Lithosphere types in North China: Evidence from geology and geophysics |
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Authors: | Email author" target="_blank">Ruizhao?QiuEmail author Jinfu?Deng Su?Zhou Jinfa?Li Qinghui?Xiao Zongxu?Wu Cui?Liu |
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Institution: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Development and Research Center, China Geological Survey, Beijing 100037, China 2. China University of Geosciences, Beijing 100083, China 3. China University of Geosciences, Wuhan 430074, China 4. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Development and Research Center, China Geological Survey, Beijing 100037, China;Information Center of Ministry of Land and Resources, Beijing 100812, China 5. Institute of Geology, State Seismological Bureau, Beijing 100029, China |
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Abstract: | On the basis of the characteristics of geology and geophysics in North China, three types of lithosphere, namely, the cratonic,
the orogenic and the rift lithospheres can be classified In terms of petrological method (based on the information from Precambrian
rock assemblages, igneous activities, deep-seated enclaves, etc.) and the relationship between seismic velocity and rock compositions,
the crust-mantle petrological and chemical structure models can be set up. Researching results indicate that the geology and
geophysics of North China platform bears the similar characteristics in comparison with those of the global typical cratons.
The Eerduosi(Ordos) block located in the west of the North China Platform is a remnant of cratonic lithosphere after the North
China platform had undergone “activation” in Mesozoic and “reconstruction” in Cenozoic times. The continental crust consists
mainly of TTG rock assemblage while the subcontinental lithosphere mantle mainly consists of strongly depleted harzburgite.
The craton was finally formed in late Archaean and early Proterozoic, and has been kept in stability up to present; its crustal-mantle
petrological structures of lithosphere can be set up as a reference for the study of North China craton and even Sino-Korean
craton. In the Mesozoic period, the middle and east areas of North China platform were activated in the Yanshanian orogenic
process, the continental crust was reformed by material and heat-transfer of convective mantle and the original crustal TTG
component was reconstructed to be granitic crust, and the subcontinental lithosphere mantle was replaced by the Yanshanian
harzburgite-lherzolite. The Yanshan-Taihang Mountains were the remnants of orogenic lithosphere after the rifting in eastern
North China in Cenozoic. The present thickness of continental crust and lithosphere in the Yanshan-Taihang Mountains is not
equal to their thickness during the Yanshanian orogenic movement because they had undergone the crustal extensional thinning
in Cenozoic, however, the material and structure of lithosphere mantle-crust were formed during the Yanshanian orogenic movement.
In the Cenozoic Period, the rift-type lithosphere, as represented by the North China plain, was formed by the continental
rifting occurring in the eastern part of North China. The continental granitic crust, which had been “acidified” at the Yanshanian
period, was basified again by the eruption of basalt magma along the continental rifting, and the subcontinental lithosphere
mantle formed in Yanshanian was destroyed and replaced by the Himalayan mantle which consists mainly of lherzolite. Both the
crust and the lithospheric mantle in the rift have undergone extensional thinning and thermal erosion at lithospheric-scale,
the material and structure of the present mantle-crust lithosphere, attained from geophysical exploration, was formed in Cenozoic.
The formation and evolution of lithosphere in North China indicate that the material and heat transferred by convective mantle
into the continental crust was the key for different types of lithosphere forming, and the crust-mantle petrologic structure
was the records of lithosphere evolution, and it was the integrated results of the deep processes of the China continental
dynamic system and the Pacific Plate subduction located in the eastern margin of the North China platform in Mesozoic-Cenozoic
time |
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Keywords: | lithospheric types evidence of geology and geophysics crust-mantle petrological structure deep process |
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