Mid-late Neoproterozoic tectonic evolution of the northern margin of the Yangtze Block, South China, as constrained from the detrital zircon record

The northern margin of the Yangtze Block (NYB) experienced distinct tectono-magmatic evolution during the mid-and late-Neoproterozoic, as compared with the northwestern margins of the Yangtze Block (NWYB), although the geodynamic mecha-nism remains controversial. The South Qin-ling Belt (SQB), which forms the northern-most NYB, is a significant target for studying the Neoproterozoic tectonic evolution of the NYB. Here we present U-Pb geochronology and Lu-Hf isotopes of detrital zircons from clastic rocks belonging to the Yaolinghe and Wudangshan Groups in the SQB. The U-Pb ages reveal that the maximum depositional ages are respectively ca. 630 Ma and ca. 680 Ma for the Yaolinghe and Wudangshan Groups in the Ankang and Wudang Uplifts. Based on the compilation of U-Pb ages and Hf-Nd-O isotopic data as well as multidi-mensional scaling (MDS) analysis, clastic rocks of the Yaolinghe Group are suggested to be sourced mainly from the NWYB, whereas those of the Wudangshan Group were derived mostly from the NWYB and the NYB. The data compiled also indicate ca. 800-680 Ma northeastward migration of magmatism in response to slab rollback and ca. 680-600 Ma eastward migration of magmatism resulting from slab tearing. A tectonic model is proposed that envisages an arcuate subduction system around the Yang-tze Block during the mid-late Neoprotero-zoic. The continuous slab rollback and slab tearing underneath the NYB resulted in an extensional environment at that time. The rocks in the NWYB underwent uplift and erosion, and the detritus was transported to the NYB. The new model can well account for the two distinct groups of volcanic rocks in the Yaolinghe Group.

Automated summary

This study investigates the provenance of clastic rocks in the South Qinling Belt by analyzing the U-Pb ages and Lu-Hf isotopes of sandstone samples from the Ankang and Wudang Uplifts. The results indicate that the southwestern rocks mainly originated from the northwestern margin of the Yangtze Block, while the northeastern rocks were derived from both the northwestern and Yangtze Blocks. It is also found that there was northeastward migration of magmatism during the late Neoproterozoic (ca. 800-680 Ma) and eastward migration during the mid-Neoproterozoic (ca. 680-600 Ma).