The banded iron formations (BIF) are sedimentary rocks with a high iron content (at least 15%). They represent 90% of the iron ore exploited in the world. The rock is called itabirite. The particularity of the Banalia deposit is its extremely high iron content (more than 63%) whereas the usual content of itabirites is often less than 45% Fe. The iron enrichment of the ore comes from an intense leaching that has taken the sterile gangue, the ore is then porous, but very rich. This leaching comes from its proximity to an imposing massive granite intrusive. It is responsible for the recovery of the sedimentary layers which are found in a subvertical position. The last phase of consolidation of this granite is the hydrothermal phase characterized by an increase in pressure. The high pressure and high temperature hyrothermal liquids escape from the granite massif by crossing the rocks that adjoin this granite. The sedimentary layers being straightened, these hydrothermal flows must cross them, which explains the effectiveness of this leaching. This hydrothermal phase is also responsible for the gold mineralization caused by hydrothermal flows. It is therefore logical to preferentially look for this gold mineralization in the fault zones that were transport vectors of these flows.