Introduction
The famous deep crustal section of the Ivrea-Verbano Zone in northwest Italy has received enormous attention over the last three decades as one of the best examples of continental “magmatic underplating.” Within it, early Permian gabbroic rocks, reaching thicknesses >8 km in the southern Ivrea-Verbano Zone, intruded amphibolite- to granulite-faces paragneiss while they were present in the deep crust. The broader magmatic context of these voluminous intrusions remained unclear until Quick et al. (2009) demonstrated that a silicic volcanic complex, including extensive caldera deposits, was coeval with underlying silicic plutonic rocks of the Serie dei Laghi and gabbroic rocks of the Ivrea-Verbano Zone. In this paper, we review published data for this Permian igneous association, which we refer to as the Sesia magmatic system,.