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Pressure-induced phase transition in MnCO3and its implications on the deep carbon cycle
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Edité par HAL CCSD ; American Geophysical Union
International audience. The high-pressure behavior of manganese-rich carbonate, rhodochrosite, has been characterizedup to 62GPa by synchrotron-based midinfrared spectroscopy and X-ray diffraction. Modifications in boththe infrared spectra and the X-ray diffraction patterns were observed above ~35GPa, indicating the presenceof a high-pressure phase transition at these pressures. We found that rhodochrosite adopts a structure closeto CaCO3-VI with a triclinic unit cell (a=2.87Å, b = 4.83 Å, c=5.49Å, α = 99.86°, β = 94.95°, and γ=90.95° at62 GPa). Using first-principles calculations based on density functional theory, we confirmed these observationsand assigned modes in the new infrared signature of the high-pressure phase. These results suggest thathigh-pressure metastable phase of calcite may play an important role in carbon storage and transport in thedeep Earth.