Decomposition of brucite up to 20 GPa: evidence for high MgO-solubility in the liquid phase
Fukui, Hiroshi; Inoue, Toru; Yasui, Tetsuro; Katsura, Tomoo; Funakoshi, Ken-Ichi; Ohtaka, Osamu
European Journal of Mineralogy Volume 17 Number 2 (2005), p. 261 - 267
published: Apr 29, 2005
ArtNo. ESP147051702010, Price: 29.00 €
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 incon-gruent 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.