Remnants of a Neoproterozoic Collisional Orogenic Belt in the Core of the Phanerozoic Qinling Orogenic Belt (China)

NW-SE trending paleotectonics are recognized from the WNW-ESE trending Qinling complex in the core of the Qinling belt. They consist of trending stratum, boundary shear zones, deformed linear plutons and ophiolite. The field relationships and ages of the deformation, magmatism and metamorphism suggest that the paleotectonics formed in Neoproterozoic. The ages of deformed and undeformed plutons approximately constrain the peak deformation during 958-889 Ma. Both the two trending tectonics constitute an orogen-scale tectonic replacement by S2 (Phanerozoic WNW-ESE tectonics) of S1 (NNW-SSE trending Neoproterozoic), similar to structural replacement in outcrop. The strong contractional deformation, (high-pressure) metamorphism, and granitic magmatism that evolved from syn-collisional (S-type), to post-collisional (I-type) and to post-collisional (A-type), as well as regional extension at 885-700 Ma in Qinling, display a cycle of a collisional orogeny. Thus, the NW-SE trending paleotectonics could be remnants of a collisional orogenic belt. The belt originally could trend NNW-SSE, if reworking and modification of Paleozoic and/or Mesozoic NNE-SSW contractional deformation are eliminated. Accordingly, assemblage and breakup of some continental blocks occurred in Neoproterozoic in Qinling, which seems to correspond to assemblage and breakup of Rodinia supercontinent in the world. This study provides new insight into the evolution of the Qinling orogenic belt and the reconstruction of Proterozoic supercontinent of China, and also presents a case study of recognition of an old orogen from a young orogen.