Seamount‐Volcanic Island Transition and Evolution From Fissural to Central Activity Inferred by the Magnetic Modeling of Salina Island (Tyrrhenian Sea)

Abstract

Volcanic islands represent the later stage of an early submarine volcanic activity and show different morphologies reflecting the geometry of shallow plumbing systems, magma output rate, gravitational instability, and erosive phases. Two end-member morphologies may be recognized: (a) rift-like elongated edifices and 'stellate' volcanoes and (b) cone-shaped, central-type volcanoes. While the evolution from early conical shapes to stellate shapes is relatively well known, the reverse is less constrained, commonly lacking geophysical and geological data to support it. We present magnetic forward and 3-D inverse models of the volcanic island of Salina (244-15 ka; Aeolian Arc, Southern Tyrrhenian Sea) to characterize its shallow plumbing system. The detected magnetic sources are interpreted as the crystallized portions of dykes and vertical conduits. The dykes mainly characterize the offshore of Salina Island, whereas subcircular conduits are located onshore. The results show that the early, mainly submarine phases of Salina concentrated along dykes following weakness zones of tectonic significance. As the volcanism proceeded, the subaerial activity focused on two main cone-shaped stratovolcanoes (Monte Fossa delle Felci and Monte dei Porri). The intersections among dykes and the progressive loading of volcanic products during the early growth of Salina are responsible for the transition from an early fissural basaltic activity to a later, basaltic to a last, more evolved central-type volcanism. We conclude that intrusions along pre-existing tectonic structures, dyke intersections, and loading processes related to the formation of a volcanic pile regulate the morphology and structural evolution of volcanic islands from the early, submarine phase to the later subaerial activity.

High Resolution, Low Altitude Aeromagnetic Surveys of the Active ”la Fossa Di Vulcano Caldera and Lipari Islands Volcanic Complex (Aeolian Archipelago, South Italy)

“…The long wavelength A anomaly lies between Lipari and Salina islands, it is not completely sampled by the 2003 survey and is part of a group of NS oriented features lying to the South of Salina (De Ritis et al, 2007 andCocchi et al, 2019). The well-rounded B anomaly is placed a few hundred meters off the Northern coast of Lipari (up to 280 nT max intensity and a lateral extent of about 1000 m).…”

“…Several high-resolution aeromagnetic surveys were previously carried out in the Vulcano, Lipari and Salina islands and different maps were published (Supper et al, 2004;De Ritis et al, 2005;Blanco Montenegro et al, 2007;Okuma et al, 2006;De Ritis et al, 2007;De Ritis et al, 2013 andCocchi et al, 2019). The magnetic modelling of these data was targeted to the local volcanic structures and to the whole Vulcano-Lipari-Salina volcanic ridge (hereafter VLS, in Figure 1a).…”