Bodaybo gold deposit

BODAYBO GOLD DEPOSIT (RU: Бодайбинское месторождение золота) is situated within the basin of the Bodaybo river, within the eastern Siberia. For the development of the Bodaybo deposit, there has been created during the 1853 the "Lena Gold Extraction Fellowship", which has been later transformed into the "Lenzoloto" Joint Stock Company. The deposit is situated within the southern part of the large synclinorium, which is formed by the folded strata of the Proterozoic schists, sandstones, gritstones, and conglomerates. Within the axial zones of the anticlines, there are concentrated the gold-bearing quartzous veins and venules, with the destruction of which there is associated the forming of the gold-bearing placers. There have the major industrial importance the gold-bearing layers, which are mixed with clay, pebbles, and crushed gravel (sometimes they are multi-layered, up to 4 horizons, with the thickness of up to 5 metres), and which are buried under the stratum of the glacial clayish loams with boulders, of the clayish pebble soils, sands, and silts from the alluvial placers of the Quaternary age.

The gold-bearing depositions are mainly situated at the bed of the buried valley, and on the 2-3 terraces, at the depth of 10-100 metres, or sometimes more. Gold concentrates itself within the lower parts of the gold-bearing layers, penetrating into the cracks within the country rocks of the bedrock at the depth, which is reaching 1.5 metres. The gold particles (with the millesimal fineness of 870-930) are relatively large, rounded, and worn out; there are usual the findings of the nuggets (often with the inclusion of quartz). Modern alluvial placers with the tiny flake-shaped gold particles are confined to the depositions of the terraces above the floodplain within the lower reaches of the Bodaybo river. The development of the deeply embedded buried placers is performed by the underground mines. The unsealing of the industrial gold-bearing layers, which are embedded at the shallow depth (10-15 metres), is performed with the help of bulldozers and excavators. The major method for the development of the gold-bearing placers is with the usage of the dredges, with the preliminary stripping of the "peats" according to the scheme of the excavator, which is followed by the dredge.