Post-perovskite phase transition and mineral chemistry in the pyrolitic lowermost mantle

[1] Phase relations of a natural mantle composition were determined up to 126 GPa and 2450 K by in-situ x-ray diffraction measurements in a laser-heated diamond-anvil cell (LHDAC). MgSiO3-rich perovskite (MgPv) transforms to a post-perovskite phase (MgPP) at about 113 GPa and 2500 K (400-km above the core-mantle boundary) and the lowermost mantle consists of MgPP, (Mg, Fe)O magnesiowustite (Mw), and CaSiO3-rich perovskite (CaPv). Chemical analyses on recovered samples using transmission electron microscope (TEM) show that the distribution of iron significantly changes at the post-perovskite phase transition. A strong enrichment of iron in Mw leads to the unique geophysical and geochemical properties of the lowermost mantle.