Supercritical fluid in the mantle transition zone deduced from H–D interdiffusion of wadsleyite

Wei Sun, Takashi Yoshino, Naoya Sakamoto, Hisayoshi Yurimoto

    Research output: Contribution to journalArticlepeer-review

    9 Citations (Scopus)

    Abstract

    Knowledge of the distribution of water in the Earth's mantle is key to understanding the mantle convection and geochemical evolution of the Earth. As wadsleyite and ringwoodite can incorporate large amounts of water in their crystal structures, proton conduction has been invoked to account for the widespread conductive anomalies observed in the mantle wedge, where descending slab stagnates at the transition zone. However, there is a lot of controversy on whether proton conduction by itself is able to explain such anomalies, because of large discrepancy in the extent of the water effect deduced from previous electrical conductivity measurements on hydrous polycrystalline wadsleyite and ringwoodite. Here we report the hydrogen self-diffusion coefficient obtained from H–D interdiffusion experiments in wadsleyite single-crystal couples. Our results demonstrate that the effect of water on the electrical conductivity of wadsleyite is limited and hydrous wadsleyite by itself is unable to explain conductive anomalies in the transition zone. In contrast, the expected hydrogen effective diffusion does not allow the wide propagation of water between the stagnant slab and surrounding mantle, probably leading to persistence of local water saturation and continuous release of supercritical fluids at the stagnant slab roof on geological time scales. This phenomenon provides an alternative explanation for both the high-conductivity and seismic-velocity anomalies observed in the mantle wedge at the transition-zone depth.

    Original languageEnglish
    Pages (from-to)309-317
    Number of pages9
    JournalEarth and Planetary Science Letters
    Volume484
    DOIs
    Publication statusPublished - Feb 15 2018

    Keywords

    • H–D interdiffusion
    • electrical conductivity
    • mantle transition zone
    • supercritical fluid
    • wadsleyite

    ASJC Scopus subject areas

    • Geophysics
    • Geochemistry and Petrology
    • Earth and Planetary Sciences (miscellaneous)
    • Space and Planetary Science

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