Hydrogen diffusion mechanism in the mantle deduced from H-D interdiffusion in wadsleyite

Wei Sun, Takashi Yoshino, Naoya Sakamoto, Hisayoshi Yurimoto

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Classical view has interpreted deuterons in nominally anhydrous minerals (NAMs) diffuse slightly slower than protons by the Knudsen limit of 2, whereas here we report deuteron diffusion is about 3∼7 times faster than proton one in Mg2SiO4 wadsleyite based on the H-D interdiffusion couple experiments using a pair of wadsleyite single crystal at 16 GPa and 900-1300 K. Our results indicate hydrogen diffusion in wadsleyite is affected by multiple diffusion mechanisms, of which, proton (deuteron) migrating along interstitial defects is particularly efficient to separate hydrogen isotopes in crystalline network probably owing to a quantum sieving effect. The resulting diffusion-driven H/D fractionation can explain common observations of deuterium depletion of NAMs in mantle xenoliths, suggesting that MORB inclusions hosted in xenoliths are more reliable for indicating the hydrogen isotope composition of the mantle rather than the xenolithic NAMs.

    Original languageEnglish
    Article number116815
    JournalEarth and Planetary Science Letters
    Volume561
    DOIs
    Publication statusPublished - May 1 2021

    Keywords

    • asymmetric
    • deuterium
    • diffusion
    • hydrogen
    • mantle
    • wadsleyite

    ASJC Scopus subject areas

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

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