The Atacora Structural Unit (ASU) is part of the Pan-African belt located in Northwestern Bénin Republic. It consists of metasedimentary rocks of greenschist facies and composed of quartzites, mica schists and chlorite-sericite-quartz schists. A petrochemical study of these rock types was undertaken, geared at inferring their paleoweathering, provenance and tectonic setting. Texturally, the rocks are, medium to coarse-grained with angular to rounded clasts. Detrital component statistics classified them as sublitharenite/quartzarenite. Geochemically, they can be classified as arkose/subarkose and sublitharenite rocks. The average values for PIA, CIA, and CIW for the quartzites, mica schists and schists range from 75% to 98%, reflecting an intensive degree of chemical weathering. The LREE enrichment (LaN/YbN = 9.56), negative europium anomaly (Eu/Eu* = 0.77), and fractionated HREE patterns of chondrite-normalized, are comparable to melts generated from crustal continental materials. The geochemical studies show that the studied rocks were sourced from ancient quartzose sedimentary rocks. Trace element ratios Cr/Th, Zr/Sc, Th/Sc, Th/Co and La/Th and rare earth elements of the source components indicate that these mature materials were chiefly derived from felsic rocks, though the involvement of basic rocks (basalts) cannot be ruled out. Chondrite-normalized REE patterns indicate that the metasedimentary rocks are sourced from pre-existing sedimentary rocks in the ASU, which rocks were mainly derived from the Dahomeyide basement and probably from the Amazonia craton. The major and trace elements discriminant diagrams suggest these metasediments were deposited in a passive-margin setting, though continental island arc setting signature was also identified.

阿塔科拉结构单元 (ASU) 是位于贝宁共和国西北部的泛非带的一部分。它由绿片岩相变沉积岩组成，由石英岩、云母片岩和绿泥石-绢云母-石英片岩组成。对这些岩石类型进行了石化研究，旨在推断它们的古风化、来源和构造环境。在质地上，岩石是中等至粗粒的，有棱角到圆形的碎屑。碎屑成分统计将它们分类为亚斜纹岩/石英岩。在地球化学上，它们可以归类为长石/亚长石和亚斜纹石。石英岩、云母片岩和片岩的 PIA、CIA 和 CIW 平均值在 75% 至 98% 之间，反映了强烈的化学风化程度。LREE 富集 (LaN/YbN = 9.56)，负铕异常 (Eu/Eu* = 0.77) 和球粒陨石标准化的分馏 HREE 模式，与地壳大陆材料产生的熔体相当。地球化学研究表明，所研究的岩石来源于古代石英沉积岩。源组分的微量元素比 Cr/Th、Zr/Sc、Th/Sc、Th/Co 和 La/Th 以及稀土元素表明，这些成熟物质主要来源于长英质岩，尽管有基性岩（玄武岩）的参与) 不能排除。球粒陨石归一化 REE 模式表明变沉积岩来自 ASU 中预先存在的沉积岩，这些岩石主要来自达荷美德基底，可能来自亚马逊克拉通。