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Stability and Thermoelasticity of Diaspore by Synchrotron X-ray Diffraction and Raman Spectroscopy TEXT SIZE: A A A

The thermoelasticity and stability of diaspore (alpha-AlOOH, Al1.002Fe0.003OOH) were investigated in this study by in situ synchronous X-ray diffraction (XRD) and Raman spectroscopy methods at high pressure and high temperature conditions. The results indicate that diaspore is stable within the pressure and temperature (P-T) region examined in this study. With increasing pressure, the Raman peaks move toward the high wave number direction, the intensity of the Raman peaks increases, and the vibration mode of diaspore changes linearly. Pressure-volume data from in situ high-pressure XRD experiments were fitted by the third-order Birch-Murnaghan equation of state (EoS) with the zero-pressure unit-cell volume V (0) = 118.15 (4) angstrom(3), the zero-pressure bulk modulus K (V0) = 153 (2) GPa, and its pressure derivative K'(V0) = 2.4 (3). When K'(V0) was fixed at 4, the obtained K (V0) = 143 (1) GPa. The axial compressional behavior of diaspore was also fitted with a linearized third-order Birch-Murnaghan EoS, showing slight compression anisotropy with K (a0) = 137 (5) GPa, K (b0) = 169 (7) GPa and K (c0) = 178 (6) GPa. In addition, the temperature-volume data from in situ high-temperature XRD experiments were fitted by Fei's thermal equation with the thermal expansion coefficients alpha ( V ) = 2.7 (2) x 10(-5) K-1, alpha ( a ) = 1.13 (9) x 10(-5) K-1, alpha ( b ) = 0.77 (5) x 10(-5) K-1, and alpha ( c ) = 0.85 (9) x 10(-5) K-1 for diaspore, which shows that diaspore exhibits slightly anisotropic thermal expansion. Furthermore, in situ synchrotron-based single-crystal XRD under simultaneously high P-T conditions indicates that the P-T stability of diaspore is up to similar to 10.9 GPa and 700 K. Combined with previous results, we infer that diaspore can be subducted to similar to 390 km under cold subduction conditions based on existing experimental data and is a good candidate for transporting water to the deep Earth.

Publication name

 FRONTIERS IN EARTH SCIENCE Volume9 Article Number752566 DOI10.3389/feart.2021.752566 PublishedSEP 24 2021

Author(s)

 Huang, Shijie; Xu, Jingui; Liu, Daorong; Li, Bo; Ye, Zhilin; Chen, Wei; Kuang, Yunqian; Chi, Fangli; Fan, Dawei; Ma, Maining; Zhou, Wenge

Corresponding author(s) 

 FAN Dawei
 fandawei@vip.gyig.ac.cn
 -Chinese Acad Sci, Inst Geochem, Key Lab High Temp & High Pressure Lab High Temp &, Guiyang, Peoples R China
 Ma, Maining
 mamn@ucas.ac.cn
 -Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Key Lab Computat Geodynam, Beijing, Peoples R China

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