The Geology, Alteration And Mineralogy Of The Bullfrog Gold Deposit, Nye County, Nevada

The Bullfrog and Montgomery-Shoshone deposits, outside Beatty, Nevada, have a combined drill-indicated reserve of 17.4 M tons of ore with an average grade of 0.103 oz/t Au and 0.240 oz/t Ag. The deposits occur in Miocene volcanic rocks which underwent large-scale movement within a detachment-faulted terrane. The principal host to gold mineralization is a strongly welded rhyolitic tuff which experienced brittle deformation during plate movement. Open-space fractures and breccia were filled with quartz, calcite, and adularia accompanied by lesser pyrite, gold, and acanthite. Gold occurs as micron-sized particles within and adjacent to the low-angle fault and along associated listric-normal and tear faults.