Geology of the Butte Ore Deposit

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geochemistry, porphyry, Butte, Montana


Dr. John Dilles discusses the geochemistry of the porphyry Cu-Mo resource found at at Butte, Montana. The porphyry formed from dilute magmatic fluids that contained 1,000s of ppm Cu between 66 and 64 Ma, and at depths of ~8 km. The porphory is zoned from innermost Cu (Ag) ore; to mixed intermediate Cu (Zn, Ag) / Zn-MJn-Ag (Cu, Pb, Au) ore; to an outer Mn-Ag (Pb) ore that grades to barren quartz.

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Dr. Dilles holds degrees from Caltech and Stanford University and has been as professor of geology at OSU since 1986 where he teaches petrology-geochemistry, field geology, and minerals deposits courses. John and his graduate students do research in the geology of Cordilleran porphyry copper deposits from Chile to Alaska, magmatic processes that generate metal and sulfur-bearing hydrothermal fluids, fields-based structural geology, and geochemistry and geochronology. He and his brother, Peter Dilles, have been exploration geologists for Hunt, Ware, and Proffett.