Journal of African Earth Sciences最新文献

{"title":"Zircon and Titanite U-Pb geochronology, petrology and P-T path of garnet-bearing amphibolites from Tadoumet area (Assodé-Issalane terrane, Central Hoggar, Algeria)","authors":"Sofiane Dahmani ,&nbsp;Khadidja Ouzegane ,&nbsp;Amar Drareni ,&nbsp;Carlos J. Garrido ,&nbsp;Manuel J. Román-Alpiste ,&nbsp;Sidali Doukkari ,&nbsp;Amar Arab","doi":"10.1016/j.jafrearsci.2025.105675","DOIUrl":"10.1016/j.jafrearsci.2025.105675","url":null,"abstract":"<div><div>The garnet-bearing amphibolites of the Tadoumet area (Assodé-Issalane terrane, Orosirian Stripe, Hoggar), show three principal metamorphic stages. (i) A pre-peak metamorphic stage, characterized by mineral inclusions of quartz, plagioclase, epidote, rutile, and titanite encapsulated within garnet porphyroblasts (M0); (ii) A relatively high-grade stage, represented by a coarse-grained paragenesis comprising garnet porphyroblasts, amphibole, clinopyroxene, quartz, titanite, and rutile (M1); (iii) A retrograde stage, marked by the development of amphibole‒plagioclase‒K-feldspar coronae assemblages around garnet with titanite (M2).Microprobe analysis indicates that garnet compositions range between X_Alm = 0.47–0.58, X_Gr = 0.25–0.35, and X_Py = 0.06–0.16. Clinopyroxenes exhibit zoning, with cores depleted in Mg relative to the rims (X_Mg core = 0.57, X_Mg rim = 0.65). Furthermore, amphibole associated with the M1 stage displays compositions indicative of magnesio-hornblende, whereas the M2 stage is characterized by magnesian-hastingsite coronae (Si &lt; 6.25 and X_Mg = 0.4–0.6). Tschermakite, with X_Mg values of 0.51–0.60, is found in association with clinopyroxene and plagioclase (X_An = 0.34–0.48).Calculated P-T pseudosections suggest peak P–T conditions of 13.5 ± 1 kbar and 700 ± 50 °C (M1), characterizing a mineral assemblage comprising hornblende, diopside, garnet, K-feldspar, plagioclase, rutile, titanite, and melt, based on garnet core compositions. Additionally, decompression stage corresponds to high temperature conditions (750 ± 50 °C, M2a) followed by cooling (600 ± 50 °C, M2b) at 6.5 ± 1 kbar, using the compositions of garnet rims, secondary diopside, amphibole, and plagioclase isopleths and Ti in amphibole geothermometer. This study constitutes the first geochronological investigation of metamorphism in the Tadoumet area, utilizing in situ U–Pb dating of zircon and titanite. The findings indicate a protolith age of 712 ± 20 Ma (derived from zircons) and an amphibolite-facies metamorphic age of 599 ± 4 Ma (obtained from titanite). The P–T trajectory recorded in the garnet-bearing amphibolites is interpreted as reflecting a distinct sequence of continental collision, in which crustal thickening denotes the peak of metamorphism, followed by decompression driven probably by extensional processes.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105675"},"PeriodicalIF":2.2,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143902428","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":"Integrated geological and geophysical analysis of the active Sidi–Thabet fault in northeastern Tunisia: insights into recent deformation and seismotectonic implications","authors":"Lassaad Mejri ,&nbsp;Chahreddine Naji ,&nbsp;Nermine Sayah ,&nbsp;Amara Masrouhi ,&nbsp;Olivier Bellier","doi":"10.1016/j.jafrearsci.2025.105672","DOIUrl":"10.1016/j.jafrearsci.2025.105672","url":null,"abstract":"<div><div>The Sidi-Thabet fault, a key structure within the Atlas-Tell orogenic belt in northern Tunisia, illustrates the complex interplay between inherited Tethyan extensional features and subsequent compressional deformation during Tertiary African-Eurasian plate convergence. This study provides insights into the recent activity and seismotectonic significance of the fault by combining geological mapping, shallow geophysical surveys and morphotectonic analysis with seismic and focal mechanism studies. Steeply dipping fault planes, brittle fracture zones and vertical displacements affecting Quaternary and Cretaceous strata are evident from seismic refraction and electrical resistivity tomography. The evidence for recent fault reactivation is further supported by morphotectonic markers. These include displaced calcrete beds, fresh scarps, and disrupted landforms. The focal mechanism analysis indicates a predominantly compressional tectonic regime with secondary normal faulting. This emphasizes that this fault accommodates both transpressional shortening and vertical uplift along its segmented trace. The presence of ductile salt layers enhances deformation complexity, driving differential uplift and influencing the architecture of fault-related folds. These results confirm that the Sidi-Thabet Fault is a major zone of active deformation within the Tunisian Atlas, emphasizing its critical role in seismic hazard assessment, especially given its proximity to Tunis, a city of three million people located just south of the fault.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105672"},"PeriodicalIF":2.2,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143876504","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 geological and economic legacy of the Pan-african Damara Belt and Lufilian Arc of south-central africa","authors":"Benjamin Siyowi Mapani ,&nbsp;Kabang'u Grace Sakuwaha ,&nbsp;Kawawa Banda","doi":"10.1016/j.jafrearsci.2025.105662","DOIUrl":"10.1016/j.jafrearsci.2025.105662","url":null,"abstract":"<div><div>The Neoproterozoic belts of southern Africa, which include the Damara Belt and the Lufilian Arc, have had a significant impact on the understanding of the geology of Southern Africa and related regions. Above all, both belts are economically important as they host metallic and non-metallic mineral deposits of the Kalahari and Central African Copperbelt which are mined in Namibia, Democratic Republic of Congo (DRC), and Zambia respectively. The Damara Belt continues in a north-easterly direction into Botswana, where it continues below the Phanerozoic cover of the Karoo and Kalahari Supergroups to connect in the subsurface with the Lufilian Arc in western Angola and Zambia. The two belts record a full Wilson cycle and form part of a transcontinental suture zone which resulted from the collision between the Archean Congo and Kalahari cratons. The Damara Belt in Namibia, records a progressive increase in metamorphic grade and deformation intensity from sub-greenschist facies on the northern platform to HT/LP granulite facies in the core of the orogen. Similarly, the Lufilian Arc also records a gradual increase in metamorphic grade from sub-greenschist facies in the north (in the DRC) to amphibolite facies in the in the Domes Region in Zambia. Mineralization in these belts differs in style, shape, and size, which can be attributed to the differences in the nature and characteristics of the original sub-basins that formed during rifting, and subsequent deformation. In the Lufilian Arc, ore reserves for individual mines are in the order of 50–810 Mt of ore at 0.5–3 % Cu. This scale is simply not comparable to that in the Damara Belt with tonnages of up to 35 Mt with grades of 0.1–2 % Cu. Both regions also contain numerous smaller copper deposits. On the other hand, the Damara Belt hosts the world class Rossing and Husab uranium mines of Namibia (with grades of 310–450 ppm U) but no major uranium deposits occur in the Lufilian Arc. The Damara uranium deposits occur associated with syn-to post-tectonic granites in the core of the orogen where granite formation was initiated by anatexis of the metasedimentary rocks of the Swakop Group. In contrast, the associated Pb-Zn ± Cu mineralization in both belts appears to be remarkably similar, with comparable deposit sizes, grades, and estimated reserves. The legacy of these two orogenic belts is significant in that the Lufilian Arc serves as the standard or type locality for understanding sediment-hosted Cu-Co deposits globally, whereas the Damara Belt has been the key to understanding granite melt generation by anatexis and formation of granite-hosted uranium deposits in the world.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105662"},"PeriodicalIF":2.2,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143900095","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":"Jurassic tectonic and paleogeographic evolution of the junction zone between the Middle Atlas and High Atlas (Morocco)","authors":"Youssef Ouahzizi,&nbsp;Mohammed Charroud,&nbsp;Driss El Azzab","doi":"10.1016/j.jafrearsci.2025.105673","DOIUrl":"10.1016/j.jafrearsci.2025.105673","url":null,"abstract":"<div><div>The Middle Atlas (MA) and High Atlas (HA) chains are considered intraplate basins developed during the Mesozoic Era. The Jurassic structural evolution of the junction between MA-HA recorded three successive tectonic events beginning with a NE-SW extensional tectonic regime responsible for the differentiation between a nearshore environment to northwest with sandstone and pelite deposits, the platform domain with its metric carbonate marls, and a basin domain filled with black marls and limestones with an euxinic character during the Toarcian. In this episode, the sedimentary thickness is controlled by High Atlas trending faults (N120-N110). The second tectonic event corresponds to a tectonic extension regime with an NW-SE to NNW-SSE directed σ3 axis, causing subsidence towards the southeastern part delimited by the Middle Atlas direction faults (NE-SW). The sedimentary series indicates an evolution from a continental environment in the northwest (conglomerates and sandstones) to platform and basin sedimentation in the southeast, noted by the intercalation of marls and bioclastic limestones of the Aalenian–Bajocian age. During the third tectonic event (Bathonian–Barremian), the sedimentary series becomes continental lagoonal deposits represented by marls with limestones, grading into sandstone and gypsum marl, and conglomerates overlain by marls and sandstones of the \"Red beds\". This evolution associated with by the establishment of a transpressional tectonic regime with NNE-SSW compression σ1 axis responsible for uplift using High Atlas direction faults (E-W to ENE-WSW), caused marine regression; this compression is accompanied by WNW-ESE extension σ3 axis responsible for subsidence towards the southern part with the establishment of basalt lava flows and gabbroic dykes of the Bathonian–Barremian magmatism complex.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105673"},"PeriodicalIF":2.2,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852245","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":"Optimizing permeability and porosity prediction with advanced machine learning: A case study unlocking the complexities of late cretaceous reservoirs, gulf of suez, Egypt","authors":"Amer A. Shehata ,&nbsp;Mohamed Ahmed ,&nbsp;Ahmed A. Kassem ,&nbsp;Ramadan Abdelrehim ,&nbsp;Takeshi Tsuji ,&nbsp;Amir Ismail","doi":"10.1016/j.jafrearsci.2025.105670","DOIUrl":"10.1016/j.jafrearsci.2025.105670","url":null,"abstract":"<div><div>Permeability and porosity are critical parameters that influence the evaluation and management of hydrocarbon reservoirs. Conventional permeability and porosity estimation techniques are constrained by data scarcity and geological variability, necessitating advanced predictive models. This study presents a fully automated machine learning (AML) framework that combines four advanced models—Gradient Boosting Machine (GBM), Distributed Random Forest (DRF), Generalized Linear Model (GLM), and Deep Neural Network (DNN)—to predict permeability and porosity based on well log data. The approach integrates twelve well-log responses (i.e. caliper, gamma ray, sonic, density, porosity, water saturation, volume of shale, resistivity) from five wells (inputs), demonstrating enhanced prediction accuracy for permeability and porosity in the Late Cretaceous reservoirs of the Gulf of Suez, Egypt. To ensure robust model training and validation, the dataset was divided into training (60 %), validation (20 %), and testing (20 %) subsets, and model performance was evaluated using Nash-Sutcliffe Efficiency (NSE), correlation coefficient (r), normalized root mean square error (NRMSE), and bias (B). The DNN model excelled in permeability estimation (testing: NRMSE: 0.57 ± 0.09; NSE: 0.68 ± 0.14; r: 0.82 ± 0.10; B: 9.17), while the DRF model outperformed in predicting porosity (testing: NRMSE: 0.72 ± 0.02; r: 0.69 ± 0.03; NSE: 0.47 ± 0.04; B: 0.93) compared to other models, showcasing superior performance metrics such as Nash-Sutcliff efficiency, correlation coefficients, and normalized root mean square error. The GLM model exhibits the least favorable performance when compared to other ML models. Additionally, this study identifies key well log responses, such as sonic, gamma ray, and deep resistivity logs, as major controlling factors for permeability and porosity predictions, highlighting their nonlinear relationships. The developed AML models provide a cost-efficient, computationally effective, and scalable solution for petrophysical property estimation, enhancing reservoir characterization and enabling broader applications in hydrocarbon exploration and beyond.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105670"},"PeriodicalIF":2.2,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143859738","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":"Application of time domain induced polarization technique to study perched groundwater at the northwestern coast of Egypt: A case study of Fuka basin","authors":"Ahmed Elshenawy","doi":"10.1016/j.jafrearsci.2025.105671","DOIUrl":"10.1016/j.jafrearsci.2025.105671","url":null,"abstract":"<div><div>Perched groundwater resources, essential for drinking, tourism, and irrigation, have not been extensively studied. These resources are finite, vary in salinity, and are threatened by overexploitation, contamination, and rising sea levels due to climate change. A survey using Two-Dimensional Electrical Resistivity Tomography (2DERT) and Time Domain Induced Polarization (2DTDIP) techniques was conducted in the Fuka basin to map the shallow perched aquifer, determine stratigraphic units, and assess the effectiveness of differentiating between aquifer and aquitard deposits with low resistivity. The study tested the condition of perched groundwater by performed two synthetic models. These models can considerably help in the interpretation of real field measurements since they provide a reference for predicted observations under known settings. Moreover, four combined 2DERT/2DTDIP profiles were carried out in Fuka basin where the low permeability clay bands were investigated in the subsurface succession. The comprehensive examination of four 2DERT/2DTDIP lines reveals significant differences in electrical resistivity, chargeability, and normalized chargeability profiles. The 2DTDIP effectively identified the perched water zone at various depths between 20 and 30 m, indicated by high chargeability and normalized chargeability associated with clay bands which underlain the floating perched water layer. Low resistivity (11–23 Ω m) longitudinal anomalies were interpreted as saturated fracture limestone, allowing penetrating rainfalls to accumulate above this zone. High chargeability anomalies (20-25mv/v) appearing directly below fractured limestone were inferred to impermeable lenses of clay. The simultaneous interpretation of electrical resistivity and induced polarization datasets successfully differentiate between aquifer and aquitard deposits offering a highly promising strategy for identifying perched water zones at conductive at low resistivity deposits.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105671"},"PeriodicalIF":2.2,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143864978","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 Volta basin in Burkina Faso: Lithologic and structural geology constraints along the leading edge of the foreland Dahomeyide fold-thrust belt","authors":"Kim A.A. Hein ,&nbsp;Stephan Séjourné ,&nbsp;Clément Ouédraogo ,&nbsp;Gnissa Sidibé ,&nbsp;Richard Dahl ,&nbsp;Guy Kevin Coulibaly","doi":"10.1016/j.jafrearsci.2025.105660","DOIUrl":"10.1016/j.jafrearsci.2025.105660","url":null,"abstract":"<div><div>The Volta basin in Ghana, Togo and Benin has a narrow NE-striking panhandle extension into Burkina Faso where the Pan-African Dahomeyide fold-thrust belt approaches Paleoproterozoic basement rocks (ca. 2.25–2.10 Ga). We present the results of integrated stratigraphic, structural geology studies of the Volta Basin in Burkina Faso that combines interpretations of high-resolution remote sensing imagery, radiometrics and magnetics to appraise the metasedimentary sequences and stratigraphic setting. We evaluate the degree of deformation and metamorphism across the Volta basin in Burkina Faso and contextualize the tectonic domains with reference to published data for the broader Volta Basin.</div><div>The results indicate that felspathic sandstones and greywackes of the Madjoari and Gobnangou massifs were deposited in the Tonian Period (ca. 1000-855 Ma) in a shallow marine environment along the Rodinia continental passive margin. Diamictites, dolomite, chert, phosphorite (576 ± 13 Ma) of the Kodjari Group and siltstone-shale sequences of the Porga Group were deposited in an offshore basin in the middle Ediacaran Period (ca. 635-538 Ma) syn-to post Ediacaran glaciation and possibly during a period of deglaciation.</div><div>These metasedimentary rocks were deformed during two deformation events, D1 and D2. D1 ductile-brittle deformation was concomitant to NW-directed fold-thrust formation within the foreland Dahomeyide fold-thrust belt. The intensity of deformation decreases across the panhandle (SE to NW) from isoclinal folding and thrust formation in Atacora Structural Unit, to open style low fold forms near the Madjoari and Gobnangou massifs. In concert, metamorphic grade decreases from greenschist-amphibolite to very low grade (anchimetamorphic).</div><div>D2 brittle deformation was progressive, with incremental development of joints, fracture-corridors, fracture-faults and open fold forms during east-west directed shortening.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105660"},"PeriodicalIF":2.2,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852246","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 potential of Middle Eocene to early Miocene benthic foraminifera as paleoecological indicators in the Qattara Depression, Western desert, Egypt","authors":"Abdalla Shahin,&nbsp;Samar El Khawagah,&nbsp;Banan Shahin","doi":"10.1016/j.jafrearsci.2025.105668","DOIUrl":"10.1016/j.jafrearsci.2025.105668","url":null,"abstract":"<div><div>A comprehensive investigation and analysis were conducted on a total of 105 benthic foraminiferal species. They were extracted from the subsurface Middle Eocene to Lower Miocene strata in the N. El Faras - 1X Well, located in the Qattara Depression of the northern Western Desert, Egypt. The stratigraphic succession primarily encompasses the upper part of the Apollonia Formation (middle to late Eocene), the Dabaa Formation (late Eocene and Oligocene), and the lower part of the Moghra Formation (Early Miocene). Paleoecological multi-proxies analysis were leveraged, including Total Foraminiferal Number (TFN), Planktonic/Benthic Ratio (%P), Species Richness (SR), Diversity Index (Fisher alpha index), Ternary plot for foraminiferal assemblage structure, Agglutinated/Calcareous Ratio (Aggl/Calc), Epifaunal/Infaunal Ratio (Ep/In), and the Trophic-Oxygen (TROX) Model.</div><div>Qualitative and quantitative analyses of the encountered benthic foraminifera, alongside CONISS cluster analysis, facilitated the delineation of five distinct clusters, each characterized by unique fossil content and paleoenvironmental attributes. Generally, the first cluster was characterized by oxic to dysoxic conditions and oligotrophic to highly oligotrophic conditions within middle to outer neritic setting. Clusters 2 and 3 were characterized by oxic to dysoxic conditions and oligotrophic to mesotrophic settings. The fourth cluster exhibited oxic to dysoxic conditions alongside mesotrophic to eutrophic conditions, and situated within a middle neritic and euphotic zone. Lastly, the fifth cluster demonstrated a gradual decrease in paleodepth within the inner neritic and euphotic zone, featuring a well oxygenated environment and mesotrophic to eutrophic conditions.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105668"},"PeriodicalIF":2.2,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834842","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":"Zircon U–Pb ages and Sr-Nd isotope ratios for the mafic microgranular enclaves in the sirstan cretaceous granitoids, NE Iraq: Evidence of cogenetic magmatic origin","authors":"Imad Kadhim Abdulzahra ,&nbsp;Yoshihiro Asahara ,&nbsp;Yousif Mohammad ,&nbsp;Irfan Yara","doi":"10.1016/j.jafrearsci.2025.105665","DOIUrl":"10.1016/j.jafrearsci.2025.105665","url":null,"abstract":"<div><div>Mafic microgranular enclaves (MMEs) are observed in the Sirstan granitoid (SG) body in the Shalair Valley area, northeastern Iraq, within the Zagros Orogenic Belt. Zircon U–Pb ages for the MMEs are 110 Ma with an I-type affinity closely resembling the enclosing rocks. The MMEs are gabbroic-diorite to diorite in composition, and the main mineral assemblage are plagioclase, hornblende, and K-feldspar. The MMEs are intermediate in composition and have low SiO₂ (52.0–60.2 wt%) and high Fe₂O₃, Al₂O₃, TiO₂ and CaO contents (Fe₂O₃ = 8.7–13.3 wt%; Al₂O₃ = 14.8–17.2 wt%; TiO₂ = 0.71–1.02 wt%; CaO = 3.4–11.4 wt%). The enclaves have analogous Sr and Nd isotope compositions with positive εNd_(t) values (⁸⁷Sr/⁸⁶Sr(i) = 0.7047 to 0.7058; εNd_(t) = +2.0 to +2.5) as their host granitoids (⁸⁷Sr/⁸⁶Sr(i) = 0.7044 to 0.7057; εNd_(t) = +0.1 to +2.7). The uniform REE patterns and the fractionation trends of major and trace elements of the MMEs with their host rocks indicate simultaneous crystallization by fractionation from the same magma source. According to the geochemical aspects of the MMEs and their host SG rocks with young T_DM ages (676–720 Ma), the low ratios of the Rb/Sr and Nb/Y ratios, in addition to the same ages and Sr-Nd isotope ratios, infer that the same source magma was derived from a young depleted mantle without the contribution of ancient crustal components.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105665"},"PeriodicalIF":2.2,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143854861","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 structure of Precambrian crust in sub-Saharan Africa: An AfricaArray synthesis and review","authors":"Alexandra Sabattier ,&nbsp;Andrew Nyblade ,&nbsp;Raymond Durrheim ,&nbsp;Fenitra Andriampenomanana ,&nbsp;Andriamiranto Raveloson ,&nbsp;Islam Fadel ,&nbsp;Mark van der Meijde ,&nbsp;Amanda Willet","doi":"10.1016/j.jafrearsci.2025.105664","DOIUrl":"10.1016/j.jafrearsci.2025.105664","url":null,"abstract":"<div><div>We combine new estimates of crustal thickness and shear wave velocities from 48 broadband seismic stations in Mozambique, Namibia, South Africa and Uganda with previously published results to review and examine Precambrian crustal structure in sub-Saharan Africa for secular trends. The ensemble of crustal structure estimates used relies heavily on data obtained through the AfricaArray initiative, which is briefly reviewed. Whether or not Precambrian crustal structure exhibits notable changes from the Mesoarchean through the Neoproterozoic places a key constraint on continental crustal genesis and evolution. Our 48 new estimates of Moho depth and crustal shear wave velocity profiles, combined with results from similar previous studies, yield an average crustal thickness for all Precambrian terranes of 39 ± 4 km. We find that average crustal thicknesses are essentially identical for Mesoarchean (38 ± 3 km), Neoarchean (39 ± 4 km), Paleoproterozoic (40 ± 4 km), Mesoproterozoic (40 ± 4 km) and Neoproterozoic (39 ± 4 km) terranes. The average thickness of the mafic lower crust, identified by high velocity layering (Vs &gt; 4.0 km/s), is also almost identical in Archean and Proterozoic terranes (7 ± 4 km and 6 ± 4 km, respectively). Finally, the average crustal shear wave velocities for all terranes fall within 1 standard deviation of a mean velocity of 3.7 km/s. These results are consistent with findings from other studies highlighting a lack of evidence for secular variation in crustal structure or composition within Precambrian terranes in sub-Saharan Africa, suggesting that secular trends, if they existed at the time of crust formation, have been obscured by crustal reworking during later orogenic and/or magmatic events.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105664"},"PeriodicalIF":2.2,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834841","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}