Journal of African Earth Sciences最新文献_第8页

Spatiotemporal analysis of mining-induced land use and land cover changes in Zvishavane District of Zimbabwe 津巴布韦Zvishavane地区采矿引起的土地利用和土地覆盖变化的时空分析

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-25 DOI: 10.1016/j.jafrearsci.2025.105938

Elvis Batsirai Gumbo, Mark Makomborero Matsa, Pedzisai Kowe, John Hove

Chrome mining plays a pivotal role in the local economy of Mhondongori Ward 5 and Mapirimira Ward 6 of Zvishavane District. However, it has also emerged as a dominant driver of land degradation in these mineral-rich rural communities. Despite the growing concern over environmental degradation, a gap persists in systematically quantifying mining footprints using remote sensing and GIS tools in Zimbabwe's rural areas. This study addresses the gap by integrating supervised classification of Landsat 5 Thematic Mapper (TM) and Landsat 8/9 Operational Land Imager (OLI) data using the Support Vector Machine (SVM) and Normalized Difference Vegetation Index (NDVI) time-series analysis in ArcMap 10.5. Further, the Binary Logistic Regression (BLR) was done using IBM Statistical Package for Social Sciences 25.0 (IBM SPSS 25.0) to evaluate land degradation extent and intensity. The analysis investigates the spatiotemporal patterns of mining-induced land use land cover (LULC) changes in these wards of Zvishavane District from 2000 to 2024 using geospatial techniques. Results reveal a dual transformation with spatial expansion and ecological entrenchment of chrome mining, prominent between 2000 and 2013 with continued consolidation up to 2024. Mining land increased from 0.2 km² to 1.8 km² whilst bareland and forest areas declined by 3.4 km² and 7.7 km², respectively. NDVI analysis consistently indicates lower vegetation health in mining zones compared to control areas with peak degradation observed post-2013. Regression outputs confirm mining as a more significant driver of land degradation than cultivation which is largely reactive and driven by survival needs. The study concludes that mining-induced land changes are non-cyclical and structurally displace traditional land uses, undermining ecological resilience and local livelihoods. It advocates for integrative land use planning frameworks that combine geospatial monitoring, socio-ecological restoration and inclusive governance to support Zimbabwe's land degradation neutrality and achievement of socio-ecological related sustainable development goals.

铬矿开采在Zvishavane区的Mhondongori第5区和Mapirimira第6区当地经济中起着关键作用。然而，它也成为这些矿产丰富的农村社区土地退化的主要驱动因素。尽管人们日益关注环境退化问题，但在使用遥感和地理信息系统工具系统地量化津巴布韦农村地区的采矿足迹方面仍然存在差距。本研究利用arcmap10.5中支持向量机（SVM）和归一化植被指数（NDVI）时间序列分析，将Landsat 5 Thematic Mapper （TM）和Landsat 8/9 Operational Land Imager （OLI）数据进行监督分类，解决了这一问题。利用IBM SPSS 25.0 （IBM Statistical Package for Social Sciences 25.0）对土地退化程度和强度进行二元Logistic回归（BLR）评价。利用地理空间分析方法，研究了2000 - 2024年兹维沙瓦内地区采矿业土地利用和土地覆被变化的时空格局。研究结果表明：2000 - 2013年，中国铬矿开采呈现空间扩张和生态堑沟化的双重转型特征，并持续巩固至2024年。矿区用地从0.2 km2增加到1.8 km2，裸地和林地面积分别减少了3.4 km2和7.7 km2。NDVI分析一致表明，与对照区相比，矿区植被健康状况较差，2013年后出现退化高峰。回归结果证实，采矿是比耕作更重要的土地退化驱动因素，而耕作主要是被动的，受生存需要驱动。该研究的结论是，采矿引起的土地变化是非周期性的，并且在结构上取代了传统的土地利用方式，破坏了生态恢复能力和当地生计。它倡导综合土地利用规划框架，将地理空间监测、社会生态恢复和包容性治理结合起来，以支持津巴布韦的土地退化中性和实现与社会生态相关的可持续发展目标。

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引用次数: 0

Tectono-sedimentary evolution of early syn-rift deposits in a hangingwall dip-slope setting, northern Duwi half-graben, red sea, Egypt 埃及红海Duwi半地堑北部上壁倾坡背景下早期同裂谷沉积的构造-沉积演化

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-25 DOI: 10.1016/j.jafrearsci.2025.105943

Tawfeek Mahran, Reham Youssef

Studies comprehensively characterizing early syn-rift continental sedimentation in hangingwall settings are limited. To improve our understanding of how these deposits evolved, we must investigate the growth faults and related folds during rift-initiation. These structures significantly influenced the development of early syn-rift stratigraphic sequences along the strike and down the dip-slope. This study examines the stratal arrangement and sedimentology of the Late Oligocene-Early Miocene syn-rift lacustrine succession, which is consistently exposed along the hangingwall dip-slope strike in the northern Duwi half-graben sub-basin in the Red Sea Rift, Egypt. Detailed field-based description supported by petrographic investigations of the early syn-rift rocks enabled the discrimination of eight subassociations types that form three distinctive genetically-related facies associations deposited primarily in distal fluvial to lacustrine/palustrine carbonate-dominated environments. From a sequence stratigraphic perspective, three unconformity-bounded depositional sequences (DSQ-1, DSQ-2, and DSQ-3) have been identified, representing three successive phases of carbonate lake development. These sequences reflect transgressive-regressive cycles that record a major transition from open, shallow-lacustrine carbonate to fluvio-lacustrine carbonate, culminating in restricted lacustrine carbonate deposits. This study documents the interplay between hangingwall dip-slope tilting associated with growth segmented NW-SE-trending fault system, paleoclimate and provenance, proposing a new tectono-sedimentological model for rift initiation. The results of study have implications for other hangingwall dip-slopes in the Red Sea rift sub-basins.

全面表征上盘背景下早期同裂谷陆相沉积的研究十分有限。为了更好地了解这些沉积是如何演化的，我们必须研究裂谷起裂过程中的生长断层和相关褶皱。这些构造对早期同裂谷层序的发育有重要影响。本文研究了埃及红海裂谷北部Duwi半地堑次盆地沿上壁倾坡走向连续出露的晚渐新世—早中新世同裂谷湖泊序列的地层排列和沉积学。通过对早期同裂谷岩的岩石学研究，详细的野外描述可以区分出8种亚组合类型，这些亚组合形成了3种不同的遗传相关相组合，主要沉积在远端河流到湖/滩碳酸盐岩为主的环境中。从层序地层学角度，确定了3个不整合沉积层序（DSQ-1、DSQ-2和DSQ-3），代表了碳酸盐岩湖泊发育的3个连续阶段。这些层序反映了海侵-退回旋回，记录了从开放的浅湖相碳酸盐岩到河流湖相碳酸盐岩的主要转变，最终形成了局限的湖相碳酸盐岩矿床。研究记录了与nw -se向分段断裂系统生长相关的上盘倾斜与古气候、物源等因素的相互作用，提出了一种新的构造-沉积学裂谷起裂模式。研究结果对红海裂谷次盆地其他上盘倾坡具有指导意义。

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引用次数: 0

Fluoride distribution in volcanic rocks of the Aluto volcano complex, Main Ethiopian Rift 埃塞俄比亚主要裂谷Aluto火山杂岩中氟化物的分布

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-25 DOI: 10.1016/j.jafrearsci.2025.105946

Lioba Virchow , Franziska Wilke , Gezahegn Yirgu , Thomas Neumann , Simona Regenspurg

High fluoride in groundwaters of the Main Ethiopian Rift is of geogenic origin. Although the involvement of volcanic rocks in fluoride enrichment is well documented, the specific mineralogical sources and dissolution mechanisms remain incompletely understood. This study characterized the mineralogical sources of fluoride in volcanic rocks of the Aluto volcano complex, identifying the specific mineral phases and their fluoride concentration that control fluoride availability in volcanic aquifer systems. Pyrohydrolysis was employed for precise fluoride determination, while X-ray fluorescence and electron microprobe analyses enabled phase-specific fluoride distribution and quantification of fluoride-bearing minerals. Water-rock leaching experiments were performed to quantify fluoride release and characterize associated ion dissolution patterns for mineral phase identification. The study shows that: (1) The younger volcanic deposits like pumice and obsidian generally contain high fluoride concentrations of up to 0.32 wt%, while the older ignimbrites show lower concentrations between 0.11 and 0.15 wt%. (2) Fluoride behaves as an incompatible element in the post-caldera rocks showing strong linear correlations with other incompatible elements such as Zr, Nb, and Y (R² > 0.98). (3) Microprobe analyses of thin sections indicate that fluoride is incorporated into the glassy rock matrix, into apatite, and into the sodium amphibole riebeckite (the latter two occur only as accessory minerals). Mass calculations reveal that the largest proportion of fluoride is bound in the fine-grained matrix, as this phase represents 40 to 100 wt% of each rock sample. Thus, volcanic glass – particularly pumice – and glass-rich rocks have the highest potential to release fluoride, indicating that this phase controls fluoride availability in the rift groundwater system.

埃塞俄比亚主裂谷地下水中的高氟化物是地质成因的。虽然火山岩在氟化物富集中的作用已得到充分的记载，但具体的矿物学来源和溶解机制仍不完全清楚。本研究对Aluto火山杂岩中氟化物的矿物学来源进行了表征，确定了控制火山含水层系统中氟化物有效性的特定矿物相及其氟化物浓度。采用热解水解法精确测定氟化物，而x射线荧光和电子探针分析则实现了含氟矿物的相特异性氟化物分布和定量。进行了水岩浸出实验，以量化氟化物释放并表征矿物相鉴定的相关离子溶解模式。研究表明：(1)较年轻的火山沉积物如浮石和黑曜岩一般含有较高的氟化物浓度，最高可达0.32 wt%，而较老的火成岩的氟化物浓度较低，在0.11 ~ 0.15 wt%之间。(2)氟化物在破火山口后岩石中表现为不相容元素，与其他不相容元素如Zr、Nb、Y表现出较强的线性相关性（R2 > 0.98）。(3)薄片显微探针分析表明，氟化物被掺入玻璃状岩石基质、磷灰石和钠角闪石中（后两者仅作为辅助矿物出现）。质量计算表明，最大比例的氟化物被束缚在细粒基质中，因为这一阶段占每个岩石样品的40%至100%。因此，火山玻璃-特别是浮石-和富含玻璃的岩石释放氟化物的潜力最大，表明这一阶段控制着裂谷地下水系统中氟化物的可用性。

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引用次数: 0

Mineralogical and morphological characteristics of Mn oxide phases in terrestrial ferromanganese deposits: A case study of wad and nodules from the Highveld region, North-West Province of South Africa 陆相锰铁矿床中锰氧化物相的矿物学和形态特征：以南非西北省Highveld地区的块状和结核为例

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-24 DOI: 10.1016/j.jafrearsci.2025.105945

Benedict Kinshasa Pharoe , Irina Mikhailovna Gembitskaya , Alexandr Nikolaevich Evdokimov , Natalia Ivanovna Vorontsova , Christopher Baiyegunhi , Sergei Alexandrovich Voropaev

Fe-Mn nodules and crusts in terrestrial environments are predominantly associated with well-developed lateritic soil profiles. In this study, we report on the mineralogical and chemical characteristics of terrestrial Fe-Mn nodules from the North-West Manganese Deposit in South Africa. The primary objective is to characterize mineral associations, ore paragenetic sequences, morphologies, formation conditions, and chemical composition, with particular emphasis on the composition of Mn and strategic metals (i.e., Ni, Co, Cu, Ba, etc.). The distribution of these metals and their respective Mn oxide host phases was evaluated. To achieve the study's objectives, an integrated analytical approach using optical microscopy, High-Resolution Scanning Electron Microscopy with Energy-Dispersive Spectroscopy, X-ray Powder Diffraction, and Inductively Coupled Plasma Mass Spectrometry was used to investigate the ore micro-morphologies, microstructural textures, and modes of mineral occurrences and associations. Based on microscopic examinations and analytical data, Fe–Mn nodules display characteristic ore textures and morphologies, including botryoidal, colloform banding, and dendritic to radial-acicular forms, typical of cryptomelane, romanechite, hollandite, and lithiophorite. The gangue assemblage comprises detrital quartz and clay mica, which are mainly associated with early Mn oxide phases, whereas detrital zircon and ilmenite are confined to the clay-rich matrix. Lithiophorite was identified as the main host for Ni, Cu, and Co. Ba enrichment is associated with romanechite, while Nb and Ti are associated with ilmenite grains. The ore mineral paragenetic sequence revealed manganite and vernadite as the early phases to precipitate, followed by pyrolusite, cryptomelane, and romanechite, with lithiophorite representing the latest stage of mineragenesis. The presence of distinct Ce and Eu anomalies suggests that Fe-Mn nodules were formed through hydrogenetic processes.

陆地环境中的铁锰结核和结壳主要与发育良好的红土剖面有关。本文报道了南非西北锰矿陆相铁锰结核的矿物学和化学特征。主要目标是描述矿物组合、矿石共生序列、形态、形成条件和化学组成，特别强调锰和战略金属（即镍、钴、铜、钡等）的组成。对这些金属及其各自的锰氧化物宿主相的分布进行了评价。为了实现研究目标，利用光学显微镜、带能量色散光谱的高分辨率扫描电子显微镜、x射线粉末衍射和电感耦合等离子体质谱等综合分析方法，研究了矿石的微观形态、微观结构纹理以及矿物赋存和组合模式。根据显微检查和分析数据，Fe-Mn结核显示出典型的矿石结构和形态，包括矿体状、胶状带状、枝状到放射状针状，典型的隐黑石、罗马石、荷兰石和石斛石。脉石组合包括碎屑石英和粘土云母，主要与早期氧化锰相有关，而碎屑锆石和钛铁矿则局限于富粘土基质中。镍、铜、钴主要富集于石斑岩中，Ba富集于菱铁矿中，铌、钛富集于钛铁矿中。矿石矿物共生序列显示，锰矿和铅锌矿为早期沉淀阶段，其次为软锰矿、隐锰矿和菱镁矿，而石斑岩为最晚成矿阶段。明显的Ce和Eu异常表明铁锰结核是通过氢作用形成的。

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引用次数: 0

Post-Variscan Ore occurrence from the Middle Atlas of Morocco: An example of Riedel brittle shear-related lead-rich sulfide veins 摩洛哥中阿特拉斯地区后variscan矿床：与Riedel脆性剪切相关的富铅硫化物矿脉实例

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-21 DOI: 10.1016/j.jafrearsci.2025.105914

Ayoub Aabi , Abdellatif Aarab , Mohammed Amine Nguidi , Youness Ahmed Laaziz , Abdellah Nait Bba , Younes Hejja , Samir Samaoui , Abdelhakim Jilali , Lahssen Baidder

The Tizi n'Oubadou ore occurrence, studied here for the first time, is hosted within the lower Liassic limestones of the Imouzzer-Marmoucha syncline located in the central part of the Middle Atlas belt (Morocco). Mineralization is generally lead-bearing, hosted either in calcite bodies and/or directly embedded in the hosting rocks. In this study, we propose an integrated approach that combines portable X-ray fluorescence (pXRF) geochemistry, electrical resistivity tomography (ERT), and field-based structural analysis to assess the geometric and depth features of mineralized structures and gain insights into their tectonic control. Structural mapping depicts a network of mineralized sulfide veins and veinlets sheltered within NNW-SSE to NNE-SSW dextral oblique-slip faults which acted as a P-brittle/Riedel shear, i.e., Filon Principal, locally displaying a horsetail splay pattern. The mineralization in multi-scale veins is organized en-echelon with a particular tension gash or pull-apart geometry. These structures appear to be associated with the Tizi n'Oubadou dextral strike-slip fault, which is interpreted as R′-Riedel brittle-shear and hints at a WSW-ENE shortening direction, previously linked regionally to ante-Cretaceous deformation. pXRF spectroscopy analyses reveal a Pb-dominated paragenesis (i.e., galena) with variable Mn, V, and Cd enrichments, reflecting hydrothermal alteration and interaction with the carbonate-argillaceous host rocks. ERT geophysical data show that Lead-sulfide bodies are concentrated beyond 26 m depth, suggesting promising economic potential.

本文首次研究的Tizi n'Oubadou矿床赋存于中阿特拉斯带（摩洛哥）中部Imouzzer-Marmoucha向斜的下叠统灰岩中。矿化通常是含铅的，要么赋存于方解石体中，要么直接嵌套在赋存岩中。在这项研究中，我们提出了一种综合方法，将便携式x射线荧光（pXRF）地球化学、电阻率层析成像（ERT）和基于现场的构造分析相结合，以评估矿化构造的几何和深度特征，并深入了解其构造控制作用。构造图描绘了在NNW-SSE至NNE-SSW右斜滑断层中隐藏的矿化硫化物脉和脉网络，该断层作为p -脆性/Riedel剪切，即Filon Principal，局部显示马尾状展布模式。多尺度脉体的矿化以特定的张拉裂隙或拉分几何形状呈阶梯式组织。这些构造可能与Tizi n' oubadou右走滑断层有关，该断层被解释为R ' -Riedel脆性剪切，暗示了WSW-ENE缩短方向，之前与区域前白垩纪变形有关。pXRF光谱分析显示，该矿床为铅矿共生（方铅矿），锰、钒、镉富集程度不同，反映了热液蚀变及其与碳酸盐-泥质宿主岩的相互作用。ERT地球物理数据显示，铅化物矿体集中在26 m深度以下，具有良好的经济潜力。

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引用次数: 0

An evaluation of spatial and temporal variations of land surface temperature in Biskra, Algeria using remote sensing and GIS 利用遥感和GIS对阿尔及利亚比斯克拉地表温度时空变化的评价

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-21 DOI: 10.1016/j.jafrearsci.2025.105942

Zohra Abdelkrim , Saeid Eslamian

Urban heat stress in semi-arid Algerian cities, such as Biskra, remains insufficiently studied. Investigating its spatial and temporal dynamics through integrated RS and GIS approaches is crucial for advancing sustainable urban planning and climate adaptation strategies.

This study aims to analyze the spatial and temporal variations in land surface temperature (LST) between 2011 and 2022 in Biskra, Algeria, using Remote Sensing (RS) and Geographic Information Systems (GIS) techniques. It further seeks to identify the zones most affected by elevated LST and to examine their relationship with vegetation, built-up, and water indices (NDVI, NDBI, NDWI).

The results reveal significant seasonal and decadal variations in land surface temperature (LST). During the summer months, LST exceeded 45 °C in several urban zones, reflecting strong heat accumulation and limited vegetation cover. In contrast, cooler months recorded temperatures below 20 °C, associated with higher vegetation and water presence, indicating improved ecological quality. Overall, the findings highlight how urban expansion and seasonal variability have intensified heat stress and degraded environmental conditions in Biskra semi-arid context.

The analysis reveals marked seasonal and decadal variations in urban heat across Biskra, with higher LST, intensified Surface Urban Heat Island (SUHI), and lower Urban Thermal Field Variance Index (UTFVI) values indicating pronounced heat stress and reduced ecological quality during summer, contrasted by cooler and more balanced conditions in other seasons. These results emphasize the impact of urban expansion and seasonal variability on thermal stress and the vulnerability of Biskra urban environment, highlighting the need for vegetation-oriented and sustainable urban planning. Future research should employ higher-resolution data and predictive modeling to better understand urban thermal dynamics under climate change.

在半干旱的阿尔及利亚城市，如比斯克拉，城市热应激仍然没有得到充分的研究。通过综合遥感和地理信息系统方法研究其时空动态对于推进可持续城市规划和气候适应战略至关重要。利用遥感（RS）和地理信息系统（GIS）技术，对阿尔及利亚比斯克拉2011 - 2022年的地表温度（LST）时空变化进行了分析。它进一步寻求确定受地表温度升高影响最大的区域，并研究它们与植被、建筑和水指数（NDVI、NDBI、NDWI）的关系。结果显示地表温度具有显著的季节和年代际变化。夏季，部分城区地表温度超过45℃，反映了强烈的热量积累和有限的植被覆盖。相比之下，较冷的月份记录的温度低于20°C，与植被和水的增加有关，表明生态质量得到改善。总体而言，研究结果强调了城市扩张和季节变化如何加剧了比斯克拉半干旱地区的热应激和环境条件退化。分析表明，整个比斯卡拉地区的城市热量存在明显的季节和年代际变化，地表温度较高，地表城市热岛（SUHI）加剧，城市热场方差指数（UTFVI）值较低，表明夏季热应激明显，生态质量下降，而其他季节则较为凉爽和平衡。这些结果强调了城市扩张和季节变化对比斯克拉城市环境热应力和脆弱性的影响，强调了以植被为导向和可持续的城市规划的必要性。未来的研究应采用更高分辨率的数据和预测模型来更好地理解气候变化下的城市热动力学。

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引用次数: 0

Insights into L4 ordinary chondrites from the Gueltat Zemmour fall, Morocco: Modal mineralogy, chondrule characteristics, and magnetic signatures 对来自摩洛哥Gueltat Zemmour陨落的L4普通球粒陨石的洞察：模态矿物学、球粒特征和磁特征

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-21 DOI: 10.1016/j.jafrearsci.2025.105944

E. El Hachimi , H. Chennaoui Aoudjehane , S. Russell , B. Devouard , J. Gattacceca

The Gueltat Zemmour meteorite, an L4 ordinary chondrite that fell in southern Morocco on 21 August 2018, was investigated through petrographic, mineralogical, geochemical, and magnetic analyses. X-ray diffraction indicates a modal composition dominated by forsteritic olivine (39.7(4) weight %), enstatite (32.4(3) %), plagioclase (7.3(1) %), troilite (3.7(1) %), and Fe–Ni metal phases (16.9 %, kamacite-dominated). Chondrules represent ∼82 % of the surface area, with porphyritic olivine–pyroxene and porphyritic olivine as the dominant types, and an average diameter of ∼500 μm. Gamma spectrometry confirmed the presence of short-lived cosmogenic radionuclides (e.g., ⁷Be, ²²Na, ²⁶Al, ⁴⁸V), with a ²²Na/²⁶Al activity ratio consistent with a recent fall. Magnetic hysteresis properties and the preservation of tetrataenite in cloudy zone textures indicate slow cooling during parent-body metamorphism. The sulfide assemblage, dominated by troilite with rare pentlandite, combined with Fe/S (∼0.98) and Fe_ox/Si (∼0.36) ratios, reflects reducing redox conditions near the iron–wüstite buffer and minimal secondary alteration. These integrated results confirm the classification of Gueltat Zemmour as an equilibrated L4 chondrite and provide new insights into the thermal history and redox state of L-group parent bodies, contributing to a broader understanding of the early evolution of ordinary chondrites.

Gueltat Zemmour陨石是一颗L4级普通球粒陨石，于2018年8月21日落在摩洛哥南部，研究人员通过岩石学、矿物学、地球化学和磁分析对其进行了研究。x射线衍射表明其模态组成主要为橄榄石（39.7(4)%）、顽辉石（32.4(3)%）、斜长石（7.3(1)%）、三辉石（3.7(1)%）和Fe-Ni金属相（16.9%，以卡马长石为主）。球粒占表面积的约82%，以斑状橄榄石-辉石和斑状橄榄石为主，平均直径约为~ 500 μm。伽马能谱法证实了短寿命宇宙生成放射性核素的存在（例如，7Be, 22Na, 26Al, 48V）， 22Na/26Al的活度比与最近的下降相一致。磁滞特性和浑浊带织构中四长石的保存表明在母体变质过程中冷却缓慢。硫化物组合以三黄铁矿和稀有镍黄铁矿为主，结合Fe/S（~ 0.98）和Fe_ox/Si（~ 0.36）比值，反映了铁-钨钛矿缓冲带附近的还原氧化还原条件和最小的次生蚀变。这些综合结果证实了Gueltat Zemmour为平衡L4球粒陨石的分类，并为l群母体的热历史和氧化还原状态提供了新的见解，有助于更广泛地了解普通球粒陨石的早期演化。

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引用次数: 0

Magnetic signatures and modeling of the Late Ediacaran dyke swarm in the central Saghro massif (Eastern Anti-Atlas, Morocco) 摩洛哥东部阿特拉斯东部Saghro地块中部晚埃迪卡拉世岩脉群的磁特征与模拟

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-19 DOI: 10.1016/j.jafrearsci.2025.105937

Ahmed Baamar , Ezzoura Errami , Brahim Karaoui , Mourad Essalhi , Mostapha Bouzekraoui , Mourad Guernouche , Said Haidatte , Abderrahman Ben Ichou , Zakarya Yajioui , Hasna Er-raqqady

The Central Part of the Saghro massif (CPSM), located in the Eastern Anti-Atlas, is characterized by a significant dyke swarm. These dykes remain insufficiently characterized from a geophysical perspective. The aim of this study is to apply a geophysical approach based on the ground magnetic method in order to better understanding the CPSM dyke swarm, as well as their host rocks. To achieve this objective, the magnetic data were subjected to a series of processing operations, including various filters and transformations. The qualitative analysis of the pole-reduced data reveals a strong correlation between the observed magnetic anomalies and the distribution of outcropping dykes in the metasedimentary basement of the Saghro Group and the volcano-sedimentary series of the Ouarzazate Supergroup. These anomalies are manifested by variations in magnetic intensity that follow the orientation of the dyke swarm mapped on surface, confirming their distinct magnetic signature. Complementary analysis of the magnetic data identified magnetic lineaments consistent with the surface mapped dykes. These lineaments appear as elongated anomalies reflecting the presence of continuous magnetic structures in the subsurface. In addition, the estimated depths of anomalous sources, obtained by Euler deconvolution from ground magnetic data, reveal values of up to 1000 m. Complementing the qualitative data analysis, a quantitative interpretation using 2D and 3D modeling was applied to the high-amplitude anomalies associated with the dyke's zones. The results obtained indicate that dykes correspond to sub-vertical structures, deeply rooted beyond 3 km.

萨格罗地块（CPSM）中部位于反阿特拉斯东部，其特征是一个显著的岩脉群。从地球物理角度来看，这些堤坝的特征仍然不够充分。本研究的目的是应用基于地磁方法的地球物理方法，以便更好地了解CPSM岩脉群及其寄主岩石。为了实现这一目标，对磁性数据进行了一系列处理操作，包括各种滤波和转换。通过对极减资料的定性分析，发现磁异常与Saghro群变质沉积基底和Ouarzazate超群火山-沉积系的露头脉分布具有较强的相关性。这些异常表现在磁场强度的变化上，磁场强度随岩脉群的方向变化而变化，从而证实了岩脉群独特的磁场特征。磁资料的补充分析确定了与地表岩脉相一致的磁线。这些线条表现为细长的异常，反映了地下连续磁性结构的存在。此外，利用欧拉反褶积法对地磁资料估计的异常震源深度可达1000 m。作为定性数据分析的补充，利用2D和3D建模对与堤防带相关的高振幅异常进行了定量解释。结果表明，岩脉为亚垂直构造，深埋于3 km以上。

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引用次数: 0

Mesozoic Pb-Zn hydrothermal veins in the Jebilet, Morocco: Constraints from mineralogy, fluid inclusions and stable isotope data 摩洛哥Jebilet中生代铅锌热液脉：矿物学、流体包裹体和稳定同位素数据的约束

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-19 DOI: 10.1016/j.jafrearsci.2025.105940

Samira Essarraj , Félix Nshimiyimana , Mohamed Hibti , Philippe Boulvais , Michel Cathelineau

The Sarhlef, Bir N'Has, Bramram, and Bamega Pb-Zn vein deposits are hosted within the Carboniferous schistose series of the Jebilet Massif, Morocco. All four deposits share similar structural pattern and mineralization history. Early Variscan barren N-S quartz veins (Stage 1) crosscut the schist and are followed by E-W quartz-carbonate veins bearing Pb-Zn-(Cu) mineralization (Stage 2). Mineral paragenesis (stage 1) begins with pyrite, followed by minor arsenides (stage 1), associated with metamorphic carbonic to aqueous-carbonic fluids (7–18.4 wt% NaCl equivalent; 250° to >410 °C), attributed to Variscan events in the Jebilet. The Pb-Zn ore stage (stage 2) comprises two polyphase episodes. The first episode begins with the deposition of carbonates (siderite-dolomite), followed by quartz (geodic comb then saccharoidal). The second episode is marked by ore deposition, with Fe-dolomite and minor calcite as gangue minerals. Barite crystallized locally (stage 2), followed by Fe-rich sphalerite, galena, and chalcopyrite. The ore stage is associated with aqueous brines (ore brines: ∼9–27 wt% NaCl equivalent; 69°–212 °C). Ore precipitation was likely driven by cooling and dilution of brines through mixing with recharge fluids.

Stable carbon and oxygen isotope data from carbonates (stage 2) suggest that carbon was derived from fluids that interacted with organic-rich schist. The oxygen and hydrogen isotope compositions of the ore brines (δ¹⁸O: 1.8 ‰ to +2.4 ‰ ± 0.1 ‰ _V-SMOW; δD: 60.4 ‰ _V-SMOW) are typical of general basinal brines. Sulfur isotopes from galena and sphalerite (+3.1 ‰ to +12.9 ‰) suggest a sulfur source from Triassic evaporated seawater/Triassic evaporites for stage 2 (ore stage).

The ore veins that crosscut post-Variscan microdiorite dikes are at least Mesozoic. We propose that the ore-forming brines originated from Triassic sedimentary and evaporitic sequences within Atlasic basins. Structural traps for Pb-Zn mineralization likely formed during Mesozoic extensional tectonics associated with the early rifting of the Atlantic Ocean. The Pb-Zn ore stage (stage 2) is genetically distinct from the earlier Variscan magmatic and metamorphic events (i.e. stage 1).

Sarhlef、Bir N'Has、Bramram和Bamega铅锌矿床赋存于摩洛哥Jebilet地块石炭系片岩系列中。4个矿床具有相似的构造模式和成矿史。早期Variscan期N-S型贫瘠石英脉（第1阶段）横切片岩，其后为E-W型含铅锌（Cu）矿化石英-碳酸盐脉（第2阶段）。矿物共生（第1阶段）以黄铁矿开始，随后是少量砷化物（第1阶段），与变质的碳水-碳流体（7-18.4 wt% NaCl当量，250°至410°C）有关，归因于Jebilet的Variscan事件。铅锌矿阶段（第二阶段）包括两个多相期段。第一阶段以碳酸盐（菱铁矿-白云岩）的沉积开始，接着是石英（地质体梳状体，然后是糖块）的沉积。第二期以矿床沉积为标志，脉石矿物为铁白云石和少量方解石。重晶石局部结晶（第二阶段），其次是富铁闪锌矿、方铅矿和黄铜矿。矿石阶段与水卤水有关（矿卤水：约9-27 wt% NaCl当量；69°-212°C）。矿石沉淀很可能是由于盐水与补给液混合而冷却和稀释所致。碳酸盐岩（第二阶段）的稳定碳氧同位素数据表明，碳来源于与富有机质片岩相互作用的流体。矿石卤水的氧、氢同位素组成（δ18O: 1.8‰~ +2.4‰±0.1‰V-SMOW, δD: 60.4‰V-SMOW）具有一般盆地卤水的典型特征。方铅矿和闪锌矿的硫同位素（+3.1‰~ +12.9‰）表明硫源为三叠系蒸发海水/三叠系蒸发岩。横切瓦力斯坎后微闪长岩脉的矿脉至少为中生代。我们认为成矿盐水来源于大西洋盆地的三叠纪沉积和蒸发层序。与大西洋早期裂陷有关的中生代伸展构造可能形成了铅锌成矿的构造圈闭。铅锌矿阶段（第2阶段）在遗传学上不同于早期的Variscan岩浆和变质事件（即第1阶段）。

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引用次数: 0

Utilizing planktic foraminifera and calcareous nannofossils to identify geological events of the Late Cretaceous in West-Central Sinai, Egypt 利用浮游有孔虫和钙质纳米化石识别埃及西奈中西部晚白垩世地质事件

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-11-19 DOI: 10.1016/j.jafrearsci.2025.105939

Orabi H. Orabi , Saeedeh Senemari

The Campanian/Maastrichtian boundary in Gebel Mukattab is marked by the first appearance of flaring heterohelicids with multiple chambers (e.g., Planoglobulina), where the last appearance of Aspidolithus parcus constrictus in zone CC23 further marks the Campanian–Maastrichtian boundary in the eastern Tethys.

Oxygen-depleted conditions are inferred from the abundance of Heterohelix species, especially in zones CF8b and CF5a. The dominance of double-keeled foraminifera like G. aegyptiaca indicates a late Campanian transgressive event. The biostratigraphic study of the Mukattab section reveals four key bioevents in the late Campanian–Maastrichtian sequence: (1) the G. aegyptiaca Zone above Globotruncanella havanensis, marking the Late Campanian Event (LCE); (2) R. rotundata (CF7a) and Planoglobulina acervulinoides (CF7c), aligned with the Campanian–Maastrichtian Boundary Event (CMBE); (3) C. contusa (CF6), associated with the Mid-Maastrichtian Event (MME); and (4) the CF1 zone, indicating the Late Maastrichtian Event (LME) near the K/Pg boundary.

Gebel Mukattab地区坎帕尼亚/马斯特里赫特边界的标志是首次出现带有多个腔室的异质螺旋体（如Planoglobulina），其中CC23地区最后出现的Aspidolithus parcus constrictus进一步标志着特提斯东部坎帕尼亚-马斯特里赫特边界。从杂螺旋物种的丰度推断出缺氧条件，特别是在CF8b和CF5a区。双龙骨有孔虫如埃及古埃及有孔虫占主导地位，表明这是晚坎帕纪的海侵事件。Mukattab剖面的生物地层学研究揭示了晚坎帕尼亚—马strichtian层序的四个关键生物事件：(1)Globotruncanella havanensis上方的埃及古埃及G. aegypaca带标志着晚坎帕尼亚事件（LCE）；(2) R. rotundata （CF7a）和Planoglobulina acervulinoides (CF7c)，与Campanian-Maastrichtian边界事件（CMBE）一致；(3)与中马斯特里赫特事件（MME）有关的C. contusa (CF6)；(4) CF1带，表明晚马斯特里赫特事件（LME）发生在K/Pg边界附近。

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引用次数: 0