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Geochronological Framework of the Mesozoic Granitic Magmatism in the Liaodong Peninsula, Northeast China

WU Fu-yuan1, YANG Jin-hui1, LIU Xiao-ming2   

  1. 1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 2. Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
  • Received:2005-09-20 Revised:2005-09-20 Online:2005-09-20 Published:2005-09-20

Abstract: Liaodong Peninsula, located in the northeastern part of the North China Craton (NCC), is one of the important areas where the Mesozoic granitoid rocks are widely distributed. It is traditionally thought that the granitoids in this area were mainly emplaced during Triassic to early-middle Jurassic. In this paper, more than 60 samples of zircons have been run for U-Pb geochronological dating using SHRIMP, TIMS and LA-ICPMS techniques. Based on these new data, three stages of granitic magmatism are identified: Triassic (233 -212 Ma), Jurassic (180- 156 Ma) and Early Cretaceous (131 - 117 Ma). The Triassic plutons include alkaline syenite (Saima- Bolinchuan), dolerite, diorite and monzogranite. The Jurassic granites are characterized by ductile deformation and a lot of inherited zircons. Some plutons of this stage were considered as Archean tonalite and Proterozoic intrusions or migmatites. The Early Cretaceous intrusions are consisted of numerous rock types, including dolerite, diorite, monzonite, porphyritic granite, highly fractionated alkali feldspar granite and A-type granite, and occurred usually as large batholiths. Magma mixing is extensively developed between the diorite and granite. The major difference from the previous thought after throughout geochronological analyses is that the early Cretaceous is the most important period of granitic magmatism in this area. Comprehensive comparisons with granitoids in other areas of the NCC, it is found that the Triassic-Jurassic granitoids are mostly exposed in the eastern part of the NCC, whereas the Early Cretaceous granitoids are developed in all areas. This geochronological framework provides important informa- tion to constrain the Mesozoic tectonic evolution of the NCC.