Mineral exploration under deep cover: Improving the effectiveness of ZTEM surveys for porphyry copper exploration in the Canadian cordillera

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As the discoveryrate of new mineral deposits diminishes in mature exploration regions such as the Cordillera of western Canada, exploration is increasinglyfocusing on harder-to-find deposits that are either covered by younger geological formations, or form extensions of known deposits at depth.The most common tools used for this type of subsurface exploration are airborne geophysical methods, such as electromagnetic (EM) and magnetic surveys. Airborne EM has proven particularlyeffective in identifying ore-bodies consisting of metal-sulfide minerals, because of their high electrical conductivityrelative to many other common rocks and minerals. Combined with other methods such as aeromagnetic surveys, EM surveys have been successfullyused to locate mineralized zones within exposed ore-forming systems. However, where the target is deeplyburied or covered byyounger rock sequences, these geophysical signals cannot currentlybe uniquelyinterpreted, with the result that exploration companies must expend significant time and moneyto drill targets that commonlyprove to be barren.Inan attempt to provide more constraints on the interpretation of deep EM surveys, we propose to evaluate andimprove the effectiveness of one particular airborne EM method, ZTEM (Z-axis Tipper Electromagnetic survey), which is widelyused for deep (down to 2 km) mineral exploration and for exploration in covered terrains. ZTEM is a proprietarytechnique of Geotech Ltd. We will do this byusing a large ZTEM database made available to us byour industrypartners, which we will calibrate over known mineral deposits. We will then use these calibrations to test the abilityof the method to uniquelyidentifymineralized zones within partiallyexposed or partiallyexplored deposits. Finally, we will evaluate the method's potential to identifynewmineralization targets in completelyblind settings, for example beneath younger cover rocks.