TY - JOUR
T1 - A nearly water-saturated mantle transition zone inferred from mineral viscosity
AU - Fei, Hongzhan
AU - Yamazaki, Daisuke
AU - Sakurai, Moe
AU - Miyajima, Nobuyoshi
AU - Ohfuji, Hiroaki
AU - Katsura, Tomoo
AU - Yamamoto, Takafumi
N1 - Funding Information:
We acknowledge S. Yamashita for help in FT-IR measurement and J. Ando, T. Yoshino, C. Zhao, F. Xu, L. Xie, and L. Wang for discussions. Funding: This work was supported by Japan Society for the Promotion of Science funding to H.F. (no. 25003327) and partially supported by Deutsche Forschungsgemeinschaft (DFG) funding to T.K. (no. KA3434/9-1) and DFG grant no. INST 91/315-1 FUGG.
Publisher Copyright:
2017 © The Authors, some rights reserved.
PY - 2017/6
Y1 - 2017/6
N2 - 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.
AB - 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.
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U2 - 10.1126/sciadv.1603024
DO - 10.1126/sciadv.1603024
M3 - Article
C2 - 28630912
AN - SCOPUS:85033564180
VL - 3
JO - Science advances
JF - Science advances
SN - 2375-2548
IS - 6
M1 - e1603024
ER -