Consideration and practice of the construction of litho stratigraphic systems in high-grade metamorphic terrains —Acase study in the Daqingshan-Wulashan area

Abstract：The early Precambrian stratigraphic system in the Daqingshan-Wulashan area is reconstructed based on recent regional geological survey. A Meidaizhao Group-complex is eslatlished and classified as the Paleoproterozoic. The high-grade metamorphic rocks in the area are regrouped, i.e. the granulite sequence is subdivided into two formation complexes, which are merged into the Sanggan Group-complex, and the Wulashan Group-complex is subdivided into two subgroup-complex, a lower subgroup complex. and an upper subgroup complex.The former is known as the gneiss sequence and the latter is equivalent to the Jining Group, a khondalite sequence. The major structural patterns of the high-grade terrain in the area are characterized by dome structures and fold groups between the domes (simply called ｀dome-fold＇ structures). It is suggested that the large-scale ledding detachment system is a key factor for determining the spatial distrilution,composition and interrelations of high-grade metamorphic rocks.The new ways and methods of estallishing lithostatigraphic systems in high-grade metamorphic terrains are proposed in the paper.