Abstract
The Sergipano Belt is part of the Southern Subprovince of the Borborema Province (NE Brazil) and separates the Pernambuco-Alagoas Domain from the Sao Francisco Craton. The Macurure Domain is the largest unit of the Sergipano Belt and comprises a basement of Paleoproterozoic age (Jirau do Ponciano Dome) and a supracrustal succession (Macurure Complex). Here we present the results of field, petrographic and structural work and of geochronological dating conducted in an area in the southern part of Alagoas state, northeast of the city of Sao Bras. The lithological associations of the Macurure Complex include quartzite, schist and banded metasedimentary rocks (metarhythmites). The main foliation shows a gentle dip to the southwest and is associated with a SW-plunging mineral lineation. The mineral assemblage muscovite+biotite+garnet±kyanite±staurolite in schist and metarhythmite indicates medium pressure and temperature conditions (amphibolite facies) typical of Barrovian metamorphism. U-Pb dating of detrital zircon grains from a quartzite sample yielded dominantly Tonian ages, showing a large age peak at c. 985 Ma. These zircon grains are thus derived from sources related to the Cariris Velhos event. The youngest grain has a 206Pb/238U age of 939±36 Ma (2s), which is considered as the maximum age of deposition. Two smaller age populations of c. 2.0 Ga and 1.1 Ga are also present. The most probable provenance of c. 2.0 Ga zircon grains is the nearby Jirau do Ponciano Dome. The other age group is more enigmatic and could be related to erosion of A-type rocks formed during local extensional events preceding the Cariris Velhos event.
Highlights
IntroductionThe Borborema Province of northeastern Brazil is one of the several Brasiliano/Pan-African belts formed during the assemblage of West Gondwana (Van Schmus et al 2008; Neves 2015 and references therein)
The Macururé Domain is the largest unit of the Sergipano Belt and comprises a basement of Paleoproterozoic age (Jirau do Ponciano Dome) and a supracrustal succession (Macururé Complex)
The Borborema Province of northeastern Brazil is one of the several Brasiliano/Pan-African belts formed during the assemblage of West Gondwana (Van Schmus et al 2008; Neves 2015 and references therein)
Summary
The Borborema Province of northeastern Brazil is one of the several Brasiliano/Pan-African belts formed during the assemblage of West Gondwana (Van Schmus et al 2008; Neves 2015 and references therein). The province is divided in three subprovinces by the Patos and Pernambuco dextral shear zone systems (Fig. 1a). The Southern Subprovince is further subdivided in the Pernambuco-Alagoas (PEAL) Domain and the Sergipano and Riacho do Pontal belts. The Sergipano Belt has been divided in several lithostratigraphic domains (Davison and Santos 1989; D’el-Rey Silva 1999; Oliveira et al 2006, 2010) (Fig. 1b). We report the results of geological mapping, petrographic and structural studies and geochronological dating of an area in the middle portion of the Macururé Domain in the state of Alagoas We discuss the structural style, metamorphic grade, the age of deposition and the provenance of the metasedimentary rocks in order to contribute to the understanding of the geological evolution of the Sergipano Belt
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