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Тезисы международной конференции

Рудный потенциал щелочного, кимберлитового

 и карбонатитового магматизма

Abstracts of International conference

Ore potential of alkaline, kimberlite

and carbonatite magmatism

Peculiar features of accessory mineralization of vein series of carbonatites

from Chetlassky complex (Middle Timan)

Udoratina O.V.*, Kozyreva I.V. *, Shvetsova I.V. *, Nedosekova I.L. **, Kapitanova V.A. *

*Institute of Geology Komi SC UB RAS, Syktyvkar, Russia

**IGG UB RAS, Ekaterinburg, Russia



Rare earth-thorium-rare metal mineralization is known in phenites as well as in carbonatites and in vein rocks related to Chetlassky magmatites developed within Middle Timan (Ivensen, 1954, Cherny, 1972, Stepanenko, 1975, 1979, 1984, Kostyakhin, Stepanenko, 1987).

The Chetlassky complex of dyke ultrabasic rocks is close to the early and medium stages of autonomous picrite-lamprophyric series associated with ultrabasic alkaline complexes with its specificity and lack of feldspatholites and presence of kimpicrites and aylikites (Nedosekova et al., 2011).

A number of dyke aggregates and related fields are determined in the basins of Kosyua and Bobrovaya rivers. This is SN trending Kosyuskoe→Bobrovskoe→Oktyabrskoe, where smaller areas are determined. The depth of drilling decreas in the same direction. Within the fields in different areas picrites and carbonatites, different phenites (melanocratic and leucocratic) and also vein structures are determined. Hydrothermal-metasomatic rocks are confined, as magmatites, to faults with NE inclination. The areas of their localization represent metasomatically transformed areas of enclosing rocks – phenites. The zones have a complex configuration due to inhomogeneous structure and transformation of sedimentary metamorphic rocks related to the Chetlassky series.

The phenites compose zones with symmetrically zonal pattern, where axial (rear) part is composed of carbonatites, and external parts – by phenites changing to aegirinized and amphibolized varieties of sedimentary metamorphic rocks. With the absence of carbonatites in the rear zones, the phenites look like vein-like bodies in sedimentary metamorphic rocks, which they are connected with by gradual transitions.

The development of structures of vein series, goethite-feldspar and quartz-goethite-hematite, is observed within all the fields. Rare earth-rare metal minerals are concentrated in these rocks and form large groups.

The collection of mineral monofractions from vein rocks (crushed samples by V.I. Stepanenko, I.V.Shvetsova, B.Ya. Yatskevich) was studied by scanning electron microscope (JSM-6400) with energy-dispersive spectrometer (ISIS Link) and wave spectrometer (Microspec) in Institute of Geology, Komi SC UB RAS. New data on crystal morphology and their chemical composition were received.

The Kosyuskoe field (Kosyu site), late carbonatite veinlets 2545 (dolomite-phlogopite-chalcopyrite vein), 2556 (quartz-calcite-khlorite-pyrite vein). The known minerals of carbonatites (Ivensen, 1964, Kostykhin, Stepanenko, 1984, Kovalchuk et al., 2011, Kovalchuk, 2011): zircon, monazite, kodazite, ilmenorutile, columbite, pyrochlore. The known minerals of phenites and vein series, described earlier (Ivensen, 1964): zircon, monazite, ilmenorutile, columbite, allanite, pherritorite.

Bobrovskoe field (Novobobrovsky site) № 460 – phenite, № 8, 10-A-1 – quartz-goethite vein. The known minerals of phenites and vein series, described earlier (Ivensen, 1964): Mn-columbite, ilmenorutile, pyrochlore, monazite, auerlite, codazzite, xenotime, tengerite, hydrothorite, chiblite, galenite, zircon, apatite, allanite and pherrithorite.

Oktyabrskoe field (Oktyabrsky site) №751, 753, 754, 756 – phenite (albitites). The known minerals of phenites and vein series, described earlier (Ivensen, 1964): apatite, xenotime, ilmenorutile, monazite, hematite.

The studied crushed samples, apart from rock-forming minerals of plagioclase group (albite) and K feldspar (orthoclase and microcline), quartz, micas,  rare earth-thorium-rare metal minerals are represented by monazite, xenotime, columbite, ilmenorutile and unusual varieties of thorium phases in rare earth carbonates up to clear thorium silicate. The observed associations often have mixed contents, divided into different groups and suggesting that we observe isomorphous range of ferrous phosphate ↔ thorium silicate. Strontium apatite is observed (SrO content to 8 wt%).

Rare minerals Nb, Ta, V in vein rocks are represented by minerals: columbite, ilmenorutile. Vanadium doesn’t form minerals and is included in ilmenorutile (up to 6-13 wt%).

Columbite is observed as grains in phenites and carbonatite veins, it forms large crystals and crystal joints in vein rocks. According to our data columbite from carbonatite veins contains (wt%) Nb2O5 72-79, MnO ­ not above 2, FeO at level of 20 and related to pherrocolumbites. TiO2 content is not above 1.5 wt % , and maximal content Та is 2 wt %. Columbite from veins contains (wt %) Nb2O5 ­ 76, MnO ­up to 14, FeO ­ 7, and also small quantity of V2O5 (0.1), TiO2 (1) and related to Mn-columbites. All columbites possess a characteristic typomorphic feature – the presence of ilmenorutile inclusions.

Thus, process trend: vein carbonatites (Fe-Col) → phenites (Col (Mn=Fe)) → quartz-goethite veins (Mn-Col or Col (Mn³Fe)) is marked by wave-like input of Mn and Fe and change of pherrocolumpbite of vein carbonatites to phenite columbite and further to mangancolumbite of quartz-goethite veins.

In ilmenorutiles from phenites, as inclusions in columbites, Nb2O5 content makes 20 wt.% and more, and V2O5 content increases to 6, and ilmenorutiles contain up to 13 wt.% of inclusions in columbites from veins.

The rare earth minerals are represented by monazite, xenotime, rare earth carbonates. Monazite forms crystals and I observed as small inclusions in various minerals.

Monazite in veins and associated with Mn-columbite contains wt.%: La2O3 at level 8, Ce2O3 - 26-28, Nd2O3 – 16-18, ThO2 at level 5. Thus, cerium dominates in monazite; the high concentration of neodymium is observed; and thorium is constantly present; however strontium content varies even within one grain.

According to N.S.Kovalchuk et al. monazite from carbonatites at microlevel has various structures like small grains (several mcm in size), forms different aggregates and is observed in different mineral associations (Kovalchuk et al., 2011). Chemically they are subdivided into three groups by predominating cation: type 1 (La2O3≥Ce2O3), type 2 (La2O3=Ce2O3), type 3 (Ce2O3 >La2O3).

Xenotime is observed as crystals and grains and also as inclusions in other minerals. Microprobe studies reveal xenotime as poikolite inclusions in complex, hard-to-diagnose, but stable phases. We define the phases as isomorphous Fe[PO4]-Th[SiO4] minerals. However taking into account that earlier works mentioned the presence of hattonite Th[SiO4] (structural analog of monazite), we seem to deal with P-hattonite CeThSi[PO8]) or Th, Si-rabdophanite (CeThP[SiO8]×3H2O), and then the stable ferric admixture can be resulted from goethite or hydrogoethite admixture in the mineral. Further structural investigations will find answers to these questions.

Rare earth carbonates. In such minerals as bastnaesite – mineral from carbonate group – iron is always present. Images show the presence of rare earth phases in matrix of siderite or ankerite. Thorium-rich phases are well defined. However thinner intergrowths are preset that is like graphic, where alternation of Ca and Fe rich carbonates is observed; more Fe-rich ones show higher content of REE and Sr. Generally La2O3 и Ce2O3 content makes 15-30 wt.% with predominance of cerium.

The studied features of mineral chemical composition of vein carbonatites from Chetlassky complex can support sorting source areas for gold-bearing and diamondiferous placers in Middle Timan.

Minerals of rare earth, radioactive and rare metals occur in vein carbonatites developed within the Chetlassky Kamen in Middle Timan. The formation of mineralization is connected with the effect of evolutioning mantle fluid on sedimentary metamorphic rocks.


The investigations are carried out within the framework of RAS Program 12-P-5-1015 (block 4).



Ivensen Yu. P. Magmatism of Timan and Kanin peninsula. M.-L.: Nauka, 1964, 126 pp.

Kovalchuk N.S., Shumilova T.G., Kozyreva I.V. Morphology and features of chemical composition of monazite in carbonatites from Kosyu massif (Middle Timan) // Bulletin of Komi SC UB RAS, No.1(5). 2011. Pp. 49-53.

Kovalchuk N.S. Evolution of chemical composition of pyrochlore  from carbonatites of Kosyu massif (Middle Tima) // Structure, substance, history of lithosphere of Timan-Norther Ural segment. Proceedings of 20th scince conference. Syktyvklar: Geoprint, 2011. Pp. 74-76.

Kostyukhin M.N., Stepanenko V.I. Baikalian magmatism of Kanin-Timan region. L.: Nauka, 1987. 232 pp.

Nedosekova I.L., Udoratina O.V., Vladykin N.V., Pribavkin S.V., Gulyaeva T.Ya. Petrochemistry and geochemistry of dyke ultrabasites and carbonatites of Chetlassky complex (Middle Timan) / Yearbook-2010, IGG UB RAS works, issue 158, 2011, pp.122-130.

Stepanenko V.I. Alkaline pycrites of Middle Timan // Geology of marmatic structures of Northern Urals and timan. Syktyvkar, 1984, pp.3-15 (Works of Institute of Geology Komi Branch USSRAS, issue 48).

Stepanenko V.I., Likhachev V.V., Shvetsova I.V. Alkaline metasomatosis and niobium mineralization in Riphean terrigenous carbonate structures in Timan // Endogenic complexes of European North-East of USSR. Syktyvkar, 1988, pp. 33-46. (Works of Institute of Geology Komi Branch USSRAS, issue 65).

Cherny V.G. Genetic types of rare metal ores connected with ultrabasic-alkaline magmatic formation in Timan // Metasomatism and ore formation. L., 1972. Pp. 205-206.