HR: 1340h
AN: H23F-1485    [Abstracts]
TI: Strontium Isotopes as a Geochemical Tracer for the Evolution of Brines in Permian Evaporite Deposits of the Central European Basin, Germany
AU: * Klaus, J S
EM: jklaus@gwdg.de
AF: Geoscience Center of the University of Goettingen, Goldschmidtstr. 3, Goettingen, 37077 Germany
AU: * Klaus, J S
EM: jklaus@gwdg.de
AF: K+S Aktiengesellschaft, Bertha-von-Suttner-Str. 7, Kassel, 34111 Germany
AU: Hansen, B T
EM: bhansen@gwdg.de
AF: Geoscience Center of the University of Goettingen, Goldschmidtstr. 3, Goettingen, 37077 Germany
AU: Beer, W W
EM: wolfgang.beer@k-plus-s.com
AF: K+S Aktiengesellschaft, Bertha-von-Suttner-Str. 7, Kassel, 34111 Germany
AB: Seepages of formation water into salt mines bear the potential of flooding. This hazard poses a high risk for the salt mining industry all over the world. Recent tests of water draining drillholes into the enclosing bedrock of a salt dome in northern Germany have been performed. These tests show good results in reducing the inflow rate of the formation water into the mine openings. The risk of weakening the salt flank due to drilling activities increases the potential for inflow. Hence, the specific source of the intrusion has to be localized to minimize the number of drillholes. Former studies determined the stable isotopes δD and δ¹⁸O to be the most suitable isotopic tracers for concentrated saline solutions. We have applied Sr isotopes as an additional tool to further define the source. Sr isotope compositions and concentrations will be monitored over the following years to detect possible time-dependent fluctuations. Recent preliminary Sr analyses of one brine inflow in a potash mine in the upper Permian Zechstein series, Germany, show a trend for Sr to be extracted from detritus of salt clay layers, which are intercalated in a sequence of rock salt with anhydrites. This clayey material shows the highest ⁸⁷Sr/⁸⁶Sr ratios of the whole sequence, however, still lower than the formation water which has been discharged from the superimposed Triassic (Buntsandstein). We assume for these preliminary data that during migration, the solution increases its moderate Sr concentration by first solving the anhydrite layer at the margin of the salt dome. The saline solution then drains through the rock salt sequence. In this part, mainly the salt clay layers seem to be leached, probably due to the very low pH of the brine. The final solution has a Sr concentration that is about 3.5 times higher than in the formation water, but the ⁸⁷Sr/⁸⁶Sr ratio is almost the same. These preliminary data suggest that the Sr isotope composition is rather affected by the salt clay detritus than by halite or anhydrite. Therefore, we may be able to further delimit the source regions of intruding formation waters.
DE: 1040 Radiogenic isotope geochemistry
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: Fall Meeting 2005