Ground geophysical surveys over the McClean uranium deposits, northern Saskatchewan

"Geophysical test surveys were conducted with various methods (EM, lP, gravity and magnetic) over the McClean uranium deposits of the Canadian Oxy- lnco Joint Venture. The result s were assessed to judge the contribution each method might make toward further discoveries of graphite-associated uranium occurrences.The best drill targets have proven to be discontinuities in graphitic conductors and locations where the tatter are intersected by fracture zones in the Athabasca. The tests demonstrated that the preferred combination of geophysical survey s is horizontal loop EM to locate graphitic conductors in the basement and VLF-EM to locate the fractures.IntroductionThe discoveries of the McClean North and South uranium deposit s (Fig. 1) are essentially geophysical successes resulting from drilling MaxMin delineations of INPUT airborne electromagnetic responses (Saracoglu et al., 1983). After the initial discovery in 1979, various geophysical methods, techniques and instruments were employed to test their effectiveness in this environment and to guide exploration for other deposit s of a similar nature in the remainder of the 260 km2 property.The McClean uranium deposits lie below 150 m to 180 m of overburden and Athabasca Group. Radioactive signatures might be expected; however, the Athabasca Group acts as a barrier to radioactive emanations. Fortunately, the uranium mineralization is associated with graphite in the crystalline basement. Prior drilling of ground electromagnetic anomalies confirmed that EM surveys could locate and out line basement graphitic conductors. However, as there were many anomalies, most of which could not reasonably be expected to be associated with uranium , there was need to identify additional parameters, related to mineralization, which could be detected geophysically and used to narrow the search."