UAV Aeromagnetic Survey of the Valimyaki Complex (Northern Ladoga Area): First Estimates of the Buried Intrusion Structure

The Valimyaki intrusive complex is an early-orogenic gabbroid body of the Northern Ladoga region, composed predominantly of pyroxenites, gabbros, and diorites and historically known for titanium-magnetite mineralization concentrated in its near-surface marginal zones. At present, no reliable three-dimensional model of the Valimyaki massif exists, and its investigation is significantly constrained by difficult terrain accessibility. Multi-altitude UAV-based aeromagnetic surveying provides new opportunities for obtaining information on the deep structure of the intrusive complex. In 2023–2025, a series of surveys was carried out over the Valimyaki massif and Mäkisalo Island, the two main known surface expressions of the Valimyaki complex. As a result, maps of the anomalous magnetic field were obtained at several flight altitudes, enabling direct calculation of the vertical magnetic field gradient. The multi-level dataset considerably expanded the interpretational potential and the application of various field transformation and inversion techniques, including the equivalent-source method. Integrated analysis of the aeromagnetic data using spectral and mounting inversion methods yielded a consistent model of both deep-seated and near-surface magnetic sources, refining the internal structure and spatial extent of the Valimyaki massif.