Partition of magnesium and iron between Olivine and spinel,and between pyroxene and spinel |
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| Authors: | Osamu Nishizawa Syun-iti Akimoto |
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| Institution: | (1) Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, 106 Tokyo, Japan;(2) Present address: Department of Earth Sciences, University of Nagoya, 464 Nagoya, Japan |
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| Abstract: | Partition of Fe2+ and Mg between coexisting (Mg, Fe)2SiO4 spinel and (Mg, Fe)SiO3 pyroxene was investigated at pressures 80 and 90 kbar and at temperatures 840 and 1050° C, using tetrahedral-anvil type of high pressure apparatus. Olivine-spinel solid solution equilibria in the system Mg2SiO4-Fe2SiO4 were discussed in the light of the partition reaction. Partition of Fe2+ and Mg in both olivine-spinel and pyroxene-spinel systems can not be regarded as that between ideal solid solutions. By applying the simple solution model for the partition of Fe2+ and Mg, sign of the heat of mixing was estimated to be positive for all olivine, spinel and pyroxene. Relative concentration of Fe2+ in spinel in the pyroxene-spinel system is likely to cause some change in the chemical composition of modified spinel ( ) or spinel ( ) in the transition zone of the mantle. A considerable change is also expected in the transition pressure of to ( + ) and ( + ) to .Presented at the symposium  Recent Advances in the Studies of Rocks and Minerals at High Pressures and Temperatures held in Montreal, 1972. Jointly sponsored by the International Mineralogical Association and the Commission on Experimental Petrology. |
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