A geophysical and geotechnical study to determine the hydrological regime of the Central Manitoba gold mine tailings deposit

Abstract

Extraction of gold from quartz–carbonate shear zones has left a barren deposit of tailings at Central Manitoba mine, which remains unchanged after 70 years. In this study, the shape of the basin, the groundwater and surface water flow regime, and the electrical conductivity of the tailings have been delineated using a combination of geotechnical, geophysical, and geochemical techniques. Groundwater and surface water flow from the north–south-fractured bedrock outwards to the east and west. A component of upward groundwater movement in the deposit is due to evaporation in hot, dry summers, limited recharge from precipitation, and the tailings basin being a local groundwater discharge zone. Electromagnetic surveys indicate that the thickness of the tailings and underlying peat bog material increases from ∼1 m at the south of the tailings to ∼5 m at the north. The surveys provided an effective way of mapping the spatial distribution of acidic pore fluids and associated increased salinity. Zones of acidification, occurring mainly on the south side of the tailings, support the hypothesis that acidification is due to differential settling during the initial discharge of carbonate and sulfide minerals.

Geophysical delineation of acidity and salinity in the Central Manitoba gold mine tailings pile, Manitoba, Canada

“…The results (Fig. 4) showed that the enhanced conductivity occurs within the upper meter of the tailings and extends up to 0.5 m vertically (Sherriff et al, 2009). The zones of high conductivity are particularly prominent on steeply sloping areas at the southern side of the tailings pile.…”

“…Studies at this site (Davidson, 2005;Gupton, 2004;Gupton et al, 2004;Salzsauler, 2001;Sherriff et al, 2007Sherriff et al, , 2009) have provided constraints on the geological and geotechnical properties of the tailings and suggested its suitability for examining the ability of geophysical methods to map pH. Previous ground conductivity meter (EM38, EM31, and EM34) surveys at the tailings identified several areas of enhanced conductivity that were interpreted to correspond to zones of acid mine drainage (Sherriff et al, 2009). In the present study EM31 and DC-resistivity measurements were made along a carefully selected profile through a zone of enhanced conductivity.…”

“…The geochemistry of the tailings and process of AMD production is discussed in more detail in Sherriff et al (2007Sherriff et al ( , 2009). Oxidation of pyrite (FeS 2 ) is the main mechanism for acid production:…”

“…4). The geophysical surveys took place over a 1.5 ha area of the tailings (Sherriff et al, 2009). Within this area, the zones of highest conductivity correlated with increasing acidity as measured in relatively sparse locations at 25 cm depth (Sherriff et al, 2007).…”

Using Geoelectrical Imaging to Recognize Zn-Pb Post-Mining Waste Deposits

“…For the same purpose Lghoul et al applied a combination of ERT and seismic refraction tomography in Morocco [21], and HuotariHalkosaari and Lerssi [22] a combination of ERT and transient electromagnetic methods (TEM) in Finland. The electromagnetic methods capacitate fast geophysical reconnaissance of the polluted area [23]. Cabala et al [1] obtained promising results in distinguishing clear sands and two kinds of waste based on the results of EM measurements in the Olkusz region.…”