Abstract
The enthalpies of phase transformation can be combined with free energies obtained from high pressure experiments to obtain accurate estimates of entropies of transition and independent assessment of pressure-temperature slopes. Transitions in the systems CoO- SiO2, 'FeO'-SiO2, and MgO-GeO2 have been studied by calorimetry, and the thermochemical and phase equilibrium data are in good agreement for the olivine-spinel transition, and stability fields of alpha , beta , and gamma -Co2SiO4, and the formation and breakdown of pyroxene. However, some discrepancies exist between calculated and experimental P-T slopes of spinel disproportionation reactions. Conclusions concerning crystal chemical systematics are drawn from NaC1-CsC1, DELTA SoC is not constant but varies strongly with DELTA VoC. The calorimetric data argue against any major changes in glass structure (coordination number) in these high pressure glasses.-Authors
Original language | English (US) |
---|---|
Pages (from-to) | 465-477 |
Number of pages | 13 |
Journal | Unknown Journal |
State | Published - 1982 |
ASJC Scopus subject areas
- General Environmental Science
- General Earth and Planetary Sciences