The Post-Eocene Evolution of the Doruneh Fault Region (Central Iran): The Intraplate Response to the Reorganization of the Arabia-Eurasia Collision Zone

The Cenozoic deformation history of Central Iran has been dominantly accommodated by the activation of major intracontinental strike-slip fault zones, developed in the hinterland domain of the Arabia-Eurasia convergent margin. Few quantitative temporal and kinematic constraints are available from these strike-slip deformation zones, hampering a full assessment of the style and timing of intraplate deformation in Iran and the understanding of the possible linkage to the tectonic reorganization of the Zagros collisional zone. This study focuses on the region to the north of the active trace of the sinistral Doruneh Fault. By combing structural and low-temperature apatite fission track (AFT) and (U-Th)/He (AHe) thermochronology investigations, we provide new kinematic and temporal constraints to the deformation history of Central Iran. Our results document a post-Eocene polyphase tectonic evolution dominated by dextral strike-slip tectonics, whose activity is constrained since the early Miocene in response to an early, NW-SE oriented paleo-σ1 direction. A major phase of enhanced cooling/exhumation is constrained at the Miocene/Pliocene boundary, caused by a switch of the maximum paleo-σ1 direction to N-S. When integrated into the regional scenario, these data are framed into a new tectonic reconstruction for the Miocene-Quaternary time lapse, where strike-slip deformation in the intracontinental domain of Central Iran is interpreted as guided by the reorganization of the Zagros collisional zone in the transition from an immature to a mature stage of continental collision

Buildup of a dynamically supported orogenic plateau : Numerical modeling of the Zagros/Central Iran case study

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 × 590 km) numerical models of continental subduction models 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 during the development of the continental subduction/collision phase largely contributes to this process by controlling the timing and depth of slab break-off