Casto Ring Zone: A 4,500-km2 fossil hydrothermal system in the Challis Volcanic Field, central Idaho

Abstract

Research Article| June 01, 1984 Casto Ring Zone: A 4,500-km2 fossil hydrothermal system in the Challis Volcanic Field, central Idaho R. E. Criss; R. E. Criss 1U.S. Geological Survey, National Center, Reston, Virginia 22092 Search for other works by this author on: GSW Google Scholar E. B. Ekren; E. B. Ekren 2U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar R. F. Hardyman R. F. Hardyman 2U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Geology (1984) 12 (6): 331–334. https://doi.org/10.1130/0091-7613(1984)12<331:CRZAKF>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R. E. Criss, E. B. Ekren, R. F. Hardyman; Casto Ring Zone: A 4,500-km2 fossil hydrothermal system in the Challis Volcanic Field, central Idaho. Geology 1984;; 12 (6): 331–334. doi: https://doi.org/10.1130/0091-7613(1984)12<331:CRZAKF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract δ18O analyses of granitic and volcanic rocks reveal the largest hydrothermal system ever documented around a single granite pluton, occupying a 4,500-km2 area in central Idaho. The remains of this meteoric-hydrothermal system are principally preserved within a sharply bounded, 15-km-wide, 70-km-diameter annulus of low δ18O rock (+2.0 to −8.8‰) termed the Casto Ring Zone. The zone centered on a less depleted (+4.5) core zone consisting of granitic rocks of the Casto pluton. This 700-km2 Eocene subvolcanic batholith has intruded, domed, and hydrothermally metamorphosed a thick sequence of Challis Volcanics, the stratigraphically low rocks in the 2,000-km2 Van Horn Peak and the 1,000-km2 Thunder Mountain cauldron complexes being most strongly altered. Less extreme 18O depletions occur in the youngest major ash-flow sheets of these complexes, indicating a vertical 18O gradient. Water/rock ratios of geothermal systems are surprisingly insensitive to the circulation scale. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.