Rheological Control of Lateral Growth of the Tibetan Plateau: Numerical Results

Abstract

The collision and continued convergence between the Indian and Eurasian plates in the past ~50 million years has raised the Tibetan Plateau, but whether or not, and how, the plateau has grown laterally remain controversial. Here we show that useful insights can be gained by studying lithospheric deformation across the frontal 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 visco-plastic 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.

InSAR Evidence Indicates a Link Between Fluid Injection for Salt Mining and the 2019 Changning (China) Earthquake Sequence

“…The Sichuan basin is completely encircled on all sides by fold and thrust systems and withstands most of the eastward movement of the Tibetan Plateau along its western flank (Sun & Liu, 2018), where the 2008 Mw 7.9 Wenchuan earthquake ruptured the Longmenshan fault (e.g., Xu et al, 2010) (Figure 1a). The unconformities and missed sedimentary sequences document that the basin has experienced multiple stages of tectonic movements (e.g., Yang et al, 2017; Zhang et al, 2007; Zhu et al, 2016).…”

Lithospheric structures of and tectonic implications for the central–east Tibetan plateau inferred from joint tomography of receiver functions and surface waves

“…On profile a-a' that crosses through the western Kunlun-Qilian orogen (including Qaidam), a high upper-mantle velocity block beneath the Tarim and Qaidam basins seems overthrusting southwards to the northern Tibetan plateau and forms a dome-shaped Moho offset beneath southern Qaidam. Numerical modelling results (Sun & Liu 2018) showed that different rheological contrasts between the plateau and surrounding blocks caused different ways of lateral growth of the plateau. Therefore, it is not surprising that the Qaidam basin, characterized by higher crustal and upper-mantle velocities, and thus by higher viscosities, behaves like a rigid block when the plateau tries to expand across the KF.…”

A Numerical Study of Lithospheric Deformation and Strain Partitioning Across the Longmen Shan Orogenic Belt, Eastern Tibetan Plateau

“…The Arbitrary Lagrange-Euler (Fullsack, 1995) and the marker-in-cell method (Gerya & Yuen, 2003) were used to solve these equations. The code has been tested and used in the previous studies (Sun, Fan, et al, 2018;Sun & Liu, 2018).…”

“…It is important to determine what causes the tectonic differences across the southern and northern segments of the Longmen Shan orogenic belt. Numerical results indicate that large rheological contrasts lead to the formation of the steep topography along the eastern margin of the Tibetan Plateau, and the strain and deformation are more likely to accumulate along the contact boundary (Chen et al, 2013;Sun & Liu, 2018). Therefore, an investigation of the detailed rheological structure can provide clues to the variation in deformation.…”