Comparison of results of recent seismic profiles with tectonic models of the North China craton
The geometry and timing of amalgamation of the North China craton (NCC) have been controversial, with three main models with significantly different interpretations of regional structure, geochronology, and geological relationships. The model of Zhao G C et al. suggests that the eastern and western blocks of the NCC formed separately in the Archean, and an active margin was developed on the eastern block between 2.5 and 1.85 Ga, when the two blocks collided above an east dipping subduction zone. The model of Kusky et al. presumes that the eastern block rifted from an unknown larger continent at circa 2.7 Ga, and experienced a collision with an arc (perhaps attached to the western block) above a west-dipping subduction zone at 2.5 Ga, and the 1.85 Ga metamorphism is related to a collision along the northern margin of the craton when the NCC joined the Columbia supercontinent. The model of Faure et al. suggests two collisions in the central orogenic belt, at 2.1 and 1.88 Ga. Recent seismic results support both the models of Kusky et al. and Faure et al., showing that subduction beneath the central orogenic belt (COB) was west-directed, and that there is a second, west-dipping paleosubduction zone located to the east of the COB dipping beneath the western block (Ordos craton). The boundaries identified through geophysics do not correlate with the boundaries of the Trans-North China orogen suggested in the Zhao et al. model, and the subduction polarity is opposite that predicted by that model. The seismic profiles are consistent with an Archean collision above a west-dipping subduction zone beneath the COB predicted by the models of Kusky et al., and the second west-dipping subduction zone is consistent with the two events suggested in the Faure et al. model.