In situ strength measurements on natural upper-mantle minerals |
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| Authors: | Junji Yamamoto Jun-ichi Ando Hiroyuki Kagi Toru Inoue Akihiro Yamada Daisuke Yamazaki Tetsuo Irifune |
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| Institution: | (1) Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA;(2) Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Beppu 874-0903, Japan;(3) Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Kagami-yama 1-3-1, Higashi-Hiroshima 739-8526, Japan;(4) Geochemical Laboratory, Graduate School of Science, The University of Tokyo, Hongo, Tokyo 113-0033, Japan;(5) Present address: Department of Geology, University of California Davis, One Shields Avenue, Davis, CA 95616, USA;(6) Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan;(7) Institute for Study of the Earth’s Interior, Okayama University, Yamada 827, Misasa 682-0193, Japan |
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| Abstract: | Using in situ strength measurements at pressures up to 10 GPa and at room temperature, 400, 600, and 700°C, we examined rheological
properties of olivine, orthopyroxene, and chromian-spinel contained in a mantle-derived xenolith. Mineral strengths were estimated
using widths of X-ray diffraction peaks as a function of pressure, temperature, and time. Differential stresses of all minerals
increase with increasing pressure, but they decrease with increasing temperature because of elastic strain on compression
and stress relaxation during heating. During compression at room temperature, all minerals deform plastically at differential
stress of 4–6 GPa. During subsequent heating, thermally induced yielding is observed in olivine at 600°C. Neither orthopyroxene
nor spinel shows complete stress relaxation, but both retain some stress even at 700°C. The strength of the minerals decreases
in the order of chromian-spinel ≈ orthopyroxene > olivine for these conditions. This order of strength is consistent with
the residual pressure of fluid inclusions in mantle xenoliths. |
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| Keywords: | Rheology X-ray diffraction measurement Mantle mineral Fluid inclusion Geobarometry |
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