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

Abstract

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.

Geological characteristics of the Serra do Navio Formation, Guiana Shield, Brazil, and its manganiferous ores: queluzite as a source rock of oxide and carbonate manganese ores

“…All of these rocks are metamorphosed into the amphibolite facies, and intruded by granitic rocks. In two small areas, one in the mid-course of the Jari River, and the other extending from the mid-course of the Falsino River (Scarpelli 1969) to near Tartarugal, the lithologies of the basement and of the Vila Nova Group were metamorphosed to the granulite facies (Scarpelli 1966, João et al 1979, Scarpelli and Horikava 2018.…”

“…In the central zone of Amapá and northwest of Pará, the Vila Nova Group presents a column of metasediments covering the Jornal Formation. They were deposited in a former basin that extended for, at least, 700 kilometers from east to west and 90 kilometers from north to south (Scarpelli and Horikava 2018).…”

“…(Scarpelli W. 1966, and Analysis from Chisonga (Chisonga B.C. et al 2012) The first regional metamorphic episode originated fold axis striking north-northeast, with a gentle plunge to the north, and with a foliation dipping to the east (Scarpelli and Horikava 2018). Staurolite, cordierite, and andalusite were formed in the quartz-silicate lithologies of the formation.…”

Water quality of streams associated with artisanal gold mining; Suárez, Department of Cauca, Colombia

“…It is considered that gold exploitation, according to recent estimations release up to 1600 tons of elemental mercury (Hg) per year onto the planet ( Black et al., 2017 ; Rajaee et al., 2015 ), inducing the alteration and affectation of ecosystemic services associated with the supply, principally of the hydric resource and changes in soil use, removing the edaphic horizons and depositing the rocky material from mine openings; residual sludge and sand from the operations are thrown directly into hydric sources. This rocky and sandy material is formed by mineral compounds that contain metals, like iron (Fe) in form of (magnetite, pyrite, and siderite), Manganese (Mn) (pyrolusite, magnesite), chromium (Cr) (chromite), cadmium (Cd) (otavite), lead (Pb) (galena, litharge), and arsenic, (As) (arsenopyrite), among others ( Ramanaidou et al., 2015 ; Scarpelli, and Horikava, 2018 ; Gutiérres-Mosquera et al., 2018 ).…”