Continental Deep Subduction Versus Subduction Cessation: The Fate of Collisional Orogens

Abstract

The contrasting fates of collisional orogens, i.e., continental deep subduction or subduction cessation, are widely recognized by petrological, paleomagnetic and geophysical observations. However, the mechanisms of such different collisional modes, especially the dynamics of continental deep subduction, are controversial. In this study, we integrate the phase transition‐induced density evolution into a thermo‐mechanical numerical model. Combing the systematic petrological‐thermo‐mechanical models with force balance analyses, we find that the high metamorphic transformation degree, mildly depleted mantle composition of the subcontinental lithosphere, and a long preceding oceanic slab, increase the driving force for continental deep subduction. Additionally, the rheologically weak continental crust and asthenospheric mantle decrease the resistance force and promote deep subduction. Otherwise, the continental subduction cessation mode is favored. The calculations of slab negative buoyancy indicate that the phase transition‐induced metamorphic densification of the subducted continental crust and the mildly to moderately depleted lithospheric mantle can provide a great slab pull force to sustain the continued continental deep subduction; however, the positive buoyancy of highly depleted Archean lithospheric mantle impedes deep subduction and causes subduction cessation. Based on systematic numerical models, we also evaluate the crustal mass balance or deficit in continental collisional system, which indicates that ∼12%‐47% of pre‐collisional felsic crust could be subducted deeply with the sinking slab in the regime of continental deep subduction. In contrast, the recycled felsic crust is negligible in the regime of subduction cessation. Thus, the different modes of continental collision play a crucial role in the global crustal recycling and related mantle heterogeneities.This article is protected by copyright. All rights reserved.

Sedimentological Evidence for Pre‐Early Permian Continental Subduction in the Dabie Orogen, Central‐East China

“…Thermomechanical numerical modeling studies can also help constrain the dynamics of deep continental subduction and subsequent exhumation. An increase in density during metamorphism of the subducted continental lithosphere can enhance slab pull during progressive continental deep subduction, driving it to greater depths (Y. Wang et al., 2023). While in contrast to magma‐rich margins, magma‐poor rifted margins that reach UHP conditions can exhume back to shallower levels as they lack thick layers of basaltic rocks that become negatively buoyant during metamorphism that hinders subsequent exhumation (Ganade et al., 2023).…”