The Xinyuan granitic pluton, located at the North side of the Mianxian—Lveyang (MianLve) suture zone, Southern Qinling Moutains, occurs in bathollith with an outcrop area of 200 km2. It consists of granodiorite, mafic microgranular enclaves (MME) and granitic aplite. Zircon SHRIMP UPb datings yielded an age of 219.6±4.6 Ma for the granodiorite and 221.5±4.2 Ma for the MME, which were later than the closing time of the MianL〖AKu¨D〗e ocean basin (242～221Ma). In the basis of the studies on petrology and geochemistry of the granite and enclaves, combined with the regional geological features, we believed that the Xinyuan pluton was formed in intracontinental collision setting after Yangtze plate subduction northward. In that setting, lithospheric delamination led to mantle upwelling with a lot of mantle material and hot energy, causing partial melting of lower crust to generate granitic magma. Partly ascended mantle magma mixed with the granitic magma during the period of transition from compression to extension in orogen, forming the granodiorite and the mafic microgranular enclaves.