Reconstruction of Mesoproterozoic tectonic evolution and paleogeography in the southwestern Yangtze Block: evidence from the clastic sedimentary rocks of the Fifth Member of the Tongan Formation

This study focuses on the detrital rocks of the Fifth Member of Mid-Mesoproterozoic Tongan Formation (TA-5) in the southwestern marginal Yangtze Block. Through whole-rock major and trace element analysis with existing zircon U-Pb age data combined, we conducted a comprehensive study to clarify the provenance characteristics, define the sedimentary tectonic setting, and furthermore reconstruct the paleogeographic position of the Yangtze Block during this period. Results reveal that the TA-5 sediments were primarily sourced from intermediate to felsic igneous rocks and deposited in an active continental margin setting, recording a regional tectonic transition from convergence to collision. Comparison of zircon ages reveals that the southwestern marginal Yangtze Block during the Mid-Mesoproterozoic has a significant affinity with the western Laurentia, southern Australia and East Antarctica, while its northern margin is closely related to the western Laurentia and southern Siberia. These findings support the adjacency of the Yangtze Block to the aforementioned blocks in the Columbia supercontinent, providing new evidence for reconstructing the paleogeographic position of the Yangtze Block in the supercontinent.