Abstract: This study presents new geochemical, zircon U-Pb and Lu-Hf isotopic data for the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group in eastern Guangxi. Geochemical data show that the meta-sedimentary rocks of the Yingyangguan Group have moderate composition maturity and weathering extent, and their rare earth element (REE) patterns are similar to that of the Post-Archaean Australian Shale (PAAS), with moderate Eu negative anomalies. The trace element distributions diagram shows that some samples are depleted in U, with higher Co and Ni contents compared with those of the meta-sedimentary rocks in the Nanling range, suggesting that the provenance was mostly intermediate to mafic rocks. The matrix of the Yingyangguan tectonic mélange contains a component of meta-sedimentary rocks. The detrital zircon U-Pb dating results give a maximum depositional age (660 Ma) of the matrix part of the tectonic mélange. Combined with previous results, we suggest that the Yingyangguan tectonic mélange was formed in the Middle-Late Neoproterozoic, and resulted from reworking by the Early Mesozoic thermal events. Provenance analysis reveals that the Neoproterozoic meta-edimentary rocks of the Yingyangguan Group are mainly of felsic components, combined with zircon cathodoluminescence image characteristics, zircon U-Pb geochronological characteristics, Hf model age of the second stage (TDM2) and relevant regional geological data, we suggest that the intermediate to mafic provenance in the meta-sedimentary rocks mainly originated from the Yingyangguan area or the adjacent terranes, suggesting a close affinity of the Yingyangguan Group with the Cathaysia Block. Combined with the characteristics of regional tectonic evolution, it is inferred that the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group were deposited in a post-orogenic extension rift basin.

Key words: meta-sedimentary rocks, zircon U-Pb ages, Lu-Hf isotopes, the Neoproterozoic, the Yingyangguan Group in eastern Guangxi