GEOLOGICAL AND STRUCTURAL REGULARITIES OF GOLD AND PLATINUM DISTRIBUTION IN BLACK SHALES OF THE KOTERA SYNCLINORIUM (Northern Prebaikalia)

The carbonaceous deposits in the Riphean stratified series’ of the Kotera Synclinorium gravitate to the middle and upper parts of the Nyandoni Formation and lower parts of the Barguzin Formation. They were most intensely accumulated in the local paleodepression in the northeast of the territory (lower reaches of the Nyandoni R.). With great abundance of carbonaceous silt shales, there often occurs veined-disseminated sulfide (predominantly pyrite) and quartz-sulfide mineralization with elevated contents of gold, platinum, and palladium. Formation of ore objects is more pronounced at the sites of abundant occurrence of gently pitching fracture-fold small structural forms confined either to near-dike space (“dike swarms”) in black shale-terrigenous-carbonate series of the Nyandoni Formation and partly Barguzin Formation or to the contacts of blocks of the above-mentioned plastic series with under- and overlying brittle bodies (psammites, occasionally marbled dolomites). At the sites of mineralized zones with elevated contents of gold and platinoids, the major portion of gold is represented by gold microparticles of 0.01–0.05 mm in size. Ore objects are more efficiently estimated for gold when structural and geological studies of promising areas are combined with mineralogical and geochemical investigation of sulfide concentrates of artificial blacksand samples.