Magma storage and ascent during the largest eruption of Somma-Vesuvius volcano: Pomici di Base (22 ka) Plinian event

The reconstruction of the pre-eruptive storage conditions as well as syn-eruptive magma ascent dynamics of past eruptions is of fundamental importance to decipher the relationship between surface-monitored signals and the sub-volcanic processes in order to learn more about the eruptive behaviour of active volcanoes. The Pomici di Base Plinian eruption is the first (22 ka) and largest (> 4.4 km³) event of the Somma-Vesuvius volcanic complex. Here we present the preliminary results of a geochemical, isotopic, two-dimensional and three-dimensional textural study performed on volcanic products emitted during the Plinian phase of this eruptive event with the aim to reconstruct in more details the magmatic evolution of this large caldera-forming eruption. Particularly, it was fed by chemically and thermally zoned magmas extracted from a crystal mush zone in a magma chamber with top at ~4.5 km depth. During this eruption, crustal (limestone) contamination and subsequent CO₂ emissions as well as changes in degassing mechanisms mainly controlled the eruptive dynamics.