Pub Date : 2025-11-11DOI: 10.1016/j.jafrearsci.2025.105930
Mohammad Abdelfattah Sarhan , El Sayed Selim
This study provides an integrated petrophysical evaluation of conventional (Matulla sandstones) and unconventional (Thebes carbonates) reservoirs in the Geisum Field, Gulf of Suez, Egypt. Wireline log data from four wells (G-9, GA-5, GA-2, and GA-1), supported by seismic interpretation, were analyzed to determine shale volume, porosity, water and hydrocarbon saturation, and net-to-gross ratios. The Matulla Formation represents a thick, laterally continuous siliciclastic reservoir characterized by effective porosity of 0.20–0.26, hydrocarbon saturation exceeding 0.70, and net-to-gross ratios up to 0.59 (GA-5). Correlation among wells reveals lateral continuity of sand bodies but with fault-controlled thickness and depth variations, indicating strong structural influence on reservoir quality. In contrast, the Thebes Formation behaves as an unconventional carbonate reservoir with moderate effective porosity (0.14–0.19), heterogeneous pay zones (25–55 ft), and net-to-gross ratios of 0.23–0.49. Correlation between GA-2 and G-9 shows marked reservoir compartmentalization governed by fracture intensity and structural position rather than depositional facies. The comparison demonstrates that while the Matulla acts as a high-quality, laterally extensive conventional reservoir, the Thebes is a fracture-enhanced, compartmentalized unconventional play. Integrating petrophysical and structural analyses therefore provides a strong framework for optimizing hydrocarbon exploration and development in fault-controlled rift basins.
{"title":"Integrated petrophysical evaluation of conventional and unconventional reservoirs: The Matulla sandstones and Thebes carbonates in the Geisum Field, Gulf of Suez, Egypt","authors":"Mohammad Abdelfattah Sarhan , El Sayed Selim","doi":"10.1016/j.jafrearsci.2025.105930","DOIUrl":"10.1016/j.jafrearsci.2025.105930","url":null,"abstract":"<div><div>This study provides an integrated petrophysical evaluation of conventional (Matulla sandstones) and unconventional (Thebes carbonates) reservoirs in the Geisum Field, Gulf of Suez, Egypt. Wireline log data from four wells (G-9, GA-5, GA-2, and GA-1), supported by seismic interpretation, were analyzed to determine shale volume, porosity, water and hydrocarbon saturation, and net-to-gross ratios. The Matulla Formation represents a thick, laterally continuous siliciclastic reservoir characterized by effective porosity of 0.20–0.26, hydrocarbon saturation exceeding 0.70, and net-to-gross ratios up to 0.59 (GA-5). Correlation among wells reveals lateral continuity of sand bodies but with fault-controlled thickness and depth variations, indicating strong structural influence on reservoir quality. In contrast, the Thebes Formation behaves as an unconventional carbonate reservoir with moderate effective porosity (0.14–0.19), heterogeneous pay zones (25–55 ft), and net-to-gross ratios of 0.23–0.49. Correlation between GA-2 and G-9 shows marked reservoir compartmentalization governed by fracture intensity and structural position rather than depositional facies. The comparison demonstrates that while the Matulla acts as a high-quality, laterally extensive conventional reservoir, the Thebes is a fracture-enhanced, compartmentalized unconventional play. Integrating petrophysical and structural analyses therefore provides a strong framework for optimizing hydrocarbon exploration and development in fault-controlled rift basins.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105930"},"PeriodicalIF":2.2,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527435","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":"Reply to “Interpretation of 40Ar/39Ar geochronological data to infer mineralisation events in Archean terranes: Comment on Bineli Betsi et al. (2025)","authors":"Thierry Bineli Betsi , Tebogo Kelepile , Kazuyasu Shindo , Read Brown Mapeo , Alfredo Camacho","doi":"10.1016/j.jafrearsci.2025.105928","DOIUrl":"10.1016/j.jafrearsci.2025.105928","url":null,"abstract":"","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105928"},"PeriodicalIF":2.2,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527119","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}
<div><div>The Motaghairat layered mafic-ultramafic intrusion in the Southern Eastern Desert (SED) of Egypt is relatively metamorphosed with no evidence for tectonic contacts with country rocks. This study deals with the geology, petrography, and mineral chemistry of the Motaghairat intrusion, as one of the best examples in the SED, to shed light on its emplacement thermodynamic conditions (P, T, ƒO2) and post-magmatic processes, including metasomatic history and microscale element transferring. The ultramafic rocks comprise plagioclase-bearing peridotite (dunite, lherzolite) and wehrlite with subordinate clinopyroxenite, while the mafic ones include gabbroic rocks with subordinate hornblendite and anorthosite, showing cumulate textures. The analyzed olivine grains are compositionally homogenous with narrow Fo content ranging from 85 in dunite to 81 in olivine gabbro, where their NiO content is generally low (<0.3 wt%). Clinopyroxene is mainly diopside with subordinate augite (Wo<sub>30.76–49.21</sub>En<sub>39.53–56.81</sub>Fs<sub>4.52–19.60</sub>) and its Mg# decreases systematically from 0.92 in ultramafic rocks to 0.69 in mafic rocks. Orthopyroxene is enstatite in composition (Wo<sub>0.19 – 11.47</sub>En<sub>68.64–84.11</sub>Fs<sub>8.26–30.1</sub>) with a high Mg# (0.91) of ultramafic rocks relative to the low Mg# (0.7) of mafic ones. The mineral chemistry and back-scattered chemical mapping of coarse spinel grains reveal a marked heterogeneity with reversed chemical zoning represented by Cr-Fe-rich cores and Mg-Al-rich rims, forming Cr-spinel grains surrounded by a thin rim of Al-spinel. The occurrence of homogeneous Al-spinel (pale green) and Cr-spinel (dark brownish color) with rims of Al-spinel in ultramafic rocks suggests the formation of the former due to the interaction between spinel and melts, but the latter was formed because of a micro-scale element (Al, Mg, Cr, Fe) transfer between Cr-spinel and Al-rich silicate phases at the sub-solidus state. Some Cr-spinel grains show exsolved texture of Ti-rich ferritchromite due to subsolidus equilibration under slow cooling rates for the spinel-type solid solution. The Motaghairat mafic-ultramafic rocks fractionally crystallized from hydrous tholeiitic basaltic magma (parent melts). They are considered as a late-orogenic layered intrusion generated during the intra-arc rifting in the supra-subduction zone of the Arabian Nubian Shield. These rocks were generated in a slightly oxidizing (ΔNNO +0.03) to moderately oxidizing (ΔNNO +1.7) environment under low pressure (∼4.47 ± 0.33 kbar) and shallow depth (∼16.5 ± 1 km) conditions. Their estimated crystallization temperature shows wide ranges from ∼850 to 1200 °C (∼1000 °C on average) because of variable fractional crystallization degrees that may, in turn, result in different magmatic compositions during cooling. The occurrence of fresh dunite, wehrlite, and clinopyroxenite dykes/veins in serpentinized peridotite, along with the mineral chemist
{"title":"Mineral chemistry of the Neoproterozoic mafic-ultramafic intrusion in the Nubian shield: Evidence of microscale element transferring during post-magmatic processes","authors":"Mohamed Zaki Khedr , Shoji Arai , Fatemeh Sepidbar , Sherif Mansour , Tehseen Zafar , Zaheen Ullah , Rabea A.M. Ali","doi":"10.1016/j.jafrearsci.2025.105927","DOIUrl":"10.1016/j.jafrearsci.2025.105927","url":null,"abstract":"<div><div>The Motaghairat layered mafic-ultramafic intrusion in the Southern Eastern Desert (SED) of Egypt is relatively metamorphosed with no evidence for tectonic contacts with country rocks. This study deals with the geology, petrography, and mineral chemistry of the Motaghairat intrusion, as one of the best examples in the SED, to shed light on its emplacement thermodynamic conditions (P, T, ƒO2) and post-magmatic processes, including metasomatic history and microscale element transferring. The ultramafic rocks comprise plagioclase-bearing peridotite (dunite, lherzolite) and wehrlite with subordinate clinopyroxenite, while the mafic ones include gabbroic rocks with subordinate hornblendite and anorthosite, showing cumulate textures. The analyzed olivine grains are compositionally homogenous with narrow Fo content ranging from 85 in dunite to 81 in olivine gabbro, where their NiO content is generally low (<0.3 wt%). Clinopyroxene is mainly diopside with subordinate augite (Wo<sub>30.76–49.21</sub>En<sub>39.53–56.81</sub>Fs<sub>4.52–19.60</sub>) and its Mg# decreases systematically from 0.92 in ultramafic rocks to 0.69 in mafic rocks. Orthopyroxene is enstatite in composition (Wo<sub>0.19 – 11.47</sub>En<sub>68.64–84.11</sub>Fs<sub>8.26–30.1</sub>) with a high Mg# (0.91) of ultramafic rocks relative to the low Mg# (0.7) of mafic ones. The mineral chemistry and back-scattered chemical mapping of coarse spinel grains reveal a marked heterogeneity with reversed chemical zoning represented by Cr-Fe-rich cores and Mg-Al-rich rims, forming Cr-spinel grains surrounded by a thin rim of Al-spinel. The occurrence of homogeneous Al-spinel (pale green) and Cr-spinel (dark brownish color) with rims of Al-spinel in ultramafic rocks suggests the formation of the former due to the interaction between spinel and melts, but the latter was formed because of a micro-scale element (Al, Mg, Cr, Fe) transfer between Cr-spinel and Al-rich silicate phases at the sub-solidus state. Some Cr-spinel grains show exsolved texture of Ti-rich ferritchromite due to subsolidus equilibration under slow cooling rates for the spinel-type solid solution. The Motaghairat mafic-ultramafic rocks fractionally crystallized from hydrous tholeiitic basaltic magma (parent melts). They are considered as a late-orogenic layered intrusion generated during the intra-arc rifting in the supra-subduction zone of the Arabian Nubian Shield. These rocks were generated in a slightly oxidizing (ΔNNO +0.03) to moderately oxidizing (ΔNNO +1.7) environment under low pressure (∼4.47 ± 0.33 kbar) and shallow depth (∼16.5 ± 1 km) conditions. Their estimated crystallization temperature shows wide ranges from ∼850 to 1200 °C (∼1000 °C on average) because of variable fractional crystallization degrees that may, in turn, result in different magmatic compositions during cooling. The occurrence of fresh dunite, wehrlite, and clinopyroxenite dykes/veins in serpentinized peridotite, along with the mineral chemist","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105927"},"PeriodicalIF":2.2,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527483","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}
Pub Date : 2025-11-08DOI: 10.1016/j.jafrearsci.2025.105913
Younes Oubaki , Papa Sagne , Said El Moussaoui , Issam Etebaai , Hajar El Talibi
Understanding the short-term morphodynamics of sandy beaches is essential for anticipating erosion risks and informing coastal management strategies, particularly in data-scarce regions like the Moroccan Mediterranean. This study investigates the seasonal morphological evolution of six representative beaches in the Bay of Al Hoceima by integrating cross-shore beach profile surveys and numerical wave modeling using SWAN (Simulating WAves Nearshore). Field data collected between summer 2022 and spring 2023 reveal significant seasonal variations in beach width and sediment volumes, with most sites exhibiting erosion during winter and partial accretion during summer. SWAN simulations, based on seasonal average wave conditions, show spatial differences in significant wave height and dominant wave direction, influenced by local bathymetry, beach orientation, and nearshore islands. These patterns align with observed sediment redistribution trends and highlight the role of local controls in modulating beach responses. The methodology provides robust insights into seasonal dynamics. Findings underscore the value of coupling morphological monitoring with wave modeling to improve understanding of sediment budgets and to support adaptive coastal planning.
{"title":"Seasonal morphodynamic evolution of the Bay of Al Hoceima (Moroccan Mediterranean Coast): Insights from SWAN modeling and beach profile monitoring","authors":"Younes Oubaki , Papa Sagne , Said El Moussaoui , Issam Etebaai , Hajar El Talibi","doi":"10.1016/j.jafrearsci.2025.105913","DOIUrl":"10.1016/j.jafrearsci.2025.105913","url":null,"abstract":"<div><div>Understanding the short-term morphodynamics of sandy beaches is essential for anticipating erosion risks and informing coastal management strategies, particularly in data-scarce regions like the Moroccan Mediterranean. This study investigates the seasonal morphological evolution of six representative beaches in the Bay of Al Hoceima by integrating cross-shore beach profile surveys and numerical wave modeling using SWAN (Simulating WAves Nearshore). Field data collected between summer 2022 and spring 2023 reveal significant seasonal variations in beach width and sediment volumes, with most sites exhibiting erosion during winter and partial accretion during summer. SWAN simulations, based on seasonal average wave conditions, show spatial differences in significant wave height and dominant wave direction, influenced by local bathymetry, beach orientation, and nearshore islands. These patterns align with observed sediment redistribution trends and highlight the role of local controls in modulating beach responses. The methodology provides robust insights into seasonal dynamics. Findings underscore the value of coupling morphological monitoring with wave modeling to improve understanding of sediment budgets and to support adaptive coastal planning.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105913"},"PeriodicalIF":2.2,"publicationDate":"2025-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577575","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}
Pub Date : 2025-11-06DOI: 10.1016/j.jafrearsci.2025.105915
Zaineb Hajjar , Isabel Fanlo , Said Ilmen , Rachida Bendaoud , Fernando Gervilla
Co-Ni-Fe-bearing arsenide ores in the Bou Azzer district (Anti-Atlas, Morocco) occur alongside serpentinite and are mainly found as contact-type ores or serpentinite-hosted ores. There is a clear zoning pattern in the contact-type ores, evolving from Ni-Co ores and Co-Ni ores filling fault-related open spaces at the serpentinite contact to Fe-Co types within the serpentinite itself. This trend is supported by drill core geochemistry. In serpentinite-hosted orebodies, the arsenide minerals are primarily Fe-Co ores, which preserve cores of Co-Fe ores.
Our key contribution is to identify the chemical evolution of the ore-forming fluid. Co and Fe enrichment facilitated the progressive transition from Ni-Co to Co-Fe ores, while subsequent Ni depletion and Fe enrichment generated the disseminated Co-Fe ores (i.e., contact-type ores). Further circulation of these ore-forming fluids through intra-serpentinite weak fault zones tends to precipitate Fe-Co ores surrounding Co-Fe ores (i.e., serpentinite-hosted ores). Critically, we show that the established west-to-east district zoning (decreasing Co, increasing Ni) is specific to contact-type ores and may be influenced by the composition of the adjacent country rock (high Ni content is related to mafic layer in the contact. Serpentinite-hosted ores in the Ait Ahmane area appear to follow this west-east zoning process.
{"title":"An overview of the Co-Ni-Fe arsenide ore zoning in the Bou Azzer mining district (Central Anti-Atlas, Morocco)","authors":"Zaineb Hajjar , Isabel Fanlo , Said Ilmen , Rachida Bendaoud , Fernando Gervilla","doi":"10.1016/j.jafrearsci.2025.105915","DOIUrl":"10.1016/j.jafrearsci.2025.105915","url":null,"abstract":"<div><div>Co-Ni-Fe-bearing arsenide ores in the Bou Azzer district (Anti-Atlas, Morocco) occur alongside serpentinite and are mainly found as contact-type ores or serpentinite-hosted ores. There is a clear zoning pattern in the contact-type ores, evolving from Ni-Co ores and Co-Ni ores filling fault-related open spaces at the serpentinite contact to Fe-Co types within the serpentinite itself. This trend is supported by drill core geochemistry. In serpentinite-hosted orebodies, the arsenide minerals are primarily Fe-Co ores, which preserve cores of Co-Fe ores.</div><div>Our key contribution is to identify the chemical evolution of the ore-forming fluid. Co and Fe enrichment facilitated the progressive transition from Ni-Co to Co-Fe ores, while subsequent Ni depletion and Fe enrichment generated the disseminated Co-Fe ores (i.e., contact-type ores). Further circulation of these ore-forming fluids through intra-serpentinite weak fault zones tends to precipitate Fe-Co ores surrounding Co-Fe ores (i.e., serpentinite-hosted ores). Critically, we show that the established west-to-east district zoning (decreasing Co, increasing Ni) is specific to contact-type ores and may be influenced by the composition of the adjacent country rock (high Ni content is related to mafic layer in the contact. Serpentinite-hosted ores in the Ait Ahmane area appear to follow this west-east zoning process.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105915"},"PeriodicalIF":2.2,"publicationDate":"2025-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527434","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}
Pub Date : 2025-11-06DOI: 10.1016/j.jafrearsci.2025.105925
Yusuf Abdullahi Abdulkarim , Abdulwahab Muhammad Bello , Khalid Al-Ramadan
This study aimed to understand the reservoir potential of the Cretaceous Bima Sandstone in the Upper Benue Trough, Nigeria, by examining its petrographic and geochemical characteristics. Our goal was to ascertain its petrofacies, provenance, and tectonic setting, and critically assess how these fundamental geological attributes impact reservoir quality. An integrated approach combining detailed petrography, major and trace element geochemistry, and various weathering indices was systematically applied to the Upper and Lower Bima units. The results indicate that the Bima Sandstone comprises predominantly subarkose and quartz arenites, with some sublitharenite, and exhibits variable mineralogical maturity. Geochemical proxies such as SiO2 (19.94–89.55), Zr (8.00 ppm–865.00 ppm), Chemical Index of Alteration (CIA, 19.00 to 97.00), and Index of Compositional Variability (ICV, 0.00 to 4.70) revealed provenance from highly weathered felsic igneous to mixed felsic-mafic sources, suggesting derivation from the continental crust under transitional to humid climates. Discrimination plots predominantly indicate a passive continental margin with a localized active continental margin influence. These geological characteristics, coupled with the depositional environment, influence the distribution and interconnectivity of porosity and permeability. The Upper Bima, with its high chemical maturity and intense weathering, shows better primary porosity (average 12.8), making it a promising hydrocarbon reservoir. Conversely, Lower Bima, with its varied provenance and lower maturity, shows higher heterogeneity and generally low porosity (average 5.5). The study has revealed the varied reservoir quality of the Bima Sandstone, which is essential for the strategic enhancement of hydrocarbon exploration and development in the Upper Benue Trough.
{"title":"Provenance, diagenesis and reservoir quality of the Aptian-Albian Bima sandstone, Upper Benue Trough, NE Nigeria","authors":"Yusuf Abdullahi Abdulkarim , Abdulwahab Muhammad Bello , Khalid Al-Ramadan","doi":"10.1016/j.jafrearsci.2025.105925","DOIUrl":"10.1016/j.jafrearsci.2025.105925","url":null,"abstract":"<div><div>This study aimed to understand the reservoir potential of the Cretaceous Bima Sandstone in the Upper Benue Trough, Nigeria, by examining its petrographic and geochemical characteristics. Our goal was to ascertain its petrofacies, provenance, and tectonic setting, and critically assess how these fundamental geological attributes impact reservoir quality. An integrated approach combining detailed petrography, major and trace element geochemistry, and various weathering indices was systematically applied to the Upper and Lower Bima units. The results indicate that the Bima Sandstone comprises predominantly subarkose and quartz arenites, with some sublitharenite, and exhibits variable mineralogical maturity. Geochemical proxies such as SiO<sub>2</sub> (19.94–89.55), Zr (8.00 ppm–865.00 ppm), Chemical Index of Alteration (CIA, 19.00 to 97.00), and Index of Compositional Variability (ICV, 0.00 to 4.70) revealed provenance from highly weathered felsic igneous to mixed felsic-mafic sources, suggesting derivation from the continental crust under transitional to humid climates. Discrimination plots predominantly indicate a passive continental margin with a localized active continental margin influence. These geological characteristics, coupled with the depositional environment, influence the distribution and interconnectivity of porosity and permeability. The Upper Bima, with its high chemical maturity and intense weathering, shows better primary porosity (average 12.8), making it a promising hydrocarbon reservoir. Conversely, Lower Bima, with its varied provenance and lower maturity, shows higher heterogeneity and generally low porosity (average 5.5). The study has revealed the varied reservoir quality of the Bima Sandstone, which is essential for the strategic enhancement of hydrocarbon exploration and development in the Upper Benue Trough.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105925"},"PeriodicalIF":2.2,"publicationDate":"2025-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527436","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}
Pub Date : 2025-11-05DOI: 10.1016/j.jafrearsci.2025.105918
Samar Ghareeb , Rami Ibrahim , Toshiaki Yokoi , Mahmoud El-Hadidy , Mohsen M. Attia , Amr El-Sharkawy , Abdelbaset M. Abudeif
Northern Egypt is a vital region for investment, tourism, and oil and gas production, hosting critical infrastructure and high-rise buildings. Despite its low-to-moderate seismic activity, assessing seismic hazard is challenging due to limited strong motion records. Ground Motion Prediction Equations (GMPEs) from tectonically similar regions are often adopted for such studies, but their predictive accuracy remains unverified for this area. This study employs theoretical rejection criteria to filter unsuitable GMPEs and evaluates 184 earthquake records from local and regional seismological networks. The GMPEs of Akkar–Sandıkkaya–Bommer (ASB14), Zhao (Zea06), and Abrahamson–Silva–Kamai (ASK14) models were selected because of the theoretical tests. The first version of Synthetic waveforms was generated and compared with the observed records by the empirical simulation methods stands for Time Series Processing Programs (TSSP), with residual analysis conducted to refine GMPE coefficients. A second version of the synthetic waveforms was obtained using the modified GMPEs. A comparison between the observed waveforms, first synthetics, and second synthetics was undertaken. The analysis determined that the Zea06 model is unsuitable for future seismic hazard assessments in Northern Egypt. However, the modified ASK14 model demonstrated superior performance in estimating seismic hazards for source-to-site distances ≤50 km, while the modified ASB14 model proved most effective for distances greater than 50 km.
埃及北部是投资、旅游和油气生产的重要地区，拥有重要的基础设施和高层建筑。尽管该地区的地震活动较低至中等，但由于强震记录有限，评估地震危险性具有挑战性。此类研究通常采用构造相似区域的地震动预测方程（GMPEs），但其预测精度尚未得到验证。本研究采用理论剔除准则对不合适的GMPEs进行筛选，并对184个来自地方和区域地震台网的地震记录进行评价。考虑到理论检验，本文选择Akkar-Sandıkkaya-Bommer （ASB14）、Zhao （Zea06）和Abrahamson-Silva-Kamai （ASK14）模型的GMPEs。利用时间序列处理程序（Time Series Processing Programs， TSSP）的经验模拟方法生成第一版的合成波形，并与观测记录进行对比，通过残差分析细化GMPE系数。利用改进的GMPEs获得了第二个版本的合成波形。对观察到的波形、第一合成波和第二合成波进行了比较。分析确定，Zea06模型不适合用于埃及北部未来的地震危险性评估。然而，改进后的ASK14模型在震源到站点距离≤50 km时表现出优越的地震危险性估计性能，而改进后的ASB14模型在震源到站点距离大于50 km时表现出最有效的效果。
{"title":"Evaluation and selection of ground motion prediction equations for seismic hazard analysis in Northern Egypt","authors":"Samar Ghareeb , Rami Ibrahim , Toshiaki Yokoi , Mahmoud El-Hadidy , Mohsen M. Attia , Amr El-Sharkawy , Abdelbaset M. Abudeif","doi":"10.1016/j.jafrearsci.2025.105918","DOIUrl":"10.1016/j.jafrearsci.2025.105918","url":null,"abstract":"<div><div>Northern Egypt is a vital region for investment, tourism, and oil and gas production, hosting critical infrastructure and high-rise buildings. Despite its low-to-moderate seismic activity, assessing seismic hazard is challenging due to limited strong motion records. Ground Motion Prediction Equations (GMPEs) from tectonically similar regions are often adopted for such studies, but their predictive accuracy remains unverified for this area. This study employs theoretical rejection criteria to filter unsuitable GMPEs and evaluates 184 earthquake records from local and regional seismological networks. The GMPEs of Akkar–Sandıkkaya–Bommer (ASB14), Zhao (Zea06), and Abrahamson–Silva–Kamai (ASK14) models were selected because of the theoretical tests. The first version of Synthetic waveforms was generated and compared with the observed records by the empirical simulation methods stands for Time Series Processing Programs (TSSP), with residual analysis conducted to refine GMPE coefficients. A second version of the synthetic waveforms was obtained using the modified GMPEs. A comparison between the observed waveforms, first synthetics, and second synthetics was undertaken. The analysis determined that the Zea06 model is unsuitable for future seismic hazard assessments in Northern Egypt. However, the modified ASK14 model demonstrated superior performance in estimating seismic hazards for source-to-site distances ≤50 km, while the modified ASB14 model proved most effective for distances greater than 50 km.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105918"},"PeriodicalIF":2.2,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145475978","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}
Pub Date : 2025-11-05DOI: 10.1016/j.jafrearsci.2025.105917
May R. ElKotby
Coastal zones are well acknowledged as the epicenters of the most serious effects of climate change (CC) and sea-level rise (SLR). These regions experience recurrent inundation of low-lying areas, heightened flood worries from storm surges and tsunamis, faster coastal erosion, and significant damage due to cyclones. In response to these escalating risks, numerous strategies have been developed for assessing and mitigating coastal vulnerability. Selecting a suitable climate adaptation plan necessitates a thorough evaluation of the effects of climate change and establishes the level of risk for different areas impacted. The Coastal Vulnerability Index (CVI) is an indispensable instrument due to its efficacy and adaptability. This article aims to review, comprehend, and analyze relevant works on the CVI to evaluate the readiness of coastal communities for CC, drawing from a total of thirty-five academic publications. Three factors set—coastal characteristics, coastal forcing, and socioeconomic factors—are utilized, entirely or partially, to promote knowledge about coastal vulnerability. Of the 35 studies that used coastal driving variables, only 17 research studies included socioeconomic characteristics.
Historically, data and information dearth were the main obstacles to comprehending vulnerability assessments. However, technological advancements like image processing, satellite remote sensing, and Geographic Information Systems (GIS) have made data collection and analysis easier. Traditional approaches to coastal vulnerability assessment have mostly focused on empirical and GIS-based methodologies; however, the CVI is expected to shift toward AI-driven, climate-responsive frameworks that use machine learning techniques such as logistic regression (LR), decision tree (DT), K-nearest neighbor (KNN), and Random Forest (RF) to improve model impartiality and forecast accuracy.
Finally, this research proved that there is no magic bullet or optimal approach for determining sensitivity and hazards in coastal areas because it depends heavily on the data's accessibility and application context.
{"title":"Progression in Coastal Vulnerability Index (CVI) approaches for assessing risk: A comprehensive review","authors":"May R. ElKotby","doi":"10.1016/j.jafrearsci.2025.105917","DOIUrl":"10.1016/j.jafrearsci.2025.105917","url":null,"abstract":"<div><div>Coastal zones are well acknowledged as the epicenters of the most serious effects of climate change (CC) and sea-level rise (SLR). These regions experience recurrent inundation of low-lying areas, heightened flood worries from storm surges and tsunamis, faster coastal erosion, and significant damage due to cyclones. In response to these escalating risks, numerous strategies have been developed for assessing and mitigating coastal vulnerability. Selecting a suitable climate adaptation plan necessitates a thorough evaluation of the effects of climate change and establishes the level of risk for different areas impacted. The Coastal Vulnerability Index (CVI) is an indispensable instrument due to its efficacy and adaptability. This article aims to review, comprehend, and analyze relevant works on the CVI to evaluate the readiness of coastal communities for CC, drawing from a total of thirty-five academic publications. Three factors set—coastal characteristics, coastal forcing, and socioeconomic factors—are utilized, entirely or partially, to promote knowledge about coastal vulnerability. Of the 35 studies that used coastal driving variables, only 17 research studies included socioeconomic characteristics.</div><div>Historically, data and information dearth were the main obstacles to comprehending vulnerability assessments. However, technological advancements like image processing, satellite remote sensing, and Geographic Information Systems (GIS) have made data collection and analysis easier. Traditional approaches to coastal vulnerability assessment have mostly focused on empirical and GIS-based methodologies; however, the CVI is expected to shift toward AI-driven, climate-responsive frameworks that use machine learning techniques such as logistic regression (LR), decision tree (DT), K-nearest neighbor (KNN), and Random Forest (RF) to improve model impartiality and forecast accuracy.</div><div>Finally, this research proved that there is no magic bullet or optimal approach for determining sensitivity and hazards in coastal areas because it depends heavily on the data's accessibility and application context.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105917"},"PeriodicalIF":2.2,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145476007","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}
Pub Date : 2025-11-05DOI: 10.1016/j.jafrearsci.2025.105916
Noomen Dkhaili , Narjes El Euch , Salwa Bey , Adnen Amiri , Rafika Ben Lasmar , Mohamed Gasmi
In the southern region of Tunisia, the depositional environments and architecture of the Silurian Acacus Formation are regarded as among the most complex in the area. To uncover the factors influencing deposition in this part of the Ghadames Basin, an integrated approach was employed utilizing core samples, well logs, and 3D seismic datasets. This study concentrates on analyzing and interpreting the Lower Member A of the Acacus Formation, which is a proven and productive, multi-layered, oil and gas clastic reservoir. The top of the Acacus A is difficult to interpret on seismic data, which also makes it harder to map its base in time and depth. As consequence, Top Tannezuft Formation was interpreted and considered as base of Acacus A reservoir. The depth map defines a progressive deepening trend from northeast to southwest, highlighting the presence of numerous potential deep, four-way closure structures that facilitate the Silurian Acacus A oil and gas accumulations. Seismic attributes were not visualized until the completion of a high-resolution sequence stratigraphic analysis, which provided reliable vertical and lateral interpretations. Numerous, repetitive, transgressive and regressive cycles, with vertical scales below the limits of seismic resolution, were identified. The interbedded shaly and sandy lithotype architecture constitutes potential stratigraphic traps for oil and gas when exhibiting favorable reservoir properties. A set of precise seismic attributes incorporating the phase and frequency components were applied to interpret the depositional history of clastic sedimentation within the Acacus A. Several notable features, onlapping, toplapping, downlapping, truncation and progradational reflection configurations, were interpreted based on the cosine of the phase attribute as potential stratigraphic traps. This analysis revealed geometries associated with deposition in a shallow marine, deltaic environment. It includes distributary channels of multiple scales and orientations, delta lobes, and tidal sandbars that are indeed some of the most porous and permeable areas in deltaic and coastal environment.
{"title":"Integrated 3D seismic and high-resolution sequence stratigraphy for the Silurian Acacus A succession and stratigraphic traps arrangement in the Ghadames Basin, southern Tunisia","authors":"Noomen Dkhaili , Narjes El Euch , Salwa Bey , Adnen Amiri , Rafika Ben Lasmar , Mohamed Gasmi","doi":"10.1016/j.jafrearsci.2025.105916","DOIUrl":"10.1016/j.jafrearsci.2025.105916","url":null,"abstract":"<div><div>In the southern region of Tunisia, the depositional environments and architecture of the Silurian Acacus Formation are regarded as among the most complex in the area. To uncover the factors influencing deposition in this part of the Ghadames Basin, an integrated approach was employed utilizing core samples, well logs, and 3D seismic datasets. This study concentrates on analyzing and interpreting the Lower Member A of the Acacus Formation, which is a proven and productive, multi-layered, oil and gas clastic reservoir. The top of the Acacus A is difficult to interpret on seismic data, which also makes it harder to map its base in time and depth. As consequence, Top Tannezuft Formation was interpreted and considered as base of Acacus A reservoir. The depth map defines a progressive deepening trend from northeast to southwest, highlighting the presence of numerous potential deep, four-way closure structures that facilitate the Silurian Acacus A oil and gas accumulations. Seismic attributes were not visualized until the completion of a high-resolution sequence stratigraphic analysis, which provided reliable vertical and lateral interpretations. Numerous, repetitive, transgressive and regressive cycles, with vertical scales below the limits of seismic resolution, were identified. The interbedded shaly and sandy lithotype architecture constitutes potential stratigraphic traps for oil and gas when exhibiting favorable reservoir properties. A set of precise seismic attributes incorporating the phase and frequency components were applied to interpret the depositional history of clastic sedimentation within the Acacus A. Several notable features, onlapping, toplapping, downlapping, truncation and progradational reflection configurations, were interpreted based on the cosine of the phase attribute as potential stratigraphic traps. This analysis revealed geometries associated with deposition in a shallow marine, deltaic environment. It includes distributary channels of multiple scales and orientations, delta lobes, and tidal sandbars that are indeed some of the most porous and permeable areas in deltaic and coastal environment.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105916"},"PeriodicalIF":2.2,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527482","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}
Pub Date : 2025-11-04DOI: 10.1016/j.jafrearsci.2025.105900
Mohammed El Azmi , Mohamed Aissa , Azizi Moussaid , Hafid Mezougane , Said Ilmen , Panagiotis Voudouris , Mohmed Aissa , Ilyasse Loudaoued , Ait Addi Mohamed , Muhammad Souiri , Ilya Prokopyev , El Haouiti Issmail , Safouane Admou , Mohamed Zouhair , Lhou Maacha
The Açdif gold deposit, recently discovered and exploited (∼100 koz) within the Zenaga inlier of the Moroccan Anti-Atlas, is located 30 km SW of Tazenakht. It is hosted by the Eburnean metamorphic rocks (mica schists and gneiss) of the southwestern part of the inlier. These crystalline rocks are intruded by the Tazenakht granite and the Azeguermerzi granodiorite. The assembly is intersected by a swarm of mafic dykes (gabbro and dolerite) of different directions. The gold mineralization is associated with a kilometric shear zone of WSW-ENE trending direction, which has recorded several phases of hydrothermal alterations and polyphase deformations (ductile, ductile-brittle, and brittle). Mineralized bodies are formed as quartz veins and veinlets with sulfides, or as disseminated sulfides (pyrite) in deformed metamorphic rocks. The mineral paragenesis consists mainly of pyrite, chalcopyrite, arsenopyrite, galena, scheelite, kupcikite, and Au-Ag alloy. The gangue is dominated by three distinct generations of quartz and late carbonates. Gold is refractory in pyrite, or free as grains in quartz. Electron Probe Microanalysis (EPMA) and LA-ICP-MS chemical analysis of trace elements in pyrite have distinguished two generations of pyrite: Pyrite I, forming the core of the crystals, rich in Au, Ag, Bi, Cu, and Pb, and pyrite II, forming the clear rim of the crystals, showing dominance of elements As, Co, and Ni. This chemical zoning of pyrites, notably their gold content, could inform on their origins and the gold depositional process (diagenetic origin for pyrite I and hydrothermal-metamorphic for pyrite II). The succession of deformation events and fluid circulation has resulted in two phases of gold enrichment in the deposit: The first phase, during the ductile-brittle transition, contributed to the liberation of invisible gold contained in pyrite I and its reconcentration in microfractures or as inclusions in pyrite II along with other mineral (chalcopyrite, galena, and kupcikite). The second enrichment phase is linked to the extensive brittle event, allowing the precipitation of a new generation of gold associated with the iron oxides filling the quartz veins. The Açdif gold deposit corresponds to an orogenic gold mineralization where trace elements in pyrites can be considered as indicators for the exploration of similar ore deposits at the regional scale and elsewhere.
{"title":"Multi-stage gold mineralization in the Açdif orogenic deposit (Zenaga inlier, central Anti-Atlas, Morocco): Constraints from LA-ICP-MS analysis of pyrites and structural controls","authors":"Mohammed El Azmi , Mohamed Aissa , Azizi Moussaid , Hafid Mezougane , Said Ilmen , Panagiotis Voudouris , Mohmed Aissa , Ilyasse Loudaoued , Ait Addi Mohamed , Muhammad Souiri , Ilya Prokopyev , El Haouiti Issmail , Safouane Admou , Mohamed Zouhair , Lhou Maacha","doi":"10.1016/j.jafrearsci.2025.105900","DOIUrl":"10.1016/j.jafrearsci.2025.105900","url":null,"abstract":"<div><div>The Açdif gold deposit, recently discovered and exploited (∼100 koz) within the Zenaga inlier of the Moroccan Anti-Atlas, is located 30 km SW of Tazenakht. It is hosted by the Eburnean metamorphic rocks (mica schists and gneiss) of the southwestern part of the inlier. These crystalline rocks are intruded by the Tazenakht granite and the Azeguermerzi granodiorite. The assembly is intersected by a swarm of mafic dykes (gabbro and dolerite) of different directions. The gold mineralization is associated with a kilometric shear zone of WSW-ENE trending direction, which has recorded several phases of hydrothermal alterations and polyphase deformations (ductile, ductile-brittle, and brittle). Mineralized bodies are formed as quartz veins and veinlets with sulfides, or as disseminated sulfides (pyrite) in deformed metamorphic rocks. The mineral paragenesis consists mainly of pyrite, chalcopyrite, arsenopyrite, galena, scheelite, kupcikite, and Au-Ag alloy. The gangue is dominated by three distinct generations of quartz and late carbonates. Gold is refractory in pyrite, or free as grains in quartz. Electron Probe Microanalysis (EPMA) and LA-ICP-MS chemical analysis of trace elements in pyrite have distinguished two generations of pyrite: Pyrite I, forming the core of the crystals, rich in Au, Ag, Bi, Cu, and Pb, and pyrite II, forming the clear rim of the crystals, showing dominance of elements As, Co, and Ni. This chemical zoning of pyrites, notably their gold content, could inform on their origins and the gold depositional process (diagenetic origin for pyrite I and hydrothermal-metamorphic for pyrite II). The succession of deformation events and fluid circulation has resulted in two phases of gold enrichment in the deposit: The first phase, during the ductile-brittle transition, contributed to the liberation of invisible gold contained in pyrite I and its reconcentration in microfractures or as inclusions in pyrite II along with other mineral (chalcopyrite, galena, and kupcikite). The second enrichment phase is linked to the extensive brittle event, allowing the precipitation of a new generation of gold associated with the iron oxides filling the quartz veins. The Açdif gold deposit corresponds to an orogenic gold mineralization where trace elements in pyrites can be considered as indicators for the exploration of similar ore deposits at the regional scale and elsewhere.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"234 ","pages":"Article 105900"},"PeriodicalIF":2.2,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621208","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}
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