Isotopic and geochemical indicators for groundwater flow and multi-component mixing near disturbed salt anticlines

In the present study, a set of environmental tracers was applied to establish aquifer fingerprints and chemical equilibria in groundwater of highly saline environments in contact with the Zechstein formation. With this approach it was possible to resolve prevailing multi-component mixing processes in the groundwater which were found to occur on three time scales: A modern groundwater component could be identified and quantified by the presence of 3H and 3Hetri in the samples which indicates young apparent groundwater ages (0–50 a). The presence of 14C in the samples could be used for a classification between the modern groundwater component, and an old groundwater component. Contact between meteoric water and Zechstein salts (naturally or anthropogenically induced) could be identified by the presence or absence of Permian crystallization water from the dissolution of e.g. Carnallite and/or Kieserite. Using this, localized interactions between water-bearing strata and saline formations were identified. Noble gas values (He, Ne, 3He/4He) showed strong variations and unusually high excess air values. Qualitatively, these could be explained by the impact of the highly saline environment on noble gas diffusion. Implications relating to potentially on-going salt dissolution in areas of the thickest (Stassfurt) salt series induced by groundwater flow are discussed, as the investigated area is heavily affected by ongoing subrosion.

► Environmental tracer application in brines.
► Salt-induced noble gas diffusion.
► Impact of crystallization water.
► Role of groundwater in subrosion processes of the Zechstein formation.