Geology, geochemistry, fluid inclusion and genesis of the Guijeh Qaleh IOA-type iron ore deposit, north of Takab district, Northwestern Iran

Abstract

The Guijeh Qaleh iron deposit, located in the Takab district of northwestern Iran contains ca. 0.3 million metric tons (Mt) of ore at 48 wt. % Fe. The host rocks are Eocene to Oligocene volcano-sedimentary sequences consisting of andesite, trachy-andesite to basaltic andesite flows intruded by granites to granodiorite intrusions. The hydrothermal alterations include argillic, sericitic, silicified, carbonate, and hematitic zones. Silicified and hematitic alteration zones are spatially associated with the mineralization and occur proximal to ore bodies, whereas sericite, carbonate, and argillic alteration zones are distal to main ore bodies. Iron mineralization occurred as several quartz-hematite-specularite veins, 0.5- to 5-m wide and 10- to 20-m long, which were formed within and along normal and strike-slip fault zones. The mineralogy of ore bodies consists of hematite, specularite, pyrite, subordinate magnetite and apatite together with minor malachite (after chalcopyrite) with open space-filling, disseminated, massive, and breccia textures. Geochemical analyses of high-grade ore bodies show that Fe concentration is strongly correlated with Mo, Zn, Mn, Pb, SiO2, MgO, TiO2, and P2O5. The chondrite-normalized REE patterns of the altered and mineralized ore bodies displays with LREE/HREE ratio with a negative Eu anomaly and low Eu/Eu* values characteristic of the Kiruna-type IOA deposits. Fluid inclusion studies from quartz occurring with the mineralization characterized mineralizing fluids with homogenization temperatures ranging from 133 to 464 °C, and apparent salinities between 0.2 to 23.2 wt. % NaCl equ. Interpretation of fluid inclusion data suggest that mixing of magmatic and meteoric fluids and cooling caused ore precipitation. Geology, mineralogy, ore textures, geochemistry, and fluid inclusion data suggest that iron mineralization in the Guijeh Qaleh deposit is similar to Kiruna-type IOA deposits. The presented data show that the Takab district has the potential for hosting Kiruna-type IOA mineralization in the northwest of Iran. © 2020 Elsevier B.V.