Evidence From PaleoProterozoic Brazil With Implications on Supercontinent Atlantica Reconstructions

Paleoproterozoic crust-formation and reworking events in the tocantins province, central brazil: a contribution for atlantica supercontinent reconstruction

Authors:

Fuck et al

Abstract:

The Natividade-Cavalcanti crustal block is a Paleoproterozoic sialic terrain which forms the basement of sedimentary sequences belonging to the Neoproterozoic Brasília Belt in central Brazil. Two main domains were recognized in this crustal block, the limits of which are not well constrained due to the lack of geological maps at an appropriate scale. The northeastern domain is characterized by narrow supracrustal belts which wrap around gneiss domes. At least three rock-forming events are recorded in the calc-alkaline, metaluminous basement gneisses of this domain: (i) In the Almas-Dianópolis area, granitoids were dated at ca. 2.2 Ga, (ii) Early Paleoproterozoic magmatism was dated at ca. 2.3-2.4 Ga in the Natividade-Conceição do Tocantins area, and (iii) younger additions were dated at 2144 ± 21 Ma. TDM model ages range between 2.24 and 3.11 Ga, and ɛNd(t) values range from +2 to close to zero, suggesting juvenile sources. Bordering this domain west- and southwards, extending from Cavalcante to Arraias, Paranã and Pindorama do Tocantins, mostly peraluminous granitoids of the Aurumina Suite are exposed. Geochronological data for Aurumina granitoid rocks of this sector point to magmatic events between 2.13 and 2.18 Ga, whereas TDM model ages range between 2.21 and 2.92 Ga with generally negative ɛNd(t) values. An exception is a largely undeformed tonalite sample from close to Arraias, dated at 2042 ±12 Ma