Matter at Extreme Conditions: III
Ferrous iron partitioning in the lower mantle: consequences for seismic velocities and heterogeneities
10:00 am – 10:12 amIron partitioning among lower mantle phases has non-monotonic behavior owing to a high-spin to low-spin state change in iron in ferropericlase (Fp), the second most abundant phase in this region, at relevant pressure-temperature conditions. The potential effects of this partitioning have long been recognized and the actual partitioning coefficient between bridgmanite (Bm) and Fp, KD, has been investigated in different aggregates multiple times. However, numerous inconsistencies remain. Here, we systematically investigate the behavior of KD using ab initio simulation methods and non-ideal solid solution models for the main phases. We also address the effect of the non-monotonic KD on lower mantle velocities and temperature-induced velocity heterogeneities for the first time. Such KD is expected to be more complex in aggregates containing ferric iron-, aluminum-, and calcium-bearing Bm, or during the Bm to post-perovskite phase transition.