Lithosphere delamination in continental collisional orogens: A systematic numerical study

Abstract

Lithosphere delamination is believed to have played a major role in mountain building; however, the mechanism and dynamics of delamination remain poorly understood. Using a 2‐D high‐resolution thermomechanical model, we systematically investigated the conditions for the initiation of lithosphere delamination during orogenesis of continental collision and explored the key factors that control the various modes of delamination. Our results indicate that the negative buoyancy from lithosphere thickening during orogenesis could cause delamination, when the reference density of the lithospheric mantle is not lower than that of the asthenosphere. In these cases, compositional rejuvenation of depleted continental lithosphere by magmatic/metasomatic plume‐ and/or subduction‐induced processes may play crucial roles for subsequent lithosphere delamination. If the reference density of the lithospheric mantle is less than that of the asthenosphere, additional promoting factors, such as lower crust eclogitization, are required for delamination. Our numerical simulations predict three basic modes of lithosphere delamination: pro‐plate delamination, retro‐plate delamination, and a transitional double‐plates (both the pro‐plate and retro‐plate) delamination. Pro‐plate delamination is favored by low convergence rates, high lithospheric density, and relatively strong retro‐plate, whereas retro‐plate delamination requires a weak retro‐plate. The Northern Apennines and Central Northern Tibetan Plateau are possible geological analogs for the pro‐plate and retro‐plate delamination modes, respectively. Our model also shows significant impact of delamination on the topographic evolution of orogens. Large‐scale lithosphere delamination in continental collision zones would lead to wide and flat plateaus, whereas relatively narrow and steep mountain belts are predicted in orogens without major delamination.

On the Role of Lower Crust and Midlithosphere Discontinuity for Cratonic Lithosphere Delamination and Recycling

“…This can be related to compositional contrasts, thermal weakening, partial melting, or fluid percolation (Shinevar et al, ). The critical stress ranging from ~100 to 800 MPa or more is in agreement with plate margins and continental plateaux settings where tectonic stress is large and/or lower crustal eclogitization might occur (Capitanio et al, ; Huangfu et al, ; Krystopowicz & Currie, ; Li et al, ), but unlikely values for stress within cratonic interiors. This indicates that delamination at lower crustal depths (20–70 km deep) can initiate near cratonic margins with over thickened crust, whereas it is unlikely to initiate within cratonic interiors.…”

“…Delamination along the lower crust was first proposed interpreting lithospheric thinning and surface uplift process of the Colorado plateau (Bird, ). This hypothesis has been tested by means of numerical models (e.g., Göğüş & Pysklywec, ; Krystopowicz & Currie, ; Le Pourhiet et al, ; Li, Liu, & Gerya, ; Magni et al, ; Schott & Schmeling, ; Ueda et al, ), which have illustrated viable mechanisms to describe the regional thinning, uplift, decompression melting and extension processes, and/or flat Moho within or near orogenic belts of various ages, including the Andean Cordillera, Sierra Nevada, Appalachians, Variscides, Carpathians, Alps, and Tibetan Plateau (e.g., Nelson, ). This process is also inferred to have occurred in the eastern part of the North China Craton (NCC), where a flat Moho, thinned lower crust with large Poisson's ratio, magmatism related to eclogite‐peridotite interactions, is present (Gao, Zhang, et al, ; Gao et al, , ).…”

Craton Destruction 1: Cratonic Keel Delamination Along a Weak Midlithospheric Discontinuity Layer

“…Bird, ; Gao et al, , ; Kay & Kay, ). Based on this conceptual model, many authors have described and studied scenarios in which a dense lithospheric root rapidly peels along the weak and/or deepened Moho (Bao et al, ; Bird, ; Gray & Pysklywec, ; Krystopowicz & Currie, ; Z. H. Li et al, ; Morency & Doin, ). Most of these studies highlight that the negative buoyancy of the lithospheric mantle is what triggers delamination, with possible additional contributions from an eclogitized lower crust.…”

Dynamic processes and mechanisms for collision to post‐orogenic extension in the Western Dabie Orogen: Insights from numerical modeling

“…The velocity boundary conditions are free slip for the left, right, and top boundaries. The lower boundary is permeable, along which a mass‐conservative permeable boundary condition is imposed (Gerya & Stöckhert, ; Gerya, Perchuk, & Burg, ; Gerya et al, ; Gerya & Yuen, ; Li, ; Li, Gerya, & Xu, ; Li, Gerya, & Burg, ; Li, Xu, & Gerya, ; Li et al, ). The pro‐ and retro‐plate could be pushed by prescribing constant convergence rates ( V L and V R , respectively) in small internal domains of the pro‐ and retro‐lithosphere that remains fixed with respect to the Eulerian coordinate (Figure ).…”

“…In addition to the systematic geological studies, analog and numerical modeling (e.g., Göğüş, Pysklywec, Corbi, & Faccenna, ; Li et al, ; Morency & Doin, ; Valera, Negredo, & Jiménez‐Munt, ) has increasingly become a more and more important method for investigating the dynamics of post‐orogen extension. Although these numerical studies well simulate the delamination process and later thermal evolution of the post‐orogen stage induced by slab breakup (Duretz & Gerya, ; Faccenda, Gerya, & Chakraborty, ; Gerya & Yuen, ) and eclogitization of the lower crust (Krystopowicz & Currie, ), they have not addressed the entire evolutionary process of the orogen from the initial collision to lithosphere delamination and the inherited relationship between collision and post‐orogen extension.…”