Heat flow and geothermal resources in northern Italy

•Subsurface temperature and surface heat-flow data in the northern Italy.•Hydrothermal systems of the Alps and the Northern Apennines.•Thermal convection in the deep carbonate aquifer of the Po Plain.

This paper gives an up-to-date overview of the surface heat flow and the geothermal resources of northern Italy on the basis of both already processed data and new pieces of information. Temperature data up to 7240 m depth, derived from exploration oil wells, were processed and thermal conductivity was estimated under any possible condition of depth. Radiogenic heat was evaluated by means of both natural gamma-ray logs and gamma-ray spectrometry measurements on core samples. These data together with information from previous investigations allow us to map the temperature at a depth of 2000 m in the Po Plain and to give a new picture of the surface heat flow throughout northern Italy. The most important hydrothermal systems occur in the Alps and the Northern Apennines, in areas where meteoric water leaks to shallow–medium depth and originates thermo-artesian springs. In the eastern sector of the Po Plain, important thermal anomalies appear to be controlled by the morphology of the deep carbonate formation. Thermal rather than forced convection can take place in this formation, which acts as a reservoir hosting low-medium enthalpy water.