Institute of Geology, Karelia Science Center, Russian Academy of Sciences, Petrozavodsk, Russia:

V. I. Ivashchenko, Leading Researcher, Candidate of Geological and Mineralogical Sciences, ivashche@krc.karelia.ru

As a region with favorable geographic and climatic conditions and the developed infrastructure, Karelia is attractive for commercial-scale mining of mineral resources which enjoy high demand in the modern economy. Such resources include platinum group metals and gold. Promising occurrences of these minerals are detected in the Ladoga region, in associations with intrusive rocks of Kaalamo clinopyroxenite–gabbro norite–diorite system aged as 1888.3±5.2 million years. With respect to the age and petrochemistry, this rock system is somewhat similar to Kotalahti and Vammala Nickel Belts in Finland. Noble metals in Kaalamo intrusions belong to the syngenetic and epigenetic types. The syngenetic ore genesis started at the late magmatic stage (~800 °C) of intrusions, evolved and finished at the hydrothermal–metasomatic stage (<271 °C). The syngenetic mineralization (Araminlampi, Saouth Kaalamo, Keinoset, Ninimyaki) represents strata (to 10–11 m thick) impregnated with sulfides (pyrrhotine, chalcopyrite) and with noble metals in meta pyroxenite and hornblendite at the contents: ΣPd, Pt, Au—0.2–1.1 g/t; Сu—0.1–1.0%, Ni—0.03–0.1%, Co—0.01–0.03%. The epigenetic mineralization originated at the temperature of ~500–<230 °C in the zones (to 3.5 m thick) of intense shear deformation and low-temperature metasomatism (actinolite, tremolite, chlorite, prehnite, albite, quartz, calcite) and, among other things, transformed the older ore shoots. The ore content of the largest occurrences of this type (Surisuo, Rantamyaki) varies greatly: ΣPd, Pt, Au—0.1–11 g/t; Сu—0.2–2.0%, Ni—0.03–0.2%, Co—0.01–0.05%. The test ores contain up to 50 noble metals; both mineralization types are dominated by palladium bismuth–tellurides and sperrylites. The geological, mineralogical, physicochemical and geochemical data are reflective of the probable effect exerted on the ore genesis by the Svekofennian regional metamorphism and granite formation. The undiscovered potential resources of ΣPt, Pd, Au in four out of seven detected ore occurrences total approximately 9 tons. The overall mineral resource potential of Kaalamo magmatic system embraces 20–30 t of noble metals, 50–60 kt of copper and 10 kt of scandium (all meta pyroxenites, including nonmetallic, have steadily consistent contents of Sc—70–90 g/t).
The study was carried out under the state contract with the Karelia Science Center of the Russian Academy of Sciences, R&D Topic No. 121040600173-1.

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