Geochemical evolution of pore waters in the Rotliegend (Early Permian) of northern Germany

Abstract

The distribution of early cements within Permian Rotliegend sandstones closely resembles cementation patterns within modern playa lake basins. The isotopic compositions of eogenetic cements in the thick Rotliegend sequence of Germany show continental signatures typical of minerals precipitated in such an environment. Carbon, sulphur and strontium isotopic ratios of many Rotliegend cements which formed during burial suggest formation from a mixture of Rotliegend fluids and waters from the overlying Zechstein evaporites. A two-component mixing model for the evolution of Rotliegend pore waters indicates that the isotopic signatures in these cements may result from the introduction of only minor amounts of Zechstein fluid (< 10%). Cements from most wells in Germany show almost no Zechstein influence on precipitation. Significant influx of Zechstein fluids is noted only in wells lying on or near uplifted horst blocks, suggesting the lateral flow of fluids from the Zechstein into the Rotliegend.