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Kuibas |
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Russia |
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Fe Ti
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Kuibas magnetite deposit is located approximately 15 km NE of Magnitogorsk in the central Ural Mountains of Russia.
The deposit is contained within a large roof pendant in the northern part of the Magnitogorsk pluton, occuring as an inlier of Late Devonian and Early Carboniferous basic and acid volcanics with rare interlayers of volcanosedimentary rocks and limestone which have been completely replaced by garnet, pyroxene-garnet and epidote-garnet skarn. The volcanics are commonly altered to fine-grained feldspathic and quartzo-feldspathic rocks containing actinolite, chlorite, prehnite and sericite.
The metasomatically altered rocks embracing the deposit are as follows:
i). Pyroxene-labradorite and amphibole-oligoclase hornfels formed by isochemical contact metamorphism.
ii). Hornfels-like fine-grained quartz-feldspathic and substantially feldspathic rocks with actinolite, chlorite, and epidote; including both sodic (albite- and oligoclase-bearing) and potassic (orthoclasebearing) varieties.
iii). Garnet and pyroxene-garnet skam with epidote, vesuvianite and prelinite.
iv). Magnetite and rare "mushketovite" ore with Co-bearing pyrite.
v). Segregations of pyrite, pyrrhotite, chalcopyrite, actinolite, calcite, epidote and apatite in the skarn and ore.
A succession of Intrusive rocks, from older to younger, are i). olivine two-pyroxene gabbro with a cumulative titanomagnetite ore; ii). clinopyroxene-amphibole gabbro, gabbrodiorite, monzodiorite, and granite (products of basic magma fractionation) accompanied by magnetite skarn mineralization; iii). postmineral granitic rocks, and iv). dykes of lamprophyre and lamproite.
The emplacement of of the first 3 phases was straddled to the Early-Middle Carboniferous boundary (dated at around 330 Ma). The youngest intrusives at the Kuibas deposit are thin (1 to 2 m thick) lamproite dykes.
Early phase mineralisation is represented by a cumulate titanomagnetite ore occuring as steeply dipping, up to 10 to15 m thick layers, hosted by olivine gabbronorite. Massive titanomagnetite bodies are surrounded by haloes of titanomagnetite disseminations within gabbroic rocks. The skarn alteration and related magnetite mineralisation overprints the titanomagnetite ore and the host cumulative gabbro as a veinlet network and magnetite disseminations in skarn minerals. The exposed gabbro, which is around 200 m thick, dips at an angle of 45°W, and is truncated by granitoids both above and below. The host olivine gabbronorite with abundant titanomagnetite occurs at the base of the gabbroic intrusion, with the amount of titanomagnetite and femic minerals gradually decreasing upwards, as olivine is gradually replaced by hornblende. The intrusive also gradually changes to become a monzodiorite in its upper section, where it is strongly albitised. At a depth of 600 m, the layered series is cut by a postore granosyenite with xenoliths of feldspar "hornfels", skarn, and magnetite ore. In turn, the granosyenite is altered with the formation of secondary albite, epidote, and carbonate. The granite and granite porphyry is also altered to skarn with magnetite mineralisation. In contrast, the postmineral granite contains abundant angular fragments of all preceding igneous rocks, "hornfels", skarn and magnetite ore. In tum, the postmineral granite itself experienced late epidotization, chloritisation, and carbonatization.
The magnetite deposit comprises a set of numerous small bodies of massive and disseminated magnetite ore whose shape and size are controlled by the morphology of xenoliths and cross-cutting intrusives. They are mostly steep, irregular bodies whose correlation between drill holes has proved difficult.
The deposit has a reserve of >60Mt at grades similar to those at the Magnitogorsk deposits, which averages: 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 most recent source geological information used to prepare this decription was dated: 2000.
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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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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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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