Abstract The Amazon Craton exhibits preserved volcano-sedimentary paleo-basins with age intervals of 2.0–1.96 Ga, 1.90–1.87 Ga and 1.80–1.60 Ga. Recent works in this craton have shown the efficacy of the description and organization of volcanic and sedimentary lithofacies as a tool to postulate stratigraphic frameworks. In the present work we propose the first formal stratigraphy for the Beneficente Group (BG), a Statherian (~1.74 Ga) volcano-sedimentary unit outcropping in the southwestern portion of the Amazon Craton. The BG is divided into three formations: (1) Pedro Sara Formation (PSF), composed of felsic volcanic rocks represented by thick lava-like and densely welded tuffs, normal-graded tuffs, both from pyroclastic density currents, and laminated ash-fall tuffs; (2) Camaiu Formation (CF), comprising sheetfloods, low-energy alluvial channels, non-cohesive sediment-gravity flows, rubbly pahoehoe basaltic flows, stream-channel deposits, and deposits reworked in foreshore/superior shoreface settings, and; (3) Vila do Carmo Formation (VCF), formed by delta front and pro-delta lithofacies associations. The sequence of sedimentary rocks contains clasts exclusively from the related volcanic rocks (PSF), with no clasts from other volcanic sequences nearby. Geochronological analyses evidence a Statherian age for the sequence. A pheno-latite from PSF yielded a crystallization age of 1743.6 ± 7.5 Ma, the youngest zircons of a sandstone from CF have ages between 1746 and 1732 Ma and the youngest zircons of a sandstone from VCF have 1760 Ma to 1601 Ma. The Beneficente paleo-basin is preserved as a NW-SE rift in the margin of the Tapajos-Parima Province. This structure remained as an active depositional locus during the Paleozoic and is the location of the main courses of modern rivers. The development of BG is akin to Statherian taphrogenic systems which were widespread in the Amazon, Sao Francisco-Congo and North China cratons, and are a key tectonic feature before the Columbia (Nuna) supercontinent break-up.

中文翻译：

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Statherian 火山沉积 Beneficente 群的地层学、沉积环境和锆石 U-Pb (LA-ICP-MS) 年龄：对亚马逊克拉通西南构造和金矿化的影响

摘要 亚马逊克拉通展示了保存完好的火山-沉积古盆地，年代间隔为 2.0-1.96 Ga、1.90-1.87 Ga 和 1.80-1.60 Ga。最近在该克拉通的工作显示了火山和沉积岩相的描述和组织的有效性作为假设地层框架的工具。在目前的工作中，我们提出了 Beneficente Group (BG) 的第一个正式地层，这是一个在亚马逊克拉通西南部出露的 Statherian (~1.74 Ga) 火山沉积单元。BG 分为三个地层： (1) Pedro Sara 组 (PSF)，由以厚熔岩状和致密熔结凝灰岩为代表的长英质火山岩、正常级配的凝灰岩，均来自火山碎屑密度流和层状灰落凝灰岩；(2) Camaiu 组 (CF)，包括层流，低能量冲积河道、非粘性沉积物重力流、碎石帕霍霍玄武岩流、河道沉积物以及在前滨/上层岸面环境中改造的沉积物，以及；(3) Vila do Carmo组(VCF)，由三角洲前缘和前三角洲岩相组合形成。沉积岩层序包含完全来自相关火山岩 (PSF) 的碎屑，没有来自附近其他火山层序的碎屑。地质年代学分析证明该序列属于斯泰瑟时代。来自 PSF 的酚红岩的结晶年龄为 1743.6 ± 7.5 Ma，来自 CF 砂岩的最年轻锆石的年龄在 1746 至 1732 Ma 之间，来自 VCF 砂岩的最年轻锆石的年龄为 1760 Ma 至 1601 Ma。Beneficente 古盆地作为一个 NW-SE 裂谷保存在 Tapajos-Parima 省的边缘。该构造在古生代仍然是一个活跃的沉积场所，是现代河流的主要河道所在。BG 的发展类似于广泛分布于亚马逊、圣弗朗西斯科-刚果和华北克拉通的 Statherian 渗流系统，并且是哥伦比亚 (Nuna) 超大陆破裂之前的一个关键构造特征。