Geology and genesis of granites and polymetallic skarn ores at Pitkaranta, Ladoga Karelia, Russia

The Pitkaranta ores are located northeast of Lake Ladoga in the southeastern part of the Fennoscandian Shield. They are hosted by Lower Proterozoic metamorphosed supracrustal rocks, < 1 km from the 1.54 Ga Salmi rapakivi batholith. The Pitkaranta ores constitute a classical skarn type, formed when granite-related hydrothermal fluids reacted with marble. Combined U-Pb and Lu-Hf studies of zircons in small granite stocks, stockscheider pegmatites and stratiform pegmatites, outside the main Salmi Batholith, indicate severely disturbed U-Pb systems in these ore-related granites and pegmatites, which are considered to be caused by the ore-forming hydrothermal activity. Based on metal contents and ore mineral parageneses, several ore types have been identified. These types are not restricted to individual mines or mining districts but considered to reflect zoning within each ore body, which in turn reflect variations in the depositional conditions for the individual metals and respective mineral. The elevated contents of Cu, Zn, Pb, Ag, In, Sn, W, Mo and Be in the Pitkaranta ores, together with matching Pb isotope signatures between ore galena and potassium feldspar in the Salmi Batholith, confirm a rapakivi-related origin for the ores.