A nearly water-saturated mantle transition zone inferred from mineral viscosity

Hongzhan Fei, Daisuke Yamazaki, Moe Sakurai, Nobuyoshi Miyajima, Hiroaki Ohfuji, Tomoo Katsura, Takafumi Yamamoto

    Research output: Contribution to journalArticlepeer-review

    49 Citations (Scopus)

    Abstract

    An open question for solid-earth scientists is the amount of water in Earth’s interior. The uppermost mantle and lower mantle contain little water because their dominant minerals, olivine and bridgmanite, have limited water storage capacity. In contrast, the mantle transition zone (MTZ) at a depth of 410 to 660 km is considered to be a potential water reservoir because its dominant minerals, wadsleyite and ringwoodite, can contain large amounts of water [up to 3 weight % (wt %)]. However, the actual amount of water in the MTZ is unknown. Given that water incorporated into mantle minerals can lower their viscosity, we evaluate the water content of the MTZ by measuring dislocation mobility, a property that is inversely proportional to viscosity, as a function of temperature and water content in ringwoodite and bridgmanite. We find that dislocation mobility in bridgmanite is faster by two orders of magnitude than in anhydrous ringwoodite but 1.5 orders of magnitude slower than in water-saturated ringwoodite. To fit the observed mantle viscosity profiles, ringwoodite in the MTZ should contain 1 to 2 wt % water. The MTZ should thus be nearly water-saturated globally.

    Original languageEnglish
    Article numbere1603024
    JournalScience Advances
    Volume3
    Issue number6
    DOIs
    Publication statusPublished - Jun 2017

    ASJC Scopus subject areas

    • General

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