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Proterozoic accretionary belts in the Amazonian Craton

2007; Geological Society of America; Linguagem: Inglês

10.1130/2007.1200(14)

0072-1069

Umberto G. Cordani, Wilson Teixeira,

Geography and Environmental Studies

Within the Amazonian Craton, Archean crust is restricted to the Carajás granite-greenstone terrain. The younger Maroni-Itacaiunas province, including supra-crustal sequences and associated calc-alkaline granitoids, is linked with the Birimian system in West Africa, making up a large Paleoproterozoic cratonic nucleus. Beginning at ca. 2.0 Ga, accretionary belts formed along the southwestern margin of this nucleus, giving rise to the Ventuari-Tapajós (2000–1800 Ma), Rio Negro–Juruena (1780–1550 Ma), and Rondonian–San Ignacio (1500–1300 Ma) tectonic provinces. Continued soft-collision/accretion processes driven by subduction produced a very large “basement” in which granitoid rocks predominate, many of them with juvenile-like Nd isotopic signatures. Felsic volcanics are also widespread; however, there is no evidence of Archean basement inliers, and regions with high-grade metamorphics are restricted.