Late Oligocene to Recent episodes of magmatism in and around the Tyrrhenian Sea: implications for the processes of opening in a young inter-arc basin of intra-orogenic (Mediterranean) type

Abstract

Five episodes of magmatic activity as deduced from geochronological data affected the Tyrrhenian and Peri-Tyr-rhenian areas from the Late Oligocene (32 Ma) to Recent times. The episodes of W-E migration of magmatism from the islands of Sardinia and Corsica to the Eolian islands and the Roman Comagmatic Region of central Italy are related to the anti-clockwise drift-movements of the Apenninic chain and clockwise drifting of the Sicilian part of the Maghrebian chain. Magmatic activity in the Tyrrhenian Sea initiated in Late Miocene times (8.5–6.5 Ma) in concomitance with a significant change of the geodynamic regime from compressional to tensional. The Tyrrhenian bathyal plain was affected by two episodes of spreading: the first episode occurred around 7 Ma and the second from about 1.9 to 1.3 Ma. These spreading events apparently developed during times of magmatic quiescence in the Peri-Tyrrhenian areas. Two subsequent episodes of volcanism of the seamount type occurred in the bathyal plain, one from 5 to 1.8 and the other from 1.3 to Recent. They are contemporaneously with extensive manifestations in the Peri-Tyrrhenian areas. The different types of magmatism of the Late Miocene, back-arc spreading in the central bathyal plain and acidic manifestations of intra-crustal anatectic origin in the northern continental platform and slope (i.e., islands of Capraia, Elba and Montecristo, and seamount Vercelli), are possibly related to movements of upwelling of the astenosphere which, in the southern Tyrrhenian Sea, developed with a much stronger intensity. Timing of the volcanism in relationship with the overall structural evolution through time in the basin and neighbouring lands is considered.