3D reconstruction of volcanic and ore-forming environments of a giant VMS system: A case study from the Kidd Creek Mine, Canada

Abstract

The Archean North Rhyolite is a bimodal suite of rocks located directly northwest of, but structurally separate from, the Kidd Creek volcanogenic massive sulfide deposit, which has produced 140.4 million tonnes of ore grading 2.29 wt% Cu, 6.15 wt% Zn, 0.22% Pb and 86.2 g/t Ag. The stratigraphy of the North Rhyolite is identical to that of the Kidd Creek mine consisting, from oldest to youngest, of ultramafic flows, aphyric rhyolite, quartz porphyritic rhyolite, and basalt flows, divisible into a “low TiO2” basalt unit (<1.55 wt%) and a “high TiO2” basalt unit (>1.55 wt%), with minor interflow graphitic argillites.The North Rhyolite is interpreted to be the folded continuation of the Kidd Creek mine stratigraphy. Similar alteration patterns in the North Rhyolite and the Kidd Creek mine stratigraphy, as well as significant copper and zinc values within the thickest portions of rhyolite domes and ridges of the North Rhyolite, suggests the potential for economically significant mineralization within the North Rhyolite stratigraphy. Correlation between alteration, mineralization and the rhyolite domes and ridges demonstrate the volcanic structures through which the rhyolite was extruded also acted as hydrothermal fluid pathways and were controlling structures in ore formation.A 3D volcanic reconstruction, showing the paleo-seafloor at the time of ore-formation, illustrates that the rhyolite flows of the North Rhyolite were emplaced into the same subsidence structure as the strata of the Kidd Creek mine area. This 3D model, generated by translating complex geological data acquired through core logging and underground mapping indicates the volcanic setting of, and ore-forming environment at, Kidd Creek is much larger than previously thought and provides new spatial data that can be used in exploration targeting.