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Several models were proposed to account for the tectonic evolution of Tibetan Plateau, among which delamination of the Tibetan lithosphere is suggested to be a leading process. However, direct evidence for the removed Tibetan lithosphere in the deep mantle remains highly lacking. Here we image the mantle transition zone (MTZ) structure beneath western Tibet and Himalaya by common conversion point stacking of 25254 receiver functions (RFs) with unprecedented clarity. One striking feature is the significant depression (15–20 km) of 660‐km discontinuity beneath Himalaya, which indicates the presence of the detached Lhasa lithospheric mantle (∼26 Ma) at the bottom of the MTZ. Our results also show ∼15 km uplift of 410‐km discontinuity (d410) and small d410 amplitude beneath western Tibet, which we ascribe to the more recently delaminated Qiangtang lithosphere (∼15 Ma). Furthermore, the small dependence of d410 amplitude on frequency indicates that the MTZ is anhydrous in the study area. Plain Language Summary: The fate of the original Tibetan lithosphere during the continental collision and its role in the tectonic evolution of the plateau remain highly debated. Here we image the mantle transition zone bounded by 410‐km (d410) and 660‐km (d660) discontinuities beneath western Tibet and Himalaya, suggesting the stepwise delamination of the Tibetan lithosphere. Our results show the significantly depressed d660 beneath the Himalaya terrane, which we interpret as reflecting the delaminated Lhasa lithosphere (∼26 Ma) stagnant near the d660. Our image also reveals prominent uplift and small amplitude of d410 beneath western Tibet, indicating the presence of delaminated Qiangtang lithosphere (∼15 Ma) in the vicinity of d410. The MTZ in the study region is anhydrous through multifrequency analysis of receiver functions, which shows small variations in d410 amplitude in all the frequency bands considered here. Key Points: Detailed structure of the mantle transition zone (MTZ) beneath western Tibet and Himalaya suggests stepwise delamination of Tibetan lithosphereThe depressed 660‐km discontinuity beneath Himalaya is due to the delaminated Lhasa lithosphere (∼26 Ma) stagnant at the bottom of the MTZThe uplifted 410‐km discontinuity beneath western Tibet is caused by the delaminated Qiangtang lithosphere (∼15 Ma) [ABSTRACT FROM AUTHOR]

Cratons have a long history of evolution. In this paper, applications of the magnetotelluric method used in the study of craton lithosphere over the past 30 years were reviewed, examining case studies of cratons in North America, South America, Asia, Australia, and Africa. The nuclei of the Archean cratons, for example the Kalahari Craton and Rae Craton, are usually characterized by thick and highly resistive lithospheric roots. During or after the formation of the cratons, tectonothermal events, such as collision, mantle plume, and asthenosphere upwelling led to the formation of high-conductivity zones in the craton lithosphere, which could be attributed to the increased hydrogen content (of nominally anhydrous minerals), higher iron content, and formation of graphite films or sulfides along the grain boundary of minerals. These conductive zones are characterized by resistivity discontinuities in craton lithosphere. In particular, the conductive zones include (1) large-scale lithospheric mantle conductors beneath the Slave Craton, Gawler Craton, and central part of North China Craton(Trans-North China Orogen); (2) near-vertical high-conductivity zone associated with the fossil subduction zone beneath the Dharwar Craton and Slave Craton; and (3) regional lateral electrical discontinuities, such as a conductive anomaly under the Bushveld Complex of the Kaapvaal Craton. The eMoho refers to the electrical discontinuity in the crust-mantle boundary. In existing research, this has been detected under the condition of extremely high lithospheric resistivity with only a slight decrease in the lower crust, and in the case of a very thin conductive lower crust or the lack thereof. In the resistivity model, the unique "mushroom-like" lower crust-lithosphere mantle conductor and very thin lower crust layer of the North China Craton may represent lithosphere destruction and/or thinning. We also find that some of the cratons are still not well understood. Therefore, extensive three-dimensional inversion and joint interpretation of geochemical, geophysical, and geologic data are necessary to understand the tectonic evolutionary history of craton lithosphere. [ABSTRACT FROM AUTHOR]

Abstract: Seismic tomography can provide both fine P-wave and S-wave velocity structures of the crust and upper mantle. In addition, with proper computation, Poisson’s ratio images from the seismic velocities can be determined. However, it is unknown whether Poisson’s ratio images have any advantages when compared with the P-wave and S-wave velocity images. For the purposes of this study, high-resolution seismic tomography under the eastern part of North China region was used to determine detailed 3-D crustal P- and S-wave seismic velocities structure, as well as Poisson’s ratio images. Results of Poisson’s ratio imaging show high Poisson’s ratio (high-PR) anomalies located in the Hengshan-North Taihang-Zhangjiakou (H-NT-Z) region, demonstrating that Poisson’s ratio imaging can provide new geophysical constraints for regional tectonic evolution. The H-NT-Z region shows a prominent and continuous high-PR anomaly in the upper crust. Based on Poisson’s ratio images at different depths, we find that this high-PR anomaly is extending down to the middle crust with thickness up to about 26km. According to rock physical property measurements and other geological data, this crustal Poisson’s ratio anomaly can be explained by Mesozoic partial melting of the upper mantle and basaltic magma underplating related to the lithospheric thinning of the North China craton. [Copyright &y& Elsevier]