AUTHOR=Wang Zining , Xiong Xiaosong , Wu Guowei , Li Zhichao , Ye Zhuo , Jin Zhongyuan 

TITLE=Crustal structure and deformation mechanism of the western northeast Tibetan Plateau

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 11 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2023.1255813

DOI=10.3389/feart.2023.1255813

ISSN=2296-6463

ABSTRACT=The collision between the Indian and Eurasian plates continues to drive significant deformation and uplift within the Tibetan Plateau's interior, along with its outward expansion along the margins. In particular, the North Qilian Shan fold-thrust belt (NQLS) and the Hexi Corridor basins (HXBS) represents the northernmost region of the NE Tibetan Plateau. This area serves as a natural laboratory for deciphering mechanisms of crustal deformation and thickening along the plateau's margins. Specifically, the Northeastern Tibetan Plateau has been attributed to (1) southward underthrusting of the Asian lithosphere, (2) distributed shortening and crustal thickening, (3) vertical inflation of the Tibetan crust due to mid-lower crustal channel flow, and (4) intracontinental subduction facilitated by large-scale strike-slip faults. The exact mechanism behind the most concentrated convergent stress in the western segment of the NQLS-HXBS remains debated. To address this uncertainty, we gathered seismic data along a 130-km-long linear array that extends northward from the NQLS, traversing the Jiuquan basin and reaching the Huahai basin. Our analysis, conducted through the receiver function method, reveals intriguing findings. The Moho depth deepens from 45-50 km beneath the Huahai basin to 55-60 km beneath the NQLS. Notably, a double Moho structure emerged, marked by a distinctive near-flat positive amplitude at a depth of 45-50 km beneath the NQLS within a distance of 0-50 km. Our study presents a comprehensive crust-scale deformation mechanism, shedding light on key aspects: 1) the development of a decollement at 12-20 km depth decoupling the upper and lower crust; 2) the upper crust& apos;s deformation occurring through southdipping brittle thrust faults, while the lower crust features imbricate structures and duplexes; 3) evidence pointing to the underthrusting of the Beishan Block beneath the NQLS, indicated by the double Moho beneath the NQLS; 4) the formation of a Moho ramp beneath the Jiuquan basin, facilitating the transfer of shortening stress from beneath the NQLS and the HXBS to the north. In the context of the western segment of the NQLS and the HXBS, our speculation is that coupled distributed shortening and Beishan Block subduction beneath the NQLS work in tandem to accommodate crustal deformation.