Nickel in shungite deposits

Hydrothermal fluids are a major medium for metal redistribution and deposition in the Earth's crust. The spatial relationship of metallic ores and hydrocarbons suggests that fluid hydrocarbons play a role in the transportation of metals and can be found in sufficient quantities to be economically exploitable. Examples of these include Carlin-type and Mississippi Valley-type (MVT) deposits. Paleoproterozoic carbonaceous metasediments are host to several metal rich deposits across Scandinavia and Russia. Ni occurs in the low-grade black-shale hosted Talvivaara deposit, Finland, which has been intermittently mined since 2008. This study aims to investigate mineralization found in shungite, a carbonaceous metasediment from Karelia, Russia as an analogue to mineralization found at the Talvivaara deposit. Two samples of shungite were analysed using SEM. The first sample which was dull and bedded-type shungite, showed no evidence of metal enrichment. The second sample from a vein-type shungite, a product of hydrocarbon migration, showed an enrichment of Ni, which demonstrates that Ni was transported by hydrocarbons. Given the similarity and proximity of shungite deposits and the Talvivaara host rocks, we infer that hydrocarbons played a role in metal transport in Ni mineralization.