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ID 55450
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Yoshino, Takashi Institute for Planetary Materials, Okayama University
Zhang, Baohua Key Laboratory for High-Temperature and High-Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences
Rhymer, Brandon Department of Geosciences, State University of New York at Stony Brook
Zhao, Chengcheng Institute for Planetary Materials, Okayama University
Fei, Hongzhan Bayerisches Geoinstitut, University of Bayreuth
Abstract
Electrical conductivity of dry forsterite has been measured in muli-anvil apparatus to investigate the pressure dependence of ionic conduction in forsterite. The starting materials for the conductivity experiments were a synthetic forsterite single crystal and a sintered forsterite aggregate synthesized from oxide mixture. Electrical conductivities were measured at 3.5, 6.7, 9.6, 12.1, and 14.9 GPa between 1300 and 2100 K. In the measured temperature range, the conductivity of single crystal forsterite decreases in the order of [001], [010], and [100]. In all cases, the conductivity decreases with increasing pressure and then becomes nearly constant for [100] and [001] and slightly increases above 7 GPa for [010] orientations and a polycrystalline forsterite sample. Pressure dependence of forsterite conductivity was considered as a change of the dominant conduction mechanism composed of migration of both magnesium and oxygen vacancies in forsterite. The activation energy (ΔE) and activation volume (ΔV) for ionic conduction due to migration of Mg vacancy were 1.8–2.7 eV and 5–19 cm3/mol, respectively, and for that due to O vacancy were 2.2–3.1 eV and −1.1 to 0.3 cm3/mol, respectively. The olivine conductivity model combined with small polaron conduction suggests that the most part of the upper mantle is controlled by ionic conduction rather than small polaron conduction. The previously observed negative pressure dependence of the conductivity of olivine with low iron content (Fo90) can be explained by ionic conduction due to migration of Mg vacancies, which has a large positive activation volume.
Note
This is an article published by Taylor & Francis Group
Published Date
2017-01-14
Publication Title
Journal of Geophysical Research. Solid Earth
Volume
volume122
Issue
issue1
Publisher
American Geophysical Union
Start Page
158
End Page
171
ISSN
2169-9313
NCID
AA10819743
Content Type
Journal Article
language
英語
OAI-PMH Set
岡山大学
Copyright Holders
https://creativecommons.org/licenses/by-nc-nd/4.0/deed.ja
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DOI
Web of Sience KeyUT
Related Url
https://doi.org/10.1002/2016JB013555