Horses for (conductive) courses: DHEM and DHMMR

Abstract

A test drillhole magnetometric resistivity (DHMMR) survey has recently been carried out at a nickel prospect in Western Australia to compare the effectiveness of this relatively new method with that of drillhole electromagnetics (DHEM), which is routinely used for nickel sulphide exploration. The DHMMR clearly defined a zone of shallower matrix sulphides which were only weakly detected by some of the earlier DHEM surveys (and then only in hindsight). In contrast, the DHMMR only weakly responded to the massive sulphides that had been well defined by the DHEM. Thus, these two methods can be considered, at least for this type of target, as complementary methods, with the DHMMR responding well to bodies with a relatively large cross-sectional area and DHEM to bodies of much larger long-sectional area. Although usually of lower grade, the matrix sulphides at this prospect, with their larger cross-sectional area and hence bigger tonnage, may make a more attractive economic proposition.