Inkai, Munkuduk, Budennovskoe, Akdala, Uvanas, Muyunkum, Kanzhugan, Karamurun, Zarechnoye, Kharasan


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Major uranium deposits are located in the adjacent Chu-Saryssu and Syr-Darya uranium provinces in central-south Kazakhstan, which are within a 200 km radius from north-northeast to south-east from the city of Kyzylorda. Kyzylorda is located on the major Syrdarya River which flows north-west into the Aral Sea and is some 850 km to the south of Astana and approximately 950 km west of Almarty.

The two provinces host roll-front type sandstone hosted uranium deposits, within two extensive Cretaceous-Cenozoic artesian basins. The Chu-Saryssu which is up to 250 km wide and extends for more than 1000 km from the foothills of the Tien Shan Mountains to the south and SE, merging into the flats of the Aral Sea depression to the NW. The parallel Syr-Darya basin to the SW is separated by the NW-SE trending Karatau Mountains which were uplifted in the Quaternary.

The deposits within the Chu-Saryssu province occur in two connected strings around portions of the margins of an NW-SE elongated oval shaped 150 x 110 km mineralised pattern. Mineralisation occurs at a number of stratigraphic levels in these deposits and at progressively higher levels from the north-west to the south-east.   One such string of deposits extends from the south-western margin of the oval shaped feature, around the northern margin to the north-eastern margin, over a distance of approximately 175 km, with a number of superposed, ribbon like accumulations at different stratigraphic positions, distributed within a 15 km width.

The deposits within this group include, from the south-west Budennovskoe, Inkai and Munkuduk (Mynkuduk) to the east. A semi-parallel belt of mineralisation at a higher level, some 35 to 10 km (converging to the east) to the south, increasing in significance to the east includes the Sholak-Espe and Akdala deposits, while higher again and 30 km to the south of Akdala is the Uvanas mine.   Akdala and Uvanas are located on the rim of the oval shaped pattern of mineralisation detailed above. The deposits mined in the eastern part of this group are known as the Stepnoye Mining Group.

Another string of major deposits are distributed over a 70 km length on the south-eastern margin of the oval shaped pattern of mineralisation. Deposits include Muyunkum (Moinkum or Moyon-Kum) and Kandjugan (Kanzhugan). These deposits represent the Centralnoye Mining Group.

Deposits within the Syr-Darya province include: Karamurun (Kara-Murun), Kharasan, Irkol and Zarechnoye of the #6 Mining Group.

The sediments of the Chu-Saryssu and Syr-Darya basins are composed of up to 320 m of continental sediments and a 140 to 220 m thick Palaeogene marine grey to green clays and siltstones. These are overlain in turn by 200 m of red coloured, sandy-clay Oligocene sediments and up to 60 m of Quaternary alluvial sands, clays and loam.   This sequence is unconformably underlain and flanked by folded Proterozoic and Palaeozoic units, including the basement uplift of the Karatau Mountains.

In general the Chu-Saryssu Basin occurs as an asymmetric, NW-SE aligned syncline with a broad, gently dipping, north-eastern limb which plunges to over 700 m below surface, and an active, short, up-faulted NW-SE limb forming the margin of the Karatau Mountains uplift/horst structure.

The uranium mineralisation within the Inkai and Mynkuduk string of deposits occurs in a sandstone roll front setting, developed along a regional system of superimposed mineralised fronts in the Upper Cretaceous sediments of the Chu-Saryssu basin. The sands are generally feldspathic, typically containing 50 to 60% quartz and 10 to 15% feldspar. The clay content is in the range of 5 to 10% at Inkai and 10 to 20% at Mynkuduk.

The host sediments on the north-western half of the mineralised oval pattern, directly overlie older basement, and have been divided into three units, as follows, from the base:

i). The 40 to 90 m thick Mynkuduk horizon, which is around 500 m below the surface and comprises coarse grained grey alluvial sediments at the base, where it hosts the uranium mineralisation, and grades upwards into fine-grained sands;
ii). The 105 to 130 m thick Inkuduk horizon, which commences with coarse basal gravels, grading upwards into fine to medium-grained sands with interbedded clays;
iii). The 20 to 80 m thick Jalpak horizon, which comprises medium-grained grey to green sands grading upwards to red and brown clays. This horizon hosts the Akdala deposits.

The host sediments and the uranium mineralisation, are interpreted to have been weathered from the Ordovician and Silurian granites, granodiorites, crystalline schists and slates of the Tien Shan Mountains which are exposed on the margin of the basins to the south and southeast. The Karatau Mountains and the Palaeozoic uplands to the north are also a minor source of sediments.

Groundwater within the Chu-Saryssu Basin flows towards the north-westerly discharge areas. The poorly consolidated Upper Cretaceous sediments provide an excellent groundwater aquifer/reseevoir which is some 250 to 300 m thick, confined by the underlying Palaeozoic rocks and the overlying thick Paleogene marine clays. To varying degrees there is a further confinement created by the three sedimentation cycles, with each cycle including fine sands to silts and occasional clay seams at the top.

The sand units have high horizontal permeabilities. The coarse sands at Inkai generally have filtration coefficients in the range of 20 to 30 m/day, and of the order of 10 m/day at Mynkuduk. The confined Upper Cretaceous aquifers produce artesian conditions where the topography is depressed below the piezometric surface of about 135 to 140 m above sea level. The general water table is at a depth of 8 to 10 m at Inkai and 80 m at Mynkuduk.

The uranium mineralisation was precipitated under reducing conditions by a variety of reducing agents in the sandstones, including carbonaceous material, sulphides and hydrocarbons. It is principally composed of micron-sized globules and spherical aggregates of sooty pitchblende and tiny crystals of coffinite. No elevated levels of deleterious trace elements have been detected. The uranium mineralisation is reported to be essentially clean and mono-metallic.

At the Inkai deposit, which is 55 km long and has ribbons of mineralisation developed over a width of 17 km, abutted to the south by the South Inkai deposit which has a length of a further 17 km. Mineralisation has been delineated at 8 mineralised beds, 3 within the Mynkuduk horizon and 5 within the Inkuduk horizon. The main roll fronts in the Mynkuduk horizon may reach a thickness of 20 m, but commonly average 7 to 10 m at their thickest and 1 to 2 m on the limbs. They may form a simple "C" shape or irregular amoeboid shapes throughout the favourable horizons, resulting in stacked bodies. Grades range from 0.02 to 0.07% U.

The uranium mineralisation at Kandjugan and the other deposits of the Centralnoye Mining Group on the southern margin of the oval shaped pattern of mineralisation in the Chu-Saryssu basin is hosted by the lower stratigraphic-structural unit of the 80 to150 m thick, 35 to 22 Ma, Eocene sequence which includes five sandy horizons separated by 3.5 to 30 m thick clay-silt layers. Two of the sandy horizons, Kanzhugan and Uyuk, carry uranium mineralisation. Uranium is essentially present as coffinite in roll front and tabular bodies which occur in sinuous redox fronts that extend for a length of as much as about 10 km and widths of 40 to 800 m. Thicknesses vary between 1 and 20 m and average 5.3 m.

Published reserve and resource figure include:

Inkai deposit (2005):
      Proven reserve - 22.7 Mt @ 0.06% U3O8, 12 880 t U3O8;
      Probable reserve - 63.7 Mt @ 0.05% U
3O8, 28 780 t U3O8;
      Total reserve - 86.4 Mt @ 0.05% U
3O8, 41 660 t U3O8;
      Indicated resource 3.6 Mt @ 0.04% U
3O8, 1320 t U3O8;
      Inferred resource 253.9 Mt @ 0.05% U
3O8, 122 000 t U3O8;

Munkuduk deposit reserve:
      49 000 tonnes U at a grade of 0.035% U, within a broader resource in the West, Central and East Munkuduk
          sections of approximately 100 000 tonnes U.

Budennovskoe deposit resource:
      282 000 tonnes U.

Kharasan deposit reserve:
      5300 tonnes U at a grade of 0.20% U (proven), and 29 050 t U at a grade of 0.095% U (probable);

Muyunkum deposit resource:
      82 000 tonnes U at a grade of 0.035% U, including;
        Proven + probable reserve - 49 000 t U at a grade of 0.035% U;

Kandjugan deposit resource:
      30 000 to 50 000 tonnes U.

Uvanas deposit resource:
      up to 20 000 tonnes U.

North & South Karamurun reserve in existing mines:
      29 500 tonnes U;

Irkol desposit reserve:
      34 000 tonnes U;

Zarechnoye deposit reserve:
      14 500 tonnes U at a grade of 0.10% U (proven), and 4500 t U at a grade of 0.11% U (probable);

Current and planned future production is all from in situ leaching (ISL). Average mining recoveries at the various mines range from 85 to 93% of the available U, while subsequent processing plant recoveries vary from 93 to 99% (2003).

Much of the information in this description has been summarised from Catchpole (1997); Pool & Wallis (1995-96); and OECD (2003).

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

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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