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

Abstract

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][31][32][33][34][35]. 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 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.

Tectono‐sedimentary evolution of the northern Iranian Plateau: insights from middle–late Miocene foreland‐basin deposits

“…Our definition of the plateau realm therefore differs from previous definitions, which included different sectors of the Arabia–Eurasia collision zone (e.g. Allen et al ., , ; Hatzfeld & Molnar, ; Mouthereau, ; Mouthereau et al ., ; Madanipour et al ., ; François et al ., ,b).…”

“…Regarding the long‐term evolution of the plateau, it has been suggested that the IP reached its present‐day size through shortening and thickening processes during outward propagation from the suture zone to the NE, possibly starting from ~25–22 Ma (Mouthereau, ; Mouthereau et al ., ; François et al ., ,b). The deformation fronts should have reached the UDMA, either between 17 and 10 Ma Mouthereau, ; Mouthereau et al ., ; François et al ., ,b) or during the last 10 Ma (Morley et al ., ).…”

“…The paucity of field‐based data in the plateau realm, however, hampers our understanding of the mechanisms responsible for the Mio‐Pliocene growth of the plateau and the chronology of plateau‐building events. Unresolved issues concerning plateau formation in this region include the following topics: (1) it is still not clear, if the plateau has accommodated shortening during collisional deformation or if shortening rather affected adjacent regions (Allen et al ., ; Mouthereau, ; McQuarrie & van Hinsbergen, ); (2) it has remained enigmatic what parameters controlled the spatio‐temporal pattern of sedimentation and subsidence during the deposition of the terrestrial middle–late Miocene deposits of the Upper Red Formation (URF), and when these sediments were uplifted, eroded and incorporated into the plateau realm (Morley et al ., ; François et al ., ); (3) it is unknown what mechanisms may have controlled the vertical and lateral growth of the plateau (Allen et al ., ; Hatzfeld & Molnar, ; Mouthereau, ; Van Hunen & Allen, ; Bottrill et al ., ; Faccenna et al ., ; François et al ., ).…”

Mantle dynamics, isostasy, and the support of high terrain

“…Many authors have suggested that elevation contrasts supported by tractions applied to the base of the lithosphere by the convecting mantle are of order a few hundred meters-the remaining <10% of the range of regional surface heights [e.g., Braun, 2010;François et al, 2014;Kaban et al, 1999Kaban et al, , 2004Le Stunff and Ricard, 1995;Solomatov, 2011, 2012;Christensen, 1994, 1999;White, 2000, 2002]. Some, however, contend that surface height variations > 1 km, and even 2 or 3 km, are maintained by stresses associated with mantle convection [e.g., Boschi et al, 2010;Flament, 2014;Flament et al, 2013Flament et al, , 2014Forte et al, 1993Forte et al, , 2010Gurnis, 1993;Husson et al, 2014;Lithgow-Bertelloni and Silver, 1998;Moucha and Forte, 2011;Moucha et al, 2009].…”

Zircon U–Pb ages, geochemical and Sr–Nd–Pb–Hf isotopic constraints on petrogenesis of the Tarom-Olya pluton, Alborz magmatic belt, NW Iran

“…Moreover, the timing of the Arabia-Eurasia continental collision is so controversial, ranging from Late Cretaceous (Berberian and King, 1981) to Miocene-Pliocene time (Guest et al, 2006b;McQuarrie et al, 2003). Recent studies indicate several lines of evidence in support of initial collision at latest Eocene to Early/Late Oligocene time (Agard et al, 2011;Allen and Armstrong, 2008;Ballato et al, 2011;Boulton and Robertson, 2007;Ershov et al, 2003;François et al, 2014;Hafkenscheid et al, 2006;Hessami et al, 2001;Homke et al, 2009Homke et al, , 2010Jolivet and Faccenna, 2000;Kargaranbafghi and Neubauer, 2015;Keskin, 2003;Morley et al, 2009;Robertson et al, 2006;Vincent et al, 2007). On the other hand, recent studies in the Turkish Plateau (e.g., Sosson et al, 2010 and references therein) propose northern and southern branches of the Neotethyan ocean with distinct subduction zones.…”