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Streltsovka or Streltsovsky Uranium Field - Malo Tulukuevskoye, Streltsovskoe, Streltzovskoe, Antei, Argunskoye |
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Siberia, Russia |
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U F Mo
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Streltsovka (Streltsovsky, Streltsovskoe, Strel'tzovskoe or Strel'tsovskoe) uranium field is one of the largest volcanic associated cluster of uranium deposits in the world. The field comprises 20 separate deposits within a 20 km diameter rhyolite caldera near the Chinese border within Chita Oblast of the Transbaikalia region of far eastern Russia. The mines include the exhausted Malo-Tulukuevskoe (Malo-Tulukuevskoye) open pit and the operating Streltsovskoe and Antei (Antaeus) underground mines. Other deposits within the district unclude Argunskoye, Luchistoye, Oktyabrskoye, Yubileynoye, Dalnee, Zherlovoye and Pyatiletnee.
(#Location: Streltsovskoe - 50° 4' 22"N, 118° 15' 10"E).
The Streltsovka caldera was developed on a basement of mainly Hercynian (300 Ma) granites and is typically filled with >500 to 900 m, but up to 1400 m in peripheral sections of the caldera, by late Jurassic volcanics (basalt, andesite, trachyandesite and rhyolite) and intercalated sediments. The last eruptive episode comprised rhyolites dated at 142 ±7 Ma, accounting for 30 to 35% of the bulk of the volcanics preserved within the caldera.
Uranium mineralisation is hosted by any of the volcanic lithologies within the caldera, and has also been encountered within the granitic basement in deep drilling. It generally occurs as subvertical veins or stockworks, although it may also spread along permeable tuff, sandstone and conglomerate units intersected by mineralised structures. Mineralisation was emplaced immediately following the cessation of volcanic activity in the early Cretaceous. Grades range from 0.2 to 0.6% U3O8 in large stockworks and up to 1% U3O8 in veins. In addition, smaller occurrences representing remobilisation in younger sediments are found surrounding the caldera.
At Tulukuevskoe, mineralisation was distributed over an 800 m thickness of the host sequence as a stockwork and was restricted to the volcano-sedimentary pile with an exploited reserve of 35 000 tonnes of contained U3O8.
The Streltsovskoe U-fluorite deposit accounts for ~20% of the ~250 kt U reserves in the mineralised district (Seltmann et al., 2010). The deposit occupies ~10 km2 and occurs as a north-south trending belt of ~4 x 25 km. Two structural levels are recognised: i). a lower level of leucocratic granite porphyry; and ii). an upper level composed of Upper Jurassic and Lower Cretaceous sequences that are ~1000 m thick and form a 5 to 10° dipping monocline (Ischukova 1995). The Upper Jurassic sequence comprises conglomerates, basalts and trachydacites, whilst the Lower Cretaceous rocks include conglomerates, basalts and felsic lavas. Mineralisation is controlled by numerous subvertical zones of intense faulting, fracturing and brecciation, and has a vertical extent of ~480 m. The bulk of the U reserves are concentrated at depths of between 300 and 550 m below the surface, forming large subvertical stockworks and veins, with grades typically of about 0.20 to 0.30, but locally up to 2 wt.% U and more (Ischukova 1995). Mineralisation is also found in the underlying leucogranites. The most significant of the latter style is the Antei deposit that underlies the Streltsovskoe (Seltmann et al., 2010). Streltsovskoe and Antei together comprise a series of parallel veins over a width of around 400 m hosted in the volcanics and basement with a resource of 60 000 tonnes of contained U3O8 (Chabiron et al., 2003)
Mineralisation was formed in the Early Cretaceous between 140 and 125 Ma during several mineralising stages. The early stage is represented by hydrothermal alteration of the host volcanic rocks producing hydromicas, carbonates (siderite, ankerite, calcite), chlorite, quartz and locally kaolinite. Brecciated veins in this stage have a cement of fine- grained quartz containing finely disseminated iordizite and low-Fe sphalerite. The next major U-bearing, stage included the formation of pitchblende, with variable amounts of brannerite and coffinite, and local uraninite (Ischukova 1995; Aleshin et al., 2007). This mineralisation is accompanied by abundant dark-purple fluorite, and by intense albitisation and hematitisation of the country rocks. Formation of abundant fluorite continued in the later stages, together with carbonate, chlorite, hydromicas and sulphides, mainly pyrite, galena, chalcopyrite, pyrrhotite and tennantite-tetrahedrite (Seltmann et al., 2010).
Chabiron et al. (2003) describe the same stages of mineralisation and alteration as follows:
Stage I - local albitisation, deep in the mineralised system.
Stage II - the most intense alteration involving the development of hydromicas - illite, phengite and/or chlorite, with illite dominating to 1800 m and phengite below that, although in the lower parts of the system potassic micas are represented. The illite and phengite are dated at 139 to 130 Ma
Stage III - involved the emplacement of quartz veins with variable quantities of carbonate, pyrite, hydromica, largely without uranium mineralistion, although locally anomalous uranium has been detected, but in the absence of recognisable uranium minerals.
Stage IV - represents the main stage of quartz-molybdenite-pitchblende mineralisation, dated at 133 ±4 Ma. The pitchblende is present as isolated spherolites on the margins of other minerals or as disseminations in breccia cements, with accompanying coffinite. Brannerite is also present and earlier than coffinite or pitchblende. Pyrite, galena and molybdenite are associated with the urnium minerals which exhibit a vertical zonation. Molybdenite and pitchblende occur together in the upper levels of the system, followed by a pitchblende-coffinite-brannerite association from 800 to 1300 m, while brannerite predominates below 1300 m. A first generation of fluorite accompanied stage IV, while a second was emplaced post uranium mineralisation.
The total production + reserve + resource in the deposits of the Streltsovka uranium field are:
280 000 tonnes of U3O8 at an average grade of 0.2% U3O8.
Including:
Tulukuevskoe open pit - 35 000 tonnes of U3O8
Streltsovkoe-Antei underground mine - 60 000 tonnes of U3O8.
The Argunskoye deposit, which contained approximately 15% of the total initial resources of the district, was undeveloped in 2005 and is expected to commence production prior to 2010. The resources at the Tulukuevskoye and Luchistoye deposits had been almost completely depleted by 2005. Around 25 to 45% of initial resources at the Streltsovskoye, Antaeus, Oktyabrskoye and Yubileynoye deposits had been mined in 2005, while much of the Malo-Tulukuevskoye, Dalnee, Zherlovoye and Pyatiletnee deposits were yet to be developed, although these are comparatively small, characterised by leaner ore and except for Zherlovoye, are located at some distance from the main operations. Remaining resources in 2005 have been quoted at 150 000 t U3O8.
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2010.
Record last updated: 3/1/2021
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.
Streltsovskoe
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Selected References:
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Chabiron A, Cuney M, Poty B 2003 - Possible uranium sources for the largest uranium district associated with volcanism: the Streltsovka caldera (Transbaikalia, Russia): in Mineralium Deposita v38 pp 127-140
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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.
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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, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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