深反射地震成像揭示的班公湖-怒江缝合带中段Moho断阶及其大地构造意义OA北大核心CSTPCD

Knowledge of the Moho in the Bangong-Nujiang suture(BNS)is geodynamically of importance to understand the subduction of Meso-Tethys oceanic crust and the genesis of southern Qiangtang depression.Based on deep-reflection seismic data(88°30′E)across the BNS,depth-domain seismic profile and velocity field with high-resolution Moho geometry are obtained by deep-reflection seismic imaging using such techniques as mid/long wavelength static correction,noise elimination,optimal stacking,and PSDM.The depth-domain imaging shows that the Moho of the BNS located at a depth of 65～80 km tends to discontinuously uplift northwards,indicating a few lithospheric mantle terraces(up to 15 km)developed between the Lhasa and Qiangtang terranes.The geometry of the Moho in the BNS demonstrates that the terraces have been driven by southern lithospheric mantle subduction at 19.5° northward and northern crustal uplifting of southern Qiangtang basin due to possible deep partial melting.The Moho structure suggests that southern Qiangtang basin was evolved from marginal marine into foreland basin during the Late Jurassic to the Early Cretaceous along with the Meso-Tethys closure.