Abstracts Travel
Program Organizing committee

Geochemical features and ore potential of rare-metal alkaline

granites of Central Asia

Vladykin N.V.


Rare-metal alkaline granites occur in Siberia, Trans Baikal Area and Mongolia. They are related to deposits of rare elements (Zr, Nb, Ta, TR, Y, Li, Be and F). The complexes of alkaline rocks are found either in the shields (Aldan shield) or fold zones (Eastern Sayan, Trans Baikal Area and Mongolia). They include the Katugin massif in the south-west and Ulkan in the south-east edge of the Aldan shield; Ulan-Tanzek and Zashikhinski  massifs in the Eastern Sayan, Ermakovka massif in the Trans Baikal Area, Khaldzan-Buretinsk and Khan-Bogda massifs in Mongolia. The age of the massifs in the Aldan shield is the Proterozoic (1800 Ma) while in the fold zones the massif are of the Paleozoic age. We discuss three types of rare-metal deposits associated with the above granite massifs: Zr-Tr-Nb in the Khan-Bogda, Nb-Zr-Y-TR in the Katugin  and Be-F in Ermakovka. All  deposits differ in mineral composition of ores.  The major element in the Khan-Bogda massif is Zr and ores include alpidite-armstrongite and Nb and TR silicates. Ores comprise veined arfvedsonite-aegirine  granites and pegmatites. Zr content can reach as high as 7%. In the Katugin massif the ores include granites and hydrothermal cryolite-gagarinite rocks. The ores comprise pyrochlore, zircon and gagarinite. In the Ermakovka rare-metal occurrence the fluid-magmatic ores are composed of silicate Be-phenakite, bertrandite and fluorite with microcline. They are genetic derivatives of volcanic comendites. All described types of granites demonstrate similar plots on spider-diagrams but possess significant difference in the concentrations of these elements. Moreover in the first two types of deposits ore-bearing and barren granites differ only in concentrations of elements. In the Ermakovka occurrence both plots and contents of elements significantly differ between granites and ores. This difference results from the genetic features of rare-metal ores.