Problems in Ore Metal Partitioning: Melt-Vapor-Brine Equilibria

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Intellectual Merit. Prior experimental studies of melt-vapor-brine systems showed conclusively that copper partitions strongly in favor of a brine relative to a vapor. However, many studies of natural fluid inclusions from magmatic-hydrothermal ores and barren systems show the reverse behavior. This fundamental disagreement must be reconciled to arrive at realistic models for (1) formation of magmatic-hydrothermal ores; (2) the mobility of elements in the Earth's upper crust; and (3) exploration for the resources contained in magmatic-hydrothermal deposits. It is proposed to test experimentally the influences of various intensive parameters (including temperature and fugacities of O2, H2S, HCl, CO2 and other components) on Cu partitioning between vapor and coexisting brine. Experiments will be performed using cold-seal hydrothermal techniques, with vapor and brine phases trapped in situ in fractured quartz at run P&T. Cu, Ag, Zn and other cations will be analyzed in vapor and brine inclusions trapped in quartz (as well as coexisting the melt phase where present).Broader Impacts. Beyond the collection of important data on vapor+brine+/-melt equilibria, and the fundamentals of partitioning and element redistribution in the crust, these data will also serve as a basis for the construction of exploration models for porphyry and related deposits. The project will also support a mix of high school, undergraduate, masters and doctoral students. The graduate students are also involved in undergraduate teaching. Additionally, the PIs and students will highlight this research in campus outreach activities. Furthermore, the PIs actively participate in outreach in a variety of other formats (science lectures in a retirement community and a church group; Partners in Education Program (PEP) sponsored by GSA; training for the Ranger Interpreter Program in Yosemite National Park for the National Park Service; and visits to local Maryland elementary schools as part of the earth science curriculum).