Structure of the lower crust and detachment and subduction of the lithosphere of the South Qinling

Abstract：According to the lead isotopic composition and geochemical study of rocks, this paper further verifies that the xenoliths of the lower crust carried by an Early Mesozoic andesite-basaltic breccia pipe developed in the Minggang area on the northern boundary of the North Qinling belong to the South Qinling. From below upward the reconstructed section of the lower crust below the South Qinling consists of underplating gabbro, basic granulite (which contains lenses of granulite and gabbro) and acid granulite. The general lithosphere model of the Qinling orogenic belt is as follows: the South Qinling crust (Yangtze block) is detached and subducted northward, the North Qinling crust is obducted toward North China, and the lithosphere beneath North China is injected as a wedge into the Qinling orogenic belt, with the detachment surface lying between the middle and lower crusts. In a plan view, the subducting slab of the South Qinling possibly extends 400 km until it reaches here.