9316059 Einaudi The focus of recent studies of epithermal deposits has been on sources and physiochemical characteristics of hydrothermal fluids in the context of geothermal analogy. Less well studied are links between such fluids and tectonic- volcanic evolution in a given ore district. This link will be studied in the Jarbidge Rhyolite and associated epithermal Au-Ag veins, Jarbidge mining district, Nevada. The primary questions to be addressed are: (1) style of volcanism and relation to tectonics and structural evolution, (2) spatial and temporal links between hydrothermal activity and the plutonic-volcanic-tectonic cycle, (3) absolute age, duration, and cyclicity of faulting, volcanism, and hydrothermal activity, and (4) vertical and lateral changes in hydrology and hydrothermal fluid characteristics as a function of time, space, and topographic/recharge characteristics at the paleosurface. Detailed mapping will document the space-time distribution and relative ages of volcanic rocks, faults, and hydrothermal veins and alteration. Sample collection, binocular study of rock slabs and petrographic studies of thin sections will be concurrent with mapping. Laboratory studies will focus on mineralogical and chemical characterization of volcanic rocks and hydrothermal alteration products, fluid inclusion studies of vein minerals, and age dating of sanidine and adularia by high- precision 40Ar/39Ar techniques. The research will allow further interpretation of the tectonic and volcanic control of other epithermal districts.
