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.

中文翻译：

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Xambioá 片麻岩穹顶的结构演化和 U/Pb 锆石年龄，对 Araguaia 褶皱带构造历史的贡献

摘要 巴西中部的阿拉瓜亚带是重新进入古代地质环境的重要关键，因为它记录了冈瓦纳大陆的凝集和大洋盆地闭合的最后阶段。小的基底内层出现在 Araguaia 带的横向位置，可能构成亚马逊克拉通的延伸。Xambioa 片麻岩穹顶区域的结构分析表明，三个主要的变形事件导致了实际情况。第一个变形事件是 NW-SE 非同轴压缩事件 (Dn)，它导致从先前的 Sn-1 结构、轴向平面叶理和间隔叶理 (Sn)，在地幔变沉积序列中，以及圆顶岩石中的糜棱叶理 (Sn)。该事件与在区域绿片岩下发育至局部上部角闪岩相的逆冲系统有关。第二个变形事件 Dn+1 的特征是重新折叠与 Sn 转位，然后是不对称的 Fn+1 折叠和转位叶理 (Sn+1)，以及形成 boudins 和 Ln+1 线状的局部拉伸模式。第三次变形事件 Dn+2 以 WNW-ESE 左旋横流断层 (Sn+2) 为代表，该断层切割 Dn 构造并形成不同尺度的剪切带。片麻岩和 Xambioa 圆顶混合岩中的 U-Pb 锆石年龄表明中太古代 (~2.93 Ga) 结晶年龄。来自 Xambioa 圆顶边界的变沉积岩的 U-Pb 锆石物源年龄显示太古代对新元古代源的重要贡献。