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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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    Integrating principal component analysis and U-statistics for mapping polluted areas in mining districts

    Seyedrahimi-Niaraq M.Mahdiyanfar H.Mokhtari A.R.
    15页
    查看更多>>摘要：? 2021 Elsevier B.V.Detecting metal contaminations and mapping the areas affected by pollutants surrounding the mining activities are essential issues in environmental geochemistry. Toxic metals can be broadly distributed around the mines owing to the effects of dust, water, and diverse anthropogenic activities. In this study, the effects of metal pollution from mining activities in Irankuh Pb-Zn mine, located in central Iran, on the surrounding environment have been investigated. Toxic metals, especially lead and zinc, dispersed in the agricultural area in the south of the Irankuh mine have been deemed environmental stressors. This study introduces a new combined methodology based on principal component analysis (PCA) and U-statistics modeling to recognize the zones afflicted by toxic metal pollution. The stepwise principal component analysis (SPCA) is a multi-stage dimension reduction technique applied to extract significant pollution sources of toxic metals around agricultural areas. After five stages of SPCA, the Pollution Principal Factor (PPF) was determined based on the rotated component matrix, and the toxic metals related to the pollution area were identified. For mapping the multivariate metal contamination, the U-statistics method was applied to the PPF for identification of toxic metal anomalies. The concentration-area fractal method was also utilized for separating and mapping different populations of Pb, Zn, As, Mn, Ba, and Cd. To apply this method, ordinary Kriging was used to grid and interpolate raw data. The U-values of PPF in the proposed method were delineated and compared to the results of the fractal method. The proposed approach displays more accurate results for pollution mapping. The methodology adopted here can be applied to other case studies for the source apportionment of toxic metals.
      原文链接:
    • NSTL
    • Elsevier

    Lithogeochemical and isotopic characterization of Devonian molybdenite mineralization in the Pabineau Falls Granite, northeastern New Brunswick, Canada

    Mohammadi N.Lentz D.R.McFarlane C.R.M.Rogers N....
    13页
    查看更多>>摘要：? 2021 Elsevier B.V.An unusual molybdenite occurrence in northeastern New Brunswick, referred to herein as the Pabineau Lake Mo (PLM), is situated to the south of Bathurst. This occurrence consists of high-grade molybdenite-bearing granites that occur within the large Pabineau Falls Granite (PFG). To help evaluate the evolution of this occurrence, a large composite sample containing disseminated, very coarse molybdenite (up to 5.02 wt% MoS2) was collected from mineralized granitic blocks excavated from a blasted trench. Although the host rocks are assumed to be PFG, being the only defined intrusive body in the area, major- and trace-element geochemical data together with U-Pb geochronological results suggest that the molybdenite is hosted by an intrusion distinct from the PFG. The radiogenic Sr-Nd-Hf-Pb isotopic data of the host intrusion are consistent with Gander Zone granites of the Appalachians orogenic system. The PLM's granitic host rock is characterized by a high silica content (78.93 wt% SiO2), an enrichment in incompatible elements, and a high molybdenum content. The high initial 87Sr/86Sr of 0.71268, negative εNd of ?1.28, and high Pb isotope ratios together with trace- and major-element concentrations indicate a moderately to highly radiogenic Sr source and derivation from a significant amount of supracrustal materials, with a contribution from the upper mantle; a source similar to that proposed for the Gander Zone Siluro-Devonian granitic bodies. A positive εHf (+1.34) also suggests involvement of sedimentary components. This is consistent with elevated Cr (20 ppm) and Ni (20 ppm). The involvement of a pelagic sedimentary component is invoked to explain the enrichment in elements commonly associated with mafic compositions. A new precise, LA ICP-MS zircon crystallization age of 390±1 Ma makes the PLM host granite Middle Devonian, which argues against a direct relationship with the older PFG (397.2±1.9 Ma). The new age opens the possibility of an as yet undelineated, mineralized intrusion within the Gander Zone, which has perhaps been missed during previous investigations due to the extensive glacio-fluvial cover and very limited bedrock exposures. Alternatively, the younger age could be attributed to very slow cooling and/or intra-pluton fractionation, resulting in a younger much more fractionated phase of the PFG. However, there is no geochemical evidence for such a prolonged continuous fractional crystallization process. Notably, recent geophysical surveys on the Bathurst Mining Camp indicate that the PFG is substantively larger than its surface expression as it continues to the east beneath the Carboniferous unconformity. Comparing ages of PLM and PFG with the nearby Nicholas-Denys Granodiorite (381±4 Ma) and Antinouri Lake Granite (372±4 Ma), it appears that magmatic activity in the region occurred every 10 Myr over a span of about 30 Myr. Collectively, this evidence suggests the potential of significant buried intrusions within this tectonic belt of the Gander Zone. At the PLM, this might include exposure of an otherwise hidden intrusion that is younger and much more fractionated than the PFG. More detailed geophysical and geochemical analyses would be required to revise the current geological map and, most importantly, trace unmapped units at depth to possible additional mineralized sequences.
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    • NSTL
    • Elsevier

    Comparison of four nickel hyperaccumulator species in the temperate climate zone of Central Europe

    Hipfinger C.Laux M.Puschenreiter M.
    10页
    查看更多>>摘要：? 2022 The AuthorsAgromining of Ni is the use of Ni hyperaccumulator plants for extracting Ni. The efficiency of agromining is quantified by the Ni yield, which is the product of harvested biomass and shoot Ni concentration. The present field experiment evaluated the agromining efficiency on an Austrian serpentine soil by comparison of four potential Ni hyperaccumulator plants: Berkheya coddii Roessler, Bornmuellera tymphaea (Hausskn.) Hausskn., Bornmuellera emarginata (Boiss.) Re?etnik and Odontarrhena chalcidica Waldst. & Kit. Additionally, a large-scale plot with O. chalcidica was established in order to gain a representative assessment for agromining in the temperate climate zone of Central Europe. A consecutive three-year planting with O. chalcidica provided a perspective for agromining in the long-run. Nickel yields were clearly highest for O. chalcidica (94.3 kg ha?1) due to highest biomass production (5.93 t ha?1). Shoot Ni concentration did not differ between B. tymphaea (17.1 g kg?1 DW), B. emarginata (17.6 g kg?1 DW) and O. chalcidica (16.0 g kg?1 DW) and had no considerable effect on Ni yields. Berkheya coddii was significantly lowest in biomass production (1.08 t ha?1), shoot Ni concentrations (7.94 g kg?1 DW) and Ni yields (8.54 kg ha?1). Soil concentrations of potentially bioavailable Ni fractions (NiDTPA) were replenished until the next growing season, suggesting that Ni concentrations in shoots will remain constant in consecutive growing seasons. We conclude that O. chalcidica has the greatest potential for agromining on a serpentine soil in the temperate climate zone of Central Europe.
      原文链接:
    • NSTL
    • Elsevier

    Regolith-hosted rare earth exploration in the Chilean Coastal Range of the Central Andes

    Marquardt C.Cordeiro P.Belmar A.Bustos N....
    17页
    查看更多>>摘要：? 2022 Elsevier B.V.Regolith-hosted rare earth element deposits (RH-REE) are well-known in Asia, especially China, and are becoming increasingly important with the growing global demand for such metals. Ore formation controls of these deposits in Asia, which include sub-tropical to temperate climate, and mainly calc-alkaline granites with variable HREE and LREE bearing-minerals, are used to search for compatible exploration targets. However, the poor understanding of parameters controlling the formation of RH-REE mineralization outside China, e.g., Chile, might be hindering exploration efforts world-wide. This work addresses RH-REE mineralization in the Nahuelbuta Range, the local name of the Chilean Coastal Range between the Biobío and Araucanía regions. The studied prospect is associated with late Carboniferous–early Permian I-type biotite tonalite and amphibole-biotite tonalite. Mineralogical analysis (TIMA-X) indicates that allanite and monazite are the main REE-bearing minerals in the host rocks. The regolith in the study area is up to 60 m deep and contains an exchangeable-REE concentration up to 2000 ppm, as determined by portable X-ray fluorescence (pXRF) and ICP-MS. The mineralization is divided into two types: 1) Preserved regoliths (e.g. drillhole RLS-09) where mineralization is HREE-dominant (56% of total REE, (La/Yb)N ~2) and is covered by a leached upper pedolith; and 2) partially eroded regoliths (e.g. drillhole RLS-07) where mineralization is LREE-dominant (58% of total REE, (La/Yb)N ~4) and exposed. A morphometric analysis (SCM and swath profiles) and two 3D models (geomorphic and geochemical) indicate the current preservation of pediments and ore. Analyses of the exchangeable REE-fraction show that pedogenesis, leading to the deposit, is associated with REE-fractionation processes, most notably: a positive cerium anomaly (Ce/Ce*) in the upper pedolith and preferential adsorption of LREE at shallower depths, revealed by decreasing (La/Yb)N ratio with depth. We propose a mineralization model where the advance of the pedolith/saprolith horizon during progressive weathering and the breakdown of allanite and monazite was responsible for the neoformation of RH-REE clays at the base of the pedolith. Additionally, the landscape evolution of the Nahuelbuta Range controlled the preservation of ore bodies, which are either cropping out or hidden underneath the upper pedolith. A good understanding of the interplay between tonalite regolith development controls and regolith preservation during landscape evolution provide a strategy for REE exploration in the region. Moreover, the search for pediplains on suitable lithologies, mapping of regolith profiles, and their analysis via pXRF in the field by quantifying yttrium, appears to be a suitable strategy for early exploration of RH-REE deposits in the Chilean Coastal Range.
      原文链接:
    • NSTL
    • Elsevier

    Seawater intrusion and hydrogeochemical processes in the Ischia Island groundwater system

    Daniele L.Schmidlin D.Quiroga I.Tardani D....
    11页
    查看更多>>摘要：? 2021Ischia is a volcanic island located NW of the Gulf of Naples (South Italy). The island of Ischia is a structurally complex hydrothermal active system that hosts a fractured aquifer system whose geometry and hydraulic properties are still partly unknown. The aquifer system of Ischia, composed mainly of Quaternary volcanic deposits and marine sediments, exhibits physically and chemically heterogeneous waters. The intense seismicity and hydrothermal activity are expressed by numerous fumaroles and thermal springs, which have been exploited since ancient times, promoting, and supporting the world-renowned tourist activities that constitute the main economic activity of the island. The aim of this study is to determine the hydrogeochemical processes in the Ischia aquifer system. Also, we calculated the proportion of seawater in the aquifer system of Ischia using historical hydrogeochemical data relative to two sampling campaigns. Sixty-nine groundwater and thermal spring samples collected in July 2000 were analyzed and compared with previously published data to identify the changes in seawater contribution. The sample analysis shows that different physicochemical processes occur in the groundwater of Ischia Island, where recharge water, seawater and deep fluids interact and overlap with different intensity. The calculated saline factor indicates a seawater content of up to 70% in some samples near the coast, suggesting that seawater intrusion is the main process in these areas. Later data show that seawater intrusion increases around the coastline with up to 93% seawater content. Finally, data analysis shows that although a change in chemical composition is observed, no variation in thermal water temperature is recorded over time.
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    • NSTL
    • Elsevier

    Geochemical anomaly mapping using sparse principal component analysis in Jining, Inner Mongolia, China

    Wang H.Yuan Z.Zhang S.Cheng Q....
    8页
    查看更多>>摘要：? 2022 Elsevier B.V.Mapping geochemical anomalies is one of the most important tasks in mineral exploration. Sparse principal component analysis (SPCA) can be applied to investigate the correlations among geochemical elements and geological variables, which forces the loading values of the partial elements to zero. In this paper, the robust SPCA algorithm was used to process geochemical exploration data on a scale of 1:50,000 for identifying geochemical anomalies related to mineralization. The results show SPC1 and SPC3 indicate the spatial distribution of the Hannuoba basalt and Jining Group formation, respectively. The outcropped Hannuoba formations are located in high-value area of scores map of SPC1. The element association of W-Mo on SPC2 is related to molybdenum (Mo) mineralization. The spatial distribution of SPC2 scores suggests the distribution of Mo mineralization. The discovered Mo polymetallic deposits are located in the anomalous area of SPC2 scores. The SPCs identify localized geochemical anomalies and disambiguate the effects of outliers, which improve interpretability. These results indicate SPCA is a powerful tool for mapping geochemical anomalies.
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    • NSTL
    • Elsevier

    Geochemistry of surface waters around four hard-rock lithium deposits in Central Europe

    Toupal J.Vann D.R.Giere R.Zhu C....
    14页
    查看更多>>摘要：? 2022 Elsevier B.V.There are several Li-mica and spodumene deposits in Central Europe. The Cínovec deposit on the border of the Czech Republic and Germany is the largest known hard-rock Li deposit in Europe and is currently being explored. Weathering and mining of such deposits could release Li and F to the environment. Both elements are associated with potential health effects when ingested via drinking water, yet little is known about the aqueous geochemistry of streams and creeks around Li hard-rock deposits. In this study, we sampled surface waters (n = 47) near three Li-mica and one spodumene deposit to examine a potential public health risk resulting from the weathering of Li-minerals. At the Cínovec and Homolka (also in the Czech Republic) sites, several water samples have elevated Li contents relative to those in typical surface waters, but they are all below the U.S. EPA-recommended threshold of 0.7 mg/L. Three of the ten samples from Cínovec contain F in concentrations that are above World Health Organization's 1.5 mg/L drinking water limit, and thus these waters (max. concentration: 3.8 mg/L) may represent a public health hazard. Based on geochemical modeling and statistical analysis, the lithium in the water comes from Li-micas and the fluoride is derived from a combination of Li-micas and fluorite, depending on the specific site analyzed. Lithium seems to be scavenged by clay minerals.
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    • NSTL
    • Elsevier

    Evaluating Sn mineralization potential at the Haobugao skarn Zn–Pb deposit (NE China) using whole-rock and zircon geochemistry

    Yu F.Zeng Q.Ma S.Wei L....
    11页
    查看更多>>摘要：? 2022 Elsevier B.V.The metal association in a skarn deposit is largely controlled by the magma redox state and fractionation degree. The Haobugao skarn deposit in northeastern China contains significant Zn–Pb sulfides, with subordinate by-products Cu and Fe ores. Recent explorations also found minor cassiterite occurring locally in the deposit, inspiring the speculation of Sn mineralization. To better evaluate the Sn mineralization potential at Haobugao, the geochemical compositions of the ore-related biotite granite porphyry and its magmatic zircons have been investigated to quantify the oxidation state and the degree of magmatic evolution, which provide constraints on the capability of the Haobugao intrusion to produce economic Sn mineralization. The causative biotite granite porphyry (~140 Ma) of the Haobugao skarn is a typical I-type granite that belongs to high-K calc-alkaline series. It contains 68.88–72.27 wt% SiO2 and 0.52–1.38 wt% MgO, and has a Rb/Sr ratio range of 0.82–2.07 and a Nb/Ta ratio range of 8.69–22.49, indicating that it is moderately fractionated. The zircon Ce and Eu anomalies have been used as proxies for magma redox state, and the results (CeN/CeN* = 36–213, EuN/EuN* = 0.17–0.52) suggest that the ore-forming magmas are relatively oxidized, with an estimated ΔFMQ range of ?0.4 to +3.5 (+1.0 in average). This is also consistent with the high whole-rock Fe2O3/(FeO + Fe2O3) mass ratios (0.54–0.76) and the occurrence of abundant ferric garnet in the skarn (i.e., andradite). These results collectively show that the ore-related granitic intrusion at Haobugao is generally more oxidized but less evolved when compared with other intrusions responsible for typical skarn Sn mineralization worldwide. Therefore, it is unlikely for the Haobugao intrusion to produce Sn mineralization of economic significance. The present study demonstrates that the whole-rock and zircon geochemistry data are useful in evaluating the mineralization potential of metals like Sn in a given mineral deposit or prospect, which may help guide exploration.
      原文链接:
    • NSTL
    • Elsevier

    Geochemical studies of snow over mineral accumulations under conditions of their overlap by sedimentary rocks of the platform cover

    Sobolev I.S.Gavrilov R.Y.Isupova A.A.Baranovskaya N.V....
    17页
    查看更多>>摘要：? 2022 Elsevier B.V.In geochemical exploration, the seasonal snow cover is a convenient natural material for identifying under deep covered mineral accumulations. Snow has shielding and accumulating properties sufficient for the occurrence of dispersion of geochemical halos. The snow horizon of geochemical sampling is protected from atmospheric and landscape factors of replenishment of its chemical composition for most of the winter. The filtrate of snow melted water is cleaned of large-sized solid material, and chemical compounds are in the dissolved and finely dispersed solid phase of submicron dimension. Therefore, in terms of the physical and chemical properties of the analyzed substance, snow geochemical survey is close to selective methods. Test surveys were carried out on single profiles of snow sampling at two ore occurrences (Au, Pb-Zn) and an oil field within the West Siberian plate. Concentrations of a wide range of chemical elements in snowmelt water filtrate were determined by the ICP-MS method. As a result of statistical processing of geochemical data, a low variability of concentrations of chemical elements has been established. Correlation and regression analyzes demonstrate the presence of linear dependences in the distribution of trace elements, which reflect the ability of elements to form easily soluble and hardly soluble occurrence forms. The variability of the local geochemical background is mainly due to the content of hardly soluble phases that entered the snow layer during its deposition on the ground. Presumably, they are represented by particles of aeolian dust, needles and scales of tree bark captured by snow from tree and shrub crowns. In the area of study with high heterogeneity of elementary landscapes, the influence of this factor is comparable in amplitude to the contrast of superimposed geochemical halos. Normalization of the concentrations of trace elements by the sum of rare earth elements (REE) allows to strengthen the useful geochemical signal. Geochemical anomalies detected in snow in space quite accurately coincide with the position of mineral deposits buried the platform cover terrains, and also find confirmation in the chemical composition of soils and soil air. The good potential of snow metallometric surveying for prospecting of deep-seated mineral resources needs to be confirmed by studying the vertical and lateral migration of chemical elements in the snow cover.
      原文链接:
    • NSTL
    • Elsevier

    In situ LA-ICP-MS trace element analysis of magnetite as a vector towards mineral exploration: A comparative case study of Fe-skarn deposits from SW Iberia (Ossa-Morena Zone)

    Maia M.Nogueira P.Mirao J.Barrulas P....
    25页
    查看更多>>摘要：? 2022 Elsevier B.V.The Azenhas and Alvito Fe-deposits are located at SW of the Iberian Variscan belt, in a wide Fe-Zn ore district (Montemor-Ficalho Belt), part of the Ossa-Morena Zone. Both deposits are dominantly composed of magnetite ores that display distinct ore formation processes and, at the Azenhas deposit, massive magnetite ores are mainly hosted in amphibolites (Middle Cambrian – Ordovician), with a genesis arguably associated with metamorphic-metasomatic reactions promoted by fluid circulation through several thrust faults that led to and expressive tectonic pilling. Contrastingly, the Alvito massive magnetite ores are formed by the emplacement of a gabbro-dioritic suite in contact with calcite-dolomite marbles, constituting a typical calcic exoskarn Fe-skarn deposit. Primary and secondary magnetite were identified and characterized, and further selected for in situ laser ablation coupled inductively mass spectroscopy (LA-ICP-MS) trace element analysis. Results show that primary magnetite (Mag I) from the Azenhas deposit is discriminated by higher concentrations of Mg, Cr, Mn, Zn, Co, and Sn, whereas secondary magnetite (Mag II) is depleted in most trace elements, although displaying relatively higher concentrations of V, Ga, Mo, and Pb. The application of TMg-Mag geothermometer reinforced the discriminatory indexes, with Mag I displaying higher-temperature estimations (ca. 770 °C) when compared to Mag II (ca. 420 °C), thus suggesting that primary ores are associated to higher temperature processes than previously assumed. Characterization of the ores from Alvito deposit revealed primary magnetite characterized by abundant ilmenite and Al-spinel oxy-exsolutions which led to high measured Al concentrations in magnetite. The trace element content indicates high-temperature hydrothermal magnetite, underlining the contribution of hot hydrothermal fluids from the igneous body emplacement, also supported by the TMg-Mag geothermometer (ca. 685 °C). The anomalous presence of Co (max. 156 ppm) and Ni (max. 100 ppm) concentrations in Mag I from Alvito, along with pentlandite-magnetite assemblages, suggest that prone conditions were sustained for the development of Ni-bearing ores and that magnetite composition could be an interesting geochemical proxy for the exploration of such mineralization. The Mn + Al versus Ti + V discriminant diagram shows that primary ores from both deposits plot in the skarn field. The combination of magnetite analyses with whole-rock geochemistry and field geology, allowed us to define criteria that can be applied in the discrimination of Fe-deposits and contribute to improve the geological models of the studied ore deposits, thus beneficiating future exploration in SW Iberia.
      原文链接:
    • NSTL
    • Elsevier