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Temporal, Spatial, and Chemical Evolution of Quaternary High-Silica Rhyolites in the Mineral Mountains, Utah

Professional Paper 1890-K
By: , , , and 
https://doi.org/10.3133/pp1890K

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Abstract

The Mineral Mountains in southwestern Utah are a structurally controlled core complex at the confluence of the Colorado Plateau and the Basin and Range physiographic provinces. Aside from hosting Utah’s largest batholith, the Mineral Mountains host some of the State’s youngest high-silica rhyolites, which have been linked to a magma source that is presently being utilized as an enhanced geothermal system. The high-silica rhyolites take the form of effusive lavas and domes, and explosive products are rare. Previous K-Ar dating of these Pleistocene rhyolites placed eruptions between about 790 and 500 kilo-annum (ka) with contemporaneous basalts erupting in the valley to the east of the Mineral Mountains. Large uncertainties on these ages obscured the tempo of eruptions and thus hindered attempts to constrain the timescales of the petrogenetic processes that produced the rhyolites. In this study, we build on previous studies conducted in the 1970s and 1980s by using new geochronologic and geochemical data to investigate the temporal and spatial evolution of the youngest phase of volcanism in the Mineral Mountains. We identify two major eruptive periods, from approximately 850 to 750 ka and from approximately 590 to 480 ka. The older phase is characterized by the eruption of several basaltic lavas, two obsidian flows, and a series of coalescing porphyritic rhyolite domes. The younger phase included the eruption of six evolved high-silica rhyolite domes and one pyroclastic deposit, followed by the eruption of trachyandesite in the adjacent valley to the east. Whole-rock geochemical data indicate that the rhyolites can be divided into three chemical groups, with more evolved compositions erupting through time. The youngest rhyolites along the range crest have the lowest total iron and TiO2 concentrations and the highest incompatible element concentrations, indicative of increasing differentiation with time and elevation. Improved precision on the eruption ages indicates a recurrence interval of approximately 20 thousand years. The eruptive flux for both periods of rhyolitic volcanism is about 0.01 cubic kilometers per thousand years, which is less than the magma resurgence flux rates for syn-caldera and post-caldera eruptions of the Valles Caldera and Yellowstone Caldera volcanic systems. Collectively, these geochemical, geochronological, and volumetric data may facilitate a better understanding of heat flux and the longevity of magmatic sources related to geothermal resources in similar small-volume, silicic systems.

Suggested Citation

Rivera, T.A., Jicha, B.R., Kirby, S., and Peacock, H.B., 2024, Temporal, spatial, and chemical evolution of Quaternary high-silica rhyolites in the Mineral Mountains, Utah, chap. K of Poland, M.P., Ort, M.H., Stovall, W.K., Vaughan, G.R., Connor, C.B., and Rumpf, M.E., eds., Distributed volcanism—Characteristics, processes, and hazards: U.S. Geological Survey Professional Paper 1890, 19 p., https://doi.org/10.3133/pp1890K.

ISSN: 2330-7102 (online)

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Table of Contents

  • Abstract
  • Introduction
  • Materials and Methods
  • Results
  • Discussion
  • Conclusions
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Temporal, spatial, and chemical evolution of Quaternary high-silica rhyolites in the Mineral Mountains, Utah
Series title Professional Paper
Series number 1890
Chapter K
DOI 10.3133/pp1890K
Year Published 2024
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Volcano Science Center
Description v, 19 p.
Country United States
State Utah
Online Only (Y/N) Y
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