The Eastern khoy metamorphic complex of NW Iran: A jurassic ophiolite or continuation of the Sanandaj-Sirjan zone?

Abstract

The Khoy complex in NW Iran has been widely regarded to consist of both Jurassic and Cretaceous ophiolites, but whereas the western Late Cretaceous ophiolite is unequivocal the nature of the eastern Jurassic body has been unclear. Field observations show that the presumed eastern meta-ophiolite has no similarities to an ophiolite sequence. Here, we report geological and zircon–rutile–titanite U–Pb data for rocks from the presumed Jurassic ophiolite obtained to verify whether these are real ophiolitic units and to understand their relations either to the Late Cretaceous Zagros–Bitlis ophiolites in western Iran–southern Anatolia or to the Sevan–Akera (northern Armenia) and Izmir–Ankara (southern Pontides) complexes. The new U–Pb ages show that the ‘presumed’ ophiolite is in fact a collage of Ediacaran to Cambrian (c. 606–517 Ma) and Jurassic (c. 160 Ma) meta-igneous rocks, similar to ages obtained for igneous rocks of the Sanandaj–Sirjan Zone, which has been interpreted as a Jurassic continental rift. The Jurassic igneous rocks contain abundant Ediacaran, Ordovician–Silurian and Carboniferous–Permian inherited zircons, further suggesting involvement of pre-existing continental crust. Our results indicate that Jurassic continental rifting provided a lithospheric weakness along which a new subduction zone formed in Late Cretaceous times.