Lithospheric structure of the Qinling intracontinental orogen

Abstract：The authors have constructed a new lithospheric structural model of the Qinling orogen by reprocessing and reinterpreting the seismic reflection profile from Yexian to Nanzhang and integrating and using the geophysical and geochemical data from seismic profiles for petroleum exploration, magnetotelluric sounding, heat flow and gasometry. The following major structures of varying ages have been recognized for the crust under the Qinling orogen：(1) crocodile structure formed by subduction of the North China craton beneath the Qinling microplate in the Caledonian period;(2) negative flower structure composed of a number of huge thrust faults centering around the Nanyang area formed by ramping-up, strike-slip motion and soft collision of the Yangtze craton and Qinling microplate during the Indosinian-Yanshan;(3) a dome of crystalline basement consisting of alternating orthogneiss and paragneiss formed after the Cretaceous; and (4) folded basement formed by nearly transparent Proterozoic low-grade metamorphic strata, overlying the crystalline basement. After the Cretaceous, as was the case with other areas in eastern China, a mushroom cloud-shaped structure was formed in the lithospheric mantle under the Qinling area due to the uplift of the asthenosphere and the lithosphere was reactivated, thus seriously affecting the tectonic evolution.