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Caractérisation et modélisation des transferts de traceurs naturels dans les argilites de Tournemire

Abstract : The French Institute for Protection and Nuclear Safety (IPSN) is investigating the argillaceous formation of Tournemire (France) as a methodological underground laboratory for conducting research on the feasibility of deep geological repositories for radioactive waste in argillites. Because of the very low water content and hydraulic conductivity of the argillites, the migration through this media should be very low. The fluid flow regime and transport have been studied using natural tracers from the interstitial water.

The deuterium and chloride of interstitial water have been chosen for their conservative behavior. After the development of a protocol for the chloride extraction from the water, and tests on the vacuum distillation method for the water extraction from the rock, systematic data acquisition has been performed on the argillaceous sequence of the massif and near the fracture areas. Both chloride and deuterium profiles suggest that transfers are mainly diffusive at the massif scale. But the profiles show an enrichment in ?D and ?18O of the interstitial solution in the area of one meter adjacent to a fracture compared to pore water of samples located at further distance. Therefore, these observations are suggesting that a second process could generate specific transfers, at the vicinity of faults.

The hypothesis of the molecular diffusion as a dominant process for transport was successfully tested using a transport model, over periods of several tenth of millions years, taking into account geodynamical features of the region (such as tectonic and induced faults), and assuming that some variations of the tracer concentrations at the system boundaries occurred during the major climate-change periods.
Even if tracers' transfers are mainly diffusive at the massif scale, they are or should have been affected by a second process causing heterogeneity of concentrations at the vicinity of faults. This process involves either, intrusion of salted solutions or internal transfers due to overpressures.
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Contributor : Delphine Patriarche <>
Submitted on : Tuesday, March 16, 2004 - 2:33:08 AM
Last modification on : Wednesday, October 14, 2020 - 4:02:27 AM
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Delphine Patriarche. Caractérisation et modélisation des transferts de traceurs naturels dans les argilites de Tournemire. Géochimie. École Nationale Supérieure des Mines de Paris, 2001. Français. ⟨NNT : 2001ENMP1017⟩. ⟨tel-00005352⟩

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