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Title: Quaternary rhyolite from the Mineral Mountains, Utah, USA. Final report, Volume 77-10

Abstract

A suite of silicic volcanic rocks is associated with the Roosevelt Hot Springs geothermal area in southwestern Utah. The volcanic sequence includes Tertiary rhyolite 8 My old and obsidian, ash and rhyolite of Quaternary age. The Quaternary lavas are characterized by high silica content (76.5% Si0/sub 2/) and total alkalies in excess of 9 percent. Obsidians commonly contain greater amounts of fluorine than water. Two older flows (0.8 My) can be distinguished from younger dome and pyroclastic material (approximately 0.5 My) by subtle differences in their chemistry. The mineralogy of the rhyolites consists of alkali feldspar, plagioclase, and small amounts of Fe-Ti oxides, biotite, hornblende and rare allanite. Fe-Ti oxide temperatures are 740 to 785/sup 0/C for the flows and 635 to 665/sup 0/C for the domes; two feldspar temperatures give similar results. The phase relationships of bulk rock, glass and feldspar compositions demonstrate that the younger Quaternary rhyolites could have been derived from the earlier magma type, represented by the obsidian flows, by a process of crystal fractionation. The major phases which must fractionate are alkali feldspar, plagioclase and quartz with minor amounts of biotite, magnetite and ilmenite participating also. Trace element patterns support this scheme as well. Themore » Tertiary lavas cannot be related to the Quaternary rhyolites and are thought to represent a separate event.« less

Authors:
;
Publication Date:
Research Org.:
Univ. of Utah, Salt Lake City, UT (United States)
OSTI Identifier:
5696814
Report Number(s):
IDO-1601-T7
DOE Contract Number:  
EY-76-S-07-1601
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; FELDSPARS; CRYSTALLIZATION; RHYOLITES; MINERALOGY; PETROGRAPHY; VOLCANIC ROCKS; BIOTITE; ELECTRON MICROPROBE ANALYSIS; GEOCHEMISTRY; GEOLOGY; GEOTHERMOMETRY; HORNBLENDE; PETROGENESIS; QUATERNARY PERIOD; UTAH; AMPHIBOLE; CENOZOIC ERA; CHEMICAL ANALYSIS; CHEMISTRY; GEOLOGIC AGES; IGNEOUS ROCKS; MICA; MICROANALYSIS; MINERALS; NORTH AMERICA; PHASE TRANSFORMATIONS; ROCKS; ROCKY MOUNTAIN REGION; USA; Geothermal Legacy; 150201* - Geology & Hydrology of Geothermal Systems- USA- (-1989)

Citation Formats

Evans, Jr, S H, and Nash, W P. Quaternary rhyolite from the Mineral Mountains, Utah, USA. Final report, Volume 77-10. United States: N. p., 1978. Web. doi:10.2172/5696814.
Evans, Jr, S H, & Nash, W P. Quaternary rhyolite from the Mineral Mountains, Utah, USA. Final report, Volume 77-10. United States. https://doi.org/10.2172/5696814
Evans, Jr, S H, and Nash, W P. 1978. "Quaternary rhyolite from the Mineral Mountains, Utah, USA. Final report, Volume 77-10". United States. https://doi.org/10.2172/5696814. https://www.osti.gov/servlets/purl/5696814.
@article{osti_5696814,
title = {Quaternary rhyolite from the Mineral Mountains, Utah, USA. Final report, Volume 77-10},
author = {Evans, Jr, S H and Nash, W P},
abstractNote = {A suite of silicic volcanic rocks is associated with the Roosevelt Hot Springs geothermal area in southwestern Utah. The volcanic sequence includes Tertiary rhyolite 8 My old and obsidian, ash and rhyolite of Quaternary age. The Quaternary lavas are characterized by high silica content (76.5% Si0/sub 2/) and total alkalies in excess of 9 percent. Obsidians commonly contain greater amounts of fluorine than water. Two older flows (0.8 My) can be distinguished from younger dome and pyroclastic material (approximately 0.5 My) by subtle differences in their chemistry. The mineralogy of the rhyolites consists of alkali feldspar, plagioclase, and small amounts of Fe-Ti oxides, biotite, hornblende and rare allanite. Fe-Ti oxide temperatures are 740 to 785/sup 0/C for the flows and 635 to 665/sup 0/C for the domes; two feldspar temperatures give similar results. The phase relationships of bulk rock, glass and feldspar compositions demonstrate that the younger Quaternary rhyolites could have been derived from the earlier magma type, represented by the obsidian flows, by a process of crystal fractionation. The major phases which must fractionate are alkali feldspar, plagioclase and quartz with minor amounts of biotite, magnetite and ilmenite participating also. Trace element patterns support this scheme as well. The Tertiary lavas cannot be related to the Quaternary rhyolites and are thought to represent a separate event.},
doi = {10.2172/5696814},
url = {https://www.osti.gov/biblio/5696814}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 1978},
month = {Wed Mar 01 00:00:00 EST 1978}
}