Discrete Element Modeling of Southeast Asia's 3D Lithospheric Deformation During the Indian Collision

Abstract

The Indian collision has deformed the eastern Asian continent in a multifaceted way, uplifting Tibet and surrounding mountains, activating ≥1,000 km‐long strike‐slip faults, and opening Tertiary rifts and oceanic basins up to ≈3,000 km away from the Himalayas. Modeling such broad‐scale tectonics has been challenging. While continent‐scale, lithospheric deformation appears to have been primarily taken‐up by long, narrow, inter‐connected shear‐zones with large offsets, the contribution of processes such as channel‐flow, collapse, delamination, etc… has remained contentious. Here, based on increasing 4G (Geological, Geophysical, Geochronological, Geodetic) evidence including kinematic and timing constraints on the main mechanisms at play, we use Discrete Element (DE) Modeling to simulate and further understand the evolution of 3D strain across east Asia since the onset of collision, ≈55 Ma ago. The planar, 50 million km2, 125 km‐thick models are scaled for gravity. The approach permits mega‐fault generation and evolution without pre‐arranged initial settings. The results provide insight into fault birth, propagation and motion, as well as mountain building and plateau growth. They corroborate that continental crustal thickening across Tibet alternated with the extrusion of large blocks that rifted apart in the far field. Remarkably, without changes in boundary conditions or indentation rate, the DE model also vindicates slip reversal along initial strike‐slip shear zones.

Present‐Day Strike‐Slip Faulting and Intracontinental Deformation of North China: Constraints From Improved GPS Observations

“…An essential aspect of understanding intracontinental deformation of a region in the context of transition between the South China and North China Blocks is determining the slip rates of faults that play a critical role in accommodating strain. A key structure in continental China is the ∼3,500 km long left‐lateral strike‐slip Altyn Tagh‐Haiyuan‐Qinling fault system (AHQFS), which is proposed to be the primary boundary fault system that accommodates the eastward extrusion of the Tibetan Plateau and South China Block with respect to North China in the lateral extrusion hypothesis (Jiao et al., 2023; Peltzer et al., 1985; Tapponnier et al., 1982, 2001; Y. Q. Zhang et al., 1995, 2003). To test the eastward extrusion model and to explain the mechanisms of extensional tectonics in North China, an extensive geodetic effort has been dedicated to determine the slip rates of the Altyn Tagh Fault (e.g., Bendick et al., 2000; Gan et al., 2007; He et al., 2013; Y. C. Li et al., 2018, 2022; Loveless & Meade, 2011; Shen et al., 2001; G. Zheng et al., 2017), Haiyuan Fault (e.g., B. Li et al., 2015; X. N. Li et al., 2021; Y. C. Li et al., 2015; Y. H. Li et al., 2018; Thatcher, 2007; H. Wang et al., 2011; W. Wang et al., 2017; G. Zheng et al., 2017; W. J. Zheng et al., 2013), and Qinling Fault (e.g., Hao et al., 2016; Huang et al., 2018; Jin et al., 2007; Middleton, 2016; Qu et al., 2014; H. Wang et al., 2011; W. Wang et al., 2022).…”

“…An essential aspect of understanding intracontinental deformation of a region in the context of transition between the South China and North China Blocks is determining the slip rates of faults that play a critical role in accommodating strain. A key structure in continental China is the ∼3,500 km long left-lateral strike-slip Altyn Tagh-Haiyuan-Qinling fault system (AHQFS), which is proposed to be the primary boundary fault system that accommodates the eastward extrusion of the Tibetan Plateau and South China Block with respect to North China in the lateral extrusion hypothesis (Jiao et al, 2023;Peltzer et al, 1985;Tapponnier et al, 1982Tapponnier et al, , 2001; Y. Q. Zhang et al, 1995Zhang et al, , 2003.…”

Modeling Deep Rooted Thrust Mechanism of Crustal Thickening in Eastern Tibet

“…Nevertheless, with respect to the LMTB, the YTB is spreading more over the craton, making a smoother topographic transition between the high plateau and the foreland (Figure 1b). Such spreading is most probably due to the propagation of crustal thickening along the strike-slip fault of XianShuiHe, as shown in the north of the plateau along the Altyn Tagh fault (Jiao et al, 2023;Tapponnier et al, 2001).…”

A timeline of the Cenozoic tectonic–magmatic–metamorphic evolution and development of ore resources in the Himalayas

“…Coincident with the further splitting of Gondwana, the Indian Block and the Australian Block split in the late Jurassic, the northward drift of the Indian Block accelerated and the Neo‐Tethys Ocean gradually contracted (Figure 2d). By the early Cenozoic, the Indian Block collided with the Eurasian Blocks and the Neo‐Tethys Ocean disappeared, forming the world‐prominent Himalayan orogenic Belt (Jiao et al, 2023) (Figure 2e). Mesozoic–Cenozoic magmatism includes Late Triassic basic volcanic rocks (Huang, Zhang, et al, 2019; Wang, Zeng, et al, 2020), Late Jurassic–Early Cretaceous bimodal volcanic rocks (Wang, Ding, et al, 2022) and Eocene–Miocene leucogranite (Cao, Pei, et al, 2022; Cao, Pei, Yu, Cao, et al, 2023; Wu et al, 2020).…”