College of Earth Sciences，Jilin University，Changchun 130061，China

The authors studied geochronology and geochemical data of the Songjianghe biotite monzogranite in the southern Zhangguangcai Ｒange in order to determine its formation age， magma source，and tectonic environ- ment． The results indicate that the Songjianghe biotite monzogranite was formed in the Middle Jurassic with an age of 168． 2 ±2． 0 Ma (MSWD =0． 93)． The monzogranite was characterized by high alkali and low CaO and MgO，belonging to high- potassium calc- alkaline，metaluminous I- type granite． The rock is enriched in large ion lithophile elements such as Ｒb，Ba，and K and strongly depleted high field strength elements such as P，Ti， Nb，and Ta． It is concluded that the Songjianghe biotite monzogranite was derived from partial melting of am- phibolite facies metamorphism mafic lower- crust and its formation was controlled by the Pacific Plate subduc- tion．