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High and highly anisotropic electrical conductivity of the asthenosphere due to hydrogen diffusion in olivine TEXT SIZE: A A A

Experimental studies on electrical conductivity in hydrated olivine had been made only at relatively low temperatures. The extrapolation of these data to asthenosphere temperatures shows that explaining high and highly anisotropic conductivity by hydrogen is difficult. We present new experimental results on the electrical conductivity in hydrated olivine single crystals measured under a broader temperature range than before (T (temperature) = 573-1373 K at P (pressure) = 4 GPa). The new results agree well with the previous results at low temperatures (T <900 K), whereas at higher temperatures (T > 1000 K) substantial deviations from the previous results are observed: (i) anisotropy in conductivity increases with temperature, and (ii) activation energies at high temperature regime are substantially higher than those at lower T. The high temperature behavior is consistent with a model invoking diffusion of two-protons at M-site vacancy, whereas the low temperature behavior suggests conduction by more mobile species such as free proton. The present results (i) explain the discrepancy between different previous studies conducted under different temperature regimes, and (ii) show that most of geophysical observations on the electrical conductivity in the asthenosphere including the high and highly anisotropic conductivity can be explained by high water content in the asthenosphere that is consistent with the geochemical model. Combining with a previous model of low seismic wave velocity of the asthenosphere, a subsolidus model invoking the role of hydrogen provides a unified explanation for the geophysical anomalies of the asthenosphere. (C) 2014 Elsevier B.V. All rights reserved.

Publication name

 EARTH AND PLANETARY SCIENCE LETTERS, 408 79-86; 10.1016/j.eps1.2014.10.003 DEC 15 2014

Author(s)

 Dai, Lidong; Karato, Shun-ichiro

Corresponding author 

 Karato, Shun-ichiro
 shun-ichiro.karato@yale.edu
 Yale Univ, Dept Geol & Geophys, New Havena, CT 06520 USA 

Author(s) from IGCAS   DAI Lidong

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