Investigating Magma Ocean Solidification on Earth Through Laser-Heated Diamond Anvil Cell Experiments.

Area of Science:

• Geochemistry
• Mineral Physics
• Planetary Science

Background:

• Understanding Earth's early magma ocean is key to its evolution.
• Previous models lacked detailed lower mantle crystallization data.

Purpose of the Study:

• To investigate silicate fractional crystallization at lower mantle pressures.
• To construct a melting phase diagram for a pyrolitic magma ocean.

Main Methods:

• Laser-heated diamond anvil cell experiments.
• Determination of phase relations and compositional evolution.
• Assembly of a melting phase diagram.

Main Results:

• Iron-depleted, calcium-bearing bridgmanite is the first mineral to crystallize.
• Buoyant bridgmanite forms from the initial 33%-36% of the magma ocean.
• High calcium solubility in bridgmanite delays calcium silicate perovskite crystallization.
• Residual melts become iron-enriched and denser than solids.

Conclusions:

• Experimental data support the terrestrial basal magma ocean hypothesis.
• Magma ocean crystallization influences deep mantle composition and structure.