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

Abstract

The India–Asia collision, starting from 55 ± 5 Ma, leads to the formation of the Himalayas and Tibetan Plateau with great gravity potential energy and large forces acting on the surrounding blocks. However, the subduction transference/jump does not occur in the southern Indian continental margin or the northern Indian oceanic plate as supposed to happen repeatedly during the preceding Tethys evolution. Instead, the continental collision and orogeny continues until present day. The total amount of convergence during the India–Asia collision has been estimated to be ∼2,900–4,000 km and needs to be accommodated by shortening/extrusion of the Tibetan plate and/or subduction of the Greater Indian plate, which is a challenging issue. In order to study the collision mode selection, deformation partition, and continental mass conservation, we integrate the reconstruction-based convergence rate of the India–Asia collision into a large-scale thermomechanical numerical model and systematically investigate the effects of overriding Tibetan lithospheric strength and the amount of convergence. The model results indicate that the absence of subduction transference during the India–Asia collision may be attributed to strain localization and shortening of the rheologically weak Tibetan plate. In case of the India–Asia collision for ∼50 Myr with a total convergence of ∼2,900 km, the model with the intermediately weak Tibetan plate could reconcile the general deformation partition and continental mass balance of the Himalayan–Tibetan system. However, the longer period of India–Asia collision for ∼55 Myr leads to significant shortening of the overriding plate that is not consistent with the Tibetan observations, in which case an oceanic basin may be required for the Greater Indian continent.

Numerical constraints on the one‐stage and two‐stage Greater India collision models

“…The model results are further compared with the multiple geological observations of the Tibetan system. The main observational constraints include (1) the overriding Tibetan plate shortening of ~1600–1700 km (Li et al, 2022; van Hinsbergen et al, 2019; Yin & Harrison, 2000), (2) the current Himalayan width in the north–south direction of <500 km (DeCelles et al, 2002; Liu et al, 2021), (3) the average Tibetan crust thickness of ~60–70 km (Replumaz, Negredo, Guillot, et al, 2010; Xia et al, 2023; Yakovlev & Clark, 2014), and (4) the present Indian continental lithosphere subduction of ~300–700 km (Replumaz, Negredo, Villaseñor, et al, 2010; Zhao et al, 2010), which may also be supported by the amount of continental lithosphere subduction based on reconstructed models (e.g., Ingalls et al, 2016; Yakovlev & Clark, 2014).…”

“…In the GIC model, the continental lithosphere has been subducted for ~700–2400 km since the beginning of collision; and the scraped upper crustal materials are presented in the Himalayan sequence or eroded and deposited in the northern Indian Ocean (Ali & Aitchison, 2005; DeCelles et al, 2002; Wang et al, 2022). However, the GIC model may be only compatible with current observations if the India‐Asia collision occurred at ≤50 Ma (Li et al, 2022). Otherwise, if the collision occurred earlier (i.e., at 55 or 60 Ma), it would lead to a much higher amount of overriding plate shortening than the current observation.…”

“…(b) The general deep structure of the present India‐Asia collision zone, corresponding to the profile A‐A′ in (a). (c) The compilation of time‐dependent convergence rates during India‐Asia collision (Copley et al, 2010; Lee & Lawver, 1995; Molnar & Stock, 2009; Müller et al, 2008; van Hinsbergen et al, 2011), with the red line for the averaged convergence rate (Li et al, 2022). (d) The one‐stage collision model, in which the entire Greater Indian plate has continental affinity.…”