Mesozoic tectonics in the Eastern Block of the North China Craton: Implications for subduction of the Pacific plate beneath the Eurasian plate

Abstract

The Jiao-Liao massif is located in the hanging wall of the north-dipping Dabie-Sulu suture zone and is an important part of the Eastern Block of the North China Craton. Several important tectonic models for the tectonic evolution of Eastern Asia rely on critical information from the Jiao-Liao massif. This paper combines new sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages of the Dandong Granite in the southern Liaoning Province, China, with extensive field data for the eastern North China Craton, including the Bohai Bay Basin. Combined with other recent SHRIMP dating, we use this information to summarize the Mesozoic tectonic reactivation and evolutionary processes of the Jiao-Liao massif of the Eastern Block of the North China Craton. In this study we identify a c. 160 Ma episode of partial melting of Palaeoproterozoic plutons in the Jiao-Liao massif. Cathode luminescence and backscatter electron imagery reveal c. 167-157 Ma magmatic euhedral single zircons and magmatic zircon rims surrounding c. 2100 Ma cores in the Dandong Granites near the Liaonan Neoarchaean terrane. This partial melting is probably related to in situ remelting of ancient lower continental material, mostly the North China Craton. The Dandong plutons are aligned in a NE-SW direction and are extensively deformed by subhorizontal ductile thrust-related shearing and subsequent NNE-SSW trending folds. Here, we show that for the Dandong area the first deformation occurred between 195 and 193 Ma, based on K-Ar and 40Ar/39Ar ages of muscovites from east-west-trending shear zones on the Liaodong Peninsula. Based on the field relationships between the plutons and structural fabrics, a range from 153 to 145 Ma is defined as the duration of the second deformation in the Dandong Granites. The third deformation is marked by the formation of NNE-SSW strike-slip faults between 135 and 95 Ma. This deduced age range is similar to an 40Ar/39Ar age range of 128-132 Ma of initial sinistral strike-slip faulting of the Tan-Lu fault in Anhui Province and to a biotite cooling age of 100 ± 2.3 Ma of the Yilan-Yitong segment of the Tan-Lu fault in the Jilin Province. These faults are transtensive and controlled the formation of pull-apart basins. However, during the third deformation, some metamorphic core complexes in Eastern China formed in the overlapping area between the largescale sinistral faults. Our SHRIMP data also indicate that the Liaodong basement and its Early Mesozoic magmatism are similar to the Jiaodong basement and its Mesozoic magmatism. Therefore, the Early Mesozoic evolution of the Liaodong area, similar to that of the Jiaodong area, was also closely related to the Sulu orogen in the Early Mesozoic and to the Pacific subduction throughout the Mesozoic. © The Geological Society of London 2007.