Post-collisional Tectonic Evolution and Metallogenesis in Northern Xinjiang,China
WANG Jingbin~ 1,2) , XU Xin~ 2) 1) Beijing Institute of Geology for Mineral Resources, Beijing, 100012 2) Xinjiang Resources and environment Center, Urümqi, 830000
Post-collisional period follows the major collision, which is marked by the ocean closure and the ophiolite emplacement between/among the continental blocks, and ends with the exhaustion of large-scale granitic magma. According to these indicators, the major collision period of the northern Xinjiang is from the end of Devonian to the beginning of Carboniferous, while the post-collisional stage is from Early Carboniferous (Visean Stage) to Permian time. The data demonstrate that the post-collisional stage in northern Xinjiang experienced strong mantle-crust mutual action and was characterized by episodic and oriented evolution. Two extensional-compressive episodes, the extension in Early Carboniferous and compression in Late Carboniferous, and the extension in Early Permian and compression in Late Permian, are recognized. It is suggested that the two extensional periods in the post-collisional stage may be caused by lithosphere delamination in Early Carboniferous after major impact and mantel magma underplating in Early Permian. Thus, the compression caused by collision was exhausted by episodic extensions, and gradually finished solidification of the crust during post-collisional stage. The extensional stage and the transition period from compression to extension are the most important periods for large-scale mineralization in the post-collisional regime.