Ongoing unrest at Campi Flegrei, Italy: clues from the antecrystic records

Abstract

The largest deformation since the start of the ongoing unrest at Campi Flegrei caldera, Italy, was recorded in 2023 with an average uplift rate of 17 cm/year [1]. This coincides with the exponential increase of seismic events since 2017 by a factor of 32 (i.e., 6065 events in 2023 versus 3181 in 2022, 2232 in 2021, 1520 in 2020, 799 in 2019, etc.). Such observations raise questions regarding the origin and the future of the ongoing unrest especially in determining if the underlying cause involves ascent of magmatic fluids only or if magma is also involved. To this end, a forensic approach focusing on the characterisation of crystal cargoes from past eruptions help understanding of the conditions and pre-eruptive processes that occur within magmatic plumbing system prior to eruptions of different styles and comparing these possible scenarios with the current unrest. Juvenile clasts found in the base layer from deposits of past eruptions (e.g., Agnano-Monte Spina, Solfatara, Averno, Astroni, Monte Nuovo) of different eruption styles and size were collected. The 1538 eruption of Monte Nuovo is the ideal benchmark to link the petrological evidence to the precursory deformation documented, whereas the historical eruptions selected allow for consideration of a wider range of eruption scenarios. We will present machine learning thermobarometric data and chemical patterns inferred by clustering techniques used to constrain the temperature-pressure paths of the magma and to identify possible systematics during the period of magma migration to the surface preceding the eruption. Ultimately, we aim to link the petrological signatures conveyed by antecrysts with the deformation triggered during magma intrusion and expansion of volatiles upon ascent. Reference: [1] INGV. Bollettini di sorveglianza dei vulcani campani. http://www.ov.ingv.it/ov/bollettini-campi-flegrei/ (2016-2023).