The thesis area is located along the south shore of Grassy Portage Bay and along the west shore of Redgut Bay of Rainy Lake, in the townships of Watten and Halkirk in the Fort Francis Mining Division of Western Ontario. It is underlain by a series of metamorphised basic intrusives, volcanic rocks, sedimentary rocks and two granitic intrusive of early (?) Precambrian age. All intrusives are apparently younger than the stratified rocks; the granites are probably the youngest rocks in the area. The meta-basic intrusives consist of a main mass of hornblende gabbro and lesser amounts of associated rocks which are thought to be differentiates of the gabbro magma.

This thesis contains the results of an investigation into the stratigraphy and paleontology of the early Middle Ordovician Chazy group in the St. Lawrence Lowland. As such, it forms part of a series of studies of the Ordovician formations in this region, carried out by graduate geology students at McGill University. It follows the work of Harris (1933) and Okulitch (1934) on the Black River group, and that of Byrne (1958) on the Beekmantown group. Despite the excellent accessibility of the best exposures in the vicinity of Montreal, the Chazy group here, as a unit by itself, has not previously been studied in detail.

Chemical weathering of rocks including anorthosite is studied experimentally. Photographic expression of anorthosite is then outlined and statistical studies of slopes and grain size of products of weathering are made. Then tone of aerial photographs and color photography are considered. It is concluded that anorthosite should weather faster in areas where vegetation is present, and that the geomorphic expression of anorthosite is mainly related to jointing; in other aspects of surface expression, anorthosite is not different from other rock types.

A Precambrian layered gabbroic intrusion about 560 km^2 in area, of the Skaergaard type, crops out on the middle north coast of Labrador. Border zones and a Layered series are recognized, and have the following characteristics and approximate mean thicknesses. The intrusion displays extreme fractionation resulting in larvikite consisting of mesoperthite, fayalite, ferroaugite, and ore as the uppermost differentiate. Mineral variation and differentiation are described by means of quantitative mineralogy.

The composition and structural features of feldspars from the rocks of Mounts Royal, Bruno, Johnson, St. Hilaire, Rougemont, Yamaska, Shefford and Brome have been studied by optical and x-ray diffraction methods. Extensive diffraction work did not disclose the presence of highly disordered feldspars (high comparative forms). However, the plagioclases of these rocks belong to a distinct series whose order-disorder relations are in agreement with the geological setting of the intrusives and would classify the rocks as hypabyssal rocks (shallow seated rocks). The alkali feldspars of the Monteregian rocks belong to the low-albite--orthoclase series. The presence of this series of alkali feldspars and the absence of feldspars of the low-albite--microcline series is a characteristic of these rocks that is regarded to be a consequence of their cooling history. The rate of cooling of the igneous masses and the annealing of the rocks under predominantly dry conditions are thought to have been the principal factors responsible for the incomplete ordering of the feldspars. The trends of crystallization and the interrelations between the rock types are discussed on the basis of the compositional data obtained on the feldspars. A qualitative diagram for pressures of approximately 1000 bars has been presented to explain the paragenesis of the feldspar associations encountered in the Monteregian Rocks.

Some copper sulphide minerals recrystallized when heated in a temperature gradient in an argon-sulphur atmosphere, and acicular and lenticular crystals grew down gradient. The crystal composition was determined by the composition of the starting material, temperature, and the sulphur vapour pressure. The purpose of these experiments was to determine: (i) what effect the texture of the surface over which the copper sulphide migrated had upon the diffusing mineral, (ii) what relationship existed between temperature and the weight of the mineral transferred under a constant temperature gradient, (iii) what were the critical factors causing the migration, and, (iv) whether chalcopyrite (CuFeS2) and bornite (Cu5FeS4) would migrate to the same degree under similar conditions.

The Oka anorthosite, lying thirty miles northwest of Montreal, was mapped with particular attention to the distribution of the anorthosite varieties present and the geological structure of these occurrences. It was found that the anorthosite varieties were irregularly distributed within the area, even within an individual outcrop. All the anorthosite was classified according to Buddington’s classification of anorthosites. Samples were collected upon which detailed petrographic studies were made. These studies included flat stage and universal stage work on the plagioclase, determination of the anorthite content of the plagioclase by means of immersion oils, and identification of the accessory minerals. Modal analyses were made on a number of thin sections to insure accuracy of naming.

The South Hopewell Sound area is one of complex Precambrian geology. The present study was suggested by Professor E. H. Kranck of McGill University who visited the area during a journey of research along the east coast of Hudson Bay and James Bay in the summer of 1947. Field work in the area was carried out during the summers of 1959 and 1960. The McGill Carnegie Arctic Institute financed the summer work in 1959. The field work of the summer of 1960 was carried out under the auspices of the Quebec Department of Natural Resources. The area studied is approximately 480 square miles in extent, including the mainland and the coastal islands. The mainland is part of the province of Quebec and the coastal islands are part of the Keewatin District of the Northwest Territories.

This investigation is essentially a combined mineralogical and geochemical study of the St. Lawrence Lowland Paleozoic shales, with the greater emphasis placed upon mineralogy. The principal objective was to determine the mineralogical composition of these shales and to relate variations in mineralogy to changes in the overall geological picture. With a few minor exceptions, no previous work of this type had ever been undertaken within this region. It has been found that differences in shale mineralogy, as determined by X-ray diffraction procedures, could be directly related to variations in tectonic activity of the Canadian Shield and the land mass of Vermontia, the two principal source areas from which the clastic sediments of the St. Lawrence Lowland were derived.

Garnets from kimberlite occurrences in the Republic of South Africa, South West Africa, Southern Rhodesia, Tanganyika, Guinea and Sierra Leone were analysed, by physical methods of analysis. The purpose of making the analysis was two-fold: 1. To compare the composition of garnets from diamond-bearing, with those from non diamond-bearing kimberlites. 2. To evaluate the results of analysis by physical methods, by comparing them with the results of chemical analyses. Analyses by physical methods were made by measuring the refractive indices, the lattice constants and the specific gravities of the garnets and plotting them, along with chemical composition, on a three dimensional tetrahedral diagram (after Winchell, 1958). No difference was found between the garnets from diamond bearing and those from non diamond-bearing kimberlites. Analysis by physical methods was found to be almost as good, and in the case of small samples, probably better than chemical analyses.