Chromium, iron, gold and manganese in Amapá and northern Pará, Brazil

摘要

Information is presented on the geology and mineral deposits in greenstone belts and mafic-ultramafic complexes in Amapá and northern Pará, with the emphasis in iron, gold, manganese, and chromium. At Santa Maria, the Vila Nova Group presents deposits of iron and gold, the latter in carbonatic metasediments crossed by a north-south shear. The group is intruded by the Bacuri Mafic-Ultramafic Complex, with mineable deposits of chromite and magnetite. The overlaying 21 Grande Formation presents minor gold mineralization. At Serra das Coambas there is a significant show of iron formation, and, at its flank, the 21 Grande Formation presents extensive areas exploited by gold miners for gold. Serra do Ipitinga, in Pará, contains the greatest units of iron formation of the area, accompanied by frequent shows of alluvial and primary gold mineralization. The distribution of manganesiferous metasediments identified by mining companies indicate that they were deposited in an about 90 km long narrow basin oriented to northwest, with Serra do Navio near its center. The exposures of iron formation indicate that they were deposited on a belt greater than 350 km long and 100 km wide, oriented and still open to northeast, covering areas of different ages of metamorphism and tectonical stabilization.