Tunguska Coalfield

one of the largest coalfields in the USSR, located mainly in Krasnoiarsk Krai and partially in the Yakut ASSR and Irkutsk Oblast, RSFSR. The field has an area of more than 1 million sq km. It extends 1,800 km from north to south, from the Khatanga River to the Trans-Siberian Railroad, and 1,150 km from west to east, between the Enisei and Lena rivers. The Tunguska Coalfield occupies a significant part of the Central Siberian Plateau. It has not been adequately studied. According to the 1968 survey, total geological coal reserves are estimated at 2,345 billion tons (to a depth of 600 m). In the northwest is the Noril’sk Coal Region, with an area of about 60,000 sq km; it is the most thoroughly investigated and developed part of the field.

The existence of coal in the Tunguska Coalfield became known in the second half of the 19th century. The existence of coal-bearing beds over extensive areas was established in the northern part of the field by A. L. Chekanovskii in the period 1873–75, in the southern part by P. K. Iavorovskii in 1898, and in the polar region by A. G. Rzhonsnitskii and I. P. Tolmachev in the period 1915–17. Among the other researchers who did important work was the Soviet geologist S. V. Obruchev, who conducted expeditionary studies in Eastern Siberia from 1917 to 1924. Obruchev was the first to express the idea that there was a single Tunguska field of Upper Paleozoic age. Systematic studies were subsequently carried out, primarily near the Noril’sk Mining and Metallurgical Combine, where several deposits were found: the No-ril’sk-1 (Mount Shmidt and Mount Nadezhda), Kaierkan, and Imangda. The Kaiak (Kotui) and Kokui deposits in the southern part of the field were also explored. The approximate boundaries of the productive beds were established, and many sections with commercial coal were identified and the material composition and quality of the coal were studied.

The coal of the field is to some extent associated with Middle and Upper Carboniferous continental beds 100–300 m thick, but primarily with Permian beds whose thickness ranges from 200 to 1,500 m. The coal seam is subdivided into five formations: Tushama (C₂), Listviaga (C₂₊₃), Klintaiga (P₁¹) and Burguklin (P₁²), Peliatka (P₂²), and Degali (P₂²). The Listviaga and Burguklin formations, which have the thickest coal seams, are of the greatest commercial importance. The working seams are mostly 1–5 m thick, in places up to 12–15 m. The Great Seam in the Ko-kui deposit has an average thickness of 60 m.

Tectonically, the field belongs to the western part of the Siberian Platform. It encompasses such major secondary structures as the Noril’sk syncline, the Tunguska syneclise, and the western part of the Angara syneclise, all of which are separated by gentle ridges and uplifts. Normal faults along which igneous rocks intruded into the coal-bearing stratum in the late Paleozoic and early Mesozoic are widespread; igneous sills, stocks, and dikes penetrate the productive beds and break them into small and large blocks, in many cases partially assimilating the coal seams. Igneous rocks constitute 10–75 percent of the coal-bearing formation in cross section. A tuff-lava trap formation overlaps the coal stratum in the northern and central parts of the Tunguska syneclise.

The coals are humic, primarily clarain-durain coals, with 9–25 percent ash and 0.2–1.0 percent sulfur. The heat of the intrusion led to sharp and irregular variation in the yield of volatile substances and the elementary composition, and therefore also in the grade composition of the coals, which range from brown coals to anthracites.

Most of the known deposits in the field are located in inaccessible regions with difficult natural conditions. Primitive mining was carried on sporadically during the prerevolutionary period, and planned development began in the Noril’sk region in 1935. Coal extraction at the Kaierkan and Kotui deposits is 600,000 and 38,000 tons per year, respectively (1974). The coals are used as fuel in power engineering. Significant coal reserves for opencut mining have been explored in the Tunguska Coalfield.

Cupro-nickel, graphite, and Iceland spar deposits, as well as deposits of various building materials, are worked in the Tunguska Coalfield, and iron ores have been identified. The cities of Noril’sk and Mirnyi and the settlements of Tura, Turukhansk, Baikit, Motygino, Boguchany, and Taseevo are located in the coalfield.