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Hydrothermal alteration of the Late Eocene Caetano ash-flow caldera, north-central Nevada: A field and ASTER remote sensing study

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Abstract

Geologic mapping and analysis of ASTER remote sensing data were used to define the effects of a large hydrothermal system in the 12–18 by 22 km Caetano caldera. The caldera formed at ~33.8Ma during eruption of >1100km3 of the rhyolitic Caetano Tuff that left a 1 km deep basin which was partly filled by a lake. Magma resurgence resulted in shallow(<1 km) emplacement of the Redrock Canyon granite porphyry intrusion into caldera fill in the southwestern part of the caldera. Field and petrographic studies indicate that heat from the pluton or from deeper residual Caetano magma caused a large hydrothermal system to form that altered both the pluton and intracaldera Caetano Tuff throughout the western half of the caldera. ASTER-based mineral mapping shows that the most intense alteration, including local alunite, developed primarily along the southwestern and western caldera margins. Alteration was most intense in the Redrock Canyon intrusion itself and in the upper unit of the Caetano Tuff, which is a sequence of thin ash flows interlayered with finely bedded sedimentary rocks and mesobreccia. Hydrothermally altered intracaldera tuff was domed and crosscut by the unaltered 33.78 ± 0.05 Ma Carico Lake pluton, indicating that caldera formation, magma resurgence, pluton emplacement, and hydrothermal activity all occurred in less than about 100 ka.

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Publication type Conference Paper
Publication Subtype Conference Paper
Title Hydrothermal alteration of the Late Eocene Caetano ash-flow caldera, north-central Nevada: A field and ASTER remote sensing study
Year Published 2010
Language English
Publisher Geological Society of Nevada
Contributing office(s) Central Mineral and Environmental Resources Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, Western Mineral and Environmental Resources Science Center
Description 29 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Proceedings of the Geological Society of Nevada 2010 symposium
First page 1055
Last page 1083
Conference Title Geological Society of Nevada 2010 Symposium
Conference Location Reno, NV
Conference Date May 14–22, 2010
Country United States
State Nevada
Other Geospatial Caetano caldera
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