Hydrogeological Characterization of a Geothermal system: the case of the Thermo-mineral area ofMondragone (Campania, Italy)

This paper dealswith thermo-mineral groundwater of theMondragone plain (Campania, southern
Italy) and the possibility to use this low enthalpy geothermal resource. In the NW sector of this plain, at the
bottom of Mt. Pizzuto, near the sea, there are thermo-mineral waters (50 °C) of sodium-chloride type,
sulfureous and rich in CO2 whose recharge is from the Mt. Pizzuto groundwater body. In the SE sector of the
plain, close to the calcareous Mt. Petrino, a 80 m deep well has intercepted, in the carbonate basement of the
plain, thermo-mineral groundwater (33 °C), sulfureous and rich in CO2, as in the NW sector, but displaying a
calcium-bicarbonate composition. The chemical and the isotopic analyses allowed to verify that these types
of groundwater are due both to meteoric waters infiltration and to enrichment of endogenous CO2 and H2S, at
fairly high temperature. In the Petrinum well, the gases involve “connate waters”, affecting upwards the
groundwater body of Mt. Petrino. Moreover, the rising of the gases increases the dissolution of the carbonate
aquifer, determining very high values of HCO3 ions in the thermo-mineral groundwater. In the case of Mt.
Pizzuto, the upwelling gas intercepts also evaporitic formation and, probably, causes saltwater intrusion. The
upwelling of the gases occurs along the major fault that crosses NE-SW the plain of Mondragone. Finally, the
understanding of the mineralization patterns allowed to identify in the plain the best location for a geothermal
exploration well.