Geodynamic significance of the Aeolian volcanism (Southern Tyrrhenian Sea, Italy) in light of structural, seismological and geochemical data

Abstract

The Aeolian volcanoes are located between the Southern Tyrrhenian Sea back arc and the Calabrian Arc forearc region. Structural, geochemical and seismological data indicate that the early phases of volcanic activity (1.3 Myr) developed in the western sector along WNW-ESE tear faults controlling the southeastward migration of the forearc-back arc system. This magmatism ceased when delamination processes affected the Calabrian Arc. At 0.8 Myr, the volcanism migrated southeastward and concentrated on the "new" formed NNW-SSE tear faults related to the postsubduction extensional strain. The compressive strain deduced by focal mechanism of earthquakes in the western sector explains the volcanism ending. The still active volcanism in the central and eastern sectors develops on a NNW-SSE striking lithospheric discontinuity that crosses the ring-shaped volcanic belt. Moho upwelling occurs in the area of active volcanism. Fault-slip data and focal mechanisms from M > 5 earthquakes indicate that the NNW-SSE discontinuity moves in response to an oblique (strike-slip/normal) stress related to a WNW-ESE extension. This direction of extension is consistent with that of the forearc region, where thrust-type events are lacking and the last compressive phases occurred during Pliocene. The later phases of the Aeolian volcanism are related to the melting of shallower source(s) consistent with a continental rift magmatism. The Aeolian Islands represent a postcollisional, rift-type volcanism emplaced in an older collision zone.