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  • Title: Disproportionation of (Mg,Fe)SiO₃ perovskite in Earth's deep lower mantle.
    Author: Zhang L, Meng Y, Yang W, Wang L, Mao WL, Zeng QS, Jeong JS, Wagner AJ, Mkhoyan KA, Liu W, Xu R, Mao HK.
    Journal: Science; 2014 May 23; 344(6186):877-82. PubMed ID: 24855264.
    Abstract:
    The mineralogical constitution of the Earth's mantle dictates the geophysical and geochemical properties of this region. Previous models of a perovskite-dominant lower mantle have been built on the assumption that the entire lower mantle down to the top of the D″ layer contains ferromagnesian silicate [(Mg,Fe)SiO3] with nominally 10 mole percent Fe. On the basis of experiments in laser-heated diamond anvil cells, at pressures of 95 to 101 gigapascals and temperatures of 2200 to 2400 kelvin, we found that such perovskite is unstable; it loses its Fe and disproportionates to a nearly Fe-free MgSiO3 perovskite phase and an Fe-rich phase with a hexagonal structure. This observation has implications for enigmatic seismic features beyond ~2000 kilometers depth and suggests that the lower mantle may contain previously unidentified major phases.
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