- © The Mineralogical Society Of America
The creation of thermodynamic databases may be one of the greatest advances in the field of geochemistry of the past century. These databases facilitate creation of phase diagrams describing which mineral phases are stable as a function of temperature and pressure, enabling detailed interpretation of metamorphic systems (e.g., Essene 1982; Spear and Cheney 1989; Zaho et al. 2000). The versatility of these databases provide insight into the fate and consequences of subsurface storage of radioactive waste (e.g., van der Lee and De Windt 2001; Lichtner et al. 2004; Zhang et al. 2008), toxic waste (e.g., Glynn and Brown 1996; Steefel et al. 2005), and CO2 (e.g., Knauss et al. 2005; Oelkers and Schott 2005; Oelkers and Cole 2008; Oelkers et al. 2008).
The impressive utility of thermodynamic databases has lead to their incorporation into ‘user-friendly’ chemical speciation, reactive path, and reactive transport computer codes including EQ3 (Wolery 1983), PHREEQC (Parkhurst and Appelo 1999), and CHESS (van der Lee et al. 2002) allowing rapid calculation of mineral solubility and solute speciation in a variety of geochemical systems. A selected list of chemical speciation codes is provided in Table 1⇓. These codes differ is ease of use, but all accurately solve for the equilibrium assemblages of minerals and aqueous species, and mineral solubilities within the limits of their thermodynamics databases. The quality of the results of each of these codes is directly related to the quality of these databases.
Geochemical modeling codes such as those listed in Table 1⇑ have advantages and disadvantages. On one hand these computer algorithms allow calculation or prediction of the equilibrium state and/or the evolution of geochemical systems as a function …