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Kimpersay - Donskoy Mining Complex, 10th Anniversary, Molodezhnaya, Yuzhny, Voskhod |
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Kazakhstan |
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Cr
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All available as eBOOKS
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The Kimpersay ultramafic massif is located near the southern end of the Ural Mountains in north-western Kazakhstan, and includes the current (2012) mines 10th Anniversary, Molodezhnaya and Yuzhny of the Donskoy Mining Complex and the Voskhod operation, near the town of Khromtau (#Location: 50° 15' 29"N, 58° 27' 3"E).
Historic mines surrounding Khromtau also includes the Millionoye, Almaz-Zhemchuzhina, Pervomaisk, 20 let Kazakh, 40 let Kazakh and Molodezhnoe, some of which are earlier names for the current mines.
The Kimpersay ultramafic massif is located within the Uraltau Anticlinorium, flanked by Proterozoic and lower Palaeozoic sediments. It is 82 km long and from <1 to 32 km in width, covering an area of 920 sq km. It is elongated in a north-south direction, parallel to the axis of the Uralian Fold Belt. The massif is tear shaped, with the large chromite deposits being localised in the broad, bulbous southern end. The attitudes of the northern and southern sections of the massif are markedly different. In the north it is basically conformable with the schistosity of the Proterozoic in the hangingwall, and with the Ordovician sediments of the footwall. The eastern footwall contact is, in many cases, tectonic. The northern part of the massif is a homoclinally dipping body, up to 2.5 km thick, with a dip to the west of 40 to 60° (Smirnov, 1977).
Based on geophysical data and an age dating, the time of the intrusion has been estimated at between 404 and 380 Ma (Smirnov, 1977).
The Kimpersay ultramafic massif is composed mainly of peridotite, in which harzburgite predominates. The primary minerals of the harzburgites are olivine, orthopyroxene, and accessory chrome spinel, with minor amounts of serpentinite, amphibole (tremolite), chlorite (clinochlore), brucite, powdery magnetite, talc and very rarely phlogopite. Other components, which are generally present in markedly subordinate amounts, include dunite and enstatite-dunite; wehrlite, lherzolite and amphibole peridotite; and troctolite (Smirnov, 1977).
Within the southern section of the intrusion, four ore fields have been delineated, encompassing about 160 deposits and ore showings. In the south the uplifts and respective ore fields are the Stepninsk, South-western, Tagashasai and Main. The Main uplift hosts most of the major occurrences and is the south-eastern most. In the north a fifth ore field, the Batamshinsk is associated with the uplift of the same name (Smirnov, 1977).
The chromite bodies of the Stepninsk ore field are developed in a junction zone between troctolites and harzburgites, and are all small, with lateral extents of a few tens of metres, and a thickness of 3 m. The ores are of low quality due to the paucity of Cr2O3 (40%), and high Al2O3 (>30%). The deposits and ore shows of the Batamshinsk, South-western and Tagashasai ore fields occur amongst peridotites with insignificant segregations of dunite. The mineralised occurrences are somewhat larger than those of the Stepninsk ore field, although their dimensions do not normally exceed 100 m in strike and 10 m thickness. However, the amount of Cr2O3 in the chrome spinel concentrate in some cases reaches 43 to 45% (Smirnov, 1977).
All of the commercial deposits of high quality chromite ores are concentrated in the South-eastern uplift of the Main ore field. The Main ore field is divided into two sub-parallel, near north-south zones, the Eastern and Western. The Western zone trends in a NNW direction, and is some 22 km long. It includes the historic mines of Millionoye, Almaz-Zhemchuzhina, Pervomaisk and 20 Years of the Kazakh SSR (20 let Kazakh) deposits. These bodies dip to the west at 15 to 75° The Eastern zone is of the same length as the Western zone, and includes the historic mines of 40 Years of the Kazakh SSR (40 let Kazakh), Molodezhnoe and other deposits, and merges with the Western zone to the north. The deposits of the Eastern zone have an easterly dip of 0 to 50°. Both zones lie above the feeder zone to the Kimpersay ultramafic massif, within the trace of its projected outer margin (Smirnov, 1977).
The main mines within the Main ore field in 2012 were 10th Anniversary, Molodezhnaya, Yuzhny and Voskhod.
Within the Main ore field the Eastern and Western zones are recognised by the wide development of large dunite segregations in the peridotite, and by the concentration of ore segregations in them. There is a wide variation in the relative dimensions, size and clustering of orebodies. Individual orebodies vary in thickness from thin sheet or vein like accumulations a few metres, up to 150 m in thickness, while laterally they range from a few tens of metres up to 1500 m. The number of orebodies comprising a particular deposit varies from a single large mass as at Molodezhnoe (adjacent to 40 let Kazakh), while Almaz-Zhemchuzhina is composed of five orebodies, 40 let Kazakh has 15 and the Millionoye deposit is made up of 99 individual, close spaced orebodies (Smirnov, 1977).
Each orebody is characterised by different ore textures and internal structures. In addition there is generally a higher density of chromite, often approaching massive accumulations, in the internal sections of the orebodies relative to the peripheries, where a greater diversity of textures are found. This is apparent both vertically and laterally. The chrome spinels may be disseminated, from densely to sparsely, and from fine grained (<1 mm), medium (1 to 3 mm), to coarse grained (>3 mm). The commercial high grade ores of the Main ore field are characterised by densely disseminated varieties with 70 to 90% chrome spinels, and 10 to 30% gangue. The chrome spinels may also occur as nodular disseminations, usually 1 to 2 cm across, or as uniform-massive accumulations of medium to coarse crystals of chrome spinel with insignificant quantities of gangue. (Smirnov, 1977).
The densely-disseminated, massive and nodular varieties are often all found in the large orebodies. Grade varies in each of these mineralisation varieties, as illustrated by Almaz-Zhemchuzhina where the following grades are encountered: i). massive-uniform - 58 to 59% Cr2O3; ii). densely disseminated - 50 to 57% Cr2O3; iii). medium-disseminated - 37 to 49% Cr2O3; iv). rarely-disseminated - 28 to 36% Cr2O3.
The average for the orebody is 49.5% Cr2O3, with 12.5% FeO, 8.1% SiO2, 0.42% CaO and 0.002% P (Smirnov, 1977).
The mineralogy of primary chrome-spinel ores is simple, generally comprising only chrome spinel and olivine. In some ores periclase is also present, usually as finely dispersed grains within chrome spinels. Most of the ores have undergone prolonged and intense post-magmatic alteration, producing up to 30 minerals in different parts of the complex. These include olivine, chrome-spinel, chrome-actinolite, garnet (uvarovite), serpentine (lizardite and chrysotile), chrome chlorites (kŠmmerite and rhodochrome), fuchsite, brucite, magnetite, hematite, sulphides (pyrrhotite, mackinawite, pentlandite, pyrite, marcasite, chalcopyrite and maucherite), hydroapatite and native copper. The chrome-spinels include mangochromite (Mg,Fe)2O4, alumochromite (Mg,Fe)(Cr,Al)2O4, subferrichromite (Mg,Fe)(Cr,Fe)2O4 and subferrialumochromite (Mg,Fe)(Cr,Fe,Al)2O4. In the Main ore field the ore forming chrome spinels are mangochromite. Different host phases contain different spinels and different Cr2O3 contents. For example in the Main ore field the following rock types have the following average compositions: dunites - 58.7% Cr2O3, 11.7% Al2O3; pyroxene dunites - 49.4% Cr2O3, 19.0% Al2O3; and harzburgites - 39.6% Cr2O3, 29.4% Al2O3 (Smirnov, 1977).
The 40 let Kazakh, deposit is located within the Eastern zone of the Main ore field of the Kimpersay ultramafic massif, near the town of Kromtau in the southern Urals. It is 4 km to the ENE of the 20 let Kazakh (20 Years of the Kazakh SSR), which is within the Western zone. Drilling has shown that 40 let Kazakh and the nearby Molodezhnoe orebody are developed in an en echelon pattern relative to each other, and together total 90 Mt @ 50% Cr2O3. This reserve is contained in 23 separate orebodies which are also developed in an en echelon pattern. The orebodies strike near north-south, with dips that vary from near flat to 10 to 25°W. In the north ore outcrops, while to the south it is at a depth of 300 to 350 m. The most extensive orebody, No. 4, has plan dimensions of 934 x 200 m, with a maximum thickness of 65 m, while No. 3, the next in size is 665 x 280 x 85 m. Others are 50 to 420 m long, 50 to 100 m wide and 5 to 40 m thick. All occur in serpentinised dunite, among which are separate bodies of harzburgite, pyroxene dunite and sulphide bearing dunites (Smirnov, 1977).
The Molodezhnoe deposit is the largest in the group, with plan dimensions of 1540 x 200 to 300 m and a maximum thickness of 140 m. It does not outcrop, being at a depth of 420 to 600 m. It is elongated in a north-east direction and dips at 25°SE in the north, flattening southwards. The orebody is cut by generally east-west faults with throws of 8 to 40 m (Smirnov, 1977).
Remaining ore reserves and mineral resources at the Donskoy Mining Complex, December 31, 2012 (ENRC Annual Report, 2012), were:
10th Anniversary, underground - proved + probable reserves - 168.1 Mt @ 42.4% Cr2O3;
Molodezhnaya, underground - proved + probable reserves - 22.9 Mt @ 38.6% Cr2O3;
Yuzhny, open-pit - proved + probable reserves - 2.6 Mt @ 42.5% Cr2O3;
included within -
10th Anniversary, underground - measured + indicated + inferred resources - 272.1 Mt @ 50.2% Cr2O3;
Molodezhnaya, underground - measured + indicated + inferred resources - 20.7 Mt @ 51.0% Cr2O3;
Yuzhny, open-pit - measured + indicated + inferred resources - 2.4 Mt @ 48.8% Cr2O3.
Ore reserves at the Voskhod mine (Mechel OAO website, 2013) were:
proved + probable reserves - 19.5 Mt of ore at unspecified grades
The most recent source geological information used to prepare this decription was dated: 1999.
Record last updated: 9/9/2013
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.
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Selected References:
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Melcher F, Grum W, Thalhammer T V, Thalhammer O A R 1999 - The giant chromite deposits at Kempirsai, Urals: constraints from trace element (PGE, REE) and isotope data: in Mineralium Deposita v34 pp 250-272
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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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