Practical Aspects of Mineral Thermobarometry
Solid Solutions
This section deals with the thermodynamic treatment of mineral solid solutions, from the practical viewpoint of finding simple but effective expressions for estimating the activities of end members (phase components) to use in P-T calculations. The topic is treated in chapter 7 of Spear's Metamorphic Phase Equilibria. There are several sub-sections:
Energy of mixing, chemical
potential, and activity
A brief introduction to the thermodynamics of solid solutions, and the
definition of activity.
Mixing on sites
Ionic model, one site, multi-site, end members with part-filled
sites (normalisation)
Non-ideal solutions
Simple energetics of non-ideal solutions. Regular and sub-regular
models. Multicomponent solutions.
Reciprocal solutions
Interactions between sites
Simplified models, and Darken's
quadratic formalism (DQF)
Useful simplified relationships for a-X relations in complex
phases
Activity calculations
Recommended models, implemented in Holland's AX program
[ Work is in progress on some of these pages ]
Sources and further reading
This topic is treated quite thoroughly by
- Spear (1993) Ch 7, pp. 175-190.
- Powell (1978) Equilibrium Thermodynamics in Petrology
This page last modified 12 October 2004