Geodynamic Modeling of Lithospheric Removal and Surface Deformation: Application to Intraplate Uplift in Central Mongolia

Abstract

Intraplate surface deformation is enigmatic and the underlying mechanisms responsible are not fully understood. We use thermo-mechanical numerical modeling to explore the conditions under which lithospheric removal processes can occur and investigate the timing and amplitude of consequent surface deformation. We allow lithospheric removal to develop dynamically and self-consistently by applying a phase transition and density jump that is hypothesized to be a consequence of metamorphic eclogitization in a thickened crust, rather than simply imposing an initial dense block. By systematically varying parameters, we test their influence and control on lithospheric removal. We confirm that a weak and dense lower crust, a hot crust-mantle boundary, and a convergent regime are critical requirements for delamination-style removal. We apply these results to central Mongolia, which is an ideal natural laboratory for studying intraplate surface uplift because of its high topography and location in the continental interior. We determine that the physical parameters and structure inferred in this region match the conditions for delamination. Thus, model outputs are evaluated against the available observational evidence. We find that the removal of the lithosphere by delamination can explain: the dome-shaped topographic pattern and elevated surface; the thin lithosphere and its structure; the elevated temperature at the crust-mantle boundary. Additionally, it is hypothesized that delamination leads to magmatism due to mantle decompression melting, consistent with intraplate volcanism. Ultimately, the results suggest that lithospheric removal by delamination is a physically plausible mechanism and a potential explanation for intraplate uplift.