| Abstract: | The largest fossil hydrothermal system occupying a 4500 km2 area in central Idaho is revealed by delta 18O studies. The remains of this meteoric-hydrothermal system are preserved within a sharply bounded, 15 km wide, 70-km-diameter annulus of low delta 18O rock (+2.0 to -8.8per mille) termed the Castro ring zone. The zone is centred on a less depleted (+4.5) core zone consisting of granitic rocks of the Castro 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 2000-km2 Van Horn Peak and the 1000-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.-L.-di H. |
| Genre: | Article |
| ProdID: | 70013982 |
| Citation Author: | Criss, R. E.; Ekren, E. B.; Hardyman, R. F. |
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| Citation End Page: | 334 |
| Citation Issue: | 6 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geology |
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| Citation Number Of Pages: | 4 |
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| Citation Search Results Text: | Castro ring zone: a 4,500-km2 fossil hydrothermal system in the Challis volcanic field, central Idaho.; 1984; Article; Journal; Geology; Criss, R. E.; Ekren, E. B.; Hardyman, R. F. |
| Citation Start Page: | 331 |
| Citation Volume: | 12 |
| Citation Year: | 1984 |
| Type: | citation/reference |
| Text: | Castro ring zone: a 4,500-km2 fossil hydrothermal system in the Challis volcanic field, central Idaho.; 1984; Article; Journal; Geology; Criss, R. E.; Ekren, E. B.; Hardyman, R. F. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sun, 1 Jan 1984 00:00 -0600 |
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