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

Journal Article · Sun Jan 01 04:00:00 EST 1978 · J. Res. U.S. Geol. Surv.; (United States)

OSTI ID:5012504

Lipman, P W; Rowley, P D; Mehnert, H H; Evans, Jr, S H; Nash, W P; Brown, F H

Little-eroded rhyolitic tuffs, flows, and domes extend over about 25 km/sup 2/ along the western side of the Mineral Mountains, southwestern Utah, which is along the eastern edge of the Roosevelt KGRA (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 to 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.

• OSTI ID: 5012504
• Journal Information: J. Res. U.S. Geol. Surv.; (United States), Journal Name: J. Res. U.S. Geol. Surv.; (United States) Vol. 6:1; ISSN JRGSA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150201* -- Geology & Hydrology of Geothermal Systems-- USA-- (-1989)
AGE ESTIMATION
ARCHAEOLOGY
CENOZOIC ERA
CHALCOGENIDES
GEOLOGIC AGES
GEOLOGY
GEOTHERMAL FIELDS
GEOTHERMAL SYSTEMS
GRANITES
IGNEOUS ROCKS
KGRA
LAVA
MAGMA SYSTEMS
NORTH AMERICA
ORIGIN
OXIDES
OXYGEN COMPOUNDS
QUARTZ
QUATERNARY PERIOD
RHYOLITES
ROCKS
ROCKY MOUNTAIN REGION
SILICON COMPOUNDS
SILICON OXIDES
STRATIGRAPHY
TUFF
USA
UTAH
VOLCANIC ROCKS
VOLCANISM