Ulug-Tanzek Rare-Metal Igneous Complex and Its Occurrence in the Structures of Sangilen (the Southwestern Flank of the Tuva-Mongolian Superterrane)

Geochronological studies of zircons from rare-metal granites of the Verkhnekundus Nb‒Ta and REE deposit located on the southwestern flank of Tuva-Mongolian massif are carried out. The age of 295 ± 4 Ma is obtained, that is in good agreement with the age of other alkaline rocks in this region, rare-metal granites of the Ulug-Tanzek deposit. The isotopic studies show the similarity of the Nd isotopic compositions of the rocks from the Verkhnekundus and Ulug-Tanzek deposits. Considering the isotope characteristics of the rocks from the Sangilen block, corresponding to the Mesoproterozoic crust, it is concluded that the rare-metal granites were formed with the participation of juvenile material.