GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 1.2 122 AN OVERVIEW OF THE MT. ETNA SUMMIT ACTIVITY BETWEEN JULY 2019 AND JANUARY 2020 FROM A CRYSTAL CHEMISTRY PLUS GEOPHYSICAL PERSPECTIVE F. Zuccarello 1 ,M. Giuffrida 1 , M. 1 , Giorgio Costa 1 , M. Sciotto 2 , A. Cannata 1,2 , M. Viccaro 1,2* 1 Università degli Studi di Catania, Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Corso Italia 57, I-95129, Catania, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania, Osservatorio Etneo, Piazza Roma 2, I-95125 Catania, Italy Introduction Mt. Etna’s summit activity in 2019-2020 have been highly variable, generating ash puff and Strombolian explosions of different intensity from the summit craters, along with lava flows from the New South East Crater (NSEC) in May and July 2019 and from Voragine (VOR) toward the end of 2019 ( Fig. 1 ). During the first months of the 2019, the North East Crater (NEC) and Bocca Nuova (BN) displayed continuous degassing and sporadic ash emission. On May 30, 2019 two fracture systems opened and propagated along the southeastern and northern flanks of the NSEC, gene- rating weak Strombolian explosions and lava overflows ( Fig. 1) . On the second half of July, two further eruptive episodes occurred at NSEC, the first on July 18-20 and the second on July 27-28, both producing Strombolian explosions from the summit and lava flows from lateral fractures. On September 8, Strombolian activity began at NEC, followed shortly after by the reactivation of VOR. Voragine awoke on September 12, 2019 with ash puffs that increased gradually in fre- quency until turning into mild-to-high intensity Strombolian explosions that continued for the next eight months. More intense intra-crateric explosions were observed in November 2019 and January-February 2020, together with small lava flows that flowed into the adjacent BN crater. The reawakening of VOR after years of volcanic activity dominated by the NSEC eruptions po- ses the challenge to clarify the storage conditions and internal dynamics that move magmas to erupt, to date. In this work, we present an overview of Mt. Etna eruptions at NSEC and VOR from July 2019 to early 2020, focusing on textures and zoning of plagioclase and olivine crystals. We also used Fe-Mg diffusion in olivine to estimate the time at which episodes of magmatic intru- sions into the plumbing system have occurred. Petrological data and results are integrated with real-time geophysical data acquired through distinct monitoring techniques, including volcanic tremor and infrasound. All the available data have been finally correlated with volcanological observations in order to get insights into the existing relationships between modes of magma supply and changes in the state of volcanic activity at the surface. The sequence of 2019-2020 magmatic events detected for the 2019-2020 period is here interpreted in the framework of the most recent activity of Mt. Etna, by giving special attention to the short-term variability in storage conditions and ascent dynamics that has been recognized as the engine for past eruptions. Con- siderations on the recent eruptive record are used to test the recurrence of magmatic conditions and processes that may have caused changes in the current state of volcanic activity. Petrologic and geophysical data integration and interpretation Textural and compositional information preserved in erupted olivine and plagioclase crystals were elaborated and integrated together with volcanic tremor and infrasound data collected from the permanent monitoring network of Mt. Etna during the March2019 – January 2020 period of activity. Plagioclase crystals were categorized based on textural features and chemical zonation in An (mol%) and FeO (wt.%), allowing to distinguish them in four types: 1) clear fine-scale (~1 mol%