Multiple magma recharges over prolonged period ultimately trigger eruptions at Vulcano, Aeolian Islands

The compositional heterogeneity of clinopyroxene in products of the 1888-90 eruption at La Fossa of Vulcano has been used to constrain times of the plumbing system reactivation before the eruption. We have also investigated the temporal trend of the SO₂ flux at La Fossa crater since 1978 to gather information about the origin, depths and quantity of magma involved in the recent degassing crises. Petrological data emphasizes migration of deep-seated magmas and their emplacement in the shallow system, clearly supporting the involvement of three distinct phases of mafic replenishments occurred respectively 85-140, 16-35 and 2-7 years before the 1888-90 eruption. These results reconcile with the dynamics of magma emplacement and degassing inferred for the recent periods of unrest. SO₂ data for the period January 1978 - September 2024 imply a volume of intrusive magma of ~ 26-86 × 10⁶ m³, which is comparable to the order of magnitude of magma volumes erupted during the 1888-90 cycle. Our petrological and geochemical data suggest that shallow reservoirs have been already largely pressurized by multiple mafic injections occurred over the last century.