Structural setting of the Ischia resurgent caldera (southern Tyrrhenian Sea, Italy) by integrated 3D gravity inversion and geological models

Abstract

Abstract The structural setting of the Ischia resurgent caldera and its magmatic system has been investigated by a joint interpretation of a 3D inversion of previously collected gravimetric data and all the available geological, geophysical and petrological data. Starting from the available Bouguer gravity map of the Neapolitan volcanic area and a previous 2.5D modelling, a selection of on land and offshore gravity data has been used to perform a 3D inversion, adapting and merging the basic ideas of two already tested methods, used to detect isolated bodies and layered discontinuities respectively. The base of the map is a set of gravity values, covering the whole Neapolitan volcanic area and the Gulf of Naples, which results from the union of 862 offshore and about 2000 on land extant gravity data, made uniform and re-analysed. The final model proposed here allows us to outline a very detailed and well-constrained structural setting of the crustal sector beneath Ischia. In particular, the 3D gravity inversion allowed us to outline a body with negative density contrast under Mt Epomeo, interpreted as the resurgent block, and to describe the magmatic system underneath it as a complex system of intrusions, rather than a uniformly distributed laccolithic body.