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 Uatuma-Anaua 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 (Anaua Complex). Younger and undeformed (with local discrete NE-SW shear zones) Igarape Azul and Caroebe granites (I-type, calc-alkaline Agua 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 Igarape Azul granitoid rocks (southern UAD), and amethyst is associated to pegmatites of the Moderna A-type granites.