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

9315048布兰农我们希望通过对成矿流体的广泛地球化学研究，提高对密西西比河谷型(MVT)矿床起源的科学认识。我们将利用同位素信息限制成矿流体的来源，并提供矿石和相关脉石矿物的直接放射性测年。我们还将使用精确的同位素稀释分析来提供几种关键元素的化学表征。流体包裹体将与宿主矿物机械分离，以便对这些组分进行更详细的表征。该计划的一个重要部分是研究Rb-Sr系统，它为87Sr/86Sr比值和放射性年龄测定提供了重要的同位素示踪剂。主要的硫化物矿石是专门用于Rb-Sr分析的。我们还将利用铅的同位素组成作为地球化学示踪剂，不仅研究以铅为主要或辅助成分的矿物，而且研究以铅为微量元素的矿物。将对北美中部几个MVT地区的晚期方解石进行分析，并对Pine Point地区(加拿大西北地区)、田纳西中部地区以及密苏里州东南部拟议的MVT矿床流体通道ReelFoot Rift进行详细研究。

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.