjrile Shell / I ^ ^ \ \ \ / / / ^'^^S-V-^ ^ Or, She,, 1 * | -f : I \ H Lo- Grcie C i A ! i I /; // \ \I A / \ ' M / , M tf p Core Deep R .ng / APPENDIX C Computer Programs Used in the Study C A PROGRAM 10 PLOT CHALCOPYRITE ON CROSS-SECTION A-A C FORMATING IS CCMPATA6LE WITH POPLARLOG C CPYI IS CHALCOPYRITE INTENSITY - CPYri IS ITS MODE OF OCCURENCE; BOTH ARE ON RANKED SCALES C ALL ELSE IS FOUND IN "11.B.C. PLOT" INTEGER SYM,CPYI,CPYH LOGICAL*! CO 1, COMMI 5) LOGICAL** EQCMP CALL PLCTRLI'METRIC1,0.0) CALL SY<waHl3 .30 ,.75 ,0.25,'C<OSS-SECriiJSAL PLOT OF CHALCOPYRITE ALONG LINE A-A ',0.0,511 CALL SY130LI9. 5,0.25,0.25,'WITH SUPPERIMPOSEO ZONES OF MOLYSOENITE.K-FELOSPAR,BIOTITE,PHYLLIC AND ARGILLIC ALTERATION1.0.0,90) 5 READI5, l0,E.-n=-?99IC0M,C?YH,CPYI ,CASTG,DEPTH 10 FORMAT!Al,57X.2II.22X,F8.3,2X,F8.J) IFIE 5CMPII,•3•, COM)) GO TO 100 UP = 11 00.00-OEP TH UP=IUP/52tf.0)»12.0*.<.-l.*.39* ESTG = (F. ASTG/528.01*12.0*0.',*2.12 IFI CPYI .EQ.O) SYM=15 1FICPYI.E0.1ISY"*16 IFICPYI.E0.2)SYM=17 IFICPYI.EQ.3)SYM=18 lF(CPVl.E'J.<tlSYJ»19 IF (CPYI .t'0.51 SYM=20 1FICPYI.EC.6ISYM=22 IFICPYI.E3.7)SYM=23 IFICPYI .EQ.B)SY.M = 26 IFICPYI.EJ.9)SYM=27 CALL SYMrtOLIESTG.UP.O.19.SYM.O.O.-l1 ii GO II) 5 100 RFA0(5,110,END = 9991 ICOMMI Jl ,J»l,5l .EL.RGT 110 FOH MAT I5A I »3<,F5.2,F7.21 EL= 1100.0-EL EL=(EL/529.01*12.0*0.*-l.0*0.39% RGT=(RGT/528.0)»12.0*0.%*2.12 CALL SYMHOLUGT,EL,0.20,COMM,0.0,5) GO TO 5 999 CALL PLCTRLI'METRIC', 11 CALL AxCTRLI ' X CR I & ' ,0.0) CALL AXCTRLI'YORIG',0.0) CALL AXPLOTI'EASTING ALONG X-SECTION A-A I ME T CR S) ; ' , 0.0 ,9 3 . 726, 11 203. 0 , 1 3. 2) CALL AXPLOTI'ELEVATION ABOVE SEA LEVAL (METERS);',90.0,2%.1%,616.35,13.2) CALL PLOTNO STOP END cn COMPUTER- PROGRAM "SMLRK1- PLOTS THE GEOLOGY ALONG CROSS-SECTION A-A FORMATING IS COPA 7 IHL E WITH POPLARLOG INFORMATION OF ROCK NAMES ARE GIVEN IN APPENDIX B ALL OTHCR INFORMATION IS IN "U. 8. C. PLOT" I NTESER SYM LOGICAL»l COMMI5),COM(1),RKU2) LOGICAL** EQCMP ,RK2 CALL PLC T RL('METRIC.0) CALL SYMrtQL(,0.25,'CROSS-SECTIONAL PLOT OF GEOLOGY ALONG LINE A -5 READl5.lO,EN:)=9 99 ICOM,RKl,RK2,EASTG,OEPTH 10 njRMATUl,/X,2Al,A<,,69X,F8.3,2X,F8.3) IFIEQCMPII,'J>,COM(1))IGO TO 103 0P=1100.0-OEPTH UP= (UP/52 3.0) * 12.0*0. V-l .0*0.3 94 E STG=( EASTG/52 9.0)* 12.a*0.<V»2. 12 SYM=30 IFIE<JC 'PPBF',RK.2)>SYM = 3 IF! E3CM»( <,, 'PP XX' ,RK2) | SYM. U IF(FOCMPI*.,,PPFQ,,RK2))SYM=1 IFir.-JCMPI^.'PPFL' .RK2) )SYM=2 IFIE3CMPI*,'dXIN',RK2MSYM=17 IFl E3CMPI MORN' tRK2) ) SYM = <,3 IF(ETCMO(<v,<FELS,.RK21,SYM=37 IF I E3CMP! • TRAC ,RK2 ) )SY,M=5 CALL SY.M30L ( ESTG. UP , C. 07 t SYM, 0.0,-1 ) IF!SYM.NE.301 GO TO 5 WRITE(6,lOICJM,RKl,RK2,£ASTG,DEPTH GO TO 5 100 REA0(5,U0.EN3 = 999) (COMMIJ) ,J»1.5),EL.RGT 110 FORMAT!5AI,5X,F5.2,F7.2) EL=1100.0-EL i\ EL = ( EL/523.0)*12.0*0.4-1.0*. 39* RGT = IRGT/52f).J)*12.0»0.4*2.t2 CALL SYMBOL IRGT,EL,0.2 0,COMM.0.0,5J GO TO 5 999 CALL PI CIRLI* METRIC,11 CALL AXCTRLI 'XORIG' ,0.01 CALL AXCTRLI•YCRIG',0.0J CALL AXPLOTI 'EASTING ALONG X-SECTIUN A-A (METRES) ; ' ,0.0,93. 726,11203.0,13 CALL AXPLOTI 'ELEVAT ION ABOVE SEA LEVEL (METRES) ;*,90.0,2*.l<>»616.35,13.2) CALL PLOTNO STOP END C » PROGRAM TO CHANGE FORTRN CHARACTERS TO FORTRAN REAL NUMBERS C THIS REQUIRES USE OF CCMMAND •ETJAC' C FORMATTING IS COMPARABLE TO POPLARLOG LOGICAL ECJC LOGICAL*l COM(1) DIMENSION ALT I (50) , XMINU 50 >, L TI 1 50) .MINI I 501 10 KE \0(5, 20, ENO = 999)COM,(LTI(I 1,1 = 1,10),(MINI(J1,J»1,9) 20 FORMAT ( I Al ,29X ,61 1 I I, IX) , IX ,4(1 11 ,1 X) , 3X.9I II 1, IX) ) IF (EOUCI1T1,COM)) GO TO 10 IF (EOUC( 18•,COM 1) GU TO 10 C 00 100 1=1.10 IF(LT I (I ) .E 3.01ALT1[I 1=0.0 IF ILT11 I 1 .EJ. 1 1ALTII I)=2.5 IF (LT 11 I I .h'3.2 1 AL TI (I ) = 7.5 IFIL TII I) .£ 3. 3 I ALII (I I = 12.5 IFILT K I 1.E3.%1ALTI 111 = 17.5 IFILTIII).EQ.5)ALTI(I)=25.5 IFILTI I I).E0.6)ALTII I 1 = 3 5.5 1 F I LT I ( I 1 -EQ. 7 1 ALTI I I )=<,5.5 ir(LTI(II.E3.9)ALTI(I)=55.5 IF ILT 11 I 1.E0.9)ALTII I)*65.5 100 CONTINUE C 00 200 J=1.9 1 FI MINI(J>.EJ.01XMINl (Jl=0.0 ;! ir(MIN|(Jl.E7.1)XMINJIJI=0.01 IF I MINI(JI.E 3.21XMINI (J) = .13 , irI MINI IJ).F 3.31XM1NIIJi = .37 IF(MINI(J1.E3.%)XMINI(J)».75 IFIMINKJ1.E3.51 XMI N I I Jl = I . 5 IF(MINi(J).E3.6 1XMlNIIJ)=3.0 IF I VI Nl I J 1 .E 7IXMINI I J) = 6.0 1F(MINI(J).E3.8)XMINI(JI»12.0 IFIMINI IJ).EJ.91XMINI (Jl-2%.0 200 CONTINUE C HRI TE (6,3001 ( ALTK I 1 . 1-1 ,91 ,( XMINI ( J) , J-l .7) 300 F0RM4T(9F5.2,1X,7F5.2) GO TO 10 999 STOP E SO 17 8 APPENDIX D Thin Section Descriptions Rock Unit: Skeena Group (Unit 1); crystal tuff. Thin Section No. 30; Sample No. PT-116 Location: 5,4 4 ON; 11.61.7.E 179 Mineral Mode quartz crystals 5% chlorite (clots) 10% clay (clots) 20% groundmass 65Description: Broken 0.1-1.0 mm quartz crystals, locally sphera-litic, in altered groundmass of clay, chlorite, and limonite. Pseudomorphs of chlorite after mafics (?) are 0.1-1.5 mm in dia meter. Clay patches, pseudomorphic after plagioclase, are 0.5-1.5 mm in diameter. Rock Unit: hornblende quartz monzodiorite (Unit 3a) Thin Section No. 29; Sample No. PT-115 Location: 5,370N; 11,640E Mineral Mode plagioclase phenocrysts 25% hornblende phenocrysts 10% quartz phenocrysts 2% epidote 10magnetite 2% groundmass 51Description: Propylitic alteration; hornblende phenocrysts are 1-3 mm in length, and are still fresh. Plagioclase phenocrysts (An31) range from 1-3 mm, and are altered to carbonate, albite, and epidote. Groundmass plagioclase (45%) is less than 0.1 mm in diameter. Magnetite ranges from 0.1-1 mm in v/idth. Rock Unit: biotite quartz monzonite (Unit 3b) Thin Section No. 1; Sample No. PT-1 Location: 6,087N; 11,567E 180 Mineral Mode plagioclase phenocrysts 50% quartz phenocrysts 15% biotite phenocrysts 5% groundmass plagioclase 15% K-feldspar 10quartz 5% Description: Crowded glomerophyritic plagioclase phenocrysts range from 0.5-4 mm in width-and are locally zoned. Some plagio clase replaced by sericite and carbonate. No An determined. An hedral quartz phenocrysts range from 0.5-2 mm in diameter. Bio tite phenocrysts are mostly fresh; some are altered to chlorite. Minor biotite in groundmass is interstitial to quartz and plag ioclase. Groundmass is equigranular 0.0 5-0.1 mm anhedral cryst als of quartz, biotite, K-feldspar, and plagioclase. Rock Unit: intrusive breccia (Unit 3b) Thin Section No. 80 Location: D. D. H. 24- 567 ft. Mineral Mode Matrix biotite 30% magnetite (?) 3plagioclase 40% K-feldspar 17quartz 10% Clasts: porphyritic quartz monzonite Description: Euhedral to anhedral 0.01-0.5 mm brown biotite in-tergrown in mats. Plagioclase phenocrysts are zoned and glomero-porphyritic. Most are cloudy and are altered to albite and K-feldspar (?). Groundmass plagioclase is 0.025 mm in length, and is cloudy. Anhedral K-feldspar and quartz, 0.01-0.0 5 mm across in groundmass. Euhedral cubic magnetite (?) is interspersed in the groundmass with biotite. Rock Unit: porphyritic dacite (Unit 4a) Thin Section No. 76 Location: D. D. H. 36- 375 ft. 181 Mineral Mode plagioclase phenocrysts 10% hornblende phenocrysts 2% biotite phenocrysts 3% quartz phenocrysts 10% groundmass 7 5% Description: Porphyritic texture; normal zoning in 1-4 mm glome-roporphyritic plagioclase, locally resorbed (rounded with react ion rim), and albitized. Extremely high carbonate alteration of plagioclase phenocrysts, and in groundmass. Hornblende pheno crysts altered to chlorite and clay magnetite sericite. 1-3 mm biotite phenocrysts are fresh. Groundmass is too fine grained to identify. Rock Unit: porphyritic ryolite (Unit 5) Thin Section No. 56 Location: D. D. H. 29- 154 ft. Mineral Mode plagioclase phenocrysts 15% biotite phenocrysts 5% quartz phenocrystsgroundmass 7 5% Description: Clots of clay and carbonate, o.5-2 mm across, re-, place plagioclase phenocrysts. Pseudomorphs after biotite are chlorite; replacements along cleavage is evident. Quartz pheno crysts are rounded and 1-5 mm in diameter. Quartz is locally po-lycrystalline. Groundmass consists of very fine grained anhedral quartz, orthoclase, and plagioclase (?). Rock Unit: andesite (Unit 6) Thin Section: No. 72 '•'> Location: D. D. H. 34- 435 ft. 18 2 Mineral Mode quartz phenocrysts 1% chlorite after hornblende 5% plagioclase phenocrysts 1% groundmass 93Description: Quartz and plagioclase phenocrysts are 0.5-1 mm across. Plagioclase is altered to carbonate and clay. Clots of chlorite and carbonate replace hornblende. Groundmass consists of 0.1-0.2 mm plagioclase with minor quartz and magnetite. Pla gioclase is altered to carbonate and clay or sericite. Rock Unit: Ootsa Lake Group (Unit 7) Thin Section No. 7; Sample No. PT-51 Location: 5,900N; 10,800E Mineral Mode plagioclase phenocrysts 20% hornblende phenocrysts 3% groundmass plagioclase 50% K-feldspar 5quartz 20% apatite 1opaques % Description: Zoned 1 mm plagioclase phenocrysts (An2g) are slightly altered to carbonate. Some plagioclase phenocrysts are albitized and some are stained from hematite inclusions. 1-2 mm hornblende is. altered to chlorite and carbonate. Groundmass is fresh, opaques include limonite, hematite, and magnetite. Small carbonate vein cuts thin section. 


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