2012

News Registration Abstract submission Deadlines Excursions Accommodation Organizing committee
First circular Second circular Abstracts Seminar History Program Travel Contact us
Новости
Первый циркуляр
Второй циркуляр
Регистрация
Оформление тезисов
Тезисы
Программа
Участники
Размещение
Экскурсии
Проезд
Важные даты
Оргкомитет
Обратная связь

Тезисы международной конференции

Рудный потенциал щелочного, кимберлитового

 и карбонатитового магматизма

Abstracts of International conference

Ore potential of alkaline, kimberlite

and carbonatite magmatism

Rb-Sr, Sm-Nd, U-Pb, Lu-Hf isotope systems and geochemical specificity

Il’meno-Vishnevogorsky Alkaline-Carbonatite Complex (Urals, Russia)

Nedosekova I.L.

Institute of Geology and Geochemistry UB RAS, Ekaterinburg, Russia

vladi49@yandex.ru

 

Il’meno-Vishnevogorsky Alkaline Carbonatite Complex (IVAC) is one of the largest alkaline complexes of miaskites, fenites and carbonatites with REE-Zr-Nb mineralization located within the Urals Fold Belt. We have dated by different isotope methods including Rb-Sr and Sm-Nd isochrons on WR and rock-forming minerals, SHRIMP U-Pb zircon and U-Pb pyrochlore dating, the main rock types of IVAC and studied Lu-Hf isotope systematics and trace element patterns of various components of the complex. The isotope dating has detected numerous age clusters for the IVAC rocks – 446-410, 390-360, 335-325 and 280-230 Ma. These age clusters correspond to the major stages of tectonic development of the Ural fold belt (rifting, early and late collisions, postcollisional extension) [Puchkov, 2010] and recorded by isotopic dating in other structural-material complexes of the Southern Urals [Echtler et al., 1997].

The isotope signatures of the IVAC main rock types: miaskite-carbonatite complex (epsilon Sr = -6...-10, epsilon Nd = +3…+6, epsilon Hf = +4…+6) and Buldym ultrabasic massif and related carbonatites (87Sr/86Sr = 0.70421–0.70470, εSr (+6…+8), εNd (+1…-3) и εHf (0…-2) show moderately depleted to moderately enriched (type EM1) isotopic compositions and require the depleted mantle source [Kramm et al, 1983; Nedosekova et al, 2009; Nedosekova et al, 2010]. A close resemblance exists between the isotope characteristics and lines of isotopic systems of the IVAC and carbonatites of rift platform ultramafic-alkaline carbonatite complexes (UACP) Kola, Maymecha-Kotuy Alkaline Provinces and other, which are located within Precambrian cratons. This suggests that the origin of these alkaline-ultrabasic complexes is connected with deep seated mantle sources, possibly to an upwelling mantle plume and/or further mixing plume component with enriched component EM1[Bell, 2001; Kramm 1993; Kramm, Kogarko, 1994; Kogarko et al., 2010 and other]. Therefore it is very possible the IVAC has the similar source. But at the present the origin of alkaline magmas of the IVAC due to melting of the UACP rocks or oceanic crust rocks with the same isotope signatures is not ruled out. 

Close resemblance of the IVAC and UACP complexes according to isotope and geochemical characteristics are fixed (divergent). IVAC have much in common with the rift UACP and with the collision carbonatite-alkaline complexes formed in the final stages of development of orogens during postcollisional extension. Thus, IVAC miaskites and carbonatites have significant content of HFSENb, Zr, etc., which are similar to the rifting UACP complexes and differs from the collision carbonatite complexes, which are usually depleted in HFSE. However, IVAC miaskites and carbonatites are enriched large ion lithophile elements (LILE) primarily Sr, to a lesser extent Ba, K, Rb, LREE, which is characteristic for a collision alkaline and carbonatite rocks, localized in linear post-collision zones. It should be noted that collision alkaline-carbonatite complexes in contrast to the IVAC have more enriched ("crust ") isotopic compositions [Hou, 2006].

Isotopic-geochemical divergence is probably due to a long history of IVAC formation. Geochronological data indicate the IVAC has been introduced in the crystalline basement rocks (PR1) in the lower Paleozoic and has undergone a significant transformation during the evolution of the Ural folded region. The geochronological data for the IVAC specify the intrusion of alkaline rocks and carbonatites (3) and long-lasted metamorphic stage of the IVAC formation, with which are connected the processes of anatexis, pegmatite genesis, metasomatose, and re-loading of carbonatites, wide developed within the IVAC at collision (D2-3, C1) and post-collision (P-T) stages of the Urals Belt evolution.

 

This study was financially supported by programm of interdisciplinary projects Ural Division, Siberian Branch and DO of the Russian Academy of Science № 12-С-5-103 and by president programm № 12-П-5-2015.

 

References

Bell K. Сarbonatites: relationships to mantle plume activity. In: Ernst R, Buchan KL (eds) Mantle plumes: their identification through time. Geol. Soc. Am. Spec. Paper. 2001. P. 267-290.

Echtler H.P., Ivanov K.S., Ronkin Y.L. et al. The Tectono-metamorphic evolution of gneiss complexes in the Middle Urals, Russia // Tectonophysics. 1997. V. 276. P. 229-251.

Hou Z., Tian S., Yuan Z et al. The Himalayan collision zone carbonatites in western Sichuan, SW China: Petrogenesis, mantle source and tectonic implication // Earth and Planetary Science Letters. 2006. 244. P. 234-250.

Kramm U. Mantle components of carbonatite from the Kola Alkaline Province, Russia and Finland: a Nd–Sr stady // Eur. J. Mineral. 1993. № 5. P. 985-989.

Kramm U., Blaxland A.B., Kononova V.A., Grauert B. Origin of the Ilmenogorsk-Vishnevogorsk nepheline syenites, Urals, USSR, and their time of emplasement during the history of the Ural fold belt: a Rb-Sr study // J.Geol., 1983. V. 91. P. 427-435.

Kramm U., Kogarko L.N. Nd and Sr isotope signatures of the Khibina and Lovozero agpaitic centers, Kola alkaline province, Russia. Lithos, 1994. V. 32. Р. 225-242.

Kogarko L.N., Lahaye Y., Brey G.P. Plume-related mantle source of super-large rare metal deposits from the Lovozero and Khibina massifs on the Kola Peninsula, Eastern part of Baltic shield: Sr, Nd and Hf isotope systematics. Miner Petrol. 2010. V. 98. P. 197-208.

Nedosekova I.L., Vladykin N.V., Pribavkin S.V. et al. Il’meno-Vishnevogorsky miaskite-carbonatite complex: origin, ore-bearing, sources (Urals, Russia) // Geol. Ore. Depos., 2009. V. 51. № 2. P. 157-181.

Nedosekova I.L., Belousova Е.А., Sharygin V.V. Sources of Il’meno-Vishnevogorsky alkaline complex  according to Lu–Hf-isotope in the zircons // DAN. 2010. V. 435. № 2. P. 234-239.

Puchkov V.N. Geology of Urals. Ufa: Design Polygraph Service, 2010. 280 p.