CO2 Degassing over Seismic Areas: The Role of Mechanochemical Production at the Study Case of Central Apennines |
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Authors: | F Italiano G Martinelli P Plescia |
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Institution: | (1) INGV Istituto Nazionale Geofisica e Vulcanologia, Sezione di Palermo, Italy;(2) ARPA Environmental Protection Agency of Emilia Romagna, Via Amendola 2, 42100 Reggio Emilia, Italy;(3) CNR Istituto Studio Materiali Nanostrutturati, Montelibretti RM, Italy |
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Abstract: | Field observations coupled with experimental results show that CO2 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 CO2 flux not associated with the presence of mantle or thermometamorphic-derived fluids. On the other hand, new experimental
results highlight the possibility of producing CO2 by mechanical energy that acts on the calcite crystalline lattice. While the CO2 released over the geothermal areas (e.g., Larderello Geothermal Field) is obviously derived by mantle-derived activities,
this is not the case of the huge amount of CO2 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 CO2 and thus could explain the presence of CO2 degassing over tectonic areas where the influence of the mantle is low. |
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