Letter | Published:

Experimental evidence for the origin of lead enrichment in convergent-margin magmas

Nature volume 378, pages 5456 (02 November 1995) | Download Citation

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Abstract

IT has been proposed1–5 that the low Ce/Pb ratio of subduction-related basalts, relative to their oceanic counterparts, arises by the preferential transfer of lead to the mantle wedge (overlying the subducting slab) by non-magmatic processes. Fluxing of the mantle wedge by low-Ce/Pb fluids, generated by the dehydration of sub-ducted oceanic crust, is one mechanism favoured for this process (see, for example, ref. 5). Here we report the results of a series of high-pressure experiments, which confirm that low-Ce/Pb fluids coexist with the dominant mineral phases (garnet and clinopyroxene) produced during high-pressure dehydration of altered basalt. Our results show that the production of subduction-zone magmas from mantle sources fluxed by basalt-derived fluid is a mechanism by which relatively lead-rich, cerium-poor, mantle-derived material is added to the continents. The lead enrichment of the Earth's continental crust is thus a continuing process occurring at conver-gent margins.

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Affiliations

  1. Earth Sciences Division, Lawrence Livermore National Laboratory, PO Box 808, L-202, Livermore, California 94551, USA

    • James M. Brenan
    • , Henry F. Shaw
    •  & Frederick J. Ryerson
  2. Institute for Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, PO Box 808, L-202, Livermore, California 94551, USA

    • Frederick J. Ryerson

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https://doi.org/10.1038/378054a0

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