Abstract The age and tectonic setting of Mesoproterozoic to Neoproterozoic covers that occur along the southwestern margins of the Sao Francisco Craton (SFC) are still uncertain. This study reports new 207 Pb/ 206 Pb LA-ICPMS ages of detrital zircon grains from metasedimentary rocks of the Passos Nappe units and Canastra Group, and combined U–Pb and Lu–Hf analyses on igneous zircon from orthogneisses within the metasedimentary units. The U-Pb age spectra of detrital zircon grains of the Canastra Group comprises a wide range from ∼ 1.30-2.71 Ga with a significant Rhyacian component source ( ∼ 2.1 Ga). The second major source is represented by Statherian grains ( ∼ 1.6-1.7 Ga), and are similar to the Statherian interval at Espinhaco Basin. The youngest ages fall around ∼ 1.30 Ga. This peak age is compatible with the initial extension and sedimentation of the Carandai and Middle Espinhaco basins, which mark the second intracratonic rifting of the Sao Francisco Craton. Zircon grains from the metasedimentary rocks the Passos Nappe yielded a very prominent Rhyacian peak at ca. 2.10 Ga with some Statherian and Neoarchean contributions. All samples from the metasedimentary units show a prominent peaks at ca. 2.10 Ga, suggesting that most sedimentary sources derived from a Rhyacian substratum similar to the Mineiro belt, Natividade-Cavalcanti block, Campinorte Complex and Juiz de Fora Complex. Rhyacian age is compatible with U-Pb crystallization ages of felsic orthogneisses (2122 ± 67 and 2117 ± 23), enclosed as tectonic lenses in the Passos Nappe and the Canastra Group. These rocks show initial e Hf(t) values between +2.1 to -13.0 and +10.0 and -1.8, indicating that these orthogneisses are derived from Rhyacian granitic rocks, which were formed either by fractionation or re-melting of juvenile magmas, and by the reworking of more ancient, mainly Archean crust. The new data and regional geologic correlations suggest evidence of Paleoproterozoic terrain in the southwestern margin of the SFC.

中文翻译：

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Canastra 群和 Passos Nappe 单元的碎屑锆石颗粒的 U-Pb 年龄以及来自正片麻岩的 U-Pb 和 Lu-Hf 同位素分析：来源和构造意义，巴西巴西利亚带南部，巴西

摘要 圣弗朗西斯科克拉通 (SFC) 西南边缘的中元古代至新元古代盖层的年龄和构造环境尚不确定。本研究报告了 Passos Nappe 单元和 Canastra 群变沉积岩中碎屑锆石颗粒的新 207 Pb/206 Pb LA-ICPMS 年龄，以及对来自变沉积单元内正片麻岩的火成岩锆石的 U-Pb 和 Lu-Hf 组合分析。Canastra 组碎屑锆石颗粒的 U-Pb 年龄光谱包括从 ~ 1.30-2.71 Ga 的宽范围，具有重要的 Rhyacian 成分源 (~ 2.1 Ga)。第二个主要来源以 Statherian 颗粒（~1.6-1.7 Ga）为代表，类似于 Espinhaco 盆地的 Statherian 层段。最年轻的年龄约为 1.30 Ga。这个高峰时代与 Carandai 和 Middle Espinhaco 盆地的初始伸展和沉积相一致，这标志着圣弗朗西斯科克拉通的第二次克拉通内裂谷。来自 Passos Nappe 变质沉积岩的锆石颗粒在大约 100 米处产生了一个非常突出的 Rhyacian 峰。2.10 Ga 有一些 Statherian 和 Neoarchean 贡献。来自变沉积单元的所有样品在约 2.10 Ga，表明大多数沉积源来自类似于 Mineiro 带、Natividade-Cavalcanti 地块、Campinorte 杂岩体和 Juiz de Fora 杂岩体的 Rhyacian 基质。Rhyacian 年龄与长英质正片麻岩的 U-Pb 结晶年龄（2122 ± 67 和 2117 ± 23）兼容，作为构造透镜包含在 Passos Nappe 和 Canastra Group 中。这些岩石显示出 +2 之间的初始 e Hf(t) 值。1 到 -13.0 和 +10.0 和 -1.8，表明这些正方麻岩来自 Rhyacian 花岗岩，它们是由年轻岩浆的分馏或重新熔化，以及更古老的，主要是太古宙地壳的再加工形成的。新数据和区域地质相关性表明 SFC 西南边缘存在古元古代地形的证据。