PRELIMINARY CHARACTERIZATION OF GOLD OCCURRENCE IN THE FIRE CREEK EPITHERMAL DEPOSIT, NORTH CENTRAL NEVADA
Gold at Fire Creek occurs in four types and associations: 60-70% of gold occurs in discrete, up to cm-thick, bands on or near the wall rock contact, very fine grained gold occurs throughout the veins and in the wall rock, crystalline gold can occur in open spaces or vugs, and gold is hosted in fault gouge and clay zones of uncertain origin. Some gold is associated with sulfide minerals.
Gold in the Vonnie Vein was characterized by reflected light microscopy and SEM-EDS. Vein gold crystallized near the wall rock contact is skeletal dendritic electrum with individual dendrites up to 2 mm in length. The Au:Ag at.% ratio of dendritic crystals varies systematically from Au48 near the contact with the wall rock to Au41 at the dendrite tips approximately 1 cm into the vein. Isolated electrum grains (10-40 micrometers diameter) in the wall rock or in the vein near the wall rock contact have higher Au:Ag ratios, averaging Au56.