–Geochemical behaviour of groundwater within gypsum series. (a) Solubilities of gypsum, calcite and quartz according to temperature. (b) Mass balance of groundwater in equilibrium with (1) a calcareous aquifer, (2) contact with gypsum leads to calcite precipitation and which (3) is even higher in the presence of dolomite. Silica precipitation may occur at any step if the temperature falls. HYTEC geochemical modelling (Van Der Lee et al., 2003).