Magmatic and Hydrothermal Processes in Porphyry Copper Deposits Below 3km Depth

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9418931 Dilles The origin of porphyry copper mineralization has been broadly related to magmatic hydrothermal fluids that evolve during crystallization of upper crustal, granitic magma chambers. The research will provide critical geochemical data from porphyry copper granites that are exposed in cross- section from 1 to 6 km depth (e.g. the Yerington district, Nevada). The data will provide a field laboratory test of the current theoretical and experimental models of granite crystallization and evolution of highly saline, copper- and sulfur-rich fluids that precipitated ores. The research will emphasize analysis of copper, sulfur, zinc, and copper contents of granite biotite, magnetite, hornblende, and sulfides (pyrite, chalcopyrite). Analyses will be done by electron microprobe and ion microprobe, allowing quantification of contents to the one part-per-million level. The behavior of the trace elements can then be used to estimate at what depths and when during crystallization that granites reached water saturation and lose copper and sulfur. The isotopic and compositional data will allow quantification of the importance of the non-magmatic fluids as source of ore components.