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Timan, Tyman - Sredne-Timansky, Vezhayu-Vorykvinskoye, Verkhne-Shchugorskoye
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The currently operated Timan bauxite deposits and Sredne-Timansky bauxite mine are located to the northeast of Ukhta in the Komi Republic of northwestern Russia, ~250 km west of the Ural Mountains, ~500 km south of the Arctic Ocean and ~725 km NNW of Yekaterinburg.

The following description is of the geology and bauxite deposits of the South Timan district from Smirnov (1977), which is assumed to be representative of the Timan bauxite deposits. In 2022, operations at Timan were nearing completion in the No. 1 and No. 3 opent pits on the Vezhayu-Vorykvinskoye deposit, but continued at open pit No. 2 on the Verkhne-Shchugorskoye deposit, with a new No. 4 pit coming on-stream at Vezhayu-Vorykvinskoye. The current Timan Bauxite enterprise was founded in December 1992. In 2019, the production capacity of the operation was 3 221 214 tonnes of bauxite per annum. The pre-mining reserves in the No. 4 pit were 14 Mt of bauxite (Rusal release 2021). Measured + Indicated Mineral Resources at Timan as at 31 December 2020 was 176.6 Mt of bauxite (Rusal Annual Report, 2020).

The bauxite deposits of the South Timan were discovered in 1951 at a depth of 177 m within Visean rocks of the Lower Carboniferous (Abramov, 1970). The oldest rocks in the district are a Neoproterozoic (Riphean) metamorphic suite, which is overlain above a marked angular unconformity by almost horizontal Devonian, Carboniferous and Permian sequences. These are almost everywhere overlain by Quaternary sediments.

The Neoproterozoic metamorphic suite is exposed in the western part of the district where it comprises a lower succession of interbedded limestones and dolomites with layers of clay-chlorite-quartz and quartz-carbonaceous shales, and an upper uniform sequence of intercalated grey, greenish-grey, and black chlorite-sericite and feldspar-quartz schists, the Ochparm Group. The overlying sequence commences with Middle and Upper Devonian strata, including Eifelian, Givetian and lower Frasnian units composed of clays, sandstones and siltstones with rare intercalations of limestones in the upper sections. The upper Frasnian suite comprises a lower organic limestone with bands of clays, and an upper section characterised by an alternating gypsum, anhydrite, dolomite, limestone, clay, and gypsum-dolomite rocks, the lfkhta Group. The overlying lower Famennian sequence is composed of limestone, dolomitised limestone and gypsum depleted dolomite with seam of sandstone and clay. The Devonian sequence is 300 to 350 m thick, including the 130 to 180 m of the lower Frasnian.

The Carboniferous includes Visean, Namurian, Bashkirian and Moscovian age rocks. The Visean units are bauxite-bearing, and are widely developed, resting on the eroded surface of the Famennian, and in the southeastern part of the region on relicts of a Tournaisian unit. They comprise terrigenous sediments of the Tula and lower Aleksa Formations, clay-carbonate deposits of the upper Aleksa Formation, and dolomites and dolomitised limestones of the Mikhailovsk, Venevsk, Tarus, and Steshevsk formations and the Upper Carboniferous Namurian Stage. The bauxites are developed within the terrigenous deposits of the lower Aleksa and Tula formations and rest on carbonate and carbonate-clay rocks of the Upper Devonian, or on a deluvial bed, and are overlain by Middle Carboniferous Visean carbonate deposits that are up to 70 m thick. The bauxite bearing beds rarely outcrop, and then only in river valleys where thay are composed of kaolinite clays and argillites.

The Tula and lower Aleksa formations terrigenous sequence varies from a few up to 30 metres in thickness in uplifts, but in basins in the pre-Visean relief, it may reach 100 m and more, largely due to an increase in thickness of the sub-bauxite member which may reach up to 75 m. It has been subdivided into four members, from the base upwards, namely, the:
Sub-bauxite rocks, as described above;
Deluvial Bed, which is only known where bauxites is found, occurring in small, but relatively deep-seated, 10 to 15 m, erosional hollows in the upper surface of the Devonian limestones. It is composed of poorly rounded cobbles, pebbles, blocks and rubble of a Devonian finely-stratified argillaceous limestone. The matrix is composed of clay and argillite of varying colour, often with an oolite-pisolite-clastic fabric.
Bauxite-bearing Member, which occurs as a band of varying width distributed along the slopes of uplifts, where it rests on either sub-bauxite Devonian limestones or on the deluvial bed. In the basins, it overlies Devonian limestones of the sub-bauxite member. It is composed of kaolinitic clays, alumina-rich lateritic clays, and various lithological varieties of bauxites. Bauxite segregations occur in the middle section of the member. Upward and on the periphery, the bauxite horizon passes into alumina-rich lateritic clays, and then into a kaolinitic argillite. The member varies in thickness from 0.8 to 12 m, and is usually 4 to 6 m. The bauxite segregations have an elongate form with wavy outlines. They occur at depths of 10 to 180, and most commonly 40 to 100 m. The average thickness of the member varies from 57 to 77 m.
Carbonaceous-mottled Member - which is more extensively distributed than the bauxite-bearing member. Its lower section includes a layer of carbonaceous argillites, which pass upwards into silty or argillite-like platy carbonaceous clays, gradually grading upwards into dark-grey and grey siltstones. The total thickness of the member is 8 to 28 m, and commonly 15 to 20 m. The carbonaceous rocks are overlain to the north by mottled silts, argillaceous siltstones and silts, and silty clays.

The bauxites of the South Timan region are characterised by high-alumina, high-silica, low-iron, and often high-sulphur contents. They contain: 40 to 70 wt.% Al2O3; 12.0 to 28 wt.% SiO2; 3.6 to 12.72 wt.% Fe2O3; 0.38 to 3.0 wt.% S (mainly as pyrite). The bauxites belong to the kaolinite-gibbsite- boehmite and kaolinite-boehmite types. The former is developed in the NW, and the latter, in the SE of the district (Smirnov, 1977).

The Timan operation is 100% owned by the Russian company, United Company RUSAL.

The geological information in summary is drawn from Smirnov, V.I., (Ed.), 1977 - The Ore Deposits of the USSR; Pitman Publishing, v.1, pp. 313-316.

The most recent source geological information used to prepare this decription was dated: 1977.    
This description is a summary from published sources, the chief of which are listed below.
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