The ongoing unrest at the Campi Flegrei caldera (CFc) in southern Italy is prompting explorationof its poorly studied offshore sector. We report on a multidisciplinary investigation of the Secca delleFumose (SdF), a submarine relief known since antiquity as the largest degassing structure of the offshoresector of CFc. We combined high-resolution morphobathymetric and seismostratigraphic data with onshoregeological information to propose that the present-day SdF morphology and structure developed duringthe initial stages of the last CFc eruption at Monte Nuovo in AD 1538. We suggest that the SdF relief standson the eastern uplifted border of a N-S-trending graben-like structure formed during the shallow emplacementof the Monte Nuovo feeding dike. We also infer that the high-angle bordering faults that generatedthe SdF relief now preferentially allow the ascent of hot brines (with an equilibrium temperature of 1798C),thereby sustaining hydrothermal degassing on the seafloor. Systematic vertical seawater profiling showsthat hydrothermal seafloor venting generates a sizeable CO2, pH, and temperature anomaly in the overlyingseawater column. Data for the seawater vertical profile can be used to estimate the CO2 and energy (heat)outputs from the SdF area at 50 tons/d (0.53 kg/s) and 80 MW, respectively. In view of the cause-effectrelationship with the Monte Nuovo eruption, and the substantial gas and energy outputs, we consider thatthe SdF hydrothermal system needs to be included in monitoring programs of the ongoing CFc unrest.
|Numero di pagine||26|
|Rivista||Geochemistry, Geophysics, Geosystems|
|Stato di pubblicazione||Published - 2016|
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