New Data on the Age and Nature of the Khan-Bogd Alkaline Granites, Mongolia

摘要

New age dating (291 Ma) was obtained for one of the largest alkaline granite massifs in the world, the Khan-Bogd Massif (Mongolia). For the first time, apart from zircon, other zirconium silicates, elpidite and armstrongite, have been analyzed. Our determinations showed the highly depleted nature of the mantle sources of granites with epsilon(Nd) = 12. All the studied Zr-silicates demonstrate positive Eu anomalies in the REE patterns, which indicate a low oxidation potential during alkaline granite formation.