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Geology, alteration and mineralization on the Hank property, northwestern British Columbia : a near-surface,… Kaip, Andrew William 1997

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GEOLOGY, ALTERATION AND MINERALIZATION ON THE HANK PROPERTY, NORTHWESTERN BRITISH COLUMBIA: A NEAR-SURFACE, LOW-SULFIDATION EPITHERMAL SYSTEM by Andrew William Kaip B.Sc, Carleton University, 1992 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF 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 January, 1997 © Andrew William Kaip , 1 9 9 7 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 or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) 11 A B S T R A C T Hydrothermal alteration on the Hank property, northwestern British Columbia, is hosted by andesitic to basaltic volcaniclastic breccias, flows and sills of the Upper Triassic Stuhini Group; Lower Jurassic sedimentary rocks; and, a hypabyssal, Middle Jurassic (185±3 Ma) potassium-feldspar megacrystic porphyry which intrudes the stratified rocks. Alteration on the property forms two sub-parallel northeast trending zones (Upper and Lower alteration zones) which are capped by broad tabular zones at higher elevations (Felsite Hill and Rojo Grande). The lower alteration zone (LAZ) strikes northeasterly and dips steeply to the southeast cutting the stratigraphy on the property and is characterized by intense illite-dominant alteration. The pit area of the Upper alteration zone (UAZ) is semiconformable to stratigraphy, strikes northeast and dips moderately to the southeast. The pit area of the UAZ is hosted within volcaniclastic breccias with footwall and hanging wall defined by flows or sills. Alteration is characterized by illite/smectite which grades into illite/smectite+kaolinite-dominant alteration near the top of the zone. Above the UAZ, alteration comprises kaolinite-dominant alteration containing minor natroalunite within the volcanic and overlying sedimentary sequences. This transition from illite/smectite to kaolinite-dominant alteration is marked by a zone of intense, multiphase silicification dipping gently to the south. Alteration mineralogy on the Hank property is characteristic of a near-surface, low-sulphidation epithermal environment dominated by illite alteration at depth and illite/smectite and kaolinite alteration at higher elevations. The overall morphology of these alteration zones suggests that the LAZ is a conduit for hydrothermal fluids which cuts stratigraphy. The UAZ, and the Flats Zone (FZ) are semiconformable to stratigraphy, indicating lateral movement of hydrothermal fluids along a permeable horizon outward from the central conduit. The silicified zone, which lies above the UAZ, may indicate a zone of increased permeability or the presence of a paleo-water table or aquifer. Above the silicified zone, tabular zones of kaolinite-dominant alteration reflect the upper parts of an epithermal environment, derived from acidic, vapour condensate above the paleo-water table. Illite/smectite alteration within the potassium-feldspar megacrystic porphyry suggests that it intruded during the final stages of hydrothermal activity and may be the causative intrusion. I l l Alteration and mineralization on the Hank property represents one extreme of a continuum of mineralization styles throughout the Iskut River area including porphyry, vein and exhalative examples, all co-temporal with Middle Jurassic intrusions. iv T A B L E O F C O N T E N T S ABSTRACT H TABLE OF CONTENTS TV LIST OF FIGURES VTU LIST OF TABLES X LIST OF PLATES . XI ACKNOWLEDGMENTS XUI 1.0 INTRODUCTION 1 1.1 LOCATION AND ACCESS 1 1.2 PHYSIOGRAPHY 2 1.3 PREVIOUS WORK 2 1.3. 1 Regional Mapping 2 1. 3.2 Exploration History 4 L 3.3 Property Investigations -6 1.4 PURPOSE 6 2.0 GEOLOGY , 8 2.1 TECTONIC SETTING 8 2.2 REGIONAL GEOLOGY 8 2.2.1 Stikine Assemblage / / 2.2.2 Upper Triassic Stuhini Group 12 2.2.3 Lower Jurassic Strata 17 2.2.4 Lower to Middle Jurassic Hazelton Group 18 2.3 REGIONAL STRUCTURE 19 2.4 REGIONAL METALLOGENY 21 3.0 PROPERTY GEOLOGY.... 23 V 3.1 INTRODUCTION 23 3.2 STRATIGRAPHY 25 3.1.1 Upper Triassic Stuhini Group 25 3.1.2 Lower Jurassic 32 3.1.3 Middle Jurassic 33 3.2 INTRUSIONS 34 3.2.1 Bald Bluff Porphyry 34 3.2.2 Goat Peak Diorite 35 3.3 STRUCTURE 38 3.4 GEOCHEMISTRY 41 3.4.1 Volcanic strata 43 3.4.2 Tectonic Setting 46 3.4.3 Intrusions 47 3.5 GEOLOGICAL ENVIRONMENT 47 4.0 ALTERATION 51 4.1 ALTERATION ASSEMBLAGES 51 4.2.1 Introduction 57 4.1.2 Kaolinite 54 4.1.2 Transitional (Illite/smectite+kaolinite) 57 4.1.3 Silicification 61 4.1.4 Illite/smectite 62 4.1.5 Adularia±illite/smectite 66 4.1.6 Illite 71 4.1.7 Chlorite 73 4.2 ALTERATION ZONES 75 4.2.1 Introduction 75 4.2.1 Quartz Stockwork zone 75 4.2.2 Lower A Iteration Zone 78 4.2.3 Flats Zone 81 4.2.4 Upper A Iteration Zone 83 4.2.5 Silicified Zone 87 vi 4.2.6 FelsiteHill 87 4.2.7 Rojo Grande - Rojo Chico 91 4.4 ALTERATION GEOCHEMISTRY 92 4.4.1 Introduction 92 4.4.2 Volcanic stratigraphy 93 4.4.4 Bald Bluff porphyry 101 4.4 SPATIAL TRENDS IN MINERAL CRYSTALLLNITY 101 5.0 MINERALIZATION 105 5.1 INTRODUCTION 105 5.2 VEIN PARAGENESIS 105 5.2.1 Quartz Stockwork Zone 106 5.2.2 Lower Alteration Zone 106 5.2.3 Flats Zone 109 5.2.4 Upper Alteration Zone (UAZ) 112 5.2.5 FelsiteHill .' 114 5.3 MINERAL ZONATION 114 5.7 PB ISOTOPES 120 6.0 DISCUSSION 124 6.1 INTRODUCTION 124 6.1 INTERPRETATION 127 6.1.1 Deposit type 127 6.1.2 Alteration • 129 6.1.3 Oreparagenesis 134 6.2 DEPOSIT MODEL 136 7.0 CONCLUSIONS 140 8.0 REFERENCES 143 APPENDIX A 153 APPENDIX B 156 APPENDIX C APPENDIX D APPENDIX E APPENDIX F L I S T O F F I G U R E S Vlll Figure 1.1 Location of the Hank property. 1 Figure 1.2 Map showing the field areas for each regional mapping program. 3 Figure 1.3 Map of the Hank Property outlining the geographic position of the alteration zones on the property. 5 Figure 2.1 Tectonic assemblage map of the Canadian Cordillera outlining the major tectonostratigraphic belts and terrains which comprise each belt. 9 Figure 2.2 Legend for the southern half of the Telegraph Creek map area. 12 Figure 2.3 Geology of the southern half of the Telegraph Creek map area (104G). 13 Figure 2.4 A composite stratigraphic section for the Paleozoic Stikine assemblage. 14 Figure 2.5 Representative stratigraphic sections for the Upper Triassic Stnhini Group. 15 Figure 2.6 Structures within the south half of the Telegraph Creek map area. 18 Figure 2.7 Mineral occurrences within the southern half of the Telegraph Creek map area 21 Figure 3.1 Geology of the Hank property. 23 Figure 3.2 Detailed geology of the Hank property. (in pocket) Figure 3.3 Concordia diagram for the Bald Bluff porphyry. 34 Figure 3.4 Cross section A-A' and Cross-section B-B'. 38 Figure 3.5 Stereoplots for bedding, jointing, veining and mineralized veins on the Hank property. 39 Figure 3.6 Orientation of faults and bedding on the Hank property. 41 Figure 3.7 Plot of whole rock samples from volcanic strata on the Hank property. 43 Figure 3.8 Incompatible immobile element plots for volcanic strata on the Hank property. 44 Figure 3.9 Normalized abundance plot for average compositions for Unit 1 and Unit 2. 45 Figure 3.10 Regional geochemical correlations. 47 Figure 3.11 a) Volcanic arc granite, b) tectonic affinity, and c) rare earth element plots for the Goat Peak diorite and Bald Bluff porphyry. 48 Figure 4.1 Distribution of alteration zones on the Hank. 51 Figure 4.2 X-ray diffraction patterns for a) distal, b) medial, and c) proximal alteration. 57 Figure 4.3 X-ray diffraction patterns for transitional alteration. 61 Figure 4.4 X-ray diffraction patterns for a) upper, b) medial, and c) vein illite/smectite alteration. 63 Figure 4.5 X-ray diffraction patterns adularia+illite/smectite alteration. 66 Figure 4.6 X-ray diffraction patterns for a) medial, and b) peripheral illite alteration. 70 Figure 4.7 X-ray diffraction patterns for a) chlorite illite/smectite, and b) chlorite -t-illite alteration 72 Figure 4.8 Detailed cross-section through the Lower alteration zone. (in pocket) ix Figure 4.9 Detailed cross-section through the Flats zone. (in pocket) Figure 4.10 Detailed cross section through the 200 pit area of the UAZ. (in pocket) Figure 4.11 Detailed cross section through the 200 pit area of the UAZ. (in pocket) Figure 4.12 Location of alteration zones on the Hank property. 77 Figure 4.13 Section 1 through the Lower alteration zone. 79 Figure 4.14 Section 2 through the Flats zone. 80 Figure 4.15 Detailed geology of the pit area of the Upper alteration zone and Felsite Hill. 82 Figure 4.16 Section through the pit area of the Upper alteration zone. 84 Figure 4.17 Detailed geology of the Rojo Grande - Rojo Chico area. 90 Figure 4.18 Immobile element plots for altered and precursor samples. 93 Figure 4.19 Relative mass changes for major oxides. 94 Figure 4.20 Mass changes for major oxides. 96 Figure 4.21 Lateral mass changes in the LAZ. 97 Figure 4.22 a) Total mass change - ASi02, and b) AA1203 - ASi0 2. 99 Figure 4.23 Plot of illite Kubler indices with increasing elevation. 101 Figure 5.1 Paragenetic sequence for the Quartz Stockwork zone. 103 Figure 5.2 Paragenetic sequence for the Lower alteration zone. 104 Figure 5.3 Paragenetic sequence for the Flats zone. 106 Figure 5.4 Paragenetic sequence for veining in the UAZ. 110 Figure 5.5 Paragenetic sequence for Felsite Hill. 112 Figure 5.6 Gold values for wall rock samples from the LAZ to Felsite Hill. 117 Figure 5. 7 Lead isotope compositions for galena and feldspar for the Hank property. 119 Figure 6.1 Temperatures of formation for alteration minerals in active low-sulphidation epithermal systems and temperatures of formation for alteration assemblages on the Hank property. 129 Figure 6.2 Kubler indicies and location of anomalous disseminated gold mineralization at Hank. 132 Figure 6.3 A reconstructed model of the Hank hydrothermal system. 135 Figure D.l Representative X-ray diffraction patterns. 175 Figure F. 1 Fractionation trends for a) Al203-Zr, b) A1203-Y, and c) Ti02-Zr. 187 Figure F.2 Fractionation trends for a) Si02-Zr, b) CaO-Zr, c) FeO-Zr, and d) MgO-Zr. 188 Figure F.3 Fractionation trends for a) K 20-Y, b) Na20-Y, c) MnO-Zr, and d) P205-Zr. 189 Figure F.4 Plot of Al 20 3-Ti0 2 for altered and precursor samples from the Bald Bluff porphyry. 190 X L I S T O F T A B L E S Table 2. 1 Tectonostratigraphic packages for the southern Half of the Telegraph map area. 10 Table 2. 2 Description of deformation within the Telegraph Map Area. 20 Table 2.3 The spatial distribution of the main ages of mineralization in the southern half of the Telegraph map area. 21 Table 3.1 Lithological description of the various units underlying the Hank property. 25 Table 3.2 U-Pb isotopic analyses for the Bald Bluff Porphyry. 34 Table 4.1 Characteristic alteration assemblages and sub-types. 52 Table 4.2 Peak positions and Kubler Indices for diagnostic peaks for each alteration assemblage. 54 Table 4.3 Characteristics of the various alteration zones. 76 Table 4.4 Types of hydrothermal breccias on Felsite Hill. 86 Table 4.5 Peak positions and Kubler Indicies determined from X-ray diffraction analyses. 100 Table 5.1 Types of veining in the LAZ 105 Table 5.2 Types of veining within the pit area of the UAZ. 109 Table 5.3 Types of veining within Felsite Hill. I l l Table 5.4 Gold mineralization in the LAZ, Flats zone, pit area of the UAZ and Felsite Hill. 116 Table 5.5 Pb-isotopic analyses for galena and orthoclase. 118 Table 6.1 Defined alteration assemblages and their distribution. 121 Table 6.2 characteristics of alteration types and their spatial distribution. 122 Table 6.3 Alteration and ore mineralogy of Low- and High-sulphidation systems and at Hank. 124 Table 6.4 Characteristic of Low-sulphidation epithermal environments. 125 Table A. 1 Mineral occurances in the southern half of the Telegraph map area. 149 Table B. 1 Petrographic descriptions of precursor samples on the Hank property. 152 Table C. 1 Whole rock chemistry of intrusive and volcanic rocks for the Hank property. 159 Table C.2 Analytical standards; summary of statistical data. 169 Table D. 1 List of diagnostic peaks for clay minerals. 174 Table D.2 Diagnostic peaks for accessory minerals. 174 Table D.3 Effect of diagnostic treatments on first low-angle diffraction of clay minerals. 174 Table E. 1 Changes in the intensity of alteration based on mineralogy. 178 Table E.2 Petrographic, X-ray diffraction observations and calculated alteration index numbers (AI#) for altered and precursor whole rock samples. 179 Table F. 1 Calculated mass change for altered and precursor whole rock samples from Unit 1 and 2. 191 Table F.2 Calculated mass change for the Bald Bluff porphyry. 199 L I S T O F P L A T E S X I Plate 3.1 a) Andesite lapilli tuff of Unit la, and b) photomicrograph of tuff showing the plagioclase and volcanic ash-rich matrix of this unit. 29 Plate 3.2 a) Massive to porphyritic flows, sills and dykes of Unit Id. b) Photomicrograph showing excellent preservation of pyroxene and plagioclase. 29 Plate 3.3 a) Massive flows/sills of Unit 2a and b) photomicrograph of biotite porphyritic sub-unit. 29 Plate 3.4 a) Large pieces of fossilized wood, and b) well bedded, calcareous sandstones of unit 4. 36 Plate 3.5 a) Amygdaloidal flows of unit 5a, and b) flow banded rhyolite of 5b . 36 Plate 3.6 a) Bald Bluff porphyry; large orthoclase phenocrysts in matrix of plagioclase, and b) contact breccia along the margin of the Bald Bluff porphyry. 36 Plate 4.1 a) white, amorphous kaolinite, and b) hematitic distal kaolinite alteration. 59 Plate 4.2 a) Kaolinite-natroalunite veinlets and b) vuggy medial kaolinite alteration. 59 Plate 4.3 a) relict plagioclase porphyritic, b) breccia textures in proximal kaolinite alteration, c) Photomicrograph of kaolinite alteration, and c) botyoidal marcasite. 59 Plate 4.4 a) Transitional alteration displaying preservation of relict plagioclase porphyritic texture, b) and photomicrograph showing the finely mosaic of kaolinite, illite/smectite and quartz. 69 Plate 4.5 a) Pervasive silicification displaying multiphase brecciation healed by chalcedony, and b) photomicrograph of silicified rock with plagioclase phenocryst pseudomorphed by quartz. 69 Plate 4.6 a) Illite/smectite alteration showing the friable character of this type of alteration, and b) photomicrograph of medial illite/smectite showing abundant calcite within a finer grained matrix of illite/smectite and quartz. 69 Plate 4.7 a) Adularia+illite/smectite alteration with cross cutting crustiform quartz veins, and b) photomicrograph showing coarser grained quartz and adularia and irregular masses of pyrite. 69 Plate 4.8 a) Medial illite altered orthoclase porphyry dyke, b) photomicrograph of medial illite altered Unit Id, with vesicles filled by calcite and rimmed by pyrite. c) Photomicrograph of coarse grained illite surrounding a relict fragment, and c) a suite of samples showing a decrease in the intensity of alteration from medial to chlorite alteration. 76 Plate 4.9 a) Chlorite+illite/smectite alteration of Unit la near the base of the 200 pit area of the UAZ. b) Photomicrograph of chlorite+illite alteration showing abundant chlorite and calcite. 76 Plate 4.10 View to the southeast of Hank Ridge outlining the location of alteration zones on the property. 89 Plate 4.11 View to the east of the silicified zone and Felsite Hill outlining the distribution of alteration assemblages. 89 Xll Plate 5.1 Crustiform quartz-calcite vein from the Flats. Plate 5.2 Photomicrograph of massive pyrite vein showing insitu brecciation of pyrite. 110 110 Plate 5.3 a) Quartz-calcite-sulphide vein showing platy calcite along the edge of the vein and cross cutting calcite fracture fill, b) Photomicrographs of the margin of a quartz-calcite-sulphide vein showing crustiform quartz growth with coarse grained calcite, and c) barite in the core, and hydrothermal illite between coarse and fine grained quartz bands, d) Photomicrograph showing sulphide relations. 110 Plate 5.4 a) Photomicrograph of chalcedonic quartz from a quartz-pyrite vein in the Flats zone, and b) a crustiform quartz-barite vein. 116 Plate 5.5 a) Crustiform calcite vein with bladed quartz crystals, likely replacing calcite. b) Photomicrograph of feather calcite in the coarser grained portions of crustiform calcite veins, and c) photomicrograph of arsenopyrite rirnming earlier formed pyrite crystals. 116 Plate 5.6 Photomicrograph of banded calcite vein from zones of kaolinite-dominant alteration on Felsite Hill. 116 X I U A C K N O W L E D G M E N T S I am grateful to Homestake Canada Inc., in particular Ron Britten, Henry Marsden, and Margret McPherson (all formerly of Homestake Canada Inc.) for logistical and technical support of this thesis. Assistance from Dr. A.J. Sinclair, my supervisor, Dr. A.J. Macdonald, coordinator of the Iskut Project is gratefully appreciated. Particular thanks goes to Dr. J.F.H. Thompson for his encouragement, patience, editing, and ideas on low-sulphidation epithermal systems. Jim Logan and Derek Brown of the British Columbia Geological Survey aided in the regional synthesis of the Upper Triassic Stuhini Group. Thank you to Jim Mortensen and Greg Dipple for their thorough editing prior to defending. Financial support for this research was provided by the Mineral Deposit Research Unit (MDRU), as part of the Iskut River Project entitled Metallogenesis of the Iskut River Area. Funding was provided.to MDRU by thirteen mining and Exploration companies, the Science Council of British Columbia, and the National Science and Engineering Research Council (NSERC) CRD grant. Finally, I would like to thank Fiona Childe for her, constructive criticism, moral support and understanding. The completion of this thesis is very much a testament to her patience. 1 1.0 I N T R O D U C T I O N 1.1 L O C A T I O N A N D A C C E S S The Hank property is located within the Liard Mining Division in northern 3C, approximately 90 km southeast of the town of Dease Lake, BC (Figure 1.1). The property lies on NTS map sheets 104G/1,2 and is centred at latitude 57°13TSf, longitude 130o30'W. Access to the property is by vehicle or fixed wing aircraft to the Bob Quinn airstrip on Highway 37, 400km north of Smithers, BC, and then by helicopter to the property, 25 km to the northwest of the airstrip. Figure 1.1 Location of the Hank property. 2 1.2 PHYSIOGRAPHY The Hank property lies within the Boundary Ranges of the Coast Mountains. The property occupies a steep northeast trending ridge adjacent to Hank Creek which flows into Ball Creek to the northeast (Frontispiece). Local topographic relief is moderate to very steep with elevations ranging from 900 metres in the northeast corner of the property to 2050 metres in the southwest. The area exhibits characteristics typical of glaciated physiography, with wide U-shaped, drift filled valleys flanked by steep rugged mountains, cirques and deeply incised V-shaped upland drainages. Rock exposure is best along the ridge tops and saddle area in the eastern part of the property, and in the steeply incised drainages on the northwest flank of Hank Ridge. Vegetation consists mainly of alder and forests of mature fir, spruce and hemlock with minimal underbrush. Above treeline, which lies at approximately 1500 metres, vegetation changes to isolated patches of scrub alpine spruce and juniper, and a variety of alpine grasses overlying extensive felsenmeer. Several permanent snowfields and small glaciers exist on Hank Ridge and below Rojo Grande and Goat Peak. The area receives significant rainfall, and snow can lie on the higher elevations of the property until mid-July. 1.3 PREVIOUS WORK 1.3.1 Regional Mapping The first systematic geological mapping of the Telegraph Creek map-area was completed by F. A Kerr, of the Geological Survey of Canada, who examined the area adjacent to the Stikine River (Kerr, 1948). In 1956, the Geological Survey of Canada began Operation Stikine which included helicopter reconnaissance of the northern part of the Telegraph Creek map-area. During the years 1965 to 1967 and 1969, JD. Souther investigated the recent volcanic rocks of Mount Edziza and the Spectrum Ranges as well as the Mesozoic rocks of the Klastline plateau and the Ball Creek region. In 1969, J.W.H. Monger completed detailed investigations of the Late Paleozoic stratigraphy in the map-area. This initial geological mapping by the Geological Survey of Canada culminated in the publication of a 1:250,000 scale geological map of the Telegraph Creek map-area (Figure 2.1; Souther, 1972). 3 km Figurel.2 Map showing the field areas for each regional mapping program. In response to increased exploration activity within the Telegraph Creek map-area during the mid 1980's the Geological Survey of Canada and British Columbia Department of Energy, Mines and Petroleum Resources began systematic mapping of the Telegraph and adjoining Iskut River and Spatsizi map-areas to the south and east respectively. Regional mapping between 1986 and 1992 by CE. Evenchick of the Geological Survey of Canada covered the Middle Jurassic strata of the Skeena Fold and Thrust Belt (Evenchick, 1993) which lies along the western margin of Telegraph Creek map-area (Figure 1.2). Beginning in 1988, the British Columbia Department of Energy, Mines and Petroleum Resources began 1:50,000 scale geological mapping of the Telegraph Creek map-area (Figure 1.2). Between 1989 and 1992 geological mapping by D.A. Brown et al. (1989, 1990 and 1992) and by J. Logan et a/.(1989, 1992 and 1993) completed regional coverage of the southwest quadrant of the map area from the Chutine River - Tahltan Lake (104G/12W, 13) areas southeast to Moore Creek (104G/2). 4 1.3.2 Exploration History The Hank property comprises two groups of claims totaling 91 units. The Hank claims, formerly owned by Lac Minerals Ltd. and presently owned by Barrick Gold Corp., cover a large hydrothermal system that extends to the south and east onto the Panky claims, owned by Cominco Ltd. (Figure 1.3). The Hank property was initially discovered and staked by Lac Minerals Ltd. in 1983, based on regional stream sediment geochemical anomalies and the presence of prominent gossans along the main ridge (Turna, 1985). Preliminary geologic mapping and sampling in the same year outlined several broad zones of anomalous gold and arsenic values. In 1984, Lac Minerals Ltd. completed more extensive geologic mapping, sampling, trenching and geophysical surveys, resulting in the discovery of two sub-parallel, northeast trending areas of sericitization, termed the Upper and Lower alteration zones. Work identified a zone of elevated gold mineralization including 3.3 grams/tonne (gpt) Au over 13 metres on surface, coincident with a broad gold, Au > 300 parts per billion (ppb) soil anomaly within the upper zone (Turna, 1985). The area was tested by four diamond drill holes totaling 288 metres, of which drill hole DDH 84-2 returned 1.98 gpt Au over 18.0 metres. Lac completed additional mapping, trenching, sampling and geophysical surveys during 1985 and 1987 to 1989. Additional diamond drilling, totaling 11,350 metres in ninety-one holes, was targeted on both the Upper and Lower alteration zones and several less significant targets (Turna; 1986, 1988, and 1989). Drilling outlined a drill indicated geologic resource contained within the Upper alteration zone of 269,500 tonnes of 4.45 gpt Au and 238,000 tonnes of 2.29 gpt Au in the "200" and "440" pits (Turna, 1986; Figure 1.3). In 1990, Carmac Resources optioned the Hank claims and drilled five diamond drill holes totaling 1458 metres to confirm the extent of mineralization in the Lower and Upper alteration zones from previous drilling then terminated the option (Visagie, 1991). Homestake Canada Ltd. optioned the Hank claims in 1992, and completed a program of 1:2000 and 1:5000 scale geologic mapping, 8.35 line km of LP geophysical surveying, re-logging of twenty-nine drill holes from 1985 to 1990, and the collection of 11 silt samples, 270 rock samples and 631 soil samples (McPherson and Kaip, 1993). Work concentrated on exploring the extensive kaolinite alteration zones on Felsite Hill and Rojo Grande and the silicified zone lying topographically and stratigraphically above the previously identified Upper and Lower alteration zones. In 1993, Homestake Canada Ltd. drilled five holes on the Hank property totaling 659 metres. Four holes were directed to investigate the lateral extent of mineralization within and adjacent to the silicified zone and within zones of hydrothermal brecciation beneath Felsite Hill (Gaunt and Kaip, 1994). Elevated gold values of 1100 ppb Au were obtained in and adjacent to the silicified zone within kaolinite and illite/smectite alteration. Drilling to the southwest of the Flats zone intersected weakly kaolinite-altered sedimentary strata. Figure 1.3 Map of the Hank Property outlining the geographic position of the alteration zones on the property, LAZ = Lower alteration zone, UAZ = Upper alteration zone, SW = Quartz stockwork zone, SZ = Silicified zone, FZ = Flats zone, FH = Felsite Hill and RG = Rojo Grande. Numbers refer to the creeks draining the northwest slope of Hank Creek. Areas covered by dark stipple are snow and ice. 6 1.3.3 Property Investigations In 1985, E.P. Ochs completed a BSc thesis at the University of British Columbia on the wallrock alteration and vein mineralogy of the Hank gold prospect. Ochs detailed the mineralogy of quartz-calcite-sulfide veins from the Upper alteration zone and the adjacent wallrock alteration. During 1992 and 1993 the author conducted fieldwork as a part of a Homestake Canada Ltd. exploration program consisting of geologic mapping of the property and relogging of selected diamond-drill core (Kaip and McPherson, 1993; Kaip and Gaunt, 1994). Mapping was conducted at two scales, 1:5,000 property-scale mapping and 1:2,000 detailed mapping of the Felsite Hill, Bald Bluff and Rojo Grande areas. A suite of whole rock samples were collected from the property to characterize the volcanic and plutonic rocks on the property, and to document the chemical variations with increasing alteration. Representative samples of the various styles of alteration and veining were collected for X-ray diffraction and petrographic analysis to characterize the style of alteration and mineralizataion. Samples of the Bald Bluff intrusion, hornblende-porphyritic sills and limestone were collected to constrain the age of the strata and the Bald Bluff porphyry. Samples of galena from veins and potassium feldspar from the Bald Bluff porphyry were collected for Pb isotopic analysis to investigate the source of metals in the mineralized zones. 1.4 PURPOSE The focus of this research project was to document the geology, alteration and timing of precious metal mineralization on the Hank property in northwestern British Columbia. The goal was to develop a model that explains the style of hydrothermal alteration and precious metal mineralization, thereby assisting in the evaluation of the economic potential of the Hank property and serving as a guide to exploration for other similar deposits in British Columbia and elsewhere. The research project was separated into three sections of investigation; (i) fieldwork and compilation of all existing geochemical data, (ii) laboratory analysis and (iii) development of the model. The fieldwork provides the data for the production of a detailed geological map and cross-sections. The laboratory portion utilizes techniques to quantitatively describe the stratigraphy, alteration and mineralization on the Hank property. These quantitative studies on the alteration and precious metal mineralization, combined with the compilation of existing geochemical data from the Hank property, provide the basis for a model that explains the distribution of precious metal mineralization within this broad alteration system. The model assists in defining the economic potential of the prospect and other similar systems and providi general exploration criteria for near-surface, low-sulphidation epithermal environments. 8 2.0 G E O L O G Y 2.1 TECTONIC SETTING The Hank property is located on the western margin of the Intermontane Belt of the Canadian Cordillera, within northwestern Stikinia. The Canadian Cordillera is divided into five morphologic northwest trending belts. From east to west they are the Foreland, Omenica, Intermontane, Coast Plutonic Complex, and Insular belts (Figure 2.1). The Intermontane and Insular belts are composite terranes which encompass the allochthonous terranes accreted to the western margin of North America during the Mesozoic. Separating these two belts are the Coast Plutonic Complex and the Omenica belt which comprise high grade metamorphic and plutonic rocks which record the accretion of the two allochthonous composite terranes onto ancestral North America (Monger, 1982). The Stikine terrane is situated along the western margin of the Intermontane belt and is bounded to the west by metamorphic and intrusive rocks of the Coast Plutonic Complex and by volcanic and sedimentary rocks of the Cache Creek and Quesnel terranes to the east. Stikinia comprises volcanic and sedimentary strata and intrusive rocks which formed in an island arc environment from the Paleozoic to the Middle Jurassic. Regional studies by Souther (1972), Brown (1989, 1990,1992) and Logan (1989, 1992, 1993) have characterized the evolution of northern Stikinia as that of well defined periods of island arc volcano-plutonic activity separated by periods of erosion and sedimentation. 2.2 REGIONAL GEOLOGY The Hank property is located within the Telegraph Creek map-area along the western margin of northern Stikinia (Figure 2.1). The stratified rocks of northern Stikinia have been divided into four tectonostratigraphic packages (Souther, 1972; Anderson, 1989; Logan et al., 1989, 1992, 1993, and Brown et al., 1989, 1990, 1992). These include: Paleozoic volcanic, sedimentary and related intrusive rocks of the Stikine assemblage; Mesozoic sedimentary, volcanic-plutonic arc assemblages, represented by the Upper Triassic Stuhini Group and Jurassic Hazelton Group; Middle Jurassic to Early Cretaceous Bowser Lake Group, an overlap assemblage; and , Tertiary continental arc assemblages of the Spectrum Range and Mount Edziza 9 which overlie the earlier arc-related assemblages (Souther and Symons, 1974). The characteristics of the tectonostratigraphic units which comprise northern Stikinia are summarized in Table 2.1. The Coast Plutonic Complex, which record the accretion of the Insular Terrane to North America from the Late Jurassic to Early Cretaceous form a northeast trending intrusive complex along the western margin the Telegraph Creek map area. The plutonic complex dominantly intrudes strata of the Paleozoic Stikine Assemblage and comprises Upper Jurassic to Tertiary age hornblende and biotite bearing diorites, granites and monzodiorites and Eocene biotite bearing granites and quartz monzonites. Figure 2.1 Tectonic assemblage map of the Canadian Cordillera outlining the major tectonostratigraphic belts and terrains which comprise each belt (adapted from Wheeler and McFeely, 1991). The position of the Telegraph Creek map area is outlined by the open box. Table 2. 1 Tectonostratigraphic packages within the southern half of the Telegraph Creek map area. 10 Age Unit Lithological Description Tectonic Setting Tertiary Late Moicene to Recent Spectrum & Edziza Complex Peralkaline, subaerial basaltic to rhyolitic lavas and pyroclastic strata and related sub-volcanic intrusions. Continental Arc (Related to crustal extension) Mesozoic Middle Jurassic to Lower Cretaceous Bowser Lake Group Angular unconformity Overlying, shallow marine to nonmarine sandstone, chert pebble conglomerates, siltstone minor limestone and coal (Currier, McEvoy and Devil's Claw units). Basal Ashman Formation including shale, feldspathic to quartzose sandstone, greywacke and chert pebble conglomerate. Onlap Assemblage (North and easterly derived clastic sedimentation from Cache Creek during accretion of Stikinia) Mesozoic Lower to Middle Jurassic Hazelton Group Basaltic to rhyolitic flows, tuffs and related intrusions, grade upward into interbedded siltstones and ash tuffs (Salmon River Formation). Dominantely andesitic volcanic strata and related intrusions, minor sedimentary strata and felsic tuffs (Betty Creek Formation). Basal coarse clastic, volcanic and plutonic derived, sedimentary sequence (Jack Formation). Island Arc (Dominately Calc-alkaline volcanic strata, marine eastern facies and proximal, locally emergent western facies) (Calc-alkaline to Tholeiitic marine volcanic strata, eastern facies and proximal, western facies) Mesozoic Upper Triassic Stuhini Group Bioclastic limestone, shales and wacke. Basaltic to andesitic flows, tuffs and related intrusions and volcanic derived sedimentary strata. Siltstones, tuffs and silty limestones (Kitchener unit). Paleozoic Devonian to Permian Stikine Assemblage Permian Limestones and overlying andesitic volcanic and sedimentary strata. Carboniferous basaltic to felsic flows and pyroclastic, and minor sedimentary strata. Devonian basaltic to felsic tuffs, siltstones and limestones. Island Arc ( bi-modal arc construction followed by carbonate and marine sedimentation related to arc subsidence) 2.2.1 Stikine Assemblage The oldest strata in the region comprise variably deformed and metamorphosed sedimentary, volcanic and related intrusive rocks of the Devonian to Permian Stikine Assemblage which are exposed along two north-northwest trending belts in the map area (Figure 2.2 and 2.3). Stratigraphic investigations by Monger (1970), Souther (1972) and Brown et al. (1991) have identified four different fault bounded, stratigraphic successions: 11 1. Lower to Middle Devonian mafic to felsic tuffs, siltstones and thinly bedded limestones exposed near Forest Kerr Creek, located south of the Hank property in the Iskut River map area (NTS 104B). 2. Early Carboniferous basaltic to felsic flows and pyroclastic rocks capped by calcarenites exposed at Round Lake and along Mess Creek. 3. A thick sequence of andesitic volcanic and intercalated sedimentary strata overlain by a structurally thickened package of Lower Permian limestone (> 1000m) exposed in the Scud River area. 4. Latest Permian andesitic volcanic rocks which interfinger with calcarenites and grade upward into cherts and argillites overlie Lower Permian limestones in the Scud River area. Brown et al. (1991) have interpreted the Paleozoic Stikine assemblage to have formed from early bimodal volcanism and arc construction with contemporaneous carbonate reef formation and sedimentation followed by carbonate platform development, local volcanism and deep water sedimentation related to arc subsidence (Figure 2.4). Intrusive activity during the Paleozoic was limited to subvolcanic sills and dykes associated with thick piles of andesitic to basaltic flows, tuffs and epiclastics. Mapping by Logan et al. (1992) west of Moore Creek and northward to Arctic Lake has outlined a large intrusive complex comprising variably foliated diorite to granite phases previously correlated with the Lower Jurassic Yehinko Batholith to the north (Souther, 1972). K-Ar dating of this intrusion has yielded an Early Mississippian age of 346±10 Ma (Logan et al., 1992). 2.2.2 Upper Triassic Stuhini Group Unconformably above the Stikine Assemblage are Upper Triassic volcanic, sedimentary and related intrusive rocks of the Stuhini Group. The Stuhini Group, which was first described by Kerr (1948) and re-defined by Souther (1971), includes all Upper Triassic volcanic and sedimentary strata that lie above a regionally developed Middle Triassic unconformity and below limestones of the Norian Sinwa Formation. In the Telegraph Creek map area the Stuhini Group, is dominated by Norian to Carnian basaltic to andesitic volcanic and related sedimentary strata which include both marine and lesser subaerial facies which unconformably overlie strata of the Paleozoic Stikine assemblage (Brown, etal., in press). Locally, Middle Triassic siltstones, cherts, shales and minor tuffs separate the 12 Stuhini Group from the underlying Paleozoic section. Contacts between Middle Triassic and Stuhini Group strata, exposed west of Arctic Lake and west of the Hickman Batholith, appear to be conformable (Figure 2.3). Stratigraphic correlations within the Stuhini Group are difficult due to a lack of marker units, the homogeneity of volcanic rocks, and the lack of fossil age control from intercalated sedimentary units. Stratigraphic sections compiled from work by Souther (1972), Logan (1989, 1992) and Brown (in press), in the Telegraph Creek map area, show a gradual change from proximal volcanic facies in the western half of the map sheet to more distal volcanic fades in the east (Figure 2.5), suggesting that the Stuhini arc was asymmetric as originally postulated by Souther (1972). STRATIFIED ROCKS TERTIARY Basaltic to rhyolitic flows, domes, pyroclastic rocks and related subvokanio intrusions. JURASSIC (/ V V V V ^ Middle to Upper Jurassic Bowser Lake Group: silfa)tone, sandstone and conglomerate. Lower Jurassic Hazelton Group: andesitic to felsic flows, sills, tuff and lesser sedimentary rocks. Lower Jurassic heterolithic conglomerate, sandstone and lesser ash tuff. TRIASSIC Upper Traissio Stuhini Group: Basaltic to /. ->j andesitic flows, sills, tuff, greywacke and n siltstone. Middle Triassic siltstone, shale, tuff. PALEOZOIC - STIKINE A S S E M B L A G E Permian bioclastic limestone, chert and minor tuff. ^JJPJ, Permian and older limestone, metasedimentary rfi&A and metavolcanic rocks. Carboniferous limestone and basaltic flows, sills and tuff. Devonian limestone and andesitic volcanic rocks. Fault INTRUSIONS EOCENE Granite, granodiorite, diorite. JURASSIC - TERTIARY Granite, diorite and monzonite. MIDDLE JURASSIC Yen ink o Pluton: pink biotite granite. EARLY TO MIDDLE JURASSIC Syenite, monzonite and granodiorite. Megacrystic quartz monzonite. MIDDLE T O L A T E TRIASSIC + . K + Hickman and Nighout plutons: quartz diorite, granodiorite, monzonite, minor gabbro and homblendite. p^Jy Pyroxene gabbro, pyroxenite and dunite. MISSISSJPPIAN Foliated granodiorite and diorite. / / / / / / / / / Thrust fault Figure 2.2 Legend for the southern half of the Telegraph Creek map area, Figure 2.3. 14 P A L E O Z O I C S T I K I N E A S S E M B L A G E C O M P O S I T E S E C T I O N Figure 2.4 A composite stratigraphic section for the Paleozoic Stikine assemblage in northwestern Stikinia (adapted from Brown et al., 1991). In the northern part of the map sheet, Brown (in press) have divided the Stuhini Group into three members. The lowest, the Kitchener unit, consists of rhythmically banded siltstone and tuff which grade upward into plagioclase porphyry and augite-bearing volcanic breccias and are in turn overlain by silty limestone and calcareous sedimentary rocks of Carnian to probable Norian age. Overlying the Kitchener unit is a thick sequence of basaltic to andesitic flows, sills and volcanic rocks more characteristic of the Stuhini Group. Intercalated with these massive units are tufFaceous wackes interpreted as distal equivalents of the more proximal flows and breccias. The top of the Stuhini section is denned by the Upper Norian Quatrin Unit consisting of a basal bioclastic limestone unit overlain by thin bedded shale and wacke. To the south, in the Galore Creek area, the Stuhini Group comprises a thick package of andesitic to mafic flows, coarse volcaniclastics, tuffs and volcanic-derived wackes which are 15 intruded by numerous synvolcanic sills. In the Galore Creek area, the volcanic strata is tentatively divided into upper and lower sequences which are separated by calcareous sedimentary strata and bioclastic limestone. The intervening sedimentary strata marks a decrease in volcanic activity and may correlate with the upper part of the Kitchener Unit. East of Galore Creek, the Stuhini Group forms a coarsening-upwards sequence, which is exposed east of Hankin Peak (Logan et al., 1992). The base of the section comprises a thick succession of shale and wacke which grade upward into volcanic-derived wackes. Bioclastic limestone and calcareous siltstone, which may correlate with upper part of the Kitchener Unit, are occur near the middle of the section. The top of the section is characterized by a coarsening-upward sequence from marine to volcanic derived sedimentary strata, and by andesitic flows, volcaniclastic strata and related sills and dykes. Western fades Eastern Facies Proximal to volcanic center Mafic extrusive and intrusive phases subordinate marine sedimentary strata N W Telegraph Creek Map Area Galore Creek Area A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A lA A A A A A A Distal to volcanic center Epiclastic breccias, feldspathic wackes Thick sequences of marine strata Brown et al. (in press) Logan et al., 1989 Camian LEGEND Andesitic - basaltic tuff, wacke, and volcanic derived conglomerate. Mafic volcanic rocks (augite bearing). v v Andesitic volcanic rocks •^-^ (hornblende, augite bearing). 11 -'I Limy sedimentary rocks, shale and limestone. Thin bedded shale, siltstone, sandstone and wacke. || Bioclastic limestone. Logan et al. 1992 Souther. 1972 Bladed plagioclase porphyry. Figure 2.5 Representative stratigraphic sections for the Upper Triassic Stuhini Group in the Telegraph Creek map area (adapted from Logan et al., 1990; and Brown, in press). The western facies of the Stuhini arc comprise a dominantly submarine andesitic to basaltic suite with subordinate sedimentary strata. Farther eastward, the Stuhini Group is dominated by volcanic derived and marine sedimentary strata. A volcanic hiatus is recorded throughout the Telegraph Creek map area during Latest Carnian to Early Norian. 16 In the vicinity of Ball Creek, sedimentary and lesser volcanic strata dominate the lower part of the section (Souther, 1972). Here volcanic conglomerate, greywacke, chert-bearing conglomerate and tuffaceous siltstone are overlain by discontinuous lenses of bioclastic limestone and calcareous siltstone of probable Carnian age (Souther, 1972). Above the limestones, the section comprises a thick sequence of interbedded calcareous shale, chert, siliceous siltstone, greywacke and minor limestone which grade upward into volcanic derived greywacke. Overlying this lower sedimentary package are andesitic to basaltic, intercalated greywacke, siltstone and heterolithic conglomerate, atypical of the upper part of the Stuhini Group to the west. The Quartrin limestone, exposed in the northwest part of the Telegraph Creek near the top of the Stuhini section may be correlative with the Sinwa Formation which marks the top of the Upper Triassic succession in the Tulsequah and Dease Lake map areas (Souther, 1957). Intrusive rocks coeval with Stuhini volcanism include the Hickman and Nightout batholiths (Souther, 1972; and Brown et al., 1989). To the northeast of the map area, Upper Triassic intrusions including the Stikine and Hotailuh batholiths form a northeast linear in the core of the Stikine Arch (Anderson, 1983, 1984). 2.2.3 Lower Jurassic Strata East of Mess Creek, Hettangian to Sinemurian sedimentary strata lie disconformably to unconformably above the Stuhini Group (Figure 2.3). The strata contain clasts derived from the underlying volcanic strata and lenses of granite bearing conglomerate derived from unroofing of the Hickman Batholith in the northern part of the map area (Souther, 1972). This unit is interpreted to mark an erosional surface, possibly related to a deformational event which Souther (1972) named the Inklinian Orogeny based on investigations of the Lower Jurassic Laberge Group sediments to the north of the Telegraph Creek map area. To the south, Henderson et al. (1992) and Greig (1995) have described a similar unit in the McTagg Creek and Oweegee Dome areas, informally named the Jack Formation, and have interpreted this unit to reflect clastic sedimentation in response to deformation, and/or uplift during the upper most Triassic. Lowest Jurassic volcanic, and intrusive activity in the south half of the Telegraph Creek map area is centred around Galore Creek. Panteleyev (1976) subdivided the volcanic rocks at 17 Galore Creek into a lower sequence of submarine basaltic and andesitic flows and breccias, correlated with the Stuhini Group, and an overlying, partially subaerial sequence of alkaline flows and pyroclastic rocks uncharacteristic of the Stuhini Group. These orthoclase and pseudoleucite bearing flows are interpreted to be comagmatic with syenite intrusions within the area. These syenite intrusions, which yield U-Pb ages between 210 ± 1 Ma and 205.1 ± 2.3 Ma (Mortensen et al., 1995) form a multiphase complex of silica undersaturated, alkaline and metaluminous intrusions and related porphyry mineralization (Enns et al., 1995). 2.2.4 L o w e r to M i d d l e Jurass ic H a z e l t o n G r o u p Conformably overlying the Lower Jurassic strata are volcanic and sedimentary rocks of the Lower to Middle Jurassic Hazelton Group exposed east of Moore Creek (Figure 2.3). Souther (1972) initially separated the Hazelton Group into two packages. The lower package contains well indurated black to grey siltstone and intercalated basaltic to rhyolitic volcanic strata of Pliensbachian age. The overlying package consists of basaltic to andesitic pillow lava exposed east of Kiniskan Lake. Pleinsbachian age fossils observed at the top of the basaltic sequence indicate that the two packages are likely co-temporal (Evenchick, 1990). The top of the Hazelton Group succession contains a tuffaceous and sedimentary unit, informally named the pyjama beds, which are correlated with the Quock Formation of the Spatsizi Group in the Spatsizi map-area. To the south, in the Iskut River map area, Anderson and Thorkelson (1990) have correlated this sedimentary and bimodal volcanic suite with the Eskay Creek facies of the Salmon River Formation. Coeval with Hazelton age volcanic strata are numerous Early to Middle Jurassic intrusions including the Yehinko Batholith which intrudes Stuhini Group volcanic rocks east of Shaft Creek (Souther, 1972). The main phase of the intrusion comprises medium to coarse grained biotite granite and numerous aplite and rhyolite apophyses within the surrounding country rock (Brown, 1989). Diorite, gabbro and monzonite stocks, exposed south and east of Hankin Peak are also thought to be Early Jurassic in age (Logan et al., 1992, Kaip, 1993). 18 2.3 REGIONAL STRUCTURE The structural grain of the southern half of the Telegraph Creek map area is characterized by a minimum of four documented phases of deformation. Regional scale faults strike north and control the distribution of the tectonostratigraphic packages in the map area (Figure 2.6). 57" 30' 132 00' LEGEND 1. Nighout Pluton 2. Yehinko Batholith 3. Hickman Batholith A Stikine River B Scud River C Round Lake D Mess Creek E Arctic Lake F Mess Lake G Moore Creek H Ball Creek I Iskut River J Highway 37 57° 00' 130°00' 12 24 36 Km Intrusions Figure 2.6 Structures within the south half of the Telegraph map area. Dark lines show the distribution of faults including the Forrest Kerr (FFZ), and Mess Creek (MFZ) fault zones. The largest of these faults is the northward extension of the Forrest Kerr fault which juxtaposes Upper Triassic Stuhini Group strata to the east against Paleozoic metavolcanic and metasedimentary strata to the west, and records a minimum of 2 kilometres of left-lateral and east side down displacement (Figure 2.6; Logan, 1992; and Read et al, 1989). This fault system cuts Recent volcanic strata on the western flank of the Mount Edziza, and is interpreted to be the locus of volcanic activity related to the Spectrum and Edziza complex (Souther and Symons 1974). 19 Along Mess Creek, a series of north striking faults juxtapose Paleozoic and Stuhini Group strata (Figure 2.3). Apparent west side down movement on the Mess Creek fault system is interpreted to be of Early Jurassic to Recent age (Souther and Symons, 1974). To the east, the Iskut River valley is the locus of a regional fault system which juxtaposes sedimentary strata of the Jura-Cretaceous Bowser Lake Group with Upper Triassic strata to the west. Displacement on this fault system appears to decrease in magnitude to the north where volcanic strata of the Lower Jurassic Hazelton Group are in conformable contact with the overlying Middle Jurassic Bowser Lake Group. The characteristics and timing of the four main stages of deformation in the region are listed in Table 2.2. The oldest phase of deformation (Dl), informally named the Tahltanian orogeny (Souther, 1972), affects the Paleozoic strata and is interpreted to have occured prior to the onset of Mesozoic arc construction. Evidence for this early phase of deformation include: a regional unconformity at the top of the Paleozoic section; and, an early metamorphic event not observed in the overlying Mesozoic strata. Phases D2 and D3 are related to the accretion of the Insular Belt which commenced during the Middle Jurassic. Evenchick (1991) attributes the change in orientation between D2 and D3 to the Stikine Arch which acted as an immobile block which caused a change in the stress regime and the formation of northeast trending cross folds superimposed on earlier northwest trending structures. The latest phase of deformation in the area is restricted to the rocks adjacent to the Forrest Kerr fault. Folding and axial planar cleavage is developed within strata immediately adjacent to the fault system and decreases in intensity outward suggesting that D4 is related to movement along the Forrest Kerr fault system (Elsby, 1992). Within northern Stikinia the Lowest Jurassic represent a hiatus in volcanic activity and possibly tectonic uplift. Granitic clasts within Hettangian to Sinemurian age sedimentary strata and disconformable to locally unconformable contacts with underlying Stuhini Group strata indicate a hiatus in volcanic activity, local uplift and unroofing of the Stuhini volcanic arc during the Lower Jurassic (Souther, 1972, Henderson et al, 1992, Greig, 1995, Kaip and MacPherson, 1993). Souther (1972) was the first to document this regional feature and informally named it the Inklinian Orogeny. However, the origin and extent of this event remains uncertain, it is therfore not defined as a separate phase of deformation in Table 2.2. 20 Table 2.2 Description of deformation within the Telegraph Map Area O o^gan et al., 1992 and Elsby, 1992). Phase Age Megascopic Structures Microscopic Structures Metamorphism D l post-E Permian to pre-M Triassic NW-trending, east vergent isoclinal folds, west vergent thrusting. S1=NE-striking, NW-dipping, axial planar to F l -folds variable, greenschist to amphibolite. D2 post-M to L Jurassic to Cretaceous NW-trending, isoclinal to open. S2(Paleozoic strata)=NW-striking, SW-dipping, transposes St S2(Mesozoic strata)=fracture cleavage Lower Greenschist D3 post-M to L Jurassic to Cretaceous Orthogonal to D2, no folding of Paleozoic strata, E-NE-trending open folds in Mesozoic strata. S3(Paleo)=crenulation S) S3(Meso)=fracture cleavage Greenschist to amphibolite related to CPC D4 Recent Adjacent to Forrest Kerr Fault N-trending, open N to S-plunging folds. S4=steep E to W-dipping fracture cleavage 2.4 REGIONAL M E T A L L O G E N Y The southern half of the Telegraph map area contains 56 metallic mineral occurrences (B.C. Minfile, ?). These are divided into porphyry, diatreme breccia hosted, skarn, vein, disseminated, epithermal and volcanic massive sulphide (Figure 2.7; Appendix A). The age(s) of mineralization for the various showings are poorly constrained, however a comparison of host lithologies and the age of related intrusions for each mineral occurrence suggests there are five main episodes of mineralization within the map area (Table 2.3). The distribution, types, and inferred ages of deposits appear to be controlled by regional scale faulting. Down faulted blocks of Mesozoic strata in the Galore, Shaft and Ball Creek areas expose high level styles of mineralization which are absent from the Paleozoic strata. The distribution of mineral occurrences appear to be spatially related to large intrusive centres at Galore and Shaft Creek where vein, diatreme breccia and disseminated styles of mineralization form peripheral to major porphyry Cu-Au and Cu-Mo centers. Alteration and mineralization at the Hank property is hosted by both Upper Triassic Stuhini Group and Lower Jurassic strata. The style of alteration, which is dominated by illite, kaolinite and illite-smectite assemblages is characteristic of an epithermal environment and may be similar to other Mesozoic occurrences including the CAM, Paydirt and MAI showings. However, unlike most Mesozoic occurrences, the Hank does not appear to have formed 21 peripheral to a larger porphyry system. The setting and inferred Middle Jurassic age of mineralization suggests that the Hank may represent a unique metalogenic event in the map area. Table 2.3 The spatial distribution of the main ages of mineralization in the southern half of the Telegraph map area and the types mineralization present. Age Location Type Host* Major occurance Cretaceous-Tertiary Stikine River area Vein Ps, uTs, CPC Lower Jurassic Ball Creek Epithermal uTs, eJmz Hank (107) Lowest Jurassic Galore Creek Porphyry Vein Diatreme Breccia Skam Disseminated uTs, Uv, eJsy uTs uTs, eJmz Ps, eJsy uTs, eJmz Galore Creek (90-99)(b) Upper Triassic Shaft Ck. - Arctic Lk. Porphyry Vein Skarn uTs, ITH P, uTs, ITH P, ITH Paleozoic SW of Moore Ck. VMS Skarn Pv Pis Formore (146) Dundee GLA (137) * Litholigies include: Ps = Paleozoic Stikine, D = Devonian, P = Permian (v) volcanic, (Is) limestone, uTs = Upper Triassic Stuhini Group, Uv = Lower Jurassic Hazelton, Uh = Lower Jurassic Hazelton, ITH = Hickman Batholith, eJsy,mz = Early Jurassic syenite, monzonite, CPC = Coast Plutonic complex. 014 LEGEND 108 E Mineral occurrence • Epithermal • Disseminated O Porphyry X Diatreme breccia • Skam A Vein • Vein/Stockwork © Volcanic massive sulphide (VMS) South half of the Telegraph Creek map area (NTS 104G) 30 km Figure 2. 7 The location of mineral occurrences within the southern half of the Telegraph Creek map area. 22 3.0 P R O P E R T Y G E O L O G Y 3.1 INTRODUCTION The Hank property is underlain by a succession of Upper Triassic Stuhini Group flows, sills, tuff, epiclastic and minor sedimentary rocks; Lower Jurassic siltstone, wacke and conglomerate; as well as; vesicular basalt, flow banded rhyolite and minor epiclastic rocks of probable Lower to Middle Jurassic age (Figure 3.1). The stratified rocks on the property are intruded by an orthoclase-megacrystic monzonite stock, termed the Bald Bluff porphyry, and an elongate hornblende diorite intrusion exposed on Goat Peak. The Stuhini Group strata on the property form a homoclinal sequence which strikes northeast and dips moderately to the southeast. In contrast, Lower Jurassic sedimentary strata, south of Bald Bluff, are folded about a northwest trending syncline. The West Hank fault, lies along the western margin of the property and juxtaposes volcanic strata of the Stuhini Group to the northeast with siltstone and wacke also of the Stuhini Group and a wedge of probably Lower Jurassic volcanic strata to the southwest. Seven alteration zones are present on the Hank property with characteristic alteration assemblages described by Kaip and McPherson (1993) and Kaip and Gaunt (1994). They include: the Quartz stockwork zone (QZ); the Lower alteration zone (LAZ); the Flats zone (FZ); the Upper alteration zone (UAZ); the Silicified zone (SZ); Felsite Hill (FH); and, Rojo Grande (RG) (Figure 3.1). The property geology was mapped at a scale of 1:5,000 using existing grids developed by Lac Minerals Ltd. on the northwest slope of Hank Ridge, and grids developed by Homestake Canada Ltd. on Felsite Hill and Rojo Grande. Detailed mapping of Bald Bluff and the alteration zones on Felsite Hill and Rojo Grande was completed at a scale of 1:2,000. In areas of limited exposure below Bald Bluff and northeast of Felsite Hill examination of drill core provided more complete geological control. Details of outcrop distribution, lithological descriptions, style and intensity of alteration, and structural measurements are presented in Figure 3.2. 23 LEGEND STRATIGRAPHY Jurassic Hazelton Group Amygdaloidal basalt flows and flow breccia, minor volcaniclastic rocks (Unit 5a). [jjigjgjjj F'ow banded rhyolite (Unit 5b). Lower Jurassic Upper Triassic Stuhini Group Lower volcanic sequence Siltstone, feldspathic wacke, sandstone and heterolithic conglomerate (Unit 4). Upper Triassic Stuhini Group Well bedded feldspathic sandstone, greywacke volcanic conglomerate and minor siltstone (Unit 3). Upper volcanic sequence Bioclastic and silty limestone (Unit 2c). Andesitic hornblende, plagioclase and lesser pyroxene porphyritic to aphanitic flows and sills (Unit Id). Interbedded siltstone and fine grained sandstone (Unit lc). Basaltic biotite, plagioclase porphyritic lapilli and tuff breccia, and flows (Unit lb). Andesitic plagioclase porphyritic lapilli, block and ash tuff, minor volcanic siltstone (Unit la). Basaltic flow breccia (Unit 2b). Basaltic, pyroxene, plagioclase and lessor biotite porphyritic flows and sills (Unit 2a). Figure 3.1 Geology of the Hank property. INTRUSIONS + v V V \ V V V »• V V \ Bald Bluff porphyry Goat Peak diorite Minor faults Alteration zones 24 3.2 STRATIGRAPHY The stratified rocks on the Hank property have been divided into five units on the basis of lithology and age (Figure 3.1). On the northeast side of the West Hank fault, the Upper Triassic Stuhini Group is divided into a lower and upper volcanic sequence. The lower sequence (Unit 1) consists of andesitic to basaltic tuff, flows, sills and dykes and minor epiclastic sediments. Near the base of the lower stratigraphic sequence interbedded siltstone and sandstone and basaltic flows and breccias dominate the section. The upper sequence (Unit 2) is characterized by basaltic sills, flows and flow breccias and minor limestone. Overlying the volcanic succession of the Stuhini Group are Lower Jurassic siltstone, sandstone, wacke and pebble conglomerate of Unit 4. On the west side of the West Hank fault, well-bedded, volcanic derived sandstones, conglomerates, greywacke and siltstone of the Upper Triassic Stuhini Group (Unit 3) are exposed along the north flank of Goat Peak (Logan et al., 1992). A wedge of Middle Jurassic (?) interlayered basalt flows, flow-banded rhyolites and minor volcaniclastic sediments of Unit 5 are exposed along the eastern flank of Goat Peak. The Middle Jurassic sequence is in fault contact with Stuhini Group strata to the northeast along the West Hank fault, and the western contact is obscured by the Goat Peak diorite (Figure 3.1). The following section provides a lithological description of the various stratigraphic units which underlie the property. Characteristics of the upper and lower volcanic sequences from field observations and petrographic studies are summarized in Table 3.1. 3.1.1 Upper Triassic Stuhini Group Upper Volcanic Sequence UNIT la On the northeastern side of the West Hank fault, the most volumetrically abundant unit consists of green, black and maroon lapilli to block tuff and minor ash tuff. Rocks in this unit are poorly sorted and display weak normal grading from lapilli to block sized fragments up-section. Individual layers are difficult to identify, imparting an overall massive appearance to much of the 25 unit. Lapilli and tuff breccias of Unit la are matrix supported with fragments constituting up to 35 percent of the unit. Table 3.1 Lithe-logical description of the various units underlying the Hank property. Unit la Unit lb Unitlc Unit Id Unit 2a Unit2a(bi) Unit 2b Rock type tufT breccia lapUli tuff ash tuff porphyritic flows, tuff breccia siltstone, fektspattuc wacke porphyritic -apbanhic flows, sills and dykes porphyritic -aphanitic flows, sills and dykes porphyritic -aphanitic flows, sills and dykes tuff breccia Mineralogy Pyroxene <5% 10-20% 5-15% 15-20% 5-15% 5-15% 1-4 mm 0.2 - 5 mm 1-15 mm 0.5- 10 mm 0.5 -2 mm eq,fg eq,f& eq, ph & gm eq.plT eq, gm +/-ph eq, gm +/-ph Hornblende <5% 10% 5 -10% <5% 5% 5% 1-8 mm 1-4 mm 1-30 mm 1-4 mm 1-5 mm 1-5 mm ps,fg ps, fg & mx ps, ph & gm ps,ph ps,ph ps,ph Biotite 5% >1 mm eu, fg 5 -10% >5 mm eu, gm & ph Plagioclase 40 - 50% 30% > 60% 35 - 50% 50 - 60% 35 - 50% 0.1-3 mm 0.5-3 mm > 1 mm 0.5 - 3 mm 0.5 -6 mm 0.5-3 mm la,mx,fg la, mx, fg bk grains la, gm +/- ph la, gm & ph la, gm +/- ph K-feldspar <5% X 10-15% X 5% <5% <1 mm <0.5mm > 0.5 mm, > 0.0 mm <0.5 mm < 0.5 mm mx, alt an, mx, alt an, mx mx, alt gm, an, alt gm, an Texture fragmental fragmental clastic mas, amy mas, +/- ves mas bx, mono fg = 5-30% fg = 20-35% fw = 80% por-aph por-fgr aph -fgr fg = 25 - 40% mx = ash & xls mx = ash & xls mx > 10% cement = cc mx = fg Assessory Magnetite <5% 0.1 -0.5 mm gm & mf, eq 5 - 7% 0.1-0.5 mm gm & mf, eq <5% 0.1 -0.5 mm gm & mf, eq Rutile Apatite Incipient mf=chl+oc mf=chl+cc mf=chl+cc mf=chl+cc mf=chl+cc mf=chl+cc Alteration pl=cc+ill pl=cc+ill pl=cc+ill pl=cc+ill pl=cc+ill pl=cc+ill mx=chl+cc+ill mx=chl+cc+ill mx=chl+cc+ill mx=chl+cc+ill mx=chl+cc+ill mx=chl+cc+ill Abreviations: an = anhedral, aph = aphanitic, bk = broken, chl = chlorite, cc = calcite, eq = equant, fg = fine grained, gm = groundmass, ill = illite, la = lath-shapped, mx = matrix, mf = maphic, pi = plagioclase, ph = phenocryst phase, por = porphyritic, ps = prismatic. Fragments are angular, vary in size from 2 to 50 centimetres and consist of plagioclase minor hornblende and pyroxene crystals within a fine grained matrix of plagioclase and chloritic ash (Plate 3.1a). The matrix of tuffs is similar in composition to the fragments, consisting of abundant plagioclase crystals and altered volcanic ash (Plate 3.1b). Well-bedded green crystal tuffs form discontinuous beds near the top of the sequence. Individual beds are less than 1 metre thick and are discontinuous over tens of metres. 26 Poorly indurated, maroon to green calcareous volcaniclastic siltstone are exposed at the top of Unit la in Creek 13 (Figure 3,2). The siltstones lie above a thick flow of Unit Id and form a wedge bounded to the west by a fault. UNIT lb At the base of Creeks 8, 9 and 10, a lens of plagioclase and biotite-phyric lapilli tuff interfingers with Unit la (Figure 3.1). The tuff contains subrounded fragments which range in size from 2 to 20 centimetres and comprise 15 to 30 percent of the rock. Several different types of volcanic fragments are present including: pyroxene and plagioclase-phyric; vesicular; and pyroxene, biotite and plagioclase-phyric; and, rare granitoid fragments. Volcanic fragments have a crystalline groundmass unlike the matrix of tuff which consists of abundant plagioclase, chloritized volcanic ash and minor pyroxene and biotite. Mapping on the ridge to the north detailed a sequence of biotite and plagioclase-phyric flows and block tuff similar to Unit lb on Hank Ridge. Individual flows are massive to amygdaloidal, vary from 20 to 30 metres thick and likely represent the source of volcanic fragments within tuffs of Unit lb. UNITlc Overlying Unit lb are finely laminated siltstone interbedded with grey and brown fine to medium grained sandstone (Figure 3.1). Individual sandstone beds vary in thickness from 2 to 20 centimetres and load structures indicate that beds are upright. The thickness of this unit varies from 20 to greater than 50 metres. Rounded grains (>0.05 mm), of plagioclase comprise 70 to 80 percent of the rock. The cement consists of abundant authigenic clay minerals and calcite. UNIT Id Maroon to grey coloured, strongly magnetic, aphanitic to plagioclase-, hornblende-, and pyroxene-porphyritic flows, sills and dykes intrude and interfinger with tuffs of Unit la (Figure 3.1). On the west half of the property, flows and sills of are less abundant than lapilli and block tuff. Here flows and sills form thin units which are discontinuous and rarely exceed 100 metres in 27 length. East of Creek 7, a series of flows and sills up to 70 metres thick dominate the lower volcanic sequence. Distinguishing flows and sills of Unit Id is limited by poor exposure, but possible distinctions were made on the basis of more irregular lower contacts containing abundant calcite and hematitic silica filled vesicles in flows compared to sharp contacts for sills. Porphyritic sills and flows of Unit Id contain prismatic hornblende phenocrysts which are up to 4 centimeters long, locally equant pyroxene crystals, and abundant plagioclase within the groundmass (Plate 3.2a). Hornblende phenocrysts are typically altered to an assemblage of chlorite and calcite and are commonly rimmed by magnetite. Pyroxene occurs as equant, pale green crystals 2 to 10 mm in size, and rare radiating clusters (Plate 3.2b). Plagioclase is the most abundant phenocryst phase, forming lath shaped crystals up to 7 millimetres long. The groundmass of Unit Id consists of abundant lath shaped plagioclase crystals, subhedral magnetite and minor concentrations of calcite and chlorite. Accessory minerals include rutile and apatite. Upper Volcanic Sequence UNIT 2a The base of the upper volcanic sequence consists of a thick pile of dark green to grey, magnetic, pyroxene and plagioclase porphyritic to aphanitic sills exposed along Hank Ridge (Figure 3.1). These sills are volumetrically most abundant on the eastern margin of the property where they attain a minimum thickness of 600 metres. The distribution of sills elsewhere on the property is poorly constrained due to limited outcrop. Drill core and limited surface exposure suggests that biotite-bearing sills occur adjacent to and below zones of pervasive alteration on Rojo Grande, Felsite Hill and in the Flats zone. At the top of the sequence, 1 to 10 metre thick flows of Unit 2a are recognized containing large (> 1 cm) pyroxene phenocrysts within a groundmass of crowded plagioclase and rare biotite (Plate 3.3a). Locally, clasts of limestone are observed within flows and flow breccias at the top of the section along Hank Ridge. Plate 3.1 a) andesite lapilli tuff of Unit la, and b) photomicrograph of tuff showing the plagioclase and volcanic ash-rich matrix of this unit (field of view = 5.1 mm). Plate 3.2 a) massive to porphyritic flows, sills and dykes of Unit Id, and b) photomicrograph showing excellent preservation of pyroxene and plagioclase (field of view = 5.1 mm). Plate 3.3 a) massive flows/sills of Unit 2a, and b) photomicrograph of biotite porphyritic sub-unit showing subhedral biotite (field of view = 5.1 mm). 29 30 Pyroxene is the main phenocryst phase, forming equant crystals up to 1.5 centimetres. Biotite is observed as a phenocryst patches at lower elevations within Unit 2 where it forms euhedral crystals up to 5 millimetres (Plate 3.3b). Near the top of the section biotite is less abundant, forming small (< 1 mm) crystals within the groundmass. The size and abundance of plagioclase crystals varies considerably from sparse phenocrysts to crowded, fine grained crystals in an aphanitic groundmass. The groundmass comprises abundant (<1 mm) lath shaped plagioclase crystals, equant fine grained magnetite within an aphanitic groundmass of potassium feldspar. Assessory minerals include hornblende, magnetite and rutile. UNIT 2b On Hank Ridge monolithic, volcanic breccia separate flows of Unit 2a. The breccia is massive, poorly sorted and consist of angular to well-rounded fragments which comprise up to thirty percent of the unit. The size of fragments varies from centimetres up to 1.5 metres within a fine grained volcanic matrix. Fragments within this unit are texturally similar to Unit 2a and are likely derived from the margins of flows. UNIT 2c Lenses of partially recrystallized, bioclastic and silty limestone intercalated with flows of Unit 2a are exposed on Hank Ridge and east of Felsite Hill (Figure 3.1). The limestone contains bivalve and gastropod fossil fragments interbedded with well-laminated, fine grained silty limestone. The silty limestone contains rare, well rounded volcanic clasts of Unit 2. Samples of the limestone were submitted to the Geological Survey of Canada for macro-, and micro-fossil identification, but failed to yield diagnostic fossils to constrain the age of formation. UNIT 3 On the west side of the West Hank fault, pale green to buff, well-bedded, volcanic derived sandstone, conglomerate, greywacke and thin bedded siltstone are exposed along the north flank of Goat Peak, and have been correlated with the Upper Triassic Stuhini Group (Logan et al., 31 1992). Sandstone beds contain abundant, lath shaped and minor pyroxene crystals. The matrix is composed of green silt cemented by quartz and calcite. Conglomerate beds are commonly heterolithic and composed of pyroxene and plagioclase-phyric volcanic, black siltstone and rare limestone clasts. Clasts are angular to subrounded, 2 to 10 cm in size, and comprise thirty to fifty percent of the rock with the matrix consisting of sand sized particles of plagioclase and pyroxene. West of the property, plagioclase-bearing fine grained sandstone is interbedded with recessive weathering finely laminated siltstone with carbonaceous plant fragments along bedding planes. 3.1.2 L o w e r Jurass ic UNIT 4 Unconformably overlying Unit 2 are poorly indurated, maroon green and black siltstone, brown and green well-bedded, calcareous sandstone, and heterolithic conglomerate. These rocks are exposed in the saddle between Felsite Hill and Rojo Grande, and along the southwest margin of Bald Bluff (Figure 3.1). Diamond drilling northeast of the Flats zones intersected black siltstone, sandstone and conglomerate of Unit 4 beneath an area of extensive felsenmeer and overburden. The base of the sequence, exposed on Felsite Hill comprises volcanic derived conglomerate which grade laterally into maroon siltstone south of Bald Bluff. The conglomerate varies from matrix to clast supported, and are composed of 0.5 to 10 centimetre sized angular to subrounded clasts of siltstone and clasts from the underlying volcanic units within a matrix of maroon silt. The siltstone units are massive. Overlying the maroon volcanic sedimentary rocks are pale green feldspathic wacke and siltstone units. The wackes contain up to seventy percent, 1 to 3 mm sized plagioclase crystals within a matrix of green silt and calcite cement. The top of the sequence consists of sandstone, siltstone and pebble to cobble conglomerate which exhibit several coarsening-up sequences. Sandstone beds vary from coarse to medium grained, are calcareous and display low-angle, cross trough bedding with pebble lags along foresets. Typically, the sandstone beds contain well rounded grains of quartz and feldspar, and carbonaceous plant fragments along bedding planes. Clasts in the conglomerate beds are well-rounded, vary in size from 0.5 to 12 centimetres, and are dominantly volcanic, with lesser 32 intraforrnational siltstone and sandstone clasts. Exotic clasts including siliceous siltstone, chert, quartz and granite are also present. Large fossilized wood fragments, up to 1 m in diameter, are present throughout the upper part of the sequence (Plate 3.4), and bivalves (Weyla) have been identified within the sandstones (Turna, 1985). Distal equivalents of the coarse clastic rocks were observed on the ridge to the northwest of the Hank property and consist of well-bedded siltstone with lenses of cross-bedded medium grained sandstone and minor chert pebble conglomerate. On the Hank property, Unit 4 appears to be disconformable with the underlying volcanic sequence. On the ridge to the northwest of the Hank property, an angular unconformity exists between Unit 4 and the underlying volcanic sequence. Contact relations with the underlying Stuhini Group, presence of granitoid clasts, and the heterolithic nature of the unit are characteristic of Lower Jurassic sedimentary strata described by Souther (1972), Henderson et al. (1992) and Greig (1995) in northern Stikinia. On the basis of these similarities, Unit 4 is tentatively assigned a Lower Jurassic age. 3.1.3 Middle Jurassic UNITS Dark green to black amygdaloidal flows and flow breccia (unit 5 a) interlayered with rusty, pyritic, flow-banded rhyolite (unit 5b), are exposed on the east flank of Goat Peak along the southwest side of the West Hank fault (Figure 3.1). Thin, discontinuous beds of maroon coloured epiclastic siltstone separate the basalt and rhyolite sequences. The basalts contain abundant chlorite- and pyrite-filled vesicles and are pyroxene-bearing (Plate 3.5a). Pyroxene crystals, up to 2 millimetres in length, are chlorite altered and are contained within an aphanitic matrix. The rhyolite is aphanitic, weakly flow banded and contains rare drusy cavities. Fine grained disseminated pyrite within the unit imparts a dark grey colouring to the fresh surface (Plate 3.5b). Contacts between Unit 5 strata and other units on the property are faulted along the West Hank fault and obscured by the Goat Peak diorite, thereby making age correlations difficult. Previously, strata of Unit 5 were assigned a Upper Triassic age (Souther, 1972), however the bimodal volcanic sequence is more similar to Hazelton Group strata to the east in the Kinaskan Lake area (Souther, 1972; Evenchick, 1990). This evidence, and the scarcity of felsic volcanism during the Upper Triassic suggest that the strata of Unit 5 be tentatively correlated with the Lower to Middle Jurassic Hazelton Group. 3.2 INTRUSIONS 3.2.1 Bald Bluff Porphyry An orthoclase porphyritic intrusion is exposed on Bald Bluff, west of Felsite Hill. At lower elevations, a illite altered orthoclase porphyritic dyke, similar in composition to the intrusion underlying Bald Bluff outcrops in Creek 7, within the Lower alteration zone (Figure 3.1). On Bald Bluff, the intrusion is well foliated on its margins with the foliation subparallel to the margins, changing from steep along the edges to shallow at the top of the intrusion. Flat lying compositional layering is also observed near the top of the intrusion. Locally, the margins of the Bald Bluff porphyry are brecciated, consisting of angular fragments of the foliated intrusive cemented by calcite, iron-bearing carbonate and grey to red silica (Plate 3.6a). Contact relationships between the Bald Bluff porphyry and sedimentary strata of Unit 4 are intrusive with minor biotite hornfelsing and pyritization of the sedimentary rocks adjacent to the contact. Equant orthoclase phenocrysts up to 1.5 centimetres in length comprise ten percent of the rock. Orthoclase phenocrysts are characterized by oscillatory growth zoning and inclusions of plagioclase feldspar (Plate 3.6b). Hornblende phenocrysts comprise up to ten percent of the rock and form elongate crystals 0.5 to 4 millimetres in length. Plagioclase crystals comprise up to fifty percent of the rock and form lath shaped crystals, 0.5 to 7 millimetres in size. The groundmass consists of < 0.2 mm sized crystals of plagioclase, orthoclase, hornblende and euhedral quartz crystals. A sample (AK92-3) was collected from the Bald Bluff porphyry to determine the age of the intrusion using U-Pb zircon techniques. The sample was processed and analyzed at the University of British Columbia by Dr. J.K. Mortensen. A total of four fractions were analyzed and yielded an age of 185.2 + 4.5/- 1.2 Ma (Table 3.2). The calculated age was based on a concordant analysis for fraction C (Figure 3.3, Mortensen, pers. comm.). For a description of techniques and analytical procedures used see Mortensen et al. (1995). 3 4 3.2.2 Goat Peak Diorite A plug of medium grained equigranular hornblende diorite crops out on Goat Peak west of the West Hank fault (Figure 3.1). The diorite is composed of fifty-five percent subhedral to euhedral lath-shaped plagioclase crystals, 1 to 6 millimetres in length, which are variably saussuritized. Hornblende phenocrysts vary from 0.2 to 7 millimetres in length and comprise the remaining forty-five percent of the rock. Table 3.2 U-Pb zircon analytical data for the Bald Bluff Porphyry. Fraction1 Wt U Pb5 JM p b J Pb4 I M P b 5 2 0 6 p ^ 3 . 6 2 0 7Pb 3* 6 Isotopic dates (Ma42a) " W W mg ppm ppm i M Pb Pg % 2 0 6 p b AK92-3 A 0.104 320 9 1572 39 9.5 0.02920 ±0.30 0.2021 ±0.33 0.05020 ±0.10 204.2 ±4.6 AK92-3B 0.078 336 10 347 147 10.6 0.02905 ±0.34 0.2014 ±0.59 0.05029 ±0.41 208.2 ±19.2 AK92-3C 0.061 619 18 1758 40 9.2 0.02912 ±0.31 0.1999 ±0.33 0.04979 ±0.10 185.2 ±4.5 AK92-3 D 0.036 665 19 587 73 8.7 0.02818 ±0.31 0.1931 ±0.65 0.04969 ±0.54 180.5 ±25.5 1 All fractions are air abraided 2 Radiogenic Pb 3 Measured ratio corrected for spike and Pb fractionation of 0.0043/ainu±20% (Daly collector) 4 Total common Pb based on blank isotopic composition 5Isotopic ratios (±lo\%) 6 corrected for blank Pb, U and common Pb (Stacey-Kramers model Pb composition at the 2 0 7Pb/ 2 0 6Pb date of fraction, or age of sample). 35 Plate 3.4 a) large pieces of fossilized wood, and b) well bedded, calcareous sandstones of unit 4 (hammer for scale). Plate 3.5 a) amygdaloidal flows of unit 3a, and b) flow banded rhyolite of 3b. Plate 3.6 a) Bald Bluff porphyry, b) a large orthoclase phenocrysts in a matrix of plagioclase (field of view = 5.1 mm), and c) contact breccia along the margin of the Bald Bluff porphyry. The breccia is cemented by hematitic silica and carbonate. 36 37 Hornblende occurs as anhedral crystals between plagioclase crystals and as larger, subhedral crystals. Hornblende is less altered than plagioclase and is variably replaced by calcite and chlorite. Locally, the diorite exhibits more coarse grained phases with plagioclase crystals approaching several centimeters in length. The margins of the intrusion are characterized by abundant quartz veining and epidote in the form of veinlets and disseminations. Adjacent to the West Hank fault, exposures of diorite are altered to sericite and contain up to 5 percent disseminated pyrite. Altered portions of the diorite are in close proximity to the Flats zone, however the style of alteration differs from the adularialdllite/smectite alteration exposed within the Flats zone. Alteration in the diorite, adjacent to the West Hank fault is interpreted to have formed from fluid movement along the fault zone. 3.3 STRUCTURE The West Hank fault lies along the southwestern margin of the property, trends north-northwest, dips sub-vertically and is marked by abundant white calcite veining, brecciation and disrupted bedding along its trace (Figure 3.1). The fault forms the southeast continuation of a larger, regional structure mapped by Logan et al. (1992) to the northwest. Alteration on Rojo Grande is truncated along the West Hank fault and on this basis the fault is likely post mineral. Bedding in the Upper Triassic Stuhini Group strata, east of the West Hank Fault, strikes northeast and dips shallowly to the southeast, forming a homoclinal sequence along Hank Ridge (Figure 3.4a). In the northern part of the map area, bedding within sedimentary strata of Unit lc strikes to the north and dips moderately to the east. On the ridge to the northwest of the property (Figure 3.2), the strata dip shallowly to the northwest. This change in the orientation of bedding across Hank Creek is attributed to either a northeast trending anticline or fault, the trace of which follows Hank Creek. Poles to bedding define a moderately developed cluster in the northwest quadrant for the Upper Triassic strata and are inconclusive in identifying a fold structure. Evidence for a fault along Hank Creek is also tenuous and is not supported by field evidence. Lower Jurassic strata of Unit 4 lie unconformably above the volcanic strata of the Stuhini Group and are affected by: (i) a northwest trending syncline along the east side of Rojo Grande; and, (ii) doming related to the emplacement of the Bald Bluff porphyry (Figure 3.2). East of Rojo Grande, an asymmetric syncline is characterized by shallowly southwest dipping strata on the northeast limb and steep northeast dipping to overturned strata on the southwest limb (Figure 38 3.4b). Poles to bedding within the sedimentary strata define a moderately developed girdle which defines an asymmetric syncline, trending 124° and plunging shallowly to the southeast (Figure 3.5). This syncline forms a portion of a larger, regional scale fold mapped by Souther (1972) which extends southeastward to the Iskut River (Figure 2.3). Adjacent to the Bald bluff porphyry, the strata of Unit 4 strike sub-parallel to the margins of the intrusion and progressively steepen towards the contact. Figure 3.4 Cross section A-A' looking northeast through Hank Ridge (a) and Cross-section B-B' looking northwest along Hank Ridge (b). Section lines are located on Figure 3.1. 39 Southwest of the West Hank Fault, Stuhini Group strata dip steeply to the west. Adjacent to the fault, bedding is disrupted, strikes east and dips to the south suggesting an apparent left lateral displacement along the West Hank fault (Figure 3.2). Jointing and fracture planes were measured on the property to determine if there was a preferred orientation. Fractures are most abundant within the more massive lithologies of Units 1 and 2 and form a weakly developed cluster with no preferred orientation (Figure 3.5a). (d) Poles to veining. (d) Poles to mineralized (total data set) veins. Figure 3.5 Stereoplots for bedding (a) Jointing (b), veining (c) and mineralized veins (d) on the Hank property. 40 Mineralized and unmineralized veins were measured on surface to determine if veins, in particular those exposed within the Lower alteration zone, displayed a preferential orientation (Figure 3.5c and 5d). Unmineralized veins include carbonate, and carbonate-quartz veins with no visible sulphides whereas mineralized veins contain sulphide minerals and altered selvages. Both mineralized and unmineralized veins can be separated into three dominant orientations: (i) northeast striking, moderate to steeply southeast dipping; (ii) southwest striking, moderately northwest dipping; and, (iii) northeast-southwest striking and vertical. The orientation of these veins forms a weakly developed conjugate set, coincident with southwest-northeast directed compression. Within strata of the Upper Triassic Stuhini Group, north to northwest striking faults have been identified in outcrop. These faults typically have offsets of less than 100 metres and appear to be syn-volcanic since they control the distribution of volcanic breccias Unit 2b on Hank Ridge and volcanic siltstones at the top of Creek 13 and do not affect the overlying strata. Hydrothermal alteration on the property is elongate in a north-northeast direction defined by the Upper and Lower alteration zones, and a north direction, denned by the elongate form of alteration underlying Felsite Hill (Figure 3.6). In the LAZ and pit area of the UAZ, faults with apparent normal displacement are documented in the core of these zones and likely controlled the distribution of hydrothermal alteration. Structures which may have controlled the distribution of alteration on Felsite Hill have been obscured by pervasive hydrothermal alteration, however, a structural control for this alteration is supported by both large- and small-scale features. A north-trending structure beneath Felsite Hill is supported by and abrupt change in bedding to the east of the zone (Figure 3.6). Here bedding dips moderately to the southeast, striking perpendicular to the strata along Hank Ridge. North and north-northeast striking, steeply dipping zones of fracture controlled illite alteration in outcrop to the east of Felsite Hill also support a structural control. 3.4 GEOCHEMISTRY Whole rock geochemistry samples were collected from the upper and lower volcanic sequences, Bald Bluff porphyry and the Goat Peak diorite to: (i) characterize the intrusions and volcanic strata on the property; (ii) compare the volcanic strata on the Hank property with a 41 regional data base for the Stuhini Group (Logan et al., 1989, 1992; Brown et al., 1989, 1992); and, (iii) provide a geochemical framework to quantify the effects of progressive alteration. Figure 3.6 Orientation of faults and bedding (form lines) on the Hank property. Thin dashed lines refer to syn-volcanic faults, thick dashed lines are inferred structures which control the distribution of hydrothermal alteration on the property. 42 To contrast between unaltered "precursor" and hydrothermally altered samples, an alteration index (Al) was developed to qualitatively measure the intensity of alteration based on replacement of phenocryst, groundmass and matrix by secondary minerals (Appendix E). Petrographic descriptions and the Al were used to define a numerical range for samples exhibiting incipient alteration. Samples with Al above this range are considered to be effected by varying intensities of hydrothermal alteration. Using these criteria, thirty four precursor whole rock samples were collected from the various stratified and intrusive units on the property. Petrographic descriptions for each precursor sample are detailed in Appendix B. The locations for whole rock samples collected from outcrop are plotted on Figure 3.2 and the locations of samples collected from core are presented in Figures 4.8 to 4.11 (in the pocket). 3.4.1 Volcanic strata The Upper Triassic Stuhini Group volcanic rocks on the Hank property vary from sub-alkaline basalt to trachyandesite in composition (48.5 to 61.5 wt.% Si02) and straddle the high-K calcalkaline and shoshonite fields (Figure 3.7a and b). In contrast, Zr/Y ratios range from 3.7 to 12.6 suggesting that the volcanic rocks are transitional between tholeiitic and calc-alkaline (Barrett and McLean, 1994; Figure 3.8a). The majority of samples which plot within the calc-alkaline field (Zr/Y > 7), are of the biotite porphyritic phase of Unit 2. This sub-unit also exhibits elevated Th concentrations relative to Units 1 and 2 (Figure 3.8b). Samples with tholeiitic affinities contain elevated Ti02 concentrations (> 1.1 wt. %), and include a sample of basaltic breccia from Unit lb and several samples collected from Units 1 and 2 from the top of Creek 14. Samples of the volcanic strata form a well defined, concave upward fractionation trend on a Al203-Zr plot (Figure 3.8c). A similar, albeit less defined trend is observed between Zr and Ti02 (Figure 3.8d). In both plots, dispersion of points from the observed fractionation trends is attributed to the effects of alteration which corresponds to the movement of data points towards (mass gain) or away (mass loss) from the fractionation trend along a linear path through the origin (Barrett and MacLean, 1994). Samples with anomalous Ti02 values (>1.0 wt. %) may also reflect an increase in the concentration of mafic phases, In both plots, the biotite porphyritic sub-unit, which underlies Felsite Hill, Rojo Grande and the Flats zone, forms a well defined cluster of points on the fractionation line at higher Zr and lower Ti concentrations. Figure 3.7 Plot of unaltered whole rock geochemistry samples from volcanic strata on the Hank property. Data plots in the subalkaline basalt to trachyandesite fields (a), defined by Winchester and Floyd (1977), and straddle the high-K to shoshonite field (b), modified after Le Maitre (1989). H "A O <g K> S w bo Th (ppm) Y (ppm) O T3 s. § a" C L 0 1 g-o cr. o .3. © o 1 ' ' ' ' 1 a • o o o (> < > 1 ««**>° > ,„ _ >iotite porpl iub-unit 7 0 >iotite porpl iub-unit 7 0 I .3. \ ° Q •j 1.f.111. s s* s> o* ^ fe* ^ *5 s 3. o O 3 o o 3 a 0 • w ts 'a 1 Ti02 (wt%) A1203 (wt%) N _ 3 t>t> 45 Both AfeCVZr and TiGvZr relations suggests that the volcanic volcanic units on the property were likely derived from the same source area and linked by fractionation or melting processes. 3.4.2 Tectonic Setting Normalized abundance and rare earth element patterns (REE) for average compositions for the Upper Triassic volcanic strata on the Hank property display similar light rare earth element enrichment patterns (LREE) relative to chondrite (Figure 3.9). When compared with patterns from other tectonic settings, samples from the Hank property are enriched in LREE relative to enriched (E-MORB) and normalized (N-MORB) mid-ocean ridge basalt, and less enriched in LREE, but enriched in large ion lithophile (LLLE) elements relative to oceanic island basalts (OLB). Normalized abundance plots also display negative Ti and Th anomalies and a slight Nb depletion characteristic of an island arc origin for the volcanic strata on the property (Sun and McDonough, 1989). Figure 3.9 Normalized abundance plot for average compositions for Unit 1, Unit 2 and the biotite porphyritic sub-unit compared with average compositions for OIB, E- and N-type MORB, normalized to PRIM (Sun and McDonough, 1989). Rare earth element plots are displayed in the insert, normalized to chondrite (Pearce, 1982). 46 Regional lithogeochemical data collected by Logan et al. (1989, 1992) in the Galore Creek area, and by Brown et ar/.(1990, 1992) in the Telegraph Creek area characterize the Stuhini Group as dominantly tholeiitic in contrast to the transitional affinity of the volcanic rock on the Hank property (Figure 3.10a). Regional data which plot closest to the field defined by the Hank samples are located in the Galore Creek area to the west of the property. Normalized abundance plots for regional samples define a pattern characterized by a negative slope and LILE enrichment. Samples from the Hank property plot along the upper range defined by regional samples and are slightly more enriched in LILE (Figure 3.10b). Based on the limited data set, the Stuhini Group appears to exhibit a change from predominately tholeiitic affinity in the Telegraph Creek area to a transitional to mildly calcalkaline affinity in the Galore and Hank Creek areas in the southern part of the map area. North-south variations may be attributed to lateral changes in the magmatic source of Stuhini Group volcanic strata, or alternatively reflect a vertical change in Stuhini Group chemistry. 3.4.3 Intrusions The Bald Bluff porphyry and Goat peak diorite are separated by the West Hank fault and are interpreted to represent different episodes of intrusive activity. Both intrusions are metaluminous and plot within the volcanic arc granite field (Pearce et al., 1994; Figure 3.11a) The immobile plot of Y-Zr indicate that the Goat Peak diorite has a tholeiitic affinity in contrast to the Bald Bluff* porphyry which exhibits a more transitional affinity (Figure 3.11b). REE element patterns for the two intrusions also support different origins for the two intrusions because the Bald Bluff porphyry displays a greater LREE enrichment than the Goat Peak diorite (Figure 3.11c). A positive Eu anomaly for the Goat Peak diorite is attributed to the concentration of plagioclase. 3.5 GEOLOGICAL ENVIRONMENT The thick succession of immature volcaniclastic, flows and subvolcanic sills and dykes of the Upper Triassic Stuhini Group volcanic strata likely formed within a a proximal volcanic environment. 4 7 50 45 40 35 30 25 20 15 10 5 0 £ (a) 1000 100 k 10 0.1 0.01 n i 1 r i r T .-' o Tholeiitic A O x Logan etal. (1990) o Brown etal. (1989) A Kaip (this study) Transitional ODD O X .--O O O O O o i i A A A A A A (TO O Calc-alkaline o--I I I L J I I L 0 20 40 60 80 100 120 140 160 180 200 220 Zr (ppm) F 1 1 1 1 r ~i 1 1 1 r ™ O g CQ P H Figure 3.10 Plot of Y-Zr (a), and extended trace element plot (b) for samples from the Hank property plotted with regional samples for the Stuhini Group. Y (ppm) R b ( p p m ) £.(§' Q. C l £ •a s >3 s. & ere LA - J Ln to o o 3 3 o o; o* n i7 g 3 •o cT o !->> N .3. o ' 1 1 -fr.O -o 2 3 - B ST *n SB i i i Zr/Y-2 Tholeiitic Transil Transil o 3 » + + JL Zr/Y=7 1 1 Bald Bluff -porphyry s cr n o* 3 CD B TEL *0 & 0 a. J? 1 Ou ST 2 3 m e O ? p i H 3 T 1 1 1 — I I I ! 1 1 1 1 — N i l _l I I 1 I I I I _1 1 1 I I I I I I 8fr 49 In addition, the poorly sorted character, and lack of bedding within the tuff sequence is characteristic of volcaniclastic rocks derived from mass wasting and debris flow deposits formed on the flanks of a volcanic edifice. At the base of the sequence, plagioclase-bearing sandstones of Unit lc, typical of more distal volcanic centres, suggest that the Triassic sequence exposed on the Hank property forms a coarsening-upward sequence. The volcanic derived sedimentary strata of Unit lc increases in thickness, to the northeast of the property where the volcanic tuff sequence becomes volumetrically subordinate (H. Marsden, Pers. Comm.). Silty and bioclastic beds, and clasts of limestone in flows and tuff breccias of Unit 2 near the top of the succession suggest that volcanic activity was dominantly submarine. The absence of limestone lower in the sequence, and transition from volcanic derived sedimentary strata to tuff breccias, flows and sills, lateraly and up section suggests that the sequence underlying the Hank property likely forming proximal to a submarine volcanic edifice. In the region, the Stuhini strata on the Hank property is similar to the upper part of the Ball Creek section where andesitic to basaltic breccias and volcaniclastic rocks dominate the section (Souther, 1972). Uplift and erosion of the Stuhini arc most likely occurred during the earliest Jurassic (Souther, 1972, Henderson, 1992, Greig, 1995). On the Hank property, Lower Jurassic strata contain a large proportion of volcanic and intrusive detritus and fossilized wood and record an episode of uplift and denudation of the underlying Stuhini strata, and likely a transition from a dominantly submarine to subareial environment. Large pieces of petrified wood, some in excess of 2 metres in diameter, the presence of leaf casts, and the coarse clastic nature of the strata all attest to a shallow water, near shore to fluvial environment. The Lower Jurassic strata on the property forms a coarsening up sequence indicating a transition from a shallow marine to terrestrial environment. Lower Jurassic strata on the ridge to the northwest display channel and large scale cross bedding characteristic of a fluvial environments (Walker and Cant, 1984). The age, composition and orthoclase porphyritic texture of the Bald Bluff porphyry are characteristic of the Texas Creek intrusive suite which are genetically related to mineralization in the Sulphurets and Bronson Creek areas of the Iskut River area to the south (Davies and Macdonald, 1993; Rhys, 1993). The flow foliation and carapace breccia along the margin of the Bald Bluff intrusion, and lack of extensive hornfelsing of the adjacent strata suggests that the porphyry was emplaced near the surface. 50 4.0 A L T E R A T I O N Seven zones of alteration, distributed over a 12 km2 area and exposed for over 800 metres in elevation, are recognized on the Hank property. They include; the Quartz Stockwork zone (QZ), the Lower alteration zone (LAZ), Flats zone (FZ), silicified zone (SZ), Upper alteration zone (UAZ), Felsite Hill, and the Rojo Grande-Rojo Chico area (Figure 4.1). The names given to the various zones reflect their geographical position rather than the dominant style of alteration, therefore alteration assemblages will be discussed in order of their spatial relationships from illite dominant zones at lower elevations, upward to stratigraphically higher zones of illite/smectite, adularia, silicification and kaolinite-dominant zones. Individual types of alteration are defined according to the most dominant phyllosilicate mineral or quartz or adularia. Major assemblages include sub-types which are distinguished by the presence or absence of important accessory minerals. Names given to each alteration type reflect the dominant mineral present in accordance with modern terminology for epithermal models developed by Reyes (1990) and Corbet and Leach (1994). Sub-types are named according to their spatial distribution within the various zones. The spatial relationships between alteration types within the various zones, changes in illite crystallinity and mass change calculations used to quantify the various styles of alteration, are presented in the following sections. 4.1 ALTERATION ASSEMBLAGES 4.2.1 Introduction Incipient alteration on the Hank property involves the partial replacement of mafic phenocrysts by chlorite and calcite, and the saussuritization of plagioclase. The intensity of replacement is lithologically controlled; massive and aphanitic sills of Units Id and 2a display little or no alteration of phenocrysts, whereas block tuffs of Unit la contain abundant chlorite and calcite replacing the volcanic ash matrix and illite and calcite replacing plagioclase. The transition between incipient and more intense alteration on the property is marked by the addition of finely disseminated pyrite within lapilli and block tuffs of Unit la and by the replacement of magnetite by pyrite within flows and sills of Units 1 and 2. 51 Alteration zones and characteristic assemblages within the various zones on the Hank property have been described previously by Kaip and McPherson (1993) and Kaip and Gaunt (1994) and are presented in Table 4.1. Peak positions of the diagnostic minerals which define individual assemblages are presented in Table 4.2. Figure 4.1 Distribution of alteration zones on the Hank property and the dominant style of hydrothermal alteration. The characteristics of the various alteration assemblages are based on field observations, drill core examination, petrography and extensive X-ray diffraction analysis. Due to the fine grained nature of most alteration assemblages, X-ray diffraction was the principal discrimination tool between styles of alteration whose outward appearance are similar. Peak position, shape and breadth of the diffraction maximum (peak), particularly for illite (001) and illite/smectite (001) peaks were instrumental in distinguishing alteration assemblages. Table 4.1 Distinguishing characteristic the various alteration types and sub-types and their locations. Alteration Type Diagnostic Minerals Accessory Minerals Location Kaolinite Distal Medial Proximal kaol kaol, qz kaol, py, qz, mar, chal qz, alu, hem, ba py, alu, ba, fl cc, doi, ba FH,RG FH, RG-RC UAZ-RH, RG Transitional (illite/smectite+kaolinite) ill/smec, kaol, smec qz, py, cc, doi UAZ (200-440 pit) Silicificauon qz ba, py, cc, ill, hem UAZ-FH, RG Chert Knoll, QZ Illite/smectite Upper Medial Vein ill/smec, qz ill/smec, qz, cc, doi, ill/smec py, cc, doi py, hem qz, py, cc, doi UAZ (200-440 pit), CK3 UAZ (200-440 pit) UAZ,FZ Adularia Adularia+quartz Adularia+illite/smectite qz, ksp ill/smec, ksp, mar, chal ill/smec, py, cc, doi qz, py, cc, doi FZ L A Z , F Z Ilhte Illite Illite+kaolinite illite ill, kaol qz, py, cc. doi hem, py, qz, cc, doi, ga, sph LAZ LAZ Chlorite Chlorite+illite/smectite Chlorite+illite chl, ill/smec chl, ill cc, doi, ksp, qz, doi cc, doi, py qz FZ LAZ Mineral abbreviations: kaol=kaolinite, qz=quartz, alu=natroalunite, py=pyrite, ill/smec=interstratified illite and smectite (illitic clay), cc=calcite, dol=dolomite, ill=illite, ksp=adularia, chl=chlorite, fl=flourite, ru=rutile, ap= apatite, hem=hematite, ga=galena, sph=sphalerite, cpy=chalcopyrite, an=anhydrite/gypsum, ba=barite, Locations: FH=Felsite Hill, RG=Rojo Grande, RC=Rojo Chico, UAZ=Upper alteration zone, LAZ=Lower alteration zone, QZ=Quartz stockwork zone, FZ=Flats zone The breadth of illite peaks, also termed the Kubler Index, is a function of peak sharpness. It is obtained by measuring the width of the illite (001) peak at half its height. The index reflects illite crystallinity and is an indication of temperature; illite formed at higher temperatures display a greater degree of crystallinity (lower Kubler Index) than illite formed at lower temperatures (Eaton and Setterfield, 1993). The X-ray diffraction techniques used to distinguish the dominant phyllosilicate mineralogy are presented in Appendix III, and definitions of the various type 53 assemblages are described in the text. The following abbreviations are used for Figures 4.2 to 4.7; Ki,2 = kaolinite (001, 002), Qi,2 = quartz (100, 101), Ci = calcite (104), Dj = dolomite (104), Pi = pyrite (200), ISi>2 = illite/smectite (001, 002), Ai = orthoclase (220), and CH 1 > 2 = chlorite (001, 002) peaks. 4.1.2 Kaolinite Kaolinite alteration on the Hank property consists of pervasive replacement of rocks by a fine grained mosaic of kaolinite accompanied by varying amounts of microcrystalline quartz. Three distinct subtypes of this alteration occur: kaolinite, accompanied by minor concentrations of microcrystalline quartz; kaolinite, with variable concentrations of micro-crystalline quartz and lesser pyrite, calcite and dolomite; and pervasive kaolinite, quartz and pyrite alteration, minor calcite and dolomite. Distinctions between the three sub-types are characterized by subtle differences in mineralogy, and contacts between the various sub-types are often gradational. Kaolinite±quartz alteration occurs along the margins, and upper portions of kaolinite alteration zones and is transitional into unaltered rocks. Kaolinite+quartz±pyrite alteration develops near the top of kaolinite zones, and forms vertical zones which cross cut kaolinite+quartz+pyrite alteration. Kaolinite+quartz+pyrite alteration is the most abundant type of kaolinite alteration extending from the top of the observed kaolinite zones to the lower contact with deeper alteration zones. Discrete zones of kaolinite+quartz+pyrite alteration are also developed in the upper portions of illite-dominant zones at depth. Based on the spatial distribution of the three sub-types, kaolinite+quartz is termed distal kaolinite, kaolinite+quartz±pyrite is termed medial kaolinite and kaolinite+quartz+ pyrite is termed proximal kaolinite alteration. Distal kaolinite: is characterized by soft white, pale green and maroon coloured amorphous kaolinite and minor microcrystalline quartz (Plate 4.1). Accessory minerals include natroalunite, hematite and barite. The intensity of alteration varies from texturally destructive adjacent to medial kaolinite decreasing in intensity, laterally into areas where relict igneous and sedimentary textures are readily preserved. Distal kaolinite is characterized by progressive replacement of the matrix followed by alteration of clasts and phenocrysts towards proximal kaolinite alteration. o e o 3 . 3 . + + o I f f 5- 8. sr e-S. s 9* 5 2 g. 8-. 3 B. o 2 | n 3 9 ? I 8 1 m * i 2.8 18 •= 8 ksp 111/! 1 5 3 3 3 3 3 J8 J? 3 1 1 8 8 < 8 8 8 8 If 1 1 o o 8 8 21 05 o , a o 1° 1-0 oo oo I O S 1 3 >T3 oo oo K 0 0 3 ° 3 ° I, B (O [3 O oo Ii B Ji II •fe. u, g 3 ° 3 ° Ii 5 Ji 11 j o U i V. o £ T3 "0 3 3 3 , S Ji 11 .^0 ^ ^rj hrj "^o 1 j i j i \ j ! i \ W W M M M M jo In jo ^. io in oo ON 0 0 K> o 3 ° v» H oo NO bo ON 3 3 3 3 3 3 A 11 oo oo £ 2 A II oo oo T O N * • t o II * A 11 oo oo II II ~j oo oo ^ 1 0 0 O N a a a II I i 0 0 oo A " oo oo ~ J NO b> oo r I 1 O E 8 A II P o £ bo O N oo A « O o oo O N Fl O p O © o o JT u> O N © r r A II P o >o Ln O o II „ O o 1 t o 1 O N r r r r r II » I I » I I o p o p o k> — — ~ k> w w oo * * r r & JL U ) © 0 0 O v . r r r r r A Ji A j i A Ji O N O t o ( O ON r r © Ji r r r r A II A II P o p o (o <_n "-• u> O o 0 ° O N I ft 8*' o 55 In thin section, distal kaolinite alteration comprises fine grained kaolinite crystals intergrown with lesser amounts of microcrystalline quartz. Coarser grained kaolinite is observed in irregular shaped masses. Hematite, where present, is finely disseminated imparting a maroon colour to the rock. Rare alunite forms fine grained euhedral crystals (> 1 mm) disseminated in the matrix. A total of 12 X-ray diffraction analyses of distal kaolinite alteration were acquired from surface exposures on Felsite Hill and Rojo Grande. Diffraction patterns for this type of alteration are characterized by a prominent kaolinite (001), less distinct quartz (101) peak and by a lack of pyrite, calcite and dolomite (Figure 4.2a). The position and Kubler index for the (001) kaolinite peak are consistent with the presence of well ordered kaolinite with no interstratified minerals (Table 4.2). Medial Kaolinite: comprises buff to white coloured, amorphous kaolinite and microcrystalline quartz. It is distinguished from distal kaolinite alteration by the increased abundance of quartz, and minor concentrations of pyrite, calcite and dolomite. Field criteria used to differentiate between these two styles of alteration included the development of irregular and/or equant cavities formed from the preferential removal of plagioclase or pyrite and the presence of jarosite on weathered surfaces. Locally, kaolinite veinlets, containing minor concentrations of natroalunite cut medial kaolinite alteration (Plate 4.2a). Where medial kaolinite alteration forms adjacent to proximal kaolinite, the transition is marked by an abundance of soft, white kaolinite filling voids, forming irregular masses and cross-cutting veinlets with partial preservation of primary textures. Away from the contact, the concentration of quartz increases, and either forms pervasive, texturally destructive alteration, or zones of vuggy silica, minor kaolinite and abundant jarosite (Plate 4.2b). Pyrite forms sub-euhedral grains disseminated through the rock or concentrations of larger anhedral masses. Where present pyrite occurs as isolated crystals, as disseminations in the core of breccia fragments, and in pods of brown to grey chalcedony. Calcite and dolomite are developed along the margins of medial kaolinite zones where they form large euhedral grains which overprint the matrix of kaolinite and quartz and occur within veinlets. Amorphous kaolinite-microcrystalline quartz veinlets with subequant crystals of natroalunite, identified by X-ray diffraction and petrographic analysis, cross cut medial kaolinite 56 alteration. Veins of amourphous translucent melanterite, an iron sulphate mineral, infill fractures at lower elevations. A total of sixteen X-ray diffraction analyses of medial kaolinite alteration were acquired from surface and core samples from Felsite Ffill and Rojo Grande. Patterns show a well ordered kaolinite (001) peak and variably developed quartz (101) peak, which corresponds to the relative concentration of quartz in the alteration assemblage (Figure 4.2b). Proximal Kaolinite: consists of pervasive replacement of the host rock by kaolinite and microcrystalline quartz with up to fifteen percent finely disseminated pyrite which imparts a blue-grey colour to the rock. On surface, proximal kaolinite is texturally destructive, with relict textures more recognizable adjacent to zones of medial kaolinite alteration. In core, biotite and plagioclase-phyric, and breccia textures are preserved in the less altered portions of proximal kaolinite zones (Plate 4.3a and b). In this section, proximal kaolinite alteration comprises a mosaic of fine grained kaolinite and quartz (Plate 4.c). Radiating, botryoidal pyrite, possibly reflecting replacement of marcasite occurs in proximal kaolinite zones (Plate 4.4d). Calcite and dolomite locally form part of the alteration assemblage; where present, they form rhombehedral crystals which overprint kaolinite and microcrystalline quartz. Dolomite is common within proximal kaolinite alteration, whereas calcite is more common at depth. Alunite was identified rarely. A total of forty-eight X-ray diffraction analyses were acquired of proximal kaolinite from surface and core. The diagnostic characteristics of proximal kaolinite alteration include the presence of a pyrite (200) peak, a well ordered kaolinite (001) peak and a quartz (101) peak (Figure 4.2c). The relative intensity of the kaolinite (001) and quartz (101) peak suggests that the ratio between kaolinite and quartz varies considerably in zones of proximal kaolinite alteration. 4.1.2 Transitional (Illite/smectite+kaolinite) Transitional alteration contains both kaolinite and illite/smectite and forms intermediate between overlying kaolinite and underlying illite/smectite-dominant alteration. Locally, it forms discrete bodies within illite/smectite and chlorite+illite/smectite zones. It consists of pervasive replacement of the host rock by a fine grained mixture of illite/smectite, lesser kaolinite and quartz with accessory pyrite, calcite, dolomite and rutile (Plate 4b). 57 100 Sub-type: Distal kaolinite peak = 12.36 K.I. = 0.17 t-Tf-l-r 3 5 ° - 2 r t . f . r , r . r n r , . | ^ . h / , , .^jp., , ^| r r i f f f \ v | ^ t f '"r"T l i "> T '• r-^'i n - ^ - ' i • i • i • i • i • i 15 20 25 30 35 degrees two-theta 10 100 Sub-type: medial kaolinite K , peak= 12.34 K.I. = 0.17 s 3 "r I T H ' T P i" ' I'r i" 10 Q 2 Q, I 10 15 20 25 I T . ' i i-1 . ' r i m •• 'TTi ' -r -r .r i - i fj* 15 20 25 Degrees two-theta K < f"-i i 'Tv>- i i r r M ' t i V ' h ^ 30 35 3 5 100 s 0 Sub-type: proximal kaolinite K , peak= 12.35 ICI. = 0.17 i'T-+i?'-rH*r'rY'ii-rr"rl"-r-T-riwi' 'Vi-rr i—r-i-iTt-t• i r T ^ - f ^ K n T ' r n - V H ' - r I , P T T ' ^ , I " I " I 3 5 10 15 20 25 30 35 degrees two-theta Figure 4.2 Diagnostic X-ray diffraction patterns for distal (a), medial (b) and proximal (c) alteration showing the position and relative intensities of the various peaks. The solid and dashed X-ray diffraction patterns for medial kaolinite show the range in relative abundance for kaolinite and quartz. C , D, 58 Plate 4.1 a) Distal kaolinite alteration showing the characteristic appearance with soft amorphous kaolinite, and b) red colouring caused by finely disseminated hematite within the alteration assemblage, likely derived from the host lithology. Plate 4.2 a) White, fine grained kaolinite veinlets with minor natroalunite cutting medial kaolinite alteration, and b) vuggy medial kaolinite alteration. Plate 4.3 a) Sowing the preservation of original feldspar porphyritic, and b) breccia textures, c) Photomicrograph of kaolinite alteration with barite filling voids (field of view = 1.2 mm). The matrix contains a felted mass of kaolinite, quartz and finely disseminated pyrite. Locally, d) botryoidal masses of marcasite are present (field of view = 1 . 2 mm). 60 The resulting rock is typically friable and medium grey coloured, owing to the presence of finely disseminated pyrite. Contacts with kaolinite and illite/smectite dominant alteration are gradational. The pervasive character of this type of alteration favours the destruction of original textures, however selective replacement of plagioclase crystals by illite/smectite can result in the enhancement of feldspar-phyric textures within the volcanic host rocks (Plate 4a). Transitional alteration is characterized by a broad (002) illite peak with an average value of 0.76° two-theta and a well ordered kaolinite (001) peak (Figure 4.3). Of the forty-two samples analysed, the majority of patterns display a broad peak at» 5.87° 20, which corresponds to the smectite (001) peak position. The breadth of the illite (001) peak and gradual slope of the peak at lower degrees 20 for untreated samples indicate the presence of interstratified smectite and illite. The relative amount of interstratified smectite was determined by analyzing glycolated samples transitional alteration. Based on a comparison of the change of the illite (001) peak shape after glycolation with those reported by Moore and Reynolds (1989), it is estimated that there is between ten and fifteen percent interstratified smectite. 4.1.3 Silicification Silicification is defined by the pervasive replacement of rocks by microcrystalline quartz and is usually associated with multiphase brecciation (Plate 4.5a). The resultant rock is aphanitic, and light grey to dark blue-grey in colour; the colour is attributed to finely disseminated pyrite. Barite and calcite infill late fractures and vugs. Silicification is texturally destructive, however relict plagioclase and biotite crystals replaced by microcrystalline quartz have been identified in thin section (Plate 5b), and relict pebbles in conglomerate of Unit 4 are identified in outcrop along the upper contact of silicification. The transition between zones of silicification and other styles of alteration are generally abrupt and strongly brecciated, with the matrix of the breccia consisting of adjacent types of alteration. Typically silicification is bounded by illite/smectite-dominant alteration below and kaolinite-dominant alteration above. At least three phases of brecciation are recognized in the zone. The earliest phase is characterized by white to grey angular fragments in a fine grained, grey quartz matrix. The second phase is characterized by re-brecciation and partial cementation by microcrystalline quartz. Drusy cavities at the interstices between angular fragments, and chalcedonic veinlets up to 2 millimetres wide are characteristic of this phase. The latest phase of brecciation comprises brittle fracturing with barite and carbonate infilling. 61 Transitional alteration 1°° 1 (Glycolatcd) I is, 10 15 degrees two-theta lift/r^fli 20 25 100 j a s Transitional Alteration (Heated) IS, L.JLl.k.JtLL.| y i * i 1 i • i 1 i • 3 5 10 15 20 degrees two-theta 25 Figure 4.3 Diagnostic X-ray diffraction pattern for transitional alteration (a). Glycolated (b) and heated (c) patterns confirm kaolinite as part of the assemblage, and a prominent shoulder on the illite/smectite peak at lower 29 values is characteristic of up to 10% interstratified smectite. 4.1.4 Illite/smectite Illite/smectite alteration is defined by pervasive replacement of host lithologies by interstratified illite and smectite, and varying concentrations of quartz, calcite, dolomite and pyrite. Accessory minerals include hematite and rutile. Illite/smectite alteration is separated into three sub-types: illite/smectite accompanied by fine grained quartz, and carbonate; illite/smectite and quartz with no carbonate; and illite/smectite with abundant carbonate and little or no quartz. Distinctions between the three sub-types are characterized by subtle differences in mineralogy, 62 and spatial distribution of the various sub-types. Illite/smectite+quartz alteration is generally restricted to the area immediately below transitional zones and adjacent to the silicified zone and is termed upper illite/smectite. Illite/smectite+quartz+ carbonate alteration, termed medial illite/smectite forms beneath zones of upper illite/smectite alteration and is the dominant type of alteration in the pit area of the UAZ. Illite/smectite+carbonate alteration, commonly forms envelopes to veins, as pervasive wallrock alteration in zones of veining and locally transitional between medial illite/smectite and chlorite+illite/smectite alteration and is termed vein related illite/smectite. Medial illite/smectite: is characterized by pervasive illite/smectite, fine grained quartz and carbonate alteration with minor hematite and rutile. The resultant rock is typically medium grey to buff coloured, massive and friable (Plate 4.6a). Plagioclase-phyric, and to a lesser extent relict fragmental textures are commonly preserved. Primary textures are best preserved along the margins of medial illite/smectite zones. The transition between illite/smectite and chlorite+illite/smectite is characterized by chlorite in the matrix while fragments are often replaced by an assemblage of illite/smectite, quartz and carbonate. This transition is also characterized an increase in disseminated hematite which imparts a red colour to the altered rock. Due to the friable nature of illite/smectite alteration, only a few, carefully prepared thin sections were analyzed and the definition of medial illite/smectite zones relied primarily on X-ray diffraction techniques. In thin section, illite/smectite alteration is characterized by intergrown illite/smectite and microcrystalline quartz, and abundant calcite within the matrix and as cross cutting veinlets (Plate 4.6b). Fine grained pyrite is disseminated throughout the rock, occurring as anhedral crystals. A total of 84 X-ray diffraction analyses were completed of medial illite/smectite alteration from four sections in the 200 and 440 pit area of the UAZ. Illite/smectite patterns are characterized by a broad illite/smectite peak with an average Kubler Index of 0.8° 20, an average peak position of 8.43° 29 for the (001) peak, and a wide variation in the Kubler Index and peak position (Figure 4.4a). The breadth and shift of the (001) peak to lower degrees 29 relative to the illite (001) peak indicates the presence of varying amounts of interstratified smectite within illite crystals. 63 100 I J5 IS, (Glycoltfvd) 3 3 1 0 13 20 23 3 0 is. 3 5 10 15 20 25 30 35 degrees two-theta Illite/smectite Alteration Sub-type: upper illite/smectite IS, peak= 8.51 K.I. = 0.79 fx | >^ f^VT'•H'"'^ '^ T^ '^  100 IS, 3 3 10 13 20 23 30 is. Q. Illite/smectite Alteration Sub-type: medial illite/smectite IS, peak= 8.43 K.I. = 0.80 3 5 15 20 25 30 35 degrees two-theta 100 IS, L 13 20 23 3 0 is, IS, 3 5 10 15 Illite/smectite Alteration Sub-type: vein illite/smectite I S i peak= 8.45 K.I. = 0.78 '' i 'i r i'r*i""i' -An 20 degrees two-theta 25 30 35 Figure 4.4 Diagnostic X-ray diffraction patterns for (a) upper, (b) medial(a), and (c), vein illite/smectite alteration (c). Insets show the well developed shoulder or peak formed adjacent to the illite(OOl) after grlycollation, characteristic of illite with greater than 10 percent interstratified smectite. 64 Glycolation of medial illite/smectite samples displays a separation of the illite/smectite (001) peak into two distinct peaks. The shape of the glycolated peak is typical of interstatified illite with up to twenty percent interstratified smectite (Moore and Reynolds, 1989). Medial Illite/smectite samples also display well developed quartz (100) and (101) peaks and pyrite (200), and calcite and dolomite (104) peaks. Upper Illite/smectite: is distinguished from medial illite/smectite alteration by its spatial distribution, absence of calcite and dolomite, and by its habit. Upper illite/smectite alteration is developed adjacent to zones of silicification and at the base of kaolinite zones. This style of alteration results in the pervasive replacement of host lithologies by illite/smectite, quartz, pyrite. Carbonate, where present occurs adjacent to carbonate and quartz-carbonate veining. Upper illite/smectite alteration is texturally destructive, preserving only faint relict breccia and plagioclase-phyric textures. The resultant rock is medium grey coloured and extremely friable. In thin section illite/smectite+quartz alteration is characterized by a complete replacement of the rock by fine grained interstratified illite/smectite and quartz. Pyrite forms anhedral to subhedral crystals up to 1 mm which are disseminated and form small clots of coarser grained pyrite. Upper illite/smectite is characterized by a broad (0.79° 26) illite/smectite peak, and displacement of the illite peak to lower 29 values relative to the illite (001) peak (Figure 4.4b). Unlike medial illite/smectite alteration, the variation in Kubler Index and peak position is less extreme (Table 4.2). The quartz (101) peak commonly forms the most intense peak followed by the illite (001) peak. Glycolation of upper illite/smectite samples results in an illite (001) peak with a prominent shoulder at lower degrees 20 typical of up to ten percent interstratified smectite (Moore and Reynolds, 1989). Vein-related illite/smectite : typically forms adjacent to carbonate and quartz-carbonate veins and adjacent to chlorite+illite/smectite zones. It is typically pale grey to white in colour, texturally destructive and easily identified by its soft habit. X-ray diffraction analysis was the primary technique used to differentiate it from other types of illite/smectite alteration since the friable nature of the alteration type made thin-section preparation difficult. Patterns for vein-related illite/smectite alteration are characterized by a well developed illite/smectite (001/002) peak which varies from 0.78° and 1.2° 20 in breadth (Figure 4.4c). When glycolated, illite/smectite peaks develop a pronounced shoulder at lower degree 20 values 65 typical of greater than ten percent interstratified smectite (Figure 4.1 lc). Quartz (002) peaks are absent or obscured by a more intense illite (003) peak. Calcite (104), dolomite (104) and pyrite (200) peaks are typically present with relative intensities below five percent. 4.1.5 Adularia+illite/smectite This type of alteration is defined by the pervasive replacement of host lithologies by quartz, lesser adularia (hydrothermal potassium feldspar) and varying concentrations of interstratified illite/smectite and minor pyrite, calcite and dolomite (Plate 4.7a). Pyrite occurs as fine grained disseminated crystals and as small clots of coarser grained pyrite with triple junctions. Fine grained, needle shaped pyrite may form pseudomorphs after marcasite. Adularia+illite/smectite is separated into two sub-types: adularia+quartz and adularia+illite smectite. Distinctions between the two sub-types are based on the identification of illite/smectite peak by X-ray diffraction analyses. Pervasive adularia+quartz alteration forms discrete zones which grade laterally into illite/smectite+adularia and illite/smectite alteration. Contact relationships and the identification of illite/smectite crystals overprinting earlier formed adularia crystals suggest that adularia+quartz formed prior to adularia+illite/smectite assemblages. Adularia+quartz: comprises the pervasive replacement of the host lithology by a mosaic of fine grained quartz and adularia. Chalcedonic quartz is locally present and forms clusters of radiating crystals in the matrix. Where present illite/smectite appears as crystals adjacent to and overgrowing adularia. Carbonate minerals, including calcite and dolomite occur as late fracture and void fillings and less commonly intergrown with illite/smectite. Rutile is a common accessory mineral and forms anhedral crystals (<0.2 mm) disseminated throughout the rock. Adularia+quartz alteration is also characterized by abundant quartz filled microfractures less than 1 millimetre wide. Adularia+illite/smectite: consists of illite/smectite, adularia and quartz with lesser concentrations of pyrite calcite and dolomite. Fine grained illite/smectite, calcite and dolomite are observed replacing plagioclase phenocrysts and intergrown with quartz and lesser adularia within the matrix (Plate 4.7b). Mineral relations suggest that illite/smectite, calcite and dolomite replace earlier 66 formed adularia and quartz. Accessory rutile forms anhedral grains (< 5 microns) disseminated in the matrix and within relict biotite crystals. X-ray diffraction patterns of adularia+illite/smectite contain a well defined quartz (101) peak and a less intense potassium feldspar peak developed adjacent to the quartz peak. Weakly developed illite/smectite peaks are typically broad, averaging 0.72° 29, with peak positions varying between 7.9° and 8.9° 29 (Figure 4.5). IOO i is. Adularia+quartz Alteration 0 |" ' i l ^ T r T ^ T ^ - h - m -l-l-l-H 1 3 5 10 J M C , D - P I 15 20 25 degrees two-theta 30 35 100 i • 4 0 w A »,„.,,A<AX ^ J Adularia+illite/smectite Alteration I IS. peak= 8.42 k.1. = 0.72 3 5 1 0 1 5 2 0 25 30 Qi is. 0 . ^ i c ^ t I •L|uJr"'|*h-Jl'T-^- ltT''f<t lVri ' I'ftt-' I 10 15 20 v^ i1..l,«YJi^  3 5 25 30 35 degrees two-theta Figure 4.5 Diagnostic X-ray diffraction pattern for adularia+illite/smectite alteration characterized by a dominant quartz peak and minor illite/smectite and adularia peaks. 67 Plate 4.4 a) Transitional alteration displaying preservation of relict plagioclase porphyritic texture and friable nature of the assemblage, b) Photomicrograph showing the finely mosaic of kaolinite, illite/smectite and microcrystalline quartz (Field of view = 1.2 mm). Plate 4.5 a) Pervasive silicification displaying multiphase brecciation healed by chalcedony, and b) photomicrograph of silicified rock with plagioclase phenocryst pseudomorphed by quartz (field of view = 2.65 mm). Plate 4.6 a) Illite/smectite alteration showing the friable character of this type of alteration, b) Photomicrograph of medial illite/smectite showing abundant calcite within a finer grained matrix of illite/smectite and quartz (field of view = 2.65 mm). Plate 4.7 a) Adularia+illite/smectite alteration with cross cutting crustiform quartz veins, b) Photomicrograph of alteration showing coarser grained quartz and adularia and irregular masses of pyrite in adularia+quartz zones (field of view = 1.2 mm). 68 69 4.1.6 Dike Illite alteration zones are developed at lower elevations on the Hank property, and consist of pervasive replacement of the rocks by fine grained illite and quartz, lesser amounts of calcite and dolomite. Accessory minerals include rutile, adularia, hematite, epidote, sphalerite and chalcopyrite. Illite, as defined by Brindley and Brown (1984) is used to designate only non-expansible 10 A, dioctahedral fine grained micas, exhibiting, \Md, \M, and 2M\ structures. Comparissons between X-ray diffraction analyses of illites and those for the different structure types for illite, suggest that illites from alteration zones on the property are dominantly 2Mi-type illites. Illite alteration is characterized by its uniform white to light grey colour and competent habit. Two sub-types are recognized in illite zones: illite+quartz+pyrite+carbonate; and illite+kaolinite+pyrite and minor calcite and dolomite. Disseminated and vein controlled hematite are characteristic of both sub-types. Illite+quartz+pyrite+carbonate alteration forms in the core of illite-dominant zones and is termed medial illite alteration. Medial illite zones grade laterally into illite+kaolinite+quartz +pyrite+carbonate alteration termed peripheral illite zones. Peripheral illite alteration grades outward into chlorite+illite alteration. Medial illite: contains illite with lesser amounts of quartz, pyrite, calcite and dolomite. Rutile, and minor epidote are common accessory mineral. Alteration is characteristically uniform and intense, however relict breccia, plagioclase porphyritic, and intrusive textures are preserved (Plate 8a). Alteration is white to buff coloured, and consists of pervasive illite, quartz and carbonate and disseminated pyrite. Pyrite also occurs rimming and replacing relict volcanic fragments or vesicles (Plate 4.8a). Illite is typically fine grained, and intergrown with quartz and lesser calcite. Locally, illite, calcite and minor epidote are observed replacing plagioclase crystals Larger illite crystals, up to 3 millimetres, are locally observed within a felted mat of finer grained illite (Plate 4.8c). Rutile forms irregular shaped crystals (>0.1 mm), disseminated throughout the rock. X-ray diffraction of illite alteration indicates that it contains well ordered illite with a peak position of 8.74° 28 and an average breadth of 0.32° 20. The diffraction pattern displays well developed quartz (001) and (002) peaks, calcite, and dolomite peaks (Figure 4.6a). 70 Peripheral Illite: is characterized by a well ordered illite peak and lesser concentrations of kaolinite, calcite and dolomite. Diagnostic of peripheral illite zones is the presence of disseminated hematite (Plate 8d), and quartz hematite veining. Important accessory minerals include pyrite, calcite and dolomite. Peripheral illite alteration is typically fine grained, and varies from buff to pink in colour with varying concentrations of hematite in the alteration assemblage. Relict textures are commonly preserved. In thin section, peripheral illite alteration contains a mixture of fine grained illite, kaolinite and quartz in the matrix and replacing feldspars. Dolomite, and lesser calcite are observed as large crystals which overprint the matrix and a cross-cutting veinlets. X-ray diffraction patterns for peripheral illite altered samples are characterized by a well defined illite (001), and less intense kaolinite (001) peak (Figure 4.6b). 100 i s J3 Illite Alteration Sub-type: medial illite I, peak= 8.75 K.I. = 0.26 ' ' D. | l l L | . . ^ ^ . i i | n > r , p 1 - ( i h l r T ' r T " ' * r i *f*i '"I ' i ' I" 5 10 15 20 degrees two-theta 25 30 35 100 J3 0 Q. ' • t ' l ' T r r r Illite Alteration Sub-type: peripheral illite I. peak= 8.72 K.I. = 0.31 K, peak= 12.36 K.I. = 0.20 - i - r •Art 3 5 i ' i ' i ' i 25 i | i i i 15 20 degrees two-theta Figure 4.6 Diagnostic X-ray diffraction patterns for medial (a), and peripheral illite alteration (b) 30 35 71 4.1.7 Chlorite Chlorite alteration forms peripheral to, and as discrete zones within kaolinite-, illite/smectite- and illite-dominant alteration. Locally, discrete zones of chlorite-dominant alteration, occur within pervasive illite- and illite/smectite-dominant zones. The location of these zones is controlled by lithology; occurring within less permeable lithologies. Chlorite alteration consists of progressive replacement of mafic phenocrysts and the groundmass of volcanic units by chlorite, and illite or illite/smectite. Pyrite, hematite, calcite, dolomite, albite, quartz, epidote and rutile are common accessory minerals. Two subtypes of chlorite alteration occur on the Hank property, chlorite+illite/smectite and chlorite+illite. The distinctions between these two types of alteration are based on the type of illite present and spatial distribution. Chlorite+illite/smectite: is dominated by chlorite with a significant concentration of interstratified illite/smectite. It is distinguished from chlorite+illite alteration (discussed later) by the breadth and shift of the illite/smectite (001) peak towards lower 20 values relative to the illite (001) peak. Important accessory minerals in this type of alteration include calcite and dolomite and lesser amounts of pyrite, rutile and adularia. Carbonate, carbonate-sulphide veining and minor quartz-pyrite veining are commonly associated with this style of alteration. The intensity of alteration varies, however chlorite+illite/smectite alteration is typically less destructive than either the kaolinite or illite/smectite dominant alteration assemblages and relict igneous textures are commonly preserved (Plate 4.9a). Chlorite+illite/smectite alteration is typically friable and varies from dark green to pale green based on the relative abundance of illite/smectite. In thin section chlorite+illite/smectite alteration comprises abundant chlorite, calcite, dolomite, quartz and minor adularia, pyrite, epidote and rutile. Plagioclase phenocrysts are replaced by coarse calcite, dolomite and minor quartz. Mafic phenocrysts are replaced by chlorite, calcite and dolomite. Voids are filled by radiating chlorite followed by calcite. X-ray diffraction patterns for chlorite/illite smectite are characterized by well defined chlorite (002) and (004) peaks and a broad illite/smectite peak (Figure 4.7a). Carbonate peaks vary in relative intensity and quartz (001) and (101) peaks are only moderately developed. A weakly developed potassium feldspar peak is commonly developed on the side of the quartz (101) 72 peak. Glycolated chlorite+illite/smectite samples display a shift in the illite (001) peak towards lower degrees 20. is, Chlorite Alteration Sub-type: chlorite+illite/smectite C H , peak= 12.50 K.I. = 0.25 C H , o J i IS peak= 8.62 K.I. = 0.67 degrees two-theta 100 C H . C H . in re- o |ii|»<..|.h|^i/ Q. Chlorite Alteration Sub-type: lower chlorite C H . peak= 12.44 K.I. = 0.20 I. peak= 8.69 K.I. = 0.25 10 15 20 degrees two-theta 25 30 35 Figure 4.7 Diagnostic X-ray diffraction patterns for chlorite illite/smectite (a) and chlorite +illite alteration (b). Both sub-types are characterized by minor concentrations of quartz and abundant dolomite and calcite. In contrast chlorite+illite/smectite displays a broad illite peak and an adularia (220) peak whereas chlorite illite/smectite is characterized by a well order illite peak. Chlorite+illite: is differentiated from chlorite+illite/smectite alteration by the presence of well ordered illite peak and absence of adularia. Accessory minerals include quartz, pyrite, dolomite and calcite. Chlorite+illite alteration commonly forms a pale green pervasive style of alteration with well preserved relict textures. In thin section chlorite, illite, calcite and quartz replace plagioclase phenocrysts and the groundmass as a fine grained mosaic of crystals (Plate 9.b). Mafic phenocrysts are altered to chlorite calcite and pyrite (after magnetite). Pyrite is typically fine grained and disseminated through the rock. X-ray diffraction patterns for chlorite+illite alteration are characterized by well developed chlorite (002) and (004) peaks and varying intensity of quartz, pyrite, calcite and dolomite (Figure 4.7b). 4.2 ALTERATION ZONES 4.2.1 Introduction The distribution of alteration zones on the Hank property provide a natural cross section through the hydrothermal system, exposed for over 800 metres in elevation (Plate 4.10). From lower stratigraphic positions, alteration changes from structurally controlled zones in the Quartz stockwork, Lower alteration and northeastern portion of the Upper alteration zone, to broad tabular zones of semi-conformable alteration at higher elevations in the 200 and 440 pit area of the Upper alteration zone - Felsite Hill area, Flats zone and Rojo Grande areas. Coincident with the change in the morphology of alteration zones, hydrothermal alteration exhibits a change with increasing elevation from illite-dominant in the LAZ, to illite/smectite and lesser adularia in the FZ and upper portions of the UAZ, to kaolinite-dominant alteration on Felsite Hill and Rojo Grande -Rojo Chico (Figure 4.12). Alteration is also characterized by vertical and lateral variations within individual zones. The characteristics of each zone are presented in the following sections and summarized in Table 4.3. The geology, assay data and sample locations which provide the basis of interpretations are illustrated in Figures 4.8 to 4.11 (in the pocket). 4.2.1 Quartz Stockwork zone The Quartz stockwork zone (QZ), located at the base of Creek 4, is the deepest expression of hydrothermal alteration on the Hank property. The zone measures 10 metres wide and 150 metres long and is hosted by block tuffs of Unit la and comprises pervasive silicification which grades laterally into medial illite and chlorite+illite alteration. Plate 4.8 a) Medial illite altered orthoclase porphyry dyke, b) Photomicrograph of medial illite altered Unit Id with vesicles filled by calcite and rimmed by pyrite (field of view = 5.2 mm), c) Photomicrograph of coarse grained illite surrounding a relict fragment (field of view = 5.2 mm), and d) a suite of samples showing a decrease in the intensity of alteration from medial to chlorite alteration. Peripheral illite alteration is characterized finely disseminated hematite imparting a red colouring to the core. Plate 4.9 a) Chlorite+illite/smectite alteration of Unit la near the base of the 200 pit area of the UAZ. The groundmass is pervasively altered to illite/smectite where as the fragments are altered to chlorite+illite/smectite. b) Photomicrograph of chlorite+illite alteration showing abundant chlorite and calcite (field of view = 1.2 mm). 75 76 Table 4.3 Characteristics of the various alteration zones on the Hank property. Alteration Zone Alteration Types Morphology Rojo Grande - Rojo Chico Distal kaolinite Medial kaolinite Proximal kaolinite Silicification Transitional Irregular, developed at margins of zone Irregular to tabular, cuts proximal kaolinite Tabular (?) Vertical (structurally controlled) Developed at depth Felsite Hill - UAZ (200-440 pit) Distal kaolinite Medial kaolinite Proximal kaolinite Silicification Transitional Upper illite/smectite Illite/smectite Vein-related Illite/smectite Chlorite+illite/smectite Tabular, peripheral Tabular, vertical (structurally controlled) Tabular Tabular, vertical (structurally controlled) Tabular, between kaolinite and illite/smectite zones, locally developed at depth. Tabular Tabular Vertical (structurally controlled) Tabular, footwall UAZ (northeastern) Illite Chlorite+illite Adularia+quartz Vertical Vertical, marginal Vertical (structurally controlled) Flats Zone Adularia+quartz Adularia+illite/smectite Vertical (structurally controlled) Tabular LAZ Illite Illite+kaolinite Chlorite+illite Vertical Vertical Peripheral Quartz Stockwork Silicification Illite Vertical (?) Peripheral Intense silicification in the core comprises up to 80 percent fine grained quartz, 10 percent disseminated illite, minor pyrite and rutile. Pyrite forms anhedral crystals disseminated through the rock. Crustiform quartz-carbonate veins within the zone strike northeast and dip vertical. Outward from the core of the zone, alteration decreases in intensity to medial illite and peripheral chlorite+illite. Peripheral to the QZ, relict block tuff textures are readily identifiable within surrounding medial illite alteration. 4.2.2 Lower Alteration Zone The Lower alteration zone (LAZ) forms a north-northeast linear trend, characterized by a central core of pervasive illite alteration. Alteration decreases laterally into chlorite-dominant alteration along the margins of the zone. The zone measures 2.7 kilometres long and 260 metres at its widest, and cuts the volcanic strata at a high angle. The LAZ has a vertical extent of 400 77 metres based on outcrop and drill core (Figures 3.2 and 4.13)._Pervasive illite alteration terminates adjacent to Hank Creek along the northern margin of the zone, and grades laterally into chlorite alteration to the south in Creek 3. Discrete zones of illite alteration in Creeks 1 and 2 likely correspond to the southern continuation of the LAZ. Figure 4.12 Location of alteration zones on the Hank property, outlining the dominant style of alteration and the location of Figures 4.8 and 4.9. Hydrothermal alteration within the LAZ forms a series of sub-parallel zones cored by medial illite alteration, which grades laterally into peripheral illite and chlorite+illite alteration along the margins of the zones. On surface, the transition between the illite-dominant and chlorite+illite alteration coincides with a prominent change in the colour of creek gullies from 78 rusty yellow in illite zones to a medium green color within chlorite+illite zones. The transition between incipient alteration and chlorite+illite alteration related to the hydrothermal system corresponds to the addition of finely disseminated pyrite within the alteration assemblage. Along the northwestern margin of the LAZ this transition is abrupt and is situated approximately 200 metres from the core of the zone (Figure 3.2). To the east, the transition between chlorite+illite and incipient alteration is diffuse, occurring over a broad area characterized by discrete zones of unaltered strata within a broader zone of chlorite+illite alteration. Within this region, several discrete zones of medial illite alteration were mapped (Figure 3.2). These satellite zones may correspond to smaller, discontinuous zones of hydrothermal alteration hosted along subsidiary structures, which at depth coalesce with either the Lower or Upper alteration zones. Hematite within the LAZ occurs as fine disseminations and stockwork veinlets. The distribution of hematite is controlled by alteration type, lithology and elevation. Finely disseminated hematite forms part of the peripheral illite alteration assemblage, and is most pronounced adjacent to flows/sills of Unit Id. Stockwork hematite is characteristic of both medial and peripheral illite alteration and is observed near the top of the exposed section, within and above flows and sills of Unit 1 (Figure 4.8). The core of the LAZ coincides with a structural break within the volcanic strata (Figure 4.13). Detailed logging of a section through the LAZ has identified a high angle fault with apparent west side down displacement within the core of the zone. Movement along this fault may have formed a zone of dilation with increased permeability. The distribution of alteration within the LAZ is also controlled by lithology. Lapilli and tuff breccias of Unit la are more extensively altered and may form zones of enhanced permeability, fluid flow and fluid - rock interaction. In contrast, massive sills, flows and dykes of Unit Id show limited alteration except on their margins where alteration assemblages are telescoped over short intervals. Alteration within these more massive units rapidly grades outward from pervasive medial illite to fracture controlled peripheral illite and chlorite+illite (Figure 4.13). Veins within the LAZ predominantly strike northeast, dip steeply and comprise carbonate-sulphide, quartz-carbonate-sulphide, quartz-sulphide and quartz-hematite-sulphide. Envelopes to veins are characterized by pervasive illite with lesser amounts of carbonate and quartz, often imparting a friable nature to the rock. Detailed descriptions of the style of veining within the LAZ are presented in Chapter 5. 79 Figure 4.13 Section 1 through the Lower alteration zone showing the distribution of alteration within the zone. Faults, identified in drill core occur within the centre of the LAZ and may control the locus of hydrothermal alteration. 4.2.3 Flats Zone The Flats zone (FZ) which forms a poorly exposed zone of alteration hosted by biotite porphyritic flows or sills of Unit 2a is exposed at the head of Creeks 1 and 2 (Figure 4.12). Based on drill core and limited exposure the FZ forms a northeast elongate zone measuring 650 metres by 400 metres with a vertical extent of 100 metres in drill core sections. Adularia+illite/smectite is the dominant type of alteration and exhibits a wide variation in intensity of alteration from pervasive to discrete, stockwork controlled zones of alteration which cross-cut chlorite+illite/smectite alteration. Within the pervasively altered portions of the Flats 80 zone, several discrete zones of adularia+quartz form vertical structures which cross-cut adjacent adularia+illite/smectite alteration (Figure 4.14). In thin section, illite/smectite is observed replacing adularia suggesting that illite/smectite may overprint earlier formed adularia. NW S E F L A T S Z O N E S E C T I O N 2 1 4 0 0 0 5 0 Figure 4.14 Section 2 through the Flats zone showing the distribution of alteration within the zone. Adularia +iilite/smectite alteration grades downward into illite-dominant alteration which may correspond to the southern extension of the LAZ. At depth an increase in illite crystallinity of illite/smectite and absence of adularia within the alteration assemblage suggests that alteration grades vertically into medial illite alteration at depth. Similarities between alteration at depth in the Flats zone and alteration within the LAZ suggest that it may overlie a sub-vertical, structurally controlled zone of illite-dominant alteration. On surface, the base of the Flats zone contains discrete, structurally controlled zones of medial illite alteration, hosting crustiform quartz stockwork veinlets within variably chlorite+illite/smectite altered lapilli tuffs of Unit la. Veining within the FZ primarily consists of cross-cutting white to pale pink calcite stockwork veining and rare crustiform quartz-calcite veins. Quartz microveinlets (1.5 mm) are locally abundant in adularia quartz zones. Detailed descriptions of the style of veining within the FZ are presented in Chapter 5. 81 4.2.4 U p p e r A l t e r a t i o n Z o n e The Upper Alteration Zone (UAZ) is separated into two zones of contrasting hydrothermal alteration. The northeastern portion of the UAZ, situated between Creeks 8 and 14 is a structurally controlled zone dominated by medial illite and illite+chlorite alteration similar to the LAZ (Figure 4.12). In contrast the 200 and 440 pit area of the UAZ is semi-conformable to stratigraphy and dominated chlorite+illite/smectite and illite/smectite alteration which grades vertically into kaolinite dominant alteration beneath Felsite Hill (Figure 4.15). UAZ- northeast extension The northeastern part of the UAZ strikes sub-parallel to the LAZ, measures 2 kilometers long and is up to 270 metres at its widest. The zone contains a central core of medial illite which grades laterally into peripheral illite and chlorite+illite alteration. Discrete zones of pervasive adularia+quartz are developed within the core of the alteration zone, strike north to northeast and are similar to those observed in the LAZ and Flats zones. Alteration affects both tuffs and breccias of Unit la and massive flows/sills of Unit Id gradually cutting up section to the south. UAZ - 200 and 440 pit area The 200 and 440 pit area of the UAZ forms a zone of pervasive alteration which is broadly zoned from chlorite+illite/smectite to illite/smectite alteration with increasing elevation. At higher elevations illite/smectite alteration within the 200 and 440 pit area grades vertically into kaolinite dominant alteration beneath Felsite Hill (Figures 4.16a and 4.16b). The transition between illite/smectite and kaolinite alteration corresponds to the trace of the Silicified zone. Alteration is hosted by lapilli and tuff breccias of Unit la which overlie a thick flow/sill of Unit Id and underlie flows and sills of Unit 2a. Due to the pervasive nature of illite/smectite alteration the contact between Unit la and 2a is diffuse. Alteration assemblages, with the exception of vein-related illite/smectite form tabular zones which dip gently southeast and are semi-conformable to stratigraphy. The footwall of the 200 and 440 pit area, coincides with the contact between andesitic tuffs of Unit la and underlying flows/sills of Unit Id. Footwall alteration comprises pervasive chlorite+illite/smectite which rapidly grades downward into structurally controlled zones of chlorite+illite/smectite alteration. Near vertical zones of illite/smectite bounded by chlorite+illite/smectite cross-cut massive flows/sills of Unit Id with alteration assemblages telescoped over short intervals. These zones form within normal faults which cut and likely represent areas of increased permeability and fluid flow (Figure 4.16a). Figure 4.15 Detailed geology of the pit area of the Upper alteration zone, extending south to Felsite Hill. 83 Immediately above the footwall, the intensity of alteration increases from chlorite-dominant to illite/smectite alteration within tuffs and breccias of Unit la. The rapid change in the intensity of alteration may reflect zones of increased permeability and fluid flow within tuffs of Unit la in contrast to the underlying flows and sills of Unit Id. The transition between chlorite+illite/smectite and illite/smectite alteration is characterized by disseminated hematite. Locally, discrete zones of chlotite+illite extend into overlying zones of illite/smectite alteration. These zones appear to spatially overlie normal faults which cut the footwall (Figure 4.11, 4.16a). Illite/smectite alteration within the pit area of the UAZ is vertically zoned from medial illite/smectite to upper illite/smectite near the base of the Silicified zone. The transition corresponds to a decrease in the abundance of calcite and dolomite and may coincide with the contact between tuffs of Unit la and overlying massive flows/sills of Unit 2a. Between the 200 and 440 pit areas, discrete zones of transitional alteration are common within zones of illite/smectite-dominant alteration. Transitional alteration in this area may reflect zones of increased permeability or the telescoping of alteration assemblages formed from the downward migration of cool, meteoric fluids. To the west of the pit area, diamond drill holes completed by Lac Minerals Ltd. in 1987 and 1988 intersected variably illite/smectite and chlorite illite/smectite altered breccias and flows/sills of the lower volcanic sequence below Bald Bluff. Alteration in this area likely formed from the lateral migration of hydrothermal fluids from the pit area of the UAZ, which is more pervasively altered. Alternatively this region may overlie a vertical, structurally controlled zone of alteration which may corresponding to southern continuation of the UAZ beneath the pit area towards the Flats zone. Veining within the 200 and 440 pit area of the UAZ increases adjacent to zones of faulting and fracturing which cut the footwall. Adjacent to veining the intensity of alteration increases and is characterized by illite/smectite and an absence of quartz. Within the UAZ, six types of veining are recognized: quartz-carbonate-sulphide; barite±pyrite; quartz-pyrite; pyrite; massive calcite; and, crustiform calcite veins. Veining in the pit area of the UAZ is variable with an increase in the density of veining above and adjacent to faults which cut the footwall of the zone. Detailed descriptions of the style of veining within the LAZ are presented in Chapter 5. 8 4 N W S E C T I O N 4 0 ^ ^ J 1 0 O 1600 m e t r e s S i l i c i f i e d \ S E L E G E N D Distal kaolinite Medial kaolinite Proximal kaolinite Transitional (kaolinite+illite/smectite) Silicification Upper illite/smectite Illite/smectite Chlorite+illite/smectite Contact \ ^ Section line • 1 Hydrothermal breccia (1 =type) Figure 4.16 Section 3 (a) and Section 4 (b) through the pit area of the Upper alteration zone, extending south to Felsite Hill. Alteration forms semi-conformable zones which grade vertically from chlorite+illite/smectite in the footwall, upward into illite/smectite and kaolinite-dominant alteration with increasing elevation. The silicified zone forms a semi-conformable zone, is situated near the top of illite/smectite zones, and as vertical zones at higher elevations. 85 4.2.5 S i l i c i f ied Z o n e The Silicified zone forms a series of discontinuous zones of pervasive silicification exposed on surface and in drill core from Felsite Hill southwest to Bald Bluff. The zones are tabular and vary in thickness along strike from several metres beneath Felsite Hill to greater than 10 metres below Bald Bluff (Figure 4.15; Plate 11). The tabular bodies of pervasive silicification are semi-conformable to stratigraphy, and shallowly cut up section to the southwest. Underlying Felsite Hill pervasive silicification is hosted within biotite porphyritic flows and sills of Unit 2a; to the southwest silicification occurs at the upper contact of Unit 2a within sedimentary rocks of Unit 4. Large blocks of intense silicification located in the upper part of Creek 3 are derived from this zone suggesting that it had a greater lateral extent and may have formed a broad tabular zone above the flat, and vegetation covered area below Bald Bluff. On surface, tabular zones of silicification are surrounded by friable, deeply weathered zones of clay. In drill core tabular zones of silicification are located within a zone of upper illite/smectite alteration, up to 70 metres wide, which is characterized by a decrease in the abundance of quartz, calcite and dolomite within the alteration assemblage (Figure 4.16). Carbonate stockwork veinlets composed of white to pink calcite, 1 to 2 centimetres wide, and abundant pyrite veinlets are common within this zone. 4.2.6 Felsi te H i l l Alteration on Felsite Hill forms a broad oval zone with a north-trending long axis and is both vertically and laterally zoned. Hydrothermal alteration is predominately hosted by biotite porphyritic portions of Unit 2a and extends up into sedimentary strata of Unit 4 along the southern margin of Felsite Hill. Alteration on Felsite Hill forms the vertical continuation of alteration within the pit area of the UAZ from illite/smectite upwards through pervasive silicification (Silicified zone) to transitional and kaolinite alteration assemblages. Lateral variations in kaolinite-dominant alteration are observed on the top of Felsite Hill where proximal kaolinite grades laterally and vertically to medial and distal kaolinite alteration and outwards into unaltered host rock (Figure 4.15; Plate 11). Vertical zones of pervasive silicification cut transitional and medial kaolinite alteration below Felsite Hill (Figure 4.16a); a discrete zones of silicification exposed on Felsite Hill and Rojo Grande suggest that these zones are vertically 86 extensive. In drill core, zones of silicification form narrow (>2 metres) zones with sharp contacts characterized by multiple bands of finely disseminated pyrite, parallel to the margins of these zones. Medial kaolinite alteration forms a sheet-like zone above proximal kaolinite. Contacts between the two styles of alteration are diffuse and characterized by a gradual decrease in pyrite and increase in jarosite towards medial kaolinite zones. Jarosite present on fractures and weathered surfaces is attributed to supergene weathering. Vuggy textures within medial kaolinite appear to reflect the leaching of feldspars and pyrite. Within vuggy medial kaolinite zones microcrystalline quartz is the dominant alteration mineral with kaolinite forming a minor constituent. Typically feldspar and pyrite casts are lined with jarosite which may in part be derived from hypogene oxidation. In addition to forming tabular zones, medial kaolinite alteration forms vertical, funnel shaped zones hosted by hydrothermal breccias which likely formed zones of increased permeability. Cutting these zones are late fractures containing melanterite, identified by X-ray diffraction. Distal kaolinite forms along the margins of alteration on Felsite Hill and grades laterally into unaltered host rock (Figure 4.15). Locally this transition is sharp, occurring over several metres. The transition between distal and medial kaolinite is commonly diffuse. Proximal kaolinite alteration is exposed on surface and extends to depth where it overlies illite/smectite-dominant alteration. The change from kaolinite-dominant alteration to illite/smectite alteration at depth forms a broad, tabular zone of transitional alteration (Figure 4.16). On Felsite Hill, discrete zones of brecciation are hosted within massive flows and or sills of Unit 2a. Abrupt contacts, serrate margins of the clasts, and restricted extent of these zones suggest that they are derived from hydrothermal processes (Table 4.4). Table 4. 4 Type of hydrothermal breccias on Felsite Hill. Breccia type Alteration Lithology Matrix Textures Type 1 kaol+qz kaol+qz+py volcanic Early kaol, py and qz Late kaol, minor qz angular to rounded fragments, matrix supported Type 2 kaol+qz volcanic sedimentary black carbonaceous microcrystalline qz angular fragments, matrix supported Type 3 kaol+qz+py volcanic qz, kaol, py angular fragments with serrate margins Type 4 kaol+qz+py volcanic kaol, py rounded 87 Plate 4.10 View to the southeast of Hank Ridge outlining the location of alteration zones on the property (red dashed lines). The yellow dashed line marks the trace of the West Hank fault. Plate 4.11 View to the east of the silicified zone and Felsite Hill outlining the distribution of alteration assemblages. The gossanous slopes in the fore ground are deeply weathered illite/smectite zones below the trace of the silicified zone. 88 10 Goat Peak 89 Type 1 breccias are characterized by fragments of kaolinite and kaolinite+quarz+pyrite altered volcanic fragments in a matrix of quartz, kaolinite and pyrite and late porcellanous kaolinite and microcrystalline quartz. Type 2 breccias are present in medial kaolinite zones and contain kaolinite+quartz altered volcanic and sedimentary fragments in a matrix of black silica. Type 3 breccia consists of kaolinite+quartz+pyrite altered fragments with serrate margins. The matrix of these breccias is similar to Type 1 breccias comprising fine grained quartz, kaolinite and pyrite and late white porcellanous kaolinite and microcrystalline quartz. In drill core Type 3 breccia are cored by discrete zones of vuggy medial kaolinite alteration. Type 4 breccias are observed in diamond-drill hole 93-2A, and comprises rounded kaolinite+quartz+pyrite altered fragments in a matrix of soft amorphous kaolinite and fine grained disseminated pyrite. 4.2.7 R o j o G r a n d e - R o j o C h i c o Southwest of Felsite Hill, a broad zone of kaolinite-dominant alteration extends from Rojo Chico southeast to Rojo Grande (Figure 4.17). Hydrothermal alteration on Rojo Grande lies at a similar stratigraphic level as that observed on Felsite Hill and affects both the volcanic strata of the upper volcanic sequence and overlying sedimentary strata. Lateral and vertical zoning is less pronounced than on Felsite Hill, but is similar grading from proximal to medial kaolinite alteration vertically, and into distal kaolinite along the margins of the zone. Along the west side of Rojo Grande transitional alteration is observed at the base of the zone suggesting a changes from kaolinite- to illite/smectite-dominant at depth. Discrete zones of pervasive silicification, exposed on Rojo Grande form a north striking linear, of sub-vertical, structurally controlled zones of alteration similar to those observed on Felsite Hill. Alteration on Rojo Grande terminates abruptly adjacent to the West Hank fault which is interpreted as a late feature. Rojo Chico, situated to the west of Rojo Grande is altered to proximal kaolinite and is separated from Rojo Grande by talus of kaolinite altered rocks and ferricrete. North of Rojo Chico a broad talus field of diorite derived from Goat peak has obscured relationships between kaolinite alteration at higher elevations with alteration exposed in the Flats zone. In addition, azone of kaolinite alteration is exposed near the top of Goat Peak. The style of alteration is similar to zones of proximal kaolinite alteration exposed on the property, however the relationship to alteration northeast of the West Hank fault is uncertain. 90 4.4 A L T E R A T I O N G E O C H E M I S T R Y 4.4.1 I n t r o d u c t i o n Major and trace element analyses were completed for a suite of 45 samples collected from the various alteration zones on the property to describe the effects of increasing degrees of hydrothermal alteration. The samples collected form a transect from the Lower alteration zone to Felsite Hill , thereby providing a near complete section through the hydrothermal system. Samples from Rojo Grande and the Flats zone are incorporated into the transect to provide information on 91 lateral zonation within the hydrothermal system. Samples from discrete zones of illite/smectite alteration on Bald Bluff are also incorporated to identify similarities between alteration on Bald Bluff with adjacent zones of alteration on Felsite Hill, the pit area of the UAZ and in the Flats zone. Within the various zones, host lithologies are highly altered with the intensity of alteration decreasing laterally. Although major element concentrations are strongly affected, ratios of immobile elements as the high field strength elements (HFSE) Zr, Y, Yb and Th remain essentially unchanged (MacLean and Kranidiotis, 1987; MacLean, 1990; and Barrett and MacLean, 1994). To augment mass change calculations, detailed petrography and X-ray diffraction patterns were first completed for each whole rock sample to determine the minerallogy and intensity of alteration. Petrographic descriptions, X-ray diffraction results and intensity of alteration are presented in Appendix VI. The location of whole rock samples are plotted on Figure 3.2 and in Figures 4.8 to 4.11 (in the pocket). Whole rock analyses are presented in Appendix V. 4.4.2 V o l c a n i c s t r a t i g r a p h y Hydrothermal alteration on the Hank property primarily affects Units 1 and biotite porphyritic sub-unit of Unit 2a. At higher elevations, sedimentary strata of Unit 4 are affected by the hydrothermal system, however the heterolithic nature of the sedimentary strata make it unsuitable for mass change calculations. A multiple precursor approach (Barrett and MacLean, 1994) was employed to study the effects of hydrothermal alteration since the unaltered volcanic rocks on the property exhibit a range of compositions which are related by fractionation (see Chapter 3). To determine the affinity of altered samples, Zr/Y ratios were compared with precursor samples to determine their affinity. Detailed mapping and core logging suggest that alteration primarily affects Unit 1 and the biotite porphyritic sub-unit of Unit 2. These observations are supported by comparing Y-Zr relations between altered and unaltered samples. Samples collected in the vicinity of Creek 14, which are characterized by elevated Ti (>1.1 wt.%) form a distinct trend on the Y-Zr plot at lower Zr/Y ratios and appear to be unaffected by alteration (Figure 4.18a). In the Y-Zr plot, several altered samples are significantly removed from trend lines suggesting that Y or Zr may have been mobile during pervasive alteration. Samples which depart 92 from these trends were collected from silicified, illite/smectite and kaolinite altered biotite-porphyry on Felsite Hill and Rojo Grande. To determine if HFSE mobility occurred during pervasive alteration, Zr and Y are plotted versus Lu (Figure 4.18b and c). Altered and precursor samples form a line passing through the origin corresponding to the affects of fractionation and alteration. In both plots, several samples lie of the line and correspond to samples collected from intensely silicified and kaolinite altered samples. However, the majority of samples show constant Zr/Y, suggesting that the two HFSE were immobile during hydrothermal alteration. Mass changes for altered samples, presented in Appendix VI, are calculated using Al203-Zr, AI2O3-Y and Ti02-Zr to determine the enrichment factors for Zr and Y and the reconstructed compositions for the oxides. Mass Change Trends for the major oxides (raw data) are presented for a transect from the LAZ to Felsite Hill with the dashed or shaded areas representing the average composition for precursor samples.(Figure 4.19). Relative changes in the weight percent of the major oxide species are useful since they illustrate the types of mass changes which might be expected. Changes in oxide concentrations between altered and precursor samples suggest that Na20 is depleted throughout the hydrothermal system on the Hank property. Both CaO and MgO exhibit relative depletion, except within chlorite+illite smectite zones at the base of the UAZ and within zones of transitional alteration. Potassium exhibits relative enrichment within the LAZ, UAZ, and the FZ where it displays the greatest enrichment in zones of adularia-dominant alteration. Above the silicified zone K 20 displays increasing depletion with elevation within kaolinite altered rocks. Both Si02 and AI2O3 display relative enrichment above the silicified zone and opposing trends of Al203 depletion and Si02 enrichment at lower elevations. Calculated mass changes through the same transect substantiate and quantify the relative changes observed by comparing oxide concentrations (anhydrous data) between altered and precursor samples. Overall, alteration displays a cyclical pattern of mass gain and loss in the LAZ, FZ and pit area of the UAZ, and mass loss within the upper portions of the hydrothermal system underlying Felsite Hill (Figure 4.20). Lu (ppm) Y ( p p m ) o o T3 3 to o o o © © ©N O © \0 © © N 1-1 3 \ 0 to • • 4 & 5 1 § * g • s i s cr 3 fio rs FT 3 § 8 N o B. I. o s Is O ° eo " cn H— • C II § N CL ^ S o. T3 T l i f ^ £ B> OO n O 3 i tTcT O n C 3 3 . 2 ~ 3 g o s w • J "8 Cf. l/l §•» i i -§'§. >->  O a to w o m Y ( p p m ) e TJ 3 o © ON o <*> O o •. «» i f 94 FeO (wt.%) MgO (wt.%) Si02 (wt.%) Figure 4.19 Relative mass changes for major oxides (anhydrous data; solid line) for a transect from the LAZ to Felsite Hill compared with precursor compositions (dashed line). 95 An exception to this trend is observed within and adjacent to the silicified zone where kaolinite and illite/smectite alteration display negligible mass change whereas the silicified zone displays extreme mass gain due to the addition of silica. Alteration within the hydrothermal system is also characterized by mass loss of Na20 and MgO, likely due to the destruction of plagioclase and mafic phases during alteration. In the Lower alteration zone, illite alteration is characterized by mass gain for Si, Al and K, with the largest additions occuring at depth (Figure 4.20). Lateral changes between peripheral chlorite+illite and illite zones include increasing Si, Al and K additions and FeO loss toward the core of the zone (Figure 4.21). Alteration in the LAZ also exhibit losses in Na, Mg and Ca, with Ca depletion greatest in the core of the zone. Additions of Si, Al and K in concert with losses in Na, Ca, Mg and Fe likely reflect the destruction of plagioclase and mafic phases in precursor rocks and the abundance of illite within the alteration assemblages. Extreme loss of Ca in the core of the LAZ may reflect a decrease in the abundance of calcite within illite alteration relative to chlorite+illite and peripheral illite assemblages. Pervasive, adularia+illite/smectite alteration within the Flats zone shows mass addition of K, Al, Si and Fe and depletion in Na, Ca, and Mg. Large additions of silica within the zone are restricted to zones of adularia+quartz alteration. From the base of the pit area of the UAZ to Felsite Hill, mass changes for alteration types displays a cyclical pattern of mass loss and gain. Overall, alteration from the pit area to Felsite Hill exhibits mass gain in FeO which is likely due to the abundant disseminated pyrite throughout the zone. At the base of the UAZ, chlorite+illite/smectite and medial illite/smectite zones display an irregular pattern of mass gain and loss. Addition of Ca is restricted to illite/smectite zones immediately above footwall in the pit area of the UAZ, and gradually decreases in magnitude up section. At higher elevations upper illite/smectite forms a more regular trend of increasing mass loss caused by the depletion of CaO, K 20, Si20 and Al203. Adjacent to the silicified zone, transitional alteration and upper illite smectite alteration exhibit mass gains in Si02, and K20. The change between transitional and overlying kaolinite-dominant alteration at the top of the hydrothermal system is abrupt and characterized by large mass losses of K 20, Al203 and Si02, likely related to the change in mineralogy from illite/smectite to kaolinite-dominant. Figure 4.20 Claculated mass changes for oxide species and total mass change for a transect from the LAZ to Felsite Hill. 97 16.00 -12.00J • . • — ' - "~; : . ; r-Figure 4.21 Lateral mass changes in the LAZ are characterized by an increase in K, Al and Si and decrease in Ca, Mg and Fe from peripheral chlorite+illite to illite alteration in the core of the zone. Extreme mass gain of silica within the silicified zone is likely the result of initial pervasive replacement of the host rock by fine grained quartz and the addition of quartz during multiphase brecciation and quartz infill. However, the magnitude of Si addition is suspect since Y and Zr may have been mobile during alteration. The characteristic mass changes for the different type of alteration can also be compared by observing trends between total mass change, AAI2Q3 and ASiC*2 (Figure 4.22). Relations between total mass change and A S i 0 2 indicate that chlorite altered samples are not significantly displaced from precursor values. Illite and illite/smectite altered samples also plot near precursor values and exhibit only minor gains in AS1O2. Kaolinite and transitional alteration form a linear trend toward increasing losses in both total mass and A S i 0 2 . In contrast, silicification and to a lesser extent adularia+illite/smectite alteration display additions in both total mass and A S i 0 2 . Relations between AAI2O3 and ASiC>2 are more effective in contrasting illite and illite/smectite altered samples (Figure 4.22b). Illite/smectite altered samples plot near precursor values whereas illite altered samples form a linear trend towards increasing AA^O^ and ASiC*2. 98 4.4.4 Bald Bluff porphyry A single precursor approach (Barrett and MacLean, 1994) was employed to study the effects of hydrothermal alteration on Bald Bluff (Appendix VI). Calculated mass changes for illite/smectite zones located on Bald Bluff exhibit mass loss for all the major oxide species with the greatest loses occurring for Si02 and AI2O3 (Appendix VI). To compare alteration on Bald Bluff with alteration in the pit area of the UAZ, samples of illite/smectite porphyry are plotted on Figure 4.22. Illite/smectite altered samples on Bald Bluff form a linear trend defined by kaolinite and transitional altered samples and display little similarity to illite/smectite altered samples from the UAZ. Similarities in mass changes between illite/smectite alteration on Bald Bluff and kaolinite-dominant alteration on Felsite Hill may in part be related to position within the hydrothermal system. Samples collected on Bald Bluff and Felsite Hill are representative of alteration formed within the upper most portions of the observed alteration system. Therefore it is likely that although alteration mineralogy differed, the hydrothermal processes were similar and mineralogy may be a function of some other variable, i.e. temperature, pH, activity of K+. 4.4 SPATIAL TRENDS IN MINERAL CRYSTALLINITY In addition to characterizing the different styles of alteration on the property illite, illite/smectite, chlorite, and kaolinite, crystallinity can be used to provide information about vertical and lateral changes within the hydrothermal system. Quantification of mineral crystallintiy is obtained by measuring the peak sharpness or breadth of the illite (101) peak and is termed the Kubler Index (Kl; Eaton and Setterfield, 1993). Due to inconsistencies in sample preparation and measurment accuracy the Kl cannot be considered a robust method (Robinson, 1990), however, Eaton and Setterfield (1993) suggest that if illites dispay increasing KI's with increasing elevation in a hydrothermal system, it is likely that this technique, although semi-qualitative can be used to discriminate between different alteration assemblages and their spatial distribution. To compare vertical and lateral changes between the various alteration zones on the Hank property, KI's for illite and illite/smectite kaolinite and chlorite are presented in Table 4.5. 99 2 o <N 3 40-30-20 -10-A X • o -40 -30 -20 -10 T o D -40 --50 -| ^ o 1 1 30 40 1 1 Kaolinite f"~] Transitional O Illite/smectite X Chlorite+illite/smectite A Adularia+illite/smectite © Illite X Chlorite+illite •% Bald Bluff (illite/smectite) /^^ ~) precursor A 1 50 Si02 8 -6-4 -2 -1 1 1 1 : ^ 1 1 1 1 ^ CU--40 -30 -20 -10 J p ? § • ( = p • -4 -• 11 • • o -8 --10 --12 -20 30 40 50 Si02 Figure 4.22 Plot of total mass change-ASi02 (a), and AAl203-ASi02 showing the characteristic trends for each type of alteration assemblage. Illite/smectite alteration on Bald Bluff and kaolinite-dominant alteration on Felsite Hill show similar trends in mass loss. 100 Table 4.5 Peak positions and Kubler Indicies determined from X-ray diffraction analyses. Alteration Type Peak Position (°29) Kubler Index (°29) Location Kaolinite Distal Medial Proximal P ^ r 12.36 P k ^ r 12.34 P L i - 12.35 K-Ltoon 0.17 K.I.t.or 0.17 K.I.taoi=0.17 FTLRG FH.RG FH, RG-RC UAZ-RH, RG Transitional (illite/smectite+kaolinite) Pfll/im<>c= 8.41 PU*= 12.40 K.I.ai/miec= 0.81 K.I.taoi= 0.19 UAZ-FH, RG Chert Knoll, QZ Silicification UAZ (200-440 pit) Illite/smectite Upper Medial Vein Pill/nnoc= 8.51 Pill/tmoc= 8.43 Pai/Bnec= 8.45 K.I.ai/««c= 0.79 K.I.ai/imec= 0.80 K.I.Ul / imoc = 0.78 UAZ (200-440 pit), CK3 UAZ (200-440 pit) UAZ, FZ Adularia+illite/smectite Pai/imec= 8.42 K.I.UL/HnecP 0.72 L A Z , F Z Illite Medial Peripheral Pui= 8.75 Pai= 8.72 Ptooi= 12.36 K.I.ai= 0.26 K.I.ai=0.31 K.I.boi= 0.20 LAZ LAZ Chlorite Chlorite+illite/smectite Chlorite+illite Pchi= 12.50 Pai/«moc= 8.62 Pchi= 12.44 Pai- 8.69 K.I.chl= 0.25 K.I.ai/imec= 0.67 K.1.M= 0.20 K.I.ai= 0.25 UAZ (200-440 pit), FZ LAZ Locations: FH=Felsite Hill, RG=Rojo Grande, RC=Rojo Chico, UAZ=Upper alteration zone, LAZ=Lower alteration zone, QZ=Quartz stockwork zone, FZ=Flats zone. Kubler Index reported are average values from Table 4.2. Based on X-ray diffraction patterns, kaolinite (001) and chlorite (002) peaks are sharp (Kl < 0.3 ° 20) suggesting that kaolinite and chlorite display a high degree of crystallinity and exhibit little variation between the different zones on the property. In contrast illites exhibit a wide range of KI's and are useful in comparing lateral and vertical changes in hydrothermal alteration. Overall, KI's for illites appear to increase with increasing elevation from the LAZ to the pit area of the UAZ (Figure 4.24). Kubler indices for illites from medial illite, peripheral illite and chlorite+illite alteration in and adjacent to the LAZ are low (< 0.3° 20), and suggest that illites at depth exhibit a high degree of crystallinity. In contrast, KI's for illites from the FZ and pit area of the UAZ increase abruptly, averaging between 0.72 to 0.81° 20. Large KI's for illites, from the FZ and pit area of the UAZ, are characteristic of illites which contain varying concentrations of interstratified smectite. The pressence of interstratified illite/smectite as the dominant illite in these zones was confirmed by glycolating samples prior to analysis (Appendix D). From the FZ to the pit area of the UAZ, KI's for illites gradually increase from 0.72° in adularia+illite/smectite zones to 0.81° 20 in transitional alteration zones at the top of the UAZ. In addition, illites in the 101 FZ and pit area of the UAZ also exhibit a wide range of KI's for illites collected from similar elevation suggesting considerable lateral variations in the crystallinity of illites within these zones (Figure 4.24). 1600 T 1400 A ^ 1200 *—* a o •a z 1000 800 600 • L A Z o o TYPES OF ALTERATION # Transitional Q Illite/smectite (all types) O Adularia+illite/smectite • Chlorite+illite/smectite O Medial illite O Peripheral illite • Chlorite+illite 0.25 0.5 0.75 1 1.25 Kubler Index (degrees two-theta) 1.5 1.75 Figure 4.23 Plot of illite KI's for the various alteration assemblages with elevation showing a trend towards larger K l with increasing elevation. 102 5.0 MINERALIZATION 5.1 INTRODUCTION Zones of hydrothermal alteration on the Hank property contain both vein and disseminated styles of gold mineralization. Gold mineralization at lower elevations, within the LAZ and northeastern portion of the UAZ, is hosted within sulphide bearing quartz-calcite veins. At higher elevations, within the pit area of the UAZ and the Flats zone, gold is hosted within sulphide bearing quartz-calcite, carbonate and pyrite veins and the adjacent wallrock. Disseminated gold mineralization in the pit area of the Upper alteration zone is associated with finely disseminated pyrite in illite/smectite-dominant alteration. Gold mineralization occurs in a gently southeast dipping, tabular zone at a uniform level above the footwall. Drilling by Lac Minerals defined a geological resource within the pit area of the Upper alteration zone of 269,500 tonnes of 4.45 gpt Au and 238,000 tonnes of 2.29 gpt Au in the "200" and "440" pits (Turna, 1986). Vein styles and their paragenetic sequence, as well as the spatial distribution of gold mineralization and isotopic constraints for mineralization are presented in the following sections. 5.2 VEIN PARAGENESIS Veins on the Hank property include, quartz-calcite-sulphide, massive pyrite, banded quartz-sulphide, and massive calcite and barite veins. Gold is hosted within sulphide bearing quartz-calcite veins which exhibit vertical zonation from sphalerite, galena, chalcopyrite, tetrahedrite at depth to predominately pyrite and lesser arsenopyrite, sphalerite, chalcopyrite, and tetrahedrite at higher elevations. Overall, vein textures suggest early, multiphase quartz and minor pyrite followed by calcite with sulphide precipitation following initial quartz growth. Bladed quartz, likely replacing calcite, is observed at depth, but is most abundant in the upper part of the hydrothermal system. X-ray diffraction analyses of vein carbonates from each zone were completed to identify vertical or lateral changes in the dominant carbonate species. Calcite and minor dolomite were identified as the dominant species and no systematic zoning in vein carbonates was identified. The following is a description of the style of veining and vein paragenesis for each zone. 5.2.1 Quartz Stockwork Zone 103 Veins within the Quartz stockwork (QZ) comprise early, crustiform quartz and rare illite followed by calcite and minor quartz (Plate 5.1). Sulphide mineralization consists of pyrite associated with early phase quartz. Late calcite veins cut quartz carbonate veins (Figure 5.1). Minor concentrations of hydrothermal illite and pyrite are present between quartz crystals on the margins of veins. Paragenetic sequence Quartz Stockwork zone Early Late Quartz Pyrite Calcite Wallrock Alteration: medial illite silicification Figure 5.1 Paragenetic sequence for veins from the Quartz Stockwork zone comprises early crustiform quartz growth and pyrite mineralization followed by calcite growth. 5.2.2 Lower Alteration Zone The Lower alteration zone (LAZ) contains abundant quartz-calcite, quartz, calcite, and massive pyrite veins and veinlets (Table 5.1). Relations between veins suggest early pyrite mineralization followed by quartz and minor pyrite followed by calcite with lesser barite and quartz and sulphide mineralization including sphalerite, chalcopyrite, galena and tretrahedrite. Early formed massive pyrite veins, up to 20 cm wide, comprise coarse grained, anhedral pyrite which has been brecciated, and cemented by quartz (Plate 5.2). Quartz veins, contain pyrite and rare chalcopyrite and commonly occur in medial illite zones containing disseminated and hematite veining. In these veins, crustiform quartz crystals form perpendicular to vein walls and radiate inward. Quartz veins contain altered wall rock fragments, also forms in discrete zones of hydrothermal brecciation. Quartz veins are cut by pyrite veinlets. 1 0 4 Quartz-calcite-sulphide veins are the most abundant type of veining and display a minimum of two phases of quartz precipitation followed by calcite quartz, lesser barite, hydrothermal illite and sulphides. In addition to forming in the core of the veins calcite also occurs as fracture infill, and as platy calcite along the margins of quartz-calcite-sulphide veins (Plate 5.3a). Early formed crustiform quartz is coarse grained and followed by fine grained quartz and late crustiform quartz growth along the margins of the veins (Plate 5.3b). Hydrothermal illite is observed along the boundary between early coarse grained quartz and later quartz precipitation (Plate 5.3c). Sulphide mineralization within the quartz-rich margins of the veins primarily occurs within fine grained quartz bands and comprises isolated gains of fine grained pyrite. In the core of quartz-sulphide veins, calcite forms large equant crystals with minor bladed barite and locally, bladed crystals forms pseudomorphed by anhedral quartz, possibly replacing bladed calcite crystals (Simmons and Christenson, 1996). Paragenetic Sequence Lower Alteration Zone Figure 5.2 Paragenesis of veins in the LAZ. Veining is characterized by early stage quartz growth, hydrothermal illite and minor pyrite and chalcopyrite mineralization. Sulphide mineralization including sphalerite, galena, pyrite, chalcopyrite and tetrahedrite occurs with calcite and barite in the centre of veins. 105 Table 5.1 Description of the types of veining in the LAZ Type Size Sulphides Gangue Textures Massive pyrite >20 cm py qz brecciated with quartz infill. Quartz > 10 cm py.cpy (rare) qz, hem,±cc Crustiform quartz, breccia fragments, locally disseminated hematite. Pyrite > 5 nun py cc semi massive, fine grained py and cc locally in the interstices Calcite > 2 cm ±py cc, ba Coarse grained, massive pink to white carbonate veins Quartz-calcite-sulphide up to 1 m py, sph, cpy, ga, tet, aspy. qz, cc, ba, ill Crustiform qz along margins, calcite in core. Sulphides are most abundant with calcite. Calcite up to 1 m ±py cc, qz, ba Coarse grained, weakly colliform banded cc, locally prismatic qz cystals, rare barite. Abbreviations: py = pyrite, cpy = chalcopyrite, aspy = arsenopyrite, tet = terahedrite, ga = galena qz = quartz, cc = calcite, ba = barite, ill = hydrothermal illite. Sulphide minerals in the calcite-rich center of quartz-calcite-sulphide veins include pyrite, sphalerite, chalcopyrite, galena and tetrahedrite (Plate 5.3d). Pyrite is the earliest formed sulphide, commonly forming dodecahedrons. Large, anhedral to subhedral crystals of sphalerite contain numerous chalcopyrite and lesser galena blebs. Chalcopyrite forms anhedral crystals which coalesce into larger aggregates. Fine grained, anhedral chalcopyrite crystals occur along the margins of well formed sphalerite suggesting that chalcopyrite formed after sphalerite. Anhedral crystals of galena, contain chalcopyrite and lesser bournonite exsolutions (Ochs, 1985). Anhedral chalcopyrite crystals adjacent to well developed galena suggest chalcopyrite precipitated after galena. Tetrahedrite forms anhedral crystals adjacent to chalcopyrite and sphalerite. SEM analyses completed by Ochs (1985) on tetrahedrite suggest it contains appreciable concentrations of silver. Pyrite veinlets, less than 5 millimetres wide cut calcite veinlets and, in turn, are cut by late pink to white carbonate veins up to 30 centimetres wide. Coarse grained calcite to weakly banded calcite veins, up to 1 metre wide in drill core occur throughout the Lower alteration zone. These veins contain large, prismatic quartz crystals and contain trace pyrite. Gypsum and anhydrite fill the latest set of fractures with crystal growth typically perpendicular to walls of the fractures. 106 5.2.3 Flats Zone Veining in the Flats zone consists of quartz-carbonate, quartz, pyrite and calcite veins. Quartz veining occurs throughout the FZ and occurs as veins and veinlets of fine grained saccharoidal quartz and crustiform quartz with bladed barite in the core of veins. Minor concentrations of anhedral pyrite occurs on both types of quartz veins. Locally, fine grained saccharoidal quartz veins contain radiating clusters of chalcedonic quartz (Plate 5.4a). Pyrite veinlets, >1 mm wide, consist of fine grained, anhedral pyrite in calcite and are ubiquitous. Quartz-calcite veins display several episodes of crustiform quartz growth along the margins of veins with the core of veins containing calcite and bladed barite (Figure 5.3; Plate 5.4b). Hydrothermal illite is present within veins and occurs between episodes of quartz growth. Minor concentrations of fine grained, anhedral pyrite occurs throughout the vein. Figure 5. 3 Paragenetic sequence for the Flats zone, quartz growth followed by calcite and barite growth, precipitation. Veining is characterized by two episodes of early crustiform Pyrite precipitation occurs during the second stage of quartz 107 Plate 5.1 Crustifonn quartz-calcite vein from the Flats Zone, prismatic quartz crystals radiate inward from vein walls field of view = 5.2 mm). Plate 5.2 Photomicrograph of massive pyrite vein showing insitu brecciation of pyrite and precipitation of quartz (field of view = 5.2 mm). Plate 5.3 a) Quartz-calcite-sulphide vein showing platy calcite along the edge of the vein and cross cutting calcite (white) fracture fill, b) Photomicrographs of the margin of a quartz-calcite-sulphide vein showing crustiform quartz growth with coarse grained calcite and barite in the core, and c) hydrothermal illite between coarse and fine grained quartz bands (field of view =1.2 mm), d) Photomicrograph showing sulphide relations with chalcopyrite and tetrahedrite forming after pyrite and sphalerite growth (field of view = 5.2 mm). 108 109 5.2.4 Upper Alteration Zone (UAZ) Veining in the pit area of the UAZ includes quartz-carbonate-sulphide, barite, quartz-pyrite, pyrite, carbonate and crustiform carbonate veins (Table 5.2). Quartz-carbonate veins contain crustiform quartz along the margins with calcite and bladed barite in the centre of veins. Quartz shows multiple stages of growth characterized by early crustiform quartz, fine grained quartz and calcite followed by crustiform quartz. Table 5.2 Description of the types of veining within the pit area of the UAZ. Type Size Sulphides Gangue Textures Quartz-calcite >20 cm py, cpy, aspy qz, cc, ba, pyrobitumen Early crustiform qz, cc in centre Quartz-sulphide > 10 cm py qz Pyrite > 5 mm py cc semi massive, fine grained py and cc locally in the interstices Calcite >2cm ±py cc, ba Coarse grained, massive pink to white carbonate veins Barite up to 50 cm ±py ba Coarse grained bladed barite, wall rock fragments an crackle breccias common. Crustiform calcite up to 1 m ±py, cpy cc, qz, ba Finely banded pink, white and brown calcite with coarse bladed qz. Abbreviations: py = pyrite, cpy = chalcopyrite, aspy = arsenopyrite, tet = terahedrite, qz = quartz, cc = calcite, ba = barite. Pyrite mineralization occurs adjacent to crustiform quartz and as isolated euhedral grains within calcite gangue. Isolated arsenopyrite crystals occur within the calcite-rich center of veins. Massive calcite veins comprise coarse rhombohedral and lattice calcite and contain minor concentrations of quartz and bladed barite. Calcite veins display at least two phases of growth. Early formed rhombohedral and lattice calcite is fine grained and contains minor concentrations of quartz, illite and sulphides. Later formed calcite is coarse grained, and consists of lattice calcite with minor concentrations of barite and rare pyrite. Sulphide minerals include pyrite, sphalerite, chalcopyrite and tetrahedrite which appear to be contemporaneous with calcite precipitation. Arsenopyrite rims early formed pyrite and appears to be later. Crustiform calcite veins contain rhythmic bands of pink, brown and white calcite separated by coarse grained calcite (Plate 5.5a). Calcite growth within rhythmically banded portions of the veins form elongate, feather-like crystals which radiate inward (Plate 5.5b). Barite and minor 110 pyrite mineralization occur in the coarser grained portions of calcite veins which exhibit rhombohedral and lattice calcite. Barite veins commonly contain wall rock fragments and are characterized by coarse grained bladed barite with minor disseminated pyrite. Quartz-pyrite veins contain euhedral coarse grained pyrite along the margins with quartz in the core. Pyrite veinlets, less than 1 centimetre in width are abundant in the upper zone and cut and are cut by white to pink carbonate veinlets. Cross-cutting relations and gangue paragenesis suggest that quartz-sulphide veins are the earliest formed followed by quartz-calcite, and massive and crustiform calcite veins (Figure 5.4). Barite deposition likely occurred throughout vein formation since both early formed quartz and later calcite veins contain barite. Pyrite veinlets are ubiquitous and both cut and are cut calcite veins; they likely have a protracted history. Sulphide relations suggest that pyrite, chalcopyrite Paragenetic Sequence Pit area of the UAZ Quartz-calcite, calcite-barite and pyrite veins Early Late Quartz Calcite Barite Pyrite Chalcopyrite Crustiform calcite veins Tetrahedrite bladed qz Arsenopyrite Wallrock Alteration: Illite/smectite py ca Figure 5.4 Timing relations between different types of veining and paragenetic sequence for veining in the UAZ. I l l 5.2.5 Felsite Hill The types and paragenetic sequence of veining in kaolinite alteration zones underlying Felsite Hill (FH)are similar to relationships observed in the pit area of the UAZ. The types of veining recognized include quartz-carbonate, quartz-sulphide, pyrite, and both massive and banded carbonate veins (Table 5.3), however, veins within kaolinite-dominant zones on FH are weakly mineralized in contrast with quartz-calcite-sulphide veins in the LAZ and pit area of the UAZ. Veins of pale green, amorphous melanterite, a iron-sulphate mineral, fill the latest fracture set and are likely related to supergene weathering. Table 5.3 Types of veining within Felsite Hill. Type Size Sulphides Gangue Textures Quartz-calcite 1-2 cm py, cpy, aspy qz, cc, ba Early crustiform qz, cc in centre Quartz-sulphide > 1 cm py qz Pyrite > 5 mm py cc semi massive, fine grained py and cc locally in the interstices Calcite > 1 cm ±py cc, ba Coarse grained, massive pink to white cc veins Crustiform Calcite > 5 cm ±py cc, qz, Finely banded white calcite with episodic qz fine grained qz and cc. Abbreviations: py = pyrite, cpy = chalcopyrite, aspy = arsenopyrite, qz = quartz, cc = calcite, ba = barite. Cross cutting relationships between the different types of veins suggest that pyrite and quartz-pyrite are the earliest formed veins and are cut by later banded carbonate veins. Massive calcite veins likely represent the latest veins (Figure 5.5). Quartz-carbonate veins display a more protracted history of early open-spaced quartz followed by later calcite, and are similar to those observed throughout zones of hydrothermal alteration on the property. Pyrite is present as anhedral crystals commonly located along grain boundaries or as inclusions in quartz. In crustiform calcite veins, pyrite is located in the fine grained bands of calcite and quartz and less commonly between calcite crystals in the wider growth bands (Plate 5.6). Bladed barite crystals are locally observed in coarse grained calcite veins. 5.3 MINERAL ZONATION To determine the spatial distribution of gold within the various zones, drill assays compared for the different zones on the property. Sample intervals were selected on the basis of 112 alteration and the presence of veining. The database is limited since the majority of the drill holes were assayed only for gold, thereby precluding correlations between gold other metallic elements including Ag, Cu, Pb, Zn, As, Sb, Hg. The range, average and standard deviations for gold assays within the different alteration types are presented in Table 5.4. The assay data for each alteration type is further sub-divided into vein+wall rock and wall rock populations. The data were obtained from different labs using ICP, and fire assay with AA finish. Analyses below detection level were assigned a value of half the detection limit. Overall, the data demonstrate gross zonation patterns in gold mineralization, but no rigorous statistical methods were employed because of insufficient sample density. Paragenetic Sequence FelsiteHill Quartz-calcite, calcite-barite and pyrite veins Early Late Quartz Pyrite Calcite Barite Banded calcite veins Wallrock Alteration: Transitional (kaolinite+illite/smectite) Proximal kaolinite - py . qz+py Figure 5.5 Paragenetic sequenve for Felsite Hi l l . 113 Plate 5.4 a) Photomicrograph of chalcedonic quartz from a quartz-pyrite vein in the Flats zone (field of view =1.5 mm), and b) a crustiform quartz-barite vein (field of view = 5.2 mm). Plate 5.5 a) Crustiform calcite vein with bladed quartz crystals after calcite. b) Photomicrograph of feather calcite in the coarser grained portions of crustiform calcite veins (field of view = 5.2 mm), and c), photomicrograph of arsenopyrite rimming earlier formed pyrite crystals (filed of view = 2.6 mm). Plate 5.6 a) Photomicrograph of banded calcite vein from zones of kaolinite-dominant alteration on Felsite Hill. Calcite veins show rhythmic bands, alternating between coarse grained, feather calcite and fine grained calcite (field of view = 5.2 mm). 1 1 4 115 In Table 5.4, assay data is separated into different alteration types, and sub-divided into wall rock and vein populations in an effort to compare vein-hosted and disseminated styles of mineralization within the hydrothermal system. From the table it is apparent that gold grades are elevated in intervals containing abundant veining when compared with wall rock intervals. This trend is particularily evident in the LAZ where assays intervals including quartz-calcite-sulphide veins return gold values up to 35.5 gpt whereas assays from altered wall rock average below 100 ppb Au. The assay data also suggest that vein-hosted gold mineralization is both vertically and laterally zoned. Gold grades for vein intervals are highest in the core of the LAZ within illite zones (1,700 ppb Au) and decrease laterally, within peripheral illite zones (222 ppb Au), and vertically in adularia+illite/smectite, illite/smectite and kaolinite zones within the FZ and UAZ which average between 200 and 500 ppb. Vertical zoning of vein-hosted gold mineralization also varies with sulphide mineralogy. In the LAZ, high grade gold is hosted within quartz-calcite veins containing sphalerite, galena, chalcopyrite and tetrahedrite. In contrast, quartz-calcite veins from the UAZ and FZ, which are less mineralized, contain pyrite with lesser concentrations of arsenopyrite, chalcopyrite and tetrahedrite. Gold is rarely visible in thin section and likely forms mircon sized inclusions within the various sulphide phases. In addition, correlation between assay values and the type of sulphide mineralogy suggest that the highest grade gold mineralization appears to be assocoated with poly metallic sulphide mineralization including; sphalerite, chalcopyrite, galena, and tetrahedrite relative to veins which contain only pyrite mineralization. Assay data from wall rock samples suggest that disseminated gold mineralization increases with increasing elevation (Table 5.4). Within the LAZ, assays of illite and chlorite+illite altered wallrock average below 100 ppb, whereas illite/smectite zones at higher elevations average between 140 and 164 ppb Au. Disseminated gold mineralization is even more anomalous in the Flats Zone where assays of wall rock return an average of 260 ppb Au. Detailed sections through the 200 pit area of the Upper alteration zone suggest that significantly higher grades for disseminated gold mineralization form a tabular zone within illite/smectite-dominant alteration, hosting discrete pods of chlorite+illite/smectite alteration, approximately 30 metres above the footwall (Figure 3.10). Disseminated gold mineralization also coincides with zones of disseminated hematite, an increase in pyrite mineralization and veining. Above illite/smectite alteration, zones of silicification, transitional and kaolinite alteration contain 116 significantly lower concentrations in gold, averaging below 100 ppb Au. This change in gold mineralization is abrupt and coincides with the addition of kaolinite in the alteration assemblage. Table 5.4 Distribution of gold mineralization within the LAZ, Flats zone, pit area of the UAZ and Felsite Hill from drill core samples. Disseminated and vein-hosted styles of gold mineralization for the different alteration types are distinguished for comparative purposes. Gold values are in ppb. Alteration Zones n Range Anverage Std. Dev. Location Proximal kaolinite 160 520 -d.l. 69 I l l FH Transitional 59 960 - d.l. 97 170 FH - UAZ (200-440 pit) (veined) 42 2700 - d.l. 249 438 Silicification 22 238 - 36 98 57 F H - U A Z Illite/smectite UAZ (200-440 pit) Upper 82 967 - 10 140 132 (veined) 19 225 - d.l. 271 267 Medial 192 7,200 - d.l. 164 581 (veined) 226 17,143 - d.l. 461 1517 Vein 49 4,200 - d.l. 385 716 Adularia+illite/smectite 49 1,000 - 15 269 208 FZ (veined) 50 3,500 - 10 331 528 Illite LAZ Illite 193 344-5 78 70 (veined) 73 35,584 -31 1,734 5,721 Peripheral illite 32 225 - d.l. 45 46 (veined) 19 1,370 - 15 222 340 Chlorite Chlorite+illite/smectite 91 800 - d.l. 69 148 FZ, UAZ (200-440 pit) (veined) 61 8,700 - 5 413 1,373 Chlorite+illite 45 273 - d.l. 43 57 LAZ (veined) 19 1,410-5 184 364 Abbreviations: n = population, d.l.= detection level. A plot of gold values for the different types of alteration from the various zones graphically illustrates the observed increase in disseminated gold mineralization with increasing elevation (Figure 5.6). The data exhibit an abrupt increase in the tenor of disseminated gold values between the FZ and pit area of the UAZ when compared with the LAZ. In addition, disseminated gold mineralization in the FZ and pit area of the UAZ exhibit a wide variation in gold grades for assays at similar elevations. This suggests that there is considerable lateral variation in the tenor of disseminated gold mineralization within these zones. At the base of the pit area of the UAZ, there is an abrupt increase in gold grades within illite/smectite-dominant alteration which coincides with the tabular zone of mineralization identified in Figure 3.10. Here disseminated mineralization is hosted within a zone of abrupt changes in alteration between illite/smectite and chlorite+illite/smectite alteration which is interpreted to lie above a fault which cuts the footwall of the pit area. It is postulated that elevated disseminated gold mineralization is 117 in part be related to these zones of abrupt changes in alteration which overlie faults and that gold grades decrease laterally away from these thereby explaining the lateral variation in disseminated gold mineralization. Above these zones, gold grades decrease rapidly within transitional and kaolinite zones at higher elevations. 5.7 Pb ISOTOPES To evaluate the relationship between mineralization on the Hank property and known mineralizing events within the region, Pb isotope analyses were completed on galena from auriferous quartz-carbonate-sulphide veins from the LAZ and Creek 14 and compared to values for mineralization of known age within northern Stikinia. Orthoclase from the Bald Bluff porphyry was also analyzed for comparison with galena from mineralized veins to determine if the porphyry could have been the source of Pb, and by analogy other metals. Analyses for both galena and orthoclase are presented in Table 5.4 and Figure 5.7. o 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Gold (ppb) Figure 5.6 Gold values for wall rock samples from the LAZ to Felsite Hill. Disseminated gold mineralization is concentrated within the pit area of the UAZ. 118 Lead isotopic compositions of galena from sulphide bearing quartz-carbonate veins from the LAZ and a vein distal to the main alteration zones are indistinguishable within analytical error, suggesting a homogenous source for vein lead. The Pb isotopic composition of orthoclase from the Bald Bluff porphyry is similar to that of galena, suggesting that the lead from galena within mineralized veins could be derived from the Bald Bluff porphyry via magmatic fluids or from the leaching of a larger portion of the porphyry at depth. The Pb isotopic composition of galena and orthoclase from the Hank property were compared with Pb isotopic compositions for mineralizing events of known age within northern Stikinia (Alldrick, 1987, and Childe, 1994). The Pb isotopic signature of galena and orthoclase from the Hank property plot within the cluster defined by Alldrick (1987) for Middle Jurassic magmatism and mineralization in the Stewart area, 120 kilometres to the south of the property. Table 5.5 Pb isotopic compositions for galena from quartz-carbonate-sulphide veins and orthoclase from the Bald Bluff porphyry. Sample Location Miner 206Pb/204P 2 0 7 p b / 2 0 4 p 208Pb/204P 207Pb/206P 2 0 8 p b / 2 0 6 p b a l 1 ' b b b b Number (error)2'3 (error)2-3 (error)2,3 (error)2'3 (error)2'3 54134 Creek 14 g l 18.802 15.622 38.487 0.83086 2.047 (0.024) (0.028) (0.036) (0.0001) (0.0016) 31133-1A1 LAZ g l 18.821 15.642 38.526 0.83109 2.047 (0.08) (0.081) (0.085) (0.00014) (0.0018) 31133-1A2 LAZ g l 18.82 15.636 38.524 0.83084 2.047 (0.025) (0 03) (005) (0.0011) (0.003) AK92-3 Bald Bluff kf 18.835 15.628 38.532 0.82972 2.0458 (0.026) (0.03) (0.038) (0.00012) (.0.0018) AK92-23 Bald Bluff kf 18.836 15.624 38.525 0.82947 2.0453 (0.02) (0.024) (0.034) (0.00012) (0.0016) mineral abbreviations: gl=galena, kf = potassium feldspar. 2 errors are quoted at the 2a (95% confidence) level. 3 values are corrected for instrumental mass fractionation by normalization based on replicate analyses of the NBS-981 standard. During field investigations, a spatial link between the Bald Bluff porphyry and alteration on the Hank property was demonstrated on basis of the location of the porphyry central to the upper portions of alteration on the property. A possible genetic link was postulated based on the presence of an altered dyke of the intrusion within the LAZ. Although no Pb isotopic analyses 119 were completed for the host Stuhini Group or from other rocks which might underlie the alteration system at depth, the similar Pb isotopic compositions for the Bald Bluff porphyry and sulphide mineralization suggest that leaching of pre-Jurassic rocks did not contribute significant lead. By analogy, it is likely that the underlying host strata were not the primary source of gold. Therefore, gold mineralization on the Hank property was likely derived from the leaching of portions of the Bald Bluff porphyry or from magmatic fluids derived from the porphyry at depth. Since selective leaching of only the porphyry is unlikely, a magmatic fluid model, consistent with the spatial relationship between the Bald Bluff porphyry and alteration, is the preferred model for the source of Pb and other metals, including gold. 208Pb 204Pb 38.7 38.6 38.5 38.4 38.3 15.7 207Pb 15.6 204Pb 15.5 15.4 18.5 / K-Feldspar ^ Galena O Jurassic Cluster (Alldrick et al., 1987) _L 18.7 . 18.9 206Pb/204Pb 19.1 Figure 5. 7 Pb isotopic compositions for galena and feldspar from the Hank property compared with the Jurassic cluster defined by Aldrick et al. (1987). 120 6.0 DISCUSSION 6.1 INTRODUCTION Hydrothermal alteration on the Hank property, northwestern British Columbia, is hosted by andesitic to basaltic volcaniclastic breccias, flows and sills of the Upper Triassic Stuhini Group and unconformably overlying sedimentary rocks of the Lower Jurassic Hazelton Group. The volcanic rocks vary from basalt to trachyandesite in composition, and exhibit a dominantly transitional magmatic affinity. Normalized abundance and rare earth element plots for the Stuhini Group volcanic rocks are characteristic of an island arc setting. The stratified rocks on the property are intruded by an orthoclase-megacrystic monzonite stock, termed the Bald Bluff porphyry and the Goat Peak diorite. The Bald Bluff porphyry, which hosts discrete zones of hydrothermal alteration, is dated at 185.2 +4.5/-1.2 Ma and is significantly younger than the host strata it intrudes. The Bald Bluff porphyry and Goat Peak diorite are separated by the West Hank fault. Both intrusions are metaluminous and formed within an island arc setting, however the Bald Bluff porphyry exhibits a calcalkaline magmatic affinity whereas the Goat Peak diorite is more primitive with a tholeiitic affinity. The age of the Goat Peak diorite is unknown, however the differences in magmatic affinity and separation of the two intrusions by the West Hank fault suggest that the two intrusions are not related. The Upper Triassic strata on the property form a homoclinal sequence which strikes northeast and dips shallowly to the southeast. Overlying Lower Jurassic sedimentary strata are folded about a southeast plunging syncline and warped by the intrusion of the Bald Bluff porphyry. The West Hank fault, cuts across the southwest corner of the property, and forms the southeast continuation of a regional structure. Alteration on Rojo Grande terminates against the West Hank fault suggesting that movement along the fault post dates hydrothermal activity. Alteration on the property forms two sub-parallel northeast trending zones which are capped by broad tabular zones at higher elevations. Alteration zones in order of increasing elevation include: the quartz stockwork zone (QZ); the Lower alteration zone (LAZ); the Flats zone (FZ); the Upper alteration zone (UAZ), separated into the northeat extension and the pit area; the silicified zone (SZ), and the Felsite Hill (FH) and Rojo Grande-Rojo Chico (RG) zones. Alteration on the property exhibits both structural and lithological controls. With increasing elevation, alteration changes from structurally controlled zones in the QZ, LAZ and northeastern 121 extension of the UAZ, to broad tabular zones of semi-conformable alteration at higher elevations in the pit area of the UAZ - FH area, FZ and RG areas. The north elongate form of alteration from RG to FH, abrupt change in bedding adjacent to FH, and northeast striking normal faults in the pit area of the UAZ suggest that semi-conformable alteration within the upper portions of the alteration system were likely influenced by pre-existing structures. Petrography and X-ray diffraction investigations have defined six main alteration types based on mineralogy, and are subdivided into sub-types to distinguish between differences in important accessory minerals and spatial variations in alteration (Table 6.1). Table 6.1 Defined alteration assemblages and their distribution. Alteration Type Diagnostic Minerals Accessory Minerals Location Kaolinite Distal Medial Proximal kaol kaol, qz kaol, py, qz, mar, chal FH, RG qz, alu, hem, ba FH,RG py, alu, ba, fl FH, RG-RC cc, doi, ba UAZ-RH, RG Transitional (illite/smectite+kaolinite) ill/smec, kaol, smec qz, py, cc, doi UAZ (200-440 pit) Silicification qz ba, py, cc, ill, hem UAZ-FH, RG Chert Knoll, QZ Illite/smectite Upper Main Vein ill/smec, qz ill/smec, qz, cc, doi, ill/smec py, cc, doi UAZ (200-440 pit), CK3 py, hem UAZ (200-440 pit) qz, py, cc, doi UAZ, FZ Adularia Adularia+quartz Adularia+illite/smectite qz, ksp ill/smec, ksp, mar, chal ill/smec, py, cc, doi FZ, LAZ, NE ext. UAZ qz, py, cc, doi LAZ, FZ Illite Illite Illite+kaolinite illite ill, kaol qz, py, cc. doi LAZ, NE ext. UAZ hem, py, qz, cc, LAZ doi, ga, sph Chlorite Chlorite+illite/smectite Chlorite+illite chl, ill/smec chl, ill cc, doi, ksp, qz, doi FZ cc, doi, py qz LAZ Mineral abbreviations: kaol=kaolinite, qz=quartz, alu=natroalunite, py=pyrite, ill/smec=interstratified illite and smectite (illitic clay), cc=calcite, dol=dolomite, ill=illite, ksp=adularia, chl=chlorite, fl=flourite, ru=rutile, ap=apatite, hem=hematite, ga=galena, sph=sphalerite, cpy=chalcopyrite, an=anhydrite/gypsum, ba=barite, Locations: FH=Felsite Hill, RG=Rojo Grande, RC=Rojo Chico, UAZ=Upper alteration zone, LAZ=Lower alteration zone, QZ=Quartz stockwork zone, FZ=Flats zone. Coincident with the change in the morphology of alteration zones, hydrothermal alteration exhibits a change with increasing elevation from illite-dominant in the LAZ and northeastern extension of the UAZ, to illite/smectite and lesser adularia in the FZ and and pit area of the UAZ, to kaolinite-dominant alteration on FH and RG areas. Zones of silicification occur at the lowest 122 exposed level of the hydrothermal system in the QZ, and at the transition between illite/smectite and kaolinite-dominant alteration in the silicified zone. The characteristics of alteration types and their spatial distribution within the different alteration zones are presented in Table 6.2. Table 6.2 characteristics of alteration types and their spatial distribution within the different alteration zones. Alteration Zone Alteration Types Morphology Rojo Grande - Rojo Chico Distal kaolinite Medial kaolinite Irregular, developed at margins of zone Irregular to tabular, cuts proximal kaolinite Proximal kaolinite Tabular Silicification vertical (structurally controlled) Transitional Developed at depth Felsite Hill - UAZ Distal kaolinite Tabular, peripheral (200-440 pit) Medial kaolinite Tabular, vertical conduits Proximal kaolinite Tabular Silicification Tabular, vertical Transitional Tabular, between kaolinite and illite/smectite Upper illite/smectite zones, locally developed at depth. Tabular Illite/smectite Tabular Vein-related Illite/smectite Chlorite+illite/smectite Vertical (structurally controlled) Tabular, footwall UAZ (northeastern) Illite Vertical Chlorite+illite Vertical, marginal Silicification+adularia Vertical (structurally controlled) Flats Zone Silicificauon+adularia Adularia+illite/smectite Vertical (structurally controlled) Tabular LAZ Illite Vertical Illite+kaolinite Vertical Chlorite+illite Peripheral Quartz Stockwork Silicification Core, vertical (?) Illite Peripheral Zones of hydrothermal alteration on the Hank property contain both vein and disseminated styles of gold mineralization. Gold mineralization at lower elevations, within the LAZ and northeastern portion of the UAZ, is hosted within sulphide bearing quartz- carbonate veins. At higher elevations, within the pit area of the UAZ, and the FZ, gold is hosted within sulphide bearing quartz-carbonate, carbonate and pyrite veins. Disseminated gold mineralization, in the pit area of the UAZ coincides with zones of finely disseminated pyrite exhibiting abrupt changes in alteration which overlie faults. Within these zones, disseminated gold mineralization forms a gently southeast dipping tabular body with gold grades decreasing gradually away from these zones. 123 Sulphide bearing quartz-calcite veins are the most abundant style of veining on the property. Sulphides are vertically zoned from sphalerite, galena, chalcopyrite, tetrahedrite at depth to pyrite and lesser arsenopyrite, sphalerite, chalcopyrite, and tetrahedrite at higher elevations. Vein textures suggest early, multiphase quartz growth and minor sulphide mineralization including pyrite and lesser chalcopyrite followed by calcite, barite and poly metallic sulphide mineralization and gold mineralization. Overall, alteration displays a cyclical pattern of mass gain and loss in the LAZ, FZ and pit area of the UAZ, and mass loss within the upper portions of the hydrothermal system underlying Felsite Hill (Figure 4.20). An exception to this trend is observed within and adjacent to the silicified zone where kaolinite and illite/smectite alteration display negligible mass change whereas the silicified zone displays extreme mass gain due to the addition of silica. Alteration within the hydrothermal system is also characterized by mass loss of Na20 and MgO, likely due to the destruction of plagioclase and mafic phases during alteration. Similarities in mass changes between illite/smectite alteration on Bald Bluff and kaolinite-dominant alteration on Felsite Hill may in part be related to position within the hydrothermal system. 6.1 INTERPRETATION 6.1.1 Deposit type Hydrothermal alteration and mineralization on the Hank property is characteristic of a near-surface, low-sulphidation epithermal environment dominated by illite alteration at depth and kaolinite alteration at higher elevations. Gold mineralization is associated with quartz-calcite-base metal sulphides at depth and within semi-conformable zones of disseminated pyrite and quartz-calcite-pyrite veins at higher elevations. A high-sulphidation origin for alteration and mineralization on the Hank property is discounted based on differences of alteration and ore mineralogy discussed below. The characteristics of low- and high-sulphidation epithermal environments are documented by White (1991) and White and Hedenquist (1995). Differences between the two types of hydrothermal system were initially made on the basis of mineralogy, i.e., acid sulphate and adularia-sericite (Heald et al, 1987), however, more recent classifications are based on the sulphidation state of minerals and hydrothermal fluids (White, 1991 and White and Hedenquist, 124 1995). Both classifications are valid since the alteration and mineral assemblages for low- and High-sulphidation styles are characteristic of the types of fluids they are derived from. Alteration and ore minerals present in each type of system, and at the Hank property are presented in Table 6.3. Table 6.3 Alterationand ore mineralogy of low- and high-sulphidation systems and within zones of hydrothermal alteration on the Hank property (modified from White and Hedenquist, 1995). Mineral Low Sulphidation High Sulphidation Hank property Alteration Quartz ubiquitous (abundant) ubiquitous (abundant) ubiquitos (abundant) Chalcedony common (variable) uncommon (minor) present (re-crystallized) Calcite common (variable) absent (ecept as over print) common (abundant) Adularia common (variable) absent minor (dominately in FZ) Illite common (abundant) uncommon (minor) common (abundant in LAZ) Kaolinite common (as overprint) common (minor) common (FZ and RG) Pyrophyllite-Diaspore absent (except as overprint) common (variable) absent Al unite absent (except as over print) common (minor) minor (cross cutting veins) Barite common (vert minor) common (minor) common (minor) Ore pyrite ubiquitous(abundant) ubiquitous(abundant) ubiquitous(abundant) sphalerite common (variable) common (very minor) common (LAZ) galena common (variable) common (very minor) common (LAZ) chalcopyrite common (very minor) common (minor) minor (LAZ) enargite-luzonite rare (very minor) ubiquitous (variable) absent (?) tennentite-tetrahedrite common (very minor) common (minor) minor (UAZ, LAZ) covellite uncommon (very minor) common (minor) absent arsenopyrite common (minor) rare (very minor) minor (UAZ) electrum common (variable) common (minor) absent (?) native gold common (very minor) uncommon (minor) absent (?) High-sulpidation systems are characterized by a mineralized core of vuggy silica+alunite, bounded by kaolinite and alunite which may grade vertically to pyrophyllite, illite and alunite at depth (White and Hedequist, 1995). In contrast, low-sulphidation systems are characterized by adularia and illite-dominant alteration adjacent to ore zones (tyically veins or stockworks) with alteration grading vertically to illite/smectite and smectite at shallower elevations. The characteristics of Low-sulphidation environments from the liturature systems are tabulated below (Table 6.4). Based on the spatial distribution, morphology and alteration minerallogy of the various zones on the property, the Hank system is interpreted to represent a low-sulpidation epithermal environment. 125 Characteristic of the upper portions of both high- and low-sulphidation environments are tabular and vertical zones of steam-heated alteration which may overprint pre-existing hydrothermal alteration (Schoen et al., 1974; and, White and Hedenquist, 1995). Steam-heated alteration forms from acidic fluids, derived from the condensation and oxidation of vapours, in the vadose zone, derived from the underlying hydrothermal system, with extreme acidities of fluids caused by the atmospheric oxidation of H2S (Hedenquist, 1994) and form broad, tabular zones characterized by kaolinite+alunite near the surface and grade vertically to kaolinite-smectite and illite/smectite at depth. Broad tabular zones of kaolinite-dominant alteration on Rojo Grande and Felsite Hill, and underlying zones of transitional alteration comprising kaolinite and illite/smectite are likely products of steam-heated alteration. Table 6.4 Characteristic of Low-sulphidation epithermal environments (modified from Heald et al., 1987; and White and Hedenquist, 1995). Fluid chemistry Dominated by meteoric fluids, can contain aqueous and reactive gases (CO2, SO2, HC1) of magmatic origin. Fluids rise from depth, equilibrate with host rock giving rise to reduced, near neutral pH fluids. Veins Low sulphide, cavity filling veins with sharp contacts Typically structurally controlled, forming stockworks of thin veinlets. Gangue mineralogy = quartz, chalcedony, carbonate, adularia, illite (rare kaolinite as overprint) Textures = banded, crustiform quartz, chalcedony veins, drusy lined cavities, multiphase breccias, lattice and bladed calcite. Ore mineralogy Low sulphidauon state minerals including: pyrite, chalcopyrite, sphalerite, galena, arsenopyrite; tetrahedrite, electrum, native gold, tellurides-selenides Alteration zoning illite±adularia at depth, illite and smectite at intermediate levels and smectite near the surface. Rhythmically banded silica sinters form at thesurface. Steam heated overprint of kaolinite and alunite grading vertically downward into kaoliniteismectite and illite±smectite±pyrite at depth. Metal signature Anomalously high Au, Ag, As, Sb, Hg, Zn, Pb, Se, K, Ag/Au. Anomalously low Cu, Te/Se 6.1.2 Alteration Alteration zoning on the Hank property is consistent with descriptions for low-sulphidation systems (Table 6.3, 6.4). In addition, the vertical cross-section of hydrothermal alteration on the property has assisted in the interpretation of alteration zones. The LAZ, and northeastern extension of the UAZ, comprise zones of pervasive illite -dominant alteration and represent the lowest exposed portions of a low-sulphidation system. These two zones are 126 interpreted to be conduits for upwelling hydrothermal fluids which formed semi-conformable zones of alteration at higher elevations in the FZ and pit area of the UAZ. Detailed investigations into the LAZ and northeast extension of the UAZ suggest that the two zones are cored by faults which likely formed zones of increased permeability. In the FZ, adularia+quartz-dominant alteration forms discrete, structurally controlled zones, whereas adularia+illite/smectite alteration forms broad zones of peripheral to adularia+quartz zones. Differences in the style of alteration may reflect their proximity to zones of dilation with adularia+quartz zones forming proximal to and adualria+illite/smectite peripheral to structurally controlled zones of hydrothermal fluid flow. Illite-dominant alteration at the base of the FZ may correspond the southern continuation of the LAZ. The change in the style of alteration between pervasive illite alteration at depth and overlying, tabular zones of adularia+illite/smectite are attributed differences in the host lithology. Pervasive illite-dominant alteration, in the LAZ, is hosted within tuffs, cut by sub-vertical normal faults, which likely formed zones of increased fluid flow. In contrast, alteration in the FZ is hosted by massive flows and sills of Unit 2, which may have inhibited hydrothermal fluid flow, resulting in larger variations in the intensity of alteration with the most intense alteration forming within zones of enhanced permeability (i.e. faults and fractures). Flat lying zones of fracture controlled illite/smectite alteration, similar to those in the FZ, are present at Creede, Colorado. At Creede, illite/smectite alteration locally overprints earlier formed zones of potassic alteration adjacent to structurally controlled mineralization, in the OH and Amsthyst vein systems, and are interpreted to have formed from vapour condensation and subsequent downward migration of the resultant fluids (Haybaefa/., 1985). Alteration on Felsite Hill and Rojo Grande represent the highest stratigraphic expression of hydrothermal alteration on the Hank property and are characteristic of zones of vapour condensate alteration which form above and/or adjacent to a low-sulphidation epithermal systems (Hayba et al., 1985). On Felsite Hill, kaolinite-dominant alteration grades with depth to kaolinite+illite/smectite alteration and is consistent with a vapour condensate origin for alteration. Leached cavities, abundant jarosite, cross cutting, and gradational contacts with underlying proximal kaolinite zones could be interpreted to suggest that medial kaolinite alteration formed from the supergene oxidation of proximal kaolinite zones. However, kaolinites from medial kaolinite alteration exhibit sharp (001) peaks (breadth > 0.3° 20), indicating that they formed during hydrothermal alteration rather than supergene processes. Similar criteria have been used to 127 distinguish between hydrothermal and supergene kaolinites within the Tavua volcanic feild, Fiji, Furgeson (1985). The pit area of the UAZ forms a semi-conformable zone of alteration, intermediate between structurally controlled zones at depth (LAZ and northeastern extension of the UAZ) and zones of vapour condensate alteration near surface (FH and RG). Although poorly exposed, the pit area of the UAZ is interpreted to overlie the structurally controlled, illite-dominant alteration within the northeast extension of the UAZ. The tabular morphology of the zone contrasts with underlying near vertical zones, suggesting that upwelling hydrothermal fluids may have migrated laterally along a zone of increased permeability. Illite/smectite alteration is also characterized by both lateral and vertical variations in crystallinity and amount of interstratified smectite. Similar zones of illite/smectite alteration have been observed in active geothermal systems (Reyes, 1990) and are interpreted to form zones of interaction between cooling of upwelling hydrothermal fluids and descending vapour condensate fluids. In epithermal environments, it has been demonstrated that illite crystallinity is related to temperature of formation (Reyes, 1990; Eaton and Setterfield, 1993). Temperatures of formation for illites in active geothermal fields vary between 230° and 320°C, with illite formed at high temperatures exhibiting a greater degree of cyrstallinity than illites formed at lower temperatures (Reyes, 1990). With increasing concentrations of interstratified smectite, temperatures of formation for illites decrease from 220° to 160°C, below which smectite is the dominant clay mineral (Reyes, 1990). By inference, variations in the crystallinity of illites and illite/smectites in the pit area of the UAZ, can be attributed to lateral and vertical changes in the temperature of hydrothermal fluids. Increasing Kubler Indices (Kl) for illite/smectites with increasing elevation in the pit area suggest that overall, temperatures of hydrothermal fluids decreased vertically. Variations in KI's for illite/smectites, at similar elevations, likely correspond to lateral changes in the temperature of hydrthermal fluids, and suggest that the pit area formed a complex zone of mixing and overprinting alteration derived from upwelling hydrothermal and descending vapour condensate derived fluids. Zones of silicification form a series of a semi-conformable zones between illite/smectite and kaolinite-dominant alteration. Displaced blocks of silicified rock in Creek 3 suggest that the zone may have been much larger prior to erosion. Multi-phase breccia textures and fine grained quartz infill are characteristic of episodic brecciation and quartz deposition. Tabular zones of silicification, comprising hydrothermally brecciated massive chalcedony and opal, are exposed 128 within zones of advanced argillic alteration at Santa Cecilia, Chile (Villa and Sillitoe, 1991), and are interpreted as shallow paleoaquifers or paleo water tables.. Similarities between zones of silicification at Santa Cecilia and the Hank property suggest that the silicifed zone likely formed within a similar environment. Tabular zones of silicification within the vadose zone are interpreted to form from the neutralizing of acid fluids (vapour condensates), resulting in the precipitation of Si02 (Fournier, 1985). Comparison of temperatures of formation of alteration minerals in active low-sulphidation epithermal systems (Reyes, 1990; and, Reyes, 1991) and alteration assemblages in the various zones suggest a decrease in the temperature of the Hank system with increasing elevation (Figure 6.1). Illite-dominant alteration at lower elevations likely formed at moderate temperatures (> 220°C) in contrast to illite/smectite-dominant alteration at higher elevations which likely formed between 220° and 180°C. Overlying zones of kaolinite-dominant alteration likely formed at temperatures below 180°C, whereas medial and peripheral kaolinite zones formed at temperatures below 100°C. The origin of carbonates minerals within the various zones of alteration can be attributed either to the heating of descending bicarbonate fluids or to the boiling of ascending hydrothermal fluids (Fournier, 1985; Simmons and Christenson, 1994). Disseminated, or replacement carbonates in zones of alteration are present as; coarse grained crystals which overprint earlier formed alteration minerals, fine grained disseminations in the matrix; platy calcite, and, replacing feldspars with minor concentrations of illite/smectite and kaolinite at upper elevations and with illite and epidote at lower elevations. Simmons and Christenson (1994) suggest that replacement carbonates within zones of interstratified illite and clay-dominant alteration in the Broadlands-Ohaaki geothermal system, New Zealand, form from the heating of descending bicarbonate fluids and occur with a diversity of alteration assemblages over a temperature range from 125° to 290°C (Simmons and Christenson, 1994). Similarities between replacement calcite at the Hank and Broadlands-Ohaaki suggest that calcite replacing feldspars and coarse grained calcite in illite/smectite and kaolinite-dominant alteration zones in the pit area of the UAZ and on Felsite Hill likely formed from cool (170°C) descending bicarbonate fluids (Simmons and Christenson, 1994). In addition, bladed quartz, likely replacing calcite in veins in the pit area of the UAZ, suggest that boiling of upwelling C02-rich fluids may also have contributed to the abundance of replacement calcite in these zones. 129 Figure 6.1 Temperatures of formation for alteration minerals in active low-sulphidation epithermal systems and probable temperatures of formation for alteration assemblages on the Hank property. Platy calcite adjacent to veins, and calcite and epidote replacing feldspar crystals in the LAZ, suggest that temperatures of hydrothermal fluids were higher than those in the pit area of the UAZ and on Felsite Hill, likely averaged above 160°C. Calcite with minor concentrations of epidote suggest that temperatures may have locally exceeded 290°C within this zone (Simmons and Christenson, 1994). Platy calcite in altered wall rock adjacent to veins in this zone sugests that boiling persisted well below zones of semi-conformable alteration in the pit area of the UAZ. 130 In addition, the presence of platy calcite suggests that replacement calcite in the LAZ is likely related to phase separation of C02-rich fluids and the heating of cooler, meteoric fluids. 6.1.3 Ore paragenesis Gold mineralization on the Hank property is hosted within sulphide-bearing veins, and within semi-conformable zones of disseminated pyrite. Overall, vein textures suggest early, multiphase quartz followed by calcite with sulphide mineralization vertically zoned from sphalerite, galena, chalcopyrite, tetrahedrite in the LAZ an northeastern extension of the UAZ, to pyrite and lesser arsenopyrite, sphalerite, chalcopyrite, and tetrahedrite in the FZ and pit area of the UAZ. Gold mineralization appears to be related to sulphide deposition, and is interpreted to occur late in vein development, primarily occuring in the calcite-rich cores of veins. Vein paragenesis suggests at least two stages of quartz growth followed by calcite deposition. In the LAZ, vein sulphides are coarser grained relative to vein sulphides in the pit area of the UAZ and in the FZ. Bladed and platy calcite veins from the LAZ and pit area of the UAZ, and chalcedonic quartz in the FZ indicate that boiling occurred throughout the hydrothermal system, and likely was an important contributing factor in sulphide and associated gold deposition (Dowling and Morrison, 1989). The differences in sulphide grain size between these zones may reflect a longer period of sulpide precipitation, coincident with boiling, for veins in the LAZ relative to veins at higher elevations. Disseminated gold mineralization in the pit area of the UAZ occurs in zones of finely disseminated pyrite and increased veining which form gently southeast dipping, tabular zones at a relatively uniform level above the footwall. These zones are hosted by pervasively illite/smectite altered tuffs. A plot of Kubler Indices for illite/smectites against gold assays for the pit area of the UAZ (Figure 6.2) suggest that elevated gold minealization coincides with with an abrupt variation in illite crystallinity, which is interpreted to reflect changes in temperature caused by the mixing of ascending hydrothermal fluids and descending vapour condensate derived fluids. In addition, detailed sections through zones of disseminated mineralization indicate that they are spatially associated with discrete pods of chlorite+illite/smectite alteration, and overlie faults zones which cut the footwall to the pit area. Chlorite+ilite/smectite alteration in these zones exhibit lower KI's than illites from adjacent illite/smectite zones suggesting that temperatures of formation may have been higher. These discrete zones of chlorite+illite/smectite may have formed 131 within zones of upwelling hydrothermal fluids, coincident with disseminated gold mineralization. The spatial pattern of chlorite+illite (illite/smectite) adjacent and immediately overlying zones of structurally controlled mineralization which grade laterally, and vertically into illite/smectite alteration is also documented at Hishikari (Izawa, 1990). Investigations into the distribution of gold mineralization suggest that boiling and mixing of hydrothermal fluids, and their effects on sulphide deposition were likely the principal factors contributing to gold precipitation. In epithermal systems it is well documented that gold is primarily transported as a bisulfide complex (Romberger, 1991; Seward, 1988). Mechanisms of deposition are summarized by Romberger (1991), and include a decrease in H2S activity, and/or the oxidation of hydrothermal fluids, which in natural hydrothermal systems can be achieved by boiling, solution mixing, and wall rock interactions. All three processes are interpreted to cause a decrease in temperature and H2S activity in the transporting fluid. The rapid release of H2S and C0 2 gasses during boiling above a throttle point has also been demonstrated to be an effective means of precipitating gold (Hedenquist and Henley, 1985). Bladed calcite and chalcedonic quartz in veins suggest that boiling occurred throughout the system and that gold precipitation was likely related several processes including an increase in the fluid pH, oxygen activity, and salinity, and a corresponding decrease in the mass fraction of water in the mineralizing fluid (Romberger, 1991), as well as a loss of H2S and C0 2 gasses during boiling. The relatively low grade of gold mineralization at the Hank and its association with base metal sulphides suggests that if gold precipitation was related to boiling that it occurred below a throttle point, where losses in H2S and C0 2 were insufficient to destabilize gold bisulphide complexes, resulting in high grade mineralization (Hedenquist and Henley, 1985). Disseminated mineralization in the pit area of the UAZ coincides with a zone of solution mixing, resulting in an increase in oxygen activity and mass fraction of water, and decrease in salinity. Wall rock alteration, resulting in an increase in pH and salinity, and a decrease in the mass fraction of fluids, likely contributed to gold mineralization, particularily in the pit area of the UAZ, since disseminated mineralization forms adjacent to areas of increased veining which correspond to zones of fluid upflow. Lead isotope compositions for orthoclase from the Bald Bluff porphyry are similar to galena Pb isotope compositions from veins within and peripheral to the Lower alteration zone suggesting that gold mineralization on the Hank property was likely derived from the leaching of portions of the Bald Bluff porphyry or from magmatic fluids derived from the porphyry at depth. 132 Since selective leaching of only the porphyry is unlikely, a magmatic fluid model for the lead and other metals, including gold, is preferred. 1600 A 1400 1200 e 0 1 W 1000 A 800 600 Felsite Hill (vapour condensate alteration) Descending, vapour condensate fluids lateral flow . rf<-G > o • • °°o Zone of disseminated gold mineralization # Transitional O mite/smectite O Adularia+illite/smectite O Peripheral illite O JUite • Chlorite+illite • Chlorite+illite/smectite 0.25 0.5 0.75 1 L25 Kubler Index (degrees two-theta) 1.5 1.75 Figure 6.2 Kubler indicies and level of anomalous disseminated gold mineralization in the pit area of the UAZ. 6.2 DEPOSIT MODEL Topography, combined with outcrop and diamond-drill hole data from the Hank property has preserved the primary zonation of a near surface, low-sulphidation epithermal environment from structurally controlled zones at depth to zones of acid condensate alteration which form near surface in active hydrothermal systems (Henley, 1985; Heddenquist and Henley, 1985; and, Reyes, 1990). Investigations of alteration, veining and styles of mineralization at Hank provide the data to develop a model which explains the style of hydrothermal alteration and precious metal mineralization (Figure 6.3), thereby assisting in the evaluation of the economic potential of the 133 Hank property and serving as a guide to exploration for other similar deposits in British Columbia and elsewhere. The overall morphology of alteration zones on the Hank property suggests that the LAZ and northeastern extension of the UAZ are conduits for hydrothermal fluids which cut stratigraphy. The pit area of the UAZ is semiconformable to stratigraphy and indicates lateral movement of hydrothermal fluids along a permeable horizon outward from the central conduit, which coincides with either the LAZ or the northeastern extension of the UAZ (Figure 6.3). The silicified zone, which lies above the pit area of the UAZ formed along a zone of increased permeability, which likely coincides with the presence of a paleo water table or aquifer above which vapour condesate alteration formed broad zones of kaolinite-dominant alteration now exposed on Felsite Hill and Rojo Grande. The observed decrease in illite crystallinity indicatea that temperatures decreased up section which is confirmed by comparing temperatures of formation for alteration minerals in active geothermal fields, and those on the Hank property. Paleo-isotherms, constructed using the observed alteration mineralogy indicate that the LAZ and northeast extension of the UAZ formed zones of upwelling with temperatures decreasing upward and outward. Furthermore, the high degree of variation in illite crystallinity, in both the pit area of the UAZ and the FZ indicate that these zones formed areas of fluid mixing between higher temperature (lower Kl) hydrothermal fluids, and encroaching, lower temperature (high Kl) fluids derived from vapour condensate and bicorbonate-rich fluids.. At depth gold mineralization is hosted within quartz-calcite-sulphide veins. At higher elevations gold is hosted within semi-conformable zones of veining and disseminated pyrite mineralization proximal to zones of hydrothermal upwelling. Gold mineralization in veins is postulated to be related to boiling, which caused an increase in pH, oxygen activity, and salinity of the mineralizing fluids and loss of H2S and C0 2 vapour. The relatively low gold grades, and the association with base metals in quartz-carbonate-sulphide veins in the LAZ suggest that gold precipitation likely occurred within a deep boiling zone where loss of H2S vapour was not sufficient to destabilized gold bisulphide complexes. Local zones of high grade, vein-hosted mineralization may correspond to abrupt changes in pressure, or "throttle points" where rapid boiling, and loss of H2S occurs (Hedenquist and Henley, 1985). Zones of disseminated mineralization in the pit area of the UAZ are likely related to solution mixing and wall rock-fluid interaction, above and adjacent to zones of fluid upflow. 134 Boiling within these zones likely contributed to gold precipitation, however, the sub-economic concentrations of disseminated gold mineralization at the current level of suggest that the temperature of hydrothermal fluids may have been to low, or that the chemistry of the mineralizing fluid was conducive for gold precipitation, as implied by the alteration mineralogy. This suggests that the recognition of semi-conformable zones of illite/smectite alteration within near-surface environments represent a negative exploration feature. Alternatively, if the origin of illite/smectite alteration can be demonstrated, the recognition of fluid up-flow zones by comparing subtle differences in alteration mineralogy (i.e. addition of chlorite) can be used to vector exploration towards potential zones of mineralization at depth. At the Hank property, discrete pods of chlorite in zones of semi-conformable illite/smectite alteration define up flow areas which may overlie structurally controlled of gold mineralization at depth. This is analogous to Hishikari where chlorite alteration proximal to high grade gold veins at depth, persists upwards into tabular zones of illite/smectite. With increasing elevation disseminated gold mineralization at Hank drops of abruptly above the silicified zone, where kaolinite-dominant alteration, derived from vapour condensates forms broad, tabular zones which obscur underlying zones of mineralization. Lead isotopic compositions of vein galena and orthoclase from the Bald Bluff porphyry are consistent with the close spatial relationship between the porphyry and alteration and suggest that the source of Pb and other metals, including gold were derived from magmatic fluids. Overall, illite crystallinity appears to decrease with increasing elevation and distance from zones of hydrothermal alteration, and exhibit large variations in Kubler indicies within zones of disseminated gold mineralization. Illite crystallinity may represent an effective method to predict the level of disseminated styles of gold mineralization within a near surface, low-sulphidation system. In addition, zones of kaolinite-dominant alteration, attributed to acid fluids derived from vapour condensates are interpreted to overlie structurally controlled boiling zones (Berger and Henley, 1988), and can typically obscure underlying zones of gold mineralization. Interpretation of tabular zones of kaolinite-dominant alteration and their position within a low-sulphidation environment provide useful criteria in identifying zones of mineralization at depth. Low grade, disseminated gold mineralization in the pit area of the UAZ likely formed beneath a large kaolinite cap which has largely been removed. Illite crystallinity and the spatial distribution of kaolinite-dominant alteration and their relation to gold mineralization at the Hank property may assist in exploration of similar zones of hydrothermal alteration in British Columbia and elsewhere. 135 FELSITE HILL Legend Q Peripheral kaolinite H Medial kaolinite Ej Proximal kaolinite H Silicification Transitional F?l Illite/smectite Rl Medial Illite Zone of gold deposition . Peripheral illite Hydrothermal fluid flow Boiling Figure 6.3 A reconstructed model of the Hank system, outlining the primary zonation and zones of gold mineralization. The LAZ and northeastern extension formed structural conduits for overlying zones of semi-conformable alteration in the pit area and FH. Pale-isotherms suggest that hydrothermal temperatures decreased with increasing elevation. The Pb isotopic composition of vein galena and orthoclase from the Bald Bluff porphyry plot within the cluster for Middle Jurassic magmatism and mineralization in the Stewart area, 120 kilometres to the south of the property. The age of the intrusion (185+4.5/-1.2 Ma) and related mineralization may be unique in the Telegraph map area and is more characteristic of mineralization to the south, within the Iskut map area, where 190-185 Ma intrusions are associated with significant precious metal mineralization in the Bronson Creek area (Rhys, 1995), and in the Sulphurets area (Macdonald et. al.; 1997). Alteration and mineralization at the Hank property may form the northern terminus of this metallogenic event. 136 7.0 CONCLUSIONS The Hank property in northwestern British Columbia is underlain by andesitic to basaltic volcaniclastic breccias, flows and sills of the Upper Triassic Stuhini Group and unconformably overlying sedimentary rocks of the Lower Jurassic Hazelton Group. The Upper Triassic strata form a homoclinal sequence which dips shallowly to the southeast. Overlying Lower Jurassic sedimentary strata are folded about a southeast plunging syncline and affected by the intrusion of the Bald Bluff porphyry. The West Hank fault, in the southwest corner of the property, cuts alteration on Rojo Grande and is largely post-mineral, suggesting that movement along the fault post dates hydrothermal activity. Volcanic rocks are basalt to trachyandesite in composition, exhibit a dominantly transitional magmatic affinity and are characteristic of an island arc setting. Stratified rocks are intruded by the Bald Bluff porphyry (185.2 + 4.5/-1.2) Ma and the Goat Peak diorite which are metaluminous, island arc derived intrusions. The calcakaline affinity of the Bald Bluff porphyry and tholeiitic affinity of the Goat Peak diorite suggest the two intrusions are unrelated. Topography on the property has preserved the primary zonation of a near surface, low-sulphidation epithermal environment. Alteration zones in order of increasing elevation include: the Quartz stockwork zone (QZ); the Lower alteration zone (LAZ); the Flats zone (FZ); the Upper alteration zone (UAZ), separated into the northeast extension and the pit area; the Silicified zone (SZ); Felsite Hill (FH) and Rojo Grande-Rojo Chico (RG). The overall morphology of alteration zones on the Hank property suggest that the LAZ and northeastern extension of the UAZ mark conduits for hydrothermal fluids which cross cut stratigraphy, whereas the pit area of the UAZ is semi-conformable to stratigraphy and reflect lateral movement of hydrothermal fluids along permeable horizons, outward from central conduits. The Silicified zone, which lies above the pit area of the UAZ formed along a zone of increased permeability represents a paleo water table or aquifer above which alteration, derived from vapour condensates, form broad zones of kaolinite-dominant alteration on Felsite Hill and Rojo Grande. Illite/smectite alteration in the pit area of the UAZ and FZ exhibit vertical and lateral changes in illite crystillinity and likely formed in zones of fluid mixing between upwelling hydrothermal and descending vapour condensate fluids. Alteration displays a pattern of mass gain and loss in the LAZ, FZ and pit area of the UAZ, mass loss in kaolinite-dominant zones on Felsite Hill, and mass loss of Na20 and MgO. 137 Adjacent to the Silicified zone, alteration displays negligible mass change whereas the Silicified zone exhibits extreme mass gain in silica. Gold mineralization is hosted within sulphide-bearing veins, and within semi-conformable zones of disseminated pyrite. Vein textures suggest early, multiphase quartz followed by calcite with sulphide mineralization vertically zoned from sphalerite, galena, chalcopyrite, tetrahedrite in the LAZ, a northeastern extension of the UAZ, to pyrite and lesser arsenopyrite, sphalerite, chalcopyrite, and tetrahedrite in the FZ and pit area of the UAZ. Gold precipitation in veins was caused by the boiling of hydrothermal fluids, in contrast to zones of disseminated mineralization where gold deposition, mineralization is related to solution mixing and wall rock fluid interaction. Lead isotopic compositions of galena from mineralized veins and orthoclase from the Bald Bluff porphyry are consistent with spatial relationships between the porphyry and alteration and suggest that source of Pb and other metals including gold were likely derived from magmatic fluids. The age of intrusion and related mineralization on the property is unique in the region and more typical of mineralization in the Iskut map area, where 190-185 Ma age intrusions are associated with precious metal mineralization at the Snip mine and Sulphurets area. The unique setting and age of alteration and mineralization at the Hank property may form the northern terminus of this intrusive activity and related mineralization. Investigations of alteration, veining and styles of mineralization on the Hank provide the data to form a model which explains the style of hydrothermal alteration and precious metal mineralization, thereby assisting in the evaluation of the economic potential of the Hank property and serving as a guide to exploration for other similar deposits in British Columbia and elsewhere. Detailed investigations of alteration through petrographic and X-ray diffraction methods provide useful criteria in determining the origin of alteration and constraining the temperature under which the various alteration assemblages formed. Illite crystallinity exhibits large variations in zones of disseminated gold mineralization and may represent an effective method to predict the level of disseminated styles of mineralization within a near surface, low-sulphidation system. 138 8.0 REFERENCES Alldrick, D.J., Gabites, J.E., and Godwin, CI., 1987 , Lead isotope data from the Stewart mining camp (104B/1), in Grant, B., and Newell, J.M., ed., Geological Fieldwork 1986, British Columbia Ministry of Energy, Mines and Petroleum Resources Paper 1987-1, p. 93-102. Anderson, G.G., (1982): U-Pb isotopic ages of zircon from the Jurassic Plutonic suite, Hotailuh Batholith, north-central British Columbia; in Current Research, Geological Survey of Canada, Paper 82-IC, pages 133-137. Anderson, G.G., (1984): Late Triassic and Jurassic magmatism along the Stikine Arch and the geology of the Stikine Batholith, north-central British Columbia; in Current Research, Geological Survey of Canada, Paper 84-1 A, pages 67-73. 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Cu, Pb, Zn uTs, eJmz 185+/-2(2) Epithermal, Dis Biskut Sh(146) 104G/2E Au, Ag, Cu, Pb, Zn uTs Epithermal, Dis MAI Sh (147) 104G/2E Cu, Zn, Au, Ag uTs Epithermal, Dis Shaft Creek (c) DP (015) 104G/6E Cu, Mo, Au, Ag uTH 185+/-5(1) Porphyry Mary Sh(018) 104G/8W Mo, Cu uTs, J-Cqdi Porphyry Nabs 21 Sh(030) 104G/6E Cu uTs, qmz Porphyry Joan & MB Sh(047) 104G/4W Cu uTs, eJsy Porphyry Stikine East Sh(066) 104G/3W Cu uTs, eJsy Porphyry Stikine North Sh(067) 104G/3W Cu uTs, eJsy Porphyry Galore Ck. (d) DP (090) 104G/3W Cu, Au, Ag Uv, eJsy Porphyry BAM 10, BAM DP (110) 104G/2W Au, Ag. Bi, Sb uTH Porphyry Copper Canyon (e) DP (017) 104G/3W Cu, Au, Ag uTs, eJmz Porphyry, SW Run, Mix Sh (040) 104G/7W Cu, Au, Mo uTs, uTH Porphyry, Vein LOI Sh(016) 104G/3W Cu, Au, Pb, Ag uTs, eJmz Porphyry, Vein Jack Wilson Ck. Sh(021) 104G/4E Cu, Au, Ag uTs, eJmz Porphyry, Vein Ann, SU, Split Ck. DP (023) 104G/4E Cu uTs, eJmz 48.S+/-2 (1) Porphyry, Vein Shal 27, Kim Sh(029) 104G/3W Cu, Pb, Zn, Au, Ag uTs,CPC Porphyry, Vein Lucifer Sh(145) 104G/2E Cu, Au uTs, eJmz Porphyry, Vein Mess Ck., BIK Sh(049) 104G/2W Cu, Ag, Zn, Pb Ps, eJsy Skam Hummingbird Sh(050) 104G/3W Cu, Au, Ag P.uTH Skarn Dundee G L A P(137) 104G/2W Fe, Cu, Zn, Ag D Skam Alberta Sh(006) 104G/6E Cu uTs,uTH Vein Nabs 13 Sh(031) 104G/6E Cu uTs, gr.qmz Vein Hicks Sh (037) 104G/6E Cu uTs, uTH Vein Ball Creek, Rog Sh (042) 104G/8W Cu, Mo, Pb, Zn, Au, Ag uTs, mz Vein Cot and Bull sh (057) 104G/7W Ag, Cu, Au P, uTmz Vein Cos Sh (062) 104G/5E Cu Ps, Uqmz Vein GU Sh(075) 104G/5E Cu, Pb, Zn, Mo, W uTs, mJgd Vein BB38 Sh(U9) 104G/7W Cu uTs ,Cqmz Vein Brownie Sh(127) 104G/6W Cu, Pb, Zn, Ag uTs Vein Jameson Sh(138) 104G/5E Zn,Cu Ps Vein Snow Sh(139) 104G/5E Cu, Zn, Ag Ps Vein Oksa Gold 3 Sh(140) 104G/5E Au, Ag, Cu, Zn, Pb Ps,gr Vein JD-1, Scud R. Sh(141) 104G/5E Cu, Au, Pb Ps Vein Actic Lk., Bam (f) DP (027) 104G/2W Cu, Ag, As, Zn, Sb P,uTH Vein Jay Sh(046) 104G/3E Cu, Au, Ag uTH Vein Jack Sh(048) 104G/4E Pb, Zn, Ag, Cu uTs Vein CW Sh(051) 104G/3W Cu, Au uTs Vein SAL, REX, RUM Sh (052) 104G/4E Cu uTs, Jdi Vein Horn Sh (059) 104G/4E Cu uTs Vein Perelesin Sh(061) 104G/4E Cu,Zn CPC Vein Ridge JW Sh(124) 104G/4E Au, Ag, Cu uTs,CPC Vein JW 6 Sh(126) 104G/4E Au uTs,CPC Vein PL-1, Scud R. Sh(142) 104G/4E Cu, Zn, Au CPC Vein Trophy, Ptarmigan DP (053) 104G/3W Au, Ag, Cu, Pb, Zn P.uTH Tertiary (3) Vein,Bx Middle Scud, BIK Sh(055) 104G/6W Cu,Ag uTs Vein, Massive ARC, Port, Rose Sh(079) 104G/6E Cu uTs, Cqmz Vein, Massive Snow Ball Sh(143) 104G/1W Au, Ag, Cu, Pb, Zn, As uTs Vein, Massive Ben, Decker Ck. Sh(014) 104G/5W Mo, W, Ag. Cu mJgr Vein,SW Marg Sh (058) 104G/5E Cu, Mo, W, Pb, Au uTs, Egr Vein,SW Late Sh(063) 104G/6E Cu, Au uTs,gr Vein,SW 150 Name Status/ Location Commodoties Host Age Deposit Type Minfile # Map Sheet Ma Dago, Silver Run Sh(120) 104COTE Cu, Ag, Pb, Zn uTsy Vein,SW BJ Sh(070) 104G/2W Au, Cu, Pb, Zn, Ag, Bi Ps 192+/-7(1) Vein,SW Glacier Sh(123) 104G/3E Cu, Zn, Ag uTs Vein, SW GOZRDN P(144) 104G/2 Au, Ag. Cu, Pb, Zn IJh Vein,SW Formore Sh(148) 104G/2W Zn, Pb, Cu, Ag D VMS (a) 0.18 Mt 3.8 gpt Au (1) K-Ar age on biotite (b) 0.23 Mt 4.4 gpt Au (2) U-Pb zircon (c) 330 Mt, 0.4% Cu, 0.02% Mo (3) Pb-Pb galena (d) 125 Mt 1.06% Cu incl. 27 Mt, 0.92% Cu, 0.37 gpt Au (e) 32.4 Mt, 17 gpt Ag, 1.2 gpt Au, 0.7% Cu (f) 0.3 Mt, 0.76% Cu Abbreviations: DP = developed prospect ,P = prospect, sh = showing: stratified rocks; Ps = Paleozoic Stikine assemblage, P = Permian, D = Devonian, uTs = Upper Triassic Stuhini Group, IJh = Lower Jurassic Hazelton, Uv = Lower Jurassic volcanics, intrusive rocks; CPC = Coast Plutonic Complex, Egr = Eocene granite, Cqdi = Jurassic to Cretaceous quartz diorite, Cqrnz = Cretaceous quartz monzonite, Jdi = Jurassic diorite, mJgr, gd = Middle Jurassic granite, granodiorite, eJmz = early Jurassic monzonite, Uqmz = Lower Jurassic quartz monzonite, uTH = Upper Triassic Hickman Batholith, uTmz = Upper Triassic monzonite, qmz = quartz monzonite, eJsy = early Jurassic syenite,, gr - granite, mz = monzonite, Uqmz = Lower Jurassic quartz monzonite,, uTsy = Upper Triassic syenite. 151 APPENDIX B Petrographic description of unaltered whole rock samples II B -x A o II r - — i s . oo u i *3 K> O p Ui o Ul u> a Ui 5 ?^ P o 7' <» o K> © a £ o Ul _ (O Ui a £ 03 Ul 5- a to? 3 fO to 1 w I LJ 5- a 5-IO 00 Ui a 2? 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Us 3 3 I VO 3 3 o § 3. a. | 5 a. 03 M 03 SSI APPENDIX C Whole rock analyses 157 This section describes the sample preparation, analysis and standards for whole rock geochemistry samples described in Sections 3.4 and 4.4, and listed in Table C. 1. Samples were collected by the author in 1992 and 1993. Samples were analyzed by X-Ray Assay Labratories, Toronto, Ontario, using their MER research grade package. Sample preparation was completed using the method outlined below. Sample Size Approximately one metre of split BQ drill core was collected from core samples. A minimum of four kilograms was collected for samples from surface. Method The following procedure was established by Arne Thoma and Art Etlinger of MDRU to achieve uniform, uncontaminated -200 mess powder for analysis at X-Ray Assay Labratories. 1. Thoroughly clean surface of sample to remove soil, dirt and as much weathered material as possible. 2. Retain a representative sample for thin section analysis. 3. Thoroughly clean jaw crusher with a stiff wire brush and compressed air before processing each sample. 4. Crush sample in jaw crusher at the closest setting. If the sample is too coarse, crush at a wider setting and reduce until the closest setting is achieved. 5. Thoroughly clean the chrome ring mill with water and compressed air before processing each sample. Crush each sample for 40 seconds. 6. Clean sample splitter and sample trays thoroughly with a soft brush and compressed air prior to processing each sample. Repeat splitting of milled rock until a 60 gram sample is achieved. 7. Submit 60 gram sample for analysis and archive the remainder. 158 Analytical methods The analytical methods for each batch of samples listed in Table C. 1, and the abbreviations used in the compilation of geochemistry analyses are as follows: Headers Sample Units Method D.L. Lithology AL# Location Drill hole Interval NTSe NTSn Batch Descriptions Sample, inicating year and number. Measurment units Analytical technique: AA Atomic absorption spectrophotometry Wet Wet chemistry NA Neutron activation XRF (F) X-ray flourescence Specrtometry, (F) fused disk COULOM Coulometry Spectrometry LECO Leco analyzer ICP Inductively coupled plasma spectrometry GFAA Graphite furnace AA ICPMS ICP mass spectrometry DCP Direct Coupled Plasma Spectrometry Grav Gravimetric Detection limit determined by X-RAL Based on units defined in chapter 2. Alteration index number (Appendix E) General location of sample. Drill hole year and number, location of sample in drill hole in metres. UTM easting. UTM northing Batch number Quality control A minimum of 10% internal standards were sent with each sample batch. The standards used were UBC-MDRU internal standards: P-l (Porteau Cove dacite), WP-1 (Watts Point dacite), QGRM 100, QGRM 101, ALB1 and MBX 1. A statistical summary of these analyses is presented in Table C.2. The summary includes the maximum, minimum, mean, standard deviation and coefficients of variance for each of the rock standards. A minimum of 5% duplicates were included with each sample batch. These data have been tabulated by A. Toma (MDRU). 159 Table C. 1 Whole rock chemistry of intrusive and volcanic rocks for the Hank property, analyzed at X-Ral. Units Method D.L. AK92-10 AK93-77 AK93-78 AK93-65 AK93-36 AK92-6 AK92-32 Lithology la la la la la la la Alt Index 11 II 12.5 13 13 13.5 14.5 Alt Type chl+ill chl+ill chl+ill chl+il/sm chl+il/sm chl+ill chl+il/sm Location Crk 1 LAZ LAZ UAZ UAZ(200) Crk 14 UAZext Drill bole 87-1 85-36 Interval (m) 26.5-27 86.5-88 NTSe NTSn Batch 11 12 12 12 12 11 11 S.02 % XRFF 0.1 48.5 56.4 46.4 55 56.3 48.9 46 A1203 % XRFF 0.1 16.4 18.1 15.8 16.4 16.1 15.2 15.3 Fe203 % XRFF 0.1 7.46 7.82 10.2 5.69 5.88 9.04 8.05 Ti02 % XRFF 0.1 0.983 0.45 0.774 0.742 0.734 1.06 0.835 MnO % XRFF 0.1 0.25 0.22 0.22 0.2 0.2 0.17 0.25 MgO % XRFF 0.1 0.89 0.99 3.53 1.87 1.87 2.7 2.85 Na20 % XRFF 0.1 2.79 3.44 2.09 0.87 0.94 1.35 0.57 CaO % XRFF 0.1 9.28 4.46 10.1 6.67 5.98 8.04 9.56 K20 % XRFF 0.1 2.5 2.89 1.82 3.88 3.64 2.47 3.07 P205 % XRFF 0.1 0.42 0.46 0.26 0.35 0.33 0.33 0.34 H20+ % WET 0 3 2.7 3.8 3.1 3 4.1 4 C02 % COULOM 0.01 6.95 2.94 7.45 5.24 4.78 5.92 7.79 S % LECO 0.005 0.01 0.146 0.279 1.08 0.258 0.014 0.4 SUM % 99.4 99.8 98.6 98.6 98.2 99 98.1 LOI % 9.7 4.45 7.35 6.85 6.05 9.65 II Ba ppm XRF 1.0 1450 860 644 960 1730 668 2160 Rb ppm XRF 2.0 54 72 40 107 . 104 45 76 Sr ppm XRF 1.0 442 590 325 137 133 193 382 Nb ppm XRF 2.0 10 8 4 8 10 7 7 Zr ppm XRF 1.0 141 139 88 120 120 99 101 Y ppm ICP 1.0 31 11 15 20 19 25 21 Au ppb NA 2.0 -2 7 5 130 7 -2 -2 Ag ppm ICP 0.1 0.4 0.2 0.2 0.7 0.5 0.5 0.3 Cu ppm ICP 0.5 2.2 84.3 155 21 17.4 41.3 34.3 Pb ppm ICP 2.0 -2 9 -2 -2 -2 -2 -2 Zn ppm ICP 0.5 109 67.1 101 74.1 73.2 100 90.2 As ppm NA 0.1 1 5.3 1.2 99 15 1.1 3.5 Sb ppm NA 0.1 0.9 0.9 0.7 7 3.7 1.1 2.8 Hg ppm WET 5.0 14 70 17 141 132 34 51 Co ppm ICP 1.0 10 12 21 8 6 19 14 Cr ppm NA 2.0 16 87 22 31 21 24 16 B ppm DCP 10.0 23 18 17 39 38 28 43 Cl ppm XRF 100.0 100 108 -100 108 107 -100 -100 Sc ppm ICP 0.05 11.4 10.6 21.7 10.6 10.5 19.7 18.5 V ppm DCP 2.0 167 176 236 142 140 244 217 Ni ppm ICP 1.0 -1 15 4 -1 -1 2 7 Ge ppm DCP 10.0 -10 -10 -10 -10 -10 -10 -10 Se ppm NA 1.0 -1 -1 -1 -1 -1 -1 -1 Mo ppm ICP 1.0 -1 -1 -1 -1 -1 -1 -1 Cd ppm AA 0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 Te ppm GFAA 0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 Cs ppm NA 1.0 2 1.5 2.1 3.8 3.9 3 3 La ppm ICPMS 0.1 20 17 8.4 19.1 17.5 16.3 15 Ce ppm ICPMS 0.1 39 31.4 17.9 39.6 36.3 32.6 31 Pr ppm ICPMS 0.1 4.9 3.6 2.3 4.9 4.5 4.2 4.1 Nd ppm ICPMS 0.1 21.1 14.5 10.5 20.3 18.8 18.1 17.6 Sm ppm ICPMS 0.1 5.8 3.3 3.1 5.2 4.7 5.1 4.7 Eu ppm ICPMS 0.05 2.19 0.98 1.03 1.4 1.67 1.76 2.15 Gd ppm ICPMS 0.1 6.4 3.1 3 5.1 4.7 5.2 6.6 Tb ppm ICPMS 0.1 0.9 0.5 0.5 0.8 0.7 0.8 0.7 Dy ppm ICPMS 0.1 5.3 2.8 3.3 4.8 4.4 4.9 4.3 Ho ppm ICPMS 0.05 1.03 0.57 0.7 0.96 0.91 0.98 0.82 Er ppm ICPMS 0.1 3 1.6 2 2.9 2.6 2.8 2.3 Tm ppm ICPMS 0.1 0.4 0.3 0.3 0.4 0.4 0.4 0.3 Yb ppm ICPMS 0.1 2.8 1.7 1.9 2.8 2.6 2.5 2.2 Lu ppm ICPMS 0.05 0.43 0.28 0.3 0.43 0.4 0.38 0.34 W ppm NA 1.0 -1 -1 2 2 2 2 -1 Tl ppm ICPMS 0.1 0.4 0.3 0.3 1 0.9 0.4 1.4 Bi ppm ICPMS 1.0 -1 -1 -1 -1 -1 -1 -1 Th ppm NA 0.5 3.8 5.1 1.6 4.1 3.8 2.6 3.3 U ppm NA 0.1 2.1 5 1.1 2.8 2.2 1.5 1.6 160 Tabled AK92-30 AK92-28 AK93-120 AK93-68 AK93-124 AK93-121 AK93-117 AK93-127 AK93-105 Lithology la la la la la la la la la Alt Index 15 16 17 17 17 18 18.5 18.5 19 Alt Type chl+il/sm chl+ill ill vn il/sm chl+ill per ill transitional per ill ill Location CP LAZ LAZ UAZ(200) LAZ LAZ UAZ(200) LAZ LAZ Drill hole 88-5 87-1 90-1 90-1 90-5 90-1 89-8 Interval (m) 49.5 55-55.5 207-208 193-194 60-61 271-272.5 89-89.5 NTSe NTSn Batch 11 11 12 12 12 12 12 12 12 Si02 55 49 50 52.3 53.9 53.3 54.3 51.S 60 A1203 15.6 16.3 16.2 13.8 15.5 16.5 14.1 16 14.3 Fe203 6.54 7.78 8.89 6.89 9.14 6.65 6.63 8.51 6.85 Ti02 0.776 0.928 0.746 0.878 0.724 0.802 0.658 0.605 0.548 MnO 0.23 0.24 0.17 0.47 0.24 0.15 0.38 0.13 0.11 MgO 2.52 2.24 4.43 1.72 2.76 2.79 1.9 1.55 1.03 Na20 0.5 2.18 2.4 0.15 3.18 0.65 0.26 0.26 0.25 CaO 6.12 7.9 5.69 8.36 4.12 4.52 6.71 5.93 2.77 K20 3.44 3.17 2.16 3.9 2.26 4 3.74 4.23 4.01 P205 0.36 0.44 0.23 0.37 0.27 0.26 0.31 0.22 0.35 H20+ 1.6 2.7 3.8 2.4 2.2 2.1 2.1 2.6 2.5 C02 4.26 6.02 2.87 7.97 4 5.89 8.11 5.18 1.77 S 0.017 0.041 4.22 2.94 5.74 4.12 1.43 6.1 5.32 SUM 99.2 99.1 98.2 95.6 99 97.1 96.1 97 99 LOI 7.95 8.65 7.25 6.7 6.8 7.35 7 6.93 6.23 Ba 966 2010 385 647 834 989 1070 7120 22700 Rb 95 66 61 122 43 94 115 108 103 Sr 105 380 211 160 316 310 167 540 409 Nb 8 II 6 7 9 7 9 7 4 Zr 115 117 70 101 98 88 113 77 32 Y 20 24 12 17 12 15 19 13 7 Au -2 -2 11 860 42 120 190 110 77 Ag 0.2 0.7 0.4 4.5 1.1 0.8 0.5 4.5 0.7 Cu 37.7 5.9 65.9 52.1 124 140 20.4 528 31.2 Pb -2 -2 2 -2 35 14 -2 84 43 Zn 91 96.7 80.3 44.8 99.3 52.1 71.8 98.3 35.4 As 1.1 2.2 15 290 44 71 290 95 150 Sb 1.7 2.5 1.6 6.9 2.3 1.7 7.8 8.9 7 Hg 18 39 14 91 8 93 16 62 26 Co 10 10 24 14 14 19 5 23 11 Cr 18 18 47 24 63 50 18 27 78 B 56 43 24 41 23 32 29 38 37 CI -100 -100 -100 127 -100 -100 -100 -100 -100 Sc 12.1 13.5 22.9 15.8 16.5 19.9 10.4 12.3 9.45 V 154 169 247 210 174 220 126 182 98 Ni -1 -1 10 -1 -1 4 -1 3 7 Ge -10 14 -10 -10 -10 -10 -10 -10 -10 Se -1 -1 6 -1 -1 -1 -1 19 14 Mo -1 -1 -1 -1 -1 -1 -1 -1 -1 Cd -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 Te -0.02 -0.02 0.22 -0.02 0.22 0.16 -0.02 2 0.45 Cs 2 3 9.1 4.4 2.5 2.3 4.1 3.8 3.3 La 26.3 21.4 5.8 16 9.1 7.4 16 10.4 9 Ce 42.1 41.6 12.8 32.4 19.2 16.8 33.1 20.9 17.3 Pr 5.8 5.2 1.7 4 2.5 2.2 4.1 2.6 2.1 Nd 23.7 21.6 7.7 17.2 II 10.1 17.3 11.1 8.6 Sm 5.7 5.6 2.3 4.6 3 3 4.3 2.9 2.3 Eu 2.05 2.29 0.73 0.78 0.91 0.81 1.22 1.43 1.8 Gd 5.9 7 2.4 4.3 3 3 4.4 2.9 2.2 Tb 0.8 0.8 0.4 0.7 0.5 0.5 0.7 0.5 0.3 Dy 4.8 5 2.8 4.2 3.1 3.4 4.2 2.9 1.8 Ho 0.89 0.95 0.59 0.88 0.65 0.7 0.86 0.6 0.36 Er 2.6 2.7 1.7 2.4 1.8 2 2.5 1.7 1.1 Tm 0.3 0.4 0.3 0.4 0.3 0.3 0.4 0.3 0.2 Yb 2.3 2.5 1.6 2.4 1.8 2 2.5 1.7 1.1 Lu 0.35 0.38 0.26 0.37 0.29 0.31 0.38 0.26 0.17 W 3 -1 6 9 5 3 4 3 6 Tl 1.4 1.4 1 1.6 0.7 1.4 1 1.2 1.2 Bi -1 -1 2 -1 1 2 -1 2 1 Th 3.7 4.6 1.6 3.8 1.9 1.7 3.2 1.9 2.4 U 1.6 1.5 0.9 2.2 1.3 0.5 2.3 0.9 1.2 161 Table C.l AK93-U8 AK93-128 AK93-44 AK93-45 AK92-5 AK92-9 AK92-29 AK93-111 AK92-7 Lithology la la la la lb Id Id Id Id Alt Index 20 20 20.5 20.5 na 7 8 11 11.5 Alt Type medial il/sm per ill upper il/sm medial il/sm incipient incipient incipient chl+ill chl+ill Location UAZ(200) LAZ UAZ(320) UAZ(320) Crk 12 Crk 14 CP LAZ Crk 14 Drillhole 90-5 90-1 85-30 83-30 89-8 Interval (m) 4041 296.5-297.5 60.35-61.35 93-94 148-149 NTSe NTSn Batch 12 12 12 12 11 11 11 12 11 Si02 53.6 51 56.9 51.1 44.2 52.3 51.9 50 49.4 A1203 16.9 15.6 17.9 15.9 13.4 17.4 17.7 16.1 17.1 Fe203 6.79 8.46 8.4 7.66 10.2 8.35 8.27 11.9 8.37 Ti02 0.691 0.727 0.921 0.811 1.08 1.06 0.861 0.883 1.07 MnO 0.21 0.11 0.02 0.42 0.19 0.22 0.19 0.27 0.24 MgO 1.06 2.54 0.42 1.03 7.35 3.01 2.72 4.69 2.75 Na20 0.21 0.32 0.26 0.31 3.38 4.03 3.94 2.09 5 CaO 6.2 5.42 0.38 6.67 9.52 6.63 6.31 9.15 5.87 K20 4.44 3.54 3.61 4.03 1.26 2.76 3.36 2.52 1.73 P205 0.33 0.23 0.38 0.32 0.5 0.42 0.43 0.25 0.43 H20+ 3.2 2.9 3.9 2.7 3.7 1.4 1 1.9 2.7 C02 4.42 8.07 0.01 4.78 4.37 0.52 1.15 1.74 3.43 S 4.8 2.32 6.35 5.19 0.073 0.009 0.007 0.411 0.014 SUM 97.4 96.7 100 96.2 98.7 98.3 98.4 99.4 98.5 LOI 6.8 8.6 10.6 7.85 7.4 1.8 1.9 1.4 6.45 Ba 1310 1090 2020 636 1360 1670 6280 1550 632 Rb 140 90 84 108 36 49 63 31 35 Sr 135 295 2510 140 520 836 1080 551 585 Nb 10 3 10 9 7 10 11 7 9 Zr 125 78 275 118 82 135 108 84 133 Y 21 12 25 13 20 30 19 13 29 Au 39 6 9 33 -2 -2 -2 -2 -2 Ag 1.6 -0.1 -0.1 0.5 0.8 0.3 0.4 0.4 0.4 Cu 20.1 81.4 26.9 16.8 172 19.2 8.4 49.8 12.9 Pb -2 -2 -2 -2 -2 -2 -2 2 -2 Zn 68.6 43 91.9 56.8 78.5 102 95.9 115 92.4 As 68 0.7 25 64 21 2.5 3.2 12 2.5 Sb 9.2 1.1 43 11 1.2 1 0.8 2.2 0.9 Hg 592 19 2010 141 7 -5 -5 -5 6 Co 7 20 6 8 31 16 13 23 14 Cr 16 44 15 34 26 34 30 61 18 B 48 27 75 44 20 27 35 -10 33 CI -100 -100 117 113 120 171 188 219 -100 Sc 9.97 16.9 13.2 9.87 38 19.2 13.2 29 16.7 V 136 228 203 151 365 207 210 328 232 Ni -1 4 -1 -1 17 -1 -1 10 .1 Ge -10 -10 -10 -10 -10 -10 -10 -10 -10 Se -1 12 -1 -1 -1 -1 -1 -1 -1 Mo -1 -1 -1 -1 -1 -1 -1 -1 -1 Cd -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 Te -0.02 0.12 1.6 -0.02 -0.02 -0 02 -0.02 -0.02 -0.02 Cs 5 3.3 5.5 6.3 3 2 2 1.7 4 La 17.8 7 20.4 15.7 17 20.9 21.3 7.1 20.9 Ce 36.4 14.9 42 32.8 36.3 40.7 40.6 15.1 40.5 Pr 4.4 1.9 5.1 4 4.9 5.1 4.9 2 5 Nd 18.3 8.6 22 17.1 22 22 19.9 8.9 21.3 Sm 4.6 2.5 5.9 4.4 5.8 6 5.2 2.7 5.9 Eu 1.42 0.85 2.03 1.22 2.18 2.18 3.43 0.95 2.01 Gd 4.5 2.6 6.5 4.2 6.3 6.4 7.8 2.8 5.8 Tb 0.7 0.4 1.1 0.7 0.8 0.9 0.7 0.5 0.9 Dy 4.3 2.8 6.6 4.2 4.4 5.9 4.5 2.9 5.8 Ho 0.89 0.58 1.41 0.87 0.8 1.19 0.84 0.61 1.15 Er 2.5 1.7 4 2.5 2.3 3.4 2.5 1.7 3.3 Tm 0.4 0.3 0.6 0.4 0.3 0.5 0.4 0.2 0.5 Yb 2.5 1.6 3.8 2.4 1.9 3.2 2.4 1.6 3.1 Lu 0.38 0.26 0.62 0.39 0.28 0.49 0.35 0.28 0.47 W 5 -1 2 3 2 1 2 2 4 Tl 1.4 1.6 2.6 14 0.5 0.3 1 0.3 0.3 Bi -1 -1 3 -1 -1 -1 -1 1 -1 Th 4.1 1.7 4.5 4.1 2 4.2 3.6 1.7 3.8 U 2.8 0.8 2.6 2.3 0.9 2 1.8 1 1.8 162 Table C.l AK93-U4 AK92-20 AK92-25 AK93-26 AK93-115 AK92-22 AK92-24 AK93-56 AK93-70 Lithology Id Id Id Id Id Id Id Id Id Alt Index 14 14.5 13.5 15 15 16 16.5 18 18 Alt Type chl+il/sm chl+ill chl+ill chl+il/sm chl+il/sm ill ill chl+il/sm chl+il/sm Location UAZ(200) Crk 12 Crk 3 UAZ UAZ(200) Crk 12 Crk 3 UAZ(320) UAZ(200) Drillhole 90-5 90-5 85^0 87-1 Interval (m) 157-158 125-127 43.5^ 4.5 90.5-92 NTSe NTSn Batch 12 11 11 12 12 II 11 12 12 Si02 50.5 59.3 50.3 49.2 45.6 61 49.9 45 54.3 A1203 17.6 17.6 17.3 17 14.2 17.6 17.3 19.4 17.7 Fe203 9.41 5.01 6.64 9.28 12.6 4.33 6.58 9.9 9.5 Ti02 0.871 0.585 0.839 0.822 0.931 0.591 0.815 0.944 0.917 MnO 0.19 0.16 0.27 0.29 0.28 0.12 0.38 0.28 0.15 MgO 2.28 1.4 2.69 2.67 3.44 1.87 1.74 2.97 2.21 Na20 1.53 5.35 3.49 0.17 0.64 4.49 2.93 0.51 0.28 CaO 5.14 2.67 6.73 7.37 7.4 1.73 7.76 6.29 2.88 K20 6.6 4.25 3.1 3.89 2.57 2.29 3.23 5.03 4.4 P205 0.44 0.22 0.42 0.43 0.39 0.21 0.42 0.46 0.35 H20+ 2.6 1.2 3.2 4.1 4.2 2.3 2.7 4.1 4.2 C02 3.27 0.75 4.68 5.63 5.51 0.34 7.06 5 1.8 S 0.031 0.027 0.042 0.044 4.7 2.64 1.12 2 1.05 SUM 99.1 98.3 99.4 98.9 95.3 98.6 98.9 96.6 99.2 LOI 4.15 1.4 7.4 7.65 7.1 4.1 765 5.65 6.2 Ba 3300 2200 1670 1490 1590 1210 1180 1170 2880 Rb 136 84 67 116 76 52 72 150 111 Sr 291 874 501 187 152 731 392 155 104 Nb 7 12 9 7 9 13 9 13 11 Zr 106 151 108 105 92 150 107 119 91 Y 19 18 18 22 21 18 20 19 16 Au -2 -2 -2 -2 4 -2 -2 56 4 Ag 0.4 0.5 0.4 0.3 0.6 0.5 0.1 0.7 0.4 Cu 6.5 27 2.3 8.7 51.2 29.7 2.3 5.5 131 Pb -2 -2 -2 -2 -2 -2 -2 10 7 Zn 85.6 59 88 106 90.6 121 63.5 107 146 As 4.1 3.6 3.2 2.8 8.8 2.5 5.6 86 5.7 Sb 6.6 1.6 2.5 5.5 5.3 1.2 2.7 9.4 5.5 Hg 37 -5 18 19 86 42 40 12 130 Co 9 9 11 9 19 12 9 10 12 Cr 15 54 16 15 17 30 24 12 25 B 17 30 32 40 34 42 39 40 35 Cl 103 -100 106 -100 -100 -100 -100 110 138 Sc 12.7 9.85 12.2 13.6 20.1 8.51 12.1 13.2 12.1 V 222 121 156 205 245 113 167 223 217 Ni -1 1 -1 -1 2 2 -1 -1 -1 Ge -10 -10 13 -10 -10 -10 -10 -10 -10 Se -1 -1 -1 -1 -1 -1 -1 -1 -1 Mo -1 -1 -1 -1 -1 2 -1 -1 -1 Cd -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 Te -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 Cs 7.7 1 1 4.5 4.2 4 2 7.7 6.6 La 18.2 20.1 21.2 19.5 15.2 21.7 16.6 22.3 15 Ce 36.1 36.4 40.4 37 31.9 40.9 31.8 48 31.1 Pr 4.3 4.2 4.9 4.5 4.1 4.8 3.9 5.8 4 Nd 18.1 16.3 20.1 19.1 17.7 19.6 16.5 24.4 17.8 Sm 4.5 3.9 4.9 4.9 4.7 4.8 4.5 6.2 4.8 Eu 1.37 1.83 1.95 1.56 1.47 1.8 1.7 2.1 2.12 Gd 4.4 4.4 5.6 4.7 4.6 4.9 4.8 6 4.4 Tb 0.7 0.6 0.7 0.7 0.8 0.7 0.7 1 0.7 Dy 4.1 3.5 3.8 4.4 4.4 4.1 3.8 5.6 4 Ho 0.84 0.67 0.72 0.88 0.92 0.75 0.78 1.09 0.83 Er 2.4 2 2.1 2.5 2.7 2.2 2.2 3.1 2.4 Tm 0.4 0.3 0.3 0.4 0.4 0.3 0.3 0.5 0.4 Yb 2.3 2.1 2.1 2.4 2.5 2 2.2 2.9 2.5 Lu 0.38 0.33 0.32 0.38 0.38 0.31 0.31 0.44 0.4 W 4 5 6 2 2 6 6 4 3 Tl 1.8 1.3 1.9 1.4 0.7 1.5 1.7 2.2 2 Bi 1 -1 -1 -1 -1 -1 -1 -1 -1 Th 4.3 6.5 3.9 4.2 3.4 7.2 3.7 4.6 4.4 U 2 3.9 1.5 2.2 2 4 1.5 2.1 2.6 163 T a b l e d AK93-87 AK93-1I0 AK93-U2 AK92-21 AK9341 AK92-3I AK92-8 AK92-14 AK92-15 Lithology Id Id Id Id Id Id 2a 2a 2a Alt Index 18.5 18.5 20 20.5 21 na na na na Alt Type ill per ill per ill ill upper il/sm incipient incipient incipient incipient Location LAZ LAZ LAZ Crk 12 UAZ(320) Crk 1 Crk 14 HR HR Drill bole 88-2 89-8 89-8 85-29 Interval (m) 97.5-98.5 136-137 176-177 91-92 NTSe NTSn Batch 12 12 12 11 12 II 11 11 11 Si02 52.7 43.7 56.4 54.8 55.7 45 57.8 46.8 53.6 A1203 16.2 14.5 17.2 23.7 17.9 13.9 17.2 16.7 17.7 Fe203 6.64 16.4 6.75 4.97 7.75 5.7 5.1 10.4 7.05 Ti02 0.551 0.816 0.878 1.09 0.901 0.41 0.56 1.23 0.989 MnO 0.17 0.33 0.18 0.05 0.04 0.42 0.15 0.22 0.18 MgO 1.31 2.05 1.97 0.78 0.8 2.3 1 3.34 2.97 Na20 0.48 0.25 0.29 0.91 0.33 3.62 3.91 4.74 5.04 CaO 4.64 5.55 3.08 0.09 0.75 12.8 4.59 7.21 3.67 K20 8.77 3.52 4.7 6.2 3.83 4.16 4.34 1.5 3.62 P205 0.98 0.28 0.27 0.23 0.2 0.19 0.21 0.46 0.46 H20+ 1.4 2.5 2.7 2.6 4.3 1.1 1.5 2.3 1.8 C02 3.38 7.29 4.31 0.02 -0.01 8.99 2.61 3.75 0.56 S 4.65 9.81 3.36 3.03 5.49 0.115 0.008 0.008 0.011 SUM 98.4 99 98.2 98.6 100.2 98.6 99 98.8 98.2 LOI 5.15 11.4 6.25 5.4 11.6 9.7 3.85 5.95 2.4 Ba 7020 1510 2150 3770 3420 2970 2120 1480 2190 Rb 156 70 99 156 91 79 89 24 63 Sr 441 188 167 71 448 661 793 610 2000 Nb 5 3 5 12 9 6 10 8 12 Zr 80 62 78 146 145 80 144 111 176 Y 10 12 12 8 17 12 17 30 30 Au 11 170 19 -2 16 -2 -2 -2 -2 Ag 0.3 2.4 0.5 0.2 0.1 0.9 0.6 0.2 0.6 Cu 11.3 118 9.9 26.6 22.2 49.2 30.4 30 7.3 Pb 97 31 114 -2 -2 -2 -2 -2 -2 Zn 74 75.9 50.2 61.9 49.2 55.9 61.9 100 103 As 26 150 40 0.9 19 6.4 1.5 4.9 7.5 Sb 1.5 4.1 1.3 0.9 37 0.9 0.9 0.6 0.7 Hg 18 10 5 10 1470 21 11 69 7 Co 12 32 15 12 7 14 10 19 10 Cr 100 94 70 22 12 28 31 16 15 B 18 20 30 39 90 25 37 26 49 CI -100 -100 -100 -100 123 133 110 122 236 Sc 9.78 22.7 24.7 17.8 15.1 12.3 9.4 24.4 12 V 152 271 279 252 177 125 126 295 197 Ni 11 10 5 2 -1 11 1 -1 -1 Ge -10 -10 -10 -10 -10 -10 -10 19 -10 Se 11 -1 -1 -1 -1 -1 -1 -1 -1 Mo -1 -1 1 2 1 -1 -1 -1 -1 Cd -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 Te 0.06 1.42 0.16 -0.02 1.02 -0.02 -0.02 -0.02 -0.02 Cs 2.9 1.6 1.9 3 6 1 5 1 4 La 13 7.7 8.7 5.5 19.4 10.4 20.4 19.4 24 Ce 24.5 16.1 19.1 14.3 39.9 18 36.3 40.3 46.1 Pr 2.9 2.1 2.6 2.3 4.8 2.2 4.2 5.2 5.7 Nd 11.9 9.4 11.5 10.1 19.5 8.9 16.2 22.3 24 Sm 2.9 2.7 3.3 3.4 4.1 2.3 3.9 6.3 6.3 Eu 1.74 0.92 0.9 1.91 1.27 1.69 1.78 2.38 2.62 Gd 2.8 2.7 3.4 3.3 3.8 4.7 4.3 6.9 6.9 Tb 0.4 0.5 0.6 0.4 0.6 0.4 0.6 1 1 Dy 2.4 2.9 3.6 2.6 4.4 2.2 3.4 6.1 6.3 Ho 0.49 0.6 0.76 0.56 0.94 0.48 0.64 1.19 1.23 Er 1.4 1.7 2.2 1.9 2.8 1.4 2 3.5 3.6 Tm 0.2 0.3 0.3 0.3 0.4 0.2 0.3 0.5 0.5 Yb 1.3 1.7 2.1 2 2.6 1.5 2 3.1 3.4 Lu 0.21 0.28 0.33 0.35 0.43 0.25 0.33 0.48 0.52 W 3 -1 -I 8 5 3 2 3 4 Tl 2.2 1 1.4 2.4 2.7 0.8 0.6 0.4 0.6 Bi 1 1 -1 -1 -1 -1 • -1 -1 -1 Th 3.6 1.6 1.6 6.3 4.1 2.1 7.4 3.2 4.9 U 1.9 0.9 1.4 2.3 2.2 2.1 3.5 1.6 2.2 164 Tabled AK92-16 AK92-17 AK92-18 AK92-19 AK93-8 AK93-2 AK93-144 AK93-1 AK92-1 Lithology 2a 2a 2a 2a 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) Alt Index na na na na 10 10.5 11 11.5 14.5 Alt Type incipient incipient incipient incipient incipient incipient chl+il/sm incipient il/sm Location HR HR HR HR RG RG FZ RG RG Drill hole 87-7 Interval (m) 114-115 NTSe NTSn Batch 11 11 II 11 12 12 12 12 II Si02 49.1 49.9 53.9 53.1 57.7 50.7 55 64 60.9 AI203 17.3 17.8 17.6 17.9 175 17.5 16.1 15.3 17.1 Fe203 8.75 9.9 6.89 6.84 6.44 9.36 6.3 5.97 4.98 Ti02 1.02 1.04 0.855 0.891 0.632 1.13 0.604 0.505 0.683 MnO 0.46 0.2 0.33 0.13 0.17 0.19 0.27 0.1 0.03 MgO 0.84 1.39 2.66 1.55 1.59 1.59 1.7 1.19 1.15 Na20 3.13 3.55 3.85 4.14 4.1 3.44 1.27 1.77 3.26 CaO 9.8 7.11 5.91 7.13 5.91 8.41 6.05 2.42 0.79 K20 2.18 2.9 2.86 2.56 3.18 1.93 6.16 4.15 3.86 P205 0.37 0.39 0.36 0.38 0.29 0.39 0.28 0.23 0.28 H20+ 1.4 2 1.6 1.3 1.1 1.8 2.5 2.9 3 C02 4.2 2.64 1.19 2.77 2.07 3.69 4.62 1.62 0.01 S 0.017 0.024 0.01 0.191 0.091 0.017 0.182 0.049 3.27 SUM 98.3 99.2 98.3 98.5 100.3 99.8 100 100.3 99.3 LOI 5 4.7 2.7 3.55 2.5 5.05 6 4.45 6.1 Ba 1870 2110 2390 2080 2760 1230 2600 2360 1440 Rb 34 49 46 40 59 40 141 85 82 Sr 993 846 893 878 845 634 330 127 258 Nb 11 11 12 12 11 10 12 11 13 Zr 119 119 129 117 156 148 143 125 149 Y 21 20 21 21 17 21 16 15 17 Au -2 -2 -2 -2 -2 -2 5 -2 4 Ag 1 0.5 0.8 0.4 0.3 0.5 0.7 0.5 0.3 Cu 21 27 14.3 15.8 17.6 23.4 53.7 23.6 25.8 Pb -2 -2 -2 -2 -2 -2 -2 3 -2 Zn 101 128 100 84.2 76 316 62.5 54.9 190 As 3 0.8 0.4 0.6 3.8 2.4 10 3.5 24 Sb 0.2 0.3 -0.1 -0.1 11 0.5 36 3.5 1.3 Hg 134 253 13 35 25 9 342 40 5830 Co 14 12 13 16 7 9 II 7 14 Cr 20 17 37 39 37 17 30 23 31 B 12 17 26 16 -10 -10 -10 17 38 Cl -100 -100 -100 -100 -100 -100 138 106 -100 Sc 25.4 24.7 15.8 15.6 11.3 17.9 14.4 8.23 10.1 V 192 246 184 169 139 202 177 74 127 Ni -1 -1 -1 -1 -1 -1 -1 -1 2 Ge -10 -10 -10 -10 -10 -10 -10 -10 -10 Se -1 -1 -] -1 -1 -1 -1 -1 -1 Mo -1 -1 -1 -1 -1 -1 -1 -1 -1 Cd -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 Te -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 Cs 1 2 1 1 2.5 5.1 8.1 5.2 3 La 19.1 20.6 20.6 19.6 19.5 175 21.9 20.5 12.1 Ce 38.2 39.8 40.6 37.8 36.5 35.8 40.8 35.8 25.5 Pr 4.8 5 5 4.8 43 4.5 4.7 4.4 3.3 Nd 20.4 20.5 20.5 20.4 17.2 19 18.7 17.2 15.1 Sm 5.3 5.3 5.3 5.3 4 4.9 4.5 4 4.2 Eu 2.23 2.13 2.4 2.29 1.56 1.72 1.56 1.15 1.54 Gd 6.6 5.6 5.9 6.4 4 4.9 4.3 3.9 3.5 Tb 0.8 0.7 0.7 0 8 0.6 0.8 0.6 0.6 0.5 Dy 4.5 4.3 4.5 4.8 3.5 4.6 3.6 3.3 3.3 Ho 0.86 0.8 0.83 0.86 0.69 0.94 0.8 0.65 0.69 Er 2.4 2.3 2.4 2.5 2 2.6 2 1.9 2.1 Tm 0.3 0.3 0.3 0.4 0.3 0.4 0.3 0.3 0.3 Yb 2.3 2.1 2.2 2.4 2 2.5 2.1 1.9 2.1 Lu 0.34 0.32 0.33 0.35 0.32 0.38 0.32 0.3 0.34 W 3 9 5 5 -1 2 2 5 7 Tl 0.5 0.5 0.6 0.5 0.3 0.1 2.1 0.7 1.7 Bi -1 -1 -1 -1 -1 -1 2 -1 -1 Th 3 2.9 3.5 2.7 4.9 3.2 9.4 9.1 7.1 U 1.6 1.6 1.6 1.8 3.7 2.1 3.5 4.4 3.8 165 Table C.l AK92-2 AK93-143 AK93-33 AK93-155 AK93-140 AK93-141 AK93-158 AK93-151 AK93-249 Lithology 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) Alt Index 10 16.5 19 20 20.5 20.5 21 21.5 21.5 Alt Type il/sm ksp+il/sm prxml kaol transitional ksp+il/sm ksp+il/sm prxml kaol medial il/sm upper il/sm Location RG FZ RG FH FZ FZ FH FH FH Drillhole 87-7 934 87-7 87-7 934 93-3 93-2A Interval (m) 93-93.5 56-57 30.5-31.5 40-41 158.5-159 38.641.8 133-134 NTSe NTSn Batch 11 12 12 12 12 12 12 12 12 Si02 57.2 61.3 53.2 54.9 60 643 53.5 58 60.8 A1203 17.3 16.7 15.9 15.9 15.1 12.2 16.2 16.7 16.2 Fe203 6.21 5.98 7.39 9.38 6.73 7.24 6.94 7.12 6.95 Ti02 0.63 0.677 0.524 0.709 0.602 0.555 0.749 0.67 0.689 MnO 0.16 0.03 0.14 0.06 0.03 0.04 0.16 0.1 0.03 MgO 2.04 0.67 1.32 2.81 0.79 0.52 1.91 1.03 1.47 Na20 3.61 0.32 0.25 0.17 0.24 0.28 0.4 0.32 0.3 CaO 5.69 0.51 6.58 2 0.75 0.44 5.94 2.94 0.62 K20 2.91 7.58 5.4 3.35 7.24 6.43 3.31 4.16 4.52 P205 0.31 0.28 0.22 0.31 0.23 0.25 0.33 0.33 0.39 H20+ 1.9 2.4 3.4 3.2 2.7 2 3.3 3.1 3.2 C02 2.51 0.02 6.16 2.26 0.02 0.03 5.06 1.9 0.02 S 0.038 3.96 0.029 6.18 4.67 5.24 5.04 5.37 5.45 SUM 100.4 100.5 98.7 100.4 100.2 100.3 99.4 99.2 100.1 LOI 4 6.25 7.65 10.8 8.3 7.08 9.8 7.7 7.8 Ba 2150 1800 1170 189 1800 8430 1230 1480 2910 Rb 58 152 89 86 178 149 86 100 116 Sr 755 105 95 55 72 129 124 187 260 Nb 12 11 12 8 10 7 12 13 10 Zr 127 129 140 111 123 84 110 126 135 Y 19 16 19 14 13 II 16 17 14 Au -2 42 -2 130 300 1700 63 220 390 Ag 0.5 0.7 0.5 0.4 0.6 6.8 0.5 0.4 0.2 Cu 18.2 69.3 29.5 16.1 40.9 49.5 17.7 21.1 26.1 Pb 190 12 -2 28 -2 -2 49 89 58 Zn 108 51.2 59.4 358 46.1 71.4 67.5 65.1 92.7 As 1.4 98 0.1 22 250 1100 29 47 96 Sb 0.3 110 2.8 8.5 63 220 13 22 27 Hg 177 2790 185 373 1550 7610 56 83 198 Co 7 16 9 11 10 11 10 9 9 Cr 32 39 14 24 29 61 30 20 30 B 26 -10 14 85 52 65 64 132 107 CI 122 143 146 112 131 115 124 101 -100 Sc 11.3 16 11 11.6 13.6 11.2 13.2 11.4 9.32 V 136 183 104 164 121 76 164 155 137 Ni -1 2 -1 -1 -1 1 -1 -1 -1 Ge -10 -10 -10 -10 -10 -10 -10 -10 -10 Se -1 -1 -1 -1 -1 -1 24 12 19 Mo -1 -1 -1 163 1 -1 13 39 13 Cd -0.2 -0.2 -0.2 1.1 -0.2 -0.2 -0.2 -0.2 0.9 Te -0.02 0.98 -0.02 0.18 1.42 0.45 0.04 0.43 0.49 Cs 3 5.4 4.5 9.3 30.5 13.3 7.4 8.4 9.5 La 22.3 21.7 14.1 15.2 18.8 16.2 17.2 17.8 19.1 Ce 40.3 44 28.5 30 353 29.3 33.9 33.5 40.2 Pr 4.7 5.3 3.3 3.5 4 3.3 4 3.9 4.9 Nd 18.3 20.9 13.3 14.1 15.4 13 4 16.6 15.8 20.2 Sm 4.6 5.1 4.1 3.7 3.3 3.2 4.1 4 4.9 Eu 1.78 1.43 1.42 0.9 0.91 1.13 111 2.08 1.34 Gd 4.4 4.3 4.7 3.6 3.2 2.9 3.8 3.7 4.5 Tb 0.6 0.6 0.7 0.6 0.5 0.4 0.6 0.6 0.7 Py 3.6 3.5 4.3 3.3 2.8 2.4 3.5 3.4 3.8 Ho 0.71 0.73 0.87 0.67 0.59 0.47 0.71 0.68 0.75 Er 2.1 2.1 2.5 2 1.7 1.3 2 2 2.2 Tm 0.3 0.3 0.4 0.3 0.3 0.2 0.3 0.3 0.3 Yb 2 2.1 2.4 1.9 1.9 1.4 2 2 2.1 Lu 0.32 0.34 0.38 0.32 0.3 0.23 0.31 0.3 0.33 W 4 6 1 5 10 7 -1 6 II Tl 0.3 4.1 18 2.3 3.8 19.2 1.7 10.9 4.4 Bi -1 1 -1 2 1 1 4 3 -1 Th 4.8 9.7 9.4 7.1 8.8 7.4 7 8 8.2 U 2.7 7.2 5.6 6 5.6 3.3 5.3 6.1 5.6 166 Table C.l AK93-7 AK93-152 AK93-11 AK93-153 AK93-154 AK93-250 AK93-10 AK92-3 AK92-4 Lithology 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a(bi) 2a A A Alt Index 22 22 22.5 22.5 23 24 21 na na Alt Type prxml kaol transitional prxml kaol prxml kaol transitional silicification prxml kaol incipient incipient Location RG FH RG FH FH SZ RG BB BB Drill hole 93-4 93-4 93-4 Interval (m) 23-24 43.6-44.2 48.5-49.5 NTSe NTSn Batch 12 12 12 12 12 12 12 11 11 Si02 61.3 52.7 54.6 63 51.4 97.1 57.4 59.8 57.2 A1203 20.3 20 20.3 16.9 20.2 0.34 19.3 17.6 17.5 Fe203 5.79 9.76 8.8 6.12 10.4 0.54 7.8 3.68 2.72 Ti02 0.782 1.25 1.02 0.981 1.17 0.479 0.813 0.306 0.321 MnO 0.02 0.03 0.04 0.02 0.02 0.02 0.03 0.14 0.14 MgO 0.09 0.42 0.04 0.22 0.62 0.05 0.69 0.66 0.91 Na20 0.14 0.17 0.19 0.27 0.27 0.13 0.15 4.36 4.05 CaO 0.08 0.21 0.12 0.27 0.29 0.03 0.06 4.37 5.54 K20 0.11 1.67 0.04 1.4 2.45 0.04 2.6 3.5 3.87 P205 0.35 0.58 0.27 0.58 0.43 0.02 0.39 0.16 0.18 H20+ 7 6.4 7.2 5.1 5.8 0.2 5.5 1.6 2 C02 -0.01 0.02 -0.01 0.01 0.02 0.02 -0.01 2.1 4.1 S 4.53 6.87 7.12 4.94 7.97 0.096 5.56 0.011 0.069 SUM 99.9 100.4 100.2 99.7 99.9 99.5 100.3 98.8 98.6 LOI 10.9 12.5 12.6 9.4 12.5 0.55 10.8 37 5.8 Ba 639 10300 19500 4740 1190 1880 2220 3500 3000 Rb 6 46 -2 27 51 5 65 74 80 Sr 2900 193 1250 3480 2780 76 87 832 690 Nb 15 12 13 9 12 10 12 9 8 Zr 328 116 191 298 294 72 125 89 89 Y 13 13 26 5 16 0 19 14 12 Au 6 -2 77 -2 -2 38 4 -2 -2 Ag 0.5 0.2 -0.1 -0.1 -0.1 0.1 0.3 0.2 1.1 Cu 23.6 11.4 28 19.5 11.6 4.1 33.3 7.3 8.8 Pb -2 -2 7 -2 -2 11 -2 -2 -2 Zn 31.7 149 4.5 17.4 116 6.5 128 62.4 51.4 As 10 80 24 48 47 3.2 8.7 0.6 1 Sb 11 22 9.4 12 14 8.2 1 2.8 3.2 Hg 832 886 707 731 1300 18 1060 268 240 Co 9 13 14 4 13 -1 15 4 4 Cr 33 14 17 20 35 430 25 36 30 B -10 69 -10 53 101 41 60 32 33 Cl -100 -100 -100 -100 -100 -100 -100 -100 -100 Sc 10.4 14 16.5 9.59 28.3 0.28 14.4 3.68 3.95 V 176 243 157 187 253 7 209 65 84 Ni -1 -1 -1 -1 -1 2 -1 -1 -1 Ge -10 -10 -10 -10 -10 -10 -10 -10 -10 Se -1 14 6 2 14 -1 2 -1 -1 Mo -1 -1 -1 -1 -1 23 2 -1 -1 Cd -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 Te -0.02 3.48 -0.02 0.74 0.98 -0.02 -0.02 -0.02 -0.02 Cs -0.5 15.4 -0.5 0.9 3.7 -0.5 5.8 3 3 La 20.3 19.8 26.1 20.7 25.6 0.4 21.3 27.4 32.1 Ce 37.6 44.5 46 41.3 48.7 0.6 36.7 46.3 53.2 Pr 4.4 5.6 5.7 5.1 6.1 -0.1 4.3 5 5.8 Nd 16.7 23.7 24 22.2 25.7 0.3 17.9 18.5 21.8 Sm 3.1 5.9 6 5.7 7.3 -0.1 4.9 3.9 4.7 Eu 0.78 0.81 1.78 1.94 2.45 0.1 1.64 2.07 2.15 Gd 2.7 5.1 5.4 5 9.2 0.1 5 4.7 5.3 Tb 0.4 0.8 0.7 0.6 2 -0.1 0.8 0.5 0.5 Dy 2.6 4.4 4.4 2.4 13 0.2 4.6 2.7 3 Ho 0.6 0.88 0.98 0.39 2.63 -0.05 0.91 0.52 0.55 Er 2 2.5 3.1 1.3 6.6 0.1 2.5 1.5 1.6 Tm 0.3 0.4 0.5 0.2 0.9 -0.1 0.4 0.2 0.2 Yb 2.3 2.5 3.6 1.7 4.9 0.2 2.6 1.6 1.7 Lu 0.36 0.38 0.64 0.28 0.7 -0.05 0.41 0.26 0.27 W 4 -1 3 3 -1 3 5 2 3 Tl 0.2 1.6 0.2 1.4 1.8 -0.1 1.5 0.5 0.5 Bi -1 2 1 2 1 -1 -1 -1 -1 Th 11 5.9 10 4.9 5.4 0.6 8.1 6.4 6.6 U 8.4 2.3 8.5 2.7 2.7 0.7 6.3 2.4 2.8 167 Table C.l AK92-23 AK92-26 AK92-27 AK93-31 AK93-32 AK93-30 AK92-I1 AK92-12 AK92 Lithology A A A A A A B B B Alt Index na 13 17.5 11.5 16.5 11 na na na Alt Type incipient il/sm il/sm chl+il/sm il/sm il/sm Location BB BB BB BB BB BB GP GP GP Drillhole Interval (m) NTSe NTSn Batch 11 II 11 12 12 12 II 11 11 Si02 59.6 61.9 58.5 62.4 64.6 59.6 51.2 47.6 50.7 A1203 17.7 21.1 17.8 20.9 19.8 19.3 16.5 16.3 15.1 Fe203 3.67 1.4 3.84 0.82 0.96 3.91 7.63 7.83 8.5 Ti02 0.34 0.383 0.344 0.397 0.374 0.335 0.408 0.447 0.525 MnO 0.12 -0.01 0.12 0.02 0.02 0.08 0.15 0.16 0.16 MgO 0.52 0.23 0.54 0.31 0.3 0.69 7.22 7.8 7.03 Na20 4.82 0.6 2.42 0.67 0.66 2.92 2.85 1.57 2.8 CaO 3.96 0.02 3.72 0.1 0.09 2.61 8.59 12.8 10.1 K20 3.87 7.79 6.07 7.74 8.48 5.07 1.94 1.2 1.09 P205 0.16 0.09 0.19 0.17 0.13 0.17 0.06 0.06 0.08 H20+ 1.2 3.2 2 3 5 2.8 -0.1 1.4 1.9 2.1 C02 1.7 0.02 2.46 0.01 -0.01 1.67 0.12 0.84 0.4 S 0.005 0.771 0.015 0.02 0.152 0.022 0.012 0.092 0.113 SUM 98.1 98.4 98.4 98.6 100 98.8 99.2 98.1 98.1 LOI 2.8 4.55 4.55 4.75 4.15 3.75 2.5 2.3 1.95 Ba 4160 3160 2810 2740 3830 3060 782 278 488 Rb 78 155 119 139 153 88 36 22 17 Sr 878 119 312 94 112 151 387 292 343 Nb 6 8 10 10 9 7 5 4 5 Zr 95 87 84 95 93 84 43 35 47 Y 16 9 10 9 10 12 14 10 14 Au -2 -2 -2 -2 -2 -2 -2 -2 -2 Ag 0.2 0.5 0.7 -0.1 0.2 0.4 0.1 0.2 0.2 Cu 7.8 16.3 9.7 3.8 3.3 6.4 14.9 69 18.3 Pb 4 -2 -2 -2 -2 5 -2 -2 -2 Zn 64.1 3.7 47.5 11.1 -0.5 89.6 26.5 42.6 21 As 1 17 0.5 5.5 6 3.5 4.5 4.2 4.9 Sb 3.6 15 8 25 20 3 0.3 1.3 0.7 Hg 508 1760 5860 1070 1580 103 7 5 -5 Co 3 4 3 -1 -1 1 28 32 30 Cr 43 23 22 15 29 15 90 440 49 B 187 31 36 24 11 13 31 40 35 CI -100 -100 -100 -100 -100 -100 456 391 557 Sc 3.66 3.05 3.35 2.14 2.13 2.77 40.1 46.1 43.2 V 73 53 57 68 48 65 187 212 223 Ni -1 -1 -1 14 -1 -1 16 71 9 Ge -10 -10 -10 -10 -10 -10 -10 10 -10 Se -1 -1 -1 -1 -1 -1 -1 -1 -1 Mo -1 -1 -1 1 -1 -1 -1 -1 -1 Cd -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 •0.2 Te -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 -0.02 Cs 3 2 4 3.7 2.9 2.9 1 -1 1 La 31 37.8 31.4 30.1 26.1 28.9 4.4 2.9 6.6 Ce 46.7 64.7 52.4 51.9 41.7 49.1 9.5 5.6 15.1 Pr 5.6 7 5.7 5.7 4.5 5.4 1.4 0.8 2.1 Nd 20.8 26.2 21.3 21.3 17 20.2 6.1 3.6 8.6 Sm 4.5 5.6 4.5 4.4 3.5 4.2 2 1.3 2.4 Eu 2.43 2.51 2.02 1.42 1.27 1.35 0.88 0.69 0.91 Gd 5.3 5.8 4.8 3.8 3.1 3.9 2.8 1.8 3 Tb 0.5 0.6 0.5 0.5 0.4 0.5 0.4 0.3 0.4 Dy 3.1 3.6 3 2.6 2.3 3 2.7 1.9 3 Ho 0.58 0.62 0.55 0.46 0.46 0.57 0.56 0.4 0.62 Er 1.8 1.8 1.6 1.4 1.5 1.7 1.6 1.2 1.8 Tm 0.3 0.3 0.2 0.2 0.2 0.3 0.2 0.2 0.3 Yb 1.9 1.9 1.7 1.5 1.8 1.8 1.6 1.2 1.7 Lu 0.3 0.3 0.28 0.25 0.3 0.28 0.25 0.17 0.26 W 16 5 1 3 4 2 3 2 3 Tl 1.7 2.5 1.9 1.8 1.9 0.4 0.5 0.4 0.4 Bi -1 -1 -1 -1 -1 -1 _| -1 -1 Th 6.9 7.9 6.8 9.5 8.7 9 -0.5 -0.5 0.6 U 2.9 3.3 2.8 5.7 4.8 4 0.3 -0.1 0.6 - x w I I - 2 8 ' - x 2 | £ ' 2 8 - x 2 11 2 8 < o < OO O ~J CTv .z I OO K> W — — H P ^ 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Each sample was prepared using a ring-mill to coarse-crush the sample which was then ground into a fine powder using a porcelain mortar and pestal. The powder was then suspended in water and pipeted onto a glass slide and allowed to air-dry. Ethylene glycolated samples were placed in a desiccator for a minimum of 36 hours, removed and analyzed immediately. Heated samples were placed in an oven at 550-600°C for 1 to 1.5 hours allowed to cool for 15 minutes and analyzed. Each sample was analyzed using a Siemens Diffraktometer D5000 at 40.0 kV and 30.0 mA using Cu K-alpha radiation and scanned at 0.02° 29 intervals for 0.8 s between 3.0° and 40.0° two-theta. Oriented samples were used since they enhance the basal 001 section of the various phyllosilicate without compromising those diffraction peaks characteristic of other minerals. Tables D.l and D.2 list the diagnostic peaks for phyllosilicate and important accessory minerals used to define individual alteration assemblages on the Hank property. The interpretation of X-ray diffraction patterns is based on three parameters; peak position, shape, and breadth. Peak position is related to Braggs equation nA,=2dsin6. Moore and Reynolds (1989) indicate that at small diffraction angles (29<40°) the various members of the (001) series for a given mineral are equidistant when one-dimensional (oriented) analyses are made (Figure D. 1). This criterion is used to determine if one or more minerals are present since regularly spaced diffraction peaks will be the product of a single mineral whereas irregular spacing is the product of two or more minerals. Representative X-ray diffraction patterns for illite, smectite, chlorite, kaolinite and dickite are presented in Figure D.l. Diffraction patterns for illite, smectite and chlorite are easily distinguished, whereas kaolinite and dickite diffraction patterns are more similar. Distinctions between kaolinite and dickite are based on a more intense kaolinite (002) peak at 24.8° 20 than the dickite (004) peak, and a prominent dickite (022) peak at 23.4° 29. The breath of a diffraction peak is defined as the width of the diffraction maximum (peak) at half its height and is related to the optically coherent dimensions of a mineral, normal to the diffracting planes. Therfore well crystallized minerals will have sharp peaks whereas less crystallized minerals will have broad peaks. When more than one mineral is present with a similar d-spacing, a greater breath of the 001 diffractions will be evident. Moore and Reynolds (1989) 174 indicate that peaks which are broad (>0.2-0.3° 0) reflect the presence of more than one clay mineral. The crystallinity of a mineral, and in particular clay minerals, can be made by measuring the differences in the breadth of diffraction maximum, termed the Kubler Index (Kubler, 1963; Robinson, 1990; and, Eaton and Setterfield, 1993). Table D. 1 List of diagnostic peaks for clay minerals from 3-30° 29, d-spacings and 29 values. Kaolinite Dickite Smectite (Ca,Mg) Illite Chlorite Muscovite {hkl) 001 d 7.16 °29 12.36 002 3.573 24.92 003 004 005 006 °29 7.162 12.36 3.581 24.86 d 15.0 5.89 5.0 17.74 3.75 °29 23.7 d 10.1 8.76 5.0 17.74 3.38 26.37 °29 d 14.2 6.22 7.1 12.47 4.74 18.72 3.55 °29 27.7 d °29 10.01 8.83 5.02 17.66 3.53 26.6 d(!) and 29^) from Bailey, (1980) and Brindley, (1980); d(j) and 29^) from Moore and Reynolds, (1989). Table D.2 Diagnostic peaks for accessory minerals d-spacings and 29 values. Quartz Microcline orthoclase calcite dolomite pyrite hkl d °2 9 100 4.26 20.8 101 3.34 26.6 hkl d °29 201 4.21 21.1 112 3.47 25.65 220 3.25 27.45 hkl d °29 201 4.22 21.05 112 3.46 25.75 220 3.31 26.75 hkl d °29 104 3.04 28.89 hkl d °29 104 2.89 30.94 hkl d °29 111 3.13 28.52 200 2.71 33.05 210 2.42 37.15 Table D.3 Effect of diagnostic treatments on first low-angle diffraction of clay minerals; d-spacings and 26 are approximate. Mineral Air-dried Ethylene glycol 500-600°C Remarks Kaolinite 7 7 disappears occasionally weak broad band at 12-14 A at 500-550°C Dickite 7 7 disappears occassionally broad reflection at 14 A at 550-700°C Smectite, Mg, Ca 15 17 10 (montmorillonite) Illite 10 10 10 Chlorite 14 14 14 14 A intensity increases at 500-600°C Muscovite 2Mj 10 10 10 From Brown and Brindley, (1980) and Moore and Reynolds, (1989). 175 Shape, in conjunction with breadth and peak position is used to discern those peaks which belong to a single mineral or whether a peak belongs to more than one mineral, and in the case of clay minerals whether the clay minerals are interstratified. If a peak is sufficiently broad, glycolation and heating are used to resolve the types of clay minerals present. Table D.3 lists the changes in d-spacing for individual phyllosilicate minerals in response to glycolation and heat treatment of oriented samples. (0 )1) (O D2) i Kaolinite II 1 1 (0C 1 3) (<X 32) (02 ) (CX Dickite M) M M ! 1, (006) 1 1 . -Dl) (0 02) (CK I I I . Smectite )3) 1 -(0 1 1 I 1 1 Dl) (OC i i i I I I I I I ' 2) i i i i i ((K I )3) -r4— Illite ' i l l , ! Ill , I I I 5 10 15 20 25 30 35 " , ' Degrees two-theta Figure D. l Representative X-ray diffraction patterns for illite, smectite, kaolinite and dickite with the (001) series of diffractions for each species shown as dashed lines to illustrate the regular spacing of the (001) peaks.. The identification of kaolinite and dickite are made by comparing the kaolinite (002) and dickite (022) peaks. 176 A P P E N D I X E Alteration Index and detailed alteration descriptions for whole rock samples. 177 A L T E R A T I O N I N D E X To quantify changes in the intensity of alteration on the Hank property, each whole rock sample was assigned as Alteration Index number (AI#) based on petrographic and X-ray diffraction investigations. The method used to define the AI# was based on five factors which include: (i) the progressive alteration of mafic phases, including pyroxene, hornblende and biotite; (ii) progressive alteration of plagioclase; (iii) the replacement of the matrix of groundmass, and matrix; (iv) the dominant alteration mineralogy; and (v), the presence or absence of calcite and dolomite. Each sample was given and AI# with an increasing score representing more intense stages of alteration. Table E.2 summarizes the petrographic and X-ray diffraction observations, and AI# for whole rock samples for precursor and altered samples. The following outlines the criterion used to calculate a AI# for each samples. 1. The progressive replacement of mafics (pyroxene, hornblende and biotite), plagioclase, and the groundmass or matrix of a sample were given an increasing number based on the degree of replacement by alteration minerals (Total possible score = 15) 1= pristine (>10% replaced) 2=moderately replaced (10 to 50% replaced) 3=strongly replaced (>50%) 4=total replacement 5= outlines no longer visible Note: Progressive increase in alteration is recorded by 0.5 point increases, i.e. 2.5 would represent a 30 to 50% replacement of plagioclase. 2. A scale of alteration minerals was developed to represent the observed increases in alteration identified in the field. Based on this scale, chlorite-dominant alteration was considered less intense than illite-dominant alteration (Table E T ) . The disappearance of earlier formed alteration minerals was also used to define an increase in alteration (total possible score = 7) 178 Table E. 1 Changes in the intensity of alteration based on mineralogy. Introduction of: Disappearance of: Score Chlorite 1 Chlorite+illite 2 Illite and/or Chlorite 3 potassium feldspar Illite/smectite 4 Kaolinite+illite/sm 5 ectite Kaolinite Illite and/or potassium feldspar 6 Silicification kaolinite 7 3 . The presence or absence of the carbonate species calcite, dolomite were used to distinguish intensity of alteration (carbonate present=l, abscent=2). The alteration index was developed as a means to quantitatively compare the intensity of alteration between samples. Since it is a measure of the intensity of alteration, those whole rock samples with low AI# scores were identified as least altered, or precursor samples. Also, the alteration index was used to confirm spatial patterns in the intensity of alteration observed in the field. Whole rock samples were specifically collected from different alteration assemblages interpreted to represent increasing degrees of alteration within the various zones on the property. Since each altered sample was given an AI#, these hypothesized spatial patterns were evaluated with a more robust method. Alteration Type sph •a ••< rutile T3 hematite quartz kaolinite illite/smectite illite adularia carbonate chlorite Alteration minerals/habit AHeration Index maiics plag mx/gm Alteration cb Index # |UnK/affljilty •o S T tt chl+ill • g • 10-15% ds mx, rp • • 20% rpf, mx >5% dsmx 20-30% ds mx, rp 3 S * «? » 93-77 chl+ill V 5 8-2% ds, fg, eu 1 - V 3 ty» • 10-15% rpf, pv 2-5% ds mx 20% rpf, mx 15-20% mx B . - - - S Z la 92-10 chl+il/sm • 5-7% ds, fgr eu • • 30% rpf, mx • • 30% pvmx,rp T) — 0? ^ 13 » H H H1 y ^ U Ul Ul E" 93-66 chl+ill • 5-7% ds, fgr eu • 3 LA i £ • • 15-20% rpf, mx • •a © < <# 15-20% rpm, pv mx K> _ K) w 1 » J** Ol 5" 93-78 chl+il/sm • 7% ds, fg eu • • KJ LA < o • • 20-25% pv a - w w £ u «T 93-65 chl+ill V 8- S * • 3 V 3 LA 5 £ • • 15-20% rpf, mx • 10-15% rpf, mx _ to 3 o ? - K> W !" oi la 92-6 chl+il/sm • 1-2% ds, fgan • • 10-15% rp, ds mx • X o •a ui 20-25% pv E — K, £ *. .U Ol » 92-32 chl+il/sm 8-3-5% bimodal 1 3 LA • • 30% rp,pv • i * 40% . rpm, mx 5 - M *. *. 5" 92-30 chl+ill 8-V 8- S 0s KJ 8- ^ 8- | • 5-10% rpm ~ — K> y. *. *. 92-28 == V 8-5-7% bimodal • LA • • 20% rpf. pv • _ t»> •a o •* -9 tf-15% rpm, mx 5 - - - t £ 1 la | 93-120 vn il/sm X 8-15% ds, fgeu • 30-40% pv i <^ N - W LA -fe. J> to VO u> A N 00 chl+ill X l%withpy 7-10% ds, rpfg • 8- 2 «v • 25% rpf, dsmx 20% rpf, ds mx • "! « w w w m -4 1 93-124 1 6L\ • 3 £ • 00 <T 3 5' K on S ii a I 8- 1 8.? q* I I 8 5 £ I I t l I T s-I I ft 3* W $ ro o 2 5' 3 ps era ft* ; i ? s 6 S £ 3 -3 -s n I f 2 8 I | 7 -a E I | i f I TO <S » a f £ < § i' p-Alteration Type sph 3 rutile pyrite hematite quartz kaolinite illite/smectite illite adularia carbonate chlorite Alteration minerals/habit Alteration Index mafics plag mx/gm Alteration cb IndexU Unit/affinity Sample # per ill X X ? 15% bimodal • 8* S XRD • Ul •a o < # • 20-25% pv • H - t>i Ul .fet Ul ST 93-121 per ill X X e-7-10% bimodal • 5-10% ds XRD 1 u. -o © "= ©? • 15% • ^ _ — Ul Ul Ul Ul 5* 93-127 = X X # 8-* ~ J 5 • 5-10% ds • • •g 8 • " Ul •3 # 1 ^ — Ui Ul Ui Ul «> 93-105 transitional 1% withpy 10-15% ds, fg eu 8* XRD Ul •a o • • •3 KJ r*i o • « - * yi * w (X -* ft* 93-117 per ill KJ 8-5% bimodal 5% ds, with py 10-15% pv XRD • _ 0\ •a o < J? • 8- * • g — * Ul Ul Ul s* 93-128 incipient • • 5% ds, with mt • • • 3 5 1 2 ^ - W - KJ ^ a. 92-9 incipient 8-• • • • * 1 1 I 1 ? 3 ^ H - KI Ki r - a. 92-29 incipient • 1 • • > 1 i 1 • 10% rpf, ds, ves •3 5 3 £ *C — Kl Kl Kl Kl a. | 93-111 incipient 8-• <B IS • • 3 9 • 10-15% ds 5-10% rpm ^ ^ Kl Ki Ki Ui 1 id ! | 92-7 j chl+il/sm • 1 g • 1 £ • 20% rpf, mx • 25-30% pv ^ — Ki Ui Ul Ul a! 1 93-115 chl+il/sm * a * 1-2% gm 1 .3 I * • 3 ui R * 3 CA •1 M w ^ w u Ul cZ 1 93-114 chl+ill 8-• i i $ • T*> Ul i * 15-20% pv 12% rpm, mx M — Kl Ui !** J> a. 1 92-25 1 i m 081 f JI 8- i §-7 S: |. 2. q I I 3 tr 5- 3 3 oo §• =• £ & P SI 3 5? P ">3 A . II II &1 <j 00 >Q « II P i £ $ 3 w * | g» S f 1 ^ 8 I I 7 -a 3 S c ; II t 8-00 < 1 o? oo II I ? II a if Alteration Type sph rutile pyrite hematite quartz kaolinite illite/smectite illite adularia carbonate chlorite Alteration minerals/habit Alteration Index mafics plag mx/gm Alteration cb Index# e Sample U s • 2% ds, rpmt • 1 2 • • o • a 1 1 ^ M * • £ * • 5! 92-20 chl+il/sm 8-5-7% ds, rpmt • • • • 10% rpm, ves 5 - M *• *• *• a. 93-26 = 1-2% ds 10-12% bimodal • 1 3 • • •a © 0s • 1 • g; — u a. 92-22 = A 1 3 • • 10% rpf.ds 3 Ui X •3 ^ 0> — LO . U . U • Ol a. 92-24 per ill &• 10-15% ds, bimodal • 10% vfg,ds XRD • 45% pv, rpf 3 Ui 15-20% ds, pa • — LO Ul • • 0» Ul Ui a. 93-110 = X 1-2% ds | 10-15% ves, an, ds • 10% fgr, ds • • •3 5 • 8* 5o • S • u « ^ ^ oe ui ui a. 93-87 per ill A 7% bimodal • 10-15% ds, fgr - cgr XRD • 30-40% pv • 1 $ • a. 93-112 = 1-2% ds | 5-10% fgr-cgr, an * 1 • • 70% pv, vfg • • • K> LO Ui Ul Ul IX. 92-21 il/sm 8-5% fgr, ds • 8- ^ • 20% rpf, gm • a _ *§ £ • * ~ M M d £ KJ P g | 92-2 il/sm 5% fgr, ds 1-2% gm 10-15% rpf, ves • • 1 3 • Q M W Kl KJ M 1 2a (bi) 1 92-1 incipient • • « a. 1 15% rpf, mx a ."•> ui 1 * 3 £ g K» — K) K» LO 1 2a (bi) 1 1 93-8 1 chl+il/sm 10% fgr, an • 8- | ft 5 i * 3 ° i * - - K» LO N H Ul Ul Kl P g 1 93-144 1 I ft ffl 181 T 3 > =/ 00 S Ii I— ft II S: 3 3 S 8'* • e oo | g- it S. M i lU § §' § S £ | 9 | B s- & k 8. „ * i i & ar p 8 « o a 5- 3' 3 p oo c* ? s> a 1 f £ * i < II 1 15 2 ; I 5. a» ™ IJ* 00 13 « | | P I a * n p & § ° 8-o » • I 3" S H i II -3 ± s. M. % S 2s 5 J p oo <; ^ | o ? « M a 5* ft Alteration Type sph •9 rutile pyrite hematite quartz kaolinite illite/smectite illite adularia carbonate chlorite Alteration minerals/habit Alteration Index mafics plag mx/gm Alteration cb Index U Unit/affinity 1 Sample # chl+il/sm • • • • • 15% rpf, gm • • 10-15% rpf, gm 5-10% gm J* — KJ !*" W KJ If, « 2a (bi) 93-1 ksp+il/sm 1-2% 7% rpbi, fgr ds 1 10% vfgrds • <f s * * < • 3 5 • i « W U * * Ul *-* 2a (bi) 93-143 prxml kaol 1-2% ds 5% fgr, eu • 10-15% ds • • < © • ^ "* ON .fc .fc KJ 2a(bi) 93-33 il/sm V e-7% frg, an • 10-15% pv • • • • • 2a (bi) 93-10 ksp+il/sm & 15% bimodal • 15% an, chal • 20% rpf, pv • 3 J* £ 5 5% fgr, ds • ?» — fc u> J> it oi 1 2a (bi) | 93-140 transitional 8-12% vfr, eu • 30% am, pv UJ •o o • • 5-10% pv • J - u i » » w 1 2a (bi) | 93-155 med il/sm KJ 8-7% bimodal • 10-15% vfr ds, pa • 50% vfgr, pv • • 10-12% mx, rpf • 3 _ fc KJ, £ U. Ol 1 2a (bi) | 93-151 med il/sm # 8-5-10% bimodal • 10% fgr, ds • 55% fgr, pv, rpf • i 10% fgr, pv • 1 2a (bi) 93-45 upper il/sm 8- -• V KJl • • 3 V 3 KJi • 1 2a (bi) | 93-44 | ksp+il/sm &• 10-12% frg, an - col • •o £ < # • 20% fgr, ds - fr 1 • KJ ^ P W JV Ul W • o i KJ P g | 93-141 | transitional i? 8-15% bimodal A - 20% am, pv "5 ° "= o? • < $ • £J •— ON KJI fc. KJ, KJ P g 1 93-158 1 upper il/sm 8-a- o L u» E i? • 10-15% ds • • • • a *. J* W Ul Ul ; Ut Ol 2a (bi) 1 93-249 1 I: W 381 Alteration Type • § • cpy rutile pyrite hematite quartz kaolinite illite/smectite illite adularia carbonate chlorite Alteration minerals/habit Alteration Index mafics plag mx/gm Alteration cb Index # Unit/affinity 1 Sample # transitional 1-2% ds 15% cgagg • •a ? 12 H 5 o? 30% vfgr, pv <f g <: • • • • y K ) Ul Ul Ul Ui 2a (bi) 93-154 prxml kaol &• 2-10% bimodal • 10-15% ds 60-70% am, pv • • • • • Kl Ov Ul JJ. Ul 2a (bi) 93-7 prxml kaol K J &• 15% ds, fibrous • a •? -&• < • • • • • K> . w W ^ U > • Ul (X 2a (bi) 93-153 prxml kaol 8-5% fgr, eu • g o 60-70% am, pv • • • • • Kl ^ J*» KJ CT* Ul • Ul tx -* K J » 93-11 silicification 8" • 5% vfgr, ds • SO "9 S ©•• • • • • • • ^ KJ Ul Ul Ul 1 2a (bi) 93-250 il/sm • • • • • KJ • • 10% rpf, ds • - - K J H H w Ul Ul > 93-30 il/sm 8-( J ? V r» ui 8- * • • 40% rpf, gm • Ut • • Ol M U » ^ t. > 93-32 chl+il/sm • • • • -i M ft? _ u> 10-15% Tpf, gm •3 V 1 ? Ul J» — K J I J J K J • tx > | 93-31 il/sm 1 2-3% fgr, an • 13 • 10-15% rpf, ds • "5 ° 10-15% • . K J LO ^ 1 - U U • • « « Ul > 1 92-26 il/sm * 8-1-2% fgr.ds 11 40% rpf, pv 6^  ' i • ^ U U J> * > 1 92-27 i m £81 APPENDIX F Mass change calculations for alterated sample 185 PROCEDURE VOLCANIC ROCKS A multiple precursor method for mass change calculations was employed for quantitatively describing the effects of alteration after Barrett and MacLean (1994), and MacLean (1990). A multiple precursor approach was used since the volcanic strata on the Hank property form a continuous range of composition, varying from basalt to andesite, prior to alteration. The procedure used is summarized in the following section. Initial whole rock, precursor and reconstructed compositions and mass changes are presented in Table F. 1 for unaltered and altered rocks. 1. Whole rock analyses were re-calculated to a volatile-free basis and Fe203 was converted to FeO. 2. Samples were sorted into affinity groups using Zr/Y ratios in conjunction with discriminant criteria defined for precursor samples in Chapter 4. Based on the relations between altered and precursor samples, Unit 1 and the biotite porphyritic sub unit of Unit 2 were determined to be the primary host lithologies to alteration on the property. 3. To determine fractionation trends, unaltered samples were plotted in terms of A^Os-Zr, AI2O3-Y and Ti02-Zr (Figure F. 1). Fractionation lines were fit to the data using a quadratic (y=ax2+bx+c) equation . The intersection of fractionation lines and alteration lines (y=mx) for each sample were calculated by solving the quadratic equation for y=±b*SQRT(a2-4ac/2a). From the intersection of fractionation and alteration lines the original (precursor) composition of Zr and Y and oxide element were determined. Enrichment factors for the immobile elements were calculated for each sample by the equation: EF^mmobileprecunor/Inimobileaitered sample-4. A range of Precursor and EF were calculate for Zr based on intersection of fractionation and alteration lines calculated from Al203-Zr and Ti02-Zr. An averaged value for the Zr^ursor and EF were used in mass calculations for oxide species. Zr^^or and EF for both methods and the average Zr^ursor and EF are presented in Table F. 1 for reference. 186 5. Fractionation lines for the oxide species Si02, FeO, MgO, etc. are determined by Oxide-Immobile plots using Zr or Y (Figures F.2 and F.3). Correlation coefficients for each oxide fractionation trend are shown on the corresponding plot. 6. Oxideprecrsor values each altered samples were calculated by substituting the Zr^ unoror Ypreamor into the oxide fractionation equation. Reconstructed compositions for oxide elements were computed for each altered sample by the equation: RC = EF x wt% or ppm component. 7. Mass change for the oxide components in altered samples were calculated by the equation: Mass change = RC - precursor. BALD BLUFF PORPHYRY Mass change calculations for the Bald Bluff porphyry were calculated using a single precursor method (Barrett and MacLean, 1994 and MacLean and Kranidiotis, 1987). The procedure used is summarized in Barrett and MacLean, 1994. Initial whole rock, precursor and reconstructed compositions and mass changes are presented in Table F.2 for unaltered and altered rocks. 1. Whole rock analyses were re-calculated to a volatile-free basis and Fe2C»3 was converted to FeO. 2. AI2O3, Ti02, Zr and Y were tested for immobility. Precursor samples for the intrusion exhibited variations in both Zr and Y likely related to crystal sorting. In contrast, AI2O3, Ti02 ratios are more constant in precursor samples and were used to calculate precursor compositions (Figure F.4) 3. An average composition was calculated for precursor samples of the Bald Bluff porphyry (Table F.2). 4. Enrichment factors for the immobile elements were calculated for each sample by the equation: EF=Immobileprecureor/Irnmobileaiiered sample-5. Reconstructed (RC) compositions for altered samples were calculated using the equation: RC = EF x wt% component of the altered sample. 6. Mass change = RC - precursor. A1203 wt*/. 9 ft a f a s 8 cr. 0 1 o s T3 s si E o sr 5 «» O co S oo eg sr 2. sr s: O i—• o 5' a. s n \ e p -o" > P I LEGEND Altered Preeursc LEGEND N ui o B nples samples jpm) K> nples samples jpm) O K> ui o o o \ ° 0 \ 0 • \ ":\ O O A • o o \ \ o > II II b P S A \ U l o o ^ t+7.51 0 Ti02 ( w t . % ) A1203 (wt.%) CL tf 6 IN £ ST CL •a s I 3 3 8 cr. 0 1 o 3 8 3s LSI I 190 .* Mass loss o A Mass addition LEGEND • Precursor samples O Altered samples 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 Ti02(wt .%) Figure F.4 Plot of A1203-Ti02 for altered and precursor samples from the Bald Bluff porphyry. Effects of alteration shown by dashed line. 191 Table F. 1 Calculated mass change for altered and precursor whole rock samples from Unit 1 and 2. Mass changes are reported in wt.%. Mass change calculations for Unit 1 and 2 Sample # AK92-10 AK93-78 AK93-65 AK93-66 AK92-6 AK92-32 AK92-30 AK93-77 UNIT la la la la la la(alt) la(alt) la Alt Index 11 12.5 13 13 13.5 14.5 15 11 Precursor Compositions Ti02(p) 0.81 0.87 0.77 0.77 0.88 0.86 0.80 0.51 AveA1203(p) 18.35 17.39 18.79 18.75 18.50 18.71 18.86 18.76 Si02 (p) 58.69 52.25 58.03 58.19 52.95 55.46 57.78 59.10 FeO(p) 6.66 9.72 7.26 7.13 9.51 8.61 7.43 5.81 CaO(p) 6.21 9.58 6.88 6.74 9.35 8.37 7.07 5.29 MgO(p) 6.21 9.58 6.88 6.74 9.35 8.37 7.07 5.29 MnO(p) 0.20 0.25 0.21 0.21 0.25 0.23 0.21 0.19 K20(p) 2.63 3.52 3.64 3.66 3.09 3.51 3.60 2.57 Na(p) 3.51 4.13 4.29 4.29 3.88 4.20 4.26 3.22 P205(p) 0.30 0.47 0.34 0.33 0.46 0.42 0.35 0.24 AveZr(p) 138.82 97.83 130.73 132.47 100.67 112.61 128.41 150.08 Sum(p) 103.58 107.76 107.09 106.81 108.20 108.74 107.44 100.98 Normalized Precursor compositions Ti02(p) 0.79 0.81 0.72 0.72 0.81 0.79 0.75 0.50 Ave AI203(p) 17.72 16.14 17.55 17.56 17.10 17.21 17.55 18.58 Si02 (p) 56.66 48.49 54.19 54.48 48.94 51.01 53.78 58.52 FeO(p) 6.43 9.02 6.78 6.68 8.79 7.92 6.92 5.76 CaO(p) 6.00 8.89 6.42 6.31 8.64 7.69 6.58 5.24 MgO(p) 6.00 8.89 6.42 6.31 8.64 7.69 6.58 5.24 MnO(p) 0.19 0.23 0.20 0.20 0.23 0.21 0.20 0.19 K20(p) 2.54 3.27 3.40 3.42 2.85 3.22 3.35 2.55 Na(p) 3.39 3.83 4.00 4.02 3.58 3.86 3.97 3.19 P205(p) 0.29 0.43 0.32 0.31 0.42 0.39 0.33 0.24 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted compositions (using Zr(p) ave.) Ti02 (RC) 0.97 0.86 0.81 0.81 1.08 0.93 0.87 0.49 AI203 (RC) 16.15 17.57 17.87 17.77 15.46 17.06 17.42 19.54 Si02 (RC) 47.75 51.58 59.92 62.15 49.72 51.29 61.42 60.90 FeO(RC) 6.61 10.21 5.58 5.84 8.27 8.08 6.57 7.60 CaO(RC) 9.14 11.23 7.27 6.60 8.18 10.66 6.83 4.82 MgO(RC) 0.88 3.92 2.04 2.06 2.75 3.18 2.81 1.07 MnO(RC) 0.25 0.24 0.22 0.22 0.17 0.28 0.26 0.24 K20(RC) 2.74 2.01 4.47 4.25 3.04 3.83 4.19 2.12 Na20 (RC) 3.06 2.31 1.00 1.10 1.66 0.71 0.61 2.53 P205 (RC) 0.41 0.29 0.38 0.36 0.34 0.38 0.40 0.50 Sum (RC) 87.95 100.22 99.54 101.17 90.66 96.39 101.38 99.80 Mass Change Ti02 0.18 0.05 0.09 0.09 0.27 0.14 0.12 -0.01 A1203ave -1.57 1.43 0.32 0.22 -1.64 -0.15 -0.13 0.97 Si02 -8.91 3.09 5.73 7.66 0.79 0.28 7.63 2.37 FeO 0.18 1.19 -1.20 -0.83 -0.51 0.16 -0.35 1.84 CaO 3.14 2.34 0.84 0.30 -0.46 2.97 0.26 -0.42 MgO -5.12 -4.96 -4.39 -4.24 -5.89 -4.52 -3.76 -4.17 MnO 0.05 0.01 0.02 0.02 -0.06 0.06 0.06 0.05 K20 0.20 -1.26 1.07 0.82 0.18 0.60 0.84 -0.43 Na20 -0.33 -1.53 -3.00 -2.92 -1.92 -3.15 -3.36 -0.66 P205 0.12 -0.14 0.06 0.05 -0.09 -0.01 0.07 0.26 Mass Change -12.05 0.22 -0.46 1.17 -9.34 -3.61 1.38 -0.20 192 Mass change cal Sample # AK92-28 AK93-120 AK93-68 AK93-124 AK93-121 AK93-117 AK93-127 AK93-105 UNIT la(aH) la(ah) la(alt) la(alt) la(alt) la(alt) la(alt) la(alt) AH. Index 16 17 17 17 18 18.5 18.5 19 Precursor Com Ti02(p) 0.85 0.88 0.87 0.83 0.88 0.75 0.85 0.71 Ave A1203(p) 18.83 15.17 18.80 16.85 17.04 18.92 16.09 10.87 Si02 (p) 56.77 45.02 56.45 55.66 51.10 58.72 50.95 26.30 FeO(p) 8.02 11.49 8.18 8.53 10.05 6.61 10.09 14.56 CaO(p) 7.71 11.52 7.89 8.28 9.94 6.16 9.99 14.90 MgO(p) 7.71 11.52 7.89 8.28 9.94 6.16 9.99 14.90 MnO(p) 0.22 0.28 0.23 0.23 0.26 0.20 0.26 0.33 K20(p) 3.37 3.03 3.63 3.13 3.46 3.54 3.24 2.15 Na(p) 4.10 3.65 4.29 3.74 4.06 4.22 3.85 2.83 P205(p) 0.39 0.51 0.40 0.41 0.48 0.30 0.48 0.52 AveZr(p) 120.54 74.17 118.39 113.67 93.43 139.46 92.87 33.00 Sum(p) 107.98 103.07 108.63 105.95 107.20 105.58 105.77 88.08 Normalized Pre Ti02 (p) 0.79 0.85 0.80 0.78 0.82 0.71 0.80 0.81 Ave A1203(p) 17.44 14.72 17.31 15.90 15.90 17.92 15.21 12.34 Si02 (p) 52.57 43.68 51.96 52.53 47.67 55.62 48.17 29.86 FeO(p) 7.43 11.14 7.53 8.06 9.37 6.26 9.54 16.53 CaO(p) 7.14 11.18 7.26 7.81 9.27 5.84 9.44 16.92 MgO(p) 7.14 11.18 7.26 7.81 9.27 5.84 9.44 16.92 MnO(p) 0.21 0.27 0.21 0.22 0.24 0.19 0.24 0.37 K2C<p) 3.12 2.94 3.35 2.95 3.22 3.35 3.06 2.44 Na(p) 3.80 3.54 3.95 3.53 3.79 4.00 3.64 3.21 P205(p) 0.36 0.50 0.37 0.39 0.45 0.28 0.45 0.59 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted c Ti02 (RC) 0.96 0.79 1.03 0.84 0.85 0.81 0.73 0.57 A1203 (RC) 16.79 17.16 16.18 17.98 17.52 17.40 19.30 14.75 Si02 (RC) 50.48 52.98 61.31 62.52 56.59 67.01 62.48 61.87 FeO(RC) 7.21 8.48 7.27 9.54 6.35 7.36 9.24 6.36 CaO(RC) 8.14 6.03 9.80 4.78 4.80 8.28 7.15 2.86 MgO(RC) 2.31 4.69 2.02 3.20 2.96 2.34 1.87 1.06 MnOfRC) 0.25 0.18 0.55 0.28 0.16 0.47 0.16 0.11 K20(RC) 3.70 2.01 5.35 2.27 4.14 5.06 4.23 3.28 Na20(RC) 2.54 2.24 0.21 3.19 0.67 0.35 0.26 0.20 P205 (RC) 0.45 0.24 0.43 0.31 0.28 0.38 0.27 0.36 Sum (RC) 92.83 94.81 104.13 104.90 94.32 109.48 105.68 91.41 Mass Change Ti02 0.17 -0.06 0.23 0.06 0.03 0.10 -0.07 -0.25 A1203ave -0.64 2.45 -1.14 2.08 1.62 -0.52 4.09 2.40 Si02 -2.09 9.29 9.34 9.99 8.92 11.39 14.31 32.01 FeO -0.21 -2.67 -0.26 1.49 -3.02 1.10 -0.30 -10.17 CaO 0.99 -5.15 2.53 -3.04 -4.47 2.45 -2.29 -14.06 MgO -4.84 -6.49 -5.25 -4.61 -6.31 -3.49 -7.57 -15.86 MnO 0.04 -0.09 0.34 0.06 -0.08 0.28 -0.09 -0.26 K20 0.57 -0.92 2.00 -0.69 0.91 1.71 1.17 0.84 Na20 -1.25 -1.30 -3.74 -0.35 -3.12 -3.65 -3.38 -3.01 P205 0.09 -0.26 0.07 -0.08 -0.17 0.10 -0.19 -0.23 Mass Change -7.17 -5.19 4.13 4.90 -5.68 9.48 5.68 -8.59 193 Mass change cal Sample # AK93-118 AK93-128 AK93-44 AK93-45 AK92-9 AK92-29 AK93-111 AK92-7 UNIT la(alt) la(alt) la(alt) la(alt) Id Id Id Id Alt Index 20 20 20.5 20.5 7 8 11 11.5 Precursor Com Ti02 (p) 0.73 0.88 0.52 0.81 0.85 0.85 0.88 0.85 Ave A1203(p) 18.83 15.99 17.15 17.39 18.63 18.14 16.40 18.67 Si02(p) 58.41 49.66 55.04 57.77 57.60 54.61 48.91 57.51 FeO(p) 6.95 10.43 2.49 7.44 7.55 8.94 10.62 7.61 CaO(p) 6.53 10.36 1.64 7.08 7.20 8.73 10.56 7.26 MgO(p) 6.53 10.36 1.64 7.08 7.20 8.73 10.56 7.26 MnO(p) 0.21 0.26 0.13 0.21 0.22 0.24 0.27 0.22 K20(p) 3.63 3.12 3.48 3.25 2.94 3.65 3.22 3.00 Na(p) 4.28 3.73 4.18 3.86 3.76 4.26 3.83 3.80 P205(p) 0.32 0.49 - 0.35 0.36 0.43 0.50 0.36 AveZr(p) 134.94 88.33 194.53 128.29 126.81 108.21 85.82 126.07 Sum(p) 106.41 105.27 86.27 105.25 106.31 108.58 105.75 106.55 Normalized Pre Ti02 (p) 0.68 0.83 0.60 0.77 0.80 0.78 0.83 0.80 Ave A1203(p) 17.69 15.19 19.88 16.53 17.52 16.70 15.51 17.52 Si02 (p) 54.89 47.18 63.79 54.89 54.18 50.30 46.25 53.98 FeO(p) 6.53 9.91 2.89 7.07 7.10 8.24 10.04 7.14 CaO(p) 6.14 9.84 1.90 6.73 6.77 8.04 9.99 6.81 MgO(p) 6.14 9.84 1.90 6.73 6.77 8.04 9.99 6.81 MnO(p) 0.19 0.25 0.16 0.20 0.20 0.22 0.25 0.20 K20(p) 3.41 2.96 4.03 3.09 2.77 3.36 3.05 2.81 Na(p) 4.02 3.54 4.84 3.67 3.54 3.93 3.62 3.57 P205(p) 0.30 0.47 - 0.34 0.34 0.40 0.47 0.34 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted c Ti02 (RC) 0.75 0.82 0.65 0.88 1.00 0.86 0.90 1.01 A1203 (RC) 18.24 17.67 12.66 17.29 16.34 17.73 16.45 16.21 Si02 (RC) 57.86 57.76 40.25 55.56 49.13 52.00 51.08 46.82 FeO(RC) 6.60 8.62 5.35 7.50 7.06 7.46 10.94 7.14 CaO(RC) 6.69 6.14 0.27 7.25 6.23 6.32 9.35 5.56 MgCKRC) 1.14 2.88 0.30 1.12 2.83 2.73 4.79 2.61 MnO(RC) 0.23 0.12 0.01 0.46 0.21 0.19 0.28 0.23 K20(RC) 4.98 3.51 3.84 4.07 2.93 3.48 2.50 1.88 Na20 (RC) 0.24 0.32 0.28 0.31 4.28 4.08 2.07 5.43 P205 (RC) 0.36 0.26 0.27 0.35 0.39 0.43 0.26 0.41 Sum (RC) 97.08 98.10 63.88 94.78 90.40 95.28 98.62 87.30 Mass Change Ti02 0.06 -0.01 0.05 0.11 0.20 0.08 0.07 0.21 A1203ave 0.55 2.48 -7.22 0.76 -1.18 1.03 0.94 -1.31 Si02 2.97 10.58 -23.54 0.67 -5.05 1.70 4.84 -7.15 FeO 0.07 -1.28 2.46 0.42 -0.05 -0.78 0.90 0.00 CaO 0.55 -3.70 -1.63 0.53 -0.54' -1.72 -0.64 -1.25 MgO -4.99 -6.96 -1.60 -5.61 -3.94 -5.31 -5.20 -4.21 MnO 0.03 -0.12 -0.14 0.25 0.00 -0.03 0.03 0.02 K20 1.57 0.55 -0.19 0.99 0.16 0.12 -0.55 -0.93 Na20 -3.79 -3.23 -4.57 -3.35 0.74 0.15 -1.55 1.86 P205 0.05 -0.20 - 0.01 0.06 0.03 -0.21 0.07 Mass Change -2.92 -1.90 -36.39 -5.22 -9.60 -4.72 -1.38 -12.70 194 Mass change cal Sample # AK93-114 AK92-20 AK92-25 AK93-26 AK93-115 AK92-22 AK92-24 AK93-56 UNIT Id Id ld(ah) ld(alt) ld(alt) ld(alt) ld(att) ld(alt) Ah. Index 14 14.5 13.5 15 15 16 16.5 18 Precursor Com Ti02(p) 0.86 0.58 0.85 0.85 0.88 0.58 0.84 0.85 Ave A1203(p) 18.12 18.36 18.10 18.53 18.64 18.37 18.37 17.84 Si02(p) 54.17 59.10 55.14 54.93 53.44 59.11 55.15 54.73 FeO(p) 9.10 5.46 8.74 8.82 9.35 5.52 8.74 8.90 CaO(p) 8.90 4.89 8.51 8.60 9.17 4.96 8.50 8.68 MgO(p) 8.90 4.89 8.51 8.60 9.17 4.96 8.50 8.68 MnO(p) 0.24 0.18 0.24 0.24 0.24 0.18 0.23 0.24 K20(p) 3.65 3.61 3.63 3.59 3.36 3.61 3.66 3.57 Na(p) 4.27 4.22 4.24 4.26 4.09 4.22 4.29 4.17 P205(p) 0.44 0.21 0.42 0.43 0.45 0.22 0.42 0.43 Ave Zr(p) 106.09 154.89 110.87 109.79 102.77 154.04 110.92 108.78 Sum(p) 108.65 101.51 108.37 108.83 108.81 101.74 108.72 108.08 Normalized Pre Ti02 (p) 0.79 0.57 0.78 0.78 0.81 0.57 0.77 0.79 Ave A1203(p) 16.67 18.09 16.71 17.02 17.13 18.05 16.89 16.50 Si02(p) 49.86 58.22 50.88 50.47 49.11 58.10 50.73 50.64 FeO(p) 8.38 5.37 8.07 8.11 8.59 5.42 8.04 8.23 CaO(p) 8.19 4.82 7.85 7.90 8.43 4.88 7.82 8.03 MgO(p) 8.19 4.82 7.85 7.90 8.43 4.88 7.82 8.03 MnO(p) 0.22 0.18 0.22 0.22 0.22 0.18 0.22 0.22 K20(p) 3.36 3.56 3.35 3.30 3.09 3.55 3.37 3.30 Na(p) 3.93 4.16 3.91 3.91 3.76 4.15 3.95 3.86 P205(p) 0.41 0.21 0.39 0.39 0.42 0.21 0.39 0.40 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted c Ti02 (RC) 0.87 0.60 0.86 0.86 1.04 0.61 0.84 0.86 A1203 (RC) 17.61 18.05 17.76 17.78 15.86 18.07 17.93 17.73 Si02 (RC) 50.54 60.83 51.64 51.45 50.94 62.64 51.73 41.14 FeO(RC) 8.48 4.63 6.13 8.73 12.67 4.00 6.14 8.14 CaO(RC) 5.14 2.74 6.91 7.71 8.27 1.78 8.04 5.75 MgO(RC) 2.28 1.44 2.76 2.79 3.84 1.92 1.80 2.71 MnO(RC) 0.19 0.16 0.28 0.30 0.31 0.12 0.39 0.26 K20(RC) 6.88 4.35 3.25 4.35 3.44 2.34 3.49 4.58 Na20 (RC) 1.60 5.47 3.66 0.19 0.86 4.59 3.17 0.46 P205 (RC) 0.44 0.23 0.43 0.45 0.44 0.22 0.44 0.42 Sum (RC) 94.04 98.49 93.67 94.61 97.66 96.30 93.98 82.07 Mass Change Ti02 0.08 0.03 0.08 0.08 0.23 0.03 0.07 0.08 A1203ave 0.94 -0.04 1.05 0.75 -1.27 0.02 1.04 1.23 Si02 0.68 2.61 0.76 0.97 1.82 4.55 1.00 -9.50 FeO 0.10 -0.75 -1.93 0.62 4.08 -1.42 -1.90 -0.09 CaO -3.05 -2.08 -0.94 -0.19 -0.16 -3.10 0.22 -2.28 MgO -5.91 -3.39 -5.09 -5.11 -4.59 -2.96 -6.02 -5.32 MnO •O.03 -0.02 0.06 0.09 0.09 -0.06 0.18 0.04 K20 3.52 0.79 -0.10 1.06 0.35 -1.21 0.12 1.29 Na20 -2.33 1.31 -0.26 -3.72 -2.90 0.44 -0.78 -3.40 P205 0.03 0.02 0.04 0.06 0.02 0.00 0.04 0.02 Mass Change -5.96 -1.51 -6.33 -5.39 -2.34 -3.70 -6.02 -17.93 195 Mass change cal Sample # AK93-70 AK93-87 AK93-110 AK93-112 AK92-21 AK93-41 AK92-8 AK92-15 UNIT loXatt) ld(alt) ld(alt) lo(art) ld(alt) ld(alt) 2a 2a Alt Index 18 18.5 18.5 20 20.5 21 Precursor Com Ti02(p) 0.88 0.81 0.84 0.87 0.83 0.77 0.58 0.73 Ave A1203(p) 16.87 16.39 15.66 15.65 18.01 18.11 18.25 18.42 Si02(p) 49.18 52.60 41.16 45.07 55.23 58.65 59.11 59.08 FeO(p) 10.55 9.61 12.24 11.48 8.71 6.70 5.60 5.36 CaO(p) 10.49 9.46 12.35 11.51 8.47 6.26 5.05 4.79 MgO(p) 10.49 9.46 12.35 11.51 8.47 6.26 5.05 4.79 MnO(p) 0.26 0.25 0.29 0.28 0.23 0.20 0.18 0.18 K20(p) 3.45 2.61 3.28 2.89 1.65 3.52 3.58 3.00 Na(p) 4.05 3.26 3.88 3.52 2.37 4.13 4.18 3.80 P205(p) 0.49 0.46 0.53 0.51 0.42 0.31 0.22 0.20 AveZr(p) 86.74 99.23 64.09 74.30 111.37 138.24 153.00 156.14 Sum(p) 106.71 104.92 102.57 103.29 104.39 104.91 101.81 100.37 Normalized Pre Ti02 (p) 0.83 0.77 0.81 0.85 0.80 0.74 0.57 0.73 Ave A1203(p) 15.81 15.62 15.27 15.15 17.25 17.26 17.93 18.36 Si02 (p) 46.09 50.13 40.13 43.63 52.91 55.90 58.06 58.86 FeO(p) 9.88 9.16 11.93 11.11 8.34 6.39 5.50 5.34 CaO(p) 9.83 9.02 12.04 11.14 8.11 5.97 4.96 4.77 MgO(p) 9.83 9.02 12.04 11.14 8.11 5.97 4.96 4.77 MnO(p) 0.25 0.24 0.28 0.27 0.22 0.19 0.18 0.18 K20(p) 3.23 2.49 3.19 2.80 1.58 3.36 3.51 2.99 Na(p) 3.80 3.10 3.79 3.40 2.27 3.94 4.11 3.79 P205(p) 0.46 0.44 0.51 0.50 0.41 0.29 0.22 0.20 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted c Ti02 (RC) 0.87 0.68 0.84 0.84 0.83 0.86 0.59 0.88 A1203 (RC) 16.87 20.09 14.99 16.38 18.08 17.07 18.27 15.70 Si02 (RC) 51.76 65.37 45.18 53.72 41.80 53.10 61.41 47.55 FeO (RC) 8.15 7.41 15.26 5.79 3.41 6.65 4.88 5.63 CaO(RC) 2.75 5.76 5.74 2.93 0.07 0.72 4.88 3.26 MgO(RC) 2.11 1.62 2.12 1.88 0.60 0.76 1.06 2.63 MnOfRC) 0.14 0.21 0.34 0.17 0.04 0.04 0.16 0.16 K20(RC) 4.23 7.27 3.93 3.97 2.58 3.73 4.48 3.80 Na20 (RC) 0.27 0.40 0.28 0.25 0.38 0.32 4.04 5.29 P205 (RC) 0.33 1.22 0.29 0.26 0.18 0.19 0.22 0.41 Sum (RC) 87.48 110.03 88.96 86.18 67.97 83.44 99.99 85.31 Mass Change Ti02 0.05 -0.09 0.03 -0.01 0.03 0.12 0.03 0.15 A1203ave 1.06 4.47 -0.28 1.23 0.83 -0.19 0.34 -2.65 Si02 5.67 15.23 5.05 10.09 -11.11 -2.80 3.35 -11.31 FeO -1.73 -1.75 3.33 -5.32 -4.93 0.26 -0.62 0.29 CaO -7.08 -3.27 -6.30 -8.21 -8.04 -5.25 -0.08 -1.52 MgO -7.72 -7.40 -9.92 -9.27 -7.52 -5.21 -3.90 -2.14 MnO -0.10 -0.03 0.06 -0.10 -0.19 -0.15 -0.02 -0.02 K20 1.00 4.78 0.74 1.18 1.01 0.37 0.97 0.81 Na20 -3.53 -2.70 -3.51 -3.16 -1.89 -3.61 -0.07 1.50 P205 -0.13 0.77 -0.22 -0.24 -0.23 -0.10 0.01 0.21 Mass Change -12.52 10.03 -11.04 -13.82 -32.03 -16.56 -0.01 -14.69 196 Mass change cal Sample # AK92-16 AK92-17 AK92-18 AK92-19 AK93-8 AK93-2 AK93-144 AK93-1 UNIT 2a 2a 2a 2a 2ab 2ab 2ab 2ab(alt) Alt Index 10 10.5 12 11.5 Precursor Com Ti02(p) 0.87 0.87 0.80 0.84 0.60 0.84 0.61 0.60 Ave A1203(p) 18.70 18.49 18.76 18.54 18.13 18.79 18.23 18.23 Si02(p) 55.76 55.23 57.80 55.89 59.07 58.36 59.09 59.10 FeO(p) 8.49 8.71 7.42 8.43 5.32 6.99 5.41 5.79 CaO(p) 8.23 8.47 7.05 8.17 4.74 6.58 4.84 5.27 MgO(p) 8.23 8.47 7.05 8.17 4.74 6.58 4.84 5.27 MnO(p) 0.23 0.23 0.21 0.23 0.18 0.21 0.18 0.19 K20(p) 3.64 3.66 3.65 3.66 3.56 3.65 3.58 3.57 Na(p) 4.29 4.29 4.29 4.29 4.16 4.29 4.19 4.17 P205(p) 0.41 0.42 0.35 0.41 0.20 0.33 0.21 0.24 AveZr(p) 114.27 111.33 128.58 115.02 156.73 134.32 155.53 150.36 Sum(p) 108.85 108.84 107.40 108.63 100.70 106.62 101.18 102.42 Normalized Pre Ti02 (p) 0.80 0.80 0.74 0.77 0.59 0.79 0.61 0.58 Ave A1203(p) 17.18 16.99 17.47 17.07 18.01 17.62 18.01 17.80 Si02 (p) 51.23 50.74 53.82 51.45 58.66 54.73 58.40 57.70 FeO(p) 7.80 8.00 6.91 7.76 5.28 6.56 5.34 5.66 CaO(p) 7.56 7.78 6.57 7.52 4.71 6.17 4.79 5.14 MgO(p) 7.56 7.78 6.57 7.52 4.71 6.17 4.79 5.14 MnO(p) 0.21 0.22 0.20 0.21 0.18 0.19 0.18 0.18 K20(p) 3.35 3.36 3.40 3.37 3.53 3.42 3.54 3.48 Na(p) 3.94 3.94 4.00 3.95 4.13 4.03 4.14 4.07 P205(p) 0.38 0.39 0.33 0.38 0.20 0.30 0.20 0.23 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted c Ti02 (RC) 0.98 0.97 0.85 0.88 0.63 1.03 0.66 0.61 A1203 (RC) 16.61 16.65 17.54 17.60 17.58 15.88 17.51 18.40 Si02 (RC) 47.15 46.68 53.73 52.20 57.97 46.01 59.82 76.98 FeO(RC) 7.56 8.34 6.18 6.05 5.82 7.65 6.17 6.46 CaO(RC) 9.41 6.65 5.89 7.01 5.94 7.63 6.58 2.91 MgO(RC) 0.81 1.30 2.65 1.52 1.60 1.44 1.85 1.43 MnO(RC) 0.44 0.19 0.33 0.13 0.17 0.17 0.29 0.12 K20 (RC) 2.38 3.02 3.06 2.68 3.20 2.08 6.81 4.80 Na20 (RC) 3.42 3.70 4.12 4.34 4.13 3.70 1.40 2.05 P205 (RC) 0.36 0.36 0.36 0.37 0.29 0.35 0.30 0.28 Sum (RC) 89.11 87.88 94.71 92.78 97.34 85.95 101.39 114.04 Mass Change Ti02 0.18 0.17 0.11 0.10 0.04 0.24 0.05 0.03 A1203ave -0.57 -0.34 0.08 0.53 -0.43 -1.74 -0.50 0.60 Si02 -4.08 -4.05 -0.10 0.75 -0.69 -8.72 1.42 19.28 FeO -0.24 0.33 -0.73 -1.71 0.54 1.09 0.82 0.81 CaO 1.85 -1.13 -0.68 -0.51 1.23 1.46 1.80 -2.23 MgO -6.75 -6.48 -3.92 -6.00 -3.11 -4.73 -2.94 -3.71 MnO 0.23 -0.03 0.13 -0.08 -0.01 -0.02 0.11 -0.06 K20 -0.97 -0.34 -0.34 -0.68 -0.33 -1.34 3.27 1.32 Na20 -0.53 -0.24 0.12 0.39 0.00 -0.32 -2.74 -2.03 P205 -0.02 -0.02 0.03 0.00 0.09 0.05 0.10 0.04 Mass Change -10.89 -12.12 -5.29 -7.22 -2.66 -14.05 1.39 14.04 197 Mass change cal Sample # AK92-1 AK92-2 AK93-143 AK93-33 AK93-155 AK93-140 AK93-141 AK93-158 UNIT 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) AH. Index 14.5 10 16.5 19 20 20.5 20.5 21 Precursor Com Ti02(p) 0.65 0.68 0.71 0.56 0.78 0.68 0.80 0.81 Ave A1203(p) 18.25 18.57 18.14 18.75 17.67 17.67 17.76 18.11 Si02 (p) 59.11 58.59 58.74 59.05 57.52 59.00 57.25 56.97 FeO(p) 5.66 6.77 6.59 5.26 7.60 6.15 7.77 7.92 CaO(p) 5.12 6.33 6.14 4.68 7.26 5.66 7.43 7.60 MgO(p) 5.12 6.33 6.14 4.68 7.26 5.66 7.43 7.60 MnO(p) 0.19 0.20 0.20 0.18 0.22 0.19 0.22 0.22 K20(p) 3.58 3.66 3.54 3.65 3.40 3.36 3.44 3.58 Na(p) 4.19 4.28 4.14 4.29 4.00 3.96 4.05 4.18 P205(p) 0.23 0.31 0.30 0.19 0.36 0.27 0.37 0.38 AveZr(p) 152.20 137.36 139.69 157.50 126.12 145.56 123.96 121.89 Sum(p) 102.08 105.72 104.63 101.30 106.07 102.60 106.51 107.37 Normalized Pre Ti02 (p) 0.64 0.64 0.67 0.56 0.74 0.66 0.75 0.75 Ave AI203(p) 17.88 17.57 17.33 18.51 16.66 17.22 16.67 16.87 Si02 (p) 57.91 55.42 56.14 58.29 54.22 57.51 53.75 53.05 FeO(p) 5.54 6.40 6.30 5.19 7.17 6.00 7.29 7.38 CaO(p) 5.01 5.99 5.87 4.62 6.84 5.52 6.98 7.08 MgO(p) 5.01 5.99 5.87 4.62 6.84 5.52 6.98 7.08 MnO(p) 0.18 0.19 0.19 0.18 0.20 0.19 0.21 0.21 K20(p) 3.51 3.46 3.38 3.60 3.20 3.27 3.23 3.33 Na(p) 4.11 4.05 3.96 4.24 3.77 3.86 3.80 3.90 P205(p) 0.22 0.29 0.28 0.19 0.34 0.26 0.35 0.36 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted c Ti02 (RC) 0.70 0.68 0.73 0.59 0.81 0.71 0.82 0.83 A1203 (RC) 17.47 18.71 18.08 17.89 18.07 17.87 18.00 17.95 Si02 (RC) 62.21 61.87 66.38 59.85 62.38 71.00 94.89 59.28 FeO(RC) 4.58 6.04 5.83 7.48 9.59 7.17 9.62 6.92 CaOTRC) 0.81 6.15 0.55 7.40 2.27 0.89 0.65 6.58 MgO(RC) 1.17 2.21 0.73 1.49 3.19 0.93 0.77 2.12 MnO(RC) 0.03 0.17 0.03 0.16 0.07 0.04 0.06 0.18 K20(RC) 4.02 3.10 7.95 6.39 3.53 7.94 8.95 3.63 Na20 (RC) 3.39 3.85 0.34 0.30 0.18 0.26 0.39 0.44 P205 (RC) 0.29 0.34 0.30 0.25 0.35 0.27 0.37 0.37 Sum (RC) 94.66 103.13 100.92 101.79 100.44 107.09 134.51 98.29 Mass Change Ti02 0.06 0.04 0.06 0.03 0.07 0.05 0.07 0.08 A1203ave -0.41 1.14 0.75 -0.62 1.41 0.65 1.33 1.08 Si02 4.30 6.45 10.24 1.56 8.15 13.50 41.14 6.23 FeO -0.96 -0.35 -0.47 2.29 2.42 1.17 2.32 -0.46 CaO -4.20 0.16 -5.32 2.78 -4.57 -4.63 -6.33 -0.50 MgO -3.84 -3.78 -5.14 -3.13 -3.65 -4.58 -6.21 -4.97 MnO -0.15 -0.02 -0.16 -0.02 -0.14 -0.15 -0.15 -0.03 K20 0.51 -0.35 4.57 2.79 0.33 4.67 5.72 0.30 Na20 -0.71 -0.20 -3.62 -3.94 -3.60 -3.60 -3.41 -3.46 P205 0.06 0.04 0.02 0.06 0.01 0.01 0.02 0.01 Mass Change -5.34 3.13 0.92 1.79 0.44 7.09 34.51 -1.71 198 Mass change cal Sample # AKGC93-151 AK93-249 AK93-7 AK93-152 AK93-11 AK93-153 AK93-154 AK93-250 UNIT 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) 2ab(alt) 2ab(ah) 2ab(alt) Alt Index 21.5 21.5 22 22 22.5 22.5 23 24 Precursor Com Ti02(p) 0.71 0.69 0.39 0.88 0.71 0.51 0.59 0.80 Ave A1203(p) 18.36 17.68 14.81 17.64 18.75 14.04 15.73 17.81 Si02 (p) 58.60 59.02 53.37 50.69 59.11 53.58 56.16 46.07 FeO(p) 6.75 6.11 1.91 10.16 5.54 1.97 2.96 0.02 CaO(p) 6.32 5.61 1.00 10.06 4.99 1.07 2.15 -MgO(p) 6.32 5.61 1.00 10.06 4.99 1.07 2.15 -MnO(p) 0.20 0.19 0.13 0.26 0.18 0.13 0.14 0.09 K20(p) 3.61 3.36 2.69 2.73 3.60 1.52 3.18 3.40 Na(p) 4.22 3.97 3.33 3.36 4.27 2.26 3.79 4.12 P205(p) 0.31 0.26 - 0.48 0.22 - - -AveZr(p) 137.55 146.14 202.38 91.92 153.73 201.49 188.27 227.72 Sum(p) 105.39 102.52 78.63 106.32 102.36 76.15 86.87 72.32 Normalized Pre Ti02 (p) 0.67 0.68 0.50 0.83 0.70 0.67 0.68 1.10 Ave A1203(p) 17.42 17.25 18.84 16.59 18.32 18.44 18.11 24.63 Si02 (p) 55.60 57.57 67.88 47.67 57.75 70.36 64.65 63.71 FeO(p) 6.41 5.96 2.43 9.56 5.41 2.59 3.41 0.02 CaO(p) 5.99 5.47 1.27 9.47 4.87 1.40 2.48 -MgO(p) 5.99 5.47 1.27 9.47 4.87 1.40 2.48 -MnO(p) 0.19 0.19 0.16 0.24 0.18 0.17 0.16 0.13 K20(p) 3.42 3.28 3.42 2.56 3.52 2.00 3.66 4.70 Na(p) 4.00 3.87 4.24 3.16 4.17 2.96 4.37 5.70 P205(p) 0.29 0.26 - 0.45 0.21 - - -Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Reconstituted c Ti02 (RC) 0.73 0.75 0.48 0.99 0.82 0.66 0.75 1.51 A1203 (RC) 18.23 17.54 12.53 15.85 16.34 11.43 12.94 1.08 Si02 (RC) 63.32 65.82 37.82 41.76 43.95 42.60 32.91 307.11 FeO (RC) 7.00 6.77 3.22 6.96 6.37 3.72 5.99 1.54 CaO(RC) 3.21 0.67 0.05 0.17 0.10 0.18 0.19 0.09 MgO(RC) 1.12 1.59 0.06 0.33 0.03 0.15 0.40 0.16 MnO(RC) 0.11 0.03 0.01 0.02 0.03 0.01 0.01 0.06 K20(RC) 4.48 4.63 0.07 1.16 0.04 0.78 1.91 2.24 Na20(RC) 0.34 0.31 0.09 0.12 0.18 0.15 0.21 7.27 P205 (RC) 0.36 0.42 0.22 0.46 0.22 0.39 0.28 0.06 Sum (RC) 98.90 98.53 54.55 67.82 68.07 60.08 55.59 321.13 Mass Change Ti02 0.06 0.07 -0.02 0.16 0.12 -0.01 0.07 0.41 A1203ave 0.81 0.29 -6.31 -0.74 -1.98 -7.01 -5.18 -23.55 Si02 7.71 8.25 -30.06 -5.91 -13.80 -27.76 -31.73 243.40 FeO 0.59 0.81 0.79 -2.59 0.96 1.13 2.58 1.52 CaO -2.79 -4.80 -1.22 -9.30 -4.78 -1.22 -2.29 -MgO -4.87 -3.88 -1.21 -9.13 -4.84 -1.25 -2.08 -MnO -0.08 -0.16 -0.15 -0.22 -0.15 -0.15 -0.15 -0.07 K20 1.05 1.35 -3.35 -1.40 -3.48 -1.22 -1.75 -2.47 Na20 -3.66 -3.56 -4.14 -3.05 -3.99 -2.81 -4.16 1.57 P205 0.07 0.17 - 0.01 0.00 - - -Mass Change -1.10 -1.47 -45.67 -32.18 -31.93 -40.31 -44.69 220.81 Table F.2 Calculated mass change for the Bald Bluff porphyry. Mass changes are reported in wt.%. Precursor Stddev AK92-GC-26 AK92-GC-27 AKGC93-31 AKGC93-32 AKGC93-30 Ti02 0.34 " 0.02 0.41 0.37 0.42 0.39 0.35 Ti(EF) 0.84 0.93 0.81 0.88 0.97 Si02 62.67 0.70 66.19 62.54 66.72 67.70 62.95 Ti02 0.34 0.02 0.41 0.37 0.42 0.39 0.35 A1203 18.74 0.17 22.56 19.03 22.35 20.75 20.38 FeO 3.21 0.49 1.35 3.69 0.79 0.91 3.72 MnO 0.14 0.01 0.00 0.13 0.02 0.02 0.08 MgO 0.74 0.22 0.25 0.58 0.33 0.31 0.73 CaO 4.93 0.95 0.02 3.98 0.11 0.09 2.76 Na20 4.69 0.36 0.64 2.59 0.72 0.69 3.08 K20 3.99 0.26 8.33 6.49 8.28 8.89 5.35 P205 0.18 0.01 0.10 0.20 0.18 0.14 0.18 Cr 38.63 6.48 24.60 23.52 16.04 30.39 15.84 Sc 4.01 0.23 3.26 3.58 2.29 2.23 2.93 V 78.88 11.19 56.68 60.93 72.71 50.31 68.65 Sb 3.41 0.42 16.04 8.55 26.73 20.96 3.17 Rb 82.37 4.15 165.75 127.21 148.62 160.35 92.94 Cs 3.19 0.04 2.14 4.28 3.96 3.04 3.06 Ba 3778.81 576.17 3379.21 3003.93 2929.64 4014.09 3231.77 Sr 850.92 93.41 127.26 333.53 100.51 117.38 159.48 Sum 99.64 3.19 99.85 99.59 99.91 99.90 99.59 Reconstructed Composition AK92-GC-26 AK92-GC-27 AKGC93-31 AKGC93-32 AKGC93-30 Ti02 0.41 0.37 0.42 0.39 0.35 Ti02 EF 0.84 0.93 0.81 0.88 0.97 Si02 55.47 58.37 53.95 59.28 61.06 Ti02 0.34 0.34 0.34 0.34 0.34 A1203 18.91 17.76 18.07 18.17 19.77 FeO 1.13 3.45 0.64 0.79 3.61 MnO 0.00 0.12 0.02 0.02 0.08 MgO 0.21 0.54 0.27 0.28 0.71 CaO 0.02 3.71 0.09 0.08 2.67 Na20 0.54 2.41 0.58 0.61 2.99 K20 6.98 6.06 6.69 7.78 5.19 P205 0.08 0.19 0.15 0.12 0.17 Sum (RC) 83.67 92.95 80.78 87.47 96.61 Mass Change AK92-GC-26 AK92-GC-27 AKGC93-31 AKGC93-32 AKOC93-30 Si02 -10.72 -4.17 -12.77 -8.42 -1.88 Ti02 -0.07 -0.02 -0.08 -0.05 -0.01 A1203 -3.66 -1.27 -4.28 -2.58 -0.61 FeO -0.22 -0.25 -0.15 -0.11 -0.11 MnO 0.00 -0.01 0.00 0.00 0.00 MgO -0.04 -0.04 -0.06 -0.04 -0.02 CaO 0.00 -0.27 -0.02 -0.01 -0.08 Na20 -0.10 -0.17 -0.14 -0.09 -0.09 K20 -1.35 -0.43 -1.58 -1.11 -0.16 P205 -0.02 -0.01 -0.03 -0.02 -0.01 Cr -3.98 -1.57 -3.07 -3.78 -0.47 Sc -0.53 -0.24 -0.44 -0.28 -0.09 V -9.18 -4.06 -13.92 -6.26 -2.06 Sb -2.60 -0.57 -5.12 -2.61 -0.09 Rb -26.85 -8.49 -28.45 -19.95 -2.78 Cs -0.35 -0.29 -0.76 -0.38 -0.09 Ba -547.48 -200.37 -560.87 -499.37 -96.76 Sr -20.62 -22.25 -19.24 -14.60 -4.77 Sum -16.18 -6.64 -19.13 -12.43 -2.98 

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