The thermal and mineral springs of Aitoloakarnania Prefecture: function mechanism and origin of groundwater

The study area is located in the northwestern part of Greece, in Aitoloakarnania prefecture. In this region, where no volcanic activity exists, thermal springs such as Kremasta and Kokkino Stefani, well-known for their healing properties occur. The objective of this study was the investigation of these springs, as well as the study of the chemical composition and origin of water. Relationships between these springs were also examined. The geological setting of the area comprises sedimentary rocks of the Pindos, Gavrovo-Tripolis and Ionian geotectonic zones, deformed by orogenic movements followed by Neogene extensional tectonism. The thermal and mineral springs were classified into three main groups. The first group is characterized by Ca-HCO3 water type and low water temperatures. It corresponds to the springs that are hosted in the Ionian zone and their possible enrichment in SO4 is mainly attributed to the evaporites. The other two groups consist of alkaline thermal water mainly hosted in the formations of Gavrovo-Tripolis zone. In these two groups, the very strong reducing conditions that prevail are expressed by high amounts of NH3 and H2S. Moreover, Na, F, Li, Sr and Ba display elevated concentrations. The second includes mineral waters of (Ca)-Na-HCO3 type that are depleted in calcium. Their residence time is rather long and they originate from deep water circulation through siliceous rocks. The third group includes thermal waters of Ca-Mg-Na-HCO3 water type of higher water temperatures that reveal characteristics of deep circulation directly associated with the underlain limestones.