Journal of African Earth Sciences最新文献

{"title":"Accommodation of the extension regime of the East African rift system within the Tanzania Craton after impingement of the eastern branch on the Craton","authors":"Gabriel D. Mulibo","doi":"10.1016/j.jafrearsci.2025.105586","DOIUrl":"10.1016/j.jafrearsci.2025.105586","url":null,"abstract":"<div><div>Variations in stress regimes within the Tanzania Craton and at the suture between the Pan-African Mozambique Belt (MB) and the Craton are evaluated using stress tensor inversion of focal mechanisms. The change in fault pattern and the difference in earthquake focal mechanisms along these faults as the Eastern branch (EB) of the East African rift system (EARS) crosses into the Craton from MB have also been examined. Results from the stress inversion indicate that as the fault arrays change, when the EB crosses into the Craton, from NNE-SSW in the MB to NE-SW and NW-SE in the Eyasi-Wembere (EWR) and Bahi-KwaMtoro (BKR) regions within and along the Craton boundary, so does the stress pattern. The strain in the area is accommodated primarily by dextral strike-slip faults along NE- and NW-striking faults in EWR and BKR, respectively. The observed coexistence pattern of normal and strike-slip earthquakes in EWR is explained by border fault linkage through transfer faults. The pattern in BKR argues fault linkage through transfer faults where two rift segments, the southern extent of Eyasi and Manyara segments, are linked by an oblique dextral transfer zone. The findings also show that the overall WNW-ESE extension direction introduced by the EARS into the Craton is accommodated by two orthogonal-oriented stresses (Shmin) within the Craton, showing NNW-SSE and ENE-WNW in EWR and BKR, respectively. The different stress orientations in EWR and BKR might be attributed to the resistance exerted by the Craton, leading to restricted deformation along the Craton margin and, in some parts, to lateral delamination of the Craton. The variations in the stress field lead to differences in the fault array as depicted by strain accommodation in normal and strike-slip faults in places like Eyasi-Wembere and Balangida depression in the north and BKR in the south.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105586"},"PeriodicalIF":2.2,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519304","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":"Sequence stratigraphy and petrophysical evaluation controls on fluvial to fluvio-marine reservoirs in the syn- and post-rift sediments: Insights into in the Kharita and Bahariya Formations, West Beni Suef basin","authors":"Amer A. Shehata ,&nbsp;Mohammad Abdelfattah Sarhan ,&nbsp;Ramadan Abdelrehim ,&nbsp;Kamal Abdelrahman ,&nbsp;Mohammed S. Fnais ,&nbsp;Amir Ismail","doi":"10.1016/j.jafrearsci.2025.105568","DOIUrl":"10.1016/j.jafrearsci.2025.105568","url":null,"abstract":"<div><div>Hydrocarbon occurrence in rift basins is largely governed by tectonic styles and basin-fill stratigraphy, with abundant potential reservoirs found throughout the syn-rift and post-rift successions. This study conducts a sequence stratigraphic analysis and petrophysical evaluation of the Albian-Cenomanian syn- and post-rift successions in the Beni Suef (BS) rift basin. The Albian Fluviatile Kharita Formation is deposited in the syn-rift phase, while the fluvio-marine Bahariya Formation is deposited in the post-rift phase of the BS basin. The studied succession is divided into three depositional sequences: SQLKH-1 &amp; SQUKH-2 in the Kharita Formation and SQBAH-3 in the Bahariya Formation. SQLKH-1 and SQUKH-2 are siliciclastic-dominated units developed in a long-lasting fluviatile setting with some shallow marine shale deposits in the lower levels of SQLKH-1, while the SQBAH-3 is a siliciclastic unit with carbonate interbeds developed initially in fluvio-deltaic setting and become shallow marine upwards. Petrophysical analysis has been conducted to evaluate hydrocarbon potential and reservoir characteristics of the Kharita and Bahariya formations across several wells. With effective porosity values between 0.09 and 0.14 and average shale volumes of about 0.10, the Kharita Formation exhibits good reservoir quality but limited hydrocarbon saturation, indicating potential suitability for CO₂ sequestration rather than hydrocarbon production. The Bahariya Formation demonstrates superior reservoir potential, with low shale volumes (&lt;10%) and effective porosity ranging from 10% to 20%, highlighting its suitability for hydrocarbon exploration. The considerable variation in water saturation between wells from 25% to 75% highlights localized heterogeneity. Potential hydrocarbon accumulation zones are identified in wells with lower water saturation, like Azhar A2 and Azhar E−2X. These results highlight the importance of site-specific reservoir management to maximize production and the Bahariya Formation's superior suitability for hydrocarbon exploration when compared to the Kharita Formation.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105568"},"PeriodicalIF":2.2,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143508954","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":"Geochemical constraints on argillic altered rocks in the Bashgol district, Tarom-Hashtjin metallogenic province, central-northern Iran","authors":"Ali Abedini ,&nbsp;Ali Asghar Calagari","doi":"10.1016/j.jafrearsci.2025.105588","DOIUrl":"10.1016/j.jafrearsci.2025.105588","url":null,"abstract":"<div><div>The Bashgol district constitutes a part of the Tarom-Hashtjin metallogenic province in central-northern Iran. The intrusion of granitic igneous bodies of Oligocene age into the middle Eocene dacitic rocks in this district is associated with the extensive hydrothermal alteration zones consisting mainly of argillic alteration zone (AAZ). The X-ray diffractometry (XRD) data featured that quartz and kaolinite are two major mineral assemblages in the AAZ, which are accompanied by lesser amounts of minerals such as halloysite, smectite, alunite, pyrite, rutile, goethite, illite, plagioclase, and svanbergite-woodhouseite. Depletion of elements like Zr, Nb, Th, Ta, and Y during the development of the AAZ is affiliated with the low-pH hydrothermal fluids, high water/rock ratios, and abundance of complexing ions. The significant enrichment of Mo, Sb, and As coupled with positive correlation of these three elements with sulfur, very low Rb/Sr ratio, mineral assemblages of the AAZ, and occurrence of vein-veinlet-type mineralization indicate that the Bashgol district possesses favorable conditions for the formation of epithermal deposits with high-sulfidation style. This study revealed that alunite, svanbergite-woodhouseite, kaolinite, smectite, halloysite, and goethite as alteration products controlled the geochemistry of rare earth elements (REE) in the AAZ. The occurrence of negative Ce anomaly in AAZ shows the destruction of zircon by oxidizing-acidic fluids. The occurrence of negative Eu anomaly during the development of the AAZ attests to destruction of plagioclase and hornblende by strongly acidic hydrothermal solutions and provides firm reasoning for high ƒO₂ of the environment.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105588"},"PeriodicalIF":2.2,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453791","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":"Subsurface lateral magma propagation from Nyiragongo volcano in the Western Rift Zone of the East African Rift","authors":"Virginie Pinel ,&nbsp;Catherine A. Mériaux","doi":"10.1016/j.jafrearsci.2025.105569","DOIUrl":"10.1016/j.jafrearsci.2025.105569","url":null,"abstract":"<div><div>Lateral magma propagation is a common feature of rift zones, with opening against the minimum compressive stress and vertical dykes flowing parallel to the rift direction. Depending on the competition between vertical and lateral magma migration, these dykes may either feed an eruption or not. In this context, the topography which includes the edifice load acts against the rise of the magma and favours lateral migration radially away from the edifice central area, thus feeding peripheral vents. Here, we focus on the Nyiragongo volcano, a volcanic edifice located in the western branch of the East African Rift and culminating at 3,470 meters above sea level. In practice, we study the combined effect of the extension induced by the rifting of the EAR and the topographic loading of the Nyiragongo volcano on the orientation of the dyke propagation plane and on the balance between the lateral and vertical propagation of the magma in this propagation plane. Using analytical and numerical models taking into account the effect of topography and the rift-induced west-east extensional stress field, we show that the path of a dyke originating from the volcanic edifice is first influenced by the load of the volcano, leading to a radial propagation. Beyond 5 km, however, the rift-induced extensional stress field dominates leading to a north–south propagation towards Lake Kivu. These results are consistent with the path of the magma deduced from the position of the vents and geophysical observations for the last two eruptive events of the Nyiragongo volcano (2002 and 2021). On the other hand, the lateral propagation over more than 20 km, where the magma remains trapped beneath the lake, is shown to be controlled by depth-dependent extension and reduced magma buoyancy and, to a lesser extent, the downslope towards Lake Kivu and the slight increase in rift extension towards the south.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105569"},"PeriodicalIF":2.2,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using a Bayesian isotope mixing model to assess nitrate sources in groundwater: A case study of Granvillebrook and Kingtom dumpsites, Sierra Leone","authors":"Abdul Aziz Sankoh ,&nbsp;Nana Sarfo Agyemang Derkyi ,&nbsp;Cynthia Laar ,&nbsp;Augustine Ovie Edegbene ,&nbsp;Jacob Asomaning ,&nbsp;Joseph Amara ,&nbsp;Ronnie Frazer-Williams","doi":"10.1016/j.jafrearsci.2025.105585","DOIUrl":"10.1016/j.jafrearsci.2025.105585","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The stable isotope mixing model in R (SIMMR) proves to be a robust method for quantifying the relative contributions of multiple sources to a mixture. In this study, we integrated the stable isotopes of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and hydrochemical data into the SIMMR model to assess the proportional sources of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in groundwater samples at the Granvillebrook and Kingtom dumpsites. The bi-plot analysis of δ&lt;sup&gt;15&lt;/sup&gt;N versus δ&lt;sup&gt;18&lt;/sup&gt;O-&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; revealed that the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in the dumpsites predominantly originated from manure and leachate (MAL), soil organic-N (SON) and domestic wastewater (DW) confirming the prevalence of denitrification and ammonia volatilization. Furthermore, SIMMR analysis of δ&lt;sup&gt;15&lt;/sup&gt;N versus δ&lt;sup&gt;18&lt;/sup&gt;O-&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; provided detailed insights. At the Granvillebrook dumpsite, SON emerged as the primary contributor (43.6%) to &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in groundwater, followed by MAL (31%) and DW (17%). In the Kingtom area, significant contributions came from MAL (32.2%), SON (28.0%), and DW (26.3%). Additionally, SIMMR analysis of δ&lt;sup&gt;15&lt;/sup&gt;N versus dissolved oxygen (DO) indicated that MAL played a predominant role (61.1%) in contributing &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; to the groundwaters of the Granvillebrook dumpsite, followed by SON (23.8%) and DW (15.1%). In the Kingtom dumpsite, DW (55.0%), SON (29.1%), and MAL (15.9%) were identified as the major contributors to &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in groundwater. The study underscores that coupling δ&lt;sup&gt;15&lt;/sup&gt;N and DO in the SIMMR model is a more efficient method for quantifying the contributions of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; sources from MAL, SON, and DW. This research bridges a knowledge gap by providing novel insights into &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; source analysis, serving as a foundational resource for future &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; isotope studies in groundwaters near dumpsites. Assessing the temporal variations and sources of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; can support the development of improved agricultural management practices and sewage disposal programs, to ","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105585"},"PeriodicalIF":2.2,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445196","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":"Cretaceous source rocks evaluation inferred from geochemical analysis and basin modeling in Northern-Central Atlas of Tunisia: A guide for exploration","authors":"Ines Ghribi ,&nbsp;Fares Khemiri ,&nbsp;Mohsen Layeb","doi":"10.1016/j.jafrearsci.2025.105576","DOIUrl":"10.1016/j.jafrearsci.2025.105576","url":null,"abstract":"<div><div>We present a petroleum system assessment of the late Albian and late Cenomanian–early Turonian source rocks of the lower Fahdene and Bahloul Fms in Northern Tunisia in the region around Jebel Ech-Cheid and the Bouarada plain. Rock-Eval pyrolysis and basin modeling of drilled wells and seismic-based pseudo-wells were used in the present study. Analyses were performed on samples from outcrops and wells. The results indicate a moderate to good Albian lower Fahdene source rock of mixed type II/III oil and Gas-prone kerogen. The late Cenomanian–early Turonian Bahloul Fm bears a moderate to very good source rock containing oil-prone type II kerogen. Parameters including production index (PI) and T_max indicate that the maturity varies from immature late diagenetic to the Gas generation stage, mainly depending on burial history within the irregular basin architecture. 1D basin modeling of petroleum wells and 2D seismic based pseudo-wells at different structural positions reveals different burial and thermal histories. Regional compression during the Atlas orogeny aborted hydrocarbon maturation at an early stage in uplifted and folded zones. However, transverse grabens experienced continuous burial, leading to advanced hydrocarbon maturity and significant expulsion. These grabens are key exploration targets for finding preserved traps, both within the grabens and at graben edges.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105576"},"PeriodicalIF":2.2,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143526824","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 first assessment of surface water quality in Lksob river (Essaouira, Morocco): Physico-chemical parameters and nutrients distribution","authors":"Youssef El kabdani,&nbsp;Zainab Damsiri,&nbsp;Fatima Ezzahra Ait Ballagh,&nbsp;Khalid El kalay,&nbsp;Karima Khalil","doi":"10.1016/j.jafrearsci.2025.105584","DOIUrl":"10.1016/j.jafrearsci.2025.105584","url":null,"abstract":"<div><div>Rivers play a critical role in the hydrological-cycle, by transporting organic and inorganic materials to the oceans. Despite their importance, the processes driving the distribution of physicochemical parameters and nutrients in rivers, as well as the factors affecting water quality, are not fully understood, especially in semi-arid regions as Essaouira city located in the southwest of Morocco. This work is the first study conducted on the assessment of the surface water quality in Lksob River and aims to understand the functioning of this ecosystem through a spatio-temporal distribution of physicochemical parameters and nutrients. Weekly water samples were collected from March 2022 to March 2023 at seven stations from upstream station (S1) to the downstream (S7). temperature, salinity, pH, electrical conductivity, dissolved oxygen, orthophosphate, ammonium, nitrite and nitrate were measured. Our results showed spatial variations in key parameters along Lksob river. The highest water temperature (25.8 ± 0.45 °C) occurred at station S3 in summer 2022, while the lowest (14.57 ± 1.46 °C) was in winter 2023. Dissolved oxygen varied significantly and reached the highest levels (15.15 ± 0.22 mg/L) at station S1 in winter 2022 and the lowest (5.78 ± 0.82 mg/L and 6.64 ± 0.20 mg/L) at stations S5 and S2 in summer 2022. Electrical conductivity (1766 ± 998.08 μS/cm to 4211.5 ± 143.53 μS/cm) indicated moderate to high pollution according to Moroccan standards. Ammonium concentrations ranged from (10.70 ± 1.39 to 61.46 ± 2.01 μmol/L). The highest values were recorded at S2, S7, S6 during summer, and S5 during spring-winter, highlighting significant seasonal and spatial variations. Lksob River was well-oxygenated and relatively rich in nutrients compared to other studies in Morocco such as Loukkos, Tiflet and Oum Er-Rabia Rivers. These study results provide the first data on physicochemical and nutrient concentrations, enabling researchers to understand the functioning of this small river ecosystem.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105584"},"PeriodicalIF":2.2,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453792","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":"Uranium mineralization associated with albitization in a Paleoproterozoic granite: Example of the Saraya granite, (Eastern Senegal, West Africa)","authors":"Moumar Dieye ,&nbsp;Cheikh Ibrahima Faye ,&nbsp;Mahamadane Diene ,&nbsp;Michel Cuney ,&nbsp;Marc Brouand ,&nbsp;Mamadou Gueye","doi":"10.1016/j.jafrearsci.2025.105570","DOIUrl":"10.1016/j.jafrearsci.2025.105570","url":null,"abstract":"<div><div>The uranium mineralization occurrences hosted within the Saraya episyenites (hydrothermally altered granites) were discovered between 1985 and 1960 during an airborne regional survey conducted by prospectors from the Commissariat à l'Energie Atomique (C.E.A). Following this discovery, a strategic and tactical exploration program led by the Compagnie Générale des Matières Nucléaires (COGEMA) was undertaken between 1974 and 1984, which significantly contributed to the improved delineation of these occurrences. Recent investigations carried out by AREVA from 2008 to 2010 have facilitated the collection of fresh materials from drill core samples of mineralized zones, along with detailed petro-mineralogical and geochemical studies.</div><div>Our results show that the uranium mineralization developed from peraluminous leucogranitic granites, initially characterized by albitization is associated with dequartzification during the episyenitization phase. This dequartzification resulted in the formation of vugs that were subsequently filled by chlorite, uranium minerals, including coffinite, uraninite, and other uranium oxides, along with Ti-oxides (rutile and anatase). Post ore-stage alteration led to the development of carbonate minerals and argillization, in association with the leaching of the primary uranium mineralization, as well as the remobilization of carbonaceous matter. Enrichment in Medium Rare Earth Elements (MREE) and Heavy Rare Earth Elements (HREE), as well as in yttrium, was also observed within the mineralized facies.</div><div>This mineralization event is part of a broader event spanning from the Paleoproterozoic to the Mesoproterozoic, which also affected other uranium provinces in central Ukraine, Canada, China, Australia, India, southern Morocco, and Guyana (Cuney et al., 2008).</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105570"},"PeriodicalIF":2.2,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551253","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":"Site classification and soil liquefaction evaluation based on shear wave velocity via HoliSurface approach","authors":"Albert Kafui Klu ,&nbsp;Michael Affam ,&nbsp;Anthony Ewusi ,&nbsp;Yao Yevenyo Ziggah ,&nbsp;Emmanuel Kofi Boateng","doi":"10.1016/j.jafrearsci.2025.105574","DOIUrl":"10.1016/j.jafrearsci.2025.105574","url":null,"abstract":"<div><div>This study employs the HoliSurface technique, a geophysical method, to classify sites and evaluate liquefaction susceptibility in the southwestern Greater Accra Region of Ghana. Shear wave velocity (Vs) profiles to a depth of 13 m were acquired from 26 surveyed sites. A reliable extrapolation method was then used to estimate the Vs₃₀ (Vs₃₀₍₁₃₎) of each site, allowing classification based on the Eurocode 8 system. Most sites (20) were classified as Site Class C (Vs₃₀: 180–360 m/s), indicating moderately dense soils with improved geomechanical properties at depth. Five sites exhibited high stiffness and resistance to liquefaction (Site Class B). The site at Tetegu East (Vs₃₀: 110 m/s, FoS: 0.525) was, however, found to be extremely weak (Site Class D), hence prone to seismic failure. Airport City (Vs₃₀: 190 m/s, FoS: 0.647), despite a Site Class C classification, exhibited a low FoS value, indicating liquefaction susceptibility. A key limitation of this study was the inability to acquire Vs data to a depth of 30 m due to spatial constraints at most sites, necessitating the use of extrapolated Vs₃₀ values, which may introduce uncertainties. Additionally, joint inversion of group velocity dispersion with HVSR or RMP curves, which could enhance reliability, was not employed due to the preliminary nature of this study. Despite these limitations, the findings align with established standards and provide critical insights for urban planning, highlighting the need for interventions in high-risk zones to mitigate potential disasters.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"225 ","pages":"Article 105574"},"PeriodicalIF":2.2,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403279","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":"Petrogenesis of rare-metal pegmatites in northeastern part of Nasarawa, northcentral basement complex of Nigeria","authors":"Anthony Chukwu ,&nbsp;Smart Chika Obiora ,&nbsp;Theophilus C. Davies","doi":"10.1016/j.jafrearsci.2025.105565","DOIUrl":"10.1016/j.jafrearsci.2025.105565","url":null,"abstract":"<div><div>The pegmatites in Nasarawa region of northcentral Nigeria are within the Pan-African remobilized belt of Basement rocks of Nigeria, along Eggon-Wamba axis. Pan African orogenic events gave rise to reworked, crustal thickening and decompression which resulted to syn-to post-collision rocks (granitic rocks and pegmatites). The rare-metal pegmatites are classified as albite-muscovite pegmatites and biotite-microcline pegmatites. The area is predominantly underlain by migmatitic banded gneiss and localized biotite-muscovite gneiss which host most of the rare-metal pegmatites. The pegmatites mostly occur in NNW-SSE direction with few NE-SW orientations. The rare metal pegmatites contain albite, muscovite, quartz and microcline, while garnet, black tourmaline (schorl), apatite, beryl, ilmenites and minor Sn-Nb-Ta oxides occur as accessory. The biotite-microcline pegmatites possess less accessory minerals. The host rocks are made up of quartz, albite-andesine, microcline, biotite, muscovite and hornblende. Minor constituents include orthopyroxene, cordierite, sillimanite, garnet and chlorite. The rocks in the area (pegmatites and migmatitic rocks) show extreme peraluminous and exhibiting similar geochemical signatures suggesting genetic relationship. The albite-muscovite pegmatites are enriched in Rb, B, Li, Cs, Sn, Nb &gt; Ta, W, Be and Ga over the biotite-microcline pegmatites and exhibit low values of K/Rb, Mg/Li and Zr/Hf across the zones. They have higher potential for cassiterite and columbite over tantalite. Modal equilibrium batch melting model supports anatexis of the migmatitic-gneiss complex at depth rather than the Pan-African granites origin as earlier believed.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"225 ","pages":"Article 105565"},"PeriodicalIF":2.2,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403278","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}