Comparison of rhyolites from continental rift, continental arc and oceanic island arc: Implication for the mechanism of silicic magma generation

Dereje Ayalew, Akira Ishiwatari

    Research output: Contribution to journalReview articlepeer-review

    25 Citations (Scopus)

    Abstract

    We discuss the chemical compositions of rhyolites from three distinct tectonic settings: (i) the continental rift from Ethiopia (both Oligocene-Miocene and Quaternary rhyolites); (ii) the early Miocene continental arc of Japan (the Mt Wasso rhyolites related to the rifting of the Japan Sea); and (iii) the oceanic Izu-Bonin Island Arc. The comparison reveals that the oceanic island arc rhyolites have high contents of CaO, Al2O3, and Sr, and extremely low abundance of trace elements including K2O. In contrast, the Ethiopian continental rift rhyolites are characterized by low contents of CaO, Al2O3, and Sr, and high contents of K2O, and are enriched in the whole range of trace elements. The continental arc Mt Wasso rhyolites are apparently low in Nb content, although they display similar chemical trends to those of the Ethiopian rhyolites. This obvious difference in the chemical signatures of the rhyolites from the three tectonic settings is the consequence of their derivation from different sources. The implication of this result is that fractional crystallization processes were dominant in the rift-related rhyolites both from continental rift and continental arc regardless of the prevailing tectonic setting and the nature of the crust (age, thickness, composition), whereas the oceanic island arc rhyolites may form through partial melting of young, mafic crust.

    Original languageEnglish
    Pages (from-to)78-93
    Number of pages16
    JournalIsland Arc
    Volume20
    Issue number1
    DOIs
    Publication statusPublished - 2011 Mar 1

    Keywords

    • Continental arc
    • Continental rift
    • Fractionation of mantle-derived magma
    • Oceanic island arc
    • Partial melting of mafic crust
    • Rhyolites

    ASJC Scopus subject areas

    • Geology

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