Geosystems and Geoenvironment最新文献_第4页

Geochemical and mineralogical constraints on lithium mineralization in rare-metal pegmatites of the Amareshwar region, Eastern Dharwar Craton, India 印度东Dharwar克拉通Amareshwar地区稀有金属伟晶岩中锂矿化的地球化学和矿物学约束

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-07-25 DOI: 10.1016/j.geogeo.2025.100439

C.S. Sindhuja , M. Satyanarayanan , Srijita Banerjee , Soumi Chatterjee

Around 50 percent of global lithium resources are hosted in the rare-metal pegmatites. The present study deals with whole-rock geochemistry as well as zinnwaldite mineral chemistry of rare-metal pegmatites from Amareshwar, Gurugunta schist belt, Eastern Dharwar Craton to understand the source of lithium bearing ore fluids in these pegmatites and to evaluate their mineralization potential. Detailed petrography and mineral chemistry of Amareshwar pegmatites indicate that lithium is hosted in both spodumene and zinnwaldite. The zinnwaldite mineral chemistry elucidates the incorporation of lithium in mica crystal lattice along the vector Al₂(R²⁺)_–3. The whole rock geochemical signatures suggest that these pegmatites are alkaline to calc-alkaline in nature, peraluminous and emplaced in S-type and syn-collisional tectonic setting. The chondrite normalized REE patterns are characterized by prominent negative Eu anomalies coupled with significant LREE enrichment and HREE depletion indicating fractional crystallization with plagioclase separation. Elevated concentrations of Li (Avg. = 1355 ppm), Cs (Avg. = 246 ppm), Ta (Avg. = 124 ppm), Sr (Avg. = 105 ppm) and Rb (Avg. = 2234 ppm) coupled with their geochemical characteristics classify them as LCT type of rare-metal pegmatites. The relationship between La/Ta versus Mg/Li and Zr/Hf versus Nb/Ta attest that the studied samples are lithium mineralized pegmatites of magmatic-hydrothermal origin. Extremely low ratios of Mg/Li (0.004), K/Rb (0.004), K/Cs (0.05), K/Ba (0.07), Al/Ga (0.23) fingerprint that these pegmatites have evolved from highly fractionated, fertile parental granitic magma having promising economic potential.

全球约50%的锂资源蕴藏在稀有金属伟晶岩中。本文对东Dharwar克拉通Amareshwar、Gurugunta片岩带稀有金属伟晶岩进行了全岩地球化学和锌walite矿物化学研究，以了解这些伟晶岩中含锂矿流体的来源，并评价其成矿潜力。阿玛列什瓦尔伟晶岩的详细岩石学和矿物化学特征表明，锂在锂辉石和锌walite中均有赋存。锌walite矿物化学解释了锂沿矢量Al2(R2+) -3在云母晶格中的掺入。整体岩石地球化学特征表明，这些伟晶岩为碱性至钙碱性，过铝质，位置于s型和同碰撞构造环境。球粒陨石归一化稀土模式的特征是显著的负Eu异常，伴随着明显的LREE富集和HREE亏缺，表明斜长石分离的分馏结晶。Li （Avg = 1355 ppm）、Cs （Avg = 246 ppm）、Ta （Avg = 124 ppm）、Sr （Avg = 105 ppm）和Rb （Avg = 2234 ppm）含量的升高，结合其地球化学特征，将其归类为LCT型稀土晶岩。La/Ta与Mg/Li、Zr/Hf与Nb/Ta的关系表明，研究样品为岩浆热液型锂矿化晶岩。极低的Mg/Li（0.004）、K/Rb（0.004）、K/Cs（0.05）、K/Ba（0.07）、Al/Ga（0.23）指纹图谱表明，这些辉晶岩是由高分馏、肥沃的母花岗质岩浆演化而来，具有广阔的经济潜力。

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引用次数: 0

Paradox of the Сrystal peaceful underground nuclear explosion site (Yakutia, 1974): Evidence from electrical resistivity tomography and water runoff chemistry Сrystal和平地下核爆炸场的悖论（雅库特，1974）：电阻率层析成像和水径流化学的证据

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-10-18 DOI: 10.1016/j.geogeo.2025.100467

Svetlana Yurievna Artamonova

This paper comprehensively discusses data from electrical resistivity tomography, land geomagnetic surveys, radionuclides, and the major-ion chemistry of water flowing at the epicenter of the Crystal peaceful underground nuclear explosion (it was carried out in 1974). The integrity of the seal at the emplacement hole cap was compromised during the explosion, the soils at the epicenter were contaminated by radionuclides. To immobilize these radionuclides cryogenically and prevent migration of radionuclides from the central explosion area (at a depth of 98 meters), the head of the emplacement hole and its surroundings were buried in 1992 with block-rubble stone material composed of pure limestone and dolomite fragments. Additionally, the block-rubble artificial cover was further reinforced in 2006. The artificial cover is revealed to remain unfrozen and waterlogged nowadays. Snowmelt and rainwater are observed to seep through this cover, while air convection within it likely leads to the condensation of atmospheric moisture. The bicarbonate magnesium-calcium waters that originate from the percolation of rain, melted snow, and atmospheric condensate through the cover are enriched with technogenic ions such as SO₄²⁻, Mg²⁺, Ca²⁺, Li⁺, K⁺, and Sr, alongside natural components like Cl⁻, Mg²⁺, Ca²⁺, K⁺, Na⁺, Br, Sr, I, and Li⁺, which are derived from underground natural gas-brine fluids that rise along the open emplacement hole and the damage zone. It is hypothesized that Li⁺ could be a component of the nuclear explosive device. Given the low current activity of radionuclides in water flowing from beneath the artificial cover (measured in Bq/dm³): ³H, 4–12; ⁹⁰Sr, 0.004–0.4, and diminishing levels of ²³⁹^,²⁴⁰Pu (<10⁻⁶), the current migration of technogenic radionuclides with water is assessed as insignificant. Therefore, there is no immediate need for additional measures to strengthen or modify the block-rubble artificial cover.

本文综合讨论了1974年进行的水晶和平地下核爆炸震中的电阻率层析成像、陆地地磁测量、放射性核素和水的主要化学成分。在爆炸期间，安置孔盖密封的完整性受到破坏，震中的土壤受到放射性核素的污染。为了低温固定这些放射性核素，防止放射性核素从中心爆炸区域（深度98米）迁移，1992年用纯石灰岩和白云岩碎片组成的块状碎石材料掩埋了安置孔的头部及其周围。此外，2006年还进一步加固了块石人工覆盖层。时至今日，人工覆盖层仍未结冰，并被水浸透。人们观察到融雪和雨水通过这个覆盖层渗透，而其中的空气对流可能导致大气水分的凝结。碳酸氢盐镁钙水来自雨水、融化的雪和穿过井盖的大气冷凝水，富含SO₄²⁻、Mg 2⁺、Ca 2⁺、Li⁺、K⁺和Sr等技术离子，以及Cl⁻、Mg 2⁺、Ca 2⁺、K⁺、Na⁺、Br、Sr、I和Li⁺等天然成分，这些天然成分来自地下天然气-盐水流体，这些流体沿着露天的安置孔和破坏区上升。据推测，Li +可能是核爆炸装置的一个组成部分。考虑到从人工掩体下流出的水中放射性核素的低电流活度（以Bq/dm³测量）：³H, 4-12；9⁰Sr, 0.004-0.4，以及²³⁹，²⁴⁰Pu （<10⁻⁶）的减少水平，目前的技术核素随水迁移被评估为微不足道。因此，不需要立即采取额外的措施来加强或改造块石人工覆盖层。

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引用次数: 0

Paleoproterozoic rift-related volcanism and associated ore mineralization in the Alwar Basin, India 印度阿尔瓦尔盆地古元古代裂谷相关火山作用及成矿作用

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-09-06 DOI: 10.1016/j.geogeo.2025.100455

R. Sajeev , Dinesh Pandit , M. Santosh , Cheng-Xue Yang

Alwar Basin, located within the North Delhi Fold Belt (NDFB) of India, is a key area to study the processes of Precambrian geological history and related mineralization. In this study, we document two discrete pulses of volcanic activity in the Alwar Basin, dated at 1.865 ± 0.021 Ga and 1.635 ± 0.017 Ga, recorded by weighted‐mean zircon U–Pb ages. These episodic eruptions generated a compositional spectrum from basalt through rhyolite, emplacing volcanic sequences in a shallow‐marine, within‐plate rift environment. Subsequent percolation of metal‐rich hydrothermal fluids – driven by sustained heat flux and extensional fracturing – focused along stratigraphic contacts and pre‐existing weak planes, precipitating Cu–Pb–Zn sulfide mineralization within quartz–carbonate veins. Geochemical signatures, including peraluminous major‐ and trace‐element patterns and characteristic REE anomalies, further attest to syn-rift magma evolution and crustal assimilation. This pulsatory volcanism and linked hydrothermal activity were pivotal in concentrating base metals, revealing the interplay between Precambrian rifting and ore genesis in the North Delhi Fold Belt.

Alwar盆地位于印度北德里褶皱带（NDFB）内，是研究前寒武纪地质历史和成矿作用过程的重点地区。本文通过加权平均锆石U-Pb年龄记录了阿尔瓦尔盆地火山活动的两个离散脉冲，分别为1.865±0.021 Ga和1.635±0.017 Ga。这些间歇喷发产生了从玄武岩到流纹岩的成分谱，将火山序列置于浅海相板块裂谷环境中。随后，在持续的热通量和伸展性压裂的驱动下，富金属热液沿着地层接触面和预先存在的薄弱面渗透，在石英-碳酸盐脉中沉淀出铜-铅-锌硫化物矿化。地球化学特征，包括过铝主要元素和微量元素模式以及特征REE异常，进一步证明了同裂谷岩浆演化和地壳同化。这种脉动性火山活动和相关的热液活动是贱金属富集的关键，揭示了北德里褶皱带前寒武纪裂陷作用与成矿的相互作用。

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引用次数: 0

Paleo-weathering and paleoclimate of the Miocene syn-rift sandstones in the Midyan Basin, NW Saudi Arabia: Petrographic and geochemical constrains 沙特阿拉伯西北部米甸盆地中新世同裂谷砂岩的古风化和古气候：岩石学和地球化学约束

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-08-15 DOI: 10.1016/j.geogeo.2025.100451

Madyan A. Yahya , Hamdalla A. Wanas , Faisal A. Alqahtani , Amara Masrouhi , Murad R. Abdulfarraj

This study aims to investigate the provenance, tectonic setting, paleo-weathering, and paleoclimate of sandstones of the syn-rift Oligocene?-Middle-Miocene Sharik and Nutaysh formations in the Midyan Basin, located in the northwestern portion of Saudi Arabia. This has been achieved by a multidisciplinary approach combining fieldwork, petrographic analysis, and bulk-rock geochemistry (major, trace and rare earth elements) of sandstones of the Sharik and Nutaysh formations. Integrated petrographic and geochemical data indicate that the studied sandstones are predominantly of sublithic and subarkose arenites. These sandstones were mainly derived from felsic plutonic igneous (mainly granite) and volcanic (mainly andesite and rhyolite tuff) rocks, with a lesser contribution from recycled sedimentary (mainly sandstone, mudrock and chert) and metamorphic (mainly gneiss) sources. These source rocks are typical of a craton interior with notable input from transitional continental and quartzose recycled orogenic tectonic provenance. They were belonged to the nearby Neoproterozoic basement rocks located in the northwest of the study area, as indicated by paleocurrent direction. These source rocks were tecttonically linked to an active continental margin to a continental island arc. These tectonic settings were subsequently influenced by rifting, as evidenced by discrimination function diagrams based on the high-and low-silica sandstone samples. In terms of paleoweathering and paleoclimate,the studied sandstones experienced a week to moderate chemical weathering under semi-arid to semi-humid climatic condition (low to moderate rainfall ranges from 250 to 1000 mm per year). With respect to tectono-sedimentary evolution, the alluvial sandstones of the Sharik Formation were deposited during the initial stages of continental extension and gradual subsidence linked to the early syn-rift phase in the Oligocene?-Early Miocene. The deposition of the deep-sea sandstones of the Nutaysh Formation were deposited during a period of accelerated subsidence in the Early-Middle Miocene, corresponding to the rift climax. Findings of the present study is consistent with the Oligo-Miocene broader tectono-sedimentary evolution of the region.

本研究旨在探讨同裂谷渐新统砂岩的物源、构造背景、古风化和古气候特征。中中新世Sharik和Nutaysh组位于沙特阿拉伯西北部的Midyan盆地。这是通过多学科方法结合实地考察、岩石学分析和Sharik和Nutaysh地层砂岩的整体岩石地球化学（主要、痕量和稀土元素）来实现的。综合岩石学和地球化学资料表明，研究的砂岩主要为亚岩屑砂质和亚花岗岩砂质砂质。这些砂岩主要来自长英质深生火成岩（主要是花岗岩）和火山（主要是安山岩和流纹岩凝灰岩），少量来自再循环沉积（主要是砂岩、泥岩和燧石）和变质岩（主要是片麻岩）。这些烃源岩是典型的克拉通内部烃源岩，有明显的过渡性大陆和石英再循环造山带构造物源输入。从古水流方向看，它们属于研究区西北部附近新元古代基底岩。这些烃源岩在构造上与活动大陆边缘和大陆岛弧相连。基于高硅砂岩和低硅砂岩样品的判别函数图表明，这些构造环境随后受到裂谷作用的影响。在古风化和古气候方面，研究的砂岩在半干旱至半湿润气候条件下（年降雨量250 ~ 1000 mm）经历了一周至中度的化学风化。在构造-沉积演化方面，沙里克组的冲积砂岩沉积于渐新世早期同裂谷期的大陆伸展和逐渐沉降的初始阶段。中新世初期。Nutaysh组深海砂岩沉积于中新世早-中加速沉降期，与裂谷高潮期相对应。本研究结果与渐新世-中新世更广泛的构造-沉积演化相一致。

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引用次数: 0

Uncovering the Late Cretaceous paleoenvironment and paleoclimate of the Agbaja Plateau, Bida Basin, Nigeria: An inorganic geochemical analysis of shales and implications for organic matter enrichment 揭示尼日利亚比达盆地Agbaja高原晚白垩世古环境和古气候：页岩无机地球化学分析及其有机质富集意义

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-09-02 DOI: 10.1016/j.geogeo.2025.100452

Olusola J. Ojo , Suraju A. Adepoju , Ayodeji Awe , Moses O. Adeoye , Emmanuel G. Olumayede , Otobong S. Ndukwe , Sikiru O. Abdulraman , Abdulrazaq K. Haruna , Yusuf A. Jimoh

The bulk geochemical composition of the shale samples of the Maastrichtian Patti Formation exposed at the Agbaja Plateau, southern Bida Basin, Nigeria was studied using X-ray fluorescence (XRF) and inductive coupled plasma mass spectrophotometry (ICPMS) techniques. The objectives of this study are to decipher their paleoenvironment, palaeoclimate and examine the influence of the paleogeographic conditions on the hydrocarbon source rock potential. The geochemical proxies indicate that the shales were deposited under oxic and warm and humid conditions. The plots of V/(V + Ni) vs. U/Th and Ni/Co vs. U/Th support the oxic setting for the shales. The slight Ce anomalies (0.93–1.26), ΣREE (39.40–1607.37 ppm) and (La/Yb)_N ratio (4.11–10.78 ppm) are in support of the sub-oxic to oxic condition. The studied shales show Th/U values from 1.98 to 4.38 which indicates prevalence of high primary paleoproductivity. The clustering of the analyzed samples near the A-K line in the A-CN-K (Al₂O₃-CaO + Na₂O-K₂O) ternary diagram depicts an intense chemical weathering in the source region. In conclusion, the obtained paleogeographic scenario in the study area (warm temperature, high precipitation, oxic to dysoxic condition, and moderate to high primary paleoproductivity) typical of the west Africa upper Cretaceous and freshwater to brackish water environment would have supported the development of moderate organic matter rich source beds with potential for gas and oil in the Bida Basin. This study has underscored the significance of understanding the interplay between sedimentary environment, organic productivity and organic matter enrichment in predicting and exploring hydrocarbon source rocks.

利用x射线荧光（XRF）和电感耦合等离子体质分光光度（ICPMS）技术研究了尼日利亚Bida盆地南部Agbaja高原Maastrichtian Patti组页岩样品的整体地球化学组成。本研究的目的是破译其古环境、古气候，探讨古地理条件对烃源岩潜力的影响。地球化学指标表明，页岩沉积在缺氧和温暖潮湿的条件下。V/(V + Ni) vs. U/Th和Ni/Co vs. U/Th图支持页岩的氧化环境。微量Ce异常（0.93 ~ 1.26）、ΣREE异常（39.40 ~ 1607.37 ppm）和La/Yb N异常（4.11 ~ 10.78 ppm）支持亚氧—氧条件。研究页岩Th/U值为1.98 ~ 4.38，具有较高的原生古生产力。在A-CN-K （Al2O3-CaO + Na2O-K2O）三元图中，分析样品在A-K线附近聚集，说明源区化学风化作用强烈。综上所述，研究区典型的西非上白垩统、淡水-微咸水环境（温、高降水、缺氧-缺氧、初级古生产力中-高）古地理情景支持了比达盆地中富有机质、具油气潜力的烃源层发育。该研究强调了认识沉积环境、有机质生产力和有机质富集之间的相互作用对烃源岩预测和勘探的重要意义。

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引用次数: 0

Interpretation of gravity-seismic joint inversion and its application in Longmenshan region 重震联合反演解释及其在龙门山地区的应用

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-10-25 DOI: 10.1016/j.geogeo.2025.100469

Wenyue Zhou, Yanyun Sun, Wan Zhang, Guotao Yao, Ruohan Wu

Analysis and research of large complex phenomena before and after the devastating earthquake is of great significance to reduce the threat of natural disasters. Understanding the complex structural deformation of the Longmenshan Fault Zone is essential for elucidating crustal deformation and seismic dynamic mechanisms. This paper analyzes the gravity anomaly distribution characteristics in the Wenchuan Earthquake zone, and subsequently applies edge detection method to invert the pre-earthquake gravity anomalies of the Longmenshan region. The fault distribution characteristics in the Longmenshan region and its adjacent areas before the earthquake have been determined. Besides, morphology difference and possible earthquake formation have been analyzed through the Euler deconvolution results of gravity anomaly profile before and after the earthquake. Finally, a 2-D interactive joint inversion was performed based on the existing seismic and gravity data. The subsurface structure was revealed, and the earthquake formation mechanism was discussed by comparing the underground changes before and after the event.

分析和研究破坏性地震前后的大型复杂现象，对减少自然灾害的威胁具有重要意义。了解龙门山断裂带的复杂构造变形对阐明地壳变形和地震动力机制具有重要意义。本文分析了汶川地震带重力异常分布特征，并应用边缘检测方法反演了龙门山地区的震前重力异常。确定了龙门山及其邻区震前断层的分布特征。通过地震前后重力异常剖面的欧拉反褶积结果，分析了地震形态差异和可能的地震成因。最后，基于已有地震和重力资料进行二维交互联合反演。通过对比地震前后的地下变化，揭示了地震的地下构造，探讨了地震的形成机制。

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引用次数: 0

Urbanization induced heat wave risk assessment of Khulna City, Bangladesh: A 30-years analysis of land surface temperature, climate trends and forecasting 孟加拉国库尔纳市城市化引发的热浪风险评估：地表温度、气候趋势和预测的30年分析

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-08-05 DOI: 10.1016/j.geogeo.2025.100448

Nusrat Jahan Suborna , Raian Islam Evan , Mostafa Jaman Rabby , Maksudur Rahman , Arabe Khan , Md Mahmudul Hasan Rakib , Rahat Khan , Irteja Hasan , Dhiman Kumer Roy

This study examines how urbanization has influenced heatwave risk in Khulna, Bangladesh, from 1993 to 2023 by analyzing changes in land surface temperature (LST) and land use land cover (LULC) using satellite imagery and statistical methods. Over the 30‐year period, mean LST rose by 7 °C, with 23.7 % of Khulna now classified as an excessive heat zone. The Mann–Kendall (MK) test and Sen’s slope (SS) estimator confirm a significant warming trend, particularly during the warmest months. Pearson correlation (PC) analysis indicates a negative relationship between temperature and humidity, exacerbating heatwave severity. LULC results reveal that urbanized areas have expanded approximately threefold while vegetation cover has decreased by nearly 50 %. Using a seasonal-trend decomposition based on LOESS with an auto regressive integrated moving average (STL‐ARIMA) model, the study forecasts 29 additional heatwave days exceeding 36 °C over the next five years. This projection suggests a likely intensification of the urban heat island (UHI) effect driven by rapid urban growth and diminished natural spaces, heightening heat‐related hazards. The findings support the need for sustainable urban development strategies in Khulna, such as increasing green cover and improving water management to inform policy interventions aimed at mitigating rising heat risks in the city’s expanding urban environment.

本研究利用卫星图像和统计方法分析了1993年至2023年孟加拉国库尔纳的地表温度（LST）和土地利用土地覆盖（LULC）的变化，探讨了城市化如何影响热浪风险。在30年期间，平均地表温度上升了7°C，库尔纳的23.7% %现在被列为过热区。Mann-Kendall （MK）检验和Sen’s slope （SS）估计证实了显著的变暖趋势，特别是在最温暖的月份。Pearson相关（PC）分析表明，温度和湿度呈负相关，加剧了热浪的严重程度。LULC结果显示，城市化面积扩大了约三倍，而植被覆盖却减少了近50% %。利用基于黄土的季节趋势分解和自回归综合移动平均（STL‐ARIMA）模型，该研究预测了未来五年超过36°C的额外29个热浪天。这一预测表明，在城市快速增长和自然空间减少的驱动下，城市热岛效应可能会加剧，从而加剧与热有关的危害。研究结果支持了库尔纳需要制定可持续城市发展战略，例如增加绿化覆盖和改善水资源管理，以便为旨在减轻城市不断扩大的城市环境中不断上升的高温风险的政策干预提供信息。

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引用次数: 0

Morphological, mineralogical and geochemical characterization of Ngaoundal soils (Adamawa-Cameroon): Implications for weathering mechanisms and trajectories in tropical zones Ngaoundal土壤（Adamawa-Cameroon）的形态、矿物学和地球化学特征：对热带地区风化机制和轨迹的影响

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-08-08 DOI: 10.1016/j.geogeo.2025.100450

Abdoul Aboubakar , Ilalie Bertille Kentsa Manefouet , Loique Rodolph Mbounou Azefack , Yannick Langollo Tchedele , Dalil Adoulko , Demonstel Yvan Ntomb , Abakar Mahamat , Jacques Wadjou Wassouo , Quentin marc Anaba Fotze

Ngaoundal, located in the Adamaoua region of Cameroon, has a tropical climate and is known for its characteristic soils. The aim of the present study was to evaluate the action of weathering on Ngaoundal's lateritic soils. Morpho-structural, mineralogical and geochemical analyses enabled us to carry out this study. The morphological study carried out on 15 soil samples shows a variation in colour from reddish (2.5YR 5/8) to dark brown (7.5YR 6/8), varying from reddish yellow (7.5YR 6/8), orange brown (10YR 5/6) and yellowish brown (10YR 5/4), and have clayey to sandy-clayey matrices with nodules of the order of millimetres to centimetres. X-ray diffractometry and x-ray fluorescence show the following mineral phases in Ngaoundal's lateritic soils: quartz, goethite, gibbsite, kaolinite, hematite, magnetite, anatase and boehmite. Geochemical analysis of these soils shows high average levels of SiO₂ (36.41 %), Fe₂O₃ (31.48 %) and Al₂O₃ (17.72 %), and low average levels of TiO₂ (1.02 %) and CaO (0.36 %), which characterise characteristic soils rich in ferruginous oxide and alumina oxide. The weathering indices of Ngaoundal soils (sesquioxide ratio) vary between 0.22 and 2.98 with an average of 1.09. This average value qualifies these soils as lateritic soils rich in gibbsite and kaolinite (average CIA = 96.38 %) and resulting from chemical alteration of the hydrolysis type (alloying and monosiallitisation).

Ngaoundal位于喀麦隆的Adamaoua地区，属于热带气候，以其特有的土壤而闻名。本研究的目的是评价风化作用对恩昂达尔红土的影响。形态构造、矿物学和地球化学分析使我们得以开展这项研究。对15个土壤样品进行的形态学研究表明，土壤的颜色从红色（2.5年5/8）到深棕色（7.5年6/8）不等，从红黄色（7.5年6/8）、橙棕色（10年5/6）和黄褐色（10年5/4）不等，具有粘土到砂质粘土基质，具有毫米至厘米级的结节。x射线衍射和x射线荧光显示，在恩翁达尔红土中有以下矿物相：石英、针铁矿、三长石、高岭石、赤铁矿、磁铁矿、锐钛矿和薄铝石。土壤的地球化学分析表明，SiO2（36.41 %）、Fe2O3（31.48 %）和Al2O3（17.72 %）的平均含量较高，TiO2（1.02 %）和CaO（0.36 %）的平均含量较低，具有富含氧化亚铁和氧化氧化铝的特征。Ngaoundal土的风化指数（倍半氧化物比）在0.22 ~ 2.98之间变化，平均为1.09。这个平均值表明这些土壤是红土土，富含三长石和高岭石（平均CIA = 96.38 %），是由水解类型（合金化和单唾液化）的化学变化造成的。

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引用次数: 0

Developing a riverbank erosion susceptibility index: A pragmatic approach to reveal the level of vulnerability in coastal Bangladesh 开发河岸侵蚀敏感性指数：揭示孟加拉国沿海地区脆弱性水平的实用方法

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-09-16 DOI: 10.1016/j.geogeo.2025.100459

Arabe Khan , Md Mahmudul Hasan Rakib , Irteja Hasan , Apurba Roy , Mehedi Hasan Ovi , Md Mostafa Jaman Rabby , Raian Islam Evan , Nusrat Jahan Suborna , Maksudur Rahman , Rahat Khan , Dhiman Kumer Roy

Riverbank erosion is one of the significant natural hazards affecting the livelihoods of communities living along riverbanks in Bangladesh. This study develops a novel riverbank erosion susceptibility index (RESI) to quantitatively assess community susceptibility to this hazard. The RESI framework integrates five core dimensions: exposure, susceptibility, sensitivity, adaptability, and resilience, encompassing 34 context-specific indicators derived from household surveys, interviews, and field observations. The RESI scoring scale ranges from -1 (most resilient) to +1 (most susceptible), where higher positive scores indicate greater susceptibility to riverbank erosion. The findings in this study conclude that Chadpur Union is the most susceptible (RESI score: 0.47), followed by Shambupur (0.36) and Chanchra (0.29) union. These scores are further validated with historical remote-sensing analysis, and sensitivity tests show that varying indicator weights (equal, expert, or PCA) do not change the relative union ranking, underscoring the model’s robustness. The analysis highlights key drivers of vulnerability: frequent erosion occurrences, high population density along riverbanks, considerable losses in land and assets, and recurrent displacement due to erosion. All three unions are facing significant challenges in building adaptability and resilience, as indicated by low scores in infrastructure, financial resources, and social support systems. The study emphasizes the need for targeted interventions to reduce susceptibility, which include reinforcing protective structures, improving access to financial and technical resources, and promoting livelihood diversification strategies. Integrating the RESI into planning enables decision-makers to prioritize high-risk areas and allocate resources more effectively.

河岸侵蚀是影响孟加拉国沿河社区生计的重大自然灾害之一。本文提出了一种新的河岸侵蚀敏感性指数（RESI）来定量评价群落对河岸侵蚀的易感性。RESI框架整合了五个核心维度：暴露、易感性、敏感性、适应性和复原力，包括34个根据家庭调查、访谈和实地观察得出的具体情况指标。RESI评分范围从-1（最具弹性）到+1（最易受影响），越高的正分数表明越容易受到河岸侵蚀。本研究结果表明，Chadpur工会最易受感染（RESI得分：0.47），其次是Shambupur工会（0.36）和Chanchra工会（0.29）。这些分数通过历史遥感分析进一步验证，敏感性测试表明，不同的指标权重（平等，专家，或PCA）不会改变相对联合排名，强调模型的鲁棒性。该分析强调了脆弱性的主要驱动因素：频繁发生侵蚀、河岸人口密度高、土地和资产的大量损失以及侵蚀导致的经常性流离失所。从基础设施、财政资源和社会支持系统的低得分可以看出，这三个工会在建立适应性和弹性方面都面临着重大挑战。该研究强调需要有针对性的干预措施来降低易感性，其中包括加强保护结构，改善获得财政和技术资源的机会，以及促进生计多样化战略。将RESI纳入规划，使决策者能够优先考虑高风险领域，并更有效地分配资源。

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引用次数: 0

A lacustrine record of rainfall-induced variations in the pedogenic and weathering processes during the Late Holocene 在晚全新世期间降雨引起的成土和风化过程变化的湖相记录

Geosystems and Geoenvironment

Pub Date : 2026-02-01 Epub Date: 2025-07-25 DOI: 10.1016/j.geogeo.2025.100441

Adichinalniravel S. Yamuna , Anish K. Warrier , Bharti Sharma , Kizhur Sandeep , Mamilla Venkateshwarlu , Powravi Sai , George S. Joju , Geetha H. Aravind , Abdul K. Rafaz , Kakunja V. Reshma , Rajveer Sharma

In recent decades, extreme weather events have become more frequent across the globe. It necessitates a deeper understanding of the underlying driving mechanisms. This study reconstructs the paleoclimatic variability of southern India, particularly the coastal Karnataka, over the past two millennia using a multiproxy approach (geochronology, environmental magnetism, sedimentology, inorganic geochemical analysis, Fourier Transform Infrared Spectroscopy, Diffuse Reflectance Spectroscopy, and loss-on-ignition). The study was conducted on a 1.54-m-long lacustrine sediment core covering the past 1566 years, from 2005 to 439 cal yr BP. Four distinct climatic phases were delineated, reflecting successive stages of the Indian Summer Monsoon (ISM) strengthening in the Late Holocene. Phase 1, which spans from 2000 to 1550 cal yr BP, experienced moderately low rainfall and weak pedogenesis. In Phase 2 (1550–1230 cal yr BP), the monsoon strengthened, leading to strong precipitation, intense weathering and pedogenesis, and high lake levels. Phases 3 (1230–570 cal yr BP) and 4 (570–439 cal yr BP) experienced stronger monsoons and a burst of rainfall that strengthened catchment streams, elevated lake levels, and increased productivity and sedimentation rate. A comparative study with regional records suggests a similar trend in broad climate variability, revealing a global teleconnection. The climatic evolution of coastal Karnataka aligns with the shifts in the Intertropical Convergence Zone (ITCZ), El Niño Southern Oscillation (ENSO), and Total Solar Irradiance (TSI). Additionally, the signatures of global factors like ITCZ, ENSO, and TSI have been overprinted by the signatures of regional factors such as sea surface temperature (SST), especially during periods of active Indian Ocean Dipole (IOD).

近几十年来，极端天气事件在全球范围内变得越来越频繁。这需要对潜在的驱动机制有更深的理解。本研究利用多代理方法（地质年代学、环境磁学、沉积学、无机地球化学分析、傅里叶变换红外光谱、漫反射光谱和着火损失）重建了印度南部，特别是卡纳塔克邦沿海地区过去两千年的古气候变化。该研究是在一个1.54米长的湖泊沉积物岩心上进行的，覆盖了过去1566年，从2005年到439 calyr BP。描述了四个不同的气候阶段，反映了晚全新世印度夏季风（ISM）增强的连续阶段。第1阶段为2000 ~ 1550 calyr BP，降水偏少，成土作用弱。第2阶段（1550-1230 calyr BP），季风增强，降水强，风化作用强，成土作用强，湖泊水位高。第3阶段（1230-570 cal yr BP）和第4阶段（570-439 cal yr BP）经历了更强的季风和降雨，这些降雨加强了流域溪流，提高了湖泊水位，增加了生产力和沉积速率。一项与区域记录的比较研究表明，广泛的气候变率也有类似的趋势，揭示了全球遥相关。沿海卡纳塔克邦的气候演变与热带辐合带（ITCZ）、厄尔尼诺Niño南方涛动（ENSO）和太阳总辐照度（TSI）的变化一致。此外，ITCZ、ENSO和TSI等全球因子的特征已经被海温（SST）等区域因子的特征叠加，特别是在印度洋偶极子（IOD）活跃期间。

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引用次数: 0