Comparison of Magnetic-Susceptibility Models From UAV-borne and Ground Measurements in Enåsen Area, Sweden

Sammanfattning: Mapping anomalies in the Earth’s magnetic field is one method used in applied geophysics, for exploring buried structures and objects. Magnetic surveys can be ground-based or made airborne, onboard airplanes, helicopters, or unmanned aerial vehicles (UAV), also known as drones. The measurements in this project were made as part of a mapping project by the Swedish Geological Survey (SGU) in the Enåsen area in Hälsingland, central Sweden. The magnetic data were collected by SGU in the field summer of 2021. The aim of this project is to model the data from UAV-borne surveys and validate them by checking the response with the measure ground-based data collected by SGU and compare several different profiles to investigate the different results from ground-based vs. UAV-borne surveys. Two models from two different UAV flight lines were made using the software Potent, to show anomalies in the magnetic field intensity. The modelling results show a relatively good correlation between the response from the model and ground-based data. However, there are detailed variations in the ground-based data that are not resolved by the UAV data. This is partly because of the height difference and partly different sampling. The magnetic anomalies in the project area were interpreted, with the help of the modelled profiles, as being caused mainly by geological units consisting of metasedimentary rock/migmatite. These units generally dip with 30-50°, some of them containing Cuand Au-mineralizations. The dip, rock type, and magnetic susceptbilities of these units match the field data from SGU relatively well and are also backed up by SGU models of electrical resistivity from the same area.