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Title:
Thermodynamic properties and the conditions of formation of heideite FeTi2S4 in meteorites
Authors:
Petaev, M. I.; Gavrichev, K. S.; Gurevich, V. M.; Osadchii, E. G.; Stoliarova, T. A.
Publication:
Geokhimiia (ISSN 0016-7525), Jan. 1987, p. 64-75. In Russian.
Publication Date:
01/1987
Category:
Lunar and Planetary Exploration
Origin:
STI
NASA/STI Keywords:
IRON COMPOUNDS, METEORITIC COMPOSITION, MINERALS, THERMODYNAMIC PROPERTIES, ENTHALPY, ENTROPY, SPECIFIC HEAT, SULFIDES, TITANIUM COMPOUNDS
Bibliographic Code:
1987Geokh.......64P

Abstract

To determine the natural conditions for the synthesis of meteoritic heideite, a compound detected in Bustee aubrite by Keil and Brett (1974) and found to have a FeTi2S4 approximate composition, the FeTi2S4 was synthesized in vacuo at 750 C. The thermodynamic properties of FeTi2S4 were determined at temperatures between 4.75 and 338 K, together with the enthalpy of its formation (on the basis of its reaction with metal Zn). The values for the specific heat and the entropy of the heideite were found to be (at 298.15 K) 208.62 J/mol per K, 226.97 J/mol per K, respectively. The enthalpy of heideite formation was determined to be -662 kJ/mol. Thermodynamic analysis shows that, relative to simple sulfides of Ti and Fe, FeTi2S4 is metastable at low temperatures. It is argued that heideite could not have been formed in the protoplanetary nebula environment as a result of the condensation of gaseous phase of solar composition even at C/O = 1. Thus, the genesis of heideite in the Bustee is still unclear.
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