Geochronology and geochemistry of middle Permian-Middle Triassic intrusive rocks from central-eastern Jilin Province, NE China: Constraints on the tectonic evolution of the eastern segment of the Paleo-Asian Ocean

摘要

To constrain the Permian-Early Mesozoic tectonic evolution of the eastern segment of the Paleo-Asian Ocean, we conducted zircon U-Pb dating and whole-rock geochemical analyses on six middle Permian-Middle Triassic intrusive plutons in central-eastern Jilin Province, NE China. Zircons from the six plutons display distinct oscillatory zoning and striped absorption in cathodoluminescence (CL) images, and Th/U ratios of 0.11-1.41, indicating a magmatic origin. Zircon U-Pb dating indicates that the intrusive rocks formed in the middle Permian (ca.260 Ma) to Middle Triassic (ca.245 Ma). In central-eastern Jilin Province, the middle Permian and Middle Triassic plutons are composed mainly of strongly deformed monzogranites with affinities to adakitic rocks, which are formed from partial melting of thickened mafic lower crust. In contrast, the late Permian-the Early Triassic plutons in central-eastern Jilin Province consist of a bimodal association (including gabbros and granitoids) and deformed monzonites, which typically form in extensional settings. These observations, along with the results of previous studies on early-middle Permian granitoids in western Jilin Province, indicate that the eastern segment of the Paleo-Asian Ocean underwent the initial closure in central-western Jilin Province during the middle Permian and the final closure in eastern Jilin Province in the Middle Triassic. (C) 2015 Elsevier B.V. All rights reserved.