Provenance and source area weathering of sandstones from the Tarkwaian Group at the northeastern extent of the Paleoproterozoic Ashanti Belt, Ghana: Constraints from petrography and geochemistry

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences Pub Date : 2025-01-09 DOI:10.1016/j.jafrearsci.2025.105536

Victor Sedziafa , Ying Song , Emmanuel Daanoba Sunkari , Daniel Kwayisi , Chris Y. Anani , Daniel K. Asiedu

{"title":"Provenance and source area weathering of sandstones from the Tarkwaian Group at the northeastern extent of the Paleoproterozoic Ashanti Belt, Ghana: Constraints from petrography and geochemistry","authors":"Victor Sedziafa , Ying Song , Emmanuel Daanoba Sunkari , Daniel Kwayisi , Chris Y. Anani , Daniel K. Asiedu","doi":"10.1016/j.jafrearsci.2025.105536","DOIUrl":null,"url":null,"abstract":"<div><div>An integrated geochemical and petrographic study was conducted on the Paleoproterozoic sandstones of the Tarkwaian Group exposed at the northeastern extent of the Ashanti Belt, Ghana. Recognizing the economic importance of the Tarkwaian Group, particularly owing to its extensive gold deposits, the primary objective was to investigate the provenance, tectonic setting, and crustal evolution of the Tarkwaian Group. The dominant quartz (polycrystalline and monocrystalline), together with minor muscovite, feldspar, hematite, and lithic fragments, characterize the sandstones and thus, the sandstones are classified as sublitharenite, and lithicsubarkose. Based on mineralogical composition and major element content, the sandstones can be classified as litharenite, sublitharenite, and minor greywacke. The high values of SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> (average: 12.74), relatively moderate values of K<sub>2</sub>O/NaO<sub>2</sub> (average: 1.42), and high quartz content (average: 88%) suggest that the sediments are compositionally sub-mature to mature. The sandstones likely underwent low to moderate levels of sedimentary sorting and recycling owing to angular to sub-rounded grains and moderate Zr/Sc and Th/Sc values. The high Chemical Index of Alteration (CIA) signature (average: 76.79 wt%), Plagioclase Index of Alteration (PIA) values (average: 90.13 wt%), and Index of Compositional Variability (ICV) (average: 0.61 wt%) suggest moderate to intense chemical weathering within the region of origin. Overall, the mineralogical and geochemical features of the sandstones, such as a high proportion of quartz and feldspar, and elevated concentrations of elements such as Zr, Sc and Th, and moderate to high ratios of Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> and La/Sc indicate that they were likely sourced from felsic to intermediate igneous rocks and deposited in an active continental margin such as magmatic arc setting.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105536"},"PeriodicalIF":2.2000,"publicationDate":"2025-01-09","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/S1464343X25000032","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

An integrated geochemical and petrographic study was conducted on the Paleoproterozoic sandstones of the Tarkwaian Group exposed at the northeastern extent of the Ashanti Belt, Ghana. Recognizing the economic importance of the Tarkwaian Group, particularly owing to its extensive gold deposits, the primary objective was to investigate the provenance, tectonic setting, and crustal evolution of the Tarkwaian Group. The dominant quartz (polycrystalline and monocrystalline), together with minor muscovite, feldspar, hematite, and lithic fragments, characterize the sandstones and thus, the sandstones are classified as sublitharenite, and lithicsubarkose. Based on mineralogical composition and major element content, the sandstones can be classified as litharenite, sublitharenite, and minor greywacke. The high values of SiO₂/Al₂O₃ (average: 12.74), relatively moderate values of K₂O/NaO₂ (average: 1.42), and high quartz content (average: 88%) suggest that the sediments are compositionally sub-mature to mature. The sandstones likely underwent low to moderate levels of sedimentary sorting and recycling owing to angular to sub-rounded grains and moderate Zr/Sc and Th/Sc values. The high Chemical Index of Alteration (CIA) signature (average: 76.79 wt%), Plagioclase Index of Alteration (PIA) values (average: 90.13 wt%), and Index of Compositional Variability (ICV) (average: 0.61 wt%) suggest moderate to intense chemical weathering within the region of origin. Overall, the mineralogical and geochemical features of the sandstones, such as a high proportion of quartz and feldspar, and elevated concentrations of elements such as Zr, Sc and Th, and moderate to high ratios of Al₂O₃/TiO₂ and La/Sc indicate that they were likely sourced from felsic to intermediate igneous rocks and deposited in an active continental margin such as magmatic arc setting.

查看原文本刊更多论文

加纳阿散蒂古元古代带东北部Tarkwaian群砂岩物源及源区风化：岩石学和地球化学约束

对加纳阿散蒂带东北部Tarkwaian群古元古代砂岩进行了地球化学和岩石学综合研究。认识到Tarkwaian群的经济重要性，特别是由于其广泛的金矿床，主要目的是研究Tarkwaian群的物源、构造环境和地壳演化。砂岩主要以石英（多晶和单晶）和少量白云母、长石、赤铁矿和岩屑碎屑为主，可分为亚岩屑砂岩和岩屑砂岩。根据矿物组成和主要元素含量，砂岩可分为岩屑岩、次岩屑岩和次灰屑岩。SiO2/Al2O3较高（平均为12.74），K2O/NaO2相对中等（平均为1.42），石英含量较高（平均为88%），表明沉积物成分为亚成熟至成熟。砂岩颗粒呈角状至亚圆形，Zr/Sc和Th/Sc值适中，可能经历了低至中等程度的沉积分选和再循环。高化学蚀变指数（CIA）特征（平均为76.79 wt%）、斜长石蚀变指数（PIA）特征（平均为90.13 wt%）和成分变异指数（ICV）特征（平均为0.61 wt%）表明成矿区内存在中度至强烈的化学风化作用。总体而言，砂岩的矿物学和地球化学特征（石英和长石比例高，Zr、Sc和Th等元素浓度高，Al2O3/TiO2和La/Sc比值中高）表明它们可能来自长英质至中火成岩，沉积于岩浆弧等活动大陆边缘环境。

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分钟内获得全文求助全文

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.