Zhang, Q (reprint author), Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China.
It is the subject that people pay attention to continental lower crust delamination. The paper puts out that there are at least three conditions for lower crust delamination: (1) the thickened crust is the prerequisite that the delamination make the lower Crust eclogite. (2) the extensive magma shifts Out a large amount of low density acid magma, enables the crust density to be greater than the mantle density. Because the lower crust eclogitation and some magma melting are of the geochemistry characteristics of adakite, the lower crust delamination is the prerequisite and essential condition with the extensive adakite melted out. (3) that the lithosphere mantle transfers into the asthenoshpere mantle enables the lower crust into mantle. The mantle under continent crust is cold and rigidity originally, difficult to flow, and will be soften with heat and water joining, make into the asthenosphere heat, plasticity and easy flow. So that the transition between the lithosphere mantle and the asthenosphere mantle is the essential factor and precondition of the lower crust delamination. The author thinks that the crust will not delaminate as a wholly, otherwise, it will delaminate as the snow flake float probably. If the density of the lower crust is reduced (lower than the underlying mantle), and there is not heat Supply in mantle, and the asthenosphere under continent crust turn into the lithosphere mantle again, delamination will stop promptly. In the article we discussed the possibility of lower crust delamination in the eastern China during Mesozoic Era, and the thinning mechanism of the lithospliere. We think that the lower crust is not necessary, is not possible to delaminate together with the lithosphere mantle as well.