The Lost Horse intrusives are minor plutonic bodies occurring to the north and northeast of Copper Mountain, B.C. The rocks of the intrusives were classified by megascopic examination. It was felt that microscopic examinations of the rocks might bring out relationships which were obscure megascopically. Such was the case. The nine specimens examined, which were divided megascopically into six types, were found to consist of only three distinct rock types. The identity of the three rock types had been obscured by weathering and by different types of hydrothermal alteration. Now that the changes brought about by weathering and hydrothermal alteration are recognized, fewer rock types will appear .on the detailed maps and, in addition, zones of alteration may be outlined. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Lead isotope analyses of galena from multiple ore deposits restricted to specific tectono-stratigraphic terranes can provide information on the age and origin of the lead. In this thesis, three separate studies of lead isotopes applied to the metallogenesis of parts of the Canadian Cordillera are presented. Lead isotope data from quartz-gold vein deposits and volcanogenic and related deposits in the Insular Belt group plot in four distinct clusters on Pb-Pb plots. Each cluster corresponds to a specific deposit type and host rock category. Two parallel evolutionary trends in the lead isotopic composition exist: 1) Sicker-hosted volcanogenic deposits to Sicker-hosted veins, and 2) Karmutsen and Bonanza-hosted volcanogenic and related deposits to Karmutsen and Bonanza-hosted veins. The trends indicate a genetic relationship between host rock and isotopic composition. These observations favour a host rock source for the lead in vein deposits and, by association, a comparable source for the gold. Plutonic or abyssal direct sources of metals are not consistent with the lead isotopic data. It is suggested that the gold was extracted from the country rock, and concentrated as veins by hydrothermal activity related to Tertiary plutons. Vein deposits are isotopically distinct from volcanogenic and related deposits, providing an empirical test for distinguishing syngenetic from epigenetic deposits. Karmutsen and Bonanza-hosted deposits are more depleted in 207Pb than similar deposits in Sicker Group rocks, indicating significantly different sources for volcanic components of these two important rock units. Lead isotope data from quartz-gold veins in the Cariboo area of the Omineca Belt, and from similar veins in the adjacent Intermontane Belt indicate that these two vein types are genetically unrelated. A mid-Mesozoic model age calculated for the Cariboo gold mineralisation event indicates that all of the deposits examined are clearly epigenetic, despite reported stratiform textures at the Mosquito Creek mine. K-Ar dates from a quartz-barite vein and from regionally metamorphosed phyllite support a synmetamorphic origin for the veins, but a distal plutonic origin is not ruled out. Recent work by Godwin and Sinclair (1982) has shown that syngenetic, shale-hosted, sedimentary exhalative deposits in the autochthonous part of the Canadian Cordillera contain lead which has evolved in a high U/Pb environment. This 'shale' curve evolution model applies to deposits which have an upper crustal (host-rock) lead source. Ainsworth-Bluebell, Carmi and Slocan camps, and lead associated with the Moyie intrusions, all contain lead which plots substantially and variably below the 'shale' curve. Their departures from this curve provide evidence for a second, uranium poor, possibly lower crustal lead source, for which a growth curve, referred to as the Bluebell curve, can be constructed. The lead data are interpreted within the framework provided by these two growth curves. Mixing of lead between these two lead reservoirs is proposed to explain the linear array of data from Slocan and Carmi camps. Mixing lines, joining points of equal time on the two growth curves, provide a method for interpreting lead data from these deposits. Introduction of relatively unradiogenic lead into the upper crust via magmas which originated in the lower crust is invoked to explain the mixing. The three studies considered here illustrate the differences in lead isotopic characteristics of different tectono-stratigraphic terranes and show that the development of local models for the interpretation of common lead isotope data has application to exploration. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Silver Queen polymetallic vein system south of Houston, B.C., can be treated as a 2-dimensional problem for purposes of reserve/resource estimation. Complexities in obtaining reserve/resource estimates arise from (i) uncertainties in geological interpolation and extrapolation of the vein system, (ii) uncertainties in the distinction between vein and highly altered wallrock in some old drill logs, (iii) complex and multivariable geological character of the vein, (iv) a limited number of exploration drill holes and (v) a different support for drift and drill hole data. Each of these problems has been considered in detail. The study comprises geological analysis, data analysis, point kriging (analysis of thickness and metal distribution) block kriging and comparison of reserve/resource estimation by various procedures including ordinary kriging, inverse squared distance weighting, and polygonal methods. A novel component of the investigation is the use of correlograms (in reality, 1 minus the correlogram) as a substitute for the variogram in geostatistical estimates. This procedure was tested as a means of defining continuity of DDH and Drift assay data of differing support. Ordinary kriging of large polygonal blocks provides metal contents more or less comparable to but locally more conservative than polygonal results reported in a recent feasibility study. Differences are in part due to the use of somewhat different data for the two procedures. The effect of the volume of the selective mining unit on the recovered tonnage and grade is described and limitations of the indirect lognormal method are presented. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

The Dolly Varden camp, Alice Arm area, northwestern British Columbia, is characterized by stratiform and volcanogenic silver-lead-zinc-barite deposits in Early to Middle Jurassic calc-alkaline volcanic rocks of the Hazelton Group. These deposits, containing exceptional silver and significant base metal values, are in andesitic tuffaceous rocks, and occur typically as layers of quartz, carbonate, barite and jasper, with lesser amounts of pyrite, sphalerite and galena, and sparse chalcopyrite. Production from three deposits, the Dolly Varden, Northstar and Torbrit mines, totaled 1,284,902 tonnes of ore that averaged 484g silver per tonne, 0.38 percent lead and 0.02 percent zinc. The Hazelton Group is a thick, widespread assemblage of basaltic to rhyolitic volcanic flow rocks, their tuffaceous equivalents, and derived sedimentary rocks. Dolly Varden camp is underlain by more than 3,000m of Hazelton Group rocks comprised of one major volcanic and one major sedimentary formation. Volcanic rocks underlie sedimentary rocks and have been subdivided into footwall and hangingwall units based on stratigraphic position relative to the mineralized stratiform horizon. Footwall volcanic rocks consist of green ± maroon basaltic-andesite tuff, green ± maroon porphyritic andesite and green andesite shard tuff. Stratiform mineralization rests conformably upon the underlying green andesite shard tuff. Hangingwall volcanic rocks above the stratiform layer consist of pale grey basaltic-andesite ash tuff, maroon basaltic-andesite ash-lapilli tuff, grey-green porphyritic andesite, and pale green andesite ash tuff. Hangingwall volcanics are unconformably capped by sedimentary rocks consisting of maroon siltstone, calcareous and fossiliferous wacke, and black siltstone and shale; black siltstone and shale form the youngest rock unit of the Hazelton Group in the Dolly Varden area. Basalt and lamprophyre dykes intrude all rocks of the Hazelton Group. The rocks of the Hazelton group exposed in the Dolly Varden camp are folded into a series of anticlines and synclines with gentle, northwestern plunges. Two major sets of nearly vertical block faults cut all rock units; earlier faults trend northwest and younger faults trend north-northeast. Geological mapping, combined with petrologic, petrographic and isotopic data, indicate that the stratiform deposits probably formed as submarine exhalative deposits associated with andesitic volcanism of the Hazelton Group during the Early to Middle Jurassic. Evidence for a volcanogenic origin is the conformity of layered mineralization with stratigraphy, lateral and vertical mineral zonation patterns, consistent hangingwall versus footwall contact relationships, fragments of stratiform ore within tuffaceous volcanic rocks of the hangingwall, consistent differences in the stable isotopic compositions between the sulfides versus barite, quartz and carbonate gangue, and the Jurassic "fingerprint" for the lead-bearing deposits of the Dolly Varden camp. The Dolly Varden deposits display criteria for classification of a new, previously unrecognized, stratiform and volcanogenic, deposit type, named here, the "Dolly Varden type", and is characterized by silver-rich, low sulfide and high oxide stratiform mineralization within andesitic volcanic rocks. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Lead isotope compositions have been obtained from five major volcanic and intrusive rock suites and several ore deposits on Vancouver Island. Lead, uranium and thorium concentrations and strontium isotope ratios have been obtained for a subset of these samples. The rock suites examined are the Paleozoic Sicker Group, Triassic Karmutsen Formation, Jurassic Island Intrusions and Bonanza Group volcanic rocks, and the Eocene Catface intrusions. Isotope geochemistry of the Sicker Group is consistent with the interpretation that it formed as an island arc. Relatively high 207pb/204pb ratios indicate sediment involvement in the subduction process, which suggests that the Sicker Group formed close to a continent. Buttle Lake ore deposits display decreasingly radiogenic lead isotope ratios with time, suggesting that the associated magmas become increasingly primitive. This supports the hypothesis that these deposits formed during the establishment of rifting in a back-arc environment. Karmutsen Formation flood basalts display isotopic mixing between an ocean island-type mantle source and average crust. Isotopic evidence is used to support a Northern Hemisphere origin for these basalts. Mixing is apparent in the lead and strontium isotope signatures of the Island Intrusions and Bonanza Group volcanic rocks, between depleted mantle and crustal (possibly trench sediments) components. This is consistent with formation of these rocks in an island arc environment. Eocene Catface intrusions have relatively high 207pb/204pb indicating that crustal material was involved in their formation. There are two groups of plutons corresponding to an east belt and west belt classification. Galena from the Zeballos mining camp related to the Eocene Zeballos pluton indicates that the mineralization was derived from the pluton. Galena lead isotope data from Vancouver Island may be interpreted in a general way by comparison with data from deposits elsewhere of known age and origin. No single growth curve model can be applied. Lead isotope characteristics of Vancouver Island are clearly different from those of the North American craton, reflecting the oceanic affinities of this terrane. A new technique has been developed to compare 207pb/204pb ratios between samples with differing 206pb/204pb ratios. The procedure projects 207pb/204pb ratios along suitable isochrons until they intersect a reference value of 206pb/204pb. This technique can be used for interpreting lead isotope data from old terranes, in which lead and uranium may have undergone loss or gain, and if lead and uranium abundances have not been measured. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate