Multiple isotopic components in Quaternary volcanic rocks of the Cascade Arc near Crater lake, Oregon
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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.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Multiple isotopic components in Quaternary volcanic rocks of the Cascade Arc near Crater lake, Oregon |
| Series title | Journal of Petrology |
| DOI | 10.1093/petrology/35.6.1521 |
| Volume | 35 |
| Issue | 6 |
| Year Published | 1994 |
| Language | English |
| Publisher | Oxford Academic |
| Contributing office(s) | Volcano Science Center |
| Description | 36 p. |
| First page | 1521 |
| Last page | 1556 |
| Country | United States |
| State | Oregon |
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