The mantle transition zone structure beneath the Tarim Craton and deep-seated dynamics

The deep-seated mantle dynamics beneath the Tarim Craton remain highly elusive. The active mantle plume model and passive mantle upwelling model caused by subduction and delamination have been suggested. In this research, we imaged the mantle transition zone (MTZ) structure beneath Tarim Craton using more than 50000 P-wave receiver functions obtained from the newly deployed seismic array in the basin and previously collected seismic data. To obtain the accurate true depths of the 410-km discontinuity (d410) and 660-km discontinuity (d660), we conduct crustal and mantle correction using several high-resolution 3-D crustal and mantle velocity models during time-to-depth migration. The depressed d410 (~10-15 km) and d660 are suggested by our previous research, which is interpreted to be caused by the mantle upwelling originating from the delaminated lithosphere stagnant near the d660 (Wu and Bao, 2024). However, the new preliminary results show a thinned MTZ beneath majority of the Tarim Craton, caused by the depressed d410 and uplifted d660. In the meanwhile, a thickened MTZ beneath the eastern Tarim Craton is imaged, resulting from the slightly depressed d410 and significantly depressed d660. Accordingly, the new results may indicate deep mantle upwelling beneath the Tarim Craton, consistent with the global-scale tomographic models. The lithospheric delamination near d660 beneath the eastern Tarim Craton is supported. But the origins and dynamics of the mantle upwelling and delamination should be further investigated using various methods such as thermo-mechanical numerical modeling.

 

Reference

Wu, Y., & Bao, X. (2024). The Mantle transition zone structure beneath the Pamir Plateau and western Tian Shan and adjacent regions. Journal of Geophysical Research: Solid Earth, 129, e2023JB028129. https://doi.org/10.1029/2023JB028129.