The Source Characteristics of Mt. Etna Magmas Erupted During the Last 60 ka

During the last decades, Mt. Etna volcano attracted the attention of the scientific community due to its odd geodynamic location and geochemical signature of the erupted lavas. Indeed, they have OIB-like compositions although the edifice is placed above the front of a compressive regional tectonic setting. During the 500 ka of life, Mt. Etna has shown a complex geochemical variability, with sub-alkaline products erupted during the first stage of activity followed since ∼220 ka by an alkaline stage. The various phases of the alkaline stage exhibit long-term geochemical variations, which chiefly derive from the superimposition of several evolutionary processes that magma underwent at various levels of the plumbing system during ascent to the surface. However, Mt. Etna lavas also display short-term changes in specific eruptive periods. Since the 1971 eruption, as an example, an increase in some LILEs and volatiles coupled with marked changes in Sr-Nd-Pb-Hf isotope ratios was observed [e.g., Clocchiatti et al., 1988; Michaud, 1995; Métrich et al., 2004; Viccaro and Cristofolini, 2008; Viccaro et al., 2011]. The evolution of a volcano studied in terms of long vs. short-term geochemical variations is one of the best ways to get important responses on: 1) the geodynamic significance; 2) the mechanism of partial melting; 3) the processes able to modify the pristine compositions of magmas and their eventual repetition through time; 4) the link with possible changes of the eruptive behavior.