Advective heat transport associated with regional Earth degassing in central Apennine (Italy)

• We computed the advective heat flux affecting central Apennine aquifers.
• Central Apennine are affected by very high advective heat fluxes, up to 300–400 mW m−2.
• The heat is transported from depth by CO2 rich fluids.
• Vp and Bouguer anomalies are consistent with the high heat flux.
• The thermal anomaly may be associated to a magmatic intrusion in the lower crust.

In this work we show that the main springs of the central Apennine transport a total amount of heat of ∼2.2×109 J s−1. Most of this heat (57%) is the result of geothermal warming while the remaining 43% is due to gravitational potential energy dissipation. This result indicates that a large area of the central Apennines is very hot with heat flux values >300 mW m−2. These values are higher than those measured in the magmatic and famously geothermal provinces of Tuscany and Latium and about 1/3 of the total heat discharged at Yellowstone. This finding is surprising because the central Apennines have been thought to be a relatively cold area. Translated by CO2 rich fluids, this heat anomaly suggests the existence of a thermal source such as a large magmatic intrusion at depth. Recent tomographic images of the area support the presence of such an intrusion visible as a broad negative velocity anomaly in seismic waves. Our results indicate that the thermal regime of tectonically active areas of the Earth, where meteoric waters infiltrate and deeply circulate, should be revised on the basis of mass and energy balances of the groundwater systems.