Thermodynamics, Geochemical Modeling and Related Considerations

In this chapter we intend (1) to briefly recall the thermodynamic functions and the relations linking them which are of use in geochemical applications, (2) to present the software package SUPCRT92, which is used to calculate the standard molal thermodynamic properties of minerals, gases, aqueous species, and H2O, as well as of the reactions involving these entities, as a function of temperature and pressure, from 0 to 1000°C and from 1 bar to 5 kbar, (3) to summarize the main aspects of equilibrium state models and reaction path models, focusing of multicomponent chemical geothermometry, which is a reaction path model of special interest. In particular, the simple equations linking the Gibbs free energy and the thermodynamic equilibrium constant of the dissolution reaction of a given solid solution to the corresponding properties of the dissolution reaction of the key endmember are presented in section 2.2.1.