Physics and Chemistry of Minerals

, Volume 40, Issue 2, pp 167–173

Heat capacity and entropy of low structural state plagioclases

Original Paper

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.

Keywords

Plagioclase Specific heat Entropy Anorthite Relaxation calorimetry Differential scanning calorimetry 

Supplementary material

269_2012_556_MOESM1_ESM.txt (41 kb)
Supplementary material 1 (TXT 41 kb)

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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Materialforschung and PhysikUniversität SalzburgSalzburgAustria
  2. 2.Department of Earth SciencesUniversity of CambridgeCambridgeUK

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