The discovery of Zaoergou angular uncomformity and establishment of Meidaizhao Group-complex in Daqing Mountains, Inner Mongolia--Paleaoproterozoic Low-grade metamorphic strata on the Khondalite series

The Daqing Mountains area is one of the areas of early Precambrian khondalite-bearing meta-morphic complexes in the western segment of the northern margin of North China craton.In addition to the widely exposed khondalite series,there occurs a suite of low-grade metamorphic clastic rocks com-posed of various types quartzites and granulitite(leptite),which was previously assigned to the Fourth Formation-complex of the Archean Wulashan Group-complex or high amphi bolite-facies khondalite series.Through detail geo logical mapping and research,it is found that this suite of low-grade metamorphic stra-ta overlies the khondalite series unconformably and was not deposited until the khondalite series underwent granulite-facies metamorphism and deformation of the lower crust and was exhumed onto the surface.It is Paleoproterozoic in age and named the Meidaizhao Group-complex.