Tungsten isotopes as tracers of core-mantle interactions: The influence of subducted sediments

O. Nebel*, P. Z. Vroon, D. F. Wiggers de Vries, F. E. Jenner, J. A. Mavrogenes

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    19 Citations (Scopus)

    Abstract

    The postulated difference in W isotopic composition of the Earth's core of ∼2 εW units, compared to the bulk silicate earth (BSE) has previously been used to search for evidence of core-mantle interaction (CMI) in ocean island basalts (OIB). The absence of W isotope anomalies has thus been taken as evidence that CMI does not occur. However, the addition of subducted sediment with high W to the sources of OIB could obscure a core signature. This possibility brings into question the utility of W isotopes as tracers for CMI. To accurately consider the effects of sediment addition to mantle sources of OIB with respect to W requires improved constraints on the abundances of W in subducting sediment. Here, we present high-precision W abundance data (and other HFSE) for a suite of sediments from the Banda subduction regime in East Indonesia. Subducting East Indonesian sediments have trace element concentrations that resemble those of average upper continental crust (UCC), making these sediments valuable to consider as typical of subducted sediments. Average W abundances of 2.1 ppm, corrected for carbon content coupled with current models of 0.5% core addition and 1% sediment addition to EM1 or HIMU plume, suggest that a model hybrid source should exhibit values of εW = -0.24 with ∼25 ppb W. Prior studies have not reported such low W isotopic compositions or high estimated W concentrations present in the sources of either Hawaiian or French Polynesian lavas, so such large additions of core material to these plume sources seems unlikely. Given these constraints, core contributions to these source, if present, can be no more than ∼0.1%.

    Original languageEnglish
    Pages (from-to)751-762
    Number of pages12
    JournalGeochimica et Cosmochimica Acta
    Volume74
    Issue number2
    DOIs
    Publication statusPublished - 15 Jan 2010

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