Petrographic, geochemical and radiometric data on Tertiary volcano-arenitic beds from the Sicilian Maghrebian Chain: Volcanic sources and geodynamic implications

The volcanic fraction of impure volcano-arenitic beds of the Reitano Flysch (Early Oligocene, Sicilian Maghrebian Chain) was investigated by petrograp hic, geochemical and radiometric techniques. Two distinct volcanic grain po pulations were recognized: (1) paleovolcanic clasts, Late-Permian in age an d calc-alkaline in character, probably linked to late-Hercynian magmatism a nd (2) alkaline (potassic) neovolcanic clasts. As regards the alkaline frac tion, it is difficult to link its provenance with the Oligocene-Miocene Sar dinia volcanism. Indeed, this latter volcanism shows a distinct calc-alkali ne character typical of subduction and/or collision-related magmas. We sugg est that the volcanic sources of this alkaline fraction could be related to magmatic events close to the sedimentary basin and associated with extensi onal processes preluding the opening of new oceanic areas (i.e. Algero-Prov encal Basin and Sardinia Rift).