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 increase in temperature 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 caldera of the Phlegraean Fields - explains Lucia Pappalardo, researcher at the INGV - emits significant quantities of carbon dioxide (CO2) every day. 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. This value makes the Phlegraean caldera one of the world's leading emitters of carbon dioxide of volcanic origin.
CO2 Campi Flegrei: the study of the magazine Geology
L'carbon dioxide It is the second most abundant volatile species in magma after water, and this has often led to the detection of massive releases of CO2 in the periods preceding eruptive events. However, its origin cannot be traced exclusively to magma, especially near calderas that host extensive hydrothermal systems such as Campi Flegrei.
Therefore, a careful 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.
This is particularly true for the Campi Flegrei which, following the latest eruption of Monte Nuovo which took place in 1538, experienced a period of calm interrupted by the recent bradyseismic crises of 1950-52, 1970-72 and 1982-84, up to the latter which began in 2005.
"The recent study - continues Gianmarco Good, researcher at the INGV - has allowed us to estimate that up to 40% of the carbon dioxide emitted originates from the dissolution of hydrothermal calcite present in the rocks of the Phlegraean subsoil, while the remaining part comes from deep magmatic sources".
Comparing the fumarolic data with those obtained with simulations of degassing magmatic, it has been 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 the Campi Flegrei "has been progressively increasing since 2005 with growth rates - continues Giovanni Chiodini, researcher at the INGV - 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 significant physical and chemical disturbances that the Phlegraean hydrothermal system is undergoing, manifested by the increasing number of superficial earthquakes and ground rise.
"In detail, leading this process is - still nails - the conversion of calcite, previously detected in abundant quantities in the Phlegraean subsoil, into carbon dioxide following the circulation of hot and acidic fluids in the rocks hosting the hydrothermal system".
The study, Buono concludes, It is part of the strategic INGV LOVE-CF project (Linking surface Observables to sub-Volcanic plumbing-system: a multidisciplinary approach for eruption forecasting at Campi Flegrei caldera - Italy) and offers a useful approach for other volcanic systems as well. The research will continue with the quantification of carbon dioxide fluxes emitted in the submarine environment, which have remained unexplored until now.
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