Early Paleozoic tectonic evolution of the Xing-Meng Orogenic Belt: constraints from detrital zircon geochronology of western Erguna-Xing'an Block, North China
Résumé
To better constrain the Early Paleozoic tectonic evolution of the western part of the Erguna-Xing'an Block, detrital zircon U-Pb dating was applied on the Ordovician to Devonian sedimentary strata along the southeast part of the China-Mongolia border. Most of the zircons from five sedimentary samples display fine-scale oscillatory growth zoning and Th/U ratios higher than 0.1, indicating a magmatic origin. All five Ordovician-Devonian samples display the similar age distribution patterns with age groups at ∼440 Ma, ∼510 Ma, ∼800 Ma, ∼950 Ma, and few Meso- to Paleo-Proterozoic and Neoarchean grains. This age distribution pattern is similar to those from adjacent blocks in the southeastern Central Asian Orogenic Belt. Considering previous tectonic studies, we propose bidirectional provenances from the Erguna-Xing'an Block and Baolidao Arc. Consequently, a new model was proposed to highlight the Early Paleozoic tectonic evolution of the western Erguna-Xing'an Block, which constrains two main Early Paleozoic tectonic events of the Xing-Meng Orogenic Belt: (a) pre-Late Cambrian collision between Erguna-Kerulen Block and Arigin Sum-Xilinhot-Xing'an Block; (b) the Early Paleozoic subduction of Paleo-Asian Ocean and pre-Late Devonian collision between Erguna-Xing'an Block and Songliao-Hunshandake Block
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