3D geothermal model of southern Italy based on the Curie isotherm depth

In this study, we build a 3D regional-scale thermal model beneath southern Italy using the Curie isotherm as the bottom boundary condition for the heat-conduction equation. The thermal model is based on solving the 3D steady-state heat conduction equation using a finite-difference approach. Our model consists of five major crustal layers, including the depth to the magnetic basement, the magnetic bottom, and the Moho. For each layer we assigned representative radiogenic heat source and thermal conductivity values based on the average crustal and thermal properties of the study area. The Curie depth, estimated from spectral analysis of aeromagnetic data, is treated as a first-order proxy for the ~ 580 °C isotherm, and it acts as the model lower boundary. Our model provides a spatially continuous image of the crustal temperature distribution across the Tyrrhenian back-arc basin, the Apennine fold-and-thrust belt, and the Adriatic-Ionian foreland. The results reveal pronounced lateral variations in the crustal thermal regime. Thermal gradients range from ~ 25 °C/km beneath the Adriatic and Ionian regions to ~ 75 °C/km beneath the Marsili Basin and Aeolian Arc in the Tyrrhenian Sea where the Curie isotherm is predicted to occur at depths of only 8-10 km. Conversely, the Curie depth is 30-34 km below the Apennine belt and the Calabrian arc, which indicates a much colder and mechanically more resistant crust. Similarly, our estimated heat flow varies from ~ 40 mW/m² in the Calabrian Arc and the central Apennines, to over 200 mW/m² in the volcanic areas of the south-eastern Tyrrhenian Sea. These patterns reflect the geodynamic evolution of the region, with asthenospheric upwelling and lithospheric thinning occurring beneath the Tyrrhenian retro-arc basin, and thicker, colder lithosphere beneath the orogenic and foreland domains. In addition, our model provides quantitative constraints on the thermal architecture and rheological structure of the lithosphere beneath southern Italy. The predicted temperature field suggests that temperatures of 150-250 °C may be reached at depths of 3-5 km in several sectors of the Tyrrhenian margin and volcanic provinces, indicating favorable conditions for geothermal exploitation where sufficient permeability is present. The proposed framework therefore offers an improved regional baseline for geothermal exploration and for future thermo-mechanical modeling of the central Mediterranean lithosphere.