Geodynamic models of the southern Tyrrhenian region: constraints from the petrology and geochemistry of the Aeolian volcanic rocks

Petrological studies of Aeolian volcanic rocks have placed serious constraints on the formulation of geodynamic models of the Tyrrhenian basin. In particular, it has been recently pointed out that: a) the subducted lithosphere is oceanic in nature; b) the mantle source of the magmas is a MORB-Iike source metasomatized by crustal components, specifically oceanic crust and pelagic sediments; c) the amount of crustal material added to the mantle increases from west to east in the arc; d) the metasomatizing agent consists of aqueous fluids or melts released from the slab in variable proportions in the three different sectors of the arc. The ages and distribution of the submerged and subaerial orogenic volcanoes reveal the presence of two volcanic arcs: the first is of Pliocene age, and developed in step with the formation of the Vavilov basin. It was followed by a second are, the present Aeolian are, which is associated with the marginal basin of Marsili. The Quaternary magmatism of Ustica, which has an intra-plate affinity, developed following the Pliocene subduction and outside the present subduction zone. The beginning of the subduction processes responsible for the opening of the Tyrrhenian basin has been set at the end of the Miocene, when a new lithosphere began plunging NW under the Appeninic margin.