| The Late Paleozoic strata in the Ordos Basin are extensively developed and rich in petroleum resources.However,the study of the Upper Paleozoic in the Southern Ordos Basin is relatively weak,and the exploration degree of oil and gas is low.There are still no major exploration breakthroughs,especially the unclear provenance in the Southern Ordos Basin severely restricts natural gas exploration.The evolution process of the Qinling Orogenic Belt plays an important role in controlling the formation and evolution,sedimentary,and the formation and transformation of oil and gas reservoirs of the Ordos Basin.However,the coupling relationship between the Qinling Orogenic Belt structure evolution and the material filling and sedimentation process in the Ordos Basin is not yet clear.Based on this,through the observation of the drilling core and field outcrop in the southern Ordos Basin,and the analysis of the paleocurrent,sandstone composition and heavy mineral component,combined with sedimentary geochemistry and detrital zircon U-Pb dating and in situ zircon Lu-Hf isotopic analyses have been comprehensively studied,focusing on the analysis of the provenance in the Shan 1 and He 8 Member of the Southern Ordos Basin,and then exploring the coupling relationship between sedimentary filling in the Southern Ordos Basin and the evolution of the peripheral orogenic belt in the Middle and Late Paleozoic.The results are as follows:(1)The paleocurrent direction,sandstone type,lithic fragment type and their relative content,heavy mineral type and their distribution characteristics are basically the same in the Shan 1-He 8 Member in the Southern Ordos Basin,and they have well inheritance.However,the above-mentioned characteristics of the southwestern and southeastern of the southern Ordos Basin are significantly different.(2)Sedimentary geochemical analysis shows that the provenance of the Shan 1–He 8 Member in the Southern Ordos Basin are mainly from the quartz cycle source area,followed by the neutral igneous and mafic rock source areas,and the sedimentary mainly from the cycle of continental crust material,followed by the material of the active orogenic belt.(3)The comprehensive provenance analysis shows that the provenance of the Shan 1–He 8 Member of the Southern Ordos Basin are mainly from the ancient cyclic material of North China Block basement,followed by the North Qinling-North Qilian Orogenic Belt source area.Compared with the southeastern area,the Mesoproterozoic and Late Neoproterozoic age group zircons appeared in the southwestern area,suggesting that there is a significant difference in provenance between the two regions.The provenance of the southwestern area mainly come from the ancient cyclic material of North China Block basement and the materials of the North Qinling-North Qilian Orogenic Belt,and a small part of the sources may be related to the Longshan diamictite and Longshoushan diamictite;the provenance of southeastern area mainly comes from the ancient cyclic material of North China Block basement and the materials of the North Qinling Orogenic Belt.From the depositional period of the Shan 1 Member to the He 8 Member,the North Qinling-North Qilian Orogenic Belt provided more filling material for the southern area of the Southern Ordos Basin,reflecting the acceleration of the uplift rate of the peripheral orogenic belt and more supply material since the deposition period of the Shan 1 Member.(4)The ~350–260 Ma age detrital zircons in the Shan1–He8 Member of the Southern Ordos Basin may be from the North Qinling Orogenic Belt,revealing that there are tectonic thermal events that have not yet been fully revealed in the range of ~ 350–260 Ma,especially ~ 320–260 Ma,in the North Qinling Orogenic Belt.(5)The study of basin mountain coupling shows that with the reduction and closure of the Qinling Ocean Basin at 420 Ma,the North Qinling began to rise as a whole and triggered the uplift of the North China Block,which continued until 360 Ma.Since the Late Paleozoic,under the background of the extension of the southern Qinling Mountains and the opening of the Mianlue Ocean Basin,the Carboniferous began,and the North China Basin subsided again to accept marine deposition.The subduction and compression of the Mianlue ocean basin in the Early Permian further uplifted the Qinling Mountains,which caused a large-scale retreat of the Ordos Basin and transferred to the continental sedimentary environment,and input a lot of material into the basin. |
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