NIOBIAN RUTILE IN Cr-V-BEARING ROCKS OF THE SLUDYANKA METAMORPHIC COMPLEX (Southern Baikal area)
L.Z. Reznitsky1, E.V. Sklyarov1,2, L.F. Suvorova3, S.V. Kanakin4, N.S. Karmanov5, I.G. Barash1
1Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, 128 ul. Lermontova 128, Irkutsk, 664033, Russia
2Far Eastern Federal University, ul. Sukhanova 8, Vladivostok, 690091, Russia
3Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, 664033, Irkutsk, Russia
4Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakhyanovoi 6a, Ulan-Ude, 670047, Russia
5V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Rutile, niobium, chromium, vanadium, isomorphism, metamorphism
Subsection: PETROLOGY, GEOCHEMISTRY, AND MINERALOGY
Abstract
Cr-V-bearing rocks of the Sludyanka metamorphic complex in the Southern Baikal area contain accessory niobian rutile with Nb contents unusually high for metamorphic rocks (10-12 to 20-25 wt.% Nb2O5, or, occasionally, up to 36-37 wt.%). Incorporation of Nb5+ into the rutile structure is balanced by Cr3+ and V3+, which reach 16 wt.% Cr2O3 and 8 wt.% (or, rarely, up to 20 wt.%) V2O3. The distribution of Nb, Cr, and V in rutile is very uneven, down to the microscale. It does not depend on PT conditions being rather controlled by crystallization kinetics of minerals competing with rutile in the paragenesis.
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