The Paleoproterozoic Araí continental rift, Central Brazil, hosts metabasaltic lava flows interbedded with a thick transgressive metasedimentary sequence at the basal portion of the Araí Group (Arraias Formation). The lava flows have basalt to basaltic andesite compositions, subalkaline, tholeiitic and within-plate geochemical signatures. These rocks still have low to moderate REEs content, negative Ta, Ti, Nb anomalies, higher La/Nb (2.69–5.06) and lower La/Ba (0.03–0.23) ratios, suggesting some degree of contamination. Isotopic geology data presented in this paper revealed zircon U–Pb crystallization age of 1783 ± 17 Ma, with a significant frequency of inherited zircon from Rhyacian (2221 ± 14 Ma), negative εNd (t) = −4.46 to −6.58, Nd T_DM model age from 2.49 to 2.72 Ga and ⁸⁷Sr/⁸⁶Sr(i) = 0.702400–0.708293. The εNd_(t) vs Nb/La and εNd_(t) vs ⁸⁷Sr/⁸⁶Sr diagrams suggest low to moderate contamination rate, linked to interactions of the plume-derived magmas with the subcontinental lithospheric mantle and the Archean-Paleoproterozoic continental old-crust, during to ascent and intrusion episodes, respectively. These new data are nicely correlated with the available isotopic data (U–Pb, Sm–Nd, Sr–Sr) on the acid volcanic and A-type granites from the basal portion of the Araí rift, indicating an important bimodal magmatic event, with volcano-plutonic characteristics, occurred during the continental syn-rift stage.

位于巴西中部的古元古代阿拉伊大陆裂谷，在阿拉伊群（Arraias地层）的基础部分上，陆生了玄武质熔岩流，中间夹杂着厚厚的海侵沉积沉积层序。熔岩流具有玄武岩到玄武岩的安山岩成分，次碱性，高生质和板内地球化学特征。这些岩石仍具有低至中等的REE含量，负的Ta，Ti，Nb异常，较高的La / Nb（2.69–5.06）和较低的La / Ba（0.03-0.23）比，表明存在一定程度的污染。本文介绍的同位素地质数据显示锆石U–Pb结晶年龄为1783±17 Ma，从Rhyacian继承的锆石的频率很高（2221±14 Ma），εNd（t）负= -4.46至-6.58，Nd T _DM模型的年龄从2.49至2.72 Ga和⁸⁷ Sr /⁸⁶ Sr（i）= 0.702400–0.708293。εNd _（t） 与Nb / La和εNd _（t） 与 ⁸⁷ Sr / ⁸⁶ Sr的关系图表明，低至中度污染率与羽状岩浆与陆下岩石圈地幔以及太古宙古古生代大陆旧大陆的相互作用有关。地壳，分别发生在上升和侵入事件中。这些新数据与来自阿拉伊裂谷基底部分的酸性火山岩和A型花岗岩的可用同位素数据（U–Pb，Sm–Nd，Sr–Sr）很好地相关，表明发生了重要的双峰岩浆事件。火山-古生代特征，发生在大陆同裂谷阶段。