LATE PALEOZOIC SEDIMENTARY TECTONIC SETTING IN SUOLUN AREA OF INNER MONGOLIA: Evidence from the Detrital Zircon Chronology of Upper Permian Zhesi Formation

The Upper Permian Zhesi Formation widely distributed in the southern Northeast China is mainly composed of sandstone, mudstone, limestone and shale, and contains brachiopod, bryozoan and gastropod fossils. The LA-ICP-MS zircon U-Pb dating data of medium-coarse feldspar lithic sandstone and fine-medium feldspar sandstone samples from Zhesi Formation in Suolun area of Inner Mongolia records four groups of age range, among which the zircons with the peak age of 272 Ma are predominant (51%) and consistent with the volcanic rocks of Dashizhai Formation and the island-arc magmatic rocks on the north, the peak ages of 403 Ma and 511 Ma are in the age range of Pan-African metamorphic complex in Northeast China and the other ancient ages are also covered by the age range of Daxinganling metamorphic basement. The above age characteristics indicate that the sources of Zhesi Formation are mainly the Early Paleozoic island-arc volcanic rocks distributed in adjacent areas, with a few from the metamorphic basement of northeast adjacent blocks. Considering the wide distribution of Zhesi Formation in Northeast China with mostly carbonate and clastic rocks, the well-preserved paleontological fossils and stable sedimentary environment, it is proved that Zhesi Formation should be continental margin deposits.