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 SommaVesuvius 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.