Heat capacity and entropy of low structural state plagioclases

Benisek, A. and Dachs, E. and Carpenter, M. A. (2013) Heat capacity and entropy of low structural state plagioclases. Physics and Chemistry of Minerals, 40 (2). pp. 167-173. ISSN 0342-1791, 1432-2021 DOI 10.1007/s00269-012-0556-2

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Abstract

The heat capacity of 11 different compositions of the low structural state plagioclase binary was measured between 5 and 773 K. The results are compared to those obtained from synthetic high structural state samples investigated in a previous study and obtained from a heat-treated natural sample of this study. The heat capacity of anorthite samples with slightly different order parameters shows large differences at ~500 K, where the Ibar1-Pbar1 phase transition occurs, which affects petrological calculations. At T = 298.15 K, the vibrational entropy versus composition behaviour of the low structural state plagioclases is almost ideal, in contrast to the high structural state plagioclases with positive excess vibrational entropies. At higher temperatures, the low structural state plagioclases show a negative deviation from ideal vibrational entropy composition behaviour in the Na-rich region.

Item Type: Article
Uncontrolled Keywords: 2012AREP; IA65;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Physics and Chemistry of Minerals
Volume: 40
Page Range: pp. 167-173
Identification Number: 10.1007/s00269-012-0556-2
Depositing User: Sarah Humbert
Date Deposited: 26 Jan 2013 11:37
Last Modified: 23 Jul 2013 10:05
URI: http://eprints.esc.cam.ac.uk/id/eprint/2660

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