Constraints Of The Upper Permian-lower Triassic Detrital Zircon Chronology On The Tectonic Evolution Of The Provenance Area In The Central North China Craton

The tectonic activity of the peripheral orogenic belt restricts the formation and evolution of the basin within the landing.Due to tectonic movement and weathering and denudation,some important geological information is preserved in the strata of the basin,so the study of the basin is particularly important.In this paper,detrital zircon U-Pb geochronology,sandstone skeleton analysis,and earth sedimentary sandstones in the Liulin area of the central part of the North China Craton and the Upper Permian Sunjiagou Formation and Lower Triassic Liujiagou Formation in the Qinshui Basin are carried out.Research on chemical main and trace elements,discussed the sediment source of the central basin of North China,and established the Paleozoic tectonic evolution model of the North China Craton.Through sandstone U-Pb geochronology,it is found that the detrital zircons of the sandstone samples from the Sunjiagou and Liujiagou formations in the Liulin area and the Qinshui Basin are mainly Paleozoic magmatic zircons and Precambrian metamorphic zircons.Liulin area Sandstones of the Sunjiagou Formation and Liujiagou Formation contain a small amount of Early Paleozoic zircons,but no Early Paleozoic zircons are found in the sandstones of the Sunjiagou Formation in the Qinshui Basin.By comparing the peak zircon age with the peak value of the potential source area in the periphery,combined with the paleocurrent direction,it is preliminarily believed that the early Paleozoic came from the Bainaimiao island arc on the northern margin of North China,and the late Paleozoic detrital zircon came from the Inner Mongolia uplift.Using the minimum age weighted average method to limit the time limit of stratum deposition,the weighted average ages of the sandstones of the Sunjiagou Formation,Liujiagou Formation and Sunjiagou Formation in Qinshui Basin in Liulin area are255 ± 7 Ma,respectively.251 ± 7 Ma and 250 ± 5 Ma,it is inferred that the sedimentary age of the Sunjiagou Formation in North China is early in the north and late in the south.Zircon trace element analysis found that depleted light rare earth elements gradually enriched heavy rare earth elements.It is believed that the zircon sources in the Liulin area and the Qinshui Basin come from the same source area.The analysis of the sandstone skeleton shows that the sandstone samples of the Sunjiagou and Liujiagou formations in the QFL and Qm-F-Lt diagrams mainly fall in the cut island arc area,and a small amount fall in the transition island arc and the recirculation orogenic belt.The tectonic environment is similar to the subduction environment of the Paleo-Asian Ocean in the early Paleozoic of the Bainaimiao island arc on the northern margin of North China.The analysis of major and trace elements in geochemistry shows that the mass fraction of sandstone oxides shows that the sandstones of the Sunjiagou Formation and Liujiagou Formation are mainly light-colored minerals with a high content of silicon and aluminum.On the whole,they are mainly silicon-rich and aluminum-rich quartz.And feldspar minerals,and contain a small amount of mica and clay minerals;from the rare earth content of sandstone samples combined with the standardized distribution model,it is believed that the Sunjiagou Formation and the Liujiagou Formation are enriched in LREE,HREE is relatively depleted,and Eu is slightly negative.It is generally believed that the average values of rare earth elements in the sandstone samples of the Sunjiagou Formation and the Liujiagou Formation are basically consistent with the rare earth element parameters of the active continental margin.In summary,it is preliminarily believed that the tectonic evolution stage of the North China Craton in the Paleozoic period is as follows:(1)In the early Early Ordovician,the Paleo-Asian Ocean began to subduct to the south,and the Bai Naimiao island arc located in the middle of the Paleo-Asian Ocean and the North China Craton The ancient Asian Ocean uplifted under the subduction effect;(2)Since the Late Devonian,the ancient Asian Ocean continued to subduct southward of the Bainaimiao island arc and eventually collided with the northern part of the North China Craton,which uplifted the northern part of North China and formed the Inner Mongolia uplift.,And formed a geographical pattern of high north and low south.(3)In the late Late Permian,the ancient Asian ocean merged with the northern part of North China under continuous subduction,and the Inner Mongolia uplift eventually became the source area of the North China Craton inland basin,providing material for the formation and evolution of the basin.