Fe2+ Partitioning in Al‐Free Pyrolite: Consequences for Seismic Velocities and Heterogeneities

Autor: Jingyi Zhuang, Renata Wentzcovitch
Jazyk: angličtina
Rok vydání: 2024
Předmět:
Zdroj: Geophysical Research Letters, Vol 51, Iss 21, Pp n/a-n/a (2024)
Druh dokumentu: article
ISSN: 1944-8007
0094-8276
DOI: 10.1029/2024GL108967
Popis: Abstract Iron partitioning among the main lower mantle phases, bridgmanite (Bm) and ferropericlase (Fp), has non‐monotonic behavior owing to the high‐spin to low‐spin crossover in ferrous iron (Fe2+) in Fp. Previously reported iron partitioning coefficient between these phases, KD, still have considerable uncertainty. Here, we investigate the Fe2+ partitioning behavior using ab initio free energy results. Although we focus on Fe2+ only, we describe the effect of this iron spin crossover (ISC) on KD and of the latter on compositions and seismic velocities in a pyrolitic aggregate. Our results suggest that its velocities are mainly affected by the ISC and less so by the Fe2+ partitioning. In contrast, iron partitioning manifests in thermally induced velocity heterogeneity ratios. Prediction of the seismological parameter RS/P ∂lnVS/∂lnVP including iron partitioning effects resembles quantitatively RS/P’s inferred from several tomographic studies down to 2,400 km depth.
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