Geosystems and Geoenvironment最新文献

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 热液源与上升流相关沉积成藏：新特提斯西部下侏罗统早期成矿过程新模式Úrkút锰矿床

Geosystems and Geoenvironment

Pub Date : 2025-12-30 DOI: 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.

匈牙利Úrkút黑色页岩锰矿床形成于全球公认的Toarcian（早侏罗世）Jenkyns事件。20世纪80年代，锰矿热液成矿过程的地球化学特征首次被发现，但其来源和地球化学特征仍存在争议。在这里，我们解决了两个关键问题：(i)为什么具有经济意义的锰矿聚集仅限于Úrkút和epl子盆地，尽管跨多瑙河山脉广泛存在与詹金斯事件相关的沉积，以及（ii）锰的来源是什么。基于新的粘土矿物学（不同形成环境的蒙脱土和贝德石的鉴定），地球化学(Fe和Mn的行为，Co-Ni-Zn和Fe-Mn-(Co-Ni-Cu)三元体系分析；Cd/Mo比值)和沉积学资料（放射虫华的证据），提出了一种新的早期成矿模式。我们认为，在詹金斯事件期间，与新特提斯洋裂谷有关的热盐水池中溶解的铁和锰在缺氧条件下进行了长距离运输。一个长期的上升流系统（从Pliensbachian晚期到Toarcian早期）导致了Bakony盆地的水混合，从而引发了Úrkút和eplacimny锰矿床的“原始矿石”的沉淀。我们的研究结果有助于更好地理解Úrkút和epl子盆地的锰富集，指出全球古环境事件与当地沉积背景之间的关键相互作用。

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引用次数: 0

Spectral dispersion matching technique for multi-class spatial-spectral feature detection of REE-fertile lithology in the Samalpatti alkaline–carbonatite complex (SACC) using Hyperion data 基于Hyperion数据的Samalpatti碱碳酸岩杂岩（SACC）富ree岩性多类空间光谱特征检测的光谱色散匹配技术

Geosystems and Geoenvironment

Pub Date : 2025-12-28 DOI: 10.1016/j.geogeo.2025.100488

P. Abishek , N.K. Libeesh , S. Arivazhagan , C. Sreejith

The Proterozoic alkaline carbonatite complex, lies along the Samalpatti shear zone, is linked to a post-collisional rift setting in the Southern Granulitic Terrain (SGT), provides a geologically intriguing and economically prospective terrain for rare earth element (REE) exploration. This study involves a multiproxy approach by integrating the hyperspectral remote sensing, machine learning, and field validation techniques to delineate the REE fertile lithology units using the EO-1 Hyperion imagery. The pre-processed dataset was subjected to noise reduction and dimensionality reduction using spectral dispersion matching (SDM) methods. SDM was performed in 3 steps; initially, noise reduction algorithms such as principal component analysis (PCA), independent component analysis (ICA), minimum noise fraction (MNF), and band ratio combinations (BRC) were applied to enhance data quality. This was followed by correlation-based feature selection using support vector machines (SVM), focusing on spectral behaviour. Subsequently, mineralogical characteristics were integrated and validated to emphasize their spectrochemical properties. Among the reduction algorithms, ICA achieved the highest spectral class separability, as confirmed by Jeffries–Matusita distance analysis, with values >1.9 for key lithological pairs. The correlation-based feature selection was performed with a radial basis function (RBF) kernel, yielding an overall accuracy of 85.56% and a Kappa coefficient of 0.80. The multiproxy approach using SDM highlights the efficacy of imaging spectroscopy combined with advanced classification techniques in complex lithological terrains and offers a scalable framework for mineral exploration targeting REE-fertile zones.

位于Samalpatti剪切带的元古代碱性碳酸盐岩杂岩与南粒状地质体（SGT）的碰撞后裂谷环境有关，为稀土元素（REE）勘探提供了一个具有地质吸引力和经济前景的地质体。本研究采用多代理方法，通过整合高光谱遥感、机器学习和现场验证技术，利用EO-1 Hyperion图像描绘REE肥沃岩性单元。利用光谱色散匹配（SDM）方法对预处理数据集进行降噪和降维处理。SDM分3步进行；首先，采用主成分分析（PCA）、独立成分分析（ICA）、最小噪声分数（MNF）和频带比组合（BRC）等降噪算法来提高数据质量。随后使用支持向量机（SVM）进行基于相关性的特征选择，重点关注光谱行为。随后，对矿物学特征进行整合和验证，以强调其光谱化学性质。在约简算法中，经Jeffries-Matusita距离分析证实，ICA实现了最高的谱类可分性，关键岩性对的值为>；1.9。采用径向基函数（RBF）核进行基于相关性的特征选择，总体准确率为85.56%，Kappa系数为0.80。使用SDM的多代理方法突出了成像光谱与复杂岩性地形中先进分类技术相结合的有效性，并为以稀土元素肥沃带为目标的矿产勘探提供了可扩展的框架。

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引用次数: 0

Electrical resistivity tomography for geohazard assessment in West Lombok’s alluvial plain 在西龙目岛冲积平原进行地质灾害评估的电阻率层析成像

Geosystems and Geoenvironment

Pub Date : 2025-12-11 DOI: 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.

电阻率层析成像（ERT）广泛应用于地下测绘，在地质灾害评估中非常有用。电阻率的变化可以提示与断裂带有关的异常，或指定特定体的沉积物分层，如沉积物填充盆地，或易于发生地震放大、液化和地面破坏的松散土壤。本研究考察了西龙目岛的两个冲积平原：马塔兰市（人口稠密的首都）和丹绒（沿海旅游区）。冲积平原特别容易受到地质灾害的影响，因为它们松散的、水饱和的沉积物会加剧地震震动，并在地震期间增加液化的风险。我们的ERT模型显示了一致的地下结构：砂占主导的层延伸超过30米，顶部是富含浮石的火山沉积物。在一些地区，探测到浅层地下水（2米深），进一步增加了液化潜力。具体的电阻率模式与已知的液化特征相匹配，这表明马塔兰曾经发生过历史液化。这些结果强调了将ERT与直接方法（如挖沟和钻孔）结合起来验证地下模型和完善危害评估的重要性。

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引用次数: 0

Origin and paleoenvironmental conditions of iron duricrust in the Paleogene N’kapa Formation, Douala sub-basin, Cameroon 喀麦隆杜阿拉亚盆地古近系N’kapa组铁质硬壳成因及古环境条件

Geosystems and Geoenvironment

Pub Date : 2025-12-11 DOI: 10.1016/j.geogeo.2025.100486

Kevin Jorex Voufor Tsafack , Ngong Roger Ngia , Christopher Fuanya , Christopher M. Agyingi , Elie Fosso Menkem , Alexandrine N’nanga , Median Yongye , Ligbwah Victor Wotanie

This paper unravels rarely studied paleoenvironmental conditions and origin of iron duricrust in the Paleogene N’kapa Formation, Douala sub-basin, Cameroon. It integrates petrographic and geochemical techniques (mineralogy, trace, major and REEs elements) and isotope of δ¹⁸O, δD and ⁸⁷Sr/⁸⁶Sr to reconstruct paleoclimate, paleoweathering, paleoredox and paleosalinity, and established mechanisms of formation of iron duricrust. The textures and mineralogy of iron duricrust indicates that they are ferricretes with brecciated to colloform textures composed of hematite, siderite, kaolinite and detrital quartz grains. Paleoclimate proxies revealed humid to semi-arid climate and variation in climatic conditions caused intense-chemical weathering, favouring a change in weathering processes from kaolinitisation to ferricretization. Paleoredox and paleosalinity proxies indicate that the iron duricrust was formed under dysoxic to dominantly oxic conditions in shallow freshwater to somewhat brackish water body with intermediate salinity. The δ¹⁸O, δD and ⁸⁷Sr/⁸⁶Sr composition of the samples indicate post-depositional alteration due to influx of meteoric waters during the duricrusting process. The equilibration with meteoric water reveals that the iron duricrusts formed primarily through supergene enrichment and diagenetic reworking of detrital sediments. However, some contribution from hydrogenous input occurred in lagoonal settings with fluctuating salinity, which probably facilitated the precipitation of iron directly from water. The remobilization of iron led to the formation of secondary hematite, which could possibly be link to early Paleogene climatic variations and eustatic sea-level changes. These findings provide valuable insights into sedimentary mineral enrichment in response to Paleogene environmental dynamics and offer a reference for comparable iron-rich deposits in African basins and other parts of the world.

本文对喀麦隆杜阿拉亚盆地古近系N’kapa组铁质硬壳的古环境条件和成因进行了研究。综合岩石学和地球化学技术（矿物学、微量元素、主元素和稀土元素）和δ18O、δD和87Sr/86Sr同位素，重建了古气候、古风化、古氧化还原和古盐度，建立了铁硬壳的形成机制。铁硬壳的结构和矿物学特征表明，它们是由赤铁矿、菱铁矿、高岭石和碎屑石英颗粒组成的角砾状至胶状结构的铁铁石体。古气候指标反映了湿润至半干旱的气候，气候条件的变化导致了强烈的化学风化作用，有利于风化过程从高岭土化到铁质化的变化。古氧化还原指标和古盐度指标表明，该铁质硬壳形成于中盐度的浅淡水到半咸淡水中，在缺氧至主要氧化条件下形成。样品的δ18O、δD和87Sr/86Sr组成表明，沉积后的蚀变是由地壳形成过程中大气水的流入引起的。与大气水的平衡表明，铁硬壳主要是通过碎屑沉积物的表生富集和成岩改造而形成的。然而，在盐度波动的泻湖环境中，氢输入产生了一些贡献，这可能促进了铁直接从水中析出。铁的再活化导致了次生赤铁矿的形成，这可能与早古近纪的气候变化和海平面上升有关。这些发现为研究古近纪环境动力学下的沉积矿物富集提供了有价值的见解，并为非洲盆地和世界其他地区类似的富铁矿床提供了参考。

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引用次数: 0

Is the expansion of oxygen minimum zones impacting the health of modern ocean basins? A review 氧最低带的扩大是否影响了现代海洋盆地的健康？回顾

Geosystems and Geoenvironment

Pub Date : 2025-11-28 DOI: 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.

氧最低带（OMZ）是指现代海洋盆地中氧浓度急剧下降。自1960年以来，这些区域的扩张被记录在案。它们在全球海洋中不断扩大，对海洋生态系统和生物地球化学循环产生深远影响。在此综述下，我们综合和整合了目前关于现代大洋盆地OMZ扩张的因素、动力和后果的知识。我们探索了有利于OMZ形成和强化的物理、化学和生物因素的相互作用，强调了海洋环流模式、人为活动引起的营养物质富集和气候变化的增强影响的作用。从海洋生物生理应激、生境压缩、群落结构变化和生物多样性潜在损失等方面探讨了海洋生物多样性对海洋生态的影响。我们还研究了它们对温室气体排放的贡献以及omz的生物地球化学意义，特别是在氮和其他营养循环的背景下。此外，这项工作强调了OMZ扩展与气候变化之间复杂的反馈循环，强调了迫切需要制定缓解和适应战略。首先，该研究讨论了未来的研究范围和管理方法，这些方法对于应对扩大海洋保护区从而确保现代海洋盆地的健康和可持续性所带来的挑战至关重要。

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引用次数: 0

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 喀麦隆北部Gouna地区i型花岗岩的成岩演化：泛非造山期碰撞后岩浆作用俯冲的地球化学证据

Geosystems and Geoenvironment

Pub Date : 2025-11-28 DOI: 10.1016/j.geogeo.2025.100485

Mahamat Abakar , Jacques Wassouo Wadjou , Amadou Diguim Kepnamou , Yaya Fodoué , Jean Marcel Abate Essi , Nguihdama Dagwai , Ngounouno Isamaila

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.

Gouna地区位于喀麦隆泛非带北部，花岗岩种类繁多，包括角闪孔花岗岩、角闪-黑云母花岗岩、黑云母花岗岩、黑云母-白云母花岗岩和含白云母的浅花岗岩。破译它们的岩浆来源和构造演化是理解泛非带地球动力学框架的关键，泛非带记录了新元古代从俯冲到后碰撞的过渡过程。结合25个薄片岩石学调查、13个代表性样品（11个花岗岩和2个石英闪长岩）的全岩地球化学分析和新的Sr-Nd同位素数据，对郭那花岗岩类的成岩演化进行了研究。岩石为铝质、钙碱性、镁质（sio2 = 67.55 ~ 73.15 wt%; K₂O/Na₂O < 1），具有含水氧化条件下的i型花岗岩特征。同位素组成（⁸⁷Sr/⁸⁶Sr′= 0.7068 ~ 0.7072;εNd (540 Ma) = - 4.8 ~ - 6.2）表明岩浆源来源于变质富集地幔，并具有不同的地壳同化作用。角闪花岗岩表现出弱REE分异（(La/Yb)n = 0.64 ~ 1.68）和明显的负Eu异常（Eu/Eu* = 0.29 ~ 0.45），而含白云母的浅长花岗岩表现出高REE分异（(La/Yb)n = 17.30 ~ 33.71）。原始地幔归一化模式显示Nb、Ta、Ti、Pb、Sr、Y和Hf的负异常，LILEs相对于hfse富集，反映了俯冲修正的来源。地球化学和同位素资料共同记录了一个多阶段的岩浆演化，标志着从弧相关的地幔岩浆作用到碰撞前后的熔融作用（600-540 Ma）的过渡，突出了泛非造山运动期间的渐进式幔壳相互作用。

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引用次数: 0

Peridotite pyroxenite and granulite xenoliths from Cenozoic Shavaryn Tsaram volcanic center (Mongolia): New data 蒙古Shavaryn Tsaram火山中心新生代橄榄岩辉石岩和麻粒岩捕虏体：新资料

Geosystems and Geoenvironment

Pub Date : 2025-11-27 DOI: 10.1016/j.geogeo.2025.100484

I.V. Ashchepkov , A.A. Tsygankov , G.N. Burmakina

Mantle lherzolites (spinel- and garnet-bearing), megacrysts and pyroxenites from Moho and lower crust xenoliths of the Cenozoic basalts of Shavaryn-Tsaram volcanic center were newly studied by the EPMA, SEM and LA-ICP methods to define more precisely their geochemical features for genetic purposes.

Thermal conditions in sampled mantle are close to the Southeastern Australian (SEA) mantle plume geotherm in 1.2–2.5 GPa divided into three intervals according to orthopyroxene-garnet barometry. The monomineral thermobarometry for ortho-, clinopyroxenes and garnets gives wider PT range to 3.0 GPa deviating to lower temperature clusters at 2–2.4 GPa. Black megacrysts show ascending from 3.0 to 1.0 GPa trend for pyroxenes and garnet accompanied by increase of Fe# for equilibrated with olivine (Ol) from 0.15 to 35 %. The intermediate Cr-bearing transitional pyroxenites are locating between the lherzolitic and black pyroxenite trends. They are referring to the primitive or slightly depleted associations according to petrographic and trace element (TRE) compositions. According to TRE of clinopyroxenes from spinel peridotites were divided into 5 groups: primitive, slightly depleted, deeply depleted; metasomatized by light rare earth (LREE); rich-Th-U (reactions with carbonatite melt) and in addition rare garnet-bearing types. Orthopyroxenes reveal decreasing to LREE straight line REE patterns and in TRE spiderdiagrams U, Ta and high Hf peaks. Some clinopyroxenes have Sr peaks and jagged left part of multicomponent spiderdiagrams (MSD). Olivines show and concaved from Eu to Tm in spider diagrams they reveal minima in Th, Nb, Pb, Zr. The Cr- bearing amphiboles reveal slightly inclined to LREE pattern at 90–60/CI (chondrite). And garnet show LREE depleted patters from Lu at 10/CI to 0.1 for La and depleted all left part at spider diagram, The pyroxenitic clinopyroxenes have flattened REE pattern or rarely depleted in heavy (HREE) and the hump from La to Sm. They reveal minima in Zr, Hf, Sr, Pb and left part starting from Nb. Garnets in black pyroxenites have higher HREE at 80/CI (chondrite) and Hf peaks and lowered jugged left part in MSD. The clinopyroxenes from black garnets pyroxenites reveal asymmetric bell- like REE with the depleted HREE to 1/CI and middle rare earth (MREE) at 12/CI. The clinopyroxenes from plagioclase-bearing varieties show flattened REE pattern at 100–80/CI and Eu minima and the MSD for megacrystic pyroxenes. Rare mantle metasomatites contain mica or amphiboles and are LREE enriched. Peridotites from Shavaryn Tsaram have no signs of essential mantle diapirism and represent ancient MORB mantle.

Determined with LA-ICP-MS age of zircon in granulite 322 ± 8 Ma refer to rifting processes in Central Mongolia and be-modal volcanism while 42 ± 0.4 Ma to Early Cenozoic plume magmatism.

本文利用EPMA、SEM和LA-ICP方法对沙瓦林-察兰火山中心新生代玄武岩的地幔热橄榄岩（含尖晶石和石榴石）、莫霍巨型晶岩和辉石岩以及下地壳包体进行了新的研究，以更精确地确定其地球化学特征。样品地幔热条件接近东南澳大利亚（SEA）地幔柱地热（1.2 ~ 2.5 GPa），根据正辉石-石榴石气压测定分为3个层段。正晶、斜辉石和石榴石的单矿物热压测量结果显示PT范围较宽，可达3.0 GPa，偏离较低的温度簇，为2-2.4 GPa。辉石和石榴石的黑色巨晶呈现3.0 ~ 1.0 GPa上升趋势，与橄榄石（Ol）平衡的fe#从0.15 ~ 35% %增加。中间含铬过渡型辉石岩位于辉石岩倾向和黑色辉石岩倾向之间。根据岩石学和微量元素（TRE）组成，它们指的是原始的或轻微枯竭的组合。根据尖晶石橄榄岩斜辉石的TRE划分为5组：原始、微贫、深贫；轻稀土（LREE）交代作用；富钍铀（与碳酸盐熔体反应）和稀有的含石榴石类型。正斜晶石呈现低稀土直线模式，并在稀土蜘蛛图中呈现U、Ta和Hf高峰。有些斜辉石在多组分蜘蛛图（MSD）上有Sr峰，左侧呈锯齿状。橄榄石在蜘蛛图中显示并从Eu到Tm凹出，它们显示Th， Nb, Pb， Zr的最小值。含铬角闪岩在90 ~ 60/CI（球粒陨石）范围内呈现轻稀土模式倾斜。辉长岩斜辉长岩在10/CI ~ 0.1范围内表现为Lu - La的LREE亏缺模式，在蜘蛛图上全部亏缺。辉长岩斜辉长岩的REE亏缺模式较为扁平，重（HREE）极少亏缺，La - Sm呈驼峰。其中Zr、Hf、Sr、Pb最小，其余部分从Nb开始。黑色辉石岩中的石榴石在80/CI（球粒岩）和Hf峰处有较高的HREE和Hf峰，在MSD中有较低的左倾部分。黑石榴石辉石中斜辉石的稀土元素呈不对称钟形，其中稀土元素的贫化程度为1/CI，中稀土元素的贫化程度为12/CI。斜长石品种斜辉石在100-80 /CI和Eu最小值处表现出平坦的REE模式，而微晶辉石的MSD则表现为均匀分布。稀有地幔交代岩含云母或角闪石，低稀土元素富集。Shavaryn Tsaram的橄榄岩没有必要的地幔底渗作用的迹象，代表了古老的MORB地幔。用LA-ICP-MS测定麻粒岩中锆石年龄（322±8 Ma）为中蒙古裂谷作用和be-modal火山作用，42±0.4 Ma为早新生代柱状岩浆作用。

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引用次数: 0

Hydrogeochemical characterization of water in the Kadey watershed (Central Africa): An approach to the dynamics of groundwater/surface water exchanges 中非Kadey流域水的水文地球化学特征：地下水/地表水交换动力学的方法

Geosystems and Geoenvironment

Pub Date : 2025-11-20 DOI: 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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引用次数: 0

Integrating satellite observations, coral Sr/Ca proxies, and model simulations to analyze sea surface temperature variability (1915-2003) in Indonesia 综合卫星观测、珊瑚Sr/Ca代用物和模式模拟分析印度尼西亚的海面温度变化（1915-2003）

Geosystems and Geoenvironment

Pub Date : 2025-11-20 DOI: 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.

珊瑚礁是过去海洋状况的重要指标，因为它们能够记录碳酸钙结构的环境变化。具体来说，珊瑚骨骼中的锶钙比（Sr/Ca）可以作为重建海温随时间变化的可靠代理。本研究的目的是评估气候模式模拟的海温（SST）变率与实际观测的相似性。该研究利用了一个综合数据集，该数据集整合了卫星衍生的海温观测和耦合模式比对项目第5阶段（CMIP5）模式模拟，以及印度尼西亚三个地点（Gili Selang， Kupang和Nusa Penida）的珊瑚Sr/Ca记录。结果表明，CCSM4模式对印度尼西亚海温变化具有较高的鲁棒性。CCSM4与OISST卫星和Sr/Ca记录的海温数据的相关性高于其他模式，相关值分别为0.7和0.32。与CCSM4的空间相关图显示，印尼地区ENSO和IOD的相位与海温（SST）分布的相关性较弱。这些低相关值表明，正如CCSM4模式模拟的那样，ENSO和IOD现象对印度尼西亚海温变率的影响很小。CCSM4海温与Niño指数和偶极子模式指数（DMI）的相关系数在-0.213 ~ 0.055之间。此外，CCSM4经常模拟与ENSO和IOD相的预期效应相反的海温响应。这些结果表明，尽管CCSM4在CMIP5模式中相对较强，但在再现ENSO和IOD对印度尼西亚海海温变率的区域影响方面仍然缺乏足够的精度。

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引用次数: 0

Advanced machine learning based gold prospectivity mapping in the Dharwar Craton, India: A hybrid knowledge-data driven paradigm integrating ensemble and deep learning 印度Dharwar克拉通基于先进机器学习的金矿远景映射：集成集成和深度学习的混合知识数据驱动范式

Geosystems and Geoenvironment

Pub Date : 2025-11-07 DOI: 10.1016/j.geogeo.2025.100473

Soumya Mitra , Saptarshi Mallick , Santu Biswas , Kshounish Patra

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.

为了满足世界范围内对矿产资源日益增长的需求，必须开发更先进、更有效的找矿方法来识别隐伏矿体。在这方面，矿产远景测绘（MPM）至关重要。本研究开创性地应用和比较了四种机器学习（ML）模型——随机森林（RF）、XGBoost （XGB）、支持向量分类器（SVC）和人工神经网络（ANN）——用于印度太古代Dharwar克拉通的金矿远景映射。主要目标包括开发和评估这些模型，通过交叉验证对其比较性能进行系统评估，特征重要分析并最终生成前景图。这项工作的最终成果是一张高分辨率的综合远景图，旨在产生一个新的远景区。根据矿区的矿产系统，对包括地质图、构造地貌、地球化学、地球物理和ASTER遥感影像在内的多种地理空间数据进行了精心整合。对于模型训练，我们仔细收集了79个已知的金矿点，以及相同数量的选定的非金矿点，将该任务构建为一个监督二元分类问题。严格的评估，采用5倍交叉验证和70:30训练测试分割，证实了这些模型的卓越能力。XGB和RF一直是表现最好的，AUC-ROC值分别为0.9992和0.9965，加上高精度、召回率和f1得分高，假阳性或阴性少。虽然人工神经网络也表现出出色的性能，但SVC虽然很强，但产生的指标相对较低。详细的特征重要性分析表明，变质玄武岩、地球化学主成分1和布格重力异常及其衍生图在该区的积极作用。成功率曲线生动地说明了模型的效率，在排名最高的20%的区域内捕获了超过76%的已知事件，显示了目标精度。生成的组合远景图是XGB、RF和ANN的强大综合，基于严格的共识标准，验证了现有知识，并精确地划定了高优先级的勘探目标，从根本上重塑了未来矿产勘探的方法。

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引用次数: 0