Solidification of the Earth’s mantle: new insight into the formation of a basal magma ocean
An international team of researchers from the Institut de physique du globe de Paris (IPGP – CNRS / IPG / Université Paris Cité) and York University has revisited the interpretation of geophysical structures rooted at the base of the Earth's mantle. Their work challenges traditional models of the solidification of Earth's primitive mantle. Through advanced numerical modeling, incorporating a multiphase fluid dynamics approach, this study sheds new light on the chemical and thermal differentiation processes that led to the formation of a basal magma ocean.
Solidification of a primordial terrestrial magma ocean gradually leading to the formation of a basal magma ocean / @Nicolas Sarter
Publication date: 27/03/2025
General public, Press, Research
A reinterpreted solidification process
Until now, the scientific community has debated where mantle solidification began: did it start deep down and progress upward, or the reverse? This study shows that this question is secondary. The key factor lies in the gravitational segregation between dense, iron-rich liquids and lighter, iron-poor solids. This natural phenomenon led to the accumulation of iron oxide-rich liquids above the Earth’s core, giving rise to a basal magma ocean.
By integrating phase relationships, melting diagrams, and the distribution of chemical elements during solidification, the numerical modeling used in this study allowed the researchers to estimate the composition and spatial distribution of primordial geochemical reservoirs. These results resonate directly with isotopic anomalies observed in ancient rocks.
Major implications for Earth’s geochemical history
The researchers also highlighted the formation of a significant amount of solids at the surface rather than at depth. This observation suggests that geochemical signatures resulting from the fractionation of surface silicates were injected into the deep mantle, challenging current understanding of the interactions between Earth’s mantle dynamics, petrology, and geochemistry during the early evolution of rocky planets.
Moreover, the study reveals that the formation of a basal magma ocean on Earth was inevitable—even under the most unfavorable conditions. In addition, the geochemical imprint of this solidification on the solid mantle is far less pronounced than previously predicted by classical geochemical models, due to intense vertical mixing during solidification.
These discoveries pave the way for a re-evaluation of geochemical and geophysical observations, enabling a more precise reconstruction of Earth’s thermal and chemical history since its formation. More broadly, they offer new insight into the diversity of rocky bodies in our solar system and beyond.
Source
Solidification of Earth’s mantle led inevitably to a basal magma ocean
Charles-Édouard Boukaré, James Badro, and Henri Samuel. Nature, March 26, 2025
DOI: https://www.nature.com/articles/s41586-025-08701-z
Publication available on IPGP Research Collection
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