Time-scales of Differentiation from Mafic Parents to Rhyolite in North American Continental Arcs期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

Time-scales of Differentiation from Mafic Parents to Rhyolite in North American Continental Arcs

Authors:	REAGAN, M. K. SIMS, K. W. W. ERICH, J. THOMAS, R. B. CHENG, H. EDWARDS, R. L. LAYNE, G. BALL, L.

Affiliation:	¹ DEPARTMENT OF GEOSCIENCE, UNIVERSITY OF IOWA, IOWA CITY, IA 52242, USA ² DEPARTMENT OF GEOLOGY AND GEOPHYSICS, WOODS HOLE OCEANOGRAPHIC INSTITUTION, WOODS HOLE, MA 02543, USA ³ EXXON-MOBIL, 800 BELL STREET, HOUSTON, TX 77002, USA ⁴ MINNESOTA ISOTOPE LABORATORY, DEPARTMENT OF GEOLOGY AND GEOPHYSICS, UNIVERSITY OF MINNESOTA, MINNEAPOLIS, MN 55455, USA

Abstract:	Young rhyolites and associated lavas and magmatic enclaves fromthe KatmaiNovarupta volcanic system (Alaskan Peninsula),and the Crater Lake and Medicine Lake volcanic system (Cascades)were analyzed for U and Th isotope abundances, as well as majorand trace element concentrations, to investigate the time-scalesof the processes that lead to rhyolite generation in continentalarcs. Basalts and basaltic andesites typically migrate fromthe mantle to the surface within several thousand years. Variationsin (²³⁰Th)/(²³²Th) and (²³⁸U)/(²³²Th) ratios with SiO₂ concentrationsin intermediate lavas appear to result from crystal fractionationcombined with assimilation of recently crystallized magmas.These data also suggest that

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