High-pressure and high-temperature behaviour of calcite, aragonite and dolomite; a Raman spectroscopic study

The room-T Raman spectra of aragonite and dolomite have been recorded up to 30 and 25 GPa respectively; no phase changes were observed during compression, at variance with calcite. The effect of T on the room-P Raman spectra of these three carbonates is reported up to 700-900 K. The relative P and T shifts of the Raman lines are greater for the lattice modes than for the internal modes of the CO (sub 3) groups. These shifts are used to calculate the mode anharmonic parameter of the observed Raman modes; they are negative and their absolute values are smaller (close to 0) for the internal CO (sub 3) modes than the lattice modes (4-17 x 10 (super -5) /K).