Geology, geochemistry and genesis of the Kosaj Fe occurrence, Takab‒Takht-e-Soleiman‒ Anguoran metalogenic zone, SW Zanjan

Kosaj Fe ore occurrence is located in the Takab‒Takht-e-Soleyman‒Angouran metallogenic zone. At Kosaj, iron mineralization occurs as lens-shaped bodies and layers parallel to the foliation of muscovite schist and actinolite-hornblende schist units (equal to Kahar Formation). Ore minerals are magnetite along with minor pyrite, and quartz and actinolite present as gangue mineral. The ore minerals show disseminated, laminated, banded, massive, lenticular, vein-veinlet and replacement textures. Three stages of mineralization can be distinguished at Kosaj. The first stage is recognized as stratiform and stratabound lenses, laminated and disseminated crystals of magnetite-quartz and magnetite-actinolite bands parallet to the foliation of host rocks. Stage-2 mineralization is recognized by folding of ore bands, σ microfabric, boudinage and elongation of magnetite crystals, quartz pressure shadows and surrounding of foliation around magnetite crystals, and recrystallization of quartz and magnetite crystals. Stage-3 is recognized by brecciated magnetite-quartz vein-veinlets. Actinolitization, silicification and hematitization are main hydrothermal alteration types at Kosaj. Chondrite-nonmineralized REE pattern of host rocks and the mineralized samples indicate that mineralized samples are depleted in REE. Characteristics of Kosaj occurrence are comparable with metamorphosed and deformed volcano-sedimentary type of iron deposits.