Abstract The Neoproterozoic Paraguay Belt in mid-eastern Mato Grosso, western Brazil, records the geological evolution of the margins of western Gondwana. The lack of absolute geochronology for the Paraguay Belt has hampered both regional and global stratigraphic correlations. Here we determine the depositional age for the Peresopolis black slate that belongs to the base of the Cuiaba Group in the Paraguay Belt using Re-Os geochronometry. We obtain a narrow Re-Os age interval of 784 ± 8 Ma and a juvenile initial 187Os/188Os composition (Osi) of 0.15 ± 0.03. These data indicate that the Peresopolis black slate is Tonian in age and was deposited in a basin strongly influenced by the weathering of juvenile material, and potentially linked to the early rifting of Rodinia on western Gondwana. These slates record a time interval that is poorly represented in Brazil and with few counterparts in other Neoproterozoic basins globally. As such, our work is a foundation for future geochemical correlations and paleoenvironmental reconstructions of this critical transition of Earth history in Brazil and elsewhere.

中文翻译：

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巴西西部巴拉圭下带的前斯图尔阶沉积时代及其与冈瓦纳西部岩浆作用的关系

摘要 巴西西部马托格罗索州中东部的新元古代巴拉圭带记录了冈瓦纳大陆西部边缘的地质演化。巴拉圭带的绝对地质年代学的缺乏阻碍了区域和全球地层相关性。在这里，我们使用 Re-Os 测年法确定了属于巴拉圭带库亚巴群底部的 Peresopolis 黑色板岩的沉积年龄。我们获得了 784 ± 8 Ma 的狭窄 Re-Os 年龄间隔和 0.15 ± 0.03 的幼鱼初始 187Os/188Os 组成 (Osi)。这些数据表明 Peresopolis 黑色板岩的年代为托尼安，沉积在受幼年物质风化影响强烈的盆地中，并可能与冈瓦纳西部 Rodinia 的早期裂谷有关。这些板岩记录的时间间隔在巴西很少见，在全球其他新元古代盆地也很少有对应物。因此，我们的工作是未来地球化学相关性和对巴西和其他地方地球历史这一关键转变的古环境重建的基础。