HYDROGEOCHEMISTRY OF THE CAMPANIA REGION IN SOUTHERN ITALY

A geochemical study of thermal springs, cold springs, stream waters and natural gas emissions has been carried out in the Campania region of southern Italy. This region hosts four Quaternary volcanic areas, and thermal springs and gas emissions occur in three of them. Most thermal springs discharge Na-Cl composition waters of connate origin derived from post-orogenic volcanic and sedimentary formations. Although high-enthalpy systems are present in two of the four volcanic areas, there appear to be no magmatic contributions to the thermal springs. Solute geothermometers are unreliable as spring waters are strongly affected by mixing with ''shallow'' brines before discharging. Thermal springs and gas emissions also occur in non-volcanic areas, where an extensive carbonate unit acts as a regional aquifer for cold, low-salinity, bicarbonate waters. Thermal features in these areas occur in fractured zones associated with active faults. Their compositions:are determined only by the type of rock encountered by solutions before surface discharge. As in other areas of north-central Italy, the widespread occurrence of hot and cold CO2-rich springs, and gas emissions in both volcanic and non-volcanic zones, suggests a deep origin for the CO2.