Mesozoic tectonic evolution of the eastern South China Block: A review on the synthesis of the regional deformation and magmatism

Knowledge of the Mesozoic tectonic evolution of the eastern South China Block (ESCB) plays a crucial role in understanding the formation of the Large Granitic Province and polymetallic mineralization. This review focuses on two controversial issues: (1) which one was the primary controlling factor of the Triassic geodynamic process of the South China Block (SCB), oceanic subduction or intracontinental convergence? (2) what was the subduction style of the Paleo-Pacific plate during the Jurassic?Cretaceous? Based on analyses of regional deformation and published geochronological, petrological, and Nd isotopic data of the magmatic rocks, we reconstruct the Mesozoic tectonic architecture and determined the temporal and spatial evolution of magmatic activities in the ESCB. The analysis of regional deformation shows that two groups of folds, including NE/NNE-trending folds in the Cathaysia Block and NW/NWW-trending folds in the inland, were formed in the Middle?Late Triassic. Subsequently, Middle?Late Jurassic NW?SE compression led to large-scale NE-trending fold-thrust deformation in the SCB, except for roughly S?N extension in the eastern Nanling tectonic belt, which caused the occurrence of the NE-striking dextral-normal oblique faults. Geochronological data indicate that magmatism in the ESCB can be divided into five separate stages: at 250?210 Ma, 210?170 Ma, 170?145 Ma, 145?120 Ma, and 120?85 Ma, respectively. In the first stage, granitic rocks consist mainly of S- and A-type granites, with subordinate I-type granites. These three types of granites were all derived from the partial melting of Proterozoic rocks. In the second stage, the magmatic activities are characterized by mantle-derived magmas in the coastal area, while they are featured by the mixing of predominantly mantle-derived melts with the Neoproterozoic crust in the inland area. In the third stage, widespread I- and A-type granites, which are characterized by the crust-mantle mixing, were formed in the Nanling tectonic belt and adjacent regions in response to the intense extension of lithosphere. In contrast, the development of crust-derived magmas in the Wuyi tectonic belt indicates a relatively weak lithosphere extension. The granitoids of the fourth stage, which are composed of I- and A-type granites, are mainly distributed in two separate areas, the eastern Jiangnan Orogenic Belt and southeastern Guangdong Province. Their petrogenesis is related to the crust-mantle mixing under the extensional setting. The magmatic activities in the last stage propagated eastward and were developed in the coastal area. The intrusive suites comprise major I- and A-type granitoids, and minor gabbroids, which were formed in an enhanced lithospheric extensional setting. Combined with the records of regional deformation, sedimentology, and magmatic evolution, we propose a new tectonic evolution model for the ESCB covering the range of ca. 270 Ma to 85 Ma. This model demonstrates that the ESCB probably experienced a coeval multi-plate convergence during the Triassic, producing an intracontinental deformation belt in the Yangtze Block and an Andean-type retro-arc foreland system in the Cathaysia Block. During the Jurassic?Cretaceous period, the subduction of the Paleo-Pacific plate beneath the SCB triggered crustal thickening, local extension, and large-scale lithospheric extension through the advance, tearing, rollback, and breakoff of the oceanic slab.