Tridem airborne conductivity mapping as a lignite exploration method

CIM Bulletin, Vol. 73, No. 817, 1980

D.H. PITCHER, Manager, Computer Processing Department, William Jamal and Associates Ltd., Toronto, Ontario, R.B. BARLOW, Geophysicist and Chief, Geophysics/Geochemistry Section, Ontario Geological Survey, M. LEWIS, Operations Manager Scintrex Limited Toronto, Ontario

The Geophysics/Geochemistry Section of the Ontario Geological Survey initiated an aerial geophysical survey in the James Bay Lowlands, Cretaceous Basin area, District of Cochrane, Ontario. The survey was contracted to Scintrex Limited and was carried out in 1978. Approximately 8000 line kilometres of airborne electromagnetic and magnetic data were recorded.The Tridem airborne electromagnetic system was employed, mounted in a twin-engined PBY Canso aircraft. This specific Tridem system uses a vertical coaxial coil configuration and measures in-phase and quadrature components of the secondary field at 500, 2000 and 8000 Hz.The primary purpose of this survey was to map subsurface conductivities and, in particular, to search for lignite deposits. Physical property measurements show that electrical methods should detect differences in conductivity between the moderately conducting clay-lignite horizons and the less conducting clay, soil, muskeg and gravel horizons. A preliminary Tridem test survey, as well as surface DC resistivity soundings, confirmed this approach. The interpretation of the present survey data indicates that Tridem is a suitable electrical method to aid lignite exploration in the James Bay Lowlands.

Keywords: Mineral exploration, Exploration techniques, Tridem system, Airborne conductivity mapping, Conductivity, Lignite exploration, Geophysical exploration, Electromagnetic surveying, James Bay Lowlands, Moose River Basin, Onakawana area.