Geochemistry and paleoceanographic setting of Central Nevada bedded barites

The bedded barite deposits of central Nevada are hosted by rocks of the Roberts Mountains allochthon and constitute the largest barite reserves in North America. Detailed geochemical studies of three barite deposits in the Devonian Slaven Chert indicate that rocks surrounding the barite have elevated concentrations of carbon and phosphorousr elative to nonbarite-bearing rocks. Rare earth element data suggest that the barites were deposited in oxygenated seawater far from a spreading center. Ratios of Al, Ti, Fe, and Mn indicate that hydrothermal input to the sediment was minor relative to detrital input. The assembled data suggest a biogenic rather than a hydrothermal origin for the barite deposits. A model is proposed in which the barites were deposited at the O2-H2S transition of a coastal upwelling system in the Late Devonian ocean. This model is consistent with recent paleoceanographica nalyses of rocks in the Roberts Mountains allochthon, and studies indicating that the Late Devonian marked the transition from an anoxic to an oxic deep ocean.