Evidence for syn-sedimentary faulting and reduced formation environment of the Ab-Bagh SEDEX-type Zn-Pb deposit, South of Shahreza, Sanandaj-Sirjan zone

The Ab-Bagh Zn-Pb deposit is located at the southeastern part of the Malayer-Esfahan metallogenic belt. This deposit is hosted by Upper Jurassic-Lower Cretaceous sedimentary sequence. Zinc and lead mineralization occurred within two horizons. The ore horizon 1 is hosted by Late Jurassic-Early Cretaceous black shale and siltstone. The ore body displays a wedge-like shape and is located close to syn-sedimentary fault. The ore horizon 2 occurs in lower Cretaceous carbonates and includes massive ore,concordant with the host rock layering; Syn-sedimentary faults, half-graben basins and related anoxic environments, had an important role in formation of SEDEX-type Zn-Pb mineralization in the Ab-Bagh and deposition of sulfides. Sedimentary debris flows and syn-sedimentary braccia within host rocks of the Ab-Bagh deposit suggests activity of normal faulting simultaneously with sedimentation of host rock and consequently development of half- graben structures. Formation of half-graben structures is one of the most important factors of redox condition of ore forming environment. This structures led to development of deeper zones within the basin, where anoxic condition were occurred. Trace and rare earth elements geochemistry of host rocks, size of pyrite framboids and presence of organic matter in the host rocks, represent anoxic to euxinic paleo-redox condition of this basin, which is caused by microbial activities and depth of the basin,associated with normal syn-sedimentary fault. Comparison of syn-sedimentary normal faulting and anoxic formation environment of the Ab-Bagh deposit with other SEDEX deposit of Iran, indicates similarity of their formational environment.