Stratigraphy of the Roraima Supergroup along the Brazil-Guyana border in the Guiana shield, Northern Amazonian Craton - results of the Brazil-Guyana Geology and Geodiversity Mapping Project

Abstract

The Geological and Geodiversity Mapping binational program along the Brazil-Guyana border zone allowed reviewing and integrating the stratigraphy and nomenclature of the Roraima Supergroup along the Pakaraima Sedimentary Block present in northeastern Brazil (Fig. 1). Of unparalleled scenic beauty, it gathers a dozen tepuys, which stand out Mount Roraima, a triple frontier between Brazil, Venezuela and Guyana (Reis 2009). The basin register a historical gold and diamond mining activity in a stratigraphic framework poorly investigated and deserving attention at the application of sequence stratigraphy, tectonic setting and geochronological studies.This paper discusses the correlation of the stratigraphy of the Roraima Supergroup on both sides of the border of Brazil with Guyana, based on the work performed during the Geological and Geodiversity (land-use) Mapping of the Brazil-Guyana Project, carried out by geologists of the CPRM -Geological Survey of Brazil and the GGMCGuyana Geology and Mines Commission. The area of geological mapping includes the three main villages of Uiramutã and Mutum on the Brazilian side and Orinduik on the Guianese side, all of them located within that buffer zone of 25 kilometers on both sides of the frontier (Fig. 2). In spite of the bad weather conditions and the impossibility to drive along the dirt roads between Karasabai Village and Monkey Mountains, it was possible to reach Orinduik by plane. During the flight, it was possible to observe an interesting area of the Roraima Supergroup where the first sedimentary rocks form cliffs overlying the Iwokrama volcanics

Composition of the Sub‐Cratonic Mantle of the Guiana Shield Inferred From Diamond‐Hosted Inclusions

“…as the Arai Formation extend that age range to at most 2.12 Ga (Priem et al, 1973;Reis et al, 2017;Santos et al, 2003). Coeval mafic dykes of the Avanavero Suite intruded the entire sequence at ∼1.79 Ga (Reis et al, 2000).…”

“…Much of the region was then unconformably overlain by the Roraima Supergroup, a stratigraphic succession dominated by interbedded 1.98–1.78 Ga sandstones and conglomerates comprised of material eroding from earlier greenstone terranes. Roraima Supergroup outliers such as the Arai Formation extend that age range to at most 2.12 Ga (Priem et al., 1973; Reis et al., 2017; Santos et al., 2003). Coeval mafic dykes of the Avanavero Suite intruded the entire sequence at ∼1.79 Ga (Reis et al., 2000).…”

A Look at Diamonds and Diamond Mining in Guyana

“…Alluvial diamonds are mined in Brazil and Suriname. In the Guiana Shield portion of northern Brazil, diamonds are recovered from alluvial terraces shed from conglomerates of the Tepequém Formation (Santos et al, 2003;Reis et al, 2017). The diamonds are generally 2-3 mm in size and occur in a flattened octahedral to dodecahedral form.…”

Análise Petrográfica Dos Ignimbritos Bem Preservados Da Formação Cachoeira Da Ilha, Centro-Norte Do Cráton Amazônico, Estado De Roraima

“…O Domínio Surumu (DS) compreende rochas associadas ao vulcano-plutonismo Orocaima (1,96-1,98 Ga, Reis et al, 2003;2,00-1,96 Ga, Fraga et al, 2017) incluídas no Grupo Surumu e na Formação Cachoeira da Ilha Estudos Geológicos v 30(1) https://periodicos.ufpe.br/revistas/estudosgeologicos/index (CPRM, 2010). Além de apresentar distribuição para a Guiana (Formação Iwokrama, Reis et al, 2017), Venezuela (Grupo Cuchivero, Gibbs e Barron 1993) e Suriname (Formação Dalbana, Gibbs e Barron 1993) ( Fig. 2A).…”