Fe-Mn Mineralization in Dolomites Equivalent to Shotori Formation in NE of Dehbid, Southern Sanandaj-Sirjan Zone, Fars Province

The Goshti-Heneshk, Goli and Cheshmeh Esi iron-manganese deposits are located in the northeast of Dehdib (Safashahr), 175 km northeast of Shiraz. These deposits are situated in the Heneshk Shear Zone, which is a part of the Complex Deformation Subzone of the Southern Sanandaj- Sirjan Zone. The oldest outcrops in the area consist of the metamorphosed Permian shale, sandstone and crystalline limestone. The Middle Triassic dolomite units (equivalent to the Shotori Formation) have been thrusted on the Upper Triassic metamorphic and deformed volcano-sedimentary rocks and chert by thrust faults. The ore-bearing dolomites are often repeated due to imbricate thrust system in the area. The host rock to the ore is only dolomite, and ore bodies formed as lenses concordant by layering. The ore texture is massive, open space filling, lamination, and disseminated. The ore minerals include hematite, magnetite, goethite, kriptomelan, psilomelan and ramsdelite together with dolomite, calcite, quartz and barite. In the geochemical studies to determine the source of mineralization, Mn/Fe, Si/Al and Na/Mg ratios of major elements indicated that Fe-Mn ore formation occurred through the hydrothermal processes in shallow marine volcano-sedimentary environment. The trace element diagrams show low contents of elements such as Ni, Co, and Cu in the Fe-Mn ores. In these diagrams, the deposits of the study area plot in the field of hydrothermal deposits. Rare Earth Element distribution patterns of the deposits are quite similar to those of hydrothermal deposits. Two ore types are distinguished based on geometry and shape of the ore bodies: primary mineralization occurred parallel and concordant with layering of the host rocks. The ore textures of this type include massive, laminated and disseminated occurring in folded chert and dolomite. The vein-type mineralization is associated with the faults and has brecciated or cataclastic texture occurring in the Middle Triassic dolomite and Permian metacarbonates. Based on the stratigraphic location, layer form of the ore body, texture, paragenetic sequence, ore-bearing chert-dolomite facies and geochemistry, the iron-manganese ores of the northeast Dehbid are stratabound carbonate-hosted deposits, which were precipitated in the shallow marine environment in the dolomites equivalent to the Middle Triasssic Shotori Formation.