The geochemistry of gold-bearing and gold-free pyrite and marcasite from the Getchell gold deposit, Humboldt County, Nevada

Petrographic and geochemical investigations of pyrite and marcasite from the Getchell Carlin-type gold deposit show that elevated concentrations of a characteristic suite of trace metals correlate with ore-stage pyrite morphology. Secondary ion mass spectrometry analyses revealed a significant positive correlation between As and Au in ore-stage Fe-sulfide minerals. High-resolution transmission electron microscopy analyses revealed that gold-bearing Fe-sulfide crystals are arsenic-rich marcasite, rather than pyrite. These analyses failed to identify gold as microinclusions in ore-stage pyrite/marcasite, and support the conclusion that gold is present in solid solution.; Analyses reflect the chemistry of fluids responsible for precipitation of the pyrite and marcasite. Near stoichiometric, pre-ore pyrite precipitated from fluids that were not saturated in Hg, Tl, As, Cu, Au and Sb. Ore-stage pyrite textures suggest rapid precipitation from fluids that contained Hg, Tl, As, Cu, Au and Sb. Late-ore stage marcasite indicates that late fluids continued to transport significant As.