Properties of lower-mantle Al-(Mg,Fe)SiO3 perovskite

The properties of the main lower-mantle phase appear to be more complex than expected. The common procedure of using the properties of the simplified MgSiO3 (and [Mg,Fe]SiO3) composition for direct analogy to the Al-bearing (Mg,Fe)SiO3 lower-mantle perovskite can lead to significant misinterpretations. The presence of Al and Fe affects the equation of state, the defect population, the ability of this phase to insert minor and trace elements, and the transport properties, etc. Some difficulties remain for the quantitative determination of these effects because of two main reasons: many experimental techniques are ineffective because silicate perovskite is metastable at ambient conditions, and the crystal chemistry of Al-(Mg,Fe)SiO3 perovskite is complex and can evolve with pressure, temperature, and chemical composition. This paper reviews the recent progress made in the determination of its properties and presents additional new results from our group. The original data concern the pressure- volume-temperature (P-V-T) equation of state of Al-(Mg,Fe)SiO3 perovskite, the change of oxidation state (dismutation) of Fe2+ into a mixture of Fe3+ and Fe0, which drives the lower-mantle oxygen fugacity to the Fe/(Mg,Fe)O buffer, and the stability of the (Mg,Fe)SiO3 perovskite to the highest pressure and temperature conditions