Heat flow in the tectonic provinces crossed by the southern segment of the European Geotraverse

Several published and unpublished surface heat-flow density (HFD) data sets have been reviewed to obtain a valid HFD estimate for the main tectonic provinces crossed by the European Geotraverse Southern Segment (EGT-S) and to produce a regional HFD map for this area. Because the quality and areal distribution of the data are rather heterogeneous, particular care has been devoted to data validation and processing. We used a geostatistical approach to estimate the regional range of influence of the HFD data in the various tectonic provinces. The HFD map has been obtained using an automatic interpolation technique (kriging). HFD values generally higher than 100 mW · m-2 are observed in the post-Eocene rifting areas, such as the Rhine Graben, the Tyrrhenian, Ligurian, Provençal and Balearic basins, the younger part of the Sardinia rift, the central part of the Sardinia-Tunisia channel and the Pantelleria rift system. The Alps show values ranging between 50 and 90 mW · m-2 and a mean value of about 70 mW · m-2, whereas the Molasse basin, lying on their northern front, exhibits a mean HFD significantly more elevated (87 mW · m-2). The northern Apennines separate the low HFD (about 40 mW · m-2) foreland Po basin from the internal zones of the chain, which shows higher HFD values and a tensional stress regime. Values higher than 200 mW · m-2 pertain to areas recently affected by magmatic and volcanic activity, such as the Tuscany-Latium geothermal area and the oceanic Tyrrhenian basin. The Atlas zone shows an HFD trend with values around 75 mW · m-2, whereas the Pelagian block and the northern edge of the Saharan platform display higher values. The Hercynian crust of Sardinia and southern Corsica is characterized by a value of about 60 mW · m-2; the higher values found along the western Corsica and Sardinia margins are probably due to a thermal event related to recent tectonic phases of the Ligurian, Provençal and Sardo-Balearic rifting. A remarkably good correspondence between the HFD field and the Bouguer gravity anomaly strongly supports the existence of transient thermal regimes in the recent deformational areas of the EGT-S, as opposed to the steady regime mostly affecting the central and northern segments of the EGT. © 1995.