Order–disorder–reorder process in thermally treated dolomite samples: a combined powder and single-crystal X-ray diffraction study

• Published in: Physics and chemistry of minerals Vol. 39; no. 4; pp. 319 - 328
• Main Authors: Zucchini, A., Comodi, P., Katerinopoulou, A., Balic-Zunic, T., McCammon, C., Frondini, F.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-04-2012; Springer Nature B.V
• Subjects: Calcium magnesium carbonate; Crystallography and Scattering Methods; Crystals; Dolomite; Domains; Earth and Environmental Science; Earth Sciences; Geochemistry; Mineral Resources; Mineralogy; Original Paper; Single crystals; Twinning; X-ray diffraction; X-ray diffraction; Twinning; Cation disorder; Dolomite; High pressure
• ISSN: 0342-1791; 1432-2021
• DOI: 10.1007/s00269-012-0489-9

A combined powder and single-crystal X-ray diffraction analysis of dolomite [CaMg(CO
3
)
2
] heated to 1,200°C at 3 GPa was made to study the order–disorder–reorder process. The order/disorder transition is inferred to start below 1,100°C, and complete disorder is attained at approximately 1,200°C. Twinned crystals characterized by high internal order were found in samples annealed over 1,100°C, and their fraction was found to increase with temperature. Evidences of twinning domains combined with probable remaining disordered portions of the structure imply that reordering processes occur during the quench. Twin domains are hereby proposed as a witness to thermally induced intra-layer-type cation disordering.