Localised magmatic constraints on continental back-arc volcanism in southern Mendoza, Argentina

the Santa Maria Volcano

Venera R. Espanon*, Allan R. Chivas, Simon P. Turner, Leslie P J Kinsley, Anthony Dosseto

*Corresponding author for this work

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    The Payún Matrú Volcanic Field constitutes part of the continental back-arc in Argentina. This volcanic field has been the focus of several regional investigations; however, geochemical analysis of recent volcanoes (<8 ka) at the scale of an individual volcano has not been conducted. We present a morphological description for the Santa Maria Volcano in addition to results from major and trace element analysis and 238U-230Th-226Ra disequilibria. The trace element evidence suggests that the Santa Maria magmatic source has a composition similar to that of the local intraplate end member (resembling an ocean island basalt-like source), with a slight contribution from subduction-related material. The U-series analyses suggest a high 226Ra excess over 230Th for this volcano, which is not derived from a shallow process such as hydrothermal alteration or upper crustal contamination. Furthermore, intermediate-depth processes such as fractional crystallisation have been inferred for the Santa Maria Volcano, but they are not capable of producing the 226Ra excess measured. The 226Ra excess is explained by deep processes like partial melting of mantle lithologies with some influence from subducted Chilean trench sediments. Due to the short half-life of 226Ra (1600 years), we infer that fast magma ascent rates are required to preserve the high 226Ra excess.

    Original languageEnglish
    Article number83
    Pages (from-to)1-13
    Number of pages13
    JournalBulletin of Volcanology
    Volume78
    Issue number11
    DOIs
    Publication statusPublished - 1 Nov 2016

    Keywords

    • Back-arc basalts
    • U-series
    • Ra-226 excess
    • Payenia Basaltic Province
    • Andean southern volcanic zone

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