U-Th isotopes in arc magmas: Implications for element transfer from the subducted crust

Chris Hawkesworth, S P Turner, F McDermott, D W Peate, P vanCalsteren

    Research output: Contribution to journalArticlepeer-review

    704 Citations (Scopus)

    Abstract

    Uranium-thorium isotope results from island are volcanic rocks were used to investigate the rates of transfer of fluids and sediments from the downgoing slab. Uranium, but not thorium, is readily mobilized in the fluid. A negative array between thorium/cerium and neodymium-143/neodymium-144 indicates that significant amounts of the thorium in are rocks are derived from subducted sediments, although perhaps only about 30 percent of the thorium in subducted sediments is returned to the crust in this way. The transfer times for fluid through the mantle wedge are about 30,000 to 120,000 years, whereas those for sediment melts may be several million years. The law average uranium/thorium ratios of bulk crust primarily reflect different crustal generation processes in the Archaean.

    Original languageEnglish
    Pages (from-to)551-555
    Number of pages5
    JournalScience
    Volume276
    Issue number5312
    Publication statusPublished - 25 Apr 1997

    Keywords

    • YOUNG VOLCANIC-ROCKS
    • ISLAND-ARC
    • DECAY-SERIES
    • MANTLE EVOLUTION
    • OCEANIC BASALTS
    • URANIUM SERIES
    • LAVAS
    • CONSTRAINTS
    • SYSTEMATICS
    • COMPONENT

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