Original paper

Internally consistent thermodynamic data for rock-forming minerals in the system SiO2-TiO2-Al2O3-Fe2O3-CaO-MgO-FeO-K2O-Na2O-H2O-CO2

Gottschalk, Matthias

European Journal of Mineralogy Volume 9 Number 1 (1996), p. 175 - 223

241 references

published: Dec 30, 1997
manuscript accepted: Sep 25, 1996
manuscript received: Jul 25, 1996

DOI: 10.1127/ejm/9/1/0175

BibTeX file

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Abstract

Abstract An internally consistent thermodynamic data set has been derived utilizing results from all available experimental phase equilibria in a simultaneous iterative regression approach using 1/T vs. In Kred plots. Simultaneous evaluation of all reactions allows the extraction of an internally consistent data set of ΔfH° and S° values with V°, cp, α and ß otherwise constrained. An objective function has been defined which requires maximum consistency with available experimental results and minimum deviation from available calorimetric data. One advantage of this procedure is that all available experimental results, compatible or not, are always visible during the calculations. Over 5300 experimental results from 244 contributions for 253 reactions involving 94 phase components have been used. The extracted data set reproduces 92% of the available phase equilibria experiments reported in the literature. It can be shown that for some phases the configurational entropy must be considered (e.g. CaAl-pyroxene, clinochlore, mullite, phlogopite). With the addition of a configurational entropy for these phases the reproduction of the available experimental results is significantly improved. The configurational entropy for these phases is chiefly responsible for the observed differences between this and other available internally consistent data sets. In these other data sets non-addition of configurational entropy for these phases is compensated for by adjustments in the enthalpy and/or in other refined thermophysical parameters such as heat capacities. The configurational entropies used here are quite straightforward and involve mostly tetrahedral Si/Al and octahedral Mg/Al disorder

Keywords

internally consistent set of thermodynamic dataenthalpy of formationthird law entropy