Fe-Mg partitioning between (Mg, Fe)SiO3 post-perovskite, perovskite, and magnesiowustite in the Earth's lower mantle -: art. no. L19301

We report here new data on pressure dependence of Fe-Mg partitioning between (Mg, Fe) SiO3 perovskite (Pv) and magnesiowustite (Mw), K-Pv/Mw, and (Mg, Fe) SiO3 postperovskite (PPv) and Mw, K-PPv/Mw, up to 123.6 GPa at 1600 K measured by synchrotron X-ray diffraction method and analytical transmission electron microscopy ( ATEM). We observed a high FeO content in PPv coexisting with Mw [K-PPv/Mw = (FeO/MgO)(PPv)/(FeO/MgO) M-w = 0.30] compared to that in Pv [K-Pv/Mw = (FeO/MgO)(Pv)/(FeO/ MgO)(Mw) = 0.12] observed from 23.0 to 95.4 GPa. K-Pv/Mw keeps a constant value of 0.12 up to the PPv phase boundary. Our results also support the possibility that a metallic phase may form in the lower mantle. The assemblage of PPv and Mw is 1.5 - 1.7% denser than the Pv bearing assemblage, which results in a gravitational stabilization of the lowermost mantle.