Destruction of the North China Craton triggered by the Triassic Yangtze continental subduction/collision: A review

摘要

The collision between the North China and Yangtze Cratons in the Middle Triassic (240–225 Ma) created the world’s largest ultrahigh-pressure (UHP) metamorphic belt (the Dabie-Sulu Orogen). The peridotitic massifs in this belt, including those derived from a lithospheric mantle (M-type) and from previous cumulates in continental crust (C-type), and mantle xenoliths captured by the Xinyang (Henan Province) Jurassic (∼160 Ma) volcanics at the southern edge of the North China Craton, are the ideal targets to investigate the crust-mantle interaction and the destruction of the North China Craton. The M-type peridotitic massifs, including those in the Zhimafang (CCSD-pp1), Xugou, Hujialing, Chijiadian and Yangkou areas in the Sulu belt and Raobazhai area in the Dabie belt, have high whole-rock Mg# (89–93) and high contents of hydrous minerals (e.g., phlogopite and Ti-clinohumite). Peridotitic xenoliths in the Xinyang volcanics have olivine Mg# (90–93) similar to the M-type peridotitic massifs, suggesting that the massifs have an affinity to the lithospheric mantle beneath the North China Craton. The peridotites of the Dabie-Sulu orogen and Xinyang may be affected by carbonate metasomatism while minor differences may be related to the complex UHP metamorphism. Both the xenoliths and the M-type peridotites have similar zircon U-Pb ages of Proterozoic and Phanerozoic. The Phanerozoic ages are mainly Early Mesozoic (∼230 Ma), reflecting the major metasomatic effects from the subduction/collision of the Yangtze Craton beneath the North China Craton; a few Early Paleozoic (∼470 Ma) zircons may results from the metasomatism due to the Paleo-Tethyan slab subduction. The geochemical and U-Pb ages similarities between the M-type peridotitic massifs and the xenoliths indicate that the modification of the marginal lithospheric mantle of the North China Craton was mainly initiated by the chemical (addition of fluids/melts from the subducted Yangtze continental crust) and the mechanical processes (crust and tectonic compression and extension) during the Triassic collision.