[S-CG44] 岩石・鉱物・資源

[SCG44-03] ZIRCON U–Pb AGES AND GEOCHEMISTRY OF GRANITOIDS FROM SOUTHWEST MONGOLIA

*Dolzodmaa Boldbaatar¹、Yasuhito Osanai¹、Nobuhiko Nakano¹、Tatsuro ADACHI¹、Ippei Kitano¹、Kundyz Syeryekhan² (1.Kyushu University、2.Golden Hill LLC)

キーワード：I-, S-type granite, zircon U–Pb age, SW Mongolia

We present new petrographic, geochemical and geochronological data for granitic rocks emplaced in the Altai (Mongolian Altai) terrane of southwest Mongolia. The data are used to constrain their evolution and to discuss the tectonic implications for the Altai terrane. The zircon U–Pb ages indicate that the magmatism can be divided into three stages: stage 1 (397–366 Ma), stage 2 (340-300 Ma) and stage 3 (208-200 Ma). The stage 1 granitic rocks are divided into two types: Bt–Hbl granites having I-type affinity with volcanic arc signature and Crd–Grt bearing Bt–Ms granites having S-type affinity. On the other hand, Stage 2 Qz–Bt syenite having shoshonitic affinity and stage 3 Kfs-porphyritic Bt granites having high-K calc-alkaline affinity with intraplate tectonic setting.