U-Pb SHRIMP dating of basement rocks of the Iriri-Xingu domain, Central Amazonian province, Amazonian craton, Brazil

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.

The 1.88 Ga Uatumã Magmatism in the Serra dos Magalhães region: petrology and implications to the extension of the south-eastern edge of the Amazonian Craton

“…The Central Amazonian Province represents one of the most poorly known areas of the AC, mainly due to the dense rainforest cover and several biological and indigenous reserves. The basement rocks consist of schists, para-and orthogneisses, and migmatitic gneisses with leucossome ages from 2155 ± 8 to 1983 ± 5 Ma, protolith age of 1990 ± 3 Ma, and inherited age of 2160 ± 8 Ma (Vasquez et al 2019). The volcano-plutonic event of the USLIP concentrates in the Central Amazonian Province and spread throughout the Tapajós-Parima, Transamazonian, and Carajás provinces.…”