DEEP STRUCTURES AND CARBON-DIOXIDE DEGASSING IN CENTRAL ITALY

In Tyrrhenian Central Italy large amounts of CO2 are produced at depth mainly by metamorphism of marine carbonate rocks. During their ascent , the gases are trapped in deep structures, made up of Mesozoic permea ble limestones covered by impermeable terrains, which become sources o f a high CO, flux toward the surface. The anomalous CO2 concentrations are delectable in groundwaters. The general map of the groundwater PC O2 values shows a decrease in the CO2 production moving from the weste rn geothermal areas of Tuscany and Latium to the eastern sector, which is characterized by a normal heat flow. The PCO2 distribution suggest s that the NW-SE extensional faults, which bound Plio-Pleistocene grab ens, provide the easiest routes for the gas ascent. The geological, ge ophysical and geothermal deep drilling data suggest that the CO2 anoma lies found in the western sector correspond to deep permeable structur es of possible geothermal interest.