Gold and Copper Speciation and Partitioning in S- and Cl- bearing Melt-Vapor-Brine Systems

美国马里兰大学的candela和piccoli将在800℃、近100 MPa的压力范围内进行实验，以确定金和铜在石英熔体+蒸汽或盐水（KCl+NaCl+HCl+H2O的起始组成）组合中（其中一些添加了硫）的形态和分配。将在硫化物饱和系统（例如磁黄铁矿-中间固溶体组合）中进行实验，以确定铜和金在蒸汽/熔体、盐水/熔体和蒸汽+盐水/熔体组合中的分配。这项工作补充了在磁铁矿、黑云母和流纹岩熔体中Au和Cu的晶体熔融分配实验。结合现有的实验数据，提出的研究将产生Cu和Au在熔融结晶-蒸汽-盐水系统中的行为的初步模型，该模型可用于测试斑岩和相关Au-Cu矿床起源的假设。鉴于Bodnar（1995）和Audetat等人（1998）对天然流体包裹体的开创性分析工作尚不清楚卤水与蒸汽、硫与含氯配体的相对作用，因此本文提出的熔融挥发相实验需求量很大。这些工作人员认为，在成矿环境中，含硫物质和气相可能对这些铜和金的输送都很重要。我们的研究旨在为确定岩浆-热液系统中铜和金分配的控制因素提供基本的热力学数据，并阐明这些重要经济金属的输运机制。

AbstractEAR-0125805Candela and PiccoliUniversity of MarylandExperiments will be performed to determine the speciation and partitioning of gold and copper in felsic melts + vapor or brine (starting composition of KCl+NaCl+HCl+H2O) assemblages, some with added sulfur, at 800 degrees C covering a range of pressures near 100 MPa. Experiments performed in sulfide-saturated systems (e.g., pyrrhotite-intermediate solid solution assemblage) will be performed to determine copper and gold partitioning in vapor/melt, brine/melt and vapor+brine/melt assemblages. This effort complements experiments on crystal-melt partitioning of Au and Cu among magnetite and biotite, and rhyolite melt. Taken together with existing experimental data, the proposed research will yield a preliminary model for the behavior of Cu and Au in melt-crystal-vapor-brine systems that can be used to test hypotheses for the origin of porphyry and related Au-Cu deposits. The melt-volatile phase experiments proposed here are in high demand given that the relative roles of brine versus vapor and sulfur versus chloride-bearing ligands are not clear in light of the pioneering analytical work on natural fluid inclusions by both Bodnar (1995) and Audetat et al. (1998). These workers have suggested that both sulfur-bearing species and the vapor phase may be important in transporting these Cu and Au in ore-forming environments. Our study is designed to provide basic thermodynamic data to determine the controls on copper and gold partitioning in magmatic-hydrothermal systems and to clarify transport mechanisms for these economically important metals.