Petrogênese e Contexto Geodinâmico das Suítes Basálticas Toleíticas (de alto-TiO2 e baixo-TiO2) do Cretáceo Inferior da Porção Centro-oriental do Enxame de Diques da Serra do Mar

• Main Author: Vieira, Artur Corval
• Publication Date: 2009
• Format: Doctoral thesis
• Language: por
• Source: Biblioteca Digital de Teses e Dissertações da UERJ
• Download full: http://www.bdtd.uerj.br/handle/1/20010
• topic: Petrogênese; Basálticas toleíticas; Cretáceo; Petrogenesis; Tholeiitic basaltic; Cretaceous; CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA

Tholeiitic basalts of Early Cretaceous age integrate the Serra do Mar Dyke Swarm (SMDS) in Southeastern Brazil. These rocks occur as dykes that intrude the Neoproterozoic, Brasiliano-Pan/African rocks of the Ribeira orogen. The SMDS can be divided in a low- and high-TiO2 suite. The petrological studies revealed the ocurrance of two low-TiO2 suite (A and B) and four high-TiO2 suite (A, B, C and D). This geochemical provinciality indicates a mantelic heterogenety in a local scale. The results of the petrogenetic modeling indicate ATA (Assimilation by Turbulent Ascent) as the likely evolutionary process for the B low-TiO2 suite. In the case of the other low- and high-TiO2 suite, it is important to note the existence of processes involving assimilation and concomitant fractional crystallisation. The building of multi- elementar diagrams, modal-batch partial melting models and discrimination of mantelic reservoir showed that the petrogenesis of the majority of the low- and high- TiO2 are related to mixing process of mantelic sources. The only exception correspond to the B low-TiO2 suite which is generated exclusively by a enriched reservoir (EM I). Binary mixing models and assimilation tests revealed that the petrogenesis of the A low-TiO2 suite involved a large amount of participation of a depleted component with small contribution of a enriched component. In contrast, the generation of the tholeiitic basalts of all the high-TiO2 suite are related to a possible mixing between enriched and fertile sources. Finally, the elaborated petrogenetic modeling in association with recent litogeochemical, geocronological and isotope data (Sr-Nd-Pb) to the tholeiitic series of SDMS permit the construction of a geodynamic scenario that must contribute to the refining of the recent proposed modeling to the mafic magmatism of Cretaceous in the center-south portion of South America Plate.