Quantification of deep CO2 fluxes from Central Italy. Examples of carbon balance for regional aquifers and of soil diffuse degassing.

Abstract In Central Italy non-volcanic CO 2 is discharged by focused degassing (strong diffuse emission and vents) and by high-CO 2 groundwater. 3 He / 4 He data and the carbon isotopic composition of CO 2 are compatible with derivation from mantle degassing and/or metamorphic decarbonation. The gases produced at depth accumulate in permeable reservoirs composed of Mesozoic carbonates. When total pressure (roughly corresponding to p CO 2 ) of the reservoir fluid exceeds hydrostatic pressure, a free gas phase forms gas reservoirs within the permeable host rocks from which gases may escape toward the surface. This process generates both the focused vents and the CO 2 -rich springs which chara…