Wedge‐Shaped Southern Indian Continental Margin Without Proper Weakness Hinders Subduction Initiation

Abstract

In the general history of the earlier Tethyan evolution, the younger oceanic plate began subduction shortly after the terrane collision and closure of the neighboring older ocean (Table S1 in the Supporting Information S1). For example, the subduction of Neo-Tethyan oceanic plate initiated at about 10-20 Myrs after the collision of Cimmerian terranes with Eurasia (Stampfli & Borel, 2002;Wan et al., 2019;Zhong & Li, 2020). However, there is no clear sign for subduction initiation (SI) in the present-day northern Indian Ocean, although it has been more than 50 Myrs since the collision between Indian and Eurasian continental plates (Stern, 2004;.The absence of SI in the Indian Ocean is thus a puzzling and widely debated issue. One possible reason is the high strain localization in the relatively weak Tibetan plate, which thus hinders the stress building in the Indian oceanic plate. However, this explanation is challenged by the high gravitational potential energy of the present

Ocean-continent subduction cannot be initiated without preceding intra-oceanic subduction!

“…Only for extreme conditions adopted in the experiments, requiring continued forced convergence instead of free subduction combined with a predefined weakness of the backward passive margin of the collided block, subduction can be initiated by subduction zone transference (Zhong and Li, 2020). In the case of the continental collision between India and Eurasia, it was the lack of sufficient weakness that prevented subduction initiation at the passive margin of India (Zhong and Li, 2022). It appears, therefore, that the two most popular scenarios for triggering ocean-continent subduction face first-order challenges in terms of consistency with plate-tectonic reconstructions and reproducibility in numerical simulations.…”

Compression at Strike‐Slip Fault Is a Favorable Condition for Subduction Initiation

“…To explain the driving force of SI, several mechanisms have been proposed in previous studies, including SI driven by negative buoyancy (e.g., Leng & Gurnis, 2015; Marques et al., 2014; Nikolaeva et al., 2010; Stern, 2004; Zhou et al., 2018), far‐field convergence (e.g., Gurnis et al., 2004; Hall, 2019; Leng & Gurnis, 2011; Mueller & Phillips, 1991; Toth & Gurnis, 1998; Zhong & Li, 2019), and SI triggered by mantle flow (e.g., Baes & Sobolev, 2017; Solomatov, 2004). However, it has also been proved that the SI is not easy because of the stiffness of lithosphere (Cloethingh et al., 1982; McKenzie, 1977; Toth & Gurnis, 1998; Zhong & Li, 2019, 2022). Thus, the lithospheric weakness is generally required for SI (Arcay et al., 2020; Gurnis et al., 2004; Hall, 2019; Lallemand & Arcay, 2021; Mueller & Phillips, 1991; Toth & Gurnis, 1998; Zhong & Li, 2021, 2022; Zhou et al., 2018).…”

“…However, it has also been proved that the SI is not easy because of the stiffness of lithosphere (Cloethingh et al., 1982; McKenzie, 1977; Toth & Gurnis, 1998; Zhong & Li, 2019, 2022). Thus, the lithospheric weakness is generally required for SI (Arcay et al., 2020; Gurnis et al., 2004; Hall, 2019; Lallemand & Arcay, 2021; Mueller & Phillips, 1991; Toth & Gurnis, 1998; Zhong & Li, 2021, 2022; Zhou et al., 2018).…”

Overriding Lithospheric Strength Affects Continental Collisional Mode Selection and Subduction Transference: Implications for the Greater India–Asia Convergent System

“…However, the southern Indian continental margin and northern Indian oceanic plate have shown no signs of SI until today, which is a puzzling issue and widely debated with several mechanisms being proposed, including the resistance from the triangular shape of southern Indian continental margin, the relatively old ocean-continent transition zone with great resistance, and the continuous shortening of the overriding Tibetan Plateau (Stern, 2004;Stern and Gerya, 2018;Cloetingh et al, 1989;Zhong and Li, 2020). In a recent study by Zhong and Li (2022), systematic 3D numerical models revealed that the wedge-shaped southern Indian continental margin without proper weakness hinders its subduction initiation after the long-term India-Asia collision. In that study, the shortening and uplift of a narrowed and simplified Tibetan plate, due to the spatial resolution limit of 3D model (Zhong and Li, 2022), does not affect the subduction transference.…”

“…In a recent study by Zhong and Li (2022), systematic 3D numerical models revealed that the wedge-shaped southern Indian continental margin without proper weakness hinders its subduction initiation after the long-term India-Asia collision. In that study, the shortening and uplift of a narrowed and simplified Tibetan plate, due to the spatial resolution limit of 3D model (Zhong and Li, 2022), does not affect the subduction transference. In this study, we further investigate this issue by applying comparable spatial and temporal scales of the Tibetan Plateau, as well as the FIGURE 1 | Tectonic background and corresponding profiles of the Indo-Eurasian system at the initial collision (A,C) and present-day Tibetan plateau(B,D) (Yi et al, 2011;Ingalls et al, 2016;Wang et al, 2019;van Hinsbergen et al, 2019;Meng et al, 2019Meng et al, , 2020Parsons et al, 2020).…”