MAGMA STORAGE AND ASCENT AT LIPARI ISLAND (AEOLIAN ARCHIPELAGO, SOUTHERN ITALY) DURING THE OLD STAGES (223-81 KA): ROLE OF CRUSTAL PROCESSES AND TECTONIC INFLUENCE

Fluid inclusion study, together with structural, volcanological and petrochemical data, allow reconstruction of the magma feeding system of basaltic-andesitic to andesitic volcanoes during the oldest and intermediate stages of development of Lipari Island (223-81 ka). A major magma storage zone is active during the overall investigated time span at depths of ~22 km close to the crust-mantle Moho transition, at which mantle-derived mafic magmas tend to accumulate due to neutral buoyancy conditions. A shallow magma reservoir is found at depths of 5.5-3.5 km in correspondence of a major lithological discontinuity within the upper crust beneath central-type volcanoes (M. Mazzacaruso, M. S.Angelo, M. Chirica-Costa d'Agosto). It is the place where magmas shortly rest (day-week time scale) before the eruption. For fissural-type volcanoes (Timpone Ospedale, Monterosa, M. Chirica), tectonic structures are suggested to intercept magma batches at different crustal depths (~14 km), thus provoking CO2-degassing and rapid magma uprising with no substantial ponding at shallow levels. Partial crustal melting processes at roof of the deep magma reservoirs are invoked to explain conditions of fluids trapping at depths of <17 km beneath the M. S.Angelo (cordierite-bearing lavas) and M. Chirica-Costa d’Agosto volcanoes, active during the intermediate stages of development of Lipari (105-81 ka). These melting processes determine the generation of felsic melts which may act as a density-barrier and prevent the uprising of mantle-derived magmas, with an influence on the subsequent evolution of the magma feeding system of Lipari.