Post-spinel transition in Mg2SiO4 determined by high P-T in situ X-ray diffractometry

被引:179
作者
Katsura, T
Yamada, H
Shinmei, T
Kubo, A
Ono, S
Kanzaki, M
Yoneda, A
Walter, MJ
Ito, E
Urakawa, S
Funakoshi, K
Utsumi, W
机构
[1] Okayama Univ, Inst Study Earths Interior, Tottori 6820193, Japan
[2] Okayama Univ, Dept Earth & Planetary Sci, Okayama 7000082, Japan
[3] Japan Synchrotron Radiat Res Inst, Mikazuki, Hyogo 6785198, Japan
[4] Japan Atom Energy Res Inst, Mikazuki, Hyogo 6785148, Japan
关键词
post-spinel transition; Mg2SiO4; 660 km discontinuity; mantle; high pressures and temperatures; in situ X-ray diffractometry;
D O I
10.1016/S0031-9201(03)00019-0
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The phase boundary of the post-spinel transition in Mg2SiO4 was re-investigated by means of high P-T in situ X-ray diffractometry with a gold pressure marker in a Kawai-type apparatus. Rapid and continuous temperature changes were conducted to initiate dissociation of spinel, which tends to be inert after long annealing. Isothermal decompression at high temperature was conducted to form spinel from perovskite plus periclase. The phase boundary is located at ca. 22 GPa in the temperature range from 1550 to 2100 K, which is 1-1.5 GPa lower than the 660 km discontinuity. This discrepancy might be explained in terms of the pressure effect of thermocouple emf and inaccurate equation of state (EOS) for the pressure maker. The transition is found to be less sensitive to temperature than reported previously, with a Clapeyron slope ranging from -2 to -0.4 MPa/K. This small Clapeyron slope implies that the post-spinel transition would not be an effective barrier to mantle convection. (C) 2003 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:11 / 24
页数:14
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