Mobility of U–Th radionuclides connected with fault porosity: A case study of the Schauenburg Fault, Rhine Graben Shoulder, Germany

摘要: Abstract This study focuses on the relationship between U- and Th-isotope distribution, porosity/permeability structure of a geological fault in uplifted Rhine Graben shoulder (SW-Germany). fault, known as Schauenburg Fault, separates basement Variscan granite from Permian rhyolite, is marked by clay-bearing cataclasite. All rock samples are characterized redistribution uranium thorium isotopes within last ∼10 6  years, whereas rhyolite only leaching (activity ratio 234 U/ 238 U > 1, record complex history sorption loss isotopes. The activity ratios higher for collected close to plane lower cataclastically deformed situated away principal displacement surface. porosity measurements cataclasite show symmetrical variations across core zone, similar pattern ratios. In order relate data with δ U value, simple exchange model was developed assuming that change results isotopic aqueous phase. Best approximations were obtained using an water/rock coefficient ranging 2.5E−06 [ −1 ] zone 2.5E−05 walls, whereby per year same dimension radioactive decay constant. Along outer increased porosity, thus permeability, resulted prolonged contact water rock. Here, phase has occurred. Within availability circulating fluids restricted resulting time 70 ka, which suggests young fluid–rock interaction event possibly related stage graben along this structure.