87Sr/86Sr Ratios in Thermal Water from the Southern Upper Rhine Graben, Germany

Abstract

The present study of thermal water from Bad Bellingen, Steinenstadt, Bad Krozingen, Mooswald, and Weinheim located in the southern part of the Upper Rhine Graben was undertaken in the framework of a multidisciplinary hydrogeochemical research project and concerns ⁸⁷Sr/⁸⁶Sr isotope investigation. The aquifer lithologies of thermal waters are Triassic Upper Muschelkalk, Jurassic Hauptrogenstein and Tertiary Miocene sediments. The ⁸⁷Sr/⁸⁶Sr ratios (N=9) range from 0.70912 to 0.71096. The Sr isotopic composition of thermal water is controlled by the fault system of the Rhine Graben rift. Fluids from Upper Muschelkalk aquifers ascent along the Eastern Boundary fault zone. The deep-water ascent most likely reaches into the crystalline basement.