Late Jurassic-Early Cretaceous sediment-hosted Zn-Pb mineralization in western Iran: a world-class example of passive margin mineralization

Iran has more than 400 Late Jurassic-Early Cretaceous sediment-hosted Zn and Pb deposits. These are valuable resources that also provide insights into the tectonic history of the northern Neo-Tethys rim in western Iran. In this review, we compiled available data for twenty-six Zn-Pb deposits in eight mineral districts in the Malayer-Esfahan Metallogenic Belt (MEMB) of western Iran to better understand this mineralization system, specifically to test if these formed on a passive margin within a Jurassic to Early Cretaceous passive margin. Basal terrigenous deposits grade upward into shallow-water carbonates, providing a favourable stratigraphic framework for mineralization. Hydrothermal circulation was driven by coeval magmatism and focused along syn-sedimentary normal faults, which acted as conduits for fluid flow. Carbon, O, S, and Pb isotope ratios indicate diverse sources for the Zn-Pb deposits: Pb from the crust, S from seawater (mediated by microbes), and host-rock sources for C and O. Hydrothermal systems involving 80–130°C brines precipitated mainly sphalerite and galena in Jurassic and Early Cretaceous carbonate and shale host rocks. We conclude that the Jurassic-Early Cretaceous Zn-Pb mineralization in western Iran occurred at a passive continental margin that was underlain by continental rift basins in a horst-graben system parallel to the Neo-Tethys Ocean.