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- Title
Partitioning of Iron Between (Mg,Fe)SiO<sub>3</sub> Liquid and Bridgmanite.
- Authors
Dragulet, Francis; Stixrude, Lars
- Abstract
The evolution of the magma ocean that occupied the early Earth is influenced by the buoyancy of crystals in silicate liquid. At lower mantle pressures, silicate crystals are denser than the iso‐chemical liquid, but heavy elements like iron can cause crystals to float if they partition into the liquid phase. Crystal flotation allows for a basal magma ocean, which might explain geochemical anomalies in mantle‐derived magmas, seismic anomalies in the lower mantle, and the source of the Earth's early magnetic field. To examine whether a basal magma ocean is gravitationally stable, we investigate the degree of iron partitioning between (Mg,Fe)SiO3 liquid and bridgmanite. By utilizing ab initio molecular dynamics simulations coupled with thermodynamic integration, we find that iron partitions into the liquid, and increasingly so with increasing pressure. Bridgmanite crystals are found to be buoyant at lower mantle conditions, stabilizing the basal magma ocean. Plain Language Summary: The early Earth may have been in a completely molten state, and its evolution during this stage depends on whether crystals float or sink in magma. While crystals typically sink in magma near the Earth's surface, we find that crystals float in the deep Earth. This is because liquid at greater depths is enriched in iron, making it denser than the crystals. This suggests that there once was a stable magma layer below the solid mantle and above the core, which might explain several properties of the Earth's deep interior. Key Points: The Fe‐Mg distribution coefficient between bridgmanite and (Mg,Fe)SiO3 liquid is computed using ab‐initio simulationsIron is incompatible in bridgmanite and partitions into silicate liquidBridgmanite crystals are buoyant in the lower mantle, allowing for a basal magma ocean to be gravitationally stable
- Subjects
INTERNAL structure of the Earth; LIQUID crystals; LIQUID alloys; LIQUID iron; SURFACE of the earth; IRON; HEAVY elements
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 12, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL107979