Volcanological and petrological evolution of Vulcano island (Aeolian arc, southern Tyrrhenian Sea)

Petrological and geochemical data are reported for volcanic rocks from Vulcano island. The subaerial volcanism (120 ka to present) built up a NW-SE elongated composite structure, affected by two intersecting multistage calderas. Volcanics older than 20 ka consist mostly of high-K calc-alkaline (HKCA) to shoshonitic (SHO) mafic rocks. These magmas interacted significantly with the continental crust, which generated variable Sr isotopic ratios (0.70412-0.70520). However, a major role was also played by input of parental liquids into the magma chamber, which prevented further evolution of the magmas. HKCA, SHO, and potassic (KS) racks formed from 20 to 8 ka, display a much larger range of SiO2 (from shoshonites to rhyolites) and higher concentrations of incompatible elements with respect to the previous stage. Sr isotopic ratios show small variations (0.70448-0.70486). Mixing of silicic and mafic liquids and fractional crystallization processes (FC) were the main evolutionary processes during this stage. Volcanics younger than 8 ka consist of SHO and leucite-bearing KS mafic rocks, with abundant intermediate and silicic products. Mafic and intermediate rocks display similar incompatible element abundances and Sr isotopic ratios as the previous stage volcanics, whereas higher Sr-87/Sr-86 (0.70494-0.70583) are observed in some rhyolites. These products originated from a complex interplay of FC, crustal assimilation, and magma mixing processes. The most mafic rocks show increasing incompatible element abundances, Rb/Sr, Rb/Ba, Mg/Al, Mg/Ca, and a decrease in large ion lithophile to high field strength element ratios, passing from older HKCA-SHO to the younger SHO-KS volcanics. These variations suggest a shifting of magma sources from a slightly metasomatized asthenosphere (fertile peridotite) to a more strongly metasomatized lithospheric mantle (residual peridotite). Time-related petrological and geochemical variations have been used to develop a model for the evolution of the Vulcano plumbing system.