Abstract The Crixas-Goias Domain, Central Brazil, comprises an association of Archean TTG (tonalite-trondhjemite-granodiorite) and Archean-Paleoproterozoic greenstone belts. The Crixas greenstone belt, located in the northern part of the domain, is constituted of Mesoarchean metakomatiites and metabasalts overlaid by Paleoproterozoic carbonaceous phyllites and metagraywackes that host important gold deposits. In this work, we present new integrated petrographical, geochemical and isotopic data to investigate the provenance and tectonic setting of the metasedimentary rocks of the Crixas greenstone belt. Mineral and textural immaturities, particularly of the metagraywackes, are consistent with a proximal source area; which is also evidenced by the chemical aspects that denote absence of significant sediment sorting and recycling. Geochemical data indicate provenance from mixed mafic and felsic sources. U-Pb detrital zircon geochronology shows unimodal age spectra, with a dominant peak at ca. 2.2 – 2.1 Ga and minor contribution of ca. 2.7 and 2.4 Ga grains. Concordia diagrams yielded upper intercepts between 2213.4 ± 5.6 and 2162.2 ± 9.2 Ma, interpreted as the age range of the main source area. The rocks present relatively homogeneous Sm-Nd model ages (2.44 to 2.34 Ga) and slightly negative to positive ƐNd, ranging from -0.27 to +1.25. We argue that the original sedimentary protoliths were deposited in a trench or forearc basin related to a ca. 2.2 - 2.1 Ga island arc formed adjacent to an Archean paleocontinent constituted of TTG-greenstone terranes. Rapid erosion of the rising intraoceanic arc resulted in syn-orogenic sedimentation that started with deep ocean black shale deposition in an anoxic environment followed by episodic turbidite currents of poorly-sorted immature sands. Sedimentary rock layers were tectonically transported to the continent and preserved in the elongated keels of Mesoarchean mafic-ultramafic volcanic rocks. This orogeny can be correlated with the amalgamation of the Goias Massif during the Siderian-Rhyacian crustal growth related to successive collage of arc-related terranes in the formation of the western margin of the Sao Francisco paleocontinent. Sediment provenance of the Crixas greenstone belt proved to be crucial to the recognition and characterization of Paleoproterozoic crust that are apparently no longer preserved in outcrops.

中文翻译：

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通过巴西中部 Crixás 绿岩带变质沉积岩的来源解开隐藏的 Rhyacian 岩浆弧

摘要 巴西中部的 Crixas-Goias 域由太古代 TTG（透长闪长岩-花岗闪长岩）和太古代-古元古代绿岩带组成。Crixas 绿岩带位于该区域的北部，由中太古代变质岩和变玄武岩组成，上覆古元古代碳质千枚岩和变灰岩，这些岩床拥有重要的金矿床。在这项工作中，我们提供了新的综合岩石学、地球化学和同位素数据，以研究 Crixas 绿岩带变质沉积岩的来源和构造环境。矿物和质地不成熟，特别是变灰岩，与近源区一致；化学方面也证明了这一点，这些方面表明没有显着的沉积物分类和再循环。地球化学数据表明来自混合的镁铁质和长英质来源。U-Pb 碎屑锆石年代学显示单峰年龄谱，主峰位于约 2.2 – 2.1 Ga 和大约的微小贡献。2.7 和 2.4 Ga 晶粒。Concordia 图在 2213.4 ± 5.6 和 2162.2 ± 9.2 Ma 之间产生了上截距，解释为主要源区的年龄范围。岩石呈现相对均质的 Sm-Nd 模型年龄（2.44 至 2.34 Ga），且 ƐNd 略微负至正，范围从 -0.27 至 +1.25。我们认为，原始的沉积原岩沉积在与约 1 年前的海沟或弧前盆地有关。2.2 - 2.1 Ga 岛弧形成于由 TTG 绿岩地体构成的太古代古大陆附近。上升的洋内弧的快速侵蚀导致同造山沉积，开始于缺氧环境中的深海黑色页岩沉积，随后是分选不良的未成熟砂岩的偶发性浊流。沉积岩层被构造输送到大陆并保存在中太古代基性-超基性火山岩的细长龙骨中。这种造山运动可能与在 Siderian-Rhyacian 地壳生长期间 Goias 地块的合并有关，这与圣弗朗西斯科古大陆西缘形成中弧形相关地体的连续拼贴有关。事实证明，Crixas 绿岩带的沉积物来源对于识别和表征显然不再保留在露头中的古元古代地壳至关重要。