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

Abstract

The structural setting of the Ischia resurgent caldera and its magmatic system has been investigated by a joined 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 off-shore 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 already existing gravity data, uniformed and re-analyzed. The final model proposed here allow to outline a very detailed and well constrained structural setting of the crustal sector beneath Ischia. In particular, the 3D gravity inversion allowed to outline a body with negative density contrast under the Mt. Epomeo, interpreted as the resurgent block, and to describe the magmatic system underneath it as a complex system of intrusions, rather than an uniformly distributed laccolithic body.