Abstract

Thermal water circulation in northern and central Calabria is investigated on the basis of the physico-chemical characteristics of the thermal springs in the area. Comparison between the chemical composition of thermal samples and that of cold springs and some stream samples, also considering the extreme heterogeneity of the lithotypes present in the area, suggests that, independently from the individual geological horizons where deep circulation occurs, there is marked contamination in the thermal systems by fossil waters and/or evaporitic material embedded in layers belonging to Neogene post orogenic formations. From this contamination derives a predominant Na-Cl composition in many thermal springs. Geothermometrically and from the water-interaction point of view all the thermal springs investigated show low-equilibration temperature. This, together with already assessed meteoric origin of the thermal fluids, points to the fact that no anomalous geothermal gradients are present in the area, and that the deep circulation and rising of the waters along fractures predominantly located at the margins of the post orogenic basins, is caused by high hydraulic heads which in their turn originated in the rugged morphology of the area. Among the thermal systems investigated those located in the peri-Tyrrhenian area present higher P <sub>CO2</sub> values (calculated) with respect to the eastern thermal emergences. This more intense deep gas activity in the peri-Tyrrhenian western sector is tentatively related to a greater superficiality of Moho in this area with respect to the eastern Ionic sector.

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