Structural evolution and U/Pb zircon age of the Xambioá gneiss dome, contributions to the Araguaia fold belt tectonic history

Abstract The Araguaia belt in central Brazil is an important key to re-access ancient geological settings, as it records the Gondwana agglutination and the final stages of an oceanic basin closure. Small basement inliers occur along transversal position in the Araguaia belt and could compose the extension of Amazonian craton. The structural analysis of the Xambioa gneiss dome region shows that three main deformational events were responsible for the actual scenario. The first deformational event was a NW-SE non-coaxial compression event (Dn), which led to the formation of ductile structures, such as open and slightly open folds (Fn), from a previous Sn-1 structures, axial plane foliation and spaced foliation (Sn), in the mantling metasedimentary sequence, and the mylonitic foliation (Sn) in dome rocks. This event was associated with a thrust system developed under regional greenschist to local upper amphibolite facies. The second deformational event Dn+1 was characterized by refolding with Sn transposition, followed by asymmetric Fn+1 folds and transposed foliation (Sn+1), and local stretching patterns forming boudins and Ln+1 lineations. The third deformational event Dn+2 is represented by WNW-ESE sinistral transcurrent faults (Sn+2) which sectioned the Dn structures and formed shear zones of different scales. U–Pb zircon ages in gneiss and in a migmatite of the Xambioa dome indicate Mesoarchean (~2.93 Ga) crystallization ages. U–Pb zircon provenance ages from metasedimentary rocks bordering the Xambioa dome show significant contribution of Archean to Neoproterozoic sources. The consistent loss of Pb in the dome rocks evidences tectono-metamorphic events presumably connected to the lithosphere ocean closure and continental collision responsible for the Araguaia Belt edification during Neoproterozoic-Cambrian period.