Udokan Ore Region

an ore-bearing region in the northern part of Chita Oblast, RSFSR, encompassing the Udokan, Kalar, and Kodar ranges. The Udokan Ore Region includes the Udokan deposit of cuprous sandstones and other deposits and manifestations of copper mineralization, the Chinei deposit of titanium-magnetite and sulfide copper-nickel ores, deposits of ferruginous quartzites (Sulumai and others), the Chitkanda and Ansat coal deposits, and deposits of other minerals.

The first information on the geology of the Udokan Ore Region was reported by D. V. Nikitin in 1918 and E. V. Pavlovskii in 1933. Systematic investigation of the region was begun in 1948, in the course of which the Soviet geologists E. I. Burova, K. K. Denisov, Iu. P. Den’gin, and I. S. Sidorov found evidence of industrial copper-bearing capacity in the watershed part of the Udokan Range. Subsequent preliminary explorations revealed a large deposit of cuprous sandstones.

The Udokan Ore Region is located within the Aldan Shield. Two structural stages are identified: the lower, which consists of complexly dislocated Archean schists and gneisses, and the upper, which is an early Proterozoic variegated copper-bearing formation, consisting of metamorphosed sandstones, shales, and the like. The upper stage is known as the Udokan Series and consists of comparatively gentle folds. The units of both structural stages have intrusions of early Proterozoic granites.

The existence of copper-bearing ores has been established in at least six different stratigraphic levels of the Udokan Series. The ore bodies are represented by layers of copper sandstones and shales containing sulfide phenocrysts in cement, ore pockets, and lenses. The copper beds of the Udokan Series are among the most ancient copper formations; a metamorphic facies of green shales, they lost the variegated rock coloring typical of their younger analogs, for example, in Dzhezkazgan. The principal ore minerals are chalcocite, bornite, and chalcopyrite; the ores are of the bornite-chalcocite and chalcopyrite-pyrite types. Zones of oxidation and secondary sulfide concentration are weakly developed; the secondary minerals of copper include malachite, azurite, and covellite.

The Udokan Ore Region is in a zone of modern seismic activity of the Mongolian-Baikal-Okhotsk seismic belt. The region is one of the chief sources of mineral raw materials for the Chul’man-Aldan Territorial Production Complex now under construction.