Iron valence and partitioning between post-perovskite and ferropericlase in the Earth’s lowermost mantle

Gialampouki, Martha A.; Xu, Shenzhen; Morgan, Dane

doi:10.1016/j.pepi.2018.06.005

Cited by 5 publications

(2 citation statements)

References 54 publications

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“…On the theoretical side, ab initio calculations of K D , sometimes combined with semiempirical modeling, have also been carried out (Muir & Brodholt, 2016;, including the partitioning between Fp and PPv (Gialampouki et al, 2018). The methodologies, compositions, and mineralogy have varied, and differences between predictions remain.…”

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confidence: 99%

Fe2+ partitioning in Al-free pyrolite: consequences for seismic velocities and heterogeneities

Zhuang,

Wentzcovitch

2024

Preprint

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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. Results of previous studies of the iron partitioning coefficient between these phases, KD, still have considerable uncertainty. Here, we investigate the Fe2+ partitioning behavior using well-documented ab initio free energy results plus new updates. 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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Section: Plain Language Summarymentioning

confidence: 99%

Fe2+ partitioning in Al-free pyrolite: consequences for seismic velocities and heterogeneities

Zhuang,

Wentzcovitch

2024

Preprint

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“…The Ca% of mid-ocean ridge basalt (MORB) is between 30-60% (Hirose 2002;Hirose et al 2005;Ricolleau et al 2010), of harzburgitic compositions about 1-3% (Michael and Bonatti 1985;Ringwood 1991), and of pyrolytic compositions around 7-13% (Kesson et al 1998;Mattern et al 2005;Ringwood 1991). Iron in the lower mantle can have multiple oxidation states (primarily +2 and +3) and structural sites (A and B) (Gialampouki et al 2018;Muir and Brodholt 2020;Wang et al 2019). To determine the effect of iron on A site mixing of Ca and Mg, we shall focus on ferrous iron at the A site.…”

Section: Introductionmentioning

confidence: 99%

Solid solution of CaSiO3 and MgSiO3 perovskites in the lower mantle: The role of ferrous iron

Zhang

Xiao

Muir

2023

American Mineralogist

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The solid solution between CaSiO 3 and MgSiO 3 perovskites is an important control on the properties of the lower mantle but the effect of one of the most important impurity elements (iron) on this solution is largely unknown. Using density functional theory (DFT), ferrous iron's influence on the reciprocal solubility of MgSiO 3 and CaSiO 3 perovskite (forming a single Ca-Mg mixed perovskite phase) was calculated under pressures and temperatures of 25 -125 GPa and 0 -3000 K, respectively. Except at iron-rich conditions, ferrous iron preferentially partitions into the mixed perovskite phase over bridgmanite. This is a small effect (partitioning coefficient K D ~ 0.25 -1), however, when compared to the partitioning of ferrous iron to ferropericlase which rules out perovskite phase mixing as a mechanism for creating iron-rich regions in the mantle. Iron increases the miscibility of Ca and Mg perovskite phases and reduces the temperature at which the two perovskite phases mix but this effect is highly nonlinear. We find that for a pyrolytic mantle (Ca%=12.5 where Ca%=Ca/ (Ca + Mg)) a perovskite ferrous iron concentration of ~13% leads to the lowest mixing temperature and the highest miscibility. With this composition, 1% ferrous iron in a pyrolytic composition would lead to mixing at This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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Toward Imaging Flow at the Base of the Mantle with Seismic, Mineral Physics, and Geodynamic Constraints

Nowacki

Cottaar

2021

Mantle Convection and Surface Expressions

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Iron valence and partitioning between post-perovskite and ferropericlase in the Earth’s lowermost mantle

Cited by 5 publications

References 54 publications

Fe2+ partitioning in Al-free pyrolite: consequences for seismic velocities and heterogeneities

Fe2+ partitioning in Al-free pyrolite: consequences for seismic velocities and heterogeneities

Solid solution of CaSiO3 and MgSiO3 perovskites in the lower mantle: The role of ferrous iron

Toward Imaging Flow at the Base of the Mantle with Seismic, Mineral Physics, and Geodynamic Constraints

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