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Decomposition of brucite up to 20 GPa

¹ Laboratoire de Minéralogie-Cristallographie, Université Pierre et Marie Curie, 4 place Jussieu, F-75252 Paris Cedex 05, France
² Graduate School of Science Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
³ Geodynamics Research Center Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
⁴ Institute of Study for Earth Interior Okayama University, 827 Yamada, Misasa, Tottori 682-0193, Japan
⁵ Japan Synchrotron Radiation Research Institute, Spring-8, 1-1 Koto 1, Sayo, Hyogo 678-5198, Japan

^* E-mail: ohtaka{at}ess.sci.osaka-u.ac.jp.

We performed in-situ X-ray diffraction and ex-situ textural observations and thermodynamic calculations in order to confirm phase relations in the system MgO-H₂O at high pressure and high temperature conditions. In-situ and ex-situ observations reveal that the brucite decomposition boundary has a negative slope from 11 GPa to 20 GPa. Phases obtained at 2.1 GPa and 1503 K were periclase and a fluid with a small MgO content while those at 12 GPa and 1473 K were periclase and an MgO-rich liquid. Quench textures suggest that brucite dehydrates at least up to 4 GPa but melts incongruently at higher pressure. The incongruent melting temperature of brucite, that is wet solidus temperature of periclase, decreases with increasing pressure up to 20 GPa. The experimental results are supported by thermodynamic calculations.

Key-words: brucite, high pressure, decomposition, dehydration, incongruent melting.

This article has been cited by other articles:

				F. Jiang, S. Speziale, and T. S. Duffy Single-crystal elasticity of brucite, Mg(OH)2, to 15 GPa by Brillouin scattering American Mineralogist, November 1, 2006; 91(11-12): 1893 - 1900. [Abstract] [Full Text] [PDF]