Drilling of EM Anomalies Caused by Overburden

CIM Bulletin, 1973

W. J. SCOTT, with Electrical Methods Section, Resource Geophysics and Geochemistry Division, Geological Survey of Canada, Dept. of Energy, Mines and Resources, Ottawa, Ontario D. C. FRASER, Chief Geophysicist, Geophysical Engineering and Surveys Limited, Toronto, Ontario

Airborne electromagnetic surveys were flown during 1965 in the Moose River area of Ontario. The systems used were INPUT Mark II and the Canadian Aero Otter. Anomalies indicated by both systems were located on the ground with vertical-loop EM. Two such anomalies were drilled, with no explanation being found in the bedrock geology. Subsequent seismic, resistivity and gravity surveys indicated that the sources of these anomalies lay in the overburden. Current work in the similar geological environment of the Winisk River area has shown that comparable AEM anomalies can still be misleading. The lesson to be, learned from these experiences is that additional geophysical work can help to resolve doubtful cases before drilling decisions are made.
Keywords: bedrock, Geological Survey of Canada, geophysics, overburden, resistivity, Canadian, Data, DIGHEM, Drilling, Geophysics, Overburden, Resistivity, Survey, Surveys, Systems