Radiometric Dating of Mississippi Valley-type Ore Deposits Utilizing U-Pb and Th-Pb for Hydrothermal Calcite and Rb-Sr for Sphalerite

9614264 Brannon拟议的工作旨在改进密西西比河谷型铅锌矿床矿化成矿年龄的同位素方法，以便为理解成矿机制提供必要的约束。拟议的研究将集中于：(1)对目前存在相互矛盾的成矿年龄的两个北美MVT矿床(伊利诺伊州-肯塔基州-萤石矿床和松点锌-铅矿床)进行放射性测年；(2)三州(密苏里州、堪萨斯州、俄克拉何马州)MVT地区矿山的矿阶段方解石和闪锌矿的年龄测定；(3)南非的两个元古界MVT矿床的年龄，这两个矿床被认为是目前已知的此类矿床中最古老的。除了测年外，Rb-Sr和U-Th-Pb同位素体系也将作为成矿流体的示踪剂。有关流体来源的信息对于评估不同地区的成矿模式和构建全球MVT的更好的成因模式是必要的。

9614264 Brannon The proposed work seeks to improve on the isotopic methodology for dating ore-stage mineralization in Mississipi Valley-type (MVT) Pb-Zn deposits in order to provide necessary constraints for understanding the mechanisms of ore formation. The proposed study will concentrate on: (1) the radiometric dating of two North American MVT ore deposits (Illinois-Kentucky-Fluorspar and Pine-Point Zn-Pb deposits) for which conflicting ages of ore formation exist at the moment; (2) dating of ore-stage calcite and sphalerite from mines of the Tri-State (Missouri, Kansas, Oklahoma) MVT district; and (3) dating two Proterozoic MVT deposits in South Africa, thought to be among the oldest deposits of this type currently known. In addition to dating, the Rb-Sr and U-Th-Pb isotopic systematics will be used as tracers of the ore-forming fluids. Information on the source of fluids is necessary to assess models of ore genesis in the various localities and to construct a better genetic model for MVT's worldwide.