Origin and Migration of Sulfur in Active Geothermal Systems: A Sulfur Isotopic Study Using the SHRIMP Ion Micro-probe

稳定同位素分析的微生物技术提供了巨大的 深入了解岩石形成过程，因为矿物含有更多 关于其起源和后来修改的资料 比常规同位素取样容易获得， 分析技术。 SHRIMP离子探针研究S同位素 揭示了矿物内部和矿物之间34S的巨大变化 在索尔顿海地热系统中，识别硫化物。 的 沉积硫化物和硫酸盐同位素平衡 矿物在变质过程中， 贫硫热液对沉积硫的再循环作用 将被审查。 根据水溶液中34S的测定 H2S与H2S之间达到同位素平衡的程度 和SO_4的含量及其相关性 H2S对岩浆热液流体的贡献 热液还原作用 将被评估。 建议扩大我们对硫同位素的研究 活火山大陆系统学 地热系统，利用新的钻芯和流体 来自Valles Caldera和Coso地热系统的样本。 的 拟议的研究补充了我们的研究， 贵金属和贱金属。 我们将继续使用 SHRIMP离子探针的30 μ m空间分辨率 用于研究微观 34S变异 矿物 测定H2S中34S的常规技术， SO_4在同时代地热流体中的分布特征 将使用矿物的同位素组成。 研究 脉状矿物中的微观34S分带模式将有助于 控矿机制 阐明 寄主植物硫源的硫同位素地球化学分布 岩石和同位素平衡的程度达到之间 在热液温度下的矿物质和含水物种将 允许更精确地模拟金属的传输和沉积， 火山热液系统

Microbean techniques of stable isotope analysis offer great insight into petrogenetic processes because minerals contain more information concerning their origins and subsequent modifications than can easily be obtained by conventional isotopic sampling and analytical techniques. S isotope studies with SHRIMP ion probe have revealed dramatic 34S variations within and among minerals in the Salton Sea geothermal system, identifying sulfides. The isotopic equilibration of sedimentary sulfide and sulfate minerals during prograde metamorphism, and the extent of recycling of sedimentary S by sulfur poor hydrothermal fluids will be examined. From determinations of 34S for aqueous S species the degree of isotopic equilibrium attained between H2S and SO4 in saline hydrothermal fluids and the relative contributions of H2S to hydrothermal fluids from igneous processes and hydrothermal reduction of host rocks evaporites will be evaluated. It is proposed to extend our studies of S isotope systematics to active silicic volcanic-hosted continental geothermal systems, making use of new drill cores and fluid samples from the Valles Caldera and Coso geothermal systems. The proposed study complements our research that are transporting precious as well as base metals. We will continue to use the unsurpassed 30 um spatial resolution of the SHRIMP ion microprobe for studying microscopic 34S variations within and among minerals. Conventional techniques to determine 34S of H2S and SO4 in coeval geothermal fluids and to characterize the bulk S isotope composition of minerals will be used. Study of microscopic 34S zoning patterns in vein minerals will help constrain mechanisms of ore precipitation. Elucidation of the distribution of S isotope geochemistry of sulfur sources in host- rocks and the degrees of isotopic equilibrium reached between minerals and aqueous species at hydrothermal temperatures will allow more accurate modeling of metal transport and deposition in volcanic-hosted hydrothermal systems.