Geological 3D-modeling of the Virtasalmi Cu deposit in eastern Finland

Modern computing power and advanced 3D-modeling software have made the modeling of geological, geophysical, geochemical and structural data a widely used method in active mine production as well as in brownfield exploration, where it can be used for visualization, planning and target generation. In this study, the Paleoproterozoic Cu-dominated VMS deposit of Virtasalmi and related mine were modeled to produce the first modern 3D-model of the deposit and to test the accuracy of the digitized historical datasets. A total of 239 drill holes from the Virtasalmi mine area were used, from which the collar locations, downhole surveys, lithological logs and geochemical assays were digitized and added to a geological database. Around 3000 Cu analyses were utilized for modeling of the general low-grade (0.2–0.7 wt.% Cu) and high-grade (>0.7 wt.% Cu) mineralization solids. The results show that before the mining operations were started, the Virtasalmi deposit consisted of several high-aspect-ratio lenses, which had a combined strike length of ~626 m near the surface and extended up to ~344 meters below the surface. The performed unofficial resource estimation indicates that the area contained a total of 4.83 Mt of mineralized material, of which ~3.51 Mt was low-grade mineralization and 1.32 Mt high-grade mineralization. Based on the model, roughly 500 000 tons of mineralized material is still left unmined in the Virtasalmi mine area.