Geology, geochemistry, and some genetic discussion of the Chador-Malu iron oxide-apatite deposit, Bafq District, Central Iran

Abstract

The Chador-Malu iron oxide-apatite system (Bafq District, Central Iran) contains the largest known iron ore deposit in Iran (pre-mining reserve of 400 Mt @ 55 % Fe), and comprises the pipe-like northern (this study) and the sill-like southern orebodies of predominantly massive ore, and a sodic-calcic alteration envelope. The geology and geochemistry of the Chador-Malu deposit demonstrates its similar characteristics to the Kiruna-type deposits. There is circumstantial evidence for rare earth elements (REE) mobilization during apatite leaching by high-temperature fluids and associated monazite nucleation. Pervasive actinolitization of the rhyolitic country rocks led to the formation of actinolite-rich metasomatic host rocks, which represent another evidence for high-temperature fluids at Chador-Malu. Hydrothermal mineralization is suggested by small iron ore veins (2–3 cm thick) and breccias cemented by iron oxides, as well as a Fe-metasomatism which overprints all types of host rock alteration. Based on REE geochemistry and spatial relationships, it is proposed that a potential source for metals and P could be late-stage Fe-P melt differentiates of the Cambrian magmatism, which is consistent with the late Fe-metasomatism of the host rocks. The proposed Fe-P melts and the mineralization would be linked by hydrothermal media through the zones of ring fracture at Chador-Malu and similar parts of the Bafq district.