Origin of the slab component in arc lavas from across-arc variation of B and Pb isotopes

Tsuyoshi Ishikawa, Eizo Nakamura

    Research output: Contribution to journalArticlepeer-review

    304 Citations (Scopus)

    Abstract

    At convergent margins, the subducting oceanic slab is thought to dehydrate, producing fluids which metasomatize the overlying mantle wedge where island-arc magma forms. However, the nature and origin of the metasomatizing fluid, its source composition and its relation to the genesis of the chemical characteristics of arc magmas are largely controversial. Across-arc variation in the chemistry of arc lavas provides a useful key to this problem, because it may reflect the changes in the physical conditions of the subducting slab that control mass transfer from slab to mantle wedge as a function of depth. Here we report clear across-arc variations in the concentrations and isotopic compositions of boronand lead observed in lavas from the Izu arc (Japan). Our data suggest that a homogeneous slab fluid contributes to all Izu volcan-oes, but that the amount of this fluid decreases continuously with increasing depth of the subducting slab. Whereas the Izu slab fluid conies primarily from altered oceanic crust, our data for high-Mg andesites from the Setouchi volcanic belt (a nearby fore-arc) indicate a significant involvement of sediment in the fluid source.

    Original languageEnglish
    Pages (from-to)205-208
    Number of pages4
    JournalNature
    Volume370
    Issue number6486
    DOIs
    Publication statusPublished - Jan 1 1994

    ASJC Scopus subject areas

    • General

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