Crustal deformation and dynamics of Early Cretaceous in the North China Craton.

The Early Cretaceous represents a peak period of the North China Craton (NCC) destruction. A comprehensive analysis of crustal deformation during this period can reveal processes and dynamics of the destruction. The peak destruction of the NCC was associated with intense extension whose representative deformation products are metamorphic core complexes (MCCs), extensional domes and rifted basins. These MCCs occurred along both northern and southern margins of the NCC, and resulted from synchronous extension and magmatism, showing difference from the typical orogen-type MCCs in many aspects. The MCCs of the Early Cretaceous were replaced by extensional domes under relatively weak extension and uplift. In contrast to a major depression-type basin of the Early Cretaceous in the western NCC, rifted basins of the same age in the eastern NCC appeared as medium- to small-scale ones extensively. In the eastern NCC, the rifted basins north of the Bohai Bay are characterized by a feature similar to an active rift whereas those south of the Bohai present similarity to a passive rift. Various sorts of extensional structures developed during the peak destruction indicate a stable stress state of NE-SE extension over the entire central to eastern NCC, consistent with the plate margin-driven stress field. Spatial distribution of the extensional structures presents an 1800 km wide back-arc extension region in the central to eastern NCC, consistent with the Paleo-Pacific slab rollback model following flat subduction. Temporal-spatial variation of initial extension and volcanic activity during the peak period also supports the rollback model right after the flat oceanic slab. The crustal deformation evolution demonstrates that the peak destruction of the NCC took place after the B-episode compression of the Yanshan Movement of the earliest Early Cretaceous and terminated with onset of the C-episode compression of the earliest Late Cretaceous. [ABSTRACT FROM AUTHOR]