During the exploitation of the Soultz-sous-Forets geothermal system, the cold fluid re-injected in the geothermal reservoir causes a strong disequilibrium between the fluid and the granite which implies dissolution/precipitation of minerals. These mineralogical transformations can potentially change the porosity, the permeability, and the flow pathways in the granitic basement. Knowledge of the mineralogical transformations was assessed by several modeling studies, which highlighted the importance of considering geochemical processes within the Soultz reservoir. The choice for representing the mineral assemblage and the precision of the thermodynamic database play a critical role in the accuracy of the modeling results. This aspect should be considered carefully, especially in the context of geothermal systems because the mineral composition is generally too much simplified in the simulations due to lack of data on the detailed mineralogy. The current work aims to test our modeling approach to produce the hydrothermal alteration assemblages in the Soultz specific conditions, particularly the high salinity and high temperatures (up to 200 degrees C) of the geothermal fluid. The approach used in the present study is based on calculation of the saturation indices of a large number of minerals in a given aqueous geothermal fluid from the activities of the aqueous species as a function of temperature. Our model accounted for a wide range of different mineral groups in order to make sure a large freedom for the numerical calculations. The modeling results showed that when the temperature of the geothermal reservoir cools, minerals like calcite, illites, quartz, clinochlore, K-feldspar, pyrite, galena, and barite show a tendency towards equilibrium state, which indicates that they may be precipitated. In contrast, other minerals initially present in the fresh granite including anorthite, K-muscovite, and annite remained unsaturated and may be dissolved. These mineral behaviors were further illustrated with mineral stability diagrams. The modeling results confirm that special attention should be paid to these minerals when studying changes in porosity and permeability of the geothermal reservoir. Future effort for extending the kinetic database for minerals should first concern these mineral phases. (C) 2016 Elsevier Ltd. All rights reserved.