The Source Of Carboniferous-Permain Sedimentary Rocks In The Beidaihe,NCC And Its Tectonic Significance

The North China Craton?NCC?undergo a long time evolutionary history with a complicated tectonism and Magmatism.Especially in Phanerozoic stage,the tectonism is active around the northern of The North China Craton which make a significant impact on the craton's structural framework.However,the research about paleogeographic evolution basin the change of terrigenous supply is very few and limited.The study area of this paper lies in the Shimenzhai area of Beidaihe,a country of Qinhuangdao City.We designed ten sampling point around the different formation.U-Pb dating,trace element analysis,XRD analysis as well as Hf isotope composition are processed against on the samples.Zircon U-Pb dating indicating there is a minimum age at²93.6Ma which giving an upper bound for the formation age,and we identify two zircons with age greater than³.0Ga.We turned 10 samples into four groups and named Unit 1,2,3 and 4 respectively.Total four age clusters can be identified from the groups all with age peak at³20Ma,⁴50Ma,¹.85Ga and².5Ga.The groups are different in age distribution when the lower age peaks,³20Ma,⁴50Ma,located in group Unit 1 and 2 and the greater age peaks,¹.85Ga and².5Ga,located in group Unit 3 and 4 mainly.Carboniferous-Permian igneous rocks are widely found in northern NCC and igneous rocks at age⁴50Ma age is widely distributed around the Qinling Orogenic Belt?QOB?,the metamorphosed basement within the carton is formed at Proterozoic.There is a significant consistency in?_Hf?t?between the sample from study area with age at³20Ma and the igneous rocks from northern NCC as well as between the sample with age at⁴50Ma and northern QOB.Based on zircon U-Pb dating,Hf isotope analysis and the predecessors'study,we infer the zircons in the sample with age at¹.85Ga is derived from the northern NCC formation and the zircons with age at².5Ga is derived from the Archean and Proterozoic formation near the study area.Based on the points discussed above,we establish one model researching on the source variation and response the closure process of Asian Ocean.