Alumina nanoparticle-induced decarbonation at subduction-zone conditions

Area of Science:

• Geochemistry
• Mineral Physics
• Climate Science

Background:

• Calcium carbonate evolution in subduction zones is critical for long-term climate dynamics and planetary habitability.
• Understanding carbonate stability under high pressure-temperature (P-T) conditions is essential for subduction zone processes.

Purpose of the Study:

• To investigate the influence of aluminum oxide particle size on calcium carbonate stability under subduction zone P-T conditions.
• To elucidate the mechanisms by which aluminum oxide nanoparticles affect carbonate destabilization.

Main Methods:

• Experimental study using a piston-cylinder press to simulate subduction zone P-T conditions.
• Analysis of calcium carbonate stability in the presence of micron-sized and nano-sized aluminum oxide particles and aluminum hydroxide.

Main Results:

• Calcium carbonate remains stable with micron-sized aluminum oxide and aluminum hydroxide across investigated P-T conditions.
• Aluminum oxide nanoparticles destabilize calcium carbonate at 0.5-2.8 GPa and 350-1050 °C, forming CaAl4O7, CO2, and graphite.
• The grain size of aluminum oxide strongly regulates calcium carbonate stability due to nanoparticle surface area and defect density.

Conclusions:

• The particle size of aluminum oxide is a key factor controlling calcium carbonate stability in subduction zones.
• This finding revises the understanding of carbon release in subduction zones, indicating shallower and more heterogeneous decarbonation.
• The results have implications for Earth's long-term climate dynamics and habitability.