Zircon U-Pb Dating From The Permian, And Its Geological Significance In Daqingmuchang Area, Inner Mongolia

The research zone resferenced in this paper is located in south of Daxinganling,geotectonicly situated in the convergence zone beteen the North China platform andthe Siberian platform.The Final suture between the North China platform and theSiberian platform has always been the focus of scholars debate.Two representativeview is Hegenshan suture zone and Xilamulun suture zone,and tend to the LatePermian eventually closed.In recent years has discovered a new mélange belt inDiyanmiao to Daqingmuchang between the two suture.The tectonic belt is lack ofresearch in the previous.This paper studies start from the detrital zircons from thematrix of Melange.By LA-ICP-MS U-Pb geochronology conducted provenanceanalysis.To provide the basis for the formation time and tectonic setting of thetectonic belt from Daqingmuchang to Diyanmiao.The results indicated that the distribution of detrital zircon age of Shoushangouformation in Xi Ujimuqin Qi areas is similar with the detrial zircon age distribution ofLinxi formation in Linxi areas and Xi Ujimuqin Qi areas.Zircon CL images showedthe typical characteristics of magmatic zircon.Reflect the information of the multiperiod magmatic arc event,Respectively~280Ma、~320Ma and~450Ma.Explain theprovenance is consistent. To further illustrate Shoushangou formation in the lowerPermian to Linxi formation in upper Permian is marine sediments from deep toshallow continuous evolution. The minimum age of detrital zircons fromShoushangou formation was307±3Ma, Probably represent the deposition limit ofShoushangou formation. And the detrital zircons of Shoushangou formation and Linxiformation have the source of information from the North China platform (1800Maand2500Ma) and Bainaimiao arc (430Ma) and Sunit arc (460Ma). Indicated that theXilamulun suture zone and the Hegenshan suture zone has been closed just before307Ma. The tectonic melange in Daqingmuchang was thrust emplaced in the lowerPermian Shoushangou formation, the age of the ophiolite in Daqingmuchang shouldbe after the limit deposited of the Shoushangou formation, which is later than307Ma.Its tectonic environment may be formed by subduction of back arc basin or before Accretionary wedge arc. The minimum age of detrital zircon of Linxi formation inDaqingmuchang was231±2Ma, the minimum age of detrital zircons Linxi formationin Linxi area was261±2Ma, indicating that the sediment bound of Linxi formationwas Late Permian to Early Triassic. Based on the previous researches, the sedimentaryenvironment evolution of Linxi formation showed a significant period of the record ofthe demise of Late Paleozoic rift zone. Therefore, as the tectonic belt formDaqingmuchang to Diyanmiao is probably closed in Late Permian to Early Triassic.