Key geochronology of Mesozoic deformation in the eastern block of the North China Craton and its constraints on regional tectonics: A case of Jiaodong and Liaodong Peninsula

Abstract

The Jiao-Liao massif is an important part of the Eastern Block of the north China Craton and located on the hanging wall of the north-dipping Dabie-Sulu suture zone. Several important tectonic models about tectonic evolution of the eastern Asia were proposed in the last decade and related closely to the Jiao-Liao massif. This paper combined our SHRIMP U-Pb zircon ages of the Dandong Granite in the Southern Liaoning Province, China, with our wide firsthand fieldworks in the east of North China Craton, our oilfield works in the Bohai Bay Basin and other recent SHRIMP dating, to summarize Mesozoic tectonic reactivation and evolutionary processes of the Eastern Block. In this study we identify an about 160 Ma partial melting of Paleoproterozoic plutons in the Jiao-Liao massif. Some magmatic, euhedral single zircons or magmatic zircon rimes around ca. 2100 Ma cores in the Dandong Granites near the Liaonan Neoarchaean terrane, are first recognized by the CL and BSE images and identified that the latest partial melting event happened at 167-157 Ma. This partial melting is most likely derived from in-situ remelting of ancient lower continental crust, mostly of North China Craton. The Dandong plutons are aligned in the NE direction and suffered intensively from the subhorizontal ductile thrust-related shearing and the subsequent NNE-trending folding. In the Dandong area, the precise timing of deformations was solved in this paper. The first deformation is identified to be from 195 to 193 Ma according to the K-Ar and 40 Ar/ 39 Ar ages of muscovites in the E-W trending shear zones of Liaodong peninsula. Based on the field relationship between the plutons and deformation foliations, a range from 153 to 145 Ma is defined as the duration of the second deformation time remained in the Dandong Granites. The NNE strike-slip faulting, i. e. the third deformation, must be constrained in a range from 135 Ma to 95 Ma. This deduced result is most similar to a range from the 40 Ar/ 39A r age of 128-132 Ma of initial sinistral strike-slipping of the Tan-Lu fault in the Anhui province to the biotite cooling age of 100 ± 2.3 Ma of the Yilan-Yitong segment of the Tanlu fault in the Jilin province. These faults are transtensive to control some pull-apart basins. However, during the third deformation, some metamorphic core complexes in the eastern China often took place in the overlapping area between the large-scale sinistral faults. It is well correlated to NW-directed subduction of the Paleo-Pacific Plate at 180-145 Ma. Our SHRIMP data also indicate that the Liaodong basement and Early Mesozoic magmatism are exactly similar to the Jiaodong basement and Mesozoic magmatism. Therefore, Early Mesozoic evolution in the Liaodong area, similar to that in the Jiaodong area, is also related closely to the Sulu Orogen in the Early Mesozoic and tightly to the Pacific subduction in the entire Mesozoic.