A PHYSICOCHEMICAL CHARACTERIZATION AND GEOCHEMICAL MODELING APPROACH FOR DETERMINING POREWATER CHEMISTRIES IN ARGILLACEOUS ROCKS

Argillaceous sediments are being investigated in many countries as pot ential host rock formations for the disposal of high level radioactive waste. Quantification of the water chemistry in such formation is oft en difficult because the groundwater flow rates are so low that reliab le samples for chemical analysis cannot be obtained. A physicochemical characterisation procedure for rock samples combined with geochemical modelling is described which allows porewater composition to be deter mined in low porosity/permeability clay rich systems. The methodology was applied to core samples of Opalinus clay within the framework of a n international investigation being carried out at Mt. Terri, Canton J ura, Switzerland. Copyright (C) 1998 Elsevier Science Ltd.