U–Pb ages of detrital zircon grains for the Canastra Group and Passos Nappe units and U–Pb and Lu–Hf isotope analyses from orthogneisses: Provenance and tectonic implications, southern Brasília Belt, Brazil
U–Pb ages of detrital zircon grains for the Canastra Group and Passos Nappe units and U–Pb and Lu–Hf isotope analyses from orthogneisses: Provenance and tectonic implications, southern Brasília Belt, Brazil
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Canastra 群和 Passos Nappe 单元碎屑锆石颗粒的 U-Pb 年龄以及正片麻岩的 U-Pb 和 Lu-Hf 同位素分析：巴西巴西利亚带南部的物源和构造意义
DOI：
10.1016/j.precamres.2020.105771
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发表时间：
2020
影响因子：
3.8
通讯作者：
R. I. Cerri
中科院分区：
文献类型：
--
作者：
Alex J.C.A. Silva;L. S. Simões;S. A. Dufrane;L. A. Alkmin;R. I. Cerri
沿着弗朗西斯科科盆地（SFC）西南缘的中元古代至新元古代盖层的时代和构造背景仍不确定。本文报道了帕索斯推覆体单元和卡纳斯特拉群变质沉积岩中碎屑锆石的207 Pb/206 Pb LA-ICPMS年龄，以及变质沉积单元内正片麻岩中岩浆锆石的U-Pb和Lu-Hf联合分析。Canastra群碎屑锆石U-Pb年龄范围为1.30- 2.71Ga，具有明显的Rhyacian组分来源（1.21Ga）。第二个主要来源是Statherian颗粒（约1.6-1.7 Ga），与Espinhaço盆地的Statherian间隔相似。最年轻的年龄约为1.30 Ga。这一高峰期与卡兰代和中埃斯皮尼亚索盆地的初始扩张和沉积相一致，这标志着圣弗朗西斯科奥陶统的第二次克拉通内裂谷作用。帕索斯推覆体变质沉积岩中的锆石颗粒在约1000年时产生了一个非常突出的Rhyacian峰。2.10 Ga与一些Statherian和新太古代的贡献。所有来自后沉积单元的样品在约100 nm处显示出显著的峰。2.10 Ga，这表明大多数沉积物源来自类似于Mineiro带，Natividade-Cavalcanti块，Campinorte杂岩和Juiz de Fora杂岩的Rhyacian基底。Rhyacian年龄与帕索斯推覆体和Canastra群中长英质正片麻岩的U-Pb结晶年龄（2122±67和2117±23）一致。这些岩石的初始ε Hf（t）值介于+2.1至-13.0和+10.0至-1.8之间，表明这些正片麻岩来自于Rhyacian花岗质岩石，后者是由年轻岩浆的分离或重熔以及更古老的，主要是太古代地壳的改造形成的。新的资料和区域地质对比表明，在SFC西南缘存在古元古代地形的证据。
The age and tectonic setting of Mesoproterozoic to Neoproterozoic covers that occur along the southwestern margins of the São 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 Espinhaço Basin. The youngest ages fall around∼ 1.30 Ga. This peak age is compatible with the initial extension and sedimentation of the Carandaí and Middle Espinhaço basins, which mark the second intracratonic rifting of the São 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 ε 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.
影响因子：
3.9
作者：
Fisher, Christopher M.;Hanchar, John M.;Lam, Rebecca
通讯作者：
Lam, Rebecca