Journal of African Earth Sciences最新文献

{"title":"Mineralogical and geochemical characterization of the Wigu Hill Carbonatite dikes, Kisaki area, eastern Tanzania: Implications for rare earth elements mineralization","authors":"Almachius Tryphone Mutasingwa ,&nbsp;Akira Imai ,&nbsp;Kotaro Yonezu ,&nbsp;Akane Ito ,&nbsp;Saefudin Juhri","doi":"10.1016/j.jafrearsci.2025.105984","DOIUrl":"10.1016/j.jafrearsci.2025.105984","url":null,"abstract":"<div><div>The Wigu Hill Carbonatite is a rare-earth element (REE) deposit characterized by NW-SE and NE-SW dikes. This study combines field observations, petrography, X-ray diffractometry (XRD), X-ray fluorescence Spectroscopy (XRF), and laser ablation ICP-MS in order to understand the formation processes of the carbonatite dikes and the associated REE mineralization. The study outlines three stages in Wigu Hill Carbonatite formation: (1) the magmatic stage that includes magnetite-dolomite (Mag-Dol), apatite-dolomite (Ap-Dol), and the brecciated apatite-dolomite (brecciated Ap-Dol) carbonatites; (2) the transitional (brine-melt) stage, which includes synchysite-bastnäsite-dolomite (Syn-Bsn-Dol) and monazite-dolomite 1 (Mnz-Dol_1) carbonatites, which form by replacing the hexagonal precursor phases, and (3) the carbo-hydrothermal stage, which includes monazite-dolomite carbonatite 2 (Mnz-Dol_2) without hexagonal precursor phases. Geochemical data show that Mag-Dol has low concentrations of total light rare earth elements (∑LREE) (&lt;0.05 wt%) and total REE oxides (TREE₂O₃) (&lt;0.1 wt%). In contrast, Ap-Dol has higher contents with ∑LREE at 0.3 wt% and TREE₂O₃ at 0.5 wt%. The brecciated Ap-Dol contains ∑LREE at 1.1 wt% and TREE₂O₃ at 1.6 wt%. The Syn-Bsn-Dol contains ∑LREE at 8.9 wt% and TREE₂O₃ at 12.3 wt%. Similarly, Mnz-Dol_1 contains ∑LREE at 9.1 wt% and TREE₂O₃ at 12.6 wt%, marginally exceeding the Syn-Bsn-Dol. The Mnz-Dol_2 has ∑LREE at 6.3 wt% and TREE₂O₃ at 7.4 wt%. The REE mineralization occurred due to magmatic differentiation processes, which intensified from magmatic to transitional (brine-melt) stages, involving (1) differentiation of primary carbonatitic melts, (2) dissolution and replacement of hexagonal precursor phases, and (3) redistribution of dissolved REE into insoluble phases such as monazite.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105984"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of groundwater recharge potential zones in the Haho prefecture (Togo) using AHP and MIF models within a GIS-based framework","authors":"Komlavi Eyram Agbotsou ,&nbsp;Edupuganti Naga Dhanamjaya Rao ,&nbsp;Ayyagari Venkata Surya Satya Anand ,&nbsp;Salehe Rajabu Mayange ,&nbsp;Komi Messan Dénis Amen Hor ,&nbsp;Kissao Gnandi","doi":"10.1016/j.jafrearsci.2025.105975","DOIUrl":"10.1016/j.jafrearsci.2025.105975","url":null,"abstract":"<div><div>Sustainable groundwater resource management and development require accurate assessment grounded in contemporary technology and scientific principles. The objective of this study is to map GRPZs in the Haho Prefecture using AHP and MIF models in a geospatial framework. To achieve this, fourteen factors controlling the occurrence and flow of groundwater were selected and assigned weights. The AHP model categorized the area's GRPZs as follows: very poor (92.63 km²; 3.06 %); poor (1030.63 km²; 34.03 %); moderate (1453.38 km²; 47.98 %); good (434.88 km²; 14.36 %); and very good (17.19 km²; 0.57 %). The MIF method classified them as follows: very poor (442.25 km², 14.60 %), poor (943.19 km², 31.14 %), moderate (1057.81 km², 34.93 %), and good (585.5 km², 19.33 %). Validation through ROC curve analysis shows that the MIF model achieves a higher level of prediction accuracy (81.2 %) than the AHP approach (79.5 %). Similarly, borehole yield data show that the MIF model performs better (78.44 %) than the AHP approach (73.65 %). These results imply that the MIF model is more accurate than the AHP model in identifying GRPZs in the region. These findings will be of great assistance to decision-makers and have significant implications for ensuring sustainable development and management of groundwater in the region.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105975"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microfacies and diagenesis impact the distribution of pore types in heterogenous carbonate reservoir rock: An example from the Bai-Hassan Oilfield, Northern Iraq","authors":"Hawar A. Zangana ,&nbsp;Fraidoon Rashid","doi":"10.1016/j.jafrearsci.2025.105976","DOIUrl":"10.1016/j.jafrearsci.2025.105976","url":null,"abstract":"<div><div>This study examines both microfacies identification and diagenetic processes that impact the heterogeneous carbonate reservoir properties. The focus is on the Baba Formation (middle Oligocene) in the Bai-Hassan oilfield in northern Iraq to analyze microfacies characteristics and diagenetic changes to understand their influence on reservoir heterogeneity and quality. A detailed petrographic analysis of thin sections from core plugs and cutting samples identified five main microfacies types: nummulitic wackestone, rotaliida packstone, boundstone, dolomitized packstone and dolostone microfacies. The dolostone and dolomitized packstone rock types form good reservoir units. The rotaliida packstone and coral boundstone microfacies have moderate reservoir quality, while the nummulitic wackestone facies are impervious units. During the early diagenesis stage, the recrystallization process transforms part of the micritic matrix and produces microsparite. The recrystallization process increases the crystal size and enhances the primary porosity without creating visible porosity between the crystals. Dolomitization and dissolution processes are crucial in enhancing reservoir quality by increasing porosity and permeability, creating intercrystalline, moldic, and vuggy porosity. Fracture pores were also observed, which positively impact reservoir quality by enhancing fracture permeability and contributing to secondary porosity. In contrast, cementation and mechanical compaction significantly reduce early-formed primary porosity and some secondary porosity and, resulting in a negative impact on reservoir quality in certain intervals. This study provides insight into the impact of microfacies and diagenesis processes on reservoir quality, aiding in the accurate prediction of reservoir properties in heterogenous carbonate reservoir rock.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105976"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis of Kaiama gold mineralization, northcentral Nigeria: Evidence from fluid inclusion and stable O–H isotope","authors":"Aliyu Ohiani Umaru ,&nbsp;Olugbenga Okunlola ,&nbsp;Umaru Adamu Danbatta ,&nbsp;Yılmaz Demir ,&nbsp;Yarsé Brodivier Mavoungou ,&nbsp;Brahim Salem-Vall ,&nbsp;Hamman Ishaku Kamale","doi":"10.1016/j.jafrearsci.2025.105963","DOIUrl":"10.1016/j.jafrearsci.2025.105963","url":null,"abstract":"<div><div>The Kaiama gold deposit, located within the Proterozoic basement complex of northcentral Nigeria, is hosted predominantly in structurally controlled quartz-sulfide veins emplaced within mylonitized quartzite and talc schist units. The mineralization is spatially associated with NE–SW-trending ductile shear zones, interpreted as subsidiary structures of the regionally extensive Anka–Yauri fault system. While gold occurrences in Nigeria have been widely documented, the origin and evolution of the ore-forming fluids have continued to be a subject of debate. This study integrates fluid inclusion petrography, microthermometric analysis, and stable isotope (δ¹⁸O and δD) geochemistry to unravel the physicochemical conditions and fluid sources involved in the mineralization process. Detailed petrographic examination identifies a sulfide assemblage comprising pyrite, galena, chalcopyrite, chalcocite, and sphalerite, with quartz, sericite, and feldspar as the dominant gangue minerals. Fluid inclusion petrography revealed three distinct fluid types: Type I (carbonic aqueous three-phase fluids), Type II (vapour rich biphasic fluids), and Type III (liquid rich biphasic fluids), whose coexistence indicates fluid mixing as a key ore-forming mechanism. Microthermometric measurements yielded homogenization temperatures ranging from 169 °C to 339 °C and salinities between 0.4 and 15.3 wt% NaCl equivalent, consistent with low-to moderate-temperature, moderately saline hydrothermal fluids. Stable isotope compositions of fluid inclusions (δ¹⁸O_water = +1.57 ‰ to +7.07 ‰; δD_water = −114 ‰ to −33 ‰) point to a mixed fluid source, involving both metamorphic and meteoric components. Collectively, the results suggest that structurally focused fluid flow and mixing of contrasting fluid sources played a pivotal role in the precipitation of gold at Kaiama.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105963"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145684001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"U-Pb zircon geochronology, Sr-Nd isotope geochemistry and petrology of Carboniferous granitic rocks in Afyon Zone (NW Türkiye)","authors":"Zafer Aslan ,&nbsp;M. Selman Aydoğan ,&nbsp;Y. Kağan Kadıoğlu ,&nbsp;Özcan Yi̇ği̇t","doi":"10.1016/j.jafrearsci.2025.105953","DOIUrl":"10.1016/j.jafrearsci.2025.105953","url":null,"abstract":"<div><div>The Afyon Zone basement, regarded as part of the northern passive margin of Gondwana during the Late Paleozoic, comprises Paleozoic quartz-muscovite schists and phyllites intruded by Carboniferous metaplutonic bodies. The Triassic cover rocks consist of metadacite and ore-bearing metabasic. The plutonic assemblage in the area is represented by two principal intrusive phases: (i) metagranite porphyry and (ii) metagranite. Of these, age of the metagranite porphyry unit was determined to be 311.1 ± 5.0 Ma, and that of the metagranite to be 309.3 ± 1.9 Ma, using the U-Pb zircon SHRIMP method. Mineral chemistry analyses indicate that the temperature of the plagioclase in the metaplutonic and schist rocks is below 600 °C. The muscovite mineral in the schists is of the muscovite-ferromuscovite type and is crustal in origin.</div><div>The metaplutonic suites correspond to S-type, peraluminous granitoids with high-K calc-alkaline affinities. Trace element distribution diagrams show enrichment in large ion radius lithophile elements (LILE; K, Rb, Th and U), while some high-field-strength elements (HFSE; Nb, Y and Sr) show depletion. The rare earth element distributions, are concave in shape (average La_N/Lu_N = 4–23) and exhibit a slight negative Eu anomaly (Eu/Eu∗ = 0.40–1.06). Both plutons are tectonically associated with a volcanic arc and formed within the continental crust. The primary magmas of the metaplutonic rocks formed through magmatic interaction with partially melted metapelitic rocks in the lithospheric mantle and the lower continental crust. Metamorphic basement rocks are high in potassium and exhibit a shoshonitic character. The average primary ⁸⁷Sr/⁸⁶Sr for metaplutonic rocks is around 0.720, while the ¹⁴³Nd/¹⁴⁴Nd values range from 0.512139 to 0.512257.</div><div>These values suggest that the source area from which the plutons was originated from enriched-mantle. Accordingly, the Middle Carboniferous metagranitic magmatism in the Afyon Zone is interpreted to have developed within a continental volcanic arc setting associated with the southward subduction and progressive closure of the Paleotethys Ocean along the northern margin of Gondwana.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105953"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145684000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrative water quality assessment and Geostatistical Analysis of mining-impacted groundwater: A multi-parameter evaluation","authors":"Johnson Ayomide Ibukun ,&nbsp;Ayomide Emmanuel Olubaju ,&nbsp;Titilope Christianah Sakeye ,&nbsp;Samson Favour Thomas ,&nbsp;Sehinde Ayoola Akinbiola ,&nbsp;Rabi Elabor ,&nbsp;Olayinka Oshikoya","doi":"10.1016/j.jafrearsci.2025.105986","DOIUrl":"10.1016/j.jafrearsci.2025.105986","url":null,"abstract":"<div><div>Water quality in artisanal gold mining regions is severely threatened by a complex mixture of contaminants, yet comprehensive assessments integrating regulatory compliance, source apportionment, and spatial distribution are scarce. This study addresses this gap through an integrative assessment of groundwater in Itagunmodi, Nigeria, employing a standard framework that combines multi-parameter water quality indices (WAWQI, CCME-WQI), statistical hypothesis testing with Cohen's d effect sizes, Pearson correlation analysis, and Empirical Bayesian Kriging (EBK) geostatistics. Fifteen groundwater samples were analyzed for physicochemical parameters, heavy metals, and ions against WHO, NSDWQ, and BIS standards. Hypothesis testing revealed significant (p &lt; 0.05) exceedances of permissible limits for Lead (Pb) (100 % of samples, Cohen's d = 4.05), Cadmium (Cd) (67 %, d = 0.82), and Arsenic (As) (80 %, d = 1.25), classifying overall water quality as ‘poor’ to ‘very poor’. Correlation analysis unveiled significant (p &lt; 0.05) synergistic interactions, most notably between Mercury and Cyanide (r = 0.784, p = 0.0005), indicating joint mobilization from mining activities, and between Total Hardness and Magnesium (r = 0.934, p &lt; 0.001), revealing dolomite dissolution as a key geochemical process. EBK modeling delineated distinct spatial hotspots for individual contaminants, with Pb concentrated in the southwestern zone and As and Hg in the northeast, providing a critical evidence-based map for targeted remediation. The findings demonstrate a severe public health crisis and highlight the inadequacy of lenient regulatory standards. Beyond the local context, this study establishes a replicable, advanced methodology for pollution assessment in mining regions globally, underscoring the necessity of combining multi-index evaluation with geospatial and statistical rigor for sustainable water resource management.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105986"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145880645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of facies–diagenesis interactions in shaping geomechanical heterogeneity and mechanical stratigraphy of carbonate reservoirs, Sarvak Formation, southern Iran","authors":"Samira Akbarzadeh,&nbsp;Sepideh Davoodi,&nbsp;Vahid Tavakoli","doi":"10.1016/j.jafrearsci.2025.105968","DOIUrl":"10.1016/j.jafrearsci.2025.105968","url":null,"abstract":"<div><div>The heterogeneous nature of carbonate reservoirs necessitates an integrated evaluation of depositional, diagenetic, and mechanical attributes to predict their reservoir potential. The Sarvak Formation, a key Cretaceous carbonate reservoir in the Zagros Basin, hosts major hydrocarbon reserves in Middle East. This study combines petrographic observations, routine petrophysical measurements, and wireline logs to describe depositional microfacies, diagenetic features, geomechanical units (GMUs), and reservoir rock types. Six microfacies were identified, ranging from distal mid-ramp to lagoonal settings. Various diagenetic processes influence reservoir quality and connectivity of the pores. Four third-order sedimentary sequences were identified from the vertical stacking patterns of the microfacies. According to Lucia's classification, six reservoir rock types were defined, with reservoir quality increasing progressively from RT0 to RT5. Comprehensive geomechanical analyses, including unconfined compressive strength, Young's modulus, shear modulus, and Poisson's ratio, were conducted. The results show that these mechanical properties strongly control reservoir stiffness, ductility, and fracture susceptibility, and consequently influence fluid flow and storage capacity. Based on K-means clustering, four GMUs were identified, exhibiting a progressive increase in reservoir quality. GMU1 is predominantly associated with rock types 0 and 1, whereas GMU4 corresponds mainly to rock type 4, highlighting the systematic relationship between geomechanical behavior and reservoir rock quality. The integrated analysis of microfacies, diagenetic alterations, and geomechanical units demonstrates that reservoir quality improves from GMU1 to GMU4. Early transgressive systems tracts are mechanically stiff and contain limited porosity. In contrast, the overlying regressive systems tracts particularly in sequences 3 and 4, exhibit highly connected pore networks and superior fluid-storage capacity. These findings highlight the critical role of facies–diagenesis interactions in controlling both petrophysical and mechanical properties, providing a robust framework for reservoir characterization.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105968"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145735099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Typology, palaeoenvironmental significance and palaeoclimatic implications of calcretes in the Oued Nja Valley (South Rifian Corridor, Morocco)","authors":"Aziz Hayati ,&nbsp;Hicham EL Asmi ,&nbsp;Lahcen Gourari ,&nbsp;Mohamed Benabbou ,&nbsp;Imad EL Yakouti ,&nbsp;Aziza Lyazidi ,&nbsp;Mohammed EL Aoufir ,&nbsp;Meryem Redouane ,&nbsp;Khalil Azennoud ,&nbsp;Yassine Ait Brahim","doi":"10.1016/j.jafrearsci.2025.105952","DOIUrl":"10.1016/j.jafrearsci.2025.105952","url":null,"abstract":"<div><div>Quaternary calcretes in the Oued Nja Valley, located in the Saïss Basin, Morocco, provide an exceptional record of North African palaeoenvironmental dynamics. This multidisciplinary study, integrating sedimentological, mineralogical and diagenetic analyses, identifies nine calcrete types: root-related, nodular, laminar, massive, conglomeratic, powdery, encrusted, and fracture-filling. These formations reflect complex pedogenic and hydrochemical processes. Pedogenic calcretes, organized in distinct horizons, exhibit both biogenic (rhizoliths, pisoliths, calcified filaments) and abiotic (laminations, dense microfabrics) structures, indicating soil-atmosphere interactions under semi-arid to sub-humid climatic conditions. In contrast, hydrochemical calcretes, formed in shallow aquifers, are characterized by sparitic cements, floating grains and circumgranular cracks, suggesting rapid cementation under arid conditions. Analyses reveal a dominance of calcite (57.79–84.42 % CaCO₃) alongside siliciclastic interbeds, pointing to aeolian inputs during dry periods. The genesis and evolution of these calcretes are modulated by the Liassic carbonate substrate, local hydrology, biological activity and tectonics of the South Rifian Corridor (NE-SW, NS and NW-SE faults), recording environmental oscillations between humid phases with dense vegetation and arid periods dominated by evaporation. Compared to Mediterranean calcretes, they are distinguished by their abundance of biogenic structures and proximity to faulted zones. The findings highlight calcretes as key palaeoclimatic and geological markers, with significant implications for sustainable water resource management: massive facies indicate areas prone to aridification, while root-related facies may signal potential for enhanced groundwater recharge. Future geochemical and microstructural investigations could refine these models, enhancing regional palaeoenvironmental reconstructions.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105952"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145735100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbonate diagenesis and Mn-carbonate formation in the Paleoproterozoic Francevillian succession (Lastoursville sub-basin) of Gabon","authors":"Kevin Xavier Nzamba ,&nbsp;Hele-Riin Juhkama ,&nbsp;Mathieu Moussavou ,&nbsp;Karen Bakakas Mayika ,&nbsp;Timmu Kreitsmann ,&nbsp;Aivo Lepland ,&nbsp;Anthony R. Prave ,&nbsp;Kalle Kirsimäe","doi":"10.1016/j.jafrearsci.2025.105971","DOIUrl":"10.1016/j.jafrearsci.2025.105971","url":null,"abstract":"<div><div>The Franceville Basin of Gabon contains one of the best-preserved records of Earth's Paleoproterozoic surface environments that began with the oxygenation of the atmosphere and its association with the largest known positive carbonate carbon isotope (δ¹³C_carb) excursion – the Lomagundi-Jatuli Event (LJE). In this study, we conducted a detailed petrographic, mineralogical, and geochemical characterization of carbonate rocks to assess the influence of authigenic and diagenetic processes affecting the primary δ¹³C_carb record preserved in core LST12 obtained in the Lastoursville sub-basin. Previous studies reported an up-section trend in δ¹³C_carb from positive values (5–9 ‰) to near-zero, and further to negative values (−5 to −17 ‰). This δ¹³C_carb shift marking the termination of the typical LJE isotopic signature coincides with changing depositional facies settings. Our new results show that this isotopic shift parallels changes in carbonate mineral composition from stoichiometric dolomite with minor early diagenetic Fe-rich dolomite overgrowths to increasingly Fe- and Mn-rich carbonates formed under sediment-buffered, closed-system diagenetic conditions. The formation of complex diagenetic Ca-Mn-Fe-rich carbonate phases in the topmost manganiferous black shales of core LST12, however, was driven by open-system diagenesis. This involved microbial remineralization of organic matter during progressive basin restriction and dynamic hydrothermal influx. The declining δ¹³C_carb trend in carbonate lithologies of LST12 core is therefore interpreted to record syn-depositional variations in the dissolved inorganic carbon pool, reflecting changing environmental conditions in the Paleoproterozoic Francevillian basin.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105971"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrochemistry and pollution assessment of groundwater in the Dodoma: Implications of indices and multivariate statistics","authors":"Uwezo Frank Mao ,&nbsp;Benatus Norbert Mvile ,&nbsp;Mahamuda Abu ,&nbsp;Emmanuel Sulungu","doi":"10.1016/j.jafrearsci.2025.105974","DOIUrl":"10.1016/j.jafrearsci.2025.105974","url":null,"abstract":"<div><div>Groundwater is the primary source of freshwater in arid and semi-arid regions such as Dodoma, Tanzania, where surface water is scarce. This study assessed the hydrochemical characteristics and pollution status of groundwater in the Dodoma region using water quality indices and multivariate statistical approaches. Thirty-five groundwater samples were collected from boreholes distributed across different geological and land-use settings. Laboratory analyses revealed that the groundwater is generally alkaline (pH 5.8–8.2) with total dissolved solids (TDS) ranging from 135 mg/L to 1780 mg/L and electrical conductivity (EC) between 210 μS/cm and 2740 μS/cm. The dominant cations and anions followed the order Na⁺ &gt; Ca²⁺ &gt; Mg²⁺ &gt; K⁺ and Cl⁻ &gt; SO₄²⁻ &gt; HCO₃⁻ &gt; NO₃⁻, respectively. Piper and base-exchange plots classified the groundwater as mainly of the Cl(SO₄)–Na and Na⁺–SO₄^2- types, indicating mineralization dominated by rock–water interaction and evaporation. The Pollution Index of Groundwater (PIG) classified 74.3 % of samples as insignificantly polluted, 17.1 % as low pollution, and 8.6 % as moderate pollution, while the Percentage Pollution Index (PPI) indicated that contamination was primarily anthropogenic. Water Quality Index (WQI) values ranged from 42 to 255, showing that 61.2 % of samples were of poor to very poor quality for drinking. Irrigation suitability assessment showed that 97.1 % of samples were suitable for salt-tolerant crops based on the permeability index and salinity hazard classification. Overall, groundwater mineralization in Dodoma is controlled by both geogenic and anthropogenic processes, emphasizing the need for regular monitoring and mitigation of human-induced contamination.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"235 ","pages":"Article 105974"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}