How mantle heterogeneities drive continental subduction and magmatism in the Apennines.

Petrologic and geophysical observations floored the paradigm shift on the subduction of the continental lithosphere. In long-lived collisional boundaries like the Alpine Himalaya belt, portions of continental lithosphere are pushed down to great depths and then exhumed, as testified by outcrops of UHP materials. The Mediterranean region is a clear expression of this enigmatic process. On a short space and time scale, the Apennines exhibits a complex pattern of across-belt extension, associated with under-thrusting of continental lithosphere and a variegated suite of magmatic products. Here we show that the delamination of the crust is essential to favor the subduction of the continental lithosphere, a process that is controlled by pre-existing heterogeneity of the uppermost mantle. Teleseismic tomography revealed significant compositional anomalies in the uppermost mantle that controlled the way in which the lithosphere is delaminated. The continental subduction is associated with magmatism, where the variety of products reflects differences in mantle metasomatism that are only in part related to the subduction process.