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Geophysical constraints on mesozoic disruption of North China Craton by underplating-triggered lower-crust flow of the Archaean lithosphere

Authors


Correspondence: Dr. Zhongjie Zhang, Institute of Geology and Geophysics, Chinese Academy of Sciences, No. 19, Beituchengxilu, Chaoyang District, Beijing 100029 China. Tel.: +86-10-82998313; e-mail: zhangzj@mail.iggcas.ac.cn

Abstract

The mechanism of the disruption, both lithospheric thinning and oceanization of the commonly accepted long-term-stable Archaean craton, is still an open question. The available models, all imply a bottom to top process. With the construction of a 1660-km-long transect across the eastern North China Craton (NCC), we demonstrate that both the P-wave velocity and density in the lowermost crust beneath the central section are significantly higher than in the corresponding parts of the south and north sections on the transect. These features are interpreted as geophysical signature of lower crustal underplating, which supplies sufficiently high gravitational potential energy to trigger lateral flow of the lower crust. This magma underplating-triggered bilateral lower crust flow may facilitate the lithospheric thinning by means of asthenosphere upwelling and decompression melting, which infill the gap produced by the lower crust flow. The underplating-triggered lower crustal flow can provide an alternative mechanism to explain the NCC lithosphere disruption, which highlights the crustal feedback to Archaean lithosphere disruption, from top to bottom.

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