Using airborne magnetic and electromagnetic data to monitor mine tailings in Copper Cliff, northern Ontario

CIM Bulletin, Vol. 94, No. 1056, 2001

J. Shang, NRCan, Ottawa, Ontario B. Morris, McMaster University, Hamilton, Ontario P. Howarth, University of Waterloo, Waterloo, Ontario

Tailings from the nickel refinery in Copper Cliff, Ontario, consist of fine silicates mixed with a variable amount of conductive and magnetic minerals mainly associated with sulphides and iron oxides. Subsequent oxidation of sulphide-rich phases within the tailings results in the formation of an acidic leachate that may contain significant concentrations of trace metals. Mapping the spatial distribution of regions of higher sulphide concentration therefore provides insight into the distribution of the acid-generating potential within the tailings. Electrical conductivity is constrained by two parameters Ñ the concentration of metallic sulphides and the ionic concentration of acid in groundwater. Magnetic susceptibility is directly related to the pyrrhotite and magnetite content. It is proposed that combining information derived from airborne electromagnetic and magnetic surveys can provide an indication of metallic sulphide distribution. Preliminary investigations of airborne electromagnetic and magnetic data acquired concurrently over the sulphide-rich Copper Cliff tailings site reveal that the