The Hecate sub-basin is one of two similar sedimentary structures comprising Queen Charlotte Basin, which is located between the British Columbia mainland and the Queen Charlotte Islands. The Queen Charlotte Basin was the locale of an active but unsuccessful exploration program, including drill holes, in the 1960's. However, recent studies incorporating modern concepts of plate tectonics have indicated a re-evaluation of the resource potential of the area is warranted. The Hecate sub-basin and its southern counterpart, the Charlotte sub-basin, are filled with Tertiary sediments that are underlain by a thick sequence of Tertiary volcanics. Penetration of the latter unit using the reflection method has been difficult. Thus the thickness of the volcanics and the existence or not of more sediments below them has not been established. To address this problem an airgun/ocean bottom seismograph (OBS) refraction survey was carried out across the Hecate sub-basin in 1983. Data from the airgun shots at approximately 160 m spacings were recorded on four OBSs deployed at 20 km intervals to provide a series of reverse profiles extending over 60 km. The principal interpretation procedure involved calculation of theoretical seismograms and travel-time curves for 2-D velocity structure models and comparisons with observed record sections. The interpreted structure model shows significant lateral variations. Low velocity Pleistocene and Pliocene sediments form an upper layer varying between 0.5 and 1.0 km thick. The principal sedimentary unit is the Tertiary Skonun Formation with interpreted velocities of 2.7 km/s and a gradient averaging 0.4 km/s/km, values that are consistent with well log data. These sediments are generally thicker (approximately 2.5 km) on the western side of the sub-basin although they reach their maximum thickness of 3 km in a depression near the central part of the basin. Toward the eastern side of the basin, the Tertiary sediments thin to about 1 km as the underlying Tertiary volcanics rise toward the mainland. The maximum sediment thickness in the basin is about 4 km. The upper surface of the volcanic unit shows a pronounced topography which is consistent with the erosional nature of this surface. Velocities for the volcanics vary between 4.8 and 5.0 km/s; thickness of the unit ranges from about 0.2 km to 1.8 km. Below the Tertiary volcanics on the eastern 20 km of the model, a low velocity zone less than 1 km thick had to be introduced to satisfy the data. This zone is inferred to contain Upper Cretaceous sediments. A unit with a poorly constrained velocity of 5.9 km/s which underlies the Tertiary volcanics and low velocity zone on the eastern side is interpreted to be the Paleozoic Alexander Terrane. Most of the characteristics of this model are similar to those determined from an earlier study in the Charlotte sub-basin. An additional component of this thesis project was the development of an interactive procedure for the inversion of densely spaced seismic refraction data by wavefield continuation to derive a l-D velocity-depth profile, and its application to data derived from 2-D structures. The procedure consists of two steps: a slant stack followed by a downward continuation. The method was found to yield velocity-depth structures which, when compared with an average velocity-depth structure from the 2-D model, have very similiar gradients and velocity increases. In general the velocity depth curve from the inversion had lower velocities at deeper depths than the averaged 2-D structure. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Buttle Lake Camp is a major Paleozoic volcanogenic massive sulphide district in which the relationships between massive sulphide mineralization and associated volcanism are best explained if the ore deposits and associated lithologic units formed in a rift basin generated by rifting in an island arc system. This setting accounts for the marked linear distribution of the massive sulphide bodies, and the presence and distribution of volcanic products from four distinct source areas: a volcanic arc region, a back-arc (or intra-arc) rifting region, and two seamount areas. These interpretations were achieved largely through detailed mapping (1: 2400) of the Price Hillside and the relogging of pertinent drill core. Geology of the Buttle Lake Camp consists of newly proposed, four lowermost formations of the Paleozoic Sicker Group in the Buttle Lake uplift (in order of decreasing age): (1) the Price Formation, a thick sequence of basaltic andesite flows and related breccias; (2) the massive sulphide-bearing Myra Formation, consisting of mainly volcanic and volcaniclastic units; (3) the Thelwood Formations bedded sequence of siliceous tuffaceous sediments, subaqueous pyroclastic deposits and mafic sills; and (4) the Flower Ridge Formation, largely comprising coarse mafic pyroclastic deposits. Significant units within the Myra Formation are the lowermost, largely felsic H-W Horizon which hosts the large H-W deposit; the Lynx-Myra-Price Horizon, which contains two massive sulphide mineralized felsic volcanic units; the ultramafic G-Flow unit; and the uppermost, basaltic Upper Mafic unit. Zircon U-Pb dating yielded a Late Devonian age of 370 Ma for the Myra Formation. Volcanic units in the Price and Myra Formations are grouped into five volcanic series: two mafic to intermediate volcanic series, two felsic volcanic series, and an ultramafic to mafic volcanic series. These volcanic series are the result of at least three distinct and partly contemporaneous magmatic lineages. Source region for the ultramafic to intermediate parental magmas was an upper mantle peridotite variably enriched in large ion lithophile elements but depleted in high field strength elements (relative to N-type MORB). The felsic volcanic series were generated from two distinct sources. One series is from evolved andesitic magma whereas the other is from magma formed by partial melting of lower crustal material.' The Price and Myra Formations represent a general sequence of repeated events comprising: mafic to intermediate arc volcanism; rifting and sulphide mineralization; felsic arc.volcanism; ultramafic to mafic rift volcanism; and volcanogenic sedimentation. The sequence was repeated twice and formed two mineralized horizons (H-W and Lynx-Myra-Price). The Thelwood and Flower Ridge Formations indicate a major change in depositional style and environment from the two underlying units. The Thelwood Formation is a sediment-sill complex underlying mafic volcanic rocks of the Flower Ridge Formation. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Stikine Assemblage in the Mess Creek area consists of Mississippian aged, variably altered, deformed, metamorphosed and mineralized schists, phyllites and greenstones. Original lithologies were mafic pyroclastics and epiclastics, felsic volcanic breccias to crystal-lithic ash tuffs, graphitic sediments, and gabbroic sills. Regional dynamothermal metamorphism to lower greenschist facies occurred between Late Permian and Middle Triassic time. Four phases of deformation are recognised including two early phases of northwesterly trending isoclinal, recumbent folding followed by easterly trending kink bank and chevron style folding, and northerly trending parallel-style folding. The first phase of folding was synchronous with metamorphism and produced a penetrative axial planar foliation. Second phase folds significantly outlasted thermal effects and produced a locally pronounced crenulation cleavage. Third and fourth phase folding also affected overlying Late Triassic sediments and could be related to terrane collision in Early Jurassic time. Three stages of plutonism occurred within the Mess Creek area. Potassium-argon and rubidium-strontium dates from plutons of the Hickman batholith indicate Early to Middle Triassic ages for quartz diorites and a Middle Jurassic age for quartz monzonites. Alkalic, generally syenitic plutons, commonly associated with porphyry Cu-Au deposits yield Early Jurassic ages. Gold and silver mineralization is hosted by structurally controlled quartz and quartz-carbonate veins and associated alteration. Two ages of alteration have been identified. Widespread and commonly conformable silicification and potassium metasomatism, characterized by a quartz-muscovite- carbonate assemblage, is pre-kinematic and attributed to volcanogenic hydrothermal systems. Foliation-parallel quartz veins associated with this alteration are ubiquitous but generally barren of precious metals. Later alteration, which consists of intense carbonatization, silicification and sericitization, is fracture controlled and commonly hosts gold and silver bearing veins that cut all deformation fabrics. Gangue and alteration mineralogy includes ankerite, siderite, quartz, albite, muscovite, fuchsite, chlorite, manganiferous dolomite, barite and lanthanide group phosphates. Ore mineralogy includes pyrite, sphalerite, tetrahedrite, arsenopyrite, chalcopyrite, galena, silver and bismuth tellurides, electrum and gold. Sulphide concentrations within veins range from massive to sparsely disseminated. Hydrogen metasomatism associated with mineralization produced compositional changes within host rocks that include the removal of Ca and Na and the addition of K and H. Precipitation of quartz, carbonates and sulphides was caused by a pH increase due to hydrolysis reactions with wall rocks. Potassium-argon and rubidium-strontium dating of alteration and mineralization yields Early Jurassic ages, which coincide with regional alkalic plutonism and possible time of tectonic accrection of allochthonous terranes. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Mount Breakenridge area is underlain by metamorphosed strata of the Upper Paleozoic (?) or older Breakenridge Formation, the Upper Paleozoic (?) or Mesozoic Cairn Needle Formation and the Lower Cretaceous Peninsula Formation. These rocks and enclosed ultramafic pods were subjected to Barrovian-type metamorphism prior to the mid-Cretaceous. Locally, pelitic schists developed andalusite and sillimanite in contact aureoles around Late Cretaceous quartz diorites. Ultramafic and related rocks in the map-area and in the Southern Coast Crystalline Complex and the Northern Cascade Mountains may have formed in a marginal basin which was in existence from Mississippian to Late Triassic. Rock and mineral chemistry of pelites indicates that the composition of white mica is sensitive to metamorphic grade, and composition of plagioclase is controlled by rock bulk chemistry. No obvious relationship exists between biotite and staurolite compositions and rock chemistry or metamorphic grade. Distribution of chemical species between coexisting chlorite, biotite, garnet and staurolite implies a close approach to chemical equilibrium. Linear regression analyses of minerals indicate that assemblages in the sillimanite and kyanite zones are dependent on rock bulk chemistry and that apparent univariant reaction assemblages act as local fH2O buffers. The minerals talc (T), forsterite (F), ehstatite (E), anthophyllite (A) in ultramafites may have formed by the following reaction sequence. The reaction T + F = E produced E at 7kb. Uplift and subsequent reduction in pressure rendered enstatite unstable and anthophyllite formed by the reaction T + F = A. Thermodynamic calculations confirm that the equilibrium temperature of the vapour-absent reaction E + T = A is extremely sensitive to iron solid solution so that the topologies of reactions in the system MgO-SiO2-H20 may be a function of the Mg- content of the system. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

. High grade metamorphic rocks belonging to the Shuswap Complex crop out in the southern Okanagan region of British Columbia. An area of these rocks previously mapped by Bostock (1940) as the Vaseaux Formation was studied. A local structural lithologic succession is postulated comprising. of four units, whose present thicknesses are variable but do not generally exceed 100 ft. Four phases of penetrative deformation are recognized. The first, recumbent isoclinal with northerly trends, was succeeded by a second recumbent isoclinal phase, with northwesterly trends. Phase 3 produced easterly trending upright close folds, and later open upright northwesterly and northerly trending folds characterize phase 4. Five intrusive events punctuate the structural history. Two precede phase 2 and three postdate it. Rb-Sr isotopic dating of these intrusions provides a Tertiary age for phase 4, and a pre-mid-Jurassic age for phase 2. The existence of a mid-Jurassic metamorphism can also be inferred from the isotopic data. Based on interpretations of data from adjacent areas it appears that phases 1, 2 and 3, and related events are all facets of the Lower Mississippian Caribooan Orogeny. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Shulaps ultramafite lies at the eastern edge of the Coast Plutonic Complex approximately 150 miles from Vancouver, B.C. It is one of the largest "alpine-type" peridotites in British Columbia, consisting primarily of harzburgite and subordinate dunite lying in an elongate zone trending northwest. Irregular bodies of gabbro and clinopyroxenite occur on the western side of the ultramafite associated with pillowed volcanic rocks. The ultramafite is bounded on the northeast by the Yalakom fault, a major regional structure, and on the southwest by rocks on the Fergusson Group, an assemblage of chert, clastic and volcanic rocks, probably of Triassic age. This study outlines the distribution of peridotite, gabbro and other rocks in the area just west of Shulaps Peak, a major topographic feature in the area. The peridotite is almost completely serpentinized and pervasively sheared. It is in tectonic contact with all other rock types, and contains isolated inliers, ranging from a few feet to over 500 feet, of gabbro, greenstone, chert and clastic rocks. Within the area mapped, the serpentinite could be termed a tectonic melange. An interesting feature of the serpentinite is the irregular occurrence of olivine porphyroblasts, formed by the reaction serpentine + brucite = olivine. The gabbro is foliated and in places layered, although no cumulate textures were observed. It is in gradational contact with pillowed volcanic rocks and in tectonic contact with serpentinite. The evidence gathered by previous workers and during this study argues strongly for the hypothesis that the Shulaps ultramafite, and perhaps some of the associated rocks, are an allocthonous piece of oceanic crust (ophiolite) which has been emplaced into its present position by plate-tectonic processes. This emplacement probably took place between Middle Triassic and Lower Jurassic time. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Poplar copper-molybdenum porphyry deposit, located 270 km west of Prince George, is centered in a late Upper Cretaceous differentiated calc-alkaline stock, which intruded Lower and Upper Cretaceous sedimentary rocks. The stock is capped by late Upper Cretaceous volcanic flow rocks. The lower Cretaceous Skeena Group consists of intermediate tuff, siltstone, and interbedded sandstone, which steeply dip to the south. This unit is unconformably overlain by a moderately sorted polylithic pebble conglomerate belonging to the Upper Cretaceous Kasalka Group. The Poplar Stock, which hosts mineralization, includes a border phase of hornblende quartz monzodiorite porphyry which grades in to a central biotite quartz monzonite porphyry. The stock is intruded by several post-ore dyke units, which include porphyritic dacite, porphyritic rhyolite, felsite, and andesite. Ootsa Lake porphyritic volcanic flow rocks overly the deposit, and are dacite in composition. Pre-ore, and post-ore rock units have been K-Ar dated, and are within analytical error of each other, having a mean age of 74.8 ±2.6 Ma. The deposit is covered extensively with glacial till and alluvial sediments. Therefore the majority of geologic information was obtained from logging the drill core from 34 diamond drill holes, twelve of which were logged in detail using a computer compatible logging format. Information logged in this manner was used in statistical studies , and for producing computer generated graphic logs and plots of various geologic parameters, along two cross-sections through the deposit. Alteration zoning at the Poplar porphyry consists of a 600 m by 500 m potassic alteration annulus which surrounds a 300 m by 150 m argillic alteration core. These are enclosed by 750 m wide phyllic alteration zone, which is itself bordered by a low intensity propylitic alteration zone. Phyllic alteration is defined by the occurence of sericite, and is the most abundant type of alteration present. Potassic alteration, recognized by the occurence cf secondary K-feldspar and/or secondary biotite, is most closely associated with chalcopyrite and molybdenite. At least two episodes of alteration are recognized at the Poplar porphyry. The first was contemporaneous with mineralization, following intrusion and crystallization of the Poplar Stock. This episode consisted of potassic alteration in the center of the deposit, which surrounded a 'low grade1 core, and graded out to phyllic and propylitic alteration facies at the periphery. The second alteration event took place after the intrusion of the post-ore dykes and consisted mainly of hydrolytic alteration of pre-existing alteration zones which were adjacent to more permeable centers, such as faults, contacts, and highly jointed areas. This alteration event is responsible for the anomalous central argillic zone, and the alteration of dykes, in addition to probably intensifying and widening the phyllic alteration halo surrounding the deposit. Chalcopyrite and molybdenite were deposited in the potassic zone at approximately 375° C and less than 250 bars, with relatively low oxygen, and relatively high sulfer, activities and moderate pH. As the potassic alteration zone was invaded by more acidic solutions feldspars were altered sericite and clay, and chalcopyrite was destroyed to form pyrite and hematite. Copper was removed from the system. Statistical studies include univariant one-way and two-way correlation matrices, and multivariant regression analysis. Statistical correlations generally support empirical correlations made in the field. These include positive correlations between various potassic alteration facies minerals, and these minerals and chalcopyrite and molybdenite. Multivariant regression analysis was used to determine which alteration minerals were best suited for indicating chalcopyrite and molybdenite. These minerals are quartz, biotite, magnetite, sericite, K-feldspar, and pyrite. Large error limits and poor correlation statistics in the results from these studies are attributed to deviations from normal distributions for all minerals. A possible cause of this may have been the multistage alteration events that the deposit has undergone. / 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

On the recent lobe of the Fraser River Delta, peat deposition is occurring in three distinct settings: the distal delta plain, the transitional upper delta to lower delta plain, and the upper delta plain to alluvial plain. Each de-positional setting contains a unique sequence of lithofacies and biofacies. Distal lower delta plain peats, although widespread, form a thin, discontinuous peat network dominated by a sedge-grass facies. The peats contain numerous intercalations of silt and silty clay, with a moderate to high pH and a high concentration of sulphur values. The peats overlie a thin fluvial sequence, which in turn overlies a thick coarsening upward sequence of prodelta clay and silty clay. Peats from this environment will form thin lenticular seams of high ash and high sulphur coal. The coal maceral precursors in the peat suggest that the base of the coal will be comprised mainly of desmocol1inite, whereas near the top of the seam oxyfusinite, macrinite, and interlaminated cutinite and vit-rodetrinite would be common. Initial lower delta plain-upper delta plain peats developed from interdistributary brackish marshes. High concentrations of sulphur and ash in these peats decreased in overlying freshwater sedge-grass facies as the delta prograded and the natural levees formed. Sphagnum dominated communities eventually succeeded in areas where fluvial influence was minimal. Laterally, however, along active channel margins, sedge-grass peats intercalate with silty clay overbank and sandy splay deposits. A thin fluvial unit of fining upward sand, silt and clay and a thick sequence of coarsening upward prodelta clay and silty clay underly the deposit. These peats will form relatively thick, widespread coal seams. The seams will be thin and possibly discontinuous adjacent to channels and areas where extensive splaying has occurred. High sulphur concentrations will be confined to the base of seams. The maceral precursors suggest that interbanded telenite, cu-tinite and cerenite will be abundant in the base of the seam and will grade vertically into suberinite, telocollinite, and telenite rich coal. Stumps which will form massive telenite will occur locally. Alluvial plain peats accumulated in freshwater backswamp environments. Earliest sedge-clay and gyttjae peats developed over thin fining upward cycles of silty sand, silt and clay and inter laminated silt, and silty clay of flood origin. Overlying sedge grass and Sphagnum peats are horizontally stratified and form sharp contacts with.bordering flood sediments, at active channel margins, sedge-grass peats intercalate with overbank silty clay to form well developed natural levees, these peats will form a thick seam of high quality coal. The microlithotype composition is comprised of vitritic carbar-gillites and liptites near the base of the seams, and will shift to a clarite and then primarily vitrite near the top. Compared to delta plain peats, maceral distribution will be less complex. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Thor-Odin gneiss dome is one of several structural culminations along the eastern margin of the Shuswap terrain. The gneiss domes have previously been ascribed both to diapiric uprise of granitic gneisses and to interference of late-stage buckle folds. The ages of rocks in the gneiss domes have also been the subject of controversy. Age estimates range from Archean to Mesozoic. This study provides the basis for a detailed model for a new interpretation of the structural evolution of the Thor-Odin gneiss dome. Prior to doming, this area was characterized by the formation of large-scale nappe structures and imbrication of Archean basement rocks with the cover rock sequence. The first period of deformation (Phase One) consisted of large-scale infolding of the cover rock sequence into the basement rocks. The Pingston fold in the core of the dome is a product of this event. The second period of deformation (Phase Two) was marked by the forcing of wedges of basement into the cores of northerly-moving nappes. The third period of deformation (Phase Three) was co-axial with Phase Two and consisted of imbrication and refolding of the upper levels of the stack of Phase Two nappes. Strain analysis based on fold shape, distorted lineation patterns and elliptical strain markers demonstrate that finite strains are highest in the imbricated zone between the Basement Cored Nappe Domain and the Cover Rock Domain. Flattening strains are anomalously low in the Autochthonous Core Gneiss Domain. Analysis of Phase Two fold axes distorted into flattened small circles by Phase Three folds shows that Phase Three strain magnitude √(λ₂/ λ₁) varies from 0.81 to 0.49. Rb-Sr whole rock geochronometry has revealed evidence for three Precambrian events within the basement gneisses. Unmigmatized metasedi-mentary basement gneisses form a six-point errorchron with an age of 2.73±0.20 Ga. Granitic gneisses previously dated at 1.96 Ga by the U-Pb zircon technique, give reset ages for gneiss/vein whole rock suites with ages in the range 750 to 860 Ma. Common lead systematics of stratabound sulfide deposits in the cover rock sequence suggest that the cover rocks are Cambrian in age, in agreement with earlier lithological correlations. The lead isotope ratios suggest the deposits were ultimately derived from an approximately 2.0 Ga basement terrain. The outcropping gneissic basement rocks of the Shuswap are dominantly granitic gneisses which give 2.0 to 2.2 Ga Rb-Sr whole rock dates.; Ductile deformation in the terrain appears to have ended by 150 Ma, as this corresponds to the ages of several post-tectonic intrusions which crosscut Phase Three folds and impose a contact metamorphic overprint on the regional metamorphic pattern. The Nelson Batholith is a post-tectonic batholith which intrudes both the Shuswap terrain and the Kootenay Arc to the east. Two sample suites were collected from the different batho-lithic phases and analyzed by Rb-Sr whole rock methods with the following results: Suite I - Porphyritic monzonite with alkali feldspar megacrysts from the West Arm of Kootenay Lake give a seven-point isochron with an age of 158 ± 16 Ma and an initial ratio of 0.7069 ± 0.0001. Suite I has a Rb-Sr feldspar, date of 153 ± 26 Ma, a K-Ar hornblende date of 143 ± 5 Ma, and a K-Ar biotite date of 60 ± 2 Ma. It seems likely that the K-Ar dates have been disturbed by thermal events subsequent to emplacement of the batholith. Suite II- Medium grained granodiorite from the southern tail of the Nelson Batholith gives a nine-point whole rock isochron with an age of 162 ± 6 with an initial ratio of 0.7065 ± 0.0001. Taken together, these data provide significant new information on the nature and timing of the events that formed the metamorphic core zone of the southern Canadian Cordillera. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate