Dynamics of magmas at Mount Etna

Abstract

The mineralogical, petrographic, geochemical and isotopic data collected in recent years on the entire Etnean succession have been examined in order to recognize the most important compositional variations and to relate them to important changes in parameters that control the genesis and transport of magmas. Building on this data set, the most important ideas on magmatic processes and magma dynamics in the plumbing system of Mt.Etna are summarized. Interpretative models presented by various research teams indicate that the geochemical characters of Etnean magmas have changed and are still changing. Moreover, even if depth of formation, melting processes and first stages of differentiation of Etnean magmas are still largely unconstrained, the sources and compositional evolution are influenced by the complicated geodynamic environments in which the volcano developed. Multi-stage, polybaric, fractional crystallization of phenocryst-forming minerals is the main process responsible for the differentiation of Etnean magmas, but at shallow depths, contamination, mainly by interaction with fluids or rocks belonging to the sedimentary basement, plays an important role. Both petrologic and geophysical data demonstrate that magma ascent and depth of magma storage are largely controlled by buoyancy, and exclude the present-day occurrence of large active crustal reservoirs. Finally, recent studies of Etnean explosive activity show the most violent eruptions have been fed by both evolved and pristine magmas. Consequently the pre-eruptive volatile content, devolatilisation and magma degassing rate during ascent are processes that must be adequately considered to evaluate the dynamics of magmas within this volcano and their relationship to eruptive style.