2004 Denver Annual Meeting (November 7–10, 2004)

Paper No. 3
Presentation Time: 8:00 AM-12:00 PM


LAMBIE, Katherine1, FRAPE, Shaun1, STOTLER, Randy2, RUSKEENIEMI, Timo3 and HOBBS, Monique4, (1)Earth Sciences, Univ of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada, (2)Earth Sciences, Univ of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, (3)Geol Survey of Finland, SF-02150, Espoo, Finland, (4)Ontario Power Generation, 700 University Ave, Toronto, ON M5G 1X6, Canada, kelambie@scimail.uwaterloo.ca

Fractures in crystalline rock environments are important in radioactive waste disposal because they are the dominant pathways for radionuclide migration. Fracture minerals are of interest for determining the long-term stability of a repository site for disposal because they record paleo-fluid chemistry. In this study stable isotope analyses (δ13C and δ18O) were conducted on calcite samples, one of the dominant fracture filling minerals found in the Canadian Shield, obtained from boreholes drilled at the Lupin mine site in Nunavit, Canada. Measured δ13C and δ18O signatures ranged between –25.13 to + 29.53 ‰ PDB and –37.84 to –5.5‰ PDB, respectively. These values exceed the normal calcite geochemistry range that one would typically expect in a Shield environment (δ13C –20 to +10‰, δ18O –30 to –4‰ PDB). The δ13C values are among the heaviest recorded, suggesting a possible hydrothermal origin. The fluid inclusion experiments were conducted to determine the origin of water from which the calcite precipitated. Chemical analyses of crushed and leached rock samples coupled with the isotopic results, aid in determining paleo-hydrogeological processes that have occurred within this site, ultimately assessing rock performance for the long-term suitability for radioactive waste disposal.