Thermodynamic phase relations of the MgO-FeO-SiO_2 system in the lower mantle

The perovskite (Pv) to post-perovskite (PPv) phase transition at pressures near the Earth's core-mantle boundary (CMB) is currently the favored candidate for explaining most, if not all, of the peculiarities of the D'' layer (~200 km region above core) [1, 2]. The intense interest in this layer is motivated by its role in determining the boundary condition on the bottom of the convecting mantle, thereby greatly affecting mantle dynamics. The post-perovskite phase boundary in pure MgSiO_3 is fairly well known, but the experimental and calculated results on the partitioning of Fe among the stable coexisting phases and its influence on the transition pressure are currently contradictory [3-5].