Geosystems and Geoenvironment最新文献_第10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 : 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

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 : 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

Assessment of the potential for using PET waste as geomaterials in soil micro-reinforcement PET废弃物作为土壤微加固材料的潜力评价

Geosystems and Geoenvironment

Pub Date : 2025-07-21 DOI: 10.1016/j.geogeo.2025.100438

Carlos J.P. Graça , Luís M. Ferreira-Gomes , Luis Andrade Pais , Antonio Albuquerque , Maria Vitoria Morais , André Studart , Leonardo Marchiori

The use of synthetic fibers to enhance soil properties is a growing area of research. This study investigates the incorporation of granulated polyethylene terephthalate (PET) waste – derived from crushed plastic soda bottles – into dune sand at 3 % and 5 % ratios to develop a novel composite material and promote PET fiber reuse as a sustainable solution. By valorizing PET waste, this approach reduces plastic pollution and mitigates the demand for natural resource extraction. Physical and mechanical characterization tests, including specific gravity, particle size distribution, normal proctor compaction, direct shear (DS), consolidated isotropic drained (CID) triaxial, and oedometric tests, were conducted on the dune sand, soil-PET mixtures, and pure PET residue. Results demonstrate that the addition of PET significantly influences the friction angle of the composite material, as evidenced by DS and triaxial CID tests. Specifically, the soil-PET mixtures exhibited enhanced shear strength compared to pure sand, while introducing 5 % of PET, the internal friction angle increased up to 12 % and 22 %, according to DS and CID triaxial tests, respectively, maintaining cohesionless behavior. These improvements are attributed to the reinforcing effect and interlocking behavior of PET particles within the sand matrix. The results indicate that PET addition enhances the shear strength and stability of sandy soils, supporting its use in earthworks. This study highlights the dual environmental and mechanical advantage of PET micro-reinforcement, providing a feasible route for plastic waste reuse in geotechnical engineering.

利用合成纤维增强土壤特性是一个日益发展的研究领域。本研究研究了将颗粒状聚对苯二甲酸乙二醇酯（PET）废料（来自破碎的塑料汽水瓶）以3%和5%的比例掺入沙丘沙中，以开发一种新型复合材料，并促进PET纤维的再利用，作为一种可持续的解决方案。通过使PET废物增值，这种方法减少了塑料污染，减轻了对自然资源开采的需求。对沙丘砂、土壤-PET混合物和纯PET残渣进行了物理力学表征试验，包括比重、粒径分布、正常普罗克特压实、直剪（DS）、固结各向同性排水（CID）三轴和径测试验。结果表明，PET的加入对复合材料的摩擦角有明显的影响，这是DS和三轴CID试验的结果。具体来说，与纯砂相比，土-PET混合物的抗剪强度得到了提高，根据DS和CID三轴试验，当引入5%的PET时，内摩擦角分别增加了12%和22%，保持了无粘结性。这些改进是由于PET颗粒在砂基体中的增强作用和联锁行为。结果表明，PET的加入提高了砂土的抗剪强度和稳定性，支持其在土方工程中的应用。本研究突出了PET微增强材料的环境和力学双重优势，为塑料废弃物在岩土工程中的再利用提供了一条可行的途径。

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引用次数: 0

Hydrostratigraphic characterization using geoelectrostratigraphic information and hydraulic flow unit analysis for high-resolution aquifer mapping in heterogeneous systems 利用地电地层信息和水力流动单元分析进行非均质系统高分辨率含水层制图的水文地层表征

Geosystems and Geoenvironment

Pub Date : 2025-07-16 DOI: 10.1016/j.geogeo.2025.100434

Ndifreke I. Udosen , Kufre R. Ekanem , Nyakno J. George

Accurate characterization of aquifers requires comprehensive understanding of groundwater hydraulic properties. Traditional aquifer assessment techniques are usually insufficient in characterizing hydrostratigraphic variability, leading to inaccurate prediction of aquifer flow dynamics. To address these limitations, this work integrated geoelectrical stratigraphy with hydraulic flow unit, flow zone indicator, and stratigraphic modified Lorenz plot strategies, the goal being to enhance the resolution of aquifer characterization along river channels and tributaries in Akwa Ibom State, Southern Nigeria. Unlike conventional approaches, the stratigraphic modified Lorenz plot (SMLP) provided a more precise strategy for quantifying permeability distribution within the heterogeneous aquifer system, enabling enhanced prediction of aquifer performance. Furthermore, SMLP delineated flow efficiency across the distinct hydrostratigraphic units. Results indicated the presence of four hydraulic flow units, with individual units exhibiting distinctive transmissivity properties. Computed inclination angles of the four flow units were 34°, 29°, 49°, and 33°, respectively, and these indicated the extent of hydraulic efficiency. Hydraulic flow units 1, 3, and 4 had higher transmissivity and were key conduits for groundwater flow. Hydraulic flow unit 2, on the other hand, had reduced transmissivity, indicating restricted fluid migration. The techniques employed in this study enhanced subsurface characterization and generated high-resolution and cost-effective strategies for delineating high-yield aquifer zones within river channels and tributaries with better accuracy than with use of traditional hydrogeological models. These findings are important for optimizing groundwater resource management in the study area and analogous hydrogeological settings worldwide.

准确表征含水层需要对地下水水力特性有全面的了解。传统的含水层评价技术在表征水文地层变异性方面往往存在不足，导致含水层流动动态预测不准确。为了解决这些限制，本研究将地电地层学与水力流动单元、流动带指示器和地层修正洛伦兹图策略结合起来，目的是提高尼日利亚南部阿夸伊博姆州沿河道和支流的含水层表征的分辨率。与传统方法不同，地层修正洛伦兹图（SMLP）提供了一种更精确的策略来量化非均质含水层系统内的渗透率分布，从而增强了对含水层性能的预测。此外，SMLP还描绘了不同水文地层单元的流动效率。结果表明存在四个水力流动单元，每个单元表现出不同的透射率特性。四个流动单元的计算倾角分别为34°、29°、49°和33°，这表明了水力效率的程度。水力流单元1、3、4具有较高的透水性，是地下水渗流的关键通道。另一方面，水力流量单元2的透过率降低，表明流体运移受到限制。本研究中采用的技术增强了地下特征，并产生了高分辨率和成本效益的策略，用于描绘河道和支流内的高含水含水层，其准确性优于使用传统水文地质模型。这些发现对于优化研究区和世界范围内类似水文地质环境的地下水资源管理具有重要意义。

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引用次数: 0

Spatial distribution and source apportionment of potentially toxic elements in residential soil from Nsuta, a typical manganese mine community in Tarkwa, Southwestern Ghana 加纳西南部塔克瓦典型锰矿社区Nsuta居住土壤中潜在有毒元素的空间分布及来源解析

Geosystems and Geoenvironment

Pub Date : 2025-07-16 DOI: 10.1016/j.geogeo.2025.100435

Eric Gyimah , Samuel Kwamena , Shadrack Fosu , Emmanuel Daanoba Sunkari , David Edem Dinku , Yao Yevenyo Ziggah

The environmental quality of residential areas of urban communities has been threatened by rapid industrial growth, substantial technological innovation, and urban expansion. The present study provides chemometric receptor model-based source apportionment, the ecotoxicological status, and the spatial distribution of arsenic, cadmium, lead, mercury, manganese and iron in residential soils in a mining community in Tarkwa. The distributions of the heavy metals showed a widespread pattern, while the eastern fringe of the study area was identified as a hotspot for mercury contamination. Agreement among the cluster analysis (CA), principal component analysis (PCA), and positive matrix factorization (PMF) along with the correlation matrix (CM) reasonably identified the sources of arsenic, manganese, and iron contamination of residential soils of the Nsuta community to be governed by geogenic influences such as the weathering and hydromorphic dispersion from the metavolcanic rocks. Noteworthily, atmospheric deposition is considered a prioritized source for mercury contamination, with a PMF contribution of 78.50%. Vehicular emission as well as other anthropogenic activities contribute to lead (48.00%) and cadmium (66.20%) contamination of the residential soil within the study area. Ecotoxicological assessment reveals a combined toxic risk index (TRI) of 29.80, with mercury contributing to about 97.50% of the total risk. Moreover, the modified hazard quotient (mHQ_i) for the single metals also indicated that mercury (Hg) has the highest ecological toxicity level with a mHQ_i value of 7.00. The present study provides baseline data that could be valuable for proper environmental management and policy-making to reduce the myriad influx of heavy metal contamination in the study area. To provide a thorough understanding of metal pollution in the Nsuta community, future research on metal speciation, bioavailability, bioaccumulation, potential modes of action in soils, and the implications for human health is also necessary.

城市社区居住区的环境质量受到快速工业增长、大量技术创新和城市扩张的威胁。本研究基于化学计量受体模型进行了塔尔克瓦矿区居住土壤中砷、镉、铅、汞、锰和铁的源解析、生态毒理学状况和空间分布。重金属分布呈广泛分布，研究区东部边缘为汞污染热点地区。聚类分析（CA）、主成分分析（PCA）和正矩阵分解（PMF）与相关矩阵（CM）的一致，合理地确定了Nsuta群落居住土壤中砷、锰和铁的污染来源受变质火山岩风化和水形态分散等地质因素的影响。值得注意的是，大气沉积被认为是汞污染的优先来源，PMF贡献了78.50%。车辆排放和其他人为活动对研究区内居住土壤的铅（48.00%）和镉（66.20%）污染有贡献。生态毒理学评估显示，综合毒性风险指数（TRI）为29.80，汞约占总风险的97.50%。此外，单一金属的修正危害商（mHQi）也表明汞（Hg）具有最高的生态毒性水平，其mHQi值为7.00。本研究提供的基线数据可能对适当的环境管理和决策有价值，以减少研究地区大量重金属污染的流入。为了全面了解Nsuta群落的金属污染，还需要进一步研究金属在土壤中的形态、生物利用度、生物积累、潜在的作用方式以及对人类健康的影响。

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引用次数: 0

Accessory graphite in phyllites as indicator of metamorphic grade and stage (Szendrő Mts., NE Hungary) 千层岩中的副石墨作为变质等级和阶段的指示物（szzendrermts .， NE匈牙利）

Geosystems and Geoenvironment

Pub Date : 2025-07-12 DOI: 10.1016/j.geogeo.2025.100431

Lívia Leskóné Majoros , Máté Zs. Leskó , Krisztián Fintor , Ferenc Móricz , Délia Bulátkó-Debus , Sándor Szakáll , Ferenc Kristály

The metamorphic temperature of rock bodies can be estimated from the degree of graphitization of carbonaceous material, best determined by Raman spectroscopy. Graphite-bearing rocks from intensely folded black phyllites (black schists) near Meszes village in the Szendrő Mts., NE-Hungary, were analyzed using ore microscopy, scanning electron microscopy (SEM-EDX), X-ray powder diffraction (XRD), Raman spectroscopy and X-ray fluorescence spectrometry (XRF). The exposed Szendrő Phyllite Formation is of Carboniferous age, represents a gradually deepening basin fill, metamorphosed under greenschist facies conditions. Due to its low quantity and the presence of significant muscovite (± illite) 2M₁, clinochlore and quartz content, graphite is not directly detectable by XRD. Graphite occurs as intensely deformed 50–150 μm sized flakes persistently with kink-band microstructure and undulose extinction. The absence of S and Cl (confirmed by EDX) indicates a total maturation of the carbonaceous material into pure, disordered graphite with higher crystal ordering supported also by the initial splitting of S2 Raman band. The average formation temperature is estimated at 425°C (±50°C) by the Beyssac-method and 417°C (±50°C) by the Aoya-method.

岩石的变质温度可由碳质物质的石墨化程度来估计，用拉曼光谱测定效果最好。采用矿石显微镜、扫描电镜（SEM-EDX）、x射线粉末衍射（XRD）、拉曼光谱（Raman spectroscopy）和x射线荧光光谱（XRF）等技术对匈牙利东北部szendrermts . Meszes村附近强烈褶皱黑色千层岩（black片岩）中的含石墨岩石进行了分析。出露的森德尔格千层岩组为石炭世，为逐渐加深的盆地充填，在绿片岩相条件下变质。由于石墨的含量低，且含有大量白云母（±伊利石）2M1、斜沸石和石英，因此不能用XRD直接检测到石墨。石墨以50 ~ 150 μm大小的薄片剧烈变形，具有扭带结构和不灭光。缺少S和Cl （EDX证实）表明碳质材料完全成熟为具有较高晶体有序度的纯净无序石墨，这也支持了S2拉曼带的初始分裂。beyssac方法估计的平均地层温度为425°C（±50°C）， aoya方法估计的平均地层温度为417°C（±50°C）。

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引用次数: 0

Spatiotemporal rainfall trend analysis and drought identification in agro-climatic zones of Odisha, Eastern India 印度东部奥里萨邦农业气候带降水时空趋势分析与干旱识别

Geosystems and Geoenvironment

Pub Date : 2025-07-10 DOI: 10.1016/j.geogeo.2025.100430

Laxmikanta Rana , Siba Sankar Sahu , Bubun Mahata , Mukul Maity , Simanchal Nayak

Drought is the outcome of unequal rainfall distribution over time and space which negatively impacts agricultural productivity and social well-being. Analyzing the spatiotemporal drought variability in terms of intensity and magnitude is necessary for improving agricultural productivity. The main goal of the study is to analyze the long-term rainfall trend and measure the frequency and severity of droughts in 10 Agro-Climatic Zones (ACZs) of Odisha, India from 1988 to 2022. Secondary data sources, like rainfall data of Special Relief Commissioner (SRC), Standardized Precipitation-Evapotranspiration Index (SPEI) database, Landsat 8 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) data and GLDAS-2.2: Global Land Data Assimilation System data are used to achieve the objective. Moreover, field data is collected to validate drought scenario. In this study, Innovative Trend Analysis (ITA) is used to evaluate rainfall trends. Drought scenario mapping is done through Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI) method and various drought indices like Vegetation Condition Index (VCI), Temperature Condition Index (TCI), Precipitation Condition Index (PCI), and Integrated Drought Severity Index (IDSI). The study found highly increasing trend in rainfall in 2006–2022 compared to 1989–2005, over Eastern Ghat High Land (EGHL), Northwestern Plateau (NWP), North Central Plateau (NCP), and Northeastern Ghat (NEG). While moderately decreasing trend observed over Northeastern Coastal Plain (NECP) and Eastern and Southeastern Coastal Plain (ESECP). High drought frequency with extreme severity noticed over NECP, and severe over Western Undulating Zone (WUZ) and Western Central Table Land (WCTL). Low IDSI values reflecting severe drought effects which noticed over WCTL, WUZ and Mid Central Table Land (MCTL) in 2016, WCTL and ESECP in 2018 and MCTL, ESECP, and NCP in 2022. The study provides critical insights to the current scenario of knowledge of drought condition for better understanding the drought and agricultural planning in each ACZ of Odisha.

干旱是降雨随时间和空间分布不均的结果，对农业生产力和社会福祉产生负面影响。分析干旱时空变化的强度和幅度，是提高农业生产力的必要条件。该研究的主要目标是分析1988年至2022年印度奥里萨邦10个农业气气带（acz）的长期降雨趋势，并测量干旱的频率和严重程度。次要数据源包括美国特别救援专员（SRC）降雨数据、标准化降水-蒸散发指数（SPEI）数据库、Landsat 8 Operational Land Imager (OLI) and Thermal Infrared Sensor （TIRS）数据以及GLDAS-2.2: Global Land data Assimilation System数据。此外，还收集了现场数据来验证干旱情景。本研究采用创新趋势分析（ITA）来评估降雨趋势。通过标准化降水指数（SPI）、标准化降水蒸散指数（SPEI）方法和植被条件指数（VCI）、温度条件指数（TCI）、降水条件指数（PCI）、综合干旱严重程度指数（IDSI）等多种干旱指数完成干旱情景制图。研究发现，与1989-2005年相比，2006-2022年东高止高原（EGHL）、西北高原（NWP）、中北部高原（NCP）和东北高止高原（NEG）的降雨量呈高度增加趋势。东北沿海平原（NECP）和东、东南沿海平原（ESECP）呈中等下降趋势。东北东北地区干旱频次高，旱情严重，西部起伏带和中西部台地旱情严重。低IDSI值反映了2016年WCTL、WUZ和中部高原（MCTL）、2018年WCTL和ESECP以及2022年MCTL、ESECP和NCP的严重干旱效应。该研究为了解奥里萨邦每个ACZ的干旱和农业规划提供了重要的见解。

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引用次数: 0

Integrated pore size and grain size characterization of geomaterials from Ewekoro, Eastern Dahomey Basin 达荷美盆地东部Ewekoro地区岩土体孔隙及粒度综合表征

Geosystems and Geoenvironment

Pub Date : 2025-07-05 DOI: 10.1016/j.geogeo.2025.100428

Olawale Babatunde Olatinsu , Mathew Osaretin Ogieva , Kehinde Saheed Ishola , Amidu Abiola Ige-Adeyeye

The pore and grain size of rocks and geomaterials are very crucial factors in evaluating their usefulness in industrial productions, geological and petrophysical assessments, geotechnical engineering projects and environmental studies. The study techniques include low field NMR measurements via CPMG pulse sequence on fully saturated disc-shaped samples and grain size analysis on sample fragments. NMR Relaxation curves were inverted via conventional regularized least-squares inversion routine to generate pore size distribution (PSD). Grain size analysis using sieve method was based on grain size distribution (GSD) and statistical parameters (mean (Mz), sorting (σ_i), skewness (SK_i), and kurtosis (K_G)). PSD depicts the presence of micropore and mesopores in all samples, with macropores detected only in limestone. All samples manifest well connected multiple peak pore systems. Sandstone and glauconite samples exhibit bimodal PSD. PSD for Limestone samples is trimodal which is a manifestation of a more complex pore system common in carbonate rocks mainly due to the composition of grains, matrix and cement. M_z values reveal more of medium/coarse grain composition across samples, implying an intermediate to high energy depositional environment. σ_i values indicate poor to medium sorting which reveals that the rock sediments were likely deposited in fluvial-continental environments. K_G values are a mix of mesokurtic, leptokurtic and platykurtic, indicating a combination of depositional environments. Observed spread in skewness values also corroborates the diverse nature of sediment transport for rock formation and existence of mixed or transitional environment.

岩石和地质材料的孔隙和粒度是评价其在工业生产、地质和岩石物理评价、岩土工程项目和环境研究中的用途的非常关键的因素。研究技术包括利用CPMG脉冲序列对完全饱和的圆盘状样品进行低场核磁共振测量和对样品碎片进行粒度分析。利用常规正则化最小二乘反演方法反演核磁共振弛豫曲线，得到孔隙尺寸分布。粒度分析采用筛分法，基于粒度分布（GSD）和统计参数（均数（Mz）、分选（σi）、偏度（SKi）、峰度（KG））。PSD描述了微孔和中孔在所有样品中的存在，大孔仅在石灰石中检测到。所有样品均表现出连接良好的多峰孔隙系统。砂岩和海绿石样品呈现双峰PSD。石灰石样品的PSD为三峰型，这是碳酸盐岩中常见的更复杂的孔隙系统的表现，主要是由于颗粒、基质和胶结物的组成。Mz值更多地揭示了样品的中/粗颗粒组成，暗示了中至高能量的沉积环境。σi值表明分选差至中等，表明岩石沉积物可能沉积于河流-陆相环境。KG值为中斑岩、细斑岩和扁斑岩的混合值，反映了沉积环境的组合。观测到的偏度值的分布也证实了岩层输沙的多样性和混合或过渡环境的存在。

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引用次数: 0

Geochemistry of the metavolcanic rocks from the Archean Bikélélé greenstone belt (Chaillu Massif, Republic of the Congo): Petrogenesis and tectonic implications 刚果（金）Chaillu地块太古代bikk<s:1> <s:1>青岩带变质火山岩地球化学：岩石成因及其构造意义

Geosystems and Geoenvironment

Pub Date : 2025-07-05 DOI: 10.1016/j.geogeo.2025.100429

Yarsé Brodivier Mavoungou , Noël Watha-Ndoudy , Hardy Medry Dieu-Veill Nkodia , Anthony Temidayo Bolarinwa , Aliyu Ohiani Umaru , Georges Muhindo Kasay

The Bikélélé greenstone belt belongs to the Chaillu Massif, which corresponds to the northwestern part of the Congo Craton outcropping in the southwestern Republic of the Congo. It mainly consists of metavolcanic lithological sequences composed of amphibolites, clinopyroxene amphibolites, epidote amphibolites, amphibole gneisses and amphibole-chlorite schists. These rocks show granoblastic to grano-nematoblastic textures, and contain amphibole, plagioclase, alkali feldspar, quartz, chlorite, clinopyroxene, biotite, sericite, sphene and opaque minerals. They have high contents in SiO₂, Fe₂O₃, Al₂O₃, CaO and MgO, with subordinate Na₂O and K₂O. In the REE chondrite-normalised diagrams, the metavolcanic rocks show flat to LREE-enriched and flat HREE patterns. However, in the primitive mantle-normalised diagrams, most of the samples show depletion in Nb, Ta and Ti. Trace and rare earth element (REE) data suggest that their protoliths correspond to basalts and basaltic andesites of tholeiitic and calc-alkaline affinity. The metavolcanic rocks likely formed by 2.5–4 % partial melting of a subcontinental lithospheric mantle source that was enriched through metasomatism involving sediment-derived melts and subduction-related fluids. The results of this study suggest that the protoliths of the Bikélélé metavolcanic rocks were emplaced in a subduction-related back-arc environment, during the second magmatic episode recorded in the Chaillu Massif and underwent metamorphic grade up to amphibolite facies during the Neoarchean tectono-metamorphic event.

biksamuelise绿岩带属于Chaillu地块，与刚果克拉通在刚果共和国西南部露头的西北部相对应。主要由角闪岩、斜辉石角闪岩、绿帘石角闪岩、角闪片麻岩和角闪绿泥岩片岩组成的变火山岩性序列组成。这些岩石呈花岗母-花岗母织构，含有角闪石、斜长石、碱长石、石英、绿泥石、斜辉石、黑云母、绢云母、榍石和不透明矿物。SiO2、Fe2O3、Al2O3、CaO、MgO含量较高，其次为Na2O和K2O。在稀土球粒正规化图中，变质火山岩表现为低稀土-低稀土富平型和三稀土平型。然而，在原始地幔归一化图中，大多数样品显示Nb， Ta和Ti的耗尽。微量元素和稀土元素（REE）数据表明，它们的原岩对应于玄武岩和玄武岩安山岩，具有拉斑岩和钙碱性亲和力。变质火山岩可能是由2.5-4 %的次大陆岩石圈地幔源部分熔融形成的，该地幔源通过涉及沉积物衍生熔体和俯冲相关流体的交代作用而富集。研究结果表明，该变质火山岩原岩在柴鲁地块记录的第二次岩浆期处于与俯冲有关的弧后环境，并在新太古代构造变质事件中经历了变质等级上升到角闪岩相的过程。

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引用次数: 0

Mantle amphiboles from the lithospheric keel of the Siberian Craton: Reconstructions using new thermobarometry and geochemistry 西伯利亚克拉通岩石圈龙骨中的地幔角闪石：用新的热气压计和地球化学方法重建

Geosystems and Geoenvironment

Pub Date : 2025-06-28 DOI: 10.1016/j.geogeo.2025.100427

I.V. Ashchepkov , S.A. Babushkina , S.I. Kostrovitsky , O.B. Oleinikov , A.V. Travin , D.S. Yudin , A.S. Ivanov , N.S. Medvedev

Cr-bearing amphiboles frequently occur in the subcratonic lithospheric mantle of Siberian Craton particularly in northern kimberlite fields like West Ukukit, Kuranakh, Kuoika, Kharamai, as well as in the central part of Yakutia – in Alakit and Daldyn fields and in Aldan and Chompolo fields. In the Leningrad pipe of the West Ukukit field, Cr-bearing amphiboles range from Cr-hornblendes to pargasites, edenites, katophorites, and K-richterites, showing an increase in K and Si content, as well as pressure, as determined using the updated amphibole thermobarometer. The P–T estimates for amphiboles are consistent with the results of garnet thermobarometry, supporting the division into seven horizons (interpreted as paleo-subducted slabs).

Typically, the lower to middle pressure levels and the lithospheric boundary are more heated and Fe-rich, which suggests interaction between melts and peridotites within low-pressure traps for hydrous melts.

K-richterites from the lithosphere–asthenosphere boundary exhibit steeply inclined and enriched trace element patterns, characterized by elevated levels of large ion lithophile elements (LILE), Sr, and Rb, along with pronounced negative anomalies in Nb and Pb. The low to middle pressure Na-rich varieties exhibit peaks in Rb, Ba, and Th, but show significantly lower rare earth element (REE) concentrations with marked depressions in the MREE range. Pargasites and hornblendes display concave REE patterns with distinct Eu anomalies, as well as peaks in Ba, U, and Sr and troughs in high field strength elements (HFSE), reflecting subduction-related signatures. Clinopyroxenes show Th, U, and Sr peaks, indicative of plume-related processes. The pargasites and hornblendes show concave REE patterns with Eu anomalies and Ba, U, Sr peaks and troughs in HFSE reflecting subduction-related signs. Clinopyroxenes reveal Th, U, Sr peaks related to plumes. Amphiboles are commonly Cl-bearing and typically associated with subduction-related processes. In the Leningrad pipe, amphibole ages range from 2.67 Ga – indicating early mantle hydration – to 1370, 500, and 370 Ma, which correspond to re-equilibration during major plume events.

含铬角闪岩经常出现在西伯利亚克拉通的次克拉通岩石圈地幔中，特别是在北部的金伯利岩田，如西Ukukit、Kuranakh、Kuoika、Kharamai，以及雅库特中部的Alakit和Daldyn田、Aldan和Chompolo田。在西Ukukit油田的列宁格勒管道中，含铬角闪石从cr角闪石到parparites、etenites、katophiites和K-richterites，显示出K和Si含量的增加，以及压力的增加。角闪石的P-T估计与石榴石热压测量结果一致，支持将其划分为7个层位（解释为古俯冲板块）。通常，中低压力层和岩石圈边界温度较高，富铁，表明熔体和橄榄岩在低压圈闭内相互作用。岩石圈-软流圈边界的K-richterites表现出明显倾斜和富集的微量元素模式，其特征是大离子亲石元素（LILE）、Sr和Rb水平升高，Nb和Pb呈明显的负异常。中低压富na品种Rb、Ba、Th含量最高，而稀土元素（REE）含量较低，在MREE范围内呈明显的下降。寄生体和角闪石呈凹形REE模式，Eu异常明显，Ba、U、Sr呈峰状，高场强元素呈谷状，反映了俯冲相关特征。斜辉石岩中有Th、U、Sr峰，表明与羽相关的过程。寄生体和角闪石呈凹形REE模式，Eu异常和HFSE中Ba、U、Sr的波谷反映了与俯冲有关的标志。斜辉石岩显示与羽状物有关的Th、U、Sr峰。角闪岩通常含cl，通常与俯冲作用有关。在列宁格勒管道中，角闪洞年龄从2.67 Ga（表明早期地幔水化）到1370、500和370 Ma，对应于主要地幔柱事件期间的再平衡。

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引用次数: 0