Geology and lithogeochemistry of the Ren gold prospect, Elko County, Nevada - the role of rock sampling in exploration for deep Carlin-type deposits

The Ren gold prospect, Elko County, Nevada, is in the northern part of the Carlin trend, two kilometers northwest of the recently-discovered, high-grade Purple Vein deposit. The Ren area is underlain mainly by Paleozoic sedimentary rocks, consisting of limestone, calcareous siltstone, and mudstone of the eastern (carbonate) assemblage, overlain in thrust contact by chert, quartzite, and mudstone of the western (siliceous) assemblage. Cretaceous(?) granodiorite porphyry and hornblende porphyry dikes have intruded the sedimentary rocks along north-striking faults. Three stages of mineralization include a pre- or syntectonic base metal-barite assemblage, a middle stage of Ag- and Sb-rich jasperoid, and a late Au-rich stage responsible for the potentially economic mineralization at the prospect. The latter two stages of alteration and mineralization were focused along steep east-dipping faults and dikes, and the nearly flat-lying contact between lower massive limestone and laminated calcareous siltstone. Mineralization is present between 380 and 500 m below the surface. Alteration includes decalcification and weak silicification in siltstone, and formation of massive jasperoid in the upper part of the limestone unit. Alteration of dikes is mainly sericite-quartz-pyrite, with late pyrite-quartz-kaolinite.