Palladian gold from the Cau iron mine, Itabira District, Minas Gerais, Brazil

Palladian gold from the Cau ~ iron mine, Itabira District, Minas Gerais, Brazil is found in horizons of hydrothermally-altered Lake Superior-type oxide-facies iron-formation locally called jacutinga. Palladium content of the gold grains varies from 1 % to 20%, high palladium values being associated with palladium-copper-oxide inclusions and showing island-mainland and replacement (relict) textures in the Corpo Y and Corpo X orebodies. In the Aba Leste orebody, palladium is homogeneously distributed throughout the gold grains. Palladium and gold mineralization was synchronous with intense D1 shearing. Palladium was deposited early during the generation of Sl-mylonitic foliation, and was replaced by gold during progressive deformation. At high oxygen fugacities (hematite stability field) and high temperatures (up to 600 ~ Pd and Au may have been transported as chloride complexes, and their deposition may have occurred mainly as a result of changes in pH, but dilution of C1 concentrations may have also caused Pd and Au precipitation. Deposition of Pd as selenide may have taken place early during the creation of Sl-fabrics. K~VWOROS: gold, palladium, Itabira, Brazil, iron-formation, jacutinga