Geology and petrography of paleoproterozoic granitoid rocks from Uatumã- Anauá Domain, central region of Guyana Shield, southeastern Roraima, Brazil

Abstract

Regional mapping carried out in the Uatumã-Anauá Domain (UAD), Guyana Shield, southeastern Roraima (Brazil), has showed widespread calc-alkaline granitic to alkaline magmatism and local peraluminous granites. These granitoid rocks are distributed into several magmatic associations with different Paleoproterozoic (1.97-1.89 Ga) ages, structural and geochemical affinities. In this paper, detailed mapping and petrographic studies have distinguished two main subdomains in UAD. In the northern UAD, the Martins Pereira I-type, calc-alkaline granitoid rocks and Serra Dourada S-type granite (1.97-1.96 Ga) are deformed and affected by NE-SW and E-W shear zones. Basement inliers (2.03 Ga) crop out to the northeastern part of this area, and are formed by rocks from metavolcano-sedimentary sequence (Cauarane Group) and TTG-like calc-alkaline association (Anauá Complex). Younger and undeformed (with local discrete NE-SW shear zones) Igarapé Azul and Caroebe granites (I-type, calc-alkaline Água Branca suite) crop out in the southern UAD. A-type granites such as Moderna (1.81 Ga) and Mapuera (1.87 Ga) plutons, cross cut both areas of UAD. Gold mineralization is observed in the Martins Pereira granitoid rocks (northern UAD), alluvial columbite-tantalite is related to the Igarapé Azul granitoid rocks (southern UAD), and amethyst is associated to pegmatites of the Moderna A-type granites.

New geological and single-zircon Pb evaporation data from the Central Guyana Domain, southeastern Roraima, Brazil: Tectonic implications for the central region of the Guyana Shield

“…2) and Igarapé Azul calc-alkaline granitoid rocks. These granitoid rocks were associated with the Iricoumé volcanic rocks Reis et al, 2000) and subordinate charnockitoid plutons , and altogether comprise the ''undeformed" Igarapé Azul-Água Branca granitic terrain located on the Southern Uatumã-Anauá Domain (SUAD, Almeida and Macambira, 2007). Several A-type granite plutons (Fig.…”

“…2). Altogether, they comprise the 1.96-2.03 Ga Martins Pereira-Anauá granitic terrain or the Northern Uatumã-Anauá Domain (NUAD, Almeida and Macambira, 2007) taken as the ''deformed" portion of the UAD. Younger, unmetamorphosed and undeformed sequences are represented by the Caroebe (Água Branca Suite, Fig.…”

The 1.90–1.88Ga magmatism in the southernmost Guyana Shield, Amazonas, Brazil: Geology, geochemistry, zircon geochronology, and tectonic implications

“…Santos and Reis Neto (1982) and Cunha et al (1994) interpreted the Neoproterozoic Prosperança Formation as an alluvial-fluviallacustrine deposit. However, Nogueira (1999) suggested that the formation was deposited on felsic volcanic rocks of the Iricoumé Group in WNW-ESE and NE-SW trending graben in a restricted coastal environment represented by flood plain, bay-outlet, bay-in- (CPRM, 2006;Valério et al, 2006;Ferron et al, 2006;Almeida and Macambira, 2007). ter-distributary and shoreface environments. Storm-related deposits have also been found in sub-surface (Nogueira, 1999).…”

https://jgsb.cprm.gov.br/index.php/journal/issue/view/24

“…Macambira et al (2002) found an age of 1.89 Ga (Table 1) for the volcanic group of the Jatapu River hydroelectric plant. These authors maintained the name "Iricoumé" for these rocks, but observed its association with the Água Branca granitoids, interpreted as formed in a postcollisional setting (Almeida and Macambira 2007).…”