Geothermal mineralization; I, The mechanism of formation of the Beowawe, Nevada, siliceous sinter deposit

Abstract

The siliceous sinter deposit at Beowawe, Nev., has a volume of 7.71 x 10/sup 7/ m/sup 3/ and contains 1.28 x 10/sup 11/ kg silica. This silica precipitated from geothermal solutions that welled-up along the Malpais Fault, a graben bounding fault. Sinter formation involved three steps. (1) Geothermal solutions saturated with quartz in the reservoir moved to the surface where they cooled and became supersaturated with amorphous silica. (2) Amorphous silica particles nucleated (heterogeneously) to produce a colloidal suspension. (3) The amorphous silica particles agglomerated and were cemented together by amorphous silica precipitating in the embayments between the particles. At least 5.58 x 10/sup 14/ kg of geothermal solution must have been produced over time to account for the mass of silica in the Beowawe Deposit. This fluid would have carried at least 4.95 x 10/sup 17/ kJ of heat to the surface. 21 references, 6 figures, 1 table.