Investigation of a graphite deposit with drone-based semi-airborne electromagnetics
Year: 2026
Type: article
Abstract: ABSTRACT The shift toward renewable energy sources necessitates a stable supply of essential raw materials and calls for advanced, noninvasive techniques to explore deep-seated mineral resources. In the past few years, the semi-airborne electromagnetic (SAEM) method has been further developed to efficiently investigate the subsurface down to 1 km depth. The Kropfmühl graphite deposit in Lower Bavaria comprises high-grade metamorphic graphite-bearing gneisses. Although mining reaches depths of 200 m, the western extent of the deposit remains unknown. To verify the western extension and continuity of the Kropfmühl graphite deposit, a drone-based SAEM survey was conducted, combining a dense spatial sampling of magnetic fields using a UAV (Unmanned Aerial Vehicle) system and a high signal strength with controlled-source electromagnetic transmitters on the ground. The survey area spanned approximately 1.8 × 2.5 km2, using four galvanically coupled dipole transmitters and multiple UAV flights over 4 days. To increase depth sensitivity, a total-field magnetometer alongside a three-component induction coil system was used. To derive a reliable subsurface conductivity model, a 3D inversion of multifrequency, multisource SAEM data from vector and scalar magnetic field data was conducted. The obtained model revealed three east–west trending conductive anomalies, interpreted as graphite-rich zones. The main anomaly (C1), 200 m south of the active mine, indicates possible fault-controlled displacement. Borehole resistivity logs and available helicopter-borne electromagnetic data correlate well with conductive zones and graphite enrichment. The results highlight the potential of UAV-based SAEM to image complex subsurface structures. The method delivers high-resolution, cost-effective data acquisition, with a high data coverage and only the transmitters requiring ground installation. This renders the method suitable for imaging geologically complex settings in hard-to-access areas.
Source: Geophysics
Institution: LIAG Institute for Applied Geophysics
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W7124882215