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岩石学报 2008
Lower crust and lithospheric mantle beneath the North China Craton before the Mesozoic lithospheric disruption
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Abstract:
The North China Craton (NCC) is one of the oldest cratons in the world, which has complicated tectonic history with 3.8Ga continental rocks. The NCC fundamentally formed at the end of Archean, and underwent high-grade metamotphism and ultimately completed cratonization at Paleoproterozoic of 1.9~1.85Ga. A Mesozoic tectonic inversion occurred in eastern North China with a large-scale lithospheric thinning beneath the sub-continent. Disruption of the western part of the NCC was not critical, therefore its present lithosphere may roughly indicates the state of the lithosphere before Mesozoic thinning. The granulite terrain represents the Paleoproterozoic lower crust, and the xenoliths of granulites from Meszoic-Cenozoic basalts represent the present lower crust. The thickness of the lithosphere beneath the western NCC is about 200km based on the petrological, geochemical and seismological data, the crust is about 45km~50km in Paleoproterozoic period (~1.9Ga), which is consistent with those of other cratons in the world. Moreover, the lower crust and lithospheric mantle in the eastern North China Craton (NCC) was thinned in the Mesozoic, with large-scale partial melting of lower crust and magmatic underplating, indicating an intensive decoupling of mantle-crust, leading to lithospheric disruption and re-construction of the craton.