CO2 Degassing over Seismic Areas: The Role of Mechanochemical Production at the Study Case of Central Apennines

Abstract

Field observations coupled with experimental results show that CO 2 can be produced by mechanical energy applied to carbonate rocks becoming an unexpected additional gas source besides that degassed from the mantle or produced by thermometamorphism. The evidence that a large amount of carbon dioxide associated with radiogenic-type helium (R/Ra as low as 0.01-0.08) is released through continental areas, denotes the absence of a contribution from the mantle or from mantle-derived fluids. Data collected during the seismic crisis which struck the Central Apennines in 1997-98 have shown an enhanced CO 2 flux not associated with the presence of mantle or thermometamorphic-derived fluids. On the other hand, new experimental results highlight the possibility of producing CO 2 by mechanical energy that acts on the calcite crystalline lattice. While the CO 2 released over the geothermal areas (e.g., Larderello Geothermal Field) is obviously derived by mantlederived activities, this is not the case of the huge amount of CO 2 released over the seismically active areas where the presence mantle-derived products is ruled out. We propose that mechanical energy, e.g., released during seismic events, microseismicity or creeping processes is a possible additional energy source able to produce CO 2 and thus could explain the presence of CO 2 degassing over tectonic areas where the influence of the mantle is low.

The high pCO2 Caprese Reservoir (Northern Apennines, Italy): Relationships between present- and paleo-fluid geochemistry and structural setting

“…However, gases discharged in this Apennine sector yield He isotopic signature typical of the continental crust (R a = 0.03), thereby suggesting the occurrence of crustal sources in the system and long residences times of fluids in crustal traps (e.g. Minissale et al, 1997Minissale et al, , 2000Minissale, 2004;Italiano et al, 2008;Chiodini et al, 2011). Indeed, the inferred structural assessment is also compatible with a CO 2 and N 2 contribution from thermometamorphic-hydrothermal degradation of Mesozoic carbonates and Burano Fm.…”

Thermal decomposition of carbonates in fault zones: Slip‐weakening and temperature‐limiting effects

“…The CO 2 of the Nojima fault might thus be attributed to the decomposition of biogenic carbonates. In the Central Apennines, Italiano et al [2008] also reported enhanced fluxes of crustal CO 2 (i.e. not mantellic) during the 1997 -1998 seismic crisis of major faults, and proposed that coseismic decarbonation was responsible for the CO 2 emission.…”

Identifications and removal of diurnal and semidiurnal variations in radon time series data of Hsinhua monitoring station in SW Taiwan using singular spectrum analysis

“…Despite several years of research, the use of advanced equipment and the efforts of many dedicated scientists, the task of predicting earthquakes is still a distant goal. Since the 1960s, geochemical signals preceding significant earthquakes have been used for earthquake prediction study worldwide (Yang et al , 2011Hartmann and Levy 2005;Italiano et al 2008;Einarsson et al 2008;Cicerone et al 2009;Kumar et al 2009Kumar et al , 2013aWalia et al 2009Walia et al , 2013. Among the potential geochemical precursors, radon changes are probably the most frequently used for earthquake monitoring/predicting purposes.…”