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Magnitogorsk, Maliy Kuibas, Berezky, Dimitrovskoye |
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Russia |
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Fe
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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.
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The Magnitogorsk magnetite deposits were located in the central Ural Mountains of Russia (#Location: 53° 25' 26"N, 59° 07' 23"E).
The magnetite deposits of the Magnitogorsk region was the basis of the large iron and steel complex developed in the city in the 1930s which formed the backbone of Russian production during the second world war. The main deposits of the region are Magnitogorsk (2 main bodies of comparable size, the Main and Far orebodies, separated by a normal fault with a displacement of ~300 m), Maliy Kuibas, Berezky and Dimitrovskoye. In addition the district holds another 30 smaller deposits. The original Magnitogorsk resource of some 500 Mt of ore is practically exhausted and the only major mine in the region in 2002 was the open-pit exploiting the ~60 Mt Kuibas deposit.
The geological structure of the region is dominated by the Devonian to lower Carboniferous volcano-sedimentary rocks, the major part of which comprise subduction related volcanics which are host to major volcanic-hosted massive sulphide deposits (Herrington et al., 2001). The structural grain of the region is dominated by a sequence of parasitic anticlines and synclines aligned sub-parallel to the main N-S trend, with granitic bodies intruded into the cores the fold cores.
These granitoids form two series. The older Devonian suite is comagmatic with the Devonian arc rocks, while the second series is associated with the magnetite skarn-like deposits which are of early Carboniferous age. These younger intrusive massifs are comagmatic with the early Carboniferous volcanics which they intrude. The intrusives show an evolution from gabbro (first stage) to amphibole sub-alkaline granites and syenites (later stage). The ore bodies are located: (a) at the contacts between granites and meta-volcanites (eg. Maliy Kuibas), (b) within granites (eg. Beresky) and (c) along the exocontacts (e.g., Magnitogorskoye, Dmitrovskoye etc.). The sequence has been dated at between 333 and 330 Ma (Ronkin 1989). Emplacement of these intrusives is controlled by a major NNE trending structure. The intrusive igneous suite shows clear evidence of fractionating gabbro to diorite from a common source, with the latest granitic intrusions developed as thin sheets marginal to the gabbros (Fershtater et al., 1997, Fershtater 2000). The main pluton is also zoned from the base, from a lower gabbro to a transitional gabbro-granite breccia to an upper granite. The composition of the plutonic rocks is typical for moderately alkaline continental rift series, comparable to igneous suites from the Afar Rift (Fershtater 2000).
The magnetite bodies at Magnitogorsk itself occur as exoskarns, formed largely at the expense of Tournaisian and Lower Visean (lower Carboniferous) limestones, located on the southern contact of the Magnitogorsk intrusion. The host limestone unit is 100 to 200 m thick and dips at 10 to 30°W, and is underlain by Late Devonian basalts. The footwall is intensely albite-altered close to the limestone unit and the magnetite body, while the overlying Carboniferous volcanics are albitised and overprinted with skarn alteration. The ore-bearing skarn comprises andradite-grossulargarnet, diopside, epidote, calcite and apatite. Numerous north-south trending basic and acid dykes, ranging from 1 to 10 m in thickness, are strongly altered by to skarn and ore.
The ores are largely magnetite with minor pyrite (carrying up to 5% Co), pyrrhotite and chalcopyrite. Sulphides often form inter-granular aggregates within the magnetite as well as more discrete sulphide-rich lenses.
The Maliy Kuibas orebody is situated 14 km to the NNE of the Magnitogorsk deposit, along the northern flank of the Kuibas granite intrusive. From a structural perspective, as at Magnitogorsk, the deposit lies within the core of a branched anticline of folded volcanic and volcanosedimentary rocks. The structure is intruded and metamorphosed by the granitoid massif. The deposit itself is clearly related to a tectonic zone within the anticlinal structure. The wall rocks comprise mafic volcanic units, including metamorphosed dolerites and their tuffaceous equivalents, which are plagioclase and pyroxene phyric. In addition, there are granites, gabbros and various hornfels facies which are now represented by a fine-grained rock composed of quartz, plagioclase, hornblende and pyroxene with secondary and accessory leucoxene, epidote, chlorite and titanite. In the central part of the deposit, pyroxene-feldspar and quartz-feldspar hornfels are developed with skarn and magnetite bodies. These form a zone measuring 200 to 600 x 2500 m in extent, elongated parallel to the NNE trend and dipping westwards at 70 to 85°. Many apophyses and metre wide veins of granite are injected into the ore-zone and separate ore blocks. In detail, there are actually more than 50 individual magnetite lenses in the deposit with sizes varying from 50 x 50 to 500 x 300 m, with thicknesses of between 2 and 50 m.
In the limits of the ore zones, granites have progressive transitional contacts with hornfels, tuffs and dolerites. Skarns occurs as rims around magnetite ore bodies and veins, and as lens-like inclusions within the ores, granites and hornfels. The mineralogical composition of the skarns comprises: garnet (andradite-grossular, andradite), diopside-hedenbergite, calcite, tremolite, actinolite, bluish hornblende, vesuvianite, scapolite, albite, epidote, chlorites, hematite, pyrrhotite, pyrite, siderite, magnetite and apatite. There are many different mineralogical associations within the skarns, but usually they are dominated by a pyroxenegarnet- association. Skarns are coarse-grain and form zonal veins with cavities and druzy aggregates.
The ore mineralogy is dominated by magnetite with minor pyrrhotite and pyrite, although cobalt is an important trace element. The ores are coarse grained, massive or banded, with breccias being present in places. In the northern part of deposit there is a titano-magnetite-bearing ore body with 16-25% TiO2, ulvospinel and herzinite. The deposit is capped by a 5 to 30 m thick supergene blanket.
The Magnitogorsk orebodies are predominantly stratabound, although steeply dipping lodes of limited thickness follow dykes. The magnetite ore is mainly hosted in the upper part of the limestone unit and locally replaces the limestone completely. The ore is composed of magnetite, pyrite containing 4-5% Co, rare pyrrhotite and chalcopyrite with a guange of calcite, epidote, garnet, clinopyroxene and apatite. Locally the ore is represented by "mushketovite". The average ore composition is: 48.6% Fe; 1.98% S; 0.04% P; 0.018% Co; 8.3% SiO2, 0.21% Ti02; 12.8% Cao; 1.02% MgO; 0.08% MnO; 0.03% V205.
The composition of typical ores from Maliy Kuibas (Herrington et al., 2002) is: 38.5% Fe; 0.02% Co; 0.01% Ni; 0.17% Mn; 0.41% TiO2; 0.05% V2O3; 1.83% S; 0.06% P; 16.0% SiO2; 5.9% Al2O3; 7.8% CaO; 1.42% MgO.
The most recent source geological information used to prepare this decription was dated: 2002.
Record last updated: 10/9/2013
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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Fershtater G, 2000 - The Magnitogorsk gabbro-granite series and related titanomagnetite ore and magnetite skarn deposits: in Seltmann R, Koroteev V, Fershtater G and Smirnov V, 2000 The Eroded Uralian Paleozoic Ocean to Continent Transition Zone; Granitoids and Related Ore Deposits IUGS/UNESCO, IGCP Project 373, International Field Conference in the Urals, Russia, 18-30 July, 2000, Excursion Guidebook, Publication #14, IGCP Project 373, Natural History Museum, London, pp 58-68
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Herrington R, Smith M, Maslennikov V, Belogub E and Armstrong R, 2002 - A Short Review of Palaeozoic Hydrothermal Magnetite Iron-Oxide Deposits of the South and Central Urals, and their Geological Setting: in Porter T M (Ed.), 2002 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, PGC Publishing, Adelaide v.2 pp. 343-353
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