Tectonic Evolution of Southeast Central Asian Orogenic Belt: Evidence from Geochronological Data and Paleontology of the Early Paleozoic Deposits in Inner Mongolia

In this study, we present detrital zircon U-Pb dating and paleontological data for the newly identified Ayadeng Formation in the northern margin of the North China Block (NCB) and Xibiehe Formation (molasse) in the Bainaimiao arc belt (BAB), which could provide strong evidence indicating the affinit...

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Published in:	Journal of earth science (Wuhan, China) China), 2020-08, Vol.31 (4), p.743-756
Main Authors:	Wang, Shijie, Li, Shichao, Li, Wenjie, Xu, Zhongyuan, Zhang, Jinfeng, Li, Changhai, Shi, Qiang, Liu, Yang, Wang, Wenlong, Guan, Qingbin
Format:	Article
Language:	eng
Subjects:	Affinity Belts Biogeosciences Corals Data Dating Earth and Environmental Science Earth Sciences Evolution Fossil animals Fossils Geochemistry Geochronology Geochronometry Geological time Geology Geotechnical Engineering & Applied Earth Sciences Geotectology Gondwana Heredity Isotopes Lead Magma Marine molluscs Ordovician Orogeny Palaeontology Paleontology Paleozoic Radiometric dating Sandstone Sedimentary rocks Siltstone Tectonics Zircon
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Summary:	In this study, we present detrital zircon U-Pb dating and paleontological data for the newly identified Ayadeng Formation in the northern margin of the North China Block (NCB) and Xibiehe Formation (molasse) in the Bainaimiao arc belt (BAB), which could provide strong evidence indicating the affinity of the BAB and the evolution of the southeast Central Asian orogenic belt (CAOB). Zircon U-Pb data of siltstone samples and paleontological data indicate the Ayadeng Formation dates back to the Early Ordovician. Although its location is near the NCB, its zircon age spectra and paleontology share a closer affinity with those of Tarim and NE Gondwana, as the U-Pb data suggest an age range of 490–2 192 Ma (peak age=629, 788, 965 and 1 935 Ma), and similar gastropod fossils are found in Tarim and NE Gondwana. The U-Pb ages of meta-sandstone samples in the Xuniwusu Formation indicate a shared inheritance with the Ayadeng Formation (before 440 Ma), and the U-Pb ages of sandstone samples in the Xibiehe Formation are concentrated, with age peaks centered at ca. 420 Ma. Fossil corals occur in these two formations, and their age components also indicate a collisional setting. Therefore, it is speculated that the BAB drifted away from Tarim or NE Gondwana during the Ordovician and became attached to northern NCB between 440–420 Ma as an exotic terrane. During the Early Paleozoic, there may have occurred a collision between an arc and a continental block.
ISSN:	1674-487X 1867-111X