Abstract:ABSTRACT:Greenstone belts with deposits of gold, iron and manganese are common in the Paleoproterozoic Maroni-Itacaiunas Tectonic Province of the Guiana Shield. In Brazil, in the State of Amapá and northwest of Pará, they are represented by the Vila Nova Group, constituted by a basal unit of metabasalts, covered by metasediments of clastic and chemical origin. The basal metasediments, the Serra do Navio Formation, are made of a cyclothem with lenses of manganese marbles at the top of each cycle. Under the inte… Show more
“…We revise the published information, updating it with observations recently made in the field by one of the authors. We show that exposures at new mining excavations and aero-geophysical information demonstrate that the mafic-ultramafic complex is intrusive in the Vila Nova Group, similarly to what we saw at the area of the Serra da Canga (Scarpelli & Horikava 2017), and that the auriferous quartzite-conglomerate unit of the area occurs at the top, and not at the base, of the column of metasediments, actually overlaying the Vila Nova Group. Examining the Água Boa auriferous deposit, we saw a very good degree of similarity between the principal structural control of the gold mineralization of this deposit with that of the Tucano Mine, practically outlining a pattern worth to follow in general exploration for gold in the MIP.…”
Section: Introductionsupporting
confidence: 75%
“…A detailed petrographic study of the Amapari Greenstone belt at Serra do Navio has shown that it was subject twice to regional metamorphism, with an intermediate episode of thermal metamorphism caused by syntectonic granitic intrusions. Local fold axis and elongation of greenstone to north and northeast suggest that these structures might be remnants of the first regional metamorphism (Scarpelli & Horikava 2017).…”
Section: General Geologymentioning
confidence: 99%
“…These rocks are covered by a well foliated biotite schist and, closing up the cycle, with graphite schist locally with a lens of fine to medium-grained spessartite-bearing rhodochrosite marble. Gondites, formed by coarse-grained spessartite, manganese silicates and graphite, appear in the transition zone between the manganesiferous marble and the graphite schists (Scarpelli & Horikava 2017). This formation was only seen around Serra do Navio.…”
Section: General Geologymentioning
confidence: 99%
“…The Jornal Formation orthoamphibolites are massive, medium to coarse grained, nematoblastic without a clear layering, formed mostly by hornblende, plagioclase, quartz and accessory magnetite. Occasionally, there are intercalations of quartz-mica schist, well banded actinolite schists and other schists (Scarpelli & Horikava 2017).…”
Section: General Geologymentioning
confidence: 99%
“…Following our description of the geology of the Amapari Greenstone Belt near Serra do Navio, Amapá, and its deposits of manganese, iron and gold (Scarpelli & Horikava 2017), we now expand laterally the limits of our area of observation and describe other areas of the Paleoproterozoic Maroni-Itacaiúnas Tectonic Province (MIP) presenting similar geology and mineralization. Actually, the area object of the present note covers the MIP from the coast of Amapá, at east, to the headwaters of the Ipitinga River, in the north of the Pará State, at west.…”
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.
“…We revise the published information, updating it with observations recently made in the field by one of the authors. We show that exposures at new mining excavations and aero-geophysical information demonstrate that the mafic-ultramafic complex is intrusive in the Vila Nova Group, similarly to what we saw at the area of the Serra da Canga (Scarpelli & Horikava 2017), and that the auriferous quartzite-conglomerate unit of the area occurs at the top, and not at the base, of the column of metasediments, actually overlaying the Vila Nova Group. Examining the Água Boa auriferous deposit, we saw a very good degree of similarity between the principal structural control of the gold mineralization of this deposit with that of the Tucano Mine, practically outlining a pattern worth to follow in general exploration for gold in the MIP.…”
Section: Introductionsupporting
confidence: 75%
“…A detailed petrographic study of the Amapari Greenstone belt at Serra do Navio has shown that it was subject twice to regional metamorphism, with an intermediate episode of thermal metamorphism caused by syntectonic granitic intrusions. Local fold axis and elongation of greenstone to north and northeast suggest that these structures might be remnants of the first regional metamorphism (Scarpelli & Horikava 2017).…”
Section: General Geologymentioning
confidence: 99%
“…These rocks are covered by a well foliated biotite schist and, closing up the cycle, with graphite schist locally with a lens of fine to medium-grained spessartite-bearing rhodochrosite marble. Gondites, formed by coarse-grained spessartite, manganese silicates and graphite, appear in the transition zone between the manganesiferous marble and the graphite schists (Scarpelli & Horikava 2017). This formation was only seen around Serra do Navio.…”
Section: General Geologymentioning
confidence: 99%
“…The Jornal Formation orthoamphibolites are massive, medium to coarse grained, nematoblastic without a clear layering, formed mostly by hornblende, plagioclase, quartz and accessory magnetite. Occasionally, there are intercalations of quartz-mica schist, well banded actinolite schists and other schists (Scarpelli & Horikava 2017).…”
Section: General Geologymentioning
confidence: 99%
“…Following our description of the geology of the Amapari Greenstone Belt near Serra do Navio, Amapá, and its deposits of manganese, iron and gold (Scarpelli & Horikava 2017), we now expand laterally the limits of our area of observation and describe other areas of the Paleoproterozoic Maroni-Itacaiúnas Tectonic Province (MIP) presenting similar geology and mineralization. Actually, the area object of the present note covers the MIP from the coast of Amapá, at east, to the headwaters of the Ipitinga River, in the north of the Pará State, at west.…”
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.