Late cenozoic exhumation of the Nodoushan plutonic complex constrained by low-temperature thermochronology: evidence for Arabia–Eurasia collision in the southeastern Iranian Plateau

Abstract

ABSTRACT The Nodoushan plutonic complex in the central part of the Urumieh–Dokhtar Magmatic Belt developed mainly in the Cenozoic in response to the final stages of subduction-related magmatism that preceded the post-Oligocene collision between the Arabian and Eurasian Plates. Despite numerous recent studies examining the deformation and related exhumation history of the Arabia–Eurasia collision zone, the exhumation history of the Urumieh–Dokhtar Magmatic Belt (making up the majority of the Iranian Plateau) is largely unknown. In this work, apatite and zircon (U-Th)/He thermochronometry and thermal modelling analysis are applied to the (mainly) granitoid intrusive bodies in the Nodushan Plutonic complex in order to unravel the exhumation history of this region in the context of collisional tectonics. The results document two main phases of exhumation in the early Miocene (~ 22–20 Ma) and middle Miocene (~ 11 Ma). The distribution of (U-Th)/He ages suggests that these deformation episodes are related to the collision between the Arabian and Eurasian Plates. The ‘soft’ initial stages of Arabia–Eurasia collision in the Nodoushan plutonic complex occurred when the stretched Arabian passive margin reached the subduction zone in the early Miocene. Subsequently, the final ‘hard’ collision with the harder continental margin occurred in the middle Miocene. The results of this work mark the first thermochronometric data related to SE Iranian Plateau evolution and identify exhumation that initiated in the early Miocene and developed regionally during middle Miocene times.