Near Real-Time Petrologic Monitoring on Volcanic Glass to Infer Magmatic Processes During the February–April 2021 Paroxysms of the South-East Crater, Etna

Abstract

The South-East crater of Etna (SEC) is the most active summit crater over the last 20 years, producing lava fountains in 2000, 2007-08, and 2011-14. It has been monitored by the INGV Etna Observatory by instrumental networks, field surveys and petrologic monitoring. The syn-eruptive petrologic monitoring comprises sample collections, archiving, sample preparation, analyses of glass compositions using SEM-EDS and data interpretation. This procedure is generally carried out within 24 hours from the moment the sample was emplaced, to detect possible changes of magma composition episode by episode, as well as over a longer period. This paper presents the variation of volcanic glass compositions during the paroxysmal activity of the SEC, which began in December 2020 and climaxed with 17 episodes from 16 February to 1 April 2021. We infer pre-eruptive magmatic processes (e.g., fractional crystallization and mixing) based on temporal trends of some key compositional parameters (i.e. CaO/Al2O3; FeOtot/MgO). Correlation between magma dynamics and volcanological characteristics of the paroxysms requires future studies.