K-Ar analyses of the post-caldera lavas of Bratan volcano in Bali Island, Indonesia - Ar isotope mass fractionation to light isotope enrichment

Sunyoung Ryu, Hiroshi Kitagawa, Eizo Nakamura, Tetsumaru Itaya, Koichiro Watanabe

    Research output: Contribution to journalArticlepeer-review

    5 Citations (Scopus)

    Abstract

    The post-caldera lavas of Bratan volcano in Bali Island, Indonesia were collected for whole rock chemical analyses and K-Ar analyses. Major and trace element chemistry shows that the lavas are basalts to andesites and typical of subduction-related tectonic setting. The 38Ar/36Ar ratios are 0.1851±3-0.1875±2 and the 40Ar/36Ar, 294.3±0.3-301.6±0.1, which strongly suggest that the mass fractionation to light isotope enrichment took place. The effect of the groundwater on magma is common on the basis of systematic mass fractionation of the atmospheric Ar enriched in lighter isotopes. This case was under the mass fractionation law analyzed numerically, giving the mass fractionation correction ages (14±15, 31±6, 55±22, 66±23, 94±32 and 125±51ka) consistent with the volcano stratigraphy though the magma composition that changed frequently in time.

    Original languageEnglish
    Pages (from-to)107-116
    Number of pages10
    JournalJournal of Volcanology and Geothermal Research
    Volume264
    DOIs
    Publication statusPublished - Aug 15 2013

    Keywords

    • Ar isotope mass fractionation
    • Bali island
    • Bratan volcano
    • K-Ar age
    • Late Pleistocene volcanic rocks
    • Sunda-Banda island arc

    ASJC Scopus subject areas

    • Geophysics
    • Geochemistry and Petrology

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