Geochemical discrimination between barren and mineralized intrusions in the Svecofennian (1.9 Ga) Kotalahti Nickel Belt, Finland

The geochemistry of 11 Svecofennian (1.9 Ga) mafic–ultramafic intrusions in the Kotalahti Nickel Belt in Finland was studied. The intrusions were classified into three groups: 1) mineralized, 2) intermediate and 3) barren. The classification was made on the basis of the amount and composition of the sulfides found in each intrusion. The whole-rock geochemical results show evidence of country rock contamination in mineralized intrusions. Contamination is best seen in elevated Al2O3/CaO ratio and Zr, P2O5, Th and LREE contents in peridotites. Olivines in mineralized intrusions show nickel depletion, which in some intrusions is interpreted as in situ depletion. Barren intrusions have nickel undepleted olivines, or olivines with low Fo and low Ni.