Provenance and tectonic setting of the Paleo- to Mesoproterozoic sedimentary basin in the southwestern Yangtze Block of South China: Implications on the reconstruction of the Columbia supercontinent

The late Paleoproterozoic to early Mesoproterozoic strata in the southwestern Yangtze Block of South China are of great significance for deciphering the tectonic evolution of the Yangtze Block and the reconstruction of the Columbia supercontinent. The present study focuses on the less followed Tongan Formation with comprehensive petrological, geochronological, and geochemical analyses. Zircon U-Pb dating shows that the initial deposition of the First Member (TA-1) of the Tongan Formation occurred at ca. 1787 Ma, and the Fourth Member (TA-4) was deposited after 1453 Ma. Based on discrimination of tectonic settings using major and trace elements, detrital zircon age distribution patterns, and associated magmatic rocks, the Tongan Formation and its contemporaneous Dongchuan and Hekou groups are interpreted to have been deposited in a continental rift to passive margin setting. With the development of the rift, an ocean formed in the early Mesoproterozoic to separate the Tongan and Hekou sequences. The U-Pb ages and Lu-Hf isotopic characteristics of the detrital zircon under study indicate that the Tongan Formation predominantly derived its sediments from the interior of the Yangtze Block. Specifically, detrital materials of ca. 2700 Ma originated from the northern part of the Yangtze Block, while the remaining sediments were sourced from its southwestern region. The source rocks are mainly felsic rocks. By comparing sedimentary, magmatic, metamorphic, and mineralization events, these comparisons suggest that the Yangtze Block in the Columbia supercontinent was connected to northern Laurentia and southern Siberia and adjacent to northern Australia.