Zashikhinsky massif (Irkutsk region) is confined to late Paleozoic East Sayan Mountains zone of alkaline rare-metal granite magmatism. New data of mineral, petrographical, chemical and microelemental composition of rocks of the massif are considered. Three facies variaties of rocks of the massif according to their differentiation grade and ore mineralization are distinguished. The earliest amphiboliferous microcline-albite granites are replaced with leucocratic quartz-albite granites changing into essentially albite varieties. Albitites are the most rare-metal rocks of the deposit; the REE content is over 10 000 g/t in some places reaches 15 440 g/t. In double correlation plots of rock-forming and rare elements common compositional trends are observed; that may indicate the origin of all facies varieties of massif rocks from common primary magma in the process of its differentiation from early to late facies. The REE Spectra of all facies of alcalic rocks are of the same type and differ in their total contents only. Spider-giagrams of these rocks are also similar and differ with minor variations of anomaly sizes. The obtained geological, petrographical and geochemical data indicate the magmatic genesis of rare-metal granites and albitites. The main minerals concentrating rare elements in rocks and ores of the massif are columbite, struverite-ilmenorutile, zircon and xenotime. The massif granites do not show metasomatic zonation and replacement of some minerals by the others that is common for metasomatic rocks. On the basis of all characteristics, the Zashikhinskoe deposit is estimated as one of the largest tantalum rare-metal deposits of alkaline-granite type in Russia.

Alymova Natalya Viktorovna, Candidate of Sciences (Geology and Mineralogy), Senior Scientific Worker, Institute of Geochemistry SB RAS, 1a, Favorsky st., Irkutsk, 664033, Russian Federation, tel.: (3952)42-99-64, e-mail: alymova@igc.irk.ru 

Vladykin Nikolay Vasil'evich, Doctor of of Sciences (Geology and Mineralogy), Head of the Laboratory, Institute of Geochemistry SB RAS, 1a, Favorsky st., Irkutsk, 664033, Russian Federation, tel.: (3952)42-55-12, Irkutsk Scientific Center SB RAS, 134, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 45-30-70, e-mail: vlad@igc.irk.ru

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