Isotopic investigation of CO {sub 2}, H {sub 2} O steam and alkanes out-gassed by the argilites of the Callovo-Oxfordian at Bure (Parisian Basin); Etude isotopique du CO {sub 2}, de la vapeur d'eau et des alcanes degazes par les argilites du Callovo-Oxfordien de Bure (Bassin de Paris)

摘要: The isotopic composition of the Callovo-Oxfordian argilites of Bure site (Eastern Paris basin) has been used to determine the nature of the pore water and of the water-rock interactions. A specific degassing apparatus has been implemented for the extraction and purification of gases from argilite core samples (CO{sub 2}, water vapor, methane, ethane and propane). {sup 18}O and {sup 13}C contents have been determined by mass spectroscopy (IRMS and GC-C-IRMS). Results indicate the marine inorganic origin of the CO{sub 2} and the deep extra-formation origin of the desorbed hydrocarbons. They confirm the meteoric origin of the interstitial water and the very limited bacterial activity. The main advantage of this method is that no pore water extraction is needed, which protects the clay-water system from any irreversible disturbance. (J.S.)