Geochemical Model of the Granite-Bentonite-Groundwater at Äspö (LOT Experiment)

A geochemical modelling of one of the experimental parcels of the LOT experiment (Äspö, Sweden) is presented. The model consists on a 2D reactive transport model of a perpendicular section of the experimental borehole with a stationary temperature gradient ranging from 130 to 15°C. The results of the model show that temperature has an important effect on the geochemical evolution of the system. Due to the temperature effect, anhydrite replaces gypsum and hematite precipitates instead of Fe(OH)3(am). Calcite and siderite dissolve in the warmer part of bentonite; whereas a major replacement of Na by Ca in the bentonite takes place close to the bentonite-granite boundary. pH is buffered by the equilibrium with calcite, although the effect of temperature leads to a decrease in pH