Volcanological evolution of the Rivi–Capo Volcanic Complex at Salina, Aeolian Islands: magma storage processes and ascent dynamics

Lava flows and pyroclastic deposits from strombolian fallout related to the activity of the Rivi and Capo volcanoes, which are representative of early subaerial volcanoes on Salina (Aeolian Islands), have been investigated through a geological–petrological approach. Our geological field survey shows that Rivi and Capo volcanoes are part of a single N50°E aligned volcanic complex, here named Rivi–Capo Volcanic Complex (RCVC). Stratigraphically specific rock sampling has allowed reconstruction of the magma feeding processes through time. Whole rock major element compositions, together with core-to-rim profiles of plagioclase and clinopyroxene crystals, show a general evolution toward more basic compositions through the three formations constituting the Capo volcano and within the Rivi center. MELTS simulations and mass balance modeling suggest that the RCVC rocks are the result of fractional crystallization of plagioclase, clinopyroxene, and olivine (ca. 45 % of solid removed) from a primary magma. In addition to fractional crystallization, continuous recharge and mixing with more basic magma coming from deeper parts of the magmatic plumbing system contributed to the final volcanic rock compositions. Our textural and microanalytical data on plagioclase and clinopyroxene crystals allow the definition of a multilevel magmatic storage system with reservoirs at ~20 and ~3 km below sea level. When processes of magma differentiation, ascent, and storage are considered together with the stratigraphic position of each sample, a history of continuous modification of the RCVC plumbing system can be constructed. Volcanism may have been characterized by fissure-type eruptions during the early stages (Lower Capo, Lower Rivi, and Middle Capo Formations), gradually changing later to central-type volcanism (Upper Capo and Upper Rivi Formations).