The Early Proterozoic Suurikuusikko refractory gold deposit, Kittila, Western Finnish Lapland

The Suurikuusikko epigenetic refractory pyrite-arsenopyrite gold deposit, discovered by the Geological Survey of Finland in 1987 at Kittila, Northern Finland, represents an new gold ore type in Finland. It is hosted within early Proterozoic (ca. 2.0 ea) mafic tholeiitic graphite-bearing carbonate-albite-altered tuffs and quartz-carbonate veins within a shear zone. Average Au contents analysed from arsenian pyrite and arsenopyrite by electron probe micro analysis (EPMA) are 46 and 279 ppm and by secondary ion mass spectrometry(SIMS) 69 and 217 ppm, respectively. Direct cyanidation tests leach 3-7 % of the gold from the ore samples. Tests of processing the ore by grinding, notation, bio-oxidation and cyanidation give an estimated total gold recovery of about 85 %. The mineral resources are about 2.5M t with average 6.6 g/t Au.