Aeromagnetic anomalies reveal hidden tectonic and volcanic structures in the central sector of the Aeolian Islands, Southern Tyrrhenian Sea, Italy

Salina Island (Italy) is located in the central sector of the Aeolian Islands and represents the northernmost volcanic structure of an elongated ridge emplaced on a regional shear zone characterized by NNW-SSE strike-slip faults and by second order N-S and NE-SW faults. High-resolution, low-altitude aeromagnetic data collected in 2003 and 2005 allow us to study the subsurface structure of Salina Island. The magnetic data show a pattern with a wide range of wavelengths and intensities. Magnetic modeling constrained by volcanological data allow us to reconstruct the inner structure of the Salina volcanoes and surrounding marine regions. Long wavelength negative anomalies overlap E-W elongated sedimentary basin related to the Early Pliocene-Pleistocene opening of the Southern Tyrrhenian Sea back-arc basin. The shorter wavelength positive magnetic anomalies are related to the Late Pleistocene-Holocene volcanic (conduits, dikes) and tectonic (faults) structures. The magnetic and volcanological data indicate that the early (168- about 100 ka), basaltic to basaltic andesitic Salina volcanism developed along N-S and NE-SW tectonic structure, whereas the more recent basaltic andesitic to rhyolitic products (about 100-13ka) were emitted by vents related to the main NW-SE fault tectonic structures. The tectonic structures also control the location of the seamounts around the island and the geometry of the volcano-tectonic collapses. The Salina volcanism emplaced on a NNW-SSE regional discontinuity that represents a tear fault of the present-day roll-backing slab in the Southern Tyrrhenian Sea.