Barrick Gold – Hemlo Mine, Ontario, Canada

The Hemlo property is in the south-central part of the Hemlo greenstone belt (HGB) between the Pukaskwa batholith and the Cedar Creek stock, near a change in direction of a structural trend. The area hosts volcano-sedimentary lithotectonic units which includes various metamorphic and volcanic rocks. Gold mineralization in this area is associated with a contact between porphyritic felsic metavolcanics and intermediate to felsic volcaniclastic sediments, making it essential to locate this contact. Although the area is already rich in data, exploration is challenging due to complex geology and variations in ore distribution, thus the need for advanced exploration methods to pinpoint mesothermal orogenic gold deposits.

Our solution – Unmanned Aerial Vehicle (UAV) magnetic surveying

From 2019 to 2021, Abitibi Geophysics was commissioned to conduct several UAV magnetic surveys over unexplored areas of the HGB to map faulting structures and lithological units that may host gold mineralization.

Magnetic surveys are common in mineral exploration, mainly because they are sensitive to lithologic and structural variations in igneous and metamorphic terranes that commonly host mineral deposits. In addition, the method can be readily applied using drones for aeromagnetic surveys, allowing for large areas to be covered rapidly and efficiently. With AeroVision® Drone-MAG, Abitibi Geophysics offers a high-end geophysical survey with unmatched resolution.

Results

In phase 1 and 2 of the Hemlo Blackfly zone project, the interpretation and inversion of the AeroVision magnetic data, and their integration with the known geology, improved the understanding of the geological setting and provided a detailed structural map of the study area. Integrating data from phase 3 of the project and interpreting the combined drone magnetic data from all three phases of the project further improved the understanding of the geological setting of the Hemlo Western Extension Project. Analysis of the total magnetic intensity and its normalized derivatives show that the geology can be understood with delineation of magnetic axes and the recovered subsurface magnetic susceptibility.

CET* unsupervised predictive target analysis was performed using the UAV magnetic data. Two target zones in phase 2 and three to four favourable targets in phase 3 were identified. Lithogeochemical prospecting should be carried out over these targets to prioritize exploration targets.

*Clustered Ensemble of Trees