Experiments have been performed on the system MgO-SiO2-Cr-O at 0 - 2. 88 Gpa and 1100 -- 1450℃, focusing on the stability of Cr2+ in olivine (Ol), orthopyroxene (Opx) and spinel (SP) and its partitioning between these phases. Analytical reagent grade chemicals, MgO, SiO2, Cr2O3, and Cr were used to make starting mixtures. Excess Cr (50 % ) was then added in these mixtures to ensure that the resultant phases were in equilibrium with the metal Cr. Flux of BaO + B2O3 (% ) was added for facilitating experimental equilibrium and crystal growth. Cr was used as capsule material. All phases in the product were identified by X-ray and analyzed by electron microprobe. The contents of CrO in the different phases (O1, Opx and SP) were calculated according to stoichiometry. The Obtained results of calculation indicate that C/+ in O1 and OPx is negligible. The experimental results show: (a) with increasing temperature and decreasing pressure, Cr2 + solubility in O1, OPx and SP increases; (b) with increasing temperature, the partitioning coefficient of Mg and Cr2 + between O1 and Opx decreases, that between Opx and Sp increases, and that between O1 and Sp remains almost unchanged; (c) the effect of pressure on all partitioning coefficients is negligible.
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