Heat capacity measurements of CaAlSiO4F from 5 to 850 K and its standard entropy

作者：Tropper Peter^*; Troitzsch Ulrike; Dachs Edgar; Benisek Artur

来源：American Mineralogist, 2018, 103(7): 1165-1168.

DOI：10.2138/am-2018-6500

• F-Al titanite
• PPMS
• DSC
• standard entropy

Heat capacity (C-P) data of Al-F-bearing titanite are presented that yield the standard entropy S-298.15 degrees of F-Al-titanite CaAlFSiO4 (FAT). C-P of synthetic FAT was measured with relaxation calorimetry and differential scanning calorimetry between 5 and 764 K. The results constrain S-298.15 degrees to be 115.4 +/- 2.0 J/(mol.K) and subsequently the standard Gibbs free energy of formation from the elements, Delta(f)G degrees, of CaAlSiO4F to be between -2583 +/- 3.0 and -2588 +/- 3.0 kJ/mol, and the standard enthalpy of formation from the elements, Delta H-f degrees, to lie between -2728 +/- 3.0 and -2733 +/- 3.0 kJ/mol depending on the thermodynamic data retrieval approach. These data, in turn, can be used to quantitatively model highgrade and UHP fluid-rock interaction. The calculation of future petrogenetic grids involving F-bearing minerals and titanite solid solutions in the system CaTiSiO4O-CaAlSiO4F will only be possible by expanding existing internally consistent thermodynamic databases to the F-system.

• 出版日期2018-7