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Physical Geography of Northern Eurasia

Tectonics and Geology of Northern Eurasia

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Non-renewable Resources of Northern Eurasia

Northern Eurasia is extremely rich in natural resources. Within its limits, fuel, minerals, as well as ore and non-metallic resources are mined (Khain et al, 1991).

Oil and Gas

Oil- and gas-bearing fields on the East European platform are widespread on the Volga-Urals anticline, where the first oil was extracted in 1929. The most important oil- and gas-bearing levels are the sandy-clayey sediments of the middle and, especially, upper Devonian. The productive levels are found at depths of 1.5-2 km and the greater part of the deposit is related to the arches of the gently sloping platform folds. Oil- and gas-bearing fields have long been known within the rift structures of the lower Permian, whereas gas fields are known within the Carboniferous deposits (Gabrielyants, 1991). The Pripyat rift has oil- and gas-bearing fields, related to the upper Devonian sediments, whereas within the Dnieper-Donetsk rift they are developed along the whole sequence, beginning with the Carboniferous and ending with the Jurassic. Within the Caspian basin up to twenty oil- and gas-bearing levels occur in the Permian, Triassic, Jurassic and Cretaceous deposits. Within the limits of the Timan-Pechora Plate there are over thirty deposits of oil, gas, and gas condensates, related to the middle and upper Devonian and Carboniferous. Industrial oil-bearing levels are recognized within the Silurian and Permian sediments (Geodinamika, 1993).

The greatest oil- and gas-bearing area of Northern Eurasia is the West Siberian Epi-Paleozoic Plate, where the first industrial oil was extracted in 1959. Since then, numerous oil and gas deposits have been found, related to the Mesozoic terrigenous deposits of the cover. The major oil deposits are related to the upper and middle Jurassic as well as to the lower part of the lower Cretaceous (Neftegazonosnie kompleksy, 1988). The largest oil deposits are associated with the Cretaceous in the Surgut and Nizhnevartovsk regions. Gas deposits are largely associated with the Nadym-Tazovsk syncline on the northern part of the plate, within which they are connected with the sandstone beds within the clayey series of the upper Cretaceous (Perrodon, 1985).

As far as the Siberian platform is concerned only small oil deposits are known, associated with the Vendian and lower Cambrian carbonate sediments. In the Vilyuy syncline extensive gas and gas condensate deposits have been found, related to the sandy-clayey Jurassic sediments (Bakirov, 1979).

The Skythian Epi-Paleozoic Plate, within the limits of the Crimean plain and Northern Caucasus, contains a number of oil and gas deposits. In the west of the Crimea small deposits are concentrated within the carbonate rocks of the Pliocene, whereas gas deposits in the north are related to the Oligocene-lower Miocene sandstones. Gas and gas condensate deposits in the western Cis-Caucasus are associated with sandstones of the upper part of the lower Cretaceous as they also are in the north of the plate within the Donetsk-Promyslovsky region. Oil deposits of the eastern part of the Cis-Caucasus are associated with deposits of the middle and upper Jurassic and lower Cretaceous. The gas deposits of the Stavropol area are found within the sediments of the Maikop series (Oligocene-lower Miocene). South of the Skythian Plate oil and, rarely, gas deposits are found within the West Kuban and Terek-Caspian foredeeps, where they are associated with the sandy and carbonate sequences of the Mesozoic and Cenozoic. These deposits are connected with the narrow anticlinal folds within the inner zones of the foredeeps. In the east of the Terek-Caspian oil basin, deposits are located in the littoral zone of the Caspian Sea. In these regions the major productive level is represented by limestones of the upper Cretaceous and sandstones of the middle and lower Miocene (Perrodon, 1985). Numerous oil- and gas-bearing fields, the main productive level of which is the middle Pliocene sandy sequence, are located in the Kura intermountain basin and at the extreme east of the Greater Caucasus on the Apsheron peninsula and the adjoining Caspian shelf. Oil deposits are traced to the boundaries of western Turkmenistan, to the east of the Apsheron peninsula, where they are associated with the red-coloured sequence of the upper Pliocene. In the southern part of the Turanian Plate, belonging to the Mediterranean belt, over seventy gas and gas condensate deposits, among which there are large ones, are associated with the sandy rocks of the middle Jurassic and Cretaceous as well as to the carbonate sequences of the upper Jurassic. Within the Manghyshlak peninsula there are oil deposits, whose productive levels are middle Jurassic sandstones.

The north-eastern part of the Pacific belt, within the limits of Northern Eurasia, contains gas condensate deposits within the outer zone of the Cis-Verkhoyansk edge basin. Oil and gas deposits are known in the northern Sakhalin and the shelf, where they are associated with the middle Miocene and middle Pliocene sandy-clayey sediments.

Coal

Northern Eurasia contains very extensive coal deposits. The oldest region of coal mining in the East European platform is the Donetsk basin (Donbass), where numerous layers of high quality coal are found within the summits of the lower, middle and upper Carboniferous. In the lower Carboniferous, extensive coal deposits are recognized in the Lvov-Volyn basin in the west of the platform.

In the north of the Cis-Urals foredeep, in the region of Vorkuta in the European north-east, the extensive deposits of coal are related to the Permian sediments. While the numerous coal deposits are spread along the whole fold structure of the Urals, in the south the coal deposits are connected with the Triassic sediments, deposited in the grabens.

The largest coal deposits in the world are recognized within the Siberian platform, related to Paleozoic and Cenozoic rocks. The major coal deposits in the Tungus syncline belong to the middle Carboniferous-Permian. The Lena coal basin, in which the Jurassic and Cretaceous sediments are coal-bearing, is related to the Cis-Verkhoyansk edge basin and partially to the Vilyuy syncline. The South Yakutian coal basin is located on the Aldan shield of the Siberian platform in the Chulyman and Takin basins, within which numerous layers of coal are found in Jurassic continental sediments. The Irkutsk coal basin is associated with the Irkutsk basin, while that of the Kansk-Achinsk is associated with the Kansk basin. Both are located in the south-west of the Siberian platform and contain thick layers of coal in Jurassic sediments. In the lower reaches of the Amur river coal deposits exist in the Cretaceous, Paleogene, and Neogene continental deposits, forming juxtaposed basins. Major coal deposits are related to lower Cretaceous sediment, with a thickness of up to 5 km in Zyryansk basin in the north-east of Russia. About one hundred coal layers are recognized within this sequence. On the island of Sakhalin the industrial coal-bearing strata are mainly related to the middle Miocene littoral-marine sediments.

Metal Ores and Diamonds

Northern Eurasia has a rich range of ore deposits. The Kursk metamorphogenous iron ore basin on the south-western slope of Voronezh anticline of the East European platform is one of the largest basins in the world for ore reserves. The main deposits are associated with the lower Proterozoic iron quartzite and weathering crust. Similar types of deposits are developed on the Ukrainian shield in the Krivoy Rog basin and on the Kola peninsula on the Baltic shield. Within these regions magmatic iron ore deposits are found. On the Siberian platform, iron ores are extensive in the southern part. The most important are the magnetite ores in the Irkutsk area, which formed along the contacts of the trap intrusives and Silurian sediments. In the Altay-Sayan area, iron ore deposits are related to the Caledonian granites and serve as a basis for the metallurgy of the whole of Western Siberia. More than a hundred varied iron ore deposits are concentrated in the Urals and of prime importance are the sedimentary siderite and magnetite ores within the Riphean sequences and the skarn deposits near Magnitogorsk. Iron ore deposits in Kazakhstan are associated with the Precambrian iron quartzites, skarns, and volcanogenic series.

Copper and nickel deposits are widespread on the Kola peninsula, where sulphide ores are associated with the lower Proterozoic basic and ultrabasic intrusions. An extremely large copper-nickel sulphide deposit is located on the Taymyr peninsula near Norilsk, in the north-west of the Siberian platform. Copper deposits of hydrothermal type are developed in Kounrad and Dzhezkazgan in Kazakhstan. In the Urals, within the limits of the copper-bearing belt, stretching for 1000 km, hundreds of copper-pyrite deposits occur, mainly related to Devonian volcanites. Important deposits of nickel and cobalt occur in the southern Urals, where they are found within the weathering crust of ultrabasites. Bauxite layer deposits (aluminium) are concentrated on the eastern slope of the Urals and are associated with the lower and middle Devonian carbonate rocks. On the Siberian platform bauxites in the Cretaceous-Paleogene weathering crust are developed within the limits of the Yenisey Ridge.

On the Siberian platform there are about 200 kimberlite pipes, where diamonds are found. The first diamond-bearing pipe 'Zarnitsa' was opened in 1954. Three main phases of kimberlite pipes are established: Carboniferous, middle and late Triassic, and early Cretaceous. Diamond-bearing pipes are now known to occur on the East European platform, near the White Sea, in the region of Arkhangelsk.

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