The study represents a step forward in understanding the current Phlegraean bradyseismic crisis and underlines the importance of continuous monitoring
A team of researchers of the Vesuvius Observatory of the National Institute of Geophysics and Volcanology (INGV - OV), in collaboration with theUniversity of Palermo, the University of Cambridge and Woods Hole Oceanographic Institute, has identified an important anomaly in the composition of the gases of the fumaroles of the Solfatara dei Campi Flegrei, linked to the contribution of magmatic gases. The study, "Escalation of caldera unrest indicated by increasing emission of isotopically light sulphur", has just been published in the scientific journal Nature Geoscience.
Since the end of 2018, the concentrations of hydrogen sulfide, the sulfur species present in the Solfatara fumaroles, have recorded an increase whose significance has been investigated with the most modern analytical techniques.
"Our analysis demonstrates that the observed variations in the composition of fumaroles are not exclusively attributable to superficial hydrothermal processes. Our study highlights that the sulfur anomaly recorded in fumaroles is attributable to an increasing contribution of gas from the magma that feeds the volcanic system of the Phlegraean Fields, supporting the hypothesis of magmatic involvement in the current bradyseismic crisis of the Phlegraean Fields", explains Alexander Aiuppa, Professor at the University of Palermo.
Through systematic sampling and chemical analyses, the study identified an increasing contribution of magmatic gases coming from an ascending magma in the Earth's crust, between 9 and 6 km deep. The increasing transport of these gases towards the surface, inducing the heating of the hydrothermal system and contributing to the generation of the seismicity observed at Campi Flegrei in recent years, could have determined an increasing re-mobilization of sulfur trapped in hydrothermal minerals, contributing to the sulfur anomaly observed in fumaroles.
"An increasing release of sulfur from fumaroles is typical of quiescent volcanoes that are going through a phase of possible gradual reactivation", adds the team, which compared the data obtained at Campi Flegrei with those of other volcanic systems.
Prior to this study, hydrogen sulfide concentrations were thought to be regulated by low-temperature equilibrium reactions with sulfur minerals occurring in the shallow part of the hydrothermal system.
"The real novelty of our work is having documented a clear evolution in the origin of sulfur. The increasing magmatic contribution in the gases suggests an important evolution in the dynamics of the Phlegraean volcanic system since 2018”, points out Giovanni Chiodini, Associate Research Director at INGV.
Although the results do not imply the imminence of a volcanic eruption, the study highlights the need to maintain attention on the Phlegraean system.
"These results improve our understanding of the ongoing bradyseismic crisis and remind us of the importance of constant monitoring.", he adds Stephen Caliro, Chief Technologist responsible for the geochemical monitoring of Campanian volcanoes at INGV-OV and first author of the study.
The research was based on one of the most complete fumarole composition datasets in the world, with data collected from 1980 to today. The researchers analyzed gas samples collected regularly in the Solfatara dei Campi Flegrei area in the laboratory, and used numerical modeling to interpret the data.
"The analytical accuracy and continuity over time of this dataset are fundamental to understanding the evolution of the system", he claims Caliro.
Further developments of this research will be obtained from the continuous monitoring of the fumaroles and from further and more sophisticated analyses that will allow interpretations of ever greater detail.
"In this and other ongoing studies on the Campi Flegrei caldera, the fundamental importance of continuous multi-parametric monitoring of the caldera emerges, both in the emerged and submerged portions. The combination of all the data will offer an increasingly accurate vision of the possible evolution of the system.", he claims Mauro A. DiVito, Director of INGV-OV and co-author of the article.
"Studying the minerals of the hydrothermal system will allow us to better understand the role of sulfur remobilization"he concludes Help me, stressing that any new data will be crucial to understanding the evolution of the volcanic system.
This study represents a further step in the understanding of an area of significant scientific and social interest, contributing to the conscious management of one of the most complex volcanic systems in the world.
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National Institute of Geophysics and Volcanology (INGV)
Photo 1: Overview of the Solfatara crater of Pozzuoli, Phlegraean Fields
Photo 2: Big Mouth Fumarole (Solfatara Crater)
Photo 3: Hydrothermal sulfur mineral deposition around Solfatara fumaroles