Abstract：Xinchang section is one of the candidate fields in Beishan area，Gansu Province—the preselected area for China¢s high-level radioactive waste repository. The results show that the dominant rock characteriastics from Xinchang section are monolithic granite and granodiorite. The minor dominant rock is the quartz diorite. Mineral assemblage such as hornblende，magnetite，sphene，titanite，etc. show that the kinds of minerals mentioned above are of syntectic or I-typed granite. Some mineral assemblages of granodiorites such as muscovite，garnet，etc. are found during upper crust forming. The petrochemistry composition belongs to high potassium Ca-alkaline series，showing the special feature of syntectic or I-typed granite.
