Abstract:

In spite of tectonicplate environments surrounding the Chinese continent having no obvious variation in the recent about 40 Ma, the tectonic activities in the eastern North China Craton in the Neogene showed obvious difference with those in the Paleogene. For example, regional lithosphere seems to be thickened, TangshanXingtai faults became active, but the activities of the Taihangshan Piedmont faults reduced. Some evidences showed that the dynamical effects caused by the uplift and extending of the Tibetan plateau which is often attributed to the IndoEuarasin collision controlled the dynamics of North China in horizontal direction in the Paleogene, and in the time after about 8 Ma, however, the influences and reformations caused by the extending are weaker than the vertical reformation of eastern North China attributed to the Pacific plate subduction beneath the Asian continent; the former was less important even in the period of 823 Ma in the horizontal direction than the latter. Previous studies showed that the Pacific plate movement underwent some obvious changes at  about 47 Ma. If we only consider the Pacific plate subduction just since this time, we could find that the subduction slab can reach eastern North China after about 20 Ma (at about 27 Ma ago), and the slab may have been destructed completely at this position. In the 20Mamovement processes, the evolution of the cold slab could be divided into several stages with the slab being heated and destructed. In different evolution stages, the slab also could result in different effects on the overlying asthenosphere and lithosphere. The slab evolution showed some temporal consistence with the tectonic activities in eastern North China, and also with the Japan Sea opening. Furthermore, the possible effects acted on the overlying lithosphere by the slab in different stages could interpret the tectonic events mentioned above. Thus, the bottomup effects  attributed to the Pacific subduction mainly controlled the evolution of eastern North China in the Cenozoic, and they are also the dominant factors controlling the dynamics of North China even in the horizontal during about 823 Ma.

Key words: eastern North China Craton, subduction slab, neotectonics, lithosphere evolution