Muon Radiography and Two-Point Tomography in Mining: The St. Christoph Skarn Case Study

Muon imaging, or muography, is a novel cosmic-ray-based geophysical technique offering a non-invasive approach to visualising subsurface density variations. This study applies muon radiography and two-point tomography to the polymetallic St. Christoph skarn deposit in Erzgebirge, eastern Germany, to map ore body density, detect historical mine voids, and evaluate muographic methodologies for mineral exploration. While traditional methods like seismic, gravimetric, and electromagnetic surveys offer valuable insights, they often face resolution and geological constraints. Muography also has limitations, such as exposure time and angular coverage, but it can directly probe subsurface density contrasts using atmospheric muons, revealing concealed ore bodies and voids. Using a Multi-Wire Proportional Chamber (MWPC)-type muon telescope at two shallow underground sites, muon flux variations were measured from multiple angles. The resulting radiography and inversion tomography delineated known and previously unrecognised features, confirming incomplete historical ore extraction. These results show that two-point muon tomography provides meaningful density contrast interpretations when density variation is sufficient, detector resolution is high, and the target is adequately sized. These findings highlight the potential of muography as a non-invasive, high-resolution tool for subsurface characterisation and risk mitigation in active and legacy mining environments, where it can complement or partially replace conventional geophysical methods.