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Age of volcanism, intrusion, and mineralization in the Thomas Range, Keg Mountain, and Desert Mountain, western Utah

Journal of Research of the U.S. Geological Survey
By: , , and 

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Abstract

Twenty-six new age determinations by the fission-track method establish a chronology for volcanism, intrusion, and mineralization in the Thomas Range, Keg Mountain, and Desert Mountain, in western Utah. The fission-track ages confirm D. R. Shawe's three-fold classification of igneous rocks. The oldest group of rocks consists of flows, agglomerates, and some ash-flow tuffs that were deposited 38-39 m.y. ago. The middle group contains widespread rhyolitic ash-flow tuffs that originated from local volcanic centers 30-32 m.y. ago. A dike emplaced along the probable ring-fracture zone of the Keg caldera about 31 m.y. ago indicates that caldera collapse occurred soon after eruption of ash-flow tuffs. Rocks believed to belong-to the middle group also were intruded by the quartz monzonite of Desert Mountain 27-30 m.y. ago. Little or no igneous activity took place within the next 20 m.y., during which time the region was strongly broken by Basin-and-Range faulting. Rhyolites of the youngest group were extruded 8-10 m.y. ago in the Keg Mountain area and 6-7 m.y. ago in the Thomas Range. The beryllium-fluorite mineralization at Spor Mountain occurred after the rhyolitic volcanism in the Thomas Range.

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Publication type Article
Publication Subtype Journal Article
Title Age of volcanism, intrusion, and mineralization in the Thomas Range, Keg Mountain, and Desert Mountain, western Utah
Series title Journal of Research of the U.S. Geological Survey
Volume 3
Issue 5
Year Published 1975
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 8 p.
First page 597
Last page 604
Country United States
State Utah
Other Geospatial Thomas Range, Keg Mountain, Desert Mountain
Online Only (Y/N) N
Additional Online Files (Y/N) N
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