Partitioning of iron between perovskite/postperovskite and ferropericlase in the lower mantle

The Fe 2+ ‐Mg distribution coefficients ( K D ) between perovskite/postperovskite and ferropericlase were determined in a (Mg 0.9 Fe 0.1 ) 2 SiO 4 bulk composition. High‐pressure and high‐temperature experiments were carried out between 36 and 128 GPa and 1760–2170 K in a laser‐heated diamond anvil cell (LHDAC). Chemical analyses were made on recovered samples with transmission electron microscope (TEM) and field‐emission‐type scanning electron microscope (FE‐SEM). All the samples exhibited a strong heterogeneity in iron content caused by relatively large temperature gradient during laser‐heating, being depleted at the center of the hot spot and enriched at the margin. The K D values measured from coexisting perovskite/postperovskite and ferropericlase showed apparently very large variation in each sample, which could be the source of considerable discrepancy among previous measurements of K D using the LHDAC techniques. Nevertheless, the data obtained from a specific portion of the sample that retained the original bulk composition may represent the equilibrium partitioning. Present results demonstrate that the iron partitioning between perovskite/postperovskite and ferropericlase changes little at a given temperature throughout the lower mantle pressures. Both electronic transition of iron and postperovskite phase transition have small effects on iron partitioning.