Deposit-scale evolution of the Kiskamavaara Cu–Co deposit, northern Norrbotten, Sweden

This study presents a geological characterisation of the Kiskamavaara Cu–Co deposit in northern Norrbotten, Sweden, with the aim of clarifying how lithology, alteration, and structural controls contributed to Cu–Co system development in Norrbotten. Kiskamavaara is a pyrite-dominated cobalt resource, historically estimated at 3.2 Mt at 0.065% Co and 0.37% Cu. The deposit differs from similar deposits in the region that are generally chalcopyrite-dominated, which makes it interesting to study the mineralisation controls. To analyse the connection between lithology, alteration, and structural controls, this study employed drill core logging, structural measurements, whole rock geochemistry, petrography, XCT-scanning, and 3D modelling. Key results show that the metavolcanic rocks of the Kiskamavaara deposit comprise three geochemically distinct groups of intermediate volcanic protoliths, intruded by two geochemically distinct sets of basaltic-andesitic and basaltic dykes. Hydrothermal alteration is dominated by Ca–Fe (biotite + magnetite ± scapolite) and K–Fe (K-feldspar + magnetite + pyrite + chalcopyrite ± biotite) chemofacies, which overprint all protoliths. Mineralisation manifests in the K–Fe chemofacies and occurs as hydraulic breccia with a cobaltian pyrite + magnetite ± chalcopyrite matrix that overprint the primary intermediate volcanic, mainly andesitic, supracrustal protoliths. 3D-modelling of the mineralisation and alteration shows that first and second order shear zone junctions and low strain zones within the larger structure system play a critical role in localising high-grade mineralisation. These findings underscore the importance of the interplay between structural framework and hydrothermal fluids for deposit evolution of similar styled deposits in Norrbotten and globally.