Single-Crystal Elasticity of the Deep-Mantle Magnesite at High Pressure and Temperature

Magnesite is believed to be a major candidate carbon host in the Earth's mantle. Studying thermal elastic properties of magnesite under relevant high pressure-temperature conditions of the mantle is thus important for our understanding of the deep-carbon storage. Thus far, the elasticity of magnesite has only been reported at ambient condition. Here we have conducted Brillouin light scattering measurements on the compressional wave (Vp) and shear wave (Vs) velocities of single-crystal magnesite in a high pressure-temperature diamond anvil cell (DAC) at relevant conditions of the Earth's mantle. Based on the experimentally-measured velocities, we have derived full elastic constants and have modeled the elasticity and elastic anisotropies of magnesite at expected upper-mantle P-T conditions. These results are important for our understanding of the potential effects of magnesite carbonate on the seismic profiles and seismic anisotropies in the carbonated eclogite and peridotite in the upper mantle and a subducting slab. Here we have applied the experimental results and modeled velocity profiles and seismic anisotropies to provide mineral physics references and constraints for seismic detections of potentially carbonated regions in the Earth's interior.