Mineralogical data from the Forsmark Site show that smectite and calcite occur at all depths in Forsmark fractures, with no evidence for removal/dissolution by previous glacial episodes. This natural analogue information implies that these minerals may not have been eroded/dissolved during previous glacial episodes.
Available thermodynamic data suggest that repository-depth Forsmark groundwaters are in equilibrium (steady-state) with montmorillonite and saponite and these minerals may control pH, PCO2, SiO2(aq) and Na/Ca in groundwaters (and any future intruding glacial meltwaters) in the near-field at the site. This conclusion would not be evident from modelling approaches using mixing only.
Modelling of the reaction of montmorillonite in the buffer with Forsmark groundwater shows a trend towards conversion of montmorillonite to saponite, suggesting that the buffer may be partially altered prior to glacial meltwater intrusion.