Abstract
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.
Highlights
A greater knowledge of how critical element such as selenium (Se) and tellurium (Te) concentrate and are spatially distributed in solid ore rock and the associated weathered profile is of increasing economic importance
The Kisgruva site is characterised by sporadic exposures of previously worked sulphide ore and metamorphic bedrock
The metamorphic bedrock contains a high abundance of quartz (∼40% of modal mineralogy), plagioclase (∼30%), biotite (∼10%), chlorite (∼5%), hornblende (∼5%) and amphibole (∼5%)
Summary
A greater knowledge of how critical element such as selenium (Se) and tellurium (Te) concentrate and are spatially distributed in solid ore rock and the associated weathered profile is of increasing economic importance This is relevant as the worldwide demand for viable sources of Se and Te continue to grow. The former Kisgruva sulphide mine in the Kongsberg region of Buskerud (Norway) is known to host high Se and Te concentrations, though well-constrained data from the region are limited (NGU, 1981, 2017; Bjerkgård, 2015; Kotková et al, 2018). The growing necessity for sources of E-tech elements has led to an increasing focus on new potential concentrated Se and Te deposits and a review of former ore mining sites, such as the Kisgruva site
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