Thermodynamic mixing behavior of synthetic Ca-Tschermak-diopside pyroxene solid solutions: I. Volume and heat capacity of mixing

Etzel, Katja, Benisek, Artur, Dachs, E. and Cemic, L. (2007) Thermodynamic mixing behavior of synthetic Ca-Tschermak-diopside pyroxene solid solutions: I. Volume and heat capacity of mixing Physics and Chemistry of Minerals, 34 (10). pp. 733-746. DOI 10.1007/s00269-007-0191-5.

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Abstract

The unite cell parameters and heat capacities of a series of synthetic clinopyroxenes on the join Ca-Tschermak (CaTs)-diopside (Di) were measured using X-ray powder diffraction and calorimetric methods, respectively. The volume of mixing at 298 K shows a negative asymmetric deviation from ideality. A two-parameter Margules fit to the data yields W-CaTs-Di(V) = -0.29 +/- 0.11 cm(3) mol(-1) and W-Di-CaTs(V) = -1.14 +/- 0.14 cm(3) mol(-1). Heat capacities were determined between 5 and 923 K by heat-pulse at 5-302 K and differential-scanning calorimetry at 143-923 K. The precision of the low and high temperature C (p) data is better than +/- 1%. Polynomials of the form C (p) = a + bT(-1/2) + cT(-2) + dT(-3) were fitted to the C (p) data in the temperature range between 250 and 925 K. Thermal entropy values [S (298) - S (0)] and [S (900) -S (0)] as well as enthalpies [H (298) - H (0)] and [H (900) - H (0)] were calculated for all members of the solid solution series. No significant deviation from ideal mixing behavior was observed.

Document Type: Article
Keywords: Tschermakitic pyroxene heat capacity molar volume entropy enthalpy subsolidus phase-relations clinopyroxene geobarometry system cao-mgo-al2o3-sio2 magmatic rocks thermobarometry anthophyllite wollastonite iherzolite enstatite minerals
Research affiliation: Kiel University
DOI etc.: 10.1007/s00269-007-0191-5
ISSN: 0342-1791
Date Deposited: 12 Jan 2012 05:05
Last Modified: 08 Oct 2012 10:20
URI: http://eprints.uni-kiel.de/id/eprint/15908

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