Solidification of Earth's mantle led inevitably to a basal magma ocean
Abstract
Current interpretation of deep-rooted geophysical structures in the mantle 1 is that they stem from the top-down solidification of Earth's primitive basal magma ocean above the core. 2, 3, 4, 5, 6 However, it remains debated whether solids first formed at the bottom of the mantle, solidifying upward, or above the melts, solidifying downward. We show that gravitational segregation of dense, iron-rich melts from lighter, iron-poor solids drives mantle evolution, regardless of where melting curves and geotherms intersect. This process results in the accumulation of iron oxide rich melts above the core, forming a basal magma ocean. We numerically model mantle solidification using a novel multiphase fluid dynamics approach that integrates melting phase relations and geochemical models. This allows estimating the compositional signature and spatial distribution of primordial geochemical reservoirs, that may be directly linked to the isotopic anomalies measured in Archean rocks. 7, 8, 9, 10, 11 Interestingly, we find that a significant amount of solids is produced at the planet's surface, not at depth, injecting geochemical signatures of shallow silicate fractionation in the deep mantle. This work could serve as a foundation for re-examining the intricate interplay between mantle dynamics, petrology, and geochemistry during the first billion years of the evolution of rocky planets.
Related
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BibTeX
@article{boukare2026solidification,
title = {{Solidification of Earth's mantle led inevitably to a basal magma ocean}},
author = {Charles-Édouard Boukaré and James Badro and Henri Samuel},
journal = {Nature},
year = {2026},
month = sep,
doi = {10.1038/s41586-025-08701-z},
url = {https://hal.science/hal-04987217v2},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Solidification of Earth's mantle led inevitably to a basal magma ocean
AU - Charles-Édouard Boukaré
AU - James Badro
AU - Henri Samuel
PY - 2026
DA - 2026/09/21
JO - Nature
DO - 10.1038/s41586-025-08701-z
UR - https://hal.science/hal-04987217v2
AB - Current interpretation of deep-rooted geophysical structures in the mantle 1 is that they stem from the top-down solidification of Earth's primitive basal magma ocean above the core. 2, 3, 4, 5, 6 However, it remains debated whether solids first formed at the bottom of the mantle, solidifying upward, or above the melts, solidifying downward. We show that gravitational segregation of dense, iron-rich melts from lighter, iron-poor solids drives mantle evolution, regardless of where melting curves and geotherms intersect. This process results in the accumulation of iron oxide rich melts above the core, forming a basal magma ocean. We numerically model mantle solidification using a novel multiphase fluid dynamics approach that integrates melting phase relations and geochemical models. This allows estimating the compositional signature and spatial distribution of primordial geochemical reservoirs, that may be directly linked to the isotopic anomalies measured in Archean rocks. 7, 8, 9, 10, 11 Interestingly, we find that a significant amount of solids is produced at the planet's surface, not at depth, injecting geochemical signatures of shallow silicate fractionation in the deep mantle. This work could serve as a foundation for re-examining the intricate interplay between mantle dynamics, petrology, and geochemistry during the first billion years of the evolution of rocky planets.
SN - 0028-0836
SN - 1476-4687
ER -