The Faina gold deposit, located in the Pitangui Greenstone Belt, NW of the Quadrilátero Ferrífero, Brazil, has produced gold from the oxidized portion of the deposit between June 2010 and June 2013. However, the deeper hypogene (sulfide-rich) section of the deposit has shown lower-than-expected recovery rates after direct leaching, leading to the interruption of gold production. This research pres-ents a multi-methodological approach (drill core description, multi-element geochemical analyses and mineral characterization using microscopy and X-ray diffraction) to investigate describe the Faina gold deposit and identify the cause of low recoveries from the hypogene zone. The stratigraphy at Faina consists of a sequence of meta-mafic and meta-sedimentary rocks with a thick (>40m) saprolite horizon (oxidized portion). Both the meta-mafic rocks and saprolite host gold mineralization, which is identified by distinct geochemical and mineral signatures: 1) Au-As-W in the hypogene zone, with gold associated with sulfides or as disseminations in silicates and 2) Au-As-W in the oxide-rich shallower section with free-milling gold associated with quartz, iron oxide-hydroxides and clay minerals. Geochemical, miner-al and textural relationships in the hypogene zone show that submicroscopic gold particles associated with minerals that consume leaching solution minerals (arsenopyrite, pyrrhotite and berthierite) may cause refractoriness during direct leaching. Separation of gold from these mineral phases, in addition to concentration methods during ore processing may increase gold recovery. The results presented in this research emphasize the importance of a detailed geochemical and mineral characterization to reveal the contrasting mineral and chemical compositions between hypogene and oxidized zone, which may influence gold recovery.
