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The Arabia – Eurasia collision zone in the central part of the Alpine – Himalayan orogenic system has had a complex deformation history since the Palaeozoic. In Iran, the collision zone consists of the Alborz‐Talesh, Kopeh Dagh and Zagros foldbelts and the intervening Central Iran area. In this review paper, we summarize the structural architecture and tectonostratigraphic characteristics of these domains and attempt to correlate regional deformation events between them. The results show that six regional‐scale deformation phases can be recognized and correlated in Iran over a time interval extending from the Late Palaeozoic to the Late Cenozoic. Late Palaeozoic rifting in northern Gondwana and subsequent oceanic spreading resulted in the separation of the Central and North Iran blocks from the Arabian Platform. These blocks later converged and collided with the southern margin of Eurasia due to the subduction of the intervening PalaeoTethys lithosphere ("Cimmerian orogeny": Late Triassic). The convergent setting resulted in the initial development of the Alborz‐Talesh foldbelt in present‐day northern Iran, while extensional basins developed in the forebulge area in Central Iran. Continuing northward subduction of NeoTethyan oceanic lithosphere at the southern Eurasia margin produced Early Cretaceous back‐arc extension and associated volcanism in Central Iran and the Alborz‐Talesh area to the north. A phase of compressional deformation in the Late Cretaceous was related to the collision of a series of microcontinents derived from Northern Gondwana, including the Ercinjan and Bitlis massifs, with the Central Iran block, and is recorded in the Alborz‐Talesh foldbelt and in Central Iran. Further back‐arc extension in the late Paleocene – Eocene was accompanied by pervasive volcanism and volcaniclastic sedimentation throughout northern and Central Iran. The final closure of NeoTethys and convergence between the Arabian and Eurasian Plates evolved through phases of early Oligocene "soft" collision and middle Miocene "hard" collision. This was accompanied by thrusting in the internal parts of the Zagros foldbelt and by folding and subordinate thrusting in the more external parts, with related development of the flexural Mesopotamian Basin in the foreland to the SW. [ABSTRACT FROM AUTHOR]

The exhumation of actively deforming orogenic systems is commonly due to the incision of river systems in response to tectonically driven surface uplift. However, a regional base level and/or climatic variations can also cause erosional exhumation. The temporal and spatial distinction of the dominant mechanism during the topographic evolution of orogens is challenging. Using detailed morphological analyses and thermal modelling of an intrusive body through triple dating (zircon U–Pb, ZHe, and AHe), combined with the previously published structural, detrital, and bedrock low‐temperature thermochronometry (apatite fission track and apatite helium) analysis, the transition from early Oligocene (~27 Ma) and middle Miocene (~12 Ma) tectonic exhumation to late Miocene–early Pliocene (~7–5 Ma) river incision and erosional exhumation in the Talesh Mountains in the NW of the Arabia–Eurasia collision zone was documented. The late Miocene‐early Pliocene incision and the contemporaneous rapid exhumation documented in the Talesh Mountains are related to the base‐level fall of the Caspian Sea due to its isolation from the Paratethys domain. The effect of this base‐level fall then migrated to the margin of the Iranian Plateau and captured the overspilled basins (~4 Ma). [ABSTRACT FROM AUTHOR]

The interpretation of low-temperature thermochronology (LTT) data in magmatic and metallogenic provinces requires a knowledge of the geothermal field through time. There, the challenge is differentiating rapid cooling following transient perturbations of the geotherms (reheating) from exhumational cooling induced by erosion during tectonic uplift or normal faulting. The Takab Range Complex (NW Iran) is a basement-cored range of the Arabia-Eurasia collision zone that experienced voluminous Eocene to Miocene magmatism and mineralization. Our new apatite and zircon (U-Th-Sm)/He and apatite fission track data, together with field observations, a dedicated numerical thermal model, and a re-evaluation of available geochronology data document the occurrence of a complex geological and thermal history including: (a) late Cretaceous-Paleocene exhumation possibly controlled by regional contractional deformation followed by Eocene deposition; (b) Oligocene to possibly early Miocene (29 to 22-20 Ma) exhumation of basement rocks from 13 to 8 km of depth, most likely through normal faulting during a thermal anomaly that led to migmatization and partial melting; (c) early to late Miocene (~22-20 or earlier to 11-10 Ma) regional subsidence with deposition of an up to ~2- to 3-km-thick Oligo-Miocene sedimentary sequence in association with the emplacement of shallow intrusions, which led to a partial to total reset of our LTT systems sometime between 18 and 13 Ma; and (e) erosional exhumation after 11-10 Ma with the development of a transpressional system and a master, right-lateral, strike slip fault (Chahartagh Fault). Our data highlights the impact of magmatic reheating on LTT ages in areas affected by intense magmatism. [ABSTRACT FROM AUTHOR]

Magmatic activity that accompanied the collision between Arabia and Eurasia at ~27 Ma, provides unique opportunities for understanding the triggers and magma reservoirs for collisional magmatism and its different styles in magmatic fronts and back-arcs. We present new ages and geochemical-isotopic results for magmatic rocks that formed during the collision between Arabia and Eurasia in NE Iran, which was a back-arc region to the main magmatic arcs of Iran. Our new zircon U-Pb ages indicate that collisional magmatism began at ~24 Ma in the NE Iran back-arc, although magmatism in this area started in the Late Cretaceous time and continued until the Pleistocene. The collisional igneous rocks are characteristically bimodal, and basaltic-andesitic and dacitic-rhyolitic components show significant isotopic differences; eNd(t) = +4.4 to +7.4 and eHf(t) = +5.4 to +9.5 for mafic rocks and eNd(t) = +0.2 to +8.4 and eHf(t) = +3.4 to +12.3 for silicic rocks. The isotopic values and modeling suggest that fractional crystallization and assimilation-fractional crystallization played important roles in the genesis of felsic rocks in the NE Iran collisional zone. Trace element and isotopic modeling further emphasize that the main triggers of the magmatism in NE Iran comprise a depleted to the enriched mantle and the Cadomian continental crust of Iran. Our results also emphasize the temporal magmatic variations in the NE Iran back-arc from Late Cretaceous to Pleistocene. [ABSTRACT FROM AUTHOR]