Andrea Parsons

Nova Scotia has a number of uranium occurrences within sedimentary sequences of the Carboniferous Horton Group. These occurrences pose a potential risk to human health if the uranium enters drinking water supplies. This research focuses on a uranium bearing occurrence of the Horton Group strata to establish both the nature of the uranium distribution in the Horton Group and to determine whether uranium in the strata may become chemically mobile under present day weathering conditions. The main outcrop section of interest is currently undergoing active weathering, and is located upslope from a small stream. Samples were taken from two sandstone and two siltstone layers, as well as from unconsolidated outwash material located at the base of the outcrop. The samples were analyzed to determine major, trace, and rare earth element geochemistry, and also underwent artificial weathering to determine what elements may be liberated from the rocks during weathering. Geochemical data indicate that there are differences in uranium levels in the samples, but does not indicate that levels are linked to lithology within the Formation. The highest uranium concentration is from one of the siltstones (212 ppm) and the second highest value is from one of the sandstones (109 ppm). Geochemical data also indicate that higher uranium values correspond to higher values of copper, vanadium and titanium. Positive correlations exist between uranium and copper, lead, and vanadium for the samples analysed. Values for uranium, copper, vanadium and titanium are all lowest in the sample taken from the outwash material near the stream, liberation of uranium during weathering. Water samples from artificial weathering experiments indicate that a number of elements, including uranium, are mobilized during weathering. Values for total uranium in water samples were as high as 24 µg/L, exceeding the recommended guideline for Canadian drinking water.

Keywords:
Pages: 75
Supervisor: Anne-Marie Ryan