Heat-flux budget in the southeastern continental margin of the Tyrrhenian basin

Abstract

We evaluate the different components contributing to the surface heat flux of the Sicilian–Calabrian margin in the Tyrrhenian back-arc basin. The stretching factor, estimated from the change in crustal thickness, and the observed surface heat flux reveal a quite regular pattern, increasing from the coastline to the oceanic domain. The average value of the stretching factor is 2, while that of the surface heat flux, excluding data close to the Aeolian volcanic arc and those affected by hydrothermal circulation, is 125 mW m −2. A heat-flux model taking into account the stretching processes, the lithospheric radiogenic heat source and the heat flux from the asthenosphere cannot account for these average values. A likely source of the energy required to balance the 33 mW m −2 heat-flux deficit should be searched in the active subduction process occurring beneath the basin. The results show that when a moderately hot asthenosphere (in excess of 90 °C with respect to the normal) moves from high to low pressure with little change in entropy, it crosses its solidus and can generate partial melt. The produced magma is able to ascend and to pond at the base of the crust. By incorporating the heat produced by a 3.4 km thick magma layer and a crustal growth correction on the lithosphere extension, the thermal budget fits the observed surface heat flux. This indicates that extension, besides subduction, might have generated continental margin magmatism, and it requires a thermally anomalous mantle.