Duration of hydrothermal activity at Steamboat Springs, Nevada, from ages of spatially associated volcanic rocks

Abstract

Steamboat Springs is a presently active equivalent of epithermal gold-silver ore-forming systems. Hot-spring sinter deposits contain small amounts of gold, silver, mercury, antimony, and arsenic. Hot-spring activity probably started before extrusion of the basaltic andesite of Steamboat Springs. Old sinter from the Steamboat Springs system occurs in gravels above and below the basaltic andesite. Intense hydrothermal alteration, including almost complete replacement by hydrothermal potassium-feldspar, has affected the basaltic andesite. Three plagioclase separates of differing potassium content from fresh basaltic andesite yielded potassium-argon ages of 2.52-2.55 m.y. Basaltic andesite almost completely replaced by potassium-feldspar yielded a n age of 1.1 m y. The thermal area lies approximately on a line connecting four rhyolite domes, the largest of which is 3 km southwest of the springs and the others are to the northeast. Several domes occupy vents from which tephra of pre-and post-basaltic andesite age was erupted, as indicated by pumice blocks up to 5 cm diameter in gravel underlying the andesite, and isolated pumice fragments lying on the andesite. The source of energy for the thermal convection system is probably a large rhyolitic magma chamber that supplied the pumice and from which the rhyolite domes were emplaced. Sanidine and obsidian from four of the rhyolite domes yielded potassium-argon ages of 1.15-1.52 m.y. and obsidian from one of the northeastern domes yielded apparent ages of 2.97 and 3.03 m.y. The data indicate that hydrothermal activity has occurred at Steamboat Springs, possibly intermittently, for more t h a n 2% m.y. These data agree with other radiogenic age studies indicating 1and 2-m.y. lifetimes for the hydrothermal systems that generate epithermal gold-silver deposits.

Effect of Reduced Spatial Resolution on Mineral Mapping Using Imaging Spectrometry—Examples Using Hyperspectral Infrared Imager (HyspIRI)-Simulated Data

“…This geothermal system, located just south of Reno, Nevada is associated with four rhyolite domes. Thermal activity may be as old as 1.1 Ma, and has probably been continuous for at least the past 0.1 m.y [38]. Numerous wells have been drilled at Steamboat for geothermal energy and to obtain hot water for local resort facilities.…”

The solubility and speciation of molybdenum in water vapour at elevated temperatures and pressures: Implications for ore genesis

“…If the measured Mo solubility data are extrapolated to 600°C, a typical temperature for a porphyry system (Silberman and White, 1975;Christiansen, 1984). In light of this calculation, a reassessment of current models for porphyry Mo deposits may be necessary.…”

The Role of Low-Angle Extensional Tectonics, Flat Fracture Domains, and Gravity Slides in Hydrothermal and EGS Resources of the Western United States

“…Cinder cones assigned to the Lousetown mark vent locations at the crest of the SBH. The SBH are co-aligned with a series of 1.15-1.52 Ma rhyolitic volcanic centers (Silberman et al, 1979) extending from the SW crest of the hills (Figure 1) to a point about 15 km ENE. The pumiceous, 1.15 Ma rhyolite dome in the SBH is believed to be too old to be associated with a felsic magma chamber still providing heat for the active geothermal system.…”

“…The primary source of heat for the feeder is probably deep circulation, but, based on results of helium-isotope analysis, Kennedy (2003) believes that there could be a minor magmatic-gas input to the Steamboat production fluids. Silberman et al (1979), based on spatial relationships between alteration, siliceous sinter, and radiometrically dated volcanic rocks, have estimated the age of the SBH hydrothermal system to be 0.1-3 Ma. These authors concede that if the older figure is realistic, the SBH system almost certainly has been intermittently rather than continuously active for such a long span of time.…”