高圧地球科学のフロンティア　　アルミニウムを含む下部マントル物質の鉱物化学

概要

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Recent high-pressure and high-temperature experiments strongly imply the possibility of non-stoichiometry for Al, Fe3+ containing MgSiO3 perovskite and the related Al-phases. Therefore, the non-stoichiometric behavior of perovskites in the MgSiO3-MgAlO2.5 system and also in the multi-component system which are similar to natural mantle minerals and rocks was discussed by considering the trivalent cation substitution mechanism: 2VI Si4+ ⇔ 2VI (Al3+, Fe3+) + VO••. Since the behavior of Al coupled with iron in the MgSiO3 perovskite is much more complicated because of the issue of fO2 conditions, it is still under discussion. For dealing with the chemical behavior of Fe3+ in the perovskite, the electron energy-loss spectroscopy (EELS) in transmission electron microscopy (TEM) is becoming a powerful tool by which we can determine the Fe3+ / ΣFe ratio of coexisting phases separately on a nanometer order of resolution. It is expected that the EELS method combined with TEM techniques will be very useful to characterize synthetic high-pressure mantle minerals.
日本高圧力学会の論文