Bromine and stable isotopic profiles of formation waters from potash mine-shafts, Saskatchewan, Canada

Sixty-five inflow samples from access shafts were collected at three separate potash mines in order to construct three 1000 m deep hydrochemical profiles. Bromine concentrations, and δD and δ18O stable isotopic compositions, increase with depth in each case. Measured isotopic ratios have not changed in 15+ years since the mine-inflows were first sampled, implying little change in the hydraulic regimes at the mines over time. However, the bromine concentrations are typically a factor of five lower than previously reported. Newer analytical techniques have improved the accuracy, precision and resolution of the hydrochemical profiles. Results indicate that the salinity of the inflow waters originated as mixtures of evaporatively concentrated seawater, meteoric water, and brine derived from halite dissolution. Extremely concentrated brines (TDS > 525 g/L) were found at the Cory and Allan potash mines some 55 km apart, but their role in the paleohydrogeology of the basin remains uncertain.