Geologic, volcanologic, and tectonic setting of the Vico-Cimino area, Italy

Abstract

Although the Cimino and Vico volcanic complexes are located close to each other in a structural low, they belong to two different provinces: Cimino is connected to the Tuscan-Roman anatectic magmatic province and Vico to the Roman-Campanian potassic alkaline province (Barberi et al., 1971; Marinelli, 1975). The two volcanic centers lie on a basement formed by clays and sands of a Miocene-Pliocene aged sedimentary cycle. The Mount Cimino complex forms a central volcano composed of a series of rhyodacitic domes. It was emplaced along a NW-SE trending fracture zone which can be followed for about 16 km. Cimino volcano was active from 1.4 m.y. to 0.95 m.y. ago. Eruption of rhyodacitic ignimbrites were preceded and followed by the emplacement of domes of the same composition. Fluid lavas of latitic and olivine-latitic composition were emitted from the central volcano during the final phase of activity. Vico is a central volcano, mainly composed of lava, with a composite summit caldera. It was emplaced along a NE-SW trending fracture system. The Vico stratovolcano is formed by lavas of various compositions including phonolitic tephrites, tephritic phonolites and slightly undersaturated trachytes. The construction of the stratovolcano, the most ancient exposed products of which have an age of 0.4 m.y., was followed by the eruption of four pyroclastic flows totalling several cubic kilometers, which are dated at 0.3–0.15 m.y. The collapse of the caldera is most likely connected to the eruption of these pyroclastic flows. The ring fractures of the caldera are associated with the emplacement of a pyroclastic unit, most of which erupted along the inner northeast and north rim of the caldera. Post-caldera activity is characterized by the emission of tephritic-phonolitic and tephritic products that form the intra-caldera stratovolcano named Mount Venere. The Vico-Cimino area (northern Latium), located between the Apennine chain and the Tyrrhenian sea, lies along the circum-Tyrrhenian belt (that extends from northern Tuscany to Campania). This zone has experienced post-orogenic tensional movements. Since the Middle Miocene, the teconic evolution of the Tyrrhenian basin is closely associated with acid anatectic and potassic alkaline volcanism along the Tyrrhenian margin of the Apennines. The age, composition, and geographic position of the volcanoes are controlled by different magnitudes of tensional tectonics and crustal thinning processes of the western margin of the Apennine chain.