Pub Date : 2026-05-01Epub Date: 2025-11-28DOI: 10.1016/j.geogeo.2025.100483
Arvind Kumar Singh , Aditya Abha Singh , Kumail Ahmad
Oxygen minimum zones (OMZ) are represented by sharply depleted oxygen concentrations in the modern ocean basins. The expansion of these zones is documented since 1960. They have been expanding globally in the world's oceans with profound implications for marine ecosystems and biogeochemical cycles. Under this review, we synthesize and integrate the current knowledge on the factors, dynamics and consequences of OMZ expansion in the modern ocean basins. We have explored the interplay of physical, chemical and biological factors conducive to OMZ formation and intensification, highlighting the role of ocean circulation patterns, nutrient enrichment from anthropogenic activities and augmenting influence of climate change. The impact of OMZs on marine ecology are explored with the focus on physiological stress on marine organisms, habitat compression, shifts in community structure and potential loss of biodiversity. We have also investigated their contribution to greenhouse gas emissions and the biogeochemical significance of OMZs, particularly in the context of nitrogen and other nutrient cycles. Further, this work emphasizes on the complex feedback loops between OMZ expansion and climate change underscoring the urgent need for mitigation and adaptation strategies. At the outset, the study discusses the future research scopes and management approaches crucial for addressing the challenges posed by expanding OMZs thereby ensuring the health and sustainability of modern ocean basins.
{"title":"Is the expansion of oxygen minimum zones impacting the health of modern ocean basins? A review","authors":"Arvind Kumar Singh , Aditya Abha Singh , Kumail Ahmad","doi":"10.1016/j.geogeo.2025.100483","DOIUrl":"10.1016/j.geogeo.2025.100483","url":null,"abstract":"<div><div>Oxygen minimum zones (OMZ) are represented by sharply depleted oxygen concentrations in the modern ocean basins. The expansion of these zones is documented since 1960. They have been expanding globally in the world's oceans with profound implications for marine ecosystems and biogeochemical cycles. Under this review, we synthesize and integrate the current knowledge on the factors, dynamics and consequences of OMZ expansion in the modern ocean basins. We have explored the interplay of physical, chemical and biological factors conducive to OMZ formation and intensification, highlighting the role of ocean circulation patterns, nutrient enrichment from anthropogenic activities and augmenting influence of climate change. The impact of OMZs on marine ecology are explored with the focus on physiological stress on marine organisms, habitat compression, shifts in community structure and potential loss of biodiversity. We have also investigated their contribution to greenhouse gas emissions and the biogeochemical significance of OMZs, particularly in the context of nitrogen and other nutrient cycles. Further, this work emphasizes on the complex feedback loops between OMZ expansion and climate change underscoring the urgent need for mitigation and adaptation strategies. At the outset, the study discusses the future research scopes and management approaches crucial for addressing the challenges posed by expanding OMZs thereby ensuring the health and sustainability of modern ocean basins.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100483"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-12-30DOI: 10.1016/j.geogeo.2025.100489
Máté Zs. Leskó , Boglárka A. Topa , Ferenc Móricz , Ferenc Kristály , Délia H. Debus-Bulátkó , Richárd Z. Papp , Tamás G. Weiszburg , József Pálfy , Tamás Vigh , Péter Majoros , Lívia Leskóné Majoros , Norbert Zajzon
The black shale-hosted manganese ore deposit of Úrkút in Hungary formed during the globally recognized Toarcian (Early Jurassic) Jenkyns Event. Although geochemical signatures of hydrothermal processes involved in the metallogenesis of manganese ores were first recognized in the 1980s, their source and geochemical characterisation remained controversial. Here, we address two key questions: (i) why economically significant manganese ore accumulation is exclusively restricted to the Úrkút and Eplény sub-basins, despite the widespread Jenkyns Event-related sedimentation across the Transdanubian Range, and (ii) what was the source of the manganese. Based on new clay mineralogical (identification of montmorillonite and beidellite with distinct formation environments), geochemical (behaviour of Fe and Mn; Co-Ni-Zn and Fe-Mn-(Co-Ni-Cu) ternary system analysis; Cd/Mo ratio), and sedimentological data (evidence for radiolarian blooms), we propose a new early-stage ore-forming model. We suggest that dissolved Fe and Mn from hot brine pools associated with the rifting of the Neotethys Ocean were transported over long distances under anoxic conditions during the Jenkyns Event. A long-lived upwelling system (from the Late Pliensbachian to Early Toarcian) caused water mixing in the Bakony basin, which triggered the precipitation of the “proto-ore” of the Úrkút and Eplény manganese ore deposits. Our results contribute to a better understanding of the manganese enrichment in the Úrkút and Eplény sub-basins, pointing to the critical interplay between global paleoenvironmental events and local depositional settings.
{"title":"Hydrothermal source and upwelling-related sedimentary accumulation: A new model for early-stage ore forming processes of the western Neotethyan lower Jurassic Úrkút manganese ore deposit","authors":"Máté Zs. Leskó , Boglárka A. Topa , Ferenc Móricz , Ferenc Kristály , Délia H. Debus-Bulátkó , Richárd Z. Papp , Tamás G. Weiszburg , József Pálfy , Tamás Vigh , Péter Majoros , Lívia Leskóné Majoros , Norbert Zajzon","doi":"10.1016/j.geogeo.2025.100489","DOIUrl":"10.1016/j.geogeo.2025.100489","url":null,"abstract":"<div><div>The black shale-hosted manganese ore deposit of Úrkút in Hungary formed during the globally recognized Toarcian (Early Jurassic) Jenkyns Event. Although geochemical signatures of hydrothermal processes involved in the metallogenesis of manganese ores were first recognized in the 1980s, their source and geochemical characterisation remained controversial. Here, we address two key questions: (i) why economically significant manganese ore accumulation is exclusively restricted to the Úrkút and Eplény sub-basins, despite the widespread Jenkyns Event-related sedimentation across the Transdanubian Range, and (ii) what was the source of the manganese. Based on new clay mineralogical (identification of montmorillonite and beidellite with distinct formation environments), geochemical (behaviour of Fe and Mn; Co-Ni-Zn and Fe-Mn-(Co-Ni-Cu) ternary system analysis; Cd/Mo ratio), and sedimentological data (evidence for radiolarian blooms), we propose a new early-stage ore-forming model. We suggest that dissolved Fe and Mn from hot brine pools associated with the rifting of the Neotethys Ocean were transported over long distances under anoxic conditions during the Jenkyns Event. A long-lived upwelling system (from the Late Pliensbachian to Early Toarcian) caused water mixing in the Bakony basin, which triggered the precipitation of the “proto-ore” of the Úrkút and Eplény manganese ore deposits. Our results contribute to a better understanding of the manganese enrichment in the Úrkút and Eplény sub-basins, pointing to the critical interplay between global paleoenvironmental events and local depositional settings.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100489"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Chittagong-Tripura Fold Belt (CTFB) is part of the active accretionary wedge of the Indo-Burman Ranges (IBR), spanning more than 100 km in width. Although the tectonic evolution and signature of active tectonics are evident from tectonogeomorphic and structural features, the assessment of active tectonics in the CTFB area—especially along the Chittagong Coastal Fault (CCF) and Kaladan Fault—remains limited. The present study attempts to comprehensively analyze fracture orientations and geomorphic features of the area to assess the level of active tectonics. The WSW-ENE generalized compressional direction, deciphered from the fracture set analysis, represents the normal component of present-day Indian Plate motion. Different morphometric parameter values of the seven watresheds in the CTFB area assign the range of the index of active tectonics (IAT): Class 1 is highly active (1.375–1.500), Class 2 is moderately active (1.501–1.875), and Class 3 is low/less active (1.876–2.250). The best-fit curves with the power-law (R2 values) for linear, exponential, logarithmic, and power functions for seven master streams from seven watersheds and sixteen other streams from four different regions reflect the relative levels of active tectonics. Overall, the western margin of the CTFB along the Frontal Thrust/CCF appears to be relatively more active than the eastern margin along the Kaladan Fault and is therefore more prone to seismic hazards.
{"title":"Quantitative assessment of active tectonics of Chittagong-Tripura Fold Belt, Bengal Basin, Bangladesh","authors":"Md. Sakawat Hossain , Mery Biswas , Md. Sharif Hossain Khan , Dilruba Yesmin Shetu , Probir Biswas , Zakia Sultana","doi":"10.1016/j.geogeo.2026.100493","DOIUrl":"10.1016/j.geogeo.2026.100493","url":null,"abstract":"<div><div>The Chittagong-Tripura Fold Belt (CTFB) is part of the active accretionary wedge of the Indo-Burman Ranges (IBR), spanning more than 100 km in width. Although the tectonic evolution and signature of active tectonics are evident from tectonogeomorphic and structural features, the assessment of active tectonics in the CTFB area—especially along the Chittagong Coastal Fault (CCF) and Kaladan Fault—remains limited. The present study attempts to comprehensively analyze fracture orientations and geomorphic features of the area to assess the level of active tectonics. The WSW-ENE generalized compressional direction, deciphered from the fracture set analysis, represents the normal component of present-day Indian Plate motion. Different morphometric parameter values of the seven watresheds in the CTFB area assign the range of the index of active tectonics (IAT): Class 1 is highly active (1.375–1.500), Class 2 is moderately active (1.501–1.875), and Class 3 is low/less active (1.876–2.250). The best-fit curves with the power-law (<em>R</em><sup>2</sup> values) for linear, exponential, logarithmic, and power functions for seven master streams from seven watersheds and sixteen other streams from four different regions reflect the relative levels of active tectonics. Overall, the western margin of the CTFB along the Frontal Thrust/CCF appears to be relatively more active than the eastern margin along the Kaladan Fault and is therefore more prone to seismic hazards.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100493"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146037328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-12-11DOI: 10.1016/j.geogeo.2025.100487
Yayat Sudrajat , Ilham Arisbaya , Lina Handayani , Karit L. Gaol , M. Maruf Mukti , Bambang Sugiarto , Syamsuddin , Bachtiar W. Mutaqin , Clément Virmoux , Franck Lavigne
Electrical resistivity tomography (ERT) is widely used for mapping subsurface conditions and is very useful for assessing geohazards. Variations in resistivity can suggest anomalies that can be linked to fault zones, or sediment layering that specifies a particular body, such as sediment-filled basins, or loose soils that are prone to earthquake amplification, liquefaction, and ground failure. This study examines two alluvial plains in West Lombok: Mataram city (the densely populated capital) and Tanjung (a coastal tourist area). Alluvial plains are especially vulnerable to geohazards because their loose, water-saturated sediments intensify seismic shaking and raise liquefaction risks during earthquakes. Our ERT models show a consistent subsurface structure: sand-dominated layers extending beyond 30 meters, topped by pumice-rich volcanic deposits. In some areas, shallow groundwater (<2 meters deep) was detected, further increasing liquefaction potential. Specific resistivity patterns match known liquefaction features, which suggest historical liquefaction had occurred in Mataram. These results emphasize the importance of combining ERT with direct methods, such as trenching and boreholes, to verify subsurface models and refine hazard assessments.
{"title":"Electrical resistivity tomography for geohazard assessment in West Lombok’s alluvial plain","authors":"Yayat Sudrajat , Ilham Arisbaya , Lina Handayani , Karit L. Gaol , M. Maruf Mukti , Bambang Sugiarto , Syamsuddin , Bachtiar W. Mutaqin , Clément Virmoux , Franck Lavigne","doi":"10.1016/j.geogeo.2025.100487","DOIUrl":"10.1016/j.geogeo.2025.100487","url":null,"abstract":"<div><div>Electrical resistivity tomography (ERT) is widely used for mapping subsurface conditions and is very useful for assessing geohazards. Variations in resistivity can suggest anomalies that can be linked to fault zones, or sediment layering that specifies a particular body, such as sediment-filled basins, or loose soils that are prone to earthquake amplification, liquefaction, and ground failure. This study examines two alluvial plains in West Lombok: Mataram city (the densely populated capital) and Tanjung (a coastal tourist area). Alluvial plains are especially vulnerable to geohazards because their loose, water-saturated sediments intensify seismic shaking and raise liquefaction risks during earthquakes. Our ERT models show a consistent subsurface structure: sand-dominated layers extending beyond 30 meters, topped by pumice-rich volcanic deposits. In some areas, shallow groundwater (<2 meters deep) was detected, further increasing liquefaction potential. Specific resistivity patterns match known liquefaction features, which suggest historical liquefaction had occurred in Mataram. These results emphasize the importance of combining ERT with direct methods, such as trenching and boreholes, to verify subsurface models and refine hazard assessments.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100487"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-21DOI: 10.1016/j.geogeo.2026.100496
Apratim Kumar Rai , Satyabrata Behera , Alok Kumar , Vivek P. Malviya
The Bundelkhand Craton, though relatively underexplored compared to other Archean cratons of India, exhibits geological and geochemical similarities with mineralised terrains globally, suggesting its potential to host economic mineralisation. In 21st-century exploration, where large geochemical datasets are available, robust statistical methods are essential to decode intricate patterns hidden within these data. This study applies R-mode factor analysis to centered log-ratio transformed stream sediment geochemical data (2808 samples, 62 elements) from the central Bundelkhand Craton to identify mineralisation-related signatures. Three key factors were extracted, explaining 52% of the total variance: (1) a lithological factor (26%) reflecting granitoid-mafic dyke assemblages, (2) a rare earth element (REE)-rare metal factor (20%) linked to potassic granitoids, and (3) a gold-bismuth-selenium factor (6%) spatially associated with shear zones. The centered log-ratio transformation effectively addressed compositional data constraints, while varimax rotation produced interpretable factors aligned with known geology. Spatial analysis revealed high-priority exploration targets, viz. REE anomalies in the south correlate with alkaline granitoids, while gold-bismuth-selenium anomalies along the Bundelkhand Tectonic Zone and Raksha Shear Zone confirm structurally controlled gold mineralisation. Scandium anomalies, coinciding with Fe-Mg-Ca-rich zones, indicate mafic-ultramafic intrusions. These findings not only validate historical gold occurrences but also reveal new critical mineral potential (Indium, Thalium and Scandium) in the craton. The study demonstrates how multivariate statistics, when integrated with geological knowledge, can transform regional geochemical data into actionable exploration targets. The methodology provides a replicable framework for assessing mineral potential in under-explored cratons, supporting India’s strategic mineral security initiatives.
{"title":"R-mode factor analysis of stream sediment geochemical data: A multivariate statistical approach for critical mineral exploration in the Bundelkhand Craton, India","authors":"Apratim Kumar Rai , Satyabrata Behera , Alok Kumar , Vivek P. Malviya","doi":"10.1016/j.geogeo.2026.100496","DOIUrl":"10.1016/j.geogeo.2026.100496","url":null,"abstract":"<div><div>The Bundelkhand Craton, though relatively underexplored compared to other Archean cratons of India, exhibits geological and geochemical similarities with mineralised terrains globally, suggesting its potential to host economic mineralisation. In 21st-century exploration, where large geochemical datasets are available, robust statistical methods are essential to decode intricate patterns hidden within these data. This study applies R-mode factor analysis to centered log-ratio transformed stream sediment geochemical data (2808 samples, 62 elements) from the central Bundelkhand Craton to identify mineralisation-related signatures. Three key factors were extracted, explaining 52% of the total variance: (1) a lithological factor (26%) reflecting granitoid-mafic dyke assemblages, (2) a rare earth element (REE)-rare metal factor (20%) linked to potassic granitoids, and (3) a gold-bismuth-selenium factor (6%) spatially associated with shear zones. The centered log-ratio transformation effectively addressed compositional data constraints, while varimax rotation produced interpretable factors aligned with known geology. Spatial analysis revealed high-priority exploration targets, viz. REE anomalies in the south correlate with alkaline granitoids, while gold-bismuth-selenium anomalies along the Bundelkhand Tectonic Zone and Raksha Shear Zone confirm structurally controlled gold mineralisation. Scandium anomalies, coinciding with Fe-Mg-Ca-rich zones, indicate mafic-ultramafic intrusions. These findings not only validate historical gold occurrences but also reveal new critical mineral potential (Indium, Thalium and Scandium) in the craton. The study demonstrates how multivariate statistics, when integrated with geological knowledge, can transform regional geochemical data into actionable exploration targets. The methodology provides a replicable framework for assessing mineral potential in under-explored cratons, supporting India’s strategic mineral security initiatives.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100496"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Developing more sophisticated as well as efficient exploration methods to identify the hidden ore bodies are necessary to meet the world wide increasing demand of mineral resources. In this regard, mineral prospectivity mapping (MPM) is crucial. This study undertakes a pioneering effort to apply and compare four machine learning (ML) models—random forest (RF), XGBoost (XGB), support vector classifier (SVC) and artificial neural network (ANN)—for gold prospectivity mapping within the Archean Dharwar Craton, India. The primary goals included the development and evaluation of these models, a systematic assessment of their comparative performance through cross-validation, feature important analysis and ultimately, production of prospectivity map. The culmination of this work is a high-resolution, combined prospectivity map, designed to produce a new prospectivity areas. Diverse geospatial data was meticulously integrated as per mineral system of the area, including geological maps, structural lineaments, geochemical, geophysical and ASTER remote sensing imagery. For model training, 79 known gold occurrences were carefully collected alongside an equal number of selected non-occurrence locations, framing the task as a supervised binary classification problem. Rigorous evaluation, employing 5-fold cross-validation and a 70:30 train-test split, confirmed the exceptional capabilities of these models. XGB and RF consistently emerged as top performers, with impressive AUC-ROC values of 0.9992 and 0.9965, respectively, coupled with high precision, recall and F1-scores and few false positives or negatives. While ANN also showed excellent performance, SVC, though strong, yielded comparatively lower metrics. A detailed feature importance analysis exhibits the positive role of Meta-Basalt, geochemical principal component 1 and Bouguer gravity anomaly and its derivative maps. Success-rate curves vividly illustrated the models' efficiency capturing over 76% of known occurrences within just 20% of the highest-ranked areas shows targeting precision. The generated combined prospectivity map, a robust synthesis from XGB, RF and ANN, based on a stringent consensus criterion validates existing knowledge and precisely delineates high-priority exploration targets, fundamentally reshaping the approach to future mineral exploration.
{"title":"Advanced machine learning based gold prospectivity mapping in the Dharwar Craton, India: A hybrid knowledge-data driven paradigm integrating ensemble and deep learning","authors":"Soumya Mitra , Saptarshi Mallick , Santu Biswas , Kshounish Patra","doi":"10.1016/j.geogeo.2025.100473","DOIUrl":"10.1016/j.geogeo.2025.100473","url":null,"abstract":"<div><div>Developing more sophisticated as well as efficient exploration methods to identify the hidden ore bodies are necessary to meet the world wide increasing demand of mineral resources. In this regard, mineral prospectivity mapping (MPM) is crucial. This study undertakes a pioneering effort to apply and compare four machine learning (ML) models—random forest (RF), XGBoost (XGB), support vector classifier (SVC) and artificial neural network (ANN)—for gold prospectivity mapping within the Archean Dharwar Craton, India. The primary goals included the development and evaluation of these models, a systematic assessment of their comparative performance through cross-validation, feature important analysis and ultimately, production of prospectivity map. The culmination of this work is a high-resolution, combined prospectivity map, designed to produce a new prospectivity areas. Diverse geospatial data was meticulously integrated as per mineral system of the area, including geological maps, structural lineaments, geochemical, geophysical and ASTER remote sensing imagery. For model training, 79 known gold occurrences were carefully collected alongside an equal number of selected non-occurrence locations, framing the task as a supervised binary classification problem. Rigorous evaluation, employing 5-fold cross-validation and a 70:30 train-test split, confirmed the exceptional capabilities of these models. XGB and RF consistently emerged as top performers, with impressive AUC-ROC values of 0.9992 and 0.9965, respectively, coupled with high precision, recall and F1-scores and few false positives or negatives. While ANN also showed excellent performance, SVC, though strong, yielded comparatively lower metrics. A detailed feature importance analysis exhibits the positive role of Meta-Basalt, geochemical principal component 1 and Bouguer gravity anomaly and its derivative maps. Success-rate curves vividly illustrated the models' efficiency capturing over 76% of known occurrences within just 20% of the highest-ranked areas shows targeting precision. The generated combined prospectivity map, a robust synthesis from XGB, RF and ANN, based on a stringent consensus criterion validates existing knowledge and precisely delineates high-priority exploration targets, fundamentally reshaping the approach to future mineral exploration.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100473"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145618442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Gouna region, located in the northern part of the Pan-African belt in Cameroon, comprises a diverse suite of granitoids, including amphibole granites, amphibole–biotite granites, biotite granites, biotite–muscovite granites, and muscovite-bearing leucogranites. Deciphering their magmatic sources and tectonic evolution is key to understanding the geodynamic framework of the Pan-African Belt, which records the transition from subduction-related to post-collisional regimes during the Neoproterozoic.
This study integrates petrographic investigations of 25 thin sections, whole-rock geochemical analyses of 13 representative samples (11 granites and 2 quartz diorites), and new Sr–Nd isotopic data to constrain the petrogenetic evolution of the Gouna granitoids. The rocks are metaluminous, calc-alkaline, and magnesian (SiO₂ = 67.55–73.15 wt%; K₂O/Na₂O < 1), characteristic of I-type granites emplaced under hydrous, oxidizing conditions. Isotopic compositions (⁸⁷Sr/⁸⁶Srᵢ = 0.7068–0.7072; εNd (540 Ma) = −4.8 to −6.2) suggest hybrid magma sources derived from a metasomatized enriched mantle with variable crustal assimilation.
Amphibole granites display weak REE fractionation ((La/Yb)n = 0.64–1.68) and pronounced negative Eu anomalies (Eu/Eu* = 0.29–0.45), whereas muscovite-bearing leucogranites are highly fractionated ((La/Yb)n = 17.30–33.71). Primitive mantle–normalized patterns show consistent negative anomalies in Nb, Ta, Ti, Pb, Sr, Y, and Hf, and enrichment in LILEs relative to HFSEs, reflecting a subduction-modified source.
The geochemical and isotopic data collectively record a polyphase magmatic evolution, marking the transition from arc-related mantle magmatism to syn- and post-collisional anatexis (600–540 Ma), and highlight progressive mantle–crust interaction during the Pan-African orogeny.
{"title":"Petrogenetic evolution of I-type granitoids in the Gouna region, Northern Cameroon: Geochemical evidence for subduction-related to post-collisional magmatism during the Pan-African orogeny","authors":"Mahamat Abakar , Jacques Wassouo Wadjou , Amadou Diguim Kepnamou , Yaya Fodoué , Jean Marcel Abate Essi , Nguihdama Dagwai , Ngounouno Isamaila","doi":"10.1016/j.geogeo.2025.100485","DOIUrl":"10.1016/j.geogeo.2025.100485","url":null,"abstract":"<div><div>The Gouna region, located in the northern part of the Pan-African belt in Cameroon, comprises a diverse suite of granitoids, including amphibole granites, amphibole–biotite granites, biotite granites, biotite–muscovite granites, and muscovite-bearing leucogranites. Deciphering their magmatic sources and tectonic evolution is key to understanding the geodynamic framework of the Pan-African Belt, which records the transition from subduction-related to post-collisional regimes during the Neoproterozoic.</div><div>This study integrates petrographic investigations of 25 thin sections, whole-rock geochemical analyses of 13 representative samples (11 granites and 2 quartz diorites), and new Sr–Nd isotopic data to constrain the petrogenetic evolution of the Gouna granitoids. The rocks are metaluminous, calc-alkaline, and magnesian (SiO₂ = 67.55–73.15 wt%; K₂O/Na₂O < 1), characteristic of I-type granites emplaced under hydrous, oxidizing conditions. Isotopic compositions (⁸⁷Sr/⁸⁶Sr<span>ᵢ</span> = 0.7068–0.7072; εNd (540 Ma) = −4.8 to −6.2) suggest hybrid magma sources derived from a metasomatized enriched mantle with variable crustal assimilation.</div><div>Amphibole granites display weak REE fractionation ((La/Yb)<sub>n</sub> = 0.64–1.68) and pronounced negative Eu anomalies (Eu/Eu* = 0.29–0.45), whereas muscovite-bearing leucogranites are highly fractionated ((La/Yb)<sub>n</sub> = 17.30–33.71). Primitive mantle–normalized patterns show consistent negative anomalies in Nb, Ta, Ti, Pb, Sr, Y, and Hf, and enrichment in LILEs relative to HFSEs, reflecting a subduction-modified source.</div><div>The geochemical and isotopic data collectively record a polyphase magmatic evolution, marking the transition from arc-related mantle magmatism to syn- and post-collisional anatexis (600–540 Ma), and highlight progressive mantle–crust interaction during the Pan-African orogeny.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100485"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-11-20DOI: 10.1016/j.geogeo.2025.100482
P.S. Kouassy Kalédjé , A. Njueya Kopa , C.G. Belinga Mboussame , Z. Mfonka , L. Kengni , J.-R. Ndam Ngoupayou
The Kadey watershed, a hydrogeochemical system in a quasi-isotropic fissured basement environment, presents distinct groundwater/surface water exchange functions. The analysis and interpretations of hydropluviometric, hydrodynamic, and hydrochemical data are used to understand these exchanges and their impact on the hydrodynamic behavior of the system. The results reveal that the watercourse and groundwater act as communicating vessels, with the direction of flow depending on the season. It also found that the river water and the groundwater predominantly originate from rain, as indicated by a principal components analysis (PCA). The first results show that the waters of the Kadey watershed are acidic (5.85 < pH < 6.17) and very weakly to weakly mineralized (18 < CE < 140 µS/cm) with two dominant facies: calcium-magnesium bicarbonate (HCO3-Ca-Mg) and the sodium-potassium bicarbonate facies (HCO3-Na-K). Several environmental factors control the quality of the waters of this basin: lithology, anthropogenic activities and climate. It is also at the origin of the noted presence of ETMs (Fe > Mn > Pb > Cr > Cu > Zn > Cd > As > CN) in the groundwaters of the locality. These insights contribute to the understanding of water exchange mechanism and have implications for the management of water resources in the Kadey watershed.
Kadey流域是一个准各向同性裂隙基底环境的水文地球化学系统，具有明显的地下水/地表水交换功能。通过分析和解释水雨量学、水动力学和水化学数据来了解这些交换及其对系统水动力学行为的影响。结果表明，河道和地下水在不同季节的流动方向上起着沟通的作用。通过主成分分析（PCA）还发现，河水和地下水主要来源于雨水。第一个结果表明，Kadey流域水体呈酸性（5.85 < pH < 6.17），呈极弱至弱矿化（18 < CE < 140µS/cm），具有两种优势相：碳酸氢钙镁相（HCO3-Ca-Mg）和碳酸氢钠钾相（HCO3-Na-K）。几个环境因素控制着这个盆地的水质：岩性、人为活动和气候。这也是当地地下水中显著存在的ETMs （Fe > Mn > Pb > Cr > Cu > Zn > Cd > As >； CN）的起源。这些见解有助于理解水交换机制，并对Kadey流域的水资源管理具有启示意义。
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Pub Date : 2026-05-01Epub Date: 2025-11-20DOI: 10.1016/j.geogeo.2025.100481
Adinda Maharani , Rima Rachmayani , Adnya P.P. Pratiwi , Zulfikar Kartadimaja , Mutiara R. Putri , Ivonne M. Radjawane , Susanna Nurdjaman , Lamona I. Bernawis , Suliskania Nurfitri
Coral reefs are vital indicators of past oceanic conditions due to their ability to record environmental changes in their calcium carbonate structures. Specifically, the strontium-to-calcium ratio (Sr/Ca) in coral skeletons serves as a reliable proxy for reconstructing SST over time. The purpose of this study is to evaluate the similarity between sea surface temperature (SST) variability simulated by climate models and actual observations. The study utilized a comprehensive dataset that integrates satellite-derived SST observations and Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations with coral Sr/Ca records from three locations in Indonesia: Gili Selang, Kupang, and Nusa Penida. Based on the result, CCSM4 is the model with high robustness for simulation the sea surface temperature variability in Indonesia. CCSM4 has a higher correlation than other models when comparing data SST with OISST satellite and Sr/Ca record, whose correlation values are 0.7 and 0.32. The phases of ENSO and IOD exhibit a weak relationship with sea surface temperature (SST) distribution in the Indonesian region, as indicated by the low correlation values in the spatial correlation maps with CCSM4. These low correlation values suggest that the ENSO and IOD phenomena have a minimal impact on SST variability over Indonesia, as simulated by the CCSM4 model. The correlation coefficients between CCSM4 SST and the Niño index and Dipole Mode Index (DMI) during the two periods range from -0.213 to 0.055. Moreover, CCSM4 often simulates SST responses that are opposite to the expected effects of ENSO and IOD phases. These results indicate that, despite its relative strength among CMIP5 models, CCSM4 still lacks sufficient accuracy in reproducing the regional impacts of ENSO and IOD on SST variability in the Indonesian seas.
{"title":"Integrating satellite observations, coral Sr/Ca proxies, and model simulations to analyze sea surface temperature variability (1915-2003) in Indonesia","authors":"Adinda Maharani , Rima Rachmayani , Adnya P.P. Pratiwi , Zulfikar Kartadimaja , Mutiara R. Putri , Ivonne M. Radjawane , Susanna Nurdjaman , Lamona I. Bernawis , Suliskania Nurfitri","doi":"10.1016/j.geogeo.2025.100481","DOIUrl":"10.1016/j.geogeo.2025.100481","url":null,"abstract":"<div><div>Coral reefs are vital indicators of past oceanic conditions due to their ability to record environmental changes in their calcium carbonate structures. Specifically, the strontium-to-calcium ratio (Sr/Ca) in coral skeletons serves as a reliable proxy for reconstructing SST over time. The purpose of this study is to evaluate the similarity between sea surface temperature (SST) variability simulated by climate models and actual observations. The study utilized a comprehensive dataset that integrates satellite-derived SST observations and Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations with coral Sr/Ca records from three locations in Indonesia: Gili Selang, Kupang, and Nusa Penida. Based on the result, CCSM4 is the model with high robustness for simulation the sea surface temperature variability in Indonesia. CCSM4 has a higher correlation than other models when comparing data SST with OISST satellite and Sr/Ca record, whose correlation values are 0.7 and 0.32. The phases of ENSO and IOD exhibit a weak relationship with sea surface temperature (SST) distribution in the Indonesian region, as indicated by the low correlation values in the spatial correlation maps with CCSM4. These low correlation values suggest that the ENSO and IOD phenomena have a minimal impact on SST variability over Indonesia, as simulated by the CCSM4 model. The correlation coefficients between CCSM4 SST and the Niño index and Dipole Mode Index (DMI) during the two periods range from -0.213 to 0.055. Moreover, CCSM4 often simulates SST responses that are opposite to the expected effects of ENSO and IOD phases. These results indicate that, despite its relative strength among CMIP5 models, CCSM4 still lacks sufficient accuracy in reproducing the regional impacts of ENSO and IOD on SST variability in the Indonesian seas.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100481"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-11-20DOI: 10.1016/j.geogeo.2025.100480
Rima Rachmayani , Nabilah Shafira Milennianti
Climate change and steric variables influence sea level rise in the modern era. This study used the Community Climate System Model version 4 (CCSM4) to compare sea surface temperature (SST) and sea level height (SSH) in Indonesia during the mid-Holocene (MH), pre-industrial (PI), and future periods in 2300 with Representative Concentration Pathways 8.5 (RCP8.5). The results show that the average SST value is lower in the MH, with a change in values of around −1°C in the MAM season and increases in the future by around 2°C, whereas the average SSH value is lower in the MH with a change in values of around −0.1 m during the SON season in Western Sumatra and increases in the future over the SON season by around 0.1 m in Northern Papua, compared to PI. The average correlation between the two metrics is positive, with values of 0.55 (MH-PI) and 0.8 (RCP8.5-PI). SST and SSH climatological patterns in Western Sumatra, the Banda Sea, and Northern Papua reveal that SST and SSH fall during the JJA season and increase during the SON season, respectively. This fluctuation is produced by either a lag in insolation or the winter remnant effect. Signal analysis with Fourier transform reveals that the major signal spectrum for changes in SST and SSH is contributed by annual and semi-annual periodicity in the three regions. A notable interannual periodicity exists; however, it is not predominant, leading to variable interannual influences on SST and SSH in Indonesia.
{"title":"Astronomical and greenhouse gas configuration from past to future simulation: An analysis of sea surface temperature's impact on sea levels in Indonesia","authors":"Rima Rachmayani , Nabilah Shafira Milennianti","doi":"10.1016/j.geogeo.2025.100480","DOIUrl":"10.1016/j.geogeo.2025.100480","url":null,"abstract":"<div><div>Climate change and steric variables influence sea level rise in the modern era. This study used the Community Climate System Model version 4 (CCSM4) to compare sea surface temperature (SST) and sea level height (SSH) in Indonesia during the mid-Holocene (MH), pre-industrial (PI), and future periods in 2300 with Representative Concentration Pathways 8.5 (RCP8.5). The results show that the average SST value is lower in the MH, with a change in values of around −1°C in the MAM season and increases in the future by around 2°C, whereas the average SSH value is lower in the MH with a change in values of around −0.1 m during the SON season in Western Sumatra and increases in the future over the SON season by around 0.1 m in Northern Papua, compared to PI. The average correlation between the two metrics is positive, with values of 0.55 (MH-PI) and 0.8 (RCP8.5-PI). SST and SSH climatological patterns in Western Sumatra, the Banda Sea, and Northern Papua reveal that SST and SSH fall during the JJA season and increase during the SON season, respectively. This fluctuation is produced by either a lag in insolation or the winter remnant effect. Signal analysis with Fourier transform reveals that the major signal spectrum for changes in SST and SSH is contributed by annual and semi-annual periodicity in the three regions. A notable interannual periodicity exists; however, it is not predominant, leading to variable interannual influences on SST and SSH in Indonesia.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"5 2","pages":"Article 100480"},"PeriodicalIF":0.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146037327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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