A west-east geochemical and isotopic traverse along the volcanism of the Aeolian Island arc, Southern Tyrrhenian Sea, Italy: Inferences on mantle source processes

The Aeolian Island arc, emplaced on continental lithosphere, is composed of seven islands and several seamounts, which have evidence of magmatic activity from 1.3 Ma (Sisifo seamounts) to present time (Vulcano, Stromboli). The rock compositions belong to different magmatic series and show a large silica range (48–76 wt%). Calc-alkaline and high-K calc-alkaline volcanics are present in all the islands, except for Vulcano. Shoshonitic volcanics are only lacking at Alicudi, Filicudi, and Salina. Potassic volcanics have been erupted at Vulcano and Stromboli. The different parental magmas originated in a heterogeneous mid-ocean-ridge basalt (MORB)–like mantle wedge, variously metasomatized by subduction-related components (oceanic crust + sediments, released as either fl uids or sediment melts). Trace-element and Sr-Nd isotopic ratios show clear geographical west-east variations among Calc-alkaline rocks. The composition of the mantle source of Stromboli is strongly infl uenced by the addition of a sedimentary component recycled into the mantle wedge; it shows evidence of a higher amount (~2%) than in all the other islands (<0.5%). Furthermore, the islands from the central sector of the arc are characterized by a higher proportion of slab-derived fl uids, which promotes a higher degree of melting. In this frame, the high Pb isotopic ratios (HIMU-like [high μ–like]) of the rocks of the central and western branch of the arc are explained with the high 206Pb/204Pb carried from a fl uid component derived from the dehydration of the ancient subducting Ionian oceanic crust. On the contrary, the low Pb isotope signature of Stromboli magmas is dictated by the sediment input, as for Sr and Nd isotopes.