Deep Crustal Contact Between the Pamir and Tarim Basin Deduced From Receiver Functions

The deep crustal deformation in the east Pamir in response to the Cenozoic collision with the Tien Shan and the Tarim Basin is so far poorly constrained. We present new insights into the crustal structure of the east Pamir and its surrounding regions using P receiver functions from 40 temporary and permanent seismic stations. The crustal thickness reaches a maximum of 88 km beneath the central and southern east Pamir and decreases sharply to 50-60 km along the southern Tien Shan and to 41-50 km below the Tarim Basin. The most prominent crustal structures involve a double Moho, suggesting eastward underthrusting of the Pamir lower crust beneath southern east Pamir, and two Moho offsets, supporting delamination of Asian lower crust below the central east Pamir and pure shear shortening along the northeastern margin between the Pamir and Tarim Basin. Plain Language Summary The Pamir orogen is located at the leading edge of the Indo-Asian collision zone and has translated northward by about 300 km with respect to the Himalaya-Tibetan plateau since the Late Cenozoic. It protruded the formerly connected Tajik and Tarim basins and formed a curviplanar front with the Tajik Basin to the west, Tien Shan to the north, and Tarim Basin to the east. Previous studies revealed that the Pamir is underthrusted by the Asian crust from the west and the north; however, it is still unclear how the contact between Pamir and the Tarim basin crust looks like. This study elucidates the deep crustal interaction between the two tectonic blocks by receiver functions with data from a recent seismic experiment in the region. The Pamir crust is extended into the western tip of the Tarim basin and is thickened by horizontal shortening, while in the south it is underthrusting beneath the West Kunlun Shan and Tarim Basin into the mantle to a depth of >100 km. Key Points The Asian lower crust is delaminated beneath the central east Pamir The northeast Pamir crust extends into the Tarim Basin and thickens by pure shear shortening The southeast Pamir crust is underthrusting beneath West Kunlun Shan and Tarim Basin

Automated summary

This study presents new insights into the crustal structure of the east Pamir and its surrounding regions, including variations in crustal thickness, Moho structure, and crustal interaction patterns.