Abstract The precursor basin of the Aracuai – West Congo Orogenic System (AWCO) formed a large gulf within the Sao Francisco – Congo Paleocontinent (SFCP), where sedimentary successions ascribed to the Jequitinhonha Complex and Macaubas Group were deposited in the Neoproterozoic. This precursor basin system comprises an aborted continental rift of Early Tonian age and a Cryogenian rift that evolved to ocean-floor spreading up to the Early Ediacaran. The Jequitinhonha Complex is an extensive metasedimentary unit located in the northeastern Aracuai Orogen, consisting of Al-rich paragneiss (kinzigite), sillimanite-graphite gneiss and associated economic deposits of flake graphite, quartzite and lenses of calc-silicate rock, metamorphosed variably to upper amphibolite or granulite facies around 570–550 Ma. U-Pb (LA-MC-ICP-MS) data of 110 detrital zircon grains from the paleosome of a migmatitic paragneiss yield five main age peaks at 2564 ± 35 Ma (5% of the grains), 2012 ± 21 Ma (7%), 1807 ± 19 Ma (12%), 960 ± 8 Ma (29%) and 662 ± 6 Ma (48%), with the youngest grains around 630–609 Ma, and a major age gap from the Statherian to Stenian. The U-Pb age spectrum coupled with Lu-Hf in zircon (LA-MC-ICP-MS) data for 106 zircon grains suggest the following sources: Neoarchean to Orosirian grains were sourced from the SFCP basement, Early Tonian grains from the anorogenic magmatic province, and Cryogenian to Early Ediacaran grains were provided by the Southern Bahia Alkaline Province and Rio Doce magmatic arc. The eHf(t) values show a predominant contribution from evolved crust, with minor involvement of moderately juvenile crust. The sedimentation of Jequitinhonha Complex protoliths developed on the SFCP margin from the Cryogenian to Early Ediacaran, within anoxic marine environments favorable to the preservation of organic matter. This deposit formed the huge graphite deposits and lots of smaller occurrences found in the region, accumulating probably more than one billion tons of raw graphite. The youngest detrital zircon population suggests that the deposition record of the Jequitinhonha Complex covers the Cryogenian continental rifting event followed by the development of oceanic crust to the onset of subduction and building of the Rio Doce magmatic arc in the Early Ediacaran. The regional accumulation and preservation of carbon-rich sediments (now graphite-rich gneiss) most probably represent one of the largest storages of Ediacaran carbon around the world.

中文翻译：

---

碎屑锆石 U-Pb 和 Lu-Hf 数据限制了埃迪卡拉纪巨大碳储量的年代（Jequitinhonha Complex，Araçuaí Orogen，巴西东南部）

摘要 Aracuai-西刚果造山系统（AWCO）的前身盆地在圣弗朗西斯科-刚果古大陆（SFCP）内形成了一个巨大的海湾，其中新元古代沉积了属于Jequitinhonha杂岩群和Macaubas群的沉积层序。这个前身盆地系统包括一个早期托尼安时代流产的大陆裂谷和一个演化为海底扩展到早期埃迪卡拉纪的低温纪裂谷。Jequitinhonha 杂岩体是位于阿拉库艾造山带东北部的一个广泛的变沉积单元，由富铝的副片麻岩（kinzigite）、硅线石-石墨片麻岩和相关的片状石墨、石英岩和钙硅酸盐岩透镜的经济矿床组成，变质到上部570-550 Ma 左右的角闪岩或麻粒岩相。来自混合质副片麻岩古体的 110 个碎屑锆石颗粒的 U-Pb (LA-MC-ICP-MS) 数据在 2564 ± 35 Ma（颗粒的 5%）、2012 ± 21 Ma（7%）处产生五个主要年龄峰)、1807 ± 19 Ma (12%)、960 ± 8 Ma (29%) 和 662 ± 6 Ma (48%)，最年轻的晶粒在 630-609 Ma 左右，从 Statherian 到 Stenian 的年龄差距很大。106 个锆石颗粒的 U-Pb 年龄谱与锆石中的 Lu-Hf (LA-MC-ICP-MS) 数据表明以下来源：新太古代至奥罗斯纪颗粒来自 SFCP 基底，早期托尼阶颗粒来自非造山岩浆南巴伊亚碱性省和里约多西岩浆弧提供了低温纪到早埃迪卡拉纪的颗粒。eHf(t) 值显示演化地壳的主要贡献，中度幼年地壳的次要参与。Jequitinhonha 杂岩原岩的沉积发育在 SFCP 边缘，从低温纪到早埃迪卡拉纪，在有利于有机质保存的缺氧海洋环境中。该矿床形成了该地区发现的巨大石墨矿床和许多较小的矿床，累计可能超过 10 亿吨原石墨。最年轻的碎屑锆石群表明，Jequitinhonha 杂岩体的沉积记录涵盖了低温纪大陆裂谷事件，随后是大洋地壳的发育，直到埃迪卡拉纪早期的里约多西岩浆弧开始俯冲和建造。富碳沉积物（现在是富石墨片麻岩）的区域积累和保存很可能代表了世界上最大的埃迪卡拉纪碳储存库之一。