Exploring microstructures in lower mantle mineral assemblages with synchrotron x-rays

Area of Science:

• Mineral physics
• Geodynamics
• High-pressure research

Background:

• Understanding lower mantle mineral dynamics is key to Earth's evolution.
• Bridgmanite and ferropericlase are major lower mantle phases.
• Their spatial distribution and phase transformations influence mantle convection.

Purpose of the Study:

• Investigate mineral formation and microstructure at lower mantle pressures.
• Characterize the spatial distribution and grain-scale properties of bridgmanite and ferropericlase.
• Determine mechanisms controlling seismic anisotropy in the upper lower mantle.

Main Methods:

• Multigrain crystallography (MGC) using synchrotron X-rays.
• Laser-heated diamond anvil cell experiments at 30 GPa.
• Analysis of individual crystal orientations and stress evolution at the grain scale.

Main Results:

• Observed an interconnected network of smaller-grained ferropericlase.
• Identified {110} twinning in iron-depleted bridgmanite.
• Estimated grain-scale stress evolution and provided microstructural insights.

Conclusions:

• The interconnected ferropericlase network may influence slab dynamics.
• {110} twinning in bridgmanite aids stress relaxation and explains low seismic anisotropy.
• These findings refine models of Earth's deep interior evolution.