Journal of Geochemical Exploration最新文献

The hydrogeochemical signature of the discharged water can reveal significant information on the circulation and evolution of geothermal water, which can further guide the exploration and utilization of geothermal water resources. In this study, the source of major ions, reservoir temperature, and cycle time of geothermal fluids were clarified by the Ion relationship analysis, integrated multicomponent solute geothermometry method, and ¹⁴C isotope analysis, respectively, in the Wugongshan area of South China. Results show that the eastern and western parts of the Wugongshan area have distinct types of geothermal fluids, i.e. HCO₃-Na and SO₄HCO₃-Na, respectively. The major source of HCO₃⁻ and Na⁺ is the hydrolysis of silicate minerals, partially accompanied by cation exchange. While gypsum hydrolysis and sulfide oxidation are the primary producers of SO₄²⁻. Moreover, higher TDS, PH, and degree of cation exchange of geothermal fluids were found in the western part than that in the eastern part. The reservoir temperatures in the eastern and western portions are comparable (115–150 °C). However, the cycle time of the geothermal fluids in the western part (15,743 years on average) is much greater than in the eastern part (2160 years on average), which is considered to be the main reason for the difference in hydrogeochemical characteristics. This study can provide theoretical support for the rational development and usage of geothermal water resources.

Identifying the factors and their interactive effects on soil heavy metals (HMs) accumulation in karst areas is a significant challenge in preventing and controlling soil contamination by HMs. A total of 1043 topsoil (0–20 cm) samples were collected from northwestern Guizhou to determine the concentrations of HMs (Cd, Pb, Zn, Cr, Cu, and Ni). Then, the optimal parameter based geographic detector (OPGD) model was used to identify the driving factors and interactions of natural variables (such as strata, soil organic matter, terrain, etc.) and human activity variables (such as distance from mining sites (DFM), distance from road (DFR), population density (DOP), etc.) on the spatial accumulation of soil HMs in the region. The findings revealed that the average concentrations of all HMs exceeded the corresponding background values of soil in Guizhou Province. Cd had the highest accumulation, followed by Cu, Ni, and Cr. Moran's I and inverse distance interpolation results showed clear clustering trends in the spatial distribution of HMs. The high-high clusters of Cd, Pb, and Zn were concentrated in the northern and southern parts of the study area, while the high-high clusters of Ni, Cr, and Cu were distributed mainly in the eastern and western parts of the study area. OPGD analysis results indicated that soil Cd, Pb, and Zn accumulation was influenced primarily by SOM, DFM, and stratigraphic distribution, followed by pH and soil type. Whereas Ni, Cr, and Cu were mainly affected by stratigraphic distribution. Additionally, DOP, terrain, and soil type were secondary factors affecting the accumulation of these three types of HMs. Notably, the interactive effects among these factors were found to have a more significant impact on HMs accumulation than individual factors alone. Overall, this study provides valuable insights into the main factors influencing the spatial distribution of HMs and their interactive relationships, contributing to the theoretical basis for preventing and controlling HMs pollution in the study area.

Nickel (Ni) and cobalt (Co) are recognized as critical strategic metals by major industrialized nations. In recent years, substantial advancements have been achieved in Ni-Co resource exploration within China, generating a promising prospect for future discoveries. This review provides a comprehensive analysis of significant Ni and Co mineralization events in China, covering metallogenic provinces, deposit types, metallogenic epochs, and associated tectonic settings. Sedimentary Co deposits predominantly formed during the middle Paleoproterozoic (2200–1800 Ma) and early Mesoproterozoic (1600–1400 Ma) ages. In contrast, magmatic Ni-Co and hydrothermal metasomatic Co deposits are concentrated in the early Neoproterozoic (1100–700 Ma) and Paleozoic (220–430 Ma) ages. The intricate correlation between magmatic Ni-Co and hydrothermal metasomatic Co mineralization is linked to the evolution of primitive komatiitic and tholeiitic basalts. The formation of mineralized mafic-ultramafic intrusive rocks is identified as a key factor in the formation of magmatic Ni-Cu sulfide deposits, with the exception of sedimentary Co deposits, which represent a distinct geological event. The primary source of Ni-Co deposits in China can be attributed to a pyroxene-enriched mantle magma source. This is supported by platinum-group element (PGE) characteristics of magmatic Ni-Co deposits, which consistently indicate mineralization associated with partial melting processes within the mantle. Furthermore, sulfur (S) and rhenium-osmium (Re-Os) isotopes in magmatic Ni-Co deposits reveal that crustal materials played a significant role in sulfur saturation during magmatic differentiation and mineralization. Ni-Co resources in China primarily consist of orogenic Ni-Co deposits, intricately linked to the multi-stage orogenic events that shaped the region's geological history. The orogenic Ni-Co system in China exhibits a distinctive profile marked by multi-stage and diversified mineralization. This includes the accumulation of Ni metal through prior mineralization events and the subsequent superposition of Co within pre-existing ore belts, reflecting complex geological processes and interactions. This review aims to contribute to a comprehensive understanding of Ni and Co resources in China, facilitating future exploration and resource management strategies.

The Abiete-Toko Gold District (ATGD), in the Nyong Complex, NW edge of the Congo Craton, is one of the numerous Cameroonian mining districts producing alluvial gold. Although numerous works were focused on the ATGD alluvial gold deposits, their primary source(s) remain(s) unknown. This study combines the chemistry of pyrite and chalcopyrite which were determined by inductively coupled plasma-mass spectrometry (LA-ICP-MS), the chemistry of alluvial gold grains determined by electron probe microanalysis (EPMA), and whole rock composition determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results provide the first evidence of gold in the rocks, and its genesis is subsequently discussed. Gold in the ATGD rocks is essentially invisible and lattice bound in pyrite and chalcopyrite, which intake up to 3.11 ppm and up to 32.6 ppm Au, respectively. The gold-bearing metatexites (garnet migmatite) and ultrabasites (serpentinised peridotites) are here therefore, interpreted as possible sources of the ATGD alluvial gold deposits and occurrences. In metatexite, pyrite and chalcopyrite occur within quartz biotite veins, while in ultrabasites pyrite and chalcopyrite are disseminated grains of millimetric sizes, and ovoid or cubic shapes. Gold mineralisation is shear-hosted and, shows evidence of hydrothermal alteration (sulphidation) induced by circulating magmatic and Co-rich (0.01–1.53 %) fluids.

Sulfide minerals and secondary minerals associated with sulfide oxidation were characterized using automated quantitative mineralogy techniques in samples of weathered and freshly blasted waste rock from the Detour Lake Mine, Ontario, Canada. Associations and mineral habits of secondary minerals suggest heterogeneous and dynamic geochemical conditions within the historical waste-rock pile, and the formation of secondary minerals in microenvironments associated with oxidizing sulfide minerals. Electron-probe microanalyses of sulfide grains and alteration rims applied to the modal mineralogy determined by quantitative mineralogy permitted a calculation of trace elements in these reservoirs. The calculations revealed an under-estimation of trace elements by quantitative mineralogy when mass-balance calculations were considered.

Temporal–spatial variations of soil respiration and the controlling factors is important for understanding the global carbon cycle process. In this research, the Global Soil Respiration Database (SRDB) and Global Geochemical Baseline (GGB) dataset were used, temporal–spatial variations of soil respiration from 1991 to 2015 and the controlling factors in soils developed from different soil parent materials were analyzed. We found, for the first time, soil respiration was significantly varied in soils developed from different soil parent materials on a global scale, which was mainly controlled by geochemical indexes such as Al/Si, MnO, CaO and P₂O₅. We also found that temporal variations of soil respiration during 1991–2015 in acidic plutonic rocks, acidic volcanic rocks, metamorphic rocks, siliciclastic sedimentary rocks and unconsolidated sediments–developed soils was significantly controlled by temperature, while that of basic plutonic rocks, basic volcanic rocks, intermediate volcanic rocks, mixed sedimentary rocks and carbonate rocks–developed soils was less sensitive to temperature relatively. We conclude that temporal–spatial variations of soil respiration were correlated with soil geochemistry, which mainly depends on the stability difference caused by the bonding between soil organic carbon and soil minerals. The findings may be helpful to understand the temporal–spatial pattern of global soil respiration, moreover reveal the importance of soil geochemistry in influencing soil respiration on global scale.

Determining the hydrochemical variations and groundwater mixing is crucial for mining safety and water resource management in the Sulin mining area in North China, especially after mining activities. In this study, 94 groundwater samples were collected from the main aquifers in the Sulin mining area during the early and late stages of mining. Water-rock interactions, spatiotemporal variations in hydrochemistry, and groundwater level characteristics during the early and late stages of mining were determined by analyzing data on major ions, hydrogen and oxygen isotopes, and groundwater level. Analytical methods included Piper diagram, principal component analysis, ionic ratio analysis, and Kriging interpolation. A comprehensive conceptual model was proposed to describe the spatiotemporal variations and mixed patterns of the multi-aquifer systems. Results showed that groundwater level in the study area remained relatively consistent before and after mining, with no significant changes observed. The distribution of regional geological structures significantly affects on the groundwater distribution characteristics, which, in turn, determines the spatial variations in groundwater hydrogeochemistry and mixing patterns of groundwater under natural conditions. Moreover, there was significant temporal variation in hydrochemistry in areas of strong drainage. Mining activities led to a decrease in groundwater level, resulting in regional differences in water-rock interactions and groundwater mixing patterns. The Bayesian isotope mixing model (MixSIAR) and the hydrogeological conceptual model can be applied to quantitatively verify the groundwater mixing and the hydrogeochemical process. The study offers insights into the spatiotemporal variations and mixing patterns of groundwater under the impact of exploitation.

Lead‑zinc deposits on the Egyptian Red Sea coast are hosted within a syn-rift system's carbonate platform; however, their origin is still under discussion. This study has used an integrated geological, petrographic, and geochemical analysis of these deposits along seven localities to investigate the record of the main processes that controlled their onset and evolution. Two main zones of mineralization are distinguished: an exposed upper zone composed essentially of smithsonite, hydrozincite, hemimorphite, goethite, and hematite with relics of galena, and a lower zone composed mainly of galena, sphalerite, and pyrite with minor amounts of marcasite. Geochemically, these deposits are depleted in Na, K, Al, Ti, and Nb but are enriched in Mo, Cd, and As. The chondrite-normalized patterns of Pb-Zn-bearing samples show pronounced negative Ce and Eu anomalies, whereas the pattern of the host rocks shows a distinctive pattern with pronounced negative Ce and positive Eu anomalies. The isotope geochemistry analysis of the present lead‑zinc-host rocks shows negative values of δ¹⁸O and δ¹³C in the saddle dolomite-II, dolomite-III, and Zn-dolomite, all of which reflect the effects of dolomitization by hydrothermal fluids. Based on mode of occurrence, texture, mineralogy, and geochemistry, the studied lead‑zinc deposits were formed in two stages: an early stage marked by the participation of primary sulfide ores from hydrothermal solutions, and a late stage involving the replacement of the precursor primary sulfides by means of surface water. These Pb-Zn ore deposits hosted in carbonate rocks are genetically considered to be of Mississippi Valley-type and could constitute important clues, taking into account their wide distribution, for the exploration of new targets of lead‑zinc in addition to a better understanding of the origin of lead‑zinc deposits in the Middle East area and provides important information to improve future mining in the area.

The potential immobilization of cobalt in various environments can be achieved through the incorporation of Co into carbonate minerals, forming solid solutions of (Ca_1-xCo_x)CO₃. However, the thermodynamic properties of these minerals are not well-understood due to conflicting data from natural observations and experiments. In this work, a series of mixed calcium‑cobalt carbonates were prepared and their interaction with aqueous solution was investigated. Depending on the Co/(Ca + Co) mol ratio (X_Co) of the mixed solution, ranging from 0.00 to 1.00, pure calcite, Co-bearing calcite, Co-bearing aragonite, Ca-bearing spherocobaltite and pure spherocobaltite were successively synthesized using a precipitation method. Upon dissolution of the Co-bearing solids (X_Co = 0.10–1.00) in N₂-degassed water (NW) and air-saturated water (AW), the Co concentration of the aqueous solutions increased gradually to a stable state of 0.017–0.191 and 0.018–0.186 mmol/L after 240–360 d dissolution, respectively. When the dissolution occurred in CO₂-saturated water (CW), the Co concentration initially spiked to 0.372–2.258 mmol/L within 6 h ∼ 15 d and then decreased to a stable range of 0.030–0.559 mmol/L after 240–360 d. The Co/(Ca + Co) mol ratio in the aqueous solution (X_Co2+,AS) was significantly lower than the Co/(Ca + Co) atomic ratio in the solids (X_Co,SS), particularly when dissolved in NW and AW. During these dissolution processes in NW, AW and CW at 25 °C, the average log IAP values at the final stable state were determined as follows: for calcite (CaCO₃), the values were −8.25 ± 0.03 in NW, −8.34 ± 0.11 in AW, and −8.10 ± 0.08 in CW; for spherocobaltite (CoCO₃), they were −9.24 ± 0.26 in NW, −9.39 ± 0.23 in AW, and −9.38 ± 0.09 in CW. Furthermore, the log IAP values increased from those typical for calcite to −7.89 ± 0.01 ∼ −7.84 ± 0.10 for the solid with X_Co,SS = 0.187 as X_Co,SS increased, eventually aligning with those typical of spherocobaltite. Lippmann diagrams, constructed using the Guggenheim parameters a₀ = 2.30 and a₁ = 0.265 for the “subregular” calcite-spherocobaltite solid solutions [(Ca_1-xCo_x)CO₃] with a miscibility gap ranging from X_Co,SS = 0.251 to 0.858, highlighted the “peritectic” point at X_Co2+,AS = 0.0538 on the solutus. This analysis revealed that the solids dissolved non-stoichiometrically in water. Consequently, the Co-poor aqueous solution would reach equilibrium with the Co-rich calcite-structure phase at the solid surface.

Scheelite is a widespread mineral in several geological settings and its trace element composition provides valuable information about the source and composition of the hydrothermal fluids. In this study, scheelite from 22 magmatic-hydrothermal deposits and 2 orogenic Au deposits (Hangar Flats and Corcoesto) were analyzed by EPMA and LA-ICP-MS. Magmatic-hydrothermal scheelite, together with literature data are investigated using partial least square-discriminant analysis (PLS-DA) and Random Forest (RF) classifier, to evaluate the use of scheelite as a robust indicator mineral for W-bearing deposit targeting. Cathodoluminescence images show that scheelite is texturally homogeneous in reduced intrusion-related gold systems (RIRGS) and varies from homogeneous to heterogeneous in other magmatic-hydrothermal and orogenic Au deposits. Scheelite displays six REE chondrite-normalized patterns, which are a function of the source and composition (mainly salinity) of the mineralizing fluids and partitioning with co-genetic minerals (e.g., garnet, clinopyroxene). The PLS-DA highlights that scheelite trace element composition from magmatic-hydrothermal deposits varies following different deposit types (e.g., oxidized and reduced skarns, porphyry WMo, RIRGS, quartz-vein/greisen SnW), and that such compositional variation reflects mainly the difference of fO₂ and composition of mineralizing fluids. Additionally, scheelite from magmatic-hydrothermal deposits are chemically distinct to those formed dominantly by metamorphic fluids in orogenic settings as shown by their higher Mo, Nb and Mn, and lower Sr contents and predominantly negative Eu anomalies. Metamorphic scheelite can be discriminated from that of orogenic Au deposits by their lower Pb, As and REE contents and LREE/HREE ratios, which are related to local host rock composition and metamorphic grade. Using Na, Mg, Mn, As, Sr, Y, Nb, Mo, Pb, ΣREE concentrations and Eu anomaly as predictors, the RF model yields an overall prediction accuracy of 97 % for test data as function of deposit types (89.2 % for RIRGS, 100 % for porphyry WMo, 97.8 % for quartz-vein/greisen SnW, 96.9 % for oxidized skarn, 98.1 % for reduced skarn and 99.3 % for orogenic Au deposits). Application of RF classifier to scheelite composition from orogenic Au and skarn- and greisen-type W deposits from literature yields an overall prediction of ∼79 % (91 % for oxidized skarn, 71.4 % for quartz-vein/greisen SnW and 74.2 % for orogenic Au deposits) showing that scheelite is an efficient indicator mineral for Au and W deposits targeting. Metamorphic scheelite is predicted mostly as orogenic Au scheelite (83 %), reflecting the genesis of metamorphic fluids and similar geological setting, suggesting that RF classifier can be also used to predict the fluid sources.