Litogeoquímica do Complexo Campos Gerais e granitoides intrusivos, Arqueano/Paleoproterozoico, Brasil

Abstract

The Campos Gerais Complex is located near the southwestern border of the São Francisco Craton, in the Brasília Belt. It consists of mesoarqueans migmatized orthogneiss (Campos Gerais and Mandembo orthogneisses), associated with neoarchean granitoids, granites and tonalites with probably Paleoproterozoic age. The Campos Gerais Orthogneiss shows a migmatitic stromatic structure, with tonalitic to monzogranitic mesosome, composing a sub-alkaline, calc-alkaline, metaluminous to peraluminous suite. This unit exhibits 3.2 Ga TDM model age (εNd: -4.6). The Mandembo Orthogneiss shows diatexitic to nebulitic structure. Its composition is predominantly tonalitic to syenogranitic forming a sub-alkaline, calc-alkaline, peraluminous high-K series, with 3.4 to 3.2 Ga TDM ages (εNd ≈ -8). The Grão Mogol metagranitoid is intrusive in the Campos Gerais Orthogneiss, composing a series of rocks with sub-alkaline, calc-alkaline, peraluminous, high-K affinity. Metatonalitic bodies are intrusive in the units described above, and show model ages (TDM) very close to the absolute ages (2.85 to 2.77 Ga) and εNd close to zero. The Itapixé Granite is isotropic granite, slightly foliated, with sub-alkaline, calc-alkaline, peraluminous, high-K affinity. The Córrego do Sapateiro Granite has an isotropic, medium to coarse-grained texture and pinkish color. It belongs to a sub-alkaline, calc-alkaline, peraluminous, high-K series. The lithogeochemical data suggest that the Campos Gerais Complex protoliths are related to the melting of metamorphosed oceanic crust (orthogneiss Campos Gerais) and anatexis of TTG crust (orthogneiss Mandembo).