Combined high-pressure and high-temperature vibrational studies of dolomite: phase diagram and evidence of a new distorted modification
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A combined high-pressure mid-infrared absorption and Raman spectroscopy study on a natural CaMg0.98Fe0.02(CO3)2 dolomite sample was performed both at ambient and high temperatures. A pressure–temperature phase diagram was constructed for all the reported dolomite ambient- and high-pressure polymorphs. In addition, a local distortion of the ambient-pressure dolomite structure was identified close to 11 GPa, just before the transition toward the first known high-pressure phase. All the Clausius–Clapeyron slopes are found to be positive with similar magnitudes. Complementary first-principles calculations suggest a metastable nature of the high-pressure dolomite polymorphs. Finally, theoretical spectroscopy is used to interpret and discuss the observed changes in the measured vibrational spectra.
KeywordsDolomite Phase diagram High-pressure transitions Vibrational spectroscopy First-principles
We thank Prof. Wilhelm Heinrich for providing us with the natural dolomite samples, Hans-Peter Nabein for the XRD measurements at ambient conditions, and Dr. Eglof Ritter for his assistance with the SR-MIR experiments. We thank HZB for the allocation of synchrotron radiation beamtime. This study was partly supported by a Grant from Deutsche Forschungsgemeinschaft within the Research Unit FOR2125 under Grant KO1260/16 and JA1469/9.
- Fiquet G, Guyot F, Itie J-P (1994) High-pressure X-ray diffraction study of carbonates: MgCO3, CaMg(CO3)2, and CaCO3. Am Miner 79:15–23Google Scholar
- Gillet P, Biellmann C, Reynard B, McMillan P (1993) Raman spectroscopic studies of carbonates part I: high-pressure and high-temperature behaviour of calcite, magnesite, dolomite and aragonite. Phys Chem Miner 20:1–18Google Scholar
- Mao Z, Armentrout M, Rainey E et al (2011) Dolomite III: a new candidate lower mantle carbonate. Geophys Res Lett 38:L22303Google Scholar
- Reeder RJ, Dollase WA (1989) Structural variation in the dolomite-ankerite solid-solution series: an X-ray, Mössbauer, and TEM study. Am Miner 74:1159–1167Google Scholar
- Reeder RJ, Wenk H-R (1983) Structure refinements of some thermally disordered dolomite. Am Miner 68:769–776Google Scholar
- Ross NL, Reeder RJ (1992) High-pressure structural study of dolomite and ankerite. Am Miner 77:412–421Google Scholar
- Steinfink H, Sans FT (1959) Refinement of the crystal structure of dolomite. Am Miner 44:679–682Google Scholar
- White WB (1974) The Infrared Spectra of Minerals. In: Farmer VC (ed). Mineralogical Society Monograph, London, p 227–279Google Scholar