Relative roles of rifting tectonics and magma ascent processes: Inferences from geophysical, structural, volcanological, and geochemical data for the Neapolitan volcanic region (southern Italy)

Abstract

[1] The Neapolitan volcanic region is located within the graben structure of the Campanian Plain (CP), which developed between the western sector of the Appenine Chain and the eastern margin of the Tyrrhenian Sea. Two volcanic areas, spaced less than 10 km apart, are situated within the CP: the SommaVesuvius Volcano (SVV) and the Phlegraean Volcanic District (PVD). SVV is a typical stratovolcano, whereas PVD, including Campi Flegrei, Procida, and Ischia, is composed mostly of monogenetic centers. This contrast is due to different magma supply systems: a widespread fissure-type system beneath the PVD and a central-type magma supply system for the SVV. Volcanological, geophysical, and geochemical data show that magma viscosity, magma supply rate, and depth of magma storage are comparable at PVD and SVV, whereas different structural arrangements characterize the two areas. On the basis of geophysical data and magma geochemistry, an oblique-extensional tectonic regime is proposed within the PVD, whereas in the SVV area a compressive stress regime dominates over extension. Geophysical data suggest that the area with the maximum deformation rate extends between the EW-running 41st parallel and the NE-running Magnaghi-Sebeto fault systems. The PVD extensional area is a consequence of the Tyrrhenian Sea opening and is decoupled from the surrounding areas (Roccamonfina and Somma-Vesuvius) which are still dominated by Adriatic slab dynamics. Spatially, we argue that the contribution of the asthenospheric wedge become much less important from W-NW to E-SE in the CP. The development of the two styles of volcanism in the CP reflects the different tectonic regimes acting in the area.Components: 15,031 words, 9 figures, 1 table.

Evaluating fracture patterns within a resurgent caldera: Campi Flegrei, Italy

“…1, inset;Carrara et al 1973;Finetti and Morelli 1974;Fedi and Rapolla 1987;Rapolla et al 1989;Orsi et al 1996). The erupted magmas (0.15 MaPresent) range from trachytes and alkali trachytes to trachybasalts and latites (Armienti et al 1983;Rosi and Sbrana 1987;Vezzoli 1988;Piochi et al 2005). NE-SW and subordinate NW-SE extensional structures predominate throughout the District, controlling volcanic activity (Di Girolamo and Rolandi 1975;Orsi et al 1996;Bruno et al 2003;Acocella and Funiciello 2006).…”

“…The Neapolitan area, comprising the volcanic districts of Campi Flegrei and Vesuvio, constitutes the active southernmost portion of this volcanic belt (Fig. 1 inset; Piochi et al 2005, and references therein). The central part of the Campanian Plain is a NW-SE trending PlioQuaternary extensional basin bordered by Mesozoic carbonate platforms (Carrara et al 1973;Bruno et al 1998).…”

Transverse systems along the extensional Tyrrhenian margin of central Italy and their influence on volcanism

“…In fact, the local structural variations, including the Quaternary NE-SW, NW-SE, and N-S strike-slip faults [Marra, 2001;Sani et al, 2004;Piochi et al, 2005] are here interpreted as the result of orthogonal extension to the back of the arcuate thrust front of the Apennines (Figure 12). …”

The Vesuvius and the other volcanoes of Central Italy

“…A change from trachy-basaltic to tephritic occurred between the AP1 and 79 AD eruptions, reflecting in the changes recorded by highly evolved magmas (from trachyte and phonolite to leucititic phonolite). Magma recharge to the shallow reservoirs together with carbonate assimilation and "mixing and mingling with previously contaminated magmas at shallow depths and/or by entrapment of crystal mush generated during previous magma storage in the crust" has been proposed by Piochi et al (2005) to explain the change in composition with time of Vesuvius magmas. 1) Slightly silica-undersaturated (to saturated) magmas (light orange field in Fig.…”