| Abstract: | The majority offelsic rocks from composite centers in teh southernmost Cascades have geochemical and Sr, Nd and Pb isotopic ratios that suggest derivation by partial melting of lower crust that is compositionally similar to cale-alkaline basalts observed in the region. Only a few felsic rocks have ???18O and Pb isotopic compositions that indicate interaction with the upper crust. Mineralogical and geochemical differences among the felsic magmas results primarily from melting under variable f(H2O) and lower temperature conditions leaves an amphibole-rich residuum, and produced magmas that have amphibole ?? biotite phenocrysts, relatively high silica contents, and pronounced middle rare earch element depletions. These conclusions are consistent with published thermal models that suggest that reasonable volumes of basaltic magma emplaced beneath large composite centers in the southernmost Cascades can serve as the eat source for melting of the lower crust. Melting of the lower crust under varible f(H2O contents of these basaltic magmas. |
| Genre: | Article |
| ProdID: | 70021296 |
| Citation Author: | Borg, L. E.; Clynne, M. A. |
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| Citation End Page: | 1222 |
| 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: | 26 |
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| Citation Search Results Text: | The petrogenesis of felsic calc-alkaline magmas from the southernmost Cascades, California: origin by partial melting of basaltic lower crust; 1998; Article; Journal; Journal of Petrology; Borg, L. E.; Clynne, M. A. |
| Citation Start Page: | 1197 |
| Citation Volume: | 39 |
| Citation Year: | 1998 |
| Type: | citation/reference |
| Text: | The petrogenesis of felsic calc-alkaline magmas from the southernmost Cascades, California: origin by partial melting of basaltic lower crust; 1998; Article; Journal; Journal of Petrology; Borg, L. E.; Clynne, M. A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Thu, 1 Jan 1998 00:00 -0600 |
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