Insights into core-mantle differentiation from bulk Earth melt simulations

Area of Science:

• Planetary Science
• Geochemistry
• Computational Materials Science

Background:

• Earth's early history involved complex physicochemical changes during accretion and magma ocean stages.
• Understanding these fundamental evolutionary processes is crucial for planetary formation models.

Purpose of the Study:

• To investigate the behavior of a bulk Earth melt system at high pressure.
• To simulate elemental partitioning and phase separation in early Earth conditions.

Main Methods:

• Utilized molecular dynamics simulations with a deep neural network potential trained on first-principles data.
• Simulated a bulk Earth melt composition (Fe35.7Mg19.0Si15.2O30.2 wt%) at 3000 K and 29.1 GPa.
• Employed coordination and space-decomposition analyses for phase identification.

Main Results:

• Observed phase separation into two distinct domains: an iron-rich metallic phase and a silicate magma ocean phase.
• The metallic domain comprised 96.2% Fe, 1.9% Si, and 1.7% O, while the magma ocean domain contained 29.7% Mg, 22.0% Si, and 45.3% O.
• Higher temperatures led to increased silicon and oxygen in the metallic domain and more iron oxides in the magma ocean.

Conclusions:

• The simulated segregation accurately predicts the formation of Earth's metallic core and silicate mantle.
• Results align well with experimental data for high-pressure metal-silicate equilibrium.
• This study provides fundamental insights into the physicochemical evolution of the early Earth.