No abstract included. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The main features of a syenitic complex located near Kamloops B.C. are described. The most noteworthy of these is the abundance of andradite garnet in the rocks. The mineral is believed to have crystallized from a melt that had the composition of quartz syenite. The melt, prior to its consolidation, intruded and apparently assimilated limestone. This caused the rocks to be differentiated at or near their present site by the crystallization of calcium silicates such as the andradite garnet. Quartz -rich rocks were produced first and ultimately nepheline -bearing ones. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Twenty-one galena specimens from 16 mineral deposits in the Kootenay district analysed isotopically in replicate have a linear relationship of isotopic compositions on a Pb²º⁶/Pb²º⁴ versus Pb²º⁷/Pb²º⁴ graph. Twelve of the galenas, including two from Sullivan mine (East Kootenay district), were analysed by an intercomparison technique; the first application of the intercomparison method to an anomalous lead suite. Intercomparison results verify the linear compositional pattern (slope = 0.1084 ± 0.0033). These results indicate that: 1. Kootenay arc leads are multi-stage leads. 2. Sullivan-type lead is the parent common lead from which the anomalous suite developed. 3. Kootenay arc mineral deposits formed during one major mineralizing episode. Time of anomalous lead mineralization, tm, is probably Jurassic as deduced from potassium-argon dates and crosscutting relations of ores and igneous rocks. Assuming tm = 180 m.y. time of emplacement of uranium and thorium that produced the radiogenic component of the anomalous leads is approximately 1700 m.y., possibly the age of Lower Purcell strata of the East Kootenay district. Lead isotopic compositions show no obvious correlations with age of wallrock, type of wallrock, geological nature of ore deposits, or minor element content of galena. Post-ore thermal metamorphism and hydrothermal alteration do not appear to have changed lead isotopic compositions. The history of evolution of Kootenay arc anomalous leads is interpreted as follows: 1. Formation of source rocks containing uranium and thorium about 1700 m.y. ago. 2. Introduction of Sullivan-type lead into source rocks about 1340 m.y. ago. 3. Mixing of Sullivan-type lead with radiogenic lead formed by decay of uranium and thorium, and transportation and deposition of these "lead mixtures” to form anomalous lead deposits during Coast Range orogeny. Geologic and isotopic data from Sullivan mine are reconciled most easily with an epigenetic origin of the Sullivan orebody, and probably with a genetic relation of Sullivan ore fluids with the source magma of Moyie Intrusions. Holmes-Houtermans model age for Sullivan ore, based on intercomparison data, is 1340 m.y. Sullivan lead evolved in a source with U²³⁸/Pb²º⁴ = 9.02, Th²³²/Pb²º⁴ = 36.71, and Th/U = 4.07 (in terms of present day abundances). A method of estimating volume of source rock of anomalous lead deposits is outlined. Calculations for Jersey, Reeves Macdonald and Bluebell mines indicate that the radiogenic lead component of these deposits could have been derived from 1 to 10 cubic kilometers of source rock containing 3 ppm uranium (and approximately 12 ppm Th) if only one-third to one-half of the radiogenic lead in the source were extracted during a period of concentration and mineralization. Kootenay arc deposits can be divided into two classes on the basis of minor element contents of galenas. This division closely corresponds to the following geological types of deposits: 1. replacement deposits with no evidence of open space filling, and 2. deposits with evidence of open space filling and variable amounts of wallrock replacement. Minor element contents of galenas from Salmo-type replacement deposits suggest but do not prove a fairly low temperature of mineral deposition. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Mineralization at Galore Creek consists mainly of disseminated chalcopyrite, bornite and pyrite. Biotite and orthoclase are the dominant alteration minerals with commonly associated anhydrite, garnet, apatite, calcite and magnetite. The mineralization occurs in altered syenites, metavolcanics and brecciated equivalents of these along the contacts of a complex of syenite porphyries which display many characteristics of epizonal intrusions. Exsolution textures of bornite and chalcopyrite indicate a minimum temperature of deposition of 475°C. This leads to the conclusion that the deposit formed at a relatively high temperature and a shallow depth and therefore may be classified as xenothermal. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Lorraine property area occupies the north eastern part of the Duckling Creek syenite located within the central part of the Hogem batholith in British Columbia. The rocks of the Lorraine property area consist of "metasomatic syenites" or "fenites" formed by the metasomatism of the fractured Hogem diorite. They are believed to have been derived from a hypothetical alkaline magma formed beneath the diorite. The residual magma differentiated from the alkaline magma, produced late dykes and hydrothermal fluid. A K-Ar date, 170±8 m. y.(Lower Jurassic) may correspond to both the minimum age of the fenites and the maximum age of the sulphide mineralization at the Lorraine property. Also, the age may mark the time point dividing the first division and the second division of the Hogem batholith. The characteristic minerals of the successive stages of alteration are 1. biotite, 2. albite, 3. orthoclase, if. quartz, 5. sericite, 6. chlorite, and 7. epidote. The altering fluid contained concentrations of soda, potash, silica, hydrogen sulphide, water, and a minor amount of lime. The primary sulphides are bornite, chalcopyrite, and pyrite. The Lorraine deposit posseses no noticeable gossan, but contains secondary copper minerals such as covellite, chalcocite, azurite and malachite. The deposit is divided in plan into three mineral zones on the basis of the primary sulphide assemblages. The dykes, mafic rocks, and fractures were the main controls of mineralization. The composition of the hydro thermal, fluid changed as sulphur reacted with iron of the host rock to form pyrite. The reduced sulphur ratio appears to have caused deposition of bornite and chalcopyrite. In the mineral zones pyrite was replaced progressively by chalcopyrite and bornite. The best classification for the Lorraine deposit is xenothermal. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Copper Mountain intrusions, which include the Voigt and Smelter Lake dioritic stocks, Armstrong Bluffs monzonite-syenite complex, and the differentiated Copper Mountain stock are part of a continuous alkali-calcic rock series ranging in composition from pyroxenite to perthosite pegmatite. The series is believed to be derived from a single parent magma of basic diorite composition and to have formed through crystallization differentiation. The age of the series, determined by potassium-argon methods, is about 195 m.y. Parent magma was intruded into Nicola group (Upper Triassic) rocks by forceful injection with structural readjustment of the country rock. The Voigt and Smelter Lake stocks (diorite) crystallized without apparent differentiation. Armstrong Bluffs monzonite-syenite complex is believed to have formed, by repeated tapping of a differentiating magma which was emplaced at intervals after crystallization of diorite in Voigt and Smelter Lake stocks. In Copper Mountain stock, after crystallization of a dioritic roof and outer zone, magma differentiated to form a continuous series from pyroxenite to perthosite pegmatite Differentiation resulted through a combination of thermal convection, chemical diffusion, crystal armoring and crystal settling. Differentiation began with the formation of gabbro and was initiated by convection currents which were formed as a result of temperature gradients in a mobile, volatile-charged magma. When the composition of the magma approached the Ab-Or side of the Ab-Or-An ternary system, subsolvus crystalliza- tion was succeeded by hypersolvus crystallization and the development of perthosite pegmatite. Feldspars from the Copper Mountain intrusions, studied by X-ray powder technique, exhibit a range of thermal state from intermediate to low temperature types. Feldspar geothermometry suggests a range of crystallization from above 8.20°C to about 500°C. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate