Geochemical and mineralogical controls on metal(loid) dispersion in streams and stream sediments in the Prairie Creek district, NWT

Abstract

The Prairie Creek district contains several types of carbonate-hosted Zn-Pb-Ag mineralization, including stratabound replacement sulphides, quartz-carbonate-sulphide veins, and classic Mississippi Valley-type. It is located in in the southern Mackenzie Mountains of northwestern Canada and within the boundaries of Nahanni National Park Reserve. The Prairie Creek district does not produce a strong geochemical signal in comparison to other mineralized areas of similar deposit types. Stream waters and sediments draining the district were sampled to determine the concentrations of Pb, Zn, Ag, As, Cd, Cu, Hg, Sb, and Se, and investigate the minerals hosting these elements, to investigate the geochemical controls on the mobility of these elements and any trends in dispersion. Results indicate that Zn and Pb are the most useful pathfinder elements, with anomalous concentrations in water downstream from Mississippi-Valley type mineralization and in sediments downstream from quartz-carbonate-sulphide vein mineralization. Zinc is more mobile than Pb, but elevated concentrations of neither element persist downstream of the metal source. Microanalytical examination of silt sediments indicate that Zn and Pb are associated with goethite and hematite, confirming active chemical weathering in this subarctic alpine environment.