Upper crustal differentiation processes and their role in 238U-230Th disequilibria at the San Pedro-Linzor volcanic chain (Central Andes)

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dc.contributor.authorGodoy, Benigno
dc.contributor.authorMcGee, Lucy
dc.contributor.authorGonzalez Maurel, Osvaldo
dc.contributor.authorRodriguez, Ines
dc.contributor.authorle Roux, Petrus
dc.contributor.authorMorata, Diego
dc.contributor.authorMenzies, Andrew
dc.date2020
dc.date.accessioned2021-04-30T17:06:06Z
dc.date.available2021-04-30T17:06:06Z
dc.description.abstractU-series data are combined with major and trace element constraints to construct a detailed view of the magmatic system feeding the San Pedro-Linzor volcanic chain, aiding the understanding of how stratovolcanoes in extremely thick arc crust evolve. Lavas from the Quaternary San Pedro-Linzor volcanic chain (Central Andes) have (U-238/Th-230) ranging from 1.015 to 1.072, with U-238 excess even in the less evolved (similar to 57 wt% SiO2) analyzed lavas. Contrary to well-established trends between fluid mobile elements and U-238 excess, ((238)u/Th-230)(0) shows no systematic correlation with ratios indicative of fluid-driven melting (e.g. Ba/Hf and K/La). Moreover, the inverse correlation between (U-238/Th-232) with the amount of slab-derived fluid and the oxidation state of the mantle below Central Andes, which decreases eastwards, suggests that the main control of the U-238 excess is not associated with hydration of the mantle wedge. Changes in (U-238/Th-232) and (Th-230/Th-232)(0) are observed with variations in SiO2 and CaO + Al2O3 contents, and Sr-87/Sr-86 and Dy/Dy* ratios of the lavas. These changes correspond to increasing (U-238/Th-232) with decreasing Dy/Dy* and CaO + Al2O3 ratios, which is attributed to changes in crystallization of mineralogical phases within magmatic chambers during differentiation. Also, Th-230 in-growth is produced during stagnation within magmatic chambers located below the San Pedro-Linzor volcanic chain. Finally, a positive correlation between (Th-230/Th-232)(0) and Sr-87/Sr-86 indicates an important role of crustal contamination, and of new mafic inputs during evolution of the volcanic chain with time. Our observations suggest that better constraints of all magmatic processes are needed to fully understand the U-series disequilibria recognized for the different volcanic structures developed within subduction-related tectonic environments.
dc.identifier.citationJOURNAL OF SOUTH AMERICAN EARTH SCIENCES,Vol.102,,2020
dc.identifier.doi10.1016/j.jsames.2020.102672
dc.identifier.urihttp://repositoriodigital.uct.cl/handle/10925/4019
dc.language.isoen
dc.publisherPERGAMON-ELSEVIER SCIENCE LTD
dc.sourceJOURNAL OF SOUTH AMERICAN EARTH SCIENCES
dc.subject.englishU-series disequilibria
dc.subject.englishSan Pedro - Linzor volcanic chain
dc.subject.englishU-238 excess
dc.subject.englishSubduction zone magmatism
dc.subject.englishAmphibole fractionation
dc.titleUpper crustal differentiation processes and their role in 238U-230Th disequilibria at the San Pedro-Linzor volcanic chain (Central Andes)
dc.typeArticle
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