High-Pressure Behavior of Ferromagnesite (Mg0.81Fe0.19)CO3 by Synchrotron X-Ray Diffraction and Raman Spectroscopy up to 53 GPa

Ferromagnesite (Mg, Fe)CO 3 with 20 mol% iron is a potential host mineral for carbon transport and storage in the Earth mantle. The high-pressure behavior of synthetic ferromagnesite (Mg 0.81 Fe 0.19 )CO 3 up to 53 GPa was investigated by synchrotron X-ray diffraction (XRD) and Raman spectroscopy. The iron bearing carbonate underwent spin transition at around 44–46 GPa accompanied by a volume collapse of 1.8%, which also demonstrated a variation in the d ν i /d P slope of the Raman modes. The pressure-volume data was fitted by a third-order Birch-Murnaghan equation of state (BM-EoS) for the high spin phase. The best-fit K 0 = 108(1) GPa and K 0 ′ = 4.2(1). Combining the d ν i /d P and the K 0 , the mode Grüneisen parameters of each vibrational mode ( T, L, ν 4 and ν 1 ) were calculated. The effects of iron concentration on the Mg 1− x Fe x CO 3 system related to high-pressure compressibility and vibrational properties are discussed. These results expand the knowledge of the physical properties of carbonates and provide insights to the potential deep carbon host.