Locating hidden palaeo-channels in the Cariboo Mining District, BC, Canada, using high resolution SkyTEM survey data

A high resolution time domain electromagnetic and magnetic survey was flown over parts of the Cariboo mining district in British Columbia, Canada, using the helicopter-borne SkyTEM system. The objective of this survey was to locate palaeo-channels which are known for their placer gold potential in this area. Assuming conductive channel fills incised in more resistive bedrock, narrow elongated conductivity features were picked from the conductivity-depth data sets. The magnetic data set was used for structural analysis. In addition, the analytical signal of the magnetic field was computed which displays narrow increased amplitudes following the course of the previously identified conductivity features. Subsequent to the integrated interpretation of the airborne geophysical data and field mapping, a reverse circulation drilling program was launched on one of the selected conductivity features which were supposed to indicate a hidden palaeo-channel. Seven boreholes were sunk, all indicating glaciofluvial sediments, mostly clay and mud with intercalated layers or lenses of pebble and gravel. As yet, the source of the analytical signal anomalies occurring over the channel fillings has not been followed up. The combined evaluation of high resolution time domain electromagnetic and magnetic data in the search for hidden palaeo-channels in the Cariboo mining district has proven outstandingly successful.