Industria, Petrozavodsk, Russia:

K. A. Konevin, Geologist

Institute of Geology, Karelian Research Center, Russian Academy of Sciences, Petrozavodsk, Russia:
V. I. Ivashchenko, Leading Researcher, Candidate of Geologo-Mineralogical Sciences, ivashche@krc.karelia.ru

The article describes scientific research results and field data (exploration and appraisal stage) on Proterozoic gabbro–dolerite intrusion Motko in Central Karelia. The geology of the structure, differentiation and lithology are characterized in brief. It is shown that the currently used geological and geophysical survey techniques are the optimized package tool for tracing and delineating the titanium–magnetite horizon. The noble metal mineralization spatially adjoins the titanium–magnetite mineralization in the intrusion and is accompanied by the copper sulphide mineralization. Native gold and platinoids represented by bismuth–telluride, arsenide and stibioarsenide of palladium and platinum, and seldom—by phases of high-temperature platinoids (Ir, Os, Ru), are associated with chalcopyrite and highly ferruginous Cl-containing (to 1%) ferrohastingsite. Cotulskite and sperillite with particles no more than 10 μm in size prevail. According to geophysical data and assaying results, within the intrusion, five ore zones are identified (length of 4–9 km, average thickness of 3 m, Pd_y content of 1.5 g/t), with the total probable reserves of noble metal category Р₂ of 62 t.

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