Age and Mineralogy of the Steamboat Springs Silica Sinter Deposit, Nevada, U.S.A.: a Preliminary Report on Core SNLG 87-29

Abstract

In 1993, a geothermal exploration slim hole, SNLG 87-29, was drilled to 1219.5 m at Steamboat Springs, Nevada, U.S.A. The purpose of the drilling was to develop a fast, cost-effective method of drilling continuously cored, small diameter exploration holes in hard fiactured geothermal reservoir rock. Three principal lithologies were penetrated and all were fractured: Quaternary hot spring siliceous sinter with intercalated alluvium, Tertiary volcanic breccias and lahars, and an underlying Cretaceous granodiorite. The well only produced hot water from 248.1 m. Sinter occurs at depths from 2.62 m to 16.92 m, with >14 metres of continuous sinter core recovered. The objectives of this study were to: (1) utilise silica sinter deposits to assess past climates and environments; (2) evaluate the influence of depositional and post-depositional conditions on silica mineral phases and their maturation pathways; (3) identify the paragenetic sequence associated with Steamboat Springs sinter diagenesis; and (4) determine the factors that produce coloured, metal-rich sinters. Radiocarbon dating of three core samples (6283 +/- 60 BP to 11493 +/- 70 BP) and X-ray powder diffraction analysis reveal that an unknown mechanism has influenced both the silica maturation "profile" as well as the I4C signature because neither reflect a stratigraphic trend.