From basalt to dacite: origin and evolution of the calc-alkaline series ofSalina, Aeolian Arc, Italy

The island of Salina comprises one of the most distinct calc-alkaline serie s of the Aeolian are (Italy), in which calc-alkaline, high-K calc-alkaline, shoshonitic and leucite-shoshonitic magma series are developed. Detailed p etrological, geochemical and isotopic (Sr, Nd, Pbl O) data are reported for a stratigraphically well-established sequence of lavas and pyroclastic roc ks from the Middle Pleistocene volcanic cycle (430-127 ka) of Salina, which is characterized by an early period of basaltic volcanism (Corvo; Capo; Ri vi; Fossa delle Felci, group 1) and a sequence of basaltic andesites, and a ndesites and dacites in the final stages of activity (Fossa delle Felci, gr oups 2-8). Major and trace element compositional trends, rare earth element (REE) abundances and mineralogy reveal the importance of crystal fractiona tion of plagioclase + clinopyroxene + olivine/orthopyroxene +/- titanomagne tite +/- amphibole +/- apatite in generating the more evolved magma types f rom parental basaltic magmas, and plagioclase accumulation in producing the high Al2O3 contents of some of the more evolved basalts. Sr isotope ratios range from 0.70410 to 0.70463 throughout the suite and show a well-defined negative correlation with Nd-143/Nd-144 (0.51275-0.51279). Pb isotope comp ositions are distinctly radiogenic with relatively large variations in Pb-2 06/Pb-204 (19.30-19.66), fairly constant Pb-207/Pb-204 (15.68-15.76) and mi nor variations in Pb-208/Pb-204 ratios (39.15-39.51). Whole-rock delta(18)O values range from + 6.4 to + 8.5 parts per thousand, and correlate positiv ely with Sr isotope raties. Overall, the isotopic variations are correlated with the degree of differentiation of the rocks, indicating that only smal l degrees of crustal assimilation are overprinting the dominant evolution b y crystal-liquid fractionation (AFC-type processes). The radiogenic and oxy gen isotope composition of the Salina basalts suggests derivation from prim ary magmas from a depleted mantle source contaminated by slab-derived fluid s and subducted sediments with an isotopic signature of typical upper conti nental crust. These magmas then evolved further to andesitic and dacitic co mpositions through the prevailing process of low-pressure fractional crysta llization in a shallow magma reservoir, accompanied by minor assimilation o f crustal lithologies similar to those of the Calabrian lower crust.