Scientific publications

The Bolshozero structure is a small depression superimposed on granites and folded Lopian rocks and bounded by NW- (az. ca. 340°), NE- (az. ca. 40-50.) and near-E-W-trending zones. The structure is filled with Paleoproterozoic (Sumian-Sariolian) volcanics, conglomerates and sediments cut by gabbro-dolerites. The metamorphic paragenesis of the Lopian rocks is characterized by the presence of chloritoid, staurolite, garnet, micas and magnetite. Occurring in the andesite-basalts and pebbles of conglomerates, considered as part of the Sumian-Sariolian complex are garnet, hornblende or cummingtonite, biotite and epidote. Layered metasandstones are cut by pegmatite veins and are locally biotitized and tourmalinized. NE-striking rocks and zshaped folds are characteristic of the western Bolshozero structure, whereas schistosity and left-hand NW deformation shifts are typical of the eastern part of the structure. Iron formation occurrences are known in the Lopian rim of the structure. Associated with poor sulphide dissemination in granites and granite-aplites and a crust of weathering after them are individual high gold concentrations (up to 1.3-3.8 g/t) revealed by VSEGEI geologists. Quartz veins also cut Paleoproterozoic rocks. Associated with slightly deformed gabbro-dolerites (PR1) are albitites, epidosites and poor sulphide mineralization (chalcopyrite and pyrite).