A reconnaissance of U-Pb zircon ages in the Cerro Galan system, NW Argentina: Prolonged magma residence, crystal recycling, and crustal assimilation

Christopher Folkes, Shanaka De Silva, Axel Schmitt, Raymond Cas

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    Abstract

    (206)Pb/(238)U ages obtained from Secondary Ionization Mass Spectrometry (SIMS) analyses of zircon crystals in eight ignimbrites from Cerro Galan (Central Andes) reveal insights into magma dynamics and crystallization histories of a sustained (>3.5 Ma), large-volume, crystal-rich magmatic system. This makes the Galan volcanic system an excellent example of repeated large-volume ignimbrite eruptions from a single magmatic system with eruptive recurrence intervals between similar to 50 ka and possibly >1 Ma. (40)Ar/(39)Ar sanidine and biotite ages indicate eruption ages between similar to 2.0 and 5.6 Ma, although biotite results are likely affected by extraneous (40)Ar. In each ignimbrite, interiors of zircon autocrysts frequently crystallized up to several 100 s ka prior to eruption, consistent with long upper-crustal residence times of the pre-eruptive Galan magmas.
    Original languageEnglish
    Pages (from-to)136 - 147
    Number of pages12
    JournalJournal of Volcanology and Geothermal Research
    Volume206
    Issue number3-4
    DOIs
    Publication statusPublished - 2011

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