Noble gases in Canadian Shield groundwaters from the Con Mine, Yellowknife, NWT

Abstract

Dissolved noble gas concentrations in Canadian Shield groundwaters from various depths of the Miramar Con Mine, Yellowknife, were examined for paleotemperature information and isotopic ratios. A high-vacuum stainless steel line with reactive gas gettering, isotope spike dilution and quadrupole mass spectrometer was constructed, tested and calibrated prior to sample analysis. In addition to noble gases, groundwater flow rates and formational pressures, as well as the major ions, stable isotopes and tritium values, were also measured. Data collected on flow rates and formational pressures was compared to that published by Intera Consultants Ltd. (1997). Trends indicate an almost universal decline in both parameters over the four year period, reflective of changing mine conditions. The major ions in solution are represented primarily by Ca, Na, Cl, SO 4, and HCO3, at shallow depths. In the deep subsurface, Ca, Na, and Cl become the dominant species, forming a Ca-Na/CI brine characteristic of the Canadian Shield that reaches a TDS of 304 g/L. (Abstract shortened by UMI.)