Neoproterozoic tectonic evolution of North Qinling Orogenic Belt, Central China: Evidence from clastic rocks

The Kuanping Group is located in the northernmost North Qinling Orogenic Belt (NQB). The provenance and depositional age of clastic rocks from the Kuanping Group are pivotal for reconstructing the tectonic evolution of the NQB and the entire Qinling Orogenic Belt in Central China. The clastic rocks in the Kuanping Group have high CIA (66-73) and PIA (72-87) values similar to those of the post-Archean Australian shale (PAAS), implying the source materials experienced moderate to strong weathering. They have low values of ferromagnesian (e.g. Cr, Co, and Ni) and high field strength elements (e.g. Zr, Hf, Nb, Ta, and Y), indicating that they sourced from materials in an active continental margin. Detrital zircons from four samples of the clastic rocks have similar age spectra, which were dominated by early Neoproterozoic zircons (900-1000 Ma) with four subordinate populations (2400-2600 Ma, 1100-1300 Ma, 700-850 Ma). The main provenance of these clastic rocks was most likely the early Neoproterozoic granitoids that intruded in the oldest basement rocks (namely the Qinling Group) of the NQB, suggesting that the NQB has no tectonic affinity to the Yangtze and North China cratons during this period. Based on the youngest detrital zircons, the deposition age of the clastic rocks in the Kuanping Group is confined to the early Paleozoic (ca. 529-507 Ma). Based on the age distribution of detrital zircons and coeval rock assemblages, we suggest that the clastic rocks were likely deposited in a passive continental margin setting, which corresponds to the breakup of the Rodinia supercontinent.