Pb Zn Ag Research Articles

Mapping of Gold Prospectivity in the Qingchengzi Pb–Zn–Ag–Au Polymetallic District, China, with Ensemble Learning Algorithms

Mapping of Gold Prospectivity in the Qingchengzi Pb–Zn–Ag–Au Polymetallic District, China, with Ensemble Learning Algorithms

3D geometry of the Dugald River Shear Zone, Mount Isa Inlier, Australia

The Dugald River Shear Zone is a structurally complex, anastomosing shear zone that hosts high-grade Zn mineralisation within the Dugald River Slate. The Dugald River Zn–Pb–Ag mine is situated within the Mount Isa Inlier, Australia and developed through two phases of mineralisation with high-grade Zn mineralisation intimately associated with the development of the brittle–ductile Dugald River Shear Zone. The first phase of mineralisation occurred during the regionally extensive, D2 ductile fold and axial planar cleavage forming event and resulted in the development of a sulfide horizon. This horizon was a preferential site for strain partitioning during early D4 ductile deformation, which resulted in transposition-related concentration and thickening of a sulfide horizon marking the second phase of mineralisation. The Dugald River Shear Zone developed during D4 wherein strain rate incompatibilities between a ductile-deforming sulfide horizon and the brittle-deforming Dugald River Slate resulted in the development of a Riedel shear zone. A high-resolution 3D model of the shear zone was constructed from robust drilling and mapping datasets in which releasing and restraining bends highlight the thickening and thinning of ore lenses, respectively. The 3D model with detailed structural analysis and observations allows for predictive modelling of dilational zones within throughgoing Y-shears, which are prospective sites for remobilisation of high-grade Zn sulfides as the ore body developed coevally with progressive shearing.

Pyrite in-situ S–Fe isotope constraints on the ore-forming sources and mineralization processes of gold and polymetallic deposits in the Liaodong Peninsula, North China Craton

Plenty of gold and polymetallic deposits are widespread in the eastern part of the North China Craton. They are associated with mafic to felsic dikes and hosted by Precambrian basement or Mesozoic granitoids. However, the sources of gold and other metals in the ore-forming fluids remain controversial. Here we present in-situ S and Fe isotopes and trace element contents of pyrites from various gold and Pb–Zn–(Ag) deposits in the Liaodong Peninsula, China. Pyrites from quartz vein-type gold deposit hosted by Mesozoic granites in the Wulong deposit have relatively homogeneous magmatic-like S isotopes (δ34S values of 0.9 ‰ to 2.5 ‰) and Co/Ni ratios, indicating derivation of sulfur and, by inference, of ore fluids/materials most likely from Mesozoic magmas. In contrast, pyrites from gold and Pb–Zn–(Ag) deposits in the Qingchengzi orefield hosted by Precambrian basement have high and variable δ34S values (9.7 ‰ to 12.7 ‰ for the Wandigou altered rock-type gold deposit and 4.7 ‰ to 8.5 ‰ for the Xiquegou Pb–Zn deposit and the Zhenzigou Pb–Zn–Ag deposit), identical to those of host rocks, indicating the important contributions of gold and other metals from wall rocks to the ore deposits. Pyrites from the various deposits have variable δ56Fe values of 0.08 ‰ to 0.63 ‰ for the Pb–Zn–Ag deposit, –0.58 ‰ to 1.23 ‰ for the altered rock-type gold deposit, and –0.68 ‰ to 0.77 ‰ for the quartz vein-type gold deposit, indicating distinct mineralization processes. Rapid precipitation of pyrites (with negative δ56Fe values) in the alteration rock and subsequent deposition of pyrites (with positive δ56Fe values) from the residual fluids in an Fe-open hydrothermal system during intensive ore-forming fluid-wall rock interaction account for the Pb–Zn–Ag mineralization, while weak fluid-rock interaction and pyrites precipitation from a Fe-closed hydrothermal system contribute to gold mineralization. Our observations provide a robust S–Fe isotope evidence for the contribution of various sources and metallogenic processes for distinct gold and polymetallic deposits.

Genesis of the Haopinggou breccia-hosted Au deposit, western Henan Province, China

Breccia-hosted Au deposits within the North China Craton (NCC) exhibit a complex genesis, with some breccias being genetically linked to Au mineralization and others unrelated. Understanding the origin of these breccias is crucial for elucidating the genesis of associated ore deposits and guiding exploration strategies. The Haopinggou deposit in the Xiong’ershan district, on the southern margin of the NCC, comprises quartz-carbonate vein-hosted Ag–Pb–Zn–Au deposits and related breccia pipe in metamorphic rocks of the late Archean to early Paleoproterozoic Taihua Group. The origin of the Haopinggou breccia is crucial to understand the Xiayu Ag-Pb-Zn-Au mineralization (5640 t Ag). In this study, we evaluate the genetic links between breccia and Ag-Pb-Zn-Au mineralization, with new insights obtained from the Haopinggou deposit characteristics, breccia characteristics, breccia-hosted Au mineralization, and isotopic data, which refine our understanding of Haopinggou Ag-Pb-Zn-Au hydrothermal systems and exploration models in discordant breccia pipes. Recent underground tunnel surveys and drill-core logging reveal a close spatial link between the breccia and hidden granite porphyry. Juvenile magmatic clasts (granite porphyry) and cement (K-feldspar and quartz crystallized from granite porphyry) are present in the breccia pipe above a granite porphyry apophysis, indicating that the breccia was formed by phreatomagmatic brecciation caused by emplacement of the granite porphyry. Fluidization at the cm- to 100-m-scale reveals that the movement direction of clasts inside the breccia pipe was from northwest to southeast after crypto-explosion, creating a northwest-trending breccia zone. Anhedral monazite (131.2 ± 7.6 Ma) encapsulated in pyrite from the breccia constrains the upper limit of brecciation. The δ34S values of pyrite in rock powder and hydrothermal cements range from 3.8 ‰ to 5.3 ‰ (mean: 4.8 ‰) and 2.7 ‰ to 7.5 ‰ (mean: 5.2 ‰), respectively, with δ34S-sphalerite in hydrothermal cement ranging from 5.7 ‰ to 6.1 ‰ (mean: 5.9 ‰) and δ34S-chalcopyrite ranging from − 0.9 ‰ to 5.6 ‰ (mean: 2.9 ‰). The S isotope characteristics of vein-hosted and breccia-hosted mineralization zones are consistent, with complete alignment of the sulfide assemblages and alteration features. These pieces of evidence collectively indicate that both vein- and breccia-hosted mineralization zones are products of magmatic activity. The metallogenic model for the Haopinggou breccia pipe underscores its unique formation mechanism, driven by pre-existing northwest-striking structural weaknesses and fluidization, indicative of a predominant northwest–southeast clast movement, and suggesting the potential for deep-seated porphyry-type Au mineralization.

Lazerckerite, Ag3.75Pb4.5(Sb7.75Bi4)S24, from Kutná Hora, Czech Republic: a new Sb–Bi member of the andorite branch of the lillianite homologous series

Abstract. Lazerckerite, ideally Ag3.75Pb4.5(Sb7.75Bi4)S24, is a new mineral species found in medieval mine dumps of the historic Ag–Pb–Zn Kutná Hora ore district, Czech Republic. The mineral is associated with other Sb–Bi lillianite homologues (terrywallaceite, gustavite, holubite) and Ag,Bi-bearing galena, most frequently as grain aggregates and replacement rims of earlier Ag–Pb–Bi minerals, growing together in aggregates of up to 0.6×0.3 mm. Lazerckerite is opaque, is steel grey in colour, and has a metallic lustre; the calculated density is 5.920 g cm−3. In reflected light lazerckerite is greyish white, and bireflectance and pleochroism are weak with grey tints. Anisotropy is weak to moderate with grey to bluish-grey rotation tints. Internal reflections are not observed. Electron microprobe analyses yielded the empirical formula, based on 44 apfu, (Ag3.61Cu0.04)Σ3.65(Pb4.55Fe0.01Cd0.01)Σ4.57(Sb7.87Bi3.75)Σ11.62(S24.15Se0.01)Σ24.16. Its unit cell parameters are a=13.2083(9), b=19.4595(8), c=8.4048(13), β=90.032(7)°, V=2160.3(4) Å3, space group P21/c, and Z=2. The structure of lazerckerite contains two Pb sites (Pb1 and Pb2) in bicapped trigonal prismatic coordination, 8 independent octahedral sites, and 13 distinct sulfur positions. Four of the octahedral sites are mixed (Sb,Bi) and (Bi,Sb) sites, one is a mixed (Ag,Bi) site, and one is a mixed (Sb,Pb) site. The new mineral belongs to the andorite branch of the lillianite homologous series with N=4 and is a new addition to the group of Sb–Bi mixed members of the series. Lazerckerite is defined as a lillianite homologue with the three following requirements: N=4, L (Ag++ (Bi3+, Sb3+) ↔ 2 Pb2+ substitution) ≈ 90 %–95 %, and approximately one-third of atom percentage of antimony is replaced by bismuth (Bi/(Bi+Sb) ≈ 0.30–0.38). The new mineral has been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA 2022-113) and named after Lazarus Ercker, the supreme Royal Bergmeister of the Kingdom of Bohemia and the Master of Prague Mint.

Magmatic evolution and sources of metals and fluids in the large granite-related Xiasai vein-type Ag–Pb–Zn(–Sn) deposit, northern Yidun terrane, SW China

The Xiasai Ag–Pb–Zn–(Sn) deposit in the northern Yidun terrane (eastern Tethys), hosted in Late Triassic metasandstones, is genetically associated with Late Cretaceous granites. We present chemical and Sr–Nd–Pb–Li–B isotope data of Late Cretaceous granites and their mafic microgranular enclaves (MME), late aplites, and Late Triassic metasedimentary rocks. The narrow range of 87Sr/86Sr99 (0.70627–0.70953) and εNd99 (–6.1 to –5.2) values of most Late Cretaceous granites reflects a mixed source with contributions from the mantle and Paleoproterozoic felsic crust. These granites have high SiO2 contents (>69 wt%) and strong depletions in Sr, Ba, and Eu. Major and trace element contents correlate with the fractionation index 1/TiO2, indicating that they experienced extensive fractionation. Local late aplite dikes were derived from similar source rocks, but seem to be younger.The Pb isotopic compositions reflect that the metal Pb was derived from the granite with variable contributions from the Late Triassic sedimentary rocks. Weakly and moderately altered metasandstones have similar δ7Li and δ11B values as most granites (δ7Li: 0.00 to 2.68 ‰; δ11B values: –14.93 to –12.36 ‰), indicating magmatic fluid sources. The magmatic fluids resulted in the initial enrichment of Sn, Cu, Pb, and Zn. Strong alteration of feldspar and biotite resulted in the metasandstones in negligible change of Li concentrations, significant loss of Sr, Na2O, CaO, MgO, and Fe2O3, but significant addition of B. This alteration lowered δ7Li from 1.01 to –3.65 ‰ and lowered δ11B from –9.43 to –19.18 ‰. The low δ7Li values and extremely low δ11B values reflect external fluids from the Late Triassic sedimentary wall rocks, which interacted with granites and mobilized metals (e.g., Sn, Ag, Pb, and Zn) from the granite and/or the sedimentary wall rocks. The location of the Xiasai deposit is controlled by regional NNW-trending faults induced by Late Cretaceous extension.

Gold occurrence in the footwall of the Lappberget Deposit, Garpenberg Mine, Sweden: Implications for recovery efficiency

By-product metals have a significant potential to bring additional economic benefits to mines. However, a detailed characterization of their distribution is generally required to fulfill this potential and should preferably be integrated into a geometallurgical assessment. This contribution presents a detailed mineralogical and textural investigation of gold-bearing phases at the footwall of the Zn–Pb–Ag–(Cu–Au) Lappberget Deposit, Garpenberg Mine, Sweden, using optical microscopy, scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), electron probe microanalysis (EPMA), laser ablation-inductively coupled plasma mass spectrometer (LA-ICPMS), and bulk chemical analysis applied to drill core and Knelson concentrator samples. Gold is a by-product at the Garpenberg mine, but it is unclear how the mineralogy, occurrence, and distribution of gold-bearing phases impact on gold recoveries during mineral processing. Our results show that Au-dominant electrum is the most abundant gold-bearing phase in the footwall of the Lappberget deposit, occurring strongly associated to sulfides in a variety of textures and grain sizes. Electrum grains commonly occur within sulfide borders, as inclusions, intergrowth and overgrowths of chalcopyrite, pyrite, galena, sphalerite, and pyrrhotite. Gangue minerals may also contain disseminated electrum and inclusions. Electrum grain sizes range from ∼5 µm to 300 µm, predominantly below 100 µm. The potential of sulfide lattice-bound invisible gold in the form of solid-solution gold and colloidal gold was also investigated, showing Au depletion within the analyzed sulfide carriers. The analysis of the concentrate samples from the Knelson gravity concentrator showed 584 and 431 ppm of gold content. High degree of liberation is observed among the gold-bearing phases in the concentrate, and gold recovery is highest among fractions coarser than 106 µm mesh. Pyrite and galena are the most abundant minerals in the concentrate samples. The gold-bearing phases were categorized based on its mineralogy, texture, grain size, and association and their influence on gold processing, especially textures and grain size, which implicates its liberation in milling and recovery by the gravity separator.

Determination of structural lineaments of the mafic-ultramafic belt of the Southern Argentine Precordillera

In central-western Argentina, an Early Paleozoic belt including mafic-ultramafic bodies and marine metasedimentary rocks occurs along the western margin of the Precordillera and in the eastern Frontal Cordillera. In this paper, we present the analysis of aeromagnetic data and its processing focused on mapping geological limits, structures and the relation at depth of the southern Precordillera. With this main objective were applied filtering algorithms, reduction to the pole, tilt derivative, analytic signal, and particularly, the use of Improved Logistic Function (IL) as a new method of edge detection, in combination with the inversion map obtained from the Magnetization Vector Inversion (MVI) method. The results allow us to describe at depth the main trend of the Southern Precordillera Mafic Ultramafic Belt as two separated bocks, one in Peñasco and another in Cerro (Co.) Cortaderas, passing through Cerro (Co.) Pozos with a possible NNE-SSW direction. The combination of this techniques also can be used as prospecting guide to Pb–Zn–Ag vein deposits and High sulfidation Au-Epitermal deposits.

Application of portable multi-component gas analyzer to mineral exploration in semi-arid steppes of northern China: A case study from the Qinjiaying Ag–Pb–Zn prospect

Soil gases, particularly sulfur gases, have not been widely used in mineral exploration due to their high mobility and reactivity. However, our team developed a portable multi-component gas analyzer (PMGA) capable of on-site and real-time measurement of H2S, SO2, CH4, and CO2 concentrations in soil gas. This study showcases the applicability and effectiveness of PMGA in the geochemical exploration of concealed ore deposits in the Qinjiaying Ag–Pb prospect in semi-arid steppes. Comparison tests between different analyzers and periods were conducted in the Qinjiaying Ag–Pb prospect. The results showed that PMGA has high stability, consistency, and reproducibility. Then, soil gas geochemical surveys were carried out by applying PMGA along eight prospecting lines, with three prospecting lines passing through the known mineralized zone and the remaining five prospecting lines focusing on the covered areas. Three composite anomalies of H2S, SO2, CH4, and CO2 were identified. The No. 1 soil gas anomaly corresponds well to the known No. I mineralized zone. The No. 3 gas anomaly is characterized by large-scale and strong multi-gas anomalies, indicating the presence of great prospecting potentials. Finally, drilling verification revealed a medium-sized Ag–Pb–Zn deposit in the No. 3 gas anomaly. The results demonstrate that PMGA is a powerful tool for mineral exploration in the study area. This successful practice provides a paradigm for applying PMGA in mineral exploration in semi-arid steppes.

Cenozoic Pb–Zn–Ag mineralization in the Western Alps

Abstract Metallogenic models of polyphase mountain belts critically rely on robust geochronology. We combine petrology with Rb–Sr and U–Th–Pb in situ geochronology, paired at thin-section scale, to date mineralization in deformed hydrothermal Pb–Zn–Ag deposits along an east-west transect in the Western Alps, France. The Pb–Zn–Ag veins occur in shear zones with kinematic structures consistent with the mylonitized host rocks. The ore consists mainly of galena in a quartz-phengite gangue. The paragenesis can be related to hydrothermal crystallization during periods of variable strain. Both isotope systems yield only Cenozoic ages (ca. 35 Ma and 15–20 Ma) without any pre-Alpine inheritance, clearly indicating orogenic mineralization. The metallogenic model proposed here includes significant fluid circulation along major tectonic contacts between basement and sedimentary cover during Alpine convergence.

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.

Chronological sequence of charcas igneous complex and their relationships with Zn–Pb–Ag mineralization events, San Luis Potosi state, Mexico

The Charcas Intrusive Complex (CIC), comprised of monzogranites and granodiorites is located at the eastern edge of the Mesa Central in México. The CIC was dated by U/Pb on zircon crystals, from Tithonian to Rupelian ages and three distinct magmatic pulses were identified: (1) Tithonian (∼150 Ma), (3) Ypresian to Lutetian (∼55–∼44 Ma), and (3) Rupelian (∼30–∼27 Ma). The Early Cretaceous to Lutetian major and trace element magma compositions, suggest that the arc monzogranites were emplaced in a growing continental crust while the Ypresian granodiorites show typical boron enrichment observed in central Mexico. The Lutetian and Rupelian granodiorites plot inside the field of cordilleran granites or continental arc magmatism where magma mixing is common and are considered as I-type granites presenting high concentration of Ba and Sr, and high Sr/Y and La/Yb ratio values. The most developed and intensely mineralized (Zn–Pb) hydrothermal event is Lutetian in age, corresponding to the peak of magma fertility conditions determined by zircon trace element chemistry and is well correlated to the skarn occurrences at around ∼47 Ma. The Ag mineralization event is related to the Rupelian dike's emplacement. Inherited zircon grains found in the magmas highlight the shallow position of the magma plumbing and the importance of the early Cretaceous magmatic intrusion in the formation of the Rupelian silver mineralization.

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.

Provenance of Coastal and Seabed Sediments Relative to Mining and Processing Wastes: The Case of Lavrion, Attiki Peninsula, Greece

A detailed textural, mineralogical, and geochemical investigation of beach sands and seabed sediments from Thorikos and Oxygono bays of the eastern coast of Lavrion is performed, with the objective the provenance of the ore types exploited, the processing and beneficiation types employed, and the respective exploitation periods. The Oxygono Bay beach and seabed sands are highly heterogeneous, predominated by lithic clasts originating from surrounding lithologies. Examination of the fine-grained fraction from the seabed core revealed that only the upper 50 cm was affected by recent and ancient mining activity. Combining the mineralogy and geochemistry of Oxygono Bay sands with the radiochronological model of Pappa et al. (2018), four periods of recent exploitation (mid-19th—late 20th century) are distinguished: (1) The “1860–1875 A.D.”, involving exploitation of the ancient smelter slags, (2) the “1875–1900 A.D.”, with ongoing ancient smelter slag processing and the commencement of underground sulfide ore exploitation, (3) the “1900–1930 A.D.”, where heavy mining of the carbonate-hosted Pb–Zn–Ag ore occurs, (4) the “1930–1980”), where the implementation of flotation-type processing assisted in the exploitation of the poor skarn and porphyry-type ores. The latest “1980 A.D.—to date” period depicts the cessation of all mining and processing activities. The southern Thorikos Bay beach sands are homogeneous and fine-grained, are mainly composed of gangue and pyrite, and show elevated Fe, As, Pb, Zn, and Mn content. The southern Thorikos Bay beach sands clearly point to exploitation and processing by flotation of the carbonate-hosted Pb–Zn–Ag sulfide ore, and the tailings were disposed of from the nearby facilities to southern Thorikos Bay without any environmental concern during the “1930–1980 A.D.” period.

Sulphide petrology and ore genesis of the stratabound Sheep Creek sediment-hosted Zn–Pb–Ag–Sn prospect, and U–Pb zircon constraints on the timing of magmatism in the northern Alaska Range

The Sheep Creek prospect is a stratabound Zn–Pb–Ag–Sn massive sulfide occurrence in the Bonnifield mining district, northern Alaska Range. The prospect is within a quartz–sericite–graphite–chlorite schist unit associated with Devonian carbonaceous and siliceous metasedimentary rocks. Volcanogenic massive sulfide (VMS) deposits in the district are hosted in felsic metavolcanic rocks (362 ± 2 Ma) associated with siliciclastic and carbonaceous sedimentary rocks that overlie the stratigraphic sequence hosting the Sheep Creek prospect. Felsic metaigneous rocks in underlying units are 372 ± 4 to 366 ± 4 Ma. Sheep Creek is atypical of the other sulfide deposits in the district in (1) having Sn grades up to 1.2%; (2) being contained in fine-grained, quartz-rich rocks and quartz–pebble conglomerate that likely originated as chert and chert-clast sediment, respectively; and (3) showing minimal evidence of volcanic components in the host rocks. Comparison of immobile trace-element proportions for graphitic and siliceous rocks from the Sheep Creek area with those for argillite associated with the Bonnifield VMS deposits indicates a continental volcanic-arc provenance for the former and a within-plate and passive margin provenance for the latter. In contrast to previously published interpretations, our data analysis supports a clastic-dominated (CD) rather than a VMS affinity for the Sheep Creek prospect. In our model, Zn–Pb–Ag–Sn mineralization formed by syngenetic or early diagenetic processes on or beneath the seafloor, possibly in the shallow-water environment of an outer continental shelf setting. Potential analogues are the Paleozoic CD deposits in the Canadian Selwyn Basin outboard of the Laurentian continental margin.

Distribution of In, Sn, Ga, Ge, and other critical metals in sulfide ores from epithermal listvenite-associated Badovc Pb–Zn–Sb–Ni deposit (Kosovo): Insights from mineralogy and geochemistry

This work presents a mineralogical and geochemical study of sulfide ores from the epithermal listvenite-associated Badovc Pb–Zn–Sb–Ni deposit, which is located in the central part of the Kizhnica-Hajvalia-Badovc ore field, in the Trepça Mineral Belt (TMB) in Kosovo. Badovc is an example of one of many base-metal Pb–Zn–Ag deposits associated with the Serbo-Macedonian metallogenic province. There are three types of ores, the first two associated with polymetallic epithermal IS veins (massive-banded Pb–Zn–Sb and rhodochrosite-stibnite breccia) and disseminated ores associated with listvenites, which are hydrothermally altered mafic and ultramafic rocks. The mineralogy of these ores was described using EPMA in combination with reflected and transmitted light microscopy. The mineralogy of massive-banded Pb–Zn–Sb and rhodochrosite-stibnite breccia ores is relatively limited: sphalerite + rhodochrosite-siderite + pyrite/marcasite ± Pb–Sb sulfosalts ± stibnite. Listvenite Pb–Zn–Sb–Ni ores are more mineralogically variable due to the multi-stage formation of these rocks and the overprint of polymetallic mineralization. Apart from typical base-metal sulfides such as sphalerite, pyrite, galena, and chalcopyrite, the listvenite ores contain Fe–Mn carbonates, quartz, and Ni–Fe ± As ± Sb association (gersdorffite, ullmannite, millerite, and Ni–Fe thiospinels), Sn minerals (stannite and cassiterite). The LA-ICP-MS technique was used to determine critical metals occurring as minor and trace elements and substitution mechanisms in sphalerite, pyrite, stibnite, chalcopyrite and stibnite. The main critical metals, such as In, Sn, Ga, and Ge, are hosted by sphalerite in all types of ores. The highest concentrations of tin in sphalerite are observed in massive-banded Pb–Zn–Sb ores, which substitutes within the 3Zn2+ ↔ 2(Cu, Ag)+ + Sn4+ mechanism. The highest concentrations of indium are observed in sphalerites from listvenites, indicating the 2Zn2+ ↔ Cu+ + In3+ substitution. Low-temperature sphalerites from rhodochrosite-stibnite breccia exhibit elevated concentrations of Ga, Ge, and Ag, which incorporate into the structure through 2Zn2+ ↔ (Ag, Cu)+ + Ga3+, and 3Zn2+ ↔ 2(Cu, Ag)+ + Ge4+ mechanisms. The specific crystallization temperatures using GGIMFis for sphalerite are: 248–332 °C for massive-banded Pb–Zn–Sb ores, 208 °C for rhodochrosite-stibnite breccia, and 2112–344 °C for listvenite Pb–Zn–Sb–Ni ores. Additionally, stibnite from Badovc exhibits substitutions such as As3+ ↔ Sb3+ and (Cu+ + Ag+) + Pb2+ ↔ Sb3+ + □, and can incorporate various monovalent elements other than copper, including Ag+ and Tl+. Studies of epithermal listvenite-associated Badovc Pb–Zn–Sb–Ni deposits suggest that similar deposits spread across the Balkans may hold considerable prospectivity.

Magma-related origin for Pb–Zn–Ag vein formation at the Aerhada deposit, Inner Mongolia, NE China: Constraints from fluid inclusion, C–H–O–S–Pb isotopic compositions, and geochronological studies

The Aerhada Pb–Zn–Ag deposit is on the western margin of the Great Xing’an Range in NE China. Prior studies on this deposit lack information regarding precise mineralization age and convincing genetic interpretation, which limits both the prospecting at Aerhada and the reconstruction of the regional metallogenic evolution. Based on a detailed field investigation and microscopic observation, in this study, our aim was to determine the origin and evolution of the hydrothermal system and the timing of magmatism and mineralization, as well as to develop a possible metallogenic model, by revealing information regarding the mineralization paragenetic relationship, fluid inclusions, H–O–C–S–Pb isotopes, and sphalerite Rb–Sr and zircon U–Pb ages. Three successive mineralization stages were recognized: stage I quartz-arsenopyrite-pyrite, stage II quartz-sphalerite-galena, and stage III fluorite-calcite-pyrite. Four types of fluid inclusions were also identified in host minerals: CH4-rich two-phase, halite-bearing, vapor-rich two-phase, and liquid-rich two-phase. Fluid inclusion and microthermometric results showed that the homogenization temperatures were 287–341 °C for stage I, 237–291 °C for stage II, and 162–230 °C for stage III, with respective salinities of 1.7–40.2 wt%, 6.7–10.9 wt%, and 4.2–8.8 wt% NaCl equivalent. The δ18Ofluid and δDfluid values of quartz in stage I (δ18Ofluid = 8.6–10.3 ‰, δDfluid = -126.6 to −124.3 ‰) indicated that initial magmatic water interacted with organic strata, while decreasing the values of quartz in stage II (δ18Ofluid = 3.9–6.8 ‰, δDfluid = -129.1 to −127.6 ‰) and calcite in stage III (δ18Ofluid = -3.5 to −1.0 ‰, δDfluid = -115.5 to −113.4 ‰), showing a trend of dilution and cooling by meteoric water. The negative δCfluid values (δCfluid = -15.9 to −12.6 ‰) of quartz fluid inclusions from stages I and II emphasize that organic carbon was added to the hydrothermal system through water–rock interactions. The δ34S values (δ34Ssulfides = 1.2–7.5 ‰) and lead isotope data of sulfides (206Pb/204Pb = 18.153–18.684, 207Pb/204Pb = 15.370–15.750, 208Pb/204Pb = 37.653–39.301), coupled with those of the hidden biotite granite and Devonian strata, indicate that the ore-forming material was primarily derived from magma and wall rocks. The sphalerite samples produced a Rb–Sr isochron age of 154.1 ± 3.5 Ma (2σ, MSWD = 0.82, n = 8), which was like the zircon U–Pb age of biotite granite (156.3 ± 1.4 Ma, 2σ, MSWD = 0.89, n = 14). Combining the alteration pattern, fluid inclusions, and isotopic and geochronological studies, it was concluded that Aerhada is a magma-related hydrothermal Pb–Zn deposit formed under the post-collision extension setting following the Mongol–Okhotsk Ocean closure during the Late Jurassic period. The proposed metallogenic model is expected to assist in the exploration and development of polymetallic mineralization in the Great Xing’an Range.

Lithostratigraphy of a portion of the Neoproterozoic Rosh Pinah formation: Host rocks of the Western Orefield, Rosh Pinah mine, southern Namibia

The Rosh Pinah Zn–Pb–Ag deposit in southern Namibia comprises a significant sulphidic Zn–Pb resource (19.94 Mt @ 7.3 wt% Zn, 1.83 wt% Pb and 27.7 g/t Ag) occurring mainly as sphalerite and galena. The ore minerals as well as pyrite are hosted by the Ore Equivalent Horizon (OEH), a part of the Neoproterozoic Rosh Pinah Formation. Details on original rock types and depositional environment of the OEH units remain unclear despite past work. Here, we combine detailed drillhole logging data, drillhole logging database and drillcore photographs, underground and near-mine outcrop observations coupled with detailed petrographic observations to elucidate original rock types and depositional environments. The OEH is comprised of three mappable lithofacies (carbonaceous argillite and siltstones, volcanic/volcaniclastic rocks, and carbonate rocks) enclosed within a sequence of arkose. The lateral transition from coarse-grained arkose to the fine-grained carbonaceous rocks of the OEH reflects subaqueous fan type deposition. The presence of diagenetic textures in the carbonate rocks in form of cloudy, isopachous fibrous dolomitic cements point to subaqueous depositional environments. The geometry of carbonate bodies in the OEH at the Rosh Pinah mine and in nearby surface outcrop exposures suggest local accumulations with a pronounced topographic relief above the surrounding sediments, reminiscent of carbonate buildups. The OEH appears to represent a limited interval of marine or lacustrine deposition that may be related to syn-sedimentary extensional conditions.

Structural controls on formation of the Xiayu vein-hosted Ag–Pb–Zn–Au orefield during intracontinental extension along the southern margin of the North China Craton

The Xiayu Ag–Pb–Zn–Au deposit, situated in the Early Cretaceous Xiong’er shan area on the southern edge of the North China Craton, comprises the Haopinggou, Shagou, Tieluping, and Houzhanggou deposits, making it the largest Ag producer in the southern North China Craton. Despite significant research efforts, the connection between extensional faults and vein–hosted Ag–Pb–Zn–Au deposits in this area is still not well understood. To address this issue, we introduce new structural data, fault–slip data analysis, and information on epithermal Ag–Pb–Zn–Au mineralization. Two separate paleo–stress inversion methods were applied to determine that the region was affected by two discrete stress fields: E–W transtension and NW–SE transtension. Our palaeostress reconstruction indicates that transtensional tectonics would have affected the emplacement of fault–fill veins (stage I) and extensional veins (stage II). Both types of geometric veins show two distinct stages of formation. The first stage (I) involves the development of quartz–pyrite within hydraulic breccia, transitioning into crack–seal laminated shear veins. These likely formed during a period of regional extension in an east–west direction. The second stage (II) features the deposition of undeformed quartz–sphalerite–galena within pre–existing dilational sites near newly formed normal faults or stage I veins. This second stage likely occurred during a regional extension in a northwest–southeast direction.

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.