The depth-to-surface dynamics of silicic peralkaline magmas from Pantelleria Island

Silicic peralkaline magmas are characterized by unusually low viscosity and responsible for a wide spectrum of eruptive styles, ranging from effusive to highly explosive Plinian eruptions. This apparent paradox challenges classical models of magma fragmentation and eruption dynamics. This thesis investigates the physical and chemical processes controlling magma ascent, degassing, fragmentation dynamics and eruptive behaviour in peralkaline silicic systems, using Pantelleria Island (Italy) as a natural laboratory. The study integrates textural analyses of juvenile products, anhydrous glass viscosity measurements, Raman spectroscopy, melt inclusion analyses and simultaneous thermal and evolved gas analyses (STA-EGA-MS) on products from four eruptions with similar bulk compositions but different eruptive styles: Cinque Denti (caldera-formingeruption), Green Tuff (caldera-forming-eruption), Zinedi (Sub-Plinian eruption) and Cuddia Mida (low-energy-Strombolian eruption). Integrated laboratory analyses are further used to perform numerical simulation of conduit dynamics. The results show that variations in eruptive style are primarily controlled by differences in ascent dynamics, volatile content and conduit geometry rather than bulk composition alone. Despite their low viscosities, peralkaline magmas can fragment due to their high water content concentration. Overall, this work provides new constraints on the mechanisms governing fragmentation and eruption dynamics of peralkaline magmas and contributes to improving rheological models for these compositions, with implications for volcanic hazard assessment in peralkaline volcanic regions