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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS011 Oral Presentation 2123
Mantle derived CO2 degassing in Italy
Dr. Carlo Cardellini
Dipartimento di Scienze della Terra Universit di Perugia IAVCEI
Chiodini Giovanni, Frondini Francesco, Caliro Stefano, Avino Rosario, Baldini
Angela, Granieri Domenico, Morgantini Nicola
Central and southern are affected by an active and intense process of CO2 Earth degassing. Recent
studies, pointed out the presence of two large CO2 degassing structures (62000 km2): a northern one,
the tuscan roman degassing structure (TRDS) and a southern one, the campanian degassing structure
(CDS). These two structures are characterized by the presence of numerous CO2 rich gas emissions.
The deeply derived CO2 released by these two structures was estimated in about 9.2 Mt/y and resulted
globally relevant, being about 10% of the estimated global CO2 discharge from subaerial volcanoes.
Based on the extension and magnitude of the CO2 degassing and on the geochemical-isotopic features
of the gas released, it is our opinion that the two degassing structures are the surface expression of two
large plumes of fluids derived by a crusally metasomatised mantle. These CO2 rich fluids heat the crust
and saturate with gas the crustal permeable structures. The existence of a mantle wedge
metasomatised by crustal materials is also strongly suggested by the geochemical features of the
magmas of the Tuscany, Roman magmatic provinces.At regional scale, was also observed a strong
relation between CO2 degassing and the earthquakes location. The anomalous CO2 flux suddenly
disappears in the Apennine in correspondence of a narrow band where most of seismicity concentrates.
Here, at the eastern borders of TRDS and CDS plumes, the CO2 from the mantle intrudes and
accumulate in crustal traps generating overpressurised reservoirs two of which have been reached by 4-
5 km deep wells in the northern Apennine. These CO2 overpressurised level can play a major role in
triggering the Apennine earthquakes by reducing fault strength and potentially controlling the nucleation
of earthquakes. Understanding the mechanism of mantle degassing, its flux through the crust, and its
contribution to crustal deformation can provide useful information for the reconstruction of the
geodynamic scenario of our region, as well as in many other tectonically active regions of the world.
Keywords: co2, degassing, mantle