The petrology of Achaean biotite- and amphibole-rich metagranites, the geochemistry of Fe-occurrences and heavy mineral concentrations in stream sediments from Olounou (Ntem complex) help to constrain their inter-relationships. These metagranites display granoblastic textures outlined by microcline, biotite, amphibole and oxides. Ilmenite (60 to 80%), zircon (15 to 20%) and rutile (1 to 2%) are the mineral fractions in pan concentrates. Two types of Fe-mineralization as silicified veins crosscut the above rocks: hematite± magnetite quartzites with primary hematite enclosing magnetite relicts contain high average Fe2O3 (69.05 wt %) and TiO2 (0.73wt %); banded magnetite-rich quartzites with magnetite partially replaced by hematite are characterized byFe2O3 (52.15 wt %), TiO2 (0.27 wt %), relatively high W (286 ppm) and Ni (108 ppm). Both types have Zn, Cu, Ga contents below 10 ppm, positive Eu anomalies, HREE enrichment over LREEs and low ∑REE (9.76 to 12.07). Iron and SiO2 were derived from weathering of Archean biotite and amphibole metagranites, deposited in existing Post-Archean intra-cratonic basins under greenschist facies and impacted by sub-marine hydrothermal solutions. These results are genetically comparable to other Precambrian BIFs and underline the iron potential of Olounou. They equally contribute to iron ore exploration in Cameroon and worldwide.