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Single-grain zircon U-Pb dating was carried out to constrain the emplacement timing of granitic plutons at Chaxinzi, Xiaoweishahe and Longtou in the Tonghua area, south of Jilin Province. The results show that these plutons formed in the Triassic with ages of 203—217 Ma. Geological and geochemical characteristics indicate that the plutons are composed of quartz diorite and granite. The former was derived from partial melting of mafic lower crust, whereas the latter originated from thickened crust with garnet as the residue in the source. It appears that protoliths of these two types of granitits are different although they have the same emplacement age. Considering that these plutons are petrologically different from the coeval granites in the Xingmeng (Xing抋n-Mongolian) to Jihei (Jilin-Heilongjiang) orogenic belt in the north, it is suggested that their formation was related to the Dabie-Sulu ultrahigh-pressure collisional orogenesis since their ages are only 10—20 Ma younger than timing of the ultrahigh-pressure metamorphism, but comparable to that of the first rapid exhumation of the ultrahigh-pressure metamorphic rocks and the emplacement of the post-collisional granites.
The results show that these plutons formed in the Triassic with ages of 203- 217 Ma. Geological and geochemical characteristics indicate that the plutons are composed of quartz diorite and granite. The former was derived from partial melting of mafic lower crust, but the latter originated from thickened crust with garnet as the residue in the source. It appears that consider these those types of granitits are different from the coeval granites in the Xingmeng (Xing 抋 n-Mongolian) to Jihei (Jilin-Heilongjiang) orogenic belt in the north , it is suggested that their formation was related to the Dabie-Sulu ultrahigh-pressure collisional orogenesis since their ages are only 10-20 Ma younger th an timing of the ultrahigh-pressure metamorphism, but comparable to that of the first rapid exhumation of the ultrahigh-pressure metamorphic rocks and the emplacement of the post-collisional granites.