DISTRIBUTION OF DEEP CARBON-DIOXIDE IN RELATION TO THE STRUCTURE AND TECTONIC EVOLUTION OF SOUTH-EAST FRANCE

Throughout SE France, C-13-values of CO2 releases suggest that a variable part of the CO2 emission derives from mantle and/or lower crust. Carbon dioxide emission takes place in various geological settings. Geodynamical analyses lead to the identification of five provinces: the Sub-Alpine Ranges, the French Massif Central, the Mediterranean part of the Languedoc, the western Pyrenees and the Alps at the West of the Penninic front. Possible correlations are suggested between CO2 flux and tectonic history of the structural provinces. Possible processes by which CO2 is extracted from the mantle, stored and transferred to the surface are investigated for each of these provinces. Major crustal scale gas movements may have taken place during the Carboniferous (Variscan and Late Variscan tectogenesis), the Lias and Dogger (rifting), the Upper Cretaceous and the Cenozoic (Alpine tectogenesis), A model of successive circulations of fluids on the scale of the whole Southeastern France CO2-belt is proposed. This integrated isotopic and geodynamic approach contributes to a better understanding of the regional CO2 flux.