Volcanological and geochemical evolution of Filicudi (Aeolian Islands, south Tyrrhenian Sea, Italy)

Abstract

This paper reports on field, petrological, geochemical and isotopic characteristics of volcanic rocks from Filicudi island (Aeolian Arc, southern Tyrrhenian Sea) with particular attention to the recognition of temporal and geochemical variations of magma activity. The Filicudi volcano consists of basaltic, basaltic andesitic, and high-K andesitic lavas, and pyroclastic deposits. It represents the emergent part of a complex structure, parallel to the main regional structural lineaments. Stratigraphic investigations and dating have defined four main cycles of activity interrupted by periods of quiescence. The main stratigraphic sequences reconstructed on Filicudi display irregular variations of rock evolution over time, with recurrent reversals to more basic compositions. Magmas erupted from different vents during the first three cycles of activity display overall similar petrological and geochemical characteristics. Some major and trace elements define slightly scattered correlations with silica. Sr abundances are particularly scattered with a large range of values in basic rocks. Sr isotope ratios range between 0.704270 and 0.704740 and do not exhibit good correlations with geochemical parameters. Fractional crystallization associated with several episodes of mixing processes and crust assimilation are considered to be responsible for the complex evolution of the Filicudi magma. Mafic magmas erupted during the last cycle of activity at La Canna centre show increasing K/Na, Mg/Al, Rb/Sr and decreasing Ba/Nb, Ba/Rb ratios in respect to the older basalts. These characteristics are considered to reflect a derivation from a different mantle source.