Zn Ore Research Articles

U–Pb geochronology of carbonate-hosted Pb–Zn ores reveals plate-tectonic evolution of eastern Asia during the early Paleozoic

The Mississippi Valley–type (MVT) deposits reached their maximum abundance during the final assembly of Pangea. The intense orogenic activity during this assembly in relatively low latitudes created abundant opportunities for the migration of sedimentary brines into the interior carbonate platforms landward of the orogenic belts, leading to the formation of MVT deposits. Thus, dating the MVT deposits can potentially aid in the reconstruction of the plate tectonic evolution during the assembly of Pangea. The Yangtze Craton hosts significant carbonate-hosted Zn–Pb deposits (> 60 Mt Pb + Zn metals), accounting for 30% of China’s Zn–Pb resources. However, determining the timing of zinc and lead mineralization in these reservoirs is challenging. This study employs LA-ICP-MS U–Pb geochronology on calcites to date Zn–Pb deposits hosted in Lower Cambrian limestone in the Huayuan orefield. Three generations of calcite formation were dated: the first recorded the pre-ore deposition of Lower Cambrian limestone at 517 ± 10 Ma, the second marked a hydrothermal event linked to stratiform sphalerite ore formation at 501.4 ± 8.4 Ma, and the third was associated with discordant breccia-hosted Zn–Pb mineralization at 397.5 ± 9.6 Ma. Our results indicate that Paleozoic carbonate-hosted Pb–Zn mineralization in the Yangtze Craton is linked to (1) the final assembly of Gondwana in the late Cambrian-early Ordovician (520–480 Ma); and (2) the intracontinental orogeny response to Jiangnan Uplift (420–400 Ma). This study highlights the temporal relationship between low temperature carbonate-hosted mineralization and orogenic events that are consistent with classic MVT models worldwide. It also contributes geochronological data for the reconstruction of plate-tectonic evolution during Pangea assembly. Furthermore, it demonstrates the potential of in situ U–Pb calcite geochronology to date ore deposits lacking syn-ore minerals suitable for traditional dating methods.

Middle Triassic Cu–Pb–Zn Skarn mineralization in the Wulonggou gold ore field, Eastern Kunlun Orogen, NW China: Insights from phlogopite Ar–Ar and zircon U–Pb dating and Sr–Nd–Pb–Hf isotopes

The skarn is one of the most significant Cu–Pb–Zn mineralization worldwide. The timing of the magmatic-hydrothermal activity is of importance for understanding the Cu–Pb–Zn mineralization process. The Cu–Pb–Zn skarn mineralization has been recognized in the northwestern section of the Wulonggou gold ore field, Eastern Kunlun Orogen (EKLO), NW China. However, no precise geochronological data has been measured for the Cu–Pb–Zn mineralization, and the source of ore-forming materials is also not well studied. In this study, we present new LA-ICPMS U–Pb ages and Sr–Nd–Hf isotopic compositions for granodiorite and diorite in the northern section of the Wulonggou gold ore field, as well as an Ar–Ar age for phlogopite and Pb isotopic compositions for sulfides and intrusions, further to constrain the ages of mineralization and magmatism, and the source of ore-forming materials. Two granodiorite samples yield mean ages of 245 ± 2 to 243 ± 2 Ma and a diorite has a mean age of 245 ± 2 Ma. A phlogopite sample, which is associated with Cu–Pb–Zn mineralization, has been chosen to precisely date the formation of Cu–Pb–Zn ores by Ar–Ar method and yields a well–defined plateau age of 240.4 ± 1.2 Ma. These results indicate that the Cu–Pb–Zn skarn mineralization formed in the Middle Triassic and is closely related to the coeval magmatism. The εHf(t) values of the ore-related granodioritic and dioritic rocks range from −2.8 to +2.5, whereas an un-mineralized granodiorite sample (WHFG–1) shows lower εHf(t) values of –9.3 to –3.4, indicating that these magmatic rocks are derived from the mixing of magma with different proportions of mantle- and crust-components. A mixing model with ∼40–70 % mantle contribution involved in the formation of ore-related granodiorite and diorite was revealed by Sr–Nd–Hf isotopic compositions. Combined with Pb isotopic compositions for sulfides, feldspar, and bulk rocks, we consider a common source for the ore-forming materials and magmatism. In addition, higher εHf(t) and εNd(t) values for ore-related magmatism implicate that mantle-derived melts show a vital role in the Cu–Pb–Zn skarn mineralization process.

Formation of the giant Maoping Mississippi Valley-type Pb–Zn (Ge) deposit via fluid mixing: Evidence from trace element and sulfur isotope geochemistry of pyrite

The SYG (Sichuan–Yunnan–Guizhou) area is one of the most economically significant Mississippi Valley Type (MVT) ore provinces, providing approximately 27 % of the Pb–Zn resources in China. The Pb-Zn deposits in this region are renowned for their high grade, and the Maoping deposit with 20.3 % Pb-Zn grade is one prime example. However, the mechanism of such high-grade mineralization remains unclear, and pyrite may record valuable ore-forming information before and during Pb-Zn mineralization. Based on field geology and petrography, three hydrothermal stages were identified in the Maoping deposit: dolomite–pyrite vein (stage I), dolomite–sphalerite–galena vein (stage II), and calcite vein (stage III). Three types of pyrite are recognized: Py1 and Py2 occur in stage I, and Py3 is closely associated with sphalerite and galena in stage II. Py1 exhibits the highest concentrations of S, Pb, Sb, Cu, Co, Ni, V, Ag, Mn, Se, and Mo, and Py3 shows the highest Fe and As contents but the lowest levels of S, Pb, Sb, Cr, Ti, Co, Ni, Mn, and Mo. The element composition of Py2 shows transitional characteristics between those of Py1 and Py3. The Co and Ni contents gradually decrease from Py1 through Py2 to Py3, while their ratios remain within the range of 0.1–1.0. Compared with Py1 and Py2, Py3 exhibits suddenly elevated As levels and apparent acicular structures, indicating that a rapidly precipitating environment was likely triggered by an abrupt temperature decrease. Py1 exhibits δ34S values of 19.7–21.5 ‰, followed by Py2 between 18.6 and 21.1 ‰; both indicate that the sulfur was sourced from sulfates by thermochemical sulfate reduction (TSR). In contrast, Py3 exhibits lower δ34S values ranging from 7.5 to 11.0 ‰, potentially attributed to bacterial sulfate reduction (BSR). The differences in mineral structure, element composition, and sulfur isotopes among the three pyrite types indicate the involvement of two distinct fluids: metal-bearing basin brine and fluid containing reduced sulfur. The former was derived from basin brine that extracted ore metals (Pb2+ and Zn2+) from host sedimentary piles. The latter originated from carbonate strata in the Maoping area containing reduced sulfur formed by BSR. We propose that the ore-bearing basin brine reacted with organic matter in the wallrock through TSR to generate Py1 and Py2 in stage I and then mixed with the positioned fluid containing reduced sulfur via BSR to precipitate Py3, sphalerite, and galena in stage II. Hence, fluid mixing is the primary ore-forming mechanism and effectively accounts for the high-grade Pb–Zn ores in the Maoping deposit.

Oblique distribution patterns and the underlying mechanical model of orebody groups controlled by structures at different scales

The oblique distribution of orebodies is a basic feature of the spatial distribution of orebody groups in hydrothermal deposits, and it is closely related to the shearing effect. However, the oblique distribution patterns of orebody groups controlled by ore-controlling/ore-forming structures at different scales (orebody, ore deposit and ore field scales) and the underlying formation mechanism are unclear but could be used to directly constrain mineral exploration and prospecting breakthroughs in the deep and peripheral areas of ore deposits. This paper uses the northeastern Yunnan Ge-rich Pb–Zn ore concentration area in the Sichuan–Yunnan–Guizhou metallogenic area as an example to analyse and demonstrate the oblique distribution patterns of orebodies (orebody groups) controlled by ore-forming/ore-controlling structures at different scales and the underlying mechanical model based on the Theory and Methods of Ore field Geomechanics. The results indicate that in 3D space, the oblique distributions of orebodies (veins), orebody groups and ore deposits are controlled by the mechanical properties, kinematic characteristics, and tectonic stress fields of ore-forming/ore-controlling fault structures of different sequences during the mineralization period. This study has an important guiding role for ore field-scale exploration deployment, evaluation of deep and peripheral prospecting, and exploration project arrangement, with the aim of helping mining companies increase resource reserves and production.

Compositional balance analysis: A novel method for tectono-geochemical anomaly identification and blind ore deposit prediction

Tectono-geochemical exploration always involves the study of tectono-geochemical primary halos. From the perspective of compositional data analysis, this study introduced how to use compositional balance analysis (CoBA) method to recognize tectono-geochemical anomalies and infer blind ore deposits in the deep. A case study for prediction of concealed Pb–Zn ore deposits based on tectono-geochemical data in the Huangzhuguan ore cluster, Gansu Province, China, was employed to demonstrate the potential applications of the CoBA method. First, an optimal element combination (i.e., Pb–Zn –Cd) related to near-ore halo was determined by means of CoBA method and receiver operating characteristic curve analysis. Then, according to the element zonation sequences of the primary halo in the hydrothermal deposit, the front halo element combination (i.e., As–Sb–Hg) and the tail halo element combination (i.e., W–Sn–Mo–Bi) were selected for compositional balance analysis. Finally, based on knowledge-driven CoBA method, three types of tectono-geochemical primary halos were customized to evaluate blind Pb–Zn deposits in the Huangzhuguan ore cluster. The results indicate that the CoBA method combined with the superimposed characteristics of tectono-geochemical primary haloes, proves to be effective and straightforward in interpreting Pb–Zn mineralization-related anomalies and predicting hidden Pb–Zn targets.

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.

Thermodynamic behavior and kinetic analysis of carbothermal reduction process of low-grade oxysulfur lead–zinc ore

During the exploitation of sphalerite resources, a considerable amount of low-grade oxysulfur Pb–Zn deposits is generated, which poses a significant threat to the environment and soil and water conservation in mining areas. Therefore, low-grade Pb–Zn resources urgently require source emission reduction and appropriate utilization. This study applied a mineral technology and conducted X-ray diffraction and scanning electron microscopy–energy dispersive X-ray spectroscopy to investigate the phase transformation and the mechanism underlying the volatilization of Pb and Zn at different times and temperatures. The Pb–Zn volatilization kinetics of a low-grade oxysulfur Pb–Zn ore by a one-step pyrometallurgical process in an argon atmosphere was studied, and the effects of different temperature conditions on the Zn volatilization process were investigated. The results showed that the Zn-containing phase in the raw material was decomposed to ZnO and ZnS upon heating. Moreover, ZnO was reduced via carbothermal reduction, whereas ZnS was reduced via a CaO-assisted carbothermal reaction and volatilized in the form of gaseous Zn. In the Pb-containing phase, PbSO4 generated PbO, Pb, and PbS in the presence of Fe, FeS, and CaO. PbO was volatilized in the form of gaseous Pb through carbothermal reduction and interactions between PbS and PbO. The Pb–Zn volatilization reaction conformed to the shrinking core model with a constant size, and the volatilization-based removal of Pb and Zn process was controlled by internal diffusion. A macroscopic kinetic model of the reaction was established on the basis of experimental data. The apparent activation energy of Pb and Zn volatilization was 163.90 and 328.19 kJ/mol, respectively. This study promotes the utilization of the low-grade oxysulfur Pb–Zn ore through a pyrometallurgical method to provide theoretical support for large-scale industrial treatments.

Ore deposit prospecting using the chlorine and bromine secondary dispersion halos

The Cland Brions, that form complex compounds with metals, produce secondary dispersion halos in the hypergenesis zone at Au, Ag, Cu, Pb, and Zn ore deposits which ore bodies are controlled by fracturing and fault structures. The appearance of anomalies of the highly mobile water-soluble ions, manifested on the surface and in the wall rocks, is explained by their transfer from the deep sources to the surface by a gas flow. The migration of the ions to the earth's surface and further into the atmosphere is influenced by many factors (atmospheric pressure, temperature, humidity, rock porosity, etc.) that complicate the observation results.

Myauchan Ore Field (Northeastern Asia), an Example of Weakly Eroded Ag–Pb–Zn Volcanoplutonic Mineralization

Abstract —The Myauchan ore field located in the Omsukchan zone of the Okhotsk–Chukotka Volcanic Belt is described. The Korennoe and Malyutka Ag–Pb–Zn ore occurrences forming this field are localized at the center of anticlinal fold of NW strike made up of Upper Triassic carbonate-terrigenous deposits intruded by stock-like bodies and dikes of Upper Cretaceous andesite, monzodiorite, granite-porphyry, and rhyolite-porphyry. Sulfide–carbonate–fluorite–quartz veins and vein–veinlet zones with arsenopyrite, pyrite, sphalerite, galena, chalcopyrite, and Ag-tetrahedrite are localized both in intrusions and in terrigenous strata. The field bears As–Sb–Ag–Pb–Au–Bi–Cu–Zn–W mineralization. Study of fluid inclusions and REE and ore element patterns show that the field ores formed from chloride solutions with the participation of surface waters in hydrothermal-magmatic system under epithermal conditions. The ores were deposited from solutions with TDS = 0.5–9.0 wt.% NaCl equiv. in the temperature range 106–287 ºC. The ores containing ca. 70 ppm Ag and up to 1.2% Pb formed through boiling-off of solutions enriched in iron salts. The ores with Ag < 7 ppm and Pb ≤ 25 ppm were generated from diluted hydrothermal solutions with predominant sodium salts and potassium admixture. Mineralization of the Myauchan ore field marks the upper level of the Ag–Pb–Zn ore system similar to the Gol’tsovoe deposit.

Indium mineralization and genesis of the Bainiuchang Ag–Sn–polymetallic deposit in southeast Yunnan, China: Evidence from mineral chemistry and U–Pb geochronology

The Bainiuchang Ag–Sn–polymetallic deposit is located in the world-calss Southeast Yunnan Indium Metallogenic Belt (SYIMB). The deposit contains approximately 1000 tons of In, but the mechanisms of mineralization and hosts of In in this deposit remain unclear. To clarify these ambiguities, we carried out fieldwork, major- and trace-element analyses of In-bearing minerals, and cassiterite and zircon U–Pb geochronology. Five ore zones were identified, which, from contact of the granitic intrusion upwards, are the In-poor magnetite–cassiterite ore zone, the In-poor Cu ore zone, the In-rich Zn–Sn ore zone, the In-rich Sn–Pb–Zn ore zone, and the In-poor Pb–Zn ore zone. Cassiterite and zircon U–Pb geochronology demonstrate that mineralization at Bainiuchang occurred at ca. 85.80±0.45 Ma (MSWD = 1.5), which is similar to the 85.34±0.42 Ma (MSWD = 1.7) age of the granitic intrusion. This temporal relationship suggests that there is a genetic link between In mineralization and granitic magmatism in this deposit. Ore petrography and mineral chemical analyses indicate that sphalerite, chalcopyrite, and stannite are main In-bearing minerals. From a mass balance perspective, sphalerite is the most important In-bearing mineral, accounting for ∼85% of the In budget at Bainiuchang. Indium is incorporated into sphalerite via the coupled substitution 2Zn2+ ↔ Cu+ + In3+ and/or 3Zn2+ ↔ Ag+ + Sn2+(+In3+). Two generations of sphalerite occur in the deposit, SpI and SpII, which formed during the cassiterite–sulfide and carbonate–sulfide stages, respectively. Based on textural relationships, SpI is further subdivided into SpIa, SpIb, and SpIc. These temporally and texturally distinct sphalerite have variable In contents, with SpIa having the highest In content (0.08–0.44 wt%), followed by SpIb (0.02–0.39 wt%), SpIc (187–236 ppm), and SpII (0.64–7.14 ppm). It is suggested here that the variations in In contents of the sphalerite reflect the evolution of the magmatic–hydrothermal fluids from which the sphalerite precipitated under different fS2 and temperature. By comparing the Bainiuchang deposit to other In-bearing deposits in the southwestern Yangtze Block, it is evident that that the nature and source of the associated granites, and the degree of fractionation of the granitic magmas are likely important controls on In mineralization in the SYIMB and other regions.

Heavy metal fraction, pollution, and source-oriented risk assessment in biofilms on a river system polluted by mining activities

The Lanping Pb–Zn mine is the largest source of Pb and Zn ores in China, thus posing a great threat to local ecosystems and human health. A total of seven heavy metals (Zn, Pb, Ni, Cu, Cr, Cd, and As) in the Bijiang River near the Pb–Zn mine were measured in winter and summer to assess their spatial–temporal enrichment, ecological risk, and source-oriented health risk in periphytic biofilms. Positive matrix factorization (PMF) receptor model and clustering analysis were used to quantitatively identify pollution sources. The results of PMF were then imported into the health risk assessment to further determine the carcinogenic and noncarcinogenic risks of various pollution sources. The results indicated distinct seasonal patterns in metal concentrations, with much higher concentrations in winter. Sites near the Pb–Zn mine tailing reservoir exhibited higher metal contamination levels than other sites. A strong correlation between the enrichment factor and the levels of nonresidual fraction suggested that anthropogenic inputs were the main source of these metals. Mining industries (Cd, Zn, and Pb), natural sources (As, Ni, and Cu), and agricultural activities (Cr) were the primary sources of heavy metal pollution in biofilms, accounting for 44.43%, 33.32%, and 22.26% of the total metal accumulation, respectively. Moreover, the carcinogenic and noncarcinogenic risks via dermal contact of the studied elements in biofilms were typically acceptable. Notably, as concentration was the main factor influencing these risks in children and adults. This study provides evidence that natural epilithic periphyton may be a potential metal biomonitor in aquatic systems and provide supporting information for effective source regulation.

Apatite as a record of ore-forming processes: Magmatic-hydrothermal evolution of the Hutouya Cu–Fe–Pb–Zn ore district in the Qiman Tagh Metallogenic Belt, NW China

Apatite is a common accessory phase in magmatic rocks and associated hydrothermal deposits that holds information about the evolution from magma to ore-forming fluid. In this study, we systematically studied the geochronological and geochemical characteristics of apatites hosted in the Fe skarn ores and associated intrusions of syenogranite and monzogranite in the Hutouya polymetallic Fe–Cu–Pb–Zn ore district, Qiman Tagh Metallogenic Belt (QTMB), NW China, in order to gain insight into the metallogenic processes from magmatic crystallization to hydrothermal fluid exsolution. The apatite U–Pb dating results of skarns and related intrusions are 229–228 Ma, and the monzogranite emplacement is slightly later than the syenogranite emplacement and skarn formation. The REE concentrations of the apatites from the skarn-related intrusions are characterized by LREE-enriched patterns and weak negative Eu anomalies. However, the apatites from the skarn ores have high HREE contents, and are characterized by flat chondrite-normalized patterns and strong negative Eu anomalies. These data, combined with variations of element concentrations and ratios in the apatites (eg., Sr, SO3, F, Cl, REE, (La/Yb)N, (Sm/Nd)N, (La/Sm)N, (Eu/Eu*)N, (Ce/Ce*)N), record the transition of ore-forming processes from the magmatic crystallization to hydrothermal exsolution, and indicate that the skarn-related magmas with moderately reduced signatures may have been derived from partial melting of crustal materials potentially affected by the limited mantle input under an extensional environment.

How a basement fault has controlled Pb- Zn ore deposition within the Zagros Fold-Thrust Belt? a focus on remote sensing approaches

ABSTRACT The Zagros fold and thrust belt as one of the structurally complex areas have been considered chiefly only for hydrocarbon reserves, despite having other mineral deposits like the Surmeh lead and Zinc mine. This study was conducted in the Fars region, one of the structural zones in the Zagros, to detect hydrothermal alteration minerals associated with Pb–Zn mineralization and fracture distribution using ASTER, Landsat 8, and Sentinel 2 satellite imagery. Using different algorithms and approaches, we demonstrate the interesting distribution of Pb-Zn-related mineral deposits controlled by structures on different scales. These methods included the spectral band ratios and spectral angle mapping for alteration detection and manual extraction of structural lineaments (i.e. fault and fractures) from ETM+. Also, an augmented circular scanline method, along with areal sampling, was used to prepare a fracture intensity map of the area. According to the results, the intersection of NW-SE and N-S trending fracture sets are promising areas for Pb-Zn-related mineral exploration. These fracture sets are likely associated with the main Karebas tear fault and its horsetail splay terminal. The findings of this study were validated by field observation of the Pb-Zn deposit and its related mineral associations in the area.

Genesis of the Shibaogou Mo–Pb–Zn deposit in the Luanchuan ore district, China: Constraints from geochronology, fluid inclusion, and H–O–S–Pb isotopes

The Shibaogou deposit is located in the Luanchuan ore district within the East Qinling orogenic belt (EQOB), central China, which is a newly discovered Mo–Pb–Zn skarn deposit. The skarn and Mo–Pb–Zn ore bodies are mostly hosted in the contact zones between the Shibaogou porphyritic granite and carbonaceous sedimentary rocks from the Luanchuan and Guandaokou sets. A study combined of geochronology, fluid inclusion (FI), and stable isotopes was performed to constrain the mineralization age, source of ore materials, and the origin and evolution of the ore-forming fluids and their relationship with the subduction of the Paleo-Pacific Plate. The mineralization process includes skarn and quartz–sulfide episodes, which has four stages: skarn (I), quartz–molybdenite (II), quartz–galena–sphalerite (III), and quartz–calcite (IV). Molybdenite Re-Os dating suggests that the deposit was formed in the Late Jurassic (147.4 ± 7.2 Ma). Reportedly, there are five primary types of fluid inclusions: L-type, V-type, H-type, S-type, and C-type. In the skarn stage, coexisting H-type (35.58 wt%–46.05 wt% NaCl equiv.) and low-salinity V-type (0.35 wt%–5.7 wt% NaCl equiv.) fluid inclusions show similar homogenization temperatures, which suggests that fluid boiling occurred at 513–550°C and 580–650 bar (2.19–2.45 km). In the quartz–molybdenite stage, the homogenization temperatures of L-type, V-type, minor H-type, and S-type fluid inclusions indicate continued fluid boiling at 324–387°C and 180–250 bar (0.49–0.94 km). In the quartz–galena–sphalerite stage, a fewer number of coexisting V-type and L-type fluid inclusions in quartz shows different salinities with similar homogenization temperatures, indicating that they are trapped at 303–347°C and <150 bar in the boiling process (<0.56 km hydrostatic depth). The minor primary L-type fluid inclusions that have lower salinities of 0.88 wt%–11.34 wt% NaCl equiv were observed in quartz and calcite in the quartz–calcite stage; in addition, their homogenization temperatures are 103–247°C (typical post-ore conditions). This study found that the ore-forming fluids at the Shibaogou deposit were dominantly magmatic water at the early stage, with input of atmospheric water during fluid evolution, with δ18Ofluid values from −1.168‰ to 8.997‰ and δ18Dfluid values from −106.5‰ to −79.9‰, based on the O and H isotope data from garnet, quartz, and calcite. Furthermore, the S isotopic compositions were measured ranging from 0.8‰ to 14.7‰, and it demonstrated that the ore-forming fluid was mainly derived from magmatic sources. The relatively homogeneous Pb isotopic compositions are similar to those of Shibaogou granite porphyry, which demonstrated that the ore-forming materials were mainly derived from magmatic sources. Molybdenite was precipitated as a result of fluid–rock interactions and fluid boiling, and the galena and sphalerite were precipitated as a result of the decreasing temperature. The subduction of the Paleo-Pacific plate has a critical impact on the complex evolution of ore formation in the Shibaogou skarn deposit in EQOB.

Identification of Pb–Zn ore under the condition of low count rate detection of slim hole based on PGNAA technology

The grade analysis of lead-zinc ore is the basis for the optimal development and utilization of deposits. In this study, a method combining Prompt Gamma Neutron Activation Analysis (PGNAA) technology and machine learning is proposed for lead-zinc mine borehole logging, which can identify lead-zinc ores of different grades and gangue in the formation, providing real-time grade information qualitatively and semi-quantitatively. Firstly, Monte Carlo simulation is used to obtain a gamma-ray spectrum data set for training and testing machine learning classification algorithms. These spectra are broadened, normalized and separated into inelastic scattering and capture spectra, and then used to fit different classifier models. When the comprehensive grade boundary of high- and low-grade ores is set to 5%, the evaluation metrics calculated by the 5-fold cross-validation show that the SVM (Support Vector Machine), KNN (K-Nearest Neighbor), GNB (Gaussian Naive Bayes) and RF (Random Forest) models can effectively distinguish lead-zinc ore from gangue. At the same time, the GNB model has achieved the optimal accuracy of 91.45% when identifying high- and low-grade ores, and the F1 score for both types of ores is greater than 0.9.

Statistical approach to interpretation of geochemical data of stream sediment in Pleše mining area

The Ba, Pb and Zn ore deposit Pleše near Ljubljana is one of the formerly productive mines. The stream sediments were sampled and analysed by XRF to establish the effect of grain size, mineralization, and downstream location of sampling sites on geochemical composition based on various statistical analyses. Statistical analyses of the geochemical data confirm the impact of mineralization. The parametric t-test, non-parametric Mann-Whitney test and cluster analysis showed only minor differences in the geochemical composition of the samples with different grain sizes (< 0.063 mm and 0.063-2 mm). The parametric and non-parametric correlation coefficients as well as cluster analysis indicate that the contents of Si, Al, K, Rb, and Fe are associated with weathered rock forming minerals such as micas, and clay minerals, whereas Nb and Zr are associated with minerals resistant to weathering. Ca and Mg are associated with carbonates. S, Ba, Sr, Pb, Zn, and Mn indicate local mineralization with sulphates and sulphides. The results of the t-test and analysis of variance, Mann-Whitney tests and Kruskal-Wallis ANOVA of the groups established by the cluster analysis confirm that the contents of Ba, Pb and Sr have a statistically significant influence on the classification of the cluster group - i.e., the influence of sediment mineralization. There are no differences in elemental contents in the sediment samples downstream. The statistical approach to evaluate the geochemical data has proven useful and provides a good basis for further interpretation.

Genetic Relationship between Mississippi Valley-Type Pb–Zn Mineralization and Hydrocarbon Accumulation in the Wusihe Deposits, Southwestern Margin of the Sichuan Basin, China

The coexistence of numerous Mississippi Valley-type (MVT) Pb–Zn deposits and oil/gas reservoirs in the world suggests a close genetic relationship between mineralization and hydrocarbon accumulation. The Wusihe MVT Pb–Zn deposits are located along the southwestern margin of the Sichuan Basin. Based on the spatiotemporal relation between Pb–Zn deposits and paleo-oil/gas reservoirs, ore material sources, and processes of mineralization and hydrocarbon accumulation, a new genetic relationship between mineralization and hydrocarbon accumulation is suggested for these deposits. The Wusihe Pb–Zn deposits are hosted in the Ediacaran Dengying Formation dolostone, accompanied by a large amount of thermally cracked bitumen in the ore bodies. The Pb–Zn deposits and paleo-oil/gas reservoirs are distributed along the paleokarst interface; they overlap spatially, and the ore body occupies the upper part of the paleo-oil/gas reservoirs. Both the Pb–Zn ore and sphalerite are rich in thermally cracked bitumen, in which µm sized galena and sphalerite may be observed, and the contents of lead and zinc in the bitumen are higher than those required for Pb–Zn mineralization. The paleo-oil/gas reservoirs experienced paleo-oil reservoir formation, paleo-gas reservoir generation, and paleo-gas reservoir destruction. The generation time of the paleo-gas reservoirs is similar to the metallogenic time. The source rocks from the Cambrian Qiongzhusi Formation not only provided oil sources for paleo-oil reservoirs but also provided ore-forming metal elements for mineralization. Liquid oil with abundant ore-forming metals accumulated to form paleo-oil reservoirs with mature organic matter in source rocks. As paleo-oil reservoirs were buried, the oil underwent in situ thermal cracking to form overpressure paleo-gas reservoirs and a large amount of bitumen. Along with the thermal cracking of the oil, the metal elements decoupled from organic matter and H2S formed by thermochemical sulfate reduction (TSR) and minor decomposition of the organic matter dissolved in oilfield brine to form the ore fluid. The large-scale Pb–Zn mineralization is mainly related to the destruction of the overpressured paleo-gas reservoir; the sudden pressure relief caused the ore fluid around the gas–water interface to migrate upward into the paleo-gas reservoirs and induced extensive metal sulfide precipitation in the ore fluid, resulting in special spatiotemporal associated or paragenetic relations of galena, sphalerite, and bitumen.

Analytical studies on medieval lead ingots from Wrocław and Kraków (Poland): a step towards understanding bulk trade of lead from Kraków and Silesia Upland Pb–Zn deposits

Origins of medieval lead artefacts are hard to establish due to re-smelting and mixing. One can obtain conclusive evidence from ingots that served for bulk trade and originated directly from the mines. This paper aims to analyse the thirteenth century lead ingot from Wrocław (Poland). To establish its origins we analysed its structure and chemical composition. We used archaeometric methods: light and electron microscopic observations, X-ray fluorescence spectrometry, X-ray diffraction, infrared spectroscopy, inductively coupled plasma-optical emission spectrometry and Pb isotopic analysis. We compared our measurements with measurements of analogical ingot found on Kraków Market Square and a database of lead ores from Europe and the Middle East. The research indicated that both ingots originated from -Kraków and Silesia Upland Pb–Zn ore deposits (Poland), intensively mined from the twelfth century. The results complement the view of trade routes established based on written records and add valuable data for future comparative studies.

Constraints on the genesis of the Laochang Pb–Zn ore, Gejiu district, Yunnan: Evidence from sulfide trace element and isotope geochemistry

The Laochang deposit is an important part of the Gejiu Sn–Cu polymetallic district, containing abundant reserves of tin, copper, lead, zinc and tungsten. The recently discovered sulfide Pb–Zn ore is located 1000 m underground in the Laochang deposit, and its genesis is not clear. In this study, the trace element concentrations and sulfur and lead isotope compositions of sulfides from the newly discovered Laochang Pb–Zn ore were analyzed to constrain mineralization conditions and genesis. Our results show that sphalerite from Laochang Pb-Zn ore contains high Fe, Cu, Ga, Ag, In and Sn, low Co, Ni, Ge and As and moderate Mn and Cd. Pyrite is enriched in Ag, Sb, Pb and As and poor in Co, Ni, Se, Ti and Mn. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) ablation profiles of sphalerite show that Fe, Cd, Mn, Ga, and In occur as solid solutions and/or lattice-bound ions, whereas Ag, Cu, Pb, Sb, and Sn are present in both mineral inclusions and solid solutions. Moreover, the profiles of pyrite indicate that Co, Ni and As enter the pyrite lattice by ion replacement and that Sn, Ag, Pb and Sb occur in both solid solutions and mineral inclusions.The Fe/Zn calculation temperature of sphalerites ranges from 299 °C to 344 °C (mean of 320 °C), while the sphalerite geothermometer (GGIMFis) temperatures range from 268 °C to 312 °C, with an average of 290 °C. These results indicate that the Laochang Pb–Zn ore formed under moderate- to high-temperature conditions. The sphalerites in the Laochang Pb–Zn ore is enriched in Ga and In, is poor in Ge, and has moderate contents of Cd which implies that it may be related to magmatic-hydrothermal fluid. Pyrites in this study have relatively low Co and Ni concentrations and low Co/Ni ratios, which also indicate magmatic-hydrothermal origin.The overall sulfur isotope compositions of sulfides from the Laochang Pb–Zn ore, ranging from −1.2 ‰ to +3.7 ‰, indicate that the S may be derived from the Laoka granite with some contribution from the wallrock. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of galena in the five samples range from 18.400 to 18.447, 15.656 to 15.697, and 38.478 to 38.968, respectively. These results imply that the ore-forming metals in the Pb–Zn ore were derived from the upper crust. Therefore, we believe that the Pb–Zn ore may be of magmatic-hydrothermal origin and represents the distal mineralization of the Laoka metallogenic system.

Thermodynamic analysis of zinc ferrite (ZnFe2O4) formation inside the HIsarna off-gas system

ABSTRACT HIsarna reactor is characterized by a high raw materials versatility and is therefore attractive for processing secondary iron sources. Among the materials that can be recycled through HIsarna, zinc-bearing material has drawn a special attention. Based on the plant data, once dust-containing Zinc was injected into the main reactor, a final collected dust with a zinc content of 16% was achieved which opened up possibilities of higher enrichment for direct reuse in Zn smelting as a secondary source and an alternative for Zn ore (the primary source). However Zn vapor can react with iron oxide to form zinc ferrite (ZnFe2O4), which is an undesired product. Hence, the main focus of this study is to minimize the formation of ZnFe2O using thermodynamic (FactSage) and computational fluid dynamic tools. After detecting regions with high potential of ZnFe2O4 formation, proper geometrical and operational modifications of the off-gas system is proposed to minimize the formation of zinc ferrite.