Mineralogical and Isotopic Properties of Hydrothermal Pyrite in Relation to Their Formational Mechanisms

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The main objectives of this project are: (1) to understand the relationship among various properties of pyrite (e.g. reflectivity, hardness, anisotropy, lattice cells, sulfur deficiency, conductivity, surface reactivity, 34S), the specific pathways of pyrite formation (e.g. replacement of stable or metastable iron monosulfide, direct precipitation from hydrothermal fluids), and the mechanisms of polysulfide generation (e.g. H2 diffusion, H2S - SO42-reaction) that are involved in the formation of hydrothermal pyrites, and (2) to determine the kinetic and the equilibrium sulfur isotopic fractionation factors between pyrite and various aqueous sulfur species. These objectives will be pursued by a variety of hydrothermal experiments to synthesize iron disulfide minerals at 200oC - 350oC, by mineralogical, chemical, electrochemical and sulfur isotopic investigations of the experimental run products. The results from this project may provide a set of mineralogical and isotopic indicators of geochemical processes and environments of ore formation, and of chemical and isotopic compositions of hydrothermal fluids as well as information useful for the development of pyrite as a semiconductor.