Origin of groundwater in the tertiary volcanic complex in central Slovakia

On the inner side of the Carpathian Mountain arch in central Slovakia, there is a sequence of Miocene to Pleistocene volcanic rocks predominantly of andesite type and their pyroclastics, forming a stratovolcanic structure up to 1500 m thick over an area of about 5400 km2. The volcanics are underlain by Mesozoic carbonate and by earlier crystalline rocks. The andesites were considered to be poor aquifers. A recent systematic hydrogeological investigation has confirmed that there is a concentration of groundwater flow in fractured zones along faults, this flow discharging into streams. The isotope analyser helped to explain the groundwater structure in the volcanic rocks in relation to the earlier structures, and contributed to knowledge on the development of groundwater and the evaluation of its resources. 2 figs, 1 tab