Pleistocene rhyolite of the Mineral Mountains, Utah: Geothermal and archeological significance

Journal of Research of the U.S. Geological Survey
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Abstract

Little-eroded rhyolitic tuffs, flows, and domes extend over about 25 km2 along the western side of the Mineral Mountains, southwestern Utah, which is along the eastern edge of the Roosevelt KGBA (Known Geothermal Resource Area). Initial eruptions resulted in two low-viscosity lava flows of nonporphyritic rhyolite. These were followed by bedded pumice falls and nonwelded ash flows. The youngest activity produced at least nine viscous domes and small lava flows of rhyolite that contain 1-5 percent phenocrysts of quartz, plagioclase, sodic sanidine, and biotite; distinction between domes and eroded flow segments locally is difficult.

Potassium-argon ages indicate that all the rhyolite of the Mineral Mountains was erupted between 0.8 and 0.5 m.y. ago. The rhyolite rests on dissected granite of the Mineral Mountains pluton, the largest intrusion in Utah, which has yielded published K-Ar ages of 9 and 15 m.y. A small older dissected rhyolite dome, about 8 m.y. old, occurs just west of the range front. Whether the young ages of the pluton represent time of intrusion or of later reheating, they, in conjunction with the Pleistocene rhyolite in the Mineral Mountains, do indicate a major late Cenozoic thermal anomaly, the size and age of which is significant to evaluation of the Roosevelt KGRA. The rhyolite is also the only known source of implement-grade obsidian in the southwest between eastern California and northern New Mexico.

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Publication type Article
Publication Subtype Journal Article
Title Pleistocene rhyolite of the Mineral Mountains, Utah: Geothermal and archeological significance
Series title Journal of Research of the U.S. Geological Survey
Volume 6
Issue 1
Year Published 1978
Language English
Publisher U.S. Geological Survey
Description 15 p.
First page 133
Last page 147
Country United States
State Utah
Other Geospatial Mineral Mountains
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