The purposees of this master thesis are on the one hand to assess if dedolomitisation is still an ongoing process in the underground of the Rovte area (W Slovenia) and on the other hand to characterise the hydrochemistry of thermal wells and subthermal springs in NW-Slovenia.

To achieve these purposes, waters from deep wells and springs in the Rovte area and waters from thermal wells and subthermal springs in the Cerkno/Kranj area were analysed. Hydrochemical analysis was done by spectrophotometry, ion chromatography and atom absorption spectrometry. Isotope analysis (δ2H and δ18O) was done with the automated Picarro L2130-i analyser.

The wells Z (Zavčan), R (Rodofov Mlin) and B (Bizjakov Mlin) penetrate gypsum strata at a depth of several hundred meters. Thus, samples from wells Z and R show high SO42- concentrations and molar-Mg2+/Ca2+-ratios lower than 1. In contrast, water samples from surface springs show very low SO42- but high NO3- and Cl- concentrations. These samples are clearly impacted anthropogenically. The isotopes (δ2H and δ18O) of the wells Z and R are in the same range suggesting that the waters from Z and R derive from the same aquifer system. The Calculation of saturation indices with PHREEQC shows that most samples from the wells were supersaturated with respect to calcite and mostly undersaturated with respect to dolomite. Furthermore, the diagram of pH vs. SO42- concentration from Z and R show a negative correlation. This and the preferential removal of Mg2+, as suggested by the molar-Mg2+/Ca2+-ratios lower than 1, indicates that dedolomitisation might still be occurring.

The hydrochemical analysis of the waters from thermal wells and subthermal springs revealed that a deep flow pattern exists in NW-Slovenia. The boreholes probably drain the deep aquifer system (namely the Upper Triassic Norian stage grey stratified dolomite).