Alteration associated with gold deposition at the Getchell, Carlin-type gold deposit, north-central Nevada

摘要

Alteration at the Getchell deposit was examined to determine the effects of ore-bearing fluids on host lithologies and the relationship between K-bearing alteration minerals and Au deposition. The geochemistry of unaltered to highly altered and mineralized rocks from the Getchell deposit was quantified for 54 samples collected along 14 transects in calcareous siltstone, carbonaceous limestone, and a rhyodacitic dike. Each transect was collected along a single homogeneous bed that could be followed from visibly unaltered waste rock into high-grade ore.Calculated elemental gains and losses record an increase in the concentrations of Au, Hg, Sb, Se, Si, Te, Tl, and W, and a decrease in the concentrations of Ca, Mn, Se, and Sr. Gold concentration correlates positively with Ag, Hg, Sb, Se, Si, Te, and Tl and negatively with Ca, Mn, and Sc. Gold is concentrated equally in siltstone and carbonate host rocks and shows no correlation to the amount of material gained or lost through alteration at the Getchell deposit. Silicification, decarbonatization, and argillization are spatially associated with gold mineralization.Illite abundance exhibits a positive correlation with gold (R 2 = 0.782), and SEM images of illite intergrown with ore-stage pyrite support a hydrothermal origin for illite. If dated, these illite grains could possibly provide the age of gold mineralization at the Getchell deposit.