Abstract:

It is a suitable method to roughly determine partial detachment in lithosphere or at the bottom of lithosphere, used by data of magmatic source depth at strong magmatism areas in eastern China.In the North Sinian stage（Eocene-Oligocene）, partial tectonic detachments mainly occurred at the intersection among the bottom of lithosphere and pre-existing NW or N-E and NNE striking lithospheric faults.In the Himalayan stage（Miocene-Early Pleistocene）, detachments widely occurred at the intersection among the bottom of lithosphere and three NE and NNE trending lithospheric faults（Taihangshan, Tan-Lu and southeast coastal of China）.In the Neotectonic stage（since Middle Pleistocene） according to the seismic data, detachments mainly occurred near Moho discontinuity and intermediate crust, with sheety-like, but not in south China.The recent gravity gradient zone is the division line between continental and oceanic lithosphere mantle, also indicates the division of the strong and weak area of magmatism, migrating eastwards at most about 200 km, compared with that from Cretaceous to present.Therefore, the authors suggested that tectonic detachment was occurred by main brench faults, and the type, characteristics and distribution of magmatic rocks and earthquakes were controlled by the detachments, occurred at the intersection area of the faults and different tectono-spheres in the lithosphere.Neither mantle plume nor hot magma uplifting widely existed, and no large-scale extension-thinning process occurred in eastern China lithosphere during Cenozoic.

Key words: lithosphere, tectonic detachment, fault, magmatic activity, earthquake