U-Pb ages of detrital zircon grains from the Donghe Group in the Southern Qinling Microcontinent: Implications for tectonic evolution.

The Southern Qinling Microcontinent is an important tectonic unit of the Qinling orogenic belt. The Early Cretaceous sedimentary sequence is useful to trace the tectonic evolution of the Southern Qinling Microcontinent and sedimentary provenances. Detrital zircon grains from the Early Cretaceous sediments in Southern Qinling Microcontinent yield five U-Pb age clusters of 2600 similar to 2300Ma, 2050 similar to 1800Ma, 1200 similar to 750Ma, 650 similar to 400Ma and 350 similar to 200Ma, corresponding five supercontinental events, namely Kenor, Columbia, Rodinia, Gondwana and Pangaea, respectively. The zircon grains have very complicated sources, but mainly from the Northern Qinling Accretionary Belt and North China Craton, implying that the Southern Qinling Microcontinent was a part of the Qinling-North China united continent, never being an isolated continent, during Late Paleozoic. The youngest age peak constrained that the subduction duration of the Mian-Lue ocean plate northwardly beneath the Qinling-North China united continent was 350 similar to 200Ma; and that the continental collision between the Yangtze Craton and the Qinling-North China united continent began at the Triassic-Jurassic transition, and culminated in Jurassic, instead of in Triassic or earlier suggested in previous studies.