Structural setting of a typical alkali-potassic volcano: Roccamonfina, southern Italy

The structural setting of Roccamonfina volcano is reconstructed using gravity and magnetotelluric plus time domain electromagnetic data. A 887 m deep bore-hole, drilled within the summit caldera, was utilized to constrain the inversion models. Roccamonfina volcano appears located at the intersection of two east-northeast- and north-trending narrow grabens. The location of historical seismic activity indicates that at least one of them (the north-trending) is still active. MT+TDEM apparent resistivity curves show the existence of a ubiquitous conductive layer which includes hydrothermally altered volcanic rocks and flysch formations. The average thickness of the volcanic sequence is about 800-1000 m. No evidence was found for the presence of the intracrustal magmatic reservoir which is required to justify the chemistry of magmas erupted during the second and final stage of activity of the volcano. © 1992.