A PHYSICAL MODEL FOR THE ORIGIN OF VOLCANISM OF THE TYRRHENIAN MARGIN - THE CASE OF NEAPOLITAN AREA

The onset of volcanism in the Neapolitan area and the tensile tectonics of the Tyrrhenian margin of the Apennine chain have been related to the opening of the Tyrrhenian Basin, which may have resulted in horizontal asthenosphere flows giving rise, in turn, to crustal distension, local mantle upwellings and ensuing volcanism. Geological and structural data were taken into consideration: the existence of a shallow crust-mantle discontinuity in the Neapolitan area, the onset of volcanism in a graben-type structure, the distribution of volcanism along three main directions. These facts are all consistent with processes of crustal deformation associated with "hot masses" as well as fracture systems along three branches, often separated by a 120-degrees angle. Such fracture mechanism was therefore analyzed in physical terms on the assumption of an elasto-plastic behaviour of the crust and with reference to the "limit analysis theorems".