A PRELIMINARY STABLE-ISOTOPE STUDY ON A POTENTIAL RADIOACTIVE-WASTE REPOSITORY SITE IN THE MECSEK MOUNTAINS, SOUTHERN HUNGARY

A potential repository site for high-activity radioactive waste is inv estigated in the vicinity of a former uranium mine in the Mecsek Mts. (S. Hungary). In order to evaluate the usefulness of the site, stable H, C and O isotope compositions of shallow groundwaters, repository si te waters, carbonate veins and fluid inclusions of the veins have been measured. Shallow groundwaters have H and O isotope compositions iden tical to those of the present day local precipitation water, whereas r epository site waters show delta D and delta(18)O values characteristi c of Pleistocene meteoric waters. Based on delta(13)C, delta(18)O and delta D (inclusion fluid) data, the calcite veins might have been form ed by movements of meteoric water originating from precipitation In a warmer climate of the geological past. The results indicate that no si gnificant infiltration of surface waters to the investigated repositor y site occurs, but signs of migration of Pleistocene waters along the veins has been observed.