Drone-Based Aeromagnetic Survey of Kodal, Norway: Efficiently Mapping Mineral Deposits

Abstract The Kodal deposit, located in the Permian Oslo Rift of southern Norway, hosts Fe-Ti-P mineralization with apatite and magnetite as the main ore minerals. In addition to phosphorus, an essential nutrient used extensively in the fertilizer industry, apatite contains rare earth elements (REEs), Critical Raw Materials used in manufacturing permanent magnets. The deposit represents a possible source of both fertilizer components and Critical Raw Materials as defined by the European Union. The presence of magnetite within the ore body generates a distinct magnetic signature relative to the surrounding monzonite and syenite host rocks, which are dominated by alkali and potassic feldspars. High-resolution aeromagnetic data acquired with a multipurpose unmanned aerial vehicle (UAV; i.e., drone) equipped with a three-component fluxgate magnetometer provide a detailed characterization of the magnetic anomaly. A discrepancy between the measured magnetic anomaly amplitude and the magnetic susceptibility of collected rock samples indicates a dominant contribution from remanent magnetization, whose orientation partially cancels the induced magnetization. This effect results in a lower-than-expected bulk magnetization at the deposit scale, despite high local magnetization values. Incorporating measured remanent magnetization is essential to accurately reconstruct the ore body’s 3D geometry from drone-based magnetic data. Operational challenges encountered during drone deployments are also identified, along with proposed solutions to improve the robustness and repeatability of drone-based magnetic surveys.