Comparison of geophysical inversion programs run on aeromagnetic data collected over the Highland Valley Copper district, British Columbia, Canada

As part of the Natural Sciences and Engineering Research Council of Canada–Canada Mining Innovation Council (NSERC-CMIC) Mineral Exploration Footprints project, three selected magnetic inversion programs (VPmg, MAG3D and VINV) were used to process the same aeromagnetic data set from the Highland Valley Copper district, British Columbia, Canada. In each case, the inversion was constrained using available geological and physical property constraints. Analysis of magnetic susceptibility data suggests that the observed aeromagnetic anomaly pattern includes effects associated with boundaries between lithological units and fault zone alteration resulting from removal of magnetite. Susceptibility contrast associated with alteration is greater than that associated with changes in lithology. The inversions seek to define the three-dimensional geometry of geological boundaries and the fractures are treated as high-frequency noise. Results from the three programs, although similar, are sensitive to attributes of the different algorithms. VPmg emphasises physical boundaries between geological domains, MAG3D produces a more blurred image, whereas VINV produces reasonable geological images. Computer performance using the different programs ranges from reasonable for VPmg to computer intensive for MAG3D and VINV. Differences in the results reflect the inherent uncertainty in producing inversions from “noisy” aeromagnetic data.