Marco Donnini [1,2], Francesco Frondini [1], Carlo Cardellini [1], Stefano Caliro [3], Giovanni Chiodini [3], Ivan Marchesini [2], Fausto Guzzetti [2], 2013, First preliminary map of deep CO2 degassing in Alpine region, Goldschmidt 2013, Firenze, 25-30 Agosto 2013,
URL: http://www.cnr.it/prodotto/i/308410

Processes of CO2 degassing affect almost all tectonically active areas and metamorphic environments. Here we show the first preliminary map of deep-CO2 degassing of the Alps based on more than 1000 chemical analyses of springs (both data from litterature and new data). Using PHREEQC, for each point we estimated the total dissolved inorganic carbon (TDIC) and through an isotopic and mass balance approach we estimated the values of Ccarb, carbon deriving from carbonate dissolution, and Cinf, the sum between atmospheric CO2 dissolved by rainwater and biogenic CO2. Cdeep, carbon deriving from deep degassing, has been computed considering that [1]: TDIC = Ccarb + Cinf + Cdeep. Ccarb, given by Ca+Mg-SO4, has been estimated for sprigs fed by carbonate aquifers. The flux of deep CO2 associated to each spring discharge is given by Cdeep X Q/A, (Q: flow rate, A_ recharge area), or by Cdeep X IE, (IE: effective infltration, IE=Q/A). IE for each basin have been estimated using a water balance model [2]. Finally we prepared the CO2 degassing map using GSLIB [3]. The results show that CO2 production of Alps is 3 times lower than CO2 production in Central Italy [4], but locally (like in Engadine, Lucomagno Pass, Valtellina etc..) CO2 fluxes are one order of magnitude higher than the baseline of geothermal regions [5]. The highest deep-CO2 degassing areas are located along the more important alpine tectonic structures and in the basins external to the alpine chain. In these areas more detailed investigations should be performed in order to obtain a complete evaluation of the extent and distribution of the CO2 anomalies of the Alps. [1] Chiodini et al.. (2000) Journal of Geophysical Research 105. [2] Rossi et al. (2013) XIV GRASS e GFOSS meeting. [3] Deutsch and Journel (1988) Oxford Univ. Press [4] Chiodini et al.. (2004) Geophysical Research Letters 31. [5] Kerrick et al.. (1995) Chemical Geology 121.

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