Depositional age, provenance characteristics and tectonic setting of the Meso- and Neoproterozoic sequences in SE Yangtze Block, China: Implications on Proterozoic supercontinent reconstructions

Meso- to Neoproterozoic sedimentary successions along the southeastern margin of the Yangtze Block in South China have been investigated for their depositional ages, provenance and tectonic setting. The 1524 Ma, 834 Ma and 763 Ma U-Pb ages of detrital zircons for here investigated Tianli Schists, Liuyuan and Wengjialing sandstone constrain the maximum depositional ages for the respective sedimentary protoliths. Considerable time lag between onset of sedimentation and the age of source rocks suggests that the sedimentary protolith of the Tianli Schists received detritus from a wide range of cratonic sources in a tectonically passive scenario, as indicated by their elevated Zr/Sc ratios. Extraneous source for the 2700-2600 Ma detritus indicates that the sedimentary protolith for the Tianli Schists itself was deposited in a basin that received detritus from the Yangtze Block during the fragmentation of the Columbia/Nuna supercontinent. On the other hand, profuse syn-sedimentary magmatic (804-849 Ma) detritus for the Liuyuan sandstone indicates a continental arc setting, also supported by the La-Th-Sc and Th-Co-Zr signatures. The Wengjialing Formation and its equivalents were deposited in a continental rift basin, coeval with the breakup of Rodinia supercontinent, with addition of newly formed arc-related rocks (≥820 Ma) and syn-rifting magmatic rocks (810-760 Ma) as the predominant sources. These features provide substantial evidence for the paleogoegraphic reconstructions of the southeastern Yangtze Block within the Proterozoic supercontinent configurations.