Isotopic signature of hydrothermal sulfares from Carlin-type ore deposit

Stable isotopes from sulfates of three origins in Carlin-type deposits (CTDs) from western North America fall into distinct clusters and can be utilized to discriminate between barite of Paleozoic (sedimentary exhalative) origin, barite of hydrothermal origin related to gold mineralization, and supergene alunite and jarosite of weathering origin. Although the latter are obvious from field relations, the distinction between hydrothermal and sedex barite is not always so clear. Sedex sulfate sulfur was probably reduced and mobilized during gold mineralization, equilibrated with hydrothermal fluids, and then precipitated as sulfate during the late stages of mineralization, with a distinctly different sulfur and oxygen isotope signature. Isotopic signatures of sulfates may, therefore, be utilized as a mineral exploration tool for CTDs.