Mineralogy and spectral reflectance of soils and tailings from historical gold mines, Nova Scotia

Gold was mined in 64 districts in southern Nova Scotia between 1861 and the early 1940s, followed by limited, intermittent production up to the present. There is extensive dispersion of arsenic-and mercury-bearing mine tailings in the receiving environment downstream from many of these sites. Elevated mercury concentrations, highest near old stamp mill foundations, occur because of the mercury amalgamation process used to extract gold until the 1940s. Arsenic, on the other hand, occurs naturally in arsenopyrite, which is associated with the gold-bearing quartz veins and host rocks. Tailings are composed of fine sand-to silt-sized quartz, feldspar, illite and chlorite, and represent the primary rock-forming minerals in the metasedimentary host rocks of the Cambro-Ordovician Meguma Supergroup. Carbonate and sulphide minerals occur in minor to trace amounts, along with secondary minerals such as scorodite (FeAsO4 center dot 2H(2)O). The extent of tailings dispersal can be mapped through hyperspectral remote sensing methods, as these major mineral components provide an identifiable spectral signature through visible, near infrared and short-wave infrared regions. This paper examines the mineralogy of soils, tills and tailings in the Upper and Lower Seal Harbour gold districts of Nova Scotia. Ground-truthing of space-borne hyperspectral data demonstrates the potential for remote mapping of the spatial extent of these historical mine wastes.