Magnetic modeling of the Phlegraean Volcanic District with extension to the Ponza archipelago, Italy

A 3D modeling of the residual aeromagnetic anomalies of the area including the Phlegraean Volcanic District (PVD; Campi Flegrei caldera (CFc), and Ischia and Procida–Vivara islands) and two volcanic islands of the Ponza archipelago (Ventotene and S. Stefano) has been carried out. The observed residual anomalies have been reproduced with several large magnetized bodies located at 2–10 km depth in the crust. A volcanological interpretation has been made possible only for those bodies that have been constrained by geological, geothermal and other geophysical data. The magnetized structures associated with CFc and Ischia, Procida–Vivara, Ventotene and Santo Stefano islands, have been interpreted as igneous bodies that may be solidified intrusions or magma reservoirs. On the basis of magnetic data, volcanological and magmatological history and geothermal heat flux distribution, the existence of a partially solidified magma chamber is suggested at Ischia. A speculation shows that the magnetization intensity assumed for the magnetic bodies located at Procida and south–west of Ventotene matches quite well with the calculated composition of a cooled residual magma resulting from crystallization processes within a chamber.