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Journal of Geochemical Exploration
Elsevier
Journal of Geochemical Exploration

Elsevier

0375-6742

Journal of Geochemical Exploration/Journal Journal of Geochemical ExplorationSCIISTPEIAHCI
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    Tritium as a tool to assess leachate contamination: An example from Conversano landfill (Southern Italy)

    Brunella R.Raffaele B.
    13页
    查看更多>>摘要：? 2021This paper describes the geochemical and isotopic data processing combined with statistical analysis aimed to fine-tune the tritium background threshold limits to identify groundwater contamination due to leachate dispersion at a very high level of sensitivity. The selected case study refers to a landfill located in area subjected to marine intrusion and intense anthropic pressure due to agricultural activities. The investigated aquifer pertains to a karst system with a geological structure that potentially allows an easy spread of contamination. Twenty wells, with depth ranging from 179 to 462 m, and 4 leachate samples, were collected and analysed for main dissolved ions, some minor and trace species (NH4+, NO2?, Br?) and isotope content (δ18O, δ2H and tritium). The adopted approach allowed defining the geochemical background of groundwater tritium content, and confirming that tritium content is an effective leachate tracer, both for the high contrast between groundwater and leachate, and for its conservative characteristics. These characteristics make tritium the leachate tracer par excellence, far preferable to any chemical or other isotopic parameters, whose variations may be influenced by chemical and physical processes other than leachate contamination.
      原文链接:
    • NSTL
    • Elsevier

    Application of geographically weighted regression (GWR) and singularity analysis to identify stream sediment geochemical anomalies, case study, Takab Area, NW Iran

    Nazarpour A.Rostami Paydar G.Mehregan F.Hejazi S.J....
    12页
    查看更多>>摘要：? 2022 Elsevier B.V.In geologically and lithologically complex areas, distinguishing weak geochemical anomalies from background and defining a valid threshold value are central issues in mineral exploration. This study benefited from using geographically weighted regression (GWR), ordinary least square regression (OLSR), singularity analysis, and a combined model of GWR and singularity analysis to identify geochemical anomalies related to Pb–Zn mineralization in the Takab area (Iran). In the analyses, major oxides were considered independent geo-variables related to upstream of stream sediment samples and on-site rock types. The results of GWR revealed the non-stationary effect of independent geo-variables on Pb–Zn geochemical anomalies, on local R2 among geo-variables, and on measured values of trace elements, which suggested a meaningful improvement in trace element prediction in comparison with OLSR. The results of singularity model showed that geochemical anomalies were closely coincident with known carbonate-hosted Pb–Zn deposits and with carbonaceous geological units in the Takab area. Anomalies delineated by singularity model illustrated another potential for follow-up mineral exploration. The results of the combined model of GWR and singularity model—based on consideration of Type I and Type II errors—exhibited not only higher coincidence with known mineral deposits but also introduced new potential exploration targets in the Takab area; that is, the combined model led to a more profound recognition of weak anomalies in a geologically and lithologically complex area.
      原文链接:
    • NSTL
    • Elsevier

    Terrestrial and aquatic ecotoxicity of iron ore tailings after the failure of VALE S.A mining dam in Brumadinho (Brazil)

    Alexandre K.Carneiro M.Bertolino L.C.Domingos L....
    15页
    查看更多>>摘要：? 2022 Elsevier B.V.This study consists of an ecotoxicological assessment related to one the most important environmental Brazilian disasters: the failure of an iron mining dam of the Vale S.A. in Brumadinho (Minas Gerais State, Brazil). Tailing samples (mixed with many other materials) were collected in three areas: (i) Zona Quente (n = 9) – close to the dam collapse; (ii) Parque das Cachoeiras (n = 3) – downstream of the Zona Quente; and (iii) Alberto Flores (n = 3), closer to Paraopeba river (an important tributary of one of the most important Brazilian watersheds). Acute ecotoxicological tests with Eisenia andrei and Daphnia similis and chronic reproduction tests with Folsomia candida and Chlorella vulgaris were performed. The bioassays with aquatic organisms were carried out with elutriates of the samples. Metal concentrations and physical, chemical and mineralogical properties of the samples were determined to support the interpretation of the ecotoxicological data. The increase of the particle density values (significantly correlated to an anomalous iron-enrichment and positive ΔpH values) seem to play a relevant role in the toxicity. As a result of iron-enrichment, the reduction of organic matter contents and water holding capacity were also crucial in the toxicity. Metal-enrichment factors showed abnormally high values, especially for Fe, Mn and Ni, while toxic metals concentrations exceeded the limits established by Brazilian law. Reproduction chronic effects were more intense than the acute ones, for both aquatic and soil organisms. Such extremely low reproduction levels of F. candida and C. vulgaris should be highlighted, since such organisms have a key ecological relevance. The samples collected in the Zona Quente were significantly different from the samples collected in downstream areas — fact that might be related to a high energy and turbulent flux of tailings in zones closer to dam, and the reduction of its energy in downstream areas.
      原文链接:
    • NSTL
    • Elsevier

    Genesis of the Carboniferous karstic bauxites in Qingzhen region, central Guizhou, southwest China

    Luo C.Yang R.Chen J.Gao L....
    21页
    查看更多>>摘要：? 2022 Elsevier B.V.In addition to the major source of aluminum, karstic bauxite also contains high concentrations of trace elements such as Li, Ga, V, Sc, Co, Nb, Zr, Ni, U and REE. At present, more than 33.9 million tons of early Carboniferous bauxite overlies the karstic surface of the Cambrian carbonate rocks in Qingzhen region, central Guizhou, southwest China. Here, new mineralogical and geochemical evidence of the Lindai bauxite in Qingzhen region have been provided, aiming to identify parental affinity, discuss the provenance differences between the Qingzhen and Xiuwen areas, illustrate the mineral phase transformation, analyze the factors affecting the distribution of critical elements, and reveal the ore-forming process. Mineralogically, the bauxite ores are dominated by diaspore, boehmite, illite, kaolinite and anatase, with small amount of zircon, hematite, pyrite, cassiterite and medium-low temperature hydrothermal minerals such as barite, chalcopyrite, galena, arsenopyrite. Textural characteristics are dominated by matrix-supported clastic texture, followed by pseudo-breccias, recrystallizational and ooidal textures. Clastic grains with various sizes and shapes are often mixed together without obvious sorting and directional structures, indicating that bauxite ores have undergone short-distance transportation in the form of gravity flow. Provenance analysis indicates that the protoliths of the Lindai bauxite were a mixed lithology including underlying Cambrian Shilengshui Formation dolomite, hydromica claystone and purple-red mudstone rather than single dolomite considered by previous studies. Particularly, the presence of hydromica claystone and purple-red mudstone has a significant contribution to high concentrations of trace elements and REE in the Jiujialu Formation. Studies of mineral genesis have shown that the formation of diaspore includes supergene crystallization and metamorphism. R-mode factor analysis revealed that (i) these elements including Al, Ti, Ga and HFSE are relatively stable and immobile during weathering process, and tend to be enriched in the karstic bauxite, (ii) the distributions of HREE are controlled by the REE minerals and Fe oxide-hydroxides, (iii) vanadate minerals have crucial roles in the distribution of LREE in addition to the phosphate minerals, and (iv) the enrichment of Ni is related to the adsorption of hydroxo complex of uranium. The studies reported in this paper provide new insights into the provenance and mineral phase transformation of the Carboniferous karstic bauxite in central Guizhou area.
      原文链接:
    • NSTL
    • Elsevier

    A regional-scale geochemical survey of stream sediment samples in Nappe zone, northern Tunisia: Implications for mineral exploration

    Ayari J.Barhoumi A.Belkhiria W.Braham A....
    12页
    查看更多>>摘要：? 2022 Elsevier B.V.The Nappe Zone (NZ) is a main major metallogenic zone in Tunisia, containing lead, zinc, iron and copper deposits. Complex geological, structural conditions and wide variety of ore deposit types could result in different geochemical patterns and geochemical anomalies. In this study, a regional geochemical data set containing 8307 stream sediment samples (<177 μm) analyzed for As, Ba, Co, Cr, Fe, Mn, Ni, Pb, Sb, Sr, V and Zn, was used to better understanding of the geochemical patterns and genesis of Pb–Zn deposits. Due to compositional nature of geochemical data, a robust principal component analysis (RPCA) was used to identify the assemblages of elements related to mineralization. Geochemical anomalies for ore-forming elements and element assemblages were delineated based on median absolute deviation (MAD). The data were then visualized and analyzed using classical dot maps, which were gathered with geological units, tectonic, and database of the ore deposits of Tunisia using a geographic information system (GIS). RPCA, based on minimum covariance determinant (MCD) revealed that Pb–Zn deposits in the Nappe zone belong to two genetic types: a Pb–Zn–Ba–Sr Mississippi-valley-type (MVT) hosted by carbonates (limestone and dolomites) and a Pb–As–Sb SEDEX type mainly hosted by Miocene shales. The geochemical anomalies delineated by the Median ± 2MAD method revealed that Pb–Zn–Ba–Sr mineralization displays zoning along the NE–SW-trending faults, while Pb–As–Sb mineralization displays zoning along the E–W-trending lineaments. The spatial associations of numerous anomalies with some regional structures suggest that this region can have good ore-potentiality. The results would not only be valuable to identify the ore-related geochemical associations and potential exploration targets, but also enhance the classification of mineralization in Nappe zone.
      原文链接:
    • NSTL
    • Elsevier

    Dictionary learning for multivariate geochemical anomaly detection for mineral exploration targeting

    Chen Y.Shayilan A.
    14页
    查看更多>>摘要：? 2022 Elsevier B.V.Dictionary learning is usually used to train an overcomplete dictionary composed of basis vectors (i.e., atoms) to best sparsely represent the training dataset. The sparse representation of a data point is a sparse linear combination of the atoms derived from the well-trained overcomplete dictionary. The sparse representations of all the training data points constitute a supporting set of the population distribution of the training dataset. In this paper, geochemical exploration data was used as the training data of the five dictionary learning algorithms to train overcomplete dictionaries. The sparse representations of all the geochemical data points were used to describe the (complex) geochemical background, and the Euclidean distance between a data point and its sparse representation was used to express the anomality of the data point in multivariate geochemical anomaly detection. For demonstration purposes, the Chengde district in Hebei Province (China) was used as the case study area, and five dictionary learning models were established for multivariate geochemical anomaly detection for gold mineral exploration targeting. The performances of the five dictionary learning models were compared with that of the k-nearest neighbor (KNN) model, combined KNN model, and Gaussian mixture model (GMM) in gold mineral exploration targeting. The results show that (a) the five dictionary learning models are superior to the KNN model, the combined KNN model, and the GMM model either in terms of receiver operating characteristic curve (ROC) or in terms of area under the curve (AUC), and (b) the gold prospective areas optimally delineated in the study area accounts for a small proportion of the area, but contains most of the known gold deposits, and have spatial correlation with the favorable ore-forming factors such as the outer contact zone of multistage magmatic intrusion and the NE-trending fault zone. Therefore, the dictionary learning algorithms are feasible techniques of multivariate geochemical anomaly detection for mineral exploration targeting. It is worth to further test the usefulness of the dictionary learning algorithms in different areas with complex geochemical backgrounds.
      原文链接:
    • NSTL
    • Elsevier

    A Comparative study of the mineral composition of Macrotermes and Cubitermes termite mounds in Lualaba, D.R. Congo: Contribution to strategic prospecting for Cu and Co deposits

    Ilunga Ngoy S.Auclerc A.Watteau F.Callec Y....
    14页
    查看更多>>摘要：? 2022 Elsevier B.V.This work focuses on the comparative analysis of the influence of two termites of the Macrotermes (fungus-growing) and Cubitermes (soil-feeding termites) genera on the dynamics of soil lithogeochemical facies. The aim was to establish a general systematic recognition of the lithology of a large area, including its potential for Cu and Co mineralization. Eighty-eight samples of the mound material were collected from termite mounds of these two species along a 50 km transect in Lualaba Province, Democratic Republic of Congo (DRC) in order to carry out major and trace element analyses. Interpretation of the data was carried out through exploratory analysis, using the Ascending Hierarchical Classification (AHC) method and Principal Component Analysis (PCA), followed by statistical modeling using linear regression. After clustering the termite mounds into classes by AHC, an initial PCA was used to map the lithology of these classes using major elements. The results highlight the dependance of the lithological composition of the mounds on the behavior specific to each of the two termite species. Linear regression modeling allowed a delineation of the area of supply of building materials for each species, indicating the possible incorporation of Cu and Co mineralizations likely to be present in the environment of the termite mounds. The use of termite mounds as a tool in mining exploration is discussed.
      原文链接:
    • NSTL
    • Elsevier

    Gold prospectivity mapping and exploration targeting in Hutti-Maski schist belt, India: Synergistic application of Weights-of-Evidence (WOE), Fuzzy Logic (FL) and hybrid (WOE-FL) models

    Behera S.Panigrahi M.K.
    29页
    查看更多>>摘要：? 2022 Elsevier B.V.Our study attempts to map gold prospectivity for deriving optimal exploration targets using data-driven, knowledge-driven and hybrid approaches. Prospectivity models viz. Weights of Evidence (WOE), Fuzzy Logic (FL) and a hybrid model that combines the data-driven and knowledge-driven components (WOE-FL) were applied to a part of the auriferous Hutti-Maski schist belt of 1352 km2 area with 20 known gold occurrences. With a pixel resolution of 500 m, 16 spatial evidential raster layers were created on a GIS platform encompassing viable predictive indicators, critical in gold exploration. Modelling inputs include essential ingredients and mappable criteria of the conceived orogenic gold mineral system in the study area. Multi-source geological data such as lithostratigraphic units, favourable litho-contacts, structural deformation sites, geochemical anomalies of selected gold pathfinder elements, and hydrothermal alteration zones derived from digital image processing of Landsat 8 OLI satellite imagery were integrated to generate prospectivity maps for delineation of future targets. A quantitative evaluation of the resulting three prospectivity maps was performed using concentration-area (C-A) fractal analysis, prediction–area (P–A) plot, fitting-rate curve (FRC) and area under curve (AUC). Comparative analysis indicates that the performance of the hybrid model (WOE-FL) stands out to be the most efficient, with a prediction rate of 87% and AUC of 91.40% compared to WOE and FL. A risk assessment was performed combining the outputs of prospectivity models that returned 10% of the study area as potential exploration targets out of which the low-risk exploration targets comprises merely 4.5% representing the optimal targets for gold exploration in the study area.
      原文链接:
    • NSTL
    • Elsevier

    Recognition and incorporation of mineralization-efficient fault systems to produce a strengthened anisotropic geochemical singularity

    Ghasemzadeh S.Maghsoudi A.Yousefi M.Mihalasky M.J....
    14页
    查看更多>>摘要：? 2022 Elsevier B.V.Identification of geochemical anomalies using singularity theory is a topic of interest in the field of mineral exploration. The ordinary singularity mapping technique does not consider the critical role of geological structures in the ore-forming environment. Therefore, models of spatially weighted singularity have been developed through the incorporation of fault systems, which might play an important role in ore-forming processes, and thus, are key factors in spatial analysis of mineralization indicators. In this study, we proposed a strengthened singularity mapping technique that was spatially enhanced and weighted by mineralization-efficient fault systems. For this, we applied distance distribution analysis to distinguish “efficient” (linked to mineralization) and “inefficient” (not linked to mineralization) fault systems, and then, used the former to generate the strengthened spatially weighted singularity models of geochemical indicator elements. The rationale is that faults with different orientations are the result of various geological processes, of which only some are linked to the ore-forming processes. We also integrated the strengthened models of geochemical anomalies by using random forest (RF) and principal component analysis (PCA) techniques to produce a stronger geochemical clue. Comparison of the integration results demonstrated that the former, a strengthened anisotropic geochemical singularity modeling technique proposed in this paper through the incorporation of efficient fault systems and RF method, is superior to the later, an existing anisotropic geochemical singularity modeling technique through the incorporation of all faults and PCA method. Data related to porphyry copper mineralization in Sarduiyeh district, Iran, was used to illustrate the procedure applied.
      原文链接:
    • NSTL
    • Elsevier