Understanding the accretion of an oceanic island arc to a craton is a major issue in unravelling the evolution of the continents. P-T-t conditions registered in metamorphic rocks, the boron isotopic compositions of tourmaline provide essential information to delimit the accretionary processes. The Tonian-Cryogenian São Gabriel Terrane is a prominent juvenile structure in the southern Brasiliano Orogen that records key information about accretionary processes. Limited previous studies have investigated the São Gabriel Terrane, with little presently known about the metamorphic conditions. To pursue the objective, we combined multiple methods, including pseudosection modeling, U-Pb garnet geochronology and δ¹¹B isotopes of tourmaline applied to one key sample from the Serrinha Formation of the São Gabriel Terrane. The recorded peak P-T conditions occurred at 4.5–5.1 kbar and 536–555 °C. U-Pb dating of low-U (<1 ppm) garnet yielded a lower intercept age of 721 ± 14 Ma for the bulk garnet growth. Dravite isotopic δ¹¹B (+0.51 to + 3.39) compositions indicate oceanic crust components present in the island arc rocks. The calculated P-T conditions correspond to the metamorphic peak from heat pulses during burial events. Collision and thrusting of the São Gabriel arc against and over the Rio de La Plata Craton occurred at 721 ± 14 Ma. The evaluation of the parameters obtained in this study indicate a Barrovian-type evolution and a Late Tonian age of metamorphism for the Serrinha Basin. The sedimentation of the Serrinha Basin occurred in a forearc basin of the São Gabriel island arc. Collision of the oceanic arc with the craton is thus better constrained. Our study contains one point in the evolution of the protracted, complex amalgamation of the supercontinent Gondwana during the Brasiliano Orogeny.

了解海洋岛弧向克拉通的增生是解开大陆演化的一个主要问题。在变质岩中记录的 PTt 条件，电气石的硼同位素组成为界定增生过程提供了必要的信息。Tonian-Cryogenian São Gabriel Terrane 是巴西利亚诺造山带南部一个突出的幼年结构，记录了有关增生过程的关键信息。之前有限的研究对 São Gabriel Terrane 进行了调查，但目前对变质条件知之甚少。为了实现这一目标，我们结合了多种方法，包括假截面建模、U-Pb 石榴石年代学和 δ ¹¹电气石的 B 同位素应用于来自 São Gabriel Terrane 的 Serrinha 地层的一个关键样品。记录的峰值 PT 条件发生在 4.5–5.1 kbar 和 536–555 °C。低 U (<1 ppm) 石榴石的 U-Pb 测年产生了 721 ± 14 Ma 的较低截距年龄，用于大块石榴石生长。Dravite同位素δ ¹¹B (+0.51 to + 3.39) 成分表明岛弧岩石中存在洋壳成分。计算的 PT 条件对应于埋藏事件期间热脉冲的变质峰。圣加布里埃尔弧与拉普拉塔克拉通的碰撞和冲撞发生在 721 ± 14 Ma。对本研究中获得的参数的评估表明，塞里尼亚盆地属于 Barrovian 型演化和晚 Tonian 变质时代。Serrinha 盆地的沉积发生在 São Gabriel 岛弧的弧前盆地。因此，大洋弧与克拉通的碰撞得到了更好的限制。我们的研究包含了巴西造山运动期间冈瓦纳超大陆长期复杂合并演化的一点。