Mapping the 3D lithofacies architecture of a VMS ore system on a curvilinear-faulted grid: A case study from the Flin Flon mining camp, Canada

Abstract

The 3D lithofacies architecture of the thrust-imbricated Paleoproterozoic 85.5 Mt Flin Flon volcanogenic massive sulfide (VMS) ore system, Trans-Hudson orogen, Canada has been mapped in 3D using a numerical grid modeling methodology. This methodology is based on the Structural Knowledge Universal Approach (SKUA®) modeling work flow developed for modeling hydrocarbon reservoirs. One of the major advantages of applying this methodology to mineral exploration is that it allows exploiting knowledge on the structural setting of the ore deposit without the need to determine all kinematic constraints that would be required for a full 3D balanced restoration. The work flow proceeds by modeling the volume of the thrust-repeated mine horizon on a curvilinear faulted grid that is conformable to the enveloping geological structure and that includes discontinuities to model fault offsets. It then uses a coordinate transformation to partly remove the influence of geological structure on Euclidean distance-based geostatistical estimations. It subsequently applies the inverse of this coordinate transformation to represent the interpolated or simulated lithofacies distribution in the finite deformed state. Randomized validation experiments show that the geostatistical analysis resulted in an estimated overall 74% accuracy of the predicted lithofacies classes over the grid. The lithofacies grid models provide insight into the post-depositional deformation history of the ore system and the rifted volcanic arc setting in which the Flin Flon massive sulfide ore was deposited. The lithofacies grid models also serve as stratified containers for generating lithochemical property models that can be used for spatially characterizing ore-forming processes, such as hydrothermal alteration and ore metal zoning.