The image of the crust and upper mantle along the Hotan-Baicheng section using the receiver function method

Abstract：Using data collected from an 750-kilometer-long seismic array and receiver function method, we obtain an image of the crust and upper mantle along the Hotan-Baicheng section across the Tarim basin. In the image, Hotan depression, Markit slope, Bachu uplift, Awat depression, Tabei uplift, Kuqa depression and the boundary faults of these blocks are clearly seen. The crust is divided into six layers that are Neogene-Quternary deposition, Sinian-Paleogene deposition, upper crust crystalline basement, mid-crust low density layer, lower crust high density layer, and lower crust low density layer. Generally, the density increase with depth, but two layers are abnormal. The density of the mid-crust is lower than the upper crust crystalline basement, and in the lower crust the density of the lower layer is lower than the upper layer. The mid-crust low density layer is a discontinuous 3~9-km-thick layer, at about 25 km depth. The lower crust low density layer is a continuous 5~10-km-thick layer, at about 45km depth. The depth of Moho is 40~50 km in the northern basin and 50~60km in the southern basin. The depth of the underside of lithosphere is 75~85 km. The lithosphere mantle of the Tarim block underthrust the West Kunlun block, but does not the crust. It indicates the decoupling between the crust and the mantle. In the north of the Tumxuk fault, the North Tarim block is deformed weakly. In the south, the South Tarim block is deformed intensively. The Hotan-Markit-Bachu block is whole and deformed intensively. The five large decollements or thrusts cause imbrication and shortening of the lower crust. But, the sedimental covers deformed very little indicating that the deformation in the South Tarim block had occurred before Sinian or Devonian. Since Neogene, these large decollements or thrusts became active again.