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Abstract The relative composition of Earth's core and mantle were set during core formation. By determining how elements partition between metal and silicate at high pressures and temperatures, measurements of the mantle composition and geophysical observations of the core can be used to understand the mechanisms by which Earth formed. Here we present the results of metal‐silicate partitioning experiments for a range of nominally lithophile elements (Al, Ca, K, Mg, O, Si, Th, and U) and S to 85 GPa and up to 5400 K. With our results and a compilation of literature data, we developed a parameterization for partitioning that accounts for compositional dependencies in both the metal and silicate phases. Using this parameterization in a range of planetary growth models, we find that, in general, lithophile element partitioning into the metallic phase is enhanced at high temperatures. The relative abundances of FeO, SiO2, and MgO in the mantle vary significantly between planetary growth models, and the mantle abundances of these elements can be used to provide important constraints on Earth's accretion. To match Earth's core mass and mantle composition, Earth's building blocks must have been enriched in Fe and depleted in Si compared with CI chondrites. Finally, too little Mg, Si, and O are partitioned into the core for precipitation of oxides to be a major source of energy for the geodynamo. In contrast, several ppb of U can be partitioned into the core at high temperatures, and this energy source must be accounted for in thermal evolution models.
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This content will become publicly available on August 28, 2025
Large‐Scale Atomistic Simulations of Magnesium Oxide Exsolution Driven by Machine Learning Potentials: Implications for the Early Geodynamo
Abstract The precipitation of magnesium oxide (MgO) from the Earth's core has been proposed as a potential energy source to power the geodynamo prior to the inner core solidification. Yet, the stable phase and exact amount of MgO exsolution remain elusive. Here we utilize an iterative learning scheme to develop a unified deep learning interatomic potential for the Mg‐Fe‐O system valid over a wide pressure‐temperature range. This potential enables direct, large‐scale simulations of MgO exsolution processes at the Earth's core‐mantle boundary. Our results suggest that Mg exsolve in the form of crystalline Fe‐poor ferropericlase as opposed to a liquid MgO component presumed previously. The solubility of Mg in the core is limited, and the present‐day core is nearly Mg‐free. The resulting exsolution rate is small yet nonnegligible, suggesting that MgO exsolution may provide a potentially important energy source, although it alone may be difficult to drive an early geodynamo.
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- Award ID(s):
- 2242946
- PAR ID:
- 10549435
- Publisher / Repository:
- American Geophysical Union (AGU)
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 51
- Issue:
- 16
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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