The Bajgan Complex revealed as a Cretaceous ophiolite-bearing subduction complex: A key to unravel the geodynamics of Makran (southeast Iran)

Abstract

• The Bajgan Complex consists of meta -ophiolites. • The mafic rocks have MOR-, OIB- and E-MOR affinity. • The ages of intrusive protholiths range from Late Jurassic to Early Cretaceous . • The Bajgan Complex represents a Cretaceous fossil accretionary wedge. In the Makran area, a wide accretionary wedge is originated by the north-dipping subduction of the Neo-Tethyan oceanic lithosphere. The rear of the accretionary wedge is represented by the North Makran Domain that consists of an imbricate stack of tectonic units derived from the closure of the North Makran oceanic basin. This oceanic basin opened southward of the Eurasia continental margin during the Early Cretaceous. The Bajgan Complex is interpreted as an Early Paleozoic or older metamorphic basement representing the remnants of the Bajgan-Durkan continental microplate located at the southern rim of the North Makran oceanic basin. This microplate plays thus a key-role in the so far proposed reconstructions of the evolution of the whole Makran area. The Bajgan Complex consists of Late Jurassic to Early Cretaceous meta -ophiolites and related meta -sediments, both affected by HP-LT metamorphism. The HP-LT metamorphism has been overprinted by epidote amphibolite to greenschist facies metamorphism in the Late Cretaceous during the progressive exhumation of the Bajgan Complex up to shallow structural levels. The incompatible trace elements ratios of meta -igneous rocks indicate a subduction-unrelated chemical affinity for these meta -ophiolites. Our study clearly indicates that the Bajgan Complex cannot be considered as a continental basement of pre-Mesozoic age. Consequently, the closure of the North Makran oceanic basin cannot be related to a collision between a microcontinent and the continental margin of the Lut Block.