| Abstract: | Quaternary lavas and pyroclastic rocks of Mount Mazama, Crater lake caldera, and the surrounding area have variable Sr, Nd, and Pb isotopic compositions. High-alumina olivine tholeiites have 87Ar/86Ar ratios of 0.70346-0.70364; basaltic andesite, 0.70349-0.70372; shoshonitic basaltic andesite, 0.70374-0.70388; and andesite, 0.70324-0.70383. Dacites of Mount Mazama have 87Sr/ 86Sr ratios of 0.70348-0.70373. Most rhyodacites converge on 0.7037. Andesitic to mafic-cumulate scoriae of the climatic eruption, and enclaves in pre-climactic rhyodacites, cluster in two groups but show nearly the entire 87Sr/86Sr range of the data set, confirming previously suggested introduction of diverse parental magmas into the growing climactic chamber. Magma evolution is described. -from Authors |
| Genre: | Article |
| ProdID: | 70017556 |
| Citation Author: | Bacon, C. R.; Gunn, S. H.; Lanphere, M. A.; Wooden, J. L. |
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| Citation End Page: | 1556 |
| Citation Issue: | 6 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Petrology |
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| Citation Number Of Pages: | 36 |
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| Citation Search Results Text: | Multiple isotopic components in Quaternary volcanic rocks of the Cascade Arc near Crater lake, Oregon; 1994; Article; Journal; Journal of Petrology; Bacon, C. R.; Gunn, S. H.; Lanphere, M. A.; Wooden, J. L. |
| Citation Start Page: | 1521 |
| Citation Volume: | 35 |
| Citation Year: | 1994 |
| Type: | citation/reference |
| Text: | Multiple isotopic components in Quaternary volcanic rocks of the Cascade Arc near Crater lake, Oregon; 1994; Article; Journal; Journal of Petrology; Bacon, C. R.; Gunn, S. H.; Lanphere, M. A.; Wooden, J. L. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
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