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Shaimerden |
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Kazakhstan |
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Zn Pb
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Shaimerden high grade massive supergene non-sulphide zinc deposit is located in the southern Urals of north-western Kazakhstan, 240 km SSW of the city of Kostani.
For details of the regional setting, see the Regional Setting section of the 50 Let Oktyabrya record.
Shaimerden is located on the eastern side of the north-south trending transcontinental Urals Orogenic belt within the 700 km long Valerianovsky belt characterised by Carboniferous sediments and volcanics.
The Urals Orogenic belt is divided by the major north-south Main Urals fault. To the west are Precambrian and early Palaeozoic shield and intraplate rift basins. The east is characterised by a mainly oceanic crustal regime with ophiolitic complexes and island arc related volcano-sedimentary basins (andesite-basalt, spilite and trachyte), as well as volcano-plutonic belts and intervening sedimentary basins characteristic of an active continental margin. Arc complex rocks of Silurian to Carboniferous age are preserved adjacent to the Main Urals fault, while late Devonian to Permian synorogenic granitoid complexes are found in the southern section of the eastern Urals.
The Shaimerden deposit is located within the southern end of a NE trending syncline of lower Palaeozoic clastic and carbonate meta-sediments and volcanics which also contains major iron deposits and bauxite ores. Near Shaimerden the Valerianovsky belt is composed of three suites of rocks, namely:
i). The lower Sarbai Formation of andesitic volcanics with lesser andesite porphyry.
ii). The Sokolov Formation - dominated by dolomitised intertidal to open marine Carboniferous limestone, largely a bioclastic micrite and algal micrite with pseudomorphs after anhydrite and gypsum. Bioclastic packstones and grainstones with sparry cement are also interbedded with the micrites, as are some polymict breccias and conglomerates. This formation, which hosts the Shaimerden mineralisation, dips at 20 to 30°NW with a maximum thickness of 300 m and may be traced for 30 km along strike. Hematite alteration is extensive as are late crosscutting calcite veins and vugs.
iii). The upper Kurzhunkul Formation - a mixed sequence of sediments and volcanics (andesites and tuffs) dipping at 10 to 20°WNW. These are unconformably overlain by middle to late Carboniferous molassic sediments and intruded by small late Carboniferous bodies of diorite and granite as well as sub-volcanic plugs.
All of these are in turn overlain by Triassic and Cretaceous clays and Quaternary sediments.
The ore deposit is found within a 450 x 150 m, east-west elongated karst depression in the Sokolov Formation limestone and overlain by Cretaceous clays and then by 40 m of Quaternary sediments. The base of the depression at its deepest is 240 m below the current surface. The mineralisation within this has lateral dimensions of 300 x 150 m, being in the deepest parts of the depression, with the remainder being filled by the Cretaceous clays. The deposit occurs on an east-west flexure in a well defined north-west trending geophysical lineament. Remnant sulphide ores in the centre of the non-sulphide ore zone are hosted by intertidal algal micrite with evaporites and occur as breccias or conglomerates with sulphide clasts set in a bioclastic matrix, replacing both carbonates and sediments. The limestones were hydrothermally dolomitised prior to the sulphide introduction, and subsequently hematite altered.
The main Shaimerden orebody comprises supergene oxidised zinc ores with remnant sulphides towards the centre, indicating oxidation from the outside margins to the centre of the deposit. There is an outward zoning from:
i). Remnant massive sulphides comprising 90% sphalerite with minor galena and pyrite (as described above) with an average grade of 46% Zn, 1.2% Pb, 6.1 g/t Ag,
ii). Surrounding massive, fine grained hemimorphite-smithsonite clasts in a fine grained carbonate-hemimorphite-smithsonite matrix which has a sharp 2 to 5 mm transition to the massive sulphides, with a similar texture and always intimately related to the massive sulphides. There are additional gangue mineral clays, carbonates and oxides. This ore type assays 30 to 45% Zn, with an average resource grade of 35.2% Zn.
iii). Stony ore within mineralised clays surrounding the massive sulphides and hemimorphite-smithsonite ores. It is a dark green to dark red weathered competent but locally friable rock with a relict breccia texture composed of hemimorphite, smithsonite, minor sauconite and other clays and carbonates.
iv). Mineralised clays - comprising - a). CL3 - grey-green chlorite-smectite, kaolinite and/or montmorillonite clays with more than 40% gritty material (hemimorphite and smithsonite with minor sauconite and zincite) and a gangue of lesser calcite, dolomite, siderite and quartz and grades averaging 24.9% Zn, b). CL2 - similar grey-green clays to CL3 but with 10 to 40% gritty material (hemimorphite and smithsonite again) with grades averaging 13.1% Zn. c). CL1mottled, multicoloured, white to orange brown, massive and plastic clays with a grit content of less than 10% and averaging 1.8% Zn which is found above and sometimes laterally to the main massive sulphides and massive hemimorphite-smithsonite.
A resource has been outlined of: 4.645 Mt @ 21.6% Zn, 0.8% Pb.
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2003.
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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Boland M B, Kelly J G, Schaffalitzky C 2003 - The Shaimerden supergene zinc deposit, Kazakhstan: a preliminary examination: in Econ. Geol. v98 pp 787-795
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Vikentyev, I.V., Belogub, E.V., Novoselov, K.A. and Moloshag, V.P., 2017 - Metamorphism of volcanogenic massive sulphide deposits in the Urals. Ore geology: in Ore Geology Reviews v.85, pp. 30-63.
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