Ferrous iron partitioning in the lower mantle: consequences for seismic velocities and heterogeneities*

Iron partitioning among lower mantle phases has non-monotonic behavior owing to the high-spin to a low-spin crossover of iron in ferropericlase (Fp) at pressure-temperature conditions of this region. The potential effects of this partitioning have long been recognized and the actual partitioning coefficient between bridgmanite (Bm) and ferropericlase (Fp), K_D, has been investigated in different aggregates multiple times. Here, we systematically investigate the behavior of K_D using ab initio simulation methods and non-ideal or quasi-ideal solid solution models for the main phases. We also address the effect of this variable K_D on lower mantle velocities and temperature-induced heterogeneities.