The Lipari – Vulcano volcanic complex: insights into the plumbing system of the last 1000 years

New whole rock and microanalytical data on mineral phases provide constraints for a comprehensive model of the Lipari-Vulcano plumbing system, at least during the last 1000 years. The eruptive activity between 1100-1200 AD represents an important phase of the Lipari-Vulcano volcanic complex (LVVC) for several reasons: 1) fairly contemporaneous activity at Vulcanello and Fossa vents at Vulcano island and at Rocche Rosse on Lipari island, along a common N-S alignment; 2) simultaneous eruptions at Lipari and Vulcano at 1230±40 AD; 3) since this date latitic products, associated or not with rhyolitic magmas, have always been erupted with variable eruptive styles and volumes. Shoshonitic products erupted at Vulcanello at the end of XII century are the least differentiated of the last 1000 years. Whole rock, mineral phase and mineral-hosted melt inclusion data show that latitic products emitted at both islands have several geochemical affinitites. In particular, latites show superimposed trends of REE and incompatible elements for whole rock and all mineralogical phases. Whole rocks Sr-Nd isotopic data indicate that Vulcano and Vulcanello latites are intermediate between those of Lipari, with poor Sr-Nd isotope correlation. Micro-Sr isotopic data performed by microdrilling techniques (Micromill + TIMS instruments), on clinopyroxenes, plagioclases and groundmasses belonging to the Pietre Cotte lava flow (1720 AD) and 1888-90 products of La Fossa eruptions show small but consistent variations of Sr isotopes (0.70458-0.70492), which increase from plagioclase core to rim and then groundmass. These variations can indicate: i) mixing with more Sr-radiogenic magmas; ii) crustal contamination; iii) crystal recycling from a crystal mush related to the previous and less Sr-radiogenic activity of Vulcano. Textural observations and core-to-rim profiles on plagioclases show that dynamics of magma ascent and storage are markedly different in the Fossa and Vulcanello system of Vulcano. Transfer mechanisms are however almost unchanged in each system during the considered timespan. Petrological data suggest that the historical eruptions of Lipari and Vulcano islands could be fed by a common plumbing system at depth, hosting shoshonitic basalts to shoshonites. Shoshonites were erupted only at the end XII-early XIII century AD (e.g. early Vulcanello). Magma ascent occurred through a polibaric storage system allowing the eruption of mafic and prevalently degassed magmas (Vulcanello), but also the repeated storage and differentiation to latites and rhyolites at intermediate and very shallow depth (late Vulcanello, La Fossa and Rocche Rosse at Lipari). Differentiation models suggest that latites can be obtained by AFC process starting from the shoshonite. Latites are the prevalent magmas erupted in historical times and are always involved in the rhyolitic eruptions, indicating the recurrent occurrence of mingling following refilling events.