The Songpan-Garze fold belt (SGFB) on the eastern margin of the Qinghai-Tibetan Plateau covers a huge triangular area bounded by Yangtze (South China), North China and Qinghai-Tibetan Plateau blocks. The authors studied petrology, geochemical composition and zircon U-Pb chronological characteristics of Lanniba and Yangfanggou granitoids in the southern part of the Songpan-Garze fold belt as well as their petrogenesis and geological significance. Field geological and geochemical characteristics indicate that the granitoids contained mantle components, thus providing heat and part of source materials for the Mesozoic granites in Songpan-Garze fold belt. The involvement of mantle-derived magma and the existence of ultrahigh-K calc-alkaline I-type granitoids (211±2 Ma) indicate that the Songpan-Garze orogen was under an extensional scheme at least in Late Triassic period.hemas-microsoft-com:office:office" />