Saline groundwater in the Munsterland Cretaceous Basin, Germany: clues to its origin and evolution

Saline groundwater (TDS up to 250,000 mg/l) occurs in subsurface coal mines. wells, and artesian springs in the area of the halite-free Munsterland Cretaceous Basin (MCB) in Germany. The origin and evolution of the saline groundwater in the MCB are poorly understood. An investigation of the hydrochemistry and stable isotope (O, H, Sr) composition of a small sample set of present-day saline groundwater from the MCB has been carried out to improve our understanding of its origin and evolution within the framework of the complex geological history of the area. The data provide evidence for: (1) halite dissolution, (2) A ater-rock interaction of highly saline fluids with siliciclastic sediments, (3) mixing of highly saline fluids with less saline waters of marine isotopic composition, (4) fault-controlled upward movement of warm saline Sr-87-enriched groundwater from the Paleozoic bedrock into the overlying Late Cretaceous limestone aquifer, (5) water-rock interaction of ascending saline groundwater with the limestone aquifer, and (6) dilution by meteoric water. For the investigated sample set, the subrecent processes of mixing of different saline groundwaters, water-rock interaction, and dilution by modern meteoric water are volumetrically predominant, so that inferences about the early groundwater-forming processes have to rely mainly on our present understanding of the geological history of the area. The results of this study have a bearing on questions related to the timing and origin of Pb-Zn and strontianite mineralizations within and in the periphery of the MCB, and are of direct interest to the small, but vibrant, salt-water spa industry in the area. (C) 2002 Elsevier Science Ltd. All rights reserved.