Rb-Sr and Pb-U Systematics of Mississippi Valley-Type Ore Deposits - Sulfides, Gangue Minerals, and Fluid Inclusions

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9315048 Brannon We expect to improve the scientific understanding of the origin of Mississippi Valley-type (MVT) ore deposits through a broad geochemical study of ore-forming fluids. We will use isotopic information to provide constraints on the provenance of ore-forming fluids and to provide direct radiometric dating of ores and associated gangue minerals. We will also use precise isotopic dilution analysis to provide chemical characterization for several key elements. fluid inclusions will be mechanically separated from host minerals to allow more detailed characterization of these components. AN important part of this program is study of the Rb-Sr system, which provides an important isotopic tracer in the 87Sr/86Sr ratio as well as radiometric age determinations. The major sulfides ores are specifically targeted for Rb-Sr analysis. We will also use Pb isotopic compositions as a geochemical tracer, studying not only the minerals in which Pb is a major or accessory constituent but also those in which it is a trace element. Analyses of late- stage calcites from several MVT districts in the midcontinent of North America and detailed studies of the Pine Point district (Northwest Territories, Canada), the Central Tennessee district, and the Reelfoot Rift, a proposed fluid channel for MVT deposits in southeast Missouri will be carried out.