Successful Application of Electro-Magnetics in the Reid Brook Zone: Targeting Economic Needles in a Highly Conductive Haystack

Abstract

Recent drilling in Voisey?s Bay has uncovered significant wallrock mineralization in what was before thought to be a sub-economic occurrence of sulphides within the Reid Brook Dyke. Although technically disseminated, the sulphides within the dyke are electrically well connected and can act as a single conductor of kilometres in size and with a conductance of thousands of siemens. Using the standard transmitting frequency of time, we were unable to discriminate the conductance of the disseminated from the massive sulphides. In 2003 we revisited the area with BHEM transmitting at 1Hz with more success. From the low frequency data, we saw evidence for the first time of conductive features that did not coincide with the dyke orientation. In 2004 we began to utilize the superposition of two data sets from two separate transmitting loops to adjust the angle of the inducing field and null couple to these in-dyke disseminated sulphides. In doing so, we obtained greater precision on the orientations of the conductors, and were able to discriminate between in-dyke conductivity, and wall rock related conductivity. We are now integrating this method with other structural techniques to further develop the deposit model.