Elkonsky, Elkonskoye, Elkon, Yuzhnoye, Yuzhnaya, Kurung, Neprohodimo, Druzhnoye, Severnoye, Intersnoye, Lunnoe, Vesenneye, Agdinskoye, Snezhnoye

Siberia, Russia

Main commodities: U Au
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The Elkonsky, Elkonskoye, Elkon or El'kon uranium ore district is located ~20 km south of the town of Tommot, ~375 km SSE of Yakutia in the Republic of Sakha (Yakutia), Siberia, in eastern Russia. The district contains a series of deposits, including the largest cluster, the 30 x 20 km Yuzhnoye (Yuzhnaya) Zone which includes a central NW-SE trend that includes from the NW, the Elkon, Elkon Plateau, Kurung, Neprohodimo and Druzhnoye deposits distributed over a strike length of ~20 km. These are flanked by parallel but lesser trends, including the Severnoye deposit 5 km NE of Kurung, the Intersnoye deposit 5 km to the SW of Elkonskoye Plateau and Lunnoe 10 km SW of Druzhnoye. Other deposits in the district include Vesenneye, Agdinskoye and Snezhnoye. (#Location - Kurung: 58° 40' 56"N, 126° 16' 10").

Mineralisation was discovered at Elkom in 1960, and subjected to exploration and resource definition from then until 1980. The Elkom Uranium Mining Company was established in 2007. Technical studies have continued and the deposit is expected to be put into operation after 2035 (ARM Rosatom website, viewed 2020).

The deposits lie within the Central Aldan Granulite Belt of the Aldan Shield in eastern Siberia. The Aldan Shield represents the south-eastern segment of the Siberian Craton. The Archaean Aldan Shield is divided into blocks by a series of north-south to NW-SE trending faults. The main blocks comprise the eastern Batomga and western Olekma-Chara which are both typical granite-greenstone terranes, separated by the Central Aldan Block or Granulite Belt, a granulite-gneiss terrane. The greenstone belts of the eastern and western blocks trend north-south, are bounded by faults, metamorphosed to greenschist to amphibolite facies and have a late Archaean age.

The Central Aldan Block comprises the lower Yengra (Iengra) Series of granulite facies metamorphosed terrigenous sediments which include thick quartzites and high alumina gneisses, overlain by the 3.0 Ga Aldan Complex Timpton-Dzheltala Series composed of mafic volcanics, overlain by more terrigenous sediments with some carbonates. The granulite metamorphism of the Central Aldan Block has been dated at around 2 Ga.

The mineralisation of the El'kon district occurs within a zone of Mesozoic tectono-magmatic activation of the Archaean Central Aldan crystalline complex granulites, which were also extensively granitised during the late Neoarchaean to early Paleoproterozoic.

The inner part of the Central Aldan Block is characterised by a giant granite-gneiss dome coinciding with the development of varied Mesozoic sub-volcanic calc-alkaline-alkaline intrusions and consisting of a series of complex isoclinal folds inclined towards the centre of the structure, while thrust sheets and nappes are developed in the internal part of the Block. The El'kon district is found on the periphery of this dome.

The individual deposits are localised in ore-bearing structures of four types: i). Rejuvenated ancient regional faults, ii). Mesozoic structures partially inherited from older structural elements, iii). Exo-contacts of pre-ore Mesozoic dykes, and iv). Mesozoic radial and ring fracture zones cutting the crystalline basement and platform cover, influenced by early Paleoproterozoic faulting, and controlling the distribution of Mesozoic magmatic rocks.

Approximately 80% of the uranium resources are confined to Mesozoic rejuvenated older faults, occurring as Mesozoic age metasomatic U-Au bearing breccias hosted in particular by the fractures of the Elkon Horst.

According to a technical report released by ARMZ Uranium Holding Co (a subsidiary of Rosatom) in 2009, the main central trend in the Yuzhnoye Zone contains ~20 orebodies that occupy 3 anastomosing ore zones within the blastomylonites and cataclasites of the up to 100 m thick Yuzhnaya fault zone. The individual ore bodies have a complex morphological structure with significant variations in thickness over short intervals as orebodies pinch and swell. The orebodies are composed of closely-adjacent and parallel veins/linear stockworks. Individual orebodies have strike lengths of 50 to 400 m, and locally up to 700 m, vary in thickness from 0.9 to 4 m, averaging 1.3 m, and persist down dip for 100 to 200 m. Mineralisation has been traced to depths of 1 km down the steep SW dip.

Persistant multistage mineralising processes developed several mineral assemblages that were superimposed on each other within the ore-bearing structures. Pre-ore pyrite-carbonate-potassium feldspar assemblages are the most abundant, occurring in all ore-bearing zones, and host all of the ore bodies. These metasomatites have a general zonation, comprising an outer pyrite-carbonate-sericite zones surrounding an inner pyrite-carbonate-potassium feldspar zones with areas of adularia development. Uranium ores are closely related to pyrite-carbonate-K feldspar metasomatites, which are rich in K2O, CO2, and sulphide sulphur and contain an Au admixture of a few g/t.

The principal primary uranium mineral in the El'kon ores is the medium- to low-temperature brannerite, and cements micro-breccias as well as filling short veinlets, within the pyrite-carbonate-potassium feldspar zones. The brannerite has been altered by postore intra-vein metasomatism and hypergene processes, as in the northwestern part of the district, where primary brannerite ores were transformed into uraninite by post-ore Mesozoic alkaline intrusions. The overall mineralogy of the ores comprises brannerite, uraninite, coffinite, native gold, pyrite, chalcopyrite, hematite and molybdenite.

According to ARMZ Uranium Holding Co (2009), breccia fragments may contain pyrite and uranium minerals in calcite-fluorite veins, while the breccia fragments are cemented by brannerite or by a brannerite-coffinite-pyrite cements.

Geological, thermo-barometric and isotope data show that the ores of the El'kon district are hydrothermal medium- to low-depth types, and that the ore components were derived from Archaean granitised rocks with elevated uranium contents. The hydrothermal activity was initiated and stimulated by Mesozoic calc-alkaline-alkaline magmatic processes between 140 and 90 Ma.

Gold occurs as sub-micron grains or micron sized inclusions in pyrite and galena. The sulphides occur in quartz and calcite as inclusions and in fractures and on grain surfaces.

The average grade of the ores is around 0.1 to 0.15% U
3O8, with 1 up to several g/t Au.

The resource requires underground mining of relatively thin 2 to 5 m thick, relatively low grade ore bodies.

In the main deposit within the district, Yuzhnoye (Yuzhnaya), ore has been found over a strike length of almost 25 km along strike and for more than 2 km down dip without reaching its lower limit. This deposit has reserves variously quoted at between 240 and 345 000 t U
3O8 (based on a USD 80 to 130/kg U cost), while the district is quoted as having a resource potential of 600 000 t U3O8 and 1000 t Au.

ARMZ Uranium Holding Co (2009) quoted Russian B+Ci+C2 Resources in the main central Yuzhnaya trend of 257 800 t of U, 140.8 t of Au; in the Severnaya trend of 58 600 t of U, 29.2 t of Au; and in the Interesnaya trend of 2800 t of U. The average ore grade in the broader Elkom district is quoted as 0.146% U, 0.84 g/t Au.

The most recent source geological information used to prepare this summary was dated: 2007.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Seltmann, R., Soloviev, R., Shatov, V., Pirajno, F., Naumov, E. and Cherkasov, S.,  2010 - Metallogeny of Siberia: tectonic, geologic and metallogenic settings of selected significant deposits: in    Australian J. of Earth Sciences   v.57, pp. 655-706.

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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