Abstract Precambrian orogenic belts are key areas to understand how the continental crust formed and evolved with time, and to constrain when plate tectonics began on planet Earth. The Itabuna-Salvador-Curaca Orogen, in the Sao Francisco Craton, is an orogenic belt over 800 km long that is interpreted as the result of collision of four blocks during the Paleoproterozoic. However, its geological history before the final continental collision and the time span of collision are not well constrained. Here, we present new field relationships, in situ zircon U–Pb ages and Hf isotope data for gneisses and granites from the orogen and one of the blocks (Gaviao block) that collided during the Paleoproterozoic. Most of the samples were collected along a geological traverse across the northern area of the orogen. The geochronological results indicate ages of 3335 Ma and 3307 Ma for gneisses of the Mairi Complex (Gaviao block), 2637 Ma, 2620 Ma and 2581 Ma for gneisses of the Caraiba Complex within the orogen, and ages between 2100 Ma and 2058 Ma for the collisional granitoids from the Itabuna-Salvador-Curaca Orogen. The slightly negative eHf(t) values (−1.9 and −4.5) for samples of the Mairi Complex suggest contribution from older continental crust in the genesis of the gneisses protoliths. For the Caraiba Complex, positive to negative eHf(t) values (0.9 to −3.7) for the orthogneisses, coupled with similar whole-rock eNd(t) signature from the literature, suggest a continental arc setting for emplacement of the Caraiba Complex orthogneisses. The eHf(t) values (−12.1 and −13.4) for one collisional granitoid indicate it can have originated from the partial melting (reworking) of the Caraiba Complex crust. From the tectonic point of view, the ages of the Caraiba Complex become younger from west to east and this age variation can be interpreted in terms of a continental arc that formed by trench/slab retreat on the edge of the Gaviao block. This model is supported also by the occurrence in the Gaviao block of coeval (2595 ± 21 Ma) volcanic rocks in the Mundo Novo greenstone belt (interpreted in the literature as formed in a back-arc basin) and some metamorphosed clastic sedimentary rocks of the Saude Complex with provenance solely from sources older than 2500 Ma. On the other hand, the ages of the collisional granites can be used to constrain the timing and duration of the orogen's evolution. Accordingly, the early collisional granites with ages between 2100 Ma and 2094 Ma set a minimum age for the beginning of collision. The syn-to late-transcurrent granites were emplaced from 2084 Ma to 2060 Ma, and the post-collisional granites from about 2058 Ma until 2027 Ma. Therefore, block collision to form the Itabuna-Salvador-Curaca Orogen has lasted at least 70 million years.

中文翻译：

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重访伊塔布纳-萨尔瓦多-库拉萨造山带，巴西圣弗朗西斯科克拉通：新的锆石 U-Pb 年龄和 Hf 数据支持在块体碰撞期间从太古代大陆弧到古元古代地壳改造的演化

摘要 前寒武纪造山带是了解大陆地壳如何随时间形成和演化以及限制板块构造何时在地球上开始的关键领域。位于圣弗朗西斯科克拉通的伊塔布纳-萨尔瓦多-库拉卡造山带是一条长达 800 多公里的造山带，被解释为古元古代四个地块碰撞的结果。然而，其最后一次大陆碰撞前的地质历史和碰撞的时间跨度并没有得到很好的限制。在这里，我们提出了新的场关系，原位锆石 U-Pb 年龄和来自造山带的片麻岩和花岗岩的 Hf 同位素数据，以及在古元古代发生碰撞的一个块体（Gavio 块体）。大部分样品是沿着穿越造山带北部地区的地质横断面收集的。年代学结果表明，Mairi 杂岩体（加维亚奥块）片麻岩的年龄为 3335 Ma 和 3307 Ma，造山带内 Caraiba 杂岩体片麻岩的年龄为 2637 Ma、2620 Ma 和 2581 Ma，而造山带内的 Caraiba 杂岩体的年龄为 2100 Ma 至 2058 Ma来自 Itabuna-Salvador-Curaca Orogen 的碰撞花岗岩。Mairi 杂岩体样本的 eHf(t) 值略为负值（-1.9 和 -4.5）表明旧大陆地壳对片麻岩原岩的成因有贡献。对于 Caraiba Complex，正麻岩的 eHf(t) 值从正到负（0.9 到 -3.7），再加上文献中类似的全岩 eNd(t) 特征，表明 Caraiba 杂岩正麻岩就位的大陆弧设置. eHf(t) 值（-12.1 和 -13。4) 对于一个碰撞花岗岩，表明它可能起源于 Caraiba Complex 地壳的部分熔化（再加工）。从构造的角度来看，Caraiba 杂岩的年龄从西向东逐渐变年轻，这种年龄变化可以解释为由加维亚奥地块边缘的海沟/板条退缩形成的大陆弧。该模型也得到了在新世界绿岩带（在文献中解释为形成于弧后盆地）的同时期（2595±21 Ma）火山岩和一些变质碎屑沉积岩的支持。 Saude Complex 的出处完全来自 2500 Ma 以上的来源。另一方面，碰撞花岗岩的年龄可用于限制造山带演化的时间和持续时间。因此，年龄在 2100 Ma 到 2094 Ma 之间的早期碰撞花岗岩设定了碰撞开始的最小年龄。2084 Ma～2060 Ma为同向至晚横流花岗岩，碰撞后花岗岩为2058 Ma～2027 Ma。因此，形成伊塔布纳-萨尔瓦多-库拉卡造山带的块体碰撞至少持续了 7000 万年。