HR: 1340h
AN: T53C-1442    [Abstracts]
TI: Quantification of Deeply Derived Carbon Dioxide in Central and Southern Italy.
AU: * Cardellini, C
EM: geochem@unipg.it
AF: Dipartimento di Scienze della Terra, Università di Perugia, Piazza Università, Perugia, 06100 Italy
AU: Chiodini, G
EM: chiod@ov.ingv.it
AF: Osservatorio Vesuviano - INGV, Via Diocleziano, 328, Naples, 80124 Italy
AU: Caliro, S
EM: caliro@ov.ingv.it
AF: Osservatorio Vesuviano - INGV, Via Diocleziano, 328, Naples, 80124 Italy
AU: Frondini, F
EM: frondini@unip.it
AF: Dipartimento di Scienze della Terra, Università di Perugia, Piazza Università, Perugia, 06100 Italy
AU: Morgantini, N
EM: nic.morgan@tiscali.it
AF: Dipartimento di Scienze della Terra, Università di Perugia, Piazza Università, Perugia, 06100 Italy
AB: A large portion of the total water discharge from the Apennine carbonate aquifers (~ 58 %) has been sampled and analysed for major chemical components and for the isotopic composition of dissolved inorganic carbon (DIC). On the basis the carbon mass balance has been estimated that DIC derives from the dissolution of carbonates hosting the aquifers (~ 33 %), from the biogenic CO₂ of the soils (~ 24 %), and for the greatest part from a deep source (~ 43 %). The modelling of the water-rock-gas interaction allowed to assess that groundwater composition is compatible with the evolution of infiltrating waters dissolving variable amounts of deeply derived CO₂ with an isotopic composition in the range of that of the CO₂ emitted in Italy from active volcanoes, geothermal fields, and cold gas emissions located in the western sector of the central and southern Italy. On the base of the computed deeply derived carbon dissolved in the groundwater a regional map of CO₂ Earth degassing has been recently elaborated (Chiodini et al., 2004), pointing out the presence in the Tyrrhenian side of the Italian peninsula of two large regional degassing structures that, for the magnitude and for the geochemical features, can be related to a regional process of mantle degassing. In the western part of these regions is characterized by the presence of many CO₂ rich gas emission releasing by soil diffuse degassing significant amount of CO₂, geothermal systems, dissolved carbon in volcanic aquifers (Gambardella et.al., 2004) and large travertine deposits. Here, at smaller scale, a strong correlation between shallow geological structures and CO₂ diffuse degassing was observed, suggesting that in this sector mantle fluids may enter the lower crust and move upwards through the interconnected network of extensional fractures and normal faults, accumulate in shallow reservoir and generate the high CO₂ flux anomalies at the surface. On contrary, in the Adriatic foreland, which is characterized by a thicker crust, was hypothesized, that CO₂ released from the mantle intrudes the deeper, now inactive thrusts affecting the Moho and the upper crustal levels at the boundary between the Tyrrhenian hinterland and the Adriatic foreland. Here at depth CO₂ may accumulate in crustal traps generating overpressurized reservoirs, favoring the seismogenesis. This is suggested by the strong correlation at regional scale between CO₂ degassing and seismicity and by data suggesting the presence of such deep reservoirs, e.g., deep well, seismogenetic low angle faults (e.g., Collettini, 2002) and the seismic crises of Colfiorito 1997 (Miller et al., 2004) Moreover, the quantitative results of this study, according with the independent estimations of deep CO₂ degassing for Tuscany (Frondini et al., 2005) and for northern Latium (Gambardella et al., 2004), pointed out the global significance of the amount of CO₂ released by the region together with the present underestimation of the CO₂ globally released by the Earth. References Chiodini G. et al. (2004). Geophys. Res. Lett., 31, 7. L07615, 10.1029/2004GL019480; Collettini C. (2002). Boll. Soc. Geol. It. 1, 873-880; Gambardella B. et al., (2004). J. of Volcanol. and Geother. Res., 136, 31-52; Frondini F. et al. (2005). Earth and Planet. Chang. In print; Miller S. A. et al. (2004). Nature, 427, 724-727.
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1034 Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424)
DE: 8010 Fractures and faults
SC: Tectonophysics [T]
MN: Fall Meeting 2005