The heart of China revisited, I. Proterozoic tectonics of the Qin mountains in the core of supercontinent Rodinia

Abstract

The Qinling‐Dabie orogenic collage, central China, constitutes the geographic, geologic, and cultural heart of China; it plays a key role in understanding the amalgamation and breakup of the Rodinia supercontinent and the subduction and exhumation of continental crust under ultrahigh‐pressure conditions. Herein, we investigate the Proterozoic evolution of the Qinling‐Dabie orogenic collage and surrounding segments of the bounding South China craton (SCC) and North China craton (NCC), employing published and new U/Th–Pb geochronology. The Kongling, Hong'an‐Dabie, and Douling‐Foping complexes constitute the nucleus of the Yangtze block, recording a common ~2.0 Ga orogenic event that integrated the Yangtze block into the supercontinent Columbia. The ~1.10–0.95 Ga Miaowan “ophiolite”‐Shennongjia arc association of the Huangling dome‐Shennongjia massif seems to have split and reassembled that nucleus. It formed earlier than or contemporaneously with the Sibao orogeny along the southeastern margin of the Yangtze block. The ~0.95–0.80 Ga Mian‐Lue complex comprises an oceanic accretionary wedge that formed outboard of an associated fore‐arc‐arc system represented by the Bikou‐Hannan‐Micangshan massifs along the north(western) margin of the Yangtze block. The Qinling complex, currently sandwiched between the SCC and NCC, lacks pre‐Mesoproterozoic cratonal basement, and its igneous rocks intruded a ~1.7–1.0 Ga old clastic wedge that incorporates meta‐basites; it might have been part of the extended passive margin of East Antarctica and/or Australia. Neoproterozoic Qinling‐complex magmatism spanned ~260 Myr and evolved from partial melting of the thick clastic sequence over an arc to a rift setting; most Qinling‐complex paragneisses are erosional products of these igneous rocks. The ~1.0–0.85 Ga Qinling‐complex magmatism formed independently from that along the north(west)ern Yangtze‐block margin, but its ~0.8–0.7 Ga magmatism, peaking at ~750 Ma, is widespread throughout the Yangtze block; this suggests post‐ ~ 825 Ma accretion of the Qinling complex to the Yangtze block. The Daba and Wudang Shan, Douling, and Hong'an‐Dabie areas of the northern Yangtze block are dominated by ~0.8–0.6 Ga bimodal continental‐rift igneous rocks; in accordance with similar ages in the Qinling complex and the entire SCC, continental rifting appears to have been most active at ~750 Ma. Our Rodinia scenario suggests that the Qinling‐Dabie orogenic collage records the final stages of the assemblage of the core of Rodinia, and this was completed not earlier than ~825 Ma, and its breakup, which was most active at ~750 Ma.