Etna 2011–2022: Discoveries from a decade of activity at the volcano

We present here a comprehensive petrological investigation of products emitted during the December 2020 – February 2022 paroxysmal sequence occurred at the South East Crater of Mt. Etna, interpreting results within the framework of the post-2011 activity at the volcano in order to provide a realistic illustration of the evolution of the volcano plumbing system throughout the last decade. We have combined thermodynamic modeling on whole rock 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. Whole rock major element compositions indicate changes in storage conditions and transfer dynamics starting from eruptions at the Voragine on December 2015. These data also highlight that the 2020–22 eruptions have been fed by the most mafic magma with respect to all the eruptions of the last decade. Chemical heterogeneities of olivine crystals confirm the activation, during the first months of 2021, of the most mafic magmatic environments characterizing the feeding system of Mt. Etna if compared to the whole last decade. This mafic magma has permeated all the plumbing system of Mt. Etna throughout the 2021, driving periods of more frequent eruptions depending on the possibility to have efficient drainage at shallow levels, with patterns similar to those observed during the 2011–13 sequence. Fe-Mg diffusion chronometry applied to zoned olivine from the first phase of the 2020–22 sequence (December 13, 2020 – April 1, 2021) allows us to detect fast migration of the mafic magma from the deepest level of the plumbing system upward to intermediate and shallow levels, with times comparable to those leading to the astonishing paroxysmal eruptions of 2015–16 at Voragine. Connections among the magmatic environments during the second phase of the paroxysmal sequence (May 19, 2021 – February 21, 2022) chiefly involve the intermediate and shallow levels of the volcano feeding system, with timescales of magma transfer slower than those registered during the first phase. This study highlights that replenishment by volatile-rich magmas from the deepest levels of the plumbing system is a recurrent trend over the last decade at Mt. Etna and that the effusive vs. explosive activity at the surface is related with the injected volumes and the magma ability to degas during the ascent.