The role of stable isotopes, particularly 37C1 and 81Br, in groundwater evolution in crystalline and sedimentary rocks

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The origin and evolution of highly saline fluids in crystalline and sedimentary rock environments continues to be a highly debated subject among many geoscientists. The crustal evolutionary aspects of this research have significant impacts on geological issues as diverse as paleoclimate/paleohydrology, evolution of ore deposits and applied research such as the long term effectiveness of nuclear waste repositories. The driving forces behind continued research in water/rock interaction studies are (a) the ongoing interest world-wide in the geochemical and hydrogeological nature of the groundwater environment to be expected near a radioactive waste repository, and (b) the scientific aspects of the geochemical reactions associated with low temperature crustal evolution. Detailed site investigations will be conducted underground at mine sites in Canada and Scandinavia to sample fluids, gases and fracture infilling minerals. Many of the chemical controls on the evolution of fluids and gases have been previously described, but a large amount of information on cold climate recharge and the recognition of such fluids is still necessary. The use of secondary fracture filling mineral phases to determine paleofluid composition and paleotemperatures is an important aspect of these studies. As well, large research projects and research sites in Greenland and Axel Heiberg Island adjacent to continental ice sheets are being used as proxies for extensive ice age paleo conditions over North America and Scandinavia. Boreholes and natural springs provide access to groundwaters and fracture minerals to observe geochemical and hydrogeological conditions in these environments. Finally, new analytical procedures and applications of stable isotopes of Cl, Br and Ca along with Sr and other widely used stable isotopes allow the research group a unique opportunity to add significantly to our knowledge of crustal fluids.