Geochemistry and provenance of Birimian metasedimentary rocks of Téra area, Leo-Man Shield, West Niger

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Journal of African Earth Sciences Pub Date : 2025-03-10 DOI:10.1016/j.jafrearsci.2025.105609

Hamidou Garba Saley , Moussa Konate , Olugbenga Akindeji Okunlola

{"title":"Geochemistry and provenance of Birimian metasedimentary rocks of Téra area, Leo-Man Shield, West Niger","authors":"Hamidou Garba Saley , Moussa Konate , Olugbenga Akindeji Okunlola","doi":"10.1016/j.jafrearsci.2025.105609","DOIUrl":null,"url":null,"abstract":"<div><div>This study presents the provenance of metasedimentary rocks (including amphibolites, mica schists, quartzites, and gondites) of the Téra area, using petrographic and geochemical (whole rock) analyses.</div><div>The methodology employed in this study involves a field investigation (sampling and mapping) followed by a petrographic analysis using a transmitted light polarized microscope and finally, a geochemical analysis through ICP-MS method. The major oxides (SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> vs K<sub>2</sub>O/Na<sub>2</sub>O diagram) and trace elements (La-Th diagram) show that all the samples come from Archean sediments, except for three amphibolite samples which are highly enriched in La and Th due to contamination. The geochemical classification plot [log (Na<sub>2</sub>O/K<sub>2</sub>O) vs log (SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub>)] shows a shale-sand-ferruginous composition of sediments. Calculation of the Index of Compositional Variability (ICV) indicates that the amphibolites and gondites sediments characterized by high ICV values are derived from immature sediments, reflecting a proximal source rock and rapid deposition. on the other hand, the mica schist samples, with low ICV values, be mature sediments derived from a distal source rock. The quartzite samples are a mixture. The Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> ratios, the TiO<sub>2</sub> vs. Zr plot and the La/Th vs. Hf diagram suggest a mafic, intermediate to felsic igneous parent source origin with an intermediate source predominant from active tectonic setting (magmatic arc). The LILE group (Sr, Ba, Rb, K) and incompatible elements (Ce, La, Nb, Th) concentrations of mica schists, amphibolites, and quartzites samples are close to those of crust continental, except for gondites and two quartzite samples (A1 and A3) which are close to Morb, and show LILE depletion. The evaluation of the alteration degree shows that all amphibolites and quartzites (except one) samples have the lowest degrees of alteration. While the mica schists and the fresh gondite samples (at the bottom of hills) have a moderate degree of alteration. The gondite samples located towards the top of hills have extreme degrees of alteration. These high alterations suggest a chemical weathering in warm and humid climatic conditions.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"227 ","pages":"Article 105609"},"PeriodicalIF":2.2000,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of African Earth Sciences","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1464343X25000767","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}

引用次数: 0

Abstract

This study presents the provenance of metasedimentary rocks (including amphibolites, mica schists, quartzites, and gondites) of the Téra area, using petrographic and geochemical (whole rock) analyses.

The methodology employed in this study involves a field investigation (sampling and mapping) followed by a petrographic analysis using a transmitted light polarized microscope and finally, a geochemical analysis through ICP-MS method. The major oxides (SiO₂/Al₂O₃ vs K₂O/Na₂O diagram) and trace elements (La-Th diagram) show that all the samples come from Archean sediments, except for three amphibolite samples which are highly enriched in La and Th due to contamination. The geochemical classification plot [log (Na₂O/K₂O) vs log (SiO₂/Al₂O₃)] shows a shale-sand-ferruginous composition of sediments. Calculation of the Index of Compositional Variability (ICV) indicates that the amphibolites and gondites sediments characterized by high ICV values are derived from immature sediments, reflecting a proximal source rock and rapid deposition. on the other hand, the mica schist samples, with low ICV values, be mature sediments derived from a distal source rock. The quartzite samples are a mixture. The Al₂O₃/TiO₂ ratios, the TiO₂ vs. Zr plot and the La/Th vs. Hf diagram suggest a mafic, intermediate to felsic igneous parent source origin with an intermediate source predominant from active tectonic setting (magmatic arc). The LILE group (Sr, Ba, Rb, K) and incompatible elements (Ce, La, Nb, Th) concentrations of mica schists, amphibolites, and quartzites samples are close to those of crust continental, except for gondites and two quartzite samples (A1 and A3) which are close to Morb, and show LILE depletion. The evaluation of the alteration degree shows that all amphibolites and quartzites (except one) samples have the lowest degrees of alteration. While the mica schists and the fresh gondite samples (at the bottom of hills) have a moderate degree of alteration. The gondite samples located towards the top of hills have extreme degrees of alteration. These high alterations suggest a chemical weathering in warm and humid climatic conditions.

查看原文

微信好友朋友圈 QQ好友复制链接

本刊更多论文

本研究采用的方法包括实地调查（取样和绘图），然后使用透射光偏振显微镜进行岩相分析，最后通过 ICP-MS 方法进行地球化学分析。主要氧化物（SiO2/Al2O3 与 K2O/Na2O 图）和微量元素（La-Th 图）显示，除了三个闪长岩样品由于受到污染而导致 La 和 Th 元素高度富集外，所有样品均来自于奥陶纪沉积物。地球化学分类图[对数（Na2O/K2O）与对数（SiO2/Al2O3）]显示沉积物的成分为页岩-砂岩-铁屑岩。成分变异指数（ICV）的计算表明，ICV 值较高的闪长岩和岗闪岩沉积物来自未成熟沉积物，反映了近源岩和快速沉积。石英岩样本是一种混合物。Al2O3/TiO2比值、TiO2与Zr的关系图以及La/Th与Hf的关系图都表明，样品的母岩来源为黑云母火成岩、中间岩火成岩和长英岩火成岩，其中中间岩火成岩主要来自活动构造环境（岩浆弧）。云母片岩、闪长岩和石英岩样品的锂辉石族（Sr、Ba、Rb、K）和不相容元素（Ce、La、Nb、Th）浓度与地壳大陆接近，只有贡长岩和两个石英岩样品（A1 和 A3）与莫尔布接近，出现锂辉石族贫化。蚀变程度评价表明，所有闪长岩和石英岩样品（除一个样品外）的蚀变程度最低。而云母片岩和新鲜的刚玉岩样品（位于山丘底部）则具有中等程度的蚀变。位于山顶的刚玉岩样本的蚀变程度极高。这些高度蚀变表明在温暖潮湿的气候条件下发生了化学风化作用。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文去求助

来源期刊

Journal of African Earth Sciences 地学-地球科学综合

CiteScore

4.70

自引率

4.30%

发文量

240

审稿时长

12 months

期刊介绍： The Journal of African Earth Sciences sees itself as the prime geological journal for all aspects of the Earth Sciences about the African plate. Papers dealing with peripheral areas are welcome if they demonstrate a tight link with Africa. The Journal publishes high quality, peer-reviewed scientific papers. It is devoted primarily to research papers but short communications relating to new developments of broad interest, reviews and book reviews will also be considered. Papers must have international appeal and should present work of more regional than local significance and dealing with well identified and justified scientific questions. Specialised technical papers, analytical or exploration reports must be avoided. Papers on applied geology should preferably be linked to such core disciplines and must be addressed to a more general geoscientific audience.