Build-up of a dynamically supported orogenic plateau: numerical modelling of the Zagros/Central Iran Case Study
Résumé
The Iranian plateau is a vast inland region with a smooth average elevation of c. 1.5 km formed
at the rear of the Zagros orogen as a result of the Arabia-Eurasia collision (i.e., over the last 30–35 Myr). This
collision zone is of particular interest due to its disputed resemblance to the faster Himalayan collision,
which gave birth to the Tibetan plateau around 50 Myr ago. Recent studies have suggested that a recent
(10–5 Ma) slab break-off event below Central Iran caused the formation of the Iranian plateau. Here, we test
several hypotheses through large-scale (3082
3
590 km) numerical models of continental subduction mod-
els that incorporate a free upper surface erosion, rheological stratification, brittle-elastic-ductile rheologies,
and metamorphic phase changes (density and physical properties) and account for the specific crustal and
thermal structure of the Arabian and Iranian continental lithospheres. We test the impact of the transition
from oceanic to continental subduction and the topographic consequences of the progressive slowdown of
the convergence rate during continental subduction. Our results demonstrate the role of mantle flow
beneath the overriding plate, initiated as an indirect consequence of slab break-off. This flow creates a
dynamic topography support during continental subduction and results in delamination of the overriding
plate lithospheric mantle followed by isostatic readjustment, hence of further uplift and maintenance of a
plateau-like topography without significant crustal thickening. The slowdown of the convergence rate dur-
ing the development of the continental subduction/collision phase largely contributes to this process by
controlling the timing and depth of slab break-off