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The petrogenesis of felsic calc-alkaline magmas from the southernmost Cascades, California: origin by partial melting of basaltic lower crust

Journal of Petrology

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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.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The petrogenesis of felsic calc-alkaline magmas from the southernmost Cascades, California: origin by partial melting of basaltic lower crust
Series title:
Journal of Petrology
Volume
39
Issue:
6
Year Published:
1998
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1197
Last page:
1222
Number of Pages:
26