LE3 .A278 2006

2006

Stanley, Cliff

Acadia University

Master of Science

Masters

Geology

Earth & Environmental Sciences

The Fimiston Superpit is a mesothermal gold vein deposit located in Kalgoorlie, Western Australia. Mineralization is hosted by the differentiated Golden Mile dolerite sill (GMD), which is extensively deformed and intensely altered. Replacement of silicate minerals and local obliteration of igneous textures can impede efforts to identify the horizontally stratified GMD units. A petrologic and lithogeochemical evaluation of drill core samples has identified mineralogical and geochemical parameters that allow determination of stratigraphic position within the GMD stratigraphy, and characterization of the nature, intensity and spatial extent of hydrothermal alteration. Results confirm that the GMD formed from a single Fe tholeiite melt, and underwent pyroxene, plagioclase, magnetite and immiscible sulphide liquid fractionation. Trace element concentrations within the melt (P, Zr, Ti, V, Cu, Ni, Cr) were controlled by preferential incorporation into or exclusion from these fractionating phases. Despite extensivealteration, consistent chemostratigraphic marker horizons can be recognized using specific molar element ratios that allow accurate navigation within the igneous stratigraphy, and facilitate structural reconstructions of the complicated local geology. Proximal hydrothermal alteration about Au veins exhibits a muscovite, pyrite, ankerite and albite assemblage produced by K, S, CO2, Na and H2O metasomatism, whereas distal alteration exhibits a chlorite and calcite assemblage produced by only H2O and CO2 metasomatism. The spatial distribution, mineral assemblage and intensity can be used to discriminate between alteration associated with deuteric, metamorphic and hydrothermal processes. Future exploration in the GMD will benefit from this refined understanding of alteration and associated metasomatism.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat.

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https://scholar.acadiau.ca/islandora/object/theses:2787