22. Interaction between Subducted Oceanic Slab and Wedge Mantle Inferred from Across-arc Variations of Pb, Sr and Nd Isotopic Compositions in Northeastern Japan

Tomovuki Shibata, Eizo Nakamura

    Research output: Contribution to journalArticlepeer-review

    6 Citations (Scopus)

    Abstract

    Isotopic compositions of Pb, Sr and Nd have been determined for island arc basalts from northeastern Japan. The Sr and Pb isotopic ratios decrease, and Nd isotopic ratios increase from the volcanic front towards the back-arc side. The isotopic compositions at the most back-arc side are nearly identical to those of MORB, indicating that the across-arc isotopic variations were caused by a two-component mixing between MORB-type wedge mantle and oceanic sediments with different degrees of sediment involvement which depend on the depth of subducting oceanic slab. The abundance ratios among Pb, Sr and Nd in the subducted oceanic sediment were estimated from the mixing relationships in the isotope compositions. The estimated Sr/Pb ratio of subducted sediments does not change during subduction, while the Nd/Sr and Nd/Pb increase towards the back-arc side. These observations suggest that the subduction component was added to the wedge mantle as a fluid through the dehydration of subducted oceanic sediment and the degree of dehydration decreases with increase in the depth of slab, and that the subducting oceanic slab does not melt beneath northeastern Japan.

    Original languageEnglish
    Pages (from-to)115-120
    Number of pages6
    JournalProceedings of the Japan Academy Series B: Physical and Biological Sciences
    Volume67
    Issue number7
    DOIs
    Publication statusPublished - 1991

    Keywords

    • Pb Sr and Nd isotopic compositions
    • dehydration
    • oceanic slab
    • partial melting
    • subduction
    • wedge mantle

    ASJC Scopus subject areas

    • Agricultural and Biological Sciences(all)
    • Physics and Astronomy(all)

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