Provenance and tectonic settings of the Late Paleozoic sandstones in central Inner Mongolia,NE China: Constraints on the evolution of the southeastern Central Asian Orogenic Belt |
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| Institution: | 1. Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process (Ministry of Education of China), China University of Mining and Technology, Xuzhou 221116, China;2. Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Mineral, Shandong University of Science and Technology, Qingdao 266590, China;3. School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China;4. Asian Tectonics Research Group, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;5. PetroChina Huabei Oilfield Company, Renqiu 062552, China;1. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China;2. Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, USA;3. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an, China;1. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;2. Earth Systems Science Programme, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China;3. Collaborative Innovation Centre of Continental Tectonics, Northwest University, Xi''an, Shaanxi Province, China;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;3. Department of Geology, University of Leicester, Leicester LE1 7RH, UK;1. Hebei GEO University, Shijiazhuang, Hebei 050031, China;2. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China;3. School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, China;4. Department of Earth Science, University of Adelaide, Adelaide 5005, Australia |
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| Abstract: | Late Paleozoic sedimentary strata outcrop extensively in central Inner Mongolia, and are a key to understanding the tectonic evolution of the southeastern Central Orogenic Belt. A combined analysis of petrography, whole-rock major and trace element, and Nd isotope is carried out on representative sandstones from the Late Paleozoic sedimentary strata (420–270 Ma). The sandstones are mainly wackes and litharenites in lithology, with low SiO2/Al2O3 of 2.85–9.47 (averagely 5.22) and poor textural and compositional maturities, implying short sediment transportation between the depositional basins and provenances. The trace element compositions are generally comparable to that of the average upper continent crust (UCC), with negatively-sloping chondrite-normalized rare earth element distribution patterns ((La/Yb)N = 3.43–11; averagely 6.94) and flat UCC-normalized trace element distribution patterns. The Nd isotopic compositions show great variation (?Nd(t) = ?5.01 to 5.35) with depositional time of the sandstones, and coincide well with the arc magmatic phases in central Inner Mongolia. The geochemical signatures of the sandstones indicate that the dominant provenances are intermediate to felsic arc magmatic rocks that have ages approximating the deposition, although old, recycled sediments may have made a minor contribution. An active continental arc setting during the Late Paleozoic in central Inner Mongolia, controlled by the northward subduction of the Paleo-Asian oceanic slab, was the most likely depositional tectonic setting of the sandstones. This active continental arc setting continued to at least 270 Ma, implying that the final closure of the Paleo-Asian Ocean along the Solonker suture zone most likely occurred sometime during the Late Permian to Early Triassic. The northward subduction of the Paleo-Asian Ocean is likely of West Pacific-style, in which the present-day Baolidao arc has a close genetic link with the South Mongolian microcontinent and, likely, the former originally formed as the arc margin of the latter. |
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