Origin of groundwater mineralization in coarse-grained lower Badenian aquifer in the Czech part of the Upper Silesian Coal Basin

The coarse-grained aquifer of lower Badenian forms the most important hydrostructure in the Czech part of the Upper Silesian Coal Basin (USCB). In order to determine the sources of its groundwater mineralization the hydrochemical relationships between ion concentrations and other specific parameters were examined. Most of the water was probably derived from the seawater, evaporated to a various extent, but not reaching halite crystallization point.Water with higher TDS may represent mixture between evaporated seawater and the residual brine (after halite crystallization). In less mineralized waters of HCO3-Na type, elevated concentrations of Br and I could be attributed to the decay of organic matter. For the most samples of waters representing Cl-Na type, the differentiation in Br and I concentrations was controlled independently.