GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.3 177 LINKING CRYSTAL CHEMISTRY AND GROUND DEFORMATIONS FOR A HIGH-RESOLUTION DETECTION OF MAGMA DYNAMICS AT MT. ETNA M. Giuffrida 1 , F. Zuccarello 1 , M. Borzì 1 , M. Palano 2 , M. Viccaro 1,2 1 Università di Catania, Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Catania, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania, Osservatorio Etneo, Catania, Italy Introduction. During the last decade, Mt. Etna has given birth to a wide range of eruptions from both the summit craters and the volcano’s flank, passing from periods of entirely effusive activity to strongly explosive (i.e., violent Strombolian to lava fountains). Since 2011, the eruptive behavior was dominantly explosive with two major cycles of paroxysmal eruptions as those of 2011-2013 at the New South East Crater (NSEC) and those of December 2015 and May 2016 at the Voragine Crater (VOR). In particular, the eruptions at VOR were among the most explosive recorded during the last two decades. A new change of the eruptive behavior was observed during 2017, when the activity turns again to dominantly effusive, giving rise to a short sequence of weak Strombolian explosions and lava flow emissions from the NSEC. The most recent history of the volcano has seen the opening of eruptive fissures on the eastern flank of the NSEC cone on December 24-27, 2018 (Fig. 1). Eruptive fissures rapidly propagated southeastward, followed by resumption of low-intensity explosive activity at the summit vents. The short-lived episode of December 2018 took place about 10 years after the last flank eruption of May 2008 (Aloisi et al. , 2009). This eruption has been here considered within the framework of the changing mechanisms of magmatic replenishment and transfer that affected the Etna plumbing system since June 2016 (Viccaro et al. , 2019). Indeed, the ending of the paroxysmal activity at VOR on May 2016 marks the beginning of a period characterized by a significant decreasing of the eruptive frequency and emitted magma volumes, despite the evidence of continuous magma replenishment from depth. These observations lead us to envisage the occurrence of important changes in the modes of magma storage and transfer beneath the volcano. The detection and investigation of such dynamics required a multidisciplinary approach in which crystal chemical zoning, diffusion chronometry and ground deformation data have been combined. The extended petrologic and geodetic dataset presented in this study allows for the spatial localization of active magmatic sources, and also the definition of their temporal activation throughout the 2016-2018 eruptive periods. Data elaboration and integration. The compositional and temporal information preserved in volcanic crystals were elaborated Fig. 1 - (a) Digital Elevation Model of Mt. Etna with location of the GPS stations used in this study (yellow squares), the eruptive fracture (pink areas) and the lava flow field (red areas) related to the December 24- 27, 2018 volcanic events. The EDAM-EINT baseline is traced with a black line. BN: Bocca Nuova; VOR: Voragine; NEC: North East Crater; SEC: South East Crater; NSEC: New South East Crater. (b) View of the fissure eruption on the eastern flank of NSEC cone during the afternoon of December 24, 2018.