Palaeohydrogeology: A methodology based on fracture mineral studies

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• 作者：Eva-Lena Tullborg ; Henrik Drake ; Bjö ; rn S ; strö ; m
• 关键词：Musculoskeletal symptoms ; Age management ; Workload– ; strain analysis ; Automotive industry ; Assembly work
• 刊名：Applied Geochemistry
• 出版年：2008
• 期刊代码：5_08832927
• 类别：ce
• 出版时间：July 2008
• 卷：23
• 期：7
• 页码：1881-1897
• 文件大小：959 K

摘要

Two sites on the east coast of Sweden (Forsmark and Laxemar/Simpevarp) are currently being investigated as potential geologic hosts for a deep repository isolating high-level nuclear waste. In this paper, a methodology for fracture mineral studies is suggested with focus on the variation in depth of the fresh/saline water interface and location of the redox front in the bedrock. The most commonly precipitated fracture minerals in crystalline rocks are chlorite, calcite, quartz, K-feldspar, Ca–Al-silicates like epidote, prehnite and laumontite, sulphides and Fe-oxides. Of these, calcite is the mineral best suited for palaeohydrological studies since it precipitates during a wide range of conditions including low-temperature conditions during the Pleistocene and Holocene epochs. Sulphides and Fe-oxides/hydroxides provide information on the position of the redox front. In order to carry out palaeohydrological studies, a number of prerequisites are required such as; high quality drill core material, geological knowledge of the sequence of fracture mineralizations; the post-glacial (Holocene) evolution in the area; high quality groundwater chemistry, including stable isotopes; and a conceptual model of the hydrogeochemistry that is to be tested. The choice of methods used here is based on the fact that both the Forsmark and Laxemar/Simpevarp sites are situated in Palaeoproterozoic crystalline rocks with reactivation of fractures over at least 1.5 Ga, and they have been exposed to glaciations/deglaciations and transgressions/regressions of the Baltic Sea during the Quaternary. This has resulted in a palaeohydrology with a range of groundwaters of quite different chemistry and stable isotopic composition. The suggested scheme for solving the variation in depth of the fresh/saline water interface focuses on fracture calcite. It includes a step-by-step procedure with;

(1) Initial δ¹⁸O and δ¹³C, analyses and complementary petrographic studies of thin sections and crystal morphology followed by