Large-volume, low-δ18O rhyolites of the central Snake River Plain, Idaho, USA

Scott Boroughs, John Wolff, Bill Bonnichsen, Martha Godchaux, Peter Larson

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65 Scopus citations


The Miocene Bruneau-Jarbidge and adjacent volcanic fields of the central Snake River Plain, southwest Idaho, are dominated by high-temperature rhyolitic tuffs and lavas having an aggregate volume estimated as 7000 km3. Samples from units representing at least 50% of this volume are strongly depleted in 18O, with magmatic feldspar δ18OVSMOW (Vienna standard mean ocean water) values between -1.4‰ and 3.8‰. The magnitude of the 18O depletion and the complete lack of any rhyolites with normal values (7‰-10‰) combine to suggest that assimilation or melting of a caldera block altered by near-contemporaneous hydrothermal activity is unlikely. Instead, we envisage generation of the high-temperature rhyolites by shallow melting of Idaho Batholith rocks, under the influence of the Yellowstone hotspot, affected by Eocene meteoric-hydrothermal events. The seeming worldwide scarcity of strongly 18O-depleted rhyolites may simply reflect a similar scarcity of suitable crustal protoliths.

Original languageEnglish (US)
Pages (from-to)821-824
Number of pages4
Issue number10
StatePublished - Oct 2005

Bibliographical note

Copyright 2013 Elsevier B.V., All rights reserved.


  • Meteoric-hydrothermal alteration
  • Oxygen isotopes
  • Rhyolites
  • Snake River Plain


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