Abstract The Carajás (3.0–2.5 Ga) and Xingu-Iricoumé (1.99–1.86 Ga) blocks comprise the Central Amazonia Province (CAP) that is in contact with the Maroni-Itacaiúnas Province (MIP) within the Amazonian craton. The CAP is the oldest portion (Nd-TDM) of the craton and corresponds to an Archean nucleus bordered by younger Paleo-Mesoproterozoic mobile belts, including the MIP. Because the location and tectonic boundaries between these provinces are insufficiently known, we carried out a geological survey along the Middle Xingu River, cutting the WNW-ESE regional trend, to further understand cratonic evolution of the MIP and its southeastern boundary in this key area. Geochronologic results (Pb-evaporation and U-Pb SHRIMP in zircon and monazite), supported by petrographic and field observations, allowed identification of the following lithotypes and their ages: migmatitic gneisses (2859–2080 Ma), tonalitic gneisses (2554 ± 3 Ma, 2480 ± 9 Ma), enderbites (2114 ± 3 Ma), charnockites (2094 ± 4 Ma, 2084 ± 2 Ma), granodiorites (2079 ± 3 Ma), leucogranitic vein (2075 ± 2 Ma), and pelitic paragneisses (2062 ± 8 Ma). These ages are related to the reworking of Archean crust during Rhyacian magmatic arc amalgamation (2.22–2.13 Ga) and collision in the Transamazonian cycle (ca. 2.1 Ga).

Abstract The Iriri-Xingu domain, located in the central part of the Amazonian craton, consists of extensive occurrences of Paleoproterozoic volcanic rocks and granites with published ages of ca. 1990 to 1840 Ma, which show a strong crustal contribution for their magmas. Exposures of basement rocks are small and rare. Samples from two areas were dated in this work by U-Pb SHRIMP in zircon. In the northern Maribel area, a high-grade pelitic paragneiss presented an age of 2160 ± 8 Ma and the leucosome of a migmatitic orthogneiss, probably a diatexite, crystallized at 2149 ± 20 Ma. These Rhyacian ages suggest that it is part of the Bacajá domain, related to the Trans-Amazonian cycle. The Morro Grande area occurs in the central part of Iriri-Xingu domain, where a high-grade muscovite gneiss with a protolith of 2120-2180 Ma is dated at 1982 ± 7 Ma, and the leucosome of a migmatitic orthogneiss is crystallized at 1979 ± 8 Ma. These are the first records of high-grade metamorphism at ca. 1980 Ma in the Central Brazil shield and may be related to the generation of this Orosirian felsic magmatism, which is widespread throughout the nearby Ventuari-Tapajós province.

RESUMO: O Domínio Tapajós, localizado na porção sul do Cráton Amazônico, é um domínio tectônico da Província Tapajós-Parima, um cinturão orogênico Paleoproterozoico, adjacente a uma crosta arqueana retrabalhada, a Província Amazônia Central. Esse domínio foi interpretado como resultado da acreção de sucessivos arcos magmáticos, seguidos por um magmatismo pós-orogênico do tipo A, representado por granitos de ca. 1880 Ma da Suíte Intrusiva Maloquinha. Este estudo foi realizado em quatro granitos dessa suíte (Igarapé Tabuleiro, Dalpaiz, Mamoal e Serra Alta) da porção leste do Domínio Tapajós, assim como um granito tipo I (Igarapé Salustiano), relacionado à Suíte Intrusiva Parauari. Os granitos tipo A são sienogranitos e monzogranitos, e subordinadamente feldspato alcalino granitos e quartzo sienitos. Essas rochas são ferrosas, alcalicálcica a alcalinas e dominantemente peraluminosas, com anomalias negativas de Ba, Sr, P e Ti, e alto conteúdo de elementos terras raras (ETR) com pronunciada anomalia negativa de Eu. Esse conjunto de características é típico de granitos tipo A. O Granito Igarapé Salustiano apresenta monzogranitos e quartzo monzonitos magnesianos, cálcicos a calcioalcalinos, alto K e dominantemente metaluminosos, com alto conteúdo de Ba e Sr, e empobrecidos em high field strength elements (HFSE) e ETR pesados, característicos de granitos do tipo I. A fonte do magma dos granitos tipo A é similar a de granitos pós-colisionais, enquanto os granitos tipo I mantêm assinatura sincolisional. A maioria dos granitos estudados tem ε Nd (-3,85 a -0,76) e idades modelo Nd T DM (2,22 a 2,46 Ga) compatíveis com a crosta paleoproterozoica do Domínio Tapajós. Conclui-se que fonte crustal arqueana (ε Nd de -5,01 e Nd T DM de 2,6 Ga) é local para os granitos tipo A.

ABSTRACT: The Tapajós Domain, located in the southern portion of the Amazonian Craton, is a tectonic domain of the Tapajós-Parima Province, a Paleoproterozoic orogenic belt adjacent to a reworked Archean crust, the Central Amazonian Province. This domain has been interpreted as the product of an assemblage of successive magmatic arcs followed by post-orogenic A-type magmatism formed ca. 1880 Ma-old granites of the Maloquinha Intrusive Suite. The study presented here was carried out in four granitic bodies of this suite (Igarapé Tabuleiro, Dalpaiz, Mamoal and Serra Alta) from the eastern part of the Tapajós Domain, as well as an I-type granite (Igarapé Salustiano) related to the Parauari Intrusive Suite. The A-type granites are syenogranites and monzogranites, and alkali feldspar granites and quartz syenites occur subordinately. These rocks are ferroan, alkalic-calcic to alkalic and dominantly peraluminous, with negative anomalies of Ba, Sr, P and Ti and high rare earth elements (REE) contents with pronounced negative Eu anomaly. This set of features is typical of A-type granites. The Igarapé Salustiano granite encompasses monzogranites and quartz monzonites, which are magnesian, calcic to calc-alkalic, high-K and mainly metaluminous, with high Ba and Sr contents and depleted pattern in high field strength elements (HFSE) and heavy rare earth elements (HREE), characteristic of I-type granites. The source of magma of these A-type granites is similar to post-collisional granites, while the I-type granite keeps syn-collisional signature. Most of the studied granites have εNd (-3.85 to -0.76) and Nd TDM model ages (2.22 to 2.46 Ga) compatible with the Paleoproterozoic crust of the Tapajós Domain. We conclude that the Archean crust source (εNd of -5.01 and Nd TDM of 2.6 Ga) was local for these A-type granites.