Tectonics, structural evolution and caldera formation on Vulcano Island (Aeolian Archipelago, southern Tyrrhenian Sea)

Abstract

A detailed structural study and a review of the eruptive history of the island of Vulcano (Aeolian Arc—southern Tyrrhenian Sea) have been carried out with the purpose of understanding the evolution of both volcanic and tectonic structures. The island is composed of four main volcanoes which date from about 120 ka to historical times. Two calderas occur in the central sector of the island. The time-space evolution of the volcanism indicates a shifting of the activity from the southeastern sectors towards the northwest. Two main systems of NW—SE-trending right-lateral strike-slip faults affect the island. NE—SW- and N—S-trending normal faults are also present. Geophysical investigation indicate the NW—SE-trending strike-slip faults are likely to be the surface expression of a main regional crustal structure. This system of discontinuity is related with the stress field acting in the southern sector of the Aeolian Archipelago. Normal N—S- and NE—SW-oriented faults represent extensional fractures. The NE—SW-trending structures are related to a local stress field. The results of the kinematic analysis, as well as the geometric relationships between the faults and the constant subsidence velocities, are consistent with the opening of a pull-apart basin. Volcanological and geochronological data are also consistent with the proposed model. In the general deformative style affecting the island, the calderas can be explained as the consequence of different opening phases of a pull-apart basin.