Variations in pyrite chemistry as clues to gold deposition at the Goldstrike system, Carlin Trend, Nevada USA

摘要

Pyrite and quartz in the Goldstrike system were examined to better understand the depositional history of submicron gold associated with trace element-rich pyrite. Petrography and chemistry were used to identify discrete populations of pyrite and marcasite that precipitated prior to gold deposition, throughout the gold ore event, and following gold deposition. Petrography, fluid inclusions, and cathodoluminescence studies were used to identify various stages of quartz precipitation. Pre-ore pyrites contain major elements Fe and S, but few trace elements in low concentrations. Alternatively, ore-stage, gold-bearing pyrites contain elevated concentrations of Au, As, Sb, Hg, and Cu. Late-ore pyrites and marcasites also contain elevated concentrations of some or all of these trace elements but contain nil to low gold. As, Sb and Cu are present in late-ore fluids in abundances such that minerals, in which these elements are major elements, precipitated. These minerals include realgar, orpiment, stibnite, miargyrite, bismuthinite-stibnite solid solution, and chalcopyrite-disease bearing sphalerite.