Uplifting and exhumation history in Southern Qiangtang Depression of Qinghai-Tibet Plateau since Cretaceous: constrain from low-temperature thermochronology

Abstract

The uplifting and exhumation history of the Southern Qiangtang Depression was studied for reconstructing the evolution of the Qinghai-Tibet Plateau and evaluating the oil-gas preservation conditions in the Qiangtang Basin. Samples of Jurassic sandstone from Gaeraobao area in the center of Southern Qiangtang Depression were analyzed using zircon and apatite (U-Th)/He and apatite fission track (AFT) techniques, and the data showed that most grains experienced a full annealing phase. Based on the inversion of the thermal history of the basin from the experimental data and combined with the study of regional low temperature thermochronology, it is believed that the Southern Qiangtang Depression has experienced three major uplifting and exhumation episodes: the Early Cretaceous, the Paleocene-Eocene and since the Miocene, and experienced exhumations of 1.7-2.6 km, 1.89 km, and 1.13 km, respectively in the center of Southern Qiangtang Depression. And the thermal history showed that the center of Southern Qiangtang Depression suffered exhumation first in the Early Cretaceous, and then the denudation gradually spread to the north and south. The three episodes correspond to the collision between Qiangtang and Lhasa terranes, the collision between Indian and Asian plates and the movement of N-S strike fault under the continuous convergence of the Indian and Asian continents, respectively. The thermal history of samples at different tectonic locations in the Southern Qiangtang Depression showed that they have undergone different exhumation processes, which may have been controlled by the different activity of regional N-S faults caused by the collision between Indian and Asian plates and its subsequent continued convergence. Based on the differences of thermal histories of the samples at different tectonic locations, it suggested that the regional N-S faults activated since 65-45 Ma.

Keywords

• zircon and apatite (u-th)/he
• apatite fission track
• low-temperature thermochronology
• uplifting and exhumation history
• tectonic evolution
• southern qiangtang depression
• qiangtang basin