The Revelation of the Crustal Geometry of the Western Qilian Mountains, NE Tibetan Plateau 6 January 2021

The revelation of the crustal geometry of the western Qilian Mountains, NE Tibetan Plateau 6 January 2021

the northeast boundary of the Plateau, was uplifted and became part of the present Qinghai-Tibet Plateau during the Middle Miocene, according to the latest chronology results. Therefore, as one of the youngest parts of the Qinghai-Tibet Plateau, the western Qilian Mountains is one of the key areas to test various proposed models of the formation of the Qinghai-Tibet Plateau.

The crustal deformation mechanism in the northeast margin of Qinghai-Tibet Plateau has been proposed by many predecessors. However, with the deepening of the research, more and more evidence has been revealed, and the previously proposed crustal deformation mechanisms have (a) Current lithospheric structure across the western been unable to fully explain much new evidence. Qilian Mountains and adjacent regions by combining our The differences in resolution of various means of result with previous geological and geophysical results. studying the interior of the earth's crust undoubtedly (b) The construction process of the Qilian Mountains. add to the divergence. Therefore, earth scientists Abbreviations: DS, Danghe Nan Mountains; TNS, Tuolai call for more precise methods to reveal the crustal Nan Mountains; TS, Tuolai Mountains; NQLS, north structure in the northeast margin of the Qinghai- Qilian Mountains. Credit: Science China Press Tibet Plateau. The deep seismic reflection profiling is one of the internationally recognized methods for revealing high precision crustal structural image. Therefore, using the crustal structural image As the largest orogenic plateau on Earth, the revealed by the deep seismic reflection profile to Qinghai-Tibet Plateau was caused by a complex study the crustal deformation pattern in the crustal deformation process during the continuous northeast margin of Qinghai-Tibet Plateau in this collision and compression process between the paper will undoubtedly provide very important data Indian and Eurasian continents starting at least of scientific significance and reference value for the 60-50 Ma ago. The formation of the Qinghai-Tibet study of this area. Plateau records the collision of the two continents and the deformation process and mechanism The researchers reprocessed the high-resolution within the continents. Therefore, the Qinghai-Tibet deep seismic reflection data, which were originally Plateau is considered as a natural ideal laboratory collected in the 1990s, for a transect across the NE for the study of continent-continent collision and margin of the western Qilian Mountains and the dynamics. At present, the continuous collision Hexi Corridor. The reprocessed seismic image has between Eurasia and Indian continents is still a higher signal-to-noise ratio compared with the ongoing, resulting in the fact that the Qinghai-Tibet first published result, which imaged the southward Plateau is still continuing to expand outward. The dipping north Qilian Mountains fault (NQSF) and a western section of the Qilian Mountains on the southerly dipping fault extending downward into the northeast margin of The Qinghai-Tibet Plateau, as

1 / 3

lower crust, which was named the north border thrust (NBT). In addition to these results, the reprocessed image more clearly delineates the geometry of the crust beneath the junction between the western Qilian Mountains and Hexi Corridor, yielding a better understanding of the processes responsible for the outward growth of the Tibetan Plateau.

The reprocessed seismic profile across the junction of the north margin of the western Qilian Mountains and the Hexi Corridor reveals the decoupled crustal deformation that is partitioned by the intra-crustal decollement layer at a depth of 14-24 km. The crustal deformation above the decollment is mainly characterized by a series of southward-dipping thrust faults downward ended at the decollement layer. Crustal-scale duplexing presents in the crustal layer beneath the decollement layer. The imbricate Moho structure beneath the study region implies that the Asian lithospheric mantle is being underthrust beneath the northeastern margin of the Tibetan Plateau. Integrating the results with previous geological and geophysical observations, the researchers propose an evolutionary model regarding the outward growth across the western Qilian Mountains, northeastern margin of the Tibetan Plateau.

This result enriches the crustal structure research on the northeast margin of Qinghai-Tibet Plateau. It is not only of great significance to the study of crustal deformation mechanism in the northeast margin of the Qinghai-Tibet Plateau, but also of great reference value to the understanding of crustal deformation mechanism in the Qinghai-Tibet Plateau.

More information: Xingfu Huang et al, Seismic reflection evidence of crustal duplexing and lithospheric underthrusting beneath the western Qilian Mountains, northeastern margin of the Tibetan Plateau, Science China Earth Sciences (2020). DOI: 10.1007/s11430-020-9677-y

Provided by Science China Press APA citation: The revelation of the crustal geometry of the western Qilian Mountains, NE Tibetan Plateau (2021, January 6) retrieved 29 September 2021 from https://phys.org/news/2021-01-revelation-crustal-

2 / 3

geometry-western-qilian.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

3 / 3