Modeling the magma plumbing system of Vulcano (Aeolian Isalnds, Italy) by integrated fluid inclusion geo-barometry, petrology and geophysics.

Abstract

An integrated petrological, geophysical, and fluid-inclusion model is presented for the internal structure of the active Vulcano Island, Southern Tyrrhenian Sea. The present structure of the magma storage system in the crust consists of two major deep accumulation zones located at 17–21 km and 8–13 km depth, plus a minor one at 1–5 km depth, beneath Fossa Cone. The deepest magma accumulation zone contains mafic melts and is located at the transition between the upper mantle and a granulitic lower crust. This reservoir has been active since the onset of the exposed volcanism, and has undergone continuous fractional crystallization, crustal assimilation, and mixing with primary melts from the mantle. Slightly differentiated magmas from the deep reservoir feed a shallower accumulation zone in the middle and upper crust, or erupt directly to the surface through lateral vents. Deep melts probably enter the shallowest reservoir shortly before magma outbreak at the surface, and may represent the trigger of eruptions. According to our model, magmatic eruptions at Vulcano are related to deep magma dynamics, whereas most of the changes in the geochemical and geophysical parameters observed at the active cone in the last century could be due to shallow depth modification of rock permeability, possibly as a result of cone gravitative instability and/or tectonic events. Implications for strategies of volcano monitoring and for forecasting eruptions are briefly discussed.