Smart solution to a sticky problem: in-mine clay mapping using high-resolution geophysics

Abstract

Within the Mesa J pisolite iron ore mine, clay is distributed unevenly and often forms pods and channels less than 10 m in width. The mine resource model, based on 50 m ´ 50 m spaced drilling, has been unable to accurately delineate the clay for scheduling and mining purposes. Therefore, alternative methods for mapping the clay-contaminated ore were sought. Predictive clay mapping will significantly reduce production costs at Mesa J through improved selective mining practices, more accurate scheduling, reduced wear on mining equipment and minimising the need for maintenance of haul roads and ramps. High lateral resolution electromagnetic (EM) surveying using the Geonics EM31 tool can quickly delineate the extent and orientation of the clays. A block model based on the interpretation of the EM data accurately predicts the volume and tonnage of ore and waste material. While rip-line mapping, infill drilling, ground penetrating radar and gravity can delineate clay to varying degrees of success, none were as efficient as EM31.