The Aeolian volcanism District: volcanism and magmatism.

The Aeolian Volcanic District is a geologically complex region characterised by a wide spectrum of volcanism and compositionally variable magmatism younger than 1-1.3 Ma. Submarine and subaerial volcanic activities formed seven large strato-volcanoes, that upraise from ~1500-2000 m b.s.l., and several seamounts. The Aeolian volcanism is the result of the long interplaying among collision, subduction and extension processes occurred in the Mediterranean area affected by multiple geodynamic processes. Geophysical, seismological and geochemical data allow recognition of three main sectors, each characterized by remarkably similar structural, volcanological and compositional features. The eastern sector (including Stromboli-Panarea) is characterised by a prevailing nne-ssw to ne-sw striking fault system, deep seismicity and magmas with variable affinity, from CA to KS, generally outpured through low-intensity eruptions. The central sector (including Lipari, Vulcano and the younger part of Salina) is strongly affected by the presence of the nnw-sse oriented strike-slip lithospheric fault system known as ‘Tindari-Letojanni’. Eruptive activity in the central sector shows the wider spectrum of magma compositions in the archipelago – ranging from basalts to rhyolites, with CA, HKCA, SHO and KS affinity – and the eruptions with the highest intensity and magnitude. The western sector (including the older part of Salina, Filicudi and Alicudi) is characterized by a main wnw-ese striking fault system that conditioned the development of both subaerial and submarine volcanoes, basically characterized by CA to HKCA mafic and intermediate magmas of subduction origin. Going from east to west, a general increase of crust thickness (from ~17 km below Stromboli up to ~25 km below the western sector) and magma composition variations (with a general decrease of Sr-isotopes and an increase of Nd-, Pb-isotope and LILE/HFSE ratios) are observed. Overall, trace elements and radiogenic isotopes signatures variations along the avd indicate modifications in the nature and intensity of metasomatic processes occurred in the Aeolian mantle. The eruptive history of each island is reconstructed by giving special emphasis to the chronostratigraphic role played by fossil marine conglomerates intercalated to volcanic products. Older and more primitive CA basalt to basalt-andesite volcanic products related to strombolian and effusive volcanic activity were emplaced on Salina and Filicudi in a poorly constrained time span started around 430-400 ka. After an apparently long period of quiescence, volcanic activity started again between ~220 and 124 ka on Filicudi, Salina, Lipari and Panarea, with the emplacement of CA basalt-andesite to andesite and dacite volcanics related to mainly strombolian and effusive activity, with a minor role for explosive hydromagmatic eruptions. Between ~124 and 80 ka, HKCA andesitic and subordinate dacitic volcanic products related to both explosive (mainly hydromagmatic) and effusive volcanic activity were emplaced on Lipari, and Alicudi, whereas on Vulcano and Stromboli SHO products were erupted together with minor HKCA lavas. Starting from ~80 ka, more evolved CA and HKCA andesitic to daci-trachytic -up to rhyolitic products were mainly erupted on Lipari and Salina and to a lesser extent on Panarea, Alicudi and Filicudi. Most of these magmas were produced by effusive activity (mainly dome-forming) and associated high-energy explosive eruptions. In the last 25 ka ca., a growing and intensification of the volcanism in the central sector – probably associated to increased activity of the Tindari-Letojanni fault system – occurred; whereas volcanism ceased in the western sector and was regular and almost continuous in the eastern one through Stromboli. At present time Vulcano, Stromboli and submarine area of Panarea show active volcanic phoenomena.