Pb-Zn Mineralization Research Articles

Changes in soil microbe-mediated carbon, nitrogen and phosphorus cycling during spontaneous succession in abandoned Pb[sbnd]Zn mining areas

The mechanism through which soil microorganisms mediate carbon and nutrient cycling during mine wasteland restoration remained unknown. Using soil metagenome sequencing, we investigated the dynamic changes in soil microbial potential metabolic functions during the transition from biological soil crusts (BSC) to mixed broad-conifer forest (MBF) in a typical PbZn mine. The results showed soil microorganisms favored carbon sequestration through anaerobic and microaerobic pathways, predominantly using efficient, low-energy pathways during succession. Genes governing carbon degradation and aerobic respiration increased by 19.56 % and 24.79 %, respectively, reflecting change toward more efficient and intensive soil carbon utilization in late succession. Nitrogen-cycling genes mediated by soil microorganisms met their maximum influence during early succession (sparse grassland, SGL), leading to a respective increase of 75.29 % and 76.81 % in the net potential nitrification rate and total nitrogen content. Mantel and correlation analyses indicated that TOC, TN, Zn and Cd contents were the main factors affecting the soil carbon and phosphorus cycles. Soil AP content emerged as the primary influencer of genes associated with the nitrogen cycle. These results shed light on the dynamic shifts in microbial metabolic activities during succession, providing a genetic insight into biogeochemical cycling mechanisms and underscoring crucial factors influencing soil biogeochemical processes in mining regions.

Quantifying the Contribution of Soil Heavy Metals to Ecological and Health Risk Sources

Quantifying the risk of soil heavy metal sources can identify the main pollution sources. It can provide a scientific basis for reducing the ecological and human health risks of soil heavy metals. Taking the shallow soil in a Pb-Zn mine watershed in northern Guangxi as a research object， ecological and human health risk assessments were conducted using potential ecological risk assessment （RI） and human health risk assessment （HRA）， and the source apportionment of soil heavy metals was completed using the absolute principal component-multiple linear regression receptor （APCS-MLR） model and random forest （RF） model. Then， a combined risk assessment model， consisting of RI， HRA， and APCS-MLR， was used to quantify the risk of soil heavy metal sources. The results showed that the contents of Pb， Zn， Cu， and Cd exceeded the environmental screening values for agricultural land with mean values of 342.77， 693.34， 61.27， and 3.08 mg·kg-1， respectively， and there was a certain degree of contamination. Pb， Cr， and As were the main health risk impact factors， with higher health risks for children than for adults. Three sources were identified： mining activities （Source Ⅰ）， soil parent material sources and original formation （Source Ⅱ）， and unknown sources. Pb， Zn， Cu， and Cd were mainly derived from Source Ⅰ， and Cr and As were controlled by unknown sources and Source Ⅱ. The source risk assessment results of soil heavy metals indicated that the potential ecological risk and non-carcinogenic risk were mainly from Source Ⅰ and Source Ⅱ， and carcinogenic risk was mainly from unknown sources. The unknown sources had a high proportion in source apportionment and risk assessment， and should be further researched to provide scientific basis for soil heavy metal control. The combined risk assessment model based on source analysis， focusing on the risk characteristics of different sources， can accurately identify high-risk pollution sources. It is a more reasonable and reliable risk assessment method.

Genesis of Pb–Zn Mineralization in the Pulang Cu Polymetallic Deposit in Yunnan Province, China: Insights from Analyses of Geology, Fluid Inclusions and C–H–O–S Isotopes

The Pulang super-large porphyry Cu polymetallic deposit, located in the Sanjiang area of Yunnan Province, is one of the largest Cu deposits in China. This deposit hosts Cu resources of ~5 × 106 t and other ore-forming elements, such as Mo, Au, Ag, Pb, Zn, Pt and Pd. Recently, obvious hydrothermal vein-type Pb–Zn mineralization, with a Pb + Zn resource of ~0.4 × 106 t, has been detected in the North Ore Section of the deposit. However, the genesis of these Pb–Zn ore bodies, especially their relationship to the major Cu ore bodies in the South Ore Section, remains controversial. We conducted geologic description, fluid inclusion petrography and microthermometry, and C, H, O and S isotope studies to uncover the genesis of Pb–Zn vein-type mineralization in North Pulang. As a result, three types of Pb–Zn veins were identified: a quartz–pyrrhotite–chalcopyrite–sphalerite–galena vein, a quartz–pyrrhotite–sphalerite–galena vein, and a calcite–quartz–pyrrhotite–galena vein. All fluid inclusions in the quartz from different veins are liquid-rich inclusions, with homogenization temperatures in the range of 184 °C–235 °C and salinities between 10.4 wt.% and 17.8 wt.% NaCl eq., indicating that the Pb–Zn ore-forming fluid was a single-phase fluid with a low temperature and low-to-medium salinity. Hydrothermal quartz in different stages displays δDwater values ranging from −46.9‰ to −120.0‰ (V-SMOW), and the calculated δ18Owater values range from 2.4‰ to 4.3‰ (V-SMOW), implying that the mineralization fluids likely originated from magma, with a minor involvement of meteoric water. The δ13CCal values (−2.3‰ to −7.9‰ V-PDB) of calcite indicate that C likely originated from a deep-seated source. The δ34S values of chalcopyrite, pyrite, pyrrhotite and sphalerite reveal that S was possibly derived from magmatic rocks. Based on the above data, it is suggested that the Pb–Zn mineralization in North Pulang was the result of the northward migration of ore-forming fluids that originated from South Pulang along the NE-trending structural fractures. A strong water–rock interaction occurred during the migration process. However, the involvement of meteoric water and accompanied cooling of fluids were most likely responsible for the precipitation of galena and sphalerite.

Magmatic-hydrothermal fluid evolution of the tin-polymetallic metallogenic systems from the Weilasituo ore district, Northeast China

The large Weilasituo Sn-polymetallic deposit is a recent exploration discovery in the southern Great Xing’an Range, northeast China. The ore cluster area shows horizontal mineralization zoning, from the inner granite body outward, consisting of high-T Sn–W–Li mineralization, middle-T Cu–Zn mineralization and peripheral low-T Pb–Zn–Ag mineralization. However, the intrinsic genetic relationship between Sn-W-Li mineralization and peripheral vein-type Pb–Zn–Ag–Cu mineralization, the formation mechanism and the deep geological background are still insufficiently understood. Here, we use fluid inclusions, trace elements concentrations in quartz and sphalerite, and H–O isotope studies to determine the genetic mechanism and establish a metallogenic model. Fluid inclusion microthermometry and Laser Raman spectroscopic analysis results demonstrates that the aqueous ore-forming fluids evolved from low-medium salinity, medium–high temperature to low salinity, low-medium temperature fluids. Laser Raman spectroscopic analysis shows that CH4 is ubiquitous in fluid inclusions of all ore stages. Early ore fluids have δ18OH2O (v–SMOW) values from + 5.5 to + 6.2‰ and δD values of approximately − 67‰, concordant with a magmatic origin. However, the late ore fluids shifted toward lower δ18OH2O (v–SMOW) (as low as 0.3‰) and δD values (~ − 136‰), suggesting mixing between external fluids derived from the wall rocks and a contribution from meteoric water. Ti-in-quartz thermometry indicates a magmatic crystallization temperature of around 700 °C at a pressure of 1.5 kbar for the magmatic ore stage. Cathodoluminescence (CL) imaging and trace element analysis of quartz from a hydrothermal vug highlight at least three growth episodes that relate to different fluid pulses; each episode begins with CL-bright, Al-Li-rich quartz, and ends with CL-dark quartz with low Al and Li contents. Quartz from Episode 1 formed from early Sn-(Zn)-rich fluids which were likely derived from the quartz porphyry. Quartz from episodes 2 and 3 formed from Zn-(Sn)-Cu-rich fluid. The early magmatic fluid is characterized by low fS2. The SO2 produced by magma degassing reacted with heated water to form SO42−, causing the shift from low fS2 to high fS2. The SO42− generated was converted to S2– by mixing with CH4-rich, Fe and Zn-bearing external fluid which led to late-stage alteration and dissolution of micas in vein walls, thus promoting crystallization of pyrrhotite, Fe-rich sphalerite and chalcopyrite and inhibiting the precipitation of anhydrite. This study shows that ore formation encompassed multiple episodes involving steadily evolved fluids, and that the addition of external fluids plays an important role in the formation of the later Cu–Zn and Ag–Pb–Zn mineralization in the Weilasituo ore district.

LA-ICP-MS zircon U-Pb dating of tuffites in the Sachakou Pb-Zn mining area, Karakorum, Xinjiang and its establishment of Early Triassic strata

LA-ICP-MS zircon U-Pb dating of tuffites in the Sachakou Pb-Zn mining area, Karakorum, Xinjiang and its establishment of Early Triassic strata

Adaptation to lead in a Pb/Zn-mine population of Marrubium cuneatum

Marrubium cuneatum is an endemic Iranian plant species, which can be found in lead-contaminated environments. This study aimed to investigate the effects of lead on the growth and germination in two M. cuneatum populations, from metalliferous, Pb-contaminated and uncontaminated soil, respectively. Soil and plant samples of the Tang-e Douzan Pb-Zn mine and Morghab Spring (non-contaminated site) were collected and analysed. Germination and growth were recorded under increasing Pb exposure in the non-metallicolous (NM) and the metallicolous (M) local M. cuneatum populations. Germination percentage (GP), mean germination time (MGT), germination index (GI), healthy plant percentage (HPP), seedling death (SD), fresh weight (FW) and dry weight (DW), were measured. Primary assessments showed toxic levels of lead in soil samples of the Tang-e Douzan mine and in leaves of plants growing at the mine site. Germination experiments showed that the germination parameters were stimulated by low concentrations of Pb in both populations, but inhibited by high concentrations. However, the adverse effects of Pb at high concentrations on GP, GI, and HPP were significantly less in the M population. The mortality of germinating seeds (SD) was consistently associated with fungal infection, which gradually decreased with increasing Pb exposure, but to the same degree in both populations. Growth experiments clearly demonstrated Pb hypertolerance in the M population. In the NM population, seedling growth is more sensitive to excess Pb than seed germination, compared to the M population. The M population has high biomass and a relatively high Pb accumulation in its shoots, which suggests it is a suitable candidate for phyto-extraction of Pb.

Genetic link between Mississippi Valley-type (MVT) Pb–Zn mineralization and hydrocarbon accumulation in the Niujiaotang ore field, SW China

The Niujiaotang MVT Pb-Zn ore field is located at the southwestern end of the West Hunan-East Guizhou (WHEG) metallogenic belt, which overlaps spatially with the Majiang paleo-oil reservoir. The Pb-Zn mineralization is closely associated with oil-gas accumulation processes. However, the genetic link between the paleo-oil reservoir and the Pb-Zn deposits remains unclear. In this paper, we present new findings of bitumen (paleo-oil reservoir) and its features in the deposits, and apply various isotopic geochemical methods and 2D seismic data to elucidate the source rock and coupling relationship of the paleo-oil reservoir and the Pb-Zn deposits. This study reveals that the ore has a simple mineral composition, mainly comprising sphalerite, pyrite, and dolomite. Solid bitumen occurs widely in the ore and the host dolostone, and coexists with minerals from the mineralization stage. Laser Raman spectroscopy shows that the bitumen in the wall rocks of the Chengong deposit and the Danzhai paleo-oil reservoir are both overmature, and their carbon isotope compositions (δ13CPDB = –29.17 ‰ – –31.20 ‰, average –30.10 ‰, n = 6) and initial 187Os/188Os ratio (1.08±0.19) suggest that they have the Lower Cambrian source rock similar to the Majiang paleo-oil reservoir. The δ34S value of pyrite in the bitumen from the wall rocks in the Chengong deposit ranges from +28.15 ‰ to +44.12 ‰ (average +33.28 ‰, n = 18), which is consistent with the sulfur isotope composition of the ore sulfide reported previously, indicating that they both derived from sulfate in the Middle-Upper Cambrian strata. Bitumen Re-Os and sphalerite Rb-Sr isotopic dating indicate that oil reservoir accumulation in the ore-hosting strata preceded Pb-Zn mineralization, occurring at 424±160 Ma (MSWD = 1.3) and 398±4.7 Ma (MSWD = 0.66), respectively. The initial 87Sr/86Sr ratio of sphalerite is 0.709983±0.000027, which, after comparison and in combination with previous studies, suggests that the metallogenic metals mainly originated from the underlying strata and basement. 2D seismic data show that the Zaolou fault (F2) that controls the mineralization is a deep fault that extends to the basin basement, and acts as a migration pathway for hydrocarbon fluids and ore-forming materials. We propose that liquid hydrocarbons played a significant role in Pb-Zn mineralization, acting as reductants to reduce sulfate through the thermochemical sulfate reduction (TSR) reaction and provide abundant reduced sulfur (H2S/HS−) for Pb-Zn mineralization. Finally, we present a comprehensive model of hydrocarbon accumulation and mineralization in the Niujiaotang ore field.

Distribution, speciation, and assessment of heavy metals in sediments from Wadi Asal, Red Sea, Egypt

Globally, the environmental contamination of stream sediments due to geogenic and anthropogenic sources is of growing concern. In this study, the heavy metals (Cd, Co, Cr, Cu, Ni, Pb, and Zn) in 22 superficial sediments in Wadi Asal, Red Sea, Egypt, were explored to assess sediment sources, the mobility of chemical species, and the degree of contamination in sediments. Therefore, the total heavy metal values in the fine fraction (< 63 μm), a five-step sequential extraction on selective samples, risk assessment, and principal component analysis (PCA) were applied. The mobility of heavy metals in Wadi Asal sediments, according to non-residual fraction percent, declines in the following order: Cd (90.9%) > Pb (85.2%) > Co (84.4%) > Cu (80.8%) > Zn (75.9%) > Ni (48.4%) > Cr (39.6%); indicating the high mobility of Cd, Zn, Pb, Cu, and Co. The mean metal contamination factor (CF) order is Cd (10.96) > Ni (3.91) > Cr (2.77) > Zn (2.18) > Pb (2.10) > Co (1.12) > Cu (0.70). The Geo-accumulation Index (Igeo) is decreased in the following order: Cd (2.19) > Ni (0.78) > Cr (0.55) > Zn (0.44) > Pb (0.42) > Co (0.22) > Cu (0.14). The risk assessment code (RAC) revealed very high to high risk for Cd, Co, and Pb. The results pointed out that the metals Cr, Co, Cu, and Ni are from geogenic sources, while Zn, Cd, and Pb are from anthropogenic sources due to Pb–Zn mining activities. Based on the threshold effect level (TEL), Cd, Cr, Ni, and Pb have adverse effects on living organisms. According to these findings, the area along Wadi Asal and the downstream regions on the beach are highly polluted and heavy metal monitoring in sediments and aquatic organisms is recommended.

Deposit type discrimination based on trace elements in sphalerite

Sphalerite can form in different geological environments and is the main ore mineral of most Pb-Zn deposits. Trace elements in sphalerite combined with machine learning (ML) methods have been used for deposit type discrimination. However, the performance of different multivariate and ML methods is not systematically compared. Here more than four thousand laser ablation inductively coupled plasma mass spectrometry data from more than one hundred deposits were compiled and investigated by different multivariate and ML methods. Unsupervised multivariate and ML methods including principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE), and supervised multivariate and ML methods including partial least squares-discriminant analysis (PLS-DA), logistic regression (LR), support vector machine (SVM), K-nearest neighbors (KNN), random forest (RF), naïve Bayes (NB), and neural network (NN) are used to classify deposit types. The models are constructed for five deposit types, Mississippi Valley-type (MVT), Volcanogenic Massive Sulfide (VMS), sedimentary exhalative (SEDEX), Epithermal, and Skarn deposits, based on twelve elements in sphalerite, Fe, Pb, Mn, Co, Cu, Ga, Ge, Ag, Cd, In, Sn, and Sb.The PCA and PLS-DA methods show similar clustering results, where Epithermal, MVT, SEDEX, and Skarn deposits can be separated from other deposit types. The t-SNE method is only efficient in discriminating MVT, SEDEX, and Epithermal deposits. The KNN, RF, and NN methods show better performance than LR, SVM, and NB in terms of average accuracy and precision. The PCA, t-SNE, and PLS-DA methods have advantages in data visualization, whereas KNN, NN, and RF methods are more suitable for classification tasks. Feature importance analyses of the PLS-DA and RF methods show that the most important discriminant elements in the classification are Ge, Mn, In, Sn, Ga, and Sb. The models based on PCA, PLS-DA, KNN, NN, and RF are used to predict sphalerite samples with uncertain origins. All the models give similar classification results for deposit types, which are consistent with the ore-forming geological setting. The multivariate and ML models, including discrimination diagrams of PCA and PLS-DA, can be used as the first screening for the type of Pb-Zn mineralization in mineral exploration.

Origin of Zn-Pb Mineralization of the Vein Bt23C, Bytíz Deposit, Příbram Uranium and Base-Metal Ore District, Czech Republic: Constraints from Occurrence of Immiscible Aqueous–Carbonic Fluids

The mineralogical, fluid inclusion, and stable isotope (C, O) study was conducted on a Late Variscan Zn-Pb vein Bt23C, Příbram uranium and base-metal district, Bohemian Massif, Czech Republic. The vein is hosted by folded Proterozoic clastic sediments in exo-contact of a Devonian-to-Lower-Carboniferous granitic pluton. Siderite, dolomite-ankerite, calcite, quartz, baryte, galena, sphalerite, V-rich mica (roscoelite to an unnamed V-analogue of illite), and chlorite (chamosite) form the studied vein samples. The banded texture of the vein was modified by the episodic dissolution of earlier carbonates and/or sphalerite. Petrographic, microthermometric, and Raman studies of fluid inclusions proved a complicated fluid evolution, related to the activity of aqueous fluids and to an episode involving an aqueous–carbonic fluid mixture. Homogenization temperatures of aqueous inclusions decreased from ~210 to ~50 °C during the evolution of the vein, and salinity varied significantly from pure water up to 27 wt.% NaCl eq. The aqueous–carbonic fluid inclusions hosted by late quartz show highly variable phase compositions caused by the entrapment of accidental mixtures of a carbonic and an aqueous phase. Carbonic fluid is dominated by CO2 with minor CH4 and N2, and the associated aqueous solution has a medium salinity (6–14 wt.% NaCl eq.). The low calculated fluid δ18O values (−4.7 to +3.6‰ V-SMOW) suggest a predominance of surface waters during the crystallization of dolomite-ankerite and calcite, combined with a well-mixed source of carbon with δ13C values ranging between −8.2 and −10.5‰ V-PDB. The participation of three fluid endmembers is probable: (i) early high-temperature high-salinity Na&gt;Ca-Cl fluids from an unspecified “deep” source; (ii) late low-salinity low-temperature waters, likely infiltrating from overlying Permian freshwater partly evaporated piedmont basins; (iii) late high-salinity chloridic solutions with both high and low Ca/Na ratios, which can represent externally derived marine brines, and/or local shield brines. The source of volatiles can be (i) in deep crust, (ii) from interactions of fluids with sedimentary wall rocks and/or (iii) in overlying Permian piedmont basins containing, in places, coal seams. The event dealing with heterogeneous CO2-bearing fluids yielded constraints on pressure conditions of ore formation (100–270 bar) as well as on the clarification of some additional genetic aspects of the Příbram’s ores, including the reasons for the widespread dissolution of older vein fill, the possible re-cycling of some ore-forming components, pH changes, and occasionally observed carbon isotope shift due to CO2 degassing.

Zinc isotopes revealed the role of ore-hosting carbonate rocks in the formation of MVT deposits: A case study of the Huize Pb[sbnd]Zn deposit, SW China

Although carbonate rocks are important for carbonate-hosted PbZn deposits, there is no effective constraint on the role of carbonate rocks during the PbZn mineralization process. This paper uses the giant Huize PbZn deposit (>7 Mt. metals @ 25–35 % Pb + Zn) as a case study and employs zinc isotopes to gain new insights into such issue. The Huize deposit, located in the Sichuan-Yunnan-Guizhou (SYG) PbZn metallogenic province, is the largest carbonate-hosted deposit in the western Yangtze Block, SW China. Zinc isotope compositions of sphalerite, altered carbonate rocks and fresh carbonate rocks from the Huize deposit are of +0.39 ‰ to +0.68 ‰ (mean + 0.52 ‰, n = 20), −0.25 ‰ to +0.34 ‰ (mean + 0.07 ‰, n = 11) and + 0.35 ‰ to +0.71 ‰ (mean + 0.51 ‰, n = 6), respectively. The initial δ66Zn value of hydrothermal fluids calculated by the Rayleigh fractionation simulation is +0.4 ‰. Such zinc isotope signatures are significantly different from those of potential source rocks, such as the basement Proterozoic metamorphic rocks (δ66Zn = +0.10 ‰ to +0.34 ‰, mean + 0.22 ‰), the host Upper Ediacaran to Middle Permian sedimentary rocks (δ66Zn = −0.24 ‰ to +0.35 ‰, mean + 0.1 ‰) and the cover Upper Permian Emeishan basalts (δ66Zn = +0.30 ‰ to +0.44 ‰, mean + 0.35 ‰). Hence, it is likely that the carbonate rocks acted zinc source and provided heavy zinc isotopes for the PbZn mineralization. The ore-forming fluids extracted the heavy zinc isotopes of the ore-hosting carbonate rocks, resulting in the zinc isotopes of the altered carbonate rocks being far lighter than those of the marine carbonate rocks (δ66Zn = +0.24 ‰ to +1.32 ‰). The sulfur isotope compositions (+12.9 ‰ to +15.6 ‰, mean + 14.3 ‰, n = 20) of sphalerite from the Huize deposit also suggested that the source of reduced sulfur is the marine sulfate minerals within the ore-hosting carbonate rocks. Therefore, carbonate rocks play key roles in the formation of carbonate-hosted PbZn deposits: 1) provide ore-forming elements and ore-hosting space through dissolution; 2) cause isotope variation (e.g., zinc isotopes) by isotope exchange; 3) act as a carbonate buffer to adjust physicochemical conditions (e.g., pH) via cyclical carbonate dissolution, CO2 degassing and recrystallization. On the other hand, the zinc isotope mapping shows that the western part of the SYG PbZn metallogenic province has lighter zinc isotopes than those of the eastern part. This suggests that the migration pathway of hydrothermal fluids is likely west to east, which provides a new clue for regional PbZn ore prospecting. The outcomes have important benefits for understanding the genesis of PbZn deposits, the role of carbonate rocks and the application of zinc isotopes.

Fingerprinting Pb-Zn mineralization events in the SW Yangtze Block, South China: A case from Yuanbaoshan deposit

The southwestern Yangtze Block represents one of the world’s largest lead–zinc provinces, comprises more than 400 known carbonate-hosted Pb-Zn deposits and contains over 30 million tons (Mt) of total Pb + Zn reserves. The Pb-Zn deposits in this area have been studied extensively by economic geologists, but the origin and mineralization processes of these deposits are still controversial. The Yuanbaoshan deposit is a typical carbonate-hosted Pb-Zn deposit of medium scale (0.19 Mt P + Zn reserves @ 0.7–26.31 wt%), which is in the northern part of the Pb-Zn mineral belt in the southwest margin of the Yangtze Block. In this study, we have conducted LA-ICP-MS sulfides trace elements, S isotope analyses, together with gangue carbonate C-O stable isotope analyses and pyrite Rb-Sr dating. We present Rb-Sr isotopic data on the pyrite that yields an isochron age of 196.4 ± 2.3 Ma. The mineralization temperature at Yuanbaoshan, as determined by the Ga, Ge, In, Mn and Fe (GGIMF) in sphalerite geothermometer, ranges from 161 to 264 ℃ (Sp1) and 141 to 246 ℃ (Sp2). The δ13CPDB values range from −0.66 to 0.61 ‰, δ18OSMOW values range from 15.6 to 17.3 ‰. In situ S isotopes show that the δ34S values of sulfides range from −1.4 to 17.73 ‰. The field, petrologic, geochemical and isotopic data from our study lead to the following salient findings. (1) The dissolved carbon and oxygen of ore forming-fluids of these Pb-Zn deposits were mainly derived from sedimentary carbonate dissolution. (2) The reduced S in the sulfide of the Yuanbaoshan Pb-Zn deposit is mainly derived from the thermochemical sulfate reduction (TRS) and the reduced S produced by the pyrolysis of S-containing organic matter in the carbonaceous mudstone of the Ebian Group. (3) The large-scale Pb-Zn mineralization in the southwest margin of the Yangtze Block was influenced by the post-collision extension between the Indosinian Block and the South China Block during ca. 200 Ma.

Ecological Risk Assessment of Potentially Toxic Metals in Arable Soils around Adudu Lead – Zinc Mine, North-Central Nigeria

Mining is a major source of toxic heavy metals into the soil when mine wastes are discharged into the nearby farmlands used for the cultivation of food crops. This study investigated the influence of Pb–Zn mining on the quality and ecological risk of arable soils around active mining sites in Adudu, Nasarawa State, Nigeria. Composite soil samples were collected at 0–20 cm depth, pulverized, and analyzed for heavy metal (Al, As, Cr, Cu, Fe, Mn, Pb, and Zn) concentration using X–ray fluorescence technique. Enrichment factor, geo–accumulation index, improved Nemerow index (IIN), contamination factor (CF), degree of contamination (Cd), pollution load index (PLI), and ecological risk assessment (ERA) were used to evaluate the effect of the mining activities on the environment. Results showed elevated levels of Pb, Zn, Cu, Fe, Mn, and Cr in arable soils around the mine and lower levels of these metals in the control soil. IIN, Cd, and PLI showed that the mine and the nearby arable soils were the most deteriorated, and soil quality improved away from the mining vicinity. ERA revealed that the mine and the closest arable soils (sites F1 and F4) have significant to high ecological risk index as a result of the dominant presence of Pb, Zn, and Cu at the sites. Thus, arable soils which are disposal channels for mine wastes are not good for growing food crops. This study clearly shows that Pb–Zn mining activities introduced heavy metals into the arable soils surrounding the mine.

Genesis of the Supergiant Shuangjianzishan Ag–Pb–Zn Deposit in the Southern Great Xing’an Range, NE China: Constraints from Geochronology, Isotope Geochemistry, and Fluid Inclusion

The supergiant Shuangjianzishan (SJS) Ag–Pb–Zn deposit, located in the southern Great Xing’an Range (SGXR), is the largest Ag deposit in China. The SJS deposit can be divided into two ore blocks: the Shuangjianzishan ore block and the Xinglongshan ore block. Given the importance of the Xinglongshan ore block in the SJS deposit, our work is focused on the Xinglongshan ore block. The vein orebodies in the Xionglongshan ore block mainly occur in the NW-, NNW-, and NNE-trending fault zones, and its mineralization is mainly related to a deep concealed syenogranite. Here, we present new geochronology, isotope geochemistry, and fluid inclusion data for the Xinglongshan ore block and provide additional insights into the metallogenic mechanism of the deposit. The dating results show that the syenogranite related to the mineralization formed at approximately 137 Ma, which is coherent with some previous age determinations in sulfides from the ore deposit. The mineralization of the Xinglongshan ore block can be divided into four stages: sphalerite–arsenopyrite–pyrite–chalcopyrite–quartz stage (stage I), sphalerite–galena–pyrite–silver-bearing mineral–quartz stage (stage II), sphalerite–galena–silver-bearing mineral–quartz–calcite stage (stage III), and weakly mineralized quartz–calcite stage (stage IV). Four types of fluid inclusions (FIs) have been identified within quartz and calcite veins: liquid-rich, gas-rich, pure-liquid, and pure-gas FIs. The homogenization temperatures in the four stages exhibit a gradual decrease, with stage I ranging from 253 to 302 °C, stage II from 203 to 268 °C, stage III from 184 to 222 °C, and stage IV from 153 to 198 °C, respectively. The salinity for stages I, II, III, and IV falls within the ranges of 3.4–6.6 wt% NaCl eqv., 2.6–7.2 wt% NaCl eqv., 2.9–7.0 wt% NaCl eqv., and 1.2–4.8 wt% NaCl eqv., respectively, indicative of a low-salinity ore-forming fluid. The δ18Owater and δD values of the ore-forming fluid span from −13.9‰ to 7.4‰ and −145‰ to −65‰, with δ13CV-PDB values between −11.0‰ and −7.9‰. These values suggest that the ore-forming fluid predominantly originated from a mixture of magmatic and meteoric water. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of sulfides range from 18.278 to 18.361, 15.530 to 15.634, and 38.107 to 38.448, respectively. These ratios imply that the ore-forming material was primarily derived from the Early Cretaceous granitic magma, which resulted from the mixing of depleted mantle- and crustal-derived magmas. The fluid mixing was the dominant mechanism for mineral precipitation. The Xinglongshan ore block belongs to a magmatic-hydrothermal vein-type deposit related to the Early Cretaceous syenogranite, and the Shuangjianzishan ore block belongs to an intermediate sulfidation epithermal deposit related to coeval subvolcanic rocks. The Ag–Pb–Zn mineralization at Shuangjianzishan is genetically related to the Early Cretaceous volcanic–intrusive complex.

Geochemistry of neutral mine drainage at sulfide deposits ‒ example of the „Grot“ Pb-Zn mine, South-Eastern Serbia

This study examines the chemistry of mine waters of the ?Grot? Pb? ?Zn mine and identifies the hydrogeochemical factors that influence the formation of mine waters chemical composition. Eleven mine water samples were collected at six locations across the area of Kriva Feja in order to determine their chemical composition. Data analysis revealed that the waters belong to the HCO3 -?SO4 2-?Ca2+ and SO4 2-?Ca2+ water types, with neutral pH values. The concentrations of metals in these waters (zinc, lead, barium, copper, chromium) are generally low, and most of the samples meet drinking water quality criteria (USEPA standards). Modelling using the PHREEQC software indicates that the dominant processes in the formation of the chemical composition of these waters are the dissolution of carbonate minerals and the oxidation of sulphide minerals. Carbonate minerals have a scarcer occurrence compared to sulphide minerals, such as galena, sphalerite and pyrite, which are dominantly distributed. The low intensity of sulphide mineral oxidation is interpreted to result from a rapid water exchange and reduced contact time between the water and the rock. The occurrence of this process is localized only in the ore body zone. This study highlights the importance of kinetics (in terms of the chemical reaction rate) as the main factor influencing the oxidation of sulphide minerals and, subsequently the quality of mine waters.

Evaluation on Stabilizers for Fluorine-contaminated Cultivated Land around the Sambo Pb-Zn Mine

Evaluation on Stabilizers for Fluorine-contaminated Cultivated Land around the Sambo Pb-Zn Mine

Metal sources and fluid pathways of karst-hosted Mississippi Valley-type Zn–Pb deposits in the fold-thrust belt: A case study of the Changdong deposit in the southeastern Himalayan-Tibetan orogen

The metal sources and fluid pathways for Mississippi Valley-type (MVT) Zn–Pb deposits in fold-thrust belts remain open topics of debate. To develop a more comprehensive understanding of these issues, this study presents the sulfide morphology, S and Pb isotopes, and trace element data of the paleokarst-hosted Changdong MVT Zn–Pb deposit in the “Sanjiang” fold-thrust belt. Bulk Pb isotopic ratios for galena were homogenous and indicated potential metal sources. These sources include Triassic to Early Jurassic volcanic rocks at the western margin of the Simao Basin, Cenozoic intrusive rocks at the eastern margin, and Jurassic clastic rocks. The spatial distribution of the in situ Pb isotopic ratios, combined with the spatial relationship between the faults and ore bodies, suggest that the tensile faults acted as vertical pathways for the fluid. The galena grains displayed oscillatory zones of As and Sb elements, indicating that alternating ore-forming fluids with varying chemical compositions entered the local reservoir. The δ34SV-CDT values of sulfides in substage I range from −19.3 to 29.6 ‰, and in substage II, they range from −21.2 to 52.6 ‰. The high fractionation degree (approximately 38.9 ‰) and the presence of microspherulitic morphology suggest that the reduced sulfur originated from a bacterial sulfate reduction. A GGIMFis geothermometer revealed that the precipitation temperatures of substage I sphalerite ranged from 56.68 to 211.58 °C and were higher than substage II. This indicated that the mixing of Zn–Pb-bearing fluid with reduced sulfur was the main controlling factor for sphalerite precipitation, and the temperature decrease represented another important factor. In the fold-thrust system, the complete process of Zn–Pb mineralization was established as follows: the fluid extracted metals from regional rocks and then migrated laterally over long distances. During the regional transition from compression to extension, metal-bearing fluid was injected into the deposit along the normal faults through seismic pumping. The fluid was then mixed with reduced sulfur to precipitate Zn–Pb sulfides. This study provides new insights into the metal sources and fluid pathways of MVT Zn–Pb deposits developed in a fold-thrust belt.

Contamination and health risks brought by arsenic, lead and cadmium in a water-soil-plant system nearby a non-ferrous metal mining area

Heavy metal(loid)s contamination prevails in the water-soil-plant system around non-ferrous metal mining areas. The present study aimed to evaluate the heavy metal(loid)s contamination in Nandan Pb-Zn mining area (Guangxi, China). A total of 36 river water samples, 75 paired paddy soil and rice samples, and 128 paired upland soil and plant samples were collected from this area. The concentrations of arsenic (As), lead (Pb), and cadmium (Cd) in these samples were measured. Results showed that the average water quality indexes (WQIs) at the 12 sampling sites along the main river ranged from 41 to 5008, indicating the water qualities decreasing from “Excellent” to “Undrinkable”. The WQIs nearby tailings or industrial park were significantly higher than those at the other sites. 34.0% and 64.5% of soil samples exceeded the risk screening values for As and Cd. The Pb and Cd concentrations in all rice samples exceeded the Chinese food safety limits by 18.7% and 82.7%, respectively. Leafy vegetables had a higher concentration of As, Pb, and Cd than other vegetables, exceeding the maximum permissible limits by 14.1%, 61.2%, and 40.0%, respectively. The biological accumulation coefficient (BAC) of Cd was the highest in rice and lettuce leaves. The hazard quotients (HQs) of As and Cd, indicating non-carcinogenic risks, were 4.15 and 1.76 in adult males, and 3.40 and 1.45 in adult females, all higher than the permitted level (1.0). The carcinogenic probabilities of As and Cd from rice and leafy vegetables consumption were all higher than 1 × 10−4. We conclude that metal(loid)s contamination of the water-soil-plant system has posed great non-carcinogenic and carcinogenic risks to the local population.

Superimposed multi-stage mineralization in the Qingchengzi Pb-Zn ore district, North China: Evidence from geochronology and sulfide geochemistry

The Qingchengzi Pb-Zn polymetallic ore district in northern China records two stages of Pb-Zn mineralization in the Paleoproterozoic and Mesozoic, respectively. The Paleoproterozoic sedimentary-metamorphic stage (stage I) of mineralization was primarily recorded by stratiform ores, and the Mesozoic magmatic-hydrothermal stage (stage II) of mineralization mostly formed vein-type ores. The apatites coexisting with the stage I sulfides yield U-Pb isotopic ages of (1882–1857 Ma), corresponding to the regional metamorphism pervaded in the Paleoproterozoic in the Liaodong region. Zircons from a granite porphyry that is spatially associated with the stage-II mineralization have a U-Pb age of 228.5 ± 5.8 Ma.Stage-I fine-grained sulfides (Py1a and Sp1a) are of SEDEX origin and the fluid is fertile in metals such as Co, Ni, Zn, As, Mn and V. The metals are likely to be sourced from the Liaohe Group, which contains high concentration of those metals. Stage-I recrystallized sulfides (Py1b and Sp1b) show trace elements such as Co, Ni, Cu, As and Au of pyrite and the Cu, Cd, In, Ag, Sb of sphalerite were remobilized out from their crystal lattice under metamorphism. Stage-II sulfides (Py2 and Sp2) are more enriched in Au, As, Cu, Ag, Sb, Pb compared to stage-I sulfides. LA-ICP-MS mapping reveals multigenerational texture of Py2 which features a Cu and Zn enriched core (Py2a) and an overgrowth rim (Py2b) of enrichment in Au, As, Co and Ni. The compositionally distinct core and rim presumably suggest that two episodes of magmatic fluids are involved in the formation of stage-II sulfides. The sedimentary pyrite from Liaohe Group and the stage-I sulfides have δ34S value in the ranges of 10.4–17.04 ‰ and 4.10–9.37 ‰, respectively, suggesting that sulfur was probably derived from seawater sulfate reduction. The sulfur isotopes of stage-II sulfides (δ34S = 4.10–9.02 ‰) reflects a mixing of magmatic sulfur with sulfur leached from meta-volcanic-sedimentary source. This process was associated with the upward migration of magmatic hydrothermal fluids and subsequent fluid-rock interaction, which leached heavy sulfur isotopes along with Cu, Zn, Co, Ni, V metals from wall rocks of mica schist from the Dashiqiao and Gaixian Formations. Integrated mineral assemblage, sulfide texture, trace element and sulfur isotope signatures and geochronological constraints reveal the primary Paleoproterozoic SEDEX mineralization was intensively overprinted by later metamorphism and Mesozoic magmatic hydrothermal events for the Pb-Zn deposits in the Qingchengzi ore district.

Exploring Greenockite: Occurrences and Geological Setting

Greenockite, mineral containing cadmium, is of significant scientific interest owing to its remarkable properties and potential applications in the field of science. It commonly forms in hydrothermal ore deposits as a secondary mineral due to complex cadmium-sulfur interactions influenced by temperature. Typically, it replaces zinc minerals like sphalerite, depending on the abundance of cadmium and zinc in hydrothermal fluids. Solid solubility in the ZnS CdS system occurs at high temperatures, with immiscibility observed under specific conditions. Greenockite forms at relatively low temperatures (100°C to 200°C) and is influenced by factors such as oxygen fugacity, hydrogen sulfide activity, and chloride ion content. Its hexagonal zinc blende structure results in diverse crystal forms, including rods, wires, and whiskers, often adorned with bismuth drops. Experimental studies have identified factors affecting its formation, such as solid solubility, precipitation mechanisms, pH levels, and fluid composition. Its vibrant coloration, attributed to cadmium concentration, varies from pale yellow to deep orange-red. Geologically, it is present in diverse settings, including metamorphosed zinc oxide mineralization, granites, fumaroles, pegmatites, and sediment-hosted Pb-Zn deposits, with a unique occurrence in gabbroic rock at the Babbitt deposit. In India, Greenockite has been identified in the Bagada orogenic gold prospect, situated within the Paleoproterozoic Mahakoshal belt, Central Indian Tectonic Zone (CITZ). Additionally, it is found in hydrothermal deposits of Pb-Zn mines of Zawar. It is exclusively encountered within specific geological settings, primarily as a secondary product. This paper provides a comprehensive exploration of its geological occurrences, distribution, associations, and exceptions.