The collision and continued convergence between the Indian and Eurasian plates in the past ~50 million years have raised the Tibetan Plateau, but whether or not, and how, the plateau has grown laterally remains controversial. Here we show that useful insights can be gained by studying lithospheric deformation across the front margins of the Tibetan Plateau. Crossing its northern and eastern sides where the plateau is bounded by the Tarim and Sichuan blocks, the topographic slope is steep and crustal deformation is localized near the margins of the plateau, whereas across northeastern Tibetan Plateau the topographic slope is gentle and crustal deformation is diffuse over a broad transition zone. Using a suite of two‐dimensional viscoplastic finite element models, we reproduced the major features of the two types of plateau margins with different rheological contrasts between the Tibetan Plateau and the bounding Asian blocks. Our results suggest that the bounding Asian blocks with a strong mantle lithosphere, such as the Tarim and the Sichuan Basins, have restricted the lateral growth of the Tibetan Plateau, although limited lateral expansion of the plateau can occur where the upper crust of these bounding blocks are relatively weak. Major lateral growth of the Tibetan Plateau mainly occurred northeastward, where numerous terranes with relatively weak mantle lithosphere are readily deformed and incorporated into the Tibetan Plateau. This growth front has reached the strong Alashan and Ordos blocks. Further lateral growth of the Tibetan Plateau depends on whether or not the Tibetan tectonics can weaken the mantle lithosphere of these Asian blocks.

Since ~40 Ma the eastward extrusion of the Songpan‐Ganzi Terrane (SGT), induced by the continuous convergence of the Indian Plate and Eurasia, was resisted by the Sichuan Basin which led to complex crustal rotational deformation of the basin edge. The interaction between the eastward extrusion of the SGT and crustal rotational movement of the Sichuan Basin is the key to understand the Cenozoic crustal deformation of the eastern edge of the Tibetan Plateau. However, we lack information about the dynamic mechanism of the branching of the eastward extrusion of the SGT and the characteristics of the crustal rotation of the Sichuan Basin. In the present study, the comprehensive analysis of Cretaceous and Paleogene paleomagnetic data from the southern edge of the Sichuan Basin shows a significant correlation between the locations of sampling sections on the edge of the basin and their corresponding amount of rotation. This indicates that since the time no earlier than 40 Ma (more likely since the Late Paleogene), the upper crust of the Sichuan Basin commenced passive integral clockwise rotation, relative to the eastern edge of the South China Block/Europe, which not only played an important role in promoting the eastward extrusion of the SGT dividing into the northeastern and southern branches at the eastern edge of the Tibetan Plateau, but was also probably correlative with the partial decoupling between the upper and lower crusts of the eastern edge of the Tibetan Plateau.

The Tibetan Plateau, induced by the India-Eurasian collision, has the highest average altitude in the world. During its uplift vertically, the Tibetan Plateau has been considered to expand laterally. However, there are several strong and almost non-deformable cratons on its periphery, such as the Tarim, North China craton, and South China block. The present landform features show that these cratons limit the expansion of the Tibetan Plateau. However, there is still much controversy over whether the deformation can be transmitted to periphery orogens or reactivate ancient orogens in the cratons. This study used numerical models to investigate the effect of rheological heterogeneities on the lithospheric deformation of the Tibetan Plateau and its neighbouring regions. The results show that the lateral heterogeneities of the lithosphere have an important influence on the deformation or strain partitioning. Generally, during the lateral expansion of the Tibetan Plateau, its peripheral cratons can transmit the deformation or high strain to neighbouring weak orogens. This case can be used to understand the Tian Shan orogen, which was reactivated by the India-Eurasian collision. However, when the orogens inside the cratons have high lithospheric strength, high strain is difficult to distribute on them and the expanding Tibetan Plateau is constrained by its peripheral cratons. These results can be used to explain the ancient orogens that are not strongly deformed, such as the Jiangnan orogen in the South China block. Because these orogens formed at the same time as the cratons and have relatively high lithospheric strength. In addition, the large lithospheric thickness difference and low crustal rheological contrast favor high strain rates localized on the lithosphere of the ancient orogen in the craton, such as the Trans-North China orogen in the North China craton.

With the constraint of GPS observation, the tectonic deformation of the Bayan Har block and its periphery faults is investigated based on an elastoplastic plane-stress finite element model. The results show that the elastic model cannot explain the current GPS observation in the Bayan Har block. When East Kunlun fault and Yushu-Xianshuihe fault are under plastic yield state or high strain localization, the calculated velocities fit well with the observation values. It indicates that most of the current shear deformations or strain localizations are absorbed by these two large strike-slip faults. In addition, if the recurrence intervals of large earthquakes are used to limit the relative yield strength of major faults, the order of entering the plastic yield state of the major faults around Bayan Har block is as follows. The first faults to enter the yield state are Yushu-Xianshuihe faults and the middle segment of East Kunlun faults. Then, Margaichaka-RolaKangri faults (Mani segment) and Heishibeihu faults would enter the yield state. The last faults to enter the yield state are the eastern segment of East Kunlun faults and Longmenshan faults, respectively. These results help us to understand the slip properties of faults around the southeastward moving Bayan Har block.