Journal article
Time-scales of Differentiation from Mafic Parents to Rhyolite in North American Continental Arcs
Journal of petrology, Vol.44(9), pp.1703-1726
09/2003
DOI: 10.1093/petrology/egg057
Abstract
Young rhyolites and associated lavas and magmatic enclaves from the Katmai–Novarupta 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 major and trace element concentrations, to investigate the time-scales of the processes that lead to rhyolite generation in continental arcs. Basalts and basaltic andesites typically migrate from the mantle to the surface within several thousand years. Variations in (230Th)/(232Th) and (238U)/(232Th) ratios with SiO2 concentrations in intermediate lavas appear to result from crystal fractionation combined with assimilation of recently crystallized magmas. These data also suggest that ∼104–105 years of mafic magmatism are required at a volcanic center to generate silicic andesites and dacites. Rhyolite genesis involves varying proportions of crystal fractionation of intermediate magmas and assimilation of crust. The near-equilibrium (238U)/(230Th) ratios for all of the rhyolites suggest an average time since U was last fractionated from Th for the constituents making up these rhyolites of >105 years. Therefore, the residence times of continental magmas and their entrained crystals appear to increase by a minimum of 2–3 orders of magnitude with increasing SiO2 concentrations from basalt to rhyolite.
Details
- Title: Subtitle
- Time-scales of Differentiation from Mafic Parents to Rhyolite in North American Continental Arcs
- Creators
- M. K Reagan - University of IowaK. W. W Sims - Woods Hole Oceanographic InstitutionJ Erich - ExxonMobilR. B Thomas - University of MinnesotaH Cheng - University of MinnesotaR. L Edwards - University of MinnesotaG Layne - Woods Hole Oceanographic InstitutionL Ball - Woods Hole Oceanographic Institution
- Resource Type
- Journal article
- Publication Details
- Journal of petrology, Vol.44(9), pp.1703-1726
- Publisher
- Oxford University Press
- DOI
- 10.1093/petrology/egg057
- ISSN
- 0022-3530
- eISSN
- 1460-2415
- Language
- English
- Date published
- 09/2003
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229297902771
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