Ophiolites of Iran: Keys to understanding the tectonic evolution of SW Asia: (II) Mesozoic ophiolites

Abstract

Iran is a mosaic of continental terranes of Cadomian (520–600Ma) age, stitched together along sutures decorated by Paleozoic and Mesozoic ophiolites. Here we present the current understanding of the Mesozoic (and rare Cenozoic) ophiolites of Iran for the international geoscientific audience. We summarize field, chemical and geochronological data from the literature and our own unpublished data. Mesozoic ophiolites of Iran are mostly Cretaceous in age and are related to the Neotethys and associated backarc basins on the S flank of Eurasia. These ophiolites can be subdivided into five belts: 1. Late Cretaceous Zagros outer belt ophiolites (ZOB) along the Main Zagros Thrust including Late Cretaceous–Early Paleocene Maku–Khoy–Salmas ophiolites in NW Iran as well as Kermanshah–Kurdistan, Neyriz and Esfandagheh (Haji Abad) ophiolites, also Late Cretaceous–Eocene ophiolites along the Iraq–Iran border; 2. Late Cretaceous Zagros inner belt ophiolites (ZIB) including Nain, Dehshir, Shahr-e-Babak and Balvard–Baft ophiolites along the southern periphery of the Central Iranian block and bending north into it; 3. Late Cretaceous–Early Paleocene Sabzevar–Torbat-e-Heydarieh ophiolites of NE Iran; 4. Early to Late Cretaceous Birjand–Nehbandan–Tchehel–Kureh ophiolites in eastern Iran between the Lut and Afghan blocks; and 5. Late Jurassic–Cretaceous Makran ophiolites of SE Iran including Kahnuj ophiolites. Most Mesozoic ophiolites of Iran show supra-subduction zone (SSZ) geochemical signatures, indicating that SW Asia was a site of plate convergence during Late Mesozoic time, but also include a significant proportion showing ocean-island basalt affinities, perhaps indicating the involvement of subcontinental lithospheric mantle.