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

Marcelo Lacerda Vasquez,Jaime Dos Passos De Oliveira Barbosa,Kei Sato,Maria Telma Lins Faraco,Umberto Giuseppe Cordani,Victor Câmara Maurer

doi:10.1590/2317-4889201920190067

Marcelo Lacerda Vasquez, Jaime Dos Passos De Oliveira Barbosa + Show 4 more

Open Access

https://doi.org/10.1590/2317-4889201920190067

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Abstract

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 Bacaja 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-Tapajos province.

Highlights

The Central Amazonian province of the Amazonian craton was originally defined by Cordani et al (1979)
Based on Nd isotopic data for rocks of the younger pulse, Sato and Tassinari (1997) identified Archean crustal sources for these parent magmas, with strongly negative εNd (-5.4 to -12.1) and Mesoarchean to Neoarchean TDM model ages (3.3 to 2.6 Ga). Their measurements contrasted with the mainly juvenile Nd isotope signature of rocks from the Tapajós domain (TJD) in the adjacent Paleoproterozoic Ventuari-Tapajós tectonic province to the west, which forms at least part of the Iriri-Xingu domain (IXD) basement
We present zircon U-Pb ages and discuss their bearing on tectonic evolution of the IXD and of the entire Amazonian craton

Summary

INTRODUCTION

The Central Amazonian province of the Amazonian craton was originally defined by Cordani et al (1979). Based on Nd isotopic data for rocks of the younger pulse, Sato and Tassinari (1997) identified Archean crustal sources for these parent magmas, with strongly negative εNd (-5.4 to -12.1) and Mesoarchean to Neoarchean TDM model ages (3.3 to 2.6 Ga) Their measurements contrasted with the mainly juvenile Nd isotope signature of rocks from the TJD in the adjacent Paleoproterozoic Ventuari-Tapajós tectonic province to the west, which forms at least part of the IXD basement. In the original proposal (SUDAM, Geomitec 1972), they were named Iriri Formation, but Silva et al (1974) revised, changed it to Iriri Group, and individualized some andesites and dacites as the Sobreiro Formation These felsic rocks have been related to the Uatumã magmatism (Macambira and Vale 1997, Teixeira et al 2002), which represents the main Paleoproterozoic volcanic-plutonic event of the Amazonian craton at ca.

Method

Findings

DISCUSSION AND CONCLUSIONS