Geochemistry and emplacement chronology of collisional granites in the Sergipano belt, NE-Brazil

Author(s)

Juliana Finoto Bueno

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Geociências
• Defense date: 2008-12-17

Examining board members

Elson Paiva de Oliveira; Carlos Jose Archanjo; Antenor Zanardo; Ticiano José Saraiva dos Santos; Monica da Costa Pereira Lavalle Heilbron

• Advisor: Elson Paiva de Oliveira
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Indexed in: Base Acervus-UNICAMP; Biblioteca Digital da UNICAMP
• Location: Universidade Estadual de Campinas. Instituto de Geociências. Biblioteca Conrado Paschoale

Abstract

The Sergipano Belt is one of the most significant Precambrian orogenic belts of Northeastern Brazil because it contains several structural and lithologic domains that allow it to be compared with Phanaerozoic orogens, like Himalayas. The Sergipano Belt was formed through continental collision between the Congo- São Francisco Craton and the Pernambuco-Alagoas Massif during the Brasiliano/Pan-African Orogeny and it comprises five lithostructural domains: Canindé, Poço Redondo-Marancó, Macururé, Vaza Barris and Estância and it is a key belt for reconstructing part of the history of West Gondwana. Three main events of regional deformation (D1-D3) are recognized in the supracrustal rocks of the belt and the D2 event is the main collision event in the belt, most granites were emplaced during this event in the Macururé and Poço Redondo-Marancó domains. Granites found in these domains can be divided into two groups: (1) ~ 625 Maold granites formed by: (i) arc-type granites in the Poço Redondo-Marancó domain (Queimada Grande Granodiorite) and in the Macururé Domain (Camará tonalite and Coronel João Sá granodiorite) and (ii) crustal granites in the Poço Redondo-Marancó domain (Sítios Novos and Poço Redondo granites) and (2) ~ 580 Ma-old collision-related granites in the Macururé domain. The Queimada Grande, Camará and Coronel João Sá granites are plutons of high-K calc-alkaline, metaluminous, magnesian, I-type volcanic arc granites. These granites were originated by partial melting of basic crustal sources derived from mantle or lower crust of basaltic composition with variable ratios of continental crust contamination. The Poço Redondo and Sítios Novos granites were generated by partial melting of local migmatites and the collisional granites of the Macururé domain by high degree of partial melting of the Macururé micaschists. The abundance of collisional granites in the Macururé domain indicates that this domain acted as a ductile channel flow during the Neoproterozoic limited by regional. To delimit the collision duration that results in the formation of Sergipano belt was used the 628±12 Ma age obtained for the pre-D2 Camará Tonalite, which mark the maximum age for beginning of D2 event, and the 571±9 Ma age obtained for the syn- to tardi- D2 Pedra Furada granite that mark the minimum age for end of the D2 event; using these numbers without the associated errors, we conclude that the main Neoproterozoic collisional (D2) event in the Sergipano Belt may have lasted at least 57 million years. The Queimada Grande, Camará and Coronel João Sá granites are the record of continental arc in the Sergipano belt formed during the Neoproterozoic collision and its presence indicates that the Macururé domain was connected in the Poço Redondo-Marancó domain before the beginning of the Brasiliano orogeny. (AU)