Origin of formation waters of S-E parts of the Bohemian Massif and the Vienna basin |
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| Institution: | 1. Institute of Biology and Environmental Sciences, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Str. 9-11, 26111 Oldenburg, Germany;2. Institute of Chemistry and Biology of the Marine Environment, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Str. 9-11, 26111 Oldenburg, Germany;3. Helmholtz Institute for Functional Marine Biodiversity Oldenburg (HIFMB), Ammerländer Heerstraße 231, 23129 Oldenburg, Germany;4. Centre of Excellence for Coral Reef Studies and School of Marine and Tropical Biology, James Cook University, Queensland, Australia;1. Department of Earth and Environmental Sciences, University of Milano-Bicocca, Italy;2. Department of Earth Sciences, University of Pisa, Italy |
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| Abstract: | Deep formation waters were sampled from boreholes on the S-E slopes of the Bohemian Massif. They are Na ClHCO3 waters with TDS in the range 6–52 g L?1. Some of them are associated with gas and oil deposits. The waters are rich in Br and I and their δDandδ180 isotope compositions vary from ?12 to ?77‰ and + 4.6 to ?10‰ respectively.The processes of concentration and dilution have been discussed based on deuterium and conservative element contents of the waters. Three regional groups can be identified in the plots Br vs I and Cl vs I: the Vienna Basin samples (VB), southern (S) and northern (N) flanks of the Bohemian Massif (BM). The VB samples have as an end member brackish water with about 7 g L?1 Cl (about 40% marine component) enriched in Br and I. This water has been later diluted by meteoric water of recent isotopic composition. Only 3 VB samples can be considered as derived from the dissolution of evaporites. The salt content of the S and N end members is very close to or higher than sea water with an isotopic composition similar to the brackish water. Subaerial evaporation of diluted sea water is suggested as the process increasing salt content. The evaporative enrichment of primary brackish solution can be estimated from extrapolation of Cl vs I and Br vs I plots to zero I (about 25 mg L?1 Br and 6 g L?1 Cl for the southern flanks of the BM). Evaporated solutions were later diluted by meteoric waters with δD in the range from ?50 to ?80‰ (southern flanks) and about ?80‰ (northern flanks). |
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