Cu-Ni-PGE mineralization at Rometölväs,Koillismaa layered igneous complex,Finland

Sulphides, tellurides and sulpharsenides, with special reference to the platinum-group minerals (PGM), have been studied from a subeconomic Cu-Ni-PGE mineralization encountered within the Syöte section of the Lower Proterozoic (2.44 Ga) Koillismaa layered igneous complex (KLIC) in northern Finland using electron microprobe and ore-microscopical methods. The ore minerals occur partly as strata-bound patches and spots associated with spots of light-coloured secondary low-temperature silicates in the gabbronorite IV of the general igneous stratigraphic column of the complex and partly as a fine-grained impregnation in the penecontemporaneous basic sills and dykes. Among the PGM sperrylite, michenerite and a palladian bismuthian melonite have been encountered. The chemical composition is reported for these minerals as well as for the rest of the ore minerals (chalcopyrite, pentlandite, pyrrhotite, pyrite, sphalerite, cobaltite and hessite). It is concluded that volatile components played a significant role in the solution, transport and the final deposition of the sulphides and the PGM.