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Vico volcano has erupted potassic and ultrapotassic magmas, ranging from silica-saturated to silica-undersaturated types, in three distinct volcanic periods over the past 0·5 Myr. During Period I magma compositions changed from latite to trachyte and rhyolite, with minor phono-tephrite; during Periods II and III the erupted magmas were primarly phono-tephrite to tephri-phonolite and phonolite; however, magmatic episodes involving leucite-free eruptives with latitic, trachytic and olivine latitic compositions also occurred. In Period II, leucite-bearing magmas ( 87 Sr/ 86 Sr initial  = 0·71037–0·71115) were derived from a primitive tephrite parental magma. Modelling of phonolites with different modal plagioclase and Sr contents indicates that low-Sr phonolitic lavas differentiated from tephri-phonolite by fractional crystallization of 7% olivine + 27% clinopyroxene + 54% plagioclase + 10% Fe–Ti oxides + 4% apatite at low pressure, whereas high-Sr phonolitic lavas were generated by fractional crystallization at higher pressure. More differentiated phonolites were generated from the parental magma of the high-Sr phonolitic tephra by fractional crystallization of 10–29% clinopyroxene + 12–15% plagioclase + 44–67% sanidine + 2–4% phlogopite + 1–3% apatite + 7–10% Fe–Ti oxides. In contrast, leucite-bearing rocks of Period III ( 87 Sr/ 86 Sr initial  = 0·70812–0·70948) were derived from a potassic trachybasalt by assimilation–fractional crystallization with 20–40% of solid removed and  r  = 0·4–0·5 (where  r  is assimilation rate/crystallization rate) at different pressures. Silica-saturated magmas of Period II ( 87 Sr/ 86 Sr initial  = 0·71044–0·71052) appear to have been generated from an olivine latite similar to some of the youngest erupted products. A primitive tephrite, a potassic trachybasalt and an olivine latite are inferred to be the parental magmas at Vico. These magmas were generated by partial melting of a veined lithospheric mantle sources with different vein–peridotite/wall-rock proportions, amount of residual apatite and distinct isolation times for the veins.

Evolution and Genesis of Magmas from Vico Volcano, Central Italy: Multiple Differentiation Pathways and Variable Parental Magmas