We investigated the electrical conductivity of Ti-H-doped synthetic olivine aggregates at 4 GPa,873–1273 K, and controlled oxygen fugacities. Under a given pressure and temperature, electricalconductivity depends on both hydrogen and Ti content, but these samples show different conductivitybehavior from that observed in Tipoor sample such as San Carlos olivine. We found that when Ti content iscomparable to or larger than hydrogen content, Ti has notable effects on electrical conductivity, but theeffects of Ti is different between the Hrich and the Hpoor regimes. In the Hrich regime, electricalconductivity of olivine is weakly dependent on Ti content but has different sensitivity to water content than aTipoor olivine. In contrast, in the Hpoor regime, electrical conductivity of Tirich olivine issubstantially higher than the conductivity of Tipoor olivine. As a consequence, the effect of hydrogen for theTirich synthetic olivine on electrical conductivity is smaller than for the Tipoor (natural) olivine forthe modest H content expected in the asthenosphere, whereas in the Hpoor lithosphere Ti will enhance theelectrical conductivity substantially. Possible models to explain these observations are proposed includingthe interaction of Ti related defects and Hrelated defects as well as the charge transfer caused by thehopping conduction due to Ti3+？ Ti4+under the Hpoor conditions. We conclude that the addition of Ti toolivine affects the behavior of Hrelated defects, and therefore the applications of results from Tiricholivine samples to the Tipoor real Earth need to be made with great care.
| Journal of Geophysical Research: Solid Earth, 2020, 125(10), e2020JB020309 |
| Dai Lidong and Karato Shun-ichiro |
1. Key Laboratory of High‐Temperature and High‐Pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
2. Department of Earth and Planetary Sciences, Yale University, New Haven, CT, USA
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