Iron Partitioning in Ferropericlase

Abstract:

Ferropericlase, (Mg,Fe)O, is the second most abundant mineral in the Earth’s lower mantle. Whether iron favours the liquid or solid phase of (Mg,Fe)O has important implications for the Earth’s mantle, both chemically and dynamically. As iron is much heavier than magnesium, the partitioning of iron between liquid and solid will lead to a contrast in densities. This difference in density will lead one phase to be more buoyant than the other and would help, in part, to explain how the mantle crystallised from the magma ocean of the Hadean eon to its current state. The partitioning of iron between the two phases is characterized by partition coefficients. Using ab-initio methods, thermodynamic integration and adiabatic switching these coefficients have been determined. Results are presented for pressures encompassing the region between the upper mantle and the core-mantle boundary (10-140GPa).