Origin of early Earth’s felsic crust is a matter of growing debate in which the rock record from old cratons plays a key role. In northeast Brazil, the São Francisco Craton preserves the oldest felsic rocks of South America and understanding its Archean evolution is an important piece of this debate. Here we present new SHRIMP U-Pb zircon ages and whole-rock geochemistry, as well as a large, compiled dataset to discuss the evolution of the south Gavião Block (GB), a major component of this craton. The GB contains Paleo- to Mesoarchean (3.36–3.18 Ga) TTGs, high-K granites, and minor diorites of the Gavião Complex followed by renewed magmatism, reworking and anatexis between 3.27 and 3.22 Ga. The TTG rocks of Gavião Complex can be divided into high-Sr (high pressure) and low-Sr (low- to medium pressure), evidencing that the sodic magmatism likely occurred at different depths diachronically between 3.36 and 3.20 Ga. We report a crystallization age of a ca. 3.35 Ga for an Archean unusual high-K calc-alkaline meta-granite which marks the first potassic magmatism of the Gavião Complex, suggesting reworking of preexisting TTGs. Zircon U-Pb dates from a TTG migmatite constrained an age of ca. 3.27 Ga, interpreted as a metamorphic event within the basement of the GB, stretching back in ca. 120 My the oldest metamorphic age known so far for the whole São Francisco Craton. Additionally, at ca. 2.7 Ga, the GB was intruded by the intraplate, alkaline magmatism of the Caraguataí Suite, marking thus the stability of this Block during Neoarchean. We argue that crustal reworking was the main mechanism responsible for the formation of the GB during the Paleo- to Mesoarchean. The data suggest the GB rocks share an old source possibly including Hadean components. We propose that the formation of the TTGs of GB is a result of the melting of low-K mafic crust at the base of a progressively thicker oceanic plateau.

早期地球长英质地壳的起源是一个日益激烈的争论，其中来自古老克拉通的岩石记录起着关键作用。在巴西东北部，圣弗朗西斯科克拉通保留了南美洲最古老的长英质岩石，了解其太古代演化是这场辩论的重要组成部分。在这里，我们展示了新的 SHRIMP U-Pb 锆石年龄和全岩地球化学，以及一个大型编译数据集，以讨论南 Gavião 地块 (GB) 的演化，这是该克拉通的主要组成部分。GB 包含 Gavião 杂岩的古至中太古代 (3.36–3.18 Ga) TTG、高 K 花岗岩和次要闪长岩，随后在 3.27 至 3.22 Ga 之间发生了更新的岩浆作用、再加工和贫矿。 Gavião 杂岩的 TTG 岩石可以被划分分为高 Sr（高压）和低 Sr（低至中压），证明钠岩浆活动可能发生在 3.36 和 3.20 Ga 之间历时的不同深度。我们报告了大约 1 的结晶年龄。3.35 Ga 太古宙不寻常的高 K 钙碱性元-花岗岩，标志着 Gavião 复合体的第一次钾质岩浆作用，表明对先前存在的 TTG 进行了改造。锆石 U-Pb 来自 TTG 混合岩，其年龄限制为约 10 年。3.27 Ga，解释为 GB 地下室的变质事件，回溯约 120 迄今为止，整个圣弗朗西斯科克拉通已知的最古老的变质时代。此外，在约。2.7 Ga，GB 被 Caraguataí Suite 的板内碱性岩浆作用侵入，从而标志着该地块在新太古代时期的稳定性。我们认为，地壳改造是古至中太古代形成 GB 的主要机制。数据表明 GB 岩石共享一个古老的来源，可能包括冥王星成分。