Thermodynamics for clay minerals: Calculation tools and application to the case of illite/smectite interstratified minerals

We present two computing tools, ClayTherm and ISTherm, devoted to the estimation of thermodynamic properties both anhydrous hydrated clay minerals (ClayTherm), illite/smectite (I/S) mineral series (ISTherm). The first tool, ClayTherm, is property estimates for minerals. It combines several previously published models, including hydration aspects. Verification provided, against a set solubility data, selected from previous literature. A specific application ISTherm was subsequently developed based on tool. focuses smectite-to-illite transformation, able calculate interstratified minerals, starting composition single I/S sample. functions have been completed mixing energies tool then used in order investigate case natural hydrothermal Shinzan geothermal field (Japan). Activity diagrams calculated phase relations are found be agreement with mineralogical observations solution chemical analyses. further investigated through reactive transport modelling by using site-specific, augmented version geochemical database. Illitization formation predicted over realistic reaction times, consistently available observations.