Geology and mineral deposits of the Rossi Mine area, Elko County, Nevada

Abstract

The stratigraphy of the northern part of the Rossi Mine area consists of cherts, siliciclastics, mudrocks, and quartzites of the Ordovician Vinini Formation. Cherts and mudrocks of the Devonian Slaven Chert, and siliciclastics, lime-stones, and cherts of the Silurian-Devonian Roberts Mountains Formation comprise the southern part of the area in structurally-interleaved blocks. Isolated blocks of Overlap Assemblage (Roberts et al., 1967) rocks exist throughout the area. The Late Paleozoic Antler orogeny caused the juxtaposition of oceanic silica-rich strata over shelf carbonates. The Jurassic-Cretaceous Nevadan orogeny resulted in intense folding and the interleaving of Slaven Chert and Roberts Mountains siltstones. Basin and Range extension resulted in small-scale folding and abundant high-angle faulting. Devonian (?) lamprophyre dikes intrude Slaven strata. Jurassic-Cretaceous (?) dikes of unknown composition intrude all lower Paleozoic formations and comprise a swarm trending northwest-southeast through the southwestern part of the area. An altered dolomite-rich stock of unknown age occurs in the west-central part of the area, and Tertiary tuffaceous deposits cover a major part of the surface area.