The origin of the carbon dioxide fluxes emitted at the Campi Flegrei caldera has been investigated. The study led to important information on the dynamics of magmatic outgassing in progress.
A percentage between 20% and 40% of the carbon dioxide emitted in the Campi Flegrei area comes from non-magmatic sources and this value has been progressively increasing since 2005, with growth rates similar to those of the temperature increase of the hydrothermal system. These are the results of the study "Discriminating carbon dioxide sources during volcanic unrest: The case of Campi Flegrei caldera (Italy)", published by the journal 'Geology' and conducted by a team of researchers from the National Institute of Geophysics and Volcanology (INGV).
“The Campi Flegrei caldera emits large quantities of carbon dioxide (CO2) every day” explains Lucia Pappalardo, a researcher at INGV. “The flows of this gas are mainly concentrated near the Solfatara crater in Pozzuoli and have progressively increased during the recent bradyseismic crisis, which began in 2005, reaching the current level of 3000-5000 tons per day. A value that makes the Phlegrean caldera one of the main emitters of carbon dioxide of volcanic origin in the world”.
Carbon dioxide is the second volatile species contained in magma after water, and this has often led to the detection of a massive release of CO2 in the periods preceding the eruptive events. However, its origin is not exclusively attributable to magma, especially in the calderas that host extensive hydrothermal systems such as Campi Flegrei. Therefore, an accurate investigation and quantification of the origin of CO2 fluxes in active volcanic areas, as well as helium and nitrogen, is essential to reconstruct what is happening in the deep magmatic system and in the more superficial hydrothermal system. It is particularly so for the Campi Flegrei which, following the last eruption of Monte Nuovo which took place in 1538, experienced a phase of calm interrupted by the recent bradyseismic crises of 1950-52, 1970-72 and 1982-84, until to the latter started in 2005.
“The recent study”, continues Gianmarco Buono, an INGV researcher, “has made it possible to estimate that up to 40% of the carbon dioxide emitted originates from the dissolution of the hydrothermal calcite present in the rocks of the Phlegrean subsoil, while the remaining part derives from deep magmatic springs”.
By comparing the fumarolic data with those obtained with magmatic degassing simulations, it was possible to estimate that between 20% and 40% of the CO2 emitted in this area is released from non-magmatic sources.
“The value of carbon dioxide emitted by these non-magmatic sources from Campi Flegrea has been progressively increasing since 2005 with growth rates surprisingly similar to those of the temperature increase of the hydrothermal system. The origin of this additional source of CO2 is to be found in the important physical and chemical perturbations that the Phlegrean hydrothermal system is undergoing, manifested by the growing number of surface earthquakes and ground elevation”, continues Giovanni Chiodini, INGV researcher. "In detail, this process is driven by the conversion of calcite, previously found in abundant quantities in the Phlegrean subsoil, into carbon dioxide following the circulation of hot and acidic fluids in the rocks that host the hydrothermal system".
“The study”, concludes Gianmarco Buono, “is part of the strategic project of INGV LOVE-CF (Linking surface Observables to sub-Volcanic plumbing-system: a multidisciplinary approach for Eruption forecasting at Campi Flegrei caldera - Italy) and offers a also useful for other volcanic systems. The research will continue with the quantification of the carbon dioxide fluxes emitted in the underwater environment, which have remained unexplored until now".
Link to the study:
Link to the LOVE-CF project
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Solfatara crater
Location (a) and diffuse flux of carbon dioxide from soils (b) of the Solfatara area.
Variations of carbon dioxide emitted by non-magmatic sources (CO 2,add ) estimated for twodifferent magmatic outgassing scenarios, compared with those of the system temperature
hydrothermal and ground deformations in the central sector of the caldera.