Abstract:

Located at the front edge of the subduction zone, the northern Himalayan tectonic zone is one of the typical regions to study crustal thickening and deep crustal magmatism during continental collision. The northern Himalayan gneiss domes (NHGD), as a critical extensional unit of the tectonic zone, have a formation process closely related to crustal thickening from orogenic movement and crustal flow due to partial melting. In this study, we used common-conversion-point stacking of teleseismic P-wave receiver functions to image the crustal structure beneath the recently discovered Cuonadong dome. We found large crustal structural variations from east to west of the Cuonadong dome with the occurrence of several discontinuous crustal interfaces, even crustal faulting. We also found a low velocity zone in the upper and middle crust beneath the Cona rifts and Cuonadong dome. Combining the above results and previous studies, we consider that the southeastern Himalayan lithosphere underwent crustal-scale tensional deformation as a result of continuing Indo-Eurasian collision. Under the long-term continental subduction, crustal thickening and continuous high-temperature metamorphism, the middle and upper crust underwent partial melting following the extension and decompression of the southern Tibet detachment (STD). The subsequent continuous magma upwelling along the weakened STD and magma accumulation beneath the dome region resulted in the weakened crustal zone, which promoted the east-west regional extension and then formed the Cuonadong dome through magmatic diapirism.

Key words: Cuonadong dome, short-period dense array, teleseismic P-wave receiver function, common-conversion-point (CCP) stacking, crustal structure