Zircon dating, Sr and Nd isotopes, and element geochemistry of the Khalifan pluton, NW Iran: Evidence for Variscan magmatism in a supposedly Cimmerian superterrane

The Khalifan pluton of the Sanandaj-Sirjan Zone is composed of A-type peraluminous leucogranites with Nd model ages around 1.2 Ga. It intrudes an unfossiliferous sedimentary sequence previously considered as Cretaceous by analogy with neighboring areas. However, zircon U–Pb SHRIMP and Pb–Pb sequential evaporation dating have revealed that Khalifan granites are Carboniferous, with a precise age of 315 ± 2 Ma. This is the first reliable Variscan age obtained so far in this area, but there are geological indicators that other small plutonic bodies might also be Variscan. The existence of Carboniferous granite rocks in the Sanandaj-Sirjan Zone casts doubts on whether it was a part of the Cimmerian superterrane detached from east Gondwanide terranes because these characteristically lack Variscan magmatism. The age, chemical features and Nd isotopes of Khalifan granites are similar to those of the southernmost Urals and Tien Shan, so that we tentatively suggest that this area bears a Middle Asian instead of Cimmerian linkage.

Research highlights
► The crystallization age of the Khalifan pluton is 315 ± 2 Ma.
► Khalifan is not Cretaceous, as previously believed, but Late Carboniferous.
► Khalifan is not the only Variscan pluton in the Sanandaj-Sirjan Zone.
► The Sanandaj-Sirjan Zone was not a part of the Cimmerian superterrane.
► The Sanandaj-Sirjan Zone derived from Middle Asian terranes.