Reconciling subduction dynamics during Tethys closure with large-scale Asian tectonics: Insights from numerical modeling

Abstract

We use three-dimensional numerical models to investigate the relation between subduction dynamics and large-scale tectonics of continent interiors. The models show how the balance between forces at the plate margins such as subduction, ridge push, and far-field forces, controls the coupled plate margins and interiors evolution. Removal of part of the slab by lithospheric break-off during subduction destabilizes the convergent margin, forcing migration of the subduction zone, whereas in the upper plate large-scale lateral extrusion, rotations, and back-arc stretching ensue. When external forces are modeled, such as ridge push and far-field forces, indentation increases, with large collisional margin advance and thickening in the upper plate. The balance between margin and external forces leads to similar convergent margin evolutions, whereas major differences occur in the upper plate interiors. Here, three strain regimes are found: large-scale extrusion, extrusion and thickening along the collisional margin, and thickening only, when negligible far-field forces, ridge push, and larger far-field forces, respectively, add to the subduction dynamics. The extrusion tectonics develops a strong asymmetry toward the oceanic margin driven by largescale subduction, with no need of preexisting heterogeneities in the upper plate. Because the slab break-off perturbation is transient, the ensuing plate tectonics is time-dependent. The modeled deformation and its evolution are remarkably similar to the Cenozoic Asian tectonics, explaining large-scale lithospheric faulting and thickening, and coupling of indentation, extrusion and extension along the Asian convergent margin as a result of large-scale subduction process.

Geodynamics of divergent double subduction: 3‐D numerical modeling of a Cenozoic example in the Molucca Sea region, Indonesia

“…In general, an oceanic lithosphere is consumed on one side of a plate as it subducts, while the other side borders another plate at a mid-oceanic ridge (e.g., the Pacific plate). Subduction leads to formation and migration of magmatic arcs, opening of back-arc basins, fragment of continents, or accretion of crustal fragments [e.g., Rey and Müller, 2010;Gerya and Meilick, 2011;Moresi et al, 2014;Capitanio et al, 2015]. Interactions between the subducting slab, the overriding plate, and the ambient upper mantle are also responsible for magmatism, metamorphism, and earthquake activity at subduction zones [e.g., Gutscher et al, 2000;Liu and Stegman, 2012;Pownall et al, 2013;Bouilhol et al, 2015;Ji et al, 2016].…”

Current Deformation in the Tibetan Plateau: A Stress Gauge in the India‐Asia Collision Tectonics

“…The models in this configuration are then perturbed adding ridge push and far-field forces and run for <5 Myr to achieve the new configuration. It is important to note that the trench disruption only occurs upon continent entrainment, so that the difference between the perturbed models presented here and that with external forcing since the initial stage (Capitanio et al, 2015) are negligible.…”

“…The force balance of continental tectonics as the result of subduction dynamics has been addressed by several publications. Modeling the subduction of a heterogeneous plate embedding oceanic and continental lithosphere beneath an upper plate and coupled mantle, provides a proxy for the large-scale Tethys closure and collision with Asian plate (Bajolet et al, 2013;Capitanio et al, 2015;Chen et al, 2017;Iaffaldano et al, 2006;Li et al, 2013;Pusok & Kaus, 2015;Sternai et al, 2016).…”

“…Several works addressed the Cenozoic dynamics of Asian tectonics by means of numerical and analog modeling, where the self-consistent force balance results into boundary forces and deformation inside the plate during subduction, slab break-off and collision (Bajolet et al, 2013;Capitanio et al, 2015;Capitanio & Replumaz, 2013;Pusok & Kaus, 2015;Sternai et al, 2016). These models showed that thickening and lateral motions are the results of subduction and far-field forces, such as the Indian slab pull, the ridge push, traction beneath India and the Pacific subduction (Becker & Faccenna, 2011;Capitanio et al, 2010;Ghosh et al, 2006;Schellart et al, 2019), and large-scale mantle tractions beneath Asia (Sternai et al, 2016).…”

“…Numerical models of large-scale plate-mantle interactions are used to quantify the driving forces during subduction and collision and the coupled deformation and motions. The models share the same setup of Capitanio et al (2015) and embed the main features of the subduction of oceanic and continental lithosphere in the mantle beneath the Asian continental upper plate. While the insights such models provide into the Cenozoic evolution are discussed elsewhere (Capitanio et al, 2015;Replumaz et al, 2014), here the focus is on the comparison with the GPS velocity of the Tibetan area (Gan et al, 2007;Zhang et al, 2004;Zubovich et al, 2010), as the only area with relevant surface strain (e.g., Kreemer et al, 2014), Tibetan lithospheric thickness and the mantle seismic anisotropy, as a proxy for mantle strain, to provide an assessment of the forces at play.…”