Temporal and spatial variations of Mesozoic magmatism and deformation in the North China Craton: Implications for lithospheric thinning and decratonization

Mesozoic (Triassic–Cretaceous) magmatic rocks and structural deformation are widely distributed in the North China Craton (NCC) and are crucial to understanding the timing, location, and geodynamic mechanisms of lithospheric thinning and decratonization of the NCC. Our new geochronological, geochemical and structural data combined with previously published results on Mesozoic magmatic rocks and deformational structures in the NCC indicate a temporal and spatial migration of magmatism and deformation from its margins to its cratonal interior. Triassic and Early Jurassic igneous rocks are only distributed along the northern, southern and eastern margins of the NCC. In contrast, Cretaceous magmatic rocks are widely distributed in whole eastern and central parts of the NCC. There is a younging trend for Mesozoic magmatic rocks from the northern and eastern parts (Yanshan, Jiaodong Peninsula and Liaodong) to the central part of the NCC (Taihangshan). Mesozoic deformation in the NCC exhibits a similar migration trend from craton margins to its inland areas. Triassic–Early Jurassic deformation mainly occurred in the margins of the NCC and transformed from compression during the Early–Middle Triassic to extension during the Late Triassic to Early Jurassic in its northern margin. Middle–Late Jurassic to earliest Cretaceous deformation is widely distributed in the NCC and exhibited non-unique contractional directions usually perpendicular to boundaries of the NCC and its Ordos block, indicating that it was likely controlled by multiple tectonic regimes during the Middle–Late Jurassic to earliest Cretaceous. Early Cretaceous deformation was characterized by near unique NW–SE extension that was likely controlled by unique geodynamic regime that probably related to the far-field effect of Cretaceous Paleo-Pacific plate subduction. The above mentioned temporal and spatial migrations of Mesozoic magmatic rocks and deformation indicate that lithospheric thinning and decratonization of the NCC was diachronous and complex. The lithospheric thinning and decratonization of the NCC initially started from its northern and eastern margins as a result of post-collisional/post-orogenic lithospheric delamination during the Middle–Late Triassic, and then spread to the interior of the craton during the Late Mesozoic. Interactions of the surrounding orogenesis and the small size of the NCC may have played important roles on its Late Mesozoic lithospheric thinning and decratonization.