Tectonomagmatic reconstruction of the Upper Mesozoic-Cenozoic Neotethyan arcs in the Lut block, East Iran: a review and synthesis

Authors: REZA ARJMANDZADEH, SAEED ALIREZAEI, ALIREZA ALMASI

Abstract: The Lut Block in east Iran with a widespread record of arc-type Mesozoic-Cenozoic magmatic rocks is bordered by the Birjand (Sistan) ophiolitic assemblage to the east and the Sabzevar ophiolitic assemblage to the north. The nature and tectonomagmatic setting of these sutures and associated arcs are controversial. The geochemical attributes of the Upper Cretaceous-Paleogene intrusive and extrusive rocks in the central (CLB) and the northern Lut block (NLB) and in the Sabzevar ophiolite zone (SOZ), Late Cretaceous calc-alkaline and adakitic rocks to the east of the Sistan suture (CAS), and the Bazman intrusives to the west are consistent with a subduction-related volcanic arc setting. The Najmabad granitoids in the NLB compositionally overlap with the Eocene Sabzevar calcalkaline and adakitic lava flows (ESA), implying a common magmatic source and a similar trend of evolution. The island arc basalt-like geochemical patterns and the initial Sr and Nd isotope compositions for the CLB intrusive bodies suggest that the parent magmas formed by partial melting in a suprasubduction mantle wedge. The initial ⁸⁷Sr/⁸⁶¹Sr and εNd(t) values for the CAS, the Bazman intrusives, the ESA, and the Najmabad granitoids are similar and overlap those of the Sabzevar ophiolitic rocks. Here, we review the previously proposed one-sided subduction models for the Lut block and the Sabzevar suture zone, and discuss in favour of a two-sided asymmetric subduction as an alternative geodynamic model.

Keywords: Lut block, Sistan Ocean, Birjand ophiolite, Sabzevar ophiolite, East Iran, two-sided asymmetric subduction

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