Age and petrogenesis of volcanic and intrusive rocks in the Sulphur Spring Range, central Nevada: Comparisons with ore-associated Eocene magma systems in the Great Basin

Abstract

Widespread base- and precious-metal anomalies, oxidized sulfide veins, silicified calcareous shales and carbonates, and altered porphyry intrusions occur in the northeastern Sulphur Spring Range, Nevada, 80 km south of important gold deposits in the Carlin trend. The small historic mines and prospects in the area are spatially and perhaps genetically related to a suite of variably altered dikes, small lava flows, silicic domes, and related pyroclastic rocks. New major- and trace-element data and U-Pb zircon ages show that the East Sulphur Spring volcanic suite is Eo-Oligocene in age (36–31 Ma) and ranges in composition from high MgO-basaltic andesite to peraluminous rhyolite. The major- and trace-element compositions of the volcanic rocks are characteristic of continental margin subduction zone magmas and form a high-K, calc-alkaline suite with low Fe/Mg ratios. In addition, the rocks have negative Nb and Ti anomalies and elevated Ba, K, and Pb on normalized trace-element diagrams. Crustal melting is indicated by the eruption of a peraluminous garnet-bearing ignimbrite and as a component in hybridized andesite.