Time of definition and geological meaning for metamorphic intrusive rock body in Xiaohongshan region, Beishan area of Gansu and Inner Mongolia

The metamorphic intrusive rock body have first been discovered in Xiaohongshan of Beishan region of Gansu and Inner Mongolia, the north margin of Tarim paleoplate.With the zircon U-Pb age 2 656±146 Ma,its geologic age should be the end of Late Archean-Early Proterozoic.Magmatic genesis belong to Ⅰ-type which formed from the mantle and the crust by fusioning partly in Lüliang Period when the pre-orogenic basements were developing.There is an important significance that the metamorphic intrusive rock body was discovered,with which to study on the crystalline basements of Tarim paleolate and the early evolution for magma and strucure in the region of Beishan of Gansu and Inner Mongolia.