A 4D reconstruction of magma movements into the Etna plumbing system throughout a decade of eruptions at the volcano

The Etna South East Crater produced during December 2020 – February 2022 a sequence of sixty-two episodes of powerful lava fountains after nearly two years of continuous, though weak, explosive activity at the summit. With regard to the eruptions of the last decade, the observation of frequent changes in the eruptive style and shifts in the location of volcanic activity in the summit area poses the need of defining how the conditions of storage, transfer and interaction of magmas have changed over time. In this contribution, the whole rock, crystal and glass chemistry of tephra from the 2020-22 paroxysmal sequence have been inspected in the framework of the previous post-2011 volcanic activity in order to document the plumbing system evolution throughout the last decade. Thermodynamic modeling on whole rock has been combined with micro-analytical data on volcanic crystals and glasses to investigate the physical and chemical conditions of magmas involved and the kinetics of magma movements among the different levels of the plumbing system. The Fe-Mg compositional zoning of olivine crystals have been also analyzed and modelled by diffusion chronometry with the aim of identifying the ascent pathways of magmas through the volcano plumbing system and inferring temporal changes in conditions of magma accumulation, recharge and ascent driving the eruptions. Our constraints on the whole rock major element distribution over the whole decade indicate significant changes in storage and transfer dynamics starting from the eruptions at the crater Voragine on December 2015. The whole rock composition also highlights that the 2020-22 eruptions have been fed by the most basic magma emitted since 2011. Olivine zoning confirms the activation, during the first months of 2021, of the most basic magmatic environments characterizing the feeding system of Mt. Etna. This basic magma entered the intermediate (170 – 250 MPa) plumbing system of Mt. Etna throughout the 2021, driving volcanic periods of more frequent eruptions, as during February 16 – April 1 and May 19 – July 14, 2021. The entire dataset for the 2020-22 activity suggests patterns of magma ascent similar to those observed during the 2011-13 sequence, yet very different kinetics of processes. Indeed, timescales of magma movements associated to the first months of the 2020-22 paroxysmal eruptions are significantly faster than those registered during the 2011-13 for almost all the connections between magmatic environments (days to weeks vs. weeks to months, respectively), presenting conversely great similarities with the timescales of transfer leading to the powerful eruptions at Voragine during 2015-16 (days to weeks).