Pyrite geochemistry across the Betze-Post deposit, northern Carlin Trend, Nevada

Petrographic, geochemical, and statistical analyses show that stratigraphy and structural controls promoted ore stage fluid flow. For example, ore stage pyrites occur within brecciated rocks and small-scale fractures within the Wispy Member of the Popovich Formation. Ore stage pyrites have trace element signatures that suggest that the fluid was evolving both temporally and spatially. The associated ore stage trace elements include: Au, Cu, Hg, Tl, As, and Sb. Sb has the highest concentration at North Betze and Betze, suggesting that the J-B series faults transported ore fluids that were chemically distinct. As has the highest concentration along the southern part of the deposit and along the Post fault. Trace elements in pyrite decrease in concentration from the ore stage to the late-ore stage; Pre-ore stage sulfur isotope values of multiple morphologies of pyrite overlap with values characteristic of sedimentary sulfur sources and delta 34S ranges from -15.2 to 52.3‰. However, one type of pre-ore pyrite is interpreted to have derived from the Goldstrike stock. The ore stage pyrite analyses exhibit a more narrow delta34S range of -0.8 to 4.2‰, and are consistent with a magmatic origin; however, the values also overlap with a sedimentary source. The late-ore stage pyrite delta34S signatures extend to higher values of 5.9 to 15.5‰, which suggests that the magmatic or sedimentary ore sulfur source had been diluted by a second sulfur source with a higher sulfur isotope signature, perhaps of sedimentary origin