Lucieth Cruz Vieira

Isótopos estáveis (C, O, S) e geoquímica de rocha total de carbonatitos da Província Ígnea Alto Paranaíba – SE Brasil

2Faculdade de Ciências e Tecnologia, Universidade Federal de Goiás – UFG, Goiânia (GO), Brazil. E-mail: jabrod@gmail.com, tcjbrod@gmail.com, elisa.barbosa@uol.com.br 3Centro Regional para o Desenvolvimento Tecnológico e Inovação, Universidade Federal de Goiás – UFG, Goiânia (GO), Brazil. E-mail: jabrod@gmail.com 4Instituto de Geociências, Campus Universitário Darcy Ribeiro, Universidade de Brasília – UnB, Brasília (DF), Brazil. E-mail: lucieth@gmail.com, rventura@unb.br 5CICTERRA, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina. E-mail: ipetrinovic@yahoo.com 6Laboratório de Estudos Geodinamicos e Ambientais, Campus Universitário Darcy Ribeiro, Universidade de Brasília – UnB, Brasília (DF), Brazil. E-mail: lmancini@unb.brThe present work investigates the relationship between whole-rock geochemistry and stable isotope composition from carbonatites belonging to the Tapira, Araxa, Salitre, Serra Negra, Catalao I, and Catalao II alkaline-carbonatite complexes of the Alto Paranaiba Igneous Province (APIP), central Brazil and from the Jacupiranga Complex, of the Ponta Grossa Province, southeast Brazil. The APIP complexes are ultrapotassic, comprising bebedourites, phoscorites, nelsonites, and carbonatites, whereas Jacupiranga is a sodic complex composed of ijolite-series rocks, syenites, carbonatites, and alkaline gabbros. The geochemistry data allied to mineralogical constraints allowed us to classify the carbonatites into five groups, and to devise a chemical index (BaO/(BaO+SrO)) to gauge the magmatic evolution of the studied carbonatites.The APIP carbonatites evolve from apatite-rich calciocarbonatites toward Ba-, Sr-, and rare earth element (REE)-rich magnesiocarbonatites. This evolution is mostly driven by apatite, phlogopite, dolomite, and calcite fractionation and consequent enrichment in monazite, norsethite, and strontianite. Stable isotope data show a wide diversity of petrogenetic processes in play at the APIP, relatively to the Jacupiranga Complex, which is interpreted as a result of the shallower intrusion levels of the APIP complexes. Such shallower emplacement, at low lithostatic pressure, allowed for a complex interplay of fractional crystallization, liquid immiscibility, degassing, and interaction with hydrothermal and carbohydrothermal systems.

A Formação Sete Lagoas em sua área-tipo: fácies, estratigrafia e

Detailed facies analysis and stratigrafic measurement, description and interpretation of 12 quarry and road-cut sections across a 80.5 km long transect lead to recognition of 11 sedimentary facies of the Sete Lagoas Formation, 2 facies of Carrancas Conglomerado and 3 facies at the base of the Santa Helena Formation. Such facies are comprised into 9 facies associations regarding 3 depositional sequences. The described stratigraphic sequences are characterized by transgressive and higstand systems tracts, with minor preservation of one lowstand system tract, being the first two correlated with the carbonatic Sete Lagoas Formation and the last to the overlying siliciclastic Serra de Santa Helena Formation. The stratigraphic distribution of facies associations reveals an evolution from a CaCO 3 oversaturated carbonate ramp to a storm dominated ramp that progressively becomes distally steepened, and finely a clastic-dominated margin in the last sequence. The geographic distribution of facies associations reveals a transition from shallow water environments in the West to deeper water environments towards the East of the studied area.