Chronology And Significance Of Baiyinbaolage In Bayan Obo Group In Inner Mongolia

The North China craton(NCC) underwent the Metamorphic event(lvliang movement, or Zhongtiao orogeny) during late Paleoproterozoic, after that the NCC begin to enter the stage of basement evolution. From now on, the growth and evolution of rift system in the North China begins. During this process, three main taphrogenic troughs inside NCC, Yan Liao taphrogenic trough, Yu Shan taphrogenic trough and zha,ertai-Bayan Obo taphrogenic trough, opened in turn and accept the deposition to develop multiperiodic magmation. Furthermore, formation of Bayan Obo taphrogenic trough and zha,ertai mountain taphrogenic trough is processed in the rifting event of North China plate.Bayan Obo group of Inner Mongolia is located at the north side of the NCC, it has been concerned because of its huge storage of REE-Nb-Fe mineral. In addition, the views on the stage of forming the Bayan Obo group are different, such as paleozoic and mesoproterozoic etc. The objects in this paper is the detrital zircon of quartz sandstone based on baiyinbaolage formation in the Bayan Obo group of Siziwang Banner area which is located at north side of the NCC. The high ratios of Th/U of detrital zircon with 0.34-1.68 are given by three stone samples based on baiyinbaolage formation. They are zircon formed by magma. The U-Pb age exists in 1183Ma-2903 Ma. Furthermore, three main crests can be seen with 2.6Ga, 1.8-1.6Ga and 1.2-1.4Ga, the first two crests correspond to the cratonization of North China plate in neo-archean and opening of aulacogen of early NCC in Mesoproterozoic and, the magmatic event, the third crest perhaps represents the Grenville orogeny-thermal event. As a result, the researchers think that the time forming Bayan Obo group should be in Early-proterozoic to Mid-proterozoic. By analyzing the stage and provenance, we speculate that the evolution of the NCC in the later period of Mesoproterozoic may hold a relationship with the Grenville orogeny-thermal event and provide clue to the relationship between Rodinia and evolution of North China.