Crustal-mantle detachment of the North China craton in Late Mesozoic: Rheological constraints
华北克拉通晚中生代壳-幔拆离作用: 岩石流变学约束

Rheological structure of the continental lithosphere fundamentally influences on the deep processes of the lithosphere (crust/mantle process), which is directly shown by the crust-mantle structure of the lithosphere and also by shallow structures. Crustal extension, detachment faulting and thinning of the crust during thinning of the lithosphere of North China craton in Late Mesozoic are exactly shown by occurrence and variation of macro- and micro-structures, and due to changing rheology of the crust. The inhomogeneity of Late Mesozoic lithosphere is deduced from the present geophysical lithosphere structure and regional structural analysis. Lithosphere rheology is influenced by several factors including the absence and presence of H2O dominated geological fluids. Coupling and decoupling relationships of the crust and mantle during regional extension of the lithosphere of North China craton are discussed from the variation of thicknesses of the crust, the lithosphere mantle and the lithosphere, and the varying contents of water in rocks from the lower crust and upper mantle. We present the crust-mantle detachment model to interpret the basic phenomena and deep processes for lithosphere thinning of North China craton during Late Mesozoic. We would argue that regional extension is the dominant dynamic factor of lithosphere thinning during Late Mesozoic. During this event, the crust and mantle are decoupled in the eastern part of the craton, and therefore, the upper crust, the lower crust and the upper mantle are detached at the same time, but in different ways. There is, however, a coupling relationship in the western part of the craton. Thus the lower crust and the upper mantle constitute a layer of high rheological strength and they are not strongly detached during extension of the lithosphere in Late Mesozoic.