Selenium and tellurium resources in Kisgruva Proterozoic volcanogenic massive sulphide deposit (Norway)

The former mining site at Kisgruva near Kongsberg, Norway, is primarily composed of worked sulphide ore deposits, of hydrothermal origin, which occur within Precambrian metamorphic basement. Though the original targets at the Kisgruva mine site were extraction of copper (Cu), sulphur (S) and iron (Fe), the sulphide ore also contains exceptionally high concentrations of selenium (Se) and tellurium (Te), hosted within selenides (clausthalite and minor naumannite) and tellurides (hessite and minor altaite and tellurobismuthite). Both Se and Te are also present within the sulphide ore in pyrite and chalcopyrite, which contain exceptionally high concentrations of up to 688 ppm Se and 81 ppm Te. Additionally, oxidative weathering of the exposed bedrock has resulted in the accumulation of hyper-enriched, unconsolidated weathered crust deposits at surface (Se up to 1590 ppm; Te up to 63 ppm), containing selenite (SeO32-) and tellurite (TeO32-) ions. Concentrations of Se and Te are subsequently higher in the weathering products than in the sulphide ore, due to fixation on to organic matter (-0.4% in weathered ore crusts), jarosite (formed from oxidation of sulphides from the primary ore), ferric oxide and hydroxide phases (goethite and haematite). Increasing demand for Se and Te to use in green technologies has led to the reassessment of these orebodies and their associated weathered ore crust deposits. Though these elements are currently considered mining contaminants, this and similar sites may be of future economic importance, particularly as demand for Se and Te continues to rise.