Detachments and Magmatic Source Depth in Lithosphere of Eastern China During Yanshanian and Sichuanian Stages

Abstract

It is an important project for present tectonics, to precisely research the time and space of detachment formation in the lithosphere, in geological history. According to collect a lot of collected data of on the magmatic source depths for of Eastern China during Yanshanian (205–135 Ma) and Sichuanian (135–52 Ma) tectonic stages, it is a suitable to roughly determine the local tectonic detachment, partial decoupling decoupling, and interaction between spheres in the lithosphere or at the bottom of the lithosphere. The results showed that the tectonic detachment, partial decoupling decoupling, and interaction between spheres were are exhibited and concentrated at the intersections among among the middle crust, Moho discontinuity, and regional main faults of Eastern China. During the Yanshanian and Sichuanian tectonic stages, however, obvious detachment or migration in those stages at the bottom of the lithosphere does not exist obvious detachment or migration in those stages. The violent magmatic area of Eastern China during the Jurassic and Cretaceous are mainly distributed east to of the boundary of Dahingganling–western Shanxi–Wulingshan–Siwandashan, and to the west to of this boundary the magmatism was is very weak. The authors propose that there was is a continental type of lithosphere at the west to of that boundary, and oceanic-continental transition type of lithosphere (continental crust with oceanic lithospheric mantle) at to the east to of that boundary. The lithosphere transformation and thinning of in Eastern China, in the Jurassic probably resulteded neitherfrom from the mantle plume, un-rooting, upsurge of heat mantle materials, and continental rifting,, nor directly from the subduction of the Pacific plate.