Provenance Analysis Of Permian And Its Constraints On Sedimentary Basin Evolution In Dashizhai Area,Inner Mongolia

The Xing'an-Neimeng orogenic belt is located in the southeast margin of the Central Asia orogenic belt,which is of great significance to reveal the tectonic evolution of the accretive orogenic belt and the late Paleozoic.In this paper,zircon ages and provenance characteristics of Permian in Dashizhai area are selected to constrain the evolution of Permian sedimentary basinsDashizhai area in the study area is located in the east of Xingmeng orogenic belt,with a large area of Late Paleozoic Permian strata exposed.The Permian strata can be divided into five parts: Wujiatun formation ? Shoushangou formation ? Dashizhai formation?Zhesi formation and Linxi formation.Based on the petrological and isotopic chronology of the samples,the youngest age of the argillaceous slate and detrital zircon of the Shoushangou formation is 348 Ma;the feldspar fine sandstone of the Zhesi Formation,the youngest age of zircon is 252 Ma;the youngest ages of detrital zircons in Linxi formation are 241 Ma and 258 Ma.According to the zircon characteristics and provenance analysis,the zircon ages of clastic rocks are mostly concentrated in the early Devonian Late Permian,representing the age information of collision and amalgamation of North China plate and Siberian plate;350-850 Ma,representing the age information of amalgamation of Xing'an landmass?Erguna landmass and southern margin of Siberian plate;1000-1400 Ma Zircon ages show the basement ages of the micro plates in the southern margin of the Siberian plate;the zircon ages of 1800-2500 Ma are more likely to come directly or indirectly from the northern margin of the North China plate or the southern margin of the Siberian plat.Therefore,the Permian strata have the characteristics of multi-source supply,but the main body comes from the Northeast landmass which is amalgamated by each landmass,and part of the provenance comes from the northern margin of the North China plate and the southern margin of the Siberian plate.The minimum age of zircons in Linxi formation is 241 Ma and 258 Ma respectively,which indicates that the Dashizhai melange belt was closed before the Late Permian Early Triassic.According to the zircon age characteristics of the Permian strata and previous research results,it is possible that Dashizhai structural melange belt and Hegenshan structural melange belt have the same structural attribute,and their Dashizhai structural melange belt is inferred as the eastern extension of structural mélange belt.Combined with previous studies on the stratigraphic sequence,sedimentary facies and tectonic evolution history of the Dashizhai area,the Early Permian in the Dashizhai area consisted of a set of trench-arc-basin depositional systems consisting of the Wujiatun Formation?Dashizhai Formation?Shoushangou Formation,Zhesi formation is the sedimentary characteristics of the residual sea and the continental Linxi Formation,it may be better to limit the formation time of the Dashizhai mixed rock to after the 296 Ma before the Zhesi Formation,and the Permian Basin in the study area has regressed in the Late Permian Early Triassic,forming a land environment.